mirror of
https://github.com/pragma-/pbot.git
synced 2024-12-31 15:12:33 +01:00
9ddd38038a
I really, really need to clean this mess up and combine c99std.pl, c11std.pl and c23std.pl into one script!
48811 lines
2.2 MiB
Vendored
48811 lines
2.2 MiB
Vendored
<html>
|
|
<body>
|
|
<h2>N3047 working draft — August 4, 2022 ISO/IEC 9899:2023 (E)</h2>
|
|
<a name='ABSTRACT.'></a>
|
|
<hr>
|
|
<h3>ABSTRACT. [Abstract]</h3>
|
|
<pre>(This cover sheet to be replaced by ISO.)
|
|
|
|
This document specifies the form and establishes the interpretation of programs expressed in the
|
|
programming language C. Its purpose is to promote portability, reliability, maintainability, and
|
|
efficient execution of C language programs on a variety of computing systems.
|
|
|
|
Clauses are included that detail the C language itself and the contents of the C language execution
|
|
library. Annexes summarize aspects of both of them, and enumerate factors that influence the
|
|
portability of C programs.
|
|
|
|
Although this document is intended to guide knowledgeable C language programmers as well as
|
|
implementors of C language translation systems, the document itself is not designed to serve as a
|
|
tutorial.
|
|
|
|
Recipients of this draft are invited to submit, with their comments, notification of any relevant
|
|
patent rights of which they are aware and to provide supporting documentation.
|
|
|
|
The following documents, for all intents and purposes, have been applied to this draft from before
|
|
and during the October 2019 Meeting:
|
|
|
|
DR 476 volatile semantics for lvalues
|
|
DR 488 c16rtomb() on wide characters encoded as multiple char16_t
|
|
DR 494 Part 1: Alignment specifier expression evaluation
|
|
DR 496 offsetof and subobjects (with editorial modification)
|
|
DR 497 "white-space character" defined in two places
|
|
DR 499 Anonymous structure in union behavior
|
|
DR 500 Ambiguous specification for FLT_EVAL_METHOD
|
|
DR 501 make DECIMAL_DIG obsolescent
|
|
FP DR 13 totalorder parameters
|
|
FP DR 20 changes for obsolescing DECIMAL_DIG
|
|
FP DR 21 printf of one-digit character string
|
|
FP DR 22 changes for obsolescing DECIMAL_DIG, Part 2
|
|
FP DR 23 llquantexp invalid case
|
|
FP DR 24 remainder NaN case
|
|
FP DR 25 totalorder parameters
|
|
N2124 and N2319 rounding direction macro FE_TONEARESTFROMZERO
|
|
N2186 Alternative to N2166
|
|
N2212 type generic cbrt (with editorial changes)
|
|
N2260 Clarifying the restrict Keyword v2
|
|
N2265 Harmonizing static_assert with C++
|
|
N2267 nodiscard attribute
|
|
N2270 maybe_unused attribute
|
|
N2271 CR for pow divide-by-zero case
|
|
N2293 Alignment requirements for memory management functions
|
|
N2314 TS 18661-1 plus CR/DRs for C2X
|
|
N2322 preprocessor line numbers unspecified
|
|
N2325 DBL_NORM_MAX etc
|
|
N2326 floating-point zero and other normalization
|
|
N2334 deprecated attribute
|
|
N2335 attributes
|
|
N2337 strftime, with ’b’ and ’B’ swapped
|
|
N2338 error indicator for encoding errors in fgetwc
|
|
N2341 TS 18661-2 plus CR/DRs for C2X
|
|
N2345 editors, resolve ambiguity of a semicolon
|
|
N2349 the memccpy function
|
|
N2350 defining new types in offsetof
|
|
N2353 the strdup and strndup functions
|
|
N2356 update for payload functions
|
|
N2358 no internal state for mblen
|
|
N2359 part 2 (remove WANT macros from numbered clauses) and part 3 (version macros for
|
|
changed library clauses)
|
|
N2401 TS 18661-4a for C2X
|
|
N2408 The fallthrough attribute
|
|
N2412 Two’s complement sign representation for C2x
|
|
N2417 Section 6: Add time conversion functions that are relatively thread-safe
|
|
N2418 Adding the u8 character prefix
|
|
N2432 Remove support for function definitions with identifier lists
|
|
N2508 Free Positioning of Labels Inside Compound Statements
|
|
N2554 Minor attribute wording cleanups
|
|
|
|
The following documents have been applied to this draft from the October 2019 Meeting:
|
|
|
|
N2379 *_IS_IEC_60559 Feature Test Macros.
|
|
N2416 Floating Point Negation and Conversion.
|
|
N2384 Annex <a href='#F.8'>F.8</a> Update for Implementation Extensions and Rounding.
|
|
N2424 Why logp1 as a Function Name.
|
|
N2406 Signaling NaN Initializers.
|
|
N2393 _Bool Definitions For true and false.
|
|
|
|
The following documents have been applied to this draft from the March/April 2020 Virtual
|
|
Meeting:
|
|
|
|
N2444 More optionally per-thread state for the library.
|
|
N2446 printf of NAN().
|
|
N2448 [[Nodiscard("should have a reason")]].
|
|
N2459 Add an interface to query resolution of time bases, v3.
|
|
N2464 Zero-size Reallocations are Undefined Behavior.
|
|
N2476 Names and Locations of Floating Point Entities.
|
|
N2480 Allowing unnamed parameters in function definitions.
|
|
N2490 Why no wide string strfrom functions.
|
|
|
|
The following documents have been applied to this draft from the August 2020 Virtual Meeting:
|
|
|
|
N2491 powr justification
|
|
N2492 Note About Math Function Properties.
|
|
N2506 Range Errors in Math Functions.
|
|
N2508 Free Positioning of Labels.
|
|
N2517 Clarification Request for C17 Example of Undefined Behavior.
|
|
N2532 Min-max Functions.
|
|
N2553 Querying Attribute Support.
|
|
N2554 Minor Attribute Wording Cleanup.
|
|
|
|
The following documents have been applied to this draft from the October and November 2020
|
|
Virtual Meetings:
|
|
|
|
N2546 Missing DEC_EVAL_METHOD
|
|
N2547 Missing const in decimal getpayload functions
|
|
N2548 intmax_t removal from FP functions
|
|
N2549 Binary Literals
|
|
N2552 Editorial cleanup for rounding macros
|
|
N2557 Allow Duplicate Attributes
|
|
N2560 FP hex formatting precision
|
|
N2562 Unclear type relationship between a format specifier and its argument
|
|
N2563 Character encoding of diagnostic text
|
|
N2564 Range errors and math functions (updated previous version, N2506)
|
|
N2570 Feature and WANT macros for Annex F functions
|
|
N2571 snprintf nonnegative clarification
|
|
N2572 What We Think We Reserve
|
|
N2580 Decimal Floating Point Triples
|
|
N2586 Sufficient Formatting Precision
|
|
N2594 Remove Mixed Wide String Literal Concatenation
|
|
N2559 Update to IEC 60559:2020
|
|
N2600 Update to IEC 60559:2020 (updates previous version, N2559)
|
|
N2602 Infinity/NAN Macros, Editorial Fixes
|
|
N2607 Compatibility of Pointers to Arrays with Qualifiers
|
|
|
|
The following documents have been applied to this draft from the March/April 2021 Virtual
|
|
Meeting:
|
|
|
|
N2524 String Functions for Freestanding Implementations
|
|
N2626 Digit Separators
|
|
N2630 Formatting Input/Output of Binary Integer Numbers
|
|
N2640 Missing DEC_EVAL_METHOD, Take 2
|
|
N2641 Missing +(x) in Table
|
|
N2643 Negative vs. Less Than Zero
|
|
N2645 Add Support for Preprocessing Directives #elifdef and #elifndef
|
|
N2680 Specific Width Length Modifier for Formatting
|
|
The following documents have been applied to this draft from the June 2021 Virtual Meeting:
|
|
|
|
N2651 fabs and copysign Cleanup
|
|
N2662 [[maybe_unused]] for Labels
|
|
N2665 Zero-size Reallocations Are No Longer an Obsolescent Feature
|
|
N2670 Zeros Compare Equal
|
|
N2671 Negative Values
|
|
N2672 §<a href='#5.2.4.2.2'>5.2.4.2.2</a> Cleanup
|
|
N2683 Towards Integer Safety
|
|
N2751 signbit Cleanup
|
|
N2763 Adding a Fundamental Type for N-bit Integers
|
|
|
|
The following documents have been applied to this draft from the August/September 2021 Virtual
|
|
Meeting:
|
|
|
|
N2686 #warning Directive
|
|
N2688 Sterile Characters
|
|
N2710 SNAN Fixes
|
|
N2711 fmin, fmax
|
|
N2713 Integer Constant Expressions
|
|
N2714 hypot Changes
|
|
N2715 cr_ Prefix Potentially Reserved for Identifiers
|
|
N2716 Fix "numerically"/"numerically equal" Usage
|
|
N2726 _Imaginary_I and _Complex_I Qualifiers
|
|
|
|
N2728 char16_t & char32_t String Literals Shall be UTF-16 & UTF-32
|
|
N2745 Range Error Definition
|
|
N2748 Effects of fenv Exception Functions
|
|
N2749 IEC 60559 Bindings
|
|
N2755 Static Initialization of Decimal Floating Point
|
|
N2776 ckd_* Identifiers Should be Potentially Reserved Identifiers
|
|
N2799 __has_include for C
|
|
|
|
The following documents have been applied to this draft from the November/December 2021
|
|
Virtual Meeting:
|
|
|
|
N2747 Annex F Overflow and Underflow
|
|
N2770 Remove UB from Incomplete Types in Function Parameters
|
|
N2778 Require Variably-Modified Types
|
|
N2781 Types do not have Types (with meeting-agreed changes plus some editorial changes)
|
|
N2790 "remquo" Changes
|
|
N2805 Overflow and Underflow Definitions
|
|
N2806 §<a href='#5.2.4.2.2'>5.2.4.2.2</a> Cleanup, Again
|
|
N2808 Allow 16-bit ptrdiff_t
|
|
N2823 Freestanding CFP Functions
|
|
N2838 Types and Sizes
|
|
N2837 Clarifying Integer Terms (also, delete Annex H and replace with the Floating Point TS
|
|
/ Annex merge)
|
|
N2842 Normal and Subnormal Classification
|
|
N2843 Clarification of Max Exponent Macros
|
|
N2845 feraiseexcept Update
|
|
N2846 Clarification about Expression Transformations
|
|
N2848 INFINITY Macro Contradictions (Wording 1 only!)
|
|
N2872 Require Exact-Width Integer Type Interfaces, Part I (Change from proposal’s §<a href='#3.1'>3.1</a> only)
|
|
|
|
The following documents have been applied to this draft from the January/February 2022 Virtual
|
|
Meeting, Parts 1 and 2:
|
|
|
|
N2653 char8_t: A type for UTF-8 characters and strings
|
|
N2701 @, $, and ‘ in the source/execution character set
|
|
N2754 Decimal Floating Point: Quantum Exponent of NaN
|
|
N2762 Fixes for Potentially Reserved Identifiers
|
|
N2764 The _Noreturn Attribute
|
|
N2775 Literal Suffixes for Bit-Precise Integers
|
|
N2797 *_HAS_SUBNORM == 0 Implies What?
|
|
N2810 calloc Overflow Handling
|
|
N2819 Disambiguate the Storage Class of Some Compound Literals
|
|
N2826 unreachable()
|
|
N2828 Unicode Sequences More Than 21 Bits are a Constraint Violation
|
|
N2829 Make assert() user friendly in C
|
|
N2836 Unicode Syntax Identifiers for C
|
|
N2840 Make call_once() Mandatory
|
|
N2841 No Function Declarators without Prototypes
|
|
N2844 Remove default promotions for _FloatN Types
|
|
N2847 Revised Suggestions of Change for Numerically Equal / Equivalent
|
|
N2879 <a href='#5.2.4.2.2'>5.2.4.2.2</a> Cleanup, Again Again
|
|
N2880 Overflow and Underflow Definitions Update
|
|
N2881 Normal and Subnormal Classification Update
|
|
N2882 Clarification for the Max Exponent Macros
|
|
N2900 Consistent, Warningless, and Intuitive Initialization with {}
|
|
N2927 Not-So-Magic: typeof(...)
|
|
N2931 Macros and Macro Spellings from C Floating Point Integration
|
|
N2934 Revised Spelling of Keywords
|
|
N2935 Make false and true Language Features
|
|
N2937 Properly Define Blocks in the Grammar
|
|
|
|
The following documents have been applied to this draft from the May 2022 Virtual Meeting:
|
|
|
|
N2601 Annex X (replacing Annex H) for IEC 60599 Interchange (ratified early 2021 but
|
|
integrated over a long period of time).
|
|
N2861 Indeterminate Values and Trap Representations
|
|
N2867 Checked N-Bit Integers? (Not Now)
|
|
N2886 Remove ATOMIC_VAR_INIT
|
|
N2888 Require Exact-width Integer Type Interfaces, Part II
|
|
N2897 memset_explicit
|
|
N2992 Wording Clarification for Variably-Modified Types
|
|
|
|
The following documents have been applied to this draft from the July 2022 Virtual Meeting:
|
|
|
|
N2930 Change remove_quals to typeof_unqual
|
|
N2939 Identifier Syntax Fixes
|
|
N2940 Remove Trigraphs??!
|
|
N2969 (nice) Bit-Precise Bit Fields
|
|
N2974 Queryable Pointer Alignment
|
|
N3029 Improved Normal Enumerations
|
|
N2975 Relax requirements for va_start
|
|
N2993 Make *_HAS_SUBNORM Obsolete
|
|
N3011 Oops, Empty Initializers in Compound Literals
|
|
N3030 Enhanced Enumerations
|
|
N2951 Freestanding C and IEC 60559 Conformance Scope Reduction
|
|
N2956 Unsequenced Functions
|
|
N3033 Comma Ommission and Deletion (__VA_OPT__ and Preprocessor Wording Improve-
|
|
ments)
|
|
N3035 _BitInt(...) Fixes
|
|
|
|
N3006 Underspecified Object Declarations
|
|
N3007 Type Inference for Object Declarations
|
|
N3018 constexpr for Object Definitions
|
|
N3038 Introduce Storage Class Specifiers for Compound Literals
|
|
N3034 Identifier Primary Expressions
|
|
N3042 Introduce the nullptr_t constant, nullptr
|
|
N2929 Memory Layout of union s
|
|
N3037 Improved Tag Compatibility
|
|
N3020 Qualifier-preserving Standard Functions
|
|
N3022 Modern Bit Utilities - without Rotate Left/Right, Memory Reversal ("byteswap"), or
|
|
Endian-Aware Load/Store
|
|
N3017 #embed
|
|
N2957 New Optional Time Bases
|
|
|
|
In addition to these, the document has undergone some editorial changes, including the following.
|
|
|
|
— The synopsis lists in Annex B are now generated automatically and classified according to
|
|
the feature test or WANT macros that are required to make them available.
|
|
— A new non-normative clause <a href='#J.6'>J.6</a> added to Annex J categorizes identifiers used by this
|
|
document.
|
|
— Renaming of the syntax term "struct declaration", "struct declaration list" "struct declarator",
|
|
and "struct declarator list" to the more appropriate "member declaration", "member declaration
|
|
list", "member declarator" and "member declarator list", respectively.
|
|
— Misspelling of "invokation" fixed to "invocation".
|
|
— A positional reference to a table was changed to be a more direct reference due to unfortunate
|
|
page breaks.
|
|
— Missing macros were added to from <float.h> and <limits.h>.
|
|
— A footnote added for simple atomic assignment (<a href='#6.5.16'>6.5.16</a>).
|
|
— The _Bool expansion macros were properly defined and fixed for true and false.
|
|
— An issue with "modifying object" being removed from an earlier draft was fixed. This was a
|
|
mistake: side effects do include modifying an object.
|
|
— The Decimal Floating Point Initialization text was not well-worded. It was fixed after the
|
|
paper adding the wording was integrated.
|
|
— Examples using poor phrasing for objects and their types were fixed to say "object(s) of type
|
|
int" and similar.
|
|
— The terms "floating-point type" and "floating-point constant" were changed to just be
|
|
"floating type" and "floating constant", as are defined in the standard, respectively.
|
|
— The wording "thread-local storage" was normalized to be "thread storage" everywhere, as
|
|
intended (this is the word defined by the standard, the other just fell naturally out of casual
|
|
usage and thought).
|
|
— A footnote clarifying the role for valid pointers with zero size was added to the library
|
|
frontmatter, specifically concerning functions like memcpy and memset.
|
|
— Various duplicate spellings (e.g. "function functions" and similar) were removed and typos
|
|
were fixed (e.g., "stirng" and similar).
|
|
— The pp-number production was incorrect for digit separators. Adjusted and fixed.
|
|
— The wording for freestanding heads for <string.h> were very poorly done. It was changed
|
|
to have better wording.
|
|
— The introductory sentence for the implementation limits was very wordy and deeply confus-
|
|
ing to normal users. The sentence was adjusted to read much better and more clearly.
|
|
— In a sentence using "respectively" for fmin and fmax descriptions, the order of the respective
|
|
items was swapped. This gave the wrong definitions to each item. They were put in the
|
|
proper order.
|
|
— A missing closing parenthesis in Annex J was fixed.
|
|
— The term "floating-point multiply add" was changed to "fused multiply add", matching
|
|
naming conventions in reality.
|
|

|
|
</pre>
|
|
<a name='CONTENTS.'></a>
|
|
<hr>
|
|
<h3>CONTENTS. [Contents]</h3>
|
|
<pre><a href='#FOREWORD.'>Foreword</a>
|
|
|
|
<a href='#INTRO.'>Introduction</a>
|
|
|
|
<a href='#1.'>1.</a> Scope
|
|
|
|
<a href='#2.'>2.</a> Normative references
|
|
|
|
<a href='#3.'>3.</a> Terms, definitions, and symbols
|
|
|
|
<a href='#4.'>4.</a> Conformance
|
|
|
|
<a href='#5.'>5.</a> Environment
|
|
<a href='#5.1'>5.1</a> Conceptual models
|
|
<a href='#5.1.1'>5.1.1</a> Translation environment
|
|
<a href='#5.1.2'>5.1.2</a> Execution environments
|
|
<a href='#5.2'>5.2</a> Environmental considerations
|
|
<a href='#5.2.1'>5.2.1</a> Character sets
|
|
<a href='#5.2.2'>5.2.2</a> Character display semantics
|
|
<a href='#5.2.3'>5.2.3</a> Signals and interrupts
|
|
<a href='#5.2.4'>5.2.4</a> Environmental limits
|
|
|
|
|
|
<a href='#6.1'>6.1</a> Notation
|
|
<a href='#6.2'>6.2</a> Concepts
|
|
<a href='#6.2.1'>6.2.1</a> Scopes of identifiers
|
|
<a href='#6.2.2'>6.2.2</a> Linkages of identifiers
|
|
<a href='#6.2.3'>6.2.3</a> Name spaces of identifiers
|
|
<a href='#6.2.4'>6.2.4</a> Storage durations of objects
|
|
<a href='#6.2.5'>6.2.5</a> Types
|
|
<a href='#6.2.6'>6.2.6</a> Representations of types
|
|
<a href='#6.2.7'>6.2.7</a> Compatible type and composite type
|
|
<a href='#6.2.8'>6.2.8</a> Alignment of objects
|
|
<a href='#6.2.9'>6.2.9</a> Encodings
|
|
<a href='#6.3'>6.3</a> Conversions
|
|
<a href='#6.3.1'>6.3.1</a> Arithmetic operands
|
|
<a href='#6.3.2'>6.3.2</a> Other operands
|
|
<a href='#6.4'>6.4</a> Lexical elements
|
|
<a href='#6.4.1'>6.4.1</a> Keywords
|
|
<a href='#6.4.2'>6.4.2</a> Identifiers
|
|
<a href='#6.4.3'>6.4.3</a> Universal character names
|
|
<a href='#6.4.4'>6.4.4</a> Constants
|
|
<a href='#6.4.5'>6.4.5</a> String literals
|
|
<a href='#6.4.6'>6.4.6</a> Punctuators
|
|
<a href='#6.4.7'>6.4.7</a> Header names
|
|
<a href='#6.4.8'>6.4.8</a> Preprocessing numbers
|
|
<a href='#6.4.9'>6.4.9</a> Comments
|
|
<a href='#6.5'>6.5</a> Expressions
|
|
<a href='#6.5.1'>6.5.1</a> Primary expressions
|
|
<a href='#6.5.2'>6.5.2</a> Postfix operators
|
|
<a href='#6.5.3'>6.5.3</a> Unary operators
|
|
<a href='#6.5.4'>6.5.4</a> Cast operators
|
|
<a href='#6.5.5'>6.5.5</a> Multiplicative operators
|
|
<a href='#6.5.6'>6.5.6</a> Additive operators
|
|
<a href='#6.5.7'>6.5.7</a> Bitwise shift operators
|
|
<a href='#6.5.8'>6.5.8</a> Relational operators
|
|
<a href='#6.5.9'>6.5.9</a> Equality operators
|
|
<a href='#6.5.10'>6.5.10</a> Bitwise AND operator
|
|
<a href='#6.5.11'>6.5.11</a> Bitwise exclusive OR operator
|
|
<a href='#6.5.12'>6.5.12</a> Bitwise inclusive OR operator
|
|
<a href='#6.5.13'>6.5.13</a> Logical AND operator
|
|
<a href='#6.5.14'>6.5.14</a> Logical OR operator
|
|
<a href='#6.5.15'>6.5.15</a> Conditional operator
|
|
<a href='#6.5.16'>6.5.16</a> Assignment operators
|
|
<a href='#6.5.17'>6.5.17</a> Comma operator
|
|
<a href='#6.6'>6.6</a> Constant expressions
|
|
<a href='#6.7'>6.7</a> Declarations
|
|
<a href='#6.7.1'>6.7.1</a> Storage-class specifiers
|
|
<a href='#6.7.2'>6.7.2</a> Type specifiers
|
|
<a href='#6.7.3'>6.7.3</a> Type qualifiers
|
|
<a href='#6.7.4'>6.7.4</a> Function specifiers
|
|
<a href='#6.7.5'>6.7.5</a> Alignment specifier
|
|
<a href='#6.7.6'>6.7.6</a> Declarators
|
|
<a href='#6.7.7'>6.7.7</a> Type names
|
|
<a href='#6.7.8'>6.7.8</a> Type definitions
|
|
<a href='#6.7.9'>6.7.9</a> Type inference
|
|
<a href='#6.7.10'>6.7.10</a> Initialization
|
|
<a href='#6.7.11'>6.7.11</a> Static assertions
|
|
<a href='#6.7.12'>6.7.12</a> Attributes
|
|
<a href='#6.8'>6.8</a> Statements and blocks
|
|
<a href='#6.8.1'>6.8.1</a> Labeled statements
|
|
<a href='#6.8.2'>6.8.2</a> Compound statement
|
|
<a href='#6.8.3'>6.8.3</a> Expression and null statements
|
|
<a href='#6.8.4'>6.8.4</a> Selection statements
|
|
<a href='#6.8.5'>6.8.5</a> Iteration statements
|
|
<a href='#6.8.6'>6.8.6</a> Jump statements
|
|
<a href='#6.9'>6.9</a> External definitions
|
|
<a href='#6.9.1'>6.9.1</a> Function definitions
|
|
<a href='#6.9.2'>6.9.2</a> External object definitions
|
|
<a href='#6.10'>6.10</a> Preprocessing directives
|
|
<a href='#6.10.1'>6.10.1</a> Conditional inclusion
|
|
<a href='#6.10.2'>6.10.2</a> Source file inclusion
|
|
<a href='#6.10.3'>6.10.3</a> Binary resource inclusion
|
|
<a href='#6.10.4'>6.10.4</a> Macro replacement
|
|
<a href='#6.10.5'>6.10.5</a> Line control
|
|
<a href='#6.10.6'>6.10.6</a> Diagnostic directives
|
|
<a href='#6.10.7'>6.10.7</a> Pragma directive
|
|
<a href='#6.10.8'>6.10.8</a> Null directive
|
|
<a href='#6.10.9'>6.10.9</a> Predefined macro names
|
|
<a href='#6.10.10'>6.10.10</a> Pragma operator
|
|
<a href='#6.11'>6.11</a> Future language directions
|
|
<a href='#6.11.1'>6.11.1</a> Floating types
|
|
<a href='#6.11.2'>6.11.2</a> Linkages of identifiers
|
|
<a href='#6.11.3'>6.11.3</a> External names
|
|
<a href='#6.11.4'>6.11.4</a> Character escape sequences
|
|
<a href='#6.11.5'>6.11.5</a> Storage-class specifiers
|
|
<a href='#6.11.6'>6.11.6</a> Pragma directives
|
|
<a href='#6.11.7'>6.11.7</a> Predefined macro names
|
|
|
|
|
|
<a href='#7.1'>7.1</a> Introduction
|
|
<a href='#7.1.1'>7.1.1</a> Definitions of terms
|
|
<a href='#7.1.2'>7.1.2</a> Standard headers
|
|
<a href='#7.1.3'>7.1.3</a> Reserved identifiers
|
|
<a href='#7.1.4'>7.1.4</a> Use of library functions
|
|
<a href='#7.2'>7.2</a> Diagnostics <assert.h>
|
|
<a href='#7.2.1'>7.2.1</a> Program diagnostics
|
|
<a href='#7.3'>7.3</a> Complex arithmetic <complex.h>
|
|
<a href='#7.3.1'>7.3.1</a> Introduction
|
|
<a href='#7.3.2'>7.3.2</a> Conventions
|
|
<a href='#7.3.3'>7.3.3</a> Branch cuts
|
|
<a href='#7.3.4'>7.3.4</a> The CX_LIMITED_RANGE pragma
|
|
<a href='#7.3.5'>7.3.5</a> Trigonometric functions
|
|
<a href='#7.3.6'>7.3.6</a> Hyperbolic functions
|
|
<a href='#7.3.7'>7.3.7</a> Exponential and logarithmic functions
|
|
<a href='#7.3.8'>7.3.8</a> Power and absolute-value functions
|
|
<a href='#7.3.9'>7.3.9</a> Manipulation functions
|
|
<a href='#7.4'>7.4</a> Character handling <ctype.h>
|
|
<a href='#7.4.1'>7.4.1</a> Character classification functions
|
|
<a href='#7.4.2'>7.4.2</a> Character case mapping functions
|
|
<a href='#7.5'>7.5</a> Errors <errno.h>
|
|
<a href='#7.6'>7.6</a> Floating-point environment <fenv.h>
|
|
<a href='#7.6.1'>7.6.1</a> The FENV_ACCESS pragma
|
|
<a href='#7.6.2'>7.6.2</a> The FENV_ROUND pragma
|
|
<a href='#7.6.3'>7.6.3</a> The FENV_DEC_ROUND pragma
|
|
<a href='#7.6.4'>7.6.4</a> Floating-point exceptions
|
|
<a href='#7.6.5'>7.6.5</a> Rounding and other control modes
|
|
<a href='#7.6.6'>7.6.6</a> Environment
|
|
<a href='#7.7'>7.7</a> Characteristics of floating types <float.h>
|
|
<a href='#7.8'>7.8</a> Format conversion of integer types <inttypes.h>
|
|
<a href='#7.8.1'>7.8.1</a> Macros for format specifiers
|
|
<a href='#7.8.2'>7.8.2</a> Functions for greatest-width integer types
|
|
<a href='#7.9'>7.9</a> Alternative spellings <iso646.h>
|
|
<a href='#7.10'>7.10</a> Characteristics of integer types <limits.h>
|
|
<a href='#7.11'>7.11</a> Localization <locale.h>
|
|
<a href='#7.11.1'>7.11.1</a> Locale control
|
|
<a href='#7.11.2'>7.11.2</a> Numeric formatting convention inquiry
|
|
<a href='#7.12'>7.12</a> Mathematics <math.h>
|
|
<a href='#7.12.1'>7.12.1</a> Treatment of error conditions
|
|
<a href='#7.12.2'>7.12.2</a> The FP_CONTRACT pragma
|
|
<a href='#7.12.3'>7.12.3</a> Classification macros
|
|
<a href='#7.12.4'>7.12.4</a> Trigonometric functions
|
|
<a href='#7.12.5'>7.12.5</a> Hyperbolic functions
|
|
<a href='#7.12.6'>7.12.6</a> Exponential and logarithmic functions
|
|
<a href='#7.12.7'>7.12.7</a> Power and absolute-value functions
|
|
<a href='#7.12.8'>7.12.8</a> Error and gamma functions
|
|
<a href='#7.12.9'>7.12.9</a> Nearest integer functions
|
|
<a href='#7.12.10'>7.12.10</a> Remainder functions
|
|
<a href='#7.12.11'>7.12.11</a> Manipulation functions
|
|
<a href='#7.12.12'>7.12.12</a> Maximum, minimum, and positive difference functions
|
|
<a href='#7.12.13'>7.12.13</a> Fused multiply-add
|
|
<a href='#7.12.14'>7.12.14</a> Functions that round result to narrower type
|
|
<a href='#7.12.15'>7.12.15</a> Quantum and quantum exponent functions
|
|
<a href='#7.12.16'>7.12.16</a> Decimal re-encoding functions
|
|
<a href='#7.12.17'>7.12.17</a> Comparison macros
|
|
<a href='#7.13'>7.13</a> Non-local jumps <setjmp.h>
|
|
<a href='#7.13.1'>7.13.1</a> Save calling environment
|
|
<a href='#7.13.2'>7.13.2</a> Restore calling environment
|
|
<a href='#7.14'>7.14</a> Signal handling <signal.h>
|
|
<a href='#7.14.1'>7.14.1</a> Specify signal handling
|
|
<a href='#7.14.2'>7.14.2</a> Send signal
|
|
<a href='#7.15'>7.15</a> Alignment <stdalign.h>
|
|
<a href='#7.16'>7.16</a> Variable arguments <stdarg.h>
|
|
<a href='#7.16.1'>7.16.1</a> Variable argument list access macros
|
|
<a href='#7.17'>7.17</a> Atomics <stdatomic.h>
|
|
<a href='#7.17.1'>7.17.1</a> Introduction
|
|
<a href='#7.17.2'>7.17.2</a> Initialization
|
|
<a href='#7.17.3'>7.17.3</a> Order and consistency
|
|
<a href='#7.17.4'>7.17.4</a> Fences
|
|
<a href='#7.17.5'>7.17.5</a> Lock-free property
|
|
<a href='#7.17.6'>7.17.6</a> Atomic integer types
|
|
<a href='#7.17.7'>7.17.7</a> Operations on atomic types
|
|
<a href='#7.17.8'>7.17.8</a> Atomic flag type and operations
|
|
<a href='#7.18'>7.18</a> Bit and byte utilities <stdbit.h>
|
|
<a href='#7.18.1'>7.18.1</a> General
|
|
<a href='#7.18.2'>7.18.2</a> Endian
|
|
<a href='#7.18.3'>7.18.3</a> Count Leading Zeros
|
|
<a href='#7.18.4'>7.18.4</a> Count Leading Ones
|
|
<a href='#7.18.5'>7.18.5</a> Count Trailing Zeros
|
|
<a href='#7.18.6'>7.18.6</a> Count Trailing Ones
|
|
<a href='#7.18.7'>7.18.7</a> First Leading Zero
|
|
<a href='#7.18.8'>7.18.8</a> First Leading One
|
|
<a href='#7.18.9'>7.18.9</a> First Trailing Zero
|
|
<a href='#7.18.10'>7.18.10</a> First Trailing One
|
|
<a href='#7.18.11'>7.18.11</a> Count Ones
|
|
<a href='#7.18.12'>7.18.12</a> Count Zeros
|
|
<a href='#7.18.13'>7.18.13</a> Single-bit Check
|
|
<a href='#7.18.14'>7.18.14</a> Bit Width
|
|
<a href='#7.18.15'>7.18.15</a> Bit Floor
|
|
<a href='#7.18.16'>7.18.16</a> Bit Ceiling
|
|
<a href='#7.19'>7.19</a> Boolean type and values <stdbool.h>
|
|
<a href='#7.20'>7.20</a> Checked Integer Arithmetic <stdckdint.h>
|
|
<a href='#7.20.1'>7.20.1</a> The ckd_ Checked Integer Operation Macros
|
|
<a href='#7.21'>7.21</a> Common definitions <stddef.h>
|
|
<a href='#7.21.1'>7.21.1</a> The unreachable macro
|
|
<a href='#7.21.2'>7.21.2</a> The nullptr_t type
|
|
<a href='#7.22'>7.22</a> Integer types <stdint.h>
|
|
<a href='#7.22.1'>7.22.1</a> Integer types
|
|
<a href='#7.22.2'>7.22.2</a> Widths of specified-width integer types
|
|
<a href='#7.22.3'>7.22.3</a> Width of other integer types
|
|
<a href='#7.22.4'>7.22.4</a> Macros for integer constants
|
|
<a href='#7.22.5'>7.22.5</a> Maximal and minimal values of integer types
|
|
<a href='#7.23'>7.23</a> Input/output <stdio.h>
|
|
<a href='#7.23.1'>7.23.1</a> Introduction
|
|
<a href='#7.23.2'>7.23.2</a> Streams
|
|
<a href='#7.23.3'>7.23.3</a> Files
|
|
<a href='#7.23.4'>7.23.4</a> Operations on files
|
|
<a href='#7.23.5'>7.23.5</a> File access functions
|
|
<a href='#7.23.6'>7.23.6</a> Formatted input/output functions
|
|
<a href='#7.23.7'>7.23.7</a> Character input/output functions
|
|
<a href='#7.23.8'>7.23.8</a> Direct input/output functions
|
|
<a href='#7.23.9'>7.23.9</a> File positioning functions
|
|
<a href='#7.23.10'>7.23.10</a> Error-handling functions
|
|
<a href='#7.24'>7.24</a> General utilities <stdlib.h>
|
|
<a href='#7.24.1'>7.24.1</a> Numeric conversion functions
|
|
<a href='#7.24.2'>7.24.2</a> Pseudo-random sequence generation functions
|
|
<a href='#7.24.3'>7.24.3</a> Memory management functions
|
|
<a href='#7.24.4'>7.24.4</a> Communication with the environment
|
|
<a href='#7.24.5'>7.24.5</a> Searching and sorting utilities
|
|
<a href='#7.24.6'>7.24.6</a> Integer arithmetic functions
|
|
<a href='#7.24.7'>7.24.7</a> Multibyte/wide character conversion functions
|
|
<a href='#7.24.8'>7.24.8</a> Multibyte/wide string conversion functions
|
|
<a href='#7.24.9'>7.24.9</a> Alignment of memory
|
|
<a href='#7.25'>7.25</a> _Noreturn <stdnoreturn.h>
|
|
<a href='#7.26'>7.26</a> String handling <string.h>
|
|
<a href='#7.26.1'>7.26.1</a> String function conventions
|
|
<a href='#7.26.2'>7.26.2</a> Copying functions
|
|
<a href='#7.26.3'>7.26.3</a> Concatenation functions
|
|
<a href='#7.26.4'>7.26.4</a> Comparison functions
|
|
<a href='#7.26.5'>7.26.5</a> Search functions
|
|
<a href='#7.26.6'>7.26.6</a> Miscellaneous functions
|
|
<a href='#7.27'>7.27</a> Type-generic math <tgmath.h>
|
|
<a href='#7.28'>7.28</a> Threads <threads.h>
|
|
<a href='#7.28.1'>7.28.1</a> Introduction
|
|
<a href='#7.28.2'>7.28.2</a> Initialization functions
|
|
<a href='#7.28.3'>7.28.3</a> Condition variable functions
|
|
<a href='#7.28.4'>7.28.4</a> Mutex functions
|
|
<a href='#7.28.5'>7.28.5</a> Thread functions
|
|
<a href='#7.28.6'>7.28.6</a> Thread-specific storage functions
|
|
<a href='#7.29'>7.29</a> Date and time <time.h>
|
|
<a href='#7.29.1'>7.29.1</a> Components of time
|
|
<a href='#7.29.2'>7.29.2</a> Time manipulation functions
|
|
<a href='#7.29.3'>7.29.3</a> Time conversion functions
|
|
<a href='#7.30'>7.30</a> Unicode utilities <uchar.h>
|
|
<a href='#7.30.1'>7.30.1</a> Restartable multibyte/wide character conversion functions
|
|
<a href='#7.31'>7.31</a> Extended multibyte and wide character utilities <wchar.h>
|
|
<a href='#7.31.1'>7.31.1</a> Introduction
|
|
<a href='#7.31.2'>7.31.2</a> Formatted wide character input/output functions
|
|
<a href='#7.31.3'>7.31.3</a> Wide character input/output functions
|
|
<a href='#7.31.4'>7.31.4</a> General wide string utilities
|
|
<a href='#7.31.4.1'>7.31.4.1</a> Wide string numeric conversion functions
|
|
<a href='#7.31.4.2'>7.31.4.2</a> Wide string copying functions
|
|
<a href='#7.31.4.3'>7.31.4.3</a> Wide string concatenation functions
|
|
<a href='#7.31.4.4'>7.31.4.4</a> Wide string comparison functions
|
|
<a href='#7.31.4.5'>7.31.4.5</a> Wide string search functions
|
|
<a href='#7.31.4.6'>7.31.4.6</a> Introduction
|
|
<a href='#7.31.4.7'>7.31.4.7</a> Miscellaneous functions
|
|
<a href='#7.31.5'>7.31.5</a> Wide character time conversion functions
|
|
<a href='#7.31.6'>7.31.6</a> Extended multibyte/wide character conversion utilities
|
|
<a href='#7.31.6.1'>7.31.6.1</a> Single-byte/wide character conversion functions
|
|
<a href='#7.31.6.2'>7.31.6.2</a> Conversion state functions
|
|
<a href='#7.31.6.3'>7.31.6.3</a> Restartable multibyte/wide character conversion functions
|
|
<a href='#7.31.6.4'>7.31.6.4</a> Restartable multibyte/wide string conversion functions
|
|
<a href='#7.32'>7.32</a> Wide character classification and mapping utilities <wctype.h>
|
|
<a href='#7.32.1'>7.32.1</a> Introduction
|
|
<a href='#7.32.2'>7.32.2</a> Wide character classification utilities
|
|
<a href='#7.32.2.1'>7.32.2.1</a> Wide character classification functions
|
|
<a href='#7.32.2.2'>7.32.2.2</a> Extensible wide character classification functions
|
|
<a href='#7.32.3'>7.32.3</a> Wide character case mapping utilities
|
|
<a href='#7.32.3.1'>7.32.3.1</a> Wide character case mapping functions
|
|
<a href='#7.32.3.2'>7.32.3.2</a> Extensible wide character case mapping functions
|
|
<a href='#7.33'>7.33</a> Future library directions
|
|
<a href='#7.33.1'>7.33.1</a> Complex arithmetic <complex.h>
|
|
<a href='#7.33.2'>7.33.2</a> Character handling <ctype.h>
|
|
<a href='#7.33.3'>7.33.3</a> Errors <errno.h>
|
|
<a href='#7.33.4'>7.33.4</a> Floating-point environment <fenv.h>
|
|
<a href='#7.33.5'>7.33.5</a> Characteristics of floating types <float.h>
|
|
<a href='#7.33.6'>7.33.6</a> Format conversion of integer types <inttypes.h>
|
|
<a href='#7.33.7'>7.33.7</a> Localization <locale.h>
|
|
<a href='#7.33.8'>7.33.8</a> Mathematics <math.h>
|
|
<a href='#7.33.9'>7.33.9</a> Signal handling <signal.h>
|
|
<a href='#7.33.10'>7.33.10</a> Atomics <stdatomic.h>
|
|
<a href='#7.33.11'>7.33.11</a> Boolean type and values <stdbool.h>
|
|
<a href='#7.33.12'>7.33.12</a> Bit and byte utilities <stdbit.h>
|
|
<a href='#7.33.13'>7.33.13</a> Checked Arithmetic Functions <stdckdint.h>
|
|
<a href='#7.33.14'>7.33.14</a> Integer types <stdint.h>
|
|
<a href='#7.33.15'>7.33.15</a> Input/output <stdio.h>
|
|
<a href='#7.33.16'>7.33.16</a> General utilities <stdlib.h>
|
|
<a href='#7.33.17'>7.33.17</a> String handling <string.h>
|
|
<a href='#7.33.18'>7.33.18</a> Date and time <time.h>
|
|
<a href='#7.33.19'>7.33.19</a> Threads <threads.h>
|
|
<a href='#7.33.20'>7.33.20</a> Extended multibyte and wide character utilities <wchar.h>
|
|
<a href='#7.33.21'>7.33.21</a> Wide character classification and mapping utilities <wctype.h>
|
|
|
|
<a href='#A.'>Annex A</a> (informative) Language syntax summary
|
|
|
|
<a href='#B.'>Annex B</a> (informative) Library summary
|
|
|
|
<a href='#C.'>Annex C</a> (informative) Sequence points
|
|
|
|
<a href='#D.'>Annex D</a> (informative) Universal character names for identifiers
|
|
|
|
<a href='#E.'>Annex E</a> (informative) Implementation limits
|
|
|
|
<a href='#F.'>Annex F</a> (normative) IEC 60559 floating-point arithmetic
|
|
|
|
<a href='#G.'>Annex G</a> (normative) IEC 60559-compatible complex arithmetic
|
|
|
|
<a href='#H.'>Annex H</a> (normative) IEC 60559 interchange and extended types
|
|
|
|
<a href='#I.'>Annex I</a> (informative) Common warnings
|
|
|
|
<a href='#J.'>Annex J</a> (informative) Portability issues
|
|
<a href='#K.'>Annex K</a> (normative) Bounds-checking interfaces
|
|
|
|
<a href='#L.'>Annex L</a> (normative) Analyzability
|
|
|
|
<a href='#M.'>Annex M</a> (informative) Change History
|
|
|
|
</pre>
|
|
<a name='FOREWORD.'></a>
|
|
<hr>
|
|
<h3>FOREWORD. [Foreword]</h3>
|
|
<a name='FOREWORD.p1'></a>
|
|
<pre>1 ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
|
|
Commission) form the specialized system for worldwide standardization. National bodies that
|
|
are member of ISO or IEC participate in the development of International Standards through
|
|
technical committees established by the respective organization to deal with particular fields of
|
|
technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
|
|
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also
|
|
take part in the work. In the field of information technology, ISO and IEC have established a joint
|
|
technical committee, ISO/IEC JTC 1.
|
|
</pre>
|
|
<a name='FOREWORD.p2'></a>
|
|
<pre>2 The procedures used to develop this document and those intended for its further maintenance are
|
|
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for
|
|
the different types of document should be noted. This document was drafted in accordance with the
|
|
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
|
|
</pre>
|
|
<a name='FOREWORD.p3'></a>
|
|
<pre>3 Attention is drawn to the possibility that some of the elements of this document may be the subject
|
|
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
|
|
rights. Details of any patent rights identified during the development of the document will be in the
|
|
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
|
|
</pre>
|
|
<a name='FOREWORD.p4'></a>
|
|
<pre>4 Any trade name used in this document is information given for the convenience of users and does
|
|
not constitute an endorsement.
|
|
</pre>
|
|
<a name='FOREWORD.p5'></a>
|
|
<pre>5 For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
|
|
expressions related to conformity assessment, as well as information about ISO’s adherence to
|
|
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see the
|
|
following URL: www.iso.org/iso/foreword.html.
|
|
</pre>
|
|
<a name='FOREWORD.p6'></a>
|
|
<pre>6 This document was prepared by Technical Committee ISO/IEC JTC 1, Information technology, Sub-
|
|
committee SC 22, Programming languages, their environments and system software interfaces.
|
|
</pre>
|
|
<a name='FOREWORD.p7'></a>
|
|
<pre>7 This fifth edition cancels and replaces the fourth edition, ISO/IEC 9899:2018. A complete change
|
|
history can be found in Annex M.
|
|
</pre>
|
|
<a name='INTRO.'></a>
|
|
<hr>
|
|
<h3>INTRO. [Introduction]</h3>
|
|
<a name='INTRO.p1'></a>
|
|
<pre>1 With the introduction of new devices and extended character sets, new features could be added to
|
|
this document. Subclauses in the language and library clauses warn implementors and programmers
|
|
of usages which, though valid in themselves, could conflict with future additions.
|
|
</pre>
|
|
<a name='INTRO.p2'></a>
|
|
<pre>2 Certain features are obsolescent, which means that they could be considered for withdrawal in future
|
|
revisions of this document. They are retained because of their widespread use, but their use in
|
|
new implementations (for implementation features) or new programs (for language [<a href='#6.11'>6.11</a>] or library
|
|
features [<a href='#7.33'>7.33</a>]) is discouraged.
|
|
</pre>
|
|
<a name='INTRO.p3'></a>
|
|
<pre>3 This document is divided into four major subdivisions:
|
|
|
|
— preliminary elements (Clauses 1–4);
|
|
— the characteristics of environments that translate and execute C programs (Clause 5);
|
|
— the language syntax, constraints, and semantics (Clause 6);
|
|
|
|
— the library facilities (Clause 7).
|
|
|
|
</pre>
|
|
<a name='INTRO.p4'></a>
|
|
<pre>4 Examples are provided to illustrate possible forms of the constructions described. Footnotes are
|
|
provided to emphasize consequences of the rules described in that subclause or elsewhere in this
|
|
document. References are used to refer to other related subclauses. Recommendations are provided
|
|
to give advice or guidance to implementors. Annexes define optional features, provide additional
|
|
information and summarize the information contained in this document. A bibliography lists
|
|
documents that were referred to during the preparation of this document.
|
|
</pre>
|
|
<a name='INTRO.p5'></a>
|
|
<pre>5 The language clause (Clause 6) is derived from "The C Reference Manual".
|
|
</pre>
|
|
<a name='INTRO.p6'></a>
|
|
<pre>6 The library clause (Clause 7) is based on the 1984 /usr/group Standard.
|
|
</pre>
|
|
<a name='INTRO.p7'></a>
|
|
<pre>7 The Working Group responsible for this document (WG 14) maintains a site on the World Wide Web
|
|
at http://www.open-std.org/JTC1/SC22/WG14/ containing ancillary information that may be of
|
|
interest to some readers such as a Rationale for many of the decisions made during its preparation
|
|
and a log of Defect Reports and Responses.
|
|
|
|
|
|
</pre>
|
|
<a name='1.'></a>
|
|
<hr>
|
|
<h3>1. [Scope]</h3>
|
|
<a name='1.p1'></a>
|
|
<pre>1 This document specifies the form and establishes the interpretation of programs written in the C
|
|
programming language.<a href='#FOOTNOTE.1'><sup>[1]</sup></a> It specifies
|
|
|
|
— the representation of C programs;
|
|
— the syntax and constraints of the C language;
|
|
— the semantic rules for interpreting C programs;
|
|
|
|
— the representation of input data to be processed by C programs;
|
|
— the representation of output data produced by C programs;
|
|
— the restrictions and limits imposed by a conforming implementation of C.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.1'>
|
|
<pre><i><b>Footnote 1)</b> This document is designed to promote the portability of C programs among a variety of data-processing systems. It is
|
|
intended for use by implementors and programmers. Annex J gives an overview of portability issues that a C program might
|
|
encounter.
|
|
</i></pre>
|
|
</a>
|
|
<a name='1.p2'></a>
|
|
<pre>2 This document does not specify
|
|
|
|
— the mechanism by which C programs are transformed for use by a data-processing system;
|
|
|
|
— the mechanism by which C programs are invoked for use by a data-processing system;
|
|
— the mechanism by which input data are transformed for use by a C program;
|
|
— the mechanism by which output data are transformed after being produced by a C program;
|
|
— the size or complexity of a program and its data that will exceed the capacity of any specific
|
|
data-processing system or the capacity of a particular processor;
|
|
— all minimal requirements of a data-processing system that is capable of supporting a conform-
|
|
ing implementation.
|
|
</pre>
|
|
<a name='2.'></a>
|
|
<hr>
|
|
<h3>2. [Normative references]</h3>
|
|
<a name='2.p1'></a>
|
|
<pre>1 The following documents are referred to in the text in such a way that some or all of their content
|
|
constitutes requirements of this document. For dated references, only the edition cited applies.
|
|
For undated references, the latest edition of the referenced document (including any amendments)
|
|
applies.
|
|
</pre>
|
|
<a name='2.p2'></a>
|
|
<pre>2 ISO/IEC 2382:2015, Information technology — Vocabulary. Available from the ISO online browsing
|
|
platform at http://www.iso.org/obp.
|
|
</pre>
|
|
<a name='2.p3'></a>
|
|
<pre>3 ISO 4217, Codes for the representation of currencies and funds.
|
|
</pre>
|
|
<a name='2.p4'></a>
|
|
<pre>4 ISO 8601, Data elements and interchange formats — Information interchange — Representation of dates and
|
|
times.
|
|
</pre>
|
|
<a name='2.p5'></a>
|
|
<pre>5 ISO/IEC 10646, Information technology —Universal Coded Character Set (UCS). Available from the
|
|
ISO/IEC Information Technology Task Force (ITTF) web site at http://isotc.iso.org/livelink/
|
|
livelink/fetch/2000/2489/Ittf_Home/PubliclyAvailableStandards.htm.
|
|
</pre>
|
|
<a name='2.p6'></a>
|
|
<pre>6 ISO/IEC 60559:2020, Floating-point arithmetic.
|
|
</pre>
|
|
<a name='2.p7'></a>
|
|
<pre>7 ISO 80000–2, Quantities and units — Part 2: Mathematical signs and symbols to be used in the natural
|
|
sciences and technology.
|
|
</pre>
|
|
<a name='2.p8'></a>
|
|
<pre>8 The Unicode Consortium. Unicode Standard Annex, UAX #44, Unicode Character Database [online].
|
|
Edited by Ken Whistler and Laurentiu Iancu. Available at http://www.unicode.org/reports/
|
|
tr44.
|
|
</pre>
|
|
<a name='2.p9'></a>
|
|
<pre>9 The Unicode Consortium. The Unicode Standard, Derived Core Properties. Available at https:
|
|
//www.unicode.org/Public/UCD/latest/ucd/DerivedCoreProperties.txt.
|
|
</pre>
|
|
<a name='3.'></a>
|
|
<hr>
|
|
<h3>3. [Terms, definitions, and symbols]</h3>
|
|
<a name='3.p1'></a>
|
|
<pre>1 For the purposes of this document, the terms and definitions given in ISO/IEC 2382, ISO 80000–2,
|
|
and the following apply.
|
|
</pre>
|
|
<a name='3.p2'></a>
|
|
<pre>2 ISO and IEC maintain terminological databases for use in standardization at the following addresses:
|
|
|
|
— ISO Online browsing platform: available at https://www.iso.org/obp
|
|
|
|
— IEC Electropedia: available at http://www.electropedia.org/
|
|
|
|
</pre>
|
|
<a name='3.p3'></a>
|
|
<pre>3 Additional terms are defined where they appear in italic type or on the left side of a syntax rule.
|
|
Terms explicitly defined in this document are not to be presumed to refer implicitly to similar terms
|
|
defined elsewhere.
|
|
|
|
</pre>
|
|
<a name='3.1'></a>
|
|
<hr>
|
|
<h3>3.1 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.1p1'></a>
|
|
<pre>1 access (verb)
|
|
⟨execution-time action⟩ to read or modify the value of an object
|
|
</pre>
|
|
<a name='3.1p2'></a>
|
|
<pre>2 Note 1 to entry: Where only one of these two actions is meant, "read" or "modify" is used.
|
|
</pre>
|
|
<a name='3.1p3'></a>
|
|
<pre>3 Note 2 to entry: "Modify" includes the case where the new value being stored is the same as the previous value.
|
|
</pre>
|
|
<a name='3.1p4'></a>
|
|
<pre>4 Note 3 to entry: Expressions that are not evaluated do not access objects.
|
|
|
|
</pre>
|
|
<a name='3.2'></a>
|
|
<hr>
|
|
<h3>3.2 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.2p1'></a>
|
|
<pre>1 alignment
|
|
requirement that objects of a particular type be located on storage boundaries with addresses that
|
|
are particular multiples of a byte address
|
|
|
|
</pre>
|
|
<a name='3.3'></a>
|
|
<hr>
|
|
<h3>3.3 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.3p1'></a>
|
|
<pre>1 argument
|
|
actual argument (DEPRECATED: actual parameter)
|
|
expression in the comma-separated list bounded by the parentheses in a function call expression, or
|
|
a sequence of preprocessing tokens in the comma-separated list bounded by the parentheses in a
|
|
function-like macro invocation
|
|
|
|
</pre>
|
|
<a name='3.4'></a>
|
|
<hr>
|
|
<h3>3.4 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.4p1'></a>
|
|
<pre>1 behavior
|
|
external appearance or action
|
|
|
|
</pre>
|
|
<a name='3.4.1'></a>
|
|
<hr>
|
|
<h3>3.4.1 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.4.1p1'></a>
|
|
<pre>1 implementation-defined behavior
|
|
unspecified behavior where each implementation documents how the choice is made
|
|
</pre>
|
|
<a name='3.4.1p2'></a>
|
|
<pre>2 Note 1 to entry: <a href='#J.3'>J.3</a> gives an overview over properties of C programs that lead to implementation-defined behavior.
|
|
</pre>
|
|
<a name='3.4.1p3'></a>
|
|
<pre>3 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit when a signed integer
|
|
is shifted right.
|
|
|
|
</pre>
|
|
<a name='3.4.2'></a>
|
|
<hr>
|
|
<h3>3.4.2 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.4.2p1'></a>
|
|
<pre>1 locale-specific behavior
|
|
behavior that depends on local conventions of nationality, culture, and language that each implemen-
|
|
tation documents
|
|
</pre>
|
|
<a name='3.4.2p2'></a>
|
|
<pre>2 Note 1 to entry: <a href='#J.4'>J.4</a> gives an overview over properties of C programs that lead to locale-specific behavior.
|
|
</pre>
|
|
<a name='3.4.2p3'></a>
|
|
<pre>3 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for characters other than
|
|
the 26 lowercase Latin letters.
|
|
|
|
|
|
</pre>
|
|
<a name='3.4.3'></a>
|
|
<hr>
|
|
<h3>3.4.3 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.4.3p1'></a>
|
|
<pre>1 undefined behavior
|
|
behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which
|
|
this document imposes no requirements
|
|
</pre>
|
|
<a name='3.4.3p2'></a>
|
|
<pre>2 Note 1 to entry: Possible undefined behavior ranges from ignoring the situation completely with unpredictable results,
|
|
to behaving during translation or program execution in a documented manner characteristic of the environment (with or
|
|
without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic
|
|
message).
|
|
</pre>
|
|
<a name='3.4.3p3'></a>
|
|
<pre>3 Note 2 to entry: <a href='#J.2'>J.2</a> gives an overview over properties of C programs that lead to undefined behavior.
|
|
</pre>
|
|
<a name='3.4.3p4'></a>
|
|
<pre>4 EXAMPLE An example of undefined behavior is the behavior on dereferencing a null pointer.
|
|
|
|
|
|
</pre>
|
|
<a name='3.4.4'></a>
|
|
<hr>
|
|
<h3>3.4.4 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.4.4p1'></a>
|
|
<pre>1 unspecified behavior
|
|
behavior, that results from the use of an unspecified value, or other behavior upon which this
|
|
document provides two or more possibilities and imposes no further requirements on which is
|
|
chosen in any instance
|
|
</pre>
|
|
<a name='3.4.4p2'></a>
|
|
<pre>2 Note 1 to entry: <a href='#J.1'>J.1</a> gives an overview over properties of C programs that lead to unspecified behavior.
|
|
</pre>
|
|
<a name='3.4.4p3'></a>
|
|
<pre>3 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are evaluated.
|
|
|
|
|
|
</pre>
|
|
<a name='3.5'></a>
|
|
<hr>
|
|
<h3>3.5 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.5p1'></a>
|
|
<pre>1 bit
|
|
unit of data storage in the execution environment large enough to hold an object that can have one
|
|
of two values
|
|
</pre>
|
|
<a name='3.5p2'></a>
|
|
<pre>2 Note 1 to entry: It need not be possible to express the address of each individual bit of an object.
|
|
|
|
|
|
</pre>
|
|
<a name='3.6'></a>
|
|
<hr>
|
|
<h3>3.6 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.6p1'></a>
|
|
<pre>1 byte
|
|
addressable unit of data storage large enough to hold any member of the basic character set of the
|
|
execution environment
|
|
</pre>
|
|
<a name='3.6p2'></a>
|
|
<pre>2 Note 1 to entry: It is possible to express the address of each individual byte of an object uniquely.
|
|
</pre>
|
|
<a name='3.6p3'></a>
|
|
<pre>3 Note 2 to entry: A byte is composed of a contiguous sequence of bits, the number of which is implementation-defined. The
|
|
least significant bit is called the low-order bit; the most significant bit is called the high-order bit.
|
|
|
|
|
|
</pre>
|
|
<a name='3.7'></a>
|
|
<hr>
|
|
<h3>3.7 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.7p1'></a>
|
|
<pre>1 character
|
|
⟨abstract⟩ member of a set of elements used for the organization, control, or representation of data
|
|
|
|
</pre>
|
|
<a name='3.7.1'></a>
|
|
<hr>
|
|
<h3>3.7.1 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.7.1p1'></a>
|
|
<pre>1 character
|
|
single-byte character
|
|
⟨C⟩ bit representation that fits in a byte
|
|
|
|
</pre>
|
|
<a name='3.7.2'></a>
|
|
<hr>
|
|
<h3>3.7.2 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.7.2p1'></a>
|
|
<pre>1 multibyte character
|
|
sequence of one or more bytes representing a member of the extended character set of either the
|
|
source or the execution environment
|
|
</pre>
|
|
<a name='3.7.2p2'></a>
|
|
<pre>2 Note 1 to entry: The extended character set is a superset of the basic character set.
|
|
</pre>
|
|
<a name='3.7.3'></a>
|
|
<hr>
|
|
<h3>3.7.3 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.7.3p1'></a>
|
|
<pre>1 wide character
|
|
value representable by an object of type wchar_t, capable of representing any character in the
|
|
current locale
|
|
|
|
</pre>
|
|
<a name='3.8'></a>
|
|
<hr>
|
|
<h3>3.8 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.8p1'></a>
|
|
<pre>1 constraint
|
|
restriction, either syntactic or semantic, by which the exposition of language elements is to be
|
|
interpreted
|
|
|
|
</pre>
|
|
<a name='3.9'></a>
|
|
<hr>
|
|
<h3>3.9 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.9p1'></a>
|
|
<pre>1 correctly rounded result
|
|
representation in the result format that is nearest in value, subject to the current rounding mode, to
|
|
what the result would be given unlimited range and precision
|
|
</pre>
|
|
<a name='3.9p2'></a>
|
|
<pre>2 Note 1 to entry: In this document, when the words "correctly rounded" are not immediately followed by "result", this is the
|
|
intended usage.
|
|
</pre>
|
|
<a name='3.9p3'></a>
|
|
<pre>3 Note 2 to entry: IEC 60559 or implementation-defined rules apply for extreme magnitude results if the result format contains
|
|
infinity.
|
|
|
|
</pre>
|
|
<a name='3.10'></a>
|
|
<hr>
|
|
<h3>3.10 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.10p1'></a>
|
|
<pre>1 diagnostic message
|
|
message belonging to an implementation-defined subset of the implementation’s message output
|
|
|
|
</pre>
|
|
<a name='3.11'></a>
|
|
<hr>
|
|
<h3>3.11 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.11p1'></a>
|
|
<pre>1 forward reference
|
|
reference to a later subclause of this document that contains additional information relevant to this
|
|
subclause
|
|
|
|
</pre>
|
|
<a name='3.12'></a>
|
|
<hr>
|
|
<h3>3.12 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.12p1'></a>
|
|
<pre>1 implementation
|
|
particular set of software, running in a particular translation environment under particular con-
|
|
trol options, that performs translation of programs for, and supports execution of functions in, a
|
|
particular execution environment
|
|
|
|
</pre>
|
|
<a name='3.13'></a>
|
|
<hr>
|
|
<h3>3.13 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.13p1'></a>
|
|
<pre>1 implementation limit
|
|
restriction imposed upon programs by the implementation
|
|
|
|
</pre>
|
|
<a name='3.14'></a>
|
|
<hr>
|
|
<h3>3.14 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.14p1'></a>
|
|
<pre>1 memory location
|
|
either an object of scalar type, or a maximal sequence of adjacent bit-fields all having nonzero width
|
|
</pre>
|
|
<a name='3.14p2'></a>
|
|
<pre>2 Note 1 to entry: Two threads of execution can update and access separate memory locations without interfering with each
|
|
other.
|
|
</pre>
|
|
<a name='3.14p3'></a>
|
|
<pre>3 Note 2 to entry: A bit-field and an adjacent non-bit-field member are in separate memory locations. The same applies to
|
|
two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the two are separated by a
|
|
zero-length bit-field declaration, or if they are separated by a non-bit-field member declaration. It is not safe to concurrently
|
|
update two non-atomic bit-fields in the same structure if all members declared between them are also (nonzero-length)
|
|
bit-fields, no matter what the sizes of those intervening bit-fields happen to be.
|
|
</pre>
|
|
<a name='3.14p4'></a>
|
|
<pre>4 EXAMPLE A structure declared as
|
|
|
|
struct {
|
|
char a;
|
|
int b:5, c:11,:0, d:8;
|
|
struct { int ee:8; } e;
|
|
}
|
|
|
|
|
|
contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate memory locations,
|
|
and can be modified concurrently without interfering with each other. The bit-fields b and c together constitute the fourth
|
|
memory location. The bit-fields b and c cannot be concurrently modified, but b and a, for example, can be.
|
|
|
|
|
|
</pre>
|
|
<a name='3.15'></a>
|
|
<hr>
|
|
<h3>3.15 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.15p1'></a>
|
|
<pre>1 object
|
|
region of data storage in the execution environment, the contents of which can represent values
|
|
</pre>
|
|
<a name='3.15p2'></a>
|
|
<pre>2 Note 1 to entry: When referenced, an object can be interpreted as having a particular type; see <a href='#6.3.2.1'>6.3.2.1</a>.
|
|
|
|
|
|
</pre>
|
|
<a name='3.16'></a>
|
|
<hr>
|
|
<h3>3.16 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.16p1'></a>
|
|
<pre>1 parameter
|
|
formal parameter
|
|
DEPRECATED: formal argument
|
|
object declared as part of a function declaration or definition that acquires a value on entry to the
|
|
function, or an identifier from the comma-separated list bounded by the parentheses immediately
|
|
following the macro name in a function-like macro definition
|
|
|
|
</pre>
|
|
<a name='3.17'></a>
|
|
<hr>
|
|
<h3>3.17 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.17p1'></a>
|
|
<pre>1 recommended practice
|
|
specification that is strongly recommended as being in keeping with the intent of the standard, but
|
|
that might be impractical for some implementations
|
|
|
|
</pre>
|
|
<a name='3.18'></a>
|
|
<hr>
|
|
<h3>3.18 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.18p1'></a>
|
|
<pre>1 runtime-constraint
|
|
requirement on a program when calling a library function
|
|
</pre>
|
|
<a name='3.18p2'></a>
|
|
<pre>2 Note 1 to entry: Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by <a href='#3.8'>3.8</a>, and need not be
|
|
diagnosed at translation time.
|
|
</pre>
|
|
<a name='3.18p3'></a>
|
|
<pre>3 Note 2 to entry: Implementations that support the extensions in Annex K are required to verify that the runtime-constraints
|
|
for a library function are not violated by the program; see <a href='#K.3.1.4'>K.3.1.4</a>.
|
|
</pre>
|
|
<a name='3.18p4'></a>
|
|
<pre>4 Note 3 to entry: Implementations that support Annex L are permitted to invoke a runtime-constraint handler when they
|
|
perform a trap.
|
|
|
|
|
|
</pre>
|
|
<a name='3.19'></a>
|
|
<hr>
|
|
<h3>3.19 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19p1'></a>
|
|
<pre>1 value
|
|
precise meaning of the contents of an object when interpreted as having a specific type
|
|
|
|
</pre>
|
|
<a name='3.19.1'></a>
|
|
<hr>
|
|
<h3>3.19.1 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19.1p1'></a>
|
|
<pre>1 implementation-defined value
|
|
unspecified value where each implementation documents how the choice is made
|
|
|
|
</pre>
|
|
<a name='3.19.2'></a>
|
|
<hr>
|
|
<h3>3.19.2 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19.2p1'></a>
|
|
<pre>1 indeterminate representation
|
|
object representation that either represents an unspecified value or is a non-value representation
|
|
|
|
</pre>
|
|
<a name='3.19.3'></a>
|
|
<hr>
|
|
<h3>3.19.3 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19.3p1'></a>
|
|
<pre>1 unspecified value
|
|
valid value of the relevant type where this document imposes no requirements on which value is
|
|
chosen in any instance
|
|
</pre>
|
|
<a name='3.19.4'></a>
|
|
<hr>
|
|
<h3>3.19.4 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19.4p1'></a>
|
|
<pre>1 non-value representation
|
|
an object representation that does not represent a value of the object type
|
|
|
|
</pre>
|
|
<a name='3.19.5'></a>
|
|
<hr>
|
|
<h3>3.19.5 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.19.5p1'></a>
|
|
<pre>1 perform a trap
|
|
interrupt execution of the program such that no further operations are performed<a href='#FOOTNOTE.2'><sup>[2]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.2'>
|
|
<pre><i><b>Footnote 2)</b> Note that fetching a non-value representation might perform a trap but is not required to (see <a href='#6.2.6.1'>6.2.6.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='3.19.5p2'></a>
|
|
<pre>2 Note 1 to entry: Implementations that support Annex L are permitted to invoke a runtime-constraint handler when they
|
|
perform a trap.
|
|
|
|
</pre>
|
|
<a name='3.20'></a>
|
|
<hr>
|
|
<h3>3.20 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.20p1'></a>
|
|
<pre>1 ⌈x⌉
|
|
ceiling of x
|
|
the least integer greater than or equal to x
|
|
</pre>
|
|
<a name='3.20p2'></a>
|
|
<pre>2 EXAMPLE ⌈2.4⌉ is 3, ⌈−2.4⌉ is −2.
|
|
|
|
</pre>
|
|
<a name='3.21'></a>
|
|
<hr>
|
|
<h3>3.21 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.21p1'></a>
|
|
<pre>1 ⌊x⌋
|
|
floor of x
|
|
the greatest integer less than or equal to x
|
|
</pre>
|
|
<a name='3.21p2'></a>
|
|
<pre>2 EXAMPLE ⌊2.4⌋ is 2, ⌊−2.4⌋ is −3.
|
|
|
|
</pre>
|
|
<a name='3.22'></a>
|
|
<hr>
|
|
<h3>3.22 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.22p1'></a>
|
|
<pre>1 wraparound
|
|
the process by which a value is reduced modulo 2N , where N is the width of the resulting type
|
|
</pre>
|
|
<a name='4.'></a>
|
|
<hr>
|
|
<h3>4. [Conformance]</h3>
|
|
<a name='4.p1'></a>
|
|
<pre>1 In this document, "shall" is to be interpreted as a requirement on an implementation or on a program;
|
|
conversely, "shall not" is to be interpreted as a prohibition.
|
|
</pre>
|
|
<a name='4.p2'></a>
|
|
<pre>2 If a "shall" or "shall not" requirement that appears outside of a constraint or runtime-constraint is
|
|
violated, the behavior is undefined. Undefined behavior is otherwise indicated in this document by
|
|
the words "undefined behavior" or by the omission of any explicit definition of behavior. There is
|
|
no difference in emphasis among these three; they all describe "behavior that is undefined".
|
|
</pre>
|
|
<a name='4.p3'></a>
|
|
<pre>3 A program that is correct in all other aspects, operating on correct data, containing unspecified
|
|
behavior shall be a correct program and act in accordance with <a href='#5.1.2.3'>5.1.2.3</a>.
|
|
</pre>
|
|
<a name='4.p4'></a>
|
|
<pre>4 The implementation shall not successfully translate a preprocessing translation unit containing a
|
|
#error preprocessing directive unless it is part of a group skipped by conditional inclusion.
|
|
</pre>
|
|
<a name='4.p5'></a>
|
|
<pre>5 A strictly conforming program shall use only those features of the language and library specified
|
|
in this document.<a href='#FOOTNOTE.3'><sup>[3]</sup></a> It shall not produce output dependent on any unspecified, undefined, or
|
|
implementation-defined behavior, and shall not exceed any minimum implementation limit.
|
|
</pre>
|
|
<a name='FOOTNOTE.3'>
|
|
<pre><i><b>Footnote 3)</b> A strictly conforming program can use conditional features (see <a href='#6.10.9.3'>6.10.9.3</a>) provided the use is guarded by an appropriate
|
|
conditional inclusion preprocessing directive using the related macro. For example:
|
|
#ifdef __STDC_IEC_60559_BFP__ /* FE_UPWARD defined */
|
|
/* ... */
|
|
fesetround(FE_UPWARD);
|
|
/* ... */
|
|
#endif
|
|
</i></pre>
|
|
</a>
|
|
<a name='4.p6'></a>
|
|
<pre>6 The two forms of conforming implementation are hosted and freestanding. A conforming hosted
|
|
implementation shall accept any strictly conforming program. A conforming freestanding implementation
|
|
shall accept any strictly conforming program in which the use of the features specified in the library
|
|
clause (Clause 7) is confined to the contents of the standard headers <float.h>, <iso646.h>,
|
|
<limits.h>, <stdalign.h>, <stdarg.h>, <stdbit.h>, <stdbool.h>, <stddef.h>, <stdint.h>,
|
|
and <stdnoreturn.h>. Additionally, a conforming freestanding implementation shall accept any
|
|
strictly conforming program where:
|
|
|
|
— the features specified in the header <string.h> are used, except the following functions:
|
|
strdup, strndup, strcoll, strxfrm, strerror; and/or,
|
|
|
|
the selected function memalignment from <stdlib.h> is used.
|
|
|
|
A conforming implementation may have extensions (including additional library functions), pro-
|
|
vided they do not alter the behavior of any strictly conforming program<a href='#FOOTNOTE.4'><sup>[4]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.4'>
|
|
<pre><i><b>Footnote 4)</b> This implies that a conforming implementation reserves no identifiers other than those explicitly reserved in this
|
|
document.
|
|
</i></pre>
|
|
</a>
|
|
<a name='4.p7'></a>
|
|
<pre>7 The strictly conforming programs that shall be accepted by a conforming freestanding implementa-
|
|
tion that defines __STDC_IEC_60559_BFP__ or __STDC_IEC_60559_DFP__ may also use features in
|
|
the contents of the standard headers <fenv.h>, <math.h>, and the strto * floating-point numeric
|
|
conversion functions (<a href='#7.24.1'>7.24.1</a>) of the standard header <stdlib.h>, provided the program does not
|
|
set the state of the FENV_ACCESS pragma to "ON".
|
|
All identifiers that are reserved when <stdlib.h> is included in a hosted implementation are
|
|
reserved when it is included in a freestanding implementation.
|
|
</pre>
|
|
<a name='4.p8'></a>
|
|
<pre>8 A conforming program is one that is acceptable to a conforming implementation. <a href='#FOOTNOTE.5'><sup>[5]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.5'>
|
|
<pre><i><b>Footnote 5)</b> Strictly conforming programs are intended to be maximally portable among conforming implementations. Conforming
|
|
programs can depend upon nonportable features of a conforming implementation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='4.p9'></a>
|
|
<pre>9 An implementation shall be accompanied by a document that defines all implementation-defined
|
|
and locale-specific characteristics and all extensions.
|
|
Forward references: conditional inclusion (<a href='#6.10.1'>6.10.1</a>), error directive (<a href='#6.10.6'>6.10.6</a>), characteristics of floating
|
|
types <float.h> (<a href='#7.7'>7.7</a>), alternative spellings <iso646.h> (<a href='#7.9'>7.9</a>), sizes of integer types <limits.h>
|
|
(<a href='#7.10'>7.10</a>), alignment <stdalign.h> (<a href='#7.15'>7.15</a>), variable arguments <stdarg.h> (<a href='#7.16'>7.16</a>), boolean type and
|
|
values <stdbool.h> (<a href='#7.19'>7.19</a>), common definitions <stddef.h> (<a href='#7.21'>7.21</a>), integer types <stdint.h> (<a href='#7.22'>7.22</a>),
|
|
<stdnoreturn.h> (<a href='#7.25'>7.25</a>).
|
|
</pre>
|
|
<a name='5.'></a>
|
|
<hr>
|
|
<h3>5. [Environment]</h3>
|
|
<a name='5.p1'></a>
|
|
<pre>1 An implementation translates C source files and executes C programs in two data-processing-system
|
|
environments, which will be called the translation environment and the execution environment in this
|
|
document. Their characteristics define and constrain the results of executing conforming C programs
|
|
constructed according to the syntactic and semantic rules for conforming implementations.
|
|
Forward references: In this clause, only a few of many possible forward references have been
|
|
noted.
|
|
|
|
</pre>
|
|
<a name='5.1'></a>
|
|
<hr>
|
|
<h3>5.1 [Conceptual models]</h3>
|
|
<a name='5.1.1'></a>
|
|
<hr>
|
|
<h3>5.1.1 [Translation environment]</h3>
|
|
<a name='5.1.1.1'></a>
|
|
<hr>
|
|
<h3>5.1.1.1 [Program structure]</h3>
|
|
<a name='5.1.1.1p1'></a>
|
|
<pre>1 A C program need not all be translated at the same time. The text of the program is kept in units
|
|
called source files, (or preprocessing files) in this document. A source file together with all the headers
|
|
and source files included via the preprocessing directive #include is known as a preprocessing
|
|
translation unit. After preprocessing, a preprocessing translation unit is called a translation unit.
|
|
Previously translated translation units may be preserved individually or in libraries. The separate
|
|
translation units of a program communicate by (for example) calls to functions whose identifiers have
|
|
external linkage, manipulation of objects whose identifiers have external linkage, or manipulation
|
|
of data files. Translation units may be separately translated and then later linked to produce an
|
|
executable program.
|
|
Forward references: linkages of identifiers (<a href='#6.2.2'>6.2.2</a>), external definitions (<a href='#6.9'>6.9</a>), preprocessing direc-
|
|
tives (<a href='#6.10'>6.10</a>).
|
|
|
|
</pre>
|
|
<a name='5.1.1.2'></a>
|
|
<hr>
|
|
<h3>5.1.1.2 [Translation phases]</h3>
|
|
<a name='5.1.1.2p1'></a>
|
|
<pre>1 The precedence among the syntax rules of translation is specified by the following phases.<a href='#FOOTNOTE.6'><sup>[6]</sup></a>
|
|
|
|
1. Physical source file multibyte characters are mapped, in an implementation-defined manner, to
|
|
the source character set (introducing new-line characters for end-of-line indicators) if necessary.
|
|
|
|
2. Each instance of a backslash character (\ ) immediately followed by a new-line character is
|
|
deleted, splicing physical source lines to form logical source lines. Only the last backslash on
|
|
any physical source line shall be eligible for being part of such a splice. A source file that is
|
|
not empty shall end in a new-line character, which shall not be immediately preceded by a
|
|
backslash character before any such splicing takes place.
|
|
|
|
3. The source file is decomposed into preprocessing tokens<a href='#FOOTNOTE.7'><sup>[7]</sup></a> and sequences of white-space
|
|
characters (including comments). A source file shall not end in a partial preprocessing token or
|
|
in a partial comment. Each comment is replaced by one space character. New-line characters
|
|
are retained. Whether each nonempty sequence of white-space characters other than new-line
|
|
is retained or replaced by one space character is implementation-defined.
|
|
|
|
4. Preprocessing directives are executed, macro invocations are expanded, and _Pragma unary
|
|
operator expressions are executed. If a character sequence that matches the syntax of a univer-
|
|
sal character name is produced by token concatenation (<a href='#6.10.4.3'>6.10.4.3</a>), the behavior is undefined. A
|
|
#include preprocessing directive causes the named header or source file to be processed from
|
|
phase 1 through phase 4, recursively. All preprocessing directives are then deleted.
|
|
5. Each source character set member and escape sequence in character constants and string
|
|
literals is converted to the corresponding member of the execution character set. Each instance
|
|
of a source character or escape sequence for which there is no corresponding member is
|
|
converted in an implementation-defined manner to some member of the execution character
|
|
set other than the null (wide) character.<a href='#FOOTNOTE.8'><sup>[8]</sup></a>
|
|
|
|
6. Adjacent string literal tokens are concatenated.
|
|
|
|
7. White-space characters separating tokens are no longer significant. Each preprocessing token
|
|
is converted into a token. The resulting tokens are syntactically and semantically analyzed
|
|
and translated as a translation unit.
|
|
|
|
8. All external object and function references are resolved. Library components are linked to
|
|
satisfy external references to functions and objects not defined in the current translation. All
|
|
such translator output is collected into a program image which contains information needed
|
|
for execution in its execution environment.
|
|
|
|
Forward references: universal character names (<a href='#6.4.3'>6.4.3</a>), lexical elements (<a href='#6.4'>6.4</a>), preprocessing direc-
|
|
tives (<a href='#6.10'>6.10</a>), external definitions (<a href='#6.9'>6.9</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.6'>
|
|
<pre><i><b>Footnote 6)</b> This requires implementations to behave as if these separate phases occur, even though many are typically folded
|
|
together in practice. Source files, translation units, and translated translation units need not necessarily be stored as files,
|
|
nor need there be any one-to-one correspondence between these entities and any external representation. The description is
|
|
conceptual only, and does not specify any particular implementation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.7'>
|
|
<pre><i><b>Footnote 7)</b> As described in <a href='#6.4'>6.4</a>, the process of dividing a source file’s characters into preprocessing tokens is context-dependent. For
|
|
example, see the handling of < within a #include preprocessing directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.8'>
|
|
<pre><i><b>Footnote 8)</b> An implementation may convert each instance of the same non-corresponding source character to a different member of
|
|
the execution character set.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.1.3'></a>
|
|
<hr>
|
|
<h3>5.1.1.3 [Diagnostics]</h3>
|
|
<a name='5.1.1.3p1'></a>
|
|
<pre>1 A conforming implementation shall produce at least one diagnostic message (identified in an
|
|
implementation-defined manner) if a preprocessing translation unit or translation unit contains a
|
|
violation of any syntax rule or constraint, even if the behavior is also explicitly specified as undefined
|
|
or implementation-defined. Diagnostic messages need not be produced in other circumstances.<a href='#FOOTNOTE.9'><sup>[9]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.9'>
|
|
<pre><i><b>Footnote 9)</b> An implementation is encouraged to identify the nature of, and where possible localize, each violation. Of course, an
|
|
implementation is free to produce any number of diagnostic messages, often referred to as warnings, as long as a valid
|
|
program is still correctly translated. It can also successfully translate an invalid program. Annex I lists a few of the more
|
|
common warnings.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.1.3p2'></a>
|
|
<pre>2 EXAMPLE An implementation is required to issue a diagnostic for the translation unit:
|
|
|
|
char i;
|
|
int i;
|
|
|
|
|
|
because in those cases where wording in this document describes the behavior for a construct as being both a constraint error
|
|
and resulting in undefined behavior, the constraint error is still required to be diagnosed.
|
|
|
|
</pre>
|
|
<a name='5.1.2'></a>
|
|
<hr>
|
|
<h3>5.1.2 [Execution environments]</h3>
|
|
<a name='5.1.2p1'></a>
|
|
<pre>1 Two execution environments are defined: freestanding and hosted. In both cases, program startup
|
|
occurs when a designated C function is called by the execution environment. All objects with static
|
|
storage duration shall be initialized (set to their initial values) before program startup. The manner
|
|
and timing of such initialization are otherwise unspecified. Program termination returns control to
|
|
the execution environment.
|
|
Forward references: storage durations of objects (<a href='#6.2.4'>6.2.4</a>), initialization (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
</pre>
|
|
<a name='5.1.2.1'></a>
|
|
<hr>
|
|
<h3>5.1.2.1 [Freestanding environment]</h3>
|
|
<a name='5.1.2.1p1'></a>
|
|
<pre>1 In a freestanding environment (in which C program execution may take place without any ben-
|
|
efit of an operating system), the name and type of the function called at program startup are
|
|
implementation-defined. Any library facilities available to a freestanding program, other than the
|
|
minimal set required by Clause 4, are implementation-defined.
|
|
</pre>
|
|
<a name='5.1.2.1p2'></a>
|
|
<pre>2 The effect of program termination in a freestanding environment is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='5.1.2.2'></a>
|
|
<hr>
|
|
<h3>5.1.2.2 [Hosted environment]</h3>
|
|
<a name='5.1.2.2p1'></a>
|
|
<pre>1 A hosted environment need not be provided, but shall conform to the following specifications if
|
|
present.
|
|
</pre>
|
|
<a name='5.1.2.2.1'></a>
|
|
<hr>
|
|
<h3>5.1.2.2.1 [Program startup]</h3>
|
|
<a name='5.1.2.2.1p1'></a>
|
|
<pre>1 The function called at program startup is named main. The implementation declares no prototype
|
|
for this function. It shall be defined with a return type of int and with no parameters:
|
|
|
|
int main(void) { /* ... */ }
|
|
|
|
|
|
or with two parameters (referred to here as argc and argv, though any names may be used, as they
|
|
are local to the function in which they are declared):
|
|
|
|
int main(int argc, char *argv[]) { /* ... */ }
|
|
|
|
|
|
or equivalent<a href='#FOOTNOTE.10'><sup>[10]</sup></a> ; or in some other implementation-defined manner.
|
|
</pre>
|
|
<a name='FOOTNOTE.10'>
|
|
<pre><i><b>Footnote 10)</b> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char
|
|
** argv, and so
|
|
on.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.2.1p2'></a>
|
|
<pre>2 If they are declared, the parameters to the main function shall obey the following constraints:
|
|
|
|
— The value of argc shall be nonnegative.
|
|
|
|
— argv[argc] shall be a null pointer.
|
|
|
|
— If the value of argc is greater than zero, the array members argv[0] through argv[argc-1]
|
|
inclusive shall contain pointers to strings, which are given implementation-defined values
|
|
by the host environment prior to program startup. The intent is to supply to the program
|
|
information determined prior to program startup from elsewhere in the hosted environment.
|
|
If the host environment is not capable of supplying strings with letters in both uppercase and
|
|
lowercase, the implementation shall ensure that the strings are received in lowercase.
|
|
|
|
— If the value of argc is greater than zero, the string pointed to by argv[0] represents the
|
|
program name; argv[0][0] shall be the null character if the program name is not available
|
|
from the host environment. If the value of argc is greater than one, the strings pointed to by
|
|
argv[1] through argv[argc-1] represent the program parameters.
|
|
|
|
— The parameters argc and argv and the strings pointed to by the argv array shall be modifiable
|
|
by the program, and retain their last-stored values between program startup and program
|
|
termination.
|
|
|
|
</pre>
|
|
<a name='5.1.2.2.2'></a>
|
|
<hr>
|
|
<h3>5.1.2.2.2 [Program execution]</h3>
|
|
<a name='5.1.2.2.2p1'></a>
|
|
<pre>1 In a hosted environment, a program may use all the functions, macros, type definitions, and objects
|
|
described in the library clause (Clause 7).
|
|
|
|
</pre>
|
|
<a name='5.1.2.2.3'></a>
|
|
<hr>
|
|
<h3>5.1.2.2.3 [Program termination]</h3>
|
|
<a name='5.1.2.2.3p1'></a>
|
|
<pre>1 If the return type of the main function is a type compatible with int, a return from the initial call
|
|
to the main function is equivalent to calling the exit function with the value returned by the main
|
|
function as its argument;<a href='#FOOTNOTE.11'><sup>[11]</sup></a> reaching the } that terminates the main function returns a value of 0. If
|
|
the return type is not compatible with int, the termination status returned to the host environment
|
|
is unspecified.
|
|
Forward references: definition of terms (<a href='#7.1.1'>7.1.1</a>), the exit function (<a href='#7.24.4.4'>7.24.4.4</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.11'>
|
|
<pre><i><b>Footnote 11)</b> In accordance with <a href='#6.2.4'>6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main will have ended in the
|
|
former case, even where they would not have in the latter.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.3'></a>
|
|
<hr>
|
|
<h3>5.1.2.3 [Program execution]</h3>
|
|
<a name='5.1.2.3p1'></a>
|
|
<pre>1 The semantic descriptions in this document describe the behavior of an abstract machine in which
|
|
issues of optimization are irrelevant.
|
|
</pre>
|
|
<a name='5.1.2.3p2'></a>
|
|
<pre>2 An access to an object through the use of an lvalue of volatile-qualified type is a volatile access. A
|
|
volatile access to an object, modifying an object, modifying a file, or calling a function that does any
|
|
of those operations are all side effects<a href='#FOOTNOTE.12'><sup>[12]</sup></a> , which are changes in the state of the execution environment.
|
|
Evaluation of an expression in general includes both value computations and initiation of side effects.
|
|
Value computation for an lvalue expression includes determining the identity of the designated
|
|
object.
|
|
</pre>
|
|
<a name='FOOTNOTE.12'>
|
|
<pre><i><b>Footnote 12)</b> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status flags and control
|
|
modes. Floating-point operations implicitly set the status flags; modes affect result values of floating-point operations.
|
|
Implementations that support such floating-point state are required to regard changes to it as side effects — see Annex F for
|
|
details. The floating-point environment library <fenv.h> provides a programming facility for indicating when these side
|
|
effects matter, freeing the implementations in other cases.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.3p3'></a>
|
|
<pre>3 Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations executed by a
|
|
single thread, which induces a partial order among those evaluations. Given any two evaluations
|
|
A and B, if A is sequenced before B, then the execution of A shall precede the execution of B.
|
|
(Conversely, if A is sequenced before B, then B is sequenced after A.) If A is not sequenced before or
|
|
after B, then A and B are unsequenced. Evaluations A and B are indeterminately sequenced when A is
|
|
sequenced either before or after B, but it is unspecified which.<a href='#FOOTNOTE.13'><sup>[13]</sup></a> The presence of a sequence point
|
|
between the evaluation of expressions A and B implies that every value computation and side effect
|
|
associated with A is sequenced before every value computation and side effect associated with B. (A
|
|
summary of the sequence points is given in Annex C.)
|
|
</pre>
|
|
<a name='FOOTNOTE.13'>
|
|
<pre><i><b>Footnote 13)</b> The executions of unsequenced evaluations can interleave. Indeterminately sequenced evaluations cannot interleave, but
|
|
can be executed in any order.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.3p4'></a>
|
|
<pre>4 In the abstract machine, all expressions are evaluated as specified by the semantics. An actual
|
|
implementation need not evaluate part of an expression if it can deduce that its value is not used
|
|
and that no needed side effects are produced (including any caused by calling a function or through
|
|
volatile access to an object).
|
|
</pre>
|
|
<a name='5.1.2.3p5'></a>
|
|
<pre>5 When the processing of the abstract machine is interrupted by receipt of a signal, the values of objects
|
|
that are neither lock-free atomic objects nor of type volatile sig_atomic_t are unspecified, as is
|
|
the state of the dynamic floating-point environment. The representation of any object modified by
|
|
the handler that is neither a lock-free atomic object nor of type volatile sig_atomic_t becomes
|
|
indeterminate when the handler exits, as does the state of the dynamic floating-point environment if
|
|
it is modified by the handler and not restored to its original state.
|
|
</pre>
|
|
<a name='5.1.2.3p6'></a>
|
|
<pre>6 The least requirements on a conforming implementation are:
|
|
|
|
— Volatile accesses to objects are evaluated strictly according to the rules of the abstract machine.
|
|
— At program termination, all data written into files shall be identical to the result that execution
|
|
of the program according to the abstract semantics would have produced.
|
|
— The input and output dynamics of interactive devices shall take place as specified in <a href='#7.23.3'>7.23.3</a>.
|
|
The intent of these requirements is that unbuffered or line-buffered output appear as soon as
|
|
possible, to ensure that prompting messages actually appear prior to a program waiting for
|
|
input.
|
|
|
|
This is the observable behavior of the program.
|
|
</pre>
|
|
<a name='5.1.2.3p7'></a>
|
|
<pre>7 What constitutes an interactive device is implementation-defined.
|
|
</pre>
|
|
<a name='5.1.2.3p8'></a>
|
|
<pre>8 More stringent correspondences between abstract and actual semantics may be defined by each
|
|
implementation.
|
|
</pre>
|
|
<a name='5.1.2.3p9'></a>
|
|
<pre>9 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual semantics: at every
|
|
sequence point, the values of the actual objects would agree with those specified by the abstract semantics. The keyword
|
|
volatile would then be redundant.
|
|
|
|
</pre>
|
|
<a name='5.1.2.3p10'></a>
|
|
<pre>10 Alternatively, an implementation might perform various optimizations within each translation unit, such that the actual
|
|
semantics would agree with the abstract semantics only when making function calls across translation unit boundaries. In
|
|
such an implementation, at the time of each function entry and function return where the calling function and the called
|
|
function are in different translation units, the values of all externally linked objects and of all objects accessible via pointers
|
|
therein would agree with the abstract semantics. Furthermore, at the time of each such function entry the values of the
|
|
parameters of the called function and of all objects accessible via pointers therein would agree with the abstract semantics. In
|
|
this type of implementation, objects referred to by interrupt service routines activated by the signal function would require
|
|
explicit specification of volatile storage, as well as other implementation-defined restrictions.
|
|
</pre>
|
|
<a name='5.1.2.3p11'></a>
|
|
<pre>11 EXAMPLE 2 In executing the fragment
|
|
|
|
char c1, c2;
|
|
/* ... */
|
|
c1 = c1 + c2;
|
|
|
|
|
|
the "integer promotions" require that the abstract machine promote the value of each variable to int size and then add the
|
|
two ints and truncate the sum. Provided the addition of two chars can be done without integer overflow, or with integer
|
|
overflow wrapping silently to produce the correct result, the actual execution need only produce the same result, possibly
|
|
omitting the promotions.
|
|
</pre>
|
|
<a name='5.1.2.3p12'></a>
|
|
<pre>12 EXAMPLE 3 Similarly, in the fragment
|
|
|
|
float f1, f2;
|
|
double d;
|
|
/* ... */
|
|
f1 = f2 * d;
|
|
|
|
|
|
the multiplication can be executed using single-precision arithmetic if the implementation can ascertain that the result would
|
|
be the same as if it were executed using double-precision arithmetic (for example, if d were replaced by the constant 2.0,
|
|
which has type double).
|
|
</pre>
|
|
<a name='5.1.2.3p13'></a>
|
|
<pre>13 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate semantics. Values are
|
|
independent of whether they are represented in a register or in memory. For example, an implicit spilling of a register is
|
|
not permitted to alter the value. Also, an explicit store and load is required to round to the precision of the storage type. In
|
|
particular, casts and assignments are required to perform their specified conversion. For the fragment
|
|
|
|
double d1, d2;
|
|
float f;
|
|
d1 = f = expression;
|
|
d2 = (float) expression;
|
|
|
|
|
|
the values assigned to d1 and d2 are required to have been converted to float.
|
|
</pre>
|
|
<a name='5.1.2.3p14'></a>
|
|
<pre>14 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in precision as well as
|
|
range. The implementation cannot generally apply the mathematical associative rules for addition or multiplication, nor
|
|
the distributive rule, because of roundoff error, even in the absence of overflow and underflow. Likewise, implementations
|
|
cannot generally replace decimal constants in order to rearrange expressions. In the following fragment, rearrangements
|
|
suggested by mathematical rules for real numbers are often not valid (see <a href='#F.9'>F.9</a>).
|
|
|
|
double x, y, z;
|
|
/* ... */
|
|
x = (x * y) * z; // not equivalent to x *= y * z;
|
|
z = (x - y) + y; // not equivalent to z = x;
|
|
z = x + x * y; // not equivalent to z = x * (1.0 + y);
|
|
y = x / 5.0; // not equivalent to y = x * 0.2;
|
|
|
|
|
|
</pre>
|
|
<a name='5.1.2.3p15'></a>
|
|
<pre>15 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
|
|
|
|
int a, b;
|
|
/* ... */
|
|
a = a + 32760 + b + 5;
|
|
|
|
|
|
the expression statement behaves exactly the same as
|
|
|
|
a = (((a + 32760) + b) + 5);
|
|
|
|
|
|
due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is next added to b, and
|
|
that result is then added to 5 which results in the value assigned to a. On a machine in which integer overflows produce
|
|
an explicit trap and in which the range of values representable by an int is [−32768, +32767], the implementation cannot
|
|
rewrite this expression as
|
|
|
|
a = ((a + b) + 32765);
|
|
|
|
|
|
since if the values for a and b were, respectively, −32754 and −15, the sum a + b would produce a trap while the original
|
|
expression would not; nor can the expression be rewritten either as
|
|
a = ((a + 32765) + b);
|
|
|
|
|
|
or
|
|
|
|
a = (a + (b + 32765));
|
|
|
|
|
|
since the values for a and b might have been, respectively, 4 and −8 or −17 and 12. However, on a machine in which integer
|
|
overflow silently generates some value and where positive and negative integer overflows cancel, the above expression
|
|
statement can be rewritten by the implementation in any of the above ways because the same result will occur.
|
|
</pre>
|
|
<a name='5.1.2.3p16'></a>
|
|
<pre>16 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the following fragment
|
|
|
|
#include <stdio.h>
|
|
int sum;
|
|
char *p;
|
|
/* ... */
|
|
sum = sum * 10 - ’0’ + (*p++ = getchar());
|
|
|
|
|
|
the expression statement is grouped as if it were written as
|
|
|
|
sum = (((sum * 10) - ’0’) + ((*(p++)) = (getchar())));
|
|
|
|
|
|
but the actual increment of p can occur at any time between the previous sequence point and the next sequence point (the ;),
|
|
and the call to getchar can occur at any point prior to the need of its returned value.
|
|
|
|
Forward references: expressions (<a href='#6.5'>6.5</a>), type qualifiers (<a href='#6.7.3'>6.7.3</a>), statements (<a href='#6.8'>6.8</a>), floating-point envi-
|
|
ronment <fenv.h> (<a href='#7.6'>7.6</a>), the signal function (<a href='#7.14'>7.14</a>), files (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
</pre>
|
|
<a name='5.1.2.4'></a>
|
|
<hr>
|
|
<h3>5.1.2.4 [Multi-threaded executions and data races]</h3>
|
|
<a name='5.1.2.4p1'></a>
|
|
<pre>1 Under a hosted implementation, a program can have more than one thread of execution (or thread)
|
|
running concurrently. The execution of each thread proceeds as defined by the remainder of this
|
|
document. The execution of the entire program consists of an execution of all of its threads.<a href='#FOOTNOTE.14'><sup>[14]</sup></a>
|
|
Under a freestanding implementation, it is implementation-defined whether a program can have
|
|
more than one thread of execution.
|
|
</pre>
|
|
<a name='FOOTNOTE.14'>
|
|
<pre><i><b>Footnote 14)</b> The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of atomic operations,
|
|
for example, allow executions inconsistent with a simple interleaving as described below.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.4p2'></a>
|
|
<pre>2 The value of an object visible to a thread T at a particular point is the initial value of the object, a
|
|
value stored in the object by T , or a value stored in the object by another thread, according to the
|
|
rules below.
|
|
</pre>
|
|
<a name='5.1.2.4p3'></a>
|
|
<pre>3 NOTE 1 In some cases, there could instead be undefined behavior. Much of this section is motivated by the desire to support
|
|
atomic operations with explicit and detailed visibility constraints. However, it also implicitly supports a simpler view for
|
|
more restricted programs.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p4'></a>
|
|
<pre>4 Two expression evaluations conflict if one of them modifies a memory location and the other one
|
|
reads or modifies the same memory location.
|
|
</pre>
|
|
<a name='5.1.2.4p5'></a>
|
|
<pre>5 The library defines a number of atomic operations (<a href='#7.17'>7.17</a>) and operations on mutexes (<a href='#7.28.4'>7.28.4</a>) that are
|
|
specially identified as synchronization operations. These operations play a special role in making
|
|
assignments in one thread visible to another. A synchronization operation on one or more memory
|
|
locations is one of an acquire operation, a release operation, both an acquire and release operation, or a
|
|
consume operation. A synchronization operation without an associated memory location is a fence and
|
|
can be either an acquire fence, a release fence, or both an acquire and release fence. In addition, there
|
|
are relaxed atomic operations, which are not synchronization operations, and atomic read-modify-write
|
|
operations, which have special characteristics.
|
|
</pre>
|
|
<a name='5.1.2.4p6'></a>
|
|
<pre>6 NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations composing the mutex.
|
|
Correspondingly, a call that releases the same mutex will perform a release operation on those same locations. Informally,
|
|
performing a release operation on A forces prior side effects on other memory locations to become visible to other threads
|
|
that later perform an acquire or consume operation on A. Relaxed atomic operations are not included as synchronization
|
|
operations although, like synchronization operations, they cannot contribute to data races.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p7'></a>
|
|
<pre>7 All modifications to a particular atomic object M occur in some particular total order, called the
|
|
modification order of M . If A and B are modifications of an atomic object M , and A happens before B,
|
|
then A shall precede B in the modification order of M , which is defined below.
|
|
</pre>
|
|
<a name='5.1.2.4p8'></a>
|
|
<pre>8 NOTE 3 This states that the modification orders are expected to respect the "happens before" relation.
|
|
</pre>
|
|
<a name='5.1.2.4p9'></a>
|
|
<pre>9 NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be combined into a single
|
|
total order for all objects. In general this will be impossible since different threads can observe modifications to different
|
|
variables in inconsistent orders.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p10'></a>
|
|
<pre>10 A release sequence headed by a release operation A on an atomic object M is a maximal contiguous
|
|
sub-sequence of side effects in the modification order of M , where the first operation is A and every
|
|
subsequent operation either is performed by the same thread that performed the release or is an
|
|
atomic read-modify-write operation.
|
|
</pre>
|
|
<a name='5.1.2.4p11'></a>
|
|
<pre>11 Certain library calls synchronize with other library calls performed by another thread. In particular,
|
|
an atomic operation A that performs a release operation on an object M synchronizes with an atomic
|
|
operation B that performs an acquire operation on M and reads a value written by any side effect in
|
|
the release sequence headed by A.
|
|
</pre>
|
|
<a name='5.1.2.4p12'></a>
|
|
<pre>12 NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as described below. Such a
|
|
requirement would sometimes interfere with efficient implementation.
|
|
</pre>
|
|
<a name='5.1.2.4p13'></a>
|
|
<pre>13 NOTE 6 The specifications of the synchronization operations define when one reads the value written by another. For atomic
|
|
variables, the definition is clear. All operations on a given mutex occur in a single total order. Each mutex acquisition "reads
|
|
the value written" by the last mutex release.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p14'></a>
|
|
<pre>14 An evaluation A carries a dependency<a href='#FOOTNOTE.15'><sup>[15]</sup></a> to an evaluation B if:
|
|
|
|
— the value of A is used as an operand of B, unless:
|
|
|
|
• B is an invocation of the kill_dependency macro,
|
|
• A is the left operand of a && or || operator,
|
|
• A is the left operand of a ?: operator, or
|
|
• A is the left operand of a , operator;
|
|
|
|
or
|
|
|
|
— A writes a scalar object or bit-field M , B reads from M the value written by A, and A is
|
|
sequenced before B, or
|
|
|
|
— for some evaluation X, A carries a dependency to X and X carries a dependency to B.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.15'>
|
|
<pre><i><b>Footnote 15)</b> The "carries a dependency" relation is a subset of the "sequenced before" relation, and is similarly strictly intra-thread.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.4p15'></a>
|
|
<pre>15 An evaluation A is dependency-ordered before<a href='#FOOTNOTE.16'><sup>[16]</sup></a> an evaluation B if:
|
|
|
|
— A performs a release operation on an atomic object M , and, in another thread, B performs a
|
|
consume operation on M and reads a value written by any side effect in the release sequence
|
|
headed by A, or
|
|
|
|
— for some evaluation X, A is dependency-ordered before X and X carries a dependency to B.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.16'>
|
|
<pre><i><b>Footnote 16)</b> The "dependency-ordered before" relation is analogous to the "synchronizes with" relation, but uses release/consume in
|
|
place of release/acquire.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.2.4p16'></a>
|
|
<pre>16 An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A is
|
|
dependency-ordered before B, or, for some evaluation X:
|
|
|
|
— A synchronizes with X and X is sequenced before B,
|
|
|
|
— A is sequenced before X and X inter-thread happens before B, or
|
|
|
|
— A inter-thread happens before X and X inter-thread happens before B.
|
|
</pre>
|
|
<a name='5.1.2.4p17'></a>
|
|
<pre>17 NOTE 7 The "inter-thread happens before" relation describes arbitrary concatenations of "sequenced before", "synchronizes
|
|
with", and "dependency-ordered before" relationships, with two exceptions. The first exception is that a concatenation is
|
|
not permitted to end with "dependency-ordered before" followed by "sequenced before". The reason for this limitation is
|
|
that a consume operation participating in a "dependency-ordered before" relationship provides ordering only with respect
|
|
to operations to which this consume operation actually carries a dependency. The reason that this limitation applies only
|
|
to the end of such a concatenation is that any subsequent release operation will provide the required ordering for a prior
|
|
consume operation. The second exception is that a concatenation is not permitted to consist entirely of "sequenced before".
|
|
The reasons for this limitation are (1) to permit "inter-thread happens before" to be transitively closed and (2) the "happens
|
|
before" relation, defined below, provides for relationships consisting entirely of "sequenced before".
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p18'></a>
|
|
<pre>18 An evaluation A happens before an evaluation B if A is sequenced before B or A inter-thread happens
|
|
before B. The implementation shall ensure that no program execution demonstrates a cycle in the
|
|
"happens before" relation.
|
|
</pre>
|
|
<a name='5.1.2.4p19'></a>
|
|
<pre>19 NOTE 8 This cycle would otherwise be possible only through the use of consume operations.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p20'></a>
|
|
<pre>20 A visible side effect A on an object M with respect to a value computation B of M satisfies the
|
|
conditions:
|
|
|
|
— A happens before B, and
|
|
|
|
— there is no other side effect X to M such that A happens before X and X happens before B.
|
|
|
|
The value of a non-atomic scalar object M , as determined by evaluation B, shall be the value stored
|
|
by the visible side effect A.
|
|
</pre>
|
|
<a name='5.1.2.4p21'></a>
|
|
<pre>21 NOTE 9 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data race and the
|
|
behavior is undefined.
|
|
</pre>
|
|
<a name='5.1.2.4p22'></a>
|
|
<pre>22 NOTE 10 This states that operations on ordinary variables are not visibly reordered. This is not actually detectable without
|
|
data races, but it is necessary to ensure that data races, as defined here, and with suitable restrictions on the use of atomics,
|
|
correspond to data races in a simple interleaved (sequentially consistent) execution.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p23'></a>
|
|
<pre>23 The value of an atomic object M , as determined by evaluation B, shall be the value stored by some
|
|
side effect A that modifies M , where B does not happen before A.
|
|
</pre>
|
|
<a name='5.1.2.4p24'></a>
|
|
<pre>24 NOTE 11 The set of side effects from which a given evaluation might take its value is also restricted by the rest of the rules
|
|
described here, and in particular, by the coherence requirements below.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p25'></a>
|
|
<pre>25 If an operation A that modifies an atomic object M happens before an operation B that modifies M ,
|
|
then A shall be earlier than B in the modification order of M .
|
|
</pre>
|
|
<a name='5.1.2.4p26'></a>
|
|
<pre>26 NOTE 12 The requirement above is known as "write-write coherence".
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p27'></a>
|
|
<pre>27 If a value computation A of an atomic object M happens before a value computation B of M , and A
|
|
takes its value from a side effect X on M , then the value computed by B shall either be the value
|
|
stored by X or the value stored by a side effect Y on M , where Y follows X in the modification
|
|
order of M .
|
|
</pre>
|
|
<a name='5.1.2.4p28'></a>
|
|
<pre>28 NOTE 13 The requirement above is known as "read-read coherence".
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p29'></a>
|
|
<pre>29 If a value computation A of an atomic object M happens before an operation B on M , then A shall
|
|
take its value from a side effect X on M , where X precedes B in the modification order of M .
|
|
</pre>
|
|
<a name='5.1.2.4p30'></a>
|
|
<pre>30 NOTE 14 The requirement above is known as "read-write coherence".
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p31'></a>
|
|
<pre>31 If a side effect X on an atomic object M happens before a value computation B of M , then the
|
|
evaluation B shall take its value from X or from a side effect Y that follows X in the modification
|
|
order of M .
|
|
</pre>
|
|
<a name='5.1.2.4p32'></a>
|
|
<pre>32 NOTE 15 The requirement above is known as "write-read coherence".
|
|
</pre>
|
|
<a name='5.1.2.4p33'></a>
|
|
<pre>33 NOTE 16 This effectively disallows compiler reordering of atomic operations to a single object, even if both operations are
|
|
"relaxed" loads. By doing so, it effectively makes the "cache coherence" guarantee provided by most hardware available to C
|
|
atomic operations.
|
|
</pre>
|
|
<a name='5.1.2.4p34'></a>
|
|
<pre>34 NOTE 17 The value observed by a load of an atomic object depends on the "happens before" relation, which in turn depends
|
|
on the values observed by loads of atomic objects. The intended reading is that there exists an association of atomic loads
|
|
with modifications they observe that, together with suitably chosen modification orders and the "happens before" relation
|
|
derived as described above, satisfy the resulting constraints as imposed here.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p35'></a>
|
|
<pre>35 The execution of a program contains a data race if it contains two conflicting actions in different
|
|
threads, at least one of which is not atomic, and neither happens before the other. Any such data
|
|
race results in undefined behavior.
|
|
</pre>
|
|
<a name='5.1.2.4p36'></a>
|
|
<pre>36 NOTE 18 It can be shown that programs that correctly use simple mutexes and memory_order_seq_cst operations to
|
|
prevent all data races, and use no other synchronization operations, behave as though the operations executed by their
|
|
constituent threads were simply interleaved, with each value computation of an object being the last value stored in that
|
|
interleaving. This is normally referred to as "sequential consistency". However, this applies only to data-race-free programs,
|
|
and data-race-free programs cannot observe most program transformations that do not change single-threaded program
|
|
semantics. In fact, most single-threaded program transformations continue to be allowed, since any program that behaves
|
|
differently as a result necessarily has undefined behavior even before such a transformation is applied.
|
|
</pre>
|
|
<a name='5.1.2.4p37'></a>
|
|
<pre>37 NOTE 19 Compiler transformations that introduce assignments to a potentially shared memory location that would not
|
|
be modified by the abstract machine are generally precluded by this document, since such an assignment might overwrite
|
|
another assignment by a different thread in cases in which an abstract machine execution would not have encountered a
|
|
data race. This includes implementations of data member assignment that overwrite adjacent members in separate memory
|
|
locations. Reordering of atomic loads in cases in which the atomics in question might alias is also generally precluded, since
|
|
this could violate the coherence requirements.
|
|
</pre>
|
|
<a name='5.1.2.4p38'></a>
|
|
<pre>38 NOTE 20 Transformations that introduce a speculative read of a potentially shared memory location might not preserve
|
|
the semantics of the program as defined in this document, since they potentially introduce a data race. However, they are
|
|
typically valid in the context of an optimizing compiler that targets a specific machine with well-defined semantics for data
|
|
races. They would be invalid for a hypothetical machine that is not tolerant of races or provides hardware race detection.
|
|
|
|
|
|
</pre>
|
|
<a name='5.2'></a>
|
|
<hr>
|
|
<h3>5.2 [Environmental considerations]</h3>
|
|
<a name='5.2.1'></a>
|
|
<hr>
|
|
<h3>5.2.1 [Character sets]</h3>
|
|
<a name='5.2.1p1'></a>
|
|
<pre>1 Two sets of characters and their associated collating sequences shall be defined: the set in which source
|
|
files are written (the source character set), and the set interpreted in the execution environment (the
|
|
execution character set). Each set is further divided into a basic character set, whose contents are given
|
|
by this subclause, and a set of zero or more locale-specific members (which are not members of the
|
|
basic character set) called extended characters. The combined set is also called the extended character
|
|
set. The values of the members of the execution character set are implementation-defined.
|
|
</pre>
|
|
<a name='5.2.1p2'></a>
|
|
<pre>2 In a character constant or string literal, members of the execution character set shall be represented by
|
|
corresponding members of the source character set or by escape sequences consisting of the backslash
|
|
\ followed by one or more characters. A byte with all bits set to 0, called the null character, shall exist
|
|
in the basic execution character set; it is used to terminate a character string.
|
|
Both the basic source and basic execution character sets shall have the following members: the 26
|
|
uppercase letters of the Latin alphabet
|
|
</pre>
|
|
<a name='5.2.1p3'></a>
|
|
<pre>3 A B C D E F G H I J K L M
|
|
N O P Q R S T U V W X Y Z
|
|
|
|
the 26 lowercase letters of the Latin alphabet
|
|
|
|
a b c d e f g h i j k l m
|
|
n o p q r s t u v w x y z
|
|
|
|
the 10 decimal digits
|
|
|
|
0 1 2 3 4 5 6 7 8 9
|
|
|
|
the following 29 graphic characters
|
|
! " # % & ’ ( ) * + , - . / :
|
|
; < = > ? [ \ ] ^ _ { | } ~
|
|
|
|
the space character, and control characters representing horizontal tab, vertical tab, and form feed.
|
|
The representation of each member of the source and execution basic character sets shall fit in a
|
|
byte. In both the source and execution basic character sets, the value of each character after 0 in
|
|
the above list of decimal digits shall be one greater than the value of the previous. In source files,
|
|
there shall be some way of indicating the end of each line of text; this document treats such an
|
|
end-of-line indicator as if it were a single new-line character. In the basic execution character set,
|
|
there shall be control characters representing alert, backspace, carriage return, and new line. If any
|
|
other characters are encountered in a source file (except in an identifier, a character constant, a string
|
|
literal, a header name, a comment, or a preprocessing token that is never converted to a token), the
|
|
behavior is undefined.
|
|
</pre>
|
|
<a name='5.2.1p4'></a>
|
|
<pre>4 A letter is an uppercase letter or a lowercase letter as defined above; in this document the term does
|
|
not include other characters that are letters in other alphabets.
|
|
</pre>
|
|
<a name='5.2.1p5'></a>
|
|
<pre>5 The universal character name construct provides a way to name other characters.
|
|
Forward references: universal character names (<a href='#6.4.3'>6.4.3</a>), character constants (<a href='#6.4.4.4'>6.4.4.4</a>), preprocessing
|
|
directives (<a href='#6.10'>6.10</a>), string literals (<a href='#6.4.5'>6.4.5</a>), comments (<a href='#6.4.9'>6.4.9</a>), string (<a href='#7.1.1'>7.1.1</a>).
|
|
|
|
</pre>
|
|
<a name='5.2.1.1'></a>
|
|
<hr>
|
|
<h3>5.2.1.1 [Multibyte characters]</h3>
|
|
<a name='5.2.1.1p1'></a>
|
|
<pre>1 The source character set may contain multibyte characters, used to represent members of the
|
|
extended character set. The execution character set may also contain multibyte characters, which
|
|
need not have the same encoding as for the source character set. For both character sets, the following
|
|
shall hold:
|
|
|
|
— The basic character set, @, $, and ` shall be present and each character shall be encoded as a
|
|
single byte.
|
|
— The presence, meaning, and representation of any additional members is locale-specific.
|
|
— A multibyte character set may have a state-dependent encoding, wherein each sequence of
|
|
multibyte characters begins in an initial shift state and enters other locale-specific shift states
|
|
when specific multibyte characters are encountered in the sequence. While in the initial shift
|
|
state, all single-byte characters retain their usual interpretation and do not alter the shift state.
|
|
The interpretation for subsequent bytes in the sequence is a function of the current shift state.
|
|
— A byte with all bits zero shall be interpreted as a null character independent of shift state. Such
|
|
a byte shall not occur as part of any other multibyte character.
|
|
|
|
</pre>
|
|
<a name='5.2.1.1p2'></a>
|
|
<pre>2 For source files, the following shall hold:
|
|
|
|
— An identifier, comment, string literal, character constant, or header name shall begin and end
|
|
in the initial shift state.
|
|
— An identifier, comment, string literal, character constant, or header name shall consist of a
|
|
sequence of valid multibyte characters.
|
|
|
|
</pre>
|
|
<a name='5.2.2'></a>
|
|
<hr>
|
|
<h3>5.2.2 [Character display semantics]</h3>
|
|
<a name='5.2.2p1'></a>
|
|
<pre>1 The active position is that location on a display device where the next character output by the
|
|
fputc function would appear. The intent of writing a printing character (as defined by the isprint
|
|
function) to a display device is to display a graphic representation of that character at the active
|
|
position and then advance the active position to the next position on the current line. The direction
|
|
of writing is locale-specific. If the active position is at the final position of a line (if there is one), the
|
|
behavior of the display device is unspecified.
|
|
</pre>
|
|
<a name='5.2.2p2'></a>
|
|
<pre>2 Alphabetic escape sequences representing non-graphic characters in the execution character set are
|
|
intended to produce actions on display devices as follows:
|
|
|
|
\a (alert) Produces an audible or visible alert without changing the active position.
|
|
|
|
\b (backspace) Moves the active position to the previous position on the current line. If the active
|
|
position is at the initial position of a line, the behavior of the display device is unspecified.
|
|
\f (form feed) Moves the active position to the initial position at the start of the next logical page.
|
|
|
|
\n (new line) Moves the active position to the initial position of the next line.
|
|
|
|
\r (carriage return) Moves the active position to the initial position of the current line.
|
|
|
|
\t (horizontal tab) Moves the active position to the next horizontal tabulation position on the current
|
|
line. If the active position is at or past the last defined horizontal tabulation position, the behavior
|
|
of the display device is unspecified.
|
|
\v (vertical tab) Moves the active position to the initial position of the next vertical tabulation
|
|
position. If the active position is at or past the last defined vertical tabulation position, the
|
|
behavior of the display device is unspecified.
|
|
|
|
</pre>
|
|
<a name='5.2.2p3'></a>
|
|
<pre>3 Each of these escape sequences shall produce a unique implementation-defined value which can be
|
|
stored in a single char object. The external representations in a text file need not be identical to the
|
|
internal representations, and are outside the scope of this document.
|
|
Forward references: the isprint function (<a href='#7.4.1.8'>7.4.1.8</a>), the fputc function (<a href='#7.23.7.3'>7.23.7.3</a>).
|
|
|
|
</pre>
|
|
<a name='5.2.3'></a>
|
|
<hr>
|
|
<h3>5.2.3 [Signals and interrupts]</h3>
|
|
<a name='5.2.3p1'></a>
|
|
<pre>1 Functions shall be implemented such that they may be interrupted at any time by a signal, or may be
|
|
called by a signal handler, or both, with no alteration to earlier, but still active, invocations’ control
|
|
flow (after the interruption), function return values, or objects with automatic storage duration.
|
|
All such objects shall be maintained outside the function image (the instructions that compose the
|
|
executable representation of a function) on a per-invocation basis.
|
|
|
|
</pre>
|
|
<a name='5.2.4'></a>
|
|
<hr>
|
|
<h3>5.2.4 [Environmental limits]</h3>
|
|
<a name='5.2.4p1'></a>
|
|
<pre>1 Both the translation and execution environments constrain the implementation of language trans-
|
|
lators and libraries. The following summarizes the language-related environmental limits on a
|
|
conforming implementation; the library-related limits are discussed in Clause 7.
|
|
|
|
</pre>
|
|
<a name='5.2.4.1'></a>
|
|
<hr>
|
|
<h3>5.2.4.1 [Translation limits]</h3>
|
|
<a name='5.2.4.1p1'></a>
|
|
<pre>1 The implementation shall be able to translate and execute a program that uses but does not exceed
|
|
the following limitations for these constructs and entities<a href='#FOOTNOTE.17'><sup>[17]</sup></a> :
|
|
|
|
— 127 nesting levels of blocks
|
|
|
|
— 63 nesting levels of conditional inclusion
|
|
|
|
— 12 pointer, array, and function declarators (in any combinations) modifying an arithmetic,
|
|
structure, union, or void type in a declaration
|
|
|
|
— 63 nesting levels of parenthesized declarators within a full declarator
|
|
|
|
— 63 nesting levels of parenthesized expressions within a full expression
|
|
|
|
— 63 significant initial characters in an internal identifier or a macro name(each universal charac-
|
|
ter name or extended source character is considered a single character)
|
|
|
|
— 31 significant initial characters in an external identifier (each universal character name specify-
|
|
ing a short identifier of 0000FFFF or less is considered 6 characters, each universal character
|
|
name specifying a short identifier of 00010000 or more is considered 10 characters, and each
|
|
extended source character is considered the same number of characters as the corresponding
|
|
universal character name, if any)<a href='#FOOTNOTE.18'><sup>[18]</sup></a>
|
|
|
|
— 4095 external identifiers in one translation unit
|
|
|
|
— 511 identifiers with block scope declared in one block
|
|
|
|
— 4095 macro identifiers simultaneously defined in one preprocessing translation unit
|
|
|
|
— 127 parameters in one function definition
|
|
|
|
— 127 arguments in one function call
|
|
|
|
— 127 parameters in one macro definition
|
|
|
|
— 127 arguments in one macro invocation
|
|
— 4095 characters in a logical source line
|
|
|
|
— 4095 characters in a string literal (after concatenation)
|
|
|
|
— 32767 bytes in an object (in a hosted environment only)
|
|
|
|
— 15 nesting levels for #included files
|
|
|
|
— 1023 case labels for a switch statement (excluding those for any nested switch statements)
|
|
|
|
— 1023 members in a single structure or union
|
|
|
|
— 1023 enumeration constants in a single enumeration
|
|
|
|
— 63 levels of nested structure or union definitions in a single member declaration list
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.17'>
|
|
<pre><i><b>Footnote 17)</b> Implementations are encouraged to avoid imposing fixed translation limits whenever possible.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.18'>
|
|
<pre><i><b>Footnote 18)</b> See "future language directions" (<a href='#6.11.3'>6.11.3</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2'></a>
|
|
<hr>
|
|
<h3>5.2.4.2 [Numerical limits]</h3>
|
|
<a name='5.2.4.2p1'></a>
|
|
<pre>1 An implementation is required to document all the limits specified in this subclause, which are
|
|
specified in the headers <limits.h> and <float.h>. Additional limits are specified in <stdint.h>.
|
|
Forward references: integer types <stdint.h> (<a href='#7.22'>7.22</a>).
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.1'></a>
|
|
<hr>
|
|
<h3>5.2.4.2.1 [Characteristics of integer types <limits.h>]</h3>
|
|
<a name='5.2.4.2.1p1'></a>
|
|
<pre>1 The values given below shall be replaced by constant expressions suitable for use in #if preprocess-
|
|
ing directives. Their implementation-defined values shall be equal or greater to those shown.
|
|
|
|
— width for an object of type bool<a href='#FOOTNOTE.19'><sup>[19]</sup></a>
|
|
|
|
BOOL_WIDTH 1
|
|
|
|
|
|
— number of bits for smallest object that is not a bit-field (byte)
|
|
|
|
CHAR_BIT 8
|
|
|
|
|
|
The macros CHAR_WIDTH, SCHAR_WIDTH, and UCHAR_WIDTH that represent the width of the
|
|
types char, signed char and unsigned char shall expand to the same value as CHAR_BIT.
|
|
|
|
— width for an object of type unsigned short int
|
|
|
|
USHRT_WIDTH 16
|
|
|
|
|
|
The macro SHRT_WIDTH represents the width of the type short int and shall expand to the
|
|
same value as USHRT_WIDTH.
|
|
|
|
— width for an object of type unsigned int
|
|
|
|
UINT_WIDTH 16
|
|
|
|
|
|
The macro INT_WIDTH represents the width of the type int and shall expand to the same value
|
|
as UINT_WIDTH.
|
|
|
|
— width for an object of type unsigned long int
|
|
|
|
ULONG_WIDTH 32
|
|
|
|
|
|
The macro LONG_WIDTH represents the width of the type long int and shall expand to the
|
|
same value as ULONG_WIDTH.
|
|
|
|
— width for an object of type unsigned long long int
|
|
ULLONG_WIDTH 64
|
|
|
|
|
|
The macro LLONG_WIDTH represents the width of the type long long int and shall expand to
|
|
the same value as ULLONG_WIDTH.
|
|
— maximum width for an object of type _BitInt or unsigned _BitInt
|
|
|
|
BITINT_MAXWIDTH /* see below */
|
|
|
|
|
|
The macro BITINT_MAXWIDTH represents the maximum width N supported by the declaration
|
|
of a bit-precise integer (<a href='#6.2.5'>6.2.5</a>) in the type specifier _BitInt( N). The value BITINT_MAXWIDTH
|
|
shall expand to a value that is greater than or equal to the value of ULLONG_WIDTH.
|
|
— maximum number of bytes in a multibyte character, for any supported locale
|
|
|
|
MB_LEN_MAX 1
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.19'>
|
|
<pre><i><b>Footnote 19)</b> This value is exact.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.1p2'></a>
|
|
<pre>2 For all unsigned integer types for which <limits.h> or <stdint.h> define a macro with suffix
|
|
_WIDTH holding its width N , there is a macro with suffix _MAX holding the maximal value 2N − 1
|
|
that is representable by the type and that has the same type as would an expression that is an object
|
|
of the corresponding type converted according to the integer promotions. If the value is in the range
|
|
of the type uintmax_t (<a href='#7.22.1.5'>7.22.1.5</a>) the macro is suitable for use in #if preprocessing directives.
|
|
</pre>
|
|
<a name='5.2.4.2.1p3'></a>
|
|
<pre>3 For all signed integer types for which <limits.h> or <stdint.h> define a macro with suffix _WIDTH
|
|
holding its width N , there are macros with suffix _MIN and _MAX holding the minimal and maximal
|
|
values −2N −1 and 2N −1 − 1 that are representable by the type and that have the same type as
|
|
would an expression that is an object of the corresponding type converted according to the integer
|
|
promotions. If the values are in the range of the type intmax_t (<a href='#7.22.1.5'>7.22.1.5</a>) the macros are suitable for
|
|
use in #if preprocessing directives.
|
|
</pre>
|
|
<a name='5.2.4.2.1p4'></a>
|
|
<pre>4 If an object of type char can hold negative values, the value of CHAR_MIN shall be the same as that of
|
|
SCHAR_MIN and the value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value
|
|
of CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of UCHAR_MAX.<a href='#FOOTNOTE.20'><sup>[20]</sup></a>
|
|
Forward references: representations of types (<a href='#6.2.6'>6.2.6</a>), conditional inclusion (<a href='#6.10.1'>6.10.1</a>), integer types
|
|
<stdint.h> (<a href='#7.22'>7.22</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.20'>
|
|
<pre><i><b>Footnote 20)</b> See <a href='#6.2.5'>6.2.5</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2'></a>
|
|
<hr>
|
|
<h3>5.2.4.2.2 [Characteristics of floating types <float.h>]</h3>
|
|
<a name='5.2.4.2.2p1'></a>
|
|
<pre>1 The characteristics of floating types are defined in terms of a model that describes a repre-
|
|
sentation of floating-point numbers and allows other values. The characteristics provide in-
|
|
formation about an implementation’s floating-point arithmetic<a href='#FOOTNOTE.21'><sup>[21]</sup></a> . An implementation that de-
|
|
fines __STDC_IEC_60559_BFP__ or __STDC_IEC_559__ shall implement floating-point types and
|
|
arithmetic conforming to IEC 60559 as specified in Annex F. An implementation that defines
|
|
__STDC_IEC_60559_COMPLEX__ or __STDC_IEC_559_COMPLEX__ shall implement complex types
|
|
and arithmetic conforming to IEC 60559 as specified in Annex G.
|
|
</pre>
|
|
<a name='FOOTNOTE.21'>
|
|
<pre><i><b>Footnote 21)</b> The floating-point model is intended to clarify the description of each floating-point characteristic and does not require
|
|
the floating-point arithmetic of the implementation to be identical.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p2'></a>
|
|
<pre>2 The following parameters are used to define the model for each floating type:
|
|
s sign (±1)
|
|
b base or radix of exponent representation (an integer > 1)
|
|
e exponent (an integer between a minimum emin and a maximum emax )
|
|
p precision (the number of base-b digits in the significand)
|
|
fk nonnegative integers less than b (the significand digits)
|
|
For each floating type, the parameters b, p, emin , and emax are fixed constants.
|
|
</pre>
|
|
<a name='5.2.4.2.2p3'></a>
|
|
<pre>3 For each floating type, a floating-point number (x) is defined by the following model:
|
|
p
|
|
x = sbe fk b−k ,
|
|
SIGMA
|
|
emin ≤ e ≤ emax
|
|
k=1
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.2p4'></a>
|
|
<pre>4 Model floating-point numbers x with f1 > 0 are called normalized floating-point numbers.
|
|
</pre>
|
|
<a name='5.2.4.2.2p5'></a>
|
|
<pre>5 Model floating-point numbers x ̸= 0 with f1 = 0 and e = emin are called subnormal floating-point
|
|
numbers.
|
|
</pre>
|
|
<a name='5.2.4.2.2p6'></a>
|
|
<pre>6 Model floating-point numbers x ̸= 0 with f1 = 0 and e > emin are called unnormalized floating-point
|
|
numbers.
|
|
</pre>
|
|
<a name='5.2.4.2.2p7'></a>
|
|
<pre>7 Model floating-point numbers x with all fk = 0 are zeros.
|
|
</pre>
|
|
<a name='5.2.4.2.2p8'></a>
|
|
<pre>8 Floating types shall be able to represent signed zeros or an unsigned zero and all normalized floating-
|
|
point numbers. In addition, floating types may be able to contain other kinds of floating-point
|
|
numbers<a href='#FOOTNOTE.22'><sup>[22]</sup></a> , such as subnormal floating-point numbers and unnormalized floating-point numbers,
|
|
and values that are not floating-point numbers, such as NaNs and (signed and unsigned) infinities.
|
|
A NaN is a value signifying Not-a-Number. A quiet NaN propagates through almost every arithmetic
|
|
operation without raising a floating-point exception; a signaling NaN generally raises a floating-point
|
|
exception when occurring as an arithmetic operand<a href='#FOOTNOTE.23'><sup>[23]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.22'>
|
|
<pre><i><b>Footnote 22)</b> Some implementations have types that include finite numbers with range and/or precision that are not covered by the
|
|
model.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.23'>
|
|
<pre><i><b>Footnote 23)</b> IEC 60559 specifies quiet and signaling NaNs. For implementations that do not support IEC 60559, the terms quiet NaN
|
|
and signaling NaN are intended to apply to values with similar behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p9'></a>
|
|
<pre>9 Wherever values are unsigned, any requirement in this document to get the sign shall produce an
|
|
unspecified sign, and any requirement to set the sign shall be ignored, unless otherwise specified<a href='#FOOTNOTE.24'><sup>[24]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.24'>
|
|
<pre><i><b>Footnote 24)</b> Bit representations of floating-point values might include a sign bit, even if the values can be regarded as unsigned.
|
|
IEC 60559 NaNs are such values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p10'></a>
|
|
<pre>10 Whether and in what cases subnormal numbers are treated as zeros is implementation-defined.
|
|
Subnormal numbers that in some cases are treated by arithmetic operations as zeros are properly
|
|
classified as subnormal. However, object representations that could represent subnormal numbers
|
|
but that are always treated by arithmetic operations as zeros are non-canonical zeros, and the
|
|
values are properly classified as zero, not subnormal. IEC 60559 arithmetic (with default exception
|
|
handling) always treats subnormal numbers as nonzero.
|
|
</pre>
|
|
<a name='5.2.4.2.2p11'></a>
|
|
<pre>11 A value is negative if and only if it compares less than 0. Thus, negative zeros and NaNs are not
|
|
negative values.
|
|
</pre>
|
|
<a name='5.2.4.2.2p12'></a>
|
|
<pre>12 An implementation may prefer particular representations of values that have multiple representa-
|
|
tions in a floating type, <a href='#6.2.6.1'>6.2.6.1</a> not withstanding.<a href='#FOOTNOTE.25'><sup>[25]</sup></a> The preferred representations of a floating type,
|
|
including unique representations of values in the type, are called canonical. A floating type may also
|
|
contain non-canonical representations, for example, redundant representations of some or all of its
|
|
values, or representations that are extraneous to the floating-point model.<a href='#FOOTNOTE.26'><sup>[26]</sup></a> Typically, floating-point
|
|
operations deliver results with canonical representations. IEC 60559 operations deliver results with
|
|
canonical representations, unless specified otherwise.
|
|
</pre>
|
|
<a name='FOOTNOTE.25'>
|
|
<pre><i><b>Footnote 25)</b> The library operations iscanonical and canonicalize distinguish canonical (preferred) representations, but this
|
|
distinction alone does not imply that canonical and non-canonical representations are of different values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.26'>
|
|
<pre><i><b>Footnote 26)</b> Some of the values in the IEC 60559 decimal formats have non-canonical representations (as well as a canonical
|
|
representation).
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p13'></a>
|
|
<pre>13 The minimum range of representable values for a floating type is the most negative finite floating-
|
|
point number representable in that type through the most positive finite floating-point number
|
|
representable in that type. In addition, if negative infinity is representable in a type, the range of
|
|
that type is extended to all negative real numbers; likewise, if positive infinity is representable in a
|
|
type, the range of that type is extended to all positive real numbers.
|
|
</pre>
|
|
<a name='5.2.4.2.2p14'></a>
|
|
<pre>14 The accuracy of the floating-point operations (+ ,- , * , / ) and of the library functions in <math.h>
|
|
and <complex.h> that return floating-point results is implementation-defined, as is the accuracy of
|
|
the conversion between floating-point internal representations and string representations performed
|
|
by the library functions in <stdio.h>, <stdlib.h>, and <wchar.h>. The implementation may state
|
|
that the accuracy is unknown. Decimal floating-point operations have stricter requirements.
|
|
</pre>
|
|
<a name='5.2.4.2.2p15'></a>
|
|
<pre>15 All integer values in the <float.h> header, except FLT_ROUNDS, shall be constant expressions
|
|
suitable for use in #if preprocessing directives; all floating values shall be constant expressions.
|
|
All except CR_DECIMAL_DIG (<a href='#F.5'>F.5</a>), DECIMAL_DIG, DEC_EVAL_METHOD, FLT_EVAL_METHOD, FLT_RADIX,
|
|
and FLT_ROUNDS have separate names for all floating types. The floating-point model representation
|
|
is provided for all values except DEC_EVAL_METHOD, FLT_EVAL_METHOD and FLT_ROUNDS.
|
|
</pre>
|
|
<a name='5.2.4.2.2p16'></a>
|
|
<pre>16 The remainder of this subclause specifies characteristics of standard floating types.
|
|
</pre>
|
|
<a name='5.2.4.2.2p17'></a>
|
|
<pre>17 The rounding mode for floating-point addition for standard floating types is characterized by the
|
|
implementation-defined value of FLT_ROUNDS. Evaluation of FLT_ROUNDS correctly reflects any
|
|
execution-time change of rounding mode through the function fesetround in <fenv.h>.
|
|
|
|
−1 indeterminable
|
|
0 toward zero
|
|
1 to nearest, ties to even
|
|
2 toward positive infinity
|
|
3 toward negative infinity
|
|
4 to nearest, ties away from zero
|
|
|
|
All other values for FLT_ROUNDS characterize implementation-defined rounding behavior.
|
|
</pre>
|
|
<a name='5.2.4.2.2p18'></a>
|
|
<pre>18 Whether a type matches an IEC 60559 format (and perhaps, operations) is characterized
|
|
by the implementation-defined values of FLT_IS_IEC_60559, DBL_IS_IEC_60559, and
|
|
LDBL_IS_IEC_60559 (this does not imply conformance to Annex F):
|
|
|
|
0 type does not match an IEC 60559 format
|
|
1 type matches an IEC 60559 format
|
|
2 type matches an IEC 60559 format and operations
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.2p19'></a>
|
|
<pre>19 The values of floating type yielded by operators subject to the usual arithmetic conversions, including
|
|
the values yielded by the implicit conversion of operands, and the values of floating constants are
|
|
evaluated to a format whose range and precision may be greater than required by the type. Such a
|
|
format is called an evaluation format. In all cases, assignment and cast operators yield values in the
|
|
format of the type. The extent to which evaluation formats are used is characterized by the value of
|
|
FLT_EVAL_METHOD:<a href='#FOOTNOTE.27'><sup>[27]</sup></a>
|
|
|
|
−1 indeterminable;
|
|
0 evaluate all operations and constants just to the range and precision of the type;
|
|
1 evaluate operations and constants of type float and double to the range and precision of
|
|
the double type, evaluate long double operations and constants to the range and precision
|
|
of the long double type;
|
|
2 evaluate all operations and constants to the range and precision of the long double type.
|
|
|
|
All other negative values for FLT_EVAL_METHOD characterize implementation-defined behavior. The
|
|
value of FLT_EVAL_METHOD does not characterize values returned by function calls (see <a href='#6.8.6.4'>6.8.6.4</a>, <a href='#F.6'>F.6</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.27'>
|
|
<pre><i><b>Footnote 27)</b> The evaluation method determines evaluation formats of expressions involving all floating types, not just real
|
|
types. For example, if FLT_EVAL_METHOD is 1, then the product of two float _Complex operands is represented in the
|
|
double _Complex format, and its parts are evaluated to double.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p20'></a>
|
|
<pre>20 The presence or absence of subnormal numbers is characterized by the implementation-defined
|
|
values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and LDBL_HAS_SUBNORM:
|
|
|
|
−1 indeterminable
|
|
0 absent (type does not support subnormal numbers)
|
|
|
|
1 present (type does support subnormal numbers)
|
|
|
|
The use of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and LDBL_HAS_SUBNORM macros is an obsolescent
|
|
feature.
|
|
</pre>
|
|
<a name='5.2.4.2.2p21'></a>
|
|
<pre>21 The signaling NaN macros
|
|
|
|
FLT_SNAN
|
|
DBL_SNAN
|
|
LDBL_SNAN
|
|
|
|
|
|
each is defined if and only if the respective type contains signaling NaNs. They expand to a constant
|
|
expression of the respective type representing a signaling NaN. If an optional unary + or - operator
|
|
followed by a signaling NaN macro is used as the initializer for initializing an object of the same
|
|
type that has static or thread storage duration, the object is initialized with a signaling NaN value.
|
|
</pre>
|
|
<a name='5.2.4.2.2p22'></a>
|
|
<pre>22 The macro
|
|
|
|
INFINITY
|
|
|
|
|
|
is defined if and only if the implementation supports an infinity for the type float. It expands to a
|
|
constant expression of type float representing positive or unsigned infinity.
|
|
</pre>
|
|
<a name='5.2.4.2.2p23'></a>
|
|
<pre>23 The macro
|
|
|
|
NAN
|
|
|
|
|
|
is defined if and only if the implementation supports quiet NaNs for the float type. It expands to a
|
|
constant expression of type float representing a quiet NaN.
|
|
</pre>
|
|
<a name='5.2.4.2.2p24'></a>
|
|
<pre>24 The values given in the following list shall be replaced by constant expressions with implementation-
|
|
defined values that are greater or equal in magnitude (absolute value) to those shown, with the
|
|
same sign:
|
|
|
|
— radix of exponent representation, b
|
|
|
|
FLT_RADIX 2
|
|
|
|
|
|
|
|
— number of base-FLT_RADIX digits in the floating-point significand, p
|
|
|
|
FLT_MANT_DIG
|
|
DBL_MANT_DIG
|
|
LDBL_MANT_DIG
|
|
|
|
|
|
|
|
— number of decimal digits, n, such that any floating-point number with p radix b digits can be
|
|
rounded to a floating-point number with n decimal digits and back again without change to
|
|
the value,
|
|
(
|
|
p log10 b if b is a power of 10
|
|
⌈1 + p log10 b⌉ otherwise
|
|
|
|
|
|
FLT_DECIMAL_DIG 6
|
|
DBL_DECIMAL_DIG 10
|
|
LDBL_DECIMAL_DIG 10
|
|
— number of decimal digits, n, such that any floating-point number in the widest of the supported
|
|
floating types and the supported IEC 60559 encodings with pmax radix b digits can be rounded
|
|
to a floating-point number with n decimal digits and back again without change to the value,
|
|
(
|
|
pmax log10 b if b is a power of 10
|
|
⌈1 + pmax log10 b⌉ otherwise
|
|
|
|
DECIMAL_DIG 10
|
|
|
|
This is an obsolescent feature, see <a href='#7.33.8'>7.33.8</a>.
|
|
— number of decimal digits, q, such that any floating-point number with q decimal digits can be
|
|
rounded into a floating-point number with p radix b digits and back again without change to
|
|
the q decimal digits,
|
|
(
|
|
p log10 b if b is a power of 10
|
|
⌊(p − 1) log10 b⌋ otherwise
|
|
|
|
FLT_DIG 6
|
|
DBL_DIG 10
|
|
LDBL_DIG 10
|
|
|
|
|
|
— minimum negative integer such that FLT_RADIX raised to one less than that power is a normal-
|
|
ized floating-point number, emin
|
|
|
|
FLT_MIN_EXP
|
|
DBL_MIN_EXP
|
|
LDBL_MIN_EXP
|
|
|
|
|
|
— minimum negative integer
|
|
 such that10 raised to that power is in the range of normalized
|
|
floating-point numbers, log10 bemin −1
|
|
|
|
FLT_MIN_10_EXP -37
|
|
DBL_MIN_10_EXP -37
|
|
LDBL_MIN_10_EXP -37
|
|
|
|
|
|
— maximum integer such that FLT_RADIX raised to one less than that power is a representable
|
|
finite floating-point number; if that representable finite floating-point number is normalized,
|
|
the value of the macro is emax
|
|
|
|
FLT_MAX_EXP
|
|
DBL_MAX_EXP
|
|
LDBL_MAX_EXP
|
|
|
|
|
|
— maximum integer such that 10 raised to that power is in the range of representable finite
|
|
floating-point numbers, ⌊log10 ((1 − b−p )bemax )⌋
|
|
|
|
FLT_MAX_10_EXP +37
|
|
DBL_MAX_10_EXP +37
|
|
LDBL_MAX_10_EXP +37
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.2p25'></a>
|
|
<pre>25 The values given in the following list shall be replaced by constant expressions with implementation-
|
|
defined values that are greater than or equal to those shown:
|
|
|
|
— maximum representable finite floating-point number; if that number is normalized, its value is
|
|
(1 − b−p )bemax
|
|
FLT_MAX 1E+37
|
|
DBL_MAX 1E+37
|
|
LDBL_MAX 1E+37
|
|
|
|
|
|
— maximum normalized floating-point number, (1 − b−p )bemax
|
|
|
|
FLT_NORM_MAX 1E+37
|
|
DBL_NORM_MAX 1E+37
|
|
LDBL_NORM_MAX 1E+37
|
|
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.2p26'></a>
|
|
<pre>26 The values given in the following list shall be replaced by constant expressions with implementation-
|
|
defined (positive) values that are less than or equal to those shown:
|
|
|
|
— the difference between 1 and the least normalized value greater than 1 that is representable in
|
|
the given floating type, b1−p
|
|
|
|
FLT_EPSILON 1E-5
|
|
DBL_EPSILON 1E-9
|
|
LDBL_EPSILON 1E-9
|
|
|
|
|
|
— minimum normalized positive floating-point number, bemin −1
|
|
|
|
FLT_MIN 1E-37
|
|
DBL_MIN 1E-37
|
|
LDBL_MIN 1E-37
|
|
|
|
|
|
— minimum positive floating-point number<a href='#FOOTNOTE.28'><sup>[28]</sup></a>
|
|
|
|
FLT_TRUE_MIN 1E-37
|
|
DBL_TRUE_MIN 1E-37
|
|
LDBL_TRUE_MIN 1E-37
|
|
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.28'>
|
|
<pre><i><b>Footnote 28)</b> If the presence or absence of subnormal numbers is indeterminable, then the value is intended to be a positive number
|
|
no greater than the minimum normalized positive number for the type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p27'></a>
|
|
<pre>27 Conversion between real floating type and decimal character sequence with at most T_DECIMAL_DIG
|
|
digits should be correctly rounded, where T is the macro prefix for the type. This assures conversion
|
|
from real floating type to decimal character sequence with T_DECIMAL_DIG digits and back, using
|
|
to-nearest rounding, is the identity function.
|
|
</pre>
|
|
<a name='5.2.4.2.2p28'></a>
|
|
<pre>28 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum requirements of this
|
|
document, and the appropriate values in a <float.h> header for type float:
|
|
6
|
|
x = s16e fk 16−k ,
|
|
P
|
|
−31 ≤ e ≤ +32
|
|
k=1
|
|
|
|
|
|
|
|
FLT_RADIX 16
|
|
FLT_MANT_DIG 6
|
|
FLT_EPSILON 9.53674316E-07F
|
|
FLT_DECIMAL_DIG 9
|
|
FLT_DIG 6
|
|
FLT_MIN_EXP -31
|
|
FLT_MIN <a href='#2.'>2.</a>93873588E-39F
|
|
FLT_MIN_10_EXP -38
|
|
FLT_MAX_EXP +32
|
|
FLT_MAX <a href='#3.'>3.</a>40282347E+38F
|
|
FLT_MAX_10_EXP +38
|
|
</pre>
|
|
<a name='5.2.4.2.2p29'></a>
|
|
<pre>29 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for single-precision and
|
|
double-precision numbers in IEC 60559,<a href='#FOOTNOTE.29'><sup>[29]</sup></a> and the appropriate values in a <float.h> header for types float and double:
|
|
24
|
|
xf = s2e fk 2−k ,
|
|
P
|
|
−125 ≤ e ≤ +128
|
|
k=1
|
|
|
|
53
|
|
xd = s2e fk 2−k ,
|
|
P
|
|
−1021 ≤ e ≤ +1024
|
|
k=1
|
|
|
|
|
|
|
|
FLT_IS_IEC_60559 2
|
|
FLT_RADIX 2
|
|
FLT_MANT_DIG 24
|
|
FLT_EPSILON <a href='#1.'>1.</a>19209290E-07F // decimal constant
|
|
FLT_EPSILON 0X1P-23F // hex constant
|
|
FLT_DECIMAL_DIG 9
|
|
FLT_DIG 6
|
|
FLT_MIN_EXP -125
|
|
FLT_MIN <a href='#1.'>1.</a>17549435E-38F // decimal constant
|
|
FLT_MIN 0X1P-126F // hex constant
|
|
FLT_TRUE_MIN <a href='#1.'>1.</a>40129846E-45F // decimal constant
|
|
FLT_TRUE_MIN 0X1P-149F // hex constant
|
|
FLT_HAS_SUBNORM 1
|
|
FLT_MIN_10_EXP -37
|
|
FLT_MAX_EXP +128
|
|
FLT_MAX <a href='#3.'>3.</a>40282347E+38F // decimal constant
|
|
FLT_MAX 0X1.fffffeP127F // hex constant
|
|
FLT_MAX_10_EXP +38
|
|
DBL_MANT_DIG 53
|
|
DBL_IS_IEC_60559 2
|
|
DBL_EPSILON <a href='#2.'>2.</a>2204460492503131E-16 // decimal constant
|
|
DBL_EPSILON 0X1P-52 // hex constant
|
|
DBL_DECIMAL_DIG 17
|
|
DBL_DIG 15
|
|
DBL_MIN_EXP -1021
|
|
DBL_MIN <a href='#2.'>2.</a>2250738585072014E-308 // decimal constant
|
|
DBL_MIN 0X1P-1022 // hex constant
|
|
DBL_TRUE_MIN <a href='#4.'>4.</a>9406564584124654E-324 // decimal constant
|
|
DBL_TRUE_MIN 0X1P-1074 // hex constant
|
|
DBL_HAS_SUBNORM 1
|
|
DBL_MIN_10_EXP -307
|
|
DBL_MAX_EXP +1024
|
|
DBL_MAX <a href='#1.'>1.</a>7976931348623157E+308 // decimal constant
|
|
DBL_MAX 0X1.fffffffffffffP1023 // hex constant
|
|
DBL_MAX_10_EXP +308
|
|
|
|
|
|
Forward references: conditional inclusion (<a href='#6.10.1'>6.10.1</a>), predefined macro names (<a href='#6.10.9'>6.10.9</a>), complex arith-
|
|
metic <complex.h> (<a href='#7.3'>7.3</a>), extended multibyte and wide character utilities <wchar.h> (<a href='#7.31'>7.31</a>), floating-
|
|
point environment <fenv.h> (<a href='#7.6'>7.6</a>), general utilities <stdlib.h> (<a href='#7.24'>7.24</a>), input/output <stdio.h>
|
|
(<a href='#7.23'>7.23</a>), mathematics <math.h> (<a href='#7.12'>7.12</a>), IEC 60559 floating-point arithmetic (Annex F), IEC 60559-
|
|
compatible complex arithmetic (Annex G).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.29'>
|
|
<pre><i><b>Footnote 29)</b> The floating-point model in that standard sums powers of b from zero, so the values of the exponent limits are one less
|
|
than shown here.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.3'></a>
|
|
<hr>
|
|
<h3>5.2.4.2.3 [Characteristics of decimal floating types in <float.h>]</h3>
|
|
<a name='5.2.4.2.3p1'></a>
|
|
<pre>1 This subclause specifies macros in <float.h> that provide characteristics of decimal floating types
|
|
(an optional feature) in terms of the model presented in <a href='#5.2.4.2.2'>5.2.4.2.2</a>. An implementation that does not
|
|
support decimal floating types shall not provide these macros. The prefixes DEC32_, DEC64_, and
|
|
DEC128_ denote the types _Decimal32 , _Decimal64 , and _Decimal128 respectively.
|
|
</pre>
|
|
<a name='5.2.4.2.3p2'></a>
|
|
<pre>2 DEC_EVAL_METHOD is the decimal floating-point analog of FLT_EVAL_METHOD (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). Its
|
|
implementation-defined value characterizes the use of evaluation formats for decimal floating
|
|
types:
|
|
|
|
−1 indeterminable;
|
|
|
|
0 evaluate all operations and constants just to the range and precision of the type;
|
|
|
|
1 evaluate operations and constants of type _Decimal32 and _Decimal64 to the range and
|
|
precision of the _Decimal64 type, evaluate _Decimal128 operations and constants to the
|
|
range and precision of the _Decimal128 type;
|
|
|
|
2 evaluate all operations and constants to the range and precision of the _Decimal128 type.
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.3p3'></a>
|
|
<pre>3 Each of the decimal signaling NaN macros
|
|
|
|
DEC32_SNAN
|
|
DEC64_SNAN
|
|
DEC128_SNAN
|
|
|
|
|
|
expands to a constant expression of the respective decimal floating type representing a signaling
|
|
NaN. If an optional unary + or - operator followed by a signaling NaN macro is used for initializing
|
|
an object of the same type that has static or thread storage duration, the object is initialized with a
|
|
signaling NaN value.
|
|
</pre>
|
|
<a name='5.2.4.2.3p4'></a>
|
|
<pre>4 The macro
|
|
|
|
DEC_INFINITY
|
|
|
|
|
|
expands to a constant expression of type _Decimal32 representing positive infinity.
|
|
</pre>
|
|
<a name='5.2.4.2.3p5'></a>
|
|
<pre>5 The macro
|
|
|
|
DEC_NAN
|
|
|
|
|
|
expands to a constant expression of type _Decimal32 representing a quiet NaN.
|
|
</pre>
|
|
<a name='5.2.4.2.3p6'></a>
|
|
<pre>6 The integer values given in the following lists shall be replaced by constant expressions suitable for
|
|
use in #if preprocessing directives:
|
|
|
|
— radix of exponent representation, b(=10)
|
|
For the standard floating types, this value is implementation-defined and is specified by the
|
|
macro FLT_RADIX. For the decimal floating types there is no corresponding macro, since the
|
|
value 10 is an inherent property of the types. Wherever FLT_RADIX appears in a description
|
|
of a function that has versions that operate on decimal floating types, it is noted that for the
|
|
decimal floating-point versions the value used is implicitly 10, rather than FLT_RADIX.
|
|
|
|
— number of digits in the coefficient
|
|
|
|
DEC32_MANT_DIG 7
|
|
DEC64_MANT_DIG 16
|
|
DEC128_MANT_DIG 34
|
|
|
|
|
|
— minimum exponent
|
|
|
|
DEC32_MIN_EXP -94
|
|
DEC64_MIN_EXP -382
|
|
DEC128_MIN_EXP -6142
|
|
|
|
|
|
— maximum exponent
|
|
DEC32_MAX_EXP 97
|
|
DEC64_MAX_EXP 385
|
|
DEC128_MAX_EXP 6145
|
|
|
|
|
|
— maximum representable finite decimal floating-point number (there are 6, 15 and 33 9’s after
|
|
the decimal points respectively)
|
|
|
|
DEC32_MAX 9.999999E96DF
|
|
DEC64_MAX 9.999999999999999E384DD
|
|
DEC128_MAX 9.999999999999999999999999999999999E6144DL
|
|
|
|
|
|
— the difference between 1 and the least value greater than 1 that is representable in the given
|
|
floating type
|
|
|
|
DEC32_EPSILON 1E-6DF
|
|
DEC64_EPSILON 1E-15DD
|
|
DEC128_EPSILON 1E-33DL
|
|
|
|
|
|
— minimum normalized positive decimal floating-point number
|
|
|
|
DEC32_MIN 1E-95DF
|
|
DEC64_MIN 1E-383DD
|
|
DEC128_MIN 1E-6143DL
|
|
|
|
|
|
— minimum positive subnormal decimal floating-point number
|
|
|
|
DEC32_TRUE_MIN 0.000001E-95DF
|
|
DEC64_TRUE_MIN 0.000000000000001E-383DD
|
|
DEC128_TRUE_MIN 0.000000000000000000000000000000001E-6143DL
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.3p7'></a>
|
|
<pre>7 For decimal floating-point arithmetic, it is often convenient to consider an alternate equivalent
|
|
model where the significand is represented with integer rather than fraction digits. With s, b, e, p,
|
|
and fk as defined in <a href='#5.2.4.2.2'>5.2.4.2.2</a>, a floating-point number x is defined by the model:
|
|
p
|
|
X
|
|
(e−p)
|
|
x=s·b fk · b(p−k)
|
|
k=1
|
|
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.3p8'></a>
|
|
<pre>8 With b fixed to 10, a decimal floating-point number x is thus:
|
|
p
|
|
X
|
|
(e−p)
|
|
x = s · 10 fk · 10(p−k)
|
|
k=1
|
|
|
|
The quantum exponent is q = e − p and the coefficient is c = f1 f2 · · · fp , which is an integer between
|
|
0 and 10(p−1) , inclusive. Thus, x = s · c · 10q is represented by the triple of integers (s, c, q). The
|
|
quantum of x is 10q , which is the value of a unit in the last place of the coefficient.
|
|
|
|
Quantum exponent ranges
|
|
|
|
Type _Decimal32 _Decimal64 _Decimal128
|
|
Maximum Quantum Exponent (qmax ) 90 369 6111
|
|
Minimum Quantum Exponent (qmin ) −101 −398 −6176
|
|
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.3p9'></a>
|
|
<pre>9 For binary floating-point arithmetic following IEC 60559, representations in the model described
|
|
in <a href='#5.2.4.2.2'>5.2.4.2.2</a> that have the same numerical value are indistinguishable in the arithmetic. However, for
|
|
decimal floating-point arithmetic, representations that have the same numerical value but different
|
|
quantum exponents, e.g., (+1, 10, −1) representing 1.0 and (+1, 100, −2) representing 1.00, are
|
|
distinguishable. To facilitate exact fixed-point calculation, operation results that are of decimal
|
|
floating type have a preferred quantum exponent, as specified in IEC 60559, which is determined
|
|
by the quantum exponents of the operands if they have decimal floating types (or by specific
|
|
rules for conversions from other types). The table below gives rules for determining preferred
|
|
quantum exponents for results of IEC 60559 operations, and for other operations specified in
|
|
this document. When exact, these operations produce a result with their preferred quantum
|
|
exponent, or as close to it as possible within the limitations of the type. When inexact, these
|
|
operations produce a result with the least possible quantum exponent. For example, the preferred
|
|
quantum exponent for addition is the minimum of the quantum exponents of the operands. Hence
|
|
(+1, 123, −2) + (+1, 4000, −3) = (+1, 5230, −3) or 1.23 + 4.000 = 5.230.
|
|
</pre>
|
|
<a name='5.2.4.2.3p10'></a>
|
|
<pre>10 The following table shows, for each operation delivering a result in decimal floating-point format,
|
|
how the preferred quantum exponents of the operands, Q(x), Q(y), etc., determine the preferred
|
|
quantum exponent of the operation result, provided the table formula is defined for the arguments.
|
|
For the cases where the formula is undefined and the function result is ±∞, the preferred quantum
|
|
exponent is immaterial because the quantum exponent of ±∞ is defined to be infinity. For the
|
|
other cases where the formula is undefined and the function result is finite, the preferred quantum
|
|
exponent is unspecified<a href='#FOOTNOTE.30'><sup>[30]</sup></a> .
|
|
|
|
Preferred quantum exponents
|
|
|
|
Operation Preferred quantum exponent of result
|
|
roundeven, round, trunc, ceil, floor, max(Q(x), 0)
|
|
rint, nearbyint
|
|
nextup, nextdown, nextafter, nexttoward least possible
|
|
remainder min(Q(x), Q(y))
|
|
fmin, fmax, fminimum, fmaximum, Q(x) if x gives the result, Q(y) if y gives the result
|
|
fminimum_mag, fmaximum_mag,
|
|
fminimum_num, fmaximum_num,
|
|
fminimum_mag_num, fmaximum_mag_num
|
|
scalbn, scalbln Q(x) + n
|
|
ldexp Q(x) + p
|
|
logb 0
|
|
+ , d32add, d64add min(Q(x), Q(y))
|
|
- , d32sub, d64sub min(Q(x), Q(y))
|
|
* , d32mul, d64mul Q(x) + Q(y)
|
|
/ , d32div, d64div Q(x) − Q(y)
|
|
sqrt, d32sqrt, d64sqrt ⌊Q(x)/2⌋
|
|
fma, d32fma, d64fma min(Q(x) + Q(y), Q(z))
|
|
conversion from integer type 0
|
|
exact conversion from non-decimal floating 0
|
|
type
|
|
inexact conversion from non-decimal floating least possible
|
|
type
|
|
conversion between decimal floating types Q(x)
|
|
*cx returned by canonicalize Q(*x )
|
|
strto, wcsto, scanf, floating constants of see <a href='#7.24.1.6'>7.24.1.6</a>
|
|
decimal floating type
|
|
-(x) , +(x) Q(x)
|
|
fabs Q(x)
|
|
copysign Q(x)
|
|
quantize Q(y)
|
|
quantum Q(x)
|
|
*encptr returned by encodedec, encodebin Q(*xptr )
|
|
*xptr returned by decodedec, decodebin Q(*encptr )
|
|
fmod min(Q(x), Q(y))
|
|
fdim min((Q(x), Q(y)) if x > y, 0 if x ≤ y
|
|
cbrt ⌊Q(x)/3⌋
|
|
hypot min(Q(x), Q(y))
|
|
pow ⌊y × Q(x)⌋
|
|
modf Q(value)
|
|
*iptr returned by modf max(Q(value), 0)
|
|
frexp Q(value) if value = 0, –(length of coefficient of
|
|
value) otherwise
|
|
*res returned by setpayload, 0 if pl does not represent a valid payload, not
|
|
setpayloadsig applicable otherwise (NaN returned)
|
|
getpayload 0 if *x is a NaN, unspecified otherwise
|
|
compoundn ⌊n × min(0, Q(x))⌋
|
|
pown ⌊n × Q(x)⌋
|
|
powr ⌊y × Q(x)⌋
|
|
rootn ⌊Q(x)/n⌋
|
|
rsqrt −⌊Q(x)/2⌋
|
|
transcendental functions 0
|
|
|
|
|
|
A function family listed in the table above indicates the functions for all decimal floating types,
|
|
where the function family is represented by the name of the functions without a suffix. For example,
|
|
ceil indicates the functions ceild32, ceild64, and ceild128.
|
|
Forward references: extended multibyte and wide character utilities <wchar.h> (<a href='#7.31'>7.31</a>), floating-
|
|
point environment <fenv.h> (<a href='#7.6'>7.6</a>), general utilities <stdlib.h> (<a href='#7.24'>7.24</a>), input/output <stdio.h>
|
|
(<a href='#7.23'>7.23</a>), mathematics <math.h> (<a href='#7.12'>7.12</a>), type-generic mathematics <tgmath.h> (<a href='#7.27'>7.27</a>), IEC 60559
|
|
floating-point arithmetic (Annex F).
|
|
</pre>
|
|
<a name='FOOTNOTE.30'>
|
|
<pre><i><b>Footnote 30)</b> Although unspecified in IEC 60559, a preferred quantum exponent of 0 for these cases would be a reasonable implemen-
|
|
tation choice.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.'></a>
|
|
<hr>
|
|
<h3>6. [Language]</h3>
|
|
<a name='6.1'></a>
|
|
<hr>
|
|
<h3>6.1 [Notation]</h3>
|
|
<a name='6.1p1'></a>
|
|
<pre>1 In the syntax notation used in this clause, syntactic categories (nonterminals) are indicated by italic
|
|
type, and literal words and character set members (terminals) by bold type. A colon (:) following
|
|
a nonterminal introduces its definition. Alternative definitions are listed on separate lines, except
|
|
when prefaced by the words "one of". An optional symbol is indicated by the subscript "opt", so
|
|
that
|
|
{ expressionopt }
|
|
indicates an optional expression enclosed in braces.
|
|
</pre>
|
|
<a name='6.1p2'></a>
|
|
<pre>2 When syntactic categories are referred to in the main text, they are not italicized and words are
|
|
separated by spaces instead of hyphens.
|
|
</pre>
|
|
<a name='6.1p3'></a>
|
|
<pre>3 A summary of the language syntax is given in Annex A.
|
|
|
|
</pre>
|
|
<a name='6.2'></a>
|
|
<hr>
|
|
<h3>6.2 [Concepts]</h3>
|
|
<a name='6.2.1'></a>
|
|
<hr>
|
|
<h3>6.2.1 [Scopes of identifiers]</h3>
|
|
<a name='6.2.1p1'></a>
|
|
<pre>1 An identifier can denote:
|
|
|
|
— an object; a function;
|
|
— a tag or a member of a structure, union, or enumeration;
|
|
— a typedef name;
|
|
— a label name;
|
|
— a macro name;
|
|
— or, a macro parameter.
|
|
|
|
The same identifier can denote different entities at different points in the program. A member
|
|
of an enumeration is called an enumeration constant. Macro names and macro parameters are not
|
|
considered further here, because prior to the semantic phase of program translation any occurrences
|
|
of macro names in the source file are replaced by the preprocessing token sequences that constitute
|
|
their macro definitions.
|
|
</pre>
|
|
<a name='6.2.1p2'></a>
|
|
<pre>2 For each different entity that an identifier designates, the identifier is visible (i.e., can be used) only
|
|
within a region of program text called its scope. Different entities designated by the same identifier
|
|
either have different scopes, or are in different name spaces. There are four kinds of scopes: function,
|
|
file, block, and function prototype. (A function prototype is a declaration of a function.)
|
|
</pre>
|
|
<a name='6.2.1p3'></a>
|
|
<pre>3 A label name is the only kind of identifier that has function scope. It can be used (in a goto statement)
|
|
anywhere in the function in which it appears, and is declared implicitly by its syntactic appearance
|
|
(followed by a : and a statement).
|
|
</pre>
|
|
<a name='6.2.1p4'></a>
|
|
<pre>4 Every other identifier has scope determined by the placement of its declaration (in a declarator or
|
|
type specifier). If the declarator or type specifier that declares the identifier appears outside of any
|
|
block or list of parameters, the identifier has file scope, which terminates at the end of the translation
|
|
unit. If the declarator or type specifier that declares the identifier appears inside a block or within the
|
|
list of parameter declarations in a function definition, the identifier has block scope, which terminates
|
|
at the end of the associated block. If the declarator or type specifier that declares the identifier
|
|
appears within the list of parameter declarations in a function prototype (not part of a function
|
|
definition), the identifier has function prototype scope, which terminates at the end of the function
|
|
declarator. If an identifier designates two different entities in the same name space, the scopes might
|
|
overlap. If so, the scope of one entity (the inner scope) will end strictly before the scope of the other
|
|
entity (the outer scope). Within the inner scope, the identifier designates the entity declared in the
|
|
inner scope; the entity declared in the outer scope is hidden (and not visible) within the inner scope.
|
|
</pre>
|
|
<a name='6.2.1p5'></a>
|
|
<pre>5 Unless explicitly stated otherwise, where this document uses the term "identifier" to refer to some
|
|
entity (as opposed to the syntactic construct), it refers to the entity in the relevant name space whose
|
|
declaration is visible at the point the identifier occurs.
|
|
</pre>
|
|
<a name='6.2.1p6'></a>
|
|
<pre>6 Two identifiers have the same scope if and only if their scopes terminate at the same point.
|
|
</pre>
|
|
<a name='6.2.1p7'></a>
|
|
<pre>7 Structure, union, and enumeration tags have scope that begins just after the appearance of the tag
|
|
in a type specifier that declares the tag. Each enumeration constant has scope that begins just after
|
|
the appearance of its defining enumerator in an enumerator list. An ordinary identifier that has an
|
|
underspecified definition has scope that starts when the definition is completed; if the same ordinary
|
|
identifier declares another entity with a scope that encloses the current block, that declaration is
|
|
hidden as soon as the inner declarator is completed<a href='#FOOTNOTE.31'><sup>[31]</sup></a> . Any other identifier has scope that begins
|
|
just after the completion of its declarator.
|
|
</pre>
|
|
<a name='FOOTNOTE.31'>
|
|
<pre><i><b>Footnote 31)</b> That means, that the outer declaration is not visible for the initializer
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.1p8'></a>
|
|
<pre>8 As a special case, a type name (which is not a declaration of an identifier) is considered to have
|
|
a scope that begins just after the place within the type name where the omitted identifier would
|
|
appear were it not omitted.
|
|
Forward references: declarations (<a href='#6.7'>6.7</a>), function calls (<a href='#6.5.2.2'>6.5.2.2</a>), function definitions (<a href='#6.9.1'>6.9.1</a>), identifiers
|
|
(<a href='#6.4.2'>6.4.2</a>), macro replacement (<a href='#6.10.4'>6.10.4</a>), name spaces of identifiers (<a href='#6.2.3'>6.2.3</a>), source file inclusion (<a href='#6.10.2'>6.10.2</a>),
|
|
statements and blocks (<a href='#6.8'>6.8</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.2'></a>
|
|
<hr>
|
|
<h3>6.2.2 [Linkages of identifiers]</h3>
|
|
<a name='6.2.2p1'></a>
|
|
<pre>1 An identifier declared in different scopes or in the same scope more than once can be made to refer
|
|
to the same object or function by a process called linkage<a href='#FOOTNOTE.32'><sup>[32]</sup></a> . There are three kinds of linkage: external,
|
|
internal, and none.
|
|
</pre>
|
|
<a name='FOOTNOTE.32'>
|
|
<pre><i><b>Footnote 32)</b> There is no linkage between different identifiers.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.2p2'></a>
|
|
<pre>2 In the set of translation units and libraries that constitutes an entire program, each declaration of a
|
|
particular identifier with external linkage denotes the same object or function. Within one translation
|
|
unit, each declaration of an identifier with internal linkage denotes the same object or function. Each
|
|
declaration of an identifier with no linkage denotes a unique entity.
|
|
</pre>
|
|
<a name='6.2.2p3'></a>
|
|
<pre>3 If the declaration of a file scope identifier for:
|
|
|
|
— an object contains any of the storage-class specifiers static or constexpr;
|
|
— or, a function contains the storage-class specifier static,
|
|
|
|
then the identifier has internal linkage<a href='#FOOTNOTE.33'><sup>[33]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.33'>
|
|
<pre><i><b>Footnote 33)</b> A function declaration can contain the storage-class specifier static only if it is at file scope; see <a href='#6.7.1'>6.7.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.2p4'></a>
|
|
<pre>4 For an identifier declared with the storage-class specifier extern in a scope in which a prior dec-
|
|
laration of that identifier is visible<a href='#FOOTNOTE.34'><sup>[34]</sup></a> , if the prior declaration specifies internal or external linkage,
|
|
the linkage of the identifier at the later declaration is the same as the linkage specified at the prior
|
|
declaration. If no prior declaration is visible, or if the prior declaration specifies no linkage, then the
|
|
identifier has external linkage.
|
|
</pre>
|
|
<a name='FOOTNOTE.34'>
|
|
<pre><i><b>Footnote 34)</b> As specified in <a href='#6.2.1'>6.2.1</a>, the later declaration might hide the prior declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.2p5'></a>
|
|
<pre>5 If the declaration of an identifier for a function has no storage-class specifier, its linkage is determined
|
|
exactly as if it were declared with the storage-class specifier extern. If the declaration of an identifier
|
|
for an object has file scope and no storage-class specifier or only the specifier auto, its linkage is
|
|
external.
|
|
</pre>
|
|
<a name='6.2.2p6'></a>
|
|
<pre>6 The following identifiers have no linkage: an identifier declared to be anything other than an object
|
|
or a function; an identifier declared to be a function parameter; a block scope identifier for an object
|
|
declared without the storage-class specifier extern.
|
|
</pre>
|
|
<a name='6.2.2p7'></a>
|
|
<pre>7 If, within a translation unit, the same identifier appears with both internal and external linkage, the
|
|
behavior is undefined.
|
|
Forward references: declarations (<a href='#6.7'>6.7</a>), expressions (<a href='#6.5'>6.5</a>), external definitions (<a href='#6.9'>6.9</a>), statements (<a href='#6.8'>6.8</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.3'></a>
|
|
<hr>
|
|
<h3>6.2.3 [Name spaces of identifiers]</h3>
|
|
<a name='6.2.3p1'></a>
|
|
<pre>1 If more than one declaration of a particular identifier is visible at any point in a translation unit, the
|
|
syntactic context disambiguates uses that refer to different entities. Thus, there are separate name
|
|
spaces for various categories of identifiers, as follows:
|
|
|
|
— label names (disambiguated by the syntax of the label declaration and use);
|
|
|
|
— the tags of structures, unions, and enumerations (disambiguated by following any35) of the
|
|
keywords struct, union, or enum);
|
|
|
|
— the members of structures or unions; each structure or union has a separate name space for its
|
|
members (disambiguated by the type of the expression used to access the member via the . or
|
|
-> operator);
|
|
|
|
— standard attributes and attribute prefixes (disambiguated by the syntax of the attribute specifier
|
|
and name of the attribute token) (<a href='#6.7.12'>6.7.12</a>);
|
|
|
|
— the trailing identifier in an attribute prefixed token; each attribute prefix has a separate name
|
|
space for the implementation-defined attributes that it introduces (disambiguated by the
|
|
attribute prefix and the trailing identifier token);
|
|
|
|
— all other identifiers, called ordinary identifiers (declared in ordinary declarators or as enumera-
|
|
tion constants).
|
|
|
|
Forward references: enumeration specifiers (<a href='#6.7.2.2'>6.7.2.2</a>), labeled statements (<a href='#6.8.1'>6.8.1</a>), structure and union
|
|
specifiers (<a href='#6.7.2.1'>6.7.2.1</a>), structure and union members (<a href='#6.5.2.3'>6.5.2.3</a>), tags (<a href='#6.7.2.3'>6.7.2.3</a>), the goto statement (<a href='#6.8.6.1'>6.8.6.1</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.4'></a>
|
|
<hr>
|
|
<h3>6.2.4 [Storage durations of objects]</h3>
|
|
<a name='6.2.4p1'></a>
|
|
<pre>1 An object has a storage duration that determines its lifetime. There are four storage durations: static,
|
|
thread, automatic, and allocated. Allocated storage is described in <a href='#7.24.3'>7.24.3</a>.
|
|
</pre>
|
|
<a name='6.2.4p2'></a>
|
|
<pre>2 The lifetime of an object is the portion of program execution during which storage is guaranteed
|
|
to be reserved for it. An object exists, has a constant address<a href='#FOOTNOTE.36'><sup>[36]</sup></a> , and retains its last-stored value
|
|
throughout its lifetime<a href='#FOOTNOTE.37'><sup>[37]</sup></a> . If an object is referred to outside of its lifetime, the behavior is undefined.
|
|
If a pointer value is used in an evaluation after the object the pointer points to (or just past) reaches
|
|
the end of its lifetime, the behavior is undefined. The representation of a pointer object becomes
|
|
indeterminate when the object the pointer points to (or just past) reaches the end of its lifetime.
|
|
</pre>
|
|
<a name='FOOTNOTE.36'>
|
|
<pre><i><b>Footnote 36)</b> The term "constant address" means that two pointers to the object constructed at possibly different times will compare
|
|
equal. The address can be different during two different executions of the same program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.37'>
|
|
<pre><i><b>Footnote 37)</b> In the case of a volatile object, the last store need not be explicit in the program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.4p3'></a>
|
|
<pre>3 An object whose identifier is declared without the storage-class specifier thread_local, and either
|
|
with external or internal linkage or with the storage-class specifier static, has static storage duration.
|
|
Its lifetime is the entire execution of the program and its stored value is initialized only once, prior
|
|
to program startup.
|
|
</pre>
|
|
<a name='6.2.4p4'></a>
|
|
<pre>4 An object whose identifier is declared with the storage-class specifier thread_local has thread
|
|
storage duration. Its lifetime is the entire execution of the thread for which it is created, and its
|
|
stored value is initialized when the thread is started. There is a distinct object per thread, and use of
|
|
the declared name in an expression refers to the object associated with the thread evaluating the
|
|
expression. The result of attempting to indirectly access an object with thread storage duration from
|
|
a thread other than the one with which the object is associated is implementation-defined.
|
|
</pre>
|
|
<a name='6.2.4p5'></a>
|
|
<pre>5 An object whose identifier is declared with no linkage and without the storage-class specifier static
|
|
has automatic storage duration, as do some compound literals. The result of attempting to indirectly
|
|
access an object with automatic storage duration from a thread other than the one with which the
|
|
object is associated is implementation-defined.
|
|
</pre>
|
|
<a name='6.2.4p6'></a>
|
|
<pre>6 For such an object that does not have a variable length array type, its lifetime extends from entry
|
|
into the block with which it is associated until execution of that block ends in any way. (Entering
|
|
an enclosed block or calling a function suspends, but does not end, execution of the current block.)
|
|
If the block is entered recursively, a new instance of the object is created each time. The initial
|
|
representation of the object is indeterminate. If an initialization is specified for the object, it is
|
|
performed each time the declaration or compound literal is reached in the execution of the block;
|
|
otherwise, the representation of the object becomes indeterminate each time the declaration is
|
|
reached.
|
|
</pre>
|
|
<a name='6.2.4p7'></a>
|
|
<pre>7 For such an object that does have a variable length array type, its lifetime extends from the declaration
|
|
of the object until execution of the program leaves the scope of the declaration<a href='#FOOTNOTE.38'><sup>[38]</sup></a> . If the scope is
|
|
entered recursively, a new instance of the object is created each time. The initial representation of
|
|
the object is indeterminate.
|
|
</pre>
|
|
<a name='FOOTNOTE.38'>
|
|
<pre><i><b>Footnote 38)</b> Leaving the innermost block containing the declaration, or jumping to a point in that block or an embedded block prior
|
|
to the declaration, leaves the scope of the declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.4p8'></a>
|
|
<pre>8 A non-lvalue expression with structure or union type, where the structure or union contains a
|
|
member with array type (including, recursively, members of all contained structures and unions)
|
|
refers to an object with automatic storage duration and temporary lifetime.<a href='#FOOTNOTE.39'><sup>[39]</sup></a> Its lifetime begins
|
|
when the expression is evaluated and its initial value is the value of the expression. Its lifetime ends
|
|
when the evaluation of the containing full expression ends. Any attempt to modify an object with
|
|
temporary lifetime results in undefined behavior. An object with temporary lifetime behaves as if it
|
|
were declared with the type of its value for the purposes of effective type. Such an object need not
|
|
have a unique address.
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>), compound literals (<a href='#6.5.2.5'>6.5.2.5</a>), declarators (<a href='#6.7.6'>6.7.6</a>),
|
|
function calls (<a href='#6.5.2.2'>6.5.2.2</a>), initialization (<a href='#6.7.10'>6.7.10</a>), statements (<a href='#6.8'>6.8</a>), effective type (<a href='#6.5'>6.5</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.39'>
|
|
<pre><i><b>Footnote 39)</b> The address of such an object is taken implicitly when an array member is accessed.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5'></a>
|
|
<hr>
|
|
<h3>6.2.5 [Types]</h3>
|
|
<a name='6.2.5p1'></a>
|
|
<pre>1 The meaning of a value stored in an object or returned by a function is determined by the type of the
|
|
expression used to access it. (An identifier declared to be an object is the simplest such expression;
|
|
the type is specified in the declaration of the identifier.) Types are partitioned into object types (types
|
|
that describe objects) and function types (types that describe functions). At various points within a
|
|
translation unit an object type may be incomplete<a href='#FOOTNOTE.40'><sup>[40]</sup></a> (lacking sufficient information to determine the
|
|
size of objects of that type) or complete (having sufficient information)41) .
|
|
</pre>
|
|
<a name='FOOTNOTE.40'>
|
|
<pre><i><b>Footnote 40)</b> An incomplete type can only be used when the size of an object of that type is not needed. It is not needed, for example,
|
|
when a typedef name is declared to be a specifier for a structure or union, or when a pointer to or a function returning a
|
|
structure or union is being declared. The specification has to be complete before such a function is called or defined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p2'></a>
|
|
<pre>2 An object declared as type bool is large enough to store the values false and true.
|
|
</pre>
|
|
<a name='6.2.5p3'></a>
|
|
<pre>3 An object declared as type char is large enough to store any member of the basic execution char-
|
|
acter set. If a member of the basic execution character set is stored in a char object, its value is
|
|
guaranteed to be nonnegative. If any other character is stored in a char object, the resulting value is
|
|
implementation-defined but shall be within the range of values that can be represented in that type.
|
|
</pre>
|
|
<a name='6.2.5p4'></a>
|
|
<pre>4 There are five standard signed integer types, designated as signed char, short int, int, long int,
|
|
and long long int. (These and other types may be designated in several additional ways, as
|
|
described in <a href='#6.7.2'>6.7.2</a>.)
|
|
</pre>
|
|
<a name='6.2.5p5'></a>
|
|
<pre>5 A bit-precise signed integer type is designated as _BitInt( N) where N is an integer constant expression
|
|
that specifies the number of bits that are used to represent the type, including the sign bit. Each
|
|
value of N designates a distinct type<a href='#FOOTNOTE.42'><sup>[42]</sup></a> . There may also be implementation-defined extended signed
|
|
integer types <a href='#FOOTNOTE.43'><sup>[43]</sup></a> . The standard signed integer types, bit-precise signed integer types, and extended
|
|
signed integer types are collectively called signed integer types. <a href='#FOOTNOTE.44'><sup>[44]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.42'>
|
|
<pre><i><b>Footnote 42)</b> Thus, _BitInt(3) is not the same type as _BitInt(4) .
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.43'>
|
|
<pre><i><b>Footnote 43)</b> Implementation-defined keywords have the form of an identifier reserved for any use as described in <a href='#7.1.3'>7.1.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.44'>
|
|
<pre><i><b>Footnote 44)</b> Any statement in this document about signed integer types also applies to the bit-precise signed integer types and the
|
|
extended signed integer types, unless otherwise noted.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p6'></a>
|
|
<pre>6 An object declared as type signed char occupies the same amount of storage as a "plain" char
|
|
object. A "plain" int object has the natural size suggested by the architecture of the execution
|
|
environment (large enough to contain any value in the range INT_MIN to INT_MAX as defined in the
|
|
header <limits.h>).
|
|
</pre>
|
|
<a name='6.2.5p7'></a>
|
|
<pre>7 For each of the signed integer types, there is a corresponding (but different) unsigned integer type
|
|
(designated with the keyword unsigned) that uses the same amount of storage (including sign
|
|
information) and has the same alignment requirements. The type bool and the unsigned integer
|
|
types that correspond to the standard signed integer types are the standard unsigned integer types. The
|
|
unsigned integer types that correspond to the extended signed integer types are the extended unsigned
|
|
integer types. The unsigned integer types that correspond to the bit-precise signed integer types
|
|
are the bit-precise unsigned integer types. The standard unsigned integer types, bit-precise unsigned
|
|
integer types, and extended unsigned integer types are collectively called unsigned integer types.<a href='#FOOTNOTE.45'><sup>[45]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.45'>
|
|
<pre><i><b>Footnote 45)</b> Any statement in this document about unsigned integer types also applies to the bit-precise unsigned integer types and
|
|
the extended unsigned integer types, unless otherwise specified.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p8'></a>
|
|
<pre>8 The standard signed integer types and standard unsigned integer types are collectively called the
|
|
standard integer types; the bit-precise signed integer types and bit-precise unsigned integer types
|
|
are collectively called the bit-precise integer types the extended signed integer types and extended
|
|
unsigned integer types are collectively called the extended integer types.
|
|
</pre>
|
|
<a name='6.2.5p9'></a>
|
|
<pre>9 For any two integer types with the same signedness and different integer conversion rank (see
|
|
<a href='#6.3.1.1'>6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a subrange of the
|
|
values of the other type.
|
|
</pre>
|
|
<a name='6.2.5p10'></a>
|
|
<pre>10 The range of nonnegative values of a signed integer type is a subrange of the corresponding unsigned
|
|
integer type, and the representation of the same value in each type is the same.<a href='#FOOTNOTE.46'><sup>[46]</sup></a> The range of
|
|
representable values for the unsigned type is 0 to 2N − 1 (inclusive). A computation involving
|
|
unsigned operands can never produce an overflow, because arithmetic for the unsigned type is
|
|
performed modulo 2N .
|
|
</pre>
|
|
<a name='FOOTNOTE.46'>
|
|
<pre><i><b>Footnote 46)</b> The same representation and alignment requirements are meant to imply interchangeability as arguments to functions,
|
|
return values from functions, and members of unions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p11'></a>
|
|
<pre>11 There are three standard floating types, designated as float, double, and long double. <a href='#FOOTNOTE.47'><sup>[47]</sup></a> The set
|
|
of values of the type float is a subset of the set of values of the type double; the set of values of the
|
|
type double is a subset of the set of values of the type long double.
|
|
</pre>
|
|
<a name='FOOTNOTE.47'>
|
|
<pre><i><b>Footnote 47)</b> See "future language directions" (<a href='#6.11.1'>6.11.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p12'></a>
|
|
<pre>12 There are three decimal floating types, designated as _Decimal32 , _Decimal64 , and _Decimal128 .
|
|
Respectively, they have the IEC 60559 formats: decimal32,<a href='#FOOTNOTE.48'><sup>[48]</sup></a> decimal64, and decimal128. Decimal
|
|
floating types are real floating types.
|
|
</pre>
|
|
<a name='FOOTNOTE.48'>
|
|
<pre><i><b>Footnote 48)</b> IEC 60559 specifies decimal32 as a data-interchange format that does not require arithmetic support; however,
|
|
_Decimal32 is a fully supported arithmetic type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p13'></a>
|
|
<pre>13 The standard floating types and the decimal floating types are collectively called the real floating
|
|
types.
|
|
</pre>
|
|
<a name='6.2.5p14'></a>
|
|
<pre>14 There are three complex types, designated as float _Complex, double _Complex, and long double
|
|
_Complex .<a href='#FOOTNOTE.49'><sup>[49]</sup></a> (Complex types are a conditional feature that implementations need not support; see
|
|
<a href='#6.10.9.3'>6.10.9.3</a>.) The real floating and complex types are collectively called the floating types.
|
|
</pre>
|
|
<a name='FOOTNOTE.49'>
|
|
<pre><i><b>Footnote 49)</b> A specification for imaginary types is in Annex G.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p15'></a>
|
|
<pre>15 For each floating type there is a corresponding real type, which is always a real floating type. For real
|
|
floating types, it is the same type. For complex types, it is the type given by deleting the keyword
|
|
_Complex from the type name.
|
|
|
|
</pre>
|
|
<a name='6.2.5p16'></a>
|
|
<pre>16 Each complex type has the same representation and alignment requirements as an array type
|
|
containing exactly two elements of the corresponding real type; the first element is equal to the real
|
|
part, and the second element to the imaginary part, of the complex number.
|
|
</pre>
|
|
<a name='6.2.5p17'></a>
|
|
<pre>17 The type char, the signed and unsigned integer types, and the floating types are collectively called
|
|
the basic types. The basic types are complete object types. Even if the implementation defines two or
|
|
more basic types to have the same representation, they are nevertheless different types.<a href='#FOOTNOTE.50'><sup>[50]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.50'>
|
|
<pre><i><b>Footnote 50)</b> An implementation can define new keywords that provide alternative ways to designate a basic (or any other) type; this
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p18'></a>
|
|
<pre>18 The three types char, signed char, and unsigned char are collectively called the character types.
|
|
The implementation shall define char to have the same range, representation, and behavior as either
|
|
signed char or unsigned char.<a href='#FOOTNOTE.51'><sup>[51]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.51'>
|
|
<pre><i><b>Footnote 51)</b> CHAR_MIN, defined in <limits.h>, will have one of the values 0 or SCHAR_MIN, and this can be used to distinguish the
|
|
two options. Irrespective of the choice made, char is a separate type from the other two and is not compatible with either.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p19'></a>
|
|
<pre>19 An enumeration comprises a set of named integer constant values. Each distinct enumeration
|
|
constitutes a different enumerated type.
|
|
</pre>
|
|
<a name='6.2.5p20'></a>
|
|
<pre>20 The type char, the signed and unsigned integer types, and the enumerated types are collectively
|
|
called integer types. The integer and real floating types are collectively called real types.
|
|
</pre>
|
|
<a name='6.2.5p21'></a>
|
|
<pre>21 Integer and floating types are collectively called arithmetic types. Each arithmetic type belongs to
|
|
one type domain: the real type domain comprises the real types, the complex type domain comprises the
|
|
complex types.
|
|
</pre>
|
|
<a name='6.2.5p22'></a>
|
|
<pre>22 The void type comprises an empty set of values; it is an incomplete object type that cannot be
|
|
completed.
|
|
</pre>
|
|
<a name='6.2.5p23'></a>
|
|
<pre>23 Any number of derived types can be constructed from the object and function types, as follows:
|
|
|
|
— An array type describes a contiguously allocated nonempty set of objects with a particular
|
|
member object type, called the element type. The element type shall be complete whenever the
|
|
array type is specified. Array types are characterized by their element type and by the number
|
|
of elements in the array. An array type is said to be derived from its element type, and if its
|
|
element type is T, the array type is sometimes called "array of T". The construction of an array
|
|
type from an element type is called "array type derivation".
|
|
|
|
— A structure type describes a sequentially allocated nonempty set of member objects (and, in
|
|
certain circumstances, an incomplete array), each of which has an optionally specified name
|
|
and possibly distinct type.
|
|
|
|
— A union type describes an overlapping nonempty set of member objects, each of which has an
|
|
optionally specified name and possibly distinct type.
|
|
|
|
— A function type describes a function with specified return type. A function type is characterized
|
|
by its return type and the number and types of its parameters. A function type is said to
|
|
be derived from its return type, and if its return type is T, the function type is sometimes
|
|
called "function returning T". The construction of a function type from a return type is called
|
|
"function type derivation".
|
|
|
|
— A pointer type may be derived from a function type or an object type, called the referenced type. A
|
|
pointer type describes an object whose value provides a reference to an entity of the referenced
|
|
type. A pointer type derived from the referenced type T is sometimes called "pointer to T".
|
|
The construction of a pointer type from a referenced type is called "pointer type derivation".
|
|
A pointer type is a complete object type.
|
|
|
|
— An atomic type describes the type designated by the construct _Atomic (type-name). (Atomic
|
|
types are a conditional feature that implementations need not support; see <a href='#6.10.9.3'>6.10.9.3</a>.)
|
|
|
|
These methods of constructing derived types can be applied recursively.
|
|
</pre>
|
|
<a name='6.2.5p24'></a>
|
|
<pre>24 Arithmetic types, pointer types, and the nullptr_t type are collectively called scalar types. Array
|
|
and structure types are collectively called aggregate types<a href='#FOOTNOTE.52'><sup>[52]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.52'>
|
|
<pre><i><b>Footnote 52)</b> Note that aggregate type does not include union type because an object with union type can only contain one member at
|
|
a time.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p25'></a>
|
|
<pre>25 An array type of unknown size is an incomplete type. It is completed, for an identifier of that type,
|
|
by specifying the size in a later declaration (with internal or external linkage). A structure or union
|
|
type of unknown content (as described in <a href='#6.7.2.3'>6.7.2.3</a>) is an incomplete type. It is completed, for all
|
|
does not violate the requirement that all basic types be different. Implementation-defined keywords have the form of an
|
|
identifier reserved for any use as described in <a href='#7.1.3'>7.1.3</a>.
|
|
declarations of that type, by declaring the same structure or union tag with its defining content later
|
|
in the same scope.
|
|
</pre>
|
|
<a name='6.2.5p26'></a>
|
|
<pre>26 A complete type shall have a size that is less than or equal to SIZE_MAX. A type has known constant
|
|
size if it is complete and is not a variable length array type.
|
|
</pre>
|
|
<a name='6.2.5p27'></a>
|
|
<pre>27 Array, function, and pointer types are collectively called derived declarator types. A declarator type
|
|
derivation from a type T is the construction of a derived declarator type from T by the application of
|
|
an array-type, a function-type, or a pointer-type derivation to T.
|
|
</pre>
|
|
<a name='6.2.5p28'></a>
|
|
<pre>28 A type is characterized by its type category, which is either the outermost derivation of a derived
|
|
type (as noted above in the construction of derived types), or the type itself if the type consists of no
|
|
derived types.
|
|
</pre>
|
|
<a name='6.2.5p29'></a>
|
|
<pre>29 Any type so far mentioned is an unqualified type. Each unqualified type has several qualified versions
|
|
of its type<a href='#FOOTNOTE.53'><sup>[53]</sup></a> , corresponding to the combinations of one, two, or all three of the const, volatile, and
|
|
restrict qualifiers. The qualified or unqualified versions of a type are distinct types that belong to
|
|
the same type category and have the same representation and alignment requirements.<a href='#FOOTNOTE.54'><sup>[54]</sup></a> An array
|
|
and its element type are always considered to be identically qualified<a href='#FOOTNOTE.55'><sup>[55]</sup></a> . Any other derived type is
|
|
not qualified by the qualifiers (if any) of the type from which it is derived.
|
|
</pre>
|
|
<a name='FOOTNOTE.53'>
|
|
<pre><i><b>Footnote 53)</b> See <a href='#6.7.3'>6.7.3</a> regarding qualified array and function types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.54'>
|
|
<pre><i><b>Footnote 54)</b> The same representation and alignment requirements are meant to imply interchangeability as arguments to functions,
|
|
return values from functions, and members of unions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.55'>
|
|
<pre><i><b>Footnote 55)</b> This does not apply to the _Atomic qualifier. Note that qualifiers do not have any direct effect on the array type itself,
|
|
but affect conversion rules for pointer types that reference an array type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p30'></a>
|
|
<pre>30 Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier designates an atomic
|
|
type. The size, representation, and alignment of an atomic type need not be the same as those of
|
|
the corresponding unqualified type. Therefore, this document explicitly uses the phrase "atomic,
|
|
qualified, or unqualified type" whenever the atomic version of a type is permitted along with the
|
|
other qualified versions of a type. The phrase "qualified or unqualified type", without specific
|
|
mention of atomic, does not include the atomic types.
|
|
</pre>
|
|
<a name='6.2.5p31'></a>
|
|
<pre>31 A pointer to void shall have the same representation and alignment requirements as a pointer to a
|
|
character type.<a href='#FOOTNOTE.54'><sup>[54]</sup></a> Similarly, pointers to qualified or unqualified versions of compatible types shall
|
|
have the same representation and alignment requirements. All pointers to structure types shall have
|
|
the same representation and alignment requirements as each other. All pointers to union types shall
|
|
have the same representation and alignment requirements as each other. Pointers to other types
|
|
need not have the same representation or alignment requirements.
|
|
</pre>
|
|
<a name='FOOTNOTE.54'>
|
|
<pre><i><b>Footnote 54)</b> The same representation and alignment requirements are meant to imply interchangeability as arguments to functions,
|
|
return values from functions, and members of unions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p32'></a>
|
|
<pre>32 EXAMPLE 1 The type designated as "float *" has type "pointer to float". Its type category is pointer, not a floating type.
|
|
The const-qualified version of this type is designated as "float * const" whereas the type designated as "const float *"
|
|
is not a qualified type — its type is "pointer to const-qualified float" and is a pointer to a qualified type.
|
|
</pre>
|
|
<a name='6.2.5p33'></a>
|
|
<pre>33 EXAMPLE 2 The type designated as "struct tag (*[5])(float)" has type "array of pointer to function returning
|
|
struct tag". The array has length five and the function has a single parameter of type float. Its type category is array.
|
|
|
|
Forward references: compatible type and composite type (<a href='#6.2.7'>6.2.7</a>), declarations (<a href='#6.7'>6.7</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.6'></a>
|
|
<hr>
|
|
<h3>6.2.6 [Representations of types]</h3>
|
|
<a name='6.2.6.1'></a>
|
|
<hr>
|
|
<h3>6.2.6.1 [General]</h3>
|
|
<a name='6.2.6.1p1'></a>
|
|
<pre>1 The representations of all types are unspecified except as stated in this subclause.
|
|
</pre>
|
|
<a name='6.2.6.1p2'></a>
|
|
<pre>2 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes, the number,
|
|
order, and encoding of which are either explicitly specified or implementation-defined.
|
|
</pre>
|
|
<a name='6.2.6.1p3'></a>
|
|
<pre>3 Values stored in unsigned bit-fields and objects of type unsigned char shall be represented using a
|
|
pure binary notation.<a href='#FOOTNOTE.56'><sup>[56]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.56'>
|
|
<pre><i><b>Footnote 56)</b> A positional representation for integers that uses the binary digits 0 and 1, in which the values represented by successive
|
|
bits are additive, begin with 1, and are multiplied by successive integral powers of 2, except perhaps the bit with the highest
|
|
position. (Adapted from the American National Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits,
|
|
_
|
|
and the values of type unsigned char range from 0 to 2CHAR BIT − 1.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.6.1p4'></a>
|
|
<pre>4 Values stored in non-bit-field objects of any other object type are represented using n× CHAR_BIT bits,
|
|
where n is the size of an object of that type, in bytes. An object that has the value may be copied into
|
|
an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is called the object
|
|
representation of the value. Values stored in bit-fields consist of m bits, where m is the size specified
|
|
for the bit-field. The object representation is the set of m bits the bit-field comprises in the addressable
|
|
storage unit holding it. Two values (other than NaNs) with the same object representation compare
|
|
equal, but values that compare equal may have different object representations.
|
|
</pre>
|
|
<a name='6.2.6.1p5'></a>
|
|
<pre>5 Certain object representations need not represent a value of the object type. If such a representation
|
|
is read by an lvalue expression that does not have character type, the behavior is undefined. If such
|
|
a representation is produced by a side effect that modifies all or any part of the object by an lvalue
|
|
expression that does not have character type, the behavior is undefined<a href='#FOOTNOTE.57'><sup>[57]</sup></a> . Such a representation is
|
|
called a non-value representation.
|
|
</pre>
|
|
<a name='FOOTNOTE.57'>
|
|
<pre><i><b>Footnote 57)</b> Thus, an automatic variable can be initialized to a non-value representation without causing undefined behavior, but the
|
|
value of the variable cannot be used until a proper value is stored in it.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.6.1p6'></a>
|
|
<pre>6 When a value is stored in an object of structure or union type, including in a member object, the bytes
|
|
of the object representation that correspond to any padding bytes take unspecified values<a href='#FOOTNOTE.58'><sup>[58]</sup></a> . The
|
|
object representation of a structure or union object is never a non-value representation, even though
|
|
the byte range corresponding to a member of the structure or union object may be a non-value
|
|
representation for that member.
|
|
</pre>
|
|
<a name='FOOTNOTE.58'>
|
|
<pre><i><b>Footnote 58)</b> Thus, for example, structure assignment need not copy any padding bits.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.6.1p7'></a>
|
|
<pre>7 When a value is stored in a member of an object of union type, the bytes of the object representation
|
|
that do not correspond to that member but do correspond to other members take unspecified values.
|
|
</pre>
|
|
<a name='6.2.6.1p8'></a>
|
|
<pre>8 Where an operator is applied to a value that has more than one object representation, which object
|
|
representation is used shall not affect the value of the result.<a href='#FOOTNOTE.59'><sup>[59]</sup></a> Where a value is stored in an object
|
|
using a type that has more than one object representation for that value, it is unspecified which
|
|
representation is used, but a non-value representation shall not be generated.
|
|
</pre>
|
|
<a name='FOOTNOTE.59'>
|
|
<pre><i><b>Footnote 59)</b> It is possible for objects x and y with the same effective type T to have the same value when they are accessed as objects
|
|
of type T, but to have different values in other contexts. In particular, if == is defined for type T, then x == y does not imply
|
|
that memcmp(&x, &y, sizeof (T))== 0. Furthermore, x == y does not necessarily imply that x and y have the same value;
|
|
other operations on values of type T might distinguish between them.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.6.1p9'></a>
|
|
<pre>9 Loads and stores of objects with atomic types are done with memory_order_seq_cst semantics.
|
|
Forward references: declarations (<a href='#6.7'>6.7</a>), expressions (<a href='#6.5'>6.5</a>), lvalues, arrays, and function designators
|
|
(<a href='#6.3.2.1'>6.3.2.1</a>), order and consistency (<a href='#7.17.3'>7.17.3</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.6.2'></a>
|
|
<hr>
|
|
<h3>6.2.6.2 [Integer types]</h3>
|
|
<a name='6.2.6.2p1'></a>
|
|
<pre>1 For unsigned integer types the bits of the object representation shall be divided into two groups:
|
|
value bits and padding bits. If there are N value bits, each bit shall represent a different power of
|
|
2 between 1 and 2N −1 , so that objects of that type shall be capable of representing values from 0
|
|
to 2N − 1 using a pure binary representation; this shall be known as the value representation. The
|
|
values of any padding bits are unspecified. The number of value bits N is called the width of the
|
|
unsigned integer type. The type bool shall have one value bit and (sizeof(bool)*CHAR_BIT)- 1
|
|
padding bits. Otherwise, there need not be any padding bits; unsigned char shall not have any
|
|
padding bits.
|
|
</pre>
|
|
<a name='6.2.6.2p2'></a>
|
|
<pre>2 For signed integer types, the bits of the object representation shall be divided into three groups:
|
|
value bits, padding bits, and the sign bit. If the corresponding unsigned type has width N , the
|
|
signed type uses the same number of N bits, its width, as value bits and sign bit. N − 1 are value
|
|
bits and the remaining bit is the sign bit. Each bit that is a value bit shall have the same value as the
|
|
same bit in the object representation of the corresponding unsigned type. If the sign bit is zero, it
|
|
shall not affect the resulting value. If the sign bit is one, it has value −(2N −1 ). There need not be any
|
|
padding bits; signed char shall not have any padding bits.
|
|
</pre>
|
|
<a name='6.2.6.2p3'></a>
|
|
<pre>3 The values of any padding bits are unspecified. A valid object representation of a signed integer
|
|
type where the sign bit is zero is a valid object representation of the corresponding unsigned type,
|
|
and shall represent the same value. For any integer type, the object representation where all the bits
|
|
are zero shall be a representation of the value zero in that type.
|
|
</pre>
|
|
<a name='6.2.6.2p4'></a>
|
|
<pre>4 The precision of an integer type is the number of value bits.
|
|
</pre>
|
|
<a name='6.2.6.2p5'></a>
|
|
<pre>5 NOTE 1 Some combinations of padding bits might generate non-value representations, for example, if one padding bit is a
|
|
parity bit. Regardless, no arithmetic operation on valid values can generate a non-value representation other than as part of
|
|
an exceptional condition such as an integer overflow, and this cannot occur with unsigned types. All other combinations of
|
|
padding bits are alternative object representations of the value specified by the value bits.
|
|
</pre>
|
|
<a name='6.2.6.2p6'></a>
|
|
<pre>6 NOTE 2 The sign representation defined in this document is called two’s complement. Previous revisions of this document
|
|
additionally allowed other sign representations.
|
|
</pre>
|
|
<a name='6.2.6.2p7'></a>
|
|
<pre>7 NOTE 3 For unsigned integer types the width and precision are the same, while for signed integer types the width is one
|
|
greater than the precision.
|
|
|
|
</pre>
|
|
<a name='6.2.7'></a>
|
|
<hr>
|
|
<h3>6.2.7 [Compatible type and composite type]</h3>
|
|
<a name='6.2.7p1'></a>
|
|
<pre>1 Two types are compatible types if they are the same. Additional rules for determining whether two
|
|
types are compatible are described in <a href='#6.7.2'>6.7.2</a> for type specifiers, in <a href='#6.7.3'>6.7.3</a> for type qualifiers, and in <a href='#6.7.6'>6.7.6</a>
|
|
for declarators<a href='#FOOTNOTE.60'><sup>[60]</sup></a> . Moreover, two complete structure, union, or enumerated types declared with the
|
|
same tag are compatible if members satisfy the following requirements:
|
|
|
|
— there shall be a one-to-one correspondence between their members such that each pair of
|
|
corresponding members are declared with compatible types;
|
|
— if one member of the pair is declared with an alignment specifier, the other is declared with an
|
|
equivalent alignment specifier;
|
|
— and, if one member of the pair is declared with a name, the other is declared with the same
|
|
name.
|
|
|
|
For two structures, corresponding members shall be declared in the same order. For two structures or
|
|
unions, corresponding bit-fields shall have the same widths. For two enumerations, corresponding
|
|
members shall have the same values; if one has a fixed underlying type, then the other shall have a
|
|
compatible fixed underlying type. For determining type compatibility, anonymous structures and
|
|
unions are considered a regular member of the containing structure or union type, and the type
|
|
of an anonymous structure or union is considered compatible to the type of another anonymous
|
|
structure or union, respectively, if their members fulfill the above requirements.
|
|
Furthermore, two structure, union, or enumerated types declared in separate translation units are
|
|
compatible in the following cases:
|
|
|
|
— both are declared without tags and they fulfill the requirements above;
|
|
— both have the same tag and are completed somewhere in their respective translation units and
|
|
they fulfill the requirements above;
|
|
— both have the same tag and at least one of the two types is not completed in its translation unit.
|
|
|
|
Otherwise, the structure, union, or enumerated types are incompatible<a href='#FOOTNOTE.61'><sup>[61]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.60'>
|
|
<pre><i><b>Footnote 60)</b> Two types need not be identical to be compatible.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.61'>
|
|
<pre><i><b>Footnote 61)</b> A structure, union, or enumerated type without a tag or an incomplete structure, union or enumerated type is not
|
|
compatible with any other structure, union or enum type declared in the same translation unit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.7p2'></a>
|
|
<pre>2 All declarations that refer to the same object or function shall have compatible type; otherwise, the
|
|
behavior is undefined.
|
|
</pre>
|
|
<a name='6.2.7p3'></a>
|
|
<pre>3 A composite type can be constructed from two types that are compatible; it is a type that is compatible
|
|
with both of the two types and satisfies the following conditions:
|
|
|
|
— If both types are array types, the following rules are applied:
|
|
• If one type is an array of known constant size, the composite type is an array of that size.
|
|
• Otherwise, if one type is a variable length array whose size is specified by an expression
|
|
that is not evaluated, the behavior is undefined.
|
|
• Otherwise, if one type is a variable length array whose size is specified, the composite
|
|
type is a variable length array of that size.
|
|
• Otherwise, if one type is a variable length array of unspecified size, the composite type is
|
|
a variable length array of unspecified size.
|
|
• Otherwise, both types are arrays of unknown size and the composite type is an array of
|
|
unknown size.
|
|
|
|
The element type of the composite type is the composite type of the two element types.
|
|
|
|
— If both types are function types, the type of each parameter in the composite parameter type
|
|
list is the composite type of the corresponding parameters.
|
|
|
|
— If one of the types has a standard attribute, the composite type also has that attribute.
|
|
|
|
These rules apply recursively to the types from which the two types are derived.
|
|
</pre>
|
|
<a name='6.2.7p4'></a>
|
|
<pre>4 For an identifier with internal or external linkage declared in a scope in which a prior declaration of
|
|
that identifier is visible<a href='#FOOTNOTE.62'><sup>[62]</sup></a> , if the prior declaration specifies internal or external linkage, the type of
|
|
the identifier at the later declaration becomes the composite type.
|
|
</pre>
|
|
<a name='FOOTNOTE.62'>
|
|
<pre><i><b>Footnote 62)</b> As specified in <a href='#6.2.1'>6.2.1</a>, the later declaration might hide the prior declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.7p5'></a>
|
|
<pre>5 EXAMPLE Given the following two file scope declarations:
|
|
|
|
int f(int (*)(char *), double (*)[3]);
|
|
int f(int (*)(char *), double (*)[]);
|
|
|
|
The resulting composite type for the function is:
|
|
|
|
int f(int (*)(char *), double (*)[3]);
|
|
|
|
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.2.8'></a>
|
|
<hr>
|
|
<h3>6.2.8 [Alignment of objects]</h3>
|
|
<a name='6.2.8p1'></a>
|
|
<pre>1 Complete object types have alignment requirements which place restrictions on the addresses at
|
|
which objects of that type may be allocated. An alignment is an implementation-defined integer
|
|
value representing the number of bytes between successive addresses at which a given object can be
|
|
allocated. An object type imposes an alignment requirement on every object of that type: stricter
|
|
alignment can be requested using the alignas keyword.
|
|
</pre>
|
|
<a name='6.2.8p2'></a>
|
|
<pre>2 A fundamental alignment is a valid alignment less than or equal to alignof (max_align_t). Funda-
|
|
mental alignments shall be supported by the implementation for objects of all storage durations.
|
|
The alignment requirements of the following types shall be fundamental alignments:
|
|
|
|
— all atomic, qualified, or unqualified basic types;
|
|
|
|
— all atomic, qualified, or unqualified enumerated types;
|
|
|
|
— all atomic, qualified, or unqualified pointer types;
|
|
|
|
— all array types whose element type has a fundamental alignment requirement;
|
|
|
|
— all types specified in Clause 7 as complete object types;
|
|
|
|
— all structure or union types all of whose elements have types with fundamental alignment
|
|
requirements and none of whose elements have an alignment specifier specifying an alignment
|
|
that is not a fundamental alignment.
|
|
|
|
</pre>
|
|
<a name='6.2.8p3'></a>
|
|
<pre>3 An extended alignment is represented by an alignment greater than alignof (max_align_t). It is
|
|
implementation-defined whether any extended alignments are supported and the storage durations
|
|
for which they are supported. A type having an extended alignment requirement is an over-aligned
|
|
type.<a href='#FOOTNOTE.63'><sup>[63]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.63'>
|
|
<pre><i><b>Footnote 63)</b> Every over-aligned type is, or contains, a structure or union type with a member to which an extended alignment has
|
|
been applied.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.8p4'></a>
|
|
<pre>4 Alignments are represented as values of the type size_t. Valid alignments include only fundamental
|
|
alignments, plus an additional implementation-defined set of values, which may be empty. Every
|
|
valid alignment value shall be a nonnegative integral power of two.
|
|
</pre>
|
|
<a name='6.2.8p5'></a>
|
|
<pre>5 Alignments have an order from weaker to stronger or stricter alignments. Stricter alignments have
|
|
larger alignment values. An address that satisfies an alignment requirement also satisfies any weaker
|
|
valid alignment requirement.
|
|
</pre>
|
|
<a name='6.2.8p6'></a>
|
|
<pre>6 The alignment requirement of a complete type can be queried using an alignof expression. The
|
|
types char, signed char, and unsigned char shall have the weakest alignment requirement.
|
|
</pre>
|
|
<a name='6.2.8p7'></a>
|
|
<pre>7 Comparing alignments is meaningful and provides the obvious results:
|
|
|
|
— Two alignments are equal when their numeric values are equal.
|
|
— Two alignments are different when their numeric values are not equal.
|
|
— When an alignment is larger than another it represents a stricter alignment.
|
|
|
|
</pre>
|
|
<a name='6.2.9'></a>
|
|
<hr>
|
|
<h3>6.2.9 [Encodings]</h3>
|
|
<a name='6.2.9p1'></a>
|
|
<pre>1 The literal encoding is an implementation-defined mapping of the characters of the execution character
|
|
set to the values in a character constant (<a href='#6.4.4.4'>6.4.4.4</a>) or string literal (<a href='#6.4.5'>6.4.5</a>). It shall support a mapping
|
|
from all the basic execution character set values into the implementation-defined encoding. It may
|
|
contain multibyte character sequences (<a href='#5.2.1.1'>5.2.1.1</a>).
|
|
</pre>
|
|
<a name='6.2.9p2'></a>
|
|
<pre>2 The wide literal encoding is an implementation-defined mapping of the characters of the execution
|
|
character set to the values in a wchar_t character constant (<a href='#6.4.4.4'>6.4.4.4</a>) or a wchar_t string literal (<a href='#6.4.5'>6.4.5</a>).
|
|
It shall support a mapping from all the basic execution character set values into the implementation-
|
|
defined encoding. The mapping shall produce values identical to the literal encoding for all the basic
|
|
execution character set values if an implementation does not define __STDC_MB_MIGHT_NEQ_WC__ .
|
|
One or more values may map to one or more values of the extended execution character set.
|
|
|
|
</pre>
|
|
<a name='6.3'></a>
|
|
<hr>
|
|
<h3>6.3 [Conversions]</h3>
|
|
<a name='6.3p1'></a>
|
|
<pre>1 Several operators convert operand values from one type to another automatically. This subclause
|
|
specifies the result required from such an implicit conversion, as well as those that result from a cast
|
|
operation (an explicit conversion). The list in <a href='#6.3.1.8'>6.3.1.8</a> summarizes the conversions performed by most
|
|
ordinary operators; it is supplemented as required by the discussion of each operator in <a href='#6.5'>6.5</a>.
|
|
</pre>
|
|
<a name='6.3p2'></a>
|
|
<pre>2 Unless explicitly stated otherwise, conversion of an operand value to a compatible type causes no
|
|
change to the value or the representation.
|
|
Forward references: cast operators (<a href='#6.5.4'>6.5.4</a>).
|
|
|
|
</pre>
|
|
<a name='6.3.1'></a>
|
|
<hr>
|
|
<h3>6.3.1 [Arithmetic operands]</h3>
|
|
<a name='6.3.1.1'></a>
|
|
<hr>
|
|
<h3>6.3.1.1 [Boolean, characters, and integers]</h3>
|
|
<a name='6.3.1.1p1'></a>
|
|
<pre>1 Every integer type has an integer conversion rank defined as follows:
|
|
|
|
— No two signed integer types shall have the same rank, even if they have the same representa-
|
|
tion.
|
|
— The rank of a signed integer type shall be greater than the rank of any signed integer type with
|
|
less precision.
|
|
— The rank of long long int shall be greater than the rank of long int, which shall be greater
|
|
than the rank of int, which shall be greater than the rank of short int, which shall be greater
|
|
than the rank of signed char.
|
|
— The rank of a bit-precise signed integer type shall be greater than the rank of any standard
|
|
integer type with less width or any bit-precise integer type with less width.
|
|
— The rank of any unsigned integer type shall equal the rank of the corresponding signed integer
|
|
type, if any.
|
|
— The rank of any standard integer type shall be greater than the rank of any extended integer
|
|
type with the same width or bit-precise integer type with the same width.
|
|
|
|
— The rank of any bit-precise integer type relative to an extended integer type of the same width
|
|
is implementation-defined.
|
|
|
|
— The rank of char shall equal the rank of signed char and unsigned char.
|
|
|
|
— The rank of bool shall be less than the rank of all other standard integer types.
|
|
|
|
— The rank of any enumerated type shall equal the rank of the compatible integer type (see
|
|
<a href='#6.7.2.2'>6.7.2.2</a>).
|
|
|
|
— The rank of any extended signed integer type relative to another extended signed integer
|
|
type with the same precision is implementation-defined, but still subject to the other rules for
|
|
determining the integer conversion rank.
|
|
|
|
— For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has greater rank than
|
|
T3 , then T1 has greater rank than T3.
|
|
|
|
|
|
</pre>
|
|
<a name='6.3.1.1p2'></a>
|
|
<pre>2 The following may be used in an expression wherever an int or unsigned int may be used:
|
|
|
|
— An object or expression with an integer type (other than int or unsigned int) whose integer
|
|
conversion rank is less than or equal to the rank of int and unsigned int.
|
|
|
|
— A bit-field of type bool, int, signed int, or unsigned int.
|
|
|
|
The value from a bit-field of a bit-precise integer type is converted to the corresponding bit-precise
|
|
type. If the original type is not a bit-precise integer type (<a href='#6.2.5'>6.2.5</a>) and if an int can represent all values
|
|
of the original type (as restricted by the width, for a bit-field), the value is converted to an int<a href='#FOOTNOTE.64'><sup>[64]</sup></a> ;
|
|
otherwise, it is converted to an unsigned int. These are called the integer promotions<a href='#FOOTNOTE.65'><sup>[65]</sup></a> . All other
|
|
types are unchanged by the integer promotions.
|
|
</pre>
|
|
<a name='FOOTNOTE.64'>
|
|
<pre><i><b>Footnote 64)</b> <a href='#E.'>E.</a>g.,
|
|
unsigned _BitInt(7): 2 is a bit-field that can hold the values −2, −1, 0, 1, and converts to
|
|
unsigned _BitInt(7).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.65'>
|
|
<pre><i><b>Footnote 65)</b> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain argument expressions, to
|
|
the operands of the unary + ,- , and ~ operators, and to both operands of the shift operators, as specified by their respective
|
|
subclauses.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.1.1p3'></a>
|
|
<pre>3 The integer promotions preserve value including sign. As discussed earlier, whether a "plain" char
|
|
can hold negative values is implementation-defined.
|
|
Forward references: enumeration specifiers (<a href='#6.7.2.2'>6.7.2.2</a>), structure and union specifiers (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='6.3.1.2'></a>
|
|
<hr>
|
|
<h3>6.3.1.2 [Boolean type]</h3>
|
|
<a name='6.3.1.2p1'></a>
|
|
<pre>1 When any scalar value is converted to bool, the result is false if the value is a zero (for arithmetic
|
|
types), null (for pointer types), or the scalar has type nullptr_t; otherwise, the result is true.
|
|
|
|
</pre>
|
|
<a name='6.3.1.3'></a>
|
|
<hr>
|
|
<h3>6.3.1.3 [Signed and unsigned integers]</h3>
|
|
<a name='6.3.1.3p1'></a>
|
|
<pre>1 When a value with integer type is converted to another integer type other than bool, if the value
|
|
can be represented by the new type, it is unchanged.
|
|
</pre>
|
|
<a name='6.3.1.3p2'></a>
|
|
<pre>2 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or subtracting
|
|
one more than the maximum value that can be represented in the new type until the value is in the
|
|
range of the new type.<a href='#FOOTNOTE.66'><sup>[66]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.66'>
|
|
<pre><i><b>Footnote 66)</b> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.1.3p3'></a>
|
|
<pre>3 Otherwise, the new type is signed and the value cannot be represented in it; either the result is
|
|
implementation-defined or an implementation-defined signal is raised.
|
|
</pre>
|
|
<a name='6.3.1.4'></a>
|
|
<hr>
|
|
<h3>6.3.1.4 [Real floating and integer]</h3>
|
|
<a name='6.3.1.4p1'></a>
|
|
<pre>1 When a finite value of standard floating type is converted to an integer type other than bool, the
|
|
fractional part is discarded (i.e., the value is truncated toward zero). If the value of the integral part
|
|
cannot be represented by the integer type, the behavior is undefined.<a href='#FOOTNOTE.67'><sup>[67]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.67'>
|
|
<pre><i><b>Footnote 67)</b> The remaindering operation performed when a value of integer type is converted to unsigned type need not be
|
|
performed when a value of real floating type is converted to unsigned type. Thus, the range of portable real floating values is
|
|
(−1, Utype_MAX + 1).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.1.4p2'></a>
|
|
<pre>2 When a finite value of decimal floating type is converted to an integer type other than bool, the
|
|
fractional part is discarded (i.e., the value is truncated toward zero). If the value of the integral part
|
|
cannot be represented by the integer type, the "invalid" floating-point exception shall be raised and
|
|
the result of the conversion is unspecified.
|
|
</pre>
|
|
<a name='6.3.1.4p3'></a>
|
|
<pre>3 When a value of integer type is converted to a standard floating type, if the value being converted
|
|
can be represented exactly in the new type, it is unchanged. If the value being converted is in the
|
|
range of values that can be represented but cannot be represented exactly, the result is either the
|
|
nearest higher or nearest lower representable value, chosen in an implementation-defined manner.
|
|
If the value being converted is outside the range of values that can be represented, the behavior is
|
|
undefined. Results of some implicit conversions may be represented in greater range and precision
|
|
than that required by the new type (see <a href='#6.3.1.8'>6.3.1.8</a> and <a href='#6.8.6.4'>6.8.6.4</a>).
|
|
</pre>
|
|
<a name='6.3.1.4p4'></a>
|
|
<pre>4 When a value of integer type is converted to a decimal floating type, if the value being converted
|
|
can be represented exactly in the new type, it is unchanged. If the value being converted cannot
|
|
be represented exactly, the result shall be correctly rounded with exceptions raised as specified in
|
|
IEC 60559.
|
|
|
|
</pre>
|
|
<a name='6.3.1.5'></a>
|
|
<hr>
|
|
<h3>6.3.1.5 [Real floating types]</h3>
|
|
<a name='6.3.1.5p1'></a>
|
|
<pre>1 When a value of real floating type is converted to a real floating type, if the value being converted
|
|
can be represented exactly in the new type, it is unchanged.
|
|
</pre>
|
|
<a name='6.3.1.5p2'></a>
|
|
<pre>2 When a value of real floating type is converted to a standard floating type, if the value being
|
|
converted is in the range of values that can be represented but cannot be represented exactly, the
|
|
result is either the nearest higher or nearest lower representable value, chosen in an implementation-
|
|
defined manner. If the value being converted is outside the range of values that can be represented,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='6.3.1.5p3'></a>
|
|
<pre>3 When a value of real floating type is converted to a decimal floating type, if the value being converted
|
|
cannot be represented exactly, the result is correctly rounded with exceptions raised as specified in
|
|
IEC 60559.
|
|
</pre>
|
|
<a name='6.3.1.5p4'></a>
|
|
<pre>4 Results of some implicit conversions may be represented in greater range and precision than that
|
|
required by the new type (see <a href='#6.3.1.8'>6.3.1.8</a> and <a href='#6.8.6.4'>6.8.6.4</a>).
|
|
|
|
</pre>
|
|
<a name='6.3.1.6'></a>
|
|
<hr>
|
|
<h3>6.3.1.6 [Complex types]</h3>
|
|
<a name='6.3.1.6p1'></a>
|
|
<pre>1 When a value of complex type is converted to another complex type, both the real and imaginary
|
|
parts follow the conversion rules for the corresponding real types.
|
|
|
|
</pre>
|
|
<a name='6.3.1.7'></a>
|
|
<hr>
|
|
<h3>6.3.1.7 [Real and complex]</h3>
|
|
<a name='6.3.1.7p1'></a>
|
|
<pre>1 When a value of real type is converted to a complex type, the real part of the complex result value is
|
|
determined by the rules of conversion to the corresponding real type and the imaginary part of the
|
|
complex result value is a positive zero or an unsigned zero.
|
|
</pre>
|
|
<a name='6.3.1.7p2'></a>
|
|
<pre>2 When a value of complex type is converted to a real type other than bool,<a href='#FOOTNOTE.68'><sup>[68]</sup></a> the imaginary part of
|
|
the complex value is discarded and the value of the real part is converted according to the conversion
|
|
rules for the corresponding real type.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.68'>
|
|
<pre><i><b>Footnote 68)</b> See <a href='#6.3.1.2'>6.3.1.2</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.1.8'></a>
|
|
<hr>
|
|
<h3>6.3.1.8 [Usual arithmetic conversions]</h3>
|
|
<a name='6.3.1.8p1'></a>
|
|
<pre>1 Many operators that expect operands of arithmetic type cause conversions and yield result types in
|
|
a similar way. The purpose is to determine a common real type for the operands and result. For the
|
|
specified operands, each operand is converted, without change of type domain, to a type whose
|
|
corresponding real type is the common real type. Unless explicitly stated otherwise, the common
|
|
real type is also the corresponding real type of the result, whose type domain is the type domain of
|
|
the operands if they are the same, and complex otherwise. This pattern is called the usual arithmetic
|
|
conversions:
|
|
|
|
If one operand has decimal floating type, the other operand shall not have standard floating,
|
|
complex, or imaginary type.
|
|
First, if the type of either operand is _Decimal128 , the other operand is converted to
|
|
_Decimal128 .
|
|
|
|
Otherwise, if the type of either operand is _Decimal64 , the other operand is converted to
|
|
_Decimal64 .
|
|
|
|
Otherwise, if the type of either operand is _Decimal32 , the other operand is converted to
|
|
_Decimal32 .
|
|
|
|
Otherwise, if the corresponding real type of either operand is long double, the other operand
|
|
is converted, without change of type domain, to a type whose corresponding real type is
|
|
long double.
|
|
|
|
Otherwise, if the corresponding real type of either operand is double, the other operand is
|
|
converted, without change of type domain, to a type whose corresponding real type is double.
|
|
Otherwise, if the corresponding real type of either operand is float, the other operand is
|
|
converted, without change of type domain, to a type whose corresponding real type is float.<a href='#FOOTNOTE.69'><sup>[69]</sup></a>
|
|
Otherwise, the integer promotions are performed on both operands. Then the following rules
|
|
are applied to the promoted operands:
|
|
If both operands have the same type, then no further conversion is needed.
|
|
Otherwise, if both operands have signed integer types or both have unsigned integer
|
|
types, the operand with the type of lesser integer conversion rank is converted to the type
|
|
of the operand with greater rank.
|
|
Otherwise, if the operand that has unsigned integer type has rank greater or equal to
|
|
the rank of the type of the other operand, then the operand with signed integer type is
|
|
converted to the type of the operand with unsigned integer type.
|
|
Otherwise, if the type of the operand with signed integer type can represent all of the
|
|
values of the type of the operand with unsigned integer type, then the operand with
|
|
unsigned integer type is converted to the type of the operand with signed integer type.
|
|
Otherwise, both operands are converted to the unsigned integer type corresponding to
|
|
the type of the operand with signed integer type.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.69'>
|
|
<pre><i><b>Footnote 69)</b> For example, addition of a double _Complex and a float entails just the conversion of the float operand to double
|
|
(and yields a double _Complex result).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.1.8p2'></a>
|
|
<pre>2 The values of floating operands and of the results of floating expressions may be represented in
|
|
greater range and precision than that required by the type; the types are not changed thereby.
|
|
See <a href='#5.2.4.2.2'>5.2.4.2.2</a> regarding evaluation formats.
|
|
</pre>
|
|
<a name='6.3.1.8p3'></a>
|
|
<pre>3 EXAMPLE 1 One consequence of _BitInt being exempt from the integer promotion rules (<a href='#6.3.1'>6.3.1</a>) is that a _BitInt operand
|
|
of a binary operator is not always promoted to an int or unsigned int as part of the usual arithmetic conversions. Instead,
|
|
a lower-ranked operand is converted to the higher-rank operand type and the result of the operation is the higher-ranked
|
|
type.
|
|
|
|
_BitInt(2) a2 = 1;
|
|
_BitInt(3) a3 = 2;
|
|
_BitInt(33) a33 = 1;
|
|
char c = 3;
|
|
|
|
a2 * a3 /* As part of the multiplication, a2 is converted to
|
|
_BitInt(3) and the result type is _BitInt(3). */
|
|
a2 * c /* As part of the multiplication, c is promoted to int,
|
|
a2 is converted to int and the result type is int. */
|
|
a33 * c /* As part of the multiplication, c is promoted to int,
|
|
then converted to _BitInt(33) and the result type
|
|
is _BitInt(33). */
|
|
|
|
void func(_BitInt(8) a1, _BitInt(24) a2) {
|
|
/* Cast one of the operands to 32-bits to guarantee the
|
|
result of the multiplication can contain all possible
|
|
values. */
|
|
_BitInt(32) a3 = a1 * (_BitInt(32))a2;
|
|
}
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.3.2'></a>
|
|
<hr>
|
|
<h3>6.3.2 [Other operands]</h3>
|
|
<a name='6.3.2.1'></a>
|
|
<hr>
|
|
<h3>6.3.2.1 [Lvalues, arrays, and function designators]</h3>
|
|
<a name='6.3.2.1p1'></a>
|
|
<pre>1 An lvalue is an expression (with an object type other than void) that potentially designates an
|
|
object;<a href='#FOOTNOTE.70'><sup>[70]</sup></a> if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
|
|
When an object is said to have a particular type, the type is specified by the lvalue used to designate
|
|
the object. A modifiable lvalue is an lvalue that does not have array type, does not have an incomplete
|
|
type, does not have a const-qualified type, and if it is a structure or union, does not have any
|
|
member (including, recursively, any member or element of all contained aggregates or unions) with
|
|
a const-qualified type.
|
|
</pre>
|
|
<a name='FOOTNOTE.70'>
|
|
<pre><i><b>Footnote 70)</b> The name "lvalue" comes originally from the assignment expression E1 = E2, in which the left operand E1 is required to
|
|
be a (modifiable) lvalue. It is perhaps better considered as representing an object "locator value". What is sometimes called
|
|
"rvalue" is in this document described as the "value of an expression".
|
|
An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary expression that is a
|
|
pointer to an object, *E is an lvalue that designates the object to which E points.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.2.1p2'></a>
|
|
<pre>2 Except when it is the operand of the sizeof operator, or the typeof operators, the unary & operator,
|
|
the ++ operator, the-- operator, or the left operand of the . operator or an assignment operator, an
|
|
lvalue that does not have array type is converted to the value stored in the designated object (and is
|
|
no longer an lvalue); this is called lvalue conversion. If the lvalue has qualified type, the value has the
|
|
unqualified version of the type of the lvalue; additionally, if the lvalue has atomic type, the value has
|
|
the non-atomic version of the type of the lvalue; otherwise, the value has the type of the lvalue. If the
|
|
lvalue has an incomplete type and does not have array type, the behavior is undefined. If the lvalue
|
|
designates an object of automatic storage duration that could have been declared with the register
|
|
storage class (never had its address taken), and that object is uninitialized (not declared with an
|
|
initializer and no assignment to it has been performed prior to use), the behavior is undefined.
|
|
</pre>
|
|
<a name='6.3.2.1p3'></a>
|
|
<pre>3 Except when it is the operand of the sizeof operator, or typeof operators, or the unary & operator,
|
|
or is a string literal used to initialize an array, an expression that has type "array of type" is converted
|
|
to an expression with type "pointer to type" that points to the initial element of the array object and
|
|
is not an lvalue. If the array object has register storage class, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.3.2.1p4'></a>
|
|
<pre>4 A function designator is an expression that has function type. Except when it is the operand of the
|
|
sizeof operator<a href='#FOOTNOTE.71'><sup>[71]</sup></a> , a typeof operator, or the unary & operator, a function designator with type
|
|
"function returning type" is converted to an expression that has type "pointer to function returning
|
|
type".
|
|
Forward references: address and indirection operators (<a href='#6.5.3.2'>6.5.3.2</a>), assignment operators (<a href='#6.5.16'>6.5.16</a>),
|
|
common definitions <stddef.h> (<a href='#7.21'>7.21</a>), initialization (<a href='#6.7.10'>6.7.10</a>), postfix increment and decrement
|
|
operators (<a href='#6.5.2.4'>6.5.2.4</a>), prefix increment and decrement operators (<a href='#6.5.3.1'>6.5.3.1</a>), the sizeof and alignof
|
|
operators (<a href='#6.5.3.4'>6.5.3.4</a>), structure and union members (<a href='#6.5.2.3'>6.5.2.3</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.71'>
|
|
<pre><i><b>Footnote 71)</b> Because this conversion does not occur, the operand of the sizeof operator remains a function designator and violates
|
|
the constraints in <a href='#6.5.3.4'>6.5.3.4</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.2.2'></a>
|
|
<hr>
|
|
<h3>6.3.2.2 [void]</h3>
|
|
<a name='6.3.2.2p1'></a>
|
|
<pre>1 The (nonexistent) value of a void expression (an expression that has type void) shall not be used in any
|
|
way, and implicit or explicit conversions (except to void) shall not be applied to such an expression.
|
|
If an expression of any other type is evaluated as a void expression, its value or designator is
|
|
discarded. (A void expression is evaluated for its side effects.)
|
|
|
|
</pre>
|
|
<a name='6.3.2.3'></a>
|
|
<hr>
|
|
<h3>6.3.2.3 [Pointers]</h3>
|
|
<a name='6.3.2.3p1'></a>
|
|
<pre>1 A pointer to void may be converted to or from a pointer to any object type. A pointer to any object
|
|
type may be converted to a pointer to void and back again; the result shall compare equal to the
|
|
original pointer.
|
|
</pre>
|
|
<a name='6.3.2.3p2'></a>
|
|
<pre>2 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to the q-qualified
|
|
version of the type; the values stored in the original and converted pointers shall compare equal.
|
|
</pre>
|
|
<a name='6.3.2.3p3'></a>
|
|
<pre>3 An integer constant expression with the value 0, such an expression cast to type void *, or the
|
|
predefined constant nullptr is called a null pointer constant<a href='#FOOTNOTE.72'><sup>[72]</sup></a> . If a null pointer constant or a value
|
|
of the type nullptr_t (which is necessarily the value nullptr) is converted to a pointer type, the
|
|
resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or
|
|
function.
|
|
</pre>
|
|
<a name='FOOTNOTE.72'>
|
|
<pre><i><b>Footnote 72)</b> The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see <a href='#7.21'>7.21</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.2.3p4'></a>
|
|
<pre>4 Conversion of a null pointer to another pointer type yields a null pointer of that type. Any two null
|
|
pointers shall compare equal.
|
|
</pre>
|
|
<a name='6.3.2.3p5'></a>
|
|
<pre>5 An integer may be converted to any pointer type. Except as previously specified, the result is
|
|
implementation-defined, might not be correctly aligned, might not point to an entity of the referenced
|
|
type, and might produce an indeterminate representation when stored into an object<a href='#FOOTNOTE.73'><sup>[73]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.73'>
|
|
<pre><i><b>Footnote 73)</b> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to be consistent with
|
|
the addressing structure of the execution environment.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.2.3p6'></a>
|
|
<pre>6 Any pointer type may be converted to an integer type. Except as previously specified, the result
|
|
is implementation-defined. If the result cannot be represented in the integer type, the behavior is
|
|
undefined. The result need not be in the range of values of any integer type.
|
|
</pre>
|
|
<a name='6.3.2.3p7'></a>
|
|
<pre>7 A pointer to an object type may be converted to a pointer to a different object type. If the resulting
|
|
pointer is not correctly aligned<a href='#FOOTNOTE.74'><sup>[74]</sup></a> for the referenced type, the behavior is undefined. Otherwise,
|
|
when converted back again, the result shall compare equal to the original pointer. When a pointer to
|
|
an object is converted to a pointer to a character type, the result points to the lowest addressed byte
|
|
of the object. Successive increments of the result, up to the size of the object, yield pointers to the
|
|
remaining bytes of the object.
|
|
</pre>
|
|
<a name='FOOTNOTE.74'>
|
|
<pre><i><b>Footnote 74)</b> In general, the concept "correctly aligned" is transitive: if a pointer to type A is correctly aligned for a pointer to type B,
|
|
which in turn is correctly aligned for a pointer to type C, then a pointer to type A is correctly aligned for a pointer to type C.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.3.2.3p8'></a>
|
|
<pre>8 A pointer to a function of one type may be converted to a pointer to a function of another type and
|
|
back again; the result shall compare equal to the original pointer. If a converted pointer is used to
|
|
call a function whose type is not compatible with the referenced type, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='6.3.2.4'></a>
|
|
<hr>
|
|
<h3>6.3.2.4 [nullptr_t]</h3>
|
|
<a name='6.3.2.4p1'></a>
|
|
<pre>1 The type nullptr_t may be converted to bool or to a pointer type. The result is false or the null
|
|
pointer value, respectively.
|
|
</pre>
|
|
<a name='6.3.2.4p2'></a>
|
|
<pre>2 The type nullptr_t may be converted to itself.
|
|
Forward references: cast operators (<a href='#6.5.4'>6.5.4</a>), equality operators (<a href='#6.5.9'>6.5.9</a>), integer types capable of
|
|
holding object pointers (<a href='#7.22.1.4'>7.22.1.4</a>), simple assignment (<a href='#6.5.16.1'>6.5.16.1</a>).
|
|
</pre>
|
|
<a name='6.4'></a>
|
|
<hr>
|
|
<h3>6.4 [Lexical elements]</h3>
|
|
<a name='6.4p1'></a>
|
|
<pre>1 Syntax
|
|
token:
|
|
keyword
|
|
identifier
|
|
constant
|
|
string-literal
|
|
punctuator
|
|
|
|
preprocessing-token:
|
|
header-name
|
|
identifier
|
|
pp-number
|
|
character-constant
|
|
string-literal
|
|
punctuator
|
|
each universal-character-name that cannot be one of the above
|
|
each non-white-space character that cannot be one of the above
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.4p2'></a>
|
|
<pre>2 Each preprocessing token that is converted to a token shall have the lexical form of a keyword, an
|
|
identifier, a constant, a string literal, or a punctuator. A single universal character name shall match
|
|
one of the other preprocessing token categories.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4p3'></a>
|
|
<pre>3 A token is the minimal lexical element of the language in translation phases 7 and 8. The categories of
|
|
tokens are: keywords, identifiers, constants, string literals, and punctuators. A preprocessing token
|
|
is the minimal lexical element of the language in translation phases 3 through 6. The categories of
|
|
preprocessing tokens are: header names, identifiers, preprocessing numbers, character constants,
|
|
string literals, punctuators, and both single universal character names as well as single non-white-
|
|
space characters that do not lexically match the other preprocessing token categories.<a href='#FOOTNOTE.75'><sup>[75]</sup></a> If a ’ or a "
|
|
character matches the last category, the behavior is undefined. Preprocessing tokens can be separated
|
|
by white space; this consists of comments (described later), or white-space characters (space, horizontal
|
|
tab, new-line, vertical tab, and form-feed), or both. As described in <a href='#6.10'>6.10</a>, in certain circumstances
|
|
during translation phase 4, white space (or the absence thereof) serves as more than preprocessing
|
|
token separation. White space may appear within a preprocessing token only as part of a header
|
|
name or between the quotation characters in a character constant or string literal.
|
|
</pre>
|
|
<a name='FOOTNOTE.75'>
|
|
<pre><i><b>Footnote 75)</b> An additional category, placemarkers, is used internally in translation phase 4 (see <a href='#6.10.4.3'>6.10.4.3</a>); it cannot occur in source
|
|
files.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4p4'></a>
|
|
<pre>4 If the input stream has been parsed into preprocessing tokens up to a given character, the next
|
|
preprocessing token is the longest sequence of characters that could constitute a preprocessing token.
|
|
There is one exception to this rule: header name preprocessing tokens are recognized only within
|
|
#include and #embed preprocessing directives, in __has_include and __has_embed expressions,
|
|
as well as in implementation-defined locations within #pragma directives. In such contexts, a
|
|
sequence of characters that could be either a header name or a string literal is recognized as the
|
|
former.
|
|
</pre>
|
|
<a name='6.4p5'></a>
|
|
<pre>5 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a valid floating or integer
|
|
constant token), even though a parse as the pair of preprocessing tokens 1 and Ex might produce a valid expression (for
|
|
example, if Ex were a macro defined as +1 ). Similarly, the program fragment 1E1 is parsed as a preprocessing number (one
|
|
that is a valid floating constant token), whether or not E is a macro name.
|
|
</pre>
|
|
<a name='6.4p6'></a>
|
|
<pre>6 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on increment operators,
|
|
even though the parse x ++ + ++ y might yield a correct expression.
|
|
|
|
Forward references: character constants (<a href='#6.4.4.4'>6.4.4.4</a>), comments (<a href='#6.4.9'>6.4.9</a>), expressions (<a href='#6.5'>6.5</a>), floating
|
|
constants (<a href='#6.4.4.2'>6.4.4.2</a>), header names (<a href='#6.4.7'>6.4.7</a>), macro replacement (<a href='#6.10.4'>6.10.4</a>), postfix increment and decrement
|
|
operators (<a href='#6.5.2.4'>6.5.2.4</a>), prefix increment and decrement operators (<a href='#6.5.3.1'>6.5.3.1</a>), preprocessing directives (<a href='#6.10'>6.10</a>),
|
|
preprocessing numbers (<a href='#6.4.8'>6.4.8</a>), string literals (<a href='#6.4.5'>6.4.5</a>).
|
|
</pre>
|
|
<a name='6.4.1'></a>
|
|
<hr>
|
|
<h3>6.4.1 [Keywords]</h3>
|
|
<a name='6.4.1p1'></a>
|
|
<pre>1 Syntax
|
|
keyword: one of
|
|
alignas enum short void
|
|
alignof extern signed volatile
|
|
auto false sizeof while
|
|
bool float static _Atomic
|
|
break for static_assert _BitInt
|
|
case goto struct _Complex
|
|
char if switch _Decimal128
|
|
const inline thread_local _Decimal32
|
|
constexpr int true _Decimal64
|
|
continue long typedef _Generic
|
|
default nullptr typeof _Imaginary
|
|
do register typeof_unqual _Noreturn
|
|
double restrict union
|
|
else return unsigned
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.1p2'></a>
|
|
<pre>2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as keywords
|
|
except in an attribute token, and shall not be used otherwise. The keyword _Imaginary is reserved
|
|
for specifying imaginary types.<a href='#FOOTNOTE.76'><sup>[76]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.76'>
|
|
<pre><i><b>Footnote 76)</b> One possible specification for imaginary types appears in Annex G.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.1p3'></a>
|
|
<pre>3 The following table provides alternate spellings for certain keywords. These can be used wherever
|
|
the keyword can<a href='#FOOTNOTE.77'><sup>[77]</sup></a> .
|
|
Keyword Alternative Spelling
|
|
alignas _Alignas
|
|
alignof _Alignof
|
|
bool _Bool
|
|
static_assert _Static_assert
|
|
thread_local _Thread_local
|
|
|
|
The spelling of these keywords, their alternate forms, and of false and true inside expressions that
|
|
are subject to the # and ## preprocessing operators is unspecified<a href='#FOOTNOTE.78'><sup>[78]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.77'>
|
|
<pre><i><b>Footnote 77)</b> These alternative keywords are obsolescent features and should not be used for new code and development.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.78'>
|
|
<pre><i><b>Footnote 78)</b> The intent of this specification is to allow but not force the implementation of the corresponding feature by means of a
|
|
predefined macro.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.2'></a>
|
|
<hr>
|
|
<h3>6.4.2 [Identifiers]</h3>
|
|
<a name='6.4.2.1'></a>
|
|
<hr>
|
|
<h3>6.4.2.1 [General]</h3>
|
|
<a name='6.4.2.1p1'></a>
|
|
<pre>1 Syntax
|
|
identifier:
|
|
identifier-start
|
|
identifier identifier-continue
|
|
|
|
|
|
|
|
identifier-start:
|
|
nondigit
|
|
XID_Start character
|
|
universal-character-name of class XID_Start
|
|
identifier-continue:
|
|
digit
|
|
nondigit
|
|
XID_Continue character
|
|
universal-character-name of class XID_Continue
|
|
|
|
|
|
|
|
nondigit: one of
|
|
_ a b c d e f g h i j k l m
|
|
n o p q r s t u v w x y z
|
|
A B C D E F G H I J K L M
|
|
N O P Q R S T U V W X Y Z
|
|
|
|
|
|
|
|
digit: one of
|
|
0 1 2 3 4 5 6 7 8 9
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.2.1p2'></a>
|
|
<pre>2 An XID_Start character is an implementation-defined character whose corresponding code point
|
|
in ISO/IEC 10646 has the XID_Start property. An XID_Continue character is an implementation-
|
|
defined character whose corresponding code point in ISO/IEC 10646 has the XID_Continue property.
|
|
An identifier is a sequence of one identifier start character followed by 0 or more identifier continue
|
|
characters, which designates one or more entities as described in <a href='#6.2.1'>6.2.1</a>. Lowercase and uppercase
|
|
letters are distinct. There is no specific limit on the maximum length of an identifier.
|
|
</pre>
|
|
<a name='6.4.2.1p3'></a>
|
|
<pre>3 The character classes XID_Start and XID_Continue are Derived Core Properties as described by
|
|
UAX #4479) . Each character and universal character name in an identifier shall designate a character
|
|
whose encoding in ISO/IEC 10646 has the XID_Continue property. The initial character (which
|
|
may be a universal character name) shall designate a character whose encoding in ISO/IEC 10646
|
|
has the XID_Start property. An identifier shall conform to Normalization Form C as specified in
|
|
ISO/IEC 10646. Annex D provides an overview of the conforming identifiers.
|
|
</pre>
|
|
<a name='6.4.2.1p4'></a>
|
|
<pre>4 NOTE 1 Uppercase and lowercase letters are considered different for all identifiers.
|
|
</pre>
|
|
<a name='6.4.2.1p5'></a>
|
|
<pre>5 NOTE 2 In translation phase 4 (4), the term identifier also includes those preprocessing tokens (<a href='#6.4.8'>6.4.8</a>) differentiated as
|
|
keywords (<a href='#6.4.1'>6.4.1</a>) in the later translation phase 7 (7).
|
|
|
|
</pre>
|
|
<a name='6.4.2.1p6'></a>
|
|
<pre>6 When preprocessing tokens are converted to tokens during translation phase 7, if a preprocessing
|
|
token could be converted to either a keyword or an identifier, it is converted to a keyword except in
|
|
an attribute token.
|
|
</pre>
|
|
<a name='6.4.2.1p7'></a>
|
|
<pre>7 Some identifiers are reserved.
|
|
|
|
— All identifiers that begin with a double underscore (__ ) or begin with an underscore (_ )
|
|
followed by an uppercase letter are reserved for any use, except those identifiers which are
|
|
lexically identical to keywords<a href='#FOOTNOTE.80'><sup>[80]</sup></a> .
|
|
|
|
— All identifiers that begin with an underscore are reserved for use as identifiers with file scope
|
|
in both the ordinary and tag name spaces.
|
|
|
|
Other identifiers may be reserved, see <a href='#7.1.3'>7.1.3</a>.
|
|
</pre>
|
|
<a name='FOOTNOTE.80'>
|
|
<pre><i><b>Footnote 80)</b> This allows a reserved identifier that matches the spelling of a keyword to be used as a macro name by the program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.2.1p8'></a>
|
|
<pre>8 If the program declares or defines an identifier in a context in which it is reserved (other than as
|
|
allowed by <a href='#7.1.4'>7.1.4</a>), the behavior is undefined.
|
|
</pre>
|
|
<a name='6.4.2.1p9'></a>
|
|
<pre>9 If the program defines a reserved identifier or attribute token described in <a href='#6.7.12.1'>6.7.12.1</a> as a macro name,
|
|
or removes (with #undef) any macro definition of an identifier in the first group listed above or
|
|
attribute token described in <a href='#6.7.12.1'>6.7.12.1</a>, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.4.2.1p10'></a>
|
|
<pre>10 Some identifiers may be potentially reserved. A potentially reserved identifier is an identifier which is
|
|
not reserved unless made so by an implementation providing the identifier (<a href='#7.1.3'>7.1.3</a>) but is anticipated
|
|
to become reserved by an implementation or a future version of this document.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.4.2.1p11'></a>
|
|
<pre>11 Implementations are encouraged to issue a diagnostic message when a potentially reserved identifier
|
|
is declared or defined for any use that is not implementation-compatible (see below) in a context
|
|
where the potentially reserved identifier may be reserved under a conforming implementation. This
|
|
brings attention to a potential conflict when porting a program to a future revision of this document.
|
|
</pre>
|
|
<a name='6.4.2.1p12'></a>
|
|
<pre>12 An implementation-compatible use of a potentially reserved identifier is a declaration of an external
|
|
name where the name is provided by the implementation as an external name and where the
|
|
declaration declares an object or function with a type that is compatible with the type of the object
|
|
or function provided by the implementation under that name.
|
|
|
|
Implementation limits
|
|
</pre>
|
|
<a name='6.4.2.1p13'></a>
|
|
<pre>13 As discussed in <a href='#5.2.4.1'>5.2.4.1</a>, an implementation may limit the number of significant initial characters
|
|
in an identifier; the limit for an external name (an identifier that has external linkage) may be more
|
|
restrictive than that for an internal name (a macro name or an identifier that does not have external
|
|
linkage). The number of significant characters in an identifier is implementation-defined.
|
|
</pre>
|
|
<a name='6.4.2.1p14'></a>
|
|
<pre>14 Any identifiers that differ in a significant character are different identifiers. If two identifiers differ
|
|
only in nonsignificant characters, the behavior is undefined.
|
|
Forward references: universal character names (<a href='#6.4.3'>6.4.3</a>), macro replacement (<a href='#6.10.4'>6.10.4</a>), reserved library
|
|
identifiers (<a href='#7.1.3'>7.1.3</a>), use of library functions (<a href='#7.1.4'>7.1.4</a>), attributes (<a href='#6.7.12.1'>6.7.12.1</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.2.2'></a>
|
|
<hr>
|
|
<h3>6.4.2.2 [Predefined identifiers]</h3>
|
|
<a name='6.4.2.2p1'></a>
|
|
<pre>1 Semantics
|
|
The identifier __func__ shall be implicitly declared by the translator as if, immediately following
|
|
the opening brace of each function definition, the declaration
|
|
|
|
static const char __func__[] = "function-name";
|
|
|
|
|
|
appeared, where function-name is the name of the lexically-enclosing function.<a href='#FOOTNOTE.81'><sup>[81]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.81'>
|
|
<pre><i><b>Footnote 81)</b> Since the name __func__ is reserved for any use by the implementation (<a href='#7.1.3'>7.1.3</a>), if any other identifier is explicitly declared
|
|
using the name __func__ , the behavior is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.2.2p2'></a>
|
|
<pre>2 This name is encoded as if the implicit declaration had been written in the source character set and
|
|
then translated into the execution character set as indicated in translation phase 5.
|
|
</pre>
|
|
<a name='6.4.2.2p3'></a>
|
|
<pre>3 EXAMPLE Consider the code fragment:
|
|
|
|
#include <stdio.h>
|
|
void myfunc(void)
|
|
{
|
|
printf("%s\n", __func__);
|
|
/* ... */
|
|
}
|
|
|
|
|
|
Each time the function is called, it will print to the standard output stream:
|
|
|
|
myfunc
|
|
|
|
|
|
Forward references: function definitions (<a href='#6.9.1'>6.9.1</a>).
|
|
</pre>
|
|
<a name='6.4.3'></a>
|
|
<hr>
|
|
<h3>6.4.3 [Universal character names]</h3>
|
|
<a name='6.4.3p1'></a>
|
|
<pre>1 Syntax
|
|
universal-character-name:
|
|
\u hex-quad
|
|
\U hex-quad hex-quad
|
|
|
|
hex-quad:
|
|
hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.4.3p2'></a>
|
|
<pre>2 A universal character name shall not designate a code point where the hexadecimal value is:
|
|
|
|
— less than 00A0 other than 0024 ($), 0040 (@), or 0060 (` );
|
|
|
|
— in the range D800 through DFFF inclusive; or
|
|
— greater than 10FFFF<a href='#FOOTNOTE.82'><sup>[82]</sup></a> .
|
|
|
|
Description
|
|
</pre>
|
|
<a name='FOOTNOTE.82'>
|
|
<pre><i><b>Footnote 82)</b> The disallowed characters are the characters in the basic character set and the code positions reserved by ISO/IEC 10646
|
|
for control characters, the character DELETE, the S-zone (reserved for use by UTF-16), and characters too large to be encoded
|
|
by ISO/IEC 10646. Disallowed universal character escape sequences can still be specified with hexadecimal and octal escape
|
|
sequences (<a href='#6.4.4.4'>6.4.4.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.3p3'></a>
|
|
<pre>3 Universal character names may be used in identifiers, character constants, and string literals to
|
|
designate characters that are not in the basic character set.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.3p4'></a>
|
|
<pre>4 The universal character name \U nnnnnnnn designates the character whose eight-digit short identifier
|
|
(as specified by ISO/IEC 10646) is nnnnnnnn.<a href='#FOOTNOTE.83'><sup>[83]</sup></a> Similarly, the universal character name \u nnnn
|
|
designates the character whose four-digit short identifier is nnnn (and whose eight-digit short
|
|
identifier is 0000nnnn).
|
|
</pre>
|
|
<a name='FOOTNOTE.83'>
|
|
<pre><i><b>Footnote 83)</b> Short identifiers for characters were first specified in ISO/IEC 10646–1:1993/Amd 9:1997.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4'></a>
|
|
<hr>
|
|
<h3>6.4.4 [Constants]</h3>
|
|
<a name='6.4.4p1'></a>
|
|
<pre>1 Syntax
|
|
constant:
|
|
integer-constant
|
|
floating-constant
|
|
enumeration-constant
|
|
character-constant
|
|
predefined-constant
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.4.4p2'></a>
|
|
<pre>2 Each constant shall have a type and the value of a constant shall be in the range of representable
|
|
values for its type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4p3'></a>
|
|
<pre>3 Each constant has a type, determined by its form and value, as detailed later.
|
|
|
|
</pre>
|
|
<a name='6.4.4.1'></a>
|
|
<hr>
|
|
<h3>6.4.4.1 [Integer constants]</h3>
|
|
<a name='6.4.4.1p1'></a>
|
|
<pre>1 Syntax
|
|
integer-constant:
|
|
decimal-constant integer-suffixopt
|
|
octal-constant integer-suffixopt
|
|
hexadecimal-constant integer-suffixopt
|
|
binary-constant integer-suffixopt
|
|
|
|
|
|
|
|
decimal-constant:
|
|
nonzero-digit
|
|
decimal-constant ’opt digit
|
|
|
|
|
|
|
|
octal-constant:
|
|
0
|
|
octal-constant ’opt octal-digit
|
|
|
|
|
|
|
|
hexadecimal-constant:
|
|
hexadecimal-prefix hexadecimal-digit-sequence
|
|
|
|
binary-constant:
|
|
binary-prefix binary-digit
|
|
binary-constant ’opt binary-digit
|
|
|
|
|
|
|
|
hexadecimal-prefix: one of
|
|
0x 0X
|
|
|
|
|
|
|
|
binary-prefix: one of
|
|
0b 0B
|
|
nonzero-digit: one of
|
|
1 2 3 4 5 6 7 8 9
|
|
|
|
|
|
|
|
octal-digit: one of
|
|
0 1 2 3 4 5 6 7
|
|
|
|
|
|
|
|
hexadecimal-digit-sequence:
|
|
hexadecimal-digit
|
|
hexadecimal-digit-sequence ’opt hexadecimal-digit
|
|
|
|
hexadecimal-digit: one of
|
|
0 1 2 3 4 5 6 7 8 9
|
|
a b c d e f
|
|
A B C D E F
|
|
|
|
|
|
|
|
binary-digit: one of
|
|
0 1
|
|
|
|
|
|
|
|
integer-suffix:
|
|
unsigned-suffix long-suffixopt
|
|
unsigned-suffix long-long-suffix
|
|
unsigned-suffix bit-precise-int-suffix
|
|
long-suffix unsigned-suffixopt
|
|
long-long-suffix unsigned-suffixopt
|
|
bit-precise-int-suffix unsigned-suffixopt
|
|
|
|
|
|
|
|
bit-precise-int-suffix: one of
|
|
wb WB
|
|
|
|
|
|
|
|
unsigned-suffix: one of
|
|
u U
|
|
|
|
|
|
|
|
long-suffix: one of
|
|
l L
|
|
|
|
|
|
|
|
long-long-suffix: one of
|
|
ll LL
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.4.4.1p2'></a>
|
|
<pre>2 An integer constant begins with a digit, but has no period or exponent part. It may have a prefix that
|
|
specifies its base and a suffix that specifies its type. An optional separating single quote character (
|
|
’ ) in an integer or floating constant is called a digit separator. Digit separators are ignored when
|
|
determining the value of the constant.
|
|
</pre>
|
|
<a name='6.4.4.1p3'></a>
|
|
<pre>3 EXAMPLE
|
|
|
|
0b11’10’11’01 /* 0b11101101 */
|
|
’1’2 /* character constant ’1’ followed by integer constant 2,
|
|
not the integer constant 12 */
|
|
11’22 /* 1122 */
|
|
0x’FFFF’FFFF /* invalid hexadecimal constant (’ cannot appear after 0x) */
|
|
0x1’2’3’4AB’C’D /* 0x1234ABCD */
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.4.4.1p4'></a>
|
|
<pre>4 A decimal constant begins with a nonzero digit and consists of a sequence of decimal digits. An
|
|
octal constant consists of the prefix 0 optionally followed by a sequence of the digits 0 through 7
|
|
only. A hexadecimal constant consists of the prefix 0x or 0X followed by a sequence of the decimal
|
|
digits and the letters a (or A) through f (or F) with values 10 through 15 respectively. A binary
|
|
constant consists of the prefix 0b or 0B followed by a sequence of the digits 0 or 1.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4.1p5'></a>
|
|
<pre>5 The value of a decimal constant is computed base 10; that of an octal constant, base 8; that of a
|
|
hexadecimal constant, base 16; that of a binary constant, base 2. The lexically first digit is the most
|
|
significant.
|
|
</pre>
|
|
<a name='6.4.4.1p6'></a>
|
|
<pre>6 The type of an integer constant is the first of the corresponding list in which its value can be
|
|
represented.
|
|
Octal, Hexadecimal or Binary
|
|
Suffix Decimal Constant Constant
|
|
none int int
|
|
long int unsigned int
|
|
long long int long int
|
|
unsigned long int
|
|
long long int
|
|
unsigned long long int
|
|
u or U unsigned int unsigned int
|
|
unsigned long int unsigned long int
|
|
unsigned long long int unsigned long long int
|
|
l or L long int long int
|
|
long long int unsigned long int
|
|
long long int
|
|
unsigned long long int
|
|
Both u or U unsigned long int unsigned long int
|
|
and l or L unsigned long long int unsigned long long int
|
|
ll or LL long long int long long int
|
|
unsigned long long int
|
|
Both u or U unsigned long long int unsigned long long int
|
|
and ll or LL
|
|
wb or WB _BitInt(N) where the width N _BitInt(N) where the width N
|
|
is the smallest N greater than is the smallest N greater than
|
|
1 which can accommodate 1 which can accommodate
|
|
the value and the sign bit. the value and the sign bit.
|
|
Both u or U unsigned _BitInt(N) where the unsigned _BitInt(N) where the
|
|
and wb or WB width N is the smallest N width N is the smallest N
|
|
greater than 0 which can greater than 0 which can
|
|
accommodate the value. accommodate the value.
|
|
</pre>
|
|
<a name='6.4.4.1p7'></a>
|
|
<pre>7 If an integer constant cannot be represented by any type in its list, it may have an extended integer
|
|
type, if the extended integer type can represent its value. If all of the types in the list for the constant
|
|
are signed, the extended integer type shall be signed. If all of the types in the list for the constant
|
|
are unsigned, the extended integer type shall be unsigned. If the list contains both signed and
|
|
unsigned types, the extended integer type may be signed or unsigned. If an integer constant cannot
|
|
be represented by any type in its list and has no extended integer type, then the integer constant has
|
|
no type.
|
|
</pre>
|
|
<a name='6.4.4.1p8'></a>
|
|
<pre>8 EXAMPLE 1 The wb suffix results in an _BitInt that includes space for the sign bit even if the value of the constant is
|
|
positive or was specified in hexadecimal or octal notation.
|
|
|
|
-3wb /* Yields an _BitInt(3) that is then negated; two value
|
|
bits, one sign bit */
|
|
-0x3wb /* Yields an _BitInt(3) that is then negated; two value
|
|
bits, one sign bit */
|
|
3wb /* Yields an _BitInt(3); two value bits, one sign bit */
|
|
3uwb /* Yields an unsigned _BitInt(2) */
|
|
-3uwb /* Yields an unsigned _BitInt(2) that is then negated,
|
|
resulting in wrap-around */
|
|
|
|
|
|
|
|
Forward references: preprocessing numbers (<a href='#6.4.8'>6.4.8</a>), numeric conversion functions (<a href='#7.24.1'>7.24.1</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.4.2'></a>
|
|
<hr>
|
|
<h3>6.4.4.2 [Floating constants]</h3>
|
|
<a name='6.4.4.2p1'></a>
|
|
<pre>1 Syntax
|
|
floating-constant:
|
|
decimal-floating-constant
|
|
hexadecimal-floating-constant
|
|
|
|
|
|
|
|
decimal-floating-constant:
|
|
fractional-constant exponent-partopt floating-suffixopt
|
|
digit-sequence exponent-part floating-suffixopt
|
|
|
|
|
|
|
|
hexadecimal-floating-constant:
|
|
hexadecimal-prefix hexadecimal-fractional-constant
|
|
binary-exponent-part floating-suffixopt
|
|
hexadecimal-prefix hexadecimal-digit-sequence
|
|
binary-exponent-part floating-suffixopt
|
|
|
|
|
|
|
|
fractional-constant:
|
|
digit-sequenceopt . digit-sequence
|
|
digit-sequence .
|
|
|
|
|
|
|
|
exponent-part:
|
|
e signopt digit-sequence
|
|
E signopt digit-sequence
|
|
|
|
|
|
|
|
sign: one of
|
|
+ -
|
|
|
|
|
|
|
|
digit-sequence:
|
|
digit
|
|
digit-sequence ’opt digit
|
|
hexadecimal-fractional-constant:
|
|
hexadecimal-digit-sequenceopt . hexadecimal-digit-sequence
|
|
hexadecimal-digit-sequence .
|
|
|
|
|
|
|
|
binary-exponent-part:
|
|
p signopt digit-sequence
|
|
P signopt digit-sequence
|
|
|
|
|
|
|
|
floating-suffix: one of
|
|
f l F L df dd dl DF DD DL
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.4.4.2p2'></a>
|
|
<pre>2 A floating suffix df, dd, dl, DF, DD, or DL shall not be used in a hexadecimal floating constant.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.4.4.2p3'></a>
|
|
<pre>3 A floating constant has a significand part that may be followed by an exponent part and a suffix that
|
|
specifies its type. The components of the significand part may include a digit sequence representing
|
|
the whole-number part, followed by a period ( .), followed by a digit sequence representing the
|
|
fraction part. Digit separators (<a href='#6.4.4.1'>6.4.4.1</a>) are ignored when determining the value of the constant. The
|
|
components of the exponent part are an e, E, p, or P followed by an exponent consisting of an
|
|
optionally signed digit sequence. Either the whole-number part or the fraction part has to be present;
|
|
for decimal floating constants, either the period or the exponent part has to be present.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4.2p4'></a>
|
|
<pre>4 The significand part is interpreted as a (decimal or hexadecimal) rational number; the digit sequence
|
|
in the exponent part is interpreted as a decimal integer. For decimal floating constants, the exponent
|
|
indicates the power of 10 by which the significand part is to be scaled. For hexadecimal floating
|
|
constants, the exponent indicates the power of 2 by which the significand part is to be scaled. For
|
|
decimal floating constants, and also for hexadecimal floating constants when FLT_RADIX is not a
|
|
power of 2, the result is either the nearest representable value, or the larger or smaller representable
|
|
value immediately adjacent to the nearest representable value, chosen in an implementation-defined
|
|
manner. For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is correctly
|
|
rounded.
|
|
</pre>
|
|
<a name='6.4.4.2p5'></a>
|
|
<pre>5 An unsuffixed floating constant has type double. If suffixed by a floating suffix it has a type
|
|
according to the following table:
|
|
|
|
Suffixes for floating constants
|
|
|
|
Suffix Type
|
|
f, F float
|
|
l, L long double
|
|
df, DF _Decimal32
|
|
dd, DD _Decimal64
|
|
dl, DL _Decimal128
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.4.4.2p6'></a>
|
|
<pre>6 The values of floating constants may be represented in greater range and precision than that required
|
|
by the type (determined by the suffix); the types are not changed thereby. See <a href='#5.2.4.2.2'>5.2.4.2.2</a> regarding
|
|
evaluation formats. <a href='#FOOTNOTE.84'><sup>[84]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.84'>
|
|
<pre><i><b>Footnote 84)</b> Hexadecimal floating constants can be used to obtain exact values in the semantic type that are independent of the
|
|
evaluation format. Casts produce values in the semantic type, though depend on the rounding mode and may raise the
|
|
inexact floating-point exception.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.2p7'></a>
|
|
<pre>7 Floating constants of decimal floating type that have the same numerical value but different quantum
|
|
exponents have distinguishable internal representations. The value shall be correctly rounded as
|
|
specified in IEC 60559. The coefficient c and the quantum exponent q of a finite converted decimal
|
|
floating-point number (see <a href='#5.2.4.2.3'>5.2.4.2.3</a>) are determined as follows:
|
|
|
|
— q is set to the value of signopt digit-sequence in the exponent part, if any, or to 0, otherwise.
|
|
|
|
— If there is a fractional constant, q is decreased by the number of digits to the right of the period
|
|
and the period is removed to form a digit sequence.
|
|
— c is set to the value of the digit sequence (after any period has been removed).
|
|
— Rounding required because of insufficient precision or range in the type of the result will
|
|
round c to the full precision available in the type, and will adjust q accordingly within the
|
|
limits of the type, provided the rounding does not yield an infinity (in which case the result
|
|
is an appropriately signed internal representation of infinity). If the full precision of the type
|
|
would require q to be smaller than the minimum for the type, then q is pinned at the minimum
|
|
and c is adjusted through the subnormal range accordingly, perhaps to zero.
|
|
|
|
</pre>
|
|
<a name='6.4.4.2p8'></a>
|
|
<pre>8 Floating constants are converted to internal format as if at translation-time. The conversion of a
|
|
floating constant shall not raise an exceptional condition or a floating-point exception at execution
|
|
time. All floating constants of the same source form <a href='#FOOTNOTE.85'><sup>[85]</sup></a> shall convert to the same internal format
|
|
with the same value.
|
|
</pre>
|
|
<a name='FOOTNOTE.85'>
|
|
<pre><i><b>Footnote 85)</b> 1.23 , 1.230 , 123e-2 , 123e-02 , and <a href='#1.'>1.</a>23L are all different source forms and thus need not convert to the same internal
|
|
format and value.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.2p9'></a>
|
|
<pre>9 EXAMPLE Following are floating constants of type _Decimal64 and their values as triples (s, c, q). Note that for
|
|
_Decimal64 , the precision (maximum coefficient length) is 16 and the quantum exponent range is −398 ≤ q ≤ 369.
|
|
|
|
|
|
0.dd (+1, 0, 0)
|
|
0.00dd (+1, 0, −2)
|
|
123.dd (+1, 123, 0)
|
|
<a href='#1.'>1.</a>23E3dd (+1, 123, 1)
|
|
<a href='#1.'>1.</a>23E+3dd (+1, 123, 1)
|
|
12.3E+7dd (+1, 123, 6)
|
|
12.0dd (+1, 120, −1)
|
|
12.3dd (+1, 123, −1)
|
|
0.00123dd (+1, 123, −5)
|
|
<a href='#1.'>1.</a>23E-12dd (+1, 123, −14)
|
|
1234.5E-4dd (+1, 12345, −5)
|
|
0E+7dd (+1, 0, 7)
|
|
12345678901234567890.dd (+1, 1234567890123457, 4) assuming default rounding and DEC_EVAL_METHOD is 0
|
|
or <a href='#FOOTNOTE.186'><sup>[186]</sup></a>
|
|
1234E-400dd (+1, 12, −398) assuming default rounding and DEC_EVAL_METHOD is 0 or 1
|
|
1234E-402dd (+1, 0, −398) assuming default rounding and DEC_EVAL_METHOD is 0 or 1
|
|
1000.dd (+1, 1000, 0)
|
|
.0001dd (+1, 1, −4)
|
|
1000.e0dd (+1, 1000, 0)
|
|
.0001e0dd (+1, 1, −4)
|
|
1000.0dd (+1, 10000, −1)
|
|
0.0001dd (+1, 1, −4)
|
|
1000.00dd (+1, 100000, −2)
|
|
00.0001dd (+1, 1, −4)
|
|
001000.dd (+1, 1000, 0)
|
|
001000.0dd (+1, 10000, −1)
|
|
001000.00dd (+1, 100000, −2)
|
|
00.00dd (+1, 0, −2)
|
|
00.dd (+1, 0, 0)
|
|
.00dd (+1, 0, −2)
|
|
00.00e-5dd (+1, 0, −7)
|
|
00.e-5dd (+1, 0, −5)
|
|
.00e-5dd (+1, 0, −7)
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.186'>
|
|
<pre><i><b>Footnote 186)</b> Thus, the attributes [[nodiscard]] and [[__nodiscard__]] can be freely interchanged. Implementations are encour-
|
|
aged to behave similarly for attribute tokens (including attribute prefixed tokens) they provide.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.2p10'></a>
|
|
<pre>10 The implementation should produce a diagnostic message if a hexadecimal constant cannot be
|
|
represented exactly in its evaluation format; the implementation should then proceed with the
|
|
translation of the program.
|
|
</pre>
|
|
<a name='6.4.4.2p11'></a>
|
|
<pre>11 The translation-time conversion of floating constants should match the execution-time conversion
|
|
of character strings by library functions, such as strtod, given matching inputs suitable for both
|
|
conversions, the same result format, and default execution-time rounding. <a href='#FOOTNOTE.87'><sup>[87]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.87'>
|
|
<pre><i><b>Footnote 87)</b> The specification for the library functions recommends more accurate conversion than required for floating constants
|
|
(see <a href='#7.24.1.5'>7.24.1.5</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.2p12'></a>
|
|
<pre>12 NOTE Floating constants do not include a sign and are negated by the unary - operator (<a href='#6.5.3.3'>6.5.3.3</a>) which negates the rounded
|
|
value of the constant. In contrast, the numeric conversion functions in the strto family (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.24.1.6'>7.24.1.6</a>) include the sign as
|
|
part of the input value and convert and round the negated input. Negating before rounding and negating after rounding
|
|
might yield different results, depending on the rounding direction and whether the results are correctly rounded. For
|
|
example, the results are the same when both are correctly rounded using rounding to nearest or rounding toward zero, but
|
|
the results are different when they are inexact and correctly rounded using rounding toward positive infinity or rounding
|
|
toward negative infinity.
|
|
Conversions yielding exact results require no rounding, so are not affected by the order of negating and rounding. For
|
|
types with radix 10, decimal floating constants expressed within the precision and range of the evaluation format convert
|
|
exactly. For types whose radix is a power of 2, hexadecimal floating constants expressed within the precision and range of the
|
|
evaluation format convert exactly.
|
|
|
|
Forward references: preprocessing numbers (<a href='#6.4.8'>6.4.8</a>), numeric conversion functions (<a href='#7.24.1'>7.24.1</a>), the
|
|
strto function family (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.24.1.6'>7.24.1.6</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.4.3'></a>
|
|
<hr>
|
|
<h3>6.4.4.3 [Enumeration constants]</h3>
|
|
<a name='6.4.4.3p1'></a>
|
|
<pre>1 Syntax
|
|
enumeration-constant:
|
|
identifier
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4.3p2'></a>
|
|
<pre>2 An identifier declared as an enumeration constant for an enumeration without a fixed underlying
|
|
type has either type int or the enumerated type, as defined in <a href='#6.7.2.2'>6.7.2.2</a>. An identifier declared
|
|
as an enumeration constant for an enumeration with a fixed underlying type has the associated
|
|
enumeration type.
|
|
</pre>
|
|
<a name='6.4.4.3p3'></a>
|
|
<pre>3 An enumeration constant may be used in an expression (or constant expression) wherever a value
|
|
of an integer type may be used.
|
|
Forward references: enumeration specifiers (<a href='#6.7.2.2'>6.7.2.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.4.4'></a>
|
|
<hr>
|
|
<h3>6.4.4.4 [Character constants]</h3>
|
|
<a name='6.4.4.4p1'></a>
|
|
<pre>1 Syntax
|
|
character-constant:
|
|
encoding-prefixopt ’ c-char-sequence ’
|
|
|
|
encoding-prefix:
|
|
u8
|
|
u
|
|
U
|
|
L
|
|
|
|
|
|
|
|
c-char-sequence:
|
|
c-char
|
|
c-char-sequence c-char
|
|
c-char:
|
|
any member of the source character set except
|
|
the single-quote ’, backslash \ , or new-line character
|
|
escape-sequence
|
|
|
|
|
|
|
|
escape-sequence:
|
|
simple-escape-sequence
|
|
octal-escape-sequence
|
|
hexadecimal-escape-sequence
|
|
universal-character-name
|
|
|
|
|
|
|
|
simple-escape-sequence: one of
|
|
\’ \" \? \\
|
|
\a \b \f \n \r \t \v
|
|
|
|
|
|
|
|
octal-escape-sequence:
|
|
\ octal-digit
|
|
\ octal-digit octal-digit
|
|
\ octal-digit octal-digit octal-digit
|
|
|
|
|
|
|
|
hexadecimal-escape-sequence:
|
|
\x hexadecimal-digit
|
|
hexadecimal-escape-sequence hexadecimal-digit
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.4.4.4p2'></a>
|
|
<pre>2 An integer character constant is a sequence of one or more multibyte characters enclosed in single-
|
|
quotes, as in ’x’ . A UTF-8 character constant is the same, except prefixed by u8. A wchar_t character
|
|
constant is prefixed by the letter L. A UTF-16 character constant is prefixed by the letter u. A UTF-32
|
|
character constant is prefixed by the letter U. Collectively, wchar_t, UTF-16, and UTF-32 character
|
|
constants are called wide character constants. With a few exceptions detailed later, the elements of
|
|
the sequence are any members of the source character set; they are mapped in an implementation-
|
|
defined manner to members of the execution character set.
|
|
</pre>
|
|
<a name='6.4.4.4p3'></a>
|
|
<pre>3 The single-quote ’, the double-quote ", the question-mark ?, the backslash \, and arbitrary integer
|
|
values are representable according to the following table of escape sequences:
|
|
single quote ’ \’
|
|
double quote " \"
|
|
question mark ? \?
|
|
backslash \ \\
|
|
octal character \ octal digits
|
|
hexadecimal character \x hexadecimal digits
|
|
</pre>
|
|
<a name='6.4.4.4p4'></a>
|
|
<pre>4 The double-quote " and question-mark ? are representable either by themselves or by the escape
|
|
sequences \" and \?, respectively, but the single-quote ’ and the backslash \ shall be represented,
|
|
respectively, by the escape sequences \’ and \\ .
|
|
</pre>
|
|
<a name='6.4.4.4p5'></a>
|
|
<pre>5 The octal digits that follow the backslash in an octal escape sequence are taken to be part of the
|
|
construction of a single character for an integer character constant or of a single wide character for a
|
|
wide character constant. The numerical value of the octal integer so formed specifies the value of
|
|
the desired character or wide character.
|
|
</pre>
|
|
<a name='6.4.4.4p6'></a>
|
|
<pre>6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape sequence
|
|
are taken to be part of the construction of a single character for an integer character constant or of a
|
|
single wide character for a wide character constant. The numerical value of the hexadecimal integer
|
|
so formed specifies the value of the desired character or wide character.
|
|
</pre>
|
|
<a name='6.4.4.4p7'></a>
|
|
<pre>7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can constitute
|
|
the escape sequence.
|
|
</pre>
|
|
<a name='6.4.4.4p8'></a>
|
|
<pre>8 In addition, characters not in the basic character set are representable by universal character names
|
|
and certain non-graphic characters are representable by escape sequences consisting of the back-
|
|
slash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t, and \v.<a href='#FOOTNOTE.88'><sup>[88]</sup></a>
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='FOOTNOTE.88'>
|
|
<pre><i><b>Footnote 88)</b> The semantics of these characters were discussed in <a href='#5.2.2'>5.2.2</a>. If any other character follows a backslash, the result is not a
|
|
token and a diagnostic is required. See "future language directions" (<a href='#6.11.4'>6.11.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.4p9'></a>
|
|
<pre>9 The value of an octal or hexadecimal escape sequence shall be in the range of representable values
|
|
for the corresponding type:
|
|
Prefix Corresponding Type
|
|
none unsigned char
|
|
u8 char8_t
|
|
L the unsigned type corresponding to wchar_t
|
|
u char16_t
|
|
U char32_t
|
|
|
|
</pre>
|
|
<a name='6.4.4.4p10'></a>
|
|
<pre>10 A UTF-8, UTF-16, or UTF-32 character constant shall not contain more than one character.<a href='#FOOTNOTE.89'><sup>[89]</sup></a> The
|
|
value shall be representable with a single UTF-8, UTF-16, or UTF-32 code unit.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.89'>
|
|
<pre><i><b>Footnote 89)</b> For example u8’ab’ violates this constraint.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.4p11'></a>
|
|
<pre>11 An integer character constant has type int. The value of an integer character constant containing
|
|
a single character that maps to a single value in the literal encoding (<a href='#6.2.9'>6.2.9</a>) is the numerical value
|
|
of the representation of the mapped character in the literal encoding interpreted as an integer.
|
|
The value of an integer character constant containing more than one character (e.g., ’ab’ ), or
|
|
containing a character or escape sequence that does not map to a single value in the literal encoding,
|
|
is implementation-defined. If an integer character constant contains a single character or escape
|
|
sequence, its value is the one that results when an object with type char whose value is that of the
|
|
single character or escape sequence is converted to type int.
|
|
</pre>
|
|
<a name='6.4.4.4p12'></a>
|
|
<pre>12 A UTF-8 character constant has type char8_t. If the UTF8 character constant is not produced
|
|
through a hexadecimal or octal escape sequence, the value of a UTF-8 character constant is equal to
|
|
its ISO/IEC 10646 code point value, provided that the code point value can be encoded as a single
|
|
UTF-8 code unit. Otherwise, the value of the UTF8 character constant is the numeric value specified
|
|
in the hexadecimal or octal escape sequence.
|
|
</pre>
|
|
<a name='6.4.4.4p13'></a>
|
|
<pre>13 A UTF-16 character constant has type char16_t which is an unsigned integer types defined in the
|
|
<uchar.h> header. If the UTF-16 character constant is not produced through a hexadecimal or octal
|
|
escape sequence, the value of a UTF-16 character constant is equal to its ISO/IEC 10646 code point
|
|
value, provided that the code point value can be encoded as a single UTF-16 code unit. Otherwise,
|
|
the value of the UTF-16 character constant is the numeric value specified in the hexadecimal or octal
|
|
escape sequence.
|
|
</pre>
|
|
<a name='6.4.4.4p14'></a>
|
|
<pre>14 A UTF-32 character constant has type char32_t which is an unsigned integer types defined in the
|
|
<uchar.h> header. If the UTF-32 character constant is not produced through a hexadecimal or octal
|
|
escape sequence, the value of a UTF-32 character constant is equal to its ISO/IEC 10646 code point
|
|
value, provided that the code point value can be encoded as a single UTF-32 code unit. Otherwise,
|
|
the value of the UTF-32 character constant is the numeric value specified in the hexadecimal or octal
|
|
escape sequence.
|
|
</pre>
|
|
<a name='6.4.4.4p15'></a>
|
|
<pre>15 A wchar_t character constant prefixed by the letter L has type wchar_t, an integer type defined in
|
|
the <stddef.h> header. The value of a wchar_t character constant containing a single multibyte
|
|
character that maps to a single member of the extended execution character set is the wide character
|
|
corresponding to that multibyte character in the implementation-defined wide literal encoding
|
|
(<a href='#6.2.9'>6.2.9</a>). The value of a wchar_t character constant containing more than one multibyte character or a
|
|
single multibyte character that maps to multiple members of the extended execution character set,
|
|
or containing a multibyte character or escape sequence not represented in the extended execution
|
|
character set, is implementation-defined.
|
|
</pre>
|
|
<a name='6.4.4.4p16'></a>
|
|
<pre>16 EXAMPLE 1 The construction ’\0’ is commonly used to represent the null character.
|
|
</pre>
|
|
<a name='6.4.4.4p17'></a>
|
|
<pre>17 EXAMPLE 2 Consider implementations that use eight bits for objects that have type char. In an implementation in which
|
|
type char has the same range of values as signed char, the integer character constant ’\xFF’ has the value −1; if type
|
|
char has the same range of values as unsigned char, the character constant ’\xFF’ has the value +255.
|
|
|
|
</pre>
|
|
<a name='6.4.4.4p18'></a>
|
|
<pre>18 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction ’\x123’ specifies an integer character
|
|
constant containing only one character, since a hexadecimal escape sequence is terminated only by a non-hexadecimal
|
|
character. To specify an integer character constant containing the two characters whose values are ’\x12’ and ’3’ , the
|
|
construction ’\0223’ can be used, since an octal escape sequence is terminated after three octal digits. (The value of this
|
|
two-character integer character constant is implementation-defined.)
|
|
</pre>
|
|
<a name='6.4.4.4p19'></a>
|
|
<pre>19 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction L’\1234’ specifies the
|
|
implementation-defined value that results from the combination of the values 0123 and ’4’ .
|
|
|
|
Forward references: common definitions <stddef.h> (<a href='#7.21'>7.21</a>), the mbtowc function (<a href='#7.24.7.2'>7.24.7.2</a>), Uni-
|
|
code utilities <uchar.h> (<a href='#7.30'>7.30</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.4.5'></a>
|
|
<hr>
|
|
<h3>6.4.4.5 [Predefined constants]</h3>
|
|
<a name='6.4.4.5p1'></a>
|
|
<pre>1 Syntax
|
|
predefined-constant:
|
|
false
|
|
true
|
|
nullptr
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.4.4.5p2'></a>
|
|
<pre>2 Some keywords represent constants of a specific value and type.
|
|
</pre>
|
|
<a name='6.4.4.5p3'></a>
|
|
<pre>3 The keywords false and true are constants of type bool with a value of 0 for false and 1 for
|
|
true<a href='#FOOTNOTE.90'><sup>[90]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.90'>
|
|
<pre><i><b>Footnote 90)</b> The constants false and true promote to type int, see <a href='#6.3.1.1'>6.3.1.1</a>. When used for arithmetic, in translation phase 4, they are
|
|
signed values and the result of such arithmetic is consistent with the results of later translation phases.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.4.5p4'></a>
|
|
<pre>4 The keyword nullptr represents a null pointer constant. Details of its type are described in <a href='#7.21.2'>7.21.2</a>.
|
|
|
|
</pre>
|
|
<a name='6.4.5'></a>
|
|
<hr>
|
|
<h3>6.4.5 [String literals]</h3>
|
|
<a name='6.4.5p1'></a>
|
|
<pre>1 Syntax
|
|
string-literal:
|
|
encoding-prefixopt " s-char-sequenceopt "
|
|
|
|
s-char-sequence:
|
|
s-char
|
|
s-char-sequence s-char
|
|
|
|
|
|
|
|
s-char:
|
|
any member of the source character set except
|
|
the double-quote ", backslash \, or new-line character
|
|
escape-sequence
|
|
Constraints
|
|
</pre>
|
|
<a name='6.4.5p2'></a>
|
|
<pre>2 If a sequence of adjacent string literal tokens includes prefixed string literal tokens, the prefixed
|
|
tokens shall all have the same prefix.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.4.5p3'></a>
|
|
<pre>3 A character string literal is a sequence of zero or more multibyte characters enclosed in double-quotes,
|
|
as in "xyz". A UTF-8 string literal is the same, except prefixed by u8. A wchar_t string literal is the
|
|
same, except prefixed by L. A UTF-16 string literal is the same, except prefixed by u. A UTF-32 string
|
|
literal is the same, except prefixed by U. Collectively, wchar_t, UTF-16, and UTF-32 string literals are
|
|
called wide string literals.
|
|
</pre>
|
|
<a name='6.4.5p4'></a>
|
|
<pre>4 The same considerations apply to each element of the sequence in a string literal as if it were in an
|
|
integer character constant (for a character or UTF-8 string literal) or a wide character constant (for a
|
|
wide string literal), except that the single-quote ’ is representable either by itself or by the escape
|
|
sequence \’, but the double-quote " shall be represented by the escape sequence \".
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.5p5'></a>
|
|
<pre>5 In translation phase 6, the multibyte character sequences specified by any sequence of adjacent
|
|
character and identically-prefixed string literal tokens are concatenated into a single multibyte
|
|
character sequence. If any of the tokens has an encoding prefix, the resulting multibyte character
|
|
sequence is treated as having the same prefix; otherwise, it is treated as a character string literal.
|
|
</pre>
|
|
<a name='6.4.5p6'></a>
|
|
<pre>6 In translation phase 7, a byte or code of value zero is appended to each multibyte character sequence
|
|
that results from a string literal or literals. <a href='#FOOTNOTE.91'><sup>[91]</sup></a> The multibyte character sequence is then used to
|
|
initialize an array of static storage duration and length just sufficient to contain the sequence. For
|
|
character string literals, the array elements have type char, and are initialized with the individual
|
|
bytes of the multibyte character sequence corresponding to the literal encoding (<a href='#6.2.9'>6.2.9</a>). For UTF-8
|
|
string literals, the array elements have type char8_t, and are initialized with the characters of the
|
|
multibyte character sequence, as encoded in UTF-8. For wide string literals prefixed by the letter
|
|
L, the array elements have type wchar_t and are initialized with the sequence of wide characters
|
|
corresponding to the wide literal encoding. For wide string literals prefixed by the letter u or U,
|
|
the array elements have type char16_t or char32_t, respectively, and are initialized sequence of
|
|
wide characters corresponding to UTF-16 and UTF-32 encoded text, respectively. The value of a
|
|
string literal containing a multibyte character or escape sequence not represented in the execution
|
|
character set is implementation-defined. Any hexadecimal escape sequence or octal escape sequence
|
|
specified in a u8, u, or U string specifies a single char8_t, char16_t, or char32_t value and may
|
|
result in the full character sequence not being valid UTF-8, UTF-16, or UTF-32.
|
|
</pre>
|
|
<a name='FOOTNOTE.91'>
|
|
<pre><i><b>Footnote 91)</b> A string literal might not be a string (see <a href='#7.1.1'>7.1.1</a>), because a null character can be embedded in it by a \0 escape sequence.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.5p7'></a>
|
|
<pre>7 It is unspecified whether these arrays are distinct provided their elements have the appropriate
|
|
values. If the program attempts to modify such an array, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.4.5p8'></a>
|
|
<pre>8 EXAMPLE 1 This pair of adjacent character string literals
|
|
|
|
"\x12" "3"
|
|
|
|
produces a single character string literal containing the two characters whose values are ’\x12’ and ’3’ , because escape
|
|
sequences are converted into single members of the execution character set just prior to adjacent string literal concatenation.
|
|
</pre>
|
|
<a name='6.4.5p9'></a>
|
|
<pre>9 EXAMPLE 2 Each of the sequences of adjacent string literal tokens
|
|
|
|
"a" "b" L"c"
|
|
"a" L"b" "c"
|
|
L"a" "b" L"c"
|
|
L"a" L"b" L"c"
|
|
|
|
is equivalent to the string literal
|
|
|
|
L"abc"
|
|
|
|
Likewise, each of the sequences
|
|
"a" "b" u"c"
|
|
"a" u"b" "c"
|
|
u"a" "b" u"c"
|
|
u"a" u"b" u"c"
|
|
|
|
is equivalent to
|
|
|
|
u"abc"
|
|
|
|
|
|
Forward references: common definitions <stddef.h> (<a href='#7.21'>7.21</a>), the mbstowcs function (<a href='#7.24.8.1'>7.24.8.1</a>),
|
|
Unicode utilities <uchar.h> (<a href='#7.30'>7.30</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.6'></a>
|
|
<hr>
|
|
<h3>6.4.6 [Punctuators]</h3>
|
|
<a name='6.4.6p1'></a>
|
|
<pre>1 Syntax
|
|
punctuator: one of
|
|
[ ] ( ) { } . ->
|
|
++ -- & * + - ~ !
|
|
/ % << >> < > <= >= == != ^ | && ||
|
|
? : :: ; ...
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
, # ##
|
|
<: :> <% %> %: %:%:
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.6p2'></a>
|
|
<pre>2 A punctuator is a symbol that has independent syntactic and semantic significance. Depending on
|
|
context, it may specify an operation to be performed (which in turn may yield a value or a function
|
|
designator, produce a side effect, or some combination thereof) in which case it is known as an
|
|
operator (other forms of operator also exist in some contexts). An operand is an entity on which an
|
|
operator acts.
|
|
</pre>
|
|
<a name='6.4.6p3'></a>
|
|
<pre>3 In all aspects of the language, the six tokens<a href='#FOOTNOTE.92'><sup>[92]</sup></a>
|
|
<: :> <% %> %: %:%:
|
|
behave, respectively, the same as the six tokens
|
|
[ ] { } # ##
|
|
except for their spelling.<a href='#FOOTNOTE.93'><sup>[93]</sup></a>
|
|
Forward references: expressions (<a href='#6.5'>6.5</a>), declarations (<a href='#6.7'>6.7</a>), preprocessing directives (<a href='#6.10'>6.10</a>), statements
|
|
(<a href='#6.8'>6.8</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.92'>
|
|
<pre><i><b>Footnote 92)</b> These tokens are sometimes called "digraphs".
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.93'>
|
|
<pre><i><b>Footnote 93)</b> Thus [ and <: behave differently when "stringized" (see <a href='#6.10.4.2'>6.10.4.2</a>), but can otherwise be freely interchanged.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.7'></a>
|
|
<hr>
|
|
<h3>6.4.7 [Header names]</h3>
|
|
<a name='6.4.7p1'></a>
|
|
<pre>1 Syntax
|
|
header-name:
|
|
< h-char-sequence >
|
|
" q-char-sequence "
|
|
|
|
|
|
|
|
h-char-sequence:
|
|
h-char
|
|
h-char-sequence h-char
|
|
h-char:
|
|
any member of the source character set except
|
|
the new-line character and >
|
|
|
|
|
|
|
|
q-char-sequence:
|
|
q-char
|
|
q-char-sequence q-char
|
|
|
|
|
|
|
|
q-char:
|
|
any member of the source character set except
|
|
the new-line character and "
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.7p2'></a>
|
|
<pre>2 The sequences in both forms of header names are mapped in an implementation-defined manner to
|
|
headers or external source file names as specified in <a href='#6.10.2'>6.10.2</a>.
|
|
</pre>
|
|
<a name='6.4.7p3'></a>
|
|
<pre>3 If the characters ’ , \ , ", // , or /* occur in the sequence between the < and > delimiters, the behavior
|
|
is undefined. Similarly, if the characters ’ , \ , // , or /* occur in the sequence between the "
|
|
delimiters, the behavior is undefined.<a href='#FOOTNOTE.94'><sup>[94]</sup></a> Header name preprocessing tokens are recognized only
|
|
within #include preprocessing directives and in implementation-defined locations within #pragma
|
|
directives.<a href='#FOOTNOTE.95'><sup>[95]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.94'>
|
|
<pre><i><b>Footnote 94)</b> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.95'>
|
|
<pre><i><b>Footnote 95)</b> For an example of a header name preprocessing token used in a #pragma directive, see <a href='#6.10.10'>6.10.10</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.7p4'></a>
|
|
<pre>4 EXAMPLE The following sequence of characters:
|
|
|
|
0x3<1/a.h>1e2
|
|
#include <1/a.h>
|
|
#define const.member@$
|
|
|
|
forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited by a { on the left
|
|
and a } on the right).
|
|
|
|
{0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
|
|
{#}{include} {<1/a.h>}
|
|
{#}{define} {const}{.}{member}{@}{$}
|
|
|
|
|
|
Forward references: source file inclusion (<a href='#6.10.2'>6.10.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.4.8'></a>
|
|
<hr>
|
|
<h3>6.4.8 [Preprocessing numbers]</h3>
|
|
<a name='6.4.8p1'></a>
|
|
<pre>1 Syntax
|
|
pp-number:
|
|
digit
|
|
. digit
|
|
pp-number identifier-continue
|
|
pp-number ’ digit
|
|
pp-number ’ nondigit
|
|
pp-number e sign
|
|
pp-number E sign
|
|
pp-number p sign
|
|
pp-number P sign
|
|
pp-number .
|
|
Description
|
|
</pre>
|
|
<a name='6.4.8p2'></a>
|
|
<pre>2 A preprocessing number begins with a digit optionally preceded by a period (.) and may be followed
|
|
by valid identifier characters and the character sequences e+, e-, E+, E-, p+, p-, P+, or P-.
|
|
</pre>
|
|
<a name='6.4.8p3'></a>
|
|
<pre>3 Preprocessing number tokens lexically include all floating and integer constant tokens.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.8p4'></a>
|
|
<pre>4 A preprocessing number does not have type or a value; it acquires both after a successful conversion
|
|
(as part of translation phase 7) to a floating constant token or an integer constant token.
|
|
|
|
</pre>
|
|
<a name='6.4.9'></a>
|
|
<hr>
|
|
<h3>6.4.9 [Comments]</h3>
|
|
<a name='6.4.9p1'></a>
|
|
<pre>1 Except within a character constant, a string literal, or a comment, the characters /* introduce a
|
|
comment. The contents of such a comment are examined only to identify multibyte characters and
|
|
to find the characters */ that terminate it.<a href='#FOOTNOTE.96'><sup>[96]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.96'>
|
|
<pre><i><b>Footnote 96)</b> Thus, /
|
|
* . . . */ comments do not nest.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.9p2'></a>
|
|
<pre>2 Except within a character constant, a string literal, or a comment, the characters // introduce a
|
|
comment that includes all multibyte characters up to, but not including, the next new-line character.
|
|
The contents of such a comment are examined only to identify multibyte characters and to find the
|
|
terminating new-line character.
|
|
</pre>
|
|
<a name='6.4.9p3'></a>
|
|
<pre>3 EXAMPLE
|
|
|
|
"a//b" // four-character string literal
|
|
#include "//e" // undefined behavior
|
|
// */ // comment, not syntax error
|
|
f = g/**//h; // equivalent to f = g / h;
|
|
//\
|
|
i(); // part of a two-line comment
|
|
/\
|
|
/ j(); // part of a two-line comment
|
|
#define glue(x,y) x##y
|
|
glue(/,/) k(); // syntax error, not comment
|
|
/*//*/ l(); // equivalent to l();
|
|
m = n//**/o
|
|
+ p; // equivalent to m = n + p;
|
|
</pre>
|
|
<a name='6.5'></a>
|
|
<hr>
|
|
<h3>6.5 [Expressions]</h3>
|
|
<a name='6.5p1'></a>
|
|
<pre>1 An expression is a sequence of operators and operands that specifies computation of a value, or that
|
|
designates an object or a function, or that generates side effects, or that performs a combination
|
|
thereof. The value computations of the operands of an operator are sequenced before the value
|
|
computation of the result of the operator.
|
|
</pre>
|
|
<a name='6.5p2'></a>
|
|
<pre>2 If a side effect on a scalar object is unsequenced relative to either a different side effect on the
|
|
same scalar object or a value computation using the value of the same scalar object, the behavior
|
|
is undefined. If there are multiple allowable orderings of the subexpressions of an expression, the
|
|
behavior is undefined if such an unsequenced side effect occurs in any of the orderings.<a href='#FOOTNOTE.97'><sup>[97]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.97'>
|
|
<pre><i><b>Footnote 97)</b> This paragraph renders undefined statement expressions such as
|
|
i = ++i + 1;
|
|
a[i++] = i;
|
|
while allowing
|
|
i = i + 1;
|
|
a[i] = i;
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5p3'></a>
|
|
<pre>3 The grouping of operators and operands is indicated by the syntax.<a href='#FOOTNOTE.98'><sup>[98]</sup></a> Except as specified later, side
|
|
effects and value computations of subexpressions are unsequenced.<a href='#FOOTNOTE.99'><sup>[99]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.98'>
|
|
<pre><i><b>Footnote 98)</b> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same as the order of the
|
|
major subclauses of this subclause, highest precedence first. Thus, for example, the expressions allowed as the operands
|
|
of the binary + operator (<a href='#6.5.6'>6.5.6</a>) are those expressions defined in <a href='#6.5.1'>6.5.1</a> through <a href='#6.5.6'>6.5.6</a>. The exceptions are cast expressions
|
|
(<a href='#6.5.4'>6.5.4</a>) as operands of unary operators (<a href='#6.5.3'>6.5.3</a>), and an operand contained between any of the following pairs of operators:
|
|
grouping parentheses () (<a href='#6.5.1'>6.5.1</a>), subscripting brackets [] (<a href='#6.5.2.1'>6.5.2.1</a>), function-call parentheses () (<a href='#6.5.2.2'>6.5.2.2</a>), and the conditional
|
|
operator ?: (<a href='#6.5.15'>6.5.15</a>).
|
|
Within each major subclause, the operators have the same precedence. Left- or right-associativity is indicated in each
|
|
subclause by the syntax for the expressions discussed therein.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.99'>
|
|
<pre><i><b>Footnote 99)</b> In an expression that is evaluated more than once during the execution of a program, unsequenced and indeterminately
|
|
sequenced evaluations of its subexpressions need not be performed consistently in different evaluations.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5p4'></a>
|
|
<pre>4 Some operators (the unary operator ~ , and the binary operators << , >> , &, ^, and |, collectively
|
|
described as bitwise operators) are required to have operands that have integer type. These operators
|
|
yield values that depend on the internal representations of integers, and have implementation-
|
|
defined and undefined aspects for signed types.
|
|
</pre>
|
|
<a name='6.5p5'></a>
|
|
<pre>5 If an exceptional condition occurs during the evaluation of an expression (that is, if the result is not
|
|
mathematically defined or not in the range of representable values for its type), the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='6.5p6'></a>
|
|
<pre>6 The effective type of an object for an access to its stored value is the declared type of the object, if
|
|
any.<a href='#FOOTNOTE.100'><sup>[100]</sup></a> If a value is stored into an object having no declared type through an lvalue having a type
|
|
that is not a non-atomic character type, then the type of the lvalue becomes the effective type of the
|
|
object for that access and for subsequent accesses that do not modify the stored value. If a value
|
|
is copied into an object having no declared type using memcpy or memmove, or is copied as an array
|
|
of character type, then the effective type of the modified object for that access and for subsequent
|
|
accesses that do not modify the value is the effective type of the object from which the value is
|
|
copied, if it has one. For all other accesses to an object having no declared type, the effective type of
|
|
the object is simply the type of the lvalue used for the access.
|
|
</pre>
|
|
<a name='FOOTNOTE.100'>
|
|
<pre><i><b>Footnote 100)</b> Allocated objects have no declared type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5p7'></a>
|
|
<pre>7 An object shall have its stored value accessed only by an lvalue expression that has one of the
|
|
following types:<a href='#FOOTNOTE.101'><sup>[101]</sup></a>
|
|
|
|
— a type compatible with the effective type of the object,
|
|
|
|
— a qualified version of a type compatible with the effective type of the object,
|
|
|
|
— a type that is the signed or unsigned type corresponding to the effective type of the object,
|
|
— a type that is the signed or unsigned type corresponding to a qualified version of the effective
|
|
type of the object,
|
|
— an aggregate or union type that includes one of the aforementioned types among its members
|
|
(including, recursively, a member of a subaggregate or contained union), or
|
|
— a character type.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.101'>
|
|
<pre><i><b>Footnote 101)</b> The intent of this list is to specify those circumstances in which an object can or cannot be aliased.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5p8'></a>
|
|
<pre>8 A floating expression may be contracted, that is, evaluated as though it were a single opera-
|
|
tion, thereby omitting rounding errors implied by the source code and the expression evalua-
|
|
tion method.<a href='#FOOTNOTE.102'><sup>[102]</sup></a> The FP_CONTRACT pragma in <math.h> provides a way to disallow contracted
|
|
expressions. Otherwise, whether and how expressions are contracted is implementation-defined.<a href='#FOOTNOTE.103'><sup>[103]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.102'>
|
|
<pre><i><b>Footnote 102)</b> The intermediate operations in the contracted expression are evaluated as if to infinite range and precision, while the
|
|
final operation is rounded to the format determined by the expression evaluation method. A contracted expression might
|
|
also omit the raising of floating-point exceptions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.103'>
|
|
<pre><i><b>Footnote 103)</b> This license is specifically intended to allow implementations to exploit fast machine instructions that combine multiple
|
|
C operators. As contractions potentially undermine predictability, and can even decrease accuracy for containing expressions,
|
|
their use needs to be well-defined and clearly documented.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5p9'></a>
|
|
<pre>9 Operators involving decimal floating types are evaluated according to the semantics of IEC 60559,
|
|
including production of results with the preferred quantum exponent as specified in IEC 60559.
|
|
Forward references: the FP_CONTRACT pragma (<a href='#7.12.2'>7.12.2</a>), copying functions (<a href='#7.26.2'>7.26.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.1'></a>
|
|
<hr>
|
|
<h3>6.5.1 [Primary expressions]</h3>
|
|
<a name='6.5.1p1'></a>
|
|
<pre>1 Syntax
|
|
primary-expression:
|
|
identifier
|
|
constant
|
|
string-literal
|
|
( expression )
|
|
generic-selection
|
|
|
|
|
|
Constraints
|
|
The identifier in an identifier primary expression shall have a visible declaration as an ordinary
|
|
identifier that declares an object or a function<a href='#FOOTNOTE.104'><sup>[104]</sup></a> .
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.104'>
|
|
<pre><i><b>Footnote 104)</b> An identifier designating an enumeration constant is a primary expression through the constant production, not the
|
|
identifier production.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.1p2'></a>
|
|
<pre>2 An identifier primary expression designating an object is an lvalue. An identifier primary expression
|
|
designating a function is a function designator.
|
|
</pre>
|
|
<a name='6.5.1p3'></a>
|
|
<pre>3 A constant is a primary expression. Its type depends on its form and value, as detailed in <a href='#6.4.4'>6.4.4</a>.
|
|
</pre>
|
|
<a name='6.5.1p4'></a>
|
|
<pre>4 A string literal is a primary expression. It is an lvalue with type as detailed in <a href='#6.4.5'>6.4.5</a>.
|
|
</pre>
|
|
<a name='6.5.1p5'></a>
|
|
<pre>5 A parenthesized expression is a primary expression. Its type, value, and semantics are identical to
|
|
those of the unparenthesized expression.
|
|
</pre>
|
|
<a name='6.5.1p6'></a>
|
|
<pre>6 A generic selection is a primary expression. Its type, value, and semantics depend on the selected
|
|
generic association, as detailed in the following subclause.
|
|
Forward references: declarations (<a href='#6.7'>6.7</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.1.1'></a>
|
|
<hr>
|
|
<h3>6.5.1.1 [Generic selection]</h3>
|
|
<a name='6.5.1.1p1'></a>
|
|
<pre>1 Syntax
|
|
generic-selection:
|
|
_Generic ( assignment-expression , generic-assoc-list )
|
|
generic-assoc-list:
|
|
generic-association
|
|
generic-assoc-list , generic-association
|
|
generic-association:
|
|
type-name : assignment-expression
|
|
default : assignment-expression
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.1.1p2'></a>
|
|
<pre>2 A generic selection shall have no more than one default generic association. The type name in a
|
|
generic association shall specify a complete object type other than a variably modified type. No two
|
|
generic associations in the same generic selection shall specify compatible types. The type of the
|
|
controlling expression is the type of the expression as if it had undergone an lvalue conversion,<a href='#FOOTNOTE.105'><sup>[105]</sup></a>
|
|
array to pointer conversion, or function to pointer conversion. That type shall be compatible with at
|
|
most one of the types named in the generic association list. If a generic selection has no default
|
|
generic association, its controlling expression shall have type compatible with exactly one of the
|
|
types named in its generic association list.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.105'>
|
|
<pre><i><b>Footnote 105)</b> An lvalue conversion drops type qualifiers.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.1.1p3'></a>
|
|
<pre>3 The controlling expression of a generic selection is not evaluated. If a generic selection has a generic
|
|
association with a type name that is compatible with the type of the controlling expression, then the
|
|
result expression of the generic selection is the expression in that generic association. Otherwise, the
|
|
result expression of the generic selection is the expression in the default generic association. None
|
|
of the expressions from any other generic association of the generic selection is evaluated.
|
|
</pre>
|
|
<a name='6.5.1.1p4'></a>
|
|
<pre>4 The type and value of a generic selection are identical to those of its result expression. It is an
|
|
lvalue, a function designator, or a void expression if its result expression is, respectively, an lvalue, a
|
|
function designator, or a void expression.
|
|
</pre>
|
|
<a name='6.5.1.1p5'></a>
|
|
<pre>5 EXAMPLE The cbrt type-generic macro could be implemented as follows:
|
|
|
|
#define cbrt(X) _Generic((X), \
|
|
long double: cbrtl, \
|
|
default: cbrt, \
|
|
float: cbrtf \
|
|
)(X)
|
|
|
|
|
|
|
|
See <a href='#7.27'>7.27</a> how such a macro could be implemented with the required rounding properties.
|
|
|
|
|
|
</pre>
|
|
<a name='6.5.2'></a>
|
|
<hr>
|
|
<h3>6.5.2 [Postfix operators]</h3>
|
|
<a name='6.5.2p1'></a>
|
|
<pre>1 Syntax
|
|
postfix-expression:
|
|
primary-expression
|
|
postfix-expression [ expression ]
|
|
postfix-expression ( argument-expression-listopt )
|
|
postfix-expression . identifier
|
|
postfix-expression -> identifier
|
|
postfix-expression ++
|
|
postfix-expression --
|
|
compound-literal
|
|
|
|
argument-expression-list:
|
|
assignment-expression
|
|
argument-expression-list , assignment-expression
|
|
</pre>
|
|
<a name='6.5.2.1'></a>
|
|
<hr>
|
|
<h3>6.5.2.1 [Array subscripting]</h3>
|
|
<a name='6.5.2.1p1'></a>
|
|
<pre>1 Constraints
|
|
One of the expressions shall have type "pointer to complete object type", the other expression shall
|
|
have integer type, and the result has type "type".
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.2.1p2'></a>
|
|
<pre>2 A postfix expression followed by an expression in square brackets [] is a subscripted designation of
|
|
an element of an array object. The definition of the subscript operator [] is that E1[E2] is identical
|
|
to (*((E1)+(E2))) . Because of the conversion rules that apply to the binary + operator, if E1 is an
|
|
array object (equivalently, a pointer to the initial element of an array object) and E2 is an integer,
|
|
E1[E2] designates the E2 -th element of E1 (counting from zero).
|
|
</pre>
|
|
<a name='6.5.2.1p3'></a>
|
|
<pre>3 Successive subscript operators designate an element of a multidimensional array object. If E is an
|
|
n-dimensional array (n ≥ 2) with dimensions i × j × · · · × k, then E (used as other than an lvalue) is
|
|
converted to a pointer to an (n − 1)-dimensional array with dimensions j × · · · × k. If the unary *
|
|
operator is applied to this pointer explicitly, or implicitly as a result of subscripting, the result is the
|
|
referenced (n − 1)-dimensional array, which itself is converted into a pointer if used as other than an
|
|
lvalue. It follows from this that arrays are stored in row-major order (last subscript varies fastest).
|
|
</pre>
|
|
<a name='6.5.2.1p4'></a>
|
|
<pre>4 EXAMPLE Consider the array object defined by the declaration
|
|
|
|
int x[3][5];
|
|
|
|
Here x is a 3 × 5 array of objects of type int; more precisely, x is an array of three element objects, each of which is an array of
|
|
five objects of type int. In the expression x[i], which is equivalent to (*((x)+(i))) , x is first converted to a pointer to the
|
|
initial array of five objects of type int. Then i is adjusted according to the type of x, which conceptually entails multiplying i
|
|
by the size of the object to which the pointer points, namely an array of five int objects. The results are added and indirection
|
|
is applied to yield an array of five objects of type int. When used in the expression x[i][j], that array is in turn converted
|
|
to a pointer to the first of the objects of type int, so x[i][j] yields an int.
|
|
|
|
Forward references: additive operators (<a href='#6.5.6'>6.5.6</a>), address and indirection operators (<a href='#6.5.3.2'>6.5.3.2</a>), array
|
|
declarators (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.2.2'></a>
|
|
<hr>
|
|
<h3>6.5.2.2 [Function calls]</h3>
|
|
<a name='6.5.2.2p1'></a>
|
|
<pre>1 Constraints
|
|
The expression that denotes the called function<a href='#FOOTNOTE.106'><sup>[106]</sup></a> shall have type pointer to function returning
|
|
void or returning a complete object type other than an array type.
|
|
</pre>
|
|
<a name='FOOTNOTE.106'>
|
|
<pre><i><b>Footnote 106)</b> Most often, this is the result of converting an identifier that is a function designator.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.2p2'></a>
|
|
<pre>2 The number of arguments shall agree with the number of parameters. Each argument shall have a
|
|
type such that its value may be assigned to an object with the unqualified version of the type of its
|
|
corresponding parameter
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.2.2p3'></a>
|
|
<pre>3 A postfix expression followed by parentheses () containing a possibly empty, comma-separated
|
|
list of expressions is a function call. The postfix expression denotes the called function. The list of
|
|
expressions specifies the arguments to the function.
|
|
</pre>
|
|
<a name='6.5.2.2p4'></a>
|
|
<pre>4 An argument may be an expression of any complete object type. In preparing for the call to a
|
|
function, the arguments are evaluated, and each parameter is assigned the value of the corresponding
|
|
argument.<a href='#FOOTNOTE.107'><sup>[107]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.107'>
|
|
<pre><i><b>Footnote 107)</b> A function can change the values of its parameters, but these changes cannot affect the values of the arguments. On the
|
|
other hand, it is possible to pass a pointer to an object, and the function can then change the value of the object pointed to. A
|
|
parameter declared to have array or function type is adjusted to have a pointer type as described in <a href='#6.7.6.3'>6.7.6.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.2p5'></a>
|
|
<pre>5 If the expression that denotes the called function has type pointer to function returning an object
|
|
type, the function call expression has the same type as that object type, and has the value determined
|
|
as specified in <a href='#6.8.6.4'>6.8.6.4</a>. Otherwise, the function call has type void.
|
|
</pre>
|
|
<a name='6.5.2.2p6'></a>
|
|
<pre>6 The arguments are implicitly converted, as if by assignment, to the types of the corresponding
|
|
parameters, taking the type of each parameter to be the unqualified version of its declared type. The
|
|
ellipsis notation in a function prototype declarator causes argument type conversion to stop after the
|
|
last declared parameter, if present. The integer promotions are performed on each trailing argument,
|
|
and trailing arguments that have type float are promoted to double. These are called the default
|
|
argument promotions. No other conversions are performed implicitly.
|
|
</pre>
|
|
<a name='6.5.2.2p7'></a>
|
|
<pre>7 If the function is defined with a type that is not compatible with the type (of the expression) pointed
|
|
to by the expression that denotes the called function, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.5.2.2p8'></a>
|
|
<pre>8 There is a sequence point after the evaluations of the function designator and the actual arguments
|
|
but before the actual call. Every evaluation in the calling function (including other function calls)
|
|
that is not otherwise specifically sequenced before or after the execution of the body of the called
|
|
function is indeterminately sequenced with respect to the execution of the called function.<a href='#FOOTNOTE.108'><sup>[108]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.108'>
|
|
<pre><i><b>Footnote 108)</b> In other words, function executions do not "interleave" with each other.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.2p9'></a>
|
|
<pre>9 Recursive function calls shall be permitted, both directly and indirectly through any chain of other
|
|
functions.
|
|
</pre>
|
|
<a name='6.5.2.2p10'></a>
|
|
<pre>10 EXAMPLE In the function call
|
|
|
|
(*pf[f1()]) (f2(), f3() + f4())
|
|
|
|
the functions f1, f2, f3, and f4 can be called in any order. All side effects have to be completed before the function pointed
|
|
to by pf[f1()] is called.
|
|
|
|
Forward references: function declarators (<a href='#6.7.6.3'>6.7.6.3</a>), function definitions (<a href='#6.9.1'>6.9.1</a>), the return statement
|
|
(<a href='#6.8.6.4'>6.8.6.4</a>), simple assignment (<a href='#6.5.16.1'>6.5.16.1</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.2.3'></a>
|
|
<hr>
|
|
<h3>6.5.2.3 [Structure and union members]</h3>
|
|
<a name='6.5.2.3p1'></a>
|
|
<pre>1 Constraints
|
|
The first operand of the . operator shall have an atomic, qualified, or unqualified structure or union
|
|
type, and the second operand shall name a member of that type.
|
|
</pre>
|
|
<a name='6.5.2.3p2'></a>
|
|
<pre>2 The first operand of the-> operator shall have type "pointer to atomic, qualified, or unqualified
|
|
structure" or "pointer to atomic, qualified, or unqualified union", and the second operand shall
|
|
name a member of the type pointed to.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.2.3p3'></a>
|
|
<pre>3 A postfix expression followed by the . operator and an identifier designates a member of a structure
|
|
or union object. The value is that of the named member,<a href='#FOOTNOTE.109'><sup>[109]</sup></a> and is an lvalue if the first expression is
|
|
an lvalue. If the first expression has qualified type, the result has the so-qualified version of the type
|
|
of the designated member.
|
|
</pre>
|
|
<a name='FOOTNOTE.109'>
|
|
<pre><i><b>Footnote 109)</b> If the member used to read the contents of a union object is not the same as the member last used to store a value in the
|
|
object, the appropriate part of the object representation of the value is reinterpreted as an object representation in the new
|
|
type as described in <a href='#6.2.6'>6.2.6</a> (a process sometimes called "type punning"). This might be a non-value representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.3p4'></a>
|
|
<pre>4 A postfix expression followed by the-> operator and an identifier designates a member of a structure
|
|
or union object. The value is that of the named member of the object to which the first expression
|
|
points, and is an lvalue.<a href='#FOOTNOTE.110'><sup>[110]</sup></a> If the first expression is a pointer to a qualified type, the result has the
|
|
so-qualified version of the type of the designated member.
|
|
</pre>
|
|
<a name='FOOTNOTE.110'>
|
|
<pre><i><b>Footnote 110)</b> If &E is a valid pointer expression (where & is the "address-of" operator, which generates a pointer to its operand), the
|
|
expression (&E)->MOS is the same as <a href='#E.'>E.</a>MOS.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.3p5'></a>
|
|
<pre>5 Accessing a member of an atomic structure or union object results in undefined behavior.<a href='#FOOTNOTE.111'><sup>[111]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.111'>
|
|
<pre><i><b>Footnote 111)</b> For example, a data race would occur if access to the entire structure or union in one thread conflicts with access to a
|
|
member from another thread, where at least one access is a modification. Members can be safely accessed using a non-atomic
|
|
object which is assigned to or from the atomic object.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.3p6'></a>
|
|
<pre>6 One special guarantee is made in order to simplify the use of unions: if a union contains several
|
|
structures that share a common initial sequence (see below), and if the union object currently contains
|
|
one of these structures, it is permitted to inspect the common initial part of any of them anywhere
|
|
that a declaration of the completed type of the union is visible. Two structures share a common initial
|
|
sequence if corresponding members have compatible types (and, for bit-fields, the same widths) for a
|
|
sequence of one or more initial members.
|
|
</pre>
|
|
<a name='6.5.2.3p7'></a>
|
|
<pre>7 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or union, f().x is a valid
|
|
postfix expression but is not an lvalue.
|
|
</pre>
|
|
<a name='6.5.2.3p8'></a>
|
|
<pre>8 EXAMPLE 2 In:
|
|
|
|
struct s { int i; const int ci; };
|
|
struct s s;
|
|
const struct s cs;
|
|
volatile struct s vs;
|
|
|
|
|
|
|
|
the various members have the types:
|
|
s.i int
|
|
s.ci const int
|
|
cs.i const int
|
|
cs.ci const int
|
|
vs.i volatile int
|
|
vs.ci volatile const int
|
|
|
|
</pre>
|
|
<a name='6.5.2.3p9'></a>
|
|
<pre>9 EXAMPLE 3 The following is a valid fragment:
|
|
|
|
union {
|
|
struct {
|
|
int alltypes;
|
|
} n;
|
|
struct {
|
|
int type;
|
|
int intnode;
|
|
} ni;
|
|
struct {
|
|
int type;
|
|
double doublenode;
|
|
} nf;
|
|
} u;
|
|
u.nf.type = 1;
|
|
u.nf.doublenode = <a href='#3.14'>3.14</a>;
|
|
/* ... */
|
|
if (u.n.alltypes == 1)
|
|
if (sin(u.nf.doublenode) == 0.0)
|
|
/* ... */
|
|
|
|
|
|
|
|
The following is not a valid fragment (because the union type is not visible within function f):
|
|
|
|
struct t1 { int m; };
|
|
struct t2 { int m; };
|
|
int f(struct t1 *p1, struct t2 *p2)
|
|
{
|
|
if (p1->m < 0)
|
|
p2->m = -p2->m;
|
|
return p1->m;
|
|
}
|
|
int g()
|
|
{
|
|
union {
|
|
struct t1 s1;
|
|
struct t2 s2;
|
|
} u;
|
|
/* ... */
|
|
return f(&u.s1, &u.s2);
|
|
}
|
|
|
|
|
|
|
|
Forward references: address and indirection operators (<a href='#6.5.3.2'>6.5.3.2</a>), structure and union specifiers
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
</pre>
|
|
<a name='6.5.2.4'></a>
|
|
<hr>
|
|
<h3>6.5.2.4 [Postfix increment and decrement operators]</h3>
|
|
<a name='6.5.2.4p1'></a>
|
|
<pre>1 Constraints
|
|
The operand of the postfix increment or decrement operator shall have atomic, qualified, or unquali-
|
|
fied real or pointer type, and shall be a modifiable lvalue.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.2.4p2'></a>
|
|
<pre>2 The result of the postfix ++ operator is the value of the operand. As a side effect, the value of the
|
|
operand object is incremented (that is, the value 1 of the appropriate type is added to it). See the
|
|
discussions of additive operators and compound assignment for information on constraints, types,
|
|
and conversions and the effects of operations on pointers. The value computation of the result is
|
|
sequenced before the side effect of updating the stored value of the operand. With respect to an
|
|
indeterminately-sequenced function call, the operation of postfix ++ is a single evaluation. Postfix
|
|
++ on an object with atomic type is a read-modify-write operation with memory_order_seq_cst
|
|
memory order semantics.<a href='#FOOTNOTE.112'><sup>[112]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.112'>
|
|
<pre><i><b>Footnote 112)</b> Where a pointer to an atomic object can be formed and E has integer type, E++ is equivalent to the following code
|
|
sequence where T is the type of E:
|
|
T *addr = &E;
|
|
T old = *addr;
|
|
T new;
|
|
do {
|
|
new = old + 1;
|
|
} while (!atomic_compare_exchange_strong(addr, &old, new));
|
|
with old being the result of the operation.
|
|
Special care is necessary if E has floating type; see <a href='#6.5.16.2'>6.5.16.2</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.4p3'></a>
|
|
<pre>3 The postfix-- operator is analogous to the postfix ++ operator, except that the value of the operand
|
|
is decremented (that is, the value 1 of the appropriate type is subtracted from it).
|
|
Forward references: additive operators (<a href='#6.5.6'>6.5.6</a>), compound assignment (<a href='#6.5.16.2'>6.5.16.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.2.5'></a>
|
|
<hr>
|
|
<h3>6.5.2.5 [Compound literals]</h3>
|
|
<a name='6.5.2.5p1'></a>
|
|
<pre>1 Syntax
|
|
compound-literal:
|
|
( storage-class-specifiersopt type-name ) braced-initializer
|
|
|
|
|
|
storage-class-specifiers:
|
|
storage-class-specifier
|
|
storage-class-specifiers storage-class-specifier
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.2.5p2'></a>
|
|
<pre>2 The type name shall specify a complete object type or an array of unknown size, but not a variable
|
|
length array type.
|
|
</pre>
|
|
<a name='6.5.2.5p3'></a>
|
|
<pre>3 All the constraints for initializer lists in <a href='#6.7.10'>6.7.10</a> also apply to compound literals.
|
|
</pre>
|
|
<a name='6.5.2.5p4'></a>
|
|
<pre>4 If the compound literal is evaluated outside the body of a function and outside of any parameter list,
|
|
it is associated with file scope; otherwise, it is associated with the enclosing block. Depending on
|
|
this association, the storage-class specifiers SC (possibly empty)<a href='#FOOTNOTE.113'><sup>[113]</sup></a> , type name T, and initializer list,
|
|
if any, shall be such that they are valid specifiers for an object definition in file scope or block scope,
|
|
respectively, of the following form,
|
|
|
|
SC typeof(T) ID = { IL };
|
|
|
|
|
|
where ID is an identifier that is unique for the whole program and where IL is a (possibly empty)
|
|
initializer list with nested structure, designators, values and types as the initializer list of the
|
|
compound literal. All the constraints for storage class specifiers in <a href='#6.7.1'>6.7.1</a> also apply correspondingly
|
|
to compound literals.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.113'>
|
|
<pre><i><b>Footnote 113)</b> If the storage-class specifiers contain the same storage-class specifier more than once, the following constraint is violated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.5p5'></a>
|
|
<pre>5 A compound literal provides an unnamed object whose value, type, storage duration and other
|
|
properties are as if given by the definition syntax in the constraints; if the storage duration is
|
|
automatic, the lifetime of the instance of the unnamed object is the current execution of the enclosing
|
|
block<a href='#FOOTNOTE.114'><sup>[114]</sup></a> . If the storage-class specifiers contain other specifiers than constexpr, static, register,
|
|
or thread_local the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.114'>
|
|
<pre><i><b>Footnote 114)</b> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types or void only, and
|
|
the result of a cast expression is not an lvalue.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.5p6'></a>
|
|
<pre>6 The value of the compound literal is that of an lvalue corresponding to the unnamed object.
|
|
</pre>
|
|
<a name='6.5.2.5p7'></a>
|
|
<pre>7 All the semantic rules for initializer lists in <a href='#6.7.10'>6.7.10</a> also apply to compound literals<a href='#FOOTNOTE.115'><sup>[115]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.115'>
|
|
<pre><i><b>Footnote 115)</b> For example, subobjects without explicit initializers are initialized to zero.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.5p8'></a>
|
|
<pre>8 EXAMPLE 1 Consider the following 2 functions:
|
|
|
|
int f(int*);
|
|
int g(char * para[f((int[27]){ 0, })]) {
|
|
/* ... */
|
|
return 0;
|
|
}
|
|
|
|
Here, each call to g creates an unnamed object of type int[27] to determine the variably-modified type of para for the
|
|
duration of the call. During that determination, a pointer to the object is passed into a call to the function f. If a pointer to the
|
|
object is kept by f, access to that object is possible during the whole execution of the call to g. The lifetime of the object ends
|
|
with the end of the call to g; for any access after that, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='6.5.2.5p9'></a>
|
|
<pre>9 String literals, and compound literals with const-qualified types, need not designate distinct ob-
|
|
jects.<a href='#FOOTNOTE.116'><sup>[116]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.116'>
|
|
<pre><i><b>Footnote 116)</b> This allows implementations to share storage for string literals and constant compound literals with the same or
|
|
overlapping representations.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.5p10'></a>
|
|
<pre>10 EXAMPLE 2 The file scope definition
|
|
|
|
int *p = (int []){2, 4};
|
|
|
|
initializes p to point to the first element of an array of two ints, the first having the value two and the second, four. The
|
|
expressions in this compound literal are required to be constant. The unnamed object has static storage duration.
|
|
</pre>
|
|
<a name='6.5.2.5p11'></a>
|
|
<pre>11 EXAMPLE 3 In contrast, in
|
|
|
|
void f(void)
|
|
{
|
|
int *p;
|
|
/*...*/
|
|
p = (int [2]){*p};
|
|
/*...*/
|
|
}
|
|
|
|
p is assigned the address of the first element of an array of two ints, the first having the value previously pointed to by p and
|
|
the second, zero. The expressions in this compound literal need not be constant. The unnamed object has automatic storage
|
|
duration.
|
|
</pre>
|
|
<a name='6.5.2.5p12'></a>
|
|
<pre>12 EXAMPLE 4 Initializers with designations can be combined with compound literals. Structure objects created using
|
|
compound literals can be passed to functions without depending on member order:
|
|
|
|
drawline((struct point){.x=1, .y=1},
|
|
(struct point){.x=3, .y=4});
|
|
|
|
Or, if drawline instead expected pointers to struct point:
|
|
|
|
drawline(&(struct point){.x=1, .y=1},
|
|
&(struct point){.x=3, .y=4});
|
|
|
|
</pre>
|
|
<a name='6.5.2.5p13'></a>
|
|
<pre>13 EXAMPLE 5 A read-only compound literal can be specified through constructions like:
|
|
|
|
(const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
|
|
|
|
</pre>
|
|
<a name='6.5.2.5p14'></a>
|
|
<pre>14 EXAMPLE 6 The following three expressions have different meanings:
|
|
|
|
"/tmp/fileXXXXXX"
|
|
(char []){"/tmp/fileXXXXXX"}
|
|
(const char []){"/tmp/fileXXXXXX"}
|
|
|
|
The first always has static storage duration and has type array of char, but need not be modifiable; the last two have
|
|
automatic storage duration when they occur within the body of a function, and the first of these two is modifiable.
|
|
</pre>
|
|
<a name='6.5.2.5p15'></a>
|
|
<pre>15 EXAMPLE 7 Like string literals, const-qualified compound literals can be placed into read-only memory and can even be
|
|
shared. For example,
|
|
|
|
(const char []){"abc"} == "abc"
|
|
|
|
might yield 1 if the literals’ storage is shared.
|
|
</pre>
|
|
<a name='6.5.2.5p16'></a>
|
|
<pre>16 EXAMPLE 8 Since compound literals are unnamed, a single compound literal cannot specify a circularly linked object. For
|
|
example, there is no way to write a self-referential compound literal that could be used as the function argument in place of
|
|
the named object endless_zeros below:
|
|
|
|
struct int_list { int car; struct int_list *cdr; };
|
|
struct int_list endless_zeros = {0, &endless_zeros};
|
|
eval(endless_zeros);
|
|
|
|
</pre>
|
|
<a name='6.5.2.5p17'></a>
|
|
<pre>17 EXAMPLE 9 Each compound literal creates only a single object in a given scope:
|
|
|
|
struct s { int i; };
|
|
|
|
int f (void)
|
|
{
|
|
struct s *p = 0, *q;
|
|
int j = 0;
|
|
|
|
again:
|
|
q = p, p = &((struct s){ j++ });
|
|
if (j < 2) goto again;
|
|
|
|
return p == q && q->i == 1;
|
|
}
|
|
|
|
The function f() always returns the value 1.
|
|
18 Note that if an iteration statement were used instead of an explicit goto and a label, the lifetime of the unnamed object would
|
|
be the body of the loop only, and on entry next time around p would have indeterminate representation, which would result
|
|
in undefined behavior.
|
|
|
|
Forward references: type names (<a href='#6.7.7'>6.7.7</a>), initialization (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.3'></a>
|
|
<hr>
|
|
<h3>6.5.3 [Unary operators]</h3>
|
|
<a name='6.5.3p1'></a>
|
|
<pre>1 Syntax
|
|
unary-expression:
|
|
postfix-expression
|
|
++ unary-expression
|
|
-- unary-expression
|
|
unary-operator cast-expression
|
|
sizeof unary-expression
|
|
sizeof ( type-name )
|
|
alignof ( type-name )
|
|
unary-operator: one of
|
|
& * + - ~ !
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.5.3.1'></a>
|
|
<hr>
|
|
<h3>6.5.3.1 [Prefix increment and decrement operators]</h3>
|
|
<a name='6.5.3.1p1'></a>
|
|
<pre>1 Constraints
|
|
The operand of the prefix increment or decrement operator shall have atomic, qualified, or unquali-
|
|
fied real or pointer type, and shall be a modifiable lvalue.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.3.1p2'></a>
|
|
<pre>2 The value of the operand of the prefix ++ operator is incremented. The result is the new value of the
|
|
operand after incrementation. The expression ++E is equivalent to (E+=1) . See the discussions of
|
|
additive operators and compound assignment for information on constraints, types, side effects,
|
|
and conversions and the effects of operations on pointers.
|
|
</pre>
|
|
<a name='6.5.3.1p3'></a>
|
|
<pre>3 The prefix-- operator is analogous to the prefix ++ operator, except that the value of the operand is
|
|
decremented.
|
|
Forward references: additive operators (<a href='#6.5.6'>6.5.6</a>), compound assignment (<a href='#6.5.16.2'>6.5.16.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.3.2'></a>
|
|
<hr>
|
|
<h3>6.5.3.2 [Address and indirection operators]</h3>
|
|
<a name='6.5.3.2p1'></a>
|
|
<pre>1 Constraints
|
|
The operand of the unary & operator shall be either a function designator, the result of a [] or unary
|
|
* operator, or an lvalue that designates an object that is not a bit-field and is not declared with the
|
|
register storage-class specifier.
|
|
</pre>
|
|
<a name='6.5.3.2p2'></a>
|
|
<pre>2 The operand of the unary * operator shall have pointer type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.3.2p3'></a>
|
|
<pre>3 The unary & operator yields the address of its operand. If the operand has type "type", the result has
|
|
type "pointer to type". If the operand is the result of a unary * operator, neither that operator nor
|
|
the & operator is evaluated and the result is as if both were omitted, except that the constraints on
|
|
the operators still apply and the result is not an lvalue. Similarly, if the operand is the result of a []
|
|
operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result
|
|
is as if the & operator were removed and the [] operator were changed to a + operator. Otherwise,
|
|
the result is a pointer to the object or function designated by its operand.
|
|
</pre>
|
|
<a name='6.5.3.2p4'></a>
|
|
<pre>4 The unary * operator denotes indirection. If the operand points to a function, the result is a function
|
|
designator; if it points to an object, the result is an lvalue designating the object. If the operand has
|
|
type "pointer to type", the result has type "type". If an invalid value has been assigned to the pointer,
|
|
the behavior of the unary * operator is undefined.<a href='#FOOTNOTE.117'><sup>[117]</sup></a>
|
|
Forward references: storage-class specifiers (<a href='#6.7.1'>6.7.1</a>), structure and union specifiers (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.117'>
|
|
<pre><i><b>Footnote 117)</b> Thus, & E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)) . It is always true that if E is a
|
|
*
|
|
function designator or an lvalue that is a valid operand of the unary & operator, *&E is a function designator or an lvalue
|
|
equal to E. If *P is an lvalue and T is the name of an object pointer type, *(T)P is an lvalue that has a type compatible with
|
|
that to which T points.
|
|
Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an address inappropriately
|
|
aligned for the type of object pointed to, and the address of an object after the end of its lifetime.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.3.3'></a>
|
|
<hr>
|
|
<h3>6.5.3.3 [Unary arithmetic operators]</h3>
|
|
<a name='6.5.3.3p1'></a>
|
|
<pre>1 Constraints
|
|
The operand of the unary + or- operator shall have arithmetic type; of the ~ operator, integer type;
|
|
of the ! operator, scalar type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.3.3p2'></a>
|
|
<pre>2 The result of the unary + operator is the value of its (promoted) operand. The integer promotions
|
|
are performed on the operand, and the result has the promoted type.
|
|
</pre>
|
|
<a name='6.5.3.3p3'></a>
|
|
<pre>3 The result of the unary- operator is the negative of its (promoted) operand. The integer promotions
|
|
are performed on the operand, and the result has the promoted type.
|
|
</pre>
|
|
<a name='6.5.3.3p4'></a>
|
|
<pre>4 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is, each bit in
|
|
the result is set if and only if the corresponding bit in the converted operand is not set). The integer
|
|
promotions are performed on the operand, and the result has the promoted type. If the promoted
|
|
type is an unsigned type, the expression ~E is equivalent to the maximum value representable in
|
|
that type minus E.
|
|
</pre>
|
|
<a name='6.5.3.3p5'></a>
|
|
<pre>5 The result of the logical negation operator ! is 0 if the value of its operand compares unequal to
|
|
0, 1 if the value of its operand compares equal to 0. The result has type int. The expression !E is
|
|
equivalent to (0==E) .
|
|
|
|
</pre>
|
|
<a name='6.5.3.4'></a>
|
|
<hr>
|
|
<h3>6.5.3.4 [The sizeof and alignof operators]</h3>
|
|
<a name='6.5.3.4p1'></a>
|
|
<pre>1 Constraints
|
|
The sizeof operator shall not be applied to an expression that has function type or an incomplete
|
|
type, to the parenthesized name of such a type, or to an expression that designates a bit-field member.
|
|
The alignof operator shall not be applied to a function type or an incomplete type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.3.4p2'></a>
|
|
<pre>2 The sizeof operator yields the size (in bytes) of its operand, which may be an expression or the
|
|
parenthesized name of a type. The size is determined from the type of the operand. The result
|
|
is an integer. If the type of the operand is a variable length array type, the operand is evaluated;
|
|
otherwise, the operand is not evaluated and the result is an integer constant.
|
|
</pre>
|
|
<a name='6.5.3.4p3'></a>
|
|
<pre>3 The alignof operator yields the alignment requirement of its operand type. The operand is not
|
|
evaluated and the result is an integer constant expression. When applied to an array type, the result
|
|
is the alignment requirement of the element type.
|
|
</pre>
|
|
<a name='6.5.3.4p4'></a>
|
|
<pre>4 When sizeof is applied to an operand that has type char, unsigned char, or signed char, (or
|
|
a qualified version thereof) the result is 1. When applied to an operand that has array type, the
|
|
result is the total number of bytes in the array.<a href='#FOOTNOTE.118'><sup>[118]</sup></a> When applied to an operand that has structure or
|
|
union type, the result is the total number of bytes in such an object, including internal and trailing
|
|
padding.
|
|
</pre>
|
|
<a name='FOOTNOTE.118'>
|
|
<pre><i><b>Footnote 118)</b> When applied to a parameter declared to have array or function type, the sizeof operator yields the size of the adjusted
|
|
(pointer) type (see <a href='#6.9.1'>6.9.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.3.4p5'></a>
|
|
<pre>5 The value of the result of both operators is implementation-defined, and its type (an unsigned
|
|
integer type) is size_t, defined in <stddef.h> (and other headers).
|
|
</pre>
|
|
<a name='6.5.3.4p6'></a>
|
|
<pre>6 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage allocators and I/O
|
|
systems. A storage-allocation function might accept a size (in bytes) of an object to allocate and return a pointer to void. For
|
|
example:
|
|
|
|
extern void *alloc(size_t);
|
|
double *dp = alloc(sizeof *dp);
|
|
|
|
The implementation of the alloc function presumably ensures that its return value is aligned suitably for conversion to a
|
|
pointer to double.
|
|
</pre>
|
|
<a name='6.5.3.4p7'></a>
|
|
<pre>7 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
|
|
|
|
sizeof array / sizeof array[0]
|
|
|
|
</pre>
|
|
<a name='6.5.3.4p8'></a>
|
|
<pre>8 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a function:
|
|
|
|
#include <stddef.h>
|
|
|
|
size_t fsize3(int n)
|
|
{
|
|
char b[n+3]; // variable length array
|
|
return sizeof b; // execution time sizeof
|
|
}
|
|
int main()
|
|
{
|
|
size_t size;
|
|
size = fsize3(10); // fsize3 returns 13
|
|
return 0;
|
|
}
|
|
|
|
|
|
Forward references: common definitions <stddef.h> (<a href='#7.21'>7.21</a>), declarations (<a href='#6.7'>6.7</a>), structure and union
|
|
specifiers (<a href='#6.7.2.1'>6.7.2.1</a>), type names (<a href='#6.7.7'>6.7.7</a>), array declarators (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.4'></a>
|
|
<hr>
|
|
<h3>6.5.4 [Cast operators]</h3>
|
|
<a name='6.5.4p1'></a>
|
|
<pre>1 Syntax
|
|
cast-expression:
|
|
unary-expression
|
|
( type-name ) cast-expression
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.4p2'></a>
|
|
<pre>2 Unless the type name specifies a void type, the type name shall specify atomic, qualified, or
|
|
unqualified scalar type, and the operand shall have scalar type.
|
|
</pre>
|
|
<a name='6.5.4p3'></a>
|
|
<pre>3 Conversions that involve pointers, other than where permitted by the constraints of <a href='#6.5.16.1'>6.5.16.1</a>, shall be
|
|
specified by means of an explicit cast.
|
|
</pre>
|
|
<a name='6.5.4p4'></a>
|
|
<pre>4 A pointer type shall not be converted to any floating type. A floating type shall not be converted to
|
|
any pointer type. The type nullptr_t shall not be converted to any type other than void, bool or a
|
|
pointer type. No type other than nullptr_t shall be converted to nullptr_t.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.4p5'></a>
|
|
<pre>5 Preceding an expression by a parenthesized type name converts the value of the expression to the
|
|
unqualified version of the named type. This construction is called a cast<a href='#FOOTNOTE.119'><sup>[119]</sup></a> . A cast that specifies no
|
|
conversion has no effect on the type or value of an expression.
|
|
</pre>
|
|
<a name='FOOTNOTE.119'>
|
|
<pre><i><b>Footnote 119)</b> A cast does not yield an lvalue.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.4p6'></a>
|
|
<pre>6 If the value of the expression is represented with greater range or precision than required by the type
|
|
named by the cast (<a href='#6.3.1.8'>6.3.1.8</a>), then the cast specifies a conversion even if the type of the expression is
|
|
the same as the named type and removes any extra range and precision.
|
|
Forward references: equality operators (<a href='#6.5.9'>6.5.9</a>), function declarators (<a href='#6.7.6.3'>6.7.6.3</a>), simple assignment
|
|
(<a href='#6.5.16.1'>6.5.16.1</a>), type names (<a href='#6.7.7'>6.7.7</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.5'></a>
|
|
<hr>
|
|
<h3>6.5.5 [Multiplicative operators]</h3>
|
|
<a name='6.5.5p1'></a>
|
|
<pre>1 Syntax
|
|
multiplicative-expression:
|
|
cast-expression
|
|
multiplicative-expression * cast-expression
|
|
multiplicative-expression / cast-expression
|
|
multiplicative-expression % cast-expression
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.5p2'></a>
|
|
<pre>2 Each of the operands shall have arithmetic type. The operands of the % operator shall have integer
|
|
type.
|
|
</pre>
|
|
<a name='6.5.5p3'></a>
|
|
<pre>3 If either operand has decimal floating type, the other operand shall not have standard floating type,
|
|
complex type, or imaginary type.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.5p4'></a>
|
|
<pre>4 The usual arithmetic conversions are performed on the operands.
|
|
</pre>
|
|
<a name='6.5.5p5'></a>
|
|
<pre>5 The result of the binary * operator is the product of the operands.
|
|
</pre>
|
|
<a name='6.5.5p6'></a>
|
|
<pre>6 The result of the / operator is the quotient from the division of the first operand by the second; the
|
|
result of the % operator is the remainder. In both operations, if the value of the second operand is
|
|
zero, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.5.5p7'></a>
|
|
<pre>7 When integers are divided, the result of the / operator is the algebraic quotient with any fractional
|
|
part discarded.<a href='#FOOTNOTE.120'><sup>[120]</sup></a> If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a;
|
|
otherwise, the behavior of both a/b and a%b is undefined.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.120'>
|
|
<pre><i><b>Footnote 120)</b> This is often called "truncation toward zero".
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.6'></a>
|
|
<hr>
|
|
<h3>6.5.6 [Additive operators]</h3>
|
|
<a name='6.5.6p1'></a>
|
|
<pre>1 Syntax
|
|
additive-expression:
|
|
multiplicative-expression
|
|
additive-expression + multiplicative-expression
|
|
additive-expression - multiplicative-expression
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.6p2'></a>
|
|
<pre>2 For addition, either both operands shall have arithmetic type, or one operand shall be a pointer to a
|
|
complete object type and the other shall have integer type. (Incrementing is equivalent to adding 1.)
|
|
</pre>
|
|
<a name='6.5.6p3'></a>
|
|
<pre>3 For subtraction, one of the following shall hold:
|
|
|
|
— both operands have arithmetic type;
|
|
|
|
— both operands are pointers to qualified or unqualified versions of compatible complete object
|
|
types; or
|
|
|
|
— the left operand is a pointer to a complete object type and the right operand has integer type.
|
|
|
|
(Decrementing is equivalent to subtracting 1.)
|
|
</pre>
|
|
<a name='6.5.6p4'></a>
|
|
<pre>4 If either operand has decimal floating type, the other operand shall not have standard floating type,
|
|
complex type, or imaginary type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.6p5'></a>
|
|
<pre>5 If both operands have arithmetic type, the usual arithmetic conversions are performed on them.
|
|
</pre>
|
|
<a name='6.5.6p6'></a>
|
|
<pre>6 The result of the binary + operator is the sum of the operands.
|
|
</pre>
|
|
<a name='6.5.6p7'></a>
|
|
<pre>7 The result of the binary- operator is the difference resulting from the subtraction of the second
|
|
operand from the first.
|
|
</pre>
|
|
<a name='6.5.6p8'></a>
|
|
<pre>8 For the purposes of these operators, a pointer to an object that is not an element of an array behaves
|
|
the same as a pointer to the first element of an array of length one with the type of the object as its
|
|
element type.
|
|
</pre>
|
|
<a name='6.5.6p9'></a>
|
|
<pre>9 When an expression that has integer type is added to or subtracted from a pointer, the result has the
|
|
type of the pointer operand. If the pointer operand points to an element of an array object, and the
|
|
array is large enough, the result points to an element offset from the original element such that the
|
|
difference of the subscripts of the resulting and original array elements equals the integer expression.
|
|
In other words, if the expression P points to the i-th element of an array object, the expressions
|
|
(P)+N (equivalently, N+(P)) and (P)-N (where N has the value n) point to, respectively, the i + n-th
|
|
and i − n-th elements of the array object, provided they exist. Moreover, if the expression P points to
|
|
the last element of an array object, the expression (P)+1 points one past the last element of the array
|
|
object, and if the expression Q points one past the last element of an array object, the expression
|
|
(Q)-1 points to the last element of the array object. If the pointer operand and the result do not point
|
|
to elements of the same array object or one past the last element of the array object, the behavior is
|
|
undefined. If the addition or subtraction produces an overflow, the behavior is undefined. If the
|
|
result points one past the last element of the array object, it shall not be used as the operand of a
|
|
unary * operator that is evaluated.
|
|
</pre>
|
|
<a name='6.5.6p10'></a>
|
|
<pre>10 When two pointers are subtracted, both shall point to elements of the same array object, or one past
|
|
the last element of the array object; the result is the difference of the subscripts of the two array
|
|
elements. The size of the result is implementation-defined, and its type (a signed integer type) is
|
|
ptrdiff_t defined in the <stddef.h> header. If the result is not representable in an object of that
|
|
type, the behavior is undefined. In other words, if the expressions P and Q point to, respectively, the
|
|
i-th and j-th elements of an array object, the expression (P)-(Q) has the value i − j provided the
|
|
value fits in an object of type ptrdiff_t. Moreover, if the expression P points either to an element of
|
|
an array object or one past the last element of an array object, and the expression Q points to the last
|
|
element of the same array object, the expression ((Q)+1)-(P) has the same value as ((Q)-(P))+1
|
|
and as-((P)-((Q)+1)) , and has the value zero if the expression P points one past the last element
|
|
of the array object, even though the expression (Q)+1 does not point to an element of the array
|
|
object.<a href='#FOOTNOTE.121'><sup>[121]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.121'>
|
|
<pre><i><b>Footnote 121)</b> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In this scheme the
|
|
integer expression added to or subtracted from the converted pointer is first multiplied by the size of the object originally
|
|
pointed to, and the resulting pointer is converted back to the original type. For pointer subtraction, the result of the difference
|
|
between the character pointers is similarly divided by the size of the object originally pointed to.
|
|
When viewed in this way, an implementation need only provide one extra byte (which can overlap another object in the
|
|
program) just after the end of the object in order to satisfy the "one past the last element" requirements.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.6p11'></a>
|
|
<pre>11 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
|
|
|
|
{
|
|
int n = 4, m = 3;
|
|
int a[n][m];
|
|
int (*p)[m] = a; // p == &a[0]
|
|
p += 1; // p == &a[1]
|
|
(*p)[2] = 99; // a[1][2] == 99
|
|
n = p - a; // n == 1
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.5.6p12'></a>
|
|
<pre>12 If array a in the above example were declared to be an array of known constant size, and pointer p were declared to be a
|
|
pointer to an array of the same known constant size (pointing to a), the results would be the same.
|
|
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>), common definitions <stddef.h> (<a href='#7.21'>7.21</a>).
|
|
|
|
</pre>
|
|
<a name='6.5.7'></a>
|
|
<hr>
|
|
<h3>6.5.7 [Bitwise shift operators]</h3>
|
|
<a name='6.5.7p1'></a>
|
|
<pre>1 Syntax
|
|
shift-expression:
|
|
additive-expression
|
|
shift-expression << additive-expression
|
|
shift-expression >> additive-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.7p2'></a>
|
|
<pre>2 Each of the operands shall have integer type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.7p3'></a>
|
|
<pre>3 The integer promotions are performed on each of the operands. The type of the result is that of the
|
|
promoted left operand. If the value of the right operand is negative or is greater than or equal to the
|
|
width of the promoted left operand, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.5.7p4'></a>
|
|
<pre>4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with zeros. If E1 has
|
|
an unsigned type, the value of the result is E1 × 2E2 , wrapped around. If E1 has a signed type and
|
|
nonnegative value, and E1 × 2E2 is representable in the result type, then that is the resulting value;
|
|
otherwise, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.5.7p5'></a>
|
|
<pre>5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type or if E1 has a
|
|
signed type and a nonnegative value, the value of the result is the integral part of the quotient of
|
|
E1/2E2 . If E1 has a signed type and a negative value, the resulting value is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='6.5.8'></a>
|
|
<hr>
|
|
<h3>6.5.8 [Relational operators]</h3>
|
|
<a name='6.5.8p1'></a>
|
|
<pre>1 Syntax
|
|
relational-expression:
|
|
shift-expression
|
|
relational-expression < shift-expression
|
|
relational-expression > shift-expression
|
|
relational-expression <= shift-expression
|
|
relational-expression >= shift-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.8p2'></a>
|
|
<pre>2 One of the following shall hold:
|
|
|
|
— both operands have real type; or
|
|
|
|
— both operands are pointers to qualified or unqualified versions of compatible object types.
|
|
|
|
</pre>
|
|
<a name='6.5.8p3'></a>
|
|
<pre>3 If either operand has decimal floating type, the other operand shall not have standard floating type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.8p4'></a>
|
|
<pre>4 If both of the operands have arithmetic type, the usual arithmetic conversions are performed.
|
|
Positive zeros compare equal to negative zeros.
|
|
</pre>
|
|
<a name='6.5.8p5'></a>
|
|
<pre>5 For the purposes of these operators, a pointer to an object that is not an element of an array behaves
|
|
the same as a pointer to the first element of an array of length one with the type of the object as its
|
|
element type.
|
|
</pre>
|
|
<a name='6.5.8p6'></a>
|
|
<pre>6 When two pointers are compared, the result depends on the relative locations in the address space
|
|
of the objects pointed to. If two pointers to object types both point to the same object, or both point
|
|
one past the last element of the same array object, they compare equal. If the objects pointed to
|
|
are members of the same aggregate object, pointers to structure members declared later compare
|
|
greater than pointers to members declared earlier in the structure, and pointers to array elements
|
|
with larger subscript values compare greater than pointers to elements of the same array with lower
|
|
subscript values. All pointers to members of the same union object compare equal. If the expression
|
|
P points to an element of an array object and the expression Q points to the last element of the same
|
|
array object, the pointer expression Q+1 compares greater than P. In all other cases, the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='6.5.8p7'></a>
|
|
<pre>7 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or
|
|
equal to) shall yield 1 if the specified relation is true and 0 if it is false.<a href='#FOOTNOTE.122'><sup>[122]</sup></a> . The result has type int.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.122'>
|
|
<pre><i><b>Footnote 122)</b> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it means (a<b)<c ; in other
|
|
words, "if a is less than b, compare 1 to c; otherwise, compare 0 to c".
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.9'></a>
|
|
<hr>
|
|
<h3>6.5.9 [Equality operators]</h3>
|
|
<a name='6.5.9p1'></a>
|
|
<pre>1 Syntax
|
|
equality-expression:
|
|
relational-expression
|
|
equality-expression == relational-expression
|
|
equality-expression != relational-expression
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.9p2'></a>
|
|
<pre>2 One of the following shall hold:
|
|
|
|
— both operands have arithmetic type;
|
|
— both operands are pointers to qualified or unqualified versions of compatible types;
|
|
— one operand is a pointer to an object type and the other is a pointer to a qualified or unqualified
|
|
version of void;
|
|
— both operands have type nullptr_t;
|
|
— one operand has type nullptr_t and the other is a null pointer constant; or,
|
|
— one operand is a pointer and the other is a null pointer constant.
|
|
|
|
</pre>
|
|
<a name='6.5.9p3'></a>
|
|
<pre>3 If either operand has decimal floating type, the other operand shall not have standard floating type,
|
|
complex type, or imaginary type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.9p4'></a>
|
|
<pre>4 The == (equal to) and != (not equal to) operators are analogous to the relational operators except for
|
|
their lower precedence<a href='#FOOTNOTE.123'><sup>[123]</sup></a> Each of the operators yields 1 if the specified relation is true and 0 if it is
|
|
false. The result has type int. For any pair of operands, exactly one of the relations is true.
|
|
</pre>
|
|
<a name='FOOTNOTE.123'>
|
|
<pre><i><b>Footnote 123)</b> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.9p5'></a>
|
|
<pre>5 If both of the operands have arithmetic type, the usual arithmetic conversions are performed.
|
|
Positive zeros compare equal to negative zeros. Values of complex types are equal if and only if both
|
|
their real parts are equal and also their imaginary parts are equal. Any two values of arithmetic
|
|
types from different type domains are equal if and only if the results of their conversions to the
|
|
(complex) result type determined by the usual arithmetic conversions are equal. If both operands
|
|
have type nullptr_t or one operand has type nullptr_t and the other is a null pointer constant,
|
|
they compare equal.
|
|
</pre>
|
|
<a name='6.5.9p6'></a>
|
|
<pre>6 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a null
|
|
pointer constant, the null pointer constant is converted to the type of the pointer. If one operand is a
|
|
pointer to an object type and the other is a pointer to a qualified or unqualified version of void, the
|
|
former is converted to the type of the latter.
|
|
</pre>
|
|
<a name='6.5.9p7'></a>
|
|
<pre>7 Two pointers compare equal if and only if both are null pointers, both are pointers to the same object
|
|
(including a pointer to an object and a subobject at its beginning) or function, both are pointers to
|
|
one past the last element of the same array object, or one is a pointer to one past the end of one array
|
|
object and the other is a pointer to the start of a different array object that happens to immediately
|
|
follow the first array object in the address space<a href='#FOOTNOTE.124'><sup>[124]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.124'>
|
|
<pre><i><b>Footnote 124)</b> Two objects can be adjacent in memory because they are adjacent elements of a larger array or adjacent members
|
|
of a structure with no padding between them, or because the implementation chose to place them so, even though they
|
|
are unrelated. If prior invalid pointer operations (such as accesses outside array bounds) produced undefined behavior,
|
|
subsequent comparisons also produce undefined behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.9p8'></a>
|
|
<pre>8 For the purposes of these operators, a pointer to an object that is not an element of an array behaves
|
|
the same as a pointer to the first element of an array of length one with the type of the object as its
|
|
element type.
|
|
|
|
</pre>
|
|
<a name='6.5.10'></a>
|
|
<hr>
|
|
<h3>6.5.10 [Bitwise AND operator]</h3>
|
|
<a name='6.5.10p1'></a>
|
|
<pre>1 Syntax
|
|
AND-expression:
|
|
equality-expression
|
|
AND-expression & equality-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.10p2'></a>
|
|
<pre>2 Each of the operands shall have integer type.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.10p3'></a>
|
|
<pre>3 The usual arithmetic conversions are performed on the operands.
|
|
</pre>
|
|
<a name='6.5.10p4'></a>
|
|
<pre>4 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in the result
|
|
is set if and only if each of the corresponding bits in the converted operands is set).
|
|
|
|
</pre>
|
|
<a name='6.5.11'></a>
|
|
<hr>
|
|
<h3>6.5.11 [Bitwise exclusive OR operator]</h3>
|
|
<a name='6.5.11p1'></a>
|
|
<pre>1 Syntax
|
|
exclusive-OR-expression:
|
|
AND-expression
|
|
exclusive-OR-expression ^ AND-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.11p2'></a>
|
|
<pre>2 Each of the operands shall have integer type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.11p3'></a>
|
|
<pre>3 The usual arithmetic conversions are performed on the operands.
|
|
</pre>
|
|
<a name='6.5.11p4'></a>
|
|
<pre>4 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit in the result
|
|
is set if and only if exactly one of the corresponding bits in the converted operands is set).
|
|
|
|
</pre>
|
|
<a name='6.5.12'></a>
|
|
<hr>
|
|
<h3>6.5.12 [Bitwise inclusive OR operator]</h3>
|
|
<a name='6.5.12p1'></a>
|
|
<pre>1 Syntax
|
|
inclusive-OR-expression:
|
|
exclusive-OR-expression
|
|
inclusive-OR-expression | exclusive-OR-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.12p2'></a>
|
|
<pre>2 Each of the operands shall have integer type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.12p3'></a>
|
|
<pre>3 The usual arithmetic conversions are performed on the operands.
|
|
</pre>
|
|
<a name='6.5.12p4'></a>
|
|
<pre>4 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in the result
|
|
is set if and only if at least one of the corresponding bits in the converted operands is set).
|
|
|
|
</pre>
|
|
<a name='6.5.13'></a>
|
|
<hr>
|
|
<h3>6.5.13 [Logical AND operator]</h3>
|
|
<a name='6.5.13p1'></a>
|
|
<pre>1 Syntax
|
|
logical-AND-expression:
|
|
inclusive-OR-expression
|
|
logical-AND-expression && inclusive-OR-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.13p2'></a>
|
|
<pre>2 Each of the operands shall have scalar type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.13p3'></a>
|
|
<pre>3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0. The
|
|
result has type int.
|
|
</pre>
|
|
<a name='6.5.13p4'></a>
|
|
<pre>4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation; if the
|
|
second operand is evaluated, there is a sequence point between the evaluations of the first and
|
|
second operands. If the first operand compares equal to 0, the second operand is not evaluated.
|
|
</pre>
|
|
<a name='6.5.14'></a>
|
|
<hr>
|
|
<h3>6.5.14 [Logical OR operator]</h3>
|
|
<a name='6.5.14p1'></a>
|
|
<pre>1 Syntax
|
|
logical-OR-expression:
|
|
logical-AND-expression
|
|
logical-OR-expression || logical-AND-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.14p2'></a>
|
|
<pre>2 Each of the operands shall have scalar type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.14p3'></a>
|
|
<pre>3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0.
|
|
The result has type int.
|
|
</pre>
|
|
<a name='6.5.14p4'></a>
|
|
<pre>4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the second
|
|
operand is evaluated, there is a sequence point between the evaluations of the first and second
|
|
operands. If the first operand compares unequal to 0, the second operand is not evaluated.
|
|
|
|
</pre>
|
|
<a name='6.5.15'></a>
|
|
<hr>
|
|
<h3>6.5.15 [Conditional operator]</h3>
|
|
<a name='6.5.15p1'></a>
|
|
<pre>1 Syntax
|
|
conditional-expression:
|
|
logical-OR-expression
|
|
logical-OR-expression ? expression : conditional-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.15p2'></a>
|
|
<pre>2 The first operand shall have scalar type.
|
|
</pre>
|
|
<a name='6.5.15p3'></a>
|
|
<pre>3 One of the following shall hold for the second and third operands<a href='#FOOTNOTE.125'><sup>[125]</sup></a> :
|
|
|
|
— both operands have arithmetic type;
|
|
|
|
— both operands have the same structure or union type;
|
|
|
|
— both operands have void type;
|
|
|
|
— both operands are pointers to qualified or unqualified versions of compatible types;
|
|
|
|
— both operands have nullptr_t type;
|
|
|
|
— one operand is a pointer and the other is a null pointer constant or has type nullptr_t; or
|
|
|
|
— one operand is a pointer to an object type and the other is a pointer to a qualified or unqualified
|
|
version of void.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.125'>
|
|
<pre><i><b>Footnote 125)</b> If a second or third operand of type nullptr_t is used that is not a null pointer constant and the other operand is not a
|
|
pointer or does not have type nullptr_t itself, a constraint is violated even if that other operand is a null pointer constant
|
|
such as 0.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.15p4'></a>
|
|
<pre>4 If either of the second or third operands has decimal floating type, the other operand shall not have
|
|
standard floating type, complex type, or imaginary type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.15p5'></a>
|
|
<pre>5 The first operand is evaluated; there is a sequence point between its evaluation and the evaluation
|
|
of the second or third operand (whichever is evaluated). The second operand is evaluated only if
|
|
the first compares unequal to 0; the third operand is evaluated only if the first compares equal to 0;
|
|
the result is the value of the second or third operand (whichever is evaluated), converted to the type
|
|
described below<a href='#FOOTNOTE.126'><sup>[126]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.126'>
|
|
<pre><i><b>Footnote 126)</b> A conditional expression does not yield an lvalue.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.15p6'></a>
|
|
<pre>6 If both the second and third operands have arithmetic type, the result type that would be determined
|
|
by the usual arithmetic conversions, were they applied to those two operands, is the type of the
|
|
result. If both the operands have structure or union type, the result has that type. If both operands
|
|
have void type, the result has void type.
|
|
</pre>
|
|
<a name='6.5.15p7'></a>
|
|
<pre>7 If both the second and third operands are pointers, the result type is a pointer to a type qualified
|
|
with all the type qualifiers of the types referenced by both operands; if one is a null pointer constant
|
|
(other than a pointer) or has type nullptr_t type, the result also has that type. Furthermore, if
|
|
both operands are pointers to compatible types or to differently qualified versions of compatible
|
|
types, the result type is a pointer to an appropriately qualified version of the composite type; if
|
|
one operand is a null pointer constant, the result has the type of the other operand; otherwise, one
|
|
operand is a pointer to void or a qualified version of void, in which case the result type is a pointer
|
|
to an appropriately qualified version of void.
|
|
</pre>
|
|
<a name='6.5.15p8'></a>
|
|
<pre>8 EXAMPLE The common type that results when the second and third operands are pointers is determined in two independent
|
|
stages. The appropriate qualifiers, for example, do not depend on whether the two pointers have compatible types.
|
|
</pre>
|
|
<a name='6.5.15p9'></a>
|
|
<pre>9 Given the declarations
|
|
|
|
const void *c_vp;
|
|
void *vp;
|
|
const int *c_ip;
|
|
volatile int *v_ip;
|
|
int *ip;
|
|
const char *c_cp;
|
|
|
|
|
|
|
|
the third column in the following table is the common type that is the result of a conditional expression in which the first two
|
|
columns are the second and third operands (in either order):
|
|
c_vp c_ip const void *
|
|
v_ip 0 volatile int *
|
|
c_ip v_ip const volatile int *
|
|
vp c_cp const void *
|
|
ip c_ip const int *
|
|
vp ip void *
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.5.16'></a>
|
|
<hr>
|
|
<h3>6.5.16 [Assignment operators]</h3>
|
|
<a name='6.5.16p1'></a>
|
|
<pre>1 Syntax
|
|
assignment-expression:
|
|
conditional-expression
|
|
unary-expression assignment-operator assignment-expression
|
|
|
|
assignment-operator: one of
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.5.16p2'></a>
|
|
<pre>2 An assignment operator shall have a modifiable lvalue as its left operand.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.16p3'></a>
|
|
<pre>3 An assignment operator stores a value in the object designated by the left operand. An assignment
|
|
expression has the value of the left operand after the assignment,<a href='#FOOTNOTE.127'><sup>[127]</sup></a> but is not an lvalue. The type of
|
|
an assignment expression is the type the left operand would have after lvalue conversion. The side
|
|
effect of updating the stored value of the left operand is sequenced after the value computations of
|
|
the left and right operands. The evaluations of the operands are unsequenced.
|
|
</pre>
|
|
<a name='FOOTNOTE.127'>
|
|
<pre><i><b>Footnote 127)</b> The implementation is permitted to read the object to determine the value but is not required to, even when the object
|
|
has volatile-qualified type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.16.1'></a>
|
|
<hr>
|
|
<h3>6.5.16.1 [Simple assignment]</h3>
|
|
<a name='6.5.16.1p1'></a>
|
|
<pre>1 Constraints
|
|
One of the following shall hold<a href='#FOOTNOTE.128'><sup>[128]</sup></a> :
|
|
|
|
— the left operand has atomic, qualified, or unqualified arithmetic type, and the right has
|
|
arithmetic type;
|
|
|
|
— the left operand has an atomic, qualified, or unqualified version of a structure or union type
|
|
compatible with the type of the right;
|
|
|
|
— the left operand has atomic, qualified, or unqualified pointer type, and (considering the type
|
|
the left operand would have after lvalue conversion) both operands are pointers to qualified
|
|
or unqualified versions of compatible types, and the type pointed to by the left has all the
|
|
qualifiers of the type pointed to by the right;
|
|
|
|
— the left operand has atomic, qualified, or unqualified pointer type, and (considering the type
|
|
the left operand would have after lvalue conversion) one operand is a pointer to an object type,
|
|
and the other is a pointer to a qualified or unqualified version of void, and the type pointed to
|
|
by the left has all the qualifiers of the type pointed to by the right;
|
|
|
|
— the left operand has an atomic, qualified, or unqualified version of the nullptr_t type and
|
|
the type of the right is nullptr_t<a href='#FOOTNOTE.129'><sup>[129]</sup></a> ;
|
|
|
|
— the left operand is an atomic, qualified, or unqualified pointer, and the type of the right is
|
|
nullptr_t
|
|
|
|
— the left operand is an atomic, qualified, or unqualified bool, and the type of the right is
|
|
nullptr_t;
|
|
|
|
— the left operand is an atomic, qualified, or unqualified pointer, and the right is a null pointer
|
|
constant; or
|
|
|
|
— the left operand has type atomic, qualified, or unqualified bool, and the right is a pointer.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.128'>
|
|
<pre><i><b>Footnote 128)</b> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion (specified
|
|
in <a href='#6.3.2.1'>6.3.2.1</a>) that changes lvalues to "the value of the expression" and thus removes any type qualifiers that were applied to the
|
|
type category of the expression (for example, it removes const but not volatile from the type int volatile * const).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.129'>
|
|
<pre><i><b>Footnote 129)</b> The assignment of an object of type nullptr_t with a value of another type, even if the value is a null pointer constant,
|
|
is a constraint violation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.16.1p2'></a>
|
|
<pre>2 In simple assignment (=), the value of the right operand is converted to the type of the assignment
|
|
expression and replaces the value stored in the object designated by the left operand. <a href='#FOOTNOTE.130'><sup>[130]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.130'>
|
|
<pre><i><b>Footnote 130)</b> As described in <a href='#6.2.6.1'>6.2.6.1</a>, a store to an object with atomic type is done with memory_order_seq_cst semantics.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.16.1p3'></a>
|
|
<pre>3 If the value being stored in an object is read from another object that overlaps in any way the
|
|
storage of the first object, then the overlap shall be exact and the two objects shall have qualified or
|
|
unqualified versions of a compatible type; otherwise, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.5.16.1p4'></a>
|
|
<pre>4 EXAMPLE 1 In the program fragment
|
|
|
|
int f(void);
|
|
char c;
|
|
/* ... */
|
|
if ((c = f()) == -1)
|
|
/* ... */
|
|
|
|
the int value returned by the function could be truncated when stored in the char, and then converted back to int width
|
|
prior to the comparison. In an implementation in which "plain" char has the same range of values as unsigned char (and
|
|
char is narrower than int), the result of the conversion cannot be negative, so the operands of the comparison can never
|
|
compare equal. Therefore, for full portability, the variable c would be declared as int.
|
|
</pre>
|
|
<a name='6.5.16.1p5'></a>
|
|
<pre>5 EXAMPLE 2 In the fragment:
|
|
char c;
|
|
int i;
|
|
long l;
|
|
|
|
l = (c = i);
|
|
|
|
the value of i is converted to the type of the assignment expression c = i, that is, char type. The value of the expression
|
|
enclosed in parentheses is then converted to the type of the outer assignment expression, that is, long int type.
|
|
</pre>
|
|
<a name='6.5.16.1p6'></a>
|
|
<pre>6 EXAMPLE 3 Consider the fragment:
|
|
|
|
const char **cpp;
|
|
char *p;
|
|
const char c = ’A’;
|
|
|
|
cpp = &p; // constraint violation
|
|
*cpp = &c; // valid
|
|
*p = 0; // valid
|
|
|
|
The first assignment is unsafe because it would allow the following valid code to attempt to change the value of the const
|
|
object c.
|
|
|
|
</pre>
|
|
<a name='6.5.16.2'></a>
|
|
<hr>
|
|
<h3>6.5.16.2 [Compound assignment]</h3>
|
|
<a name='6.5.16.2p1'></a>
|
|
<pre>1 Constraints
|
|
For the operators += and-= only, either the left operand shall be an atomic, qualified, or unqualified
|
|
pointer to a complete object type, and the right shall have integer type; or the left operand shall have
|
|
atomic, qualified, or unqualified arithmetic type, and the right shall have arithmetic type.
|
|
</pre>
|
|
<a name='6.5.16.2p2'></a>
|
|
<pre>2 For the other operators, the left operand shall have atomic, qualified, or unqualified arithmetic type,
|
|
and (considering the type the left operand would have after lvalue conversion) each operand shall
|
|
have arithmetic type consistent with those allowed by the corresponding binary operator.
|
|
</pre>
|
|
<a name='6.5.16.2p3'></a>
|
|
<pre>3 If either operand has decimal floating type, the other operand shall not have standard floating type,
|
|
complex type, or imaginary type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.16.2p4'></a>
|
|
<pre>4 A compound assignment of the form E1 op= E2 is equivalent to the simple assignment expression
|
|
E1 = E1 op (E2) , except that the lvalue E1 is evaluated only once, and with respect to an inde-
|
|
terminately-sequenced function call, the operation of a compound assignment is a single evalu-
|
|
ation. If E1 has an atomic type, compound assignment is a read-modify-write operation with
|
|
memory_order_seq_cst memory order semantics.
|
|
</pre>
|
|
<a name='6.5.16.2p5'></a>
|
|
<pre>5 NOTE Where a pointer to an atomic object can be formed and E1 and E2 have integer type, this is equivalent to the following
|
|
code sequence where T1 is the type of E1 and T2 is the type of E2:
|
|
|
|
T1 *addr = &E1;
|
|
T2 val = (E2);
|
|
T1 old = *addr;
|
|
T1 new;
|
|
do {
|
|
new = old op val;
|
|
} while (!atomic_compare_exchange_strong(addr, &old, new));
|
|
|
|
with new being the result of the operation.
|
|
If E1 or E2 has floating type, then exceptional conditions or floating-point exceptions encountered during discarded
|
|
evaluations of new would also be discarded in order to satisfy the equivalence of E1 op= E2 and E1 = E1 op (E2) . For
|
|
example, if Annex F is in effect, the floating types involved have IEC 60559 binary formats, and FLT_EVAL_METHOD is 0, the
|
|
equivalent code would be:
|
|
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
/* ... */
|
|
fenv_t fenv;
|
|
T1 *addr = &E1;
|
|
T2 val = E2;
|
|
T1 old = *addr;
|
|
T1 new;
|
|
feholdexcept(&fenv);
|
|
for (;;) {
|
|
new = old op val;
|
|
if (atomic_compare_exchange_strong(addr, &old, new))
|
|
break;
|
|
feclearexcept(FE_ALL_EXCEPT);
|
|
}
|
|
feupdateenv(&fenv);
|
|
|
|
If FLT_EVAL_METHOD is not 0, then T2 is expected to be a type with the range and precision to which E2 is evaluated in order
|
|
to satisfy the equivalence.
|
|
|
|
</pre>
|
|
<a name='6.5.17'></a>
|
|
<hr>
|
|
<h3>6.5.17 [Comma operator]</h3>
|
|
<a name='6.5.17p1'></a>
|
|
<pre>1 Syntax
|
|
expression:
|
|
assignment-expression
|
|
expression , assignment-expression
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.17p2'></a>
|
|
<pre>2 The left operand of a comma operator is evaluated as a void expression; there is a sequence point
|
|
between its evaluation and that of the right operand. Then the right operand is evaluated; the result
|
|
has its type and value.<a href='#FOOTNOTE.131'><sup>[131]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.131'>
|
|
<pre><i><b>Footnote 131)</b> A comma operator does not yield an lvalue.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.17p3'></a>
|
|
<pre>3 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot appear in contexts where
|
|
a comma is used to separate items in a list (such as arguments to functions or lists of initializers). On the other hand, it can be
|
|
used within a parenthesized expression or within the second expression of a conditional operator in such contexts. In the
|
|
function call
|
|
|
|
f(a, (t=3, t+2), c)
|
|
|
|
the function has three arguments, the second of which has the value 5.
|
|
|
|
Forward references: initialization (<a href='#6.7.10'>6.7.10</a>).
|
|
</pre>
|
|
<a name='6.6'></a>
|
|
<hr>
|
|
<h3>6.6 [Constant expressions]</h3>
|
|
<a name='6.6p1'></a>
|
|
<pre>1 Syntax
|
|
constant-expression:
|
|
conditional-expression
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.6p2'></a>
|
|
<pre>2 A constant expression can be evaluated during translation rather than runtime, and accordingly
|
|
may be used in any place that a constant may be.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.6p3'></a>
|
|
<pre>3 Constant expressions shall not contain assignment, increment, decrement, function-call, or comma
|
|
operators, except when they are contained within a subexpression that is not evaluated<a href='#FOOTNOTE.132'><sup>[132]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.132'>
|
|
<pre><i><b>Footnote 132)</b> The operand of a the typeof <a href='#6.7.2.5'>6.7.2.5</a>, sizeof, or alignof operator is usually not evaluated (<a href='#6.5.3.4'>6.5.3.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p4'></a>
|
|
<pre>4 Each constant expression shall evaluate to a constant that is in the range of representable values for
|
|
its type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.6p5'></a>
|
|
<pre>5 An expression that evaluates to a constant is required in several contexts. If a floating expression
|
|
is evaluated in the translation environment, the arithmetic range and precision shall be at least as
|
|
great as if the expression were being evaluated in the execution environment. <a href='#FOOTNOTE.133'><sup>[133]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.133'>
|
|
<pre><i><b>Footnote 133)</b> The use of evaluation formats as characterized by FLT_EVAL_METHOD and DEC_EVAL_METHOD also applies to evaluation in
|
|
the translation environment.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p6'></a>
|
|
<pre>6 A compound literal with storage-class specifier constexpr is a compound literal constant. A com-
|
|
pound literal constant is a constant expression with the type and value of the unnamed object.
|
|
</pre>
|
|
<a name='6.6p7'></a>
|
|
<pre>7 An identifier that is:
|
|
|
|
— an enumeration constant;
|
|
|
|
— a predefined constant;
|
|
|
|
— or, declared with storage-class specifier constexpr and has an object type,
|
|
|
|
is a named constant, as is a postfix expression that applies the . member access operator to a named
|
|
constant of structure or union type, even recursively. For enumeration and predefined constants,
|
|
their value and type are defined in the respective clauses; for constexpr objects, such a named
|
|
constant is a constant expression with the type and value of the declared object.
|
|
</pre>
|
|
<a name='6.6p8'></a>
|
|
<pre>8 An integer constant expression<a href='#FOOTNOTE.134'><sup>[134]</sup></a> shall have integer type and shall only have operands that are
|
|
integer constants, named and compound literal constants of integer type, character constants,
|
|
sizeof expressions whose results are integer constants, alignof expressions, and floating, named,
|
|
or compound literal constants of arithmetic type that are the immediate operands of casts. Cast
|
|
operators in an integer constant expression shall only convert arithmetic types to integer types,
|
|
except as part of an operand to the typeof operators, sizeof operator, or alignof operator.
|
|
</pre>
|
|
<a name='FOOTNOTE.134'>
|
|
<pre><i><b>Footnote 134)</b> An integer constant expression is required in a number of contexts such as the size of a bit-field member of a structure,
|
|
the value of an enumeration constant, and the size of a non-variable length array. Further constraints that apply to the integer
|
|
constant expressions used in conditional-inclusion preprocessing directives are discussed in <a href='#6.10.1'>6.10.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p9'></a>
|
|
<pre>9 More latitude is permitted for constant expressions in initializers. Such a constant expression shall
|
|
be, or evaluate to, one of the following:
|
|
|
|
— a named constant,
|
|
|
|
— a compound literal constant,
|
|
|
|
— an arithmetic constant expression,
|
|
— a null pointer constant,
|
|
— an address constant, or
|
|
— an address constant for a complete object type plus or minus an integer constant expression.
|
|
|
|
</pre>
|
|
<a name='6.6p10'></a>
|
|
<pre>10 An arithmetic constant expression shall have arithmetic type and shall only have operands that are
|
|
integer constants, floating constants, named or compound literal constants of arithmetic type, char-
|
|
acter constants, sizeof expressions whose results are integer constants, and alignof expressions.
|
|
Cast operators in an arithmetic constant expression shall only convert arithmetic types to arithmetic
|
|
types, except as part of an operand to the typeof operators, sizeof operator, or alignof operator.
|
|
</pre>
|
|
<a name='6.6p11'></a>
|
|
<pre>11 An address constant is a null pointer<a href='#FOOTNOTE.135'><sup>[135]</sup></a> , a pointer to an lvalue designating an object of static storage
|
|
duration, or a pointer to a function designator; it shall be created explicitly using the unary &
|
|
operator or an integer constant cast to pointer type, or implicitly by the use of an expression of array
|
|
or function type.
|
|
</pre>
|
|
<a name='FOOTNOTE.135'>
|
|
<pre><i><b>Footnote 135)</b> A named constant or compound literal constant of integer type and value zero is a null pointer constant. A named
|
|
constant or compound literal constant with a pointer type and a value null is a null pointer but not a null pointer constant; it
|
|
may only be used to initialize a pointer object if its type implicitly converts to the target type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p12'></a>
|
|
<pre>12 The array-subscript [] and member-access -> operator, the address & and indirection * unary
|
|
operators, and pointer casts may be used in the creation of an address constant, but the value of an
|
|
object shall not be accessed by use of these operators<a href='#FOOTNOTE.136'><sup>[136]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.136'>
|
|
<pre><i><b>Footnote 136)</b> Named constant or compound literal constants with arithmetic type, including names of constexpr objects, are valid in
|
|
offset computations such as array subscripts or int pointer casts, as long as the expression in which they occur form integer
|
|
constant expressions. In contrast, names of other objects, even if const-qualified and with static storage duration, are not
|
|
valid.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p13'></a>
|
|
<pre>13 A structure or union constant is a named constant or compound literal constant with structure or
|
|
union type, respectively.
|
|
</pre>
|
|
<a name='6.6p14'></a>
|
|
<pre>14 An implementation may accept other forms of constant expressions, however, they are not an integer
|
|
constant expression.<a href='#FOOTNOTE.137'><sup>[137]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.137'>
|
|
<pre><i><b>Footnote 137)</b> For example, in the statement int arr_or_vla[(int)+1.0];, while possible to be computed by some implementations
|
|
as an array with a size of one, still results in a variable length array declaration of automatic storage duration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p15'></a>
|
|
<pre>15 Starting from a structure or union constant, the member-access . operator may be used to form a
|
|
named constant or compound literal constant as described above.
|
|
</pre>
|
|
<a name='6.6p16'></a>
|
|
<pre>16 If the member-access operator . accesses a member of a union constant, the access member shall be
|
|
the same as the member that is initialized by the union constant’s initializer.
|
|
</pre>
|
|
<a name='6.6p17'></a>
|
|
<pre>17 The semantic rules for the evaluation of a constant expression are the same as for nonconstant
|
|
expressions<a href='#FOOTNOTE.138'><sup>[138]</sup></a> .
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>), initialization (<a href='#6.7.10'>6.7.10</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.138'>
|
|
<pre><i><b>Footnote 138)</b> Thus, in the following initialization,
|
|
static int i = 2 || 1 / 0;
|
|
the expression is a valid integer constant expression with value one.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7'></a>
|
|
<hr>
|
|
<h3>6.7 [Declarations]</h3>
|
|
<a name='6.7p1'></a>
|
|
<pre>1 Syntax
|
|
declaration:
|
|
declaration-specifiers init-declarator-listopt ;
|
|
attribute-specifier-sequence declaration-specifiers init-declarator-list ;
|
|
static_assert-declaration
|
|
attribute-declaration
|
|
declaration-specifiers:
|
|
declaration-specifier attribute-specifier-sequenceopt
|
|
declaration-specifier declaration-specifiers
|
|
declaration-specifier:
|
|
storage-class-specifier
|
|
type-specifier-qualifier
|
|
function-specifier
|
|
init-declarator-list:
|
|
init-declarator
|
|
init-declarator-list , init-declarator
|
|
init-declarator:
|
|
declarator
|
|
declarator = initializer
|
|
attribute-declaration:
|
|
attribute-specifier-sequence ;
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7p2'></a>
|
|
<pre>2 A declaration other than a static_assert or attribute declaration shall declare at least a declarator
|
|
(other than the parameters of a function or the members of a structure or union), a tag, or the
|
|
members of an enumeration.
|
|
</pre>
|
|
<a name='6.7p3'></a>
|
|
<pre>3 If an identifier has no linkage, there shall be no more than one declaration of the identifier (in a
|
|
declarator or type specifier) with the same scope and in the same name space, except that:
|
|
|
|
— a typedef name may be redefined to denote the same type as it currently does, provided that
|
|
type is not a variably modified type;
|
|
— enumeration constants and tags may be redeclared as specified in <a href='#6.7.2.2'>6.7.2.2</a> <a href='#6.7.2.3'>6.7.2.3</a>.
|
|
|
|
</pre>
|
|
<a name='6.7p4'></a>
|
|
<pre>4 All declarations in the same scope that refer to the same object or function shall specify compatible
|
|
types.
|
|
</pre>
|
|
<a name='6.7p5'></a>
|
|
<pre>5 In an underspecified declaration all declared identifiers that do not have a prior declaration shall be
|
|
ordinary identifiers.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7p6'></a>
|
|
<pre>6 A declaration specifies the interpretation and properties of a set of identifiers. A definition of an
|
|
identifier is a declaration for that identifier that:
|
|
|
|
— for an object, causes storage to be reserved for that object;
|
|
— for a function, includes the function body<a href='#FOOTNOTE.139'><sup>[139]</sup></a> ;
|
|
— for an enumeration constant, is the (only) declaration of the identifier;
|
|
— for a typedef name, is the first (or only) declaration of the identifier.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.139'>
|
|
<pre><i><b>Footnote 139)</b> Function definitions have a different syntax, described in <a href='#6.9.1'>6.9.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7p7'></a>
|
|
<pre>7 The declaration specifiers consist of a sequence of specifiers, followed by an optional attribute
|
|
specifier sequence, that indicate the linkage, storage duration, and part of the type of the entities that
|
|
the declarators denote. The init declarator list is a comma-separated sequence of declarators, each
|
|
of which may have additional type information, or an initializer, or both. The declarators contain
|
|
the identifiers (if any) being declared. The optional attribute specifier sequence in a declaration
|
|
appertains to each of the entities declared by the declarators of the init declarator list.
|
|
</pre>
|
|
<a name='6.7p8'></a>
|
|
<pre>8 If an identifier for an object is declared with no linkage, the type for the object shall be complete
|
|
by the end of its declarator, or by the end of its init-declarator if it has an initializer; in the case of
|
|
function parameters, it is the adjusted type (see <a href='#6.7.6.3'>6.7.6.3</a>) that is required to be complete.
|
|
</pre>
|
|
<a name='6.7p9'></a>
|
|
<pre>9 The optional attribute specifier sequence terminating a sequence of declaration specifiers appertains
|
|
to the type determined by the preceding sequence of declaration specifiers. The attribute specifier
|
|
sequence affects the type only for the declaration it appears in, not other declarations involving the
|
|
same type.
|
|
</pre>
|
|
<a name='6.7p10'></a>
|
|
<pre>10 Except where specified otherwise, the meaning of an attribute declaration is implementation-defined.
|
|
</pre>
|
|
<a name='6.7p11'></a>
|
|
<pre>11 EXAMPLE In the declaration for an entity, attributes appertaining to that entity may appear at the start of the declaration
|
|
and after the identifier for that declaration.
|
|
|
|
[[deprecated]] void f [[deprecated]] (void); // valid
|
|
|
|
|
|
</pre>
|
|
<a name='6.7p12'></a>
|
|
<pre>12 A declaration such that the declaration specifiers contain no type specifier or that is declared with
|
|
constexpr is said to be underspecified. If such a declaration is not a definition, if it declares no or more
|
|
than one ordinary identifier, if the declared identifier already has a declaration in the same scope, or
|
|
if the declared entity is not an object, the behavior is undefined.
|
|
Forward references: declarators (<a href='#6.7.6'>6.7.6</a>), enumeration specifiers (<a href='#6.7.2.2'>6.7.2.2</a>), initialization (<a href='#6.7.10'>6.7.10</a>), type
|
|
names (<a href='#6.7.7'>6.7.7</a>), type qualifiers (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.1'></a>
|
|
<hr>
|
|
<h3>6.7.1 [Storage-class specifiers]</h3>
|
|
<a name='6.7.1p1'></a>
|
|
<pre>1 Syntax
|
|
storage-class-specifier:
|
|
auto
|
|
constexpr
|
|
extern
|
|
register
|
|
static
|
|
thread_local
|
|
typedef
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.1p2'></a>
|
|
<pre>2 At most, one storage-class specifier may be given in the declaration specifiers in a declaration, except
|
|
that:
|
|
|
|
— thread_local may appear with static or extern;
|
|
|
|
— auto may appear with all the others except typedef<a href='#FOOTNOTE.140'><sup>[140]</sup></a> ;
|
|
|
|
— and, constexpr may appear with auto, register, or static.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.140'>
|
|
<pre><i><b>Footnote 140)</b> See "future language directions" (<a href='#6.11.5'>6.11.5</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.1p3'></a>
|
|
<pre>3 In the declaration of an object with block scope, if the declaration specifiers include thread_local,
|
|
they shall also include either static or extern. If thread_local appears in any declaration of an
|
|
object, it shall be present in every declaration of that object.
|
|
</pre>
|
|
<a name='6.7.1p4'></a>
|
|
<pre>4 thread_local shall not appear in the declaration specifiers of a function declaration. auto shall
|
|
only appear in the declaration specifiers of an identifier with file scope or along with other storage
|
|
class specifiers if the type is to be inferred from an initializer.
|
|
</pre>
|
|
<a name='6.7.1p5'></a>
|
|
<pre>5 An object declared with storage-class specifier constexpr or any of its members, even recursively,
|
|
shall not have an atomic type, or a variably modified type, or a type that is volatile or restrict
|
|
qualified. The declaration shall be a definition and shall have an initializer<a href='#FOOTNOTE.141'><sup>[141]</sup></a> . The value of
|
|
any constant expressions or of any character in a string literal of the initializer shall be exactly
|
|
representable in the corresponding target type; no change of value shall be applied<a href='#FOOTNOTE.142'><sup>[142]</sup></a> . If an object
|
|
or subobject declared with storage-class specifier constexpr has pointer, integer, or arithmetic type,
|
|
the implicit or explicit initializer value for it shall be a null pointer constant<a href='#FOOTNOTE.143'><sup>[143]</sup></a> , an integer constant
|
|
expression, or an arithmetic constant expression, respectively.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.141'>
|
|
<pre><i><b>Footnote 141)</b> The right operand of all assignment expressions of such an initializer, if any, are constant expressions or string literals,
|
|
see <a href='#6.7.10'>6.7.10</a>
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.142'>
|
|
<pre><i><b>Footnote 142)</b> In the context of arithmetic conversions, <a href='#6.3.1'>6.3.1</a> describes the details of changes of value that occur if values of arithmetic
|
|
expressions are stored in the objects that for example have a different signedness, excess precision or quantum exponent.
|
|
Whenever such a change of value is necessary, the constraint is violated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.143'>
|
|
<pre><i><b>Footnote 143)</b> The named constant or compound literal constant corresponding to an object declared with storage-class specifier
|
|
constexpr and pointer type is a constant expression with a value null, and thus a null pointer and an address constant.
|
|
However, even if it has type void* it is not a null pointer constant.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.1p6'></a>
|
|
<pre>6 Storage-class specifiers specify various properties of identifiers and declared features; storage
|
|
duration (static in block scope, thread_local, auto, register), linkage (extern, static and
|
|
constexpr in file scope, typedef), value (constexpr), and type (typedef). The meanings of the
|
|
various linkages and storage durations were discussed in <a href='#6.2.2'>6.2.2</a> and <a href='#6.2.4'>6.2.4</a>, typedef is discussed in
|
|
<a href='#6.7.8'>6.7.8</a>, and type inference is discussed in <a href='#6.7.9'>6.7.9</a>.
|
|
</pre>
|
|
<a name='6.7.1p7'></a>
|
|
<pre>7 A declaration of an identifier for an object with storage-class specifier register suggests that
|
|
access to the object be as fast as possible. The extent to which such suggestions are effective is
|
|
implementation-defined<a href='#FOOTNOTE.144'><sup>[144]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.144'>
|
|
<pre><i><b>Footnote 144)</b> The implementation can treat any register declaration simply as an auto declaration. However, whether or not
|
|
addressable storage is actually used, the address of any part of an object declared with storage-class specifier register
|
|
cannot be computed, either explicitly (by use of the unary & operator as discussed in <a href='#6.5.3.2'>6.5.3.2</a>) or implicitly (by converting
|
|
an array name to a pointer as discussed in <a href='#6.3.2.1'>6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with
|
|
storage-class specifier register is sizeof and the typeof operators.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.1p8'></a>
|
|
<pre>8 The declaration of an identifier for a function that has block scope shall have no explicit storage-class
|
|
specifier other than extern.
|
|
</pre>
|
|
<a name='6.7.1p9'></a>
|
|
<pre>9 If an aggregate or union object is declared with a storage-class specifier other than typedef, the
|
|
properties resulting from the storage-class specifier, except with respect to linkage, also apply to the
|
|
members of the object, and so on recursively for any aggregate or union member objects.
|
|
</pre>
|
|
<a name='6.7.1p10'></a>
|
|
<pre>10 If auto appears with another storage-class specifier, or if it appears in a declaration at file scope, it is
|
|
ignored for the purposes of determining a storage duration of linkage. It then only indicates that the
|
|
declared type may be inferred.
|
|
</pre>
|
|
<a name='6.7.1p11'></a>
|
|
<pre>11 An object declared with a storage-class specifier constexpr has its value permanently fixed at
|
|
translation-time; if not yet present, a const-qualification is implicitly added to the object’s type. The
|
|
declared identifier is considered a constant expression of the respective kind, see ??.
|
|
</pre>
|
|
<a name='6.7.1p12'></a>
|
|
<pre>12 NOTE An object declared in block scope with a storage-class specifier constexpr and without static has automatic storage
|
|
duration, the identifier has no linkage, and each instance of the object has a unique address obtainable with & (if it is not
|
|
declared with the register specifier), if any. Such an object in file scope has static storage duration, the corresponding identifier
|
|
has internal linkage, and each translation unit that sees the same textual definition implements a separate object with a
|
|
distinct address.
|
|
</pre>
|
|
<a name='6.7.1p13'></a>
|
|
<pre>13 NOTE The constraints for constexpr objects are intended to enforce checks for portability at translation time.
|
|
|
|
constexpr unsigned int minusOne = -1; // constraint violation
|
|
constexpr unsigned int uint_max = -1U; // ok
|
|
constexpr char string[] = { "\xFF", }; // possible constraint
|
|
violation
|
|
constexpr unsigned char unstring[] = { "\xFF", }; // ok
|
|
constexpr char8_t u8string[] = { u8"\xFF", }; // ok
|
|
constexpr double onethird = 1.0/3.0; // possible constraint
|
|
violation
|
|
constexpr double onethirdtrunc = (double)(1.0/3.0); // ok
|
|
constexpr _Decimal32 small = DEC64_TRUE_MIN * 0; // constraint violation
|
|
|
|
Using an octal or hexadecimal escape character sequence with a value greater than the largest representable value of the target
|
|
character type (such as for unstring) possibly violates a constraint. Equally, an implementation that uses excess precision for
|
|
floating-point constants violates the constraint for onethird; a diagnostic is required if a truncation of the mantissa occurs.
|
|
In contrast to that, the explicit conversion in the initializer for onethirdtrunc ensures that the definition is valid. Similarly,
|
|
the initializer of small has a quantum exponent that is larger than the largest possible quantum exponent for _Decimal32 .
|
|
</pre>
|
|
<a name='6.7.1p14'></a>
|
|
<pre>14 EXAMPLE 1 An identifier declared with the constexpr specifier may have its value used in constant expressions:
|
|
|
|
constexpr int K = 47;
|
|
enum {
|
|
A = K, // valid, constant initialization
|
|
};
|
|
constexpr int L = K; // valid, constexpr initialization
|
|
static int b = K + 1; // valid, static initialization
|
|
int array[K]; // not a VLA
|
|
|
|
</pre>
|
|
<a name='6.7.1p15'></a>
|
|
<pre>15 EXAMPLE 2 An object declared with the constexpr specifier stores the exact value of its initializer, no implicit value change
|
|
is applied:
|
|
|
|
#include <float.h>
|
|
|
|
constexpr int A = 42LL; // valid, 42 always fits in an int
|
|
constexpr signed short B = ULLONG_MAX; // constraint violation, value never
|
|
// fits
|
|
constexpr float C = 47u; // valid, exactly representable
|
|
// in single precision
|
|
|
|
#if FLT_MANT_DIG > 24
|
|
constexpr float D = 432000000; // constraint violation if float is
|
|
// 32-bit single-precision IEC 60559
|
|
#endif
|
|
|
|
#if (FLT_MANT_DIG == DBL_MANT_DIG) && (0 <= FLT_EVAL_METHOD) && (FLT_EVAL_METHOD
|
|
<= 1)
|
|
constexpr float E = 1.0 / 3.0; // only valid if double expressions
|
|
// and float objects have the same
|
|
precision
|
|
#endif
|
|
|
|
#if FLT_EVAL_METHOD == 0
|
|
constexpr float F = <a href='#1.'>1.</a>0f / <a href='#3.'>3.</a>0f; // valid, same type and precision
|
|
#else
|
|
constexpr float F = (float)(<a href='#1.'>1.</a>0f / <a href='#3.'>3.</a>0f); // needs cast to truncate the
|
|
// excess precision
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='6.7.1p16'></a>
|
|
<pre>16 EXAMPLE 3 EXAMPLE 3 This recursively applies to initializers for all elements of an aggregate object declared with the
|
|
constexpr specifier:
|
|
|
|
constexpr static unsigned short array[] = {
|
|
3000, // valid, fits in unsigned short range
|
|
300000, // constraint violation if short is 16-bit
|
|
-1 // constraint violation, target type is unsigned
|
|
};
|
|
|
|
struct S {
|
|
int x, y;
|
|
};
|
|
constexpr struct S s = {
|
|
.x = INT_MAX, // valid
|
|
.y = UINT_MAX, // constraint violation
|
|
};
|
|
Forward references: type definitions (<a href='#6.7.8'>6.7.8</a>), type definitions (<a href='#6.7.9'>6.7.9</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.2'></a>
|
|
<hr>
|
|
<h3>6.7.2 [Type specifiers]</h3>
|
|
<a name='6.7.2p1'></a>
|
|
<pre>1 Syntax
|
|
type-specifier:
|
|
void
|
|
char
|
|
short
|
|
int
|
|
long
|
|
float
|
|
double
|
|
signed
|
|
unsigned
|
|
_BitInt ( constant-expression )
|
|
bool
|
|
_Complex
|
|
_Decimal32
|
|
_Decimal64
|
|
_Decimal128
|
|
atomic-type-specifier
|
|
struct-or-union-specifier
|
|
enum-specifier
|
|
typedef-name
|
|
typeof-specifier
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2p2'></a>
|
|
<pre>2 Except where the type is inferred (<a href='#6.7.9'>6.7.9</a>), at least one type specifier shall be given in the declaration
|
|
specifiers in each declaration, and in the specifier-qualifier list in each member declaration and type
|
|
name. Each list of type specifiers shall be one of the following multisets (delimited by commas,
|
|
when there is more than one multiset per item); the type specifiers may occur in any order, possibly
|
|
intermixed with the other declaration specifiers.
|
|
|
|
— void
|
|
— char
|
|
— signed char
|
|
— unsigned char
|
|
— short, signed short, short int, or signed short int
|
|
— unsigned short, or unsigned short int
|
|
— int, signed, or signed int
|
|
— unsigned, or unsigned int
|
|
— long, signed long, long int, or signed long int
|
|
— unsigned long, or unsigned long int
|
|
— long long, signed long long, long long int, or signed long long int
|
|
— unsigned long long, or unsigned long long int
|
|
— _BitInt( constant-expression), or signed _BitInt( constant-expression)
|
|
— unsigned _BitInt( constant-expression)
|
|
— float
|
|
— double
|
|
— long double
|
|
— _Decimal32
|
|
— _Decimal64
|
|
— _Decimal128
|
|
— bool
|
|
— float _Complex
|
|
— double _Complex
|
|
— long double _Complex
|
|
— atomic type specifier
|
|
— struct or union specifier
|
|
— enum specifier
|
|
— typedef name
|
|
— typeof specifier
|
|
|
|
</pre>
|
|
<a name='6.7.2p3'></a>
|
|
<pre>3 The type specifier _Complex shall not be used if the implementation does not support complex
|
|
types, and the type specifiers _Decimal32 , _Decimal64 , and _Decimal128 shall not be used if the
|
|
implementation does not support decimal floating types (see <a href='#6.10.9.3'>6.10.9.3</a>).
|
|
</pre>
|
|
<a name='6.7.2p4'></a>
|
|
<pre>4 The parenthesized constant expression that follows the _BitInt keyword shall be an integer constant
|
|
expression N that specifies the width (<a href='#6.2.6.2'>6.2.6.2</a>) of the type. The value of N for unsigned _BitInt
|
|
shall be greater than or equal to 1. The value of N for _BitInt shall be greater than or equal to 2.
|
|
The value of N shall be less than or equal to the value of BITINT_MAXWIDTH (see <a href='#5.2.4.2.1'>5.2.4.2.1</a>).
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2p5'></a>
|
|
<pre>5 Specifiers for structures, unions, enumerations, atomic types, and typeof specifiers are discussed
|
|
in <a href='#6.7.2.1'>6.7.2.1</a> through <a href='#6.7.2.5'>6.7.2.5</a>. Declarations of typedef names are discussed in <a href='#6.7.8'>6.7.8</a>. The characteristics of
|
|
the other types are discussed in <a href='#6.2.5'>6.2.5</a>.
|
|
</pre>
|
|
<a name='6.7.2p6'></a>
|
|
<pre>6 For a declaration such that the declaration specifiers contain no type specifier a mechanism to infer
|
|
the type from an initializer is discussed in <a href='#6.7.9'>6.7.9</a>. In such a declaration, optional elements, if any,
|
|
of a sequence of declaration specifiers appertain to the inferred type (for qualifiers and attribute
|
|
specifiers) or to the declared objects (for alignment specifiers).
|
|
</pre>
|
|
<a name='6.7.2p7'></a>
|
|
<pre>7 Each of the comma-separated multisets designates the same type, except that for bit-fields, it is
|
|
implementation-defined whether the specifier int designates the same type as signed int or the
|
|
same type as unsigned int.
|
|
Forward references: atomic type specifiers (<a href='#6.7.2.4'>6.7.2.4</a>), enumeration specifiers (<a href='#6.7.2.2'>6.7.2.2</a>), structure and
|
|
union specifiers (<a href='#6.7.2.1'>6.7.2.1</a>), tags (<a href='#6.7.2.3'>6.7.2.3</a>), type definitions (<a href='#6.7.8'>6.7.8</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.2.1'></a>
|
|
<hr>
|
|
<h3>6.7.2.1 [Structure and union specifiers]</h3>
|
|
<a name='6.7.2.1p1'></a>
|
|
<pre>1 Syntax
|
|
struct-or-union-specifier:
|
|
struct-or-union attribute-specifier-sequenceopt identifieropt { member-declaration-list }
|
|
struct-or-union attribute-specifier-sequenceopt identifier
|
|
|
|
struct-or-union:
|
|
struct
|
|
union
|
|
|
|
|
|
member-declaration-list:
|
|
member-declaration
|
|
member-declaration-list member-declaration
|
|
|
|
member-declaration:
|
|
attribute-specifier-sequenceopt specifier-qualifier-list member-declarator-listopt ;
|
|
static_assert-declaration
|
|
|
|
specifier-qualifier-list:
|
|
type-specifier-qualifier attribute-specifier-sequenceopt
|
|
type-specifier-qualifier specifier-qualifier-list
|
|
|
|
type-specifier-qualifier:
|
|
type-specifier
|
|
type-qualifier
|
|
alignment-specifier
|
|
|
|
|
|
|
|
member-declarator-list:
|
|
member-declarator
|
|
member-declarator-list , member-declarator
|
|
|
|
member-declarator:
|
|
declarator
|
|
declaratoropt : constant-expression
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.1p2'></a>
|
|
<pre>2 A member declaration that does not declare an anonymous structure or anonymous union shall
|
|
contain a member declarator list.
|
|
</pre>
|
|
<a name='6.7.2.1p3'></a>
|
|
<pre>3 A structure or union shall not contain a member with incomplete or function type (hence, a structure
|
|
shall not contain an instance of itself, but may contain a pointer to an instance of itself), except that
|
|
the last member of a structure with more than one named member may have incomplete array type;
|
|
such a structure (and any union containing, possibly recursively, a member that is such a structure)
|
|
shall not be a member of a structure or an element of an array.
|
|
</pre>
|
|
<a name='6.7.2.1p4'></a>
|
|
<pre>4 The expression that specifies the width of a bit-field shall be an integer constant expression with a
|
|
nonnegative value that does not exceed the width of an object of the type that would be specified
|
|
were the colon and expression omitted<a href='#FOOTNOTE.145'><sup>[145]</sup></a> . If the value is zero, the declaration shall have no
|
|
declarator.
|
|
</pre>
|
|
<a name='FOOTNOTE.145'>
|
|
<pre><i><b>Footnote 145)</b> While the number of bits in a bool object is at least CHAR_BIT, the width of a bool can be just 1 bit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p5'></a>
|
|
<pre>5 A bit-field shall have a type that is a qualified or unqualified version of bool, signed int, unsigned
|
|
int, a bit-precise integer type, or some other implementation-defined type. It is implementation-
|
|
defined whether atomic types are permitted.
|
|
</pre>
|
|
<a name='6.7.2.1p6'></a>
|
|
<pre>6 An attribute specifier sequence shall not appear in a struct-or-union specifier without a member
|
|
declaration list, except in a declaration of the form:
|
|
struct-or-union attribute-specifier-sequence identifier ;
|
|
The attributes in the attribute specifier sequence, if any, are thereafter considered attributes of the
|
|
struct or union whenever it is named.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.1p7'></a>
|
|
<pre>7 As discussed in <a href='#6.2.5'>6.2.5</a>, a structure is a type consisting of a sequence of members, whose storage is
|
|
allocated in an ordered sequence, and a union is a type consisting of a sequence of members whose
|
|
storage overlap.
|
|
</pre>
|
|
<a name='6.7.2.1p8'></a>
|
|
<pre>8 Structure and union specifiers have the same form. The keywords struct and union indicate that
|
|
the type being specified is, respectively, a structure type or a union type.
|
|
</pre>
|
|
<a name='6.7.2.1p9'></a>
|
|
<pre>9 The optional attribute specifier sequence in a struct-or-union specifier appertains to the structure
|
|
or union type being declared. The optional attribute specifier sequence in a member declaration
|
|
appertains to each of the members declared by the member declarator list; it shall not appear if the
|
|
optional member declarator list is omitted. The optional attribute specifier sequence in a specifier
|
|
qualifier list appertains to the type denoted by the preceding type specifier qualifiers. The attribute
|
|
specifier sequence affects the type only for the member declaration or type name it appears in, not
|
|
other types or declarations involving the same type.
|
|
</pre>
|
|
<a name='6.7.2.1p10'></a>
|
|
<pre>10 The member declaration list is a sequence of declarations for the members of the structure or union.
|
|
If the member declaration list does not contain any named members, either directly or via an
|
|
anonymous structure or anonymous union, the behavior is undefined<a href='#FOOTNOTE.146'><sup>[146]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.146'>
|
|
<pre><i><b>Footnote 146)</b> For further rules affecting compatibility and completeness of structure or union types, see <a href='#6.2.7'>6.2.7</a> and <a href='#6.7.2.3'>6.7.2.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p11'></a>
|
|
<pre>11 A member of a structure or union may have any complete object type other than a variably modified
|
|
type<a href='#FOOTNOTE.147'><sup>[147]</sup></a> . In addition, a member may be declared to consist of a specified number of bits (including a
|
|
sign bit, if any). Such a member is called a bit-field 148) ; its width is preceded by a colon.
|
|
</pre>
|
|
<a name='FOOTNOTE.147'>
|
|
<pre><i><b>Footnote 147)</b> A structure or union cannot contain a member with a variably modified type because member names are not ordinary
|
|
identifiers as defined in <a href='#6.2.3'>6.2.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p12'></a>
|
|
<pre>12 A bit-field is interpreted as having a signed or unsigned integer type consisting of the specified
|
|
number of bits<a href='#FOOTNOTE.149'><sup>[149]</sup></a> . If the value 0 or 1 is stored into a nonzero-width bit-field of type bool, the value
|
|
of the bit-field shall compare equal to the value stored; a bool bit-field has the semantics of a bool.
|
|
</pre>
|
|
<a name='FOOTNOTE.149'>
|
|
<pre><i><b>Footnote 149)</b> As specified in <a href='#6.7.2'>6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int, then it is
|
|
implementation-defined whether the bit-field is signed or unsigned. This includes an int type specifier produced by
|
|
the use of the typeof specifier (<a href='#6.7.2.5'>6.7.2.5</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p13'></a>
|
|
<pre>13 An implementation may allocate any addressable storage unit large enough to hold a bit-field. If
|
|
enough space remains, a bit-field that immediately follows another bit-field in a structure shall be
|
|
packed into adjacent bits of the same unit. If insufficient space remains, whether a bit-field that
|
|
does not fit is put into the next unit or overlaps adjacent units is implementation-defined. The
|
|
order of allocation of bit-fields within a unit (high-order to low-order or low-order to high-order) is
|
|
implementation-defined. The alignment of the addressable storage unit is unspecified.
|
|
</pre>
|
|
<a name='6.7.2.1p14'></a>
|
|
<pre>14 A bit-field declaration with no declarator, but only a colon and a width, indicates an unnamed
|
|
bit-field.<a href='#FOOTNOTE.150'><sup>[150]</sup></a> As a special case, a bit-field structure member with a width of 0 indicates that no
|
|
further bit-field is to be packed into the unit in which the previous bit-field, if any, was placed.
|
|
</pre>
|
|
<a name='FOOTNOTE.150'>
|
|
<pre><i><b>Footnote 150)</b> An unnamed bit-field structure member is useful for padding to conform to externally imposed layouts.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p15'></a>
|
|
<pre>15 An unnamed member whose type specifier is a structure specifier with no tag is called an anonymous
|
|
structure; an unnamed member whose type specifier is a union specifier with no tag is called an
|
|
anonymous union. The members of an anonymous structure or union are considered to be members
|
|
of the containing structure or union, keeping their structure or union layout. This applies recursively
|
|
if the containing structure or union is also anonymous.
|
|
</pre>
|
|
<a name='6.7.2.1p16'></a>
|
|
<pre>16 Each non-bit-field member of a structure or union object is aligned in an implementation-defined
|
|
manner appropriate to its type.
|
|
</pre>
|
|
<a name='6.7.2.1p17'></a>
|
|
<pre>17 Within a structure object, the non-bit-field members and the units in which bit-fields reside have
|
|
addresses that increase in the order in which they are declared. A pointer to a structure object,
|
|
suitably converted, points to its initial member (or if that member is a bit-field, then to the unit in
|
|
which it resides), and vice versa. There may be unnamed padding within a structure object, but not
|
|
at its beginning.
|
|
</pre>
|
|
<a name='6.7.2.1p18'></a>
|
|
<pre>18 The size of a union is sufficient to contain the largest of its members. The value of at most one of the
|
|
members can be stored in a union object at any time. A pointer to a union object, suitably converted,
|
|
points to each of its members (or if a member is a bit-field, then to the unit in which it resides),
|
|
and vice versa. The members of a union object overlap in such a way that pointers to them when
|
|
converted to pointers to character types point to the same byte. There may be unnamed padding at
|
|
the end of a union object, but not at its beginning.
|
|
</pre>
|
|
<a name='6.7.2.1p19'></a>
|
|
<pre>19 There may be unnamed padding at the end of a structure or union.
|
|
</pre>
|
|
<a name='6.7.2.1p20'></a>
|
|
<pre>20 As a special case, the last member of a structure with more than one named member may have an
|
|
incomplete array type; this is called a flexible array member. In most situations, the flexible array
|
|
member is ignored. In particular, the size of the structure is as if the flexible array member were
|
|
omitted except that it may have more trailing padding than the omission would imply. However,
|
|
when a . (or-> ) operator has a left operand that is (a pointer to) a structure with a flexible array
|
|
member and the right operand names that member, it behaves as if that member were replaced with
|
|
the longest array (with the same element type) that would not make the structure larger than the
|
|
object being accessed; the offset of the array shall remain that of the flexible array member, even if
|
|
this would differ from that of the replacement array. If this array would have no elements, it behaves
|
|
as if it had one element but the behavior is undefined if any attempt is made to access that element
|
|
or to generate a pointer one past it.
|
|
</pre>
|
|
<a name='6.7.2.1p21'></a>
|
|
<pre>21 EXAMPLE 1 The following declarations illustrate the behavior when an attribute is written on a tag declaration:
|
|
|
|
struct [[deprecated]] S; // valid, [[deprecated]] appertains to struct S
|
|
void f(struct S *s); // valid, the struct S type has the [[deprecated]]
|
|
// attribute
|
|
struct S { // valid, struct S inherits the [[deprecated]] attribute
|
|
int a; // from the previous declaration
|
|
};
|
|
void g(struct [[deprecated]] S s); // invalid
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.1p22'></a>
|
|
<pre>22 EXAMPLE 2 The following illustrates anonymous structures and unions:
|
|
|
|
struct v {
|
|
union { // anonymous union
|
|
struct { int i, j; }; // anonymous structure
|
|
struct { long k, l; } w;
|
|
};
|
|
int m;
|
|
} v1;
|
|
|
|
v1.i = 2; // valid
|
|
v1.k = 3; // invalid: inner structure is not anonymous
|
|
v1.w.k = 5; // valid
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.1p23'></a>
|
|
<pre>23 EXAMPLE 3 After the declaration:
|
|
|
|
struct s { int n; double d[]; };
|
|
|
|
|
|
the structure struct s has a flexible array member d. A typical way to use this is:
|
|
|
|
int m = /* some value */;
|
|
struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
|
|
|
|
|
|
and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if p had been
|
|
declared as:
|
|
|
|
struct { int n; double d[m]; } *p;
|
|
|
|
|
|
(there are circumstances in which this equivalence is broken; in particular, the offsets of member d might not be the same).
|
|
</pre>
|
|
<a name='6.7.2.1p24'></a>
|
|
<pre>24 Following the above declaration:
|
|
|
|
struct s t1 = { 0 }; // valid
|
|
struct s t2 = { 1, { 4.2 }}; // invalid
|
|
t1.n = 4; // valid
|
|
t1.d[0] = 4.2; // might be undefined behavior
|
|
The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not contain member d.
|
|
The assignment to t1.d[0] is probably undefined behavior, but it is possible that
|
|
|
|
sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)
|
|
|
|
in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming code.
|
|
</pre>
|
|
<a name='6.7.2.1p25'></a>
|
|
<pre>25 After the further declaration:
|
|
|
|
struct ss { int n; };
|
|
|
|
the expressions:
|
|
|
|
sizeof (struct s) >= sizeof (struct ss)
|
|
sizeof (struct s) >= offsetof(struct s, d)
|
|
|
|
are always equal to 1.
|
|
</pre>
|
|
<a name='6.7.2.1p26'></a>
|
|
<pre>26 If sizeof (double) is 8, then after the following code is executed:
|
|
|
|
struct s *s1;
|
|
struct s *s2;
|
|
s1 = malloc(sizeof (struct s) + 64);
|
|
s2 = malloc(sizeof (struct s) + 46);
|
|
|
|
and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most purposes, as if the
|
|
identifiers had been declared as:
|
|
|
|
struct { int n; double d[8]; } *s1;
|
|
struct { int n; double d[5]; } *s2;
|
|
|
|
</pre>
|
|
<a name='6.7.2.1p27'></a>
|
|
<pre>27 Following the further successful assignments:
|
|
|
|
s1 = malloc(sizeof (struct s) + 10);
|
|
s2 = malloc(sizeof (struct s) + 6);
|
|
|
|
they then behave as if the declarations were:
|
|
|
|
struct { int n; double d[1]; } *s1, *s2;
|
|
|
|
and:
|
|
|
|
double *dp;
|
|
dp = &(s1->d[0]); // valid
|
|
*dp = 42; // valid
|
|
dp = &(s2->d[0]); // valid
|
|
*dp = 42; // undefined behavior
|
|
|
|
</pre>
|
|
<a name='6.7.2.1p28'></a>
|
|
<pre>28 The assignment:
|
|
|
|
*s1 = *s2;
|
|
|
|
only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes of the structure, they
|
|
are set to an indeterminate representation, that may or may not coincide with a copy of the representation of the elements of
|
|
the source array.
|
|
</pre>
|
|
<a name='6.7.2.1p29'></a>
|
|
<pre>29 EXAMPLE 4 Because members of anonymous structures and unions are considered to be members of the containing
|
|
structure or union, struct s in the following example has more than one named member and thus the use of a flexible array
|
|
member is valid:
|
|
|
|
struct s {
|
|
struct { int i; };
|
|
int a[];
|
|
};
|
|
|
|
|
|
Forward references: declarators (<a href='#6.7.6'>6.7.6</a>), tags (<a href='#6.7.2.3'>6.7.2.3</a>).
|
|
</pre>
|
|
<a name='6.7.2.2'></a>
|
|
<hr>
|
|
<h3>6.7.2.2 [Enumeration specifiers]</h3>
|
|
<a name='6.7.2.2p1'></a>
|
|
<pre>1 Syntax
|
|
enum-specifier:
|
|
enum attribute-specifier-sequenceopt identifieropt enum-type-specifieropt
|
|
{ enumerator-list }
|
|
enum attribute-specifier-sequenceopt identifieropt enum-type-specifieropt
|
|
{ enumerator-list , }
|
|
enum identifier enum-type-specifieropt
|
|
enumerator-list:
|
|
enumerator
|
|
enumerator-list , enumerator
|
|
enumerator:
|
|
enumeration-constant attribute-specifier-sequenceopt
|
|
enumeration-constant attribute-specifier-sequenceopt = constant-expression
|
|
enum-type-specifier:
|
|
: specifier-qualifier-list
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.2p2'></a>
|
|
<pre>2 All enumerations have an underlying type. The underlying type can be explicitly specified using an
|
|
enum type specifier and is its fixed underlying type. If it is not explicitly specified, the underlying type
|
|
is the enumeration’s compatible type, which is either a signed or unsigned integer type (excluding
|
|
the bit-precise integer types), or char.
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.2p3'></a>
|
|
<pre>3 For an enumeration with a fixed underlying type, the integer constant expression defining the value
|
|
of the enumeration constant shall be representable in that fixed underlying type. The definition of an
|
|
enumeration constant without a defining constant expression shall neither overflow nor wraparound
|
|
the fixed underlying type by adding 1 to the previous enumeration constant.
|
|
</pre>
|
|
<a name='6.7.2.2p4'></a>
|
|
<pre>4 For an enumeration without a fixed underlying type, the expression that defines the value of an
|
|
enumeration constant shall be an integer constant expression. For all the integer constant expressions
|
|
which make up the values of the enumeration constants, there shall be a signed or unsigned integer
|
|
type (excluding the bit-precise integer types) capable of representing all of the values.
|
|
</pre>
|
|
<a name='6.7.2.2p5'></a>
|
|
<pre>5 If an enum type specifier is present, then the longest possible sequence of tokens that can be
|
|
interpreted as a specifier qualifier list is interpreted as part of the enum type specifier. It shall name
|
|
an integer type that is neither an enumeration nor a bit-precise integer type.
|
|
</pre>
|
|
<a name='6.7.2.2p6'></a>
|
|
<pre>6 An enum specifier of the form
|
|
enum identifier enum-type-specifier
|
|
|
|
|
|
may not appear except in a declaration of the form
|
|
enum identifier enum-type-specifier ;
|
|
|
|
|
|
unless it is immediately followed by an opening brace, an enumerator list (with an optional ending
|
|
comma), and a closing brace.
|
|
</pre>
|
|
<a name='6.7.2.2p7'></a>
|
|
<pre>7 If two enum specifiers that include an enum type specifier declare the same type, the underlying
|
|
types shall be compatible.
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.2p8'></a>
|
|
<pre>8 The optional attribute specifier sequence in the enum specifier appertains to the enumeration; the
|
|
attributes in that attribute specifier sequence are thereafter considered attributes of the enumeration
|
|
whenever it is named. The optional attribute specifier sequence in the enumerator appertains to that
|
|
enumerator.
|
|
</pre>
|
|
<a name='6.7.2.2p9'></a>
|
|
<pre>9 The identifiers in an enumerator list are declared as constants of the types specified below and may
|
|
appear wherever such are permitted<a href='#FOOTNOTE.151'><sup>[151]</sup></a> . An enumerator with = defines its enumeration constant as
|
|
the value of the constant expression. If the first enumerator has no =, the value of its enumeration
|
|
constant is 0. Each subsequent enumerator with no = defines its enumeration constant as the value
|
|
of the constant expression obtained by adding 1 to the value of the previous enumeration constant.
|
|
(The use of enumerators with = may produce enumeration constants with values that duplicate
|
|
other values in the same enumeration.) The enumerators of an enumeration are also known as its
|
|
members.
|
|
</pre>
|
|
<a name='FOOTNOTE.151'>
|
|
<pre><i><b>Footnote 151)</b> Thus, the identifiers of enumeration constants declared in the same scope are all required to be distinct from each other
|
|
and from other identifiers declared in ordinary declarators.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p10'></a>
|
|
<pre>10 The type for the members of an enumeration is called the enumeration member type.
|
|
</pre>
|
|
<a name='6.7.2.2p11'></a>
|
|
<pre>11 During the processing of each enumeration constant in the enumerator list, the type of the enumera-
|
|
tion constant shall be:
|
|
|
|
— the previously declared type, if it is a redeclaration of the same enumeration constant; or,
|
|
— the enumerated type, for an enumeration with fixed underlying type; or,
|
|
— int, if there are no previous enumeration constants in the enumerator list and no explicit =
|
|
with a defining integer constant expression; or,
|
|
— int, if given explicitly with = and the value of the integer constant expression is representable
|
|
by an int; or,
|
|
— the type of the integer constant expression, if given explicitly with = and if the value of the
|
|
integer constant expression is not representable by int; or,
|
|
— the type of the value from the previous enumeration constant with 1 added to it. If such
|
|
an integer constant expression would overflow or wraparound the value of the previous
|
|
enumeration constant from the addition of 1, the type takes on either:
|
|
— a suitably sized signed integer type (excluding the bit-precise signed integer types)
|
|
capable of representing the value of the previous enumeration constant plus 1; or,
|
|
— a suitably sized unsigned integer type (excluding the bit-precise unsigned integer types)
|
|
capable of representing the value of the previous enumeration constant plus 1.
|
|
A signed integer type is chosen if the previous enumeration constant being added is of signed
|
|
integer type. An unsigned integer type is chosen if the previous enumeration constant is of
|
|
unsigned integer type. If there is no suitably sized integer type described previously which can
|
|
represent the new value, then the enumeration has no type which is capable of representing
|
|
all of its values<a href='#FOOTNOTE.152'><sup>[152]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.152'>
|
|
<pre><i><b>Footnote 152)</b> Therefore, a constraint has been violated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p12'></a>
|
|
<pre>12 For all enumerations without a fixed underlying type, each enumerated type shall be compatible
|
|
with char, a signed integer type, or an unsigned integer type (excluding the bit-precise integer
|
|
types). The choice of type is implementation-defined<a href='#FOOTNOTE.153'><sup>[153]</sup></a> , but shall be capable of representing the
|
|
values of all the members of the enumeration<a href='#FOOTNOTE.154'><sup>[154]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.153'>
|
|
<pre><i><b>Footnote 153)</b> An implementation can delay the choice of which integer type until all enumeration constants have been seen.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.154'>
|
|
<pre><i><b>Footnote 154)</b> For further rules affecting compatibility and completeness of enumerated types see <a href='#6.2.7'>6.2.7</a> and <a href='#6.7.2.3'>6.7.2.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p13'></a>
|
|
<pre>13 Enumeration constants can be redefined in the same scope with the same value as part of a redecla-
|
|
ration of the same enumerated type.
|
|
</pre>
|
|
<a name='6.7.2.2p14'></a>
|
|
<pre>14 The enumeration member type for an enumerated type without fixed underlying type upon comple-
|
|
tion is:
|
|
|
|
— int if all the values of the enumeration are representable as an int; or,
|
|
— the enumerated type<a href='#FOOTNOTE.155'><sup>[155]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.155'>
|
|
<pre><i><b>Footnote 155)</b> The integer type selected during processing of the enumerator list (before completion) of the enumeration may not be the
|
|
same as the compatible implementation-defined integer type selected for the completed enumeration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p15'></a>
|
|
<pre>15 The enumeration member type for an enumerated type with fixed underlying type is the enumerated
|
|
type. The enumerated type is compatible with the underlying type of the enumeration. After possible
|
|
lvalue conversion a value of the enumerated type behaves the same as the value with the underlying
|
|
type, in particularly with all aspects of promotion, conversion, and arithmetic<a href='#FOOTNOTE.156'><sup>[156]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.156'>
|
|
<pre><i><b>Footnote 156)</b> This means in particular that if the compatible type is bool, values of the enumerated type behave in all aspects the
|
|
same as bool and the members only have values 0 and 1. If it is a signed integer type and the constant expression of an
|
|
enumeration constant overflows, a constraint for constant expressions (<a href='#6.6'>6.6</a>) is violated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p16'></a>
|
|
<pre>16 EXAMPLE The following fragment:
|
|
|
|
enum hue { chartreuse, burgundy, claret=20, winedark };
|
|
enum hue col, *cp;
|
|
col = claret;
|
|
cp = &col;
|
|
if (*cp != burgundy)
|
|
/* ... */
|
|
|
|
makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a pointer to an object
|
|
that has that type. The enumerated values are in the set {0, 1, 20, 21}.
|
|
</pre>
|
|
<a name='6.7.2.2p17'></a>
|
|
<pre>17 EXAMPLE Even if the value of an enumeration constant is generated by the implicit addition of 1, an enumeration with a
|
|
fixed underlying type does not exhibit typical overflow behavior:
|
|
|
|
#include <limits.h>
|
|
|
|
enum us : unsigned short {
|
|
us_max = USHRT_MAX,
|
|
us_violation, /* Constraint violation:
|
|
USHRT_MAX + 1 would wraparound. */
|
|
us_violation_2 = us_max + 1, /* Maybe constraint violation:
|
|
USHRT_MAX + 1 may be promoted to "int", and
|
|
result is too wide for the
|
|
underlying type. */
|
|
us_wrap_around_to_zero = (unsigned short)(USHRT_MAX + 1) /* Okay:
|
|
conversion done in constant expression
|
|
before conversion to underlying type:
|
|
unsigned semantics okay. */
|
|
};
|
|
|
|
enum ui : unsigned int {
|
|
ui_max = UINT_MAX,
|
|
ui_violation, /* Constraint violation:
|
|
UINT_MAX + 1 would wraparound. */
|
|
ui no violation = ui_max + 1, /* Okay: Arithmetic performed as typical
|
|
_ _
|
|
unsigned integer arithmetic: conversion
|
|
from a value that is already 0 to 0. */
|
|
ui_wrap_around_to_zero = (unsigned int)(UINT_MAX + 1) /* Okay: conversion
|
|
done in constant expression before conversion to
|
|
underlying type: unsigned semantics okay. */
|
|
};
|
|
|
|
int main () {
|
|
// Same as return 0;
|
|
return ui_wrap_around_to_zero
|
|
+ us_wrap_around_to_zero;
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.2.2p18'></a>
|
|
<pre>18 EXAMPLE The following fragment:
|
|
|
|
#include <limits.h>
|
|
|
|
enum E1: short;
|
|
enum E2: short;
|
|
enum E3; /* Constraint violation: E3 forward declaration. */
|
|
enum E4 : unsigned long long;
|
|
|
|
enum E1 : short { m11, m12 };
|
|
enum E1 x = m11;
|
|
|
|
enum E2 : long { m21, m22 }; /* Constraint violation: different underlying types
|
|
*/
|
|
|
|
enum E3 {
|
|
m31,
|
|
m32,
|
|
m33 = sizeof(enum E3) /* Constraint violation: E3 is not complete here. */
|
|
};
|
|
enum E3 : int; /* Constraint violation: E3 previously had no underlying type */
|
|
|
|
enum E4 : unsigned long long {
|
|
m40 = sizeof(enum E4),
|
|
m41 = ULLONG_MAX,
|
|
m42 /* Constraint violation: unrepresentable value (wraparound) */
|
|
};
|
|
|
|
enum E5 y; /* Constraint violation: incomplete type */
|
|
enum E6 : long int z; /* Constraint violation: enum-type-specifier
|
|
with identifier in declarator */
|
|
enum E7 : long int = 0; /* Syntax violation:
|
|
enum-type-specifier with initializer */
|
|
|
|
|
|
demonstrates many of the properties of multiple declarations of enumerations with underlying types. Particularly, enum E3
|
|
is declared and defined without an underlying type first, therefore a redeclaration with an underlying type second is a
|
|
violation. Because it not complete at that time within its enumerator list, sizeof(enum E3) is a constraint violation within
|
|
the enum E3 definition. enum E4 is complete as it is being defined, therefore sizeof(enum E4) is not a constraint violation.
|
|
</pre>
|
|
<a name='6.7.2.2p19'></a>
|
|
<pre>19 EXAMPLE The following fragment:
|
|
|
|
enum no_underlying {
|
|
a0
|
|
};
|
|
|
|
int main () {
|
|
int a = _Generic(a0,
|
|
int: 2,
|
|
unsigned char: 1,
|
|
default: 0
|
|
);
|
|
int b = _Generic((enum no_underlying)a0,
|
|
int: 2,
|
|
unsigned char: 1,
|
|
default: 0
|
|
);
|
|
return a + b;
|
|
}
|
|
|
|
|
|
demonstrates the implementation-defined nature of the underlying type of enumerations using generic selection (<a href='#6.5.1.1'>6.5.1.1</a>).
|
|
The value of a after its initialization is 2. The value of b after its initialization is implementation-defined: the enumeration
|
|
must be compatible with a type large enough to fit the values of its enumeration constants. Since the only value is 0 for a0, b
|
|
may hold any of 2, 1, or 0.
|
|
Now, consider a similar fragment, but using a fixed underlying type:
|
|
|
|
enum underlying : unsigned char {
|
|
b0
|
|
};
|
|
int main () {
|
|
int a = _Generic(b0,
|
|
int: 2,
|
|
unsigned char: 1,
|
|
default: 0
|
|
);
|
|
int b = _Generic((enum underlying)b0,
|
|
int: 2,
|
|
unsigned char: 1,
|
|
default: 0
|
|
);
|
|
return 0;
|
|
}
|
|
|
|
|
|
Here, we are guaranteed that a and b are both initialized to 1. This makes enumerations with a fixed underlying type more
|
|
portable.
|
|
</pre>
|
|
<a name='6.7.2.2p20'></a>
|
|
<pre>20 EXAMPLE Enumerations with a fixed underlying type must have their braces and the enumerator list specified as part of
|
|
their declaration if they are not a standalone declaration:
|
|
|
|
void f1 (enum a : long b); /* Constraint violation */
|
|
void f2 (enum c : long { x } d);
|
|
enum e : int f3(); /* Constraint violation */
|
|
|
|
typedef enum t u; /* Constraint violation: forward declaration of t. */
|
|
typedef enum v : short W; /* Constraint violation */
|
|
typedef enum q : short { s } R;
|
|
|
|
struct s1 {
|
|
int x;
|
|
enum e : int : 1; /* Constraint violation */
|
|
int y;
|
|
};
|
|
|
|
enum forward; /* Constraint violation */
|
|
extern enum forward fwd_val0; /* Constraint violation: incomplete type */
|
|
extern enum forward* fwd_ptr0; /* Constraint violation: enums cannot be
|
|
used like other incomplete types */
|
|
extern int* fwd_ptr0; /* Constraint violation: incompatible
|
|
with incomplete type. */
|
|
|
|
enum forward1 : int;
|
|
extern enum forward1 fwd_val1;
|
|
extern int fwd_val1;
|
|
extern enum forward1* fwd_ptr1;
|
|
extern int* fwd_ptr1;
|
|
|
|
int main () {
|
|
enum e : short;
|
|
enum e : short f = 0; /* Constraint violation */
|
|
enum g : short { y } h = y;
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.2p21'></a>
|
|
<pre>21 EXAMPLE Enumerations with a fixed underlying type are complete when the enum type specifier for that specific
|
|
enumeration is complete. The enumeration e in this snippet:
|
|
|
|
enum e : typeof ((enum e : short { A })0, (short)0);
|
|
|
|
|
|
enum e is considered complete by the first opening brace within the typeof in this snippet.
|
|
|
|
Forward references: generic selection (<a href='#6.5.1.1'>6.5.1.1</a>), tags (<a href='#6.7.2.3'>6.7.2.3</a>), declarations (<a href='#6.7'>6.7</a>), declarators (<a href='#6.7.6'>6.7.6</a>),
|
|
function declarators (<a href='#6.7.6.3'>6.7.6.3</a>), type names (<a href='#6.7.7'>6.7.7</a>).
|
|
</pre>
|
|
<a name='6.7.2.3'></a>
|
|
<hr>
|
|
<h3>6.7.2.3 [Tags]</h3>
|
|
<a name='6.7.2.3p1'></a>
|
|
<pre>1 Constraints
|
|
Where two declarations that use the same tag declare the same type, they shall both use the same
|
|
choice of struct, union, or enum. If two declarations of the same type have a member-declaration
|
|
or enumerator-list, one shall not be nested within the other and both declarations shall fulfill
|
|
all requirements of compatible types (<a href='#6.2.7'>6.2.7</a>) with the additional requirement that corresponding
|
|
members of structure or union types shall have the same (and not merely compatible) types.
|
|
</pre>
|
|
<a name='6.7.2.3p2'></a>
|
|
<pre>2 A type specifier of the form
|
|
enum identifier
|
|
without an enumerator list shall only appear after the type it specifies is complete.
|
|
</pre>
|
|
<a name='6.7.2.3p3'></a>
|
|
<pre>3 A type specifier of the form
|
|
struct-or-union attribute-specifier-sequenceopt identifier
|
|
shall not contain an attribute specifier sequence<a href='#FOOTNOTE.157'><sup>[157]</sup></a> .
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.157'>
|
|
<pre><i><b>Footnote 157)</b> As specified in <a href='#6.7.2.1'>6.7.2.1</a> above, the type specifier may be followed by a ; or a member declaration list.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p4'></a>
|
|
<pre>4 All declarations of structure, union, or enumerated types that have the same scope and use the same
|
|
tag declare the same type.
|
|
</pre>
|
|
<a name='6.7.2.3p5'></a>
|
|
<pre>5 Irrespective of whether there is a tag or what other declarations of the type are in the same translation
|
|
unit, a type (except enumerated types with a fixed underlying type) is incomplete from the beginning
|
|
of the specifier until immediately after the closing brace of the list defining the content for the first
|
|
time, and complete thereafter until the beginning of the next specifier that redeclares the same type
|
|
later in the same translation unit (if any) or otherwise until the end of the translation unit.
|
|
</pre>
|
|
<a name='6.7.2.3p6'></a>
|
|
<pre>6 Enumerated types with fixed underlying type (<a href='#6.7.2.2'>6.7.2.2</a>) are complete immediately after their first
|
|
associated enum type specifier ends.
|
|
</pre>
|
|
<a name='6.7.2.3p7'></a>
|
|
<pre>7 EXAMPLE 1 The following example shows allowed redeclarations of the same structure, union, or enumerated type in the
|
|
same scope:
|
|
|
|
struct foo { struct { int x; }; };
|
|
struct foo { struct { int x; }; };
|
|
union bar { int x; float y; };
|
|
union bar { float y; int x; };
|
|
typedef struct q { int x; } q_t;
|
|
typedef struct q { int x; } q_t;
|
|
void foo(void)
|
|
{
|
|
struct S { int x; };
|
|
struct T { struct S s; };
|
|
struct S { int x; };
|
|
struct T { struct S s; };
|
|
}
|
|
enum X { A = 1, B = 1 + 1 };
|
|
enum X { B = 2, A = 1 };
|
|
|
|
</pre>
|
|
<a name='6.7.2.3p8'></a>
|
|
<pre>8 EXAMPLE 2 The following example shows invalid redeclarations of the same structure, union, or enumerated type in the
|
|
same scope:
|
|
|
|
struct foo { int (*p)[3]; };
|
|
struct foo { int (*p)[]; }; // member has different type
|
|
|
|
union bar { int x; float y; };
|
|
union bar { int z; float y; }; // member has different name
|
|
|
|
typedef struct { int x; } q_t;
|
|
typedef struct { int x; } q_t; // not the same type
|
|
struct S { int x; };
|
|
|
|
void foo(void)
|
|
{
|
|
struct T { struct S s; };
|
|
struct S { int x; };
|
|
struct T { struct S s; }; // struct S not the same type
|
|
}
|
|
|
|
enum X { A = 1, B = 2 };
|
|
enum X { A = 1, B = 3 }; // different enumeration constant
|
|
|
|
enum R { C = 1 };
|
|
enum Q { C = 1 }; // conflicting enumeration constant
|
|
enum Q { C = C }; // ok!
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.3p9'></a>
|
|
<pre>9 Two declarations of structure, union, or enumerated types which are in different scopes or use
|
|
different tags declare distinct types. Each declaration of a structure, union, or enumerated type
|
|
which does not include a tag declares a distinct type.
|
|
</pre>
|
|
<a name='6.7.2.3p10'></a>
|
|
<pre>10 A type specifier of the form
|
|
struct-or-union attribute-specifier-sequenceopt identifieropt { member-declaration-list }
|
|
or
|
|
enum attribute-specifier-sequenceopt identifieropt { enumerator-list }
|
|
or
|
|
enum attribute-specifier-sequenceopt identifieropt { enumerator-list , }
|
|
declares a structure, union, or enumerated type. The list defines the structure content, union content,
|
|
or enumeration content. If an identifier is provided<a href='#FOOTNOTE.158'><sup>[158]</sup></a> , the type specifier also declares the identifier to
|
|
be the tag of that type. The optional attribute specifier sequence appertains to the structure, union,
|
|
or enumeration type being declared; the attributes in that attribute specifier sequence are thereafter
|
|
considered attributes of the structure, union, or enumeration type whenever it is named.
|
|
</pre>
|
|
<a name='FOOTNOTE.158'>
|
|
<pre><i><b>Footnote 158)</b> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration of which it is a part.
|
|
Of course, when the declaration is of a typedef name, subsequent declarations can make use of that typedef name to declare
|
|
objects having the specified structure, union, or enumerated type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p11'></a>
|
|
<pre>11 A declaration of the form
|
|
struct-or-union attribute-specifier-sequenceopt identifier ;
|
|
specifies a structure or union type and declares the identifier as a tag of that type<a href='#FOOTNOTE.159'><sup>[159]</sup></a> . The optional
|
|
attribute specifier sequence appertains to the structure or union type being declared; the attributes
|
|
in that attribute specifier sequence are thereafter considered attributes of the structure or union type
|
|
whenever it is named.
|
|
</pre>
|
|
<a name='FOOTNOTE.159'>
|
|
<pre><i><b>Footnote 159)</b> A similar construction with enum does not exist.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p12'></a>
|
|
<pre>12 If a type specifier of the form
|
|
struct-or-union attribute-specifier-sequenceopt identifier
|
|
occurs other than as part of one of the above forms, and no other declaration of the identifier as a
|
|
tag is visible, then it declares an incomplete structure or union type, and declares the identifier as
|
|
the tag of that type.<a href='#FOOTNOTE.159'><sup>[159]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.159'>
|
|
<pre><i><b>Footnote 159)</b> A similar construction with enum does not exist.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p13'></a>
|
|
<pre>13 If a type specifier of the form
|
|
struct-or-union attribute-specifier-sequenceopt identifier
|
|
or
|
|
enum identifier
|
|
occurs other than as part of one of the above forms, and a declaration of the identifier as a tag is
|
|
visible, then it specifies the same type as that other declaration, and does not redeclare the tag.
|
|
</pre>
|
|
<a name='6.7.2.3p14'></a>
|
|
<pre>14 EXAMPLE 3 This mechanism allows declaration of a self-referential structure.
|
|
|
|
struct tnode {
|
|
int count;
|
|
struct tnode *left, *right;
|
|
};
|
|
|
|
|
|
specifies a structure that contains an integer and two pointers to objects of the same type. Once this declaration has been
|
|
given, the declaration
|
|
|
|
struct tnode s, *sp;
|
|
|
|
|
|
declares s to be an object of the given type and sp to be a pointer to an object of the given type. With these declarations, the
|
|
expression sp->left refers to the left struct tnode pointer of the object to which sp points; the expression s.right->count
|
|
designates the count member of the right struct tnode pointed to from s.
|
|
</pre>
|
|
<a name='6.7.2.3p15'></a>
|
|
<pre>15 The following alternative formulation uses the typedef mechanism:
|
|
|
|
typedef struct tnode TNODE;
|
|
struct tnode {
|
|
int count;
|
|
TNODE *left, *right;
|
|
};
|
|
TNODE s, *sp;
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.3p16'></a>
|
|
<pre>16 EXAMPLE 4 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential structures, the
|
|
declarations
|
|
|
|
struct s1 { struct s2 *s2p; /* ... */ }; // D1
|
|
struct s2 { struct s1 *s1p; /* ... */ }; // D2
|
|
|
|
|
|
specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already declared as a tag in an
|
|
enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in D2. To eliminate this context sensitivity, the
|
|
declaration
|
|
|
|
struct s2;
|
|
|
|
|
|
can be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then completes the specification
|
|
of the new type.
|
|
|
|
Forward references: declarators (<a href='#6.7.6'>6.7.6</a>), type definitions (<a href='#6.7.8'>6.7.8</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.2.4'></a>
|
|
<hr>
|
|
<h3>6.7.2.4 [Atomic type specifiers]</h3>
|
|
<a name='6.7.2.4p1'></a>
|
|
<pre>1 Syntax
|
|
atomic-type-specifier:
|
|
_Atomic ( type-name )
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.4p2'></a>
|
|
<pre>2 Atomic type specifiers shall not be used if the implementation does not support atomic types (see
|
|
<a href='#6.10.9.3'>6.10.9.3</a>).
|
|
</pre>
|
|
<a name='6.7.2.4p3'></a>
|
|
<pre>3 The type name in an atomic type specifier shall not refer to an array type, a function type, an atomic
|
|
type, or a qualified type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.4p4'></a>
|
|
<pre>4 The properties associated with atomic types are meaningful only for expressions that are lvalues.
|
|
If the _Atomic keyword is immediately followed by a left parenthesis, it is interpreted as a type
|
|
specifier (with a type name), not as a type qualifier.
|
|
</pre>
|
|
<a name='6.7.2.5'></a>
|
|
<hr>
|
|
<h3>6.7.2.5 [Typeof specifiers]</h3>
|
|
<a name='6.7.2.5p1'></a>
|
|
<pre>1 Syntax
|
|
typeof-specifier:
|
|
typeof ( typeof-specifier-argument )
|
|
typeof_unqual ( typeof-specifier-argument )
|
|
typeof-specifier-argument:
|
|
expression
|
|
type-name
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p2'></a>
|
|
<pre>2 The typeof and typeof_unqual tokens are collectively called the typeof operators.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.5p3'></a>
|
|
<pre>3 The typeof operators shall not be applied to an expression that designates a bit-field member.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.5p4'></a>
|
|
<pre>4 The typeof specifier applies the typeof operators to an expression (<a href='#6.5'>6.5</a>) or a type name. If the typeof
|
|
operators are applied to an expression, they yield the type-name representing the type of their
|
|
operand<a href='#FOOTNOTE.160'><sup>[160]</sup></a> . Otherwise, they produce the type name with any nested typeof specifier evaluated<a href='#FOOTNOTE.161'><sup>[161]</sup></a> .
|
|
If the type of the operand is a variably modified type, the operand is evaluated; otherwise, the
|
|
operand is not evaluated.
|
|
</pre>
|
|
<a name='FOOTNOTE.160'>
|
|
<pre><i><b>Footnote 160)</b> When applied to a parameter declared to have array or function type, the typeof operators yield the adjusted (pointer)
|
|
type (see <a href='#6.9.1'>6.9.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.161'>
|
|
<pre><i><b>Footnote 161)</b> If the typeof specifier argument is itself a typeof specifier, the operand will be evaluated before evaluating the current
|
|
typeof operation. This happens recursively until a typeof specifier is no longer the operand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.5p5'></a>
|
|
<pre>5 All qualifiers (<a href='#6.7.3'>6.7.3</a>) on the type from the result of a typeof_unqual operation are removed, including
|
|
the _Atomic qualifier<a href='#FOOTNOTE.162'><sup>[162]</sup></a> . Otherwise, for typeof operations, all qualifiers are preserved.
|
|
</pre>
|
|
<a name='FOOTNOTE.162'>
|
|
<pre><i><b>Footnote 162)</b> _Atomic ( type-name ) , with parentheses, is considered an _Atomic -qualified type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.5p6'></a>
|
|
<pre>6 EXAMPLE 1 Type of an expression.
|
|
|
|
typeof(1+1) main () {
|
|
return 0;
|
|
}
|
|
|
|
|
|
is equivalent to this program:
|
|
|
|
int main () {
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p7'></a>
|
|
<pre>7 EXAMPLE 2 The following program:
|
|
|
|
const _Atomic int purr = 0;
|
|
const int meow = 1;
|
|
const char* const mew[] = {
|
|
"aardvark",
|
|
"bluejay",
|
|
"catte",
|
|
};
|
|
|
|
typeof_unqual(meow) main (int argc, char* argv[]) {
|
|
typeof_unqual(purr) plain_purr;
|
|
typeof( Atomic typeof(meow)) atomic_meow;
|
|
_
|
|
typeof(mew) mew_array;
|
|
typeof_unqual(mew) mew2_array;
|
|
return 0;
|
|
}
|
|
is equivalent to this program:
|
|
|
|
const _Atomic int purr = 0;
|
|
const int meow = 1;
|
|
const char* const mew[] = {
|
|
"aardvark",
|
|
"bluejay",
|
|
"catte",
|
|
};
|
|
|
|
int main (int argc, char* argv[]) {
|
|
int plain_purr;
|
|
const _Atomic int atomic_meow;
|
|
const char* const mew_array[3];
|
|
const char* mew2_array[3];
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p8'></a>
|
|
<pre>8 EXAMPLE 3 The equivalence between sizeof and typeof’s deduction of the type means this program has no constraint
|
|
violations:
|
|
|
|
int main (int argc, char* argv[]) {
|
|
static_assert(sizeof(typeof(’p’)) == sizeof(int));
|
|
static_assert(sizeof(typeof(’p’)) == sizeof(’p’));
|
|
static_assert(sizeof(typeof((char)’p’)) == sizeof(char));
|
|
static_assert(sizeof(typeof((char)’p’)) == sizeof((char)’p’));
|
|
static_assert(sizeof(typeof("meow")) == sizeof(char[5]));
|
|
static_assert(sizeof(typeof("meow")) == sizeof("meow"));
|
|
static_assert(sizeof(typeof(argc)) == sizeof(int));
|
|
static_assert(sizeof(typeof(argc)) == sizeof(argc));
|
|
static_assert(sizeof(typeof(argv)) == sizeof(char**));
|
|
static_assert(sizeof(typeof(argv)) == sizeof(argv));
|
|
|
|
static_assert(sizeof(typeof_unqual(’p’)) == sizeof(int));
|
|
static_assert(sizeof(typeof_unqual(’p’)) == sizeof(’p’));
|
|
static_assert(sizeof(typeof_unqual((char)’p’)) == sizeof(char));
|
|
static_assert(sizeof(typeof_unqual((char)’p’)) == sizeof((char)’p’));
|
|
static_assert(sizeof(typeof_unqual("meow")) == sizeof(char[5]));
|
|
static_assert(sizeof(typeof_unqual("meow")) == sizeof("meow"));
|
|
static_assert(sizeof(typeof_unqual(argc)) == sizeof(int));
|
|
static_assert(sizeof(typeof_unqual(argc)) == sizeof(argc));
|
|
static_assert(sizeof(typeof_unqual(argv)) == sizeof(char**));
|
|
static_assert(sizeof(typeof_unqual(argv)) == sizeof(argv));
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p9'></a>
|
|
<pre>9 EXAMPLE 4 The following program with nested typeof(...):
|
|
|
|
int main (int argc, char*[]) {
|
|
float val = <a href='#6.'>6.</a>0f;
|
|
return (typeof(typeof_unqual(typeof(argc))))val;
|
|
}
|
|
|
|
|
|
is equivalent to this program:
|
|
|
|
int main (int argc, char*[]) {
|
|
float val = <a href='#6.'>6.</a>0f;
|
|
return (int)val;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p10'></a>
|
|
<pre>10 EXAMPLE 5 Variable length arrays with typeof operators performs the operation at execution time rather than translation
|
|
time.
|
|
#include <stddef.h>
|
|
|
|
size_t vla_size (int n) {
|
|
typedef char vla_type[n + 3];
|
|
vla_type b; // variable length array
|
|
return sizeof(
|
|
typeof_unqual(b)
|
|
); // execution-time sizeof, translation-time typeof operation
|
|
}
|
|
|
|
int main () {
|
|
return (int)vla_size(10); // vla_size returns 13
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p11'></a>
|
|
<pre>11 EXAMPLE 6 Nested typeof operators, arrays, and pointers do not perform array to pointer decay.
|
|
|
|
int main () {
|
|
typeof(typeof(const char*)[4]) y = {
|
|
"a",
|
|
"b",
|
|
"c",
|
|
"d"
|
|
}; // 4-element array of "pointer to const char"
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.2.5p12'></a>
|
|
<pre>12 EXAMPLE 7 Function, pointer, and array types may be substituted with typeof operations.
|
|
|
|
void f(int);
|
|
|
|
typeof(f(5)) g(double x) { // g has type "void(double)"
|
|
printf("value %g\n", x);
|
|
}
|
|
|
|
typeof(g)* h; // h has type "void(*)(double)"
|
|
typeof(true ? g : NULL) k; // k has type "void(*)(double)"
|
|
|
|
void j(double A[5], typeof(A)* B); // j has type "void(double*, double**)"
|
|
|
|
extern typeof(double[]) D; // D has an incomplete type
|
|
typeof(D) C = { 0.7, 99 }; // C has type "double[2]"
|
|
|
|
typeof(D) D = { 5, 8.9, 0.1, 99 }; // D is now completed to "double[4]"
|
|
typeof(D) E; // E has type "double[4]" from D’s completed type
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.3'></a>
|
|
<hr>
|
|
<h3>6.7.3 [Type qualifiers]</h3>
|
|
<a name='6.7.3p1'></a>
|
|
<pre>1 Syntax
|
|
type-qualifier:
|
|
const
|
|
restrict
|
|
volatile
|
|
_Atomic
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.3p2'></a>
|
|
<pre>2 Types other than pointer types whose referenced type is an object type and (possibly multi-
|
|
dimensional) array types with such pointer types as element type shall not be restrict-qualified.
|
|
</pre>
|
|
<a name='6.7.3p3'></a>
|
|
<pre>3 The _Atomic qualifier shall not be used if the implementation does not support atomic types
|
|
(see <a href='#6.10.9.3'>6.10.9.3</a>).
|
|
</pre>
|
|
<a name='6.7.3p4'></a>
|
|
<pre>4 The type modified by the _Atomic qualifier shall not be an array type or a function type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.3p5'></a>
|
|
<pre>5 The properties associated with qualified types are meaningful only for expressions that are lval-
|
|
ues.<a href='#FOOTNOTE.163'><sup>[163]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.163'>
|
|
<pre><i><b>Footnote 163)</b> The implementation can place a const object that is not volatile in a read-only region of storage. Moreover, the
|
|
implementation need not allocate storage for such an object if its address is never used.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p6'></a>
|
|
<pre>6 If the same qualifier appears more than once in the same specifier-qualifier list or as declaration
|
|
specifiers, either directly, via one or more typeof specifiers, or via one or more typedefs, the behavior
|
|
is the same as if it appeared only once. If other qualifiers appear along with the _Atomic qualifier
|
|
the resulting type is the so-qualified atomic type.
|
|
</pre>
|
|
<a name='6.7.3p7'></a>
|
|
<pre>7 If an attempt is made to modify an object defined with a const-qualified type through use of an
|
|
lvalue with non-const-qualified type, the behavior is undefined. If an attempt is made to refer to an
|
|
object defined with a volatile-qualified type through use of an lvalue with non-volatile-qualified
|
|
type, the behavior is undefined<a href='#FOOTNOTE.164'><sup>[164]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.164'>
|
|
<pre><i><b>Footnote 164)</b> This applies to those objects that behave as if they were defined with qualified types, even if they are never actually
|
|
defined as objects in the program (such as an object at a memory-mapped input/output address).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p8'></a>
|
|
<pre>8 An object that has volatile-qualified type may be modified in ways unknown to the implementation
|
|
or have other unknown side effects. Therefore any expression referring to such an object shall be
|
|
evaluated strictly according to the rules of the abstract machine, as described in <a href='#5.1.2.3'>5.1.2.3</a>. Furthermore,
|
|
at every sequence point the value last stored in the object shall agree with that prescribed by the
|
|
abstract machine, except as modified by the unknown factors mentioned previously.<a href='#FOOTNOTE.165'><sup>[165]</sup></a> What
|
|
constitutes an access to an object that has volatile-qualified type is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.165'>
|
|
<pre><i><b>Footnote 165)</b> A volatile declaration can be used to describe an object corresponding to a memory-mapped input/output port or an
|
|
object accessed by an asynchronously interrupting function. Actions on objects so declared are not allowed to be "optimized
|
|
out" by an implementation or reordered except as permitted by the rules for evaluating expressions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p9'></a>
|
|
<pre>9 An object that is accessed through a restrict-qualified pointer has a special association with that
|
|
pointer. This association, defined in <a href='#6.7.3.1'>6.7.3.1</a> below, requires that all accesses to that object use, directly
|
|
or indirectly, the value of that particular pointer.<a href='#FOOTNOTE.166'><sup>[166]</sup></a> The intended use of the restrict qualifier (like
|
|
the register storage class) is to promote optimization, and deleting all instances of the qualifier
|
|
from all preprocessing translation units composing a conforming program does not change its
|
|
meaning (i.e., observable behavior).
|
|
</pre>
|
|
<a name='FOOTNOTE.166'>
|
|
<pre><i><b>Footnote 166)</b> For example, a statement that assigns a value returned by malloc to a single pointer establishes this association between
|
|
the allocated object and the pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p10'></a>
|
|
<pre>10 If the specification of an array type includes any type qualifiers, both the array and the element type
|
|
is so-qualified. If the specification of a function type includes any type qualifiers, the behavior is
|
|
undefined.<a href='#FOOTNOTE.167'><sup>[167]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.167'>
|
|
<pre><i><b>Footnote 167)</b> This can occur through the use of typedef s. Note that this rule does not apply to the _Atomic qualifier, and that
|
|
qualifiers do not have any direct effect on the array type itself, but affect conversion rules for pointer types that reference an
|
|
array type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p11'></a>
|
|
<pre>11 For two qualified types to be compatible, both shall have the identically qualified version of a
|
|
compatible type; the order of type qualifiers within a list of specifiers or qualifiers does not affect the
|
|
specified type.
|
|
</pre>
|
|
<a name='6.7.3p12'></a>
|
|
<pre>12 EXAMPLE 1 An object declared
|
|
|
|
extern const volatile int real_time_clock;
|
|
|
|
|
|
might be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
|
|
</pre>
|
|
<a name='6.7.3p13'></a>
|
|
<pre>13 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers modify an aggregate
|
|
type:
|
|
|
|
const struct s { int mem; } cs = { 1 };
|
|
struct s ncs; // the object ncs is modifiable
|
|
typedef int A[2][3];
|
|
const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
|
|
int *pi;
|
|
const int *pci;
|
|
|
|
ncs = cs; // valid
|
|
cs = ncs; // violates modifiable lvalue constraint for =
|
|
pi = &ncs.mem; // valid
|
|
pi = &cs.mem; // violates type constraints for =
|
|
pci = &cs.mem; // valid
|
|
pi = a[0]; // invalid: a[0] has type "const int *"
|
|
|
|
</pre>
|
|
<a name='6.7.3p14'></a>
|
|
<pre>14 EXAMPLE 3 The declaration
|
|
|
|
_Atomic volatile int *p;
|
|
|
|
|
|
specifies that p has the type "pointer to volatile atomic int", a pointer to a volatile-qualified atomic type.
|
|
</pre>
|
|
<a name='6.7.3.1'></a>
|
|
<hr>
|
|
<h3>6.7.3.1 [Formal definition of restrict]</h3>
|
|
<a name='6.7.3.1p1'></a>
|
|
<pre>1 Let D be a declaration of an ordinary identifier that provides a means of designating an object P as a
|
|
restrict-qualified pointer to type T.
|
|
</pre>
|
|
<a name='6.7.3.1p2'></a>
|
|
<pre>2 If D appears inside a block and does not have storage class extern, let B denote the block. If D
|
|
appears in the list of parameter declarations of a function definition, let B denote the associated block.
|
|
Otherwise, let B denote the block of main (or the block of whatever function is called at program
|
|
startup in a freestanding environment).
|
|
</pre>
|
|
<a name='6.7.3.1p3'></a>
|
|
<pre>3 In what follows, a pointer expression E is said to be based on object P if (at some sequence point in
|
|
the execution of B prior to the evaluation of E) modifying P to point to a copy of the array object into
|
|
which it formerly pointed would change the value of E.<a href='#FOOTNOTE.168'><sup>[168]</sup></a> Note that "based" is defined only for
|
|
expressions with pointer types.
|
|
</pre>
|
|
<a name='FOOTNOTE.168'>
|
|
<pre><i><b>Footnote 168)</b> In other words, E depends on the value of P itself rather than on the value of an object referenced indirectly through P.
|
|
For example, if identifier p has type (int **restrict) , then the pointer expressions p and p+1 are based on the restricted
|
|
pointer object designated by p, but the pointer expressions *p and p[1] are not.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3.1p4'></a>
|
|
<pre>4 During each execution of B, let L be any lvalue that has &L based on P. If L is used to access the
|
|
value of the object X that it designates, and X is also modified (by any means), then the following
|
|
requirements apply: T shall not be const-qualified. Every other lvalue used to access the value of
|
|
X shall also have its address based on P. Every access that modifies X shall be considered also to
|
|
modify P, for the purposes of this subclause. If P is assigned the value of a pointer expression E that
|
|
is based on another restricted pointer object P2, associated with block B2, then either the execution
|
|
of B2 shall begin before the execution of B, or the execution of B2 shall end prior to the assignment.
|
|
If these requirements are not met, then the behavior is undefined.
|
|
</pre>
|
|
<a name='6.7.3.1p5'></a>
|
|
<pre>5 Here an execution of B means that portion of the execution of the program that would correspond to
|
|
the lifetime of an object with scalar type and automatic storage duration associated with B.
|
|
</pre>
|
|
<a name='6.7.3.1p6'></a>
|
|
<pre>6 A translator is free to ignore any or all aliasing implications of uses of restrict.
|
|
</pre>
|
|
<a name='6.7.3.1p7'></a>
|
|
<pre>7 EXAMPLE 1 The file scope declarations
|
|
|
|
int * restrict a;
|
|
int * restrict b;
|
|
extern int c[];
|
|
|
|
assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the program, then it is never
|
|
accessed using either of the other two.
|
|
</pre>
|
|
<a name='6.7.3.1p8'></a>
|
|
<pre>8 EXAMPLE 2 The function parameter declarations in the following example
|
|
|
|
void f(int n, int * restrict p, int * restrict q)
|
|
{
|
|
while (n-- > 0)
|
|
*p++ = *q++;
|
|
}
|
|
|
|
assert that, during each execution of the function, if an object is accessed through one of the pointer parameters, then it is not
|
|
also accessed through the other. The translator can make this no-aliasing inference based on the parameter declarations alone,
|
|
without analyzing the function body.
|
|
</pre>
|
|
<a name='6.7.3.1p9'></a>
|
|
<pre>9 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence analysis of function f
|
|
without examining any of the calls of f in the program. The cost is that the programmer has to examine all of those calls to
|
|
ensure that none give undefined behavior. For example, the second call of f in g has undefined behavior because each of
|
|
d[1] through d[49] is accessed through both p and q.
|
|
|
|
void g(void)
|
|
{
|
|
extern int d[100];
|
|
f(50, d + 50, d); // valid
|
|
f(50, d + 1, d); // undefined behavior
|
|
}
|
|
</pre>
|
|
<a name='6.7.3.1p10'></a>
|
|
<pre>10 EXAMPLE 3 The function parameter declarations
|
|
|
|
void h(int n, int * restrict p, int * restrict q, int * restrict r)
|
|
{
|
|
int i;
|
|
for (i = 0; i < n; i++)
|
|
p[i] = q[i] + r[i];
|
|
}
|
|
|
|
illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b are disjoint arrays,
|
|
a call of the form h(100, a, b, b) has defined behavior, because array b is not modified within function h.
|
|
</pre>
|
|
<a name='6.7.3.1p11'></a>
|
|
<pre>11 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a function call and
|
|
an equivalent nested block. With one exception, only "outer-to-inner" assignments between restricted pointers declared in
|
|
nested blocks have defined behavior.
|
|
|
|
{
|
|
int * restrict p1;
|
|
int * restrict q1;
|
|
p1 = q1; // undefined behavior
|
|
{
|
|
int * restrict p2 = p1; // valid
|
|
int * restrict q2 = q1; // valid
|
|
p1 = q2; // undefined behavior
|
|
p2 = q2; // undefined behavior
|
|
}
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.3.1p12'></a>
|
|
<pre>12 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more precisely, the
|
|
ordinary identifier used to designate it) is declared when that block finishes execution. For example, this permits new_vector
|
|
to return a vector.
|
|
|
|
typedef struct { int n; float * restrict v; } vector;
|
|
vector new_vector(int n)
|
|
{
|
|
vector t;
|
|
t.n = n;
|
|
t.v = malloc(n * sizeof (float));
|
|
return t;
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.3.1p13'></a>
|
|
<pre>13 EXAMPLE 5 Suppose that a programmer knows that references of the form p[i] and q[j] are never aliases in the body of a
|
|
function:
|
|
|
|
void f(int n, int *p, int *q) { /* ... */ }
|
|
|
|
There are several ways that this information could be conveyed to a translator using the restrict qualifier. Example 2 shows
|
|
the most effective way, qualifying all pointer parameters, and can be used provided that neither p nor q becomes based on
|
|
the other in the function body. A potentially effective alternative is:
|
|
|
|
void f(int n, int * restrict p, int * const q) { /* ... */ }
|
|
|
|
Again it is possible for a translator to make the no-aliasing inference based on the parameter declarations alone, though now
|
|
it must use subtler reasoning: that the const-qualification of q precludes it becoming based on p. There is also a requirement
|
|
that q is not modified, so this alternative cannot be used for the function in Example 2, as written.
|
|
</pre>
|
|
<a name='6.7.3.1p14'></a>
|
|
<pre>14 EXAMPLE 6 Another potentially effective alternative is:
|
|
|
|
void f(int n, int *p, int const * restrict q) { /* ... */ }
|
|
|
|
Again it is possible for a translator to make the no-aliasing inference based on the parameter declarations alone, though
|
|
now it must use even subtler reasoning: that this combination of restrict and const means that objects referenced using q
|
|
cannot be modified, and so no modified object can be referenced using both p and q.
|
|
</pre>
|
|
<a name='6.7.3.1p15'></a>
|
|
<pre>15 EXAMPLE 7 The least effective alternative is:
|
|
|
|
void f(int n, int * restrict p, int *q) { /* ... */ }
|
|
|
|
Here the translator can make the no-aliasing inference only by analyzing the body of the function and proving that q cannot
|
|
become based on p. Some translator designs may choose to exclude this analysis, given availability of the more effective
|
|
alternatives above. Such a translator is required to assume that aliases are present because assuming that aliases are not
|
|
present may result in an incorrect translation. Also, a translator that attempts the analysis may not succeed in all cases and
|
|
thus need to conservatively assume that aliases are present.
|
|
|
|
</pre>
|
|
<a name='6.7.4'></a>
|
|
<hr>
|
|
<h3>6.7.4 [Function specifiers]</h3>
|
|
<a name='6.7.4p1'></a>
|
|
<pre>1 Syntax
|
|
function-specifier:
|
|
inline
|
|
_Noreturn
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.4p2'></a>
|
|
<pre>2 Function specifiers shall be used only in the declaration of an identifier for a function.
|
|
</pre>
|
|
<a name='6.7.4p3'></a>
|
|
<pre>3 An inline definition of a function with external linkage shall not contain a definition of a modifiable
|
|
object with static or thread storage duration, and shall not contain a reference to an identifier with
|
|
internal linkage.
|
|
</pre>
|
|
<a name='6.7.4p4'></a>
|
|
<pre>4 In a hosted environment, no function specifier(s) shall appear in a declaration of main.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.4p5'></a>
|
|
<pre>5 A function specifier may appear more than once; the behavior is the same as if it appeared only
|
|
once.
|
|
</pre>
|
|
<a name='6.7.4p6'></a>
|
|
<pre>6 A function declared with an inline function specifier is an inline function. Making a function an
|
|
inline function suggests that calls to the function be as fast as possible.<a href='#FOOTNOTE.169'><sup>[169]</sup></a> The extent to which such
|
|
suggestions are effective is implementation-defined.<a href='#FOOTNOTE.170'><sup>[170]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.169'>
|
|
<pre><i><b>Footnote 169)</b> By using, for example, an alternative to the usual function call mechanism, such as "inline substitution". Inline
|
|
substitution is not textual substitution, nor does it create a new function. Therefore, for example, the expansion of a macro
|
|
used within the body of the function uses the definition it had at the point the function body appears, and not where the
|
|
function is called; and identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a single
|
|
address, regardless of the number of inline definitions that occur in addition to the external definition.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.170'>
|
|
<pre><i><b>Footnote 170)</b> For example, an implementation might never perform inline substitution, or might only perform inline substitutions to
|
|
calls in the scope of an inline declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.4p7'></a>
|
|
<pre>7 Any function with internal linkage can be an inline function. For a function with external linkage,
|
|
the following restrictions apply: If a function is declared with an inline function specifier, then it
|
|
shall also be defined in the same translation unit. If all of the file scope declarations for a function in
|
|
a translation unit include the inline function specifier without extern, then the definition in that
|
|
translation unit is an inline definition. An inline definition does not provide an external definition
|
|
for the function, and does not forbid an external definition in another translation unit. An inline
|
|
definition provides an alternative to an external definition, which a translator may use to implement
|
|
any call to the function in the same translation unit. It is unspecified whether a call to the function
|
|
uses the inline definition or the external definition.<a href='#FOOTNOTE.171'><sup>[171]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.171'>
|
|
<pre><i><b>Footnote 171)</b> Since an inline definition is distinct from the corresponding external definition and from any other corresponding inline
|
|
definitions in other translation units, all corresponding objects with static storage duration are also distinct in each of the
|
|
definitions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.4p8'></a>
|
|
<pre>8 A function declared with a _Noreturn function specifier shall not return to its caller. The _Noreturn
|
|
function specifier is an obsolescent feature (<a href='#6.7.12.6'>6.7.12.6</a>).
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='6.7.4p9'></a>
|
|
<pre>9 The implementation should produce a diagnostic message for a function declared with a _Noreturn
|
|
function specifier that appears to be capable of returning to its caller.
|
|
</pre>
|
|
<a name='6.7.4p10'></a>
|
|
<pre>10 EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external definition, or a
|
|
definition available for use only within the translation unit. A file scope declaration with extern creates an external definition.
|
|
The following example shows an entire translation unit.
|
|
inline double fahr(double t)
|
|
{
|
|
return (9.0 * t) / 5.0 + 32.0;
|
|
}
|
|
|
|
inline double cels(double t)
|
|
{
|
|
return (5.0 * (t - 32.0)) / 9.0;
|
|
}
|
|
|
|
extern double fahr(double); // creates an external definition
|
|
|
|
double convert(int is_fahr, double temp)
|
|
{
|
|
/* A translator may perform inline substitutions */
|
|
return is_fahr ? cels(temp): fahr(temp);
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.4p11'></a>
|
|
<pre>11 Note that the definition of fahr is an external definition because fahr is also declared with extern, but the definition of cels
|
|
is an inline definition. Because cels has external linkage and is referenced, an external definition has to appear in another
|
|
translation unit (see <a href='#6.9'>6.9</a>); the inline definition and the external definition are distinct and either can be used for the call.
|
|
|
|
Forward references: function definitions (<a href='#6.9.1'>6.9.1</a>).
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.5'></a>
|
|
<hr>
|
|
<h3>6.7.5 [Alignment specifier]</h3>
|
|
<a name='6.7.5p1'></a>
|
|
<pre>1 Syntax
|
|
alignment-specifier:
|
|
alignas ( type-name )
|
|
alignas ( constant-expression )
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.5p2'></a>
|
|
<pre>2 An alignment specifier shall appear only in the declaration specifiers of a declaration, or in the
|
|
specifier-qualifier list of a member declaration, or in the type name of a compound literal. An
|
|
alignment specifier shall not be used in conjunction with either of the storage-class specifiers
|
|
typedef or register, nor in a declaration of a function or bit-field.
|
|
</pre>
|
|
<a name='6.7.5p3'></a>
|
|
<pre>3 The constant expression shall be an integer constant expression. It shall evaluate to a valid funda-
|
|
mental alignment, or to a valid extended alignment supported by the implementation for an object
|
|
of the storage duration (if any) being declared, or to zero.
|
|
</pre>
|
|
<a name='6.7.5p4'></a>
|
|
<pre>4 An object shall not be declared with an over-aligned type with an extended alignment requirement
|
|
not supported by the implementation for an object of that storage duration.
|
|
</pre>
|
|
<a name='6.7.5p5'></a>
|
|
<pre>5 The combined effect of all alignment specifiers in a declaration shall not specify an alignment that is
|
|
less strict than the alignment that would otherwise be required for the type of the object or member
|
|
being declared.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.5p6'></a>
|
|
<pre>6 The first form is equivalent to alignas(alignof( type-name)).
|
|
</pre>
|
|
<a name='6.7.5p7'></a>
|
|
<pre>7 The alignment requirement of the declared object or member is taken to be the specified alignment.
|
|
An alignment specification of zero has no effect.<a href='#FOOTNOTE.172'><sup>[172]</sup></a> When multiple alignment specifiers occur in a
|
|
declaration, the effective alignment requirement is the strictest specified alignment.
|
|
</pre>
|
|
<a name='FOOTNOTE.172'>
|
|
<pre><i><b>Footnote 172)</b> An alignment specification of zero also does not affect other alignment specifications in the same declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.5p8'></a>
|
|
<pre>8 If the definition of an object has an alignment specifier, any other declaration of that object shall
|
|
either specify equivalent alignment or have no alignment specifier. If the definition of an object does
|
|
not have an alignment specifier, any other declaration of that object shall also have no alignment
|
|
specifier. If declarations of an object in different translation units have different alignment specifiers,
|
|
the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='6.7.6'></a>
|
|
<hr>
|
|
<h3>6.7.6 [Declarators]</h3>
|
|
<a name='6.7.6p1'></a>
|
|
<pre>1 Syntax
|
|
declarator:
|
|
pointeropt direct-declarator
|
|
|
|
direct-declarator:
|
|
identifier attribute-specifier-sequenceopt
|
|
( declarator )
|
|
array-declarator attribute-specifier-sequenceopt
|
|
function-declarator attribute-specifier-sequenceopt
|
|
|
|
array-declarator:
|
|
direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
|
|
direct-declarator [ static type-qualifier-listopt assignment-expression ]
|
|
direct-declarator [ type-qualifier-list static assignment-expression ]
|
|
direct-declarator [ type-qualifier-listopt * ]
|
|
|
|
function-declarator:
|
|
direct-declarator ( parameter-type-listopt )
|
|
|
|
pointer:
|
|
* attribute-specifier-sequenceopt type-qualifier-listopt
|
|
* attribute-specifier-sequenceopt type-qualifier-listopt pointer
|
|
type-qualifier-list:
|
|
type-qualifier
|
|
type-qualifier-list type-qualifier
|
|
parameter-type-list:
|
|
parameter-list
|
|
parameter-list , ...
|
|
...
|
|
parameter-list:
|
|
parameter-declaration
|
|
parameter-list , parameter-declaration
|
|
parameter-declaration:
|
|
attribute-specifier-sequenceopt declaration-specifiers declarator
|
|
attribute-specifier-sequenceopt declaration-specifiers abstract-declaratoropt
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.6p2'></a>
|
|
<pre>2 Each declarator declares one identifier, and asserts that when an operand of the same form as
|
|
the declarator appears in an expression, it designates a function or object with the scope, storage
|
|
duration, and type indicated by the declaration specifiers.
|
|
</pre>
|
|
<a name='6.7.6p3'></a>
|
|
<pre>3 A full declarator is a declarator that is not part of another declarator. If, in the nested sequence of
|
|
declarators in a full declarator, there is a declarator specifying a variable length array type, the type
|
|
specified by the full declarator is said to be variably modified. Furthermore, any type derived by
|
|
declarator type derivation from a variably modified type is itself variably modified.
|
|
</pre>
|
|
<a name='6.7.6p4'></a>
|
|
<pre>4 In the following subclauses, consider a declaration
|
|
T D1
|
|
where T contains the declaration specifiers that specify a type T (such as int) and D1 is a declarator
|
|
that contains an identifier ident. The type specified for the identifier ident in the various forms of
|
|
declarator is described inductively using this notation.
|
|
</pre>
|
|
<a name='6.7.6p5'></a>
|
|
<pre>5 If, in the declaration "T D1", D1 has the form
|
|
identifier attribute-specifier-sequenceopt
|
|
then the type specified for ident is T and the optional attribute specifier sequence appertains to the
|
|
entity that is declared.
|
|
</pre>
|
|
<a name='6.7.6p6'></a>
|
|
<pre>6 If, in the declaration "T D1", D1 has the form
|
|
(D )
|
|
then ident has the type specified by the declaration "T D". Thus, a declarator in parentheses is
|
|
identical to the unparenthesized declarator, but the binding of complicated declarators may be
|
|
altered by parentheses.
|
|
|
|
Implementation limits
|
|
</pre>
|
|
<a name='6.7.6p7'></a>
|
|
<pre>7 As discussed in <a href='#5.2.4.1'>5.2.4.1</a>, an implementation may limit the number of pointer, array, and function
|
|
declarators that modify an arithmetic, structure, union, or void type, either directly or via one or
|
|
more typedef s.
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>), type definitions (<a href='#6.7.8'>6.7.8</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.6.1'></a>
|
|
<hr>
|
|
<h3>6.7.6.1 [Pointer declarators]</h3>
|
|
<a name='6.7.6.1p1'></a>
|
|
<pre>1 Semantics
|
|
If, in the declaration "T D1", D1 has the form
|
|
* attribute-specifier-sequenceopt type-qualifier-listopt D
|
|
and the type specified for ident in the declaration "T D" is "derived-declarator-type-list T", then the
|
|
type specified for ident is "derived-declarator-type-list type-qualifier-list pointer to T". For each type
|
|
qualifier in the list, ident is a so-qualified pointer. The optional attribute specifier sequence appertains
|
|
to the pointer and not the object pointed to.
|
|
</pre>
|
|
<a name='6.7.6.1p2'></a>
|
|
<pre>2 For two pointer types to be compatible, both shall be identically qualified and both shall be pointers
|
|
to compatible types.
|
|
</pre>
|
|
<a name='6.7.6.1p3'></a>
|
|
<pre>3 EXAMPLE The following pair of declarations demonstrates the difference between a "variable pointer to a constant value"
|
|
and a "constant pointer to a variable value".
|
|
|
|
const int *ptr_to_constant;
|
|
int *const constant_ptr;
|
|
|
|
|
|
The contents of any object pointed to by ptr_to_constant cannot be modified through that pointer, but ptr_to_constant
|
|
itself can be changed to point to another object. Similarly, the contents of the int pointed to by constant_ptr can be
|
|
modified, but constant_ptr itself always points to the same location.
|
|
4 The declaration of the constant pointer constant_ptr can be clarified by including a definition for the type "pointer to int".
|
|
|
|
typedef int *int_ptr;
|
|
const int_ptr constant_ptr;
|
|
|
|
|
|
declares constant_ptr as an object that has type "const-qualified pointer to int".
|
|
|
|
</pre>
|
|
<a name='6.7.6.2'></a>
|
|
<hr>
|
|
<h3>6.7.6.2 [Array declarators]</h3>
|
|
<a name='6.7.6.2p1'></a>
|
|
<pre>1 Constraints
|
|
In addition to optional type qualifiers and the keyword static, the [ and ] may delimit an expres-
|
|
sion or * . If they delimit an expression (which specifies the size of an array), the expression shall
|
|
have an integer type. If the expression is a constant expression, it shall have a value greater than
|
|
zero. The element type shall not be an incomplete or function type. The optional type qualifiers and
|
|
the keyword static shall appear only in a declaration of a function parameter with an array type,
|
|
and then only in the outermost array type derivation.
|
|
</pre>
|
|
<a name='6.7.6.2p2'></a>
|
|
<pre>2 If an identifier is declared as having a variably modified type, it shall be an ordinary identifier (as
|
|
defined in <a href='#6.2.3'>6.2.3</a>), have no linkage, and have either block scope or function prototype scope. If an
|
|
identifier is declared to be an object with static or thread storage duration, it shall not have a variable
|
|
length array type.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.6.2p3'></a>
|
|
<pre>3 If, in the declaration "T D1", D1 has one of the forms:
|
|
D [ type-qualifier-listopt assignment-expressionopt ] attribute-specifier-sequenceopt
|
|
D [ static type-qualifier-listopt assignment-expression ] attribute-specifier-sequenceopt
|
|
D [ type-qualifier-list static assignment-expression ] attribute-specifier-sequenceopt
|
|
D [ type-qualifier-listopt * ] attribute-specifier-sequenceopt
|
|
and the type specified for ident in the declaration "T D" is "derived-declarator-type-list T", then the
|
|
type specified for ident is "derived-declarator-type-list array of T".<a href='#FOOTNOTE.173'><sup>[173]</sup></a><a href='#FOOTNOTE.174'><sup>[174]</sup></a> The optional attribute specifier
|
|
sequence appertains to the array. (See <a href='#6.7.6.3'>6.7.6.3</a> for the meaning of the optional type qualifiers and the
|
|
keyword static.)
|
|
</pre>
|
|
<a name='FOOTNOTE.173'>
|
|
<pre><i><b>Footnote 173)</b> When several "array of" specifications are adjacent, a multidimensional array is declared.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.174'>
|
|
<pre><i><b>Footnote 174)</b> The array is considered identically qualified to T according to <a href='#6.2.5'>6.2.5</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.2p4'></a>
|
|
<pre>4 If the size is not present, the array type is an incomplete type. If the size is * instead of being an
|
|
expression, the array type is a variable length array type of unspecified size, which can only be used in
|
|
declarations or type names with function prototype scope<a href='#FOOTNOTE.175'><sup>[175]</sup></a> ; such arrays are nonetheless complete
|
|
types. If the size is an integer constant expression and the element type has a known constant
|
|
size, the array type is not a variable length array type; otherwise, the array type is a variable length
|
|
array type. (Variable length arrays with automatic storage duration are a conditional feature that
|
|
implementations need not support; see <a href='#6.10.9.3'>6.10.9.3</a>.)
|
|
</pre>
|
|
<a name='FOOTNOTE.175'>
|
|
<pre><i><b>Footnote 175)</b> Thus,
|
|
* can be used only in function declarations that are not definitions (see <a href='#6.7.6.3'>6.7.6.3</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.2p5'></a>
|
|
<pre>5 If the size is an expression that is not an integer constant expression: if it occurs in a declaration at
|
|
function prototype scope, it is treated as if it were replaced by * ; otherwise, each time it is evaluated
|
|
it shall have a value greater than zero. The size of each instance of a variable length array type does
|
|
not change during its lifetime. Where a size expression is part of the operand of a typeof or sizeof
|
|
operator and changing the value of the size expression would not affect the result of the operator, it
|
|
is unspecified whether or not the size expression is evaluated. Where a size expression is part of the
|
|
operand of an alignof operator, that expression is not evaluated.
|
|
</pre>
|
|
<a name='6.7.6.2p6'></a>
|
|
<pre>6 For two array types to be compatible, both shall have compatible element types, and if both size
|
|
specifiers are present, and are integer constant expressions, then both size specifiers shall have
|
|
the same constant value. If the two array types are used in a context which requires them to be
|
|
compatible, it is undefined behavior if the two size specifiers evaluate to unequal values.
|
|
</pre>
|
|
<a name='6.7.6.2p7'></a>
|
|
<pre>7 EXAMPLE 1
|
|
|
|
float fa[11], *afp[17];
|
|
|
|
declares an array of float numbers and an array of pointers to float numbers.
|
|
</pre>
|
|
<a name='6.7.6.2p8'></a>
|
|
<pre>8 EXAMPLE 2 Note the distinction between the declarations
|
|
|
|
extern int *x;
|
|
extern int y[];
|
|
|
|
The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size (an incomplete type),
|
|
the storage for which is defined elsewhere.
|
|
</pre>
|
|
<a name='6.7.6.2p9'></a>
|
|
<pre>9 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
|
|
|
|
extern int n;
|
|
extern int m;
|
|
|
|
void fcompat(void)
|
|
{
|
|
int a[n][6][m];
|
|
int (*p)[4][n+1];
|
|
int c[n][n][6][m];
|
|
int (*r)[n][n][n+1];
|
|
p = a; // invalid: not compatible because 4 != 6
|
|
r = c; // compatible, but defined behavior only if
|
|
// n == 6 and m == n+1
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.6.2p10'></a>
|
|
<pre>10 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or function prototype scope.
|
|
Array objects declared with the thread_local, static, or extern storage-class specifier cannot have a variable length array
|
|
(VLA) type. However, an object declared with the static storage-class specifier can have a VM type (that is, a pointer to a
|
|
VLA type). Finally, all identifiers declared with a VM type have to be ordinary identifiers and cannot, therefore, be members
|
|
of structures or unions.
|
|
|
|
extern int n;
|
|
int A[n]; // invalid: file scope VLA
|
|
extern int (*p2)[n]; // invalid: file scope VM
|
|
int B[100]; // valid: file scope but not VM
|
|
|
|
void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
|
|
|
|
void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
|
|
{
|
|
typedef int VLA[m][m]; // valid: block scope typedef VLA
|
|
|
|
struct tag {
|
|
int (*y)[n]; // invalid: y not ordinary identifier
|
|
int z[n]; // invalid: z not ordinary identifier
|
|
};
|
|
int D[m]; // valid: auto VLA
|
|
static int E[m]; // invalid: static block scope VLA
|
|
extern int F[m]; // invalid: F has linkage and is VLA
|
|
int (*s)[m]; // valid: auto pointer to VLA
|
|
extern int (*r)[m]; // invalid: r has linkage and points to VLA
|
|
static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
|
|
}
|
|
|
|
|
|
Forward references: function declarators (<a href='#6.7.6.3'>6.7.6.3</a>), function definitions (<a href='#6.9.1'>6.9.1</a>), initialization (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.6.3'></a>
|
|
<hr>
|
|
<h3>6.7.6.3 [Function declarators]</h3>
|
|
<a name='6.7.6.3p1'></a>
|
|
<pre>1 Constraints
|
|
A function declarator shall not specify a return type that is a function type or an array type.
|
|
</pre>
|
|
<a name='6.7.6.3p2'></a>
|
|
<pre>2 The only storage-class specifier that shall occur in a parameter declaration is register.
|
|
</pre>
|
|
<a name='6.7.6.3p3'></a>
|
|
<pre>3 After adjustment, the parameters in a parameter type list in a function declarator that is part of a
|
|
definition of that function shall not have incomplete type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.6.3p4'></a>
|
|
<pre>4 If, in the declaration "T D1", D1 has the form
|
|
D ( parameter-type-listopt ) attribute-specifier-sequenceopt
|
|
and the type specified for ident in the declaration "T D" is "derived-declarator-type-list T", then the
|
|
type specified for ident is "derived-declarator-type-list function returning the unqualified version of T".
|
|
The optional attribute specifier sequence appertains to the function type.
|
|
</pre>
|
|
<a name='6.7.6.3p5'></a>
|
|
<pre>5 A parameter type list specifies the types of, and may declare identifiers for, the parameters of the
|
|
function.
|
|
</pre>
|
|
<a name='6.7.6.3p6'></a>
|
|
<pre>6 A declaration of a parameter as "array of type" shall be adjusted to "qualified pointer to type", where
|
|
the type qualifiers (if any) are those specified within the [ and ] of the array type derivation. If the
|
|
keyword static also appears within the [ and ] of the array type derivation, then for each call to
|
|
the function, the value of the corresponding actual argument shall provide access to the first element
|
|
of an array with at least as many elements as specified by the size expression.
|
|
</pre>
|
|
<a name='6.7.6.3p7'></a>
|
|
<pre>7 A declaration of a parameter as "function returning type" shall be adjusted to "pointer to function
|
|
returning type", as in <a href='#6.3.2.1'>6.3.2.1</a>.
|
|
</pre>
|
|
<a name='6.7.6.3p8'></a>
|
|
<pre>8 If the list terminates with an ellipsis (...), no information about the number or types of the
|
|
parameters after the comma is supplied. <a href='#FOOTNOTE.176'><sup>[176]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.176'>
|
|
<pre><i><b>Footnote 176)</b> The macros defined in the <stdarg.h> header (<a href='#7.16'>7.16</a>) can be used to access arguments that correspond to the ellipsis.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.3p9'></a>
|
|
<pre>9 The special case of an unnamed parameter of type void as the only item in the list specifies that the
|
|
function has no parameters.
|
|
</pre>
|
|
<a name='6.7.6.3p10'></a>
|
|
<pre>10 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a parameter
|
|
name, it shall be taken as a typedef name.
|
|
</pre>
|
|
<a name='6.7.6.3p11'></a>
|
|
<pre>11 If the function declarator is not part of a definition of that function, parameters may have incomplete
|
|
type and may use the [*] notation in their sequences of declarator specifiers to specify variable
|
|
length array types.
|
|
</pre>
|
|
<a name='6.7.6.3p12'></a>
|
|
<pre>12 The storage class specifier in the declaration specifiers for a parameter declaration, if present, is
|
|
ignored unless the declared parameter is one of the members of the parameter type list for a function
|
|
definition. The optional attribute specifier sequence in a parameter declaration appertains to the
|
|
parameter.
|
|
</pre>
|
|
<a name='6.7.6.3p13'></a>
|
|
<pre>13 For a function declarator without a parameter type list: the effect is as if it were declared with a
|
|
parameter type list consisting of the keyword void. A function declarator provides a prototype for
|
|
the function<a href='#FOOTNOTE.177'><sup>[177]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.177'>
|
|
<pre><i><b>Footnote 177)</b> This implies that a function definition without a parameter list provides a prototype, and that subsequent calls to that
|
|
function in the same translation unit are constrained not to provide any argument to the function call. Thus a definition of a
|
|
function without parameter list and one that has such a list consisting of the keyword void are fully equivalent.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.3p14'></a>
|
|
<pre>14 For two function types to be compatible, both shall specify compatible return types. Moreover,
|
|
the parameter type lists shall agree in the number of parameters and in use of the final ellipsis;
|
|
corresponding parameters shall have compatible types. In the determination of type compatibility
|
|
and of a composite type, each parameter declared with function or array type is taken as having the
|
|
adjusted type and each parameter declared with qualified type is taken as having the unqualified
|
|
version of its declared type.
|
|
</pre>
|
|
<a name='6.7.6.3p15'></a>
|
|
<pre>15 EXAMPLE 1 The declaration
|
|
|
|
int f(void), *fip(), (*pfi)();
|
|
|
|
|
|
declares a function f with no parameters returning an int, a function fip with no parameters returning a pointer to an int,
|
|
and a pointer pfi to a function with no parameters returning an int. It is especially useful to compare the last two. The
|
|
binding of *fip() is *(fip()) , so that the declaration suggests, and the same construction in an expression requires, the
|
|
calling of a function fip, and then using indirection through the pointer result to yield an int. In the declarator (*pfi)() ,
|
|
the extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function designator,
|
|
which is then used to call the function; it returns an int.
|
|
</pre>
|
|
<a name='6.7.6.3p16'></a>
|
|
<pre>16 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the declaration
|
|
occurs inside a function, the identifiers of the functions f and fip have block scope and either internal or external linkage
|
|
(depending on what file scope declarations for these identifiers are visible), and the identifier of the pointer pfi has block
|
|
scope and no linkage.
|
|
</pre>
|
|
<a name='6.7.6.3p17'></a>
|
|
<pre>17 EXAMPLE 2 The declaration
|
|
|
|
int (*apfi[3])(int *x, int *y);
|
|
|
|
|
|
declares an array apfi of three pointers to functions returning int. Each of these functions has two parameters that are
|
|
pointers to int. The identifiers x and y are declared for descriptive purposes only and go out of scope at the end of the
|
|
declaration of apfi.
|
|
</pre>
|
|
<a name='6.7.6.3p18'></a>
|
|
<pre>18 EXAMPLE 3 The declaration
|
|
|
|
int (*fpfi(int (*)(long), int))(int, ...);
|
|
|
|
|
|
declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two parameters: a
|
|
pointer to a function returning an int (with one parameter of type long int), and an int. The pointer returned by fpfi
|
|
points to a function that has one int parameter and accepts zero or more additional arguments of any type.
|
|
</pre>
|
|
<a name='6.7.6.3p19'></a>
|
|
<pre>19 EXAMPLE 4 The following prototype has a variably modified parameter.
|
|
|
|
void addscalar(int n, int m,
|
|
double a[n][n*m+300], double x);
|
|
int main()
|
|
{
|
|
double b[4][308];
|
|
addscalar(4, 2, b, 2.17);
|
|
return 0;
|
|
}
|
|
|
|
void addscalar(int n, int m,
|
|
double a[n][n*m+300], double x)
|
|
{
|
|
for (int i = 0; i < n; i++)
|
|
for (int j = 0, k = n*m+300; j < k; j++)
|
|
// a is a pointer to a VLA with n*m+300 elements
|
|
a[i][j] += x;
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.6.3p20'></a>
|
|
<pre>20 EXAMPLE 5 The following are all compatible function prototype declarators.
|
|
|
|
double maximum(int n, int m, double a[n][m]);
|
|
double maximum(int n, int m, double a[*][*]);
|
|
double maximum(int n, int m, double a[ ][*]);
|
|
double maximum(int n, int m, double a[ ][m]);
|
|
|
|
|
|
|
|
as are:
|
|
|
|
void f(double (* restrict a)[5]);
|
|
void f(double a[restrict][5]);
|
|
void f(double a[restrict 3][5]);
|
|
void f(double a[restrict static 3][5]);
|
|
|
|
|
|
|
|
(Note that the last declaration also specifies that the argument corresponding to a in any call to f can be expected to be a
|
|
non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
|
|
|
|
Forward references: function definitions (<a href='#6.9.1'>6.9.1</a>), type names (<a href='#6.7.7'>6.7.7</a>).
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.7'></a>
|
|
<hr>
|
|
<h3>6.7.7 [Type names]</h3>
|
|
<a name='6.7.7p1'></a>
|
|
<pre>1 Syntax
|
|
type-name:
|
|
specifier-qualifier-list abstract-declaratoropt
|
|
abstract-declarator:
|
|
pointer
|
|
pointeropt direct-abstract-declarator
|
|
direct-abstract-declarator:
|
|
( abstract-declarator )
|
|
array-abstract-declarator attribute-specifier-sequenceopt
|
|
function-abstract-declarator attribute-specifier-sequenceopt
|
|
array-abstract-declarator:
|
|
direct-abstract-declaratoropt [ type-qualifier-listopt assignment-expressionopt ]
|
|
direct-abstract-declaratoropt [ static type-qualifier-listopt assignment-expression ]
|
|
direct-abstract-declaratoropt [ type-qualifier-list static assignment-expression ]
|
|
direct-abstract-declaratoropt [ * ]
|
|
|
|
function-abstract-declarator:
|
|
direct-abstract-declaratoropt ( parameter-type-listopt )
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.7p2'></a>
|
|
<pre>2 In several contexts, it is necessary to specify a type. This is accomplished using a type name, which is
|
|
syntactically a declaration for a function or an object of that type that omits the identifier.<a href='#FOOTNOTE.178'><sup>[178]</sup></a> The
|
|
optional attribute specifier sequence in a direct abstract declarator appertains to the preceding array
|
|
or function type. The attribute specifier sequence affects the type only for the declaration it appears
|
|
in, not other declarations involving the same type.
|
|
</pre>
|
|
<a name='FOOTNOTE.178'>
|
|
<pre><i><b>Footnote 178)</b> As indicated by the syntax, empty parentheses in a type name are interpreted as "function with no parameter specifica-
|
|
tion", rather than redundant parentheses around the omitted identifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.7p3'></a>
|
|
<pre>3 EXAMPLE The constructions
|
|
|
|
(a) int
|
|
(b) int *
|
|
(c) int *[3]
|
|
(d) int (*)[3]
|
|
(e) int (*)[*]
|
|
(f) int *()
|
|
(g) int (*)(void)
|
|
(h) int (*const [])(unsigned int, ...)
|
|
|
|
name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an array of three
|
|
int s, (e) pointer to a variable length array of an unspecified number of int s, (f) function with no parameters returning
|
|
a pointer to int, (g) pointer to function with no parameters returning an int, and (h) array of an unspecified number of
|
|
constant pointers to functions, each with one parameter that has type unsigned int and an unspecified number of other
|
|
parameters, returning an int.
|
|
|
|
</pre>
|
|
<a name='6.7.8'></a>
|
|
<hr>
|
|
<h3>6.7.8 [Type definitions]</h3>
|
|
<a name='6.7.8p1'></a>
|
|
<pre>1 Syntax
|
|
typedef-name:
|
|
identifier
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.8p2'></a>
|
|
<pre>2 If a typedef name specifies a variably modified type then it shall have block scope.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.8p3'></a>
|
|
<pre>3 In a declaration whose storage-class specifier is typedef, each declarator defines an identifier to
|
|
be a typedef name that denotes the type specified for the identifier in the way described in <a href='#6.7.6'>6.7.6</a>.
|
|
Any array size expressions associated with variable length array declarators are evaluated each time
|
|
the declaration of the typedef name is reached in the order of execution. A typedef declaration
|
|
does not introduce a new type, only a synonym for the type so specified. That is, in the following
|
|
declarations:
|
|
|
|
typedef T type_ident;
|
|
type_ident D;
|
|
|
|
|
|
type_ident is defined as a typedef name with the type specified by the declaration specifiers in T
|
|
(known as T), and the identifier in D has the type "derived-declarator-type-list T" where the derived-
|
|
declarator-type-list is specified by the declarators of D. A typedef name shares the same name space
|
|
as other identifiers declared in ordinary declarators. If the identifier is redeclared in an enclosed
|
|
block the inner declaration shall not be such that the type is inferred (<a href='#6.7.9'>6.7.9</a>).
|
|
</pre>
|
|
<a name='6.7.8p4'></a>
|
|
<pre>4 EXAMPLE 1 After
|
|
|
|
typedef int MILES, KLICKSP();
|
|
typedef struct { double hi, lo; } range;
|
|
|
|
the constructions
|
|
MILES distance;
|
|
extern KLICKSP *metricp;
|
|
range x;
|
|
range z, *zp;
|
|
|
|
|
|
are all valid declarations. The type of distance is int, that of metricp is "pointer to function with no parameters returning
|
|
int", and that of x and z is the specified structure; zp is a pointer to such a structure. The object distance has a type
|
|
compatible with any other int object.
|
|
</pre>
|
|
<a name='6.7.8p5'></a>
|
|
<pre>5 EXAMPLE 2 After the declarations
|
|
|
|
typedef struct s1 { int x; } t1, *tp1;
|
|
typedef struct s2 { int x; } t2, *tp2;
|
|
|
|
|
|
type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct s1, but not compatible
|
|
with the types struct s2, t2, the type pointed to by tp2, or int.
|
|
</pre>
|
|
<a name='6.7.8p6'></a>
|
|
<pre>6 EXAMPLE 3 The following obscure constructions
|
|
|
|
typedef signed int t;
|
|
typedef int plain;
|
|
struct tag {
|
|
unsigned t:4;
|
|
const t:5;
|
|
plain r:5;
|
|
};
|
|
|
|
|
|
declare a typedef name t with type signed int, a typedef name plain with type int, and a structure with three bit-field
|
|
members, one named t that contains values in the range [0, 15], an unnamed const-qualified bit-field which (if it could
|
|
be accessed) would contain values in either the range [−15, +15] or [−16, +15], and one named r that contains values in
|
|
one of the ranges [0, 31], [−15, +15], or [−16, +15]. (The choice of range is implementation-defined.) The first two bit-field
|
|
declarations differ in that unsigned is a type specifier (which forces t to be the name of a structure member), while const is
|
|
a type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed in an inner scope
|
|
by
|
|
|
|
t f(t (t));
|
|
long t;
|
|
|
|
|
|
then a function f is declared with type "function returning signed int with one unnamed parameter with type pointer
|
|
to function returning signed int with one unnamed parameter with type signed int", and an identifier t with type
|
|
long int.
|
|
|
|
</pre>
|
|
<a name='6.7.8p7'></a>
|
|
<pre>7 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the following
|
|
declarations of the signal function specify exactly the same type, the first without making use of any typedef names.
|
|
|
|
typedef void fv(int), (*pfv)(int);
|
|
|
|
void (*signal(int, void (*)(int)))(int);
|
|
fv *signal(int, fv *);
|
|
pfv signal(int, pfv);
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.8p8'></a>
|
|
<pre>8 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the time the typedef
|
|
name is defined, not each time it is used:
|
|
|
|
void copyt(int n)
|
|
{
|
|
typedef int B[n]; // B is n ints, n evaluated now
|
|
n += 1;
|
|
B a; // a is n ints, n without += 1
|
|
int b[n]; // a and b are different sizes
|
|
for (int i = 1; i < n; i++)
|
|
a[i-1] = b[i];
|
|
}
|
|
</pre>
|
|
<a name='6.7.9'></a>
|
|
<hr>
|
|
<h3>6.7.9 [Type inference]</h3>
|
|
<a name='6.7.9p1'></a>
|
|
<pre>1 Constraints
|
|
A declaration for which the type is inferred shall contain the storage-class specifier auto.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.7.9p2'></a>
|
|
<pre>2 For such a declaration that is the definition of an object the init-declarator shall have one of the forms
|
|
direct-declarator = assignment-expression
|
|
direct-declarator = { assignment-expression }
|
|
direct-declarator = { assignment-expression , }
|
|
|
|
The declared type is the type of the assignment expression after lvalue, array to pointer or function
|
|
to pointer conversion, additionally qualified by qualifiers and amended by attributes as they appear
|
|
in the declaration specifiers, if any<a href='#FOOTNOTE.179'><sup>[179]</sup></a> . If the direct declarator is not of the form
|
|
identifier attribute-specifier-sequenceopt
|
|
, possibly enclosed in balanced pairs of parentheses, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.179'>
|
|
<pre><i><b>Footnote 179)</b> The scope rules as described in <a href='#6.2.1'>6.2.1</a> also prohibit the use of the identifier of the declarator within the assignment
|
|
expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.9p3'></a>
|
|
<pre>3 NOTE Such a declaration that also defines a structure or union type violates a constraint. Here, the identifier a which is not
|
|
ordinary but in the name space of the structure type is declared.
|
|
|
|
auto p = (struct { int a; } *)0;
|
|
|
|
Even a forward declaration of a structure tag
|
|
|
|
struct s;
|
|
auto p = (struct s { int a; } *)0;
|
|
|
|
would not change that situation. A direct use of the structure definition as the type specifier ensures the validity of the
|
|
declaration.
|
|
|
|
struct s { int a; } * p = 0;
|
|
|
|
</pre>
|
|
<a name='6.7.9p4'></a>
|
|
<pre>4 EXAMPLE 1 Consider the following file scope definitions:
|
|
|
|
static auto a = <a href='#3.5'>3.5</a>;
|
|
auto p = &a;
|
|
|
|
They are interpreted as if they had been written as:
|
|
|
|
static double a = <a href='#3.5'>3.5</a>;
|
|
double * p = &a;
|
|
|
|
So effectively a is a double and p is a double*. Note that the restrictions on the syntax of such declarations does not allow the
|
|
declarator to be *p , but that the final type here nevertheless is a pointer type.
|
|
</pre>
|
|
<a name='6.7.9p5'></a>
|
|
<pre>5 EXAMPLE 2 The scope of the identifier for which the type is inferred only starts after the end of the initializer (<a href='#6.2.1'>6.2.1</a>), so
|
|
the assignment expression cannot use the identifier to refer to the object or function that is declared, for example to take its
|
|
address. Any use of the identifier in the initializer is invalid, even if an entity with the same name exists in an outer scope.
|
|
|
|
{
|
|
double a = 7;
|
|
double b = 9;
|
|
{
|
|
double b = b * b; // undefined, uses uninitialized
|
|
// variable without address
|
|
printf("%g\n", a); // valid, uses "a" from outer scope, prints 7
|
|
auto a = a * a; // invalid, "a" from outer scope is already
|
|
shadowed
|
|
}
|
|
{
|
|
auto b = a * a; // valid, uses "a" from outer scope
|
|
auto a = b; // valid, shadows "a" from outer scope
|
|
// ...
|
|
printf("%g\n", a); // valid, uses "a" from inner scope, prints 49
|
|
}
|
|
// ...
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.7.9p6'></a>
|
|
<pre>6 EXAMPLE 3 In the following, declarations of pA and qA are valid. The type of A after array-to-pointer conversion is a pointer
|
|
type, and qA is a pointer to array.
|
|
|
|
double A[3] = { 0 };
|
|
auto pA = A;
|
|
auto qA = &A;
|
|
|
|
</pre>
|
|
<a name='6.7.9p7'></a>
|
|
<pre>7 EXAMPLE 4 Type inference can be used to capture the type of a call to a type-generic function. It ensures that the same type
|
|
as the argument x is used.
|
|
|
|
#include <tgmath.h>
|
|
auto y = cos(x);
|
|
|
|
If instead the type of y is explicitly specified to a different type than x, a diagnosis of the mismatch is not enforced.
|
|
</pre>
|
|
<a name='6.7.9p8'></a>
|
|
<pre>8 EXAMPLE 5 A type-generic macro that generalizes the div functions (<a href='#7.24.6.2'>7.24.6.2</a>) is defined and used as follows.
|
|
|
|
#define div(X, Y) _Generic((X)+(Y), int: div, long: ldiv, long long: lldiv)((X),
|
|
(Y))
|
|
auto z = div(x, y);
|
|
auto q = z.quot;
|
|
auto r = z.rem;
|
|
|
|
</pre>
|
|
<a name='6.7.9p9'></a>
|
|
<pre>9 EXAMPLE 6 Definitions of objects with inferred type are valid in all contexts that allow the initializer syntax as described.
|
|
In particular they can be used to ensure type safety of for-loop controlling expressions.
|
|
|
|
for (auto i = j; i < 2*j; ++i) {
|
|
// ...
|
|
}
|
|
|
|
Here, regardless of the integer rank or signedness of the type of j, i will have the non-atomic unqualified type of j. So, after
|
|
lvalue conversion and possible promotion, the two operands of the < operator in the controlling expression are guaranteed to
|
|
have the same type, and, in particular, the same signedness.
|
|
|
|
</pre>
|
|
<a name='6.7.10'></a>
|
|
<hr>
|
|
<h3>6.7.10 [Initialization]</h3>
|
|
<a name='6.7.10p1'></a>
|
|
<pre>1 Syntax
|
|
braced-initializer:
|
|
{ }
|
|
{ initializer-list }
|
|
{ initializer-list , }
|
|
|
|
|
|
initializer:
|
|
assignment-expression
|
|
braced-initializer
|
|
|
|
initializer-list:
|
|
designationopt initializer
|
|
initializer-list , designationopt initializer
|
|
|
|
designation:
|
|
designator-list =
|
|
designator-list:
|
|
designator
|
|
designator-list designator
|
|
designator:
|
|
[ constant-expression ]
|
|
. identifier
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.10p2'></a>
|
|
<pre>2 An empty brace pair ({}) is called an empty initializer and is referred to as empty initialization.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.10p3'></a>
|
|
<pre>3 No initializer shall attempt to provide a value for an object not contained within the entity being
|
|
initialized.
|
|
</pre>
|
|
<a name='6.7.10p4'></a>
|
|
<pre>4 The type of the entity to be initialized shall be an array of unknown size or a complete object type.
|
|
An entity of variable length array type shall not be initialized except by an empty initializer. An
|
|
array of unknown size shall not be initialized by an empty initializer.
|
|
</pre>
|
|
<a name='6.7.10p5'></a>
|
|
<pre>5 All the expressions in an initializer for an object that has static or thread storage duration or is
|
|
declared with the constexpr storage-class specifier shall be constant expressions or string literals.
|
|
</pre>
|
|
<a name='6.7.10p6'></a>
|
|
<pre>6 If the declaration of an identifier has block scope, and the identifier has external or internal linkage,
|
|
the declaration shall have no initializer for the identifier.
|
|
</pre>
|
|
<a name='6.7.10p7'></a>
|
|
<pre>7 If a designator has the form
|
|
[ constant-expression ]
|
|
then the current object (defined below) shall have array type and the expression shall be an integer
|
|
constant expression. If the array is of unknown size, any nonnegative value is valid.
|
|
</pre>
|
|
<a name='6.7.10p8'></a>
|
|
<pre>8 If a designator has the form
|
|
. identifier
|
|
then the current object (defined below) shall have structure or union type and the identifier shall be
|
|
the name of a member of that type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.10p9'></a>
|
|
<pre>9 An initializer specifies the initial value stored in an object. For objects with atomic type additional
|
|
restrictions apply, see <a href='#7.17.2'>7.17.2</a> and <a href='#7.17.8'>7.17.8</a>.
|
|
</pre>
|
|
<a name='6.7.10p10'></a>
|
|
<pre>10 Except where explicitly stated otherwise, for the purposes of this subclause unnamed members
|
|
of objects of structure and union type do not participate in initialization. Unnamed members of
|
|
structure objects have indeterminate representation even after initialization.
|
|
</pre>
|
|
<a name='6.7.10p11'></a>
|
|
<pre>11 If an object that has automatic storage duration is initialized with an empty initializer, its value
|
|
is the same as the initialization of a static storage duration object. Otherwise, if an object that has
|
|
automatic storage duration is not initialized explicitly, its representation is indeterminate. If an
|
|
object that has static or thread storage duration is not initialized explicitly, or is initialized with an
|
|
empty initializer, then default initialization:
|
|
|
|
— if it has pointer type, it is initialized to a null pointer;
|
|
|
|
— if it has decimal floating type, it is initialized to (positive or unsigned) zero, and the quantum
|
|
exponent is implementation-defined<a href='#FOOTNOTE.180'><sup>[180]</sup></a> ;
|
|
|
|
— if it has arithmetic type, and it does not have decimal floating type, it is initialized to (positive
|
|
or unsigned) zero;
|
|
|
|
— if it is an aggregate, every member is initialized (recursively) according to these rules, and any
|
|
padding is initialized to zero bits;
|
|
— if it is a union, the first named member is initialized (recursively) according to these rules, and
|
|
any padding is initialized to zero bits;
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.180'>
|
|
<pre><i><b>Footnote 180)</b> A representation with all bits zero results in a decimal floating-point zero with the most negative exponent.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.10p12'></a>
|
|
<pre>12 The initializer for a scalar shall be a single expression, optionally enclosed in braces, or it shall be
|
|
an empty initializer. If the initializer is the empty initializer, the initial value is the same as the
|
|
initialization of a static storage duration object. Otherwise, the initial value of the object is that of the
|
|
expression (after conversion); the same type constraints and conversions as for simple assignment
|
|
apply, taking the type of the scalar to be the unqualified version of its declared type.
|
|
</pre>
|
|
<a name='6.7.10p13'></a>
|
|
<pre>13 The rest of this subclause deals with initializers for objects that have aggregate or union type.
|
|
</pre>
|
|
<a name='6.7.10p14'></a>
|
|
<pre>14 The initializer for a structure or union object that has automatic storage duration shall be either
|
|
an initializer list as described below, or a single expression that has compatible structure or union
|
|
type. In the latter case, the initial value of the object, including unnamed members, is that of the
|
|
expression.
|
|
</pre>
|
|
<a name='6.7.10p15'></a>
|
|
<pre>15 An array of character type may be initialized by a character string literal or UTF-8 string literal,
|
|
optionally enclosed in braces. Successive bytes of the string literal (including the terminating null
|
|
character if there is room or if the array is of unknown size) initialize the elements of the array.
|
|
</pre>
|
|
<a name='6.7.10p16'></a>
|
|
<pre>16 An array with element type compatible with a qualified or unqualified version of wchar_t, char16_t,
|
|
or char32_t may be initialized by a wide string literal with the corresponding encoding prefix (L,
|
|
u, or U, respectively), optionally enclosed in braces. Successive wide characters of the wide string
|
|
literal (including the terminating null wide character if there is room or if the array is of unknown
|
|
size) initialize the elements of the array.
|
|
</pre>
|
|
<a name='6.7.10p17'></a>
|
|
<pre>17 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-enclosed list
|
|
of initializers for the elements or named members.
|
|
</pre>
|
|
<a name='6.7.10p18'></a>
|
|
<pre>18 Each brace-enclosed initializer list has an associated current object. When no designations are present,
|
|
subobjects of the current object are initialized in order according to the type of the current object:
|
|
array elements in increasing subscript order, structure members in declaration order, and the first
|
|
named member of a union.<a href='#FOOTNOTE.181'><sup>[181]</sup></a> In contrast, a designation causes the following initializer to begin
|
|
initialization of the subobject described by the designator. Initialization then continues forward in
|
|
order, beginning with the next subobject after that described by the designator.<a href='#FOOTNOTE.182'><sup>[182]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.181'>
|
|
<pre><i><b>Footnote 181)</b> If the initializer list for a subaggregate or contained union does not begin with a left brace, its subobjects are initialized as
|
|
usual, but the subaggregate or contained union does not become the current object: current objects are associated only with
|
|
brace-enclosed initializer lists.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.182'>
|
|
<pre><i><b>Footnote 182)</b> After a union member is initialized, the next object is not the next member of the union; instead, it is the next subobject of
|
|
an object containing the union.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.10p19'></a>
|
|
<pre>19 Each designator list begins its description with the current object associated with the closest sur-
|
|
rounding brace pair. Each item in the designator list (in order) specifies a particular member of its
|
|
current object and changes the current object for the next designator (if any) to be that member.<a href='#FOOTNOTE.183'><sup>[183]</sup></a>
|
|
The current object that results at the end of the designator list is the subobject to be initialized by the
|
|
following initializer.
|
|
</pre>
|
|
<a name='FOOTNOTE.183'>
|
|
<pre><i><b>Footnote 183)</b> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with the surrounding
|
|
brace pair. Note, too, that each separate designator list is independent.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.10p20'></a>
|
|
<pre>20 The initialization shall occur in initializer list order, each initializer provided for a particular subobject
|
|
overriding any previously listed initializer for the same subobject;<a href='#FOOTNOTE.184'><sup>[184]</sup></a> all subobjects that are not
|
|
initialized explicitly shall be initialized implicitly the same as objects that have static storage duration.
|
|
</pre>
|
|
<a name='FOOTNOTE.184'>
|
|
<pre><i><b>Footnote 184)</b> Any initializer for the subobject which is overridden and so not used to initialize that subobject might not be evaluated at
|
|
all.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.10p21'></a>
|
|
<pre>21 If the aggregate or union contains elements or members that are aggregates or unions, these rules
|
|
apply recursively to the subaggregates or contained unions. If the initializer of a subaggregate or
|
|
contained union begins with a left brace, the initializers enclosed by that brace and its matching right
|
|
brace initialize the elements or members of the subaggregate or the contained union. Otherwise, only
|
|
enough initializers from the list are taken to account for the elements or members of the subaggregate
|
|
or the first member of the contained union; any remaining initializers are left to initialize the next
|
|
element or member of the aggregate of which the current subaggregate or contained union is a part.
|
|
</pre>
|
|
<a name='6.7.10p22'></a>
|
|
<pre>22 If there are fewer initializers in a brace-enclosed list than there are elements or members of an
|
|
aggregate, or fewer characters in a string literal used to initialize an array of known size than there
|
|
are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as
|
|
objects that have static storage duration.
|
|
</pre>
|
|
<a name='6.7.10p23'></a>
|
|
<pre>23 If an array of unknown size is initialized, its size is determined by the largest indexed element with
|
|
an explicit initializer. The array type is completed at the end of its initializer list.
|
|
</pre>
|
|
<a name='6.7.10p24'></a>
|
|
<pre>24 The evaluations of the initialization list expressions are indeterminately sequenced with respect to
|
|
one another and thus the order in which any side effects occur is unspecified.<a href='#FOOTNOTE.185'><sup>[185]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.185'>
|
|
<pre><i><b>Footnote 185)</b> In particular, the evaluation order need not be the same as the order of subobject initialization.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.10p25'></a>
|
|
<pre>25 EXAMPLE 1 Provided that <complex.h> has been #included, the declarations
|
|
|
|
int i = <a href='#3.5'>3.5</a>;
|
|
double complex c = 5 + 3 * I;
|
|
|
|
|
|
define and initialize i with the value 3 and c with the value 5.0 + i3.0.
|
|
</pre>
|
|
<a name='6.7.10p26'></a>
|
|
<pre>26 EXAMPLE 2 The declaration
|
|
|
|
int x[] = { 1, 3, 5 };
|
|
|
|
|
|
defines and initializes x as a one-dimensional array object that has three elements, as no size was specified and there are three
|
|
initializers.
|
|
</pre>
|
|
<a name='6.7.10p27'></a>
|
|
<pre>27 EXAMPLE 3 The declaration
|
|
|
|
int y[4][3] = {
|
|
{ 1, 3, 5 },
|
|
{ 2, 4, 6 },
|
|
{ 3, 5, 7 },
|
|
};
|
|
|
|
|
|
is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object y[0]), namely
|
|
y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and y[2]. The initializer ends early, so y[3] is
|
|
initialized with zeros. Precisely the same effect could have been achieved by
|
|
|
|
int y[4][3] = {
|
|
1, 3, 5, 2, 4, 6, 3, 5, 7
|
|
};
|
|
|
|
|
|
The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the next three are
|
|
taken successively for y[1] and y[2].
|
|
</pre>
|
|
<a name='6.7.10p28'></a>
|
|
<pre>28 EXAMPLE 4 The declaration
|
|
|
|
int z[4][3] = {
|
|
{ 1 }, { 2 }, { 3 }, { 4 }
|
|
};
|
|
|
|
|
|
initializes the first column of z as specified and initializes the rest with zeros.
|
|
</pre>
|
|
<a name='6.7.10p29'></a>
|
|
<pre>29 EXAMPLE 5 The declaration
|
|
|
|
struct { int a[3], b; } w[] = { { 1 }, 2 };
|
|
|
|
|
|
is a definition with an inconsistently bracketed initialization. It defines an array with two element structures: w[0].a[0] is 1
|
|
and w[1].a[0] is 2; all the other elements are zero.
|
|
</pre>
|
|
<a name='6.7.10p30'></a>
|
|
<pre>30 EXAMPLE 6 The declaration
|
|
|
|
short q[4][3][2] = {
|
|
{ 1 },
|
|
{ 2, 3 },
|
|
{ 4, 5, 6 }
|
|
};
|
|
contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array object: q[0][0][0]
|
|
is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize q[2][0][0], q[2][0][1], and q[2][1][0], respectively;
|
|
all the rest are zero. The initializer for q[0][0] does not begin with a left brace, so up to six items from the current list
|
|
could be used. There is only one, so the values for the remaining five elements are initialized with zero. Likewise, the
|
|
initializers for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their respective
|
|
two-dimensional subaggregates. If there had been more than six items in any of the lists, a diagnostic message would have
|
|
been issued. The same initialization result could have been achieved by:
|
|
|
|
short q[4][3][2] = {
|
|
1, 0, 0, 0, 0, 0,
|
|
2, 3, 0, 0, 0, 0,
|
|
4, 5, 6
|
|
};
|
|
|
|
or by:
|
|
|
|
short q[4][3][2] = {
|
|
{
|
|
{ 1 },
|
|
},
|
|
{
|
|
{ 2, 3 },
|
|
},
|
|
{
|
|
{ 4, 5 },
|
|
{ 6 },
|
|
}
|
|
};
|
|
|
|
in a fully bracketed form.
|
|
</pre>
|
|
<a name='6.7.10p31'></a>
|
|
<pre>31 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to cause confusion.
|
|
</pre>
|
|
<a name='6.7.10p32'></a>
|
|
<pre>32 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the declaration
|
|
|
|
typedef int A[]; // OK - declared with block scope
|
|
|
|
the declaration
|
|
|
|
A a = { 1, 2 }, b = { 3, 4, 5 };
|
|
|
|
is identical to
|
|
|
|
int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
|
|
|
|
due to the rules for incomplete types.
|
|
</pre>
|
|
<a name='6.7.10p33'></a>
|
|
<pre>33 EXAMPLE 8 The declaration
|
|
|
|
char s[] = "abc", t[3] = "abc";
|
|
|
|
defines "plain" char array objects s and t whose elements are initialized with character string literals. This declaration is
|
|
identical to
|
|
|
|
char s[] = { ’a’, ’b’, ’c’, ’\0’ },
|
|
t[] = { ’a’, ’b’, ’c’ };
|
|
|
|
The contents of the arrays are modifiable. On the other hand, the declaration
|
|
|
|
char *p = "abc";
|
|
|
|
defines p with type "pointer to char" and initializes it to point to an object with type "array of char" with length 4 whose
|
|
elements are initialized with a character string literal. If an attempt is made to use p to modify the contents of the array, the
|
|
behavior is undefined.
|
|
</pre>
|
|
<a name='6.7.10p34'></a>
|
|
<pre>34 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using designators:
|
|
enum { member_one, member_two };
|
|
const char *nm[] = {
|
|
[member_two] = "member two",
|
|
[member_one] = "member one",
|
|
};
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.10p35'></a>
|
|
<pre>35 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
|
|
|
|
div_t answer = {.quot = 2, .rem = -1 };
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.10p36'></a>
|
|
<pre>36 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists might be misunder-
|
|
stood:
|
|
|
|
struct { int a[3], b; } w[] =
|
|
{ [0].a = {1}, [1].a[0] = 2 };
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.10p37'></a>
|
|
<pre>37 EXAMPLE 12
|
|
|
|
struct T {
|
|
int k;
|
|
int l;
|
|
};
|
|
|
|
struct S {
|
|
int i;
|
|
struct T t;
|
|
};
|
|
|
|
struct T x = {.l = 43, .k = 42, };
|
|
|
|
void f(void)
|
|
{
|
|
struct S l = { 1, .t = x, .t.l = 41, };
|
|
}
|
|
|
|
|
|
The value of l.t.k is 42, because implicit initialization does not override explicit initialization.
|
|
</pre>
|
|
<a name='6.7.10p38'></a>
|
|
<pre>38 EXAMPLE 13 Space can be "allocated" from both ends of an array by using a single designator:
|
|
|
|
int a[MAX] = {
|
|
1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
|
|
};
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.10p39'></a>
|
|
<pre>39 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less than ten, some of
|
|
the values provided by the first five initializers will be overridden by the second five.
|
|
</pre>
|
|
<a name='6.7.10p40'></a>
|
|
<pre>40 EXAMPLE 14 Any member of a union can be initialized:
|
|
|
|
union { /* ... */ } u = {.any_member = 42 };
|
|
|
|
|
|
Forward references: common definitions <stddef.h> (<a href='#7.21'>7.21</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.11'></a>
|
|
<hr>
|
|
<h3>6.7.11 [Static assertions]</h3>
|
|
<a name='6.7.11p1'></a>
|
|
<pre>1 Syntax
|
|
static_assert-declaration:
|
|
static_assert ( constant-expression , string-literal ) ;
|
|
static_assert ( constant-expression ) ;
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.11p2'></a>
|
|
<pre>2 The constant expression shall compare unequal to 0.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.11p3'></a>
|
|
<pre>3 The constant expression shall be an integer constant expression. If the value of the constant expres-
|
|
sion compares unequal to 0, the declaration has no effect. Otherwise, the constraint is violated and
|
|
the implementation shall produce a diagnostic message which should include the text of the string
|
|
literal, if present.
|
|
Forward references: diagnostics (<a href='#7.2'>7.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.12'></a>
|
|
<hr>
|
|
<h3>6.7.12 [Attributes]</h3>
|
|
<a name='6.7.12p1'></a>
|
|
<pre>1 Attributes specify additional information for various source constructs such as types, variables,
|
|
identifiers, or blocks. They are identified by an attribute token, which can either be a attribute prefixed
|
|
token (for implementation-specific attributes) or a standard attribute specified by an identifier (for
|
|
attributes specified in this document).
|
|
</pre>
|
|
<a name='6.7.12p2'></a>
|
|
<pre>2 Support for any of the standard attributes specified in this document is implementation-defined
|
|
and optional. For an attribute token (including an attribute prefixed token) not specified in this
|
|
document, the behavior is implementation-defined. Any attribute token that is not supported by the
|
|
implementation is ignored.
|
|
</pre>
|
|
<a name='6.7.12p3'></a>
|
|
<pre>3 Attributes are said to appertain to some source construct, identified by the syntactic context where
|
|
they appear, and for each individual attribute, the corresponding clause constrains the syntactic
|
|
context in which this appertainance is valid. The attribute specifier sequence appertaining to some
|
|
source construct shall contain only attributes that are allowed to apply to that source construct.
|
|
</pre>
|
|
<a name='6.7.12p4'></a>
|
|
<pre>4 In all aspects of the language, a standard attribute specified by this document as an identifier attr
|
|
and an identifier of the form __attr__ shall behave the same when used as an attribute token,
|
|
except for the spelling.<a href='#FOOTNOTE.186'><sup>[186]</sup></a>
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.186'>
|
|
<pre><i><b>Footnote 186)</b> Thus, the attributes [[nodiscard]] and [[__nodiscard__]] can be freely interchanged. Implementations are encour-
|
|
aged to behave similarly for attribute tokens (including attribute prefixed tokens) they provide.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12p5'></a>
|
|
<pre>5 It is recommended that implementations support all standard attributes as defined in this document.
|
|
|
|
</pre>
|
|
<a name='6.7.12.1'></a>
|
|
<hr>
|
|
<h3>6.7.12.1 [General]</h3>
|
|
<a name='6.7.12.1p1'></a>
|
|
<pre>1 Syntax
|
|
attribute-specifier-sequence:
|
|
attribute-specifier-sequenceopt attribute-specifier
|
|
attribute-specifier:
|
|
[ [ attribute-list ] ]
|
|
attribute-list:
|
|
attributeopt
|
|
attribute-list , attributeopt
|
|
attribute:
|
|
attribute-token attribute-argument-clauseopt
|
|
attribute-token:
|
|
standard-attribute
|
|
attribute-prefixed-token
|
|
standard-attribute:
|
|
identifier
|
|
|
|
attribute-prefixed-token:
|
|
attribute-prefix :: identifier
|
|
attribute-prefix:
|
|
identifier
|
|
attribute-argument-clause:
|
|
( balanced-token-sequenceopt )
|
|
balanced-token-sequence:
|
|
balanced-token
|
|
balanced-token-sequence balanced-token
|
|
balanced-token:
|
|
( balanced-token-sequenceopt )
|
|
[ balanced-token-sequenceopt ]
|
|
{ balanced-token-sequenceopt }
|
|
any token other than a parenthesis, a bracket, or a brace
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.12.1p2'></a>
|
|
<pre>2 The identifier in a standard attribute shall be one of:
|
|
|
|
deprecated maybe_unused noreturn unsequenced
|
|
fallthrough nodiscard _Noreturn reproducible
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.1p3'></a>
|
|
<pre>3 An attribute specifier that contains no attributes has no effect. The order in which attribute tokens
|
|
appear in an attribute list is not significant. If a keyword (<a href='#6.4.1'>6.4.1</a>) that satisfies the syntactic require-
|
|
ments of an identifier (<a href='#6.4.2'>6.4.2</a>) is contained in an attribute token, it is considered an identifier. A strictly
|
|
conforming program using a standard attribute remains strictly conforming in the absence of that
|
|
attribute. <a href='#FOOTNOTE.187'><sup>[187]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.187'>
|
|
<pre><i><b>Footnote 187)</b> Standard attributes specified by this document can be parsed but ignored by an implementation without changing the
|
|
semantics of a correct program; the same is not true for attributes not specified by this document.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.1p4'></a>
|
|
<pre>4 NOTE For each standard attribute, the form of the balanced token sequence, if any, will be specified.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.1p5'></a>
|
|
<pre>5 Each implementation should choose a distinctive name for the attribute prefix in an attribute
|
|
prefixed token. Implementations should not define attributes without an attribute prefix unless it is
|
|
a standard attribute as specified in this document.
|
|
</pre>
|
|
<a name='6.7.12.1p6'></a>
|
|
<pre>6 EXAMPLE 1 Suppose that an implementation chooses the attribute prefix hal and provides specific attributes named daisy
|
|
and rosie.
|
|
|
|
[[deprecated, hal::daisy]] double nine1000(double);
|
|
[[deprecated]] [[hal::daisy]] double nine1000(double);
|
|
[[deprecated]] double nine1000 [[hal::daisy]] (double);
|
|
|
|
|
|
Then all the following declarations should be equivalent aside from the spelling:
|
|
|
|
[[__deprecated__, __hal__::__daisy__]] double nine1000(double);
|
|
[[__deprecated__]] [[__hal__::__daisy__]] double nine1000(double);
|
|
[[__deprecated__]] double nine1000 [[__hal__::__daisy__]] (double);
|
|
|
|
|
|
These use the alternate spelling that is required for all standard attributes and recommended for prefixed attributes. These
|
|
may be better-suited for use in header files, where the use of the alternate spelling avoids naming conflicts with user-provided
|
|
macros.
|
|
</pre>
|
|
<a name='6.7.12.1p7'></a>
|
|
<pre>7 EXAMPLE 2 For the same implementation, the following two declarations are equivalent, because the ordering inside
|
|
attribute lists is not important.
|
|
|
|
[[hal::daisy, hal::rosie]] double nine999(double);
|
|
[[hal::rosie, hal::daisy]] double nine999(double);
|
|
|
|
|
|
On the other hand the following two declarations are not equivalent, because the ordering of different attribute specifiers
|
|
may affect the semantics.
|
|
|
|
[[hal::daisy]] [[hal::rosie]] double nine999(double);
|
|
[[hal::rosie]] [[hal::daisy]] double nine999(double); // may have different semantics
|
|
</pre>
|
|
<a name='6.7.12.2'></a>
|
|
<hr>
|
|
<h3>6.7.12.2 [The nodiscard attribute]</h3>
|
|
<a name='6.7.12.2p1'></a>
|
|
<pre>1 Constraints
|
|
The nodiscard attribute shall be applied to the identifier in a function declaration or to the definition
|
|
of a structure, union, or enumeration type. If an attribute argument clause is present, it shall have
|
|
the form:
|
|
( string-literal )
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.2p2'></a>
|
|
<pre>2 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 202003L
|
|
when given nodiscard as the pp-tokens operand.
|
|
</pre>
|
|
<a name='6.7.12.2p3'></a>
|
|
<pre>3 A name or entity declared without the nodiscard attribute can later be redeclared with the attribute
|
|
and vice versa. An entity is considered marked after the first declaration that marks it.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.2p4'></a>
|
|
<pre>4 A nodiscard call is a function call expression that calls a function previously declared with attribute
|
|
nodiscard, or whose return type is a structure, union, or enumeration type marked with attribute
|
|
nodiscard. Evaluation of a nodiscard call as a void expression (<a href='#6.8.3'>6.8.3</a>) is discouraged unless explicitly
|
|
cast to void. Implementations are encouraged to issue a diagnostic in such cases. This is typically
|
|
because immediately discarding the return value of a nodiscard call has surprising consequences.
|
|
</pre>
|
|
<a name='6.7.12.2p5'></a>
|
|
<pre>5 The diagnostic message should include text provided by the string literal within the attribute
|
|
argument clause of any nodiscard attribute applied to the name or entity.
|
|
</pre>
|
|
<a name='6.7.12.2p6'></a>
|
|
<pre>6 EXAMPLE 1
|
|
|
|
struct [[nodiscard]] error_info { /*...*/ };
|
|
struct error_info enable_missile_safety_mode(void);
|
|
void launch_missiles(void);
|
|
void test_missiles(void) {
|
|
enable_missile_safety_mode();
|
|
launch_missiles();
|
|
}
|
|
|
|
A diagnostic for the call to enable_missile_safety_mode is encouraged.
|
|
</pre>
|
|
<a name='6.7.12.2p7'></a>
|
|
<pre>7 EXAMPLE 2
|
|
|
|
[[nodiscard]] int important_func(void);
|
|
void call(void) {
|
|
int i = important_func();
|
|
}
|
|
|
|
No diagnostic for the call to important_func is encouraged despite the value of i not being used.
|
|
</pre>
|
|
<a name='6.7.12.2p8'></a>
|
|
<pre>8 EXAMPLE 3
|
|
|
|
[[nodiscard("must check armed state")]]
|
|
bool arm_detonator(int);
|
|
|
|
void call(void) {
|
|
arm_detonator(3);
|
|
detonate();
|
|
}
|
|
|
|
A diagnostic for the call toarm_detonator using the string literal "must check armed state" from the attribute argument
|
|
clause is encouraged.
|
|
|
|
</pre>
|
|
<a name='6.7.12.3'></a>
|
|
<hr>
|
|
<h3>6.7.12.3 [The maybe_unused attribute]</h3>
|
|
<a name='6.7.12.3p1'></a>
|
|
<pre>1 Constraints
|
|
The maybe_unused attribute shall be applied to the declaration of a structure, a union, a typedef
|
|
name, a variable, a structure or union member, a function, an enumeration, an enumerator, or a label.
|
|
No attribute argument clause shall be present.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.3p2'></a>
|
|
<pre>2 The maybe_unused attribute indicates that a name or entity is possibly intentionally unused.
|
|
</pre>
|
|
<a name='6.7.12.3p3'></a>
|
|
<pre>3 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 202106L
|
|
when given maybe_unused as the pp-tokens operand.
|
|
A name or entity declared without the maybe_unused attribute can later be redeclared with the
|
|
attribute and vice versa. An entity is considered marked with the attribute after the first declaration
|
|
that marks it.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.3p4'></a>
|
|
<pre>4 For an entity marked maybe_unused, implementations are encouraged not to emit a diagnostic that
|
|
the entity is unused, or that the entity is used despite the presence of the attribute.
|
|
</pre>
|
|
<a name='6.7.12.3p5'></a>
|
|
<pre>5 EXAMPLE
|
|
|
|
[[maybe_unused]] void f([[maybe_unused]] int i) {
|
|
[[maybe_unused]] int j = i + 100;
|
|
assert(j);
|
|
}
|
|
|
|
Implementations are encouraged not to diagnose that j is unused, whether or not NDEBUG is defined.
|
|
|
|
</pre>
|
|
<a name='6.7.12.4'></a>
|
|
<hr>
|
|
<h3>6.7.12.4 [The deprecated attribute]</h3>
|
|
<a name='6.7.12.4p1'></a>
|
|
<pre>1 Constraints
|
|
The deprecated attribute shall be applied to the declaration of a structure, a union, a typedef name,
|
|
a variable, a structure or union member, a function, an enumeration, or an enumerator.
|
|
</pre>
|
|
<a name='6.7.12.4p2'></a>
|
|
<pre>2 If an attribute argument clause is present, it shall have the form:
|
|
( string-literal )
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.4p3'></a>
|
|
<pre>3 The deprecated attribute can be used to mark names and entities whose use is still allowed, but is
|
|
discouraged for some reason. <a href='#FOOTNOTE.188'><sup>[188]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.188'>
|
|
<pre><i><b>Footnote 188)</b> In particular, deprecated is appropriate for names and entities that are obsolescent, insecure, unsafe, or otherwise unfit
|
|
for purpose.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.4p4'></a>
|
|
<pre>4 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 201904L
|
|
when given deprecated as the pp-tokens operand.
|
|
</pre>
|
|
<a name='6.7.12.4p5'></a>
|
|
<pre>5 A name or entity declared without the deprecated attribute can later be redeclared with the attribute
|
|
and vice versa. An entity is considered marked with the attribute after the first declaration that
|
|
marks it.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.4p6'></a>
|
|
<pre>6 Implementations should use the deprecated attribute to produce a diagnostic message in case the
|
|
program refers to a name or entity other than to declare it, after a declaration that specifies the
|
|
attribute, when the reference to the name or entity is not within the context of a related deprecated
|
|
entity. The diagnostic message should include text provided by the string literal within the attribute
|
|
argument clause of any deprecated attribute applied to the name or entity.
|
|
</pre>
|
|
<a name='6.7.12.4p7'></a>
|
|
<pre>7 EXAMPLE
|
|
|
|
struct [[deprecated]] S {
|
|
int a;
|
|
};
|
|
|
|
enum [[deprecated]] E1 {
|
|
one
|
|
};
|
|
enum E2 {
|
|
two [[deprecated("use ’three’ instead")]],
|
|
three
|
|
};
|
|
|
|
[[deprecated]] typedef int Foo;
|
|
|
|
void f1(struct S s) { // Diagnose use of S
|
|
int i = one; // Diagnose use of E1
|
|
int j = two; // Diagnose use of two: "use ’three’ instead"
|
|
int k = three;
|
|
Foo f; // Diagnose use of Foo
|
|
}
|
|
|
|
[[deprecated]] void f2(struct S s) {
|
|
int i = one;
|
|
int j = two;
|
|
int k = three;
|
|
Foo f;
|
|
}
|
|
|
|
struct [[deprecated]] T {
|
|
Foo f;
|
|
struct S s;
|
|
};
|
|
|
|
|
|
Implementations are encouraged to diagnose the use of deprecated entities within a context which is not itself deprecated, as
|
|
indicated for function f1, but not to diagnose within function f2 and struct T, as they are themselves deprecated.
|
|
|
|
</pre>
|
|
<a name='6.7.12.5'></a>
|
|
<hr>
|
|
<h3>6.7.12.5 [The fallthrough attribute]</h3>
|
|
<a name='6.7.12.5p1'></a>
|
|
<pre>1 Constraints
|
|
The attribute token fallthrough shall only appear in an attribute declaration (<a href='#6.7'>6.7</a>); such a declara-
|
|
tion is a fallthrough declaration. No attribute argument clause shall be present. A fallthrough decla-
|
|
ration may only appear within an enclosing switch statement (<a href='#6.8.4.2'>6.8.4.2</a>). The next block item(<a href='#6.8.2'>6.8.2</a>)
|
|
that would be encountered after a fallthrough declaration shall be a case label or default label
|
|
associated with the smallest enclosing switch statement.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.5p2'></a>
|
|
<pre>2 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 201904L
|
|
when given fallthrough as the pp-tokens operand.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.5p3'></a>
|
|
<pre>3 The use of a fallthrough declaration is intended to suppress a diagnostic that an implementation
|
|
might otherwise issue for a case or default label that is reachable from another case or default
|
|
label along some path of execution. Implementations are encouraged to issue a diagnostic if a
|
|
fallthrough declaration is not dynamically reachable.
|
|
</pre>
|
|
<a name='6.7.12.5p4'></a>
|
|
<pre>4 EXAMPLE
|
|
|
|
void f(int n) {
|
|
void g(void), h(void), i(void);
|
|
switch (n) {
|
|
case 1: /* diagnostic on fallthrough discouraged */
|
|
case 2:
|
|
g();
|
|
[[fallthrough]];
|
|
case 3: /* diagnostic on fallthrough discouraged */
|
|
h();
|
|
case 4: /* fallthrough diagnostic encouraged */
|
|
i();
|
|
[[fallthrough]]; /* constraint violation */
|
|
}
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.12.6'></a>
|
|
<hr>
|
|
<h3>6.7.12.6 [The noreturn and _Noreturn attributes]</h3>
|
|
<a name='6.7.12.6p1'></a>
|
|
<pre>1 Description
|
|
When _Noreturn is used as an attribute token (instead of a function specifier), the constraints and
|
|
semantics are identical to that of the noreturn attribute token. Use of _Noreturn as an attribute
|
|
token is an obsolescent feature<a href='#FOOTNOTE.189'><sup>[189]</sup></a> .
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='FOOTNOTE.189'>
|
|
<pre><i><b>Footnote 189)</b> [[_Noreturn]] and [[noreturn]] are equivalent attributes to support code that includes <stdnoreturn.h>, because
|
|
that header defines noreturn as a macro that expands to _Noreturn .
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.6p2'></a>
|
|
<pre>2 The noreturn attribute shall be applied to the identifier in a function declaration. No attribute
|
|
argument clause shall be present.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.12.6p3'></a>
|
|
<pre>3 The first declaration of a function shall specify the noreturn attribute if any declaration of that
|
|
function specifies the noreturn attribute. If a function is declared with the noreturn attribute in
|
|
one translation unit and the same function is declared without the noreturn attribute in another
|
|
translation unit, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.7.12.6p4'></a>
|
|
<pre>4 If a function f is called where f was previously declared with the noreturn attribute and f eventually
|
|
returns, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.7.12.6p5'></a>
|
|
<pre>5 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 202202L
|
|
when given noreturn as the pp-tokens operand.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.6p6'></a>
|
|
<pre>6 The implementation should produce a diagnostic message for a function declared with a noreturn
|
|
attribute that appears to be capable of returning to its caller.
|
|
</pre>
|
|
<a name='6.7.12.6p7'></a>
|
|
<pre>7 EXAMPLE
|
|
|
|
[[noreturn]] void f(void) {
|
|
abort(); // ok
|
|
}
|
|
|
|
[[noreturn]] void g(int i) { // causes undefined behavior if i <= 0
|
|
if (i > 0) abort();
|
|
}
|
|
|
|
[[noreturn]] int h(void);
|
|
|
|
Implementations are encouraged to diagnose the definition of g() because it is capable of returning to its caller. Implementa-
|
|
tions are similarly encouraged to diagnose the declaration of h() because it appears capable of returning to its caller due to
|
|
the non-void return type.
|
|
|
|
</pre>
|
|
<a name='6.7.12.7'></a>
|
|
<hr>
|
|
<h3>6.7.12.7 [Standard attributes for function types]</h3>
|
|
<a name='6.7.12.7p1'></a>
|
|
<pre>1 Constraints
|
|
The identifier in a standard function type attribute shall be one of:
|
|
|
|
unsequenced reproducible
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.12.7p2'></a>
|
|
<pre>2 An attribute for a function type shall be applied to a function declarator<a href='#FOOTNOTE.190'><sup>[190]</sup></a> or to a type specifier that
|
|
has a function type. The corresponding attribute is a property of the referred function type<a href='#FOOTNOTE.191'><sup>[191]</sup></a> . No
|
|
attribute argument clause shall be present.
|
|
Description
|
|
</pre>
|
|
<a name='FOOTNOTE.190'>
|
|
<pre><i><b>Footnote 190)</b> That is, they appear in the attributes right after the closing parenthesis of the parameter list, independently if the function
|
|
type is, for example, used directly to declare a function or if it is used in a pointer to function type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.191'>
|
|
<pre><i><b>Footnote 191)</b> If several declarations of the same function or function pointer are visible, regardless whether an attribute is present
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p3'></a>
|
|
<pre>3 The main purpose of the function type properties and attributes defined in this clause is to provide
|
|
the translator with information about the access of objects by a function such that certain properties
|
|
of function calls can be deduced; the properties distinguish read operations (stateless and inde-
|
|
pendent) and write operations (effectless, idempotent and reproducible) or a combination of both
|
|
(unsequenced). Although semantically attached to a function type, the attributes described are not
|
|
part of the prototype of a such annotated function, and redeclarations and conversions that drop
|
|
such an attribute are valid and constitute compatible types. Conversely, if a definition that does not
|
|
have the asserted property is accessed by a function declaration or a function pointer with a type
|
|
that has the attribute, the behavior is undefined<a href='#FOOTNOTE.192'><sup>[192]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.192'>
|
|
<pre><i><b>Footnote 192)</b> That is, the fact that a function has one of these properties is in general not determined by the specification of the
|
|
translation unit in which it is found; other translation units and specific run time conditions also condition the possible
|
|
assertion of the properties.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p4'></a>
|
|
<pre>4 To allow reordering of calls to functions as they are described here, possible access to objects with a
|
|
lifetime that starts before or ends after a call has to be restricted; effects on all objects that are accessed
|
|
during a function call are restricted to the same thread as the call and the based-on relation between
|
|
pointer parameters and lvalues (<a href='#6.7.3.1'>6.7.3.1</a>) models the fact that objects do not change inadvertently
|
|
during the call. In the following, an operation is said to be sequenced during a function call if it is
|
|
sequenced after the start of the function call<a href='#FOOTNOTE.193'><sup>[193]</sup></a> and before the call terminates. An object definition
|
|
of an object X in a function f escapes if an access to X happens while no call to f is active. An
|
|
object is local to a call to a function f if its lifetime starts and ends during the call or if it is defined
|
|
by f but does not escape. A function call and an object X synchronize if all accesses to X that are
|
|
not sequenced during the call happen before or after the call. Execution state that is described in
|
|
the library clause, such as the floating-point environment, conversion state, locale, input/output
|
|
streams, external files or errno account as objects; operations that allow to query this state, even
|
|
indirectly, account as lvalue conversions, and operations that allow to change this state account as
|
|
store operations.
|
|
</pre>
|
|
<a name='FOOTNOTE.193'>
|
|
<pre><i><b>Footnote 193)</b> The initializations of the parameters is sequenced during the function call.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p5'></a>
|
|
<pre>5 A function definition f is stateless if any definition of an object of static or thread storage duration in
|
|
f or in a function that is called by f is const but not volatile qualified.
|
|
</pre>
|
|
<a name='6.7.12.7p6'></a>
|
|
<pre>6 An object X is observed by a function call if both synchronize, if X is not local to the call, if X has a
|
|
lifetime that starts before the function call and if an access of X is sequenced during the call; the last
|
|
value of X, if any, that is stored before the call is said to be the value of X that is observed by the
|
|
call. A function pointer value f is independent if for any object X that is observed by some call to f
|
|
through an lvalue that is not based on a parameter of the call, then all accesses to X in all calls to
|
|
f during the same program execution observe the same value; otherwise if the access is based on
|
|
a pointer parameter, there shall be a unique such pointer parameter P such that any access to X
|
|
shall be to an lvalue that is based on P . A function definition is independent if the derived function
|
|
pointer value is independent.
|
|
</pre>
|
|
<a name='6.7.12.7p7'></a>
|
|
<pre>7 A store operation to an object X that is sequenced during a function call such that both synchronize
|
|
is said to be observable if X is not local to the call, if the lifetime of X ends after the call, if the stored
|
|
value is different from the value observed by the call, if any, and if it is the last value written before
|
|
the termination of the call. An evaluation of a function call<a href='#FOOTNOTE.194'><sup>[194]</sup></a> is effectless if any store operation
|
|
that is sequenced during the call is the modification of an object that synchronizes with the call; if
|
|
additionally the operation is observable, there shall be a unique pointer parameter P of the function
|
|
such that any access to X shall be to an lvalue that is based on P . A function pointer value f is
|
|
effectless if any evaluation of a function call that calls f is effectless. A function definition is effectless
|
|
if the derived function pointer value is effectless.
|
|
</pre>
|
|
<a name='FOOTNOTE.194'>
|
|
<pre><i><b>Footnote 194)</b> This considers the evaluation of the function call itself, not the evaluation of a full function call expression. Such an
|
|
evaluation is sequenced after all evaluations that determine f and the call arguments, if any, have been performed.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p8'></a>
|
|
<pre>8 An evaluation E is idempotent if a second evaluation of E can be sequenced immediately after the
|
|
original one without changing the resulting value, if any, or the observable state of the execution.
|
|
|
|
|
|
at several or just one of the declarators, it is attached to the type of the corresponding function definition, function pointer
|
|
object, or function pointer value.
|
|
A function pointer value f is idempotent if any evaluation of a function call<a href='#FOOTNOTE.195'><sup>[195]</sup></a> that calls f is
|
|
idempotent. A function definition is idempotent if the derived function pointer value is idempotent.
|
|
</pre>
|
|
<a name='FOOTNOTE.195'>
|
|
<pre><i><b>Footnote 195)</b> This considers the evaluation of the function call itself, not the evaluation of a full function call expression. Such an
|
|
evaluated is sequenced after all evaluations that determine f and the call arguments, if any, have been performed.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p9'></a>
|
|
<pre>9 A function is reproducible if it is effectless and idempotent; it is unsequenced if it is stateless, effectless,
|
|
idempotent and independent<a href='#FOOTNOTE.196'><sup>[196]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.196'>
|
|
<pre><i><b>Footnote 196)</b> A function call of an unsequenced function can be executed as early as the function pointer value, the values of the
|
|
arguments and all objects that are accessible through them, and all values of globally accessible state have been determined,
|
|
and it can be executed as late as the arguments and the objects they possibly target are unchanged and as any of its return
|
|
value or modified pointed-to arguments are accessed.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.12.7p10'></a>
|
|
<pre>10 NOTE The synchronization requirements with respect to any accessed object X for the independence of functions provide
|
|
boundaries up to which a function call may safely be reordered without changing the semantics of the program. If X is
|
|
const but not volatile qualified the reordering is unconstrained. If it is an object that is conditioned in an initialization
|
|
phase, for a single threaded program a synchronization is provided by the sequenced before relation and the reordering
|
|
may, in principle, move the call just after the initialization. For a multi-threaded program, synchronization guarantees can be
|
|
given by calls to synchronizing functions of the <threads.h> header or by an appropriate call to atomic_thread_fence at
|
|
the end of the initialization phase. If a function is known to be independent or effectless, adding restrict qualifications to
|
|
the declarations of all pointer parameters does not change the semantics of any call. Similarly, changing the memory order to
|
|
memory_order_relaxed for all atomic operations during a call to such a function preserves semantics.
|
|
|
|
</pre>
|
|
<a name='6.7.12.7p11'></a>
|
|
<pre>11 NOTE In general the functions provided by the <math.h> header do not have the properties that are defined above; many
|
|
of them change the floating-point state or errno when they encounter an error (so they have observable side effects) and the
|
|
results of most of them depend on execution wide state such as the rounding direction mode (so they are not independent).
|
|
Whether a particular C library function is reproducible or unsequenced additionally often depends on properties of the
|
|
implementation, such as implementation-defined behavior for certain error conditions.
|
|
|
|
Recommended Practice
|
|
</pre>
|
|
<a name='6.7.12.7p12'></a>
|
|
<pre>12 If possible, it is recommended that implementations diagnose if an attribute of this clause is applied
|
|
to a function definition that does not have the corresponding property. It is recommended that appli-
|
|
cations that assert the independent or effectless properties for functions qualify pointer parameters
|
|
with restrict.
|
|
Forward references: errors <errno.h> (<a href='#7.5'>7.5</a>), floating-point environment <fenv.h> (<a href='#7.6'>7.6</a>), localiza-
|
|
tion <locale.h> (<a href='#7.11'>7.11</a>), mathematics <math.h> (<a href='#7.12'>7.12</a>), fences (<a href='#7.17.4'>7.17.4</a>), input/output <stdio.h>
|
|
(<a href='#7.23'>7.23</a>), threads <threads.h> (<a href='#7.28'>7.28</a>), extended multibyte and wide character utilities <wchar.h>
|
|
(<a href='#7.31'>7.31</a>).
|
|
|
|
</pre>
|
|
<a name='6.7.12.7.1'></a>
|
|
<hr>
|
|
<h3>6.7.12.7.1 [The reproducible type attribute]</h3>
|
|
<a name='6.7.12.7.1p1'></a>
|
|
<pre>1 Description
|
|
The reproducible type attribute asserts that a function or pointed-to function with that type is
|
|
reproducible.
|
|
</pre>
|
|
<a name='6.7.12.7.1p2'></a>
|
|
<pre>2 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 202207L
|
|
when given reproducible as the pp-tokens operand.
|
|
</pre>
|
|
<a name='6.7.12.7.1p3'></a>
|
|
<pre>3 EXAMPLE 1 The attribute in the following function declaration asserts that two consecutive calls to the function will result
|
|
in the same return value. Changes to the abstract state during the call are possible as long as they are not observable, but
|
|
no other side effects will occur. Thus the function definition may for example use local objects of static or thread storage
|
|
duration to keep track of the arguments for which the function has been called and cache their computed return values.
|
|
|
|
size_t hash(char const[static 32]) [[reproducible]];
|
|
|
|
|
|
</pre>
|
|
<a name='6.7.12.7.2'></a>
|
|
<hr>
|
|
<h3>6.7.12.7.2 [The unsequenced type attribute]</h3>
|
|
<a name='6.7.12.7.2p1'></a>
|
|
<pre>1 Description
|
|
The unsequenced type attribute asserts that a function or pointed-to function with that type is
|
|
unsequenced.
|
|
</pre>
|
|
<a name='6.7.12.7.2p2'></a>
|
|
<pre>2 The __has_c_attribute conditional inclusion expression (<a href='#6.10.1'>6.10.1</a>) shall return the value 202207L
|
|
when given unsequenced as the pp-tokens operand.
|
|
</pre>
|
|
<a name='6.7.12.7.2p3'></a>
|
|
<pre>3 NOTE The unsequenced type attribute asserts strong properties for the such typed function, in particular that certain
|
|
sequencing requirements for function calls can be relaxed without affecting the state of the abstract machine. Thereby, calls
|
|
to such functions are natural candidates for optimization techniques such as common subexpression elimination, local
|
|
memoization or lazy evaluation.
|
|
</pre>
|
|
<a name='6.7.12.7.2p4'></a>
|
|
<pre>4 NOTE A proof of validity of the annotation of a function type with the unsequenced attribute may depend on the property
|
|
if a derived function pointer escapes the translation unit or not. For a function with internal linkage where no function
|
|
pointer escapes the translation unit, all calling contexts are known and it is possible, in principle, to prove that no control flow
|
|
exists such that a library function is called with arguments that trigger an exceptional condition. For a function with external
|
|
linkage such a proof may not be possible and the use of such a function then has to ensure that no exceptional condition
|
|
results from the provided arguments.
|
|
</pre>
|
|
<a name='6.7.12.7.2p5'></a>
|
|
<pre>5 NOTE The unsequenced property does not necessarily imply that the function is reentrant or that calls can be executed
|
|
concurrently. This is because an unsequenced function can read from and write to objects of static storage duration, as long
|
|
as no change is observable after a call terminates.
|
|
</pre>
|
|
<a name='6.7.12.7.2p6'></a>
|
|
<pre>6 EXAMPLE 1 The attribute in the following function declaration asserts that it doesn’t depend on any modifiable state of the
|
|
abstract machine. Calls to the function can be executed out of sequence before the return value is needed and two calls to the
|
|
function with the same argument value will result in the same return value.
|
|
|
|
bool tendency(signed char) [[unsequenced]];
|
|
|
|
Therefore such a call for a given argument value needs only to be executed once and the returned value can be reused when
|
|
appropriate. For example, calls for all possible argument values can be executed during program startup and tabulated.
|
|
</pre>
|
|
<a name='6.7.12.7.2p7'></a>
|
|
<pre>7 EXAMPLE 2 The attribute in the following function declaration asserts that it doesn’t depend on any modifiable state of
|
|
the abstract machine. Within the same thread, calls to the function can be executed out of sequence before the return value
|
|
is needed and two calls to the function will result in the same pointer return value. Therefore such a call needs only to be
|
|
executed once in a given thread and the returned pointer value can be reused when appropriate. For example, a single
|
|
call can be executed during thread startup and the return value p and the value of the object *p of type toto const can be
|
|
cached.
|
|
|
|
typedef struct toto toto;
|
|
toto const* toto_zero(void) [[unsequenced]];
|
|
|
|
</pre>
|
|
<a name='6.7.12.7.2p8'></a>
|
|
<pre>8 EXAMPLE 3 The unsequenced property of a function f can be locally asserted within a function g that uses it. For example
|
|
the library function sqrt is in generally not unsequenced because a negative argument will raise a domain error and because
|
|
the result may depend on the rounding mode. Nevertheless in contexts similar to the following function a user can prove
|
|
that it will not be called with invalid arguments, and, that the floating-point environment has the same value for all calls.
|
|
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
|
|
inline double distance (double const x[static 2]) [[reproducible]] {
|
|
#pragma FP_CONTRACT OFF
|
|
#pragma FENV_ROUND FE_TONEAREST
|
|
// We assert that sqrt will not be called with invalid arguments
|
|
// and the result only depends on the argument value.
|
|
extern typeof(sqrt) [[unsequenced]] sqrt;
|
|
return sqrt(x[0]*x[0] + x[1]*x[1]);
|
|
}
|
|
|
|
The function distance potentially has the side effect of changing the floating-point environment. Nevertheless the floating
|
|
environment is thread local, thus a change to that state outside the function is sequenced with the change within and
|
|
additionally the observed value is restored when the function returns. Thus this side effect is not observable for a caller.
|
|
Overall the function distance is stateless, effectless and idempotent and in particular it is reproducible as the attribute
|
|
indicates. Because the function can be called in a context where the floating-point environment has different state, distance
|
|
is not independent and thus it is also not unsequenced. Nevertheless, adding an unsequenced attribute where this is justified
|
|
may introduce optimization opportunities.
|
|
|
|
double g (double y[static 1], double const x[static 2]) {
|
|
// We assert that distance will not see different states of the floating
|
|
// point environment.
|
|
extern double distance (double const x[static 2]) [[unsequenced]];
|
|
y[0] = distance(x);
|
|
...
|
|
return distance(x); // replacement by y[0] is valid
|
|
}
|
|
</pre>
|
|
<a name='6.8'></a>
|
|
<hr>
|
|
<h3>6.8 [Statements and blocks]</h3>
|
|
<a name='6.8p1'></a>
|
|
<pre>1 Syntax
|
|
statement:
|
|
labeled-statement
|
|
unlabeled-statement
|
|
unlabeled-statement:
|
|
expression-statement
|
|
attribute-specifier-sequenceopt primary-block
|
|
attribute-specifier-sequenceopt jump-statement
|
|
primary-block:
|
|
compound-statement
|
|
selection-statement
|
|
iteration-statement
|
|
|
|
|
|
|
|
secondary-block:
|
|
statement
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8p2'></a>
|
|
<pre>2 A statement specifies an action to be performed. Except as indicated, statements are executed in
|
|
sequence. The optional attribute specifier sequence appertains to the respective statement.
|
|
</pre>
|
|
<a name='6.8p3'></a>
|
|
<pre>3 A block is either a primary block, a secondary block, or the block associated with a function definition;
|
|
it allows a set of declarations and statements to be grouped into one syntactic unit. Whenever a
|
|
block B appears in the syntax production as part of the definition of an enclosing block A, scopes of
|
|
identifiers and lifetimes of objects that are associated with B do not extend to the parts of A that are
|
|
outside of B. The initializers of objects that have automatic storage duration, and the variable length
|
|
array declarators of ordinary identifiers with block scope, are evaluated and the values are stored in
|
|
the objects (the representation of objects without an initializer becomes indeterminate) each time the
|
|
declaration is reached in the order of execution, as if it were a statement, and within each declaration
|
|
in the order that declarators appear.
|
|
</pre>
|
|
<a name='6.8p4'></a>
|
|
<pre>4 A full expression is an expression that is not part of another expression, nor part of a declarator
|
|
or abstract declarator. There is also an implicit full expression in which the non-constant size
|
|
expressions for a variably modified type are evaluated; within that full expression, the evaluation of
|
|
different size expressions are unsequenced with respect to one another. There is a sequence point
|
|
between the evaluation of a full expression and the evaluation of the next full expression to be
|
|
evaluated.
|
|
</pre>
|
|
<a name='6.8p5'></a>
|
|
<pre>5 NOTE Each of the following is a full expression:
|
|
|
|
— a full declarator for a variably modified type,
|
|
|
|
— an initializer that is not part of a compound literal,
|
|
|
|
— the expression in an expression statement,
|
|
|
|
— the controlling expression of a selection statement (if or switch),
|
|
|
|
— the controlling expression of a while or do statement,
|
|
|
|
— each of the (optional) expressions of a for statement,
|
|
|
|
— the (optional) expression in a return statement.
|
|
|
|
While a constant expression satisfies the definition of a full expression, evaluating it does not depend on nor produce any
|
|
side effects, so the sequencing implications of being a full expression are not relevant to a constant expression.
|
|
|
|
Forward references: expression and null statements (<a href='#6.8.3'>6.8.3</a>), selection statements (<a href='#6.8.4'>6.8.4</a>), iteration
|
|
statements (<a href='#6.8.5'>6.8.5</a>), the return statement (<a href='#6.8.6.4'>6.8.6.4</a>).
|
|
</pre>
|
|
<a name='6.8.1'></a>
|
|
<hr>
|
|
<h3>6.8.1 [Labeled statements]</h3>
|
|
<a name='6.8.1p1'></a>
|
|
<pre>1 Syntax
|
|
label:
|
|
attribute-specifier-sequenceopt identifier :
|
|
attribute-specifier-sequenceopt case constant-expression :
|
|
attribute-specifier-sequenceopt default :
|
|
labeled-statement:
|
|
label statement
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.8.1p2'></a>
|
|
<pre>2 A case or default label shall appear only in a switch statement. Further constraints on such labels
|
|
are discussed under the switch statement.
|
|
</pre>
|
|
<a name='6.8.1p3'></a>
|
|
<pre>3 Label names shall be unique within a function.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.1p4'></a>
|
|
<pre>4 Any statement may be preceded by a prefix that declares an identifier as a label name. The optional
|
|
attribute specifier sequence appertains to the label. Labels in themselves do not alter the flow of
|
|
control, which continues unimpeded across them.
|
|
Forward references: the goto statement (<a href='#6.8.6.1'>6.8.6.1</a>), the switch statement (<a href='#6.8.4.2'>6.8.4.2</a>) .
|
|
|
|
</pre>
|
|
<a name='6.8.2'></a>
|
|
<hr>
|
|
<h3>6.8.2 [Compound statement]</h3>
|
|
<a name='6.8.2p1'></a>
|
|
<pre>1 Syntax
|
|
compound-statement:
|
|
{ block-item-listopt }
|
|
block-item-list:
|
|
block-item
|
|
block-item-list block-item
|
|
block-item:
|
|
declaration
|
|
unlabeled-statement
|
|
label
|
|
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.2p2'></a>
|
|
<pre>2 A compound statement that is a function body together with the parameter type list and the optional
|
|
attribute specifier sequence between them forms the block associated with the function definition
|
|
in which it appears. Otherwise, it is a block that is different from any other block. A label shall be
|
|
translated as if it were followed by a null statement.
|
|
|
|
</pre>
|
|
<a name='6.8.3'></a>
|
|
<hr>
|
|
<h3>6.8.3 [Expression and null statements]</h3>
|
|
<a name='6.8.3p1'></a>
|
|
<pre>1 Syntax
|
|
expression-statement:
|
|
expressionopt ;
|
|
attribute-specifier-sequence expression ;
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.3p2'></a>
|
|
<pre>2 The attribute specifier sequence appertains to the expression. The expression in an expression
|
|
statement is evaluated as a void expression for its side effects.<a href='#FOOTNOTE.197'><sup>[197]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.197'>
|
|
<pre><i><b>Footnote 197)</b> Such as assignments, and function calls which have side effects.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.3p3'></a>
|
|
<pre>3 A null statement (consisting of just a semicolon) performs no operations.
|
|
</pre>
|
|
<a name='6.8.3p4'></a>
|
|
<pre>4 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the discarding of its value can
|
|
be made explicit by converting the expression to a void expression by means of a cast:
|
|
int p(int);
|
|
/* ... */
|
|
(void)p(0);
|
|
|
|
|
|
</pre>
|
|
<a name='6.8.3p5'></a>
|
|
<pre>5 EXAMPLE 2 In the program fragment
|
|
|
|
char *s;
|
|
/* ... */
|
|
while (*s++ != ’\0’)
|
|
;
|
|
|
|
|
|
a null statement is used to supply an empty loop body to the iteration statement.
|
|
|
|
Forward references: iteration statements (<a href='#6.8.5'>6.8.5</a>).
|
|
|
|
</pre>
|
|
<a name='6.8.4'></a>
|
|
<hr>
|
|
<h3>6.8.4 [Selection statements]</h3>
|
|
<a name='6.8.4p1'></a>
|
|
<pre>1 Syntax
|
|
selection-statement:
|
|
if ( expression ) secondary-block
|
|
if ( expression ) secondary-block else secondary-block
|
|
switch ( expression ) secondary-block
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.4p2'></a>
|
|
<pre>2 A selection statement selects among a set of secondary blocks depending on the value of a controlling
|
|
expression.
|
|
|
|
</pre>
|
|
<a name='6.8.4.1'></a>
|
|
<hr>
|
|
<h3>6.8.4.1 [The if statement]</h3>
|
|
<a name='6.8.4.1p1'></a>
|
|
<pre>1 Constraints
|
|
The controlling expression of an if statement shall have scalar type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.4.1p2'></a>
|
|
<pre>2 In both forms, the first substatement is executed if the expression compares unequal to 0. In the
|
|
else form, the second substatement is executed if the expression compares equal to 0. If the first
|
|
substatement is reached via a label, the second substatement is not executed.
|
|
</pre>
|
|
<a name='6.8.4.1p3'></a>
|
|
<pre>3 An else is associated with the lexically nearest preceding if that is allowed by the syntax.
|
|
|
|
</pre>
|
|
<a name='6.8.4.2'></a>
|
|
<hr>
|
|
<h3>6.8.4.2 [The switch statement]</h3>
|
|
<a name='6.8.4.2p1'></a>
|
|
<pre>1 Constraints
|
|
The controlling expression of a switch statement shall have integer type.
|
|
</pre>
|
|
<a name='6.8.4.2p2'></a>
|
|
<pre>2 If a switch statement has an associated case or default label within the scope of an identifier with
|
|
a variably modified type, the entire switch statement shall be within the scope of that identifier.<a href='#FOOTNOTE.198'><sup>[198]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.198'>
|
|
<pre><i><b>Footnote 198)</b> That is, the declaration either precedes the switch statement, or it follows the last case or default label associated with
|
|
the switch that is in the block containing the declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.4.2p3'></a>
|
|
<pre>3 The expression of each case label shall be an integer constant expression and no two of the case
|
|
constant expressions in the same switch statement shall have the same value after conversion.
|
|
There may be at most one default label in a switch statement. (Any enclosed switch statement
|
|
may have a default label or case constant expressions with values that duplicate case constant
|
|
expressions in the enclosing switch statement.)
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.4.2p4'></a>
|
|
<pre>4 A switch statement causes control to jump to, into, or past the statement that is the switch body,
|
|
depending on the value of a controlling expression, and on the presence of a default label and the
|
|
values of any case labels on or in the switch body. A case or default label is accessible only within
|
|
the closest enclosing switch statement.
|
|
</pre>
|
|
<a name='6.8.4.2p5'></a>
|
|
<pre>5 The integer promotions are performed on the controlling expression. The constant expression in
|
|
each case label is converted to the promoted type of the controlling expression. If a converted value
|
|
matches that of the promoted controlling expression, control jumps to the statement following the
|
|
matched case label. Otherwise, if there is a default label, control jumps to the statement following
|
|
the default label. If no converted case constant expression matches and there is no default label,
|
|
no part of the switch body is executed.
|
|
|
|
Implementation limits
|
|
</pre>
|
|
<a name='6.8.4.2p6'></a>
|
|
<pre>6 As discussed in <a href='#5.2.4.1'>5.2.4.1</a>, the implementation may limit the number of case values in a switch
|
|
statement.
|
|
</pre>
|
|
<a name='6.8.4.2p7'></a>
|
|
<pre>7 EXAMPLE In the artificial program fragment
|
|
|
|
switch (expr)
|
|
{
|
|
int i = 4;
|
|
f(i);
|
|
case 0:
|
|
i = 17;
|
|
/* falls through into default code */
|
|
default:
|
|
printf("%d\n", i);
|
|
}
|
|
|
|
|
|
the object whose identifier is i exists with automatic storage duration (within the block) but is never initialized, and thus if
|
|
the controlling expression has a nonzero value, the call to the printf function will access an object with an indeterminate
|
|
representation. Similarly, the call to the function f cannot be reached.
|
|
|
|
</pre>
|
|
<a name='6.8.5'></a>
|
|
<hr>
|
|
<h3>6.8.5 [Iteration statements]</h3>
|
|
<a name='6.8.5p1'></a>
|
|
<pre>1 Syntax
|
|
iteration-statement:
|
|
while ( expression ) secondary-block
|
|
do secondary-block while ( expression ) ;
|
|
for ( expressionopt ; expressionopt ; expressionopt ) secondary-block
|
|
for ( declaration expressionopt ; expressionopt ) secondary-block
|
|
Constraints
|
|
</pre>
|
|
<a name='6.8.5p2'></a>
|
|
<pre>2 The controlling expression of an iteration statement shall have scalar type.
|
|
</pre>
|
|
<a name='6.8.5p3'></a>
|
|
<pre>3 The declaration part of a for statement shall only declare identifiers for objects having storage class
|
|
auto or register.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.5p4'></a>
|
|
<pre>4 An iteration statement causes a secondary block called the loop body to be executed repeatedly until
|
|
the controlling expression compares equal to 0. The repetition occurs regardless of whether the loop
|
|
body is entered from the iteration statement or by a jump<a href='#FOOTNOTE.199'><sup>[199]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.199'>
|
|
<pre><i><b>Footnote 199)</b> Code jumped over is not executed. In particular, the controlling expression of a for or while statement is not evaluated
|
|
before entering the loop body, nor is clause-1 of a for statement.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.5p5'></a>
|
|
<pre>5 An iteration statement may be assumed by the implementation to terminate if its controlling
|
|
expression is not a constant expression<a href='#FOOTNOTE.200'><sup>[200]</sup></a> , and none of the following operations are performed in its
|
|
body, controlling expression or (in the case of a for statement) its expression-3201) :
|
|
|
|
— input/output operations
|
|
|
|
— accessing a volatile object
|
|
|
|
— synchronization or atomic operations.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.200'>
|
|
<pre><i><b>Footnote 200)</b> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.5.1'></a>
|
|
<hr>
|
|
<h3>6.8.5.1 [The while statement]</h3>
|
|
<a name='6.8.5.1p1'></a>
|
|
<pre>1 The evaluation of the controlling expression takes place before each execution of the loop body.
|
|
|
|
</pre>
|
|
<a name='6.8.5.2'></a>
|
|
<hr>
|
|
<h3>6.8.5.2 [The do statement]</h3>
|
|
<a name='6.8.5.2p1'></a>
|
|
<pre>1 The evaluation of the controlling expression takes place after each execution of the loop body.
|
|
|
|
</pre>
|
|
<a name='6.8.5.3'></a>
|
|
<hr>
|
|
<h3>6.8.5.3 [The for statement]</h3>
|
|
<a name='6.8.5.3p1'></a>
|
|
<pre>1 The statement
|
|
for (clause-1; expression-2; expression-3) statement
|
|
|
|
|
|
behaves as follows: The expression expression-2 is the controlling expression that is evaluated before
|
|
each execution of the loop body. The expression expression-3 is evaluated as a void expression after
|
|
each execution of the loop body. If clause-1 is a declaration, the scope of any identifiers it declares
|
|
is the remainder of the declaration and the entire loop, including the other two expressions; it is
|
|
reached in the order of execution before the first evaluation of the controlling expression. If clause-1
|
|
is an expression, it is evaluated as a void expression before the first evaluation of the controlling
|
|
expression.<a href='#FOOTNOTE.202'><sup>[202]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.202'>
|
|
<pre><i><b>Footnote 202)</b> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in the loop; the
|
|
controlling expression, expression-2, specifies an evaluation made before each iteration, such that execution of the loop
|
|
continues until the expression compares equal to 0; and expression-3 specifies an operation (such as incrementing) that is
|
|
performed after each iteration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.5.3p2'></a>
|
|
<pre>2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a nonzero
|
|
constant.
|
|
|
|
</pre>
|
|
<a name='6.8.6'></a>
|
|
<hr>
|
|
<h3>6.8.6 [Jump statements]</h3>
|
|
<a name='6.8.6p1'></a>
|
|
<pre>1 Syntax
|
|
jump-statement:
|
|
goto identifier ;
|
|
continue ;
|
|
break ;
|
|
return expressionopt ;
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.6p2'></a>
|
|
<pre>2 A jump statement causes an unconditional jump to another place.
|
|
|
|
</pre>
|
|
<a name='6.8.6.1'></a>
|
|
<hr>
|
|
<h3>6.8.6.1 [The goto statement]</h3>
|
|
<a name='6.8.6.1p1'></a>
|
|
<pre>1 Constraints
|
|
The identifier in a goto statement shall name a label located somewhere in the enclosing function. A
|
|
goto statement shall not jump from outside the scope of an identifier having a variably modified
|
|
type to inside the scope of that identifier.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.6.1p2'></a>
|
|
<pre>2 A goto statement causes an unconditional jump to the statement prefixed by the named label in the
|
|
enclosing function.
|
|
</pre>
|
|
<a name='6.8.6.1p3'></a>
|
|
<pre>3 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The following outline
|
|
presents one possible approach to a problem based on these three assumptions:
|
|
|
|
1. The general initialization code accesses objects only visible to the current function.
|
|
2. The general initialization code is too large to warrant duplication.
|
|
3. The code to determine the next operation is at the head of the loop. (To allow it to be reached by continue statements,
|
|
for example.)
|
|
|
|
/* ... */
|
|
goto first_time;
|
|
for (;;) {
|
|
// determine next operation
|
|
/* ... */
|
|
if (need to reinitialize) {
|
|
// reinitialize-only code
|
|
/* ... */
|
|
first_time:
|
|
// general initialization code
|
|
/* ... */
|
|
continue;
|
|
}
|
|
// handle other operations
|
|
/* ... */
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.8.6.1p4'></a>
|
|
<pre>4 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably modified types. A jump
|
|
within the scope, however, is permitted.
|
|
|
|
goto lab3; // invalid: going INTO scope of VLA.
|
|
{
|
|
double a[n];
|
|
a[j] = 4.4;
|
|
lab3:
|
|
a[j] = <a href='#3.3'>3.3</a>;
|
|
goto lab4; // valid: going WITHIN scope of VLA.
|
|
a[j] = 5.5;
|
|
lab4:
|
|
a[j] = <a href='#6.6'>6.6</a>;
|
|
}
|
|
goto lab4; // invalid: going INTO scope of VLA.
|
|
|
|
|
|
</pre>
|
|
<a name='6.8.6.2'></a>
|
|
<hr>
|
|
<h3>6.8.6.2 [The continue statement]</h3>
|
|
<a name='6.8.6.2p1'></a>
|
|
<pre>1 Constraints
|
|
A continue statement shall appear only in or as a loop body.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.6.2p2'></a>
|
|
<pre>2 A continue statement causes a jump to the loop-continuation portion of the smallest enclosing
|
|
iteration statement; that is, to the end of the loop body. More precisely, in each of the statements
|
|
|
|
|
|
while (/* ... */) { do { for (/* ... */) {
|
|
/* ... */ /* ... */ /* ... */
|
|
continue; continue; continue;
|
|
/* ... */ /* ... */ /* ... */
|
|
contin: contin: contin:
|
|
} } while (/* ... */); }
|
|
|
|
|
|
|
|
unless the continue statement shown is in an enclosed iteration statement (in which case it is
|
|
interpreted within that statement), it is equivalent to goto contin;.<a href='#FOOTNOTE.203'><sup>[203]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.203'>
|
|
<pre><i><b>Footnote 203)</b> Following the contin: label in the 2nd example is a null statement. The null statement in the first and third example is
|
|
implied by the label (<a href='#6.8.2'>6.8.2</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.6.3'></a>
|
|
<hr>
|
|
<h3>6.8.6.3 [The break statement]</h3>
|
|
<a name='6.8.6.3p1'></a>
|
|
<pre>1 Constraints
|
|
A break statement shall appear only in or as a switch body or loop body.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.6.3p2'></a>
|
|
<pre>2 A break statement terminates execution of the smallest enclosing switch or iteration statement.
|
|
|
|
</pre>
|
|
<a name='6.8.6.4'></a>
|
|
<hr>
|
|
<h3>6.8.6.4 [The return statement]</h3>
|
|
<a name='6.8.6.4p1'></a>
|
|
<pre>1 Constraints
|
|
A return statement with an expression shall not appear in a function whose return type is void. A
|
|
return statement without an expression shall only appear in a function whose return type is void .
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.6.4p2'></a>
|
|
<pre>2 A return statement terminates execution of the current function and returns control to its caller. A
|
|
function may have any number of return statements.
|
|
</pre>
|
|
<a name='6.8.6.4p3'></a>
|
|
<pre>3 If a return statement with an expression is executed, the value of the expression is returned to the
|
|
caller as the value of the function call expression. If the expression has a type different from the
|
|
return type of the function in which it appears, the value is converted as if by assignment to an
|
|
object having the return type of the function.<a href='#FOOTNOTE.204'><sup>[204]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.204'>
|
|
<pre><i><b>Footnote 204)</b> The return statement is not an assignment. The overlap restriction of <a href='#6.5.16.1'>6.5.16.1</a> does not apply to the case of function
|
|
return. The representation of floating-point values can have wider range or precision than implied by the type; a cast can be
|
|
used to remove this extra range and precision.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.8.6.4p4'></a>
|
|
<pre>4 EXAMPLE In:
|
|
|
|
struct s { double i; } f(void);
|
|
union {
|
|
struct {
|
|
int f1;
|
|
struct s f2;
|
|
} u1;
|
|
struct {
|
|
struct s f3;
|
|
int f4;
|
|
} u2;
|
|
} g;
|
|
|
|
struct s f(void)
|
|
{
|
|
return g.u1.f2;
|
|
}
|
|
|
|
/* ... */
|
|
g.u2.f3 = f();
|
|
|
|
there is no undefined behavior, although there would be if the assignment were done directly (without using a function call
|
|
to fetch the value).
|
|
</pre>
|
|
<a name='6.9'></a>
|
|
<hr>
|
|
<h3>6.9 [External definitions]</h3>
|
|
<a name='6.9p1'></a>
|
|
<pre>1 Syntax
|
|
translation-unit:
|
|
external-declaration
|
|
translation-unit external-declaration
|
|
|
|
external-declaration:
|
|
function-definition
|
|
declaration
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.9p2'></a>
|
|
<pre>2 The storage-class specifier register shall not appear in the declaration specifiers in an external
|
|
declaration.
|
|
</pre>
|
|
<a name='6.9p3'></a>
|
|
<pre>3 There shall be no more than one external definition for each identifier declared with internal linkage
|
|
in a translation unit. Moreover, if an identifier declared with internal linkage is used in an expression
|
|
there shall be exactly one external definition for the identifier in the translation unit, unless it is:
|
|
|
|
— part of the operand of a sizeof operator whose result is an integer constant;
|
|
|
|
— part of the operand of an alignof operator whose result is an integer constant;
|
|
|
|
— or, part of the operand of any typeof operator whose result is not a variably modified type.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.9p4'></a>
|
|
<pre>4 As discussed in <a href='#5.1.1.1'>5.1.1.1</a>, the unit of program text after preprocessing is a translation unit, which
|
|
consists of a sequence of external declarations. These are described as "external" because they
|
|
appear outside any function (and hence have file scope). As discussed in <a href='#6.7'>6.7</a>, a declaration that also
|
|
causes storage to be reserved for an object or a function named by the identifier is a definition.
|
|
</pre>
|
|
<a name='6.9p5'></a>
|
|
<pre>5 An external definition is an external declaration that is also a definition of a function (other than an
|
|
inline definition) or an object. If an identifier declared with external linkage is used in an expression
|
|
(other than as part of the operand of a typeof operator whose result is not a variably modified type,
|
|
or a sizeof or alignof operator whose result is an integer constant expression), somewhere in the
|
|
entire program there shall be exactly one external definition for the identifier; otherwise, there shall
|
|
be no more than one<a href='#FOOTNOTE.205'><sup>[205]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.205'>
|
|
<pre><i><b>Footnote 205)</b> Thus, if an identifier declared with external linkage is not used in an expression, there need be no external definition for
|
|
it.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.9.1'></a>
|
|
<hr>
|
|
<h3>6.9.1 [Function definitions]</h3>
|
|
<a name='6.9.1p1'></a>
|
|
<pre>1 Syntax
|
|
function-definition:
|
|
attribute-specifier-sequenceopt declaration-specifiers declarator function-body
|
|
|
|
function-body:
|
|
compound-statement
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.9.1p2'></a>
|
|
<pre>2 The identifier declared in a function definition (which is the name of the function) shall have a
|
|
function type, as specified by the declarator portion of the function definition.
|
|
</pre>
|
|
<a name='6.9.1p3'></a>
|
|
<pre>3 The return type of a function shall be void or a complete object type other than array type.
|
|
</pre>
|
|
<a name='6.9.1p4'></a>
|
|
<pre>4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or static.
|
|
</pre>
|
|
<a name='6.9.1p5'></a>
|
|
<pre>5 If the parameter list consists of a single parameter of type void, the parameter declarator shall not
|
|
include an identifier.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.9.1p6'></a>
|
|
<pre>6 The optional attribute specifier sequence in a function definition appertains to the function.
|
|
</pre>
|
|
<a name='6.9.1p7'></a>
|
|
<pre>7 The declarator in a function definition specifies the name of the function being defined and the
|
|
types (and optionally the names) of all the parameters; the declarator also serves as a function
|
|
prototype for later calls to the same function in the same translation unit. The type of each parameter
|
|
is adjusted as described in <a href='#6.7.6.3'>6.7.6.3</a>.
|
|
</pre>
|
|
<a name='6.9.1p8'></a>
|
|
<pre>8 If a function that accepts a variable number of arguments is defined without a parameter type list
|
|
that ends with the ellipsis notation, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.9.1p9'></a>
|
|
<pre>9 The parameter type list, the attribute specifier sequence of the declarator that follows the parameter
|
|
type list, and the compound statement of the function body form a single block<a href='#FOOTNOTE.206'><sup>[206]</sup></a> . Each parameter
|
|
has automatic storage duration; its identifier, if any<a href='#FOOTNOTE.207'><sup>[207]</sup></a> , is an lvalue<a href='#FOOTNOTE.208'><sup>[208]</sup></a> . The layout of the storage for
|
|
parameters is unspecified.
|
|
</pre>
|
|
<a name='FOOTNOTE.206'>
|
|
<pre><i><b>Footnote 206)</b> The visibility scope of a parameter in a function definition starts when its declaration is completed, extends to following
|
|
parameter declarations, to possible attributes that follow the parameter type list, and then to the entire function body. The
|
|
lifetime of each instance of a parameter starts when the declaration is evaluated starting a call and ends when that call
|
|
terminates.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.207'>
|
|
<pre><i><b>Footnote 207)</b> A parameter that has no declared name is inaccessible within the function body.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.208'>
|
|
<pre><i><b>Footnote 208)</b> A parameter identifier cannot be redeclared in the function body except in an enclosed block.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.9.1p10'></a>
|
|
<pre>10 On entry to the function, the size expressions of each variably modified parameter are evaluated
|
|
and the value of each argument expression is converted to the type of the corresponding parameter
|
|
as if by assignment. (Array expressions and function designators as arguments were converted to
|
|
pointers before the call.)
|
|
</pre>
|
|
<a name='6.9.1p11'></a>
|
|
<pre>11 After all parameters have been assigned, the compound statement of the function body is executed.
|
|
</pre>
|
|
<a name='6.9.1p12'></a>
|
|
<pre>12 Unless otherwise specified, if the } that terminates the function body is reached, and the value of the
|
|
function call is used by the caller, the behavior is undefined.
|
|
</pre>
|
|
<a name='6.9.1p13'></a>
|
|
<pre>13 NOTE In a function definition, the type of the function and its prototype cannot be inherited from a typedef:
|
|
|
|
typedef int F(void); // type F is "function with no parameters
|
|
// returning int"
|
|
F f, g; // f and g both have type compatible with F
|
|
F f { /* ... */ } // WRONG: syntax/constraint error
|
|
F g() { /* ... */ } // WRONG: declares that g returns a function
|
|
int f(void) { /* ... */ } // RIGHT: f has type compatible with F
|
|
int g() { /* ... */ } // RIGHT: g has type compatible with F
|
|
F *e(void) { /* ... */ } // e returns a pointer to a function
|
|
F *((e))(void) { /* ... */ } // same: parentheses irrelevant
|
|
int (*fp)(void); // fp points to a function that has type F
|
|
F *Fp; // Fp points to a function that has type F
|
|
|
|
</pre>
|
|
<a name='6.9.1p14'></a>
|
|
<pre>14 EXAMPLE 1 In the following:
|
|
|
|
extern int max(int a, int b)
|
|
{
|
|
return a > b ? a: b;
|
|
}
|
|
|
|
extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the function declarator; and
|
|
|
|
{ return a > b ? a: b; }
|
|
|
|
is the function body.
|
|
</pre>
|
|
<a name='6.9.1p15'></a>
|
|
<pre>15 EXAMPLE 2 To pass one function to another, one might say
|
|
|
|
int f(void);
|
|
/* ... */
|
|
g(f);
|
|
|
|
Then the definition of g might read
|
|
|
|
void g(int (*funcp)(void))
|
|
{
|
|
/* ... */
|
|
(*funcp)(); /* or funcp(); ...*/
|
|
}
|
|
|
|
or, equivalently,
|
|
|
|
void g(int func(void))
|
|
{
|
|
/* ... */
|
|
func(); /* or (*func)(); ...*/
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.9.2'></a>
|
|
<hr>
|
|
<h3>6.9.2 [External object definitions]</h3>
|
|
<a name='6.9.2p1'></a>
|
|
<pre>1 Semantics
|
|
If the declaration of an identifier for an object has file scope and an initializer, the declaration is an
|
|
external definition for the identifier.
|
|
</pre>
|
|
<a name='6.9.2p2'></a>
|
|
<pre>2 A declaration of an identifier for an object that has file scope without an initializer, and without a
|
|
storage-class specifier or with the storage-class specifier static, constitutes a tentative definition. If a
|
|
translation unit contains one or more tentative definitions for an identifier, and the translation unit
|
|
contains no external definition for that identifier, then the behavior is exactly as if the translation
|
|
unit contains a file scope declaration of that identifier, with the composite type as of the end of the
|
|
translation unit, with an initializer equal to { 0 } .
|
|
</pre>
|
|
<a name='6.9.2p3'></a>
|
|
<pre>3 If the declaration of an identifier for an object is a tentative definition and has internal linkage, the
|
|
declared type shall not be an incomplete type.
|
|
</pre>
|
|
<a name='6.9.2p4'></a>
|
|
<pre>4 EXAMPLE 1
|
|
|
|
int i1 = 1; // definition, external linkage
|
|
static int i2 = 2; // definition, internal linkage
|
|
extern int i3 = 3; // definition, external linkage
|
|
int i4; // tentative definition, external linkage
|
|
static int i5; // tentative definition, internal linkage
|
|
|
|
int i1; // valid tentative definition, refers to previous
|
|
int i2; // <a href='#6.2.2'>6.2.2</a> renders undefined, linkage disagreement
|
|
int i3; // valid tentative definition, refers to previous
|
|
int i4; // valid tentative definition, refers to previous
|
|
int i5; // <a href='#6.2.2'>6.2.2</a> renders undefined, linkage disagreement
|
|
|
|
extern int i1; // refers to previous, whose linkage is external
|
|
extern int i2; // refers to previous, whose linkage is internal
|
|
extern int i3; // refers to previous, whose linkage is external
|
|
extern int i4; // refers to previous, whose linkage is external
|
|
extern int i5; // refers to previous, whose linkage is internal
|
|
|
|
</pre>
|
|
<a name='6.9.2p5'></a>
|
|
<pre>5 EXAMPLE 2 If at the end of the translation unit containing
|
|
|
|
int i[];
|
|
|
|
the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to zero on program
|
|
startup.
|
|
</pre>
|
|
<a name='6.10'></a>
|
|
<hr>
|
|
<h3>6.10 [Preprocessing directives]</h3>
|
|
<a name='6.10p1'></a>
|
|
<pre>1 Syntax
|
|
preprocessing-file:
|
|
groupopt
|
|
group:
|
|
group-part
|
|
group group-part
|
|
group-part:
|
|
if-section
|
|
control-line
|
|
text-line
|
|
# non-directive
|
|
if-section:
|
|
if-group elif-groupsopt else-groupopt endif-line
|
|
if-group:
|
|
# if constant-expression new-line groupopt
|
|
# ifdef identifier new-line groupopt
|
|
# ifndef identifier new-line groupopt
|
|
elif-groups:
|
|
elif-group
|
|
elif-groups elif-group
|
|
elif-group:
|
|
# elif constant-expression new-line groupopt
|
|
# elifdef identifier new-line groupopt
|
|
# elifndef identifier new-line groupopt
|
|
else-group:
|
|
# else new-line groupopt
|
|
endif-line:
|
|
# endif new-line
|
|
control-line:
|
|
# include pp-tokens new-line
|
|
# embed pp-tokens new-line
|
|
# define identifier replacement-list new-line
|
|
# define identifier lparen identifier-listopt ) replacement-list new-line
|
|
# define identifier lparen ... ) replacement-list new-line
|
|
# define identifier lparen identifier-list , ... ) replacement-list new-line
|
|
# undef identifier new-line
|
|
# line pp-tokens new-line
|
|
# error pp-tokensopt new-line
|
|
# warning pp-tokensopt new-line
|
|
# pragma pp-tokensopt new-line
|
|
# new-line
|
|
|
|
|
|
text-line:
|
|
pp-tokensopt new-line
|
|
|
|
non-directive:
|
|
pp-tokens new-line
|
|
|
|
lparen:
|
|
a ( character not immediately preceded by white space
|
|
|
|
replacement-list:
|
|
pp-tokensopt
|
|
pp-tokens:
|
|
preprocessing-token
|
|
pp-tokens preprocessing-token
|
|
|
|
new-line:
|
|
the new-line character
|
|
|
|
identifier-list:
|
|
identifier
|
|
identifier-list , identifier
|
|
|
|
pp-parameter:
|
|
pp-parameter-name pp-parameter-clauseopt
|
|
|
|
pp-parameter-name:
|
|
pp-standard-parameter
|
|
pp-prefixed-parameter
|
|
|
|
pp-standard-parameter:
|
|
identifier
|
|
|
|
pp-prefixed-parameter:
|
|
identifier :: identifier
|
|
|
|
pp-parameter-clause:
|
|
( pp-balanced-token-sequenceopt )
|
|
|
|
|
|
pp-balanced-token-sequence:
|
|
pp-balanced-token
|
|
pp-balanced-token-sequence pp-balanced-token
|
|
|
|
pp-balanced-token:
|
|
( pp-balanced-token-sequenceopt )
|
|
[ pp-balanced-token-sequenceopt ]
|
|
{ pp-balanced-token-sequenceopt }
|
|
any pp-token other than a parenthesis, a bracket, or a brace
|
|
|
|
embed-parameter-sequence:
|
|
pp-parameter
|
|
embed-parameter-sequence pp-parameter
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.10p2'></a>
|
|
<pre>2 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the following
|
|
constraints: The first token in the sequence is a # preprocessing token that (at the start of translation
|
|
phase 4) is either the first character in the source file (optionally after white space containing no
|
|
new-line characters) or that follows white space containing at least one new-line character. The last
|
|
token in the sequence is the first new-line character that follows the first token in the sequence. <a href='#FOOTNOTE.209'><sup>[209]</sup></a>
|
|
A new-line character ends the preprocessing directive even if it occurs within what would otherwise
|
|
be an invocation of a function-like macro.
|
|
</pre>
|
|
<a name='FOOTNOTE.209'>
|
|
<pre><i><b>Footnote 209)</b> Thus, preprocessing directives are commonly called "lines". These "lines" have no other syntactic significance, as all
|
|
white space is equivalent except in certain situations during preprocessing (see the # character string literal creation operator
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10p3'></a>
|
|
<pre>3 A text line shall not begin with a # preprocessing token. A non-directive shall not begin with any of
|
|
the directive names appearing in the syntax.
|
|
</pre>
|
|
<a name='6.10p4'></a>
|
|
<pre>4 Some preprocessing directives take additional information by the use of preprocessor parameters.
|
|
A preprocessing parameter (pp-parameter) shall be either a preprocessor prefixed parameter (identified
|
|
by a pp-prefixed-parameter, for implementation-defined preprocessor parameters) or a preprocessor
|
|
standard parameter (identified with a pp-standard-parameter, for pp-parameters specified by this
|
|
document).
|
|
</pre>
|
|
<a name='6.10p5'></a>
|
|
<pre>5 In all aspects, a preprocessor standard parameter specified by this document as an identifier pp_param
|
|
and an identifier of the form __pp_param__ shall behave the same when used as a preprocessor
|
|
parameter, except for the spelling.
|
|
</pre>
|
|
<a name='6.10p6'></a>
|
|
<pre>6 EXAMPLE 1 Thus, the preprocessor parameters on the two binary resource inclusion directives (<a href='#6.10.3.1'>6.10.3.1</a>):
|
|
|
|
#embed "boop.h" limit(5)
|
|
#embed "boop.h" __limit__(5)
|
|
|
|
behave the same, and can be freely interchanged. Implementations are encouraged to behave similarly for preprocessor
|
|
parameters (including preprocessor prefixed parameters) they provide.
|
|
|
|
</pre>
|
|
<a name='6.10p7'></a>
|
|
<pre>7 When in a group that is skipped (<a href='#6.10.1'>6.10.1</a>), the directive syntax is relaxed to allow any sequence of
|
|
preprocessing tokens to occur between the directive name and the following new-line character.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.10p8'></a>
|
|
<pre>8 The only white-space characters that shall appear between preprocessing tokens within a prepro-
|
|
cessing directive (from just after the introducing # preprocessing token through just before the
|
|
terminating new-line character) are space and horizontal-tab (including spaces that have replaced
|
|
comments or possibly other white-space characters in translation phase 3).
|
|
</pre>
|
|
<a name='6.10p9'></a>
|
|
<pre>9 A preprocessor parameter shall be either a preprocessor standard parameter, or an implementation-
|
|
defined preprocessor prefixed parameter<a href='#FOOTNOTE.210'><sup>[210]</sup></a> .
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.210'>
|
|
<pre><i><b>Footnote 210)</b> An unrecognized preprocessor prefixed parameter is a constraint violation, except within has_embed expressions (<a href='#6.10.1'>6.10.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10p10'></a>
|
|
<pre>10 The implementation can process and skip sections of source files conditionally, include other source
|
|
files, and replace macros. These capabilities are called preprocessing, because conceptually they occur
|
|
before translation of the resulting translation unit.
|
|
</pre>
|
|
<a name='6.10p11'></a>
|
|
<pre>11 The preprocessing tokens within a preprocessing directive are not subject to macro expansion unless
|
|
otherwise stated.
|
|
</pre>
|
|
<a name='6.10p12'></a>
|
|
<pre>12 EXAMPLE In:
|
|
|
|
#define EMPTY
|
|
EMPTY # include <file.h>
|
|
|
|
the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not begin with a # at
|
|
the start of translation phase 4, even though it will do so after the macro EMPTY has been replaced.
|
|
|
|
</pre>
|
|
<a name='6.10p13'></a>
|
|
<pre>13 The execution of a non-directive preprocessing directive results in undefined behavior.
|
|
|
|
</pre>
|
|
<a name='6.10.1'></a>
|
|
<hr>
|
|
<h3>6.10.1 [Conditional inclusion]</h3>
|
|
<a name='6.10.1p1'></a>
|
|
<pre>1 Syntax
|
|
defined-macro-expression:
|
|
defined identifier
|
|
defined ( identifier )
|
|
h-preprocessing-token:
|
|
any preprocessing-token other than >
|
|
in <a href='#6.10.4.2'>6.10.4.2</a>, for example).
|
|
h-pp-tokens:
|
|
h-preprocessing-token
|
|
h-pp-tokens h-preprocessing-token
|
|
header-name-tokens:
|
|
string-literal
|
|
< h-pp-tokens >
|
|
has-include-expression:
|
|
__has_include ( header-name )
|
|
__has_include ( header-name-tokens )
|
|
has-embed-expression:
|
|
__has_embed ( header-name embed-parameter-sequenceopt )
|
|
__has_embed ( header-name-tokens pp-balanced-token-sequenceopt )
|
|
has-c-attribute-express:
|
|
__has_c_attribute ( pp-tokens )
|
|
|
|
|
|
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.10.1p2'></a>
|
|
<pre>2 The expression that controls conditional inclusion shall be an integer constant expression except that:
|
|
identifiers (including those lexically identical to keywords) are interpreted as described below<a href='#FOOTNOTE.211'><sup>[211]</sup></a>
|
|
and it may contain zero or more defined macro expressions, has_include expressions, has_embed
|
|
expressions, and/or has_c_attribute expressions as unary operator expressions.
|
|
</pre>
|
|
<a name='FOOTNOTE.211'>
|
|
<pre><i><b>Footnote 211)</b> Because the controlling constant expression is evaluated during translation phase 4, all identifiers either are or are not
|
|
macro names — there simply are no keywords, enumeration constants, etc.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.1p3'></a>
|
|
<pre>3 A defined macro expression evaluates to 1 if the identifier is currently defined as a macro name (that
|
|
is, if it is predefined or if it has been the subject of a #define preprocessing directive without an
|
|
intervening #undef directive with the same subject identifier), 0 if it is not.
|
|
</pre>
|
|
<a name='6.10.1p4'></a>
|
|
<pre>4 The second form of the has_include expression and has_embed expression is considered only if the
|
|
first form does not match, in which case the preprocessing tokens are processed just as in normal
|
|
text.
|
|
</pre>
|
|
<a name='6.10.1p5'></a>
|
|
<pre>5 The header or source file identified by the parenthesized preprocessing token sequence in each
|
|
contained has_include expression is searched for as if that preprocessing token were the pp-tokens
|
|
in a #include directive, except that no further macro expansion is performed. Such a directive shall
|
|
satisfy the syntactic requirements of a #include directive. The has_include expression evaluates to
|
|
1 if the search for the source file succeeds, and to 0 if the search fails.
|
|
</pre>
|
|
<a name='6.10.1p6'></a>
|
|
<pre>6 The resource (<a href='#6.10.3.1'>6.10.3.1</a>) identified by the header-name preprocessing token sequence in each contained
|
|
has_embed expression is searched for as if those preprocessing token were the pp-tokens in a #embed
|
|
directive, except that no further macro expansion is performed. Such a directive shall satisfy the
|
|
syntactic requirements of a #embed directive. The has_embed expression evaluates to:
|
|
|
|
— 0 if the search fails or if any of the embed parameters in the embed parameter sequence
|
|
specified are not supported by the implementation for the #embed directive; or,
|
|
|
|
— 1 if the search for the resource succeeds and all embed parameters in the embed parameter
|
|
sequence specified are supported by the implementation for the #embed directive and the
|
|
resource is not empty; or,
|
|
|
|
— 2 if the search for the resource succeeds and all embed parameters in the embed parameter
|
|
sequence specified are supported by the implementation for the #embed directive and the
|
|
resource is empty.
|
|
|
|
</pre>
|
|
<a name='6.10.1p7'></a>
|
|
<pre>7 NOTE Unrecognized preprocessor prefixed parameters in has_embed expressions is not a constraint violation and instead
|
|
causes the expression to be evaluate to 0, as specified above.
|
|
|
|
</pre>
|
|
<a name='6.10.1p8'></a>
|
|
<pre>8 Each has_c_attribute expression is replaced by a nonzero pp-number matching the form of an integer
|
|
constant if the implementation supports an attribute with the name specified by interpreting the
|
|
pp-tokens as an attribute token, and by 0 otherwise. The pp-tokens shall match the form of an
|
|
attribute token.
|
|
</pre>
|
|
<a name='6.10.1p9'></a>
|
|
<pre>9 Each preprocessing token that remains (in the list of preprocessing tokens that will become the
|
|
controlling expression) after all macro replacements have occurred shall be in the lexical form of a
|
|
token (<a href='#6.4'>6.4</a>).
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.1p10'></a>
|
|
<pre>10 The #ifdef, #ifndef, #elifdef, and #elifndef, and the defined conditional inclusion operator,
|
|
shall treat __has_include and __has_c_attribute as if they were the name of defined macros.
|
|
The identifiers __has_include , __has_embed , and __has_c_attribute shall not appear in any
|
|
context not mentioned in this subclause.
|
|
</pre>
|
|
<a name='6.10.1p11'></a>
|
|
<pre>11 Preprocessing directives of the forms
|
|
# if constant-expression new-line groupopt
|
|
# elif constant-expression new-line groupopt
|
|
check whether the controlling constant expression evaluates to nonzero.
|
|
</pre>
|
|
<a name='6.10.1p12'></a>
|
|
<pre>12 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become the control-
|
|
ling constant expression are replaced (except for those macro names modified by the defined unary
|
|
operator), just as in normal text. If the token defined is generated as a result of this replacement
|
|
process or use of the defined unary operator does not match one of the two specified forms prior to
|
|
macro replacement, the behavior is undefined. After all replacements due to macro expansion and
|
|
evaluations of defined macro expressions, has_include expressions, and has_c_attribute expressions
|
|
have been performed, all remaining identifiers other than true (including those lexically identical
|
|
to keywords such as false) are replaced with the pp-number 0, true is replaced with pp-number
|
|
1 , and then each preprocessing token is converted into a token. The resulting tokens compose the
|
|
controlling constant expression which is evaluated according to the rules of <a href='#6.6'>6.6</a>. For the purposes of
|
|
this token conversion and evaluation, all signed integer types and all unsigned integer types act as
|
|
if they have the same representation as, respectively, the types intmax_t and uintmax_t defined
|
|
in the header <stdint.h>. <a href='#FOOTNOTE.212'><sup>[212]</sup></a> This includes interpreting character constants, which may involve
|
|
converting escape sequences into execution character set members. Whether the numeric value for
|
|
these character constants matches the value obtained when an identical character constant occurs in
|
|
an expression (other than within a #if or #elif directive) is implementation-defined<a href='#FOOTNOTE.213'><sup>[213]</sup></a> .
|
|
Also, whether a single-character character constant may have a negative value is implementation-
|
|
defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.212'>
|
|
<pre><i><b>Footnote 212)</b> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant 0x8000 is signed and
|
|
positive within a #if expression even though it would be unsigned in translation phase 7.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.213'>
|
|
<pre><i><b>Footnote 213)</b> Thus, the constant expression in the following #if directive and if statement is not guaranteed to evaluate to the same
|
|
value in these two contexts.
|
|
#if ’z’ - ’a’ == 25
|
|
if (’z’ - ’a’ == 25)
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.1p13'></a>
|
|
<pre>13 Preprocessing directives of the forms
|
|
# ifdef identifier new-line groupopt
|
|
# ifndef identifier new-line groupopt
|
|
# elifdef identifier new-line groupopt
|
|
# elifndef identifier new-line groupopt
|
|
check whether the identifier is or is not currently defined as a macro name. Their conditions
|
|
are equivalent to #if defined identifier, #if !defined identifier, #elif defined identifier, and
|
|
#elif !defined identifier respectively.
|
|
</pre>
|
|
<a name='6.10.1p14'></a>
|
|
<pre>14 Each directive’s condition is checked in order. If it evaluates to false (zero), the group that it
|
|
controls is skipped: directives are processed only through the name that determines the directive
|
|
in order to keep track of the level of nested conditionals; the rest of the directives’ preprocessing
|
|
tokens are ignored, as are the other preprocessing tokens in the group. Only the first group whose
|
|
control condition evaluates to true (nonzero) is processed; any following groups are skipped and
|
|
their controlling directives are processed as if they were in a group that is skipped. If none of the
|
|
conditions evaluates to true, and there is a #else directive, the group controlled by the #else is
|
|
processed; lacking a #else directive, all the groups until the #endif are skipped. <a href='#FOOTNOTE.214'><sup>[214]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.214'>
|
|
<pre><i><b>Footnote 214)</b> As indicated by the syntax, no preprocessing tokens are allowed to follow a #else or #endif directive before the
|
|
terminating new-line character. However, comments can appear anywhere in a source file, including within a preprocessing
|
|
directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.1p15'></a>
|
|
<pre>15 EXAMPLE This demonstrates a way to include a header file only if it is available.
|
|
|
|
#if __has_include(<optional.h>)
|
|
# include <optional.h>
|
|
# define have_optional 1
|
|
#elif __has_include(<experimental/optional.h>)
|
|
# include <experimental/optional.h>
|
|
# define have_optional 1
|
|
# define have_experimental_optional 1
|
|
#endif
|
|
#ifndef have_optional
|
|
# define have_optional 0
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='6.10.1p16'></a>
|
|
<pre>16 EXAMPLE
|
|
|
|
/* Fallback for compilers not yet implementing this feature. */
|
|
#ifndef __has_c_attribute
|
|
#define __has_c_attribute(x) 0
|
|
#endif /* __has_c_attribute */
|
|
|
|
#if __has_c_attribute(fallthrough)
|
|
/* Standard attribute is available, use it. */
|
|
#define FALLTHROUGH [[fallthrough]]
|
|
#elif __has_c_attribute(vendor::fallthrough)
|
|
/* Vendor attribute is available, use it. */
|
|
#define FALLTHROUGH [[vendor::fallthrough]]
|
|
#else
|
|
/* Fallback implementation. */
|
|
#define FALLTHROUGH
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='6.10.1p17'></a>
|
|
<pre>17 EXAMPLE
|
|
|
|
#ifdef __STDC__
|
|
#define TITLE "ISO C Compilation"
|
|
#elifndef __cplusplus
|
|
#define TITLE "Non-ISO C Compilation"
|
|
#else
|
|
/* C++ */
|
|
#define TITLE "C++ Compilation"
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='6.10.1p18'></a>
|
|
<pre>18 EXAMPLE 1 A combination of __FILE__ (<a href='#6.10.9.1'>6.10.9.1</a>) and __has_embed could be used to check for support of specific implemen-
|
|
tation extensions for the #embed (<a href='#6.10.3.1'>6.10.3.1</a>) directive’s parameters.
|
|
|
|
#if __has_embed(__FILE__ ext::token(0xB055))
|
|
#define DESCRIPTION "Supports extended token embed"
|
|
#else
|
|
#define DESCRIPTION "Does not support extended token embed"
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='6.10.1p19'></a>
|
|
<pre>19 EXAMPLE 2 The below snippet uses __has_embed to check for support of a specific implementation-defined embed
|
|
parameter, and otherwise uses standard behavior to produce the same effect.
|
|
void parse_into_s(short* ptr, unsigned char* ptr_bytes, unsigned long long size);
|
|
|
|
int main () {
|
|
#if __has_embed ("bits.bin" ds9000::element_type(short))
|
|
/* Implementation extension: create short integers from the */
|
|
/* translation environment resource into */
|
|
/* a sequence of integer constants */
|
|
short meow[] = {
|
|
#embed "bits.bin" ds9000::element_type(short)
|
|
};
|
|
#elif __has_embed ("bits.bin")
|
|
/* no support for implementation-specific */
|
|
/* ds9000::element_type(short) parameter */
|
|
const unsigned char meow_bytes[] = {
|
|
#embed "bits.bin"
|
|
};
|
|
short meow[sizeof(meow_bytes) / sizeof(short)] = {};
|
|
/* parse meow_bytes into short values by-hand! */
|
|
parse_into_s(meow, meow_bytes, sizeof(meow_bytes));
|
|
#else
|
|
#error "cannot find bits.bin resource"
|
|
#endif
|
|
return (int)(meow[0] + meow[(sizeof(meow) / sizeof(*meow)) - 1]);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.1p20'></a>
|
|
<pre>20 EXAMPLE 3 This resource is considered empty due to the limit(0) embed parameter, always, including in __has_embed
|
|
expressions.
|
|
|
|
int main () {
|
|
#if __has_embed(</owo/uwurandom> limit(0)) == 2
|
|
// if </owo/uwurandom> exits, this
|
|
// token sequence is always taken.
|
|
return 0;
|
|
#else
|
|
// the resource does not exist
|
|
#error "The resource does not exist"
|
|
#endif
|
|
}
|
|
|
|
|
|
Forward references: macro replacement (<a href='#6.10.4'>6.10.4</a>), source file inclusion (<a href='#6.10.2'>6.10.2</a>), mandatory macros
|
|
(<a href='#6.10.9.1'>6.10.9.1</a>), largest integer types (<a href='#7.22.1.5'>7.22.1.5</a>).
|
|
|
|
</pre>
|
|
<a name='6.10.2'></a>
|
|
<hr>
|
|
<h3>6.10.2 [Source file inclusion]</h3>
|
|
<a name='6.10.2p1'></a>
|
|
<pre>1 Constraints
|
|
A #include directive shall identify a header or source file that can be processed by the implementa-
|
|
tion.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.2p2'></a>
|
|
<pre>2 A preprocessing directive of the form
|
|
|
|
|
|
# include < h-char-sequence > new-line
|
|
searches a sequence of implementation-defined places for a header identified uniquely by the
|
|
specified sequence between the < and > delimiters, and causes the replacement of that directive
|
|
by the entire contents of the header. How the places are specified or the header identified is
|
|
implementation-defined.
|
|
</pre>
|
|
<a name='6.10.2p3'></a>
|
|
<pre>3 A preprocessing directive of the form
|
|
# include " q-char-sequence " new-line
|
|
causes the replacement of that directive by the entire contents of the source file identified by
|
|
the specified sequence between the " delimiters. The named source file is searched for in an
|
|
implementation-defined manner. If this search is not supported, or if the search fails, the directive is
|
|
reprocessed as if it read
|
|
# include < h-char-sequence > new-line
|
|
with the identical contained sequence (including > characters, if any) from the original directive.
|
|
</pre>
|
|
<a name='6.10.2p4'></a>
|
|
<pre>4 A preprocessing directive of the form
|
|
# include pp-tokens new-line
|
|
(that does not match one of the two previous forms) is permitted. The preprocessing tokens after
|
|
include in the directive are processed just as in normal text. (Each identifier currently defined as a
|
|
macro name is replaced by its replacement list of preprocessing tokens.) The directive resulting after
|
|
all replacements shall match one of the two previous forms.<a href='#FOOTNOTE.215'><sup>[215]</sup></a> The method by which a sequence
|
|
of preprocessing tokens between a < and a > preprocessing token pair or a pair of " characters is
|
|
combined into a single header name preprocessing token is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.215'>
|
|
<pre><i><b>Footnote 215)</b> Note that adjacent string literals are not concatenated into a single string literal (see the translation phases in <a href='#5.1.1.2'>5.1.1.2</a>);
|
|
thus, an expansion that results in two string literals is an invalid directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.2p5'></a>
|
|
<pre>5 The implementation shall provide unique mappings for sequences consisting of one or more nondig-
|
|
its or digits (<a href='#6.4.2.1'>6.4.2.1</a>) followed by a period (.) and a single nondigit. The first character shall not be a
|
|
digit. The implementation may ignore distinctions of alphabetical case and restrict the mapping to
|
|
eight significant characters before the period.
|
|
</pre>
|
|
<a name='6.10.2p6'></a>
|
|
<pre>6 A #include preprocessing directive may appear in a source file that has been read because of a
|
|
#include directive in another file, up to an implementation-defined nesting limit (see <a href='#5.2.4.1'>5.2.4.1</a>).
|
|
</pre>
|
|
<a name='6.10.2p7'></a>
|
|
<pre>7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
|
|
|
|
#include <stdio.h>
|
|
#include "myprog.h"
|
|
|
|
</pre>
|
|
<a name='6.10.2p8'></a>
|
|
<pre>8 EXAMPLE 2 This illustrates macro-replaced #include directives:
|
|
|
|
#if VERSION == 1
|
|
#define INCFILE "vers1.h"
|
|
#elif VERSION == 2
|
|
#define INCFILE "vers2.h" // and so on
|
|
#else
|
|
#define INCFILE "versN.h"
|
|
#endif
|
|
#include INCFILE
|
|
|
|
|
|
Forward references: macro replacement (<a href='#6.10.4'>6.10.4</a>).
|
|
|
|
</pre>
|
|
<a name='6.10.3'></a>
|
|
<hr>
|
|
<h3>6.10.3 [Binary resource inclusion]</h3>
|
|
<a name='6.10.3.1'></a>
|
|
<hr>
|
|
<h3>6.10.3.1 [#embed preprocessing directive]</h3>
|
|
<a name='6.10.3.1p1'></a>
|
|
<pre>1 Description
|
|
A resource is a source of data accessible from the translation environment. An embed parameter is a
|
|
single preprocessor parameter in the embed parameter sequence. It has an implementation resource
|
|
width, which is the implementation-defined size in bits of the located resource. It also has a resource
|
|
width, which is either:
|
|
|
|
— the number of bits as computed from the optionally-provided limit embed parameter (??), if
|
|
present; or,
|
|
— the implementation resource width.
|
|
</pre>
|
|
<a name='6.10.3.1p2'></a>
|
|
<pre>2 An embed parameter sequence is a whitespace-delimited list of preprocessor parameters which may
|
|
modify the result of the replacement for the #embed preprocessing directive.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.10.3.1p3'></a>
|
|
<pre>3 An #embed directive shall identify a resource that can be processed by the implementation as a
|
|
binary data sequence given the provided embed parameters.
|
|
</pre>
|
|
<a name='6.10.3.1p4'></a>
|
|
<pre>4 Embed parameters not specified in this document shall be implementation-defined. Implementation-
|
|
defined embed parameters may change the below-defined semantics of the directive; otherwise,
|
|
#embed directives which do not contain implementation-defined embed parameters shall behave as
|
|
described in this document.
|
|
</pre>
|
|
<a name='6.10.3.1p5'></a>
|
|
<pre>5 A resource is considered empty when its resource width is zero.
|
|
</pre>
|
|
<a name='6.10.3.1p6'></a>
|
|
<pre>6 Let embed element width be either:
|
|
|
|
— an integer constant expression greater than zero determined by an implementation-defined
|
|
embed parameter; or,
|
|
— CHAR_BIT (<a href='#5.2.4.2.1'>5.2.4.2.1</a>).
|
|
|
|
The result of (resource width) % (embed element width) shall be zero<a href='#FOOTNOTE.216'><sup>[216]</sup></a> .
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='FOOTNOTE.216'>
|
|
<pre><i><b>Footnote 216)</b> This constraint helps ensure data is neither filled with padding values nor truncated in a given environment, and helps
|
|
ensure the data is portable with respect to usages of memcpy (<a href='#7.26.2.1'>7.26.2.1</a>) with character type arrays initialized from the data.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.3.1p7'></a>
|
|
<pre>7 The expansion of a #embed directive is a token sequence formed from the list of integer constant
|
|
expressions described below. The group of tokens for each integer constant expression in the list
|
|
is separated in the token sequence from the group of tokens for the previous integer constant
|
|
expression in the list by a comma. The sequence neither begins nor ends in a comma. If the list of
|
|
integer constant expressions is empty, the token sequence is empty. The directive is replaced by its
|
|
expansion and, with the presence of certain embed parameters, additional or replacement token
|
|
sequences.
|
|
</pre>
|
|
<a name='6.10.3.1p8'></a>
|
|
<pre>8 A preprocessing directive of the form
|
|
# embed < h-char-sequence > embed-parameter-sequenceopt new-line
|
|
searches a sequence of implementation-defined places for a resource identified uniquely by the spec-
|
|
ified sequence between the < and > . The search for the named resource is done in an implementation-
|
|
defined manner.
|
|
</pre>
|
|
<a name='6.10.3.1p9'></a>
|
|
<pre>9 A preprocessing directive of the form
|
|
# embed " q-char-sequence " embed-parameter-sequenceopt new-line
|
|
searches a sequence of implementation-defined places for a resource identified uniquely by the
|
|
specified sequence between the " delimiters. The search for the named resource is done in an
|
|
implementation-defined manner. If this search is not supported, or if the search fails, the directive is
|
|
reprocessed as if it read
|
|
# embed < h-char-sequence > embed-parameter-sequenceopt new-line
|
|
with the identical contained q-char-sequence (including > characters, if any) from the original
|
|
directive.
|
|
</pre>
|
|
<a name='6.10.3.1p10'></a>
|
|
<pre>10 Either form of the #embed directive specified previously behave as specified below. The values of the
|
|
integer constant expressions in the expanded sequence is determined by an implementation-defined
|
|
mapping of the resource’s data. Each integer constant expression’s value is in the range from 0 to
|
|
(2embed element width ) − 1, inclusive<a href='#FOOTNOTE.217'><sup>[217]</sup></a> . If the list of integer constant expressions:
|
|
|
|
— is used to initialize an array of a type compatible with unsigned char, or compatible with
|
|
char if char cannot hold negative values; or,
|
|
— the embed element width is equal to CHAR_BIT (??env-consider-characteristics-of-integer-
|
|
types-limits-h)),
|
|
|
|
then the contents of the initialized elements of the array are as-if the resource’s binary data is fread
|
|
(<a href='#7.23.8.1'>7.23.8.1</a>) into the array at translation time.
|
|
</pre>
|
|
<a name='FOOTNOTE.217'>
|
|
<pre><i><b>Footnote 217)</b> For example, an embed element width of 8 will yield a range of values from 0 to 255, inclusive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.3.1p11'></a>
|
|
<pre>11 A preprocessing directive of the form
|
|
# embed pp-tokens new-line
|
|
(that does not match one of the two previous forms) is permitted. The preprocessing tokens after
|
|
embed in the directive are processed just as in normal text. (Each identifier currently defined as a
|
|
macro name is replaced by its replacement list of preprocessing tokens.) The directive resulting after
|
|
all replacements shall match one of the two previous forms<a href='#FOOTNOTE.218'><sup>[218]</sup></a> . The method by which a sequence
|
|
of preprocessing tokens between a < and a > preprocessing token pair or a pair of " characters is
|
|
combined into a single resource name preprocessing token is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.218'>
|
|
<pre><i><b>Footnote 218)</b> Note that adjacent string literals are not concatenated into a single string literal (see the translation phases in <a href='#5.1.1.2'>5.1.1.2</a>);
|
|
thus, an expansion that results in two string literals is an invalid directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.3.1p12'></a>
|
|
<pre>12 An embed parameter with a preprocessor parameter token that is one of the following is a standard
|
|
embed parameter:
|
|
|
|
limit prefix suffix if_empty
|
|
|
|
|
|
The significance of these standard embed parameters is specified below.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='6.10.3.1p13'></a>
|
|
<pre>13 The #embed directive is meant to translate binary data in resources to sequence of integer constant
|
|
expressions in a way that preserves the value of the resource’s bit stream where possible.
|
|
</pre>
|
|
<a name='6.10.3.1p14'></a>
|
|
<pre>14 A mechanism similar to, but distinct from, the implementation-defined search paths used for source
|
|
file inclusion (<a href='#6.10.2'>6.10.2</a>) is encouraged.
|
|
</pre>
|
|
<a name='6.10.3.1p15'></a>
|
|
<pre>15 Implementations should take into account translation-time bit and byte orders as well as execution
|
|
time bit and byte orders to more appropriately represent the resource’s binary data from the directive.
|
|
This maximizes the chance that, if the resource referenced at translation time through the #embed
|
|
directive is the same one accessed through execution-time means, the data that is e.g. fread or
|
|
similar into contiguous storage will compare bit-for-bit equal to an array of character type initialized
|
|
from an #embed directive’s expanded contents.
|
|
</pre>
|
|
<a name='6.10.3.1p16'></a>
|
|
<pre>16 EXAMPLE 1 Placing a small image resource.
|
|
|
|
#include <stddef.h>
|
|
|
|
void have_you_any_wool(const unsigned char*, size_t);
|
|
|
|
int main (int, char*[]) {
|
|
static const unsigned char baa_baa[] = {
|
|
#embed "black_sheep.ico"
|
|
};
|
|
|
|
have_you_any_wool(baa_baa, sizeof(baa_baa));
|
|
|
|
return 0;
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.10.3.1p17'></a>
|
|
<pre>17 EXAMPLE 2 This snippet:
|
|
|
|
int main (int, char*[]) {
|
|
static const unsigned char coefficients[] = {
|
|
#embed "only_8_bits.bin" // potential constraint violation
|
|
};
|
|
return 0;
|
|
}
|
|
|
|
may violate the constraint that (resource width) % (embed element width) must be 0. The 8 bits might not be evenly
|
|
divisible by the embed element width (e.g., on a system where CHAR_BIT is 16). Issuing a diagnostic in this case may aid in
|
|
portability by calling attention to potentially incompatible expectations between implementations and their resources.
|
|
</pre>
|
|
<a name='6.10.3.1p18'></a>
|
|
<pre>18 EXAMPLE 3 Initialization of non-arrays.
|
|
|
|
int main () {
|
|
/* Braces may be kept or elided as per normal initialization rules */
|
|
int i = {
|
|
#embed "i.dat"
|
|
}; /* i value is [0, 2^(embed element width)) first entry */
|
|
int i2 =
|
|
#embed "i.dat"
|
|
; /* valid if i.dat produces 1 value,
|
|
i2 value is [0, 2^(embed element width)) */
|
|
struct s {
|
|
double a, b, c;
|
|
struct { double e, f, g; };
|
|
double h, i, j;
|
|
};
|
|
struct s x = {
|
|
/* initializes each element in
|
|
order according to initialization rules with
|
|
comma-separated list of integer constant expressions
|
|
inside of braces */
|
|
#embed "s.dat"
|
|
};
|
|
return 0;
|
|
}
|
|
|
|
Non-array types can still be initialized since the directive produces a comma-delimited lists of integer constant expressions, a
|
|
single integer constant expression, or nothing.
|
|
</pre>
|
|
<a name='6.10.3.1p19'></a>
|
|
<pre>19 EXAMPLE 4 Equivalency of bit sequence and bit order between a translation-time read and an execution-time read of the
|
|
same resource/file.
|
|
|
|
#include <string.h>
|
|
#include <stddef.h>
|
|
#include <stdio.h>
|
|
|
|
int main() {
|
|
static const unsigned char embed_data[] = {
|
|
#embed <data.dat>
|
|
};
|
|
|
|
const size_t f_size = sizeof(embed_data);
|
|
unsigned char f_data[f_size];
|
|
FILE* f_source = fopen("data.dat", "rb");
|
|
if (f_source == NULL);
|
|
return 1;
|
|
char* f_ptr = (char*)&f_data[0];
|
|
if (fread(f_ptr, 1, f_size, f_source) != f_size) {
|
|
fclose(f_source);
|
|
return 1;
|
|
}
|
|
fclose(f_source);
|
|
|
|
int is_same = memcmp(&embed_data[0], f_ptr, f_size);
|
|
// if both operations refers to the same resource/file at
|
|
// execution time and translation time, "is_same" should be 0
|
|
return is_same == 0 ? 0 : 1;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.2'></a>
|
|
<hr>
|
|
<h3>6.10.3.2 [limit parameter]</h3>
|
|
<a name='6.10.3.2p1'></a>
|
|
<pre>1 Constraints
|
|
The limit standard embed parameter may appear zero times or one time in the embed parameter
|
|
sequence. Its preprocessor argument clause shall be present and have the form:
|
|
( constant-expression )
|
|
and shall be an integer constant expression. The integer constant expression shall not evaluate to a
|
|
value less than 0.
|
|
</pre>
|
|
<a name='6.10.3.2p2'></a>
|
|
<pre>2 The token defined shall not appear within the constant expression.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.3.2p3'></a>
|
|
<pre>3 The embed parameter with a preprocessor parameter token limit denotes a balanced preprocessing
|
|
token sequence that will be used to compute the resource width. Independently of any macro
|
|
replacement done previously (e.g. when matching the form of #embed), the constant expression is
|
|
evaluated after the balanced preprocessing token sequence is processed as in normal text, using
|
|
the rules specified for conditional inclusion (<a href='#6.10.1'>6.10.1</a>), with the exception that any defined macro
|
|
expressions are not permitted.
|
|
</pre>
|
|
<a name='6.10.3.2p4'></a>
|
|
<pre>4 The resource width is:
|
|
|
|
— 0, if the integer constant expression evaluates to 0; or,
|
|
|
|
— the implementation resource width if it is less than the embed element width multiplied by
|
|
the integer constant expression; or,
|
|
|
|
— the embed element width multiplied by the integer constant expression, if it is less than or
|
|
equal to the implementation resource width.
|
|
|
|
</pre>
|
|
<a name='6.10.3.2p5'></a>
|
|
<pre>5 EXAMPLE 1 Checking the first 4 elements of a sound resource.
|
|
|
|
#include <assert.h>
|
|
|
|
int main (int, char*[]) {
|
|
static const char sound_signature[] = {
|
|
#embed <sdk/jump.wav> limit(2+2)
|
|
};
|
|
static_assert((sizeof(sound_signature) / sizeof(*sound_signature)) == 4,
|
|
"There should only be 4 elements in this array.");
|
|
|
|
// verify PCM WAV resource
|
|
assert(sound_signature[0] == ’R’);
|
|
assert(sound_signature[1] == ’I’);
|
|
assert(sound_signature[2] == ’F’);
|
|
assert(sound_signature[3] == ’F’);
|
|
assert(sizeof(sound_signature) == 4);
|
|
|
|
return 0;
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.10.3.2p6'></a>
|
|
<pre>6 EXAMPLE 2 Similar to a previous example, except it illustrates macro expansion specifically done for the limit(...)
|
|
parameter.
|
|
|
|
#include <assert.h>
|
|
|
|
#define TWO_PLUS_TWO 2+2
|
|
int main (int, char*[]) {
|
|
const char sound_signature[] = {
|
|
/* the token sequence within the parentheses
|
|
for the "limit" parameter undergoes macro
|
|
expansion, at least once, resulting in
|
|
#embed <sdk/jump.wav> limit(2+2)
|
|
*/
|
|
#embed <sdk/jump.wav> limit(TWO_PLUS_TWO)
|
|
};
|
|
static_assert((sizeof(sound_signature) / sizeof(*sound_signature)) == 4,
|
|
"There should only be 4 elements in this array.");
|
|
|
|
// verify PCM WAV resource
|
|
assert(sound_signature[0] == ’R’);
|
|
assert(sound_signature[1] == ’I’);
|
|
assert(sound_signature[2] == ’F’);
|
|
assert(sound_signature[3] == ’F’);
|
|
assert(sizeof(sound_signature) == 4);
|
|
|
|
return 0;
|
|
}
|
|
|
|
</pre>
|
|
<a name='6.10.3.2p7'></a>
|
|
<pre>7 EXAMPLE 3 A potential constraint violation from a resource that may not have enough information in an environment that
|
|
has a CHAR_BIT greater than 24.
|
|
|
|
int main (int, char*[]) {
|
|
const unsigned char arr[] = {
|
|
#embed "24_bits.bin" limit(1) // may be a constraint violation
|
|
};
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.3'></a>
|
|
<hr>
|
|
<h3>6.10.3.3 [suffix parameter]</h3>
|
|
<a name='6.10.3.3p1'></a>
|
|
<pre>1 Constraints
|
|
The suffix standard embed parameter may appear zero times or one time in the embed parameter
|
|
sequence. Its preprocessor argument clause shall be present and have the form:
|
|
( pp-balanced-token-sequenceopt )
|
|
|
|
Semantics
|
|
The embed parameter with a preprocessing parameter token suffix denotes a balanced preprocess-
|
|
ing token sequence within its preprocessor argument clause that will be placed immediately after
|
|
the result of the associated #embed directive’s expansion.
|
|
</pre>
|
|
<a name='6.10.3.3p2'></a>
|
|
<pre>2 If the resource is empty, then suffix has no effect and is ignored.
|
|
</pre>
|
|
<a name='6.10.3.3p3'></a>
|
|
<pre>3 EXAMPLE 1 Extra elements added to array initializer.
|
|
|
|
#include <string.h>
|
|
|
|
#ifndef SHADER_TARGET
|
|
#define SHADER_TARGET "edith-impl.glsl"
|
|
#endif
|
|
|
|
extern char* null_term_shader_data;
|
|
|
|
void fill_in_data () {
|
|
const char internal_data[] = {
|
|
#embed SHADER_TARGET \
|
|
suffix(,)
|
|
0
|
|
};
|
|
|
|
strcpy(null_term_shader_data, internal_data);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.4'></a>
|
|
<hr>
|
|
<h3>6.10.3.4 [prefix parameter]</h3>
|
|
<a name='6.10.3.4p1'></a>
|
|
<pre>1 Constraints
|
|
The prefix standard embed parameter may appear zero times or one time in the embed parameter
|
|
sequence. Its preprocessor parameter clause shall be present and have the form:
|
|
( pp-balanced-token-sequenceopt )
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.3.4p2'></a>
|
|
<pre>2 The embed parameter with a preprocessor parameter token prefix denotes a balanced preprocessing
|
|
token sequence within its preprocessor argument clause that will be placed immediately before the
|
|
result of the associated #embed directive’s expansion, if any.
|
|
</pre>
|
|
<a name='6.10.3.4p3'></a>
|
|
<pre>3 If the resource is empty, then prefix has no effect and is ignored.
|
|
</pre>
|
|
<a name='6.10.3.4p4'></a>
|
|
<pre>4 EXAMPLE 1 A null-terminated character array with prefixed and suffixed tokens of additional tokens when the resource is
|
|
not empty, providing null termination and a byte order mark.
|
|
|
|
#include <string.h>
|
|
#include <assert.h>
|
|
|
|
#ifndef SHADER_TARGET
|
|
#define SHADER_TARGET "ches.glsl"
|
|
#endif
|
|
|
|
extern char* merp;
|
|
|
|
void init_data () {
|
|
const char whl[] = {
|
|
#embed SHADER_TARGET \
|
|
prefix(0xEF, 0xBB, 0xBF, ) /* UTF-8 BOM */ \
|
|
suffix(,)
|
|
0
|
|
};
|
|
// always null terminated,
|
|
// contains BOM if not-empty
|
|
int is_good = (sizeof(whl) == 1 && whl[0] == ’\0’)
|
|
|| (whl[0] == ’\xEF’ && whl[1] == ’\xBB’
|
|
&& whl[2] == ’\xBF’ && whl[sizeof(whl) - 1] == ’\0’);
|
|
assert(is_good);
|
|
strcpy(merp, whl);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.5'></a>
|
|
<hr>
|
|
<h3>6.10.3.5 [if_empty parameter]</h3>
|
|
<a name='6.10.3.5p1'></a>
|
|
<pre>1 Constraints
|
|
The if_empty standard embed parameter may appear zero times or one time in the embed parameter
|
|
sequence. Its preprocessor argument clause shall be present and have the form:
|
|
( pp-balanced-token-sequenceopt )
|
|
|
|
Semantics
|
|
The embed parameter with a preprocessing parameter token if_empty denotes a balanced pre-
|
|
processing token sequence within its preprocessor argument clause that will replace the #embed
|
|
directive entirely.
|
|
If the resource is not empty, then if_empty has no effect and is ignored.
|
|
</pre>
|
|
<a name='6.10.3.5p2'></a>
|
|
<pre>2 EXAMPLE 1 This resource is considered empty due to the limit(0) embed parameter, always. This program always returns 0,
|
|
even if the resource is searched for and found successfully by the implementation.
|
|
|
|
int main () {
|
|
return
|
|
#embed </owo/uwurandom> limit(0) prefix(1) if_empty(0)
|
|
;
|
|
// becomes:
|
|
// return 0;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.5p3'></a>
|
|
<pre>3 EXAMPLE 2 An example similar to using the suffix embed parameter, but changed slightly.
|
|
|
|
#include <string.h>
|
|
|
|
#ifndef SHADER_TARGET
|
|
#define SHADER_TARGET "edith-impl.glsl"
|
|
#endif
|
|
|
|
extern char* null_term_shader_data;
|
|
|
|
void fill_in_data () {
|
|
const char internal_data[] = {
|
|
#embed SHADER_TARGET \
|
|
suffix(, 0) \
|
|
if_empty(0)
|
|
};
|
|
|
|
strcpy(null_term_shader_data, internal_data);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.3.5p4'></a>
|
|
<pre>4 EXAMPLE 3 This resource is considered empty due to the limit(0) embed parameter, always, which means any if_empty
|
|
expressions replace the directive as specified above.
|
|
|
|
int main () {
|
|
return
|
|
#include </owo/uwurandom> limit(0) if_empty(45540)
|
|
;
|
|
}
|
|
|
|
|
|
becomes:
|
|
|
|
int main () {
|
|
return 45540;
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.4'></a>
|
|
<hr>
|
|
<h3>6.10.4 [Macro replacement]</h3>
|
|
<a name='6.10.4p1'></a>
|
|
<pre>1 Constraints
|
|
Two replacement lists are identical if and only if the preprocessing tokens in both have the same
|
|
number, ordering, spelling, and white-space separation, where all white-space separations are
|
|
considered identical.
|
|
</pre>
|
|
<a name='6.10.4p2'></a>
|
|
<pre>2 An identifier currently defined as an object-like macro shall not be redefined by another #define
|
|
preprocessing directive unless the second definition is an object-like macro definition and the two
|
|
replacement lists are identical. Likewise, an identifier currently defined as a function-like macro
|
|
shall not be redefined by another #define preprocessing directive unless the second definition is a
|
|
function-like macro definition that has the same number and spelling of parameters, and the two
|
|
replacement lists are identical.
|
|
</pre>
|
|
<a name='6.10.4p3'></a>
|
|
<pre>3 There shall be white space between the identifier and the replacement list in the definition of an
|
|
object-like macro.
|
|
</pre>
|
|
<a name='6.10.4p4'></a>
|
|
<pre>4 If the identifier-list in the macro definition does not end with an ellipsis, the number of arguments
|
|
(including those arguments consisting of no preprocessing tokens) in an invocation of a function-like
|
|
macro shall equal the number of parameters in the macro definition. Otherwise, there shall be at
|
|
least as many arguments in the invocation as there are parameters in the macro definition (excluding
|
|
the ...). There shall exist a ) preprocessing token that terminates the invocation.
|
|
</pre>
|
|
<a name='6.10.4p5'></a>
|
|
<pre>5 The identifiers __VA_ARGS__ and __VA_OPT__ shall occur only in the replacement-list of a function-
|
|
like macro that uses the ellipsis notation in the parameters.
|
|
</pre>
|
|
<a name='6.10.4p6'></a>
|
|
<pre>6 A parameter identifier in a function-like macro shall be uniquely declared within its scope.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.4p7'></a>
|
|
<pre>7 The identifier immediately following the define is called the macro name. There is one name
|
|
space for macro names. Any white-space characters preceding or following the replacement list of
|
|
preprocessing tokens are not considered part of the replacement list for either form of macro.
|
|
</pre>
|
|
<a name='6.10.4p8'></a>
|
|
<pre>8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which a prepro-
|
|
cessing directive could begin, the identifier is not subject to macro replacement.
|
|
</pre>
|
|
<a name='6.10.4p9'></a>
|
|
<pre>9 A preprocessing directive of the form
|
|
# define identifier replacement-list new-line
|
|
defines an object-like macro that causes each subsequent instance of the macro name<a href='#FOOTNOTE.219'><sup>[219]</sup></a> to be replaced
|
|
by the replacement list of preprocessing tokens that constitute the remainder of the directive. The
|
|
replacement list is then rescanned for more macro names as specified below.
|
|
</pre>
|
|
<a name='FOOTNOTE.219'>
|
|
<pre><i><b>Footnote 219)</b> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens, not sequences
|
|
possibly containing identifier-like subsequences (see <a href='#5.1.1.2'>5.1.1.2</a>, translation phases), they are never scanned for macro names or
|
|
parameters.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.4p10'></a>
|
|
<pre>10 A preprocessing directive of the form
|
|
# define identifier lparen identifier-listopt ) replacement-list new-line
|
|
# define identifier lparen ... ) replacement-list new-line
|
|
# define identifier lparen identifier-list , ... ) replacement-list new-line
|
|
defines a function-like macro with parameters, whose use is similar syntactically to a function call. The
|
|
parameters are specified by the optional list of identifiers, whose scope extends from their declaration
|
|
in the identifier list until the new-line character that terminates the #define preprocessing directive.
|
|
Each subsequent instance of the function-like macro name followed by a ( as the next preprocessing
|
|
token introduces the sequence of preprocessing tokens that is replaced by the replacement list
|
|
in the definition (an invocation of the macro). The replaced sequence of preprocessing tokens is
|
|
terminated by the matching ) preprocessing token, skipping intervening matched pairs of left and
|
|
right parenthesis preprocessing tokens. Within the sequence of preprocessing tokens making up an
|
|
invocation of a function-like macro, new-line is considered a normal white-space character.
|
|
</pre>
|
|
<a name='6.10.4p11'></a>
|
|
<pre>11 The sequence of preprocessing tokens bounded by the outside-most matching parentheses forms
|
|
the list of arguments for the function-like macro. The individual arguments within the list are
|
|
separated by comma preprocessing tokens, but comma preprocessing tokens between matching
|
|
inner parentheses do not separate arguments. If there are sequences of preprocessing tokens within
|
|
the list of arguments that would otherwise act as preprocessing directives,<a href='#FOOTNOTE.220'><sup>[220]</sup></a> the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.220'>
|
|
<pre><i><b>Footnote 220)</b> Despite the name, a non-directive is a preprocessing directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.4p12'></a>
|
|
<pre>12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments (if any),
|
|
including any separating comma preprocessing tokens, are merged to form a single item: the variable
|
|
arguments. The number of arguments so combined is such that, following merger, the number of
|
|
arguments is one more than the number of parameters in the macro definition (excluding the ...),
|
|
except that if there are as many arguments as named parameters, the macro invocation behaves as if
|
|
a comma token has been appended to the argument list such that variable arguments are formed
|
|
that contain no pp-tokens.
|
|
</pre>
|
|
<a name='6.10.4.1'></a>
|
|
<hr>
|
|
<h3>6.10.4.1 [Argument substitution]</h3>
|
|
<a name='6.10.4.1p1'></a>
|
|
<pre>1 Syntax
|
|
va-opt-replacement:
|
|
__VA_OPT__ ( pp-tokensopt )
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='6.10.4.1p2'></a>
|
|
<pre>2 Argument substitution is a process during macro expansion in which identifiers corresponding to
|
|
the parameters of the macro definition and the special constructs __VA_ARGS__ and __VA_OPT__
|
|
are replaced with token sequences from the arguments of the macro invocation and possibly of the
|
|
argument of the feature __VA_OPT__ . The latter process allows to control a substitute token sequence
|
|
that is only expanded if the argument list that corresponds to a trailing ... of the parameter list is
|
|
present and has a non-empty substitution.
|
|
|
|
Constraints
|
|
</pre>
|
|
<a name='6.10.4.1p3'></a>
|
|
<pre>3 The identifier __VA_OPT__ shall always occur as part of the preprocessing token sequence va-opt-
|
|
replacement; its closing ) is determined by skipping intervening pairs of matching left and right
|
|
parentheses in its pp-tokens. The pp-tokens of a va-opt-replacement shall not contain __VA_OPT__ .
|
|
The pp-tokens shall form a valid replacement list for the current function-like macro.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.4.1p4'></a>
|
|
<pre>4 After the arguments for the invocation of a function-like macro have been identified, argument
|
|
substitution takes place. A va-opt-replacement is treated as if it were a parameter. For each parameter
|
|
in the replacement list that is neither preceded by a # or ## preprocessing token nor followed by a
|
|
## preprocessing token, the preprocessing tokens naming the parameter are replaced by a token
|
|
sequence determined as follows:
|
|
|
|
— If the parameter is of the form va-opt-replacement, the replacement preprocessing tokens are
|
|
the preprocessing token sequence for the corresponding argument, as specified below.
|
|
— Otherwise, the replacement preprocessing tokens are the preprocessing tokens of the corre-
|
|
sponding argument after all macros contained therein have been expanded. The argument’s
|
|
preprocessing tokens are completely macro replaced before being substituted as if they formed
|
|
the rest of the preprocessing file with no other preprocessing tokens being available.
|
|
|
|
</pre>
|
|
<a name='6.10.4.1p5'></a>
|
|
<pre>5 EXAMPLE 1
|
|
|
|
#define LPAREN() (
|
|
#define G(Q) 42
|
|
#define F(R, X, ...) __VA_OPT__(G R X) )
|
|
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.4.1p6'></a>
|
|
<pre>6 An identifier __VA_ARGS__ that occurs in the replacement list is treated as if it were a parameter,
|
|
and the variable arguments form the preprocessing tokens used to replace it.
|
|
</pre>
|
|
<a name='6.10.4.1p7'></a>
|
|
<pre>7 The preprocessing token sequence for the corresponding argument of a va-opt-replacement is
|
|
defined as follows. If a (hypothetical) substitution of __VA_ARGS__ as neither an operand of # nor
|
|
## consists of no preprocessing tokens, the argument consists of a single placemarker preprocessing
|
|
token (<a href='#6.10.4.3'>6.10.4.3</a>, <a href='#6.10.4.4'>6.10.4.4</a>). Otherwise, the argument consists of the results of the expansion of the
|
|
contained pp-tokens as the replacement list of the current function-like macro before removal of
|
|
placemarker tokens, rescanning, and further replacement.
|
|
</pre>
|
|
<a name='6.10.4.1p8'></a>
|
|
<pre>8 NOTE The placemarker tokens are removed before stringization (<a href='#6.10.4.2'>6.10.4.2</a>), and can be removed by rescanning and further
|
|
replacement (<a href='#6.10.4.4'>6.10.4.4</a>).
|
|
</pre>
|
|
<a name='6.10.4.1p9'></a>
|
|
<pre>9 EXAMPLE 2
|
|
|
|
#define F(...) f(0 __VA_OPT__(,) __VA_ARGS__)
|
|
#define G(X, ...) f(0, X __VA_OPT__(,) __VA_ARGS__)
|
|
#define SDEF(sname, ...) S sname __VA_OPT__(= { __VA_ARGS__ })
|
|
#define EMP
|
|
|
|
F(a, b, c) // replaced by f(0, a, b, c)
|
|
F() // replaced by f(0)
|
|
F(EMP) // replaced by f(0)
|
|
|
|
G(a, b, c) // replaced by f(0, a, b, c)
|
|
G(a, ) // replaced by f(0, a)
|
|
G(a) // replaced by f(0, a)
|
|
|
|
SDEF(foo); // replaced by S foo;
|
|
SDEF(bar, 1, 2); // replaced by S bar = { 1, 2 };
|
|
|
|
#define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__
|
|
// error: ## on line above
|
|
// may not appear at the beginning of a replacement
|
|
// list (<a href='#6.10.4.3'>6.10.4.3</a>)
|
|
|
|
#define H2(X, Y, ...) __VA_OPT__(X ## Y,) __VA_ARGS__
|
|
|
|
H2(a, b, c, d) // replaced by ab, c, d
|
|
|
|
#define H3(X, ...) #__VA_OPT__(X##X X##X)
|
|
H3(, 0) // replaced by ""
|
|
|
|
#define H4(X, ...) __VA_OPT__(a X ## X) ## b
|
|
H4(, 1) // replaced by a b
|
|
|
|
#define H5A(...) __VA_OPT__()/**/__VA_OPT__()
|
|
#define H5B(X) a ## X ## b
|
|
#define H5C(X) H5B(X)
|
|
H5C(H5A()) // replaced by ab
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.4.2'></a>
|
|
<hr>
|
|
<h3>6.10.4.2 [The # operator]</h3>
|
|
<a name='6.10.4.2p1'></a>
|
|
<pre>1 Constraints
|
|
Each # preprocessing token in the replacement list for a function-like macro shall be followed by a
|
|
parameter as the next preprocessing token in the replacement list.
|
|
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.4.2p2'></a>
|
|
<pre>2 If, in the replacement list, a parameter is immediately preceded by a # preprocessing token, both
|
|
are replaced by a single character string literal preprocessing token that contains the spelling of the
|
|
preprocessing token sequence for the corresponding argument (excluding placemarker tokens). Let
|
|
the stringizing argument be the preprocessing token sequence for the corresponding argument with
|
|
placemarker tokens removed. Each occurrence of white space between the stringizing argument’s
|
|
preprocessing tokens becomes a single space character in the character string literal. White space
|
|
before the first preprocessing token and after the last preprocessing token composing the stringizing
|
|
argument is deleted. Otherwise, the original spelling of each preprocessing token in the stringizing
|
|
argument is retained in the character string literal, except for special handling for producing the
|
|
spelling of string literals and character constants: a \ character is inserted before each " and \
|
|
character of a character constant or string literal (including the delimiting " characters), except that
|
|
it is implementation-defined whether a \ character is inserted before the \ character beginning a
|
|
universal character name. If the replacement that results is not a valid character string literal, the
|
|
behavior is undefined. The character string literal corresponding to an empty stringizing argument
|
|
is "". The order of evaluation of # and ## operators is unspecified.
|
|
</pre>
|
|
<a name='6.10.4.3'></a>
|
|
<hr>
|
|
<h3>6.10.4.3 [The ## operator]</h3>
|
|
<a name='6.10.4.3p1'></a>
|
|
<pre>1 Constraints
|
|
A ## preprocessing token shall not occur at the beginning or at the end of a replacement list for
|
|
either form of macro definition.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.4.3p2'></a>
|
|
<pre>2 If, in the replacement list of a function-like macro, a parameter is immediately preceded or followed
|
|
by a ## preprocessing token, the parameter is replaced by the corresponding argument’s preprocess-
|
|
ing token sequence; however, if an argument consists of no preprocessing tokens, the parameter is
|
|
replaced by a placemarker preprocessing token instead.<a href='#FOOTNOTE.221'><sup>[221]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.221'>
|
|
<pre><i><b>Footnote 221)</b> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that exist only within
|
|
translation phase 4.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.4.3p3'></a>
|
|
<pre>3 For both object-like and function-like macro invocations, before the replacement list is reexamined
|
|
for more macro names to replace, each instance of a ## preprocessing token in the replacement list
|
|
(not from an argument) is deleted and the preceding preprocessing token is concatenated with the
|
|
following preprocessing token. Placemarker preprocessing tokens are handled specially: concatena-
|
|
tion of two placemarkers results in a single placemarker preprocessing token, and concatenation
|
|
of a placemarker with a non-placemarker preprocessing token results in the non-placemarker pre-
|
|
processing token. If the result is not a valid preprocessing token, the behavior is undefined. The
|
|
resulting token is available for further macro replacement. The order of evaluation of ## operators is
|
|
unspecified.
|
|
</pre>
|
|
<a name='6.10.4.3p4'></a>
|
|
<pre>4 EXAMPLE In the following fragment:
|
|
|
|
#define hash_hash # ## #
|
|
#define mkstr(a) # a
|
|
#define in_between(a) mkstr(a)
|
|
#define join(c, d) in_between(c hash_hash d)
|
|
|
|
char p[] = join(x, y); // equivalent to
|
|
// char p[] = "x ## y";
|
|
|
|
|
|
The expansion produces, at various stages:
|
|
|
|
join(x, y)
|
|
|
|
in_between(x hash_hash y)
|
|
|
|
in_between(x ## y)
|
|
|
|
mkstr(x ## y)
|
|
|
|
"x ## y"
|
|
|
|
|
|
In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but this new token is
|
|
not the ## operator.
|
|
|
|
</pre>
|
|
<a name='6.10.4.4'></a>
|
|
<hr>
|
|
<h3>6.10.4.4 [Rescanning and further replacement]</h3>
|
|
<a name='6.10.4.4p1'></a>
|
|
<pre>1 After all parameters in the replacement list have been substituted and # and ## processing has
|
|
taken place, all placemarker preprocessing tokens are removed. The resulting preprocessing token
|
|
sequence is then rescanned, along with all subsequent preprocessing tokens of the source file, for
|
|
more macro names to replace.
|
|
</pre>
|
|
<a name='6.10.4.4p2'></a>
|
|
<pre>2 If the name of the macro being replaced is found during this scan of the replacement list (not
|
|
including the rest of the source file’s preprocessing tokens), it is not replaced. Furthermore, if any
|
|
nested replacements encounter the name of the macro being replaced, it is not replaced. These
|
|
nonreplaced macro name preprocessing tokens are no longer available for further replacement even
|
|
if they are later (re)examined in contexts in which that macro name preprocessing token would
|
|
otherwise have been replaced.
|
|
</pre>
|
|
<a name='6.10.4.4p3'></a>
|
|
<pre>3 The resulting completely macro-replaced preprocessing token sequence is not processed as a prepro-
|
|
cessing directive even if it resembles one, but all pragma unary operator expressions within it are
|
|
then processed as specified in <a href='#6.10.10'>6.10.10</a> below.
|
|
</pre>
|
|
<a name='6.10.4.4p4'></a>
|
|
<pre>4 EXAMPLE There are cases where it is not clear whether a replacement is nested or not. For example, given the following
|
|
macro definitions:
|
|
|
|
#define f(a) a*g
|
|
#define g(a) f(a)
|
|
|
|
the invocation
|
|
|
|
f(2)(9)
|
|
|
|
could expand to either
|
|
|
|
2*f(9)
|
|
|
|
or
|
|
|
|
2*9*g
|
|
|
|
Strictly conforming programs are not permitted to depend on such unspecified behavior.
|
|
|
|
</pre>
|
|
<a name='6.10.4.5'></a>
|
|
<hr>
|
|
<h3>6.10.4.5 [Scope of macro definitions]</h3>
|
|
<a name='6.10.4.5p1'></a>
|
|
<pre>1 A macro definition lasts (independent of block structure) until a corresponding #undef directive is
|
|
encountered or (if none is encountered) until the end of the preprocessing translation unit. Macro
|
|
definitions have no significance after translation phase 4.
|
|
</pre>
|
|
<a name='6.10.4.5p2'></a>
|
|
<pre>2 A preprocessing directive of the form
|
|
# undef identifier new-line
|
|
causes the specified identifier no longer to be defined as a macro name. It is ignored if the specified
|
|
identifier is not currently defined as a macro name.
|
|
</pre>
|
|
<a name='6.10.4.5p3'></a>
|
|
<pre>3 EXAMPLE 1 The simplest use of this facility is to define a "manifest constant", as in
|
|
|
|
#define TABSIZE 100
|
|
|
|
int table[TABSIZE];
|
|
|
|
</pre>
|
|
<a name='6.10.4.5p4'></a>
|
|
<pre>4 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments. It has the advantages
|
|
of working for any compatible types of the arguments and of generating in-line code without the overhead of function calling.
|
|
It has the disadvantages of evaluating one or the other of its arguments a second time (including side effects) and generating
|
|
more code than a function if invoked several times. It also cannot have its address taken, as it has none.
|
|
|
|
#define max(a, b) ((a) > (b) ? (a): (b))
|
|
|
|
The parentheses ensure that the arguments and the resulting expression are bound properly.
|
|
</pre>
|
|
<a name='6.10.4.5p5'></a>
|
|
<pre>5 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
|
|
|
|
#define x 3
|
|
#define f(a) f(x * (a))
|
|
#undef x
|
|
#define x 2
|
|
#define g f
|
|
#define z z[0]
|
|
#define h g(\~{ }
|
|
#define m(a) a(w)
|
|
#define w 0,1
|
|
#define t(a) a
|
|
#define p() int
|
|
#define q(x) x
|
|
#define r(x,y) x ## y
|
|
#define str(x) # x
|
|
|
|
f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
|
|
g(x+(3,4)-w) | h 5) & m
|
|
(f)^m(m);
|
|
p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
|
|
char c[2][6] = { str(hello), str() };
|
|
|
|
results in
|
|
|
|
f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
|
|
f(2 * (2+(3,4)-0,1)) | f(2 * (\~{ } 5)) & f(2 * (0,1))^m(0,1);
|
|
int i[] = { 1, 23, 4, 5, };
|
|
char c[2][6] = { "hello", "" };
|
|
</pre>
|
|
<a name='6.10.4.5p6'></a>
|
|
<pre>6 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the sequence
|
|
|
|
#define str(s) # s
|
|
#define xstr(s) str(s)
|
|
#define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
|
|
x ## s, x ## t)
|
|
#define INCFILE(n) vers ## n
|
|
#define glue(a, b) a ## b
|
|
#define xglue(a, b) glue(a, b)
|
|
#define HIGHLOW "hello"
|
|
#define LOW LOW ", world"
|
|
|
|
debug(1, 2);
|
|
fputs(str(strncmp("abc\0d", "abc", ’\4’) // this goes away
|
|
== 0) str(: @\n), s);
|
|
#include xstr(INCFILE(2).h)
|
|
glue(HIGH, LOW);
|
|
xglue(HIGH, LOW)
|
|
|
|
results in
|
|
|
|
printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
|
|
fputs(
|
|
"strncmp(\"abc\\0d\", \"abc\", ’\\4’) == 0" ": @\n",
|
|
s);
|
|
#include "vers2.h" (after macro replacement, before file access)
|
|
"hello";
|
|
"hello" ", world"
|
|
|
|
or, after concatenation of the character string literals,
|
|
|
|
printf("x1= %d, x2= %s", x1, x2);
|
|
fputs(
|
|
"strncmp(\"abc\\0d\", \"abc\", ’\\4’) == 0: @\n",
|
|
s);
|
|
#include "vers2.h" (after macro replacement, before file access)
|
|
"hello";
|
|
"hello, world"
|
|
|
|
Space around the # and ## tokens in the macro definition is optional.
|
|
</pre>
|
|
<a name='6.10.4.5p7'></a>
|
|
<pre>7 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
|
|
|
|
#define t(x,y,z) x ## y ## z
|
|
int j[] = { t(+1,2,3), t(,4,5), t(6,,7), t(8,9,),
|
|
t(10,,), t(,11,), t(,,12), t(,,) };
|
|
|
|
results in
|
|
|
|
int j[] = { 123, 45, 67, 89,
|
|
10, 11, 12, };
|
|
|
|
</pre>
|
|
<a name='6.10.4.5p8'></a>
|
|
<pre>8 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
|
|
|
|
#define OBJ_LIKE (1-1)
|
|
#define OBJ_LIKE /* white space */ (1-1) /* other */
|
|
#define FUNC_LIKE(a) (a)
|
|
#define FUNC_LIKE(a)( /* note the white space */ \
|
|
a /* other stuff on this line
|
|
*/)
|
|
|
|
But the following redefinitions are invalid:
|
|
#define OBJ_LIKE (0) // different token sequence
|
|
#define OBJ_LIKE (1 - 1) // different white space
|
|
#define FUNC_LIKE(b) (a) // different parameter usage
|
|
#define FUNC_LIKE(b) (b) // different parameter spelling
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.4.5p9'></a>
|
|
<pre>9 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
|
|
|
|
#define debug(...) fprintf(stderr, __VA_ARGS__)
|
|
#define showlist(...) puts(#__VA_ARGS__)
|
|
#define report(test, ...) ((test)?puts(#test):\
|
|
printf(__VA_ARGS__))
|
|
debug("Flag");
|
|
debug("X = %d\n", x);
|
|
showlist(The first, second, and third items.);
|
|
report(x>y, "x is %d but y is %d", x, y);
|
|
|
|
|
|
results in
|
|
|
|
fprintf(stderr, "Flag");
|
|
fprintf(stderr, "X = %d\n", x);
|
|
puts("The first, second, and third items.");
|
|
((x>y)?puts("x>y"):
|
|
printf("x is %d but y is %d", x, y));
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='6.10.5'></a>
|
|
<hr>
|
|
<h3>6.10.5 [Line control]</h3>
|
|
<a name='6.10.5p1'></a>
|
|
<pre>1 Constraints
|
|
The string literal of a #line directive, if present, shall be a character string literal.
|
|
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.5p2'></a>
|
|
<pre>2 The line number of the current source line is one greater than the number of new-line characters read
|
|
or introduced in translation phase 1 (<a href='#5.1.1.2'>5.1.1.2</a>) while processing the source file to the current token.
|
|
</pre>
|
|
<a name='6.10.5p3'></a>
|
|
<pre>3 If a preprocessing token (in particular __LINE__ ) spans two or more physical lines, it is unspecified
|
|
which of those line numbers is associated with that token. If a preprocessing directive spans two or
|
|
more physical lines, it is unspecified which of those line numbers is associated with the preprocessing
|
|
directive. If a macro invocation spans multiple physical or logical lines, it is unspecified which of
|
|
those line numbers is associated with that invocation. The line number of a preprocessing token is
|
|
independent of the context (in particular, as a macro argument or in a preprocessing directive). The
|
|
line number of a __LINE__ in a macro body is the line number of the macro invocation.
|
|
</pre>
|
|
<a name='6.10.5p4'></a>
|
|
<pre>4 A preprocessing directive of the form
|
|
# line digit-sequence new-line
|
|
causes the implementation to behave as if the following sequence of source lines begins with a
|
|
source line that has a line number as specified by the digit sequence (interpreted as a decimal integer,
|
|
ignoring any optional digit separators (<a href='#6.4.4.1'>6.4.4.1</a>) in the digit sequence). The digit sequence shall not
|
|
specify zero, nor a number greater than 2147483647.
|
|
</pre>
|
|
<a name='6.10.5p5'></a>
|
|
<pre>5 A preprocessing directive of the form
|
|
# line digit-sequence " s-char-sequenceopt " new-line
|
|
sets the presumed line number similarly and changes the presumed name of the source file to be the
|
|
contents of the character string literal.
|
|
</pre>
|
|
<a name='6.10.5p6'></a>
|
|
<pre>6 A preprocessing directive of the form
|
|
# line pp-tokens new-line
|
|
(that does not match one of the two previous forms) is permitted. The preprocessing tokens after
|
|
line on the directive are processed just as in normal text (each identifier currently defined as a
|
|
macro name is replaced by its replacement list of preprocessing tokens). The directive resulting after
|
|
all replacements shall match one of the two previous forms and is then processed as appropriate.<a href='#FOOTNOTE.222'><sup>[222]</sup></a>
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.222'>
|
|
<pre><i><b>Footnote 222)</b> Because a new-line is explicitly included as part of the #line directive, the number of new-line characters read while
|
|
processing to the first pp-token can be different depending on whether or not the implementation uses a one-pass preprocessor.
|
|
Therefore, there are two possible values for the line number following a directive of the form #line __LINE__ new-line.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.5p7'></a>
|
|
<pre>7 The line number associated with a pp-token should be the line number of the first character of the
|
|
pp-token. The line number associated with a preprocessing directive should be the line number of
|
|
the line with the first # token. The line number associated with a macro invocation should be the
|
|
line number of the first character of the macro name in the invocation.
|
|
|
|
</pre>
|
|
<a name='6.10.6'></a>
|
|
<hr>
|
|
<h3>6.10.6 [Diagnostic directives]</h3>
|
|
<a name='6.10.6p1'></a>
|
|
<pre>1 Semantics
|
|
A preprocessing directive of either form
|
|
# error pp-tokensopt new-line # warning pp-tokensopt new-line
|
|
causes the implementation to produce a diagnostic message that includes the specified sequence of
|
|
preprocessing tokens.
|
|
|
|
</pre>
|
|
<a name='6.10.7'></a>
|
|
<hr>
|
|
<h3>6.10.7 [Pragma directive]</h3>
|
|
<a name='6.10.7p1'></a>
|
|
<pre>1 Semantics
|
|
A preprocessing directive of the form
|
|
# pragma pp-tokensopt new-line
|
|
where the preprocessing token STDC does not immediately follow pragma in the directive (prior to
|
|
any macro replacement)<a href='#FOOTNOTE.223'><sup>[223]</sup></a> causes the implementation to behave in an implementation-defined man-
|
|
ner. The behavior might cause translation to fail or cause the translator or the resulting program to
|
|
behave in a non-conforming manner. Any such pragma that is not recognized by the implementation
|
|
is ignored.
|
|
</pre>
|
|
<a name='FOOTNOTE.223'>
|
|
<pre><i><b>Footnote 223)</b> An implementation is not required to perform macro replacement in pragmas, but it is permitted except for in standard
|
|
pragmas (where STDC immediately follows pragma). If the result of macro replacement in a non-standard pragma has the
|
|
same form as a standard pragma, the behavior is still implementation-defined; an implementation is permitted to behave as
|
|
if it were the standard pragma, but is not required to.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.7p2'></a>
|
|
<pre>2 If the preprocessing token STDC does immediately follow pragma in the directive (prior to any macro
|
|
replacement), then no macro replacement is performed on the directive, and the directive shall have
|
|
one of the following forms<a href='#FOOTNOTE.224'><sup>[224]</sup></a> whose meanings are described elsewhere:
|
|
standard-pragma:
|
|
# pragma STDC FP_CONTRACT on-off-switch
|
|
# pragma STDC FENV_ACCESS on-off-switch
|
|
# pragma STDC FENV_DEC_ROUND dec-direction
|
|
# pragma STDC FENV_ROUND direction
|
|
# pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
|
|
on-off-switch: one of
|
|
ON OFF DEFAULT
|
|
|
|
direction: one of
|
|
FE_DOWNWARD FE_TONEAREST FE_TONEARESTFROMZERO
|
|
FE_TOWARDZERO FE_UPWARD FE_DYNAMIC
|
|
|
|
dec-direction: one of
|
|
FE_DEC_DOWNWARD FE_DEC_TONEAREST FE_DEC_TONEARESTFROMZERO
|
|
FE_DEC_TOWARDZERO FE_DEC_UPWARD FE_DEC_DYNAMIC
|
|
Forward references: the FP_CONTRACT pragma (<a href='#7.12.2'>7.12.2</a>), the FENV_ACCESS pragma
|
|
(<a href='#7.6.1'>7.6.1</a>), the FENV_DEC_ROUND pragma (<a href='#7.6.3'>7.6.3</a>), the FENV_ROUND pragma (<a href='#7.6.2'>7.6.2</a>), the
|
|
CX_LIMITED_RANGE pragma (<a href='#7.3.4'>7.3.4</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.224'>
|
|
<pre><i><b>Footnote 224)</b> See "future language directions" (<a href='#6.11.6'>6.11.6</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.8'></a>
|
|
<hr>
|
|
<h3>6.10.8 [Null directive]</h3>
|
|
<a name='6.10.8p1'></a>
|
|
<pre>1 Semantics
|
|
A preprocessing directive of the form
|
|
# new-line
|
|
has no effect.
|
|
|
|
</pre>
|
|
<a name='6.10.9'></a>
|
|
<hr>
|
|
<h3>6.10.9 [Predefined macro names]</h3>
|
|
<a name='6.10.9p1'></a>
|
|
<pre>1 The values of the predefined macros listed in the following subclauses<a href='#FOOTNOTE.225'><sup>[225]</sup></a> (except for __FILE__ and
|
|
__LINE__ ) remain constant throughout the translation unit.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.225'>
|
|
<pre><i><b>Footnote 225)</b> See "future language directions" (<a href='#6.11.7'>6.11.7</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.9p2'></a>
|
|
<pre>2 None of these macro names, nor the identifiers defined or __has_c_attribute , shall be the subject
|
|
of a #define or a #undef preprocessing directive. Any other predefined macro names: shall begin
|
|
with a leading underscore followed by an uppercase letter; or, a second underscore; or, shall be any
|
|
of the identifiers alignas, alignof, bool, false, static_assert, thread_local, or true.
|
|
</pre>
|
|
<a name='6.10.9p3'></a>
|
|
<pre>3 The implementation shall not predefine the macro __cplusplus , nor shall it define it in any standard
|
|
header.
|
|
Forward references: standard headers (<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
</pre>
|
|
<a name='6.10.9.1'></a>
|
|
<hr>
|
|
<h3>6.10.9.1 [Mandatory macros]</h3>
|
|
<a name='6.10.9.1p1'></a>
|
|
<pre>1 The following macro names shall be defined by the implementation:
|
|
|
|
__DATE__ The date of translation of the preprocessing translation unit: a character string literal of
|
|
the form "Mmm dd yyyy", where the names of the months are the same as those generated
|
|
by the asctime function, and the first character of dd is a space character if the value is
|
|
less than 10. If the date of translation is not available, an implementation-defined valid
|
|
date shall be supplied.
|
|
__FILE__ The presumed name of the current source file (a character string literal).<a href='#FOOTNOTE.226'><sup>[226]</sup></a>
|
|
|
|
__LINE__ The presumed line number (within the current source file) of the current source line (an
|
|
integer constant).<a href='#FOOTNOTE.226'><sup>[226]</sup></a>
|
|
__STDC__ The integer constant 1 , intended to indicate a conforming implementation.
|
|
|
|
__STDC_HOSTED__ The integer constant 1 if the implementation is a hosted implementation or the
|
|
integer constant 0 if it is not.
|
|
__STDC_UTF_16__ The integer constant 1 , intended to indicate that values of type char16_t are
|
|
UTF–16 encoded.
|
|
__STDC_UTF_32__ The integer constant 1 , intended to indicate that values of type char32_t are
|
|
UTF–32 encoded.
|
|
__STDC_VERSION__ The integer constant 202311L.<a href='#FOOTNOTE.227'><sup>[227]</sup></a>
|
|
|
|
__TIME__ The time of translation of the preprocessing translation unit: a character string literal of
|
|
the form "hh:mm:ss" as in the time generated by the asctime functions. If the time of
|
|
translation is not available, an implementation-defined valid time shall be supplied.
|
|
|
|
Forward references: the asctime functions (<a href='#7.29.3.1'>7.29.3.1</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.226'>
|
|
<pre><i><b>Footnote 226)</b> The presumed source file name and line number can be changed by the #line directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.226'>
|
|
<pre><i><b>Footnote 226)</b> The presumed source file name and line number can be changed by the #line directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.227'>
|
|
<pre><i><b>Footnote 227)</b> See Annex M for the values in previous revisions. The intention is that this will remain an integer constant of type
|
|
long int that is increased with each revision of this document.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.9.2'></a>
|
|
<hr>
|
|
<h3>6.10.9.2 [Environment macros]</h3>
|
|
<a name='6.10.9.2p1'></a>
|
|
<pre>1 The following macro names are conditionally defined by the implementation:
|
|
|
|
__STDC_ISO_10646__ An integer constant of the form yyyymmL (for example, 199712L ). If this
|
|
symbol is defined, then every character in the Unicode required set, when stored in an
|
|
object of type wchar_t, has the same value as the short identifier of that character. The
|
|
Unicode required set consists of all the characters that are defined by ISO/IEC 10646, along
|
|
with all amendments and technical corrigenda, as of the specified year and month. If
|
|
some other encoding is used, the macro shall not be defined and the actual encoding
|
|
used is implementation-defined.
|
|
__STDC_MB_MIGHT_NEQ_WC__ The integer constant 1 , intended to indicate that, in the encoding for
|
|
wchar_t , a member of the basic character set need not have a code value equal to its
|
|
value when used as the lone character in an integer character constant.
|
|
|
|
Forward references: common definitions (<a href='#7.21'>7.21</a>), Unicode utilities (<a href='#7.30'>7.30</a>).
|
|
|
|
</pre>
|
|
<a name='6.10.9.3'></a>
|
|
<hr>
|
|
<h3>6.10.9.3 [Conditional feature macros]</h3>
|
|
<a name='6.10.9.3p1'></a>
|
|
<pre>1 The following macro names are conditionally defined by the implementation:
|
|
|
|
__STDC_ANALYZABLE__ The integer constant 1 , intended to indicate conformance to the specifica-
|
|
tions in Annex L (Analyzability).
|
|
__STDC_IEC_60559_BFP__ The integer constant 202311L, intended to indicate conformance to
|
|
Annex F (IEC 60559 floating-point arithmetic) for binary floating-point arithmetic.
|
|
__STDC_IEC_559__ The integer constant 1 , intended to indicate conformance to the specifications
|
|
in Annex F (IEC 60559 floating-point arithmetic) for binary floating-point arithmetic. Use
|
|
of this macro is an obsolescent feature.
|
|
__STDC_IEC_60559_DFP__ The integer constant 202311L, intended to indicate support of decimal
|
|
floating types and conformance to Annex F (IEC 60559 floating-point arithmetic) for
|
|
decimal floating-point arithmetic.
|
|
__STDC_IEC_60559_COMPLEX__ The integer constant 202311L, intended to indicate conformance
|
|
to the specifications in Annex G (IEC 60559 compatible complex arithmetic).
|
|
__STDC_IEC_60559_TYPES__ The integer constant 202311L, intended to indicate conformance to
|
|
the specification in Annex H (IEC 60559 interchange and extended types).
|
|
__STDC_IEC_559_COMPLEX__ The integer constant 1 , intended to indicate adherence to the specifi-
|
|
cations in Annex G (IEC 60559 compatible complex arithmetic). Use of this macro is an
|
|
obsolescent feature.
|
|
__STDC_LIB_EXT1__ The integer constant 202311L, intended to indicate support for the extensions
|
|
defined in Annex K (Bounds-checking interfaces)<a href='#FOOTNOTE.228'><sup>[228]</sup></a> .
|
|
__STDC_NO_ATOMICS__ The integer constant 1, intended to indicate that the implementation does
|
|
not support atomic types (including the _Atomic type qualifier) and the <stdatomic.h>
|
|
header.
|
|
__STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the implementation does
|
|
not support complex types or the <complex.h> header.
|
|
__STDC_NO_THREADS__ The integer constant 1, intended to indicate that the implementation does
|
|
not support the <threads.h> header.
|
|
__STDC_NO_VLA__ The integer constant 1 , intended to indicate that the implementation does not
|
|
support variable length arrays with automatic storage duration. Parameters declared
|
|
with variable length array types are adjusted and then define objects of automatic storage
|
|
duration with pointer types. Thus, support for such declarations is mandatory.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.228'>
|
|
<pre><i><b>Footnote 228)</b> The intention is that this will remain an integer constant of type long int that is increased with each revision of this
|
|
document.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.9.3p2'></a>
|
|
<pre>2 An implementation that defines __STDC_NO_COMPLEX__ shall not define __STDC_IEC_60559_COMPLEX__
|
|
or __STDC_IEC_559_COMPLEX__ .
|
|
|
|
</pre>
|
|
<a name='6.10.10'></a>
|
|
<hr>
|
|
<h3>6.10.10 [Pragma operator]</h3>
|
|
<a name='6.10.10p1'></a>
|
|
<pre>1 Semantics
|
|
A unary operator expression of the form:
|
|
_Pragma ( string-literal )
|
|
|
|
is processed as follows: The string literal is destringized by deleting any encoding prefix, deleting
|
|
the leading and trailing double-quotes, replacing each escape sequence \" by a double-quote, and
|
|
replacing each escape sequence \\ by a single backslash. The resulting sequence of characters
|
|
is processed through translation phase 3 to produce preprocessing tokens that are executed as if
|
|
they were the pp-tokens in a pragma directive. The original four preprocessing tokens in the unary
|
|
operator expression are removed.
|
|
</pre>
|
|
<a name='6.10.10p2'></a>
|
|
<pre>2 EXAMPLE A directive of the form:
|
|
|
|
#pragma listing on "..\listing.dir"
|
|
|
|
can also be expressed as:
|
|
|
|
_Pragma ("listing on \"..\\listing.dir\"")
|
|
|
|
|
|
The latter form is processed in the same way whether it appears literally as shown, or results from macro replacement, as in:
|
|
|
|
#define LISTING(x) PRAGMA(listing on #x)
|
|
#define PRAGMA(x) _Pragma(#x)
|
|
|
|
LISTING (..\listing.dir)
|
|
</pre>
|
|
<a name='6.11'></a>
|
|
<hr>
|
|
<h3>6.11 [Future language directions]</h3>
|
|
<a name='6.11.1'></a>
|
|
<hr>
|
|
<h3>6.11.1 [Floating types]</h3>
|
|
<a name='6.11.1p1'></a>
|
|
<pre>1 Future standardization may include additional floating types, including those with greater range,
|
|
precision, or both than long double.
|
|
|
|
</pre>
|
|
<a name='6.11.2'></a>
|
|
<hr>
|
|
<h3>6.11.2 [Linkages of identifiers]</h3>
|
|
<a name='6.11.2p1'></a>
|
|
<pre>1 Declaring an identifier with internal linkage at file scope without the static storage-class specifier
|
|
is an obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='6.11.3'></a>
|
|
<hr>
|
|
<h3>6.11.3 [External names]</h3>
|
|
<a name='6.11.3p1'></a>
|
|
<pre>1 Restriction of the significance of an external name to fewer than 255 characters (considering each
|
|
universal character name or extended source character as a single character) is an obsolescent feature
|
|
that is a concession to existing implementations.
|
|
|
|
</pre>
|
|
<a name='6.11.4'></a>
|
|
<hr>
|
|
<h3>6.11.4 [Character escape sequences]</h3>
|
|
<a name='6.11.4p1'></a>
|
|
<pre>1 Lowercase letters as escape sequences are reserved for future standardization. Other characters may
|
|
be used in extensions.
|
|
|
|
</pre>
|
|
<a name='6.11.5'></a>
|
|
<hr>
|
|
<h3>6.11.5 [Storage-class specifiers]</h3>
|
|
<a name='6.11.5p1'></a>
|
|
<pre>1 The placement of a storage-class specifier other than at the beginning of the declaration specifiers in
|
|
a declaration is an obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='6.11.6'></a>
|
|
<hr>
|
|
<h3>6.11.6 [Pragma directives]</h3>
|
|
<a name='6.11.6p1'></a>
|
|
<pre>1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
|
|
|
|
</pre>
|
|
<a name='6.11.7'></a>
|
|
<hr>
|
|
<h3>6.11.7 [Predefined macro names]</h3>
|
|
<a name='6.11.7p1'></a>
|
|
<pre>1 Macro names beginning with __STDC_ are reserved for future standardization.
|
|
</pre>
|
|
<a name='6.11.7p2'></a>
|
|
<pre>2 Uses of the __STDC_IEC_559__ and __STDC_IEC_559_COMPLEX__ macros are obsolescent features.
|
|
</pre>
|
|
<a name='7.'></a>
|
|
<hr>
|
|
<h3>7. [Library]</h3>
|
|
<a name='7.1'></a>
|
|
<hr>
|
|
<h3>7.1 [Introduction]</h3>
|
|
<a name='7.1.1'></a>
|
|
<hr>
|
|
<h3>7.1.1 [Definitions of terms]</h3>
|
|
<a name='7.1.1p1'></a>
|
|
<pre>1 A string is a contiguous sequence of characters terminated by and including the first null character.
|
|
The term multibyte string is sometimes used instead to emphasize special processing given to
|
|
multibyte characters contained in the string or to avoid confusion with a wide string. A pointer to
|
|
a string is a pointer to its initial (lowest addressed) character. The length of a string is the number
|
|
of bytes preceding the null character and the value of a string is the sequence of the values of the
|
|
contained characters, in order.
|
|
</pre>
|
|
<a name='7.1.1p2'></a>
|
|
<pre>2 The decimal-point character is the character used by functions that convert floating-point numbers
|
|
to or from character sequences to denote the beginning of the fractional part of such character
|
|
sequences.<a href='#FOOTNOTE.229'><sup>[229]</sup></a> It is represented in the text and examples by a period, but may be changed by the
|
|
setlocale function.
|
|
</pre>
|
|
<a name='FOOTNOTE.229'>
|
|
<pre><i><b>Footnote 229)</b> The functions that make use of the decimal-point character are the numeric conversion functions (<a href='#7.24.1'>7.24.1</a>, <a href='#7.31.4.1'>7.31.4.1</a>) and the
|
|
formatted input/output functions (<a href='#7.23.6'>7.23.6</a>, <a href='#7.31.2'>7.31.2</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.1p3'></a>
|
|
<pre>3 A null wide character is a wide character with code value zero.
|
|
</pre>
|
|
<a name='7.1.1p4'></a>
|
|
<pre>4 A wide string is a contiguous sequence of wide characters terminated by and including the first null
|
|
wide character. A pointer to a wide string is a pointer to its initial (lowest addressed) wide character.
|
|
The length of a wide string is the number of wide characters preceding the null wide character and the
|
|
value of a wide string is the sequence of code values of the contained wide characters, in order.
|
|
</pre>
|
|
<a name='7.1.1p5'></a>
|
|
<pre>5 A shift sequence is a contiguous sequence of bytes within a multibyte string that (potentially) causes
|
|
a change in shift state (see <a href='#5.2.1.1'>5.2.1.1</a>). A shift sequence shall not have a corresponding wide character;
|
|
it is instead taken to be an adjunct to an adjacent multibyte character.<a href='#FOOTNOTE.230'><sup>[230]</sup></a> In this clause, references to
|
|
"white-space character" refer to (execution) white-space character as defined by isspace. References to
|
|
"white-space wide character" refer to (execution) white-space wide character as defined by iswspace.
|
|
Forward references: character handling (<a href='#7.4'>7.4</a>), the setlocale function (<a href='#7.11.1.1'>7.11.1.1</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.230'>
|
|
<pre><i><b>Footnote 230)</b> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX are thus required to be large enough to
|
|
count all the bytes in any complete multibyte character plus at least one adjacent shift sequence of maximum length. Whether
|
|
these counts provide for more than one shift sequence is the implementation’s choice.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.2'></a>
|
|
<hr>
|
|
<h3>7.1.2 [Standard headers]</h3>
|
|
<a name='7.1.2p1'></a>
|
|
<pre>1 Each library function is declared in a header,<a href='#FOOTNOTE.231'><sup>[231]</sup></a> whose contents are made available by the #include
|
|
preprocessing directive. The header declares a set of related functions, plus any necessary types
|
|
and additional macros needed to facilitate their use. In addition to the provisions given in this
|
|
clause, an implementation that defines __STDC_LIB_EXT1__ shall conform to the specifications in
|
|
Annex K and Subclause <a href='#K.3'>K.3</a> should be read as if it were merged into the parallel structure of named
|
|
subclauses of this clause. Declarations of types described here or in Annex K shall not include type
|
|
qualifiers, unless explicitly stated otherwise.
|
|
</pre>
|
|
<a name='FOOTNOTE.231'>
|
|
<pre><i><b>Footnote 231)</b> A header is not necessarily a source file, nor are the < and > delimited sequences in header names necessarily valid source
|
|
file names.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.2p2'></a>
|
|
<pre>2 An implementation that does not support decimal floating types (<a href='#6.10.9.3'>6.10.9.3</a>) need not support inter-
|
|
faces or aspects of interfaces that are specific to these types.
|
|
</pre>
|
|
<a name='7.1.2p3'></a>
|
|
<pre>3 The standard headers are<a href='#FOOTNOTE.232'><sup>[232]</sup></a>
|
|
|
|
<assert.h> <fenv.h> <limits.h>
|
|
<complex.h> <float.h> <locale.h>
|
|
<ctype.h> <inttypes.h> <math.h>
|
|
<errno.h> <iso646.h> <setjmp.h>
|
|
<signal.h> <stddef.h> <tgmath.h>
|
|
<stdalign.h> <stdint.h> <threads.h>
|
|
<stdarg.h> <stdio.h> <time.h>
|
|
<stdatomic.h> <stdlib.h> <uchar.h>
|
|
<stdbool.h> <stdnoreturn.h> <wchar.h>
|
|
<stdckdint.h> <string.h> <wctype.h>
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.232'>
|
|
<pre><i><b>Footnote 232)</b> The headers <complex.h>, <stdatomic.h>, and <threads.h> are conditional features that implementations need not
|
|
support; see <a href='#6.10.9.3'>6.10.9.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.2p4'></a>
|
|
<pre>4 If a file with the same name as one of the above < and > delimited sequences, not provided as part of
|
|
the implementation, is placed in any of the standard places that are searched for included source
|
|
files, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.1.2p5'></a>
|
|
<pre>5 Standard headers may be included in any order; each may be included more than once in a given
|
|
scope, with no effect different from being included only once, except that the effect of including
|
|
<assert.h> depends on the definition of NDEBUG (see <a href='#7.2'>7.2</a>). If used, a header shall be included outside
|
|
of any external declaration or definition, and it shall first be included before the first reference to
|
|
any of the functions or objects it declares, or to any of the types or macros it defines. However, if
|
|
an identifier is declared or defined in more than one header, the second and subsequent associated
|
|
headers may be included after the initial reference to the identifier. The program shall not have any
|
|
macros with names lexically identical to keywords currently defined prior to the inclusion of the
|
|
header or when any macro defined in the header is expanded.
|
|
</pre>
|
|
<a name='7.1.2p6'></a>
|
|
<pre>6 Some standard headers define or declare identifiers that had not been present in previous versions
|
|
of this document. To allow implementations and users to adapt to that situation, they also define a
|
|
version macro for feature test of the form __STDC_VERSION_XXXX_H__ which expands to 202311L,
|
|
where XXXX is the all-caps spelling of the corresponding header <xxxx.h>.
|
|
</pre>
|
|
<a name='7.1.2p7'></a>
|
|
<pre>7 Any definition of an object-like macro described in this clause or Annex K shall expand to code that
|
|
is fully protected by parentheses where necessary, so that it groups in an arbitrary expression as if it
|
|
were a single identifier.
|
|
</pre>
|
|
<a name='7.1.2p8'></a>
|
|
<pre>8 Any declaration of a library function shall have external linkage.
|
|
</pre>
|
|
<a name='7.1.2p9'></a>
|
|
<pre>9 A summary of the contents of the standard headers is given in Annex B.
|
|
Forward references: diagnostics (<a href='#7.2'>7.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.1.3'></a>
|
|
<hr>
|
|
<h3>7.1.3 [Reserved identifiers]</h3>
|
|
<a name='7.1.3p1'></a>
|
|
<pre>1 Each header declares or defines all identifiers listed in its associated subclause, and optionally
|
|
declares or defines identifiers listed in its associated future library directions subclause and identifiers
|
|
which are always reserved either for any use or for use as file scope identifiers.
|
|
|
|
— All potentially reserved identifiers (including ones listed in the future library directions) that
|
|
are provided by an implementation with an external definition are reserved for any use. An
|
|
implementation shall not provide an external definition of a potentially reserved identifier
|
|
unless that identifier is reserved for a use where it would have external linkage. All other
|
|
potentially reserved identifiers that are provided by an implementation (including in the
|
|
form of a macro) are reserved for any use when the associated header is included. No other
|
|
potentially reserved identifiers are reserved.<a href='#FOOTNOTE.233'><sup>[233]</sup></a>
|
|
|
|
— Each macro name in any of the following subclauses (including the future library directions)
|
|
is reserved for use as specified if any of its associated headers is included; unless explicitly
|
|
stated otherwise (see <a href='#7.1.4'>7.1.4</a>).
|
|
|
|
— All identifiers with external linkage in any of the following subclauses (including the future
|
|
library directions) and errno are always reserved for use as identifiers with external linkage<a href='#FOOTNOTE.234'><sup>[234]</sup></a> .
|
|
|
|
— Each identifier with file scope listed in any of the following subclauses (including the future
|
|
library directions) is reserved for use as a macro name and as an identifier with file scope in
|
|
the same name space if any of its associated headers is included.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.233'>
|
|
<pre><i><b>Footnote 233)</b> A potentially reserved identifier becomes a reserved identifier when an implementation begins using it or a future
|
|
standard reserves it, but is otherwise available for use by the programmer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.234'>
|
|
<pre><i><b>Footnote 234)</b> The list of reserved identifiers with external linkage includes math_errhandling, setjmp, va_copy , and va_end .
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.4'></a>
|
|
<hr>
|
|
<h3>7.1.4 [Use of library functions]</h3>
|
|
<a name='7.1.4p1'></a>
|
|
<pre>1 Each of the following statements applies unless explicitly stated otherwise in the detailed descrip-
|
|
tions that follow:
|
|
|
|
— If an argument to a function has an invalid value (such as a value outside the domain of the
|
|
function, or a pointer outside the address space of the program, or a null pointer, or a pointer
|
|
to non-modifiable storage when the corresponding parameter is not const-qualified) or a type
|
|
(after default argument promotion) not expected by a function with a variable number of
|
|
arguments, the behavior is undefined.
|
|
— If a function argument is described as being an array, the pointer actually passed to the function
|
|
shall have a value such that all address computations and accesses to objects (that would be
|
|
valid if the pointer did point to the first element of such an array) are in fact valid.<a href='#FOOTNOTE.235'><sup>[235]</sup></a>
|
|
— Any function declared in a header may be additionally implemented as a function-like macro
|
|
defined in the header, so if a library function is declared explicitly when its header is included,
|
|
one of the techniques shown below can be used to ensure the declaration is not affected by
|
|
such a macro. Any macro definition of a function can be suppressed locally by enclosing
|
|
the name of the function in parentheses, because the name is then not followed by the left
|
|
parenthesis that indicates expansion of a macro function name. For the same syntactic reason,
|
|
it is permitted to take the address of a library function even if it is also defined as a macro.<a href='#FOOTNOTE.236'><sup>[236]</sup></a>
|
|
The use of #undef to remove any macro definition will also ensure that an actual function is
|
|
referred to.
|
|
— Any invocation of a library function that is implemented as a macro shall expand to code that
|
|
evaluates each of its arguments exactly once, fully protected by parentheses where necessary,
|
|
so it is generally safe to use arbitrary expressions as arguments.<a href='#FOOTNOTE.237'><sup>[237]</sup></a>
|
|
— Likewise, those function-like macros described in the following subclauses may be invoked in
|
|
an expression anywhere a function with a compatible return type could be called. <a href='#FOOTNOTE.238'><sup>[238]</sup></a>
|
|
— All object-like macros listed as expanding to integer constant expressions shall additionally be
|
|
suitable for use in #if preprocessing directives.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.235'>
|
|
<pre><i><b>Footnote 235)</b> This includes, for example, passing a valid pointer that points one-past-the-end of an array along with a size of 0, or
|
|
using any valid pointer with a size of 0.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.236'>
|
|
<pre><i><b>Footnote 236)</b> This means that an implementation is required to provide an actual function for each library function, even if it also
|
|
provides a macro for that function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.237'>
|
|
<pre><i><b>Footnote 237)</b> Such macros might not contain the sequence points that the corresponding function calls do.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.238'>
|
|
<pre><i><b>Footnote 238)</b> Because external identifiers and some macro names beginning with an underscore are reserved, implementations can
|
|
provide special semantics for such names. For example, the identifier _BUILTIN_abs could be used to indicate generation of
|
|
in-line code for the abs function. Thus, the appropriate header could specify
|
|
#define abs(x) _BUILTIN_abs(x)
|
|
for a compiler whose code generator will accept it.
|
|
In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine function can write
|
|
#undef abs
|
|
whether the implementation’s header provides a macro implementation of abs or a built-in implementation. The prototype
|
|
for the function, which precedes and is hidden by any macro definition, is thereby revealed also.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.4p2'></a>
|
|
<pre>2 Provided that a library function can be declared without reference to any type defined in a header, it
|
|
is also permissible to declare the function and use it without including its associated header.
|
|
</pre>
|
|
<a name='7.1.4p3'></a>
|
|
<pre>3 There is a sequence point immediately before a library function returns.
|
|
</pre>
|
|
<a name='7.1.4p4'></a>
|
|
<pre>4 The functions in the standard library are not guaranteed to be reentrant and may modify objects
|
|
with static or thread storage duration. <a href='#FOOTNOTE.239'><sup>[239]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.239'>
|
|
<pre><i><b>Footnote 239)</b> Thus, a signal handler cannot, in general, call standard library functions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.4p5'></a>
|
|
<pre>5 Unless explicitly stated otherwise in the detailed descriptions that follow, library functions shall
|
|
prevent data races as follows: A library function shall not directly or indirectly access objects
|
|
accessible by threads other than the current thread unless the objects are accessed directly or
|
|
indirectly via the function’s arguments. A library function shall not directly or indirectly modify
|
|
objects accessible by threads other than the current thread unless the objects are accessed directly
|
|
or indirectly via the function’s non-const arguments. <a href='#FOOTNOTE.240'><sup>[240]</sup></a> Implementations may share their own
|
|
internal objects between threads if the objects are not visible to users and are protected against data
|
|
races.
|
|
</pre>
|
|
<a name='FOOTNOTE.240'>
|
|
<pre><i><b>Footnote 240)</b> This means, for example, that an implementation is not permitted to use a static object for internal purposes without
|
|
synchronization because it could cause a data race even in programs that do not explicitly share objects between threads.
|
|
Similarly, an implementation of memcpy is not permitted to copy bytes beyond the specified length of the destination object
|
|
and then restore the original values because it could cause a data race if the program shared those bytes between threads.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.4p6'></a>
|
|
<pre>6 Unless otherwise specified, library functions shall perform all operations solely within the current
|
|
thread if those operations have effects that are visible to users.<a href='#FOOTNOTE.241'><sup>[241]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.241'>
|
|
<pre><i><b>Footnote 241)</b> This allows implementations to parallelize operations if there are no visible side effects.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.4p7'></a>
|
|
<pre>7 EXAMPLE The function atoi can be used in any of several ways:
|
|
|
|
— by use of its associated header (possibly generating a macro expansion)
|
|
|
|
#include <stdlib.h>
|
|
const char *str;
|
|
/* ... */
|
|
i = atoi(str);
|
|
|
|
— by use of its associated header (assuredly generating a true function reference)
|
|
|
|
#include <stdlib.h>
|
|
#undef atoi
|
|
const char *str;
|
|
/* ... */
|
|
i = atoi(str);
|
|
|
|
or
|
|
|
|
#include <stdlib.h>
|
|
const char *str;
|
|
/* ... */
|
|
i = (atoi)(str);
|
|
|
|
— by explicit declaration
|
|
|
|
extern int atoi(const char *);
|
|
const char *str;
|
|
/* ... */
|
|
i = atoi(str);
|
|
</pre>
|
|
<a name='7.2'></a>
|
|
<hr>
|
|
<h3>7.2 [Diagnostics <assert.h>]</h3>
|
|
<a name='7.2p1'></a>
|
|
<pre>1 The header <assert.h> defines the assert and static_assert macros and refers to another
|
|
macro,
|
|
|
|
NDEBUG
|
|
|
|
|
|
which is not defined by <assert.h>. If NDEBUG is defined as a macro name at the point in the source
|
|
file where <assert.h> is included, the assert macro is defined simply as
|
|
|
|
#define assert(...) ((void)0)
|
|
|
|
|
|
The assert macro is redefined according to the current state of NDEBUG each time that <assert.h>
|
|
is included.
|
|
</pre>
|
|
<a name='7.2p2'></a>
|
|
<pre>2 The assert macro shall be implemented as a macro with an ellipsis parameter, not as an actual
|
|
function. If the macro definition is suppressed in order to access an actual function, the behavior is
|
|
undefined.
|
|
|
|
</pre>
|
|
<a name='7.2.1'></a>
|
|
<hr>
|
|
<h3>7.2.1 [Program diagnostics]</h3>
|
|
<a name='7.2.1.1'></a>
|
|
<hr>
|
|
<h3>7.2.1.1 [The assert macro]</h3>
|
|
<a name='7.2.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <assert.h>
|
|
void assert(scalar expression);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.2.1.1p2'></a>
|
|
<pre>2 The assert macro puts diagnostic tests into programs; it expands to a void expression. When it
|
|
is executed, if expression (which shall have a scalar type) is false (that is, compares equal to 0),
|
|
the assert macro writes information about the particular call that failed (including the text of the
|
|
argument, the name of the source file, the source line number, and the name of the enclosing function
|
|
— the latter are respectively the values of the preprocessing macros __FILE__ and __LINE__ and of
|
|
the identifier __func__ ) on the standard error stream in an implementation-defined format.<a href='#FOOTNOTE.242'><sup>[242]</sup></a>
|
|
It then calls the abort function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.242'>
|
|
<pre><i><b>Footnote 242)</b> The message written might be of the form:
|
|
Assertion failed: expression, function abc, file xyz, line nnn.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.2.1.1p3'></a>
|
|
<pre>3 The assert macro returns no value.
|
|
Forward references: the abort function (<a href='#7.24.4.1'>7.24.4.1</a>).
|
|
</pre>
|
|
<a name='7.3'></a>
|
|
<hr>
|
|
<h3>7.3 [Complex arithmetic <complex.h>]</h3>
|
|
<a name='7.3.1'></a>
|
|
<hr>
|
|
<h3>7.3.1 [Introduction]</h3>
|
|
<a name='7.3.1p1'></a>
|
|
<pre>1 The header <complex.h> defines macros and declares functions that support complex arithmetic.<a href='#FOOTNOTE.243'><sup>[243]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.243'>
|
|
<pre><i><b>Footnote 243)</b> See "future library directions" (<a href='#7.33.1'>7.33.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.1p2'></a>
|
|
<pre>2 Implementations that define the macro __STDC_NO_COMPLEX__ need not provide this header nor
|
|
support any of its facilities.
|
|
</pre>
|
|
<a name='7.3.1p3'></a>
|
|
<pre>3 Each synopsis, other than for the CMPLX macros, specifies a family of functions consisting of a princi-
|
|
pal function with one or more double complex parameters and a double complex or double return
|
|
value; and other functions with the same name but with f and l suffixes which are corresponding
|
|
functions with float and long double parameters and return values.
|
|
</pre>
|
|
<a name='7.3.1p4'></a>
|
|
<pre>4 The macro
|
|
|
|
complex
|
|
|
|
|
|
expands to _Complex ; the macro
|
|
_Complex_I
|
|
|
|
|
|
expands to a constant expression of type float _Complex, with the value of the imaginary unit.<a href='#FOOTNOTE.244'><sup>[244]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.244'>
|
|
<pre><i><b>Footnote 244)</b> The imaginary unit is a number i such that i2 = −1.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.1p5'></a>
|
|
<pre>5 The macros
|
|
|
|
imaginary
|
|
|
|
|
|
and
|
|
_Imaginary_I
|
|
|
|
|
|
are defined if and only if the implementation supports imaginary types;<a href='#FOOTNOTE.245'><sup>[245]</sup></a> if defined, they expand
|
|
to _Imaginary and a constant expression of type float _Imaginary with the value of the imaginary
|
|
unit.
|
|
</pre>
|
|
<a name='FOOTNOTE.245'>
|
|
<pre><i><b>Footnote 245)</b> A specification for imaginary types is in Annex G.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.1p6'></a>
|
|
<pre>6 The macro
|
|
|
|
I
|
|
|
|
|
|
expands to either _Imaginary_I or _Complex_I . If _Imaginary_I is not defined, I shall expand to
|
|
_Complex_I .
|
|
|
|
</pre>
|
|
<a name='7.3.1p7'></a>
|
|
<pre>7 Notwithstanding the provisions of <a href='#7.1.3'>7.1.3</a>, a program may undefine and perhaps then redefine the
|
|
macros complex, imaginary, and I.
|
|
Forward references: the CMPLX macros (<a href='#7.3.9.3'>7.3.9.3</a>), IEC 60559-compatible complex arithmetic (An-
|
|
nex G).
|
|
|
|
</pre>
|
|
<a name='7.3.2'></a>
|
|
<hr>
|
|
<h3>7.3.2 [Conventions]</h3>
|
|
<a name='7.3.2p1'></a>
|
|
<pre>1 Values are interpreted as radians, not degrees. An implementation may set errno but is not required
|
|
to.
|
|
|
|
</pre>
|
|
<a name='7.3.3'></a>
|
|
<hr>
|
|
<h3>7.3.3 [Branch cuts]</h3>
|
|
<a name='7.3.3p1'></a>
|
|
<pre>1 Some of the functions below have branch cuts, across which the function is discontinuous. For
|
|
implementations with a signed zero (including all IEC 60559 implementations) that follow the
|
|
specifications of Annex G, the sign of zero distinguishes one side of a cut from another so the
|
|
function is continuous (except for format limitations) as the cut is approached from either side. For
|
|
example, for the square root function, which has a branch cut along the negative real axis, the top of
|
|
the cut, with imaginary part +0 , maps to the positive imaginary axis, and the bottom of the cut, with
|
|
imaginary part-0 , maps to the negative imaginary axis.
|
|
</pre>
|
|
<a name='7.3.3p2'></a>
|
|
<pre>2 Implementations that do not support a signed zero (see Annex F) cannot distinguish the sides of
|
|
branch cuts. These implementations shall map a cut so the function is continuous as the cut is
|
|
approached coming around the finite endpoint of the cut in a counter clockwise direction. (Branch
|
|
cuts for the functions specified here have just one finite endpoint.) For example, for the square root
|
|
function, coming counter clockwise around the finite endpoint of the cut along the negative real axis
|
|
approaches the cut from above, so the cut maps to the positive imaginary axis.
|
|
|
|
</pre>
|
|
<a name='7.3.4'></a>
|
|
<hr>
|
|
<h3>7.3.4 [The CX_LIMITED_RANGE pragma]</h3>
|
|
<a name='7.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
#pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.4p2'></a>
|
|
<pre>2 The usual mathematical formulas for complex multiply, divide, and absolute value are problem-
|
|
atic because of their treatment of infinities and because of undue overflow and underflow. The
|
|
CX_LIMITED_RANGE pragma can be used to inform the implementation that (where the state is "on")
|
|
the usual mathematical formulas are acceptable.<a href='#FOOTNOTE.246'><sup>[246]</sup></a> The pragma can occur either outside external
|
|
declarations or preceding all explicit declarations and statements inside a compound statement.
|
|
When outside external declarations, the pragma takes effect from its occurrence until another
|
|
CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit. When inside a
|
|
compound statement, the pragma takes effect from its occurrence until another CX_LIMITED_RANGE
|
|
pragma is encountered (including within a nested compound statement), or until the end of the
|
|
compound statement; at the end of a compound statement the state for the pragma is restored to
|
|
its condition just before the compound statement. If this pragma is used in any other context, the
|
|
behavior is undefined. The default state for the pragma is "off".
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.246'>
|
|
<pre><i><b>Footnote 246)</b> The purpose of the pragma is to allow the implementation to use the formulas:
|
|
(x + iy) × (u + iv) = (xu − yv) + i(yu + xv)
|
|
(x + iy) / (u + iv) = [(xu + yv) + i(yu − xv)]/(u2 + v 2 )
|
|
p
|
|
|x + iy| = x2 + y 2
|
|
where the programmer can determine they are safe.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.5'></a>
|
|
<hr>
|
|
<h3>7.3.5 [Trigonometric functions]</h3>
|
|
<a name='7.3.5.1'></a>
|
|
<hr>
|
|
<h3>7.3.5.1 [The cacos functions]</h3>
|
|
<a name='7.3.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex cacos(double complex z);
|
|
float complex cacosf(float complex z);
|
|
long double complex cacosl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.1p2'></a>
|
|
<pre>2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the interval
|
|
[−1, +1] along the real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.1p3'></a>
|
|
<pre>3 The cacos functions return the complex arc cosine value, in the range of a strip mathematically
|
|
unbounded along the imaginary axis and in the interval [0, π] along the real axis.
|
|
</pre>
|
|
<a name='7.3.5.2'></a>
|
|
<hr>
|
|
<h3>7.3.5.2 [The casin functions]</h3>
|
|
<a name='7.3.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex casin(double complex z);
|
|
float complex casinf(float complex z);
|
|
long double complex casinl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.2p2'></a>
|
|
<pre>2 The casin functions compute the complex arc sine of z, with branch cuts outside the interval
|
|
[−1, +1] along the real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.2p3'></a>
|
|
<pre>3 The casin functions return the complex arc sine value, in the range of a strip mathematically
|
|
unbounded along the imaginary axis and in the interval [− π2 , + π2 ] along the real axis.
|
|
|
|
</pre>
|
|
<a name='7.3.5.3'></a>
|
|
<hr>
|
|
<h3>7.3.5.3 [The catan functions]</h3>
|
|
<a name='7.3.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex catan(double complex z);
|
|
float complex catanf(float complex z);
|
|
long double complex catanl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.3p2'></a>
|
|
<pre>2 The catan functions compute the complex arc tangent of z, with branch cuts outside the interval
|
|
[−i, +i] along the imaginary axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.3p3'></a>
|
|
<pre>3 The catan functions return the complex arc tangent value, in the range of a strip mathematically
|
|
unbounded along the imaginary axis and in the interval [− π2 , + π2 ] along the real axis.
|
|
|
|
</pre>
|
|
<a name='7.3.5.4'></a>
|
|
<hr>
|
|
<h3>7.3.5.4 [The ccos functions]</h3>
|
|
<a name='7.3.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex ccos(double complex z);
|
|
float complex ccosf(float complex z);
|
|
long double complex ccosl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.4p2'></a>
|
|
<pre>2 The ccos functions compute the complex cosine of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.4p3'></a>
|
|
<pre>3 The ccos functions return the complex cosine value.
|
|
|
|
</pre>
|
|
<a name='7.3.5.5'></a>
|
|
<hr>
|
|
<h3>7.3.5.5 [The csin functions]</h3>
|
|
<a name='7.3.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex csin(double complex z);
|
|
float complex csinf(float complex z);
|
|
long double complex csinl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.5p2'></a>
|
|
<pre>2 The csin functions compute the complex sine of z.
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.5p3'></a>
|
|
<pre>3 The csin functions return the complex sine value.
|
|
|
|
</pre>
|
|
<a name='7.3.5.6'></a>
|
|
<hr>
|
|
<h3>7.3.5.6 [The ctan functions]</h3>
|
|
<a name='7.3.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex ctan(double complex z);
|
|
float complex ctanf(float complex z);
|
|
long double complex ctanl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.5.6p2'></a>
|
|
<pre>2 The ctan functions compute the complex tangent of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.5.6p3'></a>
|
|
<pre>3 The ctan functions return the complex tangent value.
|
|
|
|
</pre>
|
|
<a name='7.3.6'></a>
|
|
<hr>
|
|
<h3>7.3.6 [Hyperbolic functions]</h3>
|
|
<a name='7.3.6.1'></a>
|
|
<hr>
|
|
<h3>7.3.6.1 [The cacosh functions]</h3>
|
|
<a name='7.3.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex cacosh(double complex z);
|
|
float complex cacoshf(float complex z);
|
|
long double complex cacoshl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.1p2'></a>
|
|
<pre>2 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch cut at values
|
|
less than 1 along the real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.1p3'></a>
|
|
<pre>3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a half-strip of
|
|
nonnegative values along the real axis and in the interval [−iπ, +iπ] along the imaginary axis.
|
|
|
|
</pre>
|
|
<a name='7.3.6.2'></a>
|
|
<hr>
|
|
<h3>7.3.6.2 [The casinh functions]</h3>
|
|
<a name='7.3.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex casinh(double complex z);
|
|
float complex casinhf(float complex z);
|
|
long double complex casinhl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.2p2'></a>
|
|
<pre>2 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts outside the
|
|
interval [−i, +i] along the imaginary axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.2p3'></a>
|
|
<pre>3 The casinh functions return the complex arc hyperbolic sine value, in the range of a strip mathe-
|
|
matically unbounded along the real axis and in the interval [− iπ iπ
|
|
2 , + 2 ] along the imaginary axis.
|
|
|
|
</pre>
|
|
<a name='7.3.6.3'></a>
|
|
<hr>
|
|
<h3>7.3.6.3 [The catanh functions]</h3>
|
|
<a name='7.3.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex catanh(double complex z);
|
|
float complex catanhf(float complex z);
|
|
long double complex catanhl(long double complex z);
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.3p2'></a>
|
|
<pre>2 The catanh functions compute the complex arc hyperbolic tangent of z, with branch cuts outside
|
|
the interval [−1, +1] along the real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.3p3'></a>
|
|
<pre>3 The catanh functions return the complex arc hyperbolic tangent value, in the range of a strip
|
|
mathematically unbounded along the real axis and in the interval [− iπ iπ
|
|
2 , + 2 ] along the imaginary
|
|
axis.
|
|
|
|
</pre>
|
|
<a name='7.3.6.4'></a>
|
|
<hr>
|
|
<h3>7.3.6.4 [The ccosh functions]</h3>
|
|
<a name='7.3.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex ccosh(double complex z);
|
|
float complex ccoshf(float complex z);
|
|
long double complex ccoshl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.4p2'></a>
|
|
<pre>2 The ccosh functions compute the complex hyperbolic cosine of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.4p3'></a>
|
|
<pre>3 The ccosh functions return the complex hyperbolic cosine value.
|
|
|
|
</pre>
|
|
<a name='7.3.6.5'></a>
|
|
<hr>
|
|
<h3>7.3.6.5 [The csinh functions]</h3>
|
|
<a name='7.3.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex csinh(double complex z);
|
|
float complex csinhf(float complex z);
|
|
long double complex csinhl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.5p2'></a>
|
|
<pre>2 The csinh functions compute the complex hyperbolic sine of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.5p3'></a>
|
|
<pre>3 The csinh functions return the complex hyperbolic sine value.
|
|
|
|
</pre>
|
|
<a name='7.3.6.6'></a>
|
|
<hr>
|
|
<h3>7.3.6.6 [The ctanh functions]</h3>
|
|
<a name='7.3.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex ctanh(double complex z);
|
|
float complex ctanhf(float complex z);
|
|
long double complex ctanhl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.6.6p2'></a>
|
|
<pre>2 The ctanh functions compute the complex hyperbolic tangent of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.6.6p3'></a>
|
|
<pre>3 The ctanh functions return the complex hyperbolic tangent value.
|
|
|
|
</pre>
|
|
<a name='7.3.7'></a>
|
|
<hr>
|
|
<h3>7.3.7 [Exponential and logarithmic functions]</h3>
|
|
<a name='7.3.7.1'></a>
|
|
<hr>
|
|
<h3>7.3.7.1 [The cexp functions]</h3>
|
|
<a name='7.3.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex cexp(double complex z);
|
|
float complex cexpf(float complex z);
|
|
long double complex cexpl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.7.1p2'></a>
|
|
<pre>2 The cexp functions compute the complex base-e exponential of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.7.1p3'></a>
|
|
<pre>3 The cexp functions return the complex base-e exponential value.
|
|
|
|
</pre>
|
|
<a name='7.3.7.2'></a>
|
|
<hr>
|
|
<h3>7.3.7.2 [The clog functions]</h3>
|
|
<a name='7.3.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex clog(double complex z);
|
|
float complex clogf(float complex z);
|
|
long double complex clogl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.7.2p2'></a>
|
|
<pre>2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch cut along
|
|
the negative real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.7.2p3'></a>
|
|
<pre>3 The clog functions return the complex natural logarithm value, in the range of a strip mathematically
|
|
unbounded along the real axis and in the interval [−iπ, +iπ] along the imaginary axis.
|
|
|
|
</pre>
|
|
<a name='7.3.8'></a>
|
|
<hr>
|
|
<h3>7.3.8 [Power and absolute-value functions]</h3>
|
|
<a name='7.3.8.1'></a>
|
|
<hr>
|
|
<h3>7.3.8.1 [The cabs functions]</h3>
|
|
<a name='7.3.8.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double cabs(double complex z);
|
|
float cabsf(float complex z);
|
|
long double cabsl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.8.1p2'></a>
|
|
<pre>2 The cabs functions compute the complex absolute value (also called norm, modulus, or magnitude)
|
|
of z.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.8.1p3'></a>
|
|
<pre>3 The cabs functions return the complex absolute value.
|
|
|
|
</pre>
|
|
<a name='7.3.8.2'></a>
|
|
<hr>
|
|
<h3>7.3.8.2 [The cpow functions]</h3>
|
|
<a name='7.3.8.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex cpow(double complex x, double complex y);
|
|
float complex cpowf(float complex x, float complex y);
|
|
long double complex cpowl(long double complex x, long double complex y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.8.2p2'></a>
|
|
<pre>2 The cpow functions compute the complex power function xy , with a branch cut for the first parameter
|
|
along the negative real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.8.2p3'></a>
|
|
<pre>3 The cpow functions return the complex power function value.
|
|
</pre>
|
|
<a name='7.3.8.3'></a>
|
|
<hr>
|
|
<h3>7.3.8.3 [The csqrt functions]</h3>
|
|
<a name='7.3.8.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex csqrt(double complex z);
|
|
float complex csqrtf(float complex z);
|
|
long double complex csqrtl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.8.3p2'></a>
|
|
<pre>2 The csqrt functions compute the complex square root of z, with a branch cut along the negative
|
|
real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.8.3p3'></a>
|
|
<pre>3 The csqrt functions return the complex square root value, in the range of the right half-plane
|
|
(including the imaginary axis).
|
|
|
|
</pre>
|
|
<a name='7.3.9'></a>
|
|
<hr>
|
|
<h3>7.3.9 [Manipulation functions]</h3>
|
|
<a name='7.3.9.1'></a>
|
|
<hr>
|
|
<h3>7.3.9.1 [The carg functions]</h3>
|
|
<a name='7.3.9.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double carg(double complex z);
|
|
float cargf(float complex z);
|
|
long double cargl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.1p2'></a>
|
|
<pre>2 The carg functions compute the argument (also called phase angle) of z, with a branch cut along
|
|
the negative real axis.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.9.1p3'></a>
|
|
<pre>3 The carg functions return the value of the argument in the interval [−π, +π].
|
|
|
|
</pre>
|
|
<a name='7.3.9.2'></a>
|
|
<hr>
|
|
<h3>7.3.9.2 [The cimag functions]</h3>
|
|
<a name='7.3.9.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double cimag(double complex z);
|
|
float cimagf(float complex z);
|
|
long double cimagl(long double complex z);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.2p2'></a>
|
|
<pre>2 The cimag functions compute the imaginary part of z.<a href='#FOOTNOTE.247'><sup>[247]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.247'>
|
|
<pre><i><b>Footnote 247)</b> For a variable z of complex type, z == creal(z)+cimag(z) I.
|
|
*
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.9.2p3'></a>
|
|
<pre>3 The cimag functions return the imaginary part value (as a real).
|
|
|
|
</pre>
|
|
<a name='7.3.9.3'></a>
|
|
<hr>
|
|
<h3>7.3.9.3 [The CMPLX macros]</h3>
|
|
<a name='7.3.9.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex CMPLX(double x, double y);
|
|
float complex CMPLXF(float x, float y);
|
|
long double complex CMPLXL(long double x, long double y);
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.3p2'></a>
|
|
<pre>2 The CMPLX macros expand to an expression of the specified complex type, with the real part having
|
|
the (converted) value of x and the imaginary part having the (converted) value of y. The resulting
|
|
expression shall be suitable for use as an initializer for an object with static or thread storage duration,
|
|
provided both arguments are likewise suitable.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.9.3p3'></a>
|
|
<pre>3 The CMPLX macros return the complex value x + iy.
|
|
</pre>
|
|
<a name='7.3.9.3p4'></a>
|
|
<pre>4 NOTE These macros act as if the implementation supported imaginary types and the definitions were:
|
|
|
|
#define CMPLX(x, y) ((double complex)((double)(x) + \
|
|
_Imaginary_I * (double)(y)))
|
|
#define CMPLXF(x, y) ((float complex)((float)(x) + \
|
|
_Imaginary_I * (float)(y)))
|
|
#define CMPLXL(x, y) ((long double complex)((long double)(x) + \
|
|
_Imaginary_I * (long double)(y)))
|
|
|
|
|
|
</pre>
|
|
<a name='7.3.9.4'></a>
|
|
<hr>
|
|
<h3>7.3.9.4 [The conj functions]</h3>
|
|
<a name='7.3.9.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex conj(double complex z);
|
|
float complex conjf(float complex z);
|
|
long double complex conjl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.4p2'></a>
|
|
<pre>2 The conj functions compute the complex conjugate of z, by reversing the sign of its imaginary part.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.9.4p3'></a>
|
|
<pre>3 The conj functions return the complex conjugate value.
|
|
|
|
</pre>
|
|
<a name='7.3.9.5'></a>
|
|
<hr>
|
|
<h3>7.3.9.5 [The cproj functions]</h3>
|
|
<a name='7.3.9.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double complex cproj(double complex z);
|
|
float complex cprojf(float complex z);
|
|
long double complex cprojl(long double complex z);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.5p2'></a>
|
|
<pre>2 The cproj functions compute a projection of z onto the Riemann sphere: z projects to z except that
|
|
all complex infinities (even those with one infinite part and one NaN part) project to positive infinity
|
|
on the real axis. If z has an infinite part, then cproj(z) is equivalent to
|
|
|
|
INFINITY + I * copysign(0.0, cimag(z))
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.3.9.5p3'></a>
|
|
<pre>3 The cproj functions return the value of the projection onto the Riemann sphere.
|
|
|
|
</pre>
|
|
<a name='7.3.9.6'></a>
|
|
<hr>
|
|
<h3>7.3.9.6 [The creal functions]</h3>
|
|
<a name='7.3.9.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <complex.h>
|
|
double creal(double complex z);
|
|
float crealf(float complex z);
|
|
long double creall(long double complex z);
|
|
Description
|
|
</pre>
|
|
<a name='7.3.9.6p2'></a>
|
|
<pre>2 The creal functions compute the real part of z.<a href='#FOOTNOTE.248'><sup>[248]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.248'>
|
|
<pre><i><b>Footnote 248)</b> For a variable z of complex type, z == creal(z)+cimag(z) I.
|
|
*
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.3.9.6p3'></a>
|
|
<pre>3 The creal functions return the real part value.
|
|
</pre>
|
|
<a name='7.4'></a>
|
|
<hr>
|
|
<h3>7.4 [Character handling <ctype.h>]</h3>
|
|
<a name='7.4p1'></a>
|
|
<pre>1 The header <ctype.h> declares several functions useful for classifying and mapping characters.<a href='#FOOTNOTE.249'><sup>[249]</sup></a>
|
|
In all cases the argument is an int, the value of which shall be representable as an unsigned char
|
|
or shall equal the value of the macro EOF. If the argument has any other value, the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.249'>
|
|
<pre><i><b>Footnote 249)</b> See "future library directions" (<a href='#7.33.2'>7.33.2</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.4p2'></a>
|
|
<pre>2 The behavior of these functions is affected by the current locale. Those functions that have locale-
|
|
specific aspects only when not in the "C" locale are noted below.
|
|
</pre>
|
|
<a name='7.4p3'></a>
|
|
<pre>3 The term printing character refers to a member of a locale-specific set of characters, each of which
|
|
occupies one printing position on a display device; the term control character refers to a member of a
|
|
locale-specific set of characters that are not printing characters.<a href='#FOOTNOTE.250'><sup>[250]</sup></a> All letters and digits are printing
|
|
characters.
|
|
Forward references: EOF (<a href='#7.23.1'>7.23.1</a>), localization (<a href='#7.11'>7.11</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.250'>
|
|
<pre><i><b>Footnote 250)</b> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those whose values lie
|
|
from 0x20 (space) through 0x7E (tilde); the control characters are those whose values lie from 0 (NUL) through 0x1F (US),
|
|
and the character 0x7F (DEL).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.4.1'></a>
|
|
<hr>
|
|
<h3>7.4.1 [Character classification functions]</h3>
|
|
<a name='7.4.1p1'></a>
|
|
<pre>1 The functions in this subclause return nonzero (true) if and only if the value of the argument c
|
|
conforms to that in the description of the function.
|
|
|
|
</pre>
|
|
<a name='7.4.1.1'></a>
|
|
<hr>
|
|
<h3>7.4.1.1 [The isalnum function]</h3>
|
|
<a name='7.4.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isalnum(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.1p2'></a>
|
|
<pre>2 The isalnum function tests for any character for which isalpha or isdigit is true.
|
|
|
|
</pre>
|
|
<a name='7.4.1.2'></a>
|
|
<hr>
|
|
<h3>7.4.1.2 [The isalpha function]</h3>
|
|
<a name='7.4.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isalpha(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.2p2'></a>
|
|
<pre>2 The isalpha function tests for any character for which isupper or islower is true, or any character
|
|
that is one of a locale-specific set of alphabetic characters for which none of iscntrl, isdigit,
|
|
ispunct, or isspace is true.<a href='#FOOTNOTE.251'><sup>[251]</sup></a> In the "C" locale, isalpha returns true only for the characters for
|
|
which isupper or islower is true.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.251'>
|
|
<pre><i><b>Footnote 251)</b> The functions islower and isupper test true or false separately for each of these additional characters; all four combina-
|
|
tions are possible.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.4.1.3'></a>
|
|
<hr>
|
|
<h3>7.4.1.3 [The isblank function]</h3>
|
|
<a name='7.4.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isblank(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.3p2'></a>
|
|
<pre>2 The isblank function tests for any character that is a standard blank character or is one of a locale-
|
|
specific set of characters for which isspace is true and that is used to separate words within a line
|
|
of text. The standard blank characters are the following: space (’ ’ ), and horizontal tab (’\t’ ). In
|
|
the "C" locale, isblank returns true only for the standard blank characters.
|
|
</pre>
|
|
<a name='7.4.1.4'></a>
|
|
<hr>
|
|
<h3>7.4.1.4 [The iscntrl function]</h3>
|
|
<a name='7.4.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int iscntrl(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.4p2'></a>
|
|
<pre>2 The iscntrl function tests for any control character.
|
|
|
|
</pre>
|
|
<a name='7.4.1.5'></a>
|
|
<hr>
|
|
<h3>7.4.1.5 [The isdigit function]</h3>
|
|
<a name='7.4.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isdigit(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.5p2'></a>
|
|
<pre>2 The isdigit function tests for any decimal-digit character (as defined in <a href='#5.2.1'>5.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.4.1.6'></a>
|
|
<hr>
|
|
<h3>7.4.1.6 [The isgraph function]</h3>
|
|
<a name='7.4.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isgraph(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.6p2'></a>
|
|
<pre>2 The isgraph function tests for any printing character except space (’ ’ ).
|
|
|
|
</pre>
|
|
<a name='7.4.1.7'></a>
|
|
<hr>
|
|
<h3>7.4.1.7 [The islower function]</h3>
|
|
<a name='7.4.1.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int islower(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.7p2'></a>
|
|
<pre>2 The islower function tests for any character that is a lowercase letter or is one of a locale-specific set
|
|
of characters for which none of iscntrl, isdigit, ispunct, or isspace is true. In the "C" locale,
|
|
islower returns true only for the lowercase letters (as defined in <a href='#5.2.1'>5.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.4.1.8'></a>
|
|
<hr>
|
|
<h3>7.4.1.8 [The isprint function]</h3>
|
|
<a name='7.4.1.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isprint(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.8p2'></a>
|
|
<pre>2 The isprint function tests for any printing character including space (’ ’ ).
|
|
|
|
</pre>
|
|
<a name='7.4.1.9'></a>
|
|
<hr>
|
|
<h3>7.4.1.9 [The ispunct function]</h3>
|
|
<a name='7.4.1.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int ispunct(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.9p2'></a>
|
|
<pre>2 The ispunct function tests for any printing character that is one of a locale-specific set of punctuation
|
|
characters for which neither isspace nor isalnum is true. In the "C" locale, ispunct returns true
|
|
for every printing character for which neither isspace nor isalnum is true.
|
|
</pre>
|
|
<a name='7.4.1.10'></a>
|
|
<hr>
|
|
<h3>7.4.1.10 [The isspace function]</h3>
|
|
<a name='7.4.1.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isspace(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.10p2'></a>
|
|
<pre>2 The isspace function tests for any character that is a standard white-space character or is one of
|
|
a locale-specific set of characters for which isalnum is false. The standard white-space characters
|
|
are the following: space (’ ’ ), form feed (’\f’ ), new-line (’\n’ ), carriage return (’\r’ ), horizontal
|
|
tab (’\t’ ), and vertical tab (’\v’ ). In the "C" locale, isspace returns true only for the standard
|
|
white-space characters.
|
|
|
|
</pre>
|
|
<a name='7.4.1.11'></a>
|
|
<hr>
|
|
<h3>7.4.1.11 [The isupper function]</h3>
|
|
<a name='7.4.1.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isupper(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.11p2'></a>
|
|
<pre>2 The isupper function tests for any character that is an uppercase letter or is one of a locale-specific
|
|
set of characters for which none of iscntrl, isdigit, ispunct, or isspace is true. In the "C" locale,
|
|
isupper returns true only for the uppercase letters (as defined in <a href='#5.2.1'>5.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.4.1.12'></a>
|
|
<hr>
|
|
<h3>7.4.1.12 [The isxdigit function]</h3>
|
|
<a name='7.4.1.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int isxdigit(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.1.12p2'></a>
|
|
<pre>2 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href='#6.4.4.1'>6.4.4.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.4.2'></a>
|
|
<hr>
|
|
<h3>7.4.2 [Character case mapping functions]</h3>
|
|
<a name='7.4.2.1'></a>
|
|
<hr>
|
|
<h3>7.4.2.1 [The tolower function]</h3>
|
|
<a name='7.4.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int tolower(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.2.1p2'></a>
|
|
<pre>2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.4.2.1p3'></a>
|
|
<pre>3 If the argument is a character for which isupper is true and there are one or more corresponding
|
|
characters, as specified by the current locale, for which islower is true, the tolower function returns
|
|
one of the corresponding characters (always the same one for any given locale); otherwise, the
|
|
argument is returned unchanged.
|
|
|
|
</pre>
|
|
<a name='7.4.2.2'></a>
|
|
<hr>
|
|
<h3>7.4.2.2 [The toupper function]</h3>
|
|
<a name='7.4.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <ctype.h>
|
|
int toupper(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.4.2.2p2'></a>
|
|
<pre>2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
|
|
Returns
|
|
</pre>
|
|
<a name='7.4.2.2p3'></a>
|
|
<pre>3 If the argument is a character for which islower is true and there are one or more corresponding
|
|
characters, as specified by the current locale, for which isupper is true, the toupper function returns
|
|
one of the corresponding characters (always the same one for any given locale); otherwise, the
|
|
argument is returned unchanged.
|
|
</pre>
|
|
<a name='7.5'></a>
|
|
<hr>
|
|
<h3>7.5 [Errors <errno.h>]</h3>
|
|
<a name='7.5p1'></a>
|
|
<pre>1 The header <errno.h> defines several macros, all relating to the reporting of error conditions.
|
|
</pre>
|
|
<a name='7.5p2'></a>
|
|
<pre>2 The macros are
|
|
|
|
EDOM
|
|
EILSEQ
|
|
ERANGE
|
|
|
|
|
|
which expand to integer constant expressions with type int, distinct positive values, and which are
|
|
suitable for use in #if preprocessing directives; and
|
|
|
|
errno
|
|
|
|
|
|
which expands to a modifiable lvalue<a href='#FOOTNOTE.252'><sup>[252]</sup></a> that has type int and thread storage duration, the value
|
|
of which is set to a positive error number by several library functions. If a macro definition is
|
|
suppressed in order to access an actual object, or a program defines an identifier with the name
|
|
errno, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.252'>
|
|
<pre><i><b>Footnote 252)</b> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue resulting from a function
|
|
call (for example, *errno() ).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.5p3'></a>
|
|
<pre>3 The value of errno in the initial thread is zero at program startup (the initial representation of the
|
|
object designated by errno in other threads is indeterminate), but is never set to zero by any library
|
|
function<a href='#FOOTNOTE.253'><sup>[253]</sup></a> . The value of errno may be set to nonzero by a library function call whether or not there
|
|
is an error, provided the use of errno is not documented in the description of the function in this
|
|
document.
|
|
</pre>
|
|
<a name='FOOTNOTE.253'>
|
|
<pre><i><b>Footnote 253)</b> Thus, a program that uses errno for error checking would set it to zero before a library function call, then inspect it
|
|
before a subsequent library function call. Of course, a library function can save the value of errno on entry and then set it to
|
|
zero, as long as the original value is restored if errno’s value is still zero just before the return.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.5p4'></a>
|
|
<pre>4 Additional macro definitions, beginning with E and a digit or E and an uppercase letter,<a href='#FOOTNOTE.254'><sup>[254]</sup></a> may also
|
|
be specified by the implementation.
|
|
</pre>
|
|
<a name='FOOTNOTE.254'>
|
|
<pre><i><b>Footnote 254)</b> See "future library directions" (<a href='#7.33.3'>7.33.3</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6'></a>
|
|
<hr>
|
|
<h3>7.6 [Floating-point environment <fenv.h>]</h3>
|
|
<a name='7.6p1'></a>
|
|
<pre>1 The header <fenv.h> defines several macros, and declares types and functions that provide access to
|
|
the floating-point environment. The floating-point environment refers collectively to any floating-point
|
|
status flags and control modes supported by the implementation.<a href='#FOOTNOTE.255'><sup>[255]</sup></a>
|
|
A floating-point status flag is a system variable whose value is set (but never cleared) when a floating-
|
|
point exception is raised, which occurs as a side effect of exceptional floating-point arithmetic to
|
|
provide auxiliary information.<a href='#FOOTNOTE.256'><sup>[256]</sup></a> A floating-point control mode is a system variable whose value may
|
|
be set by the user to affect the subsequent behavior of floating-point arithmetic.
|
|
</pre>
|
|
<a name='FOOTNOTE.255'>
|
|
<pre><i><b>Footnote 255)</b> This header is designed to support the floating-point exception status flags and rounding-direction control modes
|
|
required by IEC 60559, and other similar floating-point state information. It is also designed to facilitate code portability
|
|
among all systems.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.256'>
|
|
<pre><i><b>Footnote 256)</b> A floating-point status flag is not an object and can be set more than once within an expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p2'></a>
|
|
<pre>2 A floating-point control mode may be constant (<a href='#7.6.2'>7.6.2</a>) or dynamic. The dynamic floating-point en-
|
|
vironment includes the dynamic floating-point control modes and the floating-point status flags.
|
|
|
|
</pre>
|
|
<a name='7.6p3'></a>
|
|
<pre>3 The dynamic floating-point environment has thread storage duration. The initial state for a thread’s
|
|
dynamic floating-point environment is the current state of the dynamic floating-point environment
|
|
of the thread that creates it at the time of creation.
|
|
</pre>
|
|
<a name='7.6p4'></a>
|
|
<pre>4 Certain programming conventions support the intended model of use for the dynamic floating-point
|
|
environment:<a href='#FOOTNOTE.257'><sup>[257]</sup></a>
|
|
|
|
— a function call does not alter its caller’s floating-point control modes, clear its caller’s floating-
|
|
point status flags, nor depend on the state of its caller’s floating-point status flags unless the
|
|
function is so documented;
|
|
|
|
— a function call is assumed to require default floating-point control modes, unless its documen-
|
|
tation promises otherwise;
|
|
|
|
— a function call is assumed to have the potential for raising floating-point exceptions, unless its
|
|
documentation promises otherwise.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.257'>
|
|
<pre><i><b>Footnote 257)</b> With these conventions, a programmer can safely assume default floating-point control modes (or be unaware of them).
|
|
The responsibilities associated with accessing the floating-point environment fall on the programmer or program that does so
|
|
explicitly.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p5'></a>
|
|
<pre>5 The feature test macro __STDC_VERSION_FENV_H__ expands to the token 202311L.
|
|
</pre>
|
|
<a name='7.6p6'></a>
|
|
<pre>6 The type
|
|
|
|
fenv_t
|
|
|
|
|
|
represents the entire dynamic floating-point environment.
|
|
</pre>
|
|
<a name='7.6p7'></a>
|
|
<pre>7 The type
|
|
|
|
femode_t
|
|
|
|
|
|
represents the collection of dynamic floating-point control modes supported by the implementation,
|
|
including the dynamic rounding direction mode.
|
|
</pre>
|
|
<a name='7.6p8'></a>
|
|
<pre>8 The type
|
|
|
|
fexcept_t
|
|
|
|
|
|
represents the floating-point status flags collectively, including any status the implementation
|
|
associates with the flags.
|
|
</pre>
|
|
<a name='7.6p9'></a>
|
|
<pre>9 Each of the macros
|
|
FE_DIVBYZERO
|
|
FE_INEXACT
|
|
FE_INVALID
|
|
FE_OVERFLOW
|
|
FE_UNDERFLOW
|
|
|
|
|
|
is defined if and only if the implementation supports the floating-point exception by means of
|
|
the functions in <a href='#7.6.4'>7.6.4</a>.<a href='#FOOTNOTE.258'><sup>[258]</sup></a> Additional implementation-defined floating-point exceptions, with
|
|
macro definitions beginning with FE_ and an uppercase letter,<a href='#FOOTNOTE.259'><sup>[259]</sup></a> may also be specified by the
|
|
implementation. The defined macros expand to integer constant expressions with values such that
|
|
bitwise ORs of all combinations of the macros result in distinct values, and furthermore, bitwise
|
|
ANDs of all combinations of the macros result in zero.<a href='#FOOTNOTE.260'><sup>[260]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.258'>
|
|
<pre><i><b>Footnote 258)</b> The implementation supports a floating-point exception if there are circumstances where a call to at least one of the
|
|
functions in <a href='#7.6.4'>7.6.4</a>, using the macro as the appropriate argument, will succeed. It is not necessary for all the functions to
|
|
succeed all the time.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.259'>
|
|
<pre><i><b>Footnote 259)</b> See "future library directions" (<a href='#7.33.4'>7.33.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.260'>
|
|
<pre><i><b>Footnote 260)</b> The macros are typically distinct powers of two.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p10'></a>
|
|
<pre>10 Decimal floating-point operations and IEC 60559 binary floating-point operations (Annex F) access
|
|
the same floating-point exception status flags.
|
|
</pre>
|
|
<a name='7.6p11'></a>
|
|
<pre>11 The macro
|
|
|
|
FE_DFL_MODE
|
|
|
|
|
|
represents the default state for the collection of dynamic floating-point control modes sup-
|
|
ported by the implementation – and has type "pointer to const-qualified femode_t". Additional
|
|
implementation-defined states for the dynamic mode collection, with macro definitions beginning
|
|
with FE_ and an uppercase letter, and having type "pointer to const-qualified femode_t", may also
|
|
be specified by the implementation.
|
|
</pre>
|
|
<a name='7.6p12'></a>
|
|
<pre>12 The macro
|
|
|
|
FE_ALL_EXCEPT
|
|
|
|
|
|
is simply the bitwise OR of all floating-point exception macros defined by the implementation. If no
|
|
such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
|
|
</pre>
|
|
<a name='7.6p13'></a>
|
|
<pre>13 Each of the macros
|
|
|
|
FE_DOWNWARD
|
|
FE_TONEAREST
|
|
FE_TONEARESTFROMZERO
|
|
FE_TOWARDZERO
|
|
FE_UPWARD
|
|
|
|
|
|
is defined if and only if the implementation supports getting and setting the represented rounding
|
|
direction by means of the fegetround and fesetround functions. Additional implementation-
|
|
defined rounding directions, with macro definitions beginning with FE_ and an uppercase letter,<a href='#FOOTNOTE.261'><sup>[261]</sup></a>
|
|
may also be specified by the implementation.<a href='#FOOTNOTE.262'><sup>[262]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.261'>
|
|
<pre><i><b>Footnote 261)</b> See "future library directions" (<a href='#7.33.4'>7.33.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.262'>
|
|
<pre><i><b>Footnote 262)</b> Even though the rounding direction macros might expand to constants corresponding to the values of FLT_ROUNDS, they
|
|
are not required to do so.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p14'></a>
|
|
<pre>14 If the implementation supports decimal floating types, each of the macros
|
|
|
|
FE_DEC_DOWNWARD
|
|
FE_DEC_TONEAREST
|
|
FE_DEC_TONEARESTFROMZERO
|
|
FE_DEC_TOWARDZERO
|
|
FE_DEC_UPWARD
|
|
is defined for use with the fe_dec_getround and fe_dec_setround functions for getting and
|
|
setting the dynamic rounding direction mode, and with the FENV_DEC_ROUND rounding control
|
|
pragma (<a href='#7.6.3'>7.6.3</a>) for specifying a constant rounding direction, for decimal floating-point operations.
|
|
The decimal rounding direction affects all (inexact) operations that produce a result of decimal
|
|
floating type and all operations that produce an integer or character sequence result and have an
|
|
operand of decimal floating type, unless stated otherwise. The macros expand to integer constant
|
|
expressions whose values are distinct nonnegative values.
|
|
</pre>
|
|
<a name='7.6p15'></a>
|
|
<pre>15 During translation, constant rounding direction modes for decimal floating-point arithmetic are
|
|
in effect where specified. Elsewhere, during translation the decimal rounding direction mode is
|
|
FE_DEC_TONEAREST.
|
|
</pre>
|
|
<a name='7.6p16'></a>
|
|
<pre>16 At program startup the dynamic rounding direction mode for decimal floating-point arithmetic is
|
|
initialized to FE_DEC_TONEAREST.
|
|
</pre>
|
|
<a name='7.6p17'></a>
|
|
<pre>17 The macro
|
|
|
|
FE_DFL_ENV
|
|
|
|
|
|
represents the default dynamic floating-point environment — the one installed at program startup
|
|
— and has type "pointer to const-qualified fenv_t". It can be used as an argument to <fenv.h>
|
|
functions that manage the dynamic floating-point environment.
|
|
</pre>
|
|
<a name='7.6p18'></a>
|
|
<pre>18 Additional implementation-defined environments, with macro definitions beginning with FE_ and
|
|
an uppercase letter,<a href='#FOOTNOTE.263'><sup>[263]</sup></a> and having type "pointer to const-qualified fenv_t", may also be specified
|
|
by the implementation.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.263'>
|
|
<pre><i><b>Footnote 263)</b> See "future library directions" (<a href='#7.33.4'>7.33.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.1'></a>
|
|
<hr>
|
|
<h3>7.6.1 [The FENV_ACCESS pragma]</h3>
|
|
<a name='7.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS on-off-switch
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.1p2'></a>
|
|
<pre>2 The FENV_ACCESS pragma provides a means to inform the implementation when a program might
|
|
access the floating-point environment to test floating-point status flags or run under non-default
|
|
floating-point control modes.<a href='#FOOTNOTE.264'><sup>[264]</sup></a> The pragma shall occur either outside external declarations or
|
|
preceding all explicit declarations and statements inside a compound statement. When outside
|
|
external declarations, the pragma takes effect from its occurrence until another FENV_ACCESS pragma
|
|
is encountered, or until the end of the translation unit. When inside a compound statement, the
|
|
pragma takes effect from its occurrence until another FENV_ACCESS pragma is encountered (including
|
|
within a nested compound statement), or until the end of the compound statement; at the end of a
|
|
compound statement the state for the pragma is restored to its condition just before the compound
|
|
statement. If this pragma is used in any other context, the behavior is undefined. If part of a
|
|
program tests floating-point status flags or establishes non-default floating-point mode settings
|
|
using any means other than the FENV_ROUND pragmas, but was translated with the state for the
|
|
FENV_ACCESS pragma "off", the behavior is undefined. The default state ("on" or "off") for the
|
|
pragma is implementation-defined. (When execution passes from a part of the program translated
|
|
with FENV_ACCESS "off" to a part translated with FENV_ACCESS "on", the state of the floating-point
|
|
status flags is unspecified and the floating-point control modes have their default settings.)
|
|
</pre>
|
|
<a name='FOOTNOTE.264'>
|
|
<pre><i><b>Footnote 264)</b> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag tests and mode changes
|
|
(e.g., global common subexpression elimination, code motion, and constant folding). In general, if the state of FENV_ACCESS
|
|
is "off", the translator can assume that the flags are not tested, and that default modes are in effect, except where specified
|
|
otherwise by an FENV_ROUND pragma.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.1p3'></a>
|
|
<pre>3 EXAMPLE
|
|
|
|
#include <fenv.h>
|
|
void f(double x)
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
void g(double);
|
|
void h(double);
|
|
/* ... */
|
|
g(x + 1);
|
|
h(x + 1);
|
|
/* ... */
|
|
}
|
|
|
|
</pre>
|
|
<a name='7.6.1p4'></a>
|
|
<pre>4 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second x + 1 might depend on
|
|
control modes set as a side effect of the call to function g, then the program has to contain an appropriately placed invocation
|
|
of #pragma STDC FENV_ACCESS ON as shown.<a href='#FOOTNOTE.265'><sup>[265]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.265'>
|
|
<pre><i><b>Footnote 265)</b> The side effects impose a temporal ordering that requires two evaluations of x + 1 . On the other hand, without the
|
|
#pragma STDC FENV_ACCESS ON pragma, and assuming the default state is "off", just one evaluation of x + 1 would suffice.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.2'></a>
|
|
<hr>
|
|
<h3>7.6.2 [The FENV_ROUND pragma]</h3>
|
|
<a name='7.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ROUND direction
|
|
#pragma STDC FENV_ROUND FE_DYNAMIC
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2p2'></a>
|
|
<pre>2 The FENV_ROUND pragma provides a means to specify a constant rounding direction for floating-
|
|
point operations for standard floating types within a translation unit or compound statement. The
|
|
pragma shall occur either outside external declarations or preceding all explicit declarations and
|
|
statements inside a compound statement. When outside external declarations, the pragma takes
|
|
effect from its occurrence until another FENV_ROUND pragma is encountered, or until the end of the
|
|
translation unit. When inside a compound statement, the pragma takes effect from its occurrence
|
|
until another FENV_ROUND pragma is encountered (including within a nested compound statement),
|
|
or until the end of the compound statement; at the end of a compound statement the static rounding
|
|
mode is restored to its condition just before the compound statement. If this pragma is used in any
|
|
other context, its behavior is undefined.
|
|
</pre>
|
|
<a name='7.6.2p3'></a>
|
|
<pre>3 direction shall be one of the names of the supported rounding direction macros for operations for
|
|
standard floating types (<a href='#7.6'>7.6</a>), or FE_DYNAMIC. If any other value is specified, the behavior is unde-
|
|
fined. If no FENV_ROUND pragma is in effect, or the specified constant rounding mode is FE_DYNAMIC,
|
|
rounding is according to the mode specified by the dynamic floating-point environment, which is the
|
|
dynamic rounding mode that was established either at thread creation or by a call to fesetround,
|
|
fesetmode, fesetenv, or feupdateenv. If the FE_DYNAMIC mode is specified and FENV_ACCESS is
|
|
"off", the translator may assume that the default rounding mode is in effect.
|
|
</pre>
|
|
<a name='7.6.2p4'></a>
|
|
<pre>4 The FENV_ROUND pragma affects operations for standard floating types. Within the scope of an
|
|
FENV_ROUND pragma establishing a mode other than FE_DYNAMIC, floating-point operators, implicit
|
|
conversions (including the conversion of a value represented in a format wider than its semantic
|
|
types to its semantic type, as done by classification macros), and invocations of functions indicated
|
|
in the table below, for which macro replacement has not been suppressed (<a href='#7.1.4'>7.1.4</a>), shall be evaluated
|
|
according to the specified constant rounding mode (as though no constant mode was specified
|
|
and the corresponding dynamic rounding mode had been established by a call to fesetround).
|
|
Invocations of functions for which macro replacement has been suppressed and invocations of
|
|
functions other than those indicated in the table below shall not be affected by constant rounding
|
|
modes – they are affected by (and affect) only the dynamic mode. Floating constants (<a href='#6.4.4.2'>6.4.4.2</a>) of
|
|
a standard floating type that occur in the scope of a constant rounding mode shall be interpreted
|
|
according to that mode.
|
|
Functions affected by constant rounding modes – for standard
|
|
floating types
|
|
|
|
Header Function families
|
|
<math.h> acos, acospi, asin, asinpi, atan, atan2, atan2pi, atanpi
|
|
<math.h> cos, cospi, sin, sinpi, tan, tanpi
|
|
<math.h> acosh, asinh, atanh
|
|
<math.h> cosh, sinh, tanh
|
|
<math.h> exp, exp10, exp10m1, exp2, exp2m1, expm1
|
|
<math.h> log, log10, log10p1, log1p, log2, log2p1, logp1
|
|
<math.h> scalbn, scalbln, ldexp
|
|
<math.h> cbrt, compoundn, hypot, pow, pown, powr, rootn, rsqrt, sqrt
|
|
<math.h> erf, erfc
|
|
<math.h> lgamma, tgamma
|
|
<math.h> rint, nearbyint, lrint, llrint
|
|
<math.h> fdim
|
|
<math.h> fma
|
|
<math.h> fadd, dadd, fsub, dsub, fmul, dmul, fdiv, ddiv, ffma, dfma, fsqrt, dsqrt
|
|
<stdlib.h> atof, strfrom, strto
|
|
<wchar.h> wcsto
|
|
<stdio.h> printf and scanf families
|
|
<wchar.h> wprintf and wscanf families
|
|
|
|
|
|
A function family listed in the table above indicates the functions for all standard floating types,
|
|
where the function family is represented by the name of the functions without a suffix. For example,
|
|
acos indicates the functions acos, acosf, and acosl.
|
|
</pre>
|
|
<a name='7.6.2p5'></a>
|
|
<pre>5 NOTE Constant rounding modes (other than FE_DYNAMIC) could be implemented using dynamic rounding modes as
|
|
illustrated in the following example:
|
|
|
|
{
|
|
#pragma STDC FENV_ROUND direction
|
|
// compiler inserts:
|
|
// #pragma STDC FENV_ACCESS ON
|
|
// int __savedrnd;
|
|
// __savedrnd = __swapround(direction);
|
|
... operations affected by constant rounding mode ...
|
|
// compiler inserts:
|
|
// __savedrnd = __swapround(__savedrnd);
|
|
... operations not affected by constant rounding mode ...
|
|
// compiler inserts:
|
|
// __savedrnd = __swapround(__savedrnd);
|
|
... operations affected by constant rounding mode ...
|
|
// compiler inserts:
|
|
// __swapround(__savedrnd);
|
|
}
|
|
|
|
where __swapround is defined by:
|
|
|
|
static inline int __swapround(const int new) {
|
|
const int old = fegetround();
|
|
fesetround(new);
|
|
return old;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='7.6.3'></a>
|
|
<hr>
|
|
<h3>7.6.3 [The FENV_DEC_ROUND pragma]</h3>
|
|
<a name='7.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
#pragma STDC FENV_DEC_ROUND dec-direction
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.3p2'></a>
|
|
<pre>2 The FENV_DEC_ROUND pragma is a decimal floating-point analog of the FENV_ROUND pragma. If
|
|
FLT_RADIX is not 10, the FENV_DEC_ROUND pragma affects operators, functions, and floating con-
|
|
stants only for decimal floating types. The affected functions are listed in the table below. If
|
|
FLT_RADIX is 10, whether the FENV_ROUND and FENV_DEC_ROUND pragmas alter the rounding direc-
|
|
tion of both standard and decimal floating-point operations is implementation-defined. dec-direction
|
|
shall be one of the decimal rounding direction macro names (FE_DEC_DOWNWARD, FE_DEC_TONEAREST,
|
|
FE_DEC_TONEARESTFROMZERO, FE_DEC_TOWARDZERO, and FE_DEC_UPWARD) defined in <a href='#7.6'>7.6</a>, to specify
|
|
a constant rounding mode, or FE_DEC_DYNAMIC, to specify dynamic rounding. The corresponding
|
|
dynamic rounding mode can be established by a call to fe_dec_setround.
|
|
|
|
Functions affected by constant rounding modes – for decimal float-
|
|
ing types
|
|
|
|
Header Function families
|
|
<math.h> acos, acospi, asin, asinpi, atan, atan2, atan2pi, atanpi
|
|
<math.h> cos, cospi, sin, sinpi, tan, tanpi
|
|
<math.h> acosh, asinh, atanh
|
|
<math.h> cosh, sinh, tanh
|
|
<math.h> exp, exp10, exp10m1, exp2, exp2m1, expm1
|
|
<math.h> log, log10, log10p1, log1p, log2, log2p1, logp1
|
|
<math.h> scalbn, scalbln, ldexp
|
|
<math.h> cbrt, compoundn, hypot, pow, pown, powr, rootn, rsqrt, sqrt
|
|
<math.h> erf, erfc
|
|
<math.h> lgamma, tgamma
|
|
<math.h> rint, nearbyint, lrint, llrint
|
|
<math.h> quantize
|
|
<math.h> fdim
|
|
<math.h> fma
|
|
<math.h> d32add, d64add, d32sub, d64sub, d32mul, d64mul, d32div, d64div,
|
|
d32fma, d64fma, d32sqrt, d64sqrt
|
|
<stdlib.h> strfrom, strto
|
|
<wchar.h> wcsto
|
|
<stdio.h> printf and scanf families
|
|
<wchar.h> wprintf and wscanf families
|
|
|
|
|
|
A function family listed in the table above indicates the functions for all decimal floating types,
|
|
where the function family is represented by the name of the functions without a suffix. For example,
|
|
acos indicates the functions acosd32, acosd64, and acosd128.
|
|
|
|
</pre>
|
|
<a name='7.6.4'></a>
|
|
<hr>
|
|
<h3>7.6.4 [Floating-point exceptions]</h3>
|
|
<a name='7.6.4p1'></a>
|
|
<pre>1 The following functions provide access to the floating-point status flags.<a href='#FOOTNOTE.266'><sup>[266]</sup></a> The int input argument
|
|
for the functions represents a subset of floating-point exceptions, and can be zero or the bitwise
|
|
OR of one or more floating-point exception macros, for example FE_OVERFLOW | FE_INEXACT. For
|
|
other argument values, the behavior of these functions is undefined.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.266'>
|
|
<pre><i><b>Footnote 266)</b> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic abstraction of flags that are either
|
|
set or clear. An implementation can endow floating-point status flags with more information — for example, the address of
|
|
the code which first raised the floating-point exception; the functions fegetexceptflag and fesetexceptflag deal with
|
|
the full content of flags.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.4.1'></a>
|
|
<hr>
|
|
<h3>7.6.4.1 [The feclearexcept function]</h3>
|
|
<a name='7.6.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feclearexcept(int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.1p2'></a>
|
|
<pre>2 The feclearexcept function attempts to clear the supported floating-point exceptions represented
|
|
by its argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.1p3'></a>
|
|
<pre>3 The feclearexcept function returns zero if the excepts argument is zero or if all the specified
|
|
exceptions were successfully cleared. Otherwise, it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.4.2'></a>
|
|
<hr>
|
|
<h3>7.6.4.2 [The fegetexceptflag function]</h3>
|
|
<a name='7.6.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetexceptflag(fexcept_t *flagp, int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.2p2'></a>
|
|
<pre>2 The fegetexceptflag function attempts to store an implementation-defined representation of the
|
|
states of the floating-point status flags indicated by the argument excepts in the object pointed to
|
|
by the argument flagp.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.2p3'></a>
|
|
<pre>3 The fegetexceptflag function returns zero if the representation was successfully stored. Otherwise,
|
|
it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.4.3'></a>
|
|
<hr>
|
|
<h3>7.6.4.3 [The feraiseexcept function]</h3>
|
|
<a name='7.6.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feraiseexcept(int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.3p2'></a>
|
|
<pre>2 The feraiseexcept function attempts to raise the supported floating-point exceptions represented
|
|
by its argument. <a href='#FOOTNOTE.267'><sup>[267]</sup></a> The order in which these floating-point exceptions are raised is unspecified,
|
|
except as stated in <a href='#F.8.6'>F.8.6</a>. Whether the feraiseexcept function additionally raises the "inexact"
|
|
floating-point exception whenever it raises the "overflow" or "underflow" floating-point exception
|
|
is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.267'>
|
|
<pre><i><b>Footnote 267)</b> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations. Hence, implemen-
|
|
tation extensions associated with raising a floating-point exception (for example, enabled traps or IEC 60559 alternate
|
|
exception handling) should be honored. The specification in <a href='#F.8.6'>F.8.6</a> is in the same spirit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.4.3p3'></a>
|
|
<pre>3 The feraiseexcept function returns zero if the excepts argument is zero or if all the specified
|
|
exceptions were successfully raised. Otherwise, it returns a nonzero value.
|
|
|
|
Recommended Practice
|
|
Implementation extensions associated with raising a floating-point exception (for example, enabled
|
|
traps or IEC 60559 alternate exception handling) should be honored by this function.
|
|
|
|
</pre>
|
|
<a name='7.6.4.4'></a>
|
|
<hr>
|
|
<h3>7.6.4.4 [The fesetexcept function]</h3>
|
|
<a name='7.6.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetexcept(int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.4p2'></a>
|
|
<pre>2 The fesetexcept function attempts to set the supported floating-point exception flags represented
|
|
by its argument. This function does not clear any floating-point exception flags. This function
|
|
changes the state of the floating-point exception flags, but does not cause any other side effects that
|
|
might be associated with raising floating-point exceptions. <a href='#FOOTNOTE.268'><sup>[268]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.268'>
|
|
<pre><i><b>Footnote 268)</b> Implementation extensions like traps for floating-point exceptions and IEC 60559 exception handling do not occur.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.4.4p3'></a>
|
|
<pre>3 The fesetexcept function returns zero if all the specified exceptions were successfully set or if the
|
|
excepts argument is zero. Otherwise, it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.4.5'></a>
|
|
<hr>
|
|
<h3>7.6.4.5 [The fesetexceptflag function]</h3>
|
|
<a name='7.6.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetexceptflag(const fexcept_t *flagp, int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.5p2'></a>
|
|
<pre>2 The fesetexceptflag function attempts to set the floating-point status flags indicated by the
|
|
argument excepts to the states stored in the object pointed to by flagp. The value of *flagp
|
|
shall have been set by a previous call to fegetexceptflag whose second argument represented at
|
|
least those floating-point exceptions represented by the argument excepts. Like fesetexcept, this
|
|
function does not raise floating-point exceptions, but only sets the state of the flags.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.5p3'></a>
|
|
<pre>3 The fesetexceptflag function returns zero if the excepts argument is zero or if all the specified
|
|
flags were successfully set to the appropriate state. Otherwise, it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.4.6'></a>
|
|
<hr>
|
|
<h3>7.6.4.6 [The fetestexceptflag function]</h3>
|
|
<a name='7.6.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fetestexceptflag(const fexcept_t * flagp, int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.6p2'></a>
|
|
<pre>2 The fetestexceptflag function determines which of a specified subset of the floating-point excep-
|
|
tion flags are set in the object pointed to by flagp. The value of *flagp shall have been set by a
|
|
previous call to fegetexceptflag whose second argument represented at least those floating-point
|
|
exceptions represented by the argument excepts. The excepts argument specifies the floating-point
|
|
status flags to be queried.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.6p3'></a>
|
|
<pre>3 The fetestexceptflag function returns the value of the bitwise OR of the floating-point exception
|
|
macros included in excepts corresponding to the floating-point exceptions set in *flagp .
|
|
|
|
</pre>
|
|
<a name='7.6.4.7'></a>
|
|
<hr>
|
|
<h3>7.6.4.7 [The fetestexcept function]</h3>
|
|
<a name='7.6.4.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fetestexcept(int excepts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.7p2'></a>
|
|
<pre>2 The fetestexcept function determines which of a specified subset of the floating-point excep-
|
|
tion flags are currently set. The excepts argument specifies the floating-point status flags to be
|
|
queried.<a href='#FOOTNOTE.269'><sup>[269]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.269'>
|
|
<pre><i><b>Footnote 269)</b> This mechanism allows testing several floating-point exceptions with just one function call.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.4.7p3'></a>
|
|
<pre>3 The fetestexcept function returns the value of the bitwise OR of the floating-point exception
|
|
macros corresponding to the currently set floating-point exceptions included in excepts.
|
|
</pre>
|
|
<a name='7.6.4.7p4'></a>
|
|
<pre>4 EXAMPLE Call f if "invalid" is set, then g if "overflow" is set:
|
|
|
|
#include <fenv.h>
|
|
/* ... */
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
int set_excepts;
|
|
feclearexcept(FE_INVALID | FE_OVERFLOW);
|
|
// maybe raise exceptions
|
|
set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
|
|
if (set_excepts & FE_INVALID) f();
|
|
if (set_excepts & FE_OVERFLOW) g();
|
|
/* ... */
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='7.6.5'></a>
|
|
<hr>
|
|
<h3>7.6.5 [Rounding and other control modes]</h3>
|
|
<a name='7.6.5p1'></a>
|
|
<pre>1 The fegetround and fesetround functions provide control of rounding direction modes. The
|
|
fegetmode and fesetmode functions manage all the implementation’s dynamic floating-point
|
|
control modes collectively.
|
|
|
|
</pre>
|
|
<a name='7.6.5.1'></a>
|
|
<hr>
|
|
<h3>7.6.5.1 [The fegetmode function]</h3>
|
|
<a name='7.6.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetmode(femode_t *modep);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.1p2'></a>
|
|
<pre>2 The fegetmode function attempts to store all the dynamic floating-point control modes in the object
|
|
pointed to by modep.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.5.1p3'></a>
|
|
<pre>3 The fegetmode function returns zero if the modes were successfully stored. Otherwise, it returns a
|
|
nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.5.2'></a>
|
|
<hr>
|
|
<h3>7.6.5.2 [The fegetround function]</h3>
|
|
<a name='7.6.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetround(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.2p2'></a>
|
|
<pre>2 The fegetround function gets the current value of the dynamic rounding direction mode.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.5.2p3'></a>
|
|
<pre>3 The fegetround function returns the value of the rounding direction macro representing the current
|
|
dynamic rounding direction or a negative value if there is no such rounding direction macro or the
|
|
current dynamic rounding direction is not determinable.
|
|
|
|
</pre>
|
|
<a name='7.6.5.3'></a>
|
|
<hr>
|
|
<h3>7.6.5.3 [The fe_dec_getround function]</h3>
|
|
<a name='7.6.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int fe_dec_getround(void);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.3p2'></a>
|
|
<pre>2 The fe_dec_getround function gets the current value of the dynamic rounding direction mode for
|
|
decimal floating-point operations.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.5.3p3'></a>
|
|
<pre>3 The fe_dec_getround function returns the value of the rounding direction macro representing the
|
|
current dynamic rounding direction for decimal floating-point operations, or a negative value if
|
|
there is no such rounding macro or the current rounding direction is not determinable.
|
|
|
|
</pre>
|
|
<a name='7.6.5.4'></a>
|
|
<hr>
|
|
<h3>7.6.5.4 [The fesetmode function]</h3>
|
|
<a name='7.6.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetmode(const femode_t *modep);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.4p2'></a>
|
|
<pre>2 The fesetmode function attempts to establish the dynamic floating-point modes represented by the
|
|
object pointed to by modep. The argument modep shall point to an object set by a call to fegetmode,
|
|
or equal FE_DFL_MODE or a dynamic floating-point mode state macro defined by the implementation.
|
|
|
|
Returns
|
|
The fesetmode fesetmode function returns zero if the modes were successfully established. Other-
|
|
wise, it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.5.5'></a>
|
|
<hr>
|
|
<h3>7.6.5.5 [The fesetround function]</h3>
|
|
<a name='7.6.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetround(int rnd);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.5p2'></a>
|
|
<pre>2 The fesetround function establishes the rounding direction represented by its argument rnd. If
|
|
the argument is not equal to the value of a rounding direction macro, the rounding direction is not
|
|
changed.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.5.5p3'></a>
|
|
<pre>3 The fesetround function returns zero if and only if the dynamic rounding direction mode was set
|
|
to the requested rounding direction.
|
|
</pre>
|
|
<a name='7.6.5.5p4'></a>
|
|
<pre>4 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the rounding direction fails.
|
|
|
|
#include <fenv.h>
|
|
#include <assert.h>
|
|
|
|
void f(int rnd_dir)
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
int save_round;
|
|
int setround_ok;
|
|
save_round = fegetround();
|
|
setround_ok = fesetround(rnd_dir);
|
|
assert(setround_ok == 0);
|
|
/* ... */
|
|
fesetround(save_round);
|
|
/* ... */
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='7.6.5.6'></a>
|
|
<hr>
|
|
<h3>7.6.5.6 [The fe_dec_setround function]</h3>
|
|
<a name='7.6.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int fe_dec_setround(int rnd);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.5.6p2'></a>
|
|
<pre>2 The fe_dec_setround function sets the dynamic rounding direction mode for decimal floating-
|
|
point operations to be the rounding direction represented by its argument rnd. If the argument is
|
|
not equal to the value of a decimal rounding direction macro, the rounding direction is not changed.
|
|
</pre>
|
|
<a name='7.6.5.6p3'></a>
|
|
<pre>3 If FLT_RADIX is not 10, the rounding direction altered by the fesetround function is independent
|
|
of the rounding direction altered by the fe_dec_setround function; otherwise if FLT_RADIX is
|
|
10, whether the fesetround and fe_dec_setround functions alter the rounding direction of both
|
|
standard and decimal floating-point operations is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.5.6p4'></a>
|
|
<pre>4 The fe_dec_setround function returns a zero value if and only if the argument is equal to a decimal
|
|
rounding direction macro (that is, if and only if the dynamic rounding direction mode for decimal
|
|
floating-point operations was set to the requested rounding direction).
|
|
|
|
</pre>
|
|
<a name='7.6.6'></a>
|
|
<hr>
|
|
<h3>7.6.6 [Environment]</h3>
|
|
<a name='7.6.6p1'></a>
|
|
<pre>1 The functions in this section manage the floating-point environment — status flags and control
|
|
modes — as one entity.
|
|
|
|
</pre>
|
|
<a name='7.6.6.1'></a>
|
|
<hr>
|
|
<h3>7.6.6.1 [The fegetenv function]</h3>
|
|
<a name='7.6.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetenv(fenv_t *envp);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.6.1p2'></a>
|
|
<pre>2 The fegetenv function attempts to store the current dynamic floating-point environment in the
|
|
object pointed to by envp.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.6.1p3'></a>
|
|
<pre>3 The fegetenv function returns zero if the environment was successfully stored. Otherwise, it returns
|
|
a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.6.2'></a>
|
|
<hr>
|
|
<h3>7.6.6.2 [The feholdexcept function]</h3>
|
|
<a name='7.6.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feholdexcept(fenv_t *envp);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.6.2p2'></a>
|
|
<pre>2 The feholdexcept function saves the current dynamic floating-point environment in the object
|
|
pointed to by envp, clears the floating-point status flags, and then installs a non-stop (continue on
|
|
floating-point exceptions) mode, if available, for all floating-point exceptions.<a href='#FOOTNOTE.270'><sup>[270]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.270'>
|
|
<pre><i><b>Footnote 270)</b> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap handling or aborting; if
|
|
the system provides only the non-stop mode then installing it is trivial. For such systems, the feholdexcept function can be
|
|
used in conjunction with the feupdateenv function to write routines that hide spurious floating-point exceptions from their
|
|
callers.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.6.2p3'></a>
|
|
<pre>3 The feholdexcept function returns zero if and only if non-stop floating-point exception handling
|
|
was successfully installed.
|
|
</pre>
|
|
<a name='7.6.6.3'></a>
|
|
<hr>
|
|
<h3>7.6.6.3 [The fesetenv function]</h3>
|
|
<a name='7.6.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetenv(const fenv_t *envp);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.6.3p2'></a>
|
|
<pre>2 The fesetenv function attempts to establish the dynamic floating-point environment represented by
|
|
the object pointed to by envp. The argument envp shall point to an object set by a call to fegetenv or
|
|
feholdexcept, or equal a dynamic floating-point environment macro. Note that fesetenv merely
|
|
installs the state of the floating-point status flags represented through its argument, and does not
|
|
raise these floating-point exceptions.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.6.3p3'></a>
|
|
<pre>3 The fesetenv function returns zero if the environment was successfully established. Otherwise, it
|
|
returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.6.6.4'></a>
|
|
<hr>
|
|
<h3>7.6.6.4 [The feupdateenv function]</h3>
|
|
<a name='7.6.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feupdateenv(const fenv_t *envp);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.6.6.4p2'></a>
|
|
<pre>2 The feupdateenv function attempts to save the currently raised floating-point exceptions in its
|
|
automatic storage, install the dynamic floating-point environment represented by the object pointed
|
|
to by envp, and then raise the saved floating-point exceptions. The argument envp shall point to an
|
|
object set by a call to feholdexcept or fegetenv, or equal a dynamic floating-point environment
|
|
macro.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.6.4p3'></a>
|
|
<pre>3 The feupdateenv function returns zero if all the actions were successfully carried out. Otherwise, it
|
|
returns a nonzero value.
|
|
</pre>
|
|
<a name='7.6.6.4p4'></a>
|
|
<pre>4 EXAMPLE Hide spurious underflow floating-point exceptions:
|
|
|
|
#include <fenv.h>
|
|
double f(double x)
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
double result;
|
|
fenv_t save_env;
|
|
if (feholdexcept(&save_env))
|
|
return /* indication of an environmental problem */;
|
|
// compute result
|
|
if (/* test spurious underflow */)
|
|
if (feclearexcept(FE_UNDERFLOW))
|
|
return /* indication of an environmental problem */;
|
|
if (feupdateenv(&save_env))
|
|
return /* indication of an environmental problem */;
|
|
return result;
|
|
}
|
|
</pre>
|
|
<a name='7.7'></a>
|
|
<hr>
|
|
<h3>7.7 [Characteristics of floating types <float.h>]</h3>
|
|
<a name='7.7p1'></a>
|
|
<pre>1 The header <float.h> defines several macros that expand to various limits and parameters of the
|
|
real floating types.
|
|
</pre>
|
|
<a name='7.7p2'></a>
|
|
<pre>2 The macros, their meanings, and the constraints (or restrictions) on their values are listed in <a href='#5.2.4.2.2'>5.2.4.2.2</a>
|
|
and <a href='#5.2.4.2.3'>5.2.4.2.3</a>. A summary is given in Annex E.
|
|
</pre>
|
|
<a name='7.8'></a>
|
|
<hr>
|
|
<h3>7.8 [Format conversion of integer types <inttypes.h>]</h3>
|
|
<a name='7.8p1'></a>
|
|
<pre>1 The header <inttypes.h> includes the header <stdint.h> and extends it with additional facilities
|
|
provided by hosted implementations.
|
|
</pre>
|
|
<a name='7.8p2'></a>
|
|
<pre>2 It declares functions for manipulating greatest-width integers and converting numeric character
|
|
strings to greatest-width integers, and it declares the type
|
|
|
|
imaxdiv_t
|
|
|
|
|
|
which is a structure type that is the type of the value returned by the imaxdiv function. For each
|
|
type declared in <stdint.h>, it defines corresponding macros for conversion specifiers for use with
|
|
the formatted input/output functions.<a href='#FOOTNOTE.271'><sup>[271]</sup></a>
|
|
Forward references: integer types <stdint.h> (<a href='#7.22'>7.22</a>), formatted input/output functions (<a href='#7.23.6'>7.23.6</a>),
|
|
formatted wide character input/output functions (<a href='#7.31.2'>7.31.2</a>).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.271'>
|
|
<pre><i><b>Footnote 271)</b> See "future library directions" (<a href='#7.33.6'>7.33.6</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.8.1'></a>
|
|
<hr>
|
|
<h3>7.8.1 [Macros for format specifiers]</h3>
|
|
<a name='7.8.1p1'></a>
|
|
<pre>1 Each of the following object-like macros expands to a character string literal containing a conversion
|
|
specifier, possibly modified by a length modifier, suitable for use within the format argument of a
|
|
formatted input/output function when converting the corresponding integer type. These macro
|
|
names have the general form of PRI (character string literals for the fprintf and fwprintf family)
|
|
or SCN (character string literals for the fscanf and fwscanf family),<a href='#FOOTNOTE.272'><sup>[272]</sup></a> followed by the conversion
|
|
specifier, followed by a name corresponding to a similar type name in <a href='#7.22.1'>7.22.1</a>. In these names, N
|
|
represents the width of the type as described in <a href='#7.22.1'>7.22.1</a>. For example, PRIdFAST32 can be used in a
|
|
format string to print the value of an integer of type int_fast32_t.
|
|
</pre>
|
|
<a name='FOOTNOTE.272'>
|
|
<pre><i><b>Footnote 272)</b> Separate macros are given for use with fprintf and fscanf functions because, in the general case, different format
|
|
specifiers might be required for fprintf and fscanf, even when the type is the same.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.8.1p2'></a>
|
|
<pre>2 The fprintf macros for signed integers are:
|
|
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
|
|
PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
|
|
</pre>
|
|
<a name='7.8.1p3'></a>
|
|
<pre>3 The fprintf macros for unsigned integers are:
|
|
PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
|
|
PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
|
|
PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
|
|
PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
|
|
</pre>
|
|
<a name='7.8.1p4'></a>
|
|
<pre>4 The fscanf macros for signed integers are:
|
|
SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
|
|
SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
|
|
</pre>
|
|
<a name='7.8.1p5'></a>
|
|
<pre>5 The fscanf macros for unsigned integers are:
|
|
SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
|
|
SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
|
|
SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
|
|
</pre>
|
|
<a name='7.8.1p6'></a>
|
|
<pre>6 For each type that the implementation provides in <stdint.h>, the corresponding fprintf macros
|
|
shall be defined and the corresponding fscanf macros shall be defined unless the implementation
|
|
does not have a suitable fscanf length modifier for the type.
|
|
</pre>
|
|
<a name='7.8.1p7'></a>
|
|
<pre>7 EXAMPLE
|
|
|
|
#include <inttypes.h>
|
|
#include <wchar.h>
|
|
int main(void)
|
|
{
|
|
uintmax_t i = UINTMAX_MAX; // this type always exists
|
|
wprintf(L"The largest integer value is %020"
|
|
PRIxMAX "\n", i);
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.8.2'></a>
|
|
<hr>
|
|
<h3>7.8.2 [Functions for greatest-width integer types]</h3>
|
|
<a name='7.8.2.1'></a>
|
|
<hr>
|
|
<h3>7.8.2.1 [The imaxabs function]</h3>
|
|
<a name='7.8.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <inttypes.h>
|
|
intmax_t imaxabs(intmax_t j);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.8.2.1p2'></a>
|
|
<pre>2 The imaxabs function computes the absolute value of an integer j. If the result cannot be represented,
|
|
the behavior is undefined.<a href='#FOOTNOTE.273'><sup>[273]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.273'>
|
|
<pre><i><b>Footnote 273)</b> The absolute value of the most negative number may not be representable.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.8.2.1p3'></a>
|
|
<pre>3 The imaxabs function returns the absolute value.
|
|
|
|
</pre>
|
|
<a name='7.8.2.2'></a>
|
|
<hr>
|
|
<h3>7.8.2.2 [The imaxdiv function]</h3>
|
|
<a name='7.8.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <inttypes.h>
|
|
imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.8.2.2p2'></a>
|
|
<pre>2 The imaxdiv function computes numer / denom and numer % denom in a single operation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.8.2.2p3'></a>
|
|
<pre>3 The imaxdiv function returns a structure of type imaxdiv_t comprising both the quotient and the
|
|
remainder. The structure shall contain (in either order) the members quot (the quotient) and rem
|
|
(the remainder), each of which has type intmax_t. If either part of the result cannot be represented,
|
|
the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='7.8.2.3'></a>
|
|
<hr>
|
|
<h3>7.8.2.3 [The strtoimax and strtoumax functions]</h3>
|
|
<a name='7.8.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <inttypes.h>
|
|
intmax_t strtoimax(const char * restrict nptr, char ** restrict endptr, int base);
|
|
uintmax_t strtoumax(const char * restrict nptr, char ** restrict endptr, int base);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.8.2.3p2'></a>
|
|
<pre>2 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll, strtoul, and
|
|
strtoull functions, except that the initial portion of the string is converted to intmax_t and
|
|
uintmax_t representation, respectively.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.8.2.3p3'></a>
|
|
<pre>3 The strtoimax and strtoumax functions return the converted value, if any. If no conversion could
|
|
be performed, zero is returned. If the correct value is outside the range of representable values,
|
|
INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the return type and sign of the
|
|
value, if any), and the value of the macro ERANGE is stored in errno.
|
|
Forward references: the strtol, strtoll, strtoul, and strtoull functions (<a href='#7.24.1.7'>7.24.1.7</a>).
|
|
|
|
</pre>
|
|
<a name='7.8.2.4'></a>
|
|
<hr>
|
|
<h3>7.8.2.4 [The wcstoimax and wcstoumax functions]</h3>
|
|
<a name='7.8.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stddef.h> // for wchar_t
|
|
#include <inttypes.h>
|
|
intmax_t wcstoimax(const wchar_t *restrict nptr, wchar_t **restrict endptr, int base);
|
|
uintmax_t wcstoumax(const wchar_t *restrict nptr, wchar_t **restrict endptr, int base);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.8.2.4p2'></a>
|
|
<pre>2 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll, wcstoul, and
|
|
wcstoull functions except that the initial portion of the wide string is converted to intmax_t and
|
|
uintmax_t representation, respectively.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.8.2.4p3'></a>
|
|
<pre>3 The wcstoimax function returns the converted value, if any. If no conversion could be performed,
|
|
zero is returned. If the correct value is outside the range of representable values, INTMAX_MAX,
|
|
INTMAX_MIN, or UINTMAX_MAX is returned (according to the return type and sign of the value, if any),
|
|
and the value of the macro ERANGE is stored in errno.
|
|
Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions (<a href='#7.31.4.1.4'>7.31.4.1.4</a>).
|
|
</pre>
|
|
<a name='7.9'></a>
|
|
<hr>
|
|
<h3>7.9 [Alternative spellings <iso646.h>]</h3>
|
|
<a name='7.9p1'></a>
|
|
<pre>1 The header <iso646.h> defines the following eleven macros (on the left) that expand to the corre-
|
|
sponding tokens (on the right):
|
|
|
|
and &&
|
|
and_eq &=
|
|
bitand &
|
|
bitor |
|
|
compl ~
|
|
not !
|
|
not_eq !=
|
|
or ||
|
|
or_eq |=
|
|
xor ^
|
|
xor_eq ^=
|
|
</pre>
|
|
<a name='7.10'></a>
|
|
<hr>
|
|
<h3>7.10 [Characteristics of integer types <limits.h>]</h3>
|
|
<a name='7.10p1'></a>
|
|
<pre>1 The header <limits.h> defines several macros that expand to various limits and parameters of the
|
|
standard integer types.
|
|
</pre>
|
|
<a name='7.10p2'></a>
|
|
<pre>2 The macros, their meanings, and the constraints (or restrictions) on their values are listed in <a href='#5.2.4.2.1'>5.2.4.2.1</a>.
|
|
A summary is given in Annex E.
|
|
</pre>
|
|
<a name='7.11'></a>
|
|
<hr>
|
|
<h3>7.11 [Localization <locale.h>]</h3>
|
|
<a name='7.11p1'></a>
|
|
<pre>1 The header <locale.h> declares two functions, one type, and defines several macros.
|
|
</pre>
|
|
<a name='7.11p2'></a>
|
|
<pre>2 The type is
|
|
|
|
struct lconv
|
|
|
|
|
|
which contains members related to the formatting of numeric values. The structure shall contain
|
|
at least the following members, in any order. The semantics of the members and their normal
|
|
ranges are explained in <a href='#7.11.2.1'>7.11.2.1</a>. In the "C" locale, the members shall have the values specified in the
|
|
comments.
|
|
|
|
char *decimal_point; // "."
|
|
char *thousands_sep; // ""
|
|
char *grouping; // ""
|
|
char *mon_decimal_point; // ""
|
|
char *mon_thousands_sep; // ""
|
|
char *mon_grouping; // ""
|
|
char *positive_sign; // ""
|
|
char *negative_sign; // ""
|
|
char *currency_symbol; // ""
|
|
char frac_digits; // CHAR_MAX
|
|
char p_cs_precedes; // CHAR_MAX
|
|
char n_cs_precedes; // CHAR_MAX
|
|
char p_sep_by_space; // CHAR_MAX
|
|
char n_sep_by_space; // CHAR_MAX
|
|
char p_sign_posn; // CHAR_MAX
|
|
char n_sign_posn; // CHAR_MAX
|
|
char *int_curr_symbol; // ""
|
|
char int_frac_digits; // CHAR_MAX
|
|
char int_p_cs_precedes; // CHAR_MAX
|
|
char int_n_cs_precedes; // CHAR_MAX
|
|
char int_p_sep_by_space; // CHAR_MAX
|
|
char int_n_sep_by_space; // CHAR_MAX
|
|
char int_p_sign_posn; // CHAR_MAX
|
|
char int_n_sign_posn; // CHAR_MAX
|
|
|
|
|
|
</pre>
|
|
<a name='7.11p3'></a>
|
|
<pre>3 The macros defined are NULL (described in <a href='#7.21'>7.21</a>); and
|
|
|
|
LC_ALL
|
|
LC_COLLATE
|
|
LC_CTYPE
|
|
LC_MONETARY
|
|
LC_NUMERIC
|
|
LC_TIME
|
|
|
|
|
|
which expand to integer constant expressions with distinct values, suitable for use as the first argu-
|
|
ment to the setlocale function.<a href='#FOOTNOTE.274'><sup>[274]</sup></a> Additional macro definitions, beginning with the characters
|
|
LC_ and an uppercase letter,<a href='#FOOTNOTE.275'><sup>[275]</sup></a> may also be specified by the implementation.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.274'>
|
|
<pre><i><b>Footnote 274)</b> ISO/IEC 9945–2 specifies locale and charmap formats that can be used to specify locales for C.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.275'>
|
|
<pre><i><b>Footnote 275)</b> See "future library directions" (<a href='#7.33.7'>7.33.7</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.11.1'></a>
|
|
<hr>
|
|
<h3>7.11.1 [Locale control]</h3>
|
|
<a name='7.11.1.1'></a>
|
|
<hr>
|
|
<h3>7.11.1.1 [The setlocale function]</h3>
|
|
<a name='7.11.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <locale.h>
|
|
char *setlocale(int category, const char *locale);
|
|
Description
|
|
</pre>
|
|
<a name='7.11.1.1p2'></a>
|
|
<pre>2 The setlocale function selects the appropriate portion of the program’s locale as specified by
|
|
the category and locale arguments. The setlocale function may be used to change or query
|
|
the program’s entire current locale or portions thereof. The value LC_ALL for category names
|
|
the program’s entire locale; the other values for category name only a portion of the program’s
|
|
locale. LC_COLLATE affects the behavior of the strcoll and strxfrm functions. LC_CTYPE affects
|
|
the behavior of the character handling functions<a href='#FOOTNOTE.276'><sup>[276]</sup></a> and the multibyte and wide character functions.
|
|
LC_MONETARY affects the monetary formatting information returned by the localeconv function.
|
|
LC_NUMERIC affects the decimal-point character for the formatted input/output functions and the
|
|
string conversion functions, as well as the nonmonetary formatting information returned by the
|
|
localeconv function. LC_TIME affects the behavior of the strftime and wcsftime functions.
|
|
</pre>
|
|
<a name='FOOTNOTE.276'>
|
|
<pre><i><b>Footnote 276)</b> The only functions in <a href='#7.4'>7.4</a> whose behavior is not affected by the current locale are isdigit and isxdigit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.11.1.1p3'></a>
|
|
<pre>3 A value of "C" for locale specifies the minimal environment for C translation; a value of "" for
|
|
locale specifies the locale-specific native environment. Other implementation-defined strings may
|
|
be passed as the second argument to setlocale.
|
|
</pre>
|
|
<a name='7.11.1.1p4'></a>
|
|
<pre>4 At program startup, the equivalent of
|
|
|
|
setlocale(LC_ALL, "C");
|
|
|
|
|
|
is executed.
|
|
</pre>
|
|
<a name='7.11.1.1p5'></a>
|
|
<pre>5 A call to the setlocale function may introduce a data race with other calls to the setlocale
|
|
function or with calls to functions that are affected by the current locale. The implementation shall
|
|
behave as if no library function calls the setlocale function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.11.1.1p6'></a>
|
|
<pre>6 If a pointer to a string is given for locale and the selection can be honored, the setlocale function
|
|
returns a pointer to the string associated with the specified category for the new locale. If the
|
|
selection cannot be honored, the setlocale function returns a null pointer and the program’s locale
|
|
is not changed.
|
|
</pre>
|
|
<a name='7.11.1.1p7'></a>
|
|
<pre>7 A null pointer for locale causes the setlocale function to return a pointer to the string associated
|
|
with the category for the program’s current locale; the program’s locale is not changed.<a href='#FOOTNOTE.277'><sup>[277]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.277'>
|
|
<pre><i><b>Footnote 277)</b> The implementation is thus required to arrange to encode in a string the various categories due to a heterogeneous locale
|
|
when category has the value LC_ALL.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.11.1.1p8'></a>
|
|
<pre>8 The pointer to string returned by the setlocale function is such that a subsequent call with that
|
|
string value and its associated category will restore that part of the program’s locale. The string
|
|
pointed to shall not be modified by the program. The behavior is undefined if the returned value
|
|
is used after a subsequent call to the setlocale function, or after the thread which called the
|
|
setlocale function to obtain the returned value has exited.
|
|
Forward references: formatted input/output functions (<a href='#7.23.6'>7.23.6</a>), multibyte/wide character conver-
|
|
sion functions (<a href='#7.24.7'>7.24.7</a>), multibyte/wide string conversion functions (<a href='#7.24.8'>7.24.8</a>), numeric conversion
|
|
functions (<a href='#7.24.1'>7.24.1</a>), the strcoll function (<a href='#7.26.4.3'>7.26.4.3</a>), the strftime function (<a href='#7.29.3.5'>7.29.3.5</a>), the strxfrm
|
|
function (<a href='#7.26.4.5'>7.26.4.5</a>).
|
|
|
|
</pre>
|
|
<a name='7.11.2'></a>
|
|
<hr>
|
|
<h3>7.11.2 [Numeric formatting convention inquiry]</h3>
|
|
<a name='7.11.2.1'></a>
|
|
<hr>
|
|
<h3>7.11.2.1 [The localeconv function]</h3>
|
|
<a name='7.11.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <locale.h>
|
|
struct lconv *localeconv(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.11.2.1p2'></a>
|
|
<pre>2 The localeconv function sets the components of an object with type struct lconv with values
|
|
appropriate for the formatting of numeric quantities (monetary and otherwise) according to the
|
|
rules of the current locale.
|
|
</pre>
|
|
<a name='7.11.2.1p3'></a>
|
|
<pre>3 The members of the structure with type char * are pointers to strings, any of which (except
|
|
decimal_point) can point to "", to indicate that the value is not available in the current locale or is
|
|
of zero length. Apart from grouping and mon_grouping, the strings shall start and end in the initial
|
|
shift state. The members with type char are nonnegative numbers, any of which can be CHAR_MAX
|
|
to indicate that the value is not available in the current locale. The members include the following:
|
|
|
|
char *decimal_point
|
|
The decimal-point character used to format nonmonetary quantities.
|
|
char *thousands_sep
|
|
The character used to separate groups of digits before the decimal-point character in
|
|
formatted nonmonetary quantities.
|
|
char *grouping
|
|
A string whose elements indicate the size of each group of digits in formatted nonmon-
|
|
etary quantities.
|
|
char *mon_decimal_point
|
|
The decimal-point used to format monetary quantities.
|
|
char *mon_thousands_sep
|
|
The separator for groups of digits before the decimal-point in formatted monetary
|
|
quantities.
|
|
char *mon_grouping
|
|
A string whose elements indicate the size of each group of digits in formatted monetary
|
|
quantities.
|
|
char *positive_sign
|
|
The string used to indicate a nonnegative-valued formatted monetary quantity.
|
|
char *negative_sign
|
|
The string used to indicate a negative-valued formatted monetary quantity.
|
|
char *currency_symbol
|
|
The local currency symbol applicable to the current locale.
|
|
char frac_digits
|
|
The number of fractional digits (those after the decimal-point) to be displayed in a
|
|
locally formatted monetary quantity.
|
|
char p_cs_precedes
|
|
Set to 1 or 0 if the currency_symbol respectively precedes or succeeds the value for a
|
|
nonnegative locally formatted monetary quantity.
|
|
char n_cs_precedes
|
|
Set to 1 or 0 if the currency_symbol respectively precedes or succeeds the value for a
|
|
negative locally formatted monetary quantity.
|
|
char p_sep_by_space
|
|
Set to a value indicating the separation of the currency_symbol, the sign string, and
|
|
the value for a nonnegative locally formatted monetary quantity.
|
|
char n_sep_by_space
|
|
Set to a value indicating the separation of the currency_symbol, the sign string, and
|
|
the value for a negative locally formatted monetary quantity.
|
|
char p_sign_posn
|
|
Set to a value indicating the positioning of the positive_sign for a nonnegative locally
|
|
formatted monetary quantity.
|
|
char n_sign_posn
|
|
Set to a value indicating the positioning of the negative_sign for a negative locally
|
|
formatted monetary quantity.
|
|
|
|
char *int_curr_symbol
|
|
The international currency symbol applicable to the current locale. The first three
|
|
characters contain the alphabetic international currency symbol in accordance with
|
|
those specified in ISO 4217. The fourth character (immediately preceding the null
|
|
character) is the character used to separate the international currency symbol from the
|
|
monetary quantity.
|
|
|
|
char int_frac_digits
|
|
The number of fractional digits (those after the decimal-point) to be displayed in an
|
|
internationally formatted monetary quantity.
|
|
|
|
char int_p_cs_precedes
|
|
Set to 1 or 0 if the int_curr_symbol respectively precedes or succeeds the value for a
|
|
nonnegative internationally formatted monetary quantity.
|
|
|
|
char int_n_cs_precedes
|
|
Set to 1 or 0 if the int_curr_symbol respectively precedes or succeeds the value for a
|
|
negative internationally formatted monetary quantity.
|
|
|
|
char int_p_sep_by_space
|
|
Set to a value indicating the separation of the int_curr_symbol, the sign string, and
|
|
the value for a nonnegative internationally formatted monetary quantity.
|
|
|
|
char int_n_sep_by_space
|
|
Set to a value indicating the separation of the int_curr_symbol, the sign string, and
|
|
the value for a negative internationally formatted monetary quantity.
|
|
|
|
char int_p_sign_posn
|
|
Set to a value indicating the positioning of the positive_sign for a nonnegative
|
|
internationally formatted monetary quantity.
|
|
|
|
char int_n_sign_posn
|
|
Set to a value indicating the positioning of the negative_sign for a negative interna-
|
|
tionally formatted monetary quantity.
|
|
|
|
</pre>
|
|
<a name='7.11.2.1p4'></a>
|
|
<pre>4 The elements of grouping and mon_grouping are interpreted according to the following:
|
|
|
|
CHAR_MAX No further grouping is to be performed.
|
|
|
|
0 The previous element is to be repeatedly used for the remainder of the digits.
|
|
|
|
other The integer value is the number of digits that compose the current group. The next
|
|
element is examined to determine the size of the next group of digits before the current
|
|
group.
|
|
|
|
</pre>
|
|
<a name='7.11.2.1p5'></a>
|
|
<pre>5 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space, and
|
|
int_n_sep_by_space are interpreted according to the following:
|
|
|
|
0 No space separates the currency symbol and value.
|
|
|
|
1 If the currency symbol and sign string are adjacent, a space separates them from the value;
|
|
otherwise, a space separates the currency symbol from the value.
|
|
|
|
2 If the currency symbol and sign string are adjacent, a space separates them; otherwise, a space
|
|
separates the sign string from the value.
|
|
For int_p_sep_by_space and int_n_sep_by_space, the fourth character of int_curr_symbol is
|
|
used instead of a space.
|
|
</pre>
|
|
<a name='7.11.2.1p6'></a>
|
|
<pre>6 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and int_n_sign_posn are inter-
|
|
preted according to the following:
|
|
|
|
|
|
0 Parentheses surround the quantity and currency symbol.
|
|
|
|
|
|
|
|
1 The sign string precedes the quantity and currency symbol.
|
|
|
|
|
|
|
|
2 The sign string succeeds the quantity and currency symbol.
|
|
|
|
|
|
|
|
3 The sign string immediately precedes the currency symbol.
|
|
|
|
|
|
|
|
4 The sign string immediately succeeds the currency symbol.
|
|
|
|
|
|
</pre>
|
|
<a name='7.11.2.1p7'></a>
|
|
<pre>7 The implementation shall behave as if no library function calls the localeconv function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.11.2.1p8'></a>
|
|
<pre>8 The localeconv function returns a pointer to the filled-in object. The structure pointed to by the
|
|
return value shall not be modified by the program, but may be overwritten by a subsequent call
|
|
to the localeconv function. In addition, calls to the setlocale function with categories LC_ALL,
|
|
LC_MONETARY, or LC_NUMERIC may overwrite the contents of the structure.
|
|
</pre>
|
|
<a name='7.11.2.1p9'></a>
|
|
<pre>9 EXAMPLE 1 The following table illustrates rules which might well be used by four countries to format monetary quantities.
|
|
Local format International format
|
|
Country Positive Negative Positive Negative
|
|
Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
|
|
Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
|
|
Country3 ƒ 1.234,56 ƒ -1.234,56 NLG 1.234,56 NLG -1.234,56
|
|
Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
|
|
|
|
</pre>
|
|
<a name='7.11.2.1p10'></a>
|
|
<pre>10 For these four countries, the respective values for the monetary members of the structure returned by localeconv could be:
|
|
Country1 Country2 Country3 Country4
|
|
mon_decimal_point "," "" "," "."
|
|
mon_thousands_sep "." "." "." ","
|
|
mon_grouping "\3" "\3" "\3" "\3"
|
|
positive_sign "" "" "" ""
|
|
negative_sign "-" "-" "-" "C"
|
|
currency_symbol "mk" "L." "\u0192" "SFrs."
|
|
frac_digits 2 0 2 2
|
|
p_cs_precedes 0 1 1 1
|
|
n_cs_precedes 0 1 1 1
|
|
p_sep_by_space 1 0 1 0
|
|
n_sep_by_space 1 0 2 0
|
|
p_sign_posn 1 1 1 1
|
|
n_sign_posn 1 1 4 2
|
|
int_curr_symbol "FIM " "ITL " "NLG " "CHF "
|
|
int_frac_digits 2 0 2 2
|
|
int_p_cs_precedes 1 1 1 1
|
|
int_n_cs_precedes 1 1 1 1
|
|
int_p_sep_by_space 1 1 1 1
|
|
int_n_sep_by_space 2 1 2 1
|
|
int_p_sign_posn 1 1 1 1
|
|
int_n_sign_posn 4 1 4 2
|
|
</pre>
|
|
<a name='7.11.2.1p11'></a>
|
|
<pre>11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members affect the
|
|
formatted value.
|
|
p_sep_by_space
|
|
p_cs_precedes p_sign_posn 0 1 2
|
|
0 0 (1.25$) (1.25 $) (1.25$)
|
|
1 +1.25$ +1.25 $ + 1.25$
|
|
2 1.25$+ 1.25 $+ 1.25$ +
|
|
3 1.25+$ 1.25 +$ 1.25+ $
|
|
4 1.25$+ 1.25 $+ 1.25$ +
|
|
1 0 ($1.25) ($ 1.25) ($1.25)
|
|
1 +$1.25 +$ 1.25 + $1.25
|
|
2 $1.25+ $ 1.25+ $1.25 +
|
|
3 +$1.25 +$ 1.25 + $1.25
|
|
4 $+1.25 $+ 1.25 $ +1.25
|
|
</pre>
|
|
<a name='7.12'></a>
|
|
<hr>
|
|
<h3>7.12 [Mathematics <math.h>]</h3>
|
|
<a name='7.12p1'></a>
|
|
<pre>1 The header <math.h> declares two types and many mathematical functions and defines several
|
|
macros. Most synopses specify a family of functions consisting of a principal function with one
|
|
or more double parameters, a double return value, or both; and other functions with the same
|
|
name but with f and l suffixes, which are corresponding functions with float and long double
|
|
parameters, return values, or both.<a href='#FOOTNOTE.278'><sup>[278]</sup></a> Integer arithmetic functions and conversion functions are
|
|
discussed later.
|
|
</pre>
|
|
<a name='FOOTNOTE.278'>
|
|
<pre><i><b>Footnote 278)</b> Particularly on systems with wide expression evaluation, a <math.h> function might pass arguments and return values
|
|
in wider format than the synopsis prototype indicates.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p2'></a>
|
|
<pre>2 The feature test macro __STDC_VERSION_MATH_H__ expands to the token 202311L.
|
|
</pre>
|
|
<a name='7.12p3'></a>
|
|
<pre>3 The types
|
|
|
|
float_t
|
|
double_t
|
|
|
|
|
|
are floating types at least as wide as float and double, respectively, and such that double_t is
|
|
at least as wide as float_t. If FLT_EVAL_METHOD equals 0, float_t and double_t are float and
|
|
double, respectively; if FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD
|
|
equals 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are otherwise
|
|
implementation-defined.<a href='#FOOTNOTE.279'><sup>[279]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.279'>
|
|
<pre><i><b>Footnote 279)</b> The types float_t and double_t are intended to be the implementation’s most efficient types at least as wide as
|
|
float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the type float_t is the narrowest type used by the
|
|
implementation to evaluate floating expressions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p4'></a>
|
|
<pre>4 The types
|
|
_Decimal32_t
|
|
_Decimal64_t
|
|
|
|
|
|
are decimal floating types at least as wide as _Decimal32 and _Decimal64 , respectively,
|
|
and such that _Decimal64_t is at least as wide as _Decimal32_t . If DEC_EVAL_METHOD
|
|
equals 0, _Decimal32_t and _Decimal64_t are _Decimal32 and _Decimal64 , respectively; if
|
|
DEC_EVAL_METHOD equals 1, they are both _Decimal64 ; if DEC_EVAL_METHOD equals 2, they are
|
|
both _Decimal128 ; and for other values of DEC_EVAL_METHOD, they are otherwise implementation-
|
|
defined.
|
|
</pre>
|
|
<a name='7.12p5'></a>
|
|
<pre>5 The macro
|
|
|
|
HUGE_VAL
|
|
|
|
|
|
expands to a double constant expression, not necessarily representable as a float, whose value is
|
|
the maximum value returned by library functions when a floating result of type double overflows
|
|
under the default rounding mode, either maximum finite number in the type or positive or unsigned
|
|
infinity. The macros
|
|
|
|
HUGE_VALF
|
|
HUGE_VALL
|
|
|
|
|
|
are respectively float and long double analogs of HUGE_VAL<a href='#FOOTNOTE.280'><sup>[280]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.280'>
|
|
<pre><i><b>Footnote 280)</b> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that supports infinities.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p6'></a>
|
|
<pre>6 The macro
|
|
|
|
HUGE_VAL_D32
|
|
|
|
|
|
expands to a constant expression of type _Decimal32 representing positive infinity. The macros
|
|
|
|
HUGE_VAL_D64
|
|
HUGE_VAL_D128
|
|
|
|
|
|
are respectively _Decimal64 and _Decimal128 analogs of HUGE_VAL_D32.
|
|
</pre>
|
|
<a name='7.12p7'></a>
|
|
<pre>7 The macro
|
|
|
|
INFINITY
|
|
|
|
|
|
is defined if and only if the implementation supports an infinity for the type float. It expands to a
|
|
constant expression of type float representing positive or unsigned infinity.
|
|
</pre>
|
|
<a name='7.12p8'></a>
|
|
<pre>8 The macro
|
|
|
|
DEC_INFINITY
|
|
|
|
|
|
expands to a constant expression of type _Decimal32 representing positive infinity.
|
|
</pre>
|
|
<a name='7.12p9'></a>
|
|
<pre>9 The macro
|
|
|
|
NAN
|
|
|
|
|
|
is defined if and only if the implementation supports quiet NaNs for the float type. It expands to a
|
|
constant expression of type float representing a quiet NaN.
|
|
</pre>
|
|
<a name='7.12p10'></a>
|
|
<pre>10 The macro
|
|
|
|
DEC_NAN
|
|
|
|
|
|
expands to a constant expression of type _Decimal32 representing a quiet NaN.
|
|
</pre>
|
|
<a name='7.12p11'></a>
|
|
<pre>11 Use of the macros INFINITY, DEC_INFINITY, NAN, and DEC_NAN in <math.h> is an obsolescent
|
|
feature. Instead, use the same macros in <float.h>.
|
|
</pre>
|
|
<a name='7.12p12'></a>
|
|
<pre>12 The number classification macros
|
|
|
|
FP_INFINITE
|
|
FP_NAN
|
|
FP_NORMAL
|
|
FP_SUBNORMAL
|
|
FP_ZERO
|
|
|
|
|
|
represent mutually exclusive kinds of floating-point values. They expand to integer constant
|
|
expressions with distinct values. Additional implementation-defined floating-point classifications,
|
|
with macro definitions beginning with FP_ and an uppercase letter, may also be specified by the
|
|
implementation.
|
|
</pre>
|
|
<a name='7.12p13'></a>
|
|
<pre>13 The math rounding direction macros
|
|
|
|
FP_INT_UPWARD
|
|
FP_INT_DOWNWARD
|
|
FP_INT_TOWARDZERO
|
|
FP_INT_TONEARESTFROMZERO
|
|
FP_INT_TONEAREST
|
|
|
|
|
|
represent the rounding directions of the functions ceil, floor, trunc, round, and roundeven,
|
|
respectively, that convert to integral values in floating-point formats. They expand to integer
|
|
constant expressions with distinct values suitable for use as the second argument to the fromfp,
|
|
ufromfp, fromfpx, and ufromfpx functions.
|
|
</pre>
|
|
<a name='7.12p14'></a>
|
|
<pre>14 The macro
|
|
|
|
FP_FAST_FMA
|
|
is optionally defined. If defined, it indicates that the fma function generally executes about as fast as,
|
|
or faster than, a multiply and an add of double operands.<a href='#FOOTNOTE.281'><sup>[281]</sup></a> The macros
|
|
|
|
FP_FAST_FMAF
|
|
FP_FAST_FMAL
|
|
|
|
|
|
are, respectively, float and long double analogs of FP_FAST_FMA. If defined, these macros expand
|
|
to the integer constant 1.
|
|
</pre>
|
|
<a name='FOOTNOTE.281'>
|
|
<pre><i><b>Footnote 281)</b> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented directly with a hardware
|
|
multiply-add instruction. Software implementations are expected to be substantially slower.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p15'></a>
|
|
<pre>15 The macros
|
|
|
|
FP_FAST_FMAD32
|
|
FP_FAST_FMAD64
|
|
FP_FAST_FMAD128
|
|
|
|
|
|
are, respectively, _Decimal32 , _Decimal64 , and _Decimal128 analogs of FP_FAST_FMA.
|
|
</pre>
|
|
<a name='7.12p16'></a>
|
|
<pre>16 Each of the macros
|
|
|
|
FP_FAST_FADD FP_FAST_DSUBL FP_FAST_FDIVL FP_FAST_FFMA
|
|
FP_FAST_FADDL FP_FAST_FMUL FP_FAST_DDIVL FP_FAST_FFMAL
|
|
FP_FAST_DADDL FP_FAST_FMULL FP_FAST_FSQRT FP_FAST_DFMAL
|
|
FP_FAST_FSUB FP_FAST_DMULL FP_FAST_FSQRTL
|
|
FP_FAST_FSUBL FP_FAST_FDIV FP_FAST_DSQRTL
|
|
|
|
|
|
is optionally defined. If defined, it indicates that the corresponding function generally executes
|
|
about as fast, or faster, than the corresponding operation or function of the argument type with
|
|
result type the same as the argument type followed by conversion to the narrower type. For
|
|
FP_FAST_FFMA, FP_FAST_FFMAL, and FP_FAST_DFMAL, the comparison is to a call to fma or fmal
|
|
followed by a conversion, not to separate multiply, add, and conversion. If defined, these macros
|
|
expand to the integer constant 1.
|
|
</pre>
|
|
<a name='7.12p17'></a>
|
|
<pre>17 The macros
|
|
|
|
FP_FAST_D32ADDD64 FP_FAST_D32MULD64 FP_FAST_D32FMAD64
|
|
FP_FAST_D32ADDD128 FP_FAST_D32MULD128 FP_FAST_D32FMAD128
|
|
FP_FAST_D64ADDD128 FP_FAST_D64MULD128 FP_FAST_D64FMAD128
|
|
FP_FAST_D32SUBD64 FP_FAST_D32DIVD64 FP_FAST_D32SQRTD64
|
|
FP_FAST_D32SUBD128 FP_FAST_D32DIVD128 FP_FAST_D32SQRTD128
|
|
FP_FAST_D64SUBD128 FP_FAST_D64DIVD128 FP_FAST_D64SQRTD128
|
|
|
|
|
|
are analogs of FP_FAST_FADD, FP_FAST_FADDL, FP_FAST_DADDL, etc., for decimal floating types.
|
|
</pre>
|
|
<a name='7.12p18'></a>
|
|
<pre>18 The macros
|
|
|
|
FP_ILOGB0
|
|
FP_ILOGBNAN
|
|
|
|
|
|
expand to integer constant expressions whose values are returned by ilogb(x) if x is zero or
|
|
NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or -INT_MAX . The value of
|
|
FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
|
|
</pre>
|
|
<a name='7.12p19'></a>
|
|
<pre>19 The macros
|
|
|
|
FP_LLOGB0
|
|
FP_LLOGBNAN
|
|
expand to integer constant expressions whose values are returned by llogb(x) if x is zero or NaN, re-
|
|
spectively. The value of FP_LLOGB0 shall be LONG_MIN if the value of FP_ILOGB0 is INT_MIN, and shall
|
|
be-LONG_MAX if the value of FP_ILOGB0 is-INT_MAX . The value of FP_LLOGBNAN shall be LONG_MAX
|
|
if the value of FP_ILOGBNAN is INT_MAX, and shall be LONG_MIN if the value of FP_ILOGBNAN is
|
|
INT_MIN.
|
|
</pre>
|
|
<a name='7.12p20'></a>
|
|
<pre>20 The macros
|
|
|
|
MATH_ERRNO
|
|
MATH_ERREXCEPT
|
|
|
|
|
|
expand to the integer constants 1 and 2, respectively; the macro
|
|
|
|
math_errhandling
|
|
|
|
|
|
expands to an expression that has type int and the value MATH_ERRNO, MATH_ERREXCEPT, the
|
|
bitwise OR of both, or 0; the value shall not be 0 in a hosted implementation. The value
|
|
of math_errhandling is constant for the duration of the program. It is unspecified whether
|
|
math_errhandling is a macro or an identifier with external linkage. If a macro definition is sup-
|
|
pressed or a program defines an identifier with the name math_errhandling, the behavior is
|
|
undefined. If the expression math_errhandling & MATH_ERREXCEPT can be nonzero, the implemen-
|
|
tation shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in <fenv.h>.
|
|
|
|
</pre>
|
|
<a name='7.12.1'></a>
|
|
<hr>
|
|
<h3>7.12.1 [Treatment of error conditions]</h3>
|
|
<a name='7.12.1p1'></a>
|
|
<pre>1 The behavior of each of the functions in <math.h> is specified for all representable values of its
|
|
input arguments, except where explicitly stated otherwise. Each function shall execute as if it were a
|
|
single operation without raising SIGFPE and without generating any of the floating-point exceptions
|
|
"invalid", "divide-by-zero", or "overflow" except to reflect the result of the function.
|
|
</pre>
|
|
<a name='7.12.1p2'></a>
|
|
<pre>2 For all functions, a domain error occurs if and only if an input argument is outside the domain over
|
|
which the mathematical function is defined. The description of each function lists any required
|
|
domain errors; an implementation may define additional domain errors, provided that such errors
|
|
are consistent with the mathematical definition of the function.<a href='#FOOTNOTE.282'><sup>[282]</sup></a> Whether a signaling NaN
|
|
input causes a domain error is implementation-defined. On a domain error, the function returns
|
|
an implementation-defined value; if the integer expression math_errhandling & MATH_ERRNO
|
|
is nonzero, the integer expression errno acquires the value EDOM; if the integer expression
|
|
math_errhandling & MATH_ERREXCEPT is nonzero, the "invalid" floating-point exception is raised.
|
|
</pre>
|
|
<a name='FOOTNOTE.282'>
|
|
<pre><i><b>Footnote 282)</b> In an implementation that supports infinities, this allows an infinity as an argument to be a domain error if the
|
|
mathematical domain of the function does not include the infinity.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.1p3'></a>
|
|
<pre>3 Similarly, a pole error (also known as a singularity or infinitary) occurs if and only if the mathematical
|
|
function has an exact infinite result as the finite input argument(s) are approached in the limit (for ex-
|
|
ample, log(0.0)). The description of each function lists any required pole errors; an implementation
|
|
may define additional pole errors, provided that such errors are consistent with the mathematical
|
|
definition of the function. On a pole error, the function returns an implementation-defined value;
|
|
if the integer expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
|
|
errno acquires the value ERANGE; if the integer expression math_errhandling & MATH_ERREXCEPT
|
|
is nonzero, the "divide-by-zero" floating-point exception is raised.
|
|
</pre>
|
|
<a name='7.12.1p4'></a>
|
|
<pre>4 Likewise, a range error occurs if and only if the result overflows or underflows, as defined below.
|
|
The description of each function lists any required range errors; an implementation may define
|
|
additional range errors, provided that such errors are consistent with the mathematical definition of
|
|
the function and are the result of either overflow or underflow<a href='#FOOTNOTE.283'><sup>[283]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.283'>
|
|
<pre><i><b>Footnote 283)</b> Range errors that are required or implementation-defined shall or may be reported, as specified in this subclause.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.1p5'></a>
|
|
<pre>5 A floating result overflows if a finite result value with ordinary accuracy<a href='#FOOTNOTE.284'><sup>[284]</sup></a> would have magnitude
|
|
(absolute value) too large for the representation with full precision in the specified type. A result
|
|
that is exactly an infinity does not overflow. If a floating result overflows and default rounding
|
|
is in effect, then the function returns the value of the macro HUGE_VAL, HUGE_VALF, or HUGE_VALL
|
|
according to the return type, with the same sign as the correct value of the function; however, for
|
|
the types with reduced-precision representations of numbers beyond the overflow threshold, the
|
|
function may return a representation of the result with less than full precision for the type. If a
|
|
floating result overflows and the integer expression math_errhandling & MATH_ERRNO is nonzero,
|
|
the integer expression errno acquires the value ERANGE. If a floating result overflows and the
|
|
integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the "overflow" floating-
|
|
point exception is raised.
|
|
</pre>
|
|
<a name='FOOTNOTE.284'>
|
|
<pre><i><b>Footnote 284)</b> Ordinary accuracy is determined by the implementation. It refers to the accuracy of the function where results are not
|
|
compromised by extreme magnitude.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.1p6'></a>
|
|
<pre>6 The result underflows if a nonzero result value with ordinary accuracy would have magnitude (abso-
|
|
lute value) less than the minimum normalized number in the type; however a zero result that is spec-
|
|
ified to be an exact zero does not underflow. Also, a result with ordinary accuracy and the magnitude
|
|
of the minimum normalized number may underflow<a href='#FOOTNOTE.285'><sup>[285]</sup></a> . If the result underflows, the function re-
|
|
turns an implementation-defined value whose magnitude is no greater than the smallest normalized
|
|
positive number in the specified type; if the integer expression math_errhandling & MATH_ERRNO is
|
|
nonzero, whether errno acquires the value ERANGE is implementation-defined; if the integer expres-
|
|
sion math_errhandling & MATH_ERREXCEPT is nonzero, whether the "underflow" floating-point
|
|
exception is raised is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.285'>
|
|
<pre><i><b>Footnote 285)</b> The term underflow here is intended to encompass both "gradual underflow" as in IEC 60559 and also "flush-to-zero"
|
|
underflow. IEC 60559 underflow can occur in cases where the magnitude of the rounded result (accurate to the full precision
|
|
of the type) equals the minimum normalized number in the format.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.1p7'></a>
|
|
<pre>7 If a domain, pole, or range error occurs and the integer expression math_errhandling & MATH_ERRNO
|
|
is zero,<a href='#FOOTNOTE.286'><sup>[286]</sup></a> then errno shall either be set to the value corresponding to the error or left unmodified. If
|
|
no such error occurs, errno shall be left unmodified regardless of the setting of math_errhandling.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.286'>
|
|
<pre><i><b>Footnote 286)</b> Math errors are being indicated by the floating-point exception flags rather than by errno.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.2'></a>
|
|
<hr>
|
|
<h3>7.12.2 [The FP_CONTRACT pragma]</h3>
|
|
<a name='7.12.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#pragma STDC FP_CONTRACT on-off-switch
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.2p2'></a>
|
|
<pre>2 The FP_CONTRACT pragma can be used to allow (if the state is "on") or disallow (if the state is
|
|
"off") the implementation to contract expressions (<a href='#6.5'>6.5</a>). Each pragma can occur either outside
|
|
external declarations or preceding all explicit declarations and statements inside a compound
|
|
statement. When outside external declarations, the pragma takes effect from its occurrence until
|
|
another FP_CONTRACT pragma is encountered, or until the end of the translation unit. When inside
|
|
a compound statement, the pragma takes effect from its occurrence until another FP_CONTRACT
|
|
pragma is encountered (including within a nested compound statement), or until the end of the
|
|
compound statement; at the end of a compound statement the state for the pragma is restored to
|
|
its condition just before the compound statement. If this pragma is used in any other context, the
|
|
behavior is undefined. The default state ("on" or "off") for the pragma is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='7.12.3'></a>
|
|
<hr>
|
|
<h3>7.12.3 [Classification macros]</h3>
|
|
<a name='7.12.3p1'></a>
|
|
<pre>1 Floating-point values can be classified as NaN, infinite, normal, subnormal, or zero, or into other
|
|
implementation-defined categories. Numbers whose magnitude is at least bemin −1 (the minimum
|
|
magnitude of normalized floating-point numbers in the type) and at most (1 − b−p )bemax (the
|
|
maximum magnitude of normalized floating-point numbers in the type), where b, p, emin , and emax
|
|
are as in <a href='#5.2.4.2.2'>5.2.4.2.2</a>, are classified as normal. Larger magnitude finite numbers represented with full
|
|
precision in the type may also be classified as normal. Nonzero numbers whose magnitude is less
|
|
than bemin −1 are classified as subnormal.
|
|
</pre>
|
|
<a name='7.12.3p2'></a>
|
|
<pre>2 In the synopses in this subclause, real-floating indicates that the argument shall be an expression of
|
|
real floating type.
|
|
|
|
</pre>
|
|
<a name='7.12.3.1'></a>
|
|
<hr>
|
|
<h3>7.12.3.1 [The fpclassify macro]</h3>
|
|
<a name='7.12.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int fpclassify(real-floating x);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.1p2'></a>
|
|
<pre>2 The fpclassify macro classifies its argument value as NaN, infinite, normal, subnormal, zero, or
|
|
into another implementation-defined category. First, an argument represented in a format wider
|
|
than its semantic type is converted to its semantic type. Then classification is based on the type of
|
|
the argument.<a href='#FOOTNOTE.287'><sup>[287]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.287'>
|
|
<pre><i><b>Footnote 287)</b> Since an expression can be evaluated with more range and precision than its type has, it is important to know the type
|
|
that classification is based on. For example, a normal long double value might become subnormal when converted to
|
|
double, and zero when converted to float.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.3.1p3'></a>
|
|
<pre>3 The fpclassify macro returns the value of the number classification macro appropriate to the value
|
|
of its argument.
|
|
|
|
</pre>
|
|
<a name='7.12.3.2'></a>
|
|
<hr>
|
|
<h3>7.12.3.2 [The iscanonical macro]</h3>
|
|
<a name='7.12.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int iscanonical(real-floating x);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.2p2'></a>
|
|
<pre>2 The iscanonical macro determines whether its argument value is canonical (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). First, an
|
|
argument represented in a format wider than its semantic type is converted to its semantic type.
|
|
Then, determination is based on the type of the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.2p3'></a>
|
|
<pre>3 The iscanonical macro returns a nonzero value if and only if its argument is canonical.
|
|
|
|
</pre>
|
|
<a name='7.12.3.3'></a>
|
|
<hr>
|
|
<h3>7.12.3.3 [The isfinite macro]</h3>
|
|
<a name='7.12.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isfinite(real-floating x);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.3p2'></a>
|
|
<pre>2 The isfinite macro determines whether its argument has a finite value (zero, subnormal, or
|
|
normal, and not infinite or NaN). First, an argument represented in a format wider than its semantic
|
|
type is converted to its semantic type. Then determination is based on the type of the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.3p3'></a>
|
|
<pre>3 The isfinite macro returns a nonzero value if and only if its argument has a finite value.
|
|
|
|
</pre>
|
|
<a name='7.12.3.4'></a>
|
|
<hr>
|
|
<h3>7.12.3.4 [The isinf macro]</h3>
|
|
<a name='7.12.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isinf(real-floating x);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.4p2'></a>
|
|
<pre>2 The isinf macro determines whether its argument value is (positive or negative) infinity. First, an
|
|
argument represented in a format wider than its semantic type is converted to its semantic type.
|
|
Then determination is based on the type of the argument.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.4p3'></a>
|
|
<pre>3 The isinf macro returns a nonzero value if and only if its argument has an infinite value.
|
|
|
|
</pre>
|
|
<a name='7.12.3.5'></a>
|
|
<hr>
|
|
<h3>7.12.3.5 [The isnan macro]</h3>
|
|
<a name='7.12.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isnan(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.5p2'></a>
|
|
<pre>2 The isnan macro determines whether its argument value is a NaN. First, an argument represented
|
|
in a format wider than its semantic type is converted to its semantic type. Then determination is
|
|
based on the type of the argument.<a href='#FOOTNOTE.288'><sup>[288]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> For the isnan macro, the type for determination does not matter unless the implementation supports NaNs in the
|
|
evaluation type but not in the semantic type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.3.5p3'></a>
|
|
<pre>3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
|
|
|
|
</pre>
|
|
<a name='7.12.3.6'></a>
|
|
<hr>
|
|
<h3>7.12.3.6 [The isnormal macro]</h3>
|
|
<a name='7.12.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isnormal(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.6p2'></a>
|
|
<pre>2 The isnormal macro determines whether its argument value is normal (neither zero, subnormal,
|
|
infinite, nor NaN). First, an argument represented in a format wider than its semantic type is
|
|
converted to its semantic type. Then determination is based on the type of the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.6p3'></a>
|
|
<pre>3 The isnormal macro returns a nonzero value if and only if its argument has a normal value.
|
|
|
|
</pre>
|
|
<a name='7.12.3.7'></a>
|
|
<hr>
|
|
<h3>7.12.3.7 [The signbit macro]</h3>
|
|
<a name='7.12.3.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int signbit(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.7p2'></a>
|
|
<pre>2 The signbit macro determines whether the sign of its argument value is negative<a href='#FOOTNOTE.289'><sup>[289]</sup></a> . If the
|
|
argument value is an unsigned zero, its sign is regarded as positive. Otherwise, if the argument
|
|
value is unsigned, the result value (zero or nonzero) is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.289'>
|
|
<pre><i><b>Footnote 289)</b> The signbit macro determines the sign of all values, including infinities, zeros, and NaNs.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.3.7p3'></a>
|
|
<pre>3 The signbit macro returns a nonzero value if and only if the sign of its argument value is determined
|
|
to be negative.
|
|
|
|
</pre>
|
|
<a name='7.12.3.8'></a>
|
|
<hr>
|
|
<h3>7.12.3.8 [The issignaling macro]</h3>
|
|
<a name='7.12.3.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int issignaling(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.8p2'></a>
|
|
<pre>2 The issignaling macro determines whether its argument value is a signaling NaN.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.8p3'></a>
|
|
<pre>3 The issignaling macro returns a nonzero value if and only if its argument is a signaling NaN.<a href='#FOOTNOTE.290'><sup>[290]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.290'>
|
|
<pre><i><b>Footnote 290)</b> <a href='#F.3'>F.3</a> specifies that issignaling (and all the other classification macros), raise no floating-point exception if the argument
|
|
is a variable, or any other expression whose value is represented in the format of its semantic type, even if the value is a
|
|
signaling NaN.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.3.9'></a>
|
|
<hr>
|
|
<h3>7.12.3.9 [The issubnormal macro]</h3>
|
|
<a name='7.12.3.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int issubnormal(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.9p2'></a>
|
|
<pre>2 The issubnormal macro determines whether its argument value is subnormal. First, an argument
|
|
represented in a format wider than its semantic type is converted to its semantic type. Then
|
|
determination is based on the type of the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.9p3'></a>
|
|
<pre>3 The issubnormal macro returns a nonzero value if and only if its argument is subnormal.
|
|
|
|
</pre>
|
|
<a name='7.12.3.10'></a>
|
|
<hr>
|
|
<h3>7.12.3.10 [The iszero macro]</h3>
|
|
<a name='7.12.3.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int iszero(real-floating x);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.10p2'></a>
|
|
<pre>2 The iszero macro determines whether its argument value is (positive, negative, or unsigned) zero.
|
|
First, an argument represented in a format wider than its semantic type is converted to its semantic
|
|
type. Then, determination is based on the type of the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.3.10p3'></a>
|
|
<pre>3 The iszero macro returns a nonzero value if and only if its argument is zero.
|
|
|
|
</pre>
|
|
<a name='7.12.4'></a>
|
|
<hr>
|
|
<h3>7.12.4 [Trigonometric functions]</h3>
|
|
<a name='7.12.4.1'></a>
|
|
<hr>
|
|
<h3>7.12.4.1 [The acos functions]</h3>
|
|
<a name='7.12.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double acos(double x);
|
|
float acosf(float x);
|
|
long double acosl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 acosd32(_Decimal32 x);
|
|
_Decimal64 acosd64(_Decimal64 x);
|
|
_Decimal128 acosd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.1p2'></a>
|
|
<pre>2 The acos functions compute the principal value of the arc cosine of x. A domain error occurs for
|
|
arguments not in the interval [−1, +1].
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.1p3'></a>
|
|
<pre>3 The acos functions return arccos x in the interval [0, π] radians.
|
|
</pre>
|
|
<a name='7.12.4.2'></a>
|
|
<hr>
|
|
<h3>7.12.4.2 [The asin functions]</h3>
|
|
<a name='7.12.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double asin(double x);
|
|
float asinf(float x);
|
|
long double asinl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 asind32(_Decimal32 x);
|
|
_Decimal64 asind64(_Decimal64 x);
|
|
_Decimal128 asind128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.2p2'></a>
|
|
<pre>2 The asin functions compute the principal value of the arc sine of x. A domain error occurs for
|
|
arguments not in the interval [−1, +1]. A range error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.2p3'></a>
|
|
<pre>3 The asin functions return arcsin x in the interval [− π2 , + π2 ] radians.
|
|
|
|
</pre>
|
|
<a name='7.12.4.3'></a>
|
|
<hr>
|
|
<h3>7.12.4.3 [The atan functions]</h3>
|
|
<a name='7.12.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double atan(double x);
|
|
float atanf(float x);
|
|
long double atanl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 atand32(_Decimal32 x);
|
|
_Decimal64 atand64(_Decimal64 x);
|
|
_Decimal128 atand128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.3p2'></a>
|
|
<pre>2 The atan functions compute the principal value of the arc tangent of x. A range error occurs if
|
|
nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.3p3'></a>
|
|
<pre>3 The atan functions return arctan x in the interval [− π2 , + π2 ] radians.
|
|
|
|
</pre>
|
|
<a name='7.12.4.4'></a>
|
|
<hr>
|
|
<h3>7.12.4.4 [The atan2 functions]</h3>
|
|
<a name='7.12.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double atan2(double y, double x);
|
|
float atan2f(float y, float x);
|
|
long double atan2l(long double y, long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 atan2d32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 atan2d64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 atan2d128(_Decimal128 y, _Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.4p2'></a>
|
|
<pre>2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both arguments
|
|
to determine the quadrant of the return value. A domain error may occur if both arguments are zero.
|
|
A range error occurs if x is positive and nonzero xy is too close to zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.4p3'></a>
|
|
<pre>3 The atan2 functions return arctan(y/x) in the interval [−π, +π] radians.
|
|
|
|
</pre>
|
|
<a name='7.12.4.5'></a>
|
|
<hr>
|
|
<h3>7.12.4.5 [The cos functions]</h3>
|
|
<a name='7.12.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double cos(double x);
|
|
float cosf(float x);
|
|
long double cosl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 cosd32(_Decimal32 x);
|
|
_Decimal64 cosd64(_Decimal64 x);
|
|
_Decimal128 cosd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.5p2'></a>
|
|
<pre>2 The cos functions compute the cosine of x (measured in radians).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.5p3'></a>
|
|
<pre>3 The cos functions return cos x.
|
|
|
|
</pre>
|
|
<a name='7.12.4.6'></a>
|
|
<hr>
|
|
<h3>7.12.4.6 [The sin functions]</h3>
|
|
<a name='7.12.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double sin(double x);
|
|
float sinf(float x);
|
|
long double sinl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 sind32(_Decimal32 x);
|
|
_Decimal64 sind64(_Decimal64 x);
|
|
_Decimal128 sind128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.6p2'></a>
|
|
<pre>2 The sin functions compute the sine of x (measured in radians). A range error occurs if nonzero x is
|
|
too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.6p3'></a>
|
|
<pre>3 The sin functions return sin x.
|
|
|
|
</pre>
|
|
<a name='7.12.4.7'></a>
|
|
<hr>
|
|
<h3>7.12.4.7 [The tan functions]</h3>
|
|
<a name='7.12.4.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double tan(double x);
|
|
float tanf(float x);
|
|
long double tanl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 tand32(_Decimal32 x);
|
|
_Decimal64 tand64(_Decimal64 x);
|
|
_Decimal128 tand128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.7p2'></a>
|
|
<pre>2 The tan functions return the tangent of x (measured in radians). A range error occurs if nonzero x is
|
|
too close to zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.7p3'></a>
|
|
<pre>3 The tan functions return tan x.
|
|
|
|
</pre>
|
|
<a name='7.12.4.8'></a>
|
|
<hr>
|
|
<h3>7.12.4.8 [The acospi functions]</h3>
|
|
<a name='7.12.4.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double acospi(double x);
|
|
float acospif(float x);
|
|
long double acospil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 acospid32(_Decimal32 x);
|
|
_Decimal64 acospid64(_Decimal64 x);
|
|
_Decimal128 acospid128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.8p2'></a>
|
|
<pre>2 The acospi functions compute the principal value of the arc cosine of x, divided by π, thus measur-
|
|
ing the angle in half-revolutions. A domain error occurs for arguments not in the interval [−1, +1].
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.8p3'></a>
|
|
<pre>3 The acospi functions return arccos(x)/π in the interval [0, 1].
|
|
|
|
</pre>
|
|
<a name='7.12.4.9'></a>
|
|
<hr>
|
|
<h3>7.12.4.9 [The asinpi functions]</h3>
|
|
<a name='7.12.4.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double asinpi(double x);
|
|
float asinpif(float x);
|
|
long double asinpil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 asinpid32(_Decimal32 x);
|
|
_Decimal64 asinpid64(_Decimal64 x);
|
|
_Decimal128 asinpid128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.9p2'></a>
|
|
<pre>2 The asinpi functions compute the principal value of the arc sine of x, divided by π, thus measuring
|
|
the angle in half-revolutions. A domain error occurs for arguments not in the interval [−1, +1]. A
|
|
range error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.9p3'></a>
|
|
<pre>3 The asinpi functions return arcsin(x)/π in the interval [− 12 , + 12 ].
|
|
|
|
</pre>
|
|
<a name='7.12.4.10'></a>
|
|
<hr>
|
|
<h3>7.12.4.10 [The atanpi functions]</h3>
|
|
<a name='7.12.4.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double atanpi(double x);
|
|
float atanpif(float x);
|
|
long double atanpil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 atanpid32(_Decimal32 x);
|
|
_Decimal64 atanpid64(_Decimal64 x);
|
|
_Decimal128 atanpid128(_Decimal128 x);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.10p2'></a>
|
|
<pre>2 The atanpi functions compute the principal value of the arc tangent of x, divided by π, thus
|
|
measuring the angle in half-revolutions. A range error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.10p3'></a>
|
|
<pre>3 The atanpi functions return arctan(x)/π. in the interval [− 12 , + 12 ].
|
|
|
|
</pre>
|
|
<a name='7.12.4.11'></a>
|
|
<hr>
|
|
<h3>7.12.4.11 [The atan2pi functions]</h3>
|
|
<a name='7.12.4.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double atan2pi(double y, double x);
|
|
float atan2pif(float y, float x);
|
|
long double atan2pil(long double y, long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 atan2pid32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 atan2pid64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 atan2pid128(_Decimal128 y, _Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.11p2'></a>
|
|
<pre>2 The atan2pi functions compute the angle, measured in half-revolutions, subtended at the origin by
|
|
the point (x, y) and the positive x-axis. Thus, the atan2pi functions compute arctan( xy )/π, in the
|
|
range [−1, +1]. A domain error may occur if both arguments are zero. A range error occurs if x is
|
|
positive and nonzero xy is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.11p3'></a>
|
|
<pre>3 The atan2pi functions return the computed angle, in the interval [−1, +1].
|
|
|
|
</pre>
|
|
<a name='7.12.4.12'></a>
|
|
<hr>
|
|
<h3>7.12.4.12 [The cospi functions]</h3>
|
|
<a name='7.12.4.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double cospi(double x);
|
|
float cospif(float x);
|
|
long double cospil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 cospid32(_Decimal32 x);
|
|
_Decimal64 cospid64(_Decimal64 x);
|
|
_Decimal128 cospid128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.12p2'></a>
|
|
<pre>2 The cospi functions compute the cosine of π × x, thus regarding x as a measurement in half-
|
|
revolutions.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.12p3'></a>
|
|
<pre>3 The cospi functions return cos(π × x).
|
|
|
|
</pre>
|
|
<a name='7.12.4.13'></a>
|
|
<hr>
|
|
<h3>7.12.4.13 [The sinpi functions]</h3>
|
|
<a name='7.12.4.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double sinpi(double x);
|
|
float sinpif(float x);
|
|
long double sinpil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 sinpid32(_Decimal32 x);
|
|
_Decimal64 sinpid64(_Decimal64 x);
|
|
_Decimal128 sinpid128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.13p2'></a>
|
|
<pre>2 The sinpi functions compute the sine of π× x, thus regarding x as a measurement in half-revolutions.
|
|
A range error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.13p3'></a>
|
|
<pre>3 The sinpi functions return sin(π × x).
|
|
|
|
</pre>
|
|
<a name='7.12.4.14'></a>
|
|
<hr>
|
|
<h3>7.12.4.14 [The tanpi functions]</h3>
|
|
<a name='7.12.4.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double tanpi(double x);
|
|
float tanpif(float x);
|
|
long double tanpil(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 tanpid32(_Decimal32 x);
|
|
_Decimal64 tanpid64(_Decimal64 x);
|
|
_Decimal128 tanpid128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.14p2'></a>
|
|
<pre>2 The tanpi functions compute the tagent of π × x, thus regarding x as a measurement in half-
|
|
revolutions. A range error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.14p3'></a>
|
|
<pre>3 The tanpi functions return tan(π × x).
|
|
|
|
</pre>
|
|
<a name='7.12.5'></a>
|
|
<hr>
|
|
<h3>7.12.5 [Hyperbolic functions]</h3>
|
|
<a name='7.12.5.1'></a>
|
|
<hr>
|
|
<h3>7.12.5.1 [The acosh functions]</h3>
|
|
<a name='7.12.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double acosh(double x);
|
|
float acoshf(float x);
|
|
long double acoshl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 acoshd32(_Decimal32 x);
|
|
_Decimal64 acoshd64(_Decimal64 x);
|
|
_Decimal128 acoshd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.1p2'></a>
|
|
<pre>2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain error occurs
|
|
for arguments less than 1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.1p3'></a>
|
|
<pre>3 The acosh functions return arcosh x in the interval [0, +∞].
|
|
|
|
</pre>
|
|
<a name='7.12.5.2'></a>
|
|
<hr>
|
|
<h3>7.12.5.2 [The asinh functions]</h3>
|
|
<a name='7.12.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double asinh(double x);
|
|
float asinhf(float x);
|
|
long double asinhl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 asinhd32(_Decimal32 x);
|
|
_Decimal64 asinhd64(_Decimal64 x);
|
|
_Decimal128 asinhd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.2p2'></a>
|
|
<pre>2 The asinh functions compute the arc hyperbolic sine of x. A range error occurs if nonzero x is too
|
|
close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.2p3'></a>
|
|
<pre>3 The asinh functions return arsinh x.
|
|
|
|
</pre>
|
|
<a name='7.12.5.3'></a>
|
|
<hr>
|
|
<h3>7.12.5.3 [The atanh functions]</h3>
|
|
<a name='7.12.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double atanh(double x);
|
|
float atanhf(float x);
|
|
long double atanhl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 atanhd32(_Decimal32 x);
|
|
_Decimal64 atanhd64(_Decimal64 x);
|
|
_Decimal128 atanhd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.3p2'></a>
|
|
<pre>2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs for arguments
|
|
not in the interval [−1, +1]. A pole error may occur if the argument equals-1 or +1 . A range error
|
|
occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.3p3'></a>
|
|
<pre>3 The atanh functions return artanh x.
|
|
|
|
</pre>
|
|
<a name='7.12.5.4'></a>
|
|
<hr>
|
|
<h3>7.12.5.4 [The cosh functions]</h3>
|
|
<a name='7.12.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double cosh(double x);
|
|
float coshf(float x);
|
|
long double coshl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 coshd32(_Decimal32 x);
|
|
_Decimal64 coshd64(_Decimal64 x);
|
|
_Decimal128 coshd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.4p2'></a>
|
|
<pre>2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the magnitude of
|
|
finite x is too large.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.4p3'></a>
|
|
<pre>3 The cosh functions return cosh x.
|
|
|
|
</pre>
|
|
<a name='7.12.5.5'></a>
|
|
<hr>
|
|
<h3>7.12.5.5 [The sinh functions]</h3>
|
|
<a name='7.12.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double sinh(double x);
|
|
float sinhf(float x);
|
|
long double sinhl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 sinhd32(_Decimal32 x);
|
|
_Decimal64 sinhd64(_Decimal64 x);
|
|
_Decimal128 sinhd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.5p2'></a>
|
|
<pre>2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the magnitude of finite
|
|
x is too large or if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.5p3'></a>
|
|
<pre>3 The sinh functions return sinh x.
|
|
|
|
</pre>
|
|
<a name='7.12.5.6'></a>
|
|
<hr>
|
|
<h3>7.12.5.6 [The tanh functions]</h3>
|
|
<a name='7.12.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double tanh(double x);
|
|
float tanhf(float x);
|
|
long double tanhl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 tanhd32(_Decimal32 x);
|
|
_Decimal64 tanhd64(_Decimal64 x);
|
|
_Decimal128 tanhd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.6p2'></a>
|
|
<pre>2 The tanh functions compute the hyperbolic tangent of x. A range error occurs if nonzero x is too
|
|
close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.5.6p3'></a>
|
|
<pre>3 The tanh functions return tanh x.
|
|
|
|
</pre>
|
|
<a name='7.12.6'></a>
|
|
<hr>
|
|
<h3>7.12.6 [Exponential and logarithmic functions]</h3>
|
|
<a name='7.12.6.1'></a>
|
|
<hr>
|
|
<h3>7.12.6.1 [The exp functions]</h3>
|
|
<a name='7.12.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp(double x);
|
|
float expf(float x);
|
|
long double expl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 expd32(_Decimal32 x);
|
|
_Decimal64 expd64(_Decimal64 x);
|
|
_Decimal128 expd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.1p2'></a>
|
|
<pre>2 The exp functions compute the base-e exponential of x. A range error occurs if the magnitude of
|
|
finite x is too large.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.1p3'></a>
|
|
<pre>3 The exp functions return ex .
|
|
|
|
</pre>
|
|
<a name='7.12.6.2'></a>
|
|
<hr>
|
|
<h3>7.12.6.2 [The exp10 functions]</h3>
|
|
<a name='7.12.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp10(double x);
|
|
float exp10f(float x);
|
|
long double exp10l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 exp10d32(_Decimal32 x);
|
|
_Decimal64 exp10d64(_Decimal64 x);
|
|
_Decimal128 exp10d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.2p2'></a>
|
|
<pre>2 The exp10 functions compute the base-10 exponential of x. A range error occurs if the magnitude of
|
|
finite x is too large.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.2p3'></a>
|
|
<pre>3 The exp10 functions return 10x .
|
|
|
|
</pre>
|
|
<a name='7.12.6.3'></a>
|
|
<hr>
|
|
<h3>7.12.6.3 [The exp10m1 functions]</h3>
|
|
<a name='7.12.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp10m1(double x);
|
|
float exp10m1f(float x);
|
|
long double exp10m1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 exp10m1d32(_Decimal32 x);
|
|
_Decimal64 exp10m1d64(_Decimal64 x);
|
|
_Decimal128 exp10m1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.3p2'></a>
|
|
<pre>2 The exp10m1 functions compute the base-10 exponential of the argument, minus 1. A range error
|
|
occurs if positive finite x is too large or if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.3p3'></a>
|
|
<pre>3 The exp10m1 functions return 10x − 1.
|
|
|
|
</pre>
|
|
<a name='7.12.6.4'></a>
|
|
<hr>
|
|
<h3>7.12.6.4 [The exp2 functions]</h3>
|
|
<a name='7.12.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp2(double x);
|
|
float exp2f(float x);
|
|
long double exp2l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 exp2d32(_Decimal32 x);
|
|
_Decimal64 exp2d64(_Decimal64 x);
|
|
_Decimal128 exp2d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.4p2'></a>
|
|
<pre>2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the magnitude of
|
|
finite x is too large.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.4p3'></a>
|
|
<pre>3 The exp2 functions return 2x .
|
|
</pre>
|
|
<a name='7.12.6.5'></a>
|
|
<hr>
|
|
<h3>7.12.6.5 [The exp2m1 functions]</h3>
|
|
<a name='7.12.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp2m1(double x);
|
|
float exp2m1f(float x);
|
|
long double exp2m1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 exp2m1d32(_Decimal32 x);
|
|
_Decimal64 exp2m1d64(_Decimal64 x);
|
|
_Decimal128 exp2m1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.5p2'></a>
|
|
<pre>2 The exp2m1 functions compute the base-2 exponential of the argument, minus 1. A range error
|
|
occurs if positive finite x is too large or if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.5p3'></a>
|
|
<pre>3 The exp2m1 functions return 2x − 1.
|
|
|
|
</pre>
|
|
<a name='7.12.6.6'></a>
|
|
<hr>
|
|
<h3>7.12.6.6 [The expm1 functions]</h3>
|
|
<a name='7.12.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double expm1(double x);
|
|
float expm1f(float x);
|
|
long double expm1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 expm1d32(_Decimal32 x);
|
|
_Decimal64 expm1d64(_Decimal64 x);
|
|
_Decimal128 expm1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.6p2'></a>
|
|
<pre>2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range error occurs
|
|
if positive finite x is too large or if nonzero x is too close to zero. <a href='#FOOTNOTE.291'><sup>[291]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.291'>
|
|
<pre><i><b>Footnote 291)</b> For small magnitude x , expm1(x) is expected to be more accurate than exp(x)-1.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.6p3'></a>
|
|
<pre>3 The expm1 functions return ex − 1.
|
|
|
|
</pre>
|
|
<a name='7.12.6.7'></a>
|
|
<hr>
|
|
<h3>7.12.6.7 [The frexp functions]</h3>
|
|
<a name='7.12.6.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double frexp(double value, int *p);
|
|
float frexpf(float value, int *p);
|
|
long double frexpl(long double value, int *p);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 frexpd32(_Decimal32 value, int *p);
|
|
_Decimal64 frexpd64(_Decimal64 value, int *p);
|
|
_Decimal128 frexpd128(_Decimal128 value, int *p);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.7p2'></a>
|
|
<pre>2 The frexp functions break a floating-point number into a normalized fraction and an integer
|
|
exponent. They store the integer in the int object pointed to by p. If the type of the function is a
|
|
standard floating type, the exponent is an integral power of 2. If the type of the function is a decimal
|
|
floating type, the exponent is an integral power of 10.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.7p3'></a>
|
|
<pre>3 If value is not a floating-point number or if the integral power is outside the range of int, the results
|
|
are unspecified. Otherwise, the frexp functions return the value x, such that x has a magnitude
|
|
in the interval [ 12 , <a href='#FOOTNOTE.1'><sup>[1]</sup></a> or zero, and value equals x × 2*p , when the type of the function is a standard
|
|
floating type; or x has a magnitude in the interval [1/10, <a href='#FOOTNOTE.1'><sup>[1]</sup></a> or zero, and value equals x × 10*p , when
|
|
the type of the function is a decimal floating type. If value is zero, both parts of the result are zero.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.1'>
|
|
<pre><i><b>Footnote 1)</b> This document is designed to promote the portability of C programs among a variety of data-processing systems. It is
|
|
intended for use by implementors and programmers. Annex J gives an overview of portability issues that a C program might
|
|
encounter.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.1'>
|
|
<pre><i><b>Footnote 1)</b> This document is designed to promote the portability of C programs among a variety of data-processing systems. It is
|
|
intended for use by implementors and programmers. Annex J gives an overview of portability issues that a C program might
|
|
encounter.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.8'></a>
|
|
<hr>
|
|
<h3>7.12.6.8 [The ilogb functions]</h3>
|
|
<a name='7.12.6.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int ilogb(double x);
|
|
int ilogbf(float x);
|
|
int ilogbl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int ilogbd32(_Decimal32 x);
|
|
int ilogbd64(_Decimal64 x);
|
|
int ilogbd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.8p2'></a>
|
|
<pre>2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they compute the
|
|
value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is a NaN they compute the
|
|
value FP_ILOGBNAN; otherwise, they are equivalent to calling the corresponding logb function and
|
|
converting the returned value to type int. A domain error or range error may occur if x is zero,
|
|
infinite, or NaN. If the correct value is outside the range of the return type, the numeric result is
|
|
unspecified and a domain error or range error may occur.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.8p3'></a>
|
|
<pre>3 The ilogb functions return the exponent of x as a signed int value.
|
|
Forward references: the logb functions (<a href='#7.12.6.17'>7.12.6.17</a>).
|
|
|
|
</pre>
|
|
<a name='7.12.6.9'></a>
|
|
<hr>
|
|
<h3>7.12.6.9 [The ldexp functions]</h3>
|
|
<a name='7.12.6.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double ldexp(double x, int p);
|
|
float ldexpf(float x, int p);
|
|
long double ldexpl(long double x, int p);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 ldexpd32(_Decimal32 x, int p);
|
|
_Decimal64 ldexpd64(_Decimal64 x, int p);
|
|
_Decimal128 ldexpd128(_Decimal128 x, int p);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.9p2'></a>
|
|
<pre>2 The ldexp functions multiply a floating-point number by an integral power of 2 when the type of
|
|
the function is a standard floating type, or by an integral power of 10 when the type of the function
|
|
is a decimal floating type. A range error occurs for some finite x, depending on p.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.9p3'></a>
|
|
<pre>3 The ldexp functions return x × 2p when the type of the function is a standard floating type, or return
|
|
x × 10p when the type of the function is a decimal floating type.
|
|
|
|
</pre>
|
|
<a name='7.12.6.10'></a>
|
|
<hr>
|
|
<h3>7.12.6.10 [The llogb functions]</h3>
|
|
<a name='7.12.6.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
long int llogb(double x);
|
|
long int llogbf(float x);
|
|
long int llogbl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
long int llogbd32(_Decimal32 x);
|
|
long int llogbd64(_Decimal64 x);
|
|
long int llogbd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.10p2'></a>
|
|
<pre>2 The llogb functions extract the exponent of x as a signed long int value. If x is zero they compute
|
|
the value FP_LLOGB0; if x is infinite they compute the value LONG_MAX; if x is a NaN they compute
|
|
the value FP_LLOGBNAN; otherwise, they are equivalent to calling the corresponding logb function
|
|
and converting the returned value to type long int. A domain error or range error may occur if x is
|
|
zero, infinite, or NaN. If the correct value is outside the range of the return type, the numeric result
|
|
is unspecified.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.10p3'></a>
|
|
<pre>3 The llogb functions return the exponent of x as a signed long int value.
|
|
Forward references: the logb functions (<a href='#7.12.6.17'>7.12.6.17</a>).
|
|
|
|
</pre>
|
|
<a name='7.12.6.11'></a>
|
|
<hr>
|
|
<h3>7.12.6.11 [The log functions]</h3>
|
|
<a name='7.12.6.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log(double x);
|
|
float logf(float x);
|
|
long double logl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 logd32(_Decimal32 x);
|
|
_Decimal64 logd64(_Decimal64 x);
|
|
_Decimal128 logd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.11p2'></a>
|
|
<pre>2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if the
|
|
argument is less than zero. A pole error may occur if the argument is zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.11p3'></a>
|
|
<pre>3 The log functions return loge x.
|
|
|
|
</pre>
|
|
<a name='7.12.6.12'></a>
|
|
<hr>
|
|
<h3>7.12.6.12 [The log10 functions]</h3>
|
|
<a name='7.12.6.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log10(double x);
|
|
float log10f(float x);
|
|
long double log10l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 log10d32(_Decimal32 x);
|
|
_Decimal64 log10d64(_Decimal64 x);
|
|
_Decimal128 log10d128(_Decimal128 x);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.12p2'></a>
|
|
<pre>2 The log10 functions compute the base-10 (common) logarithm of x. A domain error occurs if the
|
|
argument is less than zero. A pole error may occur if the argument is zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.12p3'></a>
|
|
<pre>3 The log10 functions return log10 x.
|
|
|
|
</pre>
|
|
<a name='7.12.6.13'></a>
|
|
<hr>
|
|
<h3>7.12.6.13 [The log10p1 functions]</h3>
|
|
<a name='7.12.6.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log10p1(double x);
|
|
float log10p1f(float x);
|
|
long double log10p1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 log10p1d32(_Decimal32 x);
|
|
_Decimal64 log10p1d64(_Decimal64 x);
|
|
_Decimal128 log10p1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.13p2'></a>
|
|
<pre>2 The log10p1 functions compute the base-10 logarithm of 1 plus the argument. A domain error
|
|
occurs if the argument is less than −1. A pole error may occur if the argument equals −1. A range
|
|
error occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.13p3'></a>
|
|
<pre>3 The log10p1 functions return log10 (1 + x).
|
|
|
|
</pre>
|
|
<a name='7.12.6.14'></a>
|
|
<hr>
|
|
<h3>7.12.6.14 [The log1p and logp1 functions]</h3>
|
|
<a name='7.12.6.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log1p(double x);
|
|
float log1pf(float x);
|
|
long double log1pl(long double x);
|
|
double logp1(double x);
|
|
float logp1f(float x);
|
|
long double logp1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 log1pd32(_Decimal32 x);
|
|
_Decimal64 log1pd64(_Decimal64 x);
|
|
_Decimal128 log1pd128(_Decimal128 x);
|
|
_Decimal32 logp1d32(_Decimal32 x);
|
|
_Decimal64 logp1d64(_Decimal64 x);
|
|
_Decimal128 logp1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.14p2'></a>
|
|
<pre>2 The log1p functions are equivalent to the logp1 functions.<a href='#FOOTNOTE.292'><sup>[292]</sup></a> These functions compute the base-e
|
|
(natural) logarithm of 1 plus the argument.<a href='#FOOTNOTE.293'><sup>[293]</sup></a> A domain error occurs if the argument is less than
|
|
−1. A pole error may occur if the argument equals −1. A range error occurs if nonzero x is too close
|
|
to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.292'>
|
|
<pre><i><b>Footnote 292)</b> The logp1 functions are preferred for name consistency with the log10p1 and log2p1 functions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.293'>
|
|
<pre><i><b>Footnote 293)</b> For small magnitude x , logp1(x) is expected to be more accurate than log(1 + x).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.14p3'></a>
|
|
<pre>3 The log1p and logp1 functions return loge (1 + x).
|
|
</pre>
|
|
<a name='7.12.6.15'></a>
|
|
<hr>
|
|
<h3>7.12.6.15 [The log2 functions]</h3>
|
|
<a name='7.12.6.15p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log2(double x);
|
|
float log2f(float x);
|
|
long double log2l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 log2d32(_Decimal32 x);
|
|
_Decimal64 log2d64(_Decimal64 x);
|
|
_Decimal128 log2d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.15p2'></a>
|
|
<pre>2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the argument is less
|
|
than zero. A pole error may occur if the argument is zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.15p3'></a>
|
|
<pre>3 The log2 functions return log2 x.
|
|
|
|
</pre>
|
|
<a name='7.12.6.16'></a>
|
|
<hr>
|
|
<h3>7.12.6.16 [The log2p1 functions]</h3>
|
|
<a name='7.12.6.16p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log2p1(double x);
|
|
float log2p1f(float x);
|
|
long double log2p1l(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 log2p1d32(_Decimal32 x);
|
|
_Decimal64 log2p1d64(_Decimal64 x);
|
|
_Decimal128 log2p1d128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.16p2'></a>
|
|
<pre>2 The log2p1 functions compute the base-2 logarithm of 1 plus the argument. A domain error occurs
|
|
if the argument is less than −1. A pole error may occur if the argument equals −1. A range error
|
|
occurs if nonzero x is too close to zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.16p3'></a>
|
|
<pre>3 The log2p1 functions return log2 (1+x).
|
|
|
|
</pre>
|
|
<a name='7.12.6.17'></a>
|
|
<hr>
|
|
<h3>7.12.6.17 [The logb functions]</h3>
|
|
<a name='7.12.6.17p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double logb(double x);
|
|
float logbf(float x);
|
|
long double logbl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 logbd32(_Decimal32 x);
|
|
_Decimal64 logbd64(_Decimal64 x);
|
|
_Decimal128 logbd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.17p2'></a>
|
|
<pre>2 The logb functions extract the exponent of x, as a signed integer value in floating-point format. If x
|
|
is subnormal it is treated as though it were normalized; thus, for positive finite x,
|
|
|
|
1 ≤ x × b−logb(x) < b
|
|
where b = FLT_RADIX if the type of the function is a standard floating type, or b = 10 if the type of
|
|
the function is a decimal floating type. A domain error or pole error may occur if the argument is
|
|
zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.17p3'></a>
|
|
<pre>3 The logb functions return the signed exponent of x.
|
|
|
|
</pre>
|
|
<a name='7.12.6.18'></a>
|
|
<hr>
|
|
<h3>7.12.6.18 [The modf functions]</h3>
|
|
<a name='7.12.6.18p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double modf(double value, double *iptr);
|
|
float modff(float value, float *iptr);
|
|
long double modfl(long double value, long double *iptr);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 modfd32(_Decimal32 x, _Decimal32 *iptr);
|
|
_Decimal64 modfd64(_Decimal64 x, _Decimal64 *iptr);
|
|
_Decimal128 modfd128(_Decimal128 x, _Decimal128 *iptr);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.18p2'></a>
|
|
<pre>2 The modf functions break the argument value into integral and fractional parts, each of which has
|
|
the same type and sign as the argument. They store the integral part (in floating-point format) in the
|
|
object pointed to by iptr.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.18p3'></a>
|
|
<pre>3 The modf functions return the signed fractional part of value.
|
|
|
|
</pre>
|
|
<a name='7.12.6.19'></a>
|
|
<hr>
|
|
<h3>7.12.6.19 [The scalbn and scalbln functions]</h3>
|
|
<a name='7.12.6.19p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double scalbn(double x, int n);
|
|
float scalbnf(float x, int n);
|
|
long double scalbnl(long double x, int n);
|
|
double scalbln(double x, long int n);
|
|
float scalblnf(float x, long int n);
|
|
long double scalblnl(long double x, long int n);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 scalbnd32(_Decimal32 x, int n);
|
|
_Decimal64 scalbnd64(_Decimal64 x, int n);
|
|
_Decimal128 scalbnd128(_Decimal128 x, int n);
|
|
_Decimal32 scalblnd32(_Decimal32 x, long int n);
|
|
_Decimal64 scalblnd64(_Decimal64 x, long int n);
|
|
_Decimal128 scalblnd128(_Decimal128 x, long int n);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.19p2'></a>
|
|
<pre>2 The scalbn and scalbln functions compute x × bn , where b = FLT_RADIX if the type of the function
|
|
is a standard floating type, or b = 10 if the type of the function is a decimal floating type. A range
|
|
error occurs for some finite x, depending on n.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.19p3'></a>
|
|
<pre>3 The scalbn and scalbln functions return x × bn .
|
|
|
|
</pre>
|
|
<a name='7.12.7'></a>
|
|
<hr>
|
|
<h3>7.12.7 [Power and absolute-value functions]</h3>
|
|
<a name='7.12.7.1'></a>
|
|
<hr>
|
|
<h3>7.12.7.1 [The cbrt functions]</h3>
|
|
<a name='7.12.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
|
|
#include <math.h>
|
|
double cbrt(double x);
|
|
float cbrtf(float x);
|
|
long double cbrtl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 cbrtd32(_Decimal32 x);
|
|
_Decimal64 cbrtd64(_Decimal64 x);
|
|
_Decimal128 cbrtd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.1p2'></a>
|
|
<pre>2 The cbrt functions compute the real cube root of x.
|
|
|
|
Returns
|
|
1
|
|
</pre>
|
|
<a name='7.12.7.1p3'></a>
|
|
<pre>3 The cbrt functions return x 3 .
|
|
|
|
</pre>
|
|
<a name='7.12.7.2'></a>
|
|
<hr>
|
|
<h3>7.12.7.2 [The compoundn functions]</h3>
|
|
<a name='7.12.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdint.h>
|
|
#include <math.h>
|
|
double compoundn(double x, long long int n);
|
|
float compoundnf(float x, long long int n);
|
|
long double compoundnl(long double x, long long int n);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 compoundnd32(_Decimal32 x, long long int n);
|
|
_Decimal64 compoundnd64(_Decimal64 x, long long int n);
|
|
_Decimal128 compoundnd128(_Decimal128 x, long long int n);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.2p2'></a>
|
|
<pre>2 The compoundn functions compute 1 plus x, raised to the power n. A domain error occurs if x < −1.
|
|
Depending on n, a range error occurs if either positive finite x is too large or if x is too near but not
|
|
equal to-1 . A pole error may occur if x equals −1 and n < 0.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.2p3'></a>
|
|
<pre>3 The compoundn functions return (1 + x)n .
|
|
|
|
</pre>
|
|
<a name='7.12.7.3'></a>
|
|
<hr>
|
|
<h3>7.12.7.3 [The fabs functions]</h3>
|
|
<a name='7.12.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fabs(double x);
|
|
float fabsf(float x);
|
|
long double fabsl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fabsd32(_Decimal32 x);
|
|
_Decimal64 fabsd64(_Decimal64 x);
|
|
_Decimal128 fabsd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.3p2'></a>
|
|
<pre>2 The fabs functions compute the absolute value of x.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.3p3'></a>
|
|
<pre>3 The fabs functions return |x|.
|
|
|
|
</pre>
|
|
<a name='7.12.7.4'></a>
|
|
<hr>
|
|
<h3>7.12.7.4 [The hypot functions]</h3>
|
|
<a name='7.12.7.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double hypot(double x, double y);
|
|
float hypotf(float x, float y);
|
|
long double hypotl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 hypotd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 hypotd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 hypotd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.4p2'></a>
|
|
<pre>2 The hypot functions compute the square root of the sum of the squares of x and y, without undue
|
|
overflow or underflow. A range error occurs for some finite arguments.
|
|
</pre>
|
|
<a name='7.12.7.4p3'></a>
|
|
<pre>3
|
|
Returns
|
|
p
|
|
</pre>
|
|
<a name='7.12.7.4p4'></a>
|
|
<pre>4 The hypot functions return x 2 + y2 .
|
|
|
|
</pre>
|
|
<a name='7.12.7.5'></a>
|
|
<hr>
|
|
<h3>7.12.7.5 [The pow functions]</h3>
|
|
<a name='7.12.7.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double pow(double x, double y);
|
|
float powf(float x, float y);
|
|
long double powl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 powd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 powd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 powd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.5p2'></a>
|
|
<pre>2 The pow functions compute x raised to the power y. A domain error occurs if x is finite and less than
|
|
zero and y is finite and not an integer value. A domain error may occur if x is zero and y is zero.
|
|
Depending on y, a range error occurs if either the magnitude of nonzero finite x is too large or too
|
|
near zero. A domain error or pole error may occur if x is zero and y is less than zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.5p3'></a>
|
|
<pre>3 The pow functions return xy .
|
|
|
|
</pre>
|
|
<a name='7.12.7.6'></a>
|
|
<hr>
|
|
<h3>7.12.7.6 [The pown functions]</h3>
|
|
<a name='7.12.7.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdint.h>
|
|
#include <math.h>
|
|
double pown(double x, long long int n);
|
|
float pownf(float x, long long int n);
|
|
long double pownl(long double x, long long int n);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 pownd32(_Decimal32 x, long long int n);
|
|
_Decimal64 pownd64(_Decimal64 x, long long int n);
|
|
_Decimal128 pownd128(_Decimal128 x, long long int n);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.6p2'></a>
|
|
<pre>2 The pown functions compute x raised to the nth power. A pole error may occur if x equals 0 and
|
|
n < 0. Depending on n, a range error occurs if either the magnitude of nonzero finite x is too large
|
|
or too near zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.6p3'></a>
|
|
<pre>3 The pown functions return xn .
|
|
|
|
</pre>
|
|
<a name='7.12.7.7'></a>
|
|
<hr>
|
|
<h3>7.12.7.7 [The powr functions]</h3>
|
|
<a name='7.12.7.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double powr(double y, double x);
|
|
float powrf(float y, float x);
|
|
long double powrl(long double y, long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 powrd32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 powrd64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 powrd128(_Decimal128 y, _Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.7p2'></a>
|
|
<pre>2 The powr functions compute x raised to the power y as ey loge x .<a href='#FOOTNOTE.294'><sup>[294]</sup></a> A domain error occurs if x < 0
|
|
or if x and y are both zero. Depending on y, a range error occurs if either positive nonzero finite x is
|
|
too large or too near zero. A pole error may occur if x equals zero and finite y < 0.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.294'>
|
|
<pre><i><b>Footnote 294)</b> Restricting the domain to that of the formula ey loge x is intended to better meet expectations for a continuous power
|
|
function and to allow implementations with fewer tests for special cases.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.7.7p3'></a>
|
|
<pre>3 The powr functions return ey loge x .
|
|
|
|
</pre>
|
|
<a name='7.12.7.8'></a>
|
|
<hr>
|
|
<h3>7.12.7.8 [The rootn functions]</h3>
|
|
<a name='7.12.7.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdint.h>
|
|
#include <math.h>
|
|
double rootn(double x, long long int n);
|
|
float rootnf(float x, long long int n);
|
|
long double rootnl(long double x, long long int n);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 rootnd32(_Decimal32 x, long long int n);
|
|
_Decimal64 rootnd64(_Decimal64 x, long long int n);
|
|
_Decimal128 rootnd128(_Decimal128 x, long long int n);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.8p2'></a>
|
|
<pre>2 The rootn functions compute the principal nth root of x. A domain error occurs if n is 0 or if x < 0
|
|
and n is even. If n is −1, a range error occurs if either the magnitude of nonzero finite x is too large
|
|
or too near zero. A pole error may occur if x equals zero and n < 0.
|
|
|
|
Returns
|
|
1
|
|
</pre>
|
|
<a name='7.12.7.8p3'></a>
|
|
<pre>3 The rootn functions return x n .
|
|
|
|
</pre>
|
|
<a name='7.12.7.9'></a>
|
|
<hr>
|
|
<h3>7.12.7.9 [The rsqrt functions]</h3>
|
|
<a name='7.12.7.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double rsqrt(double x);
|
|
float rsqrtf(float x);
|
|
long double rsqrtl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 rsqrtd32(_Decimal32 x);
|
|
_Decimal64 rsqrtd64(_Decimal64 x);
|
|
_Decimal128 rsqrtd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.9p2'></a>
|
|
<pre>2 The rsqrt functions compute the reciprocal of the nonnegative square root of the argument. A
|
|
domain error occurs if the argument is less than zero. A pole error may occur if the argument equals
|
|
zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.9p3'></a>
|
|
<pre>3 The rsqrt functions return √1x .
|
|
|
|
</pre>
|
|
<a name='7.12.7.10'></a>
|
|
<hr>
|
|
<h3>7.12.7.10 [The sqrt functions]</h3>
|
|
<a name='7.12.7.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double sqrt(double x);
|
|
float sqrtf(float x);
|
|
long double sqrtl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 sqrtd32(_Decimal32 x);
|
|
_Decimal64 sqrtd64(_Decimal64 x);
|
|
_Decimal128 sqrtd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.10p2'></a>
|
|
<pre>2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if the argument
|
|
is less than zero.
|
|
|
|
Returns
|
|
√
|
|
</pre>
|
|
<a name='7.12.7.10p3'></a>
|
|
<pre>3 The sqrt functions return x.
|
|
|
|
</pre>
|
|
<a name='7.12.8'></a>
|
|
<hr>
|
|
<h3>7.12.8 [Error and gamma functions]</h3>
|
|
<a name='7.12.8.1'></a>
|
|
<hr>
|
|
<h3>7.12.8.1 [The erf functions]</h3>
|
|
<a name='7.12.8.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double erf(double x);
|
|
float erff(float x);
|
|
long double erfl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 erfd32(_Decimal32 x);
|
|
_Decimal64 erfd64(_Decimal64 x);
|
|
_Decimal128 erfd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.1p2'></a>
|
|
<pre>2 The erf functions compute the error function of x. A range error occurs if nonzero x is too close to
|
|
zero.
|
|
|
|
Returns
|
|
Rx −t2
|
|
</pre>
|
|
<a name='7.12.8.1p3'></a>
|
|
<pre>3 The erf functions return erf x = √2π e dt.
|
|
0
|
|
</pre>
|
|
<a name='7.12.8.2'></a>
|
|
<hr>
|
|
<h3>7.12.8.2 [The erfc functions]</h3>
|
|
<a name='7.12.8.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double erfc(double x);
|
|
float erfcf(float x);
|
|
long double erfcl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 erfcd32(_Decimal32 x);
|
|
_Decimal64 erfcd64(_Decimal64 x);
|
|
_Decimal128 erfcd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.2p2'></a>
|
|
<pre>2 The erfc functions compute the complementary error function of x. A range error occurs if positive
|
|
finite x is too large.
|
|
|
|
Returns
|
|
R∞ −t2
|
|
</pre>
|
|
<a name='7.12.8.2p3'></a>
|
|
<pre>3 The erfc functions return erfc x = 1 − erf x = √2π e dt.
|
|
x
|
|
|
|
|
|
</pre>
|
|
<a name='7.12.8.3'></a>
|
|
<hr>
|
|
<h3>7.12.8.3 [The lgamma functions]</h3>
|
|
<a name='7.12.8.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double lgamma(double x);
|
|
float lgammaf(float x);
|
|
long double lgammal(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 lgammad32(_Decimal32 x);
|
|
_Decimal64 lgammad64(_Decimal64 x);
|
|
_Decimal128 lgammad128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.3p2'></a>
|
|
<pre>2 The lgamma functions compute the natural logarithm of the absolute value of gamma of x. A range
|
|
error occurs if positive finite x is too large. A pole error may occur if x is a negative integer or zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.8.3p3'></a>
|
|
<pre>3 The lgamma functions return loge |Γ(x)|.
|
|
|
|
</pre>
|
|
<a name='7.12.8.4'></a>
|
|
<hr>
|
|
<h3>7.12.8.4 [The tgamma functions]</h3>
|
|
<a name='7.12.8.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double tgamma(double x);
|
|
float tgammaf(float x);
|
|
long double tgammal(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 tgammad32(_Decimal32 x);
|
|
_Decimal64 tgammad64(_Decimal64 x);
|
|
_Decimal128 tgammad128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.4p2'></a>
|
|
<pre>2 The tgamma functions compute the gamma function of x. A domain error or pole error may occur
|
|
if x is a negative integer or zero. A range error occurs for some negative finite x less than zero, if
|
|
positive finite x is too large, or nonzero x is too close to zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.8.4p3'></a>
|
|
<pre>3 The tgamma functions return Γ(x).
|
|
|
|
</pre>
|
|
<a name='7.12.9'></a>
|
|
<hr>
|
|
<h3>7.12.9 [Nearest integer functions]</h3>
|
|
<a name='7.12.9.1'></a>
|
|
<hr>
|
|
<h3>7.12.9.1 [The ceil functions]</h3>
|
|
<a name='7.12.9.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double ceil(double x);
|
|
float ceilf(float x);
|
|
long double ceill(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 ceild32(_Decimal32 x);
|
|
_Decimal64 ceild64(_Decimal64 x);
|
|
_Decimal128 ceild128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.1p2'></a>
|
|
<pre>2 The ceil functions compute the smallest integer value not less than x.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.1p3'></a>
|
|
<pre>3 The ceil functions return ⌈x⌉, expressed as a floating-point number.
|
|
|
|
</pre>
|
|
<a name='7.12.9.2'></a>
|
|
<hr>
|
|
<h3>7.12.9.2 [The floor functions]</h3>
|
|
<a name='7.12.9.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double floor(double x);
|
|
float floorf(float x);
|
|
long double floorl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 floord32(_Decimal32 x);
|
|
_Decimal64 floord64(_Decimal64 x);
|
|
_Decimal128 floord128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.2p2'></a>
|
|
<pre>2 The floor functions compute the largest integer value not greater than x.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.2p3'></a>
|
|
<pre>3 The floor functions return ⌊x⌋, expressed as a floating-point number.
|
|
|
|
</pre>
|
|
<a name='7.12.9.3'></a>
|
|
<hr>
|
|
<h3>7.12.9.3 [The nearbyint functions]</h3>
|
|
<a name='7.12.9.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nearbyint(double x);
|
|
float nearbyintf(float x);
|
|
long double nearbyintl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nearbyintd32(_Decimal32 x);
|
|
_Decimal64 nearbyintd64(_Decimal64 x);
|
|
_Decimal128 nearbyintd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.3p2'></a>
|
|
<pre>2 The nearbyint functions round their argument to an integer value in floating-point format, using
|
|
the current rounding direction and without raising the "inexact" floating-point exception.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.3p3'></a>
|
|
<pre>3 The nearbyint functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.4'></a>
|
|
<hr>
|
|
<h3>7.12.9.4 [The rint functions]</h3>
|
|
<a name='7.12.9.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double rint(double x);
|
|
float rintf(float x);
|
|
long double rintl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 rintd32(_Decimal32 x);
|
|
_Decimal64 rintd64(_Decimal64 x);
|
|
_Decimal128 rintd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.4p2'></a>
|
|
<pre>2 The rint functions differ from the nearbyint functions (<a href='#7.12.9.3'>7.12.9.3</a>) only in that the rint functions
|
|
may raise the "inexact" floating-point exception if the result differs in value from the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.4p3'></a>
|
|
<pre>3 The rint functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.5'></a>
|
|
<hr>
|
|
<h3>7.12.9.5 [The lrint and llrint functions]</h3>
|
|
<a name='7.12.9.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
long int lrint(double x);
|
|
long int lrintf(float x);
|
|
long int lrintl(long double x);
|
|
long long int llrint(double x);
|
|
long long int llrintf(float x);
|
|
long long int llrintl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
long int lrintd32(_Decimal32 x);
|
|
long int lrintd64(_Decimal64 x);
|
|
long int lrintd128(_Decimal128 x);
|
|
long long int llrintd32(_Decimal32 x);
|
|
long long int llrintd64(_Decimal64 x);
|
|
long long int llrintd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.5p2'></a>
|
|
<pre>2 The lrint and llrint functions round their argument to the nearest integer value, rounding
|
|
according to the current rounding direction. If the rounded value is outside the range of the return
|
|
type, the numeric result is unspecified and a domain error or range error may occur.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.5p3'></a>
|
|
<pre>3 The lrint and llrint functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.6'></a>
|
|
<hr>
|
|
<h3>7.12.9.6 [The round functions]</h3>
|
|
<a name='7.12.9.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double round(double x);
|
|
float roundf(float x);
|
|
long double roundl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 roundd32(_Decimal32 x);
|
|
_Decimal64 roundd64(_Decimal64 x);
|
|
_Decimal128 roundd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.6p2'></a>
|
|
<pre>2 The round functions round their argument to the nearest integer value in floating-point format,
|
|
rounding halfway cases away from zero, regardless of the current rounding direction.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.6p3'></a>
|
|
<pre>3 The round functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.7'></a>
|
|
<hr>
|
|
<h3>7.12.9.7 [The lround and llround functions]</h3>
|
|
<a name='7.12.9.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
long int lround(double x);
|
|
long int lroundf(float x);
|
|
long int lroundl(long double x);
|
|
long long int llround(double x);
|
|
long long int llroundf(float x);
|
|
long long int llroundl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
long int lroundd32(_Decimal32 x);
|
|
long int lroundd64(_Decimal64 x);
|
|
long int lroundd128(_Decimal128 x);
|
|
long long int llroundd32(_Decimal32 x);
|
|
long long int llroundd64(_Decimal64 x);
|
|
long long int llroundd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.7p2'></a>
|
|
<pre>2 The lround and llround functions round their argument to the nearest integer value, rounding
|
|
halfway cases away from zero, regardless of the current rounding direction. If the rounded value is
|
|
outside the range of the return type, the numeric result is unspecified and a domain error or range
|
|
error may occur.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.7p3'></a>
|
|
<pre>3 The lround and llround functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.8'></a>
|
|
<hr>
|
|
<h3>7.12.9.8 [The roundeven functions]</h3>
|
|
<a name='7.12.9.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double roundeven(double x);
|
|
float roundevenf(float x);
|
|
long double roundevenl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 roundevend32(_Decimal32 x);
|
|
_Decimal64 roundevend64(_Decimal64 x);
|
|
_Decimal128 roundevend128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.8p2'></a>
|
|
<pre>2 The roundeven functions round their argument to the nearest integer value in floating-point format,
|
|
rounding halfway cases to even (that is, to the nearest value that is an even integer), regardless of
|
|
the current rounding direction.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.8p3'></a>
|
|
<pre>3 The roundeven functions return the rounded integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.9'></a>
|
|
<hr>
|
|
<h3>7.12.9.9 [The trunc functions]</h3>
|
|
<a name='7.12.9.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double trunc(double x);
|
|
float truncf(float x);
|
|
long double truncl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 truncd32(_Decimal32 x);
|
|
_Decimal64 truncd64(_Decimal64 x);
|
|
_Decimal128 truncd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.9p2'></a>
|
|
<pre>2 The trunc functions round their argument to the integer value, in floating format, nearest to but no
|
|
larger in magnitude than the argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.9p3'></a>
|
|
<pre>3 The trunc functions return the truncated integer value.
|
|
|
|
</pre>
|
|
<a name='7.12.9.10'></a>
|
|
<hr>
|
|
<h3>7.12.9.10 [The fromfp and ufromfp functions]</h3>
|
|
<a name='7.12.9.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdint.h>
|
|
#include <math.h>
|
|
double fromfp(double x, int rnd, unsigned int width);
|
|
float fromfpf(float x, int rnd, unsigned int width);
|
|
long double fromfpl(long double x, int rnd, unsigned int width);
|
|
double ufromfp(double x, int rnd, unsigned int width);
|
|
float ufromfpf(float x, int rnd, unsigned int width);
|
|
long double ufromfpl(long double x, int rnd, unsigned int width);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fromfpd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 fromfpd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 fromfpd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 ufromfpd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 ufromfpd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 ufromfpd128(_Decimal128 x, int rnd, unsigned int width);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.10p2'></a>
|
|
<pre>2 The fromfp and ufromfp functions round x, using the math rounding direction indicated by rnd, to
|
|
a signed or unsigned integer, respectively. If width is nonzero and the resulting integer is within the
|
|
range
|
|
|
|
— [−2(width−1) , 2(width−1) − 1], for signed
|
|
|
|
— [0, 2width − 1], for unsigned
|
|
|
|
then the functions return the integer value (represented in floating type). Otherwise, if width is
|
|
zero or x does not round to an integer within the range, the functions return a NaN (of the type of
|
|
the x argument, if available), else the value of x, and a domain error occurs. If the value of the
|
|
rnd argument is not equal to the value of a math rounding direction macro (<a href='#7.12'>7.12</a>), the direction of
|
|
rounding is unspecified. The fromfp and ufromfp functions do not raise the "inexact" floating-point
|
|
exception.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.10p3'></a>
|
|
<pre>3 The fromfp and ufromfp functions return the rounded integer value.
|
|
</pre>
|
|
<a name='7.12.9.10p4'></a>
|
|
<pre>4 EXAMPLE Upward rounding of double x to type int, without raising the "inexact" floating-point exception, is achieved by
|
|
|
|
(int)fromfp(x, FP_INT_UPWARD, INT_WIDTH)
|
|
|
|
|
|
</pre>
|
|
<a name='7.12.9.10p5'></a>
|
|
<pre>5 EXAMPLE Unsigned integer wrapping is not performed in
|
|
|
|
ufromfp(-3.0, FP_INT_UPWARD, UINT_WIDTH) /* domain error */
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.12.9.11'></a>
|
|
<hr>
|
|
<h3>7.12.9.11 [The fromfpx and ufromfpx functions]</h3>
|
|
<a name='7.12.9.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdint.h>
|
|
#include <math.h>
|
|
double fromfpx(double x, int rnd, unsigned int width);
|
|
float fromfpxf(float x, int rnd, unsigned int width);
|
|
long double fromfpxl(long double x, int rnd, unsigned int width);
|
|
double ufromfpx(double x, int rnd, unsigned int width);
|
|
float ufromfpxf(float x, int rnd, unsigned int width);
|
|
long double ufromfpxl(long double x, int rnd, unsigned int width);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fromfpxd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 fromfpxd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 fromfpxd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 ufromfpxd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 ufromfpxd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 ufromfpxd128(_Decimal128 x, int rnd, unsigned int width);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.11p2'></a>
|
|
<pre>2 The fromfpx and ufromfpx functions differ from the fromfp and ufromfp functions, respectively,
|
|
only in that the fromfpx and ufromfpx functions raise the "inexact" floating-point exception if a
|
|
rounded result not exceeding the specified width differs in value from the argument x.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.9.11p3'></a>
|
|
<pre>3 The fromfpx and ufromfpx functions return the rounded integer value.
|
|
</pre>
|
|
<a name='7.12.9.11p4'></a>
|
|
<pre>4 NOTE Conversions to integer types that are not required to raise the inexact exception can be done simply by rounding to
|
|
integral value in floating type and then converting to the target integer type. For example, the conversion of long double x
|
|
to uint64_t, using upward rounding, is done by
|
|
|
|
(uint64_t)ceill(x)
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.12.10'></a>
|
|
<hr>
|
|
<h3>7.12.10 [Remainder functions]</h3>
|
|
<a name='7.12.10.1'></a>
|
|
<hr>
|
|
<h3>7.12.10.1 [The fmod functions]</h3>
|
|
<a name='7.12.10.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmod(double x, double y);
|
|
float fmodf(float x, float y);
|
|
long double fmodl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmodd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmodd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmodd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.10.1p2'></a>
|
|
<pre>2 The fmod functions compute the floating-point remainder of x/y.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.10.1p3'></a>
|
|
<pre>3 The fmod functions return the value x − ny, for some integer n such that, if y is nonzero, the result
|
|
has the same sign as x and magnitude less than the magnitude of y. If y is zero, whether a domain
|
|
error occurs or the fmod functions return zero is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='7.12.10.2'></a>
|
|
<hr>
|
|
<h3>7.12.10.2 [The remainder functions]</h3>
|
|
<a name='7.12.10.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double remainder(double x, double y);
|
|
float remainderf(float x, float y);
|
|
long double remainderl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 remainderd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 remainderd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 remainderd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.10.2p2'></a>
|
|
<pre>2 The remainder functions compute the remainder x REM y required by IEC 60559. <a href='#FOOTNOTE.295'><sup>[295]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.295'>
|
|
<pre><i><b>Footnote 295)</b> "When y ̸= 0, the remainder r = x REM y is defined regardless of the rounding mode by the mathematical relation
|
|
r = x − ny, where n is the integer nearest the exact value of xy
|
|
; whenever |n − x
|
|
y
|
|
| = 12 , then n is even. If r = 0, its sign shall
|
|
be that of x." This definition is applicable for all implementations.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.10.2p3'></a>
|
|
<pre>3 The remainder functions return x REM y. If y is zero, whether a domain error occurs or the functions
|
|
return zero is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='7.12.10.3'></a>
|
|
<hr>
|
|
<h3>7.12.10.3 [The remquo functions]</h3>
|
|
<a name='7.12.10.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double remquo(double x, double y, int *quo);
|
|
float remquof(float x, float y, int *quo);
|
|
long double remquol(long double x, long double y, int *quo);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.10.3p2'></a>
|
|
<pre>2 The remquo functions compute the same remainder as the remainder functions. In the object pointed
|
|
to by quo they store a value whose sign is the sign of x/y and whose magnitude is congruent modulo
|
|
2n to the magnitude of the integral quotient of x/y, where n is an implementation-defined integer
|
|
greater than or equal to 3.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.10.3p3'></a>
|
|
<pre>3 The remquo functions return x REM y. If y is zero, the value stored in the object pointed to by quo
|
|
is unspecified and whether a domain error occurs or the functions return zero is implementation-
|
|
defined.
|
|
</pre>
|
|
<a name='7.12.10.3p4'></a>
|
|
<pre>4 NOTE There are no decimal floating-point versions of the remquo functions.
|
|
|
|
</pre>
|
|
<a name='7.12.11'></a>
|
|
<hr>
|
|
<h3>7.12.11 [Manipulation functions]</h3>
|
|
<a name='7.12.11.1'></a>
|
|
<hr>
|
|
<h3>7.12.11.1 [The copysign functions]</h3>
|
|
<a name='7.12.11.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double copysign(double x, double y);
|
|
float copysignf(float x, float y);
|
|
long double copysignl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 copysignd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 copysignd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 copysignd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.1p2'></a>
|
|
<pre>2 The copysign functions produce a value with the magnitude of x and the sign of y. If x or y is an
|
|
unsigned value, the sign (if any) of the result is implementation-defined. On implementations that
|
|
represent a signed zero but do not treat negative zero consistently in arithmetic operations, the
|
|
copysign functions should regard the sign of zero as positive.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.11.1p3'></a>
|
|
<pre>3 The copysign functions return a value with the magnitude of x and the sign of y.
|
|
|
|
</pre>
|
|
<a name='7.12.11.2'></a>
|
|
<hr>
|
|
<h3>7.12.11.2 [The nan functions]</h3>
|
|
<a name='7.12.11.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nan(const char *tagp);
|
|
float nanf(const char *tagp);
|
|
long double nanl(const char *tagp);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nand32(const char *tagp);
|
|
_Decimal64 nand64(const char *tagp);
|
|
_Decimal128 nand128(const char *tagp);
|
|
#endif
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.2p2'></a>
|
|
<pre>2 The nan, nanf, and nanl functions convert the string pointed to by tagp according to the following
|
|
rules. The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-sequence)", nullptr);
|
|
the call nan("") is equivalent to strtod("NAN()", nullptr). If tagp does not point to an empty
|
|
string or an n-char sequence, the call is equivalent to strtod("NAN", nullptr). Calls to nanf and
|
|
nanl are equivalent to the corresponding calls to strtof and strtold.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.11.2p3'></a>
|
|
<pre>3 The nan functions return a quiet NaN, if available, with content indicated through tagp. If the
|
|
implementation does not support quiet NaNs, the functions return zero.
|
|
Forward references: the strtod, strtof, and strtold functions (<a href='#7.24.1.5'>7.24.1.5</a>).
|
|
|
|
</pre>
|
|
<a name='7.12.11.3'></a>
|
|
<hr>
|
|
<h3>7.12.11.3 [The nextafter functions]</h3>
|
|
<a name='7.12.11.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nextafter(double x, double y);
|
|
float nextafterf(float x, float y);
|
|
long double nextafterl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nextafterd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 nextafterd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 nextafterd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.3p2'></a>
|
|
<pre>2 The nextafter functions determine the next representable value, in the type of the function, after x
|
|
in the direction of y, where x and y are first converted to the type of the function<a href='#FOOTNOTE.296'><sup>[296]</sup></a> . The nextafter
|
|
functions return y if x equals y.
|
|
A range error occurs if the magnitude of x is the largest finite value representable in the type and the
|
|
result is infinite or not representable in the type.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.296'>
|
|
<pre><i><b>Footnote 296)</b> The argument values are converted to the type of the function, even by a macro implementation of the function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.11.3p3'></a>
|
|
<pre>3 The nextafter functions return the next representable value in the specified format after x in the
|
|
direction of y.
|
|
|
|
</pre>
|
|
<a name='7.12.11.4'></a>
|
|
<hr>
|
|
<h3>7.12.11.4 [The nexttoward functions]</h3>
|
|
<a name='7.12.11.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nexttoward(double x, long double y);
|
|
float nexttowardf(float x, long double y);
|
|
long double nexttowardl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nexttowardd32(_Decimal32 x, _Decimal128 y);
|
|
_Decimal64 nexttowardd64(_Decimal64 x, _Decimal128 y);
|
|
_Decimal128 nexttowardd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.4p2'></a>
|
|
<pre>2 The nexttoward functions are equivalent to the nextafter functions except that the second param-
|
|
eter has type long double or _Decimal128 and the functions return y converted to the type of the
|
|
function if x equals y.<a href='#FOOTNOTE.297'><sup>[297]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.297'>
|
|
<pre><i><b>Footnote 297)</b> The result of the nexttoward functions is determined in the type of the function, without loss of range or precision in a
|
|
floating second argument.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.11.5'></a>
|
|
<hr>
|
|
<h3>7.12.11.5 [The nextup functions]</h3>
|
|
<a name='7.12.11.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nextup(double x);
|
|
float nextupf(float x);
|
|
long double nextupl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nextupd32(_Decimal32 x);
|
|
_Decimal64 nextupd64(_Decimal64 x);
|
|
_Decimal128 nextupd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.5p2'></a>
|
|
<pre>2 The nextup functions determine the next representable value, in the type of the function, greater
|
|
than x. If x is the negative number of least magnitude in the type of x, nextup(x) is −0 if the
|
|
type has signed zeros and is 0 otherwise. If x is zero, nextup(x) is the positive number of least
|
|
magnitude in the type of x. If x is the positive number (finite or infinite) or maximum magnitude in
|
|
the type, nextup(x) is x.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.11.5p3'></a>
|
|
<pre>3 The nextup functions return the next representable value in the specified type greater than x.
|
|
|
|
</pre>
|
|
<a name='7.12.11.6'></a>
|
|
<hr>
|
|
<h3>7.12.11.6 [The nextdown functions]</h3>
|
|
<a name='7.12.11.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double nextdown(double x);
|
|
float nextdownf(float x);
|
|
long double nextdownl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 nextdownd32(_Decimal32 x);
|
|
_Decimal64 nextdownd64(_Decimal64 x);
|
|
_Decimal128 nextdownd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.6p2'></a>
|
|
<pre>2 The nextdown functions determine the next representable value, in the type of the function, less than
|
|
x . If x is the positive number of least magnitude in the type of x , nextdown(x) is +0 if the type has
|
|
signed zeros and is 0 otherwise. If x is zero, nextdown(x) is the negative number of least magnitude
|
|
in the type of x. If x is the negative number (finite or infinite) of maximum magnitude in the type,
|
|
nextdown(x) is x .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.11.6p3'></a>
|
|
<pre>3 The nextdown functions return the next representable value in the specified type less than x.
|
|
|
|
</pre>
|
|
<a name='7.12.11.7'></a>
|
|
<hr>
|
|
<h3>7.12.11.7 [The canonicalize functions]</h3>
|
|
<a name='7.12.11.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int canonicalize(double * cx, const double * x);
|
|
int canonicalizef(float * cx, const float * x);
|
|
int canonicalizel(long double * cx, const long double * x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int canonicalized32(_Decimal32 cx, const _Decimal32 * x);
|
|
int canonicalized64(_Decimal64 cx, const _Decimal64 * x);
|
|
int canonicalized128(_Decimal128 cx, const _Decimal128 * x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.7p2'></a>
|
|
<pre>2 The canonicalize functions attempt to produce a canonical version of the floating-point repre-
|
|
sentation in the object pointed to by the argument x, as if to a temporary object of the specified
|
|
type, and store the canonical result in the object pointed to by the argument cx.<a href='#FOOTNOTE.298'><sup>[298]</sup></a> If the input *x
|
|
is a signaling NaN, the canonicalize functions are intended to store a canonical quiet NaN. If a
|
|
canonical result is not produced the object pointed to by cx is unchanged.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.298'>
|
|
<pre><i><b>Footnote 298)</b> Arguments x and cx may point to the same object.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.11.7p3'></a>
|
|
<pre>3 The canonicalize functions return zero if a canonical result is stored in the object pointed to by cx.
|
|
Otherwise they return a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.12.12'></a>
|
|
<hr>
|
|
<h3>7.12.12 [Maximum, minimum, and positive difference functions]</h3>
|
|
<a name='7.12.12.1'></a>
|
|
<hr>
|
|
<h3>7.12.12.1 [The fdim functions]</h3>
|
|
<a name='7.12.12.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fdim(double x, double y);
|
|
float fdimf(float x, float y);
|
|
long double fdiml(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fdimd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fdimd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fdimd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.1p2'></a>
|
|
<pre>2 The fdim functions determine the positive difference between their arguments:
|
|
(
|
|
x − y if x > y
|
|
+0 if x ≤ y
|
|
|
|
A range error may occur.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.1p3'></a>
|
|
<pre>3 The fdim functions return the positive difference value.
|
|
|
|
</pre>
|
|
<a name='7.12.12.2'></a>
|
|
<hr>
|
|
<h3>7.12.12.2 [The fmax functions]</h3>
|
|
<a name='7.12.12.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmax(double x, double y);
|
|
float fmaxf(float x, float y);
|
|
long double fmaxl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmaxd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaxd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaxd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.2p2'></a>
|
|
<pre>2 The fmax functions determine the maximum numeric value of their arguments.<a href='#FOOTNOTE.299'><sup>[299]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.299'>
|
|
<pre><i><b>Footnote 299)</b> Quiet NaN arguments are treated as missing data: if one argument is a quiet NaN and the other numeric, then the fmax
|
|
functions choose the numeric value. See <a href='#F.10.9.2'>F.10.9.2</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.12.2p3'></a>
|
|
<pre>3 The fmax functions return the maximum numeric value of their arguments.
|
|
|
|
</pre>
|
|
<a name='7.12.12.3'></a>
|
|
<hr>
|
|
<h3>7.12.12.3 [The fmin functions]</h3>
|
|
<a name='7.12.12.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmin(double x, double y);
|
|
float fminf(float x, float y);
|
|
long double fminl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmind32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmind64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmind128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.3p2'></a>
|
|
<pre>2 The fmin functions determine the minimum numeric value of their arguments. <a href='#FOOTNOTE.300'><sup>[300]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.300'>
|
|
<pre><i><b>Footnote 300)</b> The fmin functions are analogous to the fmax functions in their treatment of quiet NaNs.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.12.3p3'></a>
|
|
<pre>3 The fmin functions return the minimum numeric value of their arguments.
|
|
</pre>
|
|
<a name='7.12.12.3p4'></a>
|
|
<pre>4 NOTE 1 The fmax and fmin functions are similar to the fmaximum_num and fminimum_num functions, though may differ in
|
|
which signed zero is returned when the arguments are differently signed zeros and in their treatment of signaling NaNs
|
|
(see <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
</pre>
|
|
<a name='7.12.12.4'></a>
|
|
<hr>
|
|
<h3>7.12.12.4 [The fmaximum functions]</h3>
|
|
<a name='7.12.12.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmaximum(double x, double y);
|
|
float fmaximumf(float x, float y);
|
|
long double fmaximuml(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmaximumd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximumd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximumd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.4p2'></a>
|
|
<pre>2 The fmaximum functions determine the maximum value of their arguments. For these functions, +0
|
|
is considered greater than −0. These functions differ from the fmaximum_num functions only in their
|
|
treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.4p3'></a>
|
|
<pre>3 The fmaximum functions return the maximum value of their arguments.
|
|
|
|
</pre>
|
|
<a name='7.12.12.5'></a>
|
|
<hr>
|
|
<h3>7.12.12.5 [The fminimum functions]</h3>
|
|
<a name='7.12.12.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fminimum(double x, double y);
|
|
float fminimumf(float x, float y);
|
|
long double fminimuml(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fminimumd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimumd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimumd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.5p2'></a>
|
|
<pre>2 The fminimum functions determine the minimum value of their arguments. For these functions, −0
|
|
is considered less than +0. These functions differ from the fminimum_num functions only in their
|
|
treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.5p3'></a>
|
|
<pre>3 The fminimum functions return the minimum value of their arguments.
|
|
|
|
</pre>
|
|
<a name='7.12.12.6'></a>
|
|
<hr>
|
|
<h3>7.12.12.6 [The fmaximum_mag functions]</h3>
|
|
<a name='7.12.12.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmaximum_mag(double x, double y);
|
|
float fmaximum_magf(float x, float y);
|
|
long double fmaximum_magl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmaximum_magd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_magd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_magd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.6p2'></a>
|
|
<pre>2 The fmaximum_mag functions determine the value of the argument of maximum magnitude:
|
|
x if |x | > |y|, y if |y| > |x |, and fmaximum(x, y) otherwise. These functions differ from the
|
|
fmaximum_mag_num functions only in their treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.6p3'></a>
|
|
<pre>3 The fmaximum_mag functions return the value of the argument of maximum magnitude.
|
|
|
|
</pre>
|
|
<a name='7.12.12.7'></a>
|
|
<hr>
|
|
<h3>7.12.12.7 [The fminimum_mag functions]</h3>
|
|
<a name='7.12.12.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fminimum_mag(double x, double y);
|
|
float fminimum_magf(float x, float y);
|
|
long double fminimum_magl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fminimum_magd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_magd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_magd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.7p2'></a>
|
|
<pre>2 The fminimum_mag functions determine the value of the argument of minimum magnitude:
|
|
x if |x | < |y|, y if |y| < |x |, and fminimum(x, y) otherwise. These functions differ from the
|
|
fminimum_mag_num functions only in their treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.7p3'></a>
|
|
<pre>3 The fminimum_mag functions return the value of the argument of minimum magnitude.
|
|
|
|
</pre>
|
|
<a name='7.12.12.8'></a>
|
|
<hr>
|
|
<h3>7.12.12.8 [The fmaximum_num functions]</h3>
|
|
<a name='7.12.12.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmaximum_num(double x, double y);
|
|
float fmaximum_numf(float x, float y);
|
|
long double fmaximum_numl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmaximum_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_numd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.8p2'></a>
|
|
<pre>2 The fmaximum_num functions determine the maximum value of their numeric arguments. They
|
|
determine the number if one argument is a number and the other is a NaN. These functions differ
|
|
from the fmaximum functions only in their treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.8p3'></a>
|
|
<pre>3 The fmaximum_num functions return the maximum value of their numeric arguments.
|
|
|
|
</pre>
|
|
<a name='7.12.12.9'></a>
|
|
<hr>
|
|
<h3>7.12.12.9 [The fminimum_num functions]</h3>
|
|
<a name='7.12.12.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fminimum_num(double x, double y);
|
|
float fminimum_numf(float x, float y);
|
|
long double fminimum_numl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fminimum_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_numd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.9p2'></a>
|
|
<pre>2 The fminimum_num functions determine the minimum value of their numeric arguments. They
|
|
determine the number if one argument is a number and the other is a NaN. These functions differ
|
|
from the fminimum functions only in their treatment of NaN arguments (see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.9p3'></a>
|
|
<pre>3 The fminimum_num functions return the minimum value of their numeric arguments.
|
|
|
|
</pre>
|
|
<a name='7.12.12.10'></a>
|
|
<hr>
|
|
<h3>7.12.12.10 [The fmaximum_mag_num functions]</h3>
|
|
<a name='7.12.12.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fmaximum_mag_num(double x, double y);
|
|
float fmaximum_mag_numf(float x, float y);
|
|
long double fmaximum_mag_numl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmaximum_mag_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_mag_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_mag_numd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.10p2'></a>
|
|
<pre>2 The fmaximum_mag_num functions determine the value of a numeric argument of maximum mag-
|
|
nitude. They determine the number if one argument is a number and the other is a NaN. These
|
|
functions differ from the fmaximum_mag functions only in their treatment of NaN arguments
|
|
(see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.10p3'></a>
|
|
<pre>3 The fmaximum_mag_num functions return the value of a numeric argument of maximum magnitude.
|
|
|
|
</pre>
|
|
<a name='7.12.12.11'></a>
|
|
<hr>
|
|
<h3>7.12.12.11 [The fminimum_mag_num functions]</h3>
|
|
<a name='7.12.12.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fminimum_mag_num(double x, double y);
|
|
float fminimum_mag_numf(float x, float y);
|
|
long double fminimum_mag_numl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fminimum_mag_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_mag_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_mag_numd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.12.11p2'></a>
|
|
<pre>2 The fminimum_mag_num functions determine the value of a numeric argument of minimum mag-
|
|
nitude. They determine the number if one argument is a number and the other is a NaN. These
|
|
functions differ from the fminimum_mag functions only in their treatment of NaN arguments
|
|
(see <a href='#F.10.9.4'>F.10.9.4</a>, <a href='#F.10.9.5'>F.10.9.5</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.12.11p3'></a>
|
|
<pre>3 The fminimum_mag_num functions return the value of a numeric argument of mimum minagnitude.
|
|
|
|
</pre>
|
|
<a name='7.12.13'></a>
|
|
<hr>
|
|
<h3>7.12.13 [Fused multiply-add]</h3>
|
|
<a name='7.12.13.1'></a>
|
|
<hr>
|
|
<h3>7.12.13.1 [The fma functions]</h3>
|
|
<a name='7.12.13.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fma(double x, double y, double z);
|
|
float fmaf(float x, float y, float z);
|
|
long double fmal(long double x, long double y, long double z);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 fmad32(_Decimal32 x, _Decimal32 y, _Decimal32 z);
|
|
_Decimal64 fmad64(_Decimal64 x, _Decimal64 y, _Decimal64 z);
|
|
_Decimal128 fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.13.1p2'></a>
|
|
<pre>2 The fma functions compute (x × y) + z, rounded as one ternary operation: they compute the value
|
|
(as if) to infinite precision and round once to the result format, according to the current rounding
|
|
mode. A range error occurs for some finite arguments.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.13.1p3'></a>
|
|
<pre>3 The fma functions return (x × y) + z, rounded as one ternary operation.
|
|
|
|
</pre>
|
|
<a name='7.12.14'></a>
|
|
<hr>
|
|
<h3>7.12.14 [Functions that round result to narrower type]</h3>
|
|
<a name='7.12.14p1'></a>
|
|
<pre>1 The functions in this subclause round their results to a type typically narrower<a href='#FOOTNOTE.301'><sup>[301]</sup></a> than the parameter
|
|
types.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.301'>
|
|
<pre><i><b>Footnote 301)</b> In some cases the destination type might not be narrower than the parameter types. For example, double might not be
|
|
narrower than long double.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.14.1'></a>
|
|
<hr>
|
|
<h3>7.12.14.1 [Add and round to narrower type]</h3>
|
|
<a name='7.12.14.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float fadd(double x, double y);
|
|
float faddl(long double x, long double y);
|
|
double daddl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32addd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32addd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64addd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.1p2'></a>
|
|
<pre>2 These functions compute the sum of x + y, rounded to the type of the function. They compute
|
|
the sum (as if) to infinite precision and round once to the result format, according to the current
|
|
rounding mode. A range error occurs for some finite arguments. A domain error may occur for
|
|
infinite arguments.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.1p3'></a>
|
|
<pre>3 These functions return the sum of x + y, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.14.2'></a>
|
|
<hr>
|
|
<h3>7.12.14.2 [Subtract and round to narrower type]</h3>
|
|
<a name='7.12.14.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float fsub(double x, double y);
|
|
float fsubl(long double x, long double y);
|
|
double dsubl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32subd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32subd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64subd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.2p2'></a>
|
|
<pre>2 These functions compute the difference of x − y, rounded to the type of the function. They compute
|
|
the difference (as if) to infinite precision and round once to the result format, according to the current
|
|
rounding mode. A range error occurs for some finite arguments. A domain error may occur for
|
|
infinite arguments.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.2p3'></a>
|
|
<pre>3 These functions return the difference of x − y, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.14.3'></a>
|
|
<hr>
|
|
<h3>7.12.14.3 [Multiply and round to narrower type]</h3>
|
|
<a name='7.12.14.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float fmul(double x, double y);
|
|
float fmull(long double x, long double y);
|
|
double dmull(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32muld64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32muld128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64muld128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.3p2'></a>
|
|
<pre>2 These functions compute the product x × y, rounded to the type of the function. They compute the
|
|
product (as if) to infinite precision and round once to the result format, according to the current
|
|
rounding mode. A range error occurs for some finite arguments. A domain error occurs for one
|
|
infinite argument and one zero argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.3p3'></a>
|
|
<pre>3 These functions return the product of x × y, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.14.4'></a>
|
|
<hr>
|
|
<h3>7.12.14.4 [Divide and round to narrower type]</h3>
|
|
<a name='7.12.14.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float fdiv(double x, double y);
|
|
float fdivl(long double x, long double y);
|
|
double ddivl(long double x, long double y);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32divd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32divd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64divd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.4p2'></a>
|
|
<pre>2 These functions compute the quotient x ÷ y, rounded to the type of the function. They compute the
|
|
quotient (as if) to infinite precision and round once to the result format, according to the current
|
|
rounding mode. A range error occurs for some finite arguments. A domain error occurs for either
|
|
both arguments infinite or both arguments zero. A pole error occurs for a finite x and a zero y.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.4p3'></a>
|
|
<pre>3 These functions return the quotient x ÷ y, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.14.5'></a>
|
|
<hr>
|
|
<h3>7.12.14.5 [Fused multiply-add and round to narrower type]</h3>
|
|
<a name='7.12.14.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float ffma(double x, double y, double z);
|
|
float ffmal(long double x, long double y, long double z);
|
|
double dfmal(long double x, long double y, long double z);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32fmad64(_Decimal64 x, _Decimal64 y, _Decimal64 z);
|
|
_Decimal32 d32fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
_Decimal64 d64fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.5p2'></a>
|
|
<pre>2 These functions compute (x × y) + z, rounded to the type of the function. They compute (x × y) + z
|
|
(as if) to infinite precision and round once to the result format, according to the current rounding
|
|
mode. A range error occurs for some finite arguments. A domain error may occur for an infinite
|
|
argument.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.5p3'></a>
|
|
<pre>3 These functions return (x × y) + z, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.14.6'></a>
|
|
<hr>
|
|
<h3>7.12.14.6 [Square root rounded to narrower type]</h3>
|
|
<a name='7.12.14.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
float fsqrt(double x);
|
|
float fsqrtl(long double x);
|
|
double dsqrtl(long double x);
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32sqrtd64(_Decimal64 x);
|
|
_Decimal32 d32sqrtd128(_Decimal128 x);
|
|
_Decimal64 d64sqrtd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.6p2'></a>
|
|
<pre>2 These functions compute the square root of x, rounded to the type of the function. They compute the
|
|
square root (as if) to infinite precision and round once to the result format, according to the current
|
|
rounding mode. A range error occurs for some finite positive arguments. A domain error occurs if
|
|
the argument is less than zero.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.6p3'></a>
|
|
<pre>3 These functions return the nonnegative square root of x, rounded to the type of the function.
|
|
|
|
</pre>
|
|
<a name='7.12.15'></a>
|
|
<hr>
|
|
<h3>7.12.15 [Quantum and quantum exponent functions]</h3>
|
|
<a name='7.12.15.1'></a>
|
|
<hr>
|
|
<h3>7.12.15.1 [The quantizedN functions]</h3>
|
|
<a name='7.12.15.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 quantized32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 quantized64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 quantized128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.15.1p2'></a>
|
|
<pre>2 The quantizedN functions compute, if possible, a value with the numerical value of x and the
|
|
quantum exponent of y. If the quantum exponent is being increased, the value shall be correctly
|
|
rounded; if the result does not have the same value as x, the "inexact" floating-point exception shall
|
|
be raised. If the quantum exponent is being decreased and the significand of the result has more
|
|
digits than the type would allow, the result is NaN, the "invalid" floating-point exception is raised,
|
|
and a domain error occurs. If one or both operands are NaN the result is NaN. Otherwise if only one
|
|
operand is infinite, the result is NaN, the "invalid" floating-point exception is raised, and a domain
|
|
error occurs. If both operands are infinite, the result is DEC_INFINITY with the sign of x, converted
|
|
to the type of the function. The quantizedN functions do not raise the "overflow" and "underflow"
|
|
floating-point exceptions.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.15.1p3'></a>
|
|
<pre>3 The quantizedN functions return a value with the numerical value of x (except for any rounding)
|
|
and the quantum exponent of y.
|
|
|
|
</pre>
|
|
<a name='7.12.15.2'></a>
|
|
<hr>
|
|
<h3>7.12.15.2 [The samequantumdN functions]</h3>
|
|
<a name='7.12.15.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
bool samequantumd32(_Decimal32 x, _Decimal32 y);
|
|
bool samequantumd64(_Decimal64 x, _Decimal64 y);
|
|
bool samequantumd128(_Decimal128 x, _Decimal128 y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.15.2p2'></a>
|
|
<pre>2 The samequantumdN functions determine if the quantum exponents of x and y are the same. If both
|
|
x and y are NaN, or both infinite, they have the same quantum exponents; if exactly one operand
|
|
is infinite or exactly one operand is NaN, they do not have the same quantum exponents. The
|
|
samequantumdN functions raise no floating-point exception.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.15.2p3'></a>
|
|
<pre>3 The samequantumdN functions return nonzero (true) when x and y have the same quantum expo-
|
|
nents, zero (false) otherwise.
|
|
|
|
</pre>
|
|
<a name='7.12.15.3'></a>
|
|
<hr>
|
|
<h3>7.12.15.3 [The quantumdN functions]</h3>
|
|
<a name='7.12.15.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 quantumd32(_Decimal32 x);
|
|
_Decimal64 quantumd64(_Decimal64 x);
|
|
_Decimal128 quantumd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.15.3p2'></a>
|
|
<pre>2 The quantumdN functions compute the quantum (<a href='#5.2.4.2.3'>5.2.4.2.3</a>) of a finite argument. If x is infinite, the
|
|
result is +∞.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.15.3p3'></a>
|
|
<pre>3 The quantumdN functions return the quantum of x.
|
|
|
|
</pre>
|
|
<a name='7.12.15.4'></a>
|
|
<hr>
|
|
<h3>7.12.15.4 [The llquantexpdN functions]</h3>
|
|
<a name='7.12.15.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
long long int llquantexpd32(_Decimal32 x);
|
|
long long int llquantexpd64(_Decimal64 x);
|
|
long long int llquantexpd128(_Decimal128 x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.15.4p2'></a>
|
|
<pre>2 The llquantexpdN functions compute the quantum exponent (<a href='#5.2.4.2.3'>5.2.4.2.3</a>) of a finite argument. If x is
|
|
infinite or NaN, they compute LLONG_MIN, the "invalid" floating-point exception is raised, and a
|
|
domain error occurs.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.15.4p3'></a>
|
|
<pre>3 The llquantexpdN functions return the quantum exponent of x.
|
|
|
|
</pre>
|
|
<a name='7.12.16'></a>
|
|
<hr>
|
|
<h3>7.12.16 [Decimal re-encoding functions]</h3>
|
|
<a name='7.12.16p1'></a>
|
|
<pre>1 IEC 60559 specifies two different schemes to encode significands in the object representation of a
|
|
decimal floating-point object: one based on decimal encoding (which packs three decimal digits
|
|
into 10 bits), the other based on binary encoding (as a binary integer). An implementation may use
|
|
either of these encoding schemes for its decimal floating types. The re-encoding functions in this
|
|
subclause provide conversions between external decimal data with a given encoding scheme and
|
|
the implementation’s corresponding decimal floating type.
|
|
|
|
</pre>
|
|
<a name='7.12.16.1'></a>
|
|
<hr>
|
|
<h3>7.12.16.1 [The encodedecdN functions]</h3>
|
|
<a name='7.12.16.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
void encodedecd32(unsigned char encptr[restrict static 4],
|
|
const _Decimal32*restrict xptr);
|
|
void encodedecd64(unsigned char encptr[restrict static 8],
|
|
const _Decimal64*restrict xptr);
|
|
void encodedecd128(unsigned char encptr[restrict static 16],
|
|
const _Decimal128*restrict xptr);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.16.1p2'></a>
|
|
<pre>2 The encodedecdN functions convert *xptr into an IEC 60559 decimalN encoding in the encoding
|
|
scheme based on decimal encoding of the significand and store the resulting encoding as an N/8
|
|
element array, with 8 bits per array element, in the object pointed to by encptr. The order of bytes
|
|
in the array is implementation-defined. These functions preserve the value of *xptr and raise no
|
|
floating-point exceptions. If *xptr is non-canonical, these functions may or may not produce a
|
|
canonical encoding.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.16.1p3'></a>
|
|
<pre>3 The encodedecdN functions return no value.
|
|
|
|
</pre>
|
|
<a name='7.12.16.2'></a>
|
|
<hr>
|
|
<h3>7.12.16.2 [The decodedecdN functions]</h3>
|
|
<a name='7.12.16.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
void decodedecd32(_Decimal32 * restrict xptr,
|
|
const unsigned char encptr[restrict static 4]);
|
|
void decodedecd64(_Decimal64 * restrict xptr,
|
|
const unsigned char encptr[restrict static 8]);
|
|
void decodedecd128(_Decimal128 * restrict xptr,
|
|
const unsigned char encptr[restrict static 16]);
|
|
#endif
|
|
|
|
|
|
Description
|
|
15
|
|
</pre>
|
|
<a name='7.12.16.2p2'></a>
|
|
<pre>2 The decodedecdN functions interpret the N/8 element array pointed to by encptr as an IEC 60559
|
|
decimalN encoding, with 8 bits per array element, in the encoding scheme based on decimal
|
|
encoding of the significand. The order of bytes in the array is implementation-defined. These
|
|
functions convert the given encoding into a value of the decimal floating type, and store the result in
|
|
the object pointed to by xptr. These functions preserve the encoded value and raise no floating-point
|
|
exceptions. If the encoding is non-canonical, these functions may or may not produce a canonical
|
|
representation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.16.2p3'></a>
|
|
<pre>3 The decodedecdN functions return no value.
|
|
|
|
</pre>
|
|
<a name='7.12.16.3'></a>
|
|
<hr>
|
|
<h3>7.12.16.3 [The encodebindN functions]</h3>
|
|
<a name='7.12.16.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
void encodebind32(unsigned char encptr[restrict static 4],
|
|
const _Decimal32 * restrict xptr);
|
|
void encodebind64(unsigned char encptr[restrict static 8],
|
|
const _Decimal64 * restrict xptr);
|
|
void encodebind128(unsigned char encptr[restrict static 16],
|
|
const _Decimal128 * restrict xptr);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.16.3p2'></a>
|
|
<pre>2 The encodebindN functions convert *xptr into an IEC 60559 decimalN encoding in the encoding
|
|
scheme based on binary encoding of the significand and store the resulting encoding as an N/8
|
|
element array, with 8 bits per array element, in the object pointed to by encptr. The order of bytes
|
|
in the array is implementation-defined. These functions preserve the value of *xptr and raise no
|
|
floating-point exceptions. If *xptr is non-canonical, these functions may or may not produce a
|
|
canonical encoding.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.16.3p3'></a>
|
|
<pre>3 The encodebindN functions return no value.
|
|
|
|
</pre>
|
|
<a name='7.12.16.4'></a>
|
|
<hr>
|
|
<h3>7.12.16.4 [The decodebindN functions]</h3>
|
|
<a name='7.12.16.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
void decodebind32(_Decimal32 * restrict xptr,
|
|
const unsigned char encptr[restrict static 4]);
|
|
void decodebind64(_Decimal64 * restrict xptr,
|
|
const unsigned char encptr[restrict static 8]);
|
|
void decodebind128(_Decimal128 * restrict xptr,
|
|
const unsigned char encptr[restrict static 16]);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.16.4p2'></a>
|
|
<pre>2 The decodebindN functions interpret the N/8 element array pointed to by encptr as an IEC 60559
|
|
decimalN encoding, with 8 bits per array element, in the encoding scheme based on binary encoding
|
|
of the significand. The order of bytes in the array is implementation-defined. These functions convert
|
|
the given encoding into a value of decimal floating type, and store the result in the object pointed to
|
|
by xptr. These functions preserve the encoded value and raise no floating-point exceptions. If the
|
|
encoding is non-canonical, these functions may or may not produce a canonical representation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.16.4p3'></a>
|
|
<pre>3 The decodebindN functions return no value.
|
|
|
|
</pre>
|
|
<a name='7.12.17'></a>
|
|
<hr>
|
|
<h3>7.12.17 [Comparison macros]</h3>
|
|
<a name='7.12.17p1'></a>
|
|
<pre>1 The relational and equality operators support the usual mathematical relationships between numeric
|
|
values. For any ordered pair of numeric values exactly one of the relationships — less, greater, and
|
|
equal — is true. Relational operators may raise the "invalid" floating-point exception when argument
|
|
values are NaNs. For a NaN and a numeric value, or for two NaNs, just the unordered relationship
|
|
is true.<a href='#FOOTNOTE.302'><sup>[302]</sup></a> Subclauses <a href='#7.12.17.1'>7.12.17.1</a> through <a href='#7.12.17.6'>7.12.17.6</a> provide macros that are quiet versions of the
|
|
relational operators: the macros do not raise the "invalid" floating-point exception as an effect
|
|
of quiet NaN arguments. The comparison macros facilitate writing efficient code that accounts
|
|
for quiet NaNs without suffering the "invalid" floating-point exception. In the synopses in this
|
|
subclause, real-floating indicates that the argument shall be an expression of real floating type<a href='#FOOTNOTE.303'><sup>[303]</sup></a>
|
|
(both arguments need not have the same type).<a href='#FOOTNOTE.304'><sup>[304]</sup></a> If either argument has decimal floating type, the
|
|
other argument shall have decimal floating type as well.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.302'>
|
|
<pre><i><b>Footnote 302)</b> IEC 60559 requires that the built-in relational operators raise the "invalid" floating-point exception if the operands
|
|
compare unordered, as an error indicator for programs written without consideration of NaNs; the result in these cases is
|
|
false.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.303'>
|
|
<pre><i><b>Footnote 303)</b> If any argument is of integer type, or any other type that is not a real floating type, the behavior is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.304'>
|
|
<pre><i><b>Footnote 304)</b> Whether an argument represented in a format wider than its semantic type is converted to the semantic type is unspecified.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.17.1'></a>
|
|
<hr>
|
|
<h3>7.12.17.1 [The isgreater macro]</h3>
|
|
<a name='7.12.17.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isgreater(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.1p2'></a>
|
|
<pre>2 The isgreater macro determines whether its first argument is greater than its second argu-
|
|
ment. The value of isgreater(x,y) is always equal to (x)> (y) ; however, unlike (x)> (y) ,
|
|
isgreater(x,y) does not raise the "invalid" floating-point exception when x and y are unordered
|
|
and neither is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.1p3'></a>
|
|
<pre>3 The isgreater macro returns the value of (x)> (y) .
|
|
|
|
</pre>
|
|
<a name='7.12.17.2'></a>
|
|
<hr>
|
|
<h3>7.12.17.2 [The isgreaterequal macro]</h3>
|
|
<a name='7.12.17.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isgreaterequal(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.2p2'></a>
|
|
<pre>2 The isgreaterequal macro determines whether its first argument is greater than or equal to its
|
|
second argument. The value of isgreaterequal(x,y) is always equal to (x)>= (y) ; however,
|
|
unlike (x)>= (y) , isgreaterequal(x,y) does not raise the "invalid" floating-point exception
|
|
when x and y are unordered and neither is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.2p3'></a>
|
|
<pre>3 The isgreaterequal macro returns the value of (x)>= (y) .
|
|
|
|
</pre>
|
|
<a name='7.12.17.3'></a>
|
|
<hr>
|
|
<h3>7.12.17.3 [The isless macro]</h3>
|
|
<a name='7.12.17.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isless(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.3p2'></a>
|
|
<pre>2 The isless macro determines whether its first argument is less than its second argument. The value
|
|
of isless(x,y) is always equal to (x)< (y) ; however, unlike (x)< (y) , isless(x,y) does not
|
|
raise the "invalid" floating-point exception when x and y are unordered and neither is a signaling
|
|
NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.3p3'></a>
|
|
<pre>3 The isless macro returns the value of (x) < (y).
|
|
</pre>
|
|
<a name='7.12.17.4'></a>
|
|
<hr>
|
|
<h3>7.12.17.4 [The islessequal macro]</h3>
|
|
<a name='7.12.17.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int islessequal(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.4p2'></a>
|
|
<pre>2 The islessequal macro determines whether its first argument is less than or equal to its sec-
|
|
ond argument. The value of islessequal(x,y) is always equal to (x)<= (y) ; however, unlike
|
|
(x)<= (y) , islessequal(x,y) does not raise the "invalid" floating-point exception when x and y
|
|
are unordered and neither is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.4p3'></a>
|
|
<pre>3 The islessequal macro returns the value of (x)<= (y) .
|
|
|
|
</pre>
|
|
<a name='7.12.17.5'></a>
|
|
<hr>
|
|
<h3>7.12.17.5 [The islessgreater macro]</h3>
|
|
<a name='7.12.17.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int islessgreater(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.5p2'></a>
|
|
<pre>2 The islessgreater macro determines whether its first argument is less than or greater than its
|
|
second argument. The islessgreater(x,y) macro is similar to (x)< (y)|| (x)> (y) ; however,
|
|
islessgreater(x,y) does not raise the "invalid" floating-point exception when x and y are un-
|
|
ordered and neither is a signaling NaN (nor does it evaluate x and y twice).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.5p3'></a>
|
|
<pre>3 The islessgreater macro returns the value of (x)< (y)|| (x)> (y) .
|
|
|
|
</pre>
|
|
<a name='7.12.17.6'></a>
|
|
<hr>
|
|
<h3>7.12.17.6 [The isunordered macro]</h3>
|
|
<a name='7.12.17.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isunordered(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.6p2'></a>
|
|
<pre>2 The isunordered macro determines whether its arguments are unordered. It raises no floating-point
|
|
exceptions if neither argument is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.6p3'></a>
|
|
<pre>3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
|
|
|
|
</pre>
|
|
<a name='7.12.17.7'></a>
|
|
<hr>
|
|
<h3>7.12.17.7 [The iseqsig macro]</h3>
|
|
<a name='7.12.17.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int iseqsig(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.12.17.7p2'></a>
|
|
<pre>2 The iseqsig macro determines whether its arguments are equal. If an argument is a NaN, a domain
|
|
error occurs for the macro, as if a domain error occurred for a function (<a href='#7.12.1'>7.12.1</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.17.7p3'></a>
|
|
<pre>3 The iseqsig macro returns 1 if its arguments are equal and 0 otherwise.
|
|
</pre>
|
|
<a name='7.13'></a>
|
|
<hr>
|
|
<h3>7.13 [Non-local jumps <setjmp.h>]</h3>
|
|
<a name='7.13p1'></a>
|
|
<pre>1 The header <setjmp.h> defines the macro setjmp, and declares one function and one type, for
|
|
bypassing the normal function call and return discipline.<a href='#FOOTNOTE.305'><sup>[305]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.305'>
|
|
<pre><i><b>Footnote 305)</b> These functions are useful for dealing with unusual conditions encountered in a low-level function of a program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.13p2'></a>
|
|
<pre>2 The type declared is
|
|
|
|
jmp_buf
|
|
|
|
|
|
which is an array type suitable for holding the information needed to restore a calling environment.
|
|
The environment of a call to the setjmp macro consists of information sufficient for a call to the
|
|
longjmp function to return execution to the correct block and invocation of that block, were it called
|
|
recursively. It does not include the state of the floating-point status flags, of open files, or of any
|
|
other component of the abstract machine.
|
|
</pre>
|
|
<a name='7.13p3'></a>
|
|
<pre>3 It is unspecified whether setjmp is a macro or an identifier declared with external linkage. If a
|
|
macro definition is suppressed in order to access an actual function, or a program defines an external
|
|
identifier with the name setjmp, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='7.13.1'></a>
|
|
<hr>
|
|
<h3>7.13.1 [Save calling environment]</h3>
|
|
<a name='7.13.1.1'></a>
|
|
<hr>
|
|
<h3>7.13.1.1 [The setjmp macro]</h3>
|
|
<a name='7.13.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <setjmp.h>
|
|
int setjmp(jmp_buf env);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.13.1.1p2'></a>
|
|
<pre>2 The setjmp macro saves its calling environment in its jmp_buf argument for later use by the
|
|
longjmp function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.13.1.1p3'></a>
|
|
<pre>3 If the return is from a direct invocation, the setjmp macro returns the value zero. If the return is
|
|
from a call to the longjmp function, the setjmp macro returns a nonzero value.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.13.1.1p4'></a>
|
|
<pre>4 An invocation of the setjmp macro shall appear only in one of the following contexts:
|
|
|
|
— the entire controlling expression of a selection or iteration statement;
|
|
|
|
— one operand of a relational or equality operator with the other operand an integer constant
|
|
expression, with the resulting expression being the entire controlling expression of a selection
|
|
or iteration statement;
|
|
|
|
— the operand of a unary ! operator with the resulting expression being the entire controlling
|
|
expression of a selection or iteration statement; or
|
|
|
|
— the entire expression of an expression statement (possibly cast to void).
|
|
|
|
</pre>
|
|
<a name='7.13.1.1p5'></a>
|
|
<pre>5 If the invocation appears in any other context, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='7.13.2'></a>
|
|
<hr>
|
|
<h3>7.13.2 [Restore calling environment]</h3>
|
|
<a name='7.13.2.1'></a>
|
|
<hr>
|
|
<h3>7.13.2.1 [The longjmp function]</h3>
|
|
<a name='7.13.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <setjmp.h>
|
|
[[noreturn]] void longjmp(jmp_buf env, int val);
|
|
Description
|
|
</pre>
|
|
<a name='7.13.2.1p2'></a>
|
|
<pre>2 The longjmp function restores the environment saved by the most recent invocation of the setjmp
|
|
macro in the same invocation of the program with the corresponding jmp_buf argument. If there
|
|
has been no such invocation, or if the invocation was from another thread of execution, or if the
|
|
function containing the invocation of the setjmp macro has terminated execution<a href='#FOOTNOTE.306'><sup>[306]</sup></a> in the interim,
|
|
or if the invocation of the setjmp macro was within the scope of an identifier with variably modified
|
|
type and execution has left that scope in the interim, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.306'>
|
|
<pre><i><b>Footnote 306)</b> For example, by executing a return statement or because another longjmp call has caused a transfer to a setjmp
|
|
invocation in a function earlier in the set of nested calls.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.13.2.1p3'></a>
|
|
<pre>3 All accessible objects have values, and all other components of the abstract machine<a href='#FOOTNOTE.307'><sup>[307]</sup></a> have state,
|
|
as of the time the longjmp function was called, except that the representation of objects of automatic
|
|
storage duration that are local to the function containing the invocation of the corresponding
|
|
setjmp macro that do not have volatile-qualified type and have been changed between the setjmp
|
|
invocation and longjmp call is indeterminate.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.307'>
|
|
<pre><i><b>Footnote 307)</b> This includes, but is not limited to, the floating-point status flags and the state of open files.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.13.2.1p4'></a>
|
|
<pre>4 After longjmp is completed, thread execution continues as if the corresponding invocation of the
|
|
setjmp macro had just returned the value specified by val. The longjmp function cannot cause the
|
|
setjmp macro to return the value 0; if val is 0, the setjmp macro returns the value 1.
|
|
</pre>
|
|
<a name='7.13.2.1p5'></a>
|
|
<pre>5 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation might cause memory
|
|
associated with a variable length array object to be squandered.
|
|
|
|
#include <setjmp.h>
|
|
jmp_buf buf;
|
|
void g(int n);
|
|
void h(int n);
|
|
int n = 6;
|
|
|
|
void f(void)
|
|
{
|
|
int x[n]; // valid: f is not terminated
|
|
setjmp(buf);
|
|
g(n);
|
|
}
|
|
|
|
void g(int n)
|
|
{
|
|
int a[n]; // a may remain allocated
|
|
h(n);
|
|
}
|
|
|
|
void h(int n)
|
|
{
|
|
int b[n]; // b may remain allocated
|
|
longjmp(buf, 2); // might cause memory loss
|
|
}
|
|
</pre>
|
|
<a name='7.14'></a>
|
|
<hr>
|
|
<h3>7.14 [Signal handling <signal.h>]</h3>
|
|
<a name='7.14p1'></a>
|
|
<pre>1 The header <signal.h> declares a type and two functions and defines several macros, for handling
|
|
various signals (conditions that may be reported during program execution).
|
|
</pre>
|
|
<a name='7.14p2'></a>
|
|
<pre>2 The type defined is
|
|
|
|
sig_atomic_t
|
|
|
|
|
|
which is the (possibly volatile-qualified) integer type of an object that can be accessed as an atomic
|
|
entity, even in the presence of asynchronous interrupts.
|
|
</pre>
|
|
<a name='7.14p3'></a>
|
|
<pre>3 The macros defined are
|
|
|
|
SIG_DFL
|
|
SIG_ERR
|
|
SIG_IGN
|
|
|
|
|
|
which expand to constant expressions with distinct values that have type compatible with the second
|
|
argument to, and the return value of, the signal function, and whose values compare unequal to
|
|
the address of any declarable function; and the following, which expand to positive integer constant
|
|
expressions with type int and distinct values that are the signal numbers, each corresponding to
|
|
the specified condition:
|
|
|
|
SIGABRT abnormal termination, such as is initiated by the abort function
|
|
|
|
SIGFPE an erroneous arithmetic operation, such as zero divide or an operation resulting in
|
|
overflow
|
|
SIGILL detection of an invalid function image, such as an invalid instruction
|
|
SIGINT receipt of an interactive attention signal
|
|
SIGSEGV an invalid access to storage
|
|
|
|
SIGTERM a termination request sent to the program
|
|
|
|
</pre>
|
|
<a name='7.14p4'></a>
|
|
<pre>4 An implementation need not generate any of these signals, except as a result of explicit calls to the
|
|
raise function. Additional signals and pointers to undeclarable functions, with macro definitions
|
|
beginning, respectively, with the letters SIG and an uppercase letter or with SIG_ and an uppercase
|
|
letter,<a href='#FOOTNOTE.308'><sup>[308]</sup></a> may also be specified by the implementation. The complete set of signals, their semantics,
|
|
and their default handling is implementation-defined; all signal numbers shall be positive.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.308'>
|
|
<pre><i><b>Footnote 308)</b> See "future library directions" (<a href='#7.33.9'>7.33.9</a>). The names of the signal numbers reflect the following terms (respectively): abort,
|
|
floating-point exception, illegal instruction, interrupt, segmentation violation, and termination.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.14.1'></a>
|
|
<hr>
|
|
<h3>7.14.1 [Specify signal handling]</h3>
|
|
<a name='7.14.1.1'></a>
|
|
<hr>
|
|
<h3>7.14.1.1 [The signal function]</h3>
|
|
<a name='7.14.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <signal.h>
|
|
void (*signal(int sig, void (*func)(int)))(int);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.14.1.1p2'></a>
|
|
<pre>2 The signal function chooses one of three ways in which receipt of the signal number sig is to
|
|
be subsequently handled. If the value of func is SIG_DFL, default handling for that signal will
|
|
occur. If the value of func is SIG_IGN, the signal will be ignored. Otherwise, func shall point to a
|
|
function to be called when that signal occurs. An invocation of such a function because of a signal, or
|
|
(recursively) of any further functions called by that invocation (other than functions in the standard
|
|
library),<a href='#FOOTNOTE.309'><sup>[309]</sup></a> is called a signal handler.
|
|
</pre>
|
|
<a name='FOOTNOTE.309'>
|
|
<pre><i><b>Footnote 309)</b> This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler called via the abort
|
|
function).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.14.1.1p3'></a>
|
|
<pre>3 When a signal occurs and func points to a function, it is implementation-defined whether the equiva-
|
|
lent of signal(sig, SIG_DFL); is executed or the implementation prevents some implementation-
|
|
defined set of signals (at least including sig) from occurring until the current signal handling has
|
|
completed; in the case of SIGILL, the implementation may alternatively define that no action is taken.
|
|
Then the equivalent of (*func)(sig); is executed. If and when the function returns, if the value
|
|
of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined value corresponding to a
|
|
computational exception, the behavior is undefined; otherwise the program will resume execution
|
|
at the point it was interrupted.
|
|
</pre>
|
|
<a name='7.14.1.1p4'></a>
|
|
<pre>4 If the signal occurs as the result of calling the abort or raise function, the signal handler shall not
|
|
call the raise function.
|
|
</pre>
|
|
<a name='7.14.1.1p5'></a>
|
|
<pre>5 If the signal occurs other than as the result of calling the abort or raise function, the behavior is
|
|
undefined if the signal handler refers to any object with static or thread storage duration that is
|
|
not a lock-free atomic object other than by assigning a value to an object declared as volatile
|
|
sig_atomic_t, or the signal handler calls any function in the standard library other than
|
|
|
|
— the abort function,
|
|
— the _Exit function,
|
|
— the quick_exit function,
|
|
— the functions in <stdatomic.h> (except where explicitly stated otherwise) when the atomic
|
|
arguments are lock-free,
|
|
— the atomic_is_lock_free function with any atomic argument, or
|
|
— the signal function with the first argument equal to the signal number corresponding to the
|
|
signal that caused the invocation of the handler. Furthermore, if such a call to the signal
|
|
function results in a SIG_ERR return, the object designated by errno has an indeterminate
|
|
representation<a href='#FOOTNOTE.310'><sup>[310]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.310'>
|
|
<pre><i><b>Footnote 310)</b> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.14.1.1p6'></a>
|
|
<pre>6 At program startup, the equivalent of
|
|
|
|
signal(sig, SIG_IGN);
|
|
|
|
|
|
may be executed for some signals selected in an implementation-defined manner; the equivalent of
|
|
|
|
signal(sig, SIG_DFL);
|
|
|
|
|
|
is executed for all other signals defined by the implementation.
|
|
</pre>
|
|
<a name='7.14.1.1p7'></a>
|
|
<pre>7 Use of this function in a multi-threaded program results in undefined behavior. The implementation
|
|
shall behave as if no library function calls the signal function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.14.1.1p8'></a>
|
|
<pre>8 If the request can be honored, the signal function returns the value of func for the most recent
|
|
successful call to signal for the specified signal sig. Otherwise, a value of SIG_ERR is returned and
|
|
a positive value is stored in errno.
|
|
Forward references: the abort function (<a href='#7.24.4.1'>7.24.4.1</a>), the exit function (<a href='#7.24.4.4'>7.24.4.4</a>), the _Exit function
|
|
(<a href='#7.24.4.5'>7.24.4.5</a>), the quick_exit function (<a href='#7.24.4.7'>7.24.4.7</a>).
|
|
|
|
</pre>
|
|
<a name='7.14.2'></a>
|
|
<hr>
|
|
<h3>7.14.2 [Send signal]</h3>
|
|
<a name='7.14.2.1'></a>
|
|
<hr>
|
|
<h3>7.14.2.1 [The raise function]</h3>
|
|
<a name='7.14.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <signal.h>
|
|
int raise(int sig);
|
|
Description
|
|
</pre>
|
|
<a name='7.14.2.1p2'></a>
|
|
<pre>2 The raise function carries out the actions described in <a href='#7.14.1.1'>7.14.1.1</a> for the signal sig. If a signal handler
|
|
is called, the raise function shall not return until after the signal handler does.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.14.2.1p3'></a>
|
|
<pre>3 The raise function returns zero if successful, nonzero if unsuccessful.
|
|
</pre>
|
|
<a name='7.15'></a>
|
|
<hr>
|
|
<h3>7.15 [Alignment <stdalign.h>]</h3>
|
|
<a name='7.15p1'></a>
|
|
<pre>1 The header <stdalign.h> provides no content.
|
|
</pre>
|
|
<a name='7.16'></a>
|
|
<hr>
|
|
<h3>7.16 [Variable arguments <stdarg.h>]</h3>
|
|
<a name='7.16p1'></a>
|
|
<pre>1 The header <stdarg.h> declares a type and defines four macros, for advancing through a list of
|
|
arguments whose number and types are not known to the called function when it is translated.
|
|
</pre>
|
|
<a name='7.16p2'></a>
|
|
<pre>2 A function may be called with a variable number of arguments of varying types if its parameter
|
|
type list ends with an ellipsis.
|
|
</pre>
|
|
<a name='7.16p3'></a>
|
|
<pre>3 The type declared is
|
|
|
|
va_list
|
|
|
|
|
|
which is a complete object type suitable for holding information needed by the macros va_start,
|
|
va_arg, va_end, and va_copy . If access to the varying arguments is desired, the called function
|
|
shall declare an object (generally referred to as ap in this subclause) having type va_list. The object
|
|
ap may be passed as an argument to another function; if that function invokes the va_arg macro
|
|
with parameter ap, the representation of ap in the calling function is indeterminate and shall be
|
|
passed to the va_end macro prior to any further reference to ap<a href='#FOOTNOTE.311'><sup>[311]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.311'>
|
|
<pre><i><b>Footnote 311)</b> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which case the original
|
|
function can make further use of the original list after the other function returns.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.16.1'></a>
|
|
<hr>
|
|
<h3>7.16.1 [Variable argument list access macros]</h3>
|
|
<a name='7.16.1p1'></a>
|
|
<pre>1 The va_start and va_arg macros described in this subclause shall be implemented as macros,
|
|
not functions. It is unspecified whether va_copy and va_end are macros or identifiers declared
|
|
with external linkage. If a macro definition is suppressed in order to access an actual function,
|
|
or a program defines an external identifier with the same name, the behavior is undefined. Each
|
|
invocation of the va_start and va_copy macros shall be matched by a corresponding invocation of
|
|
the va_end macro in the same function.
|
|
|
|
</pre>
|
|
<a name='7.16.1.1'></a>
|
|
<hr>
|
|
<h3>7.16.1.1 [The va_arg macro]</h3>
|
|
<a name='7.16.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
type va_arg(va_list ap, type);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.16.1.1p2'></a>
|
|
<pre>2 The va_arg macro expands to an expression that has the specified type and the value of the next
|
|
argument in the call. The parameter ap shall have been initialized by the va_start or va_copy
|
|
macro (without an intervening invocation of the va_end macro for the same ap). Each invocation
|
|
of the va_arg macro modifies ap so that the values of successive arguments are returned in turn.
|
|
The behavior is undefined if there is no actual next argument. The parameter type shall be a type
|
|
name specified such that the type of a pointer to an object that has the specified type can be obtained
|
|
simply by postfixing a * to type. If type is not compatible with the type of the actual next argument
|
|
(as promoted according to the default argument promotions), the behavior is undefined, except for
|
|
the following cases:
|
|
|
|
|
|
— both types are pointers to qualified or unqualified versions of compatible types;
|
|
|
|
— one type is a signed integer type, the other type is the corresponding unsigned integer type,
|
|
and the value is representable in both types;
|
|
|
|
— one type is pointer to qualified or unqualified void and the other is a pointer to a qualified or
|
|
unqualified character type;
|
|
|
|
— or, the type of the next argument is nullptr_t and type is a pointer type that has the same
|
|
representation and alignment requirements as a pointer to a character type<a href='#FOOTNOTE.312'><sup>[312]</sup></a> .
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.312'>
|
|
<pre><i><b>Footnote 312)</b> Such types are in particular pointers to qualified or unqualified versions of void .
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.16.1.1p3'></a>
|
|
<pre>3 The first invocation of the va_arg macro after that of the va_start macro returns the value of
|
|
the first argument without an explicitly parameter, which matches the position of the ... in the
|
|
parameter list. Successive invocations return the values of the remaining arguments in succession.
|
|
</pre>
|
|
<a name='7.16.1.2'></a>
|
|
<hr>
|
|
<h3>7.16.1.2 [The va_copy macro]</h3>
|
|
<a name='7.16.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
void va_copy(va_list dest, va_list src);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.16.1.2p2'></a>
|
|
<pre>2 The va_copy macro initializes dest as a copy of src, as if the va_start macro had been applied
|
|
to dest followed by the same sequence of uses of the va_arg macro as had previously been used
|
|
to reach the present state of src. Neither the va_copy nor va_start macro shall be invoked to
|
|
reinitialize dest without an intervening invocation of the va_end macro for the same dest.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.16.1.2p3'></a>
|
|
<pre>3 The va_copy macro returns no value.
|
|
|
|
</pre>
|
|
<a name='7.16.1.3'></a>
|
|
<hr>
|
|
<h3>7.16.1.3 [The va_end macro]</h3>
|
|
<a name='7.16.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
void va_end(va_list ap);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.16.1.3p2'></a>
|
|
<pre>2 The va_end macro facilitates a normal return from the function whose variable argument list was
|
|
referred to by the expansion of the va_start macro, or the function containing the expansion of
|
|
the va_copy macro, that initialized the va_list ap. The va_end macro may modify ap so that it
|
|
is no longer usable (without being reinitialized by the va_start or va_copy macro). If there is no
|
|
corresponding invocation of the va_start or va_copy macro, or if the va_end macro is not invoked
|
|
before the return, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.16.1.3p3'></a>
|
|
<pre>3 The va_end macro returns no value.
|
|
|
|
</pre>
|
|
<a name='7.16.1.4'></a>
|
|
<hr>
|
|
<h3>7.16.1.4 [The va_start macro]</h3>
|
|
<a name='7.16.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
void va_start(va_list ap, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.16.1.4p2'></a>
|
|
<pre>2 The va_start macro shall be invoked before any access to the unnamed arguments.
|
|
</pre>
|
|
<a name='7.16.1.4p3'></a>
|
|
<pre>3 The va_start macro initializes ap for subsequent use by the va_arg and va_end macros. Neither the
|
|
va_start nor va_copy macro shall be invoked to reinitialize ap without an intervening invocation
|
|
of the va_end macro for the same ap.
|
|
</pre>
|
|
<a name='7.16.1.4p4'></a>
|
|
<pre>4 Only the first argument passed to va_start is evaluated. Any additional arguments are not used by
|
|
the macro and will not be expanded or evaluated for any reason.
|
|
</pre>
|
|
<a name='7.16.1.4p5'></a>
|
|
<pre>5 NOTE The macro allows additional arguments to be passed for va_start for compatibility with older versions of the library
|
|
only.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.16.1.4p6'></a>
|
|
<pre>6 The va_start macro returns no value.
|
|
</pre>
|
|
<a name='7.16.1.4p7'></a>
|
|
<pre>7 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not more than MAXARGS
|
|
arguments), then passes the array as a single argument to function f2. The number of pointers is specified by the first
|
|
argument to f1.
|
|
#include <stdarg.h>
|
|
#define MAXARGS 31
|
|
|
|
void f1(int n_ptrs, ...)
|
|
{
|
|
va_list ap;
|
|
char *array[MAXARGS];
|
|
int ptr_no = 0;
|
|
|
|
if (n_ptrs > MAXARGS)
|
|
n_ptrs = MAXARGS;
|
|
va_start(ap);
|
|
while (ptr_no < n_ptrs)
|
|
array[ptr_no++] = va_arg(ap, char *);
|
|
va_end(ap);
|
|
f2(n_ptrs, array);
|
|
}
|
|
|
|
Each call to f1 is required to have visible the definition of the function or a declaration such as
|
|
|
|
void f1(int, ...);
|
|
|
|
</pre>
|
|
<a name='7.16.1.4p8'></a>
|
|
<pre>8 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the indicated number of
|
|
arguments; after f2 has been called once with the whole list, the trailing part of the list is gathered again and passed to
|
|
function f4.
|
|
|
|
#include <stdarg.h>
|
|
#define MAXARGS 31
|
|
|
|
void f3(int n_ptrs, int f4_after, ...)
|
|
{
|
|
va_list ap, ap_save;
|
|
char *array[MAXARGS];
|
|
int ptr_no = 0;
|
|
if (n_ptrs > MAXARGS)
|
|
n_ptrs = MAXARGS;
|
|
_
|
|
va start(ap);
|
|
while (ptr_no < n_ptrs) {
|
|
array[ptr_no++] = va_arg(ap, char *);
|
|
if (ptr_no == f4_after)
|
|
va_copy(ap_save, ap);
|
|
}
|
|
va_end(ap);
|
|
f2(n_ptrs, array);
|
|
|
|
// Now process the saved copy.
|
|
|
|
n_ptrs -= f4_after;
|
|
ptr_no = 0;
|
|
while (ptr_no < n_ptrs)
|
|
array[ptr_no++] = va_arg(ap_save, char *);
|
|
va end(ap_save);
|
|
_
|
|
f4(n_ptrs, array);
|
|
}
|
|
|
|
</pre>
|
|
<a name='7.16.1.4p9'></a>
|
|
<pre>9 EXAMPLE 3 The function f5 is similar to f1, but instead of passing an explicit number of strings as the first argument, the
|
|
argument list is terminated with a null pointer.
|
|
|
|
#include <stdarg.h>
|
|
|
|
#define MAXARGS 31
|
|
void f5(...)
|
|
{
|
|
va_list ap;
|
|
char *array[MAXARGS];
|
|
int ptr_no = 0;
|
|
va_start(ap);
|
|
while (ptr_no < MAXARGS)
|
|
{
|
|
char *ptr = va_arg(ap, char *);
|
|
if (!ptr)
|
|
break;
|
|
array[ptr_no++] = ptr;
|
|
}
|
|
va_end(ap);
|
|
f6(ptr_no, array);
|
|
}
|
|
|
|
Each call to f5 is required to have visible the definition of the function or a declaration such as
|
|
|
|
void f5(...);
|
|
|
|
and implicitly requires the last argument to be a null pointer.
|
|
</pre>
|
|
<a name='7.17'></a>
|
|
<hr>
|
|
<h3>7.17 [Atomics <stdatomic.h>]</h3>
|
|
<a name='7.17.1'></a>
|
|
<hr>
|
|
<h3>7.17.1 [Introduction]</h3>
|
|
<a name='7.17.1p1'></a>
|
|
<pre>1 The header <stdatomic.h> defines several macros and declares several types and functions for
|
|
performing atomic operations on data shared between threads.<a href='#FOOTNOTE.313'><sup>[313]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.313'>
|
|
<pre><i><b>Footnote 313)</b> See "future library directions" (<a href='#7.33.10'>7.33.10</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.17.1p2'></a>
|
|
<pre>2 Implementations that define the macro __STDC_NO_ATOMICS__ need not provide this header nor
|
|
support any of its facilities.
|
|
</pre>
|
|
<a name='7.17.1p3'></a>
|
|
<pre>3 The macros defined are the atomic lock-free macros
|
|
|
|
ATOMIC_BOOL_LOCK_FREE
|
|
ATOMIC_CHAR_LOCK_FREE
|
|
ATOMIC_CHAR8_T_LOCK_FREE
|
|
ATOMIC_CHAR16_T_LOCK_FREE
|
|
ATOMIC_CHAR32_T_LOCK_FREE
|
|
ATOMIC_WCHAR_T_LOCK_FREE
|
|
ATOMIC_SHORT_LOCK_FREE
|
|
ATOMIC_INT_LOCK_FREE
|
|
ATOMIC_LONG_LOCK_FREE
|
|
ATOMIC_LLONG_LOCK_FREE
|
|
ATOMIC_POINTER_LOCK_FREE
|
|
|
|
|
|
which expand to constant expressions suitable for use in #if preprocessing directives and which
|
|
indicate the lock-free property of the corresponding atomic types (both signed and unsigned); and
|
|
|
|
ATOMIC_FLAG_INIT
|
|
|
|
|
|
which expands to an initializer for an object of type atomic_flag.
|
|
</pre>
|
|
<a name='7.17.1p4'></a>
|
|
<pre>4 The types include
|
|
|
|
memory_order
|
|
|
|
|
|
which is an enumerated type whose enumerators identify memory ordering constraints;
|
|
|
|
atomic_flag
|
|
|
|
|
|
which is a structure type representing a lock-free, primitive atomic flag; and several atomic analogs
|
|
of integer types.
|
|
</pre>
|
|
<a name='7.17.1p5'></a>
|
|
<pre>5 In the following synopses:
|
|
|
|
— An A refers to an atomic type.
|
|
|
|
— A C refers to its corresponding non-atomic type.
|
|
|
|
— An M refers to the type of the other argument for arithmetic operations. For atomic integer
|
|
types, M is C. For atomic pointer types, M is ptrdiff_t.
|
|
|
|
— The functions not ending in _explicit have the same semantics as the corresponding
|
|
_explicit function with memory_order_seq_cst for the memory_order argument.
|
|
|
|
|
|
</pre>
|
|
<a name='7.17.1p6'></a>
|
|
<pre>6 It is unspecified whether any generic function declared in <stdatomic.h> is a macro or an identifier
|
|
declared with external linkage. If a macro definition is suppressed in order to access an actual
|
|
function, or a program defines an external identifier with the name of a generic function, the
|
|
behavior is undefined.
|
|
</pre>
|
|
<a name='7.17.1p7'></a>
|
|
<pre>7 NOTE Many operations are volatile-qualified. The "volatile as device register" semantics have not changed in the standard.
|
|
This qualification means that volatility is preserved when applying these operations to volatile objects.
|
|
</pre>
|
|
<a name='7.17.2'></a>
|
|
<hr>
|
|
<h3>7.17.2 [Initialization]</h3>
|
|
<a name='7.17.2p1'></a>
|
|
<pre>1 An atomic object with automatic storage duration that is not initialized or such an object with
|
|
allocated storage duration initially has an indeterminate representation; equally, a non-atomic store
|
|
to any byte of the representation (either directly or, for example, by calls to memcpy or memset) makes
|
|
any atomic object have an indeterminate representation. Explicit or default initialization for atomic
|
|
objects with static or thread storage duration that do not have the type atomic_flag is guaranteed
|
|
to produce a valid state.<a href='#FOOTNOTE.314'><sup>[314]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.314'>
|
|
<pre><i><b>Footnote 314)</b> See "future library directions" (<a href='#7.33.10'>7.33.10</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.17.2p2'></a>
|
|
<pre>2 Concurrent access to an atomic object before it is set to a valid state, even via an atomic operation,
|
|
constitutes a data race. If a signal occurs other than as the result of calling the abort or raise
|
|
functions, the behavior is undefined if the signal handler reads or modifies an atomic object that has
|
|
an indeterminate representation.
|
|
</pre>
|
|
<a name='7.17.2p3'></a>
|
|
<pre>3 EXAMPLE The following definition ensure valid states for guide and head regardless if these are found in file scope or
|
|
block scope. Thus any atomic operation that is performed on them after their initialization has been met is well defined.
|
|
|
|
_Atomic int guide = 42;
|
|
static _Atomic(void*) head;
|
|
|
|
|
|
</pre>
|
|
<a name='7.17.2.1'></a>
|
|
<hr>
|
|
<h3>7.17.2.1 [The atomic_init generic function]</h3>
|
|
<a name='7.17.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_init(volatile A *obj, C value);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.2.1p2'></a>
|
|
<pre>2 The atomic_init generic function initializes the atomic object pointed to by obj to the value value,
|
|
while also initializing any additional state that the implementation might need to carry for the
|
|
atomic object. If the object has no declared type, after the call the effective type is the atomic type A.
|
|
</pre>
|
|
<a name='7.17.2.1p3'></a>
|
|
<pre>3 Although this function initializes an atomic object, it does not avoid data races; concurrent access to
|
|
the variable being initialized, even via an atomic operation, constitutes a data race.
|
|
</pre>
|
|
<a name='7.17.2.1p4'></a>
|
|
<pre>4 If a signal occurs other than as the result of calling the abort or raise functions, the behavior is
|
|
undefined if the signal handler calls the atomic_init generic function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.2.1p5'></a>
|
|
<pre>5 The atomic_init generic function returns no value.
|
|
</pre>
|
|
<a name='7.17.2.1p6'></a>
|
|
<pre>6 EXAMPLE
|
|
|
|
atomic_int guide;
|
|
atomic_init(&guide, 42);
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.17.3'></a>
|
|
<hr>
|
|
<h3>7.17.3 [Order and consistency]</h3>
|
|
<a name='7.17.3p1'></a>
|
|
<pre>1 The enumerated type memory_order specifies the detailed regular (non-atomic) memory synchro-
|
|
nization operations as defined in <a href='#5.1.2.4'>5.1.2.4</a> and may provide for operation ordering. Its enumeration
|
|
constants are as follows:<a href='#FOOTNOTE.315'><sup>[315]</sup></a>
|
|
|
|
memory_order_relaxed
|
|
memory_order_consume
|
|
memory_order_acquire
|
|
memory_order_release
|
|
memory_order_acq_rel
|
|
memory_order_seq_cst
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.315'>
|
|
<pre><i><b>Footnote 315)</b> See "future library directions" (<a href='#7.33.10'>7.33.10</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.17.3p2'></a>
|
|
<pre>2 For memory_order_relaxed, no operation orders memory.
|
|
</pre>
|
|
<a name='7.17.3p3'></a>
|
|
<pre>3 For memory_order_release, memory_order_acq_rel, and memory_order_seq_cst, a store opera-
|
|
tion performs a release operation on the affected memory location.
|
|
</pre>
|
|
<a name='7.17.3p4'></a>
|
|
<pre>4 For memory_order_acquire, memory_order_acq_rel, and memory_order_seq_cst, a load opera-
|
|
tion performs an acquire operation on the affected memory location.
|
|
</pre>
|
|
<a name='7.17.3p5'></a>
|
|
<pre>5 For memory_order_consume, a load operation performs a consume operation on the affected mem-
|
|
ory location.
|
|
</pre>
|
|
<a name='7.17.3p6'></a>
|
|
<pre>6 There shall be a single total order S on all memory_order_seq_cst operations, consistent with the
|
|
"happens before" order and modification orders for all affected locations, such that each
|
|
memory_order_seq_cst operation B that loads a value from an atomic object M observes one of
|
|
the following values:
|
|
|
|
— the result of the last modification A of M that precedes B in S, if it exists, or
|
|
— if A exists, the result of some modification of M that is not memory_order_seq_cst and that
|
|
does not happen before A, or
|
|
— if A does not exist, the result of some modification of M that is not memory_order_seq_cst.
|
|
|
|
</pre>
|
|
<a name='7.17.3p7'></a>
|
|
<pre>7 NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to an order that does
|
|
include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering.
|
|
</pre>
|
|
<a name='7.17.3p8'></a>
|
|
<pre>8 NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to memory ordering. Imple-
|
|
mentations still guarantee that any given atomic access to a particular atomic object is indivisible with respect to all other
|
|
atomic accesses to that object.
|
|
|
|
</pre>
|
|
<a name='7.17.3p9'></a>
|
|
<pre>9 For an atomic operation B that reads the value of an atomic object M , if there is a
|
|
memory_order_seq_cst fence X sequenced before B, then B observes either the last
|
|
memory_order_seq_cst modification of M preceding X in the total order S or a later mod-
|
|
ification of M in its modification order.
|
|
</pre>
|
|
<a name='7.17.3p10'></a>
|
|
<pre>10 For atomic operations A and B on an atomic object M , where A modifies M and B takes its value, if
|
|
there is a memory_order_seq_cst fence X such that A is sequenced before X and B follows X in S,
|
|
then B observes either the effects of A or a later modification of M in its modification order.
|
|
</pre>
|
|
<a name='7.17.3p11'></a>
|
|
<pre>11 For atomic modifications A and B of an atomic object M , B occurs later than A in the modification
|
|
order of M if:
|
|
|
|
— there is a memory_order_seq_cst fence X such that A is sequenced before X, and X precedes
|
|
B in S, or
|
|
— there is a memory_order_seq_cst fence Y such that Y is sequenced before B, and A precedes
|
|
Y in S, or
|
|
— there are memory_order_seq_cst fences X and Y such that A is sequenced before X, Y is
|
|
sequenced before B, and X precedes Y in S.
|
|
|
|
</pre>
|
|
<a name='7.17.3p12'></a>
|
|
<pre>12 Atomic read-modify-write operations shall always read the last value (in the modification order)
|
|
stored before the write associated with the read-modify-write operation.
|
|
</pre>
|
|
<a name='7.17.3p13'></a>
|
|
<pre>13 An atomic store shall only store a value that has been computed from constants and program input
|
|
values by a finite sequence of program evaluations, such that each evaluation observes the values of
|
|
variables as computed by the last prior assignment in the sequence. The ordering of evaluations in
|
|
this sequence shall be such that
|
|
|
|
— If an evaluation B observes a value computed by A in a different thread, then B does not
|
|
happen before A.
|
|
— If an evaluation A is included in the sequence, then all evaluations that assign to the same
|
|
variable and happen before A are also included.
|
|
|
|
</pre>
|
|
<a name='7.17.3p14'></a>
|
|
<pre>14 NOTE 3 The second requirement disallows "out-of-thin-air", or "speculative" stores of atomics when relaxed atomics are
|
|
used. Since unordered operations are involved, evaluations can appear in this sequence out of thread order. For example,
|
|
with x and y initially zero,
|
|
// Thread 1:
|
|
r1 = atomic_load_explicit(&y, memory_order_relaxed);
|
|
atomic_store_explicit(&x, r1, memory_order_relaxed);
|
|
|
|
// Thread 2:
|
|
r2 = atomic_load_explicit(&x, memory_order_relaxed);
|
|
atomic_store_explicit(&y, 42, memory_order_relaxed);
|
|
|
|
is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
|
|
|
|
atomic_store_explicit(&y, 42, memory_order_relaxed);
|
|
r1 = atomic_load_explicit(&y, memory_order_relaxed);
|
|
atomic_store_explicit(&x, r1, memory_order_relaxed);
|
|
r2 = atomic_load_explicit(&x, memory_order_relaxed);
|
|
|
|
On the other hand,
|
|
|
|
// Thread 1:
|
|
r1 = atomic_load_explicit(&y, memory_order_relaxed);
|
|
atomic_store_explicit(&x, r1, memory_order_relaxed);
|
|
|
|
// Thread 2:
|
|
r2 = atomic_load_explicit(&x, memory_order_relaxed);
|
|
atomic_store_explicit(&y, r2, memory_order_relaxed);
|
|
|
|
is not allowed to produce r1 == 42 && r2 == 42, since there is no sequence of evaluations that results in the computation
|
|
of 42. In the absence of "relaxed" operations and read-modify-write operations with weaker than memory_order_acq_rel
|
|
ordering, the second requirement has no impact.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.17.3p15'></a>
|
|
<pre>15 The requirements do not forbid r1 == 42 && r2 == 42 in the following example, with x and y
|
|
initially zero:
|
|
|
|
// Thread 1:
|
|
r1 = atomic_load_explicit(&x, memory_order_relaxed);
|
|
if (r1 == 42)
|
|
atomic_store_explicit(&y, r1, memory_order_relaxed);
|
|
|
|
// Thread 2:
|
|
r2 = atomic_load_explicit(&y, memory_order_relaxed);
|
|
if (r2 == 42)
|
|
atomic_store_explicit(&x, 42, memory_order_relaxed);
|
|
|
|
|
|
However, this is not useful behavior, and implementations should not allow it.
|
|
</pre>
|
|
<a name='7.17.3p16'></a>
|
|
<pre>16 Implementations should make atomic stores visible to atomic loads within a reasonable amount of
|
|
time.
|
|
|
|
</pre>
|
|
<a name='7.17.3.1'></a>
|
|
<hr>
|
|
<h3>7.17.3.1 [The kill_dependency macro]</h3>
|
|
<a name='7.17.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
type kill_dependency(type y);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.3.1p2'></a>
|
|
<pre>2 The kill_dependency macro terminates a dependency chain; the argument does not carry a depen-
|
|
dency to the return value.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.3.1p3'></a>
|
|
<pre>3 The kill_dependency macro returns the value of y.
|
|
</pre>
|
|
<a name='7.17.4'></a>
|
|
<hr>
|
|
<h3>7.17.4 [Fences]</h3>
|
|
<a name='7.17.4p1'></a>
|
|
<pre>1 This subclause introduces synchronization primitives called fences. Fences can have acquire seman-
|
|
tics, release semantics, or both. A fence with acquire semantics is called an acquire fence; a fence with
|
|
release semantics is called a release fence.
|
|
</pre>
|
|
<a name='7.17.4p2'></a>
|
|
<pre>2 A release fence A synchronizes with an acquire fence B if there exist atomic operations X and Y ,
|
|
both operating on some atomic object M , such that A is sequenced before X, X modifies M , Y is
|
|
sequenced before B, and Y reads the value written by X or a value written by any side effect in the
|
|
hypothetical release sequence X would head if it were a release operation.
|
|
</pre>
|
|
<a name='7.17.4p3'></a>
|
|
<pre>3 A release fence A synchronizes with an atomic operation B that performs an acquire operation on an
|
|
atomic object M if there exists an atomic operation X such that A is sequenced before X, X modifies
|
|
M , and B reads the value written by X or a value written by any side effect in the hypothetical
|
|
release sequence X would head if it were a release operation.
|
|
</pre>
|
|
<a name='7.17.4p4'></a>
|
|
<pre>4 An atomic operation A that is a release operation on an atomic object M synchronizes with an
|
|
acquire fence B if there exists some atomic operation X on M such that X is sequenced before B
|
|
and reads the value written by A or a value written by any side effect in the release sequence headed
|
|
by A.
|
|
|
|
</pre>
|
|
<a name='7.17.4.1'></a>
|
|
<hr>
|
|
<h3>7.17.4.1 [The atomic_thread_fence function]</h3>
|
|
<a name='7.17.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_thread_fence(memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.4.1p2'></a>
|
|
<pre>2 Depending on the value of order, this operation:
|
|
|
|
— has no effects, if order == memory_order_relaxed;
|
|
|
|
— is an acquire fence, if order == memory_order_acquire or order == memory_order_consume;
|
|
|
|
— is a release fence, if order == memory_order_release;
|
|
|
|
— is both an acquire fence and a release fence, if order == memory_order_acq_rel;
|
|
|
|
— is a sequentially consistent acquire and release fence, if order == memory_order_seq_cst.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.4.1p3'></a>
|
|
<pre>3 The atomic_thread_fence function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.17.4.2'></a>
|
|
<hr>
|
|
<h3>7.17.4.2 [The atomic_signal_fence function]</h3>
|
|
<a name='7.17.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_signal_fence(memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.4.2p2'></a>
|
|
<pre>2 Equivalent to atomic_thread_fence(order), except that the resulting ordering constraints are
|
|
established only between a thread and a signal handler executed in the same thread.
|
|
</pre>
|
|
<a name='7.17.4.2p3'></a>
|
|
<pre>3 NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions performed by the thread
|
|
become visible to the signal handler.
|
|
</pre>
|
|
<a name='7.17.4.2p4'></a>
|
|
<pre>4 NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with
|
|
atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would have inserted are not
|
|
emitted.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.4.2p5'></a>
|
|
<pre>5 The atomic_signal_fence function returns no value.
|
|
</pre>
|
|
<a name='7.17.5'></a>
|
|
<hr>
|
|
<h3>7.17.5 [Lock-free property]</h3>
|
|
<a name='7.17.5p1'></a>
|
|
<pre>1 The atomic lock-free macros indicate the lock-free property of integer and address atomic types. A
|
|
value of 0 indicates that the type is never lock-free; a value of 1 indicates that the type is sometimes
|
|
lock-free; a value of 2 indicates that the type is always lock-free.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.17.5p2'></a>
|
|
<pre>2 Operations that are lock-free should also be address-free. That is, atomic operations on the same
|
|
memory location via two different addresses will communicate atomically. The implementation
|
|
should not depend on any per-process state. This restriction enables communication via memory
|
|
mapped into a process more than once and memory shared between two processes.
|
|
|
|
</pre>
|
|
<a name='7.17.5.1'></a>
|
|
<hr>
|
|
<h3>7.17.5.1 [The atomic_is_lock_free generic function]</h3>
|
|
<a name='7.17.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
bool atomic_is_lock_free(const volatile A *obj);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.5.1p2'></a>
|
|
<pre>2 The atomic_is_lock_free generic function indicates whether or not atomic operations on objects
|
|
of the type pointed to by obj are lock-free.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.5.1p3'></a>
|
|
<pre>3 The atomic_is_lock_free generic function returns nonzero (true) if and only if atomic operations
|
|
on objects of the type pointed to by the argument are lock-free. In any given program execution, the
|
|
result of the lock-free query shall be consistent for all pointers of the same type.<a href='#FOOTNOTE.316'><sup>[316]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.316'>
|
|
<pre><i><b>Footnote 316)</b> obj can be a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.17.6'></a>
|
|
<hr>
|
|
<h3>7.17.6 [Atomic integer types]</h3>
|
|
<a name='7.17.6p1'></a>
|
|
<pre>1 For each line in the following table,<a href='#FOOTNOTE.317'><sup>[317]</sup></a> the atomic type name is declared as a type that has the same
|
|
representation and alignment requirements as the corresponding direct type.<a href='#FOOTNOTE.318'><sup>[318]</sup></a>
|
|
|
|
Atomic type name Direct type
|
|
atomic_bool _Atomic bool
|
|
atomic_char _Atomic char
|
|
atomic_schar _Atomic signed char
|
|
atomic_uchar _Atomic unsigned char
|
|
atomic_short _Atomic short
|
|
atomic_ushort _Atomic unsigned short
|
|
atomic_int _Atomic int
|
|
atomic_uint _Atomic unsigned int
|
|
atomic_long _Atomic long
|
|
atomic_ulong _Atomic unsigned long
|
|
atomic_llong _Atomic long long
|
|
atomic_ullong _Atomic unsigned long long
|
|
atomic_char8_t _Atomic char8_t
|
|
atomic_char16_t _Atomic char16_t
|
|
atomic_char32_t _Atomic char32_t
|
|
atomic_wchar_t _Atomic wchar_t
|
|
atomic_int_least8_t _Atomic int_least8_t
|
|
atomic_uint_least8_t _Atomic uint_least8_t
|
|
atomic_int_least16_t _Atomic int_least16_t
|
|
atomic_uint_least16_t _Atomic uint_least16_t
|
|
atomic_int_least32_t _Atomic int_least32_t
|
|
Atomic type name Direct type
|
|
atomic_uint_least32_t _Atomic uint_least32_t
|
|
atomic_int_least64_t _Atomic int_least64_t
|
|
atomic_uint_least64_t _Atomic uint_least64_t
|
|
atomic_int_fast8_t _Atomic int_fast8_t
|
|
atomic_uint_fast8_t _Atomic uint_fast8_t
|
|
atomic_int_fast16_t _Atomic int_fast16_t
|
|
atomic_uint_fast16_t _Atomic uint_fast16_t
|
|
atomic_int_fast32_t _Atomic int_fast32_t
|
|
atomic_uint_fast32_t _Atomic uint_fast32_t
|
|
atomic_int_fast64_t _Atomic int_fast64_t
|
|
atomic_uint_fast64_t _Atomic uint_fast64_t
|
|
atomic_intptr_t _Atomic intptr_t
|
|
atomic_uintptr_t _Atomic uintptr_t
|
|
atomic_size_t _Atomic size_t
|
|
atomic_ptrdiff_t _Atomic ptrdiff_t
|
|
atomic_intmax_t _Atomic intmax_t
|
|
atomic_uintmax_t _Atomic uintmax_t
|
|
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.317'>
|
|
<pre><i><b>Footnote 317)</b> See "future library directions" (<a href='#7.33.10'>7.33.10</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.318'>
|
|
<pre><i><b>Footnote 318)</b> The same representation and alignment requirements are meant to imply interchangeability as arguments to functions,
|
|
return values from functions, and members of unions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.17.6p2'></a>
|
|
<pre>2 The representation of an atomic integer type is not required to have the same size as the correspond-
|
|
ing regular type but it should have the same size whenever possible, as it eases effort required to
|
|
port existing code.
|
|
|
|
</pre>
|
|
<a name='7.17.7'></a>
|
|
<hr>
|
|
<h3>7.17.7 [Operations on atomic types]</h3>
|
|
<a name='7.17.7p1'></a>
|
|
<pre>1 There are only a few kinds of operations on atomic types, though there are many instances of those
|
|
kinds. This subclause specifies each general kind.
|
|
|
|
</pre>
|
|
<a name='7.17.7.1'></a>
|
|
<hr>
|
|
<h3>7.17.7.1 [The atomic_store generic functions]</h3>
|
|
<a name='7.17.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_store(volatile A *object, C desired);
|
|
void atomic_store_explicit(volatile A *object, C desired, memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.7.1p2'></a>
|
|
<pre>2 The order argument shall not be memory_order_acquire, memory_order_consume, nor
|
|
memory_order_acq_rel. Atomically replace the value pointed to by object with the value of
|
|
desired. Memory is affected according to the value of order.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.7.1p3'></a>
|
|
<pre>3 The atomic_store generic functions return no value.
|
|
|
|
</pre>
|
|
<a name='7.17.7.2'></a>
|
|
<hr>
|
|
<h3>7.17.7.2 [The atomic_load generic functions]</h3>
|
|
<a name='7.17.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
C atomic_load(const volatile A *object);
|
|
C atomic_load_explicit(const volatile A *object, memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.7.2p2'></a>
|
|
<pre>2 The order argument shall not be memory_order_release nor memory_order_acq_rel. Memory is
|
|
affected according to the value of order.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.7.2p3'></a>
|
|
<pre>3 Atomically returns the value pointed to by object.
|
|
</pre>
|
|
<a name='7.17.7.3'></a>
|
|
<hr>
|
|
<h3>7.17.7.3 [The atomic_exchange generic functions]</h3>
|
|
<a name='7.17.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
C atomic_exchange(volatile A *object, C desired);
|
|
C atomic_exchange_explicit(volatile A *object, C desired, memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.7.3p2'></a>
|
|
<pre>2 Atomically replace the value pointed to by object with desired. Memory is affected according to
|
|
the value of order. These operations are read-modify-write operations (<a href='#5.1.2.4'>5.1.2.4</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.7.3p3'></a>
|
|
<pre>3 Atomically returns the value pointed to by object immediately before the effects.
|
|
|
|
</pre>
|
|
<a name='7.17.7.4'></a>
|
|
<hr>
|
|
<h3>7.17.7.4 [The atomic_compare_exchange generic functions]</h3>
|
|
<a name='7.17.7.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
bool atomic_compare_exchange_strong(volatile A *object, C *expected, C desired);
|
|
bool atomic_compare_exchange_strong_explicit(volatile A *object, C *expected,
|
|
C desired, memory_order success, memory_order failure);
|
|
bool atomic_compare_exchange_weak(volatile A *object, C *expected, C desired);
|
|
bool atomic_compare_exchange_weak_explicit(volatile A *object, C *expected,
|
|
C desired, memory_order success, memory_order failure);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.7.4p2'></a>
|
|
<pre>2 The failure argument shall not be memory_order_release nor memory_order_acq_rel. The
|
|
failure argument shall be no stronger than the success argument.
|
|
</pre>
|
|
<a name='7.17.7.4p3'></a>
|
|
<pre>3 Atomically, compares the contents of the memory pointed to by object for equality with that
|
|
pointed to by expected, and if true, replaces the contents of the memory pointed to by object
|
|
with desired, and if false, updates the contents of the memory pointed to by expected with that
|
|
pointed to by object. Further, if the comparison is true, memory is affected according to the value
|
|
of success, and if the comparison is false, memory is affected according to the value of failure.
|
|
These operations are atomic read-modify-write operations (<a href='#5.1.2.4'>5.1.2.4</a>).
|
|
</pre>
|
|
<a name='7.17.7.4p4'></a>
|
|
<pre>4 NOTE 1 For example, the effect of atomic_compare_exchange_strong is
|
|
|
|
if (memcmp(object, expected, sizeof (*object)) == 0)
|
|
memcpy(object, &desired, sizeof (*object));
|
|
else
|
|
memcpy(expected, object, sizeof (*object));
|
|
|
|
|
|
</pre>
|
|
<a name='7.17.7.4p5'></a>
|
|
<pre>5 A weak compare-and-exchange operation may fail spuriously. That is, even when the contents
|
|
of memory referred to by expected and object are equal, it may return zero and store back to
|
|
expected the same memory contents that were originally there.
|
|
</pre>
|
|
<a name='7.17.7.4p6'></a>
|
|
<pre>6 NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of machines, e.g.
|
|
load-locked store-conditional machines.
|
|
</pre>
|
|
<a name='7.17.7.4p7'></a>
|
|
<pre>7 EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will be in a loop.
|
|
|
|
exp = atomic_load(&cur);
|
|
do {
|
|
des = function(exp);
|
|
} while (!atomic_compare_exchange_weak(&cur, &exp, des));
|
|
|
|
When a compare-and-exchange is in a loop, the weak version will yield better performance on some platforms. When a weak
|
|
compare-and-exchange would require a loop and a strong one would not, the strong one is preferable.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.7.4p8'></a>
|
|
<pre>8 The result of the comparison.
|
|
|
|
</pre>
|
|
<a name='7.17.7.5'></a>
|
|
<hr>
|
|
<h3>7.17.7.5 [The atomic_fetch and modify generic functions]</h3>
|
|
<a name='7.17.7.5p1'></a>
|
|
<pre>1 The following operations perform arithmetic and bitwise computations. All of these operations
|
|
are applicable to an object of any atomic integer type. None of these operations is applicable to
|
|
atomic_bool. The key, operator, and computation correspondence is:
|
|
|
|
|
|
key op computation
|
|
add + addition
|
|
sub - subtraction
|
|
or | bitwise inclusive or
|
|
xor ^ bitwise exclusive or
|
|
and & bitwise and
|
|
|
|
Synopsis
|
|
</pre>
|
|
<a name='7.17.7.5p2'></a>
|
|
<pre>2 #include <stdatomic.h>
|
|
C atomic_fetch_key(volatile A *object, M operand);
|
|
C atomic_fetch_key_explicit(volatile A *object, M operand, memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.7.5p3'></a>
|
|
<pre>3 Atomically replaces the value pointed to by object with the result of the computation applied to
|
|
the value pointed to by object and the given operand. Memory is affected according to the value
|
|
of order. These operations are atomic read-modify-write operations (<a href='#5.1.2.4'>5.1.2.4</a>). For signed integer
|
|
types, arithmetic performs silent wraparound on integer overflow; there are no undefined results.
|
|
For address types, the result may be an undefined address, but the operations otherwise have no
|
|
undefined behavior.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.7.5p4'></a>
|
|
<pre>4 Atomically, the value pointed to by object immediately before the effects.
|
|
</pre>
|
|
<a name='7.17.7.5p5'></a>
|
|
<pre>5 NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the operation of the
|
|
corresponding op= compound assignment operators. The only differences are that the compound assignment operators are
|
|
not guaranteed to operate atomically, and the value yielded by a compound assignment operator is the updated value of the
|
|
object, whereas the value returned by the atomic_fetch and modify generic functions is the previous value of the atomic
|
|
object.
|
|
|
|
</pre>
|
|
<a name='7.17.8'></a>
|
|
<hr>
|
|
<h3>7.17.8 [Atomic flag type and operations]</h3>
|
|
<a name='7.17.8p1'></a>
|
|
<pre>1 The atomic_flag type provides the classic test-and-set functionality. It has two states, set and clear.
|
|
</pre>
|
|
<a name='7.17.8p2'></a>
|
|
<pre>2 Operations on an object of type atomic_flag shall be lock free.
|
|
</pre>
|
|
<a name='7.17.8p3'></a>
|
|
<pre>3 NOTE Hence, as per <a href='#7.17.5'>7.17.5</a>, the operations should also be address-free. No other type requires lock-free operations, so the
|
|
atomic_flag type is the minimum hardware-implemented type needed to conform to this document. The remaining types
|
|
can be emulated with atomic_flag, though with less than ideal properties.
|
|
|
|
</pre>
|
|
<a name='7.17.8p4'></a>
|
|
<pre>4 The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the clear state. An
|
|
atomic_flag that is not explicitly initialized with ATOMIC_FLAG_INIT has initially an indeterminate
|
|
representation.
|
|
</pre>
|
|
<a name='7.17.8p5'></a>
|
|
<pre>5 EXAMPLE
|
|
atomic_flag guard = ATOMIC_FLAG_INIT;
|
|
|
|
|
|
</pre>
|
|
<a name='7.17.8.1'></a>
|
|
<hr>
|
|
<h3>7.17.8.1 [The atomic_flag_test_and_set functions]</h3>
|
|
<a name='7.17.8.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
bool atomic_flag_test_and_set(volatile atomic_flag *object);
|
|
bool atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
|
|
memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.8.1p2'></a>
|
|
<pre>2 Atomically places the atomic flag pointed to by object in the set state and returns the value
|
|
corresponding to the immediately preceding state. Memory is affected according to the value of
|
|
order. These operations are atomic read-modify-write operations (<a href='#5.1.2.4'>5.1.2.4</a>).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.8.1p3'></a>
|
|
<pre>3 The atomic_flag_test_and_set functions return the value that corresponds to the state of the
|
|
atomic flag immediately before the effects. The return value true corresponds to the set state and the
|
|
return value false corresponds to the clear state.
|
|
|
|
</pre>
|
|
<a name='7.17.8.2'></a>
|
|
<hr>
|
|
<h3>7.17.8.2 [The atomic_flag_clear functions]</h3>
|
|
<a name='7.17.8.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_flag_clear(volatile atomic_flag *object);
|
|
void atomic_flag_clear_explicit(volatile atomic_flag *object,
|
|
memory_order order);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.17.8.2p2'></a>
|
|
<pre>2 The order argument shall not be memory_order_acquire nor memory_order_acq_rel. Atomically
|
|
places the atomic flag pointed to by object into the clear state. Memory is affected according to the
|
|
value of order.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.8.2p3'></a>
|
|
<pre>3 The atomic_flag_clear functions return no value.
|
|
</pre>
|
|
<a name='7.18'></a>
|
|
<hr>
|
|
<h3>7.18 [Bit and byte utilities <stdbit.h>]</h3>
|
|
<a name='7.18.1'></a>
|
|
<hr>
|
|
<h3>7.18.1 [General]</h3>
|
|
<a name='7.18.1p1'></a>
|
|
<pre>1 The header <stdbit.h> defines the following macros, types, and functions, to work with the byte
|
|
and bit representation of many types, typically integer types. This header makes available the
|
|
size_t type name (<a href='#7.21'>7.21</a>) and any uintN_t, intN_t, uint_leastN_t, or int_leastN_t type names
|
|
defined by the implementation (<a href='#7.22'>7.22</a>).
|
|
</pre>
|
|
<a name='7.18.1p2'></a>
|
|
<pre>2 The most significant index is the 0-based index counting from the most significant bit, 0, to the
|
|
least significant bit, w − 1, where w is the width of the type that is having its most significant index
|
|
computed.
|
|
</pre>
|
|
<a name='7.18.1p3'></a>
|
|
<pre>3 The least significant index is the 0-based index counting from the least significant bit, 0, to the
|
|
most significant bit, w − 1, where w is the width of the type that is having its least significant index
|
|
computed.
|
|
</pre>
|
|
<a name='7.18.1p4'></a>
|
|
<pre>4 It is unspecified whether any generic function declared in <stdbit.h> is a macro or an identifier
|
|
declared with external linkage. If a macro definition is suppressed in order to access an actual
|
|
function, or a program defines an external identifier with the name of a generic function, the
|
|
behavior is unspecified.
|
|
|
|
</pre>
|
|
<a name='7.18.2'></a>
|
|
<hr>
|
|
<h3>7.18.2 [Endian]</h3>
|
|
<a name='7.18.2p1'></a>
|
|
<pre>1 Two common methods of byte ordering in multi-byte scalar types are little-endian and big-endian.
|
|
Little-endian is a format for storage of binary data in which the least significant byte is placed
|
|
first, with the rest in ascending order. Or, that the least significant byte is stored at the smallest
|
|
memory address. Big-endian is a format for storage or transmission of binary data in which the
|
|
most significant byte is placed first, with the rest in descending order. Or, that the most significant
|
|
byte is stored at the smallest memory address. Other byte orderings are also possible.
|
|
</pre>
|
|
<a name='7.18.2p2'></a>
|
|
<pre>2 The macros are:
|
|
__STDC_ENDIAN_LITTLE__
|
|
|
|
|
|
which represents a method of byte order storage least significant byte is placed first and the rest are
|
|
in ascending order, and is an integer constant expression;
|
|
__STDC_ENDIAN_BIG__
|
|
|
|
|
|
which represents a method of byte order storage most significant byte is placed first and the rest are
|
|
in descending order, and is an integer constant expression;
|
|
__STDC_ENDIAN_NATIVE__ /* see below */
|
|
|
|
|
|
which represents the method of byte order storage for the execution environment and is an integer
|
|
constant expression.
|
|
</pre>
|
|
<a name='7.18.2p3'></a>
|
|
<pre>3 __STDC_ENDIAN_NATIVE__ shall expand to an integer constant expression whose value is equiv-
|
|
alent to the value of __STDC_ENDIAN_LITTLE__ if the execution environment is little-endian.
|
|
Otherwise, __STDC_ENDIAN_NATIVE__ shall expand to an integer constant expression whose
|
|
value is equivalent to the value of __STDC_ENDIAN_BIG__ if the execution environment is big-
|
|
endian. If __STDC_ENDIAN_NATIVE__ is not equivalent to either, then the byte order for the exe-
|
|
cution environment is implementation-defined. The value of the integer constant expression for
|
|
__STDC_ENDIAN_LITTLE__ and __STDC_ENDIAN_BIG__ are not equal.
|
|
|
|
</pre>
|
|
<a name='7.18.3'></a>
|
|
<hr>
|
|
<h3>7.18.3 [Count Leading Zeros]</h3>
|
|
<a name='7.18.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_leading_zerosuc(unsigned char value);
|
|
int stdc_leading_zerosus(unsigned short value);
|
|
int stdc_leading_zerosui(unsigned int value);
|
|
int stdc_leading_zerosul(unsigned long value);
|
|
int stdc_leading_zerosull(unsigned long long value);
|
|
generic_return_type stdc_leading_zeros(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the number of consecutive 0 bits in value, starting from the most significant bit.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.4'></a>
|
|
<hr>
|
|
<h3>7.18.4 [Count Leading Ones]</h3>
|
|
<a name='7.18.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_leading_onesuc(unsigned char value);
|
|
int stdc_leading_onesus(unsigned short value);
|
|
int stdc_leading_onesui(unsigned int value);
|
|
int stdc_leading_onesul(unsigned long value);
|
|
int stdc_leading_onesull(unsigned long long value);
|
|
generic_return_type stdc_leading_ones(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the number of consecutive 1 bits in value, starting from the most significant bit.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.5'></a>
|
|
<hr>
|
|
<h3>7.18.5 [Count Trailing Zeros]</h3>
|
|
<a name='7.18.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_trailing_zerosuc(unsigned char value);
|
|
int stdc_trailing_zerosus(unsigned short value);
|
|
int stdc_trailing_zerosui(unsigned int value);
|
|
int stdc_trailing_zerosul(unsigned long value);
|
|
int stdc_trailing_zerosull(unsigned long long value);
|
|
generic_return_type stdc_trailing_zeros(generic_value_type value);
|
|
Returns
|
|
Returns the number of consecutive 0 bits in value, starting from the least significant bit.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.6'></a>
|
|
<hr>
|
|
<h3>7.18.6 [Count Trailing Ones]</h3>
|
|
<a name='7.18.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_trailing_onesuc(unsigned char value);
|
|
int stdc_trailing_onesus(unsigned short value);
|
|
int stdc_trailing_onesui(unsigned int value);
|
|
int stdc_trailing_onesul(unsigned long value);
|
|
int stdc_trailing_onesull(unsigned long long value);
|
|
generic_return_type stdc_trailing_ones(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the number of consecutive 1 bits in value, starting from the least significant bit.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.7'></a>
|
|
<hr>
|
|
<h3>7.18.7 [First Leading Zero]</h3>
|
|
<a name='7.18.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_first_leading_zerouc(unsigned char value);
|
|
int stdc_first_leading_zerous(unsigned short value);
|
|
int stdc_first_leading_zeroui(unsigned int value);
|
|
int stdc_first_leading_zeroul(unsigned long value);
|
|
int stdc_first_leading_zeroull(unsigned long long value);
|
|
generic_return_type stdc_first_leading_zero(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the most significant index of the first 0 bit in value, plus 1. If it is not found, this function
|
|
returns 0.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.8'></a>
|
|
<hr>
|
|
<h3>7.18.8 [First Leading One]</h3>
|
|
<a name='7.18.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_first_leading_oneuc(unsigned char value);
|
|
int stdc_first_leading_oneus(unsigned short value);
|
|
int stdc_first_leading_oneui(unsigned int value);
|
|
int stdc_first_leading_oneul(unsigned long value);
|
|
int stdc_first_leading_oneull(unsigned long long value);
|
|
generic_return_type stdc_first_leading_one(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the most significant index of the first 1 bit in value, plus 1. If it is not found, this function
|
|
returns 0.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.9'></a>
|
|
<hr>
|
|
<h3>7.18.9 [First Trailing Zero]</h3>
|
|
<a name='7.18.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_first_trailing_zerouc(unsigned char value);
|
|
int stdc_first_trailing_zerous(unsigned short value);
|
|
int stdc_first_trailing_zeroui(unsigned int value);
|
|
int stdc_first_trailing_zeroul(unsigned long value);
|
|
int stdc_first_trailing_zeroull(unsigned long long value);
|
|
generic_return_type stdc_first_trailing_zero(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the least significant index of the first 0 bit in value, plus 1. If it is not found, this function
|
|
returns 0.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.10'></a>
|
|
<hr>
|
|
<h3>7.18.10 [First Trailing One]</h3>
|
|
<a name='7.18.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_first_trailing_oneuc(unsigned char value);
|
|
int stdc_first_trailing_oneus(unsigned short value);
|
|
int stdc_first_trailing_oneui(unsigned int value);
|
|
int stdc_first_trailing_oneul(unsigned long value);
|
|
int stdc_first_trailing_oneull(unsigned long long value);
|
|
generic_return_type stdc_first_trailing_one(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the least significant index of the first 1 bit in value, plus 1. If it is not found, this function
|
|
returns 0.
|
|
The type-generic function (marked by its generic_value_type argument) returns the appropriate
|
|
value based on the type of the input value, so long as it is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.11'></a>
|
|
<hr>
|
|
<h3>7.18.11 [Count Ones]</h3>
|
|
<a name='7.18.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_count_onesuc(unsigned char value);
|
|
int stdc_count_onesus(unsigned short value);
|
|
int stdc_count_onesui(unsigned int value);
|
|
int stdc_count_onesul(unsigned long value);
|
|
int stdc_count_onesull(unsigned long long value);
|
|
generic_return_type stdc_count_ones(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the total number of 1 bits within the given value.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type shall be a suitably large signed integer type capable of representing
|
|
the computed result.
|
|
</pre>
|
|
<a name='7.18.12'></a>
|
|
<hr>
|
|
<h3>7.18.12 [Count Zeros]</h3>
|
|
<a name='7.18.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_count_zerosuc(unsigned char value);
|
|
int stdc_count_zerosus(unsigned short value);
|
|
int stdc_count_zerosui(unsigned int value);
|
|
int stdc_count_zerosul(unsigned long value);
|
|
int stdc_count_zerosull(unsigned long long value);
|
|
generic_return_type stdc_count_zeros(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
Returns the total number of 0 bits within the given value.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type for the type-generic function need not be the same as the type of
|
|
value. It shall be suitably large unsigned integer type capable of representing the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.13'></a>
|
|
<hr>
|
|
<h3>7.18.13 [Single-bit Check]</h3>
|
|
<a name='7.18.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
bool stdc_has_single_bituc(unsigned char value);
|
|
bool stdc_has_single_bitus(unsigned short value);
|
|
bool stdc_has_single_bitui(unsigned int value);
|
|
bool stdc_has_single_bitul(unsigned long value);
|
|
bool stdc_has_single_bitull(unsigned long long value);
|
|
bool stdc_has_single_bit(generic_value_type value);
|
|
|
|
|
|
Returns
|
|
The stdc_has_single_bit functions returns true if and only if there is a single 1 bit in value.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
</pre>
|
|
<a name='7.18.14'></a>
|
|
<hr>
|
|
<h3>7.18.14 [Bit Width]</h3>
|
|
<a name='7.18.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
int stdc_bit_widthuc(unsigned char value);
|
|
int stdc_bit_widthus(unsigned short value);
|
|
int stdc_bit_widthui(unsigned int value);
|
|
int stdc_bit_widthul(unsigned long value);
|
|
int stdc_bit_widthull(unsigned long long value);
|
|
generic_return_type stdc_bit_width(generic_value_type value);
|
|
Description
|
|
The stdc_bit_width functions compute the smallest number of bits needed to store value.
|
|
|
|
Returns
|
|
The stdc_bit_width functions return 0 if value is 0. Otherwise, they return 1 + ⌊log2(value)⌋.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
The generic_return_type type for the type-generic function need not be the same as the type of
|
|
value. It shall be suitably large signed integer type capable of representing the computed result.
|
|
|
|
</pre>
|
|
<a name='7.18.15'></a>
|
|
<hr>
|
|
<h3>7.18.15 [Bit Floor]</h3>
|
|
<a name='7.18.15p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
unsigned char stdc_bit_flooruc(unsigned char value);
|
|
unsigned short stdc_bit_floorus(unsigned short value);
|
|
unsigned int stdc_bit_floorui(unsigned int value);
|
|
unsigned long stdc_bit_floorul(unsigned long value);
|
|
unsigned long long stdc_bit_floorull(unsigned long long value);
|
|
generic_value_type stdc_bit_floor(generic_value_type value);
|
|
|
|
|
|
Description
|
|
The stdc_bit_floor functions compute the largest integral power of 2 that is not greater than
|
|
value.
|
|
|
|
Returns
|
|
The stdc_bit_floor functions return 0 if value is 0. Otherwise, they return the largest integral
|
|
power of 2 that is not greater than value.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
|
|
</pre>
|
|
<a name='7.18.16'></a>
|
|
<hr>
|
|
<h3>7.18.16 [Bit Ceiling]</h3>
|
|
<a name='7.18.16p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdbit.h>
|
|
unsigned char stdc_bit_ceiluc(unsigned char value);
|
|
unsigned short stdc_bit_ceilus(unsigned short value);
|
|
unsigned int stdc_bit_ceilui(unsigned int value);
|
|
unsigned long stdc_bit_ceilul(unsigned long value);
|
|
unsigned long long stdc_bit_ceilull(unsigned long long value);
|
|
generic_value_type stdc_bit_ceil(generic_value_type value);
|
|
Description
|
|
The stdc_bit_ceil functions compute the smallest integral power of 2 that is not less than value.
|
|
If the computation does not fit in the given return type, the behavior is undefined.
|
|
|
|
Returns
|
|
The stdc_bit_ceil functions return the smallest integral power of 2 that is not less than value.
|
|
The type-generic function (marked by its generic_value_type argument) returns the previously
|
|
described result for a given input value so long as the generic_value_type is an:
|
|
|
|
— standard unsigned integer type, excluding bool;
|
|
— extended unsigned integer type;
|
|
|
|
— or, bit-precise unsigned integer type whose width matches a standard or extended integer
|
|
type, excluding bool.
|
|
</pre>
|
|
<a name='7.19'></a>
|
|
<hr>
|
|
<h3>7.19 [Boolean type and values <stdbool.h>]</h3>
|
|
<a name='7.19p1'></a>
|
|
<pre>1 The header <stdbool.h> provides the obsolescent macro __bool_true_false_are_defined which
|
|
expands to the integer constant 1.
|
|
</pre>
|
|
<a name='7.20'></a>
|
|
<hr>
|
|
<h3>7.20 [Checked Integer Arithmetic <stdckdint.h>]</h3>
|
|
<a name='7.20p1'></a>
|
|
<pre>1 The header <stdckdint.h> defines several macros for performing checked integer arithmetic.
|
|
|
|
</pre>
|
|
<a name='7.20.1'></a>
|
|
<hr>
|
|
<h3>7.20.1 [The ckd_ Checked Integer Operation Macros]</h3>
|
|
<a name='7.20.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdckdint.h>
|
|
bool ckd_add(type1 *result, type2 a, type3 b);
|
|
bool ckd_sub(type1 *result, type2 a, type3 b);
|
|
bool ckd_mul(type1 *result, type2 a, type3 b);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.20.1p2'></a>
|
|
<pre>2 These macros perform addition, subtraction, or multiplication of the mathematical values of a and b,
|
|
storing the result of the operation in *result , (that is, *result is assigned the result of computing
|
|
a + b, a - b, or a * b). Each operation is performed as if both operands were represented in a
|
|
signed integer type with infinite range, and the result was then converted from this integer type to
|
|
type1.
|
|
</pre>
|
|
<a name='7.20.1p3'></a>
|
|
<pre>3 Both type2 and type3 shall be any integer type other than plain char, bool, a bit-precise integer
|
|
type, or an enumeration type, and they need not be the same. *result shall be a modifiable lvalue
|
|
of any integer type other than plain char, bool, a bit-precise integer type, or an enumeration type.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.20.1p4'></a>
|
|
<pre>4 It is recommended to produce a diagnostic message if type2 or type3 are not suitable integer types,
|
|
or if *result is not a modifiable lvalue of a suitable integer type.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.20.1p5'></a>
|
|
<pre>5 If these macros return false, the value assigned to *result correctly represents the mathematical
|
|
result of the operation. Otherwise, these macros return true. In this case, the value assigned to
|
|
*result is the mathematical result of the operation wrapped around to the width of *result .
|
|
</pre>
|
|
<a name='7.20.1p6'></a>
|
|
<pre>6 EXAMPLE 1 If a and b are values of type signed int, and result is a signed long, then
|
|
|
|
ckd_sub(&result, a, b);
|
|
|
|
will indicate if a - b can be expressed as a signed long. If signed long has a greater width than signed int, this will
|
|
always be possible and this macro will return false.
|
|
</pre>
|
|
<a name='7.21'></a>
|
|
<hr>
|
|
<h3>7.21 [Common definitions <stddef.h>]</h3>
|
|
<a name='7.21p1'></a>
|
|
<pre>1 The header <stddef.h> defines the following macros and declares the following types. Some are
|
|
also defined in other headers, as noted in their respective subclauses.
|
|
</pre>
|
|
<a name='7.21p2'></a>
|
|
<pre>2 The types are
|
|
|
|
ptrdiff_t
|
|
|
|
|
|
which is the signed integer type of the result of subtracting two pointers;
|
|
|
|
size_t
|
|
|
|
|
|
which is the unsigned integer type of the result of the sizeof operator;
|
|
|
|
max_align_t
|
|
|
|
|
|
which is an object type whose alignment is the greatest fundamental alignment;
|
|
|
|
wchar_t
|
|
|
|
|
|
which is an integer type whose range of values can represent distinct codes for all members of the
|
|
largest extended character set specified among the supported locales; the null character shall have
|
|
the code value zero. Each member of the basic character set shall have a code value equal to its
|
|
value when used as the lone character in an integer character constant if an implementation does
|
|
not define __STDC_MB_MIGHT_NEQ_WC__ ; and,
|
|
|
|
nullptr_t
|
|
|
|
|
|
which is the type of the nullptr predefined constant, see below.
|
|
</pre>
|
|
<a name='7.21p3'></a>
|
|
<pre>3 The macros are
|
|
|
|
NULL
|
|
|
|
|
|
which expands to an implementation-defined null pointer constant;
|
|
|
|
unreachable()
|
|
|
|
|
|
which expands to a void expression that invokes undefined behavior if it is reached during execution;
|
|
and
|
|
|
|
offsetof(type, member-designator)
|
|
|
|
|
|
which expands to an integer constant expression that has type size_t, the value of which is the
|
|
offset in bytes, to the subobject (designated by member-designator), from the beginning of any object
|
|
of type type. The type and member designator shall be such that given
|
|
|
|
static type t;
|
|
|
|
|
|
then the expression &(t. member-designator) evaluates to an address constant. If the specified type
|
|
defines a new type or if the specified member is a bit-field, the behavior is undefined.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.21p4'></a>
|
|
<pre>4 The types used for size_t and ptrdiff_t should not have an integer conversion rank greater than
|
|
that of signed long int unless the implementation supports objects large enough to make this
|
|
necessary.
|
|
|
|
</pre>
|
|
<a name='7.21.1'></a>
|
|
<hr>
|
|
<h3>7.21.1 [The unreachable macro]</h3>
|
|
<a name='7.21.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stddef.h>
|
|
void unreachable(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.21.1p2'></a>
|
|
<pre>2 A call to the function-like macro unreachable indicates that the particular flow control that leads to
|
|
the call will never be taken; it receives no arguments and expands to a void expression. The program
|
|
execution shall not reach such a call.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.1p3'></a>
|
|
<pre>3 If a macro call unreachable() is reached during execution, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.21.1p4'></a>
|
|
<pre>4 EXAMPLE 1 The following program assumes that each execution is provided with at least one command line argument.
|
|
The behavior of an execution with no arguments is undefined.
|
|
|
|
#include <stddef.h>
|
|
#include <stdio.h>
|
|
|
|
int main (int argc, char* argv[static argc + 1]) {
|
|
if (argc <= 2)
|
|
unreachable();
|
|
else
|
|
return printf("%s: we see %s", argv[0], argv[1]);
|
|
|
|
return puts("this should never be reached");
|
|
}
|
|
|
|
Here, the static array size expression and the annotation of the control flow with unreachable indicates that the pointed-to
|
|
parameter array argv will hold at least three elements, regardless of the circumstances. A possible optimization is that the
|
|
resulting executable never performs the comparison and unconditionally executes a tail call to printf that never returns to
|
|
the main function. In particular, the entire call and reference to puts can be omitted from the executable. No diagnostic is
|
|
expected.
|
|
|
|
</pre>
|
|
<a name='7.21.2'></a>
|
|
<hr>
|
|
<h3>7.21.2 [The nullptr_t type]</h3>
|
|
<a name='7.21.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stddef.h>
|
|
typedef typeof_unqual(nullptr) nullptr_t;
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.21.2p2'></a>
|
|
<pre>2 The nullptr_t type is the type of the nullptr predefined constant. It has only a very limited use
|
|
in contexts where this type is needed to distinguish nullptr from other expression types. It is an
|
|
unqualified complete scalar type that is different from all pointer or arithmetic types and is neither
|
|
an atomic or array type and has exactly one value, nullptr. Default initialization of an object of this
|
|
type is equivalent to an initialization by nullptr.
|
|
</pre>
|
|
<a name='7.21.2p3'></a>
|
|
<pre>3 The size and alignment of nullptr_t is the same as for a pointer to character type. An object
|
|
representation of the value nullptr is the same as the object representation of a null pointer value of
|
|
type void*. An lvalue conversion of an object of type nullptr_t with such an object representation
|
|
has the value nullptr; if the object representation is different, the behavior is undefined<a href='#FOOTNOTE.319'><sup>[319]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.319'>
|
|
<pre><i><b>Footnote 319)</b> Thus, during the whole program execution an object of type nullptr_t evaluates to the assumed value nullptr.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.2p4'></a>
|
|
<pre>4 NOTE Because it is considered to be a scalar type, nullptr_t may appear in many context where (void*)0 would be valid,
|
|
for example,
|
|
|
|
— as the operand of alignas, sizeof or typeof operators,
|
|
— as the operand of an implicit or explicit conversion to a pointer type,
|
|
— as the assignment expression in an assignment or initialization of an object of type nullptr_t,
|
|
— as an argument to a parameter of type nullptr_t or in a variable argument list,
|
|
— as a void expression,
|
|
— as the operand of an implicit or explicit conversion to bool,
|
|
— as an operand of a _Generic primary expression,
|
|
— as an operand of the !, &&, || or conditional operators, or
|
|
— as the controlling expression of an if or iteration statement.
|
|
</pre>
|
|
<a name='7.22'></a>
|
|
<hr>
|
|
<h3>7.22 [Integer types <stdint.h>]</h3>
|
|
<a name='7.22p1'></a>
|
|
<pre>1 The header <stdint.h> declares sets of integer types having specified widths, and defines corre-
|
|
sponding sets of macros.<a href='#FOOTNOTE.320'><sup>[320]</sup></a> It also defines macros that specify limits of integer types corresponding
|
|
to types defined in other standard headers.
|
|
</pre>
|
|
<a name='FOOTNOTE.320'>
|
|
<pre><i><b>Footnote 320)</b> See "future library directions" (<a href='#7.33.14'>7.33.14</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22p2'></a>
|
|
<pre>2 Types are defined in the following categories:
|
|
|
|
— integer types having certain exact widths;
|
|
— integer types having at least certain specified widths;
|
|
— fastest integer types having at least certain specified widths;
|
|
— integer types wide enough to hold pointers to objects;
|
|
|
|
— integer types having greatest width.
|
|
|
|
(Some of these types may denote the same type.)
|
|
</pre>
|
|
<a name='7.22p3'></a>
|
|
<pre>3 Corresponding macros specify limits of the declared types and construct suitable constants.
|
|
</pre>
|
|
<a name='7.22p4'></a>
|
|
<pre>4 For each type described herein that the implementation provides,<a href='#FOOTNOTE.321'><sup>[321]</sup></a> <stdint.h> shall declare that
|
|
typedef name and define the associated macros. Conversely, for each type described herein that
|
|
the implementation does not provide, <stdint.h> shall not declare that typedef name nor shall it
|
|
define the associated macros. An implementation shall provide those types described as "required",
|
|
but need not provide any of the others (described as "optional"). None of the types shall be defined
|
|
as a synonym for a bit-precise integer type.
|
|
</pre>
|
|
<a name='FOOTNOTE.321'>
|
|
<pre><i><b>Footnote 321)</b> Some of these types might denote implementation-defined extended integer types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22p5'></a>
|
|
<pre>5 The feature test macro __STDC_VERSION_STDINT_H__ expands to the token 202311L.
|
|
|
|
</pre>
|
|
<a name='7.22.1'></a>
|
|
<hr>
|
|
<h3>7.22.1 [Integer types]</h3>
|
|
<a name='7.22.1p1'></a>
|
|
<pre>1 When typedef names differing only in the absence or presence of the initial u are defined, they shall
|
|
denote corresponding signed and unsigned types as described in <a href='#6.2.5'>6.2.5</a>; an implementation providing
|
|
one of these corresponding types shall also provide the other.
|
|
</pre>
|
|
<a name='7.22.1p2'></a>
|
|
<pre>2 In the following descriptions, the symbol N represents an unsigned decimal integer with no leading
|
|
zeros (e.g., 8 or 24, but not 04 or 048).
|
|
|
|
</pre>
|
|
<a name='7.22.1.1'></a>
|
|
<hr>
|
|
<h3>7.22.1.1 [Exact-width integer types]</h3>
|
|
<a name='7.22.1.1p1'></a>
|
|
<pre>1 The typedef name intN_t designates a signed integer type with width N and no padding bits. Thus,
|
|
int8_t denotes such a signed integer type with a width of exactly 8 bits.
|
|
</pre>
|
|
<a name='7.22.1.1p2'></a>
|
|
<pre>2 The typedef name uintN_t designates an unsigned integer type with width N and no padding bits.
|
|
Thus, uint24_t denotes such an unsigned integer type with a width of exactly 24 bits.
|
|
</pre>
|
|
<a name='7.22.1.1p3'></a>
|
|
<pre>3 If an implementation provides standard or extended integer types with a particular width and no
|
|
padding bits, it shall define the corresponding typedef names.
|
|
|
|
</pre>
|
|
<a name='7.22.1.2'></a>
|
|
<hr>
|
|
<h3>7.22.1.2 [Minimum-width integer types]</h3>
|
|
<a name='7.22.1.2p1'></a>
|
|
<pre>1 The typedef name int_leastN_t designates a signed integer type with a width of at least N, such
|
|
that no signed integer type with lesser size has at least the specified width. Thus, int_least32_t
|
|
denotes a signed integer type with a width of at least 32 bits.
|
|
</pre>
|
|
<a name='7.22.1.2p2'></a>
|
|
<pre>2 The typedef name uint_leastN_t designates an unsigned integer type with a width of at least
|
|
N, such that no unsigned integer type with lesser size has at least the specified width. Thus,
|
|
uint_least16_t denotes an unsigned integer type with a width of at least 16 bits.
|
|
</pre>
|
|
<a name='7.22.1.2p3'></a>
|
|
<pre>3 If the typedef name intN_t is defined, int_leastN_t designates the same type. If the typedef
|
|
name uintN_t is defined, uint_leastN_t designates the same type.
|
|
</pre>
|
|
<a name='7.22.1.2p4'></a>
|
|
<pre>4 The following types are required:
|
|
int_least8_t uint_least8_t
|
|
int_least16_t uint_least16_t
|
|
int_least32_t uint_least32_t
|
|
int_least64_t uint_least64_t
|
|
|
|
|
|
All other types of this form are optional.
|
|
|
|
</pre>
|
|
<a name='7.22.1.3'></a>
|
|
<hr>
|
|
<h3>7.22.1.3 [Fastest minimum-width integer types]</h3>
|
|
<a name='7.22.1.3p1'></a>
|
|
<pre>1 Each of the following types designates an integer type that is usually fastest<a href='#FOOTNOTE.322'><sup>[322]</sup></a> to operate with
|
|
among all integer types that have at least the specified width.
|
|
</pre>
|
|
<a name='FOOTNOTE.322'>
|
|
<pre><i><b>Footnote 322)</b> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear grounds for
|
|
choosing one type over another, it will simply pick some integer type satisfying the signedness and width requirements.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.1.3p2'></a>
|
|
<pre>2 The typedef name int_fastN_t designates the fastest signed integer type with a width of at least N.
|
|
The typedef name uint_fastN_t designates the fastest unsigned integer type with a width of at
|
|
least N.
|
|
</pre>
|
|
<a name='7.22.1.3p3'></a>
|
|
<pre>3 The following types are required:
|
|
|
|
int_fast8_t uint_fast8_t
|
|
int_fast16_t uint_fast16_t
|
|
int_fast32_t uint_fast32_t
|
|
int_fast64_t uint_fast64_t
|
|
|
|
|
|
All other types of this form are optional.
|
|
|
|
</pre>
|
|
<a name='7.22.1.4'></a>
|
|
<hr>
|
|
<h3>7.22.1.4 [Integer types capable of holding object pointers]</h3>
|
|
<a name='7.22.1.4p1'></a>
|
|
<pre>1 The following type designates a signed integer type, other than a bit-precise integer type, with the
|
|
property that any valid pointer to void can be converted to this type, then converted back to pointer
|
|
to void, and the result will compare equal to the original pointer:
|
|
|
|
intptr_t
|
|
|
|
|
|
The following type designates an unsigned integer type, other than a bit-precise integer type, with
|
|
the property that any valid pointer to void can be converted to this type, then converted back to
|
|
pointer to void, and the result will compare equal to the original pointer:
|
|
|
|
uintptr_t
|
|
|
|
|
|
These types are optional.
|
|
|
|
</pre>
|
|
<a name='7.22.1.5'></a>
|
|
<hr>
|
|
<h3>7.22.1.5 [Greatest-width integer types]</h3>
|
|
<a name='7.22.1.5p1'></a>
|
|
<pre>1 The following type designates a signed integer type, other than a bit-precise integer type, capable of
|
|
representing any value of any signed integer type with the possible exceptions of signed bit-precise
|
|
integer types and of signed extended integer types that are wider than long long and that are
|
|
referred by the type definition for an exact width integer type:
|
|
|
|
intmax_t
|
|
|
|
|
|
The following type designates the unsigned integer type that corresponds to intmax_t<a href='#FOOTNOTE.323'><sup>[323]</sup></a> :
|
|
|
|
uintmax_t
|
|
|
|
|
|
These types are required.
|
|
</pre>
|
|
<a name='FOOTNOTE.323'>
|
|
<pre><i><b>Footnote 323)</b> Thus this type is capable of representing any value of any unsigned integer type with the possible exception of particular
|
|
extended integer types that are wider than unsigned long long.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.2'></a>
|
|
<hr>
|
|
<h3>7.22.2 [Widths of specified-width integer types]</h3>
|
|
<a name='7.22.2p1'></a>
|
|
<pre>1 The following object-like macros specify the width of the types declared in <stdint.h>. Each macro
|
|
name corresponds to a similar type name in <a href='#7.22.1'>7.22.1</a>.
|
|
</pre>
|
|
<a name='7.22.2p2'></a>
|
|
<pre>2 Each instance of any defined macro shall be replaced by a constant expression suitable for use in
|
|
#if preprocessing directives. Its implementation-defined value shall be equal to or greater than
|
|
the value given below, except where stated to be exactly the given value. An implementation shall
|
|
define only the macros corresponding to those typedef names it actually provides.<a href='#FOOTNOTE.324'><sup>[324]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.324'>
|
|
<pre><i><b>Footnote 324)</b> The exact-width and pointer-holding integer types are optional.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.2.1'></a>
|
|
<hr>
|
|
<h3>7.22.2.1 [Width of exact-width integer types]</h3>
|
|
<a name='7.22.2.1p1'></a>
|
|
<pre>1 INTN_WIDTH exactly N
|
|
UINTN_WIDTH exactly N
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.2.2'></a>
|
|
<hr>
|
|
<h3>7.22.2.2 [Width of minimum-width integer types]</h3>
|
|
<a name='7.22.2.2p1'></a>
|
|
<pre>1 INT_LEASTN_WIDTH exactly UINT_LEASTN_WIDTH
|
|
UINT_LEASTN_WIDTH N
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.2.3'></a>
|
|
<hr>
|
|
<h3>7.22.2.3 [Width of fastest minimum-width integer types]</h3>
|
|
<a name='7.22.2.3p1'></a>
|
|
<pre>1 INT_FASTN_WIDTH exactly UINT_FASTN_WIDTH
|
|
UINT_FASTN_WIDTH N
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.2.4'></a>
|
|
<hr>
|
|
<h3>7.22.2.4 [Width of integer types capable of holding object pointers]</h3>
|
|
<a name='7.22.2.4p1'></a>
|
|
<pre>1 INTPTR_WIDTH exactly UINTPTR_WIDTH
|
|
UINTPTR_WIDTH 16
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.2.5'></a>
|
|
<hr>
|
|
<h3>7.22.2.5 [Width of greatest-width integer types]</h3>
|
|
<a name='7.22.2.5p1'></a>
|
|
<pre>1 INTMAX_WIDTH exactly UINTMAX_WIDTH
|
|
UINTMAX_WIDTH 64
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.3'></a>
|
|
<hr>
|
|
<h3>7.22.3 [Width of other integer types]</h3>
|
|
<a name='7.22.3p1'></a>
|
|
<pre>1 The following object-like macros specify the width of integer types corresponding to types defined
|
|
in other standard headers.
|
|
</pre>
|
|
<a name='7.22.3p2'></a>
|
|
<pre>2 Each instance of these macros shall be replaced by a constant expression suitable for use in #if
|
|
preprocessing directives. Its implementation-defined value shall be equal to or greater than the
|
|
corresponding value given below. An implementation shall define only the macros corresponding
|
|
to those typedef names it actually provides.<a href='#FOOTNOTE.325'><sup>[325]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.325'>
|
|
<pre><i><b>Footnote 325)</b> A freestanding implementation need not provide all of these types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.3.1'></a>
|
|
<hr>
|
|
<h3>7.22.3.1 [Width of ptrdiff_t]</h3>
|
|
<a name='7.22.3.1p1'></a>
|
|
<pre>1 PTRDIFF_WIDTH 16
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.3.2'></a>
|
|
<hr>
|
|
<h3>7.22.3.2 [Width of sig_atomic_t]</h3>
|
|
<a name='7.22.3.2p1'></a>
|
|
<pre>1 SIG_ATOMIC_WIDTH 8
|
|
</pre>
|
|
<a name='7.22.3.3'></a>
|
|
<hr>
|
|
<h3>7.22.3.3 [Width of size_t]</h3>
|
|
<a name='7.22.3.3p1'></a>
|
|
<pre>1 SIZE_WIDTH 16
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.3.4'></a>
|
|
<hr>
|
|
<h3>7.22.3.4 [Width of wchar_t]</h3>
|
|
<a name='7.22.3.4p1'></a>
|
|
<pre>1 WCHAR_WIDTH 8
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.3.5'></a>
|
|
<hr>
|
|
<h3>7.22.3.5 [Width of wint_t]</h3>
|
|
<a name='7.22.3.5p1'></a>
|
|
<pre>1 WINT_WIDTH 16
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.4'></a>
|
|
<hr>
|
|
<h3>7.22.4 [Macros for integer constants]</h3>
|
|
<a name='7.22.4p1'></a>
|
|
<pre>1 The following function-like macros expand to integer constants suitable for initializing objects that
|
|
have integer types corresponding to types defined in <stdint.h>. Each macro name corresponds to
|
|
a similar type name in <a href='#7.22.1.2'>7.22.1.2</a> or <a href='#7.22.1.5'>7.22.1.5</a>.
|
|
</pre>
|
|
<a name='7.22.4p2'></a>
|
|
<pre>2 The argument in any instance of these macros shall be an unsuffixed integer constant (as defined
|
|
in <a href='#6.4.4.1'>6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
|
|
</pre>
|
|
<a name='7.22.4p3'></a>
|
|
<pre>3 Each invocation of one of these macros shall expand to an integer constant expression. The type of
|
|
the expression shall have the same type as would an expression of the corresponding type converted
|
|
according to the integer promotions. The value of the expression shall be that of the argument. If
|
|
the value is in the range of the type intmax_t (for a signed type) or the type uintmax_t (for an
|
|
unsigned type), see <a href='#7.22.1.5'>7.22.1.5</a>, the expression is suitable for use in #if preprocessing directives.
|
|
|
|
</pre>
|
|
<a name='7.22.4.1'></a>
|
|
<hr>
|
|
<h3>7.22.4.1 [Macros for minimum-width integer constants]</h3>
|
|
<a name='7.22.4.1p1'></a>
|
|
<pre>1 The macro INTN_C( value) expands to an integer constant expression corresponding to the type
|
|
int_leastN_t . The macro UINTN_C( value) expands to an integer constant expression corre-
|
|
sponding to the type uint_leastN_t . For example, if uint_least64_t is a name for the type
|
|
unsigned long long int, then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
|
|
|
|
</pre>
|
|
<a name='7.22.4.2'></a>
|
|
<hr>
|
|
<h3>7.22.4.2 [Macros for greatest-width integer constants]</h3>
|
|
<a name='7.22.4.2p1'></a>
|
|
<pre>1 The following macro expands to an integer constant expression having the value specified by its
|
|
argument and the type intmax_t:
|
|
|
|
INTMAX_C(value)
|
|
|
|
|
|
The following macro expands to an integer constant expression having the value specified by its
|
|
argument and the type uintmax_t:
|
|
|
|
UINTMAX_C(value)
|
|
|
|
|
|
</pre>
|
|
<a name='7.22.5'></a>
|
|
<hr>
|
|
<h3>7.22.5 [Maximal and minimal values of integer types]</h3>
|
|
<a name='7.22.5p1'></a>
|
|
<pre>1 For all integer types for which there is a macro with suffix _WIDTH holding the width, maximum
|
|
macros with suffix _MAX and, for all signed types, minimum macros with suffix _MIN are defined as
|
|
by <a href='#5.2.4.2'>5.2.4.2</a>. If it is unspecified if a type is signed or unsigned and the implementation has it as an
|
|
unsigned type, a minimum macro with extension _MIN , and value 0 of the corresponding type is
|
|
defined.
|
|
</pre>
|
|
<a name='7.23'></a>
|
|
<hr>
|
|
<h3>7.23 [Input/output <stdio.h>]</h3>
|
|
<a name='7.23.1'></a>
|
|
<hr>
|
|
<h3>7.23.1 [Introduction]</h3>
|
|
<a name='7.23.1p1'></a>
|
|
<pre>1 The header <stdio.h> defines several macros, and declares three types and many functions for
|
|
performing input and output.
|
|
</pre>
|
|
<a name='7.23.1p2'></a>
|
|
<pre>2 The types declared are size_t (described in <a href='#7.21'>7.21</a>);
|
|
|
|
FILE
|
|
|
|
|
|
which is an object type capable of recording all the information needed to control a stream, including
|
|
its file position indicator, a pointer to its associated buffer (if any), an error indicator that records
|
|
whether a read/write error has occurred, and an end-of-file indicator that records whether the end of
|
|
the file has been reached; and
|
|
|
|
fpos_t
|
|
|
|
|
|
which is a complete object type other than an array type capable of recording all the information
|
|
needed to specify uniquely every position within a file.
|
|
</pre>
|
|
<a name='7.23.1p3'></a>
|
|
<pre>3 The macros are NULL (described in <a href='#7.21'>7.21</a>);
|
|
_IOFBF
|
|
_IOLBF
|
|
_IONBF
|
|
|
|
|
|
which expand to integer constant expressions with distinct values, suitable for use as the third
|
|
argument to the setvbuf function;
|
|
|
|
BUFSIZ
|
|
|
|
|
|
which expands to an integer constant expression that is the size of the buffer used by the setbuf
|
|
function;
|
|
|
|
EOF
|
|
|
|
|
|
which expands to an integer constant expression, with type int and a negative value, that is returned
|
|
by several functions to indicate end-of-file, that is, no more input from a stream;
|
|
|
|
FOPEN_MAX
|
|
|
|
|
|
which expands to an integer constant expression that is the minimum number of files that the
|
|
implementation guarantees can be open simultaneously;
|
|
|
|
FILENAME_MAX
|
|
|
|
|
|
which expands to an integer constant expression that is the size needed for an array of char large
|
|
enough to hold the longest file name string that the implementation guarantees can be opened or, if
|
|
the implementation imposes no practical limit on the length of file name strings, the recommended
|
|
size of an array intended to hold a file name string<a href='#FOOTNOTE.326'><sup>[326]</sup></a> ;
|
|
_PRINTF_NAN_LEN_MAX
|
|
|
|
|
|
which expands to an integer constant expression (suitable for use in #if preprocessing directives)
|
|
that is the maximum number of characters output for any
|
|
[-]NAN(n-char-sequence)
|
|
sequence.<a href='#FOOTNOTE.327'><sup>[327]</sup></a> If an implementation has no support for NaNs, it shall be 0. _PRINTF_NAN_LEN_MAX
|
|
shall be less than 64;
|
|
|
|
L_tmpnam
|
|
|
|
|
|
which expands to an integer constant expression that is the size needed for an array of char large
|
|
enough to hold a temporary file name string generated by the tmpnam function;
|
|
|
|
SEEK_CUR
|
|
SEEK_END
|
|
SEEK_SET
|
|
|
|
|
|
which expand to integer constant expressions with distinct values, suitable for use as the third
|
|
argument to the fseek function;
|
|
|
|
TMP_MAX
|
|
|
|
|
|
which expands to an integer constant expression that is the minimum number of unique file names
|
|
that can be generated by the tmpnam function;
|
|
|
|
stderr
|
|
stdin
|
|
stdout
|
|
|
|
|
|
which are expressions of type "pointer to FILE" that point to the FILE objects associated, respectively,
|
|
with the standard error, input, and output streams.
|
|
</pre>
|
|
<a name='FOOTNOTE.326'>
|
|
<pre><i><b>Footnote 326)</b> Of course, file name string contents are subject to other system-specific constraints; therefore all possible strings of length
|
|
FILENAME_MAX cannot be expected to be opened successfully.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.327'>
|
|
<pre><i><b>Footnote 327)</b> If the implementation only uses the [-]NAN style, then _PRINTF_NAN_LEN_MAX would have the value 4.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.1p4'></a>
|
|
<pre>4 The header <wchar.h> declares a number of functions useful for wide character input and output.
|
|
The wide character input/output functions described in that subclause provide operations analogous
|
|
to most of those described here, except that the fundamental units internal to the program are
|
|
wide characters. The external representation (in the file) is a sequence of "generalized" multibyte
|
|
characters, as described further in <a href='#7.23.3'>7.23.3</a>.
|
|
</pre>
|
|
<a name='7.23.1p5'></a>
|
|
<pre>5 The input/output functions are given the following collective terms:
|
|
|
|
— The wide character input functions — those functions described in <a href='#7.31'>7.31</a> that perform input
|
|
into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar, fwscanf, wscanf,
|
|
vfwscanf , and vwscanf .
|
|
|
|
— The wide character output functions — those functions described in <a href='#7.31'>7.31</a> that perform output from
|
|
wide characters and wide strings: fputwc, fputws, putwc, putwchar, fwprintf, wprintf,
|
|
vfwprintf , and vwprintf.
|
|
|
|
— The wide character input/output functions — the union of the ungetwc function, the wide charac-
|
|
ter input functions, and the wide character output functions.
|
|
— The byte input/output functions — those functions described in this subclause that perform
|
|
input/output: fgetc, fgets, fprintf, fputc, fputs, fread, fscanf, fwrite, getc, getchar,
|
|
printf, putc, putchar, puts, scanf, ungetc, vfprintf , vfscanf , vprintf , and vscanf.
|
|
|
|
Forward references: files (<a href='#7.23.3'>7.23.3</a>), the fseek function (<a href='#7.23.9.2'>7.23.9.2</a>), streams (<a href='#7.23.2'>7.23.2</a>), the tmpnam func-
|
|
tion (<a href='#7.23.4.4'>7.23.4.4</a>), <wchar.h> (<a href='#7.31'>7.31</a>).
|
|
</pre>
|
|
<a name='7.23.2'></a>
|
|
<hr>
|
|
<h3>7.23.2 [Streams]</h3>
|
|
<a name='7.23.2p1'></a>
|
|
<pre>1 Input and output, whether to or from physical devices such as terminals and tape drives, or whether
|
|
to or from files supported on structured storage devices, are mapped into logical data streams, whose
|
|
properties are more uniform than their various inputs and outputs. Two forms of mapping are
|
|
supported, for text streams and for binary streams.<a href='#FOOTNOTE.328'><sup>[328]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.328'>
|
|
<pre><i><b>Footnote 328)</b> An implementation need not distinguish between text streams and binary streams. In such an implementation, there
|
|
need be no new-line characters in a text stream nor any limit to the length of a line.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.2p2'></a>
|
|
<pre>2 A text stream is an ordered sequence of characters composed into lines, each line consisting of
|
|
zero or more characters plus a terminating new-line character. Whether the last line requires a
|
|
terminating new-line character is implementation-defined. Characters may have to be added, altered,
|
|
or deleted on input and output to conform to differing conventions for representing text in the host
|
|
environment. Thus, there need not be a one-to-one correspondence between the characters in a
|
|
stream and those in the external representation. Data read in from a text stream will necessarily
|
|
compare equal to the data that were earlier written out to that stream only if: the data consist only
|
|
of printing characters and the control characters horizontal tab and new-line; no new-line character
|
|
is immediately preceded by space characters; and the last character is a new-line character. Whether
|
|
space characters that are written out immediately before a new-line character appear when read in
|
|
is implementation-defined.
|
|
</pre>
|
|
<a name='7.23.2p3'></a>
|
|
<pre>3 A binary stream is an ordered sequence of characters that can transparently record internal data.
|
|
Data read in from a binary stream shall compare equal to the data that were earlier written out to
|
|
that stream, under the same implementation. Such a stream may, however, have an implementation-
|
|
defined number of null characters appended to the end of the stream.
|
|
</pre>
|
|
<a name='7.23.2p4'></a>
|
|
<pre>4 Each stream has an orientation. After a stream is associated with an external file, but before any
|
|
operations are performed on it, the stream is without orientation. Once a wide character input/out-
|
|
put function has been applied to a stream without orientation, the stream becomes a wide-oriented
|
|
stream. Similarly, once a byte input/output function has been applied to a stream without orien-
|
|
tation, the stream becomes a byte-oriented stream. Only a call to the freopen function or the fwide
|
|
function can otherwise alter the orientation of a stream. (A successful call to freopen removes any
|
|
orientation.)<a href='#FOOTNOTE.329'><sup>[329]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.329'>
|
|
<pre><i><b>Footnote 329)</b> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.2p5'></a>
|
|
<pre>5 Byte input/output functions shall not be applied to a wide-oriented stream and wide character
|
|
input/output functions shall not be applied to a byte-oriented stream. The remaining stream
|
|
operations do not affect, and are not affected by, a stream’s orientation, except for the following
|
|
additional restrictions:
|
|
|
|
— Binary wide-oriented streams have the file-positioning restrictions ascribed to both text and
|
|
binary streams.
|
|
|
|
— For wide-oriented streams, after a successful call to a file-positioning function that leaves the
|
|
file position indicator prior to the end-of-file, a wide character output function can overwrite a
|
|
partial multibyte character; any file contents beyond the byte(s) written may henceforth not
|
|
consist of valid multibyte characters.
|
|
|
|
</pre>
|
|
<a name='7.23.2p6'></a>
|
|
<pre>6 Each wide-oriented stream has an associated mbstate_t object that stores the current parse state
|
|
of the stream. A successful call to fgetpos stores a representation of the value of this mbstate_t
|
|
object as part of the value of the fpos_t object. A later successful call to fsetpos using the same
|
|
stored fpos_t value restores the value of the associated mbstate_t object as well as the position
|
|
within the controlled stream.
|
|
</pre>
|
|
<a name='7.23.2p7'></a>
|
|
<pre>7 Each stream has an associated lock that is used to prevent data races when multiple threads of
|
|
execution access a stream, and to restrict the interleaving of stream operations performed by multiple
|
|
threads. Only one thread may hold this lock at a time. The lock is reentrant: a single thread may
|
|
hold the lock multiple times at a given time.
|
|
</pre>
|
|
<a name='7.23.2p8'></a>
|
|
<pre>8 All functions that read, write, position, or query the position of a stream lock the stream before
|
|
accessing it. They release the lock associated with the stream when the access is complete.
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.23.2p9'></a>
|
|
<pre>9 An implementation shall support text files with lines containing at least 254 characters, including
|
|
the terminating new-line character. The value of the macro BUFSIZ shall be at least 256.
|
|
Forward references: the freopen function (<a href='#7.23.5.4'>7.23.5.4</a>), the fwide function (<a href='#7.31.3.5'>7.31.3.5</a>), mbstate_t
|
|
(<a href='#7.31.1'>7.31.1</a>), the fgetpos function (<a href='#7.23.9.1'>7.23.9.1</a>), the fsetpos function (<a href='#7.23.9.3'>7.23.9.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.3'></a>
|
|
<hr>
|
|
<h3>7.23.3 [Files]</h3>
|
|
<a name='7.23.3p1'></a>
|
|
<pre>1 A stream is associated with an external file (which may be a physical device) by opening a file, which
|
|
may involve creating a new file. Creating an existing file causes its former contents to be discarded,
|
|
if necessary. If a file can support positioning requests (such as a disk file, as opposed to a terminal),
|
|
then a file position indicator associated with the stream is positioned at the start (character number
|
|
zero) of the file, unless the file is opened with append mode in which case it is implementation-
|
|
defined whether the file position indicator is initially positioned at the beginning or the end of the
|
|
file. The file position indicator is maintained by subsequent reads, writes, and positioning requests,
|
|
to facilitate an orderly progression through the file.
|
|
</pre>
|
|
<a name='7.23.3p2'></a>
|
|
<pre>2 Binary files are not truncated, except as defined in <a href='#7.23.5.3'>7.23.5.3</a>. Whether a write on a text stream causes
|
|
the associated file to be truncated beyond that point is implementation-defined.
|
|
</pre>
|
|
<a name='7.23.3p3'></a>
|
|
<pre>3 When a stream is unbuffered, characters are intended to appear from the source or at the destination
|
|
as soon as possible. Otherwise characters may be accumulated and transmitted to or from the host
|
|
environment as a block. When a stream is fully buffered, characters are intended to be transmitted
|
|
to or from the host environment as a block when a buffer is filled. When a stream is line buffered,
|
|
characters are intended to be transmitted to or from the host environment as a block when a new-line
|
|
character is encountered. Furthermore, characters are intended to be transmitted as a block to the
|
|
host environment when a buffer is filled, when input is requested on an unbuffered stream, or when
|
|
input is requested on a line buffered stream that requires the transmission of characters from the
|
|
host environment. Support for these characteristics is implementation-defined, and may be affected
|
|
via the setbuf and setvbuf functions.
|
|
</pre>
|
|
<a name='7.23.3p4'></a>
|
|
<pre>4 A file may be disassociated from a controlling stream by closing the file. Output streams are
|
|
flushed (any unwritten buffer contents are transmitted to the host environment) before the stream
|
|
is disassociated from the file. The lifetime of a FILE object ends when the associated file is closed
|
|
(including the standard text streams). Whether a file of zero length (on which no characters have
|
|
been written by an output stream) actually exists is implementation-defined.
|
|
</pre>
|
|
<a name='7.23.3p5'></a>
|
|
<pre>5 The file may be subsequently reopened, by the same or another program execution, and its contents
|
|
reclaimed or modified (if it can be repositioned at its start). If the main function returns to its original
|
|
caller, or if the exit function is called, all open files are closed (hence all output streams are flushed)
|
|
before program termination. Other paths to program termination, such as calling the abort function,
|
|
need not close all files properly.
|
|
</pre>
|
|
<a name='7.23.3p6'></a>
|
|
<pre>6 The address of the FILE object used to control a stream may be significant; a copy of a FILE object
|
|
need not serve in place of the original.
|
|
</pre>
|
|
<a name='7.23.3p7'></a>
|
|
<pre>7 At program startup, three text streams are predefined and need not be opened explicitly — standard
|
|
input (for reading conventional input), standard output (for writing conventional output), and standard
|
|
error (for writing diagnostic output). As initially opened, the standard error stream is not fully
|
|
buffered; the standard input and standard output streams are fully buffered if and only if the stream
|
|
can be determined not to refer to an interactive device.
|
|
</pre>
|
|
<a name='7.23.3p8'></a>
|
|
<pre>8 Functions that open additional (nontemporary) files require a file name, which is a string. The
|
|
rules for composing valid file names are implementation-defined. Whether the same file can be
|
|
simultaneously open multiple times is also implementation-defined.
|
|
</pre>
|
|
<a name='7.23.3p9'></a>
|
|
<pre>9 Although both text and binary wide-oriented streams are conceptually sequences of wide characters,
|
|
the external file associated with a wide-oriented stream is a sequence of multibyte characters,
|
|
generalized as follows:
|
|
|
|
— Multibyte encodings within files may contain embedded null bytes (unlike multibyte encod-
|
|
ings valid for use internal to the program).
|
|
— A file need not begin nor end in the initial shift state.<a href='#FOOTNOTE.330'><sup>[330]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.330'>
|
|
<pre><i><b>Footnote 330)</b> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has undefined behavior for a
|
|
binary stream (because of possible trailing null characters) or for any stream with state-dependent encoding that does not
|
|
assuredly end in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.3p10'></a>
|
|
<pre>10 Moreover, the encodings used for multibyte characters may differ among files. Both the nature and
|
|
choice of such encodings are implementation-defined.
|
|
</pre>
|
|
<a name='7.23.3p11'></a>
|
|
<pre>11 The wide character input functions read multibyte characters from the stream and convert them
|
|
to wide characters as if they were read by successive calls to the fgetwc function. Each conversion
|
|
occurs as if by a call to the mbrtowc function, with the conversion state described by the stream’s
|
|
own mbstate_t object. The byte input functions read characters from the stream as if by successive
|
|
calls to the fgetc function.
|
|
</pre>
|
|
<a name='7.23.3p12'></a>
|
|
<pre>12 The wide character output functions convert wide characters to multibyte characters and write them
|
|
to the stream as if they were written by successive calls to the fputwc function. Each conversion
|
|
occurs as if by a call to the wcrtomb function, with the conversion state described by the stream’s
|
|
own mbstate_t object. The byte output functions write characters to the stream as if by successive
|
|
calls to the fputc function.
|
|
</pre>
|
|
<a name='7.23.3p13'></a>
|
|
<pre>13 In some cases, some of the byte input/output functions also perform conversions between multibyte
|
|
characters and wide characters. These conversions also occur as if by calls to the mbrtowc and
|
|
wcrtomb functions.
|
|
</pre>
|
|
<a name='7.23.3p14'></a>
|
|
<pre>14 An encoding error occurs if the character sequence presented to the underlying mbrtowc function
|
|
does not form a valid (generalized) multibyte character, or if the code value passed to the underlying
|
|
wcrtomb does not correspond to a valid (generalized) multibyte character. The wide character
|
|
input/output functions and the byte input/output functions store the value of the macro EILSEQ in
|
|
errno if and only if an encoding error occurs.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.23.3p15'></a>
|
|
<pre>15 The value of FOPEN_MAX shall be at least eight, including the three standard text streams.
|
|
Forward references: the exit function (<a href='#7.24.4.4'>7.24.4.4</a>), the fgetc function (<a href='#7.23.7.1'>7.23.7.1</a>), the fopen function
|
|
(<a href='#7.23.5.3'>7.23.5.3</a>), the fputc function (<a href='#7.23.7.3'>7.23.7.3</a>), the setbuf function (<a href='#7.23.5.5'>7.23.5.5</a>), the setvbuf function (<a href='#7.23.5.6'>7.23.5.6</a>),
|
|
the fgetwc function (<a href='#7.31.3.1'>7.31.3.1</a>), the fputwc function (<a href='#7.31.3.3'>7.31.3.3</a>), conversion state (<a href='#7.31.6'>7.31.6</a>), the mbrtowc
|
|
function (<a href='#7.31.6.3.2'>7.31.6.3.2</a>), the wcrtomb function (<a href='#7.31.6.3.3'>7.31.6.3.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.4'></a>
|
|
<hr>
|
|
<h3>7.23.4 [Operations on files]</h3>
|
|
<a name='7.23.4.1'></a>
|
|
<hr>
|
|
<h3>7.23.4.1 [The remove function]</h3>
|
|
<a name='7.23.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int remove(const char *filename);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.4.1p2'></a>
|
|
<pre>2 The remove function causes the file whose name is the string pointed to by filename to be no longer
|
|
accessible by that name. A subsequent attempt to open that file using that name will fail, unless it is
|
|
created anew. If the file is open, the behavior of the remove function is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.4.1p3'></a>
|
|
<pre>3 The remove function returns zero if the operation succeeds, nonzero if it fails.
|
|
|
|
</pre>
|
|
<a name='7.23.4.2'></a>
|
|
<hr>
|
|
<h3>7.23.4.2 [The rename function]</h3>
|
|
<a name='7.23.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int rename(const char *old, const char *new);
|
|
Description
|
|
</pre>
|
|
<a name='7.23.4.2p2'></a>
|
|
<pre>2 The rename function causes the file whose name is the string pointed to by old to be henceforth
|
|
known by the name given by the string pointed to by new. The file named old is no longer accessible
|
|
by that name. If a file named by the string pointed to by new exists prior to the call to the rename
|
|
function, the behavior is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.4.2p3'></a>
|
|
<pre>3 The rename function returns zero if the operation succeeds, nonzero if it fails,<a href='#FOOTNOTE.331'><sup>[331]</sup></a> in which case if the
|
|
file existed previously it is still known by its original name.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.331'>
|
|
<pre><i><b>Footnote 331)</b> Among the reasons the implementation could cause the rename function to fail are that the file is open or that it is
|
|
necessary to copy its contents to effectuate its renaming.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.4.3'></a>
|
|
<hr>
|
|
<h3>7.23.4.3 [The tmpfile function]</h3>
|
|
<a name='7.23.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *tmpfile(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.4.3p2'></a>
|
|
<pre>2 The tmpfile function creates a temporary binary file that is different from any other existing file
|
|
and that will automatically be removed when it is closed or at program termination. If the program
|
|
terminates abnormally, whether an open temporary file is removed is implementation-defined. The
|
|
file is opened for update with "wb+" mode.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.23.4.3p3'></a>
|
|
<pre>3 It should be possible to open at least TMP_MAX temporary files during the lifetime of the program
|
|
(this limit may be shared with tmpnam) and there should be no limit on the number simultaneously
|
|
open other than this limit and any limit on the number of open files (FOPEN_MAX).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.4.3p4'></a>
|
|
<pre>4 The tmpfile function returns a pointer to the stream of the file that it created. If the file cannot be
|
|
created, the tmpfile function returns a null pointer.
|
|
Forward references: the fopen function (<a href='#7.23.5.3'>7.23.5.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.4.4'></a>
|
|
<hr>
|
|
<h3>7.23.4.4 [The tmpnam function]</h3>
|
|
<a name='7.23.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
char *tmpnam(char *s);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.4.4p2'></a>
|
|
<pre>2 The tmpnam function generates a string that is a valid file name and that is not the same as the name
|
|
of an existing file.<a href='#FOOTNOTE.332'><sup>[332]</sup></a> The function is potentially capable of generating at least TMP_MAX different
|
|
strings, but any or all of them may already be in use by existing files and thus not be suitable return
|
|
values.
|
|
</pre>
|
|
<a name='FOOTNOTE.332'>
|
|
<pre><i><b>Footnote 332)</b> Files created using strings generated by the tmpnam function are temporary only in the sense that their names are not
|
|
expected to collide with those generated by conventional naming rules for the implementation. It is still necessary to use the
|
|
remove function to remove such files when their use is ended, and before program termination.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.4.4p3'></a>
|
|
<pre>3 The tmpnam function generates a different string each time it is called.
|
|
</pre>
|
|
<a name='7.23.4.4p4'></a>
|
|
<pre>4 Calls to the tmpnam function with a null pointer argument may introduce data races with each other.
|
|
The implementation shall behave as if no library function calls the tmpnam function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.4.4p5'></a>
|
|
<pre>5 If no suitable string can be generated, the tmpnam function returns a null pointer. Otherwise, if
|
|
the argument is a null pointer, the tmpnam function leaves its result in an internal static object and
|
|
returns a pointer to that object (subsequent calls to the tmpnam function may modify the same object).
|
|
If the argument is not a null pointer, it is assumed to point to an array of at least L_tmpnam chars;
|
|
the tmpnam function writes its result in that array and returns the argument as its value.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.23.4.4p6'></a>
|
|
<pre>6 The value of the macro TMP_MAX shall be at least 25.
|
|
|
|
</pre>
|
|
<a name='7.23.5'></a>
|
|
<hr>
|
|
<h3>7.23.5 [File access functions]</h3>
|
|
<a name='7.23.5.1'></a>
|
|
<hr>
|
|
<h3>7.23.5.1 [The fclose function]</h3>
|
|
<a name='7.23.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fclose(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.1p2'></a>
|
|
<pre>2 A successful call to the fclose function causes the stream pointed to by stream to be flushed and
|
|
the associated file to be closed. Any unwritten buffered data for the stream are delivered to the host
|
|
environment to be written to the file; any unread buffered data are discarded. Whether or not the
|
|
call succeeds, the stream is disassociated from the file and any buffer set by the setbuf or setvbuf
|
|
function is disassociated from the stream (and deallocated if it was automatically allocated).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.5.1p3'></a>
|
|
<pre>3 The fclose function returns zero if the stream was successfully closed, or EOF if any errors were
|
|
detected.
|
|
|
|
</pre>
|
|
<a name='7.23.5.2'></a>
|
|
<hr>
|
|
<h3>7.23.5.2 [The fflush function]</h3>
|
|
<a name='7.23.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fflush(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.2p2'></a>
|
|
<pre>2 If stream points to an output stream or an update stream in which the most recent operation was
|
|
not input, the fflush function causes any unwritten data for that stream to be delivered to the host
|
|
environment to be written to the file; otherwise, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.23.5.2p3'></a>
|
|
<pre>3 If stream is a null pointer, the fflush function performs this flushing action on all streams for which
|
|
the behavior is defined above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.5.2p4'></a>
|
|
<pre>4 The fflush function sets the error indicator for the stream and returns EOF if a write error occurs,
|
|
otherwise it returns zero.
|
|
Forward references: the fopen function (<a href='#7.23.5.3'>7.23.5.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.5.3'></a>
|
|
<hr>
|
|
<h3>7.23.5.3 [The fopen function]</h3>
|
|
<a name='7.23.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *fopen(const char * restrict filename, const char * restrict mode);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.3p2'></a>
|
|
<pre>2 The fopen function opens the file whose name is the string pointed to by filename, and associates
|
|
a stream with it.
|
|
</pre>
|
|
<a name='7.23.5.3p3'></a>
|
|
<pre>3 The argument mode points to a string. If the string is one of the following, the file is open in the
|
|
indicated mode. Otherwise, the behavior is undefined.<a href='#FOOTNOTE.333'><sup>[333]</sup></a>
|
|
r open text file for reading
|
|
w truncate to zero length or create text file for writing
|
|
wx create text file for writing
|
|
a append; open or create text file for writing at end-of-file
|
|
rb open binary file for reading
|
|
wb truncate to zero length or create binary file for writing
|
|
wbx create binary file for writing
|
|
ab append; open or create binary file for writing at end-of-file
|
|
r+ open text file for update (reading and writing)
|
|
w+ truncate to zero length or create text file for update
|
|
w+x create text file for update
|
|
a+ append; open or create text file for update, writing at end-of-file
|
|
r+b or rb+ open binary file for update (reading and writing)
|
|
w+b or wb+ truncate to zero length or create binary file for update
|
|
w+bx or wb+x create binary file for update
|
|
a+b or ab+ append; open or create binary file for update, writing at end-of-file
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.333'>
|
|
<pre><i><b>Footnote 333)</b> If the string begins with one of the listed mode sequences, the implementation might choose to ignore the remaining
|
|
characters, or it might use them to select different kinds of a file (some of which might not conform to the properties in <a href='#7.23.2'>7.23.2</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.5.3p4'></a>
|
|
<pre>4 Opening a file with read mode (’r’ as the first character in the mode argument) fails if the file does
|
|
not exist or cannot be read.
|
|
</pre>
|
|
<a name='7.23.5.3p5'></a>
|
|
<pre>5 Opening a file with exclusive mode (’x’ as the last character in the mode argument) fails if the file
|
|
already exists or cannot be created. Otherwise, the file is created with exclusive (also known as
|
|
non-shared) access to the extent that the underlying system supports exclusive access.
|
|
</pre>
|
|
<a name='7.23.5.3p6'></a>
|
|
<pre>6 Opening a file with append mode (’a’ as the first character in the mode argument) causes all
|
|
subsequent writes to the file to be forced to the then current end-of-file, regardless of intervening
|
|
calls to the fseek function. In some implementations, opening a binary file with append mode (’b’
|
|
as the second or third character in the above list of mode argument values) may initially position the
|
|
file position indicator for the stream beyond the last data written, because of null character padding.
|
|
</pre>
|
|
<a name='7.23.5.3p7'></a>
|
|
<pre>7 When a file is opened with update mode (’+’ as the second or third character in the above list
|
|
of mode argument values), both input and output may be performed on the associated stream.
|
|
However, output shall not be directly followed by input without an intervening call to the fflush
|
|
function or to a file positioning function (fseek, fsetpos, or rewind), and input shall not be directly
|
|
followed by output without an intervening call to a file positioning function, unless the input
|
|
operation encounters end-of-file. Opening (or creating) a text file with update mode may instead
|
|
open (or create) a binary stream in some implementations.
|
|
</pre>
|
|
<a name='7.23.5.3p8'></a>
|
|
<pre>8 When opened, a stream is fully buffered if and only if it can be determined not to refer to an
|
|
interactive device. The error and end-of-file indicators for the stream are cleared.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.5.3p9'></a>
|
|
<pre>9 The fopen function returns a pointer to the object controlling the stream. If the open operation fails,
|
|
fopen returns a null pointer.
|
|
Forward references: file positioning functions (<a href='#7.23.9'>7.23.9</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.5.4'></a>
|
|
<hr>
|
|
<h3>7.23.5.4 [The freopen function]</h3>
|
|
<a name='7.23.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *freopen(const char * restrict filename, const char * restrict mode,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.4p2'></a>
|
|
<pre>2 The freopen function opens the file whose name is the string pointed to by filename and associates
|
|
the stream pointed to by stream with it. The mode argument is used just as in the fopen function.<a href='#FOOTNOTE.334'><sup>[334]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.334'>
|
|
<pre><i><b>Footnote 334)</b> The primary use of the freopen function is to change the file associated with a standard text stream (stderr, stdin,
|
|
or stdout), as those identifiers need not be modifiable lvalues to which the value returned by the fopen function could be
|
|
assigned.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.5.4p3'></a>
|
|
<pre>3 If filename is a null pointer, the freopen function attempts to change the mode of the stream to
|
|
that specified by mode, as if the name of the file currently associated with the stream had been
|
|
used. It is implementation-defined which changes of mode are permitted (if any), and under what
|
|
circumstances.
|
|
</pre>
|
|
<a name='7.23.5.4p4'></a>
|
|
<pre>4 The freopen function first attempts to close any file that is associated with the specified stream.
|
|
Failure to close the file is ignored. The error and end-of-file indicators for the stream are cleared.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.5.4p5'></a>
|
|
<pre>5 The freopen function returns a null pointer if the open operation fails. Otherwise, freopen returns
|
|
the value of stream.
|
|
|
|
</pre>
|
|
<a name='7.23.5.5'></a>
|
|
<hr>
|
|
<h3>7.23.5.5 [The setbuf function]</h3>
|
|
<a name='7.23.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void setbuf(FILE * restrict stream, char * restrict buf);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.5p2'></a>
|
|
<pre>2 Except that it returns no value, the setbuf function is equivalent to the setvbuf function invoked
|
|
with the values _IOFBF for mode and BUFSIZ for size, or (if buf is a null pointer), with the value
|
|
_IONBF for mode.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.5.5p3'></a>
|
|
<pre>3 The setbuf function returns no value.
|
|
Forward references: the setvbuf function (<a href='#7.23.5.6'>7.23.5.6</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.5.6'></a>
|
|
<hr>
|
|
<h3>7.23.5.6 [The setvbuf function]</h3>
|
|
<a name='7.23.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int setvbuf(FILE * restrict stream, char * restrict buf, int mode, size_t size);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.5.6p2'></a>
|
|
<pre>2 The setvbuf function may be used only after the stream pointed to by stream has been associated
|
|
with an open file and before any other operation (other than an unsuccessful call to setvbuf) is
|
|
performed on the stream. The argument mode determines how stream will be buffered, as follows:
|
|
|
|
_IOFBF causes input/output to be fully buffered;
|
|
|
|
_IOLBF causes input/output to be line buffered;
|
|
|
|
_IONBF causes input/output to be unbuffered.
|
|
|
|
If buf is not a null pointer, the array it points to may be used instead of a buffer allocated by the
|
|
setvbuf function<a href='#FOOTNOTE.335'><sup>[335]</sup></a> and the argument size specifies the size of the array; otherwise, size may
|
|
determine the size of a buffer allocated by the setvbuf function. The members of the array at any
|
|
time have unspecified values.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.335'>
|
|
<pre><i><b>Footnote 335)</b> The buffer has to have a lifetime at least as great as the open stream, so not closing the stream before a buffer that has
|
|
automatic storage duration is deallocated upon block exit results in undefined behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.5.6p3'></a>
|
|
<pre>3 The setvbuf function returns zero on success, or nonzero if an invalid value is given for mode or if
|
|
the request cannot be honored.
|
|
|
|
</pre>
|
|
<a name='7.23.6'></a>
|
|
<hr>
|
|
<h3>7.23.6 [Formatted input/output functions]</h3>
|
|
<a name='7.23.6p1'></a>
|
|
<pre>1 The formatted input/output functions shall behave as if there is a sequence point after the actions
|
|
associated with each specifier.<a href='#FOOTNOTE.336'><sup>[336]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.336'>
|
|
<pre><i><b>Footnote 336)</b> The fprintf functions perform writes to memory for the %n specifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1'></a>
|
|
<hr>
|
|
<h3>7.23.6.1 [The fprintf function]</h3>
|
|
<a name='7.23.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fprintf(FILE * restrict stream, const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.1p2'></a>
|
|
<pre>2 The fprintf function writes output to the stream pointed to by stream, under control of the string
|
|
pointed to by format that specifies how subsequent arguments are converted for output. If there are
|
|
insufficient arguments for the format, the behavior is undefined. If the format is exhausted while
|
|
arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored. The
|
|
fprintf function returns when the end of the format string is encountered.
|
|
</pre>
|
|
<a name='7.23.6.1p3'></a>
|
|
<pre>3 The format shall be a multibyte character sequence, beginning and ending in its initial shift state.
|
|
The format is composed of zero or more directives: ordinary multibyte characters (not %), which
|
|
are copied unchanged to the output stream; and conversion specifications, each of which results
|
|
in fetching zero or more subsequent arguments, converting them, if applicable, according to the
|
|
corresponding conversion specifier, and then writing the result to the output stream.
|
|
</pre>
|
|
<a name='7.23.6.1p4'></a>
|
|
<pre>4 Each conversion specification is introduced by the character %. After the %, the following appear in
|
|
sequence:
|
|
|
|
— Zero or more flags (in any order) that modify the meaning of the conversion specification.
|
|
|
|
— An optional minimum field width. If the converted value has fewer characters than the field
|
|
width, it is padded with spaces (by default) on the left (or right, if the left adjustment flag,
|
|
described later, has been given) to the field width. The field width takes the form of an asterisk
|
|
* (described later) or a nonnegative decimal integer.<a href='#FOOTNOTE.337'><sup>[337]</sup></a>
|
|
|
|
— An optional precision that gives the minimum number of digits to appear for the b, d, i, o, u, x,
|
|
and X conversions, the number of digits to appear after the decimal-point character for a, A, e,
|
|
E, f, and F conversions, the maximum number of significant digits for the g and G conversions,
|
|
or the maximum number of bytes to be written for s conversions. The precision takes the form
|
|
of a period (.) followed either by an asterisk * (described later) or by an optional nonnegative
|
|
decimal integer; if only the period is specified, the precision is taken as zero. If a precision
|
|
appears with any other conversion specifier, the behavior is undefined.
|
|
|
|
— An optional length modifier that specifies the size of the argument.
|
|
|
|
— A conversion specifier character that specifies the type of conversion to be applied.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.337'>
|
|
<pre><i><b>Footnote 337)</b> Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1p5'></a>
|
|
<pre>5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In this case,
|
|
an int argument supplies the field width or precision. The arguments specifying field width, or
|
|
precision, or both, shall appear (in that order) before the argument (if any) to be converted. A
|
|
negative field width argument is taken as a - flag followed by a positive field width. A negative
|
|
precision argument is taken as if the precision were omitted.
|
|
</pre>
|
|
<a name='7.23.6.1p6'></a>
|
|
<pre>6 The flag characters and their meanings are:
|
|
- The result of the conversion is left-justified within the field. (It is right-justified if this flag is
|
|
not specified.)
|
|
|
|
+ The result of a signed conversion always begins with a plus or minus sign. (It begins with a
|
|
sign only when a value with a negative sign is converted if this flag is not specified.) <a href='#FOOTNOTE.338'><sup>[338]</sup></a>
|
|
|
|
space If the first character of a signed conversion is not a sign, or if a signed conversion results in
|
|
no characters, a space is prefixed to the result. If the space and + flags both appear, the space
|
|
flag is ignored.
|
|
|
|
# The result is converted to an "alternative form". For o conversion, it increases the precision, if
|
|
and only if necessary, to force the first digit of the result to be a zero (if the value and precision
|
|
are both 0, a single 0 is printed). For b conversion, a nonzero result has 0b prefixed to it. For
|
|
x (or X) conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g, and G
|
|
conversions, the result of converting a floating-point number always contains a decimal-point
|
|
character, even if no digits follow it. (Normally, a decimal-point character appears in the
|
|
result of these conversions only if a digit follows it.) For g and G conversions, trailing zeros
|
|
are not removed from the result. For other conversions, the behavior is undefined.
|
|
|
|
0 For b, d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros (following any
|
|
indication of sign or base) are used to pad to the field width rather than performing space
|
|
padding, except when converting an infinity or NaN. If the 0 and - flags both appear, the
|
|
0 flag is ignored. For d, i, o, u, x, and X conversions, if a precision is specified, the 0 flag is
|
|
ignored. For other conversions, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.338'>
|
|
<pre><i><b>Footnote 338)</b> The results of all floating conversions of a negative zero, and of negative values that round to zero, include a minus sign.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1p7'></a>
|
|
<pre>7 The length modifiers and their meanings are:
|
|
|
|
hh Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a
|
|
signed char or unsigned char argument (the argument will have been promoted
|
|
according to the integer promotions, but its value shall be converted to signed char or
|
|
unsigned char before printing); or that a following n conversion specifier applies to a
|
|
pointer to a signed char argument.
|
|
|
|
h Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a short int
|
|
or unsigned short int argument (the argument will have been promoted accord-
|
|
ing to the integer promotions, but its value shall be converted to short int or
|
|
unsigned short int before printing); or that a following n conversion specifier applies
|
|
to a pointer to a short int argument.
|
|
|
|
l (ell) Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a long int
|
|
or unsigned long int argument; that a following n conversion specifier applies to
|
|
a pointer to a long int argument; that a following c conversion specifier applies to
|
|
a wint_t argument; that a following s conversion specifier applies to a pointer to a
|
|
wchar_t argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
|
|
specifier.
|
|
|
|
ll (ell-ell) Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a
|
|
long long int or unsigned long long int argument; or that a following n con-
|
|
version specifier applies to a pointer to a long long int argument.
|
|
|
|
j Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to an intmax_t
|
|
or uintmax_t argument; or that a following n conversion specifier applies to a pointer
|
|
to an intmax_t argument.
|
|
|
|
z Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a size_t
|
|
or the corresponding signed integer type argument; or that a following n conversion
|
|
specifier applies to a pointer to a signed integer type corresponding to size_t argument.
|
|
t Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a ptrdiff_t
|
|
or the corresponding unsigned integer type argument; or that a following n conversion
|
|
specifier applies to a pointer to a ptrdiff_t argument.
|
|
|
|
wN Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to an integer
|
|
argument with a specific width where N is a positive decimal integer with no leading
|
|
zeros (the argument will have been promoted according to the integer promotions, but
|
|
its value shall be converted to the unpromoted type); or that a following n conversion
|
|
specifier applies to a pointer to an integer type argument with a width of N bits. All
|
|
minimum-width integer types (<a href='#7.22.1.2'>7.22.1.2</a>) and exact-width integer types (<a href='#7.22.1.1'>7.22.1.1</a>) de-
|
|
fined in the header <stdint.h> shall be supported. Other supported values of N are
|
|
implementation-defined.
|
|
|
|
wfN Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a fastest
|
|
minimum-width integer argument with a specific width where N is a positive decimal
|
|
integer with no leading zeros (the argument will have been promoted according to
|
|
the integer promotions, but its value shall be converted to the unpromoted type); or
|
|
that a following n conversion specifier applies to a pointer to a fastest minimum-width
|
|
integer type argument with a width of N bits. All fastest minimum-width integer types
|
|
(<a href='#7.22.1.3'>7.22.1.3</a>) defined in the header <stdint.h> shall be supported. Other supported values
|
|
of N are implementation-defined.
|
|
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
long double argument.
|
|
|
|
H Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal32 argument.
|
|
|
|
D Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal64 argument.
|
|
|
|
DD Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal128 argument.
|
|
|
|
|
|
If a length modifier appears with any conversion specifier other than as specified above, the behavior
|
|
is undefined.
|
|
</pre>
|
|
<a name='7.23.6.1p8'></a>
|
|
<pre>8 The conversion specifiers and their meanings are:
|
|
|
|
d,i The int argument is converted to signed decimal in the style [-]dddd. The precision
|
|
specifies the minimum number of digits to appear; if the value being converted can be
|
|
represented in fewer digits, it is expanded with leading zeros. The default precision is 1.
|
|
The result of converting a zero value with a precision of zero is no characters.
|
|
b, o,u,x,X The unsigned int argument is converted to unsigned binary (b), unsigned octal (o),
|
|
unsigned decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
|
|
letters abcdef are used for x conversion and the letters ABCDEF for X conversion. The
|
|
precision specifies the minimum number of digits to appear; if the value being converted
|
|
can be represented in fewer digits, it is expanded with leading zeros. The default precision
|
|
is 1. The result of converting a zero value with a precision of zero is no characters.
|
|
f,F A double argument representing a floating-point number is converted to decimal notation
|
|
in the style [-]ddd.ddd, where the number of digits after the decimal-point character is
|
|
equal to the precision specification. If the precision is missing, it is taken as 6; if the
|
|
precision is zero and the # flag is not specified, no decimal-point character appears. If a
|
|
decimal-point character appears, at least one digit appears before it. The value is rounded
|
|
to the appropriate number of digits.
|
|
A double argument representing an infinity is converted in one of the styles [-]inf or
|
|
[-]infinity — which style is implementation-defined. A double argument representing a
|
|
NaN is converted in one of the styles [-]nan or [-]nan(n-char-sequence) — which style, and
|
|
the meaning of any n-char-sequence, is implementation-defined. The F conversion specifier
|
|
produces INF, INFINITY, or NAN instead of inf, infinity, or nan, respectively.<a href='#FOOTNOTE.339'><sup>[339]</sup></a>
|
|
e,E A double argument representing a floating-point number is converted in the style
|
|
[-]d.ddde±dd, where there is one digit (which is nonzero if the argument is nonzero) before
|
|
the decimal-point character and the number of digits after it is equal to the precision; if the
|
|
precision is missing, it is taken as 6; if the precision is zero and the # flag is not specified,
|
|
no decimal-point character appears. The value is rounded to the appropriate number of
|
|
digits. The E conversion specifier produces a number with E instead of e introducing the
|
|
exponent. The exponent always contains at least two digits, and only as many more digits
|
|
as necessary to represent the exponent. If the value is zero, the exponent is zero.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
g,G A double argument representing a floating-point number is converted in style f or e (or
|
|
in style F or E in the case of a G conversion specifier), depending on the value converted
|
|
and the precision. Let P equal the precision if nonzero, 6 if the precision is omitted, or 1 if
|
|
the precision is zero. Then, if a conversion with style E would have an exponent of X:
|
|
if P > X ≥ −4, the conversion is with style f (or F) and precision P − (X + 1).
|
|
otherwise, the conversion is with style e (or E) and precision P − 1.
|
|
Finally, unless the # flag is used, any trailing zeros are removed from the fractional portion
|
|
of the result and the decimal-point character is removed if there is no fractional portion
|
|
remaining.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
a,A A double argument representing a floating-point number is converted in the style
|
|
[-]0xh.hhhhp±d, where there is one hexadecimal digit (which is nonzero if the argument is a
|
|
normalized floating-point number and is otherwise unspecified) before the decimal-point
|
|
character<a href='#FOOTNOTE.340'><sup>[340]</sup></a> and the number of hexadecimal digits after it is equal to the precision; if the
|
|
precision is missing and FLT_RADIX is a power of 2, then the precision is sufficient for an
|
|
exact representation of the value; if the precision is missing and FLT_RADIX is not a power
|
|
of 2, then the precision is sufficient to distinguish<a href='#FOOTNOTE.341'><sup>[341]</sup></a> values of type double, except that
|
|
trailing zeros may be omitted; if the precision is zero and the # flag is not specified, no
|
|
decimal-point character appears. The letters abcdef are used for a conversion and the
|
|
letters ABCDEF for A conversion. The A conversion specifier produces a number with X and
|
|
P instead of x and p. The exponent always contains at least one digit, and only as many
|
|
more digits as necessary to represent the decimal exponent of 2. If the value is zero, the
|
|
exponent is zero.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
<a href='#FOOTNOTE.339'><sup>[339]</sup></a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning; the # and 0 flag
|
|
|
|
characters have no effect.
|
|
<a href='#FOOTNOTE.340'><sup>[340]</sup></a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so that subsequent
|
|
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
<a href='#FOOTNOTE.341'><sup>[341]</sup></a> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point character.
|
|
If an H, D, or DD modifier is present and the precision is missing, then for a decimal
|
|
floating type argument represented by a triple of integers (s, c, q), where n is the number
|
|
of significant digits in the coefficient c,
|
|
|
|
— if −(n + 5) ≤ q ≤ 0, use style f (or style F in the case of an A conversion specifier)
|
|
with formatting precision equal to −q,
|
|
— otherwise, use style e (or style E in the case of an A conversion specifier) with format-
|
|
ting precision equal to n − 1, with the exceptions that if c = 0 then the digit-sequence
|
|
in the exponent-part shall have the value q (rather than 0), and that the exponent is
|
|
always expressed with the minimum number of digits required to represent its value
|
|
(the exponent never contains a leading zero).
|
|
|
|
If the precision P is present (in the conversion specification) and is zero or at least as
|
|
large as the precision p (<a href='#5.2.4.2.2'>5.2.4.2.2</a>) of the decimal floating type, the conversion is as if the
|
|
precision were missing. If the precision P is present (and nonzero) and less than the
|
|
precision p of the decimal floating type, the conversion first obtains an intermediate result
|
|
as follows, where n is the number of significant digits in the coefficient:
|
|
|
|
— If n ≤ P , set the intermediate result to the input.
|
|
— If n > P , round the input value, according to the current rounding direction for
|
|
decimal floating-point operations, to P decimal digits, with unbounded exponent
|
|
range, representing the result with a P -digit integer coefficient when in the form
|
|
(s, c, q).
|
|
|
|
Convert the intermediate result in the manner described above for the case where the
|
|
precision is missing.
|
|
c If no l length modifier is present, the int argument is converted to an unsigned char,
|
|
and the resulting character is written.
|
|
If an l length modifier is present, the wint_t argument is converted as if by an ls
|
|
conversion specification with no precision and an argument that points to storage suitably
|
|
sized for at least two wchar_t elements, the first element containing the wint_t argument
|
|
to the lc conversion specification and the second a null wide character.
|
|
s If no l length modifier is present, the argument shall be a pointer to storage of character
|
|
type.<a href='#FOOTNOTE.342'><sup>[342]</sup></a> Characters from the storage are written up to (but not including) the terminating
|
|
null character. If the precision is specified, no more than that many bytes are written. If
|
|
the precision is not specified or is greater than the size of the storage, the storage shall
|
|
contain a null character.
|
|
If an l length modifier is present, the argument shall be a pointer to storage of wchar_t
|
|
type. Wide characters from the storage are converted to multibyte characters (each as if
|
|
by a call to the wcrtomb function, with the conversion state described by an mbstate_t
|
|
object initialized to zero before the first wide character is converted) up to and including
|
|
a terminating null wide character. The resulting multibyte characters are written up to
|
|
(but not including) the terminating null character (byte). If no precision is specified, the
|
|
storage shall contain a null wide character. If a precision is specified, no more than that
|
|
many bytes are written (including shift sequences, if any), and the storage shall contain
|
|
a null wide character if, to equal the multibyte character sequence length given by the
|
|
precision, the function would need to access a wide character one past the end of the array.
|
|
In no case is a partial multibyte character written.<a href='#FOOTNOTE.343'><sup>[343]</sup></a>
|
|
p The argument shall be a pointer to void or a pointer to a character type. The value of the
|
|
pointer is converted to a sequence of printing characters, in an implementation-defined
|
|
manner.
|
|
n The argument shall be a pointer to signed integer whose type is specified by the length
|
|
modifiers, if any, for the conversion specification, or shall be int if no length modifiers are
|
|
specified for the conversion specification. The number of characters written to the output
|
|
stream so far by this call to fprintf is stored into the integer object pointed to by the
|
|
argument. No argument is converted, but one is consumed. If the conversion specification
|
|
includes any flags, a field width, or a precision, the behavior is undefined.
|
|
% A % character is written. No argument is converted. The complete conversion specification
|
|
shall be %%.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.339'>
|
|
<pre><i><b>Footnote 339)</b> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning; the # and 0 flag
|
|
characters have no effect.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so that subsequent
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.341'>
|
|
<pre><i><b>Footnote 341)</b> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.339'>
|
|
<pre><i><b>Footnote 339)</b> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning; the # and 0 flag
|
|
characters have no effect.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so that subsequent
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.341'>
|
|
<pre><i><b>Footnote 341)</b> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.342'>
|
|
<pre><i><b>Footnote 342)</b> No special provisions are made for multibyte characters.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.343'>
|
|
<pre><i><b>Footnote 343)</b> Redundant shift sequences can result if multibyte characters have a state-dependent encoding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1p9'></a>
|
|
<pre>9 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.344'><sup>[344]</sup></a> fprintf shall behave as if it
|
|
uses va_arg with a type argument naming the type resulting from applying the default argument
|
|
promotions to the type corresponding to the conversion specification and then converting the result
|
|
of the va_arg expansion to the type corresponding to the conversion specification.<a href='#FOOTNOTE.345'><sup>[345]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.344'>
|
|
<pre><i><b>Footnote 344)</b> See "future library directions" (<a href='#7.33.15'>7.33.15</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.345'>
|
|
<pre><i><b>Footnote 345)</b> The behavior is undefined when the types differ as specified for va_arg <a href='#7.16.1.1'>7.16.1.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1p10'></a>
|
|
<pre>10 In no case does a nonexistent or small field width cause truncation of a field; if the result of a
|
|
conversion is wider than the field width, the field is expanded to contain the conversion result.
|
|
</pre>
|
|
<a name='7.23.6.1p11'></a>
|
|
<pre>11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded to a hexadecimal
|
|
floating number with the given precision.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.23.6.1p12'></a>
|
|
<pre>12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly representable
|
|
in the given precision, the result should be one of the two adjacent numbers in hexadecimal floating
|
|
style with the given precision, with the extra stipulation that the error should have a correct sign for
|
|
the current rounding direction.
|
|
</pre>
|
|
<a name='7.23.6.1p13'></a>
|
|
<pre>13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most the maximum
|
|
value M of the T_DECIMAL_DIG macros (defined in <float.h>), then the result should be correctly
|
|
rounded.<a href='#FOOTNOTE.346'><sup>[346]</sup></a> If the number of significant decimal digits is more than M but the source value is
|
|
exactly representable with M digits, then the result should be an exact representation with trailing
|
|
zeros. Otherwise, the source value is bounded by two adjacent decimal strings L < U, both having
|
|
M significant digits; the value of the resultant decimal string D should satisfy L ≤ D ≤ U, with the
|
|
extra stipulation that the error should have a correct sign for the current rounding direction.
|
|
</pre>
|
|
<a name='FOOTNOTE.346'>
|
|
<pre><i><b>Footnote 346)</b> For binary-to-decimal conversion, the result format’s values are the numbers representable with the given format specifier.
|
|
The number of significant digits is determined by the format specifier, and in the case of fixed-point conversion by the source
|
|
value as well.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.1p14'></a>
|
|
<pre>14 An uppercase B format specifier is not covered by the description above, because it used to be
|
|
available for extensions in previous versions of this standard.
|
|
Implementations that did not use an uppercase B as their own extension before are encouraged to
|
|
implement it similar to conversion specifier b as standardized above, with the alternative form (#B)
|
|
generating 0B as prefix for nonzero values.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.1p15'></a>
|
|
<pre>15 The fprintf function returns the number of characters transmitted, or a negative value if an output
|
|
or encoding error occurred or if the implementation does not support a specified width length
|
|
modifier.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.23.6.1p16'></a>
|
|
<pre>16 The number of characters that can be produced by any single conversion shall be at least 4095.
|
|
</pre>
|
|
<a name='7.23.6.1p17'></a>
|
|
<pre>17 EXAMPLE 1 To print a date and time in the form "Sunday, July 3, 10:02" followed by π to five decimal places:
|
|
|
|
#include <math.h>
|
|
#include <stdio.h>
|
|
/* ... */
|
|
char *weekday, *month; // pointers to strings
|
|
int day, hour, min;
|
|
fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
|
|
weekday, month, day, hour, min);
|
|
fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
|
|
|
|
</pre>
|
|
<a name='7.23.6.1p18'></a>
|
|
<pre>18 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the members of the extended
|
|
character set that consist of more than one byte each consist of exactly two bytes, the first of which is denoted here by a □
|
|
and the second by an uppercase letter.
|
|
</pre>
|
|
<a name='7.23.6.1p19'></a>
|
|
<pre>19 Given the following wide string with length seven,
|
|
|
|
static wchar_t wstr[] = L"□X□Yabc□Z□W";
|
|
|
|
the seven calls
|
|
|
|
fprintf(stdout, "|1234567890123|\n");
|
|
fprintf(stdout, "|%13ls|\n", wstr);
|
|
fprintf(stdout, "|%-13.9ls|\n", wstr);
|
|
fprintf(stdout, "|%13.10ls|\n", wstr);
|
|
fprintf(stdout, "|%13.11ls|\n", wstr);
|
|
fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
|
|
fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
|
|
|
|
will print the following seven lines:
|
|
|
|
|1234567890123|
|
|
| □X□Yabc□Z□W|
|
|
|□X□Yabc□Z |
|
|
| □X□Yabc□Z|
|
|
| □X□Yabc□Z□W|
|
|
| abc□Z□W|
|
|
| □Z|
|
|
|
|
</pre>
|
|
<a name='7.23.6.1p20'></a>
|
|
<pre>20 EXAMPLE 3 Following are representations of _Decimal64 arguments as triples (s, c, q) and the corresponding character
|
|
sequences fprintf produces with "%Da":
|
|
(+1, 123, 0) 123
|
|
(−1, 123, 0) -123
|
|
(+1, 123, −2) 1.23
|
|
(+1, 123, 1) <a href='#1.'>1.</a>23e+3
|
|
(−1, 123, 1) -<a href='#1.'>1.</a>23e+3
|
|
(+1, 123, −8) 0.00000123
|
|
(+1, 123, −9) <a href='#1.'>1.</a>23e-7
|
|
(+1, 120, −8) 0.00000120
|
|
(+1, 120, −9) <a href='#1.'>1.</a>20e-7
|
|
(+1, 1234567890123456, 0) 1234567890123456
|
|
(+1, 1234567890123456, 1) <a href='#1.'>1.</a>234567890123456e+16
|
|
(+1, 1234567890123456, −1) 123456789012345.6
|
|
(+1, 1234567890123456, −21) 0.000001234567890123456
|
|
(+1, 1234567890123456, −22) <a href='#1.'>1.</a>234567890123456e-7
|
|
(+1, 0, 0) 0
|
|
(−1, 0, 0) -0
|
|
(+1, 0, −6) 0.000000
|
|
(+1, 0, −7) 0e-7
|
|
(+1, 0, 2) 0e+2
|
|
(+1, 5, −6) 0.000005
|
|
(+1, 50, −7) 0.0000050
|
|
(+1, 5, −7) 5e-7
|
|
|
|
To illustrate the effects of a precision specification, the sequence:
|
|
|
|
_Decimal32 x = 6543.00DF; // (+1, 654300, -2)
|
|
fprintf(stdout, "%Ha\n", x);
|
|
fprintf(stdout, "%.6Ha\n", x);
|
|
fprintf(stdout, "%.5Ha\n", x);
|
|
fprintf(stdout, "%.4Ha\n", x);
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.0Ha\n", x);
|
|
|
|
assuming default rounding, results in:
|
|
6543.00
|
|
6543.00
|
|
6543.0
|
|
6543
|
|
<a href='#6.'>6.</a>54e+3
|
|
<a href='#6.'>6.</a>5e+3
|
|
7e+3
|
|
6543.00
|
|
|
|
To illustrate the effects of the exponent range, the sequence:
|
|
|
|
_Decimal32 x = 9543210e87DF; // (+1, 9543210, 87)
|
|
_Decimal32 y = 9500000e90DF; // (+1, 9500000, 90)
|
|
fprintf(stdout, "%.6Ha\n", x);
|
|
fprintf(stdout, "%.5Ha\n", x);
|
|
fprintf(stdout, "%.4Ha\n", x);
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", y);
|
|
|
|
assuming default rounding, results in:
|
|
9.54321e+93
|
|
9.5432e+93
|
|
9.543e+93
|
|
9.54e+93
|
|
9.5e+93
|
|
1e+94
|
|
1e+97
|
|
|
|
To further illustrate the effects of the exponent range, the sequence:
|
|
|
|
_Decimal32 x = 9512345e90DF; // (+1, 9512345, 90)
|
|
_Decimal32 y = 9512345e86DF; // (+1, 9512345, 86)
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", y);
|
|
|
|
assuming default rounding, results in:
|
|
9.51e+96
|
|
9.5e+96
|
|
1e+97
|
|
9.5e+92
|
|
|
|
Forward references: conversion state (<a href='#7.31.6'>7.31.6</a>), the wcrtomb function (<a href='#7.31.6.3.3'>7.31.6.3.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.6.2'></a>
|
|
<hr>
|
|
<h3>7.23.6.2 [The fscanf function]</h3>
|
|
<a name='7.23.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fscanf(FILE * restrict stream, const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.2p2'></a>
|
|
<pre>2 The fscanf function reads input from the stream pointed to by stream, under control of the string
|
|
pointed to by format that specifies the admissible input sequences and how they are to be converted
|
|
for assignment, using subsequent arguments as pointers to the objects to receive the converted
|
|
input. If there are insufficient arguments for the format, the behavior is undefined. If the format
|
|
is exhausted while arguments remain, the excess arguments are evaluated (as always) but are
|
|
otherwise ignored.
|
|
</pre>
|
|
<a name='7.23.6.2p3'></a>
|
|
<pre>3 The format shall be a multibyte character sequence, beginning and ending in its initial shift state.The
|
|
format is composed of zero or more directives: one or more white-space characters, an ordinary
|
|
multibyte character (neither % nor a white-space character), or a conversion specification. Each
|
|
conversion specification is introduced by the character %. After the %, the following appear in
|
|
sequence:
|
|
|
|
— An optional assignment-suppressing character *.
|
|
|
|
— An optional decimal integer greater than zero that specifies the maximum field width (in
|
|
characters).
|
|
|
|
— An optional length modifier that specifies the size of the receiving object.
|
|
|
|
— A conversion specifier character that specifies the type of conversion to be applied.
|
|
|
|
</pre>
|
|
<a name='7.23.6.2p4'></a>
|
|
<pre>4 The fscanf function executes each directive of the format in turn. When all directives have been
|
|
executed, or if a directive fails (as detailed below), the function returns. Failures are described as
|
|
input failures (due to the occurrence of an encoding error or the unavailability of input characters),
|
|
or matching failures (due to inappropriate input).
|
|
</pre>
|
|
<a name='7.23.6.2p5'></a>
|
|
<pre>5 A directive composed of white-space character(s) is executed by reading input up to the first non-
|
|
white-space character (which remains unread), or until no more characters can be read. The directive
|
|
never fails.
|
|
</pre>
|
|
<a name='7.23.6.2p6'></a>
|
|
<pre>6 A directive that is an ordinary multibyte character is executed by reading the next characters of the
|
|
stream. If any of those characters differ from the ones composing the directive,the directive fails and
|
|
the differing and subsequent characters remain unread. Similarly, if end-of-file, an encoding error,
|
|
or a read error prevents a character from being read, the directive fails.
|
|
</pre>
|
|
<a name='7.23.6.2p7'></a>
|
|
<pre>7 A directive that is a conversion specification defines a set of matching input sequences, as described
|
|
below for each specifier. A conversion specification is executed in the following steps:
|
|
</pre>
|
|
<a name='7.23.6.2p8'></a>
|
|
<pre>8 Input white-space characters are skipped, unless the specification includes a [, c, or n specifier.<a href='#FOOTNOTE.347'><sup>[347]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.347'>
|
|
<pre><i><b>Footnote 347)</b> These white-space characters are not counted against a specified field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.2p9'></a>
|
|
<pre>9 An input item is read from the stream, unless the specification includes an n specifier. An input
|
|
item is defined as the longest sequence of input characters which does not exceed any specified
|
|
field width and which is, or is a prefix of, a matching input sequence.<a href='#FOOTNOTE.348'><sup>[348]</sup></a> The first character, if any,
|
|
after the input item remains unread. If the length of the input item is zero, the execution of the
|
|
directive fails; this condition is a matching failure unless end-of-file, an encoding error, or a read
|
|
error prevented input from the stream, in which case it is an input failure.
|
|
</pre>
|
|
<a name='FOOTNOTE.348'>
|
|
<pre><i><b>Footnote 348)</b> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences that are acceptable to
|
|
strtod, strtol, etc., are unacceptable to fscanf.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.2p10'></a>
|
|
<pre>10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the count of input
|
|
characters) is converted to a type appropriate to the conversion specifier. If the input item is not a
|
|
matching sequence, the execution of the directive fails: this condition is a matching failure. Unless
|
|
assignment suppression was indicated by a *, the result of the conversion is placed in the object
|
|
pointed to by the first argument following the format argument that has not already received a
|
|
conversion result. If this object does not have an appropriate type, or if the result of the conversion
|
|
cannot be represented in the object, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.23.6.2p11'></a>
|
|
<pre>11 The length modifiers and their meanings are:
|
|
|
|
hh Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to signed char or unsigned char.
|
|
|
|
h Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to short int or unsigned short int.
|
|
|
|
l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to long int or unsigned long int; that a following a, A, e, E, f, F,
|
|
g, or G conversion specifier applies to an argument with type pointer to double; or that
|
|
a following c, s, or [ conversion specifier applies to an argument with type pointer to
|
|
wchar_t .
|
|
|
|
ll (ell-ell) Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to long long int or unsigned long long int.
|
|
|
|
j Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to intmax_t or uintmax_t.
|
|
|
|
z Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to size_t or the corresponding signed integer type.
|
|
|
|
t Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to ptrdiff_t or the corresponding unsigned integer type.
|
|
|
|
wN Specifies that a following b, d, i, o, u, x, or X, or n conversion specifier applies to an
|
|
argument which is a pointer to an integer with a specific width where N is a positive
|
|
decimal integer with no leading zeros. All minimum-width integer types (<a href='#7.22.1.2'>7.22.1.2</a>) and
|
|
exact-width integer types (<a href='#7.22.1.1'>7.22.1.1</a>) defined in the header <stdint.h> shall be supported.
|
|
Other supported values of N are implementation-defined.
|
|
|
|
wfN Specifies that a following b, d, i, o, u, x, or X, or n conversion specifier applies to an
|
|
argument which is a pointer to a fastest minimum-width integer with a specific width
|
|
where N is a positive decimal integer with no leading zeros. All fastest minimum-width
|
|
integer types (<a href='#7.22.1.3'>7.22.1.3</a>) defined in the header <stdint.h> shall be supported. Other
|
|
supported values of N are implementation-defined.
|
|
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to long double.
|
|
|
|
H Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal32 .
|
|
|
|
D Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal64 .
|
|
|
|
DD Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal128 .
|
|
|
|
If a length modifier appears with any conversion specifier other than as specified above, the behavior
|
|
is undefined.
|
|
</pre>
|
|
<a name='7.23.6.2p12'></a>
|
|
<pre>12 In the following, the type of the corresponding argument for a conversion specifier shall be a pointer
|
|
to a type determined by the length modifiers, if any, or specified by the conversion specifier. The
|
|
conversion specifiers and their meanings are:
|
|
|
|
d Matches an optionally signed decimal integer, whose format is the same as expected for
|
|
the subject sequence of the strtol function with the value 10 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
int.
|
|
|
|
b Matches an optionally signed binary integer, whose format is the same as expected for the
|
|
subject sequence of the strtol function with the value 2 for the base argument. Unless a
|
|
length modifier is specified, the corresponding argument shall be a pointer to unsigned
|
|
int.
|
|
|
|
i Matches an optionally signed integer, whose format is the same as expected for the subject
|
|
sequence of the strtol function with the value 0 for the base argument. Unless a length
|
|
modifier is specified, the corresponding argument shall be a pointer to int.
|
|
o Matches an optionally signed octal integer, whose format is the same as expected for
|
|
the subject sequence of the strtoul function with the value 8 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
|
|
u Matches an optionally signed decimal integer, whose format is the same as expected for
|
|
the subject sequence of the strtoul function with the value 10 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
|
|
x Matches an optionally signed hexadecimal integer, whose format is the same as expected
|
|
for the subject sequence of the strtoul function with the value 16 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
|
|
a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose format is
|
|
the same as expected for the subject sequence of the strtod function. Unless a length
|
|
modifier is specified, the corresponding argument shall be a pointer to float.
|
|
|
|
c Matches a sequence of characters of exactly the number specified by the field width (1 if
|
|
no field width is present in the directive).<a href='#FOOTNOTE.349'><sup>[349]</sup></a>
|
|
|
|
If no l length modifier is present, the corresponding argument shall be a pointer to char,
|
|
signed char, unsigned char, or void that points to storage large enough to accept the
|
|
sequence. No null character is added.
|
|
If an l length modifier is present, the input shall be a sequence of multibyte characters that
|
|
begins in the initial shift state. Each multibyte character in the sequence is converted to a
|
|
wide character as if by a call to the mbrtowc function, with the conversion state described
|
|
by an mbstate_t object initialized to zero before the first multibyte character is converted.
|
|
The corresponding argument shall be a pointer to storage of wchar_t large enough to
|
|
accept the resulting sequence of wide characters.No null wide character is added.
|
|
|
|
s Matches a sequence of non-white-space characters.<a href='#FOOTNOTE.349'><sup>[349]</sup></a>
|
|
If no l length modifier is present, the corresponding argument shall be a pointer to char,
|
|
signed char, unsigned char, or void that points to storage large enough to accept the
|
|
sequence and a terminating null character, which will be added automatically.
|
|
If an l length modifier is present, the input shall be a sequence of multibyte characters
|
|
that begins in the initial shift state. Each multibyte character is converted to a wide
|
|
character as if by a call to the mbrtowc function, with the conversion state described by an
|
|
mbstate_t object initialized to zero before the first multibyte character is converted. The
|
|
corresponding argument shall be a pointer to storage of wchar_t large enough to accept
|
|
the sequence and the terminating null wide character, which will be added automatically.
|
|
|
|
[ Matches a nonempty sequence of characters from a set of expected characters (the
|
|
scanset).<a href='#FOOTNOTE.349'><sup>[349]</sup></a>
|
|
If no l length modifier is present, the corresponding argument shall be a pointer to char,
|
|
signed char, unsigned char, or void that points to storage large enough to accept the
|
|
sequence and a terminating null character, which will be added automatically.
|
|
If an l length modifier is present, the input shall be a sequence of multibyte characters
|
|
that begins in the initial shift state. Each multibyte character is converted to a wide
|
|
character as if by a call to the mbrtowc function, with the conversion state described by
|
|
an mbstate_t object initialized to zero before the first multibyte character is converted.
|
|
The corresponding argument shall be a pointer that points to storage of wchar_t large
|
|
<a href='#FOOTNOTE.349'><sup>[349]</sup></a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [ conversion specifiers
|
|
|
|
— the extent of the input field is determined on a byte-by-byte basis. The resulting field is nevertheless a sequence of multibyte
|
|
characters that begins in the initial shift state.
|
|
enough to accept the sequence and the terminating null wide character, which will be
|
|
added automatically.
|
|
The conversion specifier includes all subsequent characters in the format string, up to
|
|
and including the matching right bracket (]). The characters between the brackets (the
|
|
scanlist) compose the scanset, unless the character after the left bracket is a circumflex (^),
|
|
in which case the scanset contains all characters that do not appear in the scanlist between
|
|
the circumflex and the right bracket. If the conversion specifier begins with [] or [^], the
|
|
right bracket character is in the scanlist and the next following right bracket character is
|
|
the matching right bracket that ends the specification; otherwise the first following right
|
|
bracket character is the one that ends the specification. If a - character is in the scanlist
|
|
and is not the first, nor the second where the first character is a ^, nor the last character,
|
|
the behavior is implementation-defined.
|
|
p Matches an implementation-defined set of sequences, which should be the same as the
|
|
set of sequences that may be produced by the %p conversion of the fprintf function.
|
|
The corresponding argument shall be a pointer to a pointer of void. The input item is
|
|
converted to a pointer value in an implementation-defined manner. If the input item is a
|
|
value converted earlier during the same program execution, the pointer that results shall
|
|
compare equal to that value; otherwise the behavior of the %p conversion is undefined.
|
|
n No input is consumed. The corresponding argument shall be a pointer of a signed integer
|
|
type. The number of characters read from the input stream so far by this call to the fscanf
|
|
function is stored into the integer object pointed to by the argument. Execution of a %n
|
|
directive does not increment the assignment count returned at the completion of execution
|
|
of the fscanf function. No argument is converted, but one is consumed. If the conversion
|
|
specification includes an assignment-suppressing character or a field width, the behavior
|
|
is undefined.
|
|
% Matches a single % character; no conversion or assignment occurs. The complete conversion
|
|
specification shall be %%.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.349'>
|
|
<pre><i><b>Footnote 349)</b> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [ conversion specifiers
|
|
— the extent of the input field is determined on a byte-by-byte basis. The resulting field is nevertheless a sequence of multibyte
|
|
characters that begins in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.349'>
|
|
<pre><i><b>Footnote 349)</b> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [ conversion specifiers
|
|
— the extent of the input field is determined on a byte-by-byte basis. The resulting field is nevertheless a sequence of multibyte
|
|
characters that begins in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.349'>
|
|
<pre><i><b>Footnote 349)</b> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [ conversion specifiers
|
|
— the extent of the input field is determined on a byte-by-byte basis. The resulting field is nevertheless a sequence of multibyte
|
|
characters that begins in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.349'>
|
|
<pre><i><b>Footnote 349)</b> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [ conversion specifiers
|
|
— the extent of the input field is determined on a byte-by-byte basis. The resulting field is nevertheless a sequence of multibyte
|
|
characters that begins in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.2p13'></a>
|
|
<pre>13 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.350'><sup>[350]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.350'>
|
|
<pre><i><b>Footnote 350)</b> See "future library directions" (<a href='#7.33.15'>7.33.15</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.2p14'></a>
|
|
<pre>14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as, respectively, a, e, f,
|
|
g, and x.
|
|
</pre>
|
|
<a name='7.23.6.2p15'></a>
|
|
<pre>15 Trailing white-space characters(including new-line characters) are left unread unless matched by a
|
|
directive. The success of literal matches and suppressed assignments is not directly determinable
|
|
other than via the %n directive.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.2p16'></a>
|
|
<pre>16 The fscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the function returns the number of input items
|
|
assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure or if the implementation does not support a specific width length modifier.
|
|
</pre>
|
|
<a name='7.23.6.2p17'></a>
|
|
<pre>17 EXAMPLE 1 The call:
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int n, i; float x; char name[50];
|
|
n = fscanf(stdin, "%d%f%s", &i, &x, name);
|
|
|
|
with the input line:
|
|
|
|
25 54.32E-1 thompson
|
|
|
|
|
|
will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0.
|
|
</pre>
|
|
<a name='7.23.6.2p18'></a>
|
|
<pre>18 EXAMPLE 2 The call:
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int i; float x; char name[50];
|
|
fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
|
|
|
|
with input:
|
|
|
|
56789 0123 56a72
|
|
|
|
|
|
will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the sequence 56\0. The next
|
|
character read from the input stream will be a.
|
|
</pre>
|
|
<a name='7.23.6.2p19'></a>
|
|
<pre>19 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int count; float quant; char units[21], item[21];
|
|
do {
|
|
count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
|
|
fscanf(stdin,"%*[^\n]");
|
|
} while (!feof(stdin) && !ferror(stdin));
|
|
|
|
</pre>
|
|
<a name='7.23.6.2p20'></a>
|
|
<pre>20 If the stdin stream contains the following lines:
|
|
|
|
2 quarts of oil
|
|
-12.8degrees Celsius
|
|
lots of luck
|
|
10.0LBS of
|
|
dirt
|
|
100ergs of energy
|
|
|
|
|
|
the execution of the above example will be analogous to the following assignments:
|
|
|
|
quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
|
|
count = 3;
|
|
quant = -12.8; strcpy(units, "degrees");
|
|
count = 2; // "C" fails to match "o"
|
|
count = 0; // "l" fails to match "%f"
|
|
quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
|
|
count = 3;
|
|
count = 0; // "100e" fails to match "%f"
|
|
count = EOF;
|
|
|
|
</pre>
|
|
<a name='7.23.6.2p21'></a>
|
|
<pre>21 EXAMPLE 4 In:
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int d1, d2, n1, n2, i;
|
|
i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
|
|
|
|
the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure, the value of 3 is also assigned
|
|
to n2. The value of d2 is not affected. The value 1 is assigned to i.
|
|
</pre>
|
|
<a name='7.23.6.2p22'></a>
|
|
<pre>22 EXAMPLE 5 The call:
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int n, i;
|
|
n = sscanf("foo %bar 42", "foo%%bar%d", &i);
|
|
|
|
will assign to n the value 1 and to i the value 42 because input white-space characters are skipped for both the % and d
|
|
conversion specifiers.
|
|
</pre>
|
|
<a name='7.23.6.2p23'></a>
|
|
<pre>23 EXAMPLE 6 In these examples, multibyte characters do have a state-dependent encoding, and the members of the extended
|
|
character set that consist of more than one byte each consist of exactly two bytes, the first of which is denoted here by a □
|
|
and the second by an uppercase letter, but are only recognized as such when in the alternate shift state. The shift sequences
|
|
are denoted by ↑ and ↓, in which the first causes entry into the alternate shift state.
|
|
</pre>
|
|
<a name='7.23.6.2p24'></a>
|
|
<pre>24 After the call:
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
char str[50];
|
|
fscanf(stdin, "a%s", str);
|
|
|
|
|
|
with the input line:
|
|
|
|
a↑□X□Y↓ bc
|
|
|
|
|
|
|
|
str will contain ↑□X□Y↓\\0 assuming that none of the bytes of the shift sequences (or of the multibyte characters, in the
|
|
more general case) appears to be a single-byte white-space character.
|
|
</pre>
|
|
<a name='7.23.6.2p25'></a>
|
|
<pre>25 In contrast, after the call:
|
|
|
|
#include <stdio.h>
|
|
#include <stddef.h>
|
|
/* ... */
|
|
wchar_t wstr[50];
|
|
fscanf(stdin, "a%ls", wstr);
|
|
|
|
|
|
with the same input line, wstr will contain the two wide characters that correspond to □X and □Y and a terminating null
|
|
wide character.
|
|
</pre>
|
|
<a name='7.23.6.2p26'></a>
|
|
<pre>26 However, the call:
|
|
|
|
#include <stdio.h>
|
|
#include <stddef.h>
|
|
/* ... */
|
|
wchar_t wstr[50];
|
|
fscanf(stdin, "a↑□X↓%ls", wstr);
|
|
|
|
|
|
with the same input line will return zero due to a matching failure against the ↓ sequence in the format string.
|
|
</pre>
|
|
<a name='7.23.6.2p27'></a>
|
|
<pre>27 Assuming that the first byte of the multibyte character □X is the same as the first byte of the multibyte character □Y, after the
|
|
call:
|
|
|
|
#include <stdio.h>
|
|
#include <stddef.h>
|
|
/* ... */
|
|
wchar_t wstr[50];
|
|
fscanf(stdin, "a↑□Y↓%ls", wstr);
|
|
|
|
|
|
with the same input line, zero will again be returned, but stdin will be left with a partially consumed multibyte character.
|
|
|
|
Forward references: the strtod, strtof, and strtold functions (<a href='#7.24.1.5'>7.24.1.5</a>), the strtol, strtoll,
|
|
strtoul, and strtoull functions (<a href='#7.24.1.7'>7.24.1.7</a>), conversion state (<a href='#7.31.6'>7.31.6</a>), the wcrtomb function
|
|
(<a href='#7.31.6.3.3'>7.31.6.3.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.6.3'></a>
|
|
<hr>
|
|
<h3>7.23.6.3 [The printf function]</h3>
|
|
<a name='7.23.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int printf(const char * restrict format, ...);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.3p2'></a>
|
|
<pre>2 The printf function is equivalent to fprintf with the argument stdout interposed before the
|
|
arguments to printf.
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.3p3'></a>
|
|
<pre>3 The printf function returns the number of characters transmitted, or a negative value if an output
|
|
or encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.23.6.4'></a>
|
|
<hr>
|
|
<h3>7.23.6.4 [The scanf function]</h3>
|
|
<a name='7.23.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int scanf(const char * restrict format, ...);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.4p2'></a>
|
|
<pre>2 The scanf function is equivalent to fscanf with the argument stdin interposed before the argu-
|
|
ments to scanf.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.4p3'></a>
|
|
<pre>3 The scanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the scanf function returns the number of input items
|
|
assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.23.6.5'></a>
|
|
<hr>
|
|
<h3>7.23.6.5 [The snprintf function]</h3>
|
|
<a name='7.23.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int snprintf(char * restrict s, size_t n, const char * restrict format, ...);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.5p2'></a>
|
|
<pre>2 The snprintf function is equivalent to fprintf, except that the output is written into an array
|
|
(specified by argument s) rather than to a stream. If n is zero, nothing is written, and s may be a
|
|
null pointer. Otherwise, output characters beyond the n-1st are discarded rather than being written
|
|
to the array, and a null character is written at the end of the characters actually written into the array.
|
|
If copying takes place between objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.5p3'></a>
|
|
<pre>3 The snprintf function returns the number of characters that would have been written had n been
|
|
sufficiently large, not counting the terminating null character, or a negative value if an encoding
|
|
error occurred. Thus, the null-terminated output has been completely written if and only if the
|
|
returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='7.23.6.6'></a>
|
|
<hr>
|
|
<h3>7.23.6.6 [The sprintf function]</h3>
|
|
<a name='7.23.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int sprintf(char * restrict s, const char * restrict format, ...);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.6p2'></a>
|
|
<pre>2 The sprintf function is equivalent to fprintf, except that the output is written into an array
|
|
(specified by the argument s) rather than to a stream. A null character is written at the end of the
|
|
characters written; it is not counted as part of the returned value. If copying takes place between
|
|
objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.6p3'></a>
|
|
<pre>3 The sprintf function returns the number of characters written in the array, not counting the
|
|
terminating null character, or a negative value if an encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.23.6.7'></a>
|
|
<hr>
|
|
<h3>7.23.6.7 [The sscanf function]</h3>
|
|
<a name='7.23.6.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int sscanf(const char * restrict s, const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.7p2'></a>
|
|
<pre>2 The sscanf function is equivalent to fscanf, except that input is obtained from a string (specified
|
|
by the argument s) rather than from a stream. Reaching the end of the string is equivalent to
|
|
encountering end-of-file for the fscanf function. If copying takes place between objects that overlap,
|
|
the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.6.7p3'></a>
|
|
<pre>3 The sscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the sscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.23.6.8'></a>
|
|
<hr>
|
|
<h3>7.23.6.8 [The vfprintf function]</h3>
|
|
<a name='7.23.6.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vfprintf(FILE * restrict stream, const char * restrict format, va_list arg);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.8p2'></a>
|
|
<pre>2 The vfprintf function is equivalent to fprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vfprintf function does not invoke the va_end macro<a href='#FOOTNOTE.351'><sup>[351]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.8p3'></a>
|
|
<pre>3 The vfprintf function returns the number of characters transmitted, or a negative value if an
|
|
output or encoding error occurred.
|
|
</pre>
|
|
<a name='7.23.6.8p4'></a>
|
|
<pre>4 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
|
|
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
|
|
void error(char *function_name, char *format, ...)
|
|
{
|
|
va_list args;
|
|
|
|
va_start(args, format);
|
|
// print out name of function causing error
|
|
fprintf(stderr, "ERROR in %s: ", function_name);
|
|
// print out remainder of message
|
|
vfprintf(stderr, format, args);
|
|
va_end(args);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='7.23.6.9'></a>
|
|
<hr>
|
|
<h3>7.23.6.9 [The vfscanf function]</h3>
|
|
<a name='7.23.6.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vfscanf(FILE * restrict stream, const char * restrict format, va_list arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.9p2'></a>
|
|
<pre>2 The vfscanf function is equivalent to fscanf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vfscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.9p3'></a>
|
|
<pre>3 The vfscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vfscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.23.6.10'></a>
|
|
<hr>
|
|
<h3>7.23.6.10 [The vprintf function]</h3>
|
|
<a name='7.23.6.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vprintf(const char * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.10p2'></a>
|
|
<pre>2 The vprintf function is equivalent to printf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vprintf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.10p3'></a>
|
|
<pre>3 The vprintf function returns the number of characters transmitted, or a negative value if an output
|
|
or encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.23.6.11'></a>
|
|
<hr>
|
|
<h3>7.23.6.11 [The vscanf function]</h3>
|
|
<a name='7.23.6.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vscanf(const char * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.11p2'></a>
|
|
<pre>2 The vscanf function is equivalent to scanf, with the variable argument list replaced by arg, which
|
|
shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The
|
|
vscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.11p3'></a>
|
|
<pre>3 The vscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.23.6.12'></a>
|
|
<hr>
|
|
<h3>7.23.6.12 [The vsnprintf function]</h3>
|
|
<a name='7.23.6.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsnprintf(char * restrict s, size_t n, const char * restrict format, va_list
|
|
arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.12p2'></a>
|
|
<pre>2 The vsnprintf function is equivalent to snprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vsnprintf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a> If copying takes place between
|
|
objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.12p3'></a>
|
|
<pre>3 The vsnprintf function returns the number of characters that would have been written had n been
|
|
sufficiently large, not counting the terminating null character, or a negative value if an encoding
|
|
error occurred. Thus, the null-terminated output has been completely written if and only if the
|
|
returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='7.23.6.13'></a>
|
|
<hr>
|
|
<h3>7.23.6.13 [The vsprintf function]</h3>
|
|
<a name='7.23.6.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsprintf(char * restrict s, const char * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.13p2'></a>
|
|
<pre>2 The vsprintf function is equivalent to sprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vsprintf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a> If copying takes place between objects
|
|
that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.13p3'></a>
|
|
<pre>3 The vsprintf function returns the number of characters written in the array, not counting the
|
|
terminating null character, or a negative value if an encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.23.6.14'></a>
|
|
<hr>
|
|
<h3>7.23.6.14 [The vsscanf function]</h3>
|
|
<a name='7.23.6.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsscanf(const char * restrict s, const char * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.6.14p2'></a>
|
|
<pre>2 The vsscanf function is equivalent to sscanf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vsscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.351'><sup>[351]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</b> As the functions vfprintf , vfscanf , vprintf , vscanf , vsnprintf , vsprintf , and vsscanf invoke the va_arg macro,
|
|
arg after the return has an indeterminate representation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.6.14p3'></a>
|
|
<pre>3 The vsscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vsscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.23.7'></a>
|
|
<hr>
|
|
<h3>7.23.7 [Character input/output functions]</h3>
|
|
<a name='7.23.7.1'></a>
|
|
<hr>
|
|
<h3>7.23.7.1 [The fgetc function]</h3>
|
|
<a name='7.23.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fgetc(FILE *stream);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.1p2'></a>
|
|
<pre>2 If the end-of-file indicator for the input stream pointed to by stream is not set and a next character
|
|
is present, the fgetc function obtains that character as an unsigned char converted to an int and
|
|
advances the associated file position indicator for the stream (if defined).
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.1p3'></a>
|
|
<pre>3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-of-file
|
|
indicator for the stream is set and the fgetc function returns EOF. Otherwise, the fgetc function
|
|
returns the next character from the input stream pointed to by stream. If a read error occurs, the
|
|
error indicator for the stream is set and the fgetc function returns EOF.<a href='#FOOTNOTE.352'><sup>[352]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.352'>
|
|
<pre><i><b>Footnote 352)</b> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.7.2'></a>
|
|
<hr>
|
|
<h3>7.23.7.2 [The fgets function]</h3>
|
|
<a name='7.23.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
char *fgets(char * restrict s, int n, FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.2p2'></a>
|
|
<pre>2 The fgets function reads at most one less than the number of characters specified by n from the
|
|
stream pointed to by stream into the array pointed to by s. No additional characters are read after a
|
|
new-line character (which is retained) or after end-of-file. A null character is written immediately
|
|
after the last character read into the array.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.2p3'></a>
|
|
<pre>3 The fgets function returns s if successful. If end-of-file is encountered and no characters have been
|
|
read into the array, the contents of the array remain unchanged and a null pointer is returned. If a
|
|
read error occurs during the operation, the members of the array have unspecified values and a null
|
|
pointer is returned.
|
|
|
|
</pre>
|
|
<a name='7.23.7.3'></a>
|
|
<hr>
|
|
<h3>7.23.7.3 [The fputc function]</h3>
|
|
<a name='7.23.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fputc(int c, FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.3p2'></a>
|
|
<pre>2 The fputc function writes the character specified by c (converted to an unsigned char) to the
|
|
output stream pointed to by stream, at the position indicated by the associated file position indicator
|
|
for the stream (if defined), and advances the indicator appropriately. If the file cannot support
|
|
positioning requests, or if the stream was opened with append mode, the character is appended to
|
|
the output stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.3p3'></a>
|
|
<pre>3 The fputc function returns the character written. If a write error occurs, the error indicator for the
|
|
stream is set and fputc returns EOF.
|
|
|
|
</pre>
|
|
<a name='7.23.7.4'></a>
|
|
<hr>
|
|
<h3>7.23.7.4 [The fputs function]</h3>
|
|
<a name='7.23.7.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fputs(const char * restrict s, FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.4p2'></a>
|
|
<pre>2 The fputs function writes the string pointed to by s to the stream pointed to by stream. The
|
|
terminating null character is not written.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.4p3'></a>
|
|
<pre>3 The fputs function returns EOF if a write error occurs; otherwise it returns a nonnegative value.
|
|
|
|
</pre>
|
|
<a name='7.23.7.5'></a>
|
|
<hr>
|
|
<h3>7.23.7.5 [The getc function]</h3>
|
|
<a name='7.23.7.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int getc(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.5p2'></a>
|
|
<pre>2 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it may evaluate
|
|
stream more than once, so the argument should never be an expression with side effects.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.5p3'></a>
|
|
<pre>3 The getc function returns the next character from the input stream pointed to by stream. If the
|
|
stream is at end-of-file, the end-of-file indicator for the stream is set and getc returns EOF. If a read
|
|
error occurs, the error indicator for the stream is set and getc returns EOF.
|
|
|
|
</pre>
|
|
<a name='7.23.7.6'></a>
|
|
<hr>
|
|
<h3>7.23.7.6 [The getchar function]</h3>
|
|
<a name='7.23.7.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int getchar(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.6p2'></a>
|
|
<pre>2 The getchar function is equivalent to getc with the argument stdin.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.6p3'></a>
|
|
<pre>3 The getchar function returns the next character from the input stream pointed to by stdin. If the
|
|
stream is at end-of-file, the end-of-file indicator for the stream is set and getchar returns EOF. If a
|
|
read error occurs, the error indicator for the stream is set and getchar returns EOF.
|
|
|
|
</pre>
|
|
<a name='7.23.7.7'></a>
|
|
<hr>
|
|
<h3>7.23.7.7 [The putc function]</h3>
|
|
<a name='7.23.7.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int putc(int c, FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.7p2'></a>
|
|
<pre>2 The putc function is equivalent to fputc, except that if it is implemented as a macro, it may evaluate
|
|
stream more than once, so that argument should never be an expression with side effects.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.7p3'></a>
|
|
<pre>3 The putc function returns the character written. If a write error occurs, the error indicator for the
|
|
stream is set and putc returns EOF.
|
|
|
|
</pre>
|
|
<a name='7.23.7.8'></a>
|
|
<hr>
|
|
<h3>7.23.7.8 [The putchar function]</h3>
|
|
<a name='7.23.7.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int putchar(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.8p2'></a>
|
|
<pre>2 The putchar function is equivalent to putc with the second argument stdout.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.8p3'></a>
|
|
<pre>3 The putchar function returns the character written. If a write error occurs, the error indicator for
|
|
the stream is set and putchar returns EOF.
|
|
</pre>
|
|
<a name='7.23.7.9'></a>
|
|
<hr>
|
|
<h3>7.23.7.9 [The puts function]</h3>
|
|
<a name='7.23.7.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int puts(const char *s);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.9p2'></a>
|
|
<pre>2 The puts function writes the string pointed to by s to the stream pointed to by stdout, and appends
|
|
a new-line character to the output. The terminating null character is not written.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.7.9p3'></a>
|
|
<pre>3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative value.
|
|
|
|
</pre>
|
|
<a name='7.23.7.10'></a>
|
|
<hr>
|
|
<h3>7.23.7.10 [The ungetc function]</h3>
|
|
<a name='7.23.7.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int ungetc(int c, FILE *stream);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.7.10p2'></a>
|
|
<pre>2 The ungetc function pushes the character specified by c (converted to an unsigned char) back
|
|
onto the input stream pointed to by stream. Pushed-back characters will be returned by subsequent
|
|
reads on that stream in the reverse order of their pushing. A successful intervening call (with the
|
|
stream pointed to by stream) to a file positioning function (fseek, fsetpos, or rewind) discards
|
|
any pushed-back characters for the stream. The external storage corresponding to the stream is
|
|
unchanged.
|
|
</pre>
|
|
<a name='7.23.7.10p3'></a>
|
|
<pre>3 One character of pushback is guaranteed. If the ungetc function is called too many times on the
|
|
same stream without an intervening read or file positioning operation on that stream, the operation
|
|
may fail.
|
|
</pre>
|
|
<a name='7.23.7.10p4'></a>
|
|
<pre>4 If the value of c equals that of the macro EOF, the operation fails and the input stream is unchanged.
|
|
</pre>
|
|
<a name='7.23.7.10p5'></a>
|
|
<pre>5 A successful call to the ungetc function clears the end-of-file indicator for the stream. The value
|
|
of the file position indicator for the stream after reading or discarding all pushed-back characters
|
|
shall be the same as it was before the characters were pushed back.<a href='#FOOTNOTE.353'><sup>[353]</sup></a> For a text stream, the value
|
|
of its file position indicator after a successful call to the ungetc function is unspecified until all
|
|
pushed-back characters are read or discarded. For a binary stream, its file position indicator is
|
|
decremented by each successful call to the ungetc function; if its value was zero before a call, it has
|
|
an indeterminate representation after the call<a href='#FOOTNOTE.354'><sup>[354]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.353'>
|
|
<pre><i><b>Footnote 353)</b> Note that a file positioning function could further modify the file position indicator after discarding any pushed-back
|
|
characters.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.354'>
|
|
<pre><i><b>Footnote 354)</b> See "future library directions" (<a href='#7.33.15'>7.33.15</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23.7.10p6'></a>
|
|
<pre>6 The ungetc function returns the character pushed back after conversion, or EOF if the operation
|
|
fails.
|
|
Forward references: file positioning functions (<a href='#7.23.9'>7.23.9</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.8'></a>
|
|
<hr>
|
|
<h3>7.23.8 [Direct input/output functions]</h3>
|
|
<a name='7.23.8.1'></a>
|
|
<hr>
|
|
<h3>7.23.8.1 [The fread function]</h3>
|
|
<a name='7.23.8.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
size_t fread(void * restrict ptr, size_t size, size_t nmemb,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.23.8.1p2'></a>
|
|
<pre>2 The fread function reads, into the array pointed to by ptr, up to nmemb elements whose size is
|
|
specified by size, from the stream pointed to by stream. For each object, size calls are made to
|
|
the fgetc function and the results stored, in the order read, in an array of unsigned char exactly
|
|
overlaying the object. The file position indicator for the stream (if defined) is advanced by the
|
|
number of characters successfully read. If an error occurs, the resulting representation of the file
|
|
position indicator for the stream is indeterminate. If a partial element is read, its representation is
|
|
indeterminate.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.8.1p3'></a>
|
|
<pre>3 The fread function returns the number of elements successfully read, which may be less than nmemb
|
|
if a read error or end-of-file is encountered. If size or nmemb is zero, fread returns zero and the
|
|
contents of the array and the state of the stream remain unchanged.
|
|
|
|
</pre>
|
|
<a name='7.23.8.2'></a>
|
|
<hr>
|
|
<h3>7.23.8.2 [The fwrite function]</h3>
|
|
<a name='7.23.8.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
size_t fwrite(const void * restrict ptr, size_t size, size_t nmemb,
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.8.2p2'></a>
|
|
<pre>2 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements whose size is
|
|
specified by size, to the stream pointed to by stream. For each object, size calls are made to the
|
|
fputc function, taking the values (in order) from an array of unsigned char exactly overlaying the
|
|
object. The file position indicator for the stream (if defined) is advanced by the number of characters
|
|
successfully written. If an error occurs, the resulting representation of the file position indicator for
|
|
the stream is indeterminate.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.8.2p3'></a>
|
|
<pre>3 The fwrite function returns the number of elements successfully written, which will be less than
|
|
nmemb only if a write error is encountered. If size or nmemb is zero, fwrite returns zero and the
|
|
state of the stream remains unchanged.
|
|
|
|
</pre>
|
|
<a name='7.23.9'></a>
|
|
<hr>
|
|
<h3>7.23.9 [File positioning functions]</h3>
|
|
<a name='7.23.9.1'></a>
|
|
<hr>
|
|
<h3>7.23.9.1 [The fgetpos function]</h3>
|
|
<a name='7.23.9.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fgetpos(FILE * restrict stream, fpos_t * restrict pos);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.9.1p2'></a>
|
|
<pre>2 The fgetpos function stores the current values of the parse state (if any) and file position indicator
|
|
for the stream pointed to by stream in the object pointed to by pos. The values stored contain
|
|
unspecified information usable by the fsetpos function for repositioning the stream to its position
|
|
at the time of the call to the fgetpos function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.9.1p3'></a>
|
|
<pre>3 If successful, the fgetpos function returns zero; on failure, the fgetpos function returns nonzero
|
|
and stores an implementation-defined positive value in errno.
|
|
Forward references: the fsetpos function (<a href='#7.23.9.3'>7.23.9.3</a>).
|
|
</pre>
|
|
<a name='7.23.9.2'></a>
|
|
<hr>
|
|
<h3>7.23.9.2 [The fseek function]</h3>
|
|
<a name='7.23.9.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fseek(FILE *stream, long int offset, int whence);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.9.2p2'></a>
|
|
<pre>2 The fseek function sets the file position indicator for the stream pointed to by stream. If a read or
|
|
write error occurs, the error indicator for the stream is set and fseek fails.
|
|
</pre>
|
|
<a name='7.23.9.2p3'></a>
|
|
<pre>3 For a binary stream, the new position, measured in characters from the beginning of the file, is
|
|
obtained by adding offset to the position specified by whence. The specified position is the
|
|
beginning of the file if whence is SEEK_SET, the current value of the file position indicator if
|
|
SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not meaningfully support fseek calls
|
|
with a whence value of SEEK_END.
|
|
</pre>
|
|
<a name='7.23.9.2p4'></a>
|
|
<pre>4 For a text stream, either offset shall be zero, or offset shall be a value returned by an earlier
|
|
successful call to the ftell function on a stream associated with the same file and whence shall be
|
|
SEEK_SET.
|
|
</pre>
|
|
<a name='7.23.9.2p5'></a>
|
|
<pre>5 After determining the new position, a successful call to the fseek function undoes any effects of the
|
|
ungetc function on the stream, clears the end-of-file indicator for the stream, and then establishes
|
|
the new position. After a successful fseek call, the next operation on an update stream may be
|
|
either input or output.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.9.2p6'></a>
|
|
<pre>6 The fseek function returns nonzero only for a request that cannot be satisfied.
|
|
Forward references: the ftell function (<a href='#7.23.9.4'>7.23.9.4</a>).
|
|
|
|
</pre>
|
|
<a name='7.23.9.3'></a>
|
|
<hr>
|
|
<h3>7.23.9.3 [The fsetpos function]</h3>
|
|
<a name='7.23.9.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fsetpos(FILE *stream, const fpos_t *pos);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.9.3p2'></a>
|
|
<pre>2 The fsetpos function sets the mbstate_t object (if any) and file position indicator for the stream
|
|
pointed to by stream according to the value of the object pointed to by pos, which shall be a value
|
|
obtained from an earlier successful call to the fgetpos function on a stream associated with the
|
|
same file. If a read or write error occurs, the error indicator for the stream is set and fsetpos fails.
|
|
</pre>
|
|
<a name='7.23.9.3p3'></a>
|
|
<pre>3 A successful call to the fsetpos function undoes any effects of the ungetc function on the stream,
|
|
clears the end-of-file indicator for the stream, and then establishes the new parse state and position.
|
|
After a successful fsetpos call, the next operation on an update stream may be either input or
|
|
output.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.9.3p4'></a>
|
|
<pre>4 If successful, the fsetpos function returns zero; on failure, the fsetpos function returns nonzero
|
|
and stores an implementation-defined positive value in errno.
|
|
|
|
</pre>
|
|
<a name='7.23.9.4'></a>
|
|
<hr>
|
|
<h3>7.23.9.4 [The ftell function]</h3>
|
|
<a name='7.23.9.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
long int ftell(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.9.4p2'></a>
|
|
<pre>2 The ftell function obtains the current value of the file position indicator for the stream pointed to
|
|
by stream. For a binary stream, the value is the number of characters from the beginning of the file.
|
|
For a text stream, its file position indicator contains unspecified information, usable by the fseek
|
|
function for returning the file position indicator for the stream to its position at the time of the ftell
|
|
call; the difference between two such return values is not necessarily a meaningful measure of the
|
|
number of characters written or read.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.9.4p3'></a>
|
|
<pre>3 If successful, the ftell function returns the current value of the file position indicator for the stream.
|
|
On failure, the ftell function returns −1L and stores an implementation-defined positive value in
|
|
errno.
|
|
|
|
</pre>
|
|
<a name='7.23.9.5'></a>
|
|
<hr>
|
|
<h3>7.23.9.5 [The rewind function]</h3>
|
|
<a name='7.23.9.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void rewind(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.9.5p2'></a>
|
|
<pre>2 The rewind function sets the file position indicator for the stream pointed to by stream to the
|
|
beginning of the file. It is equivalent to
|
|
|
|
(void)fseek(stream, 0L, SEEK_SET)
|
|
|
|
|
|
except that the error indicator for the stream is also cleared.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.9.5p3'></a>
|
|
<pre>3 The rewind function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.23.10'></a>
|
|
<hr>
|
|
<h3>7.23.10 [Error-handling functions]</h3>
|
|
<a name='7.23.10.1'></a>
|
|
<hr>
|
|
<h3>7.23.10.1 [The clearerr function]</h3>
|
|
<a name='7.23.10.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void clearerr(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.10.1p2'></a>
|
|
<pre>2 The clearerr function clears the end-of-file and error indicators for the stream pointed to by
|
|
stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.10.1p3'></a>
|
|
<pre>3 The clearerr function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.23.10.2'></a>
|
|
<hr>
|
|
<h3>7.23.10.2 [The feof function]</h3>
|
|
<a name='7.23.10.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int feof(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.10.2p2'></a>
|
|
<pre>2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.10.2p3'></a>
|
|
<pre>3 The feof function returns nonzero if and only if the end-of-file indicator is set for stream.
|
|
</pre>
|
|
<a name='7.23.10.3'></a>
|
|
<hr>
|
|
<h3>7.23.10.3 [The ferror function]</h3>
|
|
<a name='7.23.10.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int ferror(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.10.3p2'></a>
|
|
<pre>2 The ferror function tests the error indicator for the stream pointed to by stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.10.3p3'></a>
|
|
<pre>3 The ferror function returns nonzero if and only if the error indicator is set for stream.
|
|
|
|
</pre>
|
|
<a name='7.23.10.4'></a>
|
|
<hr>
|
|
<h3>7.23.10.4 [The perror function]</h3>
|
|
<a name='7.23.10.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void perror(const char *s);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.23.10.4p2'></a>
|
|
<pre>2 The perror function maps the error number in the integer expression errno to an error message.
|
|
It writes a sequence of characters to the standard error stream thus: first (if s is not a null pointer
|
|
and the character pointed to by s is not the null character), the string pointed to by s followed by a
|
|
colon (:) and a space; then an appropriate error message string followed by a new-line character.
|
|
The contents of the error message strings are the same as those returned by the strerror function
|
|
with argument errno.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.23.10.4p3'></a>
|
|
<pre>3 The perror function returns no value.
|
|
Forward references: the strerror function (<a href='#7.26.6.3'>7.26.6.3</a>).
|
|
</pre>
|
|
<a name='7.24'></a>
|
|
<hr>
|
|
<h3>7.24 [General utilities <stdlib.h>]</h3>
|
|
<a name='7.24p1'></a>
|
|
<pre>1 The header <stdlib.h> declares five types and several functions of general utility, and defines
|
|
several macros.<a href='#FOOTNOTE.355'><sup>[355]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.355'>
|
|
<pre><i><b>Footnote 355)</b> See "future library directions" (<a href='#7.33.16'>7.33.16</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24p2'></a>
|
|
<pre>2 The feature test macro __STDC_VERSION_STDLIB_H__ expands to the token 202311L.
|
|
</pre>
|
|
<a name='7.24p3'></a>
|
|
<pre>3 The types declared are size_t and wchar_t (both described in <a href='#7.21'>7.21</a>), once_flag (described in <a href='#7.28'>7.28</a>),
|
|
|
|
div_t
|
|
|
|
|
|
which is a structure type that is the type of the value returned by the div function,
|
|
|
|
ldiv_t
|
|
|
|
|
|
which is a structure type that is the type of the value returned by the ldiv function, and
|
|
|
|
lldiv_t
|
|
|
|
|
|
which is a structure type that is the type of the value returned by the lldiv function.
|
|
</pre>
|
|
<a name='7.24p4'></a>
|
|
<pre>4 The macros defined are NULL (described in <a href='#7.21'>7.21</a>); ONCE_FLAG_INIT (described in <a href='#7.28'>7.28</a>);
|
|
|
|
EXIT_FAILURE
|
|
|
|
|
|
and
|
|
|
|
EXIT_SUCCESS
|
|
|
|
|
|
which expand to integer constant expressions that can be used as the argument to the exit function
|
|
to return unsuccessful or successful termination status, respectively, to the host environment;
|
|
|
|
RAND_MAX
|
|
|
|
|
|
which expands to an integer constant expression that is the maximum value returned by the rand
|
|
function; and
|
|
|
|
MB_CUR_MAX
|
|
|
|
|
|
which expands to a positive integer expression with type size_t that is the maximum number of
|
|
bytes in a multibyte character for the extended character set specified by the current locale (category
|
|
LC_CTYPE), which is never greater than MB_LEN_MAX.
|
|
</pre>
|
|
<a name='7.24p5'></a>
|
|
<pre>5 The function
|
|
|
|
#include <stdlib.h>
|
|
void call_once(once_flag *flag, void (*func)(void));
|
|
|
|
|
|
is described in <a href='#7.28.2'>7.28.2</a>.
|
|
|
|
</pre>
|
|
<a name='7.24.1'></a>
|
|
<hr>
|
|
<h3>7.24.1 [Numeric conversion functions]</h3>
|
|
<a name='7.24.1p1'></a>
|
|
<pre>1 The functions atof, atoi, atol, and atoll need not affect the value of the integer expression errno
|
|
on an error. If the value of the result cannot be represented, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='7.24.1.1'></a>
|
|
<hr>
|
|
<h3>7.24.1.1 [The atof function]</h3>
|
|
<a name='7.24.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
double atof(const char *nptr);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.1p2'></a>
|
|
<pre>2 The atof function converts the initial portion of the string pointed to by nptr to double representa-
|
|
tion. Except for the behavior on error, it is equivalent to
|
|
|
|
strtod(nptr, nullptr)
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.1p3'></a>
|
|
<pre>3 The atof function returns the converted value.
|
|
Forward references: the strtod, strtof, and strtold functions (<a href='#7.24.1.5'>7.24.1.5</a>).
|
|
|
|
</pre>
|
|
<a name='7.24.1.2'></a>
|
|
<hr>
|
|
<h3>7.24.1.2 [The atoi, atol, and atoll functions]</h3>
|
|
<a name='7.24.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int atoi(const char *nptr);
|
|
long int atol(const char *nptr);
|
|
long long int atoll(const char *nptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.2p2'></a>
|
|
<pre>2 The atoi, atol, and atoll functions convert the initial portion of the string pointed to by nptr to
|
|
int, long int, and long long int representation, respectively. Except for the behavior on error,
|
|
they are equivalent to
|
|
|
|
atoi: (int)strtol(nptr, nullptr, 10)
|
|
atol: strtol(nptr, nullptr, 10)
|
|
atoll: strtoll(nptr, nullptr, 10)
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.2p3'></a>
|
|
<pre>3 The atoi, atol, and atoll functions return the converted value.
|
|
Forward references: the strtol, strtoll, strtoul, and strtoull functions (<a href='#7.24.1.7'>7.24.1.7</a>).
|
|
|
|
</pre>
|
|
<a name='7.24.1.3'></a>
|
|
<hr>
|
|
<h3>7.24.1.3 [The strfromd, strfromf, and strfroml functions]</h3>
|
|
<a name='7.24.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int strfromd(char *restrict s, size_t n, const char *restrict format, double fp);
|
|
int strfromf(char *restrict s, size_t n, const char *restrict format, float fp);
|
|
int strfroml(char *restrict s, size_t n, const char *restrict format, long double fp);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.3p2'></a>
|
|
<pre>2 The strfromd, strfromf, and strfroml functions are equivalent to snprintf(s, n, format, fp)
|
|
(<a href='#7.23.6.5'>7.23.6.5</a>), except that the format string shall only contain the character %, an optional precision that
|
|
does not contain an asterisk *, and one of the conversion specifiers a, A, e, E, f, F, g, or G, which
|
|
applies to the type (double, float, or long double) indicated by the function suffix (rather than by
|
|
a length modifier).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.3p3'></a>
|
|
<pre>3 The strfromd, strfromf, and strfroml functions return the number of characters that would
|
|
have been written had n been sufficiently large, not counting the terminating null character. Thus,
|
|
the null-terminated output has been completely written if and only if the returned value is both
|
|
nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='7.24.1.4'></a>
|
|
<hr>
|
|
<h3>7.24.1.4 [The strfromdN functions]</h3>
|
|
<a name='7.24.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int strfromd32(char*restrict s, size_t n, const char*restrict format, _Decimal32 fp);
|
|
int strfromd64(char*restrict s, size_t n, const char*restrict format, _Decimal64 fp);
|
|
int strfromd128(char*restrict s, size_t n, const char*restrict format, _Decimal128 fp);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.4p2'></a>
|
|
<pre>2 The strfromdN functions are equivalent to snprintf(s, n, format, fp) (<a href='#7.23.6.5'>7.23.6.5</a>), except the
|
|
format string contains only the character %, an optional precision that does not contain an asterisk *,
|
|
and one of the conversion specifiers a, A, e, E, f, F, g, or G, which applies to the type (_Decimal32 ,
|
|
_Decimal64 , or _Decimal128 ) indicated by the function suffix (rather than by a length modifier).
|
|
Use of these functions with any other format string results in undefined behavior.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.4p3'></a>
|
|
<pre>3 The strfromdN functions return the number of characters that would have been written had n been
|
|
sufficiently large, not counting the terminating null character. Thus, the null-terminated output has
|
|
been completely written if and only if the returned value is less than n.
|
|
|
|
</pre>
|
|
<a name='7.24.1.5'></a>
|
|
<hr>
|
|
<h3>7.24.1.5 [The strtod, strtof, and strtold functions]</h3>
|
|
<a name='7.24.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
double strtod(const char *restrict nptr, char **restrict endptr);
|
|
float strtof(const char *restrict nptr, char **restrict endptr);
|
|
long double strtold(const char *restrict nptr, char **restrict endptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.5p2'></a>
|
|
<pre>2 The strtod, strtof, and strtold functions convert the initial portion of the string pointed to by
|
|
nptr to double, float, and long double representation, respectively. First, they decompose the
|
|
input string into three parts: an initial, possibly empty, sequence of white-space characters, a subject
|
|
sequence resembling a floating constant or representing an infinity or NaN; and a final string of one
|
|
or more unrecognized characters, including the terminating null character of the input string. Then,
|
|
they attempt to convert the subject sequence to a floating-point number, and return the result.
|
|
</pre>
|
|
<a name='7.24.1.5p3'></a>
|
|
<pre>3 The expected form of the subject sequence is an optional plus or minus sign, then one of the
|
|
following:
|
|
|
|
— a nonempty sequence of decimal digits optionally containing a decimal-point character, then
|
|
an optional exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</a>, excluding any digit separators (<a href='#6.4.4.1'>6.4.4.1</a>);
|
|
— a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a decimal-
|
|
point character, then an optional binary exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</a>, excluding any digit
|
|
separators;
|
|
— INF or INFINITY, ignoring case
|
|
— NAN or NAN(n-char-sequenceopt ), ignoring case in the NAN part, where: n-char-sequence:
|
|
digit
|
|
nondigit
|
|
n-char-sequence digit
|
|
n-char-sequence nondigit
|
|
|
|
|
|
The subject sequence is defined as the longest initial subsequence of the input string, starting with
|
|
the first non-white-space character, that is of the expected form. The subject sequence contains no
|
|
characters if the input string is not of the expected form.
|
|
</pre>
|
|
<a name='7.24.1.5p4'></a>
|
|
<pre>4 If the subject sequence has the expected form for a floating-point number, the sequence of characters
|
|
starting with the first digit or the decimal-point character (whichever occurs first) is interpreted as a
|
|
floating constant according to the rules of <a href='#6.4.4.2'>6.4.4.2</a>, except that the decimal-point character is used
|
|
in place of a period, and that if neither an exponent part nor a decimal-point character appears in
|
|
a decimal floating-point number, or if a binary exponent part does not appear in a hexadecimal
|
|
floating-point number, an exponent part of the appropriate type with value zero is assumed to
|
|
follow the last digit in the string. If the subject sequence begins with a minus sign, the sequence is
|
|
interpreted as negated.<a href='#FOOTNOTE.356'><sup>[356]</sup></a>
|
|
|
|
A character sequence INF or INFINITY is interpreted as an infinity, if representable in the return type,
|
|
else like a floating constant that is too large for the range of the return type. A character sequence
|
|
NAN or NAN(n-char-sequenceopt ) is interpreted as a quiet NaN, if supported in the return type, else like
|
|
a subject sequence part that does not have the expected form; the meaning of the n-char sequence
|
|
is implementation-defined.<a href='#FOOTNOTE.357'><sup>[357]</sup></a> A pointer to the final string is stored in the object pointed to by
|
|
endptr, provided that endptr is not a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.356'>
|
|
<pre><i><b>Footnote 356)</b> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by negating the value
|
|
resulting from converting the corresponding unsigned sequence (see <a href='#F.5'>F.5</a>); the two methods could yield different results if
|
|
rounding is toward positive or negative infinity. In either case, the functions honor the sign of zero if floating-point arithmetic
|
|
supports signed zeros.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.357'>
|
|
<pre><i><b>Footnote 357)</b> An implementation can use the n-char sequence to determine extra information to be represented in the NaN’s significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.1.5p5'></a>
|
|
<pre>5 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the value resulting
|
|
from the conversion is correctly rounded.
|
|
</pre>
|
|
<a name='7.24.1.5p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.24.1.5p7'></a>
|
|
<pre>7 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.24.1.5p8'></a>
|
|
<pre>8 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and the result is
|
|
not exactly representable, the result should be one of the two numbers in the appropriate internal
|
|
format that are adjacent to the hexadecimal floating source value, with the extra stipulation that the
|
|
error should have a correct sign for the current rounding direction.
|
|
</pre>
|
|
<a name='7.24.1.5p9'></a>
|
|
<pre>9 If the subject sequence has the decimal form and at most M significant digits, where M is the
|
|
maximum value of the T_DECIMAL_DIG macros (defined in <float.h>), the result should be correctly
|
|
rounded. If the subject sequence D has the decimal form and more than M significant digits, consider
|
|
the two bounding, adjacent decimal strings L and U, both having M significant digits, such that the
|
|
values of L, D, and U satisfy L ≤ D ≤ U. The result should be one of the (equal or adjacent) values
|
|
that would be obtained by correctly rounding L and U according to the current rounding direction,
|
|
with the extra stipulation that the error with respect to D should have a correct sign for the current
|
|
rounding direction.<a href='#FOOTNOTE.358'><sup>[358]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.358'>
|
|
<pre><i><b>Footnote 358)</b> M is sufficiently large that L and U will usually correctly round to the same internal floating value, but if not will correctly
|
|
round to adjacent values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.1.5p10'></a>
|
|
<pre>10 The functions return the converted value, if any. If no conversion could be performed, zero is
|
|
returned.
|
|
If the correct value overflows and default rounding is in effect (<a href='#7.12.1'>7.12.1</a>), plus or minus HUGE_VAL,
|
|
HUGE_VALF, or HUGE_VALL is returned (according to the return type and sign of the value); if the
|
|
integer expression math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
|
|
acquires the value of ERANGE; if the integer expression math_errhandling & MATH_ERREXCEPT is
|
|
nonzero, the "overflow" floating-point exception is raised.
|
|
If the result underflows (<a href='#7.12.1'>7.12.1</a>), the functions return a value whose magnitude is no greater
|
|
than the smallest normalized positive number in the return type; if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the value ERANGE is
|
|
implementation-defined; if the integer expression math_errhandling & MATH_ERREXCEPT is
|
|
nonzero, whether the "underflow" floating-point exception is raised is implementation-defined.
|
|
</pre>
|
|
<a name='7.24.1.6'></a>
|
|
<hr>
|
|
<h3>7.24.1.6 [The strtodN functions]</h3>
|
|
<a name='7.24.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 strtod32(const char * restrict nptr, char ** restrict endptr);
|
|
_Decimal64 strtod64(const char * restrict nptr,char ** restrict endptr);
|
|
_Decimal128 strtod128(const char * restrict nptr,char ** restrict endptr);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.6p2'></a>
|
|
<pre>2 The strtodN functions convert the initial portion of the string pointed to by nptr to decimal floating
|
|
type representation. First, they decompose the input string into three parts: an initial, possibly
|
|
empty, sequence of white-space characters; a subject sequence resembling a floating constant or
|
|
representing an infinity or NaN; and a final string of one or more unrecognized characters, including
|
|
the terminating null character of the input string. Then, they attempt to convert the subject sequence
|
|
to a floating-point number, and return the result.
|
|
</pre>
|
|
<a name='7.24.1.6p3'></a>
|
|
<pre>3 The expected form of the subject sequence is an optional plus or minus sign, then one of the
|
|
following:
|
|
|
|
— a nonempty sequence of decimal digits optionally containing a decimal-point character, then
|
|
an optional exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</a>, excluding any digit separators (<a href='#6.4.4.1'>6.4.4.1</a>)
|
|
— INF or INFINITY, ignoring case
|
|
— NAN or NAN(d-char-sequenceopt ), ignoring case in the NAN part, where: d-char-sequence:
|
|
digit
|
|
nondigit
|
|
d-char-sequence digit
|
|
d-char-sequence nondigit
|
|
|
|
|
|
|
|
|
|
The subject sequence is defined as the longest initial subsequence of the input string, starting with
|
|
the first non-white-space character, that is of the expected form. The subject sequence contains no
|
|
characters if the input string is not of the expected form.
|
|
</pre>
|
|
<a name='7.24.1.6p4'></a>
|
|
<pre>4 If the subject sequence has the expected form for a floating-point number, the sequence of characters
|
|
starting with the first digit or the decimal-point character (whichever occurs first) is interpreted as a
|
|
floating constant according to the rules of <a href='#6.4.4.2'>6.4.4.2</a>, including correct rounding and determination of
|
|
the coefficient c and the quantum exponent q, with the following exceptions:
|
|
|
|
— It is not a hexadecimal floating number.
|
|
— The decimal-point character is used in place of a period.
|
|
— If neither an exponent part nor a decimal-point character appears in a decimal floating-point
|
|
number, an exponent part of the appropriate type with value zero is assumed to follow the
|
|
last digit in the string.
|
|
|
|
If the subject sequence begins with a minus sign, the sequence is interpreted as negated (before
|
|
rounding) and the sign s is set to −1, else s is set to 1. A character sequence INF or INFINITY is
|
|
interpreted as an infinity. A character sequence NAN or NAN(d-char-sequenceopt ), is interpreted as a
|
|
quiet NaN; the meaning of the d-char sequence is implementation-defined.<a href='#FOOTNOTE.359'><sup>[359]</sup></a> A pointer to the final
|
|
string is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.359'>
|
|
<pre><i><b>Footnote 359)</b> An implementation may use the d-char sequence to determine extra information to be represented in the NaN’s
|
|
significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.1.6p5'></a>
|
|
<pre>5 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.24.1.6p6'></a>
|
|
<pre>6 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.6p7'></a>
|
|
<pre>7 The strtodN functions return the correctly rounded converted value, if any. If no conversion could
|
|
be performed, the value of the triple (+1, 0, 0) is returned. If the correct value overflows:
|
|
|
|
— the value of the macro ERANGE is stored in errno if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero;
|
|
|
|
— the "overflow" floating-point exception is raised if the integer expression
|
|
math_errhandling & MATH_ERREXCEPT is nonzero.
|
|
|
|
If the result underflows (<a href='#7.12.1'>7.12.1</a>), whether errno acquires the value ERANGE if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero is implementation-defined; if the integer expres-
|
|
sion math_errhandling & MATH_ERREXCEPT is nonzero, whether the "underflow" floating-point
|
|
exception is raised is implementation-defined.
|
|
</pre>
|
|
<a name='7.24.1.6p8'></a>
|
|
<pre>8 EXAMPLE Following are subject sequences of the decimal form and the resulting triples (s, c, q) produced by strtod64.
|
|
Note that for _Decimal64 , the precision (maximum coefficient length) is 16 and the quantum exponent range is −398 ≤ q ≤ 369.
|
|
|
|
"0" (+1, 0, 0)
|
|
"0.00" (+1, 0, −2)
|
|
"123" (+1, 123, 0)
|
|
"-123" (−1, 123, 0)
|
|
"<a href='#1.'>1.</a>23E3" (+1, 123, 1)
|
|
"<a href='#1.'>1.</a>23E+3" (+1, 123, 1)
|
|
"12.3E+7" (+1, 123, 6)
|
|
"12.0" (+1, 120, −1)
|
|
"12.3" (+1, 123, −1)
|
|
"0.00123" (+1, 123, −5)
|
|
"-<a href='#1.'>1.</a>23E-12" (−1, 123, −14)
|
|
"1234.5E-4" (+1, 12345, −5)
|
|
"-0" (−1, 0, 0)
|
|
"-0.00" (−1, 0, −2)
|
|
"0E+7" (+1, 0, 7)
|
|
"-0E-7" (−1, 0, −7)
|
|
"12345678901234567890" (+1, 1234567890123457, 4) or (+1, 1234567890123456, 4) depending on rounding
|
|
mode
|
|
"1234E-400" (+1, 12, −398) or (+1, 13, −398) depending on rounding mode
|
|
"1234E-402" (+1, 0, −398) or (+1, 1, −398) depending on rounding mode
|
|
"1000." (+1, 1000, 0)
|
|
".0001" (+1, 1, −4)
|
|
"1000.e0" (+1, 1000, 0)
|
|
".0001e0" (+1, 1, −4)
|
|
"1000.0" (+1, 10000, −1)
|
|
"0.0001" (+1, 1, −4)
|
|
"1000.00" (+1, 100000, −2)
|
|
"00.0001" (+1, 1, −4)
|
|
"001000." (+1, 1000, 0)
|
|
"001000.0" (+1, 10000, −1)
|
|
"001000.00" (+1, 100000, −2)
|
|
"00.00" (+1, 0, −2)
|
|
"00." (+1, 0, 0)
|
|
".00" (+1, 0, −2)
|
|
"00.00e-5" (+1, 0, −7)
|
|
"00.e-5" (+1, 0, −5)
|
|
".00e-5" (+1, 0, −7)
|
|
"0x1.8p+4" (+1, 0, 0), and a pointer to "x1.8p+4" is stored in the object pointed to by endptr,
|
|
provided endptr is not a null pointer
|
|
"infinite" infinity, and a pointer to "inite" is stored in the object pointed to by endptr, provided
|
|
endptr is not a null pointer
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.24.1.7'></a>
|
|
<hr>
|
|
<h3>7.24.1.7 [The strtol, strtoll, strtoul, and strtoull functions]</h3>
|
|
<a name='7.24.1.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
long int strtol(const char *restrict nptr, char **restrict endptr, int base);
|
|
long long int strtoll(const char *restrict nptr, char **restrict endptr, int base);
|
|
unsigned long int strtoul(const char *restrict nptr, char **restrict endptr, int base);
|
|
unsigned long long int strtoull(const char *restrict nptr, char **restrict endptr, int
|
|
base);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.1.7p2'></a>
|
|
<pre>2 The strtol, strtoll, strtoul, and strtoull functions convert the initial portion of
|
|
the string pointed to by nptr to long int, long long int, unsigned long int, and
|
|
unsigned long long int representation, respectively. First, they decompose the input
|
|
string into three parts: an initial, possibly empty, sequence of white-space characters, a subject
|
|
sequence resembling an integer represented in some radix determined by the value of base, and a
|
|
final string of one or more unrecognized characters, including the terminating null character of the
|
|
input string. Then, they attempt to convert the subject sequence to an integer, and return the result.
|
|
</pre>
|
|
<a name='7.24.1.7p3'></a>
|
|
<pre>3 If the value of base is zero, the expected form of the subject sequence is that of an integer constant as
|
|
described in <a href='#6.4.4.1'>6.4.4.1</a>, optionally preceded by a plus or minus sign, but not including an integer suffix
|
|
or any optional digit separators. If the value of base is between 2 and 36 (inclusive), the expected
|
|
form of the subject sequence is a sequence of letters and digits representing an integer with the radix
|
|
specified by base, optionally preceded by a plus or minus sign, but not including an integer suffix
|
|
or any optional digit separators. The letters from a (or A) through z (or Z) are ascribed the values 10
|
|
through 35; only letters and digits whose ascribed values are less than that of base are permitted. If
|
|
the value of base is 2, the characters 0b or 0B may optionally precede the sequence of letters and
|
|
digits, following the sign if present. If the value of base is 16, the characters 0x or 0X may optionally
|
|
precede the sequence of letters and digits, following the sign if present.
|
|
</pre>
|
|
<a name='7.24.1.7p4'></a>
|
|
<pre>4 The subject sequence is defined as the longest initial subsequence of the input string, starting with
|
|
the first non-white-space character, that is of the expected form. The subject sequence contains no
|
|
characters if the input string is empty or consists entirely of white-space characters, or if the first
|
|
non-white-space character is other than a sign or a permissible letter or digit.
|
|
</pre>
|
|
<a name='7.24.1.7p5'></a>
|
|
<pre>5 If the subject sequence has the expected form and the value of base is zero, the sequence of characters
|
|
starting with the first digit is interpreted as an integer constant according to the rules of <a href='#6.4.4.1'>6.4.4.1</a>. If
|
|
the subject sequence has the expected form and the value of base is between 2 and 36, it is used as
|
|
the base for conversion, ascribing to each letter its value as given above. If the subject sequence
|
|
begins with a minus sign, the value resulting from the conversion is negated (in the return type). A
|
|
pointer to the final string is stored in the object pointed to by endptr, provided that endptr is not a
|
|
null pointer.
|
|
</pre>
|
|
<a name='7.24.1.7p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.24.1.7p7'></a>
|
|
<pre>7 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.1.7p8'></a>
|
|
<pre>8 The strtol, strtoll, strtoul, and strtoull functions return the converted value, if any. If
|
|
no conversion could be performed, zero is returned. If the correct value is outside the range of
|
|
representable values, LONG_MIN, LONG_MAX, LLONG_MIN, LLONG_MAX, ULONG_MAX, or ULLONG_MAX is
|
|
returned (according to the return type and sign of the value, if any), and the value of the macro
|
|
ERANGE is stored in errno.
|
|
|
|
</pre>
|
|
<a name='7.24.2'></a>
|
|
<hr>
|
|
<h3>7.24.2 [Pseudo-random sequence generation functions]</h3>
|
|
<a name='7.24.2.1'></a>
|
|
<hr>
|
|
<h3>7.24.2.1 [The rand function]</h3>
|
|
<a name='7.24.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int rand(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.1p2'></a>
|
|
<pre>2 The rand function computes a sequence of pseudo-random integers in the range 0 to RAND_MAX
|
|
inclusive.
|
|
</pre>
|
|
<a name='7.24.2.1p3'></a>
|
|
<pre>3 The rand function is not required to avoid data races with other calls to pseudo-random sequence
|
|
generation functions. The implementation shall behave as if no library function calls the rand
|
|
function.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.24.2.1p4'></a>
|
|
<pre>4 There are no guarantees as to the quality of the random sequence produced and some implementa-
|
|
tions are known to produce sequences with distressingly non-random low-order bits. Applications
|
|
with particular requirements should use a generator that is known to be sufficient for their needs.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.2.1p5'></a>
|
|
<pre>5 The rand function returns a pseudo-random integer.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.24.2.1p6'></a>
|
|
<pre>6 The value of the RAND_MAX macro shall be at least 32767.
|
|
|
|
</pre>
|
|
<a name='7.24.2.2'></a>
|
|
<hr>
|
|
<h3>7.24.2.2 [The srand function]</h3>
|
|
<a name='7.24.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void srand(unsigned int seed);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.2p2'></a>
|
|
<pre>2 The srand function uses the argument as a seed for a new sequence of pseudo-random numbers
|
|
to be returned by subsequent calls to rand. If srand is then called with the same seed value, the
|
|
sequence of pseudo-random numbers shall be repeated. If rand is called before any calls to srand
|
|
have been made, the same sequence shall be generated as when srand is first called with a seed
|
|
value of 1.
|
|
</pre>
|
|
<a name='7.24.2.2p3'></a>
|
|
<pre>3 The srand function is not required to avoid data races with other calls to pseudo-random sequence
|
|
generation functions. The implementation shall behave as if no library function calls the srand
|
|
function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.2.2p4'></a>
|
|
<pre>4 The srand function returns no value.
|
|
</pre>
|
|
<a name='7.24.2.2p5'></a>
|
|
<pre>5 EXAMPLE The following functions define a portable implementation of rand and srand.
|
|
|
|
static unsigned long int next = 1;
|
|
|
|
int rand(void) // RAND_MAX assumed to be 32767
|
|
{
|
|
next = next * 1103515245 + 12345;
|
|
return (unsigned int)(next/65536) % 32768;
|
|
}
|
|
|
|
void srand(unsigned int seed)
|
|
{
|
|
next = seed;
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.24.3'></a>
|
|
<hr>
|
|
<h3>7.24.3 [Memory management functions]</h3>
|
|
<a name='7.24.3p1'></a>
|
|
<pre>1 The order and contiguity of storage allocated by successive calls to the aligned_alloc, calloc,
|
|
malloc, and realloc functions is unspecified. The pointer returned if the allocation succeeds is
|
|
suitably aligned so that it may be assigned to a pointer to any type of object with a fundamental
|
|
alignment requirement and size less than or equal to the size requested. It may then be used to
|
|
access such an object or an array of such objects in the space allocated (until the space is explicitly
|
|
deallocated). The lifetime of an allocated object extends from the allocation until the deallocation.
|
|
Each such allocation shall yield a pointer to an object disjoint from any other object. The pointer
|
|
returned points to the start (lowest byte address) of the allocated space. If the space cannot be
|
|
allocated, a null pointer is returned. If the size of the space requested is zero, the behavior is
|
|
implementation-defined: either a null pointer is returned to indicate an error, or the behavior is as if
|
|
the size were some nonzero value, except that the returned pointer shall not be used to access an
|
|
object.
|
|
</pre>
|
|
<a name='7.24.3p2'></a>
|
|
<pre>2 For purposes of determining the existence of a data race, memory allocation functions behave as
|
|
though they accessed only memory locations accessible through their arguments and not other
|
|
static duration storage. These functions may, however, visibly modify the storage that they allocate
|
|
or deallocate. Calls to these functions that allocate or deallocate a particular region of memory
|
|
shall occur in a single total order, and each such deallocation call shall synchronize with the next
|
|
allocation (if any) in this order.
|
|
|
|
</pre>
|
|
<a name='7.24.3.1'></a>
|
|
<hr>
|
|
<h3>7.24.3.1 [The aligned_alloc function]</h3>
|
|
<a name='7.24.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *aligned_alloc(size_t alignment, size_t size);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.1p2'></a>
|
|
<pre>2 The aligned_alloc function allocates space for an object whose alignment is specified by
|
|
alignment, whose size is specified by size, and whose representation is indeterminate. If the
|
|
value of alignment is not a valid alignment supported by the implementation the function shall fail
|
|
by returning a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.1p3'></a>
|
|
<pre>3 The aligned_alloc function returns either a null pointer or a pointer to the allocated space.
|
|
|
|
</pre>
|
|
<a name='7.24.3.2'></a>
|
|
<hr>
|
|
<h3>7.24.3.2 [The calloc function]</h3>
|
|
<a name='7.24.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *calloc(size_t nmemb, size_t size);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.2p2'></a>
|
|
<pre>2 The calloc function allocates space for an array of nmemb objects, each of whose size is size. The
|
|
space is initialized to all bits zero<a href='#FOOTNOTE.360'><sup>[360]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.360'>
|
|
<pre><i><b>Footnote 360)</b> Note that this need not be the same as the representation of floating-point zero or a null pointer constant.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.3.2p3'></a>
|
|
<pre>3 The calloc function returns either a pointer to the allocated space or a null pointer if the space
|
|
cannot be allocated or if the mathematical product nmemb * size is not representable as a value of
|
|
type size_t.
|
|
|
|
</pre>
|
|
<a name='7.24.3.3'></a>
|
|
<hr>
|
|
<h3>7.24.3.3 [The free function]</h3>
|
|
<a name='7.24.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void free(void *ptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.3p2'></a>
|
|
<pre>2 The free function causes the space pointed to by ptr to be deallocated, that is, made available
|
|
for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if the argument does
|
|
not match a pointer earlier returned by a memory management function, or if the space has been
|
|
deallocated by a call to free or realloc, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.3p3'></a>
|
|
<pre>3 The free function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.24.3.4'></a>
|
|
<hr>
|
|
<h3>7.24.3.4 [The free_sized function]</h3>
|
|
<a name='7.24.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void free_sized(void *ptr, size_t size);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.4p2'></a>
|
|
<pre>2 If ptr is a null pointer or the result obtained from a call to malloc, realloc, or calloc, where size
|
|
size is equal to the requested allocation size, this function is equivalent to free(ptr). Otherwise,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.24.3.4p3'></a>
|
|
<pre>3 NOTE 1 A conforming implementation may ignore size and call free.
|
|
</pre>
|
|
<a name='7.24.3.4p4'></a>
|
|
<pre>4 NOTE 2 The result of an aligned_alloc call may not be passed to free_sized.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.24.3.4p5'></a>
|
|
<pre>5 Implementations may provide extensions to query the usable size of an allocation, or to determine
|
|
the usable size of the allocation that would result if a request for some other size were to succeed.
|
|
Such implementations should allow passing the resulting usable size as the size parameter, and
|
|
provide functionality equivalent to free in such cases.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.4p6'></a>
|
|
<pre>6 The free_sized function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.24.3.5'></a>
|
|
<hr>
|
|
<h3>7.24.3.5 [The free_aligned_sized function]</h3>
|
|
<a name='7.24.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void free_aligned_sized(void *ptr, size_t alignment, size_t size);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.5p2'></a>
|
|
<pre>2 If ptr is a null pointer or the result obtained from a call to aligned_alloc, where alignment is
|
|
equal to the requested allocation alignment and size is equal to the requested allocation size, this
|
|
function is equivalent to free(ptr). Otherwise, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.24.3.5p3'></a>
|
|
<pre>3 NOTE 1 A conforming implementation may ignore alignment and size and call free.
|
|
</pre>
|
|
<a name='7.24.3.5p4'></a>
|
|
<pre>4 NOTE 2 The result of an malloc, calloc, or realloc call may not be passed to free_aligned_sized.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.24.3.5p5'></a>
|
|
<pre>5 Implementations may provide extensions to query the usable size of an allocation, or to determine
|
|
the usable size of the allocation that would result if a request for some other size were to succeed.
|
|
Such implementations should allow passing the resulting usable size as the size parameter, and
|
|
provide functionality equivalent to free in such cases.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.5p6'></a>
|
|
<pre>6 The free_aligned_sized function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.24.3.6'></a>
|
|
<hr>
|
|
<h3>7.24.3.6 [The malloc function]</h3>
|
|
<a name='7.24.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *malloc(size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.6p2'></a>
|
|
<pre>2 The malloc function allocates space for an object whose size is specified by size and whose
|
|
representation is indeterminate.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.6p3'></a>
|
|
<pre>3 The malloc function returns either a null pointer or a pointer to the allocated space.
|
|
|
|
</pre>
|
|
<a name='7.24.3.7'></a>
|
|
<hr>
|
|
<h3>7.24.3.7 [The realloc function]</h3>
|
|
<a name='7.24.3.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *realloc(void *ptr, size_t size);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.7p2'></a>
|
|
<pre>2 The realloc function deallocates the old object pointed to by ptr and returns a pointer to a new
|
|
object that has the size specified by size. The contents of the new object shall be the same as that of
|
|
the old object prior to deallocation, up to the lesser of the new and old sizes. Any bytes in the new
|
|
object beyond the size of the old object have unspecified values.
|
|
</pre>
|
|
<a name='7.24.3.7p3'></a>
|
|
<pre>3 If ptr is a null pointer, the realloc function behaves like the malloc function for the specified size.
|
|
Otherwise, if ptr does not match a pointer earlier returned by a memory management function, or
|
|
if the space has been deallocated by a call to the free or realloc function, or if the size is zero, the
|
|
behavior is undefined. If memory for the new object is not allocated, the old object is not deallocated
|
|
and its value is unchanged.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.3.7p4'></a>
|
|
<pre>4 The realloc function returns a pointer to the new object (which may have the same value as a
|
|
pointer to the old object), or a null pointer if the new object has not been allocated.
|
|
|
|
</pre>
|
|
<a name='7.24.4'></a>
|
|
<hr>
|
|
<h3>7.24.4 [Communication with the environment]</h3>
|
|
<a name='7.24.4.1'></a>
|
|
<hr>
|
|
<h3>7.24.4.1 [The abort function]</h3>
|
|
<a name='7.24.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
[[noreturn]] void abort(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.1p2'></a>
|
|
<pre>2 The abort function causes abnormal program termination to occur, unless the signal SIGABRT is
|
|
being caught and the signal handler does not return. Whether open streams with unwritten buffered
|
|
data are flushed, open streams are closed, or temporary files are removed is implementation-
|
|
defined. An implementation-defined form of the status unsuccessful termination is returned to the
|
|
host environment by means of the function call raise(SIGABRT).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.1p3'></a>
|
|
<pre>3 The abort function does not return to its caller.
|
|
|
|
</pre>
|
|
<a name='7.24.4.2'></a>
|
|
<hr>
|
|
<h3>7.24.4.2 [The atexit function]</h3>
|
|
<a name='7.24.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int atexit(void (*func)(void));
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.2p2'></a>
|
|
<pre>2 The atexit function registers the function pointed to by func, to be called without arguments at
|
|
normal program termination.<a href='#FOOTNOTE.361'><sup>[361]</sup></a> It is unspecified whether a call to the atexit function that does
|
|
not happen before the exit function is called will succeed.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='FOOTNOTE.361'>
|
|
<pre><i><b>Footnote 361)</b> The atexit function registrations are distinct from the at_quick_exit registrations, so applications might need to call
|
|
both registration functions with the same argument.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.2p3'></a>
|
|
<pre>3 The implementation shall support the registration of at least 32 functions.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.2p4'></a>
|
|
<pre>4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
|
|
Forward references: the at_quick_exit function (<a href='#7.24.4.3'>7.24.4.3</a>), the exit function (<a href='#7.24.4.4'>7.24.4.4</a>).
|
|
|
|
</pre>
|
|
<a name='7.24.4.3'></a>
|
|
<hr>
|
|
<h3>7.24.4.3 [The at_quick_exit function]</h3>
|
|
<a name='7.24.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int at_quick_exit(void (*func)(void));
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.3p2'></a>
|
|
<pre>2 The at_quick_exit function registers the function pointed to by func, to be called without argu-
|
|
ments should quick_exit be called.<a href='#FOOTNOTE.362'><sup>[362]</sup></a> It is unspecified whether a call to the at_quick_exit
|
|
function that does not happen before the quick_exit function is called will succeed.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='FOOTNOTE.362'>
|
|
<pre><i><b>Footnote 362)</b> The at_quick_exit function registrations are distinct from the atexit registrations, so applications might need to call
|
|
both registration functions with the same argument.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.3p3'></a>
|
|
<pre>3 The implementation shall support the registration of at least 32 functions.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.3p4'></a>
|
|
<pre>4 The at_quick_exit function returns zero if the registration succeeds, nonzero if it fails.
|
|
Forward references: the quick_exit function (<a href='#7.24.4.7'>7.24.4.7</a>).
|
|
|
|
</pre>
|
|
<a name='7.24.4.4'></a>
|
|
<hr>
|
|
<h3>7.24.4.4 [The exit function]</h3>
|
|
<a name='7.24.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
[[noreturn]] void exit(int status);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.4p2'></a>
|
|
<pre>2 The exit function causes normal program termination to occur. No functions registered by the
|
|
at_quick_exit function are called. If a program calls the exit function more than once, or calls the
|
|
quick_exit function in addition to the exit function, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.24.4.4p3'></a>
|
|
<pre>3 First, all functions registered by the atexit function are called, in the reverse order of their registra-
|
|
tion,<a href='#FOOTNOTE.363'><sup>[363]</sup></a> except that a function is called after any previously registered functions that had already
|
|
been called at the time it was registered. If, during the call to any such function, a call to the longjmp
|
|
function is made that would terminate the call to the registered function, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.363'>
|
|
<pre><i><b>Footnote 363)</b> Each function is called as many times as it was registered, and in the correct order with respect to other registered
|
|
functions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.4p4'></a>
|
|
<pre>4 Next, all open streams with unwritten buffered data are flushed, all open streams are closed, and all
|
|
files created by the tmpfile function are removed.
|
|
</pre>
|
|
<a name='7.24.4.4p5'></a>
|
|
<pre>5 Finally, control is returned to the host environment. If the value of status is zero or EXIT_SUCCESS,
|
|
an implementation-defined form of the status successful termination is returned. If the value of
|
|
status is EXIT_FAILURE, an implementation-defined form of the status unsuccessful termination is
|
|
returned. Otherwise the status returned is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.4p6'></a>
|
|
<pre>6 The exit function cannot return to its caller.
|
|
</pre>
|
|
<a name='7.24.4.5'></a>
|
|
<hr>
|
|
<h3>7.24.4.5 [The _Exit function]</h3>
|
|
<a name='7.24.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
[[noreturn]] void _Exit(int status);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.5p2'></a>
|
|
<pre>2 The _Exit function causes normal program termination to occur and control to be returned to the
|
|
host environment. No functions registered by the atexit function, the at_quick_exit function,
|
|
or signal handlers registered by the signal function are called. The status returned to the host
|
|
environment is determined in the same way as for the exit function (<a href='#7.24.4.4'>7.24.4.4</a>). Whether open
|
|
streams with unwritten buffered data are flushed, open streams are closed, or temporary files are
|
|
removed is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.5p3'></a>
|
|
<pre>3 The _Exit function cannot return to its caller.
|
|
|
|
</pre>
|
|
<a name='7.24.4.6'></a>
|
|
<hr>
|
|
<h3>7.24.4.6 [The getenv function]</h3>
|
|
<a name='7.24.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
char *getenv(const char *name);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.6p2'></a>
|
|
<pre>2 The getenv function searches an environment list, provided by the host environment, for a string that
|
|
matches the string pointed to by name. The set of environment names and the method for altering
|
|
the environment list are implementation-defined. The getenv function need not avoid data races
|
|
with other threads of execution that modify the environment list.<a href='#FOOTNOTE.364'><sup>[364]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.364'>
|
|
<pre><i><b>Footnote 364)</b> Many implementations provide non-standard functions that modify the environment list.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.6p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the getenv function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.6p4'></a>
|
|
<pre>4 The getenv function returns a pointer to a string associated with the matched list member. The
|
|
string pointed to shall not be modified by the program, but may be overwritten by a subsequent call
|
|
to the getenv function. If the specified name cannot be found, a null pointer is returned.
|
|
|
|
</pre>
|
|
<a name='7.24.4.7'></a>
|
|
<hr>
|
|
<h3>7.24.4.7 [The quick_exit function]</h3>
|
|
<a name='7.24.4.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
[[noreturn]] void quick_exit(int status);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.7p2'></a>
|
|
<pre>2 The quick_exit function causes normal program termination to occur. No functions registered by
|
|
the atexit function or signal handlers registered by the signal function are called. If a program calls
|
|
the quick_exit function more than once, or calls the exit function in addition to the quick_exit
|
|
function, the behavior is undefined. If a signal is raised while the quick_exit function is executing,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.24.4.7p3'></a>
|
|
<pre>3 The quick_exit function first calls all functions registered by the at_quick_exit function, in the
|
|
reverse order of their registration,<a href='#FOOTNOTE.365'><sup>[365]</sup></a> except that a function is called after any previously registered
|
|
functions that had already been called at the time it was registered. If, during the call to any such
|
|
function, a call to the longjmp function is made that would terminate the call to the registered
|
|
function, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.365'>
|
|
<pre><i><b>Footnote 365)</b> Each function is called as many times as it was registered, and in the correct order with respect to other registered
|
|
functions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.7p4'></a>
|
|
<pre>4 Then control is returned to the host environment by means of the function call _Exit(status) .
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.7p5'></a>
|
|
<pre>5 The quick_exit function cannot return to its caller.
|
|
|
|
</pre>
|
|
<a name='7.24.4.8'></a>
|
|
<hr>
|
|
<h3>7.24.4.8 [The system function]</h3>
|
|
<a name='7.24.4.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int system(const char *string);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.8p2'></a>
|
|
<pre>2 If string is a null pointer, the system function determines whether the host environment has a
|
|
command processor. If string is not a null pointer, the system function passes the string pointed to
|
|
by string to that command processor to be executed in a manner which the implementation shall
|
|
document; this might then cause the program calling system to behave in a non-conforming manner
|
|
or to terminate.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.8p3'></a>
|
|
<pre>3 If the argument is a null pointer, the system function returns nonzero only if a command processor
|
|
is available. If the argument is not a null pointer, and the system function does return, it returns an
|
|
implementation-defined value.
|
|
|
|
</pre>
|
|
<a name='7.24.5'></a>
|
|
<hr>
|
|
<h3>7.24.5 [Searching and sorting utilities]</h3>
|
|
<a name='7.24.5p1'></a>
|
|
<pre>1 These utilities make use of a comparison function to search or sort arrays of unspecified type. Where
|
|
an argument declared as size_t nmemb specifies the length of the array for a function, nmemb can
|
|
have the value zero on a call to that function; the comparison function is not called, a search finds no
|
|
matching element, and sorting performs no rearrangement. Pointer arguments on such a call shall
|
|
still have valid values, as described in <a href='#7.1.4'>7.1.4</a>.
|
|
</pre>
|
|
<a name='7.24.5p2'></a>
|
|
<pre>2 The implementation shall ensure that the second argument of the comparison function (when called
|
|
from bsearch), or both arguments (when called from qsort), are pointers to elements of the array.<a href='#FOOTNOTE.366'><sup>[366]</sup></a>
|
|
The first argument when called from bsearch shall equal key.
|
|
</pre>
|
|
<a name='FOOTNOTE.366'>
|
|
<pre><i><b>Footnote 366)</b> That is, if the value passed is p, then the following expressions are always nonzero:
|
|
((char *)p - (char *)base) % size == 0
|
|
(char *)p >= (char *)base
|
|
(char *)p < (char *)base + nmemb * size
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.5p3'></a>
|
|
<pre>3 The comparison function shall not alter the contents of the array. The implementation may reorder
|
|
elements of the array between calls to the comparison function, but shall not alter the contents of
|
|
any individual element.
|
|
</pre>
|
|
<a name='7.24.5p4'></a>
|
|
<pre>4 When the same objects (consisting of size bytes, irrespective of their current positions in the array)
|
|
are passed more than once to the comparison function, the results shall be consistent with one
|
|
another. That is, for qsort they shall define a total ordering on the array, and for bsearch the same
|
|
object shall always compare the same way with the key.
|
|
</pre>
|
|
<a name='7.24.5p5'></a>
|
|
<pre>5 A sequence point occurs immediately before and immediately after each call to the comparison
|
|
function, and also between any call to the comparison function and any movement of the objects
|
|
passed as arguments to that call.
|
|
|
|
</pre>
|
|
<a name='7.24.5.1'></a>
|
|
<hr>
|
|
<h3>7.24.5.1 [The bsearch generic function]</h3>
|
|
<a name='7.24.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *bsearch(const void *key, const void *base, size_t nmemb, size_t size,
|
|
int (*compar)(const void *, const void *));
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.1p2'></a>
|
|
<pre>2 The bsearch generic function searches an array of nmemb objects, the initial element of which is
|
|
pointed to by base, for an element that matches the object pointed to by key. The size of each
|
|
element of the array is specified by size.
|
|
</pre>
|
|
<a name='7.24.5.1p3'></a>
|
|
<pre>3 The comparison function pointed to by compar is called with two arguments that point to the key
|
|
object and to an array element, in that order. The function shall return an integer less than, equal to,
|
|
or greater than zero if the key object is considered, respectively, to be less than, to match, or to be
|
|
greater than the array element. The array shall consist of: all the elements that compare less than, all
|
|
the elements that compare equal to, and all the elements that compare greater than the key object, in
|
|
that order.<a href='#FOOTNOTE.367'><sup>[367]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.367'>
|
|
<pre><i><b>Footnote 367)</b> In practice, the entire array is sorted according to the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.5.1p4'></a>
|
|
<pre>4 The bsearch generic function returns a pointer to a matching element of the array, or a null pointer
|
|
if no match is found. If two elements compare as equal, which element is matched is unspecified.
|
|
</pre>
|
|
<a name='7.24.5.1p5'></a>
|
|
<pre>5 The bsearch function is generic in the qualification of the type pointed to by the argument to base.
|
|
If this argument is a pointer to a const-qualified object type, the returned pointer will be a pointer
|
|
to const-qualified void. Otherwise, the argument shall be a pointer to an unqualified object type or
|
|
a null pointer constant<a href='#FOOTNOTE.368'><sup>[368]</sup></a> , and the returned pointer will be a pointer to unqualified void.
|
|
The external declaration of bsearch has the concrete type:
|
|
|
|
void * (const void *, const void *, size_t, size_t, int (*) (const void *, const
|
|
void *))
|
|
|
|
|
|
, which supports all correct uses. If a macro definition of this generic function is suppressed in order
|
|
to access an actual function, the external declaration with this concrete type is visible<a href='#FOOTNOTE.369'><sup>[369]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.368'>
|
|
<pre><i><b>Footnote 368)</b> If the argument is a null pointer and the call is executed, the behavior is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.369'>
|
|
<pre><i><b>Footnote 369)</b> This is an obsolescent feature.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.5.2'></a>
|
|
<hr>
|
|
<h3>7.24.5.2 [The qsort function]</h3>
|
|
<a name='7.24.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void qsort(void *base, size_t nmemb, size_t size,
|
|
int (*compar)(const void *, const void *));
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.2p2'></a>
|
|
<pre>2 The qsort function sorts an array of nmemb objects, the initial element of which is pointed to by
|
|
base. The size of each object is specified by size.
|
|
</pre>
|
|
<a name='7.24.5.2p3'></a>
|
|
<pre>3 The contents of the array are sorted into ascending order according to a comparison function pointed
|
|
to by compar, which is called with two arguments that point to the objects being compared. The
|
|
function shall return an integer less than, equal to, or greater than zero if the first argument is
|
|
considered to be respectively less than, equal to, or greater than the second.
|
|
</pre>
|
|
<a name='7.24.5.2p4'></a>
|
|
<pre>4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.5.2p5'></a>
|
|
<pre>5 The qsort function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.24.6'></a>
|
|
<hr>
|
|
<h3>7.24.6 [Integer arithmetic functions]</h3>
|
|
<a name='7.24.6.1'></a>
|
|
<hr>
|
|
<h3>7.24.6.1 [The abs, labs, and llabs functions]</h3>
|
|
<a name='7.24.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int abs(int j);
|
|
long int labs(long int j);
|
|
long long int llabs(long long int j);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.6.1p2'></a>
|
|
<pre>2 The abs, labs, and llabs functions compute the absolute value of an integer j. If the result cannot
|
|
be represented, the behavior is undefined<a href='#FOOTNOTE.370'><sup>[370]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.370'>
|
|
<pre><i><b>Footnote 370)</b> The absolute value of the most negative number may not be representable.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.6.1p3'></a>
|
|
<pre>3 The abs, labs, and llabs, functions return the absolute value.
|
|
|
|
</pre>
|
|
<a name='7.24.6.2'></a>
|
|
<hr>
|
|
<h3>7.24.6.2 [The div, ldiv, and lldiv functions]</h3>
|
|
<a name='7.24.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
div_t div(int numer, int denom);
|
|
ldiv_t ldiv(long int numer, long int denom);
|
|
lldiv_t lldiv(long long int numer, long long int denom);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.6.2p2'></a>
|
|
<pre>2 The div, ldiv, and lldiv, functions compute numer/denom and numer%denom in a single operation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.6.2p3'></a>
|
|
<pre>3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and lldiv_t, respec-
|
|
tively, comprising both the quotient and the remainder. The structures shall contain (in either order)
|
|
the members quot (the quotient) and rem (the remainder), each of which has the same type as
|
|
the arguments numer and denom. If either part of the result cannot be represented, the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='7.24.7'></a>
|
|
<hr>
|
|
<h3>7.24.7 [Multibyte/wide character conversion functions]</h3>
|
|
<a name='7.24.7p1'></a>
|
|
<pre>1 The behavior of the multibyte character functions is affected by the LC_CTYPE category of the current
|
|
locale. For a state-dependent encoding, each of the mbtowc and wctomb functions is placed into its
|
|
initial conversion state prior to the first call to the function and can be returned to that state by a
|
|
call for which its character pointer argument, s, is a null pointer. Subsequent calls with s as other
|
|
than a null pointer cause the internal conversion state of the function to be altered as necessary. It is
|
|
implementation-defined whether internal conversion state has thread storage duration, and whether
|
|
a newly created thread has the same state as the current thread at the time of creation, or the initial
|
|
conversion state. A call with s as a null pointer causes these functions to return a nonzero value if
|
|
encodings have state dependency, and zero otherwise.
|
|
Changing the LC_CTYPE category causes the internal object describing the conversion state of the
|
|
mbtowc and wctomb functions to have an indeterminate representation.
|
|
|
|
</pre>
|
|
<a name='7.24.7.1'></a>
|
|
<hr>
|
|
<h3>7.24.7.1 [The mblen function]</h3>
|
|
<a name='7.24.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int mblen(const char *s, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.7.1p2'></a>
|
|
<pre>2 If s is not a null pointer, the mblen function determines the number of bytes contained in the
|
|
multibyte character pointed to by s. Except that the conversion state of the mbtowc function is not
|
|
affected, it is equivalent to
|
|
|
|
mbtowc((wchar_t *)0, (const char *)0, 0);
|
|
mbtowc((wchar_t *)0, s, n);
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.7.1p3'></a>
|
|
<pre>3 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte character
|
|
encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the
|
|
mblen function either returns 0 (if s points to the null character), or returns the number of bytes
|
|
that are contained in the multibyte character (if the next n or fewer bytes form a valid multibyte
|
|
character), or returns-1 (if they do not form a valid multibyte character).
|
|
Forward references: the mbtowc function (<a href='#7.24.7.2'>7.24.7.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.24.7.2'></a>
|
|
<hr>
|
|
<h3>7.24.7.2 [The mbtowc function]</h3>
|
|
<a name='7.24.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int mbtowc(wchar_t * restrict pwc, const char * restrict s, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.7.2p2'></a>
|
|
<pre>2 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with the byte
|
|
pointed to by s to determine the number of bytes needed to complete the next multibyte character
|
|
(including any shift sequences). If the function determines that the next multibyte character is
|
|
complete and valid, it determines the value of the corresponding wide character and then, if pwc
|
|
is not a null pointer, stores that value in the object pointed to by pwc. If the corresponding wide
|
|
character is the null wide character, the function is left in the initial conversion state.
|
|
</pre>
|
|
<a name='7.24.7.2p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the mbtowc function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.7.2p4'></a>
|
|
<pre>4 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte character
|
|
encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the
|
|
mbtowc function either returns 0 (if s points to the null character), or returns the number of bytes
|
|
that are contained in the converted multibyte character (if the next n or fewer bytes form a valid
|
|
multibyte character), or returns-1 (if they do not form a valid multibyte character).
|
|
</pre>
|
|
<a name='7.24.7.2p5'></a>
|
|
<pre>5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX macro.
|
|
|
|
</pre>
|
|
<a name='7.24.7.3'></a>
|
|
<hr>
|
|
<h3>7.24.7.3 [The wctomb function]</h3>
|
|
<a name='7.24.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int wctomb(char *s, wchar_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.7.3p2'></a>
|
|
<pre>2 The wctomb function determines the number of bytes needed to represent the multibyte character
|
|
corresponding to the wide character given by wc (including any shift sequences), and stores the
|
|
multibyte character representation in the array whose first element is pointed to by s (if s is not a
|
|
null pointer). At most MB_CUR_MAX characters are stored. If wc is a null wide character, a null byte is
|
|
stored, preceded by any shift sequence needed to restore the initial shift state, and the function is
|
|
left in the initial conversion state.
|
|
</pre>
|
|
<a name='7.24.7.3p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the wctomb function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.7.3p4'></a>
|
|
<pre>4 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte character
|
|
encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the
|
|
wctomb function returns-1 if the value of wc does not correspond to a valid multibyte character, or
|
|
returns the number of bytes that are contained in the multibyte character corresponding to the value
|
|
of wc.
|
|
</pre>
|
|
<a name='7.24.7.3p5'></a>
|
|
<pre>5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
|
|
|
|
</pre>
|
|
<a name='7.24.8'></a>
|
|
<hr>
|
|
<h3>7.24.8 [Multibyte/wide string conversion functions]</h3>
|
|
<a name='7.24.8p1'></a>
|
|
<pre>1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of the current
|
|
locale.
|
|
|
|
</pre>
|
|
<a name='7.24.8.1'></a>
|
|
<hr>
|
|
<h3>7.24.8.1 [The mbstowcs function]</h3>
|
|
<a name='7.24.8.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
size_t mbstowcs(wchar_t * restrict pwcs, const char * restrict s, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.8.1p2'></a>
|
|
<pre>2 The mbstowcs function converts a sequence of multibyte characters that begins in the initial shift
|
|
state from the array pointed to by s into a sequence of corresponding wide characters and stores not
|
|
more than n wide characters into the array pointed to by pwcs. No multibyte characters that follow
|
|
a null character (which is converted into a null wide character) will be examined or converted. Each
|
|
multibyte character is converted as if by a call to the mbtowc function, except that the conversion
|
|
state of the mbtowc function is not affected.
|
|
</pre>
|
|
<a name='7.24.8.1p3'></a>
|
|
<pre>3 No more than n elements will be modified in the array pointed to by pwcs. If copying takes place
|
|
between objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.8.1p4'></a>
|
|
<pre>4 If an invalid multibyte character is encountered, the mbstowcs function returns (size_t)(-1) .
|
|
Otherwise, the mbstowcs function returns the number of array elements modified, not including a
|
|
terminating null wide character, if any.<a href='#FOOTNOTE.371'><sup>[371]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.371'>
|
|
<pre><i><b>Footnote 371)</b> The array will not be null-terminated if the value returned is n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.8.2'></a>
|
|
<hr>
|
|
<h3>7.24.8.2 [The wcstombs function]</h3>
|
|
<a name='7.24.8.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
size_t wcstombs(char * restrict s, const wchar_t * restrict pwcs, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.8.2p2'></a>
|
|
<pre>2 The wcstombs function converts a sequence of wide characters from the array pointed to by pwcs
|
|
into a sequence of corresponding multibyte characters that begins in the initial shift state, and stores
|
|
these multibyte characters into the array pointed to by s, stopping if a multibyte character would
|
|
exceed the limit of n total bytes or if a null character is stored. Each wide character is converted
|
|
as if by a call to the wctomb function, except that the conversion state of the wctomb function is not
|
|
affected.
|
|
</pre>
|
|
<a name='7.24.8.2p3'></a>
|
|
<pre>3 No more than n bytes will be modified in the array pointed to by s. If copying takes place between
|
|
objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.8.2p4'></a>
|
|
<pre>4 If a wide character is encountered that does not correspond to a valid multibyte character, the
|
|
wcstombs function returns (size_t)(-1) . Otherwise, the wcstombs function returns the number
|
|
of bytes modified, not including a terminating null character, if any.<a href='#FOOTNOTE.371'><sup>[371]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.371'>
|
|
<pre><i><b>Footnote 371)</b> The array will not be null-terminated if the value returned is n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.9'></a>
|
|
<hr>
|
|
<h3>7.24.9 [Alignment of memory]</h3>
|
|
<a name='7.24.9.1'></a>
|
|
<hr>
|
|
<h3>7.24.9.1 [The memalignment function]</h3>
|
|
<a name='7.24.9.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
size_t memalignment(const void * p);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.24.9.1p2'></a>
|
|
<pre>2 The memalignment function accepts a pointer to any object and returns the maximum alignment
|
|
satisfied by its address value. The alignment may be an extended alignment and may also be beyond
|
|
the range supported by the implementation for explicit use by alignas<a href='#FOOTNOTE.372'><sup>[372]</sup></a> . If so, it will satisfy all
|
|
alignments usable by the implementation. The value returned can be compared to the result of
|
|
alignof, and if it is greater or equal, the alignment requirement for the type operand is satisfied.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.372'>
|
|
<pre><i><b>Footnote 372)</b> The actual alignment of an object may be stricter than the alignment requested for an object by alignas or (implicitly) by
|
|
an allocation function, but will always satisfy it.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.9.1p3'></a>
|
|
<pre>3 The alignment of the pointer p, which is a power of two. If p is a null pointer, an alignment of zero is
|
|
returned.
|
|
</pre>
|
|
<a name='7.24.9.1p4'></a>
|
|
<pre>4 NOTE An alignment of zero indicates that the tested pointer cannot be used to access an object of any type.
|
|
</pre>
|
|
<a name='7.25'></a>
|
|
<hr>
|
|
<h3>7.25 [_Noreturn <stdnoreturn.h>]</h3>
|
|
<a name='7.25p1'></a>
|
|
<pre>1 The header <stdnoreturn.h> defines the macro
|
|
|
|
noreturn
|
|
|
|
|
|
which expands to _Noreturn .
|
|
</pre>
|
|
<a name='7.25p2'></a>
|
|
<pre>2 The noreturn macro and the <stdnoreturn.h> header are obsolescent features.
|
|
</pre>
|
|
<a name='7.26'></a>
|
|
<hr>
|
|
<h3>7.26 [String handling <string.h>]</h3>
|
|
<a name='7.26.1'></a>
|
|
<hr>
|
|
<h3>7.26.1 [String function conventions]</h3>
|
|
<a name='7.26.1p1'></a>
|
|
<pre>1 The header <string.h> declares one type and several functions, and defines one macro useful
|
|
for manipulating arrays of character type and other objects treated as arrays of character type.<a href='#FOOTNOTE.373'><sup>[373]</sup></a>
|
|
The type is size_t and the macro is NULL (both described in <a href='#7.21'>7.21</a>). Various methods are used for
|
|
determining the lengths of the arrays, but in all cases a char * or void * argument points to the
|
|
initial (lowest addressed) character of the array. If an array is accessed beyond the end of an object,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.373'>
|
|
<pre><i><b>Footnote 373)</b> See "future library directions" (<a href='#7.33.17'>7.33.17</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.1p2'></a>
|
|
<pre>2 Where an argument declared as size_t n specifies the length of the array for a function, n can have
|
|
the value zero on a call to that function. Unless explicitly stated otherwise in the description of a
|
|
particular function in this subclause, pointer arguments on such a call shall still have valid values, as
|
|
described in <a href='#7.1.4'>7.1.4</a>. On such a call, a function that locates a character finds no occurrence, a function
|
|
that compares two character sequences returns zero, and a function that copies characters copies
|
|
zero characters.
|
|
</pre>
|
|
<a name='7.26.1p3'></a>
|
|
<pre>3 For all functions in this subclause, each character shall be interpreted as if it had the type
|
|
unsigned char (and therefore every possible object representation is valid and has a different
|
|
value).
|
|
|
|
</pre>
|
|
<a name='7.26.2'></a>
|
|
<hr>
|
|
<h3>7.26.2 [Copying functions]</h3>
|
|
<a name='7.26.2.1'></a>
|
|
<hr>
|
|
<h3>7.26.2.1 [The memcpy function]</h3>
|
|
<a name='7.26.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memcpy(void * restrict s1, const void * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.1p2'></a>
|
|
<pre>2 The memcpy function copies n characters from the object pointed to by s2 into the object pointed to
|
|
by s1. If copying takes place between objects that overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.1p3'></a>
|
|
<pre>3 The memcpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.26.2.2'></a>
|
|
<hr>
|
|
<h3>7.26.2.2 [The memccpy function]</h3>
|
|
<a name='7.26.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memccpy(void * restrict s1, const void * restrict s2, int c, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.2p2'></a>
|
|
<pre>2 The memccpy function copies characters from the object pointed to by s2 into the object pointed to
|
|
by s1, stopping after the first occurrence of character c (converted to an unsigned char) is copied,
|
|
or after n characters are copied, whichever comes first. If copying takes place between objects that
|
|
overlap, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.2p3'></a>
|
|
<pre>3 The memccpy function returns a pointer to the character after the copy of c in s1, or a null pointer if
|
|
c was not found in the first n characters of s2.
|
|
|
|
</pre>
|
|
<a name='7.26.2.3'></a>
|
|
<hr>
|
|
<h3>7.26.2.3 [The memmove function]</h3>
|
|
<a name='7.26.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memmove(void *s1, const void *s2, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.3p2'></a>
|
|
<pre>2 The memmove function copies n characters from the object pointed to by s2 into the object pointed to
|
|
by s1. Copying takes place as if the n characters from the object pointed to by s2 are first copied
|
|
into a temporary array of n characters that does not overlap the objects pointed to by s1 and s2, and
|
|
then the n characters from the temporary array are copied into the object pointed to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.3p3'></a>
|
|
<pre>3 The memmove function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.26.2.4'></a>
|
|
<hr>
|
|
<h3>7.26.2.4 [The strcpy function]</h3>
|
|
<a name='7.26.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strcpy(char * restrict s1, const char * restrict s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.4p2'></a>
|
|
<pre>2 The strcpy function copies the string pointed to by s2 (including the terminating null character)
|
|
into the array pointed to by s1. If copying takes place between objects that overlap, the behavior is
|
|
undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.4p3'></a>
|
|
<pre>3 The strcpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.26.2.5'></a>
|
|
<hr>
|
|
<h3>7.26.2.5 [The strncpy function]</h3>
|
|
<a name='7.26.2.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strncpy(char * restrict s1, const char * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.5p2'></a>
|
|
<pre>2 The strncpy function copies not more than n characters (characters that follow a null character are
|
|
not copied) from the array pointed to by s2 to the array pointed to by s1.<a href='#FOOTNOTE.374'><sup>[374]</sup></a> If copying takes place
|
|
between objects that overlap, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.374'>
|
|
<pre><i><b>Footnote 374)</b> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will not be null-
|
|
terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.2.5p3'></a>
|
|
<pre>3 If the array pointed to by s2 is a string that is shorter than n characters, null characters are appended
|
|
to the copy in the array pointed to by s1, until n characters in all have been written.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.5p4'></a>
|
|
<pre>4 The strncpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.26.2.6'></a>
|
|
<hr>
|
|
<h3>7.26.2.6 [The strdup function]</h3>
|
|
<a name='7.26.2.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strdup(const char *s);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.6p2'></a>
|
|
<pre>2 The strdup function creates a copy of the string pointed to by s in a space allocated as if by a call to
|
|
malloc.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.6p3'></a>
|
|
<pre>3 The strdup function returns a pointer to the first character of the duplicate string. The returned
|
|
pointer can be passed to free. If no space can be allocated the strdup function returns a null pointer.
|
|
|
|
</pre>
|
|
<a name='7.26.2.7'></a>
|
|
<hr>
|
|
<h3>7.26.2.7 [The strndup function]</h3>
|
|
<a name='7.26.2.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strndup(const char *s, size_t size);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.7p2'></a>
|
|
<pre>2 The strndup function creates a string initialized with no more than size initial characters of the
|
|
array pointed to by s and up to the first null character, whichever comes first, in a space allocated
|
|
as if by a call to malloc. If the array pointed to by s does not contain a null within the first size
|
|
characters, a null is appended to the copy of the array.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.2.7p3'></a>
|
|
<pre>3 The strndup function returns a pointer to the first character of the created string. The returned
|
|
pointer can be passed to free. If space cannot be allocated the strndup function returns a null
|
|
pointer.
|
|
|
|
</pre>
|
|
<a name='7.26.3'></a>
|
|
<hr>
|
|
<h3>7.26.3 [Concatenation functions]</h3>
|
|
<a name='7.26.3.1'></a>
|
|
<hr>
|
|
<h3>7.26.3.1 [The strcat function]</h3>
|
|
<a name='7.26.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strcat(char * restrict s1, const char * restrict s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.1p2'></a>
|
|
<pre>2 The strcat function appends a copy of the string pointed to by s2 (including the terminating null
|
|
character) to the end of the string pointed to by s1. The initial character of s2 overwrites the null
|
|
character at the end of s1. If copying takes place between objects that overlap, the behavior is
|
|
undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.3.1p3'></a>
|
|
<pre>3 The strcat function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.26.3.2'></a>
|
|
<hr>
|
|
<h3>7.26.3.2 [The strncat function]</h3>
|
|
<a name='7.26.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strncat(char * restrict s1, const char * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.2p2'></a>
|
|
<pre>2 The strncat function appends not more than n characters (a null character and characters that
|
|
follow it are not appended) from the array pointed to by s2 to the end of the string pointed to by
|
|
s1. The initial character of s2 overwrites the null character at the end of s1. A terminating null
|
|
character is always appended to the result.<a href='#FOOTNOTE.375'><sup>[375]</sup></a> If copying takes place between objects that overlap,
|
|
the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.375'>
|
|
<pre><i><b>Footnote 375)</b> Thus, the maximum number of characters that can end up in the array pointed to by s1 is strlen(s1)+n+1.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.3.2p3'></a>
|
|
<pre>3 The strncat function returns the value of s1.
|
|
Forward references: the strlen function (<a href='#7.26.6.4'>7.26.6.4</a>).
|
|
|
|
</pre>
|
|
<a name='7.26.4'></a>
|
|
<hr>
|
|
<h3>7.26.4 [Comparison functions]</h3>
|
|
<a name='7.26.4p1'></a>
|
|
<pre>1 The sign of a nonzero value returned by the comparison functions memcmp, strcmp, and strncmp
|
|
is determined by the sign of the difference between the values of the first pair of characters (both
|
|
interpreted as unsigned char) that differ in the objects being compared.
|
|
|
|
</pre>
|
|
<a name='7.26.4.1'></a>
|
|
<hr>
|
|
<h3>7.26.4.1 [The memcmp function]</h3>
|
|
<a name='7.26.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int memcmp(const void *s1, const void *s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.1p2'></a>
|
|
<pre>2 The memcmp function compares the first n characters of the object pointed to by s1 to the first n
|
|
characters of the object pointed to by s2376) .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.1p3'></a>
|
|
<pre>3 The memcmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
object pointed to by s1 is greater than, equal to, or less than the object pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.26.4.2'></a>
|
|
<hr>
|
|
<h3>7.26.4.2 [The strcmp function]</h3>
|
|
<a name='7.26.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strcmp(const char *s1, const char *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.2p2'></a>
|
|
<pre>2 The strcmp function compares the string pointed to by s1 to the string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.2p3'></a>
|
|
<pre>3 The strcmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
string pointed to by s1 is greater than, equal to, or less than the string pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.26.4.3'></a>
|
|
<hr>
|
|
<h3>7.26.4.3 [The strcoll function]</h3>
|
|
<a name='7.26.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strcoll(const char *s1, const char *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.3p2'></a>
|
|
<pre>2 The strcoll function compares the string pointed to by s1 to the string pointed to by s2, both
|
|
interpreted as appropriate to the LC_COLLATE category of the current locale.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.3p3'></a>
|
|
<pre>3 The strcoll function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
string pointed to by s1 is greater than, equal to, or less than the string pointed to by s2 when both
|
|
are interpreted as appropriate to the current locale.
|
|
|
|
</pre>
|
|
<a name='7.26.4.4'></a>
|
|
<hr>
|
|
<h3>7.26.4.4 [The strncmp function]</h3>
|
|
<a name='7.26.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strncmp(const char *s1, const char *s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.4p2'></a>
|
|
<pre>2 The strncmp function compares not more than n characters (characters that follow a null character
|
|
are not compared) from the array pointed to by s1 to the array pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.4p3'></a>
|
|
<pre>3 The strncmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
possibly null-terminated array pointed to by s1 is greater than, equal to, or less than the possibly
|
|
null-terminated array pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.26.4.5'></a>
|
|
<hr>
|
|
<h3>7.26.4.5 [The strxfrm function]</h3>
|
|
<a name='7.26.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strxfrm(char * restrict s1, const char * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.5p2'></a>
|
|
<pre>2 The strxfrm function transforms the string pointed to by s2 and places the resulting string into
|
|
the array pointed to by s1. The transformation is such that if the strcmp function is applied to two
|
|
transformed strings, it returns a value greater than, equal to, or less than zero, corresponding to the
|
|
result of the strcoll function applied to the same two original strings. No more than n characters
|
|
are placed into the resulting array pointed to by s1, including the terminating null character. If n is
|
|
zero, s1 is permitted to be a null pointer. If copying takes place between objects that overlap, the
|
|
behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.5p3'></a>
|
|
<pre>3 The strxfrm function returns the length of the transformed string (not including the terminating
|
|
null character). If the value returned is n or more, the members of the array pointed to by s1 have
|
|
an indeterminate representation.
|
|
</pre>
|
|
<a name='7.26.4.5p4'></a>
|
|
<pre>4 EXAMPLE The value of the following expression is the size of the array needed to hold the transformation of the string
|
|
pointed to by s.
|
|
|
|
1 + strxfrm(NULL, s, 0)
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.26.5'></a>
|
|
<hr>
|
|
<h3>7.26.5 [Search functions]</h3>
|
|
<a name='7.26.5.1'></a>
|
|
<hr>
|
|
<h3>7.26.5.1 [Introduction]</h3>
|
|
<a name='7.26.5.1p1'></a>
|
|
<pre>1 The stateless search functions in this section (memchr, strchr, strpbrk, strrchr, strstr) are
|
|
generic functions. These functions are generic in the qualification of the array to be searched and
|
|
will return a result pointer to an element with the same qualification as the passed array. If the array
|
|
to be searched is const- qualified, the result pointer will be to a const-qualified element. If the array
|
|
to be searched is not const-qualified<a href='#FOOTNOTE.377'><sup>[377]</sup></a> , the result pointer will be to an unqualified element.
|
|
</pre>
|
|
<a name='FOOTNOTE.377'>
|
|
<pre><i><b>Footnote 377)</b> The null pointer constant is not a pointer to a const-qualified type, and therefore the result expression has the type of a
|
|
pointer to an unqualified element; however, evaluating such a call is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.5.1p2'></a>
|
|
<pre>2 The external declarations of these generic functions have a concrete function type that returns a
|
|
pointer to an unqualified element (of type char when specified as QChar, and void when specified
|
|
as QVoid), and accepts a pointer to a const-qualified array of the same type to search. This signature
|
|
supports all correct uses. If a macro definition of any of these generic functions is suppressed in
|
|
order to access an actual function, the external declaration with the corresponding concrete type is
|
|
visible<a href='#FOOTNOTE.378'><sup>[378]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.378'>
|
|
<pre><i><b>Footnote 378)</b> This is an obsolescent feature.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.5.1p3'></a>
|
|
<pre>3 The volatile and restrict qualifiers are not accepted on the elements of the array to search.
|
|
|
|
</pre>
|
|
<a name='7.26.5.2'></a>
|
|
<hr>
|
|
<h3>7.26.5.2 [The memchr generic function]</h3>
|
|
<a name='7.26.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
QVoid *memchr(QVoid *s, int c, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.2p2'></a>
|
|
<pre>2 The memchr generic function locates the first occurrence of c (converted to an unsigned char)
|
|
in the initial n characters (each interpreted as unsigned char) of the object pointed to by s. The
|
|
implementation shall behave as if it reads the characters sequentially and stops as soon as a matching
|
|
character is found.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.2p3'></a>
|
|
<pre>3 The memchr generic function returns a pointer to the located character, or a null pointer if the
|
|
character does not occur in the object.
|
|
|
|
</pre>
|
|
<a name='7.26.5.3'></a>
|
|
<hr>
|
|
<h3>7.26.5.3 [The strchr generic function]</h3>
|
|
<a name='7.26.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
QChar *strchr(QChar *s, int c);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.3p2'></a>
|
|
<pre>2 The strchr generic function locates the first occurrence of c (converted to a char) in the string
|
|
pointed to by s. The terminating null character is considered to be part of the string.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.3p3'></a>
|
|
<pre>3 The strchr generic function returns a pointer to the located character, or a null pointer if the
|
|
character does not occur in the string.
|
|
|
|
</pre>
|
|
<a name='7.26.5.4'></a>
|
|
<hr>
|
|
<h3>7.26.5.4 [The strcspn function]</h3>
|
|
<a name='7.26.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strcspn(const char *s1, const char *s2);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.4p2'></a>
|
|
<pre>2 The strcspn function computes the length of the maximum initial segment of the string pointed to
|
|
by s1 which consists entirely of characters not from the string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.4p3'></a>
|
|
<pre>3 The strcspn function returns the length of the segment.
|
|
|
|
</pre>
|
|
<a name='7.26.5.5'></a>
|
|
<hr>
|
|
<h3>7.26.5.5 [The strpbrk generic function]</h3>
|
|
<a name='7.26.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
QChar *strpbrk(QChar *s1, const char *s2);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.5p2'></a>
|
|
<pre>2 The strpbrk generic function locates the first occurrence in the string pointed to by s1 of any
|
|
character from the string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.5p3'></a>
|
|
<pre>3 The
|
|
tcodestrpbrk generic function returns a pointer to the character, or a null pointer if no character from
|
|
s2 occurs in s1.
|
|
|
|
</pre>
|
|
<a name='7.26.5.6'></a>
|
|
<hr>
|
|
<h3>7.26.5.6 [The strrchr generic function]</h3>
|
|
<a name='7.26.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
QChar *strrchr(QChar *s, int c);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.6p2'></a>
|
|
<pre>2 The strrchr generic function locates the last occurrence of c (converted to a char) in the string
|
|
pointed to by s. The terminating null character is considered to be part of the string.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.6p3'></a>
|
|
<pre>3 The strrchr generic function returns a pointer to the character, or a null pointer if c does not occur
|
|
in the string.
|
|
|
|
</pre>
|
|
<a name='7.26.5.7'></a>
|
|
<hr>
|
|
<h3>7.26.5.7 [The strspn function]</h3>
|
|
<a name='7.26.5.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strspn(const char *s1, const char *s2);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.7p2'></a>
|
|
<pre>2 The strspn function computes the length of the maximum initial segment of the string pointed to
|
|
by s1 which consists entirely of characters from the string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.7p3'></a>
|
|
<pre>3 The strspn function returns the length of the segment.
|
|
|
|
</pre>
|
|
<a name='7.26.5.8'></a>
|
|
<hr>
|
|
<h3>7.26.5.8 [The strstr generic function]</h3>
|
|
<a name='7.26.5.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
QChar *strstr(QChar *s1, const char *s2);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.8p2'></a>
|
|
<pre>2 The strstr generic function locates the first occurrence in the string pointed to by s1 of the sequence
|
|
of characters (excluding the terminating null character) in the string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.8p3'></a>
|
|
<pre>3 The strstr generic function returns a pointer to the located string, or a null pointer if the string is
|
|
not found. If s2 points to a string with zero length, the function returns s1.
|
|
|
|
</pre>
|
|
<a name='7.26.5.9'></a>
|
|
<hr>
|
|
<h3>7.26.5.9 [The strtok function]</h3>
|
|
<a name='7.26.5.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strtok(char * restrict s1, const char * restrict s2);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.9p2'></a>
|
|
<pre>2 A sequence of calls to the strtok function breaks the string pointed to by s1 into a sequence of
|
|
tokens, each of which is delimited by a character from the string pointed to by s2. The first call
|
|
in the sequence has a non-null first argument; subsequent calls in the sequence have a null first
|
|
argument. If any of the subsequent calls in the sequence is made by a different thread than the first,
|
|
the behavior is undefined. The separator string pointed to by s2 may be different from call to call.
|
|
</pre>
|
|
<a name='7.26.5.9p3'></a>
|
|
<pre>3 The first call in the sequence searches the string pointed to by s1 for the first character that is not
|
|
contained in the current separator string pointed to by s2. If no such character is found, then there
|
|
are no tokens in the string pointed to by s1 and the strtok function returns a null pointer. If such a
|
|
character is found, it is the start of the first token.
|
|
</pre>
|
|
<a name='7.26.5.9p4'></a>
|
|
<pre>4 The strtok function then searches from there for a character that is contained in the current separator
|
|
string. If no such character is found, the current token extends to the end of the string pointed to by
|
|
s1, and subsequent searches for a token will return a null pointer. If such a character is found, it is
|
|
overwritten by a null character, which terminates the current token. The strtok function saves a
|
|
pointer to the following character, from which the next search for a token will start.
|
|
</pre>
|
|
<a name='7.26.5.9p5'></a>
|
|
<pre>5 Each subsequent call, with a null pointer as the value of the first argument, starts searching from the
|
|
saved pointer and behaves as described above.
|
|
</pre>
|
|
<a name='7.26.5.9p6'></a>
|
|
<pre>6 The strtok function is not required to avoid data races with other calls to the strtok function.<a href='#FOOTNOTE.379'><sup>[379]</sup></a>
|
|
The implementation shall behave as if no library function calls the strtok function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.379'>
|
|
<pre><i><b>Footnote 379)</b> The strtok_s function can be used instead to avoid data races.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.5.9p7'></a>
|
|
<pre>7 The strtok function returns a pointer to the first character of a token, or a null pointer if there is no
|
|
token.
|
|
</pre>
|
|
<a name='7.26.5.9p8'></a>
|
|
<pre>8 EXAMPLE
|
|
|
|
#include <string.h>
|
|
static char str[] = "?a???b,,,#c";
|
|
char *t;
|
|
|
|
t = strtok(str, "?"); // t points to the token "a"
|
|
t = strtok(NULL, ","); // t points to the token "??b"
|
|
t = strtok(NULL, "#,"); // t points to the token "c"
|
|
t = strtok(NULL, "?"); // t is a null pointer
|
|
|
|
|
|
Forward references: The strtok_s function (<a href='#K.3.7.3.1'>K.3.7.3.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.26.6'></a>
|
|
<hr>
|
|
<h3>7.26.6 [Miscellaneous functions]</h3>
|
|
<a name='7.26.6.1'></a>
|
|
<hr>
|
|
<h3>7.26.6.1 [The memset function]</h3>
|
|
<a name='7.26.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memset(void *s, int c, size_t n);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.1p2'></a>
|
|
<pre>2 The memset function copies the value of c (converted to an unsigned char) into each of the first n
|
|
characters of the object pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.1p3'></a>
|
|
<pre>3 The memset function returns the value of s.
|
|
|
|
</pre>
|
|
<a name='7.26.6.2'></a>
|
|
<hr>
|
|
<h3>7.26.6.2 [The memset_explicit function]</h3>
|
|
<a name='7.26.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memset_explicit(void *s, int c, size_t n);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.2p2'></a>
|
|
<pre>2 The memset_explicit function copies the value of c (converted to an unsigned char) into each of
|
|
the first n characters of the object pointed to by s. The purpose of this function is to make sensitive
|
|
information stored in the object inaccessible<a href='#FOOTNOTE.380'><sup>[380]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.380'>
|
|
<pre><i><b>Footnote 380)</b> The intention is that the memory store is always performed (i.e., never elided), regardless of optimizations. This is in
|
|
contrast to calls to the memset function (<a href='#7.26.6.1'>7.26.6.1</a>)
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.6.2p3'></a>
|
|
<pre>3 The memset_explicit function returns the value of s.
|
|
|
|
</pre>
|
|
<a name='7.26.6.3'></a>
|
|
<hr>
|
|
<h3>7.26.6.3 [The strerror function]</h3>
|
|
<a name='7.26.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strerror(int errnum);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.3p2'></a>
|
|
<pre>2 The strerror function maps the number in errnum to a message string. Typically, the values for
|
|
errnum come from errno, but strerror shall map any value of type int to a message.
|
|
</pre>
|
|
<a name='7.26.6.3p3'></a>
|
|
<pre>3 The strerror function is not required to avoid data races with other calls to the strerror func-
|
|
tion.<a href='#FOOTNOTE.381'><sup>[381]</sup></a> The implementation shall behave as if no library function calls the strerror function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.381'>
|
|
<pre><i><b>Footnote 381)</b> The strerror_s function can be used instead to avoid data races.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.6.3p4'></a>
|
|
<pre>4 The strerror function returns a pointer to the string, the contents of which are locale-specific. The
|
|
array pointed to shall not be modified by the program. The behavior is undefined if the returned
|
|
value is used after a subsequent call to the strerror function, or after the thread which called the
|
|
function to obtain the returned value has exited.
|
|
Forward references: The strerror_s function (<a href='#K.3.7.4.2'>K.3.7.4.2</a>).
|
|
</pre>
|
|
<a name='7.26.6.4'></a>
|
|
<hr>
|
|
<h3>7.26.6.4 [The strlen function]</h3>
|
|
<a name='7.26.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strlen(const char *s);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.4p2'></a>
|
|
<pre>2 The strlen function computes the length of the string pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.4p3'></a>
|
|
<pre>3 The strlen function returns the number of characters that precede the terminating null character.
|
|
</pre>
|
|
<a name='7.27'></a>
|
|
<hr>
|
|
<h3>7.27 [Type-generic math <tgmath.h>]</h3>
|
|
<a name='7.27p1'></a>
|
|
<pre>1 The header <tgmath.h> includes the headers <math.h> and <complex.h> and defines several
|
|
type-generic macros.
|
|
</pre>
|
|
<a name='7.27p2'></a>
|
|
<pre>2 The feature test macro __STDC_VERSION_TGMATH_H__ expands to the token 202311L.
|
|
</pre>
|
|
<a name='7.27p3'></a>
|
|
<pre>3 This clause specifies a many-to-one correspondence of functions in <math.h> and <complex.h> with
|
|
type-generic macros.<a href='#FOOTNOTE.382'><sup>[382]</sup></a> Use of a type-generic macro invokes a corresponding function whose type is
|
|
determined by the types of the arguments for particular parameters called the generic parameters.<a href='#FOOTNOTE.383'><sup>[383]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.382'>
|
|
<pre><i><b>Footnote 382)</b> Like other function-like macros in standard libraries, each type-generic macro can be suppressed to make available the
|
|
corresponding ordinary function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.383'>
|
|
<pre><i><b>Footnote 383)</b> If the type of the argument is not compatible with the type of the parameter for the selected function, the behavior is
|
|
undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27p4'></a>
|
|
<pre>4 Of the <math.h> and <complex.h> functions without an f (float) or l (long double) suffix, several
|
|
have one or more parameters whose corresponding real type is double. For each such function,
|
|
except the functions that round result to narrower type (<a href='#7.12.14'>7.12.14</a>) (which are covered below) and
|
|
modf,
|
|
there is a corresponding type-generic macro. The parameters whose corresponding real type is
|
|
double in the function synopsis are generic parameters.
|
|
</pre>
|
|
<a name='7.27p5'></a>
|
|
<pre>5 Some of the <math.h> functions for decimal floating types have no unsuffixed counterpart. Of these
|
|
functions with a d64 suffix, some have one or more parameters whose type is _Decimal64 . For each
|
|
such function, except decodedecd64, encodedecd64, decodebind64, and encodebind64, there is a
|
|
corresponding type-generic macro. The parameters whose real type is _Decimal64 in the function
|
|
synopsis are generic parameters.
|
|
</pre>
|
|
<a name='7.27p6'></a>
|
|
<pre>6 If arguments for generic parameters of a type-generic macro are such that some argument has a
|
|
corresponding real type that is of standard floating type and another argument is of decimal floating
|
|
type, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.27p7'></a>
|
|
<pre>7 Except for the macros for functions that round result to a narrower type (<a href='#7.12.14'>7.12.14</a>), use of a type-
|
|
generic macro invokes a function whose generic parameters have the corresponding real type
|
|
determined by the types of the arguments for the generic parameters as follows:
|
|
|
|
|
|
— Arguments of integer type are regarded as having type _Decimal64 if any argument has
|
|
decimal floating type, and as having type double otherwise.
|
|
|
|
— If the function has exactly one generic parameter, the type determined is the corresponding
|
|
real type of the argument for the generic parameter.
|
|
|
|
— If the function has exactly two generic parameters, the type determined is the corresponding
|
|
real type determined by the usual arithmetic conversions (<a href='#6.3.1.8'>6.3.1.8</a>) applied to the arguments for
|
|
the generic parameters.
|
|
|
|
— If the function has more than two generic parameters, the type determined is the corresponding
|
|
real type determined by repeatedly applying the usual arithmetic conversions, first to the first
|
|
two arguments for generic parameters, then to that result type and the next argument for a
|
|
generic parameter, and so forth until the usual arithmetic conversions have been applied to
|
|
the last argument for a generic parameter.
|
|
|
|
|
|
If neither <math.h> and <complex.h> define a function whose generic parameters have the deter-
|
|
mined corresponding real type, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.27p8'></a>
|
|
<pre>8 For each unsuffixed function in <math.h> for which there is a function in <complex.h> with the
|
|
same name except for a c prefix, the corresponding type-generic macro (for both functions) has the
|
|
same name as the function in <math.h>. The corresponding type-generic macro for fabs and cabs
|
|
is fabs.
|
|
<math.h> <complex.h> type-generic
|
|
function function macro
|
|
acos cacos acos
|
|
asin casin asin
|
|
atan catan atan
|
|
acosh cacosh acosh
|
|
asinh casinh asinh
|
|
atanh catanh atanh
|
|
cos ccos cos
|
|
sin csin sin
|
|
tan ctan tan
|
|
cosh ccosh cosh
|
|
sinh csinh sinh
|
|
tanh ctanh tanh
|
|
exp cexp exp
|
|
log clog log
|
|
pow cpow pow
|
|
sqrt csqrt sqrt
|
|
fabs cabs fabs
|
|
If at least one argument for a generic parameter is complex, then use of the macro invokes a complex
|
|
function; otherwise, use of the macro invokes a real function.
|
|
</pre>
|
|
<a name='7.27p9'></a>
|
|
<pre>9 For each unsuffixed function in <math.h> without a c-prefixed counterpart in <complex.h> (except
|
|
functions that round result to narrower type, modf, and canonicalize), the corresponding type-
|
|
generic macro has the same name as the function. These type-generic macros are:
|
|
|
|
acospi exp2 fmod log2 rootn
|
|
asinpi expm1 frexp logb roundeven
|
|
atan2pi fdim fromfpx logp1 round
|
|
atan2 floor fromfp lrint rsqrt
|
|
atanpi fmax hypot lround scalbln
|
|
cbrt fmaximum ilogb nearbyint scalbn
|
|
ceil fmaximum_mag ldexp nextafter sinpi
|
|
compoundn fmaximum_num lgamma nextdown tanpi
|
|
copysign fmaximum_mag_num llogb nexttoward tgamma
|
|
cospi fma llrint nextup trunc
|
|
erfc fmin llround pown ufromfpx
|
|
erf fminimum log10p1 powr ufromfp
|
|
exp10m1 fminimum_mag log10 remainder
|
|
exp10 fminimum_num log1p remquo
|
|
exp2m1 fminimum_mag_num log2p1 rint
|
|
|
|
|
|
If all arguments for generic parameters are real, then use of the macro invokes a real function
|
|
(provided <math.h> defines a function of the determined type); otherwise, use of the macro is
|
|
undefined.
|
|
</pre>
|
|
<a name='7.27p10'></a>
|
|
<pre>10 For each unsuffixed function in <complex.h> that is not a c-prefixed counterpart to a function
|
|
in <math.h>, the corresponding type-generic macro has the same name as the function. These
|
|
type-generic macros are:
|
|
|
|
carg cimag conj cproj creal
|
|
|
|
|
|
Use of the macro with any argument of standard floating or complex type invokes a complex
|
|
function. Use of the macro with an argument of decimal floating type is undefined.
|
|
</pre>
|
|
<a name='7.27p11'></a>
|
|
<pre>11 The functions that round result to a narrower type have type-generic macros whose names are
|
|
obtained by omitting any suffix from the function names. Thus, the macros with f or d prefix are:
|
|
fadd fsub fmul fdiv ffma fsqrt
|
|
dadd dsub dmul ddiv dfma dsqrt
|
|
|
|
|
|
and the macros with d32 or d64 prefix are:
|
|
|
|
d32add d32sub d32mul d32div d32fma d32sqrt
|
|
d64add d64sub d64mul d64div d64fma d64sqrt
|
|
|
|
|
|
All arguments shall be real. If the macro prefix is f or d, use of an argument of decimal floating
|
|
type is undefined. If the macro prefix is d32 or d64, use of an argument of standard floating type is
|
|
undefined. The function invoked is determined as follows:
|
|
|
|
— If any argument has type _Decimal128 , or if the macro prefix is d64, the function invoked has
|
|
the name of the macro, with a d128 suffix.
|
|
— Otherwise, if the macro prefix is d32, the function invoked has the name of the macro, with a
|
|
d64 suffix.
|
|
|
|
— Otherwise, if any argument has type long double, or if the macro prefix is d, the function
|
|
invoked has the name of the macro, with an l suffix.
|
|
— Otherwise, the function invoked has the name of the macro (with no suffix).
|
|
|
|
</pre>
|
|
<a name='7.27p12'></a>
|
|
<pre>12 For each d64-suffixed function in <math.h>, except decodedecd64, encodedecd64, decodebind64,
|
|
and encodebind64, that does not have an unsuffixed counterpart, the corresponding type-generic
|
|
macro has the name of the function, but without the suffix. These type-generic macros are:
|
|
<math.h> type-generic
|
|
function macro
|
|
quantizedN quantize
|
|
samequantumdN samequantum
|
|
quantumdN quantum
|
|
llquantexpdN llquantexp
|
|
Use of the macro with an argument of standard floating or complex type or with only integer type
|
|
arguments is undefined.
|
|
</pre>
|
|
<a name='7.27p13'></a>
|
|
<pre>13 A type-generic macro corresponding to a function indicated in the table in <a href='#7.6.2'>7.6.2</a> is affected by
|
|
constant rounding modes (<a href='#7.6.4'>7.6.4</a>).
|
|
</pre>
|
|
<a name='7.27p14'></a>
|
|
<pre>14 NOTE The type-generic macro definition in the example in <a href='#6.5.1.1'>6.5.1.1</a> does not conform to this specification. A conforming
|
|
macro could be implemented as follows:
|
|
|
|
#define cbrt(X) \
|
|
_Generic((X), \
|
|
long double: _Roundwise_cbrtl, \
|
|
default: _Roundwise_cbrt, \
|
|
float: _Roundwise_cbrtf \
|
|
)(X)
|
|
|
|
where where _Roundwise_cbrtl , _Roundwise_cbrt , and _Roundwise_cbrtf are pointers to functions that are equivalent
|
|
to cbrtl, cbrt, and cbrtf, respectively, but that are guaranteed to be affected by constant rounding modes (<a href='#7.6.2'>7.6.2</a>).
|
|
</pre>
|
|
<a name='7.27p15'></a>
|
|
<pre>15 EXAMPLE With the declarations
|
|
|
|
#include <tgmath.h>
|
|
int n;
|
|
float f;
|
|
double d;
|
|
long double ld;
|
|
float complex fc;
|
|
double complex dc;
|
|
long double complex ldc;
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 d32;
|
|
_Decimal64 d64;
|
|
_Decimal128 d128;
|
|
#endif
|
|
|
|
functions invoked by use of type-generic macros are shown in the following table:
|
|
|
|
|
|
|
|
macro use invocation
|
|
exp(n) exp(n) , the function
|
|
acosh(f) acoshf(f)
|
|
sin(d) sin(d) , the function
|
|
atan(ld) atanl(ld)
|
|
log(fc) clogf(fc)
|
|
sqrt(dc) csqrt(dc)
|
|
pow(ldc, f) cpowl(ldc, f)
|
|
remainder(n, n) remainder(n, n) , the function
|
|
nextafter(d, f) nextafter(d, f) , the function
|
|
nexttoward(f, ld) nexttowardf(f, ld)
|
|
copysign(n, ld) copysignl(n, ld)
|
|
ceil(fc) undefined
|
|
rint(dc) undefined
|
|
fmaximum(ldc, ld) undefined
|
|
carg(n) carg(n) , the function
|
|
cproj(f) cprojf(f)
|
|
creal(d) creal(d) , the function
|
|
cimag(ld) cimagl(ld)
|
|
fabs(fc) cabsf(fc)
|
|
carg(dc) carg(dc) , the function
|
|
cproj(ldc) cprojl(ldc)
|
|
fsub(f, ld) fsubl(f, ld)
|
|
fdiv(d, n) fdiv(d, n) , the function
|
|
dfma(f, d, ld) dfmal(f, d, ld)
|
|
dadd(f, f) daddl(f, f)
|
|
dsqrt(dc) undefined
|
|
exp(d64) expd64(d64)
|
|
sqrt(d32) sqrtd32(d32)
|
|
fmaximum(d64, d128) fmaximumd128(d64, d128)
|
|
pow(d32, n) powd64(d32, n)
|
|
remainder(d64, d) undefined
|
|
creal(d64) undefined
|
|
remquo(d32, d32, &n) undefined
|
|
llquantexp(d) undefined
|
|
quantize(dc) undefined
|
|
samequantum(n, n) undefined
|
|
d32sub(d32, d128) d32subd128(d32, d128)
|
|
d32div(d64, n) d32divd64(d64, n)
|
|
d64fma(d32, d64, d128) d64fmad128(d32, d64, d128)
|
|
d64add(d32, d32) d64addd128(d32, d32)
|
|
d64sqrt(d) undefined
|
|
dadd(n, d64) undefined
|
|
|
|
|
|
|
|
acospi
|
|
asinpi
|
|
atan2pi
|
|
atan2
|
|
atanpi
|
|
cbrt
|
|
ceil
|
|
compoundn
|
|
copysign
|
|
cospi
|
|
erfc
|
|
erf
|
|
exp10m1
|
|
exp10
|
|
exp2m1
|
|
exp2
|
|
expm1
|
|
fdim
|
|
floor
|
|
fmax
|
|
fmaximum
|
|
fmaximum_mag
|
|
fmaximum_num
|
|
fmaximum_mag_num
|
|
fma
|
|
fmin
|
|
fminimum
|
|
fminimum_mag
|
|
fminimum_num
|
|
fminimum_mag_num
|
|
fmod
|
|
frexp
|
|
fromfpx
|
|
fromfp
|
|
hypot
|
|
ilogb
|
|
ldexp
|
|
lgamma
|
|
llogb
|
|
llrint
|
|
llround
|
|
log10p1
|
|
log10
|
|
log1p
|
|
log2p1
|
|
log2
|
|
logb
|
|
logp1
|
|
lrint
|
|
lround
|
|
nearbyint
|
|
nextafter
|
|
nextdown
|
|
nexttoward
|
|
nextup
|
|
pown
|
|
powr
|
|
remainder
|
|
remquo
|
|
rint
|
|
rootn
|
|
roundeven
|
|
round
|
|
rsqrt
|
|
scalbln
|
|
scalbn
|
|
sinpi
|
|
tanpi
|
|
tgamma
|
|
trunc
|
|
ufromfpx
|
|
ufromfp carg
|
|
cimag
|
|
conj
|
|
cproj
|
|
creal d32add
|
|
d64add
|
|
d32sub
|
|
d64sub
|
|
d32mul
|
|
d64mul
|
|
d32div
|
|
d64div
|
|
d32fma
|
|
d64fma
|
|
d32sqrt
|
|
d64sqrt fadd
|
|
dadd
|
|
fsub
|
|
dsub
|
|
fmul
|
|
dmul
|
|
fdiv
|
|
ddiv
|
|
ffma
|
|
dfma
|
|
fsqrt
|
|
dsqrt
|
|
</pre>
|
|
<a name='7.28'></a>
|
|
<hr>
|
|
<h3>7.28 [Threads <threads.h>]</h3>
|
|
<a name='7.28.1'></a>
|
|
<hr>
|
|
<h3>7.28.1 [Introduction]</h3>
|
|
<a name='7.28.1p1'></a>
|
|
<pre>1 The header <threads.h> includes the header <time.h>, defines macros, and declares types, enu-
|
|
meration constants, and functions that support multiple threads of execution<a href='#FOOTNOTE.384'><sup>[384]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.384'>
|
|
<pre><i><b>Footnote 384)</b> See "future library directions" (<a href='#7.33.19'>7.33.19</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.28.1p2'></a>
|
|
<pre>2 Implementations that define the macro __STDC_NO_THREADS__ need not provide this header nor
|
|
support any of its facilities.
|
|
</pre>
|
|
<a name='7.28.1p3'></a>
|
|
<pre>3 The macros are
|
|
|
|
ONCE_FLAG_INIT
|
|
|
|
|
|
which expands to a value that can be used to initialize an object of type once_flag; and
|
|
|
|
TSS_DTOR_ITERATIONS
|
|
|
|
|
|
which expands to an integer constant expression representing the maximum number of times that
|
|
destructors will be called when a thread terminates.
|
|
</pre>
|
|
<a name='7.28.1p4'></a>
|
|
<pre>4 The types are
|
|
|
|
cnd_t
|
|
|
|
|
|
which is a complete object type that holds an identifier for a condition variable;
|
|
|
|
thrd_t
|
|
|
|
|
|
which is a complete object type that holds an identifier for a thread;
|
|
|
|
tss_t
|
|
|
|
|
|
which is a complete object type that holds an identifier for a thread-specific storage pointer;
|
|
|
|
mtx_t
|
|
|
|
|
|
which is a complete object type that holds an identifier for a mutex;
|
|
|
|
tss_dtor_t
|
|
|
|
|
|
which is the function pointer type void (*)(void*), used for a destructor for a thread-specific
|
|
storage pointer;
|
|
|
|
thrd_start_t
|
|
|
|
|
|
which is the function pointer type int (*)(void*) that is passed to thrd_create to create a new
|
|
thread; and
|
|
|
|
once_flag
|
|
|
|
|
|
which is a complete object type that holds a flag for use by call_once.
|
|
</pre>
|
|
<a name='7.28.1p5'></a>
|
|
<pre>5 The enumeration constants are
|
|
|
|
mtx_plain
|
|
|
|
|
|
which is passed to mtx_init to create a mutex object that does not support timeout;
|
|
|
|
mtx_recursive
|
|
which is passed to mtx_init to create a mutex object that supports recursive locking;
|
|
|
|
mtx_timed
|
|
|
|
|
|
which is passed to mtx_init to create a mutex object that supports timeout;
|
|
|
|
thrd_timedout
|
|
|
|
|
|
which is returned by a timed wait function to indicate that the time specified in the call was reached
|
|
without acquiring the requested resource;
|
|
|
|
thrd_success
|
|
|
|
|
|
which is returned by a function to indicate that the requested operation succeeded;
|
|
|
|
thrd_busy
|
|
|
|
|
|
which is returned by a function to indicate that the requested operation failed because a resource
|
|
requested by a test and return function is already in use;
|
|
|
|
thrd_error
|
|
|
|
|
|
which is returned by a function to indicate that the requested operation failed; and
|
|
|
|
thrd_nomem
|
|
|
|
|
|
which is returned by a function to indicate that the requested operation failed because it was unable
|
|
to allocate memory.
|
|
Forward references: date and time (<a href='#7.29'>7.29</a>).
|
|
|
|
</pre>
|
|
<a name='7.28.2'></a>
|
|
<hr>
|
|
<h3>7.28.2 [Initialization functions]</h3>
|
|
<a name='7.28.2.1'></a>
|
|
<hr>
|
|
<h3>7.28.2.1 [The call_once function]</h3>
|
|
<a name='7.28.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void call_once(once_flag *flag, void (*func)(void));
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.2.1p2'></a>
|
|
<pre>2 The call_once function uses the once_flag pointed to by flag to ensure that func is called exactly
|
|
once, the first time the call_once function is called with that value of flag. Completion of an
|
|
effective call to the call_once function synchronizes with all subsequent calls to the call_once
|
|
function with the same value of flag.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.2.1p3'></a>
|
|
<pre>3 The call_once function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.3'></a>
|
|
<hr>
|
|
<h3>7.28.3 [Condition variable functions]</h3>
|
|
<a name='7.28.3.1'></a>
|
|
<hr>
|
|
<h3>7.28.3.1 [The cnd_broadcast function]</h3>
|
|
<a name='7.28.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_broadcast(cnd_t *cond);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.1p2'></a>
|
|
<pre>2 The cnd_broadcast function unblocks all of the threads that are blocked on the condition variable
|
|
pointed to by cond at the time of the call. If no threads are blocked on the condition variable pointed
|
|
to by cond at the time of the call, the function does nothing.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.1p3'></a>
|
|
<pre>3 The cnd_broadcast function returns thrd_success on success, or thrd_error if the request could
|
|
not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.3.2'></a>
|
|
<hr>
|
|
<h3>7.28.3.2 [The cnd_destroy function]</h3>
|
|
<a name='7.28.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void cnd_destroy(cnd_t *cond);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.2p2'></a>
|
|
<pre>2 The cnd_destroy function releases all resources used by the condition variable pointed to by cond.
|
|
The cnd_destroy function requires that no threads be blocked waiting for the condition variable
|
|
pointed to by cond.
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.2p3'></a>
|
|
<pre>3 The cnd_destroy function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.3.3'></a>
|
|
<hr>
|
|
<h3>7.28.3.3 [The cnd_init function]</h3>
|
|
<a name='7.28.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_init(cnd_t *cond);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.3p2'></a>
|
|
<pre>2 The cnd_init function creates a condition variable. If it succeeds it sets the variable pointed to by
|
|
cond to a value that uniquely identifies the newly created condition variable. A thread that calls
|
|
cnd_wait on a newly created condition variable will block.
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.3p3'></a>
|
|
<pre>3 The cnd_init function returns thrd_success on success, or thrd_nomem if no memory could be
|
|
allocated for the newly created condition, or thrd_error if the request could not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.3.4'></a>
|
|
<hr>
|
|
<h3>7.28.3.4 [The cnd_signal function]</h3>
|
|
<a name='7.28.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_signal(cnd_t *cond);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.4p2'></a>
|
|
<pre>2 The cnd_signal function unblocks one of the threads that are blocked on the condition variable
|
|
pointed to by cond at the time of the call. If no threads are blocked on the condition variable at the
|
|
time of the call, the function does nothing and returns success.
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.4p3'></a>
|
|
<pre>3 The cnd_signal function returns thrd_success on success or thrd_error if the request could not
|
|
be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.3.5'></a>
|
|
<hr>
|
|
<h3>7.28.3.5 [The cnd_timedwait function]</h3>
|
|
<a name='7.28.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_timedwait(cnd_t *restrict cond, mtx_t *restrict mtx,
|
|
const struct timespec *restrict ts);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.5p2'></a>
|
|
<pre>2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and blocks until the
|
|
condition variable pointed to by cond is signaled by a call to cnd_signal or to cnd_broadcast, or
|
|
until after the TIME_UTC-based calendar time pointed to by ts, or until it is unblocked due to an
|
|
unspecified reason. When the calling thread becomes unblocked it locks the variable pointed to by
|
|
mtx before it returns. The cnd_timedwait function requires that the mutex pointed to by mtx be
|
|
locked by the calling thread.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.5p3'></a>
|
|
<pre>3 The cnd_timedwait function returns thrd_success upon success, or thrd_timedout if the time
|
|
specified in the call was reached without acquiring the requested resource, or thrd_error if the
|
|
request could not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.3.6'></a>
|
|
<hr>
|
|
<h3>7.28.3.6 [The cnd_wait function]</h3>
|
|
<a name='7.28.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_wait(cnd_t *cond, mtx_t *mtx);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.3.6p2'></a>
|
|
<pre>2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and blocks until the condi-
|
|
tion variable pointed to by cond is signaled by a call to cnd_signal or to cnd_broadcast, or until it
|
|
is unblocked due to an unspecified reason. When the calling thread becomes unblocked it locks the
|
|
mutex pointed to by mtx before it returns. The cnd_wait function requires that the mutex pointed
|
|
to by mtx be locked by the calling thread.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.3.6p3'></a>
|
|
<pre>3 The cnd_wait function returns thrd_success on success or thrd_error if the request could not be
|
|
honored.
|
|
|
|
</pre>
|
|
<a name='7.28.4'></a>
|
|
<hr>
|
|
<h3>7.28.4 [Mutex functions]</h3>
|
|
<a name='7.28.4p1'></a>
|
|
<pre>1 For purposes of determining the existence of a data race, lock and unlock operations behave as
|
|
atomic operations. All lock and unlock operations on a particular mutex occur in some particular
|
|
total order.
|
|
</pre>
|
|
<a name='7.28.4p2'></a>
|
|
<pre>2 NOTE This total order can be viewed as the modification order of the mutex.
|
|
|
|
</pre>
|
|
<a name='7.28.4.1'></a>
|
|
<hr>
|
|
<h3>7.28.4.1 [The mtx_destroy function]</h3>
|
|
<a name='7.28.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void mtx_destroy(mtx_t *mtx);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.1p2'></a>
|
|
<pre>2 The mtx_destroy function releases any resources used by the mutex pointed to by mtx. No threads
|
|
can be blocked waiting for the mutex pointed to by mtx.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.1p3'></a>
|
|
<pre>3 The mtx_destroy function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.4.2'></a>
|
|
<hr>
|
|
<h3>7.28.4.2 [The mtx_init function]</h3>
|
|
<a name='7.28.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_init(mtx_t *mtx, int type);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.2p2'></a>
|
|
<pre>2 The mtx_init function creates a mutex object with properties indicated by type, which shall have
|
|
one of these values:
|
|
|
|
mtx_plain for a simple non-recursive mutex,
|
|
|
|
mtx_timed for a non-recursive mutex that supports timeout,
|
|
|
|
mtx_plain | mtx_recursive for a simple recursive mutex, or
|
|
|
|
mtx_timed | mtx_recursive for a recursive mutex that supports timeout.
|
|
|
|
</pre>
|
|
<a name='7.28.4.2p3'></a>
|
|
<pre>3 If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that uniquely
|
|
identifies the newly created mutex.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.2p4'></a>
|
|
<pre>4 The mtx_init function returns thrd_success on success, or thrd_error if the request could not
|
|
be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.4.3'></a>
|
|
<hr>
|
|
<h3>7.28.4.3 [The mtx_lock function]</h3>
|
|
<a name='7.28.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_lock(mtx_t *mtx);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.3p2'></a>
|
|
<pre>2 The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex is non-
|
|
recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock on the same mutex
|
|
synchronize with this operation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.3p3'></a>
|
|
<pre>3 The mtx_lock function returns thrd_success on success, or thrd_error if the request could not
|
|
be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.4.4'></a>
|
|
<hr>
|
|
<h3>7.28.4.4 [The mtx_timedlock function]</h3>
|
|
<a name='7.28.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_timedlock(mtx_t *restrict mtx, const struct timespec *restrict ts);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.4p2'></a>
|
|
<pre>2 The mtx_timedlock function endeavors to block until it locks the mutex pointed to by mtx or
|
|
until after the TIME_UTC-based calendar time pointed to by ts. The specified mutex shall support
|
|
timeout. If the operation succeeds, prior calls to mtx_unlock on the same mutex synchronize with
|
|
this operation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.4p3'></a>
|
|
<pre>3 The mtx_timedlock function returns thrd_success on success, or thrd_timedout if the time
|
|
specified was reached without acquiring the requested resource, or thrd_error if the request could
|
|
not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.4.5'></a>
|
|
<hr>
|
|
<h3>7.28.4.5 [The mtx_trylock function]</h3>
|
|
<a name='7.28.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_trylock(mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.5p2'></a>
|
|
<pre>2 The mtx_trylock function endeavors to lock the mutex pointed to by mtx. If the mutex is already
|
|
locked, the function returns without blocking. If the operation succeeds, prior calls to mtx_unlock
|
|
on the same mutex synchronize with this operation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.5p3'></a>
|
|
<pre>3 The mtx_trylock function returns thrd_success on success, or thrd_busy if the resource requested
|
|
is already in use, or thrd_error if the request could not be honored. mtx_trylock may spuriously
|
|
fail to lock an unused resource, in which case it returns thrd_busy.
|
|
|
|
</pre>
|
|
<a name='7.28.4.6'></a>
|
|
<hr>
|
|
<h3>7.28.4.6 [The mtx_unlock function]</h3>
|
|
<a name='7.28.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_unlock(mtx_t *mtx);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.4.6p2'></a>
|
|
<pre>2 The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to by mtx shall
|
|
be locked by the calling thread.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.4.6p3'></a>
|
|
<pre>3 The mtx_unlock function returns thrd_success on success or thrd_error if the request could not
|
|
be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.5'></a>
|
|
<hr>
|
|
<h3>7.28.5 [Thread functions]</h3>
|
|
<a name='7.28.5.1'></a>
|
|
<hr>
|
|
<h3>7.28.5.1 [The thrd_create function]</h3>
|
|
<a name='7.28.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_create(thrd_t *thr, thrd_start_t func, void *arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.1p2'></a>
|
|
<pre>2 The thrd_create function creates a new thread executing func(arg). If the thrd_create function
|
|
succeeds, it sets the object pointed to by thr to the identifier of the newly created thread. (A thread’s
|
|
identifier may be reused for a different thread once the original thread has exited and either been
|
|
detached or joined to another thread.) The completion of the thrd_create function synchronizes
|
|
with the beginning of the execution of the new thread.
|
|
</pre>
|
|
<a name='7.28.5.1p3'></a>
|
|
<pre>3 Returning from func has the same behavior as invoking thrd_exit with the value returned from
|
|
func.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.1p4'></a>
|
|
<pre>4 The thrd_create function returns thrd_success on success, or thrd_nomem if no memory could
|
|
be allocated for the thread requested, or thrd_error if the request could not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.5.2'></a>
|
|
<hr>
|
|
<h3>7.28.5.2 [The thrd_current function]</h3>
|
|
<a name='7.28.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
thrd_t thrd_current(void);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.2p2'></a>
|
|
<pre>2 The thrd_current function identifies the thread that called it.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.2p3'></a>
|
|
<pre>3 The thrd_current function returns the identifier of the thread that called it.
|
|
</pre>
|
|
<a name='7.28.5.3'></a>
|
|
<hr>
|
|
<h3>7.28.5.3 [The thrd_detach function]</h3>
|
|
<a name='7.28.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_detach(thrd_t thr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.3p2'></a>
|
|
<pre>2 The thrd_detach function tells the operating system to dispose of any resources allocated to the
|
|
thread identified by thr when that thread terminates. The thread identified by thr shall not have
|
|
been previously detached or joined with another thread.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.3p3'></a>
|
|
<pre>3 The thrd_detach function returns thrd_success on success or thrd_error if the request could
|
|
not be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.5.4'></a>
|
|
<hr>
|
|
<h3>7.28.5.4 [The thrd_equal function]</h3>
|
|
<a name='7.28.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_equal(thrd_t thr0, thrd_t thr1);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.4p2'></a>
|
|
<pre>2 The thrd_equal function will determine whether the thread identified by thr0 refers to the thread
|
|
identified by thr1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.4p3'></a>
|
|
<pre>3 The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to different
|
|
threads. Otherwise the thrd_equal function returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='7.28.5.5'></a>
|
|
<hr>
|
|
<h3>7.28.5.5 [The thrd_exit function]</h3>
|
|
<a name='7.28.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
[[noreturn]] void thrd_exit(int res);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.5p2'></a>
|
|
<pre>2 For every thread-specific storage key which was created with a non-null destructor and for which
|
|
the value is non-null, thrd_exit sets the value associated with the key to a null pointer value and
|
|
then invokes the destructor with its previous value. The order in which destructors are invoked is
|
|
unspecified.
|
|
</pre>
|
|
<a name='7.28.5.5p3'></a>
|
|
<pre>3 If after this process there remain keys with both non-null destructors and values, the implementation
|
|
repeats this process up to TSS_DTOR_ITERATIONS times.
|
|
</pre>
|
|
<a name='7.28.5.5p4'></a>
|
|
<pre>4 Following this, the thrd_exit function terminates execution of the calling thread and sets its result
|
|
code to res.
|
|
</pre>
|
|
<a name='7.28.5.5p5'></a>
|
|
<pre>5 The program terminates normally after the last thread has been terminated. The behavior is as if the
|
|
program called the exit function with the status EXIT_SUCCESS at thread termination time.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.5p6'></a>
|
|
<pre>6 The thrd_exit function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.5.6'></a>
|
|
<hr>
|
|
<h3>7.28.5.6 [The thrd_join function]</h3>
|
|
<a name='7.28.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_join(thrd_t thr, int *res);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.6p2'></a>
|
|
<pre>2 The thrd_join function joins the thread identified by thr with the current thread by blocking until
|
|
the other thread has terminated. If the parameter res is not a null pointer, it stores the thread’s result
|
|
code in the integer pointed to by res. The termination of the other thread synchronizes with the
|
|
completion of the thrd_join function. The thread identified by thr shall not have been previously
|
|
detached or joined with another thread.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.6p3'></a>
|
|
<pre>3 The thrd_join function returns thrd_success on success or thrd_error if the request could not
|
|
be honored.
|
|
|
|
</pre>
|
|
<a name='7.28.5.7'></a>
|
|
<hr>
|
|
<h3>7.28.5.7 [The thrd_sleep function]</h3>
|
|
<a name='7.28.5.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_sleep(const struct timespec *duration, struct timespec *remaining);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.7p2'></a>
|
|
<pre>2 The thrd_sleep function suspends execution of the calling thread until either the interval specified
|
|
by duration has elapsed or a signal which is not being ignored is received. If interrupted by a signal
|
|
and the remaining argument is not null, the amount of time remaining (the requested interval
|
|
minus the time actually slept) is stored in the interval it points to. The duration and remaining
|
|
arguments may point to the same object.
|
|
</pre>
|
|
<a name='7.28.5.7p3'></a>
|
|
<pre>3 The suspension time may be longer than requested because the interval is rounded up to an integer
|
|
multiple of the sleep resolution or because of the scheduling of other activity by the system. But,
|
|
except for the case of being interrupted by a signal, the suspension time will not be less than that
|
|
specified, as measured by the system clock TIME_UTC.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.7p4'></a>
|
|
<pre>4 The thrd_sleep function returns zero if the requested time has elapsed, −1 if it has been interrupted
|
|
by a signal, or a negative value (which may also be −1) if it fails.
|
|
|
|
</pre>
|
|
<a name='7.28.5.8'></a>
|
|
<hr>
|
|
<h3>7.28.5.8 [The thrd_yield function]</h3>
|
|
<a name='7.28.5.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void thrd_yield(void);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.5.8p2'></a>
|
|
<pre>2 The thrd_yield function endeavors to permit other threads to run, even if the current thread would
|
|
ordinarily continue to run.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.5.8p3'></a>
|
|
<pre>3 The thrd_yield function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.6'></a>
|
|
<hr>
|
|
<h3>7.28.6 [Thread-specific storage functions]</h3>
|
|
<a name='7.28.6.1'></a>
|
|
<hr>
|
|
<h3>7.28.6.1 [The tss_create function]</h3>
|
|
<a name='7.28.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int tss_create(tss_t *key, tss_dtor_t dtor);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.6.1p2'></a>
|
|
<pre>2 The tss_create function creates a thread-specific storage pointer with destructor dtor, which may
|
|
be null.
|
|
</pre>
|
|
<a name='7.28.6.1p3'></a>
|
|
<pre>3 A null pointer value is associated with the newly created key in all existing threads. Upon subsequent
|
|
thread creation, the value associated with all keys is initialized to a null pointer value in the new
|
|
thread.
|
|
</pre>
|
|
<a name='7.28.6.1p4'></a>
|
|
<pre>4 Destructors associated with thread-specific storage are not invoked at program termination.
|
|
</pre>
|
|
<a name='7.28.6.1p5'></a>
|
|
<pre>5 The tss_create function shall not be called from within a destructor.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.6.1p6'></a>
|
|
<pre>6 If the tss_create function is successful, it sets the thread-specific storage pointed to by key to a
|
|
value that uniquely identifies the newly created pointer and returns thrd_success; otherwise,
|
|
thrd_error is returned and the thread-specific storage pointed to by key is set to an indeterminate
|
|
representation.
|
|
|
|
</pre>
|
|
<a name='7.28.6.2'></a>
|
|
<hr>
|
|
<h3>7.28.6.2 [The tss_delete function]</h3>
|
|
<a name='7.28.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void tss_delete(tss_t key);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.6.2p2'></a>
|
|
<pre>2 The tss_delete function releases any resources used by the thread-specific storage identified by
|
|
key. The tss_delete function shall only be called with a value for key that was returned by a call
|
|
to tss_create before the thread commenced executing destructors.
|
|
</pre>
|
|
<a name='7.28.6.2p3'></a>
|
|
<pre>3 If tss_delete is called while another thread is executing destructors, whether this will affect the
|
|
number of invocations of the destructor associated with key on that thread is unspecified.
|
|
</pre>
|
|
<a name='7.28.6.2p4'></a>
|
|
<pre>4 Calling tss_delete will not result in the invocation of any destructors.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.6.2p5'></a>
|
|
<pre>5 The tss_delete function returns no value.
|
|
|
|
</pre>
|
|
<a name='7.28.6.3'></a>
|
|
<hr>
|
|
<h3>7.28.6.3 [The tss_get function]</h3>
|
|
<a name='7.28.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void *tss_get(tss_t key);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.6.3p2'></a>
|
|
<pre>2 The tss_get function returns the value for the current thread held in the thread-specific storage
|
|
identified by key. The tss_get function shall only be called with a value for key that was returned
|
|
by a call to tss_create before the thread commenced executing destructors.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.6.3p3'></a>
|
|
<pre>3 The tss_get function returns the value for the current thread if successful, or zero if unsuccessful.
|
|
|
|
</pre>
|
|
<a name='7.28.6.4'></a>
|
|
<hr>
|
|
<h3>7.28.6.4 [The tss_set function]</h3>
|
|
<a name='7.28.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int tss_set(tss_t key, void *val);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.28.6.4p2'></a>
|
|
<pre>2 The tss_set function sets the value for the current thread held in the thread-specific storage
|
|
identified by key to val. The tss_set function shall only be called with a value for key that was
|
|
returned by a call to tss_create before the thread commenced executing destructors.
|
|
</pre>
|
|
<a name='7.28.6.4p3'></a>
|
|
<pre>3 This action will not invoke the destructor associated with the key on the value being replaced.
|
|
Returns
|
|
</pre>
|
|
<a name='7.28.6.4p4'></a>
|
|
<pre>4 The tss_set function returns thrd_success on success or thrd_error if the request could not be
|
|
honored.
|
|
</pre>
|
|
<a name='7.29'></a>
|
|
<hr>
|
|
<h3>7.29 [Date and time <time.h>]</h3>
|
|
<a name='7.29.1'></a>
|
|
<hr>
|
|
<h3>7.29.1 [Components of time]</h3>
|
|
<a name='7.29.1p1'></a>
|
|
<pre>1 The header <time.h> defines several macros, and declares types and functions for manipulating
|
|
time. Many functions deal with a calendar time that represents the current date (according to the
|
|
Gregorian calendar) and time. Some functions deal with local time, which is the calendar time
|
|
expressed for some specific time zone, and with Daylight Saving Time, which is a temporary change
|
|
in the algorithm for determining local time. The local time zone and Daylight Saving Time are
|
|
implementation-defined.
|
|
</pre>
|
|
<a name='7.29.1p2'></a>
|
|
<pre>2 The feature test macro __STDC_VERSION_TIME_H__ expands to the token 202311L. The other macros
|
|
defined are NULL (described in <a href='#7.21'>7.21</a>);
|
|
|
|
CLOCKS_PER_SEC
|
|
|
|
|
|
which expands to an expression with type clock_t (described below) that is the number per second
|
|
of the value returned by the clock function;
|
|
|
|
TIME_UTC
|
|
TIME_MONOTONIC
|
|
|
|
|
|
which expand to integer constants greater than 0 that designates the calendar time and monotonic
|
|
time bases, respectively. Additional time base macro definitions, beginning with TIME_ and an
|
|
uppercase letter, may also be specified by the implementation<a href='#FOOTNOTE.385'><sup>[385]</sup></a> ; and,
|
|
|
|
TIME_ACTIVE
|
|
TIME_THREAD_ACTIVE
|
|
|
|
|
|
which, if defined, expand to integer values, designating overall execution and thread-specific active
|
|
processing time bases, respectively.
|
|
</pre>
|
|
<a name='FOOTNOTE.385'>
|
|
<pre><i><b>Footnote 385)</b> See future library directions (<a href='#7.33'>7.33</a>). Implementations can define additional time bases, but are only required to support a
|
|
real time clock based on UTC.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.1p3'></a>
|
|
<pre>3 The definition of macros for time bases other than TIME_UTC are optional. If defined, the correspond-
|
|
ing time bases are supported by timespec_get and timespec_getres, and their values are positive.
|
|
If defined, the value of the optional macro TIME_ACTIVE shall be different from the constants
|
|
TIME_UTC and TIME_MONOTONIC and shall not change during the same program invocation. The
|
|
optional macro TIME_THREAD_ACTIVE shall not be defined if the implementation does not support
|
|
threads; its value shall be different from TIME_UTC, TIME_MONOTONIC, and TIME_ACTIVE, it shall be
|
|
the same for all expansions of the macro for the same thread, and the value provided for one thread
|
|
shall not be used by a different thread as the base argument of timespec_get or timespec_getres.
|
|
</pre>
|
|
<a name='7.29.1p4'></a>
|
|
<pre>4 The types declared are size_t (described in <a href='#7.21'>7.21</a>);
|
|
|
|
clock_t
|
|
|
|
|
|
and
|
|
|
|
time_t
|
|
|
|
|
|
which are real types capable of representing times;
|
|
|
|
struct timespec
|
|
|
|
|
|
which holds an interval specified in seconds and nanoseconds (which may represent a calendar time
|
|
based on a particular epoch); and
|
|
|
|
struct tm
|
|
which holds the components of a calendar time, called the broken-down time.
|
|
</pre>
|
|
<a name='7.29.1p5'></a>
|
|
<pre>5 The range and precision of times representable in clock_t and time_t are implementation-defined.
|
|
The timespec structure shall contain at least the following members, in any order. The semantics of
|
|
the members and their normal ranges are expressed in the comments.<a href='#FOOTNOTE.386'><sup>[386]</sup></a>
|
|
|
|
time_t tv_sec; // whole seconds -- ≥ 0
|
|
long tv_nsec; // nanoseconds -- [0, 999999999]
|
|
|
|
|
|
The tm structure shall contain at least the following members, in any order. The semantics of the
|
|
members and their normal ranges are expressed in the comments.<a href='#FOOTNOTE.387'><sup>[387]</sup></a>
|
|
|
|
int tm_sec; // seconds after the minute -- [0, 60]
|
|
int tm_min; // minutes after the hour -- [0, 59]
|
|
int tm_hour; // hours since midnight -- [0, 23]
|
|
int tm_mday; // day of the month -- [1, 31]
|
|
int tm_mon; // months since January -- [0, 11]
|
|
int tm_year; // years since 1900
|
|
int tm_wday; // days since Sunday -- [0, 6]
|
|
int tm_yday; // days since January 1 -- [0, 365]
|
|
int tm_isdst; // Daylight Saving Time flag
|
|
|
|
|
|
The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight Saving Time
|
|
is not in effect, and negative if the information is not available.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.386'>
|
|
<pre><i><b>Footnote 386)</b> The tv_sec member is a linear count of seconds and might not have the normal semantics of a time_t.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.387'>
|
|
<pre><i><b>Footnote 387)</b> The range [0, 60] for tm_sec allows for a positive leap second.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2'></a>
|
|
<hr>
|
|
<h3>7.29.2 [Time manipulation functions]</h3>
|
|
<a name='7.29.2.1'></a>
|
|
<hr>
|
|
<h3>7.29.2.1 [The clock function]</h3>
|
|
<a name='7.29.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
clock_t clock(void);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.1p2'></a>
|
|
<pre>2 The clock function determines the processor time used.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.1p3'></a>
|
|
<pre>3 The clock function returns the implementation’s best approximation of the active processing time
|
|
associated with the program execution since the beginning of an implementation-defined era related
|
|
only to the program invocation. To determine the time in seconds, the value returned by the clock
|
|
function should be divided by the value of the macro CLOCKS_PER_SEC. If the processor time used
|
|
is not available, the function returns the value (clock_t) (−1). If the value cannot be represented,
|
|
the function returns an unspecified value<a href='#FOOTNOTE.388'><sup>[388]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.388'>
|
|
<pre><i><b>Footnote 388)</b> This could be due to overflow of the clock_t type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.2'></a>
|
|
<hr>
|
|
<h3>7.29.2.2 [The difftime function]</h3>
|
|
<a name='7.29.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
double difftime(time_t time1, time_t time0);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.2p2'></a>
|
|
<pre>2 The difftime function computes the difference between two calendar times: time1 - time0.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.2p3'></a>
|
|
<pre>3 The difftime function returns the difference expressed in seconds as a double.
|
|
</pre>
|
|
<a name='7.29.2.3'></a>
|
|
<hr>
|
|
<h3>7.29.2.3 [The mktime function]</h3>
|
|
<a name='7.29.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
time_t mktime(struct tm *timeptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.3p2'></a>
|
|
<pre>2 The mktime function converts the broken-down time, expressed as local time, in the structure
|
|
pointed to by timeptr into a calendar time value with the same encoding as that of the values
|
|
returned by the time function. The original values of the tm_wday and tm_yday components of the
|
|
structure are ignored, and the original values of the other components are not restricted to the ranges
|
|
indicated above. <a href='#FOOTNOTE.389'><sup>[389]</sup></a> On successful completion, the values of the tm_wday and tm_yday components
|
|
of the structure are set appropriately, and the other components are set to represent the specified
|
|
calendar time, but with their values forced to the ranges indicated above; the final value of tm_mday
|
|
is not set until tm_mon and tm_year are determined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.389'>
|
|
<pre><i><b>Footnote 389)</b> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that Daylight Saving Time,
|
|
respectively, is or is not in effect for the specified time. A negative value causes it to attempt to determine whether Daylight
|
|
Saving Time is in effect for the specified time.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.3p3'></a>
|
|
<pre>3 The mktime function returns the specified calendar time encoded as a value of type time_t. If the
|
|
calendar time cannot be represented, the function returns the value (time_t) (−1).
|
|
</pre>
|
|
<a name='7.29.2.3p4'></a>
|
|
<pre>4 EXAMPLE What day of the week is July 4, 2001?
|
|
|
|
#include <stdio.h>
|
|
#include <time.h>
|
|
static const char *const wday[] = {
|
|
"Sunday", "Monday", "Tuesday", "Wednesday",
|
|
"Thursday", "Friday", "Saturday", "-unknown-"
|
|
};
|
|
struct tm time_str;
|
|
/* ... */
|
|
|
|
time_str.tm_year = 2001 - 1900;
|
|
time_str.tm_mon = 7 - 1;
|
|
time_str.tm_mday = 4;
|
|
time_str.tm_hour = 0;
|
|
time_str.tm_min = 0;
|
|
time_str.tm_sec = 1;
|
|
time_str.tm_isdst = -1;
|
|
if (mktime(&time_str) == (time_t)(-1))
|
|
time_str.tm_wday = 7;
|
|
printf("%s\n", wday[time_str.tm_wday]);
|
|
|
|
|
|
</pre>
|
|
<a name='7.29.2.4'></a>
|
|
<hr>
|
|
<h3>7.29.2.4 [The timegm function]</h3>
|
|
<a name='7.29.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
time_t timegm(struct tm *timeptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.4p2'></a>
|
|
<pre>2 The timegm function converts the broken-down time, expressed as UTC time, in the structure
|
|
pointed to by timeptr into a calendar time value with the same encoding as that of the values
|
|
returned by the time function. The original values of the tm_wday and tm_yday components of the
|
|
structure are ignored, and the original values of the other components are not restricted to the ranges
|
|
indicated above. On successful completion, the values of the tm_wday and tm_yday components
|
|
of the structure are set appropriately, and the other components are set to represent the specified
|
|
calendar time, but with their values forced to the ranges indicated above; the final value of tm_mday
|
|
is not set until tm_mon and tm_year are determined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.4p3'></a>
|
|
<pre>3 The timegm function returns the specified calendar time encoded as a value of type time_t. If the
|
|
calendar time cannot be represented, the function returns the value (time_t)(-1) .
|
|
|
|
</pre>
|
|
<a name='7.29.2.5'></a>
|
|
<hr>
|
|
<h3>7.29.2.5 [The time function]</h3>
|
|
<a name='7.29.2.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
time_t time(time_t *timer);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.5p2'></a>
|
|
<pre>2 The time function determines the current calendar time. The encoding of the value is unspecified.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.5p3'></a>
|
|
<pre>3 The time function returns the implementation’s best approximation to the current calendar time.
|
|
The value (time_t) (−1) is returned if the calendar time is not available. If timer is not a null
|
|
pointer, the return value is also assigned to the object it points to.
|
|
|
|
</pre>
|
|
<a name='7.29.2.6'></a>
|
|
<hr>
|
|
<h3>7.29.2.6 [The timespec_get function]</h3>
|
|
<a name='7.29.2.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
int timespec_get(struct timespec *ts, int base);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.6p2'></a>
|
|
<pre>2 The timespec_get function sets the interval pointed to by ts to hold the current calendar time
|
|
based on the specified time base.
|
|
</pre>
|
|
<a name='7.29.2.6p3'></a>
|
|
<pre>3 If base is TIME_UTC, the tv_sec member is set to the number of seconds since an implementation-
|
|
defined epoch, truncated to a whole value and the tv_nsec member is set to the integral num-
|
|
ber of nanoseconds, rounded to the resolution of the system clock<a href='#FOOTNOTE.390'><sup>[390]</sup></a> . The optional time base
|
|
TIME_MONOTONIC is the same, but the reference point is an implementation-defined time point;
|
|
different program invocations need not refer to the same reference points<a href='#FOOTNOTE.391'><sup>[391]</sup></a> . For the same program
|
|
invocation, the results of two calls to timespec_get with TIME_MONOTONIC such that the first hap-
|
|
pens before the second shall not be decreasing. It is implementation-defined if TIME_MONOTONIC
|
|
accounts for time during which the execution environment is suspended<a href='#FOOTNOTE.392'><sup>[392]</sup></a> . For the optional time
|
|
bases TIME_ACTIVE and TIME_THREAD_ACTIVE the result is similar, but the call measures the amount
|
|
of active processing time associated with the whole program invocation or with the calling thread,
|
|
respectively.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.390'>
|
|
<pre><i><b>Footnote 390)</b> Although a struct timespec object describes times with nanosecond resolution, the available resolution is system
|
|
dependent and could even be greater than 1 second.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.391'>
|
|
<pre><i><b>Footnote 391)</b> Commonly, this reference point is the boot time of the execution environment or the start of the execution.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.392'>
|
|
<pre><i><b>Footnote 392)</b> The execution environment may, for example, not be able to track physical time that elapsed during suspension in a low
|
|
power consumption mode.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.6p4'></a>
|
|
<pre>4 If the timespec_get function is successful it returns the nonzero value base; otherwise, it returns
|
|
zero.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.29.2.6p5'></a>
|
|
<pre>5 It is recommended practice that timing results of calls to timespec_get with TIME_ACTIVE, if
|
|
defined, and of calls to clock are as close to each other as their types, value ranges, and resolutions
|
|
(obtained with timespec_getres and CLOCKS_PER_SEC, respectively) allow. Because of its wider
|
|
value range and improved indications on error, timespec_get with time base TIME_ACTIVE should
|
|
be used instead of clock by new code whenever possible.
|
|
</pre>
|
|
<a name='7.29.2.7'></a>
|
|
<hr>
|
|
<h3>7.29.2.7 [The timespec_getres function]</h3>
|
|
<a name='7.29.2.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
int timespec_getres(struct timespec *ts, int base);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.7p2'></a>
|
|
<pre>2 If ts is non-null and base is supported by the timespec_get function, the timespec_getres
|
|
function returns the resolution of the time provided by the timespec_get function for base
|
|
in the timespec structure pointed to by ts. For each supported base, multiple calls to the
|
|
timespec_getres function during the same program execution shall have identical results.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.7p3'></a>
|
|
<pre>3 If the value base is supported by the timespec_get function, the timespec_getres function returns
|
|
the nonzero value base; otherwise, it returns zero.
|
|
|
|
</pre>
|
|
<a name='7.29.3'></a>
|
|
<hr>
|
|
<h3>7.29.3 [Time conversion functions]</h3>
|
|
<a name='7.29.3p1'></a>
|
|
<pre>1 Functions with a _r suffix place the result of the conversion into the buffer referred by buf and
|
|
return that pointer. These functions and the function strftime shall not be subject to data races,
|
|
unless the time or calendar state is changed in a multi-thread execution.<a href='#FOOTNOTE.393'><sup>[393]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.393'>
|
|
<pre><i><b>Footnote 393)</b> This does not mean that these functions may not read global state that describes the time and calendar settings of the
|
|
execution, such as the LC_TIME locale or the implementation-defined specification of the local time zone. Only the setting of
|
|
that state by setlocale or by means of implementation-defined functions may constitute races.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.3p2'></a>
|
|
<pre>2 Functions asctime, ctime, gmtime, and localtime are the same as their counterparts suffixed with
|
|
_r. In place of the parameter buf, these functions use a pointer to an object and return it: one or two
|
|
broken-down time structures (for gmtime and localtime) or an array of char (commonly used by
|
|
asctime and ctime). Execution of any of the functions that return a pointer to one of these static
|
|
objects may overwrite the information returned from any previous call to one of these functions that
|
|
uses the same object. These functions are not reentrant and are not required to avoid data races with
|
|
each other. Accessing the returned pointer after the thread that called the function that returned
|
|
it has exited results in undefined behavior. The implementation shall behave as if no other library
|
|
functions call these functions.
|
|
|
|
</pre>
|
|
<a name='7.29.3.1'></a>
|
|
<hr>
|
|
<h3>7.29.3.1 [The asctime function]</h3>
|
|
<a name='7.29.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
[[deprecated]] char *asctime(const struct tm *timeptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.1p2'></a>
|
|
<pre>2 This function is obsolescent and should be avoided in new code.
|
|
</pre>
|
|
<a name='7.29.3.1p3'></a>
|
|
<pre>3 The asctime function converts the broken-down time in the structure pointed to by timeptr into a
|
|
string in the form
|
|
|
|
Sun Sep 16 01:03:52 1973\n\0
|
|
|
|
|
|
using the equivalent of the following algorithm.
|
|
|
|
[[deprecated]] char *asctime(const struct tm *timeptr)
|
|
{
|
|
static const char wday_name[7][3] = {
|
|
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
|
|
};
|
|
static const char mon_name[12][3] = {
|
|
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
|
|
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
|
|
};
|
|
static char result[26];
|
|
|
|
snprintf(result, 26, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
|
|
wday_name[timeptr->tm_wday],
|
|
mon_name[timeptr->tm_mon],
|
|
timeptr->tm_mday, timeptr->tm_hour,
|
|
timeptr->tm_min, timeptr->tm_sec,
|
|
1900 + timeptr->tm_year);
|
|
return result;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='7.29.3.1p4'></a>
|
|
<pre>4 If any of the members of the broken-down time contain values that are outside their normal ranges<a href='#FOOTNOTE.394'><sup>[394]</sup></a> ,
|
|
the behavior of the asctime function is undefined. Likewise, if the calculated year exceeds four
|
|
digits or is less than the year 1000, the behavior is undefined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.394'>
|
|
<pre><i><b>Footnote 394)</b> See <a href='#7.29.1'>7.29.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.3.1p5'></a>
|
|
<pre>5 The asctime function returns a pointer to the string.
|
|
|
|
</pre>
|
|
<a name='7.29.3.2'></a>
|
|
<hr>
|
|
<h3>7.29.3.2 [The ctime function]</h3>
|
|
<a name='7.29.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
[[deprecated]] char *ctime(const time_t *timer);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.2p2'></a>
|
|
<pre>2 This function is obsolescent and should be avoided in new code.
|
|
</pre>
|
|
<a name='7.29.3.2p3'></a>
|
|
<pre>3 The ctime function converts the calendar time pointed to by timer to local time in the form of a
|
|
string. They are equivalent to:
|
|
|
|
asctime(localtime(timer))
|
|
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.2p4'></a>
|
|
<pre>4 The ctime function returns the pointer returned by the asctime functions with that broken-down
|
|
time as argument.
|
|
Forward references: the localtime functions (<a href='#7.29.3.4'>7.29.3.4</a>).
|
|
|
|
</pre>
|
|
<a name='7.29.3.3'></a>
|
|
<hr>
|
|
<h3>7.29.3.3 [The gmtime functions]</h3>
|
|
<a name='7.29.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
struct tm *gmtime(const time_t *timer);
|
|
struct tm *gmtime_r(const time_t *timer, struct tm *buf);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.3p2'></a>
|
|
<pre>2 The gmtime functions convert the calendar time pointed to by timer into a broken-down time,
|
|
expressed as UTC.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.3p3'></a>
|
|
<pre>3 The gmtime functions return a pointer to the broken-down time, or a null pointer if the specified
|
|
time cannot be converted to UTC.
|
|
|
|
</pre>
|
|
<a name='7.29.3.4'></a>
|
|
<hr>
|
|
<h3>7.29.3.4 [The localtime functions]</h3>
|
|
<a name='7.29.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
struct tm *localtime(const time_t *timer);
|
|
struct tm *localtime_r(const time_t *timer, struct tm *buf);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.4p2'></a>
|
|
<pre>2 The localtime functions converts the calendar time pointed to by timer into a broken-down time,
|
|
expressed as local time.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.4p3'></a>
|
|
<pre>3 The localtime functions return a pointer to the broken-down time, or a null pointer if the specified
|
|
time cannot be converted to local time.
|
|
|
|
</pre>
|
|
<a name='7.29.3.5'></a>
|
|
<hr>
|
|
<h3>7.29.3.5 [The strftime function]</h3>
|
|
<a name='7.29.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
size_t strftime(char * restrict s, size_t maxsize, const char * restrict format,
|
|
const struct tm * restrict timeptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.5p2'></a>
|
|
<pre>2 The strftime function places characters into the array pointed to by s as controlled by the string
|
|
pointed to by format. The format shall be a multibyte character sequence, beginning and ending in
|
|
its initial shift state. The format string consists of zero or more conversion specifiers and ordinary
|
|
multibyte characters. A conversion specifier consists of a % character, possibly followed by an E or O
|
|
modifier character (described below), followed by a character that determines the behavior of the
|
|
conversion specifier. All ordinary multibyte characters (including the terminating null character) are
|
|
copied unchanged into the array. If copying takes place between objects that overlap, the behavior is
|
|
undefined. No more than maxsize characters are placed into the array.
|
|
</pre>
|
|
<a name='7.29.3.5p3'></a>
|
|
<pre>3 Each conversion specifier shall be replaced by appropriate characters as described in the following
|
|
list. The appropriate characters shall be determined using the LC_TIME category of the current
|
|
locale and by the values of zero or more members of the broken-down time structure pointed to
|
|
by timeptr, as specified in brackets in the description. If any of the specified values is outside the
|
|
normal range, the characters stored are unspecified.
|
|
|
|
%a is replaced by the locale’s abbreviated weekday name. [tm_wday]
|
|
%A is replaced by the locale’s full weekday name. [tm_wday]
|
|
%b is replaced by the locale’s abbreviated month name. [tm_mon]
|
|
%B is replaced by the locale’s full month name. [tm_mon]
|
|
%c is replaced by the locale’s appropriate date and time representation. [all specified in <a href='#7.29.1'>7.29.1</a>]
|
|
%C is replaced by the year divided by 100 and truncated to an integer, as a decimal number (00–99).
|
|
[tm_year]
|
|
%d is replaced by the day of the month as a decimal number (01–31). [tm_mday]
|
|
%D is equivalent to "%m/%d/%y". [tm_mon, tm_mday, tm_year]
|
|
%e is replaced by the day of the month as a decimal number (1–31); a single digit is preceded by a
|
|
space. [tm_mday]
|
|
%F is equivalent to "%Y-%m-%d" (the ISO 8601 date format). [tm_year, tm_mon, tm_mday]
|
|
%g is replaced by the last 2 digits of the week-based year (see below) as a decimal number (00–99).
|
|
[tm_year, tm_wday, tm_yday]
|
|
%G is replaced by the week-based year (see below) as a decimal number (e.g., 1997). [tm_year,
|
|
tm_wday, tm_yday]
|
|
%h is equivalent to "%b". [tm_mon]
|
|
%H is replaced by the hour (24-hour clock) as a decimal number (00–23). [tm_hour]
|
|
%I is replaced by the hour (12-hour clock) as a decimal number (01–12). [tm_hour]
|
|
%j is replaced by the day of the year as a decimal number (001–366). [tm_yday]
|
|
%m is replaced by the month as a decimal number (01–12). [tm_mon]
|
|
%M is replaced by the minute as a decimal number (00–59). [tm_min]
|
|
%n is replaced by a new-line character.
|
|
%p is replaced by the locale’s equivalent of the AM/PM designations associated with a 12-hour
|
|
clock. [tm_hour]
|
|
%r is replaced by the locale’s 12-hour clock time. [tm_hour, tm_min, tm_sec]
|
|
%R is equivalent to "%H:%M". [tm_hour, tm_min ]
|
|
%S is replaced by the second as a decimal number (00–60). [tm_sec]
|
|
%t is replaced by a horizontal-tab character.
|
|
%T is equivalent to "%H:%M:%S" (the ISO 8601 time format). [tm_hour, tm_min, tm_sec]
|
|
%u is replaced by the ISO 8601 weekday as a decimal number (1–7), where Monday is 1. [tm_wday]
|
|
%U is replaced by the week number of the year (the first Sunday as the first day of week 1) as a
|
|
decimal number (00–53). [tm_year, tm_wday, tm_yday]
|
|
%V is replaced by the ISO 8601 week number (see below) as a decimal number (01–53). [tm_year,
|
|
tm_wday, tm_yday]
|
|
%w is replaced by the weekday as a decimal number (0–6), where Sunday is 0. [tm_wday]
|
|
%W is replaced by the week number of the year (the first Monday as the first day of week 1) as a
|
|
decimal number (00–53). [tm_year, tm_wday, tm_yday]
|
|
%x is replaced by the locale’s appropriate date representation. [all specified in <a href='#7.29.1'>7.29.1</a>]
|
|
%X is replaced by the locale’s appropriate time representation. [all specified in <a href='#7.29.1'>7.29.1</a>]
|
|
%y is replaced by the last 2 digits of the year as a decimal number (00–99). [tm_year]
|
|
%Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
|
|
%z is replaced by the offset from UTC in the ISO 8601 format "-0430" (meaning 4 hours 30
|
|
minutes behind UTC, west of Greenwich), or by no characters if no time zone is determinable.
|
|
[tm_isdst]
|
|
%Z is replaced by the locale’s time zone name or abbreviation, or by no characters if no time zone is
|
|
determinable. [tm_isdst]
|
|
%% is replaced by %.
|
|
|
|
</pre>
|
|
<a name='7.29.3.5p4'></a>
|
|
<pre>4 Some conversion specifiers can be modified by the inclusion of an E or O modifier character to
|
|
indicate an alternative format or specification. If the alternative format or specification does not
|
|
exist for the current locale, the modifier is ignored.
|
|
|
|
%Ec is replaced by the locale’s alternative date and time representation.
|
|
%EC is replaced by the name of the base year (period) in the locale’s alternative representation.
|
|
%Ex is replaced by the locale’s alternative date representation.
|
|
%EX is replaced by the locale’s alternative time representation.
|
|
%Ey is replaced by the offset from %EC (year only) in the locale’s alternative representation.
|
|
%EY is replaced by the locale’s full alternative year representation.
|
|
%Ob is replaced by the locale’s abbreviated alternative month name.
|
|
%OB is replaced by the locale’s alternative appropriate full month name.
|
|
%Od is replaced by the day of the month, using the locale’s alternative numeric symbols (filled as
|
|
needed with leading zeros, or with leading spaces if there is no alternative symbol for zero).
|
|
%Oe is replaced by the day of the month, using the locale’s alternative numeric symbols (filled as
|
|
needed with leading spaces).
|
|
%OH is replaced by the hour (24-hour clock), using the locale’s alternative numeric symbols.
|
|
%OI is replaced by the hour (12-hour clock), using the locale’s alternative numeric symbols.
|
|
%Om is replaced by the month, using the locale’s alternative numeric symbols.
|
|
%OM is replaced by the minutes, using the locale’s alternative numeric symbols.
|
|
%OS is replaced by the seconds, using the locale’s alternative numeric symbols.
|
|
%Ou is replaced by the ISO 8601 weekday as a number in the locale’s alternative representation,
|
|
where Monday is 1.
|
|
%OU is replaced by the week number, using the locale’s alternative numeric symbols.
|
|
%OV is replaced by the ISO 8601 week number, using the locale’s alternative numeric symbols.
|
|
%Ow is replaced by the weekday as a number, using the locale’s alternative numeric symbols.
|
|
%OW is replaced by the week number of the year, using the locale’s alternative numeric symbols.
|
|
%Oy is replaced by the last 2 digits of the year, using the locale’s alternative numeric symbols.
|
|
|
|
</pre>
|
|
<a name='7.29.3.5p5'></a>
|
|
<pre>5 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system, weeks begin
|
|
on a Monday and week 1 of the year is the week that includes January 4th, which is also the week
|
|
that includes the first Thursday of the year, and is also the first week that contains at least four days
|
|
in the year. If the first Monday of January is the 2nd, 3rd, or 4th, the preceding days are part of the
|
|
last week of the preceding year; thus, for Saturday 2nd January 1999, %G is replaced by 1998 and %V
|
|
is replaced by 53. If December 29th, 30th, or 31st is a Monday, it and any following days are part of
|
|
week 1 of the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and %V
|
|
is replaced by 01.
|
|
</pre>
|
|
<a name='7.29.3.5p6'></a>
|
|
<pre>6 If a conversion specifier is not one of the above, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.29.3.5p7'></a>
|
|
<pre>7 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the following
|
|
specifiers are:
|
|
|
|
%a the first three characters of %A.
|
|
%A one of "Sunday", "Monday", . . . , "Saturday".
|
|
%b the first three characters of %B.
|
|
%B one of "January", "February", . . . , "December".
|
|
%c equivalent to "%a %b %e %T %Y".
|
|
%p one of "AM" or "PM".
|
|
%r equivalent to "%I:%M:%S %p".
|
|
%x equivalent to "%m/%d/%y".
|
|
%X equivalent to %T.
|
|
%Z implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.5p8'></a>
|
|
<pre>8 If the total number of resulting characters including the terminating null character is not more than
|
|
maxsize, the strftime function returns the number of characters placed into the array pointed to
|
|
by s not including the terminating null character. Otherwise, zero is returned and the members of
|
|
the array have an indeterminate representation.
|
|
</pre>
|
|
<a name='7.30'></a>
|
|
<hr>
|
|
<h3>7.30 [Unicode utilities <uchar.h>]</h3>
|
|
<a name='7.30p1'></a>
|
|
<pre>1 The header <uchar.h> declares types and functions for manipulating Unicode characters.
|
|
</pre>
|
|
<a name='7.30p2'></a>
|
|
<pre>2 The types declared are mbstate_t (described in <a href='#7.31.1'>7.31.1</a>) and size_t (described in <a href='#7.21'>7.21</a>);
|
|
|
|
char8_t
|
|
|
|
|
|
which is an unsigned integer type used for 8-bit characters and is the same type as unsigned char;
|
|
|
|
char16_t
|
|
|
|
|
|
which is an unsigned integer type used for 16-bit characters and is the same type as uint_least16_t
|
|
(described in <a href='#7.22.1.2'>7.22.1.2</a>); and
|
|
|
|
char32_t
|
|
|
|
|
|
which is an unsigned integer type used for 32-bit characters and is the same type as uint_least32_t
|
|
(also described in <a href='#7.22.1.2'>7.22.1.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.30.1'></a>
|
|
<hr>
|
|
<h3>7.30.1 [Restartable multibyte/wide character conversion functions]</h3>
|
|
<a name='7.30.1p1'></a>
|
|
<pre>1 These functions have a parameter, ps, of type pointer to mbstate_t that points to an object that can
|
|
completely describe the current conversion state of the associated multibyte character sequence,
|
|
which the functions alter as necessary. If ps is a null pointer, each function uses its own internal
|
|
mbstate_t object instead, which is initialized prior to the first call to the function to the initial
|
|
conversion state; the functions are not required to avoid data races with other calls to the same
|
|
function in this case. It is implementation-defined whether the internal mbstate_t object has thread
|
|
storage duration; if it has thread storage duration, it is initialized to the initial conversion state
|
|
prior to the first call to the function on the new thread. The implementation behaves as if no library
|
|
function calls these functions with a null pointer for ps.
|
|
|
|
</pre>
|
|
<a name='7.30.1.1'></a>
|
|
<hr>
|
|
<h3>7.30.1.1 [The mbrtoc8 function]</h3>
|
|
<a name='7.30.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t mbrtoc8(char8_t * restrict pc8, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.1p2'></a>
|
|
<pre>2 If s is a null pointer, the mbrtoc8 function is equivalent to the call:
|
|
|
|
mbrtoc8(NULL, "", 1, ps)
|
|
|
|
|
|
In this case, the values of the parameters pc8 and n are ignored.
|
|
</pre>
|
|
<a name='7.30.1.1p3'></a>
|
|
<pre>3 If s is not a null pointer, the mbrtoc8 function function inspects at most n bytes beginning with
|
|
the byte pointed to by s to determine the number of bytes needed to complete the next multibyte
|
|
character (including any shift sequences). If the function determines that the next multibyte character
|
|
is complete and valid, it determines the values of the corresponding characters and then, if pc8 is
|
|
not a null pointer, stores the value of the first (or only) such character in the object pointed to by pc8.
|
|
Subsequent calls will store successive characters without consuming any additional input until all
|
|
the characters have been stored. If the corresponding character is the null character, the resulting
|
|
state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.1p4'></a>
|
|
<pre>4 The mbrtoc8 function returns the first of the following that applies (given the current conversion
|
|
state):
|
|
|
|
0 if the next n or fewer bytes complete the multibyte character that corresponds to
|
|
the null character (which is the value stored).
|
|
between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte character (which
|
|
is the value stored); the value returned is the number of bytes that complete the
|
|
multibyte character.
|
|
|
|
(size_t) (−3) if the next character resulting from a previous call has been stored (no bytes from
|
|
the input have been consumed by this call).
|
|
|
|
(size_t) (−2) if the next n bytes contribute to an incomplete (but potentially valid) multibyte
|
|
character, and all n bytes have been processed (no value is stored).<a href='#FOOTNOTE.395'><sup>[395]</sup></a>
|
|
|
|
(size_t) (−1) if an encoding error occurs, in which case the next n or fewer bytes do not contribute
|
|
to a complete and valid multibyte character (no value is stored); the value of the
|
|
macro EILSEQ is stored in errno, and the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.395'>
|
|
<pre><i><b>Footnote 395)</b> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a sequence of redundant
|
|
shift sequences (for implementations with state-dependent encodings).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.30.1.2'></a>
|
|
<hr>
|
|
<h3>7.30.1.2 [The c8rtomb function]</h3>
|
|
<a name='7.30.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t c8rtomb(char * restrict s, char8_t c8, mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.2p2'></a>
|
|
<pre>2 If s is a null pointer, the c8rtomb function is equivalent to the call
|
|
|
|
c8rtomb(buf, u8’\0’, ps)
|
|
|
|
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.30.1.2p3'></a>
|
|
<pre>3 If s is not a null pointer, the c8rtomb function determines the number of bytes needed to represent
|
|
the multibyte character that corresponds to the character given or completed by c8 (including any
|
|
shift sequences), and stores the multibyte character representation in the array whose first element is
|
|
pointed to by s, or stores nothing if c8 does not represent a complete character. At most MB_CUR_MAX
|
|
bytes are stored. If c8 is a null character, a null byte is stored, preceded by any shift sequence needed
|
|
to restore the initial shift state; the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.2p4'></a>
|
|
<pre>4 The c8rtomb function returns the number of bytes stored in the array object (including any shift
|
|
sequences). When c8 is not a valid character, an encoding error occurs: the function stores the value
|
|
of the macro EILSEQ in errno and returns (size_t) (−1); the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='7.30.1.3'></a>
|
|
<hr>
|
|
<h3>7.30.1.3 [The mbrtoc16 function]</h3>
|
|
<a name='7.30.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t mbrtoc16(char16_t * restrict pc16, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.3p2'></a>
|
|
<pre>2 If s is a null pointer, the mbrtoc16 function is equivalent to the call:
|
|
|
|
mbrtoc16(NULL, "", 1, ps)
|
|
|
|
|
|
In this case, the values of the parameters pc16 and n are ignored.
|
|
</pre>
|
|
<a name='7.30.1.3p3'></a>
|
|
<pre>3 If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with the byte
|
|
pointed to by s to determine the number of bytes needed to complete the next multibyte character
|
|
(including any shift sequences). If the function determines that the next multibyte character is
|
|
complete and valid, it determines the values of the corresponding wide characters and then, if pc16
|
|
is not a null pointer, stores the value of the first (or only) such character in the object pointed to by
|
|
pc16. Subsequent calls will store successive wide characters without consuming any additional
|
|
input until all the characters have been stored. If the corresponding wide character is the null wide
|
|
character, the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.3p4'></a>
|
|
<pre>4 The mbrtoc16 function returns the first of the following that applies (given the current conversion
|
|
state):
|
|
|
|
0 if the next n or fewer bytes complete the multibyte character that corresponds to
|
|
the null wide character (which is the value stored).
|
|
|
|
between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte character (which
|
|
is the value stored); the value returned is the number of bytes that complete the
|
|
multibyte character.
|
|
|
|
(size_t) (−3) if the next character resulting from a previous call has been stored (no bytes from
|
|
the input have been consumed by this call).
|
|
|
|
(size_t) (−2) if the next n bytes contribute to an incomplete (but potentially valid) multibyte
|
|
character, and all n bytes have been processed (no value is stored).<a href='#FOOTNOTE.396'><sup>[396]</sup></a>
|
|
|
|
(size_t) (−1) if an encoding error occurs, in which case the next n or fewer bytes do not contribute
|
|
to a complete and valid multibyte character (no value is stored); the value of the
|
|
macro EILSEQ is stored in errno, and the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.396'>
|
|
<pre><i><b>Footnote 396)</b> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a sequence of redundant
|
|
shift sequences (for implementations with state-dependent encodings).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.30.1.4'></a>
|
|
<hr>
|
|
<h3>7.30.1.4 [The c16rtomb function]</h3>
|
|
<a name='7.30.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t c16rtomb(char * restrict s, char16_t c16, mbstate_t * restrict ps);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.4p2'></a>
|
|
<pre>2 If s is a null pointer, the c16rtomb function is equivalent to the call
|
|
|
|
c16rtomb(buf, u’\0’, ps)
|
|
|
|
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.30.1.4p3'></a>
|
|
<pre>3 If s is not a null pointer, the c16rtomb function determines the number of bytes needed to represent
|
|
the multibyte character that corresponds to the wide character given or completed by c16 (including
|
|
any shift sequences), and stores the multibyte character representation in the array whose first
|
|
element is pointed to by s, or stores nothing if c16 does not represent a complete character. At
|
|
most MB_CUR_MAX bytes are stored. If c16 is a null wide character, a null byte is stored, preceded by
|
|
any shift sequence needed to restore the initial shift state; the resulting state described is the initial
|
|
conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.4p4'></a>
|
|
<pre>4 The c16rtomb function returns the number of bytes stored in the array object (including any shift
|
|
sequences). When c16 is not a valid wide character, an encoding error occurs: the function stores the
|
|
value of the macro EILSEQ in errno and returns (size_t) (−1); the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='7.30.1.5'></a>
|
|
<hr>
|
|
<h3>7.30.1.5 [The mbrtoc32 function]</h3>
|
|
<a name='7.30.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t mbrtoc32(char32_t * restrict pc32, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.5p2'></a>
|
|
<pre>2 If s is a null pointer, the mbrtoc32 function is equivalent to the call:
|
|
|
|
mbrtoc32(NULL, "", 1, ps)
|
|
|
|
|
|
In this case, the values of the parameters pc32 and n are ignored.
|
|
</pre>
|
|
<a name='7.30.1.5p3'></a>
|
|
<pre>3 If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with the byte
|
|
pointed to by s to determine the number of bytes needed to complete the next multibyte character
|
|
(including any shift sequences). If the function determines that the next multibyte character is
|
|
complete and valid, it determines the values of the corresponding wide characters and then, if pc32
|
|
is not a null pointer, stores the value of the first (or only) such character in the object pointed to by
|
|
pc32. Subsequent calls will store successive wide characters without consuming any additional
|
|
input until all the characters have been stored. If the corresponding wide character is the null wide
|
|
character, the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.5p4'></a>
|
|
<pre>4 The mbrtoc32 function returns the first of the following that applies (given the current conversion
|
|
state):
|
|
|
|
0 if the next n or fewer bytes complete the multibyte character that corresponds to
|
|
the null wide character (which is the value stored).
|
|
|
|
between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte character (which
|
|
is the value stored); the value returned is the number of bytes that complete the
|
|
multibyte character.
|
|
|
|
(size_t) (−3) if the next character resulting from a previous call has been stored (no bytes from
|
|
the input have been consumed by this call).
|
|
|
|
(size_t) (−2) if the next n bytes contribute to an incomplete (but potentially valid) multibyte
|
|
character, and all n bytes have been processed (no value is stored).<a href='#FOOTNOTE.397'><sup>[397]</sup></a>
|
|
|
|
(size_t) (−1) if an encoding error occurs, in which case the next n or fewer bytes do not contribute
|
|
to a complete and valid multibyte character (no value is stored); the value of the
|
|
macro EILSEQ is stored in errno, and the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.397'>
|
|
<pre><i><b>Footnote 397)</b> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a sequence of redundant
|
|
shift sequences (for implementations with state-dependent encodings).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.30.1.6'></a>
|
|
<hr>
|
|
<h3>7.30.1.6 [The c32rtomb function]</h3>
|
|
<a name='7.30.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t c32rtomb(char * restrict s, char32_t c32, mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.30.1.6p2'></a>
|
|
<pre>2 If s is a null pointer, the c32rtomb function is equivalent to the call
|
|
|
|
c32rtomb(buf, U’\0’, ps)
|
|
|
|
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.30.1.6p3'></a>
|
|
<pre>3 If s is not a null pointer, the c32rtomb function determines the number of bytes needed to represent
|
|
the multibyte character that corresponds to the wide character given by c32 (including any shift
|
|
sequences), and stores the multibyte character representation in the array whose first element is
|
|
pointed to by s. At most MB_CUR_MAX bytes are stored. If c32 is a null wide character, a null byte is
|
|
stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state
|
|
described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.1.6p4'></a>
|
|
<pre>4 The c32rtomb function returns the number of bytes stored in the array object (including any shift
|
|
sequences). When c32 is not a valid wide character, an encoding error occurs: the function stores the
|
|
value of the macro EILSEQ in errno and returns (size_t) (−1);the conversion state is unspecified.
|
|
</pre>
|
|
<a name='7.31'></a>
|
|
<hr>
|
|
<h3>7.31 [Extended multibyte and wide character utilities <wchar.h>]</h3>
|
|
<a name='7.31.1'></a>
|
|
<hr>
|
|
<h3>7.31.1 [Introduction]</h3>
|
|
<a name='7.31.1p1'></a>
|
|
<pre>1 The header <wchar.h> defines four macros, and declares four data types, one tag, and many
|
|
functions.<a href='#FOOTNOTE.398'><sup>[398]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.398'>
|
|
<pre><i><b>Footnote 398)</b> See "future library directions" (<a href='#7.33.20'>7.33.20</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.1p2'></a>
|
|
<pre>2 The types declared are wchar_t and size_t (both described in <a href='#7.21'>7.21</a>);
|
|
|
|
mbstate_t
|
|
|
|
|
|
which is a complete object type other than an array type that can hold the conversion state informa-
|
|
tion necessary to convert between sequences of multibyte characters and wide characters;
|
|
|
|
wint_t
|
|
|
|
|
|
which is an integer type unchanged by default argument promotions that can hold any value
|
|
corresponding to members of the extended character set, as well as at least one value that does not
|
|
correspond to any member of the extended character set (see WEOF below);<a href='#FOOTNOTE.399'><sup>[399]</sup></a> and
|
|
|
|
struct tm
|
|
|
|
|
|
which is declared as an incomplete structure type (the contents are described in <a href='#7.29.1'>7.29.1</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.399'>
|
|
<pre><i><b>Footnote 399)</b> wchar_t and wint_t can be the same integer type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.1p3'></a>
|
|
<pre>3 The macros defined are NULL (described in <a href='#7.21'>7.21</a>); WCHAR_MIN, WCHAR_MAX, and WCHAR_WIDTH (de-
|
|
scribed in <a href='#7.22'>7.22</a>); and
|
|
|
|
WEOF
|
|
|
|
|
|
which expands to a constant expression of type wint_t whose value does not correspond to any
|
|
member of the extended character set.<a href='#FOOTNOTE.400'><sup>[400]</sup></a> It is accepted (and returned) by several functions in
|
|
this subclause to indicate end-of-file, that is, no more input from a stream. It is also used as a wide
|
|
character value that does not correspond to any member of the extended character set.
|
|
</pre>
|
|
<a name='FOOTNOTE.400'>
|
|
<pre><i><b>Footnote 400)</b> The value of the macro WEOF can differ from that of EOF and need not be negative.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.1p4'></a>
|
|
<pre>4 The functions declared are grouped as follows:
|
|
|
|
— Functions that perform input and output of wide characters, or multibyte characters, or both;
|
|
— Functions that provide wide string numeric conversion;
|
|
— Functions that perform general wide string manipulation;
|
|
— Functions for wide string date and time conversion; and
|
|
— Functions that provide extended capabilities for conversion between multibyte and wide
|
|
character sequences.
|
|
|
|
</pre>
|
|
<a name='7.31.1p5'></a>
|
|
<pre>5 Arguments to the functions in this subclause may point to arrays containing wchar_t values that do
|
|
not correspond to members of the extended character set. Such values shall be processed according
|
|
to the specified semantics, except that it is unspecified whether an encoding error occurs if such a
|
|
value appears in the format string for a function in <a href='#7.31.2'>7.31.2</a> or <a href='#7.31.5'>7.31.5</a> and the specified semantics do
|
|
not require that value to be processed by wcrtomb.
|
|
</pre>
|
|
<a name='7.31.1p6'></a>
|
|
<pre>6 Unless explicitly stated otherwise, if the execution of a function described in this subclause causes
|
|
copying to take place between objects that overlap, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='7.31.2'></a>
|
|
<hr>
|
|
<h3>7.31.2 [Formatted wide character input/output functions]</h3>
|
|
<a name='7.31.2p1'></a>
|
|
<pre>1 The formatted wide character input/output functions shall behave as if there is a sequence point
|
|
after the actions associated with each specifier.<a href='#FOOTNOTE.401'><sup>[401]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.401'>
|
|
<pre><i><b>Footnote 401)</b> The fwprintf functions perform writes to memory for the %n specifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1'></a>
|
|
<hr>
|
|
<h3>7.31.2.1 [The fwprintf function]</h3>
|
|
<a name='7.31.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwprintf(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.1p2'></a>
|
|
<pre>2 The fwprintf function writes output to the stream pointed to by stream, under control of the wide
|
|
string pointed to by format that specifies how subsequent arguments are converted for output. If
|
|
there are insufficient arguments for the format, the behavior is undefined. If the format is exhausted
|
|
while arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored.
|
|
The fwprintf function returns when the end of the format string is encountered.
|
|
</pre>
|
|
<a name='7.31.2.1p3'></a>
|
|
<pre>3 The format is composed of zero or more directives: ordinary wide characters (not %), which are
|
|
copied unchanged to the output stream; and conversion specifications, each of which results in
|
|
fetching zero or more subsequent arguments, converting them, if applicable, according to the
|
|
corresponding conversion specifier, and then writing the result to the output stream.
|
|
</pre>
|
|
<a name='7.31.2.1p4'></a>
|
|
<pre>4 Each conversion specification is introduced by the wide character %. After the %, the following
|
|
appear in sequence:
|
|
|
|
— Zero or more flags (in any order) that modify the meaning of the conversion specification.
|
|
— An optional minimum field width. If the converted value has fewer wide characters than the
|
|
field width, it is padded with spaces (by default) on the left (or right, if the left adjustment flag,
|
|
described later, has been given) to the field width. The field width takes the form of an asterisk
|
|
* (described later) or a nonnegative decimal integer.<a href='#FOOTNOTE.402'><sup>[402]</sup></a>
|
|
— An optional precision that gives the minimum number of digits to appear for the b, d, i, o, u,
|
|
x, and X conversions, the number of digits to appear after the decimal-point wide character
|
|
for a, A, e, E, f, and F conversions, the maximum number of significant digits for the g and G
|
|
conversions, or the maximum number of wide characters to be written for s conversions. The
|
|
precision takes the form of a period (.) followed either by an asterisk * (described later) or by
|
|
an optional nonnegative decimal integer; if only the period is specified, the precision is taken
|
|
as zero. If a precision appears with any other conversion specifier, the behavior is undefined.
|
|
— An optional length modifier that specifies the size of the argument.
|
|
— A conversion specifier wide character that specifies the type of conversion to be applied.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.402'>
|
|
<pre><i><b>Footnote 402)</b> Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1p5'></a>
|
|
<pre>5 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In this case,
|
|
an int argument supplies the field width or precision. The arguments specifying field width, or
|
|
precision, or both, shall appear (in that order) before the argument (if any) to be converted. A
|
|
negative field width argument is taken as a - flag followed by a positive field width. A negative
|
|
precision argument is taken as if the precision were omitted.
|
|
</pre>
|
|
<a name='7.31.2.1p6'></a>
|
|
<pre>6 The flag wide characters and their meanings are:
|
|
|
|
- The result of the conversion is left-justified within the field. (It is right-justified if this flag is
|
|
not specified.)
|
|
+ The result of a signed conversion always begins with a plus or minus sign. (It begins with a
|
|
sign only when a value with a negative sign is converted if this flag is not specified.) <a href='#FOOTNOTE.403'><sup>[403]</sup></a>
|
|
space If the first wide character of a signed conversion is not a sign, or if a signed conversion results
|
|
in no wide characters, a space is prefixed to the result. If the space and + flags both appear,
|
|
the space flag is ignored.
|
|
# The result is converted to an "alternative form". For o conversion, it increases the precision, if
|
|
and only if necessary, to force the first digit of the result to be a zero (if the value and precision
|
|
are both 0, a single 0 is printed). For b conversion, a nonzero result has 0b prefixed to it. For
|
|
x (or X) conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g, and G
|
|
conversions, the result of converting a floating-point number always contains a decimal-point
|
|
wide character, even if no digits follow it. (Normally, a decimal-point wide character appears
|
|
in the result of these conversions only if a digit follows it.) For g and G conversions, trailing
|
|
zeros are not removed from the result. For other conversions, the behavior is undefined.
|
|
0 For b, d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros (following any
|
|
indication of sign or base) are used to pad to the field width rather than performing space
|
|
padding, except when converting an infinity or NaN. If the 0 and - flags both appear, the
|
|
0 flag is ignored. For d, i, o, u, x, and X conversions, if a precision is specified, the 0 flag is
|
|
ignored. For other conversions, the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.403'>
|
|
<pre><i><b>Footnote 403)</b> The results of all floating conversions of a negative zero, and of negative values that round to zero, include a minus sign.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1p7'></a>
|
|
<pre>7 The length modifiers and their meanings are:
|
|
|
|
hh Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a
|
|
signed char or unsigned char argument (the argument will have been promoted
|
|
according to the integer promotions, but its value shall be converted to signed char or
|
|
unsigned char before printing); or that a following n conversion specifier applies to a
|
|
pointer to a signed char argument.
|
|
h Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a short int
|
|
or unsigned short int argument (the argument will have been promoted accord-
|
|
ing to the integer promotions, but its value shall be converted to short int or
|
|
unsigned short int before printing); or that a following n conversion specifier applies
|
|
to a pointer to a short int argument.
|
|
l (ell) Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a long int
|
|
or unsigned long int argument; that a following n conversion specifier applies to
|
|
a pointer to a long int argument; that a following c conversion specifier applies to
|
|
a wint_t argument; that a following s conversion specifier applies to a pointer to a
|
|
wchar_t argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
|
|
specifier.
|
|
ll (ell-ell) Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a
|
|
long long int or unsigned long long int argument; or that a following n con-
|
|
version specifier applies to a pointer to a long long int argument.
|
|
j Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to an intmax_t
|
|
or uintmax_t argument; or that a following n conversion specifier applies to a pointer
|
|
to an intmax_t argument.
|
|
z Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a size_t
|
|
or the corresponding signed integer type argument; or that a following n conversion
|
|
specifier applies to a pointer to a signed integer type corresponding to size_t argument.
|
|
t Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a ptrdiff_t
|
|
or the corresponding unsigned integer type argument; or that a following n conversion
|
|
specifier applies to a pointer to a ptrdiff_t argument.
|
|
wN Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to an integer
|
|
argument with a specific width where N is a positive decimal integer with no leading
|
|
zeros (the argument will have been promoted according to the integer promotions, but
|
|
its value shall be converted to the unpromoted type); or that a following n conversion
|
|
specifier applies to a pointer to an integer type argument with a width of N bits. All
|
|
minimum-width integer types (<a href='#7.22.1.2'>7.22.1.2</a>) and exact-width integer types (<a href='#7.22.1.1'>7.22.1.1</a>) de-
|
|
fined in the header <stdint.h> shall be supported. Other supported values of N are
|
|
implementation-defined.
|
|
wfN Specifies that a following b, d, i, o, u, x, or X conversion specifier applies to a fastest
|
|
minimum-width integer argument with a specific width where N is a positive decimal
|
|
integer with no leading zeros (the argument will have been promoted according to
|
|
the integer promotions, but its value shall be converted to the unpromoted type); or
|
|
that a following n conversion specifier applies to a pointer to a fastest minimum-width
|
|
integer type argument with a width of N bits. All fastest minimum-width integer types
|
|
(<a href='#7.22.1.3'>7.22.1.3</a>) defined in the header <stdint.h> shall be supported. Other supported values
|
|
of N are implementation-defined.
|
|
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
long double argument.
|
|
|
|
H Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal32 argument.
|
|
|
|
D Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal64 argument.
|
|
|
|
DD Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a
|
|
_Decimal128 argument.
|
|
|
|
|
|
If a length modifier appears with any conversion specifier other than as specified above, the behavior
|
|
is undefined.
|
|
</pre>
|
|
<a name='7.31.2.1p8'></a>
|
|
<pre>8 The conversion specifiers and their meanings are:
|
|
|
|
d,i The int argument is converted to signed decimal in the style [-]dddd. The precision
|
|
specifies the minimum number of digits to appear; if the value being converted can be
|
|
represented in fewer digits, it is expanded with leading zeros. The default precision is 1.
|
|
The result of converting a zero value with a precision of zero is no wide characters.
|
|
b, o,u,x,X The unsigned int argument is converted to unsigned binary (b), unsigned octal (o),
|
|
unsigned decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
|
|
letters abcdef are used for x conversion and the letters ABCDEF for X conversion. The
|
|
precision specifies the minimum number of digits to appear; if the value being converted
|
|
can be represented in fewer digits, it is expanded with leading zeros. The default precision
|
|
is 1. The result of converting a zero value with a precision of zero is no wide characters.
|
|
f,F A double argument representing a floating-point number is converted to decimal notation
|
|
in the style [-]ddd.ddd, where the number of digits after the decimal-point wide character
|
|
is equal to the precision specification. If the precision is missing, it is taken as 6; if the
|
|
precision is zero and the # flag is not specified, no decimal-point wide character appears.
|
|
If a decimal-point wide character appears, at least one digit appears before it. The value is
|
|
rounded to the appropriate number of digits.
|
|
A double argument representing an infinity is converted in one of the styles [-]inf or
|
|
[-]infinity — which style is implementation-defined. A double argument representing
|
|
a NaN is converted in one of the styles [-]nan or [-]nan(n-wchar-sequence) — which style,
|
|
and the meaning of any n-wchar-sequence, is implementation-defined. The F conversion
|
|
specifier produces INF, INFINITY, or NAN instead of inf, infinity, or nan, respectively.<a href='#FOOTNOTE.404'><sup>[404]</sup></a>
|
|
e,E A double argument representing a floating-point number is converted in the style
|
|
[-]d.ddde±dd, where there is one digit (which is nonzero if the argument is nonzero)
|
|
before the decimal-point wide character and the number of digits after it is equal to the
|
|
precision; if the precision is missing, it is taken as 6; if the precision is zero and the #
|
|
flag is not specified, no decimal-point wide character appears. The value is rounded to
|
|
the appropriate number of digits. The E conversion specifier produces a number with E
|
|
instead of e introducing the exponent. The exponent always contains at least two digits,
|
|
and only as many more digits as necessary to represent the exponent. If the value is zero,
|
|
the exponent is zero.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
g,G A double argument representing a floating-point number is converted in style f or e (or
|
|
in style F or E in the case of a G conversion specifier), depending on the value converted
|
|
and the precision. Let P equal the precision if nonzero, 6 if the precision is omitted, or 1 if
|
|
the precision is zero. Then, if a conversion with style E would have an exponent of X:
|
|
|
|
if P > X ≥ −4, the conversion is with style f (or F) and precision P − (X + 1).
|
|
otherwise, the conversion is with style e (or E) and precision P − 1.
|
|
|
|
Finally, unless the # flag is used, any trailing zeros are removed from the fractional portion
|
|
of the result and the decimal-point wide character is removed if there is no fractional
|
|
portion remaining.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
a,A A double argument representing a floating-point number is converted in the style
|
|
[-]0xh.hhhhp±d, where there is one hexadecimal digit (which is nonzero if the argument is a
|
|
normalized floating-point number and is otherwise unspecified) before the decimal-point
|
|
wide character<a href='#FOOTNOTE.405'><sup>[405]</sup></a> and the number of hexadecimal digits after it is equal to the precision;
|
|
if the precision is missing and FLT_RADIX is a power of 2, then the precision is sufficient
|
|
for an exact representation of the value; if the precision is missing and FLT_RADIX is not a
|
|
power of 2, then the precision is sufficient to distinguish<a href='#FOOTNOTE.406'><sup>[406]</sup></a> values of type double, except
|
|
that trailing zeros may be omitted; if the precision is zero and the # flag is not specified, no
|
|
decimal-point wide character appears. The letters abcdef are used for a conversion and
|
|
the letters ABCDEF for A conversion. The A conversion specifier produces a number with
|
|
X and P instead of x and p. The exponent always contains at least one digit, and only as
|
|
many more digits as necessary to represent the decimal exponent of 2. If the value is zero,
|
|
the exponent is zero.
|
|
A double argument representing an infinity or NaN is converted in the style of an f or F
|
|
conversion specifier.
|
|
If an H, D, or DD modifier is present and the precision is missing, then for a decimal
|
|
floating type argument represented by a triple of integers (s, c, q), where n is the number
|
|
of significant digits in the coefficient c,
|
|
|
|
— if −(n + 5) ≤ q ≤ 0, use style f (or style F in the case of an A conversion specifier)
|
|
with formatting precision equal to −q,
|
|
— otherwise, use style e (or style E in the case of an A conversion specifier) with format-
|
|
ting precision equal to n − 1, with the exceptions that if c = 0 then the digit-sequence
|
|
in the exponent-part shall have the value q (rather than 0), and that the exponent is
|
|
<a href='#FOOTNOTE.405'><sup>[405]</sup></a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide character so that subsequent
|
|
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
<a href='#FOOTNOTE.406'><sup>[406]</sup></a> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point wide character.
|
|
always expressed with the minimum number of digits required to represent its value
|
|
(the exponent never contains a leading zero).
|
|
|
|
If the precision P is present (in the conversion specification) and is zero or at least as
|
|
large as the precision p (<a href='#5.2.4.2.2'>5.2.4.2.2</a>) of the decimal floating type, the conversion is as if the
|
|
precision were missing. If the precision P is present (and nonzero) and less than the
|
|
precision p of the decimal floating type, the conversion first obtains an intermediate result
|
|
as follows, where n is the number of significant digits in the coefficient:
|
|
|
|
— If n ≤ P , set the intermediate result to the input.
|
|
— If n > P , round the input value, according to the current rounding direction for
|
|
decimal floating-point operations, to P decimal digits, with unbounded exponent
|
|
range, representing the result with a P -digit integer coefficient when in the form
|
|
(s, c, q).
|
|
|
|
Convert the intermediate result in the manner described above for the case where the
|
|
precision is missing.
|
|
c If no l length modifier is present, the int argument is converted to a wide character as if
|
|
by calling btowc and the resulting wide character is written.
|
|
If an l length modifier is present, the wint_t argument is converted to wchar_t and
|
|
written.
|
|
s If no l length modifier is present, the argument shall be a pointer to storage of character
|
|
type containing a multibyte character sequence beginning in the initial shift state. Charac-
|
|
ters from the storage are converted as if by repeated calls to the mbrtowc function, with
|
|
the conversion state described by an mbstate_t object initialized to zero before the first
|
|
multibyte character is converted, and written up to (but not including) the terminating
|
|
null wide character. If the precision is specified, no more than that many wide characters
|
|
are written. If the precision is not specified or is greater than the size of the converted
|
|
storage, the converted storage shall contain a null wide character.
|
|
If an l length modifier is present, the argument shall be a pointer to storage of wchar_t
|
|
type. Wide characters from the storage are written up to (but not including) a terminating
|
|
null wide character. If the precision is specified, no more than that many wide characters
|
|
are written. If the precision is not specified or is greater than the size of the array, the
|
|
storage shall contain a null wide character.
|
|
p The argument shall be a pointer to void or a pointer to a character type. The value of
|
|
the pointer is converted to a sequence of printing wide characters, in an implementation-
|
|
defined manner.
|
|
n The argument shall be a pointer to signed integer whose type is specified by the length
|
|
modifiers, if any, for the conversion specification, or shall be int if no length modifiers
|
|
are specified for the conversion specification. The number of wide characters written to
|
|
the output stream so far by this call to fwprintf is stored into the integer object pointed
|
|
to by the argument. No argument is converted, but one is consumed. If the conversion
|
|
specification includes any flags, a field width, or a precision, the behavior is undefined.
|
|
% A % wide character is written. No argument is converted. The complete conversion
|
|
specification shall be %%.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.404'>
|
|
<pre><i><b>Footnote 404)</b> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual meaning; the # and 0
|
|
flag wide characters have no effect.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.405'>
|
|
<pre><i><b>Footnote 405)</b> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide character so that subsequent
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.406'>
|
|
<pre><i><b>Footnote 406)</b> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.405'>
|
|
<pre><i><b>Footnote 405)</b> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide character so that subsequent
|
|
digits align to nibble (4-bit) boundaries. This implementation choice affects numerical values printed with a precision P
|
|
that is insufficient to represent all values exactly. Implementations with different conventions about the most significant
|
|
hexadecimal digit will round at different places, affecting the numerical value of the hexadecimal result. For example,
|
|
possible printed output for the code
|
|
#include <stdio.h>
|
|
/* ... */
|
|
double x = 123.0;
|
|
printf("%.1a", x);
|
|
include "0x1.fp+6 " and "0xf.6p+3 " whose numerical values are 124 and 123, respectively. Portable code seeking identical
|
|
numerical results on different platforms should avoid precisions P that require rounding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.406'>
|
|
<pre><i><b>Footnote 406)</b> The formatting precision P is sufficient to distinguish values of the source type if 16P > bp where b (not a power of 2)
|
|
and p are the base and precision of the source type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). A smaller P might suffice depending on the implementation’s
|
|
scheme for determining the digit to the left of the decimal-point wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1p9'></a>
|
|
<pre>9 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.407'><sup>[407]</sup></a> fwprintf shall behave as if it
|
|
uses va_arg with a type argument naming the type resulting from applying the default argument
|
|
promotions to the type corresponding to the conversion specification and then converting the result
|
|
of the va_arg expansion to the type corresponding to the conversion specification.<a href='#FOOTNOTE.408'><sup>[408]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.407'>
|
|
<pre><i><b>Footnote 407)</b> See "future library directions" (<a href='#7.33.20'>7.33.20</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.408'>
|
|
<pre><i><b>Footnote 408)</b> The behavior is undefined when the types differ as specified for va_arg <a href='#7.16.1.1'>7.16.1.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1p10'></a>
|
|
<pre>10 In no case does a nonexistent or small field width cause truncation of a field; if the result of a
|
|
conversion is wider than the field width, the field is expanded to contain the conversion result.
|
|
</pre>
|
|
<a name='7.31.2.1p11'></a>
|
|
<pre>11 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded to a hexadecimal
|
|
floating number with the given precision.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.31.2.1p12'></a>
|
|
<pre>12 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly representable
|
|
in the given precision, the result should be one of the two adjacent numbers in hexadecimal floating
|
|
style with the given precision, with the extra stipulation that the error should have a correct sign for
|
|
the current rounding direction.
|
|
</pre>
|
|
<a name='7.31.2.1p13'></a>
|
|
<pre>13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most the maximum
|
|
value M of the T_DECIMAL_DIG macros (defined in <float.h>), then the result should be correctly
|
|
rounded.<a href='#FOOTNOTE.409'><sup>[409]</sup></a> If the number of significant decimal digits is more than M but the source value is
|
|
exactly representable with M digits, then the result should be an exact representation with trailing
|
|
zeros. Otherwise, the source value is bounded by two adjacent decimal strings L < U, both having
|
|
M significant digits; the value of the resultant decimal string D should satisfy L ≤ D ≤ U, with the
|
|
extra stipulation that the error should have a correct sign for the current rounding direction.
|
|
</pre>
|
|
<a name='FOOTNOTE.409'>
|
|
<pre><i><b>Footnote 409)</b> For binary-to-decimal conversion, the result format’s values are the numbers representable with the given format specifier.
|
|
The number of significant digits is determined by the format specifier, and in the case of fixed-point conversion by the source
|
|
value as well.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.1p14'></a>
|
|
<pre>14 An uppercase B format specifier is not covered by the description above, because it used to be
|
|
available for extensions in previous versions of this standard.
|
|
Implementations that did not use an uppercase B as their own extension before are encouraged to
|
|
implement it similar to conversion specifier b as standardized above, with the alternative form (#B)
|
|
generating 0B as prefix for nonzero values.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.1p15'></a>
|
|
<pre>15 The fwprintf function returns the number of wide characters transmitted, or a negative value if
|
|
an output or encoding error occurred or if the implementation does not support a specified width
|
|
length modifier.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.31.2.1p16'></a>
|
|
<pre>16 The number of wide characters that can be produced by any single conversion shall be at least 4095.
|
|
</pre>
|
|
<a name='7.31.2.1p17'></a>
|
|
<pre>17 EXAMPLE To print a date and time in the form "Sunday, July 3, 10:02" followed by π to five decimal places:
|
|
|
|
#include <math.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
/* ... */
|
|
wchar_t *weekday, *month; // pointers to wide strings
|
|
int day, hour, min;
|
|
fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
|
|
weekday, month, day, hour, min);
|
|
fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
|
|
|
|
</pre>
|
|
<a name='7.31.2.1p18'></a>
|
|
<pre>18 EXAMPLE 1 In this example, multibyte characters do not have a state-dependent encoding, and the members of the extended
|
|
character set that consist of more than one byte each consist of exactly two bytes, the first of which is denoted here by a □
|
|
and the second by an uppercase letter.
|
|
</pre>
|
|
<a name='7.31.2.1p19'></a>
|
|
<pre>19 Given the following wide string with length seven,
|
|
|
|
static wchar_t wstr[] = L"□X□Yabc□Z□W";
|
|
|
|
the seven calls
|
|
|
|
fprintf(stdout, "|1234567890123|\n");
|
|
fprintf(stdout, "|%13ls|\n", wstr);
|
|
fprintf(stdout, "|%-13.9ls|\n", wstr);
|
|
fprintf(stdout, "|%13.10ls|\n", wstr);
|
|
fprintf(stdout, "|%13.11ls|\n", wstr);
|
|
fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
|
|
fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
|
|
|
|
will print the following seven lines:
|
|
|
|
|1234567890123|
|
|
| □X□Yabc□Z□W|
|
|
|□X□Yabc□Z |
|
|
| □X□Yabc□Z|
|
|
| □X□Yabc□Z□W|
|
|
| abc□Z□W|
|
|
| □Z|
|
|
|
|
</pre>
|
|
<a name='7.31.2.1p20'></a>
|
|
<pre>20 EXAMPLE 2 Following are representations of _Decimal64 arguments as triples (s, c, q) and the corresponding character
|
|
sequences fprintf produces with "%Da":
|
|
(+1, 123, 0) 123
|
|
(−1, 123, 0) -123
|
|
(+1, 123, −2) 1.23
|
|
(+1, 123, 1) <a href='#1.'>1.</a>23e+3
|
|
(−1, 123, 1) -<a href='#1.'>1.</a>23e+3
|
|
(+1, 123, −8) 0.00000123
|
|
(+1, 123, −9) <a href='#1.'>1.</a>23e-7
|
|
(+1, 120, −8) 0.00000120
|
|
(+1, 120, −9) <a href='#1.'>1.</a>20e-7
|
|
(+1, 1234567890123456, 0) 1234567890123456
|
|
(+1, 1234567890123456, 1) <a href='#1.'>1.</a>234567890123456e+16
|
|
(+1, 1234567890123456, −1) 123456789012345.6
|
|
(+1, 1234567890123456, −21) 0.000001234567890123456
|
|
(+1, 1234567890123456, −22) <a href='#1.'>1.</a>234567890123456e-7
|
|
(+1, 0, 0) 0
|
|
(−1, 0, 0) -0
|
|
(+1, 0, −6) 0.000000
|
|
(+1, 0, −7) 0e-7
|
|
(+1, 0, 2) 0e+2
|
|
(+1, 5, −6) 0.000005
|
|
(+1, 50, −7) 0.0000050
|
|
(+1, 5, −7) 5e-7
|
|
|
|
To illustrate the effects of a precision specification, the sequence:
|
|
|
|
_Decimal32 x = 6543.00DF; // (+1, 654300, -2)
|
|
fprintf(stdout, "%Ha\n", x);
|
|
fprintf(stdout, "%.6Ha\n", x);
|
|
fprintf(stdout, "%.5Ha\n", x);
|
|
fprintf(stdout, "%.4Ha\n", x);
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.0Ha\n", x);
|
|
|
|
assuming default rounding, results in:
|
|
6543.00
|
|
6543.00
|
|
6543.0
|
|
6543
|
|
<a href='#6.'>6.</a>54e+3
|
|
<a href='#6.'>6.</a>5e+3
|
|
7e+3
|
|
6543.00
|
|
|
|
To illustrate the effects of the exponent range, the sequence:
|
|
|
|
_Decimal32 x = 9543210e87DF; // (+1, 9543210, 87)
|
|
_Decimal32 y = 9500000e90DF; // (+1, 9500000, 90)
|
|
fprintf(stdout, "%.6Ha\n", x);
|
|
fprintf(stdout, "%.5Ha\n", x);
|
|
fprintf(stdout, "%.4Ha\n", x);
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", y);
|
|
|
|
assuming default rounding, results in:
|
|
9.54321e+93
|
|
9.5432e+93
|
|
9.543e+93
|
|
9.54e+93
|
|
9.5e+93
|
|
1e+94
|
|
1e+97
|
|
|
|
To further illustrate the effects of the exponent range, the sequence:
|
|
|
|
_Decimal32 x = 9512345e90DF; // (+1, 9512345, 90)
|
|
_Decimal32 y = 9512345e86DF; // (+1, 9512345, 86)
|
|
fprintf(stdout, "%.3Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", x);
|
|
fprintf(stdout, "%.1Ha\n", x);
|
|
fprintf(stdout, "%.2Ha\n", y);
|
|
|
|
assuming default rounding, results in:
|
|
9.51e+96
|
|
9.5e+96
|
|
1e+97
|
|
9.5e+92
|
|
|
|
Forward references: the btowc function (<a href='#7.31.6.1.1'>7.31.6.1.1</a>), the mbrtowc function (<a href='#7.31.6.3.2'>7.31.6.3.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.31.2.2'></a>
|
|
<hr>
|
|
<h3>7.31.2.2 [The fwscanf function]</h3>
|
|
<a name='7.31.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwscanf(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.2p2'></a>
|
|
<pre>2 The fwscanf function reads input from the stream pointed to by stream, under control of the wide
|
|
string pointed to by format that specifies the admissible input sequences and how they are to be
|
|
converted for assignment, using subsequent arguments as pointers to the objects to receive the
|
|
converted input. If there are insufficient arguments for the format, the behavior is undefined. If the
|
|
format is exhausted while arguments remain, the excess arguments are evaluated (as always) but
|
|
are otherwise ignored.
|
|
</pre>
|
|
<a name='7.31.2.2p3'></a>
|
|
<pre>3 The format is composed of zero or more directives: one or more white-space wide characters, an
|
|
ordinary wide character (neither % nor a white-space wide character), or a conversion specification.
|
|
Each conversion specification is introduced by the wide character %. After the %, the following
|
|
appear in sequence:
|
|
|
|
— An optional assignment-suppressing wide character *.
|
|
|
|
— An optional decimal integer greater than zero that specifies the maximum field width (in wide
|
|
characters).
|
|
|
|
— An optional length modifier that specifies the size of the receiving object.
|
|
|
|
— A conversion specifier wide character that specifies the type of conversion to be applied.
|
|
|
|
</pre>
|
|
<a name='7.31.2.2p4'></a>
|
|
<pre>4 The fwscanf function executes each directive of the format in turn. When all directives have been
|
|
executed, or if a directive fails (as detailed below), the function returns. Failures are described as
|
|
input failures (due to the occurrence of an encoding error or the unavailability of input characters),
|
|
or matching failures (due to inappropriate input).
|
|
</pre>
|
|
<a name='7.31.2.2p5'></a>
|
|
<pre>5 A directive composed of white-space wide character(s) is executed by reading input up to the first
|
|
non-white-space wide character (which remains unread), or until no more wide characters can be
|
|
read. The directive never fails.
|
|
</pre>
|
|
<a name='7.31.2.2p6'></a>
|
|
<pre>6 A directive that is an ordinary wide character is executed by reading the next wide character of
|
|
the stream. If that wide character differs from the directive,the directive fails and the differing and
|
|
subsequent wide characters remain unread. Similarly, if end-of-file, an encoding error, or a read
|
|
error prevents a wide character from being read, the directive fails.
|
|
</pre>
|
|
<a name='7.31.2.2p7'></a>
|
|
<pre>7 A directive that is a conversion specification defines a set of matching input sequences, as described
|
|
below for each specifier. A conversion specification is executed in the following steps:
|
|
</pre>
|
|
<a name='7.31.2.2p8'></a>
|
|
<pre>8 Input white-space wide characters are skipped, unless the specification includes a [, c, or n speci-
|
|
fier.<a href='#FOOTNOTE.410'><sup>[410]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.410'>
|
|
<pre><i><b>Footnote 410)</b> These white-space wide characters are not counted against a specified field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.2p9'></a>
|
|
<pre>9 An input item is read from the stream, unless the specification includes an n specifier. An input item
|
|
is defined as the longest sequence of input wide characters which does not exceed any specified
|
|
field width and which is, or is a prefix of, a matching input sequence.<a href='#FOOTNOTE.411'><sup>[411]</sup></a> The first wide character, if
|
|
any, after the input item remains unread. If the length of the input item is zero, the execution of the
|
|
directive fails; this condition is a matching failure unless end-of-file, an encoding error, or a read
|
|
error prevented input from the stream, in which case it is an input failure.
|
|
</pre>
|
|
<a name='FOOTNOTE.411'>
|
|
<pre><i><b>Footnote 411)</b> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some sequences that are
|
|
acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.2p10'></a>
|
|
<pre>10 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the count of input
|
|
wide characters) is converted to a type appropriate to the conversion specifier. If the input item is
|
|
not a matching sequence, the execution of the directive fails: this condition is a matching failure.
|
|
Unless assignment suppression was indicated by a *, the result of the conversion is placed in the
|
|
object pointed to by the first argument following the format argument that has not already received
|
|
a conversion result. If this object does not have an appropriate type, or if the result of the conversion
|
|
cannot be represented in the object, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.31.2.2p11'></a>
|
|
<pre>11 The length modifiers and their meanings are:
|
|
|
|
hh Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to signed char or unsigned char.
|
|
|
|
h Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to short int or unsigned short int.
|
|
|
|
l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to long int or unsigned long int; that a following a, A, e, E, f, F,
|
|
g, or G conversion specifier applies to an argument with type pointer to double; or that
|
|
a following c, s, or [ conversion specifier applies to an argument with type pointer to
|
|
wchar_t .
|
|
|
|
ll (ell-ell) Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to long long int or unsigned long long int.
|
|
|
|
j Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to intmax_t or uintmax_t.
|
|
|
|
z Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to size_t or the corresponding signed integer type.
|
|
|
|
t Specifies that a following b, d, i, o, u, x, X, or n conversion specifier applies to an argument
|
|
with type pointer to ptrdiff_t or the corresponding unsigned integer type.
|
|
wN Specifies that a following b, d, i, o, u, x, or X, or n conversion specifier applies to an
|
|
argument which is a pointer to an integer with a specific width where N is a positive
|
|
decimal integer with no leading zeros. All minimum-width integer types (<a href='#7.22.1.2'>7.22.1.2</a>) and
|
|
exact-width integer types (<a href='#7.22.1.1'>7.22.1.1</a>) defined in the header <stdint.h> shall be supported.
|
|
Other supported values of N are implementation-defined.
|
|
|
|
wfN Specifies that a following b, d, i, o, u, x, or X, or n conversion specifier applies to an
|
|
argument which is a pointer to a fastest minimum-width integer with a specific width
|
|
where N is a positive decimal integer with no leading zeros. All fastest minimum-width
|
|
integer types (<a href='#7.22.1.3'>7.22.1.3</a>) defined in the header <stdint.h> shall be supported. Other
|
|
supported values of N are implementation-defined.
|
|
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to long double.
|
|
|
|
H Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal32 .
|
|
|
|
D Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal64 .
|
|
|
|
DD Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to an argument
|
|
with type pointer to _Decimal128 .
|
|
|
|
If a length modifier appears with any conversion specifier other than as specified above, the behavior
|
|
is undefined.
|
|
</pre>
|
|
<a name='7.31.2.2p12'></a>
|
|
<pre>12 In the following, the type of the corresponding argument for a conversion specifier shall be a pointer
|
|
to a type determined by the length modifiers, if any, or specified by the conversion specifier. The
|
|
conversion specifiers and their meanings are:
|
|
|
|
d Matches an optionally signed decimal integer, whose format is the same as expected for
|
|
the subject sequence of the wcstol function with the value 10 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
int.
|
|
|
|
b Matches an optionally signed binary integer, whose format is the same as expected for the
|
|
subject sequence of the wcstol function with the value 2 for the base argument. Unless a
|
|
length modifier is specified, the corresponding argument shall be a pointer to unsigned
|
|
int.
|
|
|
|
i Matches an optionally signed integer, whose format is the same as expected for the subject
|
|
sequence of the wcstol function with the value 0 for the base argument. Unless a length
|
|
modifier is specified, the corresponding argument shall be a pointer to int.
|
|
|
|
o Matches an optionally signed octal integer, whose format is the same as expected for
|
|
the subject sequence of the wcstoul function with the value 8 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
|
|
u Matches an optionally signed decimal integer, whose format is the same as expected for
|
|
the subject sequence of the wcstoul function with the value 10 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
|
|
x Matches an optionally signed hexadecimal integer, whose format is the same as expected
|
|
for the subject sequence of the wcstoul function with the value 16 for the base argument.
|
|
Unless a length modifier is specified, the corresponding argument shall be a pointer to
|
|
unsigned int.
|
|
a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose format is
|
|
the same as expected for the subject sequence of the wcstod function. Unless a length
|
|
modifier is specified, the corresponding argument shall be a pointer to float.
|
|
|
|
c Matches a sequence of wide characters of exactly the number specified by the field width
|
|
(1 if no field width is present in the directive).
|
|
If no l length modifier is present, characters from the input field are converted as if
|
|
by repeated calls to the wcrtomb function, with the conversion state described by an
|
|
mbstate_t object initialized to zero before the first wide character is converted. The
|
|
corresponding argument shall be a pointer to char, signed char, unsigned char, or
|
|
void that points to storage large enough to accept the sequence. No null character is
|
|
added.
|
|
If an l length modifier is present, the corresponding argument shall be a pointer to storage
|
|
of wchar_t large enough to accept the sequence.No null wide character is added.
|
|
|
|
s Matches a sequence of non-white-space wide characters.
|
|
If no l length modifier is present, characters from the input field are converted as if
|
|
by repeated calls to the wcrtomb function, with the conversion state described by an
|
|
mbstate_t object initialized to zero before the first wide character is converted. The
|
|
corresponding argument shall be a pointer to char, signed char, unsigned char, or
|
|
void that points to storage large enough to accept the sequence and a terminating null
|
|
character, which will be added automatically.
|
|
If an l length modifier is present, the corresponding argument shall be a pointer to storage
|
|
of wchar_t large enough to accept the sequence and the terminating null wide character,
|
|
which will be added automatically.
|
|
|
|
[ Matches a nonempty sequence of wide characters from a set of expected characters (the
|
|
scanset).
|
|
If no l length modifier is present, characters from the input field are converted as if
|
|
by repeated calls to the wcrtomb function, with the conversion state described by an
|
|
mbstate_t object initialized to zero before the first wide character is converted. The
|
|
corresponding argument shall be a pointer to char, signed char, unsigned char, or
|
|
void that points to storage large enough to accept the sequence and a terminating null
|
|
character, which will be added automatically.
|
|
If an l length modifier is present, the corresponding argument shall be a pointer that
|
|
points to storage of wchar_t large enough to accept the sequence and the terminating null
|
|
wide character, which will be added automatically.
|
|
The conversion specifier includes all subsequent wide characters in the format string,
|
|
up to and including the matching right bracket (]). The wide characters between the
|
|
brackets (the scanlist) compose the scanset, unless the wide character after the left bracket
|
|
is a circumflex (^), in which case the scanset contains all wide characters that do not
|
|
appear in the scanlist between the circumflex and the right bracket. If the conversion
|
|
specifier begins with [] or [^], the right bracket wide character is in the scanlist and
|
|
the next following right bracket wide character is the matching right bracket that ends
|
|
the specification; otherwise the first following right bracket wide character is the one
|
|
that ends the specification. If a - wide character is in the scanlist and is not the first, nor
|
|
the second where the first wide character is a ^, nor the last character, the behavior is
|
|
implementation-defined.
|
|
|
|
p Matches an implementation-defined set of sequences, which should be the same as the
|
|
set of sequences that may be produced by the %p conversion of the fwprintf function.
|
|
The corresponding argument shall be a pointer to a pointer of void. The input item is
|
|
converted to a pointer value in an implementation-defined manner. If the input item is a
|
|
value converted earlier during the same program execution, the pointer that results shall
|
|
compare equal to that value; otherwise the behavior of the %p conversion is undefined.
|
|
n No input is consumed. The corresponding argument shall be a pointer of a signed integer
|
|
type. The number of wide characters read from the input stream so far by this call to the
|
|
fwscanf function is stored into the integer object pointed to by the argument. Execution
|
|
of a %n directive does not increment the assignment count returned at the completion of
|
|
execution of the fwscanf function. No argument is converted, but one is consumed. If
|
|
the conversion specification includes an assignment-suppressing wide character or a field
|
|
width, the behavior is undefined.
|
|
% Matches a single % wide character; no conversion or assignment occurs. The complete
|
|
conversion specification shall be %%.
|
|
|
|
</pre>
|
|
<a name='7.31.2.2p13'></a>
|
|
<pre>13 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.412'><sup>[412]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.412'>
|
|
<pre><i><b>Footnote 412)</b> See "future library directions" (<a href='#7.33.20'>7.33.20</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.2p14'></a>
|
|
<pre>14 The conversion specifiers A, E, F, G, and X are also valid and behave the same as, respectively, a, e, f,
|
|
g, and x.
|
|
</pre>
|
|
<a name='7.31.2.2p15'></a>
|
|
<pre>15 Trailing white-space wide characters(including new-line wide characters) are left unread unless
|
|
matched by a directive. The success of literal matches and suppressed assignments is not directly
|
|
determinable other than via the %n directive.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.2p16'></a>
|
|
<pre>16 The fwscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the function returns the number of input items
|
|
assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure or if the implementation does not support a specific width length modifier.
|
|
</pre>
|
|
<a name='7.31.2.2p17'></a>
|
|
<pre>17 EXAMPLE 1 The call:
|
|
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
/* ... */
|
|
int n, i; float x; wchar_t name[50];
|
|
n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
|
|
|
|
|
|
with the input line:
|
|
|
|
25 54.32E-1 thompson
|
|
|
|
|
|
will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0.
|
|
</pre>
|
|
<a name='7.31.2.2p18'></a>
|
|
<pre>18 EXAMPLE 2 The call:
|
|
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
/* ... */
|
|
int i; float x; double y;
|
|
fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
|
|
|
|
|
|
with input:
|
|
|
|
56789 0123 56a72
|
|
|
|
|
|
will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value 56.0. The next wide
|
|
character read from the input stream will be a.
|
|
|
|
Forward references: the wcstod, wcstof, and wcstold functions (<a href='#7.31.4.1.2'>7.31.4.1.2</a>), the wcstol, wcstoll,
|
|
wcstoul , and wcstoull functions (<a href='#7.31.4.1.4'>7.31.4.1.4</a>), the wcrtomb function (<a href='#7.31.6.3.3'>7.31.6.3.3</a>).
|
|
|
|
</pre>
|
|
<a name='7.31.2.3'></a>
|
|
<hr>
|
|
<h3>7.31.2.3 [The swprintf function]</h3>
|
|
<a name='7.31.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int swprintf(wchar_t * restrict s, size_t n, const wchar_t * restrict format,
|
|
...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.3p2'></a>
|
|
<pre>2 The swprintf function is equivalent to fwprintf, except that the argument s specifies an array of
|
|
wide characters into which the generated output is to be written, rather than written to a stream.
|
|
No more than n wide characters are written, including a terminating null wide character, which is
|
|
always added (unless n is zero).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.3p3'></a>
|
|
<pre>3 The swprintf function returns the number of wide characters written in the array, not counting the
|
|
terminating null wide character, or a negative value if an encoding error occurred or if n or more
|
|
wide characters were requested to be written.
|
|
|
|
</pre>
|
|
<a name='7.31.2.4'></a>
|
|
<hr>
|
|
<h3>7.31.2.4 [The swscanf function]</h3>
|
|
<a name='7.31.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int swscanf(const wchar_t * restrict s, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.4p2'></a>
|
|
<pre>2 The swscanf function is equivalent to fwscanf, except that the argument s specifies a wide string
|
|
from which the input is to be obtained, rather than from a stream. Reaching the end of the wide
|
|
string is equivalent to encountering end-of-file for the fwscanf function.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.4p3'></a>
|
|
<pre>3 The swscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the swscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.31.2.5'></a>
|
|
<hr>
|
|
<h3>7.31.2.5 [The vfwprintf function]</h3>
|
|
<a name='7.31.2.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int vfwprintf(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.5p2'></a>
|
|
<pre>2 The vfwprintf function is equivalent to fwprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vfwprintf function does not invoke the va_end macro<a href='#FOOTNOTE.413'><sup>[413]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.5p3'></a>
|
|
<pre>3 The vfwprintf function returns the number of wide characters transmitted, or a negative value if
|
|
an output or encoding error occurred.
|
|
</pre>
|
|
<a name='7.31.2.5p4'></a>
|
|
<pre>4 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting routine.
|
|
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
|
|
void error(char *function_name, wchar_t *format, ...)
|
|
{
|
|
va_list args;
|
|
|
|
va_start(args, format);
|
|
// print out name of function causing error
|
|
fwprintf(stderr, L"ERROR in %s: ", function_name);
|
|
// print out remainder of message
|
|
vfwprintf(stderr, format, args);
|
|
va_end(args);
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.31.2.6'></a>
|
|
<hr>
|
|
<h3>7.31.2.6 [The vfwscanf function]</h3>
|
|
<a name='7.31.2.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int vfwscanf(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.6p2'></a>
|
|
<pre>2 The vfwscanf function is equivalent to fwscanf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vfwscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.413'><sup>[413]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.6p3'></a>
|
|
<pre>3 The vfwscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vfwscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.31.2.7'></a>
|
|
<hr>
|
|
<h3>7.31.2.7 [The vswprintf function]</h3>
|
|
<a name='7.31.2.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vswprintf(wchar_t * restrict s, size_t n, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.7p2'></a>
|
|
<pre>2 The vswprintf function is equivalent to swprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vswprintf function does not invoke the va_end macro.<a href='#FOOTNOTE.413'><sup>[413]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.7p3'></a>
|
|
<pre>3 The vswprintf function returns the number of wide characters written in the array, not counting
|
|
the terminating null wide character, or a negative value if an encoding error occurred or if n or more
|
|
wide characters were requested to be generated.
|
|
|
|
</pre>
|
|
<a name='7.31.2.8'></a>
|
|
<hr>
|
|
<h3>7.31.2.8 [The vswscanf function]</h3>
|
|
<a name='7.31.2.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vswscanf(const wchar_t * restrict s, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.8p2'></a>
|
|
<pre>2 The vswscanf function is equivalent to swscanf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vswscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.413'><sup>[413]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.8p3'></a>
|
|
<pre>3 The vswscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vswscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.31.2.9'></a>
|
|
<hr>
|
|
<h3>7.31.2.9 [The vwprintf function]</h3>
|
|
<a name='7.31.2.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwprintf(const wchar_t * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.9p2'></a>
|
|
<pre>2 The vwprintf function is equivalent to wprintf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vwprintf function does not invoke the va_end macro.<a href='#FOOTNOTE.413'><sup>[413]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.9p3'></a>
|
|
<pre>3 The vwprintf function returns the number of wide characters transmitted, or a negative value if an
|
|
output or encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.31.2.10'></a>
|
|
<hr>
|
|
<h3>7.31.2.10 [The vwscanf function]</h3>
|
|
<a name='7.31.2.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwscanf(const wchar_t * restrict format, va_list arg);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.10p2'></a>
|
|
<pre>2 The vwscanf function is equivalent to wscanf, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vwscanf function does not invoke the va_end macro.<a href='#FOOTNOTE.413'><sup>[413]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</b> As the functions vfwprintf , vswprintf , vfwscanf , vwprintf , vwscanf , and vswscanf invoke the va_arg macro, the
|
|
representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.2.10p3'></a>
|
|
<pre>3 The vwscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the vwscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.31.2.11'></a>
|
|
<hr>
|
|
<h3>7.31.2.11 [The wprintf function]</h3>
|
|
<a name='7.31.2.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wprintf(const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.11p2'></a>
|
|
<pre>2 The wprintf function is equivalent to fwprintf with the argument stdout interposed before the
|
|
arguments to wprintf.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.11p3'></a>
|
|
<pre>3 The wprintf function returns the number of wide characters transmitted, or a negative value if an
|
|
output or encoding error occurred.
|
|
|
|
</pre>
|
|
<a name='7.31.2.12'></a>
|
|
<hr>
|
|
<h3>7.31.2.12 [The wscanf function]</h3>
|
|
<a name='7.31.2.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wscanf(const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.2.12p2'></a>
|
|
<pre>2 The wscanf function is equivalent to fwscanf with the argument stdin interposed before the
|
|
arguments to wscanf.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.2.12p3'></a>
|
|
<pre>3 The wscanf function returns the value of the macro EOF if an input failure occurs before the first
|
|
conversion (if any) has completed. Otherwise, the wscanf function returns the number of input
|
|
items assigned, which can be fewer than provided for, or even zero, in the event of an early matching
|
|
failure.
|
|
|
|
</pre>
|
|
<a name='7.31.3'></a>
|
|
<hr>
|
|
<h3>7.31.3 [Wide character input/output functions]</h3>
|
|
<a name='7.31.3.1'></a>
|
|
<hr>
|
|
<h3>7.31.3.1 [The fgetwc function]</h3>
|
|
<a name='7.31.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t fgetwc(FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.1p2'></a>
|
|
<pre>2 If the end-of-file indicator for the input stream pointed to by stream is not set and a next wide
|
|
character is present, the fgetwc function obtains that wide character as a wchar_t converted to a
|
|
wint_t and advances the associated file position indicator for the stream (if defined).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.1p3'></a>
|
|
<pre>3 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-of-file
|
|
indicator for the stream is set and the fgetwc function returns WEOF. Otherwise, the fgetwc function
|
|
returns the next wide character from the input stream pointed to by stream. If a read error occurs,
|
|
the error indicator for the stream is set and the fgetwc function returns WEOF. If an encoding error
|
|
occurs (including too few bytes), the error indicator for the stream is set and the value of the macro
|
|
EILSEQ is stored in errno and the fgetwc function returns WEOF.<a href='#FOOTNOTE.414'><sup>[414]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.414'>
|
|
<pre><i><b>Footnote 414)</b> An end-of-file and a read error can be distinguished by use of the feof and ferror functions. Also, errno will be set to
|
|
EILSEQ by input/output functions only if an encoding error occurs.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.3.2'></a>
|
|
<hr>
|
|
<h3>7.31.3.2 [The fgetws function]</h3>
|
|
<a name='7.31.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wchar_t *fgetws(wchar_t * restrict s, int n, FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.2p2'></a>
|
|
<pre>2 The fgetws function reads at most one less than the number of wide characters specified by n from
|
|
the stream pointed to by stream into the array pointed to by s. No additional wide characters are
|
|
read after a new-line wide character (which is retained) or after end-of-file. A null wide character is
|
|
written immediately after the last wide character read into the array.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.2p3'></a>
|
|
<pre>3 The fgetws function returns s if successful. If end-of-file is encountered and no characters have
|
|
been read into the array, the contents of the array remain unchanged and a null pointer is returned.
|
|
If a read or encoding error occurs during the operation, the array members have an indeterminate
|
|
representation and a null pointer is returned.
|
|
|
|
</pre>
|
|
<a name='7.31.3.3'></a>
|
|
<hr>
|
|
<h3>7.31.3.3 [The fputwc function]</h3>
|
|
<a name='7.31.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t fputwc(wchar_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.3p2'></a>
|
|
<pre>2 The fputwc function writes the wide character specified by c to the output stream pointed to by
|
|
stream, at the position indicated by the associated file position indicator for the stream (if defined),
|
|
and advances the indicator appropriately. If the file cannot support positioning requests, or if the
|
|
stream was opened with append mode, the character is appended to the output stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.3p3'></a>
|
|
<pre>3 The fputwc function returns the wide character written. If a write error occurs, the error indicator
|
|
for the stream is set and fputwc returns WEOF. If an encoding error occurs, the value of the macro
|
|
EILSEQ is stored in errno and fputwc returns WEOF .
|
|
|
|
</pre>
|
|
<a name='7.31.3.4'></a>
|
|
<hr>
|
|
<h3>7.31.3.4 [The fputws function]</h3>
|
|
<a name='7.31.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fputws(const wchar_t * restrict s, FILE * restrict stream);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.4p2'></a>
|
|
<pre>2 The fputws function writes the wide string pointed to by s to the stream pointed to by stream. The
|
|
terminating null wide character is not written.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.4p3'></a>
|
|
<pre>3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it returns a nonnega-
|
|
tive value.
|
|
|
|
</pre>
|
|
<a name='7.31.3.5'></a>
|
|
<hr>
|
|
<h3>7.31.3.5 [The fwide function]</h3>
|
|
<a name='7.31.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwide(FILE *stream, int mode);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.5p2'></a>
|
|
<pre>2 The fwide function determines the orientation of the stream pointed to by stream. If mode is greater
|
|
than zero, the function first attempts to make the stream wide oriented. If mode is less than zero,
|
|
the function first attempts to make the stream byte oriented.<a href='#FOOTNOTE.415'><sup>[415]</sup></a> Otherwise, mode is zero and the
|
|
function does not alter the orientation of the stream.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.415'>
|
|
<pre><i><b>Footnote 415)</b> If the orientation of the stream has already been determined, fwide does not change it.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.3.5p3'></a>
|
|
<pre>3 The fwide function returns a value greater than zero if, after the call, the stream has wide orientation,
|
|
a value less than zero if the stream has byte orientation, or zero if the stream has no orientation.
|
|
|
|
</pre>
|
|
<a name='7.31.3.6'></a>
|
|
<hr>
|
|
<h3>7.31.3.6 [The getwc function]</h3>
|
|
<a name='7.31.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t getwc(FILE *stream);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.6p2'></a>
|
|
<pre>2 The getwc function is equivalent to fgetwc, except that if it is implemented as a macro, it may
|
|
evaluate stream more than once, so the argument should never be an expression with side effects.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.6p3'></a>
|
|
<pre>3 The getwc function returns the next wide character from the input stream pointed to by stream, or
|
|
WEOF .
|
|
|
|
</pre>
|
|
<a name='7.31.3.7'></a>
|
|
<hr>
|
|
<h3>7.31.3.7 [The getwchar function]</h3>
|
|
<a name='7.31.3.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t getwchar(void);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.7p2'></a>
|
|
<pre>2 The getwchar function is equivalent to getwc with the argument stdin.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.7p3'></a>
|
|
<pre>3 The getwchar function returns the next wide character from the input stream pointed to by stdin,
|
|
or WEOF.
|
|
|
|
</pre>
|
|
<a name='7.31.3.8'></a>
|
|
<hr>
|
|
<h3>7.31.3.8 [The putwc function]</h3>
|
|
<a name='7.31.3.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t putwc(wchar_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.8p2'></a>
|
|
<pre>2 The putwc function is equivalent to fputwc, except that if it is implemented as a macro, it may
|
|
evaluate stream more than once, so that argument should never be an expression with side effects.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.8p3'></a>
|
|
<pre>3 The putwc function returns the wide character written, or WEOF.
|
|
|
|
</pre>
|
|
<a name='7.31.3.9'></a>
|
|
<hr>
|
|
<h3>7.31.3.9 [The putwchar function]</h3>
|
|
<a name='7.31.3.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t putwchar(wchar_t c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.9p2'></a>
|
|
<pre>2 The putwchar function is equivalent to putwc with the second argument stdout.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.3.9p3'></a>
|
|
<pre>3 The putwchar function returns the character written, or WEOF.
|
|
|
|
</pre>
|
|
<a name='7.31.3.10'></a>
|
|
<hr>
|
|
<h3>7.31.3.10 [The ungetwc function]</h3>
|
|
<a name='7.31.3.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t ungetwc(wint_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.3.10p2'></a>
|
|
<pre>2 The ungetwc function pushes the wide character specified by c back onto the input stream pointed
|
|
to by stream. Pushed-back wide characters will be returned by subsequent reads on that stream
|
|
in the reverse order of their pushing. A successful intervening call (with the stream pointed to by
|
|
stream) to a file positioning function (fseek, fsetpos, or rewind) discards any pushed-back wide
|
|
characters for the stream. The external storage corresponding to the stream is unchanged.
|
|
</pre>
|
|
<a name='7.31.3.10p3'></a>
|
|
<pre>3 One wide character of pushback is guaranteed, even if the call to the ungetwc function follows just
|
|
after a call to a formatted wide character input function fwscanf, vfwscanf, vwscanf, or wscanf. If
|
|
the ungetwc function is called too many times on the same stream without an intervening read or
|
|
file positioning operation on that stream, the operation may fail.
|
|
</pre>
|
|
<a name='7.31.3.10p4'></a>
|
|
<pre>4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is unchanged.
|
|
</pre>
|
|
<a name='7.31.3.10p5'></a>
|
|
<pre>5 A successful call to the ungetwc function clears the end-of-file indicator for the stream. The value of
|
|
the file position indicator for the stream after reading or discarding all pushed-back wide characters
|
|
is the same as it was before the wide characters were pushed back.<a href='#FOOTNOTE.416'><sup>[416]</sup></a> For a text or binary stream,
|
|
the value of its file position indicator after a successful call to the ungetwc function is unspecified
|
|
until all pushed-back wide characters are read or discarded.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.416'>
|
|
<pre><i><b>Footnote 416)</b> Note that a file positioning function could further modify the file position indicator after discarding any pushed-back
|
|
wide characters.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.3.10p6'></a>
|
|
<pre>6 The ungetwc function returns the wide character pushed back, or WEOF if the operation fails.
|
|
|
|
</pre>
|
|
<a name='7.31.4'></a>
|
|
<hr>
|
|
<h3>7.31.4 [General wide string utilities]</h3>
|
|
<a name='7.31.4p1'></a>
|
|
<pre>1 The header <wchar.h> declares a number of functions useful for wide string manipulation. Various
|
|
methods are used for determining the lengths of the arrays, but in all cases a wchar_t* argument
|
|
points to the initial (lowest addressed) element of the array. If an array is accessed beyond the end
|
|
of an object, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.31.4p2'></a>
|
|
<pre>2 Where an argument declared as size_t n determines the length of the array for a function, n can
|
|
have the value zero on a call to that function. Unless explicitly stated otherwise in the description of
|
|
a particular function in this subclause, pointer arguments on such a call shall still have valid values,
|
|
as described in <a href='#7.1.4'>7.1.4</a>. On such a call, a function that locates a wide character finds no occurrence, a
|
|
function that compares two wide character sequences returns zero, and a function that copies wide
|
|
characters copies zero wide characters.
|
|
|
|
</pre>
|
|
<a name='7.31.4.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.1 [Wide string numeric conversion functions]</h3>
|
|
<a name='7.31.4.1.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.1.1 [General]</h3>
|
|
<pre>This subclause describes wide string analogs of the strtod family of functions (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.24.1.6'>7.24.1.6</a>)417) .
|
|
|
|
</pre>
|
|
<a name='7.31.4.1.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.1.2 [The wcstod, wcstof, and wcstold functions]</h3>
|
|
<a name='7.31.4.1.2p1'></a>
|
|
<pre>1 #include <wchar.h>
|
|
double wcstod(const wchar_t * restrict nptr, wchar_t ** restrict endptr);
|
|
float wcstof(const wchar_t * restrict nptr, wchar_t ** restrict endptr);
|
|
long double wcstold(const wchar_t * restrict nptr, wchar_t ** restrict endptr);
|
|
|
|
|
|
Description
|
|
The wcstod, wcstof, and wcstold functions convert the initial portion of the wide string pointed to
|
|
by nptr to double, float, and long double representation, respectively. First, they decompose the
|
|
input string into three parts: an initial, possibly empty, sequence of white-space wide characters, a
|
|
subject sequence resembling a floating constant or representing an infinity or NaN; and a final wide
|
|
string of one or more unrecognized wide characters, including the terminating null wide character
|
|
of the input wide string. Then, they attempt to convert the subject sequence to a floating-point
|
|
number, and return the result.
|
|
</pre>
|
|
<a name='7.31.4.1.2p2'></a>
|
|
<pre>2 The expected form of the subject sequence is an optional plus or minus sign, then one of the
|
|
following:
|
|
|
|
— a nonempty sequence of decimal digits optionally containing a decimal-point wide character,
|
|
then an optional exponent part as defined for the corresponding single-byte characters in
|
|
<a href='#6.4.4.2'>6.4.4.2</a>, excluding any digit separators (<a href='#6.4.4.1'>6.4.4.1</a>);
|
|
— a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a decimal-
|
|
point wide character, then an optional binary exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</a>, excluding
|
|
any digit separators (<a href='#6.4.4.1'>6.4.4.1</a>);
|
|
— INF or INFINITY, or any other wide string equivalent except for case
|
|
— NAN or NAN(n-wchar-sequenceopt ), or any other wide string equivalent except for case in the NAN
|
|
part, where:
|
|
n-wchar-sequence:
|
|
digit
|
|
nondigit
|
|
n-wchar-sequence digit
|
|
n-wchar-sequence nondigit
|
|
|
|
|
|
The subject sequence is defined as the longest initial subsequence of the input wide string, starting
|
|
with the first non-white-space wide character, that is of the expected form. The subject sequence
|
|
contains no wide characters if the input wide string is not of the expected form.
|
|
</pre>
|
|
<a name='7.31.4.1.2p3'></a>
|
|
<pre>3 If the subject sequence has the expected form for a floating-point number, the sequence of wide
|
|
characters starting with the first digit or the decimal-point wide character (whichever occurs first) is
|
|
interpreted as a floating constant according to the rules of <a href='#6.4.4.2'>6.4.4.2</a>, except that the decimal-point wide
|
|
character is used in place of a period, and that if neither an exponent part nor a decimal-point wide
|
|
character appears in a decimal floating-point number, or if a binary exponent part does not appear
|
|
in a hexadecimal floating-point number, an exponent part of the appropriate type with value zero is
|
|
assumed to follow the last digit in the string.
|
|
If the subject sequence begins with a minus sign, the sequence is interpreted as negated.<a href='#FOOTNOTE.418'><sup>[418]</sup></a>
|
|
A wide character sequence INF or INFINITY is interpreted as an infinity, if representable in the
|
|
return type, else like a floating constant that is too large for the range of the return type. A wide
|
|
character sequence NAN or NAN(n-wchar-sequenceopt ) is interpreted as a quiet NaN, if supported in
|
|
the return type, else like a subject sequence part that does not have the expected form; the meaning
|
|
of the n-wchar sequence is implementation-defined.<a href='#FOOTNOTE.419'><sup>[419]</sup></a>
|
|
A pointer to the final wide string is stored in the object pointed to by endptr, provided that endptr
|
|
is not a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.418'>
|
|
<pre><i><b>Footnote 418)</b> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by negating the value
|
|
resulting from converting the corresponding unsigned sequence (see <a href='#F.5'>F.5</a>); the two methods could yield different results if
|
|
rounding is toward positive or negative infinity. In either case, the functions honor the sign of zero if floating-point arithmetic
|
|
supports signed zeros.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.419'>
|
|
<pre><i><b>Footnote 419)</b> An implementation can use the n-wchar sequence to determine extra information to be represented in the NaN’s
|
|
significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.1.2p4'></a>
|
|
<pre>4 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the value resulting
|
|
from the conversion is correctly rounded.
|
|
</pre>
|
|
<a name='7.31.4.1.2p5'></a>
|
|
<pre>5 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.31.4.1.2p6'></a>
|
|
<pre>6 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.31.4.1.2p7'></a>
|
|
<pre>7 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and the result is
|
|
not exactly representable, the result should be one of the two numbers in the appropriate internal
|
|
format that are adjacent to the hexadecimal floating source value, with the extra stipulation that the
|
|
error should have a correct sign for the current rounding direction.
|
|
</pre>
|
|
<a name='7.31.4.1.2p8'></a>
|
|
<pre>8 If the subject sequence has the decimal form and at most M significant digits, where M is the
|
|
maximum value of the T_DECIMAL_DIG macros (defined in <float.h>), the result should be correctly
|
|
rounded. If the subject sequence D has the decimal form and more than M significant digits, consider
|
|
the two bounding, adjacent decimal strings L and U, both having M significant digits, such that the
|
|
values of L, D, and U satisfy L ≤ D ≤ U. The result should be one of the (equal or adjacent) values
|
|
that would be obtained by correctly rounding L and U according to the current rounding direction,
|
|
with the extra stipulation that the error with respect to D should have a correct sign for the current
|
|
rounding direction.<a href='#FOOTNOTE.420'><sup>[420]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.420'>
|
|
<pre><i><b>Footnote 420)</b> M is sufficiently large that L and U will usually correctly round to the same internal floating value, but if not will correctly
|
|
round to adjacent values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.1.2p9'></a>
|
|
<pre>9 The functions return the converted value, if any. If no conversion could be performed, zero is
|
|
returned.
|
|
If the correct value overflows and default rounding is in effect (<a href='#7.12.1'>7.12.1</a>), plus or minus HUGE_VAL,
|
|
HUGE_VALF, or HUGE_VALL is returned (according to the return type and sign of the value); if the
|
|
integer expression math_errhandling & MATH_ERRNO is nonzero, the integer expression errno
|
|
acquires the value of ERANGE; if the integer expression math_errhandling & MATH_ERREXCEPT is
|
|
nonzero, the "overflow" floating-point exception is raised.
|
|
If the result underflows (<a href='#7.12.1'>7.12.1</a>), the functions return a value whose magnitude is no greater
|
|
than the smallest normalized positive number in the return type; if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the value ERANGE is
|
|
implementation-defined; if the integer expression math_errhandling & MATH_ERREXCEPT is
|
|
nonzero, whether the "underflow" floating-point exception is raised is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='7.31.4.1.3'></a>
|
|
<hr>
|
|
<h3>7.31.4.1.3 [The wcstodN functions]</h3>
|
|
<a name='7.31.4.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 wcstod32(const wchar_t * restrict nptr, char ** restrict endptr);
|
|
_Decimal64 wcstod64(const wchar_t * restrict nptr,char ** restrict endptr);
|
|
_Decimal128 wcstod128(const wchar_t * restrict nptr,char ** restrict endptr);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.1.3p2'></a>
|
|
<pre>2 The wcstodN functions convert the initial portion of the wide string pointed to by nptr to decimal
|
|
floating type representation. First, they decompose the input wide string into three parts: an initial,
|
|
possibly empty, sequence of white-space wide characters; a subject sequence resembling a floating
|
|
constant or representing an infinity or NaN; and a final wide string of one or more unrecognized
|
|
wide characters, including the terminating null wide character of the input wide string. Then, they
|
|
attempt to convert the subject sequence to a floating-point number, and return the result.
|
|
</pre>
|
|
<a name='7.31.4.1.3p3'></a>
|
|
<pre>3 The expected form of the subject sequence is an optional plus or minus sign, then one of the
|
|
following:
|
|
|
|
— a nonempty sequence of decimal digits optionally containing a decimal-point wide character,
|
|
then an optional exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</a>, excluding any digit separators (<a href='#6.4.4.1'>6.4.4.1</a>)
|
|
|
|
— INF or INFINITY, ignoring case
|
|
|
|
— NAN or NAN(d-wchar-sequenceopt ), ignoring case in the NAN part, where: d-wchar-
|
|
sequence:
|
|
digit
|
|
nondigit
|
|
d-wchar-sequence digit
|
|
d-wchar-sequence nondigit
|
|
The subject sequence is defined as the longest initial subsequence of the input wide string, starting
|
|
with the first non-white-space wide character, that is of the expected form. The subject sequence
|
|
contains no wide characters if the input wide string is not of the expected form.
|
|
</pre>
|
|
<a name='7.31.4.1.3p4'></a>
|
|
<pre>4 If the subject sequence has the expected form for a floating-point number, the sequence of wide
|
|
characters starting with the first digit or the decimal-point wide character (whichever occurs first) is
|
|
interpreted as a floating constant according to the rules of <a href='#6.4.4.2'>6.4.4.2</a>, including correct rounding and
|
|
determination of the coefficient c and the quantum exponent q, with the following exceptions:
|
|
|
|
— It is not a hexadecimal floating number.
|
|
— The decimal-point wide character is used in place of a period.
|
|
— If neither an exponent part nor a decimal-point wide character appears in a decimal floating-
|
|
point number, an exponent part of the appropriate type with value zero is assumed to follow
|
|
the last digit in the wide string.
|
|
|
|
If the subject sequence begins with a minus sign, the sequence is interpreted as negated (before
|
|
rounding) and the sign s is set to −1, else s is set to 1. A wide character sequence INF or INFINITY is
|
|
interpreted as an infinity. A wide character sequence NAN or NAN(d-wchar-sequenceopt ), is interpreted
|
|
as a quiet NaN; the meaning of the d-wchar sequence is implementation-defined.<a href='#FOOTNOTE.421'><sup>[421]</sup></a> A pointer to
|
|
the final wide string is stored in the object pointed to by endptr, provided that endptr is not a null
|
|
pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.421'>
|
|
<pre><i><b>Footnote 421)</b> An implementation may use the d-wchar sequence to determine extra information to be represented in the NaN’s
|
|
significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.1.3p5'></a>
|
|
<pre>5 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.31.4.1.3p6'></a>
|
|
<pre>6 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.1.3p7'></a>
|
|
<pre>7 The wcstodN functions return the correctly rounded converted value, if any. If no conversion could
|
|
be performed, the value of the triple (+1, 0, 0) is returned. If the correct value overflows:
|
|
|
|
— the value of the macro ERANGE is stored in errno if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero;
|
|
|
|
— the "overflow" floating-point exception is raised if the integer expression
|
|
math_errhandling & MATH_ERREXCEPT is nonzero.
|
|
|
|
If the result underflows (<a href='#7.12.1'>7.12.1</a>), whether errno acquires the value ERANGE if the integer expression
|
|
math_errhandling & MATH_ERRNO is nonzero is implementation-defined; if the integer expres-
|
|
sion math_errhandling & MATH_ERREXCEPT is nonzero, whether the "underflow" floating-point
|
|
exception is raised is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='7.31.4.1.4'></a>
|
|
<hr>
|
|
<h3>7.31.4.1.4 [The wcstol, wcstoll, wcstoul, and wcstoull functions]</h3>
|
|
<a name='7.31.4.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
long int wcstol(const wchar_t * restrict nptr, wchar_t ** restrict endptr,
|
|
int base);
|
|
long long int wcstoll(const wchar_t * restrict nptr, wchar_t ** restrict endptr,
|
|
int base);
|
|
unsigned long int wcstoul(const wchar_t * restrict nptr,
|
|
wchar_t ** restrict endptr, int base);
|
|
unsigned long long int wcstoull(const wchar_t * restrict nptr,
|
|
wchar_t ** restrict endptr, int base);
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.1.4p2'></a>
|
|
<pre>2 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial portion of the
|
|
wide string pointed to by nptr to long int, long long int, unsigned long int, and
|
|
unsigned long long int representation, respectively. First, they decompose the input string into
|
|
three parts: an initial, possibly empty, sequence of white-space wide characters, a subject sequence
|
|
resembling an integer represented in some radix determined by the value of base, and a final wide
|
|
string of one or more unrecognized wide characters, including the terminating null wide character
|
|
of the input wide string. Then, they attempt to convert the subject sequence to an integer, and return
|
|
the result.
|
|
</pre>
|
|
<a name='7.31.4.1.4p3'></a>
|
|
<pre>3 If the value of base is zero, the expected form of the subject sequence is that of an integer constant
|
|
as described for the corresponding single-byte characters in <a href='#6.4.4.1'>6.4.4.1</a>, optionally preceded by a plus or
|
|
minus sign, but not including an integer suffix or any optional digit separators (<a href='#6.4.4.1'>6.4.4.1</a>). If the value
|
|
of base is between 2 and 36 (inclusive), the expected form of the subject sequence is a sequence of
|
|
letters and digits representing an integer with the radix specified by base, optionally preceded by a
|
|
plus or minus sign, but not including an integer suffix or any optional digit separators. The letters
|
|
from a (or A) through z (or Z) are ascribed the values 10 through 35; only letters and digits whose
|
|
ascribed values are less than that of base are permitted. If the value of base is 2, the characters 0b or
|
|
0B may optionally precede the sequence of letters and digits, following the sign if present. If the
|
|
value of base is 16, the wide characters 0x or 0X may optionally precede the sequence of letters and
|
|
digits, following the sign if present.
|
|
</pre>
|
|
<a name='7.31.4.1.4p4'></a>
|
|
<pre>4 The subject sequence is defined as the longest initial subsequence of the input wide string, starting
|
|
with the first non-white-space wide character, that is of the expected form. The subject sequence
|
|
contains no wide characters if the input wide string is empty or consists entirely of white-space
|
|
wide characters, or if the first non-white-space wide character is other than a sign or a permissible
|
|
letter or digit.
|
|
</pre>
|
|
<a name='7.31.4.1.4p5'></a>
|
|
<pre>5 If the subject sequence has the expected form and the value of base is zero, the sequence of wide
|
|
characters starting with the first digit is interpreted as an integer constant according to the rules
|
|
of <a href='#6.4.4.1'>6.4.4.1</a>. If the subject sequence has the expected form and the value of base is between 2 and 36, it
|
|
is used as the base for conversion, ascribing to each letter its value as given above. If the subject
|
|
sequence begins with a minus sign, the value resulting from the conversion is negated (in the return
|
|
type). A pointer to the final wide string is stored in the object pointed to by endptr, provided that
|
|
endptr is not a null pointer.
|
|
</pre>
|
|
<a name='7.31.4.1.4p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be accepted.
|
|
</pre>
|
|
<a name='7.31.4.1.4p7'></a>
|
|
<pre>7 If the subject sequence is empty or does not have the expected form, no conversion is performed; the
|
|
value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.1.4p8'></a>
|
|
<pre>8 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted value, if any. If
|
|
no conversion could be performed, zero is returned. If the correct value is outside the range of
|
|
representable values, LONG_MIN, LONG_MAX, LLONG_MIN, LLONG_MAX, ULONG_MAX, or ULLONG_MAX is
|
|
returned (according to the return type sign of the value, if any), and the value of the macro ERANGE
|
|
is stored in errno.
|
|
|
|
</pre>
|
|
<a name='7.31.4.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.2 [Wide string copying functions]</h3>
|
|
<a name='7.31.4.2.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.2.1 [The wcscpy function]</h3>
|
|
<a name='7.31.4.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcscpy(wchar_t * restrict s1, const wchar_t * restrict s2);
|
|
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.2.1p2'></a>
|
|
<pre>2 The wcscpy function copies the wide string pointed to by s2 (including the terminating null wide
|
|
character) into the array pointed to by s1.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.2.1p3'></a>
|
|
<pre>3 The wcscpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.2.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.2.2 [The wcsncpy function]</h3>
|
|
<a name='7.31.4.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcsncpy(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.2.2p2'></a>
|
|
<pre>2 The wcsncpy function copies not more than n wide characters (those that follow a null wide character
|
|
are not copied) from the array pointed to by s2 to the array pointed to by s1.<a href='#FOOTNOTE.422'><sup>[422]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.422'>
|
|
<pre><i><b>Footnote 422)</b> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the result will not be
|
|
null-terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.2.2p3'></a>
|
|
<pre>3 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null wide
|
|
characters are appended to the copy in the array pointed to by s1, until n wide characters in all have
|
|
been written.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.2.2p4'></a>
|
|
<pre>4 The wcsncpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.2.3'></a>
|
|
<hr>
|
|
<h3>7.31.4.2.3 [The wmemcpy function]</h3>
|
|
<a name='7.31.4.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemcpy(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.2.3p2'></a>
|
|
<pre>2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the object pointed
|
|
to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.2.3p3'></a>
|
|
<pre>3 The wmemcpy function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.2.4'></a>
|
|
<hr>
|
|
<h3>7.31.4.2.4 [The wmemmove function]</h3>
|
|
<a name='7.31.4.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.2.4p2'></a>
|
|
<pre>2 The wmemmove function copies n wide characters from the object pointed to by s2 to the object
|
|
pointed to by s1. Copying takes place as if the n wide characters from the object pointed to by s2
|
|
are first copied into a temporary array of n wide characters that does not overlap the objects pointed
|
|
to by s1 or s2, and then the n wide characters from the temporary array are copied into the object
|
|
pointed to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.2.4p3'></a>
|
|
<pre>3 The wmemmove function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.3'></a>
|
|
<hr>
|
|
<h3>7.31.4.3 [Wide string concatenation functions]</h3>
|
|
<a name='7.31.4.3.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.3.1 [The wcscat function]</h3>
|
|
<a name='7.31.4.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcscat(wchar_t * restrict s1, const wchar_t * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.3.1p2'></a>
|
|
<pre>2 The wcscat function appends a copy of the wide string pointed to by s2 (including the terminating
|
|
null wide character) to the end of the wide string pointed to by s1. The initial wide character of s2
|
|
overwrites the null wide character at the end of s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.3.1p3'></a>
|
|
<pre>3 The wcscat function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.3.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.3.2 [The wcsncat function]</h3>
|
|
<a name='7.31.4.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcsncat(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.3.2p2'></a>
|
|
<pre>2 The wcsncat function appends not more than n wide characters (a null wide character and those
|
|
that follow it are not appended) from the array pointed to by s2 to the end of the wide string pointed
|
|
to by s1. The initial wide character of s2 overwrites the null wide character at the end of s1. A
|
|
terminating null wide character is always appended to the result.<a href='#FOOTNOTE.423'><sup>[423]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.423'>
|
|
<pre><i><b>Footnote 423)</b> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is wcslen(s1)+n+1 .
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.3.2p3'></a>
|
|
<pre>3 The wcsncat function returns the value of s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.4'></a>
|
|
<hr>
|
|
<h3>7.31.4.4 [Wide string comparison functions]</h3>
|
|
<a name='7.31.4.4p1'></a>
|
|
<pre>1 Unless explicitly stated otherwise, the functions described in this subclause order two wide charac-
|
|
ters the same way as two integers of the underlying integer type designated by wchar_t.
|
|
|
|
</pre>
|
|
<a name='7.31.4.4.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.4.1 [The wcscmp function]</h3>
|
|
<a name='7.31.4.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcscmp(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.4.1p2'></a>
|
|
<pre>2 The wcscmp function compares the wide string pointed to by s1 to the wide string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.4.1p3'></a>
|
|
<pre>3 The wcscmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
wide string pointed to by s1 is greater than, equal to, or less than the wide string pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.31.4.4.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.4.2 [The wcscoll function]</h3>
|
|
<a name='7.31.4.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcscoll(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.4.2p2'></a>
|
|
<pre>2 The wcscoll function compares the wide string pointed to by s1 to the wide string pointed to by
|
|
s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.4.2p3'></a>
|
|
<pre>3 The wcscoll function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
wide string pointed to by s1 is greater than, equal to, or less than the wide string pointed to by s2
|
|
when both are interpreted as appropriate to the current locale.
|
|
|
|
</pre>
|
|
<a name='7.31.4.4.3'></a>
|
|
<hr>
|
|
<h3>7.31.4.4.3 [The wcsncmp function]</h3>
|
|
<a name='7.31.4.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcsncmp(const wchar_t *s1, const wchar_t *s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.4.3p2'></a>
|
|
<pre>2 The wcsncmp function compares not more than n wide characters (those that follow a null wide
|
|
character are not compared) from the array pointed to by s1 to the array pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.4.3p3'></a>
|
|
<pre>3 The wcsncmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
possibly null-terminated array pointed to by s1 is greater than, equal to, or less than the possibly
|
|
null-terminated array pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.31.4.4.4'></a>
|
|
<hr>
|
|
<h3>7.31.4.4.4 [The wcsxfrm function]</h3>
|
|
<a name='7.31.4.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcsxfrm(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.4.4p2'></a>
|
|
<pre>2 The wcsxfrm function transforms the wide string pointed to by s2 and places the resulting wide
|
|
string into the array pointed to by s1. The transformation is such that if the wcscmp function is
|
|
applied to two transformed wide strings, it returns a value greater than, equal to, or less than zero,
|
|
corresponding to the result of the wcscoll function applied to the same two original wide strings.
|
|
No more than n wide characters are placed into the resulting array pointed to by s1, including the
|
|
terminating null wide character. If n is zero, s1 is permitted to be a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.4.4p3'></a>
|
|
<pre>3 The wcsxfrm function returns the length of the transformed wide string (not including the terminat-
|
|
ing null wide character). If the value returned is n or greater, the members of the array pointed to by
|
|
s1 have an indeterminate representation.
|
|
</pre>
|
|
<a name='7.31.4.4.4p4'></a>
|
|
<pre>4 EXAMPLE The value of the following expression is the length of the array needed to hold the transformation of the wide
|
|
string pointed to by s:
|
|
|
|
1 + wcsxfrm(NULL, s, 0)
|
|
|
|
|
|
</pre>
|
|
<a name='7.31.4.4.5'></a>
|
|
<hr>
|
|
<h3>7.31.4.4.5 [The wmemcmp function]</h3>
|
|
<a name='7.31.4.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wmemcmp(const wchar_t *s1, const wchar_t *s2, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.4.5p2'></a>
|
|
<pre>2 The wmemcmp function compares the first n wide characters of the object pointed to by s1 to the first
|
|
n wide characters of the object pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.4.5p3'></a>
|
|
<pre>3 The wmemcmp function returns an integer greater than, equal to, or less than zero, accordingly as the
|
|
object pointed to by s1 is greater than, equal to, or less than the object pointed to by s2.
|
|
|
|
</pre>
|
|
<a name='7.31.4.5'></a>
|
|
<hr>
|
|
<h3>7.31.4.5 [Wide string search functions]</h3>
|
|
<a name='7.31.4.6'></a>
|
|
<hr>
|
|
<h3>7.31.4.6 [Introduction]</h3>
|
|
<a name='7.31.4.6p1'></a>
|
|
<pre>1 The stateless search functions in this section (wcschr, wcspbrk, wcsrchr, wmemchr, wcsstr) are
|
|
generic functions. These functions are generic in the qualification of the array to be searched and
|
|
will return a result pointer to an element with the same qualification as the passed array. If the array
|
|
to be searched is const-qualified, the result pointer will be to a const-qualified element. If the array
|
|
to be searched is not const-qualified<a href='#FOOTNOTE.424'><sup>[424]</sup></a> , the result pointer will be to an unqualified element.
|
|
</pre>
|
|
<a name='FOOTNOTE.424'>
|
|
<pre><i><b>Footnote 424)</b> The null pointer constant is not a pointer to a const-qualified type, and therefore the result expression has the type of a
|
|
pointer to an unqualified element; however, evaluating such a call is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.6p2'></a>
|
|
<pre>2 The external declarations of these generic functions have a concrete function type that returns a
|
|
pointer to an unqualified element of type wchar_t (named QWchar_t), and accepts a pointer to a
|
|
const-qualified array of the same type to search. This signature supports all correct uses. If a macro
|
|
definition of any of these generic functions is suppressed in order to access an actual function, the
|
|
external declaration with this concrete type is visible<a href='#FOOTNOTE.425'><sup>[425]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.425'>
|
|
<pre><i><b>Footnote 425)</b> This is an obsolescent feature.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.4.6p3'></a>
|
|
<pre>3 The volatile and restrict qualifiers are not accepted on the elements of the array to search.
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.1 [The wcschr generic function]</h3>
|
|
<a name='7.31.4.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
QWchar_t *wcschr(QWchar_t *s, wchar_t c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.1p2'></a>
|
|
<pre>2 The wcschr generic function locates the first occurrence of c in the wide string pointed to by s. The
|
|
terminating null wide character is considered to be part of the wide string.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.1p3'></a>
|
|
<pre>3 The wcschr generic function returns a pointer to the located wide character, or a null pointer if the
|
|
wide character does not occur in the wide string.
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.2 [The wcscspn function]</h3>
|
|
<a name='7.31.4.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.2p2'></a>
|
|
<pre>2 The wcscspn function computes the length of the maximum initial segment of the wide string
|
|
pointed to by s1 which consists entirely of wide characters not from the wide string pointed to by
|
|
s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.2p3'></a>
|
|
<pre>3 The wcscspn function returns the length of the segment.
|
|
</pre>
|
|
<a name='7.31.4.6.3'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.3 [The wcspbrk generic function]</h3>
|
|
<a name='7.31.4.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
QWchar_t *wcspbrk(QWchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.3p2'></a>
|
|
<pre>2 The wcspbrk generic function locates the first occurrence in the wide string pointed to by s1 of any
|
|
wide character from the wide string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.3p3'></a>
|
|
<pre>3 The wcspbrk generic function returns a pointer to the wide character in s1, or a null pointer if no
|
|
wide character from s2 occurs in s1.
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.4'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.4 [The wcsrchr generic function]</h3>
|
|
<a name='7.31.4.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
QWchar_t *wcsrchr(const wchar_t *s, wchar_t c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.4p2'></a>
|
|
<pre>2 The wcsrchr generic function locates the last occurrence of c in the wide string pointed to by s. The
|
|
terminating null wide character is considered to be part of the wide string.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.4p3'></a>
|
|
<pre>3 The wcsrchr generic function returns a pointer to the wide character, or a null pointer if c does not
|
|
occur in the wide string.
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.5'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.5 [The wcsspn function]</h3>
|
|
<a name='7.31.4.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.5p2'></a>
|
|
<pre>2 The wcsspn function computes the length of the maximum initial segment of the wide string pointed
|
|
to by s1 which consists entirely of wide characters from the wide string pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.5p3'></a>
|
|
<pre>3 The wcsspn function returns the length of the segment.
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.6'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.6 [The wcsstr generic function]</h3>
|
|
<a name='7.31.4.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
QWchar_t *wcsstr(QWchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.6p2'></a>
|
|
<pre>2 The wcsstr generic function locates the first occurrence in the wide string pointed to by s1 of the
|
|
sequence of wide characters (excluding the terminating null wide character) in the wide string
|
|
pointed to by s2.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.6p3'></a>
|
|
<pre>3 The wcsstr generic function returns a pointer to the located wide string, or a null pointer if the
|
|
wide string is not found. If s2 points to a wide string with zero length, the function returns s1.
|
|
</pre>
|
|
<a name='7.31.4.6.7'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.7 [The wcstok function]</h3>
|
|
<a name='7.31.4.6.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcstok(wchar_t * restrict s1, const wchar_t * restrict s2,
|
|
wchar_t ** restrict ptr);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.7p2'></a>
|
|
<pre>2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into a sequence
|
|
of tokens, each of which is delimited by a wide character from the wide string pointed to by s2. The
|
|
third argument points to a caller-provided wchar_t pointer into which the wcstok function stores
|
|
information necessary for it to continue scanning the same wide string.
|
|
</pre>
|
|
<a name='7.31.4.6.7p3'></a>
|
|
<pre>3 The first call in a sequence has a non-null first argument and stores an initial value in the object
|
|
pointed to by ptr. Subsequent calls in the sequence have a null first argument and the object pointed
|
|
to by ptr is required to have the value stored by the previous call in the sequence, which is then
|
|
updated. The separator wide string pointed to by s2 may be different from call to call.
|
|
</pre>
|
|
<a name='7.31.4.6.7p4'></a>
|
|
<pre>4 The first call in the sequence searches the wide string pointed to by s1 for the first wide character
|
|
that is not contained in the current separator wide string pointed to by s2. If no such wide character
|
|
is found, then there are no tokens in the wide string pointed to by s1 and the wcstok function
|
|
returns a null pointer. If such a wide character is found, it is the start of the first token.
|
|
</pre>
|
|
<a name='7.31.4.6.7p5'></a>
|
|
<pre>5 The wcstok function then searches from there for a wide character that is contained in the current
|
|
separator wide string. If no such wide character is found, the current token extends to the end of the
|
|
wide string pointed to by s1, and subsequent searches in the same wide string for a token return
|
|
a null pointer. If such a wide character is found, it is overwritten by a null wide character, which
|
|
terminates the current token.
|
|
</pre>
|
|
<a name='7.31.4.6.7p6'></a>
|
|
<pre>6 In all cases, the wcstok function stores sufficient information in the pointer pointed to by ptr so
|
|
that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start
|
|
searching just past the element overwritten by a null wide character (if any).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.7p7'></a>
|
|
<pre>7 The wcstok function returns a pointer to the first wide character of a token, or a null pointer if there
|
|
is no token.
|
|
</pre>
|
|
<a name='7.31.4.6.7p8'></a>
|
|
<pre>8 EXAMPLE
|
|
|
|
#include <wchar.h>
|
|
static wchar_t str1[] = L"?a???b,,,#c";
|
|
static wchar_t str2[] = L"\t \t";
|
|
wchar_t *t, *ptr1, *ptr2;
|
|
|
|
t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
|
|
t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
|
|
t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
|
|
t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
|
|
t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='7.31.4.6.8'></a>
|
|
<hr>
|
|
<h3>7.31.4.6.8 [The wmemchr generic function]</h3>
|
|
<a name='7.31.4.6.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
QWchar_t *wmemchr(QWchar_t *s, wchar_t c, size_t n);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.6.8p2'></a>
|
|
<pre>2 The wmemchr generic function locates the first occurrence of c in the initial n wide characters of the
|
|
object pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.6.8p3'></a>
|
|
<pre>3 The wmemchr generic function returns a pointer to the located wide character, or a null pointer if the
|
|
wide character does not occur in the object.
|
|
|
|
</pre>
|
|
<a name='7.31.4.7'></a>
|
|
<hr>
|
|
<h3>7.31.4.7 [Miscellaneous functions]</h3>
|
|
<a name='7.31.4.7.1'></a>
|
|
<hr>
|
|
<h3>7.31.4.7.1 [The wcslen function]</h3>
|
|
<a name='7.31.4.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcslen(const wchar_t *s);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.7.1p2'></a>
|
|
<pre>2 The wcslen function computes the length of the wide string pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.7.1p3'></a>
|
|
<pre>3 The wcslen function returns the number of wide characters that precede the terminating null wide
|
|
character.
|
|
|
|
</pre>
|
|
<a name='7.31.4.7.2'></a>
|
|
<hr>
|
|
<h3>7.31.4.7.2 [The wmemset function]</h3>
|
|
<a name='7.31.4.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.4.7.2p2'></a>
|
|
<pre>2 The wmemset function copies the value of c into each of the first n wide characters of the object
|
|
pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.4.7.2p3'></a>
|
|
<pre>3 The wmemset function returns the value of s.
|
|
|
|
</pre>
|
|
<a name='7.31.5'></a>
|
|
<hr>
|
|
<h3>7.31.5 [Wide character time conversion functions]</h3>
|
|
<a name='7.31.5.1'></a>
|
|
<hr>
|
|
<h3>7.31.5.1 [The wcsftime function]</h3>
|
|
<a name='7.31.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
#include <wchar.h>
|
|
size_t wcsftime(wchar_t * restrict s, size_t maxsize,
|
|
const wchar_t * restrict format, const struct tm * restrict timeptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.5.1p2'></a>
|
|
<pre>2 The wcsftime function is equivalent to the strftime function, except that:
|
|
|
|
— The argument s points to the initial element of an array of wide characters into which the
|
|
generated output is to be placed.
|
|
— The argument maxsize indicates the limiting number of wide characters.
|
|
— The argument format is a wide string and the conversion specifiers are replaced by corre-
|
|
sponding sequences of wide characters.
|
|
— The return value indicates the number of wide characters.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.5.1p3'></a>
|
|
<pre>3 If the total number of resulting wide characters including the terminating null wide character is not
|
|
more than maxsize, the wcsftime function returns the number of wide characters placed into the
|
|
array pointed to by s not including the terminating null wide character. Otherwise, zero is returned
|
|
and the members of the array have an indeterminate representation.
|
|
</pre>
|
|
<a name='7.31.6'></a>
|
|
<hr>
|
|
<h3>7.31.6 [Extended multibyte/wide character conversion utilities]</h3>
|
|
<a name='7.31.6p1'></a>
|
|
<pre>1 The header <wchar.h> declares an extended set of functions useful for conversion between multibyte
|
|
characters and wide characters.
|
|
</pre>
|
|
<a name='7.31.6p2'></a>
|
|
<pre>2 Most of the following functions — those that are listed as "restartable", <a href='#7.31.6.3'>7.31.6.3</a> and <a href='#7.31.6.4'>7.31.6.4</a> — take
|
|
as a last argument a pointer to an object of type mbstate_t that is used to describe the current
|
|
conversion state from a particular multibyte character sequence to a wide character sequence (or the
|
|
reverse) under the rules of a particular setting for the LC_CTYPE category of the current locale.
|
|
</pre>
|
|
<a name='7.31.6p3'></a>
|
|
<pre>3 The initial conversion state corresponds, for a conversion in either direction, to the beginning of a
|
|
new multibyte character in the initial shift state. A zero-valued mbstate_t object is (at least) one
|
|
way to describe an initial conversion state. A zero-valued mbstate_t object can be used to initiate
|
|
conversion involving any multibyte character sequence, in any LC_CTYPE category setting. If an
|
|
mbstate_t object has been altered by any of the functions described in this subclause, and is then
|
|
used with a different multibyte character sequence, or in the other conversion direction, or with a
|
|
different LC_CTYPE category setting than on earlier function calls, the behavior is undefined.<a href='#FOOTNOTE.426'><sup>[426]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.426'>
|
|
<pre><i><b>Footnote 426)</b> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and mbsrtowcs functions as long
|
|
as they are used to step sequentially through the same multibyte character string.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.6p4'></a>
|
|
<pre>4 On entry, each function takes the described conversion state (either internal or pointed to by an
|
|
argument) as current. The conversion state described by the referenced object is altered as needed
|
|
to track the shift state, and the position within a multibyte character, for the associated multibyte
|
|
character sequence.
|
|
|
|
</pre>
|
|
<a name='7.31.6.1'></a>
|
|
<hr>
|
|
<h3>7.31.6.1 [Single-byte/wide character conversion functions]</h3>
|
|
<a name='7.31.6.1.1'></a>
|
|
<hr>
|
|
<h3>7.31.6.1.1 [The btowc function]</h3>
|
|
<a name='7.31.6.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t btowc(int c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.1.1p2'></a>
|
|
<pre>2 The btowc function determines whether c constitutes a valid single-byte character in the initial shift
|
|
state.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.1.1p3'></a>
|
|
<pre>3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c does not constitute
|
|
a valid single-byte character in the initial shift state. Otherwise, it returns the wide character
|
|
representation of that character.
|
|
|
|
</pre>
|
|
<a name='7.31.6.1.2'></a>
|
|
<hr>
|
|
<h3>7.31.6.1.2 [The wctob function]</h3>
|
|
<a name='7.31.6.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wctob(wint_t c);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.1.2p2'></a>
|
|
<pre>2 The wctob function determines whether c corresponds to a member of the extended character set
|
|
whose multibyte character representation is a single byte when in the initial shift state.
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.1.2p3'></a>
|
|
<pre>3 The wctob function returns EOF if c does not correspond to a multibyte character with length one
|
|
in the initial shift state. Otherwise, it returns the single-byte representation of that character as an
|
|
unsigned char converted to an int.
|
|
|
|
</pre>
|
|
<a name='7.31.6.2'></a>
|
|
<hr>
|
|
<h3>7.31.6.2 [Conversion state functions]</h3>
|
|
<a name='7.31.6.2.1'></a>
|
|
<hr>
|
|
<h3>7.31.6.2.1 [The mbsinit function]</h3>
|
|
<a name='7.31.6.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int mbsinit(const mbstate_t *ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.2.1p2'></a>
|
|
<pre>2 If ps is not a null pointer, the mbsinit function determines whether the referenced mbstate_t object
|
|
describes an initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.2.1p3'></a>
|
|
<pre>3 The mbsinit function returns nonzero if ps is a null pointer or if the referenced object describes an
|
|
initial conversion state; otherwise, it returns zero.
|
|
|
|
</pre>
|
|
<a name='7.31.6.3'></a>
|
|
<hr>
|
|
<h3>7.31.6.3 [Restartable multibyte/wide character conversion functions]</h3>
|
|
<a name='7.31.6.3p1'></a>
|
|
<pre>1 These functions differ from the corresponding multibyte character functions of <a href='#7.24.7'>7.24.7</a> (mblen, mbtowc,
|
|
and wctomb) in that they have an extra parameter, ps, of type pointer to mbstate_t that points
|
|
to an object that can completely describe the current conversion state of the associated multibyte
|
|
character sequence. If ps is a null pointer, each function uses its own internal mbstate_t object
|
|
instead, which is initialized prior to the first call to the function to the initial conversion state; the
|
|
functions are not required to avoid data races with other calls to the same function in this case. It
|
|
is implementation-defined whether the internal mbstate_t object has thread storage duration; if
|
|
it has thread storage duration, it is initialized to the initial conversion state prior to the first call to
|
|
the function on the new thread. The implementation behaves as if no library function calls these
|
|
functions with a null pointer for ps.
|
|
</pre>
|
|
<a name='7.31.6.3p2'></a>
|
|
<pre>2 Also unlike their corresponding functions, the return value does not represent whether the encoding
|
|
is state-dependent.
|
|
|
|
</pre>
|
|
<a name='7.31.6.3.1'></a>
|
|
<hr>
|
|
<h3>7.31.6.3.1 [The mbrlen function]</h3>
|
|
<a name='7.31.6.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t mbrlen(const char * restrict s, size_t n, mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.3.1p2'></a>
|
|
<pre>2 The mbrlen function is equivalent to the call:
|
|
|
|
mbrtowc(NULL, s, n, ps != NULL ? ps: &internal)
|
|
|
|
|
|
where internal is the mbstate_t object for the mbrlen function, except that the expression desig-
|
|
nated by ps is evaluated only once.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.3.1p3'></a>
|
|
<pre>3 The mbrlen function returns a value between zero and n, inclusive, (size_t) (−2), or (size_t) (−1).
|
|
Forward references: the mbrtowc function (<a href='#7.31.6.3.2'>7.31.6.3.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.31.6.3.2'></a>
|
|
<hr>
|
|
<h3>7.31.6.3.2 [The mbrtowc function]</h3>
|
|
<a name='7.31.6.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t mbrtowc(wchar_t * restrict pwc, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.3.2p2'></a>
|
|
<pre>2 If s is a null pointer, the mbrtowc function is equivalent to the call:
|
|
|
|
mbrtowc(NULL, "", 1, ps)
|
|
|
|
|
|
In this case, the values of the parameters pwc and n are ignored.
|
|
</pre>
|
|
<a name='7.31.6.3.2p3'></a>
|
|
<pre>3 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with the byte
|
|
pointed to by s to determine the number of bytes needed to complete the next multibyte character
|
|
(including any shift sequences). If the function determines that the next multibyte character is
|
|
complete and valid, it determines the value of the corresponding wide character and then, if pwc
|
|
is not a null pointer, stores that value in the object pointed to by pwc. If the corresponding wide
|
|
character is the null wide character, the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.3.2p4'></a>
|
|
<pre>4 The mbrtowc function returns the first of the following that applies (given the current conversion
|
|
state):
|
|
|
|
0 if the next n or fewer bytes complete the multibyte character that corresponds to
|
|
the null wide character (which is the value stored).
|
|
between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte character (which
|
|
is the value stored); the value returned is the number of bytes that complete the
|
|
multibyte character.
|
|
(size_t) (−2) if the next n bytes contribute to an incomplete (but potentially valid) multibyte
|
|
character, and all n bytes have been processed (no value is stored).<a href='#FOOTNOTE.427'><sup>[427]</sup></a>
|
|
(size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes do not contribute
|
|
to a complete and valid multibyte character (no value is stored); the value of the
|
|
macro EILSEQ is stored in errno, and the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.427'>
|
|
<pre><i><b>Footnote 427)</b> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a sequence of redundant
|
|
shift sequences (for implementations with state-dependent encodings).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.6.3.3'></a>
|
|
<hr>
|
|
<h3>7.31.6.3.3 [The wcrtomb function]</h3>
|
|
<a name='7.31.6.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcrtomb(char * restrict s, wchar_t wc, mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.3.3p2'></a>
|
|
<pre>2 If s is a null pointer, the wcrtomb function is equivalent to the call
|
|
|
|
wcrtomb(buf, L’\0’, ps)
|
|
|
|
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.31.6.3.3p3'></a>
|
|
<pre>3 If s is not a null pointer, the wcrtomb function determines the number of bytes needed to represent
|
|
the multibyte character that corresponds to the wide character given by wc (including any shift
|
|
sequences), and stores the multibyte character representation in the array whose first element is
|
|
pointed to by s. At most MB_CUR_MAX bytes are stored. If wc is a null wide character, a null byte is
|
|
stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state
|
|
described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.3.3p4'></a>
|
|
<pre>4 The wcrtomb function returns the number of bytes stored in the array object (including any shift
|
|
sequences). When wc is not a valid wide character, an encoding error occurs: the function stores the
|
|
value of the macro EILSEQ in errno and returns (size_t) (−1); the conversion state is unspecified.
|
|
|
|
</pre>
|
|
<a name='7.31.6.4'></a>
|
|
<hr>
|
|
<h3>7.31.6.4 [Restartable multibyte/wide string conversion functions]</h3>
|
|
<a name='7.31.6.4p1'></a>
|
|
<pre>1 These functions differ from the corresponding multibyte string functions of <a href='#7.24.8'>7.24.8</a> (mbstowcs and
|
|
wcstombs) in that they have an extra parameter, ps, of type pointer to mbstate_t that points to
|
|
an object that can completely describe the current conversion state of the associated multibyte
|
|
character sequence. If ps is a null pointer, each function uses its own internal mbstate_t object
|
|
instead, which is initialized prior to the first call to the function to the initial conversion state; the
|
|
functions are not required to avoid data races with other calls to the same function in this case. It
|
|
is implementation-defined whether the internal mbstate_t object has thread storage duration; if
|
|
it has thread storage duration, it is initialized to the initial conversion state prior to the first call to
|
|
the function on the new thread. The implementation behaves as if no library function calls these
|
|
functions with a null pointer for ps.
|
|
</pre>
|
|
<a name='7.31.6.4p2'></a>
|
|
<pre>2 Also unlike their corresponding functions, the conversion source parameter, src, has a pointer-to-
|
|
pointer type. When the function is storing the results of conversions (that is, when dst is not a null
|
|
pointer), the pointer object pointed to by this parameter is updated to reflect the amount of the
|
|
source processed by that invocation.
|
|
|
|
</pre>
|
|
<a name='7.31.6.4.1'></a>
|
|
<hr>
|
|
<h3>7.31.6.4.1 [The mbsrtowcs function]</h3>
|
|
<a name='7.31.6.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t mbsrtowcs(wchar_t * restrict dst, const char ** restrict src, size_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.4.1p2'></a>
|
|
<pre>2 The mbsrtowcs function converts a sequence of multibyte characters that begins in the conversion
|
|
state described by the object pointed to by ps, from the array indirectly pointed to by src into a
|
|
sequence of corresponding wide characters. If dst is not a null pointer, the converted characters are
|
|
stored into the array pointed to by dst. Conversion continues up to and including a terminating
|
|
null character, which is also stored. Conversion stops earlier in two cases: when a sequence of bytes
|
|
is encountered that does not form a valid multibyte character, or (if dst is not a null pointer) when
|
|
len wide characters have been stored into the array pointed to by dst.<a href='#FOOTNOTE.428'><sup>[428]</sup></a> Each conversion takes
|
|
place as if by a call to the mbrtowc function.
|
|
</pre>
|
|
<a name='FOOTNOTE.428'>
|
|
<pre><i><b>Footnote 428)</b> Thus, the value of len is ignored if dst is a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.6.4.1p3'></a>
|
|
<pre>3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if
|
|
conversion stopped due to reaching a terminating null character) or the address just past the last
|
|
multibyte character converted (if any). If conversion stopped due to reaching a terminating null
|
|
character and if dst is not a null pointer, the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.4.1p4'></a>
|
|
<pre>4 If the input conversion encounters a sequence of bytes that do not form a valid multibyte character,
|
|
an encoding error occurs: the mbsrtowcs function stores the value of the macro EILSEQ in errno
|
|
and returns (size_t)(-1) ; the conversion state is unspecified. Otherwise, it returns the number of
|
|
multibyte characters successfully converted, not including the terminating null character (if any).
|
|
|
|
</pre>
|
|
<a name='7.31.6.4.2'></a>
|
|
<hr>
|
|
<h3>7.31.6.4.2 [The wcsrtombs function]</h3>
|
|
<a name='7.31.6.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcsrtombs(char * restrict dst, const wchar_t ** restrict src, size_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.31.6.4.2p2'></a>
|
|
<pre>2 The wcsrtombs function converts a sequence of wide characters from the array indirectly pointed to
|
|
by src into a sequence of corresponding multibyte characters that begins in the conversion state
|
|
described by the object pointed to by ps. If dst is not a null pointer, the converted characters are then
|
|
stored into the array pointed to by dst. Conversion continues up to and including a terminating null
|
|
wide character, which is also stored. Conversion stops earlier in two cases: when a wide character
|
|
is reached that does not correspond to a valid multibyte character, or (if dst is not a null pointer)
|
|
when the next multibyte character would exceed the limit of len total bytes to be stored into the
|
|
array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb function.<a href='#FOOTNOTE.429'><sup>[429]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.429'>
|
|
<pre><i><b>Footnote 429)</b> If conversion stops because a terminating null wide character has been reached, the bytes stored include those necessary
|
|
to reach the initial shift state immediately before the null byte.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.31.6.4.2p3'></a>
|
|
<pre>3 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if
|
|
conversion stopped due to reaching a terminating null wide character) or the address just past the
|
|
last wide character converted (if any). If conversion stopped due to reaching a terminating null wide
|
|
character, the resulting state described is the initial conversion state.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.31.6.4.2p4'></a>
|
|
<pre>4 If conversion stops because a wide character is reached that does not correspond to a valid multibyte
|
|
character, an encoding error occurs: the wcsrtombs function stores the value of the macro EILSEQ
|
|
in errno and returns (size_t) (−1); the conversion state is unspecified. Otherwise, it returns the
|
|
number of bytes in the resulting multibyte character sequence, not including the terminating null
|
|
character (if any).
|
|
</pre>
|
|
<a name='7.32'></a>
|
|
<hr>
|
|
<h3>7.32 [Wide character classification and mapping utilities <wctype.h>]</h3>
|
|
<a name='7.32.1'></a>
|
|
<hr>
|
|
<h3>7.32.1 [Introduction]</h3>
|
|
<a name='7.32.1p1'></a>
|
|
<pre>1 The header <wctype.h> defines one macro, and declares three data types and many functions.<a href='#FOOTNOTE.430'><sup>[430]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.430'>
|
|
<pre><i><b>Footnote 430)</b> See "future library directions" (<a href='#7.33.21'>7.33.21</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.32.1p2'></a>
|
|
<pre>2 The types declared are wint_t described in <a href='#7.31.1'>7.31.1</a>;
|
|
|
|
wctrans_t
|
|
|
|
|
|
which is a scalar type that can hold values which represent locale-specific character mappings; and
|
|
|
|
wctype_t
|
|
|
|
|
|
which is a scalar type that can hold values which represent locale-specific character classifications.
|
|
</pre>
|
|
<a name='7.32.1p3'></a>
|
|
<pre>3 The macro defined is WEOF (described in <a href='#7.31.1'>7.31.1</a>).
|
|
</pre>
|
|
<a name='7.32.1p4'></a>
|
|
<pre>4 The functions declared are grouped as follows:
|
|
|
|
— Functions that provide wide character classification;
|
|
— Extensible functions that provide wide character classification;
|
|
|
|
— Functions that provide wide character case mapping;
|
|
— Extensible functions that provide wide character mapping.
|
|
|
|
</pre>
|
|
<a name='7.32.1p5'></a>
|
|
<pre>5 For all functions described in this subclause that accept an argument of type wint_t, the value shall
|
|
be representable as a wchar_t or shall equal the value of the macro WEOF. If this argument has any
|
|
other value, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.32.1p6'></a>
|
|
<pre>6 The behavior of these functions is affected by the LC_CTYPE category of the current locale.
|
|
|
|
</pre>
|
|
<a name='7.32.2'></a>
|
|
<hr>
|
|
<h3>7.32.2 [Wide character classification utilities]</h3>
|
|
<a name='7.32.2p1'></a>
|
|
<pre>1 The header <wctype.h> declares several functions useful for classifying wide characters.
|
|
</pre>
|
|
<a name='7.32.2p2'></a>
|
|
<pre>2 The term printing wide character refers to a member of a locale-specific set of wide characters, each of
|
|
which occupies at least one printing position on a display device. The term control wide character
|
|
refers to a member of a locale-specific set of wide characters that are not printing wide characters.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1'></a>
|
|
<hr>
|
|
<h3>7.32.2.1 [Wide character classification functions]</h3>
|
|
<a name='7.32.2.1p1'></a>
|
|
<pre>1 The functions in this subclause return nonzero (true) if and only if the value of the argument wc
|
|
conforms to that in the description of the function.
|
|
</pre>
|
|
<a name='7.32.2.1p2'></a>
|
|
<pre>2 Each of the following functions returns true for each wide character that corresponds (as if by a call
|
|
to the wctob function) to a single-byte character for which the corresponding character classification
|
|
function from <a href='#7.4.1'>7.4.1</a> returns true, except that the iswgraph and iswpunct functions may differ with
|
|
respect to wide characters other than L’ ’ that are both printing and white-space wide characters.<a href='#FOOTNOTE.431'><sup>[431]</sup></a>
|
|
Forward references: the wctob function (<a href='#7.31.6.1.2'>7.31.6.1.2</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.431'>
|
|
<pre><i><b>Footnote 431)</b> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call iswalpha(wc) also returns true.
|
|
But, if the expression isgraph(wctob(wc)) evaluates to true (which cannot occur for wc == L’’ of course), then either
|
|
iswgraph(wc) or iswprint(wc)&& iswspace(wc) is true, but not both.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.32.2.1.1'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.1 [The iswalnum function]</h3>
|
|
<a name='7.32.2.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswalnum(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.1p2'></a>
|
|
<pre>2 The iswalnum function tests for any wide character for which iswalpha or iswdigit is true.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.2'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.2 [The iswalpha function]</h3>
|
|
<a name='7.32.2.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswalpha(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.2p2'></a>
|
|
<pre>2 The iswalpha function tests for any wide character for which iswupper or iswlower is true, or any
|
|
wide character that is one of a locale-specific set of alphabetic wide characters for which none of
|
|
iswcntrl, iswdigit, iswpunct, or iswspace is true.<a href='#FOOTNOTE.432'><sup>[432]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.432'>
|
|
<pre><i><b>Footnote 432)</b> The functions iswlower and iswupper test true or false separately for each of these additional wide characters; all four
|
|
combinations are possible.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.32.2.1.3'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.3 [The iswblank function]</h3>
|
|
<a name='7.32.2.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswblank(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.3p2'></a>
|
|
<pre>2 The iswblank function tests for any wide character that is a standard blank wide character or is one
|
|
of a locale-specific set of wide characters for which iswspace is true and that is used to separate
|
|
words within a line of text. The standard blank wide characters are the following: space (L’ ’),
|
|
and horizontal tab (L’\t’). In the "C" locale, iswblank returns true only for the standard blank
|
|
characters.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.4'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.4 [The iswcntrl function]</h3>
|
|
<a name='7.32.2.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswcntrl(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.4p2'></a>
|
|
<pre>2 The iswcntrl function tests for any control wide character.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.5'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.5 [The iswdigit function]</h3>
|
|
<a name='7.32.2.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswdigit(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.5p2'></a>
|
|
<pre>2 The iswdigit function tests for any wide character that corresponds to a decimal-digit character (as
|
|
defined in <a href='#5.2.1'>5.2.1</a>).
|
|
</pre>
|
|
<a name='7.32.2.1.6'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.6 [The iswgraph function]</h3>
|
|
<a name='7.32.2.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswgraph(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.6p2'></a>
|
|
<pre>2 The iswgraph function tests for any wide character for which iswprint is true and iswspace is
|
|
false.<a href='#FOOTNOTE.433'><sup>[433]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.433'>
|
|
<pre><i><b>Footnote 433)</b> Note that the behavior of the iswgraph and iswpunct functions can differ from their corresponding functions in <a href='#7.4.1'>7.4.1</a>
|
|
with respect to printing, white-space, single-byte execution characters other than ’ ’ .
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.32.2.1.7'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.7 [The iswlower function]</h3>
|
|
<a name='7.32.2.1.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswlower(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.7p2'></a>
|
|
<pre>2 The iswlower function tests for any wide character that corresponds to a lowercase letter or is one
|
|
of a locale-specific set of wide characters for which none of iswcntrl, iswdigit, iswpunct, or
|
|
iswspace is true.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.8'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.8 [The iswprint function]</h3>
|
|
<a name='7.32.2.1.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswprint(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.8p2'></a>
|
|
<pre>2 The iswprint function tests for any printing wide character.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.9'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.9 [The iswpunct function]</h3>
|
|
<a name='7.32.2.1.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswpunct(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.9p2'></a>
|
|
<pre>2 The iswpunct function tests for any printing wide character that is one of a locale-specific set of
|
|
punctuation wide characters for which neither iswspace nor iswalnum is true.<a href='#FOOTNOTE.433'><sup>[433]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.433'>
|
|
<pre><i><b>Footnote 433)</b> Note that the behavior of the iswgraph and iswpunct functions can differ from their corresponding functions in <a href='#7.4.1'>7.4.1</a>
|
|
with respect to printing, white-space, single-byte execution characters other than ’ ’ .
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.32.2.1.10'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.10 [The iswspace function]</h3>
|
|
<a name='7.32.2.1.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswspace(wint_t wc);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.10p2'></a>
|
|
<pre>2 The iswspace function tests for any wide character that corresponds to a locale-specific set of
|
|
white-space wide characters for which none of iswalnum, iswgraph, or iswpunct is true.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.11'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.11 [The iswupper function]</h3>
|
|
<a name='7.32.2.1.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswupper(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.11p2'></a>
|
|
<pre>2 The iswupper function tests for any wide character that corresponds to an uppercase letter or is
|
|
one of a locale-specific set of wide characters for which none of iswcntrl, iswdigit, iswpunct, or
|
|
iswspace is true.
|
|
|
|
</pre>
|
|
<a name='7.32.2.1.12'></a>
|
|
<hr>
|
|
<h3>7.32.2.1.12 [The iswxdigit function]</h3>
|
|
<a name='7.32.2.1.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswxdigit(wint_t wc);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.1.12p2'></a>
|
|
<pre>2 The iswxdigit function tests for any wide character that corresponds to a hexadecimal-digit
|
|
character (as defined in <a href='#6.4.4.1'>6.4.4.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.32.2.2'></a>
|
|
<hr>
|
|
<h3>7.32.2.2 [Extensible wide character classification functions]</h3>
|
|
<a name='7.32.2.2p1'></a>
|
|
<pre>1 The functions wctype and iswctype provide extensible wide character classification as well as
|
|
testing equivalent to that performed by the functions described in the previous subclause (<a href='#7.32.2.1'>7.32.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.32.2.2.1'></a>
|
|
<hr>
|
|
<h3>7.32.2.2.1 [The iswctype function]</h3>
|
|
<a name='7.32.2.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswctype(wint_t wc, wctype_t desc);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.2.1p2'></a>
|
|
<pre>2 The iswctype function determines whether the wide character wc has the property described by
|
|
desc. The current setting of the LC_CTYPE category shall be the same as during the call to wctype
|
|
that returned the value desc.
|
|
</pre>
|
|
<a name='7.32.2.2.1p3'></a>
|
|
<pre>3 Each of the following expressions has a truth-value equivalent to the call to the wide character
|
|
classification function (<a href='#7.32.2.1'>7.32.2.1</a>) in the comment that follows the expression:
|
|
|
|
iswctype(wc, wctype("alnum")) // iswalnum(wc)
|
|
iswctype(wc, wctype("alpha")) // iswalpha(wc)
|
|
iswctype(wc, wctype("blank")) // iswblank(wc)
|
|
iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
|
|
iswctype(wc, wctype("digit")) // iswdigit(wc)
|
|
iswctype(wc, wctype("graph")) // iswgraph(wc)
|
|
iswctype(wc, wctype("lower")) // iswlower(wc)
|
|
iswctype(wc, wctype("print")) // iswprint(wc)
|
|
iswctype(wc, wctype("punct")) // iswpunct(wc)
|
|
iswctype(wc, wctype("space")) // iswspace(wc)
|
|
iswctype(wc, wctype("upper")) // iswupper(wc)
|
|
iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
|
|
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.2.2.1p4'></a>
|
|
<pre>4 The iswctype function returns nonzero (true) if and only if the value of the wide character wc has
|
|
the property described by desc. If desc is zero, the iswctype function returns zero (false).
|
|
Forward references: the wctype function (<a href='#7.32.2.2.2'>7.32.2.2.2</a>).
|
|
|
|
</pre>
|
|
<a name='7.32.2.2.2'></a>
|
|
<hr>
|
|
<h3>7.32.2.2.2 [The wctype function]</h3>
|
|
<a name='7.32.2.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wctype_t wctype(const char *property);
|
|
Description
|
|
</pre>
|
|
<a name='7.32.2.2.2p2'></a>
|
|
<pre>2 The wctype function constructs a value with type wctype_t that describes a class of wide characters
|
|
identified by the string argument property.
|
|
</pre>
|
|
<a name='7.32.2.2.2p3'></a>
|
|
<pre>3 The strings listed in the description of the iswctype function shall be valid in all locales as property
|
|
arguments to the wctype function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.2.2.2p4'></a>
|
|
<pre>4 If property identifies a valid class of wide characters according to the LC_CTYPE category of the
|
|
current locale, the wctype function returns a nonzero value that is valid as the second argument to
|
|
the iswctype function; otherwise, it returns zero.
|
|
|
|
</pre>
|
|
<a name='7.32.3'></a>
|
|
<hr>
|
|
<h3>7.32.3 [Wide character case mapping utilities]</h3>
|
|
<a name='7.32.3p1'></a>
|
|
<pre>1 The header <wctype.h> declares several functions useful for mapping wide characters.
|
|
|
|
</pre>
|
|
<a name='7.32.3.1'></a>
|
|
<hr>
|
|
<h3>7.32.3.1 [Wide character case mapping functions]</h3>
|
|
<a name='7.32.3.1.1'></a>
|
|
<hr>
|
|
<h3>7.32.3.1.1 [The towlower function]</h3>
|
|
<a name='7.32.3.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towlower(wint_t wc);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.3.1.1p2'></a>
|
|
<pre>2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.3.1.1p3'></a>
|
|
<pre>3 If the argument is a wide character for which iswupper is true and there are one or more correspond-
|
|
ing wide characters, as specified by the current locale, for which iswlower is true, the towlower
|
|
function returns one of the corresponding wide characters (always the same one for any given
|
|
locale); otherwise, the argument is returned unchanged.
|
|
|
|
</pre>
|
|
<a name='7.32.3.1.2'></a>
|
|
<hr>
|
|
<h3>7.32.3.1.2 [The towupper function]</h3>
|
|
<a name='7.32.3.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towupper(wint_t wc);
|
|
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.3.1.2p2'></a>
|
|
<pre>2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.3.1.2p3'></a>
|
|
<pre>3 If the argument is a wide character for which iswlower is true and there are one or more correspond-
|
|
ing wide characters, as specified by the current locale, for which iswupper is true, the towupper
|
|
function returns one of the corresponding wide characters (always the same one for any given
|
|
locale); otherwise, the argument is returned unchanged.
|
|
|
|
</pre>
|
|
<a name='7.32.3.2'></a>
|
|
<hr>
|
|
<h3>7.32.3.2 [Extensible wide character case mapping functions]</h3>
|
|
<a name='7.32.3.2p1'></a>
|
|
<pre>1 The functions wctrans and towctrans provide extensible wide character mapping as well as case
|
|
mapping equivalent to that performed by the functions described in the previous subclause (<a href='#7.32.3.1'>7.32.3.1</a>).
|
|
|
|
</pre>
|
|
<a name='7.32.3.2.1'></a>
|
|
<hr>
|
|
<h3>7.32.3.2.1 [The towctrans function]</h3>
|
|
<a name='7.32.3.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towctrans(wint_t wc, wctrans_t desc);
|
|
Description
|
|
</pre>
|
|
<a name='7.32.3.2.1p2'></a>
|
|
<pre>2 The towctrans function maps the wide character wc using the mapping described by desc. The
|
|
current setting of the LC_CTYPE category shall be the same as during the call to wctrans that returned
|
|
the value desc.
|
|
</pre>
|
|
<a name='7.32.3.2.1p3'></a>
|
|
<pre>3 Each of the following expressions behaves the same as the call to the wide character case mapping
|
|
function (<a href='#7.32.3.1'>7.32.3.1</a>) in the comment that follows the expression:
|
|
|
|
towctrans(wc, wctrans("tolower")) // towlower(wc)
|
|
towctrans(wc, wctrans("toupper")) // towupper(wc)
|
|
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.3.2.1p4'></a>
|
|
<pre>4 The towctrans function returns the mapped value of wc using the mapping described by desc. If
|
|
desc is zero, the towctrans function returns the value of wc .
|
|
|
|
</pre>
|
|
<a name='7.32.3.2.2'></a>
|
|
<hr>
|
|
<h3>7.32.3.2.2 [The wctrans function]</h3>
|
|
<a name='7.32.3.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wctrans_t wctrans(const char *property);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='7.32.3.2.2p2'></a>
|
|
<pre>2 The wctrans function constructs a value with type wctrans_t that describes a mapping between
|
|
wide characters identified by the string argument property.
|
|
</pre>
|
|
<a name='7.32.3.2.2p3'></a>
|
|
<pre>3 The strings listed in the description of the towctrans function shall be valid in all locales as
|
|
property arguments to the wctrans function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='7.32.3.2.2p4'></a>
|
|
<pre>4 If property identifies a valid mapping of wide characters according to the LC_CTYPE category of the
|
|
current locale, the wctrans function returns a nonzero value that is valid as the second argument to
|
|
the towctrans function; otherwise, it returns zero.
|
|
</pre>
|
|
<a name='7.33'></a>
|
|
<hr>
|
|
<h3>7.33 [Future library directions]</h3>
|
|
<a name='7.33p1'></a>
|
|
<pre>1 Although grouped under individual headers, all of the external names identified as reserved
|
|
identifiers or potentially reserved identifiers in this subclause remain so regardless of which headers
|
|
are included in the program.
|
|
|
|
</pre>
|
|
<a name='7.33.1'></a>
|
|
<hr>
|
|
<h3>7.33.1 [Complex arithmetic <complex.h>]</h3>
|
|
<a name='7.33.1p1'></a>
|
|
<pre>1 The function names
|
|
|
|
cacospi cexp10m1 clog10 crootn
|
|
casinpi cexp10 clog1p crsqrt
|
|
catanpi cexp2m1 clog2p1 csinpi
|
|
ccompoundn cexp2 clog2 ctanpi
|
|
ccospi cexpm1 clogp1 ctgamma
|
|
cerfc clgamma cpown
|
|
cerf clog10p1 cpowr
|
|
|
|
|
|
and the same names suffixed with f or l are potentially reserved identifiers and may be added to
|
|
the declarations in the <complex.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.2'></a>
|
|
<hr>
|
|
<h3>7.33.2 [Character handling <ctype.h>]</h3>
|
|
<a name='7.33.2p1'></a>
|
|
<pre>1 Function names that begin with either is or to, and a lowercase letter are potentially reserved
|
|
identifiers and may be added to the declarations in the <ctype.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.3'></a>
|
|
<hr>
|
|
<h3>7.33.3 [Errors <errno.h>]</h3>
|
|
<a name='7.33.3p1'></a>
|
|
<pre>1 Macros that begin with E and a digit or E and an uppercase letter may be added to the macros
|
|
defined in the <errno.h> header by a future revision of this document or by an implementation.
|
|
|
|
</pre>
|
|
<a name='7.33.4'></a>
|
|
<hr>
|
|
<h3>7.33.4 [Floating-point environment <fenv.h>]</h3>
|
|
<a name='7.33.4p1'></a>
|
|
<pre>1 Macros that begin with FE_ and an uppercase letter may be added to the macros defined in the
|
|
<fenv.h> header by a future revision of this document.
|
|
|
|
</pre>
|
|
<a name='7.33.5'></a>
|
|
<hr>
|
|
<h3>7.33.5 [Characteristics of floating types <float.h>]</h3>
|
|
<a name='7.33.5p1'></a>
|
|
<pre>1 Macros that begin with DBL_, DEC32_, DEC64_, DEC128_, DEC_, FLT_, or LDBL_ and an uppercase
|
|
letter are potentially reserved identifiers and may be added to the macros defined in the <float.h>
|
|
header.
|
|
</pre>
|
|
<a name='7.33.5p2'></a>
|
|
<pre>2 Use of the DECIMAL_DIG macro is an obsolescent feature. A similar type-specific macro, such as
|
|
LDBL_DECIMAL_DIG, can be used instead.
|
|
</pre>
|
|
<a name='7.33.5p3'></a>
|
|
<pre>3 The use of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and LDBL_HAS_SUBNORM macros is an obsolescent
|
|
feature.
|
|
|
|
</pre>
|
|
<a name='7.33.6'></a>
|
|
<hr>
|
|
<h3>7.33.6 [Format conversion of integer types <inttypes.h>]</h3>
|
|
<a name='7.33.6p1'></a>
|
|
<pre>1 Macros that begin with either PRI or SCN, and either a lowercase letter or X are potentially reserved
|
|
identifiers and may be added to the macros defined in the <inttypes.h> header.
|
|
</pre>
|
|
<a name='7.33.6p2'></a>
|
|
<pre>2 Function names that begin with str, or wcs and a lowercase letter are potentially reserved identifiers
|
|
may be added to the declarations in the <inttypes.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.7'></a>
|
|
<hr>
|
|
<h3>7.33.7 [Localization <locale.h>]</h3>
|
|
<a name='7.33.7p1'></a>
|
|
<pre>1 Macros that begin with LC_ and an uppercase letter may be added to the macros defined in the
|
|
<locale.h> header by a future revision of this document or by an implementation.
|
|
|
|
</pre>
|
|
<a name='7.33.8'></a>
|
|
<hr>
|
|
<h3>7.33.8 [Mathematics <math.h>]</h3>
|
|
<a name='7.33.8p1'></a>
|
|
<pre>1 Macros that begin with FP_ or MATH_ and an uppercase letter may be added to the macros defined
|
|
in the <math.h> header by a future revision of this document or by an implementation.
|
|
</pre>
|
|
<a name='7.33.8p2'></a>
|
|
<pre>2 Macros that begin with MATH_ and an uppercase letter are potentially reserved identifiers and may
|
|
be added to the macros in the <math.h> header.
|
|
</pre>
|
|
<a name='7.33.8p3'></a>
|
|
<pre>3 Function names that begin with is and a lowercase letter are potentially reserved identifiers and
|
|
may be added to the declarations in the <math.h> header.
|
|
</pre>
|
|
<a name='7.33.8p4'></a>
|
|
<pre>4 Function names that begin with cr_ are potentially reserved identifiers and may be added to the
|
|
<math.h> header. The cr_ prefix is intended to indicate a correctly rounded version of the function.
|
|
</pre>
|
|
<a name='7.33.8p5'></a>
|
|
<pre>5 Use of the macros INFINITY, DEC_INFINITY, NAN, and DEC_NAN in <math.h> is an obsolescent
|
|
feature. Instead, use the same macros in <float.h>.
|
|
|
|
</pre>
|
|
<a name='7.33.9'></a>
|
|
<hr>
|
|
<h3>7.33.9 [Signal handling <signal.h>]</h3>
|
|
<a name='7.33.9p1'></a>
|
|
<pre>1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase letter may be
|
|
added to the macros defined in the <signal.h> header by a fture revision of this document or by an
|
|
implementation.
|
|
|
|
</pre>
|
|
<a name='7.33.10'></a>
|
|
<hr>
|
|
<h3>7.33.10 [Atomics <stdatomic.h>]</h3>
|
|
<a name='7.33.10p1'></a>
|
|
<pre>1 Macros that begin with ATOMIC_ and an uppercase letter are potentially reserved identifiers and
|
|
may be added to the macros defined in the <stdatomic.h> header. Typedef names that begin with
|
|
either atomic_ or memory_, and a lowercase letter are potentially reserved identifiers and may be
|
|
added to the declarations in the <stdatomic.h> header. Enumeration constants that begin with
|
|
memory_order_ and a lowercase letter are potentially reserved identifiers and may be added to
|
|
the definition of the memory_order type in the <stdatomic.h> header. Function names that begin
|
|
with atomic_ and a lowercase letter are potentially reserved identifiers and may be added to the
|
|
declarations in the <stdatomic.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.11'></a>
|
|
<hr>
|
|
<h3>7.33.11 [Boolean type and values <stdbool.h>]</h3>
|
|
<a name='7.33.11p1'></a>
|
|
<pre>1 The macro __bool_true_false_are_defined is an obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='7.33.12'></a>
|
|
<hr>
|
|
<h3>7.33.12 [Bit and byte utilities <stdbit.h>]</h3>
|
|
<a name='7.33.12p1'></a>
|
|
<pre>1 Type and function names that begin with stdc_ are potentially reserved identifiers and may be
|
|
added to the declarations in the <stdbit.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.13'></a>
|
|
<hr>
|
|
<h3>7.33.13 [Checked Arithmetic Functions <stdckdint.h>]</h3>
|
|
<a name='7.33.13p1'></a>
|
|
<pre>1 Type and function names that begin with ckd_ are potentially reserved identifiers and may be added
|
|
to the declarations in the <stdckdint.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.14'></a>
|
|
<hr>
|
|
<h3>7.33.14 [Integer types <stdint.h>]</h3>
|
|
<a name='7.33.14p1'></a>
|
|
<pre>1 Typedef names beginning with int or uint and ending with _t are potentially reserved identifiers
|
|
and may be added to the types defined in the <stdint.h> header. Macro names beginning with
|
|
INT or UINT and ending with _MAX , _MIN , _WIDTH , or _C are potentially reserved identifiers and may
|
|
be added to the macros defined in the <stdint.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.15'></a>
|
|
<hr>
|
|
<h3>7.33.15 [Input/output <stdio.h>]</h3>
|
|
<a name='7.33.15p1'></a>
|
|
<pre>1 Lowercase letters may be added to the conversion specifiers and length modifiers in fprintf and
|
|
fscanf. Other characters may be used in extensions.
|
|
</pre>
|
|
<a name='7.33.15p2'></a>
|
|
<pre>2 The use of ungetc on a binary stream where the file position indicator is zero prior to the call is an
|
|
obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='7.33.16'></a>
|
|
<hr>
|
|
<h3>7.33.16 [General utilities <stdlib.h>]</h3>
|
|
<a name='7.33.16p1'></a>
|
|
<pre>1 Function names that begin with str or wcs and a lowercase letter are potentially reserved identifiers
|
|
and may be added to the declarations in the <stdlib.h> header.
|
|
</pre>
|
|
<a name='7.33.16p2'></a>
|
|
<pre>2 Suppressing the macro definition of bsearch in order to access the actual function is an obsolescent
|
|
feature.
|
|
</pre>
|
|
<a name='7.33.17'></a>
|
|
<hr>
|
|
<h3>7.33.17 [String handling <string.h>]</h3>
|
|
<a name='7.33.17p1'></a>
|
|
<pre>1 Function names that begin with str, mem, or wcs and a lowercase letter are potentially reserved
|
|
identifiers and may be added to the declarations in the <string.h> header.
|
|
</pre>
|
|
<a name='7.33.17p2'></a>
|
|
<pre>2 Suppressing the macro definitions of memchr, strchr, strpbrk, strrchr, or strstr in order to
|
|
access the corresponding actual function is an obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='7.33.18'></a>
|
|
<hr>
|
|
<h3>7.33.18 [Date and time <time.h>]</h3>
|
|
<pre>Macros beginning with TIME_ and an uppercase letter may be added to the macros in the <time.h>
|
|
header by a future revision of this document or by an implementation.
|
|
|
|
</pre>
|
|
<a name='7.33.19'></a>
|
|
<hr>
|
|
<h3>7.33.19 [Threads <threads.h>]</h3>
|
|
<a name='7.33.19p1'></a>
|
|
<pre>1 Function names, type names, and enumeration constants that begin with either cnd_, mtx_, thrd_, or
|
|
tss_, and a lowercase letter are potentially reserved identifiers and may be added to the declarations
|
|
in the <threads.h> header.
|
|
|
|
</pre>
|
|
<a name='7.33.20'></a>
|
|
<hr>
|
|
<h3>7.33.20 [Extended multibyte and wide character utilities <wchar.h>]</h3>
|
|
<a name='7.33.20p1'></a>
|
|
<pre>1 Function names that begin with wcs and a lowercase letter are potentially reserved identifiers and
|
|
may be added to the declarations in the <wchar.h> header.
|
|
</pre>
|
|
<a name='7.33.20p2'></a>
|
|
<pre>2 Lowercase letters may be added to the conversion specifiers and length modifiers in fwprintf and
|
|
fwscanf. Other characters may be used in extensions.
|
|
</pre>
|
|
<a name='7.33.20p3'></a>
|
|
<pre>3 Suppressing the macro definitions of wcschr, wcspbrk, wcsrchr, wmemchr, or wcsstr in order to
|
|
access the corresponding actual function is an obsolescent feature.
|
|
|
|
</pre>
|
|
<a name='7.33.21'></a>
|
|
<hr>
|
|
<h3>7.33.21 [Wide character classification and mapping utilities <wctype.h>]</h3>
|
|
<a name='7.33.21p1'></a>
|
|
<pre>1 Function names that begin with is or to and a lowercase letter are potentially reserved identifiers
|
|
and may be added to the declarations in the <wctype.h> header.
|
|
|
|
</pre>
|
|
<a name='A.'></a>
|
|
<hr>
|
|
<h3>A. [Annex A (informative) Language syntax summary]</h3>
|
|
<a name='A.p1'></a>
|
|
<pre>1 NOTE The notation is described in <a href='#6.1'>6.1</a>.
|
|
|
|
|
|
</pre>
|
|
<a name='A.1'></a>
|
|
<hr>
|
|
<h3>A.1 [Lexical grammar]</h3>
|
|
<a name='A.1.1'></a>
|
|
<hr>
|
|
<h3>A.1.1 [Lexical elements]</h3>
|
|
<pre>(<a href='#6.4'>6.4</a>) token:
|
|
keyword
|
|
identifier
|
|
constant
|
|
string-literal
|
|
punctuator
|
|
|
|
(<a href='#6.4'>6.4</a>) preprocessing-token:
|
|
header-name
|
|
identifier
|
|
pp-number
|
|
character-constant
|
|
string-literal
|
|
punctuator
|
|
each universal-character-name that cannot be one of the above
|
|
each non-white-space character that cannot be one of the above
|
|
|
|
|
|
</pre>
|
|
<a name='A.1.2'></a>
|
|
<hr>
|
|
<h3>A.1.2 [Keywords]</h3>
|
|
<pre>(<a href='#6.4.1'>6.4.1</a>) keyword: one of
|
|
alignas enum short void
|
|
alignof extern signed volatile
|
|
auto false sizeof while
|
|
bool float static _Atomic
|
|
break for static_assert _BitInt
|
|
case goto struct _Complex
|
|
char if switch _Decimal128
|
|
const inline thread_local _Decimal32
|
|
constexpr int true _Decimal64
|
|
continue long typedef _Generic
|
|
default nullptr typeof _Imaginary
|
|
do register typeof_unqual _Noreturn
|
|
double restrict union
|
|
else return unsigned
|
|
|
|
</pre>
|
|
<a name='A.1.3'></a>
|
|
<hr>
|
|
<h3>A.1.3 [Identifiers]</h3>
|
|
<pre>(<a href='#6.4.2.1'>6.4.2.1</a>) identifier:
|
|
identifier-start
|
|
identifier identifier-continue
|
|
|
|
(<a href='#6.4.2.1'>6.4.2.1</a>) identifier-start:
|
|
nondigit
|
|
XID_Start character
|
|
universal-character-name of class XID_Start
|
|
(<a href='#6.4.2.1'>6.4.2.1</a>) identifier-continue:
|
|
digit
|
|
nondigit
|
|
XID_Continue character
|
|
universal-character-name of class XID_Continue
|
|
|
|
(<a href='#6.4.2.1'>6.4.2.1</a>) nondigit: one of
|
|
_ a b c d e f g h i j k l m
|
|
n o p q r s t u v w x y z
|
|
A B C D E F G H I J K L M
|
|
N O P Q R S T U V W X Y Z
|
|
|
|
(<a href='#6.4.2.1'>6.4.2.1</a>) digit: one of
|
|
0 1 2 3 4 5 6 7 8 9
|
|
</pre>
|
|
<a name='A.1.4'></a>
|
|
<hr>
|
|
<h3>A.1.4 [Universal character names]</h3>
|
|
<pre>(<a href='#6.4.3'>6.4.3</a>) universal-character-name:
|
|
\u hex-quad
|
|
\U hex-quad hex-quad
|
|
|
|
(<a href='#6.4.3'>6.4.3</a>) hex-quad:
|
|
hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
|
|
</pre>
|
|
<a name='A.1.5'></a>
|
|
<hr>
|
|
<h3>A.1.5 [Constants]</h3>
|
|
<pre>(<a href='#6.4.4'>6.4.4</a>) constant:
|
|
integer-constant
|
|
floating-constant
|
|
enumeration-constant
|
|
character-constant
|
|
predefined-constant
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) integer-constant:
|
|
decimal-constant integer-suffixopt
|
|
octal-constant integer-suffixopt
|
|
hexadecimal-constant integer-suffixopt
|
|
binary-constant integer-suffixopt
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) decimal-constant:
|
|
nonzero-digit
|
|
decimal-constant ’opt digit
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) octal-constant:
|
|
0
|
|
octal-constant ’opt octal-digit
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) hexadecimal-constant:
|
|
hexadecimal-prefix hexadecimal-digit-sequence
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) binary-constant:
|
|
binary-prefix binary-digit
|
|
binary-constant ’opt binary-digit
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) hexadecimal-prefix: one of
|
|
0x 0X
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) binary-prefix: one of
|
|
0b 0B
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) nonzero-digit: one of
|
|
1 2 3 4 5 6 7 8 9
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) octal-digit: one of
|
|
0 1 2 3 4 5 6 7
|
|
|
|
hexadecimal-digit-sequence:
|
|
hexadecimal-digit
|
|
hexadecimal-digit-sequence ’opt hexadecimal-digit
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) hexadecimal-digit: one of
|
|
0 1 2 3 4 5 6 7 8 9
|
|
a b c d e f
|
|
A B C D E F
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) binary-digit: one of
|
|
0 1
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) integer-suffix:
|
|
unsigned-suffix long-suffixopt
|
|
unsigned-suffix long-long-suffix
|
|
unsigned-suffix bit-precise-int-suffix
|
|
long-suffix unsigned-suffixopt
|
|
long-long-suffix unsigned-suffixopt
|
|
bit-precise-int-suffix unsigned-suffixopt
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) bit-precise-int-suffix: one of
|
|
wb WB
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) unsigned-suffix: one of
|
|
u U
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) long-suffix: one of
|
|
l L
|
|
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) long-long-suffix: one of
|
|
ll LL
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) floating-constant:
|
|
decimal-floating-constant
|
|
hexadecimal-floating-constant
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) decimal-floating-constant:
|
|
fractional-constant exponent-partopt floating-suffixopt
|
|
digit-sequence exponent-part floating-suffixopt
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) hexadecimal-floating-constant:
|
|
hexadecimal-prefix hexadecimal-fractional-constant
|
|
binary-exponent-part floating-suffixopt
|
|
hexadecimal-prefix hexadecimal-digit-sequence
|
|
binary-exponent-part floating-suffixopt
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) fractional-constant:
|
|
digit-sequenceopt . digit-sequence
|
|
digit-sequence .
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) exponent-part:
|
|
e signopt digit-sequence
|
|
E signopt digit-sequence
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) sign: one of
|
|
+ -
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) digit-sequence:
|
|
digit
|
|
digit-sequence ’opt digit
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) hexadecimal-fractional-constant:
|
|
hexadecimal-digit-sequenceopt . hexadecimal-digit-sequence
|
|
hexadecimal-digit-sequence .
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) binary-exponent-part:
|
|
p signopt digit-sequence
|
|
P signopt digit-sequence
|
|
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) floating-suffix: one of
|
|
f l F L df dd dl DF DD DL
|
|
(<a href='#6.4.4.3'>6.4.4.3</a>) enumeration-constant:
|
|
identifier
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) character-constant:
|
|
encoding-prefixopt ’ c-char-sequence ’
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) encoding-prefix:
|
|
u8
|
|
u
|
|
U
|
|
L
|
|
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) c-char-sequence:
|
|
c-char
|
|
c-char-sequence c-char
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) c-char:
|
|
any member of the source character set except
|
|
the single-quote ’, backslash \ , or new-line character
|
|
escape-sequence
|
|
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) escape-sequence:
|
|
simple-escape-sequence
|
|
octal-escape-sequence
|
|
hexadecimal-escape-sequence
|
|
universal-character-name
|
|
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) simple-escape-sequence: one of
|
|
\’ \" \? \\
|
|
\a \b \f \n \r \t \v
|
|
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) octal-escape-sequence:
|
|
\ octal-digit
|
|
\ octal-digit octal-digit
|
|
\ octal-digit octal-digit octal-digit
|
|
|
|
(<a href='#6.4.4.4'>6.4.4.4</a>) hexadecimal-escape-sequence:
|
|
\x hexadecimal-digit
|
|
hexadecimal-escape-sequence hexadecimal-digit
|
|
(<a href='#6.4.4.5'>6.4.4.5</a>) predefined-constant:
|
|
false
|
|
true
|
|
nullptr
|
|
|
|
|
|
</pre>
|
|
<a name='A.1.6'></a>
|
|
<hr>
|
|
<h3>A.1.6 [String literals]</h3>
|
|
<pre>(<a href='#6.4.5'>6.4.5</a>) string-literal:
|
|
encoding-prefixopt " s-char-sequenceopt "
|
|
(<a href='#6.4.5'>6.4.5</a>) s-char-sequence:
|
|
s-char
|
|
s-char-sequence s-char
|
|
|
|
(<a href='#6.4.5'>6.4.5</a>) s-char:
|
|
any member of the source character set except
|
|
the double-quote ", backslash \, or new-line character
|
|
escape-sequence
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.1.7'></a>
|
|
<hr>
|
|
<h3>A.1.7 [Punctuators]</h3>
|
|
<pre>(<a href='#6.4.6'>6.4.6</a>) punctuator: one of
|
|
[ ] ( ) { } . ->
|
|
++ -- & * + - ~ !
|
|
/ % << >> < > <= >= == != ^ | && ||
|
|
? : :: ; ...
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
, # ##
|
|
<: :> <% %> %: %:%:
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.1.8'></a>
|
|
<hr>
|
|
<h3>A.1.8 [Header names]</h3>
|
|
<pre>(<a href='#6.4.7'>6.4.7</a>) header-name:
|
|
< h-char-sequence >
|
|
" q-char-sequence "
|
|
|
|
(<a href='#6.4.7'>6.4.7</a>) h-char-sequence:
|
|
h-char
|
|
h-char-sequence h-char
|
|
|
|
(<a href='#6.4.7'>6.4.7</a>) h-char:
|
|
any member of the source character set except
|
|
the new-line character and >
|
|
|
|
(<a href='#6.4.7'>6.4.7</a>) q-char-sequence:
|
|
q-char
|
|
q-char-sequence q-char
|
|
|
|
(<a href='#6.4.7'>6.4.7</a>) q-char:
|
|
any member of the source character set except
|
|
the new-line character and "
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.1.9'></a>
|
|
<hr>
|
|
<h3>A.1.9 [Preprocessing numbers]</h3>
|
|
<pre>(<a href='#6.4.8'>6.4.8</a>) pp-number:
|
|
digit
|
|
. digit
|
|
pp-number identifier-continue
|
|
pp-number ’ digit
|
|
pp-number ’ nondigit
|
|
pp-number e sign
|
|
pp-number E sign
|
|
pp-number p sign
|
|
pp-number P sign
|
|
pp-number .
|
|
|
|
|
|
|
|
|
|
(<a href='#6.5.1'>6.5.1</a>) primary-expression:
|
|
</pre>
|
|
<a name='A.2'></a>
|
|
<hr>
|
|
<h3>A.2 [Phrase structure grammar]</h3>
|
|
<a name='A.2.1'></a>
|
|
<hr>
|
|
<h3>A.2.1 [Expressions]</h3>
|
|
<pre>identifier
|
|
constant
|
|
string-literal
|
|
( expression )
|
|
generic-selection
|
|
(<a href='#6.5.1.1'>6.5.1.1</a>) generic-selection:
|
|
_Generic ( assignment-expression , generic-assoc-list )
|
|
(<a href='#6.5.1.1'>6.5.1.1</a>) generic-assoc-list:
|
|
generic-association
|
|
generic-assoc-list , generic-association
|
|
(<a href='#6.5.1.1'>6.5.1.1</a>) generic-association:
|
|
type-name : assignment-expression
|
|
default : assignment-expression
|
|
(<a href='#6.5.2'>6.5.2</a>) postfix-expression:
|
|
primary-expression
|
|
postfix-expression [ expression ]
|
|
postfix-expression ( argument-expression-listopt )
|
|
postfix-expression . identifier
|
|
postfix-expression -> identifier
|
|
postfix-expression ++
|
|
postfix-expression --
|
|
compound-literal
|
|
|
|
(<a href='#6.5.2'>6.5.2</a>) argument-expression-list:
|
|
assignment-expression
|
|
argument-expression-list , assignment-expression
|
|
|
|
(<a href='#6.5.2.5'>6.5.2.5</a>) compound-literal:
|
|
( storage-class-specifiersopt type-name ) braced-initializer
|
|
|
|
(<a href='#6.5.2.5'>6.5.2.5</a>) storage-class-specifiers:
|
|
storage-class-specifier
|
|
storage-class-specifiers storage-class-specifier
|
|
(<a href='#6.5.3'>6.5.3</a>) unary-expression:
|
|
postfix-expression
|
|
++ unary-expression
|
|
-- unary-expression
|
|
unary-operator cast-expression
|
|
sizeof unary-expression
|
|
sizeof ( type-name )
|
|
alignof ( type-name )
|
|
|
|
(<a href='#6.5.3'>6.5.3</a>) unary-operator: one of
|
|
& * + - ~ !
|
|
|
|
(<a href='#6.5.4'>6.5.4</a>) cast-expression:
|
|
unary-expression
|
|
( type-name ) cast-expression
|
|
|
|
(<a href='#6.5.5'>6.5.5</a>) multiplicative-expression:
|
|
cast-expression
|
|
multiplicative-expression * cast-expression
|
|
multiplicative-expression / cast-expression
|
|
multiplicative-expression % cast-expression
|
|
|
|
(<a href='#6.5.6'>6.5.6</a>) additive-expression:
|
|
multiplicative-expression
|
|
additive-expression + multiplicative-expression
|
|
additive-expression - multiplicative-expression
|
|
|
|
(<a href='#6.5.7'>6.5.7</a>) shift-expression:
|
|
additive-expression
|
|
shift-expression << additive-expression
|
|
shift-expression >> additive-expression
|
|
(<a href='#6.5.8'>6.5.8</a>) relational-expression:
|
|
shift-expression
|
|
relational-expression < shift-expression
|
|
relational-expression > shift-expression
|
|
relational-expression <= shift-expression
|
|
relational-expression >= shift-expression
|
|
(<a href='#6.5.9'>6.5.9</a>) equality-expression:
|
|
relational-expression
|
|
equality-expression == relational-expression
|
|
equality-expression != relational-expression
|
|
|
|
(<a href='#6.5.10'>6.5.10</a>) AND-expression:
|
|
equality-expression
|
|
AND-expression & equality-expression
|
|
(<a href='#6.5.11'>6.5.11</a>) exclusive-OR-expression:
|
|
AND-expression
|
|
exclusive-OR-expression ^ AND-expression
|
|
(<a href='#6.5.12'>6.5.12</a>) inclusive-OR-expression:
|
|
exclusive-OR-expression
|
|
inclusive-OR-expression | exclusive-OR-expression
|
|
(<a href='#6.5.13'>6.5.13</a>) logical-AND-expression:
|
|
inclusive-OR-expression
|
|
logical-AND-expression && inclusive-OR-expression
|
|
(<a href='#6.5.14'>6.5.14</a>) logical-OR-expression:
|
|
logical-AND-expression
|
|
logical-OR-expression || logical-AND-expression
|
|
(<a href='#6.5.15'>6.5.15</a>) conditional-expression:
|
|
logical-OR-expression
|
|
logical-OR-expression ? expression : conditional-expression
|
|
(<a href='#6.5.16'>6.5.16</a>) assignment-expression:
|
|
conditional-expression
|
|
unary-expression assignment-operator assignment-expression
|
|
|
|
(<a href='#6.5.16'>6.5.16</a>) assignment-operator: one of
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
(<a href='#6.5.17'>6.5.17</a>) expression:
|
|
assignment-expression
|
|
expression , assignment-expression
|
|
(<a href='#6.6'>6.6</a>) constant-expression:
|
|
conditional-expression
|
|
|
|
|
|
|
|
|
|
(<a href='#6.7'>6.7</a>) declaration:
|
|
</pre>
|
|
<a name='A.2.2'></a>
|
|
<hr>
|
|
<h3>A.2.2 [declaration-specifiers init-declarator-listopt ;]</h3>
|
|
<pre>Declarations
|
|
attribute-specifier-sequence declaration-specifiers init-declarator-list ;
|
|
static_assert-declaration
|
|
attribute-declaration
|
|
(<a href='#6.7'>6.7</a>) declaration-specifiers:
|
|
declaration-specifier attribute-specifier-sequenceopt
|
|
declaration-specifier declaration-specifiers
|
|
(<a href='#6.7'>6.7</a>) declaration-specifier:
|
|
storage-class-specifier
|
|
type-specifier-qualifier
|
|
function-specifier
|
|
(<a href='#6.7'>6.7</a>) init-declarator-list:
|
|
init-declarator
|
|
init-declarator-list , init-declarator
|
|
(<a href='#6.7'>6.7</a>) init-declarator:
|
|
declarator
|
|
declarator = initializer
|
|
(<a href='#6.7'>6.7</a>) attribute-declaration:
|
|
attribute-specifier-sequence ;
|
|
(<a href='#6.7.1'>6.7.1</a>) storage-class-specifier:
|
|
auto
|
|
constexpr
|
|
extern
|
|
register
|
|
static
|
|
thread_local
|
|
typedef
|
|
(<a href='#6.7.2'>6.7.2</a>) type-specifier:
|
|
void
|
|
char
|
|
short
|
|
int
|
|
long
|
|
float
|
|
double
|
|
signed
|
|
unsigned
|
|
_BitInt ( constant-expression )
|
|
bool
|
|
_Complex
|
|
_Decimal32
|
|
_Decimal64
|
|
_Decimal128
|
|
atomic-type-specifier
|
|
struct-or-union-specifier
|
|
enum-specifier
|
|
typedef-name
|
|
typeof-specifier
|
|
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-or-union-specifier:
|
|
struct-or-union attribute-specifier-sequenceopt identifieropt { member-declaration-list }
|
|
struct-or-union attribute-specifier-sequenceopt identifier
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-or-union:
|
|
struct
|
|
union
|
|
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) member-declaration-list:
|
|
member-declaration
|
|
member-declaration-list member-declaration
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) member-declaration:
|
|
attribute-specifier-sequenceopt specifier-qualifier-list member-declarator-listopt ;
|
|
static_assert-declaration
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) specifier-qualifier-list:
|
|
type-specifier-qualifier attribute-specifier-sequenceopt
|
|
type-specifier-qualifier specifier-qualifier-list
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) type-specifier-qualifier:
|
|
type-specifier
|
|
type-qualifier
|
|
alignment-specifier
|
|
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) member-declarator-list:
|
|
member-declarator
|
|
member-declarator-list , member-declarator
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) member-declarator:
|
|
declarator
|
|
declaratoropt : constant-expression
|
|
(<a href='#6.7.2.2'>6.7.2.2</a>) enum-specifier:
|
|
enum attribute-specifier-sequenceopt identifieropt enum-type-specifieropt
|
|
{ enumerator-list }
|
|
enum attribute-specifier-sequenceopt identifieropt enum-type-specifieropt
|
|
{ enumerator-list , }
|
|
enum identifier enum-type-specifieropt
|
|
(<a href='#6.7.2.2'>6.7.2.2</a>) enumerator-list:
|
|
enumerator
|
|
enumerator-list , enumerator
|
|
(<a href='#6.7.2.2'>6.7.2.2</a>) enumerator:
|
|
enumeration-constant attribute-specifier-sequenceopt
|
|
enumeration-constant attribute-specifier-sequenceopt = constant-expression
|
|
(<a href='#6.7.2.2'>6.7.2.2</a>) enum-type-specifier:
|
|
: specifier-qualifier-list
|
|
(<a href='#6.7.2.4'>6.7.2.4</a>) atomic-type-specifier:
|
|
_Atomic ( type-name )
|
|
(<a href='#6.7.2.5'>6.7.2.5</a>) typeof-specifier:
|
|
typeof ( typeof-specifier-argument )
|
|
typeof_unqual ( typeof-specifier-argument )
|
|
(<a href='#6.7.2.5'>6.7.2.5</a>) typeof-specifier-argument:
|
|
expression
|
|
type-name
|
|
|
|
(<a href='#6.7.3'>6.7.3</a>) type-qualifier:
|
|
const
|
|
restrict
|
|
volatile
|
|
_Atomic
|
|
(<a href='#6.7.4'>6.7.4</a>) function-specifier:
|
|
inline
|
|
_Noreturn
|
|
|
|
(<a href='#6.7.5'>6.7.5</a>) alignment-specifier:
|
|
alignas ( type-name )
|
|
alignas ( constant-expression )
|
|
(<a href='#6.7.6'>6.7.6</a>) declarator:
|
|
pointeropt direct-declarator
|
|
|
|
(<a href='#6.7.6'>6.7.6</a>) direct-declarator:
|
|
identifier attribute-specifier-sequenceopt
|
|
( declarator )
|
|
array-declarator attribute-specifier-sequenceopt
|
|
function-declarator attribute-specifier-sequenceopt
|
|
|
|
(<a href='#6.7.6'>6.7.6</a>) array-declarator:
|
|
direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
|
|
direct-declarator [ static type-qualifier-listopt assignment-expression ]
|
|
direct-declarator [ type-qualifier-list static assignment-expression ]
|
|
direct-declarator [ type-qualifier-listopt * ]
|
|
|
|
(<a href='#6.7.6'>6.7.6</a>) function-declarator:
|
|
direct-declarator ( parameter-type-listopt )
|
|
|
|
(<a href='#6.7.6'>6.7.6</a>) pointer:
|
|
* attribute-specifier-sequenceopt type-qualifier-listopt
|
|
* attribute-specifier-sequenceopt type-qualifier-listopt pointer
|
|
(<a href='#6.7.6'>6.7.6</a>) type-qualifier-list:
|
|
type-qualifier
|
|
type-qualifier-list type-qualifier
|
|
(<a href='#6.7.6'>6.7.6</a>) parameter-type-list:
|
|
parameter-list
|
|
parameter-list , ...
|
|
...
|
|
(<a href='#6.7.6'>6.7.6</a>) parameter-list:
|
|
parameter-declaration
|
|
parameter-list , parameter-declaration
|
|
(<a href='#6.7.6'>6.7.6</a>) parameter-declaration:
|
|
attribute-specifier-sequenceopt declaration-specifiers declarator
|
|
attribute-specifier-sequenceopt declaration-specifiers abstract-declaratoropt
|
|
(<a href='#6.7.7'>6.7.7</a>) type-name:
|
|
specifier-qualifier-list abstract-declaratoropt
|
|
(<a href='#6.7.7'>6.7.7</a>) abstract-declarator:
|
|
pointer
|
|
pointeropt direct-abstract-declarator
|
|
(<a href='#6.7.7'>6.7.7</a>) direct-abstract-declarator:
|
|
( abstract-declarator )
|
|
array-abstract-declarator attribute-specifier-sequenceopt
|
|
function-abstract-declarator attribute-specifier-sequenceopt
|
|
(<a href='#6.7.7'>6.7.7</a>) array-abstract-declarator:
|
|
direct-abstract-declaratoropt [ type-qualifier-listopt assignment-expressionopt ]
|
|
direct-abstract-declaratoropt [ static type-qualifier-listopt assignment-expression ]
|
|
direct-abstract-declaratoropt [ type-qualifier-list static assignment-expression ]
|
|
direct-abstract-declaratoropt [ * ]
|
|
|
|
(<a href='#6.7.7'>6.7.7</a>) function-abstract-declarator:
|
|
direct-abstract-declaratoropt ( parameter-type-listopt )
|
|
(<a href='#6.7.8'>6.7.8</a>) typedef-name:
|
|
identifier
|
|
|
|
(<a href='#6.7.10'>6.7.10</a>) braced-initializer:
|
|
{ }
|
|
{ initializer-list }
|
|
{ initializer-list , }
|
|
|
|
(<a href='#6.7.10'>6.7.10</a>) initializer:
|
|
assignment-expression
|
|
braced-initializer
|
|
|
|
(<a href='#6.7.10'>6.7.10</a>) initializer-list:
|
|
designationopt initializer
|
|
initializer-list , designationopt initializer
|
|
|
|
(<a href='#6.7.10'>6.7.10</a>) designation:
|
|
designator-list =
|
|
|
|
(<a href='#6.7.10'>6.7.10</a>) designator-list:
|
|
designator
|
|
designator-list designator
|
|
(<a href='#6.7.10'>6.7.10</a>) designator:
|
|
[ constant-expression ]
|
|
. identifier
|
|
(<a href='#6.7.11'>6.7.11</a>) static_assert-declaration:
|
|
static_assert ( constant-expression , string-literal ) ;
|
|
static_assert ( constant-expression ) ;
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-specifier-sequence:
|
|
attribute-specifier-sequenceopt attribute-specifier
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-specifier:
|
|
[ [ attribute-list ] ]
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-list:
|
|
attributeopt
|
|
attribute-list , attributeopt
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute:
|
|
attribute-token attribute-argument-clauseopt
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-token:
|
|
standard-attribute
|
|
attribute-prefixed-token
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) standard-attribute:
|
|
identifier
|
|
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-prefixed-token:
|
|
attribute-prefix :: identifier
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-prefix:
|
|
identifier
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) attribute-argument-clause:
|
|
( balanced-token-sequenceopt )
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) balanced-token-sequence:
|
|
balanced-token
|
|
balanced-token-sequence balanced-token
|
|
(<a href='#6.7.12.1'>6.7.12.1</a>) balanced-token:
|
|
( balanced-token-sequenceopt )
|
|
[ balanced-token-sequenceopt ]
|
|
{ balanced-token-sequenceopt }
|
|
any token other than a parenthesis, a bracket, or a brace
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.2.3'></a>
|
|
<hr>
|
|
<h3>A.2.3 [Statements]</h3>
|
|
<pre>(<a href='#6.8'>6.8</a>) statement:
|
|
labeled-statement
|
|
unlabeled-statement
|
|
(<a href='#6.8'>6.8</a>) unlabeled-statement:
|
|
expression-statement
|
|
attribute-specifier-sequenceopt primary-block
|
|
attribute-specifier-sequenceopt jump-statement
|
|
(<a href='#6.8'>6.8</a>) primary-block:
|
|
compound-statement
|
|
selection-statement
|
|
iteration-statement
|
|
|
|
(<a href='#6.8'>6.8</a>) secondary-block:
|
|
statement
|
|
|
|
(<a href='#6.8.1'>6.8.1</a>) label:
|
|
attribute-specifier-sequenceopt identifier :
|
|
attribute-specifier-sequenceopt case constant-expression :
|
|
attribute-specifier-sequenceopt default :
|
|
(<a href='#6.8.1'>6.8.1</a>) labeled-statement:
|
|
label statement
|
|
(<a href='#6.8.2'>6.8.2</a>) compound-statement:
|
|
{ block-item-listopt }
|
|
(<a href='#6.8.2'>6.8.2</a>) block-item-list:
|
|
block-item
|
|
block-item-list block-item
|
|
(<a href='#6.8.2'>6.8.2</a>) block-item:
|
|
declaration
|
|
unlabeled-statement
|
|
label
|
|
(<a href='#6.8.3'>6.8.3</a>) expression-statement:
|
|
expressionopt ;
|
|
attribute-specifier-sequence expression ;
|
|
|
|
(<a href='#6.8.4'>6.8.4</a>) selection-statement:
|
|
if ( expression ) secondary-block
|
|
if ( expression ) secondary-block else secondary-block
|
|
switch ( expression ) secondary-block
|
|
|
|
(<a href='#6.8.5'>6.8.5</a>) iteration-statement:
|
|
while ( expression ) secondary-block
|
|
do secondary-block while ( expression ) ;
|
|
for ( expressionopt ; expressionopt ; expressionopt ) secondary-block
|
|
for ( declaration expressionopt ; expressionopt ) secondary-block
|
|
|
|
(<a href='#6.8.6'>6.8.6</a>) jump-statement:
|
|
goto identifier ;
|
|
continue ;
|
|
break ;
|
|
return expressionopt ;
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.2.4'></a>
|
|
<hr>
|
|
<h3>A.2.4 [External definitions]</h3>
|
|
<pre>(<a href='#6.9'>6.9</a>) translation-unit:
|
|
external-declaration
|
|
translation-unit external-declaration
|
|
|
|
(<a href='#6.9'>6.9</a>) external-declaration:
|
|
function-definition
|
|
declaration
|
|
|
|
(<a href='#6.9.1'>6.9.1</a>) function-definition:
|
|
attribute-specifier-sequenceopt declaration-specifiers declarator function-body
|
|
|
|
(<a href='#6.9.1'>6.9.1</a>) function-body:
|
|
compound-statement
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.3'></a>
|
|
<hr>
|
|
<h3>A.3 [Preprocessing directives]</h3>
|
|
<pre>(<a href='#6.10'>6.10</a>) preprocessing-file:
|
|
groupopt
|
|
(<a href='#6.10'>6.10</a>) group:
|
|
group-part
|
|
group group-part
|
|
(<a href='#6.10'>6.10</a>) group-part:
|
|
if-section
|
|
control-line
|
|
text-line
|
|
# non-directive
|
|
(<a href='#6.10'>6.10</a>) if-section:
|
|
if-group elif-groupsopt else-groupopt endif-line
|
|
(<a href='#6.10'>6.10</a>) if-group:
|
|
# if constant-expression new-line groupopt
|
|
# ifdef identifier new-line groupopt
|
|
# ifndef identifier new-line groupopt
|
|
(<a href='#6.10'>6.10</a>) elif-groups:
|
|
elif-group
|
|
elif-groups elif-group
|
|
(<a href='#6.10'>6.10</a>) elif-group:
|
|
# elif constant-expression new-line groupopt
|
|
# elifdef identifier new-line groupopt
|
|
# elifndef identifier new-line groupopt
|
|
(<a href='#6.10'>6.10</a>) else-group:
|
|
# else new-line groupopt
|
|
(<a href='#6.10'>6.10</a>) endif-line:
|
|
# endif new-line
|
|
(<a href='#6.10'>6.10</a>) control-line:
|
|
# include pp-tokens new-line
|
|
# embed pp-tokens new-line
|
|
# define identifier replacement-list new-line
|
|
# define identifier lparen identifier-listopt ) replacement-list new-line
|
|
# define identifier lparen ... ) replacement-list new-line
|
|
# define identifier lparen identifier-list , ... ) replacement-list new-line
|
|
# undef identifier new-line
|
|
# line pp-tokens new-line
|
|
# error pp-tokensopt new-line
|
|
# warning pp-tokensopt new-line
|
|
# pragma pp-tokensopt new-line
|
|
# new-line
|
|
(<a href='#6.10'>6.10</a>) text-line:
|
|
pp-tokensopt new-line
|
|
(<a href='#6.10'>6.10</a>) non-directive:
|
|
pp-tokens new-line
|
|
(<a href='#6.10'>6.10</a>) lparen:
|
|
a ( character not immediately preceded by white space
|
|
(<a href='#6.10'>6.10</a>) replacement-list:
|
|
pp-tokensopt
|
|
(<a href='#6.10'>6.10</a>) pp-tokens:
|
|
preprocessing-token
|
|
pp-tokens preprocessing-token
|
|
(<a href='#6.10'>6.10</a>) new-line:
|
|
the new-line character
|
|
(<a href='#6.10'>6.10</a>) identifier-list:
|
|
identifier
|
|
identifier-list , identifier
|
|
(<a href='#6.10'>6.10</a>) pp-parameter:
|
|
pp-parameter-name pp-parameter-clauseopt
|
|
(<a href='#6.10'>6.10</a>) pp-parameter-name:
|
|
pp-standard-parameter
|
|
pp-prefixed-parameter
|
|
(<a href='#6.10'>6.10</a>) pp-standard-parameter:
|
|
identifier
|
|
(<a href='#6.10'>6.10</a>) pp-prefixed-parameter:
|
|
identifier :: identifier
|
|
(<a href='#6.10'>6.10</a>) pp-parameter-clause:
|
|
( pp-balanced-token-sequenceopt )
|
|
(<a href='#6.10'>6.10</a>) pp-balanced-token-sequence:
|
|
pp-balanced-token
|
|
pp-balanced-token-sequence pp-balanced-token
|
|
(<a href='#6.10'>6.10</a>) pp-balanced-token:
|
|
( pp-balanced-token-sequenceopt )
|
|
[ pp-balanced-token-sequenceopt ]
|
|
{ pp-balanced-token-sequenceopt }
|
|
any pp-token other than a parenthesis, a bracket, or a brace
|
|
(<a href='#6.10'>6.10</a>) embed-parameter-sequence:
|
|
pp-parameter
|
|
embed-parameter-sequence pp-parameter
|
|
|
|
defined-macro-expression:
|
|
defined identifier
|
|
defined ( identifier )
|
|
h-preprocessing-token:
|
|
any preprocessing-token other than >
|
|
h-pp-tokens:
|
|
h-preprocessing-token
|
|
h-pp-tokens h-preprocessing-token
|
|
header-name-tokens:
|
|
string-literal
|
|
< h-pp-tokens >
|
|
has-include-expression:
|
|
__has_include ( header-name )
|
|
__has_include ( header-name-tokens )
|
|
has-embed-expression:
|
|
__has_embed ( header-name embed-parameter-sequenceopt )
|
|
__has_embed ( header-name-tokens pp-balanced-token-sequenceopt )
|
|
has-c-attribute-express:
|
|
__has_c_attribute ( pp-tokens )
|
|
|
|
va-opt-replacement:
|
|
__VA_OPT__ ( pp-tokensopt )
|
|
|
|
(<a href='#6.10.7'>6.10.7</a>) standard-pragma:
|
|
# pragma STDC FP_CONTRACT on-off-switch
|
|
# pragma STDC FENV_ACCESS on-off-switch
|
|
# pragma STDC FENV_DEC_ROUND dec-direction
|
|
# pragma STDC FENV_ROUND direction
|
|
# pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
|
|
(<a href='#6.10.7'>6.10.7</a>) on-off-switch: one of
|
|
ON OFF DEFAULT
|
|
|
|
(<a href='#6.10.7'>6.10.7</a>) direction: one of
|
|
FE_DOWNWARD FE_TONEAREST FE_TONEARESTFROMZERO
|
|
FE_TOWARDZERO FE_UPWARD FE_DYNAMIC
|
|
|
|
(<a href='#6.10.7'>6.10.7</a>) dec-direction: one of
|
|
FE_DEC_DOWNWARD FE_DEC_TONEAREST FE_DEC_TONEARESTFROMZERO
|
|
FE_DEC_TOWARDZERO FE_DEC_UPWARD FE_DEC_DYNAMIC
|
|
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='A.4'></a>
|
|
<hr>
|
|
<h3>A.4 [Floating-point subject sequence]</h3>
|
|
<a name='A.4.1'></a>
|
|
<hr>
|
|
<h3>A.4.1 [NaN char sequence]</h3>
|
|
<pre>(<a href='#7.24.1.5'>7.24.1.5</a>) n-char-sequence:
|
|
digit
|
|
nondigit
|
|
n-char-sequence digit
|
|
n-char-sequence nondigit
|
|
|
|
</pre>
|
|
<a name='A.4.2'></a>
|
|
<hr>
|
|
<h3>A.4.2 [NaN wchar_t sequence]</h3>
|
|
<pre>(<a href='#7.31.4.1.2'>7.31.4.1.2</a>) n-wchar-sequence:
|
|
digit
|
|
nondigit
|
|
n-wchar-sequence digit
|
|
n-wchar-sequence nondigit
|
|
|
|
</pre>
|
|
<a name='A.5'></a>
|
|
<hr>
|
|
<h3>A.5 [Decimal floating-point subject sequence]</h3>
|
|
<a name='A.5.1'></a>
|
|
<hr>
|
|
<h3>A.5.1 [NaN decimal char sequence]</h3>
|
|
<pre>(<a href='#7.24.1.6'>7.24.1.6</a>) d-char-sequence:
|
|
digit
|
|
nondigit
|
|
d-char-sequence digit
|
|
d-char-sequence nondigit
|
|
|
|
</pre>
|
|
<a name='A.5.2'></a>
|
|
<hr>
|
|
<h3>A.5.2 [NaN decimal wchar_t sequence]</h3>
|
|
<pre>(<a href='#7.31.4.1.3'>7.31.4.1.3</a>) d-wchar-sequence:
|
|
digit
|
|
nondigit
|
|
d-wchar-sequence digit
|
|
d-wchar-sequence nondigit
|
|

|
|
|
|
</pre>
|
|
<a name='B.'></a>
|
|
<hr>
|
|
<h3>B. [Annex B (informative) Library summary]</h3>
|
|
<a name='B.1'></a>
|
|
<hr>
|
|
<h3>B.1 [Diagnostics <assert.h>]</h3>
|
|
<pre>NDEBUG
|
|
|
|
|
|
void assert(scalar expression);
|
|
|
|
|
|
</pre>
|
|
<a name='B.2'></a>
|
|
<hr>
|
|
<h3>B.2 [Complex <complex.h>]</h3>
|
|
<pre>__STDC_NO_COMPLEX__ imaginary
|
|
complex _Imaginary_I
|
|
_Complex_I I
|
|
|
|
|
|
#pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
double complex cacos(double complex z);
|
|
float complex cacosf(float complex z);
|
|
long double complex cacosl(long double complex z);
|
|
double complex casin(double complex z);
|
|
float complex casinf(float complex z);
|
|
long double complex casinl(long double complex z);
|
|
double complex catan(double complex z);
|
|
float complex catanf(float complex z);
|
|
long double complex catanl(long double complex z);
|
|
double complex ccos(double complex z);
|
|
float complex ccosf(float complex z);
|
|
long double complex ccosl(long double complex z);
|
|
double complex csin(double complex z);
|
|
float complex csinf(float complex z);
|
|
long double complex csinl(long double complex z);
|
|
double complex ctan(double complex z);
|
|
float complex ctanf(float complex z);
|
|
long double complex ctanl(long double complex z);
|
|
double complex cacosh(double complex z);
|
|
float complex cacoshf(float complex z);
|
|
long double complex cacoshl(long double complex z);
|
|
double complex casinh(double complex z);
|
|
float complex casinhf(float complex z);
|
|
long double complex casinhl(long double complex z);
|
|
double complex catanh(double complex z);
|
|
float complex catanhf(float complex z);
|
|
long double complex catanhl(long double complex z);
|
|
double complex ccosh(double complex z);
|
|
float complex ccoshf(float complex z);
|
|
long double complex ccoshl(long double complex z);
|
|
double complex csinh(double complex z);
|
|
float complex csinhf(float complex z);
|
|
long double complex csinhl(long double complex z);
|
|
double complex ctanh(double complex z);
|
|
float complex ctanhf(float complex z);
|
|
long double complex ctanhl(long double complex z);
|
|
double complex cexp(double complex z);
|
|
float complex cexpf(float complex z);
|
|
long double complex cexpl(long double complex z);
|
|
double complex clog(double complex z);
|
|
float complex clogf(float complex z);
|
|
 long double complex clogl(long double complex z);
|
|
double cabs(double complex z);
|
|
float cabsf(float complex z);
|
|
long double cabsl(long double complex z);
|
|
double complex cpow(double complex x, double complex y);
|
|
float complex cpowf(float complex x, float complex y);
|
|
long double complex cpowl(long double complex x, long double complex y);
|
|
double complex csqrt(double complex z);
|
|
float complex csqrtf(float complex z);
|
|
long double complex csqrtl(long double complex z);
|
|
double carg(double complex z);
|
|
float cargf(float complex z);
|
|
long double cargl(long double complex z);
|
|
double cimag(double complex z);
|
|
float cimagf(float complex z);
|
|
long double cimagl(long double complex z);
|
|
double complex CMPLX(double x, double y);
|
|
float complex CMPLXF(float x, float y);
|
|
long double complex CMPLXL(long double x, long double y);
|
|
double complex conj(double complex z);
|
|
float complex conjf(float complex z);
|
|
long double complex conjl(long double complex z);
|
|
double complex cproj(double complex z);
|
|
float complex cprojf(float complex z);
|
|
long double complex cprojl(long double complex z);
|
|
double creal(double complex z);
|
|
float crealf(float complex z);
|
|
long double creall(long double complex z);
|
|
|
|
|
|
</pre>
|
|
<a name='B.3'></a>
|
|
<hr>
|
|
<h3>B.3 [Character handling <ctype.h>]</h3>
|
|
<pre>int isalnum(int c);
|
|
int isalpha(int c);
|
|
int isblank(int c);
|
|
int iscntrl(int c);
|
|
int isdigit(int c);
|
|
int isgraph(int c);
|
|
int islower(int c);
|
|
int isprint(int c);
|
|
int ispunct(int c);
|
|
int isspace(int c);
|
|
int isupper(int c);
|
|
int isxdigit(int c);
|
|
int tolower(int c);
|
|
int toupper(int c);
|
|
|
|
|
|
</pre>
|
|
<a name='B.4'></a>
|
|
<hr>
|
|
<h3>B.4 [Errors <errno.h>]</h3>
|
|
<pre>EDOM EILSEQ ERANGE errno
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <errno.h>:
|
|
|
|
errno_t
|
|
|
|
|
|
</pre>
|
|
<a name='B.5'></a>
|
|
<hr>
|
|
<h3>B.5 [Floating-point environment <fenv.h>]</h3>
|
|
<pre>fenv_t FE_OVERFLOW FE_TOWARDZERO
|
|
fexcept_t FE_UNDERFLOW FE_UPWARD
|
|
FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
|
|
FE_INEXACT FE_DOWNWARD
|
|
FE_INVALID FE_TONEAREST
|
|
|
|
|
|
|
|
#pragma STDC FENV_ACCESS on-off-switch
|
|
#pragma STDC FENV_ROUND direction
|
|
#pragma STDC FENV_ROUND FE_DYNAMIC
|
|
int feclearexcept(int excepts);
|
|
int fegetexceptflag(fexcept_t *flagp, int excepts);
|
|
int feraiseexcept(int excepts);
|
|
int fesetexcept(int excepts);
|
|
int fesetexceptflag(const fexcept_t *flagp, int excepts);
|
|
int fetestexceptflag(const fexcept_t * flagp, int excepts);
|
|
int fetestexcept(int excepts);
|
|
int fegetmode(femode_t *modep);
|
|
int fegetround(void);
|
|
int fesetmode(const femode_t *modep);
|
|
int fesetround(int rnd);
|
|
int fegetenv(fenv_t *envp);
|
|
int feholdexcept(fenv_t *envp);
|
|
int fesetenv(const fenv_t *envp);
|
|
int feupdateenv(const fenv_t *envp);
|
|
|
|
|
|
Only if the implementation defines __STDC_IEC_60559_DFP__ :
|
|
|
|
|
|
FE_DEC_DOWNWARD FE_DEC_TONEARESTFROMZERO FE_DEC_UPWARD
|
|
FE_DEC_TONEAREST FE_DEC_TOWARDZERO
|
|
|
|
|
|
|
|
#pragma STDC FENV_DEC_ROUND dec-direction
|
|
int fe_dec_getround(void);
|
|
int fe_dec_setround(int rnd);
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='B.6'></a>
|
|
<hr>
|
|
<h3>B.6 [Characteristics of floating types <float.h>]</h3>
|
|
<pre>FLT_ROUNDS LDBL_DIG DBL_NORM_MAX
|
|
FLT_EVAL_METHOD FLT_MIN_EXP LDBL_NORM_MAX
|
|
FLT_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
|
|
DBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
|
|
LDBL_HAS_SUBNORM FLT_MIN_10_EXP LDBL_EPSILON
|
|
FLT_RADIX DBL_MIN_10_EXP FLT_MIN
|
|
FLT_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
|
|
DBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
|
|
LDBL_MANT_DIG DBL_MAX_EXP FLT_SNAN
|
|
FLT_DECIMAL_DIG LDBL_MAX_EXP DBL_SNAN
|
|
DBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_SNAN
|
|
LDBL_DECIMAL_DIG DBL_MAX_10_EXP FLT_TRUE_MIN
|
|
DECIMAL_DIG LDBL_MAX_10_EXP DBL_TRUE_MIN
|
|
FLT_IS_IEC_60559 FLT_MAX LDBL_TRUE_MIN
|
|
DBL_IS_IEC_60559 DBL_MAX INFINITY
|
|
FLT_DIG LDBL_MAX NAN
|
|
DBL_DIG FLT_NORM_MAX
|
|
</pre>
|
|
<a name='B.6.1'></a>
|
|
<hr>
|
|
<h3>B.6.1 [Characteristics of decimal floating types]</h3>
|
|
<a name='B.6.1p1'></a>
|
|
<pre>1 The following macros are provided only if the implementation defines __STDC_IEC_60559_DFP__ .
|
|
N is 32, 64 and 128.
|
|
|
|
DEC_INFINITY DECN_MANT_DIG DECN_MIN_EXP DECN_SNAN
|
|
DEC_NAN DECN_MAX_EXP DECN_MIN
|
|
DECN_EPSILON DECN_MAX DECN_TRUE_MIN
|
|
|
|
|
|
</pre>
|
|
<a name='B.7'></a>
|
|
<hr>
|
|
<h3>B.7 [Format conversion of integer types <inttypes.h>]</h3>
|
|
<pre>imaxdiv_t
|
|
|
|
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
|
|
PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
|
|
PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
|
|
PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
|
|
PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
|
|
PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
|
|
SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
|
|
SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
|
|
SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
|
|
SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
|
|
SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
|
|
|
|
intmax_t imaxabs(intmax_t j);
|
|
imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
|
|
intmax_t strtoimax(const char * restrict nptr, char ** restrict endptr, int base);
|
|
uintmax_t strtoumax(const char * restrict nptr, char ** restrict endptr, int base);
|
|
intmax_t wcstoimax(const wchar_t *restrict nptr, wchar_t **restrict endptr, int base);
|
|
uintmax_t wcstoumax(const wchar_t *restrict nptr, wchar_t **restrict endptr, int base);
|
|
|
|
|
|
</pre>
|
|
<a name='B.8'></a>
|
|
<hr>
|
|
<h3>B.8 [Alternative spellings <iso646.h>]</h3>
|
|
<pre>and bitor not_eq xor
|
|
and_eq compl or xor_eq
|
|
bitand not or_eq
|
|
|
|
|
|
</pre>
|
|
<a name='B.9'></a>
|
|
<hr>
|
|
<h3>B.9 [Sizes of integer types <limits.h>]</h3>
|
|
<pre>BOOL_WIDTH UINT_WIDTH UCHAR_MAX INT_MAX
|
|
CHAR_BIT LONG_WIDTH CHAR_MIN UINT_MAX
|
|
CHAR_WIDTH ULONG_WIDTH CHAR_MAX LONG_MIN
|
|
SCHAR_WIDTH LLONG_WIDTH MB_LEN_MAX LONG_MAX
|
|
UCHAR_WIDTH ULLONG_WIDTH SHRT_MIN ULONG_MAX
|
|
SHRT_WIDTH BOOL_MAX SHRT_MAX LLONG_MIN
|
|
USHRT_WIDTH SCHAR_MIN USHRT_MAX LLONG_MAX
|
|
INT_WIDTH SCHAR_MAX INT_MIN ULLONG_MAX
|
|
|
|
|
|
</pre>
|
|
<a name='B.10'></a>
|
|
<hr>
|
|
<h3>B.10 [Localization <locale.h>]</h3>
|
|
<pre>struct lconv LC_ALL LC_CTYPE LC_NUMERIC
|
|
NULL LC_COLLATE LC_MONETARY LC_TIME
|
|
|
|
|
|
char *setlocale(int category, const char *locale);
|
|
struct lconv *localeconv(void);
|
|
|
|
|
|
</pre>
|
|
<a name='B.11'></a>
|
|
<hr>
|
|
<h3>B.11 [Mathematics <math.h>]</h3>
|
|
<pre>float_t FP_INFINITE FP_FAST_FMAL
|
|
double_t FP_NAN FP_ILOGB0
|
|
HUGE_VAL FP_NORMAL FP_ILOGBNAN
|
|
HUGE_VALF FP_SUBNORMAL MATH_ERRNO
|
|
HUGE_VALL FP_ZERO MATH_ERREXCEPT
|
|
INFINITY FP_FAST_FMA math_errhandling
|
|
NAN FP_FAST_FMAF
|
|
|
|
|
|
|
|
#pragma STDC FP_CONTRACT on-off-switch
|
|
int fpclassify(real-floating x);
|
|
int iscanonical(real-floating x);
|
|
int isfinite(real-floating x);
|
|
int isinf(real-floating x);
|
|
int isnan(real-floating x);
|
|
int isnormal(real-floating x);
|
|
int signbit(real-floating x);
|
|
int issignaling(real-floating x);
|
|
int issubnormal(real-floating x);
|
|
int iszero(real-floating x);
|
|
double acos(double x);
|
|
float acosf(float x);
|
|
long double acosl(long double x);
|
|
double asin(double x);
|
|
float asinf(float x);
|
|
long double asinl(long double x);
|
|
double atan(double x);
|
|
float atanf(float x);
|
|
long double atanl(long double x);
|
|
double atan2(double y, double x);
|
|
float atan2f(float y, float x);
|
|
long double atan2l(long double y, long double x);
|
|
double cos(double x);
|
|
float cosf(float x);
|
|
long double cosl(long double x);
|
|
double sin(double x);
|
|
float sinf(float x);
|
|
long double sinl(long double x);
|
|
double tan(double x);
|
|
float tanf(float x);
|
|
long double tanl(long double x);
|
|
double acospi(double x);
|
|
float acospif(float x);
|
|
long double acospil(long double x);
|
|
double asinpi(double x);
|
|
float asinpif(float x);
|
|
long double asinpil(long double x);
|
|
double atanpi(double x);
|
|
float atanpif(float x);
|
|
long double atanpil(long double x);
|
|
double atan2pi(double y, double x);
|
|
float atan2pif(float y, float x);
|
|
long double atan2pil(long double y, long double x);
|
|
double cospi(double x);
|
|
float cospif(float x);
|
|
long double cospil(long double x);
|
|
double sinpi(double x);
|
|
float sinpif(float x);
|
|
long double sinpil(long double x);
|
|
double tanpi(double x);
|
|
float tanpif(float x);
|
|
long double tanpil(long double x);
|
|
double acosh(double x);
|
|
float acoshf(float x);
|
|
long double acoshl(long double x);
|
|
double asinh(double x);
|
|
float asinhf(float x);
|
|
long double asinhl(long double x);
|
|
double atanh(double x);
|
|
float atanhf(float x);
|
|
long double atanhl(long double x);
|
|
double cosh(double x);
|
|
float coshf(float x);
|
|
long double coshl(long double x);
|
|
double sinh(double x);
|
|
float sinhf(float x);
|
|
long double sinhl(long double x);
|
|
double tanh(double x);
|
|
float tanhf(float x);
|
|
long double tanhl(long double x);
|
|
double exp(double x);
|
|
float expf(float x);
|
|
long double expl(long double x);
|
|
double exp10(double x);
|
|
float exp10f(float x);
|
|
long double exp10l(long double x);
|
|
double exp10m1(double x);
|
|
float exp10m1f(float x);
|
|
long double exp10m1l(long double x);
|
|
double exp2(double x);
|
|
float exp2f(float x);
|
|
long double exp2l(long double x);
|
|
double exp2m1(double x);
|
|
float exp2m1f(float x);
|
|
long double exp2m1l(long double x);
|
|
double expm1(double x);
|
|
float expm1f(float x);
|
|
long double expm1l(long double x);
|
|
double frexp(double value, int *p);
|
|
float frexpf(float value, int *p);
|
|
long double frexpl(long double value, int *p);
|
|
int ilogb(double x);
|
|
int ilogbf(float x);
|
|
int ilogbl(long double x);
|
|
double ldexp(double x, int p);
|
|
float ldexpf(float x, int p);
|
|
long double ldexpl(long double x, int p);
|
|
long int llogb(double x);
|
|
long int llogbf(float x);
|
|
long int llogbl(long double x);
|
|
double log(double x);
|
|
float logf(float x);
|
|
long double logl(long double x);
|
|
double log10(double x);
|
|
float log10f(float x);
|
|
long double log10l(long double x);
|
|
double log10p1(double x);
|
|
float log10p1f(float x);
|
|
long double log10p1l(long double x);
|
|
double log1p(double x);
|
|
float log1pf(float x);
|
|
long double log1pl(long double x);
|
|
double logp1(double x);
|
|
float logp1f(float x);
|
|
long double logp1l(long double x);
|
|
double log2(double x);
|
|
float log2f(float x);
|
|
long double log2l(long double x);
|
|
double log2p1(double x);
|
|
float log2p1f(float x);
|
|
long double log2p1l(long double x);
|
|
double logb(double x);
|
|
float logbf(float x);
|
|
long double logbl(long double x);
|
|
double modf(double value, double *iptr);
|
|
float modff(float value, float *iptr);
|
|
long double modfl(long double value, long double *iptr);
|
|
double scalbn(double x, int n);
|
|
float scalbnf(float x, int n);
|
|
long double scalbnl(long double x, int n);
|
|
double scalbln(double x, long int n);
|
|
float scalblnf(float x, long int n);
|
|
long double scalblnl(long double x, long int n);
|
|
double cbrt(double x);
|
|
float cbrtf(float x);
|
|
long double cbrtl(long double x);
|
|
double compoundn(double x, long long int n);
|
|
float compoundnf(float x, long long int n);
|
|
long double compoundnl(long double x, long long int n);
|
|
double fabs(double x);
|
|
float fabsf(float x);
|
|
long double fabsl(long double x);
|
|
double hypot(double x, double y);
|
|
float hypotf(float x, float y);
|
|
long double hypotl(long double x, long double y);
|
|
double pow(double x, double y);
|
|
float powf(float x, float y);
|
|
long double powl(long double x, long double y);
|
|
double pown(double x, long long int n);
|
|
float pownf(float x, long long int n);
|
|
long double pownl(long double x, long long int n);
|
|
double powr(double y, double x);
|
|
float powrf(float y, float x);
|
|
long double powrl(long double y, long double x);
|
|
double rootn(double x, long long int n);
|
|
float rootnf(float x, long long int n);
|
|
long double rootnl(long double x, long long int n);
|
|
double rsqrt(double x);
|
|
float rsqrtf(float x);
|
|
long double rsqrtl(long double x);
|
|
double sqrt(double x);
|
|
float sqrtf(float x);
|
|
long double sqrtl(long double x);
|
|
double erf(double x);
|
|
float erff(float x);
|
|
long double erfl(long double x);
|
|
double erfc(double x);
|
|
float erfcf(float x);
|
|
long double erfcl(long double x);
|
|
double lgamma(double x);
|
|
float lgammaf(float x);
|
|
long double lgammal(long double x);
|
|
double tgamma(double x);
|
|
float tgammaf(float x);
|
|
long double tgammal(long double x);
|
|
double ceil(double x);
|
|
float ceilf(float x);
|
|
long double ceill(long double x);
|
|
double floor(double x);
|
|
float floorf(float x);
|
|
long double floorl(long double x);
|
|
double nearbyint(double x);
|
|
float nearbyintf(float x);
|
|
long double nearbyintl(long double x);
|
|
double rint(double x);
|
|
float rintf(float x);
|
|
long double rintl(long double x);
|
|
long int lrint(double x);
|
|
long int lrintf(float x);
|
|
long int lrintl(long double x);
|
|
long long int llrint(double x);
|
|
long long int llrintf(float x);
|
|
long long int llrintl(long double x);
|
|
double round(double x);
|
|
float roundf(float x);
|
|
long double roundl(long double x);
|
|
long int lround(double x);
|
|
long int lroundf(float x);
|
|
long int lroundl(long double x);
|
|
long long int llround(double x);
|
|
long long int llroundf(float x);
|
|
long long int llroundl(long double x);
|
|
double roundeven(double x);
|
|
float roundevenf(float x);
|
|
long double roundevenl(long double x);
|
|
double trunc(double x);
|
|
float truncf(float x);
|
|
long double truncl(long double x);
|
|
double fromfp(double x, int rnd, unsigned int width);
|
|
float fromfpf(float x, int rnd, unsigned int width);
|
|
long double fromfpl(long double x, int rnd, unsigned int width);
|
|
double ufromfp(double x, int rnd, unsigned int width);
|
|
float ufromfpf(float x, int rnd, unsigned int width);
|
|
long double ufromfpl(long double x, int rnd, unsigned int width);
|
|
double fromfpx(double x, int rnd, unsigned int width);
|
|
float fromfpxf(float x, int rnd, unsigned int width);
|
|
long double fromfpxl(long double x, int rnd, unsigned int width);
|
|
double ufromfpx(double x, int rnd, unsigned int width);
|
|
float ufromfpxf(float x, int rnd, unsigned int width);
|
|
long double ufromfpxl(long double x, int rnd, unsigned int width);
|
|
double fmod(double x, double y);
|
|
float fmodf(float x, float y);
|
|
long double fmodl(long double x, long double y);
|
|
double remainder(double x, double y);
|
|
float remainderf(float x, float y);
|
|
long double remainderl(long double x, long double y);
|
|
double remquo(double x, double y, int *quo);
|
|
float remquof(float x, float y, int *quo);
|
|
long double remquol(long double x, long double y, int *quo);
|
|
double copysign(double x, double y);
|
|
float copysignf(float x, float y);
|
|
long double copysignl(long double x, long double y);
|
|
double nan(const char *tagp);
|
|
float nanf(const char *tagp);
|
|
long double nanl(const char *tagp);
|
|
double nextafter(double x, double y);
|
|
float nextafterf(float x, float y);
|
|
long double nextafterl(long double x, long double y);
|
|
double nexttoward(double x, long double y);
|
|
float nexttowardf(float x, long double y);
|
|
long double nexttowardl(long double x, long double y);
|
|
double nextup(double x);
|
|
float nextupf(float x);
|
|
long double nextupl(long double x);
|
|
double nextdown(double x);
|
|
float nextdownf(float x);
|
|
long double nextdownl(long double x);
|
|
int canonicalize(double * cx, const double * x);
|
|
int canonicalizef(float * cx, const float * x);
|
|
int canonicalizel(long double * cx, const long double * x);
|
|
double fdim(double x, double y);
|
|
float fdimf(float x, float y);
|
|
long double fdiml(long double x, long double y);
|
|
double fmax(double x, double y);
|
|
float fmaxf(float x, float y);
|
|
long double fmaxl(long double x, long double y);
|
|
double fmin(double x, double y);
|
|
float fminf(float x, float y);
|
|
long double fminl(long double x, long double y);
|
|
double fmaximum(double x, double y);
|
|
float fmaximumf(float x, float y);
|
|
long double fmaximuml(long double x, long double y);
|
|
double fminimum(double x, double y);
|
|
float fminimumf(float x, float y);
|
|
long double fminimuml(long double x, long double y);
|
|
double fmaximum_mag(double x, double y);
|
|
float fmaximum_magf(float x, float y);
|
|
long double fmaximum_magl(long double x, long double y);
|
|
double fminimum_mag(double x, double y);
|
|
float fminimum_magf(float x, float y);
|
|
long double fminimum_magl(long double x, long double y);
|
|
double fmaximum_num(double x, double y);
|
|
float fmaximum_numf(float x, float y);
|
|
long double fmaximum_numl(long double x, long double y);
|
|
double fminimum_num(double x, double y);
|
|
float fminimum_numf(float x, float y);
|
|
long double fminimum_numl(long double x, long double y);
|
|
double fmaximum_mag_num(double x, double y);
|
|
float fmaximum_mag_numf(float x, float y);
|
|
long double fmaximum_mag_numl(long double x, long double y);
|
|
double fminimum_mag_num(double x, double y);
|
|
float fminimum_mag_numf(float x, float y);
|
|
long double fminimum_mag_numl(long double x, long double y);
|
|
double fma(double x, double y, double z);
|
|
float fmaf(float x, float y, float z);
|
|
long double fmal(long double x, long double y, long double z);
|
|
float fadd(double x, double y);
|
|
float faddl(long double x, long double y);
|
|
double daddl(long double x, long double y);
|
|
float fsub(double x, double y);
|
|
float fsubl(long double x, long double y);
|
|
double dsubl(long double x, long double y);
|
|
float fmul(double x, double y);
|
|
float fmull(long double x, long double y);
|
|
double dmull(long double x, long double y);
|
|
 float fdiv(double x, double y);
|
|
float fdivl(long double x, long double y);
|
|
double ddivl(long double x, long double y);
|
|
float ffma(double x, double y, double z);
|
|
float ffmal(long double x, long double y, long double z);
|
|
double dfmal(long double x, long double y, long double z);
|
|
float fsqrt(double x);
|
|
float fsqrtl(long double x);
|
|
double dsqrtl(long double x);
|
|
int isgreater(real-floating x, real-floating y);
|
|
int isgreaterequal(real-floating x, real-floating y);
|
|
int isless(real-floating x, real-floating y);
|
|
int islessequal(real-floating x, real-floating y);
|
|
int islessgreater(real-floating x, real-floating y);
|
|
int isunordered(real-floating x, real-floating y);
|
|
int iseqsig(real-floating x, real-floating y);
|
|
|
|
|
|
Only if the implementation defines __STDC_IEC_60559_DFP__ :
|
|
_Decimal32 acosd32(_Decimal32 x);
|
|
_Decimal64 acosd64(_Decimal64 x);
|
|
_Decimal128 acosd128(_Decimal128 x);
|
|
_Decimal32 asind32(_Decimal32 x);
|
|
_Decimal64 asind64(_Decimal64 x);
|
|
_Decimal128 asind128(_Decimal128 x);
|
|
_Decimal32 atand32(_Decimal32 x);
|
|
_Decimal64 atand64(_Decimal64 x);
|
|
_Decimal128 atand128(_Decimal128 x);
|
|
_Decimal32 atan2d32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 atan2d64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 atan2d128(_Decimal128 y, _Decimal128 x);
|
|
_Decimal32 cosd32(_Decimal32 x);
|
|
_Decimal64 cosd64(_Decimal64 x);
|
|
_Decimal128 cosd128(_Decimal128 x);
|
|
_Decimal32 sind32(_Decimal32 x);
|
|
_Decimal64 sind64(_Decimal64 x);
|
|
_Decimal128 sind128(_Decimal128 x);
|
|
_Decimal32 tand32(_Decimal32 x);
|
|
_Decimal64 tand64(_Decimal64 x);
|
|
_Decimal128 tand128(_Decimal128 x);
|
|
_Decimal32 acospid32(_Decimal32 x);
|
|
_Decimal64 acospid64(_Decimal64 x);
|
|
_Decimal128 acospid128(_Decimal128 x);
|
|
_Decimal32 asinpid32(_Decimal32 x);
|
|
_Decimal64 asinpid64(_Decimal64 x);
|
|
_Decimal128 asinpid128(_Decimal128 x);
|
|
_Decimal32 atanpid32(_Decimal32 x);
|
|
_Decimal64 atanpid64(_Decimal64 x);
|
|
_Decimal128 atanpid128(_Decimal128 x);
|
|
_Decimal32 atan2pid32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 atan2pid64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 atan2pid128(_Decimal128 y, _Decimal128 x);
|
|
_Decimal32 cospid32(_Decimal32 x);
|
|
_Decimal64 cospid64(_Decimal64 x);
|
|
_Decimal128 cospid128(_Decimal128 x);
|
|
_Decimal32 sinpid32(_Decimal32 x);
|
|
_Decimal64 sinpid64(_Decimal64 x);
|
|
_Decimal128 sinpid128(_Decimal128 x);
|
|
_Decimal32 tanpid32(_Decimal32 x);
|
|
_Decimal64 tanpid64(_Decimal64 x);
|
|
_Decimal128 tanpid128(_Decimal128 x);
|
|
_Decimal32 acoshd32(_Decimal32 x);
|
|
_Decimal64 acoshd64(_Decimal64 x);
|
|
_Decimal128 acoshd128(_Decimal128 x);
|
|
_Decimal32 asinhd32(_Decimal32 x);
|
|
_Decimal64 asinhd64(_Decimal64 x);
|
|
_Decimal128 asinhd128(_Decimal128 x);
|
|
_Decimal32 atanhd32(_Decimal32 x);
|
|
_Decimal64 atanhd64(_Decimal64 x);
|
|
_Decimal128 atanhd128(_Decimal128 x);
|
|
_Decimal32 coshd32(_Decimal32 x);
|
|
_Decimal64 coshd64(_Decimal64 x);
|
|
_Decimal128 coshd128(_Decimal128 x);
|
|
_Decimal32 sinhd32(_Decimal32 x);
|
|
_Decimal64 sinhd64(_Decimal64 x);
|
|
_Decimal128 sinhd128(_Decimal128 x);
|
|
_Decimal32 tanhd32(_Decimal32 x);
|
|
_Decimal64 tanhd64(_Decimal64 x);
|
|
_Decimal128 tanhd128(_Decimal128 x);
|
|
_Decimal32 expd32(_Decimal32 x);
|
|
_Decimal64 expd64(_Decimal64 x);
|
|
_Decimal128 expd128(_Decimal128 x);
|
|
_Decimal32 exp10d32(_Decimal32 x);
|
|
_Decimal64 exp10d64(_Decimal64 x);
|
|
_Decimal128 exp10d128(_Decimal128 x);
|
|
_Decimal32 exp10m1d32(_Decimal32 x);
|
|
_Decimal64 exp10m1d64(_Decimal64 x);
|
|
_Decimal128 exp10m1d128(_Decimal128 x);
|
|
_Decimal32 exp2d32(_Decimal32 x);
|
|
_Decimal64 exp2d64(_Decimal64 x);
|
|
_Decimal128 exp2d128(_Decimal128 x);
|
|
_Decimal32 exp2m1d32(_Decimal32 x);
|
|
_Decimal64 exp2m1d64(_Decimal64 x);
|
|
_Decimal128 exp2m1d128(_Decimal128 x);
|
|
_Decimal32 expm1d32(_Decimal32 x);
|
|
_Decimal64 expm1d64(_Decimal64 x);
|
|
_Decimal128 expm1d128(_Decimal128 x);
|
|
_Decimal32 frexpd32(_Decimal32 value, int *p);
|
|
_Decimal64 frexpd64(_Decimal64 value, int *p);
|
|
_Decimal128 frexpd128(_Decimal128 value, int *p);
|
|
int ilogbd32(_Decimal32 x);
|
|
int ilogbd64(_Decimal64 x);
|
|
int ilogbd128(_Decimal128 x);
|
|
_Decimal32 ldexpd32(_Decimal32 x, int p);
|
|
_Decimal64 ldexpd64(_Decimal64 x, int p);
|
|
_Decimal128 ldexpd128(_Decimal128 x, int p);
|
|
long int llogbd32(_Decimal32 x);
|
|
long int llogbd64(_Decimal64 x);
|
|
long int llogbd128(_Decimal128 x);
|
|
_Decimal32 logd32(_Decimal32 x);
|
|
_Decimal64 logd64(_Decimal64 x);
|
|
_Decimal128 logd128(_Decimal128 x);
|
|
_Decimal32 log10d32(_Decimal32 x);
|
|
_Decimal64 log10d64(_Decimal64 x);
|
|
_Decimal128 log10d128(_Decimal128 x);
|
|
_Decimal32 log10p1d32(_Decimal32 x);
|
|
_Decimal64 log10p1d64(_Decimal64 x);
|
|
_Decimal128 log10p1d128(_Decimal128 x);
|
|
_Decimal32 log1pd32(_Decimal32 x);
|
|
_Decimal64 log1pd64(_Decimal64 x);
|
|
_Decimal128 log1pd128(_Decimal128 x);
|
|
_Decimal32 logp1d32(_Decimal32 x);
|
|
_Decimal64 logp1d64(_Decimal64 x);
|
|
_Decimal128 logp1d128(_Decimal128 x);
|
|
_Decimal32 log2d32(_Decimal32 x);
|
|
_Decimal64 log2d64(_Decimal64 x);
|
|
_Decimal128 log2d128(_Decimal128 x);
|
|
_Decimal32 log2p1d32(_Decimal32 x);
|
|
_Decimal64 log2p1d64(_Decimal64 x);
|
|
_Decimal128 log2p1d128(_Decimal128 x);
|
|
_Decimal32 logbd32(_Decimal32 x);
|
|
_Decimal64 logbd64(_Decimal64 x);
|
|
_Decimal128 logbd128(_Decimal128 x);
|
|
_Decimal32 modfd32(_Decimal32 x, _Decimal32 *iptr);
|
|
_Decimal64 modfd64(_Decimal64 x, _Decimal64 *iptr);
|
|
_Decimal128 modfd128(_Decimal128 x, _Decimal128 *iptr);
|
|
_Decimal32 scalbnd32(_Decimal32 x, int n);
|
|
_Decimal64 scalbnd64(_Decimal64 x, int n);
|
|
_Decimal128 scalbnd128(_Decimal128 x, int n);
|
|
_Decimal32 scalblnd32(_Decimal32 x, long int n);
|
|
_Decimal64 scalblnd64(_Decimal64 x, long int n);
|
|
_Decimal128 scalblnd128(_Decimal128 x, long int n);
|
|
_Decimal32 cbrtd32(_Decimal32 x);
|
|
_Decimal64 cbrtd64(_Decimal64 x);
|
|
_Decimal128 cbrtd128(_Decimal128 x);
|
|
_Decimal32 compoundnd32(_Decimal32 x, long long int n);
|
|
_Decimal64 compoundnd64(_Decimal64 x, long long int n);
|
|
_Decimal128 compoundnd128(_Decimal128 x, long long int n);
|
|
_Decimal32 fabsd32(_Decimal32 x);
|
|
_Decimal64 fabsd64(_Decimal64 x);
|
|
_Decimal128 fabsd128(_Decimal128 x);
|
|
_Decimal32 hypotd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 hypotd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 hypotd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 powd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 powd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 powd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 pownd32(_Decimal32 x, long long int n);
|
|
_Decimal64 pownd64(_Decimal64 x, long long int n);
|
|
_Decimal128 pownd128(_Decimal128 x, long long int n);
|
|
_Decimal32 powrd32(_Decimal32 y, _Decimal32 x);
|
|
_Decimal64 powrd64(_Decimal64 y, _Decimal64 x);
|
|
_Decimal128 powrd128(_Decimal128 y, _Decimal128 x);
|
|
_Decimal32 rootnd32(_Decimal32 x, long long int n);
|
|
_Decimal64 rootnd64(_Decimal64 x, long long int n);
|
|
_Decimal128 rootnd128(_Decimal128 x, long long int n);
|
|
_Decimal32 rsqrtd32(_Decimal32 x);
|
|
_Decimal64 rsqrtd64(_Decimal64 x);
|
|
_Decimal128 rsqrtd128(_Decimal128 x);
|
|
_Decimal32 sqrtd32(_Decimal32 x);
|
|
_Decimal64 sqrtd64(_Decimal64 x);
|
|
_Decimal128 sqrtd128(_Decimal128 x);
|
|
_Decimal32 erfd32(_Decimal32 x);
|
|
_Decimal64 erfd64(_Decimal64 x);
|
|
_Decimal128 erfd128(_Decimal128 x);
|
|
_Decimal32 erfcd32(_Decimal32 x);
|
|
_Decimal64 erfcd64(_Decimal64 x);
|
|
_Decimal128 erfcd128(_Decimal128 x);
|
|
_Decimal32 lgammad32(_Decimal32 x);
|
|
_Decimal64 lgammad64(_Decimal64 x);
|
|
_Decimal128 lgammad128(_Decimal128 x);
|
|
_Decimal32 tgammad32(_Decimal32 x);
|
|
_Decimal64 tgammad64(_Decimal64 x);
|
|
_Decimal128 tgammad128(_Decimal128 x);
|
|
_Decimal32 ceild32(_Decimal32 x);
|
|
_Decimal64 ceild64(_Decimal64 x);
|
|
_Decimal128 ceild128(_Decimal128 x);
|
|
_Decimal32 floord32(_Decimal32 x);
|
|
_Decimal64 floord64(_Decimal64 x);
|
|
_Decimal128 floord128(_Decimal128 x);
|
|
_Decimal32 nearbyintd32(_Decimal32 x);
|
|
_Decimal64 nearbyintd64(_Decimal64 x);
|
|
_Decimal128 nearbyintd128(_Decimal128 x);
|
|
_Decimal32 rintd32(_Decimal32 x);
|
|
_Decimal64 rintd64(_Decimal64 x);
|
|
_Decimal128 rintd128(_Decimal128 x);
|
|
long int lrintd32(_Decimal32 x);
|
|
long int lrintd64(_Decimal64 x);
|
|
long int lrintd128(_Decimal128 x);
|
|
long long int llrintd32(_Decimal32 x);
|
|
long long int llrintd64(_Decimal64 x);
|
|
long long int llrintd128(_Decimal128 x);
|
|
_Decimal32 roundd32(_Decimal32 x);
|
|
_Decimal64 roundd64(_Decimal64 x);
|
|
_Decimal128 roundd128(_Decimal128 x);
|
|
long int lroundd32(_Decimal32 x);
|
|
long int lroundd64(_Decimal64 x);
|
|
long int lroundd128(_Decimal128 x);
|
|
long long int llroundd32(_Decimal32 x);
|
|
long long int llroundd64(_Decimal64 x);
|
|
long long int llroundd128(_Decimal128 x);
|
|
_Decimal32 roundevend32(_Decimal32 x);
|
|
_Decimal64 roundevend64(_Decimal64 x);
|
|
_Decimal128 roundevend128(_Decimal128 x);
|
|
_Decimal32 truncd32(_Decimal32 x);
|
|
_Decimal64 truncd64(_Decimal64 x);
|
|
_Decimal128 truncd128(_Decimal128 x);
|
|
_Decimal32 fromfpd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 fromfpd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 fromfpd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 ufromfpd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 ufromfpd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 ufromfpd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 fromfpxd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 fromfpxd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 fromfpxd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 ufromfpxd32(_Decimal32 x, int rnd, unsigned int width);
|
|
_Decimal64 ufromfpxd64(_Decimal64 x, int rnd, unsigned int width);
|
|
_Decimal128 ufromfpxd128(_Decimal128 x, int rnd, unsigned int width);
|
|
_Decimal32 fmodd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmodd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmodd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 remainderd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 remainderd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 remainderd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 copysignd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 copysignd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 copysignd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 nand32(const char *tagp);
|
|
_Decimal64 nand64(const char *tagp);
|
|
_Decimal128 nand128(const char *tagp);
|
|
_Decimal32 nextafterd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 nextafterd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 nextafterd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 nexttowardd32(_Decimal32 x, _Decimal128 y);
|
|
_Decimal64 nexttowardd64(_Decimal64 x, _Decimal128 y);
|
|
_Decimal128 nexttowardd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 nextupd32(_Decimal32 x);
|
|
_Decimal64 nextupd64(_Decimal64 x);
|
|
_Decimal128 nextupd128(_Decimal128 x);
|
|
_Decimal32 nextdownd32(_Decimal32 x);
|
|
_Decimal64 nextdownd64(_Decimal64 x);
|
|
_Decimal128 nextdownd128(_Decimal128 x);
|
|
int canonicalized32(_Decimal32 cx, const _Decimal32 * x);
|
|
int canonicalized64(_Decimal64 cx, const _Decimal64 * x);
|
|
int canonicalized128(_Decimal128 cx, const _Decimal128 * x);
|
|
_Decimal32 fdimd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fdimd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fdimd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmaxd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaxd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaxd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmind32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmind64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmind128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmaximumd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximumd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximumd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fminimumd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimumd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimumd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmaximum_magd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_magd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_magd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fminimum_magd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_magd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_magd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmaximum_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_numd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fminimum_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_numd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmaximum_mag_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fmaximum_mag_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fmaximum_mag_numd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fminimum_mag_numd32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 fminimum_mag_numd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 fminimum_mag_numd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 fmad32(_Decimal32 x, _Decimal32 y, _Decimal32 z);
|
|
_Decimal64 fmad64(_Decimal64 x, _Decimal64 y, _Decimal64 z);
|
|
_Decimal128 fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
_Decimal32 d32addd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32addd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64addd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 d32subd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32subd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64subd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 d32muld64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32muld128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64muld128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 d32divd64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal32 d32divd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal64 d64divd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 d32fmad64(_Decimal64 x, _Decimal64 y, _Decimal64 z);
|
|
 _Decimal32 d32fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
_Decimal64 d64fmad128(_Decimal128 x, _Decimal128 y, _Decimal128 z);
|
|
_Decimal32 d32sqrtd64(_Decimal64 x);
|
|
_Decimal32 d32sqrtd128(_Decimal128 x);
|
|
_Decimal64 d64sqrtd128(_Decimal128 x);
|
|
_Decimal32 quantized32(_Decimal32 x, _Decimal32 y);
|
|
_Decimal64 quantized64(_Decimal64 x, _Decimal64 y);
|
|
_Decimal128 quantized128(_Decimal128 x, _Decimal128 y);
|
|
bool samequantumd32(_Decimal32 x, _Decimal32 y);
|
|
bool samequantumd64(_Decimal64 x, _Decimal64 y);
|
|
bool samequantumd128(_Decimal128 x, _Decimal128 y);
|
|
_Decimal32 quantumd32(_Decimal32 x);
|
|
_Decimal64 quantumd64(_Decimal64 x);
|
|
_Decimal128 quantumd128(_Decimal128 x);
|
|
long long int llquantexpd32(_Decimal32 x);
|
|
long long int llquantexpd64(_Decimal64 x);
|
|
long long int llquantexpd128(_Decimal128 x);
|
|
void encodedecd32(unsigned char encptr[restrict static 4],
|
|
const _Decimal32*restrict xptr);
|
|
void encodedecd64(unsigned char encptr[restrict static 8],
|
|
const _Decimal64*restrict xptr);
|
|
void encodedecd128(unsigned char encptr[restrict static 16],
|
|
const _Decimal128*restrict xptr);
|
|
void decodedecd32(_Decimal32 * restrict xptr,
|
|
const unsigned char encptr[restrict static 4]);
|
|
void decodedecd64(_Decimal64 * restrict xptr,
|
|
const unsigned char encptr[restrict static 8]);
|
|
void decodedecd128(_Decimal128 * restrict xptr,
|
|
const unsigned char encptr[restrict static 16]);
|
|
void encodebind32(unsigned char encptr[restrict static 4],
|
|
const _Decimal32 * restrict xptr);
|
|
void encodebind64(unsigned char encptr[restrict static 8],
|
|
const _Decimal64 * restrict xptr);
|
|
void encodebind128(unsigned char encptr[restrict static 16],
|
|
const _Decimal128 * restrict xptr);
|
|
void decodebind32(_Decimal32 * restrict xptr,
|
|
const unsigned char encptr[restrict static 4]);
|
|
void decodebind64(_Decimal64 * restrict xptr,
|
|
const unsigned char encptr[restrict static 8]);
|
|
void decodebind128(_Decimal128 * restrict xptr,
|
|
const unsigned char encptr[restrict static 16]);
|
|
|
|
|
|
Only if the implementation defines __STDC_IEC_60559_BFP__ or __STDC_IEC_559__ and addition-
|
|
ally the user code defines __STDC_WANT_IEC_60559_EXT__ before any inclusion of <math.h>:
|
|
|
|
int totalorder(const double *x, const double *y);
|
|
int totalorderf(const float *x, const float *y);
|
|
int totalorderl(const long double *x, const long double *y);
|
|
int totalordermag(const double *x, const double *y);
|
|
int totalordermagf(const float *x, const float *y);
|
|
int totalordermagl(const long double *x, const long double *y);
|
|
double getpayload(const double *x);
|
|
float getpayloadf(const float *x);
|
|
long double getpayloadl(const long double *x);
|
|
int setpayload(double *res, double pl);
|
|
int setpayloadf(float *res, float pl);
|
|
int setpayloadl(long double *res, long double pl);
|
|
int setpayloadsig(double *res, double pl);
|
|
int setpayloadsigf(float *res, float pl);
|
|
int setpayloadsigl(long double *res, long double pl);
|
|
Only if the implementation defines __STDC_IEC_60559_DFP__ and additionally the user code
|
|
defines __STDC_WANT_IEC_60559_EXT__ before any inclusion of <math.h>:
|
|
|
|
_Decimal32_t _Decimal64_t HUGE_VAL_D32 HUGE_VAL_D64 HUGE_VAL_D128
|
|
|
|
|
|
int totalorderd32(const _Decimal32 *x, const _Decimal32 *y);
|
|
int totalorderd64(const _Decimal64 *x, const _Decimal64 *y);
|
|
int totalorderd128(const _Decimal128 *x, const _Decimal128 *y);
|
|
int totalordermagd32(const _Decimal32 *x, const _Decimal32 *y);
|
|
int totalordermagd64(const _Decimal64 *x, const _Decimal64 *y);
|
|
int totalordermagd128(const _Decimal128 *x, const _Decimal128 *y);
|
|
_Decimal32 getpayloadd32(const _Decimal32 *x);
|
|
_Decimal64 getpayloadd64(const _Decimal64 *x);
|
|
_Decimal128 getpayloadd128(const _Decimal128 *x);
|
|
int setpayloadd32(_Decimal32 *res, _Decimal32 pl);
|
|
int setpayloadd64(_Decimal64 *res, _Decimal64 pl);
|
|
int setpayloadd128(_Decimal128 *res, _Decimal128 pl);
|
|
int setpayloadsigd32(_Decimal32 *res, _Decimal32 pl);
|
|
int setpayloadsigd64(_Decimal64 *res, _Decimal64 pl);
|
|
int setpayloadsigd128(_Decimal128 *res, _Decimal128 pl);
|
|
|
|
|
|
</pre>
|
|
<a name='B.12'></a>
|
|
<hr>
|
|
<h3>B.12 [Non-local jumps <setjmp.h>]</h3>
|
|
<pre>jmp_buf
|
|
|
|
|
|
int setjmp(jmp_buf env);
|
|
[[noreturn]] void longjmp(jmp_buf env, int val);
|
|
|
|
|
|
</pre>
|
|
<a name='B.13'></a>
|
|
<hr>
|
|
<h3>B.13 [Signal handling <signal.h>]</h3>
|
|
<pre>sig_atomic_t SIG_IGN SIGILL SIGTERM
|
|
SIG_DFL SIGABRT SIGINT
|
|
SIG_ERR SIGFPE SIGSEGV
|
|
|
|
|
|
void (*signal(int sig, void (*func)(int)))(int);
|
|
int raise(int sig);
|
|
|
|
|
|
</pre>
|
|
<a name='B.14'></a>
|
|
<hr>
|
|
<h3>B.14 [Alignment <stdalign.h>]</h3>
|
|
<pre>The header <stdalign.h> provides no content.
|
|
|
|
</pre>
|
|
<a name='B.15'></a>
|
|
<hr>
|
|
<h3>B.15 [Variable arguments <stdarg.h>]</h3>
|
|
<pre>va_list
|
|
|
|
type va_arg(va_list ap, type);
|
|
void va_copy(va_list dest, va_list src);
|
|
void va_end(va_list ap);
|
|
void va_start(va_list ap, ...);
|
|
|
|
|
|
</pre>
|
|
<a name='B.16'></a>
|
|
<hr>
|
|
<h3>B.16 [Atomics <stdatomic.h>]</h3>
|
|
<pre>__STDC_NO_ATOMICS__ ATOMIC_CHAR16_T_LOCK_FREE ATOMIC_SHORT_LOCK_FREE
|
|
ATOMIC_BOOL_LOCK_FREE ATOMIC_CHAR32_T_LOCK_FREE ATOMIC_INT_LOCK_FREE
|
|
ATOMIC_CHAR_LOCK_FREE ATOMIC_WCHAR_T_LOCK_FREE ATOMIC_LONG_LOCK_FREE
|
|
ATOMIC_LLONG_LOCK_FREE atomic_ushort atomic_int_least64_t
|
|
ATOMIC_POINTER_LOCK_FREE atomic_int atomic_uint_least64_t
|
|
ATOMIC_FLAG_INIT atomic_uint atomic_int_fast8_t
|
|
memory_order atomic_long atomic_uint_fast8_t
|
|
atomic_flag atomic_ulong atomic_int_fast16_t
|
|
memory_order_relaxed atomic_llong atomic_uint_fast16_t
|
|
memory_order_consume atomic_ullong atomic_int_fast32_t
|
|
memory_order_acquire atomic_char16_t atomic_uint_fast32_t
|
|
memory_order_release atomic_char32_t atomic_int_fast64_t
|
|
memory_order_acq_rel atomic_wchar_t atomic_uint_fast64_t
|
|
memory_order_seq_cst atomic_int_least8_t atomic_intptr_t
|
|
atomic_bool atomic_uint_least8_t atomic_uintptr_t
|
|
atomic_char atomic_int_least16_t atomic_size_t
|
|
atomic_schar atomic_uint_least16_t atomic_ptrdiff_t
|
|
atomic_uchar atomic_int_least32_t atomic_intmax_t
|
|
atomic_short atomic_uint_least32_t atomic_uintmax_t
|
|
|
|
|
|
void atomic_init(volatile A *obj, C value);
|
|
type kill_dependency(type y);
|
|
void atomic_thread_fence(memory_order order);
|
|
void atomic_signal_fence(memory_order order);
|
|
bool atomic_is_lock_free(const volatile A *obj);
|
|
void atomic_store(volatile A *object, C desired);
|
|
void atomic_store_explicit(volatile A *object, C desired, memory_order order);
|
|
C atomic_load(const volatile A *object);
|
|
C atomic_load_explicit(const volatile A *object, memory_order order);
|
|
C atomic_exchange(volatile A *object, C desired);
|
|
C atomic_exchange_explicit(volatile A *object, C desired, memory_order order);
|
|
bool atomic_compare_exchange_strong(volatile A *object, C *expected, C desired);
|
|
bool atomic_compare_exchange_strong_explicit(volatile A *object, C *expected,
|
|
C desired, memory_order success, memory_order failure);
|
|
bool atomic_compare_exchange_weak(volatile A *object, C *expected, C desired);
|
|
bool atomic_compare_exchange_weak_explicit(volatile A *object, C *expected,
|
|
C desired, memory_order success, memory_order failure);
|
|
C atomic_fetch_key(volatile A *object, M operand);
|
|
C atomic_fetch_key_explicit(volatile A *object, M operand, memory_order order);
|
|
bool atomic_flag_test_and_set(volatile atomic_flag *object);
|
|
bool atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
|
|
memory_order order);
|
|
void atomic_flag_clear(volatile atomic_flag *object);
|
|
void atomic_flag_clear_explicit(volatile atomic_flag *object,
|
|
memory_order order);
|
|
|
|
|
|
</pre>
|
|
<a name='B.17'></a>
|
|
<hr>
|
|
<h3>B.17 [Bit and byte utilities <stdbit.h>]</h3>
|
|
<pre>__STDC_ENDIAN_BIG__ __STDC_ENDIAN_LITTLE__ __STDC_ENDIAN_NATIVE__
|
|
|
|
|
|
int stdc_leading_zerosuc(unsigned char value);
|
|
int stdc_leading_zerosus(unsigned short value);
|
|
int stdc_leading_zerosui(unsigned int value);
|
|
int stdc_leading_zerosul(unsigned long value);
|
|
int stdc_leading_zerosull(unsigned long long value);
|
|
generic_return_type stdc_leading_zeros(generic_value_type value);
|
|
int stdc_leading_onesuc(unsigned char value);
|
|
int stdc_leading_onesus(unsigned short value);
|
|
int stdc_leading_onesui(unsigned int value);
|
|
int stdc_leading_onesul(unsigned long value);
|
|
int stdc_leading_onesull(unsigned long long value);
|
|
generic_return_type stdc_leading_ones(generic_value_type value);
|
|
int stdc_trailing_zerosuc(unsigned char value);
|
|
int stdc_trailing_zerosus(unsigned short value);
|
|
int stdc_trailing_zerosui(unsigned int value);
|
|
int stdc_trailing_zerosul(unsigned long value);
|
|
int stdc_trailing_zerosull(unsigned long long value);
|
|
generic_return_type stdc_trailing_zeros(generic_value_type value);
|
|
int stdc_trailing_onesuc(unsigned char value);
|
|
int stdc_trailing_onesus(unsigned short value);
|
|
int stdc_trailing_onesui(unsigned int value);
|
|
int stdc_trailing_onesul(unsigned long value);
|
|
int stdc_trailing_onesull(unsigned long long value);
|
|
generic_return_type stdc_trailing_ones(generic_value_type value);
|
|
int stdc_first_leading_zerouc(unsigned char value);
|
|
int stdc_first_leading_zerous(unsigned short value);
|
|
int stdc_first_leading_zeroui(unsigned int value);
|
|
int stdc_first_leading_zeroul(unsigned long value);
|
|
int stdc_first_leading_zeroull(unsigned long long value);
|
|
generic_return_type stdc_first_leading_zero(generic_value_type value);
|
|
int stdc_first_leading_oneuc(unsigned char value);
|
|
int stdc_first_leading_oneus(unsigned short value);
|
|
int stdc_first_leading_oneui(unsigned int value);
|
|
int stdc_first_leading_oneul(unsigned long value);
|
|
int stdc_first_leading_oneull(unsigned long long value);
|
|
generic_return_type stdc_first_leading_one(generic_value_type value);
|
|
int stdc_first_trailing_zerouc(unsigned char value);
|
|
int stdc_first_trailing_zerous(unsigned short value);
|
|
int stdc_first_trailing_zeroui(unsigned int value);
|
|
int stdc_first_trailing_zeroul(unsigned long value);
|
|
int stdc_first_trailing_zeroull(unsigned long long value);
|
|
generic_return_type stdc_first_trailing_zero(generic_value_type value);
|
|
int stdc_first_trailing_oneuc(unsigned char value);
|
|
int stdc_first_trailing_oneus(unsigned short value);
|
|
int stdc_first_trailing_oneui(unsigned int value);
|
|
int stdc_first_trailing_oneul(unsigned long value);
|
|
int stdc_first_trailing_oneull(unsigned long long value);
|
|
generic_return_type stdc_first_trailing_one(generic_value_type value);
|
|
int stdc_count_onesuc(unsigned char value);
|
|
int stdc_count_onesus(unsigned short value);
|
|
int stdc_count_onesui(unsigned int value);
|
|
int stdc_count_onesul(unsigned long value);
|
|
int stdc_count_onesull(unsigned long long value);
|
|
generic_return_type stdc_count_ones(generic_value_type value);
|
|
int stdc_count_zerosuc(unsigned char value);
|
|
int stdc_count_zerosus(unsigned short value);
|
|
int stdc_count_zerosui(unsigned int value);
|
|
int stdc_count_zerosul(unsigned long value);
|
|
int stdc_count_zerosull(unsigned long long value);
|
|
generic_return_type stdc_count_zeros(generic_value_type value);
|
|
bool stdc_has_single_bituc(unsigned char value);
|
|
bool stdc_has_single_bitus(unsigned short value);
|
|
bool stdc_has_single_bitui(unsigned int value);
|
|
bool stdc_has_single_bitul(unsigned long value);
|
|
bool stdc_has_single_bitull(unsigned long long value);
|
|
bool stdc_has_single_bit(generic_value_type value);
|
|
int stdc_bit_widthuc(unsigned char value);
|
|
int stdc_bit_widthus(unsigned short value);
|
|
int stdc_bit_widthui(unsigned int value);
|
|
int stdc_bit_widthul(unsigned long value);
|
|
int stdc_bit_widthull(unsigned long long value);
|
|
generic_return_type stdc_bit_width(generic_value_type value);
|
|
 unsigned char stdc_bit_flooruc(unsigned char value);
|
|
unsigned short stdc_bit_floorus(unsigned short value);
|
|
unsigned int stdc_bit_floorui(unsigned int value);
|
|
unsigned long stdc_bit_floorul(unsigned long value);
|
|
unsigned long long stdc_bit_floorull(unsigned long long value);
|
|
generic_value_type stdc_bit_floor(generic_value_type value);
|
|
unsigned char stdc_bit_ceiluc(unsigned char value);
|
|
unsigned short stdc_bit_ceilus(unsigned short value);
|
|
unsigned int stdc_bit_ceilui(unsigned int value);
|
|
unsigned long stdc_bit_ceilul(unsigned long value);
|
|
unsigned long long stdc_bit_ceilull(unsigned long long value);
|
|
generic_value_type stdc_bit_ceil(generic_value_type value);
|
|
|
|
|
|
</pre>
|
|
<a name='B.18'></a>
|
|
<hr>
|
|
<h3>B.18 [Boolean type and values <stdbool.h>]</h3>
|
|
<pre>__bool_true_false_are_defined
|
|
|
|
</pre>
|
|
<a name='B.19'></a>
|
|
<hr>
|
|
<h3>B.19 [Common definitions <stddef.h>]</h3>
|
|
<pre>ptrdiff_t size_t wchar_t
|
|
nullptr_t max_align_t NULL
|
|
|
|
|
|
offsetof(type, member-designator)
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <stddef.h>:
|
|
|
|
rsize_t
|
|
|
|
|
|
</pre>
|
|
<a name='B.20'></a>
|
|
<hr>
|
|
<h3>B.20 [Integer types <stdint.h>]</h3>
|
|
<pre>intN_t UINT_LEASTN_MAX PTRDIFF_MAX
|
|
uintN_t UINT_LEASTN_WIDTH SIG_ATOMIC_MIN
|
|
int_leastN_t INT_FASTN_MIN SIG_ATOMIC_MAX
|
|
uint_leastN_t INT_FASTN_MAX SIG_ATOMIC_WIDTH
|
|
int_fastN_t INT_FASTN_WIDTH SIZE_MAX
|
|
uint_fastN_t UINT_FASTN_MAX SIZE_WIDTH
|
|
intptr_t UINT_FASTN_WIDTH WCHAR_MIN
|
|
uintptr_t INTPTR_MIN WCHAR_MAX
|
|
intmax_t INTPTR_MAX WCHAR_WIDTH
|
|
uintmax_t INTPTR_WIDTH WINT_MIN
|
|
INTN_MIN UINTPTR_MAX WINT_MAX
|
|
INTN_MAX UINTPTR_WIDTH WINT_WIDTH
|
|
INTN_WIDTH INTMAX_MIN INTN_C( value )
|
|
UINTN_MAX INTMAX_MAX UINTN_C( value )
|
|
UINTN_WIDTH INTMAX_WIDTH INTMAX_C( value )
|
|
INT_LEASTN_MIN UINTMAX_MAX UINTMAX_C( value )
|
|
INT_LEASTN_MAX UINTMAX_WIDTH
|
|
INT_LEASTN_WIDTH PTRDIFF_MIN
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <stdint.h>:
|
|
|
|
RSIZE_MAX
|
|
|
|
|
|
</pre>
|
|
<a name='B.21'></a>
|
|
<hr>
|
|
<h3>B.21 [Input/output <stdio.h>]</h3>
|
|
<pre>size_t _IONBF SEEK_CUR stdout
|
|
_PRINTF_NAN_LEN_MAX
|
|
FILE BUFSIZ SEEK_END
|
|
fpos_t EOF SEEK_SET
|
|
NULL FOPEN_MAX TMP_MAX
|
|
_IOFBF FILENAME_MAX stderr
|
|
_IOLBF L_tmpnam stdin
|
|
|
|
|
|
int remove(const char *filename);
|
|
int rename(const char *old, const char *new);
|
|
FILE *tmpfile(void);
|
|
char *tmpnam(char *s);
|
|
int fclose(FILE *stream);
|
|
int fflush(FILE *stream);
|
|
FILE *fopen(const char * restrict filename, const char * restrict mode);
|
|
FILE *freopen(const char * restrict filename, const char * restrict mode,
|
|
FILE * restrict stream);
|
|
void setbuf(FILE * restrict stream, char * restrict buf);
|
|
int setvbuf(FILE * restrict stream, char * restrict buf, int mode, size_t size);
|
|
int printf(const char * restrict format, ...);
|
|
int scanf(const char * restrict format, ...);
|
|
int snprintf(char * restrict s, size_t n, const char * restrict format, ...);
|
|
int sprintf(char * restrict s, const char * restrict format, ...);
|
|
int sscanf(const char * restrict s, const char * restrict format, ...);
|
|
int vfprintf(FILE * restrict stream, const char * restrict format, va_list arg);
|
|
int vfscanf(FILE * restrict stream, const char * restrict format, va_list arg);
|
|
int vprintf(const char * restrict format, va_list arg);
|
|
int vscanf(const char * restrict format, va_list arg);
|
|
int vsnprintf(char * restrict s, size_t n, const char * restrict format, va_list arg);
|
|
int vsprintf(char * restrict s, const char * restrict format, va_list arg);
|
|
int vsscanf(const char * restrict s, const char * restrict format, va_list arg);
|
|
int fgetc(FILE *stream);
|
|
char *fgets(char * restrict s, int n, FILE * restrict stream);
|
|
int fputc(int c, FILE *stream);
|
|
int fputs(const char * restrict s, FILE * restrict stream);
|
|
int getc(FILE *stream);
|
|
int getchar(void);
|
|
int putc(int c, FILE *stream);
|
|
int putchar(int c);
|
|
int puts(const char *s);
|
|
int ungetc(int c, FILE *stream);
|
|
size_t fread(void * restrict ptr, size_t size, size_t nmemb,
|
|
FILE * restrict stream);
|
|
size_t fwrite(const void * restrict ptr, size_t size, size_t nmemb,
|
|
FILE * restrict stream);
|
|
int fgetpos(FILE * restrict stream, fpos_t * restrict pos);
|
|
int fseek(FILE *stream, long int offset, int whence);
|
|
int fsetpos(FILE *stream, const fpos_t *pos);
|
|
long int ftell(FILE *stream);
|
|
void rewind(FILE *stream);
|
|
void clearerr(FILE *stream);
|
|
int feof(FILE *stream);
|
|
int ferror(FILE *stream);
|
|
void perror(const char *s);
|
|
int fprintf(FILE * restrict stream, const char * restrict format, ...);
|
|
int fscanf(FILE * restrict stream, const char * restrict format, ...);
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <stdio.h>:
|
|
L_tmpnam_s TMP_MAX_S errno_t rsize_t
|
|
|
|
|
|
errno_t tmpfile_s(FILE * restrict * restrict streamptr);
|
|
errno_t tmpnam_s(char *s, rsize_t maxsize);
|
|
errno_t fopen_s(FILE * restrict * restrict streamptr,
|
|
const char * restrict filename, const char * restrict mode);
|
|
errno_t freopen_s(FILE * restrict * restrict newstreamptr,
|
|
const char * restrict filename, const char * restrict mode,
|
|
FILE * restrict stream);
|
|
int fprintf_s(FILE * restrict stream, const char * restrict format, ...);
|
|
int fscanf_s(FILE * restrict stream, const char * restrict format, ...);
|
|
int printf_s(const char * restrict format, ...);
|
|
int scanf_s(const char * restrict format, ...);
|
|
int snprintf_s(char * restrict s, rsize_t n, const char * restrict format, ...);
|
|
int sprintf_s(char * restrict s, rsize_t n, const char * restrict format, ...);
|
|
int sscanf_s(const char * restrict s, const char * restrict format, ...);
|
|
int vfprintf_s(FILE *restrict stream, const char *restrict format, va_list arg);
|
|
int vfscanf_s(FILE *restrict stream, const char *restrict format, va_list arg);
|
|
int vprintf_s(const char * restrict format, va_list arg);
|
|
int vscanf_s(const char * restrict format, va_list arg);
|
|
int vsnprintf_s(char *restrict s, rsize_t n, const char *restrict format,
|
|
va_list arg);
|
|
int vsprintf_s(char * restrict s, rsize_t n, const char * restrict format,
|
|
va_list arg);
|
|
int vsscanf_s(const char *restrict s, const char *restrict format, va_list arg);
|
|
char *gets_s(char *s, rsize_t n);
|
|
|
|
|
|
</pre>
|
|
<a name='B.22'></a>
|
|
<hr>
|
|
<h3>B.22 [General utilities <stdlib.h>]</h3>
|
|
<pre>size_t div_t lldiv_t EXIT_FAILURE RAND_MAX
|
|
wchar_t ldiv_t NULL EXIT_SUCCESS MB_CUR_MAX
|
|
|
|
|
|
double atof(const char *nptr);
|
|
int atoi(const char *nptr);
|
|
long int atol(const char *nptr);
|
|
long long int atoll(const char *nptr);
|
|
int strfromd(char *restrict s, size_t n, const char *restrict format, double fp);
|
|
int strfromf(char *restrict s, size_t n, const char *restrict format, float fp);
|
|
int strfroml(char *restrict s, size_t n, const char *restrict format, long double fp);
|
|
|
|
double strtod(const char *restrict nptr, char **restrict endptr);
|
|
float strtof(const char *restrict nptr, char **restrict endptr);
|
|
long double strtold(const char *restrict nptr, char **restrict endptr);
|
|
long int strtol(const char *restrict nptr, char **restrict endptr, int base);
|
|
long long int strtoll(const char *restrict nptr, char **restrict endptr, int base);
|
|
unsigned long int strtoul(const char *restrict nptr, char **restrict endptr, int base);
|
|
unsigned long long int strtoull(const char *restrict nptr, char **restrict endptr, int
|
|
base);
|
|
int rand(void);
|
|
void srand(unsigned int seed);
|
|
void *aligned_alloc(size_t alignment, size_t size);
|
|
void *calloc(size_t nmemb, size_t size);
|
|
void free(void *ptr);
|
|
void free_sized(void *ptr, size_t size);
|
|
void free_aligned_sized(void *ptr, size_t alignment, size_t size);
|
|
void *malloc(size_t size);
|
|
void *realloc(void *ptr, size_t size);
|
|
[[noreturn]] void abort(void);
|
|
int atexit(void (*func)(void));
|
|
 int at_quick_exit(void (*func)(void));
|
|
[[noreturn]] void exit(int status);
|
|
[[noreturn]] void _Exit(int status);
|
|
char *getenv(const char *name);
|
|
[[noreturn]] void quick_exit(int status);
|
|
int system(const char *string);
|
|
void *bsearch(const void *key, const void *base, size_t nmemb, size_t size,
|
|
int (*compar)(const void *, const void *));
|
|
void qsort(void *base, size_t nmemb, size_t size,
|
|
int (*compar)(const void *, const void *));
|
|
int abs(int j);
|
|
long int labs(long int j);
|
|
long long int llabs(long long int j);
|
|
div_t div(int numer, int denom);
|
|
ldiv_t ldiv(long int numer, long int denom);
|
|
lldiv_t lldiv(long long int numer, long long int denom);
|
|
int mblen(const char *s, size_t n);
|
|
int mbtowc(wchar_t * restrict pwc, const char * restrict s, size_t n);
|
|
int wctomb(char *s, wchar_t wc);
|
|
size_t mbstowcs(wchar_t * restrict pwcs, const char * restrict s, size_t n);
|
|
size_t wcstombs(char * restrict s, const wchar_t * restrict pwcs, size_t n);
|
|
size_t memalignment(const void * p);
|
|
|
|
|
|
Only if the implementation defines __STDC_IEC_60559_DFP__ :
|
|
|
|
int strfromd32(char*restrict s, size_t n, const char*restrict format, _Decimal32 fp);
|
|
int strfromd64(char*restrict s, size_t n, const char*restrict format, _Decimal64 fp);
|
|
int strfromd128(char*restrict s, size_t n, const char*restrict format, _Decimal128 fp);
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <stdlib.h>:
|
|
|
|
errno_t rsize_t constraint_handler_t
|
|
|
|
|
|
constraint_handler_t set_constraint_handler_s(constraint_handler_t handler);
|
|
void abort_handler_s(const char * restrict msg, void * restrict ptr,
|
|
errno_t error);
|
|
void ignore_handler_s(const char * restrict msg, void * restrict ptr,
|
|
errno_t error);
|
|
errno_t getenv_s(size_t * restrict len, char * restrict value, rsize_t maxsize,
|
|
const char * restrict name);
|
|
void *bsearch_s(const void *key, QVoid *base, rsize_t nmemb, rsize_t size,
|
|
int (*compar)(const void *k, const void *y, void *context),
|
|
void *context);
|
|
errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
|
|
int (*compar)(const void *x, const void *y, void *context),
|
|
void *context);
|
|
errno_t wctomb_s(int *restrict status, char *restrict s, rsize_t smax,
|
|
wchar_t wc);
|
|
errno_t mbstowcs_s(size_t *restrict retval, wchar_t *restrict dst,
|
|
rsize_t dstmax, const char * restrict src, rsize_t len);
|
|
errno_t wcstombs_s(size_t * restrict retval, char * restrict dst, rsize_t dstmax,
|
|
const wchar_t * restrict src, rsize_t len);
|
|
|
|
|
|
</pre>
|
|
<a name='B.23'></a>
|
|
<hr>
|
|
<h3>B.23 [_Noreturn <stdnoreturn.h>]</h3>
|
|
<pre>noreturn
|
|
|
|
</pre>
|
|
<a name='B.24'></a>
|
|
<hr>
|
|
<h3>B.24 [ckd_ Checked Integer Operations <stdckdint.h>]</h3>
|
|
<pre>bool ckd_add(type1 *result, type2 a, type3 b);
|
|
bool ckd_sub(type1 *result, type2 a, type3 b);
|
|
bool ckd_mul(type1 *result, type2 a, type3 b);
|
|
|
|
|
|
</pre>
|
|
<a name='B.25'></a>
|
|
<hr>
|
|
<h3>B.25 [String handling <string.h>]</h3>
|
|
<pre>size_t NULL
|
|
|
|
|
|
void *memcpy(void * restrict s1, const void * restrict s2, size_t n);
|
|
void *memccpy(void * restrict s1, const void * restrict s2, int c, size_t n);
|
|
void *memmove(void *s1, const void *s2, size_t n);
|
|
char *strcpy(char * restrict s1, const char * restrict s2);
|
|
char *strncpy(char * restrict s1, const char * restrict s2, size_t n);
|
|
char *strdup(const char *s);
|
|
char *strndup(const char *s, size_t size);
|
|
char *strcat(char * restrict s1, const char * restrict s2);
|
|
char *strncat(char * restrict s1, const char * restrict s2, size_t n);
|
|
int memcmp(const void *s1, const void *s2, size_t n);
|
|
int strcmp(const char *s1, const char *s2);
|
|
int strcoll(const char *s1, const char *s2);
|
|
int strncmp(const char *s1, const char *s2, size_t n);
|
|
size_t strxfrm(char * restrict s1, const char * restrict s2, size_t n);
|
|
QVoid *memchr(QVoid *s, int c, size_t n);
|
|
QChar *strchr(QChar *s, int c);
|
|
size_t strcspn(const char *s1, const char *s2);
|
|
QChar *strpbrk(QChar *s1, const char *s2);
|
|
QChar *strrchr(QChar *s, int c);
|
|
size_t strspn(const char *s1, const char *s2);
|
|
QChar *strstr(QChar *s1, const char *s2);
|
|
char *strtok(char * restrict s1, const char * restrict s2);
|
|
void *memset(void *s, int c, size_t n);
|
|
void *memset_explicit(void *s, int c, size_t n);
|
|
char *strerror(int errnum);
|
|
size_t strlen(const char *s);
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <string.h>:
|
|
|
|
errno_t rsize_t
|
|
|
|
|
|
errno_t memcpy_s(void * restrict s1, rsize_t s1max, const void * restrict s2,
|
|
rsize_t n);
|
|
errno_t memmove_s(void *s1, rsize_t s1max, const void *s2, rsize_t n);
|
|
errno_t strcpy_s(char * restrict s1, rsize_t s1max, const char * restrict s2);
|
|
errno_t strncpy_s(char * restrict s1, rsize_t s1max, const char * restrict s2,
|
|
rsize_t n);
|
|
errno_t strcat_s(char * restrict s1, rsize_t s1max, const char * restrict s2);
|
|
errno_t strncat_s(char * restrict s1, rsize_t s1max, const char * restrict s2,
|
|
rsize_t n);
|
|
char *strtok_s(char * restrict s1, rsize_t * restrict s1max,
|
|
const char * restrict s2, char ** restrict ptr);
|
|
errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
|
|
errno_t strerror_s(char *s, rsize_t maxsize, errno_t errnum);
|
|
size_t strerrorlen_s(errno_t errnum);
|
|
size_t strnlen_s(const char *s, size_t maxsize);
|
|
|
|
|
|
</pre>
|
|
<a name='B.26'></a>
|
|
<hr>
|
|
<h3>B.26 [Type-generic math <tgmath.h>]</h3>
|
|
<pre>acos atanpi fmin logb tanpi
|
|
asin cbrt fminimum logp1 tgamma
|
|
atan ceil fminimum_mag lrint trunc
|
|
acosh compoundn fminimum_num lround ufromfpx
|
|
asinh copysign fminimum_mag_num nearbyint ufromfp
|
|
atanh cospi fmod nextafter fadd
|
|
cos erfc frexp nextdown dadd
|
|
sin erf fromfpx nexttoward fsub
|
|
tan exp10m1 fromfp nextup dsub
|
|
cosh exp10 hypot pown fmul
|
|
sinh exp2m1 ilogb powr dmul
|
|
tanh exp2 ldexp remainder fdiv
|
|
exp expm1 lgamma remquo ddiv
|
|
log fdim llogb rint ffma
|
|
pow floor llrint rootn dfma
|
|
sqrt fmax llround roundeven fsqrt
|
|
fabs fmaximum log10p1 round dsqrt
|
|
acospi fmaximum_mag log10 rsqrt
|
|
asinpi fmaximum_num log1p scalbln
|
|
atan2pi fmaximum_mag_num log2p1 scalbn
|
|
atan2 fma log2 sinpi
|
|
|
|
|
|
Only if the implementation does not define __STDC_NO_COMPLEX__ :
|
|
|
|
carg cimag conj cproj creal
|
|
|
|
|
|
Only if the implementation defines __STDC_IEC_60559_DFP__ :
|
|
|
|
d32add d64sub d32div d64fma quantize llquantexp
|
|
d64add d32mul d64div d32sqrt samequantum
|
|
d32sub d64mul d32fma d64sqrt quantum
|
|
|
|
|
|
</pre>
|
|
<a name='B.27'></a>
|
|
<hr>
|
|
<h3>B.27 [Threads <threads.h>]</h3>
|
|
<pre>__STDC_NO_THREADS__ mtx_t thrd_timedout
|
|
thread_local tss_dtor_t thrd_success
|
|
ONCE_FLAG_INIT thrd_start_t thrd_busy
|
|
TSS_DTOR_ITERATIONS once_flag thrd_error
|
|
cnd_t mtx_plain thrd_nomem
|
|
thrd_t mtx_recursive
|
|
tss_t mtx_timed
|
|
|
|
|
|
void call_once(once_flag *flag, void (*func)(void));
|
|
int cnd_broadcast(cnd_t *cond);
|
|
void cnd_destroy(cnd_t *cond);
|
|
int cnd_init(cnd_t *cond);
|
|
int cnd_signal(cnd_t *cond);
|
|
int cnd_timedwait(cnd_t *restrict cond, mtx_t *restrict mtx,
|
|
const struct timespec *restrict ts);
|
|
int cnd_wait(cnd_t *cond, mtx_t *mtx);
|
|
void mtx_destroy(mtx_t *mtx);
|
|
int mtx_init(mtx_t *mtx, int type);
|
|
int mtx_lock(mtx_t *mtx);
|
|
int mtx_timedlock(mtx_t *restrict mtx, const struct timespec *restrict ts);
|
|
int mtx_trylock(mtx_t *mtx);
|
|
int mtx_unlock(mtx_t *mtx);
|
|
 int thrd_create(thrd_t *thr, thrd_start_t func, void *arg);
|
|
thrd_t thrd_current(void);
|
|
int thrd_detach(thrd_t thr);
|
|
int thrd_equal(thrd_t thr0, thrd_t thr1);
|
|
[[noreturn]] void thrd_exit(int res);
|
|
int thrd_join(thrd_t thr, int *res);
|
|
int thrd_sleep(const struct timespec *duration, struct timespec *remaining);
|
|
void thrd_yield(void);
|
|
int tss_create(tss_t *key, tss_dtor_t dtor);
|
|
void tss_delete(tss_t key);
|
|
void *tss_get(tss_t key);
|
|
int tss_set(tss_t key, void *val);
|
|
|
|
|
|
</pre>
|
|
<a name='B.28'></a>
|
|
<hr>
|
|
<h3>B.28 [Date and time <time.h>]</h3>
|
|
<pre>NULL size_t struct timespec
|
|
CLOCKS_PER_SEC clock_t struct tm
|
|
TIME_UTC time_t
|
|
|
|
|
|
clock_t clock(void);
|
|
double difftime(time_t time1, time_t time0);
|
|
time_t mktime(struct tm *timeptr);
|
|
time_t timegm(struct tm *timeptr);
|
|
time_t time(time_t *timer);
|
|
int timespec_get(struct timespec *ts, int base);
|
|
int timespec_getres(struct timespec *ts, int base);
|
|
[[deprecated]] char *asctime(const struct tm *timeptr);
|
|
[[deprecated]] char *ctime(const time_t *timer);
|
|
struct tm *gmtime(const time_t *timer);
|
|
struct tm *gmtime_r(const time_t *timer, struct tm *buf);
|
|
struct tm *localtime(const time_t *timer);
|
|
struct tm *localtime_r(const time_t *timer, struct tm *buf);
|
|
size_t strftime(char * restrict s, size_t maxsize, const char * restrict format,
|
|
const struct tm * restrict timeptr);
|
|
|
|
|
|
Only if supported by the implementation:
|
|
|
|
TIME_MONOTONIC
|
|
TIME_ACTIVE
|
|
|
|
|
|
Only if threads are supported and it is supported by the implementation:
|
|
|
|
TIME_THREAD_ACTIVE
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <time.h>:
|
|
|
|
errno_t rsize_t
|
|
|
|
|
|
errno_t asctime_s(char *s, rsize_t maxsize, const struct tm *timeptr);
|
|
errno_t ctime_s(char *s, rsize_t maxsize, const time_t *timer);
|
|
struct tm *gmtime_s(const time_t * restrict timer, struct tm * restrict result);
|
|
struct tm *localtime_s(const time_t *restrict timer, struct tm *restrict result);
|
|
|
|
|
|
</pre>
|
|
<a name='B.29'></a>
|
|
<hr>
|
|
<h3>B.29 [Unicode utilities <uchar.h>]</h3>
|
|
<pre>mbstate_t size_t char16_t char32_t
|
|
|
|
|
|
size_t mbrtoc8(char8_t * restrict pc8, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
size_t c8rtomb(char * restrict s, char8_t c8, mbstate_t * restrict ps);
|
|
size_t mbrtoc16(char16_t * restrict pc16, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
size_t c16rtomb(char * restrict s, char16_t c16, mbstate_t * restrict ps);
|
|
size_t mbrtoc32(char32_t * restrict pc32, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
size t c32rtomb(char * restrict s, char32_t c32, mbstate_t * restrict ps);
|
|
_
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='B.30'></a>
|
|
<hr>
|
|
<h3>B.30 [Extended multibyte/wide character utilities <wchar.h>]</h3>
|
|
<pre>wchar_t wint_t WCHAR_MAX
|
|
size_t struct tm WCHAR_MIN
|
|
mbstate_t NULL WEOF
|
|
|
|
|
|
int fwprintf(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
int fwscanf(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
int swprintf(wchar_t * restrict s, size_t n, const wchar_t * restrict format,
|
|
...);
|
|
int swscanf(const wchar_t * restrict s, const wchar_t * restrict format, ...);
|
|
int vfwprintf(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vfwscanf(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vswprintf(wchar_t * restrict s, size_t n, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vswscanf(const wchar_t * restrict s, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vwprintf(const wchar_t * restrict format, va_list arg);
|
|
int vwscanf(const wchar_t * restrict format, va_list arg);
|
|
int wprintf(const wchar_t * restrict format, ...);
|
|
int wscanf(const wchar_t * restrict format, ...);
|
|
wint_t fgetwc(FILE *stream);
|
|
wchar_t *fgetws(wchar_t * restrict s, int n, FILE * restrict stream);
|
|
wint_t fputwc(wchar_t c, FILE *stream);
|
|
int fputws(const wchar_t * restrict s, FILE * restrict stream);
|
|
int fwide(FILE *stream, int mode);
|
|
wint_t getwc(FILE *stream);
|
|
wint_t getwchar(void);
|
|
wint_t putwc(wchar_t c, FILE *stream);
|
|
wint_t putwchar(wchar_t c);
|
|
wint_t ungetwc(wint_t c, FILE *stream);
|
|
long int wcstol(const wchar_t * restrict nptr, wchar_t ** restrict endptr,
|
|
int base);
|
|
long long int wcstoll(const wchar_t * restrict nptr, wchar_t ** restrict endptr,
|
|
int base);
|
|
unsigned long int wcstoul(const wchar_t * restrict nptr,
|
|
wchar_t ** restrict endptr, int base);
|
|
unsigned long long int wcstoull(const wchar_t * restrict nptr,
|
|
wchar_t ** restrict endptr, int base);
|
|
wchar t *wcscpy(wchar_t * restrict s1, const wchar_t * restrict s2);
|
|
_
|
|
wchar_t *wcsncpy(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
wchar_t *wmemcpy(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2, size_t n);
|
|
wchar_t *wcscat(wchar_t * restrict s1, const wchar_t * restrict s2);
|
|
wchar_t *wcsncat(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
 int wcscmp(const wchar_t *s1, const wchar_t *s2);
|
|
int wcscoll(const wchar_t *s1, const wchar_t *s2);
|
|
int wcsncmp(const wchar_t *s1, const wchar_t *s2, size_t n);
|
|
size_t wcsxfrm(wchar_t * restrict s1, const wchar_t * restrict s2, size_t n);
|
|
int wmemcmp(const wchar_t *s1, const wchar_t *s2, size_t n);
|
|
QWchar_t *wcschr(QWchar_t *s, wchar_t c);
|
|
size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
|
|
QWchar_t *wcspbrk(QWchar_t *s1, const wchar_t *s2);
|
|
QWchar_t *wcsrchr(const wchar_t *s, wchar_t c);
|
|
size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
|
|
QWchar_t *wcsstr(QWchar_t *s1, const wchar_t *s2);
|
|
wchar_t *wcstok(wchar_t * restrict s1, const wchar_t * restrict s2,
|
|
wchar_t ** restrict ptr);
|
|
QWchar_t *wmemchr(QWchar_t *s, wchar_t c, size_t n);
|
|
size_t wcslen(const wchar_t *s);
|
|
wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
|
|
size_t wcsftime(wchar_t * restrict s, size_t maxsize,
|
|
const wchar_t * restrict format, const struct tm * restrict timeptr);
|
|
wint_t btowc(int c);
|
|
int wctob(wint_t c);
|
|
int mbsinit(const mbstate_t *ps);
|
|
size_t mbrlen(const char * restrict s, size_t n, mbstate_t * restrict ps);
|
|
size_t mbrtowc(wchar_t * restrict pwc, const char * restrict s, size_t n,
|
|
mbstate_t * restrict ps);
|
|
size_t wcrtomb(char * restrict s, wchar_t wc, mbstate_t * restrict ps);
|
|
size_t mbsrtowcs(wchar_t * restrict dst, const char ** restrict src, size_t len,
|
|
mbstate_t * restrict ps);
|
|
size_t wcsrtombs(char * restrict dst, const wchar_t ** restrict src, size_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines
|
|
__STDC_WANT_LIB_EXT1__ before any inclusion of <wchar.h>:
|
|
|
|
errno_t rsize_t
|
|
|
|
|
|
int fwprintf_s(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
int fwscanf_s(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
int snwprintf_s(wchar_t * restrict s, rsize_t n, const wchar_t * restrict format,
|
|
...);
|
|
int swprintf_s(wchar_t * restrict s, rsize_t n, const wchar_t * restrict format,
|
|
...);
|
|
int swscanf_s(const wchar_t * restrict s, const wchar_t * restrict format, ...);
|
|
int vfwprintf_s(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vfwscanf_s(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vsnwprintf_s(wchar_t *restrict s, rsize_t n, const wchar_t *restrict format,
|
|
va_list arg);
|
|
int vswprintf_s(wchar_t *restrict s, rsize_t n, const wchar_t *restrict format,
|
|
va_list arg);
|
|
int vswscanf_s(const wchar_t * restrict s, const wchar_t * restrict format,
|
|
va_list arg);
|
|
int vwprintf_s(const wchar_t * restrict format, va_list arg);
|
|
int vwscanf_s(const wchar_t * restrict format, va_list arg);
|
|
int wprintf_s(const wchar_t * restrict format, ...);
|
|
int wscanf_s(const wchar_t * restrict format, ...);
|
|
errno_t wcscpy_s(wchar_t *restrict s1, rsize_t s1max,
|
|
const wchar_t *restrict s2);
|
|
errno t wcsncpy_s(wchar_t * restrict s1, rsize_t s1max,
|
|
_
|
|
const wchar_t * restrict s2, rsize_t n);
|
|
 errno_t wmemcpy_s(wchar_t *restrict s1, rsize_t s1max,
|
|
const wchar_t *restrict s2, rsize_t n);
|
|
errno_t wmemmove_s(wchar_t *s1, rsize_t s1max, const wchar_t *s2, rsize_t n);
|
|
errno_t wcscat_s(wchar_t * restrict s1, rsize_t s1max,
|
|
const wchar_t * restrict s2);
|
|
errno_t wcsncat_s(wchar_t * restrict s1, rsize_t s1max,
|
|
const wchar_t * restrict s2, rsize_t n);
|
|
wchar t *wcstok_s(wchar_t * restrict s1, rsize_t * restrict s1max,
|
|
_
|
|
const wchar_t * restrict s2, wchar_t ** restrict ptr);
|
|
size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
|
|
errno_t wcrtomb_s(size_t * restrict retval, char * restrict s, rsize_t smax,
|
|
wchar_t wc, mbstate_t * restrict ps);
|
|
errno_t mbsrtowcs_s(size_t * restrict retval, wchar_t * restrict dst,
|
|
rsize_t dstmax, const char ** restrict src, rsize_t len,
|
|
mbstate_t * restrict ps);
|
|
errno_t wcsrtombs_s(size_t * restrict retval, char * restrict dst,
|
|
rsize_t dstmax, const wchar_t ** restrict src, rsize_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
</pre>
|
|
<a name='B.31'></a>
|
|
<hr>
|
|
<h3>B.31 [Wide character classification and mapping utilities <wctype.h>]</h3>
|
|
<pre>wint_t wctrans_t wctype_t WEOF
|
|
|
|
|
|
int iswalnum(wint_t wc);
|
|
int iswalpha(wint_t wc);
|
|
int iswblank(wint_t wc);
|
|
int iswcntrl(wint_t wc);
|
|
int iswdigit(wint_t wc);
|
|
int iswgraph(wint_t wc);
|
|
int iswlower(wint_t wc);
|
|
int iswprint(wint_t wc);
|
|
int iswpunct(wint_t wc);
|
|
int iswspace(wint_t wc);
|
|
int iswupper(wint_t wc);
|
|
int iswxdigit(wint_t wc);
|
|
int iswctype(wint_t wc, wctype_t desc);
|
|
wctype_t wctype(const char *property);
|
|
wint_t towlower(wint_t wc);
|
|
wint_t towupper(wint_t wc);
|
|
wint_t towctrans(wint_t wc, wctrans_t desc);
|
|
wctrans_t wctrans(const char *property);
|
|

|
|
</pre>
|
|
<a name='C.'></a>
|
|
<hr>
|
|
<h3>C. [Annex C (informative) Sequence points]</h3>
|
|
<a name='C.p1'></a>
|
|
<pre>1 The following are the sequence points described in <a href='#5.1.2.3'>5.1.2.3</a>:
|
|
|
|
— Between the evaluations of the function designator and actual arguments in a function call
|
|
and the actual call. (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
— Between the evaluations of the first and second operands of the following operators: logical
|
|
AND && (<a href='#6.5.13'>6.5.13</a>); logical OR || (<a href='#6.5.14'>6.5.14</a>); comma , (<a href='#6.5.17'>6.5.17</a>).
|
|
— Between the evaluations of the first operand of the conditional ?: operator and whichever of
|
|
the second and third operands is evaluated (<a href='#6.5.15'>6.5.15</a>).
|
|
— Between the evaluation of a full expression and the next full expression to be evaluated. The
|
|
following are full expressions: a full declarator for a variably modified type; an initializer that
|
|
is not part of a compound literal (<a href='#6.7.10'>6.7.10</a>); the expression in an expression statement (<a href='#6.8.3'>6.8.3</a>); the
|
|
controlling expression of a selection statement (if or switch) (<a href='#6.8.4'>6.8.4</a>); the controlling expression
|
|
of a while or do statement (<a href='#6.8.5'>6.8.5</a>); each of the (optional) expressions of a for statement (<a href='#6.8.5.3'>6.8.5.3</a>);
|
|
the (optional) expression in a return statement (<a href='#6.8.6.4'>6.8.6.4</a>).
|
|
— Immediately before a library function returns (<a href='#7.1.4'>7.1.4</a>).
|
|
|
|
— After the actions associated with each formatted input/output function conversion specifier
|
|
(<a href='#7.23.6'>7.23.6</a>, <a href='#7.31.2'>7.31.2</a>).
|
|
— Immediately before and immediately after each call to a comparison function, and also between
|
|
any call to a comparison function and any movement of the objects passed as arguments to
|
|
that call (<a href='#7.24.5'>7.24.5</a>).
|
|
|
|
</pre>
|
|
<a name='D.'></a>
|
|
<hr>
|
|
<h3>D. [Annex D (informative) Universal character names for identifiers]</h3>
|
|
<a name='D.p1'></a>
|
|
<pre>1 This subclause describes the choices made in application of UAX #31 ("Unicode Identifier and
|
|
Pattern Syntax") to C of the requirements from UAX #31 and how they do or do not apply to C.
|
|
For UAX #31, C conforms by meeting the requirements "Default Identifiers" (<a href='#D.1'>D.1</a>) and "Equivalent
|
|
Normalized Identifiers" (<a href='#D.1'>D.1</a>). The other requirements, also listed below, are either alternatives not
|
|
taken or do not apply to C.
|
|
|
|
</pre>
|
|
<a name='D.1'></a>
|
|
<hr>
|
|
<h3>D.1 [Default Identifiers]</h3>
|
|
<a name='D.1p1'></a>
|
|
<pre>1 UAX #31 specifies a default syntax for identifiers based on properties from the Unicode Character
|
|
Database, UAX #44. The general syntax is
|
|
|
|
<Identifier> := <Start> <Continue>* (<Medial> <Continue>+)*
|
|
|
|
|
|
where <Start> has the XID_Start property, <Continue> has the XID_Continue property, and
|
|
<Medial> is a list of characters permitted between continue characters. For C we add the character
|
|
U+005F, LOW LINE, or _, to the set of permitted Start characters, the Medial set is empty, and the
|
|
Continue characters are unmodified. In the grammar used in UAX #31, this is
|
|
|
|
<Identifier> := <Start> <Continue>*
|
|
<Start> := XID_Start + U+005F
|
|
<Continue> := <Start> + XID_Continue
|
|
|
|
|
|
This is described in the C grammar (<a href='#6.4.2.1'>6.4.2.1</a>), where identifier is formed from identifier-start or identifier
|
|
followed by identifier-continue.
|
|
|
|
</pre>
|
|
<a name='D.1.1'></a>
|
|
<hr>
|
|
<h3>D.1.1 [Restricted Format Characters]</h3>
|
|
<a name='D.1.1p1'></a>
|
|
<pre>1 If an implementation of UAX #31 wishes to allow format characters such as ZERO WIDTH JOINER
|
|
or ZERO WIDTH NON-JOINER it must define a profile allowing them, or describe precisely which
|
|
combinations are permitted.
|
|
</pre>
|
|
<a name='D.1.1p2'></a>
|
|
<pre>2 C does not allow format characters in identifiers, so this does not apply.
|
|
|
|
</pre>
|
|
<a name='D.1.2'></a>
|
|
<hr>
|
|
<h3>D.1.2 [Stable Identifiers]</h3>
|
|
<a name='D.1.2p1'></a>
|
|
<pre>1 An implementation of UAX #31 may choose to guarantee that identifiers are stable across versions
|
|
of the Unicode Standard. Once a string qualifies as an identifier it does so in all future versions.
|
|
C does not make this guarantee, except to the extent that UAX #31 guarantees the stability of the
|
|
XID_Start and XID_Continue properties.
|
|
|
|
</pre>
|
|
<a name='D.2'></a>
|
|
<hr>
|
|
<h3>D.2 [Immutable Identifiers]</h3>
|
|
<a name='D.2p1'></a>
|
|
<pre>1 An implementation may choose to guarantee that the set of identifiers will never change by fixing
|
|
the set of code points allowed in identifiers forever.
|
|
</pre>
|
|
<a name='D.2p2'></a>
|
|
<pre>2 C does not choose to make this guarantee. As scripts are added to Unicode, additional characters in
|
|
those scripts may become available for use in identifiers.
|
|
|
|
</pre>
|
|
<a name='D.3'></a>
|
|
<hr>
|
|
<h3>D.3 [Pattern_White_Space and Pattern_Syntax Characters]</h3>
|
|
<a name='D.3p1'></a>
|
|
<pre>1 UAX #31 describes how languages that use or interpret patterns of characters, such as regular
|
|
expressions or number formats, may describe that syntax with Unicode properties.
|
|
</pre>
|
|
<a name='D.3p2'></a>
|
|
<pre>2 C does not do this as part of the language, deferring to library components for such usage of patterns.
|
|
This requirement does not apply to C.
|
|
|
|
</pre>
|
|
<a name='D.4'></a>
|
|
<hr>
|
|
<h3>D.4 [Equivalent Normalized Identifiers]</h3>
|
|
<a name='D.4p1'></a>
|
|
<pre>1 UAX #31 requires that implementations describe how identifiers are compared and considered
|
|
equivalent.
|
|
</pre>
|
|
<a name='D.4p2'></a>
|
|
<pre>2 C requires that identifiers be in Normalization Form C and therefore identifiers that compare the
|
|
same under NFC are equivalent. This is described in subclause <a href='#6.4.2'>6.4.2</a>.
|
|
|
|
</pre>
|
|
<a name='D.5'></a>
|
|
<hr>
|
|
<h3>D.5 [Equivalent Case-Insensitive Identifiers]</h3>
|
|
<a name='D.5p1'></a>
|
|
<pre>1 C considers case to be significant in identifier comparison, and does not do any case folding. This
|
|
requirement does not apply to C
|
|
|
|
</pre>
|
|
<a name='D.6'></a>
|
|
<hr>
|
|
<h3>D.6 [Filtered Normalized Identifiers]</h3>
|
|
<a name='D.6p1'></a>
|
|
<pre>1 If any characters are excluded from normalization, UAX #31 requires a precise specification of those
|
|
exclusions.
|
|
</pre>
|
|
<a name='D.6p2'></a>
|
|
<pre>2 C does not make any such exclusions.
|
|
|
|
</pre>
|
|
<a name='D.7'></a>
|
|
<hr>
|
|
<h3>D.7 [Filtered Case-Insensitive Identifiers]</h3>
|
|
<a name='D.7p1'></a>
|
|
<pre>1 C identifiers are case sensitive, and therefore this requirement does not apply.
|
|
|
|
</pre>
|
|
<a name='D.8'></a>
|
|
<hr>
|
|
<h3>D.8 [Hashtag Identifiers]</h3>
|
|
<a name='D.8p1'></a>
|
|
<pre>1 There are no hashtags in C, so this requirement does not apply.
|
|
|
|
|
|
</pre>
|
|
<a name='E.'></a>
|
|
<hr>
|
|
<h3>E. [Annex E (informative) Implementation limits]</h3>
|
|
<a name='E.p1'></a>
|
|
<pre>1 The contents of the header <limits.h> are given below. The values shall all be constant expressions
|
|
suitable for use in #if preprocessing directives. The components are described further in <a href='#5.2.4.2.1'>5.2.4.2.1</a>.
|
|
</pre>
|
|
<a name='E.p2'></a>
|
|
<pre>2 For the following macros, the minimum values shown shall be replaced by implementation-defined
|
|
values.
|
|
|
|
#define BOOL_WIDTH 1
|
|
#define CHAR_BIT 8
|
|
#define USHRT_WIDTH 16
|
|
#define UINT_WIDTH 16
|
|
#define ULONG_WIDTH 32
|
|
#define ULLONG_WIDTH 64
|
|
#define BITINT_MAXWIDTH 64 // ULLONG_WIDTH
|
|
#define MB_LEN_MAX 1
|
|
|
|
|
|
</pre>
|
|
<a name='E.p3'></a>
|
|
<pre>3 For the following macros, the minimum magnitudes shown shall be replaced by implementation-
|
|
defined magnitudes with the same sign that are deduced from the macros above as indicated.<a href='#FOOTNOTE.434'><sup>[434]</sup></a>
|
|
_
|
|
#define BOOL_MAX 1 // 2BOOL WIDTH − 1
|
|
#define CHAR_MAX UCHAR_MAX or SCHAR_MAX
|
|
#define CHAR_MIN 0 or SCHAR_MIN
|
|
_
|
|
#define CHAR WIDTH 8 // CHAR_BIT
|
|
_
|
|
#define INT_MAX +32767 // 2INT WIDTH−1 − 1
|
|
INT_WIDTH−1
|
|
#define INT_MIN -32768 // −2
|
|
#define INT_WIDTH 16 // UINT_WIDTH
|
|
_
|
|
#define LONG_MAX +2147483647 // 2LONG WIDTH−1 − 1
|
|
_
|
|
#define LONG_MIN -2147483648 // −2LONG WIDTH−1
|
|
#define LONG_WIDTH 32 // ULONG_WIDTH
|
|
_
|
|
#define LLONG_MAX +9223372036854775807 // 2LLONG WIDTH−1 − 1
|
|
LLONG_WIDTH−1
|
|
#define LLONG_MIN -9223372036854775808 // −2
|
|
#define LLONG_WIDTH 64 // ULLONG_WIDTH
|
|
_
|
|
#define SCHAR_MAX +127 // 2SCHAR WIDTH−1 − 1
|
|
SCHAR_WIDTH−1
|
|
#define SCHAR_MIN -128 // −2
|
|
#define SCHAR_WIDTH 8 // CHAR_BIT
|
|
_
|
|
#define SHRT_MAX +32767 // 2SHRT WIDTH−1 − 1
|
|
SHRT_WIDTH−1
|
|
#define SHRT_MIN -32768 // −2
|
|
_
|
|
#define UCHAR_MAX 255 // 2UCHAR WIDTH − 1
|
|
#define UCHAR_WIDTH 8 _
|
|
// CHAR BIT
|
|
_
|
|
#define USHRT_MAX 65535 // 2USHRT WIDTH − 1
|
|
_
|
|
#define UINT_MAX 65535 // 2UINT WIDTH − 1
|
|
_
|
|
#define ULONG_MAX 4294967295 // 2ULONG WIDTH − 1
|
|
ULLONG_WIDTH
|
|
#define ULLONG_MAX 18446744073709551615 // 2 −1
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.434'>
|
|
<pre><i><b>Footnote 434)</b> For the minimum value of a signed integer type there is no expression consisting of a minus sign and a decimal literal of
|
|
that same type. The numbers in the table are only given as indications for the values and do not represent suitable expressions
|
|
to be used for these macros.
|
|
</i></pre>
|
|
</a>
|
|
<a name='E.p4'></a>
|
|
<pre>4 The contents of the header <float.h> are given below. All integer values, except FLT_ROUNDS, shall
|
|
be constant expressions suitable for use in #if preprocessing directives; all floating values shall be
|
|
constant expressions. The components are described further in <a href='#5.2.4.2.2'>5.2.4.2.2</a> and <a href='#5.2.4.2.3'>5.2.4.2.3</a>.
|
|
</pre>
|
|
<a name='E.p5'></a>
|
|
<pre>5 The values given in the following list shall be replaced by implementation-defined expressions:
|
|
|
|
#define FLT_EVAL_METHOD
|
|
#define FLT_ROUNDS
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
#define DEC_EVAL_METHOD
|
|
#endif
|
|
|
|
|
|
</pre>
|
|
<a name='E.p6'></a>
|
|
<pre>6 The values given in the following list shall be replaced by implementation-defined constant ex-
|
|
pressions that are greater or equal in magnitude (absolute value) to those shown, with the same
|
|
sign:
|
|
|
|
#define DBL_DECIMAL_DIG 10
|
|
#define DBL_DIG 10
|
|
#define DBL_MANT_DIG
|
|
#define DBL_MAX_10_EXP +37
|
|
#define DBL_MAX_EXP
|
|
#define DBL_MIN_10_EXP -37
|
|
#define DBL_MIN_EXP
|
|
#define DECIMAL_DIG 10
|
|
#define FLT_DECIMAL_DIG 6
|
|
#define FLT_DIG 6
|
|
#define FLT_MANT_DIG
|
|
#define FLT_MAX_10_EXP +37
|
|
#define FLT_MAX_EXP
|
|
#define FLT_MIN_10_EXP -37
|
|
#define FLT_MIN_EXP
|
|
#define FLT_RADIX 2
|
|
#define LDBL_DECIMAL_DIG 10
|
|
#define LDBL_DIG 10
|
|
#define LDBL_MANT_DIG
|
|
#define LDBL_MAX_10_EXP +37
|
|
#define LDBL_MAX_EXP
|
|
#define LDBL_MIN_10_EXP -37
|
|
#define LDBL_MIN_EXP
|
|
|
|
|
|
</pre>
|
|
<a name='E.p7'></a>
|
|
<pre>7 The values given in the following list shall be replaced by implementation-defined constant expres-
|
|
sions with values that are greater than or equal to those shown:
|
|
|
|
#define DBL_MAX 1E+37
|
|
#define DBL_NORM_MAX 1E+37
|
|
#define FLT_MAX 1E+37
|
|
#define FLT_NORM_MAX 1E+37
|
|
#define LDBL_MAX 1E+37
|
|
#define LDBL_NORM_MAX 1E+37
|
|
|
|
|
|
</pre>
|
|
<a name='E.p8'></a>
|
|
<pre>8 The values given in the following list shall be replaced by implementation-defined constant expres-
|
|
sions with (positive) values that are less than or equal to those shown:
|
|
|
|
#define DBL_EPSILON 1E-9
|
|
#define DBL_MIN 1E-37
|
|
#define FLT_EPSILON 1E-5
|
|
#define FLT_MIN 1E-37
|
|
#define LDBL_EPSILON 1E-9
|
|
#define LDBL_MIN 1E-37
|
|
|
|
|
|
</pre>
|
|
<a name='E.p9'></a>
|
|
<pre>9 If the implementation supports decimal floating types, the following macros provide the parameters
|
|
of these types as exact values.
|
|
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
#define DEC32_EPSILON 1E-6DF
|
|
#define DEC32_MANT_DIG 7
|
|
#define DEC32_MAX 9.999999E96DF
|
|
#define DEC32_MAX_EXP 97
|
|
#define DEC32_MIN 1E-95DF
|
|
#define DEC32_MIN_EXP -94
|
|
#define DEC32_TRUE_MIN 0.000001E-95DF
|
|
#define DEC64_EPSILON 1E-15DD
|
|
#define DEC64_MANT_DIG 16
|
|
#define DEC64_MAX 9.999999999999999E384DD
|
|
#define DEC64_MAX_EXP 385
|
|
#define DEC64_MIN 1E-383DD
|
|
#define DEC64_MIN_EXP -382
|
|
#define DEC64_TRUE_MIN 0.000000000000001E-383DD
|
|
#define DEC128_EPSILON 1E-33DL
|
|
#define DEC128_MANT_DIG 34
|
|
#define DEC128_MAX 9.999999999999999999999999999999999E6144DL
|
|
#define DEC128_MAX_EXP 6145
|
|
#define DEC128_MIN 1E-6143DL
|
|
#define DEC128_MIN_EXP -6142
|
|
#define DEC128_TRUE_MIN 0.000000000000000000000000000000001E-6143DL
|
|
#endif
|
|
|
|
</pre>
|
|
<a name='F.'></a>
|
|
<hr>
|
|
<h3>F. [Annex F (normative) IEC 60559 floating-point arithmetic]</h3>
|
|
<a name='F.1'></a>
|
|
<hr>
|
|
<h3>F.1 [Introduction]</h3>
|
|
<a name='F.1p1'></a>
|
|
<pre>1 This annex specifies C language support for the IEC 60559 floating-point standard. The IEC 60559
|
|
floating-point standard is specifically Floating-point arithmetic (ISO/IEC 60559:2020), also designated
|
|
as IEEE Standard for Floating-Point Arithmetic (IEEE 754–2019). IEC 60559 generally refers to the
|
|
floating-point standard, as in IEC 60559 operation, IEC 60559 format, etc.
|
|
</pre>
|
|
<a name='F.1p2'></a>
|
|
<pre>2 The IEC 60559 floating-point standard specifies decimal, as well as binary, floating-point arithmetic.
|
|
It supersedes IEEE Standard for Radix-Independent Floating-Point Arithmetic (ANSI/IEEE 854–1987)
|
|
which generalized the binary arithmetic standard (IEEE 754-1985) to remove dependencies on radix
|
|
and word length.
|
|
</pre>
|
|
<a name='F.1p3'></a>
|
|
<pre>3 An implementation that defines __STDC_IEC_60559_BFP__ to 202311L shall conform to the specifi-
|
|
cations in this annex for binary floating-point arithmetic and shall also define __STDC_IEC_559__
|
|
to 1.<a href='#FOOTNOTE.435'><sup>[435]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.435'>
|
|
<pre><i><b>Footnote 435)</b> Implementations that do not define either of __STDC_IEC_60559_BFP__ and __STDC_IEC_559__ are not required to
|
|
conform to these specifications. New code should not use the obsolescent macro __STDC_IEC_559__ to test for conformance
|
|
to this annex.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.1p4'></a>
|
|
<pre>4 An implementation that defines __STDC_IEC_60559_DFP__ to 202311L shall conform to the
|
|
specifications for decimal floating-point arithmetic in the following subclauses of this annex:
|
|
|
|
|
|
— <a href='#F.2.1'>F.2.1</a> Infinities and NaNs
|
|
— <a href='#F.3'>F.3</a> Operations
|
|
— <a href='#F.4'>F.4</a> Floating to integer conversions
|
|
— <a href='#F.6'>F.6</a> The return statement
|
|
— <a href='#F.7'>F.7</a> Contracted expressions
|
|
— <a href='#F.8'>F.8</a> Floating-point environment
|
|
— <a href='#F.9'>F.9</a> Optimization
|
|
— <a href='#F.10'>F.10</a> Mathematics <math.h> and <tgmath.h>
|
|
|
|
|
|
For the purpose of specifying these conformance requirements, the macros, functions, and values
|
|
mentioned in the subclauses listed above are understood to refer to the corresponding macros,
|
|
functions, and values for decimal floating types. Likewise, the "rounding direction mode" is
|
|
understood to refer to the rounding direction mode for decimal floating-point arithmetic.
|
|
</pre>
|
|
<a name='F.1p5'></a>
|
|
<pre>5 Where a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
|
|
behavior is adopted by reference, unless stated otherwise.
|
|
|
|
</pre>
|
|
<a name='F.2'></a>
|
|
<hr>
|
|
<h3>F.2 [Types]</h3>
|
|
<a name='F.2p1'></a>
|
|
<pre>1 The C floating types match the IEC 60559 formats as follows:
|
|
|
|
— The float type matches the IEC 60559 binary32 format.
|
|
|
|
— The double type matches the IEC 60559 binary64 format.
|
|
|
|
— The long double type matches the IEC 60559 binary128 format, else an IEC 60559 binary64-
|
|
extended format, <a href='#FOOTNOTE.436'><sup>[436]</sup></a> else a non-IEC 60559 extended format, else the IEC 60559 binary64
|
|
format.
|
|
|
|
Any non-IEC 60559 extended format used for the long double type shall have more precision than
|
|
IEC 60559 binary64 and at least the range of IEC 60559 binary64.<a href='#FOOTNOTE.437'><sup>[437]</sup></a> The value of FLT_ROUNDS
|
|
applies to all IEC 60559 types supported by the implementation, but need not apply to non-IEC 60559
|
|
types.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.436'>
|
|
<pre><i><b>Footnote 436)</b> IEC 60559 binary64-extended formats include the common 80-bit IEC 60559 format.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.437'>
|
|
<pre><i><b>Footnote 437)</b> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include all double values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.2p2'></a>
|
|
<pre>2 The long double type should match the IEC 60559 binary128 format, else an IEC 60559 binary64-
|
|
extended format.
|
|
|
|
</pre>
|
|
<a name='F.2.1'></a>
|
|
<hr>
|
|
<h3>F.2.1 [Infinities and NaNs]</h3>
|
|
<a name='F.2.1p1'></a>
|
|
<pre>1 Since negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
|
|
within the range of representable values (<a href='#5.2.4.2.2'>5.2.4.2.2</a>).
|
|
</pre>
|
|
<a name='F.2.1p2'></a>
|
|
<pre>2 The NAN and INFINITY macros in <float.h> and the nan functions in <math.h> provide designa-
|
|
tions for IEC 60559 quiet NaNs and infinities. The FLT_SNAN, DBL_SNAN, and LDBL_SNAN macros in
|
|
<float.h> provide designations for IEC 60559 signaling NaNs.
|
|
</pre>
|
|
<a name='F.2.1p3'></a>
|
|
<pre>3 This annex does not require the full support for signaling NaNs specified in IEC 60559. This
|
|
annex uses the term NaN, unless explicitly qualified, to denote quiet NaNs. Where specification of
|
|
signaling NaNs is not provided, the behavior of signaling NaNs is implementation-defined (either
|
|
treated as an IEC 60559 quiet NaN or treated as an IEC 60559 signaling NaN). <a href='#FOOTNOTE.438'><sup>[438]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.438'>
|
|
<pre><i><b>Footnote 438)</b> Since NaNs created by IEC 60559 arithmetic operations are always quiet, quiet NaNs (along with infinities) are sufficient
|
|
for closure of the arithmetic.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.2.1p4'></a>
|
|
<pre>4 Any operator or <math.h> function that raises an "invalid" floating-point exception, if delivering a
|
|
floating type result, shall return a quiet NaN, unless explicitly specified otherwise.
|
|
</pre>
|
|
<a name='F.2.1p5'></a>
|
|
<pre>5 In order to support signaling NaNs as specified in IEC 60559, an implementation should adhere to
|
|
the following recommended practice.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='F.2.1p6'></a>
|
|
<pre>6 Any floating-point operator or <math.h> function or macro with a signaling NaN input, unless
|
|
explicitly specified otherwise, raises an "invalid" floating-point exception.
|
|
</pre>
|
|
<a name='F.2.1p7'></a>
|
|
<pre>7 NOTE Some functions do not propagate quiet NaN arguments. For example, hypot(x, y) returns infinity if x or y is
|
|
infinite and the other is a quiet NaN. The recommended practice in this subclause specifies that such functions (and others)
|
|
raise the "invalid" floating-point exception if an argument is a signaling NaN, which also implies they return a quiet NaN in
|
|
these cases.
|
|
|
|
</pre>
|
|
<a name='F.2.1p8'></a>
|
|
<pre>8 The <fenv.h> header defines the macro FE_SNANS_ALWAYS_SIGNAL if and only if the implemen-
|
|
tation follows the recommended practice in this subclause. If defined, FE_SNANS_ALWAYS_SIGNAL
|
|
expands to the integer constant 1.
|
|
|
|
</pre>
|
|
<a name='F.3'></a>
|
|
<hr>
|
|
<h3>F.3 [Operations]</h3>
|
|
<a name='F.3p1'></a>
|
|
<pre>1 C operators, functions, and function-like macros provide operations specified by IEC 60559 as shown
|
|
in the following table. In the table, C functions are represented by the function name without a type
|
|
suffix. Specifications for the C facilities are provided in the listed clauses. The C specifications are
|
|
intended to match IEC 60559, unless stated otherwise.
|
|
|
|
Operation binding
|
|
|
|
IEC 60559 operation C operation Clause
|
|
roundToIntegralTiesToEven roundeven <a href='#7.12.9.8'>7.12.9.8</a>, <a href='#F.10.6.8'>F.10.6.8</a>
|
|
roundToIntegralTiesAway round <a href='#7.12.9.6'>7.12.9.6</a>, <a href='#F.10.6.6'>F.10.6.6</a>
|
|
roundToIntegralTowardZero trunc <a href='#7.12.9.9'>7.12.9.9</a>, <a href='#F.10.6.9'>F.10.6.9</a>
|
|
roundToIntegralTowardPositive ceil <a href='#7.12.9.1'>7.12.9.1</a>, <a href='#F.10.6.1'>F.10.6.1</a>
|
|
roundToIntegralTowardNegative floor <a href='#7.12.9.2'>7.12.9.2</a>, <a href='#F.10.6.2'>F.10.6.2</a>
|
|
roundToIntegralExact rint <a href='#7.12.9.4'>7.12.9.4</a>, <a href='#F.10.6.4'>F.10.6.4</a>
|
|
nextUp nextup <a href='#7.12.11.5'>7.12.11.5</a>, <a href='#F.10.8.5'>F.10.8.5</a>
|
|
nextDown nextdown <a href='#7.12.11.6'>7.12.11.6</a>, <a href='#F.10.8.6'>F.10.8.6</a>
|
|
getPayload getpayload <a href='#F.10.13.1'>F.10.13.1</a>
|
|
setPayload setpayload <a href='#F.10.13.2'>F.10.13.2</a>
|
|
setPayloadSignaling setpayloadsig <a href='#F.10.13.3'>F.10.13.3</a>
|
|
quantize quantize <a href='#7.12.15.1'>7.12.15.1</a>
|
|
sameQuantum samequantum <a href='#7.12.15.2'>7.12.15.2</a>
|
|
quantum quantum <a href='#7.12.15.3'>7.12.15.3</a>
|
|
encodeDecimal encodedec <a href='#7.12.16.1'>7.12.16.1</a>
|
|
decodeDecimal decodedec <a href='#7.12.16.2'>7.12.16.2</a>
|
|
encodeBinary encodebin <a href='#7.12.16.3'>7.12.16.3</a>
|
|
decodeBinary decodebin <a href='#7.12.16.4'>7.12.16.4</a>
|
|
remainder remainder, remquo <a href='#7.12.10.2'>7.12.10.2</a>, <a href='#F.10.7.2'>F.10.7.2</a>,
|
|
<a href='#7.12.10.3'>7.12.10.3</a>, <a href='#F.10.7.3'>F.10.7.3</a>
|
|
maximum fmaximum <a href='#7.12.12.4'>7.12.12.4</a>, <a href='#F.10.9.4'>F.10.9.4</a>
|
|
minimum fminimum <a href='#7.12.12.5'>7.12.12.5</a>, <a href='#F.10.9.4'>F.10.9.4</a>
|
|
maximumMagnitude fmaximum_mag <a href='#7.12.12.6'>7.12.12.6</a>, <a href='#F.10.9.4'>F.10.9.4</a>
|
|
minimumMagnitude fminimum_mag <a href='#7.12.12.7'>7.12.12.7</a>, <a href='#F.10.9.4'>F.10.9.4</a>
|
|
maximumNumber fmaximum_num <a href='#7.12.12.8'>7.12.12.8</a>, <a href='#F.10.9.5'>F.10.9.5</a>
|
|
minimumNumber fminimum_num <a href='#7.12.12.9'>7.12.12.9</a>, <a href='#F.10.9.5'>F.10.9.5</a>
|
|
maximumMagnitudeNumber fmaximum_mag_num <a href='#7.12.12.10'>7.12.12.10</a>, <a href='#F.10.9.5'>F.10.9.5</a>
|
|
minimumMagnitudeNumber fminimum_mag_num <a href='#7.12.12.11'>7.12.12.11</a>, <a href='#F.10.9.5'>F.10.9.5</a>
|
|
scaleB scalbn, scalbln <a href='#7.12.6.19'>7.12.6.19</a>, <a href='#F.10.3.19'>F.10.3.19</a>
|
|
logB logb, ilogb, llogb <a href='#7.12.6.17'>7.12.6.17</a>, <a href='#F.10.3.17'>F.10.3.17</a>,
|
|
<a href='#7.12.6.8'>7.12.6.8</a>, <a href='#F.10.3.8'>F.10.3.8</a>,
|
|
<a href='#7.12.6.10'>7.12.6.10</a>, <a href='#F.10.3.10'>F.10.3.10</a>
|
|
addition + , fadd, faddl, daddl <a href='#6.5.6'>6.5.6</a>, <a href='#7.12.14.1'>7.12.14.1</a>,
|
|
<a href='#F.10.11'>F.10.11</a>
|
|
subtraction - , fsub, fsubl, dsubl <a href='#6.5.6'>6.5.6</a>, <a href='#7.12.14.2'>7.12.14.2</a>,
|
|
<a href='#F.10.11'>F.10.11</a>
|
|
multiplication * , fmul, fmull, dmull <a href='#6.5.5'>6.5.5</a>, <a href='#7.12.14.3'>7.12.14.3</a>,
|
|
<a href='#F.10.11'>F.10.11</a>
|
|
division / , fdiv, fdivl, ddivl <a href='#6.5.5'>6.5.5</a>, <a href='#7.12.14.4'>7.12.14.4</a>,
|
|
<a href='#F.10.11'>F.10.11</a>
|
|
squareRoot sqrt, fsqrt, fsqrtl, dsqrtl <a href='#7.12.7.10'>7.12.7.10</a>, <a href='#F.10.4.10'>F.10.4.10</a>,
|
|
<a href='#7.12.14.6'>7.12.14.6</a>, <a href='#F.10.11'>F.10.11</a>
|
|
fusedMultiplyAdd fma, ffma, ffmal, dfmal <a href='#7.12.13.1'>7.12.13.1</a>, <a href='#F.10.10.1'>F.10.10.1</a>,
|
|
<a href='#7.12.14.5'>7.12.14.5</a>, <a href='#F.10.11'>F.10.11</a>
|
|
convertFromInt cast and implicit conversion <a href='#6.3.1.4'>6.3.1.4</a>, <a href='#6.5.4'>6.5.4</a>
|
|
convertToIntegerTiesToEven fromfp, ufromfp <a href='#7.12.9.10'>7.12.9.10</a>, <a href='#F.10.6.10'>F.10.6.10</a>
|
|
convertToIntegerTowardZero
|
|
convertToIntegerTowardPositive
|
|
convertToIntegerTowardNegative
|
|
convertToIntegerTiesToAway fromfp, ufromfp, lround, <a href='#7.12.9.10'>7.12.9.10</a>, <a href='#F.10.6.10'>F.10.6.10</a>,
|
|
llround <a href='#7.12.9.7'>7.12.9.7</a>, <a href='#F.10.6.7'>F.10.6.7</a>
|
|
convertToIntegerExactTiesToEven fromfpx, ufromfpx <a href='#7.12.9.11'>7.12.9.11</a>, <a href='#F.10.6.11'>F.10.6.11</a>
|
|
convertToIntegerExactTowardZero
|
|
convertToIntegerExactTowardPositive
|
|
convertToIntegerExactTowardNegative
|
|
convertToIntegerExactTiesToAway
|
|
convertFormat - different formats cast and implicit conversions <a href='#6.3.1.5'>6.3.1.5</a>, <a href='#6.5.4'>6.5.4</a>
|
|
convertFormat - same format canonicalize <a href='#7.12.11.7'>7.12.11.7</a>, <a href='#F.10.8.7'>F.10.8.7</a>
|
|
convertFromDecimalCharacter strtod, wcstod, scanf, wscanf , <a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.31.4.1.2'>7.31.4.1.2</a>,
|
|
decimal floating constants <a href='#7.23.6.4'>7.23.6.4</a>, <a href='#7.31.2.12'>7.31.2.12</a>,
|
|
<a href='#F.5'>F.5</a>
|
|
convertToDecimalCharacter printf, wprintf , strfromd <a href='#7.23.6.3'>7.23.6.3</a>, <a href='#7.31.2.11'>7.31.2.11</a>,
|
|
<a href='#7.24.1.3'>7.24.1.3</a>, <a href='#F.5'>F.5</a>
|
|
convertFromHexCharacter strtod, wcstod, scanf, wscanf , <a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.31.4.1.2'>7.31.4.1.2</a>,
|
|
hexadecimal floating constants <a href='#7.23.6.4'>7.23.6.4</a>, <a href='#7.31.2.12'>7.31.2.12</a>,
|
|
<a href='#F.5'>F.5</a>
|
|
convertToHexCharacter printf, wprintf , strfromd <a href='#7.23.6.3'>7.23.6.3</a>, <a href='#7.31.2.11'>7.31.2.11</a>,
|
|
<a href='#7.24.1.3'>7.24.1.3</a>, <a href='#F.5'>F.5</a>
|
|
copy memcpy, memmove, +(x) <a href='#7.26.2.1'>7.26.2.1</a>, <a href='#7.26.2.3'>7.26.2.3</a>
|
|
negate -(x) <a href='#6.5.3.3'>6.5.3.3</a>
|
|
abs fabs <a href='#7.12.7.3'>7.12.7.3</a>, <a href='#F.10.4.3'>F.10.4.3</a>
|
|
copySign copysign <a href='#7.12.11.1'>7.12.11.1</a>, <a href='#F.10.8.1'>F.10.8.1</a>
|
|
compareQuietEqual == <a href='#6.5.9'>6.5.9</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareQuietNotEqual != <a href='#6.5.9'>6.5.9</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingEqual iseqsig <a href='#7.12.17.7'>7.12.17.7</a>, <a href='#F.10.14.1'>F.10.14.1</a>
|
|
compareSignalingGreater > <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingGreaterEqual >= <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingLess < <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingLessEqual <= <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingNotEqual ! iseqsig(x) <a href='#7.12.17.7'>7.12.17.7</a>, <a href='#F.10.14.1'>F.10.14.1</a>
|
|
compareSignalingNotGreater ! (x > y) <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingLessUnordered ! (x >= y) <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingNotLess ! (x < y) <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareSignalingGreaterUnordered ! (x <= y) <a href='#6.5.8'>6.5.8</a>, <a href='#F.9.3'>F.9.3</a>
|
|
compareQuietGreater isgreater <a href='#7.12.17.1'>7.12.17.1</a>
|
|
compareQuietGreaterEqual isgreaterequal <a href='#7.12.17.2'>7.12.17.2</a>
|
|
compareQuietLess isless <a href='#7.12.17.3'>7.12.17.3</a>
|
|
compareQuietLessEqual islessequal <a href='#7.12.17.4'>7.12.17.4</a>
|
|
compareQuietUnordered isunordered <a href='#7.12.17.6'>7.12.17.6</a>
|
|
compareQuietNotGreater ! isgreater(x, y) <a href='#7.12.17.1'>7.12.17.1</a>
|
|
compareQuietLessUnordered ! isgreaterequal(x, y) <a href='#7.12.17.2'>7.12.17.2</a>
|
|
compareQuietNotLess ! isless(x, y) <a href='#7.12.17.3'>7.12.17.3</a>
|
|
compareQuietGreaterUnordered ! islessequal(x, y) <a href='#7.12.17.4'>7.12.17.4</a>
|
|
compareQuietOrdered ! isunordered(x, y) <a href='#7.12.17.6'>7.12.17.6</a>
|
|
class fpclassify, signbit, <a href='#7.12.3.1'>7.12.3.1</a>, <a href='#7.12.3.7'>7.12.3.7</a>,
|
|
issignaling <a href='#7.12.3.8'>7.12.3.8</a>
|
|
isSignMinus signbit <a href='#7.12.3.7'>7.12.3.7</a>
|
|
isNormal isnormal <a href='#7.12.3.6'>7.12.3.6</a>
|
|
isFinite isfinite <a href='#7.12.3.3'>7.12.3.3</a>
|
|
isZero iszero <a href='#7.12.3.10'>7.12.3.10</a>
|
|
isSubnormal issubnormal <a href='#7.12.3.9'>7.12.3.9</a>
|
|
isInfinite isinf <a href='#7.12.3.4'>7.12.3.4</a>
|
|
isNaN isnan <a href='#7.12.3.5'>7.12.3.5</a>
|
|
isSignaling issignaling <a href='#7.12.3.8'>7.12.3.8</a>
|
|
isCanonical iscanonical <a href='#7.12.3.2'>7.12.3.2</a>
|
|
radix FLT_RADIX <a href='#5.2.4.2.2'>5.2.4.2.2</a>
|
|
totalOrder totalorder <a href='#F.10.12.1'>F.10.12.1</a>
|
|
totalOrderMag totalordermag <a href='#F.10.12.2'>F.10.12.2</a>
|
|
lowerFlags feclearexcept <a href='#7.6.4.1'>7.6.4.1</a>
|
|
raiseFlags fesetexcept <a href='#7.6.4.4'>7.6.4.4</a>
|
|
testFlags fetestexcept <a href='#7.6.4.7'>7.6.4.7</a>
|
|
testSavedFlags fetestexceptflag <a href='#7.6.4.6'>7.6.4.6</a>
|
|
restoreFlags fesetexceptflag <a href='#7.6.4.5'>7.6.4.5</a>
|
|
saveAllFlags fegetexceptflag <a href='#7.6.4.2'>7.6.4.2</a>
|
|
getBinaryRoundingDirection fegetround <a href='#7.6.5.2'>7.6.5.2</a>
|
|
setBinaryRoundingDirection fesetround <a href='#7.6.5.5'>7.6.5.5</a>
|
|
saveModes fegetmode <a href='#7.6.5.1'>7.6.5.1</a>
|
|
restoreModes fesetmode <a href='#7.6.5.4'>7.6.5.4</a>
|
|
defaultModes fesetmode(FE_DFL_MODE) <a href='#7.6.5.4'>7.6.5.4</a>, <a href='#7.6'>7.6</a>
|
|
|
|
|
|
</pre>
|
|
<a name='F.3p2'></a>
|
|
<pre>2 The IEC 60559 requirement that certain of its operations be provided for operands of different
|
|
formats (of the same radix) is satisfied by C’s usual arithmetic conversions (<a href='#6.3.1.8'>6.3.1.8</a>) and function-call
|
|
argument conversions (<a href='#6.5.2.2'>6.5.2.2</a>). For example, the following operations take float f and double d
|
|
inputs and produce a long double result:
|
|
|
|
(long double)f * d
|
|
powl(f, d)
|
|
|
|
|
|
</pre>
|
|
<a name='F.3p3'></a>
|
|
<pre>3 The functions fmin and fmax have been superseded by fminimum_num and fmaximum_num. The fmin
|
|
and fmax functions provide the minNum and maxNum operations specified in (the superseded)
|
|
IEC 60559:2011.
|
|
</pre>
|
|
<a name='F.3p4'></a>
|
|
<pre>4 Whether C assignment (<a href='#6.5.16'>6.5.16</a>) (and conversion as if by assignment) to the same format is an
|
|
IEC 60559 convertFormat or copy operation<a href='#FOOTNOTE.439'><sup>[439]</sup></a> is implementation-defined, even if <fenv.h> defines
|
|
the macro FE_SNANS_ALWAYS_SIGNAL (<a href='#F.2.1'>F.2.1</a>). If the return expression of a return statement is
|
|
evaluated to the floating-point format of the return type, it is implementation-defined whether a
|
|
convertFormat operation is applied to the result of the return expression.
|
|
</pre>
|
|
<a name='FOOTNOTE.439'>
|
|
<pre><i><b>Footnote 439)</b> Where the source and destination formats are the same, convertFormat operations differ from copy operations in
|
|
that convertFormat operations raise the "invalid" floating-point exception on signaling NaN inputs and do not propagate
|
|
non-canonical encodings.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.3p5'></a>
|
|
<pre>5 The unary + and - operators raises no floating-point exceptions, even if the operand is a signaling
|
|
NaN.
|
|
</pre>
|
|
<a name='F.3p6'></a>
|
|
<pre>6 The C classification macros fpclassify, iscanonical, isfinite, isinf, isnan, isnormal,
|
|
issignaling, issubnormal, iszero, and signbit provide the IEC 60559 operations indicated
|
|
in the table above provided their arguments are in the format of their semantic type. Then these
|
|
macros raise no floating-point exceptions, even if an argument is a signaling NaN.
|
|
</pre>
|
|
<a name='F.3p7'></a>
|
|
<pre>7 The signbit macro, providing the IEC 60559 isSignMinus operation, determines the sign of its
|
|
argument value as the sign bit of the value’s representation. This applies to all values, including
|
|
NaNs whose sign bit is not generally interpreted by IEC 60559.
|
|
</pre>
|
|
<a name='F.3p8'></a>
|
|
<pre>8 The C nearbyint functions (<a href='#7.12.9.3'>7.12.9.3</a>, <a href='#F.10.6.3'>F.10.6.3</a>) provide the nearbyinteger function recommended in
|
|
the Appendix to (superseded) ANSI/IEEE 854.
|
|
</pre>
|
|
<a name='F.3p9'></a>
|
|
<pre>9 The C nextafter (<a href='#7.12.11.3'>7.12.11.3</a>, <a href='#F.10.8.3'>F.10.8.3</a>) and nexttoward (<a href='#7.12.11.4'>7.12.11.4</a>, <a href='#F.10.8.4'>F.10.8.4</a>) functions provide the
|
|
nextafter function recommended in the Appendix to (superseded) IEC 60559:1989 (but with a
|
|
minor change to better handle signed zeros).
|
|
</pre>
|
|
<a name='F.3p10'></a>
|
|
<pre>10 The macros (<a href='#7.6'>7.6</a>) FE_DOWNWARD, FE_TONEAREST, FE_TONEARESTFROMZERO, FE_TOWARDZERO, and
|
|
FE_UPWARD, which are used in conjunction with the fegetround and fesetround functions and the
|
|
FENV_ROUND pragma, represent the IEC 60559 rounding-direction attributes roundTowardNegative,
|
|
roundTiesToEven, roundTiesToAway, roundTowardZero, and roundTowardPositive, respectively,
|
|
for binary floating-point arithmetic. Support for the roundTiesToAway attribute for binary floating-
|
|
point arithmetic, and hence for the FE_TONEARESTFROMZERO macro, is optional.
|
|
</pre>
|
|
<a name='F.3p11'></a>
|
|
<pre>11 The C fegetenv (<a href='#7.6.6.1'>7.6.6.1</a>), feholdexcept (<a href='#7.6.6.2'>7.6.6.2</a>), fesetenv (<a href='#7.6.6.3'>7.6.6.3</a>) and feupdateenv (<a href='#7.6.6.4'>7.6.6.4</a>)
|
|
functions provide a facility to manage the dynamic floating-point environment, comprising the
|
|
IEC 60559 status flags and dynamic control modes.
|
|
</pre>
|
|
<a name='F.3p12'></a>
|
|
<pre>12 IEC 60559 requires operations with specified operand and result formats. Therefore, math functions
|
|
that are bound to IEC 60559 operations (see table above) must remove any extra range and precision
|
|
from arguments or results.
|
|
</pre>
|
|
<a name='F.3p13'></a>
|
|
<pre>13 IEC 60559 requires operations that round their result to formats the same as and wider than the
|
|
operands, in addition to the operations that round their result to narrower formats (see <a href='#7.12.14'>7.12.14</a>).
|
|
Operators (+ , - , * , and / ) whose evaluation formats are wider than the semantic type (<a href='#5.2.4.2.2'>5.2.4.2.2</a>)
|
|
might not support some of the IEEE 60559 operations, because getting a result in a given format
|
|
might require a cast that could introduce an extra rounding error. The functions that round result to
|
|
narrower type (<a href='#7.12.14'>7.12.14</a>) provide the IEC 60559 operations that round result to same and wider (as
|
|
well as narrower) formats, in those cases where built-in operators and casts do not. For example,
|
|
ddivl(x, y) computes a correctly rounded double divide of float x by float y, regardless of
|
|
the evaluation method.
|
|
</pre>
|
|
<a name='F.3p14'></a>
|
|
<pre>14 Decimal versions of the remquo library function are not provided. (The decimal remainder functions
|
|
provide the remainder operation defined by IEC 60559.)
|
|
</pre>
|
|
<a name='F.3p15'></a>
|
|
<pre>15 The binding for the convertFormat operation applies to all conversions among IEC 60559 formats.
|
|
Therefore, for implementations that conform to Annex F, conversions between decimal floating types
|
|
and standard floating types with IEC 60559 formats are correctly rounded and raise floating-point
|
|
exceptions as specified in IEC 60559.
|
|
</pre>
|
|
<a name='F.3p16'></a>
|
|
<pre>16 IEC 60559 specifies the convertFromHexCharacter and convertToHexCharacter operations only for
|
|
binary floating-point arithmetic.
|
|
</pre>
|
|
<a name='F.3p17'></a>
|
|
<pre>17 The integer constant 10 provides the radix operation defined in IEC 60559 for decimal floating-point
|
|
arithmetic.
|
|
</pre>
|
|
<a name='F.3p18'></a>
|
|
<pre>18 The fe_dec_getround (<a href='#7.6.5.3'>7.6.5.3</a>) and fe_dec_setround (<a href='#7.6.5.6'>7.6.5.6</a>) functions provide the getDeci-
|
|
malRoundingDirection and setDecimalRoundingDirection operations defined in IEC 60559 for
|
|
decimal floating-point arithmetic. The macros (<a href='#7.6'>7.6</a>) FE_DEC_DOWNWARD, FE_DEC_TONEAREST,
|
|
FE_DEC_TONEARESTFROMZERO, FE_DEC_TOWARDZERO, and FE_DEC_UPWARD, which are used in con-
|
|
junction with the fe_dec_getround and fe_dec_setround functions and the FENV_DEC_ROUND
|
|
pragma, represent the IEC 60559 rounding-direction attributes roundTowardNegative, roundTiesTo-
|
|
Even, roundTiesToAway, roundTowardZero, and roundTowardPositive, respectively, for decimal
|
|
floating-point arithmetic.
|
|
</pre>
|
|
<a name='F.3p19'></a>
|
|
<pre>19 The llquantexpdN (<a href='#7.12.15.4'>7.12.15.4</a>) functions compute the (quantum) exponent q defined in IEC 60559
|
|
for decimal numbers viewed as having integer significands.
|
|
</pre>
|
|
<a name='F.3p20'></a>
|
|
<pre>20 The C functions in the following table correspond to mathematical operations recommended by
|
|
IEC 60559. However, correct rounding, which IEC 60559 specifies for its operations, is not required
|
|
for the C functions in the table. <a href='#7.33.8'>7.33.8</a> (potentially) reserves cr_ prefixed names for functions fully
|
|
matching the IEC 60559 mathematical operations. In the table, the C functions are represented by
|
|
the function name without a type suffix.
|
|
|
|
IEC 60559 operation C function Clause
|
|
exp exp <a href='#7.12.6.1'>7.12.6.1</a>, <a href='#F.10.3.1'>F.10.3.1</a>
|
|
expm1 expm1 <a href='#7.12.6.6'>7.12.6.6</a>, <a href='#F.10.3.6'>F.10.3.6</a>
|
|
exp2 exp2 <a href='#7.12.6.4'>7.12.6.4</a>, <a href='#F.10.3.4'>F.10.3.4</a>
|
|
exp2m1 exp2m1 <a href='#7.12.6.5'>7.12.6.5</a>, <a href='#F.10.3.5'>F.10.3.5</a>
|
|
exp10 exp10 <a href='#7.12.6.2'>7.12.6.2</a>, <a href='#F.10.3.2'>F.10.3.2</a>
|
|
exp10m1 exp10m1 <a href='#7.12.6.3'>7.12.6.3</a>, <a href='#F.10.3.3'>F.10.3.3</a>
|
|
log log <a href='#7.12.6.11'>7.12.6.11</a>, <a href='#F.10.3.11'>F.10.3.11</a>
|
|
log2 log2 <a href='#7.12.6.15'>7.12.6.15</a>, <a href='#F.10.3.15'>F.10.3.15</a>
|
|
log10 log10 <a href='#7.12.6.12'>7.12.6.12</a>, <a href='#F.10.3.12'>F.10.3.12</a>
|
|
logp1 log1p, logp1 <a href='#7.12.6.14'>7.12.6.14</a>, <a href='#F.10.3.14'>F.10.3.14</a>
|
|
log2p1 log2p1 <a href='#7.12.6.16'>7.12.6.16</a>, <a href='#F.10.3.16'>F.10.3.16</a>
|
|
log10p1 log10p1 <a href='#7.12.6.13'>7.12.6.13</a>, <a href='#F.10.3.13'>F.10.3.13</a>
|
|
hypot hypot <a href='#7.12.7.4'>7.12.7.4</a>, <a href='#F.10.4.4'>F.10.4.4</a>
|
|
rSqrt rsqrt <a href='#7.12.7.9'>7.12.7.9</a>, <a href='#F.10.4.9'>F.10.4.9</a>
|
|
compound compoundn <a href='#7.12.7.2'>7.12.7.2</a>, <a href='#F.10.4.2'>F.10.4.2</a>
|
|
rootn rootn <a href='#7.12.7.8'>7.12.7.8</a>, <a href='#F.10.4.8'>F.10.4.8</a>
|
|
pown pown <a href='#7.12.7.6'>7.12.7.6</a>, <a href='#F.10.4.6'>F.10.4.6</a>
|
|
pow pow <a href='#7.12.7.5'>7.12.7.5</a>, <a href='#F.10.4.5'>F.10.4.5</a>
|
|
powr powr <a href='#7.12.7.7'>7.12.7.7</a>, <a href='#F.10.4.7'>F.10.4.7</a>
|
|
sin sin <a href='#7.12.4.6'>7.12.4.6</a>, <a href='#F.10.1.6'>F.10.1.6</a>
|
|
... continued ...
|
|
... continued ...
|
|
IEC 60559 operation C function Clause
|
|
cos cos <a href='#7.12.4.5'>7.12.4.5</a>, <a href='#F.10.1.5'>F.10.1.5</a>
|
|
tan tan <a href='#7.12.4.7'>7.12.4.7</a>, <a href='#F.10.1.7'>F.10.1.7</a>
|
|
sinPi sinpi <a href='#7.12.4.13'>7.12.4.13</a>, <a href='#F.10.1.13'>F.10.1.13</a>
|
|
cosPi cospi <a href='#7.12.4.12'>7.12.4.12</a>, <a href='#F.10.1.12'>F.10.1.12</a>
|
|
tanPi tanpi <a href='#7.12.4.14'>7.12.4.14</a>, <a href='#F.10.1.14'>F.10.1.14</a>
|
|
asinPi asinpi <a href='#7.12.4.9'>7.12.4.9</a>, <a href='#F.10.1.9'>F.10.1.9</a>
|
|
acosPi acospi <a href='#7.12.4.8'>7.12.4.8</a>, <a href='#F.10.1.8'>F.10.1.8</a>
|
|
atanPi atanpi <a href='#7.12.4.10'>7.12.4.10</a>, <a href='#F.10.1.10'>F.10.1.10</a>
|
|
atan2Pi atan2pi <a href='#7.12.4.11'>7.12.4.11</a>, <a href='#F.10.1.11'>F.10.1.11</a>
|
|
asin asin <a href='#7.12.4.2'>7.12.4.2</a>, <a href='#F.10.1.2'>F.10.1.2</a>
|
|
acos acos <a href='#7.12.4.1'>7.12.4.1</a>, <a href='#F.10.1.1'>F.10.1.1</a>
|
|
atan atan <a href='#7.12.4.3'>7.12.4.3</a>, <a href='#F.10.1.3'>F.10.1.3</a>
|
|
atan2 atan2 <a href='#7.12.4.4'>7.12.4.4</a>, <a href='#F.10.1.4'>F.10.1.4</a>
|
|
sinh sinh <a href='#7.12.5.5'>7.12.5.5</a>, <a href='#F.10.2.5'>F.10.2.5</a>
|
|
cosh cosh <a href='#7.12.5.4'>7.12.5.4</a>, <a href='#F.10.2.4'>F.10.2.4</a>
|
|
tanh tanh <a href='#7.12.5.6'>7.12.5.6</a>, <a href='#F.10.2.6'>F.10.2.6</a>
|
|
asinh asinh <a href='#7.12.5.2'>7.12.5.2</a>, <a href='#F.10.2.2'>F.10.2.2</a>
|
|
acosh acosh <a href='#7.12.5.1'>7.12.5.1</a>, <a href='#F.10.2.1'>F.10.2.1</a>
|
|
atanh atanh <a href='#7.12.5.3'>7.12.5.3</a>, <a href='#F.10.2.3'>F.10.2.3</a>
|
|
|
|
|
|
</pre>
|
|
<a name='F.4'></a>
|
|
<hr>
|
|
<h3>F.4 [Floating to integer conversion]</h3>
|
|
<a name='F.4p1'></a>
|
|
<pre>1 If the integer type is bool, <a href='#6.3.1.2'>6.3.1.2</a> applies and the conversion raises no floating-point exceptions if
|
|
the floating-point value is not a signaling NaN. Otherwise, if the floating value is infinite or NaN
|
|
or if the integral part of the floating value exceeds the range of the integer type, then the "invalid"
|
|
floating-point exception is raised and the resulting value is unspecified. Otherwise, the resulting
|
|
value is determined by <a href='#6.3.1.4'>6.3.1.4</a>. Conversion of an integral floating value that does not exceed the
|
|
range of the integer type raises no floating-point exceptions; whether conversion of a non-integral
|
|
floating value raises the "inexact" floating-point exception is unspecified.<a href='#FOOTNOTE.440'><sup>[440]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.440'>
|
|
<pre><i><b>Footnote 440)</b> IEC 60559 recommends that implicit floating-to-integer conversions raise the "inexact" floating-point exception for
|
|
non-integer in-range values. In those cases where it matters, library functions can be used to effect such conversions with or
|
|
without raising the "inexact" floating- point exception. See fromfp, ufromfp, fromfpx, ufromfpx, rint, lrint, llrint, and
|
|
nearbyint in <math.h>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.5'></a>
|
|
<hr>
|
|
<h3>F.5 [Conversions between binary floating types and decimal character se-]</h3>
|
|
<a name='F.5p1'></a>
|
|
<pre>1 quences
|
|
The <float.h> header defines the macro
|
|
|
|
CR_DECIMAL_DIG
|
|
|
|
|
|
which expands to an integer constant expression suitable for use in #if preprocessing directives
|
|
whose value is a number such that conversions between all supported IEC 60559 binary formats and
|
|
character sequences with at most CR_DECIMAL_DIG significant decimal digits are correctly rounded.
|
|
The value of CR_DECIMAL_DIG shall be at least M + 3, where M is the maximum value of the
|
|
T_DECIMAL_DIG macros for IEC 60559 binary formats. If the implementation correctly rounds for
|
|
all numbers of significant decimal digits, then CR_DECIMAL_DIG shall have the value of the macro
|
|
UINTMAX_MAX.
|
|
</pre>
|
|
<a name='F.5p2'></a>
|
|
<pre>2 Conversions of types with IEC 60559 binary formats to character sequences with more than
|
|
CR_DECIMAL_DIG significant decimal digits shall correctly round to CR_DECIMAL_DIG significant
|
|
digits and pad zeros on the right.
|
|
</pre>
|
|
<a name='F.5p3'></a>
|
|
<pre>3 Conversions from character sequences with more than CR_DECIMAL_DIG significant decimal digits
|
|
to types with IEC 60559 binary formats shall correctly round to an intermediate character sequence
|
|
with CR_DECIMAL_DIG significant decimal digits, according to the applicable rounding direction,
|
|
and correctly round the intermediate result (having CR_DECIMAL_DIG significant decimal digits) to
|
|
the destination type. The "inexact" floating-point exception is raised (once) if either conversion
|
|
is inexact.<a href='#FOOTNOTE.441'><sup>[441]</sup></a> (The second conversion may raise the "overflow" or "underflow" floating-point
|
|
exception.)
|
|
</pre>
|
|
<a name='FOOTNOTE.441'>
|
|
<pre><i><b>Footnote 441)</b> The intermediate conversion is exact only if all input digits after the first CR_DECIMAL_DIG digits are 0.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.5p4'></a>
|
|
<pre>4 The specification in this subclause assures conversion between IEC 60559 binary format and decimal
|
|
character sequence follows all pertinent recommended practice. It also assures conversion from
|
|
IEC 60559 format to decimal character sequence with at least T_DECIMAL_DIG digits and back, using
|
|
to-nearest rounding, is the identity function, where T is the macro prefix for the format.
|
|
</pre>
|
|
<a name='F.5p5'></a>
|
|
<pre>5 Functions such as strtod that convert character sequences to floating types honor the rounding
|
|
direction. Hence, if the rounding direction might be upward or downward, the implementation
|
|
cannot convert a minus-signed sequence by negating the converted unsigned sequence.
|
|
</pre>
|
|
<a name='F.5p6'></a>
|
|
<pre>6 NOTE IEC 60559 specifies that conversion to one-digit character strings using roundTiesToEven when both choices have
|
|
an odd least significant digit, shall produce the value with the larger magnitude. For example, this can happen with 9.5e2
|
|
whose nearest neighbors are 9.e2 and <a href='#1.'>1.</a>e3, both of which have a single odd digit in the significand part.
|
|
|
|
</pre>
|
|
<a name='F.6'></a>
|
|
<hr>
|
|
<h3>F.6 [The return statement]</h3>
|
|
<pre>If the return expression is evaluated in a floating-point format different from the return type, the
|
|
expression is converted as if by assignment<a href='#FOOTNOTE.442'><sup>[442]</sup></a> to the return type of the function and the resulting
|
|
value is returned to the caller.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.442'>
|
|
<pre><i><b>Footnote 442)</b> Assignment removes any extra range and precision.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.7'></a>
|
|
<hr>
|
|
<h3>F.7 [Contracted expressions]</h3>
|
|
<a name='F.7p1'></a>
|
|
<pre>1 A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed zeros, sub-
|
|
normals, and the rounding directions in a manner consistent with the basic arithmetic operations
|
|
covered by IEC 60559.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='F.7p2'></a>
|
|
<pre>2 A contracted expression should raise floating-point exceptions in a manner generally consistent
|
|
with the basic arithmetic operations.
|
|
|
|
</pre>
|
|
<a name='F.8'></a>
|
|
<hr>
|
|
<h3>F.8 [Floating-point environment]</h3>
|
|
<a name='F.8p1'></a>
|
|
<pre>1 The floating-point environment defined in <fenv.h> includes the IEC 60559 floating-point exception
|
|
status flags and rounding-direction control modes. It may also include other floating-point status or
|
|
modes that the implementation provides as extensions.<a href='#FOOTNOTE.443'><sup>[443]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.443'>
|
|
<pre><i><b>Footnote 443)</b> Dynamic rounding precision and trap enablement modes are examples of such extensions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.8p2'></a>
|
|
<pre>2 This annex does not include support for IEC 60559’s optional alternate exception handling. The
|
|
specification in this annex assumes IEC 60559 default exception handling: the flag is set, a default
|
|
result is delivered, and execution continues. Implementations might provide alternate exception
|
|
handling as an extension.
|
|
|
|
</pre>
|
|
<a name='F.8.1'></a>
|
|
<hr>
|
|
<h3>F.8.1 [Environment management]</h3>
|
|
<a name='F.8.1p1'></a>
|
|
<pre>1 IEC 60559 requires that floating-point operations implicitly raise floating-point exception status
|
|
flags, and that rounding control modes can be set explicitly to affect result values of floating-point
|
|
operations. These changes to the floating-point state are treated as side effects which respect
|
|
sequence points.<a href='#FOOTNOTE.444'><sup>[444]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.444'>
|
|
<pre><i><b>Footnote 444)</b> If the state for the FENV_ACCESS pragma is "off", the implementation is free to assume the dynamic floating-point control
|
|
modes will be the default ones and the floating-point status flags will not be tested, which allows certain optimizations
|
|
(see <a href='#F.9'>F.9</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.8.2'></a>
|
|
<hr>
|
|
<h3>F.8.2 [Translation]</h3>
|
|
<a name='F.8.2p1'></a>
|
|
<pre>1 During translation, constant rounding direction modes (<a href='#7.6.2'>7.6.2</a>) are in effect where specified. Else-
|
|
where, during translation the IEC 60559 default modes are in effect:
|
|
|
|
— The rounding direction mode is rounding to nearest.
|
|
— The rounding precision mode (if supported) is set so that results are not shortened.
|
|
— Trapping or stopping (if supported) is disabled on all floating-point exceptions.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='F.8.2p2'></a>
|
|
<pre>2 The implementation should produce a diagnostic message for each translation-time floating-point
|
|
exception, other than "inexact";<a href='#FOOTNOTE.445'><sup>[445]</sup></a> the implementation should then proceed with the translation of
|
|
the program.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.445'>
|
|
<pre><i><b>Footnote 445)</b> As floating constants are converted to appropriate internal representations at translation time, their conversion is subject
|
|
to constant or default rounding modes and raises no execution-time floating-point exceptions (even where the state of the
|
|
FENV_ACCESS pragma is "on"). Library functions, for example strtod, provide execution-time conversion of numeric strings.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.8.3'></a>
|
|
<hr>
|
|
<h3>F.8.3 [Execution]</h3>
|
|
<a name='F.8.3p1'></a>
|
|
<pre>1 At program startup the dynamic floating-point environment is initialized as prescribed by IEC 60559:
|
|
|
|
— All floating-point exception status flags are cleared.
|
|
|
|
— The dynamic rounding direction mode is rounding to nearest.
|
|
|
|
— The dynamic rounding precision mode (if supported) is set so that results are not shortened.
|
|
|
|
— Trapping or stopping (if supported) is disabled on all floating-point exceptions.
|
|
|
|
</pre>
|
|
<a name='F.8.4'></a>
|
|
<hr>
|
|
<h3>F.8.4 [Constant expressions]</h3>
|
|
<a name='F.8.4p1'></a>
|
|
<pre>1 An arithmetic constant expression of floating type, other than one in an initializer for an object that
|
|
has static or thread storage duration, is evaluated (as if) during execution; thus, it is affected by any
|
|
operative floating-point control modes and raises floating-point exceptions as required by IEC 60559
|
|
(provided the state for the FENV_ACCESS pragma is "on").<a href='#FOOTNOTE.446'><sup>[446]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.446'>
|
|
<pre><i><b>Footnote 446)</b> Where the state for the FENV_ACCESS pragma is "on", results of inexact expressions like 1.0/3.0 are affected by rounding
|
|
modes set at execution time, and expressions such as 0.0/0.0 and 1.0/0.0 generate execution-time floating-point exceptions.
|
|
The programmer can achieve the efficiency of translation-time evaluation through static initialization, such as
|
|
const static double one_third = 1.0/3.0;
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.8.4p2'></a>
|
|
<pre>2 EXAMPLE
|
|
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
void f(void)
|
|
{
|
|
float w[] = { 0.0/0.0 }; // raises an exception
|
|
static float x = 0.0/0.0; // does not raise an exception
|
|
float y = 0.0/0.0; // raises an exception
|
|
double z = 0.0/0.0; // raises an exception
|
|
/* ... */
|
|
}
|
|
|
|
</pre>
|
|
<a name='F.8.4p3'></a>
|
|
<pre>3 For the static initialization, the division is done at translation time, raising no (execution-time) floating-point exceptions. On
|
|
the other hand, for the three automatic initializations the invalid division occurs at execution time.
|
|
|
|
</pre>
|
|
<a name='F.8.5'></a>
|
|
<hr>
|
|
<h3>F.8.5 [Initialization]</h3>
|
|
<a name='F.8.5p1'></a>
|
|
<pre>1 All computation for automatic initialization is done (as if) at execution time; thus, it is affected by
|
|
any operative modes and raises floating-point exceptions as required by IEC 60559 (provided the
|
|
state for the FENV_ACCESS pragma is "on"). All computation for initialization of objects that have
|
|
static or thread storage duration is done (as if) at translation time.
|
|
</pre>
|
|
<a name='F.8.5p2'></a>
|
|
<pre>2 EXAMPLE
|
|
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
void f(void)
|
|
{
|
|
float u[] = { <a href='#1.'>1.</a>1e75 }; // raises exceptions
|
|
static float v = <a href='#1.'>1.</a>1e75; // does not raise exceptions
|
|
float w = <a href='#1.'>1.</a>1e75; // raises exceptions
|
|
double x = <a href='#1.'>1.</a>1e75; // may raise exceptions
|
|
float y = <a href='#1.'>1.</a>1e75f; // may raise exceptions
|
|
long double z = <a href='#1.'>1.</a>1e75; // does not raise exceptions
|
|
/* ... */
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='F.8.5p3'></a>
|
|
<pre>3 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is done at translation
|
|
time. The automatic initialization of u and w require an execution-time conversion to float of the wider value <a href='#1.'>1.</a>1e75,
|
|
which raises floating-point exceptions. The automatic initializations of x and y entail execution-time conversion; however, in
|
|
some expression evaluation methods, the conversions is not to a narrower format, in which case no floating-point exception
|
|
is raised.<a href='#FOOTNOTE.447'><sup>[447]</sup></a> The automatic initialization of z entails execution-time conversion, but not to a narrower format, so no
|
|
floating-point exception is raised. Note that the conversions of the floating constants <a href='#1.'>1.</a>1e75 and <a href='#1.'>1.</a>1e75f to their internal
|
|
representations occur at translation time in all cases.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.447'>
|
|
<pre><i><b>Footnote 447)</b> Use of float_t and double_t variables increases the likelihood of translation-time computation. For example, the
|
|
automatic initialization
|
|
double_t x = <a href='#1.'>1.</a>1e75;
|
|
could be done at translation time, regardless of the expression evaluation method.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.8.6'></a>
|
|
<hr>
|
|
<h3>F.8.6 [Changing the environment]</h3>
|
|
<a name='F.8.6p1'></a>
|
|
<pre>1 Operations defined in <a href='#6.5'>6.5</a> and functions and macros defined for the standard libraries change
|
|
floating-point status flags and control modes just as indicated by their specifications (including
|
|
conformance to IEC 60559). They do not change flags or modes (so as to be detectable by the user) in
|
|
any other cases.
|
|
</pre>
|
|
<a name='F.8.6p2'></a>
|
|
<pre>2 If the floating-point exceptions represented by the argument to the feraiseexcept function in
|
|
<fenv.h> include both "overflow" and "inexect", then "overflow" is raised before "inexact". Simi-
|
|
larly, if the represented exceptions include both "underflow" and "inexact", then "underflow" is
|
|
raised before "inexact".
|
|
|
|
</pre>
|
|
<a name='F.9'></a>
|
|
<hr>
|
|
<h3>F.9 [Optimization]</h3>
|
|
<a name='F.9p1'></a>
|
|
<pre>1 This section identifies code transformations that might subvert IEC 60559-specified behavior, and
|
|
others that do not.
|
|
|
|
</pre>
|
|
<a name='F.9.1'></a>
|
|
<hr>
|
|
<h3>F.9.1 [Global transformations]</h3>
|
|
<a name='F.9.1p1'></a>
|
|
<pre>1 Floating-point arithmetic operations and external function calls may entail side effects which
|
|
optimization shall honor, at least where the state of the FENV_ACCESS pragma is "on". The flags
|
|
and modes in the floating-point environment may be regarded as global variables; floating-point
|
|
operations (+ , * , etc.) implicitly read the modes and write the flags.
|
|
</pre>
|
|
<a name='F.9.1p2'></a>
|
|
<pre>2 Concern about side effects may inhibit code motion and removal of seemingly useless code. For
|
|
example, in
|
|
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
void f(double x)
|
|
{
|
|
/* ... */
|
|
for (i = 0; i < n; i++) x + 1;
|
|
/* ... */
|
|
}
|
|
|
|
|
|
x+1 might raise floating-point exceptions, so cannot be removed. And since the loop body might not
|
|
execute (maybe 0 ≥ n), x+1 cannot be moved out of the loop. (Of course these optimizations are
|
|
valid if the implementation can rule out the nettlesome cases.)
|
|
</pre>
|
|
<a name='F.9.1p3'></a>
|
|
<pre>3 This specification does not require support for trap handlers that maintain information about
|
|
the order or count of floating-point exceptions. Therefore, between function calls, floating-point
|
|
exceptions need not be precise: the actual order and number of occurrences of floating-point
|
|
exceptions (> 1) may vary from what the source code expresses. Thus, the preceding loop could be
|
|
treated as
|
|
|
|
if (0 < n) x + 1;
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='F.9.2'></a>
|
|
<hr>
|
|
<h3>F.9.2 [Expression transformations]</h3>
|
|
<a name='F.9.2p1'></a>
|
|
<pre>1 Valid expression transformations must preserve numerical values.
|
|
</pre>
|
|
<a name='F.9.2p2'></a>
|
|
<pre>2 The equivalences noted below apply to expressions of standard floating types.
|
|
|
|
x/2 ↔ x × 0.5 Although similar transformations involving inexact constants generally do not
|
|
yield equivalent expressions, if the constants are exact then such transforma-
|
|
tions can be made on IEC 60559 machines and others that round perfectly.
|
|
|
|
1 × x and x/1 → x The expressions 1 × x, x/1, and x may be regarded as equivalent (on IEC 60559
|
|
machines, among others).<a href='#FOOTNOTE.448'><sup>[448]</sup></a>
|
|
|
|
x/x → 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero, infinite, or NaN.
|
|
|
|
x − y ↔ x + (−y) The expressions x − y, x + (−y), and (−y) + x are equivalent (on IEC 60559
|
|
machines, among others).
|
|
|
|
x − y ↔ −(y − x) The expressions x − y and −(y − x) are not equivalent because 1 − 1 is +0 but
|
|
−(1 − 1) is −0 (in the default rounding direction).<a href='#FOOTNOTE.449'><sup>[449]</sup></a>
|
|
|
|
x − x → 0.0 The expressions x − x and 0.0 are not equivalent if x is a NaN or infinite.
|
|
|
|
0 × x → 0.0 The expressions 0 × x and 0.0 are not equivalent if x is a NaN, infinite, or −0.
|
|
|
|
x+0→x The expressions x + 0 and x are not equivalent if x is −0, because (−0) + (+0)
|
|
yields +0 (in the default rounding direction), not −0.
|
|
|
|
x−0→x (+0) − (+0) yields −0 when rounding is downward (toward −∞), but +0
|
|
otherwise, and (−0)−(+0) always yields −0; so, if the state of the FENV_ACCESS
|
|
pragma is "off", promising default rounding, then the implementation can
|
|
replace x − 0 by x, even if x might be zero.
|
|
|
|
−x ↔ 0 − x The expressions −x and 0−x are not equivalent if x is +0, because −(+0) yields
|
|
−0, but 0 − (+0) yields +0 (unless rounding is downward).
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.448'>
|
|
<pre><i><b>Footnote 448)</b> Implementations might have non-required features that invalidate these and other transformations that remove arithmetic
|
|
operators. Examples include strict support for signaling NaNs (an optional feature) and alternate exception handling (not
|
|
included in this specification).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.449'>
|
|
<pre><i><b>Footnote 449)</b> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities. Examples include:
|
|
1/(1/±∞) is ±∞
|
|
and
|
|
conj(csqrt(z)) is csqrt(conj(z)),
|
|
for complex z.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.9.2p3'></a>
|
|
<pre>3 For expressions of decimal floating types, transformations must preserve quantum exponents, as
|
|
well as numerical values (<a href='#5.2.4.2.3'>5.2.4.2.3</a>).
|
|
</pre>
|
|
<a name='F.9.2p4'></a>
|
|
<pre>4 EXAMPLE 1. × x → x is valid for decimal floating-point expressions x, but 1.0 × x → x is not:
|
|
|
|
1. × 12.34 = (+1, 1, 0) × (+1, 1234, −2) yields (+1, 1234, −2) = 12.34
|
|
1.0 × 12.34 = (+1, 10, −1) × (+1, 1234, −2) yields (+1, 12340, −3) = 12.340
|
|
|
|
In the second case, the factor 12.34 and the result 12.340 have different quantum exponents, demonstrating that 1.0 × x and
|
|
x are not equivalent expressions.
|
|
</pre>
|
|
<a name='F.9.3'></a>
|
|
<hr>
|
|
<h3>F.9.3 [Relational operators]</h3>
|
|
<a name='F.9.3p1'></a>
|
|
<pre>1 x ̸= x → false The expression x ̸= x is true if x is a NaN.
|
|
x = x → true The expression x = x is false if x is a NaN.
|
|
x < y → isless(x, y) (and similarly for ≤, >, ≥) Though equal, these expressions are not equiv-
|
|
alent because of side effects when x or y is a NaN and the state of the
|
|
FENV_ACCESS pragma is "on". This transformation, which would be de-
|
|
sirable if extra code were required to cause the "invalid" floating-point
|
|
exception for unordered cases, could be performed provided the state of the
|
|
FENV_ACCESS pragma is "off".
|
|
|
|
The sense of relational operators shall be maintained. This includes handling unordered cases as
|
|
expressed by the source code.
|
|
</pre>
|
|
<a name='F.9.3p2'></a>
|
|
<pre>2 EXAMPLE
|
|
|
|
// calls g and raises "invalid" if a and b are unordered
|
|
if (a < b)
|
|
f();
|
|
else
|
|
g();
|
|
|
|
is not equivalent to
|
|
|
|
// calls f and raises "invalid" if a and b are unordered
|
|
if (a >= b)
|
|
g();
|
|
else
|
|
f();
|
|
|
|
nor to
|
|
|
|
// calls f without raising "invalid" if a and b are unordered
|
|
if (isgreaterequal(a,b))
|
|
g();
|
|
else
|
|
f();
|
|
|
|
nor, unless the state of the FENV_ACCESS pragma is "off", to
|
|
|
|
// calls g without raising "invalid" if a and b are unordered
|
|
if (isless(a,b))
|
|
f();
|
|
else
|
|
g();
|
|
|
|
but is equivalent to
|
|
|
|
if (!(a < b))
|
|
g();
|
|
else
|
|
f();
|
|
|
|
|
|
</pre>
|
|
<a name='F.9.4'></a>
|
|
<hr>
|
|
<h3>F.9.4 [Constant arithmetic]</h3>
|
|
<a name='F.9.4p1'></a>
|
|
<pre>1 The implementation shall honor floating-point exceptions raised by execution-time constant arith-
|
|
metic wherever the state of the FENV_ACCESS pragma is "on". (See <a href='#F.8.4'>F.8.4</a> and <a href='#F.8.5'>F.8.5</a>.) An operation
|
|
on constants that raises no floating-point exception can be folded during translation, except, if the
|
|
state of the FENV_ACCESS pragma is "on", a further check is required to assure that changing the
|
|
rounding direction to downward does not alter the sign of the result,<a href='#FOOTNOTE.450'><sup>[450]</sup></a> and implementations that
|
|
support dynamic rounding precision modes shall assure further that the result of the operation
|
|
raises no floating-point exception when converted to the semantic type of the operation.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.450'>
|
|
<pre><i><b>Footnote 450)</b> 0-0 yields-0 instead of +0 just when the rounding direction is downward.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10'></a>
|
|
<hr>
|
|
<h3>F.10 [Mathematics <math.h> and <tgmath.h>]</h3>
|
|
<a name='F.10p1'></a>
|
|
<pre>1 This subclause contains specifications of <math.h> and <tgmath.h> facilities that are particularly
|
|
suited for IEC 60559 implementations.
|
|
</pre>
|
|
<a name='F.10p2'></a>
|
|
<pre>2 The Standard C macro HUGE_VAL and its float and long double analogs, HUGE_VALF and
|
|
HUGE_VALL, expand to expressions whose values are positive infinities.
|
|
</pre>
|
|
<a name='F.10p3'></a>
|
|
<pre>3 For each single-argument function f in <math.h> whose mathematical counterpart is symmetric
|
|
(even), f(-x) is f(x) for all rounding modes and for all x in the (valid) domain of the function. For
|
|
each single-argument function f in <math.h> whose mathematical counterpart is antisymmetric
|
|
(odd), f(-x) is-f(x) for the IEC 60559 rounding modes roundTiesToEven, roundTiesToAway, and
|
|
roundTowardZero, and for all x in the (valid) domain of the function. The atan2 and atan2pi
|
|
functions are odd in their first argument.
|
|
</pre>
|
|
<a name='F.10p4'></a>
|
|
<pre>4 Special cases for functions in <math.h> are covered directly or indirectly by IEC 60559. The functions
|
|
that IEC 60559 specifies directly are identified in <a href='#F.3'>F.3</a>. The other functions in <math.h> treat infinities,
|
|
NaNs, signed zeros, subnormals, and (provided the state of the FENV_ACCESS pragma is "on") the
|
|
floating-point status flags in a manner consistent with IEC 60559 operations.
|
|
</pre>
|
|
<a name='F.10p5'></a>
|
|
<pre>5 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a nonzero value.
|
|
</pre>
|
|
<a name='F.10p6'></a>
|
|
<pre>6 The functions bound to operations in IEC 60559 (<a href='#F.3'>F.3</a>) are fully specified by IEC 60559, including
|
|
rounding behaviors and floating-point exceptions.
|
|
</pre>
|
|
<a name='F.10p7'></a>
|
|
<pre>7 The "invalid" and "divide-by-zero" floating-point exceptions are raised as specified in subsequent
|
|
subclauses of this annex.
|
|
</pre>
|
|
<a name='F.10p8'></a>
|
|
<pre>8 The "overflow" floating-point exception is raised whenever an infinity — or, because of rounding di-
|
|
rection, a maximal-magnitude finite number — is returned in lieu of a finite value whose magnitude
|
|
is too large.
|
|
</pre>
|
|
<a name='F.10p9'></a>
|
|
<pre>9 The "underflow" floating-point exception is raised whenever a computed result is tiny<a href='#FOOTNOTE.451'><sup>[451]</sup></a> and the
|
|
returned result is inexact.
|
|
</pre>
|
|
<a name='FOOTNOTE.451'>
|
|
<pre><i><b>Footnote 451)</b> Tiny generally indicates having a magnitude in the subnormal range. See IEC 60559 for details about detecting tininess.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10p10'></a>
|
|
<pre>10 Whether or when library functions not listed in the "Operation binding" table in <a href='#F.3'>F.3</a> raise the
|
|
"inexact" floating-point exception is unspecified, unless stated otherwise.
|
|
</pre>
|
|
<a name='F.10p11'></a>
|
|
<pre>11 Whether or when library functions not listed in the "Operation binding" table in <a href='#F.3'>F.3</a> raise a spurious
|
|
"underflow" floating-point exception is not specified by this annex.<a href='#FOOTNOTE.452'><sup>[452]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.452'>
|
|
<pre><i><b>Footnote 452)</b> It is intended that spurious "underflow" and "inexact" floating-point exceptions are raised only if avoiding them would
|
|
be too costly. <a href='#7.12.1'>7.12.1</a> specifies that if math_errhandling & MATH_ERREXCEPT is nonzero, then an "underflow" floating-point
|
|
exception shall not be raised unless an underflow range error occurs.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10p12'></a>
|
|
<pre>12 As implied by <a href='#F.8.6'>F.8.6</a>, library functions do not raise spurious "invalid", "overflow", or "divide-by-zero"
|
|
floating-point exceptions (detectable by the user).
|
|
</pre>
|
|
<a name='F.10p13'></a>
|
|
<pre>13 Whether the functions not listed in the "Operation binding" table in <a href='#F.3'>F.3</a> honor the rounding direction
|
|
mode is implementation-defined, unless explicitly specified otherwise.
|
|
</pre>
|
|
<a name='F.10p14'></a>
|
|
<pre>14 Functions with a NaN argument return a NaN result and raise no floating-point exception, except
|
|
where explicitly stated otherwise.
|
|
</pre>
|
|
<a name='F.10p15'></a>
|
|
<pre>15 The specifications in the following subclauses append to the definitions in <math.h>. For families of
|
|
functions, the specifications apply to all of the functions even though only the principal function
|
|
is shown. Unless otherwise specified, where the symbol "±" occurs in both an argument and the
|
|
result, the result has the same sign as the argument.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='F.10p16'></a>
|
|
<pre>16 IEC 60559 specifies correct rounding for the operations in the <a href='#F.3'>F.3</a> table of operations recommended
|
|
by IEC 60559, and thereby preserves useful mathematical properties such as symmetry, monotonicity,
|
|
and periodicity. The corresponding functions with (potentially) reserved cr_-prefixed names (<a href='#7.33.8'>7.33.8</a>)
|
|
do the same. The C functions in the table, however, are not required to be correctly rounded, but
|
|
implementations should still preserve as many of these useful mathematical properties as possible.
|
|
</pre>
|
|
<a name='F.10p17'></a>
|
|
<pre>17 If a function with one or more NaN arguments returns a NaN result, the result should be the same
|
|
as one of the NaN arguments (after possible type conversion), except perhaps for the sign.
|
|
|
|
</pre>
|
|
<a name='F.10.1'></a>
|
|
<hr>
|
|
<h3>F.10.1 [Trigonometric functions]</h3>
|
|
<a name='F.10.1.1'></a>
|
|
<hr>
|
|
<h3>F.10.1.1 [The acos functions]</h3>
|
|
<a name='F.10.1.1p1'></a>
|
|
<pre>1 — acos(1) returns +0.
|
|
— acos(x) returns a NaN and raises the "invalid" floating-point exception for |x| > 1.
|
|
|
|
</pre>
|
|
<a name='F.10.1.2'></a>
|
|
<hr>
|
|
<h3>F.10.1.2 [The asin functions]</h3>
|
|
<a name='F.10.1.2p1'></a>
|
|
<pre>1 — asin(±0) returns ±0.
|
|
— asin(x) returns a NaN and raises the "invalid" floating-point exception for |x| > 1.
|
|
|
|
</pre>
|
|
<a name='F.10.1.3'></a>
|
|
<hr>
|
|
<h3>F.10.1.3 [The atan functions]</h3>
|
|
<a name='F.10.1.3p1'></a>
|
|
<pre>1 — atan(±0) returns ±0.
|
|
— atan(±∞) returns ± π2 .
|
|
|
|
</pre>
|
|
<a name='F.10.1.4'></a>
|
|
<hr>
|
|
<h3>F.10.1.4 [The atan2 functions]</h3>
|
|
<a name='F.10.1.4p1'></a>
|
|
<pre>1 — atan2(±0, −0) returns ±π.<a href='#FOOTNOTE.453'><sup>[453]</sup></a>
|
|
— atan2(±0, +0) returns ±0.
|
|
— atan2(±0, x) returns ±π for x < 0.
|
|
— atan2(±0, x) returns ±0 for x > 0.
|
|
— atan2(y, ±0) returns − π2 for y < 0.
|
|
— atan2(y, ±0) returns π2 for y > 0.
|
|
— atan2(±y, −∞) returns ±π for finite y > 0.
|
|
— atan2(±y, +∞) returns ±0 for finite y > 0.
|
|
— atan2(±∞, x) returns ± π2 for finite x.
|
|
— atan2(±∞, −∞) returns ± 3π
|
|
4 .
|
|
|
|
— atan2(±∞, +∞) returns ± π4 .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.453'>
|
|
<pre><i><b>Footnote 453)</b> atan2(0, 0) does not raise the "invalid" floating-point exception, nor does atan2(y, 0) raise the "divide-by-zero" floating-
|
|
point exception.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10.1.5'></a>
|
|
<hr>
|
|
<h3>F.10.1.5 [The cos functions]</h3>
|
|
<a name='F.10.1.5p1'></a>
|
|
<pre>1 — cos(±0) returns 1.
|
|
— cos(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.1.6'></a>
|
|
<hr>
|
|
<h3>F.10.1.6 [The sin functions]</h3>
|
|
<a name='F.10.1.6p1'></a>
|
|
<pre>1 — sin(±0) returns ±0.
|
|
— sin(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.1.7'></a>
|
|
<hr>
|
|
<h3>F.10.1.7 [The tan functions]</h3>
|
|
<a name='F.10.1.7p1'></a>
|
|
<pre>1 — tan(±0) returns ±0.
|
|
— tan(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
</pre>
|
|
<a name='F.10.1.8'></a>
|
|
<hr>
|
|
<h3>F.10.1.8 [The acospi functions]</h3>
|
|
<a name='F.10.1.8p1'></a>
|
|
<pre>1 — acospi(+1) returns +0.
|
|
|
|
— acospi(x) returns a NaN and raises the "invalid" floating-point exception for |x| > 1.
|
|
|
|
</pre>
|
|
<a name='F.10.1.9'></a>
|
|
<hr>
|
|
<h3>F.10.1.9 [The asinpi functions]</h3>
|
|
<a name='F.10.1.9p1'></a>
|
|
<pre>1 — asinpi(±0) returns ±0.
|
|
|
|
— asinpi(x) returns a NaN and raises the "invalid" floating-point exception for |x| > 1.
|
|
|
|
</pre>
|
|
<a name='F.10.1.10'></a>
|
|
<hr>
|
|
<h3>F.10.1.10 [The atanpi functions]</h3>
|
|
<a name='F.10.1.10p1'></a>
|
|
<pre>1 — atanpi(±0) returns ±0.
|
|
|
|
— atanpi(±∞) returns ± 21 .
|
|
|
|
</pre>
|
|
<a name='F.10.1.11'></a>
|
|
<hr>
|
|
<h3>F.10.1.11 [The atan2pi functions]</h3>
|
|
<a name='F.10.1.11p1'></a>
|
|
<pre>1 — atan2pi(±0, −0) returns ±1.<a href='#FOOTNOTE.454'><sup>[454]</sup></a>
|
|
|
|
— atan2pi(±0, +0) returns ±0.
|
|
|
|
— atan2pi(±0, x) returns ±1 for x < 0.
|
|
|
|
— atan2pi(±0, x) returns ±0 for x > 0.
|
|
|
|
— atan2pi(y, ±0) returns − 12 for y < 0.
|
|
|
|
— atan2pi(y, ±0) returns + 12 for y > 0.
|
|
|
|
— atan2pi(±y, −∞) returns ±1 for finite y > 0.
|
|
|
|
— atan2pi(±y, +∞) returns ±0 for finite y > 0.
|
|
|
|
— atan2pi(±∞, x) returns ± 12 for finite x.
|
|
|
|
— atan2pi(±∞, −∞) returns ± 43 .
|
|
|
|
— atan2pi(±∞, +∞) returns ± 14 .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.454'>
|
|
<pre><i><b>Footnote 454)</b> atan2pi(0, 0) does not raise the "invalid" floating-point exception, nor does atan2pi(y, 0) raise the "divide-by-zero"
|
|
floating-point exception.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10.1.12'></a>
|
|
<hr>
|
|
<h3>F.10.1.12 [The cospi functions]</h3>
|
|
<a name='F.10.1.12p1'></a>
|
|
<pre>1 — cospi(±0) returns 1.
|
|
|
|
— cospi(n + 12 ) returns +0, for integers n.
|
|
|
|
— cospi(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.1.13'></a>
|
|
<hr>
|
|
<h3>F.10.1.13 [The sinpi functions]</h3>
|
|
<a name='F.10.1.13p1'></a>
|
|
<pre>1 — sinpi(±0) returns ±0.
|
|
|
|
— sinpi(±n) returns ±0, for positive integers n.
|
|
|
|
— sinpi(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
</pre>
|
|
<a name='F.10.1.14'></a>
|
|
<hr>
|
|
<h3>F.10.1.14 [The tanpi functions]</h3>
|
|
<a name='F.10.1.14p1'></a>
|
|
<pre>1 — tanpi(±0) returns ±0.
|
|
|
|
— tanpi(n) returns +0, for positive even and negative odd integers n.
|
|
|
|
— tanpi(n) returns −0, for positive odd and negative even integers n.
|
|
|
|
— tanpi(n + 12 ) returns +∞ and raises the "divide-by-zero" floating-point exception, for even
|
|
integers n.
|
|
|
|
— tanpi(n + 12 ) returns −∞ and raises the "divide-by-zero" floating-point exception, for odd
|
|
integers n.
|
|
|
|
— tanpi(±∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.2'></a>
|
|
<hr>
|
|
<h3>F.10.2 [Hyperbolic functions]</h3>
|
|
<a name='F.10.2.1'></a>
|
|
<hr>
|
|
<h3>F.10.2.1 [The acosh functions]</h3>
|
|
<a name='F.10.2.1p1'></a>
|
|
<pre>1 — acosh(1) returns +0.
|
|
|
|
— acosh(x) returns a NaN and raises the "invalid" floating-point exception for x < 1.
|
|
|
|
— acosh(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.2.2'></a>
|
|
<hr>
|
|
<h3>F.10.2.2 [The asinh functions]</h3>
|
|
<a name='F.10.2.2p1'></a>
|
|
<pre>1 — asinh(±0) returns ±0.
|
|
|
|
— asinh(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.2.3'></a>
|
|
<hr>
|
|
<h3>F.10.2.3 [The atanh functions]</h3>
|
|
<a name='F.10.2.3p1'></a>
|
|
<pre>1 — atanh(±0) returns ±0.
|
|
|
|
— atanh(±1) returns ±∞ and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— atanh(x) returns a NaN and raises the "invalid" floating-point exception for |x| > 1.
|
|
|
|
</pre>
|
|
<a name='F.10.2.4'></a>
|
|
<hr>
|
|
<h3>F.10.2.4 [The cosh functions]</h3>
|
|
<a name='F.10.2.4p1'></a>
|
|
<pre>1 — cosh(±0) returns 1.
|
|
|
|
— cosh(±∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.2.5'></a>
|
|
<hr>
|
|
<h3>F.10.2.5 [The sinh functions]</h3>
|
|
<a name='F.10.2.5p1'></a>
|
|
<pre>1 — sinh(±0) returns ±0.
|
|
|
|
— sinh(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.2.6'></a>
|
|
<hr>
|
|
<h3>F.10.2.6 [The tanh functions]</h3>
|
|
<a name='F.10.2.6p1'></a>
|
|
<pre>1 — tanh(±0) returns ±0.
|
|
|
|
— tanh(±∞) returns ±1.
|
|
|
|
</pre>
|
|
<a name='F.10.3'></a>
|
|
<hr>
|
|
<h3>F.10.3 [Exponential and logarithmic functions]</h3>
|
|
<a name='F.10.3.1'></a>
|
|
<hr>
|
|
<h3>F.10.3.1 [The exp functions]</h3>
|
|
<a name='F.10.3.1p1'></a>
|
|
<pre>1 — exp(±0) returns 1.
|
|
|
|
— exp(−∞) returns +0.
|
|
|
|
— exp(+∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.2'></a>
|
|
<hr>
|
|
<h3>F.10.3.2 [The exp10 functions]</h3>
|
|
<a name='F.10.3.2p1'></a>
|
|
<pre>1 — exp10(±0) returns 1.
|
|
— exp10(−∞) returns +0.
|
|
— exp10(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.3'></a>
|
|
<hr>
|
|
<h3>F.10.3.3 [The exp10m1 functions]</h3>
|
|
<a name='F.10.3.3p1'></a>
|
|
<pre>1 — exp10m1(±0) returns ±0.
|
|
— exp10m1(−∞) returns −1.
|
|
— exp10m1(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.4'></a>
|
|
<hr>
|
|
<h3>F.10.3.4 [The exp2 functions]</h3>
|
|
<a name='F.10.3.4p1'></a>
|
|
<pre>1 — exp2(±0) returns 1.
|
|
— exp2(−∞) returns +0.
|
|
— exp2(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.5'></a>
|
|
<hr>
|
|
<h3>F.10.3.5 [The exp2m1 functions]</h3>
|
|
<a name='F.10.3.5p1'></a>
|
|
<pre>1 — exp2m1(±0) returns ±0.
|
|
— exp2m1(−∞) returns −1.
|
|
— exp2m1(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.6'></a>
|
|
<hr>
|
|
<h3>F.10.3.6 [The expm1 functions]</h3>
|
|
<a name='F.10.3.6p1'></a>
|
|
<pre>1 — expm1(±0) returns ±0.
|
|
— expm1(−∞) returns −1.
|
|
— expm1(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.7'></a>
|
|
<hr>
|
|
<h3>F.10.3.7 [The frexp functions]</h3>
|
|
<a name='F.10.3.7p1'></a>
|
|
<pre>1 — frexp(±0, exp) returns ±0, and stores 0 in the object pointed to by exp.
|
|
— frexp(±∞, exp) returns ±∞, and stores an unspecified value in the object pointed to by exp.
|
|
— frexp(NaN, exp) stores an unspecified value in the object pointed to by exp (and returns a
|
|
NaN).
|
|
|
|
</pre>
|
|
<a name='F.10.3.7p2'></a>
|
|
<pre>2 frexp raises no floating-point exceptions if value is not a signaling NaN.
|
|
</pre>
|
|
<a name='F.10.3.7p3'></a>
|
|
<pre>3 The returned value is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.3.7p4'></a>
|
|
<pre>4 On a binary system, the body of the frexp function might be
|
|
|
|
{
|
|
*exp = (value == 0) ? 0: (int)(1 + logb(value));
|
|
return scalbn(value, -(*exp));
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='F.10.3.8'></a>
|
|
<hr>
|
|
<h3>F.10.3.8 [The ilogb functions]</h3>
|
|
<a name='F.10.3.8p1'></a>
|
|
<pre>1 When the correct result is representable in the range of the return type, the returned value is exact
|
|
and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.3.8p2'></a>
|
|
<pre>2 If the correct result is outside the range of the return type, the numeric result is unspecified and the
|
|
"invalid" floating-point exception is raised.
|
|
</pre>
|
|
<a name='F.10.3.8p3'></a>
|
|
<pre>3 ilogb(x), for x zero, infinite, or NaN, raises the "invalid" floating-point exception and returns the
|
|
value specified in <a href='#7.12.6.8'>7.12.6.8</a>.
|
|
</pre>
|
|
<a name='F.10.3.9'></a>
|
|
<hr>
|
|
<h3>F.10.3.9 [The ldexp functions]</h3>
|
|
<a name='F.10.3.9p1'></a>
|
|
<pre>1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
|
|
|
|
</pre>
|
|
<a name='F.10.3.10'></a>
|
|
<hr>
|
|
<h3>F.10.3.10 [The llogb functions]</h3>
|
|
<a name='F.10.3.10p1'></a>
|
|
<pre>1 The llogb functions are equivalent to the ilogb functions, except that the llogb functions determine
|
|
a result in the long int type.
|
|
|
|
</pre>
|
|
<a name='F.10.3.11'></a>
|
|
<hr>
|
|
<h3>F.10.3.11 [The log functions]</h3>
|
|
<a name='F.10.3.11p1'></a>
|
|
<pre>1 — log(±0) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— log(1) returns +0.
|
|
— log(x) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
— log(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.12'></a>
|
|
<hr>
|
|
<h3>F.10.3.12 [The log10 functions]</h3>
|
|
<a name='F.10.3.12p1'></a>
|
|
<pre>1 — log10(±0) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— log10(1) returns +0.
|
|
— log10(x) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
— log10(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.13'></a>
|
|
<hr>
|
|
<h3>F.10.3.13 [The log10p1 functions]</h3>
|
|
<a name='F.10.3.13p1'></a>
|
|
<pre>1 — log10p1(±0) returns ±0.
|
|
— log10p1(−1) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— log10p1(x) returns a NaN and raises the "invalid" floating-point exception for x < −1.
|
|
— log10p1(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.14'></a>
|
|
<hr>
|
|
<h3>F.10.3.14 [The log1p and logp1 functions]</h3>
|
|
<a name='F.10.3.14p1'></a>
|
|
<pre>1 — logp1(±0) returns ±0.
|
|
— logp1(−1) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— logp1(x) returns a NaN and raises the "invalid" floating-point exception for x < −1.
|
|
— logp1(+∞) returns +∞.
|
|
|
|
The log1p functions are equivalent to the logp1 functions.
|
|
|
|
</pre>
|
|
<a name='F.10.3.15'></a>
|
|
<hr>
|
|
<h3>F.10.3.15 [The log2 functions]</h3>
|
|
<a name='F.10.3.15p1'></a>
|
|
<pre>1 — log2(±0) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— log2(1) returns +0.
|
|
— log2(x) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
— log2(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.16'></a>
|
|
<hr>
|
|
<h3>F.10.3.16 [The log2p1 functions]</h3>
|
|
<a name='F.10.3.16p1'></a>
|
|
<pre>1 — log2p1(±0) returns ±0.
|
|
— log2p1(−1) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
— log2p1(x) returns a NaN and raises the "invalid" floating-point exception for x < −1.
|
|
— log2p1(+∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.17'></a>
|
|
<hr>
|
|
<h3>F.10.3.17 [The logb functions]</h3>
|
|
<a name='F.10.3.17p1'></a>
|
|
<pre>1 — logb(±0) returns −∞ and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— logb(±∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.17p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.3.18'></a>
|
|
<hr>
|
|
<h3>F.10.3.18 [The modf functions]</h3>
|
|
<a name='F.10.3.18p1'></a>
|
|
<pre>1 — modf(±x, iptr) returns a result with the same sign as x.
|
|
|
|
— modf(±∞, iptr) returns ±0 and stores ±∞ in the object pointed to by iptr.
|
|
|
|
— modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a NaN).
|
|
|
|
</pre>
|
|
<a name='F.10.3.18p2'></a>
|
|
<pre>2 The returned values are exact and are independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.3.18p3'></a>
|
|
<pre>3 modf behaves as though implemented by
|
|
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
double modf(double value, double *iptr)
|
|
{
|
|
int save_round = fegetround();
|
|
fesetround(FE_TOWARDZERO);
|
|
*iptr = nearbyint(value);
|
|
fesetround(save_round);
|
|
return copysign(
|
|
isinf(value) ? 0.0:
|
|
value - (*iptr), value);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='F.10.3.19'></a>
|
|
<hr>
|
|
<h3>F.10.3.19 [The scalbn and scalbln functions]</h3>
|
|
<a name='F.10.3.19p1'></a>
|
|
<pre>1 — scalbn(±0, n) returns ±0.
|
|
|
|
— scalbn(x, 0) returns x.
|
|
|
|
— scalbn(±∞, n) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.3.19p2'></a>
|
|
<pre>2 If the calculation does not overflow or underflow, the returned value is exact and independent of
|
|
the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.4'></a>
|
|
<hr>
|
|
<h3>F.10.4 [Power and absolute value functions]</h3>
|
|
<a name='F.10.4.1'></a>
|
|
<hr>
|
|
<h3>F.10.4.1 [The cbrt functions]</h3>
|
|
<a name='F.10.4.1p1'></a>
|
|
<pre>1 — cbrt(±0) returns ±0.
|
|
|
|
— cbrt(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.4.2'></a>
|
|
<hr>
|
|
<h3>F.10.4.2 [The compoundn functions]</h3>
|
|
<a name='F.10.4.2p1'></a>
|
|
<pre>1 — compoundn(x, 0) returns 1 for x ≥ −1 or x a NaN.
|
|
|
|
— compoundn(x, n) returns a NaN and raises the "invalid" floating-point exception for x < −1.
|
|
|
|
— compoundn(−1, n) returns +∞ and raises the divide-by-zero floating-point exception for n < 0.
|
|
|
|
— compoundn(−1, n) returns +0 for n > 0.
|
|
</pre>
|
|
<a name='F.10.4.3'></a>
|
|
<hr>
|
|
<h3>F.10.4.3 [The fabs functions]</h3>
|
|
<a name='F.10.4.3p1'></a>
|
|
<pre>1 fabs(x) returns a value with the same bit representation as x, except with the sign bit set to 0
|
|
(positive), for all values of x (even quiet and signaling NaNs).
|
|
</pre>
|
|
<a name='F.10.4.3p2'></a>
|
|
<pre>2 — fabs(±0) returns +0.
|
|
|
|
— fabs(±∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.4.3p3'></a>
|
|
<pre>3 fabs(x) raises no floating-point exceptions, even if x is a signaling NaN. The returned value is
|
|
independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.4.4'></a>
|
|
<hr>
|
|
<h3>F.10.4.4 [The hypot functions]</h3>
|
|
<a name='F.10.4.4p1'></a>
|
|
<pre>1 — hypot(x, y), hypot(y, x), and hypot(x, −y) are equivalent.
|
|
|
|
— hypot(x, ±0) returns the absolute value of x, if x is not a NaN.
|
|
|
|
— hypot(±∞, y) returns +∞, even if y is a NaN.
|
|
|
|
— hypot(x, NaN) returns a NaN, if x is not ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.4.5'></a>
|
|
<hr>
|
|
<h3>F.10.4.5 [The pow functions]</h3>
|
|
<a name='F.10.4.5p1'></a>
|
|
<pre>1 — pow(±0, y) returns ±∞ and raises the "divide-by-zero" floating-point exception for y an odd
|
|
integer < 0.
|
|
|
|
— pow(±0, y) returns +∞ and raises the "divide-by-zero" floating-point exception for y < 0,
|
|
finite, and not an odd integer.
|
|
|
|
— pow(±0, −∞) returns +∞.
|
|
|
|
— pow(±0, y) returns ±0 for y an odd integer > 0.
|
|
|
|
— pow(±0, y) returns +0 for y > 0 and not an odd integer.
|
|
|
|
— pow(−1, ±∞) returns 1.
|
|
|
|
— pow(+1, y) returns 1 for any y, even a NaN.
|
|
|
|
— pow(x, ±0) returns 1 for any x, even a NaN.
|
|
|
|
— pow(x, y) returns a NaN and raises the "invalid" floating-point exception for finite x < 0 and
|
|
finite non-integer y.
|
|
|
|
— pow(x, −∞) returns +∞ for |x| < 1.
|
|
|
|
— pow(x, −∞) returns +0 for |x| > 1.
|
|
|
|
— pow(x, +∞) returns +0 for |x| < 1.
|
|
|
|
— pow(x, +∞) returns +∞ for |x| > 1.
|
|
|
|
— pow(−∞, y) returns −0 for y an odd integer < 0.
|
|
|
|
— pow(−∞, y) returns +0 for y < 0 and not an odd integer.
|
|
|
|
— pow(−∞, y) returns −∞ for y an odd integer > 0.
|
|
|
|
— pow(−∞, y) returns +∞ for y > 0 and not an odd integer.
|
|
|
|
— pow(+∞, y) returns +0 for y < 0.
|
|
|
|
— pow(+∞, y) returns +∞ for y > 0.
|
|
</pre>
|
|
<a name='F.10.4.6'></a>
|
|
<hr>
|
|
<h3>F.10.4.6 [The pown functions]</h3>
|
|
<a name='F.10.4.6p1'></a>
|
|
<pre>1 — pown(x, 0) returns 1 for all x not a signalling NaN.
|
|
— pown(±0, n) returns ±∞ and raises the "divide-by-zero" floating-point exception for odd
|
|
n < 0.
|
|
— pown(±0, n) returns +∞ and raises the "divide-by-zero" floating-point exception for even
|
|
n < 0.
|
|
— pown(±0, n) returns +0 for even n > 0.
|
|
— pown(±0, n) returns ±0 for odd n > 0.
|
|
— pown(±∞, n) is equivalent to pown(±0, −n) for n not 0, except that the "divide-by-zero"
|
|
floating-point exception is not raised.
|
|
|
|
</pre>
|
|
<a name='F.10.4.7'></a>
|
|
<hr>
|
|
<h3>F.10.4.7 [The powr functions]</h3>
|
|
<a name='F.10.4.7p1'></a>
|
|
<pre>1 — powr(x, ±0) returns 1 for finite x > 0.
|
|
— powr(±0, y) returns +∞ and raises the "divide-by-zero" floating-point exception for finite
|
|
y < 0.
|
|
— powr(±0, −∞) returns +∞.
|
|
— powr(±0, y) returns +0 for y > 0.
|
|
— powr(+1, y) returns 1 for finite y.
|
|
— powr(+1, y)
|
|
— powr(x, y) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
— powr(±0, ±0) returns a NaN and raises the "invalid" floating-point exception.
|
|
— powr(+∞, ±0) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.4.8'></a>
|
|
<hr>
|
|
<h3>F.10.4.8 [The rootn functions]</h3>
|
|
<a name='F.10.4.8p1'></a>
|
|
<pre>1 — rootn(±0, n) returns ±∞ and raises the "divide-by-zero" floating-point exception for odd
|
|
n < 0.
|
|
— rootn(±0, n) returns +∞ and raises the "divide-by-zero" floating-point exception for even
|
|
n < 0.
|
|
— rootn(±0, n) returns +0 for even n > 0.
|
|
— rootn(±0, n) returns ±0 for odd n > 0.
|
|
— rootn(+∞, n) returns +∞ for n > 0.
|
|
— rootn(−∞, n) returns −∞ for odd n > 0.
|
|
— rootn(−∞, n) returns a NaN and raises the "invalid" floating-point exception for even n > 0.
|
|
— rootn(+∞, n) returns +0 for n < 0.
|
|
— rootn(−∞, n) returns −0 for odd n < 0.
|
|
— rootn(−∞, n) returns a NaN and raises the "invalid" floating-point exception for even n < 0.
|
|
— rootn(x, 0) returns a NaN and raises the "invalid" floating-point exception for all x (including
|
|
NaN).
|
|
— rootn(x, n) returns a NaN and raises the "invalid" floating-point exception for x < 0 and n
|
|
even.
|
|
</pre>
|
|
<a name='F.10.4.9'></a>
|
|
<hr>
|
|
<h3>F.10.4.9 [The rsqrt functions]</h3>
|
|
<a name='F.10.4.9p1'></a>
|
|
<pre>1 — rsqrt(±0) returns ±∞ and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— rsqrt(x) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
|
|
— rsqrt(+∞) returns +0.
|
|
|
|
</pre>
|
|
<a name='F.10.4.10'></a>
|
|
<hr>
|
|
<h3>F.10.4.10 [The sqrt functions]</h3>
|
|
<a name='F.10.4.10p1'></a>
|
|
<pre>1 — sqrt(±0) returns ±0.
|
|
|
|
— sqrt(+∞) returns +∞.
|
|
|
|
— sqrt(x) returns a NaN and raises the "invalid" floating-point exception for x < 0.
|
|
|
|
</pre>
|
|
<a name='F.10.4.10p2'></a>
|
|
<pre>2 The returned value is dependent on the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.5'></a>
|
|
<hr>
|
|
<h3>F.10.5 [Error and gamma functions]</h3>
|
|
<a name='F.10.5.1'></a>
|
|
<hr>
|
|
<h3>F.10.5.1 [The erf functions]</h3>
|
|
<a name='F.10.5.1p1'></a>
|
|
<pre>1 — erf(±0) returns ±0.
|
|
|
|
— erf(±∞) returns ±1.
|
|
|
|
</pre>
|
|
<a name='F.10.5.2'></a>
|
|
<hr>
|
|
<h3>F.10.5.2 [The erfc functions]</h3>
|
|
<a name='F.10.5.2p1'></a>
|
|
<pre>1 — erfc(−∞) returns 2.
|
|
|
|
— erfc(+∞) returns +0.
|
|
|
|
</pre>
|
|
<a name='F.10.5.3'></a>
|
|
<hr>
|
|
<h3>F.10.5.3 [The lgamma functions]</h3>
|
|
<a name='F.10.5.3p1'></a>
|
|
<pre>1 — lgamma(1) returns +0.
|
|
|
|
— lgamma(2) returns +0.
|
|
|
|
— lgamma(x) returns +∞ and raises the "divide-by-zero" floating-point exception for x a negative
|
|
integer or zero.
|
|
|
|
— lgamma(−∞) returns +∞.
|
|
|
|
— lgamma(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.5.4'></a>
|
|
<hr>
|
|
<h3>F.10.5.4 [The tgamma functions]</h3>
|
|
<a name='F.10.5.4p1'></a>
|
|
<pre>1 — tgamma(±0) returns ±∞ and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— tgamma(x) returns a NaN and raises the "invalid" floating-point exception for x a negative
|
|
integer.
|
|
|
|
— tgamma(−∞) returns a NaN and raises the "invalid" floating-point exception.
|
|
|
|
— tgamma(+∞) returns +∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6'></a>
|
|
<hr>
|
|
<h3>F.10.6 [Nearest integer functions]</h3>
|
|
<a name='F.10.6.1'></a>
|
|
<hr>
|
|
<h3>F.10.6.1 [The ceil functions]</h3>
|
|
<a name='F.10.6.1p1'></a>
|
|
<pre>1 — ceil(±0) returns ±0.
|
|
|
|
— ceil(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6.1p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.6.1p3'></a>
|
|
<pre>3 The double version of ceil behaves as though implemented by
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
double ceil(double x)
|
|
{
|
|
double result;
|
|
int save_round = fegetround();
|
|
fesetround(FE_UPWARD);
|
|
result = nearbyint(x);
|
|
fesetround(save_round);
|
|
return result;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='F.10.6.2'></a>
|
|
<hr>
|
|
<h3>F.10.6.2 [The floor functions]</h3>
|
|
<a name='F.10.6.2p1'></a>
|
|
<pre>1 — floor(±0) returns ±0.
|
|
— floor(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6.2p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.6.2p3'></a>
|
|
<pre>3 See the sample implementation for ceil in <a href='#F.10.6.1'>F.10.6.1</a>.
|
|
|
|
</pre>
|
|
<a name='F.10.6.3'></a>
|
|
<hr>
|
|
<h3>F.10.6.3 [The nearbyint functions]</h3>
|
|
<a name='F.10.6.3p1'></a>
|
|
<pre>1 The nearbyint functions use IEC 60559 rounding according to the current rounding direction. They
|
|
do not raise the "inexact" floating-point exception if the result differs in value from the argument.
|
|
|
|
— nearbyint(±0) returns ±0 (for all rounding directions).
|
|
— nearbyint(±∞) returns ±∞ (for all rounding directions).
|
|
|
|
</pre>
|
|
<a name='F.10.6.4'></a>
|
|
<hr>
|
|
<h3>F.10.6.4 [The rint functions]</h3>
|
|
<a name='F.10.6.4p1'></a>
|
|
<pre>1 The rint functions differ from the nearbyint functions only in that they do raise the "inexact"
|
|
floating-point exception if the result differs in value from the argument.
|
|
|
|
</pre>
|
|
<a name='F.10.6.5'></a>
|
|
<hr>
|
|
<h3>F.10.6.5 [The lrint and llrint functions]</h3>
|
|
<a name='F.10.6.5p1'></a>
|
|
<pre>1 The lrint and llrint functions provide floating-to-integer conversion as prescribed by IEC 60559.
|
|
They round according to the current rounding direction. If the rounded value is outside the range of
|
|
the return type, the numeric result is unspecified and the "invalid" floating-point exception is raised.
|
|
When they raise no other floating-point exception and the result differs from the argument, they
|
|
raise the "inexact" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.6.6'></a>
|
|
<hr>
|
|
<h3>F.10.6.6 [The round functions]</h3>
|
|
<a name='F.10.6.6p1'></a>
|
|
<pre>1 — round(±0) returns ±0.
|
|
— round(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6.6p2'></a>
|
|
<pre>2 The returned value is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.6.6p3'></a>
|
|
<pre>3 The double version of round behaves as though implemented by<a href='#FOOTNOTE.455'><sup>[455]</sup></a>
|
|
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
double round(double x)
|
|
{
|
|
double result;
|
|
fenv_t save_env;
|
|
feholdexcept(&save_env);
|
|
result = rint(x);
|
|
if (fetestexcept(FE_INEXACT)) {
|
|
fesetround(FE_TOWARDZERO);
|
|
result = rint(copysign(0.5 + fabs(x), x));
|
|
feclearexcept(FE_INEXACT);
|
|
}
|
|
feupdateenv(&save_env);
|
|
return result;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.455'>
|
|
<pre><i><b>Footnote 455)</b> This code does not handle signaling NaNs as required of implementations that define FE_SNANS_ALWAYS_SIGNAL.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10.6.7'></a>
|
|
<hr>
|
|
<h3>F.10.6.7 [The lround and llround functions]</h3>
|
|
<a name='F.10.6.7p1'></a>
|
|
<pre>1 The lround and llround functions differ from the lrint and llrint functions with the default
|
|
rounding direction just in that the lround and llround functions round halfway cases away from
|
|
zero and need not raise the "inexact" floating-point exception for non-integer arguments that round
|
|
to within the range of the return type.
|
|
|
|
</pre>
|
|
<a name='F.10.6.8'></a>
|
|
<hr>
|
|
<h3>F.10.6.8 [The roundeven functions]</h3>
|
|
<a name='F.10.6.8p1'></a>
|
|
<pre>1
|
|
|
|
— roundeven(±0) returns ±0.
|
|
— roundeven(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6.8p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.6.8p3'></a>
|
|
<pre>3 See the sample implementation for ceil in <a href='#F.10.6.1'>F.10.6.1</a>.
|
|
|
|
</pre>
|
|
<a name='F.10.6.9'></a>
|
|
<hr>
|
|
<h3>F.10.6.9 [The trunc functions]</h3>
|
|
<a name='F.10.6.9p1'></a>
|
|
<pre>1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current rounding
|
|
direction).
|
|
|
|
— trunc(±0) returns ±0.
|
|
— trunc(±∞) returns ±∞.
|
|
|
|
</pre>
|
|
<a name='F.10.6.9p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.6.10'></a>
|
|
<hr>
|
|
<h3>F.10.6.10 [The fromfp and ufromfp functions]</h3>
|
|
<a name='F.10.6.10p1'></a>
|
|
<pre>1 The fromfp and ufromfp functions raise the "invalid" floating-point exception and return a NaN
|
|
if the argument width is zero or if the floating-point argument x is infinite or NaN or rounds to an
|
|
integral value that is outside the range determined by the argument width (see <a href='#7.12.9.10'>7.12.9.10</a>).
|
|
</pre>
|
|
<a name='F.10.6.10p2'></a>
|
|
<pre>2 These functions do not raise the "inexact" floating-point exception.
|
|
|
|
</pre>
|
|
<a name='F.10.6.11'></a>
|
|
<hr>
|
|
<h3>F.10.6.11 [The fromfpx and ufromfpx functions]</h3>
|
|
<a name='F.10.6.11p1'></a>
|
|
<pre>1 The fromfpx and ufromfpx functions raise the "invalid" floating-point exception and return a NaN
|
|
if the argument width is zero or if the floating-point argument x is infinite or NaN or rounds to an
|
|
integral value that is outside the range determined by the argument width (see <a href='#7.12.9.11'>7.12.9.11</a>).
|
|
</pre>
|
|
<a name='F.10.6.11p2'></a>
|
|
<pre>2 These functions raise the "inexact" floating-point exception if a valid result differs in value from the
|
|
floating-point argument x.
|
|
|
|
</pre>
|
|
<a name='F.10.7'></a>
|
|
<hr>
|
|
<h3>F.10.7 [Remainder functions]</h3>
|
|
<a name='F.10.7.1'></a>
|
|
<hr>
|
|
<h3>F.10.7.1 [The fmod functions]</h3>
|
|
<a name='F.10.7.1p1'></a>
|
|
<pre>1 — fmod(±0, y) returns ±0 for y not zero.
|
|
— fmod(x, y) returns a NaN and raises the "invalid" floating-point exception for x infinite or y
|
|
zero (and neither is a NaN).
|
|
— fmod(x, ±∞) returns x for x finite x.
|
|
|
|
</pre>
|
|
<a name='F.10.7.1p2'></a>
|
|
<pre>2 When subnormal results are supported, the returned value is exact and is independent of the current
|
|
rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.7.1p3'></a>
|
|
<pre>3 The double version of fmod behaves as though implemented by
|
|
|
|
#include <math.h>
|
|
#include <fenv.h>
|
|
#pragma STDC FENV_ACCESS ON
|
|
double fmod(double x, double y)
|
|
{
|
|
double result;
|
|
result = remainder(fabs(x), (y = fabs(y)));
|
|
if (signbit(result)) result += y;
|
|
return copysign(result, x);
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='F.10.7.2'></a>
|
|
<hr>
|
|
<h3>F.10.7.2 [The remainder functions]</h3>
|
|
<a name='F.10.7.2p1'></a>
|
|
<pre>1 — remainder(±0, y) returns ±0 for y not zero.
|
|
|
|
— remainder(x, y) returns a NaN and raises the "invalid" floating-point exception for x infinite
|
|
or y zero (and neither is a NaN).
|
|
|
|
— remainder(x, ±∞) returns x for finite x.
|
|
|
|
</pre>
|
|
<a name='F.10.7.2p2'></a>
|
|
<pre>2 When subnormal results are supported, the returned value is exact and is independent of the current
|
|
rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.7.3'></a>
|
|
<hr>
|
|
<h3>F.10.7.3 [The remquo functions]</h3>
|
|
<a name='F.10.7.3p1'></a>
|
|
<pre>1 The remquo functions follow the specifications for the remainder functions.
|
|
</pre>
|
|
<a name='F.10.7.3p2'></a>
|
|
<pre>2 If a NaN is returned, the value stored in the object pointed to by quo is unspecified.
|
|
</pre>
|
|
<a name='F.10.7.3p3'></a>
|
|
<pre>3 When subnormal results are supported, the returned value is exact and is independent of the current
|
|
rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8'></a>
|
|
<hr>
|
|
<h3>F.10.8 [Manipulation functions]</h3>
|
|
<a name='F.10.8.1'></a>
|
|
<hr>
|
|
<h3>F.10.8.1 [The copysign functions]</h3>
|
|
<a name='F.10.8.1p1'></a>
|
|
<pre>1 copysign(x, y) returns a value with the bit representation of x , except with the sign bit of y, for all
|
|
values x and y (even quiet and signaling NaNs).
|
|
</pre>
|
|
<a name='F.10.8.1p2'></a>
|
|
<pre>2 copysign(x, y) raises no floating-point exceptions, even if x or y is a signaling NaN. The returned
|
|
value is independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8.2'></a>
|
|
<hr>
|
|
<h3>F.10.8.2 [The nan functions]</h3>
|
|
<a name='F.10.8.2p1'></a>
|
|
<pre>1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
|
|
</pre>
|
|
<a name='F.10.8.2p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8.3'></a>
|
|
<hr>
|
|
<h3>F.10.8.3 [The nextafter functions]</h3>
|
|
<a name='F.10.8.3p1'></a>
|
|
<pre>1 — nextafter(x, y) raises the "overflow" and "inexact" floating-point exceptions for x finite and
|
|
the function value infinite.
|
|
|
|
— nextafter(x, y) raises the "underflow" and "inexact" floating-point exceptions for the func-
|
|
tion value subnormal or zero and x ̸= y.
|
|
|
|
</pre>
|
|
<a name='F.10.8.3p2'></a>
|
|
<pre>2 Even though underflow or overflow can occur, the returned value is independent of the current
|
|
rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.8.4'></a>
|
|
<hr>
|
|
<h3>F.10.8.4 [The nexttoward functions]</h3>
|
|
<a name='F.10.8.4p1'></a>
|
|
<pre>1 No additional requirements beyond those on nextafter.
|
|
</pre>
|
|
<a name='F.10.8.4p2'></a>
|
|
<pre>2 Even though underflow or overflow can occur, the returned value is independent of the current
|
|
rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8.5'></a>
|
|
<hr>
|
|
<h3>F.10.8.5 [The nextup functions]</h3>
|
|
<a name='F.10.8.5p1'></a>
|
|
<pre>1 — nextup(+∞) returns +∞.
|
|
|
|
— nextup(−∞) returns the largest-magnitude negative finite number in the type of the function.
|
|
|
|
</pre>
|
|
<a name='F.10.8.5p2'></a>
|
|
<pre>2 nextup(x) raises no floating-point exceptions if x is not a signaling NaN. The returned value is
|
|
independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8.6'></a>
|
|
<hr>
|
|
<h3>F.10.8.6 [The nextdown functions]</h3>
|
|
<a name='F.10.8.6p1'></a>
|
|
<pre>1 — nextdown(−∞) returns −∞.
|
|
|
|
— nextdown(+∞) returns the largest-magnitude positive finite number in the type of the func-
|
|
tion.
|
|
|
|
</pre>
|
|
<a name='F.10.8.6p2'></a>
|
|
<pre>2 nextdown(x) raises no floating-point exceptions if x is not a signaling NaN. The returned value is
|
|
independent of the current rounding direction mode.
|
|
|
|
</pre>
|
|
<a name='F.10.8.7'></a>
|
|
<hr>
|
|
<h3>F.10.8.7 [The canonicalize functions]</h3>
|
|
<a name='F.10.8.7p1'></a>
|
|
<pre>1 The canonicalize functions produce<a href='#FOOTNOTE.456'><sup>[456]</sup></a> the canonical version of the representation in the object
|
|
pointed to by the argument x. If the input *x is a signaling NaN, the "invalid" floating-point
|
|
exception is raised and a (canonical) quiet NaN (which should be the canonical version of that
|
|
signaling NaN made quiet) is produced. For quiet NaN, infinity, and finite inputs, the functions
|
|
raise no floating-point exceptions.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.456'>
|
|
<pre><i><b>Footnote 456)</b> As if *x * 1e0 were computed. Note also that this implementation does not handle signaling NaNs as required of
|
|
implementations that define FE_SNANS_ALWAYS_SIGNAL.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10.9'></a>
|
|
<hr>
|
|
<h3>F.10.9 [Maximum, minimum, and positive difference functions]</h3>
|
|
<a name='F.10.9.1'></a>
|
|
<hr>
|
|
<h3>F.10.9.1 [The fdim functions]</h3>
|
|
<a name='F.10.9.1p1'></a>
|
|
<pre>1 No additional requirements.
|
|
|
|
</pre>
|
|
<a name='F.10.9.2'></a>
|
|
<hr>
|
|
<h3>F.10.9.2 [The fmax functions]</h3>
|
|
<a name='F.10.9.2p1'></a>
|
|
<pre>1 If just one argument is a NaN, the fmax functions return the other argument (if both arguments are
|
|
NaNs, the functions return a NaN).
|
|
</pre>
|
|
<a name='F.10.9.2p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.9.2p3'></a>
|
|
<pre>3 The body of the fmax function might be<a href='#FOOTNOTE.457'><sup>[457]</sup></a>
|
|
|
|
{
|
|
double r = (isgreaterequal(x, y) || isnan(y)) ? x : y;
|
|
(void) canonicalize(&r, &r);
|
|
return r;
|
|
}
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.457'>
|
|
<pre><i><b>Footnote 457)</b> Ideally, fmax would be sensitive to the sign of zero, for example fmax(−0.0, +0.0) would return +0; however, implemen-
|
|
tation in software might be impractical.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10.9.3'></a>
|
|
<hr>
|
|
<h3>F.10.9.3 [The fmin functions]</h3>
|
|
<a name='F.10.9.3p1'></a>
|
|
<pre>1 The fmin functions are analogous to the fmax functions (see <a href='#F.10.9.2'>F.10.9.2</a>).
|
|
</pre>
|
|
<a name='F.10.9.3p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.9.4'></a>
|
|
<hr>
|
|
<h3>F.10.9.4 [The fmaximum, fminimum, fmaximum_mag, and fminimum_mag functions]</h3>
|
|
<a name='F.10.9.4p1'></a>
|
|
<pre>1 These functions treat NaNs like other functions in <math.h> (see <a href='#F.10'>F.10</a>). They differ from the cor-
|
|
responding fmaximum_num, fminimum_num, fmaximum_mag_num, and fminimum_mag_num functions
|
|
only in their treatment of NaNs.
|
|
|
|
</pre>
|
|
<a name='F.10.9.5'></a>
|
|
<hr>
|
|
<h3>F.10.9.5 [The fmaximum_num, fminimum_num, fmaximum_mag_num, and fminimum_mag_num func-]</h3>
|
|
<a name='F.10.9.5p1'></a>
|
|
<pre>1 tions
|
|
These functions return the number if one argument is a number and the other is a quiet or signaling
|
|
NaN. If both arguments are NaNs, a quiet NaN is returned. If an argument is a signaling NaN, the
|
|
"invalid" floating-point exception is raised (even though the function returns the number when the
|
|
other argument is a number).
|
|
|
|
</pre>
|
|
<a name='F.10.10'></a>
|
|
<hr>
|
|
<h3>F.10.10 [Fused multiply-add]</h3>
|
|
<a name='F.10.10.1'></a>
|
|
<hr>
|
|
<h3>F.10.10.1 [The fma functions]</h3>
|
|
<a name='F.10.10.1p1'></a>
|
|
<pre>1 — fma(x, y, z) computes xy + z, correctly rounded once.
|
|
— fma(x, y, z) returns a NaN and optionally raises the "invalid" floating-point exception if one
|
|
of x and y is infinite, the other is zero, and z is a NaN.
|
|
— fma(x, y, z) returns a NaN and raises the "invalid" floating-point exception if one of x and y is
|
|
infinite, the other is zero, and z is not a NaN.
|
|
— fma(x, y, z) returns a NaN and raises the "invalid" floating-point exception if x times y is an
|
|
exact infinity and z is also an infinity but with the opposite sign.
|
|
|
|
</pre>
|
|
<a name='F.10.11'></a>
|
|
<hr>
|
|
<h3>F.10.11 [Functions that round result to narrower type]</h3>
|
|
<a name='F.10.11p1'></a>
|
|
<pre>1 The functions that round their result to narrower type (<a href='#7.12.14'>7.12.14</a>) are fully specified in IEC 60559. The
|
|
returned value is dependent on the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.11p2'></a>
|
|
<pre>2 These functions treat zero and infinite arguments like the corresponding operation or function: + ,- ,
|
|
* , / , fma, or sqrt.
|
|
|
|
</pre>
|
|
<a name='F.10.12'></a>
|
|
<hr>
|
|
<h3>F.10.12 [Total order functions]</h3>
|
|
<a name='F.10.12p1'></a>
|
|
<pre>1 This subclause specifies the total order functions required by IEC 60559.
|
|
</pre>
|
|
<a name='F.10.12p2'></a>
|
|
<pre>2 NOTE These functions are specified only in Annex F because they depend on details of IEC 60559 formats that might not be
|
|
supported if __STDC_IEC_60559_BFP__ is not defined.
|
|
|
|
</pre>
|
|
<a name='F.10.12.1'></a>
|
|
<hr>
|
|
<h3>F.10.12.1 [The totalorder functions]</h3>
|
|
<a name='F.10.12.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_EXT__
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_BFP__
|
|
int totalorder(const double *x, const double *y);
|
|
int totalorderf(const float *x, const float *y);
|
|
int totalorderl(const long double *x, const long double *y);
|
|
#endif
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int totalorderd32(const _Decimal32 *x, const _Decimal32 *y);
|
|
int totalorderd64(const _Decimal64 *x, const _Decimal64 *y);
|
|
int totalorderd128(const _Decimal128 *x, const _Decimal128 *y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='F.10.12.1p2'></a>
|
|
<pre>2 The totalorder functions determine whether the total order relationship, defined by IEC 60559, is
|
|
true for the ordered pair of *x , *y . These functions are fully specified in IEC 60559. These functions
|
|
are independent of the current rounding direction mode and raise no floating-point exceptions, even
|
|
if *x or *y is a signaling NaN.
|
|
Returns
|
|
</pre>
|
|
<a name='F.10.12.1p3'></a>
|
|
<pre>3 The totalorder functions return nonzero if and only if the total order relation is true for the ordered
|
|
pair of *x , *y .
|
|
|
|
</pre>
|
|
<a name='F.10.12.2'></a>
|
|
<hr>
|
|
<h3>F.10.12.2 [The totalordermag functions]</h3>
|
|
<a name='F.10.12.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_EXT__
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_BFP__
|
|
int totalordermag(const double *x, const double *y);
|
|
int totalordermagf(const float *x, const float *y);
|
|
int totalordermagl(const long double *x, const long double *y);
|
|
#endif
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int totalordermagd32(const _Decimal32 *x, const _Decimal32 *y);
|
|
int totalordermagd64(const _Decimal64 *x, const _Decimal64 *y);
|
|
int totalordermagd128(const _Decimal128 *x, const _Decimal128 *y);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='F.10.12.2p2'></a>
|
|
<pre>2 The totalordermag functions determine whether the total order relationship, defined by IEC 60559,
|
|
is true for the ordered pair of the magnitudes of *x , *y . These functions are fully specified in
|
|
IEC 60559. These functions are independent of the current rounding direction mode and raise no
|
|
floating-point exceptions, even if *x or *y is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='F.10.12.2p3'></a>
|
|
<pre>3 The totalordermag functions return nonzero if and only if the total order relation is true for the
|
|
ordered pair of the magnitudes of *x , *y .
|
|
|
|
</pre>
|
|
<a name='F.10.13'></a>
|
|
<hr>
|
|
<h3>F.10.13 [Payload functions]</h3>
|
|
<a name='F.10.13p1'></a>
|
|
<pre>1 IEC 60559 defines the payload to be information contained in a quiet or signaling NaN. The payload
|
|
is intended for implementation-defined diagnostic information about the NaN, such as where or
|
|
how the NaN was created. The implementation interprets the payload as a nonnegative integer
|
|
suitable for use with the functions in this subclause, which get and set payloads. The implementation
|
|
may restrict which payloads are admissible for the user to set.
|
|
</pre>
|
|
<a name='F.10.13p2'></a>
|
|
<pre>2 NOTE These functions are specified only in Annex F because they depend on details of IEC 60559 formats that might not be
|
|
supported if __STDC_IEC_60559_BFP__ is not defined.
|
|
|
|
</pre>
|
|
<a name='F.10.13.1'></a>
|
|
<hr>
|
|
<h3>F.10.13.1 [The getpayload functions]</h3>
|
|
<a name='F.10.13.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_EXT__
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_BFP__
|
|
double getpayload(const double *x);
|
|
float getpayloadf(const float *x);
|
|
long double getpayloadl(const long double *x);
|
|
#endif
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
_Decimal32 getpayloadd32(const _Decimal32 *x);
|
|
_Decimal64 getpayloadd64(const _Decimal64 *x);
|
|
_Decimal128 getpayloadd128(const _Decimal128 *x);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='F.10.13.1p2'></a>
|
|
<pre>2 The getpayload functions extract the payload of a quiet or signaling NaN input and return it as a
|
|
positive-signed floating-point integer. If *x is not a NaN, the return result is −1. These functions
|
|
raise no floating-point exceptions, even if *x is a signaling NaN.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='F.10.13.1p3'></a>
|
|
<pre>3 The getpayload functions return the payload of the NaN input as a positive-signed floating-point
|
|
integer.
|
|
|
|
</pre>
|
|
<a name='F.10.13.2'></a>
|
|
<hr>
|
|
<h3>F.10.13.2 [The setpayload functions]</h3>
|
|
<a name='F.10.13.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_EXT__
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_BFP__
|
|
int setpayload(double *res, double pl);
|
|
int setpayloadf(float *res, float pl);
|
|
int setpayloadl(long double *res, long double pl);
|
|
#endif
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int setpayloadd32(_Decimal32 *res, _Decimal32 pl);
|
|
int setpayloadd64(_Decimal64 *res, _Decimal64 pl);
|
|
int setpayloadd128(_Decimal128 *res, _Decimal128 pl);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='F.10.13.2p2'></a>
|
|
<pre>2 The setpayload functions create a quiet NaN with the payload specified by pl and a zero sign bit
|
|
and store that NaN in the object pointed to by *res . If pl is not a floating-point integer representing
|
|
an admissible payload, *res is set to +0.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='F.10.13.2p3'></a>
|
|
<pre>3 If the setpayload functions stored the specified NaN, they return a zero value, otherwise a nonzero
|
|
value (and *res is set to +0).
|
|
|
|
</pre>
|
|
<a name='F.10.13.3'></a>
|
|
<hr>
|
|
<h3>F.10.13.3 [The setpayloadsig functions]</h3>
|
|
<a name='F.10.13.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_EXT__
|
|
#include <math.h>
|
|
#ifdef __STDC_IEC_60559_BFP__
|
|
int setpayloadsig(double *res, double pl);
|
|
int setpayloadsigf(float *res, float pl);
|
|
int setpayloadsigl(long double *res, long double pl);
|
|
#endif
|
|
#ifdef __STDC_IEC_60559_DFP__
|
|
int setpayloadsigd32(_Decimal32 *res, _Decimal32 pl);
|
|
int setpayloadsigd64(_Decimal64 *res, _Decimal64 pl);
|
|
int setpayloadsigd128(_Decimal128 *res, _Decimal128 pl);
|
|
#endif
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='F.10.13.3p2'></a>
|
|
<pre>2 The setpayloadsig functions create a signaling NaN with the payload specified by pl and a zero
|
|
sign bit and store that NaN in the object pointed to by *res . If pl is not a floating-point integer
|
|
representing an admissible payload, *res is set to +0.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='F.10.13.3p3'></a>
|
|
<pre>3 If the setpayloadsig functions stored the specified NaN, they return a zero value, otherwise a
|
|
nonzero value (and *res is set to +0).
|
|
|
|
</pre>
|
|
<a name='F.10.14'></a>
|
|
<hr>
|
|
<h3>F.10.14 [Comparison macros]</h3>
|
|
<a name='F.10.14p1'></a>
|
|
<pre>1 Relational operators and their corresponding comparison macros (<a href='#7.12.17'>7.12.17</a>) produce equivalent result
|
|
values, even if argument values are represented in wider formats. Thus, comparison macro argu-
|
|
ments represented in formats wider than their semantic types are not converted to the semantic types,
|
|
unless the wide evaluation method converts operands of relational operators to their semantic types.
|
|
The standard wide evaluation methods characterized by FLT_EVAL_METHOD and DEC_EVAL_METHOD
|
|
equal to 1 or 2 (<a href='#5.2.4.2.2'>5.2.4.2.2</a>, <a href='#5.2.4.2.3'>5.2.4.2.3</a>), do not convert operands of relational operators to their semantic
|
|
types.
|
|
|
|
</pre>
|
|
<a name='F.10.14.1'></a>
|
|
<hr>
|
|
<h3>F.10.14.1 [The iseqsig macro]</h3>
|
|
<a name='F.10.14.1p1'></a>
|
|
<pre>1 The equality operator == and the iseqsig macro produce equivalent results, except that the iseqsig
|
|
macro raises the "invalid" floating-point exception if an argument is a NaN.
|
|
|
|
</pre>
|
|
<a name='G.'></a>
|
|
<hr>
|
|
<h3>G. [Annex G (normative) IEC 60559-compatible complex arithmetic]</h3>
|
|
<a name='G.1'></a>
|
|
<hr>
|
|
<h3>G.1 [Introduction]</h3>
|
|
<a name='G.1p1'></a>
|
|
<pre>1 This annex supplements Annex F to specify complex arithmetic for compatibility with IEC 60559
|
|
real floating-point arithmetic. An implementation that defines __STDC_IEC_60559_COMPLEX__ or
|
|
__STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.<a href='#FOOTNOTE.458'><sup>[458]</sup></a>
|
|
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.458'>
|
|
<pre><i><b>Footnote 458)</b> Implementations that do not define __STDC_IEC_60559_COMPLEX__ or __STDC_IEC_559_COMPLEX__ are not required
|
|
to conform to these specifications. The use of __STDC_IEC_559_COMPLEX__ for this purpose is obsolescent and should be
|
|
avoided in new code.
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.2'></a>
|
|
<hr>
|
|
<h3>G.2 [Types]</h3>
|
|
<a name='G.2p1'></a>
|
|
<pre>1 There is a new keyword _Imaginary , which is used to specify imaginary types. It is used as a type
|
|
specifier within declaration specifiers in the same way as _Complex is (thus, _Imaginary float is a
|
|
valid type name).
|
|
</pre>
|
|
<a name='G.2p2'></a>
|
|
<pre>2 There are three imaginary types, designated as float _Imaginary, double _Imaginary, and
|
|
long double _Imaginary . The imaginary types (along with the real floating and complex types)
|
|
are floating types.
|
|
</pre>
|
|
<a name='G.2p3'></a>
|
|
<pre>3 For imaginary types, the corresponding real type is given by deleting the keyword _Imaginary
|
|
from the type name.
|
|
</pre>
|
|
<a name='G.2p4'></a>
|
|
<pre>4 Each imaginary type has the same representation and alignment requirements as the corresponding
|
|
real type. The value of an object of imaginary type is the value of the real representation times the
|
|
imaginary unit.
|
|
</pre>
|
|
<a name='G.2p5'></a>
|
|
<pre>5 The imaginary type domain comprises the imaginary types.
|
|
|
|
</pre>
|
|
<a name='G.3'></a>
|
|
<hr>
|
|
<h3>G.3 [Conventions]</h3>
|
|
<a name='G.3p1'></a>
|
|
<pre>1 A complex or imaginary value with at least one infinite part is regarded as an infinity (even if its
|
|
other part is a quiet NaN). A complex or imaginary value is a finite number if each of its parts is a
|
|
finite number (neither infinite nor NaN). A complex or imaginary value is a zero if each of its parts is
|
|
a zero.
|
|
|
|
</pre>
|
|
<a name='G.4'></a>
|
|
<hr>
|
|
<h3>G.4 [Conversions]</h3>
|
|
<a name='G.4.1'></a>
|
|
<hr>
|
|
<h3>G.4.1 [Imaginary types]</h3>
|
|
<a name='G.4.1p1'></a>
|
|
<pre>1 Conversions among imaginary types follow rules analogous to those for real floating types.
|
|
|
|
</pre>
|
|
<a name='G.4.2'></a>
|
|
<hr>
|
|
<h3>G.4.2 [Real and imaginary]</h3>
|
|
<a name='G.4.2p1'></a>
|
|
<pre>1 When a value of imaginary type is converted to a real type other than bool,<a href='#FOOTNOTE.459'><sup>[459]</sup></a> the result is a positive
|
|
zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.459'>
|
|
<pre><i><b>Footnote 459)</b> See <a href='#6.3.1.2'>6.3.1.2</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.4.2p2'></a>
|
|
<pre>2 When a value of real type is converted to an imaginary type, the result is a positive imaginary zero.
|
|
|
|
</pre>
|
|
<a name='G.4.3'></a>
|
|
<hr>
|
|
<h3>G.4.3 [Imaginary and complex]</h3>
|
|
<a name='G.4.3p1'></a>
|
|
<pre>1 When a value of imaginary type is converted to a complex type, the real part of the complex result
|
|
value is a positive zero and the imaginary part of the complex result value is determined by the
|
|
conversion rules for the corresponding real types.
|
|
</pre>
|
|
<a name='G.4.3p2'></a>
|
|
<pre>2 When a value of complex type is converted to an imaginary type, the real part of the complex value
|
|
is discarded and the value of the imaginary part is converted according to the conversion rules for
|
|
the corresponding real types.
|
|
</pre>
|
|
<a name='G.5'></a>
|
|
<hr>
|
|
<h3>G.5 [Binary operators]</h3>
|
|
<a name='G.5p1'></a>
|
|
<pre>1 The following subclauses supplement <a href='#6.5'>6.5</a> in order to specify the type of the result for an operation
|
|
with an imaginary operand.
|
|
</pre>
|
|
<a name='G.5p2'></a>
|
|
<pre>2 For most operand types, the value of the result of a binary operator with an imaginary or complex
|
|
operand is completely determined, with reference to real arithmetic, by the usual mathematical
|
|
formula. For some operand types, the usual mathematical formula is problematic because of its
|
|
treatment of infinities and because of undue overflow or underflow; in these cases the result satisfies
|
|
certain properties (specified in <a href='#G.5.1'>G.5.1</a>), but is not completely determined.
|
|
|
|
</pre>
|
|
<a name='G.5.1'></a>
|
|
<hr>
|
|
<h3>G.5.1 [Multiplicative operators]</h3>
|
|
<a name='G.5.1p1'></a>
|
|
<pre>1 Semantics
|
|
If one operand has real type and the other operand has imaginary type, then the result has imaginary
|
|
type. If both operands have imaginary type, then the result has real type. (If either operand has
|
|
complex type, then the result has complex type.)
|
|
</pre>
|
|
<a name='G.5.1p2'></a>
|
|
<pre>2 If the operands are not both complex, then the result and floating-point exception behavior of the *
|
|
operator is defined by the usual mathematical formula:
|
|
* u iv u + iv
|
|
x xu i(xv) (xu) + i(xv)
|
|
iy i(yu) (−y)v ((−y)v) + i(yu)
|
|
x + iy (xu) + i(yu) ((−y)v) + i(xv)
|
|
</pre>
|
|
<a name='G.5.1p3'></a>
|
|
<pre>3 If the second operand is not complex, then the result and floating-point exception behavior of the /
|
|
operator is defined by the usual mathematical formula:
|
|
/ u iv
|
|
x x/u i((−x)/v)
|
|
iy i(y/u) y/v
|
|
x + iy (x/u) + i(y/u) (y/v) + i((−x)/v)
|
|
</pre>
|
|
<a name='G.5.1p4'></a>
|
|
<pre>4 The * and / operators satisfy the following infinity properties for all real, imaginary, and complex
|
|
operands:<a href='#FOOTNOTE.460'><sup>[460]</sup></a>
|
|
|
|
— if one operand is an infinity and the other operand is a nonzero finite number or an infinity,
|
|
then the result of the * operator is an infinity;
|
|
|
|
— if the first operand is an infinity and the second operand is a finite number, then the result of
|
|
the / operator is an infinity;
|
|
|
|
— if the first operand is a finite number and the second operand is an infinity, then the result of
|
|
the / operator is a zero;
|
|
|
|
— if the first operand is a nonzero finite number or an infinity and the second operand is a zero,
|
|
then the result of the / operator is an infinity.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.460'>
|
|
<pre><i><b>Footnote 460)</b> These properties are already implied for those cases covered in the tables, but are required for all cases (at least where the
|
|
state for CX_LIMITED_RANGE is "off").
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.5.1p5'></a>
|
|
<pre>5 If both operands of the * operator are complex or if the second operand of the / operator is complex,
|
|
the operator raises floating-point exceptions if appropriate for the calculation of the parts of the
|
|
result, and may raise spurious floating-point exceptions.
|
|
</pre>
|
|
<a name='G.5.1p6'></a>
|
|
<pre>6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note that the imaginary unit
|
|
I has imaginary type (see <a href='#G.6'>G.6</a>).
|
|
|
|
#include <math.h>
|
|
#include <complex.h>
|
|
|
|
/* Multiply z * w ...*/
|
|
double complex _Cmultd(double complex z, double complex w)
|
|
{
|
|
#pragma STDC FP_CONTRACT OFF
|
|
double a, b, c, d, ac, bd, ad, bc, x, y;
|
|
a = creal(z); b = cimag(z);
|
|
c = creal(w); d = cimag(w);
|
|
ac = a * c; bd = b * d;
|
|
ad = a * d; bc = b * c;
|
|
x = ac - bd; y = ad + bc;
|
|
if (isnan(x) && isnan(y)) {
|
|
/* Recover infinities that computed as NaN+iNaN ... */
|
|
int recalc = 0;
|
|
if (isinf(a) || isinf(b)) { // z is infinite
|
|
/* "Box" the infinity and change NaNs in the other factor to 0 */
|
|
a = copysign(isinf(a) ? 1.0: 0.0, a);
|
|
b = copysign(isinf(b) ? 1.0: 0.0, b);
|
|
if (isnan(c)) c = copysign(0.0, c);
|
|
if (isnan(d)) d = copysign(0.0, d);
|
|
recalc = 1;
|
|
}
|
|
if (isinf(c) || isinf(d)) { // w is infinite
|
|
/* "Box" the infinity and change NaNs in the other factor to 0 */
|
|
c = copysign(isinf(c) ? 1.0: 0.0, c);
|
|
d = copysign(isinf(d) ? 1.0: 0.0, d);
|
|
if (isnan(a)) a = copysign(0.0, a);
|
|
if (isnan(b)) b = copysign(0.0, b);
|
|
recalc = 1;
|
|
}
|
|
if (!recalc && (isinf(ac) || isinf(bd) ||
|
|
isinf(ad) || isinf(bc))) {
|
|
/* Recover infinities from overflow by changing NaNs to 0 ... */
|
|
if (isnan(a)) a = copysign(0.0, a);
|
|
if (isnan(b)) b = copysign(0.0, b);
|
|
if (isnan(c)) c = copysign(0.0, c);
|
|
if (isnan(d)) d = copysign(0.0, d);
|
|
recalc = 1;
|
|
}
|
|
if (recalc) {
|
|
x = INFINITY * (a * c - b * d);
|
|
y = INFINITY * (a * d + b * c);
|
|
}
|
|
}
|
|
return x + I * y;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='G.5.1p7'></a>
|
|
<pre>7 This implementation achieves the required treatment of infinities at the cost of only one isnan test in ordinary (finite) cases.
|
|
It is less than ideal in that undue overflow and underflow could occur.
|
|
</pre>
|
|
<a name='G.5.1p8'></a>
|
|
<pre>8 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
|
|
|
|
#include <math.h>
|
|
#include <complex.h>
|
|
|
|
/* Divide z / w ... */
|
|
double complex _Cdivd(double complex z, double complex w)
|
|
{
|
|
#pragma STDC FP_CONTRACT OFF
|
|
double a, b, c, d, logbw, denom, x, y;
|
|
int ilogbw = 0;
|
|
a = creal(z); b = cimag(z);
|
|
c = creal(w); d = cimag(w);
|
|
logbw = logb(fmaximum_num(fabs(c), fabs(d)));
|
|
if (isfinite(logbw)) {
|
|
ilogbw = (int)logbw;
|
|
c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
|
|
}
|
|
denom = c * c + d * d;
|
|
x = scalbn((a * c + b * d) / denom, -ilogbw);
|
|
y = scalbn((b * c - a * d) / denom, -ilogbw);
|
|
|
|
/* Recover infinities and zeros that computed as NaN+iNaN; */
|
|
/* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
|
|
|
|
if (isnan(x) && isnan(y)) {
|
|
if ((denom == 0.0) &&
|
|
(!isnan(a) || !isnan(b))) {
|
|
x = copysign(INFINITY, c) * a;
|
|
y = copysign(INFINITY, c) * b;
|
|
}
|
|
else if ((isinf(a) || isinf(b)) &&
|
|
isfinite(c) && isfinite(d)) {
|
|
a = copysign(isinf(a) ? 1.0: 0.0, a);
|
|
b = copysign(isinf(b) ? 1.0: 0.0, b);
|
|
x = INFINITY * (a * c + b * d);
|
|
y = INFINITY * (b * c - a * d);
|
|
}
|
|
else if ((logbw == INFINITY) &&
|
|
isfinite(a) && isfinite(b)) {
|
|
c = copysign(isinf(c) ? 1.0: 0.0, c);
|
|
d = copysign(isinf(d) ? 1.0: 0.0, d);
|
|
x = 0.0 * (a * c + b * d);
|
|
y = 0.0 * (b * c - a * d);
|
|
}
|
|
}
|
|
return x + I * y;
|
|
}
|
|
|
|
|
|
</pre>
|
|
<a name='G.5.1p9'></a>
|
|
<pre>9 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than for multiplication.
|
|
In the spirit of the multiplication example above, this code does not defend against overflow and underflow in the calculation
|
|
of the numerator. Scaling with the scalbn function, instead of with division, provides better roundoff characteristics.
|
|
|
|
</pre>
|
|
<a name='G.5.2'></a>
|
|
<hr>
|
|
<h3>G.5.2 [Additive operators]</h3>
|
|
<a name='G.5.2p1'></a>
|
|
<pre>1 Semantics
|
|
If both operands have imaginary type, then the result has imaginary type. (If one operand has real
|
|
type and the other operand has imaginary type, or if either operand has complex type, then the
|
|
result has complex type.)
|
|
</pre>
|
|
<a name='G.5.2p2'></a>
|
|
<pre>2 In all cases the result and floating-point exception behavior of a + or- operator is defined by the
|
|
usual mathematical formula:
|
|
+ or- u iv u + iv
|
|
x x±u x±iv (x±u)±iv
|
|
iy ±u + iy i(y±v) ±u + i(y±v)
|
|
x + iy (x±u) + iy x + i(y±v) (x±u) + i(y±v)
|
|
|
|
</pre>
|
|
<a name='G.6'></a>
|
|
<hr>
|
|
<h3>G.6 [Complex arithmetic <complex.h>]</h3>
|
|
<a name='G.6p1'></a>
|
|
<pre>1 The macros
|
|
|
|
imaginary
|
|
|
|
|
|
and
|
|
_Imaginary_I
|
|
are defined, respectively, as _Imaginary and a constant expression of type float _Imaginary with
|
|
the value of the imaginary unit. The macro
|
|
|
|
I
|
|
|
|
|
|
is defined to be _Imaginary_I (not _Complex_I as stated in <a href='#7.3'>7.3</a>). Notwithstanding the provisions of
|
|
<a href='#7.1.3'>7.1.3</a>, a program may undefine and then perhaps redefine the macro imaginary.
|
|
</pre>
|
|
<a name='G.6p2'></a>
|
|
<pre>2 This subclause contains specifications for the <complex.h> functions that are particularly suited to
|
|
IEC 60559 implementations. For families of functions, the specifications apply to all of the functions
|
|
even though only the principal function is shown. Unless otherwise specified, where the symbol "±"
|
|
occurs in both an argument and the result, the result has the same sign as the argument.
|
|
</pre>
|
|
<a name='G.6p3'></a>
|
|
<pre>3 The functions are continuous onto both√sides of their branch cuts, taking into account the sign of
|
|
zero. For example, csqrt(−2±i0) = ±i 2.
|
|
</pre>
|
|
<a name='G.6p4'></a>
|
|
<pre>4 Since complex and imaginary values are composed of real values, each function may be regarded as
|
|
computing real values from real values. Except as noted, the functions treat real infinities, NaNs,
|
|
signed zeros, subnormals, and the floating-point exception flags in a manner consistent with the
|
|
specifications for real functions in <a href='#F.10'>F.10</a>.<a href='#FOOTNOTE.461'><sup>[461]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.461'>
|
|
<pre><i><b>Footnote 461)</b> As noted in <a href='#G.3'>G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its other part is a quiet
|
|
NaN.
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.6p5'></a>
|
|
<pre>5 In subsequent subclauses in <a href='#G.6'>G.6</a> "NaN" refers to a quiet NaN. The behavior of signaling NaNs
|
|
in Annex G is implementation-defined.
|
|
</pre>
|
|
<a name='G.6p6'></a>
|
|
<pre>6 The functions cimag, conj, cproj, and creal are fully specified for all implementations, including
|
|
IEC 60559 ones, in <a href='#7.3.9'>7.3.9</a>. These functions raise no floating-point exceptions.
|
|
</pre>
|
|
<a name='G.6p7'></a>
|
|
<pre>7 Each of the functions cabs and carg is specified by a formula in terms of a real function (whose
|
|
special cases are covered in Annex F):
|
|
|
|
cabs(x + iy ) = hypot(x, y )
|
|
carg(x + iy ) = atan2(y , x)
|
|
|
|
|
|
</pre>
|
|
<a name='G.6p8'></a>
|
|
<pre>8 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by a formula in
|
|
terms of other complex functions (whose special cases are specified below):
|
|
|
|
casin(z ) = −i casinh(iz )
|
|
catan(z ) = −i catanh(iz )
|
|
ccos(z ) = ccosh(iz )
|
|
csin(z ) = −i csinh(iz )
|
|
ctan(z ) = −i ctanh(iz )
|
|
|
|
|
|
</pre>
|
|
<a name='G.6p9'></a>
|
|
<pre>9 For the other functions, the following subclauses specify behavior for special cases, including
|
|
treatment of the "invalid" and "divide-by-zero" floating-point exceptions. For families of functions,
|
|
the specifications apply to all of the functions even though only the principal function is shown. For
|
|
a function f satisfying f (conj(z)) = conj(f (z)), the specifications for the upper half-plane imply the
|
|
specifications for the lower half-plane; if the function f is also either even, f (−z) = f (z), or odd,
|
|
f (−z) = −f (z), then the specifications for the first quadrant imply the specifications for the other
|
|
three quadrants.
|
|
</pre>
|
|
<a name='G.6p10'></a>
|
|
<pre>10 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
|
|
|
|
</pre>
|
|
<a name='G.6.1'></a>
|
|
<hr>
|
|
<h3>G.6.1 [Trigonometric functions]</h3>
|
|
<a name='G.6.1.1'></a>
|
|
<hr>
|
|
<h3>G.6.1.1 [The cacos functions]</h3>
|
|
<a name='G.6.1.1p1'></a>
|
|
<pre>1 — cacos(conj(z)) = conj(cacos(z)).
|
|
|
|
— cacos(±0 + i0) returns π2 − i0.
|
|
|
|
— cacos(±0 + iNaN) returns π2 + iNaN.
|
|
— cacos(x + i∞) returns π2 − i∞, for finite x.
|
|
|
|
— cacos(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for nonzero finite x.
|
|
|
|
— cacos(−∞ + iy) returns pi − i∞, for positive-signed finite y.
|
|
|
|
— cacos(+∞ + iy) returns +0 − i∞, for positive-signed finite y.
|
|
|
|
— cacos(−∞ + i∞) returns 3 π4 − i∞.
|
|
|
|
— cacos(+∞ + i∞) returns π4 − i∞.
|
|
|
|
— cacos(±∞ + iNaN) returns NaN±i∞ (where the sign of the imaginary part of the result is
|
|
unspecified).
|
|
|
|
— cacos(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite y.
|
|
|
|
— cacos(NaN + i∞) returns NaN − i∞.
|
|
|
|
— cacos(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.2'></a>
|
|
<hr>
|
|
<h3>G.6.2 [Hyperbolic functions]</h3>
|
|
<a name='G.6.2.1'></a>
|
|
<hr>
|
|
<h3>G.6.2.1 [The cacosh functions]</h3>
|
|
<a name='G.6.2.1p1'></a>
|
|
<pre>1 — cacosh(conj(z)) = conj(cacosh(z)).
|
|
|
|
— cacosh(±0 + i0) returns +0 + iπ
|
|
2 .
|
|
|
|
|
|
— cacosh(x + i∞) returns +∞ + iπ
|
|
2 , for finite x.
|
|
|
|
|
|
— cacosh(0 + iNaN) returns NaN± iπ
|
|
2 (where the sign of the imaginary part of the result is
|
|
unspecified).
|
|
|
|
— cacosh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite nonzero x.
|
|
|
|
— cacosh(−∞ + iy) returns +∞ + iπ, for positive-signed finite y.
|
|
|
|
— cacosh(+∞ + iy) returns +∞ + i0, for positive-signed finite y.
|
|
|
|
— cacosh(−∞ + i∞) returns +∞ + i 3π
|
|
4 .
|
|
|
|
|
|
— cacosh(+∞ + i∞) returns +∞ + iπ
|
|
4 .
|
|
|
|
|
|
— cacosh(±∞ + iNaN) returns +∞ + iNaN.
|
|
|
|
— cacosh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite y.
|
|
|
|
— cacosh(NaN + i∞) returns +∞ + iNaN.
|
|
|
|
— cacosh(NaN + iNaN) returns NaN + iNaN.
|
|
</pre>
|
|
<a name='G.6.2.2'></a>
|
|
<hr>
|
|
<h3>G.6.2.2 [The casinh functions]</h3>
|
|
<a name='G.6.2.2p1'></a>
|
|
<pre>1 — casinh(conj(z)) = conj(casinh(z)). and casinh is odd.
|
|
|
|
— casinh(+0 + i0) returns 0 + i0.
|
|
|
|
— casinh(x + i∞) returns +∞ + iπ
|
|
2 for positive-signed finite x.
|
|
|
|
— casinh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite x.
|
|
|
|
— casinh(+∞ + iy) returns +∞ + i0 for positive-signed finite y.
|
|
|
|
— casinh(+∞ + i∞) returns +∞ + iπ
|
|
4 .
|
|
|
|
— casinh(+∞ + iNaN) returns +∞ + iNaN.
|
|
|
|
— casinh(NaN + i0) returns NaN + i0.
|
|
|
|
— casinh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite nonzero y.
|
|
|
|
— casinh(NaN + i∞) returns ±∞ + iNaN (where the sign of the real part of the result is
|
|
unspecified).
|
|
|
|
— casinh(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.2.3'></a>
|
|
<hr>
|
|
<h3>G.6.2.3 [The catanh functions]</h3>
|
|
<a name='G.6.2.3p1'></a>
|
|
<pre>1 — catanh(conj(z)) = conj(catanh(z)). and catanh is odd.
|
|
|
|
— catanh(+0 + i0) returns +0 + i0.
|
|
|
|
— catanh(+0 + iNaN) returns +0 + iNaN.
|
|
|
|
— catanh(+1 + i0) returns +∞ + i0 and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— catanh(x + i∞) returns +0 + iπ
|
|
2 , for finite positive-signed x.
|
|
|
|
— catanh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for nonzero finite x.
|
|
|
|
— catanh(+∞ + iy) returns +0 + iπ
|
|
2 , for finite positive-signed y.
|
|
|
|
— catanh(+∞ + i∞) returns +0 + iπ
|
|
2 .
|
|
|
|
— catanh(+∞ + iNaN) returns +0 + iNaN.
|
|
|
|
— catanh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite y.
|
|
|
|
— catanh(NaN + i∞) returns ±0 + iπ
|
|
2 (where the sign of the real part of the result is unspecified).
|
|
|
|
— catanh(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.2.4'></a>
|
|
<hr>
|
|
<h3>G.6.2.4 [The ccosh functions]</h3>
|
|
<a name='G.6.2.4p1'></a>
|
|
<pre>1 — ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
|
|
|
|
— ccosh(+0 + i0) returns 1 + i0.
|
|
|
|
— ccosh(+0 + i∞) returns NaN±i0 (where the sign of the imaginary part of the result is unspec-
|
|
ified) and raises the "invalid" floating-point exception.
|
|
|
|
— ccosh(+0 + iNaN) returns NaN±i0 (where the sign of the imaginary part of the result is
|
|
unspecified).
|
|
— ccosh(x + i∞) returns NaN + iNaN and raises the "invalid" floating-point exception, for
|
|
finite nonzero x.
|
|
|
|
— ccosh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite nonzero x.
|
|
|
|
— ccosh(+∞ + i0) returns +∞ + i0.
|
|
|
|
— ccosh(+∞ + iy) returns +∞ cis(y), for finite nonzero y.
|
|
|
|
— ccosh(+∞+i∞) returns ±∞+iNaN (where the sign of the real part of the result is unspecified)
|
|
and raises the "invalid" floating-point exception.
|
|
|
|
— ccosh(+∞ + iNaN) returns +∞ + iNaN.
|
|
|
|
— ccosh(NaN + i0) returns NaN±i0 (where the sign of the imaginary part of the result is
|
|
unspecified).
|
|
|
|
— ccosh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for all nonzero numbers y.
|
|
|
|
— ccosh(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.2.5'></a>
|
|
<hr>
|
|
<h3>G.6.2.5 [The csinh functions]</h3>
|
|
<a name='G.6.2.5p1'></a>
|
|
<pre>1 — csinh(conj(z)) = conj(csinh(z)). and csinh is odd.
|
|
|
|
— csinh(+0 + i0) returns +0 + i0.
|
|
|
|
— csinh(+0 + i∞) returns ±0 + iNaN (where the sign of the real part of the result is unspecified)
|
|
and raises the "invalid" floating-point exception.
|
|
|
|
— csinh(+0 + iNaN) returns ±0 + iNaN (where the sign of the real part of the result is unspeci-
|
|
fied).
|
|
|
|
— csinh(x + i∞) returns NaN + iNaN and raises the "invalid" floating-point exception, for
|
|
positive finite x.
|
|
|
|
— csinh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite nonzero x.
|
|
|
|
— csinh(+∞ + i0) returns +∞ + i0.
|
|
|
|
— csinh(+∞ + iy) returns +∞ cis(y), for positive finite y.
|
|
|
|
— csinh(+∞+i∞) returns ±∞+iNaN (where the sign of the real part of the result is unspecified)
|
|
and raises the "invalid" floating-point exception.
|
|
|
|
— csinh(+∞ + iNaN) returns ±∞ + iNaN (where the sign of the real part of the result is
|
|
unspecified).
|
|
|
|
— csinh(NaN + i0) returns NaN + i0.
|
|
|
|
— csinh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for all nonzero numbers y.
|
|
|
|
— csinh(NaN + iNaN) returns NaN + iNaN.
|
|
</pre>
|
|
<a name='G.6.2.6'></a>
|
|
<hr>
|
|
<h3>G.6.2.6 [The ctanh functions]</h3>
|
|
<a name='G.6.2.6p1'></a>
|
|
<pre>1 — ctanh(conj(z)) = conj(ctanh(z)) and ctanh is odd.
|
|
— ctanh(+0 + i0) returns +0 + i0.
|
|
— ctanh(0 + i∞) returns 0 + iNaN and raises the "invalid" floating-point exception.
|
|
— ctanh(x + i∞) returns NaN + iNaN and raises the "invalid" floating-point exception, for
|
|
finite nonzero x.
|
|
— ctanh(0 + iNaN) returns 0 + iNaN.
|
|
— ctanh(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite nonzero x.
|
|
— ctanh(+∞ + iy) returns 1 + i0sin(2y), for positive-signed finite y.
|
|
— ctanh(+∞ + i∞) returns 1±i0 (where the sign of the imaginary part of the result is unspeci-
|
|
fied).
|
|
— ctanh(+∞ + iNaN) returns 1±i0 (where the sign of the imaginary part of the result is unspec-
|
|
ified).
|
|
— ctanh(NaN + i0) returns NaN + i0.
|
|
— ctanh(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for all nonzero numbers y.
|
|
— ctanh(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.3'></a>
|
|
<hr>
|
|
<h3>G.6.3 [Exponential and logarithmic functions]</h3>
|
|
<a name='G.6.3.1'></a>
|
|
<hr>
|
|
<h3>G.6.3.1 [The cexp functions]</h3>
|
|
<a name='G.6.3.1p1'></a>
|
|
<pre>1 — cexp(conj(z)) = conj(cexp(z)).
|
|
— cexp(±0 + i0) returns 1 + i0.
|
|
— cexp(x + i∞) returns NaN + iNaN and raises the "invalid" floating-point exception, for finite
|
|
x.
|
|
— cexp(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point excep-
|
|
tion, for finite x.
|
|
— cexp(+∞ + i0) returns +∞ + i0.
|
|
— cexp(−∞ + iy) returns +0 cis(y), for finite y.
|
|
— cexp(+∞ + iy) returns +∞ cis(y), for finite nonzero y.
|
|
— cexp(−∞ + i∞) returns ±0±i0 (where the signs of the real and imaginary parts of the result
|
|
are unspecified).
|
|
— cexp(+∞ + i∞) returns ±∞ + iNaN and raises the "invalid" floating-point exception (where
|
|
the sign of the real part of the result is unspecified).
|
|
— cexp(−∞ + iNaN) returns ±0±i0 (where the signs of the real and imaginary parts of the result
|
|
are unspecified).
|
|
— cexp(+∞ + iNaN) returns ±∞ + iNaN (where the sign of the real part of the result is unspec-
|
|
ified).
|
|
— cexp(NaN + i0) returns NaN + i0.
|
|
— cexp(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point excep-
|
|
tion, for all nonzero numbers y.
|
|
— cexp(NaN + iNaN) returns NaN + iNaN.
|
|
</pre>
|
|
<a name='G.6.3.2'></a>
|
|
<hr>
|
|
<h3>G.6.3.2 [The clog functions]</h3>
|
|
<a name='G.6.3.2p1'></a>
|
|
<pre>1 — clog(conj(z)) = conj(clog(z)).
|
|
|
|
— clog(−0 + i0) returns −∞ + iπ and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— clog(+0 + i0) returns −∞ + i0 and raises the "divide-by-zero" floating-point exception.
|
|
|
|
— clog(x + i∞) returns +∞ + iπ
|
|
2 , for finite x.
|
|
|
|
— clog(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point excep-
|
|
tion, for finite x.
|
|
|
|
— clog(−∞ + iy) returns +∞ + iπ, for finite positive-signed y.
|
|
|
|
— clog(+∞ + iy) returns +∞ + i0, for finite positive-signed y.
|
|
|
|
— clog(−∞ + i∞) returns +∞ + i 3π
|
|
4 .
|
|
|
|
— clog(+∞ + i∞) returns +∞ + iπ
|
|
4 .
|
|
|
|
— clog(±∞ + iNaN) returns +∞ + iNaN.
|
|
|
|
— clog(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point excep-
|
|
tion, for finite y.
|
|
|
|
— clog(NaN + i∞) returns +∞ + iNaN.
|
|
|
|
— clog(NaN + iNaN) returns NaN + iNaN.
|
|
|
|
</pre>
|
|
<a name='G.6.4'></a>
|
|
<hr>
|
|
<h3>G.6.4 [Power and absolute-value functions]</h3>
|
|
<a name='G.6.4.1'></a>
|
|
<hr>
|
|
<h3>G.6.4.1 [The cpow functions]</h3>
|
|
<a name='G.6.4.1p1'></a>
|
|
<pre>1 The cpow functions raise floating-point exceptions if appropriate for the calculation of the parts of
|
|
the result, and may also raise spurious floating-point exceptions.<a href='#FOOTNOTE.462'><sup>[462]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.462'>
|
|
<pre><i><b>Footnote 462)</b> This allows cpow(z, c) to be implemented as cexp(cclog(z)) without precluding implementations that treat special cases
|
|
more carefully.
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.6.4.2'></a>
|
|
<hr>
|
|
<h3>G.6.4.2 [The csqrt functions]</h3>
|
|
<a name='G.6.4.2p1'></a>
|
|
<pre>1 — csqrt(conj(z)) = conj(csqrt(z)).
|
|
|
|
— csqrt(±0 + i0) returns +0 + i0.
|
|
|
|
— csqrt(x + i∞) returns +∞ + i∞, for all x (including NaN).
|
|
|
|
— csqrt(x + iNaN) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite x.
|
|
|
|
— csqrt(−∞ + iy) returns +0 + i∞, for finite positive-signed y.
|
|
|
|
— csqrt(+∞ + iy) returns +∞ + i0, for finite positive-signed y.
|
|
|
|
— csqrt(−∞ + iNaN) returns NaN±i∞ (where the sign of the imaginary part of the result is
|
|
unspecified).
|
|
|
|
— csqrt(+∞ + iNaN) returns +∞ + iNaN.
|
|
|
|
— csqrt(NaN + iy) returns NaN + iNaN and optionally raises the "invalid" floating-point
|
|
exception, for finite y.
|
|
|
|
— csqrt(NaN + iNaN) returns NaN + iNaN.
|
|
</pre>
|
|
<a name='G.7'></a>
|
|
<hr>
|
|
<h3>G.7 [Type-generic math <tgmath.h>]</h3>
|
|
<a name='G.7p1'></a>
|
|
<pre>1 Type-generic macros that accept complex arguments also accept imaginary arguments. If an argu-
|
|
ment is imaginary, the macro expands to an expression whose type is real, imaginary, or complex, as
|
|
appropriate for the particular function: if the argument is imaginary, then the types of cos, cosh,
|
|
fabs, carg, cimag, and creal are real; the types of sin, tan, sinh, tanh, asin, atan, asinh, and
|
|
atanh are imaginary; and the types of the others are complex.
|
|
</pre>
|
|
<a name='G.7p2'></a>
|
|
<pre>2 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh, sinh, tanh,
|
|
asin, atan, asinh, atanh is specified by a formula in terms of real functions:
|
|
|
|
cos(iy ) = cosh(y )
|
|
sin(iy ) = i sinh(y )
|
|
tan(iy ) = i tanh(y )
|
|
cosh(iy ) = cos(y )
|
|
sinh(iy ) = i sin(y )
|
|
tanh(iy ) = i tan(y )
|
|
asin(iy ) = i asinh(y )
|
|
atan(iy ) = i atanh(y )
|
|
asinh(iy ) = i asin(y )
|
|
atanh(iy ) = i atan(y )
|
|
|
|
|
|
</pre>
|
|
<a name='H.'></a>
|
|
<hr>
|
|
<h3>H. [Annex H (normative) IEC 60559 interchange and extended types]</h3>
|
|
<a name='H.1'></a>
|
|
<hr>
|
|
<h3>H.1 [Introduction]</h3>
|
|
<a name='H.1p1'></a>
|
|
<pre>1 This annex specifies extension types for programming language C that have the arithmetic inter-
|
|
change and extended floating-point formats specified in ISO/IEC/IEEE 60559. This annex also
|
|
includes functions that support the non-arithmetic interchange formats in that standard. This annex
|
|
was adapted from ISO/IEC TS 18661-3:2015, Floating-point extensions for C —Interchange and
|
|
extended types.
|
|
</pre>
|
|
<a name='H.1p2'></a>
|
|
<pre>2 An implementation that defines __STDC_IEC_60559_TYPES__ to 202311L shall conform to the
|
|
specifications in this annex. An implementation may define __STDC_IEC_60559_TYPES__ only
|
|
if it defines __STDC_IEC_60559_BFP__ , indicating support for IEC 60559 binary floating-point
|
|
arithmetic, or defines __STDC_IEC_60559_DFP__ , indicating support for IEC 60559 decimal floating-
|
|
point arithmetic (or defines both). Where a binding between the C language and IEC 60559 is
|
|
indicated, the IEC 60559-specified behavior is adopted by reference, unless stated otherwise.
|
|
|
|
</pre>
|
|
<a name='H.2'></a>
|
|
<hr>
|
|
<h3>H.2 [Types]</h3>
|
|
<pre>This clause specifies types that support IEC 60559 arithmetic interchange and extended formats. The
|
|
encoding conversion functions (<a href='#H.11.3'>H.11.3</a>) and numeric conversion functions for encodings (<a href='#H.12.3'>H.12.3</a>,
|
|
and <a href='#H.12.4'>H.12.4</a>) support the non-arithmetic interchange formats specified in IEC 60559.
|
|
|
|
</pre>
|
|
<a name='H.2.1'></a>
|
|
<hr>
|
|
<h3>H.2.1 [Interchange floating types]</h3>
|
|
<a name='H.2.1p1'></a>
|
|
<pre>1 IEC 60559 specifies interchange formats, and their encodings, which can be used for the exchange of
|
|
floating-point data between implementations. These formats are identified by their radix (binary
|
|
or decimal) and their storage width N. The two tables below give the C floating-point model
|
|
parameters<a href='#FOOTNOTE.463'><sup>[463]</sup></a> (<a href='#5.2.4.2.2'>5.2.4.2.2</a>) for the IEC 60559 interchange formats, where the function round() rounds
|
|
to the nearest integer.
|
|
|
|
Binary interchange format parameters
|
|
Parameter binary16 binary32 binary64 binary128 binaryN (N ≥ 128)
|
|
N , storage width in bits 16 32 64 128 N, a multiple of 32
|
|
p, precision in bits 11 24 53 113 N − round(4 × log2 (N )) + 13
|
|
emax , maximum exponent e 16 128 1024 16384 2(N −p−1)
|
|
emin , minimum exponent e −13 −125 −1021 −16381 3 − emax
|
|
|
|
Decimal interchange format parameters
|
|
Parameter decimal32 decimal64 decimal128 decimalN (N ≥ 32)
|
|
N , storage width in bits 32 64 128 N, a multiple of 32
|
|
p, precision in bits 7 16 34 9 × (N ÷ 32) − 2
|
|
emax , maximum exponent e 97 385 6145 3 × 2((N ÷16)+3) + 1
|
|
emin , minimum exponent e −94 −382 −6142 3 − emax
|
|
|
|
EXAMPLE For the binary160 format, p = 144, emax = 32678 and emin = −32765. For the decimal160 format, p = 43,
|
|
emax = 24577 and emin = −24574.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.463'>
|
|
<pre><i><b>Footnote 463)</b> In IEC 60559, normal floating-point numbers are expressed with the first significant digit to the left of the radix point.
|
|
Hence the exponent in the C model (shown in the tables) is 1 more than the exponent of the same number in the IEC 60559
|
|
model.
|
|
</i></pre>
|
|
</a>
|
|
<a name='H.2.1p2'></a>
|
|
<pre>2 Types designated:
|
|
_FloatN
|
|
|
|
|
|
where N is 16, 32, 64, or ≥ 128 and a multiple of 32; and, types designated
|
|
_DecimalN
|
|
|
|
|
|
where N ≥ 32 and a multiple of 32, are collectively called the interchange floating types. Each
|
|
interchange floating type has the IEC 60559 interchange format corresponding to its width (N ) and
|
|
radix (2 for _FloatN, 10 for _DecimalN). Each interchange floating type is not compatible with any
|
|
other type.
|
|
</pre>
|
|
<a name='H.2.1p3'></a>
|
|
<pre>3 An implementation that defines __STDC_IEC_60559_BFP__ and __STDC_IEC_60559_TYPES__ shall
|
|
provide _Float32 and _Float64 as interchange floating types with the same representation and
|
|
alignment requirements as float and double, respectively. If the implementation’s long double
|
|
type supports an IEC 60559 interchange format of width N > 64, then the implementation shall also
|
|
provide the type _FloatN as an interchange floating type with the same representation and alignment
|
|
requirements as long double. The implementation may provide other radix-2 interchange floating
|
|
types _FloatN; the set of such types supported is implementation-defined.
|
|
</pre>
|
|
<a name='H.2.1p4'></a>
|
|
<pre>4 An implementation that defines __STDC_IEC_60559_DFP__ provides the decimal floating
|
|
types _Decimal32 , _Decimal64 , and _Decimal128 (<a href='#6.2.5'>6.2.5</a>). If the implementation also defines
|
|
__STDC_IEC_60559_TYPES__ , it may provide other radix-10 interchange floating types _DecimalN;
|
|
the set of such types supported is implementation-defined.
|
|
|
|
</pre>
|
|
<a name='H.2.2'></a>
|
|
<hr>
|
|
<h3>H.2.2 [Non-arithmetic interchange formats]</h3>
|
|
<a name='H.2.2p1'></a>
|
|
<pre>1 An implementation supports IEC 60559 non-arithmetic interchange formats by providing the as-
|
|
sociated encoding-to-encoding conversion functions (<a href='#H.11.3.2'>H.11.3.2</a>) in <math.h> and the string-from-
|
|
encoding functions (<a href='#H.12.3'>H.12.3</a>) and string-to-encodng functions (<a href='#H.12.4'>H.12.4</a>) in <stdlib.h>.
|
|
</pre>
|
|
<a name='H.2.2p2'></a>
|
|
<pre>2 An implementation that defines __STDC_IEC_60559_BFP__ and __STDC_IEC_60559_TYPES__ sup-
|
|
ports some IEC 60559 radix-2 interchange formats as arithmetic formats by providing types _Float
|
|
N (as well as float and double) with those formats. The implementation may support other
|
|
IEC 60559 radix-2 interchange formats as non-arithmetic formats; the set of such formats supported
|
|
is implementation-defined.
|
|
</pre>
|
|
<a name='H.2.2p3'></a>
|
|
<pre>3 An implementation that defines __STDC_IEC_60559_DFP__ and __STDC_IEC_60559_TYPES__ sup-
|
|
ports some IEC 60559 radix-10 interchange formats as arithmetic formats by providing types
|
|
_DecimalN with those formats. The implementations may support other IEC 60559 radix-10 inter-
|
|
change formats as non-arithmetic formats; the set of such formats supported is implementation-
|
|
defined.
|
|
|
|
</pre>
|
|
<a name='H.2.3'></a>
|
|
<hr>
|
|
<h3>H.2.3 [Extended floating types]</h3>
|
|
<a name='H.2.3p1'></a>
|
|
<pre>1 For each of its basic formats, IEC 60559 specifies an extended format whose maximum exponent and
|
|
precision exceed those of the basic format it is associated with. Extended formats are intended for
|
|
arithmetic with more precision and exponent range than is available in the basic formats used for
|
|
the input data. The extra precision and range often mitigate round-off error and eliminate overflow
|
|
and underflow in intermediate computations. The table below gives the minimum values of these
|
|
parameters, as defined for the C floating-point model (<a href='#5.2.4.2.2'>5.2.4.2.2</a>). For all IEC 60559 extended (and
|
|
interchange) formats, emin = 3 − emax .
|
|
|
|
Extended format parameters for floating-point numbers
|
|
Extended formats associated with:
|
|
Parameter binary32 binary64 binary128 decimal64 decimal128
|
|
p digits ≥ 32 64 128 22 40
|
|
emax ≥ 1024 16384 65536 6145 24577
|
|
|
|
</pre>
|
|
<a name='H.2.3p2'></a>
|
|
<pre>2 Types designated _Float32x , _Float64x , _Float128x , _Decimal64x , and _Decimal128x support
|
|
the corresponding IEC 60559 extended formats and are collectively called the extended floating
|
|
types. The set of values of _Float32x is a subset of the set of values of _Float64x ; the set
|
|
of values of _Float64x is a subset of the set of values of _Float128x . The set of values of
|
|
_Decimal64x is a subset of the set of values of _Decimal128x . Each extended floating type is
|
|
not compatible with any other type. An implementation that defines __STDC_IEC_60559_BFP__
|
|
and __STDC_IEC_60559_TYPES__ shall provide _Float32x , and may provide one or both of the
|
|
types _Float64x and _Float128x . An implementation that defines __STDC_IEC_60559_DFP__ and
|
|
__STDC_IEC_60559_TYPES__ shall provide _Decimal64x , and may provide _Decimal128x . Which
|
|
(if any) of the optional extended floating types are provided is implementation-defined.
|
|
</pre>
|
|
<a name='H.2.3p3'></a>
|
|
<pre>3 NOTE IEC 60559 does not specify an extended format associated with the decimal32 format, nor does this annex specify an
|
|
extended type associated with the _Decimal32 type.
|
|
</pre>
|
|
<a name='H.2.3p4'></a>
|
|
<pre>4 NOTE The _Float32x type may have the same format as double. The _Decimal64x type may have the same format as
|
|
_Decimal128 .
|
|
|
|
|
|
</pre>
|
|
<a name='H.2.4'></a>
|
|
<hr>
|
|
<h3>H.2.4 [Classification of real floating types]</h3>
|
|
<a name='H.2.4p1'></a>
|
|
<pre>1 <a href='#6.2.5'>6.2.5</a> defines standard floating types as a collective name for the types float, double and
|
|
long double and it defines decimal floating types as a collective name for the types _Decimal32 ,
|
|
_Decimal64 , and _Decimal128 .
|
|
|
|
</pre>
|
|
<a name='H.2.4p2'></a>
|
|
<pre>2 <a href='#H.2.1'>H.2.1</a> defines interchange floating types and <a href='#H.2.3'>H.2.3</a> defines extended floating types.
|
|
</pre>
|
|
<a name='H.2.4p3'></a>
|
|
<pre>3 The types _FloatN and _FloatNx are collectively called binary floating types.
|
|
</pre>
|
|
<a name='H.2.4p4'></a>
|
|
<pre>4 This subclause broadens decimal floating types to include the types _DecimalN and _DecimalNx,
|
|
introduced in this annex, as well as _Decimal32 , _Decimal64 , and _Decimal128 .
|
|
</pre>
|
|
<a name='H.2.4p5'></a>
|
|
<pre>5 This sublcause broadens real floating types to include all interchange floating types and extended
|
|
floating types, as well as standard floating types.
|
|
</pre>
|
|
<a name='H.2.4p6'></a>
|
|
<pre>6 Thus, in this annex, real floating types are classified as follows:
|
|
|
|
— standard floating types, composed of float, double, long double;
|
|
|
|
— decimal floating types, composed of _DecimalN, _DecimalNx;
|
|
|
|
— binary floating types, composed of _FloatN, _FloatNx;
|
|
|
|
— interchange floating types, composed of _FloatN, _DecimalN; and,
|
|
|
|
— extended floating types, composed of _FloatNx, _DecimalNx.
|
|
|
|
</pre>
|
|
<a name='H.2.4p7'></a>
|
|
<pre>7 NOTE Standard floating types (which have an implementation-defined radix) are not included in either binary floating
|
|
types (which always have radix 2) or decimal floating types (which always have radix 10).
|
|
|
|
</pre>
|
|
<a name='H.2.5'></a>
|
|
<hr>
|
|
<h3>H.2.5 [Complex types]</h3>
|
|
<a name='H.2.5p1'></a>
|
|
<pre>1 This subclause broadens the C complex types (<a href='#6.2.5'>6.2.5</a>) to also include similar types whose correspond-
|
|
ing real parts have binary floating types. For the types _FloatN and _FloatNx, there are complex
|
|
types designated respectively as _FloatN _Complex and _FloatNx _Complex . (Complex types are a
|
|
conditional feature that implementations need not support; see <a href='#6.10.9.3'>6.10.9.3</a>.)
|
|
|
|
</pre>
|
|
<a name='H.2.6'></a>
|
|
<hr>
|
|
<h3>H.2.6 [Imaginary types]</h3>
|
|
<a name='H.2.6p1'></a>
|
|
<pre>1 This subclause broadens the C imaginary types (<a href='#G.2'>G.2</a>) to also include similar types whose correspond-
|
|
ing real parts have binary floating types. For the types _FloatN and _FloatNx, there are imaginary
|
|
types designated respectively as _FloatN _Imaginary and _FloatNx _Imaginary . The imaginary
|
|
types (along with the real floating and complex types) are floating types. (Annex G, including
|
|
imaginary types, is a conditional feature that implementations need not support; see <a href='#6.10.9.3'>6.10.9.3</a>.)
|
|
|
|
</pre>
|
|
<a name='H.3'></a>
|
|
<hr>
|
|
<h3>H.3 [Characteristics in <float.h>]</h3>
|
|
<a name='H.3p1'></a>
|
|
<pre>1 This subclause enhances the FLT_EVAL_METHOD and DEC_EVAL_METHOD macros to apply to the types
|
|
introduced in this annex.
|
|
</pre>
|
|
<a name='H.3p2'></a>
|
|
<pre>2 If FLT_RADIX is 2, the value of FLT_EVAL_METHOD (<a href='#5.2.4.2.2'>5.2.4.2.2</a>) characterizes the use of evaluation
|
|
formats for standard floating types and for binary floating types:
|
|
|
|
-1 indeterminable;
|
|
0 evaluate all operations and constants, whose semantic type comprises a set of values
|
|
that is a strict subset of the values of float, to the range and precision of float; evaluate
|
|
all other operations and constants to the range and precision of the semantic type;
|
|
1 evaluate operations and constants, whose semantic type comprises a set of values that
|
|
is a strict subset of the values of double, to the range and precision of double; evaluate
|
|
all other operations and constants to the range and precision of the semantic type;
|
|
2 evaluate operations and constants, whose semantic type comprises a set of values that is
|
|
a strict subset of the values of long double, to the range and precision of long double;
|
|
evaluate all other operations and constants to the range and precision of the semantic
|
|
type;
|
|
N where _FloatN is a supported interchange floating type, evaluate operations and con-
|
|
stants, whose semantic type comprises a set of values that is a strict subset of the values
|
|
of _FloatN, to the range and precision of _FloatN; evaluate all other operations and
|
|
constants to the range and precision of the semantic type;
|
|
N +1 where _FloatNx is a supported extended floating type, evaluate operations and con-
|
|
stants, whose semantic type comprises a set of values that is a strict subset of the values
|
|
of _FloatNx, to the range and precision of _FloatNx; evaluate all other operations and
|
|
constants to the range and precision of the semantic type.
|
|
|
|
If FLT_RADIX is not 2, the use of evaluation formats for operations and constants of binary floating
|
|
types is implementation-defined.
|
|
</pre>
|
|
<a name='H.3p3'></a>
|
|
<pre>3 The implementation-defined value of DEC_EVAL_METHOD (<a href='#5.2.4.2.3'>5.2.4.2.3</a>) characterizes the use of evalua-
|
|
tion formats for decimal floating types:
|
|
|
|
-1 indeterminable;
|
|
0 evaluate all operations and constants just to the range and precision of the type;
|
|
1 evaluate operations and constants, whose semantic type comprises a set of values that
|
|
is a strict subset of the values of _Decimal64 , to the range and precision of _Decimal64 ;
|
|
evaluate all other operations and constants to the range and precision of the semantic
|
|
type;
|
|
2 evaluate operations and constants, whose semantic type comprises a set of values that is
|
|
a strict subset of the values of _Decimal128 , to the range and precision of _Decimal128 ;
|
|
evaluate all other operations and constants to the range and precision of the semantic
|
|
type;
|
|
N where _DecimalN is a supported interchange floating type evaluate operations and
|
|
constants, whose semantic type comprises a set of values that is a strict subset of
|
|
the values of _DecimalN, to the range and precision of _DecimalN; evaluate all other
|
|
operations and constants to the range and precision of the semantic type;
|
|
N +1 where _DecimalNx is a supported extended floating type evaluate operations and
|
|
constants, whose semantic type comprises a set of values that is a strict subset of the
|
|
values of _DecimalNx, to the range and precision of _DecimalNx; evaluate all other
|
|
operations and constants to the range and precision of the semantic type.
|
|
|
|
</pre>
|
|
<a name='H.3p4'></a>
|
|
<pre>4 This subclause also specifies <float.h> macros, analogous to the macros for standard floating
|
|
types, that characterize binary floating types in terms of the model presented in <a href='#5.2.4.2.2'>5.2.4.2.2</a>. This
|
|
subclause generalizes the specification of characteristics in <a href='#5.2.4.2.3'>5.2.4.2.3</a> to include the decimal floating
|
|
types introduced in this annex. The prefix FLTN_ indicates the type _FloatN or the non-arithmetic
|
|
binary interchange format of width N . The prefix FLTNX_ indicates the type _FloatNx. The prefix
|
|
DECN_ indicates the type _DecimalN or the non-arithmetic decimal interchange format of width
|
|
N . The prefix DECNX_ indicates the type _DecimalNx. The type parameters p, emax , and emin for
|
|
extended floating types are for the extended floating type itself, not for the basic format that it
|
|
extends.
|
|
</pre>
|
|
<a name='H.3p5'></a>
|
|
<pre>5 If __STDC_WANT_IEC_60559_TYPES_EXT__ is defined (by the user) at the point in the code where
|
|
<float.h> is first included, the following applies (<a href='#H.8'>H.8</a>). For each interchange or extended floating
|
|
type that the implementation provides, <float.h> shall define the associated macros in the fol-
|
|
lowing lists. Conversely, for each such type that the implementation does not provide, <float.h>
|
|
shall not define the associated macros in the following list, except, the implementation shall define
|
|
the macros FLTN_DECIMAL_DIG and FLTN_DIG if it supports the IEC 60559 non-arithmetic binary
|
|
interchange format of width N (<a href='#H.2.2'>H.2.2</a>).
|
|
</pre>
|
|
<a name='H.3p6'></a>
|
|
<pre>6 The signaling NaN macros
|
|
The macro
|
|
|
|
FLTN_SNAN
|
|
DECN_SNAN
|
|
FLTNX_SNAN
|
|
DECNX_SNAN
|
|
|
|
|
|
expand to constant expressions of types _FloatN, _DecimalN, _FloatNx, and _DecimalNx respec-
|
|
tively, representing a signaling NaN. If an optional unary + or- operator followed by a signaling
|
|
NaN macro is used for initializing an object of the same type that has static or thread storage
|
|
duration, the object is initialized with a signaling NaN value.
|
|
</pre>
|
|
<a name='H.3p7'></a>
|
|
<pre>7 The integer values given in the following lists shall be replaced by integer constant expressions:
|
|
|
|
— radix of exponent representation, b (2 for binary, 10 for decimal)
|
|
|
|
For the standard floating types, this value is implementation-defined and is specified
|
|
by the macro FLT_RADIX. For the interchange and extended floating types there is no
|
|
corresponding macro; the radix is an inherent property of the types.
|
|
— The number of bits in the floating-point significand, p
|
|
|
|
FLTN_MANT_DIG
|
|
FLTNX_MANT_DIG
|
|
|
|
|
|
— The number of digits in the coefficient, p
|
|
|
|
DECN_MANT_DIG
|
|
DECNX_MANT_DIG
|
|
|
|
|
|
— number of decimal digits, n, such that any floating-point number with p bits can be rounded
|
|
to a floating-point number with n decimal digits and back again without change to the value,
|
|
⌈1 + p log10 (2)⌉
|
|
|
|
FLTN_DECIMAL_DIG
|
|
FLTNX_DECIMAL_DIG
|
|
|
|
|
|
— number of decimal digits, q, such that any floating-point number with q decimal digits can
|
|
be rounded to a floating-point number with p bits and back again without a change to the q
|
|
decimal digits, ⌊(p − 1) log10 (2)⌋
|
|
|
|
FLTN_DIG
|
|
FLTNX_DIG
|
|
|
|
|
|
— minimum negative integer such that the radix raised to one less than that power is a normalized
|
|
floating-point number, emin
|
|
FLTN_MIN_EXP
|
|
FLTNX_MIN_EXP
|
|
DECN_MIN_EXP
|
|
DECNX_MIN_EXP
|
|
|
|
|
|
|
|
— minimum negative integer such that 10 raised to that power is in the range of normalized
|
|
floating-point numbers, ⌈ log10 (2)emin −1 ⌉
|
|
|
|
FLTN_MIN_10_EXP
|
|
FLTNX_MIN_10_EXP
|
|
|
|
|
|
|
|
— maximum negative integer such that the radix raised to one less than that power is a repre-
|
|
sentable finite floating-point number, emax
|
|
|
|
FLTN_MAX_EXP
|
|
FLTNX_MAX_EXP
|
|
DECN_MAX_EXP
|
|
DECNX_MAX_EXP
|
|
|
|
|
|
|
|
— maximum integer such that 10 raised to that power is in the range of representable finite
|
|
floating-point numbers, ⌊ log10 ((1 − 2−p )2emax )⌋
|
|
|
|
FLTN_MAX_10_EXP
|
|
FLTNX_MAX_10_EXP
|
|
|
|
|
|
|
|
— maximum representable finite floating-pointer number, (1 − b−p )bemax
|
|
|
|
FLTN_MAX
|
|
FLTNX_MAX
|
|
DECN_MAX
|
|
DECNX_MAX
|
|
|
|
|
|
|
|
— the difference between 1 and the least value greater than 1 that is representable in the given
|
|
floating-point type, b1−p
|
|
|
|
FLTN_EPSILON
|
|
FLTNX_EPSILON
|
|
DECN_EPSILON
|
|
DECNX_EPSILON
|
|
|
|
|
|
|
|
— minimum normalized positive floating-point number, bemin −1
|
|
|
|
FLTN_MIN
|
|
FLTNX_MIN
|
|
DECN_MIN
|
|
DECNX_MIN
|
|
|
|
|
|
|
|
— minimum positive floating-point number, bemin −p
|
|
|
|
FLTN_TRUE_MIN
|
|
FLTNX_TRUE_MIN
|
|
DECN_TRUE_MIN
|
|
DECNX_TRUE_MIN
|
|
</pre>
|
|
<a name='H.4'></a>
|
|
<hr>
|
|
<h3>H.4 [Conversions]</h3>
|
|
<a name='H.4p1'></a>
|
|
<pre>1 This subclause enhances the usual arithmetic conversions (<a href='#6.3.1.8'>6.3.1.8</a>) to handle interchange and ex-
|
|
tended floating types. It supports the IEC 60559 recommendation against allowing implicit conver-
|
|
sions of operands to obtain a common type where the conversion is between types where neither is
|
|
a subset of (or equivalent to) the other.
|
|
</pre>
|
|
<a name='H.4p2'></a>
|
|
<pre>2 This subclause also broadens the operation binding in <a href='#F.3'>F.3</a> for the IEC 60559 convertFormat operation
|
|
to apply to IEC 60559 arithmetic and non-arithmetic formats.
|
|
|
|
</pre>
|
|
<a name='H.4.1'></a>
|
|
<hr>
|
|
<h3>H.4.1 [Real floating and integer]</h3>
|
|
<a name='H.4.1p1'></a>
|
|
<pre>1 When a finite value of interchange or extended floating type is converted to an integer type other
|
|
than bool, the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
|
|
the integral part cannot be represented by the integer type, the "invalid" floating-point exception
|
|
shall be raised and the result of the conversion is unspecified.
|
|
</pre>
|
|
<a name='H.4.1p2'></a>
|
|
<pre>2 When a value of integer type is converted to an interchange or extended floating type, if the value
|
|
being converted can be represented exactly in the new type, it is unchanged. If the value being
|
|
converted cannot be represented exactly, the result shall be correctly rounded with exceptions raised
|
|
as specified in IEC 60559.
|
|
|
|
</pre>
|
|
<a name='H.4.2'></a>
|
|
<hr>
|
|
<h3>H.4.2 [Usual arithmetic conversions]</h3>
|
|
<a name='H.4.2p1'></a>
|
|
<pre>1 If either operand is of floating type, the common real type is determined as follows:
|
|
|
|
— If one operand has decimal floating type, the other operand shall not have standard floating
|
|
type, binary floating type, complex type, or imaginary type.
|
|
— If only one operand has a floating type, the other operand is converted to the corresponding
|
|
real type of the operand of floating type.
|
|
— If both operands have the same corresponding real type, no further conversion is needed.
|
|
— If both operands have floating types and neither of the sets of values of their corresponding
|
|
real types is a subset of (or equivalent to) the other, the behavior is undefined.
|
|
— Otherwise, if both operands are floating types and the sets of values of their corresponding
|
|
real types are not equivalent, the operand whose set of values of its corresponding real type
|
|
is a strict subset of the set of values of the corresponding real type of the other operand is
|
|
converted, without change of type domain, to a type with the corresponding real type of that
|
|
other operand.
|
|
— Otherwise, if both operands are floating types and the sets of values of their corresponding
|
|
real types are equivalent, then the following rules are applied:
|
|
|
|
– If the corresponding real type of either operand is an interchange floating type, the other
|
|
operand is converted, without change of type domain, to a type whose corresponding
|
|
real type is that same interchange floating type.
|
|
– Otherwise, if the corresponding real type of either operand is long double, the other
|
|
operand is converted, without change of type domain, to a type whose corresponding
|
|
real type is long double.
|
|
– Otherwise, if the corresponding real type of either operand is double, the other operand
|
|
is converted, without change of type domain, to a type whose corresponding real type is
|
|
double<a href='#FOOTNOTE.464'><sup>[464]</sup></a> .
|
|
– Otherwise, if the corresponding real type of either operand is _Float128x or
|
|
_Decimal128x , the other operand is converted, without change of type domain, to a type
|
|
whose corresponding real type is _Float128x or _Decimal128x , respectively.
|
|
– Otherwise, if the corresponding real type of either operand is _Float64x or _Decimal64x ,
|
|
the other operand is converted, without change of type domain, to a type whose corre-
|
|
sponding real type is _Float64x or _Decimal64x , respectively.
|
|
</pre>
|
|
<a name='FOOTNOTE.464'>
|
|
<pre><i><b>Footnote 464)</b> All cases where float might have the same format as another type are covered above.
|
|
</i></pre>
|
|
</a>
|
|
<a name='H.4.3'></a>
|
|
<hr>
|
|
<h3>H.4.3 [Arithmetic and non-arithmetic formats]</h3>
|
|
<a name='H.4.3p1'></a>
|
|
<pre>1 The operation binding in <a href='#F.3'>F.3</a> for the IEC 60559 convertFormat operation applies to IEC 60559
|
|
arithmetic and non-arithmetic formats as follows:
|
|
|
|
— For conversions between arithmetic formats supported by floating types (same or different
|
|
radix) – casts and implicit conversions.
|
|
|
|
— For same-radix conversions between non-arithmetic interchange formats – encoding-to-
|
|
encoding conversion functions (<a href='#H.11.3.2'>H.11.3.2</a>).
|
|
|
|
— For conversions between non-arithmetic interchange formats (same or different radix) – compo-
|
|
sitions of string-from-encoding functions (<a href='#H.12.3'>H.12.3</a>) (converting exactly) and string-to-encoding
|
|
functions (<a href='#H.12.4'>H.12.4</a>).
|
|
|
|
— For same-radix conversions from interchange formats supported by interchange floating types
|
|
to non-arithmetic interchange formats – compositions of encode functions (<a href='#H.11.3.1.1'>H.11.3.1.1</a>, <a href='#7.12.16.1'>7.12.16.1</a>,
|
|
<a href='#7.12.16.3'>7.12.16.3</a>) and encoding-to-encoding functions (<a href='#H.11.3.2'>H.11.3.2</a>).
|
|
|
|
— For same radix conversions from non-arithmetic interchange formats to interchange formats
|
|
supported by interchange floating types – compositions of encoding-to-encoding conversion
|
|
functions (<a href='#H.11.3.2'>H.11.3.2</a>) and decode functions (<a href='#H.11.3.1.2'>H.11.3.1.2</a>, <a href='#7.12.16.2'>7.12.16.2</a>, <a href='#7.12.16.4'>7.12.16.4</a>). See the example in
|
|
<a href='#H.11.3.2.1'>H.11.3.2.1</a>.
|
|
|
|
— For conversions from non-arithmetic interchange formats to arithmetic formats supported
|
|
by floating types (same or different radix) – compositions of string-from-encoding functions
|
|
(<a href='#H.12.3'>H.12.3</a>) (converting exactly) and numeric conversion functions strtod, etc. (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.24.1.6'>7.24.1.6</a>).
|
|
See the example in <a href='#H.12.2'>H.12.2</a>.
|
|
|
|
— For conversions from arithmetic formats supported by floating types to non-arithmetic in-
|
|
terchange formats (same or different radix) – compositions of numeric conversion func-
|
|
tions strfromd, etc. (<a href='#7.24.1.3'>7.24.1.3</a>, <a href='#7.24.1.4'>7.24.1.4</a>) (converting exactly) and string-to-encoding functions
|
|
(<a href='#H.12.4'>H.12.4</a>).
|
|
|
|
</pre>
|
|
<a name='H.5'></a>
|
|
<hr>
|
|
<h3>H.5 [Lexical Elements]</h3>
|
|
<a name='H.5.1'></a>
|
|
<hr>
|
|
<h3>H.5.1 [Keywords]</h3>
|
|
<a name='H.5.1p1'></a>
|
|
<pre>1 This subclause expands the list of keywords (<a href='#6.4.1'>6.4.1</a>) to also include:
|
|
|
|
— _FloatN, where N is 16, 32, 64, or ≥ 128 and a multiple of 32
|
|
|
|
— _Float32x
|
|
|
|
— _Float64x
|
|
|
|
— _Float128x
|
|
|
|
— _DecimalN, where N is 96 or > 128 and a multiple of 32
|
|
|
|
— _Decimal64x
|
|
|
|
— _Decimal128x
|
|
|
|
</pre>
|
|
<a name='H.5.2'></a>
|
|
<hr>
|
|
<h3>H.5.2 [Constants]</h3>
|
|
<a name='H.5.2p1'></a>
|
|
<pre>1 This subclause specifies constants of interchange and extended floating types.
|
|
</pre>
|
|
<a name='H.5.2p2'></a>
|
|
<pre>2 This subclause expands floating-suffix (<a href='#6.4.4.2'>6.4.4.2</a>) to also include: fN, FN, fNx, FNx, dN, DN, dNx, or DNx.
|
|
</pre>
|
|
<a name='H.5.2p3'></a>
|
|
<pre>3 A floating suffix dN, DN, dNx, or DNx shall not be used in a hexadecimal-floating-constant.
|
|
</pre>
|
|
<a name='H.5.2p4'></a>
|
|
<pre>4 A floating suffix shall not designate a type that the implementation does not provide.
|
|
</pre>
|
|
<a name='H.5.2p5'></a>
|
|
<pre>5 If a floating constant is suffixed by fN or FN, it has type _FloatN. If suffixed by fNx or FNx, it has
|
|
type _FloatNx. If suffixed by dN or DN, it has type _DecimalN. If suffixed by dNx or DNx, it has type
|
|
_DecimalNx .
|
|
|
|
</pre>
|
|
<a name='H.5.2p6'></a>
|
|
<pre>6 The quantum exponent of a floating constant of decimal floating type is the same as for the result
|
|
value of the corresponding strtodN or strtodNx function (<a href='#H.12.2'>H.12.2</a>) for the same numeric string.
|
|
</pre>
|
|
<a name='H.5.2p7'></a>
|
|
<pre>7 NOTE For N = 32, 64, and 128, the suffixes dN and DN in this subclause for constants of type _DecimalN are equivalent
|
|
alternatives to the suffixes df, dd, dl, DF, DD, and DL in <a href='#6.4.4.2'>6.4.4.2</a> for the same types.
|
|
|
|
</pre>
|
|
<a name='H.6'></a>
|
|
<hr>
|
|
<h3>H.6 [Expressions]</h3>
|
|
<a name='H.6p1'></a>
|
|
<pre>1 This subclause expands the specification of expressions to also cover interchange and extended
|
|
floating types.
|
|
</pre>
|
|
<a name='H.6p2'></a>
|
|
<pre>2 Operators involving operands of interchange or extended floating type are evaluated according to
|
|
the semantics of IEC 60559, including production of decimal floating-point results with the preferred
|
|
quantum exponent as specified in IEC 60559 (see <a href='#5.2.4.2.3'>5.2.4.2.3</a>).
|
|
</pre>
|
|
<a name='H.6p3'></a>
|
|
<pre>3 For multiplicative operators (<a href='#6.5.5'>6.5.5</a>), additive operators (<a href='#6.5.6'>6.5.6</a>), relational operators (<a href='#6.5.8'>6.5.8</a>), equality
|
|
operators (<a href='#6.5.9'>6.5.9</a>), and compound assignment operators (<a href='#6.5.16.2'>6.5.16.2</a>), if either operand has decimal
|
|
floating type, the other operand shall not have standard floating type, binary floating type, complex
|
|
type, or imaginary type.
|
|
</pre>
|
|
<a name='H.6p4'></a>
|
|
<pre>4 For conditional operators (<a href='#6.5.15'>6.5.15</a>), if the second or third operand has decimal floating type, the
|
|
other of those operands shall not have standard floating type, binary floating type, complex type, or
|
|
imaginary type.
|
|
</pre>
|
|
<a name='H.6p5'></a>
|
|
<pre>5 The equivalence of expressions noted in <a href='#F.9.2'>F.9.2</a> apply to expressions of binary floating types, as well
|
|
as standard floating types.
|
|
|
|
</pre>
|
|
<a name='H.7'></a>
|
|
<hr>
|
|
<h3>H.7 [Declarations]</h3>
|
|
<a name='H.7p1'></a>
|
|
<pre>1 This subclause expands the list of type specifiers (<a href='#6.7.2'>6.7.2</a>) to also include:
|
|
|
|
— _FloatN, where N is 16, 32, 64, or ≥ 128 and a multiple of 32
|
|
|
|
— _Float32x
|
|
|
|
— _Float64x
|
|
|
|
— _Float128x
|
|
|
|
— _DecimalN, where N is 96 or > 128 and a multiple of 32
|
|
|
|
— _Decimal64x
|
|
|
|
— _Decimal128x
|
|
|
|
</pre>
|
|
<a name='H.7p2'></a>
|
|
<pre>2 The type specifiers _FloatN (where N is 16, 32, 64, or ≥ 128 and a multiple of 32), _Float32x ,
|
|
_Float64x , _Float128x , _DecimalN (where N is 96 or > 128 and a multiple of 32), _Decimal64x ,
|
|
and _Decimal128x shall not be used if the implementation does not support the corresponding
|
|
types (see <a href='#6.10.9.3'>6.10.9.3</a> and <a href='#H.2'>H.2</a>).
|
|
</pre>
|
|
<a name='H.7p3'></a>
|
|
<pre>3 This subclause also expands the list under Constraints in <a href='#6.7.2'>6.7.2</a> to also include:
|
|
|
|
— _FloatN, where N is 16, 32, 64, or ≥ 128 and a multiple of 32
|
|
|
|
— _Float32x
|
|
|
|
— _Float64x
|
|
|
|
— _Float128x
|
|
|
|
— _DecimalN, where N is 96 or > 128 and a multiple of 32
|
|
— _Decimal64x
|
|
|
|
— _Decimal128x
|
|
|
|
— _FloatN _Complex , where N is 16, 32, 64, or ≥ 128 and a multiple of 32
|
|
|
|
— _Float32x _Complex
|
|
|
|
— _Float64x _Complex
|
|
|
|
— _Float128x _Complex
|
|
|
|
</pre>
|
|
<a name='H.8'></a>
|
|
<hr>
|
|
<h3>H.8 [Identifiers in standard headers]</h3>
|
|
<a name='H.8p1'></a>
|
|
<pre>1 The identifiers added to library headers by this annex are defined or declared by their respective
|
|
headers only if the macro __STDC_WANT_IEC_60559_TYPES_EXT__ is defined (by the user) at the
|
|
point in the code where the appropriate header is first included.
|
|
|
|
</pre>
|
|
<a name='H.9'></a>
|
|
<hr>
|
|
<h3>H.9 [Complex arithmetic <complex.h>]</h3>
|
|
<a name='H.9p1'></a>
|
|
<pre>1 This subclause specifies complex functions for corresponding real types that are binary floating
|
|
types.
|
|
</pre>
|
|
<a name='H.9p2'></a>
|
|
<pre>2 Each function synopsis in <a href='#7.3'>7.3</a> specifies a family of functions including a principal function with
|
|
one or more double complex parameters and a double complex or double return value. This
|
|
subclause expands the synopsis to also include other functions, with the same name as the principal
|
|
function but with fN and fNx suffixes, which are corresponding functions whose parameters and
|
|
return values have corresponding real types _FloatN and _FloatNx.
|
|
</pre>
|
|
<a name='H.9p3'></a>
|
|
<pre>3 The following function prototypes are added to the synopses of the respective subclauses in <a href='#7.3'>7.3</a>.
|
|
For each binary floating type that the implementation provides, <complex.h> shall declare the
|
|
associated functions (see <a href='#H.8'>H.8</a>). Conversely, for each such type that the implementation does not
|
|
provide, <complex.h> shall not declare the associated functions.
|
|
(<a href='#7.3.5'>7.3.5</a>) Trigonometric functions
|
|
_FloatN complex cacosfN(_FloatN complex z);
|
|
_FloatNx complex cacosfNx(_FloatNx complex z);
|
|
_FloatN complex casinfN(_FloatN complex z);
|
|
_FloatNx complex casinfNx(_FloatNx complex z);
|
|
_FloatN complex catanfN(_FloatN complex z);
|
|
_FloatNx complex catanfNx(_FloatNx complex z);
|
|
_FloatN complex ccosfN(_FloatN complex z);
|
|
_FloatNx complex ccosfNx(_FloatNx complex z);
|
|
_FloatN complex csinfN(_FloatN complex z);
|
|
_FloatNx complex csinfNx(_FloatNx complex z);
|
|
_FloatN complex ctanfN(_FloatN complex z);
|
|
_FloatNx complex ctanfNx(_FloatNx complex z);
|
|
|
|
|
|
(<a href='#7.3.6'>7.3.6</a>) Hyperbolic functions
|
|
_FloatN complex cacoshfN(_FloatN complex z);
|
|
_FloatNx complex cacoshfNx(_FloatNx complex z);
|
|
_FloatN complex casinhfN(_FloatN complex z);
|
|
_FloatNx complex casinhfNx(_FloatNx complex z);
|
|
_FloatN complex catanhfN(_FloatN complex z);
|
|
_FloatNx complex catanhfNx(_FloatNx complex z);
|
|
_FloatN complex ccoshfN(_FloatN complex z);
|
|
_FloatNx complex ccoshfNx(_FloatNx complex z);
|
|
_FloatN complex csinhfN(_FloatN complex z);
|
|
_FloatNx complex csinhfNx(_FloatNx complex z);
|
|
_FloatN complex ctanhfN(_FloatN complex z);
|
|
_FloatNx complex ctanhfNx(_FloatNx complex z);
|
|
(<a href='#7.3.7'>7.3.7</a>) Exponential and logarithmic functions
|
|
_FloatN complex cexpfN(_FloatN complex z);
|
|
_FloatNx complex cexpfNx(_FloatNx complex z);
|
|
_FloatN complex clogfN(_FloatN complex z);
|
|
_FloatNx complex clogfNx(_FloatNx complex z);
|
|
|
|
|
|
(<a href='#7.3.8'>7.3.8</a>) Power and absolute value functions
|
|
_FloatN cabsfN(_FloatN complex z);
|
|
_FloatNx cabsfNx(_FloatNx complex z);
|
|
_FloatN complex cpowfN(_FloatN complex x, _FloatN complex y);
|
|
_FloatNx complex cpowfNx(_FloatNx complex x, _FloatNx complex y);
|
|
_FloatN complex csqrtfN(_FloatN complex z);
|
|
_FloatNx complex csqrtfNx(_FloatNx complex z);
|
|
|
|
|
|
(<a href='#7.3.9'>7.3.9</a>) Manipulation functions
|
|
_FloatN cargfN(_FloatN complex z);
|
|
_FloatNx cargfNx(_FloatNx complex z);
|
|
_FloatN cimagfN(_FloatN complex z);
|
|
_FloatNx cimagfNx(_FloatNx complex z);
|
|
_FloatN complex CMPLXFN(_FloatN x, _FloatN y);
|
|
_FloatNx complex CMPLXFNX(_FloatNx x, _FloatNx y);
|
|
_FloatN complex conjfN(_FloatN complex z);
|
|
_FloatNx complex conjfNx(_FloatNx complex z);
|
|
_FloatN complex cprojfN(_FloatN complex z);
|
|
_FloatNx complex cprojfNx(_FloatNx complex z);
|
|
_FloatN crealfN(_FloatN complex z);
|
|
_FloatNx crealfNx(_FloatNx complex z);
|
|
|
|
|
|
</pre>
|
|
<a name='H.9p4'></a>
|
|
<pre>4 For the functions listed in "future library directions" for <complex.h> (<a href='#7.33.1'>7.33.1</a>), the possible suffixes
|
|
are expanded to also include fN and fNx.
|
|
|
|
</pre>
|
|
<a name='H.10'></a>
|
|
<hr>
|
|
<h3>H.10 [Floating-point environment]</h3>
|
|
<a name='H.10p1'></a>
|
|
<pre>1 This subclause broadens the effects of the floating-point environment (<a href='#7.6'>7.6</a>) to apply to types and
|
|
formats specified in this annex.
|
|
</pre>
|
|
<a name='H.10p2'></a>
|
|
<pre>2 The same floating-point status flags are used by floating-point operations for all floating types,
|
|
including those types introduced in this annex, and by conversions for IEC 60559 non-arithmetic
|
|
interchange formats.
|
|
</pre>
|
|
<a name='H.10p3'></a>
|
|
<pre>3 Both the dynamic rounding direction mode accessed by fegetround and fesetround and the
|
|
FENV_ROUND rounding control pragma apply to operations for binary floating types, as well as
|
|
for standard floating types, and also to conversions for radix-2 non-arithmetic interchange for-
|
|
mats. Likewise, both the dynamic rounding direction mode accessed by fe_dec_getround and
|
|
fe_dec_setround and the FENV_DEC_ROUND rounding control pragmas apply to operations for all
|
|
the decimal floating types, including those decimal floating types introduced in this annex, and to
|
|
conversions for radix-10 non-arithmetic interchange formats.
|
|
</pre>
|
|
<a name='H.10p4'></a>
|
|
<pre>4 In <a href='#7.6.2'>7.6.2</a>, the table of functions affected by constant rounding modes for standard floating types
|
|
applies also for binary floating types. Each <math.h> function family listed in the table indicates
|
|
the family of functions of all standard and binary floating types (for example, the acos family
|
|
includes acosf, acosl, acosfN, and acosfNx as well as acos). The fMencfN, strfromencfN, and
|
|
strtoencfN functions are also affected by these constant rounding modes.
|
|
</pre>
|
|
<a name='H.10p5'></a>
|
|
<pre>5 In <a href='#7.6.3'>7.6.3</a>, in the table of functions affected by constant rounding modes for decimal floating types, each
|
|
<math.h> function family indicates the family of functions of all decimal floating types (for example,
|
|
the acos family includes acosdN and acosdNx). The dMencbindN, dMencdecdN, strfromencbindN,
|
|
strfromencdecdN, strtoencbindN, and strtoencdecdN functions are also affected by these con-
|
|
stant rounding modes.
|
|
</pre>
|
|
<a name='H.11'></a>
|
|
<hr>
|
|
<h3>H.11 [Mathematics <math.h>]</h3>
|
|
<a name='H.11p1'></a>
|
|
<pre>1 This subclause specifies types, functions, and macros for interchange and extended floating types,
|
|
generally corresponding to those specified in <a href='#7.12'>7.12</a> and <a href='#F.10'>F.10</a>.
|
|
</pre>
|
|
<a name='H.11p2'></a>
|
|
<pre>2 All classification macros (<a href='#7.12.3'>7.12.3</a>) and comparison macros (<a href='#7.12.17'>7.12.17</a>) naturally extend to handle inter-
|
|
change and extended floating types. For comparison macros, if neither of the sets of values of the
|
|
argument formats is a subset of (or equivalent to) the other, the behavior is undefined.
|
|
</pre>
|
|
<a name='H.11p3'></a>
|
|
<pre>3 This subclause also specifies encoding conversion functions that are part of support for the non-
|
|
arithmetic interchange formats in IEC 60559 (see <a href='#H.2.2'>H.2.2</a>).
|
|
</pre>
|
|
<a name='H.11p4'></a>
|
|
<pre>4 Most function synopses in <a href='#7.12'>7.12</a> specify a family of functions including a principal function with
|
|
one or more double parameters, a double return value, or both. The synopses are expanded to
|
|
also include functions with the same name as the principal function but with fN, fNx, dN, and dNx
|
|
suffixes, which are corresponding functions whose parameters, return values, or both are of types
|
|
_FloatN, _FloatNx , _DecimalN, and _DecimalNx, respectively.
|
|
|
|
</pre>
|
|
<a name='H.11p5'></a>
|
|
<pre>5 For each interchange or extended floating type that the implementation provides, <math.h> shall
|
|
define the associated types and macros and declare the associated functions (see <a href='#H.8'>H.8</a>). Conversely, for
|
|
each such type that the implementation does not provide, <math.h> shall not define the associated
|
|
types and macros or declare the associated functions unless explicitly specified otherwise.
|
|
</pre>
|
|
<a name='H.11p6'></a>
|
|
<pre>6 With the types
|
|
|
|
float_t
|
|
double_t
|
|
|
|
|
|
in <a href='#7.12'>7.12</a> are included the type
|
|
|
|
long_double_t
|
|
|
|
|
|
and for each supported type _FloatN, the type
|
|
_FloatN_t
|
|
|
|
|
|
and for each supported type _DecimalN , the type
|
|
_DecimalN_t
|
|
|
|
|
|
These are floating types, such that:
|
|
|
|
— each of the types has at least the range and precision of the corresponding real floating type;
|
|
|
|
— long_double_t has at least the range and precision of double_t;
|
|
— _FloatN_t
|
|
has at least the range and precision of _FloatM_t if N > M ;
|
|
— _DecimalN_t
|
|
has at least the range and precision of _DecimalM_t if N > M .
|
|
|
|
If FLT_RADIX is 2 and FLT_EVAL_METHOD (<a href='#H.3'>H.3</a>) is nonnegative, then each of the types corresponding
|
|
to a standard or binary floating type is the type whose range and precision are specified by
|
|
FLT_EVAL_METHOD to be used for evaluating operations and constants of that standard or binary
|
|
floating type. If DEC_EVAL_METHOD (<a href='#H.3'>H.3</a>) is nonnegative, then each of the types corresponding to a
|
|
decimal floating type is the type whose range and precision are specified by DEC_EVAL_METHOD to
|
|
be used for evaluating operations and constants of that decimal floating type.
|
|
</pre>
|
|
<a name='H.11p7'></a>
|
|
<pre>7 EXAMPLE If the supported standard and binary floating types are
|
|
Type IEC 60559 format
|
|
_Float16 binary16
|
|
float, _Float32 binary32
|
|
double, _Float64 , _Float32x binary64
|
|
long double, _Float64x 80-bit binary64-extended
|
|
_Float128 binary128
|
|
|
|
|
|
then the following tables gives the types with _t suffixes for various values for a FLT_EVAL_METHOD of a given value m:
|
|
|
|
_t type/m 0 1 2 32
|
|
_Float16_t float double long double _Float32
|
|
float_t float double long double float
|
|
_Float32_t _Float32 double long double _Float32
|
|
double_t double double long double double
|
|
_Float64_t _Float64 _Float64 long double _Float64
|
|
long_double_t long double long double long double long double
|
|
_Float128_t _Float128 _Float128 _Float128 _Float128
|
|
|
|
_t type/m 64 128 33 65
|
|
_Float16_t _Float64 _Float128 _Float32x _Float64x
|
|
float_t _Float64 _Float128 _Float32x _Float64x
|
|
_Float32_t _Float64 _Float128 _Float32x _Float64x
|
|
double_t double _Float128 double _Float64x
|
|
_Float64_t _Float64 _Float128 _Float64 _Float64x
|
|
long_double_t long double _Float128 long double long double
|
|
_Float128_t _Float128 _Float128 _Float128 _Float128
|
|
|
|
|
|
|
|
</pre>
|
|
<a name='H.11.1'></a>
|
|
<hr>
|
|
<h3>H.11.1 [Macros]</h3>
|
|
<a name='H.11.1p1'></a>
|
|
<pre>1 This subclause adds macros in <a href='#7.12'>7.12</a> as follows.
|
|
</pre>
|
|
<a name='H.11.1p2'></a>
|
|
<pre>2 The macros
|
|
|
|
HUGE_VAL_FN
|
|
HUGE_VAL_DN
|
|
HUGE_VAL_FNX
|
|
HUGE_VAL_DNX
|
|
|
|
|
|
expand to constant expressions of types _FloatN, _DecimalN, _FloatNx, and _DecimalNx, respec-
|
|
tively, representing positive infinity.
|
|
</pre>
|
|
<a name='H.11.1p3'></a>
|
|
<pre>3 The macros
|
|
|
|
FP_FAST_FMAFN
|
|
FP_FAST_FMADN
|
|
FP_FAST_FMAFNX
|
|
FP_FAST_FMADNX
|
|
|
|
|
|
are, respectively, _FloatN, _DecimalN, _FloatNx, and _DecimalNx analogues of FP_FAST_FMA.
|
|
</pre>
|
|
<a name='H.11.1p4'></a>
|
|
<pre>4 The macros in the following lists are interchange and extended floating type analogues of
|
|
FP_FAST_FADD, FP_FAST_FADDL, FP_FAST_DADDL, etc.
|
|
</pre>
|
|
<a name='H.11.1p5'></a>
|
|
<pre>5 For M < N , the macros
|
|
|
|
FP_FAST_FMADDFN
|
|
FP_FAST_FMSUBFN
|
|
FP_FAST_FMMULFN
|
|
FP_FAST_FMDIVFN
|
|
FP_FAST_FMFMAFN
|
|
FP_FAST_FMSQRTFN
|
|
FP_FAST_DMADDDN
|
|
FP_FAST_DMSUBDN
|
|
FP_FAST_DMMULDN
|
|
FP_FAST_DMDIVDN
|
|
FP_FAST_DMFMADN
|
|
FP_FAST_DMSQRTDN
|
|
|
|
|
|
characterize the corresponding functions whose arguments are of an interchange floating type of
|
|
width N and whose return type is an interchange floating type of width M .
|
|
</pre>
|
|
<a name='H.11.1p6'></a>
|
|
<pre>6 For M ≤ N , the macros
|
|
|
|
FP_FAST_FMADDFNX
|
|
FP_FAST_FMSUBFNX
|
|
FP_FAST_FMMULFNX
|
|
FP_FAST_FMDIVFNX
|
|
FP_FAST_FMFMAFNX
|
|
FP_FAST_FMSQRTFNX
|
|
FP_FAST_DMADDDNX
|
|
FP_FAST_DMSUBDNX
|
|
FP_FAST_DMMULDNX
|
|
FP_FAST_DMDIVDNX
|
|
FP_FAST_DMFMADNX
|
|
FP_FAST_DMSQRTDNX
|
|
|
|
|
|
characterize the corresponding functions whose arguments are of an extended floating type that
|
|
extends a format of width N and whose return type is an interchange floating type of width M .
|
|
</pre>
|
|
<a name='H.11.1p7'></a>
|
|
<pre>7 For M < N , the macros
|
|
|
|
FP_FAST_FMXADDFN
|
|
FP_FAST_FMXSUBFN
|
|
FP_FAST_FMXMULFN
|
|
FP_FAST_FMXDIVFN
|
|
FP_FAST_FMXFMAFN
|
|
FP_FAST_FMXSQRTFN
|
|
FP_FAST_DMXADDDN
|
|
FP_FAST_DMXSUBDN
|
|
FP_FAST_DMXMULDN
|
|
FP_FAST_DMXDIVDN
|
|
FP_FAST_DMXFMADN
|
|
FP_FAST_DMXSQRTDN
|
|
|
|
|
|
characterize the corresponding functions whose arguments are of an interchange floating type of
|
|
width N and whose return type is an extended floating type that extends a format of width M .
|
|
</pre>
|
|
<a name='H.11.1p8'></a>
|
|
<pre>8 For M < N , the macros
|
|
|
|
FP_FAST_FMXADDFNX
|
|
FP_FAST_FMXSUBFNX
|
|
FP_FAST_FMXMULFNX
|
|
FP_FAST_FMXDIVFNX
|
|
FP_FAST_FMXFMAFNX
|
|
FP_FAST_FMXSQRTFNX
|
|
FP_FAST_DMXADDDNX
|
|
FP_FAST_DMXSUBDNX
|
|
FP_FAST_DMXMULDNX
|
|
FP_FAST_DMXDIVDNX
|
|
FP_FAST_DMXFMADNX
|
|
FP_FAST_DMXSQRTDNX
|
|
|
|
|
|
characterize the corresponding functions whose arguments are of an extended floating type that
|
|
extends a format of width N and whose return type is an extended floating type that extends a
|
|
format of width M .
|
|
</pre>
|
|
<a name='H.11.2'></a>
|
|
<hr>
|
|
<h3>H.11.2 [Functions]</h3>
|
|
<a name='H.11.2p1'></a>
|
|
<pre>1 This sublause adds the following functions to the synopses of the respective subclauses in <a href='#7.12'>7.12</a>.
|
|
(<a href='#7.12.4'>7.12.4</a>) Trigonometric functions
|
|
_FloatN acosfN(_FloatN x);
|
|
_FloatNx acosfNx(_FloatNx x);
|
|
_DecimalN acosdN(_DecimalN x);
|
|
_DecimalNx acosdNx(_DecimalNx x);
|
|
|
|
_FloatN asinfN(_FloatN x);
|
|
_FloatNx asinfNx(_FloatNx x);
|
|
_DecimalN asindN(_DecimalN x);
|
|
_DecimalNx asindNx(_DecimalNx x);
|
|
|
|
_FloatN atanfN(_FloatN x);
|
|
_FloatNx atanfNx(_FloatNx x);
|
|
_DecimalN atandN(_DecimalN x);
|
|
_DecimalNx atandNx(_DecimalNx x);
|
|
|
|
_FloatN atan2fN(_FloatN y, _FloatN x);
|
|
_FloatNx atan2fNx(_FloatNx y, _FloatNx x);
|
|
_DecimalN atan2dN(_DecimalN y, _DecimalN x);
|
|
_DecimalNx atan2dNx(_DecimalNx y, _DecimalNx x);
|
|
|
|
_FloatN cosfN(_FloatN x);
|
|
_FloatNx cosfNx(_FloatNx x);
|
|
_DecimalN cosdN(_DecimalN x);
|
|
_DecimalNx cosdNx(_DecimalNx x);
|
|
|
|
_FloatN sinfN(_FloatN x);
|
|
_FloatNx sinfNx(_FloatNx x);
|
|
_DecimalN sindN(_DecimalN x);
|
|
_DecimalNx sindNx(_DecimalNx x);
|
|
|
|
_FloatN tanfN(_FloatN x);
|
|
_FloatNx tanfNx(_FloatNx x);
|
|
_DecimalN tandN(_DecimalN x);
|
|
_DecimalNx tandNx(_DecimalNx x);
|
|
|
|
_FloatN acospifN(_FloatN x);
|
|
_FloatNx acospifNx(_FloatNx x);
|
|
_DecimalN acospidN(_DecimalN x);
|
|
_DecimalNx acospidNx(_DecimalNx x);
|
|
|
|
_FloatN asinpifN(_FloatN x);
|
|
_FloatNx asinpifNx(_FloatNx x);
|
|
_DecimalN asinpidN(_DecimalN x);
|
|
_DecimalNx asinpidNx(_DecimalNx x);
|
|
|
|
_FloatN atanpifN(_FloatN x);
|
|
_FloatNx atanpifNx(_FloatNx x);
|
|
_DecimalN atanpidN(_DecimalN x);
|
|
_DecimalNx atanpidNx(_DecimalNx x);
|
|
|
|
_FloatN atan2pifN(_FloatN y, _FloatN x);
|
|
_FloatNx atan2pifNx(_FloatNx y, _FloatNx x);
|
|
_DecimalN atan2pidN(_DecimalN y, _DecimalN x);
|
|
_DecimalNx atan2pidNx(_DecimalNx y, _DecimalNx x);
|
|
|
|
_FloatN cospifN(_FloatN x);
|
|
_FloatNx cospifNx(_FloatNx x);
|
|
_DecimalN cospidN(_DecimalN x);
|
|
_DecimalNx cospidNx(_DecimalNx x);
|
|
|
|
_FloatN sinpifN(_FloatN x);
|
|
_FloatNx sinpifNx(_FloatNx x);
|
|
_DecimalN sinpidN(_DecimalN x);
|
|
_DecimalNx sinpidNx(_DecimalNx x);
|
|
|
|
_FloatN tanpifN(_FloatN x);
|
|
_FloatNx tanpifNx(_FloatNx x);
|
|
_DecimalN tanpidN(_DecimalN x);
|
|
_DecimalNx tanpidNx(_DecimalNx x);
|
|
|
|
|
|
(<a href='#7.12.5'>7.12.5</a>) Hyperbolic functions
|
|
_FloatN acoshfN(_FloatN x);
|
|
_FloatNx acoshfNx(_FloatNx x);
|
|
_DecimalN acoshdN(_DecimalN x);
|
|
_DecimalNx acoshdNx(_DecimalNx x);
|
|
|
|
_FloatN asinhfN(_FloatN x);
|
|
_FloatNx asinhfNx(_FloatNx x);
|
|
_DecimalN asinhdN(_DecimalN x);
|
|
_DecimalNx asinhdNx(_DecimalNx x);
|
|
|
|
_FloatN atanhfN(_FloatN x);
|
|
_FloatNx atanhfNx(_FloatNx x);
|
|
_DecimalN atanhdN(_DecimalN x);
|
|
_DecimalNx atanhdNx(_DecimalNx x);
|
|
|
|
_FloatN coshfN(_FloatN x);
|
|
_FloatNx coshfNx(_FloatNx x);
|
|
_DecimalN coshdN(_DecimalN x);
|
|
_DecimalNx coshdNx(_DecimalNx x);
|
|
|
|
_FloatN sinhfN(_FloatN x);
|
|
_FloatNx sinhfNx(_FloatNx x);
|
|
_DecimalN sinhdN(_DecimalN x);
|
|
_DecimalNx sinhdNx(_DecimalNx x);
|
|
|
|
_FloatN tanhfN(_FloatN x);
|
|
_FloatNx tanhfNx(_FloatNx x);
|
|
_DecimalN tanhdN(_DecimalN x);
|
|
_DecimalNx tanhdNx(_DecimalNx x);
|
|
|
|
|
|
(<a href='#7.12.6'>7.12.6</a>) Exponential and logarithmic functions
|
|
_FloatN expfN(_FloatN x);
|
|
_FloatNx expfNx(_FloatNx x);
|
|
_DecimalN expdN(_DecimalN x);
|
|
_DecimalNx expdNx(_DecimalNx x);
|
|
|
|
_FloatN exp10fN(_FloatN x);
|
|
_FloatNx exp10fNx(_FloatNx x);
|
|
_DecimalN exp10dN(_DecimalN x);
|
|
_DecimalNx exp10dNx(_DecimalNx x);
|
|
|
|
_FloatN exp10m1fN(_FloatN x);
|
|
_FloatNx exp10m1fNx(_FloatNx x);
|
|
_DecimalN exp10m1dN(_DecimalN x);
|
|
_DecimalNx exp10m1dNx(_DecimalNx x);
|
|
_FloatN exp2fN(_FloatN x);
|
|
_FloatNx exp2fNx(_FloatNx x);
|
|
_DecimalN exp2dN(_DecimalN x);
|
|
_DecimalNx exp2dNx(_DecimalNx x);
|
|
|
|
_FloatN exp2m1fN(_FloatN x);
|
|
_FloatNx exp2m1fNx(_FloatNx x);
|
|
_DecimalN exp2m1dN(_DecimalN x);
|
|
_DecimalNx exp2m1dNx(_DecimalNx x);
|
|
|
|
_FloatN expm1fN(_FloatN x);
|
|
_FloatNx expm1fNx(_FloatNx x);
|
|
_DecimalN expm1dN(_DecimalN x);
|
|
_DecimalNx expm1dNx(_DecimalNx x);
|
|
|
|
_FloatN frexpfN(_FloatN value, int *exp);
|
|
_FloatNx frexpfNx(_FloatNx value, int *exp);
|
|
_DecimalN frexpdN(_DecimalN value, int *exp);
|
|
_DecimalNx frexpdNx(_DecimalNx value, int *exp);
|
|
|
|
int ilogbfN(_FloatN x);
|
|
int ilogbfNx(_FloatNx x);
|
|
int ilogbdN(_DecimalNx x);
|
|
int ilogbdNx(_DecimalNx x);
|
|
|
|
_FloatN ldexpfN(_FloatN value, int exp);
|
|
_FloatNx ldexpfNx(_FloatNx value, int exp);
|
|
_DecimalN ldexpdN(_DecimalN value, int exp);
|
|
_DecimalNx ldexpdNx(_DecimalNx value, int exp);
|
|
|
|
long int llogbfN(_FloatN x);
|
|
long int llogbfNx(_FloatNx x);
|
|
long int llogbdN(_DecimalN x);
|
|
long int llogbdNx(_DecimalNx x);
|
|
|
|
_FloatN logfN(_FloatN x);
|
|
_FloatNx logfNx(_FloatNx x);
|
|
_DecimalN logdN(_DecimalN x);
|
|
_DecimalNx logdNx(_DecimalNx x);
|
|
|
|
_FloatN log10fN(_FloatN x);
|
|
_FloatNx log10fNx(_FloatNx x);
|
|
_DecimalN log10dN(_DecimalN x);
|
|
_DecimalNx log10dNx(_DecimalNx x);
|
|
|
|
_FloatN log10p1fN(_FloatN x);
|
|
_FloatNx log10p1fNx(_FloatNx x);
|
|
_DecimalN log10p1dN(_DecimalN x);
|
|
_DecimalNx log10p1dNx(_DecimalNx x);
|
|
|
|
_FloatN log1pfN(_FloatN x);
|
|
_FloatNx log1pfNx(_FloatNx x);
|
|
_FloatN logp1fN(_FloatN x);
|
|
_FloatNx logp1fNx(_FloatNx x);
|
|
_DecimalN log1pdN(_DecimalN x);
|
|
_DecimalNx log1pdNx(_DecimalNx x);
|
|
_DecimalN logp1dN(_DecimalN x);
|
|
_DecimalNx logp1dNx(_DecimalNx x);
|
|
|
|
_FloatN log2fN(_FloatN x);
|
|
_FloatNx log2fNx(_FloatNx x);
|
|
_DecimalN log2dN(_DecimalN x);
|
|
_DecimalNx log2dNx(_DecimalNx x);
|
|
|
|
_FloatN log2p1fN(_FloatN x);
|
|
_FloatNx log2p1fNx(_FloatNx x);
|
|
_DecimalN log2p1dN(_DecimalN x);
|
|
_DecimalNx log2p1dNx(_DecimalNx x);
|
|
|
|
_FloatN logbfN(_FloatN x);
|
|
_FloatNx logbfNx(_FloatNx x);
|
|
_DecimalN logbdN(_DecimalN x);
|
|
_DecimalNx logbdNx(_DecimalNx x);
|
|
|
|
_FloatN modffN(_FloatN x, _FloatN *iptr);
|
|
_FloatNx modffNx(_FloatNx x, _FloatNx *iptr);
|
|
_DecimalN modfdN(_DecimalN x, _DecimalN *iptr);
|
|
_DecimalNx modfdNx(_DecimalNx x, _DecimalNx *iptr);
|
|
|
|
_FloatN scalbnfN(_FloatN value, int exp);
|
|
_FloatNx scalbnfNx(_FloatNx value, int exp);
|
|
_DecimalN scalbndN(_DecimalN value, int exp);
|
|
_DecimalNx scalbndNx(_DecimalNx value, int exp);
|
|
|
|
_FloatN scalblnfN(_FloatN value, long int exp);
|
|
_FloatNx scalblnfNx(_FloatNx value, long int exp);
|
|
_DecimalN scalblndN(_DecimalN value, long int exp);
|
|
_DecimalNx scalblndNx(_DecimalNx value, long int exp);
|
|
|
|
|
|
|
|
(<a href='#7.12.7'>7.12.7</a>) Power and absolute-value functions
|
|
_FloatN cbrtfN(_FloatN x);
|
|
_FloatNx cbrtfNx(_FloatNx x);
|
|
_DecimalN cbrtdN(_DecimalN x);
|
|
_DecimalNx cbrtdNx(_DecimalNx x);
|
|
|
|
_FloatN compoundnfN(_FloatN x, long long int n);
|
|
_FloatNx compoundnfNx(_FloatNx x, long long int n);
|
|
_DecimalN compoundndN(_DecimalN x, long long int n);
|
|
_DecimalNx compoundndNx(_DecimalNx x, long long int n);
|
|
|
|
_FloatN fabsfN(_FloatN x);
|
|
_FloatNx fabsfNx(_FloatNx x);
|
|
_DecimalN fabsdN(_DecimalN x);
|
|
_DecimalNx fabsdNx(_DecimalNx x);
|
|
|
|
_FloatN hypotfN(_FloatN x, _FloatN y);
|
|
_FloatNx hypotfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN hypotdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx hypotdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN powfN(_FloatN x, _FloatN y);
|
|
_FloatNx powfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN powdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx powdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN pownfN(_FloatN x, long long int n);
|
|
_FloatNx pownfNx(_FloatNx x, long long int n);
|
|
_DecimalN powndN(_DecimalN x, long long int n);
|
|
_DecimalNx powndNx(_DecimalNx x, long long int n);
|
|
_FloatN powrfN(_FloatN x, _FloatN y);
|
|
_FloatNx powrfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN powrdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx powrdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN rootnfN(_FloatN x, long long int n);
|
|
_FloatNx rootnfNx(_FloatNx x, long long int n);
|
|
_DecimalN rootndN(_DecimalN x, long long int n);
|
|
_DecimalNx rootndNx(_DecimalNx x, long long int n);
|
|
|
|
_FloatN rsqrtfN(_FloatN x);
|
|
_FloatNx rsqrtfNx(_FloatNx x);
|
|
_DecimalN rsqrtdN(_DecimalN x);
|
|
_DecimalNx rsqrtdNx(_DecimalNx x);
|
|
|
|
_FloatN sqrtfN(_FloatN x);
|
|
_FloatNx sqrtfNx(_FloatNx x);
|
|
_DecimalN sqrtdN(_DecimalN x);
|
|
_DecimalNx sqrtdNx(_DecimalNx x);
|
|
|
|
|
|
(<a href='#7.12.8'>7.12.8</a>) Error and gamma functions
|
|
_FloatN erffN(_FloatN x);
|
|
_FloatNx erffNx(_FloatNx x);
|
|
_DecimalN erfdN(_DecimalN x);
|
|
_DecimalNx erfdNx(_DecimalNx x);
|
|
|
|
_FloatN erfcfN(_FloatN x);
|
|
_FloatNx erfcfNx(_FloatNx x);
|
|
_DecimalN erfcdN(_DecimalN x);
|
|
_DecimalNx erfcdNx(_DecimalNx x);
|
|
|
|
_FloatN lgammafN(_FloatN x);
|
|
_FloatNx lgammafNx(_FloatNx x);
|
|
_DecimalN lgammadN(_DecimalN x);
|
|
_DecimalNx lgammadNx(_DecimalNx x);
|
|
|
|
_FloatN tgammafN(_FloatN x);
|
|
_FloatNx tgammafNx(_FloatNx x);
|
|
_DecimalN tgammadN(_DecimalN x);
|
|
_DecimalNx tgammadNx(_DecimalNx x);
|
|
|
|
|
|
(<a href='#7.12.9'>7.12.9</a>) Nearest integer functions
|
|
_FloatN ceilfN(_FloatN x);
|
|
_FloatNx ceilfNx(_FloatNx x);
|
|
_DecimalN ceildN(_DecimalN x);
|
|
_DecimalNx ceildNx(_DecimalNx x);
|
|
|
|
_FloatN floorfN(_FloatN x);
|
|
_FloatNx floorfNx(_FloatNx x);
|
|
_DecimalN floordN(_DecimalN x);
|
|
_DecimalNx floordNx(_DecimalNx x);
|
|
|
|
_FloatN nearbyintfN(_FloatN x);
|
|
_FloatNx nearbyintfNx(_FloatNx x);
|
|
_DecimalN nearbyintdN(_DecimalN x);
|
|
_DecimalNx nearbyintdNx(_DecimalNx x);
|
|
|
|
_FloatN rintfN(_FloatN x);
|
|
_FloatNx rintfNx(_FloatNx x);
|
|
_DecimalN rintdN(_DecimalN x);
|
|
_DecimalNx rintdNx(_DecimalNx x);
|
|
|
|
long int lrintfN(_FloatN x);
|
|
long int lrintfNx(_FloatNx x);
|
|
long int lrintdN(_DecimalN x);
|
|
long int lrintdNx(_DecimalNx x);
|
|
|
|
long long int llrintfN(_FloatN x);
|
|
long long int llrintfNx(_FloatNx x);
|
|
long long int llrintdN(_DecimalN x);
|
|
long long int llrintdNx(_DecimalNx x);
|
|
|
|
_FloatN roundfN(_FloatN x);
|
|
_FloatNx roundfNx(_FloatNx x);
|
|
_DecimalN rounddN(_DecimalN x);
|
|
_DecimalNx rounddNx(_DecimalNx x);
|
|
|
|
long int lroundfN(_FloatN x);
|
|
long int lroundfNx(_FloatNx x);
|
|
long int lrounddN(_DecimalN x);
|
|
long int lrounddNx(_DecimalNx x);
|
|
|
|
long long int llroundfN(_FloatN x);
|
|
long long int llroundfNx(_FloatNx x);
|
|
long long int llrounddN(_DecimalN x);
|
|
long long int llrounddNx(_DecimalNx x);
|
|
|
|
_FloatN roundevenfN(_FloatN x);
|
|
_FloatNx roundevenfNx(_FloatNx x);
|
|
_DecimalN roundevendN(_DecimalN x);
|
|
_DecimalNx roundevendNx(_DecimalNx x);
|
|
|
|
_FloatN truncfN(_FloatN x);
|
|
_FloatNx truncfNx(_FloatNx x);
|
|
_DecimalN truncdN(_DecimalN x);
|
|
_DecimalNx truncdNx(_DecimalNx x);
|
|
|
|
_FloatN fromfpfN(_FloatN x, int rnd, unsigned int width);
|
|
_FloatNx fromfpfNx(_FloatNx x, int rnd, unsigned int width);
|
|
_DecimalN fromfpdN(_DecimalN x, int rnd, unsigned int width);
|
|
_DecimalNx fromfpdNx(_DecimalNx x, int rnd, unsigned int width);
|
|
_FloatN ufromfpfN(_FloatN x, int rnd, unsigned int width);
|
|
_FloatNx ufromfpfNx(_FloatNx x, int rnd, unsigned int width);
|
|
_DecimalN ufromfpdN(_DecimalN x, int rnd, unsigned int width);
|
|
_DecimalNx ufromfpdNx(_DecimalNx x, int rnd, unsigned int width);
|
|
|
|
_FloatN fromfpxfN(_FloatN x, int rnd, unsigned int width);
|
|
_FloatNx fromfpxfNx(_FloatNx x, int rnd, unsigned int width);
|
|
_DecimalN fromfpxdN(_DecimalN x, int rnd, unsigned int width);
|
|
_DecimalNx fromfpxdNx(_DecimalNx x, int rnd, unsigned int width);
|
|
_FloatN ufromfpxfN(_FloatN x, int rnd, unsigned int width);
|
|
_FloatNx ufromfpxfNx(_FloatNx x, int rnd, unsigned int width);
|
|
_DecimalN ufromfpxdN(_DecimalN x, int rnd, unsigned int width);
|
|
_DecimalNx ufromfpxdNx(_DecimalNx x, int rnd, unsigned int width);
|
|
|
|
|
|
|
|
(<a href='#7.12.10.2'>7.12.10.2</a>) Remainder functions
|
|
_FloatN fmodfN(_FloatN x, _FloatN y);
|
|
_FloatNx fmodfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fmoddN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fmoddNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN remainderfN(_FloatN x, _FloatN y);
|
|
_FloatNx remainderfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN remainderdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx remainderdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN remquofN(_FloatN x, _FloatN y, int *quo);
|
|
_FloatNx remquofNx(_FloatNx x, _FloatNx y, int *quo);
|
|
|
|
|
|
(<a href='#7.12.11'>7.12.11</a>) Manipulation functions
|
|
_FloatN copysignfN(_FloatN x, _FloatN y);
|
|
_FloatNx copysignfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN copysigndN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx copysigndNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN nanfN(const char *tagp);
|
|
_FloatNx nanfNx(const char *tagp);
|
|
_DecimalN nandN(const char *tagp);
|
|
_DecimalNx nandNx(const char *tagp);
|
|
|
|
_FloatN nextafterfN(_FloatN x, _FloatN y);
|
|
_FloatNx nextafterfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN nextafterdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx nextafterdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN nextupfN(_FloatN x);
|
|
_FloatNx nextupfNx(_FloatNx x);
|
|
_DecimalN nextupdN(_DecimalN x);
|
|
_DecimalNx nextupdNx(_DecimalNx x);
|
|
|
|
_FloatN nextdownfN(_FloatN x);
|
|
_FloatNx nextdownfNx(_FloatNx x);
|
|
_DecimalN nextdowndN(_DecimalN x);
|
|
_DecimalNx nextdowndNx(_DecimalNx x);
|
|
|
|
int canonicalizefN(_FloatN * cx, const _FloatN * x);
|
|
int canonicalizefNx(_FloatNx * cx, const _FloatNx * x);
|
|
int canonicalizedN(_DecimalN * cx, const _DecimalN * x);
|
|
int canonicalizedNx(_DecimalNx * cx, const _DecimalNx * x);
|
|
|
|
|
|
(<a href='#7.12.12'>7.12.12</a>) Maximum, minimum, and positive difference functions
|
|
_FloatN fdimfN(_FloatN x, _FloatN y);
|
|
_FloatNx fdimfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fdimdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fdimdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fmaximumfN(_FloatN x, _FloatN y);
|
|
_FloatNx fmaximumfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fmaximumdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fmaximumdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fminimumfN(_FloatN x, _FloatN y);
|
|
_FloatNx fminimumfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fminimumdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fminimumdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fmaximum_magfN(_FloatN x, _FloatN y);
|
|
_FloatNx fmaximum_magfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fmaximum_magdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fmaximum_magdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fminimum_magfN(_FloatN x, _FloatN y);
|
|
_FloatNx fminimum_magfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fminimum_magdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fminimum_magdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fmaximum_numfN(_FloatN x, _FloatN y);
|
|
_FloatNx fmaximum_numfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fmaximum_numdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fmaximum_numdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fminimum_numfN(_FloatN x, _FloatN y);
|
|
_FloatNx fminimum_numfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fminimum_numdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fminimum_numdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fmaximum_mag_numfN(_FloatN x, _FloatN y);
|
|
_FloatNx fmaximum_mag_numfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fmaximum_mag_numdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fmaximum_mag_numdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_FloatN fminimum_mag_numfN(_FloatN x, _FloatN y);
|
|
_FloatNx fminimum_mag_numfNx(_FloatNx x, _FloatNx y);
|
|
_DecimalN fminimum_mag_numdN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx fminimum_mag_numdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
|
|
(<a href='#7.12.13.1'>7.12.13.1</a>) Fused multiply-add
|
|
_FloatN fmafN(_FloatN x, _FloatN y, _FloatN z);
|
|
_FloatNx fmafNx(_FloatNx x, _FloatNx y, _FloatNx z);
|
|
_DecimalN fmadN(_DecimalN x, _DecimalN y, _DecimalN z);
|
|
_DecimalNx fmadNx(_DecimalNx x, _DecimalNx y, _DecimalNx z);
|
|
|
|
|
|
(<a href='#7.12.14'>7.12.14</a>) Functions that round result to narrower type
|
|
_FloatM fMaddfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatM fMaddfNx(_FloatNx x, _FloatNx y); // M ≤ N
|
|
_FloatMx fMxaddfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatMx fMxaddfNx(_FloatNx x, _FloatNx y); // M < N
|
|
_DecimalM dMadddN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalM dMadddNx(_DecimalNx x, _DecimalNx y); // M ≤ N
|
|
_DecimalMx dMxadddN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalMx dMxadddNx(_DecimalNx x, _DecimalNx y); // M < N
|
|
|
|
_FloatM fMsubfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatM fMsubfNx(_FloatNx x, _FloatNx y); // M ≤ N
|
|
_FloatMx fMxsubfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatMx fMxsubfNx(_FloatNx x, _FloatNx y); // M < N
|
|
_DecimalM dMsubdN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalM dMsubdNx(_DecimalNx x, _DecimalNx y); // M ≤ N
|
|
_DecimalMx dMxsubdN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalMx dMxsubdNx(_DecimalNx x, _DecimalNx y); // M < N
|
|
|
|
_FloatM fMmulfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatM fMmulfNx(_FloatNx x, _FloatNx y); // M ≤ N
|
|
_FloatMx fMxmulfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatMx fMxmulfNx(_FloatNx x, _FloatNx y); // M < N
|
|
_DecimalM dMmuldN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalM dMmuldNx(_DecimalNx x, _DecimalNx y); // M ≤ N
|
|
_DecimalMx dMxmuldN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalMx dMxmuldNx(_DecimalNx x, _DecimalNx y); // M < N
|
|
|
|
_FloatM fMdivfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatM fMdivfNx(_FloatNx x, _FloatNx y); // M ≤ N
|
|
_FloatMx fMxdivfN(_FloatN x, _FloatN y); // M < N
|
|
_FloatMx fMxdivfNx(_FloatNx x, _FloatNx y); // M < N
|
|
_DecimalM dMdivdN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalM dMdivdNx(_DecimalNx x, _DecimalNx y); // M ≤ N
|
|
_DecimalMx dMxdivdN(_DecimalN x, _DecimalN y); // M < N
|
|
_DecimalMx dMxdivdNx(_DecimalNx x, _DecimalNx y); // M < N
|
|
|
|
_FloatM fMfmafN(_FloatN x, _FloatN y, _FloatN z); // M < N
|
|
_FloatM fMfmafNx(_FloatNx x, _FloatNx y, _FloatNx z); // M ≤ N
|
|
_FloatMx fMxfmafN(_FloatN x, _FloatN y, _FloatN z); // M < N
|
|
_FloatMx fMxfmafNx(_FloatNx x, _FloatNx y, _FloatNx z); // M < N
|
|
_DecimalM dMfmadN(_DecimalN x, _DecimalN y, _DecimalN z); // M < N
|
|
_DecimalM dMfmadNx(_DecimalNx x, _DecimalNx y, _DecimalNx z); // M ≤ N
|
|
_DecimalMx dMxfmadN(_DecimalN x, _DecimalN y, _DecimalN z); // M < N
|
|
_DecimalMx dMxfmadNx(_DecimalNx x, _DecimalNx y, _DecimalNx z); // M < N
|
|
|
|
_FloatM fMsqrtfN(_FloatN x); // M < N
|
|
_FloatM fMsqrtfNx(_FloatNx x); // M ≤ N
|
|
_FloatMx fMxsqrtfN(_FloatN x); // M < N
|
|
_FloatMx fMxsqrtfNx(_FloatNx x); // M < N
|
|
_DecimalM dMsqrtdN(_DecimalN x); // M < N
|
|
_DecimalM dMsqrtdNx(_DecimalNx x); // M ≤ N
|
|
_DecimalMx dMxsqrtdN(_DecimalN x); // M < N
|
|
_DecimalMx dMxsqrtdNx(_DecimalNx x); // M < N
|
|
|
|
|
|
(<a href='#7.12.15'>7.12.15</a>) Quantum and quantum exponent functions
|
|
_DecimalN quantizedN(_DecimalN x, _DecimalN y);
|
|
_DecimalNx quantizedNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
bool samequantumdN(_DecimalN x, _DecimalN y);
|
|
bool samequantumdNx(_DecimalNx x, _DecimalNx y);
|
|
|
|
_DecimalN quantumdN(_DecimalN x);
|
|
_DecimalNx quantumdNx(_DecimalNx x);
|
|
|
|
long long int llquantexpdN(_DecimalN x);
|
|
long long int llquantexpdNx(_DecimalNx x);
|
|
|
|
|
|
(<a href='#7.12.16'>7.12.16</a>) Decimal re-encoding functions
|
|
|
|
void encodedecdN(unsigned char * restrict encptr,
|
|
const _DecimalN * restrict xptr);
|
|
void decodedecdN(_DecimalN * restrict xptr,
|
|
const unsigned char * restrict encptr);
|
|
void encodebindN(unsigned char * restrict encptr,
|
|
const _DecimalN * restrict xptr);
|
|
void decodebindN(_DecimalN * restrict xptr,
|
|
const unsigned char * restrict encptr);
|
|
|
|
|
|
(<a href='#F.10.12'>F.10.12</a>) Total order functions
|
|
|
|
int totalorderfN(const _FloatN *x, const _FloatN *y);
|
|
int totalorderfNx(const _FloatNx *x, const _FloatNx *y);
|
|
int totalorderdN(const _DecimalN *x, const _DecimalN *y);
|
|
int totalorderdNx(const _DecimalNx *x, const _DecimalNx *y);
|
|
int totalordermagfN(const _FloatN *x, const _FloatN *y);
|
|
int totalordermagfNx(const _FloatNx *x, const _FloatNx *y);
|
|
int totalordermagdN(const _DecimalN *x, const _DecimalN *y);
|
|
int totalordermagdNx(const _DecimalNx *x, const _DecimalNx *y);
|
|
|
|
(<a href='#F.10.13'>F.10.13</a>) Payload functions
|
|
_FloatN getpayloadfN(const _FloatN *x);
|
|
_FloatNx getpayloadfNx(const _FloatNx *x);
|
|
_DecimalN getpayloaddN(const _DecimalN *x);
|
|
_DecimalNx getpayloaddNx(const _DecimalNx *x);
|
|
|
|
int setpayloadfN(_FloatN *res, _FloatN pl);
|
|
int setpayloadfNx(_FloatNx *res, _FloatNx pl);
|
|
int setpayloaddN(_DecimalN *res, _DecimalN pl);
|
|
int setpayloaddNx(_DecimalNx *res, _DecimalNx pl);
|
|
|
|
int setpayloadsigfN(_FloatN *res, _FloatN pl);
|
|
int setpayloadsigfNx(_FloatNx *res, _FloatNx pl);
|
|
int setpayloadsigdN(_DecimalN *res, _DecimalN pl);
|
|
int setpayloadsigdNx(_DecimalNx *res, _DecimalNx pl);
|
|
|
|
|
|
</pre>
|
|
<a name='H.11.2p2'></a>
|
|
<pre>2 The specification of the frexp functions (<a href='#7.12.6.7'>7.12.6.7</a>) applies to the functions for binary floating types
|
|
like those for standard floating types: the exponent is an integral power of 2 and, when applicable,
|
|
value equals x × 2*exp .
|
|
</pre>
|
|
<a name='H.11.2p3'></a>
|
|
<pre>3 The specification of the ldexp functions (<a href='#7.12.6.9'>7.12.6.9</a>) applies to the functions for binary floating types
|
|
like those for standard floating types: they return x × 2exp .
|
|
</pre>
|
|
<a name='H.11.2p4'></a>
|
|
<pre>4 The specification of the logb functions (<a href='#7.12.6.17'>7.12.6.17</a>) applies to binary floating types, with b = 2.
|
|
</pre>
|
|
<a name='H.11.2p5'></a>
|
|
<pre>5 The specification of the scalbn and scalbln functions (<a href='#7.12.6.19'>7.12.6.19</a>) applies to binary floating types,
|
|
with b = 2.
|
|
|
|
</pre>
|
|
<a name='H.11.3'></a>
|
|
<hr>
|
|
<h3>H.11.3 [Encoding conversion functions]</h3>
|
|
<a name='H.11.3p1'></a>
|
|
<pre>1 This subclause introduces <math.h> functions that, together with the numerical conversion functions
|
|
for encodings in <a href='#H.12'>H.12</a>, support the non-arithmetic interchange formats specified by IEC 60559.
|
|
Support for these formats is an optional feature of this annex. Implementations that do not support
|
|
non-arithmetic interchange formats need not declare the functions in this subclause.
|
|
</pre>
|
|
<a name='H.11.3p2'></a>
|
|
<pre>2 Non-arithmetic interchange formats are not associated with floating types. Arrays of element
|
|
type unsigned char are used as parameters for conversion functions, to represent encodings in
|
|
interchange formats that might be non-arithmetic formats.
|
|
|
|
</pre>
|
|
<a name='H.11.3.1'></a>
|
|
<hr>
|
|
<h3>H.11.3.1 [Encode and decode functions]</h3>
|
|
<a name='H.11.3.1p1'></a>
|
|
<pre>1 This subclause specifies functions to map representations in binary floating types to and from
|
|
encodings in unsigned char arrays.
|
|
|
|
</pre>
|
|
<a name='H.11.3.1.1'></a>
|
|
<hr>
|
|
<h3>H.11.3.1.1 [The encodefN functions]</h3>
|
|
<a name='H.11.3.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <math.h>
|
|
|
|
void encodefN(unsigned char encptr[restrict static N/8],
|
|
const _FloatN * restrict xptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.11.3.1.1p2'></a>
|
|
<pre>2 The encodefN functions convert *xptr into an IEC 60559 binaryN encoding and store the resulting
|
|
encoding as an N /8 element array, with 8 bits per array element, in the object pointed to by encptr.
|
|
The order of bytes in the array is implementation-defined. These functions preserve the value of
|
|
*xptr and raise no floating-point exceptions. If *xptr is non-canonical, these functions may or may
|
|
not produce a canonical encoding.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.11.3.1.1p3'></a>
|
|
<pre>3 The encodefN functions return no value.
|
|
|
|
</pre>
|
|
<a name='H.11.3.1.2'></a>
|
|
<hr>
|
|
<h3>H.11.3.1.2 [The decodefN functions]</h3>
|
|
<a name='H.11.3.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <math.h>
|
|
|
|
void decodefN(_FloatN * restrict xptr,
|
|
const unsigned char encptr[restrict static N/8]);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.11.3.1.2p2'></a>
|
|
<pre>2 The decodefN functions interpret the N /8 element array pointed to by encptr as an IEC 60559
|
|
binaryN encoding, with 8 bits per array element. The order of bytes in the array is implementation-
|
|
defined. These functions convert the given encoding into a representation in the type _FloatN, and
|
|
store the result in the object pointed to by xptr. These functions preserve the encoded value and
|
|
raise no floating-point exceptions. If the encoding is non-canonical, these functions may or may not
|
|
produce a canonical representation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.11.3.1.2p3'></a>
|
|
<pre>3 The decodefN functions return no value.
|
|
</pre>
|
|
<a name='H.11.3.1.2p4'></a>
|
|
<pre>4 See EXAMPLE in <a href='#H.11.3.2.1'>H.11.3.2.1</a>.
|
|
|
|
</pre>
|
|
<a name='H.11.3.2'></a>
|
|
<hr>
|
|
<h3>H.11.3.2 [Encoding-to-encoding conversion functions]</h3>
|
|
<a name='H.11.3.2p1'></a>
|
|
<pre>1 An implementation shall declare an fMencfN function for each M and N equal to the width of
|
|
a supported IEC 60559 arithmetic or non-arithmetic binary interchange format, M ̸= N . An
|
|
implementation shall provide both dMencdecdN and dMencbindNfunctions for each M and N equal
|
|
to the width of a supported IEC 60559 arithmetic or non-arithmetic decimal interchange format,
|
|
M ̸= N .
|
|
|
|
</pre>
|
|
<a name='H.11.3.2.1'></a>
|
|
<hr>
|
|
<h3>H.11.3.2.1 [The fMencfN functions]</h3>
|
|
<a name='H.11.3.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <math.h>
|
|
|
|
void fMencfN(unsigned char encMptr[restrict static M/8],
|
|
const unsigned char encNptr[restrict static N/8]);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.11.3.2.1p2'></a>
|
|
<pre>2 The fMencfN functions convert between IEC 60559 binary interchange formats. These functions
|
|
interpret the N /8 element array pointed to by encNptr as an encoding of width N bits. They
|
|
convert the encoding to an encoding of width M bits and store the resulting encoding as an M /8
|
|
element array in the object pointed to by encMptr. The conversion rounds and raises floating-point
|
|
exceptions as specified in IEC 60559. The order of bytes in the arrays is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.11.3.2.1p3'></a>
|
|
<pre>3 These functions return no value.
|
|
</pre>
|
|
<a name='H.11.3.2.1p4'></a>
|
|
<pre>4 EXAMPLE If the IEC 60559 binary16 format is supported as a non-arithmetic format, data in binary16 format can be
|
|
converted to type float as follows:
|
|
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <math.h>
|
|
unsigned char b16[2]; // for input binary16 datum
|
|
float f; // for result
|
|
unsigned char b32[4];
|
|
_Float32 f32;
|
|
|
|
// store input binary16 datum in array b16
|
|
...
|
|
f32encf16(b32, b16);
|
|
decodef32(&f32, b32);
|
|
f = f32;
|
|
...
|
|
|
|
|
|
</pre>
|
|
<a name='H.11.3.2.2'></a>
|
|
<hr>
|
|
<h3>H.11.3.2.2 [The dMencdecdN and dMencbindN functions]</h3>
|
|
<a name='H.11.3.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <math.h>
|
|
|
|
void dMencdecdN(unsigned char encMptr[restrict static M/8],
|
|
const unsigned char encNptr[restrict static N/8]);
|
|
void dMencbindN(unsigned char encMptr[restrict static M/8],
|
|
const unsigned char encNptr[restrict static N/8]);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.11.3.2.2p2'></a>
|
|
<pre>2 The dMencdecdN and dMencbindN functions convert between IEC 60559 decimal interchange formats
|
|
that use the same encoding scheme. The dMencdecdN functions convert between formats using the
|
|
encoding scheme based on decimal encoding of the significand. The dMencbindN functions convert
|
|
between formats using the encoding scheme based on binary encoding of the significand. These
|
|
functions interpret the N /8 element array pointed to by encNptr as an encoding of width N bits.
|
|
They convert the encoding to an encoding of width M bits and store the resulting encoding as an M /8
|
|
element array in the object pointed to by encMptr. The conversion rounds and raises floating-point
|
|
exceptions as specified in IEC 60559. The order of bytes in the arrays is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.11.3.2.2p3'></a>
|
|
<pre>3 These functions return no value.
|
|
|
|
</pre>
|
|
<a name='H.12'></a>
|
|
<hr>
|
|
<h3>H.12 [Numeric conversion functions <stdlib.h>]</h3>
|
|
<a name='H.12p1'></a>
|
|
<pre>1 This clause expands the specification of numeric conversion functions in <stdlib.h> (<a href='#7.24.1'>7.24.1</a>) to also
|
|
include conversions of strings from and to interchange and extended floating types. The conversions
|
|
from floating are provided by functions analogous to the strfromd function. The conversions to
|
|
floating are provided by functions analogous to the strtod function.
|
|
</pre>
|
|
<a name='H.12p2'></a>
|
|
<pre>2 This clause also specifies functions to convert strings from and to IEC 60559 interchange format
|
|
encodings.
|
|
</pre>
|
|
<a name='H.12p3'></a>
|
|
<pre>3 For each interchange or extended floating type that the implementation provides, <stdlib.h> shall
|
|
declare the associated functions specified below in <a href='#H.12.1'>H.12.1</a> and <a href='#H.12.2'>H.12.2</a> (see <a href='#H.8'>H.8</a>). Conversely, for each
|
|
such type that the implementation does not provide, <stdlib.h> shall not declare the associated
|
|
functions.
|
|
</pre>
|
|
<a name='H.12p4'></a>
|
|
<pre>4 For each IEC 60559 arithmetic or non-arithmetic format that the implementation supports,
|
|
<stdlib.h> shall declare the associated functions specified below in <a href='#H.12.3'>H.12.3</a> and <a href='#H.12.4'>H.12.4</a> (see <a href='#H.8'>H.8</a>).
|
|
Conversely, for each such format that the implementation does not provide, <stdlib.h> shall not
|
|
declare the associated functions.
|
|
|
|
</pre>
|
|
<a name='H.12.1'></a>
|
|
<hr>
|
|
<h3>H.12.1 [String from floating]</h3>
|
|
<a name='H.12.1p1'></a>
|
|
<pre>1 This subclause expands <a href='#7.24.1.3'>7.24.1.3</a> and <a href='#7.24.1.4'>7.24.1.4</a> to also include functions for the interchange and
|
|
extended floating types. It adds to the synopsis in <a href='#7.24.1.3'>7.24.1.3</a> the prototypes
|
|
int strfromfN(char * restrict s, size_t n,
|
|
const char * restrict format, _FloatN fp);
|
|
int strfromfNx(char * restrict s, size_t n,
|
|
const char * restrict format, _FloatNx fp);
|
|
|
|
|
|
It encompasses the prototypes in <a href='#7.24.1.4'>7.24.1.4</a> by replacing them with
|
|
|
|
int strfromdN(char * restrict s, size_t n,
|
|
const char * restrict format, _DecimalN fp);
|
|
int strfromdNx(char * restrict s, size_t n,
|
|
const char * restrict format, _DecimalNx fp);
|
|
|
|
|
|
</pre>
|
|
<a name='H.12.1p2'></a>
|
|
<pre>2 The descriptions and returns for the added functions are analogous to the ones in <a href='#7.24.1.3'>7.24.1.3</a>
|
|
and <a href='#7.24.1.4'>7.24.1.4</a>.
|
|
|
|
</pre>
|
|
<a name='H.12.2'></a>
|
|
<hr>
|
|
<h3>H.12.2 [String to floating]</h3>
|
|
<a name='H.12.2p1'></a>
|
|
<pre>1 This subclause expands <a href='#7.24.1.5'>7.24.1.5</a> and <a href='#7.24.1.6'>7.24.1.6</a> to also include functions for the interchange and
|
|
extended floating types. It adds to the synopsis in <a href='#7.24.1.5'>7.24.1.5</a> the prototypes
|
|
_FloatN strtofN(const char * restrict nptr,
|
|
char ** restrict endptr);
|
|
_FloatNx strtofNx(const char * restrict nptr,
|
|
char ** restrict endptr);
|
|
|
|
|
|
It encompasses the prototypes in <a href='#7.24.1.6'>7.24.1.6</a> by replacing them with
|
|
_DecimalN strtodN(const char * restrict nptr,
|
|
char ** restrict endptr);
|
|
_DecimalNx strtodNx(const char * restrict nptr,
|
|
char ** restrict endptr);
|
|
|
|
|
|
</pre>
|
|
<a name='H.12.2p2'></a>
|
|
<pre>2 The descriptions and returns for the added functions are analogous to the ones in <a href='#7.24.1.5'>7.24.1.5</a> and <a href='#7.24.1.6'>7.24.1.6</a>.
|
|
</pre>
|
|
<a name='H.12.2p3'></a>
|
|
<pre>3 For implementations that support both binary and decimal floating types and a (binary or dec-
|
|
imal) non-arithmetic interchange format, the strtodN and strtodNx functions (and hence the
|
|
strtoencdecdN and strtoencbindN functions in <a href='#H.12.4.2'>H.12.4.2</a>) shall accept subject sequences that have
|
|
the form of hexadecimal floating numbers and otherwise meet the requirements of subject sequences
|
|
(<a href='#7.24.1.6'>7.24.1.6</a>). Then the decimal results shall be correctly rounded if the subject sequence has at most
|
|
M significant hexadecimal digits, where M ≥ ⌈(P − 1)/4⌉ + 1 is implementation-defined, and P is
|
|
the maximum precision of the supported binary floating types and binary non-arithmetic formats.
|
|
If all subject sequences of hexadecimal form are correctly rounded, M may be regarded as infinite.
|
|
If the subject sequence has more than M significant hexadecimal digits, the implementation may
|
|
first round to M significant hexadecimal digits according to the applicable rounding direction mode,
|
|
signaling exceptions as though converting from a wider format, then correctly round the result of
|
|
the shortened hexadecimal input to the result type.
|
|
</pre>
|
|
<a name='H.12.2p4'></a>
|
|
<pre>4 EXAMPLE If the IEC 60559 binary128 format is supported as a non-arithmetic format, data in binary128 format can be
|
|
converted to type _Decimal128 as follows:
|
|
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <stdlib.h>
|
|
#define MAXSIZE 41 // > intermediate hex string length
|
|
unsigned char b128[16]; // for input binary128 datum
|
|
_Decimal128 d128; // for result
|
|
char s[MAXSIZE];
|
|
// store input binary128 datum in array b128
|
|
...
|
|
strfromencf128(s, MAXSIZE, "%a", b128);
|
|
d128 = strtod128(s, NULL);
|
|
...
|
|
|
|
|
|
Use of "%a" for formatting assures an exact conversion of the value in binary format to character sequence. The value of that
|
|
character sequence will be correctly rounded to _Decimal128 , as specified above in this subclause. The array s for the output
|
|
of strfromencf128 need have no greater size than 41, which is the maximum length of strings of the form
|
|
[−]0xh.h . . . hp ± d
|
|
where there are up to 29 hexadecimal digits h and d has 5 digits plus 1 for the null character.
|
|
|
|
</pre>
|
|
<a name='H.12.3'></a>
|
|
<hr>
|
|
<h3>H.12.3 [String from encoding]</h3>
|
|
<a name='H.12.3p1'></a>
|
|
<pre>1 An implementation shall declare the strfromencfN function for each N equal to the width of a
|
|
supported IEC 60559 arithmetic or non-arithmetic binary interchange format. An implementation
|
|
shall declare both the strfromencdecdN and strfromencbindN functions for each N equal to the
|
|
width of a supported IEC 60559 arithmetic or non-arithmetic decimal interchange format.
|
|
|
|
</pre>
|
|
<a name='H.12.3.1'></a>
|
|
<hr>
|
|
<h3>H.12.3.1 [The strfromencf N functions]</h3>
|
|
<a name='H.12.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <stdlib.h>
|
|
|
|
int strfromencfN(char * restrict s, size_t n, const char * restrict format,
|
|
const unsigned char encptr[restrict static N/8]);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.12.3.1p2'></a>
|
|
<pre>2 The strfromencfN functions are similar to the strfromfN functions, except the input is the value of
|
|
the N /8 element array pointed to by encptr, interpreted as an IEC 60559 binaryN encoding. The
|
|
order of bytes in the arrays is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.12.3.1p3'></a>
|
|
<pre>3 The strfromencfN functions return the same values as corresponding strfromfN functions.
|
|
|
|
</pre>
|
|
<a name='H.12.3.2'></a>
|
|
<hr>
|
|
<h3>H.12.3.2 [The strfromencdecdN and strfromencbindN functions]</h3>
|
|
<a name='H.12.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <stdlib.h>
|
|
|
|
int strfromencdecdN(char * restrict s, size_t n, const char * restrict format,
|
|
const unsigned char encptr[restrict static N/8]);
|
|
int strfromencbindN(char * restrict s, size_t n, const char * restrict format,
|
|
const unsigned char encptr[restrict static N/8]);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.12.3.2p2'></a>
|
|
<pre>2 The strfromencdecdN functions are similar to the strfromdN functions except the input is the value
|
|
of the N /8 element array pointed to by encptr, interpreted as an IEC 60559 decimalN encoding in
|
|
the coding scheme based on decimal encoding of the significand. The strfromencbindN functions
|
|
are similar to the strfromdN functions except the input is the value of the N /8 element array pointed
|
|
to by encptr, interpreted as an IEC 60559 decimalN encoding in the coding scheme based on binary
|
|
encoding of the significand. The order of bytes in the arrays is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.12.3.2p3'></a>
|
|
<pre>3 The strfromencdecdN and strfromencbindN functions return the same values as corresponding
|
|
strfromdN functions.
|
|
|
|
</pre>
|
|
<a name='H.12.4'></a>
|
|
<hr>
|
|
<h3>H.12.4 [String to encoding]</h3>
|
|
<a name='H.12.4p1'></a>
|
|
<pre>1 An implementation shall declare the strtoencfN function for each N equal to the width of a
|
|
supported IEC 60559 arithmetic or non-arithmetic binary interchange format. An implementation
|
|
shall declare both the strtoencdecdN and strtoencbindN functions for each N equal to the width
|
|
of a supported IEC 60559 arithmetic or non-arithmetic decimal interchange format.
|
|
|
|
</pre>
|
|
<a name='H.12.4.1'></a>
|
|
<hr>
|
|
<h3>H.12.4.1 [The strtoencfN functions]</h3>
|
|
<a name='H.12.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <stdlib.h>
|
|
|
|
void strtoencfN(unsigned char encptr[restrict static N/8],
|
|
const char * restrict nptr, char ** restrict endptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.12.4.1p2'></a>
|
|
<pre>2 The strtoencfN functions are similar to the strtofN functions, except they store an IEC 60559
|
|
encoding of the result as an N /8 element array in the object pointed to by encptr. The order of
|
|
bytes in the arrays is implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.12.4.1p3'></a>
|
|
<pre>3 These functions return no value.
|
|
|
|
</pre>
|
|
<a name='H.12.4.2'></a>
|
|
<hr>
|
|
<h3>H.12.4.2 [The strtoencdecdN and strtoencbindN functions]</h3>
|
|
<a name='H.12.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
#include <stdlib.h>
|
|
|
|
void strtoencdecdN(unsigned char encptr[restrict static N/8],
|
|
const char * restrict nptr, char ** restrict endptr);
|
|
void strtoencbindN(unsigned char encptr[restrict static N/8],
|
|
const char * restrict nptr, char ** restrict endptr);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='H.12.4.2p2'></a>
|
|
<pre>2 The strtoencdecdN and strtoencbindNfunctions are similar to the strtodN functions, except
|
|
they store an IEC 60559 encoding of the result as an N /8 element array in the object pointed to
|
|
by encptr. The strtoencdecdN functions produce an encoding in the encoding scheme based on
|
|
decimal encoding of the significand. The strtoencbindN functions produce an encoding in the
|
|
encoding scheme based on binary encoding of the significand. The order of bytes in the arrays is
|
|
implementation-defined.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='H.12.4.2p3'></a>
|
|
<pre>3 These functions return no value.
|
|
|
|
</pre>
|
|
<a name='H.13'></a>
|
|
<hr>
|
|
<h3>H.13 [Type-generic macros <tgmath.h>]</h3>
|
|
<a name='H.13p1'></a>
|
|
<pre>1 This clause enhances the specification of type-generic macros in <tgmath.h> (<a href='#7.27'>7.27</a>) to apply to
|
|
interchange and extended floating types, as well as standard floating types.
|
|
</pre>
|
|
<a name='H.13p2'></a>
|
|
<pre>2 If arguments for generic parameters of a type-generic macro are such that some argument has
|
|
a corresponding real type that is a standard floating type or a binary floating type and another
|
|
argument is of decimal floating type, the behavior is undefined.
|
|
</pre>
|
|
<a name='H.13p3'></a>
|
|
<pre>3 The treatment of arguments of integer type in <a href='#7.27'>7.27</a> is expanded to cases where another argument
|
|
has extended type. Arguments of integer type are regarded as having type:
|
|
|
|
— _Decimal64x , if any argument has a decimal extended type; otherwise
|
|
— _Float32x , if any argument has a binary extended type; otherwise
|
|
— _Decimal64 , if any argument has decimal type; otherwise
|
|
— double
|
|
</pre>
|
|
<a name='H.13p4'></a>
|
|
<pre>4 Use of the macros carg, cimag, conj, cproj, or creal with any argument of standard floating type,
|
|
binary floating type, complex type, or imaginary type invokes a complex function. Use of the macro
|
|
with an argument of a decimal floating type results in undefined behavior.
|
|
</pre>
|
|
<a name='H.13p5'></a>
|
|
<pre>5 The functions that round results to a narrower type have type-generic macros whose names are
|
|
obtained by omitting any suffix from the function names. Thus, the macros with f or d prefix are (as
|
|
in <a href='#7.27'>7.27</a>):
|
|
|
|
fadd fmul ffma
|
|
dadd dmul dfma
|
|
fsub fdiv fsqrt
|
|
dsub ddiv dsqrt
|
|
|
|
|
|
and the macros with fM, fMx, dM, or dMx prefix are:
|
|
|
|
fMadd fMxmul dMfma
|
|
fMsub fMxdiv dMsqrt
|
|
fMmul fMxfma dMxadd
|
|
fMdiv fMxsqrt dMxsub
|
|
fMfma dMadd dMxmul
|
|
fMsqrt dMsub dMxdiv
|
|
fMxadd dMmul dMxfma
|
|
fMxsub dMdiv dMxsqrt
|
|
|
|
|
|
All arguments are generic. If any argument is not real, use of the macro results in undefined behavior.
|
|
The following specification uses the notation type1 ⊆ type2 to mean the values of type1 are a subset
|
|
of (or the same as) the values of type2. The generic parameter type T for the function invoked by the
|
|
macro is determined as follows:
|
|
|
|
— First, obtain a preliminary type P for the generic parameters: if all arguments are of integer
|
|
type, then P is double if the macro prefix is f, d, fN, or fNx and P is _Decimal64 if the macro
|
|
prefix is dN or dNx; otherwise (if some argument is not of integer type), apply the rules (for
|
|
determining the corresponding real type of the generic parameters) in <a href='#7.27'>7.27</a> for macros that
|
|
do not round result to narrower type, using the usual arithmetic conversion rules in <a href='#H.4.2'>H.4.2</a>, to
|
|
obtain P .
|
|
|
|
— If there exists a corresponding function whose generic parameters have type P , then T is P .
|
|
|
|
— Otherwise, T is determined from P and the macro prefix as follows:
|
|
|
|
• For prefix f: if P is a standard or binary floating type, then T is the first standard floating
|
|
type of either double or long double, such that P ⊆ T , if such a type T exists. Otherwise
|
|
(if no such type T exists or P is a decimal floating type), the behavior is undefined.
|
|
• For prefix d: if P is a standard or binary floating type, then T is long double if P ⊆
|
|
long double. Otherwise (if P ⊆ long double is false or P is a decimal floating type),
|
|
the behavior is undefined.
|
|
• For prefix fM: if P is a standard or binary floating type, then T is _FloatN for minimum
|
|
N > M such that P ⊆ T , if such a type T is supported; otherwise T is _FloatNx for
|
|
minimum N ≥ M such that P ⊆ T , if such a type T is supported. Otherwise (if no
|
|
such _FloatN or _FloatNx is supported or P is a decimal floating type), the behavior is
|
|
undefined.
|
|
• For prefix fMx: if P is a standard or binary floating type, then T is _FloatNx for minimum
|
|
N > M such that P ⊆ T , if such a type T is supported; otherwise T is _FloatN for
|
|
minimum N > M such that P ⊆ T , if such a type T is supported. Otherwise (if no
|
|
such _FloatNx or _FloatN is supported or P is a decimal floating type), the behavior is
|
|
undefined.
|
|
• For prefix dM: if P is a decimal floating type, then T is _DecimalN for minimum N > M
|
|
such that P ⊆ T , if such a type T is supported; otherwise T is _DecimalNx for minimum
|
|
N ≥ M such that P ⊆ T . Otherwise (P is a standard or binary floating type), the behavior
|
|
is undefined.
|
|
• For prefix dMx: if P is a decimal floating type, then T is _DecimalNx for minimum N > M
|
|
such that P ⊆ T , if such a type T is supported; otherwise T is _DecimalN for minimum
|
|
N > M such that P ⊆ T , if such a type T is supported. Otherwise (P is a standard or
|
|
binary floating type), the behavior is undefined.
|
|
|
|
</pre>
|
|
<a name='H.13p6'></a>
|
|
<pre>6 EXAMPLE With the declarations
|
|
|
|
#define __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
|
|
#include <tgmath.h>
|
|
|
|
int n;
|
|
double d;
|
|
long double ld;
|
|
double complex dc;
|
|
_Float32x f32x;
|
|
_Float64 f64;
|
|
_Float64x f64x;
|
|
_Float128 f128;
|
|
_Float64x complex f64xc;
|
|
|
|
|
|
functions invoked by use of type-generic macros are shown in the following table, where type1 ⊆ type2 means the values of
|
|
type1 are a subset of (or the same as) the values of type2, and type1 ⊂ type2 means the values of type1 are a strict subset of
|
|
the values of type2:
|
|
macro use invokes
|
|
|
|
cos(f64xc) ccosf64x
|
|
|
|
pow(dc, f128) cpowf128
|
|
|
|
pow(f64, d) powf64
|
|
|
|
pow(d, f32x) pow, the function, if _Float32x ⊆ double, else powf32x if double ⊂
|
|
_Float32x , else undefined
|
|
|
|
pow(f32, n) pow, the function
|
|
|
|
pow(f32x, n) pow32x
|
|
|
|
Macros that round the result to a narrower type. . .
|
|
macro use invokes
|
|
|
|
fsub(d, ld) fsubl
|
|
|
|
dsub(d, f32) dsubl
|
|
undefined
|
|
fmul(dc, d)
|
|
|
|
ddiv(ld, f128) ddivl if _Float128 ⊆ long double, else undefined
|
|
|
|
f32add(f64x, f64) f32addf64x
|
|
|
|
f32xsqrt(n) f32xsqrtf64
|
|
|
|
f32mul(f128, f32x) f32mulf128 if _Float32x ⊆ _Float128 , else f32mulf32x if _Float128
|
|
⊂ _Float32x , else undefined
|
|
|
|
f32fma(f32x, n, f32x) f32fmaf32x
|
|
|
|
f32add(f32, f32) f32addf64
|
|
|
|
f32xsqrt(f32) f32xsqrtf64x, as declaration above shows _Float64x is supported
|
|
|
|
f64div(f32x, f32x) f64divf128 if _Float32x ⊆ _Float128 , else f64divf64x
|
|
|
|
|
|
</pre>
|
|
<a name='I.'></a>
|
|
<hr>
|
|
<h3>I. [Annex I (informative) Common warnings]</h3>
|
|
<a name='I.p1'></a>
|
|
<pre>1 An implementation may generate warnings in many situations, none of which are specified as part
|
|
of this document. The following are a few of the more common situations.
|
|
</pre>
|
|
<a name='I.p2'></a>
|
|
<pre>2 — A new struct or union type appears in a function prototype (<a href='#6.2.1'>6.2.1</a>, <a href='#6.7.2.3'>6.7.2.3</a>).
|
|
— A block with initialization of an object that has automatic storage duration is jumped into
|
|
(<a href='#6.2.4'>6.2.4</a>).
|
|
— An implicit narrowing conversion is encountered, such as the assignment of a long int or a
|
|
double to an int, or a pointer to void to a pointer to any type other than a character type (<a href='#6.3'>6.3</a>).
|
|
|
|
— A hexadecimal floating constant cannot be represented exactly in its evaluation format (<a href='#6.4.4.2'>6.4.4.2</a>).
|
|
— An integer character constant includes more than one character or a wide character constant
|
|
includes more than one multibyte character (<a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The characters /* are found in a comment (<a href='#6.4.7'>6.4.7</a>).
|
|
— An "unordered" binary operator (not comma, &&, or ||) contains a side effect to an lvalue in
|
|
one operand, and a side effect to, or an access to the value of, the identical lvalue in the other
|
|
operand (<a href='#6.5'>6.5</a>).
|
|
— An object is defined but not used (<a href='#6.7'>6.7</a>).
|
|
|
|
— A value is given to an object of an enumerated type other than by assignment of an enumeration
|
|
constant that is a member of that type, or an enumeration object that has the same type, or the
|
|
value of a function that returns the same enumerated type (<a href='#6.7.2.2'>6.7.2.2</a>).
|
|
— An aggregate has a partly bracketed initialization (<a href='#6.7.8'>6.7.8</a>).
|
|
|
|
— A statement cannot be reached (<a href='#6.8'>6.8</a>).
|
|
— A statement with no apparent effect is encountered (<a href='#6.8'>6.8</a>).
|
|
— A constant expression is used as the controlling expression of a selection statement (<a href='#6.8.4'>6.8.4</a>).
|
|
— An incorrectly formed preprocessing group is encountered while skipping a preprocessing
|
|
group (<a href='#6.10.1'>6.10.1</a>).
|
|
— An unrecognized #pragma directive is encountered (<a href='#6.10.7'>6.10.7</a>).
|
|
|
|
</pre>
|
|
<a name='J.'></a>
|
|
<hr>
|
|
<h3>J. [Annex J (informative) Portability issues]</h3>
|
|
<a name='J.p1'></a>
|
|
<pre>1 This annex collects some information about portability that appears in this document.
|
|
|
|
</pre>
|
|
<a name='J.1'></a>
|
|
<hr>
|
|
<h3>J.1 [Unspecified behavior]</h3>
|
|
<a name='J.1p1'></a>
|
|
<pre>1 The following are unspecified:
|
|
|
|
— The manner and timing of static initialization (<a href='#5.1.2'>5.1.2</a>).
|
|
|
|
— The termination status returned to the hosted environment if the return type of main is not
|
|
compatible with int (<a href='#5.1.2.2.3'>5.1.2.2.3</a>).
|
|
|
|
— The values of objects that are neither lock-free atomic objects nor of type
|
|
volatile sig_atomic_t and the state of the floating-point environment, when the
|
|
processing of the abstract machine is interrupted by receipt of a signal (<a href='#5.1.2.3'>5.1.2.3</a>).
|
|
|
|
— The behavior of the display device if a printing character is written when the active position is
|
|
at the final position of a line (<a href='#5.2.2'>5.2.2</a>).
|
|
|
|
— The behavior of the display device if a backspace character is written when the active position
|
|
is at the initial position of a line (<a href='#5.2.2'>5.2.2</a>).
|
|
|
|
— The behavior of the display device if a horizontal tab character is written when the active
|
|
position is at or past the last defined horizontal tabulation position (<a href='#5.2.2'>5.2.2</a>).
|
|
|
|
— The behavior of the display device if a vertical tab character is written when the active position
|
|
is at or past the last defined vertical tabulation position (<a href='#5.2.2'>5.2.2</a>).
|
|
|
|
— How an extended source character that does not correspond to a universal character name
|
|
counts toward the significant initial characters in an external identifier (<a href='#5.2.4.1'>5.2.4.1</a>).
|
|
|
|
— Many aspects of the representations of types (<a href='#6.2.6'>6.2.6</a>).
|
|
|
|
— The value of padding bytes when storing values in structures or unions (<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
|
|
— The values of bytes that correspond to union members other than the one last stored into
|
|
(<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
|
|
— The representation used when storing a value in an object that has more than one object
|
|
representation for that value (<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
|
|
— The values of any padding bits in integer representations (<a href='#6.2.6.2'>6.2.6.2</a>).
|
|
|
|
— Whether two string literals result in distinct arrays (<a href='#6.4.5'>6.4.5</a>).
|
|
|
|
— The order in which subexpressions are evaluated and the order in which side effects take place,
|
|
except as specified for the function-call () , &&, ||, ?:, and comma operators (<a href='#6.5'>6.5</a>).
|
|
|
|
— The order in which the function designator, arguments, and subexpressions within the argu-
|
|
ments are evaluated in a function call (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
|
|
— The order of side effects among compound literal initialization list expressions (<a href='#6.5.2.5'>6.5.2.5</a>).
|
|
|
|
— The order in which the operands of an assignment operator are evaluated (<a href='#6.5.16'>6.5.16</a>).
|
|
|
|
— The alignment of the addressable storage unit allocated to hold a bit-field (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
— Whether a call to an inline function uses the inline definition or the external definition of the
|
|
function (<a href='#6.7.4'>6.7.4</a>).
|
|
— Whether or not a size expression is evaluated when it is part of the operand of a sizeof
|
|
operator and changing the value of the size expression would not affect the result of the
|
|
operator (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
— The order in which any side effects occur among the initialization list expressions in an
|
|
initializer (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
— The layout of storage for function parameters (<a href='#6.9.1'>6.9.1</a>).
|
|
|
|
— When a fully expanded macro replacement list contains a function-like macro name as its
|
|
last preprocessing token and the next preprocessing token from the source file is a ( , and
|
|
the fully expanded replacement of that macro ends with the name of the first macro and the
|
|
next preprocessing token from the source file is again a ( , whether that is considered a nested
|
|
replacement (<a href='#6.10.4'>6.10.4</a>).
|
|
|
|
— The order in which # and ## operations are evaluated during macro substitution (<a href='#6.10.4.2'>6.10.4.2</a>,
|
|
and <a href='#6.10.4.3'>6.10.4.3</a>).
|
|
|
|
— The line number of a preprocessing token, in particular __LINE__ , that spans multiple physical
|
|
lines (<a href='#6.10.5'>6.10.5</a>).
|
|
|
|
— The line number of a preprocessing directive that spans multiple physical lines (<a href='#6.10.5'>6.10.5</a>).
|
|
|
|
— The line number of a macro invocation that spans multiple physical or logical lines (<a href='#6.10.5'>6.10.5</a>).
|
|
|
|
— The line number following a directive of the form #line __LINE__ new-line (<a href='#6.10.5'>6.10.5</a>).
|
|
|
|
— The state of the floating-point status flags when execution passes from a part of the program
|
|
translated with FENV_ACCESS "off" to a part translated with FENV_ACCESS "on" (<a href='#7.6.1'>7.6.1</a>).
|
|
|
|
— The order in which feraiseexcept raises floating-point exceptions, except as stated in <a href='#F.8.6'>F.8.6</a>
|
|
(<a href='#7.6.4.3'>7.6.4.3</a>).
|
|
|
|
— Whether math_errhandling is a macro or an identifier with external linkage (<a href='#7.12'>7.12</a>).
|
|
|
|
— The results of the frexp functions when the specified value is not a floating-point number
|
|
(<a href='#7.12.6.7'>7.12.6.7</a>).
|
|
|
|
— The numeric result of the ilogb functions when the correct value is outside the range of the
|
|
return type (<a href='#7.12.6.8'>7.12.6.8</a>, <a href='#F.10.3.8'>F.10.3.8</a>).
|
|
|
|
— The result of rounding when the value is out of range (<a href='#7.12.9.5'>7.12.9.5</a>, <a href='#7.12.9.7'>7.12.9.7</a>, <a href='#F.10.6.5'>F.10.6.5</a>).
|
|
|
|
— The value stored by the remquo functions in the object pointed to by quo when y is zero
|
|
(<a href='#7.12.10.3'>7.12.10.3</a>).
|
|
|
|
— Whether a comparison macro argument that is represented in a format wider than its semantic
|
|
type is converted to the semantic type (<a href='#7.12.17'>7.12.17</a>).
|
|
|
|
— Whether setjmp is a macro or an identifier with external linkage (<a href='#7.13'>7.13</a>).
|
|
|
|
— Whether va_copy and va_end are macros or identifiers with external linkage (<a href='#7.16.1'>7.16.1</a>).
|
|
|
|
— The hexadecimal digit before the decimal point when a non-normalized floating-point number
|
|
is printed with an a or A conversion specifier (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— The value of the file position indicator after a successful call to the ungetc function for a text
|
|
stream, or the ungetwc function for any stream, until all pushed-back characters are read or
|
|
discarded (<a href='#7.23.7.10'>7.23.7.10</a>, <a href='#7.31.3.10'>7.31.3.10</a>).
|
|
|
|
— The details of the value stored by the fgetpos function (<a href='#7.23.9.1'>7.23.9.1</a>).
|
|
|
|
— The details of the value returned by the ftell function for a text stream (<a href='#7.23.9.4'>7.23.9.4</a>).
|
|
— Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold functions convert a
|
|
minus-signed sequence to a negative number directly or by negating the value resulting from
|
|
converting the corresponding unsigned sequence (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.31.4.1.2'>7.31.4.1.2</a>).
|
|
|
|
— The order and contiguity of storage allocated by successive calls to the calloc, malloc,
|
|
realloc, and aligned_alloc functions (<a href='#7.24.3'>7.24.3</a>).
|
|
|
|
— The amount of storage allocated by a successful call to the calloc, malloc, realloc, or
|
|
aligned_alloc function when 0 bytes was requested (<a href='#7.24.3'>7.24.3</a>).
|
|
|
|
— Whether a call to the atexit function that does not happen before the exit function is called
|
|
will succeed (<a href='#7.24.4.2'>7.24.4.2</a>).
|
|
|
|
— Whether a call to the at_quick_exit function that does not happen before the quick_exit
|
|
function is called will succeed (<a href='#7.24.4.3'>7.24.4.3</a>).
|
|
|
|
— Which of two elements that compare as equal is matched by the bsearch function (<a href='#7.24.5.1'>7.24.5.1</a>).
|
|
|
|
— The order of two elements that compare as equal in an array sorted by the qsort function
|
|
(<a href='#7.24.5.2'>7.24.5.2</a>).
|
|
|
|
— The order in which destructors are invoked by thrd_exit (<a href='#7.28.5.5'>7.28.5.5</a>).
|
|
|
|
— Whether calling tss_delete on a key while another thread is executing destructors affects the
|
|
number of invocations of the destructors associated with the key on that thread (<a href='#7.28.6.2'>7.28.6.2</a>).
|
|
|
|
— The encoding of the calendar time returned by the time function (<a href='#7.29.2.5'>7.29.2.5</a>).
|
|
|
|
— The characters stored by the strftime or wcsftime function if any of the time values being
|
|
converted is outside the normal range (<a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
|
|
— Whether an encoding error occurs if a wchar_t value that does not correspond to a member of
|
|
the extended character set appears in the format string for a function in <a href='#7.31.2'>7.31.2</a> or <a href='#7.31.5'>7.31.5</a> and the
|
|
specified semantics do not require that value to be processed by wcrtomb (<a href='#7.31.1'>7.31.1</a>).
|
|
|
|
— The conversion state after an encoding error occurs (<a href='#7.31.6.3.2'>7.31.6.3.2</a>, <a href='#7.31.6.3.3'>7.31.6.3.3</a>, <a href='#7.31.6.4.1'>7.31.6.4.1</a>, <a href='#7.31.6.4.2'>7.31.6.4.2</a>,
|
|
and <a href='#7.30.1.1'>7.30.1.1</a>, <a href='#7.30.1.2'>7.30.1.2</a>, <a href='#7.30.1.3'>7.30.1.3</a>, <a href='#7.30.1.4'>7.30.1.4</a>, <a href='#7.30.1.5'>7.30.1.5</a>, <a href='#7.30.1.6'>7.30.1.6</a>).
|
|
|
|
— The resulting value when the "invalid" floating-point exception is raised during IEC 60559
|
|
floating to integer conversion (<a href='#F.4'>F.4</a>).
|
|
|
|
— Whether conversion of non-integer IEC 60559 floating values to integer raises the "inexact"
|
|
floating-point exception (<a href='#F.4'>F.4</a>).
|
|
|
|
— Whether or when library functions in <math.h> raise the "inexact" floating-point exception in
|
|
an IEC 60559 conformant implementation (<a href='#F.10'>F.10</a>).
|
|
|
|
— Whether or when library functions in <math.h> raise an undeserved "underflow" floating-
|
|
point exception in an IEC 60559 conformant implementation (<a href='#F.10'>F.10</a>).
|
|
|
|
— The exponent value stored by frexp for a NaN or infinity (<a href='#F.10.3.7'>F.10.3.7</a>).
|
|
|
|
— The numeric result returned by the lrint, llrint, lround, and llround functions if the
|
|
rounded value is outside the range of the return type (<a href='#F.10.6.5'>F.10.6.5</a>, <a href='#F.10.6.7'>F.10.6.7</a>).
|
|
|
|
— The sign of one part of the complex result of several math functions for certain special cases
|
|
in IEC 60559 compatible implementations (<a href='#G.6.1.1'>G.6.1.1</a>, <a href='#G.6.2.2'>G.6.2.2</a>, <a href='#G.6.2.3'>G.6.2.3</a>, <a href='#G.6.2.4'>G.6.2.4</a>, <a href='#G.6.2.5'>G.6.2.5</a>, <a href='#G.6.2.6'>G.6.2.6</a>,
|
|
and <a href='#G.6.3.1'>G.6.3.1</a>, <a href='#G.6.4.2'>G.6.4.2</a>).
|
|
</pre>
|
|
<a name='J.2'></a>
|
|
<hr>
|
|
<h3>J.2 [Undefined behavior]</h3>
|
|
<a name='J.2p1'></a>
|
|
<pre>1 The behavior is undefined in the following circumstances:
|
|
|
|
— A "shall" or "shall not" requirement that appears outside of a constraint is violated (Clause 4).
|
|
|
|
— A nonempty source file does not end in a new-line character which is not immediately preceded
|
|
by a backslash character or ends in a partial preprocessing token or comment (<a href='#5.1.1.2'>5.1.1.2</a>).
|
|
|
|
— Token concatenation produces a character sequence matching the syntax of a universal charac-
|
|
ter name (<a href='#5.1.1.2'>5.1.1.2</a>).
|
|
|
|
— A program in a hosted environment does not define a function named main using one of the
|
|
specified forms (<a href='#5.1.2.2.1'>5.1.2.2.1</a>).
|
|
|
|
— The execution of a program contains a data race (<a href='#5.1.2.4'>5.1.2.4</a>).
|
|
|
|
— A character not in the basic source character set is encountered in a source file, except in an
|
|
identifier, a character constant, a string literal, a header name, a comment, or a preprocessing
|
|
token that is never converted to a token (<a href='#5.2.1'>5.2.1</a>).
|
|
|
|
— An identifier, comment, string literal, character constant, or header name contains an invalid
|
|
multibyte character or does not begin and end in the initial shift state (<a href='#5.2.1.1'>5.2.1.1</a>).
|
|
|
|
— The same identifier has both internal and external linkage in the same translation unit (<a href='#6.2.2'>6.2.2</a>).
|
|
|
|
— An object is referred to outside of its lifetime (<a href='#6.2.4'>6.2.4</a>).
|
|
|
|
— The value of a pointer to an object whose lifetime has ended is used (<a href='#6.2.4'>6.2.4</a>).
|
|
|
|
— The value of an object with automatic storage duration is used while the object has an indeter-
|
|
minate representation (<a href='#6.2.4'>6.2.4</a>, <a href='#6.7.10'>6.7.10</a>, <a href='#6.8'>6.8</a>).
|
|
|
|
— A non-value representation is read by an lvalue expression that does not have character type
|
|
(<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
|
|
— A non-value representation is produced by a side effect that modifies any part of the object
|
|
using an lvalue expression that does not have character type (<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
|
|
— Two declarations of the same object or function specify types that are not compatible (<a href='#6.2.7'>6.2.7</a>).
|
|
|
|
— A program requires the formation of a composite type from a variable length array type whose
|
|
size is specified by an expression that is not evaluated (<a href='#6.2.7'>6.2.7</a>).
|
|
|
|
— Conversion to or from an integer type produces a value outside the range that can be repre-
|
|
sented (<a href='#6.3.1.4'>6.3.1.4</a>).
|
|
|
|
— Demotion of one real floating type to another produces a value outside the range that can be
|
|
represented (<a href='#6.3.1.5'>6.3.1.5</a>).
|
|
|
|
— An lvalue does not designate an object when evaluated (<a href='#6.3.2.1'>6.3.2.1</a>).
|
|
|
|
— A non-array lvalue with an incomplete type is used in a context that requires the value of the
|
|
designated object (<a href='#6.3.2.1'>6.3.2.1</a>).
|
|
|
|
— An lvalue designating an object of automatic storage duration that could have been declared
|
|
with the register storage class is used in a context that requires the value of the designated
|
|
object, but the object is uninitialized. (<a href='#6.3.2.1'>6.3.2.1</a>).
|
|
|
|
— An lvalue having array type is converted to a pointer to the initial element of the array, and
|
|
the array object has register storage class (<a href='#6.3.2.1'>6.3.2.1</a>).
|
|
|
|
— An attempt is made to use the value of a void expression, or an implicit or explicit conversion
|
|
(except to void) is applied to a void expression (<a href='#6.3.2.2'>6.3.2.2</a>).
|
|
— Conversion of a pointer to an integer type produces a value outside the range that can be
|
|
represented (<a href='#6.3.2.3'>6.3.2.3</a>).
|
|
— Conversion between two pointer types produces a result that is incorrectly aligned (<a href='#6.3.2.3'>6.3.2.3</a>).
|
|
— A pointer is used to call a function whose type is not compatible with the referenced type
|
|
(<a href='#6.3.2.3'>6.3.2.3</a>).
|
|
— An unmatched ’ or " character is encountered on a logical source line during tokenization
|
|
(<a href='#6.4'>6.4</a>).
|
|
— A reserved keyword token is used in translation phase 7 or 8 for some purpose other than as a
|
|
keyword (<a href='#6.4.1'>6.4.1</a>).
|
|
— A universal character name in an identifier does not designate a character whose encoding
|
|
falls into one of the specified ranges (<a href='#6.4.2.1'>6.4.2.1</a>).
|
|
— The initial character of an identifier is a universal character name designating a digit (<a href='#6.4.2.1'>6.4.2.1</a>).
|
|
— Two identifiers differ only in nonsignificant characters (<a href='#6.4.2.1'>6.4.2.1</a>).
|
|
— The identifier __func__ is explicitly declared (<a href='#6.4.2.2'>6.4.2.2</a>).
|
|
— The program attempts to modify a string literal (<a href='#6.4.5'>6.4.5</a>).
|
|
— The characters ’ , \ , ", // , or /* occur in the sequence between the < and > delimiters, or the
|
|
characters ’ , \ , // , or /* occur in the sequence between the " delimiters, in a header name
|
|
preprocessing token (<a href='#6.4.7'>6.4.7</a>).
|
|
— A side effect on a scalar object is unsequenced relative to either a different side effect on the
|
|
same scalar object or a value computation using the value of the same scalar object (<a href='#6.5'>6.5</a>).
|
|
— An exceptional condition occurs during the evaluation of an expression (<a href='#6.5'>6.5</a>).
|
|
— An object has its stored value accessed other than by an lvalue of an allowable type (<a href='#6.5'>6.5</a>).
|
|
— A function is defined with a type that is not compatible with the type (of the expression)
|
|
pointed to by the expression that denotes the called function (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
— A member of an atomic structure or union is accessed (<a href='#6.5.2.3'>6.5.2.3</a>).
|
|
— The operand of the unary * operator has an invalid value (<a href='#6.5.3.2'>6.5.3.2</a>).
|
|
— A pointer is converted to other than an integer or pointer type (<a href='#6.5.4'>6.5.4</a>).
|
|
— The value of the second operand of the / or % operator is zero (<a href='#6.5.5'>6.5.5</a>).
|
|
— If the quotient a/b is not representable, the behavior of both a/b and a%b (<a href='#6.5.5'>6.5.5</a>).
|
|
— Addition or subtraction of a pointer into, or just beyond, an array object and an integer type
|
|
produces a result that does not point into, or just beyond, the same array object (<a href='#6.5.6'>6.5.6</a>).
|
|
— Addition or subtraction of a pointer into, or just beyond, an array object and an integer type
|
|
produces a result that points just beyond the array object and is used as the operand of a unary
|
|
* operator that is evaluated (<a href='#6.5.6'>6.5.6</a>).
|
|
— Pointers that do not point into, or just beyond, the same array object are subtracted (<a href='#6.5.6'>6.5.6</a>).
|
|
— An array subscript is out of range, even if an object is apparently accessible with the given
|
|
subscript (as in the lvalue expression a[1][7] given the declaration int a[4][5]) (<a href='#6.5.6'>6.5.6</a>).
|
|
— The result of subtracting two pointers is not representable in an object of type ptrdiff_t
|
|
(<a href='#6.5.6'>6.5.6</a>).
|
|
— An expression is shifted by a negative number or by an amount greater than or equal to the
|
|
width of the promoted expression (<a href='#6.5.7'>6.5.7</a>).
|
|
— An expression having signed promoted type is left-shifted and either the value of the expres-
|
|
sion is negative or the result of shifting would not be representable in the promoted type
|
|
(<a href='#6.5.7'>6.5.7</a>).
|
|
|
|
— Pointers that do not point to the same aggregate or union (nor just beyond the same array
|
|
object) are compared using relational operators (<a href='#6.5.8'>6.5.8</a>).
|
|
|
|
— An object is assigned to an inexactly overlapping object or to an exactly overlapping object
|
|
with incompatible type (<a href='#6.5.16.1'>6.5.16.1</a>).
|
|
|
|
— An expression that is required to be an integer constant expression does not have an integer
|
|
type; has operands that are not integer constants, enumeration constants, character constants,
|
|
predefined constants, sizeof expressions whose results are integer constants, alignof expres-
|
|
sions, or immediately-cast floating constants; or contains casts (outside operands to sizeof
|
|
and alignof operators) other than conversions of arithmetic types to integer types (<a href='#6.6'>6.6</a>).
|
|
|
|
— A constant expression in an initializer is not, or does not evaluate to, one of the following: an
|
|
arithmetic constant expression, a null pointer constant, an address constant, or an address
|
|
constant for a complete object type plus or minus an integer constant expression (<a href='#6.6'>6.6</a>).
|
|
|
|
— An arithmetic constant expression does not have arithmetic type; has operands that are not
|
|
integer constants, floating constants, enumeration constants, character constants, predefined
|
|
constants, sizeof expressions whose results are integer constants, or alignof expressions; or
|
|
contains casts (outside operands to sizeof or alignof operators) other than conversions of
|
|
arithmetic types to arithmetic types (<a href='#6.6'>6.6</a>).
|
|
|
|
— The value of an object is accessed by an array-subscript [], member-access . or-> , address &,
|
|
or indirection * operator or a pointer cast in creating an address constant (<a href='#6.6'>6.6</a>).
|
|
|
|
— An identifier for an object is declared with no linkage and the type of the object is incomplete
|
|
after its declarator, or after its init-declarator if it has an initializer (<a href='#6.7'>6.7</a>).
|
|
|
|
— A function is declared at block scope with an explicit storage-class specifier other than extern
|
|
(<a href='#6.7.1'>6.7.1</a>).
|
|
|
|
— A structure or union is defined without any named members (including those specified
|
|
indirectly via anonymous structures and unions) (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
— An attempt is made to access, or generate a pointer to just past, a flexible array member of a
|
|
structure when the referenced object provides no elements for that array (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
— When the complete type is needed, an incomplete structure or union type is not completed in
|
|
the same scope by another declaration of the tag that defines the content (<a href='#6.7.2.3'>6.7.2.3</a>).
|
|
|
|
— An attempt is made to modify an object defined with a const-qualified type through use of an
|
|
lvalue with non-const-qualified type (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
— An attempt is made to refer to an object defined with a volatile-qualified type through use of
|
|
an lvalue with non-volatile-qualified type (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
— The specification of a function type includes any type qualifiers (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
— Two qualified types that are required to be compatible do not have the identically qualified
|
|
version of a compatible type (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
— An object which has been modified is accessed through a restrict-qualified pointer to a const-
|
|
qualified type, or through a restrict-qualified pointer and another pointer that are not both
|
|
based on the same object (<a href='#6.7.3.1'>6.7.3.1</a>).
|
|
|
|
— A restrict-qualified pointer is assigned a value based on another restricted pointer whose
|
|
associated block neither began execution before the block associated with this pointer, nor
|
|
ended before the assignment (<a href='#6.7.3.1'>6.7.3.1</a>).
|
|
— A function with external linkage is declared with an inline function specifier, but is not also
|
|
defined in the same translation unit (<a href='#6.7.4'>6.7.4</a>).
|
|
|
|
— A function declared with a _Noreturn function specifier returns to its caller (<a href='#6.7.4'>6.7.4</a>).
|
|
|
|
— The definition of an object has an alignment specifier and another declaration of that object
|
|
has a different alignment specifier (<a href='#6.7.5'>6.7.5</a>).
|
|
|
|
— Declarations of an object in different translation units have different alignment specifiers
|
|
(<a href='#6.7.5'>6.7.5</a>).
|
|
|
|
— Two pointer types that are required to be compatible are not identically qualified, or are not
|
|
pointers to compatible types (<a href='#6.7.6.1'>6.7.6.1</a>).
|
|
|
|
— The size expression in an array declaration is not a constant expression and evaluates at
|
|
program execution time to a nonpositive value (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
— In a context requiring two array types to be compatible, they do not have compatible element
|
|
types, or their size specifiers evaluate to unequal values (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
|
|
— A declaration of an array parameter includes the keyword static within the [ and ] and the
|
|
corresponding argument does not provide access to the first element of an array with at least
|
|
the specified number of elements (<a href='#6.7.6.3'>6.7.6.3</a>).
|
|
|
|
— A storage-class specifier or type qualifier modifies the keyword void as a function parameter
|
|
type list (<a href='#6.7.6.3'>6.7.6.3</a>).
|
|
|
|
— In a context requiring two function types to be compatible, they do not have compatible return
|
|
types, or their parameters disagree in use of the ellipsis terminator or the number and type of
|
|
parameters (after default argument promotion, when there is no parameter type list) (<a href='#6.7.6.3'>6.7.6.3</a>).
|
|
|
|
— A declaration for which a type is inferred contains a pointer, array, or function declarators
|
|
(<a href='#6.7.9'>6.7.9</a>).
|
|
|
|
— A declaration for which a type is inferred contains no or more than one declarators (<a href='#6.7.9'>6.7.9</a>).
|
|
|
|
— The value of an unnamed member of a structure or union is used (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
— The initializer for a scalar is neither a single expression nor a single expression enclosed in
|
|
braces (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
— The initializer for a structure or union object that has automatic storage duration is neither an
|
|
initializer list nor a single expression that has compatible structure or union type (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
— The initializer for an aggregate or union, other than an array initialized by a string literal, is
|
|
not a brace-enclosed list of initializers for its elements or members (<a href='#6.7.10'>6.7.10</a>).
|
|
|
|
— A function definition that does not have the asserted property is called by a function decla-
|
|
ration or a function pointer with a type that has the unsequenced or reproducible attribute
|
|
(<a href='#6.7.12.7'>6.7.12.7</a>).
|
|
|
|
— An identifier with external linkage is used, but in the program there does not exist exactly
|
|
one external definition for the identifier, or the identifier is not used and there exist multiple
|
|
external definitions for the identifier (<a href='#6.9'>6.9</a>).
|
|
|
|
— A function that accepts a variable number of arguments is defined without a parameter type
|
|
list that ends with the ellipsis notation (<a href='#6.9.1'>6.9.1</a>).
|
|
|
|
— The } that terminates a function is reached, and the value of the function call is used by the
|
|
caller (<a href='#6.9.1'>6.9.1</a>).
|
|
|
|
— An identifier for an object with internal linkage and an incomplete type is declared with a
|
|
tentative definition (<a href='#6.9.2'>6.9.2</a>).
|
|
— A non-directive preprocessing directive is executed (<a href='#6.10'>6.10</a>).
|
|
|
|
— The token defined is generated during the expansion of a #if or #elif preprocessing direc-
|
|
tive, or the use of the defined unary operator does not match one of the two specified forms
|
|
prior to macro replacement (<a href='#6.10.1'>6.10.1</a>).
|
|
|
|
— The #include preprocessing directive that results after expansion does not match one of the
|
|
two header name forms (<a href='#6.10.2'>6.10.2</a>).
|
|
|
|
— The character sequence in an #include preprocessing directive does not start with a letter
|
|
(<a href='#6.10.2'>6.10.2</a>).
|
|
|
|
— There are sequences of preprocessing tokens within the list of macro arguments that would
|
|
otherwise act as preprocessing directives (<a href='#6.10.4'>6.10.4</a>).
|
|
|
|
— The result of the preprocessing operator # is not a valid character string literal (<a href='#6.10.4.2'>6.10.4.2</a>).
|
|
|
|
— The result of the preprocessing operator ## is not a valid preprocessing token (<a href='#6.10.4.3'>6.10.4.3</a>).
|
|
|
|
— The #line preprocessing directive that results after expansion does not match one of the two
|
|
well-defined forms, or its digit sequence specifies zero or a number greater than 2147483647
|
|
(<a href='#6.10.5'>6.10.5</a>).
|
|
|
|
— A non-STDC #pragma preprocessing directive that is documented as causing translation failure
|
|
or some other form of undefined behavior is encountered (<a href='#6.10.7'>6.10.7</a>).
|
|
|
|
— A #pragma STDC preprocessing directive does not match one of the well-defined forms (<a href='#6.10.7'>6.10.7</a>).
|
|
|
|
— The name of a predefined macro, or the identifier defined, is the subject of a #define or
|
|
#undef preprocessing directive (<a href='#6.10.9'>6.10.9</a>).
|
|
|
|
— An attempt is made to copy an object to an overlapping object by use of a library function,
|
|
other than as explicitly allowed (e.g., memmove) (Clause 7).
|
|
|
|
— A file with the same name as one of the standard headers, not provided as part of the implemen-
|
|
tation, is placed in any of the standard places that are searched for included source files (<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
— A header is included within an external declaration or definition (<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
— A function, object, type, or macro that is specified as being declared or defined by some
|
|
standard header is used before any header that declares or defines it is included (<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
— A standard header is included while a macro is defined with the same name as a keyword
|
|
(<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
— The program attempts to declare a library function itself, rather than via a standard header,
|
|
but the declaration does not have external linkage (<a href='#7.1.2'>7.1.2</a>).
|
|
|
|
— The program declares or defines a reserved identifier, other than as allowed by <a href='#7.1.4'>7.1.4</a> (<a href='#7.1.3'>7.1.3</a>).
|
|
|
|
— The program removes the definition of a macro whose name begins with an underscore and
|
|
either an uppercase letter or another underscore (<a href='#7.1.3'>7.1.3</a>).
|
|
|
|
— An argument to a library function has an invalid value or a type not expected by a function
|
|
with a variable number of arguments (<a href='#7.1.4'>7.1.4</a>).
|
|
|
|
— The pointer passed to a library function array parameter does not have a value such that all
|
|
address computations and object accesses are valid (<a href='#7.1.4'>7.1.4</a>).
|
|
|
|
— The macro definition of assert is suppressed in order to access an actual function (<a href='#7.2'>7.2</a>).
|
|
|
|
— The argument to the assert macro does not have a scalar type (<a href='#7.2'>7.2</a>).
|
|
— The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in any context other
|
|
than outside all external declarations or preceding all explicit declarations and statements
|
|
inside a compound statement (<a href='#7.3.4'>7.3.4</a>, <a href='#7.6.1'>7.6.1</a>, <a href='#7.12.2'>7.12.2</a>).
|
|
— The value of an argument to a character handling function is neither equal to the value of EOF
|
|
nor representable as an unsigned char (<a href='#7.4'>7.4</a>).
|
|
— A macro definition of errno is suppressed in order to access an actual object, or the program
|
|
defines an identifier with the name errno (<a href='#7.5'>7.5</a>).
|
|
— Part of the program tests floating-point status flags, sets floating-point control modes, or
|
|
runs under non-default mode settings, but was translated with the state for the FENV_ACCESS
|
|
pragma "off" (<a href='#7.6.1'>7.6.1</a>).
|
|
— The exception-mask argument for one of the functions that provide access to the floating-point
|
|
status flags has a nonzero value not obtained by bitwise OR of the floating-point exception
|
|
macros (<a href='#7.6.4'>7.6.4</a>).
|
|
— The fesetexceptflag function is used to set floating-point status flags that were not specified
|
|
in the call to the fegetexceptflag function that provided the value of the corresponding
|
|
fexcept_t object (<a href='#7.6.4.5'>7.6.4.5</a>).
|
|
|
|
— The argument to fesetenv or feupdateenv is neither an object set by a call to fegetenv or
|
|
feholdexcept, nor is it an environment macro (<a href='#7.6.6.3'>7.6.6.3</a>, <a href='#7.6.6.4'>7.6.6.4</a>).
|
|
|
|
— The value of the result of an integer arithmetic or conversion function cannot be represented
|
|
(<a href='#7.8.2.1'>7.8.2.1</a>, <a href='#7.8.2.2'>7.8.2.2</a>, <a href='#7.8.2.3'>7.8.2.3</a>, <a href='#7.8.2.4'>7.8.2.4</a>, <a href='#7.24.6.1'>7.24.6.1</a>, <a href='#7.24.6.2'>7.24.6.2</a>, <a href='#7.24.1'>7.24.1</a>).
|
|
— The program modifies the string pointed to by the value returned by the setlocale function
|
|
(<a href='#7.11.1.1'>7.11.1.1</a>).
|
|
— A pointer returned by the setlocale function is used after a subsequent call to the function,
|
|
or after the calling thread has exited (<a href='#7.11.1.1'>7.11.1.1</a>).
|
|
— The program modifies the structure pointed to by the value returned by the localeconv
|
|
function (<a href='#7.11.2.1'>7.11.2.1</a>).
|
|
— A macro definition of math_errhandling is suppressed or the program defines an identifier
|
|
with the name math_errhandling (<a href='#7.12'>7.12</a>).
|
|
— An argument to a floating-point classification or comparison macro is not of real floating type
|
|
(<a href='#7.12.3'>7.12.3</a>, <a href='#7.12.17'>7.12.17</a>).
|
|
— A macro definition of setjmp is suppressed in order to access an actual function, or the
|
|
program defines an external identifier with the name setjmp (<a href='#7.13'>7.13</a>).
|
|
— An invocation of the setjmp macro occurs other than in an allowed context (<a href='#7.13.2.1'>7.13.2.1</a>).
|
|
— The longjmp function is invoked to restore a nonexistent environment (<a href='#7.13.2.1'>7.13.2.1</a>).
|
|
— After a longjmp, there is an attempt to access the value of an object of automatic storage dura-
|
|
tion that does not have volatile-qualified type, local to the function containing the invocation
|
|
of the corresponding setjmp macro, that was changed between the setjmp invocation and
|
|
longjmp call (<a href='#7.13.2.1'>7.13.2.1</a>).
|
|
|
|
— The program specifies an invalid pointer to a signal handler function (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A signal handler returns when the signal corresponded to a computational exception (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A signal handler called in response to SIGFPE, SIGILL, SIGSEGV, or any other implementation-
|
|
defined value corresponding to a computational exception returns (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A signal occurs as the result of calling the abort or raise function, and the signal handler
|
|
calls the raise function (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A signal occurs other than as the result of calling the abort or raise function, and the signal
|
|
handler refers to an object with static or thread storage duration that is not a lock-free atomic
|
|
object other than by assigning a value to an object declared as volatile sig_atomic_t, or
|
|
calls any function in the standard library other than the abort function, the _Exit function,
|
|
the quick_exit function, the functions in <stdatomic.h> (except where explicitly stated
|
|
otherwise) when the atomic arguments are lock-free, the atomic_is_lock_free function with
|
|
any atomic argument, or the signal function (for the same signal number) (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— The value of errno is referred to after a signal occurred other than as the result of calling the
|
|
abort or raise function and the corresponding signal handler obtained a SIG_ERR return
|
|
from a call to the signal function (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A signal is generated by an asynchronous signal handler (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— The signal function is used in a multi-threaded program (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— A function with a variable number of arguments attempts to access its varying arguments
|
|
other than through a properly declared and initialized va_list object, or before the va_start
|
|
macro is invoked (<a href='#7.16'>7.16</a>, <a href='#7.16.1.1'>7.16.1.1</a>, <a href='#7.16.1.4'>7.16.1.4</a>).
|
|
— The macro va_arg is invoked using the parameter ap that was passed to a function that
|
|
invoked the macro va_arg with the same parameter (<a href='#7.16'>7.16</a>).
|
|
— A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in order to access
|
|
an actual function, or the program defines an external identifier with the name va_copy or
|
|
va_end (<a href='#7.16.1'>7.16.1</a>).
|
|
|
|
— The va_start or va_copy macro is invoked without a corresponding invocation of the va_end
|
|
macro in the same function, or vice versa (<a href='#7.16.1'>7.16.1</a>, <a href='#7.16.1.2'>7.16.1.2</a>, <a href='#7.16.1.3'>7.16.1.3</a>, <a href='#7.16.1.4'>7.16.1.4</a>).
|
|
— The type parameter to the va_arg macro is not such that a pointer to an object of that type can
|
|
be obtained simply by postfixing a * (<a href='#7.16.1.1'>7.16.1.1</a>).
|
|
— The va_arg macro is invoked when there is no actual next argument, or with a specified
|
|
type that is not compatible with the promoted type of the actual next argument, with certain
|
|
exceptions (<a href='#7.16.1.1'>7.16.1.1</a>).
|
|
— Using a null pointer constant in form of an integer expression as an argument to a ... function
|
|
and then interpreting it as a void* or char* (<a href='#7.16.1.1'>7.16.1.1</a>).
|
|
— The va_copy or va_start macro is called to initialize a va_list that was previously initialized
|
|
by either macro without an intervening invocation of the va_end macro for the same va_list
|
|
(<a href='#7.16.1.2'>7.16.1.2</a>, <a href='#7.16.1.4'>7.16.1.4</a>).
|
|
— The macro definition of a generic function is suppressed in order to access an actual function
|
|
(<a href='#7.17.1'>7.17.1</a>, <a href='#7.18'>7.18</a>).
|
|
— The type parameter of an offsetof macro defines a new type (<a href='#7.21'>7.21</a>).
|
|
— When program execution reaches an unreachable() macro call (<a href='#7.21.1'>7.21.1</a>).
|
|
— Arbitrarily copying or changing the bytes of or copying from a non-null pointer into a
|
|
nullptr_t object and then reading that object (<a href='#7.21.2'>7.21.2</a>).
|
|
|
|
— The member-designator parameter of an offsetof macro is an invalid right operand of the .
|
|
operator for the type parameter, or designates a bit-field (<a href='#7.21'>7.21</a>).
|
|
— The argument in an instance of one of the integer-constant macros is not a decimal, octal, or
|
|
hexadecimal constant, or it has a value that exceeds the limits for the corresponding type
|
|
(<a href='#7.22.4'>7.22.4</a>).
|
|
— A byte input/output function is applied to a wide-oriented stream, or a wide character
|
|
input/output function is applied to a byte-oriented stream (<a href='#7.23.2'>7.23.2</a>).
|
|
— Use is made of any portion of a file beyond the most recent wide character written to a
|
|
wide-oriented stream (<a href='#7.23.2'>7.23.2</a>).
|
|
|
|
— The value of a pointer to a FILE object is used after the associated file is closed (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— The stream for the fflush function points to an input stream or to an update stream in which
|
|
the most recent operation was input (<a href='#7.23.5.2'>7.23.5.2</a>).
|
|
|
|
— The string pointed to by the mode argument in a call to the fopen function does not exactly
|
|
match one of the specified character sequences (<a href='#7.23.5.3'>7.23.5.3</a>).
|
|
|
|
— An output operation on an update stream is followed by an input operation without an
|
|
intervening call to the fflush function or a file positioning function, or an input operation
|
|
on an update stream is followed by an output operation with an intervening call to a file
|
|
positioning function (<a href='#7.23.5.3'>7.23.5.3</a>).
|
|
|
|
— An attempt is made to use the contents of the array that was supplied in a call to the setvbuf
|
|
function (<a href='#7.23.5.6'>7.23.5.6</a>).
|
|
|
|
— There are insufficient arguments for the format in a call to one of the formatted input/output
|
|
functions, or an argument does not have an appropriate type (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.1'>7.31.2.1</a>,
|
|
and <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
|
|
— The format in a call to one of the formatted input/output functions or to the strftime or
|
|
wcsftime function is not a valid multibyte character sequence that begins and ends in its
|
|
initial shift state (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.2.1'>7.31.2.1</a>, <a href='#7.31.2.2'>7.31.2.2</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
|
|
— In a call to one of the formatted output functions, a precision appears with a conversion
|
|
specifier other than those described (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— A conversion specification for a formatted output function uses an asterisk to denote an
|
|
argument-supplied field width or precision, but the corresponding argument is not provided
|
|
(<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— A conversion specification for a formatted output function uses a # or 0 flag with a conversion
|
|
specifier other than those described (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— A conversion specification for one of the formatted input/output functions uses a length
|
|
modifier with a conversion specifier other than those described (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.1'>7.31.2.1</a>,
|
|
and <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
|
|
— An s conversion specifier is encountered by one of the formatted output functions, and the
|
|
argument is missing the null terminator (unless a precision is specified that does not require
|
|
null termination) (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— An n conversion specification for one of the formatted input/output functions includes any
|
|
flags, an assignment-suppressing character, a field width, or a precision (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>,
|
|
and <a href='#7.31.2.1'>7.31.2.1</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
|
|
— A % conversion specifier is encountered by one of the formatted input/output functions, but
|
|
the complete conversion specification is not exactly %% (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.1'>7.31.2.1</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
|
|
— An invalid conversion specification is found in the format for one of the formatted input/out-
|
|
put functions, or the strftime or wcsftime function (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.2.1'>7.31.2.1</a>,
|
|
and <a href='#7.31.2.2'>7.31.2.2</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
|
|
— The number of characters or wide characters transmitted by a formatted output function (or
|
|
written to an array, or that would have been written to an array) is greater than INT_MAX
|
|
(<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— The number of input items assigned by a formatted input function is greater than INT_MAX
|
|
(<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
— The result of a conversion by one of the formatted input functions cannot be represented in
|
|
the corresponding object, or the receiving object does not have an appropriate type (<a href='#7.23.6.2'>7.23.6.2</a>,
|
|
and <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
— A c, s, or [ conversion specifier is encountered by one of the formatted input functions, and
|
|
the array pointed to by the corresponding argument is not large enough to accept the input
|
|
sequence (and a null terminator if the conversion specifier is s or [) (<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
— A c, s, or [ conversion specifier with an l qualifier is encountered by one of the formatted
|
|
input functions, but the input is not a valid multibyte character sequence that begins in the
|
|
initial shift state (<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
— The input item for a %p conversion by one of the formatted input functions is not a value
|
|
converted earlier during the same program execution (<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
— The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, vsscanf, vfwprintf,
|
|
vfwscanf , vswprintf , vswscanf , vwprintf , or vwscanf function is called with an improperly
|
|
initialized va_list argument, or the argument is used (other than in an invocation of va_end)
|
|
after the function returns (<a href='#7.23.6.8'>7.23.6.8</a>, <a href='#7.23.6.9'>7.23.6.9</a>, <a href='#7.23.6.10'>7.23.6.10</a>, <a href='#7.23.6.11'>7.23.6.11</a>, <a href='#7.23.6.12'>7.23.6.12</a>, <a href='#7.23.6.13'>7.23.6.13</a>, <a href='#7.23.6.14'>7.23.6.14</a>,
|
|
and <a href='#7.31.2.5'>7.31.2.5</a>, <a href='#7.31.2.6'>7.31.2.6</a>, <a href='#7.31.2.7'>7.31.2.7</a>, <a href='#7.31.2.8'>7.31.2.8</a>, <a href='#7.31.2.9'>7.31.2.9</a>, <a href='#7.31.2.10'>7.31.2.10</a>).
|
|
— The contents of the array supplied in a call to the fgets or fgetws function are used after a
|
|
read error occurred (<a href='#7.23.7.2'>7.23.7.2</a>, <a href='#7.31.3.2'>7.31.3.2</a>).
|
|
— The file position indicator for a binary stream is used after a call to the ungetc function where
|
|
its value was zero before the call (<a href='#7.23.7.10'>7.23.7.10</a>).
|
|
— The file position indicator for a stream is used after an error occurred during a call to the
|
|
fread or fwrite function (<a href='#7.23.8.1'>7.23.8.1</a>, <a href='#7.23.8.2'>7.23.8.2</a>).
|
|
|
|
— A partial element read by a call to the fread function is used (<a href='#7.23.8.1'>7.23.8.1</a>).
|
|
— The fseek function is called for a text stream with a nonzero offset and either the offset was
|
|
not returned by a previous successful call to the ftell function on a stream associated with
|
|
the same file or whence is not SEEK_SET (<a href='#7.23.9.2'>7.23.9.2</a>).
|
|
— The fsetpos function is called to set a position that was not returned by a previous successful
|
|
call to the fgetpos function on a stream associated with the same file (<a href='#7.23.9.3'>7.23.9.3</a>).
|
|
— A non-null pointer returned by a call to the calloc, malloc, realloc, or aligned_alloc
|
|
function with a zero requested size is used to access an object (<a href='#7.24.3'>7.24.3</a>).
|
|
— The value of a pointer that refers to space deallocated by a call to the free or realloc function
|
|
is used (<a href='#7.24.3'>7.24.3</a>).
|
|
— The pointer argument to the free or realloc function does not match a pointer earlier
|
|
returned by a memory management function, or the space has been deallocated by a call to
|
|
free or realloc (<a href='#7.24.3.3'>7.24.3.3</a>, <a href='#7.24.3.7'>7.24.3.7</a>).
|
|
|
|
— The value of the object allocated by the malloc function is used (<a href='#7.24.3.6'>7.24.3.6</a>).
|
|
— The values of any bytes in a new object allocated by the realloc function beyond the size of
|
|
the old object are used (<a href='#7.24.3.7'>7.24.3.7</a>).
|
|
— The program calls the exit or quick_exit function more than once, or calls both functions
|
|
(<a href='#7.24.4.4'>7.24.4.4</a>, <a href='#7.24.4.7'>7.24.4.7</a>).
|
|
— During the call to a function registered with the atexit or at_quick_exit function, a call is
|
|
made to the longjmp function that would terminate the call to the registered function (<a href='#7.24.4.4'>7.24.4.4</a>,
|
|
and <a href='#7.24.4.7'>7.24.4.7</a>).
|
|
— The string set up by the getenv or strerror function is modified by the program (<a href='#7.24.4.6'>7.24.4.6</a>,
|
|
and <a href='#7.26.6.3'>7.26.6.3</a>).
|
|
— A signal is raised while the quick_exit function is executing (<a href='#7.24.4.7'>7.24.4.7</a>).
|
|
|
|
— A command is executed through the system function in a way that is documented as causing
|
|
termination or some other form of undefined behavior (<a href='#7.24.4.8'>7.24.4.8</a>).
|
|
|
|
— A searching or sorting utility function is called with an invalid pointer argument, even if the
|
|
number of elements is zero (<a href='#7.24.5'>7.24.5</a>).
|
|
|
|
— The comparison function called by a searching or sorting utility function alters the contents of
|
|
the array being searched or sorted, or returns ordering values inconsistently (<a href='#7.24.5'>7.24.5</a>).
|
|
|
|
— The array being searched by the bsearch function does not have its elements in proper order
|
|
(<a href='#7.24.5.1'>7.24.5.1</a>).
|
|
|
|
— The current conversion state is used by a multibyte/wide character conversion function after
|
|
changing the LC_CTYPE category (<a href='#7.24.7'>7.24.7</a>).
|
|
|
|
— A string or wide string utility function is instructed to access an array beyond the end of an
|
|
object (<a href='#7.26.1'>7.26.1</a>, <a href='#7.31.4'>7.31.4</a>).
|
|
|
|
— A string or wide string utility function is called with an invalid pointer argument, even if the
|
|
length is zero (<a href='#7.26.1'>7.26.1</a>, <a href='#7.31.4'>7.31.4</a>).
|
|
|
|
— The contents of the destination array are used after a call to the strxfrm, strftime, wcsxfrm,
|
|
or wcsftime function in which the specified length was too small to hold the entire null-
|
|
terminated result (<a href='#7.26.4.5'>7.26.4.5</a>, <a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.4.4.4'>7.31.4.4.4</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
|
|
— A sequence of calls of the strtok function is made from different threads (<a href='#7.26.5.9'>7.26.5.9</a>).
|
|
|
|
— The first argument in the very first call to the strtok or wcstok is a null pointer (<a href='#7.26.5.9'>7.26.5.9</a>,
|
|
and <a href='#7.31.4.6.7'>7.31.4.6.7</a>).
|
|
|
|
— A pointer returned by the strerror function is used after a subsequent call to the function, or
|
|
after the calling thread has exited (<a href='#7.26.6.3'>7.26.6.3</a>).
|
|
|
|
— The type of an argument to a type-generic macro is not compatible with the type of the
|
|
corresponding parameter of the selected function (<a href='#7.27'>7.27</a>).
|
|
|
|
— Arguments for generic parameters of a type-generic macro are such that some argument has a
|
|
corresponding real type that is of standard floating type and another argument is of decimal
|
|
floating type (<a href='#7.27'>7.27</a>).
|
|
|
|
— Arguments for generic parameters of a type-generic macro are such that neither <math.h> and
|
|
<complex.h> define a function whose generic parameters have the determined corresponding
|
|
real type (<a href='#7.27'>7.27</a>).
|
|
|
|
— A complex argument is supplied for a generic parameter of a type-generic macro that has no
|
|
corresponding complex function (<a href='#7.27'>7.27</a>).
|
|
|
|
— A decimal floating argument is supplied for a generic parameter of a type-generic macro that
|
|
expects a complex argument (<a href='#7.27'>7.27</a>).
|
|
|
|
— A standard floating or complex argument is supplied for a generic parameter of a type-generic
|
|
macro that expects a decimal floating type argument (<a href='#7.27'>7.27</a>).
|
|
|
|
— A non-recursive mutex passed to mtx_lock is locked by the calling thread (<a href='#7.28.4.3'>7.28.4.3</a>).
|
|
|
|
— The mutex passed to mtx_timedlock does not support timeout (<a href='#7.28.4.4'>7.28.4.4</a>).
|
|
|
|
— The mutex passed to mtx_unlock is not locked by the calling thread (<a href='#7.28.4.6'>7.28.4.6</a>).
|
|
|
|
— The thread passed to thrd_detach or thrd_join was previously detached or joined with
|
|
another thread (<a href='#7.28.5.3'>7.28.5.3</a>, <a href='#7.28.5.6'>7.28.5.6</a>).
|
|
— The tss_create function is called from within a destructor (<a href='#7.28.6.1'>7.28.6.1</a>).
|
|
|
|
— The key passed to tss_delete, tss_get, or tss_set was not returned by a call to tss_create
|
|
before the thread commenced executing destructors (<a href='#7.28.6.2'>7.28.6.2</a>, <a href='#7.28.6.3'>7.28.6.3</a>, <a href='#7.28.6.4'>7.28.6.4</a>).
|
|
|
|
— An attempt is made to access the pointer returned by the time conversion functions after the
|
|
thread that originally called the function to obtain it has exited (<a href='#7.29.3'>7.29.3</a>).
|
|
|
|
— At least one member of the broken-down time passed to asctime contains a value outside its
|
|
normal range, or the calculated year exceeds four digits or is less than the year 1000 (<a href='#7.29.3.1'>7.29.3.1</a>).
|
|
|
|
— The argument corresponding to an s specifier without an l qualifier in a call to the fwprintf
|
|
function does not point to a valid multibyte character sequence that begins in the initial shift
|
|
state (<a href='#7.31.2.11'>7.31.2.11</a>).
|
|
|
|
— In a call to the wcstok function, the object pointed to by ptr does not have the value stored by
|
|
the previous call for the same wide string (<a href='#7.31.4.6.7'>7.31.4.6.7</a>).
|
|
|
|
— An mbstate_t object is used inappropriately (<a href='#7.31.6'>7.31.6</a>).
|
|
|
|
— The value of an argument of type wint_t to a wide character classification or case mapping
|
|
function is neither equal to the value of WEOF nor representable as a wchar_t (<a href='#7.32.1'>7.32.1</a>).
|
|
|
|
— The iswctype function is called using a different LC_CTYPE category from the one in effect for
|
|
the call to the wctype function that returned the description (<a href='#7.32.2.2.1'>7.32.2.2.1</a>).
|
|
|
|
— The towctrans function is called using a different LC_CTYPE category from the one in effect
|
|
for the call to the wctrans function that returned the description (<a href='#7.32.3.2.1'>7.32.3.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.3'></a>
|
|
<hr>
|
|
<h3>J.3 [Implementation-defined behavior]</h3>
|
|
<a name='J.3p1'></a>
|
|
<pre>1 A conforming implementation is required to document its choice of behavior in each of the areas
|
|
listed in this subclause. The following are implementation-defined:
|
|
|
|
</pre>
|
|
<a name='J.3.1'></a>
|
|
<hr>
|
|
<h3>J.3.1 [Translation]</h3>
|
|
<a name='J.3.1p1'></a>
|
|
<pre>1 — How a diagnostic is identified (<a href='#3.10'>3.10</a>, <a href='#5.1.1.3'>5.1.1.3</a>).
|
|
|
|
— Whether each nonempty sequence of white-space characters other than new-line is retained or
|
|
replaced by one space character in translation phase 3 (<a href='#5.1.1.2'>5.1.1.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.2'></a>
|
|
<hr>
|
|
<h3>J.3.2 [Environment]</h3>
|
|
<a name='J.3.2p1'></a>
|
|
<pre>1 — The mapping between physical source file multibyte characters and the source character set in
|
|
translation phase 1 (<a href='#5.1.1.2'>5.1.1.2</a>).
|
|
|
|
— The name and type of the function called at program startup in a freestanding environment
|
|
(<a href='#5.1.2.1'>5.1.2.1</a>).
|
|
|
|
— The effect of program termination in a freestanding environment (<a href='#5.1.2.1'>5.1.2.1</a>).
|
|
|
|
— An alternative manner in which the main function may be defined (<a href='#5.1.2.2.1'>5.1.2.2.1</a>).
|
|
|
|
— The values given to the strings pointed to by the argv argument to main (<a href='#5.1.2.2.1'>5.1.2.2.1</a>).
|
|
|
|
— What constitutes an interactive device (<a href='#5.1.2.3'>5.1.2.3</a>).
|
|
|
|
— Whether a program can have more than one thread of execution in a freestanding environment
|
|
(<a href='#5.1.2.4'>5.1.2.4</a>).
|
|
|
|
— The set of signals, their semantics, and their default handling (<a href='#7.14'>7.14</a>).
|
|
|
|
— Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a computational
|
|
exception (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
— Signals for which the equivalent of signal(sig, SIG_IGN); is executed at program startup
|
|
(<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
|
|
— The set of environment names and the method for altering the environment list used by the
|
|
getenv function (<a href='#7.24.4.6'>7.24.4.6</a>).
|
|
|
|
— The manner of execution of the string by the system function (<a href='#7.24.4.8'>7.24.4.8</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.3'></a>
|
|
<hr>
|
|
<h3>J.3.3 [Identifiers]</h3>
|
|
<a name='J.3.3p1'></a>
|
|
<pre>1 — Which additional multibyte characters may appear in identifiers and their correspondence to
|
|
universal character names (<a href='#6.4.2'>6.4.2</a>).
|
|
|
|
— The number of significant initial characters in an identifier (<a href='#5.2.4.1'>5.2.4.1</a>, <a href='#6.4.2'>6.4.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.4'></a>
|
|
<hr>
|
|
<h3>J.3.4 [Characters]</h3>
|
|
<a name='J.3.4p1'></a>
|
|
<pre>1 — The number of bits in a byte (<a href='#3.6'>3.6</a>).
|
|
|
|
— The values of the members of the execution character set (<a href='#5.2.1'>5.2.1</a>).
|
|
|
|
— The unique value of the member of the execution character set produced for each of the
|
|
standard alphabetic escape sequences (<a href='#5.2.2'>5.2.2</a>).
|
|
|
|
— The value of a char object into which has been stored any character other than a member of
|
|
the basic execution character set (<a href='#6.2.5'>6.2.5</a>).
|
|
|
|
— Which of signed char or unsigned char has the same range, representation, and behavior
|
|
as "plain" char (<a href='#6.2.5'>6.2.5</a>, <a href='#6.3.1.1'>6.3.1.1</a>).
|
|
|
|
— The literal encoding, which maps of the characters of the execution character set to the values
|
|
in a character constant or string literal (<a href='#6.2.9'>6.2.9</a>, <a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The wide literal encoding, of the characters of the execution character set to the values in a
|
|
wchar_t character constant or wchar_t string literal (<a href='#6.2.9'>6.2.9</a>, <a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The mapping of members of the source character set (in character constants and string literals)
|
|
to members of the execution character set (<a href='#6.4.4.4'>6.4.4.4</a>, <a href='#5.1.1.2'>5.1.1.2</a>).
|
|
|
|
— The value of an integer character constant containing more than one character or containing a
|
|
character or escape sequence that does not map to a single-byte execution character (<a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The value of a wide character constant containing more than one multibyte character or a
|
|
single multibyte character that maps to multiple members of the extended execution character
|
|
set, or containing a multibyte character or escape sequence not represented in the extended
|
|
execution character set (<a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The current locale used to convert a wide character constant consisting of a single multibyte
|
|
character that maps to a member of the extended execution character set into a corresponding
|
|
wide character code (<a href='#6.4.4.4'>6.4.4.4</a>).
|
|
|
|
— The current locale used to convert a wide string literal into corresponding wide character
|
|
codes (<a href='#6.4.5'>6.4.5</a>).
|
|
|
|
— The value of a string literal containing a multibyte character or escape sequence not represented
|
|
in the execution character set (<a href='#6.4.5'>6.4.5</a>).
|
|
|
|
— The encoding of any of wchar_t, char16_t, and char32_t where the corresponding stan-
|
|
dard encoding macro (__STDC_ISO_10646__ , __STDC_UTF_16__ , or __STDC_UTF_32__ ) is not
|
|
defined (<a href='#6.10.9.2'>6.10.9.2</a>).
|
|
</pre>
|
|
<a name='J.3.5'></a>
|
|
<hr>
|
|
<h3>J.3.5 [Integers]</h3>
|
|
<a name='J.3.5p1'></a>
|
|
<pre>1 — Any extended integer types that exist in the implementation (<a href='#6.2.5'>6.2.5</a>).
|
|
|
|
— The rank of any extended integer type relative to another extended integer type with the same
|
|
precision (<a href='#6.3.1.1'>6.3.1.1</a>).
|
|
|
|
— The result of, or the signal raised by, converting an integer to a signed integer type when the
|
|
value cannot be represented in an object of that type (<a href='#6.3.1.3'>6.3.1.3</a>).
|
|
|
|
— The results of some bitwise operations on signed integers (<a href='#6.5'>6.5</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.6'></a>
|
|
<hr>
|
|
<h3>J.3.6 [Floating-point]</h3>
|
|
<a name='J.3.6p1'></a>
|
|
<pre>1 — The accuracy of the floating-point operations and of the library functions in <math.h> and
|
|
<complex.h> that return floating-point results (<a href='#5.2.4.2.2'>5.2.4.2.2</a>).
|
|
|
|
— The accuracy of the conversions between floating-point internal representations and string
|
|
representations performed by the library functions in <stdio.h>, <stdlib.h>, and <wchar.h>
|
|
(<a href='#5.2.4.2.2'>5.2.4.2.2</a>).
|
|
|
|
— The rounding behaviors characterized by non-standard values of FLT_ROUNDS (<a href='#5.2.4.2.2'>5.2.4.2.2</a>).
|
|
|
|
— The evaluation methods characterized by non-standard negative values of FLT_EVAL_METHOD
|
|
(<a href='#5.2.4.2.2'>5.2.4.2.2</a>).
|
|
|
|
— The evaluation methods characterized by non-standard negative values of DEC_EVAL_METHOD
|
|
(<a href='#5.2.4.2.3'>5.2.4.2.3</a>).
|
|
|
|
— If decimal floating types are supported (<a href='#6.2.5'>6.2.5</a>).
|
|
|
|
— The direction of rounding when an integer is converted to a floating-point number that cannot
|
|
exactly represent the original value (<a href='#6.3.1.4'>6.3.1.4</a>).
|
|
|
|
— The direction of rounding when a floating-point number is converted to a narrower floating-
|
|
point number (<a href='#6.3.1.5'>6.3.1.5</a>).
|
|
|
|
— How the nearest representable value or the larger or smaller representable value immediately
|
|
adjacent to the nearest representable value is chosen for certain floating constants (<a href='#6.4.4.2'>6.4.4.2</a>).
|
|
|
|
— Whether and how floating expressions are contracted when not disallowed by the
|
|
FP_CONTRACT pragma (<a href='#6.5'>6.5</a>).
|
|
|
|
— The default state for the FENV_ACCESS pragma (<a href='#7.6.1'>7.6.1</a>).
|
|
|
|
— Additional floating-point exceptions, rounding modes, environments, and classifications, and
|
|
their macro names (<a href='#7.6'>7.6</a>, <a href='#7.12'>7.12</a>).
|
|
|
|
— The default state for the FP_CONTRACT pragma (<a href='#7.12.2'>7.12.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.7'></a>
|
|
<hr>
|
|
<h3>J.3.7 [Arrays and pointers]</h3>
|
|
<a name='J.3.7p1'></a>
|
|
<pre>1 — The result of converting a pointer to an integer or vice versa (<a href='#6.3.2.3'>6.3.2.3</a>).
|
|
|
|
— The size of the result of subtracting two pointers to elements of the same array (<a href='#6.5.6'>6.5.6</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.8'></a>
|
|
<hr>
|
|
<h3>J.3.8 [Hints]</h3>
|
|
<a name='J.3.8p1'></a>
|
|
<pre>1 — The extent to which suggestions made by using the register storage-class specifier are
|
|
effective (<a href='#6.7.1'>6.7.1</a>).
|
|
|
|
— The extent to which suggestions made by using the inline function specifier are effective
|
|
(<a href='#6.7.4'>6.7.4</a>).
|
|
</pre>
|
|
<a name='J.3.9'></a>
|
|
<hr>
|
|
<h3>J.3.9 [Structures, unions, enumerations, and bit-fields]</h3>
|
|
<a name='J.3.9p1'></a>
|
|
<pre>1 — Whether a "plain" int bit-field is treated as a signed int bit-field or as an unsigned int
|
|
bit-field (<a href='#6.7.2'>6.7.2</a>, <a href='#6.7.2.1'>6.7.2.1</a>).
|
|
— Allowable bit-field types other than bool, signed int, unsigned int, and bit-precise integer
|
|
types (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
— Whether atomic types are permitted for bit-fields (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
— Whether a bit-field can straddle a storage-unit boundary (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
— The order of allocation of bit-fields within a unit (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
— The alignment of non-bit-field members of structures (<a href='#6.7.2.1'>6.7.2.1</a>). This should present no problem
|
|
unless binary data written by one implementation is read by another.
|
|
— The integer type compatible with each enumerated type (<a href='#6.7.2.2'>6.7.2.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.10'></a>
|
|
<hr>
|
|
<h3>J.3.10 [Qualifiers]</h3>
|
|
<a name='J.3.10p1'></a>
|
|
<pre>1 — What constitutes an access to an object that has volatile-qualified type (<a href='#6.7.3'>6.7.3</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.11'></a>
|
|
<hr>
|
|
<h3>J.3.11 [Preprocessing directives]</h3>
|
|
<a name='J.3.11p1'></a>
|
|
<pre>1 — The locations within #pragma directives where header name preprocessing tokens are recog-
|
|
nized (<a href='#6.4'>6.4</a>, <a href='#6.4.7'>6.4.7</a>).
|
|
— How sequences in both forms of header names are mapped to headers or external source file
|
|
names (<a href='#6.4.7'>6.4.7</a>).
|
|
— Whether the value of a character constant in a constant expression that controls conditional
|
|
inclusion matches the value of the same character constant in the execution character set
|
|
(<a href='#6.10.1'>6.10.1</a>).
|
|
— Whether the value of a single-character character constant in a constant expression that controls
|
|
conditional inclusion may have a negative value (<a href='#6.10.1'>6.10.1</a>).
|
|
— The places that are searched for an included < > delimited header, and how the places are
|
|
specified or the header is identified (<a href='#6.10.2'>6.10.2</a>).
|
|
— How the named source file is searched for in an included " " delimited header (<a href='#6.10.2'>6.10.2</a>).
|
|
— The method by which preprocessing tokens (possibly resulting from macro expansion) in a
|
|
#include directive are combined into a header name (<a href='#6.10.2'>6.10.2</a>).
|
|
|
|
— The nesting limit for #include processing (<a href='#6.10.2'>6.10.2</a>).
|
|
— Whether the # operator inserts a \ character before the \ character that begins a universal
|
|
character name in a character constant or string literal (<a href='#6.10.4.2'>6.10.4.2</a>).
|
|
— The behavior on each recognized non-STDC #pragma directive (<a href='#6.10.7'>6.10.7</a>).
|
|
— The definitions for __DATE__ and __TIME__ when respectively, the date and time of translation
|
|
are not available (<a href='#6.10.9.1'>6.10.9.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.12'></a>
|
|
<hr>
|
|
<h3>J.3.12 [Library functions]</h3>
|
|
<a name='J.3.12p1'></a>
|
|
<pre>1 — Any library facilities available to a freestanding program, other than the minimal set required
|
|
by Clause 4 (<a href='#5.1.2.1'>5.1.2.1</a>).
|
|
— The format of the diagnostic printed by the assert macro (<a href='#7.2.1.1'>7.2.1.1</a>).
|
|
— The representation of the floating-point status flags stored by the fegetexceptflag function
|
|
(<a href='#7.6.4.2'>7.6.4.2</a>).
|
|
— Whether the feraiseexcept function raises the "inexact" floating-point exception in addition
|
|
to the "overflow" or "underflow" floating-point exception (<a href='#7.6.4.3'>7.6.4.3</a>).
|
|
|
|
— Strings other than "C" and "" that may be passed as the second argument to the setlocale
|
|
function (<a href='#7.11.1.1'>7.11.1.1</a>).
|
|
|
|
— The types defined for float_t and double_t when the value of the FLT_EVAL_METHOD macro
|
|
is less than 0 (<a href='#7.12'>7.12</a>).
|
|
|
|
— The types defined for _Decimal32_t and _Decimal64_t when the value of the
|
|
DEC_EVAL_METHOD macro is less than 0 (<a href='#7.12'>7.12</a>).
|
|
|
|
— Domain errors for the mathematics functions, other than those required by this document
|
|
(<a href='#7.12.1'>7.12.1</a>).
|
|
|
|
— The values returned by the mathematics functions on domain errors or pole errors (<a href='#7.12.1'>7.12.1</a>).
|
|
|
|
— The values returned by the mathematics functions on underflow range errors, whether errno
|
|
is set to the value of the macro ERANGE when the integer expression math_errhandling &
|
|
MATH_ERRNO is nonzero, and whether the "underflow" floating-point exception is raised when
|
|
the integer expression math_errhandling & MATH_ERREXCEPT is nonzero. (<a href='#7.12.1'>7.12.1</a>).
|
|
|
|
— Whether a domain error occurs or zero is returned when an fmod function has a second
|
|
argument of zero (<a href='#7.12.10.1'>7.12.10.1</a>).
|
|
|
|
— Whether a domain error occurs or zero is returned when a remainder function has a second
|
|
argument of zero (<a href='#7.12.10.2'>7.12.10.2</a>).
|
|
|
|
— The base-2 logarithm of the modulus used by the remquo functions in reducing the quotient
|
|
(<a href='#7.12.10.3'>7.12.10.3</a>).
|
|
|
|
— The byte order of decimal floating type encodings (<a href='#7.12.16'>7.12.16</a>).
|
|
|
|
— Whether a domain error occurs or zero is returned when a remquo function has a second
|
|
argument of zero (<a href='#7.12.10.3'>7.12.10.3</a>).
|
|
|
|
— Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call of a signal
|
|
handler, and, if not, the blocking of signals that is performed (<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
|
|
— The value of __STDC_ENDIAN_NATIVE__ if the execution environment is not big-endian or
|
|
little-endian (<a href='#7.18.2'>7.18.2</a>)
|
|
|
|
— The null pointer constant to which the macro NULL expands (<a href='#7.21'>7.21</a>).
|
|
|
|
— Whether the last line of a text stream requires a terminating new-line character (<a href='#7.23.2'>7.23.2</a>).
|
|
|
|
— Whether space characters that are written out to a text stream immediately before a new-line
|
|
character appear when read in (<a href='#7.23.2'>7.23.2</a>).
|
|
|
|
— The number of null characters that may be appended to data written to a binary stream (<a href='#7.23.2'>7.23.2</a>).
|
|
|
|
— Whether the file position indicator of an append-mode stream is initially positioned at the
|
|
beginning or end of the file (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— Whether a write on a text stream causes the associated file to be truncated beyond that point
|
|
(<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— The characteristics of file buffering (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— Whether a zero-length file actually exists (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— The rules for composing valid file names (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— Whether the same file can be simultaneously open multiple times (<a href='#7.23.3'>7.23.3</a>).
|
|
— The nature and choice of encodings used for multibyte characters in files (<a href='#7.23.3'>7.23.3</a>).
|
|
|
|
— The effect of the remove function on an open file (<a href='#7.23.4.1'>7.23.4.1</a>).
|
|
|
|
— The effect if a file with the new name exists prior to a call to the rename function (<a href='#7.23.4.2'>7.23.4.2</a>).
|
|
|
|
— Whether an open temporary file is removed upon abnormal program termination (<a href='#7.23.4.3'>7.23.4.3</a>).
|
|
|
|
— Which changes of mode are permitted (if any), and under what circumstances (<a href='#7.23.5.4'>7.23.5.4</a>).
|
|
|
|
— The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar sequence
|
|
printed for a NaN (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— The output for %p conversion in the fprintf or fwprintf function (<a href='#7.23.6.1'>7.23.6.1</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— The interpretation of a- character that is neither the first nor the last character, nor the second
|
|
where a ^ character is the first, in the scanlist for %[ conversion in the fscanf or fwscanf
|
|
function (<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.1'>7.31.2.1</a>).
|
|
|
|
— The set of sequences matched by a %p conversion and the interpretation of the corresponding
|
|
input item in the fscanf or fwscanf function (<a href='#7.23.6.2'>7.23.6.2</a>, <a href='#7.31.2.2'>7.31.2.2</a>).
|
|
|
|
— The value to which the macro errno is set by the fgetpos, fsetpos, or ftell functions on
|
|
failure (<a href='#7.23.9.1'>7.23.9.1</a>, <a href='#7.23.9.3'>7.23.9.3</a>, <a href='#7.23.9.4'>7.23.9.4</a>).
|
|
|
|
— The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
|
|
converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold function (<a href='#7.24.1.5'>7.24.1.5</a>,
|
|
and <a href='#7.31.4.1.2'>7.31.4.1.2</a>).
|
|
|
|
— Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold function sets
|
|
errno to ERANGE when underflow occurs (<a href='#7.24.1.5'>7.24.1.5</a>, <a href='#7.31.4.1.2'>7.31.4.1.2</a>).
|
|
|
|
— The meaning of any d-char or d-wchar sequence in a string representing a NaN that is con-
|
|
verted by the strtod32, strtod64, strtod128, wcstod32, wcstod64, or wcstod128 function
|
|
(<a href='#7.24.1.6'>7.24.1.6</a>, <a href='#7.31.4.1.3'>7.31.4.1.3</a>).
|
|
|
|
— Whether or not the strtod32, strtod64, strtod128, wcstod32, wcstod64, or wcstod128
|
|
function sets errno to ERANGE when underflow occurs (<a href='#7.24.1.6'>7.24.1.6</a>, <a href='#7.31.4.1.3'>7.31.4.1.3</a>).
|
|
|
|
— Whether the calloc, malloc, realloc, and aligned_alloc functions return a null pointer or
|
|
a pointer to an allocated object when the size requested is zero (<a href='#7.24.3'>7.24.3</a>).
|
|
|
|
— Whether open streams with unwritten buffered data are flushed, )open streams are closed, or
|
|
temporary files are removed when the abort or _Exit function is called (<a href='#7.24.4.1'>7.24.4.1</a>, <a href='#7.24.4.5'>7.24.4.5</a>).
|
|
|
|
— The termination status returned to the host environment by the abort, exit, _Exit , or
|
|
quick_exit function (<a href='#7.24.4.1'>7.24.4.1</a>, <a href='#7.24.4.4'>7.24.4.4</a>, <a href='#7.24.4.5'>7.24.4.5</a>, <a href='#7.24.4.7'>7.24.4.7</a>).
|
|
|
|
— The value returned by the system function when its argument is not a null pointer (<a href='#7.24.4.8'>7.24.4.8</a>).
|
|
|
|
— Whether the internal state of multibyte/wide character conversion functions has thread-storage
|
|
duration, and its initial value in newly created threads (<a href='#7.24.7'>7.24.7</a>).
|
|
|
|
— The range and precision of times representable in clock_t and time_t (<a href='#7.29'>7.29</a>).
|
|
|
|
— The local time zone and Daylight Saving Time (<a href='#7.29.1'>7.29.1</a>).
|
|
|
|
— Whether TIME_MONOTONIC or TIME_ACTIVE are supported time bases (<a href='#7.29.1'>7.29.1</a>).
|
|
|
|
— Whether TIME_THREAD_ACTIVE is a supported time bases (<a href='#7.29.1'>7.29.1</a>, <a href='#7.28.1'>7.28.1</a>).
|
|
|
|
— The local time zone and Daylight Saving Time (<a href='#7.29.1'>7.29.1</a>).
|
|
|
|
— The era for the clock function (<a href='#7.29.2.1'>7.29.2.1</a>).
|
|
— The TIME_UTC epoch (<a href='#7.29.2.6'>7.29.2.6</a>).
|
|
— The replacement string for the %Z specifier to the strftime, and wcsftime functions in the
|
|
"C" locale (<a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
|
|
— Whether internal mbstate_t objects have thread storage duration (<a href='#7.30.1'>7.30.1</a>, <a href='#7.31.6.3'>7.31.6.3</a>, <a href='#7.31.6.4'>7.31.6.4</a>).
|
|
— Whether the functions in <math.h> honor the rounding direction mode in an IEC 60559
|
|
conformant implementation, unless explicitly specified otherwise (<a href='#F.10'>F.10</a>).
|
|
|
|
</pre>
|
|
<a name='J.3.13'></a>
|
|
<hr>
|
|
<h3>J.3.13 [Architecture]</h3>
|
|
<a name='J.3.13p1'></a>
|
|
<pre>1 — The values or expressions assigned to the macros specified in the headers <float.h>,
|
|
<limits.h>, and <stdint.h> (<a href='#5.2.4.2'>5.2.4.2</a>, <a href='#7.22'>7.22</a>).
|
|
|
|
— The result of attempting to indirectly access an object with automatic or thread storage duration
|
|
from a thread other than the one with which it is associated (<a href='#6.2.4'>6.2.4</a>).
|
|
— The number, order, and encoding of bytes in any object (when not explicitly specified in this
|
|
document) (<a href='#6.2.6.1'>6.2.6.1</a>).
|
|
— Whether any extended alignments are supported and the contexts in which they are supported
|
|
(<a href='#6.2.8'>6.2.8</a>).
|
|
— Valid alignment values other than those returned by an alignof expression for fundamental
|
|
types, if any (<a href='#6.2.8'>6.2.8</a>).
|
|
— The value of the result of the sizeof and alignof operators (<a href='#6.5.3.4'>6.5.3.4</a>).
|
|
|
|
</pre>
|
|
<a name='J.4'></a>
|
|
<hr>
|
|
<h3>J.4 [Locale-specific behavior]</h3>
|
|
<a name='J.4p1'></a>
|
|
<pre>1 The following characteristics of a hosted environment are locale-specific and are required to be
|
|
documented by the implementation:
|
|
|
|
— Additional members of the source and execution character sets beyond the basic character set
|
|
(<a href='#5.2.1'>5.2.1</a>).
|
|
— The presence, meaning, and representation of additional multibyte characters in the execution
|
|
character set beyond the basic character set (<a href='#5.2.1.1'>5.2.1.1</a>).
|
|
— The shift states used for the encoding of multibyte characters (<a href='#5.2.1.1'>5.2.1.1</a>).
|
|
— The direction of writing of successive printing characters (<a href='#5.2.2'>5.2.2</a>).
|
|
— The decimal-point character (<a href='#7.1.1'>7.1.1</a>).
|
|
— The set of printing characters (<a href='#7.4'>7.4</a>, <a href='#7.32.2'>7.32.2</a>).
|
|
— The set of control characters (<a href='#7.4'>7.4</a>, <a href='#7.32.2'>7.32.2</a>).
|
|
— The sets of characters tested for by the isalpha, isblank, islower, ispunct, isspace,
|
|
isupper, iswalpha, iswblank, iswlower, iswpunct, iswspace, or iswupper functions
|
|
(<a href='#7.4.1.2'>7.4.1.2</a>, <a href='#7.4.1.3'>7.4.1.3</a>, <a href='#7.4.1.7'>7.4.1.7</a>, <a href='#7.4.1.9'>7.4.1.9</a>, <a href='#7.4.1.10'>7.4.1.10</a>, <a href='#7.4.1.11'>7.4.1.11</a>, <a href='#7.32.2.1.2'>7.32.2.1.2</a>, <a href='#7.32.2.1.3'>7.32.2.1.3</a>, <a href='#7.32.2.1.7'>7.32.2.1.7</a>, <a href='#7.32.2.1.9'>7.32.2.1.9</a>,
|
|
<a href='#7.32.2.1.10'>7.32.2.1.10</a>, <a href='#7.32.2.1.11'>7.32.2.1.11</a>).
|
|
— The native environment (<a href='#7.11.1.1'>7.11.1.1</a>).
|
|
— Additional subject sequences accepted by the numeric conversion functions (<a href='#7.24.1'>7.24.1</a>, <a href='#7.31.4.1'>7.31.4.1</a>).
|
|
— The collation sequence of the execution character set (<a href='#7.26.4.3'>7.26.4.3</a>, <a href='#7.31.4.4.2'>7.31.4.4.2</a>).
|
|
— The contents of the error message strings set up by the strerror function (<a href='#7.26.6.3'>7.26.6.3</a>).
|
|
— The formats for time and date (<a href='#7.29.3.5'>7.29.3.5</a>, <a href='#7.31.5.1'>7.31.5.1</a>).
|
|
— Character mappings that are supported by the towctrans function (<a href='#7.32.1'>7.32.1</a>).
|
|
— Character classifications that are supported by the iswctype function (<a href='#7.32.1'>7.32.1</a>).
|
|
</pre>
|
|
<a name='J.5'></a>
|
|
<hr>
|
|
<h3>J.5 [Common extensions]</h3>
|
|
<a name='J.5p1'></a>
|
|
<pre>1 The following extensions are widely used in many systems, but are not portable to all implemen-
|
|
tations. The inclusion of any extension that may cause a strictly conforming program to become
|
|
invalid renders an implementation nonconforming. Examples of such extensions are new keywords,
|
|
extra library functions declared in standard headers, or predefined macros with names that do not
|
|
begin with an underscore.
|
|
|
|
</pre>
|
|
<a name='J.5.1'></a>
|
|
<hr>
|
|
<h3>J.5.1 [Environment arguments]</h3>
|
|
<a name='J.5.1p1'></a>
|
|
<pre>1 In a hosted environment, the main function receives a third argument, char *envp[], that points to
|
|
a null-terminated array of pointers to char, each of which points to a string that provides information
|
|
about the environment for this execution of the program (<a href='#5.1.2.2.1'>5.1.2.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.2'></a>
|
|
<hr>
|
|
<h3>J.5.2 [Specialized identifiers]</h3>
|
|
<a name='J.5.2p1'></a>
|
|
<pre>1 Characters other than the underscore _ , letters, and digits, that are not part of the basic source
|
|
character set (such as the dollar sign $, or characters in national character sets) may appear in an
|
|
identifier (<a href='#6.4.2'>6.4.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.3'></a>
|
|
<hr>
|
|
<h3>J.5.3 [Lengths and cases of identifiers]</h3>
|
|
<a name='J.5.3p1'></a>
|
|
<pre>1 All characters in identifiers (with or without external linkage) are significant (<a href='#6.4.2'>6.4.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.4'></a>
|
|
<hr>
|
|
<h3>J.5.4 [Scopes of identifiers]</h3>
|
|
<a name='J.5.4p1'></a>
|
|
<pre>1 A function identifier, or the identifier of an object the declaration of which contains the keyword
|
|
extern, has file scope (<a href='#6.2.1'>6.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.5'></a>
|
|
<hr>
|
|
<h3>J.5.5 [Writable string literals]</h3>
|
|
<a name='J.5.5p1'></a>
|
|
<pre>1 String literals are modifiable (in which case, identical string literals should denote distinct objects)
|
|
(<a href='#6.4.5'>6.4.5</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.6'></a>
|
|
<hr>
|
|
<h3>J.5.6 [Other arithmetic types]</h3>
|
|
<a name='J.5.6p1'></a>
|
|
<pre>1 Additional arithmetic types, such as __int128 or double double, and their appropriate conver-
|
|
sions are defined (<a href='#6.2.5'>6.2.5</a>, <a href='#6.3.1'>6.3.1</a>). Additional floating types may have more range or precision than
|
|
long double, may be used for evaluating expressions of other floating types, and may be used to
|
|
define float_t or double_t. Additional floating types may also have less range or precision than
|
|
float.
|
|
|
|
</pre>
|
|
<a name='J.5.7'></a>
|
|
<hr>
|
|
<h3>J.5.7 [Function pointer casts]</h3>
|
|
<a name='J.5.7p1'></a>
|
|
<pre>1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to be invoked
|
|
as a function (<a href='#6.5.4'>6.5.4</a>).
|
|
</pre>
|
|
<a name='J.5.7p2'></a>
|
|
<pre>2 A pointer to a function may be cast to a pointer to an object or to void, allowing a function to be
|
|
inspected or modified (for example, by a debugger) (<a href='#6.5.4'>6.5.4</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.8'></a>
|
|
<hr>
|
|
<h3>J.5.8 [Extended bit-field types]</h3>
|
|
<a name='J.5.8p1'></a>
|
|
<pre>1 A bit-field may be declared with a type other than bool, unsigned int, signed int, or a bit-precise
|
|
integer type, with an appropriate maximum width (<a href='#6.7.2.1'>6.7.2.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.9'></a>
|
|
<hr>
|
|
<h3>J.5.9 [The fortran keyword]</h3>
|
|
<a name='J.5.9p1'></a>
|
|
<pre>1 The fortran function specifier may be used in a function declaration to indicate that calls suitable
|
|
for FORTRAN should be generated, or that a different representation for the external name is to be
|
|
generated (<a href='#6.7.4'>6.7.4</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.10'></a>
|
|
<hr>
|
|
<h3>J.5.10 [The asm keyword]</h3>
|
|
<a name='J.5.10p1'></a>
|
|
<pre>1 The asm keyword may be used to insert assembly language directly into the translator output (<a href='#6.8'>6.8</a>).
|
|
The most common implementation is via a statement of the form:
|
|
|
|
asm (character-string-literal);
|
|
</pre>
|
|
<a name='J.5.11'></a>
|
|
<hr>
|
|
<h3>J.5.11 [Multiple external definitions]</h3>
|
|
<a name='J.5.11p1'></a>
|
|
<pre>1 There may be more than one external definition for the identifier of an object, with or without the
|
|
explicit use of the keyword extern; if the definitions disagree, or more than one is initialized, the
|
|
behavior is undefined (<a href='#6.9.2'>6.9.2</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.12'></a>
|
|
<hr>
|
|
<h3>J.5.12 [Predefined macro names]</h3>
|
|
<a name='J.5.12p1'></a>
|
|
<pre>1 Macro names that do not begin with an underscore, describing the translation and execution
|
|
environments, are defined by the implementation before translation begins (<a href='#6.10.9'>6.10.9</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.13'></a>
|
|
<hr>
|
|
<h3>J.5.13 [Floating-point status flags]</h3>
|
|
<a name='J.5.13p1'></a>
|
|
<pre>1 If any floating-point status flags are set on normal termination after all calls to functions registered
|
|
by the atexit function have been made (see <a href='#7.24.4.4'>7.24.4.4</a>), the implementation writes some diagnostics
|
|
indicating the fact to the stderr stream, if it is still open,
|
|
|
|
</pre>
|
|
<a name='J.5.14'></a>
|
|
<hr>
|
|
<h3>J.5.14 [Extra arguments for signal handlers]</h3>
|
|
<a name='J.5.14p1'></a>
|
|
<pre>1 Handlers for specific signals are called with extra arguments in addition to the signal number
|
|
(<a href='#7.14.1.1'>7.14.1.1</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.15'></a>
|
|
<hr>
|
|
<h3>J.5.15 [Additional stream types and file-opening modes]</h3>
|
|
<a name='J.5.15p1'></a>
|
|
<pre>1 Additional mappings from files to streams are supported (<a href='#7.23.2'>7.23.2</a>).
|
|
</pre>
|
|
<a name='J.5.15p2'></a>
|
|
<pre>2 Additional file-opening modes may be specified by characters appended to the mode argument of
|
|
the fopen function (<a href='#7.23.5.3'>7.23.5.3</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.16'></a>
|
|
<hr>
|
|
<h3>J.5.16 [Defined file position indicator]</h3>
|
|
<a name='J.5.16p1'></a>
|
|
<pre>1 The file position indicator is decremented by each successful call to the ungetc or ungetwc function
|
|
for a text stream, except if its value was zero before a call (<a href='#7.23.7.10'>7.23.7.10</a>, <a href='#7.31.3.10'>7.31.3.10</a>).
|
|
|
|
</pre>
|
|
<a name='J.5.17'></a>
|
|
<hr>
|
|
<h3>J.5.17 [Math error reporting]</h3>
|
|
<a name='J.5.17p1'></a>
|
|
<pre>1 Functions declared in <complex.h> and <math.h> raise SIGFPE to report errors instead of, or in
|
|
addition to, setting errno or raising floating-point exceptions (<a href='#7.3'>7.3</a>, <a href='#7.12'>7.12</a>).
|
|
|
|
</pre>
|
|
<a name='J.6'></a>
|
|
<hr>
|
|
<h3>J.6 [Reserved identifiers and keywords]</h3>
|
|
<a name='J.6p1'></a>
|
|
<pre>1 A lot of identifier preprocessing tokens are used for specific purposes in regular clauses or appendices
|
|
from translation phase 3 onwards. Using any of these for a purpose different from their description
|
|
in this document, even if the use is in a context where they are normatively permitted, may have an
|
|
impact on the portability of code and should thus be avoided.
|
|
|
|
</pre>
|
|
<a name='J.6.1'></a>
|
|
<hr>
|
|
<h3>J.6.1 [Rule based identifiers]</h3>
|
|
<a name='J.6.1p1'></a>
|
|
<pre>1 The following 40 regular expressions characterize identifiers that are systematically reserved by
|
|
some clause this document.
|
|
|
|
ATOMIC_[A-Z][a-zA-Z0-9_]* LC_[A-Z][a-zA-Z0-9_]*
|
|
DBL_[A-Z][a-zA-Z0-9_]* LDBL_[A-Z][a-zA-Z0-9_]*
|
|
DEC128_[A-Z][a-zA-Z0-9_]* MATH_[A-Z][a-zA-Z0-9_]*
|
|
DEC32_[A-Z][a-zA-Z0-9_]* PRI[a-zX][a-zA-Z0-9_]*
|
|
DEC64_[A-Z][a-zA-Z0-9_]* SCN[a-zX][a-zA-Z0-9_]*
|
|
DEC_[A-Z][a-zA-Z0-9_]* SIG[A-Z][a-zA-Z0-9_]*
|
|
E[0-9A-Z][a-zA-Z0-9_]* SIG_[A-Z][a-zA-Z0-9_]*
|
|
FE_[A-Z][a-zA-Z0-9_]* TIME_[A-Z][a-zA-Z0-9_]*
|
|
FLT_[A-Z][a-zA-Z0-9_]* UINT[a-zA-Z0-9_]*_C
|
|
FP_[A-Z][a-zA-Z0-9_]* UINT[a-zA-Z0-9_]*_MAX
|
|
INT[a-zA-Z0-9_]*_C UINT[a-zA-Z0-9_]*_WIDTH
|
|
INT[a-zA-Z0-9_]*_MAX _[a-zA-Z_][a-zA-Z0-9_]*
|
|
INT[a-zA-Z0-9_]*_MIN atomic_[a-z][a-zA-Z0-9_]*
|
|
INT[a-zA-Z0-9_]*_WIDTH cnd_[a-z][a-zA-Z0-9_]*
|
|
cr_[a-z][a-zA-Z0-9_]* str[a-z][a-zA-Z0-9_]*
|
|
int[a-zA-Z0-9_]*_t thrd_[a-z][a-zA-Z0-9_]*
|
|
is[a-z][a-zA-Z0-9_]* to[a-z][a-zA-Z0-9_]*
|
|
mem[a-z][a-zA-Z0-9_]* tss_[a-z][a-zA-Z0-9_]*
|
|
mtx_[a-z][a-zA-Z0-9_]* uint[a-zA-Z0-9_]*_t
|
|
stdc_[a-zA-Z0-9_]* wcs[a-z][a-zA-Z0-9_]*
|
|
|
|
|
|
</pre>
|
|
<a name='J.6.1p2'></a>
|
|
<pre>2 The following 794 identifiers or keywords match these patterns and have particular semantics
|
|
provided by this document.
|
|
|
|
atomic_bool atomic_is_lock_free
|
|
ATOMIC_BOOL_LOCK_FREE atomic_llong
|
|
atomic_char ATOMIC_LLONG_LOCK_FREE
|
|
atomic_char16_t atomic_load
|
|
ATOMIC_CHAR16_T_LOCK_FREE atomic_load_explicit
|
|
atomic_char32_t atomic_long
|
|
ATOMIC_CHAR32_T_LOCK_FREE ATOMIC_LONG_LOCK_FREE
|
|
atomic_char8_t ATOMIC_POINTER_LOCK_FREE
|
|
ATOMIC_CHAR8_T_LOCK_FREE atomic_ptrdiff_t
|
|
ATOMIC_CHAR_LOCK_FREE atomic_schar
|
|
atomic_compare_exchange_strong atomic_short
|
|
atomic_compare_exchange_strong_explicit ATOMIC_SHORT_LOCK_FREE
|
|
atomic_compare_exchange_weak atomic_signal_fence
|
|
atomic_compare_exchange_weak_explicit atomic_size_t
|
|
atomic_exchange atomic_store
|
|
atomic_exchange_explicit atomic_store_explicit
|
|
atomic_fetch_ atomic_thread_fence
|
|
atomic_fetch_add atomic_uchar
|
|
atomic_fetch_add_explicit atomic_uint
|
|
atomic_fetch_and atomic_uintmax_t
|
|
atomic_fetch_and_explicit atomic_uintptr_t
|
|
atomic_fetch_or atomic_uint_fast16_t
|
|
atomic_fetch_or_explicit atomic_uint_fast32_t
|
|
atomic_fetch_sub atomic_uint_fast64_t
|
|
atomic_fetch_sub_explicit atomic_uint_fast8_t
|
|
atomic_fetch_xor atomic_uint_least16_t
|
|
atomic_fetch_xor_explicit atomic_uint_least32_t
|
|
atomic_flag atomic_uint_least64_t
|
|
atomic_flag_clear atomic_uint_least8_t
|
|
atomic_flag_clear_explicit atomic_ullong
|
|
ATOMIC_FLAG_INIT atomic_ulong
|
|
atomic_flag_test_and_set atomic_ushort
|
|
atomic_flag_test_and_set_explicit ATOMIC_VAR_INIT
|
|
atomic_init atomic_wchar_t
|
|
atomic_int ATOMIC_WCHAR_T_LOCK_FREE
|
|
atomic_intmax_t cnd_broadcast
|
|
atomic_intptr_t cnd_destroy
|
|
atomic_int_fast16_t cnd_init
|
|
atomic_int_fast32_t cnd_signal
|
|
atomic_int_fast64_t cnd_t
|
|
atomic_int_fast8_t cnd_timedwait
|
|
atomic_int_least16_t cnd_wait
|
|
atomic_int_least32_t DBL_DECIMAL_DIG
|
|
atomic_int_least64_t DBL_DIG
|
|
atomic_int_least8_t DBL_EPSILON
|
|
ATOMIC_INT_LOCK_FREE DBL_HAS_SUBNORM
|
|
DBL_IS_IEC_60559 FE_DYNAMIC
|
|
DBL_MANT_DIG FE_INEXACT
|
|
DBL_MAX FE_INVALID
|
|
DBL_MAX_10_EXP FE_OVERFLOW
|
|
DBL_MAX_EXP FE_SNANS_ALWAYS_SIGNAL
|
|
DBL_MIN FE_TONEAREST
|
|
DBL_MIN_10_EXP FE_TONEARESTFROMZERO
|
|
DBL_MIN_EXP FE_TOWARDZERO
|
|
DBL_NORM_MAX FE_UNDERFLOW
|
|
DBL_SNAN FE_UPWARD
|
|
DBL_TRUE_MIN FLT_DECIMAL_DIG
|
|
DEC128_EPSILON FLT_DIG
|
|
DEC128_MANT_DIG FLT_EPSILON
|
|
DEC128_MAX FLT_EVAL_METHOD
|
|
DEC128_MAX_EXP FLT_HAS_SUBNORM
|
|
DEC128_MIN FLT_IS_IEC_60559
|
|
DEC128_MIN_EXP FLT_MANT_DIG
|
|
DEC128_SNAN FLT_MAX
|
|
DEC128_TRUE_MIN FLT_MAX_10_EXP
|
|
DEC32_EPSILON FLT_MAX_EXP
|
|
DEC32_MANT_DIG FLT_MIN
|
|
DEC32_MAX FLT_MIN_10_EXP
|
|
DEC32_MAX_EXP FLT_MIN_EXP
|
|
DEC32_MIN FLT_NORM_MAX
|
|
DEC32_MIN_EXP FLT_RADIX
|
|
DEC32_SNAN FLT_ROUNDS
|
|
DEC32_TRUE_MIN FLT_SNAN
|
|
DEC64_EPSILON FLT_TRUE_MIN
|
|
DEC64_MANT_DIG FP_CONTRACT
|
|
DEC64_MAX FP_FAST_D
|
|
DEC64_MAX_EXP FP_FAST_D32ADDD128
|
|
DEC64_MIN FP_FAST_D32ADDD64
|
|
DEC64_MIN_EXP FP_FAST_D32DIVD128
|
|
DEC64_SNAN FP_FAST_D32DIVD64
|
|
DEC64_TRUE_MIN FP_FAST_D32FMAD128
|
|
DEC_EVAL_METHOD FP_FAST_D32FMAD64
|
|
DEC_INFINITY FP_FAST_D32MULD128
|
|
DEC_NAN FP_FAST_D32MULD64
|
|
EDOM FP_FAST_D32SQRTD128
|
|
EILSEQ FP_FAST_D32SQRTD64
|
|
EOF FP_FAST_D32SUBD128
|
|
EOL FP_FAST_D32SUBD64
|
|
ERANGE FP_FAST_D64ADDD128
|
|
EXIT_FAILURE FP_FAST_D64DIVD128
|
|
EXIT_SUCCESS FP_FAST_D64FMAD128
|
|
FE_ALL_EXCEPT FP_FAST_D64MULD128
|
|
FE_DEC_DOWNWARD FP_FAST_D64SQRTD128
|
|
FE_DEC_DYNAMIC FP_FAST_D64SUBD128
|
|
FE_DEC_TONEAREST FP_FAST_DADDL
|
|
FE_DEC_TONEARESTFROMZERO FP_FAST_DDIVL
|
|
FE_DEC_TOWARDZERO FP_FAST_DFMAL
|
|
FE_DEC_UPWARD FP_FAST_DMULL
|
|
FE_DFL_ENV FP_FAST_DSQRTL
|
|
FE_DFL_MODE FP_FAST_DSUBL
|
|
FE_DIVBYZERO FP_FAST_F
|
|
FE_DOWNWARD FP_FAST_FADD
|
|
FP_FAST_FADDL INTMAX_WIDTH
|
|
FP_FAST_FDIV INTPTR_MAX
|
|
FP_FAST_FDIVL INTPTR_MIN
|
|
FP_FAST_FFMA intptr_t
|
|
FP_FAST_FFMAL INTPTR_WIDTH
|
|
FP_FAST_FMA int_fast16_t
|
|
FP_FAST_FMAD int_fast32_t
|
|
FP_FAST_FMAD128 int_fast64_t
|
|
FP_FAST_FMAD32 int_fast8_t
|
|
FP_FAST_FMAD64 int_least16_t
|
|
FP_FAST_FMAF int_least32_t
|
|
FP_FAST_FMAL int_least64_t
|
|
FP_FAST_FMUL int_least8_t
|
|
FP_FAST_FMULL INT_MAX
|
|
FP_FAST_FSQRT INT_MIN
|
|
FP_FAST_FSQRTL INT_WIDTH
|
|
FP_FAST_FSUB isalnum
|
|
FP_FAST_FSUBL isalpha
|
|
FP_ILOGB0 isblank
|
|
FP_ILOGBNAN iscanonical
|
|
FP_INFINITE iscntrl
|
|
FP_INT_DOWNWARD isdigit
|
|
FP_INT_TONEAREST iseqsig
|
|
FP_INT_TONEARESTFROMZERO isfinite
|
|
FP_INT_TOWARDZERO isgraph
|
|
FP_INT_UPWARD isgreater
|
|
FP_LLOGB0 isgreaterequal
|
|
FP_LLOGBNAN isinf
|
|
FP_NAN isless
|
|
FP_NORMAL islessequal
|
|
FP_SUBNORMAL islessgreater
|
|
FP_ZERO islower
|
|
INT16_C isnan
|
|
INT16_MAX isnormal
|
|
INT16_MIN isprint
|
|
int16_t ispunct
|
|
INT16_WIDTH issignaling
|
|
INT32_C isspace
|
|
INT32_MAX issubnormal
|
|
INT32_MIN isunordered
|
|
int32_t isupper
|
|
INT32_WIDTH iswalnum
|
|
INT64_C iswalpha
|
|
INT64_MAX iswblank
|
|
INT64_MIN iswcntrl
|
|
int64_t iswctype
|
|
INT64_WIDTH iswdigit
|
|
INT8_C iswgraph
|
|
INT8_MAX iswlower
|
|
INT8_MIN iswprint
|
|
int8_t iswpunct
|
|
INT8_WIDTH iswspace
|
|
INTMAX_C iswupper
|
|
INTMAX_MAX iswxdigit
|
|
INTMAX_MIN isxdigit
|
|
intmax_t iszero
|
|
LC_ALL PRIdLEAST64
|
|
LC_COLLATE PRIdMAX
|
|
LC_CTYPE PRIdPTR
|
|
LC_MONETARY PRIi32
|
|
LC_NUMERIC PRIi64
|
|
LC_TIME PRIiFAST32
|
|
LDBL_DECIMAL_DIG PRIiFAST64
|
|
LDBL_DIG PRIiLEAST32
|
|
LDBL_EPSILON PRIiLEAST64
|
|
LDBL_HAS_SUBNORM PRIiMAX
|
|
LDBL_IS_IEC_60559 PRIiPTR
|
|
LDBL_MANT_DIG PRIo32
|
|
LDBL_MAX PRIo64
|
|
LDBL_MAX_10_EXP PRIoFAST32
|
|
LDBL_MAX_EXP PRIoFAST64
|
|
LDBL_MIN PRIoLEAST32
|
|
LDBL_MIN_10_EXP PRIoLEAST64
|
|
LDBL_MIN_EXP PRIoMAX
|
|
LDBL_NORM_MAX PRIoPTR
|
|
LDBL_SNAN PRIu32
|
|
LDBL_TRUE_MIN PRIu64
|
|
MATH_ERREXCEPT PRIuFAST32
|
|
MATH_ERRNO PRIuFAST64
|
|
memalignment PRIuLEAST32
|
|
memccpy PRIuLEAST64
|
|
memchr PRIuMAX
|
|
memcmp PRIuPTR
|
|
memcpy PRIX32
|
|
memcpy_s PRIX64
|
|
memmove PRIXFAST32
|
|
memmove_s PRIXFAST64
|
|
memory_order PRIXLEAST32
|
|
memory_order_acquire PRIXLEAST64
|
|
memory_order_acq_rel PRIXMAX
|
|
memory_order_consume PRIXPTR
|
|
memory_order_relaxed SCNdMAX
|
|
memory_order_release SCNdPTR
|
|
memory_order_seq_cst SCNiMAX
|
|
memset SCNiPTR
|
|
memset_explicit SCNoMAX
|
|
memset_s SCNoPTR
|
|
mtx_destroy SCNuMAX
|
|
mtx_init SCNuPTR
|
|
mtx_lock SCNxMAX
|
|
mtx_plain SCNxPTR
|
|
mtx_recursive SIGABRT
|
|
mtx_t SIGFPE
|
|
mtx_timed SIGILL
|
|
mtx_timedlock SIGINT
|
|
mtx_trylock SIGSEGV
|
|
mtx_unlock SIGTERM
|
|
PRId32 SIG_ATOMIC_MAX
|
|
PRId64 SIG_ATOMIC_MIN
|
|
PRIdFAST32 SIG_ATOMIC_WIDTH
|
|
PRIdFAST64 SIG_DFL
|
|
PRIdLEAST32 SIG_ERR
|
|
SIG_IGN stdc_has_single_bituc
|
|
stdc_bit_ceil stdc_has_single_bitui
|
|
stdc_bit_ceiluc stdc_has_single_bitul
|
|
stdc_bit_ceilui stdc_has_single_bitull
|
|
stdc_bit_ceilul stdc_has_single_bitus
|
|
stdc_bit_ceilull stdc_leading_ones
|
|
stdc_bit_ceilus stdc_leading_onesuc
|
|
stdc_bit_floor stdc_leading_onesui
|
|
stdc_bit_flooruc stdc_leading_onesul
|
|
stdc_bit_floorui stdc_leading_onesull
|
|
stdc_bit_floorul stdc_leading_onesus
|
|
stdc_bit_floorull stdc_leading_zeros
|
|
stdc_bit_floorus stdc_leading_zerosuc
|
|
stdc_bit_width stdc_leading_zerosui
|
|
stdc_bit_widthuc stdc_leading_zerosul
|
|
stdc_bit_widthui stdc_leading_zerosull
|
|
stdc_bit_widthul stdc_leading_zerosus
|
|
stdc_bit_widthull stdc_trailing_ones
|
|
stdc_bit_widthus stdc_trailing_onesuc
|
|
stdc_count_ones stdc_trailing_onesui
|
|
stdc_count_onesuc stdc_trailing_onesul
|
|
stdc_count_onesui stdc_trailing_onesull
|
|
stdc_count_onesul stdc_trailing_onesus
|
|
stdc_count_onesull stdc_trailing_zeros
|
|
stdc_count_onesus stdc_trailing_zerosuc
|
|
stdc_count_zeros stdc_trailing_zerosui
|
|
stdc_count_zerosuc stdc_trailing_zerosul
|
|
stdc_count_zerosui stdc_trailing_zerosull
|
|
stdc_count_zerosul stdc_trailing_zerosus
|
|
stdc_count_zerosull strcat
|
|
stdc_count_zerosus strcat_s
|
|
stdc_first_leading_one strchr
|
|
stdc_first_leading_oneuc strcmp
|
|
stdc_first_leading_oneui strcoll
|
|
stdc_first_leading_oneul strcpy
|
|
stdc_first_leading_oneull strcpy_s
|
|
stdc_first_leading_oneus strcspn
|
|
stdc_first_leading_zero strdup
|
|
stdc_first_leading_zerouc strerror
|
|
stdc_first_leading_zeroui strerrorlen_s
|
|
stdc_first_leading_zeroul strerror_s
|
|
stdc_first_leading_zeroull strfromd
|
|
stdc_first_leading_zerous strfromd128
|
|
stdc_first_trailing_one strfromd32
|
|
stdc_first_trailing_oneuc strfromd64
|
|
stdc_first_trailing_oneui strfromencbind
|
|
stdc_first_trailing_oneul strfromencdecd
|
|
stdc_first_trailing_oneull strfromencf
|
|
stdc_first_trailing_oneus strfromencf128
|
|
stdc_first_trailing_zero strfromf
|
|
stdc_first_trailing_zerouc strfroml
|
|
stdc_first_trailing_zeroui strftime
|
|
stdc_first_trailing_zeroul strlen
|
|
stdc_first_trailing_zeroull strncat
|
|
stdc_first_trailing_zerous strncat_s
|
|
stdc_has_single_bit strncmp
|
|
strncpy totalordermagd
|
|
strncpy_s totalordermagd128
|
|
strndup totalordermagd32
|
|
strnlen_s totalordermagd64
|
|
strpbrk totalordermagf
|
|
strrchr totalordermagl
|
|
strspn toupper
|
|
strstr towctrans
|
|
strto towlower
|
|
strtod towupper
|
|
strtod128 tss_create
|
|
strtod32 tss_delete
|
|
strtod64 tss_dtor_t
|
|
strtoencbind tss_get
|
|
strtoencdecd tss_set
|
|
strtoencf tss_t
|
|
strtof UINT16_C
|
|
strtoimax UINT16_MAX
|
|
strtok uint16_t
|
|
strtok_s UINT16_WIDTH
|
|
strtol UINT32_C
|
|
strtold UINT32_MAX
|
|
strtoll uint32_t
|
|
strtoul UINT32_WIDTH
|
|
strtoull UINT64_C
|
|
strtoumax UINT64_MAX
|
|
struct uint64_t
|
|
strxfrm UINT64_WIDTH
|
|
thrd_busy UINT8_C
|
|
thrd_create UINT8_MAX
|
|
thrd_current uint8_t
|
|
thrd_detach UINT8_WIDTH
|
|
thrd_equal UINTMAX_C
|
|
thrd_error UINTMAX_MAX
|
|
thrd_exit uintmax_t
|
|
thrd_join UINTMAX_WIDTH
|
|
thrd_nomem UINTPTR_MAX
|
|
thrd_sleep uintptr_t
|
|
thrd_start_t UINTPTR_WIDTH
|
|
thrd_success uint_fast16_t
|
|
thrd_t uint_fast32_t
|
|
thrd_timedout uint_fast64_t
|
|
thrd_yield uint_fast8_t
|
|
TIME_ACTIVE uint_least16_t
|
|
TIME_MONOTONIC uint_least32_t
|
|
TIME_THREAD_ACTIVE uint_least64_t
|
|
TIME_UTC uint_least8_t
|
|
tolower UINT_MAX
|
|
totalorder UINT_WIDTH
|
|
totalorderd wcscat
|
|
totalorderd128 wcscat_s
|
|
totalorderd32 wcschr
|
|
totalorderd64 wcscmp
|
|
totalorderf wcscoll
|
|
totalorderl wcscpy
|
|
totalordermag wcscpy_s
|
|
wcscspn _Float128_t
|
|
wcsftime _Float16
|
|
wcslen _Float16_t
|
|
wcsncat _Float32
|
|
wcsncat_s _Float32x
|
|
wcsncmp _Float32_t
|
|
wcsncpy _Float64
|
|
wcsncpy_s _Float64x
|
|
wcsnlen_s _Float64_t
|
|
wcspbrk _Generic
|
|
wcsrchr _Imaginary
|
|
wcsrtombs _Imaginary_I
|
|
wcsrtombs_s _IOFBF
|
|
wcsspn _IOLBF
|
|
wcsstr _IONBF
|
|
wcsto _MANT_DIG
|
|
wcstod _MAX_10_EXP
|
|
wcstod128 _MAX_EXP
|
|
wcstod32 _MIN_10_EXP
|
|
wcstod64 _MIN_EXP
|
|
wcstof _Noreturn
|
|
wcstoimax _Pragma
|
|
wcstok _PRINTF_NAN_LEN_MAX
|
|
wcstok_s _SNAN
|
|
wcstol _Static_assert
|
|
wcstold _Thread_local
|
|
wcstoll _TRUE_MIN
|
|
wcstombs __alignas_is_defined
|
|
wcstombs_s __alignof_is_defined
|
|
wcstoul __bool_true_false_are_defined
|
|
wcstoull __cplusplus
|
|
wcstoumax __DATE__
|
|
wcsxfrm __deprecated__
|
|
_Alignas __fallthrough__
|
|
_Alignof __FILE__
|
|
_Atomic __func__
|
|
_BitInt __has_c_attribute
|
|
_Bool __has_embed
|
|
_Complex __has_include
|
|
_Complex_I __if_empty__
|
|
_Decimal __limit__
|
|
_Decimal128 __LINE__
|
|
_Decimal128x __maybe_unused__
|
|
_Decimal32 __nodiscard__
|
|
_Decimal32_t __noreturn__
|
|
_Decimal64 __pp_param__
|
|
_Decimal64x __prefix__
|
|
_Decimal64_t __reproducible__
|
|
_DECIMAL_DIG __STDC_ANALYZABLE__
|
|
_DIG __STDC_ENDIAN_BIG__
|
|
_EPSILON __STDC_ENDIAN_LITTLE__
|
|
_Exit __STDC_ENDIAN_NATIVE__
|
|
_EXT__ __STDC_HOSTED__
|
|
_Float __STDC_IEC_559_COMPLEX__
|
|
_Float128 __STDC_IEC_559__
|
|
_Float128x __STDC_IEC_60559_BFP__
|
|
__STDC_IEC_60559_COMPLEX__ __STDC_VERSION_STDLIB_H__
|
|
__STDC_IEC_60559_DFP__ __STDC_VERSION_TGMATH_H__
|
|
__STDC_IEC_60559_TYPES__ __STDC_VERSION_TIME_H__
|
|
__STDC_ISO_10646__ __STDC_VERSION__
|
|
__STDC_LIB_EXT1__ __STDC_WANT_IEC_60559_
|
|
__STDC_MB_MIGHT_NEQ_WC__ __STDC_WANT_IEC_60559_EXT__
|
|
__STDC_NO_ATOMICS__ __STDC_WANT_IEC_60559_TYPES_EXT__
|
|
__STDC_NO_COMPLEX__ __STDC_WANT_LIB_EXT1__
|
|
__STDC_NO_THREADS__ __STDC__
|
|
__STDC_NO_VLA__ __suffix__
|
|
__STDC_UTF_16__ __TIME__
|
|
__STDC_UTF_32__ __unsequenced__
|
|
__STDC_VERSION_FENV_H__ __VA_ARGS__
|
|
__STDC_VERSION_MATH_H__ __VA_OPT__
|
|
__STDC_VERSION_STDINT_H__ ___Noreturn__
|
|
|
|
|
|
</pre>
|
|
<a name='J.6.2'></a>
|
|
<hr>
|
|
<h3>J.6.2 [Particular identifiers or keywords]</h3>
|
|
<a name='J.6.2p1'></a>
|
|
<pre>1 The following 1358 identifiers or keywords are not covered by the above and have particular
|
|
semantics provided by this document.
|
|
|
|
abort_handler_s asind atand
|
|
abort asinf atanf
|
|
abs asinhd128 atanhd128
|
|
acosd128 asinhd32 atanhd32
|
|
acosd32 asinhd64 atanhd64
|
|
acosd64 asinhd atanhd
|
|
acosd asinhf atanhf
|
|
acosf asinhl atanhl
|
|
acoshd128 asinh atanh
|
|
acoshd32 asinl atanl
|
|
acoshd64 asinpid128 atanpid128
|
|
acoshd asinpid32 atanpid32
|
|
acoshf asinpid64 atanpid64
|
|
acoshl asinpid atanpid
|
|
acosh asinpif atanpif
|
|
acosl asinpil atanpil
|
|
acospid128 asinpi atanpi
|
|
acospid32 asin atan
|
|
acospid64 assert atexit
|
|
acospid atan2d128 atof
|
|
acospif atan2d32 atoi
|
|
acospil atan2d64 atoll
|
|
acospi atan2d atol
|
|
acos atan2f at_quick_exit
|
|
addd atan2l auto
|
|
addf atan2pid128 bitand
|
|
alignas atan2pid32 BITINT_MAXWIDTH
|
|
aligned_alloc atan2pid64 bitor
|
|
alignof atan2pid BOOL_MAX
|
|
and_eq atan2pif BOOL_WIDTH
|
|
and atan2pil bool
|
|
asctime_s atan2pi break
|
|
asctime atan2 bsearch_s
|
|
asind128 atand128 bsearch
|
|
asind32 atand32 btowc
|
|
asind64 atand64 BUFSIZ
|
|
c16rtomb ceild32 compoundnl
|
|
c32rtomb ceild64 compoundn
|
|
c8rtomb ceild conjf
|
|
cabsf ceilf conjl
|
|
cabsl ceill conj
|
|
cabs ceil constexpr
|
|
cacosf cerfc constraint_handler_t
|
|
cacoshf cerf const
|
|
cacoshl cexp10m1 continue
|
|
cacosh cexp10 copysignd128
|
|
cacosl cexp2m1 copysignd32
|
|
cacospi cexp2 copysignd64
|
|
cacos cexpf copysignd
|
|
calloc cexpl copysignf
|
|
call_once cexpm1 copysignl
|
|
canonicalized128 cexp copysign
|
|
canonicalized32 char16_t cosd128
|
|
canonicalized64 char32_t cosd32
|
|
canonicalized char8_t cosd64
|
|
canonicalizef CHAR_BIT cosd
|
|
canonicalizel CHAR_MAX cosf
|
|
canonicalize CHAR_MIN coshd128
|
|
cargf CHAR_WIDTH coshd32
|
|
cargl char coshd64
|
|
carg cimagf coshd
|
|
case cimagl coshf
|
|
casinf cimag coshl
|
|
casinhf ckd_add cosh
|
|
casinhl ckd_div cosl
|
|
casinh ckd_mul cospid128
|
|
casinl ckd_sub cospid32
|
|
casinpi ckd_ cospid64
|
|
casin clearerr cospid
|
|
catanf clgamma cospif
|
|
catanhf CLOCKS_PER_SEC cospil
|
|
catanhl clock_t cospi
|
|
catanh clock cos
|
|
catanl clog10p1 cpowf
|
|
catanpi clog10 cpowl
|
|
catan clog1p cpown
|
|
cbrtd128 clog2p1 cpowr
|
|
cbrtd32 clog2 cpow
|
|
cbrtd64 clogf cprojf
|
|
cbrtd clogl cprojl
|
|
cbrtf clogp1 cproj
|
|
cbrtl clog crealf
|
|
cbrt CMPLXF creall
|
|
ccompoundn CMPLXL creal
|
|
ccosf CMPLX CR_DECIMAL_DIG
|
|
ccoshf complex csinf
|
|
ccoshl compl csinhf
|
|
ccosh compoundnd128 csinhl
|
|
ccosl compoundnd32 csinh
|
|
ccospi compoundnd64 csinl
|
|
ccos compoundnd csinpi
|
|
ceild128 compoundnf csin
|
|
csqrtf decodebind64 erfcl
|
|
csqrtl decodebind erfc
|
|
csqrt decodebin erfd128
|
|
ctanf decodedecd128 erfd32
|
|
ctanhf decodedecd32 erfd64
|
|
ctanhl decodedecd64 erfd
|
|
ctanh decodedecd erff
|
|
ctanl decodedec erfl
|
|
ctanpi decodef erf
|
|
ctan DEC errno_t
|
|
ctgamma DEFAULT errno
|
|
ctime_s defined error
|
|
ctime define exit
|
|
currency_symbol deprecated exp10d128
|
|
CX_LIMITED_RANGE dfmal exp10d32
|
|
d32addd128 dfma exp10d64
|
|
d32addd64 difftime exp10d
|
|
d32add divd exp10f
|
|
d32divd128 divf exp10l
|
|
d32divd64 div_t exp10m1d128
|
|
d32div div exp10m1d32
|
|
d32fmad128 dmull exp10m1d64
|
|
d32fmad64 dmul exp10m1d
|
|
d32fma double_t exp10m1f
|
|
d32muld128 double exp10m1l
|
|
d32muld64 do exp10m1
|
|
d32mul dsqrtl exp10
|
|
d32sqrtd128 dsqrt exp2d128
|
|
d32sqrtd64 dsubl exp2d32
|
|
d32sqrt dsub exp2d64
|
|
d32subd128 elifdef exp2d
|
|
d32subd64 elifndef exp2f
|
|
d32sub elif exp2l
|
|
d64addd128 else exp2m1d128
|
|
d64add embed exp2m1d32
|
|
d64divd128 encbind exp2m1d64
|
|
d64div encdecd exp2m1d
|
|
d64fmad128 encf exp2m1f
|
|
d64fma encodebind128 exp2m1l
|
|
d64muld128 encodebind32 exp2m1
|
|
d64mul encodebind64 exp2
|
|
d64sqrtd128 encodebind expd128
|
|
d64sqrt encodebin expd32
|
|
d64subd128 encodedecd128 expd64
|
|
d64sub encodedecd32 expd
|
|
daddl encodedecd64 expf
|
|
dadd encodedecd expl
|
|
ddivl encodedec expm1d128
|
|
ddiv encodef expm1d32
|
|
DECIMAL_DIG endif expm1d64
|
|
decimal_point enum expm1d
|
|
Decimal erfcd128 expm1f
|
|
DECN_ erfcd32 expm1l
|
|
DECN erfcd64 expm1
|
|
decodebind128 erfcd exp
|
|
decodebind32 erfcf extern
|
|
fabsd128 float_t fmind64
|
|
fabsd32 Float fmind
|
|
fabsd64 floord128 fminf
|
|
fabsd floord32 fminimumd128
|
|
fabsf floord64 fminimumd32
|
|
fabsl floord fminimumd64
|
|
fabs floorf fminimumd
|
|
faddl floorl fminimumf
|
|
fadd floor fminimuml
|
|
fallthrough FLTN_ fminimum_magd128
|
|
false FLTN fminimum_magd32
|
|
fclose FLT fminimum_magd64
|
|
fdimd128 fmad128 fminimum_magd
|
|
fdimd32 fmad32 fminimum_magf
|
|
fdimd64 fmad64 fminimum_magl
|
|
fdimd fmad fminimum_mag_numd128
|
|
fdimf fmaf fminimum_mag_numd32
|
|
fdiml fmal fminimum_mag_numd64
|
|
fdim fmaxd128 fminimum_mag_numd
|
|
fdivl fmaxd32 fminimum_mag_numf
|
|
fdiv fmaxd64 fminimum_mag_numl
|
|
feclearexcept fmaxd fminimum_mag_num
|
|
fegetenv fmaxf fminimum_mag
|
|
fegetexceptflag fmaximumd128 fminimum_numd128
|
|
fegetmode fmaximumd32 fminimum_numd32
|
|
fegetround fmaximumd64 fminimum_numd64
|
|
feholdexcept fmaximumd fminimum_numd
|
|
femode_t fmaximumf fminimum_numf
|
|
FENV_ACCESS fmaximuml fminimum_numl
|
|
FENV_DEC_ROUND fmaximum_magd128 fminimum_num
|
|
FENV_ROUND fmaximum_magd32 fminimum
|
|
fenv_t fmaximum_magd64 fminl
|
|
feof fmaximum_magd fmin
|
|
feraiseexcept fmaximum_magf fmodd128
|
|
ferror fmaximum_magl fmodd32
|
|
fesetenv fmaximum_mag_numd128 fmodd64
|
|
fesetexceptflag fmaximum_mag_numd32 fmodd
|
|
fesetexcept fmaximum_mag_numd64 fmodf
|
|
fesetmode fmaximum_mag_numd fmodl
|
|
fesetround fmaximum_mag_numf fmod
|
|
fetestexceptflag fmaximum_mag_numl fmull
|
|
fetestexcept fmaximum_mag_num fmul
|
|
feupdateenv fmaximum_mag FOPEN_MAX
|
|
fexcept_t fmaximum_numd128 fopen_s
|
|
fe_dec_getround fmaximum_numd32 fopen
|
|
fe_dec_setround fmaximum_numd64 for
|
|
fflush fmaximum_numd fpclassify
|
|
ffmal fmaximum_numf fpos_t
|
|
ffma fmaximum_numl fprintf_s
|
|
fgetc fmaximum_num fprintf
|
|
fgetpos fmaximum fputc
|
|
fgets fmaxl fputs
|
|
fgetwc fmax fputwc
|
|
fgetws fma fputws
|
|
FILENAME_MAX fmind128 frac_digits
|
|
FILE fmind32 fread
|
|
free_aligned_sized gets ldexpd32
|
|
free_sized getwchar ldexpd64
|
|
free getwc ldexpd
|
|
freopen_s gmtime_r ldexpf
|
|
freopen gmtime_s ldexpl
|
|
frexpd128 gmtime ldexp
|
|
frexpd32 goto ldiv_t
|
|
frexpd64 grouping ldiv
|
|
frexpd HUGE_VALF lgammad128
|
|
frexpf HUGE_VALL lgammad32
|
|
frexpl HUGE_VAL_D128 lgammad64
|
|
frexp HUGE_VAL_D32 lgammad
|
|
fromfpd128 HUGE_VAL_D64 lgammaf
|
|
fromfpd32 HUGE_VAL_D lgammal
|
|
fromfpd64 HUGE_VAL_F lgamma
|
|
fromfpd HUGE_VAL limit
|
|
fromfpf hypotd128 line
|
|
fromfpl hypotd32 llabs
|
|
fromfpxd128 hypotd64 lldiv_t
|
|
fromfpxd32 hypotd lldiv
|
|
fromfpxd64 hypotf llogbd128
|
|
fromfpxd hypotl llogbd32
|
|
fromfpxf hypot llogbd64
|
|
fromfpxl ifdef llogbd
|
|
fromfpx ifndef llogbf
|
|
fromfp if_empty llogbl
|
|
fscanf_s if llogb
|
|
fscanf ignore_handler_s LLONG_MAX
|
|
fseek ilogbd128 LLONG_MIN
|
|
fsetpos ilogbd32 LLONG_WIDTH
|
|
fsqrtl ilogbd64 llquantexpd128
|
|
fsqrt ilogbd llquantexpd32
|
|
fsubl ilogbf llquantexpd64
|
|
fsub ilogbl llquantexpd
|
|
ftell ilogb llquantexp
|
|
fwide imaginary llrintd128
|
|
fwprintf_s imaxabs llrintd32
|
|
fwprintf imaxdiv_t llrintd64
|
|
fwrite imaxdiv llrintd
|
|
fwscanf_s include llrintf
|
|
fwscanf INFINITY llrintl
|
|
generic_count_type inline llrint
|
|
generic_return_type int_curr_symbol llroundd128
|
|
generic_value_type int_frac_digits llroundd32
|
|
getchar int_n_cs_precedes llroundd64
|
|
getc int_n_sep_by_space llroundd
|
|
getenv_s int_n_sign_posn llroundf
|
|
getenv int_p_cs_precedes llroundl
|
|
getpayloadd128 int_p_sep_by_space llround
|
|
getpayloadd32 int_p_sign_posn localeconv
|
|
getpayloadd64 I localtime_r
|
|
getpayloadd jmp_buf localtime_s
|
|
getpayloadf kill_dependency localtime
|
|
getpayloadl labs log10d128
|
|
getpayload lconv log10d32
|
|
gets_s ldexpd128 log10d64
|
|
log10d LONG_MIN nanf
|
|
log10f LONG_WIDTH nanl
|
|
log10l long nan
|
|
log10p1d128 lrintd128 NDEBUG
|
|
log10p1d32 lrintd32 nearbyintd128
|
|
log10p1d64 lrintd64 nearbyintd32
|
|
log10p1d lrintd nearbyintd64
|
|
log10p1f lrintf nearbyintd
|
|
log10p1l lrintl nearbyintf
|
|
log10p1 lrint nearbyintl
|
|
log10 lroundd128 nearbyint
|
|
log1pd128 lroundd32 negative_sign
|
|
log1pd32 lroundd64 nextafterd128
|
|
log1pd64 lroundd nextafterd32
|
|
log1pd lroundf nextafterd64
|
|
log1pf lroundl nextafterd
|
|
log1pl lround nextafterf
|
|
log1p L_tmpnam_s nextafterl
|
|
log2d128 L_tmpnam nextafter
|
|
log2d32 main nextdownd128
|
|
log2d64 malloc nextdownd32
|
|
log2d math_errhandling nextdownd64
|
|
log2f max_align_t nextdownd
|
|
log2l maybe_unused nextdownf
|
|
log2p1d128 mblen nextdownl
|
|
log2p1d32 mbrlen nextdown
|
|
log2p1d64 mbrtoc16 nexttowardd128
|
|
log2p1d mbrtoc32 nexttowardd32
|
|
log2p1f mbrtoc8 nexttowardd64
|
|
log2p1l mbrtowc nexttowardf
|
|
log2p1 mbsinit nexttowardl
|
|
log2 mbsrtowcs_s nexttoward
|
|
logbd128 mbsrtowcs nextupd128
|
|
logbd32 mbstate_t nextupd32
|
|
logbd64 mbstowcs_s nextupd64
|
|
logbd mbstowcs nextupd
|
|
logbf mbtowc nextupf
|
|
logbl MB_CUR_MAX nextupl
|
|
logb MB_LEN_MAX nextup
|
|
logd128 mktime nodiscard
|
|
logd32 modfd128 noreturn
|
|
logd64 modfd32 not_eq
|
|
logd modfd64 not
|
|
logf modfd nullptr_t
|
|
logl modff nullptr
|
|
logp1d128 modfl NULL
|
|
logp1d32 modf n_cs_precedes
|
|
logp1d64 mon_decimal_point n_sep_by_space
|
|
logp1d mon_grouping n_sign_posn
|
|
logp1f mon_thousands_sep N
|
|
logp1l muld offsetof
|
|
logp1 mulf OFF
|
|
log nand128 ONCE_FLAG_INIT
|
|
longjmp nand32 once_flag
|
|
long_double_t nand64 ON
|
|
LONG_MAX nand or_eq
|
|
or QWchar_t rsqrtf
|
|
perror raise rsqrtl
|
|
positive_sign RAND_MAX rsqrt
|
|
powd128 rand samequantumd128
|
|
powd32 realloc samequantumd32
|
|
powd64 register samequantumd64
|
|
powd remainderd128 samequantumd
|
|
powf remainderd32 samequantum
|
|
powl remainderd64 scalblnd128
|
|
pownd128 remainderd scalblnd32
|
|
pownd32 remainderf scalblnd64
|
|
pownd64 remainderl scalblnd
|
|
pownd remainder scalblnf
|
|
pownf remove scalblnl
|
|
pownl remquof scalbln
|
|
pown remquol scalbnd128
|
|
powrd128 remquo scalbnd32
|
|
powrd32 rename scalbnd64
|
|
powrd64 reproducible scalbnd
|
|
powrd restrict scalbnf
|
|
powrf return scalbnl
|
|
powrl rewind scalbn
|
|
powr rintd128 scanf_s
|
|
pow rintd32 scanf
|
|
pp_param rintd64 SCHAR_MAX
|
|
pragma rintd SCHAR_MIN
|
|
prefix rintf SCHAR_WIDTH
|
|
printf_s rintl SEEK_CUR
|
|
printf rint SEEK_END
|
|
PTRDIFF_MAX rootnd128 SEEK_SET
|
|
PTRDIFF_MIN rootnd32 setbuf
|
|
ptrdiff_t rootnd64 setjmp
|
|
PTRDIFF_WIDTH rootnd setlocale
|
|
putchar rootnf setpayloadd128
|
|
putc rootnl setpayloadd32
|
|
puts rootn setpayloadd64
|
|
putwchar roundd128 setpayloadd
|
|
putwc roundd32 setpayloadf
|
|
p_cs_precedes roundd64 setpayloadl
|
|
p_sep_by_space roundd setpayloadsigd128
|
|
p_sign_posn roundevend128 setpayloadsigd32
|
|
QChar roundevend32 setpayloadsigd64
|
|
qsort_s roundevend64 setpayloadsigd
|
|
qsort roundevend setpayloadsigf
|
|
quantized128 roundevenf setpayloadsigl
|
|
quantized32 roundevenl setpayloadsig
|
|
quantized64 roundeven setpayload
|
|
quantized roundf setvbuf
|
|
quantize roundl set_constraint_handler_s
|
|
quantumd128 round short
|
|
quantumd32 RSIZE_MAX SHRT_MAX
|
|
quantumd64 rsize_t SHRT_MIN
|
|
quantumd rsqrtd128 SHRT_WIDTH
|
|
quantum rsqrtd32 signal
|
|
quick_exit rsqrtd64 signbit
|
|
QVoid rsqrtd signed
|
|
sig_atomic_t tand128 truncf
|
|
sind128 tand32 truncl
|
|
sind32 tand64 trunc
|
|
sind64 tand TSS_DTOR_ITERATIONS
|
|
sind tanf tv_nsec
|
|
sinf tanhd128 tv_sec
|
|
sinhd128 tanhd32 typedef
|
|
sinhd32 tanhd64 typeof_unqual
|
|
sinhd64 tanhd typeof
|
|
sinhd tanhf UCHAR_MAX
|
|
sinhf tanhl UCHAR_WIDTH
|
|
sinhl tanh ufromfpd128
|
|
sinh tanl ufromfpd32
|
|
sinl tanpid128 ufromfpd64
|
|
sinpid128 tanpid32 ufromfpd
|
|
sinpid32 tanpid64 ufromfpf
|
|
sinpid64 tanpid ufromfpl
|
|
sinpid tanpif ufromfpxd128
|
|
sinpif tanpil ufromfpxd32
|
|
sinpil tanpi ufromfpxd64
|
|
sinpi tan ufromfpxd
|
|
sin tgammad128 ufromfpxf
|
|
sizeof tgammad32 ufromfpxl
|
|
SIZE_MAX tgammad64 ufromfpx
|
|
size_t tgammad ufromfp
|
|
SIZE_WIDTH tgammaf ULLONG_MAX
|
|
snprintf_s tgammal ULLONG_WIDTH
|
|
snprintf tgamma ULONG_MAX
|
|
snwprintf_s thousands_sep ULONG_WIDTH
|
|
sprintf_s thread_local undef
|
|
sprintf timespec_getres ungetc
|
|
sqrtd128 timespec_get ungetwc
|
|
sqrtd32 timespec union
|
|
sqrtd64 time_t unreachable
|
|
sqrtd time unsequenced
|
|
sqrtf tmpfile_s unsigned
|
|
sqrtl tmpfile USHRT_MAX
|
|
sqrt tmpnam_s USHRT_WIDTH
|
|
srand tmpnam va_arg
|
|
sscanf_s TMP_MAX_S va_copy
|
|
sscanf TMP_MAX va_end
|
|
static_assert tm_hour va_list
|
|
static tm_isdst va_start
|
|
STDC tm_mday vfprintf_s
|
|
stderr tm_min vfprintf
|
|
stdin tm_mon vfscanf_s
|
|
stdout tm_sec vfscanf
|
|
subd tm_wday vfwprintf_s
|
|
subf tm_yday vfwprintf
|
|
suffix tm_year vfwscanf_s
|
|
switch tm vfwscanf
|
|
swprintf_s true void
|
|
swprintf truncd128 volatile
|
|
swscanf_s truncd32 vprintf_s
|
|
swscanf truncd64 vprintf
|
|
system truncd vscanf_s
|
|
vscanf wctomb xdivf
|
|
vsnprintf_s wctrans_t xfmad
|
|
vsnprintf wctrans xfmaf
|
|
vsnwprintf_s wctype_t xmuld
|
|
vsprintf_s wctype xmulf
|
|
vsprintf WEOF xor_eq
|
|
vsscanf_s while xor
|
|
vsscanf WINT_MAX xsqrtd
|
|
vswprintf_s WINT_MIN xsqrtf
|
|
vswprintf wint_t xsubd
|
|
vswscanf_s WINT_WIDTH xsubf
|
|
vswscanf wmemchr X_DECIMAL_DIG
|
|
vwprintf_s wmemcmp X_DIG
|
|
vwprintf wmemcpy_s X_EPSILON
|
|
vwscanf_s wmemcpy X_MANT_DIG
|
|
vwscanf wmemmove_s X_MAX_10_EXP
|
|
warning wmemmove X_MAX_EXP
|
|
WCHAR_MAX wmemset X_MAX
|
|
WCHAR_MIN wprintf_s X_MIN_10_EXP
|
|
wchar_t wprintf X_MIN_EXP
|
|
WCHAR_WIDTH wscanf_s X_MIN
|
|
wcrtomb_s wscanf X_SNAN
|
|
wcrtomb xaddd X_TRUE_MIN
|
|
wctob xaddf X_
|
|
wctomb_s xdivd
|
|
|
|
|
|
</pre>
|
|
<a name='J.6.3'></a>
|
|
<hr>
|
|
<h3>J.6.3 [Type inference]</h3>
|
|
<a name='J.6.3p1'></a>
|
|
<pre>1 A declaration for which a type is inferred (<a href='#6.7.9'>6.7.9</a>) may additionally accept pointer declarators, function
|
|
declarators, and may have more than one declarator.
|
|
|
|
</pre>
|
|
<a name='K.'></a>
|
|
<hr>
|
|
<h3>K. [Annex K (normative) Bounds-checking interfaces]</h3>
|
|
<a name='K.1'></a>
|
|
<hr>
|
|
<h3>K.1 [Background]</h3>
|
|
<a name='K.1p1'></a>
|
|
<pre>1 Traditionally, the C Library has contained many functions that trust the programmer to provide
|
|
output character arrays big enough to hold the result being produced. Not only do these functions
|
|
not check that the arrays are big enough, they frequently lack the information needed to perform
|
|
such checks. While it is possible to write safe, robust, and error-free code using the existing library,
|
|
the library tends to promote programming styles that lead to mysterious failures if a result is too big
|
|
for the provided array.
|
|
</pre>
|
|
<a name='K.1p2'></a>
|
|
<pre>2 A common programming style is to declare character arrays large enough to handle most practical
|
|
cases. However, if these arrays are not large enough to handle the resulting strings, data can be
|
|
written past the end of the array overwriting other data and program structures. The program never
|
|
gets any indication that a problem exists, and so never has a chance to recover or to fail gracefully.
|
|
</pre>
|
|
<a name='K.1p3'></a>
|
|
<pre>3 Worse, this style of programming has compromised the security of computers and networks. Buffer
|
|
overflows can often be exploited to run arbitrary code with the permissions of the vulnerable
|
|
(defective) program.
|
|
</pre>
|
|
<a name='K.1p4'></a>
|
|
<pre>4 If the programmer writes runtime checks to verify lengths before calling library functions, then
|
|
those runtime checks frequently duplicate work done inside the library functions, which discover
|
|
string lengths as a side effect of doing their job.
|
|
</pre>
|
|
<a name='K.1p5'></a>
|
|
<pre>5 This annex provides alternative library functions that promote safer, more secure programming. The
|
|
alternative functions verify that output buffers are large enough for the intended result and return a
|
|
failure indicator if they are not. Data is never written past the end of an array. All string results are
|
|
null terminated.
|
|
</pre>
|
|
<a name='K.1p6'></a>
|
|
<pre>6 This annex also addresses another problem that complicates writing robust code: functions that are
|
|
not reentrant because they return pointers to static objects owned by the function. Such functions
|
|
can be troublesome since a previously returned result can change if the function is called again,
|
|
perhaps by another thread.
|
|
|
|
</pre>
|
|
<a name='K.2'></a>
|
|
<hr>
|
|
<h3>K.2 [Scope]</h3>
|
|
<a name='K.2p1'></a>
|
|
<pre>1 This annex specifies a series of optional extensions that can be useful in the mitigation of security
|
|
vulnerabilities in programs, and comprise new functions, macros, and types declared or defined in
|
|
existing standard headers.
|
|
</pre>
|
|
<a name='K.2p2'></a>
|
|
<pre>2 An implementation that defines __STDC_LIB_EXT1__ shall conform to the specifications in this
|
|
annex.<a href='#FOOTNOTE.465'><sup>[465]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.465'>
|
|
<pre><i><b>Footnote 465)</b> Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these specifications.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.2p3'></a>
|
|
<pre>3 Subclause <a href='#K.3'>K.3</a> should be read as if it were merged into the parallel structure of named subclauses of
|
|
Clause 7.
|
|
|
|
</pre>
|
|
<a name='K.3'></a>
|
|
<hr>
|
|
<h3>K.3 [Library]</h3>
|
|
<a name='K.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.1 [Introduction]</h3>
|
|
<a name='K.3.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.1.1 [Standard headers]</h3>
|
|
<a name='K.3.1.1p1'></a>
|
|
<pre>1 The functions, macros, and types declared or defined in <a href='#K.3'>K.3</a> and its subclauses are not declared
|
|
or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is defined as a macro which
|
|
expands to the integer constant 0 at the point in the source file where the appropriate header is first
|
|
included.
|
|
</pre>
|
|
<a name='K.3.1.1p2'></a>
|
|
<pre>2 The functions, macros, and types declared or defined in <a href='#K.3'>K.3</a> and its subclauses are declared and
|
|
defined by their respective headers if __STDC_WANT_LIB_EXT1__ is defined as a macro which ex-
|
|
pands to the integer constant 1 at the point in the source file where the appropriate header is first
|
|
included.<a href='#FOOTNOTE.466'><sup>[466]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.466'>
|
|
<pre><i><b>Footnote 466)</b> Future revisions of this document might define meanings for other values of __STDC_WANT_LIB_EXT1__ .
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.1.1p3'></a>
|
|
<pre>3 It is implementation-defined whether the functions, macros, and types declared or defined in <a href='#K.3'>K.3</a> and
|
|
its subclauses are declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is not
|
|
defined as a macro at the point in the source file where the appropriate header is first included.<a href='#FOOTNOTE.467'><sup>[467]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.467'>
|
|
<pre><i><b>Footnote 467)</b> Subclause <a href='#7.1.3'>7.1.3</a> reserves certain names and patterns of names that an implementation can use in headers. All other names
|
|
are not reserved, and a conforming implementation is not permitted to use them. While some of the names defined in <a href='#K.3'>K.3</a> and
|
|
its subclauses are reserved, others are not. If an unreserved name is defined in a header when __STDC_WANT_LIB_EXT1__ is
|
|
defined as 0, the implementation is not conforming.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.1.1p4'></a>
|
|
<pre>4 Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be defined identically for
|
|
all inclusions of any headers from Subclause <a href='#K.3'>K.3</a>. If __STDC_WANT_LIB_EXT1__ is defined differently
|
|
for any such inclusion, the implementation shall issue a diagnostic as if a preprocessor error directive
|
|
were used.
|
|
|
|
</pre>
|
|
<a name='K.3.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.1.2 [Reserved identifiers]</h3>
|
|
<a name='K.3.1.2p1'></a>
|
|
<pre>1 Each macro name in any of the following subclauses is reserved for use as specified if it is defined
|
|
by any of its associated headers when included; unless explicitly stated otherwise (see <a href='#7.1.4'>7.1.4</a>).
|
|
</pre>
|
|
<a name='K.3.1.2p2'></a>
|
|
<pre>2 All identifiers with external linkage in any of the following subclauses are reserved for use as
|
|
identifiers with external linkage if any of them are used by the program. None of them are reserved
|
|
if none of them are used.
|
|
</pre>
|
|
<a name='K.3.1.2p3'></a>
|
|
<pre>3 Each identifier with file scope listed in any of the following subclauses is reserved for use as a
|
|
macro name and as an identifier with file scope in the same name space if it is defined by any of its
|
|
associated headers when included.
|
|
|
|
</pre>
|
|
<a name='K.3.1.3'></a>
|
|
<hr>
|
|
<h3>K.3.1.3 [Use of errno]</h3>
|
|
<a name='K.3.1.3p1'></a>
|
|
<pre>1 An implementation may set errno for the functions defined in this annex, but is not required to.
|
|
|
|
</pre>
|
|
<a name='K.3.1.4'></a>
|
|
<hr>
|
|
<h3>K.3.1.4 [Runtime-constraint violations]</h3>
|
|
<a name='K.3.1.4p1'></a>
|
|
<pre>1 Most functions in this annex include as part of their specification a list of runtime-constraints. These
|
|
runtime-constraints are requirements on the program using the library.<a href='#FOOTNOTE.468'><sup>[468]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.468'>
|
|
<pre><i><b>Footnote 468)</b> Although runtime-constraints replace many cases of undefined behavior, undefined behavior still exists in this annex.
|
|
Implementations are free to detect any case of undefined behavior and treat it as a runtime-constraint violation by calling the
|
|
runtime-constraint handler. This license comes directly from the definition of undefined behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.1.4p2'></a>
|
|
<pre>2 Implementations shall verify that the runtime-constraints for a function are not violated by the
|
|
program. If a runtime-constraint is violated, the implementation shall call the currently registered
|
|
runtime-constraint handler (see set_constraint_handler_s in <stdlib.h>). Multiple runtime-
|
|
constraint violations in the same call to a library function result in only one call to the runtime-
|
|
constraint handler. It is unspecified which one of the multiple runtime-constraint violations cause
|
|
the handler to be called.
|
|
</pre>
|
|
<a name='K.3.1.4p3'></a>
|
|
<pre>3 If the runtime-constraints section for a function states an action to be performed when a runtime-
|
|
constraint violation occurs, the function shall perform the action before calling the runtime-constraint
|
|
handler. If the runtime-constraints section lists actions that are prohibited when a runtime-constraint
|
|
violation occurs, then such actions are prohibited to the function both before calling the handler and
|
|
after the handler returns.
|
|
</pre>
|
|
<a name='K.3.1.4p4'></a>
|
|
<pre>4 The runtime-constraint handler might not return. If the handler does return, the library function
|
|
whose runtime-constraint was violated shall return some indication of failure as given by the returns
|
|
section in the function’s specification.
|
|
|
|
</pre>
|
|
<a name='K.3.2'></a>
|
|
<hr>
|
|
<h3>K.3.2 [Errors <errno.h>]</h3>
|
|
<a name='K.3.2p1'></a>
|
|
<pre>1 The header <errno.h> defines a type.
|
|
</pre>
|
|
<a name='K.3.2p2'></a>
|
|
<pre>2 The type is
|
|
|
|
errno_t
|
|
which is type int.<a href='#FOOTNOTE.469'><sup>[469]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.469'>
|
|
<pre><i><b>Footnote 469)</b> As a matter of programming style, errno_t can be used as the type of something that deals only with the values that
|
|
might be found in errno. For example, a function which returns the value of errno could be declared as having the return
|
|
type errno_t.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.3'></a>
|
|
<hr>
|
|
<h3>K.3.3 [Common definitions <stddef.h>]</h3>
|
|
<a name='K.3.3p1'></a>
|
|
<pre>1 The header <stddef.h> defines a type.
|
|
</pre>
|
|
<a name='K.3.3p2'></a>
|
|
<pre>2 The type is
|
|
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t.<a href='#FOOTNOTE.470'><sup>[470]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.470'>
|
|
<pre><i><b>Footnote 470)</b> See the description of the RSIZE_MAX macro in <stdint.h>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.4'></a>
|
|
<hr>
|
|
<h3>K.3.4 [Integer types <stdint.h>]</h3>
|
|
<a name='K.3.4p1'></a>
|
|
<pre>1 The header <stdint.h> defines a macro.
|
|
</pre>
|
|
<a name='K.3.4p2'></a>
|
|
<pre>2 The macro is
|
|
|
|
RSIZE_MAX
|
|
|
|
|
|
which expands to a value<a href='#FOOTNOTE.471'><sup>[471]</sup></a> of type size_t. Functions that have parameters of type rsize_t con-
|
|
sider it a runtime-constraint violation if the values of those parameters are greater than RSIZE_MAX.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.471'>
|
|
<pre><i><b>Footnote 471)</b> The macro RSIZE_MAX need not expand to a constant expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.4p3'></a>
|
|
<pre>3 Extremely large object sizes are frequently a sign that an object’s size was calculated incorrectly. For
|
|
example, negative numbers appear as very large positive numbers when converted to an unsigned
|
|
type like size_t. Also, some implementations do not support objects as large as the maximum
|
|
value that can be represented by type size_t.
|
|
</pre>
|
|
<a name='K.3.4p4'></a>
|
|
<pre>4 For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect programming
|
|
errors. For implementations targeting machines with large address spaces, it is recommended that
|
|
RSIZE_MAX be defined as the smaller of the size of the largest object supported or (SIZE_MAX >> 1) ,
|
|
even if this limit is smaller than the size of some legitimate, but very large, objects. Implementations
|
|
targeting machines with small address spaces may wish to define RSIZE_MAX as SIZE_MAX, which
|
|
means that there is no object size that is considered a runtime-constraint violation.
|
|
|
|
</pre>
|
|
<a name='K.3.5'></a>
|
|
<hr>
|
|
<h3>K.3.5 [Input/output <stdio.h>]</h3>
|
|
<a name='K.3.5p1'></a>
|
|
<pre>1 The header <stdio.h> defines several macros and two types.
|
|
</pre>
|
|
<a name='K.3.5p2'></a>
|
|
<pre>2 The macros are
|
|
|
|
L_tmpnam_s
|
|
|
|
|
|
which expands to an integer constant expression that is the size needed for an array of char large
|
|
enough to hold a temporary file name string generated by the tmpnam_s function;
|
|
|
|
TMP_MAX_S
|
|
|
|
|
|
which expands to an integer constant expression that is the maximum number of unique file names
|
|
that can be generated by the tmpnam_s function.
|
|
</pre>
|
|
<a name='K.3.5p3'></a>
|
|
<pre>3 The types are
|
|
|
|
errno_t
|
|
|
|
|
|
which is type int; and
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t.
|
|
|
|
</pre>
|
|
<a name='K.3.5.1'></a>
|
|
<hr>
|
|
<h3>K.3.5.1 [Operations on files]</h3>
|
|
<a name='K.3.5.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.5.1.1 [The tmpfile_s function]</h3>
|
|
<a name='K.3.5.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
errno_t tmpfile_s(FILE * restrict * restrict streamptr);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.1.1p2'></a>
|
|
<pre>2 streamptr shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.1.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.1.1p4'></a>
|
|
<pre>4 The tmpfile_s function creates a temporary binary file that is different from any other existing file
|
|
and that will automatically be removed when it is closed or at program termination. If the program
|
|
terminates abnormally, whether an open temporary file is removed is implementation-defined. The
|
|
file is opened for update with "wb+" mode with the meaning that mode has in the fopen_s function
|
|
(including the mode’s effect on exclusive access and file permissions).
|
|
</pre>
|
|
<a name='K.3.5.1.1p5'></a>
|
|
<pre>5 If the file was created successfully, then the pointer to FILE pointed to by streamptr will be set to
|
|
the pointer to the object controlling the opened file. Otherwise, the pointer to FILE pointed to by
|
|
streamptr will be set to a null pointer.
|
|
|
|
Recommended practice
|
|
It should be possible to open at least TMP_MAX_S temporary files during the lifetime of the program
|
|
(this limit may be shared with tmpnam_s) and there should be no limit on the number simultaneously
|
|
open other than this limit and any limit on the number of open files (FOPEN_MAX).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.1.1p6'></a>
|
|
<pre>6 The tmpfile_s function returns zero if it created the file. If it did not create the file or there was a
|
|
runtime-constraint violation, tmpfile_s returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='K.3.5.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.5.1.2 [The tmpnam_s function]</h3>
|
|
<a name='K.3.5.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
errno_t tmpnam_s(char *s, rsize_t maxsize);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.1.2p2'></a>
|
|
<pre>2 s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX. maxsize shall be
|
|
greater than the length of the generated file name string.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.1.2p3'></a>
|
|
<pre>3 The tmpnam_s function generates a string that is a valid file name and that is not the same as the
|
|
name of an existing file.<a href='#FOOTNOTE.472'><sup>[472]</sup></a> The function is potentially capable of generating TMP_MAX_S different
|
|
strings, but any or all of them may already be in use by existing files and thus not be suitable return
|
|
values. The lengths of these strings shall be less than the value of the L_tmpnam_s macro.
|
|
</pre>
|
|
<a name='FOOTNOTE.472'>
|
|
<pre><i><b>Footnote 472)</b> Files created using strings generated by the tmpnam_s function are temporary only in the sense that their names are not
|
|
expected to collide with those generated by conventional naming rules for the implementation. It is still necessary to use the
|
|
remove function to remove such files when their use is ended, and before program termination.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.1.2p4'></a>
|
|
<pre>4 The tmpnam_s function generates a different string each time it is called.
|
|
</pre>
|
|
<a name='K.3.5.1.2p5'></a>
|
|
<pre>5 It is assumed that s points to an array of at least maxsize characters. This array will be set to
|
|
generated string, as specified below.
|
|
</pre>
|
|
<a name='K.3.5.1.2p6'></a>
|
|
<pre>6 The implementation shall behave as if no library function except tmpnam calls the tmpnam_s func-
|
|
tion.<a href='#FOOTNOTE.473'><sup>[473]</sup></a>
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.473'>
|
|
<pre><i><b>Footnote 473)</b> An implementation can have tmpnam call tmpnam_s (perhaps so there is only one naming convention for temporary files),
|
|
but this is not required.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.1.2p7'></a>
|
|
<pre>7 After a program obtains a file name using the tmpnam_s function and before the program creates a
|
|
file with that name, the possibility exists that someone else may create a file with that same name.
|
|
To avoid this race condition, the tmpfile_s function should be used instead of tmpnam_s when
|
|
possible. One situation that requires the use of the tmpnam_s function is when the program needs to
|
|
create a temporary directory rather than a temporary file.
|
|
</pre>
|
|
<a name='K.3.5.1.2p8'></a>
|
|
<pre>8 Implementations should take care in choosing the patterns used for names returned by tmpnam_s.
|
|
For example, making a thread ID part of the names avoids the race condition and possible conflict
|
|
when multiple programs run simultaneously by the same user generate the same temporary file
|
|
names.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.1.2p9'></a>
|
|
<pre>9 If no suitable string can be generated, or if there is a runtime-constraint violation, the tmpnam_s
|
|
function:
|
|
|
|
— if s is not null and maxsize is both greater than zero and not greater than RSIZE_MAX, writes a
|
|
null character to s[0]
|
|
— returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='K.3.5.1.2p10'></a>
|
|
<pre>10 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and returns zero.
|
|
|
|
Environmental limits
|
|
</pre>
|
|
<a name='K.3.5.1.2p11'></a>
|
|
<pre>11 The value of the macro TMP_MAX_S shall be at least 25.
|
|
|
|
</pre>
|
|
<a name='K.3.5.2'></a>
|
|
<hr>
|
|
<h3>K.3.5.2 [File access functions]</h3>
|
|
<a name='K.3.5.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.5.2.1 [The fopen_s function]</h3>
|
|
<a name='K.3.5.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
errno_t fopen_s(FILE * restrict * restrict streamptr,
|
|
const char * restrict filename, const char * restrict mode);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.2.1p2'></a>
|
|
<pre>2 None of streamptr, filename, or mode shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.2.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, fopen_s does not attempt to open a file. Furthermore, if
|
|
streamptr is not a null pointer, fopen_s sets *streamptr to the null pointer.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.2.1p4'></a>
|
|
<pre>4 The fopen_s function opens the file whose name is the string pointed to by filename, and associates
|
|
a stream with it.
|
|
</pre>
|
|
<a name='K.3.5.2.1p5'></a>
|
|
<pre>5 The mode string shall be as described for fopen, with the addition that modes starting with the
|
|
character ’w’ or ’a’ may be preceded by the character ’u’ , see below:
|
|
uw truncate to zero length or create text file for writing, default permissions
|
|
uwx create text file for writing, default permissions
|
|
ua append; open or create text file for writing at end-of-file, default permissions
|
|
uwb truncate to zero length or create binary file for writing, default permissions
|
|
uwbx create binary file for writing, default permissions
|
|
uab append; open or create binary file for writing at end-of-file, default permissions
|
|
uw+ truncate to zero length or create text file for update, default permissions
|
|
uw+x create text file for update, default permissions
|
|
ua+ append; open or create text file for update, writing at end-of-file, default permis-
|
|
sions
|
|
uw+b or uwb+ truncate to zero length or create binary file for update, default permissions
|
|
uw+bx or uwb+x create binary file for update, default permissions
|
|
|
|
ua+b or uab+ append; open or create binary file for update, writing at end-of-file, default permis-
|
|
sions
|
|
|
|
</pre>
|
|
<a name='K.3.5.2.1p6'></a>
|
|
<pre>6 Opening a file with exclusive mode (’x’ as the last character in the mode argument) fails if the file
|
|
already exists or cannot be created.
|
|
</pre>
|
|
<a name='K.3.5.2.1p7'></a>
|
|
<pre>7 To the extent that the underlying system supports the concepts, files opened for writing shall be
|
|
opened with exclusive (also known as non-shared) access. If the file is being created, and the first
|
|
character of the mode string is not ’u’ , to the extent that the underlying system supports it, the file
|
|
shall have a file permission that prevents other users on the system from accessing the file. If the
|
|
file is being created and first character of the mode string is ’u’ , then by the time the file has been
|
|
closed, it shall have the system default file access permissions.<a href='#FOOTNOTE.474'><sup>[474]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.474'>
|
|
<pre><i><b>Footnote 474)</b> These are the same permissions that the file would have been created with by fopen.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.2.1p8'></a>
|
|
<pre>8 If the file was opened successfully, then the pointer to FILE pointed to by streamptr will be set to
|
|
the pointer to the object controlling the opened file. Otherwise, the pointer to FILE pointed to by
|
|
streamptr will be set to a null pointer.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.2.1p9'></a>
|
|
<pre>9 The fopen_s function returns zero if it opened the file. If it did not open the file or if there was a
|
|
runtime-constraint violation, fopen_s returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='K.3.5.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.5.2.2 [The freopen_s function]</h3>
|
|
<a name='K.3.5.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
errno_t freopen_s(FILE * restrict * restrict newstreamptr,
|
|
const char * restrict filename, const char * restrict mode,
|
|
FILE * restrict stream);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.2.2p2'></a>
|
|
<pre>2 None of newstreamptr, mode, and stream shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.2.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, freopen_s neither attempts to close any file associated with
|
|
stream nor attempts to open a file. Furthermore, if newstreamptr is not a null pointer, fopen_s
|
|
sets *newstreamptr to the null pointer.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.2.2p4'></a>
|
|
<pre>4 The freopen_s function opens the file whose name is the string pointed to by filename and
|
|
associates the stream pointed to by stream with it. The mode argument has the same meaning as in
|
|
the fopen_s function (including the mode’s effect on exclusive access and file permissions).
|
|
</pre>
|
|
<a name='K.3.5.2.2p5'></a>
|
|
<pre>5 If filename is a null pointer, the freopen_s function attempts to change the mode of the stream
|
|
to that specified by mode, as if the name of the file currently associated with the stream had been
|
|
used. It is implementation-defined which changes of mode are permitted (if any), and under what
|
|
circumstances.
|
|
</pre>
|
|
<a name='K.3.5.2.2p6'></a>
|
|
<pre>6 The freopen_s function first attempts to close any file that is associated with stream. Failure to
|
|
close the file is ignored. The error and end-of-file indicators for the stream are cleared.
|
|
</pre>
|
|
<a name='K.3.5.2.2p7'></a>
|
|
<pre>7 If the file was opened successfully, then the pointer to FILE pointed to by newstreamptr will be set
|
|
to the value of stream. Otherwise, the pointer to FILE pointed to by newstreamptr will be set to a
|
|
null pointer.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.2.2p8'></a>
|
|
<pre>8 The freopen_s function returns zero if it opened the file. If it did not open the file or there was a
|
|
runtime-constraint violation, freopen_s returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3'></a>
|
|
<hr>
|
|
<h3>K.3.5.3 [Formatted input/output functions]</h3>
|
|
<a name='K.3.5.3p1'></a>
|
|
<pre>1 Unless explicitly stated otherwise, if the execution of a function described in this subclause causes
|
|
copying to take place between objects that overlap, the objects take on unspecified values.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.1 [The fprintf_s function]</h3>
|
|
<a name='K.3.5.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int fprintf_s(FILE * restrict stream, const char * restrict format, ...);
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.1p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. The %n specifier<a href='#FOOTNOTE.475'><sup>[475]</sup></a> (modified or not by flags,
|
|
field width, or precision) shall not appear in the string pointed to by format. Any argument to
|
|
fprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.475'>
|
|
<pre><i><b>Footnote 475)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the<a href='#FOOTNOTE.476'><sup>[476]</sup></a> fprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent fprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
Description
|
|
</pre>
|
|
<a name='FOOTNOTE.476'>
|
|
<pre><i><b>Footnote 476)</b> Because an implementation can treat any undefined behavior as a runtime-constraint violation, an implementation can
|
|
treat any unsupported specifiers in the string pointed to by format as a runtime-constraint violation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.1p4'></a>
|
|
<pre>4 The fprintf_s function is equivalent to the fprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.1p5'></a>
|
|
<pre>5 The fprintf_s function returns the number of characters transmitted, or a negative value if an
|
|
output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.2'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.2 [The fscanf_s function]</h3>
|
|
<a name='K.3.5.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int fscanf_s(FILE * restrict stream, const char * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.2p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. Any argument indirected though in order to
|
|
store converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the<a href='#FOOTNOTE.477'><sup>[477]</sup></a> fscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent fscanf_s performed input before discovering the
|
|
runtime-constraint violation.
|
|
Description
|
|
</pre>
|
|
<a name='FOOTNOTE.477'>
|
|
<pre><i><b>Footnote 477)</b> Because an implementation can treat any undefined behavior as a runtime-constraint violation, an implementation can
|
|
treat any unsupported specifiers in the string pointed to by format as a runtime-constraint violation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.2p4'></a>
|
|
<pre>4 The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion specifiers
|
|
apply to a pair of arguments (unless assignment suppression is indicated by a *). The first of these
|
|
arguments is the same as for fscanf. That argument is immediately followed in the argument list
|
|
by the second argument, which has type rsize_t and gives the number of elements in the array
|
|
pointed to by the first argument of the pair. If the first argument points to a scalar object, it is
|
|
considered to be an array of one element.<a href='#FOOTNOTE.478'><sup>[478]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.478'>
|
|
<pre><i><b>Footnote 478)</b> If the format is known at translation time, an implementation can issue a diagnostic for any argument used to store
|
|
the result from a c, s, or [ conversion specifier if that argument is not followed by an argument of a type compatible with
|
|
rsize_t. A limited amount of checking can be done if even if the format is not known at translation time. For example, an
|
|
implementation could issue a diagnostic for each argument after format that has of type pointer to one of char, signed char,
|
|
unsigned char, or void that is not followed by an argument of a type compatible with rsize_t. The diagnostic could warn
|
|
that unless the pointer is being used with a conversion specifier using the hh length modifier, a length argument is expected
|
|
to follow the pointer argument. Another useful diagnostic could flag any non-pointer argument following format that did
|
|
not have a type compatible with rsize_t.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.2p5'></a>
|
|
<pre>5 A matching failure occurs if the number of elements in a receiving object is insufficient to hold the
|
|
converted input (including any trailing null character).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.2p6'></a>
|
|
<pre>6 The fscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the fscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
</pre>
|
|
<a name='K.3.5.3.2p7'></a>
|
|
<pre>7 EXAMPLE 1 The call:
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int n, i; float x; char name[50];
|
|
n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
|
|
|
|
|
|
with the input line:
|
|
|
|
25 54.32E-1 thompson
|
|
|
|
|
|
will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0.
|
|
</pre>
|
|
<a name='K.3.5.3.2p8'></a>
|
|
<pre>8 EXAMPLE 2 The call:
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
/* ... */
|
|
int n; char s[5];
|
|
n = fscanf_s(stdin, "%s", s, sizeof s);
|
|
|
|
|
|
with the input line:
|
|
|
|
hello
|
|
|
|
|
|
will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an array of six characters
|
|
to store it.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.3'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.3 [The printf_s function]</h3>
|
|
<a name='K.3.5.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int printf_s(const char * restrict format, ...);
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.3p2'></a>
|
|
<pre>2 format shall not be a null pointer. The %n specifier<a href='#FOOTNOTE.479'><sup>[479]</sup></a> (modified or not by flags, field width,
|
|
or precision) shall not appear in the string pointed to by format. Any argument to printf_s
|
|
corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.479'>
|
|
<pre><i><b>Footnote 479)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.3p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the printf_s function does not attempt to produce further
|
|
output, and it is unspecified to what extent printf_s produced output before discovering the
|
|
runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.3p4'></a>
|
|
<pre>4 The printf_s function is equivalent to the printf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.3p5'></a>
|
|
<pre>5 The printf_s function returns the number of characters transmitted, or a negative value if an
|
|
output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.4'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.4 [The scanf_s function]</h3>
|
|
<a name='K.3.5.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int scanf_s(const char * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.4p2'></a>
|
|
<pre>2 format shall not be a null pointer. Any argument indirected though in order to store converted
|
|
input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.4p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the scanf_s function does not attempt to perform further
|
|
input, and it is unspecified to what extent scanf_s performed input before discovering the runtime-
|
|
constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.4p4'></a>
|
|
<pre>4 The scanf_s function is equivalent to fscanf_s with the argument stdin interposed before the
|
|
arguments to scanf_s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.4p5'></a>
|
|
<pre>5 The scanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the scanf_s function returns the
|
|
number of input items assigned, which can be fewer than provided for, or even zero, in the event of
|
|
an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.5'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.5 [The snprintf_s function]</h3>
|
|
<a name='K.3.5.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int snprintf_s(char * restrict s, rsize_t n, const char * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.5p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX.
|
|
The %n specifier<a href='#FOOTNOTE.480'><sup>[480]</sup></a> (modified or not by flags, field width, or precision) shall not appear in the string
|
|
pointed to by format. Any argument to snprintf_s corresponding to a %s specifier shall not be a
|
|
null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.480'>
|
|
<pre><i><b>Footnote 480)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.5p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX, then the snprintf_s function sets s[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.5p4'></a>
|
|
<pre>4 The snprintf_s function is equivalent to the snprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.5.3.5p5'></a>
|
|
<pre>5 The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the array pointed
|
|
to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.5p6'></a>
|
|
<pre>6 The snprintf_s function returns the number of characters that would have been written had n
|
|
been sufficiently large, not counting the terminating null character, or a negative value if a runtime-
|
|
constraint violation occurred. Thus, the null-terminated output has been completely written if and
|
|
only if the returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.6'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.6 [The sprintf_s function]</h3>
|
|
<a name='K.3.5.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int sprintf_s(char * restrict s, rsize_t n, const char * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.6p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX.
|
|
The number of characters (including the trailing null) required for the result to be written to the
|
|
array pointed to by s shall not be greater than n. The %n specifier<a href='#FOOTNOTE.481'><sup>[481]</sup></a> (modified or not by flags,
|
|
field width, or precision) shall not appear in the string pointed to by format. Any argument to
|
|
sprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.481'>
|
|
<pre><i><b>Footnote 481)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.6p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX, then the sprintf_s function sets s[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.6p4'></a>
|
|
<pre>4 The sprintf_s function is equivalent to the sprintf function except for the parameter n and the
|
|
explicit runtime-constraints listed above.
|
|
</pre>
|
|
<a name='K.3.5.3.6p5'></a>
|
|
<pre>5 The sprintf_s function, unlike snprintf_s, treats a result too big for the array pointed to by s as a
|
|
runtime-constraint violation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.6p6'></a>
|
|
<pre>6 If no runtime-constraint violation occurred, the sprintf_s function returns the number of characters
|
|
written in the array, not counting the terminating null character. If an encoding error occurred,
|
|
sprintf_s returns a negative value. If any other runtime-constraint violation occurred, sprintf_s
|
|
returns zero.
|
|
</pre>
|
|
<a name='K.3.5.3.7'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.7 [The sscanf_s function]</h3>
|
|
<a name='K.3.5.3.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
int sscanf_s(const char * restrict s, const char * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.7p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. Any argument indirected though in order to store
|
|
converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.7p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the sscanf_s function does not attempt to perform further
|
|
input, and it is unspecified to what extent sscanf_s performed input before discovering the runtime-
|
|
constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.7p4'></a>
|
|
<pre>4 The sscanf_s function is equivalent to fscanf_s, except that input is obtained from a string
|
|
(specified by the argument s) rather than from a stream. Reaching the end of the string is equivalent
|
|
to encountering end-of-file for the fscanf_s function. If copying takes place between objects that
|
|
overlap, the objects take on unspecified values.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.7p5'></a>
|
|
<pre>5 The sscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the sscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.8'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.8 [The vfprintf_s function]</h3>
|
|
<a name='K.3.5.3.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vfprintf_s(FILE *restrict stream, const char *restrict format, va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.8p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. The %n specifier<a href='#FOOTNOTE.482'><sup>[482]</sup></a> (modified or not by flags,
|
|
field width, or precision) shall not appear in the string pointed to by format. Any argument to
|
|
vfprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.482'>
|
|
<pre><i><b>Footnote 482)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.8p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vfprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent vfprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.8p4'></a>
|
|
<pre>4 The vfprintf_s function is equivalent to the vfprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.8p5'></a>
|
|
<pre>5 The vfprintf_s function returns the number of characters transmitted, or a negative value if an
|
|
output error, encoding error, or runtime-constraint violation occurred.
|
|
</pre>
|
|
<a name='K.3.5.3.9'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.9 [The vfscanf_s function]</h3>
|
|
<a name='K.3.5.3.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vfscanf_s(FILE *restrict stream, const char *restrict format, va_list arg);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.9p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. Any argument indirected though in order to
|
|
store converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.9p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vfscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent vfscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.9p4'></a>
|
|
<pre>4 The vfscanf_s function is equivalent to fscanf_s, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vfscanf_s function does not invoke the va_end macro.<a href='#FOOTNOTE.483'><sup>[483]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.483'>
|
|
<pre><i><b>Footnote 483)</b> As the functions vfprintf_s , vfscanf_s , vprintf_s , vscanf_s , vsnprintf_s , vsprintf_s , and vsscanf_s invoke
|
|
the va_arg macro, the representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.9p5'></a>
|
|
<pre>5 The vfscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vfscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.10'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.10 [The vprintf_s function]</h3>
|
|
<a name='K.3.5.3.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vprintf_s(const char * restrict format, va_list arg);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.10p2'></a>
|
|
<pre>2 format shall not be a null pointer. The %n specifier<a href='#FOOTNOTE.484'><sup>[484]</sup></a> (modified or not by flags, field width,
|
|
or precision) shall not appear in the string pointed to by format. Any argument to vprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.484'>
|
|
<pre><i><b>Footnote 484)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.10p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent vprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.10p4'></a>
|
|
<pre>4 The vprintf_s function is equivalent to the vprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.10p5'></a>
|
|
<pre>5 The vprintf_s function returns the number of characters transmitted, or a negative value if an
|
|
output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.11'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.11 [The vscanf_s function]</h3>
|
|
<a name='K.3.5.3.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vscanf_s(const char * restrict format, va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.11p2'></a>
|
|
<pre>2 format shall not be a null pointer. Any argument indirected though in order to store converted
|
|
input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.11p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vscanf_s function does not attempt to perform further
|
|
input, and it is unspecified to what extent vscanf_s performed input before discovering the runtime-
|
|
constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.11p4'></a>
|
|
<pre>4 The vscanf_s function is equivalent to scanf_s, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vscanf_s function does not invoke the va_end macro<a href='#FOOTNOTE.485'><sup>[485]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.485'>
|
|
<pre><i><b>Footnote 485)</b> As the functions vfprintf_s , vfscanf_s , vprintf_s , vscanf_s , vsnprintf_s , vsprintf_s , and vsscanf_s invoke
|
|
the va_arg macro, the representation of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.11p5'></a>
|
|
<pre>5 The vscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.12'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.12 [The vsnprintf_s function]</h3>
|
|
<a name='K.3.5.3.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsnprintf_s(char *restrict s, rsize_t n, const char *restrict format,
|
|
va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.12p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX.
|
|
The %n specifier<a href='#FOOTNOTE.486'><sup>[486]</sup></a> (modified or not by flags, field width, or precision) shall not appear in the string
|
|
pointed to by format. Any argument to vsnprintf_s corresponding to a %s specifier shall not be a
|
|
null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.486'>
|
|
<pre><i><b>Footnote 486)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.12p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.12p4'></a>
|
|
<pre>4 The vsnprintf_s function is equivalent to the vsnprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.5.3.12p5'></a>
|
|
<pre>5 The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within the array pointed
|
|
to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.12p6'></a>
|
|
<pre>6 The vsnprintf_s function returns the number of characters that would have been written had n
|
|
been sufficiently large, not counting the terminating null character, or a negative value if a runtime-
|
|
constraint violation occurred. Thus, the null-terminated output has been completely written if and
|
|
only if the returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.13'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.13 [The vsprintf_s function]</h3>
|
|
<a name='K.3.5.3.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsprintf_s(char * restrict s, rsize_t n, const char * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.13p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX.
|
|
The number of characters (including the trailing null) required for the result to be written to the array
|
|
pointed to by s shall not be greater than n. The %n specifier<a href='#FOOTNOTE.487'><sup>[487]</sup></a> (modified or not by flags, field width,
|
|
or precision) shall not appear in the string pointed to by format. Any argument to vsprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.487'>
|
|
<pre><i><b>Footnote 487)</b> It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format
|
|
when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.13p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX, then the vsprintf_s function sets s[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.13p4'></a>
|
|
<pre>4 The vsprintf_s function is equivalent to the vsprintf function except for the parameter n and the
|
|
explicit runtime-constraints listed above.
|
|
</pre>
|
|
<a name='K.3.5.3.13p5'></a>
|
|
<pre>5 The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array pointed to by s
|
|
as a runtime-constraint violation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.3.13p6'></a>
|
|
<pre>6 If no runtime-constraint violation occurred, the vsprintf_s function returns the number of char-
|
|
acters written in the array, not counting the terminating null character. If an encoding error oc-
|
|
curred, vsprintf_s returns a negative value. If any other runtime-constraint violation occurred,
|
|
vsprintf_s returns zero.
|
|
|
|
</pre>
|
|
<a name='K.3.5.3.14'></a>
|
|
<hr>
|
|
<h3>K.3.5.3.14 [The vsscanf_s function]</h3>
|
|
<a name='K.3.5.3.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vsscanf_s(const char *restrict s, const char *restrict format, va_list arg);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.3.14p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. Any argument indirected though in order to store
|
|
converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.5.3.14p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vsscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent vsscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.3.14p4'></a>
|
|
<pre>4 The vsscanf_s function is equivalent to sscanf_s, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vsscanf_s function does not invoke the va_end macro.<a href='#FOOTNOTE.488'><sup>[488]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.488'>
|
|
<pre><i><b>Footnote 488)</b> As the functions vfprintf_s , vfscanf_s , vprintf_s , vscanf_s , vsnprintf_s , vsprintf_s , and vsscanf_s invoke
|
|
the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.3.14p5'></a>
|
|
<pre>5 The vsscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.5.4'></a>
|
|
<hr>
|
|
<h3>K.3.5.4 [Character input/output functions]</h3>
|
|
<a name='K.3.5.4.1'></a>
|
|
<hr>
|
|
<h3>K.3.5.4.1 [The gets_s function]</h3>
|
|
<a name='K.3.5.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
char *gets_s(char *s, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.5.4.1p2'></a>
|
|
<pre>2 s shall not be a null pointer. n shall neither be equal to zero nor be greater than RSIZE_MAX. A new-
|
|
line character, end-of-file, or read error shall occur within reading n-1 characters from stdin.<a href='#FOOTNOTE.489'><sup>[489]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.489'>
|
|
<pre><i><b>Footnote 489)</b> The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for a line of input to
|
|
overflow the buffer to store it. Unlike the fgets function, gets_s maintains a one-to-one relationship between input lines
|
|
and successful calls to gets_s. Programs that use gets expect such a relationship.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.5.4.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, characters are read and discarded from stdin until a
|
|
new-line character is read, or end-of-file or a read error occurs, and if s is not a null pointer, s[0] is
|
|
set to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.5.4.1p4'></a>
|
|
<pre>4 The gets_s function reads at most one less than the number of characters specified by n from the
|
|
stream pointed to by stdin, into the array pointed to by s. No additional characters are read after a
|
|
new-line character (which is discarded) or after end-of-file. The discarded new-line character does
|
|
not count towards number of characters read. A null character is written immediately after the last
|
|
character read into the array.
|
|
</pre>
|
|
<a name='K.3.5.4.1p5'></a>
|
|
<pre>5 If end-of-file is encountered and no characters have been read into the array, or if a read error
|
|
occurs during the operation, then s[0] is set to the null character, and the other elements of s take
|
|
unspecified values.
|
|
|
|
Recommended practice
|
|
</pre>
|
|
<a name='K.3.5.4.1p6'></a>
|
|
<pre>6 The fgets function allows properly-written programs to safely process input lines too long to store
|
|
in the result array. In general this requires that callers of fgets pay attention to the presence or
|
|
absence of a new-line character in the result array. Consider using fgets (along with any needed
|
|
processing based on new-line characters) instead of gets_s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.4.1p7'></a>
|
|
<pre>7 The gets_s function returns s if successful. If there was a runtime-constraint violation, or if end-of-
|
|
file is encountered and no characters have been read into the array, or if a read error occurs during
|
|
the operation, then a null pointer is returned.
|
|
</pre>
|
|
<a name='K.3.6'></a>
|
|
<hr>
|
|
<h3>K.3.6 [General utilities <stdlib.h>]</h3>
|
|
<a name='K.3.6p1'></a>
|
|
<pre>1 The header <stdlib.h> defines three types.
|
|
</pre>
|
|
<a name='K.3.6p2'></a>
|
|
<pre>2 The types are
|
|
|
|
errno_t
|
|
|
|
|
|
which is type int; and
|
|
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t; and
|
|
|
|
constraint_handler_t
|
|
|
|
|
|
which has the following definition
|
|
|
|
typedef void (*constraint_handler_t)(
|
|
const char * restrict msg,
|
|
void * restrict ptr,
|
|
errno_t error);
|
|
|
|
|
|
</pre>
|
|
<a name='K.3.6.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.1 [Runtime-constraint handling]</h3>
|
|
<a name='K.3.6.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.1.1 [The set_constraint_handler_s function]</h3>
|
|
<a name='K.3.6.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
constraint_handler_t set_constraint_handler_s(constraint_handler_t handler);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.1.1p2'></a>
|
|
<pre>2 The set_constraint_handler_s function sets the runtime-constraint handler to be handler. The
|
|
runtime-constraint handler is the function to be called when a library function detects a runtime-
|
|
constraint violation. Only the most recent handler registered with set_constraint_handler_s is
|
|
called when a runtime-constraint violation occurs.
|
|
</pre>
|
|
<a name='K.3.6.1.1p3'></a>
|
|
<pre>3 When the handler is called, it is passed the following arguments in the following order:
|
|
|
|
1. A pointer to a character string describing the runtime-constraint violation.
|
|
2. A null pointer or a pointer to an implementation-defined object.
|
|
3. If the function calling the handler has a return type declared as errno_t, the return value of
|
|
the function is passed. Otherwise, a positive value of type errno_t is passed.
|
|
|
|
</pre>
|
|
<a name='K.3.6.1.1p4'></a>
|
|
<pre>4 The implementation has a default constraint handler that is used if no calls to the
|
|
set_constraint_handler_s function have been made. The behavior of the default handler is
|
|
implementation-defined, and it may cause the program to exit or abort.
|
|
</pre>
|
|
<a name='K.3.6.1.1p5'></a>
|
|
<pre>5 If the handler argument to set_constraint_handler_s is a null pointer, the implementation
|
|
default handler becomes the current constraint handler.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.6.1.1p6'></a>
|
|
<pre>6 The set_constraint_handler_s function returns a pointer to the previously registered handler.<a href='#FOOTNOTE.490'><sup>[490]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.490'>
|
|
<pre><i><b>Footnote 490)</b> If the previous handler was registered by calling set_constraint_handler_s with a null pointer argument, a pointer to
|
|
the implementation default handler is returned (not NULL).
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.6.1.2 [The abort_handler_s function]</h3>
|
|
<a name='K.3.6.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
void abort_handler_s(const char * restrict msg, void * restrict ptr,
|
|
errno_t error);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.1.2p2'></a>
|
|
<pre>2 A pointer to the abort_handler_s function shall be a suitable argument to the
|
|
set_constraint_handler_s function.
|
|
</pre>
|
|
<a name='K.3.6.1.2p3'></a>
|
|
<pre>3 The abort_handler_s function writes a message on the standard error stream in an implementation-
|
|
defined format. The message shall include the string pointed to by msg. The abort_handler_s
|
|
function then calls the abort function.<a href='#FOOTNOTE.491'><sup>[491]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.491'>
|
|
<pre><i><b>Footnote 491)</b> Many implementations invoke a debugger when the abort function is called.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.1.2p4'></a>
|
|
<pre>4 The abort_handler_s function does not return to its caller.
|
|
|
|
</pre>
|
|
<a name='K.3.6.1.3'></a>
|
|
<hr>
|
|
<h3>K.3.6.1.3 [The ignore_handler_s function]</h3>
|
|
<a name='K.3.6.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
void ignore_handler_s(const char * restrict msg, void * restrict ptr,
|
|
errno_t error);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.1.3p2'></a>
|
|
<pre>2 A pointer to the ignore_handler_s function shall be a suitable argument to the
|
|
set_constraint_handler_s function.
|
|
</pre>
|
|
<a name='K.3.6.1.3p3'></a>
|
|
<pre>3 The ignore_handler_s function simply returns to its caller.<a href='#FOOTNOTE.492'><sup>[492]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.492'>
|
|
<pre><i><b>Footnote 492)</b> If the runtime-constraint handler is set to the ignore_handler_s function, any library function in which a runtime-
|
|
constraint violation occurs will return to its caller. The caller can determine whether a runtime-constraint violation occurred
|
|
based on the library function’s specification (usually, the library function returns a nonzero errno_t).
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.1.3p4'></a>
|
|
<pre>4 The ignore_handler_s function returns no value.
|
|
|
|
</pre>
|
|
<a name='K.3.6.2'></a>
|
|
<hr>
|
|
<h3>K.3.6.2 [Communication with the environment]</h3>
|
|
<a name='K.3.6.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.2.1 [The getenv_s function]</h3>
|
|
<a name='K.3.6.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
errno_t getenv_s(size_t * restrict len, char * restrict value, rsize_t maxsize,
|
|
const char * restrict name);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.2.1p2'></a>
|
|
<pre>2 name shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX. If maxsize is not
|
|
equal to zero, then value shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.6.2.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len is not null),
|
|
and the environment list is not searched.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.2.1p4'></a>
|
|
<pre>4 The getenv_s function searches an environment list, provided by the host environment, for a string
|
|
that matches the string pointed to by name.
|
|
</pre>
|
|
<a name='K.3.6.2.1p5'></a>
|
|
<pre>5 If that name is found then getenv_s performs the following actions. If len is not a null pointer, the
|
|
length of the string associated with the matched list member is stored in the integer pointed to by
|
|
len. If the length of the associated string is less than maxsize, then the associated string is copied to
|
|
the array pointed to by value.
|
|
</pre>
|
|
<a name='K.3.6.2.1p6'></a>
|
|
<pre>6 If that name is not found then getenv_s performs the following actions. If len is not a null pointer,
|
|
zero is stored in the integer pointed to by len. If maxsize is greater than zero, then value[0] is set
|
|
to the null character.
|
|
</pre>
|
|
<a name='K.3.6.2.1p7'></a>
|
|
<pre>7 The set of environment names and the method for altering the environment list are implementation-
|
|
defined. The getenv_s function need not avoid data races with other threads of execution that
|
|
modify the environment list.<a href='#FOOTNOTE.493'><sup>[493]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.493'>
|
|
<pre><i><b>Footnote 493)</b> Many implementations provide non-standard functions that modify the environment list.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.2.1p8'></a>
|
|
<pre>8 The getenv_s function returns zero if the specified name is found and the associated string was
|
|
successfully stored in value. Otherwise, a nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.6.3'></a>
|
|
<hr>
|
|
<h3>K.3.6.3 [Searching and sorting utilities]</h3>
|
|
<a name='K.3.6.3p1'></a>
|
|
<pre>1 These utilities make use of a comparison function to search or sort arrays of unspecified type. Where
|
|
an argument declared as size_t nmemb specifies the length of the array for a function, if nmemb has
|
|
the value zero on a call to that function, then the comparison function is not called, a search finds no
|
|
matching element, sorting performs no rearrangement, and the pointer to the array may be null.
|
|
</pre>
|
|
<a name='K.3.6.3p2'></a>
|
|
<pre>2 The implementation shall ensure that the second argument of the comparison function (when called
|
|
from bsearch_s), or both arguments (when called from qsort_s), are pointers to elements of the
|
|
array.<a href='#FOOTNOTE.494'><sup>[494]</sup></a> The first argument when called from bsearch_s shall equal key.
|
|
</pre>
|
|
<a name='FOOTNOTE.494'>
|
|
<pre><i><b>Footnote 494)</b> That is, if the value passed is p, then the following expressions are always valid and nonzero:
|
|
((char *)p - (char *)base) % size == 0
|
|
(char *)p >= (char *)base
|
|
(char *)p < (char *)base + nmemb * size
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.3p3'></a>
|
|
<pre>3 The comparison function shall not alter the contents of either the array or search key. The implemen-
|
|
tation may reorder elements of the array between calls to the comparison function, but shall not
|
|
otherwise alter the contents of any individual element.
|
|
</pre>
|
|
<a name='K.3.6.3p4'></a>
|
|
<pre>4 When the same objects (consisting of size bytes, irrespective of their current positions in the array)
|
|
are passed more than once to the comparison function, the results shall be consistent with one
|
|
another. That is, for qsort_s they shall define a total ordering on the array, and for bsearch_s the
|
|
same object shall always compare the same way with the key.
|
|
</pre>
|
|
<a name='K.3.6.3p5'></a>
|
|
<pre>5 A sequence point occurs immediately before and immediately after each call to the comparison
|
|
function, and also between any call to the comparison function and any movement of the objects
|
|
passed as arguments to that call.
|
|
|
|
</pre>
|
|
<a name='K.3.6.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.3.1 [The bsearch_s generic function]</h3>
|
|
<a name='K.3.6.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
void *bsearch_s(const void *key, QVoid *base, rsize_t nmemb, rsize_t size,
|
|
int (*compar)(const void *k, const void *y, void *context),
|
|
void *context);
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.3.1p2'></a>
|
|
<pre>2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to zero, then none of
|
|
key, base, or compar shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.6.3.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the bsearch_s function does not search the array.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.3.1p4'></a>
|
|
<pre>4 The bsearch_s function searches an array of nmemb objects, the initial element of which is pointed
|
|
to by base, for an element that matches the object pointed to by key. The size of each element of the
|
|
array is specified by size.
|
|
</pre>
|
|
<a name='K.3.6.3.1p5'></a>
|
|
<pre>5 The comparison function pointed to by compar is called with three arguments. The first two point
|
|
to the key object and to an array element, in that order. The function shall return an integer less
|
|
than, equal to, or greater than zero if the key object is considered, respectively, to be less than,
|
|
to match, or to be greater than the array element. The array shall consist of: all the elements
|
|
that compare less than, all the elements that compare equal to, and all the elements that compare
|
|
greater than the key object, in that order.<a href='#FOOTNOTE.495'><sup>[495]</sup></a> The third argument to the comparison function is the
|
|
context argument passed to bsearch_s. The sole use of context by bsearch_s is to pass it to the
|
|
comparison function.<a href='#FOOTNOTE.496'><sup>[496]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.495'>
|
|
<pre><i><b>Footnote 495)</b> In practice, this means that the entire array has been sorted according to the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.496'>
|
|
<pre><i><b>Footnote 496)</b> The context argument is for the use of the comparison function in performing its duties. For example, it might specify a
|
|
collating sequence used by the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.3.1p6'></a>
|
|
<pre>6 The bsearch_s function returns a pointer to a matching element of the array, or a null pointer if no
|
|
match is found or there is a runtime-constraint violation. If two elements compare as equal, which
|
|
element is matched is unspecified.
|
|
</pre>
|
|
<a name='K.3.6.3.1p7'></a>
|
|
<pre>7 The bsearch_s function is generic in the qualification of the type pointed to by the argument to
|
|
base. If this argument is a pointer to a const-qualified object type, the returned pointer will be a
|
|
pointer to const-qualified void. Otherwise, the argument shall be a pointer to an unqualified object
|
|
type or a null pointer constant<a href='#FOOTNOTE.497'><sup>[497]</sup></a> , and the returned pointer will be a pointer to unqualified void.
|
|
</pre>
|
|
<a name='FOOTNOTE.497'>
|
|
<pre><i><b>Footnote 497)</b> If the argument is a null pointer and the call is executed, the behavior is undefined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.3.1p8'></a>
|
|
<pre>8 The external declaration of bsearch_s has the concrete type:
|
|
|
|
void * (const void *, const void *, rsize_t, rsize_t, int (*) (const void *,
|
|
const void *), void *)
|
|
|
|
|
|
|
|
, which supports all correct uses. If a macro definition of the generic function is suppressed in order
|
|
to access an actual function, the external declaration with this concrete type is visible<a href='#FOOTNOTE.498'><sup>[498]</sup></a> .
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.498'>
|
|
<pre><i><b>Footnote 498)</b> This is an obsolescent feature.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.3.2'></a>
|
|
<hr>
|
|
<h3>K.3.6.3.2 [The qsort_s function]</h3>
|
|
<a name='K.3.6.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
|
|
int (*compar)(const void *x, const void *y, void *context),
|
|
void *context);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.3.2p2'></a>
|
|
<pre>2 Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to zero, then neither
|
|
base nor compar shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.6.3.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the qsort_s function does not sort the array.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.3.2p4'></a>
|
|
<pre>4 The qsort_s function sorts an array of nmemb objects, the initial element of which is pointed to by
|
|
base. The size of each object is specified by size.
|
|
</pre>
|
|
<a name='K.3.6.3.2p5'></a>
|
|
<pre>5 The contents of the array are sorted into ascending order according to a comparison function pointed
|
|
to by compar, which is called with three arguments. The first two point to the objects being compared.
|
|
The function shall return an integer less than, equal to, or greater than zero if the first argument is
|
|
considered to be respectively less than, equal to, or greater than the second. The third argument to
|
|
the comparison function is the context argument passed to qsort_s. The sole use of context by
|
|
qsort_s is to pass it to the comparison function<a href='#FOOTNOTE.499'><sup>[499]</sup></a> .
|
|
</pre>
|
|
<a name='FOOTNOTE.499'>
|
|
<pre><i><b>Footnote 499)</b> The context argument is for the use of the comparison function in performing its duties. For example, it might specify a
|
|
collating sequence used by the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.3.2p6'></a>
|
|
<pre>6 If two elements compare as equal, their relative order in the resulting sorted array is unspecified.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.6.3.2p7'></a>
|
|
<pre>7 The qsort_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.6.4'></a>
|
|
<hr>
|
|
<h3>K.3.6.4 [Multibyte/wide character conversion functions]</h3>
|
|
<a name='K.3.6.4p1'></a>
|
|
<pre>1 The behavior of the multibyte character functions is affected by the LC_CTYPE category of the current
|
|
locale. For a state-dependent encoding, each function is placed into its initial conversion state by a
|
|
call for which its character pointer argument, s, is a null pointer. Subsequent calls with s as other
|
|
than a null pointer cause the internal conversion state of the function to be altered as necessary. A
|
|
call with s as a null pointer causes these functions to set the int pointed to by their status argument
|
|
to a nonzero value if encodings have state dependency, and zero otherwise. <a href='#FOOTNOTE.500'><sup>[500]</sup></a>
|
|
Changing the LC_CTYPE category causes the internal object describing the conversion state of these
|
|
functions to have an indeterminate representation.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.500'>
|
|
<pre><i><b>Footnote 500)</b> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide character codes, but
|
|
are grouped with an adjacent multibyte character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.4.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.4.1 [The wctomb_s function]</h3>
|
|
<a name='K.3.6.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdlib.h>
|
|
errno_t wctomb_s(int *restrict status, char *restrict s, rsize_t smax,
|
|
wchar_t wc);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.4.1p2'></a>
|
|
<pre>2 Let n denote the number of bytes needed to represent the multibyte character corresponding to the
|
|
wide character given by wc (including any shift sequences).
|
|
</pre>
|
|
<a name='K.3.6.4.1p3'></a>
|
|
<pre>3 If s is not a null pointer, then smax shall not be less than n, and smax shall not be greater than
|
|
RSIZE_MAX. If s is a null pointer, then smax shall equal zero.
|
|
</pre>
|
|
<a name='K.3.6.4.1p4'></a>
|
|
<pre>4 If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to by status,
|
|
and if s is not a null pointer, no more than smax elements in the array pointed to by s will be
|
|
accessed.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.4.1p5'></a>
|
|
<pre>5 The wctomb_s function determines n and stores the multibyte character representation of wc in the
|
|
array whose first element is pointed to by s (if s is not a null pointer). The number of characters
|
|
stored never exceeds MB_CUR_MAX or smax. If wc is a null wide character, a null byte is stored,
|
|
preceded by any shift sequence needed to restore the initial shift state, and the function is left in the
|
|
initial conversion state.
|
|
</pre>
|
|
<a name='K.3.6.4.1p6'></a>
|
|
<pre>6 The implementation shall behave as if no library function calls the wctomb_s function.
|
|
</pre>
|
|
<a name='K.3.6.4.1p7'></a>
|
|
<pre>7 If s is a null pointer, the wctomb_s function stores into the int pointed to by status a nonzero or zero
|
|
value, if multibyte character encodings, respectively, do or do not have state-dependent encodings.
|
|
</pre>
|
|
<a name='K.3.6.4.1p8'></a>
|
|
<pre>8 If s is not a null pointer, the wctomb_s function stores into the int pointed to by status either n or
|
|
−1 if wc, respectively, does or does not correspond to a valid multibyte character.
|
|
</pre>
|
|
<a name='K.3.6.4.1p9'></a>
|
|
<pre>9 In no case will the int pointed to by status be set to a value greater than the MB_CUR_MAX macro.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.6.4.1p10'></a>
|
|
<pre>10 The wctomb_s function returns zero if successful, and a nonzero value if there was a runtime-
|
|
constraint violation or wc did not correspond to a valid multibyte character.
|
|
|
|
</pre>
|
|
<a name='K.3.6.5'></a>
|
|
<hr>
|
|
<h3>K.3.6.5 [Multibyte/wide string conversion functions]</h3>
|
|
<a name='K.3.6.5p1'></a>
|
|
<pre>1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of the current
|
|
locale.
|
|
|
|
</pre>
|
|
<a name='K.3.6.5.1'></a>
|
|
<hr>
|
|
<h3>K.3.6.5.1 [The mbstowcs_s function]</h3>
|
|
<a name='K.3.6.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
errno_t mbstowcs_s(size_t *restrict retval, wchar_t *restrict dst,
|
|
rsize_t dstmax, const char * restrict src, rsize_t len);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.5.1p2'></a>
|
|
<pre>2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then neither len nor
|
|
dstmax shall be greater than RSIZE_MAX/sizeof(wchar_t). If dst is a null pointer, then dstmax
|
|
shall equal zero. If dst is not a null pointer, then dstmax shall not equal zero. If dst is not a null
|
|
pointer and len is not less than dstmax, then a null character shall occur within the first dstmax
|
|
multibyte characters of the array pointed to by src.
|
|
</pre>
|
|
<a name='K.3.6.5.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then mbstowcs_s does the following. If retval is not
|
|
a null pointer, then mbstowcs_s sets *retval to (size_t)(-1) . If dst is not a null pointer and
|
|
dstmax is greater than zero and not greater than RSIZE_MAX/sizeof(wchar_t), then mbstowcs_s
|
|
sets dst[0] to the null wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.5.1p4'></a>
|
|
<pre>4 The mbstowcs_s function converts a sequence of multibyte characters that begins in the initial shift
|
|
state from the array pointed to by src into a sequence of corresponding wide characters. If dst is
|
|
not a null pointer, the converted characters are stored into the array pointed to by dst. Conversion
|
|
continues up to and including a terminating null character, which is also stored. Conversion stops
|
|
earlier in two cases: when a sequence of bytes is encountered that does not form a valid multibyte
|
|
character, or (if dst is not a null pointer) when len wide characters have been stored into the array
|
|
pointed to by dst.<a href='#FOOTNOTE.501'><sup>[501]</sup></a> If dst is not a null pointer and no null wide character was stored into the
|
|
array pointed to by dst, then dst[len] is set to the null wide character. Each conversion takes place
|
|
as if by a call to the mbrtowc function.
|
|
</pre>
|
|
<a name='FOOTNOTE.501'>
|
|
<pre><i><b>Footnote 501)</b> Thus, the value of len is ignored if dst is a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.5.1p5'></a>
|
|
<pre>5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a sequence of
|
|
bytes that do not form a valid multibyte character, an encoding error occurs: the mbstowcs_s func-
|
|
tion stores the value (size_t)(-1) into *retval . Otherwise, the mbstowcs_s function stores into
|
|
*retval the number of multibyte characters successfully converted, not including the terminating
|
|
null character (if any).
|
|
</pre>
|
|
<a name='K.3.6.5.1p6'></a>
|
|
<pre>6 All elements following the terminating null wide character (if any) written by mbstowcs_s in the
|
|
array of dstmax wide characters pointed to by dst take unspecified values when mbstowcs_s
|
|
returns.<a href='#FOOTNOTE.502'><sup>[502]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.502'>
|
|
<pre><i><b>Footnote 502)</b> This allows an implementation to attempt converting the multibyte string before discovering a terminating null character
|
|
did not occur where required.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.5.1p7'></a>
|
|
<pre>7 If copying takes place between objects that overlap, the objects take on unspecified values.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.6.5.1p8'></a>
|
|
<pre>8 The mbstowcs_s function returns zero if no runtime-constraint violation and no encoding error
|
|
occurred. Otherwise, a nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.6.5.2'></a>
|
|
<hr>
|
|
<h3>K.3.6.5.2 [The wcstombs_s function]</h3>
|
|
<a name='K.3.6.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
errno_t wcstombs_s(size_t * restrict retval, char * restrict dst, rsize_t dstmax,
|
|
const wchar_t * restrict src, rsize_t len);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.6.5.2p2'></a>
|
|
<pre>2 Neither retval nor src shall be a null pointer. If dst is not a null pointer, then len shall not
|
|
be greater than RSIZE_MAX/sizeof(wchar_t) and dstmax shall be nonzero and not greater than
|
|
RSIZE_MAX. If dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer and
|
|
len is not less than dstmax, then the conversion shall have been stopped (see below) because a
|
|
terminating null wide character was reached or because an encoding error occurred.
|
|
</pre>
|
|
<a name='K.3.6.5.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then wcstombs_s does the following. If retval is not
|
|
a null pointer, then wcstombs_s sets *retval to (size_t)(-1) . If dst is not a null pointer and
|
|
dstmax is greater than zero and not greater than RSIZE_MAX, then wcstombs_s sets dst[0] to the
|
|
null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.6.5.2p4'></a>
|
|
<pre>4 The wcstombs_s function converts a sequence of wide characters from the array pointed to by
|
|
src into a sequence of corresponding multibyte characters that begins in the initial shift state. If
|
|
dst is not a null pointer, the converted characters are then stored into the array pointed to by dst.
|
|
Conversion continues up to and including a terminating null wide character, which is also stored.
|
|
Conversion stops earlier in two cases:
|
|
|
|
— when a wide character is reached that does not correspond to a valid multibyte character;
|
|
— (if dst is not a null pointer) when the next multibyte character would exceed the limit of n
|
|
total bytes to be stored into the array pointed to by dst. If the wide character being converted
|
|
is the null wide character, then n is the lesser of len or dstmax. Otherwise, n is the lesser of
|
|
len or dstmax-1.
|
|
|
|
If the conversion stops without converting a null wide character and dst is not a null pointer, then
|
|
a null character is stored into the array pointed to by dst immediately following any multibyte
|
|
characters already stored. Each conversion takes place as if by a call to the wcrtomb function.<a href='#FOOTNOTE.503'><sup>[503]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.503'>
|
|
<pre><i><b>Footnote 503)</b> If conversion stops because a terminating null wide character has been reached, the bytes stored include those necessary
|
|
to reach the initial shift state immediately before the null byte. However, if the conversion stops before a terminating null
|
|
wide character has been reached, the result will be null terminated, but might not end in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.5.2p5'></a>
|
|
<pre>5 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a wide
|
|
character that does not correspond to a valid multibyte character, an encoding error occurs: the
|
|
wcstombs_s function stores the value (size_t)(-1) into *retval . Otherwise, the wcstombs_s
|
|
function stores into *retval the number of bytes in the resulting multibyte character sequence, not
|
|
including the terminating null character (if any).
|
|
</pre>
|
|
<a name='K.3.6.5.2p6'></a>
|
|
<pre>6 All elements following the terminating null character (if any) written by wcstombs_s in the array of
|
|
dstmax elements pointed to by dst take unspecified values when wcstombs_s returns.<a href='#FOOTNOTE.504'><sup>[504]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.504'>
|
|
<pre><i><b>Footnote 504)</b> When len is not less than dstmax, the implementation might fill the array before discovering a runtime-constraint
|
|
violation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.6.5.2p7'></a>
|
|
<pre>7 If copying takes place between objects that overlap, the objects take on unspecified values.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.6.5.2p8'></a>
|
|
<pre>8 The wcstombs_s function returns zero if no runtime-constraint violation and no encoding error
|
|
occurred. Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='K.3.7'></a>
|
|
<hr>
|
|
<h3>K.3.7 [String handling <string.h>]</h3>
|
|
<a name='K.3.7p1'></a>
|
|
<pre>1 The header <string.h> defines two types.
|
|
</pre>
|
|
<a name='K.3.7p2'></a>
|
|
<pre>2 The types are
|
|
|
|
errno_t
|
|
|
|
|
|
which is type int; and
|
|
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t.
|
|
|
|
</pre>
|
|
<a name='K.3.7.1'></a>
|
|
<hr>
|
|
<h3>K.3.7.1 [Copying functions]</h3>
|
|
<a name='K.3.7.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.7.1.1 [The memcpy_s function]</h3>
|
|
<a name='K.3.7.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t memcpy_s(void * restrict s1, rsize_t s1max, const void * restrict s2,
|
|
rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.1.1p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n
|
|
shall not be greater than s1max. Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='K.3.7.1.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first s1max
|
|
characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than
|
|
RSIZE_MAX.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.1.1p4'></a>
|
|
<pre>4 The memcpy_s function copies n characters from the object pointed to by s2 into the object pointed
|
|
to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.1.1p5'></a>
|
|
<pre>5 The memcpy_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.7.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.7.1.2 [The memmove_s function]</h3>
|
|
<a name='K.3.7.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t memmove_s(void *s1, rsize_t s1max, const void *s2, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.1.2p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n
|
|
shall not be greater than s1max.
|
|
</pre>
|
|
<a name='K.3.7.1.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the memmove_s function stores zeros in the first s1max
|
|
characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than
|
|
RSIZE_MAX.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.1.2p4'></a>
|
|
<pre>4 The memmove_s function copies n characters from the object pointed to by s2 into the object pointed
|
|
to by s1. This copying takes place as if the n characters from the object pointed to by s2 are first
|
|
copied into a temporary array of n characters that does not overlap the objects pointed to by s1 or
|
|
s2, and then the n characters from the temporary array are copied into the object pointed to by s1.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.1.2p5'></a>
|
|
<pre>5 The memmove_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
</pre>
|
|
<a name='K.3.7.1.3'></a>
|
|
<hr>
|
|
<h3>K.3.7.1.3 [The strcpy_s function]</h3>
|
|
<a name='K.3.7.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t strcpy_s(char * restrict s1, rsize_t s1max, const char * restrict s2);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.1.3p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall
|
|
not equal zero. s1max shall be greater than strnlen_s(s2, s1max). Copying shall not take place
|
|
between objects that overlap.
|
|
</pre>
|
|
<a name='K.3.7.1.3p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.1.3p4'></a>
|
|
<pre>4 The strcpy_s function copies the string pointed to by s2 (including the terminating null character)
|
|
into the array pointed to by s1.
|
|
</pre>
|
|
<a name='K.3.7.1.3p5'></a>
|
|
<pre>5 All elements following the terminating null character (if any) written by strcpy_s in the array of
|
|
s1max characters pointed to by s1 take unspecified values when strcpy_s returns.<a href='#FOOTNOTE.505'><sup>[505]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.505'>
|
|
<pre><i><b>Footnote 505)</b> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if any of those characters
|
|
are null. Such an approach might write a character to every element of s1 before discovering that the first element was set to
|
|
the null character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.1.3p6'></a>
|
|
<pre>6 The strcpy_s function returns zero<a href='#FOOTNOTE.506'><sup>[506]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.506'>
|
|
<pre><i><b>Footnote 506)</b> A zero return value implies that all of the requested characters from the string pointed to by s2 fit within the array
|
|
pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.1.4'></a>
|
|
<hr>
|
|
<h3>K.3.7.1.4 [The strncpy_s function]</h3>
|
|
<a name='K.3.7.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t strncpy_s(char * restrict s1, rsize_t s1max, const char * restrict s2,
|
|
rsize_t n);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.1.4p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX.
|
|
s1max shall not equal zero. If n is not less than s1max, then s1max shall be greater than
|
|
strnlen_s(s2, s1max). Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='K.3.7.1.4p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.1.4p4'></a>
|
|
<pre>4 The strncpy_s function copies not more than n successive characters (characters that follow a null
|
|
character are not copied) from the array pointed to by s2 to the array pointed to by s1. If no null
|
|
character was copied from s2, then s1[n] is set to a null character.
|
|
</pre>
|
|
<a name='K.3.7.1.4p5'></a>
|
|
<pre>5 All elements following the terminating null character (if any) written by strncpy_s in the array
|
|
of s1max characters pointed to by s1 take unspecified values when strncpy_s returns a nonzero
|
|
value.<a href='#FOOTNOTE.507'><sup>[507]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.507'>
|
|
<pre><i><b>Footnote 507)</b> This allows an implementation to copy characters from s2 to s1 while simultaneously checking if any of those characters
|
|
are null. Such an approach might write a character to every element of s1 before discovering that the first element was set to
|
|
the null character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.1.4p6'></a>
|
|
<pre>6 The strncpy_s function returns zero<a href='#FOOTNOTE.508'><sup>[508]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.508'>
|
|
<pre><i><b>Footnote 508)</b> A zero return value implies that all of the requested characters from the string pointed to by s2 fit within the array
|
|
pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.1.4p7'></a>
|
|
<pre>7 EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result will not be null
|
|
terminated or that characters will be written past the end of the destination array.
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
/* ... */
|
|
char src1[100] = "hello";
|
|
char src2[7] = {’g’, ’o’, ’o’, ’d’, ’b’, ’y’, ’e’};
|
|
char dst1[6], dst2[5], dst3[5];
|
|
int r1, r2, r3;
|
|
r1 = strncpy_s(dst1, 6, src1, 100);
|
|
r2 = strncpy_s(dst2, 5, src2, 7);
|
|
r3 = strncpy_s(dst3, 5, src2, 4);
|
|
|
|
The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
|
|
The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
|
|
The third call will assign to r3 the value zero and to dst3 the sequence good\0.
|
|
|
|
</pre>
|
|
<a name='K.3.7.2'></a>
|
|
<hr>
|
|
<h3>K.3.7.2 [Concatenation functions]</h3>
|
|
<a name='K.3.7.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.7.2.1 [The strcat_s function]</h3>
|
|
<a name='K.3.7.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t strcat_s(char * restrict s1, rsize_t s1max, const char * restrict s2);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.2.1p2'></a>
|
|
<pre>2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to strcat_s.
|
|
</pre>
|
|
<a name='K.3.7.2.1p3'></a>
|
|
<pre>3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall
|
|
not equal zero. m shall not equal zero.<a href='#FOOTNOTE.509'><sup>[509]</sup></a> m shall be greater than strnlen_s(s2, m). Copying shall
|
|
not take place between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.509'>
|
|
<pre><i><b>Footnote 509)</b> Zero means that s1 was not null terminated upon entry to strcat_s.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.1p4'></a>
|
|
<pre>4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.2.1p5'></a>
|
|
<pre>5 The strcat_s function appends a copy of the string pointed to by s2 (including the terminating
|
|
null character) to the end of the string pointed to by s1. The initial character from s2 overwrites the
|
|
null character at the end of s1.
|
|
</pre>
|
|
<a name='K.3.7.2.1p6'></a>
|
|
<pre>6 All elements following the terminating null character (if any) written by strcat_s in the array of
|
|
s1max characters pointed to by s1 take unspecified values when strcat_s returns.<a href='#FOOTNOTE.510'><sup>[510]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.510'>
|
|
<pre><i><b>Footnote 510)</b> This allows an implementation to append characters from s2 to s1 while simultaneously checking if any of those
|
|
characters are null. Such an approach might write a character to every element of s1 before discovering that the first element
|
|
was set to the null character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.1p7'></a>
|
|
<pre>7 The strcat_s function returns zero<a href='#FOOTNOTE.511'><sup>[511]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.511'>
|
|
<pre><i><b>Footnote 511)</b> A zero return value implies that all of the requested characters from the string pointed to by s2 were appended to the
|
|
string pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.7.2.2 [The strncat_s function]</h3>
|
|
<a name='K.3.7.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t strncat_s(char * restrict s1, rsize_t s1max, const char * restrict s2,
|
|
rsize_t n);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.2.2p2'></a>
|
|
<pre>2 Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to strncat_s.
|
|
</pre>
|
|
<a name='K.3.7.2.2p3'></a>
|
|
<pre>3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX.
|
|
s1max shall not equal zero. m shall not equal zero.<a href='#FOOTNOTE.512'><sup>[512]</sup></a> If n is not less than m, then m shall be greater
|
|
than strnlen_s(s2, m). Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.512'>
|
|
<pre><i><b>Footnote 512)</b> Zero means that s1 was not null terminated upon entry to strncat_s.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.2p4'></a>
|
|
<pre>4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.2.2p5'></a>
|
|
<pre>5 The strncat_s function appends not more than n successive characters (characters that follow a
|
|
null character are not copied) from the array pointed to by s2 to the end of the string pointed to by
|
|
s1. The initial character from s2 overwrites the null character at the end of s1. If no null character
|
|
was copied from s2, then s1[s1max- m +n] is set to a null character.
|
|
</pre>
|
|
<a name='K.3.7.2.2p6'></a>
|
|
<pre>6 All elements following the terminating null character (if any) written by strncat_s in the array of
|
|
s1max characters pointed to by s1 take unspecified values when strncat_s returns.<a href='#FOOTNOTE.513'><sup>[513]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.513'>
|
|
<pre><i><b>Footnote 513)</b> This allows an implementation to append characters from s2 to s1 while simultaneously checking if any of those
|
|
characters are null. Such an approach might write a character to every element of s1 before discovering that the first element
|
|
was set to the null character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.2p7'></a>
|
|
<pre>7 The strncat_s function returns zero<a href='#FOOTNOTE.514'><sup>[514]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.514'>
|
|
<pre><i><b>Footnote 514)</b> A zero return value implies that all of the requested characters from the string pointed to by s2 were appended to the
|
|
string pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.2.2p8'></a>
|
|
<pre>8 EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result will not be null
|
|
terminated or that characters will be written past the end of the destination array.
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
/* ... */
|
|
char s1[100] = "good";
|
|
char s2[6] = "hello";
|
|
char s3[6] = "hello";
|
|
char s4[7] = "abc";
|
|
char s5[1000] = "bye";
|
|
int r1, r2, r3, r4;
|
|
r1 = strncat_s(s1, 100, s5, 1000);
|
|
r2 = strncat_s(s2, 6, "", 1);
|
|
r3 = strncat_s(s3, 6, "X", 2);
|
|
r4 = strncat_s(s4, 7, "defghijklmn", 3);
|
|
|
|
|
|
After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
|
|
After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
|
|
After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
|
|
After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
|
|
|
|
</pre>
|
|
<a name='K.3.7.3'></a>
|
|
<hr>
|
|
<h3>K.3.7.3 [Search functions]</h3>
|
|
<a name='K.3.7.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.7.3.1 [The strtok_s function]</h3>
|
|
<a name='K.3.7.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
char *strtok_s(char * restrict s1, rsize_t * restrict s1max,
|
|
const char * restrict s2, char ** restrict ptr);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.3.1p2'></a>
|
|
<pre>2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr shall not be a
|
|
null pointer. The value of *s1max shall not be greater than RSIZE_MAX. The end of the token found
|
|
shall occur within the first *s1max characters of s1 for the first call, and shall occur within the first
|
|
*s1max characters of where searching resumes on subsequent calls.
|
|
</pre>
|
|
<a name='K.3.7.3.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the strtok_s function does not indirect through the s1 or
|
|
s2 pointers, and does not store a value in the object pointed to by ptr.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.3.1p4'></a>
|
|
<pre>4 A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a sequence of
|
|
tokens, each of which is delimited by a character from the string pointed to by s2. The fourth argu-
|
|
ment points to a caller-provided char pointer into which the strtok_s function stores information
|
|
necessary for it to continue scanning the same string.
|
|
</pre>
|
|
<a name='K.3.7.3.1p5'></a>
|
|
<pre>5 The first call in a sequence has a non-null first argument and s1max points to an object whose value
|
|
is the number of elements in the character array pointed to by the first argument. The first call stores
|
|
an initial value in the object pointed to by ptr and updates the value pointed to by s1max to reflect
|
|
the number of elements that remain in relation to ptr. Subsequent calls in the sequence have a null
|
|
first argument and the objects pointed to by s1max and ptr are required to have the values stored
|
|
by the previous call in the sequence, which are then updated. The separator string pointed to by s2
|
|
may be different from call to call.
|
|
</pre>
|
|
<a name='K.3.7.3.1p6'></a>
|
|
<pre>6 The first call in the sequence searches the string pointed to by s1 for the first character that is not
|
|
contained in the current separator string pointed to by s2. If no such character is found, then there
|
|
are no tokens in the string pointed to by s1 and the strtok_s function returns a null pointer. If such
|
|
a character is found, it is the start of the first token.
|
|
</pre>
|
|
<a name='K.3.7.3.1p7'></a>
|
|
<pre>7 The strtok_s function then searches from there for the first character in s1 that is contained in the
|
|
current separator string. If no such character is found, the current token extends to the end of the
|
|
string pointed to by s1, and subsequent searches in the same string for a token return a null pointer.
|
|
If such a character is found, it is overwritten by a null character, which terminates the current token.
|
|
</pre>
|
|
<a name='K.3.7.3.1p8'></a>
|
|
<pre>8 In all cases, the strtok_s function stores sufficient information in the pointer pointed to by ptr so
|
|
that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start
|
|
searching just past the element overwritten by a null character (if any).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.3.1p9'></a>
|
|
<pre>9 The strtok_s function returns a pointer to the first character of a token, or a null pointer if there is
|
|
no token or there is a runtime-constraint violation.
|
|
</pre>
|
|
<a name='K.3.7.3.1p10'></a>
|
|
<pre>10 EXAMPLE
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
static char str1[] = "?a???b,,,#c";
|
|
static char str2[] = "\t \t";
|
|
char *t, *ptr1, *ptr2;
|
|
rsize_t max1 = sizeof (str1);
|
|
rsize_t max2 = sizeof (str2);
|
|
|
|
t = strtok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
|
|
t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
|
|
t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
|
|
t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
|
|
t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
|
|
|
|
|
|
</pre>
|
|
<a name='K.3.7.4'></a>
|
|
<hr>
|
|
<h3>K.3.7.4 [Miscellaneous functions]</h3>
|
|
<a name='K.3.7.4.1'></a>
|
|
<hr>
|
|
<h3>K.3.7.4.1 [The memset_s function]</h3>
|
|
<a name='K.3.7.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.4.1p2'></a>
|
|
<pre>2 s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n shall not be
|
|
greater than smax.
|
|
</pre>
|
|
<a name='K.3.7.4.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and smax is not greater than
|
|
RSIZE_MAX, the memset_s function stores the value of c (converted to an unsigned char) into each
|
|
of the first smax characters of the object pointed to by s.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.4.1p4'></a>
|
|
<pre>4 The memset_s function copies the value of c (converted to an unsigned char) into each of the first
|
|
n characters of the object pointed to by s. Unlike memset, any call to the memset_s function shall be
|
|
evaluated strictly according to the rules of the abstract machine as described in (<a href='#5.1.2.3'>5.1.2.3</a>). That is, any
|
|
call to the memset_s function shall assume that the memory indicated by s and n may be accessible
|
|
in the future and thus contains the values indicated by c.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.4.1p5'></a>
|
|
<pre>5 The memset_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.7.4.2'></a>
|
|
<hr>
|
|
<h3>K.3.7.4.2 [The strerror_s function]</h3>
|
|
<a name='K.3.7.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
errno_t strerror_s(char *s, rsize_t maxsize, errno_t errnum);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.7.4.2p2'></a>
|
|
<pre>2 s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX. maxsize shall not equal
|
|
zero.
|
|
</pre>
|
|
<a name='K.3.7.4.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then the array (if any) pointed to by s is not modified.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.4.2p4'></a>
|
|
<pre>4 The strerror_s function maps the number in errnum to a locale-specific message string. Typically,
|
|
the values for errnum come from errno, but strerror_s shall map any value of type int to a
|
|
message.
|
|
</pre>
|
|
<a name='K.3.7.4.2p5'></a>
|
|
<pre>5 If the length of the desired string is less than maxsize, then the string is copied to the array pointed
|
|
to by s.
|
|
</pre>
|
|
<a name='K.3.7.4.2p6'></a>
|
|
<pre>6 Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied from the string
|
|
to the array pointed to by s and then s[maxsize-1] is set to the null character. Then, if maxsize
|
|
is greater than 3, then s[maxsize-2], s[maxsize-3], and s[maxsize-4] are set to the character
|
|
period (.).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.4.2p7'></a>
|
|
<pre>7 The strerror_s function returns zero if the length of the desired string was less than maxsize and
|
|
there was no runtime-constraint violation. Otherwise, the strerror_s function returns a nonzero
|
|
value.
|
|
</pre>
|
|
<a name='K.3.7.4.3'></a>
|
|
<hr>
|
|
<h3>K.3.7.4.3 [The strerrorlen_s function]</h3>
|
|
<a name='K.3.7.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
size_t strerrorlen_s(errno_t errnum);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.4.3p2'></a>
|
|
<pre>2 The strerrorlen_s function calculates the length of the (untruncated) locale-specific message
|
|
string that the strerror_s function maps to errnum.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.4.3p3'></a>
|
|
<pre>3 The strerrorlen_s function returns the number of characters (not including the null character) in
|
|
the full message string.
|
|
|
|
</pre>
|
|
<a name='K.3.7.4.4'></a>
|
|
<hr>
|
|
<h3>K.3.7.4.4 [The strnlen_s function]</h3>
|
|
<a name='K.3.7.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <string.h>
|
|
size_t strnlen_s(const char *s, size_t maxsize);
|
|
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.7.4.4p2'></a>
|
|
<pre>2 The strnlen_s function computes the length of the string pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.7.4.4p3'></a>
|
|
<pre>3 If s is a null pointer,<a href='#FOOTNOTE.515'><sup>[515]</sup></a> then the strnlen_s function returns zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.515'>
|
|
<pre><i><b>Footnote 515)</b> Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints along with the values
|
|
returned for a null pointer or an unterminated string argument make strnlen_s useful in algorithms that gracefully handle
|
|
such exceptional data.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.7.4.4p4'></a>
|
|
<pre>4 Otherwise, the strnlen_s function returns the number of characters that precede the terminating
|
|
null character. If there is no null character in the first maxsize characters of s then strnlen_s
|
|
returns maxsize. At most the first maxsize characters of s shall be accessed by strnlen_s.
|
|
|
|
</pre>
|
|
<a name='K.3.8'></a>
|
|
<hr>
|
|
<h3>K.3.8 [Date and time <time.h>]</h3>
|
|
<a name='K.3.8p1'></a>
|
|
<pre>1 The header <time.h> defines two types.
|
|
</pre>
|
|
<a name='K.3.8p2'></a>
|
|
<pre>2 The types are
|
|
|
|
errno_t
|
|
|
|
|
|
which is type int; and
|
|
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t.
|
|
|
|
</pre>
|
|
<a name='K.3.8.1'></a>
|
|
<hr>
|
|
<h3>K.3.8.1 [Components of time]</h3>
|
|
<a name='K.3.8.1p1'></a>
|
|
<pre>1 A broken-down time is normalized if the values of the members of the tm structure are in their normal
|
|
rages.<a href='#FOOTNOTE.516'><sup>[516]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.516'>
|
|
<pre><i><b>Footnote 516)</b> The normal ranges are defined in <a href='#7.29.1'>7.29.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.8.2'></a>
|
|
<hr>
|
|
<h3>K.3.8.2 [Time conversion functions]</h3>
|
|
<a name='K.3.8.2p1'></a>
|
|
<pre>1 Like the strftime function, the asctime_s and ctime_s functions do not return a pointer to a static
|
|
object, and other library functions are permitted to call them.
|
|
|
|
</pre>
|
|
<a name='K.3.8.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.8.2.1 [The asctime_s function]</h3>
|
|
<a name='K.3.8.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <time.h>
|
|
errno_t asctime_s(char *s, rsize_t maxsize, const struct tm *timeptr);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.8.2.1p2'></a>
|
|
<pre>2 Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and shall not be
|
|
greater than RSIZE_MAX. The broken-down time pointed to by timeptr shall be normalized. The
|
|
calendar year represented by the broken-down time pointed to by timeptr shall not be less than
|
|
calendar year 0 and shall not be greater than calendar year 9999.
|
|
</pre>
|
|
<a name='K.3.8.2.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, there is no attempt to convert the time, and s[0] is set to a
|
|
null character if s is not a null pointer and maxsize is not zero and is not greater than RSIZE_MAX.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.8.2.1p4'></a>
|
|
<pre>4 The asctime_s function converts the normalized broken-down time in the structure pointed to by
|
|
timeptr into a 26 character (including the null character) string in the form
|
|
|
|
Sun Sep 16 01:03:52 1973\n\0
|
|
|
|
The fields making up this string are (in order):
|
|
|
|
1. The name of the day of the week represented by timeptr->tm_wday using the following three
|
|
character weekday names: Sun, Mon, Tue, Wed, Thu, Fri, and Sat.
|
|
2. The character space.
|
|
3. The name of the month represented by timeptr->tm_mon using the following three character
|
|
month names: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, and Dec.
|
|
4. The character space.
|
|
5. The value of timeptr->tm_mday as if printed using the fprintf format "%2d".
|
|
6. The character space.
|
|
7. The value of timeptr->tm_hour as if printed using the fprintf format "%.2d".
|
|
8. The character colon.
|
|
9. The value of timeptr->tm_min as if printed using the fprintf format "%.2d".
|
|
10. The character colon.
|
|
11. The value of timeptr->tm_sec as if printed using the fprintf format "%.2d".
|
|
12. The character space.
|
|
13. The value of timeptr->tm_year + 1900 as if printed using the fprintf format "%4d".
|
|
14. The character new line.
|
|
15. The null character.
|
|
|
|
Recommended practice
|
|
The strftime function allows more flexible formatting and supports locale-specific behavior. If you
|
|
do not require the exact form of the result string produced by the asctime_s function, consider
|
|
using the strftime function instead.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.8.2.1p5'></a>
|
|
<pre>5 The asctime_s function returns zero if the time was successfully converted and stored into the
|
|
array pointed to by s. Otherwise, it returns a nonzero value.
|
|
</pre>
|
|
<a name='K.3.8.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.8.2.2 [The ctime_s function]</h3>
|
|
<a name='K.3.8.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <time.h>
|
|
errno_t ctime_s(char *s, rsize_t maxsize, const time_t *timer);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.8.2.2p2'></a>
|
|
<pre>2 Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and shall not be greater
|
|
than RSIZE_MAX.
|
|
</pre>
|
|
<a name='K.3.8.2.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null pointer and
|
|
maxsize is not equal zero and is not greater than RSIZE_MAX.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.8.2.2p4'></a>
|
|
<pre>4 The ctime_s function converts the calendar time pointed to by timer to local time in the form of a
|
|
string. It is equivalent to
|
|
|
|
asctime_s(s, maxsize, localtime_s(timer, &(struct tm){ 0 }))
|
|
|
|
|
|
Recommended practice
|
|
The strftime function allows more flexible formatting and supports locale-specific behavior. If you
|
|
do not require the exact form of the result string produced by the ctime_s function, consider using
|
|
the strftime function instead.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.8.2.2p5'></a>
|
|
<pre>5 The ctime_s function returns zero if the time was successfully converted and stored into the array
|
|
pointed to by s. Otherwise, it returns a nonzero value.
|
|
|
|
</pre>
|
|
<a name='K.3.8.2.3'></a>
|
|
<hr>
|
|
<h3>K.3.8.2.3 [The gmtime_s function]</h3>
|
|
<a name='K.3.8.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <time.h>
|
|
struct tm *gmtime_s(const time_t * restrict timer, struct tm * restrict result);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.8.2.3p2'></a>
|
|
<pre>2 Neither timer nor result shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.8.2.3p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, there is no attempt to convert the time.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.8.2.3p4'></a>
|
|
<pre>4 The gmtime_s function converts the calendar time pointed to by timer into a broken-down time,
|
|
expressed as UTC. The broken-down time is stored in the structure pointed to by result.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.8.2.3p5'></a>
|
|
<pre>5 The gmtime_s function returns result, or a null pointer if the specified time cannot be converted to
|
|
UTC or there is a runtime-constraint violation.
|
|
|
|
</pre>
|
|
<a name='K.3.8.2.4'></a>
|
|
<hr>
|
|
<h3>K.3.8.2.4 [The localtime_s function]</h3>
|
|
<a name='K.3.8.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <time.h>
|
|
struct tm *localtime_s(const time_t *restrict timer, struct tm *restrict result);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.8.2.4p2'></a>
|
|
<pre>2 Neither timer nor result shall be a null pointer.
|
|
</pre>
|
|
<a name='K.3.8.2.4p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, there is no attempt to convert the time.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.8.2.4p4'></a>
|
|
<pre>4 The localtime_s function converts the calendar time pointed to by timer into a broken-down time,
|
|
expressed as local time. The broken-down time is stored in the structure pointed to by result.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.8.2.4p5'></a>
|
|
<pre>5 The localtime_s function returns result, or a null pointer if the specified time cannot be converted
|
|
to local time or there is a runtime-constraint violation.
|
|
|
|
</pre>
|
|
<a name='K.3.9'></a>
|
|
<hr>
|
|
<h3>K.3.9 [Extended multibyte and wide character utilities <wchar.h>]</h3>
|
|
<a name='K.3.9p1'></a>
|
|
<pre>1 The header <wchar.h> defines two types.
|
|
</pre>
|
|
<a name='K.3.9p2'></a>
|
|
<pre>2 The types are
|
|
|
|
errno_t
|
|
|
|
|
|
which is type int; and
|
|
|
|
rsize_t
|
|
|
|
|
|
which is the type size_t.
|
|
</pre>
|
|
<a name='K.3.9p3'></a>
|
|
<pre>3 Unless explicitly stated otherwise, if the execution of a function described in this subclause causes
|
|
copying to take place between objects that overlap, the objects take on unspecified values.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.1 [Formatted wide character input/output functions]</h3>
|
|
<a name='K.3.9.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.1 [The fwprintf_s function]</h3>
|
|
<a name='K.3.9.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int fwprintf_s(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.1p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. The %n specifier<a href='#FOOTNOTE.517'><sup>[517]</sup></a> (modified or not by flags,
|
|
field width, or precision) shall not appear in the wide string pointed to by format. Any argument to
|
|
fwprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.517'>
|
|
<pre><i><b>Footnote 517)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the fwprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent fwprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.1p4'></a>
|
|
<pre>4 The fwprintf_s function is equivalent to the fwprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.1p5'></a>
|
|
<pre>5 The fwprintf_s function returns the number of wide characters transmitted, or a negative value if
|
|
an output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.2 [The fwscanf_s function]</h3>
|
|
<a name='K.3.9.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwscanf_s(FILE * restrict stream, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.2p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. Any argument indirected though in order to
|
|
store converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the fwscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent fwscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.2p4'></a>
|
|
<pre>4 The fwscanf_s function is equivalent to fwscanf except that the c, s, and [ conversion specifiers
|
|
apply to a pair of arguments (unless assignment suppression is indicated by a *). The first of these
|
|
arguments is the same as for fwscanf. That argument is immediately followed in the argument
|
|
list by the second argument, which has type size_t and gives the number of elements in the array
|
|
pointed to by the first argument of the pair. If the first argument points to a scalar object, it is
|
|
considered to be an array of one element.<a href='#FOOTNOTE.518'><sup>[518]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.518'>
|
|
<pre><i><b>Footnote 518)</b> If the format is known at translation time, an implementation can issue a diagnostic for any argument used to store
|
|
the result from a c, s, or [ conversion specifier if that argument is not followed by an argument of a type compatible with
|
|
rsize_t. A limited amount of checking can be done if even if the format is not known at translation time. For example, an
|
|
implementation could issue a diagnostic for each argument after format that has of type pointer to one of char, signed char,
|
|
unsigned char, or void that is not followed by an argument of a type compatible with rsize_t. The diagnostic could warn
|
|
that unless the pointer is being used with a conversion specifier using the hh length modifier, a length argument is expected
|
|
to follow the pointer argument. Another useful diagnostic could flag any non-pointer argument following format that did
|
|
not have a type compatible with rsize_t.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.2p5'></a>
|
|
<pre>5 A matching failure occurs if the number of elements in a receiving object is insufficient to hold the
|
|
converted input (including any trailing null character).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.2p6'></a>
|
|
<pre>6 The fwscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the fwscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.3'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.3 [The snwprintf_s function]</h3>
|
|
<a name='K.3.9.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int snwprintf_s(wchar_t * restrict s, rsize_t n, const wchar_t * restrict format,
|
|
...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.3p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). The %n specifier<a href='#FOOTNOTE.519'><sup>[519]</sup></a> (modified or not by flags, field width, or pre-
|
|
cision) shall not appear in the wide string pointed to by format. Any argument to snwprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.519'>
|
|
<pre><i><b>Footnote 519)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.3p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero
|
|
and not greater than RSIZE_MAX/sizeof(wchar_t), then the snwprintf_s function sets s[0] to
|
|
the null wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.3p4'></a>
|
|
<pre>4 The snwprintf_s function is equivalent to the swprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.9.1.3p5'></a>
|
|
<pre>5 The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within the array pointed
|
|
to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.3p6'></a>
|
|
<pre>6 The snwprintf_s function returns the number of wide characters that would have been written
|
|
had n been sufficiently large, not counting the terminating wide null character, or a negative value
|
|
if a runtime-constraint violation occurred. Thus, the null-terminated output has been completely
|
|
written if and only if the returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.4'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.4 [The swprintf_s function]</h3>
|
|
<a name='K.3.9.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int swprintf_s(wchar_t * restrict s, rsize_t n, const wchar_t * restrict format,
|
|
...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.4p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). The number of wide characters (including the trailing null) required
|
|
for the result to be written to the array pointed to by s shall not be greater than n. The %n specifier<a href='#FOOTNOTE.520'><sup>[520]</sup></a>
|
|
(modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by
|
|
format. Any argument to swprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.520'>
|
|
<pre><i><b>Footnote 520)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.4p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX/sizeof(wchar_t), then the swprintf_s function sets s[0] to the null
|
|
wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.4p4'></a>
|
|
<pre>4 The swprintf_s function is equivalent to the swprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.9.1.4p5'></a>
|
|
<pre>5 The swprintf_s function, unlike snwprintf_s, treats a result too big for the array pointed to by s
|
|
as a runtime-constraint violation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.4p6'></a>
|
|
<pre>6 If no runtime-constraint violation occurred, the swprintf_s function returns the number of wide
|
|
characters written in the array, not counting the terminating null wide character. If an encoding
|
|
error occurred or if n or more wide characters are requested to be written, swprintf_s returns a
|
|
negative value. If any other runtime-constraint violation occurred, swprintf_s returns zero.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.5'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.5 [The swscanf_s function]</h3>
|
|
<a name='K.3.9.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int swscanf_s(const wchar_t * restrict s, const wchar_t * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.5p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. Any argument indirected though in order to store
|
|
converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.5p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the swscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent swscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.5p4'></a>
|
|
<pre>4 The swscanf_s function is equivalent to fwscanf_s, except that the argument s specifies a wide
|
|
string from which the input is to be obtained, rather than from a stream. Reaching the end of the
|
|
wide string is equivalent to encountering end-of-file for the fwscanf_s function.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.5p5'></a>
|
|
<pre>5 The swscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the swscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.6'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.6 [The vfwprintf_s function]</h3>
|
|
<a name='K.3.9.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int vfwprintf_s(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.6p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. The %n specifier<a href='#FOOTNOTE.521'><sup>[521]</sup></a> (modified or not by flags,
|
|
field width, or precision) shall not appear in the wide string pointed to by format. Any argument to
|
|
vfwprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.521'>
|
|
<pre><i><b>Footnote 521)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.6p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vfwprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent vfwprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.6p4'></a>
|
|
<pre>4 The vfwprintf_s function is equivalent to the vfwprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.6p5'></a>
|
|
<pre>5 The vfwprintf_s function returns the number of wide characters transmitted, or a negative value if
|
|
an output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.7'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.7 [The vfwscanf_s function]</h3>
|
|
<a name='K.3.9.1.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int vfwscanf_s(FILE * restrict stream, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.7p2'></a>
|
|
<pre>2 Neither stream nor format shall be a null pointer. Any argument indirected though in order to
|
|
store converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.7p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent vfwscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.7p4'></a>
|
|
<pre>4 The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument list replaced by
|
|
arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg
|
|
calls). The vfwscanf_s function does not invoke the va_end macro<a href='#FOOTNOTE.522'><sup>[522]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.522'>
|
|
<pre><i><b>Footnote 522)</b> As the functions vfwscanf_s , vwscanf_s , and vswscanf_s invoke the va_arg macro, the representation of arg after the
|
|
return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.7p5'></a>
|
|
<pre>5 The vfwscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vfwscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.8'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.8 [The vsnwprintf_s function]</h3>
|
|
<a name='K.3.9.1.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vsnwprintf_s(wchar_t *restrict s, rsize_t n, const wchar_t *restrict format,
|
|
va_list arg);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.8p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). The %n specifier<a href='#FOOTNOTE.523'><sup>[523]</sup></a> (modified or not by flags, field width, or preci-
|
|
sion) shall not appear in the wide string pointed to by format. Any argument to vsnwprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.523'>
|
|
<pre><i><b>Footnote 523)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.8p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and
|
|
not greater than RSIZE_MAX/sizeof(wchar_t), then the vsnwprintf_s function sets s[0] to the
|
|
null wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.8p4'></a>
|
|
<pre>4 The vsnwprintf_s function is equivalent to the vswprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.9.1.8p5'></a>
|
|
<pre>5 The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit within the array
|
|
pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.8p6'></a>
|
|
<pre>6 The vsnwprintf_s function returns the number of wide characters that would have been written
|
|
had n been sufficiently large, not counting the terminating null character, or a negative value if
|
|
a runtime-constraint violation occurred. Thus, the null-terminated output has been completely
|
|
written if and only if the returned value is both nonnegative and less than n.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.9'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.9 [The vswprintf_s function]</h3>
|
|
<a name='K.3.9.1.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vswprintf_s(wchar_t *restrict s, rsize_t n, const wchar_t *restrict format,
|
|
va_list arg);
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.9p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). The number of wide characters (including the trailing null) required
|
|
for the result to be written to the array pointed to by s shall not be greater than n. The %n specifier<a href='#FOOTNOTE.524'><sup>[524]</sup></a>
|
|
(modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by
|
|
format. Any argument to vswprintf_s corresponding to a %s specifier shall not be a null pointer.
|
|
No encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.524'>
|
|
<pre><i><b>Footnote 524)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.9p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero
|
|
and not greater than RSIZE_MAX/sizeof(wchar_t), then the vswprintf_s function sets s[0] to
|
|
the null wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.9p4'></a>
|
|
<pre>4 The vswprintf_s function is equivalent to the vswprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
</pre>
|
|
<a name='K.3.9.1.9p5'></a>
|
|
<pre>5 The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the array pointed to by
|
|
s as a runtime-constraint violation.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.9p6'></a>
|
|
<pre>6 If no runtime-constraint violation occurred, the vswprintf_s function returns the number of wide
|
|
characters written in the array, not counting the terminating null wide character. If an encoding
|
|
error occurred or if n or more wide characters are requested to be written, vswprintf_s returns a
|
|
negative value. If any other runtime-constraint violation occurred, vswprintf_s returns zero.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.10'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.10 [The vswscanf_s function]</h3>
|
|
<a name='K.3.9.1.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vswscanf_s(const wchar_t * restrict s, const wchar_t * restrict format,
|
|
va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.10p2'></a>
|
|
<pre>2 Neither s nor format shall be a null pointer. Any argument indirected though in order to store
|
|
converted input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.10p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vswscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent vswscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.10p4'></a>
|
|
<pre>4 The vswscanf_s function is equivalent to swscanf_s, with the variable argument list replaced by
|
|
arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg
|
|
calls). The vswscanf_s function does not invoke the va_end macro<a href='#FOOTNOTE.525'><sup>[525]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.525'>
|
|
<pre><i><b>Footnote 525)</b> As the functions vfwscanf_s , vwscanf_s , and vswscanf_s invoke the va_arg macro, the representation of arg after the
|
|
return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.10p5'></a>
|
|
<pre>5 The vswscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vswscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.11'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.11 [The vwprintf_s function]</h3>
|
|
<a name='K.3.9.1.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwprintf_s(const wchar_t * restrict format, va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.11p2'></a>
|
|
<pre>2 format shall not be a null pointer. The %n specifier<a href='#FOOTNOTE.526'><sup>[526]</sup></a> (modified or not by flags, field width, or
|
|
precision) shall not appear in the wide string pointed to by format. Any argument to vwprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.526'>
|
|
<pre><i><b>Footnote 526)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.11p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vwprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent vwprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.11p4'></a>
|
|
<pre>4 The vwprintf_s function is equivalent to the vwprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.11p5'></a>
|
|
<pre>5 The vwprintf_s function returns the number of wide characters transmitted, or a negative value if
|
|
an output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.12'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.12 [The vwscanf_s function]</h3>
|
|
<a name='K.3.9.1.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwscanf_s(const wchar_t * restrict format, va_list arg);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.12p2'></a>
|
|
<pre>2 format shall not be a null pointer. Any argument indirected though in order to store converted
|
|
input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.12p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the vwscanf_s function does not attempt to perform
|
|
further input, and it is unspecified to what extent vwscanf_s performed input before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.12p4'></a>
|
|
<pre>4 The vwscanf_s function is equivalent to wscanf_s, with the variable argument list replaced by arg,
|
|
which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls).
|
|
The vwscanf_s function does not invoke the va_end macro<a href='#FOOTNOTE.527'><sup>[527]</sup></a> .
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.527'>
|
|
<pre><i><b>Footnote 527)</b> As the functions vfwscanf_s , vwscanf_s , and vswscanf_s invoke the va_arg macro, the representation of arg after the
|
|
return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.12p5'></a>
|
|
<pre>5 The vwscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the vwscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.13'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.13 [The wprintf_s function]</h3>
|
|
<a name='K.3.9.1.13p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int wprintf_s(const wchar_t * restrict format, ...);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.13p2'></a>
|
|
<pre>2 format shall not be a null pointer. The %n specifier<a href='#FOOTNOTE.528'><sup>[528]</sup></a> (modified or not by flags, field width, or
|
|
precision) shall not appear in the wide string pointed to by format. Any argument to wprintf_s
|
|
corresponding to a %s specifier shall not be a null pointer.
|
|
</pre>
|
|
<a name='FOOTNOTE.528'>
|
|
<pre><i><b>Footnote 528)</b> It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at
|
|
by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was
|
|
L"%%n".
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.1.13p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the wprintf_s function does not attempt to produce
|
|
further output, and it is unspecified to what extent wprintf_s produced output before discovering
|
|
the runtime-constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.13p4'></a>
|
|
<pre>4 The wprintf_s function is equivalent to the wprintf function except for the explicit runtime-
|
|
constraints listed above.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.13p5'></a>
|
|
<pre>5 The wprintf_s function returns the number of wide characters transmitted, or a negative value if
|
|
an output error, encoding error, or runtime-constraint violation occurred.
|
|
|
|
</pre>
|
|
<a name='K.3.9.1.14'></a>
|
|
<hr>
|
|
<h3>K.3.9.1.14 [The wscanf_s function]</h3>
|
|
<a name='K.3.9.1.14p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
int wscanf_s(const wchar_t * restrict format, ...);
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.1.14p2'></a>
|
|
<pre>2 format shall not be a null pointer. Any argument indirected though in order to store converted
|
|
input shall not be a null pointer.
|
|
</pre>
|
|
<a name='K.3.9.1.14p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the wscanf_s function does not attempt to perform further
|
|
input, and it is unspecified to what extent wscanf_s performed input before discovering the runtime-
|
|
constraint violation.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.1.14p4'></a>
|
|
<pre>4 The wscanf_s function is equivalent to fwscanf_s with the argument stdin interposed before the
|
|
arguments to wscanf_s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.1.14p5'></a>
|
|
<pre>5 The wscanf_s function returns the value of the macro EOF if an input failure occurs before any
|
|
conversion or if there is a runtime-constraint violation. Otherwise, the wscanf_s function returns
|
|
the number of input items assigned, which can be fewer than provided for, or even zero, in the event
|
|
of an early matching failure.
|
|
|
|
</pre>
|
|
<a name='K.3.9.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.2 [General wide string utilities]</h3>
|
|
<a name='K.3.9.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.1 [Wide string copying functions]</h3>
|
|
<a name='K.3.9.2.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.1.1 [The wcscpy_s function]</h3>
|
|
<a name='K.3.9.2.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wcscpy_s(wchar_t *restrict s1, rsize_t s1max,
|
|
const wchar_t *restrict s2);
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.1.1p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). s1max shall not equal zero. s1max shall be greater than
|
|
wcsnlen_s(s2, s1max) . Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='K.3.9.2.1.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX/sizeof(wchar_t), then wcscpy_s sets s1[0] to the null wide
|
|
character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.1p4'></a>
|
|
<pre>4 The wcscpy_s function copies the wide string pointed to by s2 (including the terminating null wide
|
|
character) into the array pointed to by s1.
|
|
</pre>
|
|
<a name='K.3.9.2.1.1p5'></a>
|
|
<pre>5 All elements following the terminating null wide character (if any) written by wcscpy_s in the array
|
|
of s1max wide characters pointed to by s1 take unspecified values when wcscpy_s returns.<a href='#FOOTNOTE.529'><sup>[529]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.529'>
|
|
<pre><i><b>Footnote 529)</b> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking if any of those wide
|
|
characters are null. Such an approach might write a wide character to every element of s1 before discovering that the first
|
|
element was set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.1.1p6'></a>
|
|
<pre>6 The wcscpy_s function returns zero<a href='#FOOTNOTE.530'><sup>[530]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.530'>
|
|
<pre><i><b>Footnote 530)</b> A zero return value implies that all of the requested wide characters from the string pointed to by s2 fit within the array
|
|
pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.1.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.1.2 [The wcsncpy_s function]</h3>
|
|
<a name='K.3.9.2.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wcsncpy_s(wchar_t * restrict s1, rsize_t s1max,
|
|
const wchar_t * restrict s2, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). s1max shall not equal zero. If n is not less than s1max, then
|
|
s1max shall be greater than wcsnlen_s(s2, s1max) . Copying shall not take place between objects
|
|
that overlap.
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX/sizeof(wchar_t), then wcsncpy_s sets s1[0] to the null
|
|
wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p4'></a>
|
|
<pre>4 The wcsncpy_s function copies not more than n successive wide characters (wide characters that
|
|
follow a null wide character are not copied) from the array pointed to by s2 to the array pointed to
|
|
by s1. If no null wide character was copied from s2, then s1[n] is set to a null wide character.
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p5'></a>
|
|
<pre>5 All elements following the terminating null wide character (if any) written by wcsncpy_s in the array
|
|
of s1max wide characters pointed to by s1 take unspecified values when wcsncpy_s returns.<a href='#FOOTNOTE.531'><sup>[531]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.531'>
|
|
<pre><i><b>Footnote 531)</b> This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking if any of those wide
|
|
characters are null. Such an approach might write a wide character to every element of s1 before discovering that the first
|
|
element was set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.1.2p6'></a>
|
|
<pre>6 The wcsncpy_s function returns zero<a href='#FOOTNOTE.532'><sup>[532]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.532'>
|
|
<pre><i><b>Footnote 532)</b> A zero return value implies that all of the requested wide characters from the string pointed to by s2 fit within the array
|
|
pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.1.2p7'></a>
|
|
<pre>7 EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the result will not be null
|
|
terminated or that wide characters will be written past the end of the destination array.
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
/* ... */
|
|
wchar_t src1[100] = L"hello";
|
|
wchar_t src2[7] = {L’g’, L’o’, L’o’, L’d’, L’b’, L’y’, L’e’};
|
|
wchar_t dst1[6], dst2[5], dst3[5];
|
|
int r1, r2, r3;
|
|
r1 = wcsncpy_s(dst1, 6, src1, 100);
|
|
r2 = wcsncpy_s(dst2, 5, src2, 7);
|
|
r3 = wcsncpy_s(dst3, 5, src2, 4);
|
|
|
|
The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
|
|
The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
|
|
The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
|
|
|
|
</pre>
|
|
<a name='K.3.9.2.1.3'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.1.3 [The wmemcpy_s function]</h3>
|
|
<a name='K.3.9.2.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wmemcpy_s(wchar_t *restrict s1, rsize_t s1max,
|
|
const wchar_t *restrict s2, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.1.3p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). n shall not be greater than s1max. Copying shall not take
|
|
place between objects that overlap.
|
|
</pre>
|
|
<a name='K.3.9.2.1.3p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the first s1max wide
|
|
characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than
|
|
RSIZE_MAX/sizeof(wchar_t).
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.3p4'></a>
|
|
<pre>4 The wmemcpy_s function copies n successive wide characters from the object pointed to by s2 into
|
|
the object pointed to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.2.1.3p5'></a>
|
|
<pre>5 The wmemcpy_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.9.2.1.4'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.1.4 [The wmemmove_s function]</h3>
|
|
<a name='K.3.9.2.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wmemmove_s(wchar_t *s1, rsize_t s1max, const wchar_t *s2, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.1.4p2'></a>
|
|
<pre>2 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). n shall not be greater than s1max.
|
|
</pre>
|
|
<a name='K.3.9.2.1.4p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the first s1max
|
|
wide characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than
|
|
RSIZE_MAX/sizeof(wchar_t).
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.4p4'></a>
|
|
<pre>4 The wmemmove_s function copies n successive wide characters from the object pointed to by s2 into
|
|
the object pointed to by s1. This copying takes place as if the n wide characters from the object
|
|
pointed to by s2 are first copied into a temporary array of n wide characters that does not overlap
|
|
the objects pointed to by s1 or s2, and then the n wide characters from the temporary array are
|
|
copied into the object pointed to by s1.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.2.1.4p5'></a>
|
|
<pre>5 The wmemmove_s function returns zero if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.9.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.2 [Wide string concatenation functions]</h3>
|
|
<a name='K.3.9.2.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.2.1 [The wcscat_s function]</h3>
|
|
<a name='K.3.9.2.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wcscat_s(wchar_t * restrict s1, rsize_t s1max,
|
|
const wchar_t * restrict s2);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.2.1p2'></a>
|
|
<pre>2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to wcscat_s.
|
|
</pre>
|
|
<a name='K.3.9.2.2.1p3'></a>
|
|
<pre>3 Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). s1max shall not equal zero. m shall not equal zero.<a href='#FOOTNOTE.533'><sup>[533]</sup></a> m
|
|
shall be greater than wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.533'>
|
|
<pre><i><b>Footnote 533)</b> Zero means that s1 was not null terminated upon entry to wcscat_s .
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.1p4'></a>
|
|
<pre>4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX/sizeof(wchar_t), then wcscat_s sets s1[0] to the null wide
|
|
character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.2.1p5'></a>
|
|
<pre>5 The wcscat_s function appends a copy of the wide string pointed to by s2 (including the terminating
|
|
null wide character) to the end of the wide string pointed to by s1. The initial wide character from
|
|
s2 overwrites the null wide character at the end of s1.
|
|
</pre>
|
|
<a name='K.3.9.2.2.1p6'></a>
|
|
<pre>6 All elements following the terminating null wide character (if any) written by wcscat_s in the array
|
|
of s1max wide characters pointed to by s1 take unspecified values when wcscat_s returns.<a href='#FOOTNOTE.534'><sup>[534]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.534'>
|
|
<pre><i><b>Footnote 534)</b> This allows an implementation to append wide characters from s2 to s1 while simultaneously checking if any of those
|
|
wide characters are null. Such an approach might write a wide character to every element of s1 before discovering that the
|
|
first element was set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.1p7'></a>
|
|
<pre>7 The wcscat_s function returns zero<a href='#FOOTNOTE.535'><sup>[535]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.535'>
|
|
<pre><i><b>Footnote 535)</b> A zero return value implies that all of the requested wide characters from the wide string pointed to by s2 were appended
|
|
to the wide string pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.2.2 [The wcsncat_s function]</h3>
|
|
<a name='K.3.9.2.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
errno_t wcsncat_s(wchar_t * restrict s1, rsize_t s1max,
|
|
const wchar_t * restrict s2, rsize_t n);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p2'></a>
|
|
<pre>2 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to wcsncat_s.
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p3'></a>
|
|
<pre>3 Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than
|
|
RSIZE_MAX/sizeof(wchar_t). s1max shall not equal zero. m shall not equal zero.<a href='#FOOTNOTE.536'><sup>[536]</sup></a> If n
|
|
is not less than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take place
|
|
between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.536'>
|
|
<pre><i><b>Footnote 536)</b> Zero means that s1 was not null terminated upon entry to wcsncat_s .
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2p4'></a>
|
|
<pre>4 If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than
|
|
zero and not greater than RSIZE_MAX/sizeof(wchar_t), then wcsncat_s sets s1[0] to the null
|
|
wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p5'></a>
|
|
<pre>5 The wcsncat_s function appends not more than n successive wide characters (wide characters that
|
|
follow a null wide character are not copied) from the array pointed to by s2 to the end of the wide
|
|
string pointed to by s1. The initial wide character from s2 overwrites the null wide character at the
|
|
end of s1. If no null wide character was copied from s2, then s1[s1max- m +n] is set to a null wide
|
|
character.
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p6'></a>
|
|
<pre>6 All elements following the terminating null wide character (if any) written by wcsncat_s in the array
|
|
of s1max wide characters pointed to by s1 take unspecified values when wcsncat_s returns.<a href='#FOOTNOTE.537'><sup>[537]</sup></a>
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.537'>
|
|
<pre><i><b>Footnote 537)</b> This allows an implementation to append wide characters from s2 to s1 while simultaneously checking if any of those
|
|
wide characters are null. Such an approach might write a wide character to every element of s1 before discovering that the
|
|
first element was set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2p7'></a>
|
|
<pre>7 The wcsncat_s function returns zero<a href='#FOOTNOTE.538'><sup>[538]</sup></a> if there was no runtime-constraint violation. Otherwise, a
|
|
nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.538'>
|
|
<pre><i><b>Footnote 538)</b> A zero return value implies that all of the requested wide characters from the wide string pointed to by s2 were appended
|
|
to the wide string pointed to by s1 and that the result in s1 is null terminated.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2p8'></a>
|
|
<pre>8 EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the result will not be null
|
|
terminated or that wide characters will be written past the end of the destination array.
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
/* ... */
|
|
wchar_t s1[100] = L"good";
|
|
wchar_t s2[6] = L"hello";
|
|
wchar_t s3[6] = L"hello";
|
|
wchar_t s4[7] = L"abc";
|
|
wchar_t s5[1000] = L"bye";
|
|
int r1, r2, r3, r4;
|
|
r1 = wcsncat_s(s1, 100, s5, 1000);
|
|
r2 = wcsncat_s(s2, 6, L"", 1);
|
|
r3 = wcsncat_s(s3, 6, L"X", 2);
|
|
r4 = wcsncat_s(s4, 7, L"defghijklmn", 3);
|
|
|
|
After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0.
|
|
After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0.
|
|
After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0.
|
|
After the fourth call r4 will have the value zero and s4 will be the wide character sequence abcdef\0.
|
|
|
|
</pre>
|
|
<a name='K.3.9.2.3'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.3 [Wide string search functions]</h3>
|
|
<a name='K.3.9.2.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.3.1 [The wcstok_s function]</h3>
|
|
<a name='K.3.9.2.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
wchar_t *wcstok_s(wchar_t * restrict s1, rsize_t * restrict s1max,
|
|
const wchar_t * restrict s2, wchar_t ** restrict ptr);
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p2'></a>
|
|
<pre>2 None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr shall not be a null
|
|
pointer. The value of *s1max shall not be greater than RSIZE_MAX/sizeof(wchar_t). The end of
|
|
the token found shall occur within the first *s1max wide characters of s1 for the first call, and shall
|
|
occur within the first *s1max wide characters of where searching resumes on subsequent calls.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, the wcstok_s function does not indirect through the s1 or
|
|
s2 pointers, and does not store a value in the object pointed to by ptr.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p4'></a>
|
|
<pre>4 A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1 into a sequence
|
|
of tokens, each of which is delimited by a wide character from the wide string pointed to by s2.
|
|
The fourth argument points to a caller-provided wchar_t pointer into which the wcstok_s function
|
|
stores information necessary for it to continue scanning the same wide string.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p5'></a>
|
|
<pre>5 The first call in a sequence has a non-null first argument and s1max points to an object whose value
|
|
is the number of elements in the wide character array pointed to by the first argument. The first call
|
|
stores an initial value in the object pointed to by ptr and updates the value pointed to by s1max
|
|
to reflect the number of elements that remain in relation to ptr. Subsequent calls in the sequence
|
|
have a null first argument and the objects pointed to by s1max and ptr are required to have the
|
|
values stored by the previous call in the sequence, which are then updated. The separator wide
|
|
string pointed to by s2 may be different from call to call.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p6'></a>
|
|
<pre>6 The first call in the sequence searches the wide string pointed to by s1 for the first wide character
|
|
that is not contained in the current separator wide string pointed to by s2. If no such wide character
|
|
is found, then there are no tokens in the wide string pointed to by s1 and the wcstok_s function
|
|
returns a null pointer. If such a wide character is found, it is the start of the first token.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p7'></a>
|
|
<pre>7 The wcstok_s function then searches from there for the first wide character in s1 that is contained
|
|
in the current separator wide string. If no such wide character is found, the current token extends
|
|
to the end of the wide string pointed to by s1, and subsequent searches in the same wide string
|
|
for a token return a null pointer. If such a wide character is found, it is overwritten by a null wide
|
|
character, which terminates the current token.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p8'></a>
|
|
<pre>8 In all cases, the wcstok_s function stores sufficient information in the pointer pointed to by ptr so
|
|
that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start
|
|
searching just past the element overwritten by a null wide character (if any).
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p9'></a>
|
|
<pre>9 The wcstok_s function returns a pointer to the first wide character of a token, or a null pointer if
|
|
there is no token or there is a runtime-constraint violation.
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p10'></a>
|
|
<pre>10 EXAMPLE
|
|
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
static wchar_t str1[] = L"?a???b,,,#c";
|
|
static wchar_t str2[] = L"\t \t";
|
|
wchar_t *t, *ptr1, *ptr2;
|
|
rsize_t max1 = wcslen(str1)+1;
|
|
rsize_t max2 = wcslen(str2)+1;
|
|
|
|
t = wcstok_s(str1, &max1, "?", &ptr1); // t points to the token "a"
|
|
t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
|
|
t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
|
|
t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
|
|
t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
|
|
|
|
|
|
</pre>
|
|
<a name='K.3.9.2.4'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.4 [Miscellaneous functions]</h3>
|
|
<a name='K.3.9.2.4.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.2.4.1 [The wcsnlen_s function]</h3>
|
|
<a name='K.3.9.2.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#define __STDC_WANT_LIB_EXT1__ 1
|
|
#include <wchar.h>
|
|
size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.4.1p2'></a>
|
|
<pre>2 The wcsnlen_s function computes the length of the wide string pointed to by s.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.2.4.1p3'></a>
|
|
<pre>3 If s is a null pointer,<a href='#FOOTNOTE.539'><sup>[539]</sup></a> then the wcsnlen_s function returns zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.539'>
|
|
<pre><i><b>Footnote 539)</b> Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints along with the values
|
|
returned for a null pointer or an unterminated wide string argument make wcsnlen_s useful in algorithms that gracefully
|
|
handle such exceptional data.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.4.1p4'></a>
|
|
<pre>4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede the termi-
|
|
nating null wide character. If there is no null wide character in the first maxsize wide characters of
|
|
s then wcsnlen_s returns maxsize. At most the first maxsize wide characters of s shall be accessed
|
|
by wcsnlen_s.
|
|
|
|
</pre>
|
|
<a name='K.3.9.3'></a>
|
|
<hr>
|
|
<h3>K.3.9.3 [Extended multibyte/wide character conversion utilities]</h3>
|
|
<a name='K.3.9.3.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.3.1 [Restartable multibyte/wide character conversion functions]</h3>
|
|
<a name='K.3.9.3.1p1'></a>
|
|
<pre>1 Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the conversion state)
|
|
to be a null pointer.
|
|
|
|
</pre>
|
|
<a name='K.3.9.3.1.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.3.1.1 [The wcrtomb_s function]</h3>
|
|
<a name='K.3.9.3.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
errno_t wcrtomb_s(size_t * restrict retval, char * restrict s, rsize_t smax,
|
|
wchar_t wc, mbstate_t * restrict ps);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p2'></a>
|
|
<pre>2 Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax shall not equal
|
|
zero and shall not be greater than RSIZE_MAX. If s is not a null pointer, then smax shall be not be less
|
|
than the number of bytes to be stored in the array pointed to by s. If s is a null pointer, then smax
|
|
shall equal zero.
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is not a null pointer
|
|
and smax is greater than zero and not greater than RSIZE_MAX, then wcrtomb_s sets s[0] to the null
|
|
character. If retval is not a null pointer, then wcrtomb_s sets *retval to (size_t)(-1) .
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p4'></a>
|
|
<pre>4 If s is a null pointer, the wcrtomb_s function is equivalent to the call
|
|
|
|
wcrtomb_s(&retval, buf, sizeof buf, L’\0’, ps)
|
|
|
|
|
|
where retval and buf are internal variables of the appropriate types, and the size of buf is greater
|
|
than MB_CUR_MAX.
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p5'></a>
|
|
<pre>5 If s is not a null pointer, the wcrtomb_s function determines the number of bytes needed to represent
|
|
the multibyte character that corresponds to the wide character given by wc (including any shift
|
|
sequences), and stores the multibyte character representation in the array whose first element is
|
|
pointed to by s. At most MB_CUR_MAX bytes are stored. If wc is a null wide character, a null byte is
|
|
stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state
|
|
described is the initial conversion state.
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p6'></a>
|
|
<pre>6 If wc does not correspond to a valid multibyte character, an encoding error occurs: the wcrtomb_s
|
|
function stores the value (size_t)(-1) into *retval and the conversion state is unspecified.
|
|
Otherwise, the wcrtomb_s function stores into *retval the number of bytes (including any shift
|
|
sequences) stored in the array pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.3.1.1p7'></a>
|
|
<pre>7 The wcrtomb_s function returns zero if no runtime-constraint violation and no encoding error
|
|
occurred. Otherwise, a nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.9.3.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.3.2 [Restartable multibyte/wide string conversion functions]</h3>
|
|
<a name='K.3.9.3.2p1'></a>
|
|
<pre>1 Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not permit the ps parameter
|
|
(the pointer to the conversion state) to be a null pointer.
|
|
|
|
</pre>
|
|
<a name='K.3.9.3.2.1'></a>
|
|
<hr>
|
|
<h3>K.3.9.3.2.1 [The mbsrtowcs_s function]</h3>
|
|
<a name='K.3.9.3.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
errno_t mbsrtowcs_s(size_t * restrict retval, wchar_t * restrict dst,
|
|
rsize_t dstmax, const char ** restrict src, rsize_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p2'></a>
|
|
<pre>2 None of retval, src, *src , or ps shall be null pointers. If dst is not a null pointer, then neither
|
|
len nor dstmax shall be greater than RSIZE_MAX/sizeof(wchar_t). If dst is a null pointer, then
|
|
dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal zero. If dst is not a
|
|
null pointer and len is not less than dstmax, then a null character shall occur within the first dstmax
|
|
multibyte characters of the array pointed to by *src .
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If retval is not
|
|
a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1) . If dst is not a null pointer and
|
|
dstmax is greater than zero and not greater than RSIZE_MAX/sizeof(wchar_t), then mbsrtowcs_s
|
|
sets dst[0] to the null wide character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p4'></a>
|
|
<pre>4 The mbsrtowcs_s function converts a sequence of multibyte characters that begins in the conversion
|
|
state described by the object pointed to by ps, from the array indirectly pointed to by src into a
|
|
sequence of corresponding wide characters. If dst is not a null pointer, the converted characters are
|
|
stored into the array pointed to by dst. Conversion continues up to and including a terminating null
|
|
character, which is also stored. Conversion stops earlier in two cases: when a sequence of bytes is
|
|
encountered that does not form a valid multibyte character, or (if dst is not a null pointer) when len
|
|
wide characters have been stored into the array pointed to by dst.<a href='#FOOTNOTE.540'><sup>[540]</sup></a> If dst is not a null pointer
|
|
and no null wide character was stored into the array pointed to by dst, then dst[len] is set to the
|
|
null wide character. Each conversion takes place as if by a call to the mbrtowc function.
|
|
</pre>
|
|
<a name='FOOTNOTE.540'>
|
|
<pre><i><b>Footnote 540)</b> Thus, the value of len is ignored if dst is a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.3.2.1p5'></a>
|
|
<pre>5 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if
|
|
conversion stopped due to reaching a terminating null character) or the address just past the last
|
|
multibyte character converted (if any). If conversion stopped due to reaching a terminating null
|
|
character and if dst is not a null pointer, the resulting state described is the initial conversion state.
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p6'></a>
|
|
<pre>6 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a sequence
|
|
of bytes that do not form a valid multibyte character, an encoding error occurs: the mbsrtowcs_s
|
|
function stores the value (size_t)(-1) into *retval and the conversion state is unspecified.
|
|
Otherwise, the mbsrtowcs_s function stores into *retval the number of multibyte characters
|
|
successfully converted, not including the terminating null character (if any).
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p7'></a>
|
|
<pre>7 All elements following the terminating null wide character (if any) written by mbsrtowcs_s in the
|
|
array of dstmax wide characters pointed to by dst take unspecified values when mbsrtowcs_s
|
|
returns.<a href='#FOOTNOTE.541'><sup>[541]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.541'>
|
|
<pre><i><b>Footnote 541)</b> This allows an implementation to attempt converting the multibyte string before discovering a terminating null character
|
|
did not occur where required.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.3.2.1p8'></a>
|
|
<pre>8 If copying takes place between objects that overlap, the objects take on unspecified values.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p9'></a>
|
|
<pre>9 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no encoding error
|
|
occurred. Otherwise, a nonzero value is returned.
|
|
|
|
</pre>
|
|
<a name='K.3.9.3.2.2'></a>
|
|
<hr>
|
|
<h3>K.3.9.3.2.2 [The wcsrtombs_s function]</h3>
|
|
<a name='K.3.9.3.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
errno_t wcsrtombs_s(size_t * restrict retval, char * restrict dst,
|
|
rsize_t dstmax, const wchar_t ** restrict src, rsize_t len,
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
|
|
Runtime-constraints
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p2'></a>
|
|
<pre>2 None of retval, src, *src , or ps shall be null pointers. If dst is not a null pointer, then neither len
|
|
shall be greater than RSIZE_MAX/sizeof(wchar_t) nor dstmax shall be greater than RSIZE_MAX. If
|
|
dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not
|
|
equal zero. If dst is not a null pointer and len is not less than dstmax, then the conversion shall
|
|
have been stopped (see below) because a terminating null wide character was reached or because an
|
|
encoding error occurred.
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p3'></a>
|
|
<pre>3 If there is a runtime-constraint violation, then wcsrtombs_s does the following. If retval is not
|
|
a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1) . If dst is not a null pointer and
|
|
dstmax is greater than zero and not greater than RSIZE_MAX, then wcsrtombs_s sets dst[0] to the
|
|
null character.
|
|
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p4'></a>
|
|
<pre>4 The wcsrtombs_s function converts a sequence of wide characters from the array indirectly pointed
|
|
to by src into a sequence of corresponding multibyte characters that begins in the conversion state
|
|
described by the object pointed to by ps. If dst is not a null pointer, the converted characters are then
|
|
stored into the array pointed to by dst. Conversion continues up to and including a terminating
|
|
null wide character, which is also stored. Conversion stops earlier in two cases:
|
|
|
|
— when a wide character is reached that does not correspond to a valid multibyte character;
|
|
|
|
— (if dst is not a null pointer) when the next multibyte character would exceed the limit of n
|
|
total bytes to be stored into the array pointed to by dst. If the wide character being converted
|
|
is the null wide character, then n is the lesser of len or dstmax. Otherwise, n is the lesser of
|
|
len or dstmax-1.
|
|
|
|
If the conversion stops without converting a null wide character and dst is not a null pointer, then
|
|
a null character is stored into the array pointed to by dst immediately following any multibyte
|
|
characters already stored. Each conversion takes place as if by a call to the wcrtomb function.<a href='#FOOTNOTE.542'><sup>[542]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.542'>
|
|
<pre><i><b>Footnote 542)</b> If conversion stops because a terminating null wide character has been reached, the bytes stored include those necessary
|
|
to reach the initial shift state immediately before the null byte. However, if the conversion stops before a terminating null
|
|
wide character has been reached, the result will be null terminated, but might not end in the initial shift state.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.3.2.2p5'></a>
|
|
<pre>5 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if
|
|
conversion stopped due to reaching a terminating null wide character) or the address just past the
|
|
last wide character converted (if any). If conversion stopped due to reaching a terminating null wide
|
|
character, the resulting state described is the initial conversion state.
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p6'></a>
|
|
<pre>6 Regardless of whether dst is or is not a null pointer, if the input conversion encounters a wide
|
|
character that does not correspond to a valid multibyte character, an encoding error occurs: the
|
|
wcsrtombs_s function stores the value (size_t)(-1) into *retval and the conversion state is
|
|
unspecified. Otherwise, the wcsrtombs_s function stores into *retval the number of bytes in the
|
|
resulting multibyte character sequence, not including the terminating null character (if any).
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p7'></a>
|
|
<pre>7 All elements following the terminating null character (if any) written by wcsrtombs_s in the array
|
|
of dstmax elements pointed to by dst take unspecified values when wcsrtombs_s returns.<a href='#FOOTNOTE.543'><sup>[543]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.543'>
|
|
<pre><i><b>Footnote 543)</b> When len is not less than dstmax, the implementation might fill the array before discovering a runtime-constraint
|
|
violation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.3.2.2p8'></a>
|
|
<pre>8 If copying takes place between objects that overlap, the objects take on unspecified values.
|
|
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.3.2.2p9'></a>
|
|
<pre>9 The wcsrtombs_s function returns zero if no runtime-constraint violation and no encoding error
|
|
occurred. Otherwise, a nonzero value is returned.
|
|
|
|
|
|
</pre>
|
|
<a name='L.'></a>
|
|
<hr>
|
|
<h3>L. [Annex L (normative) Analyzability]</h3>
|
|
<a name='L.1'></a>
|
|
<hr>
|
|
<h3>L.1 [Scope]</h3>
|
|
<a name='L.1p1'></a>
|
|
<pre>1 This annex specifies optional behavior that can aid in the analyzability of C programs.
|
|
</pre>
|
|
<a name='L.1p2'></a>
|
|
<pre>2 An implementation that defines __STDC_ANALYZABLE__ shall conform to the specifications in this
|
|
annex.<a href='#FOOTNOTE.544'><sup>[544]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.544'>
|
|
<pre><i><b>Footnote 544)</b> Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these specifications.
|
|
</i></pre>
|
|
</a>
|
|
<a name='L.2'></a>
|
|
<hr>
|
|
<h3>L.2 [Definitions]</h3>
|
|
<a name='L.2.1'></a>
|
|
<hr>
|
|
<h3>L.2.1 [Definitions]</h3>
|
|
<a name='L.2.1p1'></a>
|
|
<pre>1 out-of-bounds store
|
|
an (attempted) access (<a href='#3.1'>3.1</a>) that, at run time, for a given computational state, would modify (or, for
|
|
an object declared volatile, fetch) one or more bytes that lie outside the bounds permitted by this
|
|
document.
|
|
|
|
</pre>
|
|
<a name='L.2.2'></a>
|
|
<hr>
|
|
<h3>L.2.2 [Definitions]</h3>
|
|
<a name='L.2.2p1'></a>
|
|
<pre>1 bounded undefined behavior
|
|
undefined behavior (<a href='#3.4.3'>3.4.3</a>) that does not perform an out-of-bounds store.
|
|
</pre>
|
|
<a name='L.2.2p2'></a>
|
|
<pre>2 Note 1 to entry: The behavior might perform a trap.
|
|
</pre>
|
|
<a name='L.2.2p3'></a>
|
|
<pre>3 Note 2 to entry: Any values produced might be unspecified values, and the representation of objects that are written to
|
|
might become indeterminate.
|
|
|
|
</pre>
|
|
<a name='L.2.3'></a>
|
|
<hr>
|
|
<h3>L.2.3 [Definitions]</h3>
|
|
<a name='L.2.3p1'></a>
|
|
<pre>1 critical undefined behavior
|
|
undefined behavior that is not bounded undefined behavior.
|
|
</pre>
|
|
<a name='L.2.3p2'></a>
|
|
<pre>2 Note 1 to entry: The behavior might perform an out-of-bounds store or perform a trap.
|
|
|
|
</pre>
|
|
<a name='L.3'></a>
|
|
<hr>
|
|
<h3>L.3 [Requirements]</h3>
|
|
<a name='L.3p1'></a>
|
|
<pre>1 If the program performs a trap (<a href='#3.19.5'>3.19.5</a>), the implementation is permitted to invoke a runtime-
|
|
constraint handler. Any such semantics are implementation-defined.
|
|
</pre>
|
|
<a name='L.3p2'></a>
|
|
<pre>2 All undefined behavior shall be limited to bounded undefined behavior, except for the following
|
|
which are permitted to result in critical undefined behavior:
|
|
|
|
— An object is referred to outside of its lifetime (<a href='#6.2.4'>6.2.4</a>).
|
|
|
|
— A store is performed to an object that has two incompatible declarations (<a href='#6.2.7'>6.2.7</a>),
|
|
|
|
— A pointer is used to call a function whose type is not compatible with the referenced type
|
|
(<a href='#6.2.7'>6.2.7</a>, <a href='#6.3.2.3'>6.3.2.3</a>, <a href='#6.5.2.2'>6.5.2.2</a>).
|
|
|
|
— An lvalue does not designate an object when evaluated (<a href='#6.3.2.1'>6.3.2.1</a>).
|
|
|
|
— The program attempts to modify a string literal (<a href='#6.4.5'>6.4.5</a>).
|
|
|
|
— The operand of the unary * operator has an invalid value (<a href='#6.5.3.2'>6.5.3.2</a>).
|
|
|
|
— Addition or subtraction of a pointer into, or just beyond, an array object and an integer type
|
|
produces a result that points just beyond the array object and is used as the operand of a unary
|
|
* operator that is evaluated (<a href='#6.5.6'>6.5.6</a>).
|
|
|
|
— An attempt is made to modify an object defined with a const-qualified type through use of an
|
|
lvalue with non-const-qualified type (<a href='#6.7.3'>6.7.3</a>).
|
|
— An argument to a function or macro defined in the standard library has an invalid value or a
|
|
type not expected by a function with variable number of arguments (<a href='#7.1.4'>7.1.4</a>).
|
|
— The longjmp function is called with a jmp_buf argument where the most recent invocation
|
|
of the setjmp macro in the same invocation of the program with the corresponding jmp_buf
|
|
argument is nonexistent, or the invocation was from another thread of execution, or the
|
|
function containing the invocation has terminated execution in the interim, or the invocation
|
|
was within the scope of an identifier with variably modified type and execution has left that
|
|
scope in the interim (<a href='#7.13.2.1'>7.13.2.1</a>).
|
|
— The value of a pointer that refers to space deallocated by a call to the free or realloc function is
|
|
used (<a href='#7.24.3'>7.24.3</a>).
|
|
— A string or wide string utility function accesses an array beyond the end of an object (<a href='#7.26.1'>7.26.1</a>,
|
|
and <a href='#7.31.4'>7.31.4</a>).
|
|
|
|
|
|
</pre>
|
|
<a name='M.'></a>
|
|
<hr>
|
|
<h3>M. [Annex M (informative) Change History]</h3>
|
|
<a name='M.1'></a>
|
|
<hr>
|
|
<h3>M.1 [Fifth Edition]</h3>
|
|
<a name='M.1p1'></a>
|
|
<pre>1 Major changes in this fifth edition (__STDC_VERSION__ 202311L) include:
|
|
|
|
— allowed for implementations to provide keywords such as bool, static_assert, true, false,
|
|
and others with additional support to define them as macros and enable transition of programs
|
|
easily;
|
|
|
|
— removed obsolete sign representations and integer width constraints (so-called "2’s comple-
|
|
ment");
|
|
|
|
— added a one-argument version of static_assert;
|
|
|
|
— removed support for function definitions with identifier lists;
|
|
|
|
— mandated function declarations whose parameter list is empty by the same as parameter list
|
|
which only contain a single void;
|
|
|
|
— harmonization with ISO/IEC 9945 (POSIX):
|
|
|
|
• extended month name formats for strftime
|
|
• integration of functions: gmtime_r, localtime_r, memccpy, strdup, strndup
|
|
|
|
— harmonization with floating point standard IEC 60559:
|
|
|
|
• integration of binary floating-point technical specification TS 18661-1
|
|
• integration of decimal floating-point technical specification TS 18661-2
|
|
• integration of decimal floating-point technical specification TS 18661-4a
|
|
|
|
— made the DECIMAL_DIG macro obsolescent;
|
|
|
|
— added version test macros to certain library headers to aid in upgrading and portability to be
|
|
used alongside the __STDC_VERSION__ macro;
|
|
|
|
— added the attributes feature, which includes the attributes:
|
|
|
|
• deprecated, for marking entites as discouraged for future use;
|
|
• fallthrough, for explicitly marking cases where fallthrough in switches or labels is
|
|
intended rather than accidental;
|
|
• maybe_unused, for marking entities which may end up not being used;
|
|
• nodiscard, for marking entities which, when used, should have their value handled in
|
|
some way by a program;
|
|
• reproducible, for marking function types for which inputs may always produce pre-
|
|
dictable output if given the same input (e.g., cached data) but for which the order of such
|
|
calls still matter;
|
|
• unsequenced, for marking function types which always produce predictable output and
|
|
have no dependencies upon other data (and other relevant caveats), and,
|
|
• _Noreturn , for indicating a function shall never return;
|
|
|
|
— added the u8 character prefix to match the u8 string prefix;
|
|
|
|
— mandated all u8, u, and U strings be UTF-8, UTF-16, and UTF-32, respectively, as defined by
|
|
ISO/IEC 10646;
|
|
— separated the literal, wide literal, and UTF-8 literal, UTF-16 literal, and UTF-32 literal encodings
|
|
for strings and characters and now have a solely execution-based version of these, particularly
|
|
execution and wide execution encodings;
|
|
|
|
— added mbrtoc8 and c8rtomb functions missing from <uchar.h>;
|
|
|
|
— compound literals may also include storage-class specifiers as part of the type to change the
|
|
lifetime of the compound literal (and possibly turn it into a constant expression)
|
|
|
|
— added the constexpr specifier for object definitions and improved what is recognized as a
|
|
constant expression in conjunction with the constexpr storage-class specifier;
|
|
|
|
— added the typeof and typeof_unqual operations for computing the type of an expression;
|
|
|
|
— improved tag compatibility rules, enabling more types to be compatible with other types;
|
|
|
|
— added the _BitInt the bit-precise integer types;
|
|
|
|
— improved rules for handling enumerations without underlying types;
|
|
|
|
— added a new colon-delimited type specifier for enumerations to specify a fixed underlying
|
|
type;
|
|
|
|
— added a new header <stdbit.h> and a suite of bit and byte-handling utilities for portable
|
|
access to many implementation’s most efficiency functionality;
|
|
|
|
— modified existing functions to preserve the const-ness of the type placed into the function;
|
|
|
|
— added a feature to embed binary data as faithfully as possible with a new preprocessor directive
|
|
#embed;
|
|
|
|
— added a nullptr constant and a nullptr_t type with a well-defined underlying representa-
|
|
tion identical to a pointer to void;
|
|
|
|
— added the __VA_OPT__ specifier and clarified language in the handling of macro invocation
|
|
and arguments;
|
|
|
|
— mandated support for variably-modified types (but not variable-length arrays themselves);
|
|
|
|
— ellipses on functions may appear without a preceding parameter in the parameter list of
|
|
functions and va_start no longer requires such an argument to be passed to it;
|
|
|
|
— unicode identifiers allowed in syntax;
|
|
|
|
— memset_explicit function for writing data;
|
|
|
|
— certain type definitions, bit-precise integer types, and extended integer types may exceed
|
|
the normal boundaries of intmax_t and uintmax_t for signed and unsigned integer types,
|
|
respectively;
|
|
|
|
— names of functions, macros, and variables in this document, where clarified, are potentially
|
|
reserved rather than reserved to avoid undefined behavior for a large class of identifiers used
|
|
by programs existing and to be created;
|
|
|
|
— mandated support for call_once;
|
|
|
|
— allowed ptrdiff_t to be an integer type of at least 16, rather than requiring an integer type
|
|
with a width of at least 17;
|
|
|
|
— added the __has_include feature;
|
|
|
|
— changed the type qualifiers of the _Imaginary_I and _Complex_I macros;
|
|
|
|
— added $ and $ into the source and execution character set;
|
|
— added the auto type specifier for single object definitions using type inference;
|
|
|
|
— added the #elifdef and #elifndef conditional inclusion preprocessor directives;
|
|
|
|
— added the #warning directive;
|
|
|
|
— binary integer literals and appropriate formatting for input/output of binary integer numbers;
|
|
|
|
— digit seperators with ’ ;
|
|
|
|
— removed conditional support for mixed wide and narrow string literal concatenation;
|
|
|
|
— added support for additional time bases in time.h;
|
|
|
|
— zero-sized reallocations with realloc are undefined behavior;
|
|
|
|
— added an unreachable feature which invokes undefined behavior if reached during program
|
|
execution;
|
|
|
|
</pre>
|
|
<a name='M.2'></a>
|
|
<hr>
|
|
<h3>M.2 [Fourth Edition]</h3>
|
|
<a name='M.2p1'></a>
|
|
<pre>1 There were no major changes in the fourth edition (__STDC_VERSION__ 201710L), only technical
|
|
corrections and clarifications.
|
|
|
|
</pre>
|
|
<a name='M.3'></a>
|
|
<hr>
|
|
<h3>M.3 [Third Edition]</h3>
|
|
<a name='M.3p1'></a>
|
|
<pre>1 Major changes in the third edition (__STDC_VERSION__ 201112L) included:
|
|
|
|
— conditional (optional) features (including some that were previously mandatory)
|
|
|
|
— support for multiple threads of execution including an improved memory sequencing model,
|
|
atomic objects, and thread storage (<stdatomic.h> and <threads.h>)
|
|
|
|
— additional floating-point characteristic macros (<float.h>)
|
|
|
|
— querying and specifying alignment of objects (<stdalign.h>, <stdlib.h>)
|
|
|
|
— Unicode characters and strings (<uchar.h>) (originally specified in ISO/IEC TR 19769:2004)
|
|
|
|
— type-generic expressions
|
|
|
|
— static assertions
|
|
|
|
— anonymous structures and unions
|
|
|
|
— no-return functions
|
|
|
|
— macros to create complex numbers (<complex.h>)
|
|
|
|
— support for opening files for exclusive access
|
|
|
|
— removed the gets function (<stdio.h>)
|
|
|
|
— added the aligned_alloc, at_quick_exit, and quick_exit functions (<stdlib.h>)
|
|
|
|
— (conditional) support for bounds-checking interfaces (originally specified in ISO/IEC TR 24731–
|
|
1:2007)
|
|
|
|
— (conditional) support for analyzability
|
|
</pre>
|
|
<a name='M.4'></a>
|
|
<hr>
|
|
<h3>M.4 [Second Edition]</h3>
|
|
<a name='M.4p1'></a>
|
|
<pre>1 Major changes in the second edition (__STDC_VERSION__ 199901L) included:
|
|
|
|
— restricted character set support via digraphs and <iso646.h> (originally specified in
|
|
ISO/IEC 9899:1990/Amd 1:1995)
|
|
— wide character library support in <wchar.h> and <wctype.h> (originally specified in
|
|
ISO/IEC 9899:1990/Amd 1:1995)
|
|
— more precise aliasing rules via effective type
|
|
— restricted pointers
|
|
— variable length arrays
|
|
— flexible array members
|
|
— static and type qualifiers in parameter array declarators
|
|
— complex (and imaginary) support in <complex.h>
|
|
— type-generic math macros in <tgmath.h>
|
|
— the long long int type and library functions
|
|
— extended integer types
|
|
— increased minimum translation limits
|
|
— additional floating-point characteristics in <float.h>
|
|
— remove implicit int
|
|
— reliable integer division
|
|
— universal character names (\u and \U)
|
|
— extended identifiers
|
|
— hexadecimal floating constants and %a and %A printf/scanf conversion specifiers
|
|
— compound literals
|
|
— designated initializers
|
|
— // comments
|
|
— specified width integer types and corresponding library functions in <inttypes.h> and
|
|
<stdint.h>
|
|
|
|
— remove implicit function declaration
|
|
— preprocessor arithmetic done in intmax_t/uintmax_t
|
|
— mixed declarations and statements
|
|
— new block scopes for selection and iteration statements
|
|
— integer constant type rules
|
|
— integer promotion rules
|
|
— macros with a variable number of arguments (__VA_ARGS__ )
|
|
— the vscanf family of functions in <stdio.h> and <wchar.h>
|
|
— additional math library functions in <math.h>
|
|
— treatment of error conditions by math library functions (math_errhandling)
|
|
— floating-point environment access in <fenv.h>
|
|
— IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
|
|
|
|
— trailing comma allowed in enum declaration
|
|
— %lf conversion specifier allowed in printf
|
|
— inline functions
|
|
|
|
— the snprintf family of functions in <stdio.h>
|
|
— boolean type in <stdbool.h>
|
|
— idempotent type qualifiers
|
|
— empty macro arguments
|
|
|
|
— new structure type compatibility rules (tag compatibility)
|
|
— additional predefined macro names
|
|
— _Pragma preprocessing operator
|
|
— standard pragmas
|
|
|
|
— __func__ predefined identifier
|
|
— va_copy macro
|
|
— additional strftime conversion specifiers
|
|
|
|
— LIA compatibility annex
|
|
— deprecate ungetc at the beginning of a binary file
|
|
— remove deprecation of aliased array parameters
|
|
— conversion of array to pointer not limited to lvalues
|
|
|
|
— relaxed constraints on aggregate and union initialization
|
|
— relaxed restrictions on portable header names
|
|
— return without expression not permitted in function that returns a value (and vice versa)
|
|
|
|
</pre>
|
|
<a name='M.5'></a>
|
|
<hr>
|
|
<h3>M.5 [First Edition, Amendment 1]</h3>
|
|
<a name='M.5p1'></a>
|
|
<pre>1 Major changes in the amendment to the first edition (__STDC_VERSION__ 199409L) included:
|
|
|
|
— addition of the predefined __STDC_VERSION__ macro
|
|
|
|
— restricted character set support via digraphs and <iso646.h>
|
|
— wide character library support in <wchar.h> and <wctype.h>
|
|
</pre>
|
|
|
|
</body>
|
|
</html>
|