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<h2>ISO/IEC 9899:201x Committee Draft April 12, 2011 N1570</h2>
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<a name='ABSTRACT.'></a>
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<hr>
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<h3>ABSTRACT. [Abstract]</h3>
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<pre>(Cover sheet to be provided by ISO Secretariat.)
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This International Standard specifies the form and establishes the interpretation of
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programs expressed in the programming language C. Its purpose is to promote
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portability, reliability, maintainability, and efficient execution of C language programs on
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a variety of computing systems.
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Clauses are included that detail the C language itself and the contents of the C language
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execution library. Annexes summarize aspects of both of them, and enumerate factors
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that influence the portability of C programs.
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Although this International Standard is intended to guide knowledgeable C language
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programmers as well as implementors of C language translation systems, the document
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itself is not designed to serve as a tutorial.
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Recipients of this draft are invited to submit, with their comments, notification of any
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relevant patent rights of which they are aware and to provide supporting documentation.
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Changes from the previous draft (N1539) are indicated by ‘‘diff marks’’ in the right
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margin: deleted text is marked with ‘‘∗’’, new or changed text with ‘‘ ’’.
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</pre>
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<a name='CONTENTS.'></a>
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<hr>
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<h3>CONTENTS. [Contents]</h3>
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<pre><a href='#FOREWORD.'>Foreword</a>
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<a href='#INTRO.'>Introduction</a>
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<a href='#1.'>1.</a> Scope
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<a href='#2.'>2.</a> Normative references
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<a href='#3.'>3.</a> Terms, definitions, and symbols
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<a href='#4.'>4.</a> Conformance
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<a href='#5.'>5.</a> Environment
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<a href='#5.1'>5.1</a> Conceptual models
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<a href='#5.1.1'>5.1.1</a> Translation environment
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<a href='#5.1.2'>5.1.2</a> Execution environments
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<a href='#5.2'>5.2</a> Environmental considerations
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<a href='#5.2.1'>5.2.1</a> Character sets
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<a href='#5.2.2'>5.2.2</a> Character display semantics
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<a href='#5.2.3'>5.2.3</a> Signals and interrupts
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<a href='#5.2.4'>5.2.4</a> Environmental limits
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<a href='#6.'>6.</a> Language
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<a href='#6.1'>6.1</a> Notation
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<a href='#6.2'>6.2</a> Concepts
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<a href='#6.2.1'>6.2.1</a> Scopes of identifiers
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<a href='#6.2.2'>6.2.2</a> Linkages of identifiers
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<a href='#6.2.3'>6.2.3</a> Name spaces of identifiers
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<a href='#6.2.4'>6.2.4</a> Storage durations of objects
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<a href='#6.2.5'>6.2.5</a> Types
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<a href='#6.2.6'>6.2.6</a> Representations of types
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<a href='#6.2.7'>6.2.7</a> Compatible type and composite type
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<a href='#6.2.8'>6.2.8</a> Alignment of objects
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<a href='#6.3'>6.3</a> Conversions
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<a href='#6.3.1'>6.3.1</a> Arithmetic operands
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<a href='#6.3.2'>6.3.2</a> Other operands
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<a href='#6.4'>6.4</a> Lexical elements
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<a href='#6.4.1'>6.4.1</a> Keywords
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<a href='#6.4.2'>6.4.2</a> Identifiers
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<a href='#6.4.3'>6.4.3</a> Universal character names
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<a href='#6.4.4'>6.4.4</a> Constants
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<a href='#6.4.5'>6.4.5</a> String literals
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<a href='#6.4.6'>6.4.6</a> Punctuators
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<a href='#6.4.7'>6.4.7</a> Header names
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<a href='#6.4.8'>6.4.8</a> Preprocessing numbers
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<a href='#6.4.9'>6.4.9</a> Comments
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<a href='#6.5'>6.5</a> Expressions
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<a href='#6.5.1'>6.5.1</a> Primary expressions
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<a href='#6.5.2'>6.5.2</a> Postfix operators
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<a href='#6.5.3'>6.5.3</a> Unary operators
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<a href='#6.5.4'>6.5.4</a> Cast operators
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<a href='#6.5.5'>6.5.5</a> Multiplicative operators
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<a href='#6.5.6'>6.5.6</a> Additive operators
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<a href='#6.5.7'>6.5.7</a> Bitwise shift operators
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<a href='#6.5.8'>6.5.8</a> Relational operators
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<a href='#6.5.9'>6.5.9</a> Equality operators
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<a href='#6.5.10'>6.5.10</a> Bitwise AND operator
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<a href='#6.5.11'>6.5.11</a> Bitwise exclusive OR operator
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<a href='#6.5.12'>6.5.12</a> Bitwise inclusive OR operator
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<a href='#6.5.13'>6.5.13</a> Logical AND operator
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<a href='#6.5.14'>6.5.14</a> Logical OR operator
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<a href='#6.5.15'>6.5.15</a> Conditional operator
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<a href='#6.5.16'>6.5.16</a> Assignment operators
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<a href='#6.5.17'>6.5.17</a> Comma operator
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<a href='#6.6'>6.6</a> Constant expressions
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<a href='#6.7'>6.7</a> Declarations
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<a href='#6.7.1'>6.7.1</a> Storage-class specifiers
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<a href='#6.7.2'>6.7.2</a> Type specifiers
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<a href='#6.7.3'>6.7.3</a> Type qualifiers
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<a href='#6.7.4'>6.7.4</a> Function specifiers
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<a href='#6.7.5'>6.7.5</a> Alignment specifier
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<a href='#6.7.6'>6.7.6</a> Declarators
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<a href='#6.7.7'>6.7.7</a> Type names
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<a href='#6.7.8'>6.7.8</a> Type definitions
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<a href='#6.7.9'>6.7.9</a> Initialization
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<a href='#6.7.10'>6.7.10</a> Static assertions
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<a href='#6.8'>6.8</a> Statements and blocks
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<a href='#6.8.1'>6.8.1</a> Labeled statements
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<a href='#6.8.2'>6.8.2</a> Compound statement
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<a href='#6.8.3'>6.8.3</a> Expression and null statements
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<a href='#6.8.4'>6.8.4</a> Selection statements
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<a href='#6.8.5'>6.8.5</a> Iteration statements
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<a href='#6.8.6'>6.8.6</a> Jump statements
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<a href='#6.9'>6.9</a> External definitions
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<a href='#6.9.1'>6.9.1</a> Function definitions
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<a href='#6.9.2'>6.9.2</a> External object definitions
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<a href='#6.10'>6.10</a> Preprocessing directives
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<a href='#6.10.1'>6.10.1</a> Conditional inclusion
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<a href='#6.10.2'>6.10.2</a> Source file inclusion
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<a href='#6.10.3'>6.10.3</a> Macro replacement
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 <a href='#6.10.4'>6.10.4</a> Line control
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<a href='#6.10.5'>6.10.5</a> Error directive
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<a href='#6.10.6'>6.10.6</a> Pragma directive
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<a href='#6.10.7'>6.10.7</a> Null directive
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<a href='#6.10.8'>6.10.8</a> Predefined macro names
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<a href='#6.10.9'>6.10.9</a> Pragma operator
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<a href='#6.11'>6.11</a> Future language directions
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<a href='#6.11.1'>6.11.1</a> Floating types
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<a href='#6.11.2'>6.11.2</a> Linkages of identifiers
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<a href='#6.11.3'>6.11.3</a> External names
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<a href='#6.11.4'>6.11.4</a> Character escape sequences
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<a href='#6.11.5'>6.11.5</a> Storage-class specifiers
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<a href='#6.11.6'>6.11.6</a> Function declarators
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<a href='#6.11.7'>6.11.7</a> Function definitions
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<a href='#6.11.8'>6.11.8</a> Pragma directives
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<a href='#6.11.9'>6.11.9</a> Predefined macro names
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<a href='#7.'>7.</a> Library
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<a href='#7.1'>7.1</a> Introduction
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<a href='#7.1.1'>7.1.1</a> Definitions of terms
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<a href='#7.1.2'>7.1.2</a> Standard headers
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<a href='#7.1.3'>7.1.3</a> Reserved identifiers
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<a href='#7.1.4'>7.1.4</a> Use of library functions
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<a href='#7.2'>7.2</a> Diagnostics <assert.h>
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<a href='#7.2.1'>7.2.1</a> Program diagnostics
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<a href='#7.3'>7.3</a> Complex arithmetic <complex.h>
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<a href='#7.3.1'>7.3.1</a> Introduction
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<a href='#7.3.2'>7.3.2</a> Conventions
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<a href='#7.3.3'>7.3.3</a> Branch cuts
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<a href='#7.3.4'>7.3.4</a> The CX_LIMITED_RANGE pragma
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<a href='#7.3.5'>7.3.5</a> Trigonometric functions
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<a href='#7.3.6'>7.3.6</a> Hyperbolic functions
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<a href='#7.3.7'>7.3.7</a> Exponential and logarithmic functions
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<a href='#7.3.8'>7.3.8</a> Power and absolute-value functions
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<a href='#7.3.9'>7.3.9</a> Manipulation functions
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<a href='#7.4'>7.4</a> Character handling <ctype.h>
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<a href='#7.4.1'>7.4.1</a> Character classification functions
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<a href='#7.4.2'>7.4.2</a> Character case mapping functions
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<a href='#7.5'>7.5</a> Errors <errno.h>
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<a href='#7.6'>7.6</a> Floating-point environment <fenv.h>
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<a href='#7.6.1'>7.6.1</a> The FENV_ACCESS pragma
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<a href='#7.6.2'>7.6.2</a> Floating-point exceptions
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<a href='#7.6.3'>7.6.3</a> Rounding
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<a href='#7.6.4'>7.6.4</a> Environment
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<a href='#7.7'>7.7</a> Characteristics of floating types <float.h>
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<a href='#7.8'>7.8</a> Format conversion of integer types <inttypes.h>
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<a href='#7.8.1'>7.8.1</a> Macros for format specifiers
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<a href='#7.8.2'>7.8.2</a> Functions for greatest-width integer types
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<a href='#7.9'>7.9</a> Alternative spellings <iso646.h>
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<a href='#7.10'>7.10</a> Sizes of integer types <limits.h>
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<a href='#7.11'>7.11</a> Localization <locale.h>
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<a href='#7.11.1'>7.11.1</a> Locale control
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<a href='#7.11.2'>7.11.2</a> Numeric formatting convention inquiry
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<a href='#7.12'>7.12</a> Mathematics <math.h>
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<a href='#7.12.1'>7.12.1</a> Treatment of error conditions
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<a href='#7.12.2'>7.12.2</a> The FP_CONTRACT pragma
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<a href='#7.12.3'>7.12.3</a> Classification macros
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<a href='#7.12.4'>7.12.4</a> Trigonometric functions
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<a href='#7.12.5'>7.12.5</a> Hyperbolic functions
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<a href='#7.12.6'>7.12.6</a> Exponential and logarithmic functions
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<a href='#7.12.7'>7.12.7</a> Power and absolute-value functions
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<a href='#7.12.8'>7.12.8</a> Error and gamma functions
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<a href='#7.12.9'>7.12.9</a> Nearest integer functions
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<a href='#7.12.10'>7.12.10</a> Remainder functions
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<a href='#7.12.11'>7.12.11</a> Manipulation functions
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<a href='#7.12.12'>7.12.12</a> Maximum, minimum, and positive difference functions
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<a href='#7.12.13'>7.12.13</a> Floating multiply-add
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<a href='#7.12.14'>7.12.14</a> Comparison macros
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<a href='#7.13'>7.13</a> Nonlocal jumps <setjmp.h>
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<a href='#7.13.1'>7.13.1</a> Save calling environment
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<a href='#7.13.2'>7.13.2</a> Restore calling environment
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<a href='#7.14'>7.14</a> Signal handling <signal.h>
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<a href='#7.14.1'>7.14.1</a> Specify signal handling
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<a href='#7.14.2'>7.14.2</a> Send signal
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<a href='#7.15'>7.15</a> Alignment <stdalign.h>
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<a href='#7.16'>7.16</a> Variable arguments <stdarg.h>
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<a href='#7.16.1'>7.16.1</a> Variable argument list access macros
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<a href='#7.17'>7.17</a> Atomics <stdatomic.h>
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<a href='#7.17.1'>7.17.1</a> Introduction
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<a href='#7.17.2'>7.17.2</a> Initialization
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<a href='#7.17.3'>7.17.3</a> Order and consistency
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<a href='#7.17.4'>7.17.4</a> Fences
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<a href='#7.17.5'>7.17.5</a> Lock-free property
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<a href='#7.17.6'>7.17.6</a> Atomic integer types
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<a href='#7.17.7'>7.17.7</a> Operations on atomic types
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<a href='#7.17.8'>7.17.8</a> Atomic flag type and operations
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<a href='#7.18'>7.18</a> Boolean type and values <stdbool.h>
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<a href='#7.19'>7.19</a> Common definitions <stddef.h>
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<a href='#7.20'>7.20</a> Integer types <stdint.h>
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 <a href='#7.20.1'>7.20.1</a> Integer types
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<a href='#7.20.2'>7.20.2</a> Limits of specified-width integer types
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<a href='#7.20.3'>7.20.3</a> Limits of other integer types
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<a href='#7.20.4'>7.20.4</a> Macros for integer constants
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<a href='#7.21'>7.21</a> Input/output <stdio.h>
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<a href='#7.21.1'>7.21.1</a> Introduction
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<a href='#7.21.2'>7.21.2</a> Streams
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<a href='#7.21.3'>7.21.3</a> Files
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<a href='#7.21.4'>7.21.4</a> Operations on files
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<a href='#7.21.5'>7.21.5</a> File access functions
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<a href='#7.21.6'>7.21.6</a> Formatted input/output functions
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<a href='#7.21.7'>7.21.7</a> Character input/output functions
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<a href='#7.21.8'>7.21.8</a> Direct input/output functions
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<a href='#7.21.9'>7.21.9</a> File positioning functions
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<a href='#7.21.10'>7.21.10</a> Error-handling functions
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<a href='#7.22'>7.22</a> General utilities <stdlib.h>
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<a href='#7.22.1'>7.22.1</a> Numeric conversion functions
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<a href='#7.22.2'>7.22.2</a> Pseudo-random sequence generation functions
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<a href='#7.22.3'>7.22.3</a> Memory management functions
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<a href='#7.22.4'>7.22.4</a> Communication with the environment
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<a href='#7.22.5'>7.22.5</a> Searching and sorting utilities
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<a href='#7.22.6'>7.22.6</a> Integer arithmetic functions
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<a href='#7.22.7'>7.22.7</a> Multibyte/wide character conversion functions
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<a href='#7.22.8'>7.22.8</a> Multibyte/wide string conversion functions
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<a href='#7.23'>7.23</a> _Noreturn <stdnoreturn.h>
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<a href='#7.24'>7.24</a> String handling <string.h>
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<a href='#7.24.1'>7.24.1</a> String function conventions
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<a href='#7.24.2'>7.24.2</a> Copying functions
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<a href='#7.24.3'>7.24.3</a> Concatenation functions
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<a href='#7.24.4'>7.24.4</a> Comparison functions
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<a href='#7.24.5'>7.24.5</a> Search functions
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<a href='#7.24.6'>7.24.6</a> Miscellaneous functions
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<a href='#7.25'>7.25</a> Type-generic math <tgmath.h>
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<a href='#7.26'>7.26</a> Threads <threads.h>
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<a href='#7.26.1'>7.26.1</a> Introduction
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<a href='#7.26.2'>7.26.2</a> Initialization functions
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<a href='#7.26.3'>7.26.3</a> Condition variable functions
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<a href='#7.26.4'>7.26.4</a> Mutex functions
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<a href='#7.26.5'>7.26.5</a> Thread functions
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<a href='#7.26.6'>7.26.6</a> Thread-specific storage functions
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<a href='#7.27'>7.27</a> Date and time <time.h>
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<a href='#7.27.1'>7.27.1</a> Components of time
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<a href='#7.27.2'>7.27.2</a> Time manipulation functions
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<a href='#7.27.3'>7.27.3</a> Time conversion functions
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<a href='#7.28'>7.28</a> Unicode utilities <uchar.h>
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<a href='#7.28.1'>7.28.1</a> Restartable multibyte/wide character conversion functions
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<a href='#7.29'>7.29</a> Extended multibyte and wide character utilities <wchar.h>
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<a href='#7.29.1'>7.29.1</a> Introduction
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<a href='#7.29.2'>7.29.2</a> Formatted wide character input/output functions
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<a href='#7.29.3'>7.29.3</a> Wide character input/output functions
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<a href='#7.29.4'>7.29.4</a> General wide string utilities
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<a href='#7.29.4.1'>7.29.4.1</a> Wide string numeric conversion functions
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<a href='#7.29.4.2'>7.29.4.2</a> Wide string copying functions
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<a href='#7.29.4.3'>7.29.4.3</a> Wide string concatenation functions
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<a href='#7.29.4.4'>7.29.4.4</a> Wide string comparison functions
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<a href='#7.29.4.5'>7.29.4.5</a> Wide string search functions
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<a href='#7.29.4.6'>7.29.4.6</a> Miscellaneous functions
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<a href='#7.29.5'>7.29.5</a> Wide character time conversion functions
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<a href='#7.29.6'>7.29.6</a> Extended multibyte/wide character conversion utilities
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<a href='#7.29.6.1'>7.29.6.1</a> Single-byte/wide character conversion functions
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<a href='#7.29.6.2'>7.29.6.2</a> Conversion state functions
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<a href='#7.29.6.3'>7.29.6.3</a> Restartable multibyte/wide character conversion
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functions
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<a href='#7.29.6.4'>7.29.6.4</a> Restartable multibyte/wide string conversion
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functions
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<a href='#7.30'>7.30</a> Wide character classification and mapping utilities <wctype.h>
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<a href='#7.30.1'>7.30.1</a> Introduction
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<a href='#7.30.2'>7.30.2</a> Wide character classification utilities
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<a href='#7.30.2.1'>7.30.2.1</a> Wide character classification functions
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<a href='#7.30.2.2'>7.30.2.2</a> Extensible wide character classification
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functions
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<a href='#7.30.3'>7.30.3</a> Wide character case mapping utilities
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<a href='#7.30.3.1'>7.30.3.1</a> Wide character case mapping functions
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<a href='#7.30.3.2'>7.30.3.2</a> Extensible wide character case mapping
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functions
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<a href='#7.31'>7.31</a> Future library directions
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<a href='#7.31.1'>7.31.1</a> Complex arithmetic <complex.h>
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<a href='#7.31.2'>7.31.2</a> Character handling <ctype.h>
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<a href='#7.31.3'>7.31.3</a> Errors <errno.h>
|
|
<a href='#7.31.4'>7.31.4</a> Floating-point environment <fenv.h>
|
|
<a href='#7.31.5'>7.31.5</a> Format conversion of integer types <inttypes.h>
|
|
<a href='#7.31.6'>7.31.6</a> Localization <locale.h>
|
|
<a href='#7.31.7'>7.31.7</a> Signal handling <signal.h>
|
|
<a href='#7.31.8'>7.31.8</a> Atomics <stdatomic.h>
|
|
<a href='#7.31.9'>7.31.9</a> Boolean type and values <stdbool.h>
|
|
<a href='#7.31.10'>7.31.10</a> Integer types <stdint.h>
|
|
<a href='#7.31.11'>7.31.11</a> Input/output <stdio.h>
|
|
<a href='#7.31.12'>7.31.12</a> General utilities <stdlib.h>
|
|
 <a href='#7.31.13'>7.31.13</a> String handling <string.h>
|
|
<a href='#7.31.14'>7.31.14</a> Date and time <time.h>
|
|
<a href='#7.31.15'>7.31.15</a> Threads <threads.h>
|
|
<a href='#7.31.16'>7.31.16</a> Extended multibyte and wide character utilities
|
|
<wchar.h>
|
|
<a href='#7.31.17'>7.31.17</a> Wide character classification and mapping utilities
|
|
<wctype.h>
|
|
<a href='#A.'>Annex A</a> (informative) Language syntax summary
|
|
<a href='#A.1'>A.1</a> Lexical grammar
|
|
<a href='#A.2'>A.2</a> Phrase structure grammar
|
|
<a href='#A.3'>A.3</a> Preprocessing directives
|
|
<a href='#B.'>Annex B</a> (informative) Library summary
|
|
<a href='#B.1'>B.1</a> Diagnostics <assert.h>
|
|
<a href='#B.2'>B.2</a> Complex <complex.h>
|
|
<a href='#B.3'>B.3</a> Character handling <ctype.h>
|
|
<a href='#B.4'>B.4</a> Errors <errno.h>
|
|
<a href='#B.5'>B.5</a> Floating-point environment <fenv.h>
|
|
<a href='#B.6'>B.6</a> Characteristics of floating types <float.h>
|
|
<a href='#B.7'>B.7</a> Format conversion of integer types <inttypes.h>
|
|
<a href='#B.8'>B.8</a> Alternative spellings <iso646.h>
|
|
<a href='#B.9'>B.9</a> Sizes of integer types <limits.h>
|
|
<a href='#B.10'>B.10</a> Localization <locale.h>
|
|
<a href='#B.11'>B.11</a> Mathematics <math.h>
|
|
<a href='#B.12'>B.12</a> Nonlocal jumps <setjmp.h>
|
|
<a href='#B.13'>B.13</a> Signal handling <signal.h>
|
|
<a href='#B.14'>B.14</a> Alignment <stdalign.h>
|
|
<a href='#B.15'>B.15</a> Variable arguments <stdarg.h>
|
|
<a href='#B.16'>B.16</a> Atomics <stdatomic.h>
|
|
<a href='#B.17'>B.17</a> Boolean type and values <stdbool.h>
|
|
<a href='#B.18'>B.18</a> Common definitions <stddef.h>
|
|
<a href='#B.19'>B.19</a> Integer types <stdint.h>
|
|
<a href='#B.20'>B.20</a> Input/output <stdio.h>
|
|
<a href='#B.21'>B.21</a> General utilities <stdlib.h>
|
|
<a href='#B.22'>B.22</a> _Noreturn <stdnoreturn.h>
|
|
<a href='#B.23'>B.23</a> String handling <string.h>
|
|
<a href='#B.24'>B.24</a> Type-generic math <tgmath.h>
|
|
<a href='#B.25'>B.25</a> Threads <threads.h>
|
|
<a href='#B.26'>B.26</a> Date and time <time.h>
|
|
<a href='#B.27'>B.27</a> Unicode utilities <uchar.h>
|
|
<a href='#B.28'>B.28</a> Extended multibyte/wide character utilities <wchar.h>
|
|
<a href='#B.29'>B.29</a> Wide character classification and mapping utilities <wctype.h>
|
|
<a href='#C.'>Annex C</a> (informative) Sequence points
|
|
<a href='#D.'>Annex D</a> (normative) Universal character names for identifiers
|
|
<a href='#D.1'>D.1</a> Ranges of characters allowed
|
|
<a href='#D.2'>D.2</a> Ranges of characters disallowed initially
|
|
<a href='#E.'>Annex E</a> (informative) Implementation limits
|
|
<a href='#F.'>Annex F</a> (normative) IEC 60559 floating-point arithmetic
|
|
<a href='#F.1'>F.1</a> Introduction
|
|
<a href='#F.2'>F.2</a> Types
|
|
<a href='#F.3'>F.3</a> Operators and functions
|
|
<a href='#F.4'>F.4</a> Floating to integer conversion
|
|
<a href='#F.5'>F.5</a> Binary-decimal conversion
|
|
<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>
|
|
<a href='#F.10.1'>F.10.1</a> Trigonometric functions
|
|
<a href='#F.10.2'>F.10.2</a> Hyperbolic functions
|
|
<a href='#F.10.3'>F.10.3</a> Exponential and logarithmic functions
|
|
<a href='#F.10.4'>F.10.4</a> Power and absolute value functions
|
|
<a href='#F.10.5'>F.10.5</a> Error and gamma functions
|
|
<a href='#F.10.6'>F.10.6</a> Nearest integer functions
|
|
<a href='#F.10.7'>F.10.7</a> Remainder functions
|
|
<a href='#F.10.8'>F.10.8</a> Manipulation functions
|
|
<a href='#F.10.9'>F.10.9</a> Maximum, minimum, and positive difference functions
|
|
<a href='#F.10.10'>F.10.10</a> Floating multiply-add
|
|
<a href='#F.10.11'>F.10.11</a> Comparison macros
|
|
<a href='#G.'>Annex G</a> (normative) IEC 60559-compatible complex arithmetic
|
|
<a href='#G.1'>G.1</a> Introduction
|
|
<a href='#G.2'>G.2</a> Types
|
|
<a href='#G.3'>G.3</a> Conventions
|
|
<a href='#G.4'>G.4</a> Conversions
|
|
<a href='#G.4.1'>G.4.1</a> Imaginary types
|
|
<a href='#G.4.2'>G.4.2</a> Real and imaginary
|
|
<a href='#G.4.3'>G.4.3</a> Imaginary and complex
|
|
<a href='#G.5'>G.5</a> Binary operators
|
|
<a href='#G.5.1'>G.5.1</a> Multiplicative operators
|
|
<a href='#G.5.2'>G.5.2</a> Additive operators
|
|
<a href='#G.6'>G.6</a> Complex arithmetic <complex.h>
|
|
<a href='#G.6.1'>G.6.1</a> Trigonometric functions
|
|
<a href='#G.6.2'>G.6.2</a> Hyperbolic functions
|
|
<a href='#G.6.3'>G.6.3</a> Exponential and logarithmic functions
|
|
<a href='#G.6.4'>G.6.4</a> Power and absolute-value functions
|
|
<a href='#G.7'>G.7</a> Type-generic math <tgmath.h>
|
|
<a href='#H.'>Annex H</a> (informative) Language independent arithmetic
|
|
<a href='#H.1'>H.1</a> Introduction
|
|
<a href='#H.2'>H.2</a> Types
|
|
<a href='#H.3'>H.3</a> Notification
|
|
<a href='#I.'>Annex I</a> (informative) Common warnings
|
|
<a href='#J.'>Annex J</a> (informative) Portability issues
|
|
<a href='#J.1'>J.1</a> Unspecified behavior
|
|
<a href='#J.2'>J.2</a> Undefined behavior
|
|
<a href='#J.3'>J.3</a> Implementation-defined behavior
|
|
<a href='#J.4'>J.4</a> Locale-specific behavior
|
|
<a href='#J.5'>J.5</a> Common extensions
|
|
<a href='#K.'>Annex K</a> (normative) Bounds-checking interfaces
|
|
<a href='#K.1'>K.1</a> Background
|
|
<a href='#K.2'>K.2</a> Scope
|
|
<a href='#K.3'>K.3</a> Library
|
|
<a href='#K.3.1'>K.3.1</a> Introduction
|
|
<a href='#K.3.1.1'>K.3.1.1</a> Standard headers
|
|
<a href='#K.3.1.2'>K.3.1.2</a> Reserved identifiers
|
|
<a href='#K.3.1.3'>K.3.1.3</a> Use of errno
|
|
<a href='#K.3.1.4'>K.3.1.4</a> Runtime-constraint violations
|
|
<a href='#K.3.2'>K.3.2</a> Errors <errno.h>
|
|
<a href='#K.3.3'>K.3.3</a> Common definitions <stddef.h>
|
|
<a href='#K.3.4'>K.3.4</a> Integer types <stdint.h>
|
|
<a href='#K.3.5'>K.3.5</a> Input/output <stdio.h>
|
|
<a href='#K.3.5.1'>K.3.5.1</a> Operations on files .
|
|
<a href='#K.3.5.2'>K.3.5.2</a> File access functions
|
|
<a href='#K.3.5.3'>K.3.5.3</a> Formatted input/output functions
|
|
<a href='#K.3.5.4'>K.3.5.4</a> Character input/output functions
|
|
<a href='#K.3.6'>K.3.6</a> General utilities <stdlib.h>
|
|
<a href='#K.3.6.1'>K.3.6.1</a> Runtime-constraint handling
|
|
<a href='#K.3.6.2'>K.3.6.2</a> Communication with the environment
|
|
<a href='#K.3.6.3'>K.3.6.3</a> Searching and sorting utilities
|
|
<a href='#K.3.6.4'>K.3.6.4</a> Multibyte/wide character conversion functions
|
|
<a href='#K.3.6.5'>K.3.6.5</a> Multibyte/wide string conversion functions
|
|
<a href='#K.3.7'>K.3.7</a> String handling <string.h>
|
|
<a href='#K.3.7.1'>K.3.7.1</a> Copying functions
|
|
<a href='#K.3.7.2'>K.3.7.2</a> Concatenation functions
|
|
<a href='#K.3.7.3'>K.3.7.3</a> Search functions
|
|
<a href='#K.3.7.4'>K.3.7.4</a> Miscellaneous functions
|
|
<a href='#K.3.8'>K.3.8</a> Date and time <time.h>
|
|
<a href='#K.3.8.1'>K.3.8.1</a> Components of time
|
|
<a href='#K.3.8.2'>K.3.8.2</a> Time conversion functions
|
|
 <a href='#K.3.9'>K.3.9</a> Extended multibyte and wide character utilities
|
|
<wchar.h>
|
|
<a href='#K.3.9.1'>K.3.9.1</a> Formatted wide character input/output functions
|
|
<a href='#K.3.9.2'>K.3.9.2</a> General wide string utilities
|
|
<a href='#K.3.9.3'>K.3.9.3</a> Extended multibyte/wide character conversion
|
|
utilities
|
|
<a href='#L.'>Annex L</a> (normative) Analyzability
|
|
<a href='#L.1'>L.1</a> Scope
|
|
<a href='#L.2'>L.2</a> Definitions
|
|
<a href='#L.3'>L.3</a> Requirements
|
|

|
|
</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.
|
|
</pre>
|
|
<a name='FOREWORD.p2'></a>
|
|
<pre>2 International Standards are drafted in accordance with the rules given in the ISO/IEC
|
|
Directives, Part 2. This International Standard was drafted in accordance with the fifth
|
|
edition (2004).
|
|
</pre>
|
|
<a name='FOREWORD.p3'></a>
|
|
<pre>3 In the field of information technology, ISO and IEC have established a joint technical
|
|
committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
|
|
committee are circulated to national bodies for voting. Publication as an International
|
|
Standard requires approval by at least 75% of the national bodies casting a vote.
|
|
</pre>
|
|
<a name='FOREWORD.p4'></a>
|
|
<pre>4 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.
|
|
</pre>
|
|
<a name='FOREWORD.p5'></a>
|
|
<pre>5 This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1,
|
|
Information technology, Subcommittee SC 22, Programming languages, their
|
|
environments and system software interfaces. The Working Group responsible for this
|
|
standard (WG 14) maintains a site on the World Wide Web at http://www.open-
|
|
std.org/JTC1/SC22/WG14/ containing additional information relevant to this
|
|
standard such as a Rationale for many of the decisions made during its preparation and a
|
|
log of Defect Reports and Responses.
|
|
</pre>
|
|
<a name='FOREWORD.p6'></a>
|
|
<pre>6 This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as
|
|
corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and
|
|
ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include:
|
|
— 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-local 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='FOREWORD.p7'></a>
|
|
<pre>7 Major changes in the second edition included:
|
|
— restricted character set support via digraphs and <iso646.h> (originally specified
|
|
in AMD1)
|
|
— wide character library support in <wchar.h> and <wctype.h> (originally
|
|
specified in AMD1)
|
|
— 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
|
|
— 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-point constants and %a and %A printf/scanf conversion
|
|
specifiers
|
|
— compound literals
|
|
— designated initializers
|
|
— // comments
|
|
— extended integer types and library functions in <inttypes.h> and <stdint.h>
|
|
— remove implicit function declaration
|
|
— preprocessor arithmetic done in intmax_t/uintmax_t
|
|
— mixed declarations and code
|
|
— new block scopes for selection and iteration statements
|
|
— integer constant type rules
|
|
— integer promotion rules
|
|
— macros with a variable number of arguments
|
|
— 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='FOREWORD.p8'></a>
|
|
<pre>8 Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H,
|
|
I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
|
|
the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
|
|
are also for information only.
|
|
</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 may be
|
|
added to this International Standard. Subclauses in the language and library clauses warn
|
|
implementors and programmers of usages which, though valid in themselves, may
|
|
conflict with future additions.
|
|
</pre>
|
|
<a name='INTRO.p2'></a>
|
|
<pre>2 Certain features are obsolescent, which means that they may be considered for
|
|
withdrawal in future revisions of this International Standard. 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='#7.31'>7.31</a>]) is discouraged.
|
|
</pre>
|
|
<a name='INTRO.p3'></a>
|
|
<pre>3 This International Standard 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 International Standard. References are used to refer to
|
|
other related subclauses. Recommendations are provided to give advice or guidance to
|
|
implementors. Annexes provide additional information and summarize the information
|
|
contained in this International Standard. A bibliography lists documents that were
|
|
referred to during the preparation of the standard.
|
|
</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='1.'></a>
|
|
<hr>
|
|
<h3>1. [Scope]</h3>
|
|
<a name='1.p1'></a>
|
|
<pre>1 This International Standard 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 International Standard 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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='1.p2'></a>
|
|
<pre>2 This International Standard 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
|
|
conforming implementation.
|
|
</pre>
|
|
<a name='2.'></a>
|
|
<hr>
|
|
<h3>2. [Normative references]</h3>
|
|
<a name='2.p1'></a>
|
|
<pre>1 The following referenced documents are indispensable for the application 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 31−11:1992, Quantities and units — Part 11: Mathematical signs and symbols for
|
|
use in the physical sciences and technology.
|
|
</pre>
|
|
<a name='2.p3'></a>
|
|
<pre>3 ISO/IEC 646, Information technology — ISO 7-bit coded character set for information
|
|
interchange.
|
|
</pre>
|
|
<a name='2.p4'></a>
|
|
<pre>4 ISO/IEC 2382−1:1993, Information technology — Vocabulary — Part 1: Fundamental
|
|
terms.
|
|
</pre>
|
|
<a name='2.p5'></a>
|
|
<pre>5 ISO 4217, Codes for the representation of currencies and funds.
|
|
</pre>
|
|
<a name='2.p6'></a>
|
|
<pre>6 ISO 8601, Data elements and interchange formats — Information interchange —
|
|
Representation of dates and times.
|
|
</pre>
|
|
<a name='2.p7'></a>
|
|
<pre>7 ISO/IEC 10646 (all parts), Information technology — Universal Multiple-Octet Coded
|
|
Character Set (UCS).
|
|
</pre>
|
|
<a name='2.p8'></a>
|
|
<pre>8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
|
|
designated IEC 559:1989).
|
|
</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 International Standard, the following definitions apply. Other
|
|
terms are defined where they appear in italic type or on the left side of a syntax rule.
|
|
Terms explicitly defined in this International Standard are not to be presumed to refer
|
|
implicitly to similar terms defined elsewhere. Terms not defined in this International
|
|
Standard are to be interpreted according to ISO/IEC 2382−1. Mathematical symbols not
|
|
defined in this International Standard are to be interpreted according to ISO 31−11.
|
|
</pre>
|
|
<a name='3.1'></a>
|
|
<hr>
|
|
<h3>3.1 [Terms, definitions, and symbols]</h3>
|
|
<a name='3.1p1'></a>
|
|
<pre>1 access
|
|
⟨execution-time action⟩ to read or modify the value of an object
|
|
</pre>
|
|
<a name='3.1p2'></a>
|
|
<pre>2 NOTE 1 Where only one of these two actions is meant, ‘‘read’’ or ‘‘modify’’ is used.
|
|
|
|
</pre>
|
|
<a name='3.1p3'></a>
|
|
<pre>3 NOTE 2 ‘‘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 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
|
|
actual parameter (deprecated)
|
|
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 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
|
|
implementation documents
|
|
</pre>
|
|
<a name='3.4.2p2'></a>
|
|
<pre>2 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 International Standard imposes no requirements
|
|
</pre>
|
|
<a name='3.4.3p2'></a>
|
|
<pre>2 NOTE 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 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
|
|
|
|
</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
|
|
use of an unspecified value, or other behavior where this International Standard 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 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 may
|
|
have one of two values
|
|
</pre>
|
|
<a name='3.5p2'></a>
|
|
<pre>2 NOTE 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 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 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 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='3.10'></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 International Standard 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
|
|
control 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 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 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 (non-zero-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 When referenced, an object may 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
|
|
formal argument (deprecated)
|
|
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 may 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 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 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='3.19'></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 value
|
|
either an unspecified value or a trap 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 International Standard imposes no
|
|
requirements on which value is chosen in any instance
|
|
</pre>
|
|
<a name='3.19.3p2'></a>
|
|
<pre>2 NOTE An unspecified value cannot be a trap representation.
|
|
|
|
</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 trap representation
|
|
an object representation that need 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
|
|
</pre>
|
|
<a name='3.19.5p2'></a>
|
|
<pre>2 NOTE In this International Standard, when the word ‘‘trap’’ is not immediately followed by
|
|
‘‘representation’’, this is the intended usage.<a href='#FOOTNOTE.2'><sup>[2]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.2'>
|
|
<pre><i><b>Footnote 2)</b> For example, ‘‘Trapping or stopping (if supported) is disabled...’’ (<a href='#F.8.2'>F.8.2</a>). Note that fetching a trap
|
|
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='3.20'></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='4.'></a>
|
|
<hr>
|
|
<h3>4. [Conformance]</h3>
|
|
<a name='4.p1'></a>
|
|
<pre>1 In this International Standard, ‘‘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 International Standard 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 International Standard.<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='#6.10.8.3'>6.10.8.3</a>) provided the use is guarded
|
|
by an appropriate conditional inclusion preprocessing directive using the related macro. For example:
|
|
#ifdef _ _STDC_IEC_559_ _ /* 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>, <stdbool.h>, <stddef.h>, <stdint.h>, and
|
|
<stdnoreturn.h>. A conforming implementation may have extensions (including
|
|
additional library functions), provided 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 International Standard.
|
|
</i></pre>
|
|
</a>
|
|
<a name='4.p7'></a>
|
|
<pre>7 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 may depend upon nonportable features of a conforming
|
|
implementation.
|
|
</i></pre>
|
|
</a>
|
|
<a name='4.p8'></a>
|
|
<pre>8 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='#6.10.5'>6.10.5</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='#7.18'>7.18</a>), common definitions <stddef.h> (<a href='#7.19'>7.19</a>), integer types <stdint.h> (<a href='#7.20'>7.20</a>),
|
|
<stdnoreturn.h> (<a href='#7.23'>7.23</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 International Standard. 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 International Standard. 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 directives (<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. Trigraph sequences are replaced by
|
|
corresponding single-character internal representations.
|
|
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 universal character name is produced by token
|
|
concatenation (<a href='#6.10.3.3'>6.10.3.3</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; if there is no corresponding member, it is converted to an implementation-
|
|
defined member 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 directives (<a href='#6.10'>6.10</a>), trigraph sequences (<a href='#5.2.1.1'>5.2.1.1</a>), external definitions (<a href='#6.9'>6.9</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.6'>
|
|
<pre><i><b>Footnote 6)</b> Implementations shall 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 need not convert all non-corresponding source characters to the same execution
|
|
character.
|
|
</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> The intent is that an implementation should identify the nature of, and where possible localize, each
|
|
violation. Of course, an implementation is free to produce any number of diagnostics as long as a
|
|
valid program is still correctly translated. It may also successfully translate an invalid program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.1.1.3p2'></a>
|
|
<pre>2 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
|
|
char i;
|
|
int i;
|
|
because in those cases where wording in this International Standard describes the behavior for a construct
|
|
as being both a constraint error and resulting in undefined behavior, the constraint error shall 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='#6.7.9'>6.7.9</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
|
|
benefit 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='#7.22.4.4'>7.22.4.4</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 International Standard describe the behavior of an
|
|
abstract machine in which issues of optimization are irrelevant.
|
|
</pre>
|
|
<a name='5.1.2.3p2'></a>
|
|
<pre>2 Accessing a volatile 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 accessing a volatile 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 floating-point environment. The
|
|
value 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 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:
|
|
— Accesses to volatile 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='#7.21.3'>7.21.3</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
|
|
overflow, or with 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 may 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 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 overflow silently generates some value and where positive and negative 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 environment <fenv.h> (<a href='#7.6'>7.6</a>), the signal function (<a href='#7.14'>7.14</a>), files (<a href='#7.21.3'>7.21.3</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 standard. 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 may 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='#7.26.4'>7.26.4</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 either 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. We do not include relaxed atomic operations 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 must 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
|
|
may 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.
|
|
</pre>
|
|
<a name='5.1.2.4p19'></a>
|
|
<pre>19 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='5.1.2.4p20'></a>
|
|
<pre>20 NOTE 8 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='5.1.2.4p21'></a>
|
|
<pre>21 NOTE 9 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='5.1.2.4p22'></a>
|
|
<pre>22 The visible sequence of side effects on an atomic object M, with respect to a value
|
|
computation B of M, is a maximal contiguous sub-sequence of side effects in the
|
|
modification order of M, where the first side effect is visible with respect to B, and for
|
|
every subsequent side effect, it is not the case that B happens before it. The value of an
|
|
atomic object M, as determined by evaluation B, shall be the value stored by some
|
|
operation in the visible sequence of M with respect to B. Furthermore, if a value
|
|
computation A of an atomic object M happens before a value computation B of M, and
|
|
the value computed by A corresponds to the value stored by side effect X, then the value
|
|
computed by B shall either equal the value computed by A, or be the value stored by side
|
|
effect Y , where Y follows X in the modification order of M.
|
|
</pre>
|
|
<a name='5.1.2.4p23'></a>
|
|
<pre>23 NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if
|
|
both operations are ‘‘relaxed’’ loads. By doing so, we effectively make the ‘‘cache coherence’’ guarantee
|
|
provided by most hardware available to C atomic operations.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p24'></a>
|
|
<pre>24 NOTE 11 The visible sequence depends on the ‘‘happens before’’ relation, which in turn depends on the
|
|
values observed by loads of atomics, which we are restricting here. The intended reading is that there must
|
|
exist 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='5.1.2.4p25'></a>
|
|
<pre>25 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='5.1.2.4p26'></a>
|
|
<pre>26 NOTE 12 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 must contain undefined behavior.
|
|
</pre>
|
|
<a name='5.1.2.4p27'></a>
|
|
<pre>27 NOTE 13 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 standard, 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. We also generally preclude
|
|
reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the
|
|
"visible sequence" rules.
|
|
|
|
</pre>
|
|
<a name='5.1.2.4p28'></a>
|
|
<pre>28 NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may
|
|
not preserve the semantics of the program as defined in this standard, 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.
|
|
</pre>
|
|
<a name='5.2.1p3'></a>
|
|
<pre>3 Both the basic source and basic execution character sets shall have the following
|
|
members: the 26 uppercase 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 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 International Standard 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 International
|
|
Standard 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 [Trigraph sequences]</h3>
|
|
<a name='5.2.1.1p1'></a>
|
|
<pre>1 Before any other processing takes place, each occurrence of one of the following
|
|
sequences of three characters (called trigraph sequences<a href='#FOOTNOTE.17'><sup>[17]</sup></a>) is replaced with the
|
|
corresponding single character.
|
|
??= # ??) ] ??! |
|
|
??( [ ??' ^ ??> }
|
|
??/ \ ??< { ??- ~
|
|
No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
|
|
above is not changed.
|
|
</pre>
|
|
<a name='FOOTNOTE.17'>
|
|
<pre><i><b>Footnote 17)</b> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
|
|
described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.1.1p2'></a>
|
|
<pre>2 EXAMPLE 1
|
|
??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
|
|
becomes
|
|
#define arraycheck(a, b) a[b] || b[a]
|
|
|
|
</pre>
|
|
<a name='5.2.1.1p3'></a>
|
|
<pre>3 EXAMPLE 2 The following source line
|
|
printf("Eh???/n");
|
|
becomes (after replacement of the trigraph sequence ??/)
|
|
printf("Eh?\n");
|
|
|
|
</pre>
|
|
<a name='5.2.1.2'></a>
|
|
<hr>
|
|
<h3>5.2.1.2 [Multibyte characters]</h3>
|
|
<a name='5.2.1.2p1'></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 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='5.2.1.2p2'></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 nongraphic 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
|
|
International Standard.
|
|
Forward references: the isprint function (<a href='#7.4.1.8'>7.4.1.8</a>), the fputc function (<a href='#7.21.7.3'>7.21.7.3</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 translators 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 at least one program that
|
|
contains at least one instance of every one of the following limits:<a href='#FOOTNOTE.18'><sup>[18]</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 character name or extended source character is considered a single
|
|
character)
|
|
— 31 significant initial characters in an external identifier (each universal character name
|
|
specifying 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.19'><sup>[19]</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)
|
|
— 65535 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 struct-declaration-list
|
|
</pre>
|
|
<a name='FOOTNOTE.18'>
|
|
<pre><i><b>Footnote 18)</b> Implementations should avoid imposing fixed translation limits whenever possible.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.19'>
|
|
<pre><i><b>Footnote 19)</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='#7.20'>7.20</a>).
|
|
</pre>
|
|
<a name='5.2.4.2.1'></a>
|
|
<hr>
|
|
<h3>5.2.4.2.1 [Sizes 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
|
|
preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
|
|
following shall be replaced by expressions that have the same type as would an
|
|
expression that is an object of the corresponding type converted according to the integer
|
|
promotions. Their implementation-defined values shall be equal or greater in magnitude
|
|
(absolute value) to those shown, with the same sign.
|
|
— number of bits for smallest object that is not a bit-field (byte)
|
|
CHAR_BIT 8
|
|
— minimum value for an object of type signed char
|
|
SCHAR_MIN -127 // −(27 − 1)
|
|
— maximum value for an object of type signed char
|
|
SCHAR_MAX +127 // 27 − 1
|
|
— maximum value for an object of type unsigned char
|
|
UCHAR_MAX 255 // 28 − 1
|
|
— minimum value for an object of type char
|
|
CHAR_MIN see below
|
|
— maximum value for an object of type char
|
|
CHAR_MAX see below
|
|
— maximum number of bytes in a multibyte character, for any supported locale
|
|
MB_LEN_MAX 1
|
|
— minimum value for an object of type short int
|
|
SHRT_MIN -32767 // −(215 − 1)
|
|
— maximum value for an object of type short int
|
|
SHRT_MAX +32767 // 215 − 1
|
|
— maximum value for an object of type unsigned short int
|
|
USHRT_MAX 65535 // 216 − 1
|
|
— minimum value for an object of type int
|
|
INT_MIN -32767 // −(215 − 1)
|
|
— maximum value for an object of type int
|
|
INT_MAX +32767 // 215 − 1
|
|
— maximum value for an object of type unsigned int
|
|
UINT_MAX 65535 // 216 − 1
|
|
— minimum value for an object of type long int
|
|
LONG_MIN -2147483647 // −(231 − 1)
|
|
— maximum value for an object of type long int
|
|
LONG_MAX +2147483647 // 231 − 1
|
|
— maximum value for an object of type unsigned long int
|
|
ULONG_MAX 4294967295 // 232 − 1
|
|
— minimum value for an object of type long long int
|
|
LLONG_MIN -9223372036854775807 // −(263 − 1)
|
|
— maximum value for an object of type long long int
|
|
LLONG_MAX +9223372036854775807 // 263 − 1
|
|
— maximum value for an object of type unsigned long long int
|
|
ULLONG_MAX 18446744073709551615 // 264 − 1
|
|
</pre>
|
|
<a name='5.2.4.2.1p2'></a>
|
|
<pre>2 If the value of an object of type char is treated as a signed integer when used in an
|
|
expression, 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> The value UCHAR_MAX shall equal 2CHAR_BIT − 1.
|
|
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>).
|
|
</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
|
|
representation of floating-point numbers and values that provide information about an
|
|
implementation’s floating-point arithmetic.<a href='#FOOTNOTE.21'><sup>[21]</sup></a> The following parameters are used to
|
|
define the model for each floating-point 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)
|
|
</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 A floating-point number (x) is defined by the following model:
|
|
p
|
|
x = sb e Σ f k b−k , emin ≤ e ≤ emax
|
|
k=1
|
|
|
|
</pre>
|
|
<a name='5.2.4.2.2p3'></a>
|
|
<pre>3 In addition to normalized floating-point numbers ( f 1 > 0 if x ≠ 0), floating types may be
|
|
able to contain other kinds of floating-point numbers, such as subnormal floating-point
|
|
numbers (x ≠ 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x ≠ 0,
|
|
e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and
|
|
NaNs. A NaN is an encoding 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.22'><sup>[22]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.22'>
|
|
<pre><i><b>Footnote 22)</b> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
|
|
IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
|
|
similar behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p4'></a>
|
|
<pre>4 An implementation may give zero and values that are not floating-point numbers (such as
|
|
infinities and NaNs) a sign or may leave them unsigned. Wherever such values are
|
|
unsigned, any requirement in this International Standard to retrieve the sign shall produce
|
|
an unspecified sign, and any requirement to set the sign shall be ignored.
|
|
</pre>
|
|
<a name='5.2.4.2.2p5'></a>
|
|
<pre>5 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='5.2.4.2.2p6'></a>
|
|
<pre>6 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.
|
|
</pre>
|
|
<a name='5.2.4.2.2p7'></a>
|
|
<pre>7 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 DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
|
|
and FLT_ROUNDS have separate names for all three floating-point types. The floating-
|
|
point model representation is provided for all values except FLT_EVAL_METHOD and
|
|
FLT_ROUNDS.
|
|
</pre>
|
|
<a name='5.2.4.2.2p8'></a>
|
|
<pre>8 The rounding mode for floating-point addition is characterized by the implementation-
|
|
defined value of FLT_ROUNDS:<a href='#FOOTNOTE.23'><sup>[23]</sup></a>
|
|
-1 indeterminable
|
|
0 toward zero
|
|
1 to nearest
|
|
2 toward positive infinity
|
|
3 toward negative infinity
|
|
All other values for FLT_ROUNDS characterize implementation-defined rounding
|
|
behavior.
|
|
</pre>
|
|
<a name='FOOTNOTE.23'>
|
|
<pre><i><b>Footnote 23)</b> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
|
|
the function fesetround in <fenv.h>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p9'></a>
|
|
<pre>9 Except for assignment and cast (which remove all extra range and precision), the values
|
|
yielded by operators with floating operands and values subject to the usual arithmetic
|
|
conversions and of floating constants are evaluated to a format whose range and precision
|
|
may be greater than required by the type. The use of evaluation formats is characterized
|
|
by the implementation-defined value of FLT_EVAL_METHOD:<a href='#FOOTNOTE.24'><sup>[24]</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.
|
|
</pre>
|
|
<a name='FOOTNOTE.24'>
|
|
<pre><i><b>Footnote 24)</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='5.2.4.2.2p10'></a>
|
|
<pre>10 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<a href='#FOOTNOTE.25'><sup>[25]</sup></a>
|
|
0 absent<a href='#FOOTNOTE.26'><sup>[26]</sup></a> (type does not support subnormal numbers)
|
|
1 present (type does support subnormal numbers)
|
|
</pre>
|
|
<a name='FOOTNOTE.25'>
|
|
<pre><i><b>Footnote 25)</b> Characterization as indeterminable is intended if floating-point operations do not consistently interpret
|
|
subnormal representations as zero, nor as nonzero.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.26'>
|
|
<pre><i><b>Footnote 26)</b> Characterization as absent is intended if no floating-point operations produce subnormal results from
|
|
non-subnormal inputs, even if the type format includes representations of subnormal numbers.
|
|
</i></pre>
|
|
</a>
|
|
<a name='5.2.4.2.2p11'></a>
|
|
<pre>11 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
|
|
supported floating type 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
|
|
— 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 normalized floating-point number, emin
|
|
FLT_MIN_EXP
|
|
DBL_MIN_EXP
|
|
LDBL_MIN_EXP
|
|
— minimum negative integer such that 10 raised to that power is in the range of
|
|
normalized floating-point numbers, ⎡log10 b emin −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, 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 )b emax )⎦
|
|
FLT_MAX_10_EXP +37
|
|
DBL_MAX_10_EXP +37
|
|
LDBL_MAX_10_EXP +37
|
|
</pre>
|
|
<a name='5.2.4.2.2p12'></a>
|
|
<pre>12 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, (1 − b− p )b emax
|
|
FLT_MAX 1E+37
|
|
DBL_MAX 1E+37
|
|
LDBL_MAX 1E+37
|
|
</pre>
|
|
<a name='5.2.4.2.2p13'></a>
|
|
<pre>13 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 value greater than 1 that is representable in the
|
|
given floating point type, b1− p
|
|
FLT_EPSILON 1E-5
|
|
DBL_EPSILON 1E-9
|
|
LDBL_EPSILON 1E-9
|
|
— minimum normalized positive floating-point number, b emin −1
|
|
FLT_MIN 1E-37
|
|
DBL_MIN 1E-37
|
|
LDBL_MIN 1E-37
|
|
— minimum positive floating-point number<a href='#FOOTNOTE.27'><sup>[27]</sup></a>
|
|
FLT_TRUE_MIN 1E-37
|
|
DBL_TRUE_MIN 1E-37
|
|
LDBL_TRUE_MIN 1E-37
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.27'>
|
|
<pre><i><b>Footnote 27)</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='5.2.4.2.2p14'></a>
|
|
<pre>14 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
|
|
should be the identity function.
|
|
</pre>
|
|
<a name='5.2.4.2.2p15'></a>
|
|
<pre>15 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
|
|
requirements of this International Standard, and the appropriate values in a <float.h> header for type
|
|
float:
|
|
6
|
|
x = s16e Σ f k 16−k , −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='5.2.4.2.2p16'></a>
|
|
<pre>16 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.28'><sup>[28]</sup></a> and the appropriate values in a
|
|
<float.h> header for types float and double:
|
|
24
|
|
x f = s2e Σ f k 2−k , −125 ≤ e ≤ +128
|
|
k=1
|
|
|
|
53
|
|
x d = s2e Σ f k 2−k , −1021 ≤ e ≤ +1024
|
|
k=1
|
|
FLT_RADIX 2
|
|
DECIMAL_DIG 17
|
|
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_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
|
|
If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
|
|
example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
|
|
precision), then DECIMAL_DIG would be 21.
|
|
|
|
Forward references: conditional inclusion (<a href='#6.10.1'>6.10.1</a>), complex arithmetic
|
|
<complex.h> (<a href='#7.3'>7.3</a>), extended multibyte and wide character utilities <wchar.h>
|
|
(<a href='#7.29'>7.29</a>), floating-point environment <fenv.h> (<a href='#7.6'>7.6</a>), general utilities <stdlib.h>
|
|
(<a href='#7.22'>7.22</a>), input/output <stdio.h> (<a href='#7.21'>7.21</a>), mathematics <math.h> (<a href='#7.12'>7.12</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.28'>
|
|
<pre><i><b>Footnote 28)</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='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 that declares the types of its parameters.)
|
|
</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 International Standard 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. Any
|
|
other identifier has scope that begins just after the completion of its declarator.
|
|
</pre>
|
|
<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='#6.10.3'>6.10.3</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 (<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.29'><sup>[29]</sup></a> There are
|
|
three kinds of linkage: external, internal, and none.
|
|
</pre>
|
|
<a name='FOOTNOTE.29'>
|
|
<pre><i><b>Footnote 29)</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 or a function contains the storage-
|
|
class specifier static, the identifier has internal linkage.<a href='#FOOTNOTE.30'><sup>[30]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.30'>
|
|
<pre><i><b>Footnote 30)</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 declaration of that identifier is visible,<a href='#FOOTNOTE.31'><sup>[31]</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.31'>
|
|
<pre><i><b>Footnote 31)</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,
|
|
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 any32)
|
|
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);
|
|
— all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
|
|
enumeration 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='#7.22.3'>7.22.3</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.33'><sup>[33]</sup></a> and retains
|
|
its last-stored value throughout its lifetime.<a href='#FOOTNOTE.34'><sup>[34]</sup></a> If an object is referred to outside of its
|
|
lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
|
|
the object it points to (or just past) reaches the end of its lifetime.
|
|
</pre>
|
|
<a name='FOOTNOTE.33'>
|
|
<pre><i><b>Footnote 33)</b> The term ‘‘constant address’’ means that two pointers to the object constructed at possibly different
|
|
times will compare equal. The address may be different during two different executions of the same
|
|
program.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.34'>
|
|
<pre><i><b>Footnote 34)</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 value 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 value 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.35'><sup>[35]</sup></a> If the scope is entered recursively, a new instance of the object is created
|
|
each time. The initial value of the object is indeterminate.
|
|
</pre>
|
|
<a name='FOOTNOTE.35'>
|
|
<pre><i><b>Footnote 35)</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.36'><sup>[36]</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 or full declarator ends. Any attempt to modify an object with temporary
|
|
lifetime results in undefined behavior.
|
|
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='#6.7.9'>6.7.9</a>), statements (<a href='#6.8'>6.8</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.36'>
|
|
<pre><i><b>Footnote 36)</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 (lacking sufficient information to determine the size of objects of that type) or
|
|
complete (having sufficient information).<a href='#FOOTNOTE.37'><sup>[37]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.37'>
|
|
<pre><i><b>Footnote 37)</b> A type may be incomplete or complete throughout an entire translation unit, or it may change states at
|
|
different points within a translation unit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p2'></a>
|
|
<pre>2 An object declared as type _Bool is large enough to store the values 0 and 1.
|
|
</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 character 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>.) There may also be
|
|
implementation-defined extended signed integer types.<a href='#FOOTNOTE.38'><sup>[38]</sup></a> The standard and extended
|
|
signed integer types are collectively called signed integer types.<a href='#FOOTNOTE.39'><sup>[39]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.38'>
|
|
<pre><i><b>Footnote 38)</b> Implementation-defined keywords shall 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.39'>
|
|
<pre><i><b>Footnote 39)</b> Therefore, any statement in this Standard about signed integer types also applies to the extended
|
|
signed integer types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p5'></a>
|
|
<pre>5 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='6.2.5p6'></a>
|
|
<pre>6 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 standard and extended unsigned integer types are collectively called unsigned integer
|
|
types.<a href='#FOOTNOTE.40'><sup>[40]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.40'>
|
|
<pre><i><b>Footnote 40)</b> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
|
|
unsigned integer types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p7'></a>
|
|
<pre>7 The standard signed integer types and standard unsigned integer types are collectively
|
|
called the standard integer types, the extended signed integer types and extended
|
|
unsigned integer types are collectively called the extended integer types.
|
|
</pre>
|
|
<a name='6.2.5p8'></a>
|
|
<pre>8 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='6.2.5p9'></a>
|
|
<pre>9 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.41'><sup>[41]</sup></a> A computation involving unsigned operands can never overflow,
|
|
because a result that cannot be represented by the resulting unsigned integer type is
|
|
reduced modulo the number that is one greater than the largest value that can be
|
|
represented by the resulting type.
|
|
</pre>
|
|
<a name='FOOTNOTE.41'>
|
|
<pre><i><b>Footnote 41)</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='6.2.5p10'></a>
|
|
<pre>10 There are three real floating types, designated as float, double, and long
|
|
double.<a href='#FOOTNOTE.42'><sup>[42]</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.42'>
|
|
<pre><i><b>Footnote 42)</b> See ‘‘future language directions’’ (<a href='#6.11.1'>6.11.1</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p11'></a>
|
|
<pre>11 There are three complex types, designated as float _Complex, double
|
|
_Complex, and long double _Complex.<a href='#FOOTNOTE.43'><sup>[43]</sup></a> (Complex types are a conditional
|
|
feature that implementations need not support; see <a href='#6.10.8.3'>6.10.8.3</a>.) The real floating and
|
|
complex types are collectively called the floating types.
|
|
</pre>
|
|
<a name='FOOTNOTE.43'>
|
|
<pre><i><b>Footnote 43)</b> A specification for imaginary types is in annex G.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.5p12'></a>
|
|
<pre>12 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='6.2.5p13'></a>
|
|
<pre>13 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='6.2.5p14'></a>
|
|
<pre>14 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.44'><sup>[44]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.44'>
|
|
<pre><i><b>Footnote 44)</b> An implementation may define new keywords that provide alternative ways to designate a basic (or
|
|
any other) type; this does not violate the requirement that all basic types be different.
|
|
Implementation-defined keywords shall 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='6.2.5p15'></a>
|
|
<pre>15 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.45'><sup>[45]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.45'>
|
|
<pre><i><b>Footnote 45)</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='6.2.5p16'></a>
|
|
<pre>16 An enumeration comprises a set of named integer constant values. Each distinct
|
|
enumeration constitutes a different enumerated type.
|
|
</pre>
|
|
<a name='6.2.5p17'></a>
|
|
<pre>17 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='6.2.5p18'></a>
|
|
<pre>18 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='6.2.5p19'></a>
|
|
<pre>19 The void type comprises an empty set of values; it is an incomplete object type that
|
|
cannot be completed.
|
|
</pre>
|
|
<a name='6.2.5p20'></a>
|
|
<pre>20 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='#6.10.8.3'>6.10.8.3</a>.)
|
|
These methods of constructing derived types can be applied recursively.
|
|
</pre>
|
|
<a name='6.2.5p21'></a>
|
|
<pre>21 Arithmetic types and pointer types are collectively called scalar types. Array and
|
|
structure types are collectively called aggregate types.<a href='#FOOTNOTE.46'><sup>[46]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.46'>
|
|
<pre><i><b>Footnote 46)</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='6.2.5p22'></a>
|
|
<pre>22 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 declarations of that type, by declaring the same structure or
|
|
union tag with its defining content later in the same scope.
|
|
</pre>
|
|
<a name='6.2.5p23'></a>
|
|
<pre>23 A type has known constant size if the type is not incomplete and is not a variable length
|
|
array type.
|
|
</pre>
|
|
<a name='6.2.5p24'></a>
|
|
<pre>24 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='6.2.5p25'></a>
|
|
<pre>25 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='6.2.5p26'></a>
|
|
<pre>26 Any type so far mentioned is an unqualified type. Each unqualified type has several
|
|
qualified versions of its type,<a href='#FOOTNOTE.47'><sup>[47]</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.48'><sup>[48]</sup></a> A derived type is not qualified by the
|
|
qualifiers (if any) of the type from which it is derived.
|
|
</pre>
|
|
<a name='FOOTNOTE.47'>
|
|
<pre><i><b>Footnote 47)</b> See <a href='#6.7.3'>6.7.3</a> regarding qualified array and function types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.48'>
|
|
<pre><i><b>Footnote 48)</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='6.2.5p27'></a>
|
|
<pre>27 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
|
|
Standard 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='6.2.5p28'></a>
|
|
<pre>28 A pointer to void shall have the same representation and alignment requirements as a
|
|
pointer to a character type.<a href='#FOOTNOTE.48'><sup>[48]</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.48'>
|
|
<pre><i><b>Footnote 48)</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='6.2.5p29'></a>
|
|
<pre>29 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='6.2.5p30'></a>
|
|
<pre>30 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.49'><sup>[49]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.49'>
|
|
<pre><i><b>Footnote 49)</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 2
|
|
CHAR_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 consist of n × CHAR_BIT
|
|
bits, where n is the size of an object of that type, in bytes. 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 the stored
|
|
value of an object has such a representation and 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.50'><sup>[50]</sup></a> Such a representation is called
|
|
a trap representation.
|
|
</pre>
|
|
<a name='FOOTNOTE.50'>
|
|
<pre><i><b>Footnote 50)</b> Thus, an automatic variable can be initialized to a trap 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.51'><sup>[51]</sup></a> The value of a structure or union object is never a trap
|
|
representation, even though the value of a member of the structure or union object may be
|
|
a trap representation.
|
|
</pre>
|
|
<a name='FOOTNOTE.51'>
|
|
<pre><i><b>Footnote 51)</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.52'><sup>[52]</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 trap representation shall
|
|
not be generated.
|
|
</pre>
|
|
<a name='FOOTNOTE.52'>
|
|
<pre><i><b>Footnote 52)</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 may 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 other than unsigned char, the bits of the object
|
|
representation shall be divided into two groups: value bits and padding bits (there need
|
|
not be any of the latter). If there are N value bits, each bit shall represent a different
|
|
power of 2 between 1 and 2 N −1 , so that objects of that type shall be capable of
|
|
representing values from 0 to 2 N − 1 using a pure binary representation; this shall be
|
|
known as the value representation. The values of any padding bits are unspecified.<a href='#FOOTNOTE.53'><sup>[53]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.53'>
|
|
<pre><i><b>Footnote 53)</b> Some combinations of padding bits might generate trap representations, for example, if one padding
|
|
bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
|
|
representation other than as part of an exceptional condition such as an 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.
|
|
</i></pre>
|
|
</a>
|
|
<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. There need not be any padding bits;
|
|
signed char shall not have any padding bits. There shall be exactly one 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 there are M value bits in the signed
|
|
type and N in the unsigned type, then M ≤ N ). If the sign bit is zero, it shall not affect
|
|
the resulting value. If the sign bit is one, the value shall be modified in one of the
|
|
following ways:
|
|
— the corresponding value with sign bit 0 is negated (sign and magnitude);
|
|
— the sign bit has the value −(2 M ) (two’s complement);
|
|
— the sign bit has the value −(2 M − 1) (ones’ complement).
|
|
Which of these applies is implementation-defined, as is whether the value with sign bit 1
|
|
and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones’
|
|
complement), is a trap representation or a normal value. In the case of sign and
|
|
magnitude and ones’ complement, if this representation is a normal value it is called a
|
|
negative zero.
|
|
</pre>
|
|
<a name='6.2.6.2p3'></a>
|
|
<pre>3 If the implementation supports negative zeros, they shall be generated only by:
|
|
— the &, |, ^, ~, <<, and >> operators with operands that produce such a value;
|
|
— the +, -, *, /, and % operators where one operand is a negative zero and the result is
|
|
zero;
|
|
— compound assignment operators based on the above cases.
|
|
It is unspecified whether these cases actually generate a negative zero or a normal zero,
|
|
and whether a negative zero becomes a normal zero when stored in an object.
|
|
</pre>
|
|
<a name='6.2.6.2p4'></a>
|
|
<pre>4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
|
|
and >> operators with operands that would produce such a value is undefined.
|
|
</pre>
|
|
<a name='6.2.6.2p5'></a>
|
|
<pre>5 The values of any padding bits are unspecified.<a href='#FOOTNOTE.54'><sup>[54]</sup></a> A valid (non-trap) 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='FOOTNOTE.54'>
|
|
<pre><i><b>Footnote 54)</b> Some combinations of padding bits might generate trap representations, for example, if one padding
|
|
bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
|
|
representation other than as part of an exceptional condition such as an overflow. All other
|
|
combinations of padding bits are alternative object representations of the value specified by the value
|
|
bits.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.2.6.2p6'></a>
|
|
<pre>6 The precision of an integer type is the number of bits it uses to represent values,
|
|
excluding any sign and padding bits. The width of an integer type is the same but
|
|
including any sign bit; thus for unsigned integer types the two values 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 have compatible type if their types 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.55'><sup>[55]</sup></a> Moreover, two structure,
|
|
union, or enumerated types declared in separate translation units are compatible if their
|
|
tags and members satisfy the following requirements: If one is declared with a tag, the
|
|
other shall be declared with the same tag. If both are completed anywhere within their
|
|
respective translation units, then the following additional requirements apply: 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.
|
|
</pre>
|
|
<a name='FOOTNOTE.55'>
|
|
<pre><i><b>Footnote 55)</b> Two types need not be identical to be compatible.
|
|
</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 only one type is a function type with a parameter type list (a function prototype),
|
|
the composite type is a function prototype with the parameter type list.
|
|
— If both types are function types with parameter type lists, the type of each parameter
|
|
in the composite parameter type list is the composite type of the corresponding
|
|
parameters.
|
|
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.56'><sup>[56]</sup></a> if the prior declaration specifies internal or
|
|
external linkage, the type of the identifier at the later declaration becomes the composite
|
|
type.
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.56'>
|
|
<pre><i><b>Footnote 56)</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 (*)(), double (*)[3]);
|
|
int f(int (*)(char *), double (*)[]);
|
|
The resulting composite type for the function is:
|
|
int f(int (*)(char *), double (*)[3]);
|
|
|
|
</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 represented by an alignment less than or equal to the greatest
|
|
alignment supported by the implementation in all contexts, which is equal to
|
|
_Alignof (max_align_t).
|
|
</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 contexts in which they are supported. A type having an
|
|
extended alignment requirement is an over-aligned type.<a href='#FOOTNOTE.57'><sup>[57]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.57'>
|
|
<pre><i><b>Footnote 57)</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
|
|
those values returned by an _Alignof expression for fundamental types, 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='6.3'></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 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
|
|
representation.
|
|
— 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 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.
|
|
— 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.
|
|
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; otherwise, it is converted to an unsigned
|
|
int. These are called the integer promotions.<a href='#FOOTNOTE.58'><sup>[58]</sup></a> All other types are unchanged by the
|
|
integer promotions.
|
|
</pre>
|
|
<a name='FOOTNOTE.58'>
|
|
<pre><i><b>Footnote 58)</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 is treated as signed 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 0 if the value compares equal
|
|
to 0; otherwise, the result is 1.<a href='#FOOTNOTE.59'><sup>[59]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.59'>
|
|
<pre><i><b>Footnote 59)</b> NaNs do not compare equal to 0 and thus convert to 1.
|
|
</i></pre>
|
|
</a>
|
|
<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.60'><sup>[60]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.60'>
|
|
<pre><i><b>Footnote 60)</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 real 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.61'><sup>[61]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.61'>
|
|
<pre><i><b>Footnote 61)</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 value of integer type is converted to a real 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='6.3.1.5'></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. 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='6.3.1.6'></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, 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='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:
|
|
First, 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.62'><sup>[62]</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.62'>
|
|
<pre><i><b>Footnote 62)</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.<a href='#FOOTNOTE.63'><sup>[63]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.63'>
|
|
<pre><i><b>Footnote 63)</b> The cast and assignment operators are still required to remove extra range and precision.
|
|
</i></pre>
|
|
</a>
|
|
<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.64'><sup>[64]</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.64'>
|
|
<pre><i><b>Footnote 64)</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 International Standard 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, the _Alignof operator, 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, the _Alignof operator, 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, the _Alignof operator,<a href='#FOOTNOTE.65'><sup>[65]</sup></a> 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='#7.19'>7.19</a>), initialization (<a href='#6.7.9'>6.7.9</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.65'>
|
|
<pre><i><b>Footnote 65)</b> Because this conversion does not occur, the operand of the sizeof or _Alignof 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, or such an expression cast to type
|
|
void *, is called a null pointer constant.<a href='#FOOTNOTE.66'><sup>[66]</sup></a> If a null pointer constant 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.66'>
|
|
<pre><i><b>Footnote 66)</b> The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see <a href='#7.19'>7.19</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 be a trap representation.<a href='#FOOTNOTE.67'><sup>[67]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.67'>
|
|
<pre><i><b>Footnote 67)</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.68'><sup>[68]</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.68'>
|
|
<pre><i><b>Footnote 68)</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.
|
|
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='#7.20.1.4'>7.20.1.4</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 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.
|
|
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
|
|
single non-white-space characters that do not lexically match the other preprocessing
|
|
token categories.<a href='#FOOTNOTE.69'><sup>[69]</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.69'>
|
|
<pre><i><b>Footnote 69)</b> An additional category, placemarkers, is used internally in translation phase 4 (see <a href='#6.10.3.3'>6.10.3.3</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 preprocessing directives and 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='#6.10.3'>6.10.3</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
|
|
auto ∗ if unsigned
|
|
break inline void
|
|
case int volatile
|
|
char long while
|
|
const register _Alignas
|
|
continue restrict _Alignof
|
|
default return _Atomic
|
|
do short _Bool
|
|
double signed _Complex
|
|
else sizeof _Generic
|
|
enum static _Imaginary
|
|
extern struct _Noreturn
|
|
float switch _Static_assert
|
|
for typedef _Thread_local
|
|
goto union
|
|
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
|
|
specifying imaginary types.<a href='#FOOTNOTE.70'><sup>[70]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.70'>
|
|
<pre><i><b>Footnote 70)</b> One possible specification for imaginary types appears in annex G.
|
|
</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-nondigit
|
|
identifier identifier-nondigit
|
|
identifier digit
|
|
identifier-nondigit:
|
|
nondigit
|
|
universal-character-name
|
|
other implementation-defined characters
|
|
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 identifier is a sequence of nondigit characters (including the underscore _, the
|
|
lowercase and uppercase Latin letters, and other characters) and digits, 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 Each universal character name in an identifier shall designate a character whose encoding
|
|
in ISO/IEC 10646 falls into one of the ranges specified in <a href='#D.1'>D.1</a>.<a href='#FOOTNOTE.71'><sup>[71]</sup></a> The initial character
|
|
shall not be a universal character name designating a character whose encoding falls into
|
|
one of the ranges specified in <a href='#D.2'>D.2</a>. An implementation may allow multibyte characters
|
|
that are not part of the basic source character set to appear in identifiers; which characters
|
|
and their correspondence to universal character names is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.71'>
|
|
<pre><i><b>Footnote 71)</b> On systems in which linkers cannot accept extended characters, an encoding of the universal character
|
|
name may be used in forming valid external identifiers. For example, some otherwise unused
|
|
character or sequence of characters may be used to encode the \u in a universal character name.
|
|
Extended characters may produce a long external identifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.4.2.1p4'></a>
|
|
<pre>4 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.
|
|
Implementation limits
|
|
</pre>
|
|
<a name='6.4.2.1p5'></a>
|
|
<pre>5 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='6.4.2.1p6'></a>
|
|
<pre>6 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='#6.10.3'>6.10.3</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.72'><sup>[72]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.72'>
|
|
<pre><i><b>Footnote 72)</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 specify a character whose short identifier is less than
|
|
00A0 other than 0024 ($), 0040 (@), or 0060 (‘), nor one in the range D800 through
|
|
DFFF inclusive.<a href='#FOOTNOTE.73'><sup>[73]</sup></a>
|
|
Description
|
|
</pre>
|
|
<a name='FOOTNOTE.73'>
|
|
<pre><i><b>Footnote 73)</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, and the S-zone (reserved for use by
|
|
UTF−16).
|
|
</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 \Unnnnnnnn designates the character whose eight-digit
|
|
short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<a href='#FOOTNOTE.74'><sup>[74]</sup></a> Similarly, the universal
|
|
character name \unnnn designates the character whose four-digit short identifier is nnnn
|
|
(and whose eight-digit short identifier is 0000nnnn).
|
|
</pre>
|
|
<a name='FOOTNOTE.74'>
|
|
<pre><i><b>Footnote 74)</b> Short identifiers for characters were first specified in ISO/IEC 10646−1/AMD9:1997.
|
|
</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
|
|
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
|
|
decimal-constant:
|
|
nonzero-digit
|
|
decimal-constant digit
|
|
octal-constant:
|
|
0
|
|
octal-constant octal-digit
|
|
hexadecimal-constant:
|
|
hexadecimal-prefix hexadecimal-digit
|
|
hexadecimal-constant hexadecimal-digit
|
|
hexadecimal-prefix: one of
|
|
0x 0X
|
|
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: one of
|
|
0 1 2 3 4 5 6 7 8 9
|
|
a b c d e f
|
|
A B C D E F
|
|
integer-suffix:
|
|
unsigned-suffix long-suffixopt
|
|
unsigned-suffix long-long-suffix
|
|
long-suffix unsigned-suffixopt
|
|
long-long-suffix unsigned-suffixopt
|
|
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.
|
|
</pre>
|
|
<a name='6.4.4.1p3'></a>
|
|
<pre>3 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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4.1p4'></a>
|
|
<pre>4 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
|
|
that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
|
|
</pre>
|
|
<a name='6.4.4.1p5'></a>
|
|
<pre>5 The type of an integer constant is the first of the corresponding list in which its value can
|
|
be represented.
|
|
Octal or Hexadecimal
|
|
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
|
|
</pre>
|
|
<a name='6.4.4.1p6'></a>
|
|
<pre>6 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='6.4.4.2'></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 digit
|
|
hexadecimal-fractional-constant:
|
|
hexadecimal-digit-sequenceopt .
|
|
hexadecimal-digit-sequence
|
|
hexadecimal-digit-sequence .
|
|
binary-exponent-part:
|
|
p signopt digit-sequence
|
|
P signopt digit-sequence
|
|
hexadecimal-digit-sequence:
|
|
hexadecimal-digit
|
|
hexadecimal-digit-sequence hexadecimal-digit
|
|
floating-suffix: one of
|
|
f l F L
|
|
Description
|
|
</pre>
|
|
<a name='6.4.4.2p2'></a>
|
|
<pre>2 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. 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='6.4.4.2p3'></a>
|
|
<pre>3 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='6.4.4.2p4'></a>
|
|
<pre>4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
|
|
type float. If suffixed by the letter l or L, it has type long double.
|
|
</pre>
|
|
<a name='6.4.4.2p5'></a>
|
|
<pre>5 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.75'><sup>[75]</sup></a> shall
|
|
convert to the same internal format with the same value.
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.75'>
|
|
<pre><i><b>Footnote 75)</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='6.4.4.2p6'></a>
|
|
<pre>6 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='6.4.4.2p7'></a>
|
|
<pre>7 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.76'><sup>[76]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.76'>
|
|
<pre><i><b>Footnote 76)</b> The specification for the library functions recommends more accurate conversion than required for
|
|
floating constants (see <a href='#7.22.1.3'>7.22.1.3</a>).
|
|
</i></pre>
|
|
</a>
|
|
<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 has type int.
|
|
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:
|
|
' c-char-sequence '
|
|
L' c-char-sequence '
|
|
u' c-char-sequence '
|
|
U' c-char-sequence '
|
|
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 wide character constant is the same, except prefixed by the
|
|
letter L, u, or U. 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 nongraphic characters are representable by escape sequences
|
|
consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
|
|
and \v.<a href='#FOOTNOTE.77'><sup>[77]</sup></a>
|
|
Constraints
|
|
</pre>
|
|
<a name='FOOTNOTE.77'>
|
|
<pre><i><b>Footnote 77)</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
|
|
L the unsigned type corresponding to wchar_t
|
|
u char16_t
|
|
U char32_t
|
|
Semantics
|
|
</pre>
|
|
<a name='6.4.4.4p10'></a>
|
|
<pre>10 An integer character constant has type int. The value of an integer character constant
|
|
containing a single character that maps to a single-byte execution character is the
|
|
numerical value of the representation of the mapped character 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-byte
|
|
execution character, 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='6.4.4.4p11'></a>
|
|
<pre>11 A wide character constant prefixed by the letter L has type wchar_t, an integer type
|
|
defined in the <stddef.h> header; a wide character constant prefixed by the letter u or
|
|
U has type char16_t or char32_t, respectively, unsigned integer types defined in the
|
|
<uchar.h> header. The value of a wide 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, as defined by the
|
|
mbtowc, mbrtoc16, or mbrtoc32 function as appropriate for its type, with an
|
|
implementation-defined current locale. 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, is
|
|
implementation-defined.
|
|
</pre>
|
|
<a name='6.4.4.4p12'></a>
|
|
<pre>12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
|
|
|
|
</pre>
|
|
<a name='6.4.4.4p13'></a>
|
|
<pre>13 EXAMPLE 2 Consider implementations that use two’s complement representation for integers and 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='6.4.4.4p14'></a>
|
|
<pre>14 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' may 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='6.4.4.4p15'></a>
|
|
<pre>15 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='#7.19'>7.19</a>), the mbtowc function
|
|
(<a href='#7.22.7.2'>7.22.7.2</a>), Unicode utilities <uchar.h> (<a href='#7.28'>7.28</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 "
|
|
encoding-prefix:
|
|
u8
|
|
u
|
|
U
|
|
L
|
|
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 A sequence of adjacent string literal tokens shall not include both a wide string literal and
|
|
a UTF−8 string literal.
|
|
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 wide string literal is the same, except prefixed by the letter L, u, or U.
|
|
</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. Whether differently-prefixed wide string literal
|
|
tokens can be concatenated and, if so, the treatment of the resulting multibyte character
|
|
sequence are implementation-defined.
|
|
</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.78'><sup>[78]</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. For UTF−8 string literals, the array elements have type char, 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 multibyte
|
|
character sequence, as defined by the mbstowcs function with an implementation-
|
|
defined current locale. 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 with the
|
|
sequence of wide characters corresponding to the multibyte character sequence, as
|
|
defined by successive calls to the mbrtoc16, or mbrtoc32 function as appropriate for
|
|
its type, with an implementation-defined current locale. The value of a string literal
|
|
containing a multibyte character or escape sequence not represented in the execution
|
|
character set is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.78'>
|
|
<pre><i><b>Footnote 78)</b> A string literal need not be a string (see <a href='#7.1.1'>7.1.1</a>), because a null character may 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='#7.19'>7.19</a>), the mbstowcs
|
|
function (<a href='#7.22.8.1'>7.22.8.1</a>), Unicode utilities <uchar.h> (<a href='#7.28'>7.28</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.79'><sup>[79]</sup></a>
|
|
<: :> <% %> %: %:%:
|
|
behave, respectively, the same as the six tokens
|
|
[ ] { } # ##
|
|
except for their spelling.<a href='#FOOTNOTE.80'><sup>[80]</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.79'>
|
|
<pre><i><b>Footnote 79)</b> These tokens are sometimes called ‘‘digraphs’’.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.80'>
|
|
<pre><i><b>Footnote 80)</b> Thus [ and <: behave differently when ‘‘stringized’’ (see <a href='#6.10.3.2'>6.10.3.2</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.81'><sup>[81]</sup></a> Header name
|
|
preprocessing tokens are recognized only within #include preprocessing directives and
|
|
in implementation-defined locations within #pragma directives.<a href='#FOOTNOTE.82'><sup>[82]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.81'>
|
|
<pre><i><b>Footnote 81)</b> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.82'>
|
|
<pre><i><b>Footnote 82)</b> For an example of a header name preprocessing token used in a #pragma directive, see <a href='#6.10.9'>6.10.9</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 digit
|
|
pp-number identifier-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.83'><sup>[83]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.83'>
|
|
<pre><i><b>Footnote 83)</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.84'><sup>[84]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.84'>
|
|
<pre><i><b>Footnote 84)</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.85'><sup>[85]</sup></a> Except as specified
|
|
later, side effects and value computations of subexpressions are unsequenced.<a href='#FOOTNOTE.86'><sup>[86]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.85'>
|
|
<pre><i><b>Footnote 85)</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.86'>
|
|
<pre><i><b>Footnote 86)</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.87'><sup>[87]</sup></a> If a value is stored into an object having no declared type through an
|
|
lvalue having a type that is not a 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.87'>
|
|
<pre><i><b>Footnote 87)</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.88'><sup>[88]</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.88'>
|
|
<pre><i><b>Footnote 88)</b> The intent of this list is to specify those circumstances in which an object may or may not 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
|
|
operation, thereby omitting rounding errors implied by the source code and the
|
|
expression evaluation method.<a href='#FOOTNOTE.89'><sup>[89]</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.90'><sup>[90]</sup></a>
|
|
Forward references: the FP_CONTRACT pragma (<a href='#7.12.2'>7.12.2</a>), copying functions (<a href='#7.24.2'>7.24.2</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.89'>
|
|
<pre><i><b>Footnote 89)</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.90'>
|
|
<pre><i><b>Footnote 90)</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='6.5.1'></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
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.1p2'></a>
|
|
<pre>2 An identifier is a primary expression, provided it has been declared as designating an
|
|
object (in which case it is an lvalue) or a function (in which case it is a function
|
|
designator).<a href='#FOOTNOTE.91'><sup>[91]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.91'>
|
|
<pre><i><b>Footnote 91)</b> Thus, an undeclared identifier is a violation of the syntax.
|
|
</i></pre>
|
|
</a>
|
|
<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 and value are identical to
|
|
those of the unparenthesized expression. It is an lvalue, a function designator, or a void
|
|
expression if the unparenthesized expression is, respectively, an lvalue, a function
|
|
designator, or a void expression.
|
|
</pre>
|
|
<a name='6.5.1p6'></a>
|
|
<pre>6 A generic selection is a primary expression. Its type and value 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 controlling expression of a generic selection shall have type
|
|
compatible with at most one of the types named in its 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='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)
|
|
|
|
</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 --
|
|
( type-name ) { initializer-list }
|
|
( type-name ) { initializer-list , }
|
|
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 ints; more precisely, x is an array of three element objects, each of which is an
|
|
array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
|
|
a pointer to the initial array of five ints. 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 ints. When used in the
|
|
expression x[i][j], that array is in turn converted to a pointer to the first of the ints, 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.92'><sup>[92]</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.92'>
|
|
<pre><i><b>Footnote 92)</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 If the expression that denotes the called function has a type that includes a prototype, 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.93'><sup>[93]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.93'>
|
|
<pre><i><b>Footnote 93)</b> A function may 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 may
|
|
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='#6.9.1'>6.9.1</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 If the expression that denotes the called function has a type that does not include a
|
|
prototype, the integer promotions are performed on each argument, and arguments that
|
|
have type float are promoted to double. These are called the default argument
|
|
promotions. If the number of arguments does not equal the number of parameters, the
|
|
behavior is undefined. If the function is defined with a type that includes a prototype, and
|
|
either the prototype ends with an ellipsis (, ...) or the types of the arguments after
|
|
promotion are not compatible with the types of the parameters, the behavior is undefined.
|
|
If the function is defined with a type that does not include a prototype, and the types of
|
|
the arguments after promotion are not compatible with those of the parameters after
|
|
promotion, the behavior is undefined, except for the following cases:
|
|
— one promoted type is a signed integer type, the other promoted type is the
|
|
corresponding unsigned integer type, and the value is representable in both types;
|
|
— both types are pointers to qualified or unqualified versions of a character type or
|
|
void.
|
|
</pre>
|
|
<a name='6.5.2.2p7'></a>
|
|
<pre>7 If the expression that denotes the called function has a type that does include a prototype,
|
|
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. The default argument
|
|
promotions are performed on trailing arguments.
|
|
</pre>
|
|
<a name='6.5.2.2p8'></a>
|
|
<pre>8 No other conversions are performed implicitly; in particular, the number and types of
|
|
arguments are not compared with those of the parameters in a function definition that
|
|
does not include a function prototype declarator.
|
|
</pre>
|
|
<a name='6.5.2.2p9'></a>
|
|
<pre>9 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='6.5.2.2p10'></a>
|
|
<pre>10 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.94'><sup>[94]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.94'>
|
|
<pre><i><b>Footnote 94)</b> In other words, function executions do not ‘‘interleave’’ with each other.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.2p11'></a>
|
|
<pre>11 Recursive function calls shall be permitted, both directly and indirectly through any chain
|
|
of other functions.
|
|
</pre>
|
|
<a name='6.5.2.2p12'></a>
|
|
<pre>12 EXAMPLE In the function call
|
|
(*pf[f1()]) (f2(), f3() + f4())
|
|
the functions f1, f2, f3, and f4 may 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 (including prototypes) (<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.95'><sup>[95]</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.95'>
|
|
<pre><i><b>Footnote 95)</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 trap 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.96'><sup>[96]</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.96'>
|
|
<pre><i><b>Footnote 96)</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.97'><sup>[97]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.97'>
|
|
<pre><i><b>Footnote 97)</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 unqualified 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.98'><sup>[98]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.98'>
|
|
<pre><i><b>Footnote 98)</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 must be taken 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 Constraints
|
|
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='6.5.2.5p2'></a>
|
|
<pre>2 All the constraints for initializer lists in <a href='#6.7.9'>6.7.9</a> also apply to compound literals.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.2.5p3'></a>
|
|
<pre>3 A postfix expression that consists of a parenthesized type name followed by a brace-
|
|
enclosed list of initializers is a compound literal. It provides an unnamed object whose
|
|
value is given by the initializer list.<a href='#FOOTNOTE.99'><sup>[99]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.99'>
|
|
<pre><i><b>Footnote 99)</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='6.5.2.5p4'></a>
|
|
<pre>4 If the type name specifies an array of unknown size, the size is determined by the
|
|
initializer list as specified in <a href='#6.7.9'>6.7.9</a>, and the type of the compound literal is that of the
|
|
completed array type. Otherwise (when the type name specifies an object type), the type
|
|
of the compound literal is that specified by the type name. In either case, the result is an
|
|
lvalue.
|
|
</pre>
|
|
<a name='6.5.2.5p5'></a>
|
|
<pre>5 The value of the compound literal is that of an unnamed object initialized by the
|
|
initializer list. If the compound literal occurs outside the body of a function, the object
|
|
has static storage duration; otherwise, it has automatic storage duration associated with
|
|
the enclosing block.
|
|
</pre>
|
|
<a name='6.5.2.5p6'></a>
|
|
<pre>6 All the semantic rules for initializer lists in <a href='#6.7.9'>6.7.9</a> also apply to compound literals.<a href='#FOOTNOTE.100'><sup>[100]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.100'>
|
|
<pre><i><b>Footnote 100)</b> For example, subobjects without explicit initializers are initialized to zero.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.2.5p7'></a>
|
|
<pre>7 String literals, and compound literals with const-qualified types, need not designate
|
|
distinct objects.<a href='#FOOTNOTE.101'><sup>[101]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.101'>
|
|
<pre><i><b>Footnote 101)</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='6.5.2.5p8'></a>
|
|
<pre>8 EXAMPLE 1 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='6.5.2.5p9'></a>
|
|
<pre>9 EXAMPLE 2 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='6.5.2.5p10'></a>
|
|
<pre>10 EXAMPLE 3 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='6.5.2.5p11'></a>
|
|
<pre>11 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
|
|
(const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
|
|
|
|
</pre>
|
|
<a name='6.5.2.5p12'></a>
|
|
<pre>12 EXAMPLE 5 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='6.5.2.5p13'></a>
|
|
<pre>13 EXAMPLE 6 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='6.5.2.5p14'></a>
|
|
<pre>14 EXAMPLE 7 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='6.5.2.5p15'></a>
|
|
<pre>15 EXAMPLE 8 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.
|
|
</pre>
|
|
<a name='6.5.2.5p16'></a>
|
|
<pre>16 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
|
|
lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
|
|
have an indeterminate value, which would result in undefined behavior.
|
|
|
|
Forward references: type names (<a href='#6.7.7'>6.7.7</a>), initialization (<a href='#6.7.9'>6.7.9</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 unqualified 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.102'><sup>[102]</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.102'>
|
|
<pre><i><b>Footnote 102)</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. 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.103'><sup>[103]</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.103'>
|
|
<pre><i><b>Footnote 103)</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 should ensure 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='#7.19'>7.19</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.
|
|
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 named type. This construction is called a cast.<a href='#FOOTNOTE.104'><sup>[104]</sup></a> A cast that specifies
|
|
no conversion has no effect on the type or value of an expression.
|
|
</pre>
|
|
<a name='FOOTNOTE.104'>
|
|
<pre><i><b>Footnote 104)</b> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
|
|
unqualified version of the type.
|
|
</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 (including
|
|
prototypes) (<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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.5p3'></a>
|
|
<pre>3 The usual arithmetic conversions are performed on the operands.
|
|
</pre>
|
|
<a name='6.5.5p4'></a>
|
|
<pre>4 The result of the binary * operator is the product of the operands.
|
|
</pre>
|
|
<a name='6.5.5p5'></a>
|
|
<pre>5 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='6.5.5p6'></a>
|
|
<pre>6 When integers are divided, the result of the / operator is the algebraic quotient with any
|
|
fractional part discarded.<a href='#FOOTNOTE.105'><sup>[105]</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.105'>
|
|
<pre><i><b>Footnote 105)</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.)
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.6p4'></a>
|
|
<pre>4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
|
|
them.
|
|
</pre>
|
|
<a name='6.5.6p5'></a>
|
|
<pre>5 The result of the binary + operator is the sum of the operands.
|
|
</pre>
|
|
<a name='6.5.6p6'></a>
|
|
<pre>6 The result of the binary - operator is the difference resulting from the subtraction of the
|
|
second operand from the first.
|
|
</pre>
|
|
<a name='6.5.6p7'></a>
|
|
<pre>7 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='6.5.6p8'></a>
|
|
<pre>8 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 both the pointer
|
|
operand and the result point to elements of the same array object, or one past the last
|
|
element of the array object, the evaluation shall not produce an overflow; otherwise, 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='6.5.6p9'></a>
|
|
<pre>9 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.106'><sup>[106]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.106'>
|
|
<pre><i><b>Footnote 106)</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 may 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='6.5.6p10'></a>
|
|
<pre>10 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='6.5.6p11'></a>
|
|
<pre>11 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='#7.19'>7.19</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 , reduced modulo
|
|
one more than the maximum value representable in the result type. 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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.8p3'></a>
|
|
<pre>3 If both of the operands have arithmetic type, the usual arithmetic conversions are
|
|
performed.
|
|
</pre>
|
|
<a name='6.5.8p4'></a>
|
|
<pre>4 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='6.5.8p5'></a>
|
|
<pre>5 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='6.5.8p6'></a>
|
|
<pre>6 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.107'><sup>[107]</sup></a> The result has type int.
|
|
</pre>
|
|
<a name='FOOTNOTE.107'>
|
|
<pre><i><b>Footnote 107)</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; or
|
|
— one operand is a pointer and the other is a null pointer constant.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.9p3'></a>
|
|
<pre>3 The == (equal to) and != (not equal to) operators are analogous to the relational
|
|
operators except for their lower precedence.<a href='#FOOTNOTE.108'><sup>[108]</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.108'>
|
|
<pre><i><b>Footnote 108)</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='6.5.9p4'></a>
|
|
<pre>4 If both of the operands have arithmetic type, the usual arithmetic conversions are
|
|
performed. 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.
|
|
</pre>
|
|
<a name='6.5.9p5'></a>
|
|
<pre>5 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='6.5.9p6'></a>
|
|
<pre>6 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.109'><sup>[109]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.109'>
|
|
<pre><i><b>Footnote 109)</b> Two objects may 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='6.5.9p7'></a>
|
|
<pre>7 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:
|
|
— 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;
|
|
— one operand is a pointer and the other is a null pointer constant; or
|
|
— one operand is a pointer to an object type and the other is a pointer to a qualified or
|
|
unqualified version of void.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.15p4'></a>
|
|
<pre>4 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.110'><sup>[110]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.110'>
|
|
<pre><i><b>Footnote 110)</b> A conditional expression does not yield an lvalue.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.5.15p5'></a>
|
|
<pre>5 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='6.5.15p6'></a>
|
|
<pre>6 If both the second and third operands are pointers or one is a null pointer constant and the
|
|
other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
|
|
of the types referenced by both operands. 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='6.5.15p7'></a>
|
|
<pre>7 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='6.5.15p8'></a>
|
|
<pre>8 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.111'><sup>[111]</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.111'>
|
|
<pre><i><b>Footnote 111)</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.112'><sup>[112]</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 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.112'>
|
|
<pre><i><b>Footnote 112)</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='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.
|
|
</pre>
|
|
<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 may 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 should 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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.5.16.2p3'></a>
|
|
<pre>3 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 indeterminately-sequenced function call, the operation of a compound
|
|
assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
|
|
read-modify-write operation with memory_order_seq_cst memory order
|
|
semantics.<a href='#FOOTNOTE.113'><sup>[113]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.113'>
|
|
<pre><i><b>Footnote 113)</b> 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 should 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 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 must be a type with the range and precision to which E2 is
|
|
evaluated in order to satisfy the equivalence.
|
|
</i></pre>
|
|
</a>
|
|
<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.114'><sup>[114]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.114'>
|
|
<pre><i><b>Footnote 114)</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='#6.7.9'>6.7.9</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.115'><sup>[115]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.115'>
|
|
<pre><i><b>Footnote 115)</b> The operand of 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.116'><sup>[116]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.116'>
|
|
<pre><i><b>Footnote 116)</b> The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in
|
|
the translation environment.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.6p6'></a>
|
|
<pre>6 An integer constant expression<a href='#FOOTNOTE.117'><sup>[117]</sup></a> shall have integer type and shall only have operands
|
|
that are integer constants, enumeration constants, character constants, sizeof
|
|
expressions whose results are integer constants, _Alignof expressions, and floating
|
|
constants 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 sizeof or _Alignof operator.
|
|
</pre>
|
|
<a name='FOOTNOTE.117'>
|
|
<pre><i><b>Footnote 117)</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='6.6p7'></a>
|
|
<pre>7 More latitude is permitted for constant expressions in initializers. Such a constant
|
|
expression shall be, or 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.
|
|
</pre>
|
|
<a name='6.6p8'></a>
|
|
<pre>8 An arithmetic constant expression shall have arithmetic type and shall only have
|
|
operands that are integer constants, floating constants, enumeration constants, character
|
|
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 a sizeof or
|
|
_Alignof operator.
|
|
</pre>
|
|
<a name='6.6p9'></a>
|
|
<pre>9 An address constant is a null pointer, 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. The array-subscript [] and member-access .
|
|
and -> operators, 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.
|
|
</pre>
|
|
<a name='6.6p10'></a>
|
|
<pre>10 An implementation may accept other forms of constant expressions.
|
|
</pre>
|
|
<a name='6.6p11'></a>
|
|
<pre>11 The semantic rules for the evaluation of a constant expression are the same as for
|
|
nonconstant expressions.<a href='#FOOTNOTE.118'><sup>[118]</sup></a>
|
|
Forward references: array declarators (<a href='#6.7.6.2'>6.7.6.2</a>), initialization (<a href='#6.7.9'>6.7.9</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.118'>
|
|
<pre><i><b>Footnote 118)</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 ;
|
|
static_assert-declaration
|
|
declaration-specifiers:
|
|
storage-class-specifier declaration-specifiersopt
|
|
type-specifier declaration-specifiersopt
|
|
type-qualifier declaration-specifiersopt
|
|
function-specifier declaration-specifiersopt
|
|
alignment-specifier declaration-specifiersopt
|
|
init-declarator-list:
|
|
init-declarator
|
|
init-declarator-list , init-declarator
|
|
init-declarator:
|
|
declarator
|
|
declarator = initializer
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7p2'></a>
|
|
<pre>2 A declaration other than a static_assert 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;
|
|
— tags may be redeclared as specified in <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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7p5'></a>
|
|
<pre>5 A declaration specifies the interpretation and attributes 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.119'><sup>[119]</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.119'>
|
|
<pre><i><b>Footnote 119)</b> Function definitions have a different syntax, described in <a href='#6.9.1'>6.9.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7p6'></a>
|
|
<pre>6 The declaration specifiers consist of a sequence of specifiers 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.
|
|
</pre>
|
|
<a name='6.7p7'></a>
|
|
<pre>7 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 (including in prototypes), it is the adjusted
|
|
type (see <a href='#6.7.6.3'>6.7.6.3</a>) that is required to be complete.
|
|
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='#6.7.9'>6.7.9</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:
|
|
typedef
|
|
extern
|
|
static
|
|
_Thread_local
|
|
auto
|
|
register
|
|
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.<a href='#FOOTNOTE.120'><sup>[120]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.120'>
|
|
<pre><i><b>Footnote 120)</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.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.1p5'></a>
|
|
<pre>5 The typedef specifier is called a ‘‘storage-class specifier’’ for syntactic convenience
|
|
only; it is discussed in <a href='#6.7.8'>6.7.8</a>. 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>.
|
|
</pre>
|
|
<a name='6.7.1p6'></a>
|
|
<pre>6 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.121'><sup>[121]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.121'>
|
|
<pre><i><b>Footnote 121)</b> The implementation may 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 operators that can be applied to an array declared with storage-class specifier
|
|
register are sizeof and _Alignof.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.1p7'></a>
|
|
<pre>7 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='6.7.1p8'></a>
|
|
<pre>8 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.
|
|
Forward references: type definitions (<a href='#6.7.8'>6.7.8</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
|
|
_Bool
|
|
_Complex
|
|
atomic-type-specifier
|
|
struct-or-union-specifier
|
|
enum-specifier
|
|
typedef-name
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2p2'></a>
|
|
<pre>2 At least one type specifier shall be given in the declaration specifiers in each declaration,
|
|
and in the specifier-qualifier list in each struct 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
|
|
— float
|
|
— double
|
|
— long double
|
|
— _Bool
|
|
— float _Complex
|
|
— double _Complex
|
|
— long double _Complex
|
|
— atomic type specifier
|
|
— struct or union specifier
|
|
— enum specifier
|
|
— typedef name
|
|
</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 (see <a href='#6.10.8.3'>6.10.8.3</a>).
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2p4'></a>
|
|
<pre>4 Specifiers for structures, unions, enumerations, and atomic types are discussed in <a href='#6.7.2.1'>6.7.2.1</a>
|
|
through <a href='#6.7.2.4'>6.7.2.4</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='6.7.2p5'></a>
|
|
<pre>5 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 identifieropt { struct-declaration-list }
|
|
struct-or-union identifier
|
|
struct-or-union:
|
|
struct
|
|
union
|
|
struct-declaration-list:
|
|
struct-declaration
|
|
struct-declaration-list struct-declaration
|
|
struct-declaration:
|
|
specifier-qualifier-list struct-declarator-listopt ;
|
|
static_assert-declaration
|
|
specifier-qualifier-list:
|
|
type-specifier specifier-qualifier-listopt
|
|
type-qualifier specifier-qualifier-listopt
|
|
struct-declarator-list:
|
|
struct-declarator
|
|
struct-declarator-list , struct-declarator
|
|
struct-declarator:
|
|
declarator
|
|
declaratoropt : constant-expression
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.1p2'></a>
|
|
<pre>2 A struct-declaration that does not declare an anonymous structure or anonymous union
|
|
shall contain a struct-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.122'><sup>[122]</sup></a> If the value is
|
|
zero, the declaration shall have no declarator.
|
|
</pre>
|
|
<a name='FOOTNOTE.122'>
|
|
<pre><i><b>Footnote 122)</b> While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
|
|
value bits) of a _Bool may 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, or some other implementation-defined type. It is
|
|
implementation-defined whether atomic types are permitted.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.1p6'></a>
|
|
<pre>6 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='6.7.2.1p7'></a>
|
|
<pre>7 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='6.7.2.1p8'></a>
|
|
<pre>8 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
|
|
within a translation unit. The struct-declaration-list is a sequence of declarations for the
|
|
members of the structure or union. If the struct-declaration-list does not contain any
|
|
named members, either directly or via an anonymous structure or anonymous union, the
|
|
behavior is undefined. The type is incomplete until immediately after the } that
|
|
terminates the list, and complete thereafter.
|
|
</pre>
|
|
<a name='6.7.2.1p9'></a>
|
|
<pre>9 A member of a structure or union may have any complete object type other than a
|
|
variably modified type.<a href='#FOOTNOTE.123'><sup>[123]</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;<a href='#FOOTNOTE.124'><sup>[124]</sup></a> its width is preceded by a colon.
|
|
</pre>
|
|
<a name='FOOTNOTE.123'>
|
|
<pre><i><b>Footnote 123)</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='FOOTNOTE.124'>
|
|
<pre><i><b>Footnote 124)</b> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
|
|
or arrays of bit-field objects.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p10'></a>
|
|
<pre>10 A bit-field is interpreted as having a signed or unsigned integer type consisting of the
|
|
specified number of bits.<a href='#FOOTNOTE.125'><sup>[125]</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.125'>
|
|
<pre><i><b>Footnote 125)</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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p11'></a>
|
|
<pre>11 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='6.7.2.1p12'></a>
|
|
<pre>12 A bit-field declaration with no declarator, but only a colon and a width, indicates an
|
|
unnamed bit-field.<a href='#FOOTNOTE.126'><sup>[126]</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.126'>
|
|
<pre><i><b>Footnote 126)</b> An unnamed bit-field structure member is useful for padding to conform to externally imposed
|
|
layouts.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.1p13'></a>
|
|
<pre>13 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. This applies
|
|
recursively if the containing structure or union is also anonymous.
|
|
</pre>
|
|
<a name='6.7.2.1p14'></a>
|
|
<pre>14 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='6.7.2.1p15'></a>
|
|
<pre>15 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='6.7.2.1p16'></a>
|
|
<pre>16 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.
|
|
</pre>
|
|
<a name='6.7.2.1p17'></a>
|
|
<pre>17 There may be unnamed padding at the end of a structure or union.
|
|
</pre>
|
|
<a name='6.7.2.1p18'></a>
|
|
<pre>18 As a special case, the last element 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='6.7.2.1p19'></a>
|
|
<pre>19 EXAMPLE 1 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='6.7.2.1p20'></a>
|
|
<pre>20 EXAMPLE 2 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='6.7.2.1p21'></a>
|
|
<pre>21 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='6.7.2.1p22'></a>
|
|
<pre>22 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='6.7.2.1p23'></a>
|
|
<pre>23 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='6.7.2.1p24'></a>
|
|
<pre>24 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='6.7.2.1p25'></a>
|
|
<pre>25 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 might be copied or simply overwritten with indeterminate values.
|
|
|
|
</pre>
|
|
<a name='6.7.2.1p26'></a>
|
|
<pre>26 EXAMPLE 3 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 identifieropt { enumerator-list }
|
|
enum identifieropt { enumerator-list , }
|
|
enum identifier
|
|
enumerator-list:
|
|
enumerator
|
|
enumerator-list , enumerator
|
|
enumerator:
|
|
enumeration-constant
|
|
enumeration-constant = constant-expression
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.2.2p2'></a>
|
|
<pre>2 The expression that defines the value of an enumeration constant shall be an integer
|
|
constant expression that has a value representable as an int.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.2.2p3'></a>
|
|
<pre>3 The identifiers in an enumerator list are declared as constants that have type int and
|
|
may appear wherever such are permitted.<a href='#FOOTNOTE.127'><sup>[127]</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.127'>
|
|
<pre><i><b>Footnote 127)</b> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
|
|
each other and from other identifiers declared in ordinary declarators.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p4'></a>
|
|
<pre>4 Each enumerated type shall be compatible with char, a signed integer type, or an
|
|
unsigned integer type. The choice of type is implementation-defined,<a href='#FOOTNOTE.128'><sup>[128]</sup></a> but shall be
|
|
capable of representing the values of all the members of the enumeration. The
|
|
enumerated type is incomplete until immediately after the } that terminates the list of
|
|
enumerator declarations, and complete thereafter.
|
|
</pre>
|
|
<a name='FOOTNOTE.128'>
|
|
<pre><i><b>Footnote 128)</b> An implementation may delay the choice of which integer type until all enumeration constants have
|
|
been seen.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.2p5'></a>
|
|
<pre>5 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 }.
|
|
|
|
Forward references: tags (<a href='#6.7.2.3'>6.7.2.3</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
|
|
A specific type shall have its content defined at most once.
|
|
</pre>
|
|
<a name='6.7.2.3p2'></a>
|
|
<pre>2 Where two declarations that use the same tag declare the same type, they shall both use
|
|
the same choice of struct, union, or enum.
|
|
</pre>
|
|
<a name='6.7.2.3p3'></a>
|
|
<pre>3 A type specifier of the form
|
|
enum identifier
|
|
without an enumerator list shall only appear after the type it specifies is complete.
|
|
Semantics
|
|
</pre>
|
|
<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. Irrespective of whether there is a tag or what
|
|
other declarations of the type are in the same translation unit, the type is incomplete<a href='#FOOTNOTE.129'><sup>[129]</sup></a>
|
|
until immediately after the closing brace of the list defining the content, and complete
|
|
thereafter.
|
|
</pre>
|
|
<a name='FOOTNOTE.129'>
|
|
<pre><i><b>Footnote 129)</b> An incomplete type may only by 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. (See incomplete types
|
|
in <a href='#6.2.5'>6.2.5</a>.) The specification has to be complete before such a function is called or defined.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p5'></a>
|
|
<pre>5 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='6.7.2.3p6'></a>
|
|
<pre>6 A type specifier of the form
|
|
struct-or-union identifieropt { struct-declaration-list }
|
|
or
|
|
enum identifieropt { enumerator-list }
|
|
or
|
|
enum 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.130'><sup>[130]</sup></a> the type specifier
|
|
also declares the identifier to be the tag of that type.
|
|
</pre>
|
|
<a name='FOOTNOTE.130'>
|
|
<pre><i><b>Footnote 130)</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='6.7.2.3p7'></a>
|
|
<pre>7 A declaration of the form
|
|
struct-or-union identifier ;
|
|
specifies a structure or union type and declares the identifier as a tag of that type.<a href='#FOOTNOTE.131'><sup>[131]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.131'>
|
|
<pre><i><b>Footnote 131)</b> A similar construction with enum does not exist.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p8'></a>
|
|
<pre>8 If a type specifier of the form
|
|
struct-or-union 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.131'><sup>[131]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.131'>
|
|
<pre><i><b>Footnote 131)</b> A similar construction with enum does not exist.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.2.3p9'></a>
|
|
<pre>9 If a type specifier of the form
|
|
struct-or-union 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='6.7.2.3p10'></a>
|
|
<pre>10 EXAMPLE 1 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='6.7.2.3p11'></a>
|
|
<pre>11 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='6.7.2.3p12'></a>
|
|
<pre>12 EXAMPLE 2 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;
|
|
may 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='#6.10.8.3'>6.10.8.3</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='6.7.3'></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 shall not be
|
|
restrict-qualified.
|
|
</pre>
|
|
<a name='6.7.3p3'></a>
|
|
<pre>3 The type modified by the _Atomic qualifier shall not be an array type or a function
|
|
type.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.3p4'></a>
|
|
<pre>4 The properties associated with qualified types are meaningful only for expressions that
|
|
are lvalues.<a href='#FOOTNOTE.132'><sup>[132]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.132'>
|
|
<pre><i><b>Footnote 132)</b> The implementation may 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='6.7.3p5'></a>
|
|
<pre>5 If the same qualifier appears more than once in the same specifier-qualifier-list, either
|
|
directly 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 in a specifier-qualifier-
|
|
list, the resulting type is the so-qualified atomic type.
|
|
</pre>
|
|
<a name='6.7.3p6'></a>
|
|
<pre>6 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.133'><sup>[133]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.133'>
|
|
<pre><i><b>Footnote 133)</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='6.7.3p7'></a>
|
|
<pre>7 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.134'><sup>[134]</sup></a> What constitutes an access to an object that
|
|
has volatile-qualified type is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.134'>
|
|
<pre><i><b>Footnote 134)</b> A volatile declaration may 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 shall not be ‘‘optimized out’’ by an implementation or reordered except as
|
|
permitted by the rules for evaluating expressions.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p8'></a>
|
|
<pre>8 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.135'><sup>[135]</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.135'>
|
|
<pre><i><b>Footnote 135)</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='6.7.3p9'></a>
|
|
<pre>9 If the specification of an array type includes any type qualifiers, the element type is so-
|
|
qualified, not the array type. If the specification of a function type includes any type
|
|
qualifiers, the behavior is undefined.<a href='#FOOTNOTE.136'><sup>[136]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.136'>
|
|
<pre><i><b>Footnote 136)</b> Both of these can occur through the use of typedefs.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.3p10'></a>
|
|
<pre>10 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='6.7.3p11'></a>
|
|
<pre>11 EXAMPLE 1 An object declared
|
|
extern const volatile int real_time_clock;
|
|
may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
|
|
|
|
</pre>
|
|
<a name='6.7.3p12'></a>
|
|
<pre>12 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='6.7.3p13'></a>
|
|
<pre>13 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.137'><sup>[137]</sup></a>
|
|
Note that ‘‘based’’ is defined only for expressions with pointer types.
|
|
</pre>
|
|
<a name='FOOTNOTE.137'>
|
|
<pre><i><b>Footnote 137)</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.
|
|
</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='6.7.4'></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.138'><sup>[138]</sup></a>
|
|
The extent to which such suggestions are effective is implementation-defined.<a href='#FOOTNOTE.139'><sup>[139]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.138'>
|
|
<pre><i><b>Footnote 138)</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.139'>
|
|
<pre><i><b>Footnote 139)</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.140'><sup>[140]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.140'>
|
|
<pre><i><b>Footnote 140)</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.
|
|
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 may be used for the call.
|
|
|
|
</pre>
|
|
<a name='6.7.4p12'></a>
|
|
<pre>12 EXAMPLE 2
|
|
_Noreturn void f () {
|
|
abort(); // ok
|
|
}
|
|
_Noreturn void g (int i) { // causes undefined behavior if i <= 0
|
|
if (i > 0) abort();
|
|
}
|
|
|
|
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 attribute shall not be specified in a declaration of a typedef, or a bit-field, or
|
|
a function, or a parameter, or an object declared with the register storage-class
|
|
specifier.
|
|
</pre>
|
|
<a name='6.7.5p3'></a>
|
|
<pre>3 The constant expression shall be an integer constant expression. It shall evaluate to a
|
|
valid fundamental alignment, or to a valid extended alignment supported by the
|
|
implementation in the context in which it appears, or to zero.
|
|
</pre>
|
|
<a name='6.7.5p4'></a>
|
|
<pre>4 The combined effect of all alignment attributes 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='6.7.5p5'></a>
|
|
<pre>5 The first form is equivalent to _Alignas (_Alignof (type-name)).
|
|
</pre>
|
|
<a name='6.7.5p6'></a>
|
|
<pre>6 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.141'><sup>[141]</sup></a> When multiple
|
|
alignment specifiers occur in a declaration, the effective alignment requirement is the
|
|
strictest specified alignment.
|
|
</pre>
|
|
<a name='FOOTNOTE.141'>
|
|
<pre><i><b>Footnote 141)</b> An alignment specification of zero also does not affect other alignment specifications in the same
|
|
declaration.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.5p7'></a>
|
|
<pre>7 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
|
|
( 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 * ]
|
|
direct-declarator ( parameter-type-list )
|
|
direct-declarator ( identifier-listopt )
|
|
pointer:
|
|
* type-qualifier-listopt
|
|
* 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:
|
|
declaration-specifiers declarator
|
|
declaration-specifiers abstract-declaratoropt
|
|
identifier-list:
|
|
identifier
|
|
identifier-list , identifier
|
|
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. The end of a full
|
|
declarator is a sequence point. 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
|
|
then the type specified for ident is T .
|
|
</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 typedefs.
|
|
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
|
|
* 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.
|
|
</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 shall not be modified through that pointer,
|
|
but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
|
|
int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
|
|
same location.
|
|
</pre>
|
|
<a name='6.7.6.1p4'></a>
|
|
<pre>4 The declaration of the constant pointer constant_ptr may 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 expression 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 ]
|
|
D[ static type-qualifier-listopt assignment-expression ]
|
|
D[ type-qualifier-list static assignment-expression ]
|
|
D[ type-qualifier-listopt * ]
|
|
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.142'><sup>[142]</sup></a>
|
|
(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.142'>
|
|
<pre><i><b>Footnote 142)</b> When several ‘‘array of’’ specifications are adjacent, a multidimensional array is declared.
|
|
</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.143'><sup>[143]</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 are a conditional feature that implementations need not support; see <a href='#6.10.8.3'>6.10.8.3</a>.)
|
|
</pre>
|
|
<a name='FOOTNOTE.143'>
|
|
<pre><i><b>Footnote 143)</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 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.
|
|
</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='#6.7.9'>6.7.9</a>).
|
|
</pre>
|
|
<a name='6.7.6.3'></a>
|
|
<hr>
|
|
<h3>6.7.6.3 [Function declarators (including prototypes)]</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 An identifier list in a function declarator that is not part of a definition of that function
|
|
shall be empty.
|
|
</pre>
|
|
<a name='6.7.6.3p4'></a>
|
|
<pre>4 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='6.7.6.3p5'></a>
|
|
<pre>5 If, in the declaration ‘‘T D1’’, D1 has the form
|
|
D( parameter-type-list )
|
|
or
|
|
D( identifier-listopt )
|
|
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
|
|
T ’’.
|
|
</pre>
|
|
<a name='6.7.6.3p6'></a>
|
|
<pre>6 A parameter type list specifies the types of, and may declare identifiers for, the
|
|
parameters of the function.
|
|
</pre>
|
|
<a name='6.7.6.3p7'></a>
|
|
<pre>7 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='6.7.6.3p8'></a>
|
|
<pre>8 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='6.7.6.3p9'></a>
|
|
<pre>9 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.144'><sup>[144]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.144'>
|
|
<pre><i><b>Footnote 144)</b> The macros defined in the <stdarg.h> header (<a href='#7.16'>7.16</a>) may be used to access arguments that
|
|
correspond to the ellipsis.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.3p10'></a>
|
|
<pre>10 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='6.7.6.3p11'></a>
|
|
<pre>11 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='6.7.6.3p12'></a>
|
|
<pre>12 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='6.7.6.3p13'></a>
|
|
<pre>13 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.
|
|
</pre>
|
|
<a name='6.7.6.3p14'></a>
|
|
<pre>14 An identifier list declares only the identifiers of the parameters of the function. An empty
|
|
list in a function declarator that is part of a definition of that function specifies that the
|
|
function has no parameters. The empty list in a function declarator that is not part of a
|
|
definition of that function specifies that no information about the number or types of the
|
|
parameters is supplied.<a href='#FOOTNOTE.145'><sup>[145]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.145'>
|
|
<pre><i><b>Footnote 145)</b> See ‘‘future language directions’’ (<a href='#6.11.6'>6.11.6</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.3p15'></a>
|
|
<pre>15 For two function types to be compatible, both shall specify compatible return types.<a href='#FOOTNOTE.146'><sup>[146]</sup></a>
|
|
Moreover, the parameter type lists, if both are present, shall agree in the number of
|
|
parameters and in use of the ellipsis terminator; corresponding parameters shall have
|
|
compatible types. If one type has a parameter type list and the other type is specified by a
|
|
function declarator that is not part of a function definition and that contains an empty
|
|
identifier list, the parameter list shall not have an ellipsis terminator and the type of each
|
|
parameter shall be compatible with the type that results from the application of the
|
|
default argument promotions. If one type has a parameter type list and the other type is
|
|
specified by a function definition that contains a (possibly empty) identifier list, both shall
|
|
agree in the number of parameters, and the type of each prototype parameter shall be
|
|
compatible with the type that results from the application of the default argument
|
|
promotions to the type of the corresponding identifier. (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='FOOTNOTE.146'>
|
|
<pre><i><b>Footnote 146)</b> If both function types are ‘‘old style’’, parameter types are not compared.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.6.3p16'></a>
|
|
<pre>16 EXAMPLE 1 The declaration
|
|
int f(void), *fip(), (*pfi)();
|
|
declares a function f with no parameters returning an int, a function fip with no parameter specification
|
|
returning a pointer to an int, and a pointer pfi to a function with no parameter specification 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='6.7.6.3p17'></a>
|
|
<pre>17 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='6.7.6.3p18'></a>
|
|
<pre>18 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='6.7.6.3p19'></a>
|
|
<pre>19 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='6.7.6.3p20'></a>
|
|
<pre>20 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='6.7.6.3p21'></a>
|
|
<pre>21 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 must 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 )
|
|
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 [ * ]
|
|
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.147'><sup>[147]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.147'>
|
|
<pre><i><b>Footnote 147)</b> As indicated by the syntax, empty parentheses in a type name are interpreted as ‘‘function with no
|
|
parameter specification’’, 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 ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
|
|
with no parameter specification 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.
|
|
</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
|
|
parameter specification 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 [Initialization]</h3>
|
|
<a name='6.7.9p1'></a>
|
|
<pre>1 Syntax
|
|
initializer:
|
|
assignment-expression
|
|
{ initializer-list }
|
|
{ initializer-list , }
|
|
initializer-list:
|
|
designationopt initializer
|
|
initializer-list , designationopt initializer
|
|
designation:
|
|
designator-list =
|
|
designator-list:
|
|
designator
|
|
designator-list designator
|
|
designator:
|
|
[ constant-expression ]
|
|
. identifier
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.9p2'></a>
|
|
<pre>2 No initializer shall attempt to provide a value for an object not contained within the entity
|
|
being initialized.
|
|
</pre>
|
|
<a name='6.7.9p3'></a>
|
|
<pre>3 The type of the entity to be initialized shall be an array of unknown size or a complete
|
|
object type that is not a variable length array type.
|
|
</pre>
|
|
<a name='6.7.9p4'></a>
|
|
<pre>4 All the expressions in an initializer for an object that has static or thread storage duration
|
|
shall be constant expressions or string literals.
|
|
</pre>
|
|
<a name='6.7.9p5'></a>
|
|
<pre>5 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='6.7.9p6'></a>
|
|
<pre>6 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='6.7.9p7'></a>
|
|
<pre>7 If a designator has the form
|
|
. identifier
|
|
then the current object (defined below) shall have structure or union type and the
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.9p8'></a>
|
|
<pre>8 An initializer specifies the initial value stored in an object.
|
|
</pre>
|
|
<a name='6.7.9p9'></a>
|
|
<pre>9 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 value even after initialization.
|
|
</pre>
|
|
<a name='6.7.9p10'></a>
|
|
<pre>10 If an object that has automatic storage duration is not initialized explicitly, its value is
|
|
indeterminate. If an object that has static or thread storage duration is not initialized
|
|
explicitly, then:
|
|
— if it has pointer type, it is initialized to a null pointer;
|
|
— if it has arithmetic 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='6.7.9p11'></a>
|
|
<pre>11 The initializer for a scalar shall be a single expression, optionally enclosed in braces. 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='6.7.9p12'></a>
|
|
<pre>12 The rest of this subclause deals with initializers for objects that have aggregate or union
|
|
type.
|
|
</pre>
|
|
<a name='6.7.9p13'></a>
|
|
<pre>13 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='6.7.9p14'></a>
|
|
<pre>14 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='6.7.9p15'></a>
|
|
<pre>15 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='6.7.9p16'></a>
|
|
<pre>16 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='6.7.9p17'></a>
|
|
<pre>17 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.148'><sup>[148]</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.149'><sup>[149]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.148'>
|
|
<pre><i><b>Footnote 148)</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.149'>
|
|
<pre><i><b>Footnote 149)</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='6.7.9p18'></a>
|
|
<pre>18 Each designator list begins its description with the current object associated with the
|
|
closest surrounding 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.150'><sup>[150]</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.150'>
|
|
<pre><i><b>Footnote 150)</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='6.7.9p19'></a>
|
|
<pre>19 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.151'><sup>[151]</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.151'>
|
|
<pre><i><b>Footnote 151)</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='6.7.9p20'></a>
|
|
<pre>20 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='6.7.9p21'></a>
|
|
<pre>21 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='6.7.9p22'></a>
|
|
<pre>22 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='6.7.9p23'></a>
|
|
<pre>23 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.152'><sup>[152]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.152'>
|
|
<pre><i><b>Footnote 152)</b> In particular, the evaluation order need not be the same as the order of subobject initialization.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.7.9p24'></a>
|
|
<pre>24 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='6.7.9p25'></a>
|
|
<pre>25 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='6.7.9p26'></a>
|
|
<pre>26 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='6.7.9p27'></a>
|
|
<pre>27 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='6.7.9p28'></a>
|
|
<pre>28 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='6.7.9p29'></a>
|
|
<pre>29 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 may 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='6.7.9p30'></a>
|
|
<pre>30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
|
|
cause confusion.
|
|
|
|
</pre>
|
|
<a name='6.7.9p31'></a>
|
|
<pre>31 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='6.7.9p32'></a>
|
|
<pre>32 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='6.7.9p33'></a>
|
|
<pre>33 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='6.7.9p34'></a>
|
|
<pre>34 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='6.7.9p35'></a>
|
|
<pre>35 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
|
|
might be misunderstood:
|
|
struct { int a[3], b; } w[] =
|
|
{ [0].a = {1}, [1].a[0] = 2 };
|
|
|
|
</pre>
|
|
<a name='6.7.9p36'></a>
|
|
<pre>36 EXAMPLE 12 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='6.7.9p37'></a>
|
|
<pre>37 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='6.7.9p38'></a>
|
|
<pre>38 EXAMPLE 13 Any member of a union can be initialized:
|
|
union { /* ... */ } u = { .any_member = 42 };
|
|
|
|
Forward references: common definitions <stddef.h> (<a href='#7.19'>7.19</a>).
|
|
</pre>
|
|
<a name='6.7.10'></a>
|
|
<hr>
|
|
<h3>6.7.10 [Static assertions]</h3>
|
|
<a name='6.7.10p1'></a>
|
|
<pre>1 Syntax
|
|
static_assert-declaration:
|
|
_Static_assert ( constant-expression , string-literal ) ;
|
|
Constraints
|
|
</pre>
|
|
<a name='6.7.10p2'></a>
|
|
<pre>2 The constant expression shall compare unequal to 0.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.7.10p3'></a>
|
|
<pre>3 The constant expression shall be an integer constant expression. If the value of the
|
|
constant expression compares unequal to 0, the declaration has no effect. Otherwise, the
|
|
constraint is violated and the implementation shall produce a diagnostic message that
|
|
includes the text of the string literal, except that characters not in the basic source
|
|
character set are not required to appear in the message.
|
|
Forward references: diagnostics (<a href='#7.2'>7.2</a>).
|
|
</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
|
|
compound-statement
|
|
expression-statement
|
|
selection-statement
|
|
iteration-statement
|
|
jump-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.
|
|
</pre>
|
|
<a name='6.8p3'></a>
|
|
<pre>3 A block allows a set of declarations and statements to be grouped into one syntactic unit.
|
|
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 (including storing an indeterminate value in objects without an
|
|
initializer) 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 or of a declarator.
|
|
Each of the following is a full expression: 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. There is a sequence point between the evaluation of a full expression and the
|
|
evaluation of the next full expression to be evaluated.
|
|
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
|
|
labeled-statement:
|
|
identifier : statement
|
|
case constant-expression : statement
|
|
default : 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.
|
|
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
|
|
statement
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.2p2'></a>
|
|
<pre>2 A compound statement is a block.
|
|
</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 ;
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.3p2'></a>
|
|
<pre>2 The expression in an expression statement is evaluated as a void expression for its side
|
|
effects.<a href='#FOOTNOTE.153'><sup>[153]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.153'>
|
|
<pre><i><b>Footnote 153)</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 may 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.
|
|
|
|
</pre>
|
|
<a name='6.8.3p6'></a>
|
|
<pre>6 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
|
|
statement.
|
|
while (loop1) {
|
|
/* ... */
|
|
while (loop2) {
|
|
/* ... */
|
|
if (want_out)
|
|
goto end_loop1;
|
|
/* ... */
|
|
}
|
|
/* ... */
|
|
end_loop1: ;
|
|
}
|
|
|
|
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 ) statement
|
|
if ( expression ) statement else statement
|
|
switch ( expression ) statement
|
|
Semantics
|
|
</pre>
|
|
<a name='6.8.4p2'></a>
|
|
<pre>2 A selection statement selects among a set of statements depending on the value of a
|
|
controlling expression.
|
|
</pre>
|
|
<a name='6.8.4p3'></a>
|
|
<pre>3 A selection statement is a block whose scope is a strict subset of the scope of its
|
|
enclosing block. Each associated substatement is also a block whose scope is a strict
|
|
subset of the scope of the selection statement.
|
|
</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.154'><sup>[154]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.154'>
|
|
<pre><i><b>Footnote 154)</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 labeled statement. 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 indeterminate value. 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 ) statement
|
|
do statement while ( expression ) ;
|
|
for ( expressionopt ; expressionopt ; expressionopt ) statement
|
|
for ( declaration expressionopt ; expressionopt ) statement
|
|
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 statement 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.155'><sup>[155]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.155'>
|
|
<pre><i><b>Footnote 155)</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 is a block whose scope is a strict subset of the scope of its
|
|
enclosing block. The loop body is also a block whose scope is a strict subset of the scope
|
|
of the iteration statement.
|
|
</pre>
|
|
<a name='6.8.5p6'></a>
|
|
<pre>6 An iteration statement whose controlling expression is not a constant expression,<a href='#FOOTNOTE.156'><sup>[156]</sup></a> that
|
|
performs no input/output operations, does not access volatile objects, and performs no
|
|
synchronization or atomic operations in its body, controlling expression, or (in the case of
|
|
a for statement) its expression-3, may be assumed by the implementation to
|
|
terminate.<a href='#FOOTNOTE.157'><sup>[157]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.156'>
|
|
<pre><i><b>Footnote 156)</b> An omitted controlling expression is replaced by a nonzero constant, which is a constant expression.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.157'>
|
|
<pre><i><b>Footnote 157)</b> This is intended to allow compiler transformations such as removal of empty loops even when
|
|
termination cannot be proven.
|
|
</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.158'><sup>[158]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.158'>
|
|
<pre><i><b>Footnote 158)</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.159'><sup>[159]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.159'>
|
|
<pre><i><b>Footnote 159)</b> Following the contin: label is a null statement.
|
|
</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.160'><sup>[160]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.160'>
|
|
<pre><i><b>Footnote 160)</b> The return statement is not an assignment. The overlap restriction of subclause <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 may have wider range
|
|
or precision than implied by the type; a cast may 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 specifiers auto and 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 (other than as a part of the operand of a sizeof or
|
|
_Alignof operator whose result is an integer constant), there shall be exactly one
|
|
external definition for the identifier in the translation unit.
|
|
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 sizeof or
|
|
_Alignof operator whose result is an integer constant), 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.161'><sup>[161]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.161'>
|
|
<pre><i><b>Footnote 161)</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:
|
|
declaration-specifiers declarator declaration-listopt compound-statement
|
|
declaration-list:
|
|
declaration
|
|
declaration-list declaration
|
|
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.<a href='#FOOTNOTE.162'><sup>[162]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.162'>
|
|
<pre><i><b>Footnote 162)</b> The intent is that the type category in a function definition 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
|
|
</i></pre>
|
|
</a>
|
|
<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 declarator includes a parameter type list, the declaration of each parameter shall
|
|
include an identifier, except for the special case of a parameter list consisting of a single
|
|
parameter of type void, in which case there shall not be an identifier. No declaration list
|
|
shall follow.
|
|
</pre>
|
|
<a name='6.9.1p6'></a>
|
|
<pre>6 If the declarator includes an identifier list, each declaration in the declaration list shall
|
|
have at least one declarator, those declarators shall declare only identifiers from the
|
|
identifier list, and every identifier in the identifier list shall be declared. An identifier
|
|
declared as a typedef name shall not be redeclared as a parameter. The declarations in the
|
|
declaration list shall contain no storage-class specifier other than register and no
|
|
initializations.
|
|
Semantics
|
|
</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 identifiers of its parameters. If the declarator includes a parameter type list, the
|
|
list also specifies the types of all the parameters; such a declarator also serves as a
|
|
function prototype for later calls to the same function in the same translation unit. If the
|
|
declarator includes an identifier list,<a href='#FOOTNOTE.163'><sup>[163]</sup></a> the types of the parameters shall be declared in a
|
|
following declaration list. In either case, the type of each parameter is adjusted as
|
|
described in <a href='#6.7.6.3'>6.7.6.3</a> for a parameter type list; the resulting type shall be a complete object
|
|
type.
|
|
</pre>
|
|
<a name='FOOTNOTE.163'>
|
|
<pre><i><b>Footnote 163)</b> See ‘‘future language directions’’ (<a href='#6.11.7'>6.11.7</a>).
|
|
</i></pre>
|
|
</a>
|
|
<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 Each parameter has automatic storage duration; its identifier is an lvalue.<a href='#FOOTNOTE.164'><sup>[164]</sup></a> The layout
|
|
of the storage for parameters is unspecified.
|
|
</pre>
|
|
<a name='FOOTNOTE.164'>
|
|
<pre><i><b>Footnote 164)</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 that constitutes the
|
|
body of the function definition is executed.
|
|
</pre>
|
|
<a name='6.9.1p12'></a>
|
|
<pre>12 If the } that terminates a function 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 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. The following similar definition uses the identifier-list form for the parameter
|
|
declarations:
|
|
extern int max(a, b)
|
|
int a, b;
|
|
{
|
|
return a > b ? a : b;
|
|
}
|
|
Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
|
|
that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
|
|
to the function, whereas the second form does not.
|
|
|
|
</pre>
|
|
<a name='6.9.1p14'></a>
|
|
<pre>14 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
|
|
else-group:
|
|
# else new-line groupopt
|
|
endif-line:
|
|
# endif new-line
|
|
control-line:
|
|
# include 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
|
|
# 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
|
|
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.165'><sup>[165]</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.165'>
|
|
<pre><i><b>Footnote 165)</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 in <a href='#6.10.3.2'>6.10.3.2</a>, for example).
|
|
</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 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='6.10p5'></a>
|
|
<pre>5 The only white-space characters that shall appear between preprocessing tokens within a
|
|
preprocessing 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).
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10p6'></a>
|
|
<pre>6 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='6.10p7'></a>
|
|
<pre>7 The preprocessing tokens within a preprocessing directive are not subject to macro
|
|
expansion unless otherwise stated.
|
|
</pre>
|
|
<a name='6.10p8'></a>
|
|
<pre>8 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='6.10.1'></a>
|
|
<hr>
|
|
<h3>6.10.1 [Conditional inclusion]</h3>
|
|
<a name='6.10.1p1'></a>
|
|
<pre>1 Constraints
|
|
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.166'><sup>[166]</sup></a> and it may contain unary operator expressions of the form
|
|
defined identifier
|
|
or
|
|
defined ( identifier )
|
|
which evaluate 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='FOOTNOTE.166'>
|
|
<pre><i><b>Footnote 166)</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='6.10.1p2'></a>
|
|
<pre>2 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='6.10.1p3'></a>
|
|
<pre>3 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='6.10.1p4'></a>
|
|
<pre>4 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
|
|
the controlling 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 the defined unary
|
|
operator have been performed, all remaining identifiers (including those lexically
|
|
identical to keywords) are replaced with the pp-number 0, 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.167'><sup>[167]</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.168'><sup>[168]</sup></a> Also, whether a
|
|
single-character character constant may have a negative value is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.167'>
|
|
<pre><i><b>Footnote 167)</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.168'>
|
|
<pre><i><b>Footnote 168)</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='6.10.1p5'></a>
|
|
<pre>5 Preprocessing directives of the forms
|
|
# ifdef identifier new-line groupopt
|
|
# ifndef 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 and #if !defined identifier
|
|
respectively.
|
|
</pre>
|
|
<a name='6.10.1p6'></a>
|
|
<pre>6 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. 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.169'><sup>[169]</sup></a>
|
|
Forward references: macro replacement (<a href='#6.10.3'>6.10.3</a>), source file inclusion (<a href='#6.10.2'>6.10.2</a>), largest
|
|
integer types (<a href='#7.20.1.5'>7.20.1.5</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.169'>
|
|
<pre><i><b>Footnote 169)</b> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
|
|
before the terminating new-line character. However, comments may appear anywhere in a source file,
|
|
including within a preprocessing directive.
|
|
</i></pre>
|
|
</a>
|
|
<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
|
|
implementation.
|
|
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.170'><sup>[170]</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.170'>
|
|
<pre><i><b>Footnote 170)</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 nondigits 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='#6.10.3'>6.10.3</a>).
|
|
</pre>
|
|
<a name='6.10.3'></a>
|
|
<hr>
|
|
<h3>6.10.3 [Macro replacement]</h3>
|
|
<a name='6.10.3p1'></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='6.10.3p2'></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='6.10.3p3'></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='6.10.3p4'></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 more arguments in the invocation than there are
|
|
parameters in the macro definition (excluding the ...). There shall exist a )
|
|
preprocessing token that terminates the invocation.
|
|
</pre>
|
|
<a name='6.10.3p5'></a>
|
|
<pre>5 The identifier _ _VA_ARGS_ _ shall occur only in the replacement-list of a function-like
|
|
macro that uses the ellipsis notation in the parameters.
|
|
</pre>
|
|
<a name='6.10.3p6'></a>
|
|
<pre>6 A parameter identifier in a function-like macro shall be uniquely declared within its
|
|
scope.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.3p7'></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='6.10.3p8'></a>
|
|
<pre>8 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
|
|
a preprocessing directive could begin, the identifier is not subject to macro replacement.
|
|
</pre>
|
|
<a name='6.10.3p9'></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.171'><sup>[171]</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.171'>
|
|
<pre><i><b>Footnote 171)</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='6.10.3p10'></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='6.10.3p11'></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.172'><sup>[172]</sup></a> the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.172'>
|
|
<pre><i><b>Footnote 172)</b> Despite the name, a non-directive is a preprocessing directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.3p12'></a>
|
|
<pre>12 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
|
|
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 ...).
|
|
</pre>
|
|
<a name='6.10.3.1'></a>
|
|
<hr>
|
|
<h3>6.10.3.1 [Argument substitution]</h3>
|
|
<a name='6.10.3.1p1'></a>
|
|
<pre>1 After the arguments for the invocation of a function-like macro have been identified,
|
|
argument substitution takes place. A parameter in the replacement list, unless preceded
|
|
by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
|
|
replaced by the corresponding argument after all macros contained therein have been
|
|
expanded. Before being substituted, each argument’s preprocessing tokens are
|
|
completely macro replaced as if they formed the rest of the preprocessing file; no other
|
|
preprocessing tokens are available.
|
|
</pre>
|
|
<a name='6.10.3.1p2'></a>
|
|
<pre>2 An identifier _ _VA_ARGS_ _ that occurs in the replacement list shall be treated as if it
|
|
were a parameter, and the variable arguments shall form the preprocessing tokens used to
|
|
replace it.
|
|
</pre>
|
|
<a name='6.10.3.2'></a>
|
|
<hr>
|
|
<h3>6.10.3.2 [The # operator]</h3>
|
|
<a name='6.10.3.2p1'></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='6.10.3.2p2'></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. Each occurrence of white space between the 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 argument
|
|
is deleted. Otherwise, the original spelling of each preprocessing token in the 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 argument is "". The order of evaluation of # and
|
|
## operators is unspecified.
|
|
</pre>
|
|
<a name='6.10.3.3'></a>
|
|
<hr>
|
|
<h3>6.10.3.3 [The ## operator]</h3>
|
|
<a name='6.10.3.3p1'></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='6.10.3.3p2'></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 preprocessing token sequence; however, if an argument consists of no
|
|
preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
|
|
instead.<a href='#FOOTNOTE.173'><sup>[173]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.173'>
|
|
<pre><i><b>Footnote 173)</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='6.10.3.3p3'></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: concatenation 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 preprocessing 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='6.10.3.3p4'></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='6.10.3.4'></a>
|
|
<hr>
|
|
<h3>6.10.3.4 [Rescanning and further replacement]</h3>
|
|
<a name='6.10.3.4p1'></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='6.10.3.4p2'></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='6.10.3.4p3'></a>
|
|
<pre>3 The resulting completely macro-replaced preprocessing token sequence is not processed
|
|
as a preprocessing directive even if it resembles one, but all pragma unary operator
|
|
expressions within it are then processed as specified in <a href='#6.10.9'>6.10.9</a> below.
|
|
</pre>
|
|
<a name='6.10.3.4p4'></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)
|
|
may 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='6.10.3.5'></a>
|
|
<hr>
|
|
<h3>6.10.3.5 [Scope of macro definitions]</h3>
|
|
<a name='6.10.3.5p1'></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='6.10.3.5p2'></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='6.10.3.5p3'></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='6.10.3.5p4'></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='6.10.3.5p5'></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='6.10.3.5p6'></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='6.10.3.5p7'></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='6.10.3.5p8'></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='6.10.3.5p9'></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='6.10.4'></a>
|
|
<hr>
|
|
<h3>6.10.4 [Line control]</h3>
|
|
<a name='6.10.4p1'></a>
|
|
<pre>1 Constraints
|
|
The string literal of a #line directive, if present, shall be a character string literal.
|
|
Semantics
|
|
</pre>
|
|
<a name='6.10.4p2'></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='6.10.4p3'></a>
|
|
<pre>3 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). The digit sequence shall not specify zero, nor a number greater than
|
|
2147483647.
|
|
</pre>
|
|
<a name='6.10.4p4'></a>
|
|
<pre>4 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='6.10.4p5'></a>
|
|
<pre>5 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.
|
|
</pre>
|
|
<a name='6.10.5'></a>
|
|
<hr>
|
|
<h3>6.10.5 [Error directive]</h3>
|
|
<a name='6.10.5p1'></a>
|
|
<pre>1 Semantics
|
|
A preprocessing directive of the form
|
|
# error pp-tokensopt new-line
|
|
causes the implementation to produce a diagnostic message that includes the specified
|
|
sequence of preprocessing tokens.
|
|
</pre>
|
|
<a name='6.10.6'></a>
|
|
<hr>
|
|
<h3>6.10.6 [Pragma directive]</h3>
|
|
<a name='6.10.6p1'></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.174'><sup>[174]</sup></a> causes the implementation to behave in an
|
|
implementation-defined manner. 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.174'>
|
|
<pre><i><b>Footnote 174)</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='6.10.6p2'></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.175'><sup>[175]</sup></a> whose meanings are described
|
|
elsewhere:
|
|
#pragma STDC FP_CONTRACT on-off-switch
|
|
#pragma STDC FENV_ACCESS on-off-switch
|
|
#pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
on-off-switch: one of
|
|
ON OFF DEFAULT
|
|
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 CX_LIMITED_RANGE pragma (<a href='#7.3.4'>7.3.4</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.175'>
|
|
<pre><i><b>Footnote 175)</b> See ‘‘future language directions’’ (<a href='#6.11.8'>6.11.8</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.7'></a>
|
|
<hr>
|
|
<h3>6.10.7 [Null directive]</h3>
|
|
<a name='6.10.7p1'></a>
|
|
<pre>1 Semantics
|
|
A preprocessing directive of the form
|
|
# new-line
|
|
has no effect.
|
|
</pre>
|
|
<a name='6.10.8'></a>
|
|
<hr>
|
|
<h3>6.10.8 [Predefined macro names]</h3>
|
|
<a name='6.10.8p1'></a>
|
|
<pre>1 The values of the predefined macros listed in the following subclauses<a href='#FOOTNOTE.176'><sup>[176]</sup></a> (except for
|
|
_ _FILE_ _ and _ _LINE_ _) remain constant throughout the translation unit.
|
|
</pre>
|
|
<a name='FOOTNOTE.176'>
|
|
<pre><i><b>Footnote 176)</b> See ‘‘future language directions’’ (<a href='#6.11.9'>6.11.9</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.8p2'></a>
|
|
<pre>2 None of these macro names, nor the identifier defined, 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.
|
|
</pre>
|
|
<a name='6.10.8p3'></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='6.10.8.1'></a>
|
|
<hr>
|
|
<h3>6.10.8.1 [Mandatory macros]</h3>
|
|
<a name='6.10.8.1p1'></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.177'><sup>[177]</sup></a>
|
|
_ _LINE_ _ The presumed line number (within the current source file) of the current
|
|
source line (an integer constant).<a href='#FOOTNOTE.177'><sup>[177]</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_VERSION_ _ The integer constant 201ymmL.<a href='#FOOTNOTE.178'><sup>[178]</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 function. If the time of translation is not available, an
|
|
implementation-defined valid time shall be supplied.
|
|
Forward references: the asctime function (<a href='#7.27.3.1'>7.27.3.1</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.177'>
|
|
<pre><i><b>Footnote 177)</b> The presumed source file name and line number can be changed by the #line directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.177'>
|
|
<pre><i><b>Footnote 177)</b> The presumed source file name and line number can be changed by the #line directive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.178'>
|
|
<pre><i><b>Footnote 178)</b> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
|
|
ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will
|
|
remain an integer constant of type long int that is increased with each revision of this International
|
|
Standard.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.8.2'></a>
|
|
<hr>
|
|
<h3>6.10.8.2 [Environment macros]</h3>
|
|
<a name='6.10.8.2p1'></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.
|
|
_ _STDC_UTF_16_ _ The integer constant 1, intended to indicate that values of type
|
|
char16_t are UTF−16 encoded. If some other encoding is used, the
|
|
macro shall not be defined and the actual encoding used is implementation-
|
|
defined.
|
|
_ _STDC_UTF_32_ _ The integer constant 1, intended to indicate that values of type
|
|
char32_t are UTF−32 encoded. If some other encoding is used, the
|
|
macro shall not be defined and the actual encoding used is implementation-
|
|
defined.
|
|
Forward references: common definitions (<a href='#7.19'>7.19</a>), unicode utilities (<a href='#7.28'>7.28</a>).
|
|
</pre>
|
|
<a name='6.10.8.3'></a>
|
|
<hr>
|
|
<h3>6.10.8.3 [Conditional feature macros]</h3>
|
|
<a name='6.10.8.3p1'></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 specifications in annex L (Analyzability).
|
|
_ _STDC_IEC_559_ _ The integer constant 1, intended to indicate conformance to the
|
|
specifications in annex F (IEC 60559 floating-point arithmetic).
|
|
_ _STDC_IEC_559_COMPLEX_ _ The integer constant 1, intended to indicate
|
|
adherence to the specifications in annex G (IEC 60559 compatible complex
|
|
arithmetic).
|
|
_ _STDC_LIB_EXT1_ _ The integer constant 201ymmL, intended to indicate support
|
|
for the extensions defined in annex K (Bounds-checking interfaces).<a href='#FOOTNOTE.179'><sup>[179]</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 or variably
|
|
modified types.
|
|
</pre>
|
|
<a name='FOOTNOTE.179'>
|
|
<pre><i><b>Footnote 179)</b> The intention is that this will remain an integer constant of type long int that is increased with
|
|
each revision of this International Standard.
|
|
</i></pre>
|
|
</a>
|
|
<a name='6.10.8.3p2'></a>
|
|
<pre>2 An implementation that defines _ _STDC_NO_COMPLEX_ _ shall not define
|
|
_ _STDC_IEC_559_COMPLEX_ _.
|
|
</pre>
|
|
<a name='6.10.9'></a>
|
|
<hr>
|
|
<h3>6.10.9 [Pragma operator]</h3>
|
|
<a name='6.10.9p1'></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='6.10.9p2'></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-point 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 [Function declarators]</h3>
|
|
<a name='6.11.6p1'></a>
|
|
<pre>1 The use of function declarators with empty parentheses (not prototype-format parameter
|
|
type declarators) is an obsolescent feature.
|
|
</pre>
|
|
<a name='6.11.7'></a>
|
|
<hr>
|
|
<h3>6.11.7 [Function definitions]</h3>
|
|
<a name='6.11.7p1'></a>
|
|
<pre>1 The use of function definitions with separate parameter identifier and declaration lists
|
|
(not prototype-format parameter type and identifier declarators) is an obsolescent feature.
|
|
</pre>
|
|
<a name='6.11.8'></a>
|
|
<hr>
|
|
<h3>6.11.8 [Pragma directives]</h3>
|
|
<a name='6.11.8p1'></a>
|
|
<pre>1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
|
|
</pre>
|
|
<a name='6.11.9'></a>
|
|
<hr>
|
|
<h3>6.11.9 [Predefined macro names]</h3>
|
|
<a name='6.11.9p1'></a>
|
|
<pre>1 Macro names beginning with _ _STDC_ are reserved for future standardization.
|
|
</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.180'><sup>[180]</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.180'>
|
|
<pre><i><b>Footnote 180)</b> The functions that make use of the decimal-point character are the numeric conversion functions
|
|
(<a href='#7.22.1'>7.22.1</a>, <a href='#7.29.4.1'>7.29.4.1</a>) and the formatted input/output functions (<a href='#7.21.6'>7.21.6</a>, <a href='#7.29.2'>7.29.2</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='#5.2.1.2'>5.2.1.2</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.181'><sup>[181]</sup></a>
|
|
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.181'>
|
|
<pre><i><b>Footnote 181)</b> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus 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, with a type that includes a prototype, in a header,<a href='#FOOTNOTE.182'><sup>[182]</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. Declarations of types described in this clause shall not
|
|
include type qualifiers, unless explicitly stated otherwise.
|
|
</pre>
|
|
<a name='FOOTNOTE.182'>
|
|
<pre><i><b>Footnote 182)</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 The standard headers are<a href='#FOOTNOTE.183'><sup>[183]</sup></a>
|
|
<assert.h> <math.h> <stdlib.h>
|
|
<complex.h> <setjmp.h> <stdnoreturn.h>
|
|
<ctype.h> <signal.h> <string.h>
|
|
<errno.h> <stdalign.h> <tgmath.h>
|
|
<fenv.h> <stdarg.h> <threads.h>
|
|
<float.h> <stdatomic.h> <time.h>
|
|
<inttypes.h> <stdbool.h> <uchar.h>
|
|
<iso646.h> <stddef.h> <wchar.h>
|
|
<limits.h> <stdint.h> <wctype.h>
|
|
<locale.h> <stdio.h>
|
|
</pre>
|
|
<a name='FOOTNOTE.183'>
|
|
<pre><i><b>Footnote 183)</b> The headers <complex.h>, <stdatomic.h>, and <threads.h> are conditional features that
|
|
implementations need not support; see <a href='#6.10.8.3'>6.10.8.3</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.2p3'></a>
|
|
<pre>3 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='7.1.2p4'></a>
|
|
<pre>4 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='7.1.2p5'></a>
|
|
<pre>5 Any definition of an object-like macro described in this clause 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='7.1.2p6'></a>
|
|
<pre>6 Any declaration of a library function shall have external linkage.
|
|
</pre>
|
|
<a name='7.1.2p7'></a>
|
|
<pre>7 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 identifiers that begin with an underscore and either an uppercase letter or another
|
|
underscore are always reserved for any use.
|
|
— All identifiers that begin with an underscore are always reserved for use as identifiers
|
|
with file scope in both the ordinary and tag name spaces.
|
|
— 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.184'><sup>[184]</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.184'>
|
|
<pre><i><b>Footnote 184)</b> The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
|
|
va_copy, and va_end.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.1.3p2'></a>
|
|
<pre>2 No other identifiers are reserved. 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>), or defines a reserved
|
|
identifier as a macro name, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.1.3p3'></a>
|
|
<pre>3 If the program removes (with #undef) any macro definition of an identifier in the first
|
|
group listed above, the behavior is undefined.
|
|
</pre>
|
|
<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
|
|
descriptions 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 promotion) not expected by a function
|
|
with 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. 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.185'><sup>[185]</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.186'><sup>[186]</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.187'><sup>[187]</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.185'>
|
|
<pre><i><b>Footnote 185)</b> This means that an implementation shall provide an actual function for each library function, even if it
|
|
also provides a macro for that function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.186'>
|
|
<pre><i><b>Footnote 186)</b> Such macros might not contain the sequence points that the corresponding function calls do.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.187'>
|
|
<pre><i><b>Footnote 187)</b> Because external identifiers and some macro names beginning with an underscore are reserved,
|
|
implementations may 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 may 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.188'><sup>[188]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.188'>
|
|
<pre><i><b>Footnote 188)</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.189'><sup>[189]</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.189'>
|
|
<pre><i><b>Footnote 189)</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.190'><sup>[190]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.190'>
|
|
<pre><i><b>Footnote 190)</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 may 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(ignore) ((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, 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='7.2p3'></a>
|
|
<pre>3 The macro
|
|
static_assert
|
|
expands to _Static_assert.
|
|
</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.191'><sup>[191]</sup></a> It
|
|
then calls the abort function.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.191'>
|
|
<pre><i><b>Footnote 191)</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='#7.22.4.1'>7.22.4.1</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.192'><sup>[192]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.192'>
|
|
<pre><i><b>Footnote 192)</b> See ‘‘future library directions’’ (<a href='#7.31.1'>7.31.1</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 specifies a family of functions consisting of a principal 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 const float _Complex, with the value of
|
|
the imaginary unit.<a href='#FOOTNOTE.193'><sup>[193]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.193'>
|
|
<pre><i><b>Footnote 193)</b> The imaginary unit is a number i such that i 2 = −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.194'><sup>[194]</sup></a> if defined,
|
|
they expand to _Imaginary and a constant expression of type const float
|
|
_Imaginary with the value of the imaginary unit.
|
|
</pre>
|
|
<a name='FOOTNOTE.194'>
|
|
<pre><i><b>Footnote 194)</b> A specification for imaginary types is in informative 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: IEC 60559-compatible complex arithmetic (annex 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
|
|
problematic 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.195'><sup>[195]</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.195'>
|
|
<pre><i><b>Footnote 195)</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 )
|
|
| x + iy | = √
|
|
⎯⎯⎯⎯⎯
|
|
x 2 + y2
|
|
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 [−π /2, +π /2]
|
|
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 [−π /2, +π /2]
|
|
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 mathematically unbounded along the real axis and in the interval [−iπ /2, +iπ /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 /2, +iπ /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.196'><sup>[196]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.196'>
|
|
<pre><i><b>Footnote 196)</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 + i y.
|
|
</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.197'><sup>[197]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.197'>
|
|
<pre><i><b>Footnote 197)</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.198'><sup>[198]</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.198'>
|
|
<pre><i><b>Footnote 198)</b> See ‘‘future library directions’’ (<a href='#7.31.2'>7.31.2</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.199'><sup>[199]</sup></a> All letters and digits are printing characters.
|
|
Forward references: EOF (<a href='#7.21.1'>7.21.1</a>), localization (<a href='#7.11'>7.11</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.199'>
|
|
<pre><i><b>Footnote 199)</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.200'><sup>[200]</sup></a> In the "C" locale,
|
|
isalpha returns true only for the characters for which isupper or islower is true.
|
|
</pre>
|
|
<a name='FOOTNOTE.200'>
|
|
<pre><i><b>Footnote 200)</b> The functions islower and isupper test true or false separately for each of these additional
|
|
characters; all four combinations 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.201'><sup>[201]</sup></a> that has type int and thread local 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.201'>
|
|
<pre><i><b>Footnote 201)</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 value of
|
|
errno in other threads is an indeterminate value), but is never set to zero by any library
|
|
function.<a href='#FOOTNOTE.202'><sup>[202]</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 International Standard.
|
|
</pre>
|
|
<a name='FOOTNOTE.202'>
|
|
<pre><i><b>Footnote 202)</b> Thus, a program that uses errno for error checking should 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.203'><sup>[203]</sup></a> may also be specified by the implementation.
|
|
</pre>
|
|
<a name='FOOTNOTE.203'>
|
|
<pre><i><b>Footnote 203)</b> See ‘‘future library directions’’ (<a href='#7.31.3'>7.31.3</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.204'><sup>[204]</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.205'><sup>[205]</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.204'>
|
|
<pre><i><b>Footnote 204)</b> This header is designed to support the floating-point exception status flags and directed-rounding
|
|
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.205'>
|
|
<pre><i><b>Footnote 205)</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 The floating-point environment has thread storage duration. The initial state for a
|
|
thread’s floating-point environment is the current state of the floating-point environment
|
|
of the thread that creates it at the time of creation.
|
|
</pre>
|
|
<a name='7.6p3'></a>
|
|
<pre>3 Certain programming conventions support the intended model of use for the floating-
|
|
point environment:<a href='#FOOTNOTE.206'><sup>[206]</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
|
|
documentation 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.206'>
|
|
<pre><i><b>Footnote 206)</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='7.6p4'></a>
|
|
<pre>4 The type
|
|
fenv_t
|
|
represents the entire floating-point environment.
|
|
</pre>
|
|
<a name='7.6p5'></a>
|
|
<pre>5 The type
|
|
fexcept_t
|
|
represents the floating-point status flags collectively, including any status the
|
|
implementation associates with the flags.
|
|
</pre>
|
|
<a name='7.6p6'></a>
|
|
<pre>6 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='#7.6.2'>7.6.2</a>.<a href='#FOOTNOTE.207'><sup>[207]</sup></a> Additional implementation-defined floating-point
|
|
exceptions, with macro definitions beginning with FE_ and an uppercase letter,<a href='#FOOTNOTE.208'><sup>[208]</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.209'><sup>[209]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.207'>
|
|
<pre><i><b>Footnote 207)</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='#7.6.2'>7.6.2</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.208'>
|
|
<pre><i><b>Footnote 208)</b> See ‘‘future library directions’’ (<a href='#7.31.4'>7.31.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.209'>
|
|
<pre><i><b>Footnote 209)</b> The macros should be distinct powers of two.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p7'></a>
|
|
<pre>7 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='7.6p8'></a>
|
|
<pre>8 Each of the macros
|
|
FE_DOWNWARD
|
|
FE_TONEAREST
|
|
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.210'><sup>[210]</sup></a> may also be specified by the implementation. The
|
|
defined macros expand to integer constant expressions whose values are distinct
|
|
nonnegative values.<a href='#FOOTNOTE.211'><sup>[211]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.210'>
|
|
<pre><i><b>Footnote 210)</b> See ‘‘future library directions’’ (<a href='#7.31.4'>7.31.4</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.211'>
|
|
<pre><i><b>Footnote 211)</b> Even though the rounding direction macros may expand to constants corresponding to the values of
|
|
FLT_ROUNDS, they are not required to do so.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6p9'></a>
|
|
<pre>9 The macro
|
|
FE_DFL_ENV
|
|
represents the default 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 floating-point environment.
|
|
</pre>
|
|
<a name='7.6p10'></a>
|
|
<pre>10 Additional implementation-defined environments, with macro definitions beginning with
|
|
FE_ and an uppercase letter,<a href='#FOOTNOTE.212'><sup>[212]</sup></a> and having type ‘‘pointer to const-qualified fenv_t’’,
|
|
may also be specified by the implementation.
|
|
</pre>
|
|
<a name='FOOTNOTE.212'>
|
|
<pre><i><b>Footnote 212)</b> See ‘‘future library directions’’ (<a href='#7.31.4'>7.31.4</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.213'><sup>[213]</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, sets floating-point control
|
|
modes, or runs under non-default mode settings, 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.213'>
|
|
<pre><i><b>Footnote 213)</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 default
|
|
modes are in effect and the flags are not tested.
|
|
</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 shall
|
|
contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<a href='#FOOTNOTE.214'><sup>[214]</sup></a>
|
|
|
|
</pre>
|
|
<a name='FOOTNOTE.214'>
|
|
<pre><i><b>Footnote 214)</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 [Floating-point exceptions]</h3>
|
|
<a name='7.6.2p1'></a>
|
|
<pre>1 The following functions provide access to the floating-point status flags.<a href='#FOOTNOTE.215'><sup>[215]</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.215'>
|
|
<pre><i><b>Footnote 215)</b> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
|
|
abstraction of flags that are either set or clear. An implementation may 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='7.6.2.1'></a>
|
|
<hr>
|
|
<h3>7.6.2.1 [The feclearexcept function]</h3>
|
|
<a name='7.6.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feclearexcept(int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2.1p2'></a>
|
|
<pre>2 The feclearexcept function attempts to clear the supported floating-point exceptions
|
|
represented by its argument.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.2.1p3'></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='7.6.2.2'></a>
|
|
<hr>
|
|
<h3>7.6.2.2 [The fegetexceptflag function]</h3>
|
|
<a name='7.6.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetexceptflag(fexcept_t *flagp,
|
|
int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2.2p2'></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='7.6.2.2p3'></a>
|
|
<pre>3 The fegetexceptflag function returns zero if the representation was successfully
|
|
stored. Otherwise, it returns a nonzero value.
|
|
</pre>
|
|
<a name='7.6.2.3'></a>
|
|
<hr>
|
|
<h3>7.6.2.3 [The feraiseexcept function]</h3>
|
|
<a name='7.6.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feraiseexcept(int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2.3p2'></a>
|
|
<pre>2 The feraiseexcept function attempts to raise the supported floating-point exceptions
|
|
represented by its argument.<a href='#FOOTNOTE.216'><sup>[216]</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.216'>
|
|
<pre><i><b>Footnote 216)</b> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
|
|
Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
|
|
in <a href='#F.8.6'>F.8.6</a> is in the same spirit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.2.3p3'></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.
|
|
</pre>
|
|
<a name='7.6.2.4'></a>
|
|
<hr>
|
|
<h3>7.6.2.4 [The fesetexceptflag function]</h3>
|
|
<a name='7.6.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetexceptflag(const fexcept_t *flagp,
|
|
int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2.4p2'></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. This function does not raise floating-
|
|
point exceptions, but only sets the state of the flags.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.2.4p3'></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='7.6.2.5'></a>
|
|
<hr>
|
|
<h3>7.6.2.5 [The fetestexcept function]</h3>
|
|
<a name='7.6.2.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fetestexcept(int excepts);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.2.5p2'></a>
|
|
<pre>2 The fetestexcept function determines which of a specified subset of the floating-
|
|
point exception flags are currently set. The excepts argument specifies the floating-
|
|
point status flags to be queried.<a href='#FOOTNOTE.217'><sup>[217]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.217'>
|
|
<pre><i><b>Footnote 217)</b> This mechanism allows testing several floating-point exceptions with just one function call.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.6.2.5p3'></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='7.6.2.5p4'></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='7.6.3'></a>
|
|
<hr>
|
|
<h3>7.6.3 [Rounding]</h3>
|
|
<a name='7.6.3p1'></a>
|
|
<pre>1 The fegetround and fesetround functions provide control of rounding direction
|
|
modes.
|
|
</pre>
|
|
<a name='7.6.3.1'></a>
|
|
<hr>
|
|
<h3>7.6.3.1 [The fegetround function]</h3>
|
|
<a name='7.6.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetround(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.3.1p2'></a>
|
|
<pre>2 The fegetround function gets the current rounding direction.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.3.1p3'></a>
|
|
<pre>3 The fegetround function returns the value of the rounding direction macro
|
|
representing the current rounding direction or a negative value if there is no such
|
|
rounding direction macro or the current rounding direction is not determinable.
|
|
</pre>
|
|
<a name='7.6.3.2'></a>
|
|
<hr>
|
|
<h3>7.6.3.2 [The fesetround function]</h3>
|
|
<a name='7.6.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetround(int round);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.3.2p2'></a>
|
|
<pre>2 The fesetround function establishes the rounding direction represented by its
|
|
argument round. If the argument is not equal to the value of a rounding direction macro,
|
|
the rounding direction is not changed.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.3.2p3'></a>
|
|
<pre>3 The fesetround function returns zero if and only if the requested rounding direction
|
|
was established.
|
|
</pre>
|
|
<a name='7.6.3.2p4'></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 round_dir)
|
|
{
|
|
#pragma STDC FENV_ACCESS ON
|
|
int save_round;
|
|
int setround_ok;
|
|
save_round = fegetround();
|
|
setround_ok = fesetround(round_dir);
|
|
assert(setround_ok == 0);
|
|
/* ... */
|
|
fesetround(save_round);
|
|
/* ... */
|
|
}
|
|
|
|
</pre>
|
|
<a name='7.6.4'></a>
|
|
<hr>
|
|
<h3>7.6.4 [Environment]</h3>
|
|
<a name='7.6.4p1'></a>
|
|
<pre>1 The functions in this section manage the floating-point environment — status flags and
|
|
control modes — as one entity.
|
|
</pre>
|
|
<a name='7.6.4.1'></a>
|
|
<hr>
|
|
<h3>7.6.4.1 [The fegetenv function]</h3>
|
|
<a name='7.6.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fegetenv(fenv_t *envp);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.1p2'></a>
|
|
<pre>2 The fegetenv function attempts to store the current floating-point environment in the
|
|
object pointed to by envp.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.1p3'></a>
|
|
<pre>3 The fegetenv function returns zero if the environment was successfully stored.
|
|
Otherwise, it returns a nonzero value.
|
|
</pre>
|
|
<a name='7.6.4.2'></a>
|
|
<hr>
|
|
<h3>7.6.4.2 [The feholdexcept function]</h3>
|
|
<a name='7.6.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feholdexcept(fenv_t *envp);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.2p2'></a>
|
|
<pre>2 The feholdexcept function saves the current 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.218'><sup>[218]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.218'>
|
|
<pre><i><b>Footnote 218)</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='7.6.4.2p3'></a>
|
|
<pre>3 The feholdexcept function returns zero if and only if non-stop floating-point
|
|
exception handling was successfully installed.
|
|
</pre>
|
|
<a name='7.6.4.3'></a>
|
|
<hr>
|
|
<h3>7.6.4.3 [The fesetenv function]</h3>
|
|
<a name='7.6.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int fesetenv(const fenv_t *envp);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.3p2'></a>
|
|
<pre>2 The fesetenv function attempts to establish the 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 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='7.6.4.3p3'></a>
|
|
<pre>3 The fesetenv function returns zero if the environment was successfully established.
|
|
Otherwise, it returns a nonzero value.
|
|
</pre>
|
|
<a name='7.6.4.4'></a>
|
|
<hr>
|
|
<h3>7.6.4.4 [The feupdateenv function]</h3>
|
|
<a name='7.6.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <fenv.h>
|
|
int feupdateenv(const fenv_t *envp);
|
|
Description
|
|
</pre>
|
|
<a name='7.6.4.4p2'></a>
|
|
<pre>2 The feupdateenv function attempts to save the currently raised floating-point
|
|
exceptions in its automatic storage, install the 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 floating-point environment macro.
|
|
Returns
|
|
</pre>
|
|
<a name='7.6.4.4p3'></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='7.6.4.4p4'></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 standard floating-point 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>.
|
|
</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.219'><sup>[219]</sup></a>
|
|
Forward references: integer types <stdint.h> (<a href='#7.20'>7.20</a>), formatted input/output
|
|
functions (<a href='#7.21.6'>7.21.6</a>), formatted wide character input/output functions (<a href='#7.29.2'>7.29.2</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.219'>
|
|
<pre><i><b>Footnote 219)</b> See ‘‘future library directions’’ (<a href='#7.31.5'>7.31.5</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.220'><sup>[220]</sup></a> followed by the conversion specifier, followed by a
|
|
name corresponding to a similar type name in <a href='#7.20.1'>7.20.1</a>. In these names, N represents the
|
|
width of the type as described in <a href='#7.20.1'>7.20.1</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.220'>
|
|
<pre><i><b>Footnote 220)</b> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
|
|
different format specifiers may 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.221'><sup>[221]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.221'>
|
|
<pre><i><b>Footnote 221)</b> The absolute value of the most negative number cannot be represented in two’s complement.
|
|
</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='#7.22.1.4'>7.22.1.4</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='#7.29.4.1.2'>7.29.4.1.2</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 corresponding 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 [Sizes 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>.
|
|
</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='#7.19'>7.19</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 argument to the setlocale function.<a href='#FOOTNOTE.222'><sup>[222]</sup></a> Additional macro definitions, beginning
|
|
with the characters LC_ and an uppercase letter,<a href='#FOOTNOTE.223'><sup>[223]</sup></a> may also be specified by the
|
|
implementation.
|
|
</pre>
|
|
<a name='FOOTNOTE.222'>
|
|
<pre><i><b>Footnote 222)</b> ISO/IEC 9945−2 specifies locale and charmap formats that may be used to specify locales for C.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.223'>
|
|
<pre><i><b>Footnote 223)</b> See ‘‘future library directions’’ (<a href='#7.31.6'>7.31.6</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.224'><sup>[224]</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.224'>
|
|
<pre><i><b>Footnote 224)</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.225'><sup>[225]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.225'>
|
|
<pre><i><b>Footnote 225)</b> The implementation shall 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, but may be
|
|
overwritten by a subsequent call to the setlocale function.
|
|
Forward references: formatted input/output functions (<a href='#7.21.6'>7.21.6</a>), multibyte/wide
|
|
character conversion functions (<a href='#7.22.7'>7.22.7</a>), multibyte/wide string conversion functions
|
|
(<a href='#7.22.8'>7.22.8</a>), numeric conversion functions (<a href='#7.22.1'>7.22.1</a>), the strcoll function (<a href='#7.24.4.3'>7.24.4.3</a>), the
|
|
strftime function (<a href='#7.27.3.5'>7.27.3.5</a>), the strxfrm function (<a href='#7.24.4.5'>7.24.4.5</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 nonmonetary 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 internationally 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 interpreted 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 may 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.226'><sup>[226]</sup></a>
|
|
Integer arithmetic functions and conversion functions are discussed later.
|
|
</pre>
|
|
<a name='FOOTNOTE.226'>
|
|
<pre><i><b>Footnote 226)</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 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.227'><sup>[227]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.227'>
|
|
<pre><i><b>Footnote 227)</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='7.12p3'></a>
|
|
<pre>3 The macro
|
|
HUGE_VAL
|
|
expands to a positive double constant expression, not necessarily representable as a
|
|
float. The macros
|
|
HUGE_VALF
|
|
HUGE_VALL
|
|
are respectively float and long double analogs of HUGE_VAL.<a href='#FOOTNOTE.228'><sup>[228]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.228'>
|
|
<pre><i><b>Footnote 228)</b> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
|
|
supports infinities.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p4'></a>
|
|
<pre>4 The macro
|
|
INFINITY
|
|
expands to a constant expression of type float representing positive or unsigned
|
|
infinity, if available; else to a positive constant of type float that overflows at
|
|
translation time.<a href='#FOOTNOTE.229'><sup>[229]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.229'>
|
|
<pre><i><b>Footnote 229)</b> In this case, using INFINITY will violate the constraint in <a href='#6.4.4'>6.4.4</a> and thus require a diagnostic.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12p5'></a>
|
|
<pre>5 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='7.12p6'></a>
|
|
<pre>6 The number classification macros
|
|
FP_INFINITE
|
|
FP_NAN
|
|
FP_NORMAL
|
|
FP_SUBNORMAL
|
|
FP_ZERO
|
|
represent the 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='7.12p7'></a>
|
|
<pre>7 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.230'><sup>[230]</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.230'>
|
|
<pre><i><b>Footnote 230)</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='7.12p8'></a>
|
|
<pre>8 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='7.12p9'></a>
|
|
<pre>9 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, or the bitwise OR of both. 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 suppressed 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 implementation
|
|
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 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 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.231'><sup>[231]</sup></a> 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.231'>
|
|
<pre><i><b>Footnote 231)</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 the
|
|
mathematical function has an exact infinite result as the finite input argument(s) are
|
|
approached in the limit (for example, 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 the mathematical result of the function cannot be
|
|
represented in an object of the specified type, due to extreme magnitude.
|
|
</pre>
|
|
<a name='7.12.1p5'></a>
|
|
<pre>5 A floating result overflows if the magnitude of the mathematical result is finite but so
|
|
large that the mathematical result cannot be represented without extraordinary roundoff
|
|
error in an object of the specified type. 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; 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 ‘‘overflow’’ floating-
|
|
point exception is raised.
|
|
</pre>
|
|
<a name='7.12.1p6'></a>
|
|
<pre>6 The result underflows if the magnitude of the mathematical result is so small that the
|
|
mathematical result cannot be represented, without extraordinary roundoff error, in an
|
|
object of the specified type.<a href='#FOOTNOTE.232'><sup>[232]</sup></a> If the result underflows, the function returns 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 expression
|
|
math_errhandling & MATH_ERREXCEPT is nonzero, whether the ‘‘underflow’’
|
|
floating-point exception is raised is implementation-defined.
|
|
</pre>
|
|
<a name='FOOTNOTE.232'>
|
|
<pre><i><b>Footnote 232)</b> The term underflow here is intended to encompass both ‘‘gradual underflow’’ as in IEC 60559 and
|
|
also ‘‘flush-to-zero’’ underflow.
|
|
</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.233'><sup>[233]</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.233'>
|
|
<pre><i><b>Footnote 233)</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 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.234'><sup>[234]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.234'>
|
|
<pre><i><b>Footnote 234)</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 isfinite macro]</h3>
|
|
<a name='7.12.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isfinite(real-floating x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.2p2'></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='7.12.3.2p3'></a>
|
|
<pre>3 The isfinite macro returns a nonzero value if and only if its argument has a finite
|
|
value.
|
|
</pre>
|
|
<a name='7.12.3.3'></a>
|
|
<hr>
|
|
<h3>7.12.3.3 [The isinf macro]</h3>
|
|
<a name='7.12.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isinf(real-floating x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.3p2'></a>
|
|
<pre>2 The isinf macro determines whether its argument value is an infinity (positive or
|
|
negative). 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 isinf macro returns a nonzero value if and only if its argument has an infinite
|
|
value.
|
|
</pre>
|
|
<a name='7.12.3.4'></a>
|
|
<hr>
|
|
<h3>7.12.3.4 [The isnan macro]</h3>
|
|
<a name='7.12.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isnan(real-floating x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.4p2'></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.235'><sup>[235]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.235'>
|
|
<pre><i><b>Footnote 235)</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='7.12.3.4p3'></a>
|
|
<pre>3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
|
|
</pre>
|
|
<a name='7.12.3.5'></a>
|
|
<hr>
|
|
<h3>7.12.3.5 [The isnormal macro]</h3>
|
|
<a name='7.12.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isnormal(real-floating x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.5p2'></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='7.12.3.5p3'></a>
|
|
<pre>3 The isnormal macro returns a nonzero value if and only if its argument has a normal
|
|
value.
|
|
</pre>
|
|
<a name='7.12.3.6'></a>
|
|
<hr>
|
|
<h3>7.12.3.6 [The signbit macro]</h3>
|
|
<a name='7.12.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int signbit(real-floating x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.3.6p2'></a>
|
|
<pre>2 The signbit macro determines whether the sign of its argument value is negative.<a href='#FOOTNOTE.236'><sup>[236]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.236'>
|
|
<pre><i><b>Footnote 236)</b> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
|
|
unsigned, it is treated as positive.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.3.6p3'></a>
|
|
<pre>3 The signbit macro returns a nonzero value if and only if the sign of its argument value
|
|
is negative.
|
|
</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);
|
|
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);
|
|
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].
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.2p3'></a>
|
|
<pre>3 The asin functions return arcsin x in the interval [−π /2, +π /2] 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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.3p2'></a>
|
|
<pre>2 The atan functions compute the principal value of the arc tangent of x.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.3p3'></a>
|
|
<pre>3 The atan functions return arctan x in the interval [−π /2, +π /2] 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);
|
|
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.
|
|
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);
|
|
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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.6p2'></a>
|
|
<pre>2 The sin functions compute the sine of x (measured in radians).
|
|
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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.4.7p2'></a>
|
|
<pre>2 The tan functions return the tangent of x (measured in radians).
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.4.7p3'></a>
|
|
<pre>3 The tan functions return tan 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);
|
|
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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.2p2'></a>
|
|
<pre>2 The asinh functions compute the arc hyperbolic sine of x.
|
|
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);
|
|
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.
|
|
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);
|
|
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 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);
|
|
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 x is too large.
|
|
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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.5.6p2'></a>
|
|
<pre>2 The tanh functions compute the hyperbolic tangent of x.
|
|
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);
|
|
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 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 exp2 functions]</h3>
|
|
<a name='7.12.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double exp2(double x);
|
|
float exp2f(float x);
|
|
long double exp2l(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.2p2'></a>
|
|
<pre>2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
|
|
magnitude of x is too large.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.2p3'></a>
|
|
<pre>3 The exp2 functions return 2x .
|
|
</pre>
|
|
<a name='7.12.6.3'></a>
|
|
<hr>
|
|
<h3>7.12.6.3 [The expm1 functions]</h3>
|
|
<a name='7.12.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double expm1(double x);
|
|
float expm1f(float x);
|
|
long double expm1l(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.3p2'></a>
|
|
<pre>2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
|
|
error occurs if x is too large.<a href='#FOOTNOTE.237'><sup>[237]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.237'>
|
|
<pre><i><b>Footnote 237)</b> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.3p3'></a>
|
|
<pre>3 The expm1 functions return ex − 1.
|
|
</pre>
|
|
<a name='7.12.6.4'></a>
|
|
<hr>
|
|
<h3>7.12.6.4 [The frexp functions]</h3>
|
|
<a name='7.12.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double frexp(double value, int *exp);
|
|
float frexpf(float value, int *exp);
|
|
long double frexpl(long double value, int *exp);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.4p2'></a>
|
|
<pre>2 The frexp functions break a floating-point number into a normalized fraction and an
|
|
integral power of 2. They store the integer in the int object pointed to by exp.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.4p3'></a>
|
|
<pre>3 If value is not a floating-point number or if the integral power of 2 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 [1/2, <a href='#FOOTNOTE.1'><sup>[1]</sup></a> or zero, and value equals x × 2*exp .
|
|
If value is zero, both parts of the result are zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.1'>
|
|
<pre><i><b>Footnote 1)</b> This International Standard 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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.5'></a>
|
|
<hr>
|
|
<h3>7.12.6.5 [The ilogb functions]</h3>
|
|
<a name='7.12.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int ilogb(double x);
|
|
int ilogbf(float x);
|
|
int ilogbl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.5p2'></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 casting 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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.5p3'></a>
|
|
<pre>3 The ilogb functions return the exponent of x as a signed int value.
|
|
Forward references: the logb functions (<a href='#7.12.6.11'>7.12.6.11</a>).
|
|
</pre>
|
|
<a name='7.12.6.6'></a>
|
|
<hr>
|
|
<h3>7.12.6.6 [The ldexp functions]</h3>
|
|
<a name='7.12.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double ldexp(double x, int exp);
|
|
float ldexpf(float x, int exp);
|
|
long double ldexpl(long double x, int exp);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.6p2'></a>
|
|
<pre>2 The ldexp functions multiply a floating-point number by an integral power of 2. A
|
|
range error may occur.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.6p3'></a>
|
|
<pre>3 The ldexp functions return x × 2exp .
|
|
</pre>
|
|
<a name='7.12.6.7'></a>
|
|
<hr>
|
|
<h3>7.12.6.7 [The log functions]</h3>
|
|
<a name='7.12.6.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log(double x);
|
|
float logf(float x);
|
|
long double logl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.7p2'></a>
|
|
<pre>2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
|
|
the argument is negative. A pole error may occur if the argument is zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.7p3'></a>
|
|
<pre>3 The log functions return loge x.
|
|
</pre>
|
|
<a name='7.12.6.8'></a>
|
|
<hr>
|
|
<h3>7.12.6.8 [The log10 functions]</h3>
|
|
<a name='7.12.6.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log10(double x);
|
|
float log10f(float x);
|
|
long double log10l(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.8p2'></a>
|
|
<pre>2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
|
|
occurs if the argument is negative. A pole error may occur if the argument is zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.8p3'></a>
|
|
<pre>3 The log10 functions return log10 x.
|
|
</pre>
|
|
<a name='7.12.6.9'></a>
|
|
<hr>
|
|
<h3>7.12.6.9 [The log1p functions]</h3>
|
|
<a name='7.12.6.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log1p(double x);
|
|
float log1pf(float x);
|
|
long double log1pl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.9p2'></a>
|
|
<pre>2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<a href='#FOOTNOTE.238'><sup>[238]</sup></a>
|
|
A domain error occurs if the argument is less than −1. A pole error may occur if the
|
|
argument equals −1.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.238'>
|
|
<pre><i><b>Footnote 238)</b> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.12.6.9p3'></a>
|
|
<pre>3 The log1p functions return loge (1 + x).
|
|
</pre>
|
|
<a name='7.12.6.10'></a>
|
|
<hr>
|
|
<h3>7.12.6.10 [The log2 functions]</h3>
|
|
<a name='7.12.6.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double log2(double x);
|
|
float log2f(float x);
|
|
long double log2l(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.10p2'></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='7.12.6.10p3'></a>
|
|
<pre>3 The log2 functions return log2 x.
|
|
</pre>
|
|
<a name='7.12.6.11'></a>
|
|
<hr>
|
|
<h3>7.12.6.11 [The logb functions]</h3>
|
|
<a name='7.12.6.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double logb(double x);
|
|
float logbf(float x);
|
|
long double logbl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.11p2'></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 × FLT_RADIX−logb(x) < FLT_RADIX
|
|
A domain error or pole error may occur if the argument is zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.11p3'></a>
|
|
<pre>3 The logb functions return the signed exponent of x.
|
|
</pre>
|
|
<a name='7.12.6.12'></a>
|
|
<hr>
|
|
<h3>7.12.6.12 [The modf functions]</h3>
|
|
<a name='7.12.6.12p1'></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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.12p2'></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='7.12.6.12p3'></a>
|
|
<pre>3 The modf functions return the signed fractional part of value.
|
|
</pre>
|
|
<a name='7.12.6.13'></a>
|
|
<hr>
|
|
<h3>7.12.6.13 [The scalbn and scalbln functions]</h3>
|
|
<a name='7.12.6.13p1'></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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.6.13p2'></a>
|
|
<pre>2 The scalbn and scalbln functions compute x × FLT_RADIXn efficiently, not
|
|
normally by computing FLT_RADIXn explicitly. A range error may occur.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.6.13p3'></a>
|
|
<pre>3 The scalbn and scalbln functions return x × FLT_RADIXn .
|
|
</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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.1p2'></a>
|
|
<pre>2 The cbrt functions compute the real cube root of x.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.1p3'></a>
|
|
<pre>3 The cbrt functions return x1/3 .
|
|
</pre>
|
|
<a name='7.12.7.2'></a>
|
|
<hr>
|
|
<h3>7.12.7.2 [The fabs functions]</h3>
|
|
<a name='7.12.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double fabs(double x);
|
|
float fabsf(float x);
|
|
long double fabsl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.2p2'></a>
|
|
<pre>2 The fabs functions compute the absolute value of a floating-point number x.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.2p3'></a>
|
|
<pre>3 The fabs functions return | x |.
|
|
</pre>
|
|
<a name='7.12.7.3'></a>
|
|
<hr>
|
|
<h3>7.12.7.3 [The hypot functions]</h3>
|
|
<a name='7.12.7.3p1'></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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.3p2'></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 may occur.
|
|
</pre>
|
|
<a name='7.12.7.3p3'></a>
|
|
<pre>3 Returns
|
|
</pre>
|
|
<a name='7.12.7.3p4'></a>
|
|
<pre>4 The hypot functions return √
|
|
⎯⎯⎯⎯⎯⎯
|
|
x2 + y 2 .
|
|
</pre>
|
|
<a name='7.12.7.4'></a>
|
|
<hr>
|
|
<h3>7.12.7.4 [The pow functions]</h3>
|
|
<a name='7.12.7.4p1'></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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.4p2'></a>
|
|
<pre>2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
|
|
and negative and y is finite and not an integer value. A range error may occur. A domain
|
|
error may occur if x is zero and y is zero. A domain error or pole error may occur if x is
|
|
zero and y is less than zero.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.7.4p3'></a>
|
|
<pre>3 The pow functions return xy .
|
|
</pre>
|
|
<a name='7.12.7.5'></a>
|
|
<hr>
|
|
<h3>7.12.7.5 [The sqrt functions]</h3>
|
|
<a name='7.12.7.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double sqrt(double x);
|
|
float sqrtf(float x);
|
|
long double sqrtl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.7.5p2'></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='7.12.7.5p3'></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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.1p2'></a>
|
|
<pre>2 The erf functions compute the error function of x.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.8.1p3'></a>
|
|
<pre>3 2 x
|
|
|
|
⎯⎯π ∫
|
|
−t 2
|
|
The erf functions return erf x = 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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.8.2p2'></a>
|
|
<pre>2 The erfc functions compute the complementary error function of x. A range error
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.8.2p3'></a>
|
|
<pre>3 2 ∞
|
|
⎯⎯π ∫
|
|
−t 2
|
|
The erfc functions return erfc x = 1 − erf x = 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);
|
|
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 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);
|
|
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 if the magnitude of x is
|
|
too large and may occur if the magnitude of x is too small.
|
|
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);
|
|
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);
|
|
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);
|
|
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);
|
|
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);
|
|
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);
|
|
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);
|
|
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 trunc functions]</h3>
|
|
<a name='7.12.9.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
double trunc(double x);
|
|
float truncf(float x);
|
|
long double truncl(long double x);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.9.8p2'></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='7.12.9.8p3'></a>
|
|
<pre>3 The trunc functions return the truncated integer value.
|
|
</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);
|
|
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);
|
|
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.239'><sup>[239]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.239'>
|
|
<pre><i><b>Footnote 239)</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 x/y; whenever
|
|
| n − x/y | = 1/2, 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='7.12.11'></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);
|
|
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.
|
|
They produce a NaN (with the sign of y) if x is a NaN. On implementations that
|
|
represent a signed zero but do not treat negative zero consistently in arithmetic
|
|
operations, the copysign functions 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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.2p2'></a>
|
|
<pre>2 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
|
|
sequence)", (char**) NULL); the call nan("") is equivalent to
|
|
strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
|
|
sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
|
|
NULL). 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='#7.22.1.3'>7.22.1.3</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);
|
|
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.240'><sup>[240]</sup></a> The nextafter functions return y if x equals y. A range error may occur
|
|
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.240'>
|
|
<pre><i><b>Footnote 240)</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);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.11.4p2'></a>
|
|
<pre>2 The nexttoward functions are equivalent to the nextafter functions except that the
|
|
second parameter has type long double and the functions return y converted to the
|
|
type of the function if x equals y.<a href='#FOOTNOTE.241'><sup>[241]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.241'>
|
|
<pre><i><b>Footnote 241)</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='7.12.12'></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);
|
|
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);
|
|
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.242'><sup>[242]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.242'>
|
|
<pre><i><b>Footnote 242)</b> NaN arguments are treated as missing data: if one argument is a 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);
|
|
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.243'><sup>[243]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.243'>
|
|
<pre><i><b>Footnote 243)</b> The fmin functions are analogous to the fmax functions in their treatment of 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='7.12.13'></a>
|
|
<hr>
|
|
<h3>7.12.13 [Floating 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);
|
|
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 may occur.
|
|
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 [Comparison macros]</h3>
|
|
<a name='7.12.14p1'></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.244'><sup>[244]</sup></a> The following
|
|
subclauses provide macros that are quiet (non floating-point exception raising) versions
|
|
of the relational operators, and other comparison macros that facilitate writing efficient
|
|
code that accounts for 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.245'><sup>[245]</sup></a> (both arguments need not have the same type).<a href='#FOOTNOTE.246'><sup>[246]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.244'>
|
|
<pre><i><b>Footnote 244)</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.245'>
|
|
<pre><i><b>Footnote 245)</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.246'>
|
|
<pre><i><b>Footnote 246)</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='7.12.14.1'></a>
|
|
<hr>
|
|
<h3>7.12.14.1 [The isgreater macro]</h3>
|
|
<a name='7.12.14.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isgreater(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.1p2'></a>
|
|
<pre>2 The isgreater macro determines whether its first argument is greater than its second
|
|
argument. 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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.1p3'></a>
|
|
<pre>3 The isgreater macro returns the value of (x) > (y).
|
|
</pre>
|
|
<a name='7.12.14.2'></a>
|
|
<hr>
|
|
<h3>7.12.14.2 [The isgreaterequal macro]</h3>
|
|
<a name='7.12.14.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isgreaterequal(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.2p2'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.2p3'></a>
|
|
<pre>3 The isgreaterequal macro returns the value of (x) >= (y).
|
|
</pre>
|
|
<a name='7.12.14.3'></a>
|
|
<hr>
|
|
<h3>7.12.14.3 [The isless macro]</h3>
|
|
<a name='7.12.14.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isless(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.3p2'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.3p3'></a>
|
|
<pre>3 The isless macro returns the value of (x) < (y).
|
|
</pre>
|
|
<a name='7.12.14.4'></a>
|
|
<hr>
|
|
<h3>7.12.14.4 [The islessequal macro]</h3>
|
|
<a name='7.12.14.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int islessequal(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.4p2'></a>
|
|
<pre>2 The islessequal macro determines whether its first argument is less than or equal to
|
|
its second 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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.4p3'></a>
|
|
<pre>3 The islessequal macro returns the value of (x) <= (y).
|
|
</pre>
|
|
<a name='7.12.14.5'></a>
|
|
<hr>
|
|
<h3>7.12.14.5 [The islessgreater macro]</h3>
|
|
<a name='7.12.14.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int islessgreater(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.5p2'></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 unordered (nor does it evaluate x
|
|
and y twice).
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.5p3'></a>
|
|
<pre>3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
|
|
</pre>
|
|
<a name='7.12.14.6'></a>
|
|
<hr>
|
|
<h3>7.12.14.6 [The isunordered macro]</h3>
|
|
<a name='7.12.14.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <math.h>
|
|
int isunordered(real-floating x, real-floating y);
|
|
Description
|
|
</pre>
|
|
<a name='7.12.14.6p2'></a>
|
|
<pre>2 The isunordered macro determines whether its arguments are unordered.
|
|
Returns
|
|
</pre>
|
|
<a name='7.12.14.6p3'></a>
|
|
<pre>3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
|
|
</pre>
|
|
<a name='7.13'></a>
|
|
<hr>
|
|
<h3>7.13 [Nonlocal 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.247'><sup>[247]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.247'>
|
|
<pre><i><b>Footnote 247)</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.248'><sup>[248]</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.248'>
|
|
<pre><i><b>Footnote 248)</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.249'><sup>[249]</sup></a>
|
|
have state, as of the time the longjmp function was called, except that the values 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 are
|
|
indeterminate.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.249'>
|
|
<pre><i><b>Footnote 249)</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.250'><sup>[250]</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.250'>
|
|
<pre><i><b>Footnote 250)</b> See ‘‘future library directions’’ (<a href='#7.31.7'>7.31.7</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.251'><sup>[251]</sup></a> is called a
|
|
signal handler.
|
|
</pre>
|
|
<a name='FOOTNOTE.251'>
|
|
<pre><i><b>Footnote 251)</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 equivalent 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, 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
|
|
value of errno is indeterminate.<a href='#FOOTNOTE.252'><sup>[252]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.252'>
|
|
<pre><i><b>Footnote 252)</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='#7.22.4.1'>7.22.4.1</a>), the exit function (<a href='#7.22.4.4'>7.22.4.4</a>), the
|
|
_Exit function (<a href='#7.22.4.5'>7.22.4.5</a>), the quick_exit function (<a href='#7.22.4.7'>7.22.4.7</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> defines four macros.
|
|
</pre>
|
|
<a name='7.15p2'></a>
|
|
<pre>2 The macro
|
|
alignas
|
|
expands to _Alignas; the macro
|
|
alignof
|
|
expands to _Alignof.
|
|
</pre>
|
|
<a name='7.15p3'></a>
|
|
<pre>3 The remaining macros are suitable for use in #if preprocessing directives. They are
|
|
_ _alignas_is_defined
|
|
and
|
|
_ _alignof_is_defined
|
|
which both expand to the integer constant 1.
|
|
</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. As
|
|
described in <a href='#6.9.1'>6.9.1</a>, its parameter list contains one or more parameters. The rightmost
|
|
parameter plays a special role in the access mechanism, and will be designated parmN in
|
|
this description.
|
|
</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
|
|
value 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.253'><sup>[253]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.253'>
|
|
<pre><i><b>Footnote 253)</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 may 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 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 there is no actual next argument, or 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:
|
|
— 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 void and the other is a pointer to a character type.
|
|
Returns
|
|
</pre>
|
|
<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 argument after that specified by parmN . 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, parmN);
|
|
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 The parameter parmN is the identifier of the rightmost parameter in the variable
|
|
parameter list in the function definition (the one just before the , ...). If the parameter
|
|
parmN is declared with the register storage class, with a function or array type, or
|
|
with a type that is not compatible with the type that results after application of the default
|
|
argument promotions, the behavior is undefined.
|
|
Returns
|
|
</pre>
|
|
<a name='7.16.1.4p5'></a>
|
|
<pre>5 The va_start macro returns no value.
|
|
</pre>
|
|
<a name='7.16.1.4p6'></a>
|
|
<pre>6 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, n_ptrs);
|
|
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='7.16.1.4p7'></a>
|
|
<pre>7 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, f4_after);
|
|
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='7.17'></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.254'><sup>[254]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.254'>
|
|
<pre><i><b>Footnote 254)</b> See ‘‘future library directions’’ (<a href='#7.31.8'>7.31.8</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_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 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 one of the atomic types.
|
|
— 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 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='7.17.2.1'></a>
|
|
<hr>
|
|
<h3>7.17.2.1 [The ATOMIC_VAR_INIT macro]</h3>
|
|
<a name='7.17.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
#define ATOMIC_VAR_INIT(C value)
|
|
Description
|
|
</pre>
|
|
<a name='7.17.2.1p2'></a>
|
|
<pre>2 The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an
|
|
atomic object of a type that is initialization-compatible with value. An atomic object
|
|
with automatic storage duration that is not explicitly initialized using
|
|
ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero)
|
|
initialization for objects with static or thread-local storage duration is guaranteed to
|
|
produce a valid state.
|
|
</pre>
|
|
<a name='7.17.2.1p3'></a>
|
|
<pre>3 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 EXAMPLE
|
|
atomic_int guide = ATOMIC_VAR_INIT(42);
|
|
|
|
</pre>
|
|
<a name='7.17.2.2'></a>
|
|
<hr>
|
|
<h3>7.17.2.2 [The atomic_init generic function]</h3>
|
|
<a name='7.17.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdatomic.h>
|
|
void atomic_init(volatile A *obj, C value);
|
|
Description
|
|
</pre>
|
|
<a name='7.17.2.2p2'></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.
|
|
</pre>
|
|
<a name='7.17.2.2p3'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.17.2.2p4'></a>
|
|
<pre>4 The atomic_init generic function returns no value.
|
|
</pre>
|
|
<a name='7.17.2.2p5'></a>
|
|
<pre>5 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 synchronization 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.255'><sup>[255]</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.255'>
|
|
<pre><i><b>Footnote 255)</b> See ‘‘future library directions’’ (<a href='#7.31.8'>7.31.8</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 operation 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 operation 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 memory 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 in the visible sequence of side
|
|
effects with respect to B 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 in the visible sequence of
|
|
side effects with respect to B 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. Implementations must still guarantee that any given atomic access to a particular atomic
|
|
object be 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 modification 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 operations A and B on an atomic object M, where A modifies M and B takes
|
|
its value, if 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, then B observes
|
|
either the effects of A or a later modification of M in its modification order.
|
|
</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.<a href='#FOOTNOTE.256'><sup>[256]</sup></a> 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='FOOTNOTE.256'>
|
|
<pre><i><b>Footnote 256)</b> Among other implications, atomic variables shall not decay.
|
|
</i></pre>
|
|
</a>
|
|
<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 may 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 dependency 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 semantics, 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.
|
|
</pre>
|
|
<a name='7.17.5p2'></a>
|
|
<pre>2 NOTE 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 the object
|
|
pointed to by obj is 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 the
|
|
object’s operations are lock-free. The result of a lock-free query on one object cannot be
|
|
inferred from the result of a lock-free query on another object.
|
|
</pre>
|
|
<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.257'><sup>[257]</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.258'><sup>[258]</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_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_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
|
|
</pre>
|
|
<a name='FOOTNOTE.257'>
|
|
<pre><i><b>Footnote 257)</b> See ‘‘future library directions’’ (<a href='#7.31.8'>7.31.8</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.258'>
|
|
<pre><i><b>Footnote 258)</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 semantics of the operations on these types are defined in <a href='#7.17.7'>7.17.7</a>. ∗
|
|
</pre>
|
|
<a name='7.17.6p3'></a>
|
|
<pre>3 NOTE The representation of atomic integer types need not have the same size as their corresponding
|
|
regular types. They 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(volatile A *object);
|
|
C atomic_load_explicit(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
|
|
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. Atomically, compares the value pointed to by object for equality
|
|
with that in expected, and if true, replaces the value pointed to by object with
|
|
desired, and if false, updates the value in expected with the value 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='7.17.7.4p3'></a>
|
|
<pre>3 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='7.17.7.4p4'></a>
|
|
<pre>4 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='7.17.7.4p5'></a>
|
|
<pre>5 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='7.17.7.4p6'></a>
|
|
<pre>6 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='7.17.7.4p7'></a>
|
|
<pre>7 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 ˆ 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 is defined to use two’s
|
|
complement representation with silent wrap-around on 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 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
|
|
International standard. 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 is initially in an indeterminate state.
|
|
</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 sets the value pointed to by object to true. 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 Atomically, the value of the object immediately before the effects.
|
|
</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 sets the value pointed to by object to false.
|
|
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 [Boolean type and values <stdbool.h>]</h3>
|
|
<a name='7.18p1'></a>
|
|
<pre>1 The header <stdbool.h> defines four macros.
|
|
</pre>
|
|
<a name='7.18p2'></a>
|
|
<pre>2 The macro
|
|
bool
|
|
expands to _Bool.
|
|
</pre>
|
|
<a name='7.18p3'></a>
|
|
<pre>3 The remaining three macros are suitable for use in #if preprocessing directives. They
|
|
are
|
|
true
|
|
which expands to the integer constant 1,
|
|
false
|
|
which expands to the integer constant 0, and
|
|
_ _bool_true_false_are_defined
|
|
which expands to the integer constant 1.
|
|
</pre>
|
|
<a name='7.18p4'></a>
|
|
<pre>4 Notwithstanding the provisions of <a href='#7.1.3'>7.1.3</a>, a program may undefine and perhaps then
|
|
redefine the macros bool, true, and false.<a href='#FOOTNOTE.259'><sup>[259]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.259'>
|
|
<pre><i><b>Footnote 259)</b> See ‘‘future library directions’’ (<a href='#7.31.9'>7.31.9</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.19'></a>
|
|
<hr>
|
|
<h3>7.19 [Common definitions <stddef.h>]</h3>
|
|
<a name='7.19p1'></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='7.19p2'></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 as great as is supported by the implementation
|
|
in all contexts; and
|
|
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_ _.
|
|
</pre>
|
|
<a name='7.19p3'></a>
|
|
<pre>3 The macros are
|
|
NULL
|
|
which expands to an implementation-defined null pointer constant; 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 structure member (designated by member-designator),
|
|
from the beginning of its structure (designated by 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 member is a bit-field, the behavior is undefined.)
|
|
Recommended practice
|
|
</pre>
|
|
<a name='7.19p4'></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='7.20'></a>
|
|
<hr>
|
|
<h3>7.20 [Integer types <stdint.h>]</h3>
|
|
<a name='7.20p1'></a>
|
|
<pre>1 The header <stdint.h> declares sets of integer types having specified widths, and
|
|
defines corresponding sets of macros.<a href='#FOOTNOTE.260'><sup>[260]</sup></a> It also defines macros that specify limits of
|
|
integer types corresponding to types defined in other standard headers.
|
|
</pre>
|
|
<a name='FOOTNOTE.260'>
|
|
<pre><i><b>Footnote 260)</b> See ‘‘future library directions’’ (<a href='#7.31.10'>7.31.10</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.20p2'></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='7.20p3'></a>
|
|
<pre>3 Corresponding macros specify limits of the declared types and construct suitable
|
|
constants.
|
|
</pre>
|
|
<a name='7.20p4'></a>
|
|
<pre>4 For each type described herein that the implementation provides,<a href='#FOOTNOTE.261'><sup>[261]</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’’).
|
|
</pre>
|
|
<a name='FOOTNOTE.261'>
|
|
<pre><i><b>Footnote 261)</b> Some of these types may denote implementation-defined extended integer types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.20.1'></a>
|
|
<hr>
|
|
<h3>7.20.1 [Integer types]</h3>
|
|
<a name='7.20.1p1'></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='7.20.1p2'></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='7.20.1.1'></a>
|
|
<hr>
|
|
<h3>7.20.1.1 [Exact-width integer types]</h3>
|
|
<a name='7.20.1.1p1'></a>
|
|
<pre>1 The typedef name intN_t designates a signed integer type with width N , no padding
|
|
bits, and a two’s complement representation. Thus, int8_t denotes such a signed
|
|
integer type with a width of exactly 8 bits.
|
|
</pre>
|
|
<a name='7.20.1.1p2'></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='7.20.1.1p3'></a>
|
|
<pre>3 These types are optional. However, if an implementation provides integer types with
|
|
widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
|
|
two’s complement representation, it shall define the corresponding typedef names.
|
|
</pre>
|
|
<a name='7.20.1.2'></a>
|
|
<hr>
|
|
<h3>7.20.1.2 [Minimum-width integer types]</h3>
|
|
<a name='7.20.1.2p1'></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='7.20.1.2p2'></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='7.20.1.2p3'></a>
|
|
<pre>3 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='7.20.1.3'></a>
|
|
<hr>
|
|
<h3>7.20.1.3 [Fastest minimum-width integer types]</h3>
|
|
<a name='7.20.1.3p1'></a>
|
|
<pre>1 Each of the following types designates an integer type that is usually fastest<a href='#FOOTNOTE.262'><sup>[262]</sup></a> to operate
|
|
with among all integer types that have at least the specified width.
|
|
</pre>
|
|
<a name='FOOTNOTE.262'>
|
|
<pre><i><b>Footnote 262)</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='7.20.1.3p2'></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='7.20.1.3p3'></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='7.20.1.4'></a>
|
|
<hr>
|
|
<h3>7.20.1.4 [Integer types capable of holding object pointers]</h3>
|
|
<a name='7.20.1.4p1'></a>
|
|
<pre>1 The following type designates a signed 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 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='7.20.1.5'></a>
|
|
<hr>
|
|
<h3>7.20.1.5 [Greatest-width integer types]</h3>
|
|
<a name='7.20.1.5p1'></a>
|
|
<pre>1 The following type designates a signed integer type capable of representing any value of
|
|
any signed integer type:
|
|
intmax_t
|
|
The following type designates an unsigned integer type capable of representing any value
|
|
of any unsigned integer type:
|
|
uintmax_t
|
|
These types are required.
|
|
</pre>
|
|
<a name='7.20.2'></a>
|
|
<hr>
|
|
<h3>7.20.2 [Limits of specified-width integer types]</h3>
|
|
<a name='7.20.2p1'></a>
|
|
<pre>1 The following object-like macros specify the minimum and maximum limits of the types
|
|
declared in <stdint.h>. Each macro name corresponds to a similar type name in
|
|
<a href='#7.20.1'>7.20.1</a>.
|
|
</pre>
|
|
<a name='7.20.2p2'></a>
|
|
<pre>2 Each instance of any defined macro shall be replaced by a constant expression suitable
|
|
for use in #if preprocessing directives, and this expression shall have the same type as
|
|
would an expression that is an object of the corresponding type converted according to
|
|
the integer promotions. Its implementation-defined value shall be equal to or greater in
|
|
magnitude (absolute value) than the corresponding value given below, with the same sign,
|
|
except where stated to be exactly the given value.
|
|
</pre>
|
|
<a name='7.20.2.1'></a>
|
|
<hr>
|
|
<h3>7.20.2.1 [Limits of exact-width integer types]</h3>
|
|
<a name='7.20.2.1p1'></a>
|
|
<pre>1 — minimum values of exact-width signed integer types
|
|
INTN_MIN exactly −(2 N −1 )
|
|
— maximum values of exact-width signed integer types
|
|
INTN_MAX exactly 2 N −1 − 1
|
|
— maximum values of exact-width unsigned integer types
|
|
UINTN_MAX exactly 2 N − 1
|
|
</pre>
|
|
<a name='7.20.2.2'></a>
|
|
<hr>
|
|
<h3>7.20.2.2 [Limits of minimum-width integer types]</h3>
|
|
<a name='7.20.2.2p1'></a>
|
|
<pre>1 — minimum values of minimum-width signed integer types
|
|
INT_LEASTN_MIN −(2 N −1 − 1)
|
|
— maximum values of minimum-width signed integer types
|
|
INT_LEASTN_MAX 2 N −1 − 1
|
|
— maximum values of minimum-width unsigned integer types
|
|
UINT_LEASTN_MAX 2N − 1
|
|
</pre>
|
|
<a name='7.20.2.3'></a>
|
|
<hr>
|
|
<h3>7.20.2.3 [Limits of fastest minimum-width integer types]</h3>
|
|
<a name='7.20.2.3p1'></a>
|
|
<pre>1 — minimum values of fastest minimum-width signed integer types
|
|
INT_FASTN_MIN −(2 N −1 − 1)
|
|
— maximum values of fastest minimum-width signed integer types
|
|
INT_FASTN_MAX 2 N −1 − 1
|
|
— maximum values of fastest minimum-width unsigned integer types
|
|
UINT_FASTN_MAX 2N − 1
|
|
</pre>
|
|
<a name='7.20.2.4'></a>
|
|
<hr>
|
|
<h3>7.20.2.4 [Limits of integer types capable of holding object pointers]</h3>
|
|
<a name='7.20.2.4p1'></a>
|
|
<pre>1 — minimum value of pointer-holding signed integer type
|
|
INTPTR_MIN −(215 − 1)
|
|
— maximum value of pointer-holding signed integer type
|
|
INTPTR_MAX 215 − 1
|
|
— maximum value of pointer-holding unsigned integer type
|
|
UINTPTR_MAX 216 − 1
|
|
</pre>
|
|
<a name='7.20.2.5'></a>
|
|
<hr>
|
|
<h3>7.20.2.5 [Limits of greatest-width integer types]</h3>
|
|
<a name='7.20.2.5p1'></a>
|
|
<pre>1 — minimum value of greatest-width signed integer type
|
|
INTMAX_MIN −(263 − 1)
|
|
— maximum value of greatest-width signed integer type
|
|
INTMAX_MAX 263 − 1
|
|
— maximum value of greatest-width unsigned integer type
|
|
UINTMAX_MAX 264 − 1
|
|
</pre>
|
|
<a name='7.20.3'></a>
|
|
<hr>
|
|
<h3>7.20.3 [Limits of other integer types]</h3>
|
|
<a name='7.20.3p1'></a>
|
|
<pre>1 The following object-like macros specify the minimum and maximum limits of integer
|
|
types corresponding to types defined in other standard headers.
|
|
</pre>
|
|
<a name='7.20.3p2'></a>
|
|
<pre>2 Each instance of these macros shall be replaced by a constant expression suitable for use
|
|
in #if preprocessing directives, and this expression shall have the same type as would an
|
|
expression that is an object of the corresponding type converted according to the integer
|
|
promotions. Its implementation-defined value shall be equal to or greater in magnitude
|
|
(absolute value) than the corresponding value given below, with the same sign. An
|
|
implementation shall define only the macros corresponding to those typedef names it
|
|
actually provides.<a href='#FOOTNOTE.263'><sup>[263]</sup></a>
|
|
— limits of ptrdiff_t
|
|
PTRDIFF_MIN −65535
|
|
PTRDIFF_MAX +65535
|
|
— limits of sig_atomic_t
|
|
SIG_ATOMIC_MIN see below
|
|
SIG_ATOMIC_MAX see below
|
|
— limit of size_t
|
|
SIZE_MAX 65535
|
|
— limits of wchar_t
|
|
WCHAR_MIN see below
|
|
WCHAR_MAX see below
|
|
— limits of wint_t
|
|
WINT_MIN see below
|
|
WINT_MAX see below
|
|
</pre>
|
|
<a name='FOOTNOTE.263'>
|
|
<pre><i><b>Footnote 263)</b> A freestanding implementation need not provide all of these types.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.20.3p3'></a>
|
|
<pre>3 If sig_atomic_t (see <a href='#7.14'>7.14</a>) is defined as a signed integer type, the value of
|
|
SIG_ATOMIC_MIN shall be no greater than −127 and the value of SIG_ATOMIC_MAX
|
|
shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
|
|
type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
|
|
SIG_ATOMIC_MAX shall be no less than 255.
|
|
</pre>
|
|
<a name='7.20.3p4'></a>
|
|
<pre>4 If wchar_t (see <a href='#7.19'>7.19</a>) is defined as a signed integer type, the value of WCHAR_MIN
|
|
shall be no greater than −127 and the value of WCHAR_MAX shall be no less than 127;
|
|
otherwise, wchar_t is defined as an unsigned integer type, and the value of
|
|
WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<a href='#FOOTNOTE.264'><sup>[264]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.264'>
|
|
<pre><i><b>Footnote 264)</b> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
|
|
character set.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.20.3p5'></a>
|
|
<pre>5 If wint_t (see <a href='#7.29'>7.29</a>) is defined as a signed integer type, the value of WINT_MIN shall
|
|
be no greater than −32767 and the value of WINT_MAX shall be no less than 32767;
|
|
otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
|
|
shall be 0 and the value of WINT_MAX shall be no less than 65535.
|
|
</pre>
|
|
<a name='7.20.4'></a>
|
|
<hr>
|
|
<h3>7.20.4 [Macros for integer constants]</h3>
|
|
<a name='7.20.4p1'></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='#7.20.1.2'>7.20.1.2</a> or <a href='#7.20.1.5'>7.20.1.5</a>.
|
|
</pre>
|
|
<a name='7.20.4p2'></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='7.20.4p3'></a>
|
|
<pre>3 Each invocation of one of these macros shall expand to an integer constant expression
|
|
suitable for use in #if preprocessing directives. 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.
|
|
</pre>
|
|
<a name='7.20.4.1'></a>
|
|
<hr>
|
|
<h3>7.20.4.1 [Macros for minimum-width integer constants]</h3>
|
|
<a name='7.20.4.1p1'></a>
|
|
<pre>1 The macro INTN_C(value) shall expand to an integer constant expression
|
|
corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
|
|
to an integer constant expression corresponding 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='7.20.4.2'></a>
|
|
<hr>
|
|
<h3>7.20.4.2 [Macros for greatest-width integer constants]</h3>
|
|
<a name='7.20.4.2p1'></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='7.21'></a>
|
|
<hr>
|
|
<h3>7.21 [Input/output <stdio.h>]</h3>
|
|
<a name='7.21.1'></a>
|
|
<hr>
|
|
<h3>7.21.1 [Introduction]</h3>
|
|
<a name='7.21.1p1'></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='7.21.1p2'></a>
|
|
<pre>2 The types declared are size_t (described in <a href='#7.19'>7.19</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='7.21.1p3'></a>
|
|
<pre>3 The macros are NULL (described in <a href='#7.19'>7.19</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;<a href='#FOOTNOTE.265'><sup>[265]</sup></a>
|
|
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.265'>
|
|
<pre><i><b>Footnote 265)</b> If the implementation imposes no practical limit on the length of file name strings, the value of
|
|
FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
|
|
string. 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='7.21.1p4'></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='#7.21.3'>7.21.3</a>.
|
|
</pre>
|
|
<a name='7.21.1p5'></a>
|
|
<pre>5 The input/output functions are given the following collective terms:
|
|
— The wide character input functions — those functions described in <a href='#7.29'>7.29</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='#7.29'>7.29</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 character 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='#7.21.3'>7.21.3</a>), the fseek function (<a href='#7.21.9.2'>7.21.9.2</a>), streams (<a href='#7.21.2'>7.21.2</a>), the
|
|
tmpnam function (<a href='#7.21.4.4'>7.21.4.4</a>), <wchar.h> (<a href='#7.29'>7.29</a>).
|
|
</pre>
|
|
<a name='7.21.2'></a>
|
|
<hr>
|
|
<h3>7.21.2 [Streams]</h3>
|
|
<a name='7.21.2p1'></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.266'><sup>[266]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.266'>
|
|
<pre><i><b>Footnote 266)</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='7.21.2p2'></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='7.21.2p3'></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='7.21.2p4'></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/output 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 orientation, 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.267'><sup>[267]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.267'>
|
|
<pre><i><b>Footnote 267)</b> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.2p5'></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 are henceforth indeterminate.
|
|
</pre>
|
|
<a name='7.21.2p6'></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='7.21.2p7'></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='7.21.2p8'></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='7.21.2p9'></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='#7.21.5.4'>7.21.5.4</a>), the fwide function (<a href='#7.29.3.5'>7.29.3.5</a>),
|
|
mbstate_t (<a href='#7.30.1'>7.30.1</a>), the fgetpos function (<a href='#7.21.9.1'>7.21.9.1</a>), the fsetpos function
|
|
(<a href='#7.21.9.3'>7.21.9.3</a>).
|
|
</pre>
|
|
<a name='7.21.3'></a>
|
|
<hr>
|
|
<h3>7.21.3 [Files]</h3>
|
|
<a name='7.21.3p1'></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='7.21.3p2'></a>
|
|
<pre>2 Binary files are not truncated, except as defined in <a href='#7.21.5.3'>7.21.5.3</a>. Whether a write on a text
|
|
stream causes the associated file to be truncated beyond that point is implementation-
|
|
defined.
|
|
</pre>
|
|
<a name='7.21.3p3'></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='7.21.3p4'></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 value of a pointer to a FILE object is
|
|
indeterminate after 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='7.21.3p5'></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='7.21.3p6'></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='7.21.3p7'></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='7.21.3p8'></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='7.21.3p9'></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
|
|
encodings valid for use internal to the program).
|
|
— A file need not begin nor end in the initial shift state.<a href='#FOOTNOTE.268'><sup>[268]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.268'>
|
|
<pre><i><b>Footnote 268)</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='7.21.3p10'></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='7.21.3p11'></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='7.21.3p12'></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='7.21.3p13'></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='7.21.3p14'></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='7.21.3p15'></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='#7.22.4.4'>7.22.4.4</a>), the fgetc function (<a href='#7.21.7.1'>7.21.7.1</a>), the
|
|
fopen function (<a href='#7.21.5.3'>7.21.5.3</a>), the fputc function (<a href='#7.21.7.3'>7.21.7.3</a>), the setbuf function
|
|
(<a href='#7.21.5.5'>7.21.5.5</a>), the setvbuf function (<a href='#7.21.5.6'>7.21.5.6</a>), the fgetwc function (<a href='#7.29.3.1'>7.29.3.1</a>), the
|
|
fputwc function (<a href='#7.29.3.3'>7.29.3.3</a>), conversion state (<a href='#7.29.6'>7.29.6</a>), the mbrtowc function
|
|
(<a href='#7.29.6.3.2'>7.29.6.3.2</a>), the wcrtomb function (<a href='#7.29.6.3.3'>7.29.6.3.3</a>).
|
|
</pre>
|
|
<a name='7.21.4'></a>
|
|
<hr>
|
|
<h3>7.21.4 [Operations on files]</h3>
|
|
<a name='7.21.4.1'></a>
|
|
<hr>
|
|
<h3>7.21.4.1 [The remove function]</h3>
|
|
<a name='7.21.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int remove(const char *filename);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.4.1p2'></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='7.21.4.1p3'></a>
|
|
<pre>3 The remove function returns zero if the operation succeeds, nonzero if it fails.
|
|
</pre>
|
|
<a name='7.21.4.2'></a>
|
|
<hr>
|
|
<h3>7.21.4.2 [The rename function]</h3>
|
|
<a name='7.21.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int rename(const char *old, const char *new);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.4.2p2'></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='7.21.4.2p3'></a>
|
|
<pre>3 The rename function returns zero if the operation succeeds, nonzero if it fails,<a href='#FOOTNOTE.269'><sup>[269]</sup></a> in
|
|
which case if the file existed previously it is still known by its original name.
|
|
</pre>
|
|
<a name='FOOTNOTE.269'>
|
|
<pre><i><b>Footnote 269)</b> Among the reasons the implementation may 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='7.21.4.3'></a>
|
|
<hr>
|
|
<h3>7.21.4.3 [The tmpfile function]</h3>
|
|
<a name='7.21.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *tmpfile(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.4.3p2'></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='7.21.4.3p3'></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='7.21.4.3p4'></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='#7.21.5.3'>7.21.5.3</a>).
|
|
</pre>
|
|
<a name='7.21.4.4'></a>
|
|
<hr>
|
|
<h3>7.21.4.4 [The tmpnam function]</h3>
|
|
<a name='7.21.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
char *tmpnam(char *s);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.4.4p2'></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.270'><sup>[270]</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.270'>
|
|
<pre><i><b>Footnote 270)</b> Files created using strings generated by the tmpnam function are temporary only in the sense that
|
|
their names should not 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='7.21.4.4p3'></a>
|
|
<pre>3 The tmpnam function generates a different string each time it is called.
|
|
</pre>
|
|
<a name='7.21.4.4p4'></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='7.21.4.4p5'></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='7.21.4.4p6'></a>
|
|
<pre>6 The value of the macro TMP_MAX shall be at least 25.
|
|
</pre>
|
|
<a name='7.21.5'></a>
|
|
<hr>
|
|
<h3>7.21.5 [File access functions]</h3>
|
|
<a name='7.21.5.1'></a>
|
|
<hr>
|
|
<h3>7.21.5.1 [The fclose function]</h3>
|
|
<a name='7.21.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fclose(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.1p2'></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='7.21.5.1p3'></a>
|
|
<pre>3 The fclose function returns zero if the stream was successfully closed, or EOF if any
|
|
errors were detected.
|
|
</pre>
|
|
<a name='7.21.5.2'></a>
|
|
<hr>
|
|
<h3>7.21.5.2 [The fflush function]</h3>
|
|
<a name='7.21.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fflush(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.2p2'></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='7.21.5.2p3'></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='7.21.5.2p4'></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='#7.21.5.3'>7.21.5.3</a>).
|
|
</pre>
|
|
<a name='7.21.5.3'></a>
|
|
<hr>
|
|
<h3>7.21.5.3 [The fopen function]</h3>
|
|
<a name='7.21.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *fopen(const char * restrict filename,
|
|
const char * restrict mode);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.3p2'></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='7.21.5.3p3'></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.271'><sup>[271]</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.271'>
|
|
<pre><i><b>Footnote 271)</b> If the string begins with one of the above 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='#7.21.2'>7.21.2</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.5.3p4'></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='7.21.5.3p5'></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='7.21.5.3p6'></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='7.21.5.3p7'></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='7.21.5.3p8'></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='7.21.5.3p9'></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='#7.21.9'>7.21.9</a>).
|
|
</pre>
|
|
<a name='7.21.5.4'></a>
|
|
<hr>
|
|
<h3>7.21.5.4 [The freopen function]</h3>
|
|
<a name='7.21.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
FILE *freopen(const char * restrict filename,
|
|
const char * restrict mode,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.4p2'></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.272'><sup>[272]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.272'>
|
|
<pre><i><b>Footnote 272)</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 may be assigned.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.5.4p3'></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='7.21.5.4p4'></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='7.21.5.4p5'></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='7.21.5.5'></a>
|
|
<hr>
|
|
<h3>7.21.5.5 [The setbuf function]</h3>
|
|
<a name='7.21.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void setbuf(FILE * restrict stream,
|
|
char * restrict buf);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.5p2'></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='7.21.5.5p3'></a>
|
|
<pre>3 The setbuf function returns no value.
|
|
Forward references: the setvbuf function (<a href='#7.21.5.6'>7.21.5.6</a>).
|
|
</pre>
|
|
<a name='7.21.5.6'></a>
|
|
<hr>
|
|
<h3>7.21.5.6 [The setvbuf function]</h3>
|
|
<a name='7.21.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int setvbuf(FILE * restrict stream,
|
|
char * restrict buf,
|
|
int mode, size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.5.6p2'></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.273'><sup>[273]</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 contents of the array at any time are
|
|
indeterminate.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.273'>
|
|
<pre><i><b>Footnote 273)</b> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
|
|
before a buffer that has automatic storage duration is deallocated upon block exit.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.5.6p3'></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='7.21.6'></a>
|
|
<hr>
|
|
<h3>7.21.6 [Formatted input/output functions]</h3>
|
|
<a name='7.21.6p1'></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.274'><sup>[274]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.274'>
|
|
<pre><i><b>Footnote 274)</b> The fprintf functions perform writes to memory for the %n specifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.1'></a>
|
|
<hr>
|
|
<h3>7.21.6.1 [The fprintf function]</h3>
|
|
<a name='7.21.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fprintf(FILE * restrict stream,
|
|
const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.1p2'></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='7.21.6.1p3'></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='7.21.6.1p4'></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.275'><sup>[275]</sup></a>
|
|
— An optional precision that gives the minimum number of digits to appear for the 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 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.275'>
|
|
<pre><i><b>Footnote 275)</b> Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.1p5'></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='7.21.6.1p6'></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 negative value is converted if this flag is not
|
|
specified.)<a href='#FOOTNOTE.276'><sup>[276]</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 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 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.276'>
|
|
<pre><i><b>Footnote 276)</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='7.21.6.1p7'></a>
|
|
<pre>7 The length modifiers and their meanings are:
|
|
hh Specifies that a following 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 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 according 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 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 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 conversion specifier applies to a pointer to a long long int
|
|
argument.
|
|
j Specifies that a following 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 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 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.
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
|
|
applies to a long double argument.
|
|
If a length modifier appears with any conversion specifier other than as specified above,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.21.6.1p8'></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.
|
|
o,u,x,X The unsigned int argument is converted to 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.277'><sup>[277]</sup></a>
|
|
e,E A double argument representing a floating-point number is converted in the
|
|
style [−]d.ddd e±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.hhhh p±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.278'><sup>[278]</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.279'><sup>[279]</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.
|
|
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 the initial element of a two-element array of wchar_t, 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 the initial
|
|
element of an array of character type.<a href='#FOOTNOTE.280'><sup>[280]</sup></a> Characters from the array 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 array, the array shall
|
|
contain a null character.
|
|
If an l length modifier is present, the argument shall be a pointer to the initial
|
|
element of an array of wchar_t type. Wide characters from the array 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 array 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 array 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.281'><sup>[281]</sup></a>
|
|
p The argument shall be a pointer to void. 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 into which is written the
|
|
number of characters written to the output stream so far by this call to
|
|
fprintf. 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.277'>
|
|
<pre><i><b>Footnote 277)</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.278'>
|
|
<pre><i><b>Footnote 278)</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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.279'>
|
|
<pre><i><b>Footnote 279)</b> The precision p is sufficient to distinguish values of the source type if 16 p−1 > b n where b is
|
|
FLT_RADIX and n is the number of base-b digits in the significand of the source type. 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.280'>
|
|
<pre><i><b>Footnote 280)</b> No special provisions are made for multibyte characters.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.281'>
|
|
<pre><i><b>Footnote 281)</b> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.1p9'></a>
|
|
<pre>9 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.282'><sup>[282]</sup></a> If any argument is
|
|
not the correct type for the corresponding conversion specification, the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.282'>
|
|
<pre><i><b>Footnote 282)</b> See ‘‘future library directions’’ (<a href='#7.31.11'>7.31.11</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.1p10'></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='7.21.6.1p11'></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='7.21.6.1p12'></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='7.21.6.1p13'></a>
|
|
<pre>13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
|
|
DECIMAL_DIG, then the result should be correctly rounded.<a href='#FOOTNOTE.283'><sup>[283]</sup></a> If the number of
|
|
significant decimal digits is more than DECIMAL_DIG but the source value is exactly
|
|
representable with DECIMAL_DIG 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 DECIMAL_DIG 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.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.283'>
|
|
<pre><i><b>Footnote 283)</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='7.21.6.1p14'></a>
|
|
<pre>14 The fprintf function returns the number of characters transmitted, or a negative value
|
|
if an output or encoding error occurred.
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.21.6.1p15'></a>
|
|
<pre>15 The number of characters that can be produced by any single conversion shall be at least
|
|
4095.
|
|
</pre>
|
|
<a name='7.21.6.1p16'></a>
|
|
<pre>16 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='7.21.6.1p17'></a>
|
|
<pre>17 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='7.21.6.1p18'></a>
|
|
<pre>18 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|
|
|
|
|
Forward references: conversion state (<a href='#7.29.6'>7.29.6</a>), the wcrtomb function (<a href='#7.29.6.3.3'>7.29.6.3.3</a>).
|
|
</pre>
|
|
<a name='7.21.6.2'></a>
|
|
<hr>
|
|
<h3>7.21.6.2 [The fscanf function]</h3>
|
|
<a name='7.21.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fscanf(FILE * restrict stream,
|
|
const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.2p2'></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='7.21.6.2p3'></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='7.21.6.2p4'></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='7.21.6.2p5'></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='7.21.6.2p6'></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='7.21.6.2p7'></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='7.21.6.2p8'></a>
|
|
<pre>8 Input white-space characters (as specified by the isspace function) are skipped, unless
|
|
the specification includes a [, c, or n specifier.<a href='#FOOTNOTE.284'><sup>[284]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.284'>
|
|
<pre><i><b>Footnote 284)</b> These white-space characters are not counted against a specified field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.2p9'></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.285'><sup>[285]</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.285'>
|
|
<pre><i><b>Footnote 285)</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='7.21.6.2p10'></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='7.21.6.2p11'></a>
|
|
<pre>11 The length modifiers and their meanings are:
|
|
hh Specifies that a following 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 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 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 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 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 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.
|
|
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.
|
|
If a length modifier appears with any conversion specifier other than as specified above,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.21.6.2p12'></a>
|
|
<pre>12 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. The corresponding argument shall be a pointer to
|
|
signed integer.
|
|
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. The corresponding argument shall be a pointer to signed
|
|
integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to floating.
|
|
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.286'><sup>[286]</sup></a>
|
|
If no l length modifier is present, the corresponding argument shall be a
|
|
pointer to the initial element of a character array 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 the initial element of an array 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.286'><sup>[286]</sup></a>
|
|
If no l length modifier is present, the corresponding argument shall be a
|
|
pointer to the initial element of a character array 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 the initial element of an array 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.286'><sup>[286]</sup></a>
|
|
If no l length modifier is present, the corresponding argument shall be a
|
|
pointer to the initial element of a character array 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 the initial element of an array 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 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 to 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 to
|
|
signed integer into which is to be written the number of characters read from
|
|
the input stream so far by this call to the fscanf function. 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.286'>
|
|
<pre><i><b>Footnote 286)</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.286'>
|
|
<pre><i><b>Footnote 286)</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.286'>
|
|
<pre><i><b>Footnote 286)</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='7.21.6.2p13'></a>
|
|
<pre>13 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.287'><sup>[287]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.287'>
|
|
<pre><i><b>Footnote 287)</b> See ‘‘future library directions’’ (<a href='#7.31.11'>7.31.11</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.2p14'></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='7.21.6.2p15'></a>
|
|
<pre>15 Trailing white space (including new-line characters) is 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='7.21.6.2p16'></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.
|
|
</pre>
|
|
<a name='7.21.6.2p17'></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='7.21.6.2p18'></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='7.21.6.2p19'></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='7.21.6.2p20'></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='7.21.6.2p21'></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='7.21.6.2p22'></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='7.21.6.2p23'></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='7.21.6.2p24'></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='7.21.6.2p25'></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='7.21.6.2p26'></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='7.21.6.2p27'></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='#7.22.1.3'>7.22.1.3</a>), the
|
|
strtol, strtoll, strtoul, and strtoull functions (<a href='#7.22.1.4'>7.22.1.4</a>), conversion state
|
|
(<a href='#7.29.6'>7.29.6</a>), the wcrtomb function (<a href='#7.29.6.3.3'>7.29.6.3.3</a>).
|
|
</pre>
|
|
<a name='7.21.6.3'></a>
|
|
<hr>
|
|
<h3>7.21.6.3 [The printf function]</h3>
|
|
<a name='7.21.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int printf(const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.3p2'></a>
|
|
<pre>2 The printf function is equivalent to fprintf with the argument stdout interposed
|
|
before the arguments to printf.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.6.3p3'></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='7.21.6.4'></a>
|
|
<hr>
|
|
<h3>7.21.6.4 [The scanf function]</h3>
|
|
<a name='7.21.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int scanf(const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.4p2'></a>
|
|
<pre>2 The scanf function is equivalent to fscanf with the argument stdin interposed
|
|
before the arguments to scanf.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.6.4p3'></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='7.21.6.5'></a>
|
|
<hr>
|
|
<h3>7.21.6.5 [The snprintf function]</h3>
|
|
<a name='7.21.6.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int snprintf(char * restrict s, size_t n,
|
|
const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.5p2'></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='7.21.6.5p3'></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 nonnegative and less than n.
|
|
</pre>
|
|
<a name='7.21.6.6'></a>
|
|
<hr>
|
|
<h3>7.21.6.6 [The sprintf function]</h3>
|
|
<a name='7.21.6.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int sprintf(char * restrict s,
|
|
const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.6p2'></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='7.21.6.6p3'></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='7.21.6.7'></a>
|
|
<hr>
|
|
<h3>7.21.6.7 [The sscanf function]</h3>
|
|
<a name='7.21.6.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int sscanf(const char * restrict s,
|
|
const char * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.7p2'></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='7.21.6.7p3'></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='7.21.6.8'></a>
|
|
<hr>
|
|
<h3>7.21.6.8 [The vfprintf function]</h3>
|
|
<a name='7.21.6.8p1'></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='7.21.6.8p2'></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.288'><sup>[288]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.8p3'></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='7.21.6.8p4'></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='7.21.6.9'></a>
|
|
<hr>
|
|
<h3>7.21.6.9 [The vfscanf function]</h3>
|
|
<a name='7.21.6.9p1'></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='7.21.6.9p2'></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.288'><sup>[288]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.9p3'></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='7.21.6.10'></a>
|
|
<hr>
|
|
<h3>7.21.6.10 [The vprintf function]</h3>
|
|
<a name='7.21.6.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vprintf(const char * restrict format,
|
|
va_list arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.10p2'></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.288'><sup>[288]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.10p3'></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='7.21.6.11'></a>
|
|
<hr>
|
|
<h3>7.21.6.11 [The vscanf function]</h3>
|
|
<a name='7.21.6.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
int vscanf(const char * restrict format,
|
|
va_list arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.6.11p2'></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.288'><sup>[288]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.11p3'></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='7.21.6.12'></a>
|
|
<hr>
|
|
<h3>7.21.6.12 [The vsnprintf function]</h3>
|
|
<a name='7.21.6.12p1'></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='7.21.6.12p2'></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.288'><sup>[288]</sup></a> If copying takes place between objects that overlap, the behavior is
|
|
undefined.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.12p3'></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 nonnegative and less than n.
|
|
</pre>
|
|
<a name='7.21.6.13'></a>
|
|
<hr>
|
|
<h3>7.21.6.13 [The vsprintf function]</h3>
|
|
<a name='7.21.6.13p1'></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='7.21.6.13p2'></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.288'><sup>[288]</sup></a> If copying takes place between objects that overlap, the behavior is
|
|
undefined.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.13p3'></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='7.21.6.14'></a>
|
|
<hr>
|
|
<h3>7.21.6.14 [The vsscanf function]</h3>
|
|
<a name='7.21.6.14p1'></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='7.21.6.14p2'></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.288'><sup>[288]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.288'>
|
|
<pre><i><b>Footnote 288)</b> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
|
|
vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.6.14p3'></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='7.21.7'></a>
|
|
<hr>
|
|
<h3>7.21.7 [Character input/output functions]</h3>
|
|
<a name='7.21.7.1'></a>
|
|
<hr>
|
|
<h3>7.21.7.1 [The fgetc function]</h3>
|
|
<a name='7.21.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fgetc(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.1p2'></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='7.21.7.1p3'></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.289'><sup>[289]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.289'>
|
|
<pre><i><b>Footnote 289)</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='7.21.7.2'></a>
|
|
<hr>
|
|
<h3>7.21.7.2 [The fgets function]</h3>
|
|
<a name='7.21.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
char *fgets(char * restrict s, int n,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.2p2'></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='7.21.7.2p3'></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 array contents are
|
|
indeterminate and a null pointer is returned.
|
|
</pre>
|
|
<a name='7.21.7.3'></a>
|
|
<hr>
|
|
<h3>7.21.7.3 [The fputc function]</h3>
|
|
<a name='7.21.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fputc(int c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.3p2'></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='7.21.7.3p3'></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='7.21.7.4'></a>
|
|
<hr>
|
|
<h3>7.21.7.4 [The fputs function]</h3>
|
|
<a name='7.21.7.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fputs(const char * restrict s,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.4p2'></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='7.21.7.4p3'></a>
|
|
<pre>3 The fputs function returns EOF if a write error occurs; otherwise it returns a
|
|
nonnegative value.
|
|
</pre>
|
|
<a name='7.21.7.5'></a>
|
|
<hr>
|
|
<h3>7.21.7.5 [The getc function]</h3>
|
|
<a name='7.21.7.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int getc(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.5p2'></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='7.21.7.5p3'></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='7.21.7.6'></a>
|
|
<hr>
|
|
<h3>7.21.7.6 [The getchar function]</h3>
|
|
<a name='7.21.7.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int getchar(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.6p2'></a>
|
|
<pre>2 The getchar function is equivalent to getc with the argument stdin.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.7.6p3'></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='7.21.7.7'></a>
|
|
<hr>
|
|
<h3>7.21.7.7 [The putc function]</h3>
|
|
<a name='7.21.7.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int putc(int c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.7p2'></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='7.21.7.7p3'></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='7.21.7.8'></a>
|
|
<hr>
|
|
<h3>7.21.7.8 [The putchar function]</h3>
|
|
<a name='7.21.7.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int putchar(int c);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.8p2'></a>
|
|
<pre>2 The putchar function is equivalent to putc with the second argument stdout.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.7.8p3'></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='7.21.7.9'></a>
|
|
<hr>
|
|
<h3>7.21.7.9 [The puts function]</h3>
|
|
<a name='7.21.7.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int puts(const char *s);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.9p2'></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='7.21.7.9p3'></a>
|
|
<pre>3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
|
|
value.
|
|
</pre>
|
|
<a name='7.21.7.10'></a>
|
|
<hr>
|
|
<h3>7.21.7.10 [The ungetc function]</h3>
|
|
<a name='7.21.7.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int ungetc(int c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.7.10p2'></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='7.21.7.10p3'></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='7.21.7.10p4'></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='7.21.7.10p5'></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. 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 is indeterminate after the
|
|
call.<a href='#FOOTNOTE.290'><sup>[290]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.290'>
|
|
<pre><i><b>Footnote 290)</b> See ‘‘future library directions’’ (<a href='#7.31.11'>7.31.11</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.21.7.10p6'></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='#7.21.9'>7.21.9</a>).
|
|
</pre>
|
|
<a name='7.21.8'></a>
|
|
<hr>
|
|
<h3>7.21.8 [Direct input/output functions]</h3>
|
|
<a name='7.21.8.1'></a>
|
|
<hr>
|
|
<h3>7.21.8.1 [The fread function]</h3>
|
|
<a name='7.21.8.1p1'></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='7.21.8.1p2'></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 value of the file position indicator for the stream is
|
|
indeterminate. If a partial element is read, its value is indeterminate.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.8.1p3'></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='7.21.8.2'></a>
|
|
<hr>
|
|
<h3>7.21.8.2 [The fwrite function]</h3>
|
|
<a name='7.21.8.2p1'></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='7.21.8.2p2'></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 value of the file position indicator for the stream is
|
|
indeterminate.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.8.2p3'></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='7.21.9'></a>
|
|
<hr>
|
|
<h3>7.21.9 [File positioning functions]</h3>
|
|
<a name='7.21.9.1'></a>
|
|
<hr>
|
|
<h3>7.21.9.1 [The fgetpos function]</h3>
|
|
<a name='7.21.9.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fgetpos(FILE * restrict stream,
|
|
fpos_t * restrict pos);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.9.1p2'></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='7.21.9.1p3'></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='#7.21.9.3'>7.21.9.3</a>).
|
|
</pre>
|
|
<a name='7.21.9.2'></a>
|
|
<hr>
|
|
<h3>7.21.9.2 [The fseek function]</h3>
|
|
<a name='7.21.9.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fseek(FILE *stream, long int offset, int whence);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.9.2p2'></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='7.21.9.2p3'></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='7.21.9.2p4'></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='7.21.9.2p5'></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='7.21.9.2p6'></a>
|
|
<pre>6 The fseek function returns nonzero only for a request that cannot be satisfied.
|
|
Forward references: the ftell function (<a href='#7.21.9.4'>7.21.9.4</a>).
|
|
</pre>
|
|
<a name='7.21.9.3'></a>
|
|
<hr>
|
|
<h3>7.21.9.3 [The fsetpos function]</h3>
|
|
<a name='7.21.9.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int fsetpos(FILE *stream, const fpos_t *pos);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.9.3p2'></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='7.21.9.3p3'></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='7.21.9.3p4'></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='7.21.9.4'></a>
|
|
<hr>
|
|
<h3>7.21.9.4 [The ftell function]</h3>
|
|
<a name='7.21.9.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
long int ftell(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.9.4p2'></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='7.21.9.4p3'></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='7.21.9.5'></a>
|
|
<hr>
|
|
<h3>7.21.9.5 [The rewind function]</h3>
|
|
<a name='7.21.9.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void rewind(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.9.5p2'></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='7.21.9.5p3'></a>
|
|
<pre>3 The rewind function returns no value.
|
|
</pre>
|
|
<a name='7.21.10'></a>
|
|
<hr>
|
|
<h3>7.21.10 [Error-handling functions]</h3>
|
|
<a name='7.21.10.1'></a>
|
|
<hr>
|
|
<h3>7.21.10.1 [The clearerr function]</h3>
|
|
<a name='7.21.10.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void clearerr(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.10.1p2'></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='7.21.10.1p3'></a>
|
|
<pre>3 The clearerr function returns no value.
|
|
</pre>
|
|
<a name='7.21.10.2'></a>
|
|
<hr>
|
|
<h3>7.21.10.2 [The feof function]</h3>
|
|
<a name='7.21.10.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int feof(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.10.2p2'></a>
|
|
<pre>2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.10.2p3'></a>
|
|
<pre>3 The feof function returns nonzero if and only if the end-of-file indicator is set for
|
|
stream.
|
|
</pre>
|
|
<a name='7.21.10.3'></a>
|
|
<hr>
|
|
<h3>7.21.10.3 [The ferror function]</h3>
|
|
<a name='7.21.10.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
int ferror(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.10.3p2'></a>
|
|
<pre>2 The ferror function tests the error indicator for the stream pointed to by stream.
|
|
Returns
|
|
</pre>
|
|
<a name='7.21.10.3p3'></a>
|
|
<pre>3 The ferror function returns nonzero if and only if the error indicator is set for
|
|
stream.
|
|
</pre>
|
|
<a name='7.21.10.4'></a>
|
|
<hr>
|
|
<h3>7.21.10.4 [The perror function]</h3>
|
|
<a name='7.21.10.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
void perror(const char *s);
|
|
Description
|
|
</pre>
|
|
<a name='7.21.10.4p2'></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='7.21.10.4p3'></a>
|
|
<pre>3 The perror function returns no value.
|
|
Forward references: the strerror function (<a href='#7.24.6.2'>7.24.6.2</a>).
|
|
</pre>
|
|
<a name='7.22'></a>
|
|
<hr>
|
|
<h3>7.22 [General utilities <stdlib.h>]</h3>
|
|
<a name='7.22p1'></a>
|
|
<pre>1 The header <stdlib.h> declares five types and several functions of general utility, and
|
|
defines several macros.<a href='#FOOTNOTE.291'><sup>[291]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.291'>
|
|
<pre><i><b>Footnote 291)</b> See ‘‘future library directions’’ (<a href='#7.31.12'>7.31.12</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22p2'></a>
|
|
<pre>2 The types declared are size_t and wchar_t (both described in <a href='#7.19'>7.19</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='7.22p3'></a>
|
|
<pre>3 The macros defined are NULL (described in <a href='#7.19'>7.19</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='7.22.1'></a>
|
|
<hr>
|
|
<h3>7.22.1 [Numeric conversion functions]</h3>
|
|
<a name='7.22.1p1'></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='7.22.1.1'></a>
|
|
<hr>
|
|
<h3>7.22.1.1 [The atof function]</h3>
|
|
<a name='7.22.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
double atof(const char *nptr);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.1.1p2'></a>
|
|
<pre>2 The atof function converts the initial portion of the string pointed to by nptr to
|
|
double representation. Except for the behavior on error, it is equivalent to
|
|
strtod(nptr, (char **)NULL)
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.1.1p3'></a>
|
|
<pre>3 The atof function returns the converted value.
|
|
Forward references: the strtod, strtof, and strtold functions (<a href='#7.22.1.3'>7.22.1.3</a>).
|
|
</pre>
|
|
<a name='7.22.1.2'></a>
|
|
<hr>
|
|
<h3>7.22.1.2 [The atoi, atol, and atoll functions]</h3>
|
|
<a name='7.22.1.2p1'></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='7.22.1.2p2'></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, (char **)NULL, 10)
|
|
atol: strtol(nptr, (char **)NULL, 10)
|
|
atoll: strtoll(nptr, (char **)NULL, 10)
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.1.2p3'></a>
|
|
<pre>3 The atoi, atol, and atoll functions return the converted value.
|
|
Forward references: the strtol, strtoll, strtoul, and strtoull functions
|
|
(<a href='#7.22.1.4'>7.22.1.4</a>).
|
|
</pre>
|
|
<a name='7.22.1.3'></a>
|
|
<hr>
|
|
<h3>7.22.1.3 [The strtod, strtof, and strtold functions]</h3>
|
|
<a name='7.22.1.3p1'></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='7.22.1.3p2'></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 (as specified by the isspace function), a
|
|
subject sequence resembling a floating-point 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='7.22.1.3p3'></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
|
|
character, then an optional exponent part as defined in <a href='#6.4.4.2'>6.4.4.2</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>;
|
|
— 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='7.22.1.3p4'></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.292'><sup>[292]</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.293'><sup>[293]</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.292'>
|
|
<pre><i><b>Footnote 292)</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 may 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.293'>
|
|
<pre><i><b>Footnote 293)</b> An implementation may use the n-char sequence to determine extra information to be represented in
|
|
the NaN’s significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.1.3p5'></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='7.22.1.3p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
accepted.
|
|
</pre>
|
|
<a name='7.22.1.3p7'></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='7.22.1.3p8'></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='7.22.1.3p9'></a>
|
|
<pre>9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
|
|
<float.h>) significant digits, the result should be correctly rounded. If the subject
|
|
sequence D has the decimal form and more than DECIMAL_DIG significant digits,
|
|
consider the two bounding, adjacent decimal strings L and U, both having
|
|
DECIMAL_DIG 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.294'><sup>[294]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.294'>
|
|
<pre><i><b>Footnote 294)</b> DECIMAL_DIG, defined in <float.h>, should be sufficiently large that L and U will usually round
|
|
to the same internal floating value, but if not will round to adjacent values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.1.3p10'></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), and the value of the macro ERANGE is stored in
|
|
errno. 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; whether
|
|
errno acquires the value ERANGE is implementation-defined.
|
|
</pre>
|
|
<a name='7.22.1.4'></a>
|
|
<hr>
|
|
<h3>7.22.1.4 [The strtol, strtoll, strtoul, and strtoull functions]</h3>
|
|
<a name='7.22.1.4p1'></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='7.22.1.4p2'></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 (as specified by the isspace function), 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='7.22.1.4p3'></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 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. 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. 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 16, the characters 0x or 0X may
|
|
optionally precede the sequence of letters and digits, following the sign if present.
|
|
</pre>
|
|
<a name='7.22.1.4p4'></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, or if the first non-white-space character is other than a sign or a permissible letter
|
|
or digit.
|
|
</pre>
|
|
<a name='7.22.1.4p5'></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='7.22.1.4p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
accepted.
|
|
</pre>
|
|
<a name='7.22.1.4p7'></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='7.22.1.4p8'></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='7.22.2'></a>
|
|
<hr>
|
|
<h3>7.22.2 [Pseudo-random sequence generation functions]</h3>
|
|
<a name='7.22.2.1'></a>
|
|
<hr>
|
|
<h3>7.22.2.1 [The rand function]</h3>
|
|
<a name='7.22.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int rand(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.2.1p2'></a>
|
|
<pre>2 The rand function computes a sequence of pseudo-random integers in the range 0 to
|
|
RAND_MAX.<a href='#FOOTNOTE.295'><sup>[295]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.295'>
|
|
<pre><i><b>Footnote 295)</b> There are no guarantees as to the quality of the random sequence produced and some implementations
|
|
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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.2.1p3'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.2.1p4'></a>
|
|
<pre>4 The rand function returns a pseudo-random integer.
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.22.2.1p5'></a>
|
|
<pre>5 The value of the RAND_MAX macro shall be at least 32767.
|
|
</pre>
|
|
<a name='7.22.2.2'></a>
|
|
<hr>
|
|
<h3>7.22.2.2 [The srand function]</h3>
|
|
<a name='7.22.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void srand(unsigned int seed);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.2.2p2'></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='7.22.2.2p3'></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='7.22.2.2p4'></a>
|
|
<pre>4 The srand function returns no value.
|
|
</pre>
|
|
<a name='7.22.2.2p5'></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='7.22.3'></a>
|
|
<hr>
|
|
<h3>7.22.3 [Memory management functions]</h3>
|
|
<a name='7.22.3p1'></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 then 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, 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='7.22.3p2'></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. A call to free or realloc that
|
|
deallocates a region p of memory synchronizes with any allocation call that allocates all
|
|
or part of the region p. This synchronization occurs after any access of p by the
|
|
deallocating function, and before any such access by the allocating function.
|
|
</pre>
|
|
<a name='7.22.3.1'></a>
|
|
<hr>
|
|
<h3>7.22.3.1 [The aligned_alloc function]</h3>
|
|
<a name='7.22.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *aligned_alloc(size_t alignment, size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.3.1p2'></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 value is
|
|
indeterminate. The value of alignment shall be a valid alignment supported by the
|
|
implementation and the value of size shall be an integral multiple of alignment.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.3.1p3'></a>
|
|
<pre>3 The aligned_alloc function returns either a null pointer or a pointer to the allocated
|
|
space.
|
|
</pre>
|
|
<a name='7.22.3.2'></a>
|
|
<hr>
|
|
<h3>7.22.3.2 [The calloc function]</h3>
|
|
<a name='7.22.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *calloc(size_t nmemb, size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.3.2p2'></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.296'><sup>[296]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.296'>
|
|
<pre><i><b>Footnote 296)</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='7.22.3.2p3'></a>
|
|
<pre>3 The calloc function returns either a null pointer or a pointer to the allocated space.
|
|
</pre>
|
|
<a name='7.22.3.3'></a>
|
|
<hr>
|
|
<h3>7.22.3.3 [The free function]</h3>
|
|
<a name='7.22.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void free(void *ptr);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.3.3p2'></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='7.22.3.3p3'></a>
|
|
<pre>3 The free function returns no value.
|
|
</pre>
|
|
<a name='7.22.3.4'></a>
|
|
<hr>
|
|
<h3>7.22.3.4 [The malloc function]</h3>
|
|
<a name='7.22.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *malloc(size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.3.4p2'></a>
|
|
<pre>2 The malloc function allocates space for an object whose size is specified by size and
|
|
whose value is indeterminate.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.3.4p3'></a>
|
|
<pre>3 The malloc function returns either a null pointer or a pointer to the allocated space.
|
|
</pre>
|
|
<a name='7.22.3.5'></a>
|
|
<hr>
|
|
<h3>7.22.3.5 [The realloc function]</h3>
|
|
<a name='7.22.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
void *realloc(void *ptr, size_t size);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.3.5p2'></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
|
|
indeterminate values.
|
|
</pre>
|
|
<a name='7.22.3.5p3'></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, the behavior is undefined. If memory for the new object cannot be
|
|
allocated, the old object is not deallocated and its value is unchanged.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.3.5p4'></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 could not be
|
|
allocated.
|
|
</pre>
|
|
<a name='7.22.4'></a>
|
|
<hr>
|
|
<h3>7.22.4 [Communication with the environment]</h3>
|
|
<a name='7.22.4.1'></a>
|
|
<hr>
|
|
<h3>7.22.4.1 [The abort function]</h3>
|
|
<a name='7.22.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
_Noreturn void abort(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.1p2'></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='7.22.4.1p3'></a>
|
|
<pre>3 The abort function does not return to its caller.
|
|
</pre>
|
|
<a name='7.22.4.2'></a>
|
|
<hr>
|
|
<h3>7.22.4.2 [The atexit function]</h3>
|
|
<a name='7.22.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int atexit(void (*func)(void));
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.2p2'></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.297'><sup>[297]</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.297'>
|
|
<pre><i><b>Footnote 297)</b> The atexit function registrations are distinct from the at_quick_exit registrations, so
|
|
applications may need to call both registration functions with the same argument.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.4.2p3'></a>
|
|
<pre>3 The implementation shall support the registration of at least 32 functions.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.4.2p4'></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='#7.22.4.3'>7.22.4.3</a>), the exit function
|
|
(<a href='#7.22.4.4'>7.22.4.4</a>).
|
|
</pre>
|
|
<a name='7.22.4.3'></a>
|
|
<hr>
|
|
<h3>7.22.4.3 [The at_quick_exit function]</h3>
|
|
<a name='7.22.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int at_quick_exit(void (*func)(void));
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.3p2'></a>
|
|
<pre>2 The at_quick_exit function registers the function pointed to by func, to be called
|
|
without arguments should quick_exit be called.<a href='#FOOTNOTE.298'><sup>[298]</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.298'>
|
|
<pre><i><b>Footnote 298)</b> The at_quick_exit function registrations are distinct from the atexit registrations, so
|
|
applications may need to call both registration functions with the same argument.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.4.3p3'></a>
|
|
<pre>3 The implementation shall support the registration of at least 32 functions.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.4.3p4'></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='#7.22.4.7'>7.22.4.7</a>).
|
|
</pre>
|
|
<a name='7.22.4.4'></a>
|
|
<hr>
|
|
<h3>7.22.4.4 [The exit function]</h3>
|
|
<a name='7.22.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
_Noreturn void exit(int status);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.4p2'></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='7.22.4.4p3'></a>
|
|
<pre>3 First, all functions registered by the atexit function are called, in the reverse order of
|
|
their registration,<a href='#FOOTNOTE.299'><sup>[299]</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.299'>
|
|
<pre><i><b>Footnote 299)</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='7.22.4.4p4'></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='7.22.4.4p5'></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='7.22.4.4p6'></a>
|
|
<pre>6 The exit function cannot return to its caller.
|
|
</pre>
|
|
<a name='7.22.4.5'></a>
|
|
<hr>
|
|
<h3>7.22.4.5 [The _Exit function]</h3>
|
|
<a name='7.22.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
_Noreturn void _Exit(int status);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.5p2'></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='#7.22.4.4'>7.22.4.4</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='7.22.4.5p3'></a>
|
|
<pre>3 The _Exit function cannot return to its caller.
|
|
</pre>
|
|
<a name='7.22.4.6'></a>
|
|
<hr>
|
|
<h3>7.22.4.6 [The getenv function]</h3>
|
|
<a name='7.22.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
char *getenv(const char *name);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.6p2'></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.300'><sup>[300]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.300'>
|
|
<pre><i><b>Footnote 300)</b> Many implementations provide non-standard functions that modify the environment list.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.4.6p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the getenv function.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.4.6p4'></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='7.22.4.7'></a>
|
|
<hr>
|
|
<h3>7.22.4.7 [The quick_exit function]</h3>
|
|
<a name='7.22.4.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
_Noreturn void quick_exit(int status);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.7p2'></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='7.22.4.7p3'></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.301'><sup>[301]</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.301'>
|
|
<pre><i><b>Footnote 301)</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='7.22.4.7p4'></a>
|
|
<pre>4 Then control is returned to the host environment by means of the function call
|
|
_Exit(status).
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.4.7p5'></a>
|
|
<pre>5 The quick_exit function cannot return to its caller.
|
|
</pre>
|
|
<a name='7.22.4.8'></a>
|
|
<hr>
|
|
<h3>7.22.4.8 [The system function]</h3>
|
|
<a name='7.22.4.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int system(const char *string);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.4.8p2'></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='7.22.4.8p3'></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='7.22.5'></a>
|
|
<hr>
|
|
<h3>7.22.5 [Searching and sorting utilities]</h3>
|
|
<a name='7.22.5p1'></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='7.22.5p2'></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.302'><sup>[302]</sup></a> The first argument when called from bsearch
|
|
shall equal key.
|
|
</pre>
|
|
<a name='FOOTNOTE.302'>
|
|
<pre><i><b>Footnote 302)</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='7.22.5p3'></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='7.22.5p4'></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='7.22.5p5'></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='7.22.5.1'></a>
|
|
<hr>
|
|
<h3>7.22.5.1 [The bsearch function]</h3>
|
|
<a name='7.22.5.1p1'></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='7.22.5.1p2'></a>
|
|
<pre>2 The bsearch 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='7.22.5.1p3'></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.303'><sup>[303]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.303'>
|
|
<pre><i><b>Footnote 303)</b> In practice, the entire array is sorted according to the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.5.1p4'></a>
|
|
<pre>4 The bsearch 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='7.22.5.2'></a>
|
|
<hr>
|
|
<h3>7.22.5.2 [The qsort function]</h3>
|
|
<a name='7.22.5.2p1'></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='7.22.5.2p2'></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='7.22.5.2p3'></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='7.22.5.2p4'></a>
|
|
<pre>4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.5.2p5'></a>
|
|
<pre>5 The qsort function returns no value.
|
|
</pre>
|
|
<a name='7.22.6'></a>
|
|
<hr>
|
|
<h3>7.22.6 [Integer arithmetic functions]</h3>
|
|
<a name='7.22.6.1'></a>
|
|
<hr>
|
|
<h3>7.22.6.1 [The abs, labs and llabs functions]</h3>
|
|
<a name='7.22.6.1p1'></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='7.22.6.1p2'></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.304'><sup>[304]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.304'>
|
|
<pre><i><b>Footnote 304)</b> The absolute value of the most negative number cannot be represented in two’s complement.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.6.1p3'></a>
|
|
<pre>3 The abs, labs, and llabs, functions return the absolute value.
|
|
</pre>
|
|
<a name='7.22.6.2'></a>
|
|
<hr>
|
|
<h3>7.22.6.2 [The div, ldiv, and lldiv functions]</h3>
|
|
<a name='7.22.6.2p1'></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='7.22.6.2p2'></a>
|
|
<pre>2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
|
|
denom in a single operation.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.6.2p3'></a>
|
|
<pre>3 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
|
|
lldiv_t, respectively, 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='7.22.7'></a>
|
|
<hr>
|
|
<h3>7.22.7 [Multibyte/wide character conversion functions]</h3>
|
|
<a name='7.22.7p1'></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 function is placed into its
|
|
initial conversion state at program startup 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. A call with s as a null pointer causes these functions to return a nonzero value
|
|
if encodings have state dependency, and zero otherwise.<a href='#FOOTNOTE.305'><sup>[305]</sup></a> Changing the LC_CTYPE
|
|
category causes the conversion state of these functions to be indeterminate.
|
|
</pre>
|
|
<a name='FOOTNOTE.305'>
|
|
<pre><i><b>Footnote 305)</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='7.22.7.1'></a>
|
|
<hr>
|
|
<h3>7.22.7.1 [The mblen function]</h3>
|
|
<a name='7.22.7.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int mblen(const char *s, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.7.1p2'></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);
|
|
</pre>
|
|
<a name='7.22.7.1p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the mblen function.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.7.1p4'></a>
|
|
<pre>4 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='#7.22.7.2'>7.22.7.2</a>).
|
|
</pre>
|
|
<a name='7.22.7.2'></a>
|
|
<hr>
|
|
<h3>7.22.7.2 [The mbtowc function]</h3>
|
|
<a name='7.22.7.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int mbtowc(wchar_t * restrict pwc,
|
|
const char * restrict s,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.7.2p2'></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='7.22.7.2p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the mbtowc function.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.7.2p4'></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='7.22.7.2p5'></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='7.22.7.3'></a>
|
|
<hr>
|
|
<h3>7.22.7.3 [The wctomb function]</h3>
|
|
<a name='7.22.7.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdlib.h>
|
|
int wctomb(char *s, wchar_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.22.7.3p2'></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='7.22.7.3p3'></a>
|
|
<pre>3 The implementation shall behave as if no library function calls the wctomb function.
|
|
Returns
|
|
</pre>
|
|
<a name='7.22.7.3p4'></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='7.22.7.3p5'></a>
|
|
<pre>5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
|
|
</pre>
|
|
<a name='7.22.8'></a>
|
|
<hr>
|
|
<h3>7.22.8 [Multibyte/wide string conversion functions]</h3>
|
|
<a name='7.22.8p1'></a>
|
|
<pre>1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
|
|
the current locale.
|
|
</pre>
|
|
<a name='7.22.8.1'></a>
|
|
<hr>
|
|
<h3>7.22.8.1 [The mbstowcs function]</h3>
|
|
<a name='7.22.8.1p1'></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='7.22.8.1p2'></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='7.22.8.1p3'></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='7.22.8.1p4'></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.306'><sup>[306]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.306'>
|
|
<pre><i><b>Footnote 306)</b> The array will not be null-terminated if the value returned is n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.22.8.2'></a>
|
|
<hr>
|
|
<h3>7.22.8.2 [The wcstombs function]</h3>
|
|
<a name='7.22.8.2p1'></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='7.22.8.2p2'></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='7.22.8.2p3'></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='7.22.8.2p4'></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.306'><sup>[306]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.306'>
|
|
<pre><i><b>Footnote 306)</b> The array will not be null-terminated if the value returned is n.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.23'></a>
|
|
<hr>
|
|
<h3>7.23 [_Noreturn <stdnoreturn.h>]</h3>
|
|
<a name='7.23p1'></a>
|
|
<pre>1 The header <stdnoreturn.h> defines the macro
|
|
noreturn
|
|
which expands to _Noreturn.
|
|
</pre>
|
|
<a name='7.24'></a>
|
|
<hr>
|
|
<h3>7.24 [String handling <string.h>]</h3>
|
|
<a name='7.24.1'></a>
|
|
<hr>
|
|
<h3>7.24.1 [String function conventions]</h3>
|
|
<a name='7.24.1p1'></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.307'><sup>[307]</sup></a> The type is size_t and the macro is NULL (both described in
|
|
<a href='#7.19'>7.19</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.307'>
|
|
<pre><i><b>Footnote 307)</b> See ‘‘future library directions’’ (<a href='#7.31.13'>7.31.13</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.1p2'></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='7.24.1p3'></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='7.24.2'></a>
|
|
<hr>
|
|
<h3>7.24.2 [Copying functions]</h3>
|
|
<a name='7.24.2.1'></a>
|
|
<hr>
|
|
<h3>7.24.2.1 [The memcpy function]</h3>
|
|
<a name='7.24.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memcpy(void * restrict s1,
|
|
const void * restrict s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.1p2'></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='7.24.2.1p3'></a>
|
|
<pre>3 The memcpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.24.2.2'></a>
|
|
<hr>
|
|
<h3>7.24.2.2 [The memmove function]</h3>
|
|
<a name='7.24.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memmove(void *s1, const void *s2, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.2p2'></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='7.24.2.2p3'></a>
|
|
<pre>3 The memmove function returns the value of s1.
|
|
</pre>
|
|
<a name='7.24.2.3'></a>
|
|
<hr>
|
|
<h3>7.24.2.3 [The strcpy function]</h3>
|
|
<a name='7.24.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strcpy(char * restrict s1,
|
|
const char * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.3p2'></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='7.24.2.3p3'></a>
|
|
<pre>3 The strcpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.24.2.4'></a>
|
|
<hr>
|
|
<h3>7.24.2.4 [The strncpy function]</h3>
|
|
<a name='7.24.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strncpy(char * restrict s1,
|
|
const char * restrict s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.2.4p2'></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.308'><sup>[308]</sup></a> If copying takes place between objects that overlap, the behavior is undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.308'>
|
|
<pre><i><b>Footnote 308)</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='7.24.2.4p3'></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='7.24.2.4p4'></a>
|
|
<pre>4 The strncpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.24.3'></a>
|
|
<hr>
|
|
<h3>7.24.3 [Concatenation functions]</h3>
|
|
<a name='7.24.3.1'></a>
|
|
<hr>
|
|
<h3>7.24.3.1 [The strcat function]</h3>
|
|
<a name='7.24.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strcat(char * restrict s1,
|
|
const char * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.1p2'></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='7.24.3.1p3'></a>
|
|
<pre>3 The strcat function returns the value of s1.
|
|
</pre>
|
|
<a name='7.24.3.2'></a>
|
|
<hr>
|
|
<h3>7.24.3.2 [The strncat function]</h3>
|
|
<a name='7.24.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strncat(char * restrict s1,
|
|
const char * restrict s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.3.2p2'></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.309'><sup>[309]</sup></a> If copying
|
|
takes place between objects that overlap, the behavior is undefined.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.309'>
|
|
<pre><i><b>Footnote 309)</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='7.24.3.2p3'></a>
|
|
<pre>3 The strncat function returns the value of s1.
|
|
Forward references: the strlen function (<a href='#7.24.6.3'>7.24.6.3</a>).
|
|
</pre>
|
|
<a name='7.24.4'></a>
|
|
<hr>
|
|
<h3>7.24.4 [Comparison functions]</h3>
|
|
<a name='7.24.4p1'></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='7.24.4.1'></a>
|
|
<hr>
|
|
<h3>7.24.4.1 [The memcmp function]</h3>
|
|
<a name='7.24.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int memcmp(const void *s1, const void *s2, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.1p2'></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 s2.<a href='#FOOTNOTE.310'><sup>[310]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.310'>
|
|
<pre><i><b>Footnote 310)</b> The contents of ‘‘holes’’ used as padding for purposes of alignment within structure objects are
|
|
indeterminate. Strings shorter than their allocated space and unions may also cause problems in
|
|
comparison.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.4.1p3'></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='7.24.4.2'></a>
|
|
<hr>
|
|
<h3>7.24.4.2 [The strcmp function]</h3>
|
|
<a name='7.24.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strcmp(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.2p2'></a>
|
|
<pre>2 The strcmp function compares the string pointed to by s1 to the string pointed to by
|
|
s2.
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.4.2p3'></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='7.24.4.3'></a>
|
|
<hr>
|
|
<h3>7.24.4.3 [The strcoll function]</h3>
|
|
<a name='7.24.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strcoll(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.3p2'></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='7.24.4.3p3'></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='7.24.4.4'></a>
|
|
<hr>
|
|
<h3>7.24.4.4 [The strncmp function]</h3>
|
|
<a name='7.24.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
int strncmp(const char *s1, const char *s2, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.4p2'></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='7.24.4.4p3'></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='7.24.4.5'></a>
|
|
<hr>
|
|
<h3>7.24.4.5 [The strxfrm function]</h3>
|
|
<a name='7.24.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strxfrm(char * restrict s1,
|
|
const char * restrict s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.4.5p2'></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='7.24.4.5p3'></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 contents of the array
|
|
pointed to by s1 are indeterminate.
|
|
</pre>
|
|
<a name='7.24.4.5p4'></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='7.24.5'></a>
|
|
<hr>
|
|
<h3>7.24.5 [Search functions]</h3>
|
|
<a name='7.24.5.1'></a>
|
|
<hr>
|
|
<h3>7.24.5.1 [The memchr function]</h3>
|
|
<a name='7.24.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memchr(const void *s, int c, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.1p2'></a>
|
|
<pre>2 The memchr 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='7.24.5.1p3'></a>
|
|
<pre>3 The memchr function returns a pointer to the located character, or a null pointer if the
|
|
character does not occur in the object.
|
|
</pre>
|
|
<a name='7.24.5.2'></a>
|
|
<hr>
|
|
<h3>7.24.5.2 [The strchr function]</h3>
|
|
<a name='7.24.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strchr(const char *s, int c);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.2p2'></a>
|
|
<pre>2 The strchr 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='7.24.5.2p3'></a>
|
|
<pre>3 The strchr function returns a pointer to the located character, or a null pointer if the
|
|
character does not occur in the string.
|
|
</pre>
|
|
<a name='7.24.5.3'></a>
|
|
<hr>
|
|
<h3>7.24.5.3 [The strcspn function]</h3>
|
|
<a name='7.24.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strcspn(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.3p2'></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='7.24.5.3p3'></a>
|
|
<pre>3 The strcspn function returns the length of the segment.
|
|
</pre>
|
|
<a name='7.24.5.4'></a>
|
|
<hr>
|
|
<h3>7.24.5.4 [The strpbrk function]</h3>
|
|
<a name='7.24.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strpbrk(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.4p2'></a>
|
|
<pre>2 The strpbrk 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='7.24.5.4p3'></a>
|
|
<pre>3 The strpbrk function returns a pointer to the character, or a null pointer if no character
|
|
from s2 occurs in s1.
|
|
</pre>
|
|
<a name='7.24.5.5'></a>
|
|
<hr>
|
|
<h3>7.24.5.5 [The strrchr function]</h3>
|
|
<a name='7.24.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strrchr(const char *s, int c);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.5p2'></a>
|
|
<pre>2 The strrchr 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='7.24.5.5p3'></a>
|
|
<pre>3 The strrchr function returns a pointer to the character, or a null pointer if c does not
|
|
occur in the string.
|
|
</pre>
|
|
<a name='7.24.5.6'></a>
|
|
<hr>
|
|
<h3>7.24.5.6 [The strspn function]</h3>
|
|
<a name='7.24.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strspn(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.6p2'></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='7.24.5.6p3'></a>
|
|
<pre>3 The strspn function returns the length of the segment.
|
|
</pre>
|
|
<a name='7.24.5.7'></a>
|
|
<hr>
|
|
<h3>7.24.5.7 [The strstr function]</h3>
|
|
<a name='7.24.5.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strstr(const char *s1, const char *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.7p2'></a>
|
|
<pre>2 The strstr 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='7.24.5.7p3'></a>
|
|
<pre>3 The strstr 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='7.24.5.8'></a>
|
|
<hr>
|
|
<h3>7.24.5.8 [The strtok function]</h3>
|
|
<a name='7.24.5.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strtok(char * restrict s1,
|
|
const char * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.5.8p2'></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. The separator string pointed to by s2 may be
|
|
different from call to call.
|
|
</pre>
|
|
<a name='7.24.5.8p3'></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='7.24.5.8p4'></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='7.24.5.8p5'></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='7.24.5.8p6'></a>
|
|
<pre>6 The strtok function is not required to avoid data races with other calls to the strtok
|
|
function.<a href='#FOOTNOTE.311'><sup>[311]</sup></a> The implementation shall behave as if no library function calls the strtok
|
|
function.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.311'>
|
|
<pre><i><b>Footnote 311)</b> The strtok_s function can be used instead to avoid data races.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.5.8p7'></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='7.24.5.8p8'></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='7.24.6'></a>
|
|
<hr>
|
|
<h3>7.24.6 [Miscellaneous functions]</h3>
|
|
<a name='7.24.6.1'></a>
|
|
<hr>
|
|
<h3>7.24.6.1 [The memset function]</h3>
|
|
<a name='7.24.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
void *memset(void *s, int c, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.6.1p2'></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='7.24.6.1p3'></a>
|
|
<pre>3 The memset function returns the value of s.
|
|
</pre>
|
|
<a name='7.24.6.2'></a>
|
|
<hr>
|
|
<h3>7.24.6.2 [The strerror function]</h3>
|
|
<a name='7.24.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
char *strerror(int errnum);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.6.2p2'></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='7.24.6.2p3'></a>
|
|
<pre>3 The strerror function is not required to avoid data races with other calls to the
|
|
strerror function.<a href='#FOOTNOTE.312'><sup>[312]</sup></a> The implementation shall behave as if no library function calls
|
|
the strerror function.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.312'>
|
|
<pre><i><b>Footnote 312)</b> The strerror_s function can be used instead to avoid data races.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.24.6.2p4'></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, but may be
|
|
overwritten by a subsequent call to the strerror function.
|
|
Forward references: The strerror_s function (<a href='#K.3.7.4.2'>K.3.7.4.2</a>).
|
|
</pre>
|
|
<a name='7.24.6.3'></a>
|
|
<hr>
|
|
<h3>7.24.6.3 [The strlen function]</h3>
|
|
<a name='7.24.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <string.h>
|
|
size_t strlen(const char *s);
|
|
Description
|
|
</pre>
|
|
<a name='7.24.6.3p2'></a>
|
|
<pre>2 The strlen function computes the length of the string pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='7.24.6.3p3'></a>
|
|
<pre>3 The strlen function returns the number of characters that precede the terminating null
|
|
character.
|
|
</pre>
|
|
<a name='7.25'></a>
|
|
<hr>
|
|
<h3>7.25 [Type-generic math <tgmath.h>]</h3>
|
|
<a name='7.25p1'></a>
|
|
<pre>1 The header <tgmath.h> includes the headers <math.h> and <complex.h> and
|
|
defines several type-generic macros.
|
|
</pre>
|
|
<a name='7.25p2'></a>
|
|
<pre>2 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 modf, there is a corresponding type-generic
|
|
macro.<a href='#FOOTNOTE.313'><sup>[313]</sup></a> The parameters whose corresponding real type is double in the function
|
|
synopsis are generic parameters. Use of the macro invokes a function whose
|
|
corresponding real type and type domain are determined by the arguments for the generic
|
|
parameters.<a href='#FOOTNOTE.314'><sup>[314]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.313'>
|
|
<pre><i><b>Footnote 313)</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.314'>
|
|
<pre><i><b>Footnote 314)</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='7.25p3'></a>
|
|
<pre>3 Use of the macro invokes a function whose generic parameters have the corresponding
|
|
real type determined as follows:
|
|
— First, if any argument for generic parameters has type long double, the type
|
|
determined is long double.
|
|
— Otherwise, if any argument for generic parameters has type double or is of integer
|
|
type, the type determined is double.
|
|
— Otherwise, the type determined is float.
|
|
</pre>
|
|
<a name='7.25p4'></a>
|
|
<pre>4 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='7.25p5'></a>
|
|
<pre>5 For each unsuffixed function in <math.h> without a c-prefixed counterpart in
|
|
<complex.h> (except modf), the corresponding type-generic macro has the same
|
|
name as the function. These type-generic macros are:
|
|
atan2 fma llround remainder
|
|
cbrt fmax log10 remquo
|
|
ceil fmin log1p rint
|
|
copysign fmod log2 round
|
|
erf frexp logb scalbn
|
|
erfc hypot lrint scalbln
|
|
exp2 ilogb lround tgamma
|
|
expm1 ldexp nearbyint trunc
|
|
fdim lgamma nextafter
|
|
floor llrint nexttoward
|
|
If all arguments for generic parameters are real, then use of the macro invokes a real
|
|
function; otherwise, use of the macro results in undefined behavior.
|
|
</pre>
|
|
<a name='7.25p6'></a>
|
|
<pre>6 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 conj creal
|
|
cimag cproj
|
|
Use of the macro with any real or complex argument invokes a complex function.
|
|
</pre>
|
|
<a name='7.25p7'></a>
|
|
<pre>7 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;
|
|
functions invoked by use of type-generic macros are shown in the following table:
|
|
macro use invokes
|
|
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 behavior
|
|
rint(dc) undefined behavior
|
|
fmax(ldc, ld) undefined behavior
|
|
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)
|
|
</pre>
|
|
<a name='7.26'></a>
|
|
<hr>
|
|
<h3>7.26 [Threads <threads.h>]</h3>
|
|
<a name='7.26.1'></a>
|
|
<hr>
|
|
<h3>7.26.1 [Introduction]</h3>
|
|
<a name='7.26.1p1'></a>
|
|
<pre>1 The header <threads.h> includes the header <time.h>, defines macros, and
|
|
declares types, enumeration constants, and functions that support multiple threads of
|
|
execution.<a href='#FOOTNOTE.315'><sup>[315]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.315'>
|
|
<pre><i><b>Footnote 315)</b> See ‘‘future library directions’’ (<a href='#7.31.15'>7.31.15</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.26.1p2'></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='7.26.1p3'></a>
|
|
<pre>3 The macros are
|
|
thread_local
|
|
which expands to _Thread_local;
|
|
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='7.26.1p4'></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='7.26.1p5'></a>
|
|
<pre>5 The enumeration constants are
|
|
mtx_plain
|
|
which is passed to mtx_init to create a mutex object that supports neither timeout nor
|
|
test and return;
|
|
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='#7.27'>7.27</a>).
|
|
</pre>
|
|
<a name='7.26.2'></a>
|
|
<hr>
|
|
<h3>7.26.2 [Initialization functions]</h3>
|
|
<a name='7.26.2.1'></a>
|
|
<hr>
|
|
<h3>7.26.2.1 [The call_once function]</h3>
|
|
<a name='7.26.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void call_once(once_flag *flag, void (*func)(void));
|
|
Description
|
|
</pre>
|
|
<a name='7.26.2.1p2'></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='7.26.2.1p3'></a>
|
|
<pre>3 The call_once function returns no value.
|
|
</pre>
|
|
<a name='7.26.3'></a>
|
|
<hr>
|
|
<h3>7.26.3 [Condition variable functions]</h3>
|
|
<a name='7.26.3.1'></a>
|
|
<hr>
|
|
<h3>7.26.3.1 [The cnd_broadcast function]</h3>
|
|
<a name='7.26.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_broadcast(cnd_t *cond);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.1p2'></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='7.26.3.1p3'></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='7.26.3.2'></a>
|
|
<hr>
|
|
<h3>7.26.3.2 [The cnd_destroy function]</h3>
|
|
<a name='7.26.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void cnd_destroy(cnd_t *cond);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.2p2'></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='7.26.3.2p3'></a>
|
|
<pre>3 The cnd_destroy function returns no value.
|
|
</pre>
|
|
<a name='7.26.3.3'></a>
|
|
<hr>
|
|
<h3>7.26.3.3 [The cnd_init function]</h3>
|
|
<a name='7.26.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_init(cnd_t *cond);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.3p2'></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='7.26.3.3p3'></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='7.26.3.4'></a>
|
|
<hr>
|
|
<h3>7.26.3.4 [The cnd_signal function]</h3>
|
|
<a name='7.26.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_signal(cnd_t *cond);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.4p2'></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 return
|
|
success.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.3.4p3'></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='7.26.3.5'></a>
|
|
<hr>
|
|
<h3>7.26.3.5 [The cnd_timedwait function]</h3>
|
|
<a name='7.26.3.5p1'></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='7.26.3.5p2'></a>
|
|
<pre>2 The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and
|
|
endeavors to block 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. 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='7.26.3.5p3'></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='7.26.3.6'></a>
|
|
<hr>
|
|
<h3>7.26.3.6 [The cnd_wait function]</h3>
|
|
<a name='7.26.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int cnd_wait(cnd_t *cond, mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.3.6p2'></a>
|
|
<pre>2 The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors
|
|
to block until the condition variable pointed to by cond is signaled by a call to
|
|
cnd_signal or to cnd_broadcast. 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='7.26.3.6p3'></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='7.26.4'></a>
|
|
<hr>
|
|
<h3>7.26.4 [Mutex functions]</h3>
|
|
<a name='7.26.4.1'></a>
|
|
<hr>
|
|
<h3>7.26.4.1 [The mtx_destroy function]</h3>
|
|
<a name='7.26.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void mtx_destroy(mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.1p2'></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='7.26.4.1p3'></a>
|
|
<pre>3 The mtx_destroy function returns no value.
|
|
</pre>
|
|
<a name='7.26.4.2'></a>
|
|
<hr>
|
|
<h3>7.26.4.2 [The mtx_init function]</h3>
|
|
<a name='7.26.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_init(mtx_t *mtx, int type);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.2p2'></a>
|
|
<pre>2 The mtx_init function creates a mutex object with properties indicated by type,
|
|
which must have one of the six 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='7.26.4.2p3'></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='7.26.4.2p4'></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='7.26.4.3'></a>
|
|
<hr>
|
|
<h3>7.26.4.3 [The mtx_lock function]</h3>
|
|
<a name='7.26.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_lock(mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.3p2'></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 shall synchronize with this operation.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.3p3'></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='7.26.4.4'></a>
|
|
<hr>
|
|
<h3>7.26.4.4 [The mtx_timedlock function]</h3>
|
|
<a name='7.26.4.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_timedlock(mtx_t *restrict mtx,
|
|
const struct timespec *restrict ts);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.4p2'></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 shall synchronize with this operation.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.4p3'></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='7.26.4.5'></a>
|
|
<hr>
|
|
<h3>7.26.4.5 [The mtx_trylock function]</h3>
|
|
<a name='7.26.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_trylock(mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.5p2'></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 shall synchronize with this operation.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.4.5p3'></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.
|
|
</pre>
|
|
<a name='7.26.4.6'></a>
|
|
<hr>
|
|
<h3>7.26.4.6 [The mtx_unlock function]</h3>
|
|
<a name='7.26.4.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int mtx_unlock(mtx_t *mtx);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.4.6p2'></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='7.26.4.6p3'></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='7.26.5'></a>
|
|
<hr>
|
|
<h3>7.26.5 [Thread functions]</h3>
|
|
<a name='7.26.5.1'></a>
|
|
<hr>
|
|
<h3>7.26.5.1 [The thrd_create function]</h3>
|
|
<a name='7.26.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_create(thrd_t *thr, thrd_start_t func,
|
|
void *arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.1p2'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.1p3'></a>
|
|
<pre>3 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='7.26.5.2'></a>
|
|
<hr>
|
|
<h3>7.26.5.2 [The thrd_current function]</h3>
|
|
<a name='7.26.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
thrd_t thrd_current(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.2p2'></a>
|
|
<pre>2 The thrd_current function identifies the thread that called it.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.2p3'></a>
|
|
<pre>3 The thrd_current function returns the identifier of the thread that called it.
|
|
</pre>
|
|
<a name='7.26.5.3'></a>
|
|
<hr>
|
|
<h3>7.26.5.3 [The thrd_detach function]</h3>
|
|
<a name='7.26.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_detach(thrd_t thr);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.3p2'></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='7.26.5.3p3'></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='7.26.5.4'></a>
|
|
<hr>
|
|
<h3>7.26.5.4 [The thrd_equal function]</h3>
|
|
<a name='7.26.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_equal(thrd_t thr0, thrd_t thr1);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.4p2'></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='7.26.5.4p3'></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='7.26.5.5'></a>
|
|
<hr>
|
|
<h3>7.26.5.5 [The thrd_exit function]</h3>
|
|
<a name='7.26.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
_Noreturn void thrd_exit(int res);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.5p2'></a>
|
|
<pre>2 The thrd_exit function terminates execution of the calling thread and sets its result
|
|
code to res.
|
|
</pre>
|
|
<a name='7.26.5.5p3'></a>
|
|
<pre>3 The program shall terminate normally after the last thread has been terminated. The
|
|
behavior shall be as if the program called the exit function with the status
|
|
EXIT_SUCCESS at thread termination time.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.5p4'></a>
|
|
<pre>4 The thrd_exit function returns no value.
|
|
</pre>
|
|
<a name='7.26.5.6'></a>
|
|
<hr>
|
|
<h3>7.26.5.6 [The thrd_join function]</h3>
|
|
<a name='7.26.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_join(thrd_t thr, int *res);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.6p2'></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='7.26.5.6p3'></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='7.26.5.7'></a>
|
|
<hr>
|
|
<h3>7.26.5.7 [The thrd_sleep function]</h3>
|
|
<a name='7.26.5.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int thrd_sleep(const struct timespec *duration,
|
|
struct timespec *remaining);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.7p2'></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='7.26.5.7p3'></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 shall not be less than that specified, as measured by the system clock TIME_UTC.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.5.7p4'></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 if it fails.
|
|
</pre>
|
|
<a name='7.26.5.8'></a>
|
|
<hr>
|
|
<h3>7.26.5.8 [The thrd_yield function]</h3>
|
|
<a name='7.26.5.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void thrd_yield(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.5.8p2'></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='7.26.5.8p3'></a>
|
|
<pre>3 The thrd_yield function returns no value.
|
|
</pre>
|
|
<a name='7.26.6'></a>
|
|
<hr>
|
|
<h3>7.26.6 [Thread-specific storage functions]</h3>
|
|
<a name='7.26.6.1'></a>
|
|
<hr>
|
|
<h3>7.26.6.1 [The tss_create function]</h3>
|
|
<a name='7.26.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int tss_create(tss_t *key, tss_dtor_t dtor);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.1p2'></a>
|
|
<pre>2 The tss_create function creates a thread-specific storage pointer with destructor
|
|
dtor, which may be null.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.1p3'></a>
|
|
<pre>3 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 undefined value.
|
|
</pre>
|
|
<a name='7.26.6.2'></a>
|
|
<hr>
|
|
<h3>7.26.6.2 [The tss_delete function]</h3>
|
|
<a name='7.26.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void tss_delete(tss_t key);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.2p2'></a>
|
|
<pre>2 The tss_delete function releases any resources used by the thread-specific storage
|
|
identified by key.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.2p3'></a>
|
|
<pre>3 The tss_delete function returns no value.
|
|
</pre>
|
|
<a name='7.26.6.3'></a>
|
|
<hr>
|
|
<h3>7.26.6.3 [The tss_get function]</h3>
|
|
<a name='7.26.6.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
void *tss_get(tss_t key);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.3p2'></a>
|
|
<pre>2 The tss_get function returns the value for the current thread held in the thread-specific
|
|
storage identified by key.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.3p3'></a>
|
|
<pre>3 The tss_get function returns the value for the current thread if successful, or zero if
|
|
unsuccessful.
|
|
</pre>
|
|
<a name='7.26.6.4'></a>
|
|
<hr>
|
|
<h3>7.26.6.4 [The tss_set function]</h3>
|
|
<a name='7.26.6.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <threads.h>
|
|
int tss_set(tss_t key, void *val);
|
|
Description
|
|
</pre>
|
|
<a name='7.26.6.4p2'></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.
|
|
Returns
|
|
</pre>
|
|
<a name='7.26.6.4p3'></a>
|
|
<pre>3 The tss_set function returns thrd_success on success or thrd_error if the
|
|
request could not be honored. ∗
|
|
</pre>
|
|
<a name='7.27'></a>
|
|
<hr>
|
|
<h3>7.27 [Date and time <time.h>]</h3>
|
|
<a name='7.27.1'></a>
|
|
<hr>
|
|
<h3>7.27.1 [Components of time]</h3>
|
|
<a name='7.27.1p1'></a>
|
|
<pre>1 The header <time.h> defines two macros, and declares several 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='7.27.1p2'></a>
|
|
<pre>2 The macros defined are NULL (described in <a href='#7.19'>7.19</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; and
|
|
TIME_UTC
|
|
which expands to an integer constant greater than 0 that designates the UTC time
|
|
base.<a href='#FOOTNOTE.316'><sup>[316]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.316'>
|
|
<pre><i><b>Footnote 316)</b> Implementations may define additional time bases, but are only required to support a real time clock
|
|
based on UTC.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.1p3'></a>
|
|
<pre>3 The types declared are size_t (described in <a href='#7.19'>7.19</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='7.27.1p4'></a>
|
|
<pre>4 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.<a href='#FOOTNOTE.317'><sup>[317]</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.318'><sup>[318]</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.317'>
|
|
<pre><i><b>Footnote 317)</b> The tv_sec member is a linear count of seconds and may not have the normal semantics of a
|
|
time_t. The semantics of the members and their normal ranges are expressed in the comments.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.318'>
|
|
<pre><i><b>Footnote 318)</b> The range [0, 60] for tm_sec allows for a positive leap second.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.2'></a>
|
|
<hr>
|
|
<h3>7.27.2 [Time manipulation functions]</h3>
|
|
<a name='7.27.2.1'></a>
|
|
<hr>
|
|
<h3>7.27.2.1 [The clock function]</h3>
|
|
<a name='7.27.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
clock_t clock(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.2.1p2'></a>
|
|
<pre>2 The clock function determines the processor time used.
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.2.1p3'></a>
|
|
<pre>3 The clock function returns the implementation’s best approximation to the processor
|
|
time used by the program 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 or its value cannot be represented, the function
|
|
returns the value (clock_t)(-1).<a href='#FOOTNOTE.319'><sup>[319]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.319'>
|
|
<pre><i><b>Footnote 319)</b> In order to measure the time spent in a program, the clock function should be called at the start of
|
|
the program and its return value subtracted from the value returned by subsequent calls.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.2.2'></a>
|
|
<hr>
|
|
<h3>7.27.2.2 [The difftime function]</h3>
|
|
<a name='7.27.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
double difftime(time_t time1, time_t time0);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.2.2p2'></a>
|
|
<pre>2 The difftime function computes the difference between two calendar times: time1 -
|
|
time0.
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.2.2p3'></a>
|
|
<pre>3 The difftime function returns the difference expressed in seconds as a double.
|
|
</pre>
|
|
<a name='7.27.2.3'></a>
|
|
<hr>
|
|
<h3>7.27.2.3 [The mktime function]</h3>
|
|
<a name='7.27.2.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
time_t mktime(struct tm *timeptr);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.2.3p2'></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.320'><sup>[320]</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.320'>
|
|
<pre><i><b>Footnote 320)</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='7.27.2.3p3'></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='7.27.2.3p4'></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='7.27.2.4'></a>
|
|
<hr>
|
|
<h3>7.27.2.4 [The time function]</h3>
|
|
<a name='7.27.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
time_t time(time_t *timer);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.2.4p2'></a>
|
|
<pre>2 The time function determines the current calendar time. The encoding of the value is
|
|
unspecified.
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.2.4p3'></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='7.27.2.5'></a>
|
|
<hr>
|
|
<h3>7.27.2.5 [The timespec_get function]</h3>
|
|
<a name='7.27.2.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
int timespec_get(struct timespec *ts, int base);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.2.5p2'></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='7.27.2.5p3'></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 number of nanoseconds, rounded to the resolution of the system
|
|
clock.<a href='#FOOTNOTE.321'><sup>[321]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.321'>
|
|
<pre><i><b>Footnote 321)</b> Although a struct timespec object describes times with nanosecond resolution, the available
|
|
resolution is system dependent and may even be greater than 1 second.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.2.5p4'></a>
|
|
<pre>4 If the timespec_get function is successful it returns the nonzero value base;
|
|
otherwise, it returns zero.
|
|
</pre>
|
|
<a name='7.27.3'></a>
|
|
<hr>
|
|
<h3>7.27.3 [Time conversion functions]</h3>
|
|
<a name='7.27.3p1'></a>
|
|
<pre>1 Except for the strftime function, these functions each return a pointer to one of two
|
|
types of static objects: a broken-down time structure or an array of char. Execution of
|
|
any of the functions that return a pointer to one of these object types may overwrite the
|
|
information in any object of the same type pointed to by the value returned from any
|
|
previous call to any of them and the functions are not required to avoid data races with
|
|
each other.<a href='#FOOTNOTE.322'><sup>[322]</sup></a> The implementation shall behave as if no other library functions call these
|
|
functions.
|
|
</pre>
|
|
<a name='FOOTNOTE.322'>
|
|
<pre><i><b>Footnote 322)</b> Alternative time conversion functions that do avoid data races are specified in <a href='#K.3.8.2'>K.3.8.2</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.3.1'></a>
|
|
<hr>
|
|
<h3>7.27.3.1 [The asctime function]</h3>
|
|
<a name='7.27.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
char *asctime(const struct tm *timeptr);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.3.1p2'></a>
|
|
<pre>2 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.
|
|
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];
|
|
sprintf(result, "%.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='7.27.3.1p3'></a>
|
|
<pre>3 If any of the members of the broken-down time contain values that are outside their
|
|
normal ranges,<a href='#FOOTNOTE.323'><sup>[323]</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.323'>
|
|
<pre><i><b>Footnote 323)</b> See <a href='#7.27.1'>7.27.1</a>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.27.3.1p4'></a>
|
|
<pre>4 The asctime function returns a pointer to the string.
|
|
</pre>
|
|
<a name='7.27.3.2'></a>
|
|
<hr>
|
|
<h3>7.27.3.2 [The ctime function]</h3>
|
|
<a name='7.27.3.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
char *ctime(const time_t *timer);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.3.2p2'></a>
|
|
<pre>2 The ctime function converts the calendar time pointed to by timer to local time in the
|
|
form of a string. It is equivalent to
|
|
asctime(localtime(timer))
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.3.2p3'></a>
|
|
<pre>3 The ctime function returns the pointer returned by the asctime function with that
|
|
broken-down time as argument.
|
|
Forward references: the localtime function (<a href='#7.27.3.4'>7.27.3.4</a>).
|
|
</pre>
|
|
<a name='7.27.3.3'></a>
|
|
<hr>
|
|
<h3>7.27.3.3 [The gmtime function]</h3>
|
|
<a name='7.27.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
struct tm *gmtime(const time_t *timer);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.3.3p2'></a>
|
|
<pre>2 The gmtime function converts the calendar time pointed to by timer into a broken-
|
|
down time, expressed as UTC.
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.3.3p3'></a>
|
|
<pre>3 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
|
|
specified time cannot be converted to UTC.
|
|
</pre>
|
|
<a name='7.27.3.4'></a>
|
|
<hr>
|
|
<h3>7.27.3.4 [The localtime function]</h3>
|
|
<a name='7.27.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <time.h>
|
|
struct tm *localtime(const time_t *timer);
|
|
Description
|
|
</pre>
|
|
<a name='7.27.3.4p2'></a>
|
|
<pre>2 The localtime function converts the calendar time pointed to by timer into a
|
|
broken-down time, expressed as local time.
|
|
Returns
|
|
</pre>
|
|
<a name='7.27.3.4p3'></a>
|
|
<pre>3 The localtime function returns a pointer to the broken-down time, or a null pointer if
|
|
the specified time cannot be converted to local time.
|
|
</pre>
|
|
<a name='7.27.3.5'></a>
|
|
<hr>
|
|
<h3>7.27.3.5 [The strftime function]</h3>
|
|
<a name='7.27.3.5p1'></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='7.27.3.5p2'></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='7.27.3.5p3'></a>
|
|
<pre>3 Each conversion specifier is replaced by appropriate characters as described in the
|
|
following list. The appropriate characters are 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='#7.27.1'>7.27.1</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='#7.27.1'>7.27.1</a>]
|
|
%X is replaced by the locale’s appropriate time representation. [all specified in <a href='#7.27.1'>7.27.1</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='7.27.3.5p4'></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.
|
|
%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='7.27.3.5p5'></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='7.27.3.5p6'></a>
|
|
<pre>6 If a conversion specifier is not one of the above, the behavior is undefined.
|
|
</pre>
|
|
<a name='7.27.3.5p7'></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='7.27.3.5p8'></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 contents of the array are indeterminate.
|
|
</pre>
|
|
<a name='7.28'></a>
|
|
<hr>
|
|
<h3>7.28 [Unicode utilities <uchar.h>]</h3>
|
|
<a name='7.28p1'></a>
|
|
<pre>1 The header <uchar.h> declares types and functions for manipulating Unicode
|
|
characters.
|
|
</pre>
|
|
<a name='7.28p2'></a>
|
|
<pre>2 The types declared are mbstate_t (described in <a href='#7.30.1'>7.30.1</a>) and size_t (described in
|
|
<a href='#7.19'>7.19</a>);
|
|
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='#7.20.1.2'>7.20.1.2</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='#7.20.1.2'>7.20.1.2</a>).
|
|
</pre>
|
|
<a name='7.28.1'></a>
|
|
<hr>
|
|
<h3>7.28.1 [Restartable multibyte/wide character conversion functions]</h3>
|
|
<a name='7.28.1p1'></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 at program startup to the initial conversion state; the functions are not required
|
|
to avoid data races with other calls to the same function in this case. The implementation
|
|
behaves as if no library function calls these functions with a null pointer for ps.
|
|
</pre>
|
|
<a name='7.28.1.1'></a>
|
|
<hr>
|
|
<h3>7.28.1.1 [The mbrtoc16 function]</h3>
|
|
<a name='7.28.1.1p1'></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='7.28.1.1p2'></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='7.28.1.1p3'></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='7.28.1.1p4'></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.324'><sup>[324]</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.324'>
|
|
<pre><i><b>Footnote 324)</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='7.28.1.2'></a>
|
|
<hr>
|
|
<h3>7.28.1.2 [The c16rtomb function]</h3>
|
|
<a name='7.28.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t c16rtomb(char * restrict s, char16_t c16,
|
|
mbstate_t * restrict ps);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.1.2p2'></a>
|
|
<pre>2 If s is a null pointer, the c16rtomb function is equivalent to the call
|
|
c16rtomb(buf, L'\0', ps)
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.28.1.2p3'></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 by c16
|
|
(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
|
|
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='7.28.1.2p4'></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='7.28.1.3'></a>
|
|
<hr>
|
|
<h3>7.28.1.3 [The mbrtoc32 function]</h3>
|
|
<a name='7.28.1.3p1'></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='7.28.1.3p2'></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='7.28.1.3p3'></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='7.28.1.3p4'></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.325'><sup>[325]</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.325'>
|
|
<pre><i><b>Footnote 325)</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='7.28.1.4'></a>
|
|
<hr>
|
|
<h3>7.28.1.4 [The c32rtomb function]</h3>
|
|
<a name='7.28.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <uchar.h>
|
|
size_t c32rtomb(char * restrict s, char32_t c32,
|
|
mbstate_t * restrict ps);
|
|
Description
|
|
</pre>
|
|
<a name='7.28.1.4p2'></a>
|
|
<pre>2 If s is a null pointer, the c32rtomb function is equivalent to the call
|
|
c32rtomb(buf, L'\0', ps)
|
|
where buf is an internal buffer.
|
|
</pre>
|
|
<a name='7.28.1.4p3'></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='7.28.1.4p4'></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='7.29'></a>
|
|
<hr>
|
|
<h3>7.29 [Extended multibyte and wide character utilities <wchar.h>]</h3>
|
|
<a name='7.29.1'></a>
|
|
<hr>
|
|
<h3>7.29.1 [Introduction]</h3>
|
|
<a name='7.29.1p1'></a>
|
|
<pre>1 The header <wchar.h> defines four macros, and declares four data types, one tag, and
|
|
many functions.<a href='#FOOTNOTE.326'><sup>[326]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.326'>
|
|
<pre><i><b>Footnote 326)</b> See ‘‘future library directions’’ (<a href='#7.31.16'>7.31.16</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.1p2'></a>
|
|
<pre>2 The types declared are wchar_t and size_t (both described in <a href='#7.19'>7.19</a>);
|
|
mbstate_t
|
|
which is a complete object type other than an array type that can hold the conversion state
|
|
information 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.327'><sup>[327]</sup></a> and
|
|
struct tm
|
|
which is declared as an incomplete structure type (the contents are described in <a href='#7.27.1'>7.27.1</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.327'>
|
|
<pre><i><b>Footnote 327)</b> wchar_t and wint_t can be the same integer type.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.1p3'></a>
|
|
<pre>3 The macros defined are NULL (described in <a href='#7.19'>7.19</a>); WCHAR_MIN and WCHAR_MAX
|
|
(described in <a href='#7.20.3'>7.20.3</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.328'><sup>[328]</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.328'>
|
|
<pre><i><b>Footnote 328)</b> The value of the macro WEOF may differ from that of EOF and need not be negative.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.1p4'></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='7.29.1p5'></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='#7.29.2'>7.29.2</a> or <a href='#7.29.5'>7.29.5</a> and the specified semantics do not require that value to be
|
|
processed by wcrtomb.
|
|
</pre>
|
|
<a name='7.29.1p6'></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='7.29.2'></a>
|
|
<hr>
|
|
<h3>7.29.2 [Formatted wide character input/output functions]</h3>
|
|
<a name='7.29.2p1'></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.329'><sup>[329]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.329'>
|
|
<pre><i><b>Footnote 329)</b> The fwprintf functions perform writes to memory for the %n specifier.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.1'></a>
|
|
<hr>
|
|
<h3>7.29.2.1 [The fwprintf function]</h3>
|
|
<a name='7.29.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwprintf(FILE * restrict stream,
|
|
const wchar_t * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.1p2'></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='7.29.2.1p3'></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='7.29.2.1p4'></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.330'><sup>[330]</sup></a>
|
|
— An optional precision that gives the minimum number of digits to appear for the 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 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.330'>
|
|
<pre><i><b>Footnote 330)</b> Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.1p5'></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='7.29.2.1p6'></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 negative value is converted if this flag is not
|
|
specified.)<a href='#FOOTNOTE.331'><sup>[331]</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 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 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.331'>
|
|
<pre><i><b>Footnote 331)</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='7.29.2.1p7'></a>
|
|
<pre>7 The length modifiers and their meanings are:
|
|
hh Specifies that a following 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 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 according 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 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 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 conversion specifier applies to a pointer to a long long int
|
|
argument.
|
|
j Specifies that a following 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 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 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.
|
|
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
|
|
applies to a long double argument.
|
|
If a length modifier appears with any conversion specifier other than as specified above,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.29.2.1p8'></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.
|
|
o,u,x,X The unsigned int argument is converted to 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.332'><sup>[332]</sup></a>
|
|
e,E A double argument representing a floating-point number is converted in the
|
|
style [−]d.ddd e±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.hhhh p±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.333'><sup>[333]</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.334'><sup>[334]</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.
|
|
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 the initial
|
|
element of a character array containing a multibyte character sequence
|
|
beginning in the initial shift state. Characters from the array 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 array, the converted array shall contain a
|
|
null wide character.
|
|
If an l length modifier is present, the argument shall be a pointer to the initial
|
|
element of an array of wchar_t type. Wide characters from the array 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 array
|
|
shall contain a null wide character.
|
|
p The argument shall be a pointer to void. 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 into which is written the
|
|
number of wide characters written to the output stream so far by this call to
|
|
fwprintf. 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.332'>
|
|
<pre><i><b>Footnote 332)</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.333'>
|
|
<pre><i><b>Footnote 333)</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.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.334'>
|
|
<pre><i><b>Footnote 334)</b> The precision p is sufficient to distinguish values of the source type if 16 p−1 > b n where b is
|
|
FLT_RADIX and n is the number of base-b digits in the significand of the source type. 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='7.29.2.1p9'></a>
|
|
<pre>9 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.335'><sup>[335]</sup></a> If any argument is
|
|
not the correct type for the corresponding conversion specification, the behavior is
|
|
undefined.
|
|
</pre>
|
|
<a name='FOOTNOTE.335'>
|
|
<pre><i><b>Footnote 335)</b> See ‘‘future library directions’’ (<a href='#7.31.16'>7.31.16</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.1p10'></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='7.29.2.1p11'></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='7.29.2.1p12'></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='7.29.2.1p13'></a>
|
|
<pre>13 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
|
|
DECIMAL_DIG, then the result should be correctly rounded.<a href='#FOOTNOTE.336'><sup>[336]</sup></a> If the number of
|
|
significant decimal digits is more than DECIMAL_DIG but the source value is exactly
|
|
representable with DECIMAL_DIG 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 DECIMAL_DIG 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.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.336'>
|
|
<pre><i><b>Footnote 336)</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='7.29.2.1p14'></a>
|
|
<pre>14 The fwprintf function returns the number of wide characters transmitted, or a negative
|
|
value if an output or encoding error occurred.
|
|
Environmental limits
|
|
</pre>
|
|
<a name='7.29.2.1p15'></a>
|
|
<pre>15 The number of wide characters that can be produced by any single conversion shall be at
|
|
least 4095.
|
|
</pre>
|
|
<a name='7.29.2.1p16'></a>
|
|
<pre>16 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));
|
|
|
|
Forward references: the btowc function (<a href='#7.29.6.1.1'>7.29.6.1.1</a>), the mbrtowc function
|
|
(<a href='#7.29.6.3.2'>7.29.6.3.2</a>).
|
|
</pre>
|
|
<a name='7.29.2.2'></a>
|
|
<hr>
|
|
<h3>7.29.2.2 [The fwscanf function]</h3>
|
|
<a name='7.29.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwscanf(FILE * restrict stream,
|
|
const wchar_t * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.2p2'></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='7.29.2.2p3'></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='7.29.2.2p4'></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='7.29.2.2p5'></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='7.29.2.2p6'></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='7.29.2.2p7'></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='7.29.2.2p8'></a>
|
|
<pre>8 Input white-space wide characters (as specified by the iswspace function) are skipped,
|
|
unless the specification includes a [, c, or n specifier.<a href='#FOOTNOTE.337'><sup>[337]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.337'>
|
|
<pre><i><b>Footnote 337)</b> These white-space wide characters are not counted against a specified field width.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.2p9'></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.338'><sup>[338]</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.338'>
|
|
<pre><i><b>Footnote 338)</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='7.29.2.2p10'></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='7.29.2.2p11'></a>
|
|
<pre>11 The length modifiers and their meanings are:
|
|
hh Specifies that a following 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 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 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 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 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 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.
|
|
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.
|
|
If a length modifier appears with any conversion specifier other than as specified above,
|
|
the behavior is undefined.
|
|
</pre>
|
|
<a name='7.29.2.2p12'></a>
|
|
<pre>12 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. The corresponding argument shall be a pointer to
|
|
signed integer.
|
|
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. The corresponding argument shall be a pointer to signed
|
|
integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to
|
|
unsigned integer.
|
|
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. The corresponding argument shall be a pointer to floating.
|
|
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 the initial element of a character array 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 the initial element of an array 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 the initial element of a character array 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 the initial element of an array 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 the initial element of a character array 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 the initial element of an array 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 to 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 to
|
|
signed integer into which is to be written the number of wide characters read
|
|
from the input stream so far by this call to the fwscanf function. 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='7.29.2.2p13'></a>
|
|
<pre>13 If a conversion specification is invalid, the behavior is undefined.<a href='#FOOTNOTE.339'><sup>[339]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.339'>
|
|
<pre><i><b>Footnote 339)</b> See ‘‘future library directions’’ (<a href='#7.31.16'>7.31.16</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.2p14'></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='7.29.2.2p15'></a>
|
|
<pre>15 Trailing white space (including new-line wide characters) is 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='7.29.2.2p16'></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.
|
|
</pre>
|
|
<a name='7.29.2.2p17'></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='7.29.2.2p18'></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='#7.29.4.1.1'>7.29.4.1.1</a>), the
|
|
wcstol, wcstoll, wcstoul, and wcstoull functions (<a href='#7.29.4.1.2'>7.29.4.1.2</a>), the wcrtomb
|
|
function (<a href='#7.29.6.3.3'>7.29.6.3.3</a>).
|
|
</pre>
|
|
<a name='7.29.2.3'></a>
|
|
<hr>
|
|
<h3>7.29.2.3 [The swprintf function]</h3>
|
|
<a name='7.29.2.3p1'></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='7.29.2.3p2'></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='7.29.2.3p3'></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='7.29.2.4'></a>
|
|
<hr>
|
|
<h3>7.29.2.4 [The swscanf function]</h3>
|
|
<a name='7.29.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int swscanf(const wchar_t * restrict s,
|
|
const wchar_t * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.4p2'></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='7.29.2.4p3'></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='7.29.2.5'></a>
|
|
<hr>
|
|
<h3>7.29.2.5 [The vfwprintf function]</h3>
|
|
<a name='7.29.2.5p1'></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='7.29.2.5p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.5p3'></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='7.29.2.5p4'></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='7.29.2.6'></a>
|
|
<hr>
|
|
<h3>7.29.2.6 [The vfwscanf function]</h3>
|
|
<a name='7.29.2.6p1'></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='7.29.2.6p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.6p3'></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='7.29.2.7'></a>
|
|
<hr>
|
|
<h3>7.29.2.7 [The vswprintf function]</h3>
|
|
<a name='7.29.2.7p1'></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='7.29.2.7p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.7p3'></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='7.29.2.8'></a>
|
|
<hr>
|
|
<h3>7.29.2.8 [The vswscanf function]</h3>
|
|
<a name='7.29.2.8p1'></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='7.29.2.8p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.8p3'></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='7.29.2.9'></a>
|
|
<hr>
|
|
<h3>7.29.2.9 [The vwprintf function]</h3>
|
|
<a name='7.29.2.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwprintf(const wchar_t * restrict format,
|
|
va_list arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.9p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.9p3'></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='7.29.2.10'></a>
|
|
<hr>
|
|
<h3>7.29.2.10 [The vwscanf function]</h3>
|
|
<a name='7.29.2.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdarg.h>
|
|
#include <wchar.h>
|
|
int vwscanf(const wchar_t * restrict format,
|
|
va_list arg);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.10p2'></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.340'><sup>[340]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.340'>
|
|
<pre><i><b>Footnote 340)</b> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.2.10p3'></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='7.29.2.11'></a>
|
|
<hr>
|
|
<h3>7.29.2.11 [The wprintf function]</h3>
|
|
<a name='7.29.2.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wprintf(const wchar_t * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.11p2'></a>
|
|
<pre>2 The wprintf function is equivalent to fwprintf with the argument stdout
|
|
interposed before the arguments to wprintf.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.11p3'></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='7.29.2.12'></a>
|
|
<hr>
|
|
<h3>7.29.2.12 [The wscanf function]</h3>
|
|
<a name='7.29.2.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wscanf(const wchar_t * restrict format, ...);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.2.12p2'></a>
|
|
<pre>2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
|
|
before the arguments to wscanf.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.2.12p3'></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='7.29.3'></a>
|
|
<hr>
|
|
<h3>7.29.3 [Wide character input/output functions]</h3>
|
|
<a name='7.29.3.1'></a>
|
|
<hr>
|
|
<h3>7.29.3.1 [The fgetwc function]</h3>
|
|
<a name='7.29.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t fgetwc(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.1p2'></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='7.29.3.1p3'></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 value of
|
|
the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<a href='#FOOTNOTE.341'><sup>[341]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.341'>
|
|
<pre><i><b>Footnote 341)</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='7.29.3.2'></a>
|
|
<hr>
|
|
<h3>7.29.3.2 [The fgetws function]</h3>
|
|
<a name='7.29.3.2p1'></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='7.29.3.2p2'></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='7.29.3.2p3'></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
|
|
contents are indeterminate and a null pointer is returned.
|
|
</pre>
|
|
<a name='7.29.3.3'></a>
|
|
<hr>
|
|
<h3>7.29.3.3 [The fputwc function]</h3>
|
|
<a name='7.29.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t fputwc(wchar_t c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.3p2'></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='7.29.3.3p3'></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='7.29.3.4'></a>
|
|
<hr>
|
|
<h3>7.29.3.4 [The fputws function]</h3>
|
|
<a name='7.29.3.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fputws(const wchar_t * restrict s,
|
|
FILE * restrict stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.4p2'></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='7.29.3.4p3'></a>
|
|
<pre>3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
|
|
returns a nonnegative value.
|
|
</pre>
|
|
<a name='7.29.3.5'></a>
|
|
<hr>
|
|
<h3>7.29.3.5 [The fwide function]</h3>
|
|
<a name='7.29.3.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
int fwide(FILE *stream, int mode);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.5p2'></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.342'><sup>[342]</sup></a>
|
|
Otherwise, mode is zero and the function does not alter the orientation of the stream.
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.342'>
|
|
<pre><i><b>Footnote 342)</b> If the orientation of the stream has already been determined, fwide does not change it.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.3.5p3'></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='7.29.3.6'></a>
|
|
<hr>
|
|
<h3>7.29.3.6 [The getwc function]</h3>
|
|
<a name='7.29.3.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t getwc(FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.6p2'></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='7.29.3.6p3'></a>
|
|
<pre>3 The getwc function returns the next wide character from the input stream pointed to by
|
|
stream, or WEOF.
|
|
</pre>
|
|
<a name='7.29.3.7'></a>
|
|
<hr>
|
|
<h3>7.29.3.7 [The getwchar function]</h3>
|
|
<a name='7.29.3.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t getwchar(void);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.7p2'></a>
|
|
<pre>2 The getwchar function is equivalent to getwc with the argument stdin.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.7p3'></a>
|
|
<pre>3 The getwchar function returns the next wide character from the input stream pointed to
|
|
by stdin, or WEOF.
|
|
</pre>
|
|
<a name='7.29.3.8'></a>
|
|
<hr>
|
|
<h3>7.29.3.8 [The putwc function]</h3>
|
|
<a name='7.29.3.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t putwc(wchar_t c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.8p2'></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='7.29.3.8p3'></a>
|
|
<pre>3 The putwc function returns the wide character written, or WEOF.
|
|
</pre>
|
|
<a name='7.29.3.9'></a>
|
|
<hr>
|
|
<h3>7.29.3.9 [The putwchar function]</h3>
|
|
<a name='7.29.3.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t putwchar(wchar_t c);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.9p2'></a>
|
|
<pre>2 The putwchar function is equivalent to putwc with the second argument stdout.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.3.9p3'></a>
|
|
<pre>3 The putwchar function returns the character written, or WEOF.
|
|
</pre>
|
|
<a name='7.29.3.10'></a>
|
|
<hr>
|
|
<h3>7.29.3.10 [The ungetwc function]</h3>
|
|
<a name='7.29.3.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <stdio.h>
|
|
#include <wchar.h>
|
|
wint_t ungetwc(wint_t c, FILE *stream);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.3.10p2'></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='7.29.3.10p3'></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='7.29.3.10p4'></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='7.29.3.10p5'></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. 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='7.29.3.10p6'></a>
|
|
<pre>6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
|
|
fails.
|
|
</pre>
|
|
<a name='7.29.4'></a>
|
|
<hr>
|
|
<h3>7.29.4 [General wide string utilities]</h3>
|
|
<a name='7.29.4p1'></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='7.29.4p2'></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='7.29.4.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.1 [Wide string numeric conversion functions]</h3>
|
|
<a name='7.29.4.1.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.1.1 [The wcstod, wcstof, and wcstold functions]</h3>
|
|
<a name='7.29.4.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#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
|
|
</pre>
|
|
<a name='7.29.4.1.1p2'></a>
|
|
<pre>2 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 (as specified by the iswspace
|
|
function), a subject sequence resembling a floating-point 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='7.29.4.1.1p3'></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 for the corresponding single-byte
|
|
characters in <a href='#6.4.4.2'>6.4.4.2</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>;
|
|
— 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='7.29.4.1.1p4'></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>, 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.343'><sup>[343]</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.344'><sup>[344]</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.343'>
|
|
<pre><i><b>Footnote 343)</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 may 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.344'>
|
|
<pre><i><b>Footnote 344)</b> An implementation may use the n-wchar sequence to determine extra information to be represented in
|
|
the NaN’s significand.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.4.1.1p5'></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='7.29.4.1.1p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
accepted.
|
|
</pre>
|
|
<a name='7.29.4.1.1p7'></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='7.29.4.1.1p8'></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='7.29.4.1.1p9'></a>
|
|
<pre>9 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
|
|
<float.h>) significant digits, the result should be correctly rounded. If the subject
|
|
sequence D has the decimal form and more than DECIMAL_DIG significant digits,
|
|
consider the two bounding, adjacent decimal strings L and U, both having
|
|
DECIMAL_DIG 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.345'><sup>[345]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.345'>
|
|
<pre><i><b>Footnote 345)</b> DECIMAL_DIG, defined in <float.h>, should be sufficiently large that L and U will usually round
|
|
to the same internal floating value, but if not will round to adjacent values.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.4.1.1p10'></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), and the value of the macro ERANGE is stored in
|
|
errno. 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; whether
|
|
errno acquires the value ERANGE is implementation-defined.
|
|
</pre>
|
|
<a name='7.29.4.1.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.1.2 [The wcstol, wcstoll, wcstoul, and wcstoull functions]</h3>
|
|
<a name='7.29.4.1.2p1'></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='7.29.4.1.2p2'></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 (as specified by the iswspace
|
|
function), 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='7.29.4.1.2p3'></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. 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.
|
|
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 16, the wide characters 0x or 0X may optionally precede the sequence
|
|
of letters and digits, following the sign if present.
|
|
</pre>
|
|
<a name='7.29.4.1.2p4'></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, or if the first non-white-space wide character is other
|
|
than a sign or a permissible letter or digit.
|
|
</pre>
|
|
<a name='7.29.4.1.2p5'></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='7.29.4.1.2p6'></a>
|
|
<pre>6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
accepted.
|
|
</pre>
|
|
<a name='7.29.4.1.2p7'></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='7.29.4.1.2p8'></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='7.29.4.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.2 [Wide string copying functions]</h3>
|
|
<a name='7.29.4.2.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.2.1 [The wcscpy function]</h3>
|
|
<a name='7.29.4.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcscpy(wchar_t * restrict s1,
|
|
const wchar_t * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.2.1p2'></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='7.29.4.2.1p3'></a>
|
|
<pre>3 The wcscpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.2.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.2.2 [The wcsncpy function]</h3>
|
|
<a name='7.29.4.2.2p1'></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='7.29.4.2.2p2'></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.346'><sup>[346]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.346'>
|
|
<pre><i><b>Footnote 346)</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='7.29.4.2.2p3'></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='7.29.4.2.2p4'></a>
|
|
<pre>4 The wcsncpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.2.3'></a>
|
|
<hr>
|
|
<h3>7.29.4.2.3 [The wmemcpy function]</h3>
|
|
<a name='7.29.4.2.3p1'></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='7.29.4.2.3p2'></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='7.29.4.2.3p3'></a>
|
|
<pre>3 The wmemcpy function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.2.4'></a>
|
|
<hr>
|
|
<h3>7.29.4.2.4 [The wmemmove function]</h3>
|
|
<a name='7.29.4.2.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.2.4p2'></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='7.29.4.2.4p3'></a>
|
|
<pre>3 The wmemmove function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.3'></a>
|
|
<hr>
|
|
<h3>7.29.4.3 [Wide string concatenation functions]</h3>
|
|
<a name='7.29.4.3.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.3.1 [The wcscat function]</h3>
|
|
<a name='7.29.4.3.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcscat(wchar_t * restrict s1,
|
|
const wchar_t * restrict s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.3.1p2'></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='7.29.4.3.1p3'></a>
|
|
<pre>3 The wcscat function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.3.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.3.2 [The wcsncat function]</h3>
|
|
<a name='7.29.4.3.2p1'></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='7.29.4.3.2p2'></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.347'><sup>[347]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.347'>
|
|
<pre><i><b>Footnote 347)</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='7.29.4.3.2p3'></a>
|
|
<pre>3 The wcsncat function returns the value of s1.
|
|
</pre>
|
|
<a name='7.29.4.4'></a>
|
|
<hr>
|
|
<h3>7.29.4.4 [Wide string comparison functions]</h3>
|
|
<a name='7.29.4.4p1'></a>
|
|
<pre>1 Unless explicitly stated otherwise, the functions described in this subclause order two
|
|
wide characters the same way as two integers of the underlying integer type designated
|
|
by wchar_t.
|
|
</pre>
|
|
<a name='7.29.4.4.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.4.1 [The wcscmp function]</h3>
|
|
<a name='7.29.4.4.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcscmp(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.4.1p2'></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='7.29.4.4.1p3'></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='7.29.4.4.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.4.2 [The wcscoll function]</h3>
|
|
<a name='7.29.4.4.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcscoll(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.4.2p2'></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='7.29.4.4.2p3'></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='7.29.4.4.3'></a>
|
|
<hr>
|
|
<h3>7.29.4.4.3 [The wcsncmp function]</h3>
|
|
<a name='7.29.4.4.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wcsncmp(const wchar_t *s1, const wchar_t *s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.4.3p2'></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='7.29.4.4.3p3'></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='7.29.4.4.4'></a>
|
|
<hr>
|
|
<h3>7.29.4.4.4 [The wcsxfrm function]</h3>
|
|
<a name='7.29.4.4.4p1'></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='7.29.4.4.4p2'></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='7.29.4.4.4p3'></a>
|
|
<pre>3 The wcsxfrm function returns the length of the transformed wide string (not including
|
|
the terminating null wide character). If the value returned is n or greater, the contents of
|
|
the array pointed to by s1 are indeterminate.
|
|
</pre>
|
|
<a name='7.29.4.4.4p4'></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='7.29.4.4.5'></a>
|
|
<hr>
|
|
<h3>7.29.4.4.5 [The wmemcmp function]</h3>
|
|
<a name='7.29.4.4.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wmemcmp(const wchar_t *s1, const wchar_t *s2,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.4.5p2'></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='7.29.4.4.5p3'></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='7.29.4.5'></a>
|
|
<hr>
|
|
<h3>7.29.4.5 [Wide string search functions]</h3>
|
|
<a name='7.29.4.5.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.1 [The wcschr function]</h3>
|
|
<a name='7.29.4.5.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcschr(const wchar_t *s, wchar_t c);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.1p2'></a>
|
|
<pre>2 The wcschr 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='7.29.4.5.1p3'></a>
|
|
<pre>3 The wcschr 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='7.29.4.5.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.2 [The wcscspn function]</h3>
|
|
<a name='7.29.4.5.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.2p2'></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='7.29.4.5.2p3'></a>
|
|
<pre>3 The wcscspn function returns the length of the segment.
|
|
</pre>
|
|
<a name='7.29.4.5.3'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.3 [The wcspbrk function]</h3>
|
|
<a name='7.29.4.5.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.3p2'></a>
|
|
<pre>2 The wcspbrk 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='7.29.4.5.3p3'></a>
|
|
<pre>3 The wcspbrk 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='7.29.4.5.4'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.4 [The wcsrchr function]</h3>
|
|
<a name='7.29.4.5.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.4p2'></a>
|
|
<pre>2 The wcsrchr 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='7.29.4.5.4p3'></a>
|
|
<pre>3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
|
|
not occur in the wide string.
|
|
</pre>
|
|
<a name='7.29.4.5.5'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.5 [The wcsspn function]</h3>
|
|
<a name='7.29.4.5.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.5p2'></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='7.29.4.5.5p3'></a>
|
|
<pre>3 The wcsspn function returns the length of the segment.
|
|
</pre>
|
|
<a name='7.29.4.5.6'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.6 [The wcsstr function]</h3>
|
|
<a name='7.29.4.5.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.6p2'></a>
|
|
<pre>2 The wcsstr 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='7.29.4.5.6p3'></a>
|
|
<pre>3 The wcsstr 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='7.29.4.5.7'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.7 [The wcstok function]</h3>
|
|
<a name='7.29.4.5.7p1'></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='7.29.4.5.7p2'></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='7.29.4.5.7p3'></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='7.29.4.5.7p4'></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='7.29.4.5.7p5'></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='7.29.4.5.7p6'></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='7.29.4.5.7p7'></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='7.29.4.5.7p8'></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='7.29.4.5.8'></a>
|
|
<hr>
|
|
<h3>7.29.4.5.8 [The wmemchr function]</h3>
|
|
<a name='7.29.4.5.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemchr(const wchar_t *s, wchar_t c,
|
|
size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.5.8p2'></a>
|
|
<pre>2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
|
|
the object pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.4.5.8p3'></a>
|
|
<pre>3 The wmemchr 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='7.29.4.6'></a>
|
|
<hr>
|
|
<h3>7.29.4.6 [Miscellaneous functions]</h3>
|
|
<a name='7.29.4.6.1'></a>
|
|
<hr>
|
|
<h3>7.29.4.6.1 [The wcslen function]</h3>
|
|
<a name='7.29.4.6.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcslen(const wchar_t *s);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.6.1p2'></a>
|
|
<pre>2 The wcslen function computes the length of the wide string pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.4.6.1p3'></a>
|
|
<pre>3 The wcslen function returns the number of wide characters that precede the terminating
|
|
null wide character.
|
|
</pre>
|
|
<a name='7.29.4.6.2'></a>
|
|
<hr>
|
|
<h3>7.29.4.6.2 [The wmemset function]</h3>
|
|
<a name='7.29.4.6.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.4.6.2p2'></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='7.29.4.6.2p3'></a>
|
|
<pre>3 The wmemset function returns the value of s.
|
|
</pre>
|
|
<a name='7.29.5'></a>
|
|
<hr>
|
|
<h3>7.29.5 [Wide character time conversion functions]</h3>
|
|
<a name='7.29.5.1'></a>
|
|
<hr>
|
|
<h3>7.29.5.1 [The wcsftime function]</h3>
|
|
<a name='7.29.5.1p1'></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='7.29.5.1p2'></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
|
|
corresponding sequences of wide characters.
|
|
— The return value indicates the number of wide characters.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.5.1p3'></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 contents of the array are
|
|
indeterminate.
|
|
</pre>
|
|
<a name='7.29.6'></a>
|
|
<hr>
|
|
<h3>7.29.6 [Extended multibyte/wide character conversion utilities]</h3>
|
|
<a name='7.29.6p1'></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='7.29.6p2'></a>
|
|
<pre>2 Most of the following functions — those that are listed as ‘‘restartable’’, <a href='#7.29.6.3'>7.29.6.3</a> and
|
|
<a href='#7.29.6.4'>7.29.6.4</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='7.29.6p3'></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.348'><sup>[348]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.348'>
|
|
<pre><i><b>Footnote 348)</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='7.29.6p4'></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='7.29.6.1'></a>
|
|
<hr>
|
|
<h3>7.29.6.1 [Single-byte/wide character conversion functions]</h3>
|
|
<a name='7.29.6.1.1'></a>
|
|
<hr>
|
|
<h3>7.29.6.1.1 [The btowc function]</h3>
|
|
<a name='7.29.6.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
wint_t btowc(int c);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.6.1.1p2'></a>
|
|
<pre>2 The btowc function determines whether c constitutes a valid single-byte character in the
|
|
initial shift state.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.6.1.1p3'></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='7.29.6.1.2'></a>
|
|
<hr>
|
|
<h3>7.29.6.1.2 [The wctob function]</h3>
|
|
<a name='7.29.6.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int wctob(wint_t c);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.6.1.2p2'></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='7.29.6.1.2p3'></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='7.29.6.2'></a>
|
|
<hr>
|
|
<h3>7.29.6.2 [Conversion state functions]</h3>
|
|
<a name='7.29.6.2.1'></a>
|
|
<hr>
|
|
<h3>7.29.6.2.1 [The mbsinit function]</h3>
|
|
<a name='7.29.6.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
int mbsinit(const mbstate_t *ps);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.6.2.1p2'></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='7.29.6.2.1p3'></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='7.29.6.3'></a>
|
|
<hr>
|
|
<h3>7.29.6.3 [Restartable multibyte/wide character conversion functions]</h3>
|
|
<a name='7.29.6.3p1'></a>
|
|
<pre>1 These functions differ from the corresponding multibyte character functions of <a href='#7.22.7'>7.22.7</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 at
|
|
program startup to the initial conversion state; the functions are not required to avoid data
|
|
races with other calls to the same function in this case. The implementation behaves as if
|
|
no library function calls these functions with a null pointer for ps.
|
|
</pre>
|
|
<a name='7.29.6.3p2'></a>
|
|
<pre>2 Also unlike their corresponding functions, the return value does not represent whether the
|
|
encoding is state-dependent.
|
|
</pre>
|
|
<a name='7.29.6.3.1'></a>
|
|
<hr>
|
|
<h3>7.29.6.3.1 [The mbrlen function]</h3>
|
|
<a name='7.29.6.3.1p1'></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='7.29.6.3.1p2'></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 designated by ps is evaluated only once.
|
|
Returns
|
|
</pre>
|
|
<a name='7.29.6.3.1p3'></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='#7.29.6.3.2'>7.29.6.3.2</a>).
|
|
</pre>
|
|
<a name='7.29.6.3.2'></a>
|
|
<hr>
|
|
<h3>7.29.6.3.2 [The mbrtowc function]</h3>
|
|
<a name='7.29.6.3.2p1'></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='7.29.6.3.2p2'></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='7.29.6.3.2p3'></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='7.29.6.3.2p4'></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.349'><sup>[349]</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.349'>
|
|
<pre><i><b>Footnote 349)</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='7.29.6.3.3'></a>
|
|
<hr>
|
|
<h3>7.29.6.3.3 [The wcrtomb function]</h3>
|
|
<a name='7.29.6.3.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wchar.h>
|
|
size_t wcrtomb(char * restrict s,
|
|
wchar_t wc,
|
|
mbstate_t * restrict ps);
|
|
Description
|
|
</pre>
|
|
<a name='7.29.6.3.3p2'></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='7.29.6.3.3p3'></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='7.29.6.3.3p4'></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='7.29.6.4'></a>
|
|
<hr>
|
|
<h3>7.29.6.4 [Restartable multibyte/wide string conversion functions]</h3>
|
|
<a name='7.29.6.4p1'></a>
|
|
<pre>1 These functions differ from the corresponding multibyte string functions of <a href='#7.22.8'>7.22.8</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 at program startup
|
|
to the initial conversion state; the functions are not required to avoid data races with other
|
|
calls to the same function in this case. The implementation behaves as if no library
|
|
function calls these functions with a null pointer for ps.
|
|
</pre>
|
|
<a name='7.29.6.4p2'></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='7.29.6.4.1'></a>
|
|
<hr>
|
|
<h3>7.29.6.4.1 [The mbsrtowcs function]</h3>
|
|
<a name='7.29.6.4.1p1'></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='7.29.6.4.1p2'></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.350'><sup>[350]</sup></a> Each conversion takes
|
|
place as if by a call to the mbrtowc function.
|
|
</pre>
|
|
<a name='FOOTNOTE.350'>
|
|
<pre><i><b>Footnote 350)</b> Thus, the value of len is ignored if dst is a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.29.6.4.1p3'></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='7.29.6.4.1p4'></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='7.29.6.4.2'></a>
|
|
<hr>
|
|
<h3>7.29.6.4.2 [The wcsrtombs function]</h3>
|
|
<a name='7.29.6.4.2p1'></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='7.29.6.4.2p2'></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.351'><sup>[351]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.351'>
|
|
<pre><i><b>Footnote 351)</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='7.29.6.4.2p3'></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='7.29.6.4.2p4'></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='7.30'></a>
|
|
<hr>
|
|
<h3>7.30 [Wide character classification and mapping utilities <wctype.h>]</h3>
|
|
<a name='7.30.1'></a>
|
|
<hr>
|
|
<h3>7.30.1 [Introduction]</h3>
|
|
<a name='7.30.1p1'></a>
|
|
<pre>1 The header <wctype.h> defines one macro, and declares three data types and many
|
|
functions.<a href='#FOOTNOTE.352'><sup>[352]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.352'>
|
|
<pre><i><b>Footnote 352)</b> See ‘‘future library directions’’ (<a href='#7.31.17'>7.31.17</a>).
|
|
</i></pre>
|
|
</a>
|
|
<a name='7.30.1p2'></a>
|
|
<pre>2 The types declared are
|
|
wint_t
|
|
described in <a href='#7.29.1'>7.29.1</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='7.30.1p3'></a>
|
|
<pre>3 The macro defined is WEOF (described in <a href='#7.29.1'>7.29.1</a>).
|
|
</pre>
|
|
<a name='7.30.1p4'></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='7.30.1p5'></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='7.30.1p6'></a>
|
|
<pre>6 The behavior of these functions is affected by the LC_CTYPE category of the current
|
|
locale.
|
|
</pre>
|
|
<a name='7.30.2'></a>
|
|
<hr>
|
|
<h3>7.30.2 [Wide character classification utilities]</h3>
|
|
<a name='7.30.2p1'></a>
|
|
<pre>1 The header <wctype.h> declares several functions useful for classifying wide
|
|
characters.
|
|
</pre>
|
|
<a name='7.30.2p2'></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='7.30.2.1'></a>
|
|
<hr>
|
|
<h3>7.30.2.1 [Wide character classification functions]</h3>
|
|
<a name='7.30.2.1p1'></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='7.30.2.1p2'></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.353'><sup>[353]</sup></a>
|
|
Forward references: the wctob function (<a href='#7.29.6.1.2'>7.29.6.1.2</a>).
|
|
</pre>
|
|
<a name='FOOTNOTE.353'>
|
|
<pre><i><b>Footnote 353)</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='7.30.2.1.1'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.1 [The iswalnum function]</h3>
|
|
<a name='7.30.2.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswalnum(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.1p2'></a>
|
|
<pre>2 The iswalnum function tests for any wide character for which iswalpha or
|
|
iswdigit is true.
|
|
</pre>
|
|
<a name='7.30.2.1.2'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.2 [The iswalpha function]</h3>
|
|
<a name='7.30.2.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswalpha(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.2p2'></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.354'><sup>[354]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.354'>
|
|
<pre><i><b>Footnote 354)</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='7.30.2.1.3'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.3 [The iswblank function]</h3>
|
|
<a name='7.30.2.1.3p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswblank(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.3p2'></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='7.30.2.1.4'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.4 [The iswcntrl function]</h3>
|
|
<a name='7.30.2.1.4p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswcntrl(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.4p2'></a>
|
|
<pre>2 The iswcntrl function tests for any control wide character.
|
|
</pre>
|
|
<a name='7.30.2.1.5'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.5 [The iswdigit function]</h3>
|
|
<a name='7.30.2.1.5p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswdigit(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.5p2'></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='7.30.2.1.6'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.6 [The iswgraph function]</h3>
|
|
<a name='7.30.2.1.6p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswgraph(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.6p2'></a>
|
|
<pre>2 The iswgraph function tests for any wide character for which iswprint is true and
|
|
iswspace is false.<a href='#FOOTNOTE.355'><sup>[355]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.355'>
|
|
<pre><i><b>Footnote 355)</b> Note that the behavior of the iswgraph and iswpunct functions may 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='7.30.2.1.7'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.7 [The iswlower function]</h3>
|
|
<a name='7.30.2.1.7p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswlower(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.7p2'></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='7.30.2.1.8'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.8 [The iswprint function]</h3>
|
|
<a name='7.30.2.1.8p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswprint(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.8p2'></a>
|
|
<pre>2 The iswprint function tests for any printing wide character.
|
|
</pre>
|
|
<a name='7.30.2.1.9'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.9 [The iswpunct function]</h3>
|
|
<a name='7.30.2.1.9p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswpunct(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.9p2'></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.355'><sup>[355]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.355'>
|
|
<pre><i><b>Footnote 355)</b> Note that the behavior of the iswgraph and iswpunct functions may 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='7.30.2.1.10'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.10 [The iswspace function]</h3>
|
|
<a name='7.30.2.1.10p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswspace(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.10p2'></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='7.30.2.1.11'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.11 [The iswupper function]</h3>
|
|
<a name='7.30.2.1.11p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswupper(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.11p2'></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='7.30.2.1.12'></a>
|
|
<hr>
|
|
<h3>7.30.2.1.12 [The iswxdigit function]</h3>
|
|
<a name='7.30.2.1.12p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswxdigit(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.1.12p2'></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='7.30.2.2'></a>
|
|
<hr>
|
|
<h3>7.30.2.2 [Extensible wide character classification functions]</h3>
|
|
<a name='7.30.2.2p1'></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='#7.30.2.1'>7.30.2.1</a>).
|
|
</pre>
|
|
<a name='7.30.2.2.1'></a>
|
|
<hr>
|
|
<h3>7.30.2.2.1 [The iswctype function]</h3>
|
|
<a name='7.30.2.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
int iswctype(wint_t wc, wctype_t desc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.2.1p2'></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='7.30.2.2.1p3'></a>
|
|
<pre>3 Each of the following expressions has a truth-value equivalent to the call to the wide
|
|
character classification function (<a href='#7.30.2.1'>7.30.2.1</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='7.30.2.2.1p4'></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='#7.30.2.2.2'>7.30.2.2.2</a>).
|
|
</pre>
|
|
<a name='7.30.2.2.2'></a>
|
|
<hr>
|
|
<h3>7.30.2.2.2 [The wctype function]</h3>
|
|
<a name='7.30.2.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wctype_t wctype(const char *property);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.2.2.2p2'></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='7.30.2.2.2p3'></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='7.30.2.2.2p4'></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='7.30.3'></a>
|
|
<hr>
|
|
<h3>7.30.3 [Wide character case mapping utilities]</h3>
|
|
<a name='7.30.3p1'></a>
|
|
<pre>1 The header <wctype.h> declares several functions useful for mapping wide characters.
|
|
</pre>
|
|
<a name='7.30.3.1'></a>
|
|
<hr>
|
|
<h3>7.30.3.1 [Wide character case mapping functions]</h3>
|
|
<a name='7.30.3.1.1'></a>
|
|
<hr>
|
|
<h3>7.30.3.1.1 [The towlower function]</h3>
|
|
<a name='7.30.3.1.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towlower(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.3.1.1p2'></a>
|
|
<pre>2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.3.1.1p3'></a>
|
|
<pre>3 If the argument is a wide character for which iswupper is true and there are one or
|
|
more corresponding 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='7.30.3.1.2'></a>
|
|
<hr>
|
|
<h3>7.30.3.1.2 [The towupper function]</h3>
|
|
<a name='7.30.3.1.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towupper(wint_t wc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.3.1.2p2'></a>
|
|
<pre>2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.3.1.2p3'></a>
|
|
<pre>3 If the argument is a wide character for which iswlower is true and there are one or
|
|
more corresponding 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='7.30.3.2'></a>
|
|
<hr>
|
|
<h3>7.30.3.2 [Extensible wide character case mapping functions]</h3>
|
|
<a name='7.30.3.2p1'></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='#7.30.3.1'>7.30.3.1</a>).
|
|
</pre>
|
|
<a name='7.30.3.2.1'></a>
|
|
<hr>
|
|
<h3>7.30.3.2.1 [The towctrans function]</h3>
|
|
<a name='7.30.3.2.1p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wint_t towctrans(wint_t wc, wctrans_t desc);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.3.2.1p2'></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='7.30.3.2.1p3'></a>
|
|
<pre>3 Each of the following expressions behaves the same as the call to the wide character case
|
|
mapping function (<a href='#7.30.3.1'>7.30.3.1</a>) in the comment that follows the expression:
|
|
towctrans(wc, wctrans("tolower")) // towlower(wc)
|
|
towctrans(wc, wctrans("toupper")) // towupper(wc)
|
|
Returns
|
|
</pre>
|
|
<a name='7.30.3.2.1p4'></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='7.30.3.2.2'></a>
|
|
<hr>
|
|
<h3>7.30.3.2.2 [The wctrans function]</h3>
|
|
<a name='7.30.3.2.2p1'></a>
|
|
<pre>1 Synopsis
|
|
#include <wctype.h>
|
|
wctrans_t wctrans(const char *property);
|
|
Description
|
|
</pre>
|
|
<a name='7.30.3.2.2p2'></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='7.30.3.2.2p3'></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='7.30.3.2.2p4'></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='7.31'></a>
|
|
<hr>
|
|
<h3>7.31 [Future library directions]</h3>
|
|
<a name='7.31p1'></a>
|
|
<pre>1 The following names are grouped under individual headers for convenience. All external
|
|
names described below are reserved no matter what headers are included by the program.
|
|
</pre>
|
|
<a name='7.31.1'></a>
|
|
<hr>
|
|
<h3>7.31.1 [Complex arithmetic <complex.h>]</h3>
|
|
<a name='7.31.1p1'></a>
|
|
<pre>1 The function names
|
|
cerf cexpm1 clog2
|
|
cerfc clog10 clgamma
|
|
cexp2 clog1p ctgamma
|
|
and the same names suffixed with f or l may be added to the declarations in the
|
|
<complex.h> header.
|
|
</pre>
|
|
<a name='7.31.2'></a>
|
|
<hr>
|
|
<h3>7.31.2 [Character handling <ctype.h>]</h3>
|
|
<a name='7.31.2p1'></a>
|
|
<pre>1 Function names that begin with either is or to, and a lowercase letter may be added to
|
|
the declarations in the <ctype.h> header.
|
|
</pre>
|
|
<a name='7.31.3'></a>
|
|
<hr>
|
|
<h3>7.31.3 [Errors <errno.h>]</h3>
|
|
<a name='7.31.3p1'></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.
|
|
</pre>
|
|
<a name='7.31.4'></a>
|
|
<hr>
|
|
<h3>7.31.4 [Floating-point environment <fenv.h>]</h3>
|
|
<a name='7.31.4p1'></a>
|
|
<pre>1 Macros that begin with FE_ and an uppercase letter may be added to the macros defined
|
|
in the <fenv.h> header.
|
|
</pre>
|
|
<a name='7.31.5'></a>
|
|
<hr>
|
|
<h3>7.31.5 [Format conversion of integer types <inttypes.h>]</h3>
|
|
<a name='7.31.5p1'></a>
|
|
<pre>1 Macros that begin with either PRI or SCN, and either a lowercase letter or X may be
|
|
added to the macros defined in the <inttypes.h> header.
|
|
</pre>
|
|
<a name='7.31.6'></a>
|
|
<hr>
|
|
<h3>7.31.6 [Localization <locale.h>]</h3>
|
|
<a name='7.31.6p1'></a>
|
|
<pre>1 Macros that begin with LC_ and an uppercase letter may be added to the macros defined
|
|
in the <locale.h> header.
|
|
</pre>
|
|
<a name='7.31.7'></a>
|
|
<hr>
|
|
<h3>7.31.7 [Signal handling <signal.h>]</h3>
|
|
<a name='7.31.7p1'></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.
|
|
</pre>
|
|
<a name='7.31.8'></a>
|
|
<hr>
|
|
<h3>7.31.8 [Atomics <stdatomic.h>]</h3>
|
|
<a name='7.31.8p1'></a>
|
|
<pre>1 Macros that begin with ATOMIC_ and an uppercase letter 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 may be added to the declarations in the
|
|
<stdatomic.h> header. Enumeration constants that begin with memory_order_
|
|
and a lowercase letter 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 may be added to the declarations in the <stdatomic.h> header.
|
|
</pre>
|
|
<a name='7.31.9'></a>
|
|
<hr>
|
|
<h3>7.31.9 [Boolean type and values <stdbool.h>]</h3>
|
|
<a name='7.31.9p1'></a>
|
|
<pre>1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
|
|
an obsolescent feature.
|
|
</pre>
|
|
<a name='7.31.10'></a>
|
|
<hr>
|
|
<h3>7.31.10 [Integer types <stdint.h>]</h3>
|
|
<a name='7.31.10p1'></a>
|
|
<pre>1 Typedef names beginning with int or uint and ending with _t may be added to the
|
|
types defined in the <stdint.h> header. Macro names beginning with INT or UINT
|
|
and ending with _MAX, _MIN, or _C may be added to the macros defined in the
|
|
<stdint.h> header.
|
|
</pre>
|
|
<a name='7.31.11'></a>
|
|
<hr>
|
|
<h3>7.31.11 [Input/output <stdio.h>]</h3>
|
|
<a name='7.31.11p1'></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='7.31.11p2'></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='7.31.12'></a>
|
|
<hr>
|
|
<h3>7.31.12 [General utilities <stdlib.h>]</h3>
|
|
<a name='7.31.12p1'></a>
|
|
<pre>1 Function names that begin with str and a lowercase letter may be added to the
|
|
declarations in the <stdlib.h> header.
|
|
</pre>
|
|
<a name='7.31.13'></a>
|
|
<hr>
|
|
<h3>7.31.13 [String handling <string.h>]</h3>
|
|
<a name='7.31.13p1'></a>
|
|
<pre>1 Function names that begin with str, mem, or wcs and a lowercase letter may be added
|
|
to the declarations in the <string.h> header.
|
|
</pre>
|
|
<a name='7.31.14'></a>
|
|
<hr>
|
|
<h3>7.31.14 [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.
|
|
</pre>
|
|
<a name='7.31.15'></a>
|
|
<hr>
|
|
<h3>7.31.15 [Threads <threads.h>]</h3>
|
|
<a name='7.31.15p1'></a>
|
|
<pre>1 Function names, type names, and enumeration constants that begin with either cnd_,
|
|
mtx_, thrd_, or tss_, and a lowercase letter may be added to the declarations in the
|
|
<threads.h> header.
|
|
</pre>
|
|
<a name='7.31.16'></a>
|
|
<hr>
|
|
<h3>7.31.16 [Extended multibyte and wide character utilities <wchar.h>]</h3>
|
|
<a name='7.31.16p1'></a>
|
|
<pre>1 Function names that begin with wcs and a lowercase letter may be added to the
|
|
declarations in the <wchar.h> header.
|
|
</pre>
|
|
<a name='7.31.16p2'></a>
|
|
<pre>2 Lowercase letters may be added to the conversion specifiers and length modifiers in
|
|
</pre>
|
|
<a name='7.31.17'></a>
|
|
<hr>
|
|
<h3>7.31.17 [Wide character classification and mapping utilities]</h3>
|
|
<a name='7.31.17p1'></a>
|
|
<pre>1 <wctype.h>
|
|
Function names that begin with is or to and a lowercase letter 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 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
|
|
auto ∗ if unsigned
|
|
break inline void
|
|
case int volatile
|
|
char long while
|
|
const register _Alignas
|
|
continue restrict _Alignof
|
|
default return _Atomic
|
|
do short _Bool
|
|
double signed _Complex
|
|
else sizeof _Generic
|
|
enum static _Imaginary
|
|
extern struct _Noreturn
|
|
float switch _Static_assert
|
|
for typedef _Thread_local
|
|
goto union
|
|
</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-nondigit
|
|
identifier identifier-nondigit
|
|
identifier digit
|
|
(<a href='#6.4.2.1'>6.4.2.1</a>) identifier-nondigit:
|
|
nondigit
|
|
universal-character-name
|
|
other implementation-defined characters
|
|
(<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
|
|
(<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
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) decimal-constant:
|
|
nonzero-digit
|
|
decimal-constant digit
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) octal-constant:
|
|
0
|
|
octal-constant octal-digit
|
|
(<a href='#6.4.4.1'>6.4.4.1</a>) hexadecimal-constant:
|
|
hexadecimal-prefix hexadecimal-digit
|
|
hexadecimal-constant hexadecimal-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>) 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
|
|
(<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>) integer-suffix:
|
|
unsigned-suffix long-suffixopt
|
|
unsigned-suffix long-long-suffix
|
|
long-suffix unsigned-suffixopt
|
|
long-long-suffix unsigned-suffixopt
|
|
(<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 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>) hexadecimal-digit-sequence:
|
|
hexadecimal-digit
|
|
hexadecimal-digit-sequence hexadecimal-digit
|
|
(<a href='#6.4.4.2'>6.4.4.2</a>) floating-suffix: one of
|
|
f l F L
|
|
(<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:
|
|
' c-char-sequence '
|
|
L' c-char-sequence '
|
|
u' c-char-sequence '
|
|
U' c-char-sequence '
|
|
(<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
|
|
</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>) encoding-prefix:
|
|
u8
|
|
u
|
|
U
|
|
L
|
|
(<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 digit
|
|
pp-number identifier-nondigit
|
|
pp-number e sign
|
|
pp-number E sign
|
|
pp-number p sign
|
|
pp-number P sign
|
|
pp-number .
|
|
</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>(<a href='#6.5.1'>6.5.1</a>) primary-expression:
|
|
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 --
|
|
( type-name ) { initializer-list }
|
|
( type-name ) { initializer-list , }
|
|
(<a href='#6.5.2'>6.5.2</a>) argument-expression-list:
|
|
assignment-expression
|
|
argument-expression-list , assignment-expression
|
|
(<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
|
|
</pre>
|
|
<a name='A.2.2'></a>
|
|
<hr>
|
|
<h3>A.2.2 [Declarations]</h3>
|
|
<pre>(<a href='#6.7'>6.7</a>) declaration:
|
|
declaration-specifiers init-declarator-listopt ;
|
|
static_assert-declaration
|
|
(<a href='#6.7'>6.7</a>) declaration-specifiers:
|
|
storage-class-specifier declaration-specifiersopt
|
|
type-specifier declaration-specifiersopt
|
|
type-qualifier declaration-specifiersopt
|
|
function-specifier declaration-specifiersopt
|
|
alignment-specifier declaration-specifiersopt
|
|
(<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='#6.7.1'>6.7.1</a>) storage-class-specifier:
|
|
typedef
|
|
extern
|
|
static
|
|
_Thread_local
|
|
auto
|
|
register
|
|
(<a href='#6.7.2'>6.7.2</a>) type-specifier:
|
|
void
|
|
char
|
|
short
|
|
int
|
|
long
|
|
float
|
|
double
|
|
signed
|
|
unsigned
|
|
_Bool
|
|
_Complex
|
|
atomic-type-specifier
|
|
struct-or-union-specifier
|
|
enum-specifier
|
|
typedef-name
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-or-union-specifier:
|
|
struct-or-union identifieropt { struct-declaration-list }
|
|
struct-or-union 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>) struct-declaration-list:
|
|
struct-declaration
|
|
struct-declaration-list struct-declaration
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-declaration:
|
|
specifier-qualifier-list struct-declarator-listopt ;
|
|
static_assert-declaration
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) specifier-qualifier-list:
|
|
type-specifier specifier-qualifier-listopt
|
|
type-qualifier specifier-qualifier-listopt
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-declarator-list:
|
|
struct-declarator
|
|
struct-declarator-list , struct-declarator
|
|
(<a href='#6.7.2.1'>6.7.2.1</a>) struct-declarator:
|
|
declarator
|
|
declaratoropt : constant-expression
|
|
(<a href='#6.7.2.2'>6.7.2.2</a>) enum-specifier:
|
|
enum identifieropt { enumerator-list }
|
|
enum identifieropt { enumerator-list , }
|
|
enum identifier
|
|
(<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
|
|
enumeration-constant = constant-expression
|
|
(<a href='#6.7.2.4'>6.7.2.4</a>) atomic-type-specifier:
|
|
_Atomic ( 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
|
|
( 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 * ]
|
|
direct-declarator ( parameter-type-list )
|
|
direct-declarator ( identifier-listopt )
|
|
(<a href='#6.7.6'>6.7.6</a>) pointer:
|
|
* type-qualifier-listopt
|
|
* 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:
|
|
declaration-specifiers declarator
|
|
declaration-specifiers abstract-declaratoropt
|
|
(<a href='#6.7.6'>6.7.6</a>) identifier-list:
|
|
identifier
|
|
identifier-list , identifier
|
|
(<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 )
|
|
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 [ * ]
|
|
direct-abstract-declaratoropt ( parameter-type-listopt )
|
|
(<a href='#6.7.8'>6.7.8</a>) typedef-name:
|
|
identifier
|
|
(<a href='#6.7.9'>6.7.9</a>) initializer:
|
|
assignment-expression
|
|
{ initializer-list }
|
|
{ initializer-list , }
|
|
(<a href='#6.7.9'>6.7.9</a>) initializer-list:
|
|
designationopt initializer
|
|
initializer-list , designationopt initializer
|
|
(<a href='#6.7.9'>6.7.9</a>) designation:
|
|
designator-list =
|
|
(<a href='#6.7.9'>6.7.9</a>) designator-list:
|
|
designator
|
|
designator-list designator
|
|
(<a href='#6.7.9'>6.7.9</a>) designator:
|
|
[ constant-expression ]
|
|
. identifier
|
|
(<a href='#6.7.10'>6.7.10</a>) static_assert-declaration:
|
|
_Static_assert ( constant-expression , string-literal ) ;
|
|
</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
|
|
compound-statement
|
|
expression-statement
|
|
selection-statement
|
|
iteration-statement
|
|
jump-statement
|
|
(<a href='#6.8.1'>6.8.1</a>) labeled-statement:
|
|
identifier : statement
|
|
case constant-expression : statement
|
|
default : 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
|
|
statement
|
|
(<a href='#6.8.3'>6.8.3</a>) expression-statement:
|
|
expressionopt ;
|
|
(<a href='#6.8.4'>6.8.4</a>) selection-statement:
|
|
if ( expression ) statement
|
|
if ( expression ) statement else statement
|
|
switch ( expression ) statement
|
|
(<a href='#6.8.5'>6.8.5</a>) iteration-statement:
|
|
while ( expression ) statement
|
|
do statement while ( expression ) ;
|
|
for ( expressionopt ; expressionopt ; expressionopt ) statement
|
|
for ( declaration expressionopt ; expressionopt ) statement
|
|
(<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:
|
|
declaration-specifiers declarator declaration-listopt compound-statement
|
|
(<a href='#6.9.1'>6.9.1</a>) declaration-list:
|
|
declaration
|
|
declaration-list declaration
|
|
</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
|
|
(<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
|
|
# 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
|
|
# 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
|
|

|
|
</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
|
|
static_assert
|
|
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
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
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
|
|
int feclearexcept(int excepts);
|
|
int fegetexceptflag(fexcept_t *flagp, int excepts);
|
|
int feraiseexcept(int excepts);
|
|
int fesetexceptflag(const fexcept_t *flagp,
|
|
int excepts);
|
|
int fetestexcept(int excepts);
|
|
 int fegetround(void);
|
|
int fesetround(int round);
|
|
int fegetenv(fenv_t *envp);
|
|
int feholdexcept(fenv_t *envp);
|
|
int fesetenv(const fenv_t *envp);
|
|
int feupdateenv(const fenv_t *envp);
|
|
</pre>
|
|
<a name='B.6'></a>
|
|
<hr>
|
|
<h3>B.6 [Characteristics of floating types <float.h>]</h3>
|
|
<pre>FLT_ROUNDS DBL_DIG FLT_MAX
|
|
FLT_EVAL_METHOD LDBL_DIG DBL_MAX
|
|
FLT_HAS_SUBNORM FLT_MIN_EXP LDBL_MAX
|
|
DBL_HAS_SUBNORM DBL_MIN_EXP FLT_EPSILON
|
|
LDBL_HAS_SUBNORM LDBL_MIN_EXP DBL_EPSILON
|
|
FLT_RADIX FLT_MIN_10_EXP LDBL_EPSILON
|
|
FLT_MANT_DIG DBL_MIN_10_EXP FLT_MIN
|
|
DBL_MANT_DIG LDBL_MIN_10_EXP DBL_MIN
|
|
LDBL_MANT_DIG FLT_MAX_EXP LDBL_MIN
|
|
FLT_DECIMAL_DIG DBL_MAX_EXP FLT_TRUE_MIN
|
|
DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
|
|
LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
|
|
DECIMAL_DIG DBL_MAX_10_EXP
|
|
FLT_DIG LDBL_MAX_10_EXP
|
|
</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>CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
|
|
SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
|
|
SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
|
|
UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
|
|
CHAR_MIN USHRT_MAX LONG_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 isfinite(real-floating x);
|
|
int isinf(real-floating x);
|
|
int isnan(real-floating x);
|
|
int isnormal(real-floating x);
|
|
int signbit(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 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 exp2(double x);
|
|
float exp2f(float x);
|
|
long double exp2l(long double x);
|
|
double expm1(double x);
|
|
float expm1f(float x);
|
|
long double expm1l(long double x);
|
|
double frexp(double value, int *exp);
|
|
float frexpf(float value, int *exp);
|
|
long double frexpl(long double value, int *exp);
|
|
int ilogb(double x);
|
|
int ilogbf(float x);
|
|
int ilogbl(long double x);
|
|
double ldexp(double x, int exp);
|
|
float ldexpf(float x, int exp);
|
|
long double ldexpl(long double x, int exp);
|
|
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 log1p(double x);
|
|
float log1pf(float x);
|
|
long double log1pl(long double x);
|
|
double log2(double x);
|
|
float log2f(float x);
|
|
long double log2l(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 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 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 trunc(double x);
|
|
float truncf(float x);
|
|
long double truncl(long double x);
|
|
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 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 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);
|
|
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);
|
|
</pre>
|
|
<a name='B.12'></a>
|
|
<hr>
|
|
<h3>B.12 [Nonlocal 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>alignas
|
|
_ _alignas_is_defined
|
|
</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, parmN);
|
|
</pre>
|
|
<a name='B.16'></a>
|
|
<hr>
|
|
<h3>B.16 [Atomics <stdatomic.h>]</h3>
|
|
<pre>ATOMIC_BOOL_LOCK_FREE atomic_uint
|
|
ATOMIC_CHAR_LOCK_FREE atomic_long
|
|
ATOMIC_CHAR16_T_LOCK_FREE atomic_ulong
|
|
ATOMIC_CHAR32_T_LOCK_FREE atomic_llong
|
|
ATOMIC_WCHAR_T_LOCK_FREE atomic_ullong
|
|
ATOMIC_SHORT_LOCK_FREE atomic_char16_t
|
|
ATOMIC_INT_LOCK_FREE atomic_char32_t
|
|
ATOMIC_LONG_LOCK_FREE atomic_wchar_t
|
|
ATOMIC_LLONG_LOCK_FREE atomic_int_least8_t
|
|
ATOMIC_POINTER_LOCK_FREE atomic_uint_least8_t
|
|
ATOMIC_FLAG_INIT atomic_int_least16_t
|
|
memory_order atomic_uint_least16_t
|
|
atomic_flag atomic_int_least32_t
|
|
memory_order_relaxed ∗ atomic_uint_least32_t
|
|
memory_order_consume atomic_int_least64_t
|
|
memory_order_acquire atomic_uint_least64_t
|
|
memory_order_release atomic_int_fast8_t
|
|
memory_order_acq_rel atomic_uint_fast8_t
|
|
memory_order_seq_cst atomic_int_fast16_t
|
|
atomic_bool atomic_uint_fast16_t
|
|
atomic_char atomic_int_fast32_t
|
|
atomic_schar atomic_uint_fast32_t
|
|
atomic_uchar atomic_int_fast64_t
|
|
atomic_short atomic_uint_fast64_t
|
|
atomic_ushort atomic_intptr_t
|
|
atomic_int atomic_uintptr_t
|
|
atomic_size_t atomic_intmax_t
|
|
atomic_ptrdiff_t atomic_uintmax_t
|
|
#define ATOMIC_VAR_INIT(C value)
|
|
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(volatile A *object);
|
|
C atomic_load_explicit(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 [Boolean type and values <stdbool.h>]</h3>
|
|
<pre>bool
|
|
true
|
|
false
|
|
_ _bool_true_false_are_defined
|
|
</pre>
|
|
<a name='B.18'></a>
|
|
<hr>
|
|
<h3>B.18 [Common definitions <stddef.h>]</h3>
|
|
<pre>ptrdiff_t max_align_t NULL
|
|
size_t wchar_t
|
|
offsetof(type, member-designator)
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
rsize_t
|
|
</pre>
|
|
<a name='B.19'></a>
|
|
<hr>
|
|
<h3>B.19 [Integer types <stdint.h>]</h3>
|
|
<pre>intN_t INT_LEASTN_MIN PTRDIFF_MAX
|
|
uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
|
|
int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
|
|
uint_leastN_t INT_FASTN_MIN SIZE_MAX
|
|
int_fastN_t INT_FASTN_MAX WCHAR_MIN
|
|
uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
|
|
intptr_t INTPTR_MIN WINT_MIN
|
|
uintptr_t INTPTR_MAX WINT_MAX
|
|
intmax_t UINTPTR_MAX INTN_C(value)
|
|
uintmax_t INTMAX_MIN UINTN_C(value)
|
|
INTN_MIN INTMAX_MAX INTMAX_C(value)
|
|
INTN_MAX UINTMAX_MAX UINTMAX_C(value)
|
|
UINTN_MAX PTRDIFF_MIN
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
RSIZE_MAX
|
|
</pre>
|
|
<a name='B.20'></a>
|
|
<hr>
|
|
<h3>B.20 [Input/output <stdio.h>]</h3>
|
|
<pre>size_t _IOLBF FILENAME_MAX TMP_MAX
|
|
FILE _IONBF L_tmpnam stderr
|
|
fpos_t BUFSIZ SEEK_CUR stdin
|
|
NULL EOF SEEK_END stdout
|
|
_IOFBF FOPEN_MAX SEEK_SET
|
|
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 fprintf(FILE * restrict stream,
|
|
const char * restrict format, ...);
|
|
int fscanf(FILE * restrict stream,
|
|
const char * restrict format, ...);
|
|
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);
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
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.21'></a>
|
|
<hr>
|
|
<h3>B.21 [General utilities <stdlib.h>]</h3>
|
|
<pre>size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
|
|
wchar_t lldiv_t EXIT_SUCCESS
|
|
div_t NULL RAND_MAX
|
|
double atof(const char *nptr);
|
|
int atoi(const char *nptr);
|
|
long int atol(const char *nptr);
|
|
long long int atoll(const char *nptr);
|
|
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 *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 wchar);
|
|
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);
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
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, const void *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.22'></a>
|
|
<hr>
|
|
<h3>B.22 [_Noreturn <stdnoreturn.h>]</h3>
|
|
<pre>noreturn
|
|
</pre>
|
|
<a name='B.23'></a>
|
|
<hr>
|
|
<h3>B.23 [String handling <string.h>]</h3>
|
|
<pre>size_t
|
|
NULL
|
|
void *memcpy(void * restrict s1,
|
|
const void * restrict s2, 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 *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);
|
|
void *memchr(const void *s, int c, size_t n);
|
|
char *strchr(const char *s, int c);
|
|
size_t strcspn(const char *s1, const char *s2);
|
|
char *strpbrk(const char *s1, const char *s2);
|
|
char *strrchr(const char *s, int c);
|
|
size_t strspn(const char *s1, const char *s2);
|
|
char *strstr(const char *s1, const char *s2);
|
|
char *strtok(char * restrict s1,
|
|
const char * restrict s2);
|
|
void *memset(void *s, int c, size_t n);
|
|
char *strerror(int errnum);
|
|
size_t strlen(const char *s);
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
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.24'></a>
|
|
<hr>
|
|
<h3>B.24 [Type-generic math <tgmath.h>]</h3>
|
|
<pre>acos sqrt fmod nextafter
|
|
asin fabs frexp nexttoward
|
|
atan atan2 hypot remainder
|
|
acosh cbrt ilogb remquo
|
|
asinh ceil ldexp rint
|
|
atanh copysign lgamma round
|
|
cos erf llrint scalbn
|
|
sin erfc llround scalbln
|
|
tan exp2 log10 tgamma
|
|
cosh expm1 log1p trunc
|
|
sinh fdim log2 carg
|
|
tanh floor logb cimag
|
|
exp fma lrint conj
|
|
log fmax lround cproj
|
|
pow fmin nearbyint creal
|
|
</pre>
|
|
<a name='B.25'></a>
|
|
<hr>
|
|
<h3>B.25 [Threads <threads.h>]</h3>
|
|
<pre>thread_local once_flag
|
|
ONCE_FLAG_INIT mtx_plain ∗
|
|
TSS_DTOR_ITERATIONS mtx_recursive
|
|
cnd_t mtx_timed
|
|
thrd_t thrd_timedout
|
|
tss_t thrd_success
|
|
mtx_t thrd_busy
|
|
tss_dtor_t thrd_error
|
|
thrd_start_t thrd_nomem
|
|
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.26'></a>
|
|
<hr>
|
|
<h3>B.26 [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 time(time_t *timer);
|
|
int timespec_get(timespec *ts, int base);
|
|
char *asctime(const struct tm *timeptr);
|
|
char *ctime(const time_t *timer);
|
|
struct tm *gmtime(const time_t *timer);
|
|
struct tm *localtime(const time_t *timer);
|
|
size_t strftime(char * restrict s,
|
|
size_t maxsize,
|
|
const char * restrict format,
|
|
const struct tm * restrict timeptr);
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
 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.27'></a>
|
|
<hr>
|
|
<h3>B.27 [Unicode utilities <uchar.h>]</h3>
|
|
<pre>mbstate_t size_t char16_t char32_t
|
|
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.28'></a>
|
|
<hr>
|
|
<h3>B.28 [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);
|
|
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);
|
|
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);
|
|
wchar_t *wcschr(const wchar_t *s, wchar_t c);
|
|
size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
|
|
wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
|
|
wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
|
|
size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
|
|
wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
|
|
wchar_t *wcstok(wchar_t * restrict s1,
|
|
const wchar_t * restrict s2,
|
|
wchar_t ** restrict ptr);
|
|
wchar_t *wmemchr(const wchar_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);
|
|
_ _STDC_WANT_LIB_EXT1_ _
|
|
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.29'></a>
|
|
<hr>
|
|
<h3>B.29 [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>).
|
|
— The end of a full declarator: declarators (<a href='#6.7.6'>6.7.6</a>);
|
|
— Between the evaluation of a full expression and the next full expression to be
|
|
evaluated. The following are full expressions: an initializer that is not part of a
|
|
compound literal (<a href='#6.7.9'>6.7.9</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='#7.21.6'>7.21.6</a>, <a href='#7.29.2'>7.29.2</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='#7.22.5'>7.22.5</a>).
|
|
|
|
</pre>
|
|
<a name='D.'></a>
|
|
<hr>
|
|
<h3>D. [Annex D (normative) Universal character names for identifiers]</h3>
|
|
<a name='D.p1'></a>
|
|
<pre>1 This clause lists the hexadecimal code values that are valid in universal character names
|
|
in identifiers.
|
|
</pre>
|
|
<a name='D.1'></a>
|
|
<hr>
|
|
<h3>D.1 [Ranges of characters allowed]</h3>
|
|
<a name='D.1p1'></a>
|
|
<pre>1 00A8, 00AA, 00AD, 00AF, 00B2−00B5, 00B7−00BA, 00BC−00BE, 00C0−00D6,
|
|
00D8−00F6, 00F8−00FF
|
|
</pre>
|
|
<a name='D.1p2'></a>
|
|
<pre>2 0100−167F, 1681−180D, 180F−1FFF
|
|
</pre>
|
|
<a name='D.1p3'></a>
|
|
<pre>3 200B−200D, 202A−202E, 203F−2040, 2054, 2060−206F
|
|
</pre>
|
|
<a name='D.1p4'></a>
|
|
<pre>4 2070−218F, 2460−24FF, 2776−2793, 2C00−2DFF, 2E80−2FFF
|
|
</pre>
|
|
<a name='D.1p5'></a>
|
|
<pre>5 3004−3007, 3021−302F, 3031−303F
|
|
</pre>
|
|
<a name='D.1p6'></a>
|
|
<pre>6 3040−D7FF
|
|
</pre>
|
|
<a name='D.1p7'></a>
|
|
<pre>7 F900−FD3D, FD40−FDCF, FDF0−FE44, FE47−FFFD
|
|
</pre>
|
|
<a name='D.1p8'></a>
|
|
<pre>8 10000−1FFFD, 20000−2FFFD, 30000−3FFFD, 40000−4FFFD, 50000−5FFFD,
|
|
60000−6FFFD, 70000−7FFFD, 80000−8FFFD, 90000−9FFFD, A0000−AFFFD,
|
|
B0000−BFFFD, C0000−CFFFD, D0000−DFFFD, E0000−EFFFD
|
|
</pre>
|
|
<a name='D.2'></a>
|
|
<hr>
|
|
<h3>D.2 [Ranges of characters disallowed initially]</h3>
|
|
<a name='D.2p1'></a>
|
|
<pre>1 0300−036F, 1DC0−1DFF, 20D0−20FF, FE20−FE2F
|
|
|
|
</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, in alphabetical order. The
|
|
minimum magnitudes shown shall be replaced by implementation-defined magnitudes
|
|
with the same sign. 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>.
|
|
#define CHAR_BIT 8
|
|
#define CHAR_MAX UCHAR_MAX or SCHAR_MAX
|
|
#define CHAR_MIN 0 or SCHAR_MIN
|
|
#define INT_MAX +32767
|
|
#define INT_MIN -32767
|
|
#define LONG_MAX +2147483647
|
|
#define LONG_MIN -2147483647
|
|
#define LLONG_MAX +9223372036854775807
|
|
#define LLONG_MIN -9223372036854775807
|
|
#define MB_LEN_MAX 1
|
|
#define SCHAR_MAX +127
|
|
#define SCHAR_MIN -127
|
|
#define SHRT_MAX +32767
|
|
#define SHRT_MIN -32767
|
|
#define UCHAR_MAX 255
|
|
#define USHRT_MAX 65535
|
|
#define UINT_MAX 65535
|
|
#define ULONG_MAX 4294967295
|
|
#define ULLONG_MAX 18446744073709551615
|
|
</pre>
|
|
<a name='E.p2'></a>
|
|
<pre>2 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>.
|
|
</pre>
|
|
<a name='E.p3'></a>
|
|
<pre>3 The values given in the following list shall be replaced by implementation-defined
|
|
expressions:
|
|
#define FLT_EVAL_METHOD
|
|
#define FLT_ROUNDS
|
|
</pre>
|
|
<a name='E.p4'></a>
|
|
<pre>4 The values given in the following list shall be replaced by implementation-defined
|
|
constant expressions that are greater or equal in magnitude (absolute value) to those
|
|
shown, with the same sign:
|
|
#define DLB_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 LDLB_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.p5'></a>
|
|
<pre>5 The values given in the following list shall be replaced by implementation-defined
|
|
constant expressions with values that are greater than or equal to those shown:
|
|
#define DBL_MAX 1E+37
|
|
#define FLT_MAX 1E+37
|
|
#define LDBL_MAX 1E+37
|
|
</pre>
|
|
<a name='E.p6'></a>
|
|
<pre>6 The values given in the following list shall be replaced by implementation-defined
|
|
constant expressions 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='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 Binary floating-point arithmetic for
|
|
microprocessor systems, second edition (IEC 60559:1989), previously designated
|
|
IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
|
|
(ANSI/IEEE 754−1985). IEEE Standard for Radix-Independent Floating-Point
|
|
Arithmetic (ANSI/IEEE 854−1987) generalizes the binary standard to remove
|
|
dependencies on radix and word length. IEC 60559 generally refers to the floating-point
|
|
standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
|
|
defines _ _STDC_IEC_559_ _ shall conform to the specifications in this annex.<a href='#FOOTNOTE.356'><sup>[356]</sup></a>
|
|
Where a binding between the C language and IEC 60559 is indicated, the
|
|
IEC 60559-specified behavior is adopted by reference, unless stated otherwise. Since
|
|
negative and positive infinity are representable in IEC 60559 formats, all real numbers lie
|
|
within the range of representable values.
|
|
</pre>
|
|
<a name='FOOTNOTE.356'>
|
|
<pre><i><b>Footnote 356)</b> Implementations that do not define _ _STDC_IEC_559_ _ are not required to conform to these
|
|
specifications.
|
|
</i></pre>
|
|
</a>
|
|
<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 single format.
|
|
— The double type matches the IEC 60559 double format.
|
|
— The long double type matches an IEC 60559 extended format,<a href='#FOOTNOTE.357'><sup>[357]</sup></a> else a
|
|
non-IEC 60559 extended format, else the IEC 60559 double format.
|
|
Any non-IEC 60559 extended format used for the long double type shall have more
|
|
precision than IEC 60559 double and at least the range of IEC 60559 double.<a href='#FOOTNOTE.358'><sup>[358]</sup></a>
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.357'>
|
|
<pre><i><b>Footnote 357)</b> ‘‘Extended’’ is IEC 60559’s double-extended data format. Extended refers to both the common 80-bit
|
|
and quadruple 128-bit IEC 60559 formats.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.358'>
|
|
<pre><i><b>Footnote 358)</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 an IEC 60559 extended format.
|
|
</pre>
|
|
<a name='F.2.1'></a>
|
|
<hr>
|
|
<h3>F.2.1 [Infinities, signed zeros, and NaNs]</h3>
|
|
<a name='F.2.1p1'></a>
|
|
<pre>1 This specification does not define the behavior of signaling NaNs.<a href='#FOOTNOTE.359'><sup>[359]</sup></a> It generally uses
|
|
the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
|
|
functions in <math.h> provide designations for IEC 60559 NaNs and infinities.
|
|
</pre>
|
|
<a name='FOOTNOTE.359'>
|
|
<pre><i><b>Footnote 359)</b> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
|
|
sufficient for closure of the arithmetic.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.3'></a>
|
|
<hr>
|
|
<h3>F.3 [Operators and functions]</h3>
|
|
<a name='F.3p1'></a>
|
|
<pre>1 C operators and functions provide IEC 60559 required and recommended facilities as
|
|
listed below.
|
|
— The +, −, *, and / operators provide the IEC 60559 add, subtract, multiply, and
|
|
divide operations.
|
|
— The sqrt functions in <math.h> provide the IEC 60559 square root operation.
|
|
— The remainder functions in <math.h> provide the IEC 60559 remainder
|
|
operation. The remquo functions in <math.h> provide the same operation but
|
|
with additional information.
|
|
— The rint functions in <math.h> provide the IEC 60559 operation that rounds a
|
|
floating-point number to an integer value (in the same precision). The nearbyint
|
|
functions in <math.h> provide the nearbyinteger function recommended in the
|
|
Appendix to ANSI/IEEE 854.
|
|
— The conversions for floating types provide the IEC 60559 conversions between
|
|
floating-point precisions.
|
|
— The conversions from integer to floating types provide the IEC 60559 conversions
|
|
from integer to floating point.
|
|
— The conversions from floating to integer types provide IEC 60559-like conversions
|
|
but always round toward zero.
|
|
— The lrint and llrint functions in <math.h> provide the IEC 60559
|
|
conversions, which honor the directed rounding mode, from floating point to the
|
|
long int and long long int integer formats. The lrint and llrint
|
|
functions can be used to implement IEC 60559 conversions from floating to other
|
|
integer formats.
|
|
— The translation time conversion of floating constants and the strtod, strtof,
|
|
strtold, fprintf, fscanf, and related library functions in <stdlib.h>,
|
|
<stdio.h>, and <wchar.h> provide IEC 60559 binary-decimal conversions. The
|
|
strtold function in <stdlib.h> provides the conv function recommended in the
|
|
Appendix to ANSI/IEEE 854.
|
|
— The relational and equality operators provide IEC 60559 comparisons. IEC 60559
|
|
identifies a need for additional comparison predicates to facilitate writing code that
|
|
accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
|
|
isless, islessequal, islessgreater, and isunordered) in <math.h>
|
|
supplement the language operators to address this need. The islessgreater and
|
|
isunordered macros provide respectively a quiet version of the <> predicate and
|
|
the unordered predicate recommended in the Appendix to IEC 60559.
|
|
— The feclearexcept, feraiseexcept, and fetestexcept functions in
|
|
<fenv.h> provide the facility to test and alter the IEC 60559 floating-point
|
|
exception status flags. The fegetexceptflag and fesetexceptflag
|
|
functions in <fenv.h> provide the facility to save and restore all five status flags at
|
|
one time. These functions are used in conjunction with the type fexcept_t and the
|
|
floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
|
|
FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <fenv.h>.
|
|
— The fegetround and fesetround functions in <fenv.h> provide the facility
|
|
to select among the IEC 60559 directed rounding modes represented by the rounding
|
|
direction macros in <fenv.h> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
|
|
FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
|
|
IEC 60559 directed rounding modes.
|
|
— The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
|
|
<fenv.h> provide a facility to manage the floating-point environment, comprising
|
|
the IEC 60559 status flags and control modes.
|
|
— The copysign functions in <math.h> provide the copysign function
|
|
recommended in the Appendix to IEC 60559.
|
|
— The fabs functions in <math.h> provide the abs function recommended in the
|
|
Appendix to IEC 60559.
|
|
— The unary minus (−) operator provides the unary minus (−) operation recommended
|
|
in the Appendix to IEC 60559.
|
|
— The scalbn and scalbln functions in <math.h> provide the scalb function
|
|
recommended in the Appendix to IEC 60559.
|
|
— The logb functions in <math.h> provide the logb function recommended in the
|
|
Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
|
|
— The nextafter and nexttoward functions in <math.h> provide the nextafter
|
|
function recommended in the Appendix to IEC 60559 (but with a minor change to
|
|
better handle signed zeros).
|
|
— The isfinite macro in <math.h> provides the finite function recommended in
|
|
the Appendix to IEC 60559.
|
|
— The isnan macro in <math.h> provides the isnan function recommended in the
|
|
Appendix to IEC 60559.
|
|
— The signbit macro and the fpclassify macro in <math.h>, used in
|
|
conjunction with the number classification macros (FP_NAN, FP_INFINITE,
|
|
FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
|
|
function recommended in the Appendix to IEC 60559 (except that the classification
|
|
macros defined in <a href='#7.12.3'>7.12.3</a> do not distinguish signaling from quiet NaNs).
|
|
</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 no floating-point exceptions are raised
|
|
(even for 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.360'><sup>[360]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.360'>
|
|
<pre><i><b>Footnote 360)</b> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that 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 rint, lrint, llrint, and nearbyint in
|
|
<math.h>.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.5'></a>
|
|
<hr>
|
|
<h3>F.5 [Binary-decimal conversion]</h3>
|
|
<a name='F.5p1'></a>
|
|
<pre>1 Conversion from the widest supported IEC 60559 format to decimal with
|
|
DECIMAL_DIG digits and back is the identity function.<a href='#FOOTNOTE.361'><sup>[361]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.361'>
|
|
<pre><i><b>Footnote 361)</b> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
|
|
DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
|
|
IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
|
|
DBL_DIG are 18 and 15, respectively, for these formats.)
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.5p2'></a>
|
|
<pre>2 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
|
|
particular, conversion between any supported IEC 60559 format and decimal with
|
|
DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
|
|
rounding mode), which assures that conversion from the widest supported IEC 60559
|
|
format to decimal with DECIMAL_DIG digits and back is the identity function.
|
|
</pre>
|
|
<a name='F.5p3'></a>
|
|
<pre>3 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.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.362'><sup>[362]</sup></a> to the return type of the function
|
|
and the resulting value is returned to the caller.
|
|
</pre>
|
|
<a name='FOOTNOTE.362'>
|
|
<pre><i><b>Footnote 362)</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, subnormals, 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 directed-rounding control modes. It includes also
|
|
IEC 60559 dynamic rounding precision and trap enablement modes, if the
|
|
implementation supports them.<a href='#FOOTNOTE.363'><sup>[363]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.363'>
|
|
<pre><i><b>Footnote 363)</b> This specification does not require dynamic rounding precision nor trap enablement modes.
|
|
</i></pre>
|
|
</a>
|
|
<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. When the state for the FENV_ACCESS pragma (defined in
|
|
<fenv.h>) is ‘‘on’’, these changes to the floating-point state are treated as side effects
|
|
which respect sequence points.<a href='#FOOTNOTE.364'><sup>[364]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.364'>
|
|
<pre><i><b>Footnote 364)</b> If the state for the FENV_ACCESS pragma is ‘‘off’’, the implementation is free to assume the 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 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.365'><sup>[365]</sup></a> the implementation should then
|
|
proceed with the translation of the program.
|
|
</pre>
|
|
<a name='FOOTNOTE.365'>
|
|
<pre><i><b>Footnote 365)</b> As floating constants are converted to appropriate internal representations at translation time, their
|
|
conversion is subject to 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 floating-point environment is initialized as prescribed by
|
|
IEC 60559:
|
|
— All floating-point exception status flags are cleared.
|
|
— The 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.366'><sup>[366]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.366'>
|
|
<pre><i><b>Footnote 366)</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.367'><sup>[367]</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.367'>
|
|
<pre><i><b>Footnote 367)</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 argument to the feraiseexcept function in <fenv.h> represents IEC 60559
|
|
valid coincident floating-point exceptions for atomic operations (namely ‘‘overflow’’ and
|
|
‘‘inexact’’, or ‘‘underflow’’ and ‘‘inexact’’), then ‘‘overflow’’ or ‘‘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 x/2 ↔ x × 0.5 Although similar transformations involving inexact constants
|
|
generally do not yield numerically equivalent expressions, if the
|
|
constants are exact then such transformations 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 are equivalent (on IEC 60559
|
|
machines, among others).<a href='#FOOTNOTE.368'><sup>[368]</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.369'><sup>[369]</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.368'>
|
|
<pre><i><b>Footnote 368)</b> Strict support for signaling NaNs — not required by this specification — would invalidate these and
|
|
other transformations that remove arithmetic operators.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.369'>
|
|
<pre><i><b>Footnote 369)</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.9.3'></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 numerically equal, these
|
|
expressions are not equivalent 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 desirable 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 arithmetic 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.370'><sup>[370]</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.370'>
|
|
<pre><i><b>Footnote 370)</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>]</h3>
|
|
<a name='F.10p1'></a>
|
|
<pre>1 This subclause contains specifications of <math.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 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 the basic arithmetic operations covered by IEC 60559.
|
|
</pre>
|
|
<a name='F.10p4'></a>
|
|
<pre>4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
|
|
nonzero value.
|
|
</pre>
|
|
<a name='F.10p5'></a>
|
|
<pre>5 The ‘‘invalid’’ and ‘‘divide-by-zero’’ floating-point exceptions are raised as specified in
|
|
subsequent subclauses of this annex.
|
|
</pre>
|
|
<a name='F.10p6'></a>
|
|
<pre>6 The ‘‘overflow’’ floating-point exception is raised whenever an infinity — or, because of
|
|
rounding direction, a maximal-magnitude finite number — is returned in lieu of a value
|
|
whose magnitude is too large.
|
|
</pre>
|
|
<a name='F.10p7'></a>
|
|
<pre>7 The ‘‘underflow’’ floating-point exception is raised whenever a result is tiny (essentially
|
|
subnormal or zero) and suffers loss of accuracy.<a href='#FOOTNOTE.371'><sup>[371]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.371'>
|
|
<pre><i><b>Footnote 371)</b> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
|
|
when the floating-point exception is raised.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10p8'></a>
|
|
<pre>8 Whether or when library functions raise the ‘‘inexact’’ floating-point exception is
|
|
unspecified, unless explicitly specified otherwise.
|
|
</pre>
|
|
<a name='F.10p9'></a>
|
|
<pre>9 Whether or when library functions raise an undeserved ‘‘underflow’’ floating-point
|
|
exception is unspecified.<a href='#FOOTNOTE.372'><sup>[372]</sup></a> Otherwise, as implied by <a href='#F.8.6'>F.8.6</a>, the <math.h> functions do
|
|
not raise spurious floating-point exceptions (detectable by the user), other than the
|
|
‘‘inexact’’ floating-point exception.
|
|
</pre>
|
|
<a name='FOOTNOTE.372'>
|
|
<pre><i><b>Footnote 372)</b> It is intended that undeserved ‘‘underflow’’ and ‘‘inexact’’ floating-point exceptions are raised only if
|
|
avoiding them would be too costly.
|
|
</i></pre>
|
|
</a>
|
|
<a name='F.10p10'></a>
|
|
<pre>10 Whether the functions honor the rounding direction mode is implementation-defined,
|
|
unless explicitly specified otherwise.
|
|
</pre>
|
|
<a name='F.10p11'></a>
|
|
<pre>11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
|
|
except where stated otherwise.
|
|
</pre>
|
|
<a name='F.10p12'></a>
|
|
<pre>12 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.10p13'></a>
|
|
<pre>13 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 ±π /2.
|
|
</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.373'><sup>[373]</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 −π /2 for y < 0.
|
|
— atan2(y, ±0) returns π /2 for y > 0.
|
|
— atan2(±y, −∞) returns ±π for finite y > 0.
|
|
— atan2(±y, +∞) returns ±0 for finite y > 0.
|
|
— atan2(±∞, x) returns ±π /2 for finite x.
|
|
— atan2(±∞, −∞) returns ±3π /4.
|
|
— atan2(±∞, +∞) returns ±π /4.
|
|
</pre>
|
|
<a name='FOOTNOTE.373'>
|
|
<pre><i><b>Footnote 373)</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.10.2'></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 exp2 functions]</h3>
|
|
<a name='F.10.3.2p1'></a>
|
|
<pre>1 — exp2(±0) returns 1.
|
|
— exp2(−∞) returns +0.
|
|
— exp2(+∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.3'></a>
|
|
<hr>
|
|
<h3>F.10.3.3 [The expm1 functions]</h3>
|
|
<a name='F.10.3.3p1'></a>
|
|
<pre>1 — expm1(±0) returns ±0.
|
|
— expm1(−∞) returns −1.
|
|
— expm1(+∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.4'></a>
|
|
<hr>
|
|
<h3>F.10.3.4 [The frexp functions]</h3>
|
|
<a name='F.10.3.4p1'></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.10.3.4p2'></a>
|
|
<pre>2 frexp raises no floating-point exceptions.
|
|
</pre>
|
|
<a name='F.10.3.4p3'></a>
|
|
<pre>3 When the radix of the argument is a power of 2, the returned value is exact and is
|
|
independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.3.4p4'></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.10.3.5'></a>
|
|
<hr>
|
|
<h3>F.10.3.5 [The ilogb functions]</h3>
|
|
<a name='F.10.3.5p1'></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.10.3.5p2'></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.10.3.5p3'></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='#7.12.6.5'>7.12.6.5</a>.
|
|
</pre>
|
|
<a name='F.10.3.6'></a>
|
|
<hr>
|
|
<h3>F.10.3.6 [The ldexp functions]</h3>
|
|
<a name='F.10.3.6p1'></a>
|
|
<pre>1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
|
|
</pre>
|
|
<a name='F.10.3.7'></a>
|
|
<hr>
|
|
<h3>F.10.3.7 [The log functions]</h3>
|
|
<a name='F.10.3.7p1'></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.10.3.8'></a>
|
|
<hr>
|
|
<h3>F.10.3.8 [The log10 functions]</h3>
|
|
<a name='F.10.3.8p1'></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.10.3.9'></a>
|
|
<hr>
|
|
<h3>F.10.3.9 [The log1p functions]</h3>
|
|
<a name='F.10.3.9p1'></a>
|
|
<pre>1 — log1p(±0) returns ±0.
|
|
— log1p(−1) returns −∞ and raises the ‘‘divide-by-zero’’ floating-point exception.
|
|
— log1p(x) returns a NaN and raises the ‘‘invalid’’ floating-point exception for
|
|
x < −1.
|
|
— log1p(+∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.10'></a>
|
|
<hr>
|
|
<h3>F.10.3.10 [The log2 functions]</h3>
|
|
<a name='F.10.3.10p1'></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.10.3.11'></a>
|
|
<hr>
|
|
<h3>F.10.3.11 [The logb functions]</h3>
|
|
<a name='F.10.3.11p1'></a>
|
|
<pre>1 — logb(±0) returns −∞ and raises the ‘‘divide-by-zero’’ floating-point exception.
|
|
— logb(±∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.3.11p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.3.12'></a>
|
|
<hr>
|
|
<h3>F.10.3.12 [The modf functions]</h3>
|
|
<a name='F.10.3.12p1'></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.10.3.12p2'></a>
|
|
<pre>2 The returned values are exact and are independent of the current rounding direction
|
|
mode.
|
|
</pre>
|
|
<a name='F.10.3.12p3'></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.10.3.13'></a>
|
|
<hr>
|
|
<h3>F.10.3.13 [The scalbn and scalbln functions]</h3>
|
|
<a name='F.10.3.13p1'></a>
|
|
<pre>1 — scalbn(±0, n) returns ±0.
|
|
— scalbn(x, 0) returns x.
|
|
— scalbn(±∞, n) returns ±∞.
|
|
</pre>
|
|
<a name='F.10.3.13p2'></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 fabs functions]</h3>
|
|
<a name='F.10.4.2p1'></a>
|
|
<pre>1 — fabs(±0) returns +0.
|
|
— fabs(±∞) returns +∞.
|
|
</pre>
|
|
<a name='F.10.4.2p2'></a>
|
|
<pre>2 The returned value is exact and is independent of the current rounding direction mode.
|
|
</pre>
|
|
<a name='F.10.4.3'></a>
|
|
<hr>
|
|
<h3>F.10.4.3 [The hypot functions]</h3>
|
|
<a name='F.10.4.3p1'></a>
|
|
<pre>1 — hypot(x, y), hypot(y, x), and hypot(x, −y) are equivalent.
|
|
— hypot(x, ±0) is equivalent to fabs(x).
|
|
— hypot(±∞, y) returns +∞, even if y is a NaN.
|
|
</pre>
|
|
<a name='F.10.4.4'></a>
|
|
<hr>
|
|
<h3>F.10.4.4 [The pow functions]</h3>
|
|
<a name='F.10.4.4p1'></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 +∞ and may raise the ‘‘divide-by-zero’’ floating-point
|
|
exception.
|
|
— 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.10.4.5'></a>
|
|
<hr>
|
|
<h3>F.10.4.5 [The sqrt functions]</h3>
|
|
<a name='F.10.4.5p1'></a>
|
|
<pre>1 sqrt is fully specified as a basic arithmetic operation in IEC 60559. 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 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 = rint(x); // or nearbyint instead of rint
|
|
fesetround(save_round);
|
|
return result;
|
|
}
|
|
</pre>
|
|
<a name='F.10.6.1p4'></a>
|
|
<pre>4 The ceil functions may, but are not required to, raise the ‘‘inexact’’ floating-point
|
|
exception for finite non-integer arguments, as this implementation does.
|
|
</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 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>. The floor functions may, but are
|
|
not required to, raise the ‘‘inexact’’ floating-point exception for finite non-integer
|
|
arguments, as that implementation does.
|
|
</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
|
|
#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));
|
|
}
|
|
feupdateenv(&save_env);
|
|
return result;
|
|
}
|
|
The round functions may, but are not required to, raise the ‘‘inexact’’ floating-point
|
|
exception for finite non-integer numeric arguments, as this implementation does.
|
|
</pre>
|
|
<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 trunc functions]</h3>
|
|
<a name='F.10.6.8p1'></a>
|
|
<pre>1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
|
|
rounding direction). The returned value is exact.
|
|
— trunc(±0) returns ±0.
|
|
— trunc(±∞) returns ±∞.
|
|
</pre>
|
|
<a name='F.10.6.8p2'></a>
|
|
<pre>2 The returned value is independent of the current rounding direction mode. The trunc
|
|
functions may, but are not required to, raise the ‘‘inexact’’ floating-point exception for
|
|
finite non-integer arguments.
|
|
</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 not infinite.
|
|
</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 The remainder functions are fully specified as a basic arithmetic operation in
|
|
IEC 60559.
|
|
</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. They
|
|
have no further specifications special to IEC 60559 implementations.
|
|
</pre>
|
|
<a name='F.10.7.3p2'></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.10.8'></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 is specified in the Appendix to IEC 60559.
|
|
</pre>
|
|
<a name='F.10.8.1p2'></a>
|
|
<pre>2 The returned value is exact and 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 function 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.10.9'></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.374'><sup>[374]</sup></a>
|
|
{ return (isgreaterequal(x, y) ||
|
|
isnan(y)) ? x : y; }
|
|
</pre>
|
|
<a name='FOOTNOTE.374'>
|
|
<pre><i><b>Footnote 374)</b> Ideally, fmax would be sensitive to the sign of zero, for example fmax(−0. 0, +0. 0) would
|
|
return +0; however, implementation 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.10.10'></a>
|
|
<hr>
|
|
<h3>F.10.10 [Floating 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 [Comparison macros]</h3>
|
|
<a name='F.10.11p1'></a>
|
|
<pre>1 Relational operators and their corresponding comparison macros (<a href='#7.12.14'>7.12.14</a>) produce
|
|
equivalent result values, even if argument values are represented in wider formats. Thus,
|
|
comparison macro arguments 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 equal to 1 or 2 (<a href='#5.2.4.2.2'>5.2.4.2.2</a>), do not convert
|
|
operands of relational operators to their semantic types.
|
|
|
|
</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_559_COMPLEX_ _ shall conform to the specifications in this annex.<a href='#FOOTNOTE.375'><sup>[375]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.375'>
|
|
<pre><i><b>Footnote 375)</b> Implementations that do not define _ _STDC_IEC_559_COMPLEX_ _ are not required to conform
|
|
to these specifications.
|
|
</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 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.376'><sup>[376]</sup></a> the
|
|
result is a positive zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.376'>
|
|
<pre><i><b>Footnote 376)</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) −yv (−yv) + i(yu)
|
|
|
|
x + iy (xu) + i(yu) (−yv) + 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.377'><sup>[377]</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.377'>
|
|
<pre><i><b>Footnote 377)</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 may 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(fmax(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 const
|
|
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.378'><sup>[378]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.378'>
|
|
<pre><i><b>Footnote 378)</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 NaN.
|
|
</i></pre>
|
|
</a>
|
|
<a name='G.6p5'></a>
|
|
<pre>5 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.6p6'></a>
|
|
<pre>6 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.6p7'></a>
|
|
<pre>7 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.6p8'></a>
|
|
<pre>8 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.6p9'></a>
|
|
<pre>9 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 π /2 − i0.
|
|
— cacos(±0 + iNaN) returns π /2 + iNaN.
|
|
— cacos(x + i ∞) returns π /2 − 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 π − i ∞, for positive-signed finite y.
|
|
— cacos(+∞ + iy) returns +0 − i ∞, for positive-signed finite y.
|
|
— cacos(−∞ + i ∞) returns 3π /4 − i ∞.
|
|
— cacos(+∞ + i ∞) returns π /4 − 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(x + iNaN) returns NaN + iNaN and optionally raises the ‘‘invalid’’
|
|
floating-point exception, for finite x.
|
|
— cacosh(−∞ + iy) returns +∞ + iπ , for positive-signed finite y.
|
|
— cacosh(+∞ + iy) returns +∞ + i0, for positive-signed finite y.
|
|
— cacosh(−∞ + i ∞) returns +∞ + i3π /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 unspecified) 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
|
|
unspecified).
|
|
— 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(x + i ∞) returns NaN + iNaN and raises the ‘‘invalid’’ floating-point
|
|
exception, for finite x.
|
|
— ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ‘‘invalid’’ floating-
|
|
point exception, for finite x.
|
|
— ctanh(+∞ + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
|
|
— ctanh(+∞ + i ∞) returns 1 ± i0 (where the sign of the imaginary part of the result
|
|
is unspecified).
|
|
— ctanh(+∞ + iNaN) returns 1 ± i0 (where the sign of the imaginary part of the
|
|
result is unspecified).
|
|
— 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 exception, 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 unspecified).
|
|
— cexp(NaN + i0) returns NaN + i0.
|
|
— cexp(NaN + iy) returns NaN + iNaN and optionally raises the ‘‘invalid’’ floating-
|
|
point exception, 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 exception, for finite x.
|
|
— clog(−∞ + iy) returns +∞ + iπ , for finite positive-signed y.
|
|
— clog(+∞ + iy) returns +∞ + i0, for finite positive-signed y.
|
|
— clog(−∞ + i ∞) returns +∞ + i3π /4.
|
|
— clog(+∞ + i ∞) returns +∞ + iπ /4.
|
|
— clog(±∞ + iNaN) returns +∞ + iNaN.
|
|
— clog(NaN + iy) returns NaN + iNaN and optionally raises the ‘‘invalid’’ floating-
|
|
point exception, 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.379'><sup>[379]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.379'>
|
|
<pre><i><b>Footnote 379)</b> This allows cpow( z , c ) to be implemented as cexp(c clog( 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 argument 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 (informative) Language independent arithmetic]</h3>
|
|
<a name='H.1'></a>
|
|
<hr>
|
|
<h3>H.1 [Introduction]</h3>
|
|
<a name='H.1p1'></a>
|
|
<pre>1 This annex documents the extent to which the C language supports the ISO/IEC 10967−1
|
|
standard for language-independent arithmetic (LIA−1). LIA−1 is more general than
|
|
IEC 60559 (annex F) in that it covers integer and diverse floating-point arithmetics.
|
|
</pre>
|
|
<a name='H.2'></a>
|
|
<hr>
|
|
<h3>H.2 [Types]</h3>
|
|
<a name='H.2p1'></a>
|
|
<pre>1 The relevant C arithmetic types meet the requirements of LIA−1 types if an
|
|
implementation adds notification of exceptional arithmetic operations and meets the 1
|
|
unit in the last place (ULP) accuracy requirement (LIA−1 subclause 5.2.8).
|
|
</pre>
|
|
<a name='H.2.1'></a>
|
|
<hr>
|
|
<h3>H.2.1 [Boolean type]</h3>
|
|
<a name='H.2.1p1'></a>
|
|
<pre>1 The LIA−1 data type Boolean is implemented by the C data type bool with values of
|
|
true and false, all from <stdbool.h>.
|
|
</pre>
|
|
<a name='H.2.2'></a>
|
|
<hr>
|
|
<h3>H.2.2 [Integer types]</h3>
|
|
<a name='H.2.2p1'></a>
|
|
<pre>1 The signed C integer types int, long int, long long int, and the corresponding
|
|
unsigned types are compatible with LIA−1. If an implementation adds support for the
|
|
LIA−1 exceptional values ‘‘integer_overflow’’ and ‘‘undefined’’, then those types are
|
|
LIA−1 conformant types. C’s unsigned integer types are ‘‘modulo’’ in the LIA−1 sense
|
|
in that overflows or out-of-bounds results silently wrap. An implementation that defines
|
|
signed integer types as also being modulo need not detect integer overflow, in which case,
|
|
only integer divide-by-zero need be detected.
|
|
</pre>
|
|
<a name='H.2.2p2'></a>
|
|
<pre>2 The parameters for the integer data types can be accessed by the following:
|
|
maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
|
|
ULLONG_MAX
|
|
minint INT_MIN, LONG_MIN, LLONG_MIN
|
|
</pre>
|
|
<a name='H.2.2p3'></a>
|
|
<pre>3 The parameter ‘‘bounded’’ is always true, and is not provided. The parameter ‘‘minint’’
|
|
is always 0 for the unsigned types, and is not provided for those types.
|
|
</pre>
|
|
<a name='H.2.2.1'></a>
|
|
<hr>
|
|
<h3>H.2.2.1 [Integer operations]</h3>
|
|
<a name='H.2.2.1p1'></a>
|
|
<pre>1 The integer operations on integer types are the following:
|
|
addI x + y
|
|
subI x - y
|
|
mulI x * y
|
|
divI, divtI x / y
|
|
remI, remtI x % y
|
|
negI -x
|
|
absI abs(x), labs(x), llabs(x)
|
|
eqI x == y
|
|
neqI x != y
|
|
lssI x < y
|
|
leqI x <= y
|
|
gtrI x > y
|
|
geqI x >= y
|
|
where x and y are expressions of the same integer type.
|
|
</pre>
|
|
<a name='H.2.3'></a>
|
|
<hr>
|
|
<h3>H.2.3 [Floating-point types]</h3>
|
|
<a name='H.2.3p1'></a>
|
|
<pre>1 The C floating-point types float, double, and long double are compatible with
|
|
LIA−1. If an implementation adds support for the LIA−1 exceptional values
|
|
‘‘underflow’’, ‘‘floating_overflow’’, and ‘‘"undefined’’, then those types are conformant
|
|
with LIA−1. An implementation that uses IEC 60559 floating-point formats and
|
|
operations (see annex F) along with IEC 60559 status flags and traps has LIA−1
|
|
conformant types.
|
|
</pre>
|
|
<a name='H.2.3.1'></a>
|
|
<hr>
|
|
<h3>H.2.3.1 [Floating-point parameters]</h3>
|
|
<a name='H.2.3.1p1'></a>
|
|
<pre>1 The parameters for a floating point data type can be accessed by the following:
|
|
r FLT_RADIX
|
|
p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
|
|
emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
|
|
emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
|
|
</pre>
|
|
<a name='H.2.3.1p2'></a>
|
|
<pre>2 The derived constants for the floating point types are accessed by the following:
|
|
fmax FLT_MAX, DBL_MAX, LDBL_MAX
|
|
fminN FLT_MIN, DBL_MIN, LDBL_MIN
|
|
epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
|
|
rnd_style FLT_ROUNDS
|
|
</pre>
|
|
<a name='H.2.3.2'></a>
|
|
<hr>
|
|
<h3>H.2.3.2 [Floating-point operations]</h3>
|
|
<a name='H.2.3.2p1'></a>
|
|
<pre>1 The floating-point operations on floating-point types are the following:
|
|
addF x + y
|
|
subF x - y
|
|
mulF x * y
|
|
divF x / y
|
|
negF -x
|
|
absF fabsf(x), fabs(x), fabsl(x)
|
|
exponentF <a href='#1.'>1.</a>f+logbf(x), 1.0+logb(x), <a href='#1.'>1.</a>L+logbl(x)
|
|
scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
|
|
scalblnf(x, li), scalbln(x, li), scalblnl(x, li)
|
|
intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
|
|
fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
|
|
eqF x == y
|
|
neqF x != y
|
|
lssF x < y
|
|
leqF x <= y
|
|
gtrF x > y
|
|
geqF x >= y
|
|
where x and y are expressions of the same floating point type, n is of type int, and li
|
|
is of type long int.
|
|
</pre>
|
|
<a name='H.2.3.3'></a>
|
|
<hr>
|
|
<h3>H.2.3.3 [Rounding styles]</h3>
|
|
<a name='H.2.3.3p1'></a>
|
|
<pre>1 The C Standard requires all floating types to use the same radix and rounding style, so
|
|
that only one identifier for each is provided to map to LIA−1.
|
|
</pre>
|
|
<a name='H.2.3.3p2'></a>
|
|
<pre>2 The FLT_ROUNDS parameter can be used to indicate the LIA−1 rounding styles:
|
|
truncate FLT_ROUNDS == 0
|
|
nearest FLT_ROUNDS == 1
|
|
other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
|
|
provided that an implementation extends FLT_ROUNDS to cover the rounding style used
|
|
in all relevant LIA−1 operations, not just addition as in C.
|
|
</pre>
|
|
<a name='H.2.4'></a>
|
|
<hr>
|
|
<h3>H.2.4 [Type conversions]</h3>
|
|
<a name='H.2.4p1'></a>
|
|
<pre>1 The LIA−1 type conversions are the following type casts:
|
|
cvtI’ → I (int)i, (long int)i, (long long int)i,
|
|
(unsigned int)i, (unsigned long int)i,
|
|
(unsigned long long int)i
|
|
cvtF → I (int)x, (long int)x, (long long int)x,
|
|
(unsigned int)x, (unsigned long int)x,
|
|
(unsigned long long int)x
|
|
cvtI → F (float)i, (double)i, (long double)i
|
|
cvtF’ → F (float)x, (double)x, (long double)x
|
|
</pre>
|
|
<a name='H.2.4p2'></a>
|
|
<pre>2 In the above conversions from floating to integer, the use of (cast)x can be replaced with
|
|
(cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
|
|
(cast)ceil(x), or (cast)floor(x). In addition, C’s floating-point to integer
|
|
conversion functions, lrint(), llrint(), lround(), and llround(), can be
|
|
used. They all meet LIA−1’s requirements on floating to integer rounding for in-range
|
|
values. For out-of-range values, the conversions shall silently wrap for the modulo types.
|
|
</pre>
|
|
<a name='H.2.4p3'></a>
|
|
<pre>3 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
|
|
fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
|
|
65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
|
|
to 65535.0 which can then be cast to unsigned short int. But, the
|
|
remainder() function is not useful for doing silent wrapping to signed integer types,
|
|
e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
|
|
range −32767.0 to +32768.0 which is not, in general, in the range of signed short
|
|
int.
|
|
</pre>
|
|
<a name='H.2.4p4'></a>
|
|
<pre>4 C’s conversions (casts) from floating-point to floating-point can meet LIA−1
|
|
requirements if an implementation uses round-to-nearest (IEC 60559 default).
|
|
</pre>
|
|
<a name='H.2.4p5'></a>
|
|
<pre>5 C’s conversions (casts) from integer to floating-point can meet LIA−1 requirements if an
|
|
implementation uses round-to-nearest.
|
|
</pre>
|
|
<a name='H.3'></a>
|
|
<hr>
|
|
<h3>H.3 [Notification]</h3>
|
|
<a name='H.3p1'></a>
|
|
<pre>1 Notification is the process by which a user or program is informed that an exceptional
|
|
arithmetic operation has occurred. C’s operations are compatible with LIA−1 in that C
|
|
allows an implementation to cause a notification to occur when any arithmetic operation
|
|
returns an exceptional value as defined in LIA−1 clause 5.
|
|
</pre>
|
|
<a name='H.3.1'></a>
|
|
<hr>
|
|
<h3>H.3.1 [Notification alternatives]</h3>
|
|
<a name='H.3.1p1'></a>
|
|
<pre>1 LIA−1 requires at least the following two alternatives for handling of notifications:
|
|
setting indicators or trap-and-terminate. LIA−1 allows a third alternative: trap-and-
|
|
resume.
|
|
</pre>
|
|
<a name='H.3.1p2'></a>
|
|
<pre>2 An implementation need only support a given notification alternative for the entire
|
|
program. An implementation may support the ability to switch between notification
|
|
alternatives during execution, but is not required to do so. An implementation can
|
|
provide separate selection for each kind of notification, but this is not required.
|
|
</pre>
|
|
<a name='H.3.1p3'></a>
|
|
<pre>3 C allows an implementation to provide notification. C’s SIGFPE (for traps) and
|
|
FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
|
|
can provide LIA−1 notification.
|
|
</pre>
|
|
<a name='H.3.1p4'></a>
|
|
<pre>4 C’s signal handlers are compatible with LIA−1. Default handling of SIGFPE can
|
|
provide trap-and-terminate behavior, except for those LIA−1 operations implemented by
|
|
math library function calls. User-provided signal handlers for SIGFPE allow for trap-
|
|
and-resume behavior with the same constraint.
|
|
</pre>
|
|
<a name='H.3.1.1'></a>
|
|
<hr>
|
|
<h3>H.3.1.1 [Indicators]</h3>
|
|
<a name='H.3.1.1p1'></a>
|
|
<pre>1 C’s <fenv.h> status flags are compatible with the LIA−1 indicators.
|
|
</pre>
|
|
<a name='H.3.1.1p2'></a>
|
|
<pre>2 The following mapping is for floating-point types:
|
|
undefined FE_INVALID, FE_DIVBYZERO
|
|
floating_overflow FE_OVERFLOW
|
|
underflow FE_UNDERFLOW
|
|
</pre>
|
|
<a name='H.3.1.1p3'></a>
|
|
<pre>3 The floating-point indicator interrogation and manipulation operations are:
|
|
set_indicators feraiseexcept(i)
|
|
clear_indicators feclearexcept(i)
|
|
test_indicators fetestexcept(i)
|
|
current_indicators fetestexcept(FE_ALL_EXCEPT)
|
|
where i is an expression of type int representing a subset of the LIA−1 indicators.
|
|
</pre>
|
|
<a name='H.3.1.1p4'></a>
|
|
<pre>4 C allows an implementation to provide the following LIA−1 required behavior: at
|
|
and ‘‘hard to ignore’’ message (see LIA−1 subclause 6.1.2)
|
|
</pre>
|
|
<a name='H.3.1.1p5'></a>
|
|
<pre>5 LIA−1 does not make the distinction between floating-point and integer for ‘‘undefined’’.
|
|
This documentation makes that distinction because <fenv.h> covers only the floating-
|
|
point indicators.
|
|
</pre>
|
|
<a name='H.3.1.2'></a>
|
|
<hr>
|
|
<h3>H.3.1.2 [Traps]</h3>
|
|
<a name='H.3.1.2p1'></a>
|
|
<pre>1 C is compatible with LIA−1’s trap requirements for arithmetic operations, but not for
|
|
math library functions (which are not permitted to invoke a user’s signal handler for
|
|
SIGFPE). An implementation can provide an alternative of notification through
|
|
termination with a ‘‘hard-to-ignore’’ message (see LIA−1 subclause 6.1.3).
|
|
</pre>
|
|
<a name='H.3.1.2p2'></a>
|
|
<pre>2 LIA−1 does not require that traps be precise.
|
|
</pre>
|
|
<a name='H.3.1.2p3'></a>
|
|
<pre>3 C does require that SIGFPE be the signal corresponding to LIA−1 arithmetic exceptions,
|
|
if there is any signal raised for them.
|
|
</pre>
|
|
<a name='H.3.1.2p4'></a>
|
|
<pre>4 C supports signal handlers for SIGFPE and allows trapping of LIA−1 arithmetic
|
|
exceptions. When LIA−1 arithmetic exceptions do trap, C’s signal-handler mechanism
|
|
allows trap-and-terminate (either default implementation behavior or user replacement for
|
|
it) or trap-and-resume, at the programmer’s option.
|
|
|
|
</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 International Standard. 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>).
|
|
— A function is called but no prototype has been supplied (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
— The arguments in a function call do not agree in number and type with those of the
|
|
parameters in a function definition that is not a prototype (<a href='#6.5.2.2'>6.5.2.2</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='#6.10.6'>6.10.6</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 International
|
|
Standard.
|
|
</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 certain operators can generate negative zeros and whether a negative zero
|
|
becomes a normal zero when stored in an object (<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
|
|
arguments 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='#6.7.9'>6.7.9</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='#6.10.3'>6.10.3</a>).
|
|
— The order in which # and ## operations are evaluated during macro substitution
|
|
(<a href='#6.10.3.2'>6.10.3.2</a>, <a href='#6.10.3.3'>6.10.3.3</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='#7.6.2.3'>7.6.2.3</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='#7.12.6.4'>7.12.6.4</a>).
|
|
— The numeric result of the ilogb functions when the correct value is outside the
|
|
range of the return type (<a href='#7.12.6.5'>7.12.6.5</a>, <a href='#F.10.3.5'>F.10.3.5</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='#7.12.14'>7.12.14</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</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='#7.21.7.10'>7.21.7.10</a>, <a href='#7.29.3.10'>7.29.3.10</a>).
|
|
— The details of the value stored by the fgetpos function (<a href='#7.21.9.1'>7.21.9.1</a>).
|
|
— The details of the value returned by the ftell function for a text stream (<a href='#7.21.9.4'>7.21.9.4</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='#7.22.1.3'>7.22.1.3</a>, <a href='#7.29.4.1.1'>7.29.4.1.1</a>).
|
|
— The order and contiguity of storage allocated by successive calls to the calloc,
|
|
malloc, and realloc functions (<a href='#7.22.3'>7.22.3</a>).
|
|
— The amount of storage allocated by a successful call to the calloc, malloc, or
|
|
realloc function when 0 bytes was requested (<a href='#7.22.3'>7.22.3</a>).
|
|
— Whether a call to the atexit function that does not happen before the exit
|
|
function is called will succeed (<a href='#7.22.4.2'>7.22.4.2</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='#7.22.4.3'>7.22.4.3</a>).
|
|
— Which of two elements that compare as equal is matched by the bsearch function
|
|
(<a href='#7.22.5.1'>7.22.5.1</a>).
|
|
— The order of two elements that compare as equal in an array sorted by the qsort
|
|
function (<a href='#7.22.5.2'>7.22.5.2</a>).
|
|
— The encoding of the calendar time returned by the time function (<a href='#7.27.2.4'>7.27.2.4</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='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.5.1'>7.29.5.1</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='#7.29.2'>7.29.2</a> or <a href='#7.29.5'>7.29.5</a> and the specified semantics do not require that value to be processed
|
|
by wcrtomb (<a href='#7.29.1'>7.29.1</a>).
|
|
— The conversion state after an encoding error occurs (<a href='#7.29.6.3.2'>7.29.6.3.2</a>, <a href='#7.29.6.3.3'>7.29.6.3.3</a>, <a href='#7.29.6.4.1'>7.29.6.4.1</a>,
|
|
<a href='#7.29.6.4.2'>7.29.6.4.2</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.10.3.4'>F.10.3.4</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>, <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 character 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='#5.2.1.2'>5.2.1.2</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 it is
|
|
indeterminate (<a href='#6.2.4'>6.2.4</a>, <a href='#6.7.9'>6.7.9</a>, <a href='#6.8'>6.8</a>).
|
|
— A trap 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 trap 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>).
|
|
— The operands to certain operators are such that they could produce a negative zero
|
|
result, but the implementation does not support negative zeros (<a href='#6.2.6.2'>6.2.6.2</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
|
|
represented (<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>).
|
|
— For a call to a function without a function prototype in scope, the number of
|
|
arguments does not equal the number of parameters (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
— For call to a function without a function prototype in scope where the function is
|
|
defined with a function prototype, either the prototype ends with an ellipsis or the
|
|
types of the arguments after promotion are not compatible with the types of the
|
|
parameters (<a href='#6.5.2.2'>6.5.2.2</a>).
|
|
— For a call to a function without a function prototype in scope where the function is not
|
|
defined with a function prototype, the types of the arguments after promotion are not
|
|
compatible with those of the parameters after promotion (with certain exceptions)
|
|
(<a href='#6.5.2.2'>6.5.2.2</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>).
|
|
— 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
|
|
expression is negative or the result of shifting would be 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, sizeof expressions whose results are integer constants,
|
|
_Alignof expressions, 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, 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 or when one type is specified by a function definition with an
|
|
identifier list) (<a href='#6.7.6.3'>6.7.6.3</a>).
|
|
— The value of an unnamed member of a structure or union is used (<a href='#6.7.9'>6.7.9</a>).
|
|
— The initializer for a scalar is neither a single expression nor a single expression
|
|
enclosed in braces (<a href='#6.7.9'>6.7.9</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='#6.7.9'>6.7.9</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='#6.7.9'>6.7.9</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 definition includes an identifier list, but the types of the parameters are not
|
|
declared in a following declaration list (<a href='#6.9.1'>6.9.1</a>).
|
|
— An adjusted parameter type in a function definition is not a complete object type
|
|
(<a href='#6.9.1'>6.9.1</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>).
|
|
— The token defined is generated during the expansion of a #if or #elif
|
|
preprocessing directive, 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='#6.10.3'>6.10.3</a>).
|
|
— The result of the preprocessing operator # is not a valid character string literal
|
|
(<a href='#6.10.3.2'>6.10.3.2</a>).
|
|
— The result of the preprocessing operator ## is not a valid preprocessing token
|
|
(<a href='#6.10.3.3'>6.10.3.3</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='#6.10.4'>6.10.4</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='#6.10.6'>6.10.6</a>).
|
|
— A #pragma STDC preprocessing directive does not match one of the well-defined
|
|
forms (<a href='#6.10.6'>6.10.6</a>).
|
|
— The name of a predefined macro, or the identifier defined, is the subject of a
|
|
#define or #undef preprocessing directive (<a href='#6.10.8'>6.10.8</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
|
|
implementation, 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 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='#7.6.2'>7.6.2</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='#7.6.2.4'>7.6.2.4</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='#7.6.4.3'>7.6.4.3</a>, <a href='#7.6.4.4'>7.6.4.4</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='#7.22.6.1'>7.22.6.1</a>, <a href='#7.22.6.2'>7.22.6.2</a>, <a href='#7.22.1'>7.22.1</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>).
|
|
— 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='#7.12.14'>7.12.14</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 duration 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, 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>).
|
|
— 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 parameter parmN of a va_start macro is declared with the register
|
|
storage class, with a function or array type, or with a type that is not compatible with
|
|
the type that results after application of the default argument promotions (<a href='#7.16.1.4'>7.16.1.4</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='#7.19'>7.19</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='#7.20.4'>7.20.4</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='#7.21.2'>7.21.2</a>).
|
|
— Use is made of any portion of a file beyond the most recent wide character written to
|
|
a wide-oriented stream (<a href='#7.21.2'>7.21.2</a>).
|
|
— The value of a pointer to a FILE object is used after the associated file is closed
|
|
(<a href='#7.21.3'>7.21.3</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='#7.21.5.2'>7.21.5.2</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='#7.21.5.3'>7.21.5.3</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='#7.21.5.3'>7.21.5.3</a>).
|
|
— An attempt is made to use the contents of the array that was supplied in a call to the
|
|
setvbuf function (<a href='#7.21.5.6'>7.21.5.6</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='#7.21.6.1'>7.21.6.1</a>,
|
|
<a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</a>,
|
|
<a href='#7.29.5.1'>7.29.5.1</a>).
|
|
— In a call to one of the formatted output functions, a precision appears with a
|
|
conversion specifier other than those described (<a href='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</a>).
|
|
— A conversion specification for a formatted output function uses a # or 0 flag with a
|
|
conversion specifier other than those described (<a href='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</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='#7.21.6.1'>7.21.6.1</a>,
|
|
<a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</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='#7.21.6.1'>7.21.6.1</a>,
|
|
<a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</a>).
|
|
— A % conversion specifier is encountered by one of the formatted input/output
|
|
functions, but the complete conversion specification is not exactly %% (<a href='#7.21.6.1'>7.21.6.1</a>,
|
|
<a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</a>).
|
|
— An invalid conversion specification is found in the format for one of the formatted
|
|
input/output functions, or the strftime or wcsftime function (<a href='#7.21.6.1'>7.21.6.1</a>, <a href='#7.21.6.2'>7.21.6.2</a>,
|
|
<a href='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.2.1'>7.29.2.1</a>, <a href='#7.29.2.2'>7.29.2.2</a>, <a href='#7.29.5.1'>7.29.5.1</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</a>).
|
|
— The number of input items assigned by a formatted input function is greater than
|
|
INT_MAX (<a href='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</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='#7.21.6.8'>7.21.6.8</a>, <a href='#7.21.6.9'>7.21.6.9</a>, <a href='#7.21.6.10'>7.21.6.10</a>, <a href='#7.21.6.11'>7.21.6.11</a>, <a href='#7.21.6.12'>7.21.6.12</a>, <a href='#7.21.6.13'>7.21.6.13</a>, <a href='#7.21.6.14'>7.21.6.14</a>,
|
|
<a href='#7.29.2.5'>7.29.2.5</a>, <a href='#7.29.2.6'>7.29.2.6</a>, <a href='#7.29.2.7'>7.29.2.7</a>, <a href='#7.29.2.8'>7.29.2.8</a>, <a href='#7.29.2.9'>7.29.2.9</a>, <a href='#7.29.2.10'>7.29.2.10</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='#7.21.7.2'>7.21.7.2</a>, <a href='#7.29.3.2'>7.29.3.2</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='#7.21.7.10'>7.21.7.10</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='#7.21.8.1'>7.21.8.1</a>, <a href='#7.21.8.2'>7.21.8.2</a>).
|
|
— A partial element read by a call to the fread function is used (<a href='#7.21.8.1'>7.21.8.1</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='#7.21.9.2'>7.21.9.2</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='#7.21.9.3'>7.21.9.3</a>).
|
|
— A non-null pointer returned by a call to the calloc, malloc, or realloc function
|
|
with a zero requested size is used to access an object (<a href='#7.22.3'>7.22.3</a>).
|
|
— The value of a pointer that refers to space deallocated by a call to the free or
|
|
realloc function is used (<a href='#7.22.3'>7.22.3</a>).
|
|
— The alignment requested of the aligned_alloc function is not valid or not
|
|
supported by the implementation, or the size requested is not an integral multiple of
|
|
the alignment (<a href='#7.22.3.1'>7.22.3.1</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='#7.22.3.3'>7.22.3.3</a>, <a href='#7.22.3.5'>7.22.3.5</a>).
|
|
— The value of the object allocated by the malloc function is used (<a href='#7.22.3.4'>7.22.3.4</a>).
|
|
— The value of any bytes in a new object allocated by the realloc function beyond
|
|
the size of the old object are used (<a href='#7.22.3.5'>7.22.3.5</a>).
|
|
— The program calls the exit or quick_exit function more than once, or calls both
|
|
functions (<a href='#7.22.4.4'>7.22.4.4</a>, <a href='#7.22.4.7'>7.22.4.7</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='#7.22.4.4'>7.22.4.4</a>, <a href='#7.22.4.7'>7.22.4.7</a>).
|
|
— The string set up by the getenv or strerror function is modified by the program
|
|
(<a href='#7.22.4.6'>7.22.4.6</a>, <a href='#7.24.6.2'>7.24.6.2</a>).
|
|
— A signal is raised while the quick_exit function is executing (<a href='#7.22.4.7'>7.22.4.7</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='#7.22.4.8'>7.22.4.8</a>).
|
|
— A searching or sorting utility function is called with an invalid pointer argument, even
|
|
if the number of elements is zero (<a href='#7.22.5'>7.22.5</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='#7.22.5'>7.22.5</a>).
|
|
— The array being searched by the bsearch function does not have its elements in
|
|
proper order (<a href='#7.22.5.1'>7.22.5.1</a>).
|
|
— The current conversion state is used by a multibyte/wide character conversion
|
|
function after changing the LC_CTYPE category (<a href='#7.22.7'>7.22.7</a>).
|
|
— A string or wide string utility function is instructed to access an array beyond the end
|
|
of an object (<a href='#7.24.1'>7.24.1</a>, <a href='#7.29.4'>7.29.4</a>).
|
|
— A string or wide string utility function is called with an invalid pointer argument, even
|
|
if the length is zero (<a href='#7.24.1'>7.24.1</a>, <a href='#7.29.4'>7.29.4</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='#7.24.4.5'>7.24.4.5</a>, <a href='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.4.4.4'>7.29.4.4.4</a>,
|
|
<a href='#7.29.5.1'>7.29.5.1</a>).
|
|
— The first argument in the very first call to the strtok or wcstok is a null pointer
|
|
(<a href='#7.24.5.8'>7.24.5.8</a>, <a href='#7.29.4.5.7'>7.29.4.5.7</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='#7.25'>7.25</a>).
|
|
— A complex argument is supplied for a generic parameter of a type-generic macro that
|
|
has no corresponding complex function (<a href='#7.25'>7.25</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='#7.27.3.1'>7.27.3.1</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='#7.29.2.11'>7.29.2.11</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='#7.29.4.5.7'>7.29.4.5.7</a>).
|
|
— An mbstate_t object is used inappropriately (<a href='#7.29.6'>7.29.6</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='#7.30.1'>7.30.1</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='#7.30.2.2.1'>7.30.2.2.1</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='#7.30.3.2.1'>7.30.3.2.1</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='#7.22.4.6'>7.22.4.6</a>).
|
|
— The manner of execution of the string by the system function (<a href='#7.22.4.8'>7.22.4.8</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 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>).
|
|
— Whether differently-prefixed wide string literal tokens can be concatenated and, if so,
|
|
the treatment of the resulting multibyte character sequence (<a href='#6.4.5'>6.4.5</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 standard encoding macro (_ _STDC_ISO_10646_ _,
|
|
_ _STDC_UTF_16_ _, or _ _STDC_UTF_32_ _) is not defined (<a href='#6.10.8.2'>6.10.8.2</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>).
|
|
— Whether signed integer types are represented using sign and magnitude, two’s
|
|
complement, or ones’ complement, and whether the extraordinary value is a trap
|
|
representation or an ordinary value (<a href='#6.2.6.2'>6.2.6.2</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 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, and unsigned int
|
|
(<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 recognized (<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='#6.10.3.2'>6.10.3.2</a>).
|
|
— The behavior on each recognized non-STDC #pragma directive (<a href='#6.10.6'>6.10.6</a>).
|
|
— The definitions for _ _DATE_ _ and _ _TIME_ _ when respectively, the date and
|
|
time of translation are not available (<a href='#6.10.8.1'>6.10.8.1</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='#7.6.2.2'>7.6.2.2</a>).
|
|
— Whether the feraiseexcept function raises the ‘‘inexact’’ floating-point
|
|
exception in addition to the ‘‘overflow’’ or ‘‘underflow’’ floating-point exception
|
|
(<a href='#7.6.2.3'>7.6.2.3</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>).
|
|
— Domain errors for the mathematics functions, other than those required by this
|
|
International Standard (<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>).
|
|
— 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 null pointer constant to which the macro NULL expands (<a href='#7.19'>7.19</a>).
|
|
— Whether the last line of a text stream requires a terminating new-line character
|
|
(<a href='#7.21.2'>7.21.2</a>).
|
|
— Whether space characters that are written out to a text stream immediately before a
|
|
new-line character appear when read in (<a href='#7.21.2'>7.21.2</a>).
|
|
— The number of null characters that may be appended to data written to a binary
|
|
stream (<a href='#7.21.2'>7.21.2</a>).
|
|
— Whether the file position indicator of an append-mode stream is initially positioned at
|
|
the beginning or end of the file (<a href='#7.21.3'>7.21.3</a>).
|
|
— Whether a write on a text stream causes the associated file to be truncated beyond that
|
|
point (<a href='#7.21.3'>7.21.3</a>).
|
|
— The characteristics of file buffering (<a href='#7.21.3'>7.21.3</a>).
|
|
— Whether a zero-length file actually exists (<a href='#7.21.3'>7.21.3</a>).
|
|
— The rules for composing valid file names (<a href='#7.21.3'>7.21.3</a>).
|
|
— Whether the same file can be simultaneously open multiple times (<a href='#7.21.3'>7.21.3</a>).
|
|
— The nature and choice of encodings used for multibyte characters in files (<a href='#7.21.3'>7.21.3</a>).
|
|
— The effect of the remove function on an open file (<a href='#7.21.4.1'>7.21.4.1</a>).
|
|
— The effect if a file with the new name exists prior to a call to the rename function
|
|
(<a href='#7.21.4.2'>7.21.4.2</a>).
|
|
— Whether an open temporary file is removed upon abnormal program termination
|
|
(<a href='#7.21.4.3'>7.21.4.3</a>).
|
|
— Which changes of mode are permitted (if any), and under what circumstances
|
|
(<a href='#7.21.5.4'>7.21.5.4</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='#7.21.6.1'>7.21.6.1</a>, <a href='#7.29.2.1'>7.29.2.1</a>).
|
|
— The output for %p conversion in the fprintf or fwprintf function (<a href='#7.21.6.1'>7.21.6.1</a>,
|
|
<a href='#7.29.2.1'>7.29.2.1</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.1'>7.29.2.1</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='#7.21.6.2'>7.21.6.2</a>, <a href='#7.29.2.2'>7.29.2.2</a>).
|
|
— The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
|
|
functions on failure (<a href='#7.21.9.1'>7.21.9.1</a>, <a href='#7.21.9.3'>7.21.9.3</a>, <a href='#7.21.9.4'>7.21.9.4</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='#7.22.1.3'>7.22.1.3</a>, <a href='#7.29.4.1.1'>7.29.4.1.1</a>).
|
|
— Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
|
|
function sets errno to ERANGE when underflow occurs (<a href='#7.22.1.3'>7.22.1.3</a>, <a href='#7.29.4.1.1'>7.29.4.1.1</a>).
|
|
— Whether the calloc, malloc, and realloc functions return a null pointer or a
|
|
pointer to an allocated object when the size requested is zero (<a href='#7.22.3'>7.22.3</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='#7.22.4.1'>7.22.4.1</a>, <a href='#7.22.4.5'>7.22.4.5</a>).
|
|
— The termination status returned to the host environment by the abort, exit,
|
|
_Exit, or quick_exit function (<a href='#7.22.4.1'>7.22.4.1</a>, <a href='#7.22.4.4'>7.22.4.4</a>, <a href='#7.22.4.5'>7.22.4.5</a>, <a href='#7.22.4.7'>7.22.4.7</a>).
|
|
— The value returned by the system function when its argument is not a null pointer
|
|
(<a href='#7.22.4.8'>7.22.4.8</a>).
|
|
— The range and precision of times representable in clock_t and time_t (<a href='#7.27'>7.27</a>). ∗
|
|
— The local time zone and Daylight Saving Time (<a href='#7.27.1'>7.27.1</a>).
|
|
— The era for the clock function (<a href='#7.27.2.1'>7.27.2.1</a>).
|
|
— The TIME_UTC epoch (<a href='#7.27.2.5'>7.27.2.5</a>).
|
|
— The replacement string for the %Z specifier to the strftime, and wcsftime
|
|
functions in the "C" locale (<a href='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.5.1'>7.29.5.1</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='#7.20.2'>7.20.2</a>, <a href='#7.20.3'>7.20.3</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 International Standard) (<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='#5.2.1.2'>5.2.1.2</a>).
|
|
— The shift states used for the encoding of multibyte characters (<a href='#5.2.1.2'>5.2.1.2</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='#7.30.2'>7.30.2</a>).
|
|
— The set of control characters (<a href='#7.4'>7.4</a>, <a href='#7.30.2'>7.30.2</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='#7.30.2.1.2'>7.30.2.1.2</a>, <a href='#7.30.2.1.3'>7.30.2.1.3</a>, <a href='#7.30.2.1.7'>7.30.2.1.7</a>, <a href='#7.30.2.1.9'>7.30.2.1.9</a>, <a href='#7.30.2.1.10'>7.30.2.1.10</a>, <a href='#7.30.2.1.11'>7.30.2.1.11</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='#7.22.1'>7.22.1</a>,
|
|
<a href='#7.29.4.1'>7.29.4.1</a>).
|
|
— The collation sequence of the execution character set (<a href='#7.24.4.3'>7.24.4.3</a>, <a href='#7.29.4.4.2'>7.29.4.4.2</a>).
|
|
— The contents of the error message strings set up by the strerror function
|
|
(<a href='#7.24.6.2'>7.24.6.2</a>).
|
|
— The formats for time and date (<a href='#7.27.3.5'>7.27.3.5</a>, <a href='#7.29.5.1'>7.29.5.1</a>).
|
|
— Character mappings that are supported by the towctrans function (<a href='#7.30.1'>7.30.1</a>).
|
|
— Character classifications that are supported by the iswctype function (<a href='#7.30.1'>7.30.1</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
|
|
implementations. 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 conversions 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, or
|
|
signed int, 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='#6.10.8'>6.10.8</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='#7.22.4.4'>7.22.4.4</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='#7.21.2'>7.21.2</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='#7.21.5.3'>7.21.5.3</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='#7.21.7.10'>7.21.7.10</a>,
|
|
<a href='#7.29.3.10'>7.29.3.10</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='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.380'><sup>[380]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.380'>
|
|
<pre><i><b>Footnote 380)</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 expands to the integer constant 1 at the point in the source file
|
|
where the appropriate header is first included.<a href='#FOOTNOTE.381'><sup>[381]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.381'>
|
|
<pre><i><b>Footnote 381)</b> Future revisions of this International Standard may 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.382'><sup>[382]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.382'>
|
|
<pre><i><b>Footnote 382)</b> Subclause <a href='#7.1.3'>7.1.3</a> reserves certain names and patterns of names that an implementation may 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.383'><sup>[383]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.383'>
|
|
<pre><i><b>Footnote 383)</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.384'><sup>[384]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.384'>
|
|
<pre><i><b>Footnote 384)</b> As a matter of programming style, errno_t may 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 might 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.385'><sup>[385]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.385'>
|
|
<pre><i><b>Footnote 385)</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.386'><sup>[386]</sup></a> of type size_t. Functions that have parameters of type
|
|
rsize_t consider it a runtime-constraint violation if the values of those parameters are
|
|
greater than RSIZE_MAX.
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.386'>
|
|
<pre><i><b>Footnote 386)</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.387'><sup>[387]</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.387'>
|
|
<pre><i><b>Footnote 387)</b> Files created using strings generated by the tmpnam_s function are temporary only in the sense that
|
|
their names should not 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. 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.
|
|
</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 function.<a href='#FOOTNOTE.388'><sup>[388]</sup></a>
|
|
Recommended practice
|
|
</pre>
|
|
<a name='FOOTNOTE.388'>
|
|
<pre><i><b>Footnote 388)</b> An implementation may 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.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.5.1.2p8'></a>
|
|
<pre>8 If no suitable string can be generated, or if there is a runtime-constraint violation, the
|
|
tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize
|
|
is greater than zero) and returns a nonzero value.
|
|
</pre>
|
|
<a name='K.3.5.1.2p9'></a>
|
|
<pre>9 Otherwise, the tmpnam_s function writes the string in the array pointed to by s and
|
|
returns zero.
|
|
Environmental limits
|
|
</pre>
|
|
<a name='K.3.5.1.2p10'></a>
|
|
<pre>10 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 permissions
|
|
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 permissions
|
|
</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.389'><sup>[389]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.389'>
|
|
<pre><i><b>Footnote 389)</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.390'><sup>[390]</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.390'>
|
|
<pre><i><b>Footnote 390)</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,<a href='#FOOTNOTE.391'><sup>[391]</sup></a> the 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.391'>
|
|
<pre><i><b>Footnote 391)</b> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
|
|
implementation may 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,<a href='#FOOTNOTE.392'><sup>[392]</sup></a> the 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.392'>
|
|
<pre><i><b>Footnote 392)</b> Because an implementation may treat any undefined behavior as a runtime-constraint violation, an
|
|
implementation may 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.393'><sup>[393]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.393'>
|
|
<pre><i><b>Footnote 393)</b> If the format is known at translation time, an implementation may 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 may be done if even if
|
|
the format is not known at translation time. For example, an implementation may 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 must 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.394'><sup>[394]</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.394'>
|
|
<pre><i><b>Footnote 394)</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.395'><sup>[395]</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.395'>
|
|
<pre><i><b>Footnote 395)</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 less 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 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.396'><sup>[396]</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.396'>
|
|
<pre><i><b>Footnote 396)</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 less 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.397'><sup>[397]</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.397'>
|
|
<pre><i><b>Footnote 397)</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.398'><sup>[398]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.398'>
|
|
<pre><i><b>Footnote 398)</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.3.5.3.9p5'></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.399'><sup>[399]</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.399'>
|
|
<pre><i><b>Footnote 399)</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.400'><sup>[400]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.400'>
|
|
<pre><i><b>Footnote 400)</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.3.5.3.11p5'></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.401'><sup>[401]</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.401'>
|
|
<pre><i><b>Footnote 401)</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 less 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 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.402'><sup>[402]</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.402'>
|
|
<pre><i><b>Footnote 402)</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 less 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 characters written in the array, not counting the terminating null character. If
|
|
an encoding error occurred, 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.403'><sup>[403]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.403'>
|
|
<pre><i><b>Footnote 403)</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.404'><sup>[404]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.404'>
|
|
<pre><i><b>Footnote 404)</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, s[0] is set to the null character, and characters
|
|
are read and discarded from stdin until a new-line character is read, or end-of-file or a
|
|
read error occurs.
|
|
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.405'><sup>[405]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.405'>
|
|
<pre><i><b>Footnote 405)</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.406'><sup>[406]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.406'>
|
|
<pre><i><b>Footnote 406)</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.407'><sup>[407]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.407'>
|
|
<pre><i><b>Footnote 407)</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 neither equal zero nor 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.408'><sup>[408]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.408'>
|
|
<pre><i><b>Footnote 408)</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.409'><sup>[409]</sup></a> The first argument when called from bsearch_s
|
|
shall equal key.
|
|
</pre>
|
|
<a name='FOOTNOTE.409'>
|
|
<pre><i><b>Footnote 409)</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
|
|
implementation 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 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, const void *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.410'><sup>[410]</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.411'><sup>[411]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.410'>
|
|
<pre><i><b>Footnote 410)</b> In practice, this means that the entire array has been sorted according to the comparison function.
|
|
</i></pre>
|
|
</a>
|
|
<a name='FOOTNOTE.411'>
|
|
<pre><i><b>Footnote 411)</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.3.6.3.2'></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.412'><sup>[412]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.412'>
|
|
<pre><i><b>Footnote 412)</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.413'><sup>[413]</sup></a> Changing the LC_CTYPE
|
|
category causes the conversion state of these functions to be indeterminate.
|
|
</pre>
|
|
<a name='FOOTNOTE.413'>
|
|
<pre><i><b>Footnote 413)</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. 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 less than RSIZE_MAX,
|
|
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.414'><sup>[414]</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.414'>
|
|
<pre><i><b>Footnote 414)</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 function 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.415'><sup>[415]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.415'>
|
|
<pre><i><b>Footnote 415)</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
|
|
neither len 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.3.6.5.2p3'></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 less 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.416'><sup>[416]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.416'>
|
|
<pre><i><b>Footnote 416)</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.417'><sup>[417]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.417'>
|
|
<pre><i><b>Footnote 417)</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.418'><sup>[418]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.418'>
|
|
<pre><i><b>Footnote 418)</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 should be 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.419'><sup>[419]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.419'>
|
|
<pre><i><b>Footnote 419)</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 href='#FOOTNOTE.420'><sup>[420]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.420'>
|
|
<pre><i><b>Footnote 420)</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 should be 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.421'><sup>[421]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.421'>
|
|
<pre><i><b>Footnote 421)</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.422'><sup>[422]</sup></a> m shall be greater than
|
|
strnlen_s(s2, m). Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.422'>
|
|
<pre><i><b>Footnote 422)</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.423'><sup>[423]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.423'>
|
|
<pre><i><b>Footnote 423)</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 should be 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.424'><sup>[424]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.424'>
|
|
<pre><i><b>Footnote 424)</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.425'><sup>[425]</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.425'>
|
|
<pre><i><b>Footnote 425)</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.426'><sup>[426]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.426'>
|
|
<pre><i><b>Footnote 426)</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 should be 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.427'><sup>[427]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.427'>
|
|
<pre><i><b>Footnote 427)</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 argument 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
|
|
must contain 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.428'><sup>[428]</sup></a> then the strnlen_s function returns zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.428'>
|
|
<pre><i><b>Footnote 428)</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.429'><sup>[429]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.429'>
|
|
<pre><i><b>Footnote 429)</b> The normal ranges are defined in <a href='#7.27.1'>7.27.1</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))
|
|
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.430'><sup>[430]</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.430'>
|
|
<pre><i><b>Footnote 430)</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.431'><sup>[431]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.431'>
|
|
<pre><i><b>Footnote 431)</b> If the format is known at translation time, an implementation may 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 may be done if even if
|
|
the format is not known at translation time. For example, an implementation may 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 must 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. The %n specifier<a href='#FOOTNOTE.432'><sup>[432]</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
|
|
snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding
|
|
error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.432'>
|
|
<pre><i><b>Footnote 432)</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 less than RSIZE_MAX, 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
|
|
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. 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.433'><sup>[433]</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.433'>
|
|
<pre><i><b>Footnote 433)</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 less than RSIZE_MAX, 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.434'><sup>[434]</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.434'>
|
|
<pre><i><b>Footnote 434)</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.435'><sup>[435]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.435'>
|
|
<pre><i><b>Footnote 435)</b> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
|
|
value 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. The %n specifier<a href='#FOOTNOTE.436'><sup>[436]</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
|
|
vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No
|
|
encoding error shall occur.
|
|
</pre>
|
|
<a name='FOOTNOTE.436'>
|
|
<pre><i><b>Footnote 436)</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 less than RSIZE_MAX, 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 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. 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.437'><sup>[437]</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.437'>
|
|
<pre><i><b>Footnote 437)</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 less than RSIZE_MAX, 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.438'><sup>[438]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.438'>
|
|
<pre><i><b>Footnote 438)</b> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
|
|
value 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.439'><sup>[439]</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.439'>
|
|
<pre><i><b>Footnote 439)</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.440'><sup>[440]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.440'>
|
|
<pre><i><b>Footnote 440)</b> As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the
|
|
value 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.441'><sup>[441]</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.441'>
|
|
<pre><i><b>Footnote 441)</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.
|
|
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, 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.442'><sup>[442]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.442'>
|
|
<pre><i><b>Footnote 442)</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 should be 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.443'><sup>[443]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.443'>
|
|
<pre><i><b>Footnote 443)</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.3.9.2.1.2p7'></a>
|
|
<pre>7 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.3.9.2.1.2p8'></a>
|
|
<pre>8 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 wcsnlen_s(s2, s1max). Copying shall not take place between
|
|
objects that overlap.
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p9'></a>
|
|
<pre>9 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 wcsncpy_s sets s1[0] to the
|
|
null wide character.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.2p10'></a>
|
|
<pre>10 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.3.9.2.1.2p11'></a>
|
|
<pre>11 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.444'><sup>[444]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.444'>
|
|
<pre><i><b>Footnote 444)</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 should be set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.1.2p12'></a>
|
|
<pre>12 The wcsncpy_s function returns zero<a href='#FOOTNOTE.445'><sup>[445]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.445'>
|
|
<pre><i><b>Footnote 445)</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.3.9.2.1.2p13'></a>
|
|
<pre>13 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.3.9.2.1.3p14'></a>
|
|
<pre>14 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.3.9.2.1.3p15'></a>
|
|
<pre>15 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.3.9.2.1.3p16'></a>
|
|
<pre>16 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.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.3p17'></a>
|
|
<pre>17 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.3.9.2.1.3p18'></a>
|
|
<pre>18 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.3.9.2.1.4p19'></a>
|
|
<pre>19 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.3.9.2.1.4p20'></a>
|
|
<pre>20 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.3.9.2.1.4p21'></a>
|
|
<pre>21 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.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.1.4p22'></a>
|
|
<pre>22 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.3.9.2.1.4p23'></a>
|
|
<pre>23 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.
|
|
s1max shall not equal zero. m shall not equal zero.<a href='#FOOTNOTE.446'><sup>[446]</sup></a> m shall be greater than
|
|
wcsnlen_s(s2, m). Copying shall not take place between objects that overlap.
|
|
</pre>
|
|
<a name='FOOTNOTE.446'>
|
|
<pre><i><b>Footnote 446)</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, 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.447'><sup>[447]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.447'>
|
|
<pre><i><b>Footnote 447)</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 should be 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.448'><sup>[448]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.448'>
|
|
<pre><i><b>Footnote 448)</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.3.9.2.2.2p8'></a>
|
|
<pre>8 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.3.9.2.2.2p9'></a>
|
|
<pre>9 Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to
|
|
wcsncat_s.
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p10'></a>
|
|
<pre>10 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.449'><sup>[449]</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.449'>
|
|
<pre><i><b>Footnote 449)</b> Zero means that s1 was not null terminated upon entry to wcsncat_s.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2p11'></a>
|
|
<pre>11 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 wcsncat_s sets s1[0] to the
|
|
null wide character.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.2.2.2p12'></a>
|
|
<pre>12 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.3.9.2.2.2p13'></a>
|
|
<pre>13 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.450'><sup>[450]</sup></a>
|
|
Returns
|
|
</pre>
|
|
<a name='FOOTNOTE.450'>
|
|
<pre><i><b>Footnote 450)</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 should be set to the null wide character.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.2.2.2p14'></a>
|
|
<pre>14 The wcsncat_s function returns zero<a href='#FOOTNOTE.451'><sup>[451]</sup></a> if there was no runtime-constraint violation.
|
|
Otherwise, a nonzero value is returned.
|
|
</pre>
|
|
<a name='FOOTNOTE.451'>
|
|
<pre><i><b>Footnote 451)</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.3.9.2.2.2p15'></a>
|
|
<pre>15 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 #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.3.9.2.3.1p2'></a>
|
|
<pre>2 The wcsnlen_s function computes the length of the wide string pointed to by s.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.2.3.1p3'></a>
|
|
<pre>3 If s is a null pointer,<a href='#FOOTNOTE.452'><sup>[452]</sup></a> then the wcsnlen_s function returns zero.
|
|
</pre>
|
|
<a name='FOOTNOTE.452'>
|
|
<pre><i><b>Footnote 452)</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.3.9.2.3.1p4'></a>
|
|
<pre>4 Otherwise, the wcsnlen_s function returns the number of wide characters that precede
|
|
the terminating 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.3.9.2.3.1p5'></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
|
|
|
|
K.3.9.2.4 Miscellaneous functions
|
|
K.3.9.2.4.1 The wcsnlen_s function
|
|
Synopsis
|
|
</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.3.9.3.1.1p2'></a>
|
|
<pre>2 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.3.9.3.1.1p3'></a>
|
|
<pre>3 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.3.9.3.1.1p4'></a>
|
|
<pre>4 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.3.9.3.1.1p5'></a>
|
|
<pre>5 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.3.9.3.1.1p6'></a>
|
|
<pre>6 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.3.9.3.1.1p7'></a>
|
|
<pre>7 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.3.9.3.1.1p8'></a>
|
|
<pre>8 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.3.9.3.2.1p2'></a>
|
|
<pre>2 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.3.9.3.2.1p3'></a>
|
|
<pre>3 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. 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.3.9.3.2.1p4'></a>
|
|
<pre>4 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 less than RSIZE_MAX,
|
|
then mbsrtowcs_s sets dst[0] to the null wide character.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p5'></a>
|
|
<pre>5 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.453'><sup>[453]</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.453'>
|
|
<pre><i><b>Footnote 453)</b> Thus, the value of len is ignored if dst is a null pointer.
|
|
</i></pre>
|
|
</a>
|
|
<a name='K.3.9.3.2.1p6'></a>
|
|
<pre>6 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.3.9.3.2.1p7'></a>
|
|
<pre>7 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.3.9.3.2.1p8'></a>
|
|
<pre>8 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.454'><sup>[454]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.454'>
|
|
<pre><i><b>Footnote 454)</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.3.9.3.2.1p9'></a>
|
|
<pre>9 If copying takes place between objects that overlap, the objects take on unspecified
|
|
values.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p10'></a>
|
|
<pre>10 The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
|
|
encoding error occurred. Otherwise, a nonzero value is returned.
|
|
K.3.9.3.2.2 The wcsrtombs_s function
|
|
Synopsis
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p11'></a>
|
|
<pre>11 #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.3.9.3.2.1p12'></a>
|
|
<pre>12 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. 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.3.9.3.2.1p13'></a>
|
|
<pre>13 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 less than RSIZE_MAX,
|
|
then wcsrtombs_s sets dst[0] to the null character.
|
|
Description
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p14'></a>
|
|
<pre>14 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.455'><sup>[455]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.455'>
|
|
<pre><i><b>Footnote 455)</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.3.9.3.2.1p15'></a>
|
|
<pre>15 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.3.9.3.2.1p16'></a>
|
|
<pre>16 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.3.9.3.2.1p17'></a>
|
|
<pre>17 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.456'><sup>[456]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.456'>
|
|
<pre><i><b>Footnote 456)</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.3.9.3.2.1p18'></a>
|
|
<pre>18 If copying takes place between objects that overlap, the objects take on unspecified
|
|
values.
|
|
Returns
|
|
</pre>
|
|
<a name='K.3.9.3.2.1p19'></a>
|
|
<pre>19 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.457'><sup>[457]</sup></a>
|
|
</pre>
|
|
<a name='FOOTNOTE.457'>
|
|
<pre><i><b>Footnote 457)</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 Standard.
|
|
</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 The behavior might perform a trap.
|
|
|
|
</pre>
|
|
<a name='L.2.2p3'></a>
|
|
<pre>3 NOTE 2 Any values produced or stored might be indeterminate values.
|
|
|
|
</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 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='#7.22.3'>7.22.3</a>).
|
|
— A string or wide string utility function accesses an array beyond the end of an object
|
|
(<a href='#7.24.1'>7.24.1</a>, <a href='#7.29.4'>7.29.4</a>).
|
|
</pre>
|
|
|
|
</body>
|
|
</html>
|