2012-01-16 16:34:32 +01:00
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FOREWORD. Foreword
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1 ISO (the International Organization for Standardization) and IEC (the International
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Electrotechnical Commission) form the specialized system for worldwide
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standardization. National bodies that are member of ISO or IEC participate in the
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development of International Standards through technical committees established by the
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respective organization to deal with particular fields of technical activity. ISO and IEC
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technical committees collaborate in fields of mutual interest. Other international
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organizations, governmental and non-governmental, in liaison with ISO and IEC, also
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take part in the work.
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2 International Standards are drafted in accordance with the rules given in the ISO/IEC
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Directives, Part 3.
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3 In the field of information technology, ISO and IEC have established a joint technical
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committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
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committee are circulated to national bodies for voting. Publication as an International
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Standard requires approval by at least 75% of the national bodies casting a vote.
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4 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
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ISO/IEC JTC 1, Information technology , Subcommittee SC 22, Programming languages,
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their environments and system software interfaces. The Working Group responsible for
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this standard (WG 14) maintains a site on the World Wide Web at
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http://www.open-std.org/JTC1/SC22/WG14/ containing additional
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information relevant to this standard such as a Rationale for many of the decisions made
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during its preparation and a log of Defect Reports and Responses.
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5 This second edition cancels and replaces the first edition, ISO/IEC 9899:1990, as
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amended and corrected by ISO/IEC 9899/COR1:1994, ISO/IEC 9899/AMD1:1995, and
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ISO/IEC 9899/COR2:1996. Major changes from the previous edition include:
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-- restricted character set support via digraphs and <iso646.h> (originally specified
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in AMD1)
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-- wide character library support in <wchar.h> and <wctype.h> (originally
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specified in AMD1)
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-- more precise aliasing rules via effective type
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-- restricted pointers
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-- variable length arrays
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-- flexible array members
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-- static and type qualifiers in parameter array declarators
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-- complex (and imaginary) support in <complex.h>
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-- type-generic math macros in <tgmath.h>
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-- the long long int type and library functions
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-- increased minimum translation limits
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-- additional floating-point characteristics in <float.h>
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-- remove implicit int
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-- reliable integer division
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-- universal character names (\u and \U)
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-- extended identifiers
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-- hexadecimal floating-point constants and %a and %A printf/scanf conversion
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specifiers
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-- compound literals
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-- designated initializers
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-- // comments
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-- extended integer types and library functions in <inttypes.h> and <stdint.h>
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-- remove implicit function declaration
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-- preprocessor arithmetic done in intmax_t/uintmax_t
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-- mixed declarations and code
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-- new block scopes for selection and iteration statements
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-- integer constant type rules
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-- integer promotion rules
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-- macros with a variable number of arguments
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-- the vscanf family of functions in <stdio.h> and <wchar.h>
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-- additional math library functions in <math.h>
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-- treatment of error conditions by math library functions (math_errhandling)
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-- floating-point environment access in <fenv.h>
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-- IEC 60559 (also known as IEC 559 or IEEE arithmetic) support
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-- trailing comma allowed in enum declaration
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-- %lf conversion specifier allowed in printf
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-- inline functions
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-- the snprintf family of functions in <stdio.h>
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-- boolean type in <stdbool.h>
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-- idempotent type qualifiers
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-- empty macro arguments
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-- new structure type compatibility rules (tag compatibility)
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-- additional predefined macro names
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-- _Pragma preprocessing operator
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-- standard pragmas
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-- _ _func_ _ predefined identifier
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-- va_copy macro
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-- additional strftime conversion specifiers
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-- LIA compatibility annex
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-- deprecate ungetc at the beginning of a binary file
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-- remove deprecation of aliased array parameters
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-- conversion of array to pointer not limited to lvalues
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-- relaxed constraints on aggregate and union initialization
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-- relaxed restrictions on portable header names
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-- return without expression not permitted in function that returns a value (and vice
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versa)
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6 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
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the bibliography, and the index are for information only. In accordance with Part 3 of the
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ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
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also for information only.
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INTRODUCTION. Introduction
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1 With the introduction of new devices and extended character sets, new features may be
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added to this International Standard. Subclauses in the language and library clauses warn
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implementors and programmers of usages which, though valid in themselves, may
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conflict with future additions.
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2 Certain features are obsolescent , which means that they may be considered for
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withdrawal in future revisions of this International Standard. They are retained because
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of their widespread use, but their use in new implementations (for implementation
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features) or new programs (for language [6.11] or library features [7.26]) is discouraged.
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3 This International Standard is divided into four major subdivisions:
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-- preliminary elements (clauses 1-4);
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-- the characteristics of environments that translate and execute C programs (clause 5);
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-- the language syntax, constraints, and semantics (clause 6);
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-- the library facilities (clause 7).
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4 Examples are provided to illustrate possible forms of the constructions described.
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Footnotes are provided to emphasize consequences of the rules described in that
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subclause or elsewhere in this International Standard. References are used to refer to
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other related subclauses. Recommendations are provided to give advice or guidance to
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implementors. Annexes provide additional information and summarize the information
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contained in this International Standard. A bibliography lists documents that were
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referred to during the preparation of the standard.
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5 The language clause (clause 6) is derived from ``The C Reference Manual''.
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6 The library clause (clause 7) is based on the 1984 /usr/group Standard .
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xiv Introduction
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INTERNATIONAL STANDARD <20>ISO/IEC ISO/IEC 9899:TC3
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Programming languages -- C
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1. Scope
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1 This International Standard specifies the form and establishes the interpretation of
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programs written in the C programming language.1) It specifies
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-- the representation of C programs;
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-- the syntax and constraints of the C language;
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-- the semantic rules for interpreting C programs;
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-- the representation of input data to be processed by C programs;
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-- the representation of output data produced by C programs;
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-- the restrictions and limits imposed by a conforming implementation of C.
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2 This International Standard does not specify
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-- the mechanism by which C programs are transformed for use by a data-processing
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system;
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-- the mechanism by which C programs are invoked for use by a data-processing
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system;
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-- the mechanism by which input data are transformed for use by a C program;
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-- the mechanism by which output data are transformed after being produced by a C
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program;
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-- the size or complexity of a program and its data that will exceed the capacity of any
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specific data-processing system or the capacity of a particular processor;
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1) This International Standard is designed to promote the portability of C programs among a variety of
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data-processing systems. It is intended for use by implementors and programmers.
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-- all minimal requirements of a data-processing system that is capable of supporting a
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conforming implementation.
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2. Normative references
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1 The following normative documents contain provisions which, through reference in this
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text, constitute provisions of this International Standard. For dated references,
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subsequent amendments to, or revisions of, any of these publications do not apply.
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However, parties to agreements based on this International Standard are encouraged to
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investigate the possibility of applying the most recent editions of the normative
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documents indicated below. For undated references, the latest edition of the normative
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document referred to applies. Members of ISO and IEC maintain registers of currently
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valid International Standards.
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2 ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for
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use in the physical sciences and technology .
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3 ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information
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interchange.
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4 ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental
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terms.
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5 ISO 4217, Codes for the representation of currencies and funds.
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6 ISO 8601, Data elements and interchange formats -- Information interchange --
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Representation of dates and times.
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7 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
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Character Set (UCS).
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8 IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
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designated IEC 559:1989).
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3. Terms, definitions, and symbols
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1 For the purposes of this International Standard, the following definitions apply. Other
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terms are defined where they appear in italic type or on the left side of a syntax rule.
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Terms explicitly defined in this International Standard are not to be presumed to refer
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implicitly to similar terms defined elsewhere. Terms not defined in this International
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Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
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defined in this International Standard are to be interpreted according to ISO 31-11.
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3.1
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1 access
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execution-time action to read or modify the value of an object
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2 NOTE 1 Where only one of these two actions is meant, ``read'' or ``modify'' is used.
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3 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
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4 NOTE 3 Expressions that are not evaluated do not access objects.
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3.2
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1 alignment
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requirement that objects of a particular type be located on storage boundaries with
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addresses that are particular multiples of a byte address
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3.3
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1 argument
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actual argument
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actual parameter (deprecated)
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expression in the comma-separated list bounded by the parentheses in a function call
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expression, or a sequence of preprocessing tokens in the comma-separated list bounded
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by the parentheses in a function-like macro invocation
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3.4
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1 behavior
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external appearance or action
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3.4.1
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1 implementation-defined behavior
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unspecified behavior where each implementation documents how the choice is made
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2 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
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when a signed integer is shifted right.
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3.4.2
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1 locale-specific behavior
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behavior that depends on local conventions of nationality, culture, and language that each
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implementation documents
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2 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
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characters other than the 26 lowercase Latin letters.
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3.4.3
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1 undefined behavior
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behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
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for which this International Standard imposes no requirements
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2 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
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results, to behaving during translation or program execution in a documented manner characteristic of the
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environment (with or without the issuance of a diagnostic message), to terminating a translation or
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execution (with the issuance of a diagnostic message).
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3 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
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3.4.4
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1 unspecified behavior
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use of an unspecified value, or other behavior where this International Standard provides
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two or more possibilities and imposes no further requirements on which is chosen in any
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instance
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2 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
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evaluated.
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3.5
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1 bit
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unit of data storage in the execution environment large enough to hold an object that may
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have one of two values
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2 NOTE It need not be possible to express the address of each individual bit of an object.
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3.6
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1 byte
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addressable unit of data storage large enough to hold any member of the basic character
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set of the execution environment
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2 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
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3 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
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defined. The least significant bit is called the low-order bit ; the most significant bit is called the high-order
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bit .
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3.7
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1 character
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abstract member of a set of elements used for the organization, control, or
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representation of data
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3.7.1
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1 character
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single-byte character
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C bit representation that fits in a byte
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3.7.2
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1 multibyte character
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sequence of one or more bytes representing a member of the extended character set of
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either the source or the execution environment
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2 NOTE The extended character set is a superset of the basic character set.
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3.7.3
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1 wide character
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bit representation that fits in an object of type wchar_t, capable of representing any
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character in the current locale
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3.8
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1 constraint
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restriction, either syntactic or semantic, by which the exposition of language elements is
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to be interpreted
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3.9
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1 correctly rounded result
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representation in the result format that is nearest in value, subject to the current rounding
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mode, to what the result would be given unlimited range and precision
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3.10
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1 diagnostic message
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message belonging to an implementation-defined subset of the implementation's message
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output
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3.11
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1 forward reference
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reference to a later subclause of this International Standard that contains additional
|
|
|
|
|
|
information relevant to this subclause
|
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|
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|
|
3.12
|
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|
1 implementation
|
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|
|
|
particular set of software, running in a particular translation environment under particular
|
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|
|
|
|
control options, that performs translation of programs for, and supports execution of
|
|
|
|
|
|
functions in, a particular execution environment
|
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|
|
3.13
|
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|
|
|
1 implementation limit
|
|
|
|
|
|
restriction imposed upon programs by the implementation
|
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|
|
|
3.14
|
|
|
|
|
|
1 object
|
|
|
|
|
|
region of data storage in the execution environment, the contents of which can represent
|
|
|
|
|
|
values
|
|
|
|
|
|
2 NOTE When referenced, an object may be interpreted as having a particular type; see 6.3.2.1.
|
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|
3.15
|
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|
|
|
|
1 parameter
|
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|
|
|
|
formal parameter
|
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|
|
|
|
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
|
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|
|
|
|
parentheses immediately following the macro name in a function-like macro definition
|
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|
|
|
|
3.16
|
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|
|
|
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
|
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|
|
|
3.17
|
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|
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|
|
1 value
|
|
|
|
|
|
precise meaning of the contents of an object when interpreted as having a specific type
|
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|
|
3.17.1
|
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|
|
|
|
1 implementation-defined value
|
|
|
|
|
|
unspecified value where each implementation documents how the choice is made
|
|
|
|
|
|
3.17.2
|
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|
|
|
|
1 indeterminate value
|
|
|
|
|
|
either an unspecified value or a trap representation
|
|
|
|
|
|
3.17.3
|
|
|
|
|
|
1 unspecified value
|
|
|
|
|
|
valid value of the relevant type where this International Standard imposes no
|
|
|
|
|
|
requirements on which value is chosen in any instance
|
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|
|
|
|
2 NOTE An unspecified value cannot be a trap representation.
|
|
|
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|
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|
|
3.18
|
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|
|
|
1 x
|
|
|
|
|
|
ceiling of x : the least integer greater than or equal to x
|
|
|
|
|
|
2 EXAMPLE 2. 4 is 3, -2. 4 is -2.
|
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|
|
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|
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|
|
|
|
3.19
|
|
|
|
|
|
1 x
|
|
|
|
|
|
floor of x : the greatest integer less than or equal to x
|
|
|
|
|
|
2 EXAMPLE 2. 4 is 2, -2. 4 is -3.
|
|
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|
|
4. Conformance
|
|
|
|
|
|
1 In this International Standard, ``shall'' is to be interpreted as a requirement on an
|
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|
|
|
|
implementation or on a program; conversely, ``shall not'' is to be interpreted as a
|
|
|
|
|
|
prohibition.
|
|
|
|
|
|
2 If a ``shall'' or ``shall not'' requirement that appears outside of a 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''.
|
|
|
|
|
|
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 5.1.2.3.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 A strictly conforming program shall use only those features of the language and library
|
|
|
|
|
|
specified in this International Standard.2) It shall not produce output dependent on any
|
|
|
|
|
|
unspecified, undefined, or implementation-defined behavior, and shall not exceed any
|
|
|
|
|
|
minimum implementation limit.
|
|
|
|
|
|
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 that does not
|
|
|
|
|
|
use complex types and 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>, <stdarg.h>, <stdbool.h>, <stddef.h>, and
|
|
|
|
|
|
<stdint.h>. A conforming implementation may have extensions (including additional
|
|
|
|
|
|
library functions), provided they do not alter the behavior of any strictly conforming
|
|
|
|
|
|
program.3)
|
|
|
|
|
|
2) A strictly conforming program can use conditional features (such as those in annex F) provided the
|
|
|
|
|
|
use is guarded by a #ifdef directive with the appropriate macro. For example:
|
|
|
|
|
|
#ifdef _ _STDC_IEC_559_ _ /* FE_UPWARD defined */
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
fesetround(FE_UPWARD);
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
|
|
3) This implies that a conforming implementation reserves no identifiers other than those explicitly
|
|
|
|
|
|
reserved in this International Standard.
|
|
|
|
|
|
7 A conforming program is one that is acceptable to a conforming implementation.4)
|
|
|
|
|
|
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 (6.10.1), error directive (6.10.5),
|
|
|
|
|
|
characteristics of floating types <float.h> (7.7), alternative spellings <iso646.h>
|
|
|
|
|
|
(7.9), sizes of integer types <limits.h> (7.10), variable arguments <stdarg.h>
|
|
|
|
|
|
(7.15), boolean type and values <stdbool.h> (7.16), common definitions
|
|
|
|
|
|
<stddef.h> (7.17), integer types <stdint.h> (7.18).
|
|
|
|
|
|
4) Strictly conforming programs are intended to be maximally portable among conforming
|
|
|
|
|
|
implementations. Conforming programs may depend upon nonportable features of a conforming
|
|
|
|
|
|
implementation.
|
|
|
|
|
|
5. Environment
|
|
|
|
|
|
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.
|
|
|
|
|
|
5.1 Conceptual models
|
|
|
|
|
|
5.1.1 Translation environment
|
|
|
|
|
|
5.1.1.1 Program structure
|
|
|
|
|
|
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 (6.2.2), external definitions (6.9),
|
|
|
|
|
|
preprocessing directives (6.10).
|
|
|
|
|
|
5.1.1.2 Translation phases
|
|
|
|
|
|
1 The precedence among the syntax rules of translation is specified by the following
|
|
|
|
|
|
phases.5)
|
|
|
|
|
|
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.
|
|
|
|
|
|
5) 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.
|
|
|
|
|
|
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 tokens6) 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 (6.10.3.3), 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.7)
|
|
|
|
|
|
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.
|
2012-01-23 23:24:51 +01:00
|
|
|
|
Forward references: universal character names (6.4.3), lexical elements (6.4),
|
|
|
|
|
|
preprocessing directives (6.10), trigraph sequences (5.2.1.1), external definitions (6.9).
|
|
|
|
|
|
6) As described in 6.4, 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.
|
|
|
|
|
|
7) An implementation need not convert all non-corresponding source characters to the same execution
|
|
|
|
|
|
character.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
5.1.1.3 Diagnostics
|
|
|
|
|
|
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.8)
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
5.1.2 Execution environments
|
|
|
|
|
|
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 (6.2.4), initialization (6.7.8).
|
|
|
|
|
|
5.1.2.1 Freestanding environment
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 The effect of program termination in a freestanding environment is implementation-
|
|
|
|
|
|
defined.
|
|
|
|
|
|
5.1.2.2 Hosted environment
|
|
|
|
|
|
1 A hosted environment need not be provided, but shall conform to the following
|
|
|
|
|
|
specifications if present.
|
|
|
|
|
|
8) 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.
|
|
|
|
|
|
5.1.2.2.1 Program startup
|
|
|
|
|
|
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;9) or in some other implementation-defined manner.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5.1.2.2.2 Program execution
|
|
|
|
|
|
1 In a hosted environment, a program may use all the functions, macros, type definitions,
|
|
|
|
|
|
and objects described in the library clause (clause 7).
|
|
|
|
|
|
9) 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.
|
|
|
|
|
|
5.1.2.2.3 Program termination
|
|
|
|
|
|
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;10) 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 (7.1.1), the exit function (7.20.4.3).
|
|
|
|
|
|
5.1.2.3 Program execution
|
|
|
|
|
|
1 The semantic descriptions in this International Standard describe the behavior of an
|
|
|
|
|
|
abstract machine in which issues of optimization are irrelevant.
|
|
|
|
|
|
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,11) which are changes in the state of
|
|
|
|
|
|
the execution environment. Evaluation of an expression may produce side effects. At
|
|
|
|
|
|
certain specified points in the execution sequence called sequence points, all side effects
|
|
|
|
|
|
of previous evaluations shall be complete and no side effects of subsequent evaluations
|
|
|
|
|
|
shall have taken place. (A summary of the sequence points is given in annex C.)
|
|
|
|
|
|
3 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).
|
|
|
|
|
|
4 When the processing of the abstract machine is interrupted by receipt of a signal, only the
|
|
|
|
|
|
values of objects as of the previous sequence point may be relied on. Objects that may be
|
|
|
|
|
|
modified between the previous sequence point and the next sequence point need not have
|
|
|
|
|
|
received their correct values yet.
|
|
|
|
|
|
5 The least requirements on a conforming implementation are:
|
|
|
|
|
|
-- At sequence points, volatile objects are stable in the sense that previous accesses are
|
|
|
|
|
|
complete and subsequent accesses have not yet occurred.
|
|
|
|
|
|
10) In accordance with 6.2.4, 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.
|
|
|
|
|
|
11) 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.
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
7.19.3. 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.
|
|
|
|
|
|
6 What constitutes an interactive device is implementation-defined.
|
|
|
|
|
|
7 More stringent correspondences between abstract and actual semantics may be defined by
|
|
|
|
|
|
each implementation.
|
|
|
|
|
|
8 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.
|
|
|
|
|
|
9 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.
|
|
|
|
|
|
|
|
|
|
|
|
10 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.
|
|
|
|
|
|
|
|
|
|
|
|
11 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).
|
|
|
|
|
|
|
|
|
|
|
|
12 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.
|
|
|
|
|
|
|
|
|
|
|
|
13 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 F.8).
|
|
|
|
|
|
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;
|
|
|
|
|
|
|
|
|
|
|
|
14 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.
|
|
|
|
|
|
|
|
|
|
|
|
15 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 (6.5), type qualifiers (6.7.3), statements (6.8), the
|
|
|
|
|
|
signal function (7.14), files (7.19.3).
|
|
|
|
|
|
|
|
|
|
|
|
5.2 Environmental considerations
|
|
|
|
|
|
5.2.1 Character sets
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 The universal character name construct provides a way to name other characters.
|
|
|
|
|
|
Forward references: universal character names (6.4.3), character constants (6.4.4.4),
|
|
|
|
|
|
preprocessing directives (6.10), string literals (6.4.5), comments (6.4.9), string (7.1.1).
|
|
|
|
|
|
5.2.1.1 Trigraph sequences
|
|
|
|
|
|
1 Before any other processing takes place, each occurrence of one of the following
|
|
|
|
|
|
sequences of three characters (called trigraph sequences12)) 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.
|
|
|
|
|
|
2 EXAMPLE 1
|
|
|
|
|
|
??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)
|
|
|
|
|
|
becomes
|
|
|
|
|
|
#define arraycheck(a, b) a[b] || b[a]
|
|
|
|
|
|
|
|
|
|
|
|
3 EXAMPLE 2 The following source line
|
|
|
|
|
|
printf("Eh???/n");
|
|
|
|
|
|
becomes (after replacement of the trigraph sequence ??/)
|
|
|
|
|
|
printf("Eh?\n");
|
|
|
|
|
|
|
|
|
|
|
|
5.2.1.2 Multibyte characters
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
12) 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.
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5.2.2 Character display semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 (7.4.1.8), the fputc function (7.19.7.3).
|
|
|
|
|
|
5.2.3 Signals and interrupts
|
|
|
|
|
|
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.
|
|
|
|
|
|
5.2.4 Environmental limits
|
|
|
|
|
|
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.
|
|
|
|
|
|
5.2.4.1 Translation limits
|
|
|
|
|
|
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:13)
|
|
|
|
|
|
-- 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 incomplete 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
|
|
|
|
|
|
13) Implementations should avoid imposing fixed translation limits whenever possible.
|
|
|
|
|
|
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)14)
|
|
|
|
|
|
-- 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 character string literal or wide 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
|
|
|
|
|
|
5.2.4.2 Numerical limits
|
|
|
|
|
|
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> (7.18).
|
|
|
|
|
|
5.2.4.2.1 Sizes of integer types <limits.h>
|
|
|
|
|
|
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
|
|
|
|
|
|
14) See ``future language directions'' (6.11.3).
|
2012-01-23 23:24:51 +01:00
|
|
|
|
(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
|
2012-01-16 16:34:32 +01:00
|
|
|
|
-- 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
|
|
|
|
|
|
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.15) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
|
|
|
|
|
|
Forward references: representations of types (6.2.6), conditional inclusion (6.10.1).
|
|
|
|
|
|
5.2.4.2.2 Characteristics of floating types <float.h>
|
|
|
|
|
|
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.16) The following parameters are used to
|
|
|
|
|
|
define the model for each floating-point type:
|
|
|
|
|
|
s sign (<28>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)
|
|
|
|
|
|
2 A floating-point number ( x ) is defined by the following model:
|
|
|
|
|
|
p
|
|
|
|
|
|
x = sb e
|
|
|
|
|
|
k =1
|
|
|
|
|
|
f k b-k , emin e emax
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
15) See 6.2.5.
|
|
|
|
|
|
16) 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.
|
|
|
|
|
|
arithmetic operand.17)
|
|
|
|
|
|
4 An implementation may give zero and non-numeric values (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.
|
|
|
|
|
|
5 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.
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
7 The rounding mode for floating-point addition is characterized by the implementation-
|
|
|
|
|
|
defined value of FLT_ROUNDS:18)
|
|
|
|
|
|
-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.
|
|
|
|
|
|
8 Except for assignment and cast (which remove all extra range and precision), the values
|
|
|
|
|
|
of operations 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:19)
|
|
|
|
|
|
17) 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.
|
|
|
|
|
|
18) Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
|
|
|
|
|
|
the function fesetround in <fenv.h>.
|
|
|
|
|
|
-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.
|
|
|
|
|
|
9 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 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,
|
|
|
|
|
|
19) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
10 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
|
|
|
|
|
|
11 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
|
|
|
|
|
|
Recommended practice
|
|
|
|
|
|
12 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
|
|
|
|
|
|
should be the identity function.
|
|
|
|
|
|
13 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
|
|
|
|
|
|
k =1
|
|
|
|
|
|
f k 16-k , -31 e +32
|
|
|
|
|
|
|
|
|
|
|
|
FLT_RADIX 16
|
|
|
|
|
|
FLT_MANT_DIG 6
|
|
|
|
|
|
FLT_EPSILON 9.53674316E-07F
|
|
|
|
|
|
FLT_DIG 6
|
|
|
|
|
|
FLT_MIN_EXP -31
|
|
|
|
|
|
FLT_MIN 2.93873588E-39F
|
|
|
|
|
|
FLT_MIN_10_EXP -38
|
|
|
|
|
|
FLT_MAX_EXP +32
|
|
|
|
|
|
FLT_MAX 3.40282347E+38F
|
|
|
|
|
|
FLT_MAX_10_EXP +38
|
|
|
|
|
|
|
|
|
|
|
|
14 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
|
|
|
|
|
|
single-precision and double-precision normalized numbers in IEC 60559,20) and the appropriate values in a
|
|
|
|
|
|
<float.h> header for types float and double:
|
|
|
|
|
|
24
|
|
|
|
|
|
x f = s 2e
|
|
|
|
|
|
k =1
|
|
|
|
|
|
f k 2-k , -125 e +128
|
|
|
|
|
|
|
|
|
|
|
|
53
|
|
|
|
|
|
x d = s 2e
|
|
|
|
|
|
k =1
|
|
|
|
|
|
f k 2-k , -1021 e +1024
|
|
|
|
|
|
|
|
|
|
|
|
FLT_RADIX 2
|
|
|
|
|
|
DECIMAL_DIG 17
|
|
|
|
|
|
FLT_MANT_DIG 24
|
|
|
|
|
|
FLT_EPSILON 1.19209290E-07F // decimal constant
|
|
|
|
|
|
FLT_EPSILON 0X1P-23F // hex constant
|
|
|
|
|
|
20) 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.
|
|
|
|
|
|
FLT_DIG 6
|
|
|
|
|
|
FLT_MIN_EXP -125
|
|
|
|
|
|
FLT_MIN 1.17549435E-38F // decimal constant
|
|
|
|
|
|
FLT_MIN 0X1P-126F // hex constant
|
|
|
|
|
|
FLT_MIN_10_EXP -37
|
|
|
|
|
|
FLT_MAX_EXP +128
|
|
|
|
|
|
FLT_MAX 3.40282347E+38F // decimal constant
|
|
|
|
|
|
FLT_MAX 0X1.fffffeP127F // hex constant
|
|
|
|
|
|
FLT_MAX_10_EXP +38
|
|
|
|
|
|
DBL_MANT_DIG 53
|
|
|
|
|
|
DBL_EPSILON 2.2204460492503131E-16 // decimal constant
|
|
|
|
|
|
DBL_EPSILON 0X1P-52 // hex constant
|
|
|
|
|
|
DBL_DIG 15
|
|
|
|
|
|
DBL_MIN_EXP -1021
|
|
|
|
|
|
DBL_MIN 2.2250738585072014E-308 // decimal constant
|
|
|
|
|
|
DBL_MIN 0X1P-1022 // hex constant
|
|
|
|
|
|
DBL_MIN_10_EXP -307
|
|
|
|
|
|
DBL_MAX_EXP +1024
|
|
|
|
|
|
DBL_MAX 1.7976931348623157E+308 // decimal constant
|
|
|
|
|
|
DBL_MAX 0X1.fffffffffffffP1023 // hex constant
|
|
|
|
|
|
DBL_MAX_10_EXP +308
|
2012-01-23 23:24:51 +01:00
|
|
|
|
|
|
|
|
|
|
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.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
|
|
|
|
|
|
Forward references: conditional inclusion (6.10.1), complex arithmetic
|
|
|
|
|
|
<complex.h> (7.3), extended multibyte and wide character utilities <wchar.h>
|
|
|
|
|
|
(7.24), floating-point environment <fenv.h> (7.6), general utilities <stdlib.h>
|
|
|
|
|
|
(7.20), input/output <stdio.h> (7.19), mathematics <math.h> (7.12).
|
|
|
|
|
|
6. Language
|
|
|
|
|
|
6.1 Notation
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 When syntactic categories are referred to in the main text, they are not italicized and
|
|
|
|
|
|
words are separated by spaces instead of hyphens.
|
|
|
|
|
|
3 A summary of the language syntax is given in annex A.
|
|
|
|
|
|
6.2 Concepts
|
|
|
|
|
|
6.2.1 Scopes of identifiers
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.)
|
|
|
|
|
|
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).
|
|
|
|
|
|
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 be a
|
|
|
|
|
|
strict subset of 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 Two identifiers have the same scope if and only if their scopes terminate at the same
|
|
|
|
|
|
point.
|
|
|
|
|
|
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.
|
|
|
|
|
|
Forward references: declarations (6.7), function calls (6.5.2.2), function definitions
|
|
|
|
|
|
(6.9.1), identifiers (6.4.2), name spaces of identifiers (6.2.3), macro replacement (6.10.3),
|
|
|
|
|
|
source file inclusion (6.10.2), statements (6.8).
|
|
|
|
|
|
6.2.2 Linkages of identifiers
|
|
|
|
|
|
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.21) There are
|
|
|
|
|
|
three kinds of linkage: external, internal, and none.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.22)
|
|
|
|
|
|
4 For an identifier declared with the storage-class specifier extern in a scope in which a
|
|
|
|
|
|
21) There is no linkage between different identifiers.
|
|
|
|
|
|
22) A function declaration can contain the storage-class specifier static only if it is at file scope; see
|
|
|
|
|
|
6.7.1.
|
|
|
|
|
|
prior declaration of that identifier is visible,23) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 If, within a translation unit, the same identifier appears with both internal and external
|
|
|
|
|
|
linkage, the behavior is undefined.
|
|
|
|
|
|
Forward references: declarations (6.7), expressions (6.5), external definitions (6.9),
|
|
|
|
|
|
statements (6.8).
|
|
|
|
|
|
6.2.3 Name spaces of identifiers
|
|
|
|
|
|
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 any24)
|
|
|
|
|
|
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 (6.7.2.2), labeled statements (6.8.1),
|
|
|
|
|
|
structure and union specifiers (6.7.2.1), structure and union members (6.5.2.3), tags
|
|
|
|
|
|
(6.7.2.3), the goto statement (6.8.6.1).
|
|
|
|
|
|
23) As specified in 6.2.1, the later declaration might hide the prior declaration.
|
|
|
|
|
|
24) There is only one name space for tags even though three are possible.
|
|
|
|
|
|
6.2.4 Storage durations of objects
|
|
|
|
|
|
1 An object has a storage duration that determines its lifetime. There are three storage
|
|
|
|
|
|
durations: static, automatic, and allocated. Allocated storage is described in 7.20.3.
|
|
|
|
|
|
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,25) and retains
|
|
|
|
|
|
its last-stored value throughout its lifetime.26) 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 reaches the end of its lifetime.
|
|
|
|
|
|
3 An object whose identifier is declared 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.
|
|
|
|
|
|
4 An object whose identifier is declared with no linkage and without the storage-class
|
|
|
|
|
|
specifier static has automatic storage duration.
|
|
|
|
|
|
5 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 is
|
|
|
|
|
|
reached in the execution of the block; otherwise, the value becomes indeterminate each
|
|
|
|
|
|
time the declaration is reached.
|
|
|
|
|
|
6 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.27) If the scope is entered recursively, a new instance of the object is created
|
|
|
|
|
|
each time. The initial value of the object is indeterminate.
|
|
|
|
|
|
Forward references: statements (6.8), function calls (6.5.2.2), declarators (6.7.5), array
|
|
|
|
|
|
declarators (6.7.5.2), initialization (6.7.8).
|
|
|
|
|
|
25) 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.
|
|
|
|
|
|
26) In the case of a volatile object, the last store need not be explicit in the program.
|
|
|
|
|
|
27) 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.
|
|
|
|
|
|
6.2.5 Types
|
|
|
|
|
|
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 fully describe objects), function types (types
|
|
|
|
|
|
that describe functions), and incomplete types (types that describe objects but lack
|
|
|
|
|
|
information needed to determine their sizes).
|
|
|
|
|
|
2 An object declared as type _Bool is large enough to store the values 0 and 1.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.7.2.) There may also be
|
|
|
|
|
|
implementation-defined extended signed integer types.28) The standard and extended
|
|
|
|
|
|
signed integer types are collectively called signed integer types.29)
|
|
|
|
|
|
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>).
|
|
|
|
|
|
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.30)
|
|
|
|
|
|
28) Implementation-defined keywords shall have the form of an identifier reserved for any use as
|
|
|
|
|
|
described in 7.1.3.
|
|
|
|
|
|
29) Therefore, any statement in this Standard about signed integer types also applies to the extended
|
|
|
|
|
|
signed integer types.
|
|
|
|
|
|
30) Therefore, any statement in this Standard about unsigned integer types also applies to the extended
|
|
|
|
|
|
unsigned integer types.
|
|
|
|
|
|
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.
|
|
|
|
|
|
8 For any two integer types with the same signedness and different integer conversion rank
|
|
|
|
|
|
(see 6.3.1.1), the range of values of the type with smaller integer conversion rank is a
|
|
|
|
|
|
subrange of the values of the other type.
|
|
|
|
|
|
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.31) 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.
|
|
|
|
|
|
10 There are three real floating types, designated as float, double, and long
|
|
|
|
|
|
double.32) 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.
|
|
|
|
|
|
11 There are three complex types, designated as float _Complex, double
|
|
|
|
|
|
_Complex, and long double _Complex.33) The real floating and complex types
|
|
|
|
|
|
are collectively called the floating types.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
14 The type char, the signed and unsigned integer types, and the floating types are
|
|
|
|
|
|
collectively called the basic types. Even if the implementation defines two or more basic
|
|
|
|
|
|
types to have the same representation, they are nevertheless different types.34)
|
|
|
|
|
|
|
|
|
|
|
|
31) The same representation and alignment requirements are meant to imply interchangeability as
|
|
|
|
|
|
arguments to functions, return values from functions, and members of unions.
|
|
|
|
|
|
32) See ``future language directions'' (6.11.1).
|
|
|
|
|
|
33) A specification for imaginary types is in informative annex G.
|
|
|
|
|
|
34) 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 7.1.3.
|
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|
|
|
|
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.35)
|
|
|
|
|
|
16 An enumeration comprises a set of named integer constant values. Each distinct
|
|
|
|
|
|
enumeration constitutes a different enumerated type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
19 The void type comprises an empty set of values; it is an incomplete type that cannot be
|
|
|
|
|
|
completed.
|
|
|
|
|
|
20 Any number of derived types can be constructed from the object, function, and
|
|
|
|
|
|
incomplete types, as follows:
|
|
|
|
|
|
-- An array type describes a contiguously allocated nonempty set of objects with a
|
|
|
|
|
|
particular member object type, called the element type.36) 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''.
|
|
|
|
|
|
35) 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.
|
|
|
|
|
|
36) Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
|
|
|
|
|
|
-- A pointer type may be derived from a function type, an object type, or an incomplete
|
|
|
|
|
|
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''.
|
|
|
|
|
|
These methods of constructing derived types can be applied recursively.
|
|
|
|
|
|
21 Arithmetic types and pointer types are collectively called scalar types. Array and
|
|
|
|
|
|
structure types are collectively called aggregate types.37)
|
|
|
|
|
|
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 6.7.2.3) 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.
|
|
|
|
|
|
23 A type has known constant size if the type is not incomplete and is not a variable length
|
|
|
|
|
|
array type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
26 Any type so far mentioned is an unqualified type. Each unqualified type has several
|
|
|
|
|
|
qualified versions of its type,38) 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.39) A derived type is not qualified by the
|
|
|
|
|
|
qualifiers (if any) of the type from which it is derived.
|
|
|
|
|
|
27 A pointer to void shall have the same representation and alignment requirements as a
|
|
|
|
|
|
pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
|
|
|
|
|
|
compatible types shall have the same representation and alignment requirements. All
|
|
|
|
|
|
37) Note that aggregate type does not include union type because an object with union type can only
|
|
|
|
|
|
contain one member at a time.
|
|
|
|
|
|
38) See 6.7.3 regarding qualified array and function types.
|
|
|
|
|
|
39) The same representation and alignment requirements are meant to imply interchangeability as
|
|
|
|
|
|
arguments to functions, return values from functions, and members of unions.
|
|
|
|
|
|
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.
|
|
|
|
|
|
28 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.
|
|
|
|
|
|
|
|
|
|
|
|
29 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 (6.2.7), declarations (6.7).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.2.6 Representations of types
|
|
|
|
|
|
6.2.6.1 General
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 The representations of all types are unspecified except as stated in this subclause.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 Values stored in unsigned bit-fields and objects of type unsigned char shall be
|
|
|
|
|
|
represented using a pure binary notation.40)
|
|
|
|
|
|
4 Values stored in non-bit-field objects of any other object type consist of n <20> 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.
|
|
|
|
|
|
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.41) Such a representation is called
|
|
|
|
|
|
|
|
|
|
|
|
40) 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.
|
|
|
|
|
|
a trap representation.
|
|
|
|
|
|
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.42) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.43) 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.
|
|
|
|
|
|
Forward references: declarations (6.7), expressions (6.5), lvalues, arrays, and function
|
|
|
|
|
|
designators (6.3.2.1).
|
|
|
|
|
|
6.2.6.2 Integer types
|
|
|
|
|
|
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.44)
|
|
|
|
|
|
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;
|
|
|
|
|
|
|
|
|
|
|
|
41) 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.
|
|
|
|
|
|
42) Thus, for example, structure assignment need not copy any padding bits.
|
|
|
|
|
|
43) 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.
|
|
|
|
|
|
44) 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.
|
|
|
|
|
|
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 N ) (two's complement );
|
|
|
|
|
|
-- the sign bit has the value -(2 N - 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.
|
|
|
|
|
|
3 If the implementation supports negative zeros, they shall be generated only by:
|
|
|
|
|
|
-- the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
|
|
|
|
|
|
-- the +, -, *, /, and % operators where one argument 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.
|
|
|
|
|
|
4 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
|
|
|
|
|
|
and >> operators with arguments that would produce such a value is undefined.
|
|
|
|
|
|
5 The values of any padding bits are unspecified.45) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
45) 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.
|
|
|
|
|
|
for signed integer types the width is one greater than the precision.
|
|
|
|
|
|
6.2.7 Compatible type and composite type
|
|
|
|
|
|
1 Two types have compatible type if their types are the same. Additional rules for
|
|
|
|
|
|
determining whether two types are compatible are described in 6.7.2 for type specifiers,
|
|
|
|
|
|
in 6.7.3 for type qualifiers, and in 6.7.5 for declarators.46) 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 complete types, 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, and such that if one member of a corresponding pair is declared with a name, the
|
|
|
|
|
|
other member 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.
|
|
|
|
|
|
2 All declarations that refer to the same object or function shall have compatible type;
|
|
|
|
|
|
otherwise, the behavior is undefined.
|
|
|
|
|
|
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 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, the composite type is that type.
|
|
|
|
|
|
-- 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.
|
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|
|
|
|
These rules apply recursively to the types from which the two types are derived.
|
|
|
|
|
|
4 For an identifier with internal or external linkage declared in a scope in which a prior
|
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|
|
|
|
declaration of that identifier is visible,47) if the prior declaration specifies internal or
|
|
|
|
|
|
external linkage, the type of the identifier at the later declaration becomes the composite
|
|
|
|
|
|
type.
|
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|
|
46) Two types need not be identical to be compatible.
|
|
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|
|
47) As specified in 6.2.1, the later declaration might hide the prior declaration.
|
|
|
|
|
|
5 EXAMPLE Given the following two file scope declarations:
|
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|
|
|
int f(int (*)(), double (*)[3]);
|
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|
|
|
|
int f(int (*)(char *), double (*)[]);
|
|
|
|
|
|
The resulting composite type for the function is:
|
|
|
|
|
|
int f(int (*)(char *), double (*)[3]);
|
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|
|
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|
|
|
6.3 Conversions
|
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|
|
|
1 Several operators convert operand values from one type to another automatically. This
|
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|
|
|
|
subclause specifies the result required from such an implicit conversion, as well as those
|
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|
|
|
|
that result from a cast operation (an explicit conversion). The list in 6.3.1.8 summarizes
|
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|
|
|
|
the conversions performed by most ordinary operators; it is supplemented as required by
|
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|
|
|
|
the discussion of each operator in 6.5.
|
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|
|
2 Conversion of an operand value to a compatible type causes no change to the value or the
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|
|
representation.
|
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|
|
Forward references: cast operators (6.5.4).
|
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|
6.3.1 Arithmetic operands
|
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|
6.3.1.1 Boolean, characters, and integers
|
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|
|
1 Every integer type has an integer conversion rank defined as follows:
|
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|
|
|
-- No two signed integer types shall have the same rank, even if they have the same
|
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|
|
|
representation.
|
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|
|
-- The rank of a signed integer type shall be greater than the rank of any signed integer
|
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|
|
|
type with less precision.
|
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|
|
-- The rank of long long int shall be greater than the rank of long int, which
|
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|
|
|
|
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.
|
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|
|
|
-- The rank of char shall equal the rank of signed char and unsigned char.
|
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|
|
|
|
-- 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 6.7.2.2).
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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 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, the value is converted to an int;
|
|
|
|
|
|
otherwise, it is converted to an unsigned int. These are called the integer
|
|
|
|
|
|
promotions.48) All other types are unchanged by the integer promotions.
|
|
|
|
|
|
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 (6.7.2.2), structure and union specifiers
|
|
|
|
|
|
(6.7.2.1).
|
|
|
|
|
|
6.3.1.2 Boolean type
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.3.1.3 Signed and unsigned integers
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.49)
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.3.1.4 Real floating and integer
|
|
|
|
|
|
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.50)
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
48) 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.
|
|
|
|
|
|
49) The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
|
|
|
|
|
|
50) 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).
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.3.1.5 Real floating types
|
|
|
|
|
|
1 When a float is promoted to double or long double, or a double is promoted
|
|
|
|
|
|
to long double, its value is unchanged (if the source value is represented in the
|
|
|
|
|
|
precision and range of its type).
|
|
|
|
|
|
2 When a double is demoted to float, a long double is demoted to double or
|
|
|
|
|
|
float, or a value being represented in greater precision and range than required by its
|
|
|
|
|
|
semantic type (see 6.3.1.8) is explicitly converted (including to its own 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.
|
|
|
|
|
|
6.3.1.6 Complex types
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.3.1.7 Real and complex
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.3.1.8 Usual arithmetic conversions
|
|
|
|
|
|
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.51)
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 The values of floating operands and of the results of floating expressions may be
|
|
|
|
|
|
represented in greater precision and range than that required by the type; the types are not
|
|
|
|
|
|
changed thereby.52)
|
|
|
|
|
|
51) 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).
|
|
|
|
|
|
52) The cast and assignment operators are still required to perform their specified conversions as
|
|
|
|
|
|
described in 6.3.1.4 and 6.3.1.5.
|
|
|
|
|
|
6.3.2 Other operands
|
|
|
|
|
|
6.3.2.1 Lvalues, arrays, and function designators
|
|
|
|
|
|
1 An lvalue is an expression with an object type or an incomplete type other than void;53)
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 Except when it is the operand of the sizeof 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). If the lvalue has qualified type, the value has the
|
|
|
|
|
|
unqualified 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.
|
|
|
|
|
|
3 Except when it is the operand of the sizeof 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.
|
|
|
|
|
|
4 A function designator is an expression that has function type. Except when it is the
|
|
|
|
|
|
operand of the sizeof operator54) 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 (6.5.3.2), assignment operators
|
|
|
|
|
|
(6.5.16), common definitions <stddef.h> (7.17), initialization (6.7.8), postfix
|
|
|
|
|
|
increment and decrement operators (6.5.2.4), prefix increment and decrement operators
|
|
|
|
|
|
(6.5.3.1), the sizeof operator (6.5.3.4), structure and union members (6.5.2.3).
|
|
|
|
|
|
53) 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.
|
|
|
|
|
|
54) Because this conversion does not occur, the operand of the sizeof operator remains a function
|
|
|
|
|
|
designator and violates the constraint in 6.5.3.4.
|
|
|
|
|
|
6.3.2.2 void
|
|
|
|
|
|
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.)
|
|
|
|
|
|
6.3.2.3 Pointers
|
|
|
|
|
|
1 A pointer to void may be converted to or from a pointer to any incomplete or object
|
|
|
|
|
|
type. A pointer to any incomplete or object type may be converted to a pointer to void
|
|
|
|
|
|
and back again; the result shall compare equal to the original pointer.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 An integer constant expression with the value 0, or such an expression cast to type
|
|
|
|
|
|
void *, is called a null pointer constant .55) 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.
|
|
|
|
|
|
4 Conversion of a null pointer to another pointer type yields a null pointer of that type.
|
|
|
|
|
|
Any two null pointers shall compare equal.
|
|
|
|
|
|
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.56)
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 A pointer to an object or incomplete type may be converted to a pointer to a different
|
|
|
|
|
|
object or incomplete type. If the resulting pointer is not correctly aligned57) for the
|
|
|
|
|
|
pointed-to 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
|
|
|
|
|
|
55) The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.17.
|
|
|
|
|
|
56) 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.
|
|
|
|
|
|
57) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 pointed-to type,
|
|
|
|
|
|
the behavior is undefined.
|
|
|
|
|
|
Forward references: cast operators (6.5.4), equality operators (6.5.9), integer types
|
|
|
|
|
|
capable of holding object pointers (7.18.1.4), simple assignment (6.5.16.1).
|
|
|
|
|
|
|
|
|
|
|
|
6.4 Lexical elements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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
|
|
|
|
|
|
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.58) 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 6.10, 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.
|
|
|
|
|
|
58) An additional category, placemarkers, is used internally in translation phase 4 (see 6.10.3.3); it cannot
|
|
|
|
|
|
occur in source files.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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 (6.4.4.4), comments (6.4.9), expressions (6.5),
|
|
|
|
|
|
floating constants (6.4.4.2), header names (6.4.7), macro replacement (6.10.3), postfix
|
|
|
|
|
|
increment and decrement operators (6.5.2.4), prefix increment and decrement operators
|
|
|
|
|
|
(6.5.3.1), preprocessing directives (6.10), preprocessing numbers (6.4.8), string literals
|
|
|
|
|
|
(6.4.5).
|
|
|
|
|
|
6.4.1 Keywords
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 keyword: one of
|
|
|
|
|
|
auto enum restrict unsigned
|
|
|
|
|
|
break extern return void
|
|
|
|
|
|
case float short volatile
|
|
|
|
|
|
char for signed while
|
|
|
|
|
|
const goto sizeof _Bool
|
|
|
|
|
|
continue if static _Complex
|
|
|
|
|
|
default inline struct _Imaginary
|
|
|
|
|
|
do int switch
|
|
|
|
|
|
double long typedef
|
|
|
|
|
|
else register union
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
|
|
|
|
|
|
keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
|
|
|
|
|
|
specifying imaginary types.59)
|
|
|
|
|
|
59) One possible specification for imaginary types appears in annex G.
|
|
|
|
|
|
6.4.2 Identifiers
|
|
|
|
|
|
6.4.2.1 General
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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 6.2.1. Lowercase and uppercase letters are distinct.
|
|
|
|
|
|
There is no specific limit on the maximum length of an identifier.
|
|
|
|
|
|
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 annex D.60) The initial
|
|
|
|
|
|
character shall not be a universal character name designating a digit. 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
60) 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.
|
|
|
|
|
|
Implementation limits
|
|
|
|
|
|
5 As discussed in 5.2.4.1, 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.
|
|
|
|
|
|
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 (6.4.3), macro replacement (6.10.3).
|
|
|
|
|
|
6.4.2.2 Predefined identifiers
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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.61)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 (6.9.1).
|
|
|
|
|
|
61) Since the name _ _func_ _ is reserved for any use by the implementation (7.1.3), if any other
|
|
|
|
|
|
identifier is explicitly declared using the name _ _func_ _, the behavior is undefined.
|
|
|
|
|
|
6.4.3 Universal character names
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 universal-character-name:
|
|
|
|
|
|
\u hex-quad
|
|
|
|
|
|
\U hex-quad hex-quad
|
|
|
|
|
|
hex-quad:
|
|
|
|
|
|
hexadecimal-digit hexadecimal-digit
|
|
|
|
|
|
hexadecimal-digit hexadecimal-digit
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
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.62)
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
4 The universal character name \Unnnnnnnn designates the character whose eight-digit
|
|
|
|
|
|
short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.63) Similarly, the universal
|
|
|
|
|
|
character name \unnnn designates the character whose four-digit short identifier is nnnn
|
|
|
|
|
|
(and whose eight-digit short identifier is 0000 nnnn).
|
|
|
|
|
|
62) 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).
|
|
|
|
|
|
63) Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
|
|
|
|
|
|
6.4.4 Constants
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 constant:
|
|
|
|
|
|
integer-constant
|
|
|
|
|
|
floating-constant
|
|
|
|
|
|
enumeration-constant
|
|
|
|
|
|
character-constant
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
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
|
|
|
|
|
|
3 Each constant has a type, determined by its form and value, as detailed later.
|
|
|
|
|
|
6.4.4.1 Integer constants
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.4.4.2 Floating constants
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Syntax
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1 floating-constant:
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decimal-floating-constant
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hexadecimal-floating-constant
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decimal-floating-constant:
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fractional-constant exponent-partopt floating-suffixopt
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digit-sequence exponent-part floating-suffixopt
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hexadecimal-floating-constant:
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hexadecimal-prefix hexadecimal-fractional-constant
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binary-exponent-part floating-suffixopt
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hexadecimal-prefix hexadecimal-digit-sequence
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binary-exponent-part floating-suffixopt
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fractional-constant:
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digit-sequenceopt . digit-sequence
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digit-sequence .
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exponent-part:
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e signopt digit-sequence
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E signopt digit-sequence
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sign: one of
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+ -
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digit-sequence:
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digit
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digit-sequence digit
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hexadecimal-fractional-constant:
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hexadecimal-digit-sequenceopt .
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hexadecimal-digit-sequence
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hexadecimal-digit-sequence .
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binary-exponent-part:
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p signopt digit-sequence
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P signopt digit-sequence
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hexadecimal-digit-sequence:
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hexadecimal-digit
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hexadecimal-digit-sequence hexadecimal-digit
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floating-suffix: one of
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f l F L
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Description
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2 A floating constant has a significand part that may be followed by an exponent part and a
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suffix that specifies its type. The components of the significand part may include a digit
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sequence representing the whole-number part, followed by a period (.), followed by a
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digit sequence representing the fraction part. The components of the exponent part are an
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e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
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Either the whole-number part or the fraction part has to be present; for decimal floating
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constants, either the period or the exponent part has to be present.
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Semantics
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3 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
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digit sequence in the exponent part is interpreted as a decimal integer. For decimal
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floating constants, the exponent indicates the power of 10 by which the significand part is
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to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
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by which the significand part is to be scaled. For decimal floating constants, and also for
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hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
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the nearest representable value, or the larger or smaller representable value immediately
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adjacent to the nearest representable value, chosen in an implementation-defined manner.
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For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
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correctly rounded.
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4 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
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type float. If suffixed by the letter l or L, it has type long double.
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5 Floating constants are converted to internal format as if at translation-time. The
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conversion of a floating constant shall not raise an exceptional condition or a floating-
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point exception at execution time.
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Recommended practice
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6 The implementation should produce a diagnostic message if a hexadecimal constant
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cannot be represented exactly in its evaluation format; the implementation should then
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proceed with the translation of the program.
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7 The translation-time conversion of floating constants should match the execution-time
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conversion of character strings by library functions, such as strtod, given matching
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inputs suitable for both conversions, the same result format, and default execution-time
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rounding.64)
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64) The specification for the library functions recommends more accurate conversion than required for
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floating constants (see 7.20.1.3).
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6.4.4.3 Enumeration constants
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Syntax
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1 enumeration-constant:
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identifier
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Semantics
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2 An identifier declared as an enumeration constant has type int.
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Forward references: enumeration specifiers (6.7.2.2).
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6.4.4.4 Character constants
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Syntax
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1 character-constant:
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' c-char-sequence '
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L' c-char-sequence '
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c-char-sequence:
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c-char
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c-char-sequence c-char
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c-char:
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any member of the source character set except
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the single-quote ', backslash \, or new-line character
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escape-sequence
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escape-sequence:
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simple-escape-sequence
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octal-escape-sequence
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hexadecimal-escape-sequence
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universal-character-name
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simple-escape-sequence: one of
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\' \" \? \\
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\a \b \f \n \r \t \v
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octal-escape-sequence:
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\ octal-digit
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\ octal-digit octal-digit
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\ octal-digit octal-digit octal-digit
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hexadecimal-escape-sequence:
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\x hexadecimal-digit
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hexadecimal-escape-sequence hexadecimal-digit
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Description
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2 An integer character constant is a sequence of one or more multibyte characters enclosed
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in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
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letter L. With a few exceptions detailed later, the elements of the sequence are any
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members of the source character set; they are mapped in an implementation-defined
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manner to members of the execution character set.
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3 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
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arbitrary integer values are representable according to the following table of escape
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sequences:
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single quote ' \'
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double quote " \"
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question mark ? \?
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backslash \ \\
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octal character \octal digits
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hexadecimal character \x hexadecimal digits
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4 The double-quote " and question-mark ? are representable either by themselves or by the
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escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
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shall be represented, respectively, by the escape sequences \' and \\.
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5 The octal digits that follow the backslash in an octal escape sequence are taken to be part
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of the construction of a single character for an integer character constant or of a single
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wide character for a wide character constant. The numerical value of the octal integer so
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formed specifies the value of the desired character or wide character.
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6 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
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sequence are taken to be part of the construction of a single character for an integer
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character constant or of a single wide character for a wide character constant. The
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numerical value of the hexadecimal integer so formed specifies the value of the desired
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character or wide character.
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7 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
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constitute the escape sequence.
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8 In addition, characters not in the basic character set are representable by universal
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character names and certain nongraphic characters are representable by escape sequences
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consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
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and \v.65)
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65) The semantics of these characters were discussed in 5.2.2. If any other character follows a backslash,
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the result is not a token and a diagnostic is required. See ``future language directions'' (6.11.4).
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Constraints
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9 The value of an octal or hexadecimal escape sequence shall be in the range of
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representable values for the type unsigned char for an integer character constant, or
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the unsigned type corresponding to wchar_t for a wide character constant.
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Semantics
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10 An integer character constant has type int. The value of an integer character constant
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containing a single character that maps to a single-byte execution character is the
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numerical value of the representation of the mapped character interpreted as an integer.
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The value of an integer character constant containing more than one character (e.g.,
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'ab'), or containing a character or escape sequence that does not map to a single-byte
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execution character, is implementation-defined. If an integer character constant contains
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a single character or escape sequence, its value is the one that results when an object with
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type char whose value is that of the single character or escape sequence is converted to
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type int.
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11 A wide character constant has type wchar_t, an integer type defined in the
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<stddef.h> header. The value of a wide character constant containing a single
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multibyte character that maps to a member of the extended execution character set is the
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wide character corresponding to that multibyte character, as defined by the mbtowc
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function, with an implementation-defined current locale. The value of a wide character
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constant containing more than one multibyte character, or containing a multibyte
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character or escape sequence not represented in the extended execution character set, is
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implementation-defined.
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12 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
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13 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
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bits for objects that have type char. In an implementation in which type char has the same range of
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values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
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same range of values as unsigned char, the character constant '\xFF' has the value +255.
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14 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
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specifies an integer character constant containing only one character, since a hexadecimal escape sequence
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is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
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two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
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escape sequence is terminated after three octal digits. (The value of this two-character integer character
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constant is implementation-defined.)
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15 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
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L'\1234' specifies the implementation-defined value that results from the combination of the values
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0123 and '4'.
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Forward references: common definitions <stddef.h> (7.17), the mbtowc function
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(7.20.7.2).
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6.4.5 String literals
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Syntax
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1 string-literal:
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" s-char-sequenceopt "
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L" s-char-sequenceopt "
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s-char-sequence:
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s-char
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s-char-sequence s-char
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s-char:
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any member of the source character set except
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the double-quote ", backslash \, or new-line character
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escape-sequence
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Description
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2 A character string literal is a sequence of zero or more multibyte characters enclosed in
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double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
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letter L.
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3 The same considerations apply to each element of the sequence in a character string
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literal or a wide string literal as if it were in an integer character constant or a wide
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character constant, except that the single-quote ' is representable either by itself or by the
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escape sequence \', but the double-quote " shall be represented by the escape sequence
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\".
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Semantics
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4 In translation phase 6, the multibyte character sequences specified by any sequence of
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adjacent character and wide string literal tokens are concatenated into a single multibyte
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character sequence. If any of the tokens are wide string literal tokens, the resulting
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multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
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character string literal.
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5 In translation phase 7, a byte or code of value zero is appended to each multibyte
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character sequence that results from a string literal or literals.66) The multibyte character
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sequence is then used to initialize an array of static storage duration and length just
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sufficient to contain the sequence. For character string literals, the array elements have
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type char, and are initialized with the individual bytes of the multibyte character
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sequence; for wide string literals, the array elements have type wchar_t, and are
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initialized with the sequence of wide characters corresponding to the multibyte character
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66) A character string literal need not be a string (see 7.1.1), because a null character may be embedded in
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it by a \0 escape sequence.
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sequence, as defined by the mbstowcs function with an implementation-defined current
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locale. The value of a string literal containing a multibyte character or escape sequence
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not represented in the execution character set is implementation-defined.
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6 It is unspecified whether these arrays are distinct provided their elements have the
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appropriate values. If the program attempts to modify such an array, the behavior is
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undefined.
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7 EXAMPLE This pair of adjacent character string literals
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"\x12" "3"
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produces a single character string literal containing the two characters whose values are '\x12' and '3',
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because escape sequences are converted into single members of the execution character set just prior to
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adjacent string literal concatenation.
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Forward references: common definitions <stddef.h> (7.17), the mbstowcs
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function (7.20.8.1).
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6.4.6 Punctuators
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Syntax
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1 punctuator: one of
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[ ] ( ) { } . ->
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++ -- & * + - ~ !
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/ % << >> < > <= >= == != ^ | && ||
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? : ; ...
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= *= /= %= += -= <<= >>= &= ^= |=
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, # ##
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<: :> <% %> %: %:%:
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Semantics
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|
2 A punctuator is a symbol that has independent syntactic and semantic significance.
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Depending on context, it may specify an operation to be performed (which in turn may
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yield a value or a function designator, produce a side effect, or some combination thereof)
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in which case it is known as an operator (other forms of operator also exist in some
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contexts). An operand is an entity on which an operator acts.
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3 In all aspects of the language, the six tokens67)
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<: :> <% %> %: %:%:
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behave, respectively, the same as the six tokens
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[ ] { } # ##
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except for their spelling.68)
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Forward references: expressions (6.5), declarations (6.7), preprocessing directives
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(6.10), statements (6.8).
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6.4.7 Header names
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Syntax
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1 header-name:
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< h-char-sequence >
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|
|
" 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
|
|
|
|
|
|
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 6.10.2.
|
|
|
|
|
|
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
|
|
|
|
|
|
67) These tokens are sometimes called ``digraphs''.
|
|
|
|
|
|
68) Thus [ and <: behave differently when ``stringized'' (see 6.10.3.2), but can otherwise be freely
|
|
|
|
|
|
interchanged.
|
|
|
|
|
|
sequence between the " delimiters, the behavior is undefined.69) Header name
|
|
|
|
|
|
preprocessing tokens are recognized only within #include preprocessing directives and
|
|
|
|
|
|
in implementation-defined locations within #pragma directives.70)
|
|
|
|
|
|
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 (6.10.2).
|
|
|
|
|
|
6.4.8 Preprocessing numbers
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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-.
|
|
|
|
|
|
3 Preprocessing number tokens lexically include all floating and integer constant tokens.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
69) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
|
|
|
|
|
|
70) For an example of a header name preprocessing token used in a #pragma directive, see 6.10.9.
|
|
|
|
|
|
6.4.9 Comments
|
|
|
|
|
|
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.71)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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;
|
|
|
|
|
|
71) Thus, /* ... */ comments do not nest.
|
|
|
|
|
|
6.5 Expressions
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 Between the previous and next sequence point an object shall have its stored value
|
|
|
|
|
|
modified at most once by the evaluation of an expression.72) Furthermore, the prior value
|
|
|
|
|
|
shall be read only to determine the value to be stored.73)
|
|
|
|
|
|
3 The grouping of operators and operands is indicated by the syntax.74) Except as specified
|
|
|
|
|
|
later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
|
|
|
|
|
|
of subexpressions and the order in which side effects take place are both unspecified.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 The effective type of an object for an access to its stored value is the declared type of the
|
|
|
|
|
|
object, if any.75) 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
|
|
|
|
|
|
72) A floating-point status flag is not an object and can be set more than once within an expression.
|
|
|
|
|
|
73) This paragraph renders undefined statement expressions such as
|
|
|
|
|
|
i = ++i + 1;
|
|
|
|
|
|
a[i++] = i;
|
|
|
|
|
|
while allowing
|
|
|
|
|
|
i = i + 1;
|
|
|
|
|
|
a[i] = i;
|
|
|
|
|
|
|
|
|
|
|
|
74) 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 (6.5.6) are those expressions defined in
|
|
|
|
|
|
6.5.1 through 6.5.6. The exceptions are cast expressions (6.5.4) as operands of unary operators
|
|
|
|
|
|
(6.5.3), and an operand contained between any of the following pairs of operators: grouping
|
|
|
|
|
|
parentheses () (6.5.1), subscripting brackets [] (6.5.2.1), function-call parentheses () (6.5.2.2), and
|
|
|
|
|
|
the conditional operator ?: (6.5.15).
|
|
|
|
|
|
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.
|
|
|
|
|
|
75) Allocated objects have no declared type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 An object shall have its stored value accessed only by an lvalue expression that has one of
|
|
|
|
|
|
the following types:76)
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
8 A floating expression may be contracted , that is, evaluated as though it were an atomic
|
|
|
|
|
|
operation, thereby omitting rounding errors implied by the source code and the
|
|
|
|
|
|
expression evaluation method.77) The FP_CONTRACT pragma in <math.h> provides a
|
|
|
|
|
|
way to disallow contracted expressions. Otherwise, whether and how expressions are
|
|
|
|
|
|
contracted is implementation-defined.78)
|
|
|
|
|
|
Forward references: the FP_CONTRACT pragma (7.12.2), copying functions (7.21.2).
|
|
|
|
|
|
76) The intent of this list is to specify those circumstances in which an object may or may not be aliased.
|
|
|
|
|
|
77) A contracted expression might also omit the raising of floating-point exceptions.
|
|
|
|
|
|
78) 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.
|
|
|
|
|
|
6.5.1 Primary expressions
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 primary-expression:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
constant
|
|
|
|
|
|
string-literal
|
|
|
|
|
|
( expression )
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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).79)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
3 A constant is a primary expression. Its type depends on its form and value, as detailed in 6.4.4.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
4 A string literal is a primary expression. It is an lvalue with type as detailed in 6.4.5.
|
|
|
|
|
|
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.
|
|
|
|
|
|
Forward references: declarations (6.7).
|
|
|
|
|
|
6.5.2 Postfix operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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 , }
|
|
|
|
|
|
79) Thus, an undeclared identifier is a violation of the syntax.
|
|
|
|
|
|
argument-expression-list:
|
|
|
|
|
|
assignment-expression
|
|
|
|
|
|
argument-expression-list , assignment-expression
|
|
|
|
|
|
6.5.2.1 Array subscripting
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 One of the expressions shall have type ``pointer to object type'', the other expression shall
|
|
|
|
|
|
have integer type, and the result has type ``type''.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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).
|
|
|
|
|
|
3 Successive subscript operators designate an element of a multidimensional array object.
|
|
|
|
|
|
If E is an n-dimensional array ( n 2) with dimensions i <20> j <20> . . . <20> k , then E (used as
|
|
|
|
|
|
other than an lvalue) is converted to a pointer to an ( n - 1)-dimensional array with
|
|
|
|
|
|
dimensions j <20> . . . <20> k . If the unary * operator is applied to this pointer explicitly, or
|
|
|
|
|
|
implicitly as a result of subscripting, the result is the pointed-to ( 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).
|
|
|
|
|
|
4 EXAMPLE Consider the array object defined by the declaration
|
|
|
|
|
|
int x[3][5];
|
|
|
|
|
|
Here x is a 3 <20> 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 (6.5.6), address and indirection operators
|
|
|
|
|
|
(6.5.3.2), array declarators (6.7.5.2).
|
|
|
|
|
|
|
|
|
|
|
|
6.5.2.2 Function calls
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The expression that denotes the called function80) shall have type pointer to function
|
|
|
|
|
|
returning void or returning an object type other than an array type.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 An argument may be an expression of any 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.81)
|
|
|
|
|
|
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 6.8.6.4. Otherwise, the function call has type void. If
|
|
|
|
|
|
an attempt is made to modify the result of a function call or to access it after the next
|
|
|
|
|
|
sequence point, the behavior is undefined.
|
|
|
|
|
|
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:
|
|
|
|
|
|
80) Most often, this is the result of converting an identifier that is a function designator.
|
|
|
|
|
|
81) 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 6.9.1.
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
10 The order of evaluation of the function designator, the actual arguments, and
|
|
|
|
|
|
subexpressions within the actual arguments is unspecified, but there is a sequence point
|
|
|
|
|
|
before the actual call.
|
|
|
|
|
|
11 Recursive function calls shall be permitted, both directly and indirectly through any chain
|
|
|
|
|
|
of other functions.
|
|
|
|
|
|
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) (6.7.5.3), function
|
|
|
|
|
|
definitions (6.9.1), the return statement (6.8.6.4), simple assignment (6.5.16.1).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.5.2.3 Structure and union members
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Constraints
|
|
|
|
|
|
1 The first operand of the . operator shall have a qualified or unqualified structure or union
|
|
|
|
|
|
type, and the second operand shall name a member of that type.
|
|
|
|
|
|
2 The first operand of the -> operator shall have type ``pointer to qualified or unqualified
|
|
|
|
|
|
structure'' or ``pointer to qualified or unqualified union'', and the second operand shall
|
|
|
|
|
|
name a member of the type pointed to.
|
|
|
|
|
|
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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,82) 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.
|
|
|
|
|
|
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.83) 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.
|
|
|
|
|
|
5 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 complete 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.
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
|
|
|
|
|
|
7 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
|
|
|
|
|
|
82) If the member used to access 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 6.2.6 (a process sometimes called "type
|
|
|
|
|
|
punning"). This might be a trap representation.
|
|
|
|
|
|
83) 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 E.MOS.
|
|
|
|
|
|
8 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 = 3.14;
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
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 (6.5.3.2), structure and union
|
|
|
|
|
|
specifiers (6.7.2.1).
|
|
|
|
|
|
|
|
|
|
|
|
6.5.2.4 Postfix increment and decrement operators
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The operand of the postfix increment or decrement operator shall have qualified or
|
|
|
|
|
|
unqualified real or pointer type and shall be a modifiable lvalue.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 The result of the postfix ++ operator is the value of the operand. After the result is
|
|
|
|
|
|
obtained, the value of the operand 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 side effect of updating the stored value of the operand shall occur between
|
|
|
|
|
|
the previous and the next sequence point.
|
|
|
|
|
|
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 (6.5.6), compound assignment (6.5.16.2).
|
|
|
|
|
|
6.5.2.5 Compound literals
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The type name shall specify an object type or an array of unknown size, but not a variable
|
|
|
|
|
|
length array type.
|
|
|
|
|
|
2 No initializer shall attempt to provide a value for an object not contained within the entire
|
|
|
|
|
|
unnamed object specified by the compound literal.
|
|
|
|
|
|
3 If the compound literal occurs outside the body of a function, the initializer list shall
|
|
|
|
|
|
consist of constant expressions.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
4 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.84)
|
|
|
|
|
|
5 If the type name specifies an array of unknown size, the size is determined by the
|
|
|
|
|
|
initializer list as specified in 6.7.8, 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.
|
|
|
|
|
|
84) 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.
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
7 All the semantic rules and constraints for initializer lists in 6.7.8 are applicable to
|
|
|
|
|
|
compound literals.85)
|
|
|
|
|
|
8 String literals, and compound literals with const-qualified types, need not designate
|
|
|
|
|
|
distinct objects.86)
|
|
|
|
|
|
9 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.
|
|
|
|
|
|
|
|
|
|
|
|
10 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.
|
|
|
|
|
|
|
|
|
|
|
|
11 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});
|
|
|
|
|
|
|
|
|
|
|
|
12 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
|
|
|
|
|
|
(const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
|
|
|
|
|
|
85) For example, subobjects without explicit initializers are initialized to zero.
|
|
|
|
|
|
86) This allows implementations to share storage for string literals and constant compound literals with
|
|
|
|
|
|
the same or overlapping representations.
|
|
|
|
|
|
13 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.
|
|
|
|
|
|
|
|
|
|
|
|
14 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.
|
|
|
|
|
|
|
|
|
|
|
|
15 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);
|
|
|
|
|
|
|
|
|
|
|
|
16 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.
|
|
|
|
|
|
17 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 (6.7.6), initialization (6.7.8).
|
|
|
|
|
|
|
|
|
|
|
|
6.5.3 Unary operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 unary-expression:
|
|
|
|
|
|
postfix-expression
|
|
|
|
|
|
++ unary-expression
|
|
|
|
|
|
-- unary-expression
|
|
|
|
|
|
unary-operator cast-expression
|
|
|
|
|
|
sizeof unary-expression
|
|
|
|
|
|
sizeof ( type-name )
|
|
|
|
|
|
unary-operator: one of
|
|
|
|
|
|
& * + - ~ !
|
|
|
|
|
|
6.5.3.1 Prefix increment and decrement operators
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The operand of the prefix increment or decrement operator shall have qualified or
|
|
|
|
|
|
unqualified real or pointer type and shall be a modifiable lvalue.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
|
|
|
|
|
|
operand is decremented.
|
|
|
|
|
|
Forward references: additive operators (6.5.6), compound assignment (6.5.16.2).
|
|
|
|
|
|
6.5.3.2 Address and indirection operators
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
2 The operand of the unary * operator shall have pointer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.87)
|
|
|
|
|
|
Forward references: storage-class specifiers (6.7.1), structure and union specifiers
|
|
|
|
|
|
(6.7.2.1).
|
|
|
|
|
|
6.5.3.3 Unary arithmetic operators
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
|
|
|
|
|
|
integer type; of the ! operator, scalar type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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).
|
|
|
|
|
|
87) 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.
|
|
|
|
|
|
6.5.3.4 The sizeof operator
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 When 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.88) 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.
|
|
|
|
|
|
4 The value of the result is implementation-defined, and its type (an unsigned integer type)
|
|
|
|
|
|
is size_t, defined in <stddef.h> (and other headers).
|
|
|
|
|
|
5 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.
|
|
|
|
|
|
|
|
|
|
|
|
6 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
|
|
|
|
|
|
sizeof array / sizeof array[0]
|
|
|
|
|
|
|
|
|
|
|
|
7 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
|
|
|
|
|
|
}
|
|
|
|
|
|
88) When applied to a parameter declared to have array or function type, the sizeof operator yields the
|
|
|
|
|
|
size of the adjusted (pointer) type (see 6.9.1).
|
|
|
|
|
|
int main()
|
|
|
|
|
|
{
|
|
|
|
|
|
size_t size;
|
|
|
|
|
|
size = fsize3(10); // fsize3 returns 13
|
|
|
|
|
|
return 0;
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
Forward references: common definitions <stddef.h> (7.17), declarations (6.7),
|
|
|
|
|
|
structure and union specifiers (6.7.2.1), type names (6.7.6), array declarators (6.7.5.2).
|
|
|
|
|
|
6.5.4 Cast operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 cast-expression:
|
|
|
|
|
|
unary-expression
|
|
|
|
|
|
( type-name ) cast-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Unless the type name specifies a void type, the type name shall specify qualified or
|
|
|
|
|
|
unqualified scalar type and the operand shall have scalar type.
|
|
|
|
|
|
3 Conversions that involve pointers, other than where permitted by the constraints of
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.5.16.1, shall be specified by means of an explicit cast.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Semantics
|
|
|
|
|
|
4 Preceding an expression by a parenthesized type name converts the value of the
|
|
|
|
|
|
expression to the named type. This construction is called a cast .89) A cast that specifies
|
|
|
|
|
|
no conversion has no effect on the type or value of an expression.
|
|
|
|
|
|
5 If the value of the expression is represented with greater precision or range than required
|
|
|
|
|
|
by the type named by the cast (6.3.1.8), then the cast specifies a conversion even if the
|
|
|
|
|
|
type of the expression is the same as the named type.
|
|
|
|
|
|
Forward references: equality operators (6.5.9), function declarators (including
|
|
|
|
|
|
prototypes) (6.7.5.3), simple assignment (6.5.16.1), type names (6.7.6).
|
|
|
|
|
|
89) 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.
|
|
|
|
|
|
6.5.5 Multiplicative operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 multiplicative-expression:
|
|
|
|
|
|
cast-expression
|
|
|
|
|
|
multiplicative-expression * cast-expression
|
|
|
|
|
|
multiplicative-expression / cast-expression
|
|
|
|
|
|
multiplicative-expression % cast-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have arithmetic type. The operands of the % operator shall
|
|
|
|
|
|
have integer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The usual arithmetic conversions are performed on the operands.
|
|
|
|
|
|
4 The result of the binary * operator is the product of the operands.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 When integers are divided, the result of the / operator is the algebraic quotient with any
|
|
|
|
|
|
fractional part discarded.90) If the quotient a/b is representable, the expression
|
|
|
|
|
|
(a/b)*b + a%b shall equal a.
|
|
|
|
|
|
6.5.6 Additive operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 additive-expression:
|
|
|
|
|
|
multiplicative-expression
|
|
|
|
|
|
additive-expression + multiplicative-expression
|
|
|
|
|
|
additive-expression - multiplicative-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 For addition, either both operands shall have arithmetic type, or one operand shall be a
|
|
|
|
|
|
pointer to an object type and the other shall have integer type. (Incrementing is
|
|
|
|
|
|
equivalent to adding 1.)
|
|
|
|
|
|
3 For subtraction, one of the following shall hold:
|
|
|
|
|
|
-- both operands have arithmetic type;
|
|
|
|
|
|
90) This is often called ``truncation toward zero''.
|
|
|
|
|
|
-- both operands are pointers to qualified or unqualified versions of compatible object
|
|
|
|
|
|
types; or
|
|
|
|
|
|
-- the left operand is a pointer to an object type and the right operand has integer type.
|
|
|
|
|
|
(Decrementing is equivalent to subtracting 1.)
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
4 If both operands have arithmetic type, the usual arithmetic conversions are performed on
|
|
|
|
|
|
them.
|
|
|
|
|
|
5 The result of the binary + operator is the sum of the operands.
|
|
|
|
|
|
6 The result of the binary - operator is the difference resulting from the subtraction of the
|
|
|
|
|
|
second operand from the first.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.91)
|
|
|
|
|
|
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
|
|
|
|
|
|
}
|
|
|
|
|
|
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 (6.7.5.2), common definitions <stddef.h>
|
|
|
|
|
|
(7.17).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.5.7 Bitwise shift operators
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Syntax
|
|
|
|
|
|
1 shift-expression:
|
|
|
|
|
|
additive-expression
|
|
|
|
|
|
shift-expression << additive-expression
|
|
|
|
|
|
shift-expression >> additive-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have integer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
91) 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.
|
|
|
|
|
|
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 <20> 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 <20> 2E2 is representable in the result type, then that is
|
|
|
|
|
|
the resulting value; otherwise, the behavior is undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.5.8 Relational operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 relational-expression:
|
|
|
|
|
|
shift-expression
|
|
|
|
|
|
relational-expression < shift-expression
|
|
|
|
|
|
relational-expression > shift-expression
|
|
|
|
|
|
relational-expression <= shift-expression
|
|
|
|
|
|
relational-expression >= shift-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 One of the following shall hold:
|
|
|
|
|
|
-- both operands have real type;
|
|
|
|
|
|
-- both operands are pointers to qualified or unqualified versions of compatible object
|
|
|
|
|
|
types; or
|
|
|
|
|
|
-- both operands are pointers to qualified or unqualified versions of compatible
|
|
|
|
|
|
incomplete types.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 If both of the operands have arithmetic type, the usual arithmetic conversions are
|
|
|
|
|
|
performed.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 or incomplete 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.
|
|
|
|
|
|
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.92)
|
|
|
|
|
|
The result has type int.
|
|
|
|
|
|
6.5.9 Equality operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 equality-expression:
|
|
|
|
|
|
relational-expression
|
|
|
|
|
|
equality-expression == relational-expression
|
|
|
|
|
|
equality-expression != relational-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
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 or incomplete 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
|
|
|
|
|
|
3 The == (equal to) and != (not equal to) operators are analogous to the relational
|
|
|
|
|
|
operators except for their lower precedence.93) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
92) 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''.
|
|
|
|
|
|
93) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
|
|
|
|
|
|
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 or incomplete 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.
|
|
|
|
|
|
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.94)
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.5.10 Bitwise AND operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 AND-expression:
|
|
|
|
|
|
equality-expression
|
|
|
|
|
|
AND-expression & equality-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have integer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The usual arithmetic conversions are performed on the operands.
|
|
|
|
|
|
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).
|
|
|
|
|
|
94) 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.
|
|
|
|
|
|
6.5.11 Bitwise exclusive OR operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 exclusive-OR-expression:
|
|
|
|
|
|
AND-expression
|
|
|
|
|
|
exclusive-OR-expression ^ AND-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have integer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The usual arithmetic conversions are performed on the operands.
|
|
|
|
|
|
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).
|
|
|
|
|
|
6.5.12 Bitwise inclusive OR operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 inclusive-OR-expression:
|
|
|
|
|
|
exclusive-OR-expression
|
|
|
|
|
|
inclusive-OR-expression | exclusive-OR-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have integer type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The usual arithmetic conversions are performed on the operands.
|
|
|
|
|
|
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).
|
|
|
|
|
|
|
|
|
|
|
|
6.5.13 Logical AND operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 logical-AND-expression:
|
|
|
|
|
|
inclusive-OR-expression
|
|
|
|
|
|
logical-AND-expression && inclusive-OR-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have scalar type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
|
|
|
|
|
|
yields 0. The result has type int.
|
|
|
|
|
|
4 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
|
|
|
|
|
|
there is a sequence point after the evaluation of the first operand. If the first operand
|
|
|
|
|
|
compares equal to 0, the second operand is not evaluated.
|
|
|
|
|
|
6.5.14 Logical OR operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 logical-OR-expression:
|
|
|
|
|
|
logical-AND-expression
|
|
|
|
|
|
logical-OR-expression || logical-AND-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Each of the operands shall have scalar type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
|
|
|
|
|
|
yields 0. The result has type int.
|
|
|
|
|
|
4 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
|
|
|
|
|
|
a sequence point after the evaluation of the first operand. If the first operand compares
|
|
|
|
|
|
unequal to 0, the second operand is not evaluated.
|
|
|
|
|
|
|
|
|
|
|
|
6.5.15 Conditional operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 conditional-expression:
|
|
|
|
|
|
logical-OR-expression
|
|
|
|
|
|
logical-OR-expression ? expression : conditional-expression
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 The first operand shall have scalar type.
|
|
|
|
|
|
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 or incomplete type and the other is a pointer to a
|
|
|
|
|
|
qualified or unqualified version of void.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
4 The first operand is evaluated; there is a sequence point after its evaluation. 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.95) If an attempt is made
|
|
|
|
|
|
to modify the result of a conditional operator or to access it after the next sequence point,
|
|
|
|
|
|
the behavior is undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 pointed-to 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
|
|
|
|
|
|
|
|
|
|
|
|
95) A conditional expression does not yield an lvalue.
|
|
|
|
|
|
pointer to an appropriately qualified version of void.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 *
|
|
|
|
|
|
|
|
|
|
|
|
6.5.16 Assignment operators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 assignment-expression:
|
|
|
|
|
|
conditional-expression
|
|
|
|
|
|
unary-expression assignment-operator assignment-expression
|
|
|
|
|
|
assignment-operator: one of
|
|
|
|
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 An assignment operator shall have a modifiable lvalue as its left operand.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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, but is not an
|
|
|
|
|
|
lvalue. The type of an assignment expression is the type of the left operand unless the
|
|
|
|
|
|
left operand has qualified type, in which case it is the unqualified version of the type of
|
|
|
|
|
|
the left operand. The side effect of updating the stored value of the left operand shall
|
|
|
|
|
|
occur between the previous and the next sequence point.
|
|
|
|
|
|
4 The order of evaluation of the operands is unspecified. If an attempt is made to modify
|
|
|
|
|
|
the result of an assignment operator or to access it after the next sequence point, the
|
|
|
|
|
|
behavior is undefined.
|
|
|
|
|
|
6.5.16.1 Simple assignment
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 One of the following shall hold:96)
|
|
|
|
|
|
-- the left operand has qualified or unqualified arithmetic type and the right has
|
|
|
|
|
|
arithmetic type;
|
|
|
|
|
|
-- the left operand has a qualified or unqualified version of a structure or union type
|
|
|
|
|
|
compatible with the type of the right;
|
|
|
|
|
|
-- 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;
|
|
|
|
|
|
-- one operand is a pointer to an object or incomplete 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 a pointer and the right is a null pointer constant; or
|
|
|
|
|
|
-- the left operand has type _Bool and the right is a pointer.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
96) The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
|
|
|
|
|
|
(specified in 6.3.2.1) 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).
|
|
|
|
|
|
negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
|
|
|
|
|
|
variable c should be declared as int.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.5.16.2 Compound assignment
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 For the operators += and -= only, either the left operand shall be a pointer to an object
|
|
|
|
|
|
type and the right shall have integer type, or the left operand shall have qualified or
|
|
|
|
|
|
unqualified arithmetic type and the right shall have arithmetic type.
|
|
|
|
|
|
2 For the other operators, each operand shall have arithmetic type consistent with those
|
|
|
|
|
|
allowed by the corresponding binary operator.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 A compound assignment of the form E1 op = E2 differs from the simple assignment
|
|
|
|
|
|
expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
|
|
|
|
|
|
|
|
|
|
|
|
6.5.17 Comma operator
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 expression:
|
|
|
|
|
|
assignment-expression
|
|
|
|
|
|
expression , assignment-expression
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 The left operand of a comma operator is evaluated as a void expression; there is a
|
|
|
|
|
|
sequence point after its evaluation. Then the right operand is evaluated; the result has its
|
|
|
|
|
|
type and value.97) If an attempt is made to modify the result of a comma operator or to
|
|
|
|
|
|
access it after the next sequence point, the behavior is undefined.
|
|
|
|
|
|
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 (6.7.8).
|
|
|
|
|
|
97) A comma operator does not yield an lvalue.
|
|
|
|
|
|
6.6 Constant expressions
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 constant-expression:
|
|
|
|
|
|
conditional-expression
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.98)
|
|
|
|
|
|
4 Each constant expression shall evaluate to a constant that is in the range of representable
|
|
|
|
|
|
values for its type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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 precision and range
|
|
|
|
|
|
shall be at least as great as if the expression were being evaluated in the execution
|
|
|
|
|
|
environment.
|
|
|
|
|
|
6 An integer constant expression99) shall have integer type and shall only have operands
|
|
|
|
|
|
that are integer constants, enumeration constants, character constants, sizeof
|
|
|
|
|
|
expressions whose results are integer constants, 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
|
|
|
|
|
|
operator.
|
|
|
|
|
|
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,
|
|
|
|
|
|
98) The operand of a sizeof operator is usually not evaluated (6.5.3.4).
|
|
|
|
|
|
99) An integer constant expression is used to specify the size of a bit-field member of a structure, the
|
|
|
|
|
|
value of an enumeration constant, the size of an array, or the value of a case constant. Further
|
|
|
|
|
|
constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
|
|
|
|
|
|
directives are discussed in 6.10.1.
|
|
|
|
|
|
-- an address constant, or
|
|
|
|
|
|
-- an address constant for an object type plus or minus an integer constant expression.
|
|
|
|
|
|
8 An arithmetic constant expression shall have arithmetic type and shall only have
|
|
|
|
|
|
operands that are integer constants, floating constants, enumeration constants, character
|
|
|
|
|
|
constants, and sizeof 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 operator whose result is an integer constant.
|
|
|
|
|
|
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.
|
|
|
|
|
|
10 An implementation may accept other forms of constant expressions.
|
|
|
|
|
|
11 The semantic rules for the evaluation of a constant expression are the same as for
|
|
|
|
|
|
nonconstant expressions.100)
|
|
|
|
|
|
Forward references: array declarators (6.7.5.2), initialization (6.7.8).
|
|
|
|
|
|
100) Thus, in the following initialization,
|
|
|
|
|
|
static int i = 2 || 1 / 0;
|
|
|
|
|
|
the expression is a valid integer constant expression with value one.
|
|
|
|
|
|
6.7 Declarations
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 declaration:
|
|
|
|
|
|
declaration-specifiers init-declarator-listopt ;
|
|
|
|
|
|
declaration-specifiers:
|
|
|
|
|
|
storage-class-specifier declaration-specifiersopt
|
|
|
|
|
|
type-specifier declaration-specifiersopt
|
|
|
|
|
|
type-qualifier declaration-specifiersopt
|
|
|
|
|
|
function-specifier declaration-specifiersopt
|
|
|
|
|
|
init-declarator-list:
|
|
|
|
|
|
init-declarator
|
|
|
|
|
|
init-declarator-list , init-declarator
|
|
|
|
|
|
init-declarator:
|
|
|
|
|
|
declarator
|
|
|
|
|
|
declarator = initializer
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 A 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
for tags as specified in 6.7.2.3.
|
|
|
|
|
|
4 All declarations in the same scope that refer to the same object or function shall specify
|
|
|
|
|
|
compatible types.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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;101)
|
|
|
|
|
|
-- for an enumeration constant or typedef name, is the (only) declaration of the
|
|
|
|
|
|
identifier.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
101) Function definitions have a different syntax, described in 6.9.1.
|
|
|
|
|
|
additional type information, or an initializer, or both. The declarators contain the
|
|
|
|
|
|
identifiers (if any) being declared.
|
|
|
|
|
|
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 6.7.5.3) that is required to be complete.
|
|
|
|
|
|
Forward references: declarators (6.7.5), enumeration specifiers (6.7.2.2), initialization
|
|
|
|
|
|
(6.7.8).
|
|
|
|
|
|
6.7.1 Storage-class specifiers
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 storage-class-specifier:
|
|
|
|
|
|
typedef
|
|
|
|
|
|
extern
|
|
|
|
|
|
static
|
|
|
|
|
|
auto
|
|
|
|
|
|
register
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 At most, one storage-class specifier may be given in the declaration specifiers in a
|
|
|
|
|
|
declaration.102)
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The typedef specifier is called a ``storage-class specifier'' for syntactic convenience
|
|
|
|
|
|
only; it is discussed in 6.7.7. The meanings of the various linkages and storage durations
|
|
|
|
|
|
were discussed in 6.2.2 and 6.2.4.
|
|
|
|
|
|
4 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.103)
|
|
|
|
|
|
5 The declaration of an identifier for a function that has block scope shall have no explicit
|
|
|
|
|
|
storage-class specifier other than extern.
|
|
|
|
|
|
102) See ``future language directions'' (6.11.5).
|
|
|
|
|
|
103) 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 6.5.3.2) or implicitly (by converting an array name to a pointer as discussed in
|
|
|
|
|
|
6.3.2.1). Thus, the only operator that can be applied to an array declared with storage-class specifier
|
|
|
|
|
|
register is sizeof.
|
|
|
|
|
|
6 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 (6.7.7).
|
|
|
|
|
|
6.7.2 Type specifiers
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 type-specifier:
|
|
|
|
|
|
void
|
|
|
|
|
|
char
|
|
|
|
|
|
short
|
|
|
|
|
|
int
|
|
|
|
|
|
long
|
|
|
|
|
|
float
|
|
|
|
|
|
double
|
|
|
|
|
|
signed
|
|
|
|
|
|
unsigned
|
|
|
|
|
|
_Bool
|
|
|
|
|
|
_Complex
|
|
|
|
|
|
struct-or-union-specifier
|
|
|
|
|
|
enum-specifier
|
|
|
|
|
|
typedef-name
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
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 sets (delimited by commas, when there is
|
|
|
|
|
|
more than one set on a line); 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
|
|
|
|
|
|
-- struct or union specifier
|
|
|
|
|
|
-- enum specifier
|
|
|
|
|
|
-- typedef name
|
|
|
|
|
|
3 The type specifier _Complex shall not be used if the implementation does not provide
|
|
|
|
|
|
complex types.104)
|
|
|
|
|
|
Semantics
|
2012-01-17 03:07:01 +01:00
|
|
|
|
4 Specifiers for structures, unions, and enumerations are discussed in 6.7.2.1 through 6.7.2.3.
|
|
|
|
|
|
Declarations of typedef names are discussed in 6.7.7. The characteristics of the
|
2012-01-16 16:34:32 +01:00
|
|
|
|
other types are discussed in 6.2.5.
|
|
|
|
|
|
5 Each of the comma-separated sets 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: enumeration specifiers (6.7.2.2), structure and union specifiers
|
|
|
|
|
|
(6.7.2.1), tags (6.7.2.3), type definitions (6.7.7).
|
|
|
|
|
|
104) Freestanding implementations are not required to provide complex types.
|
|
|
|
|
|
6.7.2.1 Structure and union specifiers
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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-list ;
|
|
|
|
|
|
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
|
|
|
|
|
|
2 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.
|
|
|
|
|
|
3 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. If the value is zero,
|
|
|
|
|
|
the declaration shall have no declarator.
|
|
|
|
|
|
4 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.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
5 As discussed in 6.2.5, 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.
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
7 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 contains no named
|
|
|
|
|
|
members, the behavior is undefined. The type is incomplete until after the } that
|
|
|
|
|
|
terminates the list.
|
|
|
|
|
|
8 A member of a structure or union may have any object type other than a variably
|
|
|
|
|
|
modified type.105) 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 ;106) its
|
|
|
|
|
|
width is preceded by a colon.
|
|
|
|
|
|
9 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
|
|
|
|
|
|
number of bits.107) 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.
|
|
|
|
|
|
10 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.
|
|
|
|
|
|
11 A bit-field declaration with no declarator, but only a colon and a width, indicates an
|
|
|
|
|
|
unnamed bit-field.108) 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.
|
|
|
|
|
|
105) A structure or union can not contain a member with a variably modified type because member names
|
|
|
|
|
|
are not ordinary identifiers as defined in 6.2.3.
|
|
|
|
|
|
106) 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.
|
|
|
|
|
|
107) As specified in 6.7.2 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.
|
|
|
|
|
|
108) An unnamed bit-field structure member is useful for padding to conform to externally imposed
|
|
|
|
|
|
layouts.
|
|
|
|
|
|
12 Each non-bit-field member of a structure or union object is aligned in an implementation-
|
|
|
|
|
|
defined manner appropriate to its type.
|
|
|
|
|
|
13 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.
|
|
|
|
|
|
14 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.
|
|
|
|
|
|
15 There may be unnamed padding at the end of a structure or union.
|
|
|
|
|
|
16 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.
|
|
|
|
|
|
17 EXAMPLE 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).
|
|
|
|
|
|
18 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.
|
|
|
|
|
|
19 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.
|
|
|
|
|
|
20 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;
|
|
|
|
|
|
21 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
|
|
|
|
|
|
22 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.
|
|
|
|
|
|
|
|
|
|
|
|
Forward references: tags (6.7.2.3).
|
|
|
|
|
|
6.7.2.2 Enumeration specifiers
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The identifiers in an enumerator list are declared as constants that have type int and
|
|
|
|
|
|
may appear wherever such are permitted.109) 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.
|
|
|
|
|
|
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,110) but shall be
|
|
|
|
|
|
capable of representing the values of all the members of the enumeration. The
|
|
|
|
|
|
enumerated type is incomplete until after the } that terminates the list of enumerator
|
|
|
|
|
|
declarations.
|
|
|
|
|
|
109) 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.
|
|
|
|
|
|
110) An implementation may delay the choice of which integer type until all enumeration constants have
|
|
|
|
|
|
been seen.
|
|
|
|
|
|
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 (6.7.2.3).
|
|
|
|
|
|
6.7.2.3 Tags
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 A specific type shall have its content defined at most once.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 A type specifier of the form
|
|
|
|
|
|
enum identifier
|
|
|
|
|
|
without an enumerator list shall only appear after the type it specifies is complete.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
4 All declarations of structure, union, or enumerated types that have the same scope and
|
|
|
|
|
|
use the same tag declare the same type. The type is incomplete111) until the closing brace
|
|
|
|
|
|
of the list defining the content, and complete thereafter.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 A type specifier of the form
|
|
|
|
|
|
struct-or-union identifieropt { struct-declaration-list }
|
|
|
|
|
|
or
|
|
|
|
|
|
enum identifier { enumerator-list }
|
|
|
|
|
|
or
|
|
|
|
|
|
enum identifier { enumerator-list , }
|
|
|
|
|
|
declares a structure, union, or enumerated type. The list defines the structure content ,
|
|
|
|
|
|
|
|
|
|
|
|
111) 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 6.2.5.) The specification has to be complete before such a function is called or defined.
|
|
|
|
|
|
union content , or enumeration content . If an identifier is provided,112) the type specifier
|
|
|
|
|
|
also declares the identifier to be the tag of that type.
|
|
|
|
|
|
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.113)
|
|
|
|
|
|
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.113)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
11 The following alternative formulation uses the typedef mechanism:
|
|
|
|
|
|
112) 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.
|
|
|
|
|
|
113) A similar construction with enum does not exist.
|
|
|
|
|
|
typedef struct tnode TNODE;
|
|
|
|
|
|
struct tnode {
|
|
|
|
|
|
int count;
|
|
|
|
|
|
TNODE *left, *right;
|
|
|
|
|
|
};
|
|
|
|
|
|
TNODE s, *sp;
|
|
|
|
|
|
|
|
|
|
|
|
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 (6.7.5), array declarators (6.7.5.2), type definitions
|
|
|
|
|
|
(6.7.7).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.7.3 Type qualifiers
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Syntax
|
|
|
|
|
|
1 type-qualifier:
|
|
|
|
|
|
const
|
|
|
|
|
|
restrict
|
|
|
|
|
|
volatile
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Types other than pointer types derived from object or incomplete types shall not be
|
|
|
|
|
|
restrict-qualified.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
3 The properties associated with qualified types are meaningful only for expressions that
|
|
|
|
|
|
are lvalues.114)
|
|
|
|
|
|
4 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.
|
|
|
|
|
|
114) 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.
|
|
|
|
|
|
5 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.115)
|
|
|
|
|
|
6 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 5.1.2.3. 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.116) What constitutes an access to an object that
|
|
|
|
|
|
has volatile-qualified type is implementation-defined.
|
|
|
|
|
|
7 An object that is accessed through a restrict-qualified pointer has a special association
|
|
|
|
|
|
with that pointer. This association, defined in 6.7.3.1 below, requires that all accesses to
|
|
|
|
|
|
that object use, directly or indirectly, the value of that particular pointer.117) 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).
|
|
|
|
|
|
8 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.118)
|
|
|
|
|
|
9 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.
|
|
|
|
|
|
10 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.
|
|
|
|
|
|
115) 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).
|
|
|
|
|
|
116) 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.
|
|
|
|
|
|
117) 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.
|
|
|
|
|
|
118) Both of these can occur through the use of typedefs.
|
|
|
|
|
|
11 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 *''
|
|
|
|
|
|
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.7.3.1 Formal definition of restrict
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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.
|
|
|
|
|
|
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).
|
|
|
|
|
|
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.119)
|
|
|
|
|
|
Note that ``based'' is defined only for expressions with pointer types.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
119) 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.
|
|
|
|
|
|
associated with B.
|
|
|
|
|
|
6 A translator is free to ignore any or all aliasing implications of uses of restrict.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
}
|
|
|
|
|
|
}
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.7.4 Function specifiers
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Syntax
|
|
|
|
|
|
1 function-specifier:
|
|
|
|
|
|
inline
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 Function specifiers shall be used only in the declaration of an identifier for a function.
|
|
|
|
|
|
3 An inline definition of a function with external linkage shall not contain a definition of a
|
|
|
|
|
|
modifiable object with static storage duration, and shall not contain a reference to an
|
|
|
|
|
|
identifier with internal linkage.
|
|
|
|
|
|
4 In a hosted environment, the inline function specifier shall not appear in a declaration
|
|
|
|
|
|
of main.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
5 A function declared with an inline function specifier is an inline function. The
|
|
|
|
|
|
function specifier may appear more than once; the behavior is the same as if it appeared
|
|
|
|
|
|
only once. Making a function an inline function suggests that calls to the function be as
|
|
|
|
|
|
fast as possible.120) The extent to which such suggestions are effective is
|
|
|
|
|
|
implementation-defined.121)
|
|
|
|
|
|
6 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.122)
|
|
|
|
|
|
7 EXAMPLE 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);
|
|
|
|
|
|
}
|
|
|
|
|
|
8 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 6.9); the inline definition and the external
|
|
|
|
|
|
definition are distinct and either may be used for the call.
|
|
|
|
|
|
|
|
|
|
|
|
Forward references: function definitions (6.9.1).
|
|
|
|
|
|
120) 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.
|
|
|
|
|
|
121) For example, an implementation might never perform inline substitution, or might only perform inline
|
|
|
|
|
|
substitutions to calls in the scope of an inline declaration.
|
|
|
|
|
|
122) 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.
|
|
|
|
|
|
6.7.5 Declarators
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 If, in the declaration ``T D1'', D1 has the form
|
|
|
|
|
|
identifier
|
|
|
|
|
|
then the type specified for ident is T .
|
|
|
|
|
|
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
|
|
|
|
|
|
7 As discussed in 5.2.4.1, an implementation may limit the number of pointer, array, and
|
|
|
|
|
|
function declarators that modify an arithmetic, structure, union, or incomplete type, either
|
|
|
|
|
|
directly or via one or more typedefs.
|
|
|
|
|
|
Forward references: array declarators (6.7.5.2), type definitions (6.7.7).
|
|
|
|
|
|
6.7.5.1 Pointer declarators
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
2 For two pointer types to be compatible, both shall be identically qualified and both shall
|
|
|
|
|
|
be pointers to compatible types.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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''.
|
|
|
|
|
|
|
|
|
|
|
|
6.7.5.2 Array declarators
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
2 An ordinary identifier (as defined in 6.2.3) that has a variably modified type shall have
|
|
|
|
|
|
either block scope and no linkage or function prototype scope. If an identifier is declared
|
|
|
|
|
|
to be an object with static storage duration, it shall not have a variable length array type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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 ''.123)
|
|
|
|
|
|
(See 6.7.5.3 for the meaning of the optional type qualifiers and the keyword static.)
|
|
|
|
|
|
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 with function prototype scope;124) such arrays are
|
|
|
|
|
|
nonetheless complete types. If the size is an integer constant expression and the element
|
|
|
|
|
|
|
|
|
|
|
|
123) When several ``array of'' specifications are adjacent, a multidimensional array is declared.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 EXAMPLE 1
|
|
|
|
|
|
float fa[11], *afp[17];
|
|
|
|
|
|
declares an array of float numbers and an array of pointers to float numbers.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
}
|
|
|
|
|
|
124) Thus, * can be used only in function declarations that are not definitions (see 6.7.5.3).
|
|
|
|
|
|
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 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 (6.7.5.3), function definitions (6.9.1),
|
|
|
|
|
|
initialization (6.7.8).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.7.5.3 Function declarators (including prototypes)
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Constraints
|
|
|
|
|
|
1 A function declarator shall not specify a return type that is a function type or an array
|
|
|
|
|
|
type.
|
|
|
|
|
|
2 The only storage-class specifier that shall occur in a parameter declaration is register.
|
|
|
|
|
|
3 An identifier list in a function declarator that is not part of a definition of that function
|
|
|
|
|
|
shall be empty.
|
|
|
|
|
|
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
|
|
|
|
|
|
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 ''.
|
|
|
|
|
|
6 A parameter type list specifies the types of, and may declare identifiers for, the
|
|
|
|
|
|
parameters of the function.
|
|
|
|
|
|
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.
|
|
|
|
|
|
8 A declaration of a parameter as ``function returning type'' shall be adjusted to ``pointer to
|
|
|
|
|
|
function returning type'', as in 6.3.2.1.
|
|
|
|
|
|
9 If the list terminates with an ellipsis (, ...), no information about the number or types
|
|
|
|
|
|
of the parameters after the comma is supplied.125)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.126)
|
|
|
|
|
|
15 For two function types to be compatible, both shall specify compatible return types.127)
|
|
|
|
|
|
125) The macros defined in the <stdarg.h> header (7.15) may be used to access arguments that
|
|
|
|
|
|
correspond to the ellipsis.
|
|
|
|
|
|
126) See ``future language directions'' (6.11.6).
|
|
|
|
|
|
127) If both function types are ``old style'', parameter types are not compared.
|
|
|
|
|
|
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.)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
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 (6.9.1), type names (6.7.6).
|
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|
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|
|
|
|
6.7.6 Type names
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
2 In several contexts, it is necessary to specify a type. This is accomplished using a type
|
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|
|
|
name, which is syntactically a declaration for a function or an object of that type that
|
|
|
|
|
|
omits the identifier.128)
|
|
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|
|
|
3 EXAMPLE The constructions
|
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|
|
|
(a) int
|
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|
|
|
(b) int *
|
|
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|
|
|
(c) int *[3]
|
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|
|
|
(d) int (*)[3]
|
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|
|
|
|
(e) int (*)[*]
|
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|
|
|
(f) int *()
|
|
|
|
|
|
(g) int (*)(void)
|
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|
|
|
|
(h) int (*const [])(unsigned int, ...)
|
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|
|
|
|
name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
|
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|
|
|
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.
|
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|
|
|
128) As indicated by the syntax, empty parentheses in a type name are interpreted as ``function with no
|
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|
|
|
|
parameter specification'', rather than redundant parentheses around the omitted identifier.
|
|
|
|
|
|
6.7.7 Type definitions
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 typedef-name:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
Constraints
|
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|
|
|
2 If a typedef name specifies a variably modified type then it shall have block scope.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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 6.7.5. 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
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];
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
6.7.8 Initialization
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 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
|
|
|
|
|
|
2 No initializer shall attempt to provide a value for an object not contained within the entity
|
|
|
|
|
|
being initialized.
|
|
|
|
|
|
3 The type of the entity to be initialized shall be an array of unknown size or an object type
|
|
|
|
|
|
that is not a variable length array type.
|
|
|
|
|
|
4 All the expressions in an initializer for an object that has static storage duration shall be
|
|
|
|
|
|
constant expressions or string literals.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 If a designator has the form
|
|
|
|
|
|
. identifier
|
|
|
|
|
|
then the current object (defined below) shall have structure or union type and the
|
|
|
|
|
|
identifier shall be the name of a member of that type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
8 An initializer specifies the initial value stored in an object.
|
|
|
|
|
|
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.
|
|
|
|
|
|
10 If an object that has automatic storage duration is not initialized explicitly, its value is
|
|
|
|
|
|
indeterminate. If an object that has static 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;
|
|
|
|
|
|
-- if it is a union, the first named member is initialized (recursively) according to these
|
|
|
|
|
|
rules.
|
|
|
|
|
|
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.
|
|
|
|
|
|
12 The rest of this subclause deals with initializers for objects that have aggregate or union
|
|
|
|
|
|
type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
14 An array of character type may be initialized by a character string literal, optionally
|
|
|
|
|
|
enclosed in braces. Successive characters of the character 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.
|
|
|
|
|
|
15 An array with element type compatible with wchar_t may be initialized by a wide
|
|
|
|
|
|
string literal, 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.129) 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.130)
|
|
|
|
|
|
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.131) The current object that results at the end of the
|
|
|
|
|
|
designator list is the subobject to be initialized by the following initializer.
|
|
|
|
|
|
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;132)
|
|
|
|
|
|
all subobjects that are not initialized explicitly shall be initialized implicitly the same as
|
|
|
|
|
|
objects that have static storage duration.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
22 If an array of unknown size is initialized, its size is determined by the largest indexed
|
|
|
|
|
|
element with an explicit initializer. At the end of its initializer list, the array no longer
|
|
|
|
|
|
has incomplete type.
|
|
|
|
|
|
129) 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.
|
|
|
|
|
|
130) 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.
|
|
|
|
|
|
131) 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.
|
|
|
|
|
|
132) Any initializer for the subobject which is overridden and so not used to initialize that subobject might
|
|
|
|
|
|
not be evaluated at all.
|
|
|
|
|
|
23 The order in which any side effects occur among the initialization list expressions is
|
|
|
|
|
|
unspecified.133)
|
|
|
|
|
|
24 EXAMPLE 1 Provided that <complex.h> has been #included, the declarations
|
|
|
|
|
|
int i = 3.5;
|
|
|
|
|
|
double complex c = 5 + 3 * I;
|
|
|
|
|
|
define and initialize i with the value 3 and c with the value 5. 0 + i 3. 0.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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].
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
133) In particular, the evaluation order need not be the same as the order of subobject initialization.
|
|
|
|
|
|
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.
|
|
|
|
|
|
30 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
|
|
|
|
|
|
cause confusion.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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",
|
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
|
|
34 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
|
|
|
|
|
|
div_t answer = { .quot = 2, .rem = -1 };
|
|
|
|
|
|
|
|
|
|
|
|
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 };
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
};
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
38 EXAMPLE 13 Any member of a union can be initialized:
|
|
|
|
|
|
union { /* ... */ } u = { .any_member = 42 };
|
|
|
|
|
|
|
|
|
|
|
|
Forward references: common definitions <stddef.h> (7.17).
|
|
|
|
|
|
|
|
|
|
|
|
6.8 Statements and blocks
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 statement:
|
|
|
|
|
|
labeled-statement
|
|
|
|
|
|
compound-statement
|
|
|
|
|
|
expression-statement
|
|
|
|
|
|
selection-statement
|
|
|
|
|
|
iteration-statement
|
|
|
|
|
|
jump-statement
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 A statement specifies an action to be performed. Except as indicated, statements are
|
|
|
|
|
|
executed in sequence.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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; 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. The end of a full
|
|
|
|
|
|
expression is a sequence point.
|
|
|
|
|
|
Forward references: expression and null statements (6.8.3), selection statements
|
|
|
|
|
|
(6.8.4), iteration statements (6.8.5), the return statement (6.8.6.4).
|
|
|
|
|
|
6.8.1 Labeled statements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 labeled-statement:
|
|
|
|
|
|
identifier : statement
|
|
|
|
|
|
case constant-expression : statement
|
|
|
|
|
|
default : statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 A case or default label shall appear only in a switch statement. Further
|
|
|
|
|
|
constraints on such labels are discussed under the switch statement.
|
|
|
|
|
|
3 Label names shall be unique within a function.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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 (6.8.6.1), the switch statement (6.8.4.2).
|
|
|
|
|
|
6.8.2 Compound statement
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 compound-statement:
|
|
|
|
|
|
{ block-item-listopt }
|
|
|
|
|
|
block-item-list:
|
|
|
|
|
|
block-item
|
|
|
|
|
|
block-item-list block-item
|
|
|
|
|
|
block-item:
|
|
|
|
|
|
declaration
|
|
|
|
|
|
statement
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 A compound statement is a block.
|
|
|
|
|
|
6.8.3 Expression and null statements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 expression-statement:
|
|
|
|
|
|
expressionopt ;
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 The expression in an expression statement is evaluated as a void expression for its side
|
|
|
|
|
|
effects.134)
|
|
|
|
|
|
3 A null statement (consisting of just a semicolon) performs no operations.
|
|
|
|
|
|
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);
|
|
|
|
|
|
134) Such as assignments, and function calls which have side effects.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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 (6.8.5).
|
|
|
|
|
|
6.8.4 Selection statements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 selection-statement:
|
|
|
|
|
|
if ( expression ) statement
|
|
|
|
|
|
if ( expression ) statement else statement
|
|
|
|
|
|
switch ( expression ) statement
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 A selection statement selects among a set of statements depending on the value of a
|
|
|
|
|
|
controlling expression.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.8.4.1 The if statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The controlling expression of an if statement shall have scalar type.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 An else is associated with the lexically nearest preceding if that is allowed by the
|
|
|
|
|
|
syntax.
|
|
|
|
|
|
6.8.4.2 The switch statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The controlling expression of a switch statement shall have integer type.
|
|
|
|
|
|
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.135)
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
6 As discussed in 5.2.4.1, the implementation may limit the number of case values in a
|
|
|
|
|
|
switch statement.
|
|
|
|
|
|
135) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.8.5 Iteration statements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 iteration-statement:
|
|
|
|
|
|
while ( expression ) statement
|
|
|
|
|
|
do statement while ( expression ) ;
|
|
|
|
|
|
for ( expressionopt ; expressionopt ; expressionopt ) statement
|
|
|
|
|
|
for ( declaration expressionopt ; expressionopt ) statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 The controlling expression of an iteration statement shall have scalar type.
|
|
|
|
|
|
3 The declaration part of a for statement shall only declare identifiers for objects having
|
|
|
|
|
|
storage class auto or register.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.136)
|
|
|
|
|
|
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.
|
|
|
|
|
|
136) 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.
|
|
|
|
|
|
6.8.5.1 The while statement
|
|
|
|
|
|
1 The evaluation of the controlling expression takes place before each execution of the loop
|
|
|
|
|
|
body.
|
|
|
|
|
|
6.8.5.2 The do statement
|
|
|
|
|
|
1 The evaluation of the controlling expression takes place after each execution of the loop
|
|
|
|
|
|
body.
|
|
|
|
|
|
6.8.5.3 The for statement
|
|
|
|
|
|
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.137)
|
|
|
|
|
|
2 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
|
|
|
|
|
|
nonzero constant.
|
|
|
|
|
|
6.8.6 Jump statements
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 jump-statement:
|
|
|
|
|
|
goto identifier ;
|
|
|
|
|
|
continue ;
|
|
|
|
|
|
break ;
|
|
|
|
|
|
return expressionopt ;
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 A jump statement causes an unconditional jump to another place.
|
|
|
|
|
|
137) 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.
|
|
|
|
|
|
6.8.6.1 The goto statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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
|
|
|
|
|
|
2 A goto statement causes an unconditional jump to the statement prefixed by the named
|
|
|
|
|
|
label in the enclosing function.
|
|
|
|
|
|
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
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
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] = 3.3;
|
|
|
|
|
|
goto lab4; // valid: going WITHIN scope of VLA.
|
|
|
|
|
|
a[j] = 5.5;
|
|
|
|
|
|
lab4:
|
|
|
|
|
|
a[j] = 6.6;
|
|
|
|
|
|
}
|
|
|
|
|
|
goto lab4; // invalid: going INTO scope of VLA.
|
|
|
|
|
|
|
|
|
|
|
|
6.8.6.2 The continue statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 A continue statement shall appear only in or as a loop body.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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;.138)
|
|
|
|
|
|
6.8.6.3 The break statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 A break statement shall appear only in or as a switch body or loop body.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
2 A break statement terminates execution of the smallest enclosing switch or iteration
|
|
|
|
|
|
statement.
|
|
|
|
|
|
138) Following the contin: label is a null statement.
|
|
|
|
|
|
6.8.6.4 The return statement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.139)
|
|
|
|
|
|
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).
|
|
|
|
|
|
139) The return statement is not an assignment. The overlap restriction of subclause 6.5.16.1 does not
|
|
|
|
|
|
apply to the case of function return. The representation of floating-point values may have wider range
|
|
|
|
|
|
or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
|
|
|
|
|
|
range and precision.
|
|
|
|
|
|
6.9 External definitions
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 translation-unit:
|
|
|
|
|
|
external-declaration
|
|
|
|
|
|
translation-unit external-declaration
|
|
|
|
|
|
external-declaration:
|
|
|
|
|
|
function-definition
|
|
|
|
|
|
declaration
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
2 The storage-class specifiers auto and register shall not appear in the declaration
|
|
|
|
|
|
specifiers in an external declaration.
|
|
|
|
|
|
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
|
|
|
|
|
|
operator whose result is an integer constant), there shall be exactly one external definition
|
|
|
|
|
|
for the identifier in the translation unit.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
4 As discussed in 5.1.1.1, the unit of program text after preprocessing is a translation unit,
|
|
|
|
|
|
which consists of a sequence of external declarations. These are described as ``external''
|
2012-01-17 03:07:01 +01:00
|
|
|
|
because they appear outside any function (and hence have file scope). As discussed in 6.7,
|
|
|
|
|
|
a declaration that also causes storage to be reserved for an object or a function named
|
2012-01-16 16:34:32 +01:00
|
|
|
|
by the identifier is a definition.
|
|
|
|
|
|
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 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.140)
|
|
|
|
|
|
140) Thus, if an identifier declared with external linkage is not used in an expression, there need be no
|
|
|
|
|
|
external definition for it.
|
|
|
|
|
|
6.9.1 Function definitions
|
|
|
|
|
|
Syntax
|
|
|
|
|
|
1 function-definition:
|
|
|
|
|
|
declaration-specifiers declarator declaration-listopt compound-statement
|
|
|
|
|
|
declaration-list:
|
|
|
|
|
|
declaration
|
|
|
|
|
|
declaration-list declaration
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
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.141)
|
|
|
|
|
|
3 The return type of a function shall be void or an object type other than array type.
|
|
|
|
|
|
4 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
|
|
|
|
|
|
static.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
141) 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
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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,142) 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 6.7.5.3 for a parameter type list; the resulting type shall be an object type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
9 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
|
|
|
|
|
|
effect declared at the head of the compound statement that constitutes the function body
|
|
|
|
|
|
(and therefore cannot be redeclared in the function body except in an enclosed block).
|
|
|
|
|
|
The layout of the storage for parameters is unspecified.
|
|
|
|
|
|
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.)
|
|
|
|
|
|
11 After all parameters have been assigned, the compound statement that constitutes the
|
|
|
|
|
|
body of the function definition is executed.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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:
|
|
|
|
|
|
142) See ``future language directions'' (6.11.7).
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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)(); ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
|
2012-01-17 03:07:01 +01:00
|
|
|
|
6.9.2 External object definitions
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Semantics
|
|
|
|
|
|
1 If the declaration of an identifier for an object has file scope and an initializer, the
|
|
|
|
|
|
declaration is an external definition for the identifier.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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; // 6.2.2 renders undefined, linkage disagreement
|
|
|
|
|
|
int i3; // valid tentative definition, refers to previous
|
|
|
|
|
|
int i4; // valid tentative definition, refers to previous
|
|
|
|
|
|
int i5; // 6.2.2 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
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.10 Preprocessing directives
|
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|
|
|
|
Syntax
|
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|
|
|
1 preprocessing-file:
|
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|
|
|
groupopt
|
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|
|
group:
|
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|
|
group-part
|
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|
|
group group-part
|
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|
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|
|
group-part:
|
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|
|
|
|
if-section
|
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|
|
|
|
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
|
|
|
|
|
|
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.143) A new-line character ends
|
|
|
|
|
|
the preprocessing directive even if it occurs within what would otherwise be an
|
|
|
|
|
|
|
|
|
|
|
|
143) 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 6.10.3.2, for example).
|
|
|
|
|
|
invocation of a function-like macro.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 When in a group that is skipped (6.10.1), 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
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 The preprocessing tokens within a preprocessing directive are not subject to macro
|
|
|
|
|
|
expansion unless otherwise stated.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.10.1 Conditional inclusion
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The expression that controls conditional inclusion shall be an integer constant expression
|
|
|
|
|
|
except that: it shall not contain a cast; identifiers (including those lexically identical to
|
|
|
|
|
|
keywords) are interpreted as described below;144) and it may contain unary operator
|
|
|
|
|
|
expressions of the form
|
|
|
|
|
|
144) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 (6.4).
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.6. 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>.145) 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.146) Also, whether a
|
|
|
|
|
|
single-character character constant may have a negative value is implementation-defined.
|
|
|
|
|
|
5 Preprocessing directives of the forms
|
|
|
|
|
|
145) 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.
|
|
|
|
|
|
# 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.
|
|
|
|
|
|
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.147)
|
|
|
|
|
|
Forward references: macro replacement (6.10.3), source file inclusion (6.10.2), largest
|
|
|
|
|
|
integer types (7.18.1.5).
|
|
|
|
|
|
6.10.2 Source file inclusion
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 A #include directive shall identify a header or source file that can be processed by the
|
|
|
|
|
|
implementation.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 A preprocessing directive of the form
|
|
|
|
|
|
146) 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)
|
|
|
|
|
|
|
|
|
|
|
|
147) 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.
|
|
|
|
|
|
# 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.
|
|
|
|
|
|
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.148) 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.
|
|
|
|
|
|
5 The implementation shall provide unique mappings for sequences consisting of one or
|
|
|
|
|
|
more nondigits or digits (6.4.2.1) 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.
|
|
|
|
|
|
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 5.2.4.1).
|
|
|
|
|
|
7 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
#include "myprog.h"
|
|
|
|
|
|
|
|
|
|
|
|
8 EXAMPLE 2 This illustrates macro-replaced #include directives:
|
|
|
|
|
|
148) Note that adjacent string literals are not concatenated into a single string literal (see the translation
|
|
|
|
|
|
phases in 5.1.1.2); thus, an expansion that results in two string literals is an invalid directive.
|
|
|
|
|
|
#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 (6.10.3).
|
|
|
|
|
|
6.10.3 Macro replacement
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 There shall be white-space between the identifier and the replacement list in the definition
|
|
|
|
|
|
of an object-like macro.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 A parameter identifier in a function-like macro shall be uniquely declared within its
|
|
|
|
|
|
scope.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 name149)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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,150) the behavior is undefined.
|
|
|
|
|
|
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
|
|
|
|
|
|
149) Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
|
|
|
|
|
|
not sequences possibly containing identifier-like subsequences (see 5.1.1.2, translation phases), they
|
|
|
|
|
|
are never scanned for macro names or parameters.
|
|
|
|
|
|
150) Despite the name, a non-directive is a preprocessing directive.
|
|
|
|
|
|
merger, the number of arguments is one more than the number of parameters in the macro
|
|
|
|
|
|
definition (excluding the ...).
|
|
|
|
|
|
6.10.3.1 Argument substitution
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.10.3.2 The # operator
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.10.3.3 The ## operator
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
|
|
|
|
|
|
list for either form of macro definition.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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.151)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
151) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
|
|
|
|
|
|
exist only within translation phase 4.
|
|
|
|
|
|
6.10.3.4 Rescanning and further replacement
|
|
|
|
|
|
1 After all parameters in the replacement list have been substituted and # and ##
|
|
|
|
|
|
processing has taken place, all placemarker preprocessing tokens are removed. Then, the
|
|
|
|
|
|
resulting preprocessing token sequence is rescanned, along with all subsequent
|
|
|
|
|
|
preprocessing tokens of the source file, for more macro names to replace.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.10.9 below.
|
|
|
|
|
|
6.10.3.5 Scope of macro definitions
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 EXAMPLE 1 The simplest use of this facility is to define a ``manifest constant'', as in
|
|
|
|
|
|
#define TABSIZE 100
|
|
|
|
|
|
int table[TABSIZE];
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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", "" };
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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, };
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
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));
|
|
|
|
|
|
|
|
|
|
|
|
6.10.4 Line control
|
|
|
|
|
|
Constraints
|
|
|
|
|
|
1 The string literal of a #line directive, if present, shall be a character string literal.
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
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 (5.1.1.2) while processing the source
|
|
|
|
|
|
file to the current token.
|
|
|
|
|
|
3 A preprocessing directive of the form
|
|
|
|
|
|
# line digit-sequence new-line
|
2012-01-17 03:07:01 +01:00
|
|
|
|
causes the implementation to behave as if the following sequence of source lines begins
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
6.10.5 Error directive
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
6.10.6 Pragma directive
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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)152) 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.
|
|
|
|
|
|
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 forms153) 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 (7.12.2), the FENV_ACCESS pragma
|
|
|
|
|
|
(7.6.1), the CX_LIMITED_RANGE pragma (7.3.4).
|
|
|
|
|
|
152) 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.
|
|
|
|
|
|
153) See ``future language directions'' (6.11.8).
|
|
|
|
|
|
6.10.7 Null directive
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 A preprocessing directive of the form
|
|
|
|
|
|
# new-line
|
|
|
|
|
|
has no effect.
|
|
|
|
|
|
6.10.8 Predefined macro names
|
|
|
|
|
|
1 The following macro names154) 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).155)
|
|
|
|
|
|
_ _LINE_ _ The presumed line number (within the current source file) of the current
|
|
|
|
|
|
source line (an integer constant).155)
|
|
|
|
|
|
_ _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_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_VERSION_ _ The integer constant 199901L.156)
|
|
|
|
|
|
_ _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.
|
|
|
|
|
|
154) See ``future language directions'' (6.11.9).
|
|
|
|
|
|
155) The presumed source file name and line number can be changed by the #line directive.
|
|
|
|
|
|
156) This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
|
|
|
|
|
|
ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
|
|
|
|
|
|
int that is increased with each revision of this International Standard.
|
|
|
|
|
|
2 The following macro names are conditionally defined by the implementation:
|
|
|
|
|
|
_ _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 informative annex G (IEC 60559
|
|
|
|
|
|
compatible complex arithmetic).
|
|
|
|
|
|
_ _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.
|
|
|
|
|
|
3 The values of the predefined macros (except for _ _FILE_ _ and _ _LINE_ _) remain
|
|
|
|
|
|
constant throughout the translation unit.
|
|
|
|
|
|
4 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.
|
|
|
|
|
|
5 The implementation shall not predefine the macro _ _cplusplus, nor shall it define it
|
|
|
|
|
|
in any standard header.
|
|
|
|
|
|
Forward references: the asctime function (7.23.3.1), standard headers (7.1.2).
|
|
|
|
|
|
6.10.9 Pragma operator
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 A unary operator expression of the form:
|
|
|
|
|
|
_Pragma ( string-literal )
|
|
|
|
|
|
is processed as follows: The string literal is destringized by deleting the L prefix, if
|
|
|
|
|
|
present, 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.
|
|
|
|
|
|
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 )
|
|
|
|
|
|
|
|
|
|
|
|
6.11 Future language directions
|
|
|
|
|
|
6.11.1 Floating types
|
|
|
|
|
|
1 Future standardization may include additional floating-point types, including those with
|
|
|
|
|
|
greater range, precision, or both than long double.
|
|
|
|
|
|
6.11.2 Linkages of identifiers
|
|
|
|
|
|
1 Declaring an identifier with internal linkage at file scope without the static storage-
|
|
|
|
|
|
class specifier is an obsolescent feature.
|
|
|
|
|
|
6.11.3 External names
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.11.4 Character escape sequences
|
|
|
|
|
|
1 Lowercase letters as escape sequences are reserved for future standardization. Other
|
|
|
|
|
|
characters may be used in extensions.
|
|
|
|
|
|
6.11.5 Storage-class specifiers
|
|
|
|
|
|
1 The placement of a storage-class specifier other than at the beginning of the declaration
|
|
|
|
|
|
specifiers in a declaration is an obsolescent feature.
|
|
|
|
|
|
6.11.6 Function declarators
|
|
|
|
|
|
1 The use of function declarators with empty parentheses (not prototype-format parameter
|
|
|
|
|
|
type declarators) is an obsolescent feature.
|
|
|
|
|
|
6.11.7 Function definitions
|
|
|
|
|
|
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.
|
|
|
|
|
|
6.11.8 Pragma directives
|
|
|
|
|
|
1 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
|
|
|
|
|
|
6.11.9 Predefined macro names
|
|
|
|
|
|
1 Macro names beginning with _ _STDC_ are reserved for future standardization.
|
|
|
|
|
|
7. Library
|
|
|
|
|
|
|
|
|
|
|
|
7.1 Introduction
|
|
|
|
|
|
7.1.1 Definitions of terms
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.157) It is represented in the text and examples by a period, but
|
|
|
|
|
|
may be changed by the setlocale function.
|
|
|
|
|
|
3 A null wide character is a wide character with code value zero.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 A shift sequence is a contiguous sequence of bytes within a multibyte string that
|
|
|
|
|
|
(potentially) causes a change in shift state (see 5.2.1.2). A shift sequence shall not have a
|
|
|
|
|
|
corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
|
|
|
|
|
|
character.158)
|
|
|
|
|
|
Forward references: character handling (7.4), the setlocale function (7.11.1.1).
|
|
|
|
|
|
157) The functions that make use of the decimal-point character are the numeric conversion functions
|
|
|
|
|
|
(7.20.1, 7.24.4.1) and the formatted input/output functions (7.19.6, 7.24.2).
|
|
|
|
|
|
158) 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.
|
|
|
|
|
|
7.1.2 Standard headers
|
|
|
|
|
|
1 Each library function is declared, with a type that includes a prototype, in a header ,159)
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 The standard headers are
|
|
|
|
|
|
<assert.h> <inttypes.h> <signal.h> <stdlib.h>
|
|
|
|
|
|
<complex.h> <iso646.h> <stdarg.h> <string.h>
|
|
|
|
|
|
<ctype.h> <limits.h> <stdbool.h> <tgmath.h>
|
|
|
|
|
|
<errno.h> <locale.h> <stddef.h> <time.h>
|
|
|
|
|
|
<fenv.h> <math.h> <stdint.h> <wchar.h>
|
|
|
|
|
|
<float.h> <setjmp.h> <stdio.h> <wctype.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 7.2). 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 Any declaration of a library function shall have external linkage.
|
|
|
|
|
|
7 A summary of the contents of the standard headers is given in annex B.
|
|
|
|
|
|
Forward references: diagnostics (7.2).
|
|
|
|
|
|
159) A header is not necessarily a source file, nor are the < and > delimited sequences in header names
|
|
|
|
|
|
necessarily valid source file names.
|
|
|
|
|
|
7.1.3 Reserved identifiers
|
|
|
|
|
|
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 7.1.4).
|
|
|
|
|
|
-- All identifiers with external linkage in any of the following subclauses (including the
|
|
|
|
|
|
future library directions) are always reserved for use as identifiers with external
|
|
|
|
|
|
linkage.160)
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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 7.1.4), or defines a reserved
|
|
|
|
|
|
identifier as a macro name, the behavior is undefined.
|
|
|
|
|
|
3 If the program removes (with #undef) any macro definition of an identifier in the first
|
|
|
|
|
|
group listed above, the behavior is undefined.
|
|
|
|
|
|
7.1.4 Use of library functions
|
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|
|
1 Each of the following statements applies unless explicitly stated otherwise in the detailed
|
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|
|
descriptions that follow: If an argument to a function has an invalid value (such as a value
|
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|
|
outside the domain of the function, or a pointer outside the address space of the program,
|
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|
|
or a null pointer, or a pointer to non-modifiable storage when the corresponding
|
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|
|
parameter is not const-qualified) or a type (after promotion) not expected by a function
|
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|
with variable number of arguments, the behavior is undefined. If a function argument is
|
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|
described as being an array, the pointer actually passed to the function shall have a value
|
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|
|
such that all address computations and accesses to objects (that would be valid if the
|
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|
|
pointer did point to the first element of such an array) are in fact valid. Any function
|
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declared in a header may be additionally implemented as a function-like macro defined in
|
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160) The list of reserved identifiers with external linkage includes errno, math_errhandling,
|
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|
setjmp, and va_end.
|
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|
the header, so if a library function is declared explicitly when its header is included, one
|
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of the techniques shown below can be used to ensure the declaration is not affected by
|
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|
|
|
such a macro. Any macro definition of a function can be suppressed locally by enclosing
|
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|
|
the name of the function in parentheses, because the name is then not followed by the left
|
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|
|
parenthesis that indicates expansion of a macro function name. For the same syntactic
|
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reason, it is permitted to take the address of a library function even if it is also defined as
|
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|
a macro.161) The use of #undef to remove any macro definition will also ensure that an
|
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|
actual function is referred to. Any invocation of a library function that is implemented as
|
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|
a macro shall expand to code that evaluates each of its arguments exactly once, fully
|
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|
protected by parentheses where necessary, so it is generally safe to use arbitrary
|
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|
expressions as arguments.162) Likewise, those function-like macros described in the
|
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|
|
|
following subclauses may be invoked in an expression anywhere a function with a
|
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|
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|
compatible return type could be called.163) All object-like macros listed as expanding to
|
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|
|
integer constant expressions shall additionally be suitable for use in #if preprocessing
|
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|
directives.
|
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|
|
2 Provided that a library function can be declared without reference to any type defined in a
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|
header, it is also permissible to declare the function and use it without including its
|
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|
associated header.
|
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|
|
3 There is a sequence point immediately before a library function returns.
|
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|
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4 The functions in the standard library are not guaranteed to be reentrant and may modify
|
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|
|
|
objects with static storage duration.164)
|
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|
|
161) This means that an implementation shall provide an actual function for each library function, even if it
|
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|
|
|
also provides a macro for that function.
|
|
|
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|
|
162) Such macros might not contain the sequence points that the corresponding function calls do.
|
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|
|
163) Because external identifiers and some macro names beginning with an underscore are reserved,
|
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|
|
implementations may provide special semantics for such names. For example, the identifier
|
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|
|
_BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
|
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|
|
|
appropriate header could specify
|
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|
|
|
|
#define abs(x) _BUILTIN_abs(x)
|
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|
|
|
|
for a compiler whose code generator will accept it.
|
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|
|
|
|
In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
|
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|
|
|
|
function may write
|
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|
|
|
|
#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
|
|
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|
|
|
definition, is thereby revealed also.
|
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|
|
164) Thus, a signal handler cannot, in general, call standard library functions.
|
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|
|
5 EXAMPLE The function atoi may be used in any of several ways:
|
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|
|
|
|
-- 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);
|
|
|
|
|
|
|
|
|
|
|
|
7.2 Diagnostics <assert.h>
|
|
|
|
|
|
1 The header <assert.h> defines the assert macro 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.2.1 Program diagnostics
|
|
|
|
|
|
7.2.1.1 The assert macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <assert.h>
|
|
|
|
|
|
void assert(scalar expression);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.165) It
|
|
|
|
|
|
then calls the abort function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The assert macro returns no value.
|
|
|
|
|
|
Forward references: the abort function (7.20.4.1).
|
|
|
|
|
|
165) The message written might be of the form:
|
|
|
|
|
|
Assertion failed: expression, function abc, file xyz, line nnn.
|
|
|
|
|
|
7.3 Complex arithmetic <complex.h>
|
|
|
|
|
|
7.3.1 Introduction
|
|
|
|
|
|
1 The header <complex.h> defines macros and declares functions that support complex
|
|
|
|
|
|
arithmetic.166) 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.
|
|
|
|
|
|
2 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.167)
|
|
|
|
|
|
3 The macros
|
|
|
|
|
|
imaginary
|
|
|
|
|
|
and
|
|
|
|
|
|
_Imaginary_I
|
|
|
|
|
|
are defined if and only if the implementation supports imaginary types;168) if defined,
|
|
|
|
|
|
they expand to _Imaginary and a constant expression of type const float
|
|
|
|
|
|
_Imaginary with the value of the imaginary unit.
|
|
|
|
|
|
4 The macro
|
|
|
|
|
|
I
|
|
|
|
|
|
expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
|
|
|
|
|
|
defined, I shall expand to _Complex_I.
|
|
|
|
|
|
5 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then
|
|
|
|
|
|
redefine the macros complex, imaginary, and I.
|
|
|
|
|
|
Forward references: IEC 60559-compatible complex arithmetic (annex G).
|
|
|
|
|
|
166) See ``future library directions'' (7.26.1).
|
|
|
|
|
|
167) The imaginary unit is a number i such that i 2 = -1.
|
|
|
|
|
|
168) A specification for imaginary types is in informative annex G.
|
|
|
|
|
|
7.3.2 Conventions
|
|
|
|
|
|
1 Values are interpreted as radians, not degrees. An implementation may set errno but is
|
|
|
|
|
|
not required to.
|
|
|
|
|
|
7.3.3 Branch cuts
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.3.4 The CX_LIMITED_RANGE pragma
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
#pragma STDC CX_LIMITED_RANGE on-off-switch
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.169) The pragma can occur either outside external declarations or preceding all
|
|
|
|
|
|
explicit declarations and statements inside a compound statement. When outside external
|
|
|
|
|
|
|
|
|
|
|
|
169) The purpose of the pragma is to allow the implementation to use the formulas:
|
|
|
|
|
|
( x + iy ) <20> (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.
|
|
|
|
|
|
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''.
|
|
|
|
|
|
7.3.5 Trigonometric functions
|
|
|
|
|
|
7.3.5.1 The cacos functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex cacos(double complex z);
|
|
|
|
|
|
float complex cacosf(float complex z);
|
|
|
|
|
|
long double complex cacosl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
|
|
|
|
|
|
interval [-1, +1] along the real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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, ] along the
|
|
|
|
|
|
real axis.
|
|
|
|
|
|
7.3.5.2 The casin functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex casin(double complex z);
|
|
|
|
|
|
float complex casinf(float complex z);
|
|
|
|
|
|
long double complex casinl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The casin functions compute the complex arc sine of z, with branch cuts outside the
|
|
|
|
|
|
interval [-1, +1] along the real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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 [- /2, + /2]
|
|
|
|
|
|
along the real axis.
|
|
|
|
|
|
7.3.5.3 The catan functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex catan(double complex z);
|
|
|
|
|
|
float complex catanf(float complex z);
|
|
|
|
|
|
long double complex catanl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The catan functions compute the complex arc tangent of z, with branch cuts outside the
|
|
|
|
|
|
interval [-i , +i ] along the imaginary axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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 [- /2, + /2]
|
|
|
|
|
|
along the real axis.
|
|
|
|
|
|
7.3.5.4 The ccos functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex ccos(double complex z);
|
|
|
|
|
|
float complex ccosf(float complex z);
|
|
|
|
|
|
long double complex ccosl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The ccos functions compute the complex cosine of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The ccos functions return the complex cosine value.
|
|
|
|
|
|
7.3.5.5 The csin functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex csin(double complex z);
|
|
|
|
|
|
float complex csinf(float complex z);
|
|
|
|
|
|
long double complex csinl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The csin functions compute the complex sine of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The csin functions return the complex sine value.
|
|
|
|
|
|
7.3.5.6 The ctan functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex ctan(double complex z);
|
|
|
|
|
|
float complex ctanf(float complex z);
|
|
|
|
|
|
long double complex ctanl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The ctan functions compute the complex tangent of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The ctan functions return the complex tangent value.
|
|
|
|
|
|
7.3.6 Hyperbolic functions
|
|
|
|
|
|
7.3.6.1 The cacosh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex cacosh(double complex z);
|
|
|
|
|
|
float complex cacoshf(float complex z);
|
|
|
|
|
|
long double complex cacoshl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
|
|
|
|
|
|
half-strip of non-negative values along the real axis and in the interval [-i , +i ] along
|
|
|
|
|
|
the imaginary axis.
|
|
|
|
|
|
7.3.6.2 The casinh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex casinh(double complex z);
|
|
|
|
|
|
float complex casinhf(float complex z);
|
|
|
|
|
|
long double complex casinhl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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 [-i /2, +i /2]
|
|
|
|
|
|
along the imaginary axis.
|
|
|
|
|
|
7.3.6.3 The catanh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex catanh(double complex z);
|
|
|
|
|
|
float complex catanhf(float complex z);
|
|
|
|
|
|
long double complex catanhl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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 [-i /2, +i /2]
|
|
|
|
|
|
along the imaginary axis.
|
|
|
|
|
|
7.3.6.4 The ccosh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex ccosh(double complex z);
|
|
|
|
|
|
float complex ccoshf(float complex z);
|
|
|
|
|
|
long double complex ccoshl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The ccosh functions compute the complex hyperbolic cosine of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The ccosh functions return the complex hyperbolic cosine value.
|
|
|
|
|
|
7.3.6.5 The csinh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex csinh(double complex z);
|
|
|
|
|
|
float complex csinhf(float complex z);
|
|
|
|
|
|
long double complex csinhl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The csinh functions compute the complex hyperbolic sine of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The csinh functions return the complex hyperbolic sine value.
|
|
|
|
|
|
7.3.6.6 The ctanh functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex ctanh(double complex z);
|
|
|
|
|
|
float complex ctanhf(float complex z);
|
|
|
|
|
|
long double complex ctanhl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The ctanh functions compute the complex hyperbolic tangent of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The ctanh functions return the complex hyperbolic tangent value.
|
|
|
|
|
|
7.3.7 Exponential and logarithmic functions
|
|
|
|
|
|
7.3.7.1 The cexp functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex cexp(double complex z);
|
|
|
|
|
|
float complex cexpf(float complex z);
|
|
|
|
|
|
long double complex cexpl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The cexp functions compute the complex base-e exponential of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The cexp functions return the complex base-e exponential value.
|
|
|
|
|
|
7.3.7.2 The clog functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex clog(double complex z);
|
|
|
|
|
|
float complex clogf(float complex z);
|
|
|
|
|
|
long double complex clogl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
|
|
|
|
|
|
cut along the negative real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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 [-i , +i ] along the
|
|
|
|
|
|
imaginary axis.
|
|
|
|
|
|
7.3.8 Power and absolute-value functions
|
|
|
|
|
|
7.3.8.1 The cabs functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double cabs(double complex z);
|
|
|
|
|
|
float cabsf(float complex z);
|
|
|
|
|
|
long double cabsl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The cabs functions compute the complex absolute value (also called norm, modulus, or
|
|
|
|
|
|
magnitude) of z.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The cabs functions return the complex absolute value.
|
|
|
|
|
|
7.3.8.2 The cpow functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
2 The cpow functions compute the complex power function xy , with a branch cut for the
|
|
|
|
|
|
first parameter along the negative real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The cpow functions return the complex power function value.
|
|
|
|
|
|
|
|
|
|
|
|
7.3.8.3 The csqrt functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex csqrt(double complex z);
|
|
|
|
|
|
float complex csqrtf(float complex z);
|
|
|
|
|
|
long double complex csqrtl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The csqrt functions compute the complex square root of z, with a branch cut along the
|
|
|
|
|
|
negative real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The csqrt functions return the complex square root value, in the range of the right half-
|
|
|
|
|
|
plane (including the imaginary axis).
|
|
|
|
|
|
7.3.9 Manipulation functions
|
|
|
|
|
|
7.3.9.1 The carg functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double carg(double complex z);
|
|
|
|
|
|
float cargf(float complex z);
|
|
|
|
|
|
long double cargl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The carg functions compute the argument (also called phase angle) of z, with a branch
|
|
|
|
|
|
cut along the negative real axis.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The carg functions return the value of the argument in the interval [- , + ].
|
|
|
|
|
|
7.3.9.2 The cimag functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double cimag(double complex z);
|
|
|
|
|
|
float cimagf(float complex z);
|
|
|
|
|
|
long double cimagl(long double complex z);
|
|
|
|
|
|
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The cimag functions compute the imaginary part of z.170)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The cimag functions return the imaginary part value (as a real).
|
|
|
|
|
|
7.3.9.3 The conj functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex conj(double complex z);
|
|
|
|
|
|
float complex conjf(float complex z);
|
|
|
|
|
|
long double complex conjl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The conj functions compute the complex conjugate of z, by reversing the sign of its
|
|
|
|
|
|
imaginary part.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The conj functions return the complex conjugate value.
|
|
|
|
|
|
7.3.9.4 The cproj functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double complex cproj(double complex z);
|
|
|
|
|
|
float complex cprojf(float complex z);
|
|
|
|
|
|
long double complex cprojl(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The cproj functions return the value of the projection onto the Riemann sphere.
|
|
|
|
|
|
170) For a variable z of complex type, z == creal(z) + cimag(z)*I.
|
|
|
|
|
|
7.3.9.5 The creal functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <complex.h>
|
|
|
|
|
|
double creal(double complex z);
|
|
|
|
|
|
float crealf(float complex z);
|
|
|
|
|
|
long double creall(long double complex z);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The creal functions compute the real part of z.171)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The creal functions return the real part value.
|
|
|
|
|
|
171) For a variable z of complex type, z == creal(z) + cimag(z)*I.
|
|
|
|
|
|
7.4 Character handling <ctype.h>
|
|
|
|
|
|
1 The header <ctype.h> declares several functions useful for classifying and mapping
|
|
|
|
|
|
characters.172) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.173) All letters and digits are printing characters.
|
|
|
|
|
|
Forward references: EOF (7.19.1), localization (7.11).
|
|
|
|
|
|
7.4.1 Character classification functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.4.1.1 The isalnum function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isalnum(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isalnum function tests for any character for which isalpha or isdigit is true.
|
|
|
|
|
|
7.4.1.2 The isalpha function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isalpha(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
172) See ``future library directions'' (7.26.2).
|
|
|
|
|
|
173) 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).
|
|
|
|
|
|
none of iscntrl, isdigit, ispunct, or isspace is true.174) In the "C" locale,
|
|
|
|
|
|
isalpha returns true only for the characters for which isupper or islower is true.
|
|
|
|
|
|
7.4.1.3 The isblank function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isblank(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.4.1.4 The iscntrl function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int iscntrl(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iscntrl function tests for any control character.
|
|
|
|
|
|
7.4.1.5 The isdigit function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isdigit(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isdigit function tests for any decimal-digit character (as defined in 5.2.1).
|
|
|
|
|
|
7.4.1.6 The isgraph function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isgraph(int c);
|
|
|
|
|
|
174) The functions islower and isupper test true or false separately for each of these additional
|
|
|
|
|
|
characters; all four combinations are possible.
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isgraph function tests for any printing character except space (' ').
|
|
|
|
|
|
7.4.1.7 The islower function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int islower(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 5.2.1).
|
|
|
|
|
|
7.4.1.8 The isprint function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isprint(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isprint function tests for any printing character including space (' ').
|
|
|
|
|
|
7.4.1.9 The ispunct function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int ispunct(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.4.1.10 The isspace function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isspace(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.4.1.11 The isupper function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isupper(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 5.2.1).
|
|
|
|
|
|
7.4.1.12 The isxdigit function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int isxdigit(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isxdigit function tests for any hexadecimal-digit character (as defined in 6.4.4.1).
|
|
|
|
|
|
7.4.2 Character case mapping functions
|
|
|
|
|
|
7.4.2.1 The tolower function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int tolower(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The tolower function converts an uppercase letter to a corresponding lowercase letter.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.4.2.2 The toupper function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <ctype.h>
|
|
|
|
|
|
int toupper(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The toupper function converts a lowercase letter to a corresponding uppercase letter.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.5 Errors <errno.h>
|
|
|
|
|
|
1 The header <errno.h> defines several macros, all relating to the reporting of error
|
|
|
|
|
|
conditions.
|
|
|
|
|
|
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 lvalue175) that has type int, the value of which is set to a
|
|
|
|
|
|
positive error number by several library functions. It is unspecified whether errno is a
|
|
|
|
|
|
macro or an identifier declared with external linkage. 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.
|
|
|
|
|
|
3 The value of errno is zero at program startup, but is never set to zero by any library
|
|
|
|
|
|
function.176) 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.
|
|
|
|
|
|
4 Additional macro definitions, beginning with E and a digit or E and an uppercase
|
|
|
|
|
|
letter,177) may also be specified by the implementation.
|
|
|
|
|
|
175) 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()).
|
|
|
|
|
|
176) 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.
|
|
|
|
|
|
177) See ``future library directions'' (7.26.3).
|
|
|
|
|
|
7.6 Floating-point environment <fenv.h>
|
|
|
|
|
|
1 The header <fenv.h> declares two types and several macros and functions to 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.178) 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.179) 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.
|
|
|
|
|
|
2 Certain programming conventions support the intended model of use for the floating-
|
|
|
|
|
|
point environment:180)
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
3 The type
|
|
|
|
|
|
fenv_t
|
|
|
|
|
|
represents the entire floating-point environment.
|
|
|
|
|
|
4 The type
|
|
|
|
|
|
fexcept_t
|
|
|
|
|
|
represents the floating-point status flags collectively, including any status the
|
|
|
|
|
|
implementation associates with the flags.
|
|
|
|
|
|
178) 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. Also it is
|
|
|
|
|
|
designed to facilitate code portability among all systems.
|
|
|
|
|
|
179) A floating-point status flag is not an object and can be set more than once within an expression.
|
|
|
|
|
|
180) 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.
|
|
|
|
|
|
5 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 7.6.2.181) Additional implementation-defined floating-point
|
|
|
|
|
|
exceptions, with macro definitions beginning with FE_ and an uppercase letter, 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.182)
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
7 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, may also be specified by the implementation. The
|
|
|
|
|
|
defined macros expand to integer constant expressions whose values are distinct
|
|
|
|
|
|
nonnegative values.183)
|
|
|
|
|
|
8 The macro
|
|
|
|
|
|
181) The implementation supports an exception if there are circumstances where a call to at least one of the
|
|
|
|
|
|
functions in 7.6.2, using the macro as the appropriate argument, will succeed. It is not necessary for
|
|
|
|
|
|
all the functions to succeed all the time.
|
|
|
|
|
|
182) The macros should be distinct powers of two.
|
|
|
|
|
|
183) Even though the rounding direction macros may expand to constants corresponding to the values of
|
|
|
|
|
|
FLT_ROUNDS, they are not required to do so.
|
|
|
|
|
|
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.
|
|
|
|
|
|
9 Additional implementation-defined environments, with macro definitions beginning with
|
|
|
|
|
|
FE_ and an uppercase letter, and having type ``pointer to const-qualified fenv_t'', may
|
|
|
|
|
|
also be specified by the implementation.
|
|
|
|
|
|
7.6.1 The FENV_ACCESS pragma
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
#pragma STDC FENV_ACCESS on-off-switch
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.184) 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.)
|
|
|
|
|
|
184) 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.
|
|
|
|
|
|
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);
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
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.185)
|
|
|
|
|
|
|
|
|
|
|
|
7.6.2 Floating-point exceptions
|
|
|
|
|
|
1 The following functions provide access to the floating-point status flags.186) 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.
|
|
|
|
|
|
7.6.2.1 The feclearexcept function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int feclearexcept(int excepts);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The feclearexcept function attempts to clear the supported floating-point exceptions
|
|
|
|
|
|
represented by its argument.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
185) 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.
|
|
|
|
|
|
186) 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.
|
|
|
|
|
|
7.6.2.2 The fegetexceptflag function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fegetexceptflag(fexcept_t *flagp,
|
|
|
|
|
|
int excepts);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fegetexceptflag function returns zero if the representation was successfully
|
|
|
|
|
|
stored. Otherwise, it returns a nonzero value.
|
|
|
|
|
|
7.6.2.3 The feraiseexcept function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int feraiseexcept(int excepts);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The feraiseexcept function attempts to raise the supported floating-point exceptions
|
|
|
|
|
|
represented by its argument.187) The order in which these floating-point exceptions are
|
|
|
|
|
|
raised is unspecified, except as stated in F.7.6. 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
187) 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 F.7.6 is in the same spirit.
|
|
|
|
|
|
7.6.2.4 The fesetexceptflag function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fesetexceptflag(const fexcept_t *flagp,
|
|
|
|
|
|
int excepts);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.6.2.5 The fetestexcept function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fetestexcept(int excepts);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.188)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 EXAMPLE Call f if ``invalid'' is set, then g if ``overflow'' is set:
|
|
|
|
|
|
188) This mechanism allows testing several floating-point exceptions with just one function call.
|
|
|
|
|
|
#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();
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.6.3 Rounding
|
|
|
|
|
|
1 The fegetround and fesetround functions provide control of rounding direction
|
|
|
|
|
|
modes.
|
|
|
|
|
|
7.6.3.1 The fegetround function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fegetround(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The fegetround function gets the current rounding direction.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.6.3.2 The fesetround function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fesetround(int round);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fesetround function returns zero if and only if the requested rounding direction
|
|
|
|
|
|
was established.
|
|
|
|
|
|
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);
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.6.4 Environment
|
|
|
|
|
|
1 The functions in this section manage the floating-point environment -- status flags and
|
|
|
|
|
|
control modes -- as one entity.
|
|
|
|
|
|
7.6.4.1 The fegetenv function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fegetenv(fenv_t *envp);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The fegetenv function attempts to store the current floating-point environment in the
|
|
|
|
|
|
object pointed to by envp.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The fegetenv function returns zero if the environment was successfully stored.
|
|
|
|
|
|
Otherwise, it returns a nonzero value.
|
|
|
|
|
|
7.6.4.2 The feholdexcept function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int feholdexcept(fenv_t *envp);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.189)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The feholdexcept function returns zero if and only if non-stop floating-point
|
|
|
|
|
|
exception handling was successfully installed.
|
|
|
|
|
|
7.6.4.3 The fesetenv function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int fesetenv(const fenv_t *envp);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fesetenv function returns zero if the environment was successfully established.
|
|
|
|
|
|
Otherwise, it returns a nonzero value.
|
|
|
|
|
|
7.6.4.4 The feupdateenv function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <fenv.h>
|
|
|
|
|
|
int feupdateenv(const fenv_t *envp);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The feupdateenv function returns zero if all the actions were successfully carried out.
|
|
|
|
|
|
Otherwise, it returns a nonzero value.
|
|
|
|
|
|
189) 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.
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.7 Characteristics of floating types <float.h>
|
|
|
|
|
|
1 The header <float.h> defines several macros that expand to various limits and
|
|
|
|
|
|
parameters of the standard floating-point types.
|
|
|
|
|
|
2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
|
|
|
|
|
|
in 5.2.4.2.2.
|
|
|
|
|
|
|
|
|
|
|
|
7.8 Format conversion of integer types <inttypes.h>
|
|
|
|
|
|
1 The header <inttypes.h> includes the header <stdint.h> and extends it with
|
|
|
|
|
|
additional facilities provided by hosted implementations.
|
|
|
|
|
|
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.190)
|
|
|
|
|
|
Forward references: integer types <stdint.h> (7.18), formatted input/output
|
|
|
|
|
|
functions (7.19.6), formatted wide character input/output functions (7.24.2).
|
|
|
|
|
|
7.8.1 Macros for format specifiers
|
|
|
|
|
|
1 Each of the following object-like macros191) 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),192) followed by the conversion specifier,
|
|
|
|
|
|
followed by a name corresponding to a similar type name in 7.18.1. In these names, N
|
|
|
|
|
|
represents the width of the type as described in 7.18.1. For example, PRIdFAST32 can
|
|
|
|
|
|
be used in a format string to print the value of an integer of type int_fast32_t.
|
|
|
|
|
|
2 The fprintf macros for signed integers are:
|
|
|
|
|
|
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
|
|
|
|
|
|
PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
|
|
|
|
|
|
190) See ``future library directions'' (7.26.4).
|
|
|
|
|
|
191) C++ implementations should define these macros only when _ _STDC_FORMAT_MACROS is defined
|
|
|
|
|
|
before <inttypes.h> is included.
|
|
|
|
|
|
192) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
4 The fscanf macros for signed integers are:
|
|
|
|
|
|
SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
|
|
|
|
|
|
SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
|
|
|
|
|
|
5 The fscanf macros for unsigned integers are:
|
|
|
|
|
|
SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
|
|
|
|
|
|
SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
|
|
|
|
|
|
SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
|
|
|
|
|
|
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.
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.8.2 Functions for greatest-width integer types
|
|
|
|
|
|
7.8.2.1 The imaxabs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <inttypes.h>
|
|
|
|
|
|
intmax_t imaxabs(intmax_t j);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The imaxabs function computes the absolute value of an integer j. If the result cannot
|
|
|
|
|
|
be represented, the behavior is undefined.193)
|
|
|
|
|
|
193) The absolute value of the most negative number cannot be represented in two's complement.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The imaxabs function returns the absolute value.
|
|
|
|
|
|
7.8.2.2 The imaxdiv function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <inttypes.h>
|
|
|
|
|
|
imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The imaxdiv function computes numer / denom and numer % denom in a single
|
|
|
|
|
|
operation.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.8.2.3 The strtoimax and strtoumax functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
(7.20.1.4).
|
|
|
|
|
|
7.8.2.4 The wcstoimax and wcstoumax functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
(7.24.4.1.2).
|
|
|
|
|
|
|
|
|
|
|
|
7.9 Alternative spellings <iso646.h>
|
|
|
|
|
|
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 ^=
|
|
|
|
|
|
|
|
|
|
|
|
7.10 Sizes of integer types <limits.h>
|
|
|
|
|
|
1 The header <limits.h> defines several macros that expand to various limits and
|
|
|
|
|
|
parameters of the standard integer types.
|
|
|
|
|
|
2 The macros, their meanings, and the constraints (or restrictions) on their values are listed
|
|
|
|
|
|
in 5.2.4.2.1.
|
|
|
|
|
|
|
|
|
|
|
|
7.11 Localization <locale.h>
|
|
|
|
|
|
1 The header <locale.h> declares two functions, one type, and defines several macros.
|
|
|
|
|
|
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 7.11.2.1. 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
|
|
|
|
|
|
|
|
|
|
|
|
3 The macros defined are NULL (described in 7.17); 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.194) Additional macro definitions, beginning
|
|
|
|
|
|
with the characters LC_ and an uppercase letter,195) may also be specified by the
|
|
|
|
|
|
implementation.
|
|
|
|
|
|
7.11.1 Locale control
|
|
|
|
|
|
7.11.1.1 The setlocale function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <locale.h>
|
|
|
|
|
|
char *setlocale(int category, const char *locale);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 functions196) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
194) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
|
|
|
|
|
|
195) See ``future library directions'' (7.26.5).
|
|
|
|
|
|
196) The only functions in 7.4 whose behavior is not affected by the current locale are isdigit and
|
|
|
|
|
|
isxdigit.
|
|
|
|
|
|
4 At program startup, the equivalent of
|
|
|
|
|
|
setlocale(LC_ALL, "C");
|
|
|
|
|
|
is executed.
|
|
|
|
|
|
5 The implementation shall behave as if no library function calls the setlocale function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.197)
|
|
|
|
|
|
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 (7.19.6), multibyte/wide
|
|
|
|
|
|
character conversion functions (7.20.7), multibyte/wide string conversion functions
|
|
|
|
|
|
(7.20.8), numeric conversion functions (7.20.1), the strcoll function (7.21.4.3), the
|
|
|
|
|
|
strftime function (7.23.3.5), the strxfrm function (7.21.4.5).
|
|
|
|
|
|
7.11.2 Numeric formatting convention inquiry
|
|
|
|
|
|
7.11.2.1 The localeconv function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <locale.h>
|
|
|
|
|
|
struct lconv *localeconv(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
197) The implementation shall arrange to encode in a string the various categories due to a heterogeneous
|
|
|
|
|
|
locale when category has the value LC_ALL.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 The implementation shall behave as if no library function calls the localeconv
|
|
|
|
|
|
function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 1.234,56 -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
|
|
|
|
|
|
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 "" "" "" ""
|
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|
|
negative_sign "-" "-" "-" "C"
|
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|
|
currency_symbol "mk" "L." "\u0192" "SFrs."
|
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|
|
frac_digits 2 0 2 2
|
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|
|
p_cs_precedes 0 1 1 1
|
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|
|
n_cs_precedes 0 1 1 1
|
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|
p_sep_by_space 1 0 1 0
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|
n_sep_by_space 1 0 2 0
|
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|
|
p_sign_posn 1 1 1 1
|
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|
|
n_sign_posn 1 1 4 2
|
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|
|
int_curr_symbol "FIM " "ITL " "NLG " "CHF "
|
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|
|
|
int_frac_digits 2 0 2 2
|
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|
|
|
int_p_cs_precedes 1 1 1 1
|
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|
|
int_n_cs_precedes 1 1 1 1
|
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|
|
|
int_p_sep_by_space 1 1 1 1
|
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|
|
int_n_sep_by_space 2 1 2 1
|
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|
|
int_p_sign_posn 1 1 1 1
|
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|
int_n_sign_posn 4 1 4 2
|
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|
|
11 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
|
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|
|
|
|
affect the formatted value.
|
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|
p_sep_by_space
|
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|
p_cs_precedes p_sign_posn 0 1 2
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|
0 0 (1.25$) (1.25 $) (1.25$)
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|
1 +1.25$ +1.25 $ + 1.25$
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|
2 1.25$+ 1.25 $+ 1.25$ +
|
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|
3 1.25+$ 1.25 +$ 1.25+ $
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|
|
4 1.25$+ 1.25 $+ 1.25$ +
|
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|
|
1 0 ($1.25) ($ 1.25) ($1.25)
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|
1 +$1.25 +$ 1.25 + $1.25
|
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|
|
2 $1.25+ $ 1.25+ $1.25 +
|
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|
3 +$1.25 +$ 1.25 + $1.25
|
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|
|
|
4 $+1.25 $+ 1.25 $ +1.25
|
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|
|
7.12 Mathematics <math.h>
|
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|
|
1 The header <math.h> declares two types and many mathematical functions and defines
|
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|
|
several macros. Most synopses specify a family of functions consisting of a principal
|
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|
|
|
function with one or more double parameters, a double return value, or both; and
|
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|
|
|
other functions with the same name but with f and l suffixes, which are corresponding
|
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|
|
|
functions with float and long double parameters, return values, or both.198)
|
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|
|
Integer arithmetic functions and conversion functions are discussed later.
|
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|
|
2 The types
|
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|
|
float_t
|
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|
|
double_t
|
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|
|
are floating types at least as wide as float and double, respectively, and such that
|
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|
|
double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
|
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|
|
float_t and double_t are float and double, respectively; if
|
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|
|
FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
|
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|
2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
|
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|
|
|
otherwise implementation-defined.199)
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|
|
3 The macro
|
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|
|
HUGE_VAL
|
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|
|
|
expands to a positive double constant expression, not necessarily representable as a
|
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|
|
|
float. The macros
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|
|
HUGE_VALF
|
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|
|
HUGE_VALL
|
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|
|
|
are respectively float and long double analogs of HUGE_VAL.200)
|
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|
|
4 The macro
|
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|
|
INFINITY
|
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|
|
expands to a constant expression of type float representing positive or unsigned
|
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|
|
|
infinity, if available; else to a positive constant of type float that overflows at
|
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|
|
198) Particularly on systems with wide expression evaluation, a <math.h> function might pass arguments
|
|
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|
|
|
and return values in wider format than the synopsis prototype indicates.
|
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|
|
|
199) The types float_t and double_t are intended to be the implementation's most efficient types at
|
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|
|
|
least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
|
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|
|
|
|
type float_t is the narrowest type used by the implementation to evaluate floating expressions.
|
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|
|
|
200) HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
|
|
|
|
|
|
supports infinities.
|
|
|
|
|
|
translation time.201)
|
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|
|
|
5 The macro
|
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|
|
|
NAN
|
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|
|
|
is defined if and only if the implementation supports quiet NaNs for the float type. It
|
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|
|
|
expands to a constant expression of type float representing a quiet NaN.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.202) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
201) In this case, using INFINITY will violate the constraint in 6.4.4 and thus require a diagnostic.
|
|
|
|
|
|
202) 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.
|
|
|
|
|
|
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>.
|
|
|
|
|
|
7.12.1 Treatment of error conditions
|
|
|
|
|
|
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 generating any externally visible exceptional
|
|
|
|
|
|
conditions.
|
|
|
|
|
|
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.203) 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.
|
|
|
|
|
|
3 Similarly, 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.
|
|
|
|
|
|
4 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, or if the mathematical result is an exact infinity from finite arguments (for
|
|
|
|
|
|
example log(0.0)), then the function returns the value of the macro HUGE_VAL,
|
|
|
|
|
|
203) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
``divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
|
|
|
|
|
|
infinity and the ``overflow'' floating-point exception is raised otherwise.
|
|
|
|
|
|
5 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.204) 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.
|
|
|
|
|
|
7.12.2 The FP_CONTRACT pragma
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
#pragma STDC FP_CONTRACT on-off-switch
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 (6.5). 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.
|
|
|
|
|
|
204) The term underflow here is intended to encompass both ``gradual underflow'' as in IEC 60559 and
|
|
|
|
|
|
also ``flush-to-zero'' underflow.
|
|
|
|
|
|
7.12.3 Classification macros
|
|
|
|
|
|
1 In the synopses in this subclause, real-floating indicates that the argument shall be an
|
|
|
|
|
|
expression of real floating type.
|
|
|
|
|
|
7.12.3.1 The fpclassify macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int fpclassify(real-floating x);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.205)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The fpclassify macro returns the value of the number classification macro
|
|
|
|
|
|
appropriate to the value of its argument.
|
|
|
|
|
|
4 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
|
|
|
|
|
|
#define fpclassify(x) \
|
|
|
|
|
|
((sizeof (x) == sizeof (float)) ? _ _fpclassifyf(x) : \
|
|
|
|
|
|
(sizeof (x) == sizeof (double)) ? _ _fpclassifyd(x) : \
|
|
|
|
|
|
_ _fpclassifyl(x))
|
|
|
|
|
|
|
|
|
|
|
|
7.12.3.2 The isfinite macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isfinite(real-floating x);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
205) 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.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The isfinite macro returns a nonzero value if and only if its argument has a finite
|
|
|
|
|
|
value.
|
|
|
|
|
|
7.12.3.3 The isinf macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isinf(real-floating x);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The isinf macro returns a nonzero value if and only if its argument has an infinite
|
|
|
|
|
|
value.
|
|
|
|
|
|
7.12.3.4 The isnan macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isnan(real-floating x);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.206)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
|
|
|
|
|
|
7.12.3.5 The isnormal macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isnormal(real-floating x);
|
|
|
|
|
|
206) 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.
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The isnormal macro returns a nonzero value if and only if its argument has a normal
|
|
|
|
|
|
value.
|
|
|
|
|
|
7.12.3.6 The signbit macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int signbit(real-floating x);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The signbit macro determines whether the sign of its argument value is negative.207)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The signbit macro returns a nonzero value if and only if the sign of its argument value
|
|
|
|
|
|
is negative.
|
|
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7.12.4 Trigonometric functions
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7.12.4.1 The acos functions
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Synopsis
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1 #include <math.h>
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double acos(double x);
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float acosf(float x);
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long double acosl(long double x);
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Description
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2 The acos functions compute the principal value of the arc cosine of x. A domain error
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occurs for arguments not in the interval [-1, +1].
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Returns
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3 The acos functions return arccos x in the interval [0, ] radians.
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207) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
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unsigned, it is treated as positive.
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7.12.4.2 The asin functions
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Synopsis
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1 #include <math.h>
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double asin(double x);
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float asinf(float x);
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long double asinl(long double x);
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Description
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2 The asin functions compute the principal value of the arc sine of x. A domain error
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occurs for arguments not in the interval [-1, +1].
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Returns
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3 The asin functions return arcsin x in the interval [- /2, + /2] radians.
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7.12.4.3 The atan functions
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Synopsis
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1 #include <math.h>
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double atan(double x);
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float atanf(float x);
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long double atanl(long double x);
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Description
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2 The atan functions compute the principal value of the arc tangent of x.
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Returns
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3 The atan functions return arctan x in the interval [- /2, + /2] radians.
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7.12.4.4 The atan2 functions
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Synopsis
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1 #include <math.h>
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double atan2(double y, double x);
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float atan2f(float y, float x);
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long double atan2l(long double y, long double x);
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Description
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2 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
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arguments to determine the quadrant of the return value. A domain error may occur if
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both arguments are zero.
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Returns
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3 The atan2 functions return arctan y/x in the interval [- , + ] radians.
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7.12.4.5 The cos functions
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Synopsis
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1 #include <math.h>
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double cos(double x);
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float cosf(float x);
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long double cosl(long double x);
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Description
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2 The cos functions compute the cosine of x (measured in radians).
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Returns
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3 The cos functions return cos x.
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7.12.4.6 The sin functions
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Synopsis
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1 #include <math.h>
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double sin(double x);
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float sinf(float x);
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long double sinl(long double x);
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Description
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2 The sin functions compute the sine of x (measured in radians).
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Returns
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3 The sin functions return sin x.
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7.12.4.7 The tan functions
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Synopsis
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1 #include <math.h>
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double tan(double x);
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float tanf(float x);
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long double tanl(long double x);
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Description
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2 The tan functions return the tangent of x (measured in radians).
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Returns
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3 The tan functions return tan x.
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7.12.5 Hyperbolic functions
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7.12.5.1 The acosh functions
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Synopsis
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1 #include <math.h>
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double acosh(double x);
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float acoshf(float x);
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long double acoshl(long double x);
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Description
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2 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
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error occurs for arguments less than 1.
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Returns
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3 The acosh functions return arcosh x in the interval [0, +].
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7.12.5.2 The asinh functions
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Synopsis
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1 #include <math.h>
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double asinh(double x);
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float asinhf(float x);
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long double asinhl(long double x);
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Description
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2 The asinh functions compute the arc hyperbolic sine of x.
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Returns
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3 The asinh functions return arsinh x.
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7.12.5.3 The atanh functions
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Synopsis
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1 #include <math.h>
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double atanh(double x);
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float atanhf(float x);
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long double atanhl(long double x);
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Description
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2 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
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for arguments not in the interval [-1, +1]. A range error may occur if the argument
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equals -1 or +1.
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Returns
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3 The atanh functions return artanh x.
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7.12.5.4 The cosh functions
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Synopsis
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1 #include <math.h>
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double cosh(double x);
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float coshf(float x);
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long double coshl(long double x);
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Description
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2 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
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magnitude of x is too large.
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Returns
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3 The cosh functions return cosh x.
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7.12.5.5 The sinh functions
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Synopsis
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1 #include <math.h>
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double sinh(double x);
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float sinhf(float x);
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long double sinhl(long double x);
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Description
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2 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
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magnitude of x is too large.
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Returns
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3 The sinh functions return sinh x.
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7.12.5.6 The tanh functions
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Synopsis
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1 #include <math.h>
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double tanh(double x);
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float tanhf(float x);
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long double tanhl(long double x);
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Description
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2 The tanh functions compute the hyperbolic tangent of x.
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Returns
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3 The tanh functions return tanh x.
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7.12.6 Exponential and logarithmic functions
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7.12.6.1 The exp functions
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Synopsis
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1 #include <math.h>
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double exp(double x);
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float expf(float x);
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long double expl(long double x);
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Description
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2 The exp functions compute the base-e exponential of x. A range error occurs if the
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magnitude of x is too large.
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Returns
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3 The exp functions return ex .
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7.12.6.2 The exp2 functions
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Synopsis
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1 #include <math.h>
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double exp2(double x);
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float exp2f(float x);
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long double exp2l(long double x);
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Description
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2 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
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magnitude of x is too large.
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Returns
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3 The exp2 functions return 2x .
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7.12.6.3 The expm1 functions
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Synopsis
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1 #include <math.h>
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double expm1(double x);
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float expm1f(float x);
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long double expm1l(long double x);
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Description
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2 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
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error occurs if x is too large.208)
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Returns
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3 The expm1 functions return ex - 1.
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7.12.6.4 The frexp functions
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Synopsis
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1 #include <math.h>
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double frexp(double value, int *exp);
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float frexpf(float value, int *exp);
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long double frexpl(long double value, int *exp);
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Description
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2 The frexp functions break a floating-point number into a normalized fraction and an
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integral power of 2. They store the integer in the int object pointed to by exp.
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Returns
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3 If value is not a floating-point number, the results are unspecified. Otherwise, the
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frexp functions return the value x, such that x has a magnitude in the interval [1/2, 1) or
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zero, and value equals x <20> 2*exp . If value is zero, both parts of the result are zero.
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7.12.6.5 The ilogb functions
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Synopsis
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1 #include <math.h>
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int ilogb(double x);
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int ilogbf(float x);
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int ilogbl(long double x);
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Description
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2 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
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compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
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a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
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the corresponding logb function and casting the returned value to type int. A domain
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error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
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the range of the return type, the numeric result is unspecified.
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208) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
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Returns
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3 The ilogb functions return the exponent of x as a signed int value.
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Forward references: the logb functions (7.12.6.11).
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7.12.6.6 The ldexp functions
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Synopsis
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1 #include <math.h>
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double ldexp(double x, int exp);
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float ldexpf(float x, int exp);
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long double ldexpl(long double x, int exp);
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Description
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2 The ldexp functions multiply a floating-point number by an integral power of 2. A
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range error may occur.
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Returns
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3 The ldexp functions return x <20> 2exp .
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7.12.6.7 The log functions
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Synopsis
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1 #include <math.h>
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double log(double x);
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float logf(float x);
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long double logl(long double x);
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Description
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2 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
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the argument is negative. A range error may occur if the argument is zero.
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Returns
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3 The log functions return loge x.
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7.12.6.8 The log10 functions
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Synopsis
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1 #include <math.h>
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double log10(double x);
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float log10f(float x);
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long double log10l(long double x);
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Description
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2 The log10 functions compute the base-10 (common) logarithm of x. A domain error
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occurs if the argument is negative. A range error may occur if the argument is zero.
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Returns
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3 The log10 functions return log10 x.
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7.12.6.9 The log1p functions
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Synopsis
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1 #include <math.h>
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double log1p(double x);
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float log1pf(float x);
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long double log1pl(long double x);
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Description
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2 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.209)
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A domain error occurs if the argument is less than -1. A range error may occur if the
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argument equals -1.
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Returns
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3 The log1p functions return loge (1 + x).
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7.12.6.10 The log2 functions
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Synopsis
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1 #include <math.h>
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double log2(double x);
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float log2f(float x);
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long double log2l(long double x);
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Description
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2 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
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argument is less than zero. A range error may occur if the argument is zero.
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Returns
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3 The log2 functions return log2 x.
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209) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
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7.12.6.11 The logb functions
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Synopsis
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1 #include <math.h>
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double logb(double x);
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float logbf(float x);
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long double logbl(long double x);
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Description
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2 The logb functions extract the exponent of x, as a signed integer value in floating-point
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format. If x is subnormal it is treated as though it were normalized; thus, for positive
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finite x,
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1 x <20> FLT_RADIX-logb(x) < FLT_RADIX
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A domain error or range error may occur if the argument is zero.
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Returns
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3 The logb functions return the signed exponent of x.
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7.12.6.12 The modf functions
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Synopsis
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1 #include <math.h>
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double modf(double value, double *iptr);
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float modff(float value, float *iptr);
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long double modfl(long double value, long double *iptr);
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Description
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2 The modf functions break the argument value into integral and fractional parts, each of
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which has the same type and sign as the argument. They store the integral part (in
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floating-point format) in the object pointed to by iptr.
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Returns
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3 The modf functions return the signed fractional part of value.
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7.12.6.13 The scalbn and scalbln functions
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Synopsis
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1 #include <math.h>
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double scalbn(double x, int n);
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float scalbnf(float x, int n);
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long double scalbnl(long double x, int n);
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double scalbln(double x, long int n);
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float scalblnf(float x, long int n);
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long double scalblnl(long double x, long int n);
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Description
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2 The scalbn and scalbln functions compute x <20> FLT_RADIXn efficiently, not
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normally by computing FLT_RADIXn explicitly. A range error may occur.
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Returns
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3 The scalbn and scalbln functions return x <20> FLT_RADIXn .
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7.12.7 Power and absolute-value functions
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7.12.7.1 The cbrt functions
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Synopsis
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1 #include <math.h>
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double cbrt(double x);
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float cbrtf(float x);
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long double cbrtl(long double x);
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Description
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2 The cbrt functions compute the real cube root of x.
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Returns
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3 The cbrt functions return x1/3 .
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7.12.7.2 The fabs functions
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Synopsis
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1 #include <math.h>
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double fabs(double x);
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float fabsf(float x);
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long double fabsl(long double x);
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Description
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2 The fabs functions compute the absolute value of a floating-point number x.
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Returns
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3 The fabs functions return | x |.
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7.12.7.3 The hypot functions
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Synopsis
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1 #include <math.h>
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double hypot(double x, double y);
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float hypotf(float x, float y);
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long double hypotl(long double x, long double y);
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Description
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2 The hypot functions compute the square root of the sum of the squares of x and y,
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without undue overflow or underflow. A range error may occur.
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3 Returns
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4 The hypot functions return x2 + y2 .
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7.12.7.4 The pow functions
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Synopsis
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1 #include <math.h>
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double pow(double x, double y);
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float powf(float x, float y);
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long double powl(long double x, long double y);
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Description
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2 The pow functions compute x raised to the power y. A domain error occurs if x is finite
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and negative and y is finite and not an integer value. A range error may occur. A domain
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error may occur if x is zero and y is zero. A domain error or range error may occur if x
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is zero and y is less than zero.
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Returns
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3 The pow functions return xy .
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7.12.7.5 The sqrt functions
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Synopsis
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1 #include <math.h>
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double sqrt(double x);
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float sqrtf(float x);
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long double sqrtl(long double x);
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Description
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2 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
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the argument is less than zero.
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Returns
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3 The sqrt functions return x.
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7.12.8 Error and gamma functions
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7.12.8.1 The erf functions
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Synopsis
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1 #include <math.h>
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double erf(double x);
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float erff(float x);
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long double erfl(long double x);
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Description
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2 The erf functions compute the error function of x.
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Returns
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2 x
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3
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The erf functions return erf x = e-t dt .
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2
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0
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7.12.8.2 The erfc functions
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Synopsis
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1 #include <math.h>
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double erfc(double x);
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float erfcf(float x);
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long double erfcl(long double x);
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Description
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2 The erfc functions compute the complementary error function of x. A range error
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occurs if x is too large.
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Returns
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2
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3
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The erfc functions return erfc x = 1 - erf x = e-t dt .
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2
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x
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7.12.8.3 The lgamma functions
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Synopsis
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1 #include <math.h>
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double lgamma(double x);
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float lgammaf(float x);
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long double lgammal(long double x);
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Description
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2 The lgamma functions compute the natural logarithm of the absolute value of gamma of
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x. A range error occurs if x is too large. A range error may occur if x is a negative
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integer or zero.
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Returns
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3 The lgamma functions return loge | (x) |.
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7.12.8.4 The tgamma functions
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Synopsis
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1 #include <math.h>
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double tgamma(double x);
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float tgammaf(float x);
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long double tgammal(long double x);
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Description
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2 The tgamma functions compute the gamma function of x. A domain error or range error
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may occur if x is a negative integer or zero. A range error may occur if the magnitude of
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x is too large or too small.
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Returns
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3 The tgamma functions return (x).
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7.12.9 Nearest integer functions
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7.12.9.1 The ceil functions
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Synopsis
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1 #include <math.h>
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double ceil(double x);
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float ceilf(float x);
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long double ceill(long double x);
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Description
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2 The ceil functions compute the smallest integer value not less than x.
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Returns
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3 The ceil functions return x, expressed as a floating-point number.
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7.12.9.2 The floor functions
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Synopsis
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1 #include <math.h>
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double floor(double x);
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float floorf(float x);
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long double floorl(long double x);
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Description
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2 The floor functions compute the largest integer value not greater than x.
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Returns
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3 The floor functions return x, expressed as a floating-point number.
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7.12.9.3 The nearbyint functions
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Synopsis
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1 #include <math.h>
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double nearbyint(double x);
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float nearbyintf(float x);
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long double nearbyintl(long double x);
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Description
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2 The nearbyint functions round their argument to an integer value in floating-point
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format, using the current rounding direction and without raising the ``inexact'' floating-
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point exception.
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Returns
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3 The nearbyint functions return the rounded integer value.
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7.12.9.4 The rint functions
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Synopsis
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1 #include <math.h>
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double rint(double x);
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float rintf(float x);
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long double rintl(long double x);
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Description
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2 The rint functions differ from the nearbyint functions (7.12.9.3) only in that the
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rint functions may raise the ``inexact'' floating-point exception if the result differs in
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value from the argument.
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Returns
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3 The rint functions return the rounded integer value.
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7.12.9.5 The lrint and llrint functions
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Synopsis
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1 #include <math.h>
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long int lrint(double x);
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long int lrintf(float x);
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long int lrintl(long double x);
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long long int llrint(double x);
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long long int llrintf(float x);
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long long int llrintl(long double x);
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Description
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2 The lrint and llrint functions round their argument to the nearest integer value,
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rounding according to the current rounding direction. If the rounded value is outside the
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range of the return type, the numeric result is unspecified and a domain error or range
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error may occur.
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Returns
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3 The lrint and llrint functions return the rounded integer value.
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7.12.9.6 The round functions
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Synopsis
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1 #include <math.h>
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double round(double x);
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float roundf(float x);
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long double roundl(long double x);
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Description
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2 The round functions round their argument to the nearest integer value in floating-point
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format, rounding halfway cases away from zero, regardless of the current rounding
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direction.
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Returns
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3 The round functions return the rounded integer value.
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7.12.9.7 The lround and llround functions
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Synopsis
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1 #include <math.h>
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long int lround(double x);
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long int lroundf(float x);
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long int lroundl(long double x);
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long long int llround(double x);
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long long int llroundf(float x);
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long long int llroundl(long double x);
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Description
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2 The lround and llround functions round their argument to the nearest integer value,
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rounding halfway cases away from zero, regardless of the current rounding direction. If
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the rounded value is outside the range of the return type, the numeric result is unspecified
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and a domain error or range error may occur.
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Returns
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3 The lround and llround functions return the rounded integer value.
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7.12.9.8 The trunc functions
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Synopsis
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1 #include <math.h>
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double trunc(double x);
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float truncf(float x);
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long double truncl(long double x);
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Description
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2 The trunc functions round their argument to the integer value, in floating format,
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nearest to but no larger in magnitude than the argument.
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Returns
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3 The trunc functions return the truncated integer value.
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7.12.10 Remainder functions
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7.12.10.1 The fmod functions
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Synopsis
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1 #include <math.h>
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double fmod(double x, double y);
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float fmodf(float x, float y);
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long double fmodl(long double x, long double y);
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Description
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2 The fmod functions compute the floating-point remainder of x/y.
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Returns
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3 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
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the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
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whether a domain error occurs or the fmod functions return zero is implementation-
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defined.
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7.12.10.2 The remainder functions
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Synopsis
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1 #include <math.h>
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double remainder(double x, double y);
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float remainderf(float x, float y);
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long double remainderl(long double x, long double y);
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Description
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2 The remainder functions compute the remainder x REM y required by IEC 60559.210)
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Returns
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3 The remainder functions return x REM y. If y is zero, whether a domain error occurs
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or the functions return zero is implementation defined.
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210) ``When y 0, the remainder r = x REM y is defined regardless of the rounding mode by the
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mathematical relation r = x - ny , where n is the integer nearest the exact value of x / y ; whenever
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| n - x / y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
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x .'' This definition is applicable for all implementations.
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7.12.10.3 The remquo functions
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Synopsis
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1 #include <math.h>
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double remquo(double x, double y, int *quo);
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float remquof(float x, float y, int *quo);
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long double remquol(long double x, long double y,
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int *quo);
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Description
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2 The remquo functions compute the same remainder as the remainder functions. In
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the object pointed to by quo they store a value whose sign is the sign of x/y and whose
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magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
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n is an implementation-defined integer greater than or equal to 3.
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Returns
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3 The remquo functions return x REM y. If y is zero, the value stored in the object
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|
pointed to by quo is unspecified and whether a domain error occurs or the functions
|
|
|
|
|
|
return zero is implementation defined.
|
|
|
|
|
|
7.12.11 Manipulation functions
|
|
|
|
|
|
7.12.11.1 The copysign functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The copysign functions return a value with the magnitude of x and the sign of y.
|
|
|
|
|
|
|
|
|
|
|
|
7.12.11.2 The nan functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
double nan(const char *tagp);
|
|
|
|
|
|
float nanf(const char *tagp);
|
|
|
|
|
|
long double nanl(const char *tagp);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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 (7.20.1.3).
|
|
|
|
|
|
7.12.11.3 The nextafter functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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.211) 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
|
|
|
|
|
|
3 The nextafter functions return the next representable value in the specified format
|
|
|
|
|
|
after x in the direction of y.
|
|
|
|
|
|
211) The argument values are converted to the type of the function, even by a macro implementation of the
|
|
|
|
|
|
function.
|
|
|
|
|
|
7.12.11.4 The nexttoward functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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.212)
|
|
|
|
|
|
7.12.12 Maximum, minimum, and positive difference functions
|
|
|
|
|
|
7.12.12.1 The fdim functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fdim functions return the positive difference value.
|
|
|
|
|
|
7.12.12.2 The fmax functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
double fmax(double x, double y);
|
|
|
|
|
|
float fmaxf(float x, float y);
|
|
|
|
|
|
long double fmaxl(long double x, long double y);
|
|
|
|
|
|
212) 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.
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The fmax functions determine the maximum numeric value of their arguments.213)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The fmax functions return the maximum numeric value of their arguments.
|
|
|
|
|
|
7.12.12.3 The fmin functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
2 The fmin functions determine the minimum numeric value of their arguments.214)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The fmin functions return the minimum numeric value of their arguments.
|
|
|
|
|
|
7.12.13 Floating multiply-add
|
|
|
|
|
|
7.12.13.1 The fma functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
2 The fma functions compute (x <20> 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
|
|
|
|
|
|
3 The fma functions return (x <20> y) + z, rounded as one ternary operation.
|
|
|
|
|
|
213) 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 F.9.9.2.
|
|
|
|
|
|
214) The fmin functions are analogous to the fmax functions in their treatment of NaNs.
|
|
|
|
|
|
7.12.14 Comparison macros
|
|
|
|
|
|
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.215) 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.
|
|
|
|
|
|
7.12.14.1 The isgreater macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isgreater(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The isgreater macro returns the value of (x) > (y).
|
|
|
|
|
|
7.12.14.2 The isgreaterequal macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isgreaterequal(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
215) 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.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The isgreaterequal macro returns the value of (x) >= (y).
|
|
|
|
|
|
7.12.14.3 The isless macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isless(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The isless macro returns the value of (x) < (y).
|
|
|
|
|
|
7.12.14.4 The islessequal macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int islessequal(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The islessequal macro returns the value of (x) <= (y).
|
|
|
|
|
|
7.12.14.5 The islessgreater macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int islessgreater(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
|
|
|
|
|
|
7.12.14.6 The isunordered macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <math.h>
|
|
|
|
|
|
int isunordered(real-floating x, real-floating y);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The isunordered macro determines whether its arguments are unordered.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
|
|
|
|
|
|
|
|
|
|
|
|
7.13 Nonlocal jumps <setjmp.h>
|
|
|
|
|
|
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.216)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.13.1 Save calling environment
|
|
|
|
|
|
7.13.1.1 The setjmp macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <setjmp.h>
|
|
|
|
|
|
int setjmp(jmp_buf env);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The setjmp macro saves its calling environment in its jmp_buf argument for later use
|
|
|
|
|
|
by the longjmp function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
216) These functions are useful for dealing with unusual conditions encountered in a low-level function of
|
|
|
|
|
|
a program.
|
|
|
|
|
|
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).
|
|
|
|
|
|
5 If the invocation appears in any other context, the behavior is undefined.
|
|
|
|
|
|
7.13.2 Restore calling environment
|
|
|
|
|
|
7.13.2.1 The longjmp function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <setjmp.h>
|
|
|
|
|
|
void longjmp(jmp_buf env, int val);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 function containing
|
|
|
|
|
|
the invocation of the setjmp macro has terminated execution217) 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.
|
|
|
|
|
|
3 All accessible objects have values, and all other components of the abstract machine218)
|
|
|
|
|
|
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
|
|
|
|
|
|
4 After longjmp is completed, program 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
217) 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.
|
|
|
|
|
|
218) This includes, but is not limited to, the floating-point status flags and the state of open files.
|
|
|
|
|
|
#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
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.14 Signal handling <signal.h>
|
|
|
|
|
|
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).
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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,219) 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.
|
|
|
|
|
|
219) See ``future library directions'' (7.26.9). The names of the signal numbers reflect the following terms
|
|
|
|
|
|
(respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
|
|
|
|
|
|
and termination.
|
|
|
|
|
|
7.14.1 Specify signal handling
|
|
|
|
|
|
7.14.1.1 The signal function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <signal.h>
|
|
|
|
|
|
void (*signal(int sig, void (*func)(int)))(int);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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), is called a signal
|
|
|
|
|
|
handler .
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 If the signal occurs as the result of calling the abort or raise function, the signal
|
|
|
|
|
|
handler shall not call the raise function.
|
|
|
|
|
|
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 storage duration
|
|
|
|
|
|
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, 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.220)
|
|
|
|
|
|
6 At program startup, the equivalent of
|
|
|
|
|
|
signal(sig, SIG_IGN);
|
|
|
|
|
|
220) If any signal is generated by an asynchronous signal handler, the behavior is undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7 The implementation shall behave as if no library function calls the signal function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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 (7.20.4.1), the exit function (7.20.4.3), the
|
|
|
|
|
|
_Exit function (7.20.4.4).
|
|
|
|
|
|
7.14.2 Send signal
|
|
|
|
|
|
7.14.2.1 The raise function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <signal.h>
|
|
|
|
|
|
int raise(int sig);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The raise function carries out the actions described in 7.14.1.1 for the signal sig. If a
|
|
|
|
|
|
signal handler is called, the raise function shall not return until after the signal handler
|
|
|
|
|
|
does.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The raise function returns zero if successful, nonzero if unsuccessful.
|
|
|
|
|
|
|
|
|
|
|
|
7.15 Variable arguments <stdarg.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 A function may be called with a variable number of arguments of varying types. As
|
|
|
|
|
|
described in 6.9.1, 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.
|
|
|
|
|
|
3 The type declared is
|
|
|
|
|
|
va_list
|
|
|
|
|
|
which is an 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.221)
|
|
|
|
|
|
7.15.1 Variable argument list access macros
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.15.1.1 The va_arg macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
type va_arg(va_list ap, type);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
221) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.15.1.2 The va_copy macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
void va_copy(va_list dest, va_list src);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The va_copy macro returns no value.
|
|
|
|
|
|
7.15.1.3 The va_end macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
void va_end(va_list ap);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The va_end macro returns no value.
|
|
|
|
|
|
7.15.1.4 The va_start macro
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
void va_start(va_list ap, parmN);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The va_start macro shall be invoked before any access to the unnamed arguments.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
5 The va_start macro returns no value.
|
|
|
|
|
|
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, ...);
|
|
|
|
|
|
|
|
|
|
|
|
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);
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
7.16 Boolean type and values <stdbool.h>
|
|
|
|
|
|
1 The header <stdbool.h> defines four macros.
|
|
|
|
|
|
2 The macro
|
|
|
|
|
|
bool
|
|
|
|
|
|
expands to _Bool.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then
|
|
|
|
|
|
redefine the macros bool, true, and false.222)
|
|
|
|
|
|
222) See ``future library directions'' (7.26.7).
|
|
|
|
|
|
7.17 Common definitions <stddef.h>
|
|
|
|
|
|
1 The following types and macros are defined in the standard header <stddef.h>. Some
|
|
|
|
|
|
are also defined in other headers, as noted in their respective subclauses.
|
|
|
|
|
|
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; 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_ _.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
Forward references: localization (7.11).
|
|
|
|
|
|
|
|
|
|
|
|
7.18 Integer types <stdint.h>
|
|
|
|
|
|
1 The header <stdint.h> declares sets of integer types having specified widths, and
|
|
|
|
|
|
defines corresponding sets of macros.223) It also defines macros that specify limits of
|
|
|
|
|
|
integer types corresponding to types defined in other standard headers.
|
|
|
|
|
|
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.)
|
|
|
|
|
|
3 Corresponding macros specify limits of the declared types and construct suitable
|
|
|
|
|
|
constants.
|
|
|
|
|
|
4 For each type described herein that the implementation provides,224) <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'').
|
|
|
|
|
|
7.18.1 Integer types
|
|
|
|
|
|
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 6.2.5; an
|
|
|
|
|
|
implementation providing one of these corresponding types shall also provide the other.
|
|
|
|
|
|
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).
|
|
|
|
|
|
223) See ``future library directions'' (7.26.8).
|
|
|
|
|
|
224) Some of these types may denote implementation-defined extended integer types.
|
|
|
|
|
|
7.18.1.1 Exact-width integer types
|
|
|
|
|
|
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 a signed integer
|
|
|
|
|
|
type with a width of exactly 8 bits.
|
|
|
|
|
|
2 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
|
|
|
|
|
|
uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.1.2 Minimum-width integer types
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.1.3 Fastest minimum-width integer types
|
|
|
|
|
|
1 Each of the following types designates an integer type that is usually fastest225) to operate
|
|
|
|
|
|
with among all integer types that have at least the specified width.
|
|
|
|
|
|
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 .
|
|
|
|
|
|
225) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.1.4 Integer types capable of holding object pointers
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.1.5 Greatest-width integer types
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.2 Limits of specified-width integer types
|
|
|
|
|
|
1 The following object-like macros226) specify the minimum and maximum limits of the
|
2012-01-17 03:07:01 +01:00
|
|
|
|
types declared in <stdint.h>. Each macro name corresponds to a similar type name in 7.18.1.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
226) C++ implementations should define these macros only when _ _STDC_LIMIT_MACROS is defined
|
|
|
|
|
|
before <stdint.h> is included.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.2.1 Limits of exact-width integer types
|
|
|
|
|
|
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
|
|
|
|
|
|
7.18.2.2 Limits of minimum-width integer types
|
|
|
|
|
|
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
|
|
|
|
|
|
7.18.2.3 Limits of fastest minimum-width integer types
|
|
|
|
|
|
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
|
|
|
|
|
|
7.18.2.4 Limits of integer types capable of holding object pointers
|
|
|
|
|
|
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
|
|
|
|
|
|
7.18.2.5 Limits of greatest-width integer types
|
|
|
|
|
|
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
|
|
|
|
|
|
7.18.3 Limits of other integer types
|
|
|
|
|
|
1 The following object-like macros227) specify the minimum and maximum limits of
|
|
|
|
|
|
integer types corresponding to types defined in other standard headers.
|
|
|
|
|
|
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.228)
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
227) C++ implementations should define these macros only when _ _STDC_LIMIT_MACROS is defined
|
|
|
|
|
|
before <stdint.h> is included.
|
|
|
|
|
|
228) A freestanding implementation need not provide all of these types.
|
|
|
|
|
|
WCHAR_MIN see below
|
|
|
|
|
|
WCHAR_MAX see below
|
|
|
|
|
|
-- limits of wint_t
|
|
|
|
|
|
WINT_MIN see below
|
|
|
|
|
|
WINT_MAX see below
|
|
|
|
|
|
3 If sig_atomic_t (see 7.14) 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.
|
|
|
|
|
|
4 If wchar_t (see 7.17) 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 255.229)
|
|
|
|
|
|
5 If wint_t (see 7.24) 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.
|
|
|
|
|
|
7.18.4 Macros for integer constants
|
|
|
|
|
|
1 The following function-like macros230) expand to integer constants suitable for
|
|
|
|
|
|
initializing objects that have integer types corresponding to types defined in
|
2012-01-17 03:07:01 +01:00
|
|
|
|
<stdint.h>. Each macro name corresponds to a similar type name in 7.18.1.2 or 7.18.1.5.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
2 The argument in any instance of these macros shall be an unsuffixed integer constant (as
|
|
|
|
|
|
defined in 6.4.4.1) with a value that does not exceed the limits for the corresponding type.
|
|
|
|
|
|
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.
|
|
|
|
|
|
229) The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
|
|
|
|
|
|
character set.
|
|
|
|
|
|
230) C++ implementations should define these macros only when _ _STDC_CONSTANT_MACROS is
|
|
|
|
|
|
defined before <stdint.h> is included.
|
|
|
|
|
|
7.18.4.1 Macros for minimum-width integer constants
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.18.4.2 Macros for greatest-width integer constants
|
|
|
|
|
|
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)
|
|
|
|
|
|
|
|
|
|
|
|
7.19 Input/output <stdio.h>
|
|
|
|
|
|
7.19.1 Introduction
|
|
|
|
|
|
1 The header <stdio.h> declares three types, several macros, and many functions for
|
|
|
|
|
|
performing input and output.
|
|
|
|
|
|
2 The types declared are size_t (described in 7.17);
|
|
|
|
|
|
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 an object type other than an array type capable of recording all the information
|
|
|
|
|
|
needed to specify uniquely every position within a file.
|
|
|
|
|
|
3 The macros are NULL (described in 7.17);
|
|
|
|
|
|
_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;231)
|
|
|
|
|
|
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 maximum 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.
|
|
|
|
|
|
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 7.19.3.
|
|
|
|
|
|
5 The input/output functions are given the following collective terms:
|
|
|
|
|
|
-- The wide character input functions -- those functions described in 7.24 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 7.24 that perform
|
|
|
|
|
|
output from wide characters and wide strings: fputwc, fputws, putwc,
|
|
|
|
|
|
putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
|
|
|
|
|
|
231) 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.
|
|
|
|
|
|
-- 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, gets, printf, putc, putchar, puts,
|
|
|
|
|
|
scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
|
|
|
|
|
|
Forward references: files (7.19.3), the fseek function (7.19.9.2), streams (7.19.2), the
|
|
|
|
|
|
tmpnam function (7.19.4.4), <wchar.h> (7.24).
|
|
|
|
|
|
7.19.2 Streams
|
|
|
|
|
|
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.232)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
232) 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.
|
|
|
|
|
|
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.)233)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
Environmental limits
|
|
|
|
|
|
7 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 (7.19.5.4), the fwide function (7.24.3.5),
|
|
|
|
|
|
mbstate_t (7.25.1), the fgetpos function (7.19.9.1), the fsetpos function
|
|
|
|
|
|
(7.19.9.3).
|
|
|
|
|
|
233) The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
|
|
|
|
|
|
7.19.3 Files
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 Binary files are not truncated, except as defined in 7.19.5.3. Whether a write on a text
|
|
|
|
|
|
stream causes the associated file to be truncated beyond that point is implementation-
|
|
|
|
|
|
defined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.234)
|
|
|
|
|
|
10 Moreover, the encodings used for multibyte characters may differ among files. Both the
|
|
|
|
|
|
nature and choice of such encodings are implementation-defined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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)
|
|
|
|
|
|
234) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
15 The value of FOPEN_MAX shall be at least eight, including the three standard text
|
|
|
|
|
|
streams.
|
|
|
|
|
|
Forward references: the exit function (7.20.4.3), the fgetc function (7.19.7.1), the
|
|
|
|
|
|
fopen function (7.19.5.3), the fputc function (7.19.7.3), the setbuf function
|
|
|
|
|
|
(7.19.5.5), the setvbuf function (7.19.5.6), the fgetwc function (7.24.3.1), the
|
|
|
|
|
|
fputwc function (7.24.3.3), conversion state (7.24.6), the mbrtowc function
|
|
|
|
|
|
(7.24.6.3.2), the wcrtomb function (7.24.6.3.3).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
7.19.4 Operations on files
|
|
|
|
|
|
7.19.4.1 The remove function
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int remove(const char *filename);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The remove function returns zero if the operation succeeds, nonzero if it fails.
|
2012-01-17 03:07:01 +01:00
|
|
|
|
7.19.4.2 The rename function
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int rename(const char *old, const char *new);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The rename function returns zero if the operation succeeds, nonzero if it fails,235) in
|
|
|
|
|
|
which case if the file existed previously it is still known by its original name.
|
|
|
|
|
|
7.19.4.3 The tmpfile function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
FILE *tmpfile(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
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 (7.19.5.3).
|
|
|
|
|
|
7.19.4.4 The tmpnam function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
char *tmpnam(char *s);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.236) The function is potentially capable of generating
|
|
|
|
|
|
235) 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.
|
|
|
|
|
|
236) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The tmpnam function generates a different string each time it is called.
|
|
|
|
|
|
4 The implementation shall behave as if no library function calls the tmpnam function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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
|
|
|
|
|
|
6 The value of the macro TMP_MAX shall be at least 25.
|
|
|
|
|
|
7.19.5 File access functions
|
|
|
|
|
|
7.19.5.1 The fclose function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fclose(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fclose function returns zero if the stream was successfully closed, or EOF if any
|
|
|
|
|
|
errors were detected.
|
|
|
|
|
|
7.19.5.2 The fflush function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fflush(FILE *stream);
|
|
|
|
|
|
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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 (7.19.5.3).
|
|
|
|
|
|
7.19.5.3 The fopen function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
FILE *fopen(const char * restrict filename,
|
|
|
|
|
|
const char * restrict mode);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The fopen function opens the file whose name is the string pointed to by filename,
|
|
|
|
|
|
and associates a stream with it.
|
|
|
|
|
|
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.237)
|
|
|
|
|
|
r open text file for reading
|
|
|
|
|
|
w truncate to zero length or 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
|
|
|
|
|
|
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
|
|
|
|
|
|
a+ append; open or create text file for update, writing at end-of-file
|
|
|
|
|
|
237) 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 7.19.2).
|
|
|
|
|
|
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
|
|
|
|
|
|
a+b or ab+ append; open or create binary file for update, writing at end-of-file
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 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.
|
|
|
|
|
|
6 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.
|
|
|
|
|
|
7 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
|
|
|
|
|
|
8 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 (7.19.9).
|
|
|
|
|
|
7.19.5.4 The freopen function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
FILE *freopen(const char * restrict filename,
|
|
|
|
|
|
const char * restrict mode,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.238)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
5 The freopen function returns a null pointer if the open operation fails. Otherwise,
|
|
|
|
|
|
freopen returns the value of stream.
|
|
|
|
|
|
7.19.5.5 The setbuf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
void setbuf(FILE * restrict stream,
|
|
|
|
|
|
char * restrict buf);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The setbuf function returns no value.
|
|
|
|
|
|
Forward references: the setvbuf function (7.19.5.6).
|
|
|
|
|
|
7.19.5.6 The setvbuf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int setvbuf(FILE * restrict stream,
|
|
|
|
|
|
char * restrict buf,
|
|
|
|
|
|
int mode, size_t size);
|
|
|
|
|
|
238) 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.
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 function239) 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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.6 Formatted input/output functions
|
|
|
|
|
|
1 The formatted input/output functions shall behave as if there is a sequence point after the
|
|
|
|
|
|
actions associated with each specifier.240)
|
|
|
|
|
|
7.19.6.1 The fprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fprintf(FILE * restrict stream,
|
|
|
|
|
|
const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
239) 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.
|
|
|
|
|
|
240) The fprintf functions perform writes to memory for the %n specifier.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.241)
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
241) Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
|
|
|
|
specified.)242)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
242) The results of all floating conversions of a negative zero, and of negative values that round to zero,
|
|
|
|
|
|
include a minus sign.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
2012-01-23 23:24:51 +01:00
|
|
|
|
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.243)
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
243) When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
|
|
|
|
|
|
the # and 0 flag characters have no effect.
|
|
|
|
|
|
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 character244) 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
|
|
|
|
|
|
distinguish245) 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.246) Characters from the array are
|
|
|
|
|
|
244) 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.
|
|
|
|
|
|
245) 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.
|
|
|
|
|
|
246) No special provisions are made for multibyte characters.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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.247)
|
|
|
|
|
|
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 %%.
|
|
|
|
|
|
9 If a conversion specification is invalid, the behavior is undefined.248) If any argument is
|
|
|
|
|
|
not the correct type for the corresponding conversion specification, the behavior is
|
|
|
|
|
|
undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
247) Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
|
|
|
|
|
|
248) See ``future library directions'' (7.26.9).
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.249) 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
|
|
|
|
|
|
14 The fprintf function returns the number of characters transmitted, or a negative value
|
|
|
|
|
|
if an output or encoding error occurred.
|
|
|
|
|
|
Environmental limits
|
|
|
|
|
|
15 The number of characters that can be produced by any single conversion shall be at least
|
|
|
|
|
|
4095.
|
|
|
|
|
|
16 EXAMPLE 1 To print a date and time in the form ``Sunday, July 3, 10:02'' followed by 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));
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
249) 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.
|
|
|
|
|
|
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 (7.24.6), the wcrtomb function (7.24.6.3.3).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
7.19.6.2 The fscanf function
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fscanf(FILE * restrict stream,
|
|
|
|
|
|
const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 The fscanf function executes each directive of the format in turn. 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).
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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:
|
|
|
|
|
|
8 Input white-space characters (as specified by the isspace function) are skipped, unless
|
|
|
|
|
|
the specification includes a [, c, or n specifier.250)
|
|
|
|
|
|
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.251)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
2012-01-23 23:24:51 +01:00
|
|
|
|
does not have an appropriate type, or if the result of the conversion cannot be represented
|
2012-01-16 16:34:32 +01:00
|
|
|
|
250) These white-space characters are not counted against a specified field width.
|
|
|
|
|
|
251) 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.
|
|
|
|
|
|
in the object, the behavior is undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
2012-01-23 23:24:51 +01:00
|
|
|
|
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).252)
|
|
|
|
|
|
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.252)
|
|
|
|
|
|
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
|
|
|
|
|
|
252) 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.
|
|
|
|
|
|
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 ).252)
|
|
|
|
|
|
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.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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 %%.
|
|
|
|
|
|
13 If a conversion specification is invalid, the behavior is undefined.253)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
16 The fscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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:
|
|
|
|
|
|
253) See ``future library directions'' (7.26.9).
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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));
|
|
|
|
|
|
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;
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
22 EXAMPLE 5 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.
|
|
|
|
|
|
23 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.
|
|
|
|
|
|
24 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.
|
|
|
|
|
|
25 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.
|
|
|
|
|
|
26 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 (7.20.1.3), the
|
|
|
|
|
|
strtol, strtoll, strtoul, and strtoull functions (7.20.1.4), conversion state
|
|
|
|
|
|
(7.24.6), the wcrtomb function (7.24.6.3.3).
|
|
|
|
|
|
|
|
|
|
|
|
7.19.6.3 The printf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int printf(const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The printf function is equivalent to fprintf with the argument stdout interposed
|
|
|
|
|
|
before the arguments to printf.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The printf function returns the number of characters transmitted, or a negative value if
|
|
|
|
|
|
an output or encoding error occurred.
|
|
|
|
|
|
7.19.6.4 The scanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int scanf(const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The scanf function is equivalent to fscanf with the argument stdin interposed
|
|
|
|
|
|
before the arguments to scanf.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The scanf function returns the value of the macro EOF if an input failure occurs before
|
|
|
|
|
|
any conversion. 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.
|
|
|
|
|
|
7.19.6.5 The snprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int snprintf(char * restrict s, size_t n,
|
|
|
|
|
|
const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.6.6 The sprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int sprintf(char * restrict s,
|
|
|
|
|
|
const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.6.7 The sscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int sscanf(const char * restrict s,
|
|
|
|
|
|
const char * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The sscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.6.8 The vfprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vfprintf(FILE * restrict stream,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vfprintf function returns the number of characters transmitted, or a negative
|
|
|
|
|
|
value if an output or encoding error occurred.
|
|
|
|
|
|
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);
|
|
|
|
|
|
}
|
|
|
|
|
|
254) 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.
|
|
|
|
|
|
7.19.6.9 The vfscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vfscanf(FILE * restrict stream,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vfscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.19.6.10 The vprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vprintf(const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vprintf function returns the number of characters transmitted, or a negative value
|
|
|
|
|
|
if an output or encoding error occurred.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.6.11 The vscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vscanf(const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.19.6.12 The vsnprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vsnprintf(char * restrict s, size_t n,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254) If copying takes place between objects that overlap, the behavior is
|
|
|
|
|
|
undefined.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.6.13 The vsprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vsprintf(char * restrict s,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254) If copying takes place between objects that overlap, the behavior is
|
|
|
|
|
|
undefined.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.6.14 The vsscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
int vsscanf(const char * restrict s,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.254)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vsscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.7 Character input/output functions
|
|
|
|
|
|
7.19.7.1 The fgetc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fgetc(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.255)
|
|
|
|
|
|
7.19.7.2 The fgets function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
char *fgets(char * restrict s, int n,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
255) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
|
|
|
|
|
|
7.19.7.3 The fputc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fputc(int c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.7.4 The fputs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fputs(const char * restrict s,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fputs function returns EOF if a write error occurs; otherwise it returns a
|
|
|
|
|
|
nonnegative value.
|
|
|
|
|
|
7.19.7.5 The getc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int getc(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.7.6 The getchar function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int getchar(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The getchar function is equivalent to getc with the argument stdin.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.7.7 The gets function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
char *gets(char *s);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The gets function reads characters from the input stream pointed to by stdin, into the
|
|
|
|
|
|
array pointed to by s, until end-of-file is encountered or a new-line character is read.
|
|
|
|
|
|
Any new-line character is discarded, and a null character is written immediately after the
|
|
|
|
|
|
last character read into the array.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The gets 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.
|
|
|
|
|
|
Forward references: future library directions (7.26.9).
|
|
|
|
|
|
|
|
|
|
|
|
7.19.7.8 The putc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int putc(int c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.7.9 The putchar function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int putchar(int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The putchar function is equivalent to putc with the second argument stdout.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.7.10 The puts function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int puts(const char *s);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
|
|
|
|
|
|
value.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.7.11 The ungetc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int ungetc(int c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 If the value of c equals that of the macro EOF, the operation fails and the input stream is
|
|
|
|
|
|
unchanged.
|
|
|
|
|
|
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.256)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
6 The ungetc function returns the character pushed back after conversion, or EOF if the
|
|
|
|
|
|
operation fails.
|
|
|
|
|
|
Forward references: file positioning functions (7.19.9).
|
|
|
|
|
|
256) See ``future library directions'' (7.26.9).
|
|
|
|
|
|
7.19.8 Direct input/output functions
|
|
|
|
|
|
7.19.8.1 The fread function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
size_t fread(void * restrict ptr,
|
|
|
|
|
|
size_t size, size_t nmemb,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.8.2 The fwrite function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
size_t fwrite(const void * restrict ptr,
|
|
|
|
|
|
size_t size, size_t nmemb,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.9 File positioning functions
|
|
|
|
|
|
7.19.9.1 The fgetpos function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fgetpos(FILE * restrict stream,
|
|
|
|
|
|
fpos_t * restrict pos);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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 (7.19.9.3).
|
|
|
|
|
|
7.19.9.2 The fseek function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fseek(FILE *stream, long int offset, int whence);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
6 The fseek function returns nonzero only for a request that cannot be satisfied.
|
|
|
|
|
|
Forward references: the ftell function (7.19.9.4).
|
|
|
|
|
|
7.19.9.3 The fsetpos function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int fsetpos(FILE *stream, const fpos_t *pos);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
4 If successful, the fsetpos function returns zero; on failure, the fsetpos function
|
|
|
|
|
|
returns nonzero and stores an implementation-defined positive value in errno.
|
|
|
|
|
|
7.19.9.4 The ftell function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
long int ftell(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.19.9.5 The rewind function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
void rewind(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The rewind function returns no value.
|
|
|
|
|
|
7.19.10 Error-handling functions
|
|
|
|
|
|
7.19.10.1 The clearerr function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
void clearerr(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The clearerr function clears the end-of-file and error indicators for the stream pointed
|
|
|
|
|
|
to by stream.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The clearerr function returns no value.
|
|
|
|
|
|
|
|
|
|
|
|
7.19.10.2 The feof function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int feof(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The feof function tests the end-of-file indicator for the stream pointed to by stream.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The feof function returns nonzero if and only if the end-of-file indicator is set for
|
|
|
|
|
|
stream.
|
|
|
|
|
|
7.19.10.3 The ferror function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
int ferror(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The ferror function tests the error indicator for the stream pointed to by stream.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The ferror function returns nonzero if and only if the error indicator is set for
|
|
|
|
|
|
stream.
|
|
|
|
|
|
7.19.10.4 The perror function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
void perror(const char *s);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The perror function returns no value.
|
|
|
|
|
|
Forward references: the strerror function (7.21.6.2).
|
|
|
|
|
|
7.20 General utilities <stdlib.h>
|
|
|
|
|
|
1 The header <stdlib.h> declares five types and several functions of general utility, and
|
|
|
|
|
|
defines several macros.257)
|
|
|
|
|
|
2 The types declared are size_t and wchar_t (both described in 7.17),
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The macros defined are NULL (described in 7.17);
|
|
|
|
|
|
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.
|
|
|
|
|
|
257) See ``future library directions'' (7.26.10).
|
|
|
|
|
|
7.20.1 Numeric conversion functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.20.1.1 The atof function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
double atof(const char *nptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The atof function returns the converted value.
|
|
|
|
|
|
Forward references: the strtod, strtof, and strtold functions (7.20.1.3).
|
|
|
|
|
|
7.20.1.2 The atoi, atol, and atoll functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int atoi(const char *nptr);
|
|
|
|
|
|
long int atol(const char *nptr);
|
|
|
|
|
|
long long int atoll(const char *nptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The atoi, atol, and atoll functions return the converted value.
|
|
|
|
|
|
Forward references: the strtol, strtoll, strtoul, and strtoull functions
|
|
|
|
|
|
(7.20.1.4).
|
|
|
|
|
|
7.20.1.3 The strtod, strtof, and strtold functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.4.4.2;
|
|
|
|
|
|
-- 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 6.4.4.2;
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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 6.4.4.2, 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.258)
|
|
|
|
|
|
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 sequences is implementation-defined.259) A
|
|
|
|
|
|
pointer to the final string is stored in the object pointed to by endptr, provided that
|
|
|
|
|
|
endptr is not a null pointer.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
|
|
|
|
accepted.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
258) 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 F.5); 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.
|
|
|
|
|
|
259) An implementation may use the n-char sequence to determine extra information to be represented in
|
|
|
|
|
|
the NaN's significand.
|
|
|
|
|
|
stipulation that the error with respect to D should have a correct sign for the current
|
|
|
|
|
|
rounding direction.260)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
10 The 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, 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 (7.12.1), 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.
|
2012-01-17 03:07:01 +01:00
|
|
|
|
7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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
|
|
|
|
|
|
260) 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 If the value of base is zero, the expected form of the subject sequence is that of an
|
|
|
|
|
|
integer constant as described in 6.4.4.1, 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.4.4.1. 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.
|
|
|
|
|
|
6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
|
|
|
|
accepted.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.20.2 Pseudo-random sequence generation functions
|
|
|
|
|
|
7.20.2.1 The rand function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int rand(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The rand function computes a sequence of pseudo-random integers in the range 0 to
|
|
|
|
|
|
RAND_MAX.
|
|
|
|
|
|
3 The implementation shall behave as if no library function calls the rand function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
4 The rand function returns a pseudo-random integer.
|
|
|
|
|
|
Environmental limits
|
|
|
|
|
|
5 The value of the RAND_MAX macro shall be at least 32767.
|
|
|
|
|
|
7.20.2.2 The srand function
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Synopsis
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1 #include <stdlib.h>
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void srand(unsigned int seed);
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Description
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2 The srand function uses the argument as a seed for a new sequence of pseudo-random
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numbers to be returned by subsequent calls to rand. If srand is then called with the
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same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
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called before any calls to srand have been made, the same sequence shall be generated
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as when srand is first called with a seed value of 1.
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3 The implementation shall behave as if no library function calls the srand function.
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Returns
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4 The srand function returns no value.
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5 EXAMPLE The following functions define a portable implementation of rand and srand.
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static unsigned long int next = 1;
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int rand(void) // RAND_MAX assumed to be 32767
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{
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next = next * 1103515245 + 12345;
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return (unsigned int)(next/65536) % 32768;
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}
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void srand(unsigned int seed)
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{
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next = seed;
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}
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7.20.3 Memory management functions
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1 The order and contiguity of storage allocated by successive calls to the calloc,
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malloc, and realloc functions is unspecified. The pointer returned if the allocation
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succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
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and then used to access such an object or an array of such objects in the space allocated
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(until the space is explicitly deallocated). The lifetime of an allocated object extends
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from the allocation until the deallocation. Each such allocation shall yield a pointer to an
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object disjoint from any other object. The pointer returned points to the start (lowest byte
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address) of the allocated space. If the space cannot be allocated, a null pointer is
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returned. If the size of the space requested is zero, the behavior is implementation-
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defined: either a null pointer is returned, or the behavior is as if the size were some
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nonzero value, except that the returned pointer shall not be used to access an object.
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7.20.3.1 The calloc function
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Synopsis
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1 #include <stdlib.h>
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void *calloc(size_t nmemb, size_t size);
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Description
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2 The calloc function allocates space for an array of nmemb objects, each of whose size
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is size. The space is initialized to all bits zero.261)
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Returns
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3 The calloc function returns either a null pointer or a pointer to the allocated space.
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7.20.3.2 The free function
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Synopsis
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1 #include <stdlib.h>
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void free(void *ptr);
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Description
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2 The free function causes the space pointed to by ptr to be deallocated, that is, made
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available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
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the argument does not match a pointer earlier returned by the calloc, malloc, or
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261) Note that this need not be the same as the representation of floating-point zero or a null pointer
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constant.
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realloc function, or if the space has been deallocated by a call to free or realloc,
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the behavior is undefined.
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Returns
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3 The free function returns no value.
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7.20.3.3 The malloc function
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Synopsis
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1 #include <stdlib.h>
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void *malloc(size_t size);
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Description
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2 The malloc function allocates space for an object whose size is specified by size and
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whose value is indeterminate.
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Returns
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3 The malloc function returns either a null pointer or a pointer to the allocated space.
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7.20.3.4 The realloc function
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Synopsis
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1 #include <stdlib.h>
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void *realloc(void *ptr, size_t size);
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Description
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2 The realloc function deallocates the old object pointed to by ptr and returns a
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pointer to a new object that has the size specified by size. The contents of the new
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object shall be the same as that of the old object prior to deallocation, up to the lesser of
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the new and old sizes. Any bytes in the new object beyond the size of the old object have
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indeterminate values.
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3 If ptr is a null pointer, the realloc function behaves like the malloc function for the
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specified size. Otherwise, if ptr does not match a pointer earlier returned by the
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calloc, malloc, or realloc function, or if the space has been deallocated by a call
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to the free or realloc function, the behavior is undefined. If memory for the new
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object cannot be allocated, the old object is not deallocated and its value is unchanged.
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Returns
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4 The realloc function returns a pointer to the new object (which may have the same
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value as a pointer to the old object), or a null pointer if the new object could not be
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allocated.
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7.20.4 Communication with the environment
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7.20.4.1 The abort function
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Synopsis
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|
1 #include <stdlib.h>
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|
|
void abort(void);
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Description
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2 The abort function causes abnormal program termination to occur, unless the signal
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SIGABRT is being caught and the signal handler does not return. Whether open streams
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with unwritten buffered data are flushed, open streams are closed, or temporary files are
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removed is implementation-defined. An implementation-defined form of the status
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unsuccessful termination is returned to the host environment by means of the function
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call raise(SIGABRT).
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Returns
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|
3 The abort function does not return to its caller.
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7.20.4.2 The atexit function
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Synopsis
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|
|
1 #include <stdlib.h>
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|
|
int atexit(void (*func)(void));
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Description
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|
2 The atexit function registers the function pointed to by func, to be called without
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arguments at normal program termination.
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|
Environmental limits
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|
3 The implementation shall support the registration of at least 32 functions.
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Returns
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|
4 The atexit function returns zero if the registration succeeds, nonzero if it fails.
|
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|
|
Forward references: the exit function (7.20.4.3).
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|
7.20.4.3 The exit function
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|
Synopsis
|
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|
|
1 #include <stdlib.h>
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|
|
void exit(int status);
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|
|
Description
|
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|
2 The exit function causes normal program termination to occur. If more than one call to
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|
the exit function is executed by a program, the behavior is undefined.
|
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|
|
3 First, all functions registered by the atexit function are called, in the reverse order of
|
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|
|
their registration,262) except that a function is called after any previously registered
|
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|
|
functions that had already been called at the time it was registered. If, during the call to
|
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|
|
any such function, a call to the longjmp function is made that would terminate the call
|
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|
|
to the registered function, the behavior is undefined.
|
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|
4 Next, all open streams with unwritten buffered data are flushed, all open streams are
|
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|
|
closed, and all files created by the tmpfile function are removed.
|
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|
|
5 Finally, control is returned to the host environment. If the value of status is zero or
|
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|
|
EXIT_SUCCESS, an implementation-defined form of the status successful termination is
|
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|
returned. If the value of status is EXIT_FAILURE, an implementation-defined form
|
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|
|
of the status unsuccessful termination is returned. Otherwise the status returned is
|
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|
|
implementation-defined.
|
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|
|
Returns
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|
6 The exit function cannot return to its caller.
|
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|
|
7.20.4.4 The _Exit function
|
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|
|
Synopsis
|
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|
|
|
1 #include <stdlib.h>
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|
|
void _Exit(int status);
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|
Description
|
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|
2 The _Exit function causes normal program termination to occur and control to be
|
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|
|
returned to the host environment. No functions registered by the atexit function or
|
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|
|
signal handlers registered by the signal function are called. The status returned to the
|
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|
|
host environment is determined in the same way as for the exit function (7.20.4.3).
|
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|
Whether open streams with unwritten buffered data are flushed, open streams are closed,
|
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|
|
or temporary files are removed is implementation-defined.
|
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|
Returns
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|
3 The _Exit function cannot return to its caller.
|
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|
|
262) Each function is called as many times as it was registered, and in the correct order with respect to
|
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|
|
other registered functions.
|
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|
|
|
7.20.4.5 The getenv function
|
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|
|
Synopsis
|
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|
|
|
1 #include <stdlib.h>
|
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|
|
char *getenv(const char *name);
|
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|
|
|
Description
|
|
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|
|
|
2 The getenv function searches an environment list , provided by the host environment,
|
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|
|
for a string that matches the string pointed to by name. The set of environment names
|
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|
|
and the method for altering the environment list are implementation-defined.
|
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|
|
3 The implementation shall behave as if no library function calls the getenv function.
|
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|
Returns
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|
4 The getenv function returns a pointer to a string associated with the matched list
|
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|
member. The string pointed to shall not be modified by the program, but may be
|
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|
|
overwritten by a subsequent call to the getenv function. If the specified name cannot
|
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|
be found, a null pointer is returned.
|
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|
7.20.4.6 The system function
|
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|
|
Synopsis
|
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|
|
1 #include <stdlib.h>
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|
|
int system(const char *string);
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|
Description
|
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|
2 If string is a null pointer, the system function determines whether the host
|
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|
environment has a command processor . If string is not a null pointer, the system
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|
|
function passes the string pointed to by string to that command processor to be
|
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|
executed in a manner which the implementation shall document; this might then cause the
|
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|
program calling system to behave in a non-conforming manner or to terminate.
|
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|
Returns
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|
3 If the argument is a null pointer, the system function returns nonzero only if a
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|
command processor is available. If the argument is not a null pointer, and the system
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|
function does return, it returns an implementation-defined value.
|
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|
7.20.5 Searching and sorting utilities
|
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|
|
1 These utilities make use of a comparison function to search or sort arrays of unspecified
|
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|
|
type. Where an argument declared as size_t nmemb specifies the length of the array
|
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|
|
for a function, nmemb can have the value zero on a call to that function; the comparison
|
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|
|
function is not called, a search finds no matching element, and sorting performs no
|
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|
|
rearrangement. Pointer arguments on such a call shall still have valid values, as described
|
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|
|
in 7.1.4.
|
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|
|
2 The implementation shall ensure that the second argument of the comparison function
|
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|
|
(when called from bsearch), or both arguments (when called from qsort), are
|
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|
|
pointers to elements of the array.263) The first argument when called from bsearch
|
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|
|
shall equal key.
|
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|
|
3 The comparison function shall not alter the contents of the array. The implementation
|
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|
may reorder elements of the array between calls to the comparison function, but shall not
|
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|
|
alter the contents of any individual element.
|
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|
|
4 When the same objects (consisting of size bytes, irrespective of their current positions
|
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|
|
in the array) are passed more than once to the comparison function, the results shall be
|
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|
|
consistent with one another. That is, for qsort they shall define a total ordering on the
|
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|
|
array, and for bsearch the same object shall always compare the same way with the
|
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|
|
key.
|
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|
|
5 A sequence point occurs immediately before and immediately after each call to the
|
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|
|
comparison function, and also between any call to the comparison function and any
|
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|
|
|
|
movement of the objects passed as arguments to that call.
|
|
|
|
|
|
7.20.5.1 The bsearch function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
void *bsearch(const void *key, const void *base,
|
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|
|
|
|
size_t nmemb, size_t size,
|
|
|
|
|
|
int (*compar)(const void *, const void *));
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The bsearch function searches an array of nmemb objects, the initial element of which
|
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|
|
|
|
is pointed to by base, for an element that matches the object pointed to by key. The
|
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|
|
|
|
263) That is, if the value passed is p, then the following expressions are always nonzero:
|
|
|
|
|
|
((char *)p - (char *)base) % size == 0
|
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|
|
|
(char *)p >= (char *)base
|
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|
|
|
|
(char *)p < (char *)base + nmemb * size
|
|
|
|
|
|
size of each element of the array is specified by size.
|
|
|
|
|
|
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.264)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.20.5.2 The qsort function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
void qsort(void *base, size_t nmemb, size_t size,
|
|
|
|
|
|
int (*compar)(const void *, const void *));
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 If two elements compare as equal, their order in the resulting sorted array is unspecified.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
5 The qsort function returns no value.
|
|
|
|
|
|
264) In practice, the entire array is sorted according to the comparison function.
|
|
|
|
|
|
7.20.6 Integer arithmetic functions
|
|
|
|
|
|
7.20.6.1 The abs, labs and llabs functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int abs(int j);
|
|
|
|
|
|
long int labs(long int j);
|
|
|
|
|
|
long long int llabs(long long int j);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.265)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The abs, labs, and llabs, functions return the absolute value.
|
|
|
|
|
|
7.20.6.2 The div, ldiv, and lldiv functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
2 The div, ldiv, and lldiv, functions compute numer / denom and numer %
|
|
|
|
|
|
denom in a single operation.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
265) The absolute value of the most negative number cannot be represented in two's complement.
|
|
|
|
|
|
7.20.7 Multibyte/wide character conversion functions
|
|
|
|
|
|
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 return a nonzero value if encodings have state dependency, and zero
|
|
|
|
|
|
otherwise.266) Changing the LC_CTYPE category causes the conversion state of these
|
|
|
|
|
|
functions to be indeterminate.
|
|
|
|
|
|
7.20.7.1 The mblen function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int mblen(const char *s, size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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, s, n);
|
|
|
|
|
|
3 The implementation shall behave as if no library function calls the mblen function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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 (7.20.7.2).
|
|
|
|
|
|
266) 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.
|
|
|
|
|
|
7.20.7.2 The mbtowc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int mbtowc(wchar_t * restrict pwc,
|
|
|
|
|
|
const char * restrict s,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The implementation shall behave as if no library function calls the mbtowc function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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).
|
|
|
|
|
|
5 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
|
|
|
|
|
|
macro.
|
|
|
|
|
|
7.20.7.3 The wctomb function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
int wctomb(char *s, wchar_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The implementation shall behave as if no library function calls the wctomb function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
|
|
|
|
|
|
7.20.8 Multibyte/wide string conversion functions
|
|
|
|
|
|
1 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
|
|
|
|
|
|
the current locale.
|
|
|
|
|
|
7.20.8.1 The mbstowcs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
size_t mbstowcs(wchar_t * restrict pwcs,
|
|
|
|
|
|
const char * restrict s,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.267)
|
|
|
|
|
|
267) The array will not be null-terminated if the value returned is n.
|
|
|
|
|
|
7.20.8.2 The wcstombs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdlib.h>
|
|
|
|
|
|
size_t wcstombs(char * restrict s,
|
|
|
|
|
|
const wchar_t * restrict pwcs,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.267)
|
|
|
|
|
|
|
|
|
|
|
|
7.21 String handling <string.h>
|
|
|
|
|
|
7.21.1 String function conventions
|
|
|
|
|
|
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
|
2012-01-17 03:07:01 +01:00
|
|
|
|
of character type.268) The type is size_t and the macro is NULL (both described in 7.17).
|
|
|
|
|
|
Various methods are used for determining the lengths of the arrays, but in all cases
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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.
|
|
|
|
|
|
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 7.1.4. 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.
|
|
|
|
|
|
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).
|
|
|
|
|
|
7.21.2 Copying functions
|
|
|
|
|
|
7.21.2.1 The memcpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
void *memcpy(void * restrict s1,
|
|
|
|
|
|
const void * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The memcpy function returns the value of s1.
|
|
|
|
|
|
268) See ``future library directions'' (7.26.11).
|
|
|
|
|
|
7.21.2.2 The memmove function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
void *memmove(void *s1, const void *s2, size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The memmove function returns the value of s1.
|
|
|
|
|
|
7.21.2.3 The strcpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strcpy(char * restrict s1,
|
|
|
|
|
|
const char * restrict s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The strcpy function returns the value of s1.
|
|
|
|
|
|
7.21.2.4 The strncpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strncpy(char * restrict s1,
|
|
|
|
|
|
const char * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
s1.269) If copying takes place between objects that overlap, the behavior is undefined.
|
|
|
|
|
|
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
|
|
|
|
|
|
4 The strncpy function returns the value of s1.
|
|
|
|
|
|
7.21.3 Concatenation functions
|
|
|
|
|
|
7.21.3.1 The strcat function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strcat(char * restrict s1,
|
|
|
|
|
|
const char * restrict s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The strcat function returns the value of s1.
|
|
|
|
|
|
7.21.3.2 The strncat function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strncat(char * restrict s1,
|
|
|
|
|
|
const char * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.270) If copying
|
|
|
|
|
|
|
|
|
|
|
|
269) 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.
|
|
|
|
|
|
270) Thus, the maximum number of characters that can end up in the array pointed to by s1 is
|
|
|
|
|
|
strlen(s1)+n+1.
|
|
|
|
|
|
takes place between objects that overlap, the behavior is undefined.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The strncat function returns the value of s1.
|
|
|
|
|
|
Forward references: the strlen function (7.21.6.3).
|
|
|
|
|
|
7.21.4 Comparison functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.21.4.1 The memcmp function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
int memcmp(const void *s1, const void *s2, size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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 s2.271)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.21.4.2 The strcmp function
|
|
|
|
|
|
Synopsis
|
|
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1 #include <string.h>
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int strcmp(const char *s1, const char *s2);
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Description
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2 The strcmp function compares the string pointed to by s1 to the string pointed to by
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s2.
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Returns
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3 The strcmp function returns an integer greater than, equal to, or less than zero,
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accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
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271) The contents of ``holes'' used as padding for purposes of alignment within structure objects are
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indeterminate. Strings shorter than their allocated space and unions may also cause problems in
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comparison.
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pointed to by s2.
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7.21.4.3 The strcoll function
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Synopsis
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1 #include <string.h>
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int strcoll(const char *s1, const char *s2);
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Description
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2 The strcoll function compares the string pointed to by s1 to the string pointed to by
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s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
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Returns
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3 The strcoll function returns an integer greater than, equal to, or less than zero,
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accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
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pointed to by s2 when both are interpreted as appropriate to the current locale.
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7.21.4.4 The strncmp function
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Synopsis
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1 #include <string.h>
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int strncmp(const char *s1, const char *s2, size_t n);
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Description
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2 The strncmp function compares not more than n characters (characters that follow a
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null character are not compared) from the array pointed to by s1 to the array pointed to
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by s2.
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Returns
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3 The strncmp function returns an integer greater than, equal to, or less than zero,
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accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
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to, or less than the possibly null-terminated array pointed to by s2.
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7.21.4.5 The strxfrm function
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Synopsis
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1 #include <string.h>
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size_t strxfrm(char * restrict s1,
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const char * restrict s2,
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size_t n);
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Description
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2 The strxfrm function transforms the string pointed to by s2 and places the resulting
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string into the array pointed to by s1. The transformation is such that if the strcmp
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function is applied to two transformed strings, it returns a value greater than, equal to, or
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less than zero, corresponding to the result of the strcoll function applied to the same
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two original strings. No more than n characters are placed into the resulting array
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pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
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be a null pointer. If copying takes place between objects that overlap, the behavior is
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undefined.
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Returns
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3 The strxfrm function returns the length of the transformed string (not including the
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terminating null character). If the value returned is n or more, the contents of the array
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pointed to by s1 are indeterminate.
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4 EXAMPLE The value of the following expression is the size of the array needed to hold the
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transformation of the string pointed to by s.
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1 + strxfrm(NULL, s, 0)
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7.21.5 Search functions
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7.21.5.1 The memchr function
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Synopsis
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|
|
1 #include <string.h>
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void *memchr(const void *s, int c, size_t n);
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Description
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2 The memchr function locates the first occurrence of c (converted to an unsigned
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|
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char) in the initial n characters (each interpreted as unsigned char) of the object
|
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|
|
pointed to by s.
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Returns
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3 The memchr function returns a pointer to the located character, or a null pointer if the
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character does not occur in the object.
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7.21.5.2 The strchr function
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|
|
Synopsis
|
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|
|
1 #include <string.h>
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|
|
|
char *strchr(const char *s, int c);
|
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|
|
|
Description
|
|
|
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|
|
2 The strchr function locates the first occurrence of c (converted to a char) in the
|
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|
|
string pointed to by s. The terminating null character is considered to be part of the
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string.
|
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Returns
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|
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3 The strchr function returns a pointer to the located character, or a null pointer if the
|
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|
character does not occur in the string.
|
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|
7.21.5.3 The strcspn function
|
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|
|
Synopsis
|
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|
|
1 #include <string.h>
|
|
|
|
|
|
size_t strcspn(const char *s1, const char *s2);
|
|
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|
|
|
Description
|
|
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|
|
|
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
|
|
|
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|
|
s2.
|
|
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|
|
|
Returns
|
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|
|
3 The strcspn function returns the length of the segment.
|
|
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|
7.21.5.4 The strpbrk function
|
|
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|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strpbrk(const char *s1, const char *s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The strpbrk function returns a pointer to the character, or a null pointer if no character
|
|
|
|
|
|
from s2 occurs in s1.
|
|
|
|
|
|
7.21.5.5 The strrchr function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strrchr(const char *s, int c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
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|
|
|
Returns
|
|
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|
|
|
3 The strrchr function returns a pointer to the character, or a null pointer if c does not
|
|
|
|
|
|
occur in the string.
|
|
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|
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|
|
|
7.21.5.6 The strspn function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
size_t strspn(const char *s1, const char *s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The strspn function returns the length of the segment.
|
|
|
|
|
|
7.21.5.7 The strstr function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strstr(const char *s1, const char *s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.21.5.8 The strtok function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strtok(char * restrict s1,
|
|
|
|
|
|
const char * restrict s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 The implementation shall behave as if no library function calls the strtok function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
7 The strtok function returns a pointer to the first character of a token, or a null pointer
|
|
|
|
|
|
if there is no token.
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
7.21.6 Miscellaneous functions
|
|
|
|
|
|
7.21.6.1 The memset function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
void *memset(void *s, int c, size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The memset function returns the value of s.
|
|
|
|
|
|
|
|
|
|
|
|
7.21.6.2 The strerror function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
char *strerror(int errnum);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The implementation shall behave as if no library function calls the strerror function.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.21.6.3 The strlen function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <string.h>
|
|
|
|
|
|
size_t strlen(const char *s);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The strlen function computes the length of the string pointed to by s.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The strlen function returns the number of characters that precede the terminating null
|
|
|
|
|
|
character.
|
|
|
|
|
|
|
|
|
|
|
|
7.22 Type-generic math <tgmath.h>
|
|
|
|
|
|
1 The header <tgmath.h> includes the headers <math.h> and <complex.h> and
|
|
|
|
|
|
defines several type-generic macros.
|
|
|
|
|
|
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.272) 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.273)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
2012-01-23 23:24:51 +01:00
|
|
|
|
corresponding type-generic macro for fabs and cabs is fabs.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
272) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
|
|
|
|
|
|
make available the corresponding ordinary function.
|
|
|
|
|
|
273) If the type of the argument is not compatible with the type of the parameter for the selected function,
|
|
|
|
|
|
the behavior is undefined.
|
|
|
|
|
|
<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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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)
|
|
|
|
|
|
|
|
|
|
|
|
7.23 Date and time <time.h>
|
|
|
|
|
|
7.23.1 Components of time
|
|
|
|
|
|
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.
|
|
|
|
|
|
2 The macros defined are NULL (described in 7.17); and
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The types declared are size_t (described in 7.17);
|
|
|
|
|
|
clock_t
|
|
|
|
|
|
and
|
|
|
|
|
|
time_t
|
|
|
|
|
|
which are arithmetic types capable of representing times; and
|
|
|
|
|
|
struct tm
|
|
|
|
|
|
which holds the components of a calendar time, called the broken-down time.
|
|
|
|
|
|
4 The range and precision of times representable in clock_t and time_t are
|
|
|
|
|
|
implementation-defined. 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.274)
|
|
|
|
|
|
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
|
|
|
|
|
|
274) The range [0, 60] for tm_sec allows for a positive leap second.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.23.2 Time manipulation functions
|
|
|
|
|
|
7.23.2.1 The clock function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
clock_t clock(void);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The clock function determines the processor time used.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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).275)
|
|
|
|
|
|
7.23.2.2 The difftime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
double difftime(time_t time1, time_t time0);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The difftime function computes the difference between two calendar times: time1 -
|
|
|
|
|
|
time0.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The difftime function returns the difference expressed in seconds as a double.
|
|
|
|
|
|
275) 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.
|
|
|
|
|
|
7.23.2.3 The mktime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
time_t mktime(struct tm *timeptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.276) 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
|
|
|
|
|
|
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).
|
|
|
|
|
|
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;
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
276) 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.
|
|
|
|
|
|
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]);
|
|
|
|
|
|
|
|
|
|
|
|
7.23.2.4 The time function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
time_t time(time_t *timer);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The time function determines the current calendar time. The encoding of the value is
|
|
|
|
|
|
unspecified.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.23.3 Time conversion functions
|
|
|
|
|
|
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. The implementation shall behave as if no other library
|
|
|
|
|
|
functions call these functions.
|
|
|
|
|
|
7.23.3.1 The asctime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
char *asctime(const struct tm *timeptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The asctime function returns a pointer to the string.
|
|
|
|
|
|
7.23.3.2 The ctime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
char *ctime(const time_t *timer);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The ctime function returns the pointer returned by the asctime function with that
|
|
|
|
|
|
broken-down time as argument.
|
|
|
|
|
|
Forward references: the localtime function (7.23.3.4).
|
|
|
|
|
|
|
|
|
|
|
|
7.23.3.3 The gmtime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
struct tm *gmtime(const time_t *timer);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The gmtime function converts the calendar time pointed to by timer into a broken-
|
|
|
|
|
|
down time, expressed as UTC.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.23.3.4 The localtime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
struct tm *localtime(const time_t *timer);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The localtime function converts the calendar time pointed to by timer into a
|
|
|
|
|
|
broken-down time, expressed as local time.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.23.3.5 The strftime function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <time.h>
|
|
|
|
|
|
size_t strftime(char * restrict s,
|
|
|
|
|
|
size_t maxsize,
|
|
|
|
|
|
const char * restrict format,
|
|
|
|
|
|
const struct tm * restrict timeptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 7.23.1]
|
|
|
|
|
|
%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]
|
2012-01-23 23:24:51 +01:00
|
|
|
|
%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]
|
2012-01-16 16:34:32 +01:00
|
|
|
|
%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]
|
2012-01-23 23:24:51 +01:00
|
|
|
|
%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]
|
2012-01-16 16:34:32 +01:00
|
|
|
|
%x is replaced by the locale's appropriate date representation. [all specified in 7.23.1]
|
|
|
|
|
|
%X is replaced by the locale's appropriate time representation. [all specified in 7.23.1]
|
|
|
|
|
|
%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 %.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 If a conversion specifier is not one of the above, the behavior is undefined.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.24 Extended multibyte and wide character utilities <wchar.h>
|
|
|
|
|
|
7.24.1 Introduction
|
|
|
|
|
|
1 The header <wchar.h> declares four data types, one tag, four macros, and many
|
|
|
|
|
|
functions.277)
|
|
|
|
|
|
2 The types declared are wchar_t and size_t (both described in 7.17);
|
|
|
|
|
|
mbstate_t
|
|
|
|
|
|
which is an 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);278) and
|
|
|
|
|
|
struct tm
|
|
|
|
|
|
which is declared as an incomplete structure type (the contents are described in 7.23.1).
|
|
|
|
|
|
3 The macros defined are NULL (described in 7.17); WCHAR_MIN and WCHAR_MAX
|
|
|
|
|
|
(described in 7.18.3); 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.279) 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.
|
|
|
|
|
|
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;
|
|
|
|
|
|
277) See ``future library directions'' (7.26.12).
|
|
|
|
|
|
278) wchar_t and wint_t can be the same integer type.
|
|
|
|
|
|
279) The value of the macro WEOF may differ from that of EOF and need not be negative.
|
|
|
|
|
|
-- Functions for wide string date and time conversion; and
|
|
|
|
|
|
-- Functions that provide extended capabilities for conversion between multibyte and
|
|
|
|
|
|
wide character sequences.
|
|
|
|
|
|
5 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.
|
|
|
|
|
|
7.24.2 Formatted wide character input/output functions
|
|
|
|
|
|
1 The formatted wide character input/output functions shall behave as if there is a sequence
|
|
|
|
|
|
point after the actions associated with each specifier.280)
|
|
|
|
|
|
7.24.2.1 The fwprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int fwprintf(FILE * restrict stream,
|
|
|
|
|
|
const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
280) The fwprintf functions perform writes to memory for the %n specifier.
|
|
|
|
|
|
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.281)
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.)282)
|
|
|
|
|
|
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,
|
|
|
|
|
|
|
|
|
|
|
|
281) Note that 0 is taken as a flag, not as the beginning of a field width.
|
|
|
|
|
|
282) The results of all floating conversions of a negative zero, and of negative values that round to zero,
|
|
|
|
|
|
include a minus sign.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
2012-01-23 23:24:51 +01:00
|
|
|
|
nan, respectively.283)
|
|
|
|
|
|
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 character284) 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
|
|
|
|
|
|
283) 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.
|
|
|
|
|
|
284) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
distinguish285) 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-
|
|
|
|
|
|
|
|
|
|
|
|
285) 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.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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 %%.
|
|
|
|
|
|
9 If a conversion specification is invalid, the behavior is undefined.286) If any argument is
|
|
|
|
|
|
not the correct type for the corresponding conversion specification, the behavior is
|
|
|
|
|
|
undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.287) 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
|
|
|
|
|
|
14 The fwprintf function returns the number of wide characters transmitted, or a negative
|
|
|
|
|
|
value if an output or encoding error occurred.
|
|
|
|
|
|
|
|
|
|
|
|
286) See ``future library directions'' (7.26.12).
|
|
|
|
|
|
287) 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.
|
|
|
|
|
|
Environmental limits
|
|
|
|
|
|
15 The number of wide characters that can be produced by any single conversion shall be at
|
|
|
|
|
|
least 4095.
|
|
|
|
|
|
16 EXAMPLE To print a date and time in the form ``Sunday, July 3, 10:02'' followed by 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 (7.24.6.1.1), the mbrtowc function
|
|
|
|
|
|
(7.24.6.3.2).
|
2012-01-17 03:07:01 +01:00
|
|
|
|
7.24.2.2 The fwscanf function
|
2012-01-16 16:34:32 +01:00
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int fwscanf(FILE * restrict stream,
|
|
|
|
|
|
const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 The fwscanf function executes each directive of the format in turn. 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).
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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:
|
|
|
|
|
|
8 Input white-space wide characters (as specified by the iswspace function) are skipped,
|
|
|
|
|
|
unless the specification includes a [, c, or n specifier.288)
|
|
|
|
|
|
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.289) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
288) These white-space wide characters are not counted against a specified field width.
|
|
|
|
|
|
289) 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.
|
|
|
|
|
|
object does not have an appropriate type, or if the result of the conversion cannot be
|
|
|
|
|
|
represented in the object, the behavior is undefined.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 %%.
|
|
|
|
|
|
13 If a conversion specification is invalid, the behavior is undefined.290)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
16 The fwscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
290) See ``future library directions'' (7.26.12).
|
|
|
|
|
|
Forward references: the wcstod, wcstof, and wcstold functions (7.24.4.1.1), the
|
|
|
|
|
|
wcstol, wcstoll, wcstoul, and wcstoull functions (7.24.4.1.2), the wcrtomb
|
|
|
|
|
|
function (7.24.6.3.3).
|
|
|
|
|
|
7.24.2.3 The swprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int swprintf(wchar_t * restrict s,
|
|
|
|
|
|
size_t n,
|
|
|
|
|
|
const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.2.4 The swscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int swscanf(const wchar_t * restrict s,
|
|
|
|
|
|
const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The swscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
|
|
|
|
|
|
7.24.2.5 The vfwprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vfwprintf(FILE * restrict stream,
|
|
|
|
|
|
const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vfwprintf function returns the number of wide characters transmitted, or a
|
|
|
|
|
|
negative value if an output or encoding error occurred.
|
|
|
|
|
|
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);
|
|
|
|
|
|
}
|
|
|
|
|
|
291) As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
|
|
|
|
|
|
invoke the va_arg macro, the value of arg after the return is indeterminate.
|
|
|
|
|
|
7.24.2.6 The vfwscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vfwscanf(FILE * restrict stream,
|
|
|
|
|
|
const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vfwscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.24.2.7 The vswprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vswprintf(wchar_t * restrict s,
|
|
|
|
|
|
size_t n,
|
|
|
|
|
|
const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.2.8 The vswscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vswscanf(const wchar_t * restrict s,
|
|
|
|
|
|
const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vswscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.24.2.9 The vwprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vwprintf(const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vwprintf function returns the number of wide characters transmitted, or a negative
|
|
|
|
|
|
value if an output or encoding error occurred.
|
|
|
|
|
|
|
|
|
|
|
|
7.24.2.10 The vwscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdarg.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int vwscanf(const wchar_t * restrict format,
|
|
|
|
|
|
va_list arg);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.291)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The vwscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.24.2.11 The wprintf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int wprintf(const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wprintf function is equivalent to fwprintf with the argument stdout
|
|
|
|
|
|
interposed before the arguments to wprintf.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The wprintf function returns the number of wide characters transmitted, or a negative
|
|
|
|
|
|
value if an output or encoding error occurred.
|
|
|
|
|
|
7.24.2.12 The wscanf function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int wscanf(const wchar_t * restrict format, ...);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wscanf function is equivalent to fwscanf with the argument stdin interposed
|
|
|
|
|
|
before the arguments to wscanf.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The wscanf function returns the value of the macro EOF if an input failure occurs
|
|
|
|
|
|
before any conversion. 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.
|
|
|
|
|
|
7.24.3 Wide character input/output functions
|
|
|
|
|
|
7.24.3.1 The fgetwc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wint_t fgetwc(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.292)
|
|
|
|
|
|
7.24.3.2 The fgetws function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wchar_t *fgetws(wchar_t * restrict s,
|
|
|
|
|
|
int n, FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
292) 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.3.3 The fputwc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wint_t fputwc(wchar_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.3.4 The fputws function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int fputws(const wchar_t * restrict s,
|
|
|
|
|
|
FILE * restrict stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
|
|
|
|
|
|
returns a nonnegative value.
|
|
|
|
|
|
7.24.3.5 The fwide function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
int fwide(FILE *stream, int mode);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.293)
|
|
|
|
|
|
Otherwise, mode is zero and the function does not alter the orientation of the stream.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.3.6 The getwc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wint_t getwc(FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The getwc function returns the next wide character from the input stream pointed to by
|
|
|
|
|
|
stream, or WEOF.
|
|
|
|
|
|
7.24.3.7 The getwchar function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wint_t getwchar(void);
|
|
|
|
|
|
293) If the orientation of the stream has already been determined, fwide does not change it.
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The getwchar function is equivalent to getwc with the argument stdin.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The getwchar function returns the next wide character from the input stream pointed to
|
|
|
|
|
|
by stdin, or WEOF.
|
|
|
|
|
|
7.24.3.8 The putwc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wint_t putwc(wchar_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The putwc function returns the wide character written, or WEOF.
|
|
|
|
|
|
7.24.3.9 The putwchar function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wint_t putwchar(wchar_t c);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The putwchar function is equivalent to putwc with the second argument stdout.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The putwchar function returns the character written, or WEOF.
|
|
|
|
|
|
7.24.3.10 The ungetwc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <stdio.h>
|
|
|
|
|
|
#include <wchar.h>
|
|
|
|
|
|
wint_t ungetwc(wint_t c, FILE *stream);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
|
|
|
|
|
|
unchanged.
|
|
|
|
|
|
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
|
|
|
|
|
|
6 The ungetwc function returns the wide character pushed back, or WEOF if the operation
|
|
|
|
|
|
fails.
|
|
|
|
|
|
7.24.4 General wide string utilities
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 7.1.4. 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.
|
|
|
|
|
|
|
|
|
|
|
|
7.24.4.1 Wide string numeric conversion functions
|
|
|
|
|
|
7.24.4.1.1 The wcstod, wcstof, and wcstold functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
double wcstod(const wchar_t * restrict nptr,
|
|
|
|
|
|
wchar_t ** restrict endptr);
|
|
|
|
|
|
float wcstof(const wchar_t * restrict nptr,
|
|
|
|
|
|
wchar_t ** restrict endptr);
|
|
|
|
|
|
long double wcstold(const wchar_t * restrict nptr,
|
|
|
|
|
|
wchar_t ** restrict endptr);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.4.4.2;
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
6.4.4.2;
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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
|
|
|
|
|
|
6.4.4.2, 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.294) 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 sequences is implementation-defined.295) A pointer to the
|
|
|
|
|
|
final wide string is stored in the object pointed to by endptr, provided that endptr is
|
|
|
|
|
|
not a null pointer.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
|
|
|
|
accepted.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
294) 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 F.5); 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.
|
|
|
|
|
|
295) An implementation may use the n-wchar sequence to determine extra information to be represented in
|
|
|
|
|
|
the NaN's significand.
|
|
|
|
|
|
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.296)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
10 The 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, 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 (7.12.1), 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.
|
|
|
|
|
|
296) 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.
|
|
|
|
|
|
7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.4.4.1,
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 6.4.4.1. 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.
|
|
|
|
|
|
6 In other than the "C" locale, additional locale-specific subject sequence forms may be
|
|
|
|
|
|
accepted.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.4.2 Wide string copying functions
|
|
|
|
|
|
7.24.4.2.1 The wcscpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wcscpy(wchar_t * restrict s1,
|
|
|
|
|
|
const wchar_t * restrict s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The wcscpy function returns the value of s1.
|
|
|
|
|
|
7.24.4.2.2 The wcsncpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wcsncpy(wchar_t * restrict s1,
|
|
|
|
|
|
const wchar_t * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
s1.297)
|
|
|
|
|
|
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
|
|
|
|
|
|
4 The wcsncpy function returns the value of s1.
|
|
|
|
|
|
7.24.4.2.3 The wmemcpy function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wmemcpy(wchar_t * restrict s1,
|
|
|
|
|
|
const wchar_t * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
|
|
|
|
|
|
object pointed to by s1.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The wmemcpy function returns the value of s1.
|
|
|
|
|
|
297) 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.
|
|
|
|
|
|
7.24.4.2.4 The wmemmove function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The wmemmove function returns the value of s1.
|
|
|
|
|
|
7.24.4.3 Wide string concatenation functions
|
|
|
|
|
|
7.24.4.3.1 The wcscat function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wcscat(wchar_t * restrict s1,
|
|
|
|
|
|
const wchar_t * restrict s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The wcscat function returns the value of s1.
|
|
|
|
|
|
7.24.4.3.2 The wcsncat function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
wchar_t *wcsncat(wchar_t * restrict s1,
|
|
|
|
|
|
const wchar_t * restrict s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.298)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
3 The wcsncat function returns the value of s1.
|
|
|
|
|
|
7.24.4.4 Wide string comparison functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.4.4.1 The wcscmp function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int wcscmp(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wcscmp function compares the wide string pointed to by s1 to the wide string
|
|
|
|
|
|
pointed to by s2.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.4.4.2 The wcscoll function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int wcscoll(const wchar_t *s1, const wchar_t *s2);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
298) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
|
|
|
|
|
|
wcslen(s1)+n+1.
|
|
|
|
|
|
wide string pointed to by s2 when both are interpreted as appropriate to the current
|
|
|
|
|
|
locale.
|
|
|
|
|
|
7.24.4.4.3 The wcsncmp function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
int wcsncmp(const wchar_t *s1, const wchar_t *s2,
|
|
|
|
|
|
size_t n);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.4.4.4 The wcsxfrm function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
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size_t wcsxfrm(wchar_t * restrict s1,
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const wchar_t * restrict s2,
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size_t n);
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Description
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2 The wcsxfrm function transforms the wide string pointed to by s2 and places the
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resulting wide string into the array pointed to by s1. The transformation is such that if
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the wcscmp function is applied to two transformed wide strings, it returns a value greater
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than, equal to, or less than zero, corresponding to the result of the wcscoll function
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applied to the same two original wide strings. No more than n wide characters are placed
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into the resulting array pointed to by s1, including the terminating null wide character. If
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n is zero, s1 is permitted to be a null pointer.
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Returns
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3 The wcsxfrm function returns the length of the transformed wide string (not including
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the terminating null wide character). If the value returned is n or greater, the contents of
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the array pointed to by s1 are indeterminate.
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4 EXAMPLE The value of the following expression is the length of the array needed to hold the
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transformation of the wide string pointed to by s:
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1 + wcsxfrm(NULL, s, 0)
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7.24.4.4.5 The wmemcmp function
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Synopsis
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1 #include <wchar.h>
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int wmemcmp(const wchar_t *s1, const wchar_t *s2,
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size_t n);
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Description
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2 The wmemcmp function compares the first n wide characters of the object pointed to by
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s1 to the first n wide characters of the object pointed to by s2.
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Returns
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3 The wmemcmp function returns an integer greater than, equal to, or less than zero,
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accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
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pointed to by s2.
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7.24.4.5 Wide string search functions
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7.24.4.5.1 The wcschr function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wcschr(const wchar_t *s, wchar_t c);
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Description
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2 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
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The terminating null wide character is considered to be part of the wide string.
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Returns
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3 The wcschr function returns a pointer to the located wide character, or a null pointer if
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the wide character does not occur in the wide string.
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7.24.4.5.2 The wcscspn function
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Synopsis
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1 #include <wchar.h>
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size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
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Description
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2 The wcscspn function computes the length of the maximum initial segment of the wide
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string pointed to by s1 which consists entirely of wide characters not from the wide
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string pointed to by s2.
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Returns
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3 The wcscspn function returns the length of the segment.
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7.24.4.5.3 The wcspbrk function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
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Description
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2 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
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any wide character from the wide string pointed to by s2.
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Returns
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3 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
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no wide character from s2 occurs in s1.
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7.24.4.5.4 The wcsrchr function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
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Description
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2 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
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s. The terminating null wide character is considered to be part of the wide string.
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Returns
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3 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
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not occur in the wide string.
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7.24.4.5.5 The wcsspn function
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Synopsis
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1 #include <wchar.h>
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size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
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Description
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2 The wcsspn function computes the length of the maximum initial segment of the wide
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string pointed to by s1 which consists entirely of wide characters from the wide string
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pointed to by s2.
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Returns
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3 The wcsspn function returns the length of the segment.
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7.24.4.5.6 The wcsstr function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
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Description
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2 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
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the sequence of wide characters (excluding the terminating null wide character) in the
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wide string pointed to by s2.
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Returns
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3 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
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wide string is not found. If s2 points to a wide string with zero length, the function
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returns s1.
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7.24.4.5.7 The wcstok function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wcstok(wchar_t * restrict s1,
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const wchar_t * restrict s2,
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wchar_t ** restrict ptr);
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Description
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2 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
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a sequence of tokens, each of which is delimited by a wide character from the wide string
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pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
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which the wcstok function stores information necessary for it to continue scanning the
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same wide string.
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3 The first call in a sequence has a non-null first argument and stores an initial value in the
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object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
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the object pointed to by ptr is required to have the value stored by the previous call in
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the sequence, which is then updated. The separator wide string pointed to by s2 may be
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different from call to call.
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4 The first call in the sequence searches the wide string pointed to by s1 for the first wide
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character that is not contained in the current separator wide string pointed to by s2. If no
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such wide character is found, then there are no tokens in the wide string pointed to by s1
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and the wcstok function returns a null pointer. If such a wide character is found, it is
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the start of the first token.
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5 The wcstok function then searches from there for a wide character that is contained in
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the current separator wide string. If no such wide character is found, the current token
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extends to the end of the wide string pointed to by s1, and subsequent searches in the
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same wide string for a token return a null pointer. If such a wide character is found, it is
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overwritten by a null wide character, which terminates the current token.
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6 In all cases, the wcstok function stores sufficient information in the pointer pointed to
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by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
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value for ptr, shall start searching just past the element overwritten by a null wide
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character (if any).
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Returns
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7 The wcstok function returns a pointer to the first wide character of a token, or a null
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pointer if there is no token.
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8 EXAMPLE
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#include <wchar.h>
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static wchar_t str1[] = L"?a???b,,,#c";
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static wchar_t str2[] = L"\t \t";
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wchar_t *t, *ptr1, *ptr2;
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t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
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t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
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t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
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t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
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t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
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7.24.4.5.8 The wmemchr function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wmemchr(const wchar_t *s, wchar_t c,
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size_t n);
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Description
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2 The wmemchr function locates the first occurrence of c in the initial n wide characters of
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the object pointed to by s.
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Returns
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3 The wmemchr function returns a pointer to the located wide character, or a null pointer if
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the wide character does not occur in the object.
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7.24.4.6 Miscellaneous functions
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7.24.4.6.1 The wcslen function
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Synopsis
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1 #include <wchar.h>
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size_t wcslen(const wchar_t *s);
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Description
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2 The wcslen function computes the length of the wide string pointed to by s.
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Returns
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3 The wcslen function returns the number of wide characters that precede the terminating
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null wide character.
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7.24.4.6.2 The wmemset function
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Synopsis
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1 #include <wchar.h>
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wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
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Description
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2 The wmemset function copies the value of c into each of the first n wide characters of
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the object pointed to by s.
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Returns
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3 The wmemset function returns the value of s.
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7.24.5 Wide character time conversion functions
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7.24.5.1 The wcsftime function
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Synopsis
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1 #include <time.h>
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#include <wchar.h>
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size_t wcsftime(wchar_t * restrict s,
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size_t maxsize,
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const wchar_t * restrict format,
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const struct tm * restrict timeptr);
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Description
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2 The wcsftime function is equivalent to the strftime function, except that:
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-- The argument s points to the initial element of an array of wide characters into which
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the generated output is to be placed.
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-- The argument maxsize indicates the limiting number of wide characters.
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-- The argument format is a wide string and the conversion specifiers are replaced by
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corresponding sequences of wide characters.
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-- The return value indicates the number of wide characters.
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Returns
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3 If the total number of resulting wide characters including the terminating null wide
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character is not more than maxsize, the wcsftime function returns the number of
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wide characters placed into the array pointed to by s not including the terminating null
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wide character. Otherwise, zero is returned and the contents of the array are
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indeterminate.
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7.24.6 Extended multibyte/wide character conversion utilities
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1 The header <wchar.h> declares an extended set of functions useful for conversion
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between multibyte characters and wide characters.
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2012-01-17 03:07:01 +01:00
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2 Most of the following functions -- those that are listed as ``restartable'', 7.24.6.3 and 7.24.6.4
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-- take as a last argument a pointer to an object of type mbstate_t that is used
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2012-01-16 16:34:32 +01:00
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to describe the current conversion state from a particular multibyte character sequence to
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a wide character sequence (or the reverse) under the rules of a particular setting for the
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LC_CTYPE category of the current locale.
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3 The initial conversion state corresponds, for a conversion in either direction, to the
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beginning of a new multibyte character in the initial shift state. A zero-valued
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mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
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valued mbstate_t object can be used to initiate conversion involving any multibyte
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character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
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been altered by any of the functions described in this subclause, and is then used with a
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different multibyte character sequence, or in the other conversion direction, or with a
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different LC_CTYPE category setting than on earlier function calls, the behavior is
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undefined.299)
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4 On entry, each function takes the described conversion state (either internal or pointed to
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by an argument) as current. The conversion state described by the pointed-to object is
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altered as needed to track the shift state, and the position within a multibyte character, for
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the associated multibyte character sequence.
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299) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
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mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
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character string.
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7.24.6.1 Single-byte/wide character conversion functions
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7.24.6.1.1 The btowc function
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Synopsis
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1 #include <stdio.h>
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#include <wchar.h>
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wint_t btowc(int c);
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Description
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2 The btowc function determines whether c constitutes a valid single-byte character in the
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initial shift state.
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Returns
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3 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
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does not constitute a valid single-byte character in the initial shift state. Otherwise, it
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returns the wide character representation of that character.
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7.24.6.1.2 The wctob function
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Synopsis
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1 #include <stdio.h>
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#include <wchar.h>
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int wctob(wint_t c);
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Description
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2 The wctob function determines whether c corresponds to a member of the extended
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character set whose multibyte character representation is a single byte when in the initial
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shift state.
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Returns
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3 The wctob function returns EOF if c does not correspond to a multibyte character with
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length one in the initial shift state. Otherwise, it returns the single-byte representation of
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that character as an unsigned char converted to an int.
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7.24.6.2 Conversion state functions
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7.24.6.2.1 The mbsinit function
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Synopsis
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1 #include <wchar.h>
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int mbsinit(const mbstate_t *ps);
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Description
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2 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
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mbstate_t object describes an initial conversion state.
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Returns
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|
|
|
3 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
|
|
|
|
|
|
describes an initial conversion state; otherwise, it returns zero.
|
|
|
|
|
|
7.24.6.3 Restartable multibyte/wide character conversion functions
|
|
|
|
|
|
1 These functions differ from the corresponding multibyte character functions of 7.20.7
|
|
|
|
|
|
(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 implementation behaves as if no
|
|
|
|
|
|
library function calls these functions with a null pointer for ps.
|
|
|
|
|
|
2 Also unlike their corresponding functions, the return value does not represent whether the
|
|
|
|
|
|
encoding is state-dependent.
|
|
|
|
|
|
7.24.6.3.1 The mbrlen function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
size_t mbrlen(const char * restrict s,
|
|
|
|
|
|
size_t n,
|
|
|
|
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
3 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
|
|
|
|
|
|
or (size_t)(-1).
|
|
|
|
|
|
Forward references: the mbrtowc function (7.24.6.3.2).
|
|
|
|
|
|
|
|
|
|
|
|
7.24.6.3.2 The mbrtowc function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
size_t mbrtowc(wchar_t * restrict pwc,
|
|
|
|
|
|
const char * restrict s,
|
|
|
|
|
|
size_t n,
|
|
|
|
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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).300)
|
|
|
|
|
|
(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.
|
|
|
|
|
|
|
|
|
|
|
|
300) 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).
|
|
|
|
|
|
7.24.6.3.3 The wcrtomb function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
size_t wcrtomb(char * restrict s,
|
|
|
|
|
|
wchar_t wc,
|
|
|
|
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.24.6.4 Restartable multibyte/wide string conversion functions
|
|
|
|
|
|
1 These functions differ from the corresponding multibyte string functions of 7.20.8
|
|
|
|
|
|
(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 implementation behaves as if no library function calls
|
|
|
|
|
|
these functions with a null pointer for ps.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.24.6.4.1 The mbsrtowcs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
size_t mbsrtowcs(wchar_t * restrict dst,
|
|
|
|
|
|
const char ** restrict src,
|
|
|
|
|
|
size_t len,
|
|
|
|
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.301) Each conversion takes
|
|
|
|
|
|
place as if by a call to the mbrtowc function.
|
|
|
|
|
|
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
|
|
|
|
|
|
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).
|
|
|
|
|
|
301) Thus, the value of len is ignored if dst is a null pointer.
|
|
|
|
|
|
7.24.6.4.2 The wcsrtombs function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wchar.h>
|
|
|
|
|
|
size_t wcsrtombs(char * restrict dst,
|
|
|
|
|
|
const wchar_t ** restrict src,
|
|
|
|
|
|
size_t len,
|
|
|
|
|
|
mbstate_t * restrict ps);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.302)
|
|
|
|
|
|
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
|
|
|
|
|
|
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).
|
|
|
|
|
|
302) 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.
|
|
|
|
|
|
7.25 Wide character classification and mapping utilities <wctype.h>
|
|
|
|
|
|
7.25.1 Introduction
|
|
|
|
|
|
1 The header <wctype.h> declares three data types, one macro, and many functions.303)
|
|
|
|
|
|
2 The types declared are
|
|
|
|
|
|
wint_t
|
|
|
|
|
|
described in 7.24.1;
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 The macro defined is WEOF (described in 7.24.1).
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
2012-01-23 23:24:51 +01:00
|
|
|
|
this argument has any other value, the behavior is undefined.
|
|
|
|
|
|
6 The behavior of these functions is affected by the LC_CTYPE category of the current
|
|
|
|
|
|
locale.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
303) See ``future library directions'' (7.26.13).
|
|
|
|
|
|
7.25.2 Wide character classification utilities
|
|
|
|
|
|
1 The header <wctype.h> declares several functions useful for classifying wide
|
|
|
|
|
|
characters.
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.2.1 Wide character classification functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 7.4.1 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.304)
|
|
|
|
|
|
Forward references: the wctob function (7.24.6.1.2).
|
|
|
|
|
|
7.25.2.1.1 The iswalnum function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswalnum(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswalnum function tests for any wide character for which iswalpha or
|
|
|
|
|
|
iswdigit is true.
|
|
|
|
|
|
7.25.2.1.2 The iswalpha function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswalpha(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
304) 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.
|
|
|
|
|
|
wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
|
|
|
|
|
|
is true.305)
|
|
|
|
|
|
7.25.2.1.3 The iswblank function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswblank(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.2.1.4 The iswcntrl function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswcntrl(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswcntrl function tests for any control wide character.
|
|
|
|
|
|
7.25.2.1.5 The iswdigit function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswdigit(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswdigit function tests for any wide character that corresponds to a decimal-digit
|
|
|
|
|
|
character (as defined in 5.2.1).
|
|
|
|
|
|
7.25.2.1.6 The iswgraph function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswgraph(wint_t wc);
|
|
|
|
|
|
305) The functions iswlower and iswupper test true or false separately for each of these additional
|
|
|
|
|
|
wide characters; all four combinations are possible.
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswgraph function tests for any wide character for which iswprint is true and
|
|
|
|
|
|
iswspace is false.306)
|
|
|
|
|
|
7.25.2.1.7 The iswlower function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswlower(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.2.1.8 The iswprint function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswprint(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswprint function tests for any printing wide character.
|
|
|
|
|
|
7.25.2.1.9 The iswpunct function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswpunct(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.306)
|
|
|
|
|
|
7.25.2.1.10 The iswspace function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswspace(wint_t wc);
|
|
|
|
|
|
306) Note that the behavior of the iswgraph and iswpunct functions may differ from their
|
|
|
|
|
|
corresponding functions in 7.4.1 with respect to printing, white-space, single-byte execution
|
|
|
|
|
|
characters other than ' '.
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.2.1.11 The iswupper function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswupper(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.2.1.12 The iswxdigit function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswxdigit(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The iswxdigit function tests for any wide character that corresponds to a
|
|
|
|
|
|
hexadecimal-digit character (as defined in 6.4.4.1).
|
|
|
|
|
|
7.25.2.2 Extensible wide character classification functions
|
|
|
|
|
|
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 (7.25.2.1).
|
|
|
|
|
|
7.25.2.2.1 The iswctype function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
int iswctype(wint_t wc, wctype_t desc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 Each of the following expressions has a truth-value equivalent to the call to the wide
|
|
|
|
|
|
character classification function (7.25.2.1) 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
|
|
|
|
|
|
4 The iswctype function returns nonzero (true) if and only if the value of the wide
|
|
|
|
|
|
character wc has the property described by desc.
|
|
|
|
|
|
Forward references: the wctype function (7.25.2.2.2).
|
|
|
|
|
|
7.25.2.2.2 The wctype function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
wctype_t wctype(const char *property);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wctype function constructs a value with type wctype_t that describes a class of
|
|
|
|
|
|
wide characters identified by the string argument property.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.25.3 Wide character case mapping utilities
|
|
|
|
|
|
1 The header <wctype.h> declares several functions useful for mapping wide characters.
|
|
|
|
|
|
7.25.3.1 Wide character case mapping functions
|
|
|
|
|
|
7.25.3.1.1 The towlower function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
wint_t towlower(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The towlower function converts an uppercase letter to a corresponding lowercase letter.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.3.1.2 The towupper function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
wint_t towupper(wint_t wc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The towupper function converts a lowercase letter to a corresponding uppercase letter.
|
|
|
|
|
|
Returns
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.25.3.2 Extensible wide character case mapping functions
|
|
|
|
|
|
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 (7.25.3.1).
|
|
|
|
|
|
|
|
|
|
|
|
7.25.3.2.1 The towctrans function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
wint_t towctrans(wint_t wc, wctrans_t desc);
|
|
|
|
|
|
Description
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 Each of the following expressions behaves the same as the call to the wide character case
|
|
|
|
|
|
mapping function (7.25.3.1) in the comment that follows the expression:
|
|
|
|
|
|
towctrans(wc, wctrans("tolower")) // towlower(wc)
|
|
|
|
|
|
towctrans(wc, wctrans("toupper")) // towupper(wc)
|
|
|
|
|
|
Returns
|
|
|
|
|
|
4 The towctrans function returns the mapped value of wc using the mapping described
|
|
|
|
|
|
by desc.
|
|
|
|
|
|
7.25.3.2.2 The wctrans function
|
|
|
|
|
|
Synopsis
|
|
|
|
|
|
1 #include <wctype.h>
|
|
|
|
|
|
wctrans_t wctrans(const char *property);
|
|
|
|
|
|
Description
|
|
|
|
|
|
2 The wctrans function constructs a value with type wctrans_t that describes a
|
|
|
|
|
|
mapping between wide characters identified by the string argument property.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
7.26 Future library directions
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.26.1 Complex arithmetic <complex.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.26.2 Character handling <ctype.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.26.3 Errors <errno.h>
|
|
|
|
|
|
1 Macros that begin with E and a digit or E and an uppercase letter may be added to the
|
|
|
|
|
|
declarations in the <errno.h> header.
|
|
|
|
|
|
7.26.4 Format conversion of integer types <inttypes.h>
|
|
|
|
|
|
1 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
|
|
|
|
|
|
added to the macros defined in the <inttypes.h> header.
|
|
|
|
|
|
7.26.5 Localization <locale.h>
|
|
|
|
|
|
1 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
|
|
|
|
|
|
the <locale.h> header.
|
|
|
|
|
|
7.26.6 Signal handling <signal.h>
|
|
|
|
|
|
1 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
|
|
|
|
|
|
letter may be added to the definitions in the <signal.h> header.
|
|
|
|
|
|
7.26.7 Boolean type and values <stdbool.h>
|
|
|
|
|
|
1 The ability to undefine and perhaps then redefine the macros bool, true, and false is
|
|
|
|
|
|
an obsolescent feature.
|
|
|
|
|
|
7.26.8 Integer types <stdint.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.26.9 Input/output <stdio.h>
|
|
|
|
|
|
1 Lowercase letters may be added to the conversion specifiers and length modifiers in
|
|
|
|
|
|
fprintf and fscanf. Other characters may be used in extensions.
|
|
|
|
|
|
2 The gets function is obsolescent, and is deprecated.
|
|
|
|
|
|
3 The use of ungetc on a binary stream where the file position indicator is zero prior to
|
|
|
|
|
|
the call is an obsolescent feature.
|
|
|
|
|
|
7.26.10 General utilities <stdlib.h>
|
|
|
|
|
|
1 Function names that begin with str and a lowercase letter may be added to the
|
|
|
|
|
|
declarations in the <stdlib.h> header.
|
|
|
|
|
|
7.26.11 String handling <string.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
7.26.12 Extended multibyte and wide character utilities <wchar.h>
|
|
|
|
|
|
1 Function names that begin with wcs and a lowercase letter may be added to the
|
|
|
|
|
|
declarations in the <wchar.h> header.
|
|
|
|
|
|
2 Lowercase letters may be added to the conversion specifiers and length modifiers in
|
|
|
|
|
|
fwprintf and fwscanf. Other characters may be used in extensions.
|
|
|
|
|
|
7.26.13 Wide character classification and mapping utilities
|
|
|
|
|
|
<wctype.h>
|
|
|
|
|
|
1 Function names that begin with is or to and a lowercase letter may be added to the
|
|
|
|
|
|
declarations in the <wctype.h> header.
|
|
|
|
|
|
|
|
|
|
|
|
Annex A
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
A. Language syntax summary
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 NOTE The notation is described in 6.1.
|
|
|
|
|
|
|
|
|
|
|
|
A.1 Lexical grammar
|
|
|
|
|
|
A.1.1 Lexical elements
|
|
|
|
|
|
(6.4) token:
|
|
|
|
|
|
keyword
|
|
|
|
|
|
identifier
|
|
|
|
|
|
constant
|
|
|
|
|
|
string-literal
|
|
|
|
|
|
punctuator
|
|
|
|
|
|
(6.4) preprocessing-token:
|
|
|
|
|
|
header-name
|
|
|
|
|
|
identifier
|
|
|
|
|
|
pp-number
|
|
|
|
|
|
character-constant
|
|
|
|
|
|
string-literal
|
|
|
|
|
|
punctuator
|
|
|
|
|
|
each non-white-space character that cannot be one of the above
|
|
|
|
|
|
A.1.2 Keywords
|
|
|
|
|
|
(6.4.1) keyword: one of
|
|
|
|
|
|
auto enum restrict unsigned
|
|
|
|
|
|
break extern return void
|
|
|
|
|
|
case float short volatile
|
|
|
|
|
|
char for signed while
|
|
|
|
|
|
const goto sizeof _Bool
|
|
|
|
|
|
continue if static _Complex
|
|
|
|
|
|
default inline struct _Imaginary
|
|
|
|
|
|
do int switch
|
|
|
|
|
|
double long typedef
|
|
|
|
|
|
else register union
|
|
|
|
|
|
|
|
|
|
|
|
A.1.3 Identifiers
|
|
|
|
|
|
(6.4.2.1) identifier:
|
|
|
|
|
|
identifier-nondigit
|
|
|
|
|
|
identifier identifier-nondigit
|
|
|
|
|
|
identifier digit
|
|
|
|
|
|
(6.4.2.1) identifier-nondigit:
|
|
|
|
|
|
nondigit
|
|
|
|
|
|
universal-character-name
|
|
|
|
|
|
other implementation-defined characters
|
|
|
|
|
|
(6.4.2.1) 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
|
|
|
|
|
|
(6.4.2.1) digit: one of
|
|
|
|
|
|
0 1 2 3 4 5 6 7 8 9
|
|
|
|
|
|
A.1.4 Universal character names
|
|
|
|
|
|
(6.4.3) universal-character-name:
|
|
|
|
|
|
\u hex-quad
|
|
|
|
|
|
\U hex-quad hex-quad
|
|
|
|
|
|
(6.4.3) hex-quad:
|
|
|
|
|
|
hexadecimal-digit hexadecimal-digit
|
|
|
|
|
|
hexadecimal-digit hexadecimal-digit
|
|
|
|
|
|
A.1.5 Constants
|
|
|
|
|
|
(6.4.4) constant:
|
|
|
|
|
|
integer-constant
|
|
|
|
|
|
floating-constant
|
|
|
|
|
|
enumeration-constant
|
|
|
|
|
|
character-constant
|
|
|
|
|
|
(6.4.4.1) integer-constant:
|
|
|
|
|
|
decimal-constant integer-suffixopt
|
|
|
|
|
|
octal-constant integer-suffixopt
|
|
|
|
|
|
hexadecimal-constant integer-suffixopt
|
|
|
|
|
|
(6.4.4.1) decimal-constant:
|
|
|
|
|
|
nonzero-digit
|
|
|
|
|
|
decimal-constant digit
|
|
|
|
|
|
(6.4.4.1) octal-constant:
|
|
|
|
|
|
0
|
|
|
|
|
|
octal-constant octal-digit
|
|
|
|
|
|
(6.4.4.1) hexadecimal-constant:
|
|
|
|
|
|
hexadecimal-prefix hexadecimal-digit
|
|
|
|
|
|
hexadecimal-constant hexadecimal-digit
|
|
|
|
|
|
(6.4.4.1) hexadecimal-prefix: one of
|
|
|
|
|
|
0x 0X
|
|
|
|
|
|
(6.4.4.1) nonzero-digit: one of
|
|
|
|
|
|
1 2 3 4 5 6 7 8 9
|
|
|
|
|
|
(6.4.4.1) octal-digit: one of
|
|
|
|
|
|
0 1 2 3 4 5 6 7
|
|
|
|
|
|
(6.4.4.1) hexadecimal-digit: one of
|
|
|
|
|
|
0 1 2 3 4 5 6 7 8 9
|
|
|
|
|
|
a b c d e f
|
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|
|
|
|
A B C D E F
|
|
|
|
|
|
(6.4.4.1) integer-suffix:
|
|
|
|
|
|
unsigned-suffix long-suffixopt
|
|
|
|
|
|
unsigned-suffix long-long-suffix
|
|
|
|
|
|
long-suffix unsigned-suffixopt
|
|
|
|
|
|
long-long-suffix unsigned-suffixopt
|
|
|
|
|
|
(6.4.4.1) unsigned-suffix: one of
|
|
|
|
|
|
u U
|
|
|
|
|
|
(6.4.4.1) long-suffix: one of
|
|
|
|
|
|
l L
|
|
|
|
|
|
(6.4.4.1) long-long-suffix: one of
|
|
|
|
|
|
ll LL
|
|
|
|
|
|
(6.4.4.2) floating-constant:
|
|
|
|
|
|
decimal-floating-constant
|
|
|
|
|
|
hexadecimal-floating-constant
|
|
|
|
|
|
(6.4.4.2) decimal-floating-constant:
|
|
|
|
|
|
fractional-constant exponent-partopt floating-suffixopt
|
|
|
|
|
|
digit-sequence exponent-part floating-suffixopt
|
|
|
|
|
|
|
|
|
|
|
|
(6.4.4.2) hexadecimal-floating-constant:
|
|
|
|
|
|
hexadecimal-prefix hexadecimal-fractional-constant
|
|
|
|
|
|
binary-exponent-part floating-suffixopt
|
|
|
|
|
|
hexadecimal-prefix hexadecimal-digit-sequence
|
|
|
|
|
|
binary-exponent-part floating-suffixopt
|
|
|
|
|
|
(6.4.4.2) fractional-constant:
|
|
|
|
|
|
digit-sequenceopt . digit-sequence
|
|
|
|
|
|
digit-sequence .
|
|
|
|
|
|
(6.4.4.2) exponent-part:
|
|
|
|
|
|
e signopt digit-sequence
|
|
|
|
|
|
E signopt digit-sequence
|
|
|
|
|
|
(6.4.4.2) sign: one of
|
|
|
|
|
|
+ -
|
|
|
|
|
|
(6.4.4.2) digit-sequence:
|
|
|
|
|
|
digit
|
|
|
|
|
|
digit-sequence digit
|
|
|
|
|
|
(6.4.4.2) hexadecimal-fractional-constant:
|
|
|
|
|
|
hexadecimal-digit-sequenceopt .
|
|
|
|
|
|
hexadecimal-digit-sequence
|
|
|
|
|
|
hexadecimal-digit-sequence .
|
|
|
|
|
|
(6.4.4.2) binary-exponent-part:
|
|
|
|
|
|
p signopt digit-sequence
|
|
|
|
|
|
P signopt digit-sequence
|
|
|
|
|
|
(6.4.4.2) hexadecimal-digit-sequence:
|
|
|
|
|
|
hexadecimal-digit
|
|
|
|
|
|
hexadecimal-digit-sequence hexadecimal-digit
|
|
|
|
|
|
(6.4.4.2) floating-suffix: one of
|
|
|
|
|
|
f l F L
|
|
|
|
|
|
(6.4.4.3) enumeration-constant:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
(6.4.4.4) character-constant:
|
|
|
|
|
|
' c-char-sequence '
|
|
|
|
|
|
L' c-char-sequence '
|
|
|
|
|
|
|
|
|
|
|
|
(6.4.4.4) c-char-sequence:
|
|
|
|
|
|
c-char
|
|
|
|
|
|
c-char-sequence c-char
|
|
|
|
|
|
(6.4.4.4) c-char:
|
|
|
|
|
|
any member of the source character set except
|
|
|
|
|
|
the single-quote ', backslash \, or new-line character
|
|
|
|
|
|
escape-sequence
|
|
|
|
|
|
(6.4.4.4) escape-sequence:
|
|
|
|
|
|
simple-escape-sequence
|
|
|
|
|
|
octal-escape-sequence
|
|
|
|
|
|
hexadecimal-escape-sequence
|
|
|
|
|
|
universal-character-name
|
|
|
|
|
|
(6.4.4.4) simple-escape-sequence: one of
|
|
|
|
|
|
\' \" \? \\
|
|
|
|
|
|
\a \b \f \n \r \t \v
|
|
|
|
|
|
(6.4.4.4) octal-escape-sequence:
|
|
|
|
|
|
\ octal-digit
|
|
|
|
|
|
\ octal-digit octal-digit
|
|
|
|
|
|
\ octal-digit octal-digit octal-digit
|
|
|
|
|
|
(6.4.4.4) hexadecimal-escape-sequence:
|
|
|
|
|
|
\x hexadecimal-digit
|
|
|
|
|
|
hexadecimal-escape-sequence hexadecimal-digit
|
|
|
|
|
|
A.1.6 String literals
|
|
|
|
|
|
(6.4.5) string-literal:
|
|
|
|
|
|
" s-char-sequenceopt "
|
|
|
|
|
|
L" s-char-sequenceopt "
|
|
|
|
|
|
(6.4.5) s-char-sequence:
|
|
|
|
|
|
s-char
|
|
|
|
|
|
s-char-sequence s-char
|
|
|
|
|
|
(6.4.5) s-char:
|
|
|
|
|
|
any member of the source character set except
|
|
|
|
|
|
the double-quote ", backslash \, or new-line character
|
|
|
|
|
|
escape-sequence
|
|
|
|
|
|
|
|
|
|
|
|
A.1.7 Punctuators
|
|
|
|
|
|
(6.4.6) punctuator: one of
|
|
|
|
|
|
[ ] ( ) { } . ->
|
|
|
|
|
|
++ -- & * + - ~ !
|
|
|
|
|
|
/ % << >> < > <= >= == != ^ | && ||
|
|
|
|
|
|
? : ; ...
|
|
|
|
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
|
|
|
|
, # ##
|
|
|
|
|
|
<: :> <% %> %: %:%:
|
|
|
|
|
|
A.1.8 Header names
|
|
|
|
|
|
(6.4.7) header-name:
|
|
|
|
|
|
< h-char-sequence >
|
|
|
|
|
|
" q-char-sequence "
|
|
|
|
|
|
(6.4.7) h-char-sequence:
|
|
|
|
|
|
h-char
|
|
|
|
|
|
h-char-sequence h-char
|
|
|
|
|
|
(6.4.7) h-char:
|
|
|
|
|
|
any member of the source character set except
|
|
|
|
|
|
the new-line character and >
|
|
|
|
|
|
(6.4.7) q-char-sequence:
|
|
|
|
|
|
q-char
|
|
|
|
|
|
q-char-sequence q-char
|
|
|
|
|
|
(6.4.7) q-char:
|
|
|
|
|
|
any member of the source character set except
|
|
|
|
|
|
the new-line character and "
|
|
|
|
|
|
A.1.9 Preprocessing numbers
|
|
|
|
|
|
(6.4.8) 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 .
|
|
|
|
|
|
A.2 Phrase structure grammar
|
|
|
|
|
|
A.2.1 Expressions
|
|
|
|
|
|
(6.5.1) primary-expression:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
constant
|
|
|
|
|
|
string-literal
|
|
|
|
|
|
( expression )
|
|
|
|
|
|
(6.5.2) 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 , }
|
|
|
|
|
|
(6.5.2) argument-expression-list:
|
|
|
|
|
|
assignment-expression
|
|
|
|
|
|
argument-expression-list , assignment-expression
|
|
|
|
|
|
(6.5.3) unary-expression:
|
|
|
|
|
|
postfix-expression
|
|
|
|
|
|
++ unary-expression
|
|
|
|
|
|
-- unary-expression
|
|
|
|
|
|
unary-operator cast-expression
|
|
|
|
|
|
sizeof unary-expression
|
|
|
|
|
|
sizeof ( type-name )
|
|
|
|
|
|
(6.5.3) unary-operator: one of
|
|
|
|
|
|
& * + - ~ !
|
|
|
|
|
|
(6.5.4) cast-expression:
|
|
|
|
|
|
unary-expression
|
|
|
|
|
|
( type-name ) cast-expression
|
|
|
|
|
|
(6.5.5) multiplicative-expression:
|
|
|
|
|
|
cast-expression
|
|
|
|
|
|
multiplicative-expression * cast-expression
|
|
|
|
|
|
multiplicative-expression / cast-expression
|
|
|
|
|
|
multiplicative-expression % cast-expression
|
|
|
|
|
|
(6.5.6) additive-expression:
|
|
|
|
|
|
multiplicative-expression
|
|
|
|
|
|
additive-expression + multiplicative-expression
|
|
|
|
|
|
additive-expression - multiplicative-expression
|
|
|
|
|
|
(6.5.7) shift-expression:
|
|
|
|
|
|
additive-expression
|
|
|
|
|
|
shift-expression << additive-expression
|
|
|
|
|
|
shift-expression >> additive-expression
|
|
|
|
|
|
(6.5.8) relational-expression:
|
|
|
|
|
|
shift-expression
|
|
|
|
|
|
relational-expression < shift-expression
|
|
|
|
|
|
relational-expression > shift-expression
|
|
|
|
|
|
relational-expression <= shift-expression
|
|
|
|
|
|
relational-expression >= shift-expression
|
|
|
|
|
|
(6.5.9) equality-expression:
|
|
|
|
|
|
relational-expression
|
|
|
|
|
|
equality-expression == relational-expression
|
|
|
|
|
|
equality-expression != relational-expression
|
|
|
|
|
|
(6.5.10) AND-expression:
|
|
|
|
|
|
equality-expression
|
|
|
|
|
|
AND-expression & equality-expression
|
|
|
|
|
|
(6.5.11) exclusive-OR-expression:
|
|
|
|
|
|
AND-expression
|
|
|
|
|
|
exclusive-OR-expression ^ AND-expression
|
|
|
|
|
|
(6.5.12) inclusive-OR-expression:
|
|
|
|
|
|
exclusive-OR-expression
|
|
|
|
|
|
inclusive-OR-expression | exclusive-OR-expression
|
|
|
|
|
|
(6.5.13) logical-AND-expression:
|
|
|
|
|
|
inclusive-OR-expression
|
|
|
|
|
|
logical-AND-expression && inclusive-OR-expression
|
|
|
|
|
|
(6.5.14) logical-OR-expression:
|
|
|
|
|
|
logical-AND-expression
|
|
|
|
|
|
logical-OR-expression || logical-AND-expression
|
|
|
|
|
|
(6.5.15) conditional-expression:
|
|
|
|
|
|
logical-OR-expression
|
|
|
|
|
|
logical-OR-expression ? expression : conditional-expression
|
|
|
|
|
|
(6.5.16) assignment-expression:
|
|
|
|
|
|
conditional-expression
|
|
|
|
|
|
unary-expression assignment-operator assignment-expression
|
|
|
|
|
|
(6.5.16) assignment-operator: one of
|
|
|
|
|
|
= *= /= %= += -= <<= >>= &= ^= |=
|
|
|
|
|
|
(6.5.17) expression:
|
|
|
|
|
|
assignment-expression
|
|
|
|
|
|
expression , assignment-expression
|
|
|
|
|
|
(6.6) constant-expression:
|
|
|
|
|
|
conditional-expression
|
|
|
|
|
|
A.2.2 Declarations
|
|
|
|
|
|
(6.7) declaration:
|
|
|
|
|
|
declaration-specifiers init-declarator-listopt ;
|
|
|
|
|
|
(6.7) declaration-specifiers:
|
|
|
|
|
|
storage-class-specifier declaration-specifiersopt
|
|
|
|
|
|
type-specifier declaration-specifiersopt
|
|
|
|
|
|
type-qualifier declaration-specifiersopt
|
|
|
|
|
|
function-specifier declaration-specifiersopt
|
|
|
|
|
|
(6.7) init-declarator-list:
|
|
|
|
|
|
init-declarator
|
|
|
|
|
|
init-declarator-list , init-declarator
|
|
|
|
|
|
(6.7) init-declarator:
|
|
|
|
|
|
declarator
|
|
|
|
|
|
declarator = initializer
|
|
|
|
|
|
(6.7.1) storage-class-specifier:
|
|
|
|
|
|
typedef
|
|
|
|
|
|
extern
|
|
|
|
|
|
static
|
|
|
|
|
|
auto
|
|
|
|
|
|
register
|
|
|
|
|
|
|
|
|
|
|
|
(6.7.2) type-specifier:
|
|
|
|
|
|
void
|
|
|
|
|
|
char
|
|
|
|
|
|
short
|
|
|
|
|
|
int
|
|
|
|
|
|
long
|
|
|
|
|
|
float
|
|
|
|
|
|
double
|
|
|
|
|
|
signed
|
|
|
|
|
|
unsigned
|
|
|
|
|
|
_Bool
|
|
|
|
|
|
_Complex
|
|
|
|
|
|
struct-or-union-specifier
|
|
|
|
|
|
enum-specifier
|
|
|
|
|
|
typedef-name
|
|
|
|
|
|
(6.7.2.1) struct-or-union-specifier:
|
|
|
|
|
|
struct-or-union identifieropt { struct-declaration-list }
|
|
|
|
|
|
struct-or-union identifier
|
|
|
|
|
|
(6.7.2.1) struct-or-union:
|
|
|
|
|
|
struct
|
|
|
|
|
|
union
|
|
|
|
|
|
(6.7.2.1) struct-declaration-list:
|
|
|
|
|
|
struct-declaration
|
|
|
|
|
|
struct-declaration-list struct-declaration
|
|
|
|
|
|
(6.7.2.1) struct-declaration:
|
|
|
|
|
|
specifier-qualifier-list struct-declarator-list ;
|
|
|
|
|
|
(6.7.2.1) specifier-qualifier-list:
|
|
|
|
|
|
type-specifier specifier-qualifier-listopt
|
|
|
|
|
|
type-qualifier specifier-qualifier-listopt
|
|
|
|
|
|
(6.7.2.1) struct-declarator-list:
|
|
|
|
|
|
struct-declarator
|
|
|
|
|
|
struct-declarator-list , struct-declarator
|
|
|
|
|
|
(6.7.2.1) struct-declarator:
|
|
|
|
|
|
declarator
|
|
|
|
|
|
declaratoropt : constant-expression
|
|
|
|
|
|
|
|
|
|
|
|
(6.7.2.2) enum-specifier:
|
|
|
|
|
|
enum identifieropt { enumerator-list }
|
|
|
|
|
|
enum identifieropt { enumerator-list , }
|
|
|
|
|
|
enum identifier
|
|
|
|
|
|
(6.7.2.2) enumerator-list:
|
|
|
|
|
|
enumerator
|
|
|
|
|
|
enumerator-list , enumerator
|
|
|
|
|
|
(6.7.2.2) enumerator:
|
|
|
|
|
|
enumeration-constant
|
|
|
|
|
|
enumeration-constant = constant-expression
|
|
|
|
|
|
(6.7.3) type-qualifier:
|
|
|
|
|
|
const
|
|
|
|
|
|
restrict
|
|
|
|
|
|
volatile
|
|
|
|
|
|
(6.7.4) function-specifier:
|
|
|
|
|
|
inline
|
|
|
|
|
|
(6.7.5) declarator:
|
|
|
|
|
|
pointeropt direct-declarator
|
|
|
|
|
|
(6.7.5) 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 )
|
|
|
|
|
|
(6.7.5) pointer:
|
|
|
|
|
|
* type-qualifier-listopt
|
|
|
|
|
|
* type-qualifier-listopt pointer
|
|
|
|
|
|
(6.7.5) type-qualifier-list:
|
|
|
|
|
|
type-qualifier
|
|
|
|
|
|
type-qualifier-list type-qualifier
|
|
|
|
|
|
(6.7.5) parameter-type-list:
|
|
|
|
|
|
parameter-list
|
|
|
|
|
|
parameter-list , ...
|
|
|
|
|
|
(6.7.5) parameter-list:
|
|
|
|
|
|
parameter-declaration
|
|
|
|
|
|
parameter-list , parameter-declaration
|
|
|
|
|
|
(6.7.5) parameter-declaration:
|
|
|
|
|
|
declaration-specifiers declarator
|
|
|
|
|
|
declaration-specifiers abstract-declaratoropt
|
|
|
|
|
|
(6.7.5) identifier-list:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
identifier-list , identifier
|
|
|
|
|
|
(6.7.6) type-name:
|
|
|
|
|
|
specifier-qualifier-list abstract-declaratoropt
|
|
|
|
|
|
(6.7.6) abstract-declarator:
|
|
|
|
|
|
pointer
|
|
|
|
|
|
pointeropt direct-abstract-declarator
|
|
|
|
|
|
(6.7.6) 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 )
|
|
|
|
|
|
(6.7.7) typedef-name:
|
|
|
|
|
|
identifier
|
|
|
|
|
|
(6.7.8) initializer:
|
|
|
|
|
|
assignment-expression
|
|
|
|
|
|
{ initializer-list }
|
|
|
|
|
|
{ initializer-list , }
|
|
|
|
|
|
(6.7.8) initializer-list:
|
|
|
|
|
|
designationopt initializer
|
|
|
|
|
|
initializer-list , designationopt initializer
|
|
|
|
|
|
(6.7.8) designation:
|
|
|
|
|
|
designator-list =
|
|
|
|
|
|
(6.7.8) designator-list:
|
|
|
|
|
|
designator
|
|
|
|
|
|
designator-list designator
|
|
|
|
|
|
(6.7.8) designator:
|
|
|
|
|
|
[ constant-expression ]
|
|
|
|
|
|
. identifier
|
|
|
|
|
|
A.2.3 Statements
|
|
|
|
|
|
(6.8) statement:
|
|
|
|
|
|
labeled-statement
|
|
|
|
|
|
compound-statement
|
|
|
|
|
|
expression-statement
|
|
|
|
|
|
selection-statement
|
|
|
|
|
|
iteration-statement
|
|
|
|
|
|
jump-statement
|
|
|
|
|
|
(6.8.1) labeled-statement:
|
|
|
|
|
|
identifier : statement
|
|
|
|
|
|
case constant-expression : statement
|
|
|
|
|
|
default : statement
|
|
|
|
|
|
(6.8.2) compound-statement:
|
|
|
|
|
|
{ block-item-listopt }
|
|
|
|
|
|
(6.8.2) block-item-list:
|
|
|
|
|
|
block-item
|
|
|
|
|
|
block-item-list block-item
|
|
|
|
|
|
(6.8.2) block-item:
|
|
|
|
|
|
declaration
|
|
|
|
|
|
statement
|
|
|
|
|
|
(6.8.3) expression-statement:
|
|
|
|
|
|
expressionopt ;
|
|
|
|
|
|
(6.8.4) selection-statement:
|
|
|
|
|
|
if ( expression ) statement
|
|
|
|
|
|
if ( expression ) statement else statement
|
|
|
|
|
|
switch ( expression ) statement
|
|
|
|
|
|
|
|
|
|
|
|
(6.8.5) iteration-statement:
|
|
|
|
|
|
while ( expression ) statement
|
|
|
|
|
|
do statement while ( expression ) ;
|
|
|
|
|
|
for ( expressionopt ; expressionopt ; expressionopt ) statement
|
|
|
|
|
|
for ( declaration expressionopt ; expressionopt ) statement
|
|
|
|
|
|
(6.8.6) jump-statement:
|
|
|
|
|
|
goto identifier ;
|
|
|
|
|
|
continue ;
|
|
|
|
|
|
break ;
|
|
|
|
|
|
return expressionopt ;
|
|
|
|
|
|
A.2.4 External definitions
|
|
|
|
|
|
(6.9) translation-unit:
|
|
|
|
|
|
external-declaration
|
|
|
|
|
|
translation-unit external-declaration
|
|
|
|
|
|
(6.9) external-declaration:
|
|
|
|
|
|
function-definition
|
|
|
|
|
|
declaration
|
|
|
|
|
|
(6.9.1) function-definition:
|
|
|
|
|
|
declaration-specifiers declarator declaration-listopt compound-statement
|
|
|
|
|
|
(6.9.1) declaration-list:
|
|
|
|
|
|
declaration
|
|
|
|
|
|
declaration-list declaration
|
|
|
|
|
|
A.3 Preprocessing directives
|
|
|
|
|
|
(6.10) preprocessing-file:
|
|
|
|
|
|
groupopt
|
|
|
|
|
|
(6.10) group:
|
|
|
|
|
|
group-part
|
|
|
|
|
|
group group-part
|
|
|
|
|
|
(6.10) group-part:
|
|
|
|
|
|
if-section
|
|
|
|
|
|
control-line
|
|
|
|
|
|
text-line
|
|
|
|
|
|
# non-directive
|
|
|
|
|
|
(6.10) if-section:
|
|
|
|
|
|
if-group elif-groupsopt else-groupopt endif-line
|
|
|
|
|
|
(6.10) if-group:
|
|
|
|
|
|
# if constant-expression new-line groupopt
|
|
|
|
|
|
# ifdef identifier new-line groupopt
|
|
|
|
|
|
# ifndef identifier new-line groupopt
|
|
|
|
|
|
(6.10) elif-groups:
|
|
|
|
|
|
elif-group
|
|
|
|
|
|
elif-groups elif-group
|
|
|
|
|
|
(6.10) elif-group:
|
|
|
|
|
|
# elif constant-expression new-line groupopt
|
|
|
|
|
|
(6.10) else-group:
|
|
|
|
|
|
# else new-line groupopt
|
|
|
|
|
|
(6.10) endif-line:
|
|
|
|
|
|
# endif new-line
|
|
|
|
|
|
(6.10) 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
|
|
|
|
|
|
(6.10) text-line:
|
|
|
|
|
|
pp-tokensopt new-line
|
|
|
|
|
|
(6.10) non-directive:
|
|
|
|
|
|
pp-tokens new-line
|
|
|
|
|
|
(6.10) lparen:
|
|
|
|
|
|
a ( character not immediately preceded by white-space
|
|
|
|
|
|
(6.10) replacement-list:
|
|
|
|
|
|
pp-tokensopt
|
|
|
|
|
|
|
|
|
|
|
|
(6.10) pp-tokens:
|
|
|
|
|
|
preprocessing-token
|
|
|
|
|
|
pp-tokens preprocessing-token
|
|
|
|
|
|
(6.10) new-line:
|
|
|
|
|
|
the new-line character
|
|
|
|
|
|
|
|
|
|
|
|
Annex B
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
B. Library summary
|
2012-01-16 16:34:32 +01:00
|
|
|
|
B.1 Diagnostics <assert.h>
|
|
|
|
|
|
NDEBUG
|
|
|
|
|
|
void assert(scalar expression);
|
|
|
|
|
|
B.2 Complex <complex.h>
|
|
|
|
|
|
complex imaginary I
|
|
|
|
|
|
_Complex_I _Imaginary_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 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);
|
|
|
|
|
|
B.3 Character handling <ctype.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.4 Errors <errno.h>
|
|
|
|
|
|
EDOM EILSEQ ERANGE errno
|
|
|
|
|
|
B.5 Floating-point environment <fenv.h>
|
|
|
|
|
|
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
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|
#pragma STDC FENV_ACCESS on-off-switch
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|
int feclearexcept(int excepts);
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|
int fegetexceptflag(fexcept_t *flagp, int excepts);
|
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|
|
int feraiseexcept(int excepts);
|
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|
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|
|
int fesetexceptflag(const fexcept_t *flagp,
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|
|
int excepts);
|
|
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|
|
int fetestexcept(int excepts);
|
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|
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|
|
int fegetround(void);
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|
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|
|
int fesetround(int round);
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|
|
int fegetenv(fenv_t *envp);
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|
int feholdexcept(fenv_t *envp);
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|
int fesetenv(const fenv_t *envp);
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|
|
int feupdateenv(const fenv_t *envp);
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|
|
B.6 Characteristics of floating types <float.h>
|
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|
|
|
|
FLT_ROUNDS DBL_MIN_EXP FLT_MAX
|
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|
|
|
FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
|
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|
|
|
FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
|
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|
|
|
|
FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
|
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|
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|
|
DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
|
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|
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|
|
LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
|
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|
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|
|
DECIMAL_DIG DBL_MAX_EXP FLT_MIN
|
|
|
|
|
|
FLT_DIG LDBL_MAX_EXP DBL_MIN
|
|
|
|
|
|
DBL_DIG FLT_MAX_10_EXP LDBL_MIN
|
|
|
|
|
|
LDBL_DIG DBL_MAX_10_EXP
|
|
|
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|
|
FLT_MIN_EXP LDBL_MAX_10_EXP
|
|
|
|
|
|
B.7 Format conversion of integer types <inttypes.h>
|
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|
|
|
|
imaxdiv_t
|
|
|
|
|
|
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
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|
PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
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|
|
PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
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|
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|
|
PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
|
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|
|
|
|
PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
|
|
|
|
|
|
PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
|
|
|
|
|
|
SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
|
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|
|
|
|
SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
|
|
|
|
|
|
SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
|
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|
|
|
|
SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
|
|
|
|
|
|
SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
|
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|
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|
|
intmax_t imaxabs(intmax_t j);
|
|
|
|
|
|
imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
|
|
|
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|
|
intmax_t strtoimax(const char * restrict nptr,
|
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|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
B.8 Alternative spellings <iso646.h>
|
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|
|
and bitor not_eq xor
|
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|
|
|
|
and_eq compl or xor_eq
|
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|
|
|
|
bitand not or_eq
|
|
|
|
|
|
B.9 Sizes of integer types <limits.h>
|
|
|
|
|
|
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
|
|
|
|
|
|
B.10 Localization <locale.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.11 Mathematics <math.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.12 Nonlocal jumps <setjmp.h>
|
|
|
|
|
|
jmp_buf
|
|
|
|
|
|
int setjmp(jmp_buf env);
|
|
|
|
|
|
void longjmp(jmp_buf env, int val);
|
|
|
|
|
|
B.13 Signal handling <signal.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.14 Variable arguments <stdarg.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.15 Boolean type and values <stdbool.h>
|
|
|
|
|
|
bool
|
|
|
|
|
|
true
|
|
|
|
|
|
false
|
|
|
|
|
|
_ _bool_true_false_are_defined
|
|
|
|
|
|
|
|
|
|
|
|
B.16 Common definitions <stddef.h>
|
|
|
|
|
|
ptrdiff_t size_t wchar_t NULL
|
|
|
|
|
|
offsetof(type, member-designator)
|
|
|
|
|
|
B.17 Integer types <stdint.h>
|
|
|
|
|
|
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
|
|
|
|
|
|
B.18 Input/output <stdio.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
char *gets(char *s);
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.19 General utilities <stdlib.h>
|
|
|
|
|
|
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 *calloc(size_t nmemb, size_t size);
|
|
|
|
|
|
void free(void *ptr);
|
|
|
|
|
|
void *malloc(size_t size);
|
|
|
|
|
|
void *realloc(void *ptr, size_t size);
|
|
|
|
|
|
void abort(void);
|
|
|
|
|
|
int atexit(void (*func)(void));
|
|
|
|
|
|
void exit(int status);
|
|
|
|
|
|
void _Exit(int status);
|
|
|
|
|
|
char *getenv(const char *name);
|
|
|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
B.20 String handling <string.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
B.21 Type-generic math <tgmath.h>
|
|
|
|
|
|
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
|
|
|
|
|
|
B.22 Date and time <time.h>
|
|
|
|
|
|
NULL size_t time_t
|
|
|
|
|
|
CLOCKS_PER_SEC clock_t struct tm
|
|
|
|
|
|
clock_t clock(void);
|
|
|
|
|
|
double difftime(time_t time1, time_t time0);
|
|
|
|
|
|
time_t mktime(struct tm *timeptr);
|
|
|
|
|
|
time_t time(time_t *timer);
|
|
|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
B.23 Extended multibyte/wide character utilities <wchar.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
B.24 Wide character classification and mapping utilities <wctype.h>
|
|
|
|
|
|
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);
|
|
|
|
|
|
|
|
|
|
|
|
Annex C
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
C. Sequence points
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 The following are the sequence points described in 5.1.2.3:
|
|
|
|
|
|
-- The call to a function, after the arguments have been evaluated (6.5.2.2).
|
|
|
|
|
|
-- The end of the first operand of the following operators: logical AND && (6.5.13);
|
|
|
|
|
|
logical OR || (6.5.14); conditional ? (6.5.15); comma , (6.5.17).
|
|
|
|
|
|
-- The end of a full declarator: declarators (6.7.5);
|
|
|
|
|
|
-- The end of a full expression: an initializer (6.7.8); the expression in an expression
|
|
|
|
|
|
statement (6.8.3); the controlling expression of a selection statement (if or switch)
|
|
|
|
|
|
(6.8.4); the controlling expression of a while or do statement (6.8.5); each of the
|
|
|
|
|
|
expressions of a for statement (6.8.5.3); the expression in a return statement
|
|
|
|
|
|
(6.8.6.4).
|
|
|
|
|
|
-- Immediately before a library function returns (7.1.4).
|
|
|
|
|
|
-- After the actions associated with each formatted input/output function conversion
|
|
|
|
|
|
specifier (7.19.6, 7.24.2).
|
|
|
|
|
|
-- 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 (7.20.5).
|
|
|
|
|
|
|
|
|
|
|
|
Annex D
|
|
|
|
|
|
(normative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
D. Universal character names for identifiers
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 This clause lists the hexadecimal code values that are valid in universal character names
|
|
|
|
|
|
in identifiers.
|
|
|
|
|
|
2 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
|
|
|
|
|
|
JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
|
|
|
|
|
|
sets.
|
|
|
|
|
|
Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
|
|
|
|
|
|
0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F
|
|
|
|
|
|
Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
|
|
|
|
|
|
03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
|
|
|
|
|
|
1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
|
|
|
|
|
|
1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
|
|
|
|
|
|
1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
|
|
|
|
|
|
Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
|
|
|
|
|
|
04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9
|
|
|
|
|
|
Armenian: 0531-0556, 0561-0587
|
|
|
|
|
|
Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
|
|
|
|
|
|
05F0-05F2
|
|
|
|
|
|
Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
|
|
|
|
|
|
06D0-06DC, 06E5-06E8, 06EA-06ED
|
|
|
|
|
|
Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
|
|
|
|
|
|
Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
|
|
|
|
|
|
09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
|
|
|
|
|
|
09DC-09DD, 09DF-09E3, 09F0-09F1
|
|
|
|
|
|
Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
|
|
|
|
|
|
0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
|
|
|
|
|
|
0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
|
|
|
|
|
|
Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
|
|
|
|
|
|
0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
|
|
|
|
|
|
0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
|
|
|
|
|
|
Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
|
|
|
|
|
|
0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
|
|
|
|
|
|
0B5C-0B5D, 0B5F-0B61
|
|
|
|
|
|
Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
|
|
|
|
|
|
0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
|
|
|
|
|
|
0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
|
|
|
|
|
|
Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
|
|
|
|
|
|
0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61
|
|
|
|
|
|
Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
|
|
|
|
|
|
0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
|
|
|
|
|
|
0CE0-0CE1
|
|
|
|
|
|
Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
|
|
|
|
|
|
0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61
|
|
|
|
|
|
Thai: 0E01-0E3A, 0E40-0E5B
|
|
|
|
|
|
Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
|
|
|
|
|
|
0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
|
|
|
|
|
|
0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
|
|
|
|
|
|
0EC8-0ECD, 0EDC-0EDD
|
|
|
|
|
|
Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
|
|
|
|
|
|
0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
|
|
|
|
|
|
0FB1-0FB7, 0FB9
|
|
|
|
|
|
Georgian: 10A0-10C5, 10D0-10F6
|
|
|
|
|
|
Hiragana: 3041-3093, 309B-309C
|
|
|
|
|
|
Katakana: 30A1-30F6, 30FB-30FC
|
|
|
|
|
|
Bopomofo: 3105-312C
|
|
|
|
|
|
CJK Unified Ideographs: 4E00-9FA5
|
|
|
|
|
|
Hangul: AC00-D7A3
|
|
|
|
|
|
Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
|
|
|
|
|
|
0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
|
|
|
|
|
|
0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
|
|
|
|
|
|
Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
|
|
|
|
|
|
02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
|
|
|
|
|
|
2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
|
|
|
|
|
|
2133-2138, 2160-2182, 3005-3007, 3021-3029
|
|
|
|
|
|
|
|
|
|
|
|
Annex E
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
E. Implementation limits
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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 5.2.4.2.1.
|
|
|
|
|
|
#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
|
|
|
|
|
|
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 5.2.4.2.2.
|
|
|
|
|
|
3 The values given in the following list shall be replaced by implementation-defined
|
|
|
|
|
|
expressions:
|
|
|
|
|
|
#define FLT_EVAL_METHOD
|
|
|
|
|
|
#define FLT_ROUNDS
|
|
|
|
|
|
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 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_DIG 6
|
|
|
|
|
|
#define FLT_MANT_DIG
|
|
|
|
|
|
#define FLT_MAX_10_EXP +37
|
|
|
|
|
|
#define FLT_MAX_EXP
|
|
|
|
|
|
#define FLT_MIN_10_EXP -37
|
|
|
|
|
|
#define FLT_MIN_EXP
|
|
|
|
|
|
#define FLT_RADIX 2
|
|
|
|
|
|
#define LDBL_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
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
Annex F
|
|
|
|
|
|
(normative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
F. IEC 60559 floating-point arithmetic
|
2012-01-16 16:34:32 +01:00
|
|
|
|
F.1 Introduction
|
|
|
|
|
|
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. Where
|
|
|
|
|
|
a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
|
|
|
|
|
|
behavior is adopted by reference, unless stated otherwise.
|
|
|
|
|
|
F.2 Types
|
|
|
|
|
|
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,307) 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.308)
|
|
|
|
|
|
Recommended practice
|
|
|
|
|
|
2 The long double type should match an IEC 60559 extended format.
|
|
|
|
|
|
307) ``Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
|
|
|
|
|
|
and quadruple 128-bit IEC 60559 formats.
|
|
|
|
|
|
308) A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
|
|
|
|
|
|
all double values.
|
|
|
|
|
|
F.2.1 Infinities, signed zeros, and NaNs
|
|
|
|
|
|
1 This specification does not define the behavior of signaling NaNs.309) 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.
|
|
|
|
|
|
F.3 Operators and functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
309) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
|
|
|
|
|
|
sufficient for closure of the arithmetic.
|
2012-01-23 23:24:51 +01:00
|
|
|
|
-- 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 unary minus (-) operator provides the 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.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
-- 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 7.12.3 do not distinguish signaling from quiet NaNs).
|
|
|
|
|
|
F.4 Floating to integer conversion
|
|
|
|
|
|
1 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. Whether conversion of non-integer floating values whose
|
|
|
|
|
|
integral part is within the range of the integer type raises the ``inexact'' floating-point
|
|
|
|
|
|
exception is unspecified.310)
|
|
|
|
|
|
F.5 Binary-decimal conversion
|
|
|
|
|
|
1 Conversion from the widest supported IEC 60559 format to decimal with
|
|
|
|
|
|
DECIMAL_DIG digits and back is the identity function.311)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
310) 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>.
|
|
|
|
|
|
311) 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.)
|
|
|
|
|
|
F.6 Contracted expressions
|
|
|
|
|
|
1 A contracted expression 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
|
|
|
|
|
|
2 A contracted expression should raise floating-point exceptions in a manner generally
|
|
|
|
|
|
consistent with the basic arithmetic operations. A contracted expression should deliver
|
|
|
|
|
|
the same value as its uncontracted counterpart, else should be correctly rounded (once).
|
|
|
|
|
|
F.7 Floating-point environment
|
|
|
|
|
|
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.312)
|
|
|
|
|
|
F.7.1 Environment management
|
|
|
|
|
|
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.313)
|
|
|
|
|
|
F.7.2 Translation
|
|
|
|
|
|
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
|
|
|
|
|
|
2 The implementation should produce a diagnostic message for each translation-time
|
|
|
|
|
|
312) This specification does not require dynamic rounding precision nor trap enablement modes.
|
|
|
|
|
|
313) 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 F.8).
|
|
|
|
|
|
floating-point exception, other than ``inexact'';314) the implementation should then
|
|
|
|
|
|
proceed with the translation of the program.
|
|
|
|
|
|
F.7.3 Execution
|
|
|
|
|
|
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.
|
|
|
|
|
|
F.7.4 Constant expressions
|
|
|
|
|
|
1 An arithmetic constant expression of floating type, other than one in an initializer for an
|
|
|
|
|
|
object that has static 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'').315)
|
|
|
|
|
|
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
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
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
|
|
|
|
|
|
314) 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.
|
|
|
|
|
|
315) 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;
|
|
|
|
|
|
execution time.
|
|
|
|
|
|
|
|
|
|
|
|
F.7.5 Initialization
|
|
|
|
|
|
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 storage duration is done (as if) at translation
|
|
|
|
|
|
time.
|
|
|
|
|
|
2 EXAMPLE
|
|
|
|
|
|
#include <fenv.h>
|
|
|
|
|
|
#pragma STDC FENV_ACCESS ON
|
|
|
|
|
|
void f(void)
|
|
|
|
|
|
{
|
|
|
|
|
|
float u[] = { 1.1e75 }; // raises exceptions
|
|
|
|
|
|
static float v = 1.1e75; // does not raise exceptions
|
|
|
|
|
|
float w = 1.1e75; // raises exceptions
|
|
|
|
|
|
double x = 1.1e75; // may raise exceptions
|
|
|
|
|
|
float y = 1.1e75f; // may raise exceptions
|
|
|
|
|
|
long double z = 1.1e75; // does not raise exceptions
|
|
|
|
|
|
/* ... */
|
|
|
|
|
|
}
|
|
|
|
|
|
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 1.1e75, 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.316) 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 1.1e75 and 1.1e75f to
|
|
|
|
|
|
their internal representations occur at translation time in all cases.
|
|
|
|
|
|
316) Use of float_t and double_t variables increases the likelihood of translation-time computation.
|
|
|
|
|
|
For example, the automatic initialization
|
2012-01-23 23:24:51 +01:00
|
|
|
|
double_t x = 1.1e75;
|
|
|
|
|
|
could be done at translation time, regardless of the expression evaluation method.
|
2012-01-16 16:34:32 +01:00
|
|
|
|
F.7.6 Changing the environment
|
|
|
|
|
|
1 Operations defined in 6.5 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.
|
|
|
|
|
|
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''.
|
|
|
|
|
|
F.8 Optimization
|
|
|
|
|
|
1 This section identifies code transformations that might subvert IEC 60559-specified
|
|
|
|
|
|
behavior, and others that do not.
|
|
|
|
|
|
F.8.1 Global transformations
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.)
|
|
|
|
|
|
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;
|
|
|
|
|
|
F.8.2 Expression transformations
|
|
|
|
|
|
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).317)
|
|
|
|
|
|
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).318)
|
|
|
|
|
|
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 + 0x 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 - 0x (+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
|
|
|
|
|
|
317) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
|
|
|
|
|
|
other transformations that remove arithmetic operators.
|
|
|
|
|
|
318) IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
|
|
|
|
|
|
Examples include:
|
|
|
|
|
|
1/(1/ <20> ) is <20>
|
|
|
|
|
|
and
|
|
|
|
|
|
conj(csqrt( z )) is csqrt(conj( z )),
|
|
|
|
|
|
for complex z .
|
|
|
|
|
|
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).
|
|
|
|
|
|
F.8.3 Relational operators
|
|
|
|
|
|
1 x != x false The statement x != x is true if x is a NaN.
|
|
|
|
|
|
x == x true The statement 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.
|
|
|
|
|
|
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();
|
|
|
|
|
|
|
|
|
|
|
|
F.8.4 Constant arithmetic
|
|
|
|
|
|
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 F.7.4
|
|
|
|
|
|
and F.7.5.) 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,319) 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.
|
|
|
|
|
|
F.9 Mathematics <math.h>
|
|
|
|
|
|
1 This subclause contains specifications of <math.h> facilities that are particularly suited
|
|
|
|
|
|
for IEC 60559 implementations.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 F.3. 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.
|
|
|
|
|
|
4 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
|
|
|
|
|
|
nonzero value.
|
|
|
|
|
|
5 The ``invalid'' and ``divide-by-zero'' floating-point exceptions are raised as specified in
|
|
|
|
|
|
subsequent subclauses of this annex.
|
|
|
|
|
|
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
|
|
|
|
|
|
319) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
|
|
|
|
|
|
whose magnitude is too large.
|
|
|
|
|
|
7 The ``underflow'' floating-point exception is raised whenever a result is tiny (essentially
|
|
|
|
|
|
subnormal or zero) and suffers loss of accuracy.320)
|
|
|
|
|
|
8 Whether or when library functions raise the ``inexact'' floating-point exception is
|
|
|
|
|
|
unspecified, unless explicitly specified otherwise.
|
|
|
|
|
|
9 Whether or when library functions raise an undeserved ``underflow'' floating-point
|
|
|
|
|
|
exception is unspecified.321) Otherwise, as implied by F.7.6, the <math.h> functions do
|
|
|
|
|
|
not raise spurious floating-point exceptions (detectable by the user), other than the
|
|
|
|
|
|
``inexact'' floating-point exception.
|
|
|
|
|
|
10 Whether the functions honor the rounding direction mode is implementation-defined,
|
|
|
|
|
|
unless explicitly specified otherwise.
|
|
|
|
|
|
11 Functions with a NaN argument return a NaN result and raise no floating-point exception,
|
|
|
|
|
|
except where stated otherwise.
|
|
|
|
|
|
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 ``<60>''
|
|
|
|
|
|
occurs in both an argument and the result, the result has the same sign as the argument.
|
|
|
|
|
|
Recommended practice
|
|
|
|
|
|
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.
|
2012-01-23 23:24:51 +01:00
|
|
|
|
F.9.1 Trigonometric functions
|
|
|
|
|
|
F.9.1.1 The acos functions
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 -- acos(1) returns +0.
|
|
|
|
|
|
-- acos( x ) returns a NaN and raises the ``invalid'' floating-point exception for
|
|
|
|
|
|
| x | > 1.
|
|
|
|
|
|
320) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
|
|
|
|
|
|
when the floating-point exception is raised.
|
|
|
|
|
|
321) It is intended that undeserved ``underflow'' and ``inexact'' floating-point exceptions are raised only if
|
|
|
|
|
|
avoiding them would be too costly.
|
|
|
|
|
|
F.9.1.2 The asin functions
|
|
|
|
|
|
1 -- asin(<28>0) returns <20>0.
|
|
|
|
|
|
-- asin( x ) returns a NaN and raises the ``invalid'' floating-point exception for
|
|
|
|
|
|
| x | > 1.
|
|
|
|
|
|
F.9.1.3 The atan functions
|
|
|
|
|
|
1 -- atan(<28>0) returns <20>0.
|
|
|
|
|
|
-- atan(<28>) returns <20> /2.
|
|
|
|
|
|
F.9.1.4 The atan2 functions
|
|
|
|
|
|
1 -- atan2(<28>0, -0) returns <20> .322)
|
|
|
|
|
|
-- atan2(<28>0, +0) returns <20>0.
|
|
|
|
|
|
-- atan2(<28>0, x ) returns <20> for x < 0.
|
|
|
|
|
|
-- atan2(<28>0, x ) returns <20>0 for x > 0.
|
|
|
|
|
|
-- atan2( y , <20>0) returns - /2 for y < 0.
|
|
|
|
|
|
-- atan2( y , <20>0) returns /2 for y > 0.
|
|
|
|
|
|
-- atan2(<28> y , -) returns <20> for finite y > 0.
|
|
|
|
|
|
-- atan2(<28> y , +) returns <20>0 for finite y > 0.
|
|
|
|
|
|
-- atan2(<28>, x ) returns <20> /2 for finite x .
|
|
|
|
|
|
-- atan2(<28>, -) returns <20>3 /4.
|
|
|
|
|
|
-- atan2(<28>, +) returns <20> /4.
|
|
|
|
|
|
F.9.1.5 The cos functions
|
|
|
|
|
|
1 -- cos(<28>0) returns 1.
|
|
|
|
|
|
-- cos(<28>) returns a NaN and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
F.9.1.6 The sin functions
|
|
|
|
|
|
1 -- sin(<28>0) returns <20>0.
|
|
|
|
|
|
-- sin(<28>) returns a NaN and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
322) atan2(0, 0) does not raise the ``invalid'' floating-point exception, nor does atan2( y , 0) raise
|
|
|
|
|
|
the ``divide-by-zero'' floating-point exception.
|
|
|
|
|
|
F.9.1.7 The tan functions
|
|
|
|
|
|
1 -- tan(<28>0) returns <20>0.
|
|
|
|
|
|
-- tan(<28>) returns a NaN and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
F.9.2 Hyperbolic functions
|
|
|
|
|
|
F.9.2.1 The acosh functions
|
|
|
|
|
|
1 -- acosh(1) returns +0.
|
|
|
|
|
|
-- acosh( x ) returns a NaN and raises the ``invalid'' floating-point exception for x < 1.
|
|
|
|
|
|
-- acosh(+) returns +.
|
|
|
|
|
|
F.9.2.2 The asinh functions
|
|
|
|
|
|
1 -- asinh(<28>0) returns <20>0.
|
|
|
|
|
|
-- asinh(<28>) returns <20>.
|
|
|
|
|
|
F.9.2.3 The atanh functions
|
|
|
|
|
|
1 -- atanh(<28>0) returns <20>0.
|
|
|
|
|
|
-- atanh(<28>1) returns <20> and raises the ``divide-by-zero'' floating-point exception.
|
|
|
|
|
|
-- atanh( x ) returns a NaN and raises the ``invalid'' floating-point exception for
|
|
|
|
|
|
| x | > 1.
|
|
|
|
|
|
F.9.2.4 The cosh functions
|
|
|
|
|
|
1 -- cosh(<28>0) returns 1.
|
|
|
|
|
|
-- cosh(<28>) returns +.
|
|
|
|
|
|
F.9.2.5 The sinh functions
|
|
|
|
|
|
1 -- sinh(<28>0) returns <20>0.
|
|
|
|
|
|
-- sinh(<28>) returns <20>.
|
|
|
|
|
|
F.9.2.6 The tanh functions
|
|
|
|
|
|
1 -- tanh(<28>0) returns <20>0.
|
|
|
|
|
|
-- tanh(<28>) returns <20>1.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.3 Exponential and logarithmic functions
|
|
|
|
|
|
F.9.3.1 The exp functions
|
|
|
|
|
|
1 -- exp(<28>0) returns 1.
|
|
|
|
|
|
-- exp(-) returns +0.
|
|
|
|
|
|
-- exp(+) returns +.
|
|
|
|
|
|
F.9.3.2 The exp2 functions
|
|
|
|
|
|
1 -- exp2(<28>0) returns 1.
|
|
|
|
|
|
-- exp2(-) returns +0.
|
|
|
|
|
|
-- exp2(+) returns +.
|
|
|
|
|
|
F.9.3.3 The expm1 functions
|
|
|
|
|
|
1 -- expm1(<28>0) returns <20>0.
|
|
|
|
|
|
-- expm1(-) returns -1.
|
|
|
|
|
|
-- expm1(+) returns +.
|
|
|
|
|
|
F.9.3.4 The frexp functions
|
|
|
|
|
|
1 -- frexp(<28>0, exp) returns <20>0, and stores 0 in the object pointed to by exp.
|
|
|
|
|
|
-- frexp(<28>, exp) returns <20>, 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).
|
|
|
|
|
|
2 frexp raises no floating-point exceptions.
|
|
|
|
|
|
3 On a binary system, the body of the frexp function might be
|
|
|
|
|
|
{
|
|
|
|
|
|
*exp = (value == 0) ? 0 : (int)(1 + logb(value));
|
|
|
|
|
|
return scalbn(value, -(*exp));
|
|
|
|
|
|
}
|
|
|
|
|
|
F.9.3.5 The ilogb functions
|
|
|
|
|
|
1 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.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.3.6 The ldexp functions
|
|
|
|
|
|
1 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
|
|
|
|
|
|
F.9.3.7 The log functions
|
|
|
|
|
|
1 -- log(<28>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 +.
|
|
|
|
|
|
F.9.3.8 The log10 functions
|
|
|
|
|
|
1 -- log10(<28>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 +.
|
|
|
|
|
|
F.9.3.9 The log1p functions
|
|
|
|
|
|
1 -- log1p(<28>0) returns <20>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 +.
|
|
|
|
|
|
F.9.3.10 The log2 functions
|
|
|
|
|
|
1 -- log2(<28>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 +.
|
|
|
|
|
|
F.9.3.11 The logb functions
|
|
|
|
|
|
1 -- logb(<28>0) returns - and raises the ``divide-by-zero'' floating-point exception.
|
|
|
|
|
|
-- logb(<28>) returns +.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.3.12 The modf functions
|
|
|
|
|
|
1 -- modf(<28> x , iptr) returns a result with the same sign as x .
|
|
|
|
|
|
-- modf(<28>, iptr) returns <20>0 and stores <20> in the object pointed to by iptr.
|
|
|
|
|
|
-- modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
|
|
|
|
|
|
NaN).
|
|
|
|
|
|
2 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);
|
|
|
|
|
|
}
|
|
|
|
|
|
F.9.3.13 The scalbn and scalbln functions
|
|
|
|
|
|
1 -- scalbn(<28>0, n) returns <20>0.
|
|
|
|
|
|
-- scalbn( x , 0) returns x .
|
|
|
|
|
|
-- scalbn(<28>, n) returns <20>.
|
|
|
|
|
|
F.9.4 Power and absolute value functions
|
|
|
|
|
|
F.9.4.1 The cbrt functions
|
|
|
|
|
|
1 -- cbrt(<28>0) returns <20>0.
|
|
|
|
|
|
-- cbrt(<28>) returns <20>.
|
|
|
|
|
|
F.9.4.2 The fabs functions
|
|
|
|
|
|
1 -- fabs(<28>0) returns +0.
|
|
|
|
|
|
-- fabs(<28>) returns +.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.4.3 The hypot functions
|
|
|
|
|
|
1 -- hypot( x , y ), hypot( y , x ), and hypot( x , - y ) are equivalent.
|
|
|
|
|
|
-- hypot( x , <20>0) is equivalent to fabs( x ).
|
|
|
|
|
|
-- hypot(<28>, y ) returns +, even if y is a NaN.
|
|
|
|
|
|
F.9.4.4 The pow functions
|
|
|
|
|
|
1 -- pow(<28>0, y ) returns <20> and raises the ``divide-by-zero'' floating-point exception
|
|
|
|
|
|
for y an odd integer < 0.
|
|
|
|
|
|
-- pow(<28>0, y ) returns + and raises the ``divide-by-zero'' floating-point exception
|
|
|
|
|
|
for y < 0 and not an odd integer.
|
|
|
|
|
|
-- pow(<28>0, y ) returns <20>0 for y an odd integer > 0.
|
|
|
|
|
|
-- pow(<28>0, y ) returns +0 for y > 0 and not an odd integer.
|
|
|
|
|
|
-- pow(-1, <20>) returns 1.
|
|
|
|
|
|
-- pow(+1, y ) returns 1 for any y , even a NaN.
|
|
|
|
|
|
-- pow( x , <20>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.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.4.5 The sqrt functions
|
|
|
|
|
|
1 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
|
|
|
|
|
|
F.9.5 Error and gamma functions
|
|
|
|
|
|
F.9.5.1 The erf functions
|
|
|
|
|
|
1 -- erf(<28>0) returns <20>0.
|
|
|
|
|
|
-- erf(<28>) returns <20>1.
|
|
|
|
|
|
F.9.5.2 The erfc functions
|
|
|
|
|
|
1 -- erfc(-) returns 2.
|
|
|
|
|
|
-- erfc(+) returns +0.
|
|
|
|
|
|
F.9.5.3 The lgamma functions
|
|
|
|
|
|
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 +.
|
|
|
|
|
|
F.9.5.4 The tgamma functions
|
|
|
|
|
|
1 -- tgamma(<28>0) returns <20> 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 +.
|
|
|
|
|
|
F.9.6 Nearest integer functions
|
|
|
|
|
|
F.9.6.1 The ceil functions
|
|
|
|
|
|
1 -- ceil(<28>0) returns <20>0.
|
|
|
|
|
|
-- ceil(<28>) returns <20>.
|
|
|
|
|
|
2 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;
|
|
|
|
|
|
}
|
|
|
|
|
|
F.9.6.2 The floor functions
|
|
|
|
|
|
1 -- floor(<28>0) returns <20>0.
|
|
|
|
|
|
-- floor(<28>) returns <20>.
|
|
|
|
|
|
2 See the sample implementation for ceil in F.9.6.1.
|
|
|
|
|
|
F.9.6.3 The nearbyint functions
|
|
|
|
|
|
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(<28>0) returns <20>0 (for all rounding directions).
|
|
|
|
|
|
-- nearbyint(<28>) returns <20> (for all rounding directions).
|
|
|
|
|
|
F.9.6.4 The rint functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
F.9.6.5 The lrint and llrint functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.6.6 The round functions
|
|
|
|
|
|
1 -- round(<28>0) returns <20>0.
|
|
|
|
|
|
-- round(<28>) returns <20>.
|
|
|
|
|
|
2 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 non-integer numeric arguments, as this implementation does.
|
|
|
|
|
|
F.9.6.7 The lround and llround functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
F.9.6.8 The trunc functions
|
|
|
|
|
|
1 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
|
|
|
|
|
|
rounding direction).
|
|
|
|
|
|
-- trunc(<28>0) returns <20>0.
|
|
|
|
|
|
-- trunc(<28>) returns <20>.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.7 Remainder functions
|
|
|
|
|
|
F.9.7.1 The fmod functions
|
|
|
|
|
|
1 -- fmod(<28>0, y ) returns <20>0 for y not zero.
|
|
|
|
|
|
-- fmod( x , y ) returns a NaN and raises the ``invalid'' floating-point exception for x
|
|
|
|
|
|
infinite or y zero.
|
|
|
|
|
|
-- fmod( x , <20>) returns x for x not infinite.
|
|
|
|
|
|
2 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);
|
|
|
|
|
|
}
|
|
|
|
|
|
F.9.7.2 The remainder functions
|
|
|
|
|
|
1 The remainder functions are fully specified as a basic arithmetic operation in
|
|
|
|
|
|
IEC 60559.
|
|
|
|
|
|
F.9.7.3 The remquo functions
|
|
|
|
|
|
1 The remquo functions follow the specifications for the remainder functions. They
|
|
|
|
|
|
have no further specifications special to IEC 60559 implementations.
|
|
|
|
|
|
F.9.8 Manipulation functions
|
|
|
|
|
|
F.9.8.1 The copysign functions
|
|
|
|
|
|
1 copysign is specified in the Appendix to IEC 60559.
|
|
|
|
|
|
F.9.8.2 The nan functions
|
|
|
|
|
|
1 All IEC 60559 implementations support quiet NaNs, in all floating formats.
|
|
|
|
|
|
|
|
|
|
|
|
F.9.8.3 The nextafter functions
|
|
|
|
|
|
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 .
|
|
|
|
|
|
F.9.8.4 The nexttoward functions
|
|
|
|
|
|
1 No additional requirements beyond those on nextafter.
|
|
|
|
|
|
F.9.9 Maximum, minimum, and positive difference functions
|
|
|
|
|
|
F.9.9.1 The fdim functions
|
|
|
|
|
|
1 No additional requirements.
|
|
|
|
|
|
F.9.9.2 The fmax functions
|
|
|
|
|
|
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).
|
|
|
|
|
|
2 The body of the fmax function might be323)
|
|
|
|
|
|
{ return (isgreaterequal(x, y) ||
|
|
|
|
|
|
isnan(y)) ? x : y; }
|
|
|
|
|
|
F.9.9.3 The fmin functions
|
|
|
|
|
|
1 The fmin functions are analogous to the fmax functions (see F.9.9.2).
|
|
|
|
|
|
F.9.10 Floating multiply-add
|
|
|
|
|
|
F.9.10.1 The fma functions
|
|
|
|
|
|
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.
|
|
|
|
|
|
323) 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.
|
|
|
|
|
|
Annex G
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
G. IEC 60559-compatible complex arithmetic
|
2012-01-16 16:34:32 +01:00
|
|
|
|
G.1 Introduction
|
|
|
|
|
|
1 This annex supplements annex F to specify complex arithmetic for compatibility with
|
|
|
|
|
|
IEC 60559 real floating-point arithmetic. Although these specifications have been
|
|
|
|
|
|
carefully designed, there is little existing practice to validate the design decisions.
|
|
|
|
|
|
Therefore, these specifications are not normative, but should be viewed more as
|
|
|
|
|
|
recommended practice. An implementation that defines
|
|
|
|
|
|
_ _STDC_IEC_559_COMPLEX_ _ should conform to the specifications in this annex.
|
|
|
|
|
|
G.2 Types
|
|
|
|
|
|
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).
|
|
|
|
|
|
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.
|
|
|
|
|
|
3 For imaginary types, the corresponding real type is given by deleting the keyword
|
|
|
|
|
|
_Imaginary from the type name.
|
|
|
|
|
|
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.
|
|
|
|
|
|
5 The imaginary type domain comprises the imaginary types.
|
|
|
|
|
|
G.3 Conventions
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
G.4 Conversions
|
|
|
|
|
|
G.4.1 Imaginary types
|
|
|
|
|
|
1 Conversions among imaginary types follow rules analogous to those for real floating
|
|
|
|
|
|
types.
|
|
|
|
|
|
G.4.2 Real and imaginary
|
|
|
|
|
|
1 When a value of imaginary type is converted to a real type other than _Bool,324) the
|
|
|
|
|
|
result is a positive zero.
|
|
|
|
|
|
2 When a value of real type is converted to an imaginary type, the result is a positive
|
|
|
|
|
|
imaginary zero.
|
|
|
|
|
|
G.4.3 Imaginary and complex
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
G.5 Binary operators
|
|
|
|
|
|
1 The following subclauses supplement 6.5 in order to specify the type of the result for an
|
|
|
|
|
|
operation with an imaginary operand.
|
|
|
|
|
|
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 G.5.1), but is
|
|
|
|
|
|
not completely determined.
|
|
|
|
|
|
324) See 6.3.1.2.
|
|
|
|
|
|
G.5.1 Multiplicative operators
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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.)
|
|
|
|
|
|
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 )
|
|
|
|
|
|
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 )
|
|
|
|
|
|
4 The * and / operators satisfy the following infinity properties for all real, imaginary, and
|
|
|
|
|
|
complex operands:325)
|
|
|
|
|
|
-- 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;
|
|
|
|
|
|
325) 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'').
|
|
|
|
|
|
-- 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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
6 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
|
|
|
|
|
|
that the imaginary unit I has imaginary type (see G.6).
|
|
|
|
|
|
#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;
|
|
|
|
|
|
}
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
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 (isinf(logbw) &&
|
|
|
|
|
|
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;
|
|
|
|
|
|
}
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
G.5.2 Additive operators
|
|
|
|
|
|
Semantics
|
|
|
|
|
|
1 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.)
|
|
|
|
|
|
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 <20> iv ( x <20> u) <20> iv
|
|
|
|
|
|
|
|
|
|
|
|
iy <20>u + iy i( y <20> v) <20>u + i ( y <20> v )
|
|
|
|
|
|
|
|
|
|
|
|
x + iy ( x <20> u) + iy x + i( y <20> v) ( x <20> u) + i ( y <20> v)
|
|
|
|
|
|
G.6 Complex arithmetic <complex.h>
|
|
|
|
|
|
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 7.3). Notwithstanding
|
|
|
|
|
|
the provisions of 7.1.3, a program may undefine and then perhaps redefine the macro
|
|
|
|
|
|
imaginary.
|
|
|
|
|
|
2 This subclause contains specifications for the <complex.h> functions that are
|
|
|
|
|
|
particularly suited to IEC 60559 implementations. For families of functions, the
|
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|
|
|
specifications apply to all of the functions even though only the principal function is
|
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|
|
|
|
shown. Unless otherwise specified, where the symbol ``<60>'' occurs in both an argument
|
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|
|
and the result, the result has the same sign as the argument.
|
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|
|
3 The functions are continuous onto both sides of their branch cuts, taking into account the
|
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|
|
|
sign of zero. For example, csqrt(-2 <20> i 0) = <20>i 2.
|
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|
4 Since complex and imaginary values are composed of real values, each function may be
|
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|
|
regarded as computing real values from real values. Except as noted, the functions treat
|
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|
|
|
real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
|
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|
|
|
manner consistent with the specifications for real functions in F.9.326)
|
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|
|
5 The functions cimag, conj, cproj, and creal are fully specified for all
|
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|
|
|
implementations, including IEC 60559 ones, in 7.3.9. These functions raise no floating-
|
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|
|
|
point exceptions.
|
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|
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|
|
6 Each of the functions cabs and carg is specified by a formula in terms of a real
|
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|
|
|
function (whose special cases are covered in annex F):
|
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|
|
|
cabs( x + iy ) = hypot( x , y )
|
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|
|
carg( x + iy ) = atan2( y , x )
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|
|
7 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
|
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|
|
|
|
a formula in terms of other complex functions (whose special cases are specified below):
|
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|
|
|
|
casin( z ) = -i casinh(iz )
|
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|
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|
catan( z ) = -i catanh(iz )
|
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|
ccos( z ) = ccosh(iz )
|
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|
csin( z ) = -i csinh(iz )
|
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|
ctan( z ) = -i ctanh(iz )
|
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|
|
8 For the other functions, the following subclauses specify behavior for special cases,
|
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|
|
|
including treatment of the ``invalid'' and ``divide-by-zero'' floating-point exceptions. For
|
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|
|
|
|
families of functions, the specifications apply to all of the functions even though only the
|
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|
|
|
principal function is shown. For a function f satisfying f (conj( z )) = conj( f ( z )), the
|
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|
|
|
specifications for the upper half-plane imply the specifications for the lower half-plane; if
|
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|
|
|
the function f is also either even, f (- z ) = f ( z ), or odd, f (- z ) = - f ( z ), then the
|
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|
|
|
|
specifications for the first quadrant imply the specifications for the other three quadrants.
|
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|
|
|
9 In the following subclauses, cis( y ) is defined as cos( y ) + i sin( y ).
|
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|
|
|
326) As noted in G.3, a complex value with at least one infinite part is regarded as an infinity even if its
|
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|
|
other part is a NaN.
|
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|
|
|
|
G.6.1 Trigonometric functions
|
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|
|
G.6.1.1 The cacos functions
|
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|
|
1 -- cacos(conj( z )) = conj(cacos( z )).
|
|
|
|
|
|
-- cacos(<28>0 + i 0) returns /2 - i 0.
|
|
|
|
|
|
-- cacos(<28>0 + i NaN) returns /2 + i NaN.
|
|
|
|
|
|
-- cacos( x + i ) returns /2 - i , for finite x .
|
|
|
|
|
|
-- cacos( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for nonzero finite x .
|
|
|
|
|
|
-- cacos(- + iy ) returns - i , for positive-signed finite y .
|
|
|
|
|
|
-- cacos(+ + iy ) returns +0 - i , for positive-signed finite y .
|
|
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|
|
|
-- cacos(- + i ) returns 3 /4 - i .
|
|
|
|
|
|
-- cacos(+ + i ) returns /4 - i .
|
|
|
|
|
|
-- cacos(<28> + i NaN) returns NaN <20> i (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified).
|
|
|
|
|
|
-- cacos(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite y .
|
|
|
|
|
|
-- cacos(NaN + i ) returns NaN - i .
|
|
|
|
|
|
-- cacos(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2 Hyperbolic functions
|
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|
|
|
|
G.6.2.1 The cacosh functions
|
|
|
|
|
|
1 -- cacosh(conj( z )) = conj(cacosh( z )).
|
|
|
|
|
|
-- cacosh(<28>0 + i 0) returns +0 + i /2.
|
|
|
|
|
|
-- cacosh( x + i ) returns + + i /2, for finite x .
|
|
|
|
|
|
-- cacosh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for finite x .
|
|
|
|
|
|
-- cacosh(- + iy ) returns + + i , for positive-signed finite y .
|
|
|
|
|
|
-- cacosh(+ + iy ) returns + + i 0, for positive-signed finite y .
|
|
|
|
|
|
-- cacosh(- + i ) returns + + i 3 /4.
|
|
|
|
|
|
-- cacosh(+ + i ) returns + + i /4.
|
|
|
|
|
|
-- cacosh(<28> + i NaN) returns + + i NaN.
|
|
|
|
|
|
-- cacosh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for finite y .
|
|
|
|
|
|
-- cacosh(NaN + i ) returns + + i NaN.
|
|
|
|
|
|
-- cacosh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2.2 The casinh functions
|
|
|
|
|
|
1 -- casinh(conj( z )) = conj(casinh( z )) and casinh is odd.
|
|
|
|
|
|
-- casinh(+0 + i 0) returns 0 + i 0.
|
|
|
|
|
|
-- casinh( x + i ) returns + + i /2 for positive-signed finite x .
|
|
|
|
|
|
-- casinh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for finite x .
|
|
|
|
|
|
-- casinh(+ + iy ) returns + + i 0 for positive-signed finite y .
|
|
|
|
|
|
-- casinh(+ + i ) returns + + i /4.
|
|
|
|
|
|
-- casinh(+ + i NaN) returns + + i NaN.
|
|
|
|
|
|
-- casinh(NaN + i 0) returns NaN + i 0.
|
|
|
|
|
|
-- casinh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for finite nonzero y .
|
|
|
|
|
|
-- casinh(NaN + i ) returns <20> + i NaN (where the sign of the real part of the result
|
|
|
|
|
|
is unspecified).
|
|
|
|
|
|
-- casinh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2.3 The catanh functions
|
|
|
|
|
|
1 -- catanh(conj( z )) = conj(catanh( z )) and catanh is odd.
|
|
|
|
|
|
-- catanh(+0 + i 0) returns +0 + i 0.
|
|
|
|
|
|
-- catanh(+0 + i NaN) returns +0 + i NaN.
|
|
|
|
|
|
-- catanh(+1 + i 0) returns + + i 0 and raises the ``divide-by-zero'' floating-point
|
|
|
|
|
|
exception.
|
|
|
|
|
|
-- catanh( x + i ) returns +0 + i /2, for finite positive-signed x .
|
|
|
|
|
|
-- catanh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for nonzero finite x .
|
|
|
|
|
|
-- catanh(+ + iy ) returns +0 + i /2, for finite positive-signed y .
|
|
|
|
|
|
-- catanh(+ + i ) returns +0 + i /2.
|
|
|
|
|
|
-- catanh(+ + i NaN) returns +0 + i NaN.
|
|
|
|
|
|
-- catanh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid''
|
|
|
|
|
|
floating-point exception, for finite y .
|
|
|
|
|
|
-- catanh(NaN + i ) returns <20>0 + i /2 (where the sign of the real part of the result is
|
|
|
|
|
|
unspecified).
|
|
|
|
|
|
-- catanh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2.4 The ccosh functions
|
|
|
|
|
|
1 -- ccosh(conj( z )) = conj(ccosh( z )) and ccosh is even.
|
|
|
|
|
|
-- ccosh(+0 + i 0) returns 1 + i 0.
|
|
|
|
|
|
-- ccosh(+0 + i ) returns NaN <20> i 0 (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified) and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
-- ccosh(+0 + i NaN) returns NaN <20> i 0 (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified).
|
|
|
|
|
|
-- ccosh( x + i ) returns NaN + i NaN and raises the ``invalid'' floating-point
|
|
|
|
|
|
exception, for finite nonzero x .
|
|
|
|
|
|
-- ccosh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite nonzero x .
|
|
|
|
|
|
-- ccosh(+ + i 0) returns + + i 0.
|
|
|
|
|
|
-- ccosh(+ + iy ) returns + cis( y ), for finite nonzero y .
|
|
|
|
|
|
-- ccosh(+ + i ) returns <20> + i NaN (where the sign of the real part of the result is
|
|
|
|
|
|
unspecified) and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
-- ccosh(+ + i NaN) returns + + i NaN.
|
|
|
|
|
|
-- ccosh(NaN + i 0) returns NaN <20> i 0 (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified).
|
|
|
|
|
|
-- ccosh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for all nonzero numbers y .
|
|
|
|
|
|
-- ccosh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2.5 The csinh functions
|
|
|
|
|
|
1 -- csinh(conj( z )) = conj(csinh( z )) and csinh is odd.
|
|
|
|
|
|
-- csinh(+0 + i 0) returns +0 + i 0.
|
|
|
|
|
|
-- csinh(+0 + i ) returns <20>0 + i NaN (where the sign of the real part of the result is
|
|
|
|
|
|
unspecified) and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
-- csinh(+0 + i NaN) returns <20>0 + i NaN (where the sign of the real part of the result is
|
|
|
|
|
|
unspecified).
|
|
|
|
|
|
-- csinh( x + i ) returns NaN + i NaN and raises the ``invalid'' floating-point
|
|
|
|
|
|
exception, for positive finite x .
|
|
|
|
|
|
-- csinh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite nonzero x .
|
|
|
|
|
|
-- csinh(+ + i 0) returns + + i 0.
|
|
|
|
|
|
-- csinh(+ + iy ) returns + cis( y ), for positive finite y .
|
|
|
|
|
|
-- csinh(+ + i ) returns <20> + i NaN (where the sign of the real part of the result is
|
|
|
|
|
|
unspecified) and raises the ``invalid'' floating-point exception.
|
|
|
|
|
|
-- csinh(+ + i NaN) returns <20> + i NaN (where the sign of the real part of the result
|
|
|
|
|
|
is unspecified).
|
|
|
|
|
|
-- csinh(NaN + i 0) returns NaN + i 0.
|
|
|
|
|
|
-- csinh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for all nonzero numbers y .
|
|
|
|
|
|
-- csinh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.2.6 The ctanh functions
|
|
|
|
|
|
1 -- ctanh(conj( z )) = conj(ctanh( z ))and ctanh is odd.
|
|
|
|
|
|
-- ctanh(+0 + i 0) returns +0 + i 0.
|
|
|
|
|
|
-- ctanh( x + i ) returns NaN + i NaN and raises the ``invalid'' floating-point
|
|
|
|
|
|
exception, for finite x .
|
|
|
|
|
|
-- ctanh( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite x .
|
|
|
|
|
|
-- ctanh(+ + iy ) returns 1 + i 0 sin(2 y ), for positive-signed finite y .
|
|
|
|
|
|
-- ctanh(+ + i ) returns 1 <20> i 0 (where the sign of the imaginary part of the result
|
|
|
|
|
|
is unspecified).
|
|
|
|
|
|
-- ctanh(+ + i NaN) returns 1 <20> i 0 (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified).
|
|
|
|
|
|
-- ctanh(NaN + i 0) returns NaN + i 0.
|
|
|
|
|
|
-- ctanh(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for all nonzero numbers y .
|
|
|
|
|
|
-- ctanh(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
|
|
|
|
|
|
G.6.3 Exponential and logarithmic functions
|
|
|
|
|
|
G.6.3.1 The cexp functions
|
|
|
|
|
|
1 -- cexp(conj( z )) = conj(cexp( z )).
|
|
|
|
|
|
-- cexp(<28>0 + i 0) returns 1 + i 0.
|
|
|
|
|
|
-- cexp( x + i ) returns NaN + i NaN and raises the ``invalid'' floating-point
|
|
|
|
|
|
exception, for finite x .
|
|
|
|
|
|
-- cexp( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite x .
|
|
|
|
|
|
-- cexp(+ + i 0) returns + + i 0.
|
|
|
|
|
|
-- cexp(- + iy ) returns +0 cis( y ), for finite y .
|
|
|
|
|
|
-- cexp(+ + iy ) returns + cis( y ), for finite nonzero y .
|
|
|
|
|
|
-- cexp(- + i ) returns <20>0 <20> i 0 (where the signs of the real and imaginary parts of
|
|
|
|
|
|
the result are unspecified).
|
|
|
|
|
|
-- cexp(+ + i ) returns <20> + i NaN and raises the ``invalid'' floating-point
|
|
|
|
|
|
exception (where the sign of the real part of the result is unspecified).
|
|
|
|
|
|
-- cexp(- + i NaN) returns <20>0 <20> i 0 (where the signs of the real and imaginary parts
|
|
|
|
|
|
of the result are unspecified).
|
|
|
|
|
|
-- cexp(+ + i NaN) returns <20> + i NaN (where the sign of the real part of the result
|
|
|
|
|
|
is unspecified).
|
|
|
|
|
|
-- cexp(NaN + i 0) returns NaN + i 0.
|
|
|
|
|
|
-- cexp(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for all nonzero numbers y .
|
|
|
|
|
|
-- cexp(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.3.2 The clog functions
|
|
|
|
|
|
1 -- clog(conj( z )) = conj(clog( z )).
|
|
|
|
|
|
-- clog(-0 + i 0) returns - + i and raises the ``divide-by-zero'' floating-point
|
|
|
|
|
|
exception.
|
|
|
|
|
|
-- clog(+0 + i 0) returns - + i 0 and raises the ``divide-by-zero'' floating-point
|
|
|
|
|
|
exception.
|
|
|
|
|
|
-- clog( x + i ) returns + + i /2, for finite x .
|
|
|
|
|
|
-- clog( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite x .
|
|
|
|
|
|
-- clog(- + iy ) returns + + i , for finite positive-signed y .
|
|
|
|
|
|
-- clog(+ + iy ) returns + + i 0, for finite positive-signed y .
|
|
|
|
|
|
-- clog(- + i ) returns + + i 3 /4.
|
|
|
|
|
|
-- clog(+ + i ) returns + + i /4.
|
|
|
|
|
|
-- clog(<28> + i NaN) returns + + i NaN.
|
|
|
|
|
|
-- clog(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite y .
|
|
|
|
|
|
-- clog(NaN + i ) returns + + i NaN.
|
|
|
|
|
|
-- clog(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
G.6.4 Power and absolute-value functions
|
|
|
|
|
|
G.6.4.1 The cpow functions
|
|
|
|
|
|
1 The cpow functions raise floating-point exceptions if appropriate for the calculation of
|
|
|
|
|
|
the parts of the result, and may raise spurious exceptions.327)
|
|
|
|
|
|
G.6.4.2 The csqrt functions
|
|
|
|
|
|
1 -- csqrt(conj( z )) = conj(csqrt( z )).
|
|
|
|
|
|
-- csqrt(<28>0 + i 0) returns +0 + i 0.
|
|
|
|
|
|
-- csqrt( x + i ) returns + + i , for all x (including NaN).
|
|
|
|
|
|
-- csqrt( x + i NaN) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite x .
|
|
|
|
|
|
-- csqrt(- + iy ) returns +0 + i , for finite positive-signed y .
|
|
|
|
|
|
-- csqrt(+ + iy ) returns + + i 0, for finite positive-signed y .
|
|
|
|
|
|
-- csqrt(- + i NaN) returns NaN <20> i (where the sign of the imaginary part of the
|
|
|
|
|
|
result is unspecified).
|
|
|
|
|
|
-- csqrt(+ + i NaN) returns + + i NaN.
|
|
|
|
|
|
-- csqrt(NaN + iy ) returns NaN + i NaN and optionally raises the ``invalid'' floating-
|
|
|
|
|
|
point exception, for finite y .
|
|
|
|
|
|
-- csqrt(NaN + i NaN) returns NaN + i NaN.
|
|
|
|
|
|
327) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
|
|
|
|
|
|
implementations that treat special cases more carefully.
|
|
|
|
|
|
G.7 Type-generic math <tgmath.h>
|
|
|
|
|
|
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.
|
|
|
|
|
|
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 )
|
|
|
|
|
|
|
|
|
|
|
|
Annex H
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
H. Language independent arithmetic
|
2012-01-16 16:34:32 +01:00
|
|
|
|
H.1 Introduction
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.2 Types
|
|
|
|
|
|
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).
|
|
|
|
|
|
H.2.1 Boolean type
|
|
|
|
|
|
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>.
|
|
|
|
|
|
H.2.2 Integer types
|
|
|
|
|
|
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.
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
|
|
H.2.2.1 Integer operations
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.2.3 Floating-point types
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.2.3.1 Floating-point parameters
|
|
|
|
|
|
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
|
|
|
|
|
|
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
|
|
|
|
|
|
H.2.3.2 Floating-point operations
|
|
|
|
|
|
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 1.f+logbf(x), 1.0+logb(x), 1.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.
|
|
|
|
|
|
H.2.3.3 Rounding styles
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.2.4 Type conversions
|
|
|
|
|
|
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
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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).
|
|
|
|
|
|
5 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
|
|
|
|
|
|
implementation uses round-to-nearest.
|
|
|
|
|
|
|
|
|
|
|
|
H.3 Notification
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.3.1 Notification alternatives
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.3.1.1 Indicators
|
|
|
|
|
|
1 C's <fenv.h> status flags are compatible with the LIA-1 indicators.
|
|
|
|
|
|
2 The following mapping is for floating-point types:
|
|
|
|
|
|
undefined FE_INVALID, FE_DIVBYZERO
|
|
|
|
|
|
floating_overflow FE_OVERFLOW
|
|
|
|
|
|
underflow FE_UNDERFLOW
|
|
|
|
|
|
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.
|
|
|
|
|
|
4 C allows an implementation to provide the following LIA-1 required behavior: at
|
|
|
|
|
|
program termination if any indicator is set the implementation shall send an unambiguous
|
|
|
|
|
|
and ``hard to ignore'' message (see LIA-1 subclause 6.1.2)
|
|
|
|
|
|
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.
|
|
|
|
|
|
H.3.1.2 Traps
|
|
|
|
|
|
1 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
|
|
|
|
|
|
math library functions (which are not permitted to generate any externally visible
|
|
|
|
|
|
exceptional conditions). An implementation can provide an alternative of notification
|
|
|
|
|
|
through termination with a ``hard-to-ignore'' message (see LIA-1 subclause 6.1.3).
|
|
|
|
|
|
2 LIA-1 does not require that traps be precise.
|
|
|
|
|
|
3 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
|
|
|
|
|
|
is any signal raised for them.
|
|
|
|
|
|
4 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
|
|
|
|
|
|
When 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.
|
|
|
|
|
|
|
|
|
|
|
|
Annex I
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
I. Common warnings
|
2012-01-16 16:34:32 +01:00
|
|
|
|
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.
|
|
|
|
|
|
2 -- A new struct or union type appears in a function prototype (6.2.1, 6.7.2.3).
|
|
|
|
|
|
-- A block with initialization of an object that has automatic storage duration is jumped
|
|
|
|
|
|
into (6.2.4).
|
|
|
|
|
|
-- 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 (6.3).
|
|
|
|
|
|
-- A hexadecimal floating constant cannot be represented exactly in its evaluation format
|
|
|
|
|
|
(6.4.4.2).
|
|
|
|
|
|
-- An integer character constant includes more than one character or a wide character
|
|
|
|
|
|
constant includes more than one multibyte character (6.4.4.4).
|
|
|
|
|
|
-- The characters /* are found in a comment (6.4.7).
|
|
|
|
|
|
-- 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 (6.5).
|
|
|
|
|
|
-- A function is called but no prototype has been supplied (6.5.2.2).
|
|
|
|
|
|
-- 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 (6.5.2.2).
|
|
|
|
|
|
-- An object is defined but not used (6.7).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(6.7.2.2).
|
|
|
|
|
|
-- An aggregate has a partly bracketed initialization (6.7.7).
|
|
|
|
|
|
-- A statement cannot be reached (6.8).
|
|
|
|
|
|
-- A statement with no apparent effect is encountered (6.8).
|
|
|
|
|
|
-- A constant expression is used as the controlling expression of a selection statement
|
|
|
|
|
|
(6.8.4).
|
|
|
|
|
|
-- An incorrectly formed preprocessing group is encountered while skipping a
|
|
|
|
|
|
preprocessing group (6.10.1).
|
|
|
|
|
|
-- An unrecognized #pragma directive is encountered (6.10.6).
|
|
|
|
|
|
|
|
|
|
|
|
Annex J
|
|
|
|
|
|
(informative)
|
2012-01-17 03:07:01 +01:00
|
|
|
|
J. Portability issues
|
2012-01-16 16:34:32 +01:00
|
|
|
|
1 This annex collects some information about portability that appears in this International
|
|
|
|
|
|
Standard.
|
|
|
|
|
|
J.1 Unspecified behavior
|
|
|
|
|
|
1 The following are unspecified:
|
|
|
|
|
|
-- The manner and timing of static initialization (5.1.2).
|
|
|
|
|
|
-- The termination status returned to the hosted environment if the return type of main
|
|
|
|
|
|
is not compatible with int (5.1.2.2.3).
|
|
|
|
|
|
-- The behavior of the display device if a printing character is written when the active
|
|
|
|
|
|
position is at the final position of a line (5.2.2).
|
|
|
|
|
|
-- The behavior of the display device if a backspace character is written when the active
|
|
|
|
|
|
position is at the initial position of a line (5.2.2).
|
|
|
|
|
|
-- 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 (5.2.2).
|
|
|
|
|
|
-- 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 (5.2.2).
|
|
|
|
|
|
-- How an extended source character that does not correspond to a universal character
|
|
|
|
|
|
name counts toward the significant initial characters in an external identifier (5.2.4.1).
|
|
|
|
|
|
-- Many aspects of the representations of types (6.2.6).
|
|
|
|
|
|
-- The value of padding bytes when storing values in structures or unions (6.2.6.1).
|
|
|
|
|
|
-- The value of a union member other than the last one stored into (6.2.6.1).
|
|
|
|
|
|
-- The representation used when storing a value in an object that has more than one
|
|
|
|
|
|
object representation for that value (6.2.6.1).
|
|
|
|
|
|
-- The values of any padding bits in integer representations (6.2.6.2).
|
|
|
|
|
|
-- Whether certain operators can generate negative zeros and whether a negative zero
|
|
|
|
|
|
becomes a normal zero when stored in an object (6.2.6.2).
|
|
|
|
|
|
-- Whether two string literals result in distinct arrays (6.4.5).
|
|
|
|
|
|
-- 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 (6.5).
|
|
|
|
|
|
-- The order in which the function designator, arguments, and subexpressions within the
|
|
|
|
|
|
arguments are evaluated in a function call (6.5.2.2).
|
|
|
|
|
|
-- The order of side effects among compound literal initialization list expressions
|
|
|
|
|
|
(6.5.2.5).
|
|
|
|
|
|
-- The order in which the operands of an assignment operator are evaluated (6.5.16).
|
|
|
|
|
|
-- The alignment of the addressable storage unit allocated to hold a bit-field (6.7.2.1).
|
|
|
|
|
|
-- Whether a call to an inline function uses the inline definition or the external definition
|
|
|
|
|
|
of the function (6.7.4).
|
|
|
|
|
|
-- 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 (6.7.5.2).
|
|
|
|
|
|
-- The order in which any side effects occur among the initialization list expressions in
|
|
|
|
|
|
an initializer (6.7.8).
|
|
|
|
|
|
-- The layout of storage for function parameters (6.9.1).
|
|
|
|
|
|
-- 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 (6.10.3).
|
|
|
|
|
|
-- The order in which # and ## operations are evaluated during macro substitution
|
|
|
|
|
|
(6.10.3.2, 6.10.3.3).
|
|
|
|
|
|
-- Whether errno is a macro or an identifier with external linkage (7.5).
|
|
|
|
|
|
-- 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'' (7.6.1).
|
|
|
|
|
|
-- The order in which feraiseexcept raises floating-point exceptions, except as
|
|
|
|
|
|
stated in F.7.6 (7.6.2.3).
|
|
|
|
|
|
-- Whether math_errhandling is a macro or an identifier with external linkage
|
|
|
|
|
|
(7.12).
|
|
|
|
|
|
-- The results of the frexp functions when the specified value is not a floating-point
|
|
|
|
|
|
number (7.12.6.4).
|
|
|
|
|
|
-- The numeric result of the ilogb functions when the correct value is outside the
|
|
|
|
|
|
range of the return type (7.12.6.5, F.9.3.5).
|
|
|
|
|
|
-- The result of rounding when the value is out of range (7.12.9.5, 7.12.9.7, F.9.6.5).
|
|
|
|
|
|
-- The value stored by the remquo functions in the object pointed to by quo when y is
|
|
|
|
|
|
zero (7.12.10.3).
|
|
|
|
|
|
-- Whether setjmp is a macro or an identifier with external linkage (7.13).
|
|
|
|
|
|
-- Whether va_copy and va_end are macros or identifiers with external linkage
|
|
|
|
|
|
(7.15.1).
|
|
|
|
|
|
-- The hexadecimal digit before the decimal point when a non-normalized floating-point
|
|
|
|
|
|
number is printed with an a or A conversion specifier (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- 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 (7.19.7.11, 7.24.3.10).
|
|
|
|
|
|
-- The details of the value stored by the fgetpos function (7.19.9.1).
|
|
|
|
|
|
-- The details of the value returned by the ftell function for a text stream (7.19.9.4).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.20.1.3, 7.24.4.1.1).
|
|
|
|
|
|
-- The order and contiguity of storage allocated by successive calls to the calloc,
|
|
|
|
|
|
malloc, and realloc functions (7.20.3).
|
|
|
|
|
|
-- The amount of storage allocated by a successful call to the calloc, malloc, or
|
|
|
|
|
|
realloc function when 0 bytes was requested (7.20.3).
|
|
|
|
|
|
-- Which of two elements that compare as equal is matched by the bsearch function
|
|
|
|
|
|
(7.20.5.1).
|
|
|
|
|
|
-- The order of two elements that compare as equal in an array sorted by the qsort
|
|
|
|
|
|
function (7.20.5.2).
|
|
|
|
|
|
-- The encoding of the calendar time returned by the time function (7.23.2.4).
|
|
|
|
|
|
-- The characters stored by the strftime or wcsftime function if any of the time
|
|
|
|
|
|
values being converted is outside the normal range (7.23.3.5, 7.24.5.1).
|
|
|
|
|
|
-- The conversion state after an encoding error occurs (7.24.6.3.2, 7.24.6.3.3, 7.24.6.4.1,
|
2012-01-17 01:08:26 +01:00
|
|
|
|
7.24.6.4.2,
|
2012-01-16 16:34:32 +01:00
|
|
|
|
-- The resulting value when the ``invalid'' floating-point exception is raised during
|
|
|
|
|
|
IEC 60559 floating to integer conversion (F.4).
|
|
|
|
|
|
-- Whether conversion of non-integer IEC 60559 floating values to integer raises the
|
|
|
|
|
|
``inexact'' floating-point exception (F.4).
|
|
|
|
|
|
-- Whether or when library functions in <math.h> raise the ``inexact'' floating-point
|
|
|
|
|
|
exception in an IEC 60559 conformant implementation (F.9).
|
|
|
|
|
|
-- Whether or when library functions in <math.h> raise an undeserved ``underflow''
|
|
|
|
|
|
floating-point exception in an IEC 60559 conformant implementation (F.9).
|
|
|
|
|
|
-- The exponent value stored by frexp for a NaN or infinity (F.9.3.4).
|
|
|
|
|
|
-- The numeric result returned by the lrint, llrint, lround, and llround
|
|
|
|
|
|
functions if the rounded value is outside the range of the return type (F.9.6.5, F.9.6.7).
|
|
|
|
|
|
-- The sign of one part of the complex result of several math functions for certain
|
|
|
|
|
|
exceptional values in IEC 60559 compatible implementations (G.6.1.1, G.6.2.2,
|
|
|
|
|
|
G.6.2.3, G.6.2.4, G.6.2.5, G.6.2.6, G.6.3.1, G.6.4.2).
|
|
|
|
|
|
J.2 Undefined behavior
|
|
|
|
|
|
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 (5.1.1.2).
|
|
|
|
|
|
-- Token concatenation produces a character sequence matching the syntax of a
|
|
|
|
|
|
universal character name (5.1.1.2).
|
|
|
|
|
|
-- A program in a hosted environment does not define a function named main using one
|
|
|
|
|
|
of the specified forms (5.1.2.2.1).
|
|
|
|
|
|
-- 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 (5.2.1).
|
|
|
|
|
|
-- 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 (5.2.1.2).
|
|
|
|
|
|
-- The same identifier has both internal and external linkage in the same translation unit
|
|
|
|
|
|
(6.2.2).
|
|
|
|
|
|
-- An object is referred to outside of its lifetime (6.2.4).
|
|
|
|
|
|
-- The value of a pointer to an object whose lifetime has ended is used (6.2.4).
|
|
|
|
|
|
-- The value of an object with automatic storage duration is used while it is
|
|
|
|
|
|
indeterminate (6.2.4, 6.7.8, 6.8).
|
|
|
|
|
|
-- A trap representation is read by an lvalue expression that does not have character type
|
|
|
|
|
|
(6.2.6.1).
|
2012-01-23 23:24:51 +01:00
|
|
|
|
-- 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 (6.2.6.1).
|
|
|
|
|
|
-- The arguments to certain operators are such that could produce a negative zero result,
|
|
|
|
|
|
but the implementation does not support negative zeros (6.2.6.2).
|
|
|
|
|
|
-- Two declarations of the same object or function specify types that are not compatible
|
|
|
|
|
|
(6.2.7).
|
|
|
|
|
|
-- Conversion to or from an integer type produces a value outside the range that can be
|
|
|
|
|
|
represented (6.3.1.4).
|
|
|
|
|
|
-- Demotion of one real floating type to another produces a value outside the range that
|
|
|
|
|
|
can be represented (6.3.1.5).
|
|
|
|
|
|
-- An lvalue does not designate an object when evaluated (6.3.2.1).
|
|
|
|
|
|
-- A non-array lvalue with an incomplete type is used in a context that requires the value
|
|
|
|
|
|
of the designated object (6.3.2.1).
|
|
|
|
|
|
-- 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 (6.3.2.1).
|
|
|
|
|
|
-- 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 (6.3.2.2).
|
|
|
|
|
|
-- Conversion of a pointer to an integer type produces a value outside the range that can
|
|
|
|
|
|
be represented (6.3.2.3).
|
|
|
|
|
|
-- Conversion between two pointer types produces a result that is incorrectly aligned
|
|
|
|
|
|
(6.3.2.3).
|
|
|
|
|
|
-- A pointer is used to call a function whose type is not compatible with the pointed-to
|
|
|
|
|
|
type (6.3.2.3).
|
|
|
|
|
|
-- An unmatched ' or " character is encountered on a logical source line during
|
|
|
|
|
|
tokenization (6.4).
|
|
|
|
|
|
-- A reserved keyword token is used in translation phase 7 or 8 for some purpose other
|
|
|
|
|
|
than as a keyword (6.4.1).
|
|
|
|
|
|
-- A universal character name in an identifier does not designate a character whose
|
|
|
|
|
|
encoding falls into one of the specified ranges (6.4.2.1).
|
|
|
|
|
|
-- The initial character of an identifier is a universal character name designating a digit
|
|
|
|
|
|
(6.4.2.1).
|
|
|
|
|
|
-- Two identifiers differ only in nonsignificant characters (6.4.2.1).
|
|
|
|
|
|
-- The identifier _ _func_ _ is explicitly declared (6.4.2.2).
|
|
|
|
|
|
-- The program attempts to modify a string literal (6.4.5).
|
|
|
|
|
|
-- 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 (6.4.7).
|
|
|
|
|
|
-- Between two sequence points, an object is modified more than once, or is modified
|
|
|
|
|
|
and the prior value is read other than to determine the value to be stored (6.5).
|
|
|
|
|
|
-- An exceptional condition occurs during the evaluation of an expression (6.5).
|
|
|
|
|
|
-- An object has its stored value accessed other than by an lvalue of an allowable type
|
|
|
|
|
|
(6.5).
|
|
|
|
|
|
-- An attempt is made to modify the result of a function call, a conditional operator, an
|
|
|
|
|
|
assignment operator, or a comma operator, or to access it after the next sequence
|
|
|
|
|
|
point (6.5.2.2, 6.5.15, 6.5.16, 6.5.17).
|
|
|
|
|
|
-- For a call to a function without a function prototype in scope, the number of
|
|
|
|
|
|
arguments does not equal the number of parameters (6.5.2.2).
|
|
|
|
|
|
-- 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 (6.5.2.2).
|
|
|
|
|
|
-- 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)
|
|
|
|
|
|
(6.5.2.2).
|
|
|
|
|
|
-- 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 (6.5.2.2).
|
|
|
|
|
|
-- The operand of the unary * operator has an invalid value (6.5.3.2).
|
|
|
|
|
|
-- A pointer is converted to other than an integer or pointer type (6.5.4).
|
|
|
|
|
|
-- The value of the second operand of the / or % operator is zero (6.5.5).
|
|
|
|
|
|
-- 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 (6.5.6).
|
|
|
|
|
|
-- 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 (6.5.6).
|
|
|
|
|
|
-- Pointers that do not point into, or just beyond, the same array object are subtracted
|
|
|
|
|
|
(6.5.6).
|
|
|
|
|
|
-- 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]) (6.5.6).
|
|
|
|
|
|
-- The result of subtracting two pointers is not representable in an object of type
|
|
|
|
|
|
ptrdiff_t (6.5.6).
|
|
|
|
|
|
-- An expression is shifted by a negative number or by an amount greater than or equal
|
|
|
|
|
|
to the width of the promoted expression (6.5.7).
|
|
|
|
|
|
-- 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 (6.5.7).
|
|
|
|
|
|
-- Pointers that do not point to the same aggregate or union (nor just beyond the same
|
|
|
|
|
|
array object) are compared using relational operators (6.5.8).
|
|
|
|
|
|
-- An object is assigned to an inexactly overlapping object or to an exactly overlapping
|
|
|
|
|
|
object with incompatible type (6.5.16.1).
|
|
|
|
|
|
-- 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, or
|
|
|
|
|
|
immediately-cast floating constants; or contains casts (outside operands to sizeof
|
|
|
|
|
|
operators) other than conversions of arithmetic types to integer types (6.6).
|
|
|
|
|
|
-- 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 an object type plus or minus an integer constant
|
|
|
|
|
|
expression (6.6).
|
|
|
|
|
|
-- An arithmetic constant expression does not have arithmetic type; has operands that
|
|
|
|
|
|
are not integer constants, floating constants, enumeration constants, character
|
|
|
|
|
|
constants, or sizeof expressions; or contains casts (outside operands to sizeof
|
|
|
|
|
|
operators) other than conversions of arithmetic types to arithmetic types (6.6).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(6.6).
|
|
|
|
|
|
-- 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 (6.7).
|
|
|
|
|
|
-- A function is declared at block scope with an explicit storage-class specifier other
|
|
|
|
|
|
than extern (6.7.1).
|
|
|
|
|
|
-- A structure or union is defined as containing no named members (6.7.2.1).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(6.7.2.1).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(6.7.2.3).
|
|
|
|
|
|
-- An attempt is made to modify an object defined with a const-qualified type through
|
|
|
|
|
|
use of an lvalue with non-const-qualified type (6.7.3).
|
|
|
|
|
|
-- 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 (6.7.3).
|
|
|
|
|
|
-- The specification of a function type includes any type qualifiers (6.7.3).
|
|
|
|
|
|
-- Two qualified types that are required to be compatible do not have the identically
|
|
|
|
|
|
qualified version of a compatible type (6.7.3).
|
|
|
|
|
|
-- 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 (6.7.3.1).
|
|
|
|
|
|
-- 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 (6.7.3.1).
|
|
|
|
|
|
-- A function with external linkage is declared with an inline function specifier, but is
|
|
|
|
|
|
not also defined in the same translation unit (6.7.4).
|
|
|
|
|
|
-- Two pointer types that are required to be compatible are not identically qualified, or
|
|
|
|
|
|
are not pointers to compatible types (6.7.5.1).
|
|
|
|
|
|
-- The size expression in an array declaration is not a constant expression and evaluates
|
|
|
|
|
|
at program execution time to a nonpositive value (6.7.5.2).
|
|
|
|
|
|
-- 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 (6.7.5.2).
|
|
|
|
|
|
-- 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 (6.7.5.3).
|
|
|
|
|
|
-- A storage-class specifier or type qualifier modifies the keyword void as a function
|
|
|
|
|
|
parameter type list (6.7.5.3).
|
|
|
|
|
|
-- 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) (6.7.5.3).
|
|
|
|
|
|
-- The value of an unnamed member of a structure or union is used (6.7.8).
|
|
|
|
|
|
-- The initializer for a scalar is neither a single expression nor a single expression
|
|
|
|
|
|
enclosed in braces (6.7.8).
|
|
|
|
|
|
-- 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 (6.7.8).
|
|
|
|
|
|
-- 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 (6.7.8).
|
|
|
|
|
|
-- 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 (6.9).
|
|
|
|
|
|
-- A function definition includes an identifier list, but the types of the parameters are not
|
|
|
|
|
|
declared in a following declaration list (6.9.1).
|
|
|
|
|
|
-- An adjusted parameter type in a function definition is not an object type (6.9.1).
|
|
|
|
|
|
-- A function that accepts a variable number of arguments is defined without a
|
|
|
|
|
|
parameter type list that ends with the ellipsis notation (6.9.1).
|
|
|
|
|
|
-- The } that terminates a function is reached, and the value of the function call is used
|
|
|
|
|
|
by the caller (6.9.1).
|
|
|
|
|
|
-- An identifier for an object with internal linkage and an incomplete type is declared
|
|
|
|
|
|
with a tentative definition (6.9.2).
|
|
|
|
|
|
-- 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 (6.10.1).
|
|
|
|
|
|
-- The #include preprocessing directive that results after expansion does not match
|
|
|
|
|
|
one of the two header name forms (6.10.2).
|
|
|
|
|
|
-- The character sequence in an #include preprocessing directive does not start with a
|
|
|
|
|
|
letter (6.10.2).
|
|
|
|
|
|
-- There are sequences of preprocessing tokens within the list of macro arguments that
|
|
|
|
|
|
would otherwise act as preprocessing directives (6.10.3).
|
|
|
|
|
|
-- The result of the preprocessing operator # is not a valid character string literal
|
|
|
|
|
|
(6.10.3.2).
|
|
|
|
|
|
-- The result of the preprocessing operator ## is not a valid preprocessing token
|
|
|
|
|
|
(6.10.3.3).
|
|
|
|
|
|
-- 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 (6.10.4).
|
|
|
|
|
|
-- A non-STDC #pragma preprocessing directive that is documented as causing
|
|
|
|
|
|
translation failure or some other form of undefined behavior is encountered (6.10.6).
|
|
|
|
|
|
-- A #pragma STDC preprocessing directive does not match one of the well-defined
|
|
|
|
|
|
forms (6.10.6).
|
|
|
|
|
|
-- The name of a predefined macro, or the identifier defined, is the subject of a
|
|
|
|
|
|
#define or #undef preprocessing directive (6.10.8).
|
|
|
|
|
|
-- 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 (7.1.2).
|
|
|
|
|
|
-- A header is included within an external declaration or definition (7.1.2).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.1.2).
|
|
|
|
|
|
-- A standard header is included while a macro is defined with the same name as a
|
|
|
|
|
|
keyword (7.1.2).
|
|
|
|
|
|
-- The program attempts to declare a library function itself, rather than via a standard
|
|
|
|
|
|
header, but the declaration does not have external linkage (7.1.2).
|
|
|
|
|
|
-- The program declares or defines a reserved identifier, other than as allowed by 7.1.4
|
|
|
|
|
|
(7.1.3).
|
|
|
|
|
|
-- The program removes the definition of a macro whose name begins with an
|
|
|
|
|
|
underscore and either an uppercase letter or another underscore (7.1.3).
|
|
|
|
|
|
-- An argument to a library function has an invalid value or a type not expected by a
|
|
|
|
|
|
function with variable number of arguments (7.1.4).
|
|
|
|
|
|
-- The pointer passed to a library function array parameter does not have a value such
|
|
|
|
|
|
that all address computations and object accesses are valid (7.1.4).
|
|
|
|
|
|
-- The macro definition of assert is suppressed in order to access an actual function
|
|
|
|
|
|
(7.2).
|
|
|
|
|
|
-- The argument to the assert macro does not have a scalar type (7.2).
|
|
|
|
|
|
-- 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 (7.3.4, 7.6.1, 7.12.2).
|
|
|
|
|
|
-- The value of an argument to a character handling function is neither equal to the value
|
|
|
|
|
|
of EOF nor representable as an unsigned char (7.4).
|
|
|
|
|
|
-- A macro definition of errno is suppressed in order to access an actual object, or the
|
|
|
|
|
|
program defines an identifier with the name errno (7.5).
|
|
|
|
|
|
-- 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'' (7.6.1).
|
|
|
|
|
|
-- 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 (7.6.2).
|
|
|
|
|
|
-- 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 (7.6.2.4).
|
|
|
|
|
|
-- The argument to fesetenv or feupdateenv is neither an object set by a call to
|
|
|
|
|
|
fegetenv or feholdexcept, nor is it an environment macro (7.6.4.3, 7.6.4.4).
|
|
|
|
|
|
-- The value of the result of an integer arithmetic or conversion function cannot be
|
|
|
|
|
|
represented (7.8.2.1, 7.8.2.2, 7.8.2.3, 7.8.2.4, 7.20.6.1, 7.20.6.2, 7.20.1).
|
|
|
|
|
|
-- The program modifies the string pointed to by the value returned by the setlocale
|
|
|
|
|
|
function (7.11.1.1).
|
|
|
|
|
|
-- The program modifies the structure pointed to by the value returned by the
|
|
|
|
|
|
localeconv function (7.11.2.1).
|
|
|
|
|
|
-- A macro definition of math_errhandling is suppressed or the program defines
|
|
|
|
|
|
an identifier with the name math_errhandling (7.12).
|
|
|
|
|
|
-- An argument to a floating-point classification or comparison macro is not of real
|
|
|
|
|
|
floating type (7.12.3, 7.12.14).
|
|
|
|
|
|
-- 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 (7.13).
|
|
|
|
|
|
-- An invocation of the setjmp macro occurs other than in an allowed context
|
|
|
|
|
|
(7.13.2.1).
|
|
|
|
|
|
-- The longjmp function is invoked to restore a nonexistent environment (7.13.2.1).
|
|
|
|
|
|
-- After a longjmp, there is an attempt to access the value of an object of automatic
|
|
|
|
|
|
storage class with non-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 (7.13.2.1).
|
|
|
|
|
|
-- The program specifies an invalid pointer to a signal handler function (7.14.1.1).
|
|
|
|
|
|
-- A signal handler returns when the signal corresponded to a computational exception
|
|
|
|
|
|
(7.14.1.1).
|
|
|
|
|
|
-- A signal occurs as the result of calling the abort or raise function, and the signal
|
|
|
|
|
|
handler calls the raise function (7.14.1.1).
|
|
|
|
|
|
-- 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 storage duration 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,
|
|
|
|
|
|
or the signal function (for the same signal number) (7.14.1.1).
|
|
|
|
|
|
-- 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 (7.14.1.1).
|
|
|
|
|
|
-- A signal is generated by an asynchronous signal handler (7.14.1.1).
|
|
|
|
|
|
-- 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 (7.15, 7.15.1.1, 7.15.1.4).
|
|
|
|
|
|
-- 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 (7.15).
|
|
|
|
|
|
-- 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 (7.15.1).
|
|
|
|
|
|
-- 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 (7.15.1, 7.15.1.2, 7.15.1.3,
|
|
|
|
|
|
7.15.1.4).
|
|
|
|
|
|
-- 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 * (7.15.1.1).
|
|
|
|
|
|
-- 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 (7.15.1.1).
|
|
|
|
|
|
-- 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 (7.15.1.2, 7.15.1.4).
|
|
|
|
|
|
-- 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 (7.15.1.4).
|
|
|
|
|
|
-- 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 (7.17).
|
|
|
|
|
|
-- 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 (7.18.4).
|
|
|
|
|
|
-- 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 (7.19.2).
|
|
|
|
|
|
-- Use is made of any portion of a file beyond the most recent wide character written to
|
|
|
|
|
|
a wide-oriented stream (7.19.2).
|
|
|
|
|
|
-- The value of a pointer to a FILE object is used after the associated file is closed
|
|
|
|
|
|
(7.19.3).
|
|
|
|
|
|
-- The stream for the fflush function points to an input stream or to an update stream
|
|
|
|
|
|
in which the most recent operation was input (7.19.5.2).
|
|
|
|
|
|
-- 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 (7.19.5.3).
|
|
|
|
|
|
-- 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 (7.19.5.3).
|
|
|
|
|
|
-- An attempt is made to use the contents of the array that was supplied in a call to the
|
|
|
|
|
|
setvbuf function (7.19.5.6).
|
|
|
|
|
|
-- 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 (7.19.6.1,
|
|
|
|
|
|
7.19.6.2, 7.24.2.1, 7.24.2.2).
|
|
|
|
|
|
-- 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 (7.19.6.1, 7.19.6.2, 7.23.3.5, 7.24.2.1, 7.24.2.2,
|
|
|
|
|
|
7.24.5.1).
|
|
|
|
|
|
-- In a call to one of the formatted output functions, a precision appears with a
|
|
|
|
|
|
conversion specifier other than those described (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- 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 (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- A conversion specification for a formatted output function uses a # or 0 flag with a
|
|
|
|
|
|
conversion specifier other than those described (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- A conversion specification for one of the formatted input/output functions uses a
|
|
|
|
|
|
length modifier with a conversion specifier other than those described (7.19.6.1,
|
|
|
|
|
|
7.19.6.2, 7.24.2.1, 7.24.2.2).
|
|
|
|
|
|
-- 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) (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- 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 (7.19.6.1,
|
|
|
|
|
|
7.19.6.2, 7.24.2.1, 7.24.2.2).
|
|
|
|
|
|
-- A % conversion specifier is encountered by one of the formatted input/output
|
|
|
|
|
|
functions, but the complete conversion specification is not exactly %% (7.19.6.1,
|
|
|
|
|
|
7.19.6.2, 7.24.2.1, 7.24.2.2).
|
|
|
|
|
|
-- An invalid conversion specification is found in the format for one of the formatted
|
|
|
|
|
|
input/output functions, or the strftime or wcsftime function (7.19.6.1, 7.19.6.2,
|
|
|
|
|
|
7.23.3.5, 7.24.2.1, 7.24.2.2, 7.24.5.1).
|
|
|
|
|
|
-- The number of characters transmitted by a formatted output function is greater than
|
|
|
|
|
|
INT_MAX (7.19.6.1, 7.19.6.3, 7.19.6.8, 7.19.6.10).
|
|
|
|
|
|
-- 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 (7.19.6.2, 7.24.2.2).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
[) (7.19.6.2, 7.24.2.2).
|
|
|
|
|
|
-- 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 (7.19.6.2, 7.24.2.2).
|
|
|
|
|
|
-- 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 (7.19.6.2, 7.24.2.2).
|
|
|
|
|
|
-- 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 (7.19.6.8, 7.19.6.9, 7.19.6.10, 7.19.6.11, 7.19.6.12, 7.19.6.13, 7.19.6.14,
|
|
|
|
|
|
7.24.2.5, 7.24.2.6, 7.24.2.7, 7.24.2.8, 7.24.2.9, 7.24.2.10).
|
|
|
|
|
|
-- The contents of the array supplied in a call to the fgets, gets, or fgetws function
|
|
|
|
|
|
are used after a read error occurred (7.19.7.2, 7.19.7.7, 7.24.3.2).
|
|
|
|
|
|
-- 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 (7.19.7.11).
|
|
|
|
|
|
-- The file position indicator for a stream is used after an error occurred during a call to
|
|
|
|
|
|
the fread or fwrite function (7.19.8.1, 7.19.8.2).
|
|
|
|
|
|
-- A partial element read by a call to the fread function is used (7.19.8.1).
|
|
|
|
|
|
-- 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 (7.19.9.2).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.19.9.3).
|
|
|
|
|
|
-- 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 (7.20.3).
|
|
|
|
|
|
-- The value of a pointer that refers to space deallocated by a call to the free or
|
|
|
|
|
|
realloc function is used (7.20.3).
|
|
|
|
|
|
-- The pointer argument to the free or realloc function does not match a pointer
|
|
|
|
|
|
earlier returned by calloc, malloc, or realloc, or the space has been
|
|
|
|
|
|
deallocated by a call to free or realloc (7.20.3.2, 7.20.3.4).
|
|
|
|
|
|
-- The value of the object allocated by the malloc function is used (7.20.3.3).
|
|
|
|
|
|
-- The value of any bytes in a new object allocated by the realloc function beyond
|
|
|
|
|
|
the size of the old object are used (7.20.3.4).
|
|
|
|
|
|
-- The program executes more than one call to the exit function (7.20.4.3).
|
|
|
|
|
|
-- During the call to a function registered with the atexit function, a call is made to
|
|
|
|
|
|
the longjmp function that would terminate the call to the registered function
|
|
|
|
|
|
(7.20.4.3).
|
|
|
|
|
|
-- The string set up by the getenv or strerror function is modified by the program
|
|
|
|
|
|
(7.20.4.5, 7.21.6.2).
|
|
|
|
|
|
-- A command is executed through the system function in a way that is documented as
|
|
|
|
|
|
causing termination or some other form of undefined behavior (7.20.4.6).
|
|
|
|
|
|
-- A searching or sorting utility function is called with an invalid pointer argument, even
|
|
|
|
|
|
if the number of elements is zero (7.20.5).
|
|
|
|
|
|
-- 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 (7.20.5).
|
|
|
|
|
|
-- The array being searched by the bsearch function does not have its elements in
|
|
|
|
|
|
proper order (7.20.5.1).
|
|
|
|
|
|
-- The current conversion state is used by a multibyte/wide character conversion
|
|
|
|
|
|
function after changing the LC_CTYPE category (7.20.7).
|
|
|
|
|
|
-- A string or wide string utility function is instructed to access an array beyond the end
|
|
|
|
|
|
of an object (7.21.1, 7.24.4).
|
|
|
|
|
|
-- A string or wide string utility function is called with an invalid pointer argument, even
|
|
|
|
|
|
if the length is zero (7.21.1, 7.24.4).
|
|
|
|
|
|
-- 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 (7.21.4.5, 7.23.3.5, 7.24.4.4.4,
|
|
|
|
|
|
7.24.5.1).
|
|
|
|
|
|
-- The first argument in the very first call to the strtok or wcstok is a null pointer
|
|
|
|
|
|
(7.21.5.8, 7.24.4.5.7).
|
|
|
|
|
|
-- The type of an argument to a type-generic macro is not compatible with the type of
|
|
|
|
|
|
the corresponding parameter of the selected function (7.22).
|
|
|
|
|
|
-- A complex argument is supplied for a generic parameter of a type-generic macro that
|
|
|
|
|
|
has no corresponding complex function (7.22).
|
|
|
|
|
|
-- 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 (7.24.2.11).
|
|
|
|
|
|
-- 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 (7.24.4.5.7).
|
|
|
|
|
|
-- An mbstate_t object is used inappropriately (7.24.6).
|
|
|
|
|
|
-- 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 (7.25.1).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.25.2.2.1).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.25.3.2.1).
|
2012-01-16 16:34:32 +01:00
|
|
|
|
|
|
|
|
|
|
J.3 Implementation-defined behavior
|
|
|
|
|
|
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:
|
|
|
|
|
|
J.3.1 Translation
|
|
|
|
|
|
1 -- How a diagnostic is identified (3.10, 5.1.1.3).
|
|
|
|
|
|
-- Whether each nonempty sequence of white-space characters other than new-line is
|
|
|
|
|
|
retained or replaced by one space character in translation phase 3 (5.1.1.2).
|
|
|
|
|
|
J.3.2 Environment
|
|
|
|
|
|
1 -- The mapping between physical source file multibyte characters and the source
|
|
|
|
|
|
character set in translation phase 1 (5.1.1.2).
|
|
|
|
|
|
-- The name and type of the function called at program startup in a freestanding
|
|
|
|
|
|
environment (5.1.2.1).
|
|
|
|
|
|
-- The effect of program termination in a freestanding environment (5.1.2.1).
|
|
|
|
|
|
-- An alternative manner in which the main function may be defined (5.1.2.2.1).
|
|
|
|
|
|
-- The values given to the strings pointed to by the argv argument to main (5.1.2.2.1).
|
|
|
|
|
|
-- What constitutes an interactive device (5.1.2.3).
|
|
|
|
|
|
-- The set of signals, their semantics, and their default handling (7.14).
|
|
|
|
|
|
-- Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
|
|
|
|
|
|
computational exception (7.14.1.1).
|
|
|
|
|
|
-- Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
|
|
|
|
|
|
program startup (7.14.1.1).
|
|
|
|
|
|
-- The set of environment names and the method for altering the environment list used
|
|
|
|
|
|
by the getenv function (7.20.4.5).
|
|
|
|
|
|
-- The manner of execution of the string by the system function (7.20.4.6).
|
|
|
|
|
|
J.3.3 Identifiers
|
|
|
|
|
|
1 -- Which additional multibyte characters may appear in identifiers and their
|
|
|
|
|
|
correspondence to universal character names (6.4.2).
|
|
|
|
|
|
-- The number of significant initial characters in an identifier (5.2.4.1, 6.4.2).
|
|
|
|
|
|
|
|
|
|
|
|
J.3.4 Characters
|
|
|
|
|
|
1 -- The number of bits in a byte (3.6).
|
|
|
|
|
|
-- The values of the members of the execution character set (5.2.1).
|
|
|
|
|
|
-- The unique value of the member of the execution character set produced for each of
|
|
|
|
|
|
the standard alphabetic escape sequences (5.2.2).
|
|
|
|
|
|
-- The value of a char object into which has been stored any character other than a
|
|
|
|
|
|
member of the basic execution character set (6.2.5).
|
|
|
|
|
|
-- Which of signed char or unsigned char has the same range, representation,
|
|
|
|
|
|
and behavior as ``plain'' char (6.2.5, 6.3.1.1).
|
|
|
|
|
|
-- The mapping of members of the source character set (in character constants and string
|
|
|
|
|
|
literals) to members of the execution character set (6.4.4.4, 5.1.1.2).
|
|
|
|
|
|
-- 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 (6.4.4.4).
|
|
|
|
|
|
-- The value of a wide character constant containing more than one multibyte character,
|
|
|
|
|
|
or containing a multibyte character or escape sequence not represented in the
|
|
|
|
|
|
extended execution character set (6.4.4.4).
|
|
|
|
|
|
-- 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 (6.4.4.4).
|
|
|
|
|
|
-- The current locale used to convert a wide string literal into corresponding wide
|
|
|
|
|
|
character codes (6.4.5).
|
|
|
|
|
|
-- The value of a string literal containing a multibyte character or escape sequence not
|
|
|
|
|
|
represented in the execution character set (6.4.5).
|
|
|
|
|
|
J.3.5 Integers
|
|
|
|
|
|
1 -- Any extended integer types that exist in the implementation (6.2.5).
|
|
|
|
|
|
-- 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 (6.2.6.2).
|
|
|
|
|
|
-- The rank of any extended integer type relative to another extended integer type with
|
|
|
|
|
|
the same precision (6.3.1.1).
|
|
|
|
|
|
-- 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 (6.3.1.3).
|
|
|
|
|
|
-- The results of some bitwise operations on signed integers (6.5).
|
|
|
|
|
|
J.3.6 Floating point
|
|
|
|
|
|
1 -- The accuracy of the floating-point operations and of the library functions in
|
|
|
|
|
|
<math.h> and <complex.h> that return floating-point results (5.2.4.2.2).
|
|
|
|
|
|
-- 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> (5.2.4.2.2).
|
|
|
|
|
|
-- The rounding behaviors characterized by non-standard values of FLT_ROUNDS
|
|
|
|
|
|
(5.2.4.2.2).
|
|
|
|
|
|
-- The evaluation methods characterized by non-standard negative values of
|
|
|
|
|
|
FLT_EVAL_METHOD (5.2.4.2.2).
|
|
|
|
|
|
-- The direction of rounding when an integer is converted to a floating-point number that
|
|
|
|
|
|
cannot exactly represent the original value (6.3.1.4).
|
|
|
|
|
|
-- The direction of rounding when a floating-point number is converted to a narrower
|
|
|
|
|
|
floating-point number (6.3.1.5).
|
|
|
|
|
|
-- 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 (6.4.4.2).
|
|
|
|
|
|
-- Whether and how floating expressions are contracted when not disallowed by the
|
|
|
|
|
|
FP_CONTRACT pragma (6.5).
|
|
|
|
|
|
-- The default state for the FENV_ACCESS pragma (7.6.1).
|
|
|
|
|
|
-- Additional floating-point exceptions, rounding modes, environments, and
|
|
|
|
|
|
classifications, and their macro names (7.6, 7.12).
|
|
|
|
|
|
-- The default state for the FP_CONTRACT pragma (7.12.2).
|
|
|
|
|
|
J.3.7 Arrays and pointers
|
|
|
|
|
|
1 -- The result of converting a pointer to an integer or vice versa (6.3.2.3).
|
|
|
|
|
|
-- The size of the result of subtracting two pointers to elements of the same array
|
|
|
|
|
|
(6.5.6).
|
|
|
|
|
|
|
|
|
|
|
|
J.3.8 Hints
|
|
|
|
|
|
1 -- The extent to which suggestions made by using the register storage-class
|
|
|
|
|
|
specifier are effective (6.7.1).
|
|
|
|
|
|
-- The extent to which suggestions made by using the inline function specifier are
|
|
|
|
|
|
effective (6.7.4).
|
|
|
|
|
|
J.3.9 Structures, unions, enumerations, and bit-fields
|
|
|
|
|
|
1 -- Whether a ``plain'' int bit-field is treated as a signed int bit-field or as an
|
|
|
|
|
|
unsigned int bit-field (6.7.2, 6.7.2.1).
|
|
|
|
|
|
-- Allowable bit-field types other than _Bool, signed int, and unsigned int
|
|
|
|
|
|
(6.7.2.1).
|
|
|
|
|
|
-- Whether a bit-field can straddle a storage-unit boundary (6.7.2.1).
|
|
|
|
|
|
-- The order of allocation of bit-fields within a unit (6.7.2.1).
|
|
|
|
|
|
-- The alignment of non-bit-field members of structures (6.7.2.1). This should present
|
|
|
|
|
|
no problem unless binary data written by one implementation is read by another.
|
|
|
|
|
|
-- The integer type compatible with each enumerated type (6.7.2.2).
|
|
|
|
|
|
J.3.10 Qualifiers
|
|
|
|
|
|
1 -- What constitutes an access to an object that has volatile-qualified type (6.7.3).
|
|
|
|
|
|
J.3.11 Preprocessing directives
|
|
|
|
|
|
1 -- The locations within #pragma directives where header name preprocessing tokens
|
|
|
|
|
|
are recognized (6.4, 6.4.7).
|
|
|
|
|
|
-- How sequences in both forms of header names are mapped to headers or external
|
|
|
|
|
|
source file names (6.4.7).
|
|
|
|
|
|
-- 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 (6.10.1).
|
|
|
|
|
|
-- Whether the value of a single-character character constant in a constant expression
|
|
|
|
|
|
that controls conditional inclusion may have a negative value (6.10.1).
|
|
|
|
|
|
-- The places that are searched for an included < > delimited header, and how the places
|
|
|
|
|
|
are specified or the header is identified (6.10.2).
|
|
|
|
|
|
-- How the named source file is searched for in an included " " delimited header
|
|
|
|
|
|
(6.10.2).
|
|
|
|
|
|
-- The method by which preprocessing tokens (possibly resulting from macro
|
|
|
|
|
|
expansion) in a #include directive are combined into a header name (6.10.2).
|
|
|
|
|
|
-- The nesting limit for #include processing (6.10.2).
|
|
|
|
|
|
-- Whether the # operator inserts a \ character before the \ character that begins a
|
|
|
|
|
|
universal character name in a character constant or string literal (6.10.3.2).
|
|
|
|
|
|
-- The behavior on each recognized non-STDC #pragma directive (6.10.6).
|
|
|
|
|
|
-- The definitions for _ _DATE_ _ and _ _TIME_ _ when respectively, the date and
|
|
|
|
|
|
time of translation are not available (6.10.8).
|
|
|
|
|
|
J.3.12 Library functions
|
|
|
|
|
|
1 -- Any library facilities available to a freestanding program, other than the minimal set
|
|
|
|
|
|
required by clause 4 (5.1.2.1).
|
|
|
|
|
|
-- The format of the diagnostic printed by the assert macro (7.2.1.1).
|
|
|
|
|
|
-- The representation of the floating-point status flags stored by the
|
|
|
|
|
|
fegetexceptflag function (7.6.2.2).
|
|
|
|
|
|
-- Whether the feraiseexcept function raises the ``inexact'' floating-point
|
|
|
|
|
|
exception in addition to the ``overflow'' or ``underflow'' floating-point exception
|
|
|
|
|
|
(7.6.2.3).
|
|
|
|
|
|
-- Strings other than "C" and "" that may be passed as the second argument to the
|
|
|
|
|
|
setlocale function (7.11.1.1).
|
|
|
|
|
|
-- The types defined for float_t and double_t when the value of the
|
|
|
|
|
|
FLT_EVAL_METHOD macro is less than 0 (7.12).
|
|
|
|
|
|
-- Domain errors for the mathematics functions, other than those required by this
|
|
|
|
|
|
International Standard (7.12.1).
|
|
|
|
|
|
-- The values returned by the mathematics functions on domain errors (7.12.1).
|
|
|
|
|
|
-- 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. (7.12.1).
|
|
|
|
|
|
-- Whether a domain error occurs or zero is returned when an fmod function has a
|
|
|
|
|
|
second argument of zero (7.12.10.1).
|
|
|
|
|
|
-- Whether a domain error occurs or zero is returned when a remainder function has
|
|
|
|
|
|
a second argument of zero (7.12.10.2).
|
|
|
|
|
|
-- The base-2 logarithm of the modulus used by the remquo functions in reducing the
|
|
|
|
|
|
quotient (7.12.10.3).
|
2012-01-17 01:08:26 +01:00
|
|
|
|
-- Whether a domain error occurs or zero is returned when a remquo function has a
|
|
|
|
|
|
second argument of zero (7.12.10.3).
|
|
|
|
|
|
-- 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 (7.14.1.1).
|
|
|
|
|
|
-- The null pointer constant to which the macro NULL expands (7.17).
|
|
|
|
|
|
-- Whether the last line of a text stream requires a terminating new-line character
|
|
|
|
|
|
(7.19.2).
|
|
|
|
|
|
-- Whether space characters that are written out to a text stream immediately before a
|
|
|
|
|
|
new-line character appear when read in (7.19.2).
|
|
|
|
|
|
-- The number of null characters that may be appended to data written to a binary
|
|
|
|
|
|
stream (7.19.2).
|
|
|
|
|
|
-- Whether the file position indicator of an append-mode stream is initially positioned at
|
|
|
|
|
|
the beginning or end of the file (7.19.3).
|
|
|
|
|
|
-- Whether a write on a text stream causes the associated file to be truncated beyond that
|
|
|
|
|
|
point (7.19.3).
|
|
|
|
|
|
-- The characteristics of file buffering (7.19.3).
|
|
|
|
|
|
-- Whether a zero-length file actually exists (7.19.3).
|
|
|
|
|
|
-- The rules for composing valid file names (7.19.3).
|
|
|
|
|
|
-- Whether the same file can be simultaneously open multiple times (7.19.3).
|
|
|
|
|
|
-- The nature and choice of encodings used for multibyte characters in files (7.19.3).
|
|
|
|
|
|
-- The effect of the remove function on an open file (7.19.4.1).
|
|
|
|
|
|
-- The effect if a file with the new name exists prior to a call to the rename function
|
|
|
|
|
|
(7.19.4.2).
|
|
|
|
|
|
-- Whether an open temporary file is removed upon abnormal program termination
|
|
|
|
|
|
(7.19.4.3).
|
|
|
|
|
|
-- Which changes of mode are permitted (if any), and under what circumstances
|
|
|
|
|
|
(7.19.5.4).
|
|
|
|
|
|
-- The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
|
|
|
|
|
|
sequence printed for a NaN (7.19.6.1, 7.24.2.1).
|
|
|
|
|
|
-- The output for %p conversion in the fprintf or fwprintf function (7.19.6.1,
|
|
|
|
|
|
7.24.2.1).
|
|
|
|
|
|
-- 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 (7.19.6.2, 7.24.2.1).
|
2012-01-16 16:34:32 +01:00
|
|
|
|
-- The set of sequences matched by a %p conversion and the interpretation of the
|
|
|
|
|
|
corresponding input item in the fscanf or fwscanf function (7.19.6.2, 7.24.2.2).
|
|
|
|
|
|
-- The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
|
|
|
|
|
|
functions on failure (7.19.9.1, 7.19.9.3, 7.19.9.4).
|
|
|
|
|
|
-- 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 (7.20.1.3, 7.24.4.1.1).
|
|
|
|
|
|
-- Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
|
|
|
|
|
|
function sets errno to ERANGE when underflow occurs (7.20.1.3, 7.24.4.1.1).
|
|
|
|
|
|
-- Whether the calloc, malloc, and realloc functions return a null pointer or a
|
|
|
|
|
|
pointer to an allocated object when the size requested is zero (7.20.3).
|
|
|
|
|
|
-- 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
|
|
|
|
|
|
(7.20.4.1, 7.20.4.4).
|
|
|
|
|
|
-- The termination status returned to the host environment by the abort, exit, or
|
|
|
|
|
|
_Exit function (7.20.4.1, 7.20.4.3, 7.20.4.4).
|
|
|
|
|
|
-- The value returned by the system function when its argument is not a null pointer
|
|
|
|
|
|
(7.20.4.6).
|
|
|
|
|
|
-- The local time zone and Daylight Saving Time (7.23.1).
|
|
|
|
|
|
-- The range and precision of times representable in clock_t and time_t (7.23).
|
|
|
|
|
|
-- The era for the clock function (7.23.2.1).
|
|
|
|
|
|
-- The replacement string for the %Z specifier to the strftime, and wcsftime
|
|
|
|
|
|
functions in the "C" locale (7.23.3.5, 7.24.5.1).
|
|
|
|
|
|
-- Whether the functions in <math.h> honor the rounding direction mode in an
|
|
|
|
|
|
IEC 60559 conformant implementation, unless explicitly specified otherwise (F.9).
|
|
|
|
|
|
J.3.13 Architecture
|
|
|
|
|
|
1 -- The values or expressions assigned to the macros specified in the headers
|
|
|
|
|
|
<float.h>, <limits.h>, and <stdint.h> (5.2.4.2, 7.18.2, 7.18.3).
|
|
|
|
|
|
-- The number, order, and encoding of bytes in any object (when not explicitly specified
|
|
|
|
|
|
in this International Standard) (6.2.6.1).
|
|
|
|
|
|
-- The value of the result of the sizeof operator (6.5.3.4).
|
|
|
|
|
|
|
|
|
|
|
|
J.4 Locale-specific behavior
|
|
|
|
|
|
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 (5.2.1).
|
|
|
|
|
|
-- The presence, meaning, and representation of additional multibyte characters in the
|
|
|
|
|
|
execution character set beyond the basic character set (5.2.1.2).
|
|
|
|
|
|
-- The shift states used for the encoding of multibyte characters (5.2.1.2).
|
|
|
|
|
|
-- The direction of writing of successive printing characters (5.2.2).
|
|
|
|
|
|
-- The decimal-point character (7.1.1).
|
|
|
|
|
|
-- The set of printing characters (7.4, 7.25.2).
|
|
|
|
|
|
-- The set of control characters (7.4, 7.25.2).
|
|
|
|
|
|
-- The sets of characters tested for by the isalpha, isblank, islower, ispunct,
|
|
|
|
|
|
isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
|
|
|
|
|
|
iswspace, or iswupper functions (7.4.1.2, 7.4.1.3, 7.4.1.7, 7.4.1.9, 7.4.1.10,
|
|
|
|
|
|
7.4.1.11, 7.25.2.1.2, 7.25.2.1.3, 7.25.2.1.7, 7.25.2.1.9, 7.25.2.1.10, 7.25.2.1.11).
|
|
|
|
|
|
-- The native environment (7.11.1.1).
|
|
|
|
|
|
-- Additional subject sequences accepted by the numeric conversion functions (7.20.1,
|
|
|
|
|
|
7.24.4.1).
|
|
|
|
|
|
-- The collation sequence of the execution character set (7.21.4.3, 7.24.4.4.2).
|
|
|
|
|
|
-- The contents of the error message strings set up by the strerror function
|
|
|
|
|
|
(7.21.6.2).
|
|
|
|
|
|
-- The formats for time and date (7.23.3.5, 7.24.5.1).
|
|
|
|
|
|
-- Character mappings that are supported by the towctrans function (7.25.1).
|
|
|
|
|
|
-- Character classifications that are supported by the iswctype function (7.25.1).
|
|
|
|
|
|
|
|
|
|
|
|
J.5 Common extensions
|
|
|
|
|
|
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.
|
|
|
|
|
|
J.5.1 Environment arguments
|
|
|
|
|
|
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
|
|
|
|
|
|
(5.1.2.2.1).
|
|
|
|
|
|
J.5.2 Specialized identifiers
|
|
|
|
|
|
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 (6.4.2).
|
|
|
|
|
|
J.5.3 Lengths and cases of identifiers
|
|
|
|
|
|
1 All characters in identifiers (with or without external linkage) are significant (6.4.2).
|
|
|
|
|
|
J.5.4 Scopes of identifiers
|
|
|
|
|
|
1 A function identifier, or the identifier of an object the declaration of which contains the
|
|
|
|
|
|
keyword extern, has file scope (6.2.1).
|
|
|
|
|
|
J.5.5 Writable string literals
|
|
|
|
|
|
1 String literals are modifiable (in which case, identical string literals should denote distinct
|
|
|
|
|
|
objects) (6.4.5).
|
|
|
|
|
|
J.5.6 Other arithmetic types
|
|
|
|
|
|
1 Additional arithmetic types, such as _ _int128 or double double, and their
|
|
|
|
|
|
appropriate conversions are defined (6.2.5, 6.3.1). 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.
|
|
|
|
|
|
|
|
|
|
|
|
J.5.7 Function pointer casts
|
|
|
|
|
|
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 (6.5.4).
|
|
|
|
|
|
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) (6.5.4).
|
|
|
|
|
|
J.5.8 Extended bit-field types
|
|
|
|
|
|
1 A bit-field may be declared with a type other than _Bool, unsigned int, or
|
|
|
|
|
|
signed int, with an appropriate maximum width (6.7.2.1).
|
|
|
|
|
|
J.5.9 The fortran keyword
|
|
|
|
|
|
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 (6.7.4).
|
|
|
|
|
|
J.5.10 The asm keyword
|
|
|
|
|
|
1 The asm keyword may be used to insert assembly language directly into the translator
|
|
|
|
|
|
output (6.8). The most common implementation is via a statement of the form:
|
|
|
|
|
|
asm ( character-string-literal );
|
|
|
|
|
|
J.5.11 Multiple external definitions
|
|
|
|
|
|
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 (6.9.2).
|
|
|
|
|
|
J.5.12 Predefined macro names
|
|
|
|
|
|
1 Macro names that do not begin with an underscore, describing the translation and
|
|
|
|
|
|
execution environments, are defined by the implementation before translation begins
|
|
|
|
|
|
(6.10.8).
|
|
|
|
|
|
J.5.13 Floating-point status flags
|
|
|
|
|
|
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 7.20.4.3), the implementation
|
|
|
|
|
|
writes some diagnostics indicating the fact to the stderr stream, if it is still open,
|
|
|
|
|
|
|
|
|
|
|
|
J.5.14 Extra arguments for signal handlers
|
|
|
|
|
|
1 Handlers for specific signals are called with extra arguments in addition to the signal
|
|
|
|
|
|
number (7.14.1.1).
|
|
|
|
|
|
J.5.15 Additional stream types and file-opening modes
|
|
|
|
|
|
1 Additional mappings from files to streams are supported (7.19.2).
|
|
|
|
|
|
2 Additional file-opening modes may be specified by characters appended to the mode
|
|
|
|
|
|
argument of the fopen function (7.19.5.3).
|
|
|
|
|
|
J.5.16 Defined file position indicator
|
|
|
|
|
|
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 (7.19.7.11, 7.24.3.10).
|
|
|
|
|
|
J.5.17 Math error reporting
|
|
|
|
|
|
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 (7.3, 7.12).
|
|
|
|
|
|
|
2012-01-23 23:24:51 +01:00
|
|
|
|
BIBLIOGRAPHY. Bibliography
|
2012-01-17 01:08:26 +01:00
|
|
|
|
1. ``The C Reference Manual'' by Dennis M. Ritchie, a version of which was
|
|
|
|
|
|
published in The C Programming Language by Brian W. Kernighan and Dennis
|
|
|
|
|
|
M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
|
|
|
|
|
|
2. 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
|
|
|
|
|
|
California, USA, November 1984.
|
|
|
|
|
|
3. ANSI X3/TR-1-82 (1982), American National Dictionary for Information
|
|
|
|
|
|
Processing Systems, Information Processing Systems Technical Report.
|
|
|
|
|
|
4. ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
|
|
|
|
|
|
Arithmetic .
|
|
|
|
|
|
5. ANSI/IEEE 854-1988, American National Standard for Radix-Independent
|
|
|
|
|
|
Floating-Point Arithmetic .
|
|
|
|
|
|
6. IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
|
|
|
|
|
|
second edition (previously designated IEC 559:1989).
|
|
|
|
|
|
7. ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
|
|
|
|
|
|
symbols for use in the physical sciences and technology .
|
|
|
|
|
|
8. ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
|
|
|
|
|
|
information interchange.
|
|
|
|
|
|
9. ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
|
|
|
|
|
|
Fundamental terms.
|
|
|
|
|
|
10. ISO 4217:1995, Codes for the representation of currencies and funds.
|
|
|
|
|
|
11. ISO 8601:1988, Data elements and interchange formats -- Information
|
|
|
|
|
|
interchange -- Representation of dates and times.
|
|
|
|
|
|
12. ISO/IEC 9899:1990, Programming languages -- C .
|
|
|
|
|
|
13. ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
|
|
|
|
|
|
14. ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
|
|
|
|
|
|
15. ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity .
|
|
|
|
|
|
16. ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
|
|
|
|
|
|
Interface (POSIX) -- Part 2: Shell and Utilities.
|
|
|
|
|
|
17. ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
|
|
|
|
|
|
preparation of programming language standards.
|
|
|
|
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|
18. ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
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Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
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19. ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
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ISO/IEC 10646-1:1993.
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20. ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
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ISO/IEC 10646-1:1993.
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21. ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
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Transformation Format for 16 planes of group 00 (UTF-16).
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22. ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
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Transformation Format 8 (UTF-8).
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23. ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
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24. ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
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25. ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
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syllables.
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26. ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
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27. ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
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additional characters.
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28. ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
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29. ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
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Identifiers for characters.
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30. ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
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Ethiopic .
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31. ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
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Unified Canadian Aboriginal Syllabics.
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32. ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
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Cherokee.
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33. ISO/IEC 10967-1:1994, Information technology -- Language independent
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arithmetic -- Part 1: Integer and floating point arithmetic .
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2012-01-16 16:34:32 +01:00
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99999.
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