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6 </pre>
9 <ul>
17 <ul>
19 <ul>
22 </ul>
24 <ul>
29 </ul>
30 </ul>
32 <ul>
35 <ul>
43 </ul>
45 <ul>
48 </ul>
50 <ul>
60 </ul>
62 <!--page 2 -->
63 <ul>
81 </ul>
84 <ul>
93 </ul>
95 <ul>
102 </ul>
104 <ul>
107 </ul>
109 <ul>
116 <!--page 3 -->
120 </ul>
122 <ul>
132 </ul>
133 </ul>
135 <ul>
137 <ul>
142 </ul>
144 <ul>
146 </ul>
148 <ul>
158 </ul>
160 <ul>
163 </ul>
166 <ul>
171 </ul>
174 <ul>
177 <!--page 4 -->
178 </ul>
182 <ul>
185 </ul>
187 <ul>
202 </ul>
204 <ul>
207 </ul>
209 <ul>
212 </ul>
214 <ul>
216 </ul>
220 <ul>
225 </ul>
227 <ul>
236 <!--page 5 -->
239 </ul>
241 <ul>
250 </ul>
252 <ul>
259 </ul>
262 <ul>
266 </ul>
268 <ul>
275 </ul>
276 <li><a href="#7.25"> 7.25 Wide character classification and mapping utilities <wctype.h></a>
277 <ul>
281 </ul>
283 <ul>
293 <!--page 6 -->
297 <li><a href="#7.26.13"> 7.26.13 Wide character classification and mapping utilities <wctype.h></a>
298 </ul>
299 </ul>
301 <ul>
305 </ul>
307 <ul>
331 <li><a href="#B.24"> B.24 Wide character classification and mapping utilities <wctype.h></a>
332 </ul>
337 <ul>
341 <!--page 7 -->
348 </ul>
350 <ul>
358 </ul>
360 <ul>
364 </ul>
367 <ul>
373 </ul>
376 <!--page 8 -->
377 <!--page 9 -->
378 </ul>
382 ISO (the International Organization for Standardization) and IEC (the International
383 Electrotechnical Commission) form the specialized system for worldwide
384 standardization. National bodies that are member of ISO or IEC participate in the
385 development of International Standards through technical committees established by the
386 respective organization to deal with particular fields of technical activity. ISO and IEC
387 technical committees collaborate in fields of mutual interest. Other international
388 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
389 take part in the work.
391 International Standards are drafted in accordance with the rules given in the ISO/IEC
392 Directives, Part 3.
394 In the field of information technology, ISO and IEC have established a joint technical
395 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
396 committee are circulated to national bodies for voting. Publication as an International
397 Standard requires approval by at least 75% of the national bodies casting a vote.
399 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
401 their environments and system software interfaces. The Working Group responsible for
402 this standard (WG 14) maintains a site on the World Wide Web at
403 http://www.open-std.org/JTC1/SC22/WG14/ containing additional
404 information relevant to this standard such as a Rationale for many of the decisions made
405 during its preparation and a log of Defect Reports and Responses.
410 <ul>
411 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
412 in AMD1)
413 <li> wide character library support in <a href="#7.24"><wchar.h></a> and <a href="#7.25"><wctype.h></a> (originally
414 specified in AMD1)
415 <li> more precise aliasing rules via effective type
416 <li> restricted pointers
417 <li> variable length arrays
418 <li> flexible array members
419 <li> static and type qualifiers in parameter array declarators
422 <li> the long long int type and library functions
423 <!--page 10 -->
424 <li> increased minimum translation limits
426 <li> remove implicit int
427 <li> reliable integer division
428 <li> universal character names (\u and \U)
429 <li> extended identifiers
430 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
431 specifiers
432 <li> compound literals
433 <li> designated initializers
434 <li> // comments
435 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.18"><stdint.h></a>
436 <li> remove implicit function declaration
437 <li> preprocessor arithmetic done in intmax_t/uintmax_t
438 <li> mixed declarations and code
439 <li> new block scopes for selection and iteration statements
440 <li> integer constant type rules
441 <li> integer promotion rules
442 <li> macros with a variable number of arguments
443 <li> the vscanf family of functions in <a href="#7.19"><stdio.h></a> and <a href="#7.24"><wchar.h></a>
445 <li> treatment of error conditions by math library functions (math_errhandling)
448 <li> trailing comma allowed in enum declaration
449 <li> %lf conversion specifier allowed in printf
450 <li> inline functions
453 <li> idempotent type qualifiers
454 <li> empty macro arguments
455 <!--page 11 -->
456 <li> new structure type compatibility rules (tag compatibility)
457 <li> additional predefined macro names
458 <li> _Pragma preprocessing operator
459 <li> standard pragmas
460 <li> __func__ predefined identifier
461 <li> va_copy macro
462 <li> additional strftime conversion specifiers
463 <li> LIA compatibility annex
464 <li> deprecate ungetc at the beginning of a binary file
465 <li> remove deprecation of aliased array parameters
466 <li> conversion of array to pointer not limited to lvalues
467 <li> relaxed constraints on aggregate and union initialization
468 <li> relaxed restrictions on portable header names
469 <li> return without expression not permitted in function that returns a value (and vice
470 versa)
471 </ul>
473 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
474 the bibliography, and the index are for information only. In accordance with Part 3 of the
475 ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
476 also for information only.
477 <!--page 12 -->
481 With the introduction of new devices and extended character sets, new features may be
482 added to this International Standard. Subclauses in the language and library clauses warn
483 implementors and programmers of usages which, though valid in themselves, may
484 conflict with future additions.
486 Certain features are obsolescent, which means that they may be considered for
487 withdrawal in future revisions of this International Standard. They are retained because
488 of their widespread use, but their use in new implementations (for implementation
489 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.26">7.26</a>]) is discouraged.
491 This International Standard is divided into four major subdivisions:
492 <ul>
497 </ul>
499 Examples are provided to illustrate possible forms of the constructions described.
500 Footnotes are provided to emphasize consequences of the rules described in that
501 subclause or elsewhere in this International Standard. References are used to refer to
502 other related subclauses. Recommendations are provided to give advice or guidance to
503 implementors. Annexes provide additional information and summarize the information
504 contained in this International Standard. A bibliography lists documents that were
505 referred to during the preparation of the standard.
507 The language clause (clause 6) is derived from ''The C Reference Manual''.
510 <!--page 13 -->
520 This International Standard specifies the form and establishes the interpretation of
521 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
522 <ul>
523 <li> the representation of C programs;
524 <li> the syntax and constraints of the C language;
525 <li> the semantic rules for interpreting C programs;
526 <li> the representation of input data to be processed by C programs;
527 <li> the representation of output data produced by C programs;
528 <li> the restrictions and limits imposed by a conforming implementation of C.
529 </ul>
531 This International Standard does not specify
532 <ul>
533 <li> the mechanism by which C programs are transformed for use by a data-processing
534 system;
535 <li> the mechanism by which C programs are invoked for use by a data-processing
536 system;
537 <li> the mechanism by which input data are transformed for use by a C program;
538 <li> the mechanism by which output data are transformed after being produced by a C
539 program;
540 <li> the size or complexity of a program and its data that will exceed the capacity of any
541 specific data-processing system or the capacity of a particular processor;
544 <!--page 14 -->
545 <li> all minimal requirements of a data-processing system that is capable of supporting a
546 conforming implementation.
548 </ul>
551 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
552 data-processing systems. It is intended for use by implementors and programmers.
553 </small>
557 The following normative documents contain provisions which, through reference in this
558 text, constitute provisions of this International Standard. For dated references,
559 subsequent amendments to, or revisions of, any of these publications do not apply.
560 However, parties to agreements based on this International Standard are encouraged to
561 investigate the possibility of applying the most recent editions of the normative
562 documents indicated below. For undated references, the latest edition of the normative
563 document referred to applies. Members of ISO and IEC maintain registers of currently
564 valid International Standards.
567 use in the physical sciences and technology.
570 interchange.
573 terms.
575 ISO 4217, Codes for the representation of currencies and funds.
577 ISO 8601, Data elements and interchange formats -- Information interchange --
578 Representation of dates and times.
580 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
581 Character Set (UCS).
585 <!--page 15 -->
589 For the purposes of this International Standard, the following definitions apply. Other
590 terms are defined where they appear in italic type or on the left side of a syntax rule.
591 Terms explicitly defined in this International Standard are not to be presumed to refer
592 implicitly to similar terms defined elsewhere. Terms not defined in this International
601 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
604 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
606 <p><!--para 4 -->
607 NOTE 3 Expressions that are not evaluated do not access objects.
611 <p><!--para 1 -->
612 <b> alignment</b><br>
613 requirement that objects of a particular type be located on storage boundaries with
614 addresses that are particular multiples of a byte address
617 <p><!--para 1 -->
618 <b> argument</b><br>
619 actual argument<br>
620 actual parameter (deprecated)<br>
621 expression in the comma-separated list bounded by the parentheses in a function call
622 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
623 by the parentheses in a function-like macro invocation
626 <p><!--para 1 -->
627 <b> behavior</b><br>
628 external appearance or action
631 <p><!--para 1 -->
632 <b> implementation-defined behavior</b><br>
633 unspecified behavior where each implementation documents how the choice is made
634 <p><!--para 2 -->
635 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
636 when a signed integer is shifted right.
640 <p><!--para 1 -->
641 <b> locale-specific behavior</b><br>
642 behavior that depends on local conventions of nationality, culture, and language that each
643 implementation documents
644 <!--page 16 -->
645 <p><!--para 2 -->
646 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
647 characters other than the 26 lowercase Latin letters.
651 <p><!--para 1 -->
652 <b> undefined behavior</b><br>
653 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
654 for which this International Standard imposes no requirements
655 <p><!--para 2 -->
656 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
657 results, to behaving during translation or program execution in a documented manner characteristic of the
658 environment (with or without the issuance of a diagnostic message), to terminating a translation or
659 execution (with the issuance of a diagnostic message).
661 <p><!--para 3 -->
662 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
666 <p><!--para 1 -->
667 <b> unspecified behavior</b><br>
668 use of an unspecified value, or other behavior where this International Standard provides
669 two or more possibilities and imposes no further requirements on which is chosen in any
670 instance
671 <p><!--para 2 -->
672 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
673 evaluated.
677 <p><!--para 1 -->
678 <b> bit</b><br>
679 unit of data storage in the execution environment large enough to hold an object that may
680 have one of two values
681 <p><!--para 2 -->
682 NOTE It need not be possible to express the address of each individual bit of an object.
686 <p><!--para 1 -->
687 <b> byte</b><br>
688 addressable unit of data storage large enough to hold any member of the basic character
689 set of the execution environment
690 <p><!--para 2 -->
691 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
693 <p><!--para 3 -->
694 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
695 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
696 bit.
700 <p><!--para 1 -->
701 <b> character</b><br>
702 <abstract> member of a set of elements used for the organization, control, or
703 representation of data
706 <p><!--para 1 -->
707 <b> character</b><br>
708 single-byte character
709 <C> bit representation that fits in a byte
710 <!--page 17 -->
713 <p><!--para 1 -->
714 <b> multibyte character</b><br>
715 sequence of one or more bytes representing a member of the extended character set of
716 either the source or the execution environment
717 <p><!--para 2 -->
718 NOTE The extended character set is a superset of the basic character set.
722 <p><!--para 1 -->
723 <b> wide character</b><br>
724 bit representation that fits in an object of type wchar_t, capable of representing any
725 character in the current locale
728 <p><!--para 1 -->
729 <b> constraint</b><br>
730 restriction, either syntactic or semantic, by which the exposition of language elements is
731 to be interpreted
734 <p><!--para 1 -->
735 <b> correctly rounded result</b><br>
736 representation in the result format that is nearest in value, subject to the current rounding
737 mode, to what the result would be given unlimited range and precision
740 <p><!--para 1 -->
741 <b> diagnostic message</b><br>
742 message belonging to an implementation-defined subset of the implementation's message
743 output
746 <p><!--para 1 -->
747 <b> forward reference</b><br>
748 reference to a later subclause of this International Standard that contains additional
749 information relevant to this subclause
752 <p><!--para 1 -->
753 <b> implementation</b><br>
754 particular set of software, running in a particular translation environment under particular
755 control options, that performs translation of programs for, and supports execution of
756 functions in, a particular execution environment
759 <p><!--para 1 -->
760 <b> implementation limit</b><br>
761 restriction imposed upon programs by the implementation
764 <p><!--para 1 -->
765 <b> object</b><br>
766 region of data storage in the execution environment, the contents of which can represent
767 values
768 <!--page 18 -->
769 <p><!--para 2 -->
770 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
774 <p><!--para 1 -->
775 <b> parameter</b><br>
776 formal parameter
777 formal argument (deprecated)
778 object declared as part of a function declaration or definition that acquires a value on
779 entry to the function, or an identifier from the comma-separated list bounded by the
780 parentheses immediately following the macro name in a function-like macro definition
783 <p><!--para 1 -->
784 <b> recommended practice</b><br>
785 specification that is strongly recommended as being in keeping with the intent of the
786 standard, but that may be impractical for some implementations
789 <p><!--para 1 -->
790 <b> value</b><br>
791 precise meaning of the contents of an object when interpreted as having a specific type
794 <p><!--para 1 -->
795 <b> implementation-defined value</b><br>
796 unspecified value where each implementation documents how the choice is made
799 <p><!--para 1 -->
800 <b> indeterminate value</b><br>
801 either an unspecified value or a trap representation
804 <p><!--para 1 -->
805 <b> unspecified value</b><br>
806 valid value of the relevant type where this International Standard imposes no
807 requirements on which value is chosen in any instance
808 <p><!--para 2 -->
809 NOTE An unspecified value cannot be a trap representation.
813 <p><!--para 1 -->
814 <b> [^ x ^]</b><br>
815 ceiling of x: the least integer greater than or equal to x
816 <p><!--para 2 -->
817 EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
821 <p><!--para 1 -->
822 <b> [_ x _]</b><br>
823 floor of x: the greatest integer less than or equal to x
824 <p><!--para 2 -->
825 EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
826 <!--page 19 -->
829 <p><!--para 1 -->
830 In this International Standard, ''shall'' is to be interpreted as a requirement on an
831 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
832 prohibition.
833 <p><!--para 2 -->
834 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated, the
835 behavior is undefined. Undefined behavior is otherwise indicated in this International
836 Standard by the words ''undefined behavior'' or by the omission of any explicit definition
837 of behavior. There is no difference in emphasis among these three; they all describe
838 ''behavior that is undefined''.
839 <p><!--para 3 -->
840 A program that is correct in all other aspects, operating on correct data, containing
841 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
842 <p><!--para 4 -->
843 The implementation shall not successfully translate a preprocessing translation unit
844 containing a #error preprocessing directive unless it is part of a group skipped by
845 conditional inclusion.
846 <p><!--para 5 -->
847 A strictly conforming program shall use only those features of the language and library
848 specified in this International Standard.<sup><a href="#note2"><b>2)</b></a></sup> It shall not produce output dependent on any
849 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
850 minimum implementation limit.
851 <p><!--para 6 -->
852 The two forms of conforming implementation are hosted and freestanding. A conforming
853 hosted implementation shall accept any strictly conforming program. A conforming
854 freestanding implementation shall accept any strictly conforming program that does not
855 use complex types and in which the use of the features specified in the library clause
856 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
857 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdarg.h></a>, <a href="#7.16"><stdbool.h></a>, <a href="#7.17"><stddef.h></a>, and
858 <a href="#7.18"><stdint.h></a>. A conforming implementation may have extensions (including additional
859 library functions), provided they do not alter the behavior of any strictly conforming
864 <!--page 20 -->
865 <p><!--para 7 -->
866 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note4"><b>4)</b></a></sup>
867 <p><!--para 8 -->
868 An implementation shall be accompanied by a document that defines all implementation-
869 defined and locale-specific characteristics and all extensions.
870 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
871 characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
872 (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), variable arguments <a href="#7.15"><stdarg.h></a>
873 (<a href="#7.15">7.15</a>), boolean type and values <a href="#7.16"><stdbool.h></a> (<a href="#7.16">7.16</a>), common definitions
874 <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
879 <!--page 21 -->
881 <h6>footnotes</h6>
882 <p><small><a name="note2" href="#note2">2)</a> A strictly conforming program can use conditional features (such as those in <a href="#F">annex F</a>) provided the
883 use is guarded by a #ifdef directive with the appropriate macro. For example:
885 <pre>
886 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
887 /* ... */
888 fesetround(FE_UPWARD);
889 /* ... */
890 #endif</pre>
892 </small>
893 <p><small><a name="note3" href="#note3">3)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
894 reserved in this International Standard.
895 </small>
896 <p><small><a name="note4" href="#note4">4)</a> Strictly conforming programs are intended to be maximally portable among conforming
897 implementations. Conforming programs may depend upon nonportable features of a conforming
898 implementation.
899 </small>
902 <p><!--para 1 -->
903 An implementation translates C source files and executes C programs in two data-
904 processing-system environments, which will be called the translation environment and
905 the execution environment in this International Standard. Their characteristics define and
906 constrain the results of executing conforming C programs constructed according to the
907 syntactic and semantic rules for conforming implementations.
908 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
909 have been noted.
916 <p><!--para 1 -->
917 A C program need not all be translated at the same time. The text of the program is kept
918 in units called source files, (or preprocessing files) in this International Standard. A
919 source file together with all the headers and source files included via the preprocessing
920 directive #include is known as a preprocessing translation unit. After preprocessing, a
921 preprocessing translation unit is called a translation unit. Previously translated translation
922 units may be preserved individually or in libraries. The separate translation units of a
923 program communicate by (for example) calls to functions whose identifiers have external
924 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
925 of data files. Translation units may be separately translated and then later linked to
926 produce an executable program.
927 <p><b> Forward references</b>: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
931 <p><!--para 1 -->
932 The precedence among the syntax rules of translation is specified by the following
934 <ol>
935 <li> Physical source file multibyte characters are mapped, in an implementation-
936 defined manner, to the source character set (introducing new-line characters for
937 end-of-line indicators) if necessary. Trigraph sequences are replaced by
938 corresponding single-character internal representations.
942 <!--page 22 -->
943 <li> Each instance of a backslash character (\) immediately followed by a new-line
944 character is deleted, splicing physical source lines to form logical source lines.
945 Only the last backslash on any physical source line shall be eligible for being part
946 of such a splice. A source file that is not empty shall end in a new-line character,
947 which shall not be immediately preceded by a backslash character before any such
948 splicing takes place.
949 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note6"><b>6)</b></a></sup> and sequences of
950 white-space characters (including comments). A source file shall not end in a
951 partial preprocessing token or in a partial comment. Each comment is replaced by
952 one space character. New-line characters are retained. Whether each nonempty
953 sequence of white-space characters other than new-line is retained or replaced by
954 one space character is implementation-defined.
955 <li> Preprocessing directives are executed, macro invocations are expanded, and
956 _Pragma unary operator expressions are executed. If a character sequence that
957 matches the syntax of a universal character name is produced by token
958 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
959 directive causes the named header or source file to be processed from phase 1
960 through phase 4, recursively. All preprocessing directives are then deleted.
961 <li> Each source character set member and escape sequence in character constants and
962 string literals is converted to the corresponding member of the execution character
963 set; if there is no corresponding member, it is converted to an implementation-
965 <li> Adjacent string literal tokens are concatenated.
966 <li> White-space characters separating tokens are no longer significant. Each
967 preprocessing token is converted into a token. The resulting tokens are
968 syntactically and semantically analyzed and translated as a translation unit.
969 <li> All external object and function references are resolved. Library components are
970 linked to satisfy external references to functions and objects not defined in the
971 current translation. All such translator output is collected into a program image
972 which contains information needed for execution in its execution environment.
973 </ol>
974 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
975 preprocessing directives (<a href="#6.10">6.10</a>), trigraph sequences (<a href="#5.2.1.1">5.2.1.1</a>), external definitions (<a href="#6.9">6.9</a>).
979 <!--page 23 -->
981 <h6>footnotes</h6>
982 <p><small><a name="note5" href="#note5">5)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
983 together in practice. Source files, translation units, and translated translation units need not
984 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
985 and any external representation. The description is conceptual only, and does not specify any
986 particular implementation.
987 </small>
988 <p><small><a name="note6" href="#note6">6)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
989 context-dependent. For example, see the handling of < within a #include preprocessing directive.
990 </small>
991 <p><small><a name="note7" href="#note7">7)</a> An implementation need not convert all non-corresponding source characters to the same execution
992 character.
993 </small>
996 <p><!--para 1 -->
997 A conforming implementation shall produce at least one diagnostic message (identified in
998 an implementation-defined manner) if a preprocessing translation unit or translation unit
999 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1000 specified as undefined or implementation-defined. Diagnostic messages need not be
1002 <p><!--para 2 -->
1003 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1004 <pre>
1005 char i;
1006 int i;</pre>
1007 because in those cases where wording in this International Standard describes the behavior for a construct
1008 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1011 <h6>footnotes</h6>
1012 <p><small><a name="note8" href="#note8">8)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1013 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1014 valid program is still correctly translated. It may also successfully translate an invalid program.
1015 </small>
1018 <p><!--para 1 -->
1019 Two execution environments are defined: freestanding and hosted. In both cases,
1020 program startup occurs when a designated C function is called by the execution
1021 environment. All objects with static storage duration shall be initialized (set to their
1022 initial values) before program startup. The manner and timing of such initialization are
1023 otherwise unspecified. Program termination returns control to the execution
1024 environment.
1025 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.8">6.7.8</a>).
1028 <p><!--para 1 -->
1029 In a freestanding environment (in which C program execution may take place without any
1030 benefit of an operating system), the name and type of the function called at program
1031 startup are implementation-defined. Any library facilities available to a freestanding
1032 program, other than the minimal set required by clause 4, are implementation-defined.
1033 <p><!--para 2 -->
1034 The effect of program termination in a freestanding environment is implementation-
1035 defined.
1038 <p><!--para 1 -->
1039 A hosted environment need not be provided, but shall conform to the following
1040 specifications if present.
1045 <!--page 24 -->
1048 <p><!--para 1 -->
1049 The function called at program startup is named main. The implementation declares no
1050 prototype for this function. It shall be defined with a return type of int and with no
1051 parameters:
1052 <pre>
1053 int main(void) { /* ... */ }</pre>
1054 or with two parameters (referred to here as argc and argv, though any names may be
1055 used, as they are local to the function in which they are declared):
1056 <pre>
1057 int main(int argc, char *argv[]) { /* ... */ }</pre>
1058 or equivalent;<sup><a href="#note9"><b>9)</b></a></sup> or in some other implementation-defined manner.
1059 <p><!--para 2 -->
1060 If they are declared, the parameters to the main function shall obey the following
1061 constraints:
1062 <ul>
1063 <li> The value of argc shall be nonnegative.
1064 <li> argv[argc] shall be a null pointer.
1065 <li> If the value of argc is greater than zero, the array members argv[0] through
1066 argv[argc-1] inclusive shall contain pointers to strings, which are given
1067 implementation-defined values by the host environment prior to program startup. The
1068 intent is to supply to the program information determined prior to program startup
1069 from elsewhere in the hosted environment. If the host environment is not capable of
1070 supplying strings with letters in both uppercase and lowercase, the implementation
1071 shall ensure that the strings are received in lowercase.
1072 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1073 represents the program name; argv[0][0] shall be the null character if the
1074 program name is not available from the host environment. If the value of argc is
1075 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1076 represent the program parameters.
1077 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1078 be modifiable by the program, and retain their last-stored values between program
1079 startup and program termination.
1080 </ul>
1082 <h6>footnotes</h6>
1083 <p><small><a name="note9" href="#note9">9)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1084 char ** argv, and so on.
1085 </small>
1088 <p><!--para 1 -->
1089 In a hosted environment, a program may use all the functions, macros, type definitions,
1090 and objects described in the library clause (clause 7).
1094 <!--page 25 -->
1097 <p><!--para 1 -->
1098 If the return type of the main function is a type compatible with int, a return from the
1099 initial call to the main function is equivalent to calling the exit function with the value
1100 returned by the main function as its argument;<sup><a href="#note10"><b>10)</b></a></sup> reaching the } that terminates the
1101 main function returns a value of 0. If the return type is not compatible with int, the
1102 termination status returned to the host environment is unspecified.
1103 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
1105 <h6>footnotes</h6>
1106 <p><small><a name="note10" href="#note10">10)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1107 will have ended in the former case, even where they would not have in the latter.
1108 </small>
1111 <p><!--para 1 -->
1112 The semantic descriptions in this International Standard describe the behavior of an
1113 abstract machine in which issues of optimization are irrelevant.
1114 <p><!--para 2 -->
1115 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1116 that does any of those operations are all side effects,<sup><a href="#note11"><b>11)</b></a></sup> which are changes in the state of
1117 the execution environment. Evaluation of an expression may produce side effects. At
1118 certain specified points in the execution sequence called sequence points, all side effects
1119 of previous evaluations shall be complete and no side effects of subsequent evaluations
1120 shall have taken place. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1121 <p><!--para 3 -->
1122 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1123 actual implementation need not evaluate part of an expression if it can deduce that its
1124 value is not used and that no needed side effects are produced (including any caused by
1125 calling a function or accessing a volatile object).
1126 <p><!--para 4 -->
1127 When the processing of the abstract machine is interrupted by receipt of a signal, only the
1128 values of objects as of the previous sequence point may be relied on. Objects that may be
1129 modified between the previous sequence point and the next sequence point need not have
1130 received their correct values yet.
1131 <p><!--para 5 -->
1132 The least requirements on a conforming implementation are:
1133 <ul>
1134 <li> At sequence points, volatile objects are stable in the sense that previous accesses are
1135 complete and subsequent accesses have not yet occurred.
1140 <!--page 26 -->
1141 <li> At program termination, all data written into files shall be identical to the result that
1142 execution of the program according to the abstract semantics would have produced.
1143 <li> The input and output dynamics of interactive devices shall take place as specified in
1144 <a href="#7.19.3">7.19.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1145 appear as soon as possible, to ensure that prompting messages actually appear prior to
1146 a program waiting for input.
1147 </ul>
1148 <p><!--para 6 -->
1149 What constitutes an interactive device is implementation-defined.
1150 <p><!--para 7 -->
1151 More stringent correspondences between abstract and actual semantics may be defined by
1152 each implementation.
1153 <p><!--para 8 -->
1154 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1155 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1156 abstract semantics. The keyword volatile would then be redundant.
1157 <p><!--para 9 -->
1158 Alternatively, an implementation might perform various optimizations within each translation unit, such
1159 that the actual semantics would agree with the abstract semantics only when making function calls across
1160 translation unit boundaries. In such an implementation, at the time of each function entry and function
1161 return where the calling function and the called function are in different translation units, the values of all
1162 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1163 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1164 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1165 type of implementation, objects referred to by interrupt service routines activated by the signal function
1166 would require explicit specification of volatile storage, as well as other implementation-defined
1167 restrictions.
1169 <p><!--para 10 -->
1170 EXAMPLE 2 In executing the fragment
1171 <pre>
1172 char c1, c2;
1173 /* ... */
1174 c1 = c1 + c2;</pre>
1175 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1176 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1177 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1178 produce the same result, possibly omitting the promotions.
1180 <p><!--para 11 -->
1181 EXAMPLE 3 Similarly, in the fragment
1182 <pre>
1183 float f1, f2;
1184 double d;
1185 /* ... */
1186 f1 = f2 * d;</pre>
1187 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1188 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1189 were replaced by the constant 2.0, which has type double).
1190 <!--page 27 -->
1191 <p><!--para 12 -->
1192 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1193 semantics. Values are independent of whether they are represented in a register or in memory. For
1194 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1195 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1196 perform their specified conversion. For the fragment
1197 <pre>
1198 double d1, d2;
1199 float f;
1200 d1 = f = expression;
1201 d2 = (float) expression;</pre>
1202 the values assigned to d1 and d2 are required to have been converted to float.
1204 <p><!--para 13 -->
1205 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1206 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1207 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1208 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1209 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1211 <pre>
1212 double x, y, z;
1213 /* ... */
1214 x = (x * y) * z; // not equivalent to x *= y * z;
1215 z = (x - y) + y ; // not equivalent to z = x;
1216 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1217 y = x / 5.0; // not equivalent to y = x * 0.2;</pre>
1219 <p><!--para 14 -->
1220 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1221 <pre>
1222 int a, b;
1223 /* ... */
1224 a = a + 32760 + b + 5;</pre>
1225 the expression statement behaves exactly the same as
1226 <pre>
1227 a = (((a + 32760) + b) + 5);</pre>
1228 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1229 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1230 which overflows produce an explicit trap and in which the range of values representable by an int is
1231 [-32768, +32767], the implementation cannot rewrite this expression as
1232 <pre>
1233 a = ((a + b) + 32765);</pre>
1234 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1235 while the original expression would not; nor can the expression be rewritten either as
1236 <pre>
1237 a = ((a + 32765) + b);</pre>
1238 or
1239 <pre>
1240 a = (a + (b + 32765));</pre>
1241 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1242 in which overflow silently generates some value and where positive and negative overflows cancel, the
1243 above expression statement can be rewritten by the implementation in any of the above ways because the
1244 same result will occur.
1245 <!--page 28 -->
1246 <p><!--para 15 -->
1247 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1248 following fragment
1249 <pre>
1251 int sum;
1252 char *p;
1253 /* ... */
1254 sum = sum * 10 - '0' + (*p++ = getchar());</pre>
1255 the expression statement is grouped as if it were written as
1256 <pre>
1257 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));</pre>
1258 but the actual increment of p can occur at any time between the previous sequence point and the next
1259 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1260 value.
1262 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), the
1264 <!--page 29 -->
1266 <h6>footnotes</h6>
1267 <p><small><a name="note11" href="#note11">11)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1268 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1269 values of floating-point operations. Implementations that support such floating-point state are
1270 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1271 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1272 effects matter, freeing the implementations in other cases.
1273 </small>
1278 <p><!--para 1 -->
1279 Two sets of characters and their associated collating sequences shall be defined: the set in
1280 which source files are written (the source character set), and the set interpreted in the
1281 execution environment (the execution character set). Each set is further divided into a
1282 basic character set, whose contents are given by this subclause, and a set of zero or more
1283 locale-specific members (which are not members of the basic character set) called
1284 extended characters. The combined set is also called the extended character set. The
1285 values of the members of the execution character set are implementation-defined.
1286 <p><!--para 2 -->
1287 In a character constant or string literal, members of the execution character set shall be
1288 represented by corresponding members of the source character set or by escape
1289 sequences consisting of the backslash \ followed by one or more characters. A byte with
1290 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1291 is used to terminate a character string.
1292 <p><!--para 3 -->
1293 Both the basic source and basic execution character sets shall have the following
1294 members: the 26 uppercase letters of the Latin alphabet
1295 <pre>
1296 A B C D E F G H I J K L M
1297 N O P Q R S T U V W X Y Z</pre>
1298 the 26 lowercase letters of the Latin alphabet
1299 <pre>
1300 a b c d e f g h i j k l m
1301 n o p q r s t u v w x y z</pre>
1302 the 10 decimal digits
1303 <pre>
1304 0 1 2 3 4 5 6 7 8 9</pre>
1305 the following 29 graphic characters
1306 <pre>
1309 the space character, and control characters representing horizontal tab, vertical tab, and
1310 form feed. The representation of each member of the source and execution basic
1311 character sets shall fit in a byte. In both the source and execution basic character sets, the
1312 value of each character after 0 in the above list of decimal digits shall be one greater than
1313 the value of the previous. In source files, there shall be some way of indicating the end of
1314 each line of text; this International Standard treats such an end-of-line indicator as if it
1315 were a single new-line character. In the basic execution character set, there shall be
1316 control characters representing alert, backspace, carriage return, and new line. If any
1317 other characters are encountered in a source file (except in an identifier, a character
1318 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1319 <!--page 30 -->
1320 converted to a token), the behavior is undefined.
1322 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1323 Standard the term does not include other characters that are letters in other alphabets.
1325 The universal character name construct provides a way to name other characters.
1326 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), character constants (<a href="#6.4.4.4">6.4.4.4</a>),
1327 preprocessing directives (<a href="#6.10">6.10</a>), string literals (<a href="#6.4.5">6.4.5</a>), comments (<a href="#6.4.9">6.4.9</a>), string (<a href="#7.1.1">7.1.1</a>).
1331 Before any other processing takes place, each occurrence of one of the following
1332 sequences of three characters (called trigraph sequences<sup><a href="#note12"><b>12)</b></a></sup>) is replaced with the
1333 corresponding single character.
1334 <pre>
1335 ??= # ??) ] ??! |
1336 ??( [ ??' ^ ??> }
1338 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1339 above is not changed.
1341 EXAMPLE 1
1342 <pre>
1343 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)</pre>
1344 becomes
1345 <pre>
1346 #define arraycheck(a, b) a[b] || b[a]</pre>
1349 EXAMPLE 2 The following source line
1350 <pre>
1352 becomes (after replacement of the trigraph sequence ??/)
1353 <pre>
1358 <p><small><a name="note12" href="#note12">12)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1359 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1360 </small>
1364 The source character set may contain multibyte characters, used to represent members of
1365 the extended character set. The execution character set may also contain multibyte
1366 characters, which need not have the same encoding as for the source character set. For
1367 both character sets, the following shall hold:
1368 <ul>
1369 <li> The basic character set shall be present and each character shall be encoded as a
1370 single byte.
1371 <li> The presence, meaning, and representation of any additional members is locale-
1372 specific.
1374 <!--page 31 -->
1375 <li> A multibyte character set may have a state-dependent encoding, wherein each
1376 sequence of multibyte characters begins in an initial shift state and enters other
1377 locale-specific shift states when specific multibyte characters are encountered in the
1378 sequence. While in the initial shift state, all single-byte characters retain their usual
1379 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1380 in the sequence is a function of the current shift state.
1381 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1382 state. Such a byte shall not occur as part of any other multibyte character.
1383 </ul>
1385 For source files, the following shall hold:
1386 <ul>
1387 <li> An identifier, comment, string literal, character constant, or header name shall begin
1388 and end in the initial shift state.
1389 <li> An identifier, comment, string literal, character constant, or header name shall consist
1390 of a sequence of valid multibyte characters.
1391 </ul>
1395 The active position is that location on a display device where the next character output by
1396 the fputc function would appear. The intent of writing a printing character (as defined
1397 by the isprint function) to a display device is to display a graphic representation of
1398 that character at the active position and then advance the active position to the next
1399 position on the current line. The direction of writing is locale-specific. If the active
1400 position is at the final position of a line (if there is one), the behavior of the display device
1401 is unspecified.
1403 Alphabetic escape sequences representing nongraphic characters in the execution
1404 character set are intended to produce actions on display devices as follows:
1405 <dl>
1407 <dt> \b <dd>(backspace) Moves the active position to the previous position on the current line. If
1408 the active position is at the initial position of a line, the behavior of the display
1409 device is unspecified.
1410 <dt> \f <dd>( form feed) Moves the active position to the initial position at the start of the next
1411 logical page.
1413 <dt> \r <dd>(carriage return) Moves the active position to the initial position of the current line.
1414 <dt> \t <dd>(horizontal tab) Moves the active position to the next horizontal tabulation position
1415 on the current line. If the active position is at or past the last defined horizontal
1416 tabulation position, the behavior of the display device is unspecified.
1417 <dt> \v <dd>(vertical tab) Moves the active position to the initial position of the next vertical
1418 <!--page 32 -->
1419 tabulation position. If the active position is at or past the last defined vertical
1420 tabulation position, the behavior of the display device is unspecified.
1421 </dl>
1423 Each of these escape sequences shall produce a unique implementation-defined value
1424 which can be stored in a single char object. The external representations in a text file
1425 need not be identical to the internal representations, and are outside the scope of this
1426 International Standard.
1427 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>).
1431 Functions shall be implemented such that they may be interrupted at any time by a signal,
1432 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1433 invocations' control flow (after the interruption), function return values, or objects with
1434 automatic storage duration. All such objects shall be maintained outside the function
1435 image (the instructions that compose the executable representation of a function) on a
1436 per-invocation basis.
1440 Both the translation and execution environments constrain the implementation of
1441 language translators and libraries. The following summarizes the language-related
1442 environmental limits on a conforming implementation; the library-related limits are
1443 discussed in clause 7.
1447 The implementation shall be able to translate and execute at least one program that
1448 contains at least one instance of every one of the following limits:<sup><a href="#note13"><b>13)</b></a></sup>
1449 <ul>
1453 arithmetic, structure, union, or incomplete type in a declaration
1457 universal character name or extended source character is considered a single
1458 character)
1459 <li> 31 significant initial characters in an external identifier (each universal character name
1463 <!--page 33 -->
1464 universal character name specifying a short identifier of 00010000 or more is
1465 considered 10 characters, and each extended source character is considered the same
1466 number of characters as the corresponding universal character name, if any)<sup><a href="#note14"><b>14)</b></a></sup>
1475 <li> 4095 characters in a character string literal or wide string literal (after concatenation)
1479 statements)
1483 </ul>
1486 <p><small><a name="note13" href="#note13">13)</a> Implementations should avoid imposing fixed translation limits whenever possible.
1487 </small>
1488 <p><small><a name="note14" href="#note14">14)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1489 </small>
1493 An implementation is required to document all the limits specified in this subclause,
1494 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1496 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
1500 The values given below shall be replaced by constant expressions suitable for use in #if
1501 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1502 following shall be replaced by expressions that have the same type as would an
1503 expression that is an object of the corresponding type converted according to the integer
1504 promotions. Their implementation-defined values shall be equal or greater in magnitude
1507 <!--page 34 -->
1508 (absolute value) to those shown, with the same sign.
1509 <ul>
1510 <li> number of bits for smallest object that is not a bit-field (byte)
1512 <li> minimum value for an object of type signed char
1514 <li> maximum value for an object of type signed char
1516 <li> maximum value for an object of type unsigned char
1518 <li> minimum value for an object of type char
1520 <li> maximum value for an object of type char
1522 <li> maximum number of bytes in a multibyte character, for any supported locale
1524 <li> minimum value for an object of type short int
1526 <li> maximum value for an object of type short int
1528 <li> maximum value for an object of type unsigned short int
1530 <li> minimum value for an object of type int
1532 <li> maximum value for an object of type int
1534 <li> maximum value for an object of type unsigned int
1536 <li> minimum value for an object of type long int
1538 <li> maximum value for an object of type long int
1540 <li> maximum value for an object of type unsigned long int
1542 <!--page 35 -->
1543 <li> minimum value for an object of type long long int
1545 <li> maximum value for an object of type long long int
1547 <li> maximum value for an object of type unsigned long long int
1549 </ul>
1551 If the value of an object of type char is treated as a signed integer when used in an
1552 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1553 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1554 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1555 UCHAR_MAX.<sup><a href="#note15"><b>15)</b></a></sup> The value UCHAR_MAX shall equal 2<sup>CHAR_BIT</sup> - 1.
1556 <p><b> Forward references</b>: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
1560 </small>
1562 <h5><a name="5.2.4.2.2" href="#5.2.4.2.2">5.2.4.2.2 Characteristics of floating types <float.h></a></h5>
1564 The characteristics of floating types are defined in terms of a model that describes a
1565 representation of floating-point numbers and values that provide information about an
1566 implementation's floating-point arithmetic.<sup><a href="#note16"><b>16)</b></a></sup> The following parameters are used to
1567 define the model for each floating-point type:
1569 <pre>
1570 s sign ((+-)1)
1572 e exponent (an integer between a minimum emin and a maximum emax )
1573 p precision (the number of base-b digits in the significand)
1575 A floating-point number (x) is defined by the following model:
1576 <pre>
1577 p
1582 In addition to normalized floating-point numbers ( f<sub>1</sub> > 0 if x != 0), floating types may be
1583 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1584 numbers (x != 0, e = emin , f<sub>1</sub> = 0) and unnormalized floating-point numbers (x != 0,
1585 e > emin , f<sub>1</sub> = 0), and values that are not floating-point numbers, such as infinities and
1586 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1587 through almost every arithmetic operation without raising a floating-point exception; a
1588 signaling NaN generally raises a floating-point exception when occurring as an
1591 <!--page 36 -->
1594 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1595 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1596 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1597 any requirement to set the sign shall be ignored.
1599 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1600 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1601 defined, as is the accuracy of the conversion between floating-point internal
1602 representations and string representations performed by the library functions in
1603 <a href="#7.19"><stdio.h></a>, <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a>. The implementation may state that the
1604 accuracy is unknown.
1606 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1607 expressions suitable for use in #if preprocessing directives; all floating values shall be
1608 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1609 and FLT_ROUNDS have separate names for all three floating-point types. The floating-point
1610 model representation is provided for all values except FLT_EVAL_METHOD and
1611 FLT_ROUNDS.
1613 The rounding mode for floating-point addition is characterized by the implementation-
1615 <pre>
1616 -1 indeterminable
1617 0 toward zero
1618 1 to nearest
1619 2 toward positive infinity
1621 All other values for FLT_ROUNDS characterize implementation-defined rounding
1622 behavior.
1624 Except for assignment and cast (which remove all extra range and precision), the values
1625 of operations with floating operands and values subject to the usual arithmetic
1626 conversions and of floating constants are evaluated to a format whose range and precision
1627 may be greater than required by the type. The use of evaluation formats is characterized
1628 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1632 <!--page 37 -->
1633 <pre>
1634 -1 indeterminable;
1635 0 evaluate all operations and constants just to the range and precision of the
1636 type;
1637 1 evaluate operations and constants of type float and double to the
1638 range and precision of the double type, evaluate long double
1639 operations and constants to the range and precision of the long double
1640 type;
1641 2 evaluate all operations and constants to the range and precision of the
1642 long double type.</pre>
1643 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1644 behavior.
1646 The values given in the following list shall be replaced by constant expressions with
1647 implementation-defined values that are greater or equal in magnitude (absolute value) to
1648 those shown, with the same sign:
1649 <ul>
1650 <li> radix of exponent representation, b
1652 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1653 <pre> FLT_MANT_DIG
1654 DBL_MANT_DIG
1655 LDBL_MANT_DIG</pre>
1656 <li> number of decimal digits, n, such that any floating-point number in the widest
1657 supported floating type with pmax radix b digits can be rounded to a floating-point
1658 number with n decimal digits and back again without change to the value,
1659 <pre>
1660 { pmax log10 b if b is a power of 10
1661 {
1664 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1665 can be rounded into a floating-point number with p radix b digits and back again
1666 without change to the q decimal digits,
1671 <!--page 38 -->
1672 <pre>
1673 { p log10 b if b is a power of 10
1674 {
1677 DBL_DIG 10
1679 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1680 a normalized floating-point number, emin
1681 <pre> FLT_MIN_EXP
1682 DBL_MIN_EXP
1683 LDBL_MIN_EXP</pre>
1687 DBL_MIN_10_EXP -37
1689 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1690 representable finite floating-point number, emax
1691 <pre> FLT_MAX_EXP
1692 DBL_MAX_EXP
1693 LDBL_MAX_EXP</pre>
1697 DBL_MAX_10_EXP +37
1699 </ul>
1701 The values given in the following list shall be replaced by constant expressions with
1702 implementation-defined values that are greater than or equal to those shown:
1703 <ul>
1706 DBL_MAX 1E+37
1708 </ul>
1710 The values given in the following list shall be replaced by constant expressions with
1711 implementation-defined (positive) values that are less than or equal to those shown:
1712 <ul>
1715 <!--page 39 -->
1717 DBL_EPSILON 1E-9
1721 DBL_MIN 1E-37
1723 </ul>
1726 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1727 should be the identity function.
1729 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1730 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1731 float:
1732 <pre>
1733 6
1737 <pre>
1738 FLT_RADIX 16
1739 FLT_MANT_DIG 6
1740 FLT_EPSILON 9.53674316E-07F
1741 FLT_DIG 6
1742 FLT_MIN_EXP -31
1743 FLT_MIN 2.93873588E-39F
1744 FLT_MIN_10_EXP -38
1745 FLT_MAX_EXP +32
1746 FLT_MAX 3.40282347E+38F
1750 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1751 single-precision and double-precision normalized numbers in IEC 60559,<sup><a href="#note20"><b>20)</b></a></sup> and the appropriate values in a
1753 <pre>
1754 24
1758 <pre>
1759 53
1764 <pre>
1765 FLT_RADIX 2
1766 DECIMAL_DIG 17
1767 FLT_MANT_DIG 24
1768 FLT_EPSILON 1.19209290E-07F // decimal constant
1772 <!--page 40 -->
1773 <pre>
1774 FLT_DIG 6
1775 FLT_MIN_EXP -125
1776 FLT_MIN 1.17549435E-38F // decimal constant
1778 FLT_MIN_10_EXP -37
1779 FLT_MAX_EXP +128
1780 FLT_MAX 3.40282347E+38F // decimal constant
1781 FLT_MAX 0X1.fffffeP127F // hex constant
1782 FLT_MAX_10_EXP +38
1783 DBL_MANT_DIG 53
1784 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1786 DBL_DIG 15
1787 DBL_MIN_EXP -1021
1788 DBL_MIN 2.2250738585072014E-308 // decimal constant
1790 DBL_MIN_10_EXP -307
1791 DBL_MAX_EXP +1024
1792 DBL_MAX 1.7976931348623157E+308 // decimal constant
1793 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1795 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1796 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1797 precision), then DECIMAL_DIG would be 21.
1799 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1800 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.24"><wchar.h></a>
1801 (<a href="#7.24">7.24</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.20"><stdlib.h></a>
1802 (<a href="#7.20">7.20</a>), input/output <a href="#7.19"><stdio.h></a> (<a href="#7.19">7.19</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
1803 <!--page 41 -->
1806 <p><small><a name="note16" href="#note16">16)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
1807 does not require the floating-point arithmetic of the implementation to be identical.
1808 </small>
1809 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1811 similar behavior.
1812 </small>
1813 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1815 </small>
1816 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1817 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1818 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1819 double.
1820 </small>
1821 <p><small><a name="note20" href="#note20">20)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1822 limits are one less than shown here.
1823 </small>
1829 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1830 indicated by italic type, and literal words and character set members (terminals) by bold
1831 type. A colon (:) following a nonterminal introduces its definition. Alternative
1832 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1833 optional symbol is indicated by the subscript ''opt'', so that
1834 <pre>
1836 indicates an optional expression enclosed in braces.
1838 When syntactic categories are referred to in the main text, they are not italicized and
1839 words are separated by spaces instead of hyphens.
1847 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1848 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1849 same identifier can denote different entities at different points in the program. A member
1850 of an enumeration is called an enumeration constant. Macro names and macro
1851 parameters are not considered further here, because prior to the semantic phase of
1852 program translation any occurrences of macro names in the source file are replaced by the
1853 preprocessing token sequences that constitute their macro definitions.
1855 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1856 used) only within a region of program text called its scope. Different entities designated
1857 by the same identifier either have different scopes, or are in different name spaces. There
1858 are four kinds of scopes: function, file, block, and function prototype. (A function
1859 prototype is a declaration of a function that declares the types of its parameters.)
1861 A label name is the only kind of identifier that has function scope. It can be used (in a
1862 goto statement) anywhere in the function in which it appears, and is declared implicitly
1863 by its syntactic appearance (followed by a : and a statement).
1865 Every other identifier has scope determined by the placement of its declaration (in a
1866 declarator or type specifier). If the declarator or type specifier that declares the identifier
1867 appears outside of any block or list of parameters, the identifier has file scope, which
1868 terminates at the end of the translation unit. If the declarator or type specifier that
1869 declares the identifier appears inside a block or within the list of parameter declarations in
1870 a function definition, the identifier has block scope, which terminates at the end of the
1871 associated block. If the declarator or type specifier that declares the identifier appears
1872 <!--page 42 -->
1873 within the list of parameter declarations in a function prototype (not part of a function
1874 definition), the identifier has function prototype scope, which terminates at the end of the
1875 function declarator. If an identifier designates two different entities in the same name
1876 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1877 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1878 identifier designates the entity declared in the inner scope; the entity declared in the outer
1879 scope is hidden (and not visible) within the inner scope.
1881 Unless explicitly stated otherwise, where this International Standard uses the term
1882 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1883 entity in the relevant name space whose declaration is visible at the point the identifier
1884 occurs.
1886 Two identifiers have the same scope if and only if their scopes terminate at the same
1887 point.
1889 Structure, union, and enumeration tags have scope that begins just after the appearance of
1890 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1891 begins just after the appearance of its defining enumerator in an enumerator list. Any
1892 other identifier has scope that begins just after the completion of its declarator.
1893 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
1894 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>),
1899 An identifier declared in different scopes or in the same scope more than once can be
1900 made to refer to the same object or function by a process called linkage.<sup><a href="#note21"><b>21)</b></a></sup> There are
1901 three kinds of linkage: external, internal, and none.
1903 In the set of translation units and libraries that constitutes an entire program, each
1904 declaration of a particular identifier with external linkage denotes the same object or
1905 function. Within one translation unit, each declaration of an identifier with internal
1906 linkage denotes the same object or function. Each declaration of an identifier with no
1907 linkage denotes a unique entity.
1909 If the declaration of a file scope identifier for an object or a function contains the storage-
1910 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
1912 For an identifier declared with the storage-class specifier extern in a scope in which a
1916 <!--page 43 -->
1917 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
1918 external linkage, the linkage of the identifier at the later declaration is the same as the
1919 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
1920 declaration specifies no linkage, then the identifier has external linkage.
1922 If the declaration of an identifier for a function has no storage-class specifier, its linkage
1923 is determined exactly as if it were declared with the storage-class specifier extern. If
1924 the declaration of an identifier for an object has file scope and no storage-class specifier,
1925 its linkage is external.
1927 The following identifiers have no linkage: an identifier declared to be anything other than
1928 an object or a function; an identifier declared to be a function parameter; a block scope
1929 identifier for an object declared without the storage-class specifier extern.
1931 If, within a translation unit, the same identifier appears with both internal and external
1932 linkage, the behavior is undefined.
1933 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), external definitions (<a href="#6.9">6.9</a>),
1937 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
1938 </small>
1939 <p><small><a name="note22" href="#note22">22)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
1941 </small>
1942 <p><small><a name="note23" href="#note23">23)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
1943 </small>
1947 If more than one declaration of a particular identifier is visible at any point in a
1948 translation unit, the syntactic context disambiguates uses that refer to different entities.
1949 Thus, there are separate name spaces for various categories of identifiers, as follows:
1950 <ul>
1951 <li> label names (disambiguated by the syntax of the label declaration and use);
1952 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
1953 of the keywords struct, union, or enum);
1954 <li> the members of structures or unions; each structure or union has a separate name
1955 space for its members (disambiguated by the type of the expression used to access the
1956 member via the . or -> operator);
1957 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
1958 enumeration constants).
1959 </ul>
1960 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
1961 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>), tags
1967 <!--page 44 -->
1970 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
1971 </small>
1975 An object has a storage duration that determines its lifetime. There are three storage
1976 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
1978 The lifetime of an object is the portion of program execution during which storage is
1979 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
1980 its last-stored value throughout its lifetime.<sup><a href="#note26"><b>26)</b></a></sup> If an object is referred to outside of its
1981 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
1982 the object it points to reaches the end of its lifetime.
1984 An object whose identifier is declared with external or internal linkage, or with the
1985 storage-class specifier static has static storage duration. Its lifetime is the entire
1986 execution of the program and its stored value is initialized only once, prior to program
1987 startup.
1989 An object whose identifier is declared with no linkage and without the storage-class
1990 specifier static has automatic storage duration.
1992 For such an object that does not have a variable length array type, its lifetime extends
1993 from entry into the block with which it is associated until execution of that block ends in
1994 any way. (Entering an enclosed block or calling a function suspends, but does not end,
1995 execution of the current block.) If the block is entered recursively, a new instance of the
1996 object is created each time. The initial value of the object is indeterminate. If an
1997 initialization is specified for the object, it is performed each time the declaration is
1998 reached in the execution of the block; otherwise, the value becomes indeterminate each
1999 time the declaration is reached.
2001 For such an object that does have a variable length array type, its lifetime extends from
2002 the declaration of the object until execution of the program leaves the scope of the
2003 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2004 each time. The initial value of the object is indeterminate.
2005 <p><b> Forward references</b>: statements (<a href="#6.8">6.8</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), declarators (<a href="#6.7.5">6.7.5</a>), array
2011 <!--page 45 -->
2014 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2015 times will compare equal. The address may be different during two different executions of the same
2016 program.
2017 </small>
2018 <p><small><a name="note26" href="#note26">26)</a> In the case of a volatile object, the last store need not be explicit in the program.
2019 </small>
2020 <p><small><a name="note27" href="#note27">27)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2021 embedded block prior to the declaration, leaves the scope of the declaration.
2022 </small>
2026 The meaning of a value stored in an object or returned by a function is determined by the
2027 type of the expression used to access it. (An identifier declared to be an object is the
2028 simplest such expression; the type is specified in the declaration of the identifier.) Types
2029 are partitioned into object types (types that fully describe objects), function types (types
2030 that describe functions), and incomplete types (types that describe objects but lack
2031 information needed to determine their sizes).
2035 An object declared as type char is large enough to store any member of the basic
2036 execution character set. If a member of the basic execution character set is stored in a
2037 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2038 a char object, the resulting value is implementation-defined but shall be within the range
2039 of values that can be represented in that type.
2041 There are five standard signed integer types, designated as signed char, short
2042 int, int, long int, and long long int. (These and other types may be
2043 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2044 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2045 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2047 An object declared as type signed char occupies the same amount of storage as a
2048 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2049 architecture of the execution environment (large enough to contain any value in the range
2052 For each of the signed integer types, there is a corresponding (but different) unsigned
2053 integer type (designated with the keyword unsigned) that uses the same amount of
2054 storage (including sign information) and has the same alignment requirements. The type
2055 _Bool and the unsigned integer types that correspond to the standard signed integer
2056 types are the standard unsigned integer types. The unsigned integer types that
2057 correspond to the extended signed integer types are the extended unsigned integer types.
2058 The standard and extended unsigned integer types are collectively called unsigned integer
2063 <!--page 46 -->
2065 The standard signed integer types and standard unsigned integer types are collectively
2066 called the standard integer types, the extended signed integer types and extended
2067 unsigned integer types are collectively called the extended integer types.
2069 For any two integer types with the same signedness and different integer conversion rank
2070 (see <a href="#6.3.1.1">6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a
2071 subrange of the values of the other type.
2073 The range of nonnegative values of a signed integer type is a subrange of the
2074 corresponding unsigned integer type, and the representation of the same value in each
2075 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2076 because a result that cannot be represented by the resulting unsigned integer type is
2077 reduced modulo the number that is one greater than the largest value that can be
2078 represented by the resulting type.
2080 There are three real floating types, designated as float, double, and long
2081 double.<sup><a href="#note32"><b>32)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2082 type double; the set of values of the type double is a subset of the set of values of the
2083 type long double.
2085 There are three complex types, designated as float _Complex, double
2086 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2087 are collectively called the floating types.
2089 For each floating type there is a corresponding real type, which is always a real floating
2090 type. For real floating types, it is the same type. For complex types, it is the type given
2091 by deleting the keyword _Complex from the type name.
2093 Each complex type has the same representation and alignment requirements as an array
2094 type containing exactly two elements of the corresponding real type; the first element is
2095 equal to the real part, and the second element to the imaginary part, of the complex
2096 number.
2098 The type char, the signed and unsigned integer types, and the floating types are
2099 collectively called the basic types. Even if the implementation defines two or more basic
2100 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2102 <!--page 47 -->
2104 The three types char, signed char, and unsigned char are collectively called
2105 the character types. The implementation shall define char to have the same range,
2106 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2108 An enumeration comprises a set of named integer constant values. Each distinct
2109 enumeration constitutes a different enumerated type.
2111 The type char, the signed and unsigned integer types, and the enumerated types are
2112 collectively called integer types. The integer and real floating types are collectively called
2113 real types.
2115 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2116 belongs to one type domain: the real type domain comprises the real types, the complex
2117 type domain comprises the complex types.
2119 The void type comprises an empty set of values; it is an incomplete type that cannot be
2120 completed.
2122 Any number of derived types can be constructed from the object, function, and
2123 incomplete types, as follows:
2124 <ul>
2125 <li> An array type describes a contiguously allocated nonempty set of objects with a
2126 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2127 characterized by their element type and by the number of elements in the array. An
2128 array type is said to be derived from its element type, and if its element type is T , the
2129 array type is sometimes called ''array of T ''. The construction of an array type from
2130 an element type is called ''array type derivation''.
2131 <li> A structure type describes a sequentially allocated nonempty set of member objects
2132 (and, in certain circumstances, an incomplete array), each of which has an optionally
2133 specified name and possibly distinct type.
2134 <li> A union type describes an overlapping nonempty set of member objects, each of
2135 which has an optionally specified name and possibly distinct type.
2136 <li> A function type describes a function with specified return type. A function type is
2137 characterized by its return type and the number and types of its parameters. A
2138 function type is said to be derived from its return type, and if its return type is T , the
2139 function type is sometimes called ''function returning T ''. The construction of a
2140 function type from a return type is called ''function type derivation''.
2144 <!--page 48 -->
2145 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2146 type, called the referenced type. A pointer type describes an object whose value
2147 provides a reference to an entity of the referenced type. A pointer type derived from
2148 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2149 pointer type from a referenced type is called ''pointer type derivation''.
2150 </ul>
2151 These methods of constructing derived types can be applied recursively.
2153 Arithmetic types and pointer types are collectively called scalar types. Array and
2154 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2156 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2157 that type, by specifying the size in a later declaration (with internal or external linkage).
2158 A structure or union type of unknown content (as described in <a href="#6.7.2.3">6.7.2.3</a>) is an incomplete
2159 type. It is completed, for all declarations of that type, by declaring the same structure or
2160 union tag with its defining content later in the same scope.
2162 A type has known constant size if the type is not incomplete and is not a variable length
2163 array type.
2165 Array, function, and pointer types are collectively called derived declarator types. A
2166 declarator type derivation from a type T is the construction of a derived declarator type
2167 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2168 T.
2170 A type is characterized by its type category, which is either the outermost derivation of a
2171 derived type (as noted above in the construction of derived types), or the type itself if the
2172 type consists of no derived types.
2174 Any type so far mentioned is an unqualified type. Each unqualified type has several
2175 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2176 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2177 versions of a type are distinct types that belong to the same type category and have the
2178 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2179 qualifiers (if any) of the type from which it is derived.
2181 A pointer to void shall have the same representation and alignment requirements as a
2182 pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
2183 compatible types shall have the same representation and alignment requirements. All
2186 <!--page 49 -->
2187 pointers to structure types shall have the same representation and alignment requirements
2188 as each other. All pointers to union types shall have the same representation and
2189 alignment requirements as each other. Pointers to other types need not have the same
2190 representation or alignment requirements.
2192 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2193 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2194 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2195 qualified float'' and is a pointer to a qualified type.
2199 function returning struct tag''. The array has length five and the function has a single parameter of type
2200 float. Its type category is array.
2202 <p><b> Forward references</b>: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2205 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2207 </small>
2208 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2209 signed integer types.
2210 </small>
2211 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2212 unsigned integer types.
2213 </small>
2214 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2215 arguments to functions, return values from functions, and members of unions.
2216 </small>
2217 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2218 </small>
2219 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2220 </small>
2221 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2222 any other) type; this does not violate the requirement that all basic types be different.
2223 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2225 </small>
2226 <p><small><a name="note35" href="#note35">35)</a> CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
2227 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2228 other two and is not compatible with either.
2229 </small>
2230 <p><small><a name="note36" href="#note36">36)</a> Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
2231 </small>
2232 <p><small><a name="note37" href="#note37">37)</a> Note that aggregate type does not include union type because an object with union type can only
2233 contain one member at a time.
2234 </small>
2235 <p><small><a name="note38" href="#note38">38)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2236 </small>
2237 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2238 arguments to functions, return values from functions, and members of unions.
2239 </small>
2245 The representations of all types are unspecified except as stated in this subclause.
2247 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2248 the number, order, and encoding of which are either explicitly specified or
2249 implementation-defined.
2251 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2254 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2255 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2256 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2257 called the object representation of the value. Values stored in bit-fields consist of m bits,
2258 where m is the size specified for the bit-field. The object representation is the set of m
2259 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2260 than NaNs) with the same object representation compare equal, but values that compare
2261 equal may have different object representations.
2263 Certain object representations need not represent a value of the object type. If the stored
2264 value of an object has such a representation and is read by an lvalue expression that does
2265 not have character type, the behavior is undefined. If such a representation is produced
2266 by a side effect that modifies all or any part of the object by an lvalue expression that
2267 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2269 <!--page 50 -->
2270 a trap representation.
2272 When a value is stored in an object of structure or union type, including in a member
2273 object, the bytes of the object representation that correspond to any padding bytes take
2274 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2275 representation, even though the value of a member of the structure or union object may be
2276 a trap representation.
2278 When a value is stored in a member of an object of union type, the bytes of the object
2279 representation that do not correspond to that member but do correspond to other members
2280 take unspecified values.
2282 Where an operator is applied to a value that has more than one object representation,
2283 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2284 value is stored in an object using a type that has more than one object representation for
2285 that value, it is unspecified which representation is used, but a trap representation shall
2286 not be generated.
2287 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2291 <p><small><a name="note40" href="#note40">40)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2292 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2293 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2294 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2296 </small>
2297 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2298 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2299 </small>
2300 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2301 </small>
2302 <p><small><a name="note43" href="#note43">43)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
2303 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2305 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2306 on values of type T may distinguish between them.
2307 </small>
2311 For unsigned integer types other than unsigned char, the bits of the object
2312 representation shall be divided into two groups: value bits and padding bits (there need
2313 not be any of the latter). If there are N value bits, each bit shall represent a different
2315 representing values from 0 to 2<sup>N</sup> - 1 using a pure binary representation; this shall be
2316 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2318 For signed integer types, the bits of the object representation shall be divided into three
2319 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2321 <!--page 51 -->
2322 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2323 the same bit in the object representation of the corresponding unsigned type (if there are
2324 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2325 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2326 modified in one of the following ways:
2327 <ul>
2331 </ul>
2332 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2333 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2334 complement), is a trap representation or a normal value. In the case of sign and
2335 magnitude and ones' complement, if this representation is a normal value it is called a
2336 negative zero.
2338 If the implementation supports negative zeros, they shall be generated only by:
2339 <ul>
2340 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2341 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2342 zero;
2343 <li> compound assignment operators based on the above cases.
2344 </ul>
2345 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2346 and whether a negative zero becomes a normal zero when stored in an object.
2348 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2349 and >> operators with arguments that would produce such a value is undefined.
2351 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2352 of a signed integer type where the sign bit is zero is a valid object representation of the
2353 corresponding unsigned type, and shall represent the same value. For any integer type,
2354 the object representation where all the bits are zero shall be a representation of the value
2355 zero in that type.
2357 The precision of an integer type is the number of bits it uses to represent values,
2358 excluding any sign and padding bits. The width of an integer type is the same but
2359 including any sign bit; thus for unsigned integer types the two values are the same, while
2362 <!--page 52 -->
2363 for signed integer types the width is one greater than the precision.
2366 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2367 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2368 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2369 with unsigned types. All other combinations of padding bits are alternative object representations of
2370 the value specified by the value bits.
2371 </small>
2372 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2373 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2374 representation other than as part of an exceptional condition such as an overflow. All other
2375 combinations of padding bits are alternative object representations of the value specified by the value
2376 bits.
2377 </small>
2381 Two types have compatible type if their types are the same. Additional rules for
2382 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2383 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.5">6.7.5</a> for declarators.<sup><a href="#note46"><b>46)</b></a></sup> Moreover, two structure,
2384 union, or enumerated types declared in separate translation units are compatible if their
2385 tags and members satisfy the following requirements: If one is declared with a tag, the
2386 other shall be declared with the same tag. If both are complete types, then the following
2387 additional requirements apply: there shall be a one-to-one correspondence between their
2388 members such that each pair of corresponding members are declared with compatible
2389 types, and such that if one member of a corresponding pair is declared with a name, the
2390 other member is declared with the same name. For two structures, corresponding
2391 members shall be declared in the same order. For two structures or unions, corresponding
2392 bit-fields shall have the same widths. For two enumerations, corresponding members
2393 shall have the same values.
2395 All declarations that refer to the same object or function shall have compatible type;
2396 otherwise, the behavior is undefined.
2398 A composite type can be constructed from two types that are compatible; it is a type that
2399 is compatible with both of the two types and satisfies the following conditions:
2400 <ul>
2401 <li> If one type is an array of known constant size, the composite type is an array of that
2402 size; otherwise, if one type is a variable length array, the composite type is that type.
2403 <li> If only one type is a function type with a parameter type list (a function prototype),
2404 the composite type is a function prototype with the parameter type list.
2405 <li> If both types are function types with parameter type lists, the type of each parameter
2406 in the composite parameter type list is the composite type of the corresponding
2407 parameters.
2408 </ul>
2409 These rules apply recursively to the types from which the two types are derived.
2411 For an identifier with internal or external linkage declared in a scope in which a prior
2412 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2413 external linkage, the type of the identifier at the later declaration becomes the composite
2414 type.
2419 <!--page 53 -->
2421 EXAMPLE Given the following two file scope declarations:
2422 <pre>
2423 int f(int (*)(), double (*)[3]);
2424 int f(int (*)(char *), double (*)[]);</pre>
2425 The resulting composite type for the function is:
2426 <!--page 54 -->
2427 <pre>
2431 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2432 </small>
2433 <p><small><a name="note47" href="#note47">47)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2434 </small>
2438 Several operators convert operand values from one type to another automatically. This
2439 subclause specifies the result required from such an implicit conversion, as well as those
2440 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2441 the conversions performed by most ordinary operators; it is supplemented as required by
2444 Conversion of an operand value to a compatible type causes no change to the value or the
2445 representation.
2452 Every integer type has an integer conversion rank defined as follows:
2453 <ul>
2454 <li> No two signed integer types shall have the same rank, even if they have the same
2455 representation.
2456 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2457 type with less precision.
2458 <li> The rank of long long int shall be greater than the rank of long int, which
2459 shall be greater than the rank of int, which shall be greater than the rank of short
2460 int, which shall be greater than the rank of signed char.
2461 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2462 signed integer type, if any.
2463 <li> The rank of any standard integer type shall be greater than the rank of any extended
2464 integer type with the same width.
2465 <li> The rank of char shall equal the rank of signed char and unsigned char.
2466 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2467 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2469 <li> The rank of any extended signed integer type relative to another extended signed
2470 integer type with the same precision is implementation-defined, but still subject to the
2471 other rules for determining the integer conversion rank.
2472 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2473 greater rank than T3, then T1 has greater rank than T3.
2474 </ul>
2476 The following may be used in an expression wherever an int or unsigned int may
2477 be used:
2478 <!--page 55 -->
2479 <ul>
2480 <li> An object or expression with an integer type whose integer conversion rank is less
2481 than or equal to the rank of int and unsigned int.
2482 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2483 </ul>
2484 If an int can represent all values of the original type, the value is converted to an int;
2485 otherwise, it is converted to an unsigned int. These are called the integer
2486 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2488 The integer promotions preserve value including sign. As discussed earlier, whether a
2489 ''plain'' char is treated as signed is implementation-defined.
2490 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2494 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2495 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2496 shift operators, as specified by their respective subclauses.
2497 </small>
2501 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2506 When a value with integer type is converted to another integer type other than _Bool, if
2507 the value can be represented by the new type, it is unchanged.
2509 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2510 subtracting one more than the maximum value that can be represented in the new type
2513 Otherwise, the new type is signed and the value cannot be represented in it; either the
2514 result is implementation-defined or an implementation-defined signal is raised.
2517 <p><small><a name="note49" href="#note49">49)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2518 </small>
2522 When a finite value of real floating type is converted to an integer type other than _Bool,
2523 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2524 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2526 When a value of integer type is converted to a real floating type, if the value being
2527 converted can be represented exactly in the new type, it is unchanged. If the value being
2528 converted is in the range of values that can be represented but cannot be represented
2530 <!--page 56 -->
2531 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2532 in an implementation-defined manner. If the value being converted is outside the range of
2533 values that can be represented, the behavior is undefined.
2536 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2537 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2539 </small>
2543 When a float is promoted to double or long double, or a double is promoted
2544 to long double, its value is unchanged (if the source value is represented in the
2545 precision and range of its type).
2547 When a double is demoted to float, a long double is demoted to double or
2548 float, or a value being represented in greater precision and range than required by its
2549 semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
2550 being converted can be represented exactly in the new type, it is unchanged. If the value
2551 being converted is in the range of values that can be represented but cannot be
2552 represented exactly, the result is either the nearest higher or nearest lower representable
2553 value, chosen in an implementation-defined manner. If the value being converted is
2554 outside the range of values that can be represented, the behavior is undefined.
2558 When a value of complex type is converted to another complex type, both the real and
2559 imaginary parts follow the conversion rules for the corresponding real types.
2563 When a value of real type is converted to a complex type, the real part of the complex
2564 result value is determined by the rules of conversion to the corresponding real type and
2565 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2567 When a value of complex type is converted to a real type, the imaginary part of the
2568 complex value is discarded and the value of the real part is converted according to the
2569 conversion rules for the corresponding real type.
2573 Many operators that expect operands of arithmetic type cause conversions and yield result
2574 types in a similar way. The purpose is to determine a common real type for the operands
2575 and result. For the specified operands, each operand is converted, without change of type
2576 domain, to a type whose corresponding real type is the common real type. Unless
2577 explicitly stated otherwise, the common real type is also the corresponding real type of
2578 the result, whose type domain is the type domain of the operands if they are the same,
2579 and complex otherwise. This pattern is called the usual arithmetic conversions:
2580 <!--page 57 -->
2582 <ul>
2583 <li> First, if the corresponding real type of either operand is long double, the other
2584 operand is converted, without change of type domain, to a type whose
2585 corresponding real type is long double.
2586 <li> Otherwise, if the corresponding real type of either operand is double, the other
2587 operand is converted, without change of type domain, to a type whose
2588 corresponding real type is double.
2589 <li> Otherwise, if the corresponding real type of either operand is float, the other
2590 operand is converted, without change of type domain, to a type whose
2592 <li> Otherwise, the integer promotions are performed on both operands. Then the
2593 following rules are applied to the promoted operands:
2594 <ul>
2595 <li> If both operands have the same type, then no further conversion is needed.
2596 <li> Otherwise, if both operands have signed integer types or both have unsigned
2597 integer types, the operand with the type of lesser integer conversion rank is
2598 converted to the type of the operand with greater rank.
2599 <li> Otherwise, if the operand that has unsigned integer type has rank greater or
2600 equal to the rank of the type of the other operand, then the operand with
2601 signed integer type is converted to the type of the operand with unsigned
2602 integer type.
2603 <li> Otherwise, if the type of the operand with signed integer type can represent
2604 all of the values of the type of the operand with unsigned integer type, then
2605 the operand with unsigned integer type is converted to the type of the
2606 operand with signed integer type.
2607 <li> Otherwise, both operands are converted to the unsigned integer type
2608 corresponding to the type of the operand with signed integer type.
2609 </ul>
2610 </ul>
2611 The values of floating operands and of the results of floating expressions may be
2612 represented in greater precision and range than that required by the type; the types are not
2618 <!--page 58 -->
2621 <p><small><a name="note51" href="#note51">51)</a> For example, addition of a double _Complex and a float entails just the conversion of the
2622 float operand to double (and yields a double _Complex result).
2623 </small>
2624 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2626 </small>
2630 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2632 An lvalue is an expression with an object type or an incomplete type other than void;<sup><a href="#note53"><b>53)</b></a></sup>
2633 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2634 When an object is said to have a particular type, the type is specified by the lvalue used to
2635 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2636 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2637 or union, does not have any member (including, recursively, any member or element of
2638 all contained aggregates or unions) with a const-qualified type.
2640 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2641 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2642 an lvalue that does not have array type is converted to the value stored in the designated
2643 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2644 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2645 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2646 undefined.
2648 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2649 string literal used to initialize an array, an expression that has type ''array of type'' is
2650 converted to an expression with type ''pointer to type'' that points to the initial element of
2651 the array object and is not an lvalue. If the array object has register storage class, the
2652 behavior is undefined.
2654 A function designator is an expression that has function type. Except when it is the
2655 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2656 type ''function returning type'' is converted to an expression that has type ''pointer to
2657 function returning type''.
2658 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2659 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), initialization (<a href="#6.7.8">6.7.8</a>), postfix
2660 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2661 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>).
2664 <!--page 59 -->
2667 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2668 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2669 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2670 as the ''value of an expression''.
2671 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2672 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2673 </small>
2674 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2676 </small>
2680 The (nonexistent) value of a void expression (an expression that has type void) shall not
2681 be used in any way, and implicit or explicit conversions (except to void) shall not be
2682 applied to such an expression. If an expression of any other type is evaluated as a void
2683 expression, its value or designator is discarded. (A void expression is evaluated for its
2684 side effects.)
2688 A pointer to void may be converted to or from a pointer to any incomplete or object
2689 type. A pointer to any incomplete or object type may be converted to a pointer to void
2690 and back again; the result shall compare equal to the original pointer.
2692 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2693 the q-qualified version of the type; the values stored in the original and converted pointers
2694 shall compare equal.
2696 An integer constant expression with the value 0, or such an expression cast to type
2697 void *, is called a null pointer constant.<sup><a href="#note55"><b>55)</b></a></sup> If a null pointer constant is converted to a
2698 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2699 to a pointer to any object or function.
2701 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2702 Any two null pointers shall compare equal.
2704 An integer may be converted to any pointer type. Except as previously specified, the
2705 result is implementation-defined, might not be correctly aligned, might not point to an
2706 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2708 Any pointer type may be converted to an integer type. Except as previously specified, the
2709 result is implementation-defined. If the result cannot be represented in the integer type,
2710 the behavior is undefined. The result need not be in the range of values of any integer
2711 type.
2713 A pointer to an object or incomplete type may be converted to a pointer to a different
2714 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2715 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2716 result shall compare equal to the original pointer. When a pointer to an object is
2719 <!--page 60 -->
2720 converted to a pointer to a character type, the result points to the lowest addressed byte of
2721 the object. Successive increments of the result, up to the size of the object, yield pointers
2722 to the remaining bytes of the object.
2724 A pointer to a function of one type may be converted to a pointer to a function of another
2725 type and back again; the result shall compare equal to the original pointer. If a converted
2726 pointer is used to call a function whose type is not compatible with the pointed-to type,
2727 the behavior is undefined.
2728 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
2729 capable of holding object pointers (<a href="#7.18.1.4">7.18.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
2730 <!--page 61 -->
2733 <p><small><a name="note55" href="#note55">55)</a> The macro NULL is defined in <a href="#7.17"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.17">7.17</a>.
2734 </small>
2735 <p><small><a name="note56" href="#note56">56)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2736 be consistent with the addressing structure of the execution environment.
2737 </small>
2738 <p><small><a name="note57" href="#note57">57)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2739 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2740 correctly aligned for a pointer to type C.
2741 </small>
2746 <pre>
2747 token:
2748 keyword
2749 identifier
2750 constant
2751 string-literal
2752 punctuator
2753 preprocessing-token:
2754 header-name
2755 identifier
2756 pp-number
2757 character-constant
2758 string-literal
2759 punctuator
2760 each non-white-space character that cannot be one of the above</pre>
2763 Each preprocessing token that is converted to a token shall have the lexical form of a
2764 keyword, an identifier, a constant, a string literal, or a punctuator.
2768 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2769 A preprocessing token is the minimal lexical element of the language in translation
2771 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2772 single non-white-space characters that do not lexically match the other preprocessing
2773 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2774 undefined. Preprocessing tokens can be separated by white space; this consists of
2775 comments (described later), or white-space characters (space, horizontal tab, new-line,
2776 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2777 during translation phase 4, white space (or the absence thereof) serves as more than
2778 preprocessing token separation. White space may appear within a preprocessing token
2779 only as part of a header name or between the quotation characters in a character constant
2780 or string literal.
2784 <!--page 62 -->
2785 <p><!--para 4 -->
2786 If the input stream has been parsed into preprocessing tokens up to a given character, the
2787 next preprocessing token is the longest sequence of characters that could constitute a
2788 preprocessing token. There is one exception to this rule: header name preprocessing
2789 tokens are recognized only within #include preprocessing directives and in
2790 implementation-defined locations within #pragma directives. In such contexts, a
2791 sequence of characters that could be either a header name or a string literal is recognized
2792 as the former.
2793 <p><!--para 5 -->
2794 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2795 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2796 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2797 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2798 not E is a macro name.
2800 <p><!--para 6 -->
2801 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2802 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2804 <p><b> Forward references</b>: character constants (<a href="#6.4.4.4">6.4.4.4</a>), comments (<a href="#6.4.9">6.4.9</a>), expressions (<a href="#6.5">6.5</a>),
2805 floating constants (<a href="#6.4.4.2">6.4.4.2</a>), header names (<a href="#6.4.7">6.4.7</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), postfix
2806 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2807 (<a href="#6.5.3.1">6.5.3.1</a>), preprocessing directives (<a href="#6.10">6.10</a>), preprocessing numbers (<a href="#6.4.8">6.4.8</a>), string literals
2810 <h6>footnotes</h6>
2811 <p><small><a name="note58" href="#note58">58)</a> An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
2812 occur in source files.
2813 </small>
2816 <h6>Syntax</h6>
2817 <p><!--para 1 -->
2818 <pre>
2819 keyword: one of
2820 auto enum restrict unsigned
2821 break extern return void
2822 case float short volatile
2823 char for signed while
2824 const goto sizeof _Bool
2825 continue if static _Complex
2826 default inline struct _Imaginary
2827 do int switch
2828 double long typedef
2829 else register union</pre>
2830 <h6>Semantics</h6>
2831 <p><!--para 2 -->
2832 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2833 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2838 <!--page 63 -->
2840 <h6>footnotes</h6>
2841 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2842 </small>
2847 <h6>Syntax</h6>
2848 <p><!--para 1 -->
2849 <pre>
2850 identifier:
2851 identifier-nondigit
2852 identifier identifier-nondigit
2853 identifier digit
2854 identifier-nondigit:
2855 nondigit
2856 universal-character-name
2857 other implementation-defined characters
2858 nondigit: one of
2859 _ a b c d e f g h i j k l m
2860 n o p q r s t u v w x y z
2861 A B C D E F G H I J K L M
2862 N O P Q R S T U V W X Y Z
2863 digit: one of
2864 0 1 2 3 4 5 6 7 8 9</pre>
2865 <h6>Semantics</h6>
2866 <p><!--para 2 -->
2867 An identifier is a sequence of nondigit characters (including the underscore _, the
2868 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2869 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2870 There is no specific limit on the maximum length of an identifier.
2871 <p><!--para 3 -->
2872 Each universal character name in an identifier shall designate a character whose encoding
2873 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.<sup><a href="#note60"><b>60)</b></a></sup> The initial
2874 character shall not be a universal character name designating a digit. An implementation
2875 may allow multibyte characters that are not part of the basic source character set to
2876 appear in identifiers; which characters and their correspondence to universal character
2877 names is implementation-defined.
2878 <p><!--para 4 -->
2879 When preprocessing tokens are converted to tokens during translation phase 7, if a
2880 preprocessing token could be converted to either a keyword or an identifier, it is converted
2881 to a keyword.
2884 <!--page 64 -->
2885 <h6> Implementation limits</h6>
2886 <p><!--para 5 -->
2887 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2888 characters in an identifier; the limit for an external name (an identifier that has external
2889 linkage) may be more restrictive than that for an internal name (a macro name or an
2890 identifier that does not have external linkage). The number of significant characters in an
2891 identifier is implementation-defined.
2892 <p><!--para 6 -->
2893 Any identifiers that differ in a significant character are different identifiers. If two
2894 identifiers differ only in nonsignificant characters, the behavior is undefined.
2895 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
2897 <h6>footnotes</h6>
2898 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
2899 name may be used in forming valid external identifiers. For example, some otherwise unused
2900 character or sequence of characters may be used to encode the \u in a universal character name.
2901 Extended characters may produce a long external identifier.
2902 </small>
2905 <h6>Semantics</h6>
2906 <p><!--para 1 -->
2907 The identifier __func__ shall be implicitly declared by the translator as if,
2908 immediately following the opening brace of each function definition, the declaration
2909 <pre>
2911 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
2912 <p><!--para 2 -->
2913 This name is encoded as if the implicit declaration had been written in the source
2914 character set and then translated into the execution character set as indicated in translation
2915 phase 5.
2916 <p><!--para 3 -->
2917 EXAMPLE Consider the code fragment:
2918 <pre>
2920 void myfunc(void)
2921 {
2923 /* ... */
2924 }</pre>
2925 Each time the function is called, it will print to the standard output stream:
2926 <pre>
2927 myfunc</pre>
2934 <!--page 65 -->
2936 <h6>footnotes</h6>
2937 <p><small><a name="note61" href="#note61">61)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
2938 identifier is explicitly declared using the name __func__, the behavior is undefined.
2939 </small>
2942 <h6>Syntax</h6>
2943 <p><!--para 1 -->
2944 <pre>
2945 universal-character-name:
2946 \u hex-quad
2947 \U hex-quad hex-quad
2948 hex-quad:
2949 hexadecimal-digit hexadecimal-digit
2950 hexadecimal-digit hexadecimal-digit</pre>
2951 <h6>Constraints</h6>
2952 <p><!--para 2 -->
2953 A universal character name shall not specify a character whose short identifier is less than
2954 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
2956 <h6>Description</h6>
2957 <p><!--para 3 -->
2958 Universal character names may be used in identifiers, character constants, and string
2959 literals to designate characters that are not in the basic character set.
2960 <h6>Semantics</h6>
2961 <p><!--para 4 -->
2962 The universal character name \Unnnnnnnn designates the character whose eight-digit
2963 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
2964 character name \unnnn designates the character whose four-digit short identifier is nnnn
2965 (and whose eight-digit short identifier is 0000nnnn).
2970 <!--page 66 -->
2972 <h6>footnotes</h6>
2973 <p><small><a name="note62" href="#note62">62)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
2974 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
2975 UTF-16).
2976 </small>
2977 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
2978 </small>
2981 <h6>Syntax</h6>
2982 <p><!--para 1 -->
2983 <pre>
2984 constant:
2985 integer-constant
2986 floating-constant
2987 enumeration-constant
2988 character-constant</pre>
2989 <h6>Constraints</h6>
2990 <p><!--para 2 -->
2991 Each constant shall have a type and the value of a constant shall be in the range of
2992 representable values for its type.
2993 <h6>Semantics</h6>
2994 <p><!--para 3 -->
2995 Each constant has a type, determined by its form and value, as detailed later.
2998 <h6>Syntax</h6>
2999 <p><!--para 1 -->
3000 <!--page 67 -->
3001 <pre>
3002 integer-constant:
3003 decimal-constant integer-suffix<sub>opt</sub>
3004 octal-constant integer-suffix<sub>opt</sub>
3005 hexadecimal-constant integer-suffix<sub>opt</sub>
3006 decimal-constant:
3007 nonzero-digit
3008 decimal-constant digit
3009 octal-constant:
3010 0
3011 octal-constant octal-digit
3012 hexadecimal-constant:
3013 hexadecimal-prefix hexadecimal-digit
3014 hexadecimal-constant hexadecimal-digit
3015 hexadecimal-prefix: one of
3016 0x 0X
3017 nonzero-digit: one of
3018 1 2 3 4 5 6 7 8 9
3019 octal-digit: one of
3020 0 1 2 3 4 5 6 7
3021 hexadecimal-digit: one of
3022 0 1 2 3 4 5 6 7 8 9
3023 a b c d e f
3024 A B C D E F
3025 integer-suffix:
3026 unsigned-suffix long-suffix<sub>opt</sub>
3027 unsigned-suffix long-long-suffix
3028 long-suffix unsigned-suffix<sub>opt</sub>
3029 long-long-suffix unsigned-suffix<sub>opt</sub>
3030 unsigned-suffix: one of
3031 u U
3032 long-suffix: one of
3033 l L
3034 long-long-suffix: one of
3035 ll LL</pre>
3036 <h6>Description</h6>
3037 <p><!--para 2 -->
3038 An integer constant begins with a digit, but has no period or exponent part. It may have a
3039 prefix that specifies its base and a suffix that specifies its type.
3040 <p><!--para 3 -->
3041 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3042 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3043 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3044 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3045 10 through 15 respectively.
3046 <h6>Semantics</h6>
3047 <p><!--para 4 -->
3048 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3049 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3050 <p><!--para 5 -->
3051 The type of an integer constant is the first of the corresponding list in which its value can
3052 be represented.
3053 <!--page 68 -->
3054 <table border=1>
3055 <tr><th> Suffix <th>Decimal Constant <th>Octal or Hexadecimal Constant
3056 <tr><td> none
3057 <td><pre>int
3058 long int
3059 long long int</pre>
3060 <td><pre>int
3061 unsigned int
3062 long int
3063 unsigned long int
3064 long long int
3065 unsigned long long int</pre>
3066 <tr><td> u or U
3067 <td><pre>unsigned int
3068 unsigned long int
3069 unsigned long long int</pre>
3070 <td><pre>unsigned int
3071 unsigned long int
3072 unsigned long long int</pre>
3073 <tr><td> l or L
3074 <td><pre>long int
3075 long long int</pre>
3076 <td><pre>long int
3077 unsigned long int
3078 long long int
3079 unsigned long long int</pre>
3080 <tr><td> Both u or U and l or L
3081 <td><pre>unsigned long int
3082 unsigned long long int</pre>
3083 <td><pre>unsigned long int
3084 unsigned long long int</pre>
3085 <tr><td> ll or LL
3086 <td><pre>long long int</pre>
3087 <td><pre>long long int
3088 unsigned long long int</pre>
3089 <tr><td> Both u or U and ll or LL
3090 <td><pre>unsigned long long int</pre>
3091 <td><pre>unsigned long long int</pre>
3092 </table>
3093 <p><!--para 6 -->
3094 If an integer constant cannot be represented by any type in its list, it may have an
3095 extended integer type, if the extended integer type can represent its value. If all of the
3096 types in the list for the constant are signed, the extended integer type shall be signed. If
3097 all of the types in the list for the constant are unsigned, the extended integer type shall be
3098 unsigned. If the list contains both signed and unsigned types, the extended integer type
3099 may be signed or unsigned. If an integer constant cannot be represented by any type in
3100 its list and has no extended integer type, then the integer constant has no type.
3101 <!--page 69 -->
3104 <h6>Syntax</h6>
3105 <p><!--para 1 -->
3106 <!--page 70 -->
3107 <pre>
3108 floating-constant:
3109 decimal-floating-constant
3110 hexadecimal-floating-constant
3111 decimal-floating-constant:
3112 fractional-constant exponent-part<sub>opt</sub> floating-suffix<sub>opt</sub>
3113 digit-sequence exponent-part floating-suffix<sub>opt</sub>
3114 hexadecimal-floating-constant:
3115 hexadecimal-prefix hexadecimal-fractional-constant
3116 binary-exponent-part floating-suffix<sub>opt</sub>
3117 hexadecimal-prefix hexadecimal-digit-sequence
3118 binary-exponent-part floating-suffix<sub>opt</sub>
3119 fractional-constant:
3120 digit-sequence<sub>opt</sub> . digit-sequence
3121 digit-sequence .
3122 exponent-part:
3123 e sign<sub>opt</sub> digit-sequence
3124 E sign<sub>opt</sub> digit-sequence
3125 sign: one of
3126 + -
3127 digit-sequence:
3128 digit
3129 digit-sequence digit
3130 hexadecimal-fractional-constant:
3131 hexadecimal-digit-sequence<sub>opt</sub> .
3132 hexadecimal-digit-sequence
3133 hexadecimal-digit-sequence .
3134 binary-exponent-part:
3135 p sign<sub>opt</sub> digit-sequence
3136 P sign<sub>opt</sub> digit-sequence
3137 hexadecimal-digit-sequence:
3138 hexadecimal-digit
3139 hexadecimal-digit-sequence hexadecimal-digit
3140 floating-suffix: one of
3141 f l F L</pre>
3142 <h6>Description</h6>
3143 <p><!--para 2 -->
3144 A floating constant has a significand part that may be followed by an exponent part and a
3145 suffix that specifies its type. The components of the significand part may include a digit
3146 sequence representing the whole-number part, followed by a period (.), followed by a
3147 digit sequence representing the fraction part. The components of the exponent part are an
3148 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3149 Either the whole-number part or the fraction part has to be present; for decimal floating
3150 constants, either the period or the exponent part has to be present.
3151 <h6>Semantics</h6>
3152 <p><!--para 3 -->
3153 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3154 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3155 floating constants, the exponent indicates the power of 10 by which the significand part is
3156 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3157 by which the significand part is to be scaled. For decimal floating constants, and also for
3158 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3159 the nearest representable value, or the larger or smaller representable value immediately
3160 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3161 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3162 correctly rounded.
3163 <p><!--para 4 -->
3164 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3165 type float. If suffixed by the letter l or L, it has type long double.
3166 <p><!--para 5 -->
3167 Floating constants are converted to internal format as if at translation-time. The
3168 conversion of a floating constant shall not raise an exceptional condition or a floating-
3169 point exception at execution time.
3170 <h6>Recommended practice</h6>
3171 <p><!--para 6 -->
3172 The implementation should produce a diagnostic message if a hexadecimal constant
3173 cannot be represented exactly in its evaluation format; the implementation should then
3174 proceed with the translation of the program.
3175 <p><!--para 7 -->
3176 The translation-time conversion of floating constants should match the execution-time
3177 conversion of character strings by library functions, such as strtod, given matching
3178 inputs suitable for both conversions, the same result format, and default execution-time
3184 <!--page 71 -->
3186 <h6>footnotes</h6>
3187 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3189 </small>
3192 <h6>Syntax</h6>
3193 <p><!--para 1 -->
3194 <pre>
3195 enumeration-constant:
3196 identifier</pre>
3197 <h6>Semantics</h6>
3198 <p><!--para 2 -->
3199 An identifier declared as an enumeration constant has type int.
3203 <h6>Syntax</h6>
3204 <p><!--para 1 -->
3205 <!--page 72 -->
3206 <pre>
3207 character-constant:
3208 ' c-char-sequence '
3209 L' c-char-sequence '
3210 c-char-sequence:
3211 c-char
3212 c-char-sequence c-char
3213 c-char:
3214 any member of the source character set except
3215 the single-quote ', backslash \, or new-line character
3216 escape-sequence
3217 escape-sequence:
3218 simple-escape-sequence
3219 octal-escape-sequence
3220 hexadecimal-escape-sequence
3221 universal-character-name
3222 simple-escape-sequence: one of
3223 \' \" \? \\
3224 \a \b \f \n \r \t \v
3225 octal-escape-sequence:
3226 \ octal-digit
3227 \ octal-digit octal-digit
3228 \ octal-digit octal-digit octal-digit
3229 hexadecimal-escape-sequence:
3230 \x hexadecimal-digit
3231 hexadecimal-escape-sequence hexadecimal-digit</pre>
3234 An integer character constant is a sequence of one or more multibyte characters enclosed
3235 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3236 letter L. With a few exceptions detailed later, the elements of the sequence are any
3237 members of the source character set; they are mapped in an implementation-defined
3238 manner to members of the execution character set.
3240 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3241 arbitrary integer values are representable according to the following table of escape
3242 sequences:
3243 <p><!--para 4 -->
3244 <pre>
3245 single quote ' \'
3247 question mark ? \?
3248 backslash \ \\
3249 octal character \octal digits
3250 hexadecimal character \x hexadecimal digits</pre>
3251 The double-quote " and question-mark ? are representable either by themselves or by the
3252 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3253 shall be represented, respectively, by the escape sequences \' and \\.
3254 <p><!--para 5 -->
3255 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3256 of the construction of a single character for an integer character constant or of a single
3257 wide character for a wide character constant. The numerical value of the octal integer so
3258 formed specifies the value of the desired character or wide character.
3259 <p><!--para 6 -->
3260 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3261 sequence are taken to be part of the construction of a single character for an integer
3262 character constant or of a single wide character for a wide character constant. The
3263 numerical value of the hexadecimal integer so formed specifies the value of the desired
3264 character or wide character.
3265 <p><!--para 7 -->
3266 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3267 constitute the escape sequence.
3268 <p><!--para 8 -->
3269 In addition, characters not in the basic character set are representable by universal
3270 character names and certain nongraphic characters are representable by escape sequences
3271 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3277 <!--page 73 -->
3278 <h6>Constraints</h6>
3279 <p><!--para 9 -->
3280 The value of an octal or hexadecimal escape sequence shall be in the range of
3281 representable values for the type unsigned char for an integer character constant, or
3282 the unsigned type corresponding to wchar_t for a wide character constant.
3283 <h6>Semantics</h6>
3284 <p><!--para 10 -->
3285 An integer character constant has type int. The value of an integer character constant
3286 containing a single character that maps to a single-byte execution character is the
3287 numerical value of the representation of the mapped character interpreted as an integer.
3288 The value of an integer character constant containing more than one character (e.g.,
3289 'ab'), or containing a character or escape sequence that does not map to a single-byte
3290 execution character, is implementation-defined. If an integer character constant contains
3291 a single character or escape sequence, its value is the one that results when an object with
3292 type char whose value is that of the single character or escape sequence is converted to
3293 type int.
3294 <p><!--para 11 -->
3295 A wide character constant has type wchar_t, an integer type defined in the
3296 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3297 multibyte character that maps to a member of the extended execution character set is the
3298 wide character corresponding to that multibyte character, as defined by the mbtowc
3299 function, with an implementation-defined current locale. The value of a wide character
3300 constant containing more than one multibyte character, or containing a multibyte
3301 character or escape sequence not represented in the extended execution character set, is
3302 implementation-defined.
3303 <p><!--para 12 -->
3304 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3306 <p><!--para 13 -->
3307 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3308 bits for objects that have type char. In an implementation in which type char has the same range of
3309 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3310 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3312 <p><!--para 14 -->
3313 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3314 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3315 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3316 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3317 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3318 constant is implementation-defined.)
3320 <p><!--para 15 -->
3321 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3322 L'\1234' specifies the implementation-defined value that results from the combination of the values
3323 0123 and '4'.
3325 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3327 <!--page 74 -->
3329 <h6>footnotes</h6>
3330 <p><small><a name="note65" href="#note65">65)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
3331 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3332 </small>
3335 <h6>Syntax</h6>
3336 <p><!--para 1 -->
3337 <pre>
3338 string-literal:
3341 s-char-sequence:
3342 s-char
3343 s-char-sequence s-char
3344 s-char:
3345 any member of the source character set except
3346 the double-quote ", backslash \, or new-line character
3347 escape-sequence</pre>
3350 A character string literal is a sequence of zero or more multibyte characters enclosed in
3351 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3352 letter L.
3354 The same considerations apply to each element of the sequence in a character string
3355 literal or a wide string literal as if it were in an integer character constant or a wide
3356 character constant, except that the single-quote ' is representable either by itself or by the
3357 escape sequence \', but the double-quote " shall be represented by the escape sequence
3358 \".
3361 In translation phase 6, the multibyte character sequences specified by any sequence of
3362 adjacent character and wide string literal tokens are concatenated into a single multibyte
3363 character sequence. If any of the tokens are wide string literal tokens, the resulting
3364 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3365 character string literal.
3367 In translation phase 7, a byte or code of value zero is appended to each multibyte
3368 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3369 sequence is then used to initialize an array of static storage duration and length just
3370 sufficient to contain the sequence. For character string literals, the array elements have
3371 type char, and are initialized with the individual bytes of the multibyte character
3372 sequence; for wide string literals, the array elements have type wchar_t, and are
3373 initialized with the sequence of wide characters corresponding to the multibyte character
3375 <!--page 75 -->
3376 sequence, as defined by the mbstowcs function with an implementation-defined current
3377 locale. The value of a string literal containing a multibyte character or escape sequence
3378 not represented in the execution character set is implementation-defined.
3380 It is unspecified whether these arrays are distinct provided their elements have the
3381 appropriate values. If the program attempts to modify such an array, the behavior is
3382 undefined.
3384 EXAMPLE This pair of adjacent character string literals
3385 <pre>
3387 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3388 because escape sequences are converted into single members of the execution character set just prior to
3389 adjacent string literal concatenation.
3391 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3395 <p><small><a name="note66" href="#note66">66)</a> A character string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in
3396 it by a \0 escape sequence.
3397 </small>
3402 <pre>
3403 punctuator: one of
3404 [ ] ( ) { } . ->
3405 ++ -- & * + - ~ !
3407 ? : ; ...
3409 , # ##
3413 A punctuator is a symbol that has independent syntactic and semantic significance.
3414 Depending on context, it may specify an operation to be performed (which in turn may
3415 yield a value or a function designator, produce a side effect, or some combination thereof)
3416 in which case it is known as an operator (other forms of operator also exist in some
3417 contexts). An operand is an entity on which an operator acts.
3418 <!--page 76 -->
3421 <pre>
3423 behave, respectively, the same as the six tokens
3424 <pre>
3425 [ ] { } # ##</pre>
3427 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3431 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3432 </small>
3433 <p><small><a name="note68" href="#note68">68)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3434 interchanged.
3435 </small>
3440 <pre>
3441 header-name:
3443 " q-char-sequence "
3444 h-char-sequence:
3445 h-char
3446 h-char-sequence h-char
3447 h-char:
3448 any member of the source character set except
3449 the new-line character and >
3450 q-char-sequence:
3451 q-char
3452 q-char-sequence q-char
3453 q-char:
3454 any member of the source character set except
3455 the new-line character and "</pre>
3456 <h6>Semantics</h6>
3457 <p><!--para 2 -->
3458 The sequences in both forms of header names are mapped in an implementation-defined
3460 <p><!--para 3 -->
3461 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3462 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3467 <!--page 77 -->
3468 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3469 preprocessing tokens are recognized only within #include preprocessing directives and
3470 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3471 <p><!--para 4 -->
3472 EXAMPLE The following sequence of characters:
3473 <pre>
3474 0x3<1/a.h>1e2
3475 #include <1/a.h>
3476 #define const.member@$</pre>
3477 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3478 by a { on the left and a } on the right).
3479 <pre>
3480 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3481 {#}{include} {<1/a.h>}
3482 {#}{define} {const}{.}{member}{@}{$}</pre>
3486 <h6>footnotes</h6>
3487 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3488 </small>
3489 <p><small><a name="note70" href="#note70">70)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
3490 </small>
3493 <h6>Syntax</h6>
3494 <p><!--para 1 -->
3495 <pre>
3496 pp-number:
3497 digit
3498 . digit
3499 pp-number digit
3500 pp-number identifier-nondigit
3501 pp-number e sign
3502 pp-number E sign
3503 pp-number p sign
3504 pp-number P sign
3505 pp-number .</pre>
3506 <h6>Description</h6>
3507 <p><!--para 2 -->
3508 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3509 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3510 p+, p-, P+, or P-.
3511 <p><!--para 3 -->
3512 Preprocessing number tokens lexically include all floating and integer constant tokens.
3513 <h6>Semantics</h6>
3514 <p><!--para 4 -->
3515 A preprocessing number does not have type or a value; it acquires both after a successful
3516 conversion (as part of translation phase 7) to a floating constant token or an integer
3517 constant token.
3520 <!--page 78 -->
3523 <p><!--para 1 -->
3524 Except within a character constant, a string literal, or a comment, the characters /*
3525 introduce a comment. The contents of such a comment are examined only to identify
3526 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3527 <p><!--para 2 -->
3528 Except within a character constant, a string literal, or a comment, the characters //
3529 introduce a comment that includes all multibyte characters up to, but not including, the
3530 next new-line character. The contents of such a comment are examined only to identify
3531 multibyte characters and to find the terminating new-line character.
3532 <p><!--para 3 -->
3533 EXAMPLE
3534 <pre>
3537 // */ // comment, not syntax error
3538 f = g/**//h; // equivalent to f = g / h;
3539 //\
3540 i(); // part of a two-line comment
3541 /\
3542 / j(); // part of a two-line comment
3543 #define glue(x,y) x##y
3544 glue(/,/) k(); // syntax error, not comment
3545 /*//*/ l(); // equivalent to l();
3546 m = n//**/o
3547 + p; // equivalent to m = n + p;</pre>
3552 <!--page 79 -->
3554 <h6>footnotes</h6>
3556 </small>
3559 <p><!--para 1 -->
3560 An expression is a sequence of operators and operands that specifies computation of a
3561 value, or that designates an object or a function, or that generates side effects, or that
3562 performs a combination thereof.
3563 <p><!--para 2 -->
3564 Between the previous and next sequence point an object shall have its stored value
3565 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3566 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3567 <p><!--para 3 -->
3568 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3569 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3570 of subexpressions and the order in which side effects take place are both unspecified.
3571 <p><!--para 4 -->
3572 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3573 collectively described as bitwise operators) are required to have operands that have
3574 integer type. These operators yield values that depend on the internal representations of
3575 integers, and have implementation-defined and undefined aspects for signed types.
3576 <p><!--para 5 -->
3577 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3578 result is not mathematically defined or not in the range of representable values for its
3579 type), the behavior is undefined.
3580 <p><!--para 6 -->
3581 The effective type of an object for an access to its stored value is the declared type of the
3582 object, if any.<sup><a href="#note75"><b>75)</b></a></sup> If a value is stored into an object having no declared type through an
3583 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3586 <!--page 80 -->
3587 effective type of the object for that access and for subsequent accesses that do not modify
3588 the stored value. If a value is copied into an object having no declared type using
3589 memcpy or memmove, or is copied as an array of character type, then the effective type
3590 of the modified object for that access and for subsequent accesses that do not modify the
3591 value is the effective type of the object from which the value is copied, if it has one. For
3592 all other accesses to an object having no declared type, the effective type of the object is
3593 simply the type of the lvalue used for the access.
3594 <p><!--para 7 -->
3595 An object shall have its stored value accessed only by an lvalue expression that has one of
3597 <ul>
3598 <li> a type compatible with the effective type of the object,
3599 <li> a qualified version of a type compatible with the effective type of the object,
3600 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3601 object,
3602 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3603 effective type of the object,
3604 <li> an aggregate or union type that includes one of the aforementioned types among its
3605 members (including, recursively, a member of a subaggregate or contained union), or
3606 <li> a character type.
3607 </ul>
3608 <p><!--para 8 -->
3609 A floating expression may be contracted, that is, evaluated as though it were an atomic
3610 operation, thereby omitting rounding errors implied by the source code and the
3611 expression evaluation method.<sup><a href="#note77"><b>77)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3612 way to disallow contracted expressions. Otherwise, whether and how expressions are
3614 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.21.2">7.21.2</a>).
3619 <!--page 81 -->
3621 <h6>footnotes</h6>
3622 <p><small><a name="note72" href="#note72">72)</a> A floating-point status flag is not an object and can be set more than once within an expression.
3623 </small>
3624 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3626 <pre>
3627 i = ++i + 1;
3628 a[i++] = i;</pre>
3629 while allowing
3630 <pre>
3631 i = i + 1;
3632 a[i] = i;</pre>
3634 </small>
3635 <p><small><a name="note74" href="#note74">74)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3636 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3637 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3638 <a href="#6.5.1">6.5.1</a> through <a href="#6.5.6">6.5.6</a>. The exceptions are cast expressions (<a href="#6.5.4">6.5.4</a>) as operands of unary operators
3639 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3640 parentheses () (<a href="#6.5.1">6.5.1</a>), subscripting brackets [] (<a href="#6.5.2.1">6.5.2.1</a>), function-call parentheses () (<a href="#6.5.2.2">6.5.2.2</a>), and
3643 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3644 indicated in each subclause by the syntax for the expressions discussed therein.
3645 </small>
3647 </small>
3648 <p><small><a name="note76" href="#note76">76)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3649 </small>
3650 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3651 </small>
3652 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3653 combine multiple C operators. As contractions potentially undermine predictability, and can even
3654 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3655 documented.
3656 </small>
3659 <h6>Syntax</h6>
3660 <p><!--para 1 -->
3661 <pre>
3662 primary-expression:
3663 identifier
3664 constant
3665 string-literal
3666 ( expression )</pre>
3667 <h6>Semantics</h6>
3668 <p><!--para 2 -->
3669 An identifier is a primary expression, provided it has been declared as designating an
3670 object (in which case it is an lvalue) or a function (in which case it is a function
3672 <p><!--para 3 -->
3673 A constant is a primary expression. Its type depends on its form and value, as detailed in
3675 <p><!--para 4 -->
3676 A string literal is a primary expression. It is an lvalue with type as detailed in <a href="#6.4.5">6.4.5</a>.
3677 <p><!--para 5 -->
3678 A parenthesized expression is a primary expression. Its type and value are identical to
3679 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3680 expression if the unparenthesized expression is, respectively, an lvalue, a function
3681 designator, or a void expression.
3684 <h6>footnotes</h6>
3685 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3686 </small>
3689 <h6>Syntax</h6>
3690 <p><!--para 1 -->
3691 <pre>
3692 postfix-expression:
3693 primary-expression
3694 postfix-expression [ expression ]
3695 postfix-expression ( argument-expression-list<sub>opt</sub> )
3696 postfix-expression . identifier
3697 postfix-expression -> identifier
3698 postfix-expression ++
3699 postfix-expression --
3700 ( type-name ) { initializer-list }
3701 ( type-name ) { initializer-list , }</pre>
3706 <!--page 82 -->
3707 <pre>
3708 argument-expression-list:
3709 assignment-expression
3710 argument-expression-list , assignment-expression</pre>
3713 <h6>Constraints</h6>
3714 <p><!--para 1 -->
3715 One of the expressions shall have type ''pointer to object type'', the other expression shall
3716 have integer type, and the result has type ''type''.
3717 <h6>Semantics</h6>
3718 <p><!--para 2 -->
3719 A postfix expression followed by an expression in square brackets [] is a subscripted
3720 designation of an element of an array object. The definition of the subscript operator []
3721 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3722 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3723 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3724 element of E1 (counting from zero).
3725 <p><!--para 3 -->
3726 Successive subscript operators designate an element of a multidimensional array object.
3727 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3728 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3729 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3730 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3731 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3732 that arrays are stored in row-major order (last subscript varies fastest).
3733 <p><!--para 4 -->
3734 EXAMPLE Consider the array object defined by the declaration
3735 <pre>
3736 int x[3][5];</pre>
3737 Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
3738 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3739 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3740 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3741 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3742 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3743 yields an int.
3745 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3747 <!--page 83 -->
3750 <h6>Constraints</h6>
3751 <p><!--para 1 -->
3752 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3753 returning void or returning an object type other than an array type.
3754 <p><!--para 2 -->
3755 If the expression that denotes the called function has a type that includes a prototype, the
3756 number of arguments shall agree with the number of parameters. Each argument shall
3757 have a type such that its value may be assigned to an object with the unqualified version
3758 of the type of its corresponding parameter.
3759 <h6>Semantics</h6>
3760 <p><!--para 3 -->
3761 A postfix expression followed by parentheses () containing a possibly empty, comma-
3762 separated list of expressions is a function call. The postfix expression denotes the called
3763 function. The list of expressions specifies the arguments to the function.
3764 <p><!--para 4 -->
3765 An argument may be an expression of any object type. In preparing for the call to a
3766 function, the arguments are evaluated, and each parameter is assigned the value of the
3768 <p><!--para 5 -->
3769 If the expression that denotes the called function has type pointer to function returning an
3770 object type, the function call expression has the same type as that object type, and has the
3771 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3772 an attempt is made to modify the result of a function call or to access it after the next
3773 sequence point, the behavior is undefined.
3774 <p><!--para 6 -->
3775 If the expression that denotes the called function has a type that does not include a
3776 prototype, the integer promotions are performed on each argument, and arguments that
3777 have type float are promoted to double. These are called the default argument
3778 promotions. If the number of arguments does not equal the number of parameters, the
3779 behavior is undefined. If the function is defined with a type that includes a prototype, and
3780 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3781 promotion are not compatible with the types of the parameters, the behavior is undefined.
3782 If the function is defined with a type that does not include a prototype, and the types of
3783 the arguments after promotion are not compatible with those of the parameters after
3784 promotion, the behavior is undefined, except for the following cases:
3789 <!--page 84 -->
3790 <ul>
3791 <li> one promoted type is a signed integer type, the other promoted type is the
3792 corresponding unsigned integer type, and the value is representable in both types;
3793 <li> both types are pointers to qualified or unqualified versions of a character type or
3794 void.
3795 </ul>
3796 <p><!--para 7 -->
3797 If the expression that denotes the called function has a type that does include a prototype,
3798 the arguments are implicitly converted, as if by assignment, to the types of the
3799 corresponding parameters, taking the type of each parameter to be the unqualified version
3800 of its declared type. The ellipsis notation in a function prototype declarator causes
3801 argument type conversion to stop after the last declared parameter. The default argument
3802 promotions are performed on trailing arguments.
3803 <p><!--para 8 -->
3804 No other conversions are performed implicitly; in particular, the number and types of
3805 arguments are not compared with those of the parameters in a function definition that
3806 does not include a function prototype declarator.
3807 <p><!--para 9 -->
3808 If the function is defined with a type that is not compatible with the type (of the
3809 expression) pointed to by the expression that denotes the called function, the behavior is
3810 undefined.
3811 <p><!--para 10 -->
3812 The order of evaluation of the function designator, the actual arguments, and
3813 subexpressions within the actual arguments is unspecified, but there is a sequence point
3814 before the actual call.
3815 <p><!--para 11 -->
3816 Recursive function calls shall be permitted, both directly and indirectly through any chain
3817 of other functions.
3818 <p><!--para 12 -->
3819 EXAMPLE In the function call
3820 <pre>
3821 (*pf[f1()]) (f2(), f3() + f4())</pre>
3822 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3823 the function pointed to by pf[f1()] is called.
3825 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3826 definitions (<a href="#6.9.1">6.9.1</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
3828 <h6>footnotes</h6>
3829 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3830 </small>
3831 <p><small><a name="note81" href="#note81">81)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
3832 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3833 change the value of the object pointed to. A parameter declared to have array or function type is
3835 </small>
3838 <h6>Constraints</h6>
3839 <p><!--para 1 -->
3840 The first operand of the . operator shall have a qualified or unqualified structure or union
3841 type, and the second operand shall name a member of that type.
3842 <p><!--para 2 -->
3843 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3844 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3845 name a member of the type pointed to.
3846 <!--page 85 -->
3847 <h6>Semantics</h6>
3848 <p><!--para 3 -->
3849 A postfix expression followed by the . operator and an identifier designates a member of
3850 a structure or union object. The value is that of the named member,<sup><a href="#note82"><b>82)</b></a></sup> and is an lvalue if
3851 the first expression is an lvalue. If the first expression has qualified type, the result has
3852 the so-qualified version of the type of the designated member.
3853 <p><!--para 4 -->
3854 A postfix expression followed by the -> operator and an identifier designates a member
3855 of a structure or union object. The value is that of the named member of the object to
3856 which the first expression points, and is an lvalue.<sup><a href="#note83"><b>83)</b></a></sup> If the first expression is a pointer to
3857 a qualified type, the result has the so-qualified version of the type of the designated
3858 member.
3859 <p><!--para 5 -->
3860 One special guarantee is made in order to simplify the use of unions: if a union contains
3861 several structures that share a common initial sequence (see below), and if the union
3862 object currently contains one of these structures, it is permitted to inspect the common
3863 initial part of any of them anywhere that a declaration of the complete type of the union is
3864 visible. Two structures share a common initial sequence if corresponding members have
3865 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3866 initial members.
3867 <p><!--para 6 -->
3868 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3869 union, f().x is a valid postfix expression but is not an lvalue.
3871 <p><!--para 7 -->
3872 EXAMPLE 2 In:
3873 <pre>
3874 struct s { int i; const int ci; };
3875 struct s s;
3876 const struct s cs;
3877 volatile struct s vs;</pre>
3878 the various members have the types:
3879 <pre>
3880 s.i int
3881 s.ci const int
3882 cs.i const int
3883 cs.ci const int
3884 vs.i volatile int
3885 vs.ci volatile const int</pre>
3890 <!--page 86 -->
3891 <p><!--para 8 -->
3892 EXAMPLE 3 The following is a valid fragment:
3893 <pre>
3894 union {
3895 struct {
3896 int alltypes;
3897 } n;
3898 struct {
3899 int type;
3900 int intnode;
3901 } ni;
3902 struct {
3903 int type;
3904 double doublenode;
3905 } nf;
3906 } u;
3907 u.nf.type = 1;
3909 /* ... */
3910 if (u.n.alltypes == 1)
3911 if (sin(u.nf.doublenode) == 0.0)
3912 /* ... */</pre>
3913 The following is not a valid fragment (because the union type is not visible within function f):
3914 <pre>
3915 struct t1 { int m; };
3916 struct t2 { int m; };
3917 int f(struct t1 *p1, struct t2 *p2)
3918 {
3919 if (p1->m < 0)
3920 p2->m = -p2->m;
3921 return p1->m;
3922 }
3923 int g()
3924 {
3925 union {
3926 struct t1 s1;
3927 struct t2 s2;
3928 } u;
3929 /* ... */
3930 return f(&u.s1, &u.s2);
3931 }</pre>
3933 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3935 <!--page 87 -->
3937 <h6>footnotes</h6>
3938 <p><small><a name="note82" href="#note82">82)</a> If the member used to access the contents of a union object is not the same as the member last used to
3939 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3940 as an object representation in the new type as described in <a href="#6.2.6">6.2.6</a> (a process sometimes called "type
3941 punning"). This might be a trap representation.
3942 </small>
3943 <p><small><a name="note83" href="#note83">83)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3944 its operand), the expression (&E)->MOS is the same as E.MOS.
3945 </small>
3947 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
3948 <h6>Constraints</h6>
3949 <p><!--para 1 -->
3950 The operand of the postfix increment or decrement operator shall have qualified or
3951 unqualified real or pointer type and shall be a modifiable lvalue.
3952 <h6>Semantics</h6>
3953 <p><!--para 2 -->
3954 The result of the postfix ++ operator is the value of the operand. After the result is
3955 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
3956 type is added to it.) See the discussions of additive operators and compound assignment
3957 for information on constraints, types, and conversions and the effects of operations on
3958 pointers. The side effect of updating the stored value of the operand shall occur between
3959 the previous and the next sequence point.
3960 <p><!--para 3 -->
3961 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3962 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3963 it).
3964 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
3967 <h6>Constraints</h6>
3968 <p><!--para 1 -->
3969 The type name shall specify an object type or an array of unknown size, but not a variable
3970 length array type.
3971 <p><!--para 2 -->
3972 No initializer shall attempt to provide a value for an object not contained within the entire
3973 unnamed object specified by the compound literal.
3974 <p><!--para 3 -->
3975 If the compound literal occurs outside the body of a function, the initializer list shall
3976 consist of constant expressions.
3977 <h6>Semantics</h6>
3978 <p><!--para 4 -->
3979 A postfix expression that consists of a parenthesized type name followed by a brace-
3980 enclosed list of initializers is a compound literal. It provides an unnamed object whose
3982 <p><!--para 5 -->
3983 If the type name specifies an array of unknown size, the size is determined by the
3984 initializer list as specified in <a href="#6.7.8">6.7.8</a>, and the type of the compound literal is that of the
3985 completed array type. Otherwise (when the type name specifies an object type), the type
3986 of the compound literal is that specified by the type name. In either case, the result is an
3987 lvalue.
3990 <!--page 88 -->
3991 <p><!--para 6 -->
3992 The value of the compound literal is that of an unnamed object initialized by the
3993 initializer list. If the compound literal occurs outside the body of a function, the object
3994 has static storage duration; otherwise, it has automatic storage duration associated with
3995 the enclosing block.
3996 <p><!--para 7 -->
3997 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
3999 <p><!--para 8 -->
4000 String literals, and compound literals with const-qualified types, need not designate
4002 <p><!--para 9 -->
4003 EXAMPLE 1 The file scope definition
4004 <pre>
4005 int *p = (int []){2, 4};</pre>
4006 initializes p to point to the first element of an array of two ints, the first having the value two and the
4007 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4008 has static storage duration.
4010 <p><!--para 10 -->
4011 EXAMPLE 2 In contrast, in
4012 <pre>
4013 void f(void)
4014 {
4015 int *p;
4016 /*...*/
4017 p = (int [2]){*p};
4018 /*...*/
4019 }</pre>
4020 p is assigned the address of the first element of an array of two ints, the first having the value previously
4021 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4022 unnamed object has automatic storage duration.
4024 <p><!--para 11 -->
4025 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4026 created using compound literals can be passed to functions without depending on member order:
4027 <pre>
4028 drawline((struct point){.x=1, .y=1},
4029 (struct point){.x=3, .y=4});</pre>
4030 Or, if drawline instead expected pointers to struct point:
4031 <pre>
4032 drawline(&(struct point){.x=1, .y=1},
4033 &(struct point){.x=3, .y=4});</pre>
4035 <p><!--para 12 -->
4036 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4037 <pre>
4038 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}</pre>
4043 <!--page 89 -->
4044 <p><!--para 13 -->
4045 EXAMPLE 5 The following three expressions have different meanings:
4046 <pre>
4050 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4051 two have automatic storage duration when they occur within the body of a function, and the first of these
4052 two is modifiable.
4054 <p><!--para 14 -->
4055 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4056 and can even be shared. For example,
4057 <pre>
4059 might yield 1 if the literals' storage is shared.
4061 <p><!--para 15 -->
4062 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4063 linked object. For example, there is no way to write a self-referential compound literal that could be used
4064 as the function argument in place of the named object endless_zeros below:
4065 <pre>
4066 struct int_list { int car; struct int_list *cdr; };
4067 struct int_list endless_zeros = {0, &endless_zeros};
4068 eval(endless_zeros);</pre>
4070 <p><!--para 16 -->
4071 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4072 <pre>
4073 struct s { int i; };
4074 int f (void)
4075 {
4076 struct s *p = 0, *q;
4077 int j = 0;
4078 again:
4079 q = p, p = &((struct s){ j++ });
4080 if (j < 2) goto again;
4081 return p == q && q->i == 1;
4082 }</pre>
4083 The function f() always returns the value 1.
4084 <p><!--para 17 -->
4085 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4086 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4087 have an indeterminate value, which would result in undefined behavior.
4089 <p><b> Forward references</b>: type names (<a href="#6.7.6">6.7.6</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4090 <!--page 90 -->
4092 <h6>footnotes</h6>
4093 <p><small><a name="note84" href="#note84">84)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4094 or void only, and the result of a cast expression is not an lvalue.
4095 </small>
4096 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4097 </small>
4098 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4099 the same or overlapping representations.
4100 </small>
4103 <h6>Syntax</h6>
4104 <p><!--para 1 -->
4105 <pre>
4106 unary-expression:
4107 postfix-expression
4108 ++ unary-expression
4109 -- unary-expression
4110 unary-operator cast-expression
4111 sizeof unary-expression
4112 sizeof ( type-name )
4113 unary-operator: one of
4114 & * + - ~ !</pre>
4116 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4117 <h6>Constraints</h6>
4118 <p><!--para 1 -->
4119 The operand of the prefix increment or decrement operator shall have qualified or
4120 unqualified real or pointer type and shall be a modifiable lvalue.
4121 <h6>Semantics</h6>
4122 <p><!--para 2 -->
4123 The value of the operand of the prefix ++ operator is incremented. The result is the new
4124 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4125 See the discussions of additive operators and compound assignment for information on
4126 constraints, types, side effects, and conversions and the effects of operations on pointers.
4127 <p><!--para 3 -->
4128 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4129 operand is decremented.
4130 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
4133 <h6>Constraints</h6>
4134 <p><!--para 1 -->
4135 The operand of the unary & operator shall be either a function designator, the result of a
4136 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4137 not declared with the register storage-class specifier.
4138 <p><!--para 2 -->
4139 The operand of the unary * operator shall have pointer type.
4140 <h6>Semantics</h6>
4141 <p><!--para 3 -->
4142 The unary & operator yields the address of its operand. If the operand has type ''type'',
4143 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4144 neither that operator nor the & operator is evaluated and the result is as if both were
4145 omitted, except that the constraints on the operators still apply and the result is not an
4146 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4147 <!--page 91 -->
4148 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4149 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4150 a pointer to the object or function designated by its operand.
4151 <p><!--para 4 -->
4152 The unary * operator denotes indirection. If the operand points to a function, the result is
4153 a function designator; if it points to an object, the result is an lvalue designating the
4154 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4155 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4157 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4160 <h6>footnotes</h6>
4161 <p><small><a name="note87" href="#note87">87)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4162 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4163 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4164 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4165 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4166 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4167 end of its lifetime.
4168 </small>
4171 <h6>Constraints</h6>
4172 <p><!--para 1 -->
4173 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4174 integer type; of the ! operator, scalar type.
4175 <h6>Semantics</h6>
4176 <p><!--para 2 -->
4177 The result of the unary + operator is the value of its (promoted) operand. The integer
4178 promotions are performed on the operand, and the result has the promoted type.
4179 <p><!--para 3 -->
4180 The result of the unary - operator is the negative of its (promoted) operand. The integer
4181 promotions are performed on the operand, and the result has the promoted type.
4182 <p><!--para 4 -->
4183 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4184 each bit in the result is set if and only if the corresponding bit in the converted operand is
4185 not set). The integer promotions are performed on the operand, and the result has the
4186 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4187 to the maximum value representable in that type minus E.
4188 <p><!--para 5 -->
4189 The result of the logical negation operator ! is 0 if the value of its operand compares
4190 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4191 The expression !E is equivalent to (0==E).
4196 <!--page 92 -->
4199 <h6>Constraints</h6>
4200 <p><!--para 1 -->
4201 The sizeof operator shall not be applied to an expression that has function type or an
4202 incomplete type, to the parenthesized name of such a type, or to an expression that
4203 designates a bit-field member.
4204 <h6>Semantics</h6>
4205 <p><!--para 2 -->
4206 The sizeof operator yields the size (in bytes) of its operand, which may be an
4207 expression or the parenthesized name of a type. The size is determined from the type of
4208 the operand. The result is an integer. If the type of the operand is a variable length array
4209 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4210 integer constant.
4211 <p><!--para 3 -->
4212 When applied to an operand that has type char, unsigned char, or signed char,
4213 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4214 type, the result is the total number of bytes in the array.<sup><a href="#note88"><b>88)</b></a></sup> When applied to an operand
4215 that has structure or union type, the result is the total number of bytes in such an object,
4216 including internal and trailing padding.
4217 <p><!--para 4 -->
4218 The value of the result is implementation-defined, and its type (an unsigned integer type)
4220 <p><!--para 5 -->
4221 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4222 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4223 allocate and return a pointer to void. For example:
4224 <pre>
4225 extern void *alloc(size_t);
4226 double *dp = alloc(sizeof *dp);</pre>
4227 The implementation of the alloc function should ensure that its return value is aligned suitably for
4228 conversion to a pointer to double.
4230 <p><!--para 6 -->
4231 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4232 <pre>
4233 sizeof array / sizeof array[0]</pre>
4235 <p><!--para 7 -->
4236 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4237 function:
4238 <pre>
4240 size_t fsize3(int n)
4241 {
4242 char b[n+3]; // variable length array
4243 return sizeof b; // execution time sizeof
4244 }</pre>
4248 <!--page 93 -->
4249 <pre>
4250 int main()
4251 {
4252 size_t size;
4253 size = fsize3(10); // fsize3 returns 13
4254 return 0;
4255 }</pre>
4257 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), declarations (<a href="#6.7">6.7</a>),
4258 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.6">6.7.6</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
4260 <h6>footnotes</h6>
4261 <p><small><a name="note88" href="#note88">88)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4263 </small>
4266 <h6>Syntax</h6>
4267 <p><!--para 1 -->
4268 <pre>
4269 cast-expression:
4270 unary-expression
4271 ( type-name ) cast-expression</pre>
4272 <h6>Constraints</h6>
4273 <p><!--para 2 -->
4274 Unless the type name specifies a void type, the type name shall specify qualified or
4275 unqualified scalar type and the operand shall have scalar type.
4276 <p><!--para 3 -->
4277 Conversions that involve pointers, other than where permitted by the constraints of
4279 <h6>Semantics</h6>
4280 <p><!--para 4 -->
4281 Preceding an expression by a parenthesized type name converts the value of the
4282 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4283 no conversion has no effect on the type or value of an expression.
4284 <p><!--para 5 -->
4285 If the value of the expression is represented with greater precision or range than required
4286 by the type named by the cast (<a href="#6.3.1.8">6.3.1.8</a>), then the cast specifies a conversion even if the
4287 type of the expression is the same as the named type.
4288 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4289 prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
4294 <!--page 94 -->
4296 <h6>footnotes</h6>
4297 <p><small><a name="note89" href="#note89">89)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4298 unqualified version of the type.
4299 </small>
4302 <h6>Syntax</h6>
4303 <p><!--para 1 -->
4304 <pre>
4305 multiplicative-expression:
4306 cast-expression
4307 multiplicative-expression * cast-expression
4308 multiplicative-expression / cast-expression
4309 multiplicative-expression % cast-expression</pre>
4310 <h6>Constraints</h6>
4311 <p><!--para 2 -->
4312 Each of the operands shall have arithmetic type. The operands of the % operator shall
4313 have integer type.
4314 <h6>Semantics</h6>
4315 <p><!--para 3 -->
4316 The usual arithmetic conversions are performed on the operands.
4317 <p><!--para 4 -->
4318 The result of the binary * operator is the product of the operands.
4319 <p><!--para 5 -->
4320 The result of the / operator is the quotient from the division of the first operand by the
4321 second; the result of the % operator is the remainder. In both operations, if the value of
4322 the second operand is zero, the behavior is undefined.
4323 <p><!--para 6 -->
4324 When integers are divided, the result of the / operator is the algebraic quotient with any
4325 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4326 (a/b)*b + a%b shall equal a.
4328 <h6>footnotes</h6>
4329 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4330 </small>
4333 <h6>Syntax</h6>
4334 <p><!--para 1 -->
4335 <pre>
4336 additive-expression:
4337 multiplicative-expression
4338 additive-expression + multiplicative-expression
4339 additive-expression - multiplicative-expression</pre>
4340 <h6>Constraints</h6>
4341 <p><!--para 2 -->
4342 For addition, either both operands shall have arithmetic type, or one operand shall be a
4343 pointer to an object type and the other shall have integer type. (Incrementing is
4344 equivalent to adding 1.)
4345 <p><!--para 3 -->
4346 For subtraction, one of the following shall hold:
4347 <ul>
4348 <li> both operands have arithmetic type;
4352 <!--page 95 -->
4353 <li> both operands are pointers to qualified or unqualified versions of compatible object
4354 types; or
4355 <li> the left operand is a pointer to an object type and the right operand has integer type.
4356 </ul>
4357 (Decrementing is equivalent to subtracting 1.)
4358 <h6>Semantics</h6>
4359 <p><!--para 4 -->
4360 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4361 them.
4362 <p><!--para 5 -->
4363 The result of the binary + operator is the sum of the operands.
4364 <p><!--para 6 -->
4365 The result of the binary - operator is the difference resulting from the subtraction of the
4366 second operand from the first.
4367 <p><!--para 7 -->
4368 For the purposes of these operators, a pointer to an object that is not an element of an
4369 array behaves the same as a pointer to the first element of an array of length one with the
4370 type of the object as its element type.
4371 <p><!--para 8 -->
4372 When an expression that has integer type is added to or subtracted from a pointer, the
4373 result has the type of the pointer operand. If the pointer operand points to an element of
4374 an array object, and the array is large enough, the result points to an element offset from
4375 the original element such that the difference of the subscripts of the resulting and original
4376 array elements equals the integer expression. In other words, if the expression P points to
4377 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4378 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4379 the array object, provided they exist. Moreover, if the expression P points to the last
4380 element of an array object, the expression (P)+1 points one past the last element of the
4381 array object, and if the expression Q points one past the last element of an array object,
4382 the expression (Q)-1 points to the last element of the array object. If both the pointer
4383 operand and the result point to elements of the same array object, or one past the last
4384 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4385 behavior is undefined. If the result points one past the last element of the array object, it
4386 shall not be used as the operand of a unary * operator that is evaluated.
4387 <p><!--para 9 -->
4388 When two pointers are subtracted, both shall point to elements of the same array object,
4389 or one past the last element of the array object; the result is the difference of the
4390 subscripts of the two array elements. The size of the result is implementation-defined,
4391 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4392 If the result is not representable in an object of that type, the behavior is undefined. In
4393 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4394 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4395 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4396 an array object or one past the last element of an array object, and the expression Q points
4397 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4398 <!--page 96 -->
4399 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4400 expression P points one past the last element of the array object, even though the
4401 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4402 <p><!--para 10 -->
4403 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4404 <p><!--para 11 -->
4405 <pre>
4406 {
4407 int n = 4, m = 3;
4408 int a[n][m];
4409 int (*p)[m] = a; // p == &a[0]
4410 p += 1; // p == &a[1]
4411 (*p)[2] = 99; // a[1][2] == 99
4412 n = p - a; // n == 1
4413 }</pre>
4414 If array a in the above example were declared to be an array of known constant size, and pointer p were
4415 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4416 the same.
4418 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), common definitions <a href="#7.17"><stddef.h></a>
4421 <h6>footnotes</h6>
4422 <p><small><a name="note91" href="#note91">91)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4423 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4424 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4425 original type. For pointer subtraction, the result of the difference between the character pointers is
4426 similarly divided by the size of the object originally pointed to.
4427 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4428 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4429 element'' requirements.
4430 </small>
4433 <h6>Syntax</h6>
4434 <p><!--para 1 -->
4435 <pre>
4436 shift-expression:
4437 additive-expression
4438 shift-expression << additive-expression
4439 shift-expression >> additive-expression</pre>
4440 <h6>Constraints</h6>
4441 <p><!--para 2 -->
4442 Each of the operands shall have integer type.
4443 <h6>Semantics</h6>
4444 <p><!--para 3 -->
4445 The integer promotions are performed on each of the operands. The type of the result is
4446 that of the promoted left operand. If the value of the right operand is negative or is
4447 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4452 <!--page 97 -->
4453 <p><!--para 4 -->
4454 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4455 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4456 one more than the maximum value representable in the result type. If E1 has a signed
4457 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4458 the resulting value; otherwise, the behavior is undefined.
4459 <p><!--para 5 -->
4460 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4461 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4462 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4463 resulting value is implementation-defined.
4466 <h6>Syntax</h6>
4467 <p><!--para 1 -->
4468 <pre>
4469 relational-expression:
4470 shift-expression
4471 relational-expression < shift-expression
4472 relational-expression > shift-expression
4473 relational-expression <= shift-expression
4474 relational-expression >= shift-expression</pre>
4475 <h6>Constraints</h6>
4476 <p><!--para 2 -->
4477 One of the following shall hold:
4478 <ul>
4479 <li> both operands have real type;
4480 <li> both operands are pointers to qualified or unqualified versions of compatible object
4481 types; or
4482 <li> both operands are pointers to qualified or unqualified versions of compatible
4483 incomplete types.
4484 </ul>
4485 <h6>Semantics</h6>
4486 <p><!--para 3 -->
4487 If both of the operands have arithmetic type, the usual arithmetic conversions are
4488 performed.
4489 <p><!--para 4 -->
4490 For the purposes of these operators, a pointer to an object that is not an element of an
4491 array behaves the same as a pointer to the first element of an array of length one with the
4492 type of the object as its element type.
4493 <p><!--para 5 -->
4494 When two pointers are compared, the result depends on the relative locations in the
4495 address space of the objects pointed to. If two pointers to object or incomplete types both
4496 point to the same object, or both point one past the last element of the same array object,
4497 they compare equal. If the objects pointed to are members of the same aggregate object,
4498 pointers to structure members declared later compare greater than pointers to members
4499 declared earlier in the structure, and pointers to array elements with larger subscript
4500 <!--page 98 -->
4501 values compare greater than pointers to elements of the same array with lower subscript
4502 values. All pointers to members of the same union object compare equal. If the
4503 expression P points to an element of an array object and the expression Q points to the
4504 last element of the same array object, the pointer expression Q+1 compares greater than
4505 P. In all other cases, the behavior is undefined.
4506 <p><!--para 6 -->
4507 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4508 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.<sup><a href="#note92"><b>92)</b></a></sup>
4509 The result has type int.
4511 <h6>footnotes</h6>
4512 <p><small><a name="note92" href="#note92">92)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4513 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4514 </small>
4517 <h6>Syntax</h6>
4518 <p><!--para 1 -->
4519 <pre>
4520 equality-expression:
4521 relational-expression
4522 equality-expression == relational-expression
4523 equality-expression != relational-expression</pre>
4524 <h6>Constraints</h6>
4525 <p><!--para 2 -->
4526 One of the following shall hold:
4527 <ul>
4528 <li> both operands have arithmetic type;
4529 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4530 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4531 qualified or unqualified version of void; or
4532 <li> one operand is a pointer and the other is a null pointer constant.
4533 </ul>
4534 <h6>Semantics</h6>
4535 <p><!--para 3 -->
4536 The == (equal to) and != (not equal to) operators are analogous to the relational
4537 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4538 specified relation is true and 0 if it is false. The result has type int. For any pair of
4539 operands, exactly one of the relations is true.
4540 <p><!--para 4 -->
4541 If both of the operands have arithmetic type, the usual arithmetic conversions are
4542 performed. Values of complex types are equal if and only if both their real parts are equal
4543 and also their imaginary parts are equal. Any two values of arithmetic types from
4544 different type domains are equal if and only if the results of their conversions to the
4545 (complex) result type determined by the usual arithmetic conversions are equal.
4548 <!--page 99 -->
4549 <p><!--para 5 -->
4550 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4551 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4552 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4553 qualified or unqualified version of void, the former is converted to the type of the latter.
4554 <p><!--para 6 -->
4555 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4556 same object (including a pointer to an object and a subobject at its beginning) or function,
4557 both are pointers to one past the last element of the same array object, or one is a pointer
4558 to one past the end of one array object and the other is a pointer to the start of a different
4559 array object that happens to immediately follow the first array object in the address
4561 <p><!--para 7 -->
4562 For the purposes of these operators, a pointer to an object that is not an element of an
4563 array behaves the same as a pointer to the first element of an array of length one with the
4564 type of the object as its element type.
4566 <h6>footnotes</h6>
4567 <p><small><a name="note93" href="#note93">93)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4568 </small>
4569 <p><small><a name="note94" href="#note94">94)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4570 adjacent members of a structure with no padding between them, or because the implementation chose
4571 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4572 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4573 behavior.
4574 </small>
4577 <h6>Syntax</h6>
4578 <p><!--para 1 -->
4579 <pre>
4580 AND-expression:
4581 equality-expression
4582 AND-expression & equality-expression</pre>
4583 <h6>Constraints</h6>
4584 <p><!--para 2 -->
4585 Each of the operands shall have integer type.
4586 <h6>Semantics</h6>
4587 <p><!--para 3 -->
4588 The usual arithmetic conversions are performed on the operands.
4589 <p><!--para 4 -->
4590 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4591 the result is set if and only if each of the corresponding bits in the converted operands is
4592 set).
4597 <!--page 100 -->
4600 <h6>Syntax</h6>
4601 <p><!--para 1 -->
4602 <pre>
4603 exclusive-OR-expression:
4604 AND-expression
4605 exclusive-OR-expression ^ AND-expression</pre>
4606 <h6>Constraints</h6>
4607 <p><!--para 2 -->
4608 Each of the operands shall have integer type.
4609 <h6>Semantics</h6>
4610 <p><!--para 3 -->
4611 The usual arithmetic conversions are performed on the operands.
4612 <p><!--para 4 -->
4613 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4614 in the result is set if and only if exactly one of the corresponding bits in the converted
4615 operands is set).
4618 <h6>Syntax</h6>
4619 <p><!--para 1 -->
4620 <pre>
4621 inclusive-OR-expression:
4622 exclusive-OR-expression
4623 inclusive-OR-expression | exclusive-OR-expression</pre>
4624 <h6>Constraints</h6>
4625 <p><!--para 2 -->
4626 Each of the operands shall have integer type.
4627 <h6>Semantics</h6>
4628 <p><!--para 3 -->
4629 The usual arithmetic conversions are performed on the operands.
4630 <p><!--para 4 -->
4631 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4632 the result is set if and only if at least one of the corresponding bits in the converted
4633 operands is set).
4634 <!--page 101 -->
4637 <h6>Syntax</h6>
4638 <p><!--para 1 -->
4639 <pre>
4640 logical-AND-expression:
4641 inclusive-OR-expression
4642 logical-AND-expression && inclusive-OR-expression</pre>
4643 <h6>Constraints</h6>
4644 <p><!--para 2 -->
4645 Each of the operands shall have scalar type.
4646 <h6>Semantics</h6>
4647 <p><!--para 3 -->
4648 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4649 yields 0. The result has type int.
4650 <p><!--para 4 -->
4651 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4652 there is a sequence point after the evaluation of the first operand. If the first operand
4653 compares equal to 0, the second operand is not evaluated.
4656 <h6>Syntax</h6>
4657 <p><!--para 1 -->
4658 <pre>
4659 logical-OR-expression:
4660 logical-AND-expression
4661 logical-OR-expression || logical-AND-expression</pre>
4662 <h6>Constraints</h6>
4663 <p><!--para 2 -->
4664 Each of the operands shall have scalar type.
4665 <h6>Semantics</h6>
4666 <p><!--para 3 -->
4667 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4668 yields 0. The result has type int.
4669 <p><!--para 4 -->
4670 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4671 a sequence point after the evaluation of the first operand. If the first operand compares
4672 unequal to 0, the second operand is not evaluated.
4673 <!--page 102 -->
4676 <h6>Syntax</h6>
4677 <p><!--para 1 -->
4678 <pre>
4679 conditional-expression:
4680 logical-OR-expression
4681 logical-OR-expression ? expression : conditional-expression</pre>
4682 <h6>Constraints</h6>
4683 <p><!--para 2 -->
4684 The first operand shall have scalar type.
4685 <p><!--para 3 -->
4686 One of the following shall hold for the second and third operands:
4687 <ul>
4688 <li> both operands have arithmetic type;
4689 <li> both operands have the same structure or union type;
4690 <li> both operands have void type;
4691 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4692 <li> one operand is a pointer and the other is a null pointer constant; or
4693 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4694 qualified or unqualified version of void.
4695 </ul>
4696 <h6>Semantics</h6>
4697 <p><!--para 4 -->
4698 The first operand is evaluated; there is a sequence point after its evaluation. The second
4699 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4700 only if the first compares equal to 0; the result is the value of the second or third operand
4701 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4702 to modify the result of a conditional operator or to access it after the next sequence point,
4703 the behavior is undefined.
4704 <p><!--para 5 -->
4705 If both the second and third operands have arithmetic type, the result type that would be
4706 determined by the usual arithmetic conversions, were they applied to those two operands,
4707 is the type of the result. If both the operands have structure or union type, the result has
4708 that type. If both operands have void type, the result has void type.
4709 <p><!--para 6 -->
4710 If both the second and third operands are pointers or one is a null pointer constant and the
4711 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4712 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4713 compatible types or to differently qualified versions of compatible types, the result type is
4714 a pointer to an appropriately qualified version of the composite type; if one operand is a
4715 null pointer constant, the result has the type of the other operand; otherwise, one operand
4716 is a pointer to void or a qualified version of void, in which case the result type is a
4718 <!--page 103 -->
4719 pointer to an appropriately qualified version of void.
4720 <p><!--para 7 -->
4721 EXAMPLE The common type that results when the second and third operands are pointers is determined
4722 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4723 pointers have compatible types.
4724 <p><!--para 8 -->
4725 Given the declarations
4726 <pre>
4727 const void *c_vp;
4728 void *vp;
4729 const int *c_ip;
4730 volatile int *v_ip;
4731 int *ip;
4732 const char *c_cp;</pre>
4733 the third column in the following table is the common type that is the result of a conditional expression in
4734 which the first two columns are the second and third operands (in either order):
4735 <pre>
4736 c_vp c_ip const void *
4737 v_ip 0 volatile int *
4738 c_ip v_ip const volatile int *
4739 vp c_cp const void *
4740 ip c_ip const int *
4741 vp ip void *</pre>
4744 <h6>footnotes</h6>
4745 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4746 </small>
4749 <h6>Syntax</h6>
4750 <p><!--para 1 -->
4751 <pre>
4752 assignment-expression:
4753 conditional-expression
4754 unary-expression assignment-operator assignment-expression
4755 assignment-operator: one of
4756 = *= /= %= += -= <<= >>= &= ^= |=</pre>
4757 <h6>Constraints</h6>
4758 <p><!--para 2 -->
4759 An assignment operator shall have a modifiable lvalue as its left operand.
4760 <h6>Semantics</h6>
4761 <p><!--para 3 -->
4762 An assignment operator stores a value in the object designated by the left operand. An
4763 assignment expression has the value of the left operand after the assignment, but is not an
4764 lvalue. The type of an assignment expression is the type of the left operand unless the
4765 left operand has qualified type, in which case it is the unqualified version of the type of
4766 the left operand. The side effect of updating the stored value of the left operand shall
4767 occur between the previous and the next sequence point.
4768 <p><!--para 4 -->
4769 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4770 the result of an assignment operator or to access it after the next sequence point, the
4771 behavior is undefined.
4772 <!--page 104 -->
4775 <h6>Constraints</h6>
4776 <p><!--para 1 -->
4778 <ul>
4779 <li> the left operand has qualified or unqualified arithmetic type and the right has
4780 arithmetic type;
4781 <li> the left operand has a qualified or unqualified version of a structure or union type
4782 compatible with the type of the right;
4783 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4784 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4785 right;
4786 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4787 qualified or unqualified version of void, and the type pointed to by the left has all
4788 the qualifiers of the type pointed to by the right;
4789 <li> the left operand is a pointer and the right is a null pointer constant; or
4790 <li> the left operand has type _Bool and the right is a pointer.
4791 </ul>
4792 <h6>Semantics</h6>
4793 <p><!--para 2 -->
4794 In simple assignment (=), the value of the right operand is converted to the type of the
4795 assignment expression and replaces the value stored in the object designated by the left
4796 operand.
4797 <p><!--para 3 -->
4798 If the value being stored in an object is read from another object that overlaps in any way
4799 the storage of the first object, then the overlap shall be exact and the two objects shall
4800 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4801 undefined.
4802 <p><!--para 4 -->
4803 EXAMPLE 1 In the program fragment
4804 <pre>
4805 int f(void);
4806 char c;
4807 /* ... */
4808 if ((c = f()) == -1)
4809 /* ... */</pre>
4810 the int value returned by the function may be truncated when stored in the char, and then converted back
4811 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4812 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4816 <!--page 105 -->
4817 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4818 variable c should be declared as int.
4820 <p><!--para 5 -->
4821 EXAMPLE 2 In the fragment:
4822 <pre>
4823 char c;
4824 int i;
4825 long l;
4826 l = (c = i);</pre>
4827 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4828 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4829 that is, long int type.
4831 <p><!--para 6 -->
4832 EXAMPLE 3 Consider the fragment:
4833 <pre>
4834 const char **cpp;
4835 char *p;
4836 const char c = 'A';
4837 cpp = &p; // constraint violation
4838 *cpp = &c; // valid
4839 *p = 0; // valid</pre>
4840 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4841 value of the const object c.
4844 <h6>footnotes</h6>
4845 <p><small><a name="note96" href="#note96">96)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4846 (specified in <a href="#6.3.2.1">6.3.2.1</a>) that changes lvalues to ''the value of the expression'' and thus removes any type
4847 qualifiers that were applied to the type category of the expression (for example, it removes const but
4848 not volatile from the type int volatile * const).
4849 </small>
4852 <h6>Constraints</h6>
4853 <p><!--para 1 -->
4854 For the operators += and -= only, either the left operand shall be a pointer to an object
4855 type and the right shall have integer type, or the left operand shall have qualified or
4856 unqualified arithmetic type and the right shall have arithmetic type.
4857 <p><!--para 2 -->
4858 For the other operators, each operand shall have arithmetic type consistent with those
4859 allowed by the corresponding binary operator.
4860 <h6>Semantics</h6>
4861 <p><!--para 3 -->
4862 A compound assignment of the form E1 op = E2 differs from the simple assignment
4863 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
4864 <!--page 106 -->
4867 <h6>Syntax</h6>
4868 <p><!--para 1 -->
4869 <pre>
4870 expression:
4871 assignment-expression
4872 expression , assignment-expression</pre>
4873 <h6>Semantics</h6>
4874 <p><!--para 2 -->
4875 The left operand of a comma operator is evaluated as a void expression; there is a
4876 sequence point after its evaluation. Then the right operand is evaluated; the result has its
4877 type and value.<sup><a href="#note97"><b>97)</b></a></sup> If an attempt is made to modify the result of a comma operator or to
4878 access it after the next sequence point, the behavior is undefined.
4879 <p><!--para 3 -->
4880 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4881 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4882 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4883 expression of a conditional operator in such contexts. In the function call
4884 <pre>
4885 f(a, (t=3, t+2), c)</pre>
4886 the function has three arguments, the second of which has the value 5.
4893 <!--page 107 -->
4895 <h6>footnotes</h6>
4897 </small>
4900 <h6>Syntax</h6>
4901 <p><!--para 1 -->
4902 <pre>
4903 constant-expression:
4904 conditional-expression</pre>
4905 <h6>Description</h6>
4906 <p><!--para 2 -->
4907 A constant expression can be evaluated during translation rather than runtime, and
4908 accordingly may be used in any place that a constant may be.
4909 <h6>Constraints</h6>
4910 <p><!--para 3 -->
4911 Constant expressions shall not contain assignment, increment, decrement, function-call,
4912 or comma operators, except when they are contained within a subexpression that is not
4914 <p><!--para 4 -->
4915 Each constant expression shall evaluate to a constant that is in the range of representable
4916 values for its type.
4917 <h6>Semantics</h6>
4918 <p><!--para 5 -->
4919 An expression that evaluates to a constant is required in several contexts. If a floating
4920 expression is evaluated in the translation environment, the arithmetic precision and range
4921 shall be at least as great as if the expression were being evaluated in the execution
4922 environment.
4923 <p><!--para 6 -->
4924 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
4925 that are integer constants, enumeration constants, character constants, sizeof
4926 expressions whose results are integer constants, and floating constants that are the
4927 immediate operands of casts. Cast operators in an integer constant expression shall only
4928 convert arithmetic types to integer types, except as part of an operand to the sizeof
4929 operator.
4930 <p><!--para 7 -->
4931 More latitude is permitted for constant expressions in initializers. Such a constant
4932 expression shall be, or evaluate to, one of the following:
4933 <ul>
4934 <li> an arithmetic constant expression,
4935 <li> a null pointer constant,
4940 <!--page 108 -->
4941 <li> an address constant, or
4942 <li> an address constant for an object type plus or minus an integer constant expression.
4943 </ul>
4944 <p><!--para 8 -->
4945 An arithmetic constant expression shall have arithmetic type and shall only have
4946 operands that are integer constants, floating constants, enumeration constants, character
4947 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4948 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4949 sizeof operator whose result is an integer constant.
4950 <p><!--para 9 -->
4951 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4952 storage duration, or a pointer to a function designator; it shall be created explicitly using
4953 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4954 an expression of array or function type. The array-subscript [] and member-access .
4955 and -> operators, the address & and indirection * unary operators, and pointer casts may
4956 be used in the creation of an address constant, but the value of an object shall not be
4957 accessed by use of these operators.
4958 <p><!--para 10 -->
4959 An implementation may accept other forms of constant expressions.
4960 <p><!--para 11 -->
4961 The semantic rules for the evaluation of a constant expression are the same as for
4963 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4968 <!--page 109 -->
4970 <h6>footnotes</h6>
4971 <p><small><a name="note98" href="#note98">98)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4972 </small>
4973 <p><small><a name="note99" href="#note99">99)</a> An integer constant expression is used to specify the size of a bit-field member of a structure, the
4974 value of an enumeration constant, the size of an array, or the value of a case constant. Further
4975 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
4977 </small>
4980 <pre>
4981 static int i = 2 || 1 / 0;</pre>
4982 the expression is a valid integer constant expression with value one.
4983 </small>
4986 <h6>Syntax</h6>
4987 <p><!--para 1 -->
4988 <pre>
4989 declaration:
4990 declaration-specifiers init-declarator-list<sub>opt</sub> ;
4991 declaration-specifiers:
4992 storage-class-specifier declaration-specifiers<sub>opt</sub>
4993 type-specifier declaration-specifiers<sub>opt</sub>
4994 type-qualifier declaration-specifiers<sub>opt</sub>
4995 function-specifier declaration-specifiers<sub>opt</sub>
4996 init-declarator-list:
4997 init-declarator
4998 init-declarator-list , init-declarator
4999 init-declarator:
5000 declarator
5001 declarator = initializer</pre>
5002 <h6>Constraints</h6>
5003 <p><!--para 2 -->
5004 A declaration shall declare at least a declarator (other than the parameters of a function or
5005 the members of a structure or union), a tag, or the members of an enumeration.
5006 <p><!--para 3 -->
5007 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5008 (in a declarator or type specifier) with the same scope and in the same name space, except
5010 <p><!--para 4 -->
5011 All declarations in the same scope that refer to the same object or function shall specify
5012 compatible types.
5013 <h6>Semantics</h6>
5014 <p><!--para 5 -->
5015 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5016 of an identifier is a declaration for that identifier that:
5017 <ul>
5018 <li> for an object, causes storage to be reserved for that object;
5020 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5021 identifier.
5022 </ul>
5023 <p><!--para 6 -->
5024 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5025 storage duration, and part of the type of the entities that the declarators denote. The init-
5026 declarator-list is a comma-separated sequence of declarators, each of which may have
5028 <!--page 110 -->
5029 additional type information, or an initializer, or both. The declarators contain the
5030 identifiers (if any) being declared.
5031 <p><!--para 7 -->
5032 If an identifier for an object is declared with no linkage, the type for the object shall be
5033 complete by the end of its declarator, or by the end of its init-declarator if it has an
5034 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5036 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
5039 <h6>footnotes</h6>
5040 <p><small><a name="note101" href="#note101">101)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
5041 </small>
5044 <h6>Syntax</h6>
5045 <p><!--para 1 -->
5046 <pre>
5047 storage-class-specifier:
5048 typedef
5049 extern
5050 static
5051 auto
5052 register</pre>
5053 <h6>Constraints</h6>
5054 <p><!--para 2 -->
5055 At most, one storage-class specifier may be given in the declaration specifiers in a
5057 <h6>Semantics</h6>
5058 <p><!--para 3 -->
5059 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5060 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5062 <p><!--para 4 -->
5063 A declaration of an identifier for an object with storage-class specifier register
5064 suggests that access to the object be as fast as possible. The extent to which such
5065 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5066 <p><!--para 5 -->
5067 The declaration of an identifier for a function that has block scope shall have no explicit
5068 storage-class specifier other than extern.
5072 <!--page 111 -->
5073 <p><!--para 6 -->
5074 If an aggregate or union object is declared with a storage-class specifier other than
5075 typedef, the properties resulting from the storage-class specifier, except with respect to
5076 linkage, also apply to the members of the object, and so on recursively for any aggregate
5077 or union member objects.
5080 <h6>footnotes</h6>
5081 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5082 </small>
5083 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5084 whether or not addressable storage is actually used, the address of any part of an object declared with
5085 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5086 operator as discussed in <a href="#6.5.3.2">6.5.3.2</a>) or implicitly (by converting an array name to a pointer as discussed in
5087 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with storage-class specifier
5088 register is sizeof.
5089 </small>
5092 <h6>Syntax</h6>
5093 <p><!--para 1 -->
5094 <pre>
5095 type-specifier:
5096 void
5097 char
5098 short
5099 int
5100 long
5101 float
5102 double
5103 signed
5104 unsigned
5105 _Bool
5106 _Complex
5107 struct-or-union-specifier *
5108 enum-specifier
5109 typedef-name</pre>
5110 <h6>Constraints</h6>
5111 <p><!--para 2 -->
5112 At least one type specifier shall be given in the declaration specifiers in each declaration,
5113 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5114 type specifiers shall be one of the following sets (delimited by commas, when there is
5115 more than one set on a line); the type specifiers may occur in any order, possibly
5116 intermixed with the other declaration specifiers.
5117 <ul>
5118 <li> void
5119 <li> char
5120 <li> signed char
5121 <li> unsigned char
5122 <li> short, signed short, short int, or signed short int
5123 <li> unsigned short, or unsigned short int
5124 <li> int, signed, or signed int
5125 <!--page 112 -->
5126 <li> unsigned, or unsigned int
5127 <li> long, signed long, long int, or signed long int
5128 <li> unsigned long, or unsigned long int
5129 <li> long long, signed long long, long long int, or
5130 signed long long int
5131 <li> unsigned long long, or unsigned long long int
5132 <li> float
5133 <li> double
5134 <li> long double
5135 <li> _Bool
5136 <li> float _Complex
5137 <li> double _Complex
5138 <li> long double _Complex
5139 <li> struct or union specifier *
5140 <li> enum specifier
5141 <li> typedef name
5142 </ul>
5143 <p><!--para 3 -->
5144 The type specifier _Complex shall not be used if the implementation does not provide
5146 <h6>Semantics</h6>
5147 <p><!--para 4 -->
5148 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5149 <a href="#6.7.2.3">6.7.2.3</a>. Declarations of typedef names are discussed in <a href="#6.7.7">6.7.7</a>. The characteristics of the
5151 <p><!--para 5 -->
5152 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5153 implementation-defined whether the specifier int designates the same type as signed
5154 int or the same type as unsigned int.
5155 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5156 (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5161 <!--page 113 -->
5163 <h6>footnotes</h6>
5164 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5165 </small>
5168 <h6>Syntax</h6>
5169 <p><!--para 1 -->
5170 <pre>
5171 struct-or-union-specifier:
5172 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }
5173 struct-or-union identifier
5174 struct-or-union:
5175 struct
5176 union
5177 struct-declaration-list:
5178 struct-declaration
5179 struct-declaration-list struct-declaration
5180 struct-declaration:
5181 specifier-qualifier-list struct-declarator-list ;
5182 specifier-qualifier-list:
5183 type-specifier specifier-qualifier-list<sub>opt</sub>
5184 type-qualifier specifier-qualifier-list<sub>opt</sub>
5185 struct-declarator-list:
5186 struct-declarator
5187 struct-declarator-list , struct-declarator
5188 struct-declarator:
5189 declarator
5190 declarator<sub>opt</sub> : constant-expression</pre>
5191 <h6>Constraints</h6>
5192 <p><!--para 2 -->
5193 A structure or union shall not contain a member with incomplete or function type (hence,
5194 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5195 of itself), except that the last member of a structure with more than one named member
5196 may have incomplete array type; such a structure (and any union containing, possibly
5197 recursively, a member that is such a structure) shall not be a member of a structure or an
5198 element of an array.
5199 <p><!--para 3 -->
5200 The expression that specifies the width of a bit-field shall be an integer constant
5201 expression with a nonnegative value that does not exceed the width of an object of the
5202 type that would be specified were the colon and expression omitted. If the value is zero,
5203 the declaration shall have no declarator.
5204 <p><!--para 4 -->
5205 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5206 int, unsigned int, or some other implementation-defined type.
5207 <!--page 114 -->
5208 <h6>Semantics</h6>
5209 <p><!--para 5 -->
5210 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5211 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5212 of members whose storage overlap.
5213 <p><!--para 6 -->
5214 Structure and union specifiers have the same form. The keywords struct and union
5215 indicate that the type being specified is, respectively, a structure type or a union type.
5216 <p><!--para 7 -->
5217 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5218 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5219 members of the structure or union. If the struct-declaration-list contains no named
5220 members, the behavior is undefined. The type is incomplete until after the } that
5221 terminates the list.
5222 <p><!--para 8 -->
5223 A member of a structure or union may have any object type other than a variably
5224 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5225 number of bits (including a sign bit, if any). Such a member is called a bit-field;<sup><a href="#note106"><b>106)</b></a></sup> its
5226 width is preceded by a colon.
5227 <p><!--para 9 -->
5228 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5229 number of bits.<sup><a href="#note107"><b>107)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of type
5230 _Bool, the value of the bit-field shall compare equal to the value stored.
5231 <p><!--para 10 -->
5232 An implementation may allocate any addressable storage unit large enough to hold a bit-
5233 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5234 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5235 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5236 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5237 low-order or low-order to high-order) is implementation-defined. The alignment of the
5238 addressable storage unit is unspecified.
5239 <p><!--para 11 -->
5240 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5241 unnamed bit-field.<sup><a href="#note108"><b>108)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5242 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5243 field, if any, was placed.
5246 <!--page 115 -->
5247 <p><!--para 12 -->
5248 Each non-bit-field member of a structure or union object is aligned in an implementation-
5249 defined manner appropriate to its type.
5250 <p><!--para 13 -->
5251 Within a structure object, the non-bit-field members and the units in which bit-fields
5252 reside have addresses that increase in the order in which they are declared. A pointer to a
5253 structure object, suitably converted, points to its initial member (or if that member is a
5254 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5255 padding within a structure object, but not at its beginning.
5256 <p><!--para 14 -->
5257 The size of a union is sufficient to contain the largest of its members. The value of at
5258 most one of the members can be stored in a union object at any time. A pointer to a
5259 union object, suitably converted, points to each of its members (or if a member is a bit-
5260 field, then to the unit in which it resides), and vice versa.
5261 <p><!--para 15 -->
5262 There may be unnamed padding at the end of a structure or union.
5263 <p><!--para 16 -->
5264 As a special case, the last element of a structure with more than one named member may
5265 have an incomplete array type; this is called a flexible array member. In most situations,
5266 the flexible array member is ignored. In particular, the size of the structure is as if the
5267 flexible array member were omitted except that it may have more trailing padding than
5268 the omission would imply. However, when a . (or ->) operator has a left operand that is
5269 (a pointer to) a structure with a flexible array member and the right operand names that
5270 member, it behaves as if that member were replaced with the longest array (with the same
5271 element type) that would not make the structure larger than the object being accessed; the
5272 offset of the array shall remain that of the flexible array member, even if this would differ
5273 from that of the replacement array. If this array would have no elements, it behaves as if
5274 it had one element but the behavior is undefined if any attempt is made to access that
5275 element or to generate a pointer one past it.
5276 <p><!--para 17 -->
5277 EXAMPLE After the declaration:
5278 <pre>
5279 struct s { int n; double d[]; };</pre>
5280 the structure struct s has a flexible array member d. A typical way to use this is:
5281 <pre>
5282 int m = /* some value */;
5283 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));</pre>
5284 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5285 p had been declared as:
5286 <pre>
5287 struct { int n; double d[m]; } *p;</pre>
5288 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5289 not be the same).
5290 <p><!--para 18 -->
5291 Following the above declaration:
5292 <!--page 116 -->
5293 <pre>
5294 struct s t1 = { 0 }; // valid
5296 t1.n = 4; // valid
5298 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5299 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5300 <pre>
5301 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)</pre>
5302 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5303 code.
5304 <p><!--para 19 -->
5305 After the further declaration:
5306 <pre>
5307 struct ss { int n; };</pre>
5308 the expressions:
5309 <pre>
5310 sizeof (struct s) >= sizeof (struct ss)
5311 sizeof (struct s) >= offsetof(struct s, d)</pre>
5312 are always equal to 1.
5313 <p><!--para 20 -->
5314 If sizeof (double) is 8, then after the following code is executed:
5315 <pre>
5316 struct s *s1;
5317 struct s *s2;
5318 s1 = malloc(sizeof (struct s) + 64);
5319 s2 = malloc(sizeof (struct s) + 46);</pre>
5320 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5321 purposes, as if the identifiers had been declared as:
5322 <p><!--para 21 -->
5323 <pre>
5324 struct { int n; double d[8]; } *s1;
5325 struct { int n; double d[5]; } *s2;</pre>
5326 Following the further successful assignments:
5327 <pre>
5328 s1 = malloc(sizeof (struct s) + 10);
5329 s2 = malloc(sizeof (struct s) + 6);</pre>
5330 they then behave as if the declarations were:
5331 <pre>
5332 struct { int n; double d[1]; } *s1, *s2;</pre>
5333 and:
5334 <p><!--para 22 -->
5335 <pre>
5336 double *dp;
5337 dp = &(s1->d[0]); // valid
5338 *dp = 42; // valid
5339 dp = &(s2->d[0]); // valid
5340 *dp = 42; // undefined behavior</pre>
5341 The assignment:
5342 <pre>
5343 *s1 = *s2;</pre>
5344 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5345 of the structure, they might be copied or simply overwritten with indeterminate values.
5348 <!--page 117 -->
5350 <h6>footnotes</h6>
5351 <p><small><a name="note105" href="#note105">105)</a> A structure or union can not contain a member with a variably modified type because member names
5353 </small>
5354 <p><small><a name="note106" href="#note106">106)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5355 or arrays of bit-field objects.
5356 </small>
5357 <p><small><a name="note107" href="#note107">107)</a> As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
5358 then it is implementation-defined whether the bit-field is signed or unsigned.
5359 </small>
5360 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5361 layouts.
5362 </small>
5365 <h6>Syntax</h6>
5366 <p><!--para 1 -->
5367 <pre>
5368 enum-specifier:
5369 enum identifier<sub>opt</sub> { enumerator-list }
5370 enum identifier<sub>opt</sub> { enumerator-list , }
5371 enum identifier
5372 enumerator-list:
5373 enumerator
5374 enumerator-list , enumerator
5375 enumerator:
5376 enumeration-constant
5377 enumeration-constant = constant-expression</pre>
5378 <h6>Constraints</h6>
5379 <p><!--para 2 -->
5380 The expression that defines the value of an enumeration constant shall be an integer
5381 constant expression that has a value representable as an int.
5382 <h6>Semantics</h6>
5383 <p><!--para 3 -->
5384 The identifiers in an enumerator list are declared as constants that have type int and
5385 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5386 enumeration constant as the value of the constant expression. If the first enumerator has
5387 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5388 defines its enumeration constant as the value of the constant expression obtained by
5389 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5390 = may produce enumeration constants with values that duplicate other values in the same
5391 enumeration.) The enumerators of an enumeration are also known as its members.
5392 <p><!--para 4 -->
5393 Each enumerated type shall be compatible with char, a signed integer type, or an
5394 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5395 capable of representing the values of all the members of the enumeration. The
5396 enumerated type is incomplete until after the } that terminates the list of enumerator
5397 declarations.
5402 <!--page 118 -->
5403 <p><!--para 5 -->
5404 EXAMPLE The following fragment:
5405 <pre>
5406 enum hue { chartreuse, burgundy, claret=20, winedark };
5407 enum hue col, *cp;
5408 col = claret;
5409 cp = &col;
5410 if (*cp != burgundy)
5411 /* ... */</pre>
5412 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5413 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5417 <h6>footnotes</h6>
5418 <p><small><a name="note109" href="#note109">109)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5419 each other and from other identifiers declared in ordinary declarators.
5420 </small>
5421 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5422 been seen.
5423 </small>
5426 <h6>Constraints</h6>
5427 <p><!--para 1 -->
5428 A specific type shall have its content defined at most once.
5429 <p><!--para 2 -->
5430 Where two declarations that use the same tag declare the same type, they shall both use
5431 the same choice of struct, union, or enum.
5432 <p><!--para 3 -->
5433 A type specifier of the form
5434 <pre>
5435 enum identifier</pre>
5436 without an enumerator list shall only appear after the type it specifies is complete.
5437 <h6>Semantics</h6>
5438 <p><!--para 4 -->
5439 All declarations of structure, union, or enumerated types that have the same scope and
5440 use the same tag declare the same type. The type is incomplete<sup><a href="#note111"><b>111)</b></a></sup> until the closing brace
5441 of the list defining the content, and complete thereafter.
5442 <p><!--para 5 -->
5443 Two declarations of structure, union, or enumerated types which are in different scopes or
5444 use different tags declare distinct types. Each declaration of a structure, union, or
5445 enumerated type which does not include a tag declares a distinct type.
5446 <p><!--para 6 -->
5447 A type specifier of the form
5448 <pre>
5449 struct-or-union identifier<sub>opt</sub> { struct-declaration-list }</pre>
5450 or
5451 <pre>
5452 enum identifier { enumerator-list }</pre>
5453 or
5454 <pre>
5455 enum identifier { enumerator-list , }</pre>
5456 declares a structure, union, or enumerated type. The list defines the structure content,
5458 <!--page 119 -->
5459 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5460 also declares the identifier to be the tag of that type.
5461 <p><!--para 7 -->
5462 A declaration of the form
5463 <pre>
5464 struct-or-union identifier ;</pre>
5465 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note113"><b>113)</b></a></sup>
5466 <p><!--para 8 -->
5467 If a type specifier of the form
5468 <pre>
5469 struct-or-union identifier</pre>
5470 occurs other than as part of one of the above forms, and no other declaration of the
5471 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5472 declares the identifier as the tag of that type.113)
5473 <p><!--para 9 -->
5474 If a type specifier of the form
5475 <pre>
5476 struct-or-union identifier</pre>
5477 or
5478 <pre>
5479 enum identifier</pre>
5480 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5481 tag is visible, then it specifies the same type as that other declaration, and does not
5482 redeclare the tag.
5483 <p><!--para 10 -->
5484 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5485 <pre>
5486 struct tnode {
5487 int count;
5488 struct tnode *left, *right;
5489 };</pre>
5490 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5491 declaration has been given, the declaration
5492 <pre>
5493 struct tnode s, *sp;</pre>
5494 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5495 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5496 which sp points; the expression s.right->count designates the count member of the right struct
5497 tnode pointed to from s.
5498 <p><!--para 11 -->
5499 The following alternative formulation uses the typedef mechanism:
5504 <!--page 120 -->
5505 <pre>
5506 typedef struct tnode TNODE;
5507 struct tnode {
5508 int count;
5509 TNODE *left, *right;
5510 };
5511 TNODE s, *sp;</pre>
5513 <p><!--para 12 -->
5514 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5515 structures, the declarations
5516 <pre>
5517 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5518 struct s2 { struct s1 *s1p; /* ... */ }; // D2</pre>
5519 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5520 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5521 D2. To eliminate this context sensitivity, the declaration
5522 <pre>
5523 struct s2;</pre>
5524 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5525 completes the specification of the new type.
5527 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions
5530 <h6>footnotes</h6>
5531 <p><small><a name="note111" href="#note111">111)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5532 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5533 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5534 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5535 </small>
5536 <p><small><a name="note112" href="#note112">112)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5537 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5538 can make use of that typedef name to declare objects having the specified structure, union, or
5539 enumerated type.
5540 </small>
5541 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5542 </small>
5545 <h6>Syntax</h6>
5546 <p><!--para 1 -->
5547 <pre>
5548 type-qualifier:
5549 const
5550 restrict
5551 volatile</pre>
5552 <h6>Constraints</h6>
5553 <p><!--para 2 -->
5554 Types other than pointer types derived from object or incomplete types shall not be
5555 restrict-qualified.
5556 <h6>Semantics</h6>
5557 <p><!--para 3 -->
5558 The properties associated with qualified types are meaningful only for expressions that
5560 <p><!--para 4 -->
5561 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5562 directly or via one or more typedefs, the behavior is the same as if it appeared only
5563 once.
5568 <!--page 121 -->
5569 <p><!--para 5 -->
5570 If an attempt is made to modify an object defined with a const-qualified type through use
5571 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5572 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5573 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5574 <p><!--para 6 -->
5575 An object that has volatile-qualified type may be modified in ways unknown to the
5576 implementation or have other unknown side effects. Therefore any expression referring
5577 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5578 as described in <a href="#5.1.2.3">5.1.2.3</a>. Furthermore, at every sequence point the value last stored in the
5579 object shall agree with that prescribed by the abstract machine, except as modified by the
5580 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5581 has volatile-qualified type is implementation-defined.
5582 <p><!--para 7 -->
5583 An object that is accessed through a restrict-qualified pointer has a special association
5584 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5585 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5586 use of the restrict qualifier (like the register storage class) is to promote
5587 optimization, and deleting all instances of the qualifier from all preprocessing translation
5588 units composing a conforming program does not change its meaning (i.e., observable
5589 behavior).
5590 <p><!--para 8 -->
5591 If the specification of an array type includes any type qualifiers, the element type is so-
5592 qualified, not the array type. If the specification of a function type includes any type
5594 <p><!--para 9 -->
5595 For two qualified types to be compatible, both shall have the identically qualified version
5596 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5597 does not affect the specified type.
5598 <p><!--para 10 -->
5599 EXAMPLE 1 An object declared
5600 <pre>
5601 extern const volatile int real_time_clock;</pre>
5602 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5607 <!--page 122 -->
5608 <p><!--para 11 -->
5609 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5610 modify an aggregate type:
5611 <pre>
5612 const struct s { int mem; } cs = { 1 };
5613 struct s ncs; // the object ncs is modifiable
5614 typedef int A[2][3];
5615 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5616 int *pi;
5617 const int *pci;
5618 ncs = cs; // valid
5619 cs = ncs; // violates modifiable lvalue constraint for =
5620 pi = &ncs.mem; // valid
5621 pi = &cs.mem; // violates type constraints for =
5622 pci = &cs.mem; // valid
5623 pi = a[0]; // invalid: a[0] has type ''const int *''</pre>
5626 <h6>footnotes</h6>
5627 <p><small><a name="note114" href="#note114">114)</a> The implementation may place a const object that is not volatile in a read-only region of
5628 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5629 never used.
5630 </small>
5631 <p><small><a name="note115" href="#note115">115)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
5632 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5633 address).
5634 </small>
5635 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5636 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5637 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5638 permitted by the rules for evaluating expressions.
5639 </small>
5640 <p><small><a name="note117" href="#note117">117)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5641 association between the allocated object and the pointer.
5642 </small>
5643 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5644 </small>
5647 <p><!--para 1 -->
5648 Let D be a declaration of an ordinary identifier that provides a means of designating an
5649 object P as a restrict-qualified pointer to type T.
5650 <p><!--para 2 -->
5651 If D appears inside a block and does not have storage class extern, let B denote the
5652 block. If D appears in the list of parameter declarations of a function definition, let B
5653 denote the associated block. Otherwise, let B denote the block of main (or the block of
5654 whatever function is called at program startup in a freestanding environment).
5655 <p><!--para 3 -->
5656 In what follows, a pointer expression E is said to be based on object P if (at some
5657 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5658 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note119"><b>119)</b></a></sup>
5659 Note that ''based'' is defined only for expressions with pointer types.
5660 <p><!--para 4 -->
5661 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5662 access the value of the object X that it designates, and X is also modified (by any means),
5663 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5664 used to access the value of X shall also have its address based on P. Every access that
5665 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5666 is assigned the value of a pointer expression E that is based on another restricted pointer
5667 object P2, associated with block B2, then either the execution of B2 shall begin before
5668 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5669 requirements are not met, then the behavior is undefined.
5670 <p><!--para 5 -->
5671 Here an execution of B means that portion of the execution of the program that would
5672 correspond to the lifetime of an object with scalar type and automatic storage duration
5674 <!--page 123 -->
5675 associated with B.
5676 <p><!--para 6 -->
5677 A translator is free to ignore any or all aliasing implications of uses of restrict.
5678 <p><!--para 7 -->
5679 EXAMPLE 1 The file scope declarations
5680 <pre>
5681 int * restrict a;
5682 int * restrict b;
5683 extern int c[];</pre>
5684 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5685 program, then it is never accessed using either of the other two.
5687 <p><!--para 8 -->
5688 EXAMPLE 2 The function parameter declarations in the following example
5689 <pre>
5690 void f(int n, int * restrict p, int * restrict q)
5691 {
5692 while (n-- > 0)
5693 *p++ = *q++;
5694 }</pre>
5695 assert that, during each execution of the function, if an object is accessed through one of the pointer
5696 parameters, then it is not also accessed through the other.
5697 <p><!--para 9 -->
5698 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5699 analysis of function f without examining any of the calls of f in the program. The cost is that the
5700 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5701 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5702 both p and q.
5703 <pre>
5704 void g(void)
5705 {
5706 extern int d[100];
5707 f(50, d + 50, d); // valid
5708 f(50, d + 1, d); // undefined behavior
5709 }</pre>
5711 <p><!--para 10 -->
5712 EXAMPLE 3 The function parameter declarations
5713 <pre>
5714 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5715 {
5716 int i;
5717 for (i = 0; i < n; i++)
5718 p[i] = q[i] + r[i];
5719 }</pre>
5720 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5721 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5722 modified within function h.
5724 <p><!--para 11 -->
5725 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5726 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5727 between restricted pointers declared in nested blocks have defined behavior.
5728 <!--page 124 -->
5729 <p><!--para 12 -->
5730 <pre>
5731 {
5732 int * restrict p1;
5733 int * restrict q1;
5734 p1 = q1; // undefined behavior
5735 {
5736 int * restrict p2 = p1; // valid
5737 int * restrict q2 = q1; // valid
5738 p1 = q2; // undefined behavior
5739 p2 = q2; // undefined behavior
5740 }
5741 }</pre>
5742 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5743 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5744 example, this permits new_vector to return a vector.
5745 <pre>
5746 typedef struct { int n; float * restrict v; } vector;
5747 vector new_vector(int n)
5748 {
5749 vector t;
5750 t.n = n;
5751 t.v = malloc(n * sizeof (float));
5752 return t;
5753 }</pre>
5756 <h6>footnotes</h6>
5757 <p><small><a name="note119" href="#note119">119)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
5758 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5759 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5760 expressions *p and p[1] are not.
5761 </small>
5764 <h6>Syntax</h6>
5765 <p><!--para 1 -->
5766 <pre>
5767 function-specifier:
5768 inline</pre>
5769 <h6>Constraints</h6>
5770 <p><!--para 2 -->
5771 Function specifiers shall be used only in the declaration of an identifier for a function.
5772 <p><!--para 3 -->
5773 An inline definition of a function with external linkage shall not contain a definition of a
5774 modifiable object with static storage duration, and shall not contain a reference to an
5775 identifier with internal linkage.
5776 <p><!--para 4 -->
5777 In a hosted environment, the inline function specifier shall not appear in a declaration
5778 of main.
5779 <h6>Semantics</h6>
5780 <p><!--para 5 -->
5781 A function declared with an inline function specifier is an inline function. The
5782 function specifier may appear more than once; the behavior is the same as if it appeared
5783 only once. Making a function an inline function suggests that calls to the function be as
5784 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
5786 <p><!--para 6 -->
5787 Any function with internal linkage can be an inline function. For a function with external
5788 linkage, the following restrictions apply: If a function is declared with an inline
5789 <!--page 125 -->
5790 function specifier, then it shall also be defined in the same translation unit. If all of the
5791 file scope declarations for a function in a translation unit include the inline function
5792 specifier without extern, then the definition in that translation unit is an inline
5793 definition. An inline definition does not provide an external definition for the function,
5794 and does not forbid an external definition in another translation unit. An inline definition
5795 provides an alternative to an external definition, which a translator may use to implement
5796 any call to the function in the same translation unit. It is unspecified whether a call to the
5797 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
5798 <p><!--para 7 -->
5799 EXAMPLE The declaration of an inline function with external linkage can result in either an external
5800 definition, or a definition available for use only within the translation unit. A file scope declaration with
5801 extern creates an external definition. The following example shows an entire translation unit.
5802 <p><!--para 8 -->
5803 <pre>
5804 inline double fahr(double t)
5805 {
5806 return (9.0 * t) / 5.0 + 32.0;
5807 }
5808 inline double cels(double t)
5809 {
5810 return (5.0 * (t - 32.0)) / 9.0;
5811 }
5812 extern double fahr(double); // creates an external definition
5813 double convert(int is_fahr, double temp)
5814 {
5815 /* A translator may perform inline substitutions */
5816 return is_fahr ? cels(temp) : fahr(temp);
5817 }</pre>
5818 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5819 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5820 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5821 definition are distinct and either may be used for the call.
5826 <!--page 126 -->
5828 <h6>footnotes</h6>
5829 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5830 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5831 Therefore, for example, the expansion of a macro used within the body of the function uses the
5832 definition it had at the point the function body appears, and not where the function is called; and
5833 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5834 single address, regardless of the number of inline definitions that occur in addition to the external
5835 definition.
5836 </small>
5837 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
5838 substitutions to calls in the scope of an inline declaration.
5839 </small>
5840 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
5841 corresponding inline definitions in other translation units, all corresponding objects with static storage
5842 duration are also distinct in each of the definitions.
5843 </small>
5846 <h6>Syntax</h6>
5847 <p><!--para 1 -->
5848 <pre>
5849 declarator:
5850 pointer<sub>opt</sub> direct-declarator
5851 direct-declarator:
5852 identifier
5853 ( declarator )
5854 direct-declarator [ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
5855 direct-declarator [ static type-qualifier-list<sub>opt</sub> assignment-expression ]
5856 direct-declarator [ type-qualifier-list static assignment-expression ]
5857 direct-declarator [ type-qualifier-list<sub>opt</sub> * ]
5858 direct-declarator ( parameter-type-list )
5859 direct-declarator ( identifier-list<sub>opt</sub> )
5860 pointer:
5861 * type-qualifier-list<sub>opt</sub>
5862 * type-qualifier-list<sub>opt</sub> pointer
5863 type-qualifier-list:
5864 type-qualifier
5865 type-qualifier-list type-qualifier
5866 parameter-type-list:
5867 parameter-list
5868 parameter-list , ...
5869 parameter-list:
5870 parameter-declaration
5871 parameter-list , parameter-declaration
5872 parameter-declaration:
5873 declaration-specifiers declarator
5874 declaration-specifiers abstract-declarator<sub>opt</sub>
5875 identifier-list:
5876 identifier
5877 identifier-list , identifier</pre>
5878 <h6>Semantics</h6>
5879 <p><!--para 2 -->
5880 Each declarator declares one identifier, and asserts that when an operand of the same
5881 form as the declarator appears in an expression, it designates a function or object with the
5882 scope, storage duration, and type indicated by the declaration specifiers.
5883 <p><!--para 3 -->
5884 A full declarator is a declarator that is not part of another declarator. The end of a full
5885 declarator is a sequence point. If, in the nested sequence of declarators in a full
5886 <!--page 127 -->
5887 declarator, there is a declarator specifying a variable length array type, the type specified
5888 by the full declarator is said to be variably modified. Furthermore, any type derived by
5889 declarator type derivation from a variably modified type is itself variably modified.
5890 <p><!--para 4 -->
5891 In the following subclauses, consider a declaration
5892 <pre>
5893 T D1</pre>
5894 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5895 a declarator that contains an identifier ident. The type specified for the identifier ident in
5896 the various forms of declarator is described inductively using this notation.
5897 <p><!--para 5 -->
5898 If, in the declaration ''T D1'', D1 has the form
5899 <pre>
5900 identifier</pre>
5901 then the type specified for ident is T .
5902 <p><!--para 6 -->
5903 If, in the declaration ''T D1'', D1 has the form
5904 <pre>
5905 ( D )</pre>
5906 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5907 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5908 declarators may be altered by parentheses.
5909 <h6> Implementation limits</h6>
5910 <p><!--para 7 -->
5911 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
5912 function declarators that modify an arithmetic, structure, union, or incomplete type, either
5913 directly or via one or more typedefs.
5914 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5917 <h6>Semantics</h6>
5918 <p><!--para 1 -->
5919 If, in the declaration ''T D1'', D1 has the form
5920 <pre>
5921 * type-qualifier-list<sub>opt</sub> D</pre>
5922 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5923 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5924 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5925 <p><!--para 2 -->
5926 For two pointer types to be compatible, both shall be identically qualified and both shall
5927 be pointers to compatible types.
5928 <p><!--para 3 -->
5929 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5930 to a constant value'' and a ''constant pointer to a variable value''.
5931 <!--page 128 -->
5932 <pre>
5933 const int *ptr_to_constant;
5934 int *const constant_ptr;</pre>
5935 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5936 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5937 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5938 same location.
5939 <p><!--para 4 -->
5940 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5941 type ''pointer to int''.
5942 <pre>
5943 typedef int *int_ptr;
5944 const int_ptr constant_ptr;</pre>
5945 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5949 <h6>Constraints</h6>
5950 <p><!--para 1 -->
5951 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5952 an expression or *. If they delimit an expression (which specifies the size of an array), the
5953 expression shall have an integer type. If the expression is a constant expression, it shall
5954 have a value greater than zero. The element type shall not be an incomplete or function
5955 type. The optional type qualifiers and the keyword static shall appear only in a
5956 declaration of a function parameter with an array type, and then only in the outermost
5957 array type derivation.
5958 <p><!--para 2 -->
5959 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5960 either block scope and no linkage or function prototype scope. If an identifier is declared
5961 to be an object with static storage duration, it shall not have a variable length array type.
5962 <h6>Semantics</h6>
5963 <p><!--para 3 -->
5964 If, in the declaration ''T D1'', D1 has one of the forms:
5965 <pre>
5966 D[ type-qualifier-list<sub>opt</sub> assignment-expression<sub>opt</sub> ]
5967 D[ static type-qualifier-list<sub>opt</sub> assignment-expression ]
5968 D[ type-qualifier-list static assignment-expression ]
5969 D[ type-qualifier-list<sub>opt</sub> * ]</pre>
5970 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5971 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
5972 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5973 <p><!--para 4 -->
5974 If the size is not present, the array type is an incomplete type. If the size is * instead of
5975 being an expression, the array type is a variable length array type of unspecified size,
5976 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
5977 nonetheless complete types. If the size is an integer constant expression and the element
5979 <!--page 129 -->
5980 type has a known constant size, the array type is not a variable length array type;
5981 otherwise, the array type is a variable length array type.
5982 <p><!--para 5 -->
5983 If the size is an expression that is not an integer constant expression: if it occurs in a
5984 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5985 each time it is evaluated it shall have a value greater than zero. The size of each instance
5986 of a variable length array type does not change during its lifetime. Where a size
5987 expression is part of the operand of a sizeof operator and changing the value of the
5988 size expression would not affect the result of the operator, it is unspecified whether or not
5989 the size expression is evaluated.
5990 <p><!--para 6 -->
5991 For two array types to be compatible, both shall have compatible element types, and if
5992 both size specifiers are present, and are integer constant expressions, then both size
5993 specifiers shall have the same constant value. If the two array types are used in a context
5994 which requires them to be compatible, it is undefined behavior if the two size specifiers
5995 evaluate to unequal values.
5996 <p><!--para 7 -->
5997 EXAMPLE 1
5998 <pre>
5999 float fa[11], *afp[17];</pre>
6000 declares an array of float numbers and an array of pointers to float numbers.
6002 <p><!--para 8 -->
6003 EXAMPLE 2 Note the distinction between the declarations
6004 <pre>
6005 extern int *x;
6006 extern int y[];</pre>
6007 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6008 (an incomplete type), the storage for which is defined elsewhere.
6010 <p><!--para 9 -->
6011 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6012 <pre>
6013 extern int n;
6014 extern int m;
6015 void fcompat(void)
6016 {
6017 int a[n][6][m];
6018 int (*p)[4][n+1];
6019 int c[n][n][6][m];
6020 int (*r)[n][n][n+1];
6021 p = a; // invalid: not compatible because 4 != 6
6022 r = c; // compatible, but defined behavior only if
6023 // n == 6 and m == n+1
6024 }</pre>
6029 <!--page 130 -->
6030 <p><!--para 10 -->
6031 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6032 function prototype scope. Array objects declared with the static or extern storage-class specifier
6033 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6034 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6035 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6036 <pre>
6037 extern int n;
6038 int A[n]; // invalid: file scope VLA
6039 extern int (*p2)[n]; // invalid: file scope VM
6040 int B[100]; // valid: file scope but not VM
6041 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6042 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6043 {
6044 typedef int VLA[m][m]; // valid: block scope typedef VLA
6045 struct tag {
6046 int (*y)[n]; // invalid: y not ordinary identifier
6047 int z[n]; // invalid: z not ordinary identifier
6048 };
6049 int D[m]; // valid: auto VLA
6050 static int E[m]; // invalid: static block scope VLA
6051 extern int F[m]; // invalid: F has linkage and is VLA
6052 int (*s)[m]; // valid: auto pointer to VLA
6053 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6054 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6055 }</pre>
6057 <p><b> Forward references</b>: function declarators (<a href="#6.7.5.3">6.7.5.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
6060 <h6>footnotes</h6>
6061 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6062 </small>
6063 <p><small><a name="note124" href="#note124">124)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.5.3">6.7.5.3</a>).
6064 </small>
6066 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6067 <h6>Constraints</h6>
6068 <p><!--para 1 -->
6069 A function declarator shall not specify a return type that is a function type or an array
6070 type.
6071 <p><!--para 2 -->
6072 The only storage-class specifier that shall occur in a parameter declaration is register.
6073 <p><!--para 3 -->
6074 An identifier list in a function declarator that is not part of a definition of that function
6075 shall be empty.
6076 <p><!--para 4 -->
6077 After adjustment, the parameters in a parameter type list in a function declarator that is
6078 part of a definition of that function shall not have incomplete type.
6079 <h6>Semantics</h6>
6080 <p><!--para 5 -->
6081 If, in the declaration ''T D1'', D1 has the form
6082 <pre>
6083 D( parameter-type-list )</pre>
6084 or
6085 <!--page 131 -->
6086 <pre>
6087 D( identifier-list<sub>opt</sub> )</pre>
6088 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6089 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6090 T ''.
6091 <p><!--para 6 -->
6092 A parameter type list specifies the types of, and may declare identifiers for, the
6093 parameters of the function.
6094 <p><!--para 7 -->
6095 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6096 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6097 array type derivation. If the keyword static also appears within the [ and ] of the
6098 array type derivation, then for each call to the function, the value of the corresponding
6099 actual argument shall provide access to the first element of an array with at least as many
6100 elements as specified by the size expression.
6101 <p><!--para 8 -->
6102 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6104 <p><!--para 9 -->
6105 If the list terminates with an ellipsis (, ...), no information about the number or types
6107 <p><!--para 10 -->
6108 The special case of an unnamed parameter of type void as the only item in the list
6109 specifies that the function has no parameters.
6110 <p><!--para 11 -->
6111 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6112 parameter name, it shall be taken as a typedef name.
6113 <p><!--para 12 -->
6114 If the function declarator is not part of a definition of that function, parameters may have
6115 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6116 to specify variable length array types.
6117 <p><!--para 13 -->
6118 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6119 present, is ignored unless the declared parameter is one of the members of the parameter
6120 type list for a function definition.
6121 <p><!--para 14 -->
6122 An identifier list declares only the identifiers of the parameters of the function. An empty
6123 list in a function declarator that is part of a definition of that function specifies that the
6124 function has no parameters. The empty list in a function declarator that is not part of a
6125 definition of that function specifies that no information about the number or types of the
6127 <p><!--para 15 -->
6128 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6131 <!--page 132 -->
6132 Moreover, the parameter type lists, if both are present, shall agree in the number of
6133 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6134 compatible types. If one type has a parameter type list and the other type is specified by a
6135 function declarator that is not part of a function definition and that contains an empty
6136 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6137 parameter shall be compatible with the type that results from the application of the
6138 default argument promotions. If one type has a parameter type list and the other type is
6139 specified by a function definition that contains a (possibly empty) identifier list, both shall
6140 agree in the number of parameters, and the type of each prototype parameter shall be
6141 compatible with the type that results from the application of the default argument
6142 promotions to the type of the corresponding identifier. (In the determination of type
6143 compatibility and of a composite type, each parameter declared with function or array
6144 type is taken as having the adjusted type and each parameter declared with qualified type
6145 is taken as having the unqualified version of its declared type.)
6146 <p><!--para 16 -->
6147 EXAMPLE 1 The declaration
6148 <pre>
6149 int f(void), *fip(), (*pfi)();</pre>
6150 declares a function f with no parameters returning an int, a function fip with no parameter specification
6151 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6152 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6153 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6154 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6155 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6156 designator, which is then used to call the function; it returns an int.
6157 <p><!--para 17 -->
6158 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6159 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6160 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6161 the identifier of the pointer pfi has block scope and no linkage.
6163 <p><!--para 18 -->
6164 EXAMPLE 2 The declaration
6165 <pre>
6166 int (*apfi[3])(int *x, int *y);</pre>
6167 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6168 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6169 go out of scope at the end of the declaration of apfi.
6171 <p><!--para 19 -->
6172 EXAMPLE 3 The declaration
6173 <pre>
6174 int (*fpfi(int (*)(long), int))(int, ...);</pre>
6175 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6176 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6177 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6178 additional arguments of any type.
6179 <!--page 133 -->
6180 <p><!--para 20 -->
6181 EXAMPLE 4 The following prototype has a variably modified parameter.
6182 <pre>
6183 void addscalar(int n, int m,
6184 double a[n][n*m+300], double x);
6185 int main()
6186 {
6187 double b[4][308];
6189 return 0;
6190 }
6191 void addscalar(int n, int m,
6192 double a[n][n*m+300], double x)
6193 {
6194 for (int i = 0; i < n; i++)
6195 for (int j = 0, k = n*m+300; j < k; j++)
6196 // a is a pointer to a VLA with n*m+300 elements
6197 a[i][j] += x;
6198 }</pre>
6200 <p><!--para 21 -->
6201 EXAMPLE 5 The following are all compatible function prototype declarators.
6202 <pre>
6203 double maximum(int n, int m, double a[n][m]);
6204 double maximum(int n, int m, double a[*][*]);
6205 double maximum(int n, int m, double a[ ][*]);
6206 double maximum(int n, int m, double a[ ][m]);</pre>
6207 as are:
6208 <pre>
6209 void f(double (* restrict a)[5]);
6210 void f(double a[restrict][5]);
6211 void f(double a[restrict 3][5]);
6212 void f(double a[restrict static 3][5]);</pre>
6213 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6214 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6216 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
6217 <!--page 134 -->
6219 <h6>footnotes</h6>
6220 <p><small><a name="note125" href="#note125">125)</a> The macros defined in the <a href="#7.15"><stdarg.h></a> header (<a href="#7.15">7.15</a>) may be used to access arguments that
6221 correspond to the ellipsis.
6222 </small>
6223 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6224 </small>
6225 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6226 </small>
6229 <h6>Syntax</h6>
6230 <p><!--para 1 -->
6231 <pre>
6232 type-name:
6233 specifier-qualifier-list abstract-declarator<sub>opt</sub>
6234 abstract-declarator:
6235 pointer
6236 pointer<sub>opt</sub> direct-abstract-declarator
6237 direct-abstract-declarator:
6238 ( abstract-declarator )
6239 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list<sub>opt</sub>
6240 assignment-expression<sub>opt</sub> ]
6241 direct-abstract-declarator<sub>opt</sub> [ static type-qualifier-list<sub>opt</sub>
6242 assignment-expression ]
6243 direct-abstract-declarator<sub>opt</sub> [ type-qualifier-list static
6244 assignment-expression ]
6245 direct-abstract-declarator<sub>opt</sub> [ * ]
6246 direct-abstract-declarator<sub>opt</sub> ( parameter-type-list<sub>opt</sub> )</pre>
6247 <h6>Semantics</h6>
6248 <p><!--para 2 -->
6249 In several contexts, it is necessary to specify a type. This is accomplished using a type
6250 name, which is syntactically a declaration for a function or an object of that type that
6252 <p><!--para 3 -->
6253 EXAMPLE The constructions
6254 <pre>
6255 (a) int
6256 (b) int *
6257 (c) int *[3]
6258 (d) int (*)[3]
6259 (e) int (*)[*]
6260 (f) int *()
6261 (g) int (*)(void)
6262 (h) int (*const [])(unsigned int, ...)</pre>
6263 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6264 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6265 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6266 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6267 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6268 int.
6273 <!--page 135 -->
6275 <h6>footnotes</h6>
6276 <p><small><a name="note128" href="#note128">128)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6277 parameter specification'', rather than redundant parentheses around the omitted identifier.
6278 </small>
6281 <h6>Syntax</h6>
6282 <p><!--para 1 -->
6283 <pre>
6284 typedef-name:
6285 identifier</pre>
6286 <h6>Constraints</h6>
6287 <p><!--para 2 -->
6288 If a typedef name specifies a variably modified type then it shall have block scope.
6289 <h6>Semantics</h6>
6290 <p><!--para 3 -->
6291 In a declaration whose storage-class specifier is typedef, each declarator defines an
6292 identifier to be a typedef name that denotes the type specified for the identifier in the way
6293 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6294 declarators are evaluated each time the declaration of the typedef name is reached in the
6295 order of execution. A typedef declaration does not introduce a new type, only a
6296 synonym for the type so specified. That is, in the following declarations:
6297 <pre>
6298 typedef T type_ident;
6299 type_ident D;</pre>
6300 type_ident is defined as a typedef name with the type specified by the declaration
6301 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6302 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6303 typedef name shares the same name space as other identifiers declared in ordinary
6304 declarators.
6305 <p><!--para 4 -->
6306 EXAMPLE 1 After
6307 <pre>
6308 typedef int MILES, KLICKSP();
6309 typedef struct { double hi, lo; } range;</pre>
6310 the constructions
6311 <pre>
6312 MILES distance;
6313 extern KLICKSP *metricp;
6314 range x;
6315 range z, *zp;</pre>
6316 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6317 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6318 such a structure. The object distance has a type compatible with any other int object.
6320 <p><!--para 5 -->
6321 EXAMPLE 2 After the declarations
6322 <pre>
6323 typedef struct s1 { int x; } t1, *tp1;
6324 typedef struct s2 { int x; } t2, *tp2;</pre>
6325 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6326 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6327 <!--page 136 -->
6328 <p><!--para 6 -->
6329 EXAMPLE 3 The following obscure constructions
6330 <pre>
6331 typedef signed int t;
6332 typedef int plain;
6333 struct tag {
6334 unsigned t:4;
6335 const t:5;
6336 plain r:5;
6337 };</pre>
6338 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6339 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6340 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6341 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6342 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6343 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6344 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6345 in an inner scope by
6346 <pre>
6347 t f(t (t));
6348 long t;</pre>
6349 then a function f is declared with type ''function returning signed int with one unnamed parameter
6350 with type pointer to function returning signed int with one unnamed parameter with type signed
6351 int'', and an identifier t with type long int.
6353 <p><!--para 7 -->
6354 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6355 following declarations of the signal function specify exactly the same type, the first without making use
6356 of any typedef names.
6357 <pre>
6358 typedef void fv(int), (*pfv)(int);
6359 void (*signal(int, void (*)(int)))(int);
6360 fv *signal(int, fv *);
6361 pfv signal(int, pfv);</pre>
6363 <p><!--para 8 -->
6364 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6365 time the typedef name is defined, not each time it is used:
6366 <!--page 137 -->
6367 <pre>
6368 void copyt(int n)
6369 {
6370 typedef int B[n]; // B is n ints, n evaluated now
6371 n += 1;
6372 B a; // a is n ints, n without += 1
6373 int b[n]; // a and b are different sizes
6374 for (int i = 1; i < n; i++)
6375 a[i-1] = b[i];
6376 }</pre>
6379 <h6>Syntax</h6>
6380 <p><!--para 1 -->
6381 <pre>
6382 initializer:
6383 assignment-expression
6384 { initializer-list }
6385 { initializer-list , }
6386 initializer-list:
6387 designation<sub>opt</sub> initializer
6388 initializer-list , designation<sub>opt</sub> initializer
6389 designation:
6390 designator-list =
6391 designator-list:
6392 designator
6393 designator-list designator
6394 designator:
6395 [ constant-expression ]
6396 . identifier</pre>
6397 <h6>Constraints</h6>
6398 <p><!--para 2 -->
6399 No initializer shall attempt to provide a value for an object not contained within the entity
6400 being initialized.
6401 <p><!--para 3 -->
6402 The type of the entity to be initialized shall be an array of unknown size or an object type
6403 that is not a variable length array type.
6404 <p><!--para 4 -->
6405 All the expressions in an initializer for an object that has static storage duration shall be
6406 constant expressions or string literals.
6407 <p><!--para 5 -->
6408 If the declaration of an identifier has block scope, and the identifier has external or
6409 internal linkage, the declaration shall have no initializer for the identifier.
6410 <p><!--para 6 -->
6411 If a designator has the form
6412 <pre>
6413 [ constant-expression ]</pre>
6414 then the current object (defined below) shall have array type and the expression shall be
6415 an integer constant expression. If the array is of unknown size, any nonnegative value is
6416 valid.
6417 <p><!--para 7 -->
6418 If a designator has the form
6419 <pre>
6420 . identifier</pre>
6421 then the current object (defined below) shall have structure or union type and the
6422 identifier shall be the name of a member of that type.
6423 <!--page 138 -->
6424 <h6>Semantics</h6>
6425 <p><!--para 8 -->
6426 An initializer specifies the initial value stored in an object.
6427 <p><!--para 9 -->
6428 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6429 members of objects of structure and union type do not participate in initialization.
6430 Unnamed members of structure objects have indeterminate value even after initialization.
6431 <p><!--para 10 -->
6432 If an object that has automatic storage duration is not initialized explicitly, its value is
6433 indeterminate. If an object that has static storage duration is not initialized explicitly,
6434 then:
6435 <ul>
6436 <li> if it has pointer type, it is initialized to a null pointer;
6437 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6438 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6439 <li> if it is a union, the first named member is initialized (recursively) according to these
6440 rules.
6441 </ul>
6442 <p><!--para 11 -->
6443 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6444 initial value of the object is that of the expression (after conversion); the same type
6445 constraints and conversions as for simple assignment apply, taking the type of the scalar
6446 to be the unqualified version of its declared type.
6447 <p><!--para 12 -->
6448 The rest of this subclause deals with initializers for objects that have aggregate or union
6449 type.
6450 <p><!--para 13 -->
6451 The initializer for a structure or union object that has automatic storage duration shall be
6452 either an initializer list as described below, or a single expression that has compatible
6453 structure or union type. In the latter case, the initial value of the object, including
6454 unnamed members, is that of the expression.
6455 <p><!--para 14 -->
6456 An array of character type may be initialized by a character string literal, optionally
6457 enclosed in braces. Successive characters of the character string literal (including the
6458 terminating null character if there is room or if the array is of unknown size) initialize the
6459 elements of the array.
6460 <p><!--para 15 -->
6461 An array with element type compatible with wchar_t may be initialized by a wide
6462 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6463 literal (including the terminating null wide character if there is room or if the array is of
6464 unknown size) initialize the elements of the array.
6465 <p><!--para 16 -->
6466 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6467 enclosed list of initializers for the elements or named members.
6468 <p><!--para 17 -->
6469 Each brace-enclosed initializer list has an associated current object. When no
6470 designations are present, subobjects of the current object are initialized in order according
6471 to the type of the current object: array elements in increasing subscript order, structure
6472 <!--page 139 -->
6473 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6474 designation causes the following initializer to begin initialization of the subobject
6475 described by the designator. Initialization then continues forward in order, beginning
6476 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6477 <p><!--para 18 -->
6478 Each designator list begins its description with the current object associated with the
6479 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6480 particular member of its current object and changes the current object for the next
6481 designator (if any) to be that member.<sup><a href="#note131"><b>131)</b></a></sup> The current object that results at the end of the
6482 designator list is the subobject to be initialized by the following initializer.
6483 <p><!--para 19 -->
6484 The initialization shall occur in initializer list order, each initializer provided for a
6485 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6486 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6487 objects that have static storage duration.
6488 <p><!--para 20 -->
6489 If the aggregate or union contains elements or members that are aggregates or unions,
6490 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6491 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6492 that brace and its matching right brace initialize the elements or members of the
6493 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6494 taken to account for the elements or members of the subaggregate or the first member of
6495 the contained union; any remaining initializers are left to initialize the next element or
6496 member of the aggregate of which the current subaggregate or contained union is a part.
6497 <p><!--para 21 -->
6498 If there are fewer initializers in a brace-enclosed list than there are elements or members
6499 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6500 size than there are elements in the array, the remainder of the aggregate shall be
6501 initialized implicitly the same as objects that have static storage duration.
6502 <p><!--para 22 -->
6503 If an array of unknown size is initialized, its size is determined by the largest indexed
6504 element with an explicit initializer. At the end of its initializer list, the array no longer
6505 has incomplete type.
6509 <!--page 140 -->
6510 <p><!--para 23 -->
6511 The order in which any side effects occur among the initialization list expressions is
6513 <p><!--para 24 -->
6514 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6515 <pre>
6517 double complex c = 5 + 3 * I;</pre>
6518 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6520 <p><!--para 25 -->
6521 EXAMPLE 2 The declaration
6522 <pre>
6523 int x[] = { 1, 3, 5 };</pre>
6524 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6525 and there are three initializers.
6527 <p><!--para 26 -->
6528 EXAMPLE 3 The declaration
6529 <pre>
6530 int y[4][3] = {
6531 { 1, 3, 5 },
6532 { 2, 4, 6 },
6533 { 3, 5, 7 },
6534 };</pre>
6535 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6536 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6537 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6538 been achieved by
6539 <pre>
6540 int y[4][3] = {
6541 1, 3, 5, 2, 4, 6, 3, 5, 7
6542 };</pre>
6543 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6544 next three are taken successively for y[1] and y[2].
6546 <p><!--para 27 -->
6547 EXAMPLE 4 The declaration
6548 <pre>
6549 int z[4][3] = {
6550 { 1 }, { 2 }, { 3 }, { 4 }
6551 };</pre>
6552 initializes the first column of z as specified and initializes the rest with zeros.
6554 <p><!--para 28 -->
6555 EXAMPLE 5 The declaration
6556 <pre>
6557 struct { int a[3], b; } w[] = { { 1 }, 2 };</pre>
6558 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6559 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6564 <!--page 141 -->
6565 <p><!--para 29 -->
6566 EXAMPLE 6 The declaration
6567 <pre>
6568 short q[4][3][2] = {
6569 { 1 },
6570 { 2, 3 },
6571 { 4, 5, 6 }
6572 };</pre>
6573 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6574 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
6575 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6576 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6577 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6578 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6579 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6580 diagnostic message would have been issued. The same initialization result could have been achieved by:
6581 <pre>
6582 short q[4][3][2] = {
6583 1, 0, 0, 0, 0, 0,
6584 2, 3, 0, 0, 0, 0,
6585 4, 5, 6
6586 };</pre>
6587 or by:
6588 <pre>
6589 short q[4][3][2] = {
6590 {
6591 { 1 },
6592 },
6593 {
6594 { 2, 3 },
6595 },
6596 {
6597 { 4, 5 },
6598 { 6 },
6599 }
6600 };</pre>
6601 in a fully bracketed form.
6602 <p><!--para 30 -->
6603 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6604 cause confusion.
6606 <p><!--para 31 -->
6607 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6608 declaration
6609 <pre>
6610 typedef int A[]; // OK - declared with block scope</pre>
6611 the declaration
6612 <pre>
6613 A a = { 1, 2 }, b = { 3, 4, 5 };</pre>
6614 is identical to
6615 <pre>
6616 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };</pre>
6617 due to the rules for incomplete types.
6618 <!--page 142 -->
6619 <p><!--para 32 -->
6620 EXAMPLE 8 The declaration
6621 <pre>
6623 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6624 This declaration is identical to
6625 <pre>
6626 char s[] = { 'a', 'b', 'c', '\0' },
6627 t[] = { 'a', 'b', 'c' };</pre>
6628 The contents of the arrays are modifiable. On the other hand, the declaration
6629 <pre>
6631 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6632 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6633 modify the contents of the array, the behavior is undefined.
6635 <p><!--para 33 -->
6636 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6637 designators:
6638 <pre>
6639 enum { member_one, member_two };
6640 const char *nm[] = {
6643 };</pre>
6645 <p><!--para 34 -->
6646 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6647 <pre>
6648 div_t answer = { .quot = 2, .rem = -1 };</pre>
6650 <p><!--para 35 -->
6651 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6652 might be misunderstood:
6653 <pre>
6654 struct { int a[3], b; } w[] =
6655 { [0].a = {1}, [1].a[0] = 2 };</pre>
6657 <p><!--para 36 -->
6658 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6659 <p><!--para 37 -->
6660 <pre>
6661 int a[MAX] = {
6662 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6663 };</pre>
6664 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6665 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6667 <p><!--para 38 -->
6668 EXAMPLE 13 Any member of a union can be initialized:
6669 <pre>
6670 union { /* ... */ } u = { .any_member = 42 };</pre>
6672 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6673 <!--page 143 -->
6675 <h6>footnotes</h6>
6676 <p><small><a name="note129" href="#note129">129)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6677 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6678 current object: current objects are associated only with brace-enclosed initializer lists.
6679 </small>
6680 <p><small><a name="note130" href="#note130">130)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
6681 the next subobject of an object containing the union.
6682 </small>
6683 <p><small><a name="note131" href="#note131">131)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6684 the surrounding brace pair. Note, too, that each separate designator list is independent.
6685 </small>
6686 <p><small><a name="note132" href="#note132">132)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6687 not be evaluated at all.
6688 </small>
6689 <p><small><a name="note133" href="#note133">133)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
6690 </small>
6693 <h6>Syntax</h6>
6694 <p><!--para 1 -->
6695 <pre>
6696 statement:
6697 labeled-statement
6698 compound-statement
6699 expression-statement
6700 selection-statement
6701 iteration-statement
6702 jump-statement</pre>
6703 <h6>Semantics</h6>
6704 <p><!--para 2 -->
6705 A statement specifies an action to be performed. Except as indicated, statements are
6706 executed in sequence.
6707 <p><!--para 3 -->
6708 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6709 The initializers of objects that have automatic storage duration, and the variable length
6710 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6711 stored in the objects (including storing an indeterminate value in objects without an
6712 initializer) each time the declaration is reached in the order of execution, as if it were a
6713 statement, and within each declaration in the order that declarators appear.
6714 <p><!--para 4 -->
6715 A full expression is an expression that is not part of another expression or of a declarator.
6716 Each of the following is a full expression: an initializer; the expression in an expression
6717 statement; the controlling expression of a selection statement (if or switch); the
6718 controlling expression of a while or do statement; each of the (optional) expressions of
6719 a for statement; the (optional) expression in a return statement. The end of a full
6720 expression is a sequence point.
6721 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6722 (<a href="#6.8.4">6.8.4</a>), iteration statements (<a href="#6.8.5">6.8.5</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>).
6725 <h6>Syntax</h6>
6726 <p><!--para 1 -->
6727 <pre>
6728 labeled-statement:
6729 identifier : statement
6730 case constant-expression : statement
6731 default : statement</pre>
6732 <h6>Constraints</h6>
6733 <p><!--para 2 -->
6734 A case or default label shall appear only in a switch statement. Further
6735 constraints on such labels are discussed under the switch statement.
6736 <!--page 144 -->
6737 <p><!--para 3 -->
6738 Label names shall be unique within a function.
6739 <h6>Semantics</h6>
6740 <p><!--para 4 -->
6741 Any statement may be preceded by a prefix that declares an identifier as a label name.
6742 Labels in themselves do not alter the flow of control, which continues unimpeded across
6743 them.
6744 <p><b> Forward references</b>: the goto statement (<a href="#6.8.6.1">6.8.6.1</a>), the switch statement (<a href="#6.8.4.2">6.8.4.2</a>).
6747 <h6>Syntax</h6>
6748 <p><!--para 1 -->
6749 <pre>
6750 compound-statement:
6751 { block-item-list<sub>opt</sub> }
6752 block-item-list:
6753 block-item
6754 block-item-list block-item
6755 block-item:
6756 declaration
6757 statement</pre>
6758 <h6>Semantics</h6>
6759 <p><!--para 2 -->
6760 A compound statement is a block.
6763 <h6>Syntax</h6>
6764 <p><!--para 1 -->
6765 <pre>
6766 expression-statement:
6767 expression<sub>opt</sub> ;</pre>
6768 <h6>Semantics</h6>
6769 <p><!--para 2 -->
6770 The expression in an expression statement is evaluated as a void expression for its side
6772 <p><!--para 3 -->
6773 A null statement (consisting of just a semicolon) performs no operations.
6774 <p><!--para 4 -->
6775 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6776 discarding of its value may be made explicit by converting the expression to a void expression by means of
6777 a cast:
6778 <pre>
6779 int p(int);
6780 /* ... */
6781 (void)p(0);</pre>
6785 <!--page 145 -->
6786 <p><!--para 5 -->
6787 EXAMPLE 2 In the program fragment
6788 <pre>
6789 char *s;
6790 /* ... */
6791 while (*s++ != '\0')
6792 ;</pre>
6793 a null statement is used to supply an empty loop body to the iteration statement.
6795 <p><!--para 6 -->
6796 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6797 statement.
6798 <pre>
6799 while (loop1) {
6800 /* ... */
6801 while (loop2) {
6802 /* ... */
6803 if (want_out)
6804 goto end_loop1;
6805 /* ... */
6806 }
6807 /* ... */
6808 end_loop1: ;
6809 }</pre>
6813 <h6>footnotes</h6>
6814 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
6815 </small>
6818 <h6>Syntax</h6>
6819 <p><!--para 1 -->
6820 <pre>
6821 selection-statement:
6822 if ( expression ) statement
6823 if ( expression ) statement else statement
6824 switch ( expression ) statement</pre>
6825 <h6>Semantics</h6>
6826 <p><!--para 2 -->
6827 A selection statement selects among a set of statements depending on the value of a
6828 controlling expression.
6829 <p><!--para 3 -->
6830 A selection statement is a block whose scope is a strict subset of the scope of its
6831 enclosing block. Each associated substatement is also a block whose scope is a strict
6832 subset of the scope of the selection statement.
6835 <h6>Constraints</h6>
6836 <p><!--para 1 -->
6837 The controlling expression of an if statement shall have scalar type.
6838 <h6>Semantics</h6>
6839 <p><!--para 2 -->
6840 In both forms, the first substatement is executed if the expression compares unequal to 0.
6841 In the else form, the second substatement is executed if the expression compares equal
6842 <!--page 146 -->
6843 to 0. If the first substatement is reached via a label, the second substatement is not
6844 executed.
6845 <p><!--para 3 -->
6846 An else is associated with the lexically nearest preceding if that is allowed by the
6847 syntax.
6850 <h6>Constraints</h6>
6851 <p><!--para 1 -->
6852 The controlling expression of a switch statement shall have integer type.
6853 <p><!--para 2 -->
6854 If a switch statement has an associated case or default label within the scope of an
6855 identifier with a variably modified type, the entire switch statement shall be within the
6857 <p><!--para 3 -->
6858 The expression of each case label shall be an integer constant expression and no two of
6859 the case constant expressions in the same switch statement shall have the same value
6860 after conversion. There may be at most one default label in a switch statement.
6861 (Any enclosed switch statement may have a default label or case constant
6862 expressions with values that duplicate case constant expressions in the enclosing
6863 switch statement.)
6864 <h6>Semantics</h6>
6865 <p><!--para 4 -->
6866 A switch statement causes control to jump to, into, or past the statement that is the
6867 switch body, depending on the value of a controlling expression, and on the presence of a
6868 default label and the values of any case labels on or in the switch body. A case or
6869 default label is accessible only within the closest enclosing switch statement.
6870 <p><!--para 5 -->
6871 The integer promotions are performed on the controlling expression. The constant
6872 expression in each case label is converted to the promoted type of the controlling
6873 expression. If a converted value matches that of the promoted controlling expression,
6874 control jumps to the statement following the matched case label. Otherwise, if there is
6875 a default label, control jumps to the labeled statement. If no converted case constant
6876 expression matches and there is no default label, no part of the switch body is
6877 executed.
6878 <h6> Implementation limits</h6>
6879 <p><!--para 6 -->
6880 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, the implementation may limit the number of case values in a
6881 switch statement.
6886 <!--page 147 -->
6887 <p><!--para 7 -->
6888 EXAMPLE In the artificial program fragment
6889 <pre>
6890 switch (expr)
6891 {
6892 int i = 4;
6893 f(i);
6894 case 0:
6895 i = 17;
6896 /* falls through into default code */
6897 default:
6899 }</pre>
6900 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6901 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6902 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6905 <h6>footnotes</h6>
6906 <p><small><a name="note135" href="#note135">135)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
6907 default label associated with the switch that is in the block containing the declaration.
6908 </small>
6911 <h6>Syntax</h6>
6912 <p><!--para 1 -->
6913 <pre>
6914 iteration-statement:
6915 while ( expression ) statement
6916 do statement while ( expression ) ;
6917 for ( expression<sub>opt</sub> ; expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement
6918 for ( declaration expression<sub>opt</sub> ; expression<sub>opt</sub> ) statement</pre>
6919 <h6>Constraints</h6>
6920 <p><!--para 2 -->
6921 The controlling expression of an iteration statement shall have scalar type.
6922 <p><!--para 3 -->
6923 The declaration part of a for statement shall only declare identifiers for objects having
6924 storage class auto or register.
6925 <h6>Semantics</h6>
6926 <p><!--para 4 -->
6927 An iteration statement causes a statement called the loop body to be executed repeatedly
6928 until the controlling expression compares equal to 0. The repetition occurs regardless of
6929 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
6930 <p><!--para 5 -->
6931 An iteration statement is a block whose scope is a strict subset of the scope of its
6932 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6933 of the iteration statement.
6938 <!--page 148 -->
6940 <h6>footnotes</h6>
6941 <p><small><a name="note136" href="#note136">136)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
6942 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6943 </small>
6946 <p><!--para 1 -->
6947 The evaluation of the controlling expression takes place before each execution of the loop
6948 body.
6951 <p><!--para 1 -->
6952 The evaluation of the controlling expression takes place after each execution of the loop
6953 body.
6956 <p><!--para 1 -->
6957 The statement
6958 <pre>
6959 for ( clause-1 ; expression-2 ; expression-3 ) statement</pre>
6960 behaves as follows: The expression expression-2 is the controlling expression that is
6961 evaluated before each execution of the loop body. The expression expression-3 is
6962 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6963 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6964 the entire loop, including the other two expressions; it is reached in the order of execution
6965 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6966 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
6967 <p><!--para 2 -->
6968 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6969 nonzero constant.
6971 <h6>footnotes</h6>
6972 <p><small><a name="note137" href="#note137">137)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6973 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6974 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6975 specifies an operation (such as incrementing) that is performed after each iteration.
6976 </small>
6979 <h6>Syntax</h6>
6980 <p><!--para 1 -->
6981 <pre>
6982 jump-statement:
6983 goto identifier ;
6984 continue ;
6985 break ;
6986 return expression<sub>opt</sub> ;</pre>
6987 <h6>Semantics</h6>
6988 <p><!--para 2 -->
6989 A jump statement causes an unconditional jump to another place.
6994 <!--page 149 -->
6997 <h6>Constraints</h6>
6998 <p><!--para 1 -->
6999 The identifier in a goto statement shall name a label located somewhere in the enclosing
7000 function. A goto statement shall not jump from outside the scope of an identifier having
7001 a variably modified type to inside the scope of that identifier.
7002 <h6>Semantics</h6>
7003 <p><!--para 2 -->
7004 A goto statement causes an unconditional jump to the statement prefixed by the named
7005 label in the enclosing function.
7006 <p><!--para 3 -->
7007 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7008 following outline presents one possible approach to a problem based on these three assumptions:
7009 <ol>
7010 <li> The general initialization code accesses objects only visible to the current function.
7011 <li> The general initialization code is too large to warrant duplication.
7012 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7013 continue statements, for example.)
7014 <pre>
7015 /* ... */
7016 goto first_time;
7017 for (;;) {
7018 // determine next operation
7019 /* ... */
7020 if (need to reinitialize) {
7021 // reinitialize-only code
7022 /* ... */
7023 first_time:
7024 // general initialization code
7025 /* ... */
7026 continue;
7027 }
7028 // handle other operations
7029 /* ... */
7030 }</pre>
7031 <!--page 150 -->
7032 </ol>
7033 <p><!--para 4 -->
7034 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7035 modified types. A jump within the scope, however, is permitted.
7036 <pre>
7037 goto lab3; // invalid: going INTO scope of VLA.
7038 {
7039 double a[n];
7041 lab3:
7043 goto lab4; // valid: going WITHIN scope of VLA.
7045 lab4:
7047 }
7048 goto lab4; // invalid: going INTO scope of VLA.</pre>
7052 <h6>Constraints</h6>
7053 <p><!--para 1 -->
7054 A continue statement shall appear only in or as a loop body.
7055 <h6>Semantics</h6>
7056 <p><!--para 2 -->
7057 A continue statement causes a jump to the loop-continuation portion of the smallest
7058 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7059 of the statements
7060 <pre>
7061 while (/* ... */) { do { for (/* ... */) {
7062 /* ... */ /* ... */ /* ... */
7063 continue; continue; continue;
7064 /* ... */ /* ... */ /* ... */
7065 contin: ; contin: ; contin: ;
7066 } } while (/* ... */); }</pre>
7067 unless the continue statement shown is in an enclosed iteration statement (in which
7068 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7070 <h6>footnotes</h6>
7071 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7072 </small>
7075 <h6>Constraints</h6>
7076 <p><!--para 1 -->
7077 A break statement shall appear only in or as a switch body or loop body.
7078 <h6>Semantics</h6>
7079 <p><!--para 2 -->
7080 A break statement terminates execution of the smallest enclosing switch or iteration
7081 statement.
7085 <!--page 151 -->
7088 <h6>Constraints</h6>
7089 <p><!--para 1 -->
7090 A return statement with an expression shall not appear in a function whose return type
7091 is void. A return statement without an expression shall only appear in a function
7092 whose return type is void.
7093 <h6>Semantics</h6>
7094 <p><!--para 2 -->
7095 A return statement terminates execution of the current function and returns control to
7096 its caller. A function may have any number of return statements.
7097 <p><!--para 3 -->
7098 If a return statement with an expression is executed, the value of the expression is
7099 returned to the caller as the value of the function call expression. If the expression has a
7100 type different from the return type of the function in which it appears, the value is
7101 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7102 <p><!--para 4 -->
7103 EXAMPLE In:
7104 <pre>
7105 struct s { double i; } f(void);
7106 union {
7107 struct {
7108 int f1;
7109 struct s f2;
7110 } u1;
7111 struct {
7112 struct s f3;
7113 int f4;
7114 } u2;
7115 } g;
7116 struct s f(void)
7117 {
7118 return g.u1.f2;
7119 }
7120 /* ... */
7121 g.u2.f3 = f();</pre>
7122 there is no undefined behavior, although there would be if the assignment were done directly (without using
7123 a function call to fetch the value).
7128 <!--page 152 -->
7130 <h6>footnotes</h6>
7131 <p><small><a name="note139" href="#note139">139)</a> The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
7132 apply to the case of function return. The representation of floating-point values may have wider range
7133 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7134 range and precision.
7135 </small>
7138 <h6>Syntax</h6>
7139 <p><!--para 1 -->
7140 <pre>
7141 translation-unit:
7142 external-declaration
7143 translation-unit external-declaration
7144 external-declaration:
7145 function-definition
7146 declaration</pre>
7147 <h6>Constraints</h6>
7148 <p><!--para 2 -->
7149 The storage-class specifiers auto and register shall not appear in the declaration
7150 specifiers in an external declaration.
7151 <p><!--para 3 -->
7152 There shall be no more than one external definition for each identifier declared with
7153 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7154 linkage is used in an expression (other than as a part of the operand of a sizeof
7155 operator whose result is an integer constant), there shall be exactly one external definition
7156 for the identifier in the translation unit.
7157 <h6>Semantics</h6>
7158 <p><!--para 4 -->
7159 As discussed in <a href="#5.1.1.1">5.1.1.1</a>, the unit of program text after preprocessing is a translation unit,
7160 which consists of a sequence of external declarations. These are described as ''external''
7161 because they appear outside any function (and hence have file scope). As discussed in
7162 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7163 by the identifier is a definition.
7164 <p><!--para 5 -->
7165 An external definition is an external declaration that is also a definition of a function
7166 (other than an inline definition) or an object. If an identifier declared with external
7167 linkage is used in an expression (other than as part of the operand of a sizeof operator
7168 whose result is an integer constant), somewhere in the entire program there shall be
7169 exactly one external definition for the identifier; otherwise, there shall be no more than
7175 <!--page 153 -->
7177 <h6>footnotes</h6>
7178 <p><small><a name="note140" href="#note140">140)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
7179 external definition for it.
7180 </small>
7183 <h6>Syntax</h6>
7184 <p><!--para 1 -->
7185 <pre>
7186 function-definition:
7187 declaration-specifiers declarator declaration-list<sub>opt</sub> compound-statement
7188 declaration-list:
7189 declaration
7190 declaration-list declaration</pre>
7191 <h6>Constraints</h6>
7192 <p><!--para 2 -->
7193 The identifier declared in a function definition (which is the name of the function) shall
7194 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7195 <p><!--para 3 -->
7196 The return type of a function shall be void or an object type other than array type.
7197 <p><!--para 4 -->
7198 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7199 static.
7200 <p><!--para 5 -->
7201 If the declarator includes a parameter type list, the declaration of each parameter shall
7202 include an identifier, except for the special case of a parameter list consisting of a single
7203 parameter of type void, in which case there shall not be an identifier. No declaration list
7204 shall follow.
7205 <p><!--para 6 -->
7206 If the declarator includes an identifier list, each declaration in the declaration list shall
7207 have at least one declarator, those declarators shall declare only identifiers from the
7208 identifier list, and every identifier in the identifier list shall be declared. An identifier
7209 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7210 declaration list shall contain no storage-class specifier other than register and no
7211 initializations.
7216 <!--page 154 -->
7217 <h6>Semantics</h6>
7218 <p><!--para 7 -->
7219 The declarator in a function definition specifies the name of the function being defined
7220 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7221 list also specifies the types of all the parameters; such a declarator also serves as a
7222 function prototype for later calls to the same function in the same translation unit. If the
7223 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7224 following declaration list. In either case, the type of each parameter is adjusted as
7225 described in <a href="#6.7.5.3">6.7.5.3</a> for a parameter type list; the resulting type shall be an object type.
7226 <p><!--para 8 -->
7227 If a function that accepts a variable number of arguments is defined without a parameter
7228 type list that ends with the ellipsis notation, the behavior is undefined.
7229 <p><!--para 9 -->
7230 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7231 effect declared at the head of the compound statement that constitutes the function body
7232 (and therefore cannot be redeclared in the function body except in an enclosed block).
7233 The layout of the storage for parameters is unspecified.
7234 <p><!--para 10 -->
7235 On entry to the function, the size expressions of each variably modified parameter are
7236 evaluated and the value of each argument expression is converted to the type of the
7237 corresponding parameter as if by assignment. (Array expressions and function
7238 designators as arguments were converted to pointers before the call.)
7239 <p><!--para 11 -->
7240 After all parameters have been assigned, the compound statement that constitutes the
7241 body of the function definition is executed.
7242 <p><!--para 12 -->
7243 If the } that terminates a function is reached, and the value of the function call is used by
7244 the caller, the behavior is undefined.
7245 <p><!--para 13 -->
7246 EXAMPLE 1 In the following:
7247 <pre>
7248 extern int max(int a, int b)
7249 {
7250 return a > b ? a : b;
7251 }</pre>
7252 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7253 function declarator; and
7254 <pre>
7255 { return a > b ? a : b; }</pre>
7256 is the function body. The following similar definition uses the identifier-list form for the parameter
7257 declarations:
7262 <!--page 155 -->
7263 <pre>
7264 extern int max(a, b)
7265 int a, b;
7266 {
7267 return a > b ? a : b;
7268 }</pre>
7269 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7270 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7271 to the function, whereas the second form does not.
7273 <p><!--para 14 -->
7274 EXAMPLE 2 To pass one function to another, one might say
7275 <pre>
7276 int f(void);
7277 /* ... */
7278 g(f);</pre>
7279 Then the definition of g might read
7280 <pre>
7281 void g(int (*funcp)(void))
7282 {
7283 /* ... */
7284 (*funcp)(); /* or funcp(); ... */
7285 }</pre>
7286 or, equivalently,
7287 <pre>
7288 void g(int func(void))
7289 {
7290 /* ... */
7291 func(); /* or (*func)(); ... */
7292 }</pre>
7295 <h6>footnotes</h6>
7296 <p><small><a name="note141" href="#note141">141)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
7298 <pre>
7299 typedef int F(void); // type F is ''function with no parameters
7300 // returning int''
7301 F f, g; // f and g both have type compatible with F
7302 F f { /* ... */ } // WRONG: syntax/constraint error
7303 F g() { /* ... */ } // WRONG: declares that g returns a function
7304 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7305 int g() { /* ... */ } // RIGHT: g has type compatible with F
7306 F *e(void) { /* ... */ } // e returns a pointer to a function
7307 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7308 int (*fp)(void); // fp points to a function that has type F
7309 F *Fp; // Fp points to a function that has type F</pre>
7310 </small>
7311 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7312 </small>
7315 <h6>Semantics</h6>
7316 <p><!--para 1 -->
7317 If the declaration of an identifier for an object has file scope and an initializer, the
7318 declaration is an external definition for the identifier.
7319 <p><!--para 2 -->
7320 A declaration of an identifier for an object that has file scope without an initializer, and
7321 without a storage-class specifier or with the storage-class specifier static, constitutes a
7322 tentative definition. If a translation unit contains one or more tentative definitions for an
7323 identifier, and the translation unit contains no external definition for that identifier, then
7324 the behavior is exactly as if the translation unit contains a file scope declaration of that
7325 identifier, with the composite type as of the end of the translation unit, with an initializer
7326 equal to 0.
7327 <p><!--para 3 -->
7328 If the declaration of an identifier for an object is a tentative definition and has internal
7329 linkage, the declared type shall not be an incomplete type.
7330 <!--page 156 -->
7331 <p><!--para 4 -->
7332 EXAMPLE 1
7333 <pre>
7334 int i1 = 1; // definition, external linkage
7335 static int i2 = 2; // definition, internal linkage
7336 extern int i3 = 3; // definition, external linkage
7337 int i4; // tentative definition, external linkage
7338 static int i5; // tentative definition, internal linkage
7339 int i1; // valid tentative definition, refers to previous
7341 int i3; // valid tentative definition, refers to previous
7342 int i4; // valid tentative definition, refers to previous
7344 extern int i1; // refers to previous, whose linkage is external
7345 extern int i2; // refers to previous, whose linkage is internal
7346 extern int i3; // refers to previous, whose linkage is external
7347 extern int i4; // refers to previous, whose linkage is external
7348 extern int i5; // refers to previous, whose linkage is internal</pre>
7350 <p><!--para 5 -->
7351 EXAMPLE 2 If at the end of the translation unit containing
7352 <pre>
7353 int i[];</pre>
7354 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7355 zero on program startup.
7356 <!--page 157 -->
7359 <h6>Syntax</h6>
7360 <p><!--para 1 -->
7361 <!--page 158 -->
7362 <pre>
7363 preprocessing-file:
7364 group<sub>opt</sub>
7365 group:
7366 group-part
7367 group group-part
7368 group-part:
7369 if-section
7370 control-line
7371 text-line
7372 # non-directive
7373 if-section:
7374 if-group elif-groups<sub>opt</sub> else-group<sub>opt</sub> endif-line
7375 if-group:
7376 # if constant-expression new-line group<sub>opt</sub>
7377 # ifdef identifier new-line group<sub>opt</sub>
7378 # ifndef identifier new-line group<sub>opt</sub>
7379 elif-groups:
7380 elif-group
7381 elif-groups elif-group
7382 elif-group:
7383 # elif constant-expression new-line group<sub>opt</sub>
7384 else-group:
7385 # else new-line group<sub>opt</sub>
7386 endif-line:
7387 # endif new-line
7388 control-line:
7389 # include pp-tokens new-line
7390 # define identifier replacement-list new-line
7391 # define identifier lparen identifier-list<sub>opt</sub> )
7392 replacement-list new-line
7393 # define identifier lparen ... ) replacement-list new-line
7394 # define identifier lparen identifier-list , ... )
7395 replacement-list new-line
7396 # undef identifier new-line
7397 # line pp-tokens new-line
7398 # error pp-tokens<sub>opt</sub> new-line
7399 # pragma pp-tokens<sub>opt</sub> new-line
7400 # new-line
7401 text-line:
7402 pp-tokens<sub>opt</sub> new-line
7403 non-directive:
7404 pp-tokens new-line
7405 lparen:
7406 a ( character not immediately preceded by white-space
7407 replacement-list:
7408 pp-tokens<sub>opt</sub>
7409 pp-tokens:
7410 preprocessing-token
7411 pp-tokens preprocessing-token
7412 new-line:
7413 the new-line character</pre>
7414 <h6>Description</h6>
7415 <p><!--para 2 -->
7416 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7417 following constraints: The first token in the sequence is a # preprocessing token that (at
7418 the start of translation phase 4) is either the first character in the source file (optionally
7419 after white space containing no new-line characters) or that follows white space
7420 containing at least one new-line character. The last token in the sequence is the first new-
7421 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7422 the preprocessing directive even if it occurs within what would otherwise be an
7424 <!--page 159 -->
7425 invocation of a function-like macro.
7426 <p><!--para 3 -->
7427 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7428 with any of the directive names appearing in the syntax.
7429 <p><!--para 4 -->
7430 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7431 sequence of preprocessing tokens to occur between the directive name and the following
7432 new-line character.
7433 <h6>Constraints</h6>
7434 <p><!--para 5 -->
7435 The only white-space characters that shall appear between preprocessing tokens within a
7436 preprocessing directive (from just after the introducing # preprocessing token through
7437 just before the terminating new-line character) are space and horizontal-tab (including
7438 spaces that have replaced comments or possibly other white-space characters in
7439 translation phase 3).
7440 <h6>Semantics</h6>
7441 <p><!--para 6 -->
7442 The implementation can process and skip sections of source files conditionally, include
7443 other source files, and replace macros. These capabilities are called preprocessing,
7444 because conceptually they occur before translation of the resulting translation unit.
7445 <p><!--para 7 -->
7446 The preprocessing tokens within a preprocessing directive are not subject to macro
7447 expansion unless otherwise stated.
7448 <p><!--para 8 -->
7449 EXAMPLE In:
7450 <pre>
7451 #define EMPTY
7452 EMPTY # include <file.h></pre>
7453 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7454 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7455 replaced.
7458 <h6>footnotes</h6>
7459 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7460 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7461 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7462 </small>
7465 <h6>Constraints</h6>
7466 <p><!--para 1 -->
7467 The expression that controls conditional inclusion shall be an integer constant expression
7468 except that: it shall not contain a cast; identifiers (including those lexically identical to
7469 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7470 expressions of the form
7475 <!--page 160 -->
7476 <pre>
7477 defined identifier</pre>
7478 or
7479 <pre>
7480 defined ( identifier )</pre>
7481 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7482 predefined or if it has been the subject of a #define preprocessing directive without an
7483 intervening #undef directive with the same subject identifier), 0 if it is not.
7484 <p><!--para 2 -->
7485 Each preprocessing token that remains (in the list of preprocessing tokens that will
7486 become the controlling expression) after all macro replacements have occurred shall be in
7488 <h6>Semantics</h6>
7489 <p><!--para 3 -->
7490 Preprocessing directives of the forms
7491 <pre>
7492 # if constant-expression new-line group<sub>opt</sub>
7493 # elif constant-expression new-line group<sub>opt</sub></pre>
7494 check whether the controlling constant expression evaluates to nonzero.
7495 <p><!--para 4 -->
7496 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7497 the controlling constant expression are replaced (except for those macro names modified
7498 by the defined unary operator), just as in normal text. If the token defined is
7499 generated as a result of this replacement process or use of the defined unary operator
7500 does not match one of the two specified forms prior to macro replacement, the behavior is
7501 undefined. After all replacements due to macro expansion and the defined unary
7502 operator have been performed, all remaining identifiers (including those lexically
7503 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7504 token is converted into a token. The resulting tokens compose the controlling constant
7505 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7506 token conversion and evaluation, all signed integer types and all unsigned integer types
7507 act as if they have the same representation as, respectively, the types intmax_t and
7508 uintmax_t defined in the header <a href="#7.18"><stdint.h></a>.<sup><a href="#note145"><b>145)</b></a></sup> This includes interpreting
7509 character constants, which may involve converting escape sequences into execution
7510 character set members. Whether the numeric value for these character constants matches
7511 the value obtained when an identical character constant occurs in an expression (other
7512 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7513 single-character character constant may have a negative value is implementation-defined.
7514 <p><!--para 5 -->
7515 Preprocessing directives of the forms
7519 <!--page 161 -->
7520 <pre>
7521 # ifdef identifier new-line group<sub>opt</sub>
7522 # ifndef identifier new-line group<sub>opt</sub></pre>
7523 check whether the identifier is or is not currently defined as a macro name. Their
7524 conditions are equivalent to #if defined identifier and #if !defined identifier
7525 respectively.
7526 <p><!--para 6 -->
7527 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7528 that it controls is skipped: directives are processed only through the name that determines
7529 the directive in order to keep track of the level of nested conditionals; the rest of the
7530 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7531 group. Only the first group whose control condition evaluates to true (nonzero) is
7532 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7533 group controlled by the #else is processed; lacking a #else directive, all the groups
7535 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
7538 <h6>footnotes</h6>
7539 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7540 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7541 </small>
7542 <p><small><a name="note145" href="#note145">145)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7543 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7544 translation phase 7.
7545 </small>
7546 <p><small><a name="note146" href="#note146">146)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7547 evaluate to the same value in these two contexts.
7548 <pre>
7549 #if 'z' - 'a' == 25
7550 if ('z' - 'a' == 25)</pre>
7552 </small>
7553 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7554 before the terminating new-line character. However, comments may appear anywhere in a source file,
7555 including within a preprocessing directive.
7556 </small>
7559 <h6>Constraints</h6>
7560 <p><!--para 1 -->
7561 A #include directive shall identify a header or source file that can be processed by the
7562 implementation.
7563 <h6>Semantics</h6>
7564 <p><!--para 2 -->
7565 A preprocessing directive of the form
7566 <pre>
7567 # include <h-char-sequence> new-line</pre>
7568 searches a sequence of implementation-defined places for a header identified uniquely by
7569 the specified sequence between the < and > delimiters, and causes the replacement of that
7570 directive by the entire contents of the header. How the places are specified or the header
7571 identified is implementation-defined.
7572 <p><!--para 3 -->
7573 A preprocessing directive of the form
7577 <!--page 162 -->
7578 <pre>
7580 causes the replacement of that directive by the entire contents of the source file identified
7581 by the specified sequence between the " delimiters. The named source file is searched
7582 for in an implementation-defined manner. If this search is not supported, or if the search
7583 fails, the directive is reprocessed as if it read
7584 <pre>
7586 with the identical contained sequence (including > characters, if any) from the original
7587 directive.
7589 A preprocessing directive of the form
7590 <pre>
7591 # include pp-tokens new-line</pre>
7592 (that does not match one of the two previous forms) is permitted. The preprocessing
7593 tokens after include in the directive are processed just as in normal text. (Each
7594 identifier currently defined as a macro name is replaced by its replacement list of
7595 preprocessing tokens.) The directive resulting after all replacements shall match one of
7596 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7597 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7598 single header name preprocessing token is implementation-defined.
7599 <p><!--para 5 -->
7600 The implementation shall provide unique mappings for sequences consisting of one or
7601 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7602 first character shall not be a digit. The implementation may ignore distinctions of
7603 alphabetical case and restrict the mapping to eight significant characters before the
7604 period.
7605 <p><!--para 6 -->
7606 A #include preprocessing directive may appear in a source file that has been read
7607 because of a #include directive in another file, up to an implementation-defined
7609 <p><!--para 7 -->
7610 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7611 <pre>
7615 <p><!--para 8 -->
7616 EXAMPLE 2 This illustrates macro-replaced #include directives:
7621 <!--page 163 -->
7622 <pre>
7623 #if VERSION == 1
7625 #elif VERSION == 2
7627 #else
7629 #endif
7630 #include INCFILE</pre>
7634 <h6>footnotes</h6>
7635 <p><small><a name="note148" href="#note148">148)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7636 phases in <a href="#5.1.1.2">5.1.1.2</a>); thus, an expansion that results in two string literals is an invalid directive.
7637 </small>
7640 <h6>Constraints</h6>
7641 <p><!--para 1 -->
7642 Two replacement lists are identical if and only if the preprocessing tokens in both have
7643 the same number, ordering, spelling, and white-space separation, where all white-space
7644 separations are considered identical.
7645 <p><!--para 2 -->
7646 An identifier currently defined as an object-like macro shall not be redefined by another
7647 #define preprocessing directive unless the second definition is an object-like macro
7648 definition and the two replacement lists are identical. Likewise, an identifier currently
7649 defined as a function-like macro shall not be redefined by another #define
7650 preprocessing directive unless the second definition is a function-like macro definition
7651 that has the same number and spelling of parameters, and the two replacement lists are
7652 identical.
7653 <p><!--para 3 -->
7654 There shall be white-space between the identifier and the replacement list in the definition
7655 of an object-like macro.
7656 <p><!--para 4 -->
7657 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7658 arguments (including those arguments consisting of no preprocessing tokens) in an
7659 invocation of a function-like macro shall equal the number of parameters in the macro
7660 definition. Otherwise, there shall be more arguments in the invocation than there are
7661 parameters in the macro definition (excluding the ...). There shall exist a )
7662 preprocessing token that terminates the invocation.
7663 <p><!--para 5 -->
7664 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7665 macro that uses the ellipsis notation in the parameters.
7666 <p><!--para 6 -->
7667 A parameter identifier in a function-like macro shall be uniquely declared within its
7668 scope.
7669 <h6>Semantics</h6>
7670 <p><!--para 7 -->
7671 The identifier immediately following the define is called the macro name. There is one
7672 name space for macro names. Any white-space characters preceding or following the
7673 replacement list of preprocessing tokens are not considered part of the replacement list
7674 for either form of macro.
7675 <!--page 164 -->
7676 <p><!--para 8 -->
7677 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7678 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7679 <p><!--para 9 -->
7680 A preprocessing directive of the form
7681 <pre>
7682 # define identifier replacement-list new-line</pre>
7683 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
7684 to be replaced by the replacement list of preprocessing tokens that constitute the
7685 remainder of the directive. The replacement list is then rescanned for more macro names
7686 as specified below.
7687 <p><!--para 10 -->
7688 A preprocessing directive of the form
7689 <pre>
7690 # define identifier lparen identifier-list<sub>opt</sub> ) replacement-list new-line
7691 # define identifier lparen ... ) replacement-list new-line
7692 # define identifier lparen identifier-list , ... ) replacement-list new-line</pre>
7693 defines a function-like macro with parameters, whose use is similar syntactically to a
7694 function call. The parameters are specified by the optional list of identifiers, whose scope
7695 extends from their declaration in the identifier list until the new-line character that
7696 terminates the #define preprocessing directive. Each subsequent instance of the
7697 function-like macro name followed by a ( as the next preprocessing token introduces the
7698 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7699 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7700 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7701 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7702 tokens making up an invocation of a function-like macro, new-line is considered a normal
7703 white-space character.
7704 <p><!--para 11 -->
7705 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7706 forms the list of arguments for the function-like macro. The individual arguments within
7707 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7708 between matching inner parentheses do not separate arguments. If there are sequences of
7709 preprocessing tokens within the list of arguments that would otherwise act as
7710 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
7711 <p><!--para 12 -->
7712 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7713 including any separating comma preprocessing tokens, are merged to form a single item:
7714 the variable arguments. The number of arguments so combined is such that, following
7717 <!--page 165 -->
7718 merger, the number of arguments is one more than the number of parameters in the macro
7719 definition (excluding the ...).
7721 <h6>footnotes</h6>
7722 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7723 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7724 are never scanned for macro names or parameters.
7725 </small>
7726 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
7727 </small>
7730 <p><!--para 1 -->
7731 After the arguments for the invocation of a function-like macro have been identified,
7732 argument substitution takes place. A parameter in the replacement list, unless preceded
7733 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7734 replaced by the corresponding argument after all macros contained therein have been
7735 expanded. Before being substituted, each argument's preprocessing tokens are
7736 completely macro replaced as if they formed the rest of the preprocessing file; no other
7737 preprocessing tokens are available.
7738 <p><!--para 2 -->
7739 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7740 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7741 replace it.
7744 <h6>Constraints</h6>
7745 <p><!--para 1 -->
7746 Each # preprocessing token in the replacement list for a function-like macro shall be
7747 followed by a parameter as the next preprocessing token in the replacement list.
7748 <h6>Semantics</h6>
7749 <p><!--para 2 -->
7750 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7751 token, both are replaced by a single character string literal preprocessing token that
7752 contains the spelling of the preprocessing token sequence for the corresponding
7753 argument. Each occurrence of white space between the argument's preprocessing tokens
7754 becomes a single space character in the character string literal. White space before the
7755 first preprocessing token and after the last preprocessing token composing the argument
7756 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7757 is retained in the character string literal, except for special handling for producing the
7758 spelling of string literals and character constants: a \ character is inserted before each "
7759 and \ character of a character constant or string literal (including the delimiting "
7760 characters), except that it is implementation-defined whether a \ character is inserted
7761 before the \ character beginning a universal character name. If the replacement that
7762 results is not a valid character string literal, the behavior is undefined. The character
7764 ## operators is unspecified.
7765 <!--page 166 -->
7768 <h6>Constraints</h6>
7769 <p><!--para 1 -->
7770 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7771 list for either form of macro definition.
7772 <h6>Semantics</h6>
7773 <p><!--para 2 -->
7774 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7775 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7776 argument's preprocessing token sequence; however, if an argument consists of no
7777 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7779 <p><!--para 3 -->
7780 For both object-like and function-like macro invocations, before the replacement list is
7781 reexamined for more macro names to replace, each instance of a ## preprocessing token
7782 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7783 token is concatenated with the following preprocessing token. Placemarker
7784 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7785 a single placemarker preprocessing token, and concatenation of a placemarker with a
7786 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7787 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7788 token is available for further macro replacement. The order of evaluation of ## operators
7789 is unspecified.
7790 <p><!--para 4 -->
7791 EXAMPLE In the following fragment:
7792 <pre>
7793 #define hash_hash # ## #
7794 #define mkstr(a) # a
7795 #define in_between(a) mkstr(a)
7796 #define join(c, d) in_between(c hash_hash d)
7797 char p[] = join(x, y); // equivalent to
7799 The expansion produces, at various stages:
7800 <pre>
7801 join(x, y)
7802 in_between(x hash_hash y)
7803 in_between(x ## y)
7804 mkstr(x ## y)
7806 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7807 this new token is not the ## operator.
7810 <!--page 167 -->
7812 <h6>footnotes</h6>
7813 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7814 exist only within translation phase 4.
7815 </small>
7818 <p><!--para 1 -->
7819 After all parameters in the replacement list have been substituted and # and ##
7820 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
7821 resulting preprocessing token sequence is rescanned, along with all subsequent
7822 preprocessing tokens of the source file, for more macro names to replace.
7823 <p><!--para 2 -->
7824 If the name of the macro being replaced is found during this scan of the replacement list
7825 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7826 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7827 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7828 available for further replacement even if they are later (re)examined in contexts in which
7829 that macro name preprocessing token would otherwise have been replaced.
7830 <p><!--para 3 -->
7831 The resulting completely macro-replaced preprocessing token sequence is not processed
7832 as a preprocessing directive even if it resembles one, but all pragma unary operator
7836 <p><!--para 1 -->
7837 A macro definition lasts (independent of block structure) until a corresponding #undef
7838 directive is encountered or (if none is encountered) until the end of the preprocessing
7839 translation unit. Macro definitions have no significance after translation phase 4.
7840 <p><!--para 2 -->
7841 A preprocessing directive of the form
7842 <pre>
7843 # undef identifier new-line</pre>
7844 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7845 the specified identifier is not currently defined as a macro name.
7846 <p><!--para 3 -->
7847 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7848 <pre>
7849 #define TABSIZE 100
7850 int table[TABSIZE];</pre>
7852 <p><!--para 4 -->
7853 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7854 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7855 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7856 arguments a second time (including side effects) and generating more code than a function if invoked
7857 several times. It also cannot have its address taken, as it has none.
7858 <pre>
7859 #define max(a, b) ((a) > (b) ? (a) : (b))</pre>
7860 The parentheses ensure that the arguments and the resulting expression are bound properly.
7861 <!--page 168 -->
7862 <p><!--para 5 -->
7863 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7864 <pre>
7865 #define x 3
7866 #define f(a) f(x * (a))
7867 #undef x
7868 #define x 2
7869 #define g f
7870 #define z z[0]
7871 #define h g(~
7872 #define m(a) a(w)
7873 #define w 0,1
7874 #define t(a) a
7875 #define p() int
7876 #define q(x) x
7877 #define r(x,y) x ## y
7878 #define str(x) # x
7879 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7880 g(x+(3,4)-w) | h 5) & m
7881 (f)^m(m);
7882 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7883 char c[2][6] = { str(hello), str() };</pre>
7884 results in
7885 <pre>
7886 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7887 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7888 int i[] = { 1, 23, 4, 5, };
7891 <p><!--para 6 -->
7892 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7893 sequence
7894 <pre>
7895 #define str(s) # s
7896 #define xstr(s) str(s)
7898 x ## s, x ## t)
7899 #define INCFILE(n) vers ## n
7900 #define glue(a, b) a ## b
7901 #define xglue(a, b) glue(a, b)
7904 debug(1, 2);
7906 == 0) str(: @\n), s);
7907 #include xstr(INCFILE(2).h)
7908 glue(HIGH, LOW);
7909 xglue(HIGH, LOW)</pre>
7910 results in
7911 <!--page 169 -->
7912 <pre>
7914 fputs(
7916 s);
7920 or, after concatenation of the character string literals,
7921 <pre>
7923 fputs(
7925 s);
7929 Space around the # and ## tokens in the macro definition is optional.
7931 <p><!--para 7 -->
7932 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7933 <pre>
7934 #define t(x,y,z) x ## y ## z
7935 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7936 t(10,,), t(,11,), t(,,12), t(,,) };</pre>
7937 results in
7938 <pre>
7939 int j[] = { 123, 45, 67, 89,
7940 10, 11, 12, };</pre>
7942 <p><!--para 8 -->
7943 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7944 <pre>
7945 #define OBJ_LIKE (1-1)
7946 #define OBJ_LIKE /* white space */ (1-1) /* other */
7947 #define FUNC_LIKE(a) ( a )
7948 #define FUNC_LIKE( a )( /* note the white space */ \
7949 a /* other stuff on this line
7950 */ )</pre>
7951 But the following redefinitions are invalid:
7952 <pre>
7953 #define OBJ_LIKE (0) // different token sequence
7954 #define OBJ_LIKE (1 - 1) // different white space
7955 #define FUNC_LIKE(b) ( a ) // different parameter usage
7956 #define FUNC_LIKE(b) ( b ) // different parameter spelling</pre>
7958 <p><!--para 9 -->
7959 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7960 <!--page 170 -->
7961 <pre>
7962 #define debug(...) fprintf(stderr, __VA_ARGS__)
7963 #define showlist(...) puts(#__VA_ARGS__)
7964 #define report(test, ...) ((test)?puts(#test):\
7965 printf(__VA_ARGS__))
7968 showlist(The first, second, and third items.);
7970 results in
7971 <pre>
7980 <h6>Constraints</h6>
7981 <p><!--para 1 -->
7982 The string literal of a #line directive, if present, shall be a character string literal.
7983 <h6>Semantics</h6>
7984 <p><!--para 2 -->
7985 The line number of the current source line is one greater than the number of new-line
7986 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7987 file to the current token.
7988 <p><!--para 3 -->
7989 A preprocessing directive of the form
7990 <pre>
7991 # line digit-sequence new-line</pre>
7992 causes the implementation to behave as if the following sequence of source lines begins
7993 with a source line that has a line number as specified by the digit sequence (interpreted as
7994 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7995 2147483647.
7996 <p><!--para 4 -->
7997 A preprocessing directive of the form
7998 <pre>
8000 sets the presumed line number similarly and changes the presumed name of the source
8001 file to be the contents of the character string literal.
8002 <p><!--para 5 -->
8003 A preprocessing directive of the form
8004 <pre>
8005 # line pp-tokens new-line</pre>
8006 (that does not match one of the two previous forms) is permitted. The preprocessing
8007 tokens after line on the directive are processed just as in normal text (each identifier
8008 currently defined as a macro name is replaced by its replacement list of preprocessing
8009 tokens). The directive resulting after all replacements shall match one of the two
8010 previous forms and is then processed as appropriate.
8011 <!--page 171 -->
8014 <h6>Semantics</h6>
8015 <p><!--para 1 -->
8016 A preprocessing directive of the form
8017 <pre>
8018 # error pp-tokens<sub>opt</sub> new-line</pre>
8019 causes the implementation to produce a diagnostic message that includes the specified
8020 sequence of preprocessing tokens.
8023 <h6>Semantics</h6>
8024 <p><!--para 1 -->
8025 A preprocessing directive of the form
8026 <pre>
8027 # pragma pp-tokens<sub>opt</sub> new-line</pre>
8028 where the preprocessing token STDC does not immediately follow pragma in the
8029 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8030 implementation-defined manner. The behavior might cause translation to fail or cause the
8031 translator or the resulting program to behave in a non-conforming manner. Any such
8032 pragma that is not recognized by the implementation is ignored.
8033 <p><!--para 2 -->
8034 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8035 to any macro replacement), then no macro replacement is performed on the directive, and
8036 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8037 elsewhere:
8038 <pre>
8039 #pragma STDC FP_CONTRACT on-off-switch
8040 #pragma STDC FENV_ACCESS on-off-switch
8041 #pragma STDC CX_LIMITED_RANGE on-off-switch
8042 on-off-switch: one of
8043 ON OFF DEFAULT</pre>
8044 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8050 <!--page 172 -->
8052 <h6>footnotes</h6>
8053 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8054 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8055 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8056 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8057 but is not required to.
8058 </small>
8059 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8060 </small>
8063 <h6>Semantics</h6>
8064 <p><!--para 1 -->
8065 A preprocessing directive of the form
8066 <pre>
8067 # new-line</pre>
8068 has no effect.
8071 <p><!--para 1 -->
8072 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8073 <dl>
8074 <dt> __DATE__ <dd>The date of translation of the preprocessing translation unit: a character
8076 months are the same as those generated by the asctime function, and the
8077 first character of dd is a space character if the value is less than 10. If the
8078 date of translation is not available, an implementation-defined valid date
8079 shall be supplied.
8080 <dt> __FILE__ <dd>The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8081 <dt> __LINE__ <dd>The presumed line number (within the current source file) of the current
8083 <dt> __STDC__ <dd>The integer constant 1, intended to indicate a conforming implementation.
8084 <dt> __STDC_HOSTED__ <dd>The integer constant 1 if the implementation is a hosted
8085 implementation or the integer constant 0 if it is not.
8086 <dt> __STDC_MB_MIGHT_NEQ_WC__ <dd>The integer constant 1, intended to indicate that, in
8087 the encoding for wchar_t, a member of the basic character set need not
8088 have a code value equal to its value when used as the lone character in an
8089 integer character constant.
8090 <dt> __STDC_VERSION__ <dd>The integer constant 199901L.<sup><a href="#note156"><b>156)</b></a></sup>
8091 <dt> __TIME__ <dd>The time of translation of the preprocessing translation unit: a character
8093 asctime function. If the time of translation is not available, an
8094 implementation-defined valid time shall be supplied.
8095 </dl>
8098 <!--page 173 -->
8099 <p><!--para 2 -->
8100 The following macro names are conditionally defined by the implementation:
8101 <dl>
8102 <dt> __STDC_IEC_559__ <dd>The integer constant 1, intended to indicate conformance to the
8104 <dt> __STDC_IEC_559_COMPLEX__ <dd>The integer constant 1, intended to indicate
8106 compatible complex arithmetic).
8107 <dt> __STDC_ISO_10646__ <dd>An integer constant of the form yyyymmL (for example,
8108 199712L). If this symbol is defined, then every character in the Unicode
8109 required set, when stored in an object of type wchar_t, has the same
8110 value as the short identifier of that character. The Unicode required set
8111 consists of all the characters that are defined by ISO/IEC 10646, along with
8112 all amendments and technical corrigenda, as of the specified year and
8113 month.
8114 </dl>
8115 <p><!--para 3 -->
8116 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8117 constant throughout the translation unit.
8118 <p><!--para 4 -->
8119 None of these macro names, nor the identifier defined, shall be the subject of a
8120 #define or a #undef preprocessing directive. Any other predefined macro names
8121 shall begin with a leading underscore followed by an uppercase letter or a second
8122 underscore.
8123 <p><!--para 5 -->
8124 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8125 in any standard header.
8126 <p><b> Forward references</b>: the asctime function (<a href="#7.23.3.1">7.23.3.1</a>), standard headers (<a href="#7.1.2">7.1.2</a>).
8128 <h6>footnotes</h6>
8129 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8130 </small>
8131 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8132 </small>
8133 <p><small><a name="note156" href="#note156">156)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
8134 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8135 int that is increased with each revision of this International Standard.
8136 </small>
8139 <h6>Semantics</h6>
8140 <p><!--para 1 -->
8141 A unary operator expression of the form:
8142 <pre>
8143 _Pragma ( string-literal )</pre>
8144 is processed as follows: The string literal is destringized by deleting the L prefix, if
8145 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8146 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8147 resulting sequence of characters is processed through translation phase 3 to produce
8148 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8149 directive. The original four preprocessing tokens in the unary operator expression are
8150 removed.
8152 EXAMPLE A directive of the form:
8153 <pre>
8155 can also be expressed as:
8156 <!--page 174 -->
8157 <pre>
8159 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8160 replacement, as in:
8161 <!--page 175 -->
8162 <pre>
8163 #define LISTING(x) PRAGMA(listing on #x)
8164 #define PRAGMA(x) _Pragma(#x)
8165 LISTING ( ..\listing.dir )</pre>
8171 Future standardization may include additional floating-point types, including those with
8172 greater range, precision, or both than long double.
8176 Declaring an identifier with internal linkage at file scope without the static storage-
8177 class specifier is an obsolescent feature.
8181 Restriction of the significance of an external name to fewer than 255 characters
8182 (considering each universal character name or extended source character as a single
8183 character) is an obsolescent feature that is a concession to existing implementations.
8187 Lowercase letters as escape sequences are reserved for future standardization. Other
8188 characters may be used in extensions.
8192 The placement of a storage-class specifier other than at the beginning of the declaration
8193 specifiers in a declaration is an obsolescent feature.
8197 The use of function declarators with empty parentheses (not prototype-format parameter
8198 type declarators) is an obsolescent feature.
8202 The use of function definitions with separate parameter identifier and declaration lists
8203 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8207 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8211 Macro names beginning with __STDC_ are reserved for future standardization.
8212 <!--page 176 -->
8221 A string is a contiguous sequence of characters terminated by and including the first null
8222 character. The term multibyte string is sometimes used instead to emphasize special
8223 processing given to multibyte characters contained in the string or to avoid confusion
8224 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8225 character. The length of a string is the number of bytes preceding the null character and
8226 the value of a string is the sequence of the values of the contained characters, in order.
8228 The decimal-point character is the character used by functions that convert floating-point
8229 numbers to or from character sequences to denote the beginning of the fractional part of
8230 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8231 may be changed by the setlocale function.
8233 A null wide character is a wide character with code value zero.
8235 A wide string is a contiguous sequence of wide characters terminated by and including
8236 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8237 addressed) wide character. The length of a wide string is the number of wide characters
8238 preceding the null wide character and the value of a wide string is the sequence of code
8239 values of the contained wide characters, in order.
8241 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8242 (potentially) causes a change in shift state (see <a href="#5.2.1.2">5.2.1.2</a>). A shift sequence shall not have a
8243 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8245 <p><b> Forward references</b>: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
8250 <!--page 177 -->
8253 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8254 (<a href="#7.20.1">7.20.1</a>, <a href="#7.24.4.1">7.24.4.1</a>) and the formatted input/output functions (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
8255 </small>
8256 <p><small><a name="note158" href="#note158">158)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
8257 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8258 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8259 implementation's choice.
8260 </small>
8264 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8265 whose contents are made available by the #include preprocessing directive. The
8266 header declares a set of related functions, plus any necessary types and additional macros
8267 needed to facilitate their use. Declarations of types described in this clause shall not
8268 include type qualifiers, unless explicitly stated otherwise.
8270 The standard headers are
8272 <pre>
8273 <a href="#7.2"><assert.h></a> <a href="#7.8"><inttypes.h></a> <a href="#7.14"><signal.h></a> <a href="#7.20"><stdlib.h></a>
8274 <a href="#7.3"><complex.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.15"><stdarg.h></a> <a href="#7.21"><string.h></a>
8275 <a href="#7.4"><ctype.h></a> <a href="#7.10"><limits.h></a> <a href="#7.16"><stdbool.h></a> <a href="#7.22"><tgmath.h></a>
8276 <a href="#7.5"><errno.h></a> <a href="#7.11"><locale.h></a> <a href="#7.17"><stddef.h></a> <a href="#7.23"><time.h></a>
8277 <a href="#7.6"><fenv.h></a> <a href="#7.12"><math.h></a> <a href="#7.18"><stdint.h></a> <a href="#7.24"><wchar.h></a>
8278 <a href="#7.7"><float.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.19"><stdio.h></a> <a href="#7.25"><wctype.h></a></pre>
8280 provided as part of the implementation, is placed in any of the standard places that are
8281 searched for included source files, the behavior is undefined.
8283 Standard headers may be included in any order; each may be included more than once in
8284 a given scope, with no effect different from being included only once, except that the
8285 effect of including <a href="#7.2"><assert.h></a> depends on the definition of NDEBUG (see <a href="#7.2">7.2</a>). If
8286 used, a header shall be included outside of any external declaration or definition, and it
8287 shall first be included before the first reference to any of the functions or objects it
8288 declares, or to any of the types or macros it defines. However, if an identifier is declared
8289 or defined in more than one header, the second and subsequent associated headers may be
8290 included after the initial reference to the identifier. The program shall not have any
8291 macros with names lexically identical to keywords currently defined prior to the
8292 inclusion.
8294 Any definition of an object-like macro described in this clause shall expand to code that is
8295 fully protected by parentheses where necessary, so that it groups in an arbitrary
8296 expression as if it were a single identifier.
8298 Any declaration of a library function shall have external linkage.
8306 <!--page 178 -->
8309 <p><small><a name="note159" href="#note159">159)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
8310 necessarily valid source file names.
8311 </small>
8315 Each header declares or defines all identifiers listed in its associated subclause, and
8316 optionally declares or defines identifiers listed in its associated future library directions
8317 subclause and identifiers which are always reserved either for any use or for use as file
8318 scope identifiers.
8319 <ul>
8320 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8321 underscore are always reserved for any use.
8322 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8323 with file scope in both the ordinary and tag name spaces.
8324 <li> Each macro name in any of the following subclauses (including the future library
8325 directions) is reserved for use as specified if any of its associated headers is included;
8327 <li> All identifiers with external linkage in any of the following subclauses (including the
8328 future library directions) are always reserved for use as identifiers with external
8330 <li> Each identifier with file scope listed in any of the following subclauses (including the
8331 future library directions) is reserved for use as a macro name and as an identifier with
8332 file scope in the same name space if any of its associated headers is included.
8333 </ul>
8335 No other identifiers are reserved. If the program declares or defines an identifier in a
8336 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8337 identifier as a macro name, the behavior is undefined.
8339 If the program removes (with #undef) any macro definition of an identifier in the first
8340 group listed above, the behavior is undefined.
8343 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8344 setjmp, and va_end.
8345 </small>
8349 Each of the following statements applies unless explicitly stated otherwise in the detailed
8350 descriptions that follow: If an argument to a function has an invalid value (such as a value
8351 outside the domain of the function, or a pointer outside the address space of the program,
8352 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8353 parameter is not const-qualified) or a type (after promotion) not expected by a function
8354 with variable number of arguments, the behavior is undefined. If a function argument is
8355 described as being an array, the pointer actually passed to the function shall have a value
8356 such that all address computations and accesses to objects (that would be valid if the
8357 pointer did point to the first element of such an array) are in fact valid. Any function
8358 declared in a header may be additionally implemented as a function-like macro defined in
8360 <!--page 179 -->
8361 the header, so if a library function is declared explicitly when its header is included, one
8362 of the techniques shown below can be used to ensure the declaration is not affected by
8363 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8364 the name of the function in parentheses, because the name is then not followed by the left
8365 parenthesis that indicates expansion of a macro function name. For the same syntactic
8366 reason, it is permitted to take the address of a library function even if it is also defined as
8367 a macro.<sup><a href="#note161"><b>161)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
8368 actual function is referred to. Any invocation of a library function that is implemented as
8369 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8370 protected by parentheses where necessary, so it is generally safe to use arbitrary
8371 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8372 following subclauses may be invoked in an expression anywhere a function with a
8373 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8374 integer constant expressions shall additionally be suitable for use in #if preprocessing
8375 directives.
8377 Provided that a library function can be declared without reference to any type defined in a
8378 header, it is also permissible to declare the function and use it without including its
8379 associated header.
8381 There is a sequence point immediately before a library function returns.
8383 The functions in the standard library are not guaranteed to be reentrant and may modify
8388 <!--page 180 -->
8390 EXAMPLE The function atoi may be used in any of several ways:
8391 <ul>
8392 <li> by use of its associated header (possibly generating a macro expansion)
8393 <pre>
8395 const char *str;
8396 /* ... */
8397 i = atoi(str);</pre>
8398 <li> by use of its associated header (assuredly generating a true function reference)
8399 <pre>
8401 #undef atoi
8402 const char *str;
8403 /* ... */
8404 i = atoi(str);</pre>
8405 or
8406 <pre>
8408 const char *str;
8409 /* ... */
8410 i = (atoi)(str);</pre>
8411 <li> by explicit declaration
8412 <!--page 181 -->
8413 <pre>
8414 extern int atoi(const char *);
8415 const char *str;
8416 /* ... */
8417 i = atoi(str);</pre>
8418 </ul>
8421 <p><small><a name="note161" href="#note161">161)</a> This means that an implementation shall provide an actual function for each library function, even if it
8422 also provides a macro for that function.
8423 </small>
8424 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8425 </small>
8426 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8427 implementations may provide special semantics for such names. For example, the identifier
8428 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8429 appropriate header could specify
8431 <pre>
8432 #define abs(x) _BUILTIN_abs(x)</pre>
8433 for a compiler whose code generator will accept it.
8434 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8435 function may write
8437 <pre>
8438 #undef abs</pre>
8439 whether the implementation's header provides a macro implementation of abs or a built-in
8440 implementation. The prototype for the function, which precedes and is hidden by any macro
8441 definition, is thereby revealed also.
8442 </small>
8443 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8444 </small>
8448 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8449 <pre>
8450 NDEBUG</pre>
8451 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8452 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8453 simply as
8454 <pre>
8456 The assert macro is redefined according to the current state of NDEBUG each time that
8459 The assert macro shall be implemented as a macro, not as an actual function. If the
8460 macro definition is suppressed in order to access an actual function, the behavior is
8461 undefined.
8468 <pre>
8470 void assert(scalar expression);</pre>
8473 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8474 When it is executed, if expression (which shall have a scalar type) is false (that is,
8475 compares equal to 0), the assert macro writes information about the particular call that
8476 failed (including the text of the argument, the name of the source file, the source line
8477 number, and the name of the enclosing function -- the latter are respectively the values of
8478 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8479 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8480 then calls the abort function.
8483 The assert macro returns no value.
8489 <!--page 182 -->
8493 Assertion failed: expression, function abc, file xyz, line nnn.
8494 </small>
8500 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8501 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8502 function with one or more double complex parameters and a double complex or
8503 double return value; and other functions with the same name but with f and l suffixes
8504 which are corresponding functions with float and long double parameters and
8505 return values.
8507 The macro
8508 <pre>
8509 complex</pre>
8510 expands to _Complex; the macro
8511 <pre>
8512 _Complex_I</pre>
8513 expands to a constant expression of type const float _Complex, with the value of
8516 The macros
8517 <pre>
8518 imaginary</pre>
8519 and
8520 <pre>
8521 _Imaginary_I</pre>
8522 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8523 they expand to _Imaginary and a constant expression of type const float
8524 _Imaginary with the value of the imaginary unit.
8526 The macro
8527 <pre>
8528 I</pre>
8529 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8530 defined, I shall expand to _Complex_I.
8532 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8533 redefine the macros complex, imaginary, and I.
8534 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8538 <!--page 183 -->
8541 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8542 </small>
8543 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i<sup>2</sup> = -1.
8544 </small>
8545 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8546 </small>
8550 Values are interpreted as radians, not degrees. An implementation may set errno but is
8551 not required to.
8555 Some of the functions below have branch cuts, across which the function is
8556 discontinuous. For implementations with a signed zero (including all IEC 60559
8557 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8558 one side of a cut from another so the function is continuous (except for format
8559 limitations) as the cut is approached from either side. For example, for the square root
8560 function, which has a branch cut along the negative real axis, the top of the cut, with
8561 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8562 imaginary part -0, maps to the negative imaginary axis.
8564 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8565 sides of branch cuts. These implementations shall map a cut so the function is continuous
8566 as the cut is approached coming around the finite endpoint of the cut in a counter
8567 clockwise direction. (Branch cuts for the functions specified here have just one finite
8568 endpoint.) For example, for the square root function, coming counter clockwise around
8569 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8570 so the cut maps to the positive imaginary axis.
8575 <pre>
8577 #pragma STDC CX_LIMITED_RANGE on-off-switch</pre>
8580 The usual mathematical formulas for complex multiply, divide, and absolute value are
8581 problematic because of their treatment of infinities and because of undue overflow and
8582 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8583 implementation that (where the state is ''on'') the usual mathematical formulas are
8584 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8585 explicit declarations and statements inside a compound statement. When outside external
8587 <!--page 184 -->
8588 declarations, the pragma takes effect from its occurrence until another
8589 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8590 When inside a compound statement, the pragma takes effect from its occurrence until
8591 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8592 compound statement), or until the end of the compound statement; at the end of a
8593 compound statement the state for the pragma is restored to its condition just before the
8594 compound statement. If this pragma is used in any other context, the behavior is
8595 undefined. The default state for the pragma is ''off''.
8598 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8600 <pre>
8601 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8604 </pre>
8605 where the programmer can determine they are safe.
8606 </small>
8613 <pre>
8615 double complex cacos(double complex z);
8616 float complex cacosf(float complex z);
8617 long double complex cacosl(long double complex z);</pre>
8620 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8624 The cacos functions return the complex arc cosine value, in the range of a strip
8625 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8626 real axis.
8631 <pre>
8633 double complex casin(double complex z);
8634 float complex casinf(float complex z);
8635 long double complex casinl(long double complex z);</pre>
8638 The casin functions compute the complex arc sine of z, with branch cuts outside the
8642 The casin functions return the complex arc sine value, in the range of a strip
8644 along the real axis.
8645 <!--page 185 -->
8650 <pre>
8652 double complex catan(double complex z);
8653 float complex catanf(float complex z);
8654 long double complex catanl(long double complex z);</pre>
8657 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8658 interval [-i, +i] along the imaginary axis.
8661 The catan functions return the complex arc tangent value, in the range of a strip
8663 along the real axis.
8668 <pre>
8670 double complex ccos(double complex z);
8671 float complex ccosf(float complex z);
8672 long double complex ccosl(long double complex z);</pre>
8675 The ccos functions compute the complex cosine of z.
8678 The ccos functions return the complex cosine value.
8683 <pre>
8685 double complex csin(double complex z);
8686 float complex csinf(float complex z);
8687 long double complex csinl(long double complex z);</pre>
8690 The csin functions compute the complex sine of z.
8693 The csin functions return the complex sine value.
8694 <!--page 186 -->
8699 <pre>
8701 double complex ctan(double complex z);
8702 float complex ctanf(float complex z);
8703 long double complex ctanl(long double complex z);</pre>
8706 The ctan functions compute the complex tangent of z.
8709 The ctan functions return the complex tangent value.
8716 <pre>
8718 double complex cacosh(double complex z);
8719 float complex cacoshf(float complex z);
8720 long double complex cacoshl(long double complex z);</pre>
8723 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8724 cut at values less than 1 along the real axis.
8727 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8728 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8729 the imaginary axis.
8734 <pre>
8736 double complex casinh(double complex z);
8737 float complex casinhf(float complex z);
8738 long double complex casinhl(long double complex z);</pre>
8741 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8742 outside the interval [-i, +i] along the imaginary axis.
8743 <!--page 187 -->
8746 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8748 along the imaginary axis.
8753 <pre>
8755 double complex catanh(double complex z);
8756 float complex catanhf(float complex z);
8757 long double complex catanhl(long double complex z);</pre>
8760 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8764 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8766 along the imaginary axis.
8771 <pre>
8773 double complex ccosh(double complex z);
8774 float complex ccoshf(float complex z);
8775 long double complex ccoshl(long double complex z);</pre>
8778 The ccosh functions compute the complex hyperbolic cosine of z.
8781 The ccosh functions return the complex hyperbolic cosine value.
8786 <!--page 188 -->
8787 <pre>
8789 double complex csinh(double complex z);
8790 float complex csinhf(float complex z);
8791 long double complex csinhl(long double complex z);</pre>
8794 The csinh functions compute the complex hyperbolic sine of z.
8797 The csinh functions return the complex hyperbolic sine value.
8802 <pre>
8804 double complex ctanh(double complex z);
8805 float complex ctanhf(float complex z);
8806 long double complex ctanhl(long double complex z);</pre>
8809 The ctanh functions compute the complex hyperbolic tangent of z.
8812 The ctanh functions return the complex hyperbolic tangent value.
8819 <pre>
8821 double complex cexp(double complex z);
8822 float complex cexpf(float complex z);
8823 long double complex cexpl(long double complex z);</pre>
8826 The cexp functions compute the complex base-e exponential of z.
8829 The cexp functions return the complex base-e exponential value.
8834 <!--page 189 -->
8835 <pre>
8837 double complex clog(double complex z);
8838 float complex clogf(float complex z);
8839 long double complex clogl(long double complex z);</pre>
8842 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8843 cut along the negative real axis.
8846 The clog functions return the complex natural logarithm value, in the range of a strip
8847 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8848 imaginary axis.
8855 <pre>
8857 double cabs(double complex z);
8858 float cabsf(float complex z);
8859 long double cabsl(long double complex z);</pre>
8862 The cabs functions compute the complex absolute value (also called norm, modulus, or
8863 magnitude) of z.
8866 The cabs functions return the complex absolute value.
8871 <pre>
8873 double complex cpow(double complex x, double complex y);
8874 float complex cpowf(float complex x, float complex y);
8875 long double complex cpowl(long double complex x,
8876 long double complex y);</pre>
8879 The cpow functions compute the complex power function xy , with a branch cut for the
8880 first parameter along the negative real axis.
8883 The cpow functions return the complex power function value.
8884 <!--page 190 -->
8889 <pre>
8891 double complex csqrt(double complex z);
8892 float complex csqrtf(float complex z);
8893 long double complex csqrtl(long double complex z);</pre>
8896 The csqrt functions compute the complex square root of z, with a branch cut along the
8897 negative real axis.
8900 The csqrt functions return the complex square root value, in the range of the right half-
8901 plane (including the imaginary axis).
8908 <pre>
8910 double carg(double complex z);
8911 float cargf(float complex z);
8912 long double cargl(long double complex z);</pre>
8915 The carg functions compute the argument (also called phase angle) of z, with a branch
8916 cut along the negative real axis.
8919 The carg functions return the value of the argument in the interval [-pi , +pi ].
8924 <!--page 191 -->
8925 <pre>
8927 double cimag(double complex z);
8928 float cimagf(float complex z);
8929 long double cimagl(long double complex z);</pre>
8932 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
8935 The cimag functions return the imaginary part value (as a real).
8938 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8939 </small>
8944 <pre>
8946 double complex conj(double complex z);
8947 float complex conjf(float complex z);
8948 long double complex conjl(long double complex z);</pre>
8951 The conj functions compute the complex conjugate of z, by reversing the sign of its
8952 imaginary part.
8955 The conj functions return the complex conjugate value.
8960 <pre>
8962 double complex cproj(double complex z);
8963 float complex cprojf(float complex z);
8964 long double complex cprojl(long double complex z);</pre>
8967 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8968 z except that all complex infinities (even those with one infinite part and one NaN part)
8969 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8970 equivalent to
8971 <pre>
8975 The cproj functions return the value of the projection onto the Riemann sphere.
8980 <!--page 192 -->
8985 <pre>
8987 double creal(double complex z);
8988 float crealf(float complex z);
8989 long double creall(long double complex z);</pre>
8995 The creal functions return the real part value.
9000 <!--page 193 -->
9003 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9004 </small>
9008 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9009 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9010 representable as an unsigned char or shall equal the value of the macro EOF. If the
9011 argument has any other value, the behavior is undefined.
9013 The behavior of these functions is affected by the current locale. Those functions that
9014 have locale-specific aspects only when not in the "C" locale are noted below.
9016 The term printing character refers to a member of a locale-specific set of characters, each
9017 of which occupies one printing position on a display device; the term control character
9018 refers to a member of a locale-specific set of characters that are not printing
9019 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9020 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9023 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9024 </small>
9025 <p><small><a name="note173" href="#note173">173)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
9026 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9028 </small>
9032 The functions in this subclause return nonzero (true) if and only if the value of the
9033 argument c conforms to that in the description of the function.
9038 <pre>
9040 int isalnum(int c);</pre>
9043 The isalnum function tests for any character for which isalpha or isdigit is true.
9048 <pre>
9050 int isalpha(int c);</pre>
9053 The isalpha function tests for any character for which isupper or islower is true,
9054 or any character that is one of a locale-specific set of alphabetic characters for which
9058 <!--page 194 -->
9059 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9060 isalpha returns true only for the characters for which isupper or islower is true.
9063 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9064 characters; all four combinations are possible.
9065 </small>
9070 <pre>
9072 int isblank(int c);</pre>
9075 The isblank function tests for any character that is a standard blank character or is one
9076 of a locale-specific set of characters for which isspace is true and that is used to
9077 separate words within a line of text. The standard blank characters are the following:
9078 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9079 for the standard blank characters.
9084 <pre>
9086 int iscntrl(int c);</pre>
9089 The iscntrl function tests for any control character.
9094 <pre>
9096 int isdigit(int c);</pre>
9099 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9104 <pre>
9106 int isgraph(int c);</pre>
9111 <!--page 195 -->
9114 The isgraph function tests for any printing character except space (' ').
9119 <pre>
9121 int islower(int c);</pre>
9124 The islower function tests for any character that is a lowercase letter or is one of a
9125 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9126 isspace is true. In the "C" locale, islower returns true only for the lowercase
9132 <pre>
9134 int isprint(int c);</pre>
9137 The isprint function tests for any printing character including space (' ').
9142 <pre>
9144 int ispunct(int c);</pre>
9147 The ispunct function tests for any printing character that is one of a locale-specific set
9148 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9149 locale, ispunct returns true for every printing character for which neither isspace
9150 nor isalnum is true.
9155 <pre>
9157 int isspace(int c);</pre>
9160 The isspace function tests for any character that is a standard white-space character or
9161 is one of a locale-specific set of characters for which isalnum is false. The standard
9162 <!--page 196 -->
9163 white-space characters are the following: space (' '), form feed ('\f'), new-line
9164 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9165 "C" locale, isspace returns true only for the standard white-space characters.
9170 <pre>
9172 int isupper(int c);</pre>
9175 The isupper function tests for any character that is an uppercase letter or is one of a
9176 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9177 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9183 <pre>
9185 int isxdigit(int c);</pre>
9188 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9195 <pre>
9197 int tolower(int c);</pre>
9200 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9203 If the argument is a character for which isupper is true and there are one or more
9204 corresponding characters, as specified by the current locale, for which islower is true,
9205 the tolower function returns one of the corresponding characters (always the same one
9206 for any given locale); otherwise, the argument is returned unchanged.
9207 <!--page 197 -->
9212 <pre>
9214 int toupper(int c);</pre>
9217 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9220 If the argument is a character for which islower is true and there are one or more
9221 corresponding characters, as specified by the current locale, for which isupper is true,
9222 the toupper function returns one of the corresponding characters (always the same one
9223 for any given locale); otherwise, the argument is returned unchanged.
9224 <!--page 198 -->
9228 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9229 conditions.
9231 The macros are
9232 <pre>
9233 EDOM
9234 EILSEQ
9235 ERANGE</pre>
9236 which expand to integer constant expressions with type int, distinct positive values, and
9237 which are suitable for use in #if preprocessing directives; and
9238 <pre>
9239 errno</pre>
9240 which expands to a modifiable lvalue<sup><a href="#note175"><b>175)</b></a></sup> that has type int, the value of which is set to a
9241 positive error number by several library functions. It is unspecified whether errno is a
9242 macro or an identifier declared with external linkage. If a macro definition is suppressed
9243 in order to access an actual object, or a program defines an identifier with the name
9244 errno, the behavior is undefined.
9246 The value of errno is zero at program startup, but is never set to zero by any library
9247 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9248 whether or not there is an error, provided the use of errno is not documented in the
9249 description of the function in this International Standard.
9251 Additional macro definitions, beginning with E and a digit or E and an uppercase
9252 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9257 <!--page 199 -->
9260 <p><small><a name="note175" href="#note175">175)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
9261 resulting from a function call (for example, *errno()).
9262 </small>
9263 <p><small><a name="note176" href="#note176">176)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
9264 then inspect it before a subsequent library function call. Of course, a library function can save the
9265 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9266 value is still zero just before the return.
9267 </small>
9268 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9269 </small>
9273 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9274 access to the floating-point environment. The floating-point environment refers
9275 collectively to any floating-point status flags and control modes supported by the
9276 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9277 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9278 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9279 point control mode is a system variable whose value may be set by the user to affect the
9280 subsequent behavior of floating-point arithmetic.
9282 Certain programming conventions support the intended model of use for the floating-
9284 <ul>
9285 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9286 floating-point status flags, nor depend on the state of its caller's floating-point status
9287 flags unless the function is so documented;
9288 <li> a function call is assumed to require default floating-point control modes, unless its
9289 documentation promises otherwise;
9290 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9291 unless its documentation promises otherwise.
9292 </ul>
9294 The type
9295 <pre>
9296 fenv_t</pre>
9297 represents the entire floating-point environment.
9299 The type
9300 <pre>
9301 fexcept_t</pre>
9302 represents the floating-point status flags collectively, including any status the
9303 implementation associates with the flags.
9308 <!--page 200 -->
9310 Each of the macros
9311 <pre>
9312 FE_DIVBYZERO
9313 FE_INEXACT
9314 FE_INVALID
9315 FE_OVERFLOW
9316 FE_UNDERFLOW</pre>
9317 is defined if and only if the implementation supports the floating-point exception by
9318 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9319 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9320 be specified by the implementation. The defined macros expand to integer constant
9321 expressions with values such that bitwise ORs of all combinations of the macros result in
9322 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9325 The macro
9326 <pre>
9327 FE_ALL_EXCEPT</pre>
9328 is simply the bitwise OR of all floating-point exception macros defined by the
9329 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9331 Each of the macros
9332 <pre>
9333 FE_DOWNWARD
9334 FE_TONEAREST
9335 FE_TOWARDZERO
9336 FE_UPWARD</pre>
9337 is defined if and only if the implementation supports getting and setting the represented
9338 rounding direction by means of the fegetround and fesetround functions.
9339 Additional implementation-defined rounding directions, with macro definitions beginning
9340 with FE_ and an uppercase letter, may also be specified by the implementation. The
9341 defined macros expand to integer constant expressions whose values are distinct
9344 The macro
9348 <!--page 201 -->
9349 <pre>
9350 FE_DFL_ENV</pre>
9351 represents the default floating-point environment -- the one installed at program startup
9352 -- and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9355 Additional implementation-defined environments, with macro definitions beginning with
9356 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9357 also be specified by the implementation.
9360 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9361 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9362 designed to facilitate code portability among all systems.
9363 </small>
9364 <p><small><a name="note179" href="#note179">179)</a> A floating-point status flag is not an object and can be set more than once within an expression.
9365 </small>
9366 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9367 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9368 on the programmer or program that does so explicitly.
9369 </small>
9370 <p><small><a name="note181" href="#note181">181)</a> The implementation supports an exception if there are circumstances where a call to at least one of the
9371 functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
9372 all the functions to succeed all the time.
9373 </small>
9374 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9375 </small>
9376 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9377 FLT_ROUNDS, they are not required to do so.
9378 </small>
9383 <pre>
9385 #pragma STDC FENV_ACCESS on-off-switch</pre>
9388 The FENV_ACCESS pragma provides a means to inform the implementation when a
9389 program might access the floating-point environment to test floating-point status flags or
9390 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9391 outside external declarations or preceding all explicit declarations and statements inside a
9392 compound statement. When outside external declarations, the pragma takes effect from
9393 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9394 the translation unit. When inside a compound statement, the pragma takes effect from its
9395 occurrence until another FENV_ACCESS pragma is encountered (including within a
9396 nested compound statement), or until the end of the compound statement; at the end of a
9397 compound statement the state for the pragma is restored to its condition just before the
9398 compound statement. If this pragma is used in any other context, the behavior is
9399 undefined. If part of a program tests floating-point status flags, sets floating-point control
9400 modes, or runs under non-default mode settings, but was translated with the state for the
9401 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9402 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9403 the program translated with FENV_ACCESS ''off'' to a part translated with
9404 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9405 floating-point control modes have their default settings.)
9410 <!--page 202 -->
9412 EXAMPLE
9414 <pre>
9416 void f(double x)
9417 {
9418 #pragma STDC FENV_ACCESS ON
9419 void g(double);
9420 void h(double);
9421 /* ... */
9422 g(x + 1);
9423 h(x + 1);
9424 /* ... */
9425 }</pre>
9426 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9427 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9428 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9432 <p><small><a name="note184" href="#note184">184)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
9433 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9434 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9435 modes are in effect and the flags are not tested.
9436 </small>
9437 <p><small><a name="note185" href="#note185">185)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
9438 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9439 ''off'', just one evaluation of x + 1 would suffice.
9440 </small>
9444 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9445 input argument for the functions represents a subset of floating-point exceptions, and can
9446 be zero or the bitwise OR of one or more floating-point exception macros, for example
9447 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9448 functions is undefined.
9451 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9452 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9453 flags with more information -- for example, the address of the code which first raised the floating-
9454 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9455 content of flags.
9456 </small>
9461 <pre>
9463 int feclearexcept(int excepts);</pre>
9466 The feclearexcept function attempts to clear the supported floating-point exceptions
9467 represented by its argument.
9470 The feclearexcept function returns zero if the excepts argument is zero or if all
9471 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9474 <!--page 203 -->
9479 <pre>
9481 int fegetexceptflag(fexcept_t *flagp,
9482 int excepts);</pre>
9485 The fegetexceptflag function attempts to store an implementation-defined
9486 representation of the states of the floating-point status flags indicated by the argument
9487 excepts in the object pointed to by the argument flagp.
9490 The fegetexceptflag function returns zero if the representation was successfully
9491 stored. Otherwise, it returns a nonzero value.
9496 <pre>
9498 int feraiseexcept(int excepts);</pre>
9501 The feraiseexcept function attempts to raise the supported floating-point exceptions
9502 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9503 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9504 additionally raises the ''inexact'' floating-point exception whenever it raises the
9505 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9508 The feraiseexcept function returns zero if the excepts argument is zero or if all
9509 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9514 <!--page 204 -->
9517 <p><small><a name="note187" href="#note187">187)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
9518 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9520 </small>
9525 <pre>
9527 int fesetexceptflag(const fexcept_t *flagp,
9528 int excepts);</pre>
9531 The fesetexceptflag function attempts to set the floating-point status flags
9532 indicated by the argument excepts to the states stored in the object pointed to by
9533 flagp. The value of *flagp shall have been set by a previous call to
9534 fegetexceptflag whose second argument represented at least those floating-point
9535 exceptions represented by the argument excepts. This function does not raise floating-
9536 point exceptions, but only sets the state of the flags.
9539 The fesetexceptflag function returns zero if the excepts argument is zero or if
9540 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9541 a nonzero value.
9546 <pre>
9548 int fetestexcept(int excepts);</pre>
9551 The fetestexcept function determines which of a specified subset of the floating-
9552 point exception flags are currently set. The excepts argument specifies the floating-
9556 The fetestexcept function returns the value of the bitwise OR of the floating-point
9557 exception macros corresponding to the currently set floating-point exceptions included in
9558 excepts.
9560 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9565 <!--page 205 -->
9566 <pre>
9568 /* ... */
9569 {
9570 #pragma STDC FENV_ACCESS ON
9571 int set_excepts;
9572 feclearexcept(FE_INVALID | FE_OVERFLOW);
9573 // maybe raise exceptions
9574 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
9575 if (set_excepts & FE_INVALID) f();
9576 if (set_excepts & FE_OVERFLOW) g();
9577 /* ... */
9578 }</pre>
9582 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
9583 </small>
9587 The fegetround and fesetround functions provide control of rounding direction
9588 modes.
9593 <pre>
9595 int fegetround(void);</pre>
9598 The fegetround function gets the current rounding direction.
9601 The fegetround function returns the value of the rounding direction macro
9602 representing the current rounding direction or a negative value if there is no such
9603 rounding direction macro or the current rounding direction is not determinable.
9608 <pre>
9610 int fesetround(int round);</pre>
9613 The fesetround function establishes the rounding direction represented by its
9614 argument round. If the argument is not equal to the value of a rounding direction macro,
9615 the rounding direction is not changed.
9618 The fesetround function returns zero if and only if the requested rounding direction
9619 was established.
9620 <!--page 206 -->
9622 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
9623 rounding direction fails.
9624 <pre>
9627 void f(int round_dir)
9628 {
9629 #pragma STDC FENV_ACCESS ON
9630 int save_round;
9631 int setround_ok;
9632 save_round = fegetround();
9633 setround_ok = fesetround(round_dir);
9634 assert(setround_ok == 0);
9635 /* ... */
9636 fesetround(save_round);
9637 /* ... */
9638 }</pre>
9643 The functions in this section manage the floating-point environment -- status flags and
9644 control modes -- as one entity.
9649 <pre>
9651 int fegetenv(fenv_t *envp);</pre>
9654 The fegetenv function attempts to store the current floating-point environment in the
9655 object pointed to by envp.
9658 The fegetenv function returns zero if the environment was successfully stored.
9659 Otherwise, it returns a nonzero value.
9664 <pre>
9666 int feholdexcept(fenv_t *envp);</pre>
9669 The feholdexcept function saves the current floating-point environment in the object
9670 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9671 (continue on floating-point exceptions) mode, if available, for all floating-point
9673 <!--page 207 -->
9676 The feholdexcept function returns zero if and only if non-stop floating-point
9677 exception handling was successfully installed.
9680 <p><small><a name="note189" href="#note189">189)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9681 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9682 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9683 function to write routines that hide spurious floating-point exceptions from their callers.
9684 </small>
9689 <pre>
9691 int fesetenv(const fenv_t *envp);</pre>
9694 The fesetenv function attempts to establish the floating-point environment represented
9695 by the object pointed to by envp. The argument envp shall point to an object set by a
9696 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9697 Note that fesetenv merely installs the state of the floating-point status flags
9698 represented through its argument, and does not raise these floating-point exceptions.
9701 The fesetenv function returns zero if the environment was successfully established.
9702 Otherwise, it returns a nonzero value.
9707 <pre>
9709 int feupdateenv(const fenv_t *envp);</pre>
9712 The feupdateenv function attempts to save the currently raised floating-point
9713 exceptions in its automatic storage, install the floating-point environment represented by
9714 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9715 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9716 or equal a floating-point environment macro.
9719 The feupdateenv function returns zero if all the actions were successfully carried out.
9720 Otherwise, it returns a nonzero value.
9725 <!--page 208 -->
9727 EXAMPLE Hide spurious underflow floating-point exceptions:
9728 <!--page 209 -->
9729 <pre>
9731 double f(double x)
9732 {
9733 #pragma STDC FENV_ACCESS ON
9734 double result;
9735 fenv_t save_env;
9736 if (feholdexcept(&save_env))
9737 return /* indication of an environmental problem */;
9738 // compute result
9739 if (/* test spurious underflow */)
9740 if (feclearexcept(FE_UNDERFLOW))
9741 return /* indication of an environmental problem */;
9742 if (feupdateenv(&save_env))
9743 return /* indication of an environmental problem */;
9744 return result;
9745 }</pre>
9749 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9750 parameters of the standard floating-point types.
9752 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9754 <!--page 210 -->
9758 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
9759 additional facilities provided by hosted implementations.
9761 It declares functions for manipulating greatest-width integers and converting numeric
9762 character strings to greatest-width integers, and it declares the type
9763 <pre>
9764 imaxdiv_t</pre>
9765 which is a structure type that is the type of the value returned by the imaxdiv function.
9766 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
9767 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
9768 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
9769 functions (<a href="#7.19.6">7.19.6</a>), formatted wide character input/output functions (<a href="#7.24.2">7.24.2</a>).
9772 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
9773 </small>
9777 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
9778 containing a conversion specifier, possibly modified by a length modifier, suitable for use
9779 within the format argument of a formatted input/output function when converting the
9780 corresponding integer type. These macro names have the general form of PRI (character
9781 string literals for the fprintf and fwprintf family) or SCN (character string literals
9782 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
9783 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
9784 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
9785 be used in a format string to print the value of an integer of type int_fast32_t.
9787 The fprintf macros for signed integers are:
9788 <pre>
9789 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9790 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR</pre>
9795 <!--page 211 -->
9797 The fprintf macros for unsigned integers are:
9799 <pre>
9800 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9801 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9802 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9803 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR</pre>
9804 The fscanf macros for signed integers are:
9806 <pre>
9807 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9808 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR</pre>
9809 The fscanf macros for unsigned integers are:
9811 <pre>
9812 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9813 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9814 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR</pre>
9815 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
9816 fprintf macros shall be defined and the corresponding fscanf macros shall be
9817 defined unless the implementation does not have a suitable fscanf length modifier for
9818 the type.
9820 EXAMPLE
9821 <pre>
9824 int main(void)
9825 {
9826 uintmax_t i = UINTMAX_MAX; // this type always exists
9827 wprintf(L"The largest integer value is %020"
9828 PRIxMAX "\n", i);
9829 return 0;
9830 }</pre>
9834 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
9836 </small>
9837 <p><small><a name="note192" href="#note192">192)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9838 different format specifiers may be required for fprintf and fscanf, even when the type is the
9839 same.
9840 </small>
9847 <pre>
9849 intmax_t imaxabs(intmax_t j);</pre>
9852 The imaxabs function computes the absolute value of an integer j. If the result cannot
9857 <!--page 212 -->
9860 The imaxabs function returns the absolute value.
9863 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
9864 </small>
9869 <pre>
9871 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);</pre>
9874 The imaxdiv function computes numer / denom and numer % denom in a single
9875 operation.
9878 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9879 quotient and the remainder. The structure shall contain (in either order) the members
9880 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9881 either part of the result cannot be represented, the behavior is undefined.
9886 <pre>
9888 intmax_t strtoimax(const char * restrict nptr,
9889 char ** restrict endptr, int base);
9890 uintmax_t strtoumax(const char * restrict nptr,
9891 char ** restrict endptr, int base);</pre>
9894 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9895 strtoul, and strtoull functions, except that the initial portion of the string is
9896 converted to intmax_t and uintmax_t representation, respectively.
9899 The strtoimax and strtoumax functions return the converted value, if any. If no
9900 conversion could be performed, zero is returned. If the correct value is outside the range
9901 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9902 (according to the return type and sign of the value, if any), and the value of the macro
9903 ERANGE is stored in errno.
9906 <!--page 213 -->
9911 <pre>
9914 intmax_t wcstoimax(const wchar_t * restrict nptr,
9915 wchar_t ** restrict endptr, int base);
9916 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9917 wchar_t ** restrict endptr, int base);</pre>
9920 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9921 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9922 converted to intmax_t and uintmax_t representation, respectively.
9925 The wcstoimax function returns the converted value, if any. If no conversion could be
9926 performed, zero is returned. If the correct value is outside the range of representable
9927 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9928 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9929 errno.
9932 <!--page 214 -->
9936 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9937 to the corresponding tokens (on the right):
9938 <!--page 215 -->
9939 <pre>
9940 and &&
9941 and_eq &=
9942 bitand &
9943 bitor |
9944 compl ~
9945 not !
9946 not_eq !=
9947 or ||
9948 or_eq |=
9949 xor ^
9950 xor_eq ^=</pre>
9954 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9955 parameters of the standard integer types.
9957 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9959 <!--page 216 -->
9963 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9965 The type is
9966 <pre>
9967 struct lconv</pre>
9968 which contains members related to the formatting of numeric values. The structure shall
9969 contain at least the following members, in any order. The semantics of the members and
9970 their normal ranges are explained in <a href="#7.11.2.1">7.11.2.1</a>. In the "C" locale, the members shall have
9971 the values specified in the comments.
9972 <!--page 217 -->
9974 <pre>
9975 char *decimal_point; // "."
9976 char *thousands_sep; // ""
9977 char *grouping; // ""
9978 char *mon_decimal_point; // ""
9979 char *mon_thousands_sep; // ""
9980 char *mon_grouping; // ""
9981 char *positive_sign; // ""
9982 char *negative_sign; // ""
9983 char *currency_symbol; // ""
9984 char frac_digits; // CHAR_MAX
9985 char p_cs_precedes; // CHAR_MAX
9986 char n_cs_precedes; // CHAR_MAX
9987 char p_sep_by_space; // CHAR_MAX
9988 char n_sep_by_space; // CHAR_MAX
9989 char p_sign_posn; // CHAR_MAX
9990 char n_sign_posn; // CHAR_MAX
9991 char *int_curr_symbol; // ""
9992 char int_frac_digits; // CHAR_MAX
9993 char int_p_cs_precedes; // CHAR_MAX
9994 char int_n_cs_precedes; // CHAR_MAX
9995 char int_p_sep_by_space; // CHAR_MAX
9996 char int_n_sep_by_space; // CHAR_MAX
9997 char int_p_sign_posn; // CHAR_MAX
9998 char int_n_sign_posn; // CHAR_MAX</pre>
10000 <pre>
10001 LC_ALL
10002 LC_COLLATE
10003 LC_CTYPE
10004 LC_MONETARY
10005 LC_NUMERIC
10006 LC_TIME</pre>
10007 which expand to integer constant expressions with distinct values, suitable for use as the
10008 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10009 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10010 implementation.
10013 <p><small><a name="note194" href="#note194">194)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
10014 </small>
10015 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10016 </small>
10023 <pre>
10025 char *setlocale(int category, const char *locale);</pre>
10028 The setlocale function selects the appropriate portion of the program's locale as
10029 specified by the category and locale arguments. The setlocale function may be
10030 used to change or query the program's entire current locale or portions thereof. The value
10031 LC_ALL for category names the program's entire locale; the other values for
10032 category name only a portion of the program's locale. LC_COLLATE affects the
10033 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10034 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10035 LC_MONETARY affects the monetary formatting information returned by the
10036 localeconv function. LC_NUMERIC affects the decimal-point character for the
10037 formatted input/output functions and the string conversion functions, as well as the
10038 nonmonetary formatting information returned by the localeconv function. LC_TIME
10039 affects the behavior of the strftime and wcsftime functions.
10041 A value of "C" for locale specifies the minimal environment for C translation; a value
10042 of "" for locale specifies the locale-specific native environment. Other
10043 implementation-defined strings may be passed as the second argument to setlocale.
10045 <!--page 218 -->
10047 At program startup, the equivalent of
10048 <pre>
10050 is executed.
10052 The implementation shall behave as if no library function calls the setlocale function.
10055 If a pointer to a string is given for locale and the selection can be honored, the
10056 setlocale function returns a pointer to the string associated with the specified
10057 category for the new locale. If the selection cannot be honored, the setlocale
10058 function returns a null pointer and the program's locale is not changed.
10060 A null pointer for locale causes the setlocale function to return a pointer to the
10061 string associated with the category for the program's current locale; the program's
10064 The pointer to string returned by the setlocale function is such that a subsequent call
10065 with that string value and its associated category will restore that part of the program's
10066 locale. The string pointed to shall not be modified by the program, but may be
10067 overwritten by a subsequent call to the setlocale function.
10068 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10069 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10070 (<a href="#7.20.8">7.20.8</a>), numeric conversion functions (<a href="#7.20.1">7.20.1</a>), the strcoll function (<a href="#7.21.4.3">7.21.4.3</a>), the
10071 strftime function (<a href="#7.23.3.5">7.23.3.5</a>), the strxfrm function (<a href="#7.21.4.5">7.21.4.5</a>).
10074 <p><small><a name="note196" href="#note196">196)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
10075 isxdigit.
10076 </small>
10077 <p><small><a name="note197" href="#note197">197)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
10078 locale when category has the value LC_ALL.
10079 </small>
10086 <pre>
10088 struct lconv *localeconv(void);</pre>
10091 The localeconv function sets the components of an object with type struct lconv
10092 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10093 according to the rules of the current locale.
10095 The members of the structure with type char * are pointers to strings, any of which
10096 (except decimal_point) can point to "", to indicate that the value is not available in
10097 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10099 <!--page 219 -->
10100 strings shall start and end in the initial shift state. The members with type char are
10101 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10102 available in the current locale. The members include the following:
10103 <dl>
10104 <dt> char *decimal_point
10105 <dd>
10106 The decimal-point character used to format nonmonetary quantities.
10107 <dt> char *thousands_sep
10108 <dd>
10109 The character used to separate groups of digits before the decimal-point
10110 character in formatted nonmonetary quantities.
10111 <dt> char *grouping
10112 <dd>
10113 A string whose elements indicate the size of each group of digits in
10114 formatted nonmonetary quantities.
10115 <dt> char *mon_decimal_point
10116 <dd>
10117 The decimal-point used to format monetary quantities.
10118 <dt> char *mon_thousands_sep
10119 <dd>
10120 The separator for groups of digits before the decimal-point in formatted
10121 monetary quantities.
10122 <dt> char *mon_grouping
10123 <dd>
10124 A string whose elements indicate the size of each group of digits in
10125 formatted monetary quantities.
10126 <dt> char *positive_sign
10127 <dd>
10128 The string used to indicate a nonnegative-valued formatted monetary
10129 quantity.
10130 <dt> char *negative_sign
10131 <dd>
10132 The string used to indicate a negative-valued formatted monetary quantity.
10133 <dt> char *currency_symbol
10134 <dd>
10135 The local currency symbol applicable to the current locale.
10136 <dt> char frac_digits
10137 <dd>
10138 The number of fractional digits (those after the decimal-point) to be
10139 displayed in a locally formatted monetary quantity.
10140 <dt> char p_cs_precedes
10141 <dd>
10143 succeeds the value for a nonnegative locally formatted monetary quantity.
10144 <dt> char n_cs_precedes
10145 <!--page 220 -->
10146 <dd>
10148 succeeds the value for a negative locally formatted monetary quantity.
10149 <dt> char p_sep_by_space
10150 <dd>
10151 Set to a value indicating the separation of the currency_symbol, the
10152 sign string, and the value for a nonnegative locally formatted monetary
10153 quantity.
10154 <dt> char n_sep_by_space
10155 <dd>
10156 Set to a value indicating the separation of the currency_symbol, the
10157 sign string, and the value for a negative locally formatted monetary
10158 quantity.
10159 <dt> char p_sign_posn
10160 <dd>
10161 Set to a value indicating the positioning of the positive_sign for a
10162 nonnegative locally formatted monetary quantity.
10163 <dt> char n_sign_posn
10164 <dd>
10165 Set to a value indicating the positioning of the negative_sign for a
10166 negative locally formatted monetary quantity.
10167 <dt> char *int_curr_symbol
10168 <dd>
10169 The international currency symbol applicable to the current locale. The
10170 first three characters contain the alphabetic international currency symbol
10171 in accordance with those specified in ISO 4217. The fourth character
10172 (immediately preceding the null character) is the character used to separate
10173 the international currency symbol from the monetary quantity.
10174 <dt> char int_frac_digits
10175 <dd>
10176 The number of fractional digits (those after the decimal-point) to be
10177 displayed in an internationally formatted monetary quantity.
10178 <dt> char int_p_cs_precedes
10179 <dd>
10181 succeeds the value for a nonnegative internationally formatted monetary
10182 quantity.
10183 <dt> char int_n_cs_precedes
10184 <dd>
10186 succeeds the value for a negative internationally formatted monetary
10187 quantity.
10188 <dt> char int_p_sep_by_space
10189 <!--page 221 -->
10190 <dd>
10191 Set to a value indicating the separation of the int_curr_symbol, the
10192 sign string, and the value for a nonnegative internationally formatted
10193 monetary quantity.
10194 <dt> char int_n_sep_by_space
10195 <dd>
10196 Set to a value indicating the separation of the int_curr_symbol, the
10197 sign string, and the value for a negative internationally formatted monetary
10198 quantity.
10199 <dt> char int_p_sign_posn
10200 <dd>
10201 Set to a value indicating the positioning of the positive_sign for a
10202 nonnegative internationally formatted monetary quantity.
10203 <dt> char int_n_sign_posn
10204 <dd>
10205 Set to a value indicating the positioning of the negative_sign for a
10206 negative internationally formatted monetary quantity.
10207 </dl>
10209 The elements of grouping and mon_grouping are interpreted according to the
10210 following:
10211 <dl>
10214 digits.
10216 The next element is examined to determine the size of the next group of
10217 digits before the current group.
10218 </dl>
10220 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10221 and int_n_sep_by_space are interpreted according to the following:
10222 <dl>
10224 <dt> 1 <dd>If the currency symbol and sign string are adjacent, a space separates them from the
10225 value; otherwise, a space separates the currency symbol from the value.
10227 otherwise, a space separates the sign string from the value.
10228 </dl>
10229 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10230 int_curr_symbol is used instead of a space.
10232 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10233 int_n_sign_posn are interpreted according to the following:
10234 <dl>
10240 </dl>
10241 <!--page 222 -->
10243 The implementation shall behave as if no library function calls the localeconv
10244 function.
10247 The localeconv function returns a pointer to the filled-in object. The structure
10248 pointed to by the return value shall not be modified by the program, but may be
10249 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10250 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10251 overwrite the contents of the structure.
10253 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10254 monetary quantities.
10255 <pre>
10256 Local format International format
10258 Country Positive Negative Positive Negative
10264 </pre>
10266 For these four countries, the respective values for the monetary members of the structure returned by
10267 localeconv could be:
10268 <pre>
10269 Country1 Country2 Country3 Country4
10277 frac_digits 2 0 2 2
10278 p_cs_precedes 0 1 1 1
10279 n_cs_precedes 0 1 1 1
10280 p_sep_by_space 1 0 1 0
10281 n_sep_by_space 1 0 2 0
10282 p_sign_posn 1 1 1 1
10283 n_sign_posn 1 1 4 2
10285 int_frac_digits 2 0 2 2
10286 int_p_cs_precedes 1 1 1 1
10287 int_n_cs_precedes 1 1 1 1
10288 int_p_sep_by_space 1 1 1 1
10289 int_n_sep_by_space 2 1 2 1
10290 int_p_sign_posn 1 1 1 1
10291 int_n_sign_posn 4 1 4 2
10292 </pre>
10293 <!--page 223 -->
10295 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10296 affect the formatted value.
10297 <pre>
10298 p_sep_by_space
10299 p_cs_precedes p_sign_posn 0 1 2
10313 <!--page 224 -->
10316 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10317 several macros. Most synopses specify a family of functions consisting of a principal
10318 function with one or more double parameters, a double return value, or both; and
10319 other functions with the same name but with f and l suffixes, which are corresponding
10320 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10321 Integer arithmetic functions and conversion functions are discussed later.
10323 The types
10324 <pre>
10325 float_t
10326 double_t</pre>
10327 are floating types at least as wide as float and double, respectively, and such that
10328 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10329 float_t and double_t are float and double, respectively; if
10330 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10331 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10334 The macro
10335 <pre>
10336 HUGE_VAL</pre>
10337 expands to a positive double constant expression, not necessarily representable as a
10338 float. The macros
10339 <pre>
10340 HUGE_VALF
10341 HUGE_VALL</pre>
10342 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10344 The macro
10345 <pre>
10346 INFINITY</pre>
10347 expands to a constant expression of type float representing positive or unsigned
10348 infinity, if available; else to a positive constant of type float that overflows at
10352 <!--page 225 -->
10355 The macro
10356 <pre>
10357 NAN</pre>
10358 is defined if and only if the implementation supports quiet NaNs for the float type. It
10359 expands to a constant expression of type float representing a quiet NaN.
10361 The number classification macros
10362 <pre>
10363 FP_INFINITE
10364 FP_NAN
10365 FP_NORMAL
10366 FP_SUBNORMAL
10367 FP_ZERO</pre>
10368 represent the mutually exclusive kinds of floating-point values. They expand to integer
10369 constant expressions with distinct values. Additional implementation-defined floating-
10370 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10371 may also be specified by the implementation.
10373 The macro
10374 <pre>
10375 FP_FAST_FMA</pre>
10376 is optionally defined. If defined, it indicates that the fma function generally executes
10377 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note202"><b>202)</b></a></sup> The
10378 macros
10379 <pre>
10380 FP_FAST_FMAF
10381 FP_FAST_FMAL</pre>
10382 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10383 these macros expand to the integer constant 1.
10385 The macros
10386 <pre>
10387 FP_ILOGB0
10388 FP_ILOGBNAN</pre>
10389 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10390 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10391 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10394 <!--page 226 -->
10396 The macros
10397 <pre>
10398 MATH_ERRNO
10399 MATH_ERREXCEPT</pre>
10401 <pre>
10402 math_errhandling</pre>
10403 expands to an expression that has type int and the value MATH_ERRNO,
10404 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10405 constant for the duration of the program. It is unspecified whether
10406 math_errhandling is a macro or an identifier with external linkage. If a macro
10407 definition is suppressed or a program defines an identifier with the name
10408 math_errhandling, the behavior is undefined. If the expression
10409 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10410 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10414 <p><small><a name="note198" href="#note198">198)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
10415 and return values in wider format than the synopsis prototype indicates.
10416 </small>
10417 <p><small><a name="note199" href="#note199">199)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
10419 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10420 </small>
10421 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10422 supports infinities.
10423 </small>
10424 <p><small><a name="note201" href="#note201">201)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
10425 </small>
10426 <p><small><a name="note202" href="#note202">202)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
10427 directly with a hardware multiply-add instruction. Software implementations are expected to be
10428 substantially slower.
10429 </small>
10433 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10434 values of its input arguments, except where stated otherwise. Each function shall execute
10435 as if it were a single operation without generating any externally visible exceptional
10436 conditions.
10438 For all functions, a domain error occurs if an input argument is outside the domain over
10439 which the mathematical function is defined. The description of each function lists any
10440 required domain errors; an implementation may define additional domain errors, provided
10441 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10442 domain error, the function returns an implementation-defined value; if the integer
10443 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10444 errno acquires the value EDOM; if the integer expression math_errhandling &
10445 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10447 Similarly, a range error occurs if the mathematical result of the function cannot be
10448 represented in an object of the specified type, due to extreme magnitude.
10450 A floating result overflows if the magnitude of the mathematical result is finite but so
10451 large that the mathematical result cannot be represented without extraordinary roundoff
10452 error in an object of the specified type. If a floating result overflows and default rounding
10453 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10454 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10457 <!--page 227 -->
10458 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10459 correct value of the function; if the integer expression math_errhandling &
10460 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10461 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10462 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10463 infinity and the ''overflow'' floating-point exception is raised otherwise.
10465 The result underflows if the magnitude of the mathematical result is so small that the
10466 mathematical result cannot be represented, without extraordinary roundoff error, in an
10467 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10468 implementation-defined value whose magnitude is no greater than the smallest
10469 normalized positive number in the specified type; if the integer expression
10470 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10471 value ERANGE is implementation-defined; if the integer expression
10472 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10473 floating-point exception is raised is implementation-defined.
10476 <p><small><a name="note203" href="#note203">203)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
10477 error if the mathematical domain of the function does not include the infinity.
10478 </small>
10479 <p><small><a name="note204" href="#note204">204)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
10480 also ''flush-to-zero'' underflow.
10481 </small>
10486 <pre>
10488 #pragma STDC FP_CONTRACT on-off-switch</pre>
10491 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10492 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10493 either outside external declarations or preceding all explicit declarations and statements
10494 inside a compound statement. When outside external declarations, the pragma takes
10495 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10496 the end of the translation unit. When inside a compound statement, the pragma takes
10497 effect from its occurrence until another FP_CONTRACT pragma is encountered
10498 (including within a nested compound statement), or until the end of the compound
10499 statement; at the end of a compound statement the state for the pragma is restored to its
10500 condition just before the compound statement. If this pragma is used in any other
10501 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10502 implementation-defined.
10507 <!--page 228 -->
10511 In the synopses in this subclause, real-floating indicates that the argument shall be an
10512 expression of real floating type.
10517 <pre>
10519 int fpclassify(real-floating x);</pre>
10522 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10523 subnormal, zero, or into another implementation-defined category. First, an argument
10524 represented in a format wider than its semantic type is converted to its semantic type.
10525 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10528 The fpclassify macro returns the value of the number classification macro
10529 appropriate to the value of its argument.
10531 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
10532 <pre>
10533 #define fpclassify(x) \
10534 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
10535 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
10536 __fpclassifyl(x))</pre>
10540 <p><small><a name="note205" href="#note205">205)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
10541 know the type that classification is based on. For example, a normal long double value might
10542 become subnormal when converted to double, and zero when converted to float.
10543 </small>
10548 <pre>
10550 int isfinite(real-floating x);</pre>
10553 The isfinite macro determines whether its argument has a finite value (zero,
10554 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
10555 format wider than its semantic type is converted to its semantic type. Then determination
10556 is based on the type of the argument.
10561 <!--page 229 -->
10564 The isfinite macro returns a nonzero value if and only if its argument has a finite
10565 value.
10570 <pre>
10572 int isinf(real-floating x);</pre>
10575 The isinf macro determines whether its argument value is an infinity (positive or
10576 negative). First, an argument represented in a format wider than its semantic type is
10577 converted to its semantic type. Then determination is based on the type of the argument.
10580 The isinf macro returns a nonzero value if and only if its argument has an infinite
10581 value.
10586 <pre>
10588 int isnan(real-floating x);</pre>
10591 The isnan macro determines whether its argument value is a NaN. First, an argument
10592 represented in a format wider than its semantic type is converted to its semantic type.
10593 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
10596 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
10599 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
10600 NaNs in the evaluation type but not in the semantic type.
10601 </small>
10606 <pre>
10608 int isnormal(real-floating x);</pre>
10613 <!--page 230 -->
10616 The isnormal macro determines whether its argument value is normal (neither zero,
10617 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
10618 semantic type is converted to its semantic type. Then determination is based on the type
10619 of the argument.
10622 The isnormal macro returns a nonzero value if and only if its argument has a normal
10623 value.
10628 <pre>
10630 int signbit(real-floating x);</pre>
10633 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
10636 The signbit macro returns a nonzero value if and only if the sign of its argument value
10637 is negative.
10640 <p><small><a name="note207" href="#note207">207)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
10641 unsigned, it is treated as positive.
10642 </small>
10649 <pre>
10651 double acos(double x);
10652 float acosf(float x);
10653 long double acosl(long double x);</pre>
10656 The acos functions compute the principal value of the arc cosine of x. A domain error
10660 The acos functions return arccos x in the interval [0, pi ] radians.
10665 <!--page 231 -->
10670 <pre>
10672 double asin(double x);
10673 float asinf(float x);
10674 long double asinl(long double x);</pre>
10677 The asin functions compute the principal value of the arc sine of x. A domain error
10686 <pre>
10688 double atan(double x);
10689 float atanf(float x);
10690 long double atanl(long double x);</pre>
10693 The atan functions compute the principal value of the arc tangent of x.
10701 <pre>
10703 double atan2(double y, double x);
10704 float atan2f(float y, float x);
10705 long double atan2l(long double y, long double x);</pre>
10708 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
10709 arguments to determine the quadrant of the return value. A domain error may occur if
10710 both arguments are zero.
10713 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
10714 <!--page 232 -->
10719 <pre>
10721 double cos(double x);
10722 float cosf(float x);
10723 long double cosl(long double x);</pre>
10726 The cos functions compute the cosine of x (measured in radians).
10729 The cos functions return cos x.
10734 <pre>
10736 double sin(double x);
10737 float sinf(float x);
10738 long double sinl(long double x);</pre>
10741 The sin functions compute the sine of x (measured in radians).
10744 The sin functions return sin x.
10749 <pre>
10751 double tan(double x);
10752 float tanf(float x);
10753 long double tanl(long double x);</pre>
10756 The tan functions return the tangent of x (measured in radians).
10759 The tan functions return tan x.
10760 <!--page 233 -->
10767 <pre>
10769 double acosh(double x);
10770 float acoshf(float x);
10771 long double acoshl(long double x);</pre>
10774 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
10775 error occurs for arguments less than 1.
10778 The acosh functions return arcosh x in the interval [0, +(inf)].
10783 <pre>
10785 double asinh(double x);
10786 float asinhf(float x);
10787 long double asinhl(long double x);</pre>
10790 The asinh functions compute the arc hyperbolic sine of x.
10793 The asinh functions return arsinh x.
10798 <pre>
10800 double atanh(double x);
10801 float atanhf(float x);
10802 long double atanhl(long double x);</pre>
10805 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
10808 <!--page 234 -->
10811 The atanh functions return artanh x.
10816 <pre>
10818 double cosh(double x);
10819 float coshf(float x);
10820 long double coshl(long double x);</pre>
10823 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
10824 magnitude of x is too large.
10827 The cosh functions return cosh x.
10832 <pre>
10834 double sinh(double x);
10835 float sinhf(float x);
10836 long double sinhl(long double x);</pre>
10839 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10840 magnitude of x is too large.
10843 The sinh functions return sinh x.
10848 <pre>
10850 double tanh(double x);
10851 float tanhf(float x);
10852 long double tanhl(long double x);</pre>
10855 The tanh functions compute the hyperbolic tangent of x.
10856 <!--page 235 -->
10859 The tanh functions return tanh x.
10866 <pre>
10868 double exp(double x);
10869 float expf(float x);
10870 long double expl(long double x);</pre>
10873 The exp functions compute the base-e exponential of x. A range error occurs if the
10874 magnitude of x is too large.
10882 <pre>
10884 double exp2(double x);
10885 float exp2f(float x);
10886 long double exp2l(long double x);</pre>
10889 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10890 magnitude of x is too large.
10898 <!--page 236 -->
10899 <pre>
10901 double expm1(double x);
10902 float expm1f(float x);
10903 long double expm1l(long double x);</pre>
10906 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10913 <p><small><a name="note208" href="#note208">208)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10914 </small>
10919 <pre>
10921 double frexp(double value, int *exp);
10922 float frexpf(float value, int *exp);
10923 long double frexpl(long double value, int *exp);</pre>
10926 The frexp functions break a floating-point number into a normalized fraction and an
10927 integral power of 2. They store the integer in the int object pointed to by exp.
10930 If value is not a floating-point number, the results are unspecified. Otherwise, the
10932 zero, and value equals x 2<sup>*exp</sup> . If value is zero, both parts of the result are zero.
10937 <pre>
10939 int ilogb(double x);
10940 int ilogbf(float x);
10941 int ilogbl(long double x);</pre>
10944 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10945 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10946 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10947 the corresponding logb function and casting the returned value to type int. A domain
10948 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10949 the range of the return type, the numeric result is unspecified.
10954 <!--page 237 -->
10957 The ilogb functions return the exponent of x as a signed int value.
10963 <pre>
10965 double ldexp(double x, int exp);
10966 float ldexpf(float x, int exp);
10967 long double ldexpl(long double x, int exp);</pre>
10970 The ldexp functions multiply a floating-point number by an integral power of 2. A
10971 range error may occur.
10979 <pre>
10981 double log(double x);
10982 float logf(float x);
10983 long double logl(long double x);</pre>
10986 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10987 the argument is negative. A range error may occur if the argument is zero.
10990 The log functions return loge x.
10995 <!--page 238 -->
10996 <pre>
10998 double log10(double x);
10999 float log10f(float x);
11000 long double log10l(long double x);</pre>
11003 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11004 occurs if the argument is negative. A range error may occur if the argument is zero.
11007 The log10 functions return log10 x.
11012 <pre>
11014 double log1p(double x);
11015 float log1pf(float x);
11016 long double log1pl(long double x);</pre>
11019 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11020 A domain error occurs if the argument is less than -1. A range error may occur if the
11021 argument equals -1.
11024 The log1p functions return loge (1 + x).
11027 <p><small><a name="note209" href="#note209">209)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
11028 </small>
11033 <pre>
11035 double log2(double x);
11036 float log2f(float x);
11037 long double log2l(long double x);</pre>
11040 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11041 argument is less than zero. A range error may occur if the argument is zero.
11044 The log2 functions return log2 x.
11049 <!--page 239 -->
11054 <pre>
11056 double logb(double x);
11057 float logbf(float x);
11058 long double logbl(long double x);</pre>
11061 The logb functions extract the exponent of x, as a signed integer value in floating-point
11062 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11063 finite x,
11064 <pre>
11066 A domain error or range error may occur if the argument is zero.
11069 The logb functions return the signed exponent of x.
11074 <pre>
11076 double modf(double value, double *iptr);
11077 float modff(float value, float *iptr);
11078 long double modfl(long double value, long double *iptr);</pre>
11081 The modf functions break the argument value into integral and fractional parts, each of
11082 which has the same type and sign as the argument. They store the integral part (in
11083 floating-point format) in the object pointed to by iptr.
11086 The modf functions return the signed fractional part of value.
11087 <!--page 240 -->
11092 <pre>
11094 double scalbn(double x, int n);
11095 float scalbnf(float x, int n);
11096 long double scalbnl(long double x, int n);
11097 double scalbln(double x, long int n);
11098 float scalblnf(float x, long int n);
11099 long double scalblnl(long double x, long int n);</pre>
11113 <pre>
11115 double cbrt(double x);
11116 float cbrtf(float x);
11117 long double cbrtl(long double x);</pre>
11120 The cbrt functions compute the real cube root of x.
11128 <pre>
11130 double fabs(double x);
11131 float fabsf(float x);
11132 long double fabsl(long double x);</pre>
11135 The fabs functions compute the absolute value of a floating-point number x.
11136 <!--page 241 -->
11139 The fabs functions return | x |.
11144 <pre>
11146 double hypot(double x, double y);
11147 float hypotf(float x, float y);
11148 long double hypotl(long double x, long double y);</pre>
11151 The hypot functions compute the square root of the sum of the squares of x and y,
11152 without undue overflow or underflow. A range error may occur.
11161 <pre>
11163 double pow(double x, double y);
11164 float powf(float x, float y);
11165 long double powl(long double x, long double y);</pre>
11168 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11169 and negative and y is finite and not an integer value. A range error may occur. A domain
11170 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11171 is zero and y is less than zero.
11179 <!--page 242 -->
11180 <pre>
11182 double sqrt(double x);
11183 float sqrtf(float x);
11184 long double sqrtl(long double x);</pre>
11187 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11188 the argument is less than zero.
11191 The sqrt functions return (sqrt)(x).
11198 <pre>
11200 double erf(double x);
11201 float erff(float x);
11202 long double erfl(long double x);</pre>
11205 The erf functions compute the error function of x.
11208 The erf functions return
11209 <pre>
11210 2 x
11217 <pre>
11219 double erfc(double x);
11220 float erfcf(float x);
11221 long double erfcl(long double x);</pre>
11224 The erfc functions compute the complementary error function of x. A range error
11225 occurs if x is too large.
11228 The erfc functions return
11229 <pre>
11230 2 (inf)
11232 (sqrt)(pi) x </pre>
11234 <!--page 243 -->
11238 <pre>
11240 double lgamma(double x);
11241 float lgammaf(float x);
11242 long double lgammal(long double x);</pre>
11245 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11246 x. A range error occurs if x is too large. A range error may occur if x is a negative
11247 integer or zero.
11250 The lgamma functions return loge | (Gamma)(x) |.
11255 <pre>
11257 double tgamma(double x);
11258 float tgammaf(float x);
11259 long double tgammal(long double x);</pre>
11262 The tgamma functions compute the gamma function of x. A domain error or range error
11263 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11264 x is too large or too small.
11267 The tgamma functions return (Gamma)(x).
11274 <pre>
11276 double ceil(double x);
11277 float ceilf(float x);
11278 long double ceill(long double x);</pre>
11281 The ceil functions compute the smallest integer value not less than x.
11282 <!--page 244 -->
11285 The ceil functions return [^x^], expressed as a floating-point number.
11290 <pre>
11292 double floor(double x);
11293 float floorf(float x);
11294 long double floorl(long double x);</pre>
11297 The floor functions compute the largest integer value not greater than x.
11300 The floor functions return [_x_], expressed as a floating-point number.
11305 <pre>
11307 double nearbyint(double x);
11308 float nearbyintf(float x);
11309 long double nearbyintl(long double x);</pre>
11312 The nearbyint functions round their argument to an integer value in floating-point
11313 format, using the current rounding direction and without raising the ''inexact'' floating-
11314 point exception.
11317 The nearbyint functions return the rounded integer value.
11322 <pre>
11324 double rint(double x);
11325 float rintf(float x);
11326 long double rintl(long double x);</pre>
11329 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11330 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11331 value from the argument.
11332 <!--page 245 -->
11335 The rint functions return the rounded integer value.
11340 <pre>
11342 long int lrint(double x);
11343 long int lrintf(float x);
11344 long int lrintl(long double x);
11345 long long int llrint(double x);
11346 long long int llrintf(float x);
11347 long long int llrintl(long double x);</pre>
11350 The lrint and llrint functions round their argument to the nearest integer value,
11351 rounding according to the current rounding direction. If the rounded value is outside the
11352 range of the return type, the numeric result is unspecified and a domain error or range
11353 error may occur. *
11356 The lrint and llrint functions return the rounded integer value.
11361 <pre>
11363 double round(double x);
11364 float roundf(float x);
11365 long double roundl(long double x);</pre>
11368 The round functions round their argument to the nearest integer value in floating-point
11369 format, rounding halfway cases away from zero, regardless of the current rounding
11370 direction.
11373 The round functions return the rounded integer value.
11374 <!--page 246 -->
11379 <pre>
11381 long int lround(double x);
11382 long int lroundf(float x);
11383 long int lroundl(long double x);
11384 long long int llround(double x);
11385 long long int llroundf(float x);
11386 long long int llroundl(long double x);</pre>
11389 The lround and llround functions round their argument to the nearest integer value,
11390 rounding halfway cases away from zero, regardless of the current rounding direction. If
11391 the rounded value is outside the range of the return type, the numeric result is unspecified
11392 and a domain error or range error may occur.
11395 The lround and llround functions return the rounded integer value.
11400 <pre>
11402 double trunc(double x);
11403 float truncf(float x);
11404 long double truncl(long double x);</pre>
11407 The trunc functions round their argument to the integer value, in floating format,
11408 nearest to but no larger in magnitude than the argument.
11411 The trunc functions return the truncated integer value.
11412 <!--page 247 -->
11419 <pre>
11421 double fmod(double x, double y);
11422 float fmodf(float x, float y);
11423 long double fmodl(long double x, long double y);</pre>
11426 The fmod functions compute the floating-point remainder of x/y.
11429 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11430 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11431 whether a domain error occurs or the fmod functions return zero is implementation-
11432 defined.
11437 <pre>
11439 double remainder(double x, double y);
11440 float remainderf(float x, float y);
11441 long double remainderl(long double x, long double y);</pre>
11444 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11447 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11448 or the functions return zero is implementation defined.
11453 <!--page 248 -->
11456 <p><small><a name="note210" href="#note210">210)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
11457 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11458 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11459 x.'' This definition is applicable for all implementations.
11460 </small>
11465 <pre>
11467 double remquo(double x, double y, int *quo);
11468 float remquof(float x, float y, int *quo);
11469 long double remquol(long double x, long double y,
11470 int *quo);</pre>
11473 The remquo functions compute the same remainder as the remainder functions. In
11474 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11475 magnitude is congruent modulo 2<sup>n</sup> to the magnitude of the integral quotient of x/y, where
11476 n is an implementation-defined integer greater than or equal to 3.
11479 The remquo functions return x REM y. If y is zero, the value stored in the object
11480 pointed to by quo is unspecified and whether a domain error occurs or the functions
11481 return zero is implementation defined.
11488 <pre>
11490 double copysign(double x, double y);
11491 float copysignf(float x, float y);
11492 long double copysignl(long double x, long double y);</pre>
11495 The copysign functions produce a value with the magnitude of x and the sign of y.
11496 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
11497 represent a signed zero but do not treat negative zero consistently in arithmetic
11498 operations, the copysign functions regard the sign of zero as positive.
11501 The copysign functions return a value with the magnitude of x and the sign of y.
11502 <!--page 249 -->
11507 <pre>
11509 double nan(const char *tagp);
11510 float nanf(const char *tagp);
11511 long double nanl(const char *tagp);</pre>
11516 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
11517 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
11518 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
11519 and strtold.
11522 The nan functions return a quiet NaN, if available, with content indicated through tagp.
11523 If the implementation does not support quiet NaNs, the functions return zero.
11524 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
11529 <pre>
11531 double nextafter(double x, double y);
11532 float nextafterf(float x, float y);
11533 long double nextafterl(long double x, long double y);</pre>
11536 The nextafter functions determine the next representable value, in the type of the
11537 function, after x in the direction of y, where x and y are first converted to the type of the
11538 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
11539 if the magnitude of x is the largest finite value representable in the type and the result is
11540 infinite or not representable in the type.
11543 The nextafter functions return the next representable value in the specified format
11544 after x in the direction of y.
11547 <!--page 250 -->
11550 <p><small><a name="note211" href="#note211">211)</a> The argument values are converted to the type of the function, even by a macro implementation of the
11551 function.
11552 </small>
11557 <pre>
11559 double nexttoward(double x, long double y);
11560 float nexttowardf(float x, long double y);
11561 long double nexttowardl(long double x, long double y);</pre>
11564 The nexttoward functions are equivalent to the nextafter functions except that the
11565 second parameter has type long double and the functions return y converted to the
11569 <p><small><a name="note212" href="#note212">212)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
11570 range or precision in a floating second argument.
11571 </small>
11573 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
11578 <pre>
11580 double fdim(double x, double y);
11581 float fdimf(float x, float y);
11582 long double fdiml(long double x, long double y);</pre>
11585 The fdim functions determine the positive difference between their arguments:
11586 <pre>
11587 {x - y if x > y
11588 {
11590 A range error may occur.
11593 The fdim functions return the positive difference value.
11598 <pre>
11600 double fmax(double x, double y);
11601 float fmaxf(float x, float y);
11602 long double fmaxl(long double x, long double y);</pre>
11606 <!--page 251 -->
11609 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
11612 The fmax functions return the maximum numeric value of their arguments.
11615 <p><small><a name="note213" href="#note213">213)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
11617 </small>
11622 <pre>
11624 double fmin(double x, double y);
11625 float fminf(float x, float y);
11626 long double fminl(long double x, long double y);</pre>
11629 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
11632 The fmin functions return the minimum numeric value of their arguments.
11635 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
11636 </small>
11643 <pre>
11645 double fma(double x, double y, double z);
11646 float fmaf(float x, float y, float z);
11647 long double fmal(long double x, long double y,
11648 long double z);</pre>
11651 The fma functions compute (x y) + z, rounded as one ternary operation: they compute
11652 the value (as if) to infinite precision and round once to the result format, according to the
11653 current rounding mode. A range error may occur.
11656 The fma functions return (x y) + z, rounded as one ternary operation.
11661 <!--page 252 -->
11665 The relational and equality operators support the usual mathematical relationships
11666 between numeric values. For any ordered pair of numeric values exactly one of the
11667 relationships -- less, greater, and equal -- is true. Relational operators may raise the
11668 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
11669 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
11670 subclauses provide macros that are quiet (non floating-point exception raising) versions
11671 of the relational operators, and other comparison macros that facilitate writing efficient
11672 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
11673 the synopses in this subclause, real-floating indicates that the argument shall be an
11674 expression of real floating type.
11677 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
11678 the operands compare unordered, as an error indicator for programs written without consideration of
11679 NaNs; the result in these cases is false.
11680 </small>
11685 <pre>
11687 int isgreater(real-floating x, real-floating y);</pre>
11690 The isgreater macro determines whether its first argument is greater than its second
11691 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
11692 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
11693 exception when x and y are unordered.
11696 The isgreater macro returns the value of (x) > (y).
11701 <pre>
11703 int isgreaterequal(real-floating x, real-floating y);</pre>
11706 The isgreaterequal macro determines whether its first argument is greater than or
11707 equal to its second argument. The value of isgreaterequal(x, y) is always equal
11709 not raise the ''invalid'' floating-point exception when x and y are unordered.
11713 <!--page 253 -->
11716 The isgreaterequal macro returns the value of (x) >= (y).
11721 <pre>
11723 int isless(real-floating x, real-floating y);</pre>
11726 The isless macro determines whether its first argument is less than its second
11727 argument. The value of isless(x, y) is always equal to (x) < (y); however,
11728 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
11729 exception when x and y are unordered.
11732 The isless macro returns the value of (x) < (y).
11737 <pre>
11739 int islessequal(real-floating x, real-floating y);</pre>
11742 The islessequal macro determines whether its first argument is less than or equal to
11743 its second argument. The value of islessequal(x, y) is always equal to
11745 the ''invalid'' floating-point exception when x and y are unordered.
11748 The islessequal macro returns the value of (x) <= (y).
11753 <pre>
11755 int islessgreater(real-floating x, real-floating y);</pre>
11758 The islessgreater macro determines whether its first argument is less than or
11759 greater than its second argument. The islessgreater(x, y) macro is similar to
11761 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
11762 and y twice).
11763 <!--page 254 -->
11771 <pre>
11773 int isunordered(real-floating x, real-floating y);</pre>
11776 The isunordered macro determines whether its arguments are unordered.
11780 <!--page 255 -->
11784 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
11785 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
11787 The type declared is
11788 <pre>
11789 jmp_buf</pre>
11790 which is an array type suitable for holding the information needed to restore a calling
11791 environment. The environment of a call to the setjmp macro consists of information
11792 sufficient for a call to the longjmp function to return execution to the correct block and
11793 invocation of that block, were it called recursively. It does not include the state of the
11794 floating-point status flags, of open files, or of any other component of the abstract
11795 machine.
11797 It is unspecified whether setjmp is a macro or an identifier declared with external
11798 linkage. If a macro definition is suppressed in order to access an actual function, or a
11799 program defines an external identifier with the name setjmp, the behavior is undefined.
11802 <p><small><a name="note216" href="#note216">216)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
11803 a program.
11804 </small>
11811 <pre>
11813 int setjmp(jmp_buf env);</pre>
11816 The setjmp macro saves its calling environment in its jmp_buf argument for later use
11817 by the longjmp function.
11820 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
11821 return is from a call to the longjmp function, the setjmp macro returns a nonzero
11822 value.
11825 An invocation of the setjmp macro shall appear only in one of the following contexts:
11826 <ul>
11827 <li> the entire controlling expression of a selection or iteration statement;
11828 <li> one operand of a relational or equality operator with the other operand an integer
11829 constant expression, with the resulting expression being the entire controlling
11832 <!--page 256 -->
11833 expression of a selection or iteration statement;
11834 <li> the operand of a unary ! operator with the resulting expression being the entire
11835 controlling expression of a selection or iteration statement; or
11836 <li> the entire expression of an expression statement (possibly cast to void).
11837 </ul>
11839 If the invocation appears in any other context, the behavior is undefined.
11846 <pre>
11848 void longjmp(jmp_buf env, int val);</pre>
11851 The longjmp function restores the environment saved by the most recent invocation of
11852 the setjmp macro in the same invocation of the program with the corresponding
11853 jmp_buf argument. If there has been no such invocation, or if the function containing
11854 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
11855 invocation of the setjmp macro was within the scope of an identifier with variably
11856 modified type and execution has left that scope in the interim, the behavior is undefined.
11858 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
11859 have state, as of the time the longjmp function was called, except that the values of
11860 objects of automatic storage duration that are local to the function containing the
11861 invocation of the corresponding setjmp macro that do not have volatile-qualified type
11862 and have been changed between the setjmp invocation and longjmp call are
11863 indeterminate.
11866 After longjmp is completed, program execution continues as if the corresponding
11867 invocation of the setjmp macro had just returned the value specified by val. The
11869 the setjmp macro returns the value 1.
11871 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
11872 might cause memory associated with a variable length array object to be squandered.
11877 <!--page 257 -->
11878 <!--page 258 -->
11879 <pre>
11881 jmp_buf buf;
11882 void g(int n);
11883 void h(int n);
11884 int n = 6;
11885 void f(void)
11886 {
11887 int x[n]; // valid: f is not terminated
11888 setjmp(buf);
11889 g(n);
11890 }
11891 void g(int n)
11892 {
11893 int a[n]; // a may remain allocated
11894 h(n);
11895 }
11896 void h(int n)
11897 {
11898 int b[n]; // b may remain allocated
11899 longjmp(buf, 2); // might cause memory loss
11900 }</pre>
11903 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
11904 transfer to a setjmp invocation in a function earlier in the set of nested calls.
11905 </small>
11906 <p><small><a name="note218" href="#note218">218)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
11907 </small>
11911 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
11912 for handling various signals (conditions that may be reported during program execution).
11914 The type defined is
11915 <pre>
11916 sig_atomic_t</pre>
11917 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
11918 an atomic entity, even in the presence of asynchronous interrupts.
11920 The macros defined are
11921 <pre>
11922 SIG_DFL
11923 SIG_ERR
11924 SIG_IGN</pre>
11925 which expand to constant expressions with distinct values that have type compatible with
11926 the second argument to, and the return value of, the signal function, and whose values
11927 compare unequal to the address of any declarable function; and the following, which
11928 expand to positive integer constant expressions with type int and distinct values that are
11929 the signal numbers, each corresponding to the specified condition:
11931 <pre>
11932 SIGABRT abnormal termination, such as is initiated by the abort function
11933 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
11934 resulting in overflow
11935 SIGILL detection of an invalid function image, such as an invalid instruction
11936 SIGINT receipt of an interactive attention signal
11937 SIGSEGV an invalid access to storage
11938 SIGTERM a termination request sent to the program</pre>
11939 An implementation need not generate any of these signals, except as a result of explicit
11940 calls to the raise function. Additional signals and pointers to undeclarable functions,
11941 with macro definitions beginning, respectively, with the letters SIG and an uppercase
11942 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
11943 implementation. The complete set of signals, their semantics, and their default handling
11944 is implementation-defined; all signal numbers shall be positive.
11949 <!--page 259 -->
11952 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>). The names of the signal numbers reflect the following terms
11953 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
11954 and termination.
11955 </small>
11962 <pre>
11964 void (*signal(int sig, void (*func)(int)))(int);</pre>
11967 The signal function chooses one of three ways in which receipt of the signal number
11968 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
11969 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
11970 Otherwise, func shall point to a function to be called when that signal occurs. An
11971 invocation of such a function because of a signal, or (recursively) of any further functions
11972 called by that invocation (other than functions in the standard library), is called a signal
11973 handler.
11975 When a signal occurs and func points to a function, it is implementation-defined
11976 whether the equivalent of signal(sig, SIG_DFL); is executed or the
11977 implementation prevents some implementation-defined set of signals (at least including
11978 sig) from occurring until the current signal handling has completed; in the case of
11979 SIGILL, the implementation may alternatively define that no action is taken. Then the
11980 equivalent of (*func)(sig); is executed. If and when the function returns, if the
11981 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
11982 value corresponding to a computational exception, the behavior is undefined; otherwise
11983 the program will resume execution at the point it was interrupted.
11985 If the signal occurs as the result of calling the abort or raise function, the signal
11986 handler shall not call the raise function.
11988 If the signal occurs other than as the result of calling the abort or raise function, the
11989 behavior is undefined if the signal handler refers to any object with static storage duration
11990 other than by assigning a value to an object declared as volatile sig_atomic_t, or
11991 the signal handler calls any function in the standard library other than the abort
11992 function, the _Exit function, or the signal function with the first argument equal to
11993 the signal number corresponding to the signal that caused the invocation of the handler.
11994 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
11997 At program startup, the equivalent of
11998 <pre>
11999 signal(sig, SIG_IGN);</pre>
12002 <!--page 260 -->
12003 may be executed for some signals selected in an implementation-defined manner; the
12004 equivalent of
12005 <pre>
12006 signal(sig, SIG_DFL);</pre>
12007 is executed for all other signals defined by the implementation.
12009 The implementation shall behave as if no library function calls the signal function.
12012 If the request can be honored, the signal function returns the value of func for the
12013 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12014 SIG_ERR is returned and a positive value is stored in errno.
12015 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the
12019 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12020 </small>
12027 <pre>
12029 int raise(int sig);</pre>
12032 The raise function carries out the actions described in <a href="#7.14.1.1">7.14.1.1</a> for the signal sig. If a
12033 signal handler is called, the raise function shall not return until after the signal handler
12034 does.
12037 The raise function returns zero if successful, nonzero if unsuccessful.
12038 <!--page 261 -->
12042 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12043 through a list of arguments whose number and types are not known to the called function
12044 when it is translated.
12046 A function may be called with a variable number of arguments of varying types. As
12047 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12048 parameter plays a special role in the access mechanism, and will be designated parmN in
12049 this description.
12051 The type declared is
12052 <pre>
12053 va_list</pre>
12054 which is an object type suitable for holding information needed by the macros
12055 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12056 desired, the called function shall declare an object (generally referred to as ap in this
12057 subclause) having type va_list. The object ap may be passed as an argument to
12058 another function; if that function invokes the va_arg macro with parameter ap, the
12059 value of ap in the calling function is indeterminate and shall be passed to the va_end
12063 <p><small><a name="note221" href="#note221">221)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
12064 case the original function may make further use of the original list after the other function returns.
12065 </small>
12069 The va_start and va_arg macros described in this subclause shall be implemented
12070 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12071 identifiers declared with external linkage. If a macro definition is suppressed in order to
12072 access an actual function, or a program defines an external identifier with the same name,
12073 the behavior is undefined. Each invocation of the va_start and va_copy macros
12074 shall be matched by a corresponding invocation of the va_end macro in the same
12075 function.
12080 <pre>
12082 type va_arg(va_list ap, type);</pre>
12085 The va_arg macro expands to an expression that has the specified type and the value of
12086 the next argument in the call. The parameter ap shall have been initialized by the
12087 va_start or va_copy macro (without an intervening invocation of the va_end
12089 <!--page 262 -->
12090 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12091 values of successive arguments are returned in turn. The parameter type shall be a type
12092 name specified such that the type of a pointer to an object that has the specified type can
12093 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12094 type is not compatible with the type of the actual next argument (as promoted according
12095 to the default argument promotions), the behavior is undefined, except for the following
12096 cases:
12097 <ul>
12098 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12099 type, and the value is representable in both types;
12100 <li> one type is pointer to void and the other is a pointer to a character type.
12101 </ul>
12104 The first invocation of the va_arg macro after that of the va_start macro returns the
12105 value of the argument after that specified by parmN . Successive invocations return the
12106 values of the remaining arguments in succession.
12111 <pre>
12113 void va_copy(va_list dest, va_list src);</pre>
12116 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12117 been applied to dest followed by the same sequence of uses of the va_arg macro as
12118 had previously been used to reach the present state of src. Neither the va_copy nor
12119 va_start macro shall be invoked to reinitialize dest without an intervening
12120 invocation of the va_end macro for the same dest.
12123 The va_copy macro returns no value.
12128 <pre>
12130 void va_end(va_list ap);</pre>
12133 The va_end macro facilitates a normal return from the function whose variable
12134 argument list was referred to by the expansion of the va_start macro, or the function
12135 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12136 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12137 <!--page 263 -->
12138 by the va_start or va_copy macro). If there is no corresponding invocation of the
12139 va_start or va_copy macro, or if the va_end macro is not invoked before the
12140 return, the behavior is undefined.
12143 The va_end macro returns no value.
12148 <pre>
12150 void va_start(va_list ap, parmN);</pre>
12153 The va_start macro shall be invoked before any access to the unnamed arguments.
12155 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12156 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12157 without an intervening invocation of the va_end macro for the same ap.
12159 The parameter parmN is the identifier of the rightmost parameter in the variable
12160 parameter list in the function definition (the one just before the , ...). If the parameter
12161 parmN is declared with the register storage class, with a function or array type, or
12162 with a type that is not compatible with the type that results after application of the default
12163 argument promotions, the behavior is undefined.
12166 The va_start macro returns no value.
12168 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12169 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12170 pointers is specified by the first argument to f1.
12171 <!--page 264 -->
12172 <pre>
12174 #define MAXARGS 31
12175 void f1(int n_ptrs, ...)
12176 {
12177 va_list ap;
12178 char *array[MAXARGS];
12179 int ptr_no = 0;
12180 if (n_ptrs > MAXARGS)
12181 n_ptrs = MAXARGS;
12182 va_start(ap, n_ptrs);
12183 while (ptr_no < n_ptrs)
12184 array[ptr_no++] = va_arg(ap, char *);
12185 va_end(ap);
12186 f2(n_ptrs, array);
12187 }</pre>
12188 Each call to f1 is required to have visible the definition of the function or a declaration such as
12189 <pre>
12190 void f1(int, ...);</pre>
12193 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12194 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12195 is gathered again and passed to function f4.
12196 <!--page 265 -->
12197 <pre>
12199 #define MAXARGS 31
12200 void f3(int n_ptrs, int f4_after, ...)
12201 {
12202 va_list ap, ap_save;
12203 char *array[MAXARGS];
12204 int ptr_no = 0;
12205 if (n_ptrs > MAXARGS)
12206 n_ptrs = MAXARGS;
12207 va_start(ap, f4_after);
12208 while (ptr_no < n_ptrs) {
12209 array[ptr_no++] = va_arg(ap, char *);
12210 if (ptr_no == f4_after)
12211 va_copy(ap_save, ap);
12212 }
12213 va_end(ap);
12214 f2(n_ptrs, array);
12215 // Now process the saved copy.
12216 n_ptrs -= f4_after;
12217 ptr_no = 0;
12218 while (ptr_no < n_ptrs)
12219 array[ptr_no++] = va_arg(ap_save, char *);
12220 va_end(ap_save);
12221 f4(n_ptrs, array);
12222 }</pre>
12228 The macro
12229 <pre>
12230 bool</pre>
12231 expands to _Bool.
12233 The remaining three macros are suitable for use in #if preprocessing directives. They
12234 are
12235 <pre>
12236 true</pre>
12237 which expands to the integer constant 1,
12238 <pre>
12239 false</pre>
12240 which expands to the integer constant 0, and
12241 <pre>
12242 __bool_true_false_are_defined</pre>
12243 which expands to the integer constant 1.
12245 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12251 <!--page 266 -->
12254 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12255 </small>
12259 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12260 are also defined in other headers, as noted in their respective subclauses.
12262 The types are
12263 <pre>
12264 ptrdiff_t</pre>
12265 which is the signed integer type of the result of subtracting two pointers;
12266 <pre>
12267 size_t</pre>
12268 which is the unsigned integer type of the result of the sizeof operator; and
12269 <pre>
12270 wchar_t</pre>
12271 which is an integer type whose range of values can represent distinct codes for all
12272 members of the largest extended character set specified among the supported locales; the
12273 null character shall have the code value zero. Each member of the basic character set
12274 shall have a code value equal to its value when used as the lone character in an integer
12275 character constant if an implementation does not define
12276 __STDC_MB_MIGHT_NEQ_WC__.
12278 The macros are
12279 <pre>
12280 NULL</pre>
12281 which expands to an implementation-defined null pointer constant; and
12282 <pre>
12283 offsetof(type, member-designator)</pre>
12284 which expands to an integer constant expression that has type size_t, the value of
12285 which is the offset in bytes, to the structure member (designated by member-designator),
12286 from the beginning of its structure (designated by type). The type and member designator
12287 shall be such that given
12288 <pre>
12289 static type t;</pre>
12290 then the expression &(t.member-designator) evaluates to an address constant. (If the
12291 specified member is a bit-field, the behavior is undefined.)
12294 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12295 greater than that of signed long int unless the implementation supports objects
12296 large enough to make this necessary.
12298 <!--page 267 -->
12302 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12303 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12304 integer types corresponding to types defined in other standard headers.
12306 Types are defined in the following categories:
12307 <ul>
12308 <li> integer types having certain exact widths;
12309 <li> integer types having at least certain specified widths;
12310 <li> fastest integer types having at least certain specified widths;
12311 <li> integer types wide enough to hold pointers to objects;
12312 <li> integer types having greatest width.
12313 </ul>
12314 (Some of these types may denote the same type.)
12316 Corresponding macros specify limits of the declared types and construct suitable
12317 constants.
12319 For each type described herein that the implementation provides,<sup><a href="#note224"><b>224)</b></a></sup> <a href="#7.18"><stdint.h></a> shall
12320 declare that typedef name and define the associated macros. Conversely, for each type
12321 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12322 declare that typedef name nor shall it define the associated macros. An implementation
12323 shall provide those types described as ''required'', but need not provide any of the others
12324 (described as ''optional'').
12327 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12328 </small>
12329 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12330 </small>
12334 When typedef names differing only in the absence or presence of the initial u are defined,
12335 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12336 implementation providing one of these corresponding types shall also provide the other.
12338 In the following descriptions, the symbol N represents an unsigned decimal integer with
12344 <!--page 268 -->
12348 The typedef name intN_t designates a signed integer type with width N , no padding
12349 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12350 type with a width of exactly 8 bits.
12352 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12353 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12355 These types are optional. However, if an implementation provides integer types with
12357 two's complement representation, it shall define the corresponding typedef names.
12361 The typedef name int_leastN_t designates a signed integer type with a width of at
12362 least N , such that no signed integer type with lesser size has at least the specified width.
12363 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12365 The typedef name uint_leastN_t designates an unsigned integer type with a width
12366 of at least N , such that no unsigned integer type with lesser size has at least the specified
12367 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12368 least 16 bits.
12370 The following types are required:
12371 <pre>
12372 int_least8_t uint_least8_t
12373 int_least16_t uint_least16_t
12374 int_least32_t uint_least32_t
12375 int_least64_t uint_least64_t</pre>
12376 All other types of this form are optional.
12380 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12381 with among all integer types that have at least the specified width.
12383 The typedef name int_fastN_t designates the fastest signed integer type with a width
12384 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12385 type with a width of at least N .
12390 <!--page 269 -->
12392 The following types are required:
12393 <pre>
12394 int_fast8_t uint_fast8_t
12395 int_fast16_t uint_fast16_t
12396 int_fast32_t uint_fast32_t
12397 int_fast64_t uint_fast64_t</pre>
12398 All other types of this form are optional.
12401 <p><small><a name="note225" href="#note225">225)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
12402 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12403 signedness and width requirements.
12404 </small>
12406 <h5><a name="7.18.1.4" href="#7.18.1.4">7.18.1.4 Integer types capable of holding object pointers</a></h5>
12408 The following type designates a signed integer type with the property that any valid
12409 pointer to void can be converted to this type, then converted back to pointer to void,
12410 and the result will compare equal to the original pointer:
12411 <pre>
12412 intptr_t</pre>
12413 The following type designates an unsigned integer type with the property that any valid
12414 pointer to void can be converted to this type, then converted back to pointer to void,
12415 and the result will compare equal to the original pointer:
12416 <pre>
12417 uintptr_t</pre>
12418 These types are optional.
12422 The following type designates a signed integer type capable of representing any value of
12423 any signed integer type:
12424 <pre>
12425 intmax_t</pre>
12426 The following type designates an unsigned integer type capable of representing any value
12427 of any unsigned integer type:
12428 <pre>
12429 uintmax_t</pre>
12430 These types are required.
12434 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
12435 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
12438 Each instance of any defined macro shall be replaced by a constant expression suitable
12439 for use in #if preprocessing directives, and this expression shall have the same type as
12440 would an expression that is an object of the corresponding type converted according to
12442 <!--page 270 -->
12443 the integer promotions. Its implementation-defined value shall be equal to or greater in
12444 magnitude (absolute value) than the corresponding value given below, with the same sign,
12445 except where stated to be exactly the given value.
12448 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12450 </small>
12454 <ul>
12455 <li> minimum values of exact-width signed integer types
12456 <pre>
12458 <li> maximum values of exact-width signed integer types
12459 <pre>
12461 <li> maximum values of exact-width unsigned integer types
12462 <pre>
12464 </ul>
12466 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
12468 <ul>
12469 <li> minimum values of minimum-width signed integer types
12470 <pre>
12472 <li> maximum values of minimum-width signed integer types
12473 <pre>
12475 <li> maximum values of minimum-width unsigned integer types
12476 <pre>
12478 </ul>
12480 <h5><a name="7.18.2.3" href="#7.18.2.3">7.18.2.3 Limits of fastest minimum-width integer types</a></h5>
12482 <ul>
12483 <li> minimum values of fastest minimum-width signed integer types
12484 <pre>
12486 <li> maximum values of fastest minimum-width signed integer types
12487 <pre>
12489 <li> maximum values of fastest minimum-width unsigned integer types
12490 <pre>
12492 </ul>
12494 <h5><a name="7.18.2.4" href="#7.18.2.4">7.18.2.4 Limits of integer types capable of holding object pointers</a></h5>
12496 <ul>
12497 <li> minimum value of pointer-holding signed integer type
12498 <pre>
12500 <li> maximum value of pointer-holding signed integer type
12501 <!--page 271 -->
12502 <pre>
12504 <li> maximum value of pointer-holding unsigned integer type
12505 <pre>
12507 </ul>
12509 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
12511 <ul>
12512 <li> minimum value of greatest-width signed integer type
12513 <pre>
12515 <li> maximum value of greatest-width signed integer type
12516 <pre>
12518 <li> maximum value of greatest-width unsigned integer type
12519 <pre>
12521 </ul>
12525 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
12526 integer types corresponding to types defined in other standard headers.
12528 Each instance of these macros shall be replaced by a constant expression suitable for use
12529 in #if preprocessing directives, and this expression shall have the same type as would an
12530 expression that is an object of the corresponding type converted according to the integer
12531 promotions. Its implementation-defined value shall be equal to or greater in magnitude
12532 (absolute value) than the corresponding value given below, with the same sign. An
12533 implementation shall define only the macros corresponding to those typedef names it
12535 <ul>
12536 <li> limits of ptrdiff_t
12537 <pre>
12538 PTRDIFF_MIN -65535
12539 PTRDIFF_MAX +65535
12540 </pre>
12541 <li> limits of sig_atomic_t
12542 <pre>
12543 SIG_ATOMIC_MIN see below
12544 SIG_ATOMIC_MAX see below
12545 </pre>
12546 <li> limit of size_t
12547 <pre>
12548 SIZE_MAX 65535
12549 </pre>
12550 <li> limits of wchar_t
12552 <!--page 272 -->
12553 <pre>
12554 WCHAR_MIN see below
12555 WCHAR_MAX see below
12556 </pre>
12557 <li> limits of wint_t
12558 <pre>
12559 WINT_MIN see below
12560 WINT_MAX see below
12561 </pre>
12562 </ul>
12564 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
12565 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
12566 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
12567 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
12568 SIG_ATOMIC_MAX shall be no less than 255.
12570 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
12572 otherwise, wchar_t is defined as an unsigned integer type, and the value of
12573 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note229"><b>229)</b></a></sup>
12575 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
12577 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
12581 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12583 </small>
12584 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
12585 </small>
12586 <p><small><a name="note229" href="#note229">229)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
12587 character set.
12588 </small>
12592 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
12593 initializing objects that have integer types corresponding to types defined in
12594 <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in <a href="#7.18.1.2">7.18.1.2</a> or
12597 The argument in any instance of these macros shall be an unsuffixed integer constant (as
12598 defined in <a href="#6.4.4.1">6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
12600 Each invocation of one of these macros shall expand to an integer constant expression
12601 suitable for use in #if preprocessing directives. The type of the expression shall have
12602 the same type as would an expression of the corresponding type converted according to
12603 the integer promotions. The value of the expression shall be that of the argument.
12608 <!--page 273 -->
12611 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
12613 </small>
12615 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
12617 The macro INTN_C(value) shall expand to an integer constant expression
12618 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
12619 to an integer constant expression corresponding to the type uint_leastN_t. For
12620 example, if uint_least64_t is a name for the type unsigned long long int,
12623 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
12625 The following macro expands to an integer constant expression having the value specified
12626 by its argument and the type intmax_t:
12627 <pre>
12628 INTMAX_C(value)</pre>
12629 The following macro expands to an integer constant expression having the value specified
12630 by its argument and the type uintmax_t:
12631 <!--page 274 -->
12632 <pre>
12633 UINTMAX_C(value)</pre>
12639 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
12640 performing input and output.
12643 <pre>
12644 FILE</pre>
12645 which is an object type capable of recording all the information needed to control a
12646 stream, including its file position indicator, a pointer to its associated buffer (if any), an
12647 error indicator that records whether a read/write error has occurred, and an end-of-file
12648 indicator that records whether the end of the file has been reached; and
12649 <pre>
12650 fpos_t</pre>
12651 which is an object type other than an array type capable of recording all the information
12652 needed to specify uniquely every position within a file.
12655 <pre>
12656 _IOFBF
12657 _IOLBF
12658 _IONBF</pre>
12659 which expand to integer constant expressions with distinct values, suitable for use as the
12660 third argument to the setvbuf function;
12661 <pre>
12662 BUFSIZ</pre>
12663 which expands to an integer constant expression that is the size of the buffer used by the
12664 setbuf function;
12665 <pre>
12666 EOF</pre>
12667 which expands to an integer constant expression, with type int and a negative value, that
12668 is returned by several functions to indicate end-of-file, that is, no more input from a
12669 stream;
12670 <pre>
12671 FOPEN_MAX</pre>
12672 which expands to an integer constant expression that is the minimum number of files that
12673 the implementation guarantees can be open simultaneously;
12674 <pre>
12675 FILENAME_MAX</pre>
12676 which expands to an integer constant expression that is the size needed for an array of
12677 char large enough to hold the longest file name string that the implementation
12678 <!--page 275 -->
12680 <pre>
12681 L_tmpnam</pre>
12682 which expands to an integer constant expression that is the size needed for an array of
12683 char large enough to hold a temporary file name string generated by the tmpnam
12684 function;
12685 <pre>
12686 SEEK_CUR
12687 SEEK_END
12688 SEEK_SET</pre>
12689 which expand to integer constant expressions with distinct values, suitable for use as the
12690 third argument to the fseek function;
12691 <pre>
12692 TMP_MAX</pre>
12693 which expands to an integer constant expression that is the maximum number of unique
12694 file names that can be generated by the tmpnam function;
12695 <pre>
12696 stderr
12697 stdin
12698 stdout</pre>
12699 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12700 associated, respectively, with the standard error, input, and output streams.
12702 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
12703 and output. The wide character input/output functions described in that subclause
12704 provide operations analogous to most of those described here, except that the
12705 fundamental units internal to the program are wide characters. The external
12706 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12709 The input/output functions are given the following collective terms:
12710 <ul>
12711 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
12712 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12713 fwscanf, wscanf, vfwscanf, and vwscanf.
12714 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
12715 output from wide characters and wide strings: fputwc, fputws, putwc,
12716 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12719 <!--page 276 -->
12720 <li> The wide character input/output functions -- the union of the ungetwc function, the
12721 wide character input functions, and the wide character output functions.
12722 <li> The byte input/output functions -- those functions described in this subclause that
12723 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12724 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
12725 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12726 </ul>
12727 <p><b> Forward references</b>: files (<a href="#7.19.3">7.19.3</a>), the fseek function (<a href="#7.19.9.2">7.19.9.2</a>), streams (<a href="#7.19.2">7.19.2</a>), the
12728 tmpnam function (<a href="#7.19.4.4">7.19.4.4</a>), <a href="#7.24"><wchar.h></a> (<a href="#7.24">7.24</a>).
12731 <p><small><a name="note231" href="#note231">231)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
12732 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12733 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12734 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12735 </small>
12739 Input and output, whether to or from physical devices such as terminals and tape drives,
12740 or whether to or from files supported on structured storage devices, are mapped into
12741 logical data streams, whose properties are more uniform than their various inputs and
12742 outputs. Two forms of mapping are supported, for text streams and for binary
12745 A text stream is an ordered sequence of characters composed into lines, each line
12746 consisting of zero or more characters plus a terminating new-line character. Whether the
12747 last line requires a terminating new-line character is implementation-defined. Characters
12748 may have to be added, altered, or deleted on input and output to conform to differing
12749 conventions for representing text in the host environment. Thus, there need not be a one-
12750 to-one correspondence between the characters in a stream and those in the external
12751 representation. Data read in from a text stream will necessarily compare equal to the data
12752 that were earlier written out to that stream only if: the data consist only of printing
12753 characters and the control characters horizontal tab and new-line; no new-line character is
12754 immediately preceded by space characters; and the last character is a new-line character.
12755 Whether space characters that are written out immediately before a new-line character
12756 appear when read in is implementation-defined.
12758 A binary stream is an ordered sequence of characters that can transparently record
12759 internal data. Data read in from a binary stream shall compare equal to the data that were
12760 earlier written out to that stream, under the same implementation. Such a stream may,
12761 however, have an implementation-defined number of null characters appended to the end
12762 of the stream.
12764 Each stream has an orientation. After a stream is associated with an external file, but
12765 before any operations are performed on it, the stream is without orientation. Once a wide
12766 character input/output function has been applied to a stream without orientation, the
12769 <!--page 277 -->
12770 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12771 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12772 Only a call to the freopen function or the fwide function can otherwise alter the
12773 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
12775 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12776 character input/output functions shall not be applied to a byte-oriented stream. The
12777 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12778 except for the following additional restrictions:
12779 <ul>
12780 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12781 text and binary streams.
12782 <li> For wide-oriented streams, after a successful call to a file-positioning function that
12783 leaves the file position indicator prior to the end-of-file, a wide character output
12784 function can overwrite a partial multibyte character; any file contents beyond the
12785 byte(s) written are henceforth indeterminate.
12786 </ul>
12788 Each wide-oriented stream has an associated mbstate_t object that stores the current
12789 parse state of the stream. A successful call to fgetpos stores a representation of the
12790 value of this mbstate_t object as part of the value of the fpos_t object. A later
12791 successful call to fsetpos using the same stored fpos_t value restores the value of
12792 the associated mbstate_t object as well as the position within the controlled stream.
12795 An implementation shall support text files with lines containing at least 254 characters,
12796 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12797 least 256.
12798 <p><b> Forward references</b>: the freopen function (<a href="#7.19.5.4">7.19.5.4</a>), the fwide function (<a href="#7.24.3.5">7.24.3.5</a>),
12799 mbstate_t (<a href="#7.25.1">7.25.1</a>), the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>), the fsetpos function
12805 <!--page 278 -->
12808 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
12809 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12810 line.
12811 </small>
12812 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12813 </small>
12817 A stream is associated with an external file (which may be a physical device) by opening
12818 a file, which may involve creating a new file. Creating an existing file causes its former
12819 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12820 disk file, as opposed to a terminal), then a file position indicator associated with the
12821 stream is positioned at the start (character number zero) of the file, unless the file is
12822 opened with append mode in which case it is implementation-defined whether the file
12823 position indicator is initially positioned at the beginning or the end of the file. The file
12824 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12825 facilitate an orderly progression through the file.
12827 Binary files are not truncated, except as defined in <a href="#7.19.5.3">7.19.5.3</a>. Whether a write on a text
12828 stream causes the associated file to be truncated beyond that point is implementation-
12829 defined.
12831 When a stream is unbuffered, characters are intended to appear from the source or at the
12832 destination as soon as possible. Otherwise characters may be accumulated and
12833 transmitted to or from the host environment as a block. When a stream is fully buffered,
12834 characters are intended to be transmitted to or from the host environment as a block when
12835 a buffer is filled. When a stream is line buffered, characters are intended to be
12836 transmitted to or from the host environment as a block when a new-line character is
12837 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12838 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12839 when input is requested on a line buffered stream that requires the transmission of
12840 characters from the host environment. Support for these characteristics is
12841 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12843 A file may be disassociated from a controlling stream by closing the file. Output streams
12844 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12845 the stream is disassociated from the file. The value of a pointer to a FILE object is
12846 indeterminate after the associated file is closed (including the standard text streams).
12847 Whether a file of zero length (on which no characters have been written by an output
12848 stream) actually exists is implementation-defined.
12850 The file may be subsequently reopened, by the same or another program execution, and
12851 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12852 function returns to its original caller, or if the exit function is called, all open files are
12853 closed (hence all output streams are flushed) before program termination. Other paths to
12854 program termination, such as calling the abort function, need not close all files
12855 properly.
12857 The address of the FILE object used to control a stream may be significant; a copy of a
12858 FILE object need not serve in place of the original.
12859 <!--page 279 -->
12861 At program startup, three text streams are predefined and need not be opened explicitly
12862 -- standard input (for reading conventional input), standard output (for writing
12863 conventional output), and standard error (for writing diagnostic output). As initially
12864 opened, the standard error stream is not fully buffered; the standard input and standard
12865 output streams are fully buffered if and only if the stream can be determined not to refer
12866 to an interactive device.
12868 Functions that open additional (nontemporary) files require a file name, which is a string.
12869 The rules for composing valid file names are implementation-defined. Whether the same
12870 file can be simultaneously open multiple times is also implementation-defined.
12872 Although both text and binary wide-oriented streams are conceptually sequences of wide
12873 characters, the external file associated with a wide-oriented stream is a sequence of
12874 multibyte characters, generalized as follows:
12875 <ul>
12876 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12877 encodings valid for use internal to the program).
12878 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
12879 </ul>
12881 Moreover, the encodings used for multibyte characters may differ among files. Both the
12882 nature and choice of such encodings are implementation-defined.
12884 The wide character input functions read multibyte characters from the stream and convert
12885 them to wide characters as if they were read by successive calls to the fgetwc function.
12886 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12887 described by the stream's own mbstate_t object. The byte input functions read
12888 characters from the stream as if by successive calls to the fgetc function.
12890 The wide character output functions convert wide characters to multibyte characters and
12891 write them to the stream as if they were written by successive calls to the fputwc
12892 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12893 conversion state described by the stream's own mbstate_t object. The byte output
12894 functions write characters to the stream as if by successive calls to the fputc function.
12896 In some cases, some of the byte input/output functions also perform conversions between
12897 multibyte characters and wide characters. These conversions also occur as if by calls to
12898 the mbrtowc and wcrtomb functions.
12900 An encoding error occurs if the character sequence presented to the underlying
12901 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12902 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12905 <!--page 280 -->
12906 multibyte character. The wide character input/output functions and the byte input/output
12907 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12908 occurs.
12911 The value of FOPEN_MAX shall be at least eight, including the three standard text
12912 streams.
12913 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the fgetc function (<a href="#7.19.7.1">7.19.7.1</a>), the
12914 fopen function (<a href="#7.19.5.3">7.19.5.3</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>), the setbuf function
12915 (<a href="#7.19.5.5">7.19.5.5</a>), the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>), the fgetwc function (<a href="#7.24.3.1">7.24.3.1</a>), the
12916 fputwc function (<a href="#7.24.3.3">7.24.3.3</a>), conversion state (<a href="#7.24.6">7.24.6</a>), the mbrtowc function
12917 (<a href="#7.24.6.3.2">7.24.6.3.2</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
12920 <p><small><a name="note234" href="#note234">234)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12921 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12922 with state-dependent encoding that does not assuredly end in the initial shift state.
12923 </small>
12930 <pre>
12932 int remove(const char *filename);</pre>
12935 The remove function causes the file whose name is the string pointed to by filename
12936 to be no longer accessible by that name. A subsequent attempt to open that file using that
12937 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12938 function is implementation-defined.
12941 The remove function returns zero if the operation succeeds, nonzero if it fails.
12946 <pre>
12948 int rename(const char *old, const char *new);</pre>
12951 The rename function causes the file whose name is the string pointed to by old to be
12952 henceforth known by the name given by the string pointed to by new. The file named
12953 old is no longer accessible by that name. If a file named by the string pointed to by new
12954 exists prior to the call to the rename function, the behavior is implementation-defined.
12955 <!--page 281 -->
12958 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
12959 which case if the file existed previously it is still known by its original name.
12962 <p><small><a name="note235" href="#note235">235)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
12963 or that it is necessary to copy its contents to effectuate its renaming.
12964 </small>
12969 <pre>
12971 FILE *tmpfile(void);</pre>
12974 The tmpfile function creates a temporary binary file that is different from any other
12975 existing file and that will automatically be removed when it is closed or at program
12976 termination. If the program terminates abnormally, whether an open temporary file is
12977 removed is implementation-defined. The file is opened for update with "wb+" mode.
12980 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12981 program (this limit may be shared with tmpnam) and there should be no limit on the
12982 number simultaneously open other than this limit and any limit on the number of open
12983 files (FOPEN_MAX).
12986 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12987 cannot be created, the tmpfile function returns a null pointer.
12993 <pre>
12995 char *tmpnam(char *s);</pre>
12998 The tmpnam function generates a string that is a valid file name and that is not the same
12999 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13002 <!--page 282 -->
13003 TMP_MAX different strings, but any or all of them may already be in use by existing files
13004 and thus not be suitable return values.
13006 The tmpnam function generates a different string each time it is called.
13008 The implementation shall behave as if no library function calls the tmpnam function.
13011 If no suitable string can be generated, the tmpnam function returns a null pointer.
13012 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13013 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13014 function may modify the same object). If the argument is not a null pointer, it is assumed
13015 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13016 in that array and returns the argument as its value.
13019 The value of the macro TMP_MAX shall be at least 25.
13022 <p><small><a name="note236" href="#note236">236)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
13023 their names should not collide with those generated by conventional naming rules for the
13024 implementation. It is still necessary to use the remove function to remove such files when their use
13025 is ended, and before program termination.
13026 </small>
13033 <pre>
13035 int fclose(FILE *stream);</pre>
13038 A successful call to the fclose function causes the stream pointed to by stream to be
13039 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13040 are delivered to the host environment to be written to the file; any unread buffered data
13041 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13042 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13043 (and deallocated if it was automatically allocated).
13046 The fclose function returns zero if the stream was successfully closed, or EOF if any
13047 errors were detected.
13052 <!--page 283 -->
13053 <pre>
13055 int fflush(FILE *stream);</pre>
13058 If stream points to an output stream or an update stream in which the most recent
13059 operation was not input, the fflush function causes any unwritten data for that stream
13060 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13061 undefined.
13063 If stream is a null pointer, the fflush function performs this flushing action on all
13064 streams for which the behavior is defined above.
13067 The fflush function sets the error indicator for the stream and returns EOF if a write
13068 error occurs, otherwise it returns zero.
13074 <pre>
13076 FILE *fopen(const char * restrict filename,
13077 const char * restrict mode);</pre>
13080 The fopen function opens the file whose name is the string pointed to by filename,
13081 and associates a stream with it.
13083 The argument mode points to a string. If the string is one of the following, the file is
13084 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13085 <dl>
13096 <!--page 284 -->
13100 </dl>
13102 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13103 the file does not exist or cannot be read.
13105 Opening a file with append mode ('a' as the first character in the mode argument)
13106 causes all subsequent writes to the file to be forced to the then current end-of-file,
13107 regardless of intervening calls to the fseek function. In some implementations, opening
13108 a binary file with append mode ('b' as the second or third character in the above list of
13109 mode argument values) may initially position the file position indicator for the stream
13110 beyond the last data written, because of null character padding.
13112 When a file is opened with update mode ('+' as the second or third character in the
13113 above list of mode argument values), both input and output may be performed on the
13114 associated stream. However, output shall not be directly followed by input without an
13115 intervening call to the fflush function or to a file positioning function (fseek,
13116 fsetpos, or rewind), and input shall not be directly followed by output without an
13117 intervening call to a file positioning function, unless the input operation encounters end-
13118 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13119 binary stream in some implementations.
13121 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13122 an interactive device. The error and end-of-file indicators for the stream are cleared.
13125 The fopen function returns a pointer to the object controlling the stream. If the open
13126 operation fails, fopen returns a null pointer.
13130 <p><small><a name="note237" href="#note237">237)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
13131 remaining characters, or it might use them to select different kinds of a file (some of which might not
13133 </small>
13138 <pre>
13140 FILE *freopen(const char * restrict filename,
13141 const char * restrict mode,
13142 FILE * restrict stream);</pre>
13145 The freopen function opens the file whose name is the string pointed to by filename
13146 and associates the stream pointed to by stream with it. The mode argument is used just
13147 <!--page 285 -->
13150 If filename is a null pointer, the freopen function attempts to change the mode of
13151 the stream to that specified by mode, as if the name of the file currently associated with
13152 the stream had been used. It is implementation-defined which changes of mode are
13153 permitted (if any), and under what circumstances.
13155 The freopen function first attempts to close any file that is associated with the specified
13156 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13157 stream are cleared.
13160 The freopen function returns a null pointer if the open operation fails. Otherwise,
13161 freopen returns the value of stream.
13164 <p><small><a name="note238" href="#note238">238)</a> The primary use of the freopen function is to change the file associated with a standard text stream
13165 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13166 returned by the fopen function may be assigned.
13167 </small>
13172 <pre>
13174 void setbuf(FILE * restrict stream,
13175 char * restrict buf);</pre>
13178 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13179 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13180 is a null pointer), with the value _IONBF for mode.
13183 The setbuf function returns no value.
13189 <pre>
13191 int setvbuf(FILE * restrict stream,
13192 char * restrict buf,
13193 int mode, size_t size);</pre>
13198 <!--page 286 -->
13201 The setvbuf function may be used only after the stream pointed to by stream has
13202 been associated with an open file and before any other operation (other than an
13203 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13204 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13205 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13206 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13207 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13208 specifies the size of the array; otherwise, size may determine the size of a buffer
13209 allocated by the setvbuf function. The contents of the array at any time are
13210 indeterminate.
13213 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13214 for mode or if the request cannot be honored.
13217 <p><small><a name="note239" href="#note239">239)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
13218 before a buffer that has automatic storage duration is deallocated upon block exit.
13219 </small>
13223 The formatted input/output functions shall behave as if there is a sequence point after the
13227 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13228 </small>
13233 <pre>
13235 int fprintf(FILE * restrict stream,
13236 const char * restrict format, ...);</pre>
13239 The fprintf function writes output to the stream pointed to by stream, under control
13240 of the string pointed to by format that specifies how subsequent arguments are
13241 converted for output. If there are insufficient arguments for the format, the behavior is
13242 undefined. If the format is exhausted while arguments remain, the excess arguments are
13243 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13244 the end of the format string is encountered.
13246 The format shall be a multibyte character sequence, beginning and ending in its initial
13247 shift state. The format is composed of zero or more directives: ordinary multibyte
13248 characters (not %), which are copied unchanged to the output stream; and conversion
13251 <!--page 287 -->
13252 specifications, each of which results in fetching zero or more subsequent arguments,
13253 converting them, if applicable, according to the corresponding conversion specifier, and
13254 then writing the result to the output stream.
13256 Each conversion specification is introduced by the character %. After the %, the following
13257 appear in sequence:
13258 <ul>
13259 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13260 specification.
13261 <li> An optional minimum field width. If the converted value has fewer characters than the
13262 field width, it is padded with spaces (by default) on the left (or right, if the left
13263 adjustment flag, described later, has been given) to the field width. The field width
13264 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13265 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13266 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13267 character for a, A, e, E, f, and F conversions, the maximum number of significant
13268 digits for the g and G conversions, or the maximum number of bytes to be written for
13269 s conversions. The precision takes the form of a period (.) followed either by an
13270 asterisk * (described later) or by an optional decimal integer; if only the period is
13271 specified, the precision is taken as zero. If a precision appears with any other
13272 conversion specifier, the behavior is undefined.
13273 <li> An optional length modifier that specifies the size of the argument.
13274 <li> A conversion specifier character that specifies the type of conversion to be applied.
13275 </ul>
13277 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13278 this case, an int argument supplies the field width or precision. The arguments
13279 specifying field width, or precision, or both, shall appear (in that order) before the
13280 argument (if any) to be converted. A negative field width argument is taken as a - flag
13281 followed by a positive field width. A negative precision argument is taken as if the
13282 precision were omitted.
13284 The flag characters and their meanings are:
13285 <dl>
13286 <dt> - <dd> The result of the conversion is left-justified within the field. (It is right-justified if
13287 this flag is not specified.)
13289 begins with a sign only when a negative value is converted if this flag is not
13291 <!--page 288 -->
13293 <dt> space<dd> If the first character of a signed conversion is not a sign, or if a signed conversion
13294 results in no characters, a space is prefixed to the result. If the space and + flags
13295 both appear, the space flag is ignored.
13296 <dt> # <dd> The result is converted to an ''alternative form''. For o conversion, it increases
13297 the precision, if and only if necessary, to force the first digit of the result to be a
13300 and G conversions, the result of converting a floating-point number always
13301 contains a decimal-point character, even if no digits follow it. (Normally, a
13302 decimal-point character appears in the result of these conversions only if a digit
13303 follows it.) For g and G conversions, trailing zeros are not removed from the
13304 result. For other conversions, the behavior is undefined.
13306 (following any indication of sign or base) are used to pad to the field width rather
13307 than performing space padding, except when converting an infinity or NaN. If the
13309 conversions, if a precision is specified, the 0 flag is ignored. For other
13310 conversions, the behavior is undefined.
13311 </dl>
13313 The length modifiers and their meanings are:
13314 <dl>
13316 signed char or unsigned char argument (the argument will have
13317 been promoted according to the integer promotions, but its value shall be
13318 converted to signed char or unsigned char before printing); or that
13319 a following n conversion specifier applies to a pointer to a signed char
13320 argument.
13322 short int or unsigned short int argument (the argument will
13323 have been promoted according to the integer promotions, but its value shall
13324 be converted to short int or unsigned short int before printing);
13325 or that a following n conversion specifier applies to a pointer to a short
13326 int argument.
13327 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13328 long int or unsigned long int argument; that a following n
13329 conversion specifier applies to a pointer to a long int argument; that a
13330 <!--page 289 -->
13331 following c conversion specifier applies to a wint_t argument; that a
13332 following s conversion specifier applies to a pointer to a wchar_t
13333 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13334 specifier.
13335 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13336 long long int or unsigned long long int argument; or that a
13337 following n conversion specifier applies to a pointer to a long long int
13338 argument.
13340 an intmax_t or uintmax_t argument; or that a following n conversion
13341 specifier applies to a pointer to an intmax_t argument.
13343 size_t or the corresponding signed integer type argument; or that a
13344 following n conversion specifier applies to a pointer to a signed integer type
13345 corresponding to size_t argument.
13347 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13348 following n conversion specifier applies to a pointer to a ptrdiff_t
13349 argument.
13351 applies to a long double argument.
13352 </dl>
13353 If a length modifier appears with any conversion specifier other than as specified above,
13354 the behavior is undefined.
13356 The conversion specifiers and their meanings are:
13357 <dl>
13359 precision specifies the minimum number of digits to appear; if the value
13360 being converted can be represented in fewer digits, it is expanded with
13361 leading zeros. The default precision is 1. The result of converting a zero
13362 value with a precision of zero is no characters.
13364 <!--page 290 -->
13365 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13366 letters abcdef are used for x conversion and the letters ABCDEF for X
13367 conversion. The precision specifies the minimum number of digits to appear;
13368 if the value being converted can be represented in fewer digits, it is expanded
13369 with leading zeros. The default precision is 1. The result of converting a
13370 zero value with a precision of zero is no characters.
13372 decimal notation in the style [-]ddd.ddd, where the number of digits after
13373 the decimal-point character is equal to the precision specification. If the
13374 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13375 not specified, no decimal-point character appears. If a decimal-point
13376 character appears, at least one digit appears before it. The value is rounded to
13377 the appropriate number of digits.
13378 A double argument representing an infinity is converted in one of the styles
13379 [-]inf or [-]infinity -- which style is implementation-defined. A
13380 double argument representing a NaN is converted in one of the styles
13381 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13382 any n-char-sequence, is implementation-defined. The F conversion specifier
13383 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13386 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13387 argument is nonzero) before the decimal-point character and the number of
13388 digits after it is equal to the precision; if the precision is missing, it is taken as
13389 6; if the precision is zero and the # flag is not specified, no decimal-point
13390 character appears. The value is rounded to the appropriate number of digits.
13391 The E conversion specifier produces a number with E instead of e
13392 introducing the exponent. The exponent always contains at least two digits,
13393 and only as many more digits as necessary to represent the exponent. If the
13394 value is zero, the exponent is zero.
13395 A double argument representing an infinity or NaN is converted in the style
13396 of an f or F conversion specifier.
13398 style f or e (or in style F or E in the case of a G conversion specifier),
13399 depending on the value converted and the precision. Let P equal the
13401 Then, if a conversion with style E would have an exponent of X :
13402 <ul>
13404 P - (X + 1).
13406 </ul>
13407 Finally, unless the # flag is used, any trailing zeros are removed from the
13408 <!--page 291 -->
13409 fractional portion of the result and the decimal-point character is removed if
13410 there is no fractional portion remaining.
13411 A double argument representing an infinity or NaN is converted in the style
13412 of an f or F conversion specifier.
13414 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
13415 nonzero if the argument is a normalized floating-point number and is
13416 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
13417 of hexadecimal digits after it is equal to the precision; if the precision is
13418 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
13419 an exact representation of the value; if the precision is missing and
13420 FLT_RADIX is not a power of 2, then the precision is sufficient to
13421 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
13422 omitted; if the precision is zero and the # flag is not specified, no decimal-
13423 point character appears. The letters abcdef are used for a conversion and
13424 the letters ABCDEF for A conversion. The A conversion specifier produces a
13425 number with X and P instead of x and p. The exponent always contains at
13426 least one digit, and only as many more digits as necessary to represent the
13427 decimal exponent of 2. If the value is zero, the exponent is zero.
13428 A double argument representing an infinity or NaN is converted in the style
13429 of an f or F conversion specifier.
13431 unsigned char, and the resulting character is written.
13432 If an l length modifier is present, the wint_t argument is converted as if by
13433 an ls conversion specification with no precision and an argument that points
13434 to the initial element of a two-element array of wchar_t, the first element
13435 containing the wint_t argument to the lc conversion specification and the
13436 second a null wide character.
13437 <dt> s <dd> If no l length modifier is present, the argument shall be a pointer to the initial
13438 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are
13439 <!--page 292 -->
13440 written up to (but not including) the terminating null character. If the
13441 precision is specified, no more than that many bytes are written. If the
13442 precision is not specified or is greater than the size of the array, the array shall
13443 contain a null character.
13444 If an l length modifier is present, the argument shall be a pointer to the initial
13445 element of an array of wchar_t type. Wide characters from the array are
13446 converted to multibyte characters (each as if by a call to the wcrtomb
13447 function, with the conversion state described by an mbstate_t object
13448 initialized to zero before the first wide character is converted) up to and
13449 including a terminating null wide character. The resulting multibyte
13450 characters are written up to (but not including) the terminating null character
13451 (byte). If no precision is specified, the array shall contain a null wide
13452 character. If a precision is specified, no more than that many bytes are
13453 written (including shift sequences, if any), and the array shall contain a null
13454 wide character if, to equal the multibyte character sequence length given by
13455 the precision, the function would need to access a wide character one past the
13456 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup>
13458 converted to a sequence of printing characters, in an implementation-defined
13459 manner.
13461 number of characters written to the output stream so far by this call to
13462 fprintf. No argument is converted, but one is consumed. If the conversion
13463 specification includes any flags, a field width, or a precision, the behavior is
13464 undefined.
13466 conversion specification shall be %%.
13467 </dl>
13469 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
13470 not the correct type for the corresponding conversion specification, the behavior is
13471 undefined.
13473 In no case does a nonexistent or small field width cause truncation of a field; if the result
13474 of a conversion is wider than the field width, the field is expanded to contain the
13475 conversion result.
13480 <!--page 293 -->
13482 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
13483 to a hexadecimal floating number with the given precision.
13486 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
13487 representable in the given precision, the result should be one of the two adjacent numbers
13488 in hexadecimal floating style with the given precision, with the extra stipulation that the
13489 error should have a correct sign for the current rounding direction.
13491 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
13492 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
13493 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
13494 representable with DECIMAL_DIG digits, then the result should be an exact
13495 representation with trailing zeros. Otherwise, the source value is bounded by two
13496 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
13497 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
13498 the error should have a correct sign for the current rounding direction.
13501 The fprintf function returns the number of characters transmitted, or a negative value
13502 if an output or encoding error occurred.
13505 The number of characters that can be produced by any single conversion shall be at least
13506 4095.
13508 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
13509 places:
13510 <pre>
13513 /* ... */
13514 char *weekday, *month; // pointers to strings
13515 int day, hour, min;
13516 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
13517 weekday, month, day, hour, min);
13521 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
13522 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13523 the first of which is denoted here by a and the second by an uppercase letter.
13528 <!--page 294 -->
13530 Given the following wide string with length seven,
13531 <pre>
13533 the seven calls
13534 <pre>
13535 fprintf(stdout, "|1234567890123|\n");
13536 fprintf(stdout, "|%13ls|\n", wstr);
13537 fprintf(stdout, "|%-13.9ls|\n", wstr);
13538 fprintf(stdout, "|%13.10ls|\n", wstr);
13539 fprintf(stdout, "|%13.11ls|\n", wstr);
13542 will print the following seven lines:
13543 <pre>
13544 |1234567890123|
13545 | X Yabc Z W|
13546 | X Yabc Z |
13547 | X Yabc Z|
13548 | X Yabc Z W|
13549 | abc Z W|
13550 | Z|</pre>
13552 <p><b> Forward references</b>: conversion state (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13555 <p><small><a name="note241" href="#note241">241)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
13556 </small>
13557 <p><small><a name="note242" href="#note242">242)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
13558 include a minus sign.
13559 </small>
13560 <p><small><a name="note243" href="#note243">243)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
13561 the # and 0 flag characters have no effect.
13562 </small>
13563 <p><small><a name="note244" href="#note244">244)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
13564 that subsequent digits align to nibble (4-bit) boundaries.
13565 </small>
13566 <p><small><a name="note245" href="#note245">245)</a> The precision p is sufficient to distinguish values of the source type if 16<sup>p-1</sup> > b n where b is
13567 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
13568 might suffice depending on the implementation's scheme for determining the digit to the left of the
13569 decimal-point character.
13570 </small>
13571 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
13572 </small>
13573 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
13574 </small>
13575 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13576 </small>
13577 <p><small><a name="note249" href="#note249">249)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
13578 given format specifier. The number of significant digits is determined by the format specifier, and in
13579 the case of fixed-point conversion by the source value as well.
13580 </small>
13585 <pre>
13587 int fscanf(FILE * restrict stream,
13588 const char * restrict format, ...);</pre>
13591 The fscanf function reads input from the stream pointed to by stream, under control
13592 of the string pointed to by format that specifies the admissible input sequences and how
13593 they are to be converted for assignment, using subsequent arguments as pointers to the
13594 objects to receive the converted input. If there are insufficient arguments for the format,
13595 the behavior is undefined. If the format is exhausted while arguments remain, the excess
13596 arguments are evaluated (as always) but are otherwise ignored.
13598 The format shall be a multibyte character sequence, beginning and ending in its initial
13599 shift state. The format is composed of zero or more directives: one or more white-space
13600 characters, an ordinary multibyte character (neither % nor a white-space character), or a
13601 conversion specification. Each conversion specification is introduced by the character %.
13602 After the %, the following appear in sequence:
13603 <ul>
13604 <li> An optional assignment-suppressing character *.
13605 <li> An optional decimal integer greater than zero that specifies the maximum field width
13606 (in characters).
13607 <!--page 295 -->
13608 <li> An optional length modifier that specifies the size of the receiving object.
13609 <li> A conversion specifier character that specifies the type of conversion to be applied.
13610 </ul>
13612 The fscanf function executes each directive of the format in turn. If a directive fails, as
13613 detailed below, the function returns. Failures are described as input failures (due to the
13614 occurrence of an encoding error or the unavailability of input characters), or matching
13615 failures (due to inappropriate input).
13617 A directive composed of white-space character(s) is executed by reading input up to the
13618 first non-white-space character (which remains unread), or until no more characters can
13619 be read.
13621 A directive that is an ordinary multibyte character is executed by reading the next
13622 characters of the stream. If any of those characters differ from the ones composing the
13623 directive, the directive fails and the differing and subsequent characters remain unread.
13624 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
13625 read, the directive fails.
13627 A directive that is a conversion specification defines a set of matching input sequences, as
13628 described below for each specifier. A conversion specification is executed in the
13629 following steps:
13631 Input white-space characters (as specified by the isspace function) are skipped, unless
13632 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
13634 An input item is read from the stream, unless the specification includes an n specifier. An
13635 input item is defined as the longest sequence of input characters which does not exceed
13636 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note251"><b>251)</b></a></sup>
13637 The first character, if any, after the input item remains unread. If the length of the input
13638 item is zero, the execution of the directive fails; this condition is a matching failure unless
13639 end-of-file, an encoding error, or a read error prevented input from the stream, in which
13640 case it is an input failure.
13642 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
13643 count of input characters) is converted to a type appropriate to the conversion specifier. If
13644 the input item is not a matching sequence, the execution of the directive fails: this
13645 condition is a matching failure. Unless assignment suppression was indicated by a *, the
13646 result of the conversion is placed in the object pointed to by the first argument following
13647 the format argument that has not already received a conversion result. If this object
13648 does not have an appropriate type, or if the result of the conversion cannot be represented
13651 <!--page 296 -->
13652 in the object, the behavior is undefined.
13654 The length modifiers and their meanings are:
13655 <dl>
13657 to an argument with type pointer to signed char or unsigned char.
13659 to an argument with type pointer to short int or unsigned short
13660 int.
13661 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13662 to an argument with type pointer to long int or unsigned long
13663 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
13664 an argument with type pointer to double; or that a following c, s, or [
13665 conversion specifier applies to an argument with type pointer to wchar_t.
13666 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13667 to an argument with type pointer to long long int or unsigned
13668 long long int.
13670 to an argument with type pointer to intmax_t or uintmax_t.
13672 to an argument with type pointer to size_t or the corresponding signed
13673 integer type.
13675 to an argument with type pointer to ptrdiff_t or the corresponding
13676 unsigned integer type.
13678 applies to an argument with type pointer to long double.
13679 </dl>
13680 If a length modifier appears with any conversion specifier other than as specified above,
13681 the behavior is undefined.
13683 The conversion specifiers and their meanings are:
13684 <dl>
13686 expected for the subject sequence of the strtol function with the value 10
13687 for the base argument. The corresponding argument shall be a pointer to
13688 signed integer.
13690 <!--page 297 -->
13691 for the subject sequence of the strtol function with the value 0 for the
13692 base argument. The corresponding argument shall be a pointer to signed
13693 integer.
13695 expected for the subject sequence of the strtoul function with the value 8
13696 for the base argument. The corresponding argument shall be a pointer to
13697 unsigned integer.
13699 expected for the subject sequence of the strtoul function with the value 10
13700 for the base argument. The corresponding argument shall be a pointer to
13701 unsigned integer.
13703 as expected for the subject sequence of the strtoul function with the value
13704 16 for the base argument. The corresponding argument shall be a pointer to
13705 unsigned integer.
13707 format is the same as expected for the subject sequence of the strtod
13708 function. The corresponding argument shall be a pointer to floating.
13710 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
13711 If no l length modifier is present, the corresponding argument shall be a
13712 pointer to the initial element of a character array large enough to accept the
13713 sequence. No null character is added.
13714 If an l length modifier is present, the input shall be a sequence of multibyte
13715 characters that begins in the initial shift state. Each multibyte character in the
13716 sequence is converted to a wide character as if by a call to the mbrtowc
13717 function, with the conversion state described by an mbstate_t object
13718 initialized to zero before the first multibyte character is converted. The
13719 corresponding argument shall be a pointer to the initial element of an array of
13720 wchar_t large enough to accept the resulting sequence of wide characters.
13721 No null wide character is added.
13722 <dt> s <dd> Matches a sequence of non-white-space characters.<sup><a href="#note252"><b>252)</b></a></sup>
13723 If no l length modifier is present, the corresponding argument shall be a
13724 pointer to the initial element of a character array large enough to accept the
13725 sequence and a terminating null character, which will be added automatically.
13726 If an l length modifier is present, the input shall be a sequence of multibyte
13727 <!--page 298 -->
13728 characters that begins in the initial shift state. Each multibyte character is
13729 converted to a wide character as if by a call to the mbrtowc function, with
13730 the conversion state described by an mbstate_t object initialized to zero
13731 before the first multibyte character is converted. The corresponding argument
13732 shall be a pointer to the initial element of an array of wchar_t large enough
13733 to accept the sequence and the terminating null wide character, which will be
13734 added automatically.
13737 If no l length modifier is present, the corresponding argument shall be a
13738 pointer to the initial element of a character array large enough to accept the
13739 sequence and a terminating null character, which will be added automatically.
13740 If an l length modifier is present, the input shall be a sequence of multibyte
13741 characters that begins in the initial shift state. Each multibyte character is
13742 converted to a wide character as if by a call to the mbrtowc function, with
13743 the conversion state described by an mbstate_t object initialized to zero
13744 before the first multibyte character is converted. The corresponding argument
13745 shall be a pointer to the initial element of an array of wchar_t large enough
13746 to accept the sequence and the terminating null wide character, which will be
13747 added automatically.
13748 The conversion specifier includes all subsequent characters in the format
13749 string, up to and including the matching right bracket (]). The characters
13750 between the brackets (the scanlist) compose the scanset, unless the character
13751 after the left bracket is a circumflex (^), in which case the scanset contains all
13752 characters that do not appear in the scanlist between the circumflex and the
13753 right bracket. If the conversion specifier begins with [] or [^], the right
13754 bracket character is in the scanlist and the next following right bracket
13755 character is the matching right bracket that ends the specification; otherwise
13756 the first following right bracket character is the one that ends the
13757 specification. If a - character is in the scanlist and is not the first, nor the
13758 second where the first character is a ^, nor the last character, the behavior is
13759 implementation-defined.
13761 <!--page 299 -->
13762 same as the set of sequences that may be produced by the %p conversion of
13763 the fprintf function. The corresponding argument shall be a pointer to a
13764 pointer to void. The input item is converted to a pointer value in an
13765 implementation-defined manner. If the input item is a value converted earlier
13766 during the same program execution, the pointer that results shall compare
13767 equal to that value; otherwise the behavior of the %p conversion is undefined.
13769 signed integer into which is to be written the number of characters read from
13770 the input stream so far by this call to the fscanf function. Execution of a
13771 %n directive does not increment the assignment count returned at the
13772 completion of execution of the fscanf function. No argument is converted,
13773 but one is consumed. If the conversion specification includes an assignment-
13774 suppressing character or a field width, the behavior is undefined.
13776 complete conversion specification shall be %%.
13777 </dl>
13779 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
13781 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
13782 respectively, a, e, f, g, and x.
13784 Trailing white space (including new-line characters) is left unread unless matched by a
13785 directive. The success of literal matches and suppressed assignments is not directly
13786 determinable other than via the %n directive.
13789 The fscanf function returns the value of the macro EOF if an input failure occurs
13790 before any conversion. Otherwise, the function returns the number of input items
13791 assigned, which can be fewer than provided for, or even zero, in the event of an early
13792 matching failure.
13794 EXAMPLE 1 The call:
13795 <pre>
13797 /* ... */
13798 int n, i; float x; char name[50];
13800 with the input line:
13801 <pre>
13803 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13804 thompson\0.
13807 EXAMPLE 2 The call:
13808 <pre>
13810 /* ... */
13811 int i; float x; char name[50];
13813 with input:
13817 <!--page 300 -->
13818 <pre>
13820 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13824 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13826 <pre>
13828 /* ... */
13830 do {
13832 fscanf(stdin,"%*[^\n]");
13834 If the stdin stream contains the following lines:
13835 <pre>
13836 2 quarts of oil
13837 -12.8degrees Celsius
13838 lots of luck
13839 10.0LBS of
13840 dirt
13842 the execution of the above example will be analogous to the following assignments:
13843 <pre>
13845 count = 3;
13850 count = 3;
13852 count = EOF;</pre>
13855 EXAMPLE 4 In:
13856 <pre>
13858 /* ... */
13859 int d1, d2, n1, n2, i;
13861 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13865 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13866 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13867 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13868 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13869 entry into the alternate shift state.
13871 After the call:
13872 <!--page 301 -->
13873 <pre>
13875 /* ... */
13876 char str[50];
13878 with the input line:
13879 <pre>
13880 a(uparrow) X Y(downarrow) bc</pre>
13881 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13882 characters, in the more general case) appears to be a single-byte white-space character.
13884 In contrast, after the call:
13885 <pre>
13888 /* ... */
13889 wchar_t wstr[50];
13891 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13892 terminating null wide character.
13894 However, the call:
13895 <pre>
13898 /* ... */
13899 wchar_t wstr[50];
13901 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13902 string.
13904 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13905 character Y, after the call:
13906 <pre>
13909 /* ... */
13910 wchar_t wstr[50];
13912 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13913 multibyte character.
13915 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
13916 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
13918 <!--page 302 -->
13921 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
13922 </small>
13923 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
13924 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
13925 </small>
13926 <p><small><a name="note252" href="#note252">252)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
13927 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
13928 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
13929 </small>
13930 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13931 </small>
13936 <pre>
13938 int printf(const char * restrict format, ...);</pre>
13941 The printf function is equivalent to fprintf with the argument stdout interposed
13942 before the arguments to printf.
13945 The printf function returns the number of characters transmitted, or a negative value if
13946 an output or encoding error occurred.
13951 <pre>
13953 int scanf(const char * restrict format, ...);</pre>
13956 The scanf function is equivalent to fscanf with the argument stdin interposed
13957 before the arguments to scanf.
13960 The scanf function returns the value of the macro EOF if an input failure occurs before
13961 any conversion. Otherwise, the scanf function returns the number of input items
13962 assigned, which can be fewer than provided for, or even zero, in the event of an early
13963 matching failure.
13968 <pre>
13970 int snprintf(char * restrict s, size_t n,
13971 const char * restrict format, ...);</pre>
13974 The snprintf function is equivalent to fprintf, except that the output is written into
13975 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
13976 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
13977 discarded rather than being written to the array, and a null character is written at the end
13978 of the characters actually written into the array. If copying takes place between objects
13979 that overlap, the behavior is undefined.
13980 <!--page 303 -->
13983 The snprintf function returns the number of characters that would have been written
13984 had n been sufficiently large, not counting the terminating null character, or a negative
13985 value if an encoding error occurred. Thus, the null-terminated output has been
13986 completely written if and only if the returned value is nonnegative and less than n.
13991 <pre>
13993 int sprintf(char * restrict s,
13994 const char * restrict format, ...);</pre>
13997 The sprintf function is equivalent to fprintf, except that the output is written into
13998 an array (specified by the argument s) rather than to a stream. A null character is written
13999 at the end of the characters written; it is not counted as part of the returned value. If
14000 copying takes place between objects that overlap, the behavior is undefined.
14003 The sprintf function returns the number of characters written in the array, not
14004 counting the terminating null character, or a negative value if an encoding error occurred.
14009 <pre>
14011 int sscanf(const char * restrict s,
14012 const char * restrict format, ...);</pre>
14015 The sscanf function is equivalent to fscanf, except that input is obtained from a
14016 string (specified by the argument s) rather than from a stream. Reaching the end of the
14017 string is equivalent to encountering end-of-file for the fscanf function. If copying
14018 takes place between objects that overlap, the behavior is undefined.
14021 The sscanf function returns the value of the macro EOF if an input failure occurs
14022 before any conversion. Otherwise, the sscanf function returns the number of input
14023 items assigned, which can be fewer than provided for, or even zero, in the event of an
14024 early matching failure.
14025 <!--page 304 -->
14030 <pre>
14033 int vfprintf(FILE * restrict stream,
14034 const char * restrict format,
14035 va_list arg);</pre>
14038 The vfprintf function is equivalent to fprintf, with the variable argument list
14039 replaced by arg, which shall have been initialized by the va_start macro (and
14040 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14044 The vfprintf function returns the number of characters transmitted, or a negative
14045 value if an output or encoding error occurred.
14047 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14048 <pre>
14051 void error(char *function_name, char *format, ...)
14052 {
14053 va_list args;
14054 va_start(args, format);
14055 // print out name of function causing error
14056 fprintf(stderr, "ERROR in %s: ", function_name);
14057 // print out remainder of message
14058 vfprintf(stderr, format, args);
14059 va_end(args);
14060 }</pre>
14065 <!--page 305 -->
14068 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14069 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14070 </small>
14075 <pre>
14078 int vfscanf(FILE * restrict stream,
14079 const char * restrict format,
14080 va_list arg);</pre>
14083 The vfscanf function is equivalent to fscanf, with the variable argument list
14084 replaced by arg, which shall have been initialized by the va_start macro (and
14085 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14089 The vfscanf function returns the value of the macro EOF if an input failure occurs
14090 before any conversion. Otherwise, the vfscanf function returns the number of input
14091 items assigned, which can be fewer than provided for, or even zero, in the event of an
14092 early matching failure.
14097 <pre>
14100 int vprintf(const char * restrict format,
14101 va_list arg);</pre>
14104 The vprintf function is equivalent to printf, with the variable argument list
14105 replaced by arg, which shall have been initialized by the va_start macro (and
14106 possibly subsequent va_arg calls). The vprintf function does not invoke the
14110 The vprintf function returns the number of characters transmitted, or a negative value
14111 if an output or encoding error occurred.
14112 <!--page 306 -->
14117 <pre>
14120 int vscanf(const char * restrict format,
14121 va_list arg);</pre>
14124 The vscanf function is equivalent to scanf, with the variable argument list replaced
14125 by arg, which shall have been initialized by the va_start macro (and possibly
14126 subsequent va_arg calls). The vscanf function does not invoke the va_end
14130 The vscanf function returns the value of the macro EOF if an input failure occurs
14131 before any conversion. Otherwise, the vscanf function returns the number of input
14132 items assigned, which can be fewer than provided for, or even zero, in the event of an
14133 early matching failure.
14138 <pre>
14141 int vsnprintf(char * restrict s, size_t n,
14142 const char * restrict format,
14143 va_list arg);</pre>
14146 The vsnprintf function is equivalent to snprintf, with the variable argument list
14147 replaced by arg, which shall have been initialized by the va_start macro (and
14148 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14149 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup> If copying takes place between objects that overlap, the behavior is
14150 undefined.
14153 The vsnprintf function returns the number of characters that would have been written
14154 had n been sufficiently large, not counting the terminating null character, or a negative
14155 value if an encoding error occurred. Thus, the null-terminated output has been
14156 completely written if and only if the returned value is nonnegative and less than n.
14157 <!--page 307 -->
14162 <pre>
14165 int vsprintf(char * restrict s,
14166 const char * restrict format,
14167 va_list arg);</pre>
14170 The vsprintf function is equivalent to sprintf, with the variable argument list
14171 replaced by arg, which shall have been initialized by the va_start macro (and
14172 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14173 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup> If copying takes place between objects that overlap, the behavior is
14174 undefined.
14177 The vsprintf function returns the number of characters written in the array, not
14178 counting the terminating null character, or a negative value if an encoding error occurred.
14183 <pre>
14186 int vsscanf(const char * restrict s,
14187 const char * restrict format,
14188 va_list arg);</pre>
14191 The vsscanf function is equivalent to sscanf, with the variable argument list
14192 replaced by arg, which shall have been initialized by the va_start macro (and
14193 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14197 The vsscanf function returns the value of the macro EOF if an input failure occurs
14198 before any conversion. Otherwise, the vsscanf function returns the number of input
14199 items assigned, which can be fewer than provided for, or even zero, in the event of an
14200 early matching failure.
14201 <!--page 308 -->
14208 <pre>
14210 int fgetc(FILE *stream);</pre>
14213 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14214 next character is present, the fgetc function obtains that character as an unsigned
14215 char converted to an int and advances the associated file position indicator for the
14216 stream (if defined).
14219 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14220 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14221 fgetc function returns the next character from the input stream pointed to by stream.
14222 If a read error occurs, the error indicator for the stream is set and the fgetc function
14226 <p><small><a name="note255" href="#note255">255)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
14227 </small>
14232 <pre>
14234 char *fgets(char * restrict s, int n,
14235 FILE * restrict stream);</pre>
14238 The fgets function reads at most one less than the number of characters specified by n
14239 from the stream pointed to by stream into the array pointed to by s. No additional
14240 characters are read after a new-line character (which is retained) or after end-of-file. A
14241 null character is written immediately after the last character read into the array.
14244 The fgets function returns s if successful. If end-of-file is encountered and no
14245 characters have been read into the array, the contents of the array remain unchanged and a
14246 null pointer is returned. If a read error occurs during the operation, the array contents are
14247 indeterminate and a null pointer is returned.
14252 <!--page 309 -->
14257 <pre>
14259 int fputc(int c, FILE *stream);</pre>
14262 The fputc function writes the character specified by c (converted to an unsigned
14263 char) to the output stream pointed to by stream, at the position indicated by the
14264 associated file position indicator for the stream (if defined), and advances the indicator
14265 appropriately. If the file cannot support positioning requests, or if the stream was opened
14266 with append mode, the character is appended to the output stream.
14269 The fputc function returns the character written. If a write error occurs, the error
14270 indicator for the stream is set and fputc returns EOF.
14275 <pre>
14277 int fputs(const char * restrict s,
14278 FILE * restrict stream);</pre>
14281 The fputs function writes the string pointed to by s to the stream pointed to by
14282 stream. The terminating null character is not written.
14285 The fputs function returns EOF if a write error occurs; otherwise it returns a
14286 nonnegative value.
14291 <pre>
14293 int getc(FILE *stream);</pre>
14296 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14297 may evaluate stream more than once, so the argument should never be an expression
14298 with side effects.
14299 <!--page 310 -->
14302 The getc function returns the next character from the input stream pointed to by
14303 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14304 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14305 getc returns EOF.
14310 <pre>
14312 int getchar(void);</pre>
14315 The getchar function is equivalent to getc with the argument stdin.
14318 The getchar function returns the next character from the input stream pointed to by
14319 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14320 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14321 getchar returns EOF.
14326 <pre>
14328 char *gets(char *s);</pre>
14331 The gets function reads characters from the input stream pointed to by stdin, into the
14332 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14333 Any new-line character is discarded, and a null character is written immediately after the
14334 last character read into the array.
14337 The gets function returns s if successful. If end-of-file is encountered and no
14338 characters have been read into the array, the contents of the array remain unchanged and a
14339 null pointer is returned. If a read error occurs during the operation, the array contents are
14340 indeterminate and a null pointer is returned.
14342 <!--page 311 -->
14347 <pre>
14349 int putc(int c, FILE *stream);</pre>
14352 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
14353 may evaluate stream more than once, so that argument should never be an expression
14354 with side effects.
14357 The putc function returns the character written. If a write error occurs, the error
14358 indicator for the stream is set and putc returns EOF.
14363 <pre>
14365 int putchar(int c);</pre>
14368 The putchar function is equivalent to putc with the second argument stdout.
14371 The putchar function returns the character written. If a write error occurs, the error
14372 indicator for the stream is set and putchar returns EOF.
14377 <pre>
14379 int puts(const char *s);</pre>
14382 The puts function writes the string pointed to by s to the stream pointed to by stdout,
14383 and appends a new-line character to the output. The terminating null character is not
14384 written.
14387 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
14388 value.
14389 <!--page 312 -->
14394 <pre>
14396 int ungetc(int c, FILE *stream);</pre>
14399 The ungetc function pushes the character specified by c (converted to an unsigned
14400 char) back onto the input stream pointed to by stream. Pushed-back characters will be
14401 returned by subsequent reads on that stream in the reverse order of their pushing. A
14402 successful intervening call (with the stream pointed to by stream) to a file positioning
14403 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
14404 stream. The external storage corresponding to the stream is unchanged.
14406 One character of pushback is guaranteed. If the ungetc function is called too many
14407 times on the same stream without an intervening read or file positioning operation on that
14408 stream, the operation may fail.
14410 If the value of c equals that of the macro EOF, the operation fails and the input stream is
14411 unchanged.
14413 A successful call to the ungetc function clears the end-of-file indicator for the stream.
14414 The value of the file position indicator for the stream after reading or discarding all
14415 pushed-back characters shall be the same as it was before the characters were pushed
14416 back. For a text stream, the value of its file position indicator after a successful call to the
14417 ungetc function is unspecified until all pushed-back characters are read or discarded.
14418 For a binary stream, its file position indicator is decremented by each successful call to
14419 the ungetc function; if its value was zero before a call, it is indeterminate after the
14423 The ungetc function returns the character pushed back after conversion, or EOF if the
14424 operation fails.
14430 <!--page 313 -->
14433 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14434 </small>
14441 <pre>
14443 size_t fread(void * restrict ptr,
14444 size_t size, size_t nmemb,
14445 FILE * restrict stream);</pre>
14448 The fread function reads, into the array pointed to by ptr, up to nmemb elements
14449 whose size is specified by size, from the stream pointed to by stream. For each
14450 object, size calls are made to the fgetc function and the results stored, in the order
14451 read, in an array of unsigned char exactly overlaying the object. The file position
14452 indicator for the stream (if defined) is advanced by the number of characters successfully
14453 read. If an error occurs, the resulting value of the file position indicator for the stream is
14454 indeterminate. If a partial element is read, its value is indeterminate.
14457 The fread function returns the number of elements successfully read, which may be
14458 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
14459 fread returns zero and the contents of the array and the state of the stream remain
14460 unchanged.
14465 <pre>
14467 size_t fwrite(const void * restrict ptr,
14468 size_t size, size_t nmemb,
14469 FILE * restrict stream);</pre>
14472 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
14473 whose size is specified by size, to the stream pointed to by stream. For each object,
14474 size calls are made to the fputc function, taking the values (in order) from an array of
14475 unsigned char exactly overlaying the object. The file position indicator for the
14476 stream (if defined) is advanced by the number of characters successfully written. If an
14477 error occurs, the resulting value of the file position indicator for the stream is
14478 indeterminate.
14479 <!--page 314 -->
14482 The fwrite function returns the number of elements successfully written, which will be
14483 less than nmemb only if a write error is encountered. If size or nmemb is zero,
14484 fwrite returns zero and the state of the stream remains unchanged.
14491 <pre>
14493 int fgetpos(FILE * restrict stream,
14494 fpos_t * restrict pos);</pre>
14497 The fgetpos function stores the current values of the parse state (if any) and file
14498 position indicator for the stream pointed to by stream in the object pointed to by pos.
14499 The values stored contain unspecified information usable by the fsetpos function for
14500 repositioning the stream to its position at the time of the call to the fgetpos function.
14503 If successful, the fgetpos function returns zero; on failure, the fgetpos function
14504 returns nonzero and stores an implementation-defined positive value in errno.
14510 <pre>
14512 int fseek(FILE *stream, long int offset, int whence);</pre>
14515 The fseek function sets the file position indicator for the stream pointed to by stream.
14516 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
14518 For a binary stream, the new position, measured in characters from the beginning of the
14519 file, is obtained by adding offset to the position specified by whence. The specified
14520 position is the beginning of the file if whence is SEEK_SET, the current value of the file
14521 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
14522 meaningfully support fseek calls with a whence value of SEEK_END.
14524 For a text stream, either offset shall be zero, or offset shall be a value returned by
14525 an earlier successful call to the ftell function on a stream associated with the same file
14526 and whence shall be SEEK_SET.
14527 <!--page 315 -->
14529 After determining the new position, a successful call to the fseek function undoes any
14530 effects of the ungetc function on the stream, clears the end-of-file indicator for the
14531 stream, and then establishes the new position. After a successful fseek call, the next
14532 operation on an update stream may be either input or output.
14535 The fseek function returns nonzero only for a request that cannot be satisfied.
14541 <pre>
14543 int fsetpos(FILE *stream, const fpos_t *pos);</pre>
14546 The fsetpos function sets the mbstate_t object (if any) and file position indicator
14547 for the stream pointed to by stream according to the value of the object pointed to by
14548 pos, which shall be a value obtained from an earlier successful call to the fgetpos
14549 function on a stream associated with the same file. If a read or write error occurs, the
14550 error indicator for the stream is set and fsetpos fails.
14552 A successful call to the fsetpos function undoes any effects of the ungetc function
14553 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
14554 parse state and position. After a successful fsetpos call, the next operation on an
14555 update stream may be either input or output.
14558 If successful, the fsetpos function returns zero; on failure, the fsetpos function
14559 returns nonzero and stores an implementation-defined positive value in errno.
14564 <pre>
14566 long int ftell(FILE *stream);</pre>
14569 The ftell function obtains the current value of the file position indicator for the stream
14570 pointed to by stream. For a binary stream, the value is the number of characters from
14571 the beginning of the file. For a text stream, its file position indicator contains unspecified
14572 information, usable by the fseek function for returning the file position indicator for the
14573 stream to its position at the time of the ftell call; the difference between two such
14574 return values is not necessarily a meaningful measure of the number of characters written
14575 <!--page 316 -->
14576 or read.
14579 If successful, the ftell function returns the current value of the file position indicator
14580 for the stream. On failure, the ftell function returns -1L and stores an
14581 implementation-defined positive value in errno.
14586 <pre>
14588 void rewind(FILE *stream);</pre>
14591 The rewind function sets the file position indicator for the stream pointed to by
14592 stream to the beginning of the file. It is equivalent to
14593 <pre>
14595 except that the error indicator for the stream is also cleared.
14598 The rewind function returns no value.
14605 <pre>
14607 void clearerr(FILE *stream);</pre>
14610 The clearerr function clears the end-of-file and error indicators for the stream pointed
14611 to by stream.
14614 The clearerr function returns no value.
14615 <!--page 317 -->
14620 <pre>
14622 int feof(FILE *stream);</pre>
14625 The feof function tests the end-of-file indicator for the stream pointed to by stream.
14628 The feof function returns nonzero if and only if the end-of-file indicator is set for
14629 stream.
14634 <pre>
14636 int ferror(FILE *stream);</pre>
14639 The ferror function tests the error indicator for the stream pointed to by stream.
14642 The ferror function returns nonzero if and only if the error indicator is set for
14643 stream.
14648 <pre>
14650 void perror(const char *s);</pre>
14653 The perror function maps the error number in the integer expression errno to an
14654 error message. It writes a sequence of characters to the standard error stream thus: first
14655 (if s is not a null pointer and the character pointed to by s is not the null character), the
14656 string pointed to by s followed by a colon (:) and a space; then an appropriate error
14657 message string followed by a new-line character. The contents of the error message
14658 strings are the same as those returned by the strerror function with argument errno.
14661 The perror function returns no value.
14663 <!--page 318 -->
14667 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
14671 <pre>
14672 div_t</pre>
14673 which is a structure type that is the type of the value returned by the div function,
14674 <pre>
14675 ldiv_t</pre>
14676 which is a structure type that is the type of the value returned by the ldiv function, and
14677 <pre>
14678 lldiv_t</pre>
14679 which is a structure type that is the type of the value returned by the lldiv function.
14682 <pre>
14683 EXIT_FAILURE</pre>
14684 and
14685 <pre>
14686 EXIT_SUCCESS</pre>
14687 which expand to integer constant expressions that can be used as the argument to the
14688 exit function to return unsuccessful or successful termination status, respectively, to the
14689 host environment;
14690 <pre>
14691 RAND_MAX</pre>
14692 which expands to an integer constant expression that is the maximum value returned by
14693 the rand function; and
14694 <pre>
14695 MB_CUR_MAX</pre>
14696 which expands to a positive integer expression with type size_t that is the maximum
14697 number of bytes in a multibyte character for the extended character set specified by the
14698 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
14703 <!--page 319 -->
14706 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
14707 </small>
14711 The functions atof, atoi, atol, and atoll need not affect the value of the integer
14712 expression errno on an error. If the value of the result cannot be represented, the
14713 behavior is undefined.
14718 <pre>
14720 double atof(const char *nptr);</pre>
14723 The atof function converts the initial portion of the string pointed to by nptr to
14724 double representation. Except for the behavior on error, it is equivalent to
14725 <pre>
14726 strtod(nptr, (char **)NULL)</pre>
14729 The atof function returns the converted value.
14730 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
14735 <pre>
14737 int atoi(const char *nptr);
14738 long int atol(const char *nptr);
14739 long long int atoll(const char *nptr);</pre>
14742 The atoi, atol, and atoll functions convert the initial portion of the string pointed
14743 to by nptr to int, long int, and long long int representation, respectively.
14744 Except for the behavior on error, they are equivalent to
14745 <pre>
14746 atoi: (int)strtol(nptr, (char **)NULL, 10)
14747 atol: strtol(nptr, (char **)NULL, 10)
14751 The atoi, atol, and atoll functions return the converted value.
14754 <!--page 320 -->
14756 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
14759 <pre>
14761 double strtod(const char * restrict nptr,
14762 char ** restrict endptr);
14763 float strtof(const char * restrict nptr,
14764 char ** restrict endptr);
14765 long double strtold(const char * restrict nptr,
14766 char ** restrict endptr);</pre>
14769 The strtod, strtof, and strtold functions convert the initial portion of the string
14770 pointed to by nptr to double, float, and long double representation,
14771 respectively. First, they decompose the input string into three parts: an initial, possibly
14772 empty, sequence of white-space characters (as specified by the isspace function), a
14773 subject sequence resembling a floating-point constant or representing an infinity or NaN;
14774 and a final string of one or more unrecognized characters, including the terminating null
14775 character of the input string. Then, they attempt to convert the subject sequence to a
14776 floating-point number, and return the result.
14778 The expected form of the subject sequence is an optional plus or minus sign, then one of
14779 the following:
14780 <ul>
14781 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
14784 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14785 <li> INF or INFINITY, ignoring case
14787 <pre>
14788 n-char-sequence:
14789 digit
14790 nondigit
14791 n-char-sequence digit
14792 n-char-sequence nondigit</pre>
14793 </ul>
14794 The subject sequence is defined as the longest initial subsequence of the input string,
14795 starting with the first non-white-space character, that is of the expected form. The subject
14796 sequence contains no characters if the input string is not of the expected form.
14798 If the subject sequence has the expected form for a floating-point number, the sequence of
14799 characters starting with the first digit or the decimal-point character (whichever occurs
14800 first) is interpreted as a floating constant according to the rules of <a href="#6.4.4.2">6.4.4.2</a>, except that the
14801 <!--page 321 -->
14802 decimal-point character is used in place of a period, and that if neither an exponent part
14803 nor a decimal-point character appears in a decimal floating point number, or if a binary
14804 exponent part does not appear in a hexadecimal floating point number, an exponent part
14805 of the appropriate type with value zero is assumed to follow the last digit in the string. If
14806 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
14807 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
14808 the return type, else like a floating constant that is too large for the range of the return
14809 type. A character sequence NAN or NAN(n-char-sequence<sub>opt</sub>), is interpreted as a quiet
14810 NaN, if supported in the return type, else like a subject sequence part that does not have
14811 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
14812 pointer to the final string is stored in the object pointed to by endptr, provided that
14813 endptr is not a null pointer.
14815 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
14816 value resulting from the conversion is correctly rounded.
14818 In other than the "C" locale, additional locale-specific subject sequence forms may be
14819 accepted.
14821 If the subject sequence is empty or does not have the expected form, no conversion is
14822 performed; the value of nptr is stored in the object pointed to by endptr, provided
14823 that endptr is not a null pointer.
14826 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
14827 the result is not exactly representable, the result should be one of the two numbers in the
14828 appropriate internal format that are adjacent to the hexadecimal floating source value,
14829 with the extra stipulation that the error should have a correct sign for the current rounding
14830 direction.
14832 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
14833 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
14834 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
14835 consider the two bounding, adjacent decimal strings L and U, both having
14836 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
14837 The result should be one of the (equal or adjacent) values that would be obtained by
14838 correctly rounding L and U according to the current rounding direction, with the extra
14840 <!--page 322 -->
14841 stipulation that the error with respect to D should have a correct sign for the current
14845 The functions return the converted value, if any. If no conversion could be performed,
14846 zero is returned. If the correct value is outside the range of representable values, plus or
14847 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
14848 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
14849 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
14850 than the smallest normalized positive number in the return type; whether errno acquires
14851 the value ERANGE is implementation-defined.
14854 <p><small><a name="note258" href="#note258">258)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
14855 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
14856 methods may yield different results if rounding is toward positive or negative infinity. In either case,
14857 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
14858 </small>
14859 <p><small><a name="note259" href="#note259">259)</a> An implementation may use the n-char sequence to determine extra information to be represented in
14860 the NaN's significand.
14861 </small>
14862 <p><small><a name="note260" href="#note260">260)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
14863 to the same internal floating value, but if not will round to adjacent values.
14864 </small>
14866 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
14869 <pre>
14871 long int strtol(
14872 const char * restrict nptr,
14873 char ** restrict endptr,
14874 int base);
14875 long long int strtoll(
14876 const char * restrict nptr,
14877 char ** restrict endptr,
14878 int base);
14879 unsigned long int strtoul(
14880 const char * restrict nptr,
14881 char ** restrict endptr,
14882 int base);
14883 unsigned long long int strtoull(
14884 const char * restrict nptr,
14885 char ** restrict endptr,
14886 int base);</pre>
14889 The strtol, strtoll, strtoul, and strtoull functions convert the initial
14890 portion of the string pointed to by nptr to long int, long long int, unsigned
14891 long int, and unsigned long long int representation, respectively. First,
14892 they decompose the input string into three parts: an initial, possibly empty, sequence of
14893 white-space characters (as specified by the isspace function), a subject sequence
14896 <!--page 323 -->
14897 resembling an integer represented in some radix determined by the value of base, and a
14898 final string of one or more unrecognized characters, including the terminating null
14899 character of the input string. Then, they attempt to convert the subject sequence to an
14900 integer, and return the result.
14902 If the value of base is zero, the expected form of the subject sequence is that of an
14903 integer constant as described in <a href="#6.4.4.1">6.4.4.1</a>, optionally preceded by a plus or minus sign, but
14905 expected form of the subject sequence is a sequence of letters and digits representing an
14906 integer with the radix specified by base, optionally preceded by a plus or minus sign,
14907 but not including an integer suffix. The letters from a (or A) through z (or Z) are
14910 optionally precede the sequence of letters and digits, following the sign if present.
14912 The subject sequence is defined as the longest initial subsequence of the input string,
14913 starting with the first non-white-space character, that is of the expected form. The subject
14914 sequence contains no characters if the input string is empty or consists entirely of white
14915 space, or if the first non-white-space character is other than a sign or a permissible letter
14916 or digit.
14918 If the subject sequence has the expected form and the value of base is zero, the sequence
14919 of characters starting with the first digit is interpreted as an integer constant according to
14920 the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the value of base
14921 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
14922 as given above. If the subject sequence begins with a minus sign, the value resulting from
14923 the conversion is negated (in the return type). A pointer to the final string is stored in the
14924 object pointed to by endptr, provided that endptr is not a null pointer.
14926 In other than the "C" locale, additional locale-specific subject sequence forms may be
14927 accepted.
14929 If the subject sequence is empty or does not have the expected form, no conversion is
14930 performed; the value of nptr is stored in the object pointed to by endptr, provided
14931 that endptr is not a null pointer.
14934 The strtol, strtoll, strtoul, and strtoull functions return the converted
14935 value, if any. If no conversion could be performed, zero is returned. If the correct value
14936 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
14937 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
14938 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
14939 <!--page 324 -->
14941 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
14946 <pre>
14948 int rand(void);</pre>
14951 The rand function computes a sequence of pseudo-random integers in the range 0 to
14952 RAND_MAX.
14954 The implementation shall behave as if no library function calls the rand function.
14957 The rand function returns a pseudo-random integer.
14960 The value of the RAND_MAX macro shall be at least 32767.
14965 <pre>
14967 void srand(unsigned int seed);</pre>
14970 The srand function uses the argument as a seed for a new sequence of pseudo-random
14971 numbers to be returned by subsequent calls to rand. If srand is then called with the
14972 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
14973 called before any calls to srand have been made, the same sequence shall be generated
14974 as when srand is first called with a seed value of 1.
14976 The implementation shall behave as if no library function calls the srand function.
14979 The srand function returns no value.
14981 EXAMPLE The following functions define a portable implementation of rand and srand.
14982 <!--page 325 -->
14983 <pre>
14984 static unsigned long int next = 1;
14985 int rand(void) // RAND_MAX assumed to be 32767
14986 {
14989 }
14990 void srand(unsigned int seed)
14991 {
14992 next = seed;
14993 }</pre>
14998 The order and contiguity of storage allocated by successive calls to the calloc,
14999 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15000 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15001 and then used to access such an object or an array of such objects in the space allocated
15002 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15003 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15004 object disjoint from any other object. The pointer returned points to the start (lowest byte
15005 address) of the allocated space. If the space cannot be allocated, a null pointer is
15006 returned. If the size of the space requested is zero, the behavior is implementation-
15007 defined: either a null pointer is returned, or the behavior is as if the size were some
15008 nonzero value, except that the returned pointer shall not be used to access an object.
15013 <pre>
15015 void *calloc(size_t nmemb, size_t size);</pre>
15018 The calloc function allocates space for an array of nmemb objects, each of whose size
15019 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15022 The calloc function returns either a null pointer or a pointer to the allocated space.
15025 <p><small><a name="note261" href="#note261">261)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
15026 constant.
15027 </small>
15032 <pre>
15034 void free(void *ptr);</pre>
15037 The free function causes the space pointed to by ptr to be deallocated, that is, made
15038 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15039 the argument does not match a pointer earlier returned by the calloc, malloc, or
15042 <!--page 326 -->
15043 realloc function, or if the space has been deallocated by a call to free or realloc,
15044 the behavior is undefined.
15047 The free function returns no value.
15052 <pre>
15054 void *malloc(size_t size);</pre>
15057 The malloc function allocates space for an object whose size is specified by size and
15058 whose value is indeterminate.
15061 The malloc function returns either a null pointer or a pointer to the allocated space.
15066 <pre>
15068 void *realloc(void *ptr, size_t size);</pre>
15071 The realloc function deallocates the old object pointed to by ptr and returns a
15072 pointer to a new object that has the size specified by size. The contents of the new
15073 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15074 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15075 indeterminate values.
15077 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15078 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15079 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15080 to the free or realloc function, the behavior is undefined. If memory for the new
15081 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15084 The realloc function returns a pointer to the new object (which may have the same
15085 value as a pointer to the old object), or a null pointer if the new object could not be
15086 allocated.
15087 <!--page 327 -->
15094 <pre>
15096 void abort(void);</pre>
15099 The abort function causes abnormal program termination to occur, unless the signal
15100 SIGABRT is being caught and the signal handler does not return. Whether open streams
15101 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15102 removed is implementation-defined. An implementation-defined form of the status
15103 unsuccessful termination is returned to the host environment by means of the function
15104 call raise(SIGABRT).
15107 The abort function does not return to its caller.
15112 <pre>
15114 int atexit(void (*func)(void));</pre>
15117 The atexit function registers the function pointed to by func, to be called without
15118 arguments at normal program termination.
15121 The implementation shall support the registration of at least 32 functions.
15124 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15130 <pre>
15132 void exit(int status);</pre>
15135 The exit function causes normal program termination to occur. If more than one call to
15136 the exit function is executed by a program, the behavior is undefined.
15137 <!--page 328 -->
15139 First, all functions registered by the atexit function are called, in the reverse order of
15140 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15141 functions that had already been called at the time it was registered. If, during the call to
15142 any such function, a call to the longjmp function is made that would terminate the call
15143 to the registered function, the behavior is undefined.
15145 Next, all open streams with unwritten buffered data are flushed, all open streams are
15146 closed, and all files created by the tmpfile function are removed.
15148 Finally, control is returned to the host environment. If the value of status is zero or
15149 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15150 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15151 of the status unsuccessful termination is returned. Otherwise the status returned is
15152 implementation-defined.
15155 The exit function cannot return to its caller.
15158 <p><small><a name="note262" href="#note262">262)</a> Each function is called as many times as it was registered, and in the correct order with respect to
15159 other registered functions.
15160 </small>
15165 <pre>
15167 void _Exit(int status);</pre>
15170 The _Exit function causes normal program termination to occur and control to be
15171 returned to the host environment. No functions registered by the atexit function or
15172 signal handlers registered by the signal function are called. The status returned to the
15173 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15174 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15175 or temporary files are removed is implementation-defined.
15178 The _Exit function cannot return to its caller.
15183 <!--page 329 -->
15188 <pre>
15190 char *getenv(const char *name);</pre>
15193 The getenv function searches an environment list, provided by the host environment,
15194 for a string that matches the string pointed to by name. The set of environment names
15195 and the method for altering the environment list are implementation-defined.
15197 The implementation shall behave as if no library function calls the getenv function.
15200 The getenv function returns a pointer to a string associated with the matched list
15201 member. The string pointed to shall not be modified by the program, but may be
15202 overwritten by a subsequent call to the getenv function. If the specified name cannot
15203 be found, a null pointer is returned.
15208 <pre>
15210 int system(const char *string);</pre>
15213 If string is a null pointer, the system function determines whether the host
15214 environment has a command processor. If string is not a null pointer, the system
15215 function passes the string pointed to by string to that command processor to be
15216 executed in a manner which the implementation shall document; this might then cause the
15217 program calling system to behave in a non-conforming manner or to terminate.
15220 If the argument is a null pointer, the system function returns nonzero only if a
15221 command processor is available. If the argument is not a null pointer, and the system
15222 function does return, it returns an implementation-defined value.
15223 <!--page 330 -->
15227 These utilities make use of a comparison function to search or sort arrays of unspecified
15228 type. Where an argument declared as size_t nmemb specifies the length of the array
15229 for a function, nmemb can have the value zero on a call to that function; the comparison
15230 function is not called, a search finds no matching element, and sorting performs no
15231 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15234 The implementation shall ensure that the second argument of the comparison function
15235 (when called from bsearch), or both arguments (when called from qsort), are
15236 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15237 shall equal key.
15239 The comparison function shall not alter the contents of the array. The implementation
15240 may reorder elements of the array between calls to the comparison function, but shall not
15241 alter the contents of any individual element.
15243 When the same objects (consisting of size bytes, irrespective of their current positions
15244 in the array) are passed more than once to the comparison function, the results shall be
15245 consistent with one another. That is, for qsort they shall define a total ordering on the
15246 array, and for bsearch the same object shall always compare the same way with the
15247 key.
15249 A sequence point occurs immediately before and immediately after each call to the
15250 comparison function, and also between any call to the comparison function and any
15251 movement of the objects passed as arguments to that call.
15254 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15256 <pre>
15257 ((char *)p - (char *)base) % size == 0
15258 (char *)p >= (char *)base
15260 </small>
15265 <pre>
15267 void *bsearch(const void *key, const void *base,
15268 size_t nmemb, size_t size,
15269 int (*compar)(const void *, const void *));</pre>
15272 The bsearch function searches an array of nmemb objects, the initial element of which
15273 is pointed to by base, for an element that matches the object pointed to by key. The
15276 <!--page 331 -->
15277 size of each element of the array is specified by size.
15279 The comparison function pointed to by compar is called with two arguments that point
15280 to the key object and to an array element, in that order. The function shall return an
15281 integer less than, equal to, or greater than zero if the key object is considered,
15282 respectively, to be less than, to match, or to be greater than the array element. The array
15283 shall consist of: all the elements that compare less than, all the elements that compare
15284 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note264"><b>264)</b></a></sup>
15287 The bsearch function returns a pointer to a matching element of the array, or a null
15288 pointer if no match is found. If two elements compare as equal, which element is
15289 matched is unspecified.
15292 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15293 </small>
15298 <pre>
15300 void qsort(void *base, size_t nmemb, size_t size,
15301 int (*compar)(const void *, const void *));</pre>
15304 The qsort function sorts an array of nmemb objects, the initial element of which is
15305 pointed to by base. The size of each object is specified by size.
15307 The contents of the array are sorted into ascending order according to a comparison
15308 function pointed to by compar, which is called with two arguments that point to the
15309 objects being compared. The function shall return an integer less than, equal to, or
15310 greater than zero if the first argument is considered to be respectively less than, equal to,
15311 or greater than the second.
15313 If two elements compare as equal, their order in the resulting sorted array is unspecified.
15316 The qsort function returns no value.
15321 <!--page 332 -->
15328 <pre>
15330 int abs(int j);
15331 long int labs(long int j);
15332 long long int llabs(long long int j);</pre>
15335 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
15336 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
15339 The abs, labs, and llabs, functions return the absolute value.
15342 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
15343 </small>
15348 <pre>
15350 div_t div(int numer, int denom);
15351 ldiv_t ldiv(long int numer, long int denom);
15352 lldiv_t lldiv(long long int numer, long long int denom);</pre>
15355 The div, ldiv, and lldiv, functions compute numer / denom and numer %
15356 denom in a single operation.
15359 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
15360 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
15361 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
15362 each of which has the same type as the arguments numer and denom. If either part of
15363 the result cannot be represented, the behavior is undefined.
15368 <!--page 333 -->
15370 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
15372 The behavior of the multibyte character functions is affected by the LC_CTYPE category
15373 of the current locale. For a state-dependent encoding, each function is placed into its
15374 initial conversion state by a call for which its character pointer argument, s, is a null
15375 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
15376 state of the function to be altered as necessary. A call with s as a null pointer causes
15377 these functions to return a nonzero value if encodings have state dependency, and zero
15378 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
15379 functions to be indeterminate.
15382 <p><small><a name="note266" href="#note266">266)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
15383 character codes, but are grouped with an adjacent multibyte character.
15384 </small>
15389 <pre>
15391 int mblen(const char *s, size_t n);</pre>
15394 If s is not a null pointer, the mblen function determines the number of bytes contained
15395 in the multibyte character pointed to by s. Except that the conversion state of the
15396 mbtowc function is not affected, it is equivalent to
15398 <pre>
15400 The implementation shall behave as if no library function calls the mblen function.
15403 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
15404 character encodings, respectively, do or do not have state-dependent encodings. If s is
15405 not a null pointer, the mblen function either returns 0 (if s points to the null character),
15406 or returns the number of bytes that are contained in the multibyte character (if the next n
15407 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
15408 multibyte character).
15414 <!--page 334 -->
15419 <pre>
15421 int mbtowc(wchar_t * restrict pwc,
15422 const char * restrict s,
15423 size_t n);</pre>
15426 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
15427 the byte pointed to by s to determine the number of bytes needed to complete the next
15428 multibyte character (including any shift sequences). If the function determines that the
15429 next multibyte character is complete and valid, it determines the value of the
15430 corresponding wide character and then, if pwc is not a null pointer, stores that value in
15431 the object pointed to by pwc. If the corresponding wide character is the null wide
15432 character, the function is left in the initial conversion state.
15434 The implementation shall behave as if no library function calls the mbtowc function.
15437 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
15438 character encodings, respectively, do or do not have state-dependent encodings. If s is
15439 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
15440 or returns the number of bytes that are contained in the converted multibyte character (if
15441 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
15442 form a valid multibyte character).
15444 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
15445 macro.
15450 <pre>
15452 int wctomb(char *s, wchar_t wc);</pre>
15455 The wctomb function determines the number of bytes needed to represent the multibyte
15456 character corresponding to the wide character given by wc (including any shift
15457 sequences), and stores the multibyte character representation in the array whose first
15458 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
15459 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
15460 sequence needed to restore the initial shift state, and the function is left in the initial
15461 conversion state.
15462 <!--page 335 -->
15464 The implementation shall behave as if no library function calls the wctomb function.
15467 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
15468 character encodings, respectively, do or do not have state-dependent encodings. If s is
15469 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
15470 to a valid multibyte character, or returns the number of bytes that are contained in the
15471 multibyte character corresponding to the value of wc.
15473 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
15475 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
15477 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
15478 the current locale.
15483 <pre>
15485 size_t mbstowcs(wchar_t * restrict pwcs,
15486 const char * restrict s,
15487 size_t n);</pre>
15490 The mbstowcs function converts a sequence of multibyte characters that begins in the
15491 initial shift state from the array pointed to by s into a sequence of corresponding wide
15492 characters and stores not more than n wide characters into the array pointed to by pwcs.
15493 No multibyte characters that follow a null character (which is converted into a null wide
15494 character) will be examined or converted. Each multibyte character is converted as if by
15495 a call to the mbtowc function, except that the conversion state of the mbtowc function is
15496 not affected.
15498 No more than n elements will be modified in the array pointed to by pwcs. If copying
15499 takes place between objects that overlap, the behavior is undefined.
15502 If an invalid multibyte character is encountered, the mbstowcs function returns
15503 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
15504 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
15509 <!--page 336 -->
15512 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
15513 </small>
15518 <pre>
15520 size_t wcstombs(char * restrict s,
15521 const wchar_t * restrict pwcs,
15522 size_t n);</pre>
15525 The wcstombs function converts a sequence of wide characters from the array pointed
15526 to by pwcs into a sequence of corresponding multibyte characters that begins in the
15527 initial shift state, and stores these multibyte characters into the array pointed to by s,
15528 stopping if a multibyte character would exceed the limit of n total bytes or if a null
15529 character is stored. Each wide character is converted as if by a call to the wctomb
15530 function, except that the conversion state of the wctomb function is not affected.
15532 No more than n bytes will be modified in the array pointed to by s. If copying takes place
15533 between objects that overlap, the behavior is undefined.
15536 If a wide character is encountered that does not correspond to a valid multibyte character,
15537 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
15538 returns the number of bytes modified, not including a terminating null character, if
15540 <!--page 337 -->
15546 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
15547 macro useful for manipulating arrays of character type and other objects treated as arrays
15548 of character type.<sup><a href="#note268"><b>268)</b></a></sup> The type is size_t and the macro is NULL (both described in
15549 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
15550 a char * or void * argument points to the initial (lowest addressed) character of the
15551 array. If an array is accessed beyond the end of an object, the behavior is undefined.
15553 Where an argument declared as size_t n specifies the length of the array for a
15554 function, n can have the value zero on a call to that function. Unless explicitly stated
15555 otherwise in the description of a particular function in this subclause, pointer arguments
15556 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
15557 function that locates a character finds no occurrence, a function that compares two
15558 character sequences returns zero, and a function that copies characters copies zero
15559 characters.
15561 For all functions in this subclause, each character shall be interpreted as if it had the type
15562 unsigned char (and therefore every possible object representation is valid and has a
15563 different value).
15566 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
15567 </small>
15574 <pre>
15576 void *memcpy(void * restrict s1,
15577 const void * restrict s2,
15578 size_t n);</pre>
15581 The memcpy function copies n characters from the object pointed to by s2 into the
15582 object pointed to by s1. If copying takes place between objects that overlap, the behavior
15583 is undefined.
15586 The memcpy function returns the value of s1.
15591 <!--page 338 -->
15596 <pre>
15598 void *memmove(void *s1, const void *s2, size_t n);</pre>
15601 The memmove function copies n characters from the object pointed to by s2 into the
15602 object pointed to by s1. Copying takes place as if the n characters from the object
15603 pointed to by s2 are first copied into a temporary array of n characters that does not
15604 overlap the objects pointed to by s1 and s2, and then the n characters from the
15605 temporary array are copied into the object pointed to by s1.
15608 The memmove function returns the value of s1.
15613 <pre>
15615 char *strcpy(char * restrict s1,
15616 const char * restrict s2);</pre>
15619 The strcpy function copies the string pointed to by s2 (including the terminating null
15620 character) into the array pointed to by s1. If copying takes place between objects that
15621 overlap, the behavior is undefined.
15624 The strcpy function returns the value of s1.
15629 <pre>
15631 char *strncpy(char * restrict s1,
15632 const char * restrict s2,
15633 size_t n);</pre>
15636 The strncpy function copies not more than n characters (characters that follow a null
15637 character are not copied) from the array pointed to by s2 to the array pointed to by
15638 <!--page 339 -->
15639 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
15641 If the array pointed to by s2 is a string that is shorter than n characters, null characters
15642 are appended to the copy in the array pointed to by s1, until n characters in all have been
15643 written.
15646 The strncpy function returns the value of s1.
15649 <p><small><a name="note269" href="#note269">269)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
15650 not be null-terminated.
15651 </small>
15658 <pre>
15660 char *strcat(char * restrict s1,
15661 const char * restrict s2);</pre>
15664 The strcat function appends a copy of the string pointed to by s2 (including the
15665 terminating null character) to the end of the string pointed to by s1. The initial character
15666 of s2 overwrites the null character at the end of s1. If copying takes place between
15667 objects that overlap, the behavior is undefined.
15670 The strcat function returns the value of s1.
15675 <pre>
15677 char *strncat(char * restrict s1,
15678 const char * restrict s2,
15679 size_t n);</pre>
15682 The strncat function appends not more than n characters (a null character and
15683 characters that follow it are not appended) from the array pointed to by s2 to the end of
15684 the string pointed to by s1. The initial character of s2 overwrites the null character at the
15685 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
15687 <!--page 340 -->
15688 takes place between objects that overlap, the behavior is undefined.
15691 The strncat function returns the value of s1.
15695 <p><small><a name="note270" href="#note270">270)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
15696 strlen(s1)+n+1.
15697 </small>
15701 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
15702 and strncmp is determined by the sign of the difference between the values of the first
15703 pair of characters (both interpreted as unsigned char) that differ in the objects being
15704 compared.
15709 <pre>
15711 int memcmp(const void *s1, const void *s2, size_t n);</pre>
15714 The memcmp function compares the first n characters of the object pointed to by s1 to
15715 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
15718 The memcmp function returns an integer greater than, equal to, or less than zero,
15719 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
15720 pointed to by s2.
15723 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
15724 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
15725 comparison.
15726 </small>
15731 <pre>
15733 int strcmp(const char *s1, const char *s2);</pre>
15736 The strcmp function compares the string pointed to by s1 to the string pointed to by
15737 s2.
15740 The strcmp function returns an integer greater than, equal to, or less than zero,
15741 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15743 <!--page 341 -->
15744 pointed to by s2.
15749 <pre>
15751 int strcoll(const char *s1, const char *s2);</pre>
15754 The strcoll function compares the string pointed to by s1 to the string pointed to by
15755 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
15758 The strcoll function returns an integer greater than, equal to, or less than zero,
15759 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15760 pointed to by s2 when both are interpreted as appropriate to the current locale.
15765 <pre>
15767 int strncmp(const char *s1, const char *s2, size_t n);</pre>
15770 The strncmp function compares not more than n characters (characters that follow a
15771 null character are not compared) from the array pointed to by s1 to the array pointed to
15772 by s2.
15775 The strncmp function returns an integer greater than, equal to, or less than zero,
15776 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
15777 to, or less than the possibly null-terminated array pointed to by s2.
15782 <pre>
15784 size_t strxfrm(char * restrict s1,
15785 const char * restrict s2,
15786 size_t n);</pre>
15789 The strxfrm function transforms the string pointed to by s2 and places the resulting
15790 string into the array pointed to by s1. The transformation is such that if the strcmp
15791 function is applied to two transformed strings, it returns a value greater than, equal to, or
15792 <!--page 342 -->
15793 less than zero, corresponding to the result of the strcoll function applied to the same
15794 two original strings. No more than n characters are placed into the resulting array
15795 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
15796 be a null pointer. If copying takes place between objects that overlap, the behavior is
15797 undefined.
15800 The strxfrm function returns the length of the transformed string (not including the
15801 terminating null character). If the value returned is n or more, the contents of the array
15802 pointed to by s1 are indeterminate.
15804 EXAMPLE The value of the following expression is the size of the array needed to hold the
15805 transformation of the string pointed to by s.
15806 <pre>
15815 <pre>
15817 void *memchr(const void *s, int c, size_t n);</pre>
15820 The memchr function locates the first occurrence of c (converted to an unsigned
15821 char) in the initial n characters (each interpreted as unsigned char) of the object
15822 pointed to by s.
15825 The memchr function returns a pointer to the located character, or a null pointer if the
15826 character does not occur in the object.
15831 <pre>
15833 char *strchr(const char *s, int c);</pre>
15836 The strchr function locates the first occurrence of c (converted to a char) in the
15837 string pointed to by s. The terminating null character is considered to be part of the
15838 string.
15841 The strchr function returns a pointer to the located character, or a null pointer if the
15842 character does not occur in the string.
15843 <!--page 343 -->
15848 <pre>
15850 size_t strcspn(const char *s1, const char *s2);</pre>
15853 The strcspn function computes the length of the maximum initial segment of the string
15854 pointed to by s1 which consists entirely of characters not from the string pointed to by
15855 s2.
15858 The strcspn function returns the length of the segment.
15863 <pre>
15865 char *strpbrk(const char *s1, const char *s2);</pre>
15868 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
15869 character from the string pointed to by s2.
15872 The strpbrk function returns a pointer to the character, or a null pointer if no character
15873 from s2 occurs in s1.
15878 <pre>
15880 char *strrchr(const char *s, int c);</pre>
15883 The strrchr function locates the last occurrence of c (converted to a char) in the
15884 string pointed to by s. The terminating null character is considered to be part of the
15885 string.
15888 The strrchr function returns a pointer to the character, or a null pointer if c does not
15889 occur in the string.
15890 <!--page 344 -->
15895 <pre>
15897 size_t strspn(const char *s1, const char *s2);</pre>
15900 The strspn function computes the length of the maximum initial segment of the string
15901 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
15904 The strspn function returns the length of the segment.
15909 <pre>
15911 char *strstr(const char *s1, const char *s2);</pre>
15914 The strstr function locates the first occurrence in the string pointed to by s1 of the
15915 sequence of characters (excluding the terminating null character) in the string pointed to
15916 by s2.
15919 The strstr function returns a pointer to the located string, or a null pointer if the string
15920 is not found. If s2 points to a string with zero length, the function returns s1.
15925 <pre>
15927 char *strtok(char * restrict s1,
15928 const char * restrict s2);</pre>
15931 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
15932 sequence of tokens, each of which is delimited by a character from the string pointed to
15933 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
15934 sequence have a null first argument. The separator string pointed to by s2 may be
15935 different from call to call.
15937 The first call in the sequence searches the string pointed to by s1 for the first character
15938 that is not contained in the current separator string pointed to by s2. If no such character
15939 is found, then there are no tokens in the string pointed to by s1 and the strtok function
15940 <!--page 345 -->
15941 returns a null pointer. If such a character is found, it is the start of the first token.
15943 The strtok function then searches from there for a character that is contained in the
15944 current separator string. If no such character is found, the current token extends to the
15945 end of the string pointed to by s1, and subsequent searches for a token will return a null
15946 pointer. If such a character is found, it is overwritten by a null character, which
15947 terminates the current token. The strtok function saves a pointer to the following
15948 character, from which the next search for a token will start.
15950 Each subsequent call, with a null pointer as the value of the first argument, starts
15951 searching from the saved pointer and behaves as described above.
15953 The implementation shall behave as if no library function calls the strtok function.
15956 The strtok function returns a pointer to the first character of a token, or a null pointer
15957 if there is no token.
15959 EXAMPLE
15960 <pre>
15962 static char str[] = "?a???b,,,#c";
15963 char *t;
15975 <pre>
15977 void *memset(void *s, int c, size_t n);</pre>
15980 The memset function copies the value of c (converted to an unsigned char) into
15981 each of the first n characters of the object pointed to by s.
15984 The memset function returns the value of s.
15985 <!--page 346 -->
15990 <pre>
15992 char *strerror(int errnum);</pre>
15995 The strerror function maps the number in errnum to a message string. Typically,
15996 the values for errnum come from errno, but strerror shall map any value of type
15997 int to a message.
15999 The implementation shall behave as if no library function calls the strerror function.
16002 The strerror function returns a pointer to the string, the contents of which are locale-
16003 specific. The array pointed to shall not be modified by the program, but may be
16004 overwritten by a subsequent call to the strerror function.
16009 <pre>
16011 size_t strlen(const char *s);</pre>
16014 The strlen function computes the length of the string pointed to by s.
16017 The strlen function returns the number of characters that precede the terminating null
16018 character.
16019 <!--page 347 -->
16023 The header <a href="#7.22"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
16024 defines several type-generic macros.
16026 Of the <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> functions without an f (float) or l (long
16027 double) suffix, several have one or more parameters whose corresponding real type is
16028 double. For each such function, except modf, there is a corresponding type-generic
16029 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16030 synopsis are generic parameters. Use of the macro invokes a function whose
16031 corresponding real type and type domain are determined by the arguments for the generic
16034 Use of the macro invokes a function whose generic parameters have the corresponding
16035 real type determined as follows:
16036 <ul>
16037 <li> First, if any argument for generic parameters has type long double, the type
16038 determined is long double.
16039 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16040 type, the type determined is double.
16041 <li> Otherwise, the type determined is float.
16042 </ul>
16044 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16045 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16046 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16047 corresponding type-generic macro for fabs and cabs is fabs.
16052 <!--page 348 -->
16053 <pre>
16055 function function macro
16057 acos cacos acos
16058 asin casin asin
16059 atan catan atan
16060 acosh cacosh acosh
16061 asinh casinh asinh
16062 atanh catanh atanh
16063 cos ccos cos
16064 sin csin sin
16065 tan ctan tan
16066 cosh ccosh cosh
16067 sinh csinh sinh
16068 tanh ctanh tanh
16069 exp cexp exp
16070 log clog log
16071 pow cpow pow
16072 sqrt csqrt sqrt
16073 fabs cabs fabs</pre>
16074 If at least one argument for a generic parameter is complex, then use of the macro invokes
16075 a complex function; otherwise, use of the macro invokes a real function.
16077 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16078 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16079 name as the function. These type-generic macros are:
16080 <pre>
16081 atan2 fma llround remainder
16082 cbrt fmax log10 remquo
16083 ceil fmin log1p rint
16084 copysign fmod log2 round
16085 erf frexp logb scalbn
16086 erfc hypot lrint scalbln
16087 exp2 ilogb lround tgamma
16088 expm1 ldexp nearbyint trunc
16089 fdim lgamma nextafter
16090 floor llrint nexttoward</pre>
16091 If all arguments for generic parameters are real, then use of the macro invokes a real
16092 function; otherwise, use of the macro results in undefined behavior.
16094 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16095 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16096 function. These type-generic macros are:
16097 <!--page 349 -->
16098 <pre>
16099 carg conj creal
16100 cimag cproj</pre>
16101 Use of the macro with any real or complex argument invokes a complex function.
16103 EXAMPLE With the declarations
16104 <pre>
16106 int n;
16107 float f;
16108 double d;
16109 long double ld;
16110 float complex fc;
16111 double complex dc;
16112 long double complex ldc;</pre>
16113 functions invoked by use of type-generic macros are shown in the following table:
16114 <!--page 350 -->
16115 <pre>
16116 macro use invokes
16118 exp(n) exp(n), the function
16119 acosh(f) acoshf(f)
16120 sin(d) sin(d), the function
16121 atan(ld) atanl(ld)
16122 log(fc) clogf(fc)
16123 sqrt(dc) csqrt(dc)
16124 pow(ldc, f) cpowl(ldc, f)
16125 remainder(n, n) remainder(n, n), the function
16126 nextafter(d, f) nextafter(d, f), the function
16127 nexttoward(f, ld) nexttowardf(f, ld)
16128 copysign(n, ld) copysignl(n, ld)
16129 ceil(fc) undefined behavior
16130 rint(dc) undefined behavior
16131 fmax(ldc, ld) undefined behavior
16132 carg(n) carg(n), the function
16133 cproj(f) cprojf(f)
16134 creal(d) creal(d), the function
16135 cimag(ld) cimagl(ld)
16136 fabs(fc) cabsf(fc)
16137 carg(dc) carg(dc), the function
16138 cproj(ldc) cprojl(ldc)</pre>
16141 <p><small><a name="note272" href="#note272">272)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
16142 make available the corresponding ordinary function.
16143 </small>
16144 <p><small><a name="note273" href="#note273">273)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
16145 the behavior is undefined.
16146 </small>
16152 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16153 manipulating time. Many functions deal with a calendar time that represents the current
16154 date (according to the Gregorian calendar) and time. Some functions deal with local
16155 time, which is the calendar time expressed for some specific time zone, and with Daylight
16156 Saving Time, which is a temporary change in the algorithm for determining local time.
16157 The local time zone and Daylight Saving Time are implementation-defined.
16160 <pre>
16161 CLOCKS_PER_SEC</pre>
16162 which expands to an expression with type clock_t (described below) that is the
16163 number per second of the value returned by the clock function.
16166 <pre>
16167 clock_t</pre>
16168 and
16169 <pre>
16170 time_t</pre>
16171 which are arithmetic types capable of representing times; and
16172 <pre>
16173 struct tm</pre>
16174 which holds the components of a calendar time, called the broken-down time.
16176 The range and precision of times representable in clock_t and time_t are
16177 implementation-defined. The tm structure shall contain at least the following members,
16178 in any order. The semantics of the members and their normal ranges are expressed in the
16180 <pre>
16186 int tm_year; // years since 1900
16189 int tm_isdst; // Daylight Saving Time flag</pre>
16193 <!--page 351 -->
16194 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16195 Saving Time is not in effect, and negative if the information is not available.
16198 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16199 </small>
16206 <pre>
16208 clock_t clock(void);</pre>
16211 The clock function determines the processor time used.
16214 The clock function returns the implementation's best approximation to the processor
16215 time used by the program since the beginning of an implementation-defined era related
16216 only to the program invocation. To determine the time in seconds, the value returned by
16217 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16218 the processor time used is not available or its value cannot be represented, the function
16222 <p><small><a name="note275" href="#note275">275)</a> In order to measure the time spent in a program, the clock function should be called at the start of
16223 the program and its return value subtracted from the value returned by subsequent calls.
16224 </small>
16229 <pre>
16231 double difftime(time_t time1, time_t time0);</pre>
16234 The difftime function computes the difference between two calendar times: time1 -
16235 time0.
16238 The difftime function returns the difference expressed in seconds as a double.
16243 <!--page 352 -->
16248 <pre>
16250 time_t mktime(struct tm *timeptr);</pre>
16253 The mktime function converts the broken-down time, expressed as local time, in the
16254 structure pointed to by timeptr into a calendar time value with the same encoding as
16255 that of the values returned by the time function. The original values of the tm_wday
16256 and tm_yday components of the structure are ignored, and the original values of the
16257 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16258 completion, the values of the tm_wday and tm_yday components of the structure are
16259 set appropriately, and the other components are set to represent the specified calendar
16260 time, but with their values forced to the ranges indicated above; the final value of
16261 tm_mday is not set until tm_mon and tm_year are determined.
16264 The mktime function returns the specified calendar time encoded as a value of type
16265 time_t. If the calendar time cannot be represented, the function returns the value
16266 (time_t)(-1).
16269 <pre>
16272 static const char *const wday[] = {
16275 };
16276 struct tm time_str;
16277 /* ... */</pre>
16282 <!--page 353 -->
16283 <pre>
16286 time_str.tm_mday = 4;
16287 time_str.tm_hour = 0;
16288 time_str.tm_min = 0;
16289 time_str.tm_sec = 1;
16290 time_str.tm_isdst = -1;
16292 time_str.tm_wday = 7;
16297 <p><small><a name="note276" href="#note276">276)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
16298 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
16299 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
16300 </small>
16305 <pre>
16307 time_t time(time_t *timer);</pre>
16310 The time function determines the current calendar time. The encoding of the value is
16311 unspecified.
16314 The time function returns the implementation's best approximation to the current
16315 calendar time. The value (time_t)(-1) is returned if the calendar time is not
16316 available. If timer is not a null pointer, the return value is also assigned to the object it
16317 points to.
16321 Except for the strftime function, these functions each return a pointer to one of two
16322 types of static objects: a broken-down time structure or an array of char. Execution of
16323 any of the functions that return a pointer to one of these object types may overwrite the
16324 information in any object of the same type pointed to by the value returned from any
16325 previous call to any of them. The implementation shall behave as if no other library
16326 functions call these functions.
16331 <pre>
16333 char *asctime(const struct tm *timeptr);</pre>
16336 The asctime function converts the broken-down time in the structure pointed to by
16337 timeptr into a string in the form
16338 <!--page 354 -->
16339 <pre>
16341 using the equivalent of the following algorithm.
16342 <pre>
16343 char *asctime(const struct tm *timeptr)
16344 {
16347 };
16351 };
16352 static char result[26];
16353 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
16354 wday_name[timeptr->tm_wday],
16355 mon_name[timeptr->tm_mon],
16359 return result;
16360 }
16361 </pre>
16364 The asctime function returns a pointer to the string.
16369 <pre>
16371 char *ctime(const time_t *timer);</pre>
16374 The ctime function converts the calendar time pointed to by timer to local time in the
16375 form of a string. It is equivalent to
16376 <pre>
16377 asctime(localtime(timer))</pre>
16380 The ctime function returns the pointer returned by the asctime function with that
16381 broken-down time as argument.
16383 <!--page 355 -->
16388 <pre>
16390 struct tm *gmtime(const time_t *timer);</pre>
16393 The gmtime function converts the calendar time pointed to by timer into a broken-
16394 down time, expressed as UTC.
16397 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
16398 specified time cannot be converted to UTC.
16403 <pre>
16405 struct tm *localtime(const time_t *timer);</pre>
16408 The localtime function converts the calendar time pointed to by timer into a
16409 broken-down time, expressed as local time.
16412 The localtime function returns a pointer to the broken-down time, or a null pointer if
16413 the specified time cannot be converted to local time.
16418 <pre>
16420 size_t strftime(char * restrict s,
16421 size_t maxsize,
16422 const char * restrict format,
16423 const struct tm * restrict timeptr);</pre>
16426 The strftime function places characters into the array pointed to by s as controlled by
16427 the string pointed to by format. The format shall be a multibyte character sequence,
16428 beginning and ending in its initial shift state. The format string consists of zero or
16429 more conversion specifiers and ordinary multibyte characters. A conversion specifier
16430 consists of a % character, possibly followed by an E or O modifier character (described
16431 below), followed by a character that determines the behavior of the conversion specifier.
16432 All ordinary multibyte characters (including the terminating null character) are copied
16433 <!--page 356 -->
16434 unchanged into the array. If copying takes place between objects that overlap, the
16435 behavior is undefined. No more than maxsize characters are placed into the array.
16437 Each conversion specifier is replaced by appropriate characters as described in the
16438 following list. The appropriate characters are determined using the LC_TIME category
16439 of the current locale and by the values of zero or more members of the broken-down time
16440 structure pointed to by timeptr, as specified in brackets in the description. If any of
16441 the specified values is outside the normal range, the characters stored are unspecified.
16442 <dl>
16447 <dt> %c <dd> is replaced by the locale's appropriate date and time representation. [all specified
16453 <dt> %e <dd> is replaced by the day of the month as a decimal number (1-31); a single digit is
16454 preceded by a space. [tm_mday]
16456 tm_mday]
16460 [tm_year, tm_wday, tm_yday]
16468 <dt> %p <dd> is replaced by the locale's equivalent of the AM/PM designations associated with a
16469 12-hour clock. [tm_hour]
16475 <!--page 357 -->
16476 tm_sec]
16478 is 1. [tm_wday]
16479 <dt> %U <dd> is replaced by the week number of the year (the first Sunday as the first day of week
16484 [tm_wday]
16487 <dt> %x <dd> is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16488 <dt> %X <dd> is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16490 [tm_year]
16493 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
16494 zone is determinable. [tm_isdst]
16495 <dt> %Z <dd> is replaced by the locale's time zone name or abbreviation, or by no characters if no
16496 time zone is determinable. [tm_isdst]
16498 </dl>
16500 Some conversion specifiers can be modified by the inclusion of an E or O modifier
16501 character to indicate an alternative format or specification. If the alternative format or
16502 specification does not exist for the current locale, the modifier is ignored.
16503 <dl>
16506 representation.
16510 representation.
16512 <dt> %Od <dd>is replaced by the day of the month, using the locale's alternative numeric symbols
16513 (filled as needed with leading zeros, or with leading spaces if there is no alternative
16514 symbol for zero).
16515 <dt> %Oe <dd>is replaced by the day of the month, using the locale's alternative numeric symbols
16516 (filled as needed with leading spaces).
16518 <!--page 358 -->
16519 symbols.
16521 symbols.
16526 representation, where Monday is 1.
16529 symbols.
16531 symbols.
16532 <dt> %OW <dd>is replaced by the week number of the year, using the locale's alternative numeric
16533 symbols.
16534 <dt> %Oy <dd>is replaced by the last 2 digits of the year, using the locale's alternative numeric
16535 symbols.
16536 </dl>
16538 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
16540 which is also the week that includes the first Thursday of the year, and is also the first
16541 week that contains at least four days in the year. If the first Monday of January is the
16546 %V is replaced by 01.
16548 If a conversion specifier is not one of the above, the behavior is undefined.
16550 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
16551 following specifiers are:
16552 <dl>
16563 </dl>
16564 <!--page 359 -->
16567 If the total number of resulting characters including the terminating null character is not
16568 more than maxsize, the strftime function returns the number of characters placed
16569 into the array pointed to by s not including the terminating null character. Otherwise,
16570 zero is returned and the contents of the array are indeterminate.
16571 <!--page 360 -->
16573 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
16577 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
16581 <pre>
16582 mbstate_t</pre>
16583 which is an object type other than an array type that can hold the conversion state
16584 information necessary to convert between sequences of multibyte characters and wide
16585 characters;
16586 <pre>
16587 wint_t</pre>
16588 which is an integer type unchanged by default argument promotions that can hold any
16589 value corresponding to members of the extended character set, as well as at least one
16590 value that does not correspond to any member of the extended character set (see WEOF
16592 <pre>
16593 struct tm</pre>
16594 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
16598 <pre>
16599 WEOF</pre>
16600 which expands to a constant expression of type wint_t whose value does not
16601 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
16602 by several functions in this subclause to indicate end-of-file, that is, no more input from a
16603 stream. It is also used as a wide character value that does not correspond to any member
16604 of the extended character set.
16606 The functions declared are grouped as follows:
16607 <ul>
16608 <li> Functions that perform input and output of wide characters, or multibyte characters,
16609 or both;
16610 <li> Functions that provide wide string numeric conversion;
16611 <li> Functions that perform general wide string manipulation;
16614 <!--page 361 -->
16615 <li> Functions for wide string date and time conversion; and
16616 <li> Functions that provide extended capabilities for conversion between multibyte and
16617 wide character sequences.
16618 </ul>
16620 Unless explicitly stated otherwise, if the execution of a function described in this
16621 subclause causes copying to take place between objects that overlap, the behavior is
16622 undefined.
16625 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16626 </small>
16627 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
16628 </small>
16629 <p><small><a name="note279" href="#note279">279)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
16630 </small>
16632 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
16634 The formatted wide character input/output functions shall behave as if there is a sequence
16635 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
16638 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
16639 </small>
16644 <pre>
16647 int fwprintf(FILE * restrict stream,
16648 const wchar_t * restrict format, ...);</pre>
16651 The fwprintf function writes output to the stream pointed to by stream, under
16652 control of the wide string pointed to by format that specifies how subsequent arguments
16653 are converted for output. If there are insufficient arguments for the format, the behavior
16654 is undefined. If the format is exhausted while arguments remain, the excess arguments
16655 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
16656 when the end of the format string is encountered.
16658 The format is composed of zero or more directives: ordinary wide characters (not %),
16659 which are copied unchanged to the output stream; and conversion specifications, each of
16660 which results in fetching zero or more subsequent arguments, converting them, if
16661 applicable, according to the corresponding conversion specifier, and then writing the
16662 result to the output stream.
16664 Each conversion specification is introduced by the wide character %. After the %, the
16665 following appear in sequence:
16666 <ul>
16667 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16668 specification.
16669 <li> An optional minimum field width. If the converted value has fewer wide characters
16670 than the field width, it is padded with spaces (by default) on the left (or right, if the
16673 <!--page 362 -->
16674 left adjustment flag, described later, has been given) to the field width. The field
16675 width takes the form of an asterisk * (described later) or a nonnegative decimal
16677 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16678 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16679 wide character for a, A, e, E, f, and F conversions, the maximum number of
16680 significant digits for the g and G conversions, or the maximum number of wide
16681 characters to be written for s conversions. The precision takes the form of a period
16682 (.) followed either by an asterisk * (described later) or by an optional decimal
16683 integer; if only the period is specified, the precision is taken as zero. If a precision
16684 appears with any other conversion specifier, the behavior is undefined.
16685 <li> An optional length modifier that specifies the size of the argument.
16686 <li> A conversion specifier wide character that specifies the type of conversion to be
16687 applied.
16688 </ul>
16690 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16691 this case, an int argument supplies the field width or precision. The arguments
16692 specifying field width, or precision, or both, shall appear (in that order) before the
16693 argument (if any) to be converted. A negative field width argument is taken as a - flag
16694 followed by a positive field width. A negative precision argument is taken as if the
16695 precision were omitted.
16697 The flag wide characters and their meanings are:
16698 <dl>
16699 <dt> - <dd> The result of the conversion is left-justified within the field. (It is right-justified if
16700 this flag is not specified.)
16702 begins with a sign only when a negative value is converted if this flag is not
16704 <dt> space<dd> If the first wide character of a signed conversion is not a sign, or if a signed
16705 conversion results in no wide characters, a space is prefixed to the result. If the
16706 space and + flags both appear, the space flag is ignored.
16707 <dt> # <dd> The result is converted to an ''alternative form''. For o conversion, it increases
16708 the precision, if and only if necessary, to force the first digit of the result to be a
16712 <!--page 363 -->
16713 and G conversions, the result of converting a floating-point number always
16714 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16715 decimal-point wide character appears in the result of these conversions only if a
16716 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16717 result. For other conversions, the behavior is undefined.
16719 (following any indication of sign or base) are used to pad to the field width rather
16720 than performing space padding, except when converting an infinity or NaN. If the
16722 conversions, if a precision is specified, the 0 flag is ignored. For other
16723 conversions, the behavior is undefined.
16724 </dl>
16726 The length modifiers and their meanings are:
16727 <dl>
16729 signed char or unsigned char argument (the argument will have
16730 been promoted according to the integer promotions, but its value shall be
16731 converted to signed char or unsigned char before printing); or that
16732 a following n conversion specifier applies to a pointer to a signed char
16733 argument.
16735 short int or unsigned short int argument (the argument will
16736 have been promoted according to the integer promotions, but its value shall
16737 be converted to short int or unsigned short int before printing);
16738 or that a following n conversion specifier applies to a pointer to a short
16739 int argument.
16740 <dt> l (ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16741 long int or unsigned long int argument; that a following n
16742 conversion specifier applies to a pointer to a long int argument; that a
16743 following c conversion specifier applies to a wint_t argument; that a
16744 following s conversion specifier applies to a pointer to a wchar_t
16745 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16746 specifier.
16747 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16748 long long int or unsigned long long int argument; or that a
16749 following n conversion specifier applies to a pointer to a long long int
16750 argument.
16752 <!--page 364 -->
16753 an intmax_t or uintmax_t argument; or that a following n conversion
16754 specifier applies to a pointer to an intmax_t argument.
16756 size_t or the corresponding signed integer type argument; or that a
16757 following n conversion specifier applies to a pointer to a signed integer type
16758 corresponding to size_t argument.
16760 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16761 following n conversion specifier applies to a pointer to a ptrdiff_t
16762 argument.
16764 applies to a long double argument.
16765 </dl>
16766 If a length modifier appears with any conversion specifier other than as specified above,
16767 the behavior is undefined.
16769 The conversion specifiers and their meanings are:
16770 <dl>
16772 precision specifies the minimum number of digits to appear; if the value
16773 being converted can be represented in fewer digits, it is expanded with
16774 leading zeros. The default precision is 1. The result of converting a zero
16775 value with a precision of zero is no wide characters.
16777 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16778 letters abcdef are used for x conversion and the letters ABCDEF for X
16779 conversion. The precision specifies the minimum number of digits to appear;
16780 if the value being converted can be represented in fewer digits, it is expanded
16781 with leading zeros. The default precision is 1. The result of converting a
16782 zero value with a precision of zero is no wide characters.
16784 <!--page 365 -->
16785 decimal notation in the style [-]ddd.ddd, where the number of digits after
16786 the decimal-point wide character is equal to the precision specification. If the
16787 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16788 not specified, no decimal-point wide character appears. If a decimal-point
16789 wide character appears, at least one digit appears before it. The value is
16790 rounded to the appropriate number of digits.
16791 A double argument representing an infinity is converted in one of the styles
16792 [-]inf or [-]infinity -- which style is implementation-defined. A
16793 double argument representing a NaN is converted in one of the styles
16794 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16795 any n-wchar-sequence, is implementation-defined. The F conversion
16796 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16799 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16800 argument is nonzero) before the decimal-point wide character and the number
16801 of digits after it is equal to the precision; if the precision is missing, it is taken
16802 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16803 wide character appears. The value is rounded to the appropriate number of
16804 digits. The E conversion specifier produces a number with E instead of e
16805 introducing the exponent. The exponent always contains at least two digits,
16806 and only as many more digits as necessary to represent the exponent. If the
16807 value is zero, the exponent is zero.
16808 A double argument representing an infinity or NaN is converted in the style
16809 of an f or F conversion specifier.
16811 style f or e (or in style F or E in the case of a G conversion specifier),
16812 depending on the value converted and the precision. Let P equal the
16814 Then, if a conversion with style E would have an exponent of X :
16815 <ul>
16817 P - (X + 1).
16819 </ul>
16820 Finally, unless the # flag is used, any trailing zeros are removed from the
16821 fractional portion of the result and the decimal-point wide character is
16822 removed if there is no fractional portion remaining.
16823 A double argument representing an infinity or NaN is converted in the style
16824 of an f or F conversion specifier.
16826 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16827 nonzero if the argument is a normalized floating-point number and is
16828 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
16829 number of hexadecimal digits after it is equal to the precision; if the precision
16830 is missing and FLT_RADIX is a power of 2, then the precision is sufficient
16831 <!--page 366 -->
16832 for an exact representation of the value; if the precision is missing and
16833 FLT_RADIX is not a power of 2, then the precision is sufficient to
16834 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
16835 omitted; if the precision is zero and the # flag is not specified, no decimal-
16836 point wide character appears. The letters abcdef are used for a conversion
16837 and the letters ABCDEF for A conversion. The A conversion specifier
16838 produces a number with X and P instead of x and p. The exponent always
16839 contains at least one digit, and only as many more digits as necessary to
16840 represent the decimal exponent of 2. If the value is zero, the exponent is
16841 zero.
16842 A double argument representing an infinity or NaN is converted in the style
16843 of an f or F conversion specifier.
16845 character as if by calling btowc and the resulting wide character is written.
16846 If an l length modifier is present, the wint_t argument is converted to
16847 wchar_t and written.
16848 <dt> s <dd> If no l length modifier is present, the argument shall be a pointer to the initial
16849 element of a character array containing a multibyte character sequence
16850 beginning in the initial shift state. Characters from the array are converted as
16851 if by repeated calls to the mbrtowc function, with the conversion state
16852 described by an mbstate_t object initialized to zero before the first
16853 multibyte character is converted, and written up to (but not including) the
16854 terminating null wide character. If the precision is specified, no more than
16855 that many wide characters are written. If the precision is not specified or is
16856 greater than the size of the converted array, the converted array shall contain a
16857 null wide character.
16858 If an l length modifier is present, the argument shall be a pointer to the initial
16859 element of an array of wchar_t type. Wide characters from the array are
16860 written up to (but not including) a terminating null wide character. If the
16861 precision is specified, no more than that many wide characters are written. If
16862 the precision is not specified or is greater than the size of the array, the array
16863 shall contain a null wide character.
16865 converted to a sequence of printing wide characters, in an implementation-
16866 <!--page 367 -->
16867 defined manner.
16869 number of wide characters written to the output stream so far by this call to
16870 fwprintf. No argument is converted, but one is consumed. If the
16871 conversion specification includes any flags, a field width, or a precision, the
16872 behavior is undefined.
16874 conversion specification shall be %%.
16875 </dl>
16877 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
16878 not the correct type for the corresponding conversion specification, the behavior is
16879 undefined.
16881 In no case does a nonexistent or small field width cause truncation of a field; if the result
16882 of a conversion is wider than the field width, the field is expanded to contain the
16883 conversion result.
16885 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16886 to a hexadecimal floating number with the given precision.
16889 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16890 representable in the given precision, the result should be one of the two adjacent numbers
16891 in hexadecimal floating style with the given precision, with the extra stipulation that the
16892 error should have a correct sign for the current rounding direction.
16894 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16895 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
16896 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16897 representable with DECIMAL_DIG digits, then the result should be an exact
16898 representation with trailing zeros. Otherwise, the source value is bounded by two
16899 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16900 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16901 the error should have a correct sign for the current rounding direction.
16904 The fwprintf function returns the number of wide characters transmitted, or a negative
16905 value if an output or encoding error occurred.
16907 <!--page 368 -->
16910 The number of wide characters that can be produced by any single conversion shall be at
16911 least 4095.
16913 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
16914 places:
16915 <pre>
16919 /* ... */
16920 wchar_t *weekday, *month; // pointers to wide strings
16921 int day, hour, min;
16922 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
16923 weekday, month, day, hour, min);
16926 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
16930 <p><small><a name="note281" href="#note281">281)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
16931 </small>
16932 <p><small><a name="note282" href="#note282">282)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
16933 include a minus sign.
16934 </small>
16935 <p><small><a name="note283" href="#note283">283)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
16936 meaning; the # and 0 flag wide characters have no effect.
16937 </small>
16938 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
16939 character so that subsequent digits align to nibble (4-bit) boundaries.
16940 </small>
16941 <p><small><a name="note285" href="#note285">285)</a> The precision p is sufficient to distinguish values of the source type if 16<sup>p-1</sup> > b n where b is
16942 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
16943 might suffice depending on the implementation's scheme for determining the digit to the left of the
16944 decimal-point wide character.
16945 </small>
16946 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16947 </small>
16948 <p><small><a name="note287" href="#note287">287)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
16949 given format specifier. The number of significant digits is determined by the format specifier, and in
16950 the case of fixed-point conversion by the source value as well.
16951 </small>
16956 <pre>
16959 int fwscanf(FILE * restrict stream,
16960 const wchar_t * restrict format, ...);</pre>
16963 The fwscanf function reads input from the stream pointed to by stream, under
16964 control of the wide string pointed to by format that specifies the admissible input
16965 sequences and how they are to be converted for assignment, using subsequent arguments
16966 as pointers to the objects to receive the converted input. If there are insufficient
16967 arguments for the format, the behavior is undefined. If the format is exhausted while
16968 arguments remain, the excess arguments are evaluated (as always) but are otherwise
16969 ignored.
16971 The format is composed of zero or more directives: one or more white-space wide
16972 characters, an ordinary wide character (neither % nor a white-space wide character), or a
16973 conversion specification. Each conversion specification is introduced by the wide
16974 character %. After the %, the following appear in sequence:
16975 <ul>
16976 <li> An optional assignment-suppressing wide character *.
16977 <li> An optional decimal integer greater than zero that specifies the maximum field width
16978 (in wide characters).
16979 <!--page 369 -->
16980 <li> An optional length modifier that specifies the size of the receiving object.
16981 <li> A conversion specifier wide character that specifies the type of conversion to be
16982 applied.
16983 </ul>
16985 The fwscanf function executes each directive of the format in turn. If a directive fails,
16986 as detailed below, the function returns. Failures are described as input failures (due to the
16987 occurrence of an encoding error or the unavailability of input characters), or matching
16988 failures (due to inappropriate input).
16990 A directive composed of white-space wide character(s) is executed by reading input up to
16991 the first non-white-space wide character (which remains unread), or until no more wide
16992 characters can be read.
16994 A directive that is an ordinary wide character is executed by reading the next wide
16995 character of the stream. If that wide character differs from the directive, the directive
16996 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
16997 of-file, an encoding error, or a read error prevents a wide character from being read, the
16998 directive fails.
17000 A directive that is a conversion specification defines a set of matching input sequences, as
17001 described below for each specifier. A conversion specification is executed in the
17002 following steps:
17004 Input white-space wide characters (as specified by the iswspace function) are skipped,
17005 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17007 An input item is read from the stream, unless the specification includes an n specifier. An
17008 input item is defined as the longest sequence of input wide characters which does not
17009 exceed any specified field width and which is, or is a prefix of, a matching input
17010 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17011 length of the input item is zero, the execution of the directive fails; this condition is a
17012 matching failure unless end-of-file, an encoding error, or a read error prevented input
17013 from the stream, in which case it is an input failure.
17015 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17016 count of input wide characters) is converted to a type appropriate to the conversion
17017 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17018 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17019 the result of the conversion is placed in the object pointed to by the first argument
17020 following the format argument that has not already received a conversion result. If this
17023 <!--page 370 -->
17024 object does not have an appropriate type, or if the result of the conversion cannot be
17025 represented in the object, the behavior is undefined.
17027 The length modifiers and their meanings are:
17028 <dl>
17030 to an argument with type pointer to signed char or unsigned char.
17032 to an argument with type pointer to short int or unsigned short
17033 int.
17034 <dt> l (ell) <dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17035 to an argument with type pointer to long int or unsigned long
17036 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17037 an argument with type pointer to double; or that a following c, s, or [
17038 conversion specifier applies to an argument with type pointer to wchar_t.
17039 <dt> ll (ell-ell)<dd> Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17040 to an argument with type pointer to long long int or unsigned
17041 long long int.
17043 to an argument with type pointer to intmax_t or uintmax_t.
17045 to an argument with type pointer to size_t or the corresponding signed
17046 integer type.
17048 to an argument with type pointer to ptrdiff_t or the corresponding
17049 unsigned integer type.
17051 applies to an argument with type pointer to long double.
17052 </dl>
17053 If a length modifier appears with any conversion specifier other than as specified above,
17054 the behavior is undefined.
17056 The conversion specifiers and their meanings are:
17057 <dl>
17059 expected for the subject sequence of the wcstol function with the value 10
17060 for the base argument. The corresponding argument shall be a pointer to
17061 signed integer.
17063 <!--page 371 -->
17064 for the subject sequence of the wcstol function with the value 0 for the
17065 base argument. The corresponding argument shall be a pointer to signed
17066 integer.
17068 expected for the subject sequence of the wcstoul function with the value 8
17069 for the base argument. The corresponding argument shall be a pointer to
17070 unsigned integer.
17072 expected for the subject sequence of the wcstoul function with the value 10
17073 for the base argument. The corresponding argument shall be a pointer to
17074 unsigned integer.
17076 as expected for the subject sequence of the wcstoul function with the value
17077 16 for the base argument. The corresponding argument shall be a pointer to
17078 unsigned integer.
17080 format is the same as expected for the subject sequence of the wcstod
17081 function. The corresponding argument shall be a pointer to floating.
17083 field width (1 if no field width is present in the directive).
17084 If no l length modifier is present, characters from the input field are
17085 converted as if by repeated calls to the wcrtomb function, with the
17086 conversion state described by an mbstate_t object initialized to zero
17087 before the first wide character is converted. The corresponding argument
17088 shall be a pointer to the initial element of a character array large enough to
17089 accept the sequence. No null character is added.
17090 If an l length modifier is present, the corresponding argument shall be a
17091 pointer to the initial element of an array of wchar_t large enough to accept
17092 the sequence. No null wide character is added.
17094 <!--page 372 -->
17095 If no l length modifier is present, characters from the input field are
17096 converted as if by repeated calls to the wcrtomb function, with the
17097 conversion state described by an mbstate_t object initialized to zero
17098 before the first wide character is converted. The corresponding argument
17099 shall be a pointer to the initial element of a character array large enough to
17100 accept the sequence and a terminating null character, which will be added
17101 automatically.
17102 If an l length modifier is present, the corresponding argument shall be a
17103 pointer to the initial element of an array of wchar_t large enough to accept
17104 the sequence and the terminating null wide character, which will be added
17105 automatically.
17107 characters (the scanset).
17108 If no l length modifier is present, characters from the input field are
17109 converted as if by repeated calls to the wcrtomb function, with the
17110 conversion state described by an mbstate_t object initialized to zero
17111 before the first wide character is converted. The corresponding argument
17112 shall be a pointer to the initial element of a character array large enough to
17113 accept the sequence and a terminating null character, which will be added
17114 automatically.
17115 If an l length modifier is present, the corresponding argument shall be a
17116 pointer to the initial element of an array of wchar_t large enough to accept
17117 the sequence and the terminating null wide character, which will be added
17118 automatically.
17119 The conversion specifier includes all subsequent wide characters in the
17120 format string, up to and including the matching right bracket (]). The wide
17121 characters between the brackets (the scanlist) compose the scanset, unless the
17122 wide character after the left bracket is a circumflex (^), in which case the
17123 scanset contains all wide characters that do not appear in the scanlist between
17124 the circumflex and the right bracket. If the conversion specifier begins with
17125 [] or [^], the right bracket wide character is in the scanlist and the next
17126 following right bracket wide character is the matching right bracket that ends
17127 the specification; otherwise the first following right bracket wide character is
17128 the one that ends the specification. If a - wide character is in the scanlist and
17129 is not the first, nor the second where the first wide character is a ^, nor the
17130 last character, the behavior is implementation-defined.
17132 same as the set of sequences that may be produced by the %p conversion of
17133 the fwprintf function. The corresponding argument shall be a pointer to a
17134 pointer to void. The input item is converted to a pointer value in an
17135 implementation-defined manner. If the input item is a value converted earlier
17136 during the same program execution, the pointer that results shall compare
17137 equal to that value; otherwise the behavior of the %p conversion is undefined.
17139 <!--page 373 -->
17140 signed integer into which is to be written the number of wide characters read
17141 from the input stream so far by this call to the fwscanf function. Execution
17142 of a %n directive does not increment the assignment count returned at the
17143 completion of execution of the fwscanf function. No argument is
17144 converted, but one is consumed. If the conversion specification includes an
17145 assignment-suppressing wide character or a field width, the behavior is
17146 undefined.
17148 complete conversion specification shall be %%.
17149 </dl>
17151 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17153 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17154 respectively, a, e, f, g, and x.
17156 Trailing white space (including new-line wide characters) is left unread unless matched
17157 by a directive. The success of literal matches and suppressed assignments is not directly
17158 determinable other than via the %n directive.
17161 The fwscanf function returns the value of the macro EOF if an input failure occurs
17162 before any conversion. Otherwise, the function returns the number of input items
17163 assigned, which can be fewer than provided for, or even zero, in the event of an early
17164 matching failure.
17166 EXAMPLE 1 The call:
17167 <pre>
17170 /* ... */
17171 int n, i; float x; wchar_t name[50];
17173 with the input line:
17174 <pre>
17176 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17177 thompson\0.
17180 EXAMPLE 2 The call:
17181 <pre>
17184 /* ... */
17185 int i; float x; double y;
17187 with input:
17188 <pre>
17190 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
17191 56.0. The next wide character read from the input stream will be a.
17194 <!--page 374 -->
17195 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.24.4.1.1">7.24.4.1.1</a>), the
17196 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17200 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17201 </small>
17202 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17203 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17204 </small>
17205 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17206 </small>
17211 <pre>
17213 int swprintf(wchar_t * restrict s,
17214 size_t n,
17215 const wchar_t * restrict format, ...);</pre>
17218 The swprintf function is equivalent to fwprintf, except that the argument s
17219 specifies an array of wide characters into which the generated output is to be written,
17220 rather than written to a stream. No more than n wide characters are written, including a
17221 terminating null wide character, which is always added (unless n is zero).
17224 The swprintf function returns the number of wide characters written in the array, not
17225 counting the terminating null wide character, or a negative value if an encoding error
17226 occurred or if n or more wide characters were requested to be written.
17231 <pre>
17233 int swscanf(const wchar_t * restrict s,
17234 const wchar_t * restrict format, ...);</pre>
17237 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
17238 wide string from which the input is to be obtained, rather than from a stream. Reaching
17239 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
17240 function.
17243 The swscanf function returns the value of the macro EOF if an input failure occurs
17244 before any conversion. Otherwise, the swscanf function returns the number of input
17245 items assigned, which can be fewer than provided for, or even zero, in the event of an
17246 early matching failure.
17247 <!--page 375 -->
17252 <pre>
17256 int vfwprintf(FILE * restrict stream,
17257 const wchar_t * restrict format,
17258 va_list arg);</pre>
17261 The vfwprintf function is equivalent to fwprintf, with the variable argument list
17262 replaced by arg, which shall have been initialized by the va_start macro (and
17263 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
17267 The vfwprintf function returns the number of wide characters transmitted, or a
17268 negative value if an output or encoding error occurred.
17270 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
17271 routine.
17272 <pre>
17276 void error(char *function_name, wchar_t *format, ...)
17277 {
17278 va_list args;
17279 va_start(args, format);
17280 // print out name of function causing error
17281 fwprintf(stderr, L"ERROR in %s: ", function_name);
17282 // print out remainder of message
17283 vfwprintf(stderr, format, args);
17284 va_end(args);
17285 }</pre>
17290 <!--page 376 -->
17293 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
17294 invoke the va_arg macro, the value of arg after the return is indeterminate.
17295 </small>
17300 <pre>
17304 int vfwscanf(FILE * restrict stream,
17305 const wchar_t * restrict format,
17306 va_list arg);</pre>
17309 The vfwscanf function is equivalent to fwscanf, with the variable argument list
17310 replaced by arg, which shall have been initialized by the va_start macro (and
17311 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
17315 The vfwscanf function returns the value of the macro EOF if an input failure occurs
17316 before any conversion. Otherwise, the vfwscanf function returns the number of input
17317 items assigned, which can be fewer than provided for, or even zero, in the event of an
17318 early matching failure.
17323 <pre>
17326 int vswprintf(wchar_t * restrict s,
17327 size_t n,
17328 const wchar_t * restrict format,
17329 va_list arg);</pre>
17332 The vswprintf function is equivalent to swprintf, with the variable argument list
17333 replaced by arg, which shall have been initialized by the va_start macro (and
17334 possibly subsequent va_arg calls). The vswprintf function does not invoke the
17338 The vswprintf function returns the number of wide characters written in the array, not
17339 counting the terminating null wide character, or a negative value if an encoding error
17340 occurred or if n or more wide characters were requested to be generated.
17341 <!--page 377 -->
17346 <pre>
17349 int vswscanf(const wchar_t * restrict s,
17350 const wchar_t * restrict format,
17351 va_list arg);</pre>
17354 The vswscanf function is equivalent to swscanf, with the variable argument list
17355 replaced by arg, which shall have been initialized by the va_start macro (and
17356 possibly subsequent va_arg calls). The vswscanf function does not invoke the
17360 The vswscanf function returns the value of the macro EOF if an input failure occurs
17361 before any conversion. Otherwise, the vswscanf function returns the number of input
17362 items assigned, which can be fewer than provided for, or even zero, in the event of an
17363 early matching failure.
17368 <pre>
17371 int vwprintf(const wchar_t * restrict format,
17372 va_list arg);</pre>
17375 The vwprintf function is equivalent to wprintf, with the variable argument list
17376 replaced by arg, which shall have been initialized by the va_start macro (and
17377 possibly subsequent va_arg calls). The vwprintf function does not invoke the
17381 The vwprintf function returns the number of wide characters transmitted, or a negative
17382 value if an output or encoding error occurred.
17383 <!--page 378 -->
17388 <pre>
17391 int vwscanf(const wchar_t * restrict format,
17392 va_list arg);</pre>
17395 The vwscanf function is equivalent to wscanf, with the variable argument list
17396 replaced by arg, which shall have been initialized by the va_start macro (and
17397 possibly subsequent va_arg calls). The vwscanf function does not invoke the
17401 The vwscanf function returns the value of the macro EOF if an input failure occurs
17402 before any conversion. Otherwise, the vwscanf function returns the number of input
17403 items assigned, which can be fewer than provided for, or even zero, in the event of an
17404 early matching failure.
17409 <pre>
17411 int wprintf(const wchar_t * restrict format, ...);</pre>
17414 The wprintf function is equivalent to fwprintf with the argument stdout
17415 interposed before the arguments to wprintf.
17418 The wprintf function returns the number of wide characters transmitted, or a negative
17419 value if an output or encoding error occurred.
17424 <pre>
17426 int wscanf(const wchar_t * restrict format, ...);</pre>
17429 The wscanf function is equivalent to fwscanf with the argument stdin interposed
17430 before the arguments to wscanf.
17431 <!--page 379 -->
17434 The wscanf function returns the value of the macro EOF if an input failure occurs
17435 before any conversion. Otherwise, the wscanf function returns the number of input
17436 items assigned, which can be fewer than provided for, or even zero, in the event of an
17437 early matching failure.
17444 <pre>
17447 wint_t fgetwc(FILE *stream);</pre>
17450 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17451 next wide character is present, the fgetwc function obtains that wide character as a
17452 wchar_t converted to a wint_t and advances the associated file position indicator for
17453 the stream (if defined).
17456 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17457 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
17458 the fgetwc function returns the next wide character from the input stream pointed to by
17459 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
17460 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
17461 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
17464 <p><small><a name="note292" href="#note292">292)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17465 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
17466 </small>
17471 <pre>
17474 wchar_t *fgetws(wchar_t * restrict s,
17475 int n, FILE * restrict stream);</pre>
17478 The fgetws function reads at most one less than the number of wide characters
17479 specified by n from the stream pointed to by stream into the array pointed to by s. No
17482 <!--page 380 -->
17483 additional wide characters are read after a new-line wide character (which is retained) or
17484 after end-of-file. A null wide character is written immediately after the last wide
17485 character read into the array.
17488 The fgetws function returns s if successful. If end-of-file is encountered and no
17489 characters have been read into the array, the contents of the array remain unchanged and a
17490 null pointer is returned. If a read or encoding error occurs during the operation, the array
17491 contents are indeterminate and a null pointer is returned.
17496 <pre>
17499 wint_t fputwc(wchar_t c, FILE *stream);</pre>
17502 The fputwc function writes the wide character specified by c to the output stream
17503 pointed to by stream, at the position indicated by the associated file position indicator
17504 for the stream (if defined), and advances the indicator appropriately. If the file cannot
17505 support positioning requests, or if the stream was opened with append mode, the
17506 character is appended to the output stream.
17509 The fputwc function returns the wide character written. If a write error occurs, the
17510 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
17511 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
17516 <pre>
17519 int fputws(const wchar_t * restrict s,
17520 FILE * restrict stream);</pre>
17523 The fputws function writes the wide string pointed to by s to the stream pointed to by
17524 stream. The terminating null wide character is not written.
17527 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
17528 returns a nonnegative value.
17529 <!--page 381 -->
17534 <pre>
17537 int fwide(FILE *stream, int mode);</pre>
17540 The fwide function determines the orientation of the stream pointed to by stream. If
17541 mode is greater than zero, the function first attempts to make the stream wide oriented. If
17542 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
17543 Otherwise, mode is zero and the function does not alter the orientation of the stream.
17546 The fwide function returns a value greater than zero if, after the call, the stream has
17547 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
17548 stream has no orientation.
17551 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
17552 </small>
17557 <pre>
17560 wint_t getwc(FILE *stream);</pre>
17563 The getwc function is equivalent to fgetwc, except that if it is implemented as a
17564 macro, it may evaluate stream more than once, so the argument should never be an
17565 expression with side effects.
17568 The getwc function returns the next wide character from the input stream pointed to by
17569 stream, or WEOF.
17574 <pre>
17576 wint_t getwchar(void);</pre>
17581 <!--page 382 -->
17584 The getwchar function is equivalent to getwc with the argument stdin.
17587 The getwchar function returns the next wide character from the input stream pointed to
17588 by stdin, or WEOF.
17593 <pre>
17596 wint_t putwc(wchar_t c, FILE *stream);</pre>
17599 The putwc function is equivalent to fputwc, except that if it is implemented as a
17600 macro, it may evaluate stream more than once, so that argument should never be an
17601 expression with side effects.
17604 The putwc function returns the wide character written, or WEOF.
17609 <pre>
17611 wint_t putwchar(wchar_t c);</pre>
17614 The putwchar function is equivalent to putwc with the second argument stdout.
17617 The putwchar function returns the character written, or WEOF.
17622 <pre>
17625 wint_t ungetwc(wint_t c, FILE *stream);</pre>
17628 The ungetwc function pushes the wide character specified by c back onto the input
17629 stream pointed to by stream. Pushed-back wide characters will be returned by
17630 subsequent reads on that stream in the reverse order of their pushing. A successful
17631 <!--page 383 -->
17632 intervening call (with the stream pointed to by stream) to a file positioning function
17633 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
17634 stream. The external storage corresponding to the stream is unchanged.
17636 One wide character of pushback is guaranteed, even if the call to the ungetwc function
17637 follows just after a call to a formatted wide character input function fwscanf,
17638 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
17639 on the same stream without an intervening read or file positioning operation on that
17640 stream, the operation may fail.
17642 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
17643 unchanged.
17645 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
17646 The value of the file position indicator for the stream after reading or discarding all
17647 pushed-back wide characters is the same as it was before the wide characters were pushed
17648 back. For a text or binary stream, the value of its file position indicator after a successful
17649 call to the ungetwc function is unspecified until all pushed-back wide characters are
17650 read or discarded.
17653 The ungetwc function returns the wide character pushed back, or WEOF if the operation
17654 fails.
17658 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
17659 manipulation. Various methods are used for determining the lengths of the arrays, but in
17660 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
17661 array. If an array is accessed beyond the end of an object, the behavior is undefined.
17663 Where an argument declared as size_t n determines the length of the array for a
17664 function, n can have the value zero on a call to that function. Unless explicitly stated
17665 otherwise in the description of a particular function in this subclause, pointer arguments
17666 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
17667 function that locates a wide character finds no occurrence, a function that compares two
17668 wide character sequences returns zero, and a function that copies wide characters copies
17669 zero wide characters.
17670 <!--page 384 -->
17672 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
17674 <h5><a name="7.24.4.1.1" href="#7.24.4.1.1">7.24.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
17677 <pre>
17679 double wcstod(const wchar_t * restrict nptr,
17680 wchar_t ** restrict endptr);
17681 float wcstof(const wchar_t * restrict nptr,
17682 wchar_t ** restrict endptr);
17683 long double wcstold(const wchar_t * restrict nptr,
17684 wchar_t ** restrict endptr);</pre>
17687 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
17688 string pointed to by nptr to double, float, and long double representation,
17689 respectively. First, they decompose the input string into three parts: an initial, possibly
17690 empty, sequence of white-space wide characters (as specified by the iswspace
17691 function), a subject sequence resembling a floating-point constant or representing an
17692 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
17693 including the terminating null wide character of the input wide string. Then, they attempt
17694 to convert the subject sequence to a floating-point number, and return the result.
17696 The expected form of the subject sequence is an optional plus or minus sign, then one of
17697 the following:
17698 <ul>
17699 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
17700 character, then an optional exponent part as defined for the corresponding single-byte
17703 decimal-point wide character, then an optional binary exponent part as defined in
17705 <li> INF or INFINITY, or any other wide string equivalent except for case
17706 <li> NAN or NAN(n-wchar-sequence<sub>opt</sub>), or any other wide string equivalent except for
17707 case in the NAN part, where:
17708 <pre>
17709 n-wchar-sequence:
17710 digit
17711 nondigit
17712 n-wchar-sequence digit
17713 n-wchar-sequence nondigit</pre>
17714 </ul>
17715 The subject sequence is defined as the longest initial subsequence of the input wide
17716 string, starting with the first non-white-space wide character, that is of the expected form.
17717 <!--page 385 -->
17718 The subject sequence contains no wide characters if the input wide string is not of the
17719 expected form.
17721 If the subject sequence has the expected form for a floating-point number, the sequence of
17722 wide characters starting with the first digit or the decimal-point wide character
17723 (whichever occurs first) is interpreted as a floating constant according to the rules of
17724 <a href="#6.4.4.2">6.4.4.2</a>, except that the decimal-point wide character is used in place of a period, and that
17725 if neither an exponent part nor a decimal-point wide character appears in a decimal
17726 floating point number, or if a binary exponent part does not appear in a hexadecimal
17727 floating point number, an exponent part of the appropriate type with value zero is
17728 assumed to follow the last digit in the string. If the subject sequence begins with a minus
17729 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
17730 INFINITY is interpreted as an infinity, if representable in the return type, else like a
17731 floating constant that is too large for the range of the return type. A wide character
17732 sequence NAN or NAN(n-wchar-sequence<sub>opt</sub>) is interpreted as a quiet NaN, if supported
17733 in the return type, else like a subject sequence part that does not have the expected form;
17734 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
17735 final wide string is stored in the object pointed to by endptr, provided that endptr is
17736 not a null pointer.
17738 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17739 value resulting from the conversion is correctly rounded.
17741 In other than the "C" locale, additional locale-specific subject sequence forms may be
17742 accepted.
17744 If the subject sequence is empty or does not have the expected form, no conversion is
17745 performed; the value of nptr is stored in the object pointed to by endptr, provided
17746 that endptr is not a null pointer.
17749 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17750 the result is not exactly representable, the result should be one of the two numbers in the
17751 appropriate internal format that are adjacent to the hexadecimal floating source value,
17752 with the extra stipulation that the error should have a correct sign for the current rounding
17753 direction.
17757 <!--page 386 -->
17759 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17760 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17761 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17762 consider the two bounding, adjacent decimal strings L and U, both having
17763 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17764 The result should be one of the (equal or adjacent) values that would be obtained by
17765 correctly rounding L and U according to the current rounding direction, with the extra
17766 stipulation that the error with respect to D should have a correct sign for the current
17770 The functions return the converted value, if any. If no conversion could be performed,
17771 zero is returned. If the correct value is outside the range of representable values, plus or
17772 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
17773 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
17774 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
17775 than the smallest normalized positive number in the return type; whether errno acquires
17776 the value ERANGE is implementation-defined.
17781 <!--page 387 -->
17784 <p><small><a name="note294" href="#note294">294)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
17785 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17786 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17787 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17788 </small>
17789 <p><small><a name="note295" href="#note295">295)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
17790 the NaN's significand.
17791 </small>
17792 <p><small><a name="note296" href="#note296">296)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
17793 to the same internal floating value, but if not will round to adjacent values.
17794 </small>
17796 <h5><a name="7.24.4.1.2" href="#7.24.4.1.2">7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
17799 <pre>
17801 long int wcstol(
17802 const wchar_t * restrict nptr,
17803 wchar_t ** restrict endptr,
17804 int base);
17805 long long int wcstoll(
17806 const wchar_t * restrict nptr,
17807 wchar_t ** restrict endptr,
17808 int base);
17809 unsigned long int wcstoul(
17810 const wchar_t * restrict nptr,
17811 wchar_t ** restrict endptr,
17812 int base);
17813 unsigned long long int wcstoull(
17814 const wchar_t * restrict nptr,
17815 wchar_t ** restrict endptr,
17816 int base);</pre>
17819 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
17820 portion of the wide string pointed to by nptr to long int, long long int,
17821 unsigned long int, and unsigned long long int representation,
17822 respectively. First, they decompose the input string into three parts: an initial, possibly
17823 empty, sequence of white-space wide characters (as specified by the iswspace
17824 function), a subject sequence resembling an integer represented in some radix determined
17825 by the value of base, and a final wide string of one or more unrecognized wide
17826 characters, including the terminating null wide character of the input wide string. Then,
17827 they attempt to convert the subject sequence to an integer, and return the result.
17829 If the value of base is zero, the expected form of the subject sequence is that of an
17830 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
17831 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
17833 is a sequence of letters and digits representing an integer with the radix specified by
17834 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
17836 letters and digits whose ascribed values are less than that of base are permitted. If the
17838 of letters and digits, following the sign if present.
17839 <!--page 388 -->
17841 The subject sequence is defined as the longest initial subsequence of the input wide
17842 string, starting with the first non-white-space wide character, that is of the expected form.
17843 The subject sequence contains no wide characters if the input wide string is empty or
17844 consists entirely of white space, or if the first non-white-space wide character is other
17845 than a sign or a permissible letter or digit.
17847 If the subject sequence has the expected form and the value of base is zero, the sequence
17848 of wide characters starting with the first digit is interpreted as an integer constant
17849 according to the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the
17851 letter its value as given above. If the subject sequence begins with a minus sign, the value
17852 resulting from the conversion is negated (in the return type). A pointer to the final wide
17853 string is stored in the object pointed to by endptr, provided that endptr is not a null
17854 pointer.
17856 In other than the "C" locale, additional locale-specific subject sequence forms may be
17857 accepted.
17859 If the subject sequence is empty or does not have the expected form, no conversion is
17860 performed; the value of nptr is stored in the object pointed to by endptr, provided
17861 that endptr is not a null pointer.
17864 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17865 value, if any. If no conversion could be performed, zero is returned. If the correct value
17866 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17867 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17868 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17875 <pre>
17877 wchar_t *wcscpy(wchar_t * restrict s1,
17878 const wchar_t * restrict s2);</pre>
17881 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17882 null wide character) into the array pointed to by s1.
17885 The wcscpy function returns the value of s1.
17886 <!--page 389 -->
17891 <pre>
17893 wchar_t *wcsncpy(wchar_t * restrict s1,
17894 const wchar_t * restrict s2,
17895 size_t n);</pre>
17898 The wcsncpy function copies not more than n wide characters (those that follow a null
17899 wide character are not copied) from the array pointed to by s2 to the array pointed to by
17902 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
17903 wide characters are appended to the copy in the array pointed to by s1, until n wide
17904 characters in all have been written.
17907 The wcsncpy function returns the value of s1.
17910 <p><small><a name="note297" href="#note297">297)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
17911 result will not be null-terminated.
17912 </small>
17917 <pre>
17919 wchar_t *wmemcpy(wchar_t * restrict s1,
17920 const wchar_t * restrict s2,
17921 size_t n);</pre>
17924 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
17925 object pointed to by s1.
17928 The wmemcpy function returns the value of s1.
17933 <!--page 390 -->
17938 <pre>
17940 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
17941 size_t n);</pre>
17944 The wmemmove function copies n wide characters from the object pointed to by s2 to
17945 the object pointed to by s1. Copying takes place as if the n wide characters from the
17946 object pointed to by s2 are first copied into a temporary array of n wide characters that
17947 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
17948 the temporary array are copied into the object pointed to by s1.
17951 The wmemmove function returns the value of s1.
17958 <pre>
17960 wchar_t *wcscat(wchar_t * restrict s1,
17961 const wchar_t * restrict s2);</pre>
17964 The wcscat function appends a copy of the wide string pointed to by s2 (including the
17965 terminating null wide character) to the end of the wide string pointed to by s1. The initial
17966 wide character of s2 overwrites the null wide character at the end of s1.
17969 The wcscat function returns the value of s1.
17974 <pre>
17976 wchar_t *wcsncat(wchar_t * restrict s1,
17977 const wchar_t * restrict s2,
17978 size_t n);</pre>
17981 The wcsncat function appends not more than n wide characters (a null wide character
17982 and those that follow it are not appended) from the array pointed to by s2 to the end of
17983 <!--page 391 -->
17984 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
17985 wide character at the end of s1. A terminating null wide character is always appended to
17989 The wcsncat function returns the value of s1.
17992 <p><small><a name="note298" href="#note298">298)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
17993 wcslen(s1)+n+1.
17994 </small>
17998 Unless explicitly stated otherwise, the functions described in this subclause order two
17999 wide characters the same way as two integers of the underlying integer type designated
18000 by wchar_t.
18005 <pre>
18007 int wcscmp(const wchar_t *s1, const wchar_t *s2);</pre>
18010 The wcscmp function compares the wide string pointed to by s1 to the wide string
18011 pointed to by s2.
18014 The wcscmp function returns an integer greater than, equal to, or less than zero,
18015 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18016 wide string pointed to by s2.
18021 <pre>
18023 int wcscoll(const wchar_t *s1, const wchar_t *s2);</pre>
18026 The wcscoll function compares the wide string pointed to by s1 to the wide string
18027 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18028 current locale.
18031 The wcscoll function returns an integer greater than, equal to, or less than zero,
18032 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18035 <!--page 392 -->
18036 wide string pointed to by s2 when both are interpreted as appropriate to the current
18037 locale.
18042 <pre>
18044 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18045 size_t n);</pre>
18048 The wcsncmp function compares not more than n wide characters (those that follow a
18049 null wide character are not compared) from the array pointed to by s1 to the array
18050 pointed to by s2.
18053 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18054 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18055 to, or less than the possibly null-terminated array pointed to by s2.
18060 <pre>
18062 size_t wcsxfrm(wchar_t * restrict s1,
18063 const wchar_t * restrict s2,
18064 size_t n);</pre>
18067 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18068 resulting wide string into the array pointed to by s1. The transformation is such that if
18069 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18070 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18071 applied to the same two original wide strings. No more than n wide characters are placed
18072 into the resulting array pointed to by s1, including the terminating null wide character. If
18073 n is zero, s1 is permitted to be a null pointer.
18076 The wcsxfrm function returns the length of the transformed wide string (not including
18077 the terminating null wide character). If the value returned is n or greater, the contents of
18078 the array pointed to by s1 are indeterminate.
18080 EXAMPLE The value of the following expression is the length of the array needed to hold the
18081 transformation of the wide string pointed to by s:
18082 <!--page 393 -->
18083 <pre>
18090 <pre>
18092 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18093 size_t n);</pre>
18096 The wmemcmp function compares the first n wide characters of the object pointed to by
18097 s1 to the first n wide characters of the object pointed to by s2.
18100 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18101 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18102 pointed to by s2.
18109 <pre>
18111 wchar_t *wcschr(const wchar_t *s, wchar_t c);</pre>
18114 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18115 The terminating null wide character is considered to be part of the wide string.
18118 The wcschr function returns a pointer to the located wide character, or a null pointer if
18119 the wide character does not occur in the wide string.
18124 <pre>
18126 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);</pre>
18129 The wcscspn function computes the length of the maximum initial segment of the wide
18130 string pointed to by s1 which consists entirely of wide characters not from the wide
18131 string pointed to by s2.
18132 <!--page 394 -->
18135 The wcscspn function returns the length of the segment.
18140 <pre>
18142 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);</pre>
18145 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18146 any wide character from the wide string pointed to by s2.
18149 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18150 no wide character from s2 occurs in s1.
18155 <pre>
18157 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);</pre>
18160 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18161 s. The terminating null wide character is considered to be part of the wide string.
18164 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18165 not occur in the wide string.
18170 <pre>
18172 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);</pre>
18175 The wcsspn function computes the length of the maximum initial segment of the wide
18176 string pointed to by s1 which consists entirely of wide characters from the wide string
18177 pointed to by s2.
18180 The wcsspn function returns the length of the segment.
18181 <!--page 395 -->
18186 <pre>
18188 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);</pre>
18191 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18192 the sequence of wide characters (excluding the terminating null wide character) in the
18193 wide string pointed to by s2.
18196 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
18197 wide string is not found. If s2 points to a wide string with zero length, the function
18198 returns s1.
18203 <pre>
18205 wchar_t *wcstok(wchar_t * restrict s1,
18206 const wchar_t * restrict s2,
18207 wchar_t ** restrict ptr);</pre>
18210 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
18211 a sequence of tokens, each of which is delimited by a wide character from the wide string
18212 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
18213 which the wcstok function stores information necessary for it to continue scanning the
18214 same wide string.
18216 The first call in a sequence has a non-null first argument and stores an initial value in the
18217 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
18218 the object pointed to by ptr is required to have the value stored by the previous call in
18219 the sequence, which is then updated. The separator wide string pointed to by s2 may be
18220 different from call to call.
18222 The first call in the sequence searches the wide string pointed to by s1 for the first wide
18223 character that is not contained in the current separator wide string pointed to by s2. If no
18224 such wide character is found, then there are no tokens in the wide string pointed to by s1
18225 and the wcstok function returns a null pointer. If such a wide character is found, it is
18226 the start of the first token.
18228 The wcstok function then searches from there for a wide character that is contained in
18229 the current separator wide string. If no such wide character is found, the current token
18230 <!--page 396 -->
18231 extends to the end of the wide string pointed to by s1, and subsequent searches in the
18232 same wide string for a token return a null pointer. If such a wide character is found, it is
18233 overwritten by a null wide character, which terminates the current token.
18235 In all cases, the wcstok function stores sufficient information in the pointer pointed to
18236 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
18237 value for ptr, shall start searching just past the element overwritten by a null wide
18238 character (if any).
18241 The wcstok function returns a pointer to the first wide character of a token, or a null
18242 pointer if there is no token.
18244 EXAMPLE
18245 <pre>
18247 static wchar_t str1[] = L"?a???b,,,#c";
18248 static wchar_t str2[] = L"\t \t";
18249 wchar_t *t, *ptr1, *ptr2;
18260 <pre>
18262 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
18263 size_t n);</pre>
18266 The wmemchr function locates the first occurrence of c in the initial n wide characters of
18267 the object pointed to by s.
18270 The wmemchr function returns a pointer to the located wide character, or a null pointer if
18271 the wide character does not occur in the object.
18272 <!--page 397 -->
18279 <pre>
18281 size_t wcslen(const wchar_t *s);</pre>
18284 The wcslen function computes the length of the wide string pointed to by s.
18287 The wcslen function returns the number of wide characters that precede the terminating
18288 null wide character.
18293 <pre>
18295 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);</pre>
18298 The wmemset function copies the value of c into each of the first n wide characters of
18299 the object pointed to by s.
18302 The wmemset function returns the value of s.
18309 <pre>
18312 size_t wcsftime(wchar_t * restrict s,
18313 size_t maxsize,
18314 const wchar_t * restrict format,
18315 const struct tm * restrict timeptr);</pre>
18318 The wcsftime function is equivalent to the strftime function, except that:
18319 <ul>
18320 <li> The argument s points to the initial element of an array of wide characters into which
18321 the generated output is to be placed.
18322 <!--page 398 -->
18323 <li> The argument maxsize indicates the limiting number of wide characters.
18324 <li> The argument format is a wide string and the conversion specifiers are replaced by
18325 corresponding sequences of wide characters.
18326 <li> The return value indicates the number of wide characters.
18327 </ul>
18330 If the total number of resulting wide characters including the terminating null wide
18331 character is not more than maxsize, the wcsftime function returns the number of
18332 wide characters placed into the array pointed to by s not including the terminating null
18333 wide character. Otherwise, zero is returned and the contents of the array are
18334 indeterminate.
18336 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
18338 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
18339 between multibyte characters and wide characters.
18341 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
18342 <a href="#7.24.6.4">7.24.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
18343 to describe the current conversion state from a particular multibyte character sequence to
18344 a wide character sequence (or the reverse) under the rules of a particular setting for the
18345 LC_CTYPE category of the current locale.
18347 The initial conversion state corresponds, for a conversion in either direction, to the
18348 beginning of a new multibyte character in the initial shift state. A zero-valued
18349 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
18350 valued mbstate_t object can be used to initiate conversion involving any multibyte
18351 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
18352 been altered by any of the functions described in this subclause, and is then used with a
18353 different multibyte character sequence, or in the other conversion direction, or with a
18354 different LC_CTYPE category setting than on earlier function calls, the behavior is
18357 On entry, each function takes the described conversion state (either internal or pointed to
18358 by an argument) as current. The conversion state described by the pointed-to object is
18359 altered as needed to track the shift state, and the position within a multibyte character, for
18360 the associated multibyte character sequence.
18365 <!--page 399 -->
18368 <p><small><a name="note299" href="#note299">299)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
18369 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
18370 character string.
18371 </small>
18373 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
18378 <pre>
18381 wint_t btowc(int c);</pre>
18384 The btowc function determines whether c constitutes a valid single-byte character in the
18385 initial shift state.
18388 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
18389 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
18390 returns the wide character representation of that character.
18395 <pre>
18398 int wctob(wint_t c);</pre>
18401 The wctob function determines whether c corresponds to a member of the extended
18402 character set whose multibyte character representation is a single byte when in the initial
18403 shift state.
18406 The wctob function returns EOF if c does not correspond to a multibyte character with
18407 length one in the initial shift state. Otherwise, it returns the single-byte representation of
18408 that character as an unsigned char converted to an int.
18415 <pre>
18417 int mbsinit(const mbstate_t *ps);</pre>
18420 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
18421 mbstate_t object describes an initial conversion state.
18422 <!--page 400 -->
18425 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
18426 describes an initial conversion state; otherwise, it returns zero.
18428 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
18430 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
18431 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
18432 pointer to mbstate_t that points to an object that can completely describe the current
18433 conversion state of the associated multibyte character sequence. If ps is a null pointer,
18434 each function uses its own internal mbstate_t object instead, which is initialized at
18435 program startup to the initial conversion state. The implementation behaves as if no
18436 library function calls these functions with a null pointer for ps.
18438 Also unlike their corresponding functions, the return value does not represent whether the
18439 encoding is state-dependent.
18444 <pre>
18446 size_t mbrlen(const char * restrict s,
18447 size_t n,
18448 mbstate_t * restrict ps);</pre>
18451 The mbrlen function is equivalent to the call:
18452 <pre>
18454 where internal is the mbstate_t object for the mbrlen function, except that the
18455 expression designated by ps is evaluated only once.
18458 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
18459 or (size_t)(-1).
18461 <!--page 401 -->
18466 <pre>
18468 size_t mbrtowc(wchar_t * restrict pwc,
18469 const char * restrict s,
18470 size_t n,
18471 mbstate_t * restrict ps);</pre>
18474 If s is a null pointer, the mbrtowc function is equivalent to the call:
18475 <pre>
18477 In this case, the values of the parameters pwc and n are ignored.
18479 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
18480 the byte pointed to by s to determine the number of bytes needed to complete the next
18481 multibyte character (including any shift sequences). If the function determines that the
18482 next multibyte character is complete and valid, it determines the value of the
18483 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18484 the object pointed to by pwc. If the corresponding wide character is the null wide
18485 character, the resulting state described is the initial conversion state.
18488 The mbrtowc function returns the first of the following that applies (given the current
18489 conversion state):
18490 <dl>
18492 corresponds to the null wide character (which is the value stored).
18494 character (which is the value stored); the value returned is the number
18495 of bytes that complete the multibyte character.
18497 multibyte character, and all n bytes have been processed (no value is
18500 do not contribute to a complete and valid multibyte character (no
18501 value is stored); the value of the macro EILSEQ is stored in errno,
18502 and the conversion state is unspecified.
18503 </dl>
18504 <!--page 402 -->
18507 <p><small><a name="note300" href="#note300">300)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
18508 sequence of redundant shift sequences (for implementations with state-dependent encodings).
18509 </small>
18514 <pre>
18516 size_t wcrtomb(char * restrict s,
18517 wchar_t wc,
18518 mbstate_t * restrict ps);</pre>
18521 If s is a null pointer, the wcrtomb function is equivalent to the call
18522 <pre>
18524 where buf is an internal buffer.
18526 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
18527 to represent the multibyte character that corresponds to the wide character given by wc
18528 (including any shift sequences), and stores the multibyte character representation in the
18529 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
18530 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
18531 to restore the initial shift state; the resulting state described is the initial conversion state.
18534 The wcrtomb function returns the number of bytes stored in the array object (including
18535 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
18536 the function stores the value of the macro EILSEQ in errno and returns
18537 (size_t)(-1); the conversion state is unspecified.
18539 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
18541 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
18542 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
18543 mbstate_t that points to an object that can completely describe the current conversion
18544 state of the associated multibyte character sequence. If ps is a null pointer, each function
18545 uses its own internal mbstate_t object instead, which is initialized at program startup
18546 to the initial conversion state. The implementation behaves as if no library function calls
18547 these functions with a null pointer for ps.
18549 Also unlike their corresponding functions, the conversion source parameter, src, has a
18550 pointer-to-pointer type. When the function is storing the results of conversions (that is,
18551 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
18552 to reflect the amount of the source processed by that invocation.
18553 <!--page 403 -->
18558 <pre>
18560 size_t mbsrtowcs(wchar_t * restrict dst,
18561 const char ** restrict src,
18562 size_t len,
18563 mbstate_t * restrict ps);</pre>
18566 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
18567 conversion state described by the object pointed to by ps, from the array indirectly
18568 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
18569 pointer, the converted characters are stored into the array pointed to by dst. Conversion
18570 continues up to and including a terminating null character, which is also stored.
18571 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
18572 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
18573 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
18574 place as if by a call to the mbrtowc function.
18576 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18577 pointer (if conversion stopped due to reaching a terminating null character) or the address
18578 just past the last multibyte character converted (if any). If conversion stopped due to
18579 reaching a terminating null character and if dst is not a null pointer, the resulting state
18580 described is the initial conversion state.
18583 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
18584 character, an encoding error occurs: the mbsrtowcs function stores the value of the
18585 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
18586 unspecified. Otherwise, it returns the number of multibyte characters successfully
18587 converted, not including the terminating null character (if any).
18592 <!--page 404 -->
18595 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
18596 </small>
18601 <pre>
18603 size_t wcsrtombs(char * restrict dst,
18604 const wchar_t ** restrict src,
18605 size_t len,
18606 mbstate_t * restrict ps);</pre>
18609 The wcsrtombs function converts a sequence of wide characters from the array
18610 indirectly pointed to by src into a sequence of corresponding multibyte characters that
18611 begins in the conversion state described by the object pointed to by ps. If dst is not a
18612 null pointer, the converted characters are then stored into the array pointed to by dst.
18613 Conversion continues up to and including a terminating null wide character, which is also
18614 stored. Conversion stops earlier in two cases: when a wide character is reached that does
18615 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
18616 next multibyte character would exceed the limit of len total bytes to be stored into the
18617 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
18620 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18621 pointer (if conversion stopped due to reaching a terminating null wide character) or the
18622 address just past the last wide character converted (if any). If conversion stopped due to
18623 reaching a terminating null wide character, the resulting state described is the initial
18624 conversion state.
18627 If conversion stops because a wide character is reached that does not correspond to a
18628 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
18629 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
18630 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
18631 character sequence, not including the terminating null character (if any).
18636 <!--page 405 -->
18639 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
18640 include those necessary to reach the initial shift state immediately before the null byte.
18641 </small>
18643 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
18647 The header <a href="#7.25"><wctype.h></a> declares three data types, one macro, and many functions.<sup><a href="#note303"><b>303)</b></a></sup>
18649 The types declared are
18650 <pre>
18651 wint_t</pre>
18653 <pre>
18654 wctrans_t</pre>
18655 which is a scalar type that can hold values which represent locale-specific character
18656 mappings; and
18657 <pre>
18658 wctype_t</pre>
18659 which is a scalar type that can hold values which represent locale-specific character
18660 classifications.
18664 The functions declared are grouped as follows:
18665 <ul>
18666 <li> Functions that provide wide character classification;
18667 <li> Extensible functions that provide wide character classification;
18668 <li> Functions that provide wide character case mapping;
18669 <li> Extensible functions that provide wide character mapping.
18670 </ul>
18672 For all functions described in this subclause that accept an argument of type wint_t, the
18673 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
18674 this argument has any other value, the behavior is undefined.
18676 The behavior of these functions is affected by the LC_CTYPE category of the current
18677 locale.
18682 <!--page 406 -->
18685 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
18686 </small>
18690 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
18691 characters.
18693 The term printing wide character refers to a member of a locale-specific set of wide
18694 characters, each of which occupies at least one printing position on a display device. The
18695 term control wide character refers to a member of a locale-specific set of wide characters
18696 that are not printing wide characters.
18698 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
18700 The functions in this subclause return nonzero (true) if and only if the value of the
18701 argument wc conforms to that in the description of the function.
18703 Each of the following functions returns true for each wide character that corresponds (as
18704 if by a call to the wctob function) to a single-byte character for which the corresponding
18705 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
18706 iswpunct functions may differ with respect to wide characters other than L' ' that are
18711 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
18712 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
18713 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
18714 && iswspace(wc) is true, but not both.
18715 </small>
18720 <pre>
18722 int iswalnum(wint_t wc);</pre>
18725 The iswalnum function tests for any wide character for which iswalpha or
18726 iswdigit is true.
18731 <pre>
18733 int iswalpha(wint_t wc);</pre>
18736 The iswalpha function tests for any wide character for which iswupper or
18737 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
18739 <!--page 407 -->
18740 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
18744 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
18745 wide characters; all four combinations are possible.
18746 </small>
18751 <pre>
18753 int iswblank(wint_t wc);</pre>
18756 The iswblank function tests for any wide character that is a standard blank wide
18757 character or is one of a locale-specific set of wide characters for which iswspace is true
18758 and that is used to separate words within a line of text. The standard blank wide
18759 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
18760 locale, iswblank returns true only for the standard blank characters.
18765 <pre>
18767 int iswcntrl(wint_t wc);</pre>
18770 The iswcntrl function tests for any control wide character.
18775 <pre>
18777 int iswdigit(wint_t wc);</pre>
18780 The iswdigit function tests for any wide character that corresponds to a decimal-digit
18786 <pre>
18788 int iswgraph(wint_t wc);</pre>
18793 <!--page 408 -->
18796 The iswgraph function tests for any wide character for which iswprint is true and
18800 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
18801 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
18802 characters other than ' '.
18803 </small>
18808 <pre>
18810 int iswlower(wint_t wc);</pre>
18813 The iswlower function tests for any wide character that corresponds to a lowercase
18814 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18815 iswdigit, iswpunct, or iswspace is true.
18820 <pre>
18822 int iswprint(wint_t wc);</pre>
18825 The iswprint function tests for any printing wide character.
18830 <pre>
18832 int iswpunct(wint_t wc);</pre>
18835 The iswpunct function tests for any printing wide character that is one of a locale-
18836 specific set of punctuation wide characters for which neither iswspace nor iswalnum
18837 is true.306)
18842 <pre>
18844 int iswspace(wint_t wc);</pre>
18848 <!--page 409 -->
18851 The iswspace function tests for any wide character that corresponds to a locale-specific
18852 set of white-space wide characters for which none of iswalnum, iswgraph, or
18853 iswpunct is true.
18858 <pre>
18860 int iswupper(wint_t wc);</pre>
18863 The iswupper function tests for any wide character that corresponds to an uppercase
18864 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18865 iswdigit, iswpunct, or iswspace is true.
18870 <pre>
18872 int iswxdigit(wint_t wc);</pre>
18875 The iswxdigit function tests for any wide character that corresponds to a
18878 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
18880 The functions wctype and iswctype provide extensible wide character classification
18881 as well as testing equivalent to that performed by the functions described in the previous
18887 <pre>
18889 int iswctype(wint_t wc, wctype_t desc);</pre>
18892 The iswctype function determines whether the wide character wc has the property
18893 described by desc. The current setting of the LC_CTYPE category shall be the same as
18894 during the call to wctype that returned the value desc.
18896 Each of the following expressions has a truth-value equivalent to the call to the wide
18897 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
18898 <!--page 410 -->
18899 <pre>
18900 iswctype(wc, wctype("alnum")) // iswalnum(wc)
18901 iswctype(wc, wctype("alpha")) // iswalpha(wc)
18902 iswctype(wc, wctype("blank")) // iswblank(wc)
18903 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
18904 iswctype(wc, wctype("digit")) // iswdigit(wc)
18905 iswctype(wc, wctype("graph")) // iswgraph(wc)
18906 iswctype(wc, wctype("lower")) // iswlower(wc)
18907 iswctype(wc, wctype("print")) // iswprint(wc)
18908 iswctype(wc, wctype("punct")) // iswpunct(wc)
18909 iswctype(wc, wctype("space")) // iswspace(wc)
18910 iswctype(wc, wctype("upper")) // iswupper(wc)
18914 The iswctype function returns nonzero (true) if and only if the value of the wide
18915 character wc has the property described by desc.
18921 <pre>
18923 wctype_t wctype(const char *property);</pre>
18926 The wctype function constructs a value with type wctype_t that describes a class of
18927 wide characters identified by the string argument property.
18929 The strings listed in the description of the iswctype function shall be valid in all
18930 locales as property arguments to the wctype function.
18933 If property identifies a valid class of wide characters according to the LC_CTYPE
18934 category of the current locale, the wctype function returns a nonzero value that is valid
18935 as the second argument to the iswctype function; otherwise, it returns zero. *
18936 <!--page 411 -->
18940 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
18942 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
18947 <pre>
18949 wint_t towlower(wint_t wc);</pre>
18952 The towlower function converts an uppercase letter to a corresponding lowercase letter.
18955 If the argument is a wide character for which iswupper is true and there are one or
18956 more corresponding wide characters, as specified by the current locale, for which
18957 iswlower is true, the towlower function returns one of the corresponding wide
18958 characters (always the same one for any given locale); otherwise, the argument is
18959 returned unchanged.
18964 <pre>
18966 wint_t towupper(wint_t wc);</pre>
18969 The towupper function converts a lowercase letter to a corresponding uppercase letter.
18972 If the argument is a wide character for which iswlower is true and there are one or
18973 more corresponding wide characters, as specified by the current locale, for which
18974 iswupper is true, the towupper function returns one of the corresponding wide
18975 characters (always the same one for any given locale); otherwise, the argument is
18976 returned unchanged.
18978 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
18980 The functions wctrans and towctrans provide extensible wide character mapping as
18981 well as case mapping equivalent to that performed by the functions described in the
18983 <!--page 412 -->
18988 <pre>
18990 wint_t towctrans(wint_t wc, wctrans_t desc);</pre>
18993 The towctrans function maps the wide character wc using the mapping described by
18994 desc. The current setting of the LC_CTYPE category shall be the same as during the call
18995 to wctrans that returned the value desc.
18997 Each of the following expressions behaves the same as the call to the wide character case
18998 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
18999 <pre>
19000 towctrans(wc, wctrans("tolower")) // towlower(wc)
19004 The towctrans function returns the mapped value of wc using the mapping described
19005 by desc.
19010 <pre>
19012 wctrans_t wctrans(const char *property);</pre>
19015 The wctrans function constructs a value with type wctrans_t that describes a
19016 mapping between wide characters identified by the string argument property.
19018 The strings listed in the description of the towctrans function shall be valid in all
19019 locales as property arguments to the wctrans function.
19022 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19023 category of the current locale, the wctrans function returns a nonzero value that is valid
19024 as the second argument to the towctrans function; otherwise, it returns zero.
19025 <!--page 413 -->
19029 The following names are grouped under individual headers for convenience. All external
19030 names described below are reserved no matter what headers are included by the program.
19034 The function names
19035 <pre>
19036 cerf cexpm1 clog2
19037 cerfc clog10 clgamma
19038 cexp2 clog1p ctgamma</pre>
19039 and the same names suffixed with f or l may be added to the declarations in the
19044 Function names that begin with either is or to, and a lowercase letter may be added to
19049 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19052 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19054 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19059 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19064 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19069 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19070 an obsolescent feature.
19074 Typedef names beginning with int or uint and ending with _t may be added to the
19075 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19076 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19078 <!--page 414 -->
19082 Lowercase letters may be added to the conversion specifiers and length modifiers in
19083 fprintf and fscanf. Other characters may be used in extensions.
19085 The gets function is obsolescent, and is deprecated.
19087 The use of ungetc on a binary stream where the file position indicator is zero prior to
19088 the call is an obsolescent feature.
19092 Function names that begin with str and a lowercase letter may be added to the
19097 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19100 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19102 Function names that begin with wcs and a lowercase letter may be added to the
19105 Lowercase letters may be added to the conversion specifiers and length modifiers in
19106 fwprintf and fwscanf. Other characters may be used in extensions.
19108 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19111 Function names that begin with is or to and a lowercase letter may be added to the
19113 <!--page 415 -->
19117 <pre>
19118 (informative)
19119 Language syntax summary</pre>
19127 <pre>
19128 keyword
19129 identifier
19130 constant
19131 string-literal
19132 punctuator</pre>
19134 <pre>
19135 header-name
19136 identifier
19137 pp-number
19138 character-constant
19139 string-literal
19140 punctuator
19141 each non-white-space character that cannot be one of the above</pre>
19145 <!--page 416 -->
19146 <pre>
19147 auto enum restrict unsigned
19148 break extern return void
19149 case float short volatile
19150 char for signed while
19151 const goto sizeof _Bool
19152 continue if static _Complex
19153 default inline struct _Imaginary
19154 do int switch
19155 double long typedef
19156 else register union</pre>
19160 <pre>
19161 identifier-nondigit
19162 identifier identifier-nondigit
19163 identifier digit</pre>
19165 <pre>
19166 nondigit
19167 universal-character-name
19168 other implementation-defined characters</pre>
19170 <pre>
19171 _ a b c d e f g h i j k l m
19172 n o p q r s t u v w x y z
19173 A B C D E F G H I J K L M
19174 N O P Q R S T U V W X Y Z</pre>
19176 <pre>
19181 <pre>
19182 \u hex-quad
19183 \U hex-quad hex-quad</pre>
19185 <pre>
19186 hexadecimal-digit hexadecimal-digit
19187 hexadecimal-digit hexadecimal-digit</pre>
19191 <pre>
19192 integer-constant
19193 floating-constant
19194 enumeration-constant
19195 character-constant</pre>
19197 <pre>
19198 decimal-constant integer-suffixopt
19199 octal-constant integer-suffixopt
19200 hexadecimal-constant integer-suffixopt</pre>
19202 <!--page 417 -->
19203 <pre>
19204 nonzero-digit
19205 decimal-constant digit</pre>
19207 <pre>
19208 0
19209 octal-constant octal-digit</pre>
19211 <pre>
19212 hexadecimal-prefix hexadecimal-digit
19213 hexadecimal-constant hexadecimal-digit</pre>
19215 <pre>
19218 <pre>
19221 <pre>
19224 <pre>
19225 0 1 2 3 4 5 6 7 8 9
19226 a b c d e f
19227 A B C D E F</pre>
19229 <pre>
19230 unsigned-suffix long-suffixopt
19231 unsigned-suffix long-long-suffix
19232 long-suffix unsigned-suffixopt
19233 long-long-suffix unsigned-suffixopt</pre>
19235 <pre>
19236 u U</pre>
19238 <pre>
19239 l L</pre>
19241 <pre>
19242 ll LL</pre>
19244 <pre>
19245 decimal-floating-constant
19246 hexadecimal-floating-constant</pre>
19248 <!--page 418 -->
19249 <pre>
19250 fractional-constant exponent-partopt floating-suffixopt
19251 digit-sequence exponent-part floating-suffixopt</pre>
19253 <pre>
19254 hexadecimal-prefix hexadecimal-fractional-constant
19255 binary-exponent-part floating-suffixopt
19256 hexadecimal-prefix hexadecimal-digit-sequence
19257 binary-exponent-part floating-suffixopt</pre>
19259 <pre>
19260 digit-sequenceopt . digit-sequence
19261 digit-sequence .</pre>
19263 <pre>
19264 e signopt digit-sequence
19265 E signopt digit-sequence</pre>
19267 <pre>
19268 + -</pre>
19270 <pre>
19271 digit
19272 digit-sequence digit</pre>
19274 <pre>
19275 hexadecimal-digit-sequenceopt .
19276 hexadecimal-digit-sequence
19277 hexadecimal-digit-sequence .</pre>
19279 <pre>
19280 p signopt digit-sequence
19281 P signopt digit-sequence</pre>
19283 <pre>
19284 hexadecimal-digit
19285 hexadecimal-digit-sequence hexadecimal-digit</pre>
19287 <pre>
19288 f l F L</pre>
19290 <pre>
19291 identifier</pre>
19293 <!--page 419 -->
19294 <pre>
19295 ' c-char-sequence '
19296 L' c-char-sequence '</pre>
19298 <pre>
19299 c-char
19300 c-char-sequence c-char</pre>
19302 <pre>
19303 any member of the source character set except
19304 the single-quote ', backslash \, or new-line character
19305 escape-sequence</pre>
19307 <pre>
19308 simple-escape-sequence
19309 octal-escape-sequence
19310 hexadecimal-escape-sequence
19311 universal-character-name</pre>
19313 <pre>
19314 \' \" \? \\
19315 \a \b \f \n \r \t \v</pre>
19317 <pre>
19318 \ octal-digit
19319 \ octal-digit octal-digit
19320 \ octal-digit octal-digit octal-digit</pre>
19322 <pre>
19323 \x hexadecimal-digit
19324 hexadecimal-escape-sequence hexadecimal-digit</pre>
19328 <pre>
19332 <pre>
19333 s-char
19334 s-char-sequence s-char</pre>
19336 <!--page 420 -->
19337 <pre>
19338 any member of the source character set except
19339 the double-quote ", backslash \, or new-line character
19340 escape-sequence</pre>
19344 <pre>
19345 [ ] ( ) { } . ->
19346 ++ -- & * + - ~ !
19348 ? : ; ...
19350 , # ##
19355 <pre>
19359 <pre>
19360 h-char
19361 h-char-sequence h-char</pre>
19363 <pre>
19364 any member of the source character set except
19367 <pre>
19368 q-char
19369 q-char-sequence q-char</pre>
19371 <pre>
19372 any member of the source character set except
19373 the new-line character and "</pre>
19377 <!--page 421 -->
19378 <pre>
19379 digit
19380 . digit
19381 pp-number digit
19382 pp-number identifier-nondigit
19383 pp-number e sign
19384 pp-number E sign
19385 pp-number p sign
19386 pp-number P sign
19387 pp-number .</pre>
19393 <pre>
19394 identifier
19395 constant
19396 string-literal
19397 ( expression )</pre>
19399 <pre>
19400 primary-expression
19401 postfix-expression [ expression ]
19402 postfix-expression ( argument-expression-listopt )
19403 postfix-expression . identifier
19404 postfix-expression -> identifier
19405 postfix-expression ++
19406 postfix-expression --
19407 ( type-name ) { initializer-list }
19408 ( type-name ) { initializer-list , }</pre>
19410 <pre>
19411 assignment-expression
19412 argument-expression-list , assignment-expression</pre>
19414 <pre>
19415 postfix-expression
19416 ++ unary-expression
19417 -- unary-expression
19418 unary-operator cast-expression
19419 sizeof unary-expression
19420 sizeof ( type-name )</pre>
19422 <pre>
19423 & * + - ~ !</pre>
19425 <pre>
19426 unary-expression
19427 ( type-name ) cast-expression</pre>
19429 <!--page 422 -->
19430 <pre>
19431 cast-expression
19432 multiplicative-expression * cast-expression
19433 multiplicative-expression / cast-expression
19434 multiplicative-expression % cast-expression</pre>
19436 <pre>
19437 multiplicative-expression
19438 additive-expression + multiplicative-expression
19439 additive-expression - multiplicative-expression</pre>
19441 <pre>
19442 additive-expression
19443 shift-expression << additive-expression
19444 shift-expression >> additive-expression</pre>
19446 <pre>
19447 shift-expression
19448 relational-expression < shift-expression
19449 relational-expression > shift-expression
19450 relational-expression <= shift-expression
19451 relational-expression >= shift-expression</pre>
19453 <pre>
19454 relational-expression
19455 equality-expression == relational-expression
19456 equality-expression != relational-expression</pre>
19458 <pre>
19459 equality-expression
19460 AND-expression & equality-expression</pre>
19462 <pre>
19463 AND-expression
19464 exclusive-OR-expression ^ AND-expression</pre>
19466 <pre>
19467 exclusive-OR-expression
19468 inclusive-OR-expression | exclusive-OR-expression</pre>
19470 <pre>
19471 inclusive-OR-expression
19472 logical-AND-expression && inclusive-OR-expression</pre>
19474 <pre>
19475 logical-AND-expression
19476 logical-OR-expression || logical-AND-expression</pre>
19478 <!--page 423 -->
19479 <pre>
19480 logical-OR-expression
19481 logical-OR-expression ? expression : conditional-expression</pre>
19483 <pre>
19484 conditional-expression
19485 unary-expression assignment-operator assignment-expression</pre>
19487 <pre>
19488 = *= /= %= += -= <<= >>= &= ^= |=</pre>
19490 <pre>
19491 assignment-expression
19492 expression , assignment-expression</pre>
19494 <pre>
19495 conditional-expression</pre>
19499 <pre>
19500 declaration-specifiers init-declarator-listopt ;</pre>
19502 <pre>
19503 storage-class-specifier declaration-specifiersopt
19504 type-specifier declaration-specifiersopt
19505 type-qualifier declaration-specifiersopt
19506 function-specifier declaration-specifiersopt</pre>
19508 <pre>
19509 init-declarator
19510 init-declarator-list , init-declarator</pre>
19512 <pre>
19513 declarator
19514 declarator = initializer</pre>
19516 <!--page 424 -->
19517 <pre>
19518 typedef
19519 extern
19520 static
19521 auto
19522 register</pre>
19524 <pre>
19525 void
19526 char
19527 short
19528 int
19529 long
19530 float
19531 double
19532 signed
19533 unsigned
19534 _Bool
19535 _Complex
19536 struct-or-union-specifier *
19537 enum-specifier
19538 typedef-name</pre>
19540 <pre>
19541 struct-or-union identifieropt { struct-declaration-list }
19542 struct-or-union identifier</pre>
19544 <pre>
19545 struct
19546 union</pre>
19548 <pre>
19549 struct-declaration
19550 struct-declaration-list struct-declaration</pre>
19552 <pre>
19553 specifier-qualifier-list struct-declarator-list ;</pre>
19555 <pre>
19556 type-specifier specifier-qualifier-listopt
19557 type-qualifier specifier-qualifier-listopt</pre>
19559 <pre>
19560 struct-declarator
19561 struct-declarator-list , struct-declarator</pre>
19563 <!--page 425 -->
19564 <pre>
19565 declarator
19566 declaratoropt : constant-expression</pre>
19568 <pre>
19569 enum identifieropt { enumerator-list }
19570 enum identifieropt { enumerator-list , }
19571 enum identifier</pre>
19573 <pre>
19574 enumerator
19575 enumerator-list , enumerator</pre>
19577 <pre>
19578 enumeration-constant
19579 enumeration-constant = constant-expression</pre>
19581 <pre>
19582 const
19583 restrict
19584 volatile</pre>
19586 <pre>
19587 inline</pre>
19589 <pre>
19590 pointeropt direct-declarator</pre>
19592 <pre>
19593 identifier
19594 ( declarator )
19595 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
19596 direct-declarator [ static type-qualifier-listopt assignment-expression ]
19597 direct-declarator [ type-qualifier-list static assignment-expression ]
19598 direct-declarator [ type-qualifier-listopt * ]
19599 direct-declarator ( parameter-type-list )
19600 direct-declarator ( identifier-listopt )</pre>
19602 <pre>
19603 * type-qualifier-listopt
19604 * type-qualifier-listopt pointer</pre>
19606 <pre>
19607 type-qualifier
19608 type-qualifier-list type-qualifier</pre>
19610 <!--page 426 -->
19611 <pre>
19612 parameter-list
19613 parameter-list , ...</pre>
19615 <pre>
19616 parameter-declaration
19617 parameter-list , parameter-declaration</pre>
19619 <pre>
19620 declaration-specifiers declarator
19621 declaration-specifiers abstract-declaratoropt</pre>
19623 <pre>
19624 identifier
19625 identifier-list , identifier</pre>
19627 <pre>
19628 specifier-qualifier-list abstract-declaratoropt</pre>
19630 <pre>
19631 pointer
19632 pointeropt direct-abstract-declarator</pre>
19634 <pre>
19635 ( abstract-declarator )
19636 direct-abstract-declaratoropt [ type-qualifier-listopt
19637 assignment-expressionopt ]
19638 direct-abstract-declaratoropt [ static type-qualifier-listopt
19639 assignment-expression ]
19640 direct-abstract-declaratoropt [ type-qualifier-list static
19641 assignment-expression ]
19642 direct-abstract-declaratoropt [ * ]
19643 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
19645 <pre>
19646 identifier</pre>
19648 <pre>
19649 assignment-expression
19650 { initializer-list }
19651 { initializer-list , }</pre>
19653 <pre>
19654 designationopt initializer
19655 initializer-list , designationopt initializer</pre>
19657 <!--page 427 -->
19658 <pre>
19659 designator-list =</pre>
19661 <pre>
19662 designator
19663 designator-list designator</pre>
19665 <pre>
19666 [ constant-expression ]
19667 . identifier</pre>
19671 <pre>
19672 labeled-statement
19673 compound-statement
19674 expression-statement
19675 selection-statement
19676 iteration-statement
19677 jump-statement</pre>
19679 <pre>
19680 identifier : statement
19681 case constant-expression : statement
19682 default : statement</pre>
19684 <pre>
19685 { block-item-listopt }</pre>
19687 <pre>
19688 block-item
19689 block-item-list block-item</pre>
19691 <pre>
19692 declaration
19693 statement</pre>
19695 <pre>
19696 expressionopt ;</pre>
19698 <!--page 428 -->
19699 <pre>
19700 if ( expression ) statement
19701 if ( expression ) statement else statement
19702 switch ( expression ) statement</pre>
19704 <pre>
19705 while ( expression ) statement
19706 do statement while ( expression ) ;
19707 for ( expressionopt ; expressionopt ; expressionopt ) statement
19708 for ( declaration expressionopt ; expressionopt ) statement</pre>
19710 <pre>
19711 goto identifier ;
19712 continue ;
19713 break ;
19714 return expressionopt ;</pre>
19718 <pre>
19719 external-declaration
19720 translation-unit external-declaration</pre>
19722 <pre>
19723 function-definition
19724 declaration</pre>
19726 <pre>
19727 declaration-specifiers declarator declaration-listopt compound-statement</pre>
19729 <pre>
19730 declaration
19731 declaration-list declaration</pre>
19735 <pre>
19736 groupopt</pre>
19738 <pre>
19739 group-part
19740 group group-part</pre>
19742 <pre>
19743 if-section
19744 control-line
19745 text-line
19746 # non-directive</pre>
19748 <!--page 429 -->
19749 <pre>
19750 if-group elif-groupsopt else-groupopt endif-line</pre>
19752 <pre>
19753 # if constant-expression new-line groupopt
19754 # ifdef identifier new-line groupopt
19755 # ifndef identifier new-line groupopt</pre>
19757 <pre>
19758 elif-group
19759 elif-groups elif-group</pre>
19761 <pre>
19762 # elif constant-expression new-line groupopt</pre>
19764 <pre>
19765 # else new-line groupopt</pre>
19767 <pre>
19768 # endif new-line</pre>
19770 <pre>
19771 # include pp-tokens new-line
19772 # define identifier replacement-list new-line
19773 # define identifier lparen identifier-listopt )
19774 replacement-list new-line
19775 # define identifier lparen ... ) replacement-list new-line
19776 # define identifier lparen identifier-list , ... )
19777 replacement-list new-line
19778 # undef identifier new-line
19779 # line pp-tokens new-line
19780 # error pp-tokensopt new-line
19781 # pragma pp-tokensopt new-line
19782 # new-line</pre>
19784 <pre>
19785 pp-tokensopt new-line</pre>
19787 <pre>
19788 pp-tokens new-line</pre>
19790 <pre>
19791 a ( character not immediately preceded by white-space</pre>
19793 <!--page 430 -->
19794 <pre>
19795 pp-tokensopt</pre>
19797 <pre>
19798 preprocessing-token
19799 pp-tokens preprocessing-token</pre>
19801 <!--page 431 -->
19802 <pre>
19803 the new-line character</pre>
19806 <pre>
19807 (informative)
19808 Library summary</pre>
19811 <pre>
19812 NDEBUG
19813 void assert(scalar expression);</pre>
19816 <!--page 432 -->
19817 <!--page 433 -->
19818 <pre>
19819 complex imaginary I
19820 _Complex_I _Imaginary_I
19821 #pragma STDC CX_LIMITED_RANGE on-off-switch
19822 double complex cacos(double complex z);
19823 float complex cacosf(float complex z);
19824 long double complex cacosl(long double complex z);
19825 double complex casin(double complex z);
19826 float complex casinf(float complex z);
19827 long double complex casinl(long double complex z);
19828 double complex catan(double complex z);
19829 float complex catanf(float complex z);
19830 long double complex catanl(long double complex z);
19831 double complex ccos(double complex z);
19832 float complex ccosf(float complex z);
19833 long double complex ccosl(long double complex z);
19834 double complex csin(double complex z);
19835 float complex csinf(float complex z);
19836 long double complex csinl(long double complex z);
19837 double complex ctan(double complex z);
19838 float complex ctanf(float complex z);
19839 long double complex ctanl(long double complex z);
19840 double complex cacosh(double complex z);
19841 float complex cacoshf(float complex z);
19842 long double complex cacoshl(long double complex z);
19843 double complex casinh(double complex z);
19844 float complex casinhf(float complex z);
19845 long double complex casinhl(long double complex z);
19846 double complex catanh(double complex z);
19847 float complex catanhf(float complex z);
19848 long double complex catanhl(long double complex z);
19849 double complex ccosh(double complex z);
19850 float complex ccoshf(float complex z);
19851 long double complex ccoshl(long double complex z);
19852 double complex csinh(double complex z);
19853 float complex csinhf(float complex z);
19854 long double complex csinhl(long double complex z);
19855 double complex ctanh(double complex z);
19856 float complex ctanhf(float complex z);
19857 long double complex ctanhl(long double complex z);
19858 double complex cexp(double complex z);
19859 float complex cexpf(float complex z);
19860 long double complex cexpl(long double complex z);
19861 double complex clog(double complex z);
19862 float complex clogf(float complex z);
19863 long double complex clogl(long double complex z);
19864 double cabs(double complex z);
19865 float cabsf(float complex z);
19866 long double cabsl(long double complex z);
19867 double complex cpow(double complex x, double complex y);
19868 float complex cpowf(float complex x, float complex y);
19869 long double complex cpowl(long double complex x,
19870 long double complex y);
19871 double complex csqrt(double complex z);
19872 float complex csqrtf(float complex z);
19873 long double complex csqrtl(long double complex z);
19874 double carg(double complex z);
19875 float cargf(float complex z);
19876 long double cargl(long double complex z);
19877 double cimag(double complex z);
19878 float cimagf(float complex z);
19879 long double cimagl(long double complex z);
19880 double complex conj(double complex z);
19881 float complex conjf(float complex z);
19882 long double complex conjl(long double complex z);
19883 double complex cproj(double complex z);
19884 float complex cprojf(float complex z);
19885 long double complex cprojl(long double complex z);
19886 double creal(double complex z);
19887 float crealf(float complex z);
19888 long double creall(long double complex z);</pre>
19891 <pre>
19892 int isalnum(int c);
19893 int isalpha(int c);
19894 int isblank(int c);
19895 int iscntrl(int c);
19896 int isdigit(int c);
19897 int isgraph(int c);
19898 int islower(int c);
19899 int isprint(int c);
19900 int ispunct(int c);
19901 int isspace(int c);
19902 int isupper(int c);
19903 int isxdigit(int c);
19904 int tolower(int c);
19905 int toupper(int c);</pre>
19908 <pre>
19909 EDOM EILSEQ ERANGE errno</pre>
19912 <!--page 434 -->
19913 <pre>
19914 fenv_t FE_OVERFLOW FE_TOWARDZERO
19915 fexcept_t FE_UNDERFLOW FE_UPWARD
19916 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
19917 FE_INEXACT FE_DOWNWARD
19918 FE_INVALID FE_TONEAREST
19919 #pragma STDC FENV_ACCESS on-off-switch
19920 int feclearexcept(int excepts);
19921 int fegetexceptflag(fexcept_t *flagp, int excepts);
19922 int feraiseexcept(int excepts);
19923 int fesetexceptflag(const fexcept_t *flagp,
19924 int excepts);
19925 int fetestexcept(int excepts);
19926 int fegetround(void);
19927 int fesetround(int round);
19928 int fegetenv(fenv_t *envp);
19929 int feholdexcept(fenv_t *envp);
19930 int fesetenv(const fenv_t *envp);
19931 int feupdateenv(const fenv_t *envp);</pre>
19934 <pre>
19935 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
19936 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
19937 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
19938 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
19939 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
19940 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
19941 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
19942 FLT_DIG LDBL_MAX_EXP DBL_MIN
19943 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
19944 LDBL_DIG DBL_MAX_10_EXP
19945 FLT_MIN_EXP LDBL_MAX_10_EXP</pre>
19948 <!--page 435 -->
19949 <pre>
19950 imaxdiv_t
19951 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
19952 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
19953 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
19954 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
19955 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
19956 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
19957 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
19958 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
19959 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
19960 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
19961 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
19962 intmax_t imaxabs(intmax_t j);
19963 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
19964 intmax_t strtoimax(const char * restrict nptr,
19965 char ** restrict endptr, int base);
19966 uintmax_t strtoumax(const char * restrict nptr,
19967 char ** restrict endptr, int base);
19968 intmax_t wcstoimax(const wchar_t * restrict nptr,
19969 wchar_t ** restrict endptr, int base);
19970 uintmax_t wcstoumax(const wchar_t * restrict nptr,
19971 wchar_t ** restrict endptr, int base);</pre>
19974 <pre>
19975 and bitor not_eq xor
19976 and_eq compl or xor_eq
19977 bitand not or_eq</pre>
19980 <pre>
19981 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
19982 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
19983 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
19984 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
19985 CHAR_MIN USHRT_MAX LONG_MAX</pre>
19988 <pre>
19989 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
19990 NULL LC_COLLATE LC_MONETARY LC_TIME
19991 char *setlocale(int category, const char *locale);
19992 struct lconv *localeconv(void);</pre>
19995 <!--page 436 -->
19996 <!--page 437 -->
19997 <!--page 438 -->
19998 <!--page 439 -->
19999 <!--page 440 -->
20000 <pre>
20001 float_t FP_INFINITE FP_FAST_FMAL
20002 double_t FP_NAN FP_ILOGB0
20003 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20004 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20005 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20006 INFINITY FP_FAST_FMA math_errhandling
20007 NAN FP_FAST_FMAF
20008 #pragma STDC FP_CONTRACT on-off-switch
20009 int fpclassify(real-floating x);
20010 int isfinite(real-floating x);
20011 int isinf(real-floating x);
20012 int isnan(real-floating x);
20013 int isnormal(real-floating x);
20014 int signbit(real-floating x);
20015 double acos(double x);
20016 float acosf(float x);
20017 long double acosl(long double x);
20018 double asin(double x);
20019 float asinf(float x);
20020 long double asinl(long double x);
20021 double atan(double x);
20022 float atanf(float x);
20023 long double atanl(long double x);
20024 double atan2(double y, double x);
20025 float atan2f(float y, float x);
20026 long double atan2l(long double y, long double x);
20027 double cos(double x);
20028 float cosf(float x);
20029 long double cosl(long double x);
20030 double sin(double x);
20031 float sinf(float x);
20032 long double sinl(long double x);
20033 double tan(double x);
20034 float tanf(float x);
20035 long double tanl(long double x);
20036 double acosh(double x);
20037 float acoshf(float x);
20038 long double acoshl(long double x);
20039 double asinh(double x);
20040 float asinhf(float x);
20041 long double asinhl(long double x);
20042 double atanh(double x);
20043 float atanhf(float x);
20044 long double atanhl(long double x);
20045 double cosh(double x);
20046 float coshf(float x);
20047 long double coshl(long double x);
20048 double sinh(double x);
20049 float sinhf(float x);
20050 long double sinhl(long double x);
20051 double tanh(double x);
20052 float tanhf(float x);
20053 long double tanhl(long double x);
20054 double exp(double x);
20055 float expf(float x);
20056 long double expl(long double x);
20057 double exp2(double x);
20058 float exp2f(float x);
20059 long double exp2l(long double x);
20060 double expm1(double x);
20061 float expm1f(float x);
20062 long double expm1l(long double x);
20063 double frexp(double value, int *exp);
20064 float frexpf(float value, int *exp);
20065 long double frexpl(long double value, int *exp);
20066 int ilogb(double x);
20067 int ilogbf(float x);
20068 int ilogbl(long double x);
20069 double ldexp(double x, int exp);
20070 float ldexpf(float x, int exp);
20071 long double ldexpl(long double x, int exp);
20072 double log(double x);
20073 float logf(float x);
20074 long double logl(long double x);
20075 double log10(double x);
20076 float log10f(float x);
20077 long double log10l(long double x);
20078 double log1p(double x);
20079 float log1pf(float x);
20080 long double log1pl(long double x);
20081 double log2(double x);
20082 float log2f(float x);
20083 long double log2l(long double x);
20084 double logb(double x);
20085 float logbf(float x);
20086 long double logbl(long double x);
20087 double modf(double value, double *iptr);
20088 float modff(float value, float *iptr);
20089 long double modfl(long double value, long double *iptr);
20090 double scalbn(double x, int n);
20091 float scalbnf(float x, int n);
20092 long double scalbnl(long double x, int n);
20093 double scalbln(double x, long int n);
20094 float scalblnf(float x, long int n);
20095 long double scalblnl(long double x, long int n);
20096 double cbrt(double x);
20097 float cbrtf(float x);
20098 long double cbrtl(long double x);
20099 double fabs(double x);
20100 float fabsf(float x);
20101 long double fabsl(long double x);
20102 double hypot(double x, double y);
20103 float hypotf(float x, float y);
20104 long double hypotl(long double x, long double y);
20105 double pow(double x, double y);
20106 float powf(float x, float y);
20107 long double powl(long double x, long double y);
20108 double sqrt(double x);
20109 float sqrtf(float x);
20110 long double sqrtl(long double x);
20111 double erf(double x);
20112 float erff(float x);
20113 long double erfl(long double x);
20114 double erfc(double x);
20115 float erfcf(float x);
20116 long double erfcl(long double x);
20117 double lgamma(double x);
20118 float lgammaf(float x);
20119 long double lgammal(long double x);
20120 double tgamma(double x);
20121 float tgammaf(float x);
20122 long double tgammal(long double x);
20123 double ceil(double x);
20124 float ceilf(float x);
20125 long double ceill(long double x);
20126 double floor(double x);
20127 float floorf(float x);
20128 long double floorl(long double x);
20129 double nearbyint(double x);
20130 float nearbyintf(float x);
20131 long double nearbyintl(long double x);
20132 double rint(double x);
20133 float rintf(float x);
20134 long double rintl(long double x);
20135 long int lrint(double x);
20136 long int lrintf(float x);
20137 long int lrintl(long double x);
20138 long long int llrint(double x);
20139 long long int llrintf(float x);
20140 long long int llrintl(long double x);
20141 double round(double x);
20142 float roundf(float x);
20143 long double roundl(long double x);
20144 long int lround(double x);
20145 long int lroundf(float x);
20146 long int lroundl(long double x);
20147 long long int llround(double x);
20148 long long int llroundf(float x);
20149 long long int llroundl(long double x);
20150 double trunc(double x);
20151 float truncf(float x);
20152 long double truncl(long double x);
20153 double fmod(double x, double y);
20154 float fmodf(float x, float y);
20155 long double fmodl(long double x, long double y);
20156 double remainder(double x, double y);
20157 float remainderf(float x, float y);
20158 long double remainderl(long double x, long double y);
20159 double remquo(double x, double y, int *quo);
20160 float remquof(float x, float y, int *quo);
20161 long double remquol(long double x, long double y,
20162 int *quo);
20163 double copysign(double x, double y);
20164 float copysignf(float x, float y);
20165 long double copysignl(long double x, long double y);
20166 double nan(const char *tagp);
20167 float nanf(const char *tagp);
20168 long double nanl(const char *tagp);
20169 double nextafter(double x, double y);
20170 float nextafterf(float x, float y);
20171 long double nextafterl(long double x, long double y);
20172 double nexttoward(double x, long double y);
20173 float nexttowardf(float x, long double y);
20174 long double nexttowardl(long double x, long double y);
20175 double fdim(double x, double y);
20176 float fdimf(float x, float y);
20177 long double fdiml(long double x, long double y);
20178 double fmax(double x, double y);
20179 float fmaxf(float x, float y);
20180 long double fmaxl(long double x, long double y);
20181 double fmin(double x, double y);
20182 float fminf(float x, float y);
20183 long double fminl(long double x, long double y);
20184 double fma(double x, double y, double z);
20185 float fmaf(float x, float y, float z);
20186 long double fmal(long double x, long double y,
20187 long double z);
20188 int isgreater(real-floating x, real-floating y);
20189 int isgreaterequal(real-floating x, real-floating y);
20190 int isless(real-floating x, real-floating y);
20191 int islessequal(real-floating x, real-floating y);
20192 int islessgreater(real-floating x, real-floating y);
20193 int isunordered(real-floating x, real-floating y);</pre>
20196 <pre>
20197 jmp_buf
20198 int setjmp(jmp_buf env);
20199 void longjmp(jmp_buf env, int val);</pre>
20202 <pre>
20203 sig_atomic_t SIG_IGN SIGILL SIGTERM
20204 SIG_DFL SIGABRT SIGINT
20205 SIG_ERR SIGFPE SIGSEGV
20206 void (*signal(int sig, void (*func)(int)))(int);
20207 int raise(int sig);</pre>
20210 <pre>
20211 va_list
20212 type va_arg(va_list ap, type);
20213 void va_copy(va_list dest, va_list src);
20214 void va_end(va_list ap);
20215 void va_start(va_list ap, parmN);</pre>
20218 <!--page 441 -->
20219 <pre>
20220 bool
20221 true
20222 false
20223 __bool_true_false_are_defined</pre>
20226 <pre>
20227 ptrdiff_t size_t wchar_t NULL
20228 offsetof(type, member-designator)</pre>
20231 <pre>
20232 intN_t INT_LEASTN_MIN PTRDIFF_MAX
20233 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
20234 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
20235 uint_leastN_t INT_FASTN_MIN SIZE_MAX
20236 int_fastN_t INT_FASTN_MAX WCHAR_MIN
20237 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
20238 intptr_t INTPTR_MIN WINT_MIN
20239 uintptr_t INTPTR_MAX WINT_MAX
20240 intmax_t UINTPTR_MAX INTN_C(value)
20241 uintmax_t INTMAX_MIN UINTN_C(value)
20242 INTN_MIN INTMAX_MAX INTMAX_C(value)
20243 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
20244 UINTN_MAX PTRDIFF_MIN</pre>
20247 <!--page 442 -->
20248 <!--page 443 -->
20249 <pre>
20250 size_t _IOLBF FILENAME_MAX TMP_MAX
20251 FILE _IONBF L_tmpnam stderr
20252 fpos_t BUFSIZ SEEK_CUR stdin
20253 NULL EOF SEEK_END stdout
20254 _IOFBF FOPEN_MAX SEEK_SET
20255 int remove(const char *filename);
20256 int rename(const char *old, const char *new);
20257 FILE *tmpfile(void);
20258 char *tmpnam(char *s);
20259 int fclose(FILE *stream);
20260 int fflush(FILE *stream);
20261 FILE *fopen(const char * restrict filename,
20262 const char * restrict mode);
20263 FILE *freopen(const char * restrict filename,
20264 const char * restrict mode,
20265 FILE * restrict stream);
20266 void setbuf(FILE * restrict stream,
20267 char * restrict buf);
20268 int setvbuf(FILE * restrict stream,
20269 char * restrict buf,
20270 int mode, size_t size);
20271 int fprintf(FILE * restrict stream,
20272 const char * restrict format, ...);
20273 int fscanf(FILE * restrict stream,
20274 const char * restrict format, ...);
20275 int printf(const char * restrict format, ...);
20276 int scanf(const char * restrict format, ...);
20277 int snprintf(char * restrict s, size_t n,
20278 const char * restrict format, ...);
20279 int sprintf(char * restrict s,
20280 const char * restrict format, ...);
20281 int sscanf(const char * restrict s,
20282 const char * restrict format, ...);
20283 int vfprintf(FILE * restrict stream,
20284 const char * restrict format, va_list arg);
20285 int vfscanf(FILE * restrict stream,
20286 const char * restrict format, va_list arg);
20287 int vprintf(const char * restrict format, va_list arg);
20288 int vscanf(const char * restrict format, va_list arg);
20289 int vsnprintf(char * restrict s, size_t n,
20290 const char * restrict format, va_list arg);
20291 int vsprintf(char * restrict s,
20292 const char * restrict format, va_list arg);
20293 int vsscanf(const char * restrict s,
20294 const char * restrict format, va_list arg);
20295 int fgetc(FILE *stream);
20296 char *fgets(char * restrict s, int n,
20297 FILE * restrict stream);
20298 int fputc(int c, FILE *stream);
20299 int fputs(const char * restrict s,
20300 FILE * restrict stream);
20301 int getc(FILE *stream);
20302 int getchar(void);
20303 char *gets(char *s);
20304 int putc(int c, FILE *stream);
20305 int putchar(int c);
20306 int puts(const char *s);
20307 int ungetc(int c, FILE *stream);
20308 size_t fread(void * restrict ptr,
20309 size_t size, size_t nmemb,
20310 FILE * restrict stream);
20311 size_t fwrite(const void * restrict ptr,
20312 size_t size, size_t nmemb,
20313 FILE * restrict stream);
20314 int fgetpos(FILE * restrict stream,
20315 fpos_t * restrict pos);
20316 int fseek(FILE *stream, long int offset, int whence);
20317 int fsetpos(FILE *stream, const fpos_t *pos);
20318 long int ftell(FILE *stream);
20319 void rewind(FILE *stream);
20320 void clearerr(FILE *stream);
20321 int feof(FILE *stream);
20322 int ferror(FILE *stream);
20323 void perror(const char *s);</pre>
20326 <!--page 444 -->
20327 <!--page 445 -->
20328 <pre>
20329 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
20330 wchar_t lldiv_t EXIT_SUCCESS
20331 div_t NULL RAND_MAX
20332 double atof(const char *nptr);
20333 int atoi(const char *nptr);
20334 long int atol(const char *nptr);
20335 long long int atoll(const char *nptr);
20336 double strtod(const char * restrict nptr,
20337 char ** restrict endptr);
20338 float strtof(const char * restrict nptr,
20339 char ** restrict endptr);
20340 long double strtold(const char * restrict nptr,
20341 char ** restrict endptr);
20342 long int strtol(const char * restrict nptr,
20343 char ** restrict endptr, int base);
20344 long long int strtoll(const char * restrict nptr,
20345 char ** restrict endptr, int base);
20346 unsigned long int strtoul(
20347 const char * restrict nptr,
20348 char ** restrict endptr, int base);
20349 unsigned long long int strtoull(
20350 const char * restrict nptr,
20351 char ** restrict endptr, int base);
20352 int rand(void);
20353 void srand(unsigned int seed);
20354 void *calloc(size_t nmemb, size_t size);
20355 void free(void *ptr);
20356 void *malloc(size_t size);
20357 void *realloc(void *ptr, size_t size);
20358 void abort(void);
20359 int atexit(void (*func)(void));
20360 void exit(int status);
20361 void _Exit(int status);
20362 char *getenv(const char *name);
20363 int system(const char *string);
20364 void *bsearch(const void *key, const void *base,
20365 size_t nmemb, size_t size,
20366 int (*compar)(const void *, const void *));
20367 void qsort(void *base, size_t nmemb, size_t size,
20368 int (*compar)(const void *, const void *));
20369 int abs(int j);
20370 long int labs(long int j);
20371 long long int llabs(long long int j);
20372 div_t div(int numer, int denom);
20373 ldiv_t ldiv(long int numer, long int denom);
20374 lldiv_t lldiv(long long int numer,
20375 long long int denom);
20376 int mblen(const char *s, size_t n);
20377 int mbtowc(wchar_t * restrict pwc,
20378 const char * restrict s, size_t n);
20379 int wctomb(char *s, wchar_t wchar);
20380 size_t mbstowcs(wchar_t * restrict pwcs,
20381 const char * restrict s, size_t n);
20382 size_t wcstombs(char * restrict s,
20383 const wchar_t * restrict pwcs, size_t n);</pre>
20386 <!--page 446 -->
20387 <pre>
20388 size_t
20389 NULL
20390 void *memcpy(void * restrict s1,
20391 const void * restrict s2, size_t n);
20392 void *memmove(void *s1, const void *s2, size_t n);
20393 char *strcpy(char * restrict s1,
20394 const char * restrict s2);
20395 char *strncpy(char * restrict s1,
20396 const char * restrict s2, size_t n);
20397 char *strcat(char * restrict s1,
20398 const char * restrict s2);
20399 char *strncat(char * restrict s1,
20400 const char * restrict s2, size_t n);
20401 int memcmp(const void *s1, const void *s2, size_t n);
20402 int strcmp(const char *s1, const char *s2);
20403 int strcoll(const char *s1, const char *s2);
20404 int strncmp(const char *s1, const char *s2, size_t n);
20405 size_t strxfrm(char * restrict s1,
20406 const char * restrict s2, size_t n);
20407 void *memchr(const void *s, int c, size_t n);
20408 char *strchr(const char *s, int c);
20409 size_t strcspn(const char *s1, const char *s2);
20410 char *strpbrk(const char *s1, const char *s2);
20411 char *strrchr(const char *s, int c);
20412 size_t strspn(const char *s1, const char *s2);
20413 char *strstr(const char *s1, const char *s2);
20414 char *strtok(char * restrict s1,
20415 const char * restrict s2);
20416 void *memset(void *s, int c, size_t n);
20417 char *strerror(int errnum);
20418 size_t strlen(const char *s);</pre>
20421 <pre>
20422 acos sqrt fmod nextafter
20423 asin fabs frexp nexttoward
20424 atan atan2 hypot remainder
20425 acosh cbrt ilogb remquo
20426 asinh ceil ldexp rint
20427 atanh copysign lgamma round
20428 cos erf llrint scalbn
20429 sin erfc llround scalbln
20430 tan exp2 log10 tgamma
20431 cosh expm1 log1p trunc
20432 sinh fdim log2 carg
20433 tanh floor logb cimag
20434 exp fma lrint conj
20435 log fmax lround cproj
20436 pow fmin nearbyint creal</pre>
20439 <!--page 447 -->
20440 <pre>
20441 NULL size_t time_t
20442 CLOCKS_PER_SEC clock_t struct tm
20443 clock_t clock(void);
20444 double difftime(time_t time1, time_t time0);
20445 time_t mktime(struct tm *timeptr);
20446 time_t time(time_t *timer);
20447 char *asctime(const struct tm *timeptr);
20448 char *ctime(const time_t *timer);
20449 struct tm *gmtime(const time_t *timer);
20450 struct tm *localtime(const time_t *timer);
20451 size_t strftime(char * restrict s,
20452 size_t maxsize,
20453 const char * restrict format,
20454 const struct tm * restrict timeptr);</pre>
20456 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
20457 <!--page 448 -->
20458 <!--page 449 -->
20459 <pre>
20460 wchar_t wint_t WCHAR_MAX
20461 size_t struct tm WCHAR_MIN
20462 mbstate_t NULL WEOF
20463 int fwprintf(FILE * restrict stream,
20464 const wchar_t * restrict format, ...);
20465 int fwscanf(FILE * restrict stream,
20466 const wchar_t * restrict format, ...);
20467 int swprintf(wchar_t * restrict s, size_t n,
20468 const wchar_t * restrict format, ...);
20469 int swscanf(const wchar_t * restrict s,
20470 const wchar_t * restrict format, ...);
20471 int vfwprintf(FILE * restrict stream,
20472 const wchar_t * restrict format, va_list arg);
20473 int vfwscanf(FILE * restrict stream,
20474 const wchar_t * restrict format, va_list arg);
20475 int vswprintf(wchar_t * restrict s, size_t n,
20476 const wchar_t * restrict format, va_list arg);
20477 int vswscanf(const wchar_t * restrict s,
20478 const wchar_t * restrict format, va_list arg);
20479 int vwprintf(const wchar_t * restrict format,
20480 va_list arg);
20481 int vwscanf(const wchar_t * restrict format,
20482 va_list arg);
20483 int wprintf(const wchar_t * restrict format, ...);
20484 int wscanf(const wchar_t * restrict format, ...);
20485 wint_t fgetwc(FILE *stream);
20486 wchar_t *fgetws(wchar_t * restrict s, int n,
20487 FILE * restrict stream);
20488 wint_t fputwc(wchar_t c, FILE *stream);
20489 int fputws(const wchar_t * restrict s,
20490 FILE * restrict stream);
20491 int fwide(FILE *stream, int mode);
20492 wint_t getwc(FILE *stream);
20493 wint_t getwchar(void);
20494 wint_t putwc(wchar_t c, FILE *stream);
20495 wint_t putwchar(wchar_t c);
20496 wint_t ungetwc(wint_t c, FILE *stream);
20497 double wcstod(const wchar_t * restrict nptr,
20498 wchar_t ** restrict endptr);
20499 float wcstof(const wchar_t * restrict nptr,
20500 wchar_t ** restrict endptr);
20501 long double wcstold(const wchar_t * restrict nptr,
20502 wchar_t ** restrict endptr);
20503 long int wcstol(const wchar_t * restrict nptr,
20504 wchar_t ** restrict endptr, int base);
20505 long long int wcstoll(const wchar_t * restrict nptr,
20506 wchar_t ** restrict endptr, int base);
20507 unsigned long int wcstoul(const wchar_t * restrict nptr,
20508 wchar_t ** restrict endptr, int base);
20509 unsigned long long int wcstoull(
20510 const wchar_t * restrict nptr,
20511 wchar_t ** restrict endptr, int base);
20512 wchar_t *wcscpy(wchar_t * restrict s1,
20513 const wchar_t * restrict s2);
20514 wchar_t *wcsncpy(wchar_t * restrict s1,
20515 const wchar_t * restrict s2, size_t n);
20516 wchar_t *wmemcpy(wchar_t * restrict s1,
20517 const wchar_t * restrict s2, size_t n);
20518 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
20519 size_t n);
20520 wchar_t *wcscat(wchar_t * restrict s1,
20521 const wchar_t * restrict s2);
20522 wchar_t *wcsncat(wchar_t * restrict s1,
20523 const wchar_t * restrict s2, size_t n);
20524 int wcscmp(const wchar_t *s1, const wchar_t *s2);
20525 int wcscoll(const wchar_t *s1, const wchar_t *s2);
20526 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
20527 size_t n);
20528 size_t wcsxfrm(wchar_t * restrict s1,
20529 const wchar_t * restrict s2, size_t n);
20530 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
20531 size_t n);
20532 wchar_t *wcschr(const wchar_t *s, wchar_t c);
20533 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
20534 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
20535 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
20536 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
20537 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
20538 wchar_t *wcstok(wchar_t * restrict s1,
20539 const wchar_t * restrict s2,
20540 wchar_t ** restrict ptr);
20541 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
20542 size_t wcslen(const wchar_t *s);
20543 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
20544 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
20545 const wchar_t * restrict format,
20546 const struct tm * restrict timeptr);
20547 wint_t btowc(int c);
20548 int wctob(wint_t c);
20549 int mbsinit(const mbstate_t *ps);
20550 size_t mbrlen(const char * restrict s, size_t n,
20551 mbstate_t * restrict ps);
20552 size_t mbrtowc(wchar_t * restrict pwc,
20553 const char * restrict s, size_t n,
20554 mbstate_t * restrict ps);
20555 size_t wcrtomb(char * restrict s, wchar_t wc,
20556 mbstate_t * restrict ps);
20557 size_t mbsrtowcs(wchar_t * restrict dst,
20558 const char ** restrict src, size_t len,
20559 mbstate_t * restrict ps);
20560 size_t wcsrtombs(char * restrict dst,
20561 const wchar_t ** restrict src, size_t len,
20562 mbstate_t * restrict ps);</pre>
20564 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
20565 <!--page 450 -->
20566 <!--page 451 -->
20567 <pre>
20568 wint_t wctrans_t wctype_t WEOF
20569 int iswalnum(wint_t wc);
20570 int iswalpha(wint_t wc);
20571 int iswblank(wint_t wc);
20572 int iswcntrl(wint_t wc);
20573 int iswdigit(wint_t wc);
20574 int iswgraph(wint_t wc);
20575 int iswlower(wint_t wc);
20576 int iswprint(wint_t wc);
20577 int iswpunct(wint_t wc);
20578 int iswspace(wint_t wc);
20579 int iswupper(wint_t wc);
20580 int iswxdigit(wint_t wc);
20581 int iswctype(wint_t wc, wctype_t desc);
20582 wctype_t wctype(const char *property);
20583 wint_t towlower(wint_t wc);
20584 wint_t towupper(wint_t wc);
20585 wint_t towctrans(wint_t wc, wctrans_t desc);
20586 wctrans_t wctrans(const char *property);</pre>
20589 <p><!--para 1 -->
20590 <pre>
20591 (informative)
20592 Sequence points</pre>
20594 <ul>
20595 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
20596 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
20597 logical OR || (<a href="#6.5.14">6.5.14</a>); conditional ? (<a href="#6.5.15">6.5.15</a>); comma , (<a href="#6.5.17">6.5.17</a>).
20599 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
20600 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
20601 (<a href="#6.8.4">6.8.4</a>); the controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the
20602 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
20605 <li> After the actions associated with each formatted input/output function conversion
20607 <li> Immediately before and immediately after each call to a comparison function, and
20608 also between any call to a comparison function and any movement of the objects
20610 <!--page 452 -->
20611 </ul>
20614 <p><!--para 1 -->
20615 <pre>
20616 (normative)
20617 Universal character names for identifiers</pre>
20618 This clause lists the hexadecimal code values that are valid in universal character names
20619 in identifiers.
20620 <p><!--para 2 -->
20621 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
20622 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
20623 sets.
20624 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
20625 <pre>
20626 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F</pre>
20627 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
20628 <pre>
20629 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
20630 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
20631 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
20632 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC</pre>
20633 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
20634 <pre>
20635 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9</pre>
20636 Armenian: 0531-0556, 0561-0587
20637 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
20638 <pre>
20639 05F0-05F2</pre>
20640 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
20641 <pre>
20642 06D0-06DC, 06E5-06E8, 06EA-06ED</pre>
20643 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
20644 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
20645 <pre>
20646 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
20647 09DC-09DD, 09DF-09E3, 09F0-09F1</pre>
20648 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
20649 <pre>
20650 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
20651 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74</pre>
20652 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
20653 <pre>
20654 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
20655 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0</pre>
20656 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
20657 <!--page 453 -->
20658 <pre>
20659 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
20660 0B5C-0B5D, 0B5F-0B61</pre>
20661 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
20662 <pre>
20663 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
20664 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD</pre>
20665 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
20666 <pre>
20667 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61</pre>
20668 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
20669 <pre>
20670 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
20671 0CE0-0CE1</pre>
20672 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
20673 <pre>
20674 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61</pre>
20675 Thai: 0E01-0E3A, 0E40-0E5B
20676 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
20677 <pre>
20678 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
20679 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
20680 0EC8-0ECD, 0EDC-0EDD</pre>
20681 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
20682 <pre>
20683 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
20684 0FB1-0FB7, 0FB9</pre>
20685 Georgian: 10A0-10C5, 10D0-10F6
20686 Hiragana: 3041-3093, 309B-309C
20687 Katakana: 30A1-30F6, 30FB-30FC
20688 Bopomofo: 3105-312C
20689 CJK Unified Ideographs: 4E00-9FA5
20690 Hangul: AC00-D7A3
20691 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
20692 <pre>
20693 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
20694 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33</pre>
20695 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
20696 <!--page 454 -->
20697 <pre>
20698 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
20699 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
20700 2133-2138, 2160-2182, 3005-3007, 3021-3029</pre>
20703 <p><!--para 1 -->
20704 <pre>
20705 (informative)
20706 <h6> Implementation limits</h6></pre>
20707 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
20708 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
20709 with the same sign. The values shall all be constant expressions suitable for use in #if
20710 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
20711 <p><!--para 2 -->
20712 <pre>
20713 #define CHAR_BIT 8
20714 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
20715 #define CHAR_MIN 0 or SCHAR_MIN
20716 #define INT_MAX +32767
20717 #define INT_MIN -32767
20718 #define LONG_MAX +2147483647
20719 #define LONG_MIN -2147483647
20720 #define LLONG_MAX +9223372036854775807
20721 #define LLONG_MIN -9223372036854775807
20722 #define MB_LEN_MAX 1
20723 #define SCHAR_MAX +127
20724 #define SCHAR_MIN -127
20725 #define SHRT_MAX +32767
20726 #define SHRT_MIN -32767
20727 #define UCHAR_MAX 255
20728 #define USHRT_MAX 65535
20729 #define UINT_MAX 65535
20730 #define ULONG_MAX 4294967295
20731 #define ULLONG_MAX 18446744073709551615</pre>
20732 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
20733 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
20734 directives; all floating values shall be constant expressions. The components are
20736 <p><!--para 3 -->
20737 The values given in the following list shall be replaced by implementation-defined
20738 expressions:
20739 <p><!--para 4 -->
20740 <pre>
20741 #define FLT_EVAL_METHOD
20742 #define FLT_ROUNDS</pre>
20743 The values given in the following list shall be replaced by implementation-defined
20744 constant expressions that are greater or equal in magnitude (absolute value) to those
20745 shown, with the same sign:
20746 <!--page 455 -->
20747 <p><!--para 5 -->
20748 <pre>
20749 #define DBL_DIG 10
20750 #define DBL_MANT_DIG
20751 #define DBL_MAX_10_EXP +37
20752 #define DBL_MAX_EXP
20753 #define DBL_MIN_10_EXP -37
20754 #define DBL_MIN_EXP
20755 #define DECIMAL_DIG 10
20756 #define FLT_DIG 6
20757 #define FLT_MANT_DIG
20758 #define FLT_MAX_10_EXP +37
20759 #define FLT_MAX_EXP
20760 #define FLT_MIN_10_EXP -37
20761 #define FLT_MIN_EXP
20762 #define FLT_RADIX 2
20763 #define LDBL_DIG 10
20764 #define LDBL_MANT_DIG
20765 #define LDBL_MAX_10_EXP +37
20766 #define LDBL_MAX_EXP
20767 #define LDBL_MIN_10_EXP -37
20768 #define LDBL_MIN_EXP</pre>
20769 The values given in the following list shall be replaced by implementation-defined
20770 constant expressions with values that are greater than or equal to those shown:
20771 <p><!--para 6 -->
20772 <pre>
20773 #define DBL_MAX 1E+37
20774 #define FLT_MAX 1E+37
20775 #define LDBL_MAX 1E+37</pre>
20776 The values given in the following list shall be replaced by implementation-defined
20777 constant expressions with (positive) values that are less than or equal to those shown:
20778 <!--page 456 -->
20779 <pre>
20780 #define DBL_EPSILON 1E-9
20781 #define DBL_MIN 1E-37
20782 #define FLT_EPSILON 1E-5
20783 #define FLT_MIN 1E-37
20784 #define LDBL_EPSILON 1E-9
20785 #define LDBL_MIN 1E-37</pre>
20788 <pre>
20789 (normative)
20790 IEC 60559 floating-point arithmetic</pre>
20793 <p><!--para 1 -->
20794 This annex specifies C language support for the IEC 60559 floating-point standard. The
20795 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
20796 microprocessor systems, second edition (IEC 60559:1989), previously designated
20797 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
20798 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
20799 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
20800 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
20801 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
20802 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
20803 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
20804 behavior is adopted by reference, unless stated otherwise.
20807 <p><!--para 1 -->
20808 The C floating types match the IEC 60559 formats as follows:
20809 <ul>
20810 <li> The float type matches the IEC 60559 single format.
20811 <li> The double type matches the IEC 60559 double format.
20812 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
20813 non-IEC 60559 extended format, else the IEC 60559 double format.
20814 </ul>
20815 Any non-IEC 60559 extended format used for the long double type shall have more
20816 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
20817 <h6> Recommended practice</h6>
20818 <p><!--para 2 -->
20819 The long double type should match an IEC 60559 extended format.
20824 <!--page 457 -->
20826 <h6>footnotes</h6>
20827 <p><small><a name="note307" href="#note307">307)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
20828 and quadruple 128-bit IEC 60559 formats.
20829 </small>
20830 <p><small><a name="note308" href="#note308">308)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
20831 all double values.
20832 </small>
20835 <p><!--para 1 -->
20836 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
20837 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
20838 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
20840 <h6>footnotes</h6>
20841 <p><small><a name="note309" href="#note309">309)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
20842 sufficient for closure of the arithmetic.
20843 </small>
20846 <p><!--para 1 -->
20847 C operators and functions provide IEC 60559 required and recommended facilities as
20848 listed below.
20849 <ul>
20850 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
20851 divide operations.
20852 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
20853 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
20854 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
20855 with additional information.
20856 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
20857 floating-point number to an integer value (in the same precision). The nearbyint
20858 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
20859 Appendix to ANSI/IEEE 854.
20860 <li> The conversions for floating types provide the IEC 60559 conversions between
20861 floating-point precisions.
20862 <li> The conversions from integer to floating types provide the IEC 60559 conversions
20863 from integer to floating point.
20864 <li> The conversions from floating to integer types provide IEC 60559-like conversions
20865 but always round toward zero.
20866 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
20867 conversions, which honor the directed rounding mode, from floating point to the
20868 long int and long long int integer formats. The lrint and llrint
20869 functions can be used to implement IEC 60559 conversions from floating to other
20870 integer formats.
20871 <li> The translation time conversion of floating constants and the strtod, strtof,
20872 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
20873 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
20874 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
20875 Appendix to ANSI/IEEE 854.
20877 <!--page 458 -->
20878 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
20879 identifies a need for additional comparison predicates to facilitate writing code that
20880 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
20882 supplement the language operators to address this need. The islessgreater and
20883 isunordered macros provide respectively a quiet version of the <> predicate and
20884 the unordered predicate recommended in the Appendix to IEC 60559.
20885 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
20886 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20887 exception status flags. The fegetexceptflag and fesetexceptflag
20888 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
20889 one time. These functions are used in conjunction with the type fexcept_t and the
20890 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
20892 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
20893 to select among the IEC 60559 directed rounding modes represented by the rounding
20895 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
20896 IEC 60559 directed rounding modes.
20897 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
20898 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
20899 the IEC 60559 status flags and control modes.
20900 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
20901 recommended in the Appendix to IEC 60559.
20902 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
20903 Appendix to IEC 60559.
20904 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
20905 recommended in the Appendix to IEC 60559.
20906 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
20907 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
20908 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
20909 function recommended in the Appendix to IEC 60559 (but with a minor change to
20910 better handle signed zeros).
20911 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
20912 the Appendix to IEC 60559.
20913 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
20914 Appendix to IEC 60559.
20915 <!--page 459 -->
20916 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
20917 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
20918 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
20919 function recommended in the Appendix to IEC 60559 (except that the classification
20921 </ul>
20924 <p><!--para 1 -->
20925 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
20926 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
20927 resulting value is unspecified. Whether conversion of non-integer floating values whose
20928 integral part is within the range of the integer type raises the ''inexact'' floating-point
20931 <h6>footnotes</h6>
20932 <p><small><a name="note310" href="#note310">310)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
20933 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
20934 cases where it matters, library functions can be used to effect such conversions with or without raising
20935 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
20937 </small>
20940 <p><!--para 1 -->
20941 Conversion from the widest supported IEC 60559 format to decimal with
20942 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
20943 <p><!--para 2 -->
20944 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
20945 particular, conversion between any supported IEC 60559 format and decimal with
20946 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
20947 rounding mode), which assures that conversion from the widest supported IEC 60559
20948 format to decimal with DECIMAL_DIG digits and back is the identity function.
20949 <p><!--para 3 -->
20950 Functions such as strtod that convert character sequences to floating types honor the
20951 rounding direction. Hence, if the rounding direction might be upward or downward, the
20952 implementation cannot convert a minus-signed sequence by negating the converted
20953 unsigned sequence.
20958 <!--page 460 -->
20960 <h6>footnotes</h6>
20961 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
20962 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
20963 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
20964 DBL_DIG are 18 and 15, respectively, for these formats.)
20965 </small>
20968 <p><!--para 1 -->
20969 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
20970 rounding directions in a manner consistent with the basic arithmetic operations covered
20971 by IEC 60559.
20972 <h6> Recommended practice</h6>
20973 <p><!--para 2 -->
20974 A contracted expression should raise floating-point exceptions in a manner generally
20975 consistent with the basic arithmetic operations. A contracted expression should deliver
20976 the same value as its uncontracted counterpart, else should be correctly rounded (once).
20979 <p><!--para 1 -->
20980 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
20981 point exception status flags and directed-rounding control modes. It includes also
20982 IEC 60559 dynamic rounding precision and trap enablement modes, if the
20985 <h6>footnotes</h6>
20986 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
20987 </small>
20990 <p><!--para 1 -->
20991 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
20992 status flags, and that rounding control modes can be set explicitly to affect result values of
20993 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
20994 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
20997 <h6>footnotes</h6>
20998 <p><small><a name="note313" href="#note313">313)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
20999 point control modes will be the default ones and the floating-point status flags will not be tested,
21001 </small>
21004 <p><!--para 1 -->
21005 During translation the IEC 60559 default modes are in effect:
21006 <ul>
21007 <li> The rounding direction mode is rounding to nearest.
21008 <li> The rounding precision mode (if supported) is set so that results are not shortened.
21009 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21010 </ul>
21011 <h6> Recommended practice</h6>
21012 <p><!--para 2 -->
21013 The implementation should produce a diagnostic message for each translation-time
21018 <!--page 461 -->
21019 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
21020 proceed with the translation of the program.
21022 <h6>footnotes</h6>
21023 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
21024 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
21025 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
21026 strtod, provide execution-time conversion of numeric strings.
21027 </small>
21030 <p><!--para 1 -->
21031 At program startup the floating-point environment is initialized as prescribed by
21032 IEC 60559:
21033 <ul>
21034 <li> All floating-point exception status flags are cleared.
21035 <li> The rounding direction mode is rounding to nearest.
21036 <li> The dynamic rounding precision mode (if supported) is set so that results are not
21037 shortened.
21038 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21039 </ul>
21042 <p><!--para 1 -->
21043 An arithmetic constant expression of floating type, other than one in an initializer for an
21044 object that has static storage duration, is evaluated (as if) during execution; thus, it is
21045 affected by any operative floating-point control modes and raises floating-point
21046 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
21048 <p><!--para 2 -->
21049 EXAMPLE
21050 <p><!--para 3 -->
21051 <pre>
21053 #pragma STDC FENV_ACCESS ON
21054 void f(void)
21055 {
21056 float w[] = { 0.0/0.0 }; // raises an exception
21057 static float x = 0.0/0.0; // does not raise an exception
21058 float y = 0.0/0.0; // raises an exception
21059 double z = 0.0/0.0; // raises an exception
21060 /* ... */
21061 }</pre>
21062 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
21063 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
21066 <!--page 462 -->
21067 execution time.
21070 <h6>footnotes</h6>
21071 <p><small><a name="note315" href="#note315">315)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
21072 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
21073 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
21074 efficiency of translation-time evaluation through static initialization, such as
21076 <pre>
21077 const static double one_third = 1.0/3.0;</pre>
21078 </small>
21081 <p><!--para 1 -->
21082 All computation for automatic initialization is done (as if) at execution time; thus, it is
21083 affected by any operative modes and raises floating-point exceptions as required by
21084 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
21085 for initialization of objects that have static storage duration is done (as if) at translation
21086 time.
21087 <p><!--para 2 -->
21088 EXAMPLE
21089 <p><!--para 3 -->
21090 <pre>
21092 #pragma STDC FENV_ACCESS ON
21093 void f(void)
21094 {
21095 float u[] = { 1.1e75 }; // raises exceptions
21096 static float v = 1.1e75; // does not raise exceptions
21097 float w = 1.1e75; // raises exceptions
21098 double x = 1.1e75; // may raise exceptions
21099 float y = 1.1e75f; // may raise exceptions
21100 long double z = 1.1e75; // does not raise exceptions
21101 /* ... */
21102 }</pre>
21103 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
21104 done at translation time. The automatic initialization of u and w require an execution-time conversion to
21105 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
21106 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
21107 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note316"><b>316)</b></a></sup> The
21108 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
21109 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
21110 their internal representations occur at translation time in all cases.
21115 <!--page 463 -->
21117 <h6>footnotes</h6>
21118 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
21119 For example, the automatic initialization
21121 <pre>
21122 double_t x = 1.1e75;</pre>
21123 could be done at translation time, regardless of the expression evaluation method.
21124 </small>
21127 <p><!--para 1 -->
21128 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
21129 change floating-point status flags and control modes just as indicated by their
21130 specifications (including conformance to IEC 60559). They do not change flags or modes
21131 (so as to be detectable by the user) in any other cases.
21132 <p><!--para 2 -->
21133 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
21134 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
21135 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
21136 before ''inexact''.
21139 <p><!--para 1 -->
21140 This section identifies code transformations that might subvert IEC 60559-specified
21141 behavior, and others that do not.
21144 <p><!--para 1 -->
21145 Floating-point arithmetic operations and external function calls may entail side effects
21146 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
21147 ''on''. The flags and modes in the floating-point environment may be regarded as global
21148 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
21149 flags.
21150 <p><!--para 2 -->
21151 Concern about side effects may inhibit code motion and removal of seemingly useless
21152 code. For example, in
21153 <pre>
21155 #pragma STDC FENV_ACCESS ON
21156 void f(double x)
21157 {
21158 /* ... */
21159 for (i = 0; i < n; i++) x + 1;
21160 /* ... */
21161 }</pre>
21162 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
21163 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
21164 course these optimizations are valid if the implementation can rule out the nettlesome
21165 cases.)
21166 <p><!--para 3 -->
21167 This specification does not require support for trap handlers that maintain information
21168 about the order or count of floating-point exceptions. Therefore, between function calls,
21169 floating-point exceptions need not be precise: the actual order and number of occurrences
21170 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
21171 the preceding loop could be treated as
21172 <!--page 464 -->
21173 <pre>
21174 if (0 < n) x + 1;</pre>
21177 <p><!--para 1 -->
21178 x / 2 <-> x * 0.5 Although similar transformations involving inexact
21179 <pre>
21180 constants generally do not yield numerically equivalent
21181 expressions, if the constants are exact then such
21182 transformations can be made on IEC 60559 machines
21183 and others that round perfectly.</pre>
21184 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
21185 <pre>
21187 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
21188 <pre>
21189 can be zero, infinite, or NaN.</pre>
21190 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
21191 <pre>
21192 are equivalent (on IEC 60559 machines, among others).</pre>
21193 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
21194 <pre>
21195 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
21197 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
21198 <pre>
21199 x is a NaN or infinite.</pre>
21200 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
21201 <pre>
21202 x is a NaN, infinite, or -0.</pre>
21203 x + 0->x The expressions x + 0 and x are not equivalent if x is
21204 <pre>
21205 -0, because (-0) + (+0) yields +0 (in the default
21206 rounding direction), not -0.</pre>
21207 x - 0->x (+0) - (+0) yields -0 when rounding is downward
21208 <pre>
21209 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
21210 yields -0; so, if the state of the FENV_ACCESS pragma
21211 is ''off'', promising default rounding, then the
21212 implementation can replace x - 0 by x, even if x</pre>
21215 <!--page 465 -->
21216 <pre>
21217 might be zero.</pre>
21218 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
21219 <pre>
21220 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
21221 (unless rounding is downward).</pre>
21223 <h6>footnotes</h6>
21224 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
21225 other transformations that remove arithmetic operators.
21226 </small>
21227 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
21228 Examples include:
21230 <pre>
21231 1/(1/ (+-) (inf)) is (+-) (inf)</pre>
21232 and
21234 <pre>
21235 conj(csqrt(z)) is csqrt(conj(z)),</pre>
21236 for complex z.
21237 </small>
21240 <p><!--para 1 -->
21241 x != x -> false The statement x != x is true if x is a NaN.
21242 x == x -> true The statement x == x is false if x is a NaN.
21243 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
21244 <pre>
21245 equal, these expressions are not equivalent because of
21246 side effects when x or y is a NaN and the state of the
21247 FENV_ACCESS pragma is ''on''. This transformation,
21248 which would be desirable if extra code were required to
21249 cause the ''invalid'' floating-point exception for
21250 unordered cases, could be performed provided the state
21251 of the FENV_ACCESS pragma is ''off''.</pre>
21252 The sense of relational operators shall be maintained. This includes handling unordered
21253 cases as expressed by the source code.
21254 <p><!--para 2 -->
21255 EXAMPLE
21256 <pre>
21257 // calls g and raises ''invalid'' if a and b are unordered
21258 if (a < b)
21259 f();
21260 else
21261 g();</pre>
21262 is not equivalent to
21263 <pre>
21264 // calls f and raises ''invalid'' if a and b are unordered
21265 if (a >= b)
21266 g();
21267 else
21268 f();</pre>
21269 nor to
21270 <pre>
21271 // calls f without raising ''invalid'' if a and b are unordered
21272 if (isgreaterequal(a,b))
21273 g();
21274 else
21275 f();</pre>
21276 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
21277 <!--page 466 -->
21278 <pre>
21279 // calls g without raising ''invalid'' if a and b are unordered
21280 if (isless(a,b))
21281 f();
21282 else
21283 g();</pre>
21284 but is equivalent to
21285 <pre>
21286 if (!(a < b))
21287 g();
21288 else
21289 f();</pre>
21293 <p><!--para 1 -->
21294 The implementation shall honor floating-point exceptions raised by execution-time
21295 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
21296 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
21297 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
21298 further check is required to assure that changing the rounding direction to downward does
21299 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
21300 precision modes shall assure further that the result of the operation raises no floating-
21301 point exception when converted to the semantic type of the operation.
21303 <h6>footnotes</h6>
21304 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
21305 </small>
21308 <p><!--para 1 -->
21309 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
21310 for IEC 60559 implementations.
21311 <p><!--para 2 -->
21312 The Standard C macro HUGE_VAL and its float and long double analogs,
21313 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
21314 infinities.
21315 <p><!--para 3 -->
21316 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
21317 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
21318 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
21319 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
21320 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
21321 <p><!--para 4 -->
21322 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
21323 nonzero value.
21324 <p><!--para 5 -->
21325 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
21326 subsequent subclauses of this annex.
21327 <p><!--para 6 -->
21328 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
21329 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
21332 <!--page 467 -->
21333 whose magnitude is too large.
21334 <p><!--para 7 -->
21335 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
21337 <p><!--para 8 -->
21338 Whether or when library functions raise the ''inexact'' floating-point exception is
21339 unspecified, unless explicitly specified otherwise.
21340 <p><!--para 9 -->
21341 Whether or when library functions raise an undeserved ''underflow'' floating-point
21342 exception is unspecified.<sup><a href="#note321"><b>321)</b></a></sup> Otherwise, as implied by <a href="#F.7.6">F.7.6</a>, the <a href="#7.12"><math.h></a> functions do
21343 not raise spurious floating-point exceptions (detectable by the user), other than the
21344 ''inexact'' floating-point exception.
21345 <p><!--para 10 -->
21346 Whether the functions honor the rounding direction mode is implementation-defined,
21347 unless explicitly specified otherwise.
21348 <p><!--para 11 -->
21349 Functions with a NaN argument return a NaN result and raise no floating-point exception,
21350 except where stated otherwise.
21351 <p><!--para 12 -->
21352 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
21353 For families of functions, the specifications apply to all of the functions even though only
21354 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
21355 occurs in both an argument and the result, the result has the same sign as the argument.
21356 <h6> Recommended practice</h6>
21357 <p><!--para 13 -->
21358 If a function with one or more NaN arguments returns a NaN result, the result should be
21359 the same as one of the NaN arguments (after possible type conversion), except perhaps
21360 for the sign.
21362 <h6>footnotes</h6>
21363 <p><small><a name="note320" href="#note320">320)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
21364 when the floating-point exception is raised.
21365 </small>
21366 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
21367 avoiding them would be too costly.
21368 </small>
21373 <p><!--para 1 -->
21374 <ul>
21375 <li> acos(1) returns +0.
21376 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
21377 | x | > 1.
21382 <!--page 468 -->
21383 </ul>
21386 <p><!--para 1 -->
21387 <ul>
21388 <li> asin((+-)0) returns (+-)0.
21389 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
21390 | x | > 1.
21391 </ul>
21394 <p><!--para 1 -->
21395 <ul>
21396 <li> atan((+-)0) returns (+-)0.
21397 <li> atan((+-)(inf)) returns (+-)pi /2.
21398 </ul>
21401 <p><!--para 1 -->
21402 <ul>
21404 <li> atan2((+-)0, +0) returns (+-)0.
21405 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
21406 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
21407 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
21408 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
21409 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
21410 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
21411 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
21412 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
21413 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
21414 </ul>
21416 <h6>footnotes</h6>
21417 <p><small><a name="note322" href="#note322">322)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
21418 the ''divide-by-zero'' floating-point exception.
21419 </small>
21422 <p><!--para 1 -->
21423 <ul>
21424 <li> cos((+-)0) returns 1.
21425 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21426 </ul>
21429 <p><!--para 1 -->
21430 <ul>
21431 <li> sin((+-)0) returns (+-)0.
21432 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21437 <!--page 469 -->
21438 </ul>
21441 <p><!--para 1 -->
21442 <ul>
21443 <li> tan((+-)0) returns (+-)0.
21444 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21445 </ul>
21450 <p><!--para 1 -->
21451 <ul>
21452 <li> acosh(1) returns +0.
21453 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
21454 <li> acosh(+(inf)) returns +(inf).
21455 </ul>
21458 <p><!--para 1 -->
21459 <ul>
21460 <li> asinh((+-)0) returns (+-)0.
21461 <li> asinh((+-)(inf)) returns (+-)(inf).
21462 </ul>
21465 <p><!--para 1 -->
21466 <ul>
21467 <li> atanh((+-)0) returns (+-)0.
21468 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21469 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
21470 | x | > 1.
21471 </ul>
21474 <p><!--para 1 -->
21475 <ul>
21476 <li> cosh((+-)0) returns 1.
21477 <li> cosh((+-)(inf)) returns +(inf).
21478 </ul>
21481 <p><!--para 1 -->
21482 <ul>
21483 <li> sinh((+-)0) returns (+-)0.
21484 <li> sinh((+-)(inf)) returns (+-)(inf).
21485 </ul>
21488 <p><!--para 1 -->
21489 <ul>
21490 <li> tanh((+-)0) returns (+-)0.
21491 <li> tanh((+-)(inf)) returns (+-)1.
21492 <!--page 470 -->
21493 </ul>
21498 <p><!--para 1 -->
21499 <ul>
21500 <li> exp((+-)0) returns 1.
21501 <li> exp(-(inf)) returns +0.
21502 <li> exp(+(inf)) returns +(inf).
21503 </ul>
21506 <p><!--para 1 -->
21507 <ul>
21508 <li> exp2((+-)0) returns 1.
21509 <li> exp2(-(inf)) returns +0.
21510 <li> exp2(+(inf)) returns +(inf).
21511 </ul>
21514 <p><!--para 1 -->
21515 <ul>
21516 <li> expm1((+-)0) returns (+-)0.
21517 <li> expm1(-(inf)) returns -1.
21518 <li> expm1(+(inf)) returns +(inf).
21519 </ul>
21522 <p><!--para 1 -->
21523 <ul>
21524 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
21525 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
21526 pointed to by exp.
21527 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
21528 (and returns a NaN).
21529 </ul>
21530 <p><!--para 2 -->
21531 frexp raises no floating-point exceptions.
21532 <p><!--para 3 -->
21533 On a binary system, the body of the frexp function might be
21534 <pre>
21535 {
21536 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
21537 return scalbn(value, -(*exp));
21538 }</pre>
21541 <p><!--para 1 -->
21542 If the correct result is outside the range of the return type, the numeric result is
21543 unspecified and the ''invalid'' floating-point exception is raised.
21544 <!--page 471 -->
21547 <p><!--para 1 -->
21548 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
21551 <p><!--para 1 -->
21552 <ul>
21553 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21554 <li> log(1) returns +0.
21555 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21556 <li> log(+(inf)) returns +(inf).
21557 </ul>
21560 <p><!--para 1 -->
21561 <ul>
21562 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21563 <li> log10(1) returns +0.
21564 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21565 <li> log10(+(inf)) returns +(inf).
21566 </ul>
21569 <p><!--para 1 -->
21570 <ul>
21571 <li> log1p((+-)0) returns (+-)0.
21572 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21573 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
21574 x < -1.
21575 <li> log1p(+(inf)) returns +(inf).
21576 </ul>
21579 <p><!--para 1 -->
21580 <ul>
21581 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21582 <li> log2(1) returns +0.
21583 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21584 <li> log2(+(inf)) returns +(inf).
21585 </ul>
21588 <p><!--para 1 -->
21589 <ul>
21590 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21591 <li> logb((+-)(inf)) returns +(inf).
21592 <!--page 472 -->
21593 </ul>
21596 <p><!--para 1 -->
21597 <ul>
21598 <li> modf((+-)x, iptr) returns a result with the same sign as x.
21599 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
21600 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
21601 NaN).
21602 </ul>
21603 <p><!--para 2 -->
21604 modf behaves as though implemented by
21605 <pre>
21608 #pragma STDC FENV_ACCESS ON
21609 double modf(double value, double *iptr)
21610 {
21611 int save_round = fegetround();
21612 fesetround(FE_TOWARDZERO);
21613 *iptr = nearbyint(value);
21614 fesetround(save_round);
21615 return copysign(
21616 isinf(value) ? 0.0 :
21617 value - (*iptr), value);
21618 }</pre>
21621 <p><!--para 1 -->
21622 <ul>
21623 <li> scalbn((+-)0, n) returns (+-)0.
21624 <li> scalbn(x, 0) returns x.
21625 <li> scalbn((+-)(inf), n) returns (+-)(inf).
21626 </ul>
21631 <p><!--para 1 -->
21632 <ul>
21633 <li> cbrt((+-)0) returns (+-)0.
21634 <li> cbrt((+-)(inf)) returns (+-)(inf).
21635 </ul>
21638 <p><!--para 1 -->
21639 <ul>
21640 <li> fabs((+-)0) returns +0.
21641 <li> fabs((+-)(inf)) returns +(inf).
21642 <!--page 473 -->
21643 </ul>
21646 <p><!--para 1 -->
21647 <ul>
21648 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
21649 <li> hypot(x, (+-)0) is equivalent to fabs(x).
21650 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
21651 </ul>
21654 <p><!--para 1 -->
21655 <ul>
21656 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
21657 for y an odd integer < 0.
21658 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
21659 for y < 0 and not an odd integer.
21660 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
21661 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
21662 <li> pow(-1, (+-)(inf)) returns 1.
21663 <li> pow(+1, y) returns 1 for any y, even a NaN.
21664 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
21665 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
21666 finite x < 0 and finite non-integer y.
21667 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
21668 <li> pow(x, -(inf)) returns +0 for | x | > 1.
21669 <li> pow(x, +(inf)) returns +0 for | x | < 1.
21670 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
21671 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
21672 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
21673 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
21674 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
21675 <li> pow(+(inf), y) returns +0 for y < 0.
21676 <li> pow(+(inf), y) returns +(inf) for y > 0.
21677 <!--page 474 -->
21678 </ul>
21681 <p><!--para 1 -->
21682 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
21687 <p><!--para 1 -->
21688 <ul>
21689 <li> erf((+-)0) returns (+-)0.
21690 <li> erf((+-)(inf)) returns (+-)1.
21691 </ul>
21694 <p><!--para 1 -->
21695 <ul>
21696 <li> erfc(-(inf)) returns 2.
21697 <li> erfc(+(inf)) returns +0.
21698 </ul>
21701 <p><!--para 1 -->
21702 <ul>
21703 <li> lgamma(1) returns +0.
21704 <li> lgamma(2) returns +0.
21705 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
21706 x a negative integer or zero.
21707 <li> lgamma(-(inf)) returns +(inf).
21708 <li> lgamma(+(inf)) returns +(inf).
21709 </ul>
21712 <p><!--para 1 -->
21713 <ul>
21714 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21715 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
21716 negative integer.
21717 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21718 <li> tgamma(+(inf)) returns +(inf).
21719 </ul>
21724 <p><!--para 1 -->
21725 <ul>
21726 <li> ceil((+-)0) returns (+-)0.
21727 <li> ceil((+-)(inf)) returns (+-)(inf).
21728 </ul>
21729 <p><!--para 2 -->
21730 The double version of ceil behaves as though implemented by
21731 <!--page 475 -->
21732 <pre>
21735 #pragma STDC FENV_ACCESS ON
21736 double ceil(double x)
21737 {
21738 double result;
21739 int save_round = fegetround();
21740 fesetround(FE_UPWARD);
21741 result = rint(x); // or nearbyint instead of rint
21742 fesetround(save_round);
21743 return result;
21744 }</pre>
21747 <p><!--para 1 -->
21748 <ul>
21749 <li> floor((+-)0) returns (+-)0.
21750 <li> floor((+-)(inf)) returns (+-)(inf).
21751 </ul>
21752 <p><!--para 2 -->
21756 <p><!--para 1 -->
21757 The nearbyint functions use IEC 60559 rounding according to the current rounding
21758 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
21759 value from the argument.
21760 <ul>
21761 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
21762 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
21763 </ul>
21766 <p><!--para 1 -->
21767 The rint functions differ from the nearbyint functions only in that they do raise the
21768 ''inexact'' floating-point exception if the result differs in value from the argument.
21771 <p><!--para 1 -->
21772 The lrint and llrint functions provide floating-to-integer conversion as prescribed
21773 by IEC 60559. They round according to the current rounding direction. If the rounded
21774 value is outside the range of the return type, the numeric result is unspecified and the
21775 ''invalid'' floating-point exception is raised. When they raise no other floating-point
21776 exception and the result differs from the argument, they raise the ''inexact'' floating-point
21777 exception.
21778 <!--page 476 -->
21781 <p><!--para 1 -->
21782 <ul>
21783 <li> round((+-)0) returns (+-)0.
21784 <li> round((+-)(inf)) returns (+-)(inf).
21785 </ul>
21786 <p><!--para 2 -->
21787 The double version of round behaves as though implemented by
21788 <pre>
21791 #pragma STDC FENV_ACCESS ON
21792 double round(double x)
21793 {
21794 double result;
21795 fenv_t save_env;
21796 feholdexcept(&save_env);
21797 result = rint(x);
21798 if (fetestexcept(FE_INEXACT)) {
21799 fesetround(FE_TOWARDZERO);
21800 result = rint(copysign(0.5 + fabs(x), x));
21801 }
21802 feupdateenv(&save_env);
21803 return result;
21804 }</pre>
21805 The round functions may, but are not required to, raise the ''inexact'' floating-point
21806 exception for non-integer numeric arguments, as this implementation does.
21809 <p><!--para 1 -->
21810 The lround and llround functions differ from the lrint and llrint functions
21811 with the default rounding direction just in that the lround and llround functions
21812 round halfway cases away from zero and need not raise the ''inexact'' floating-point
21813 exception for non-integer arguments that round to within the range of the return type.
21816 <p><!--para 1 -->
21817 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
21818 rounding direction).
21819 <ul>
21820 <li> trunc((+-)0) returns (+-)0.
21821 <li> trunc((+-)(inf)) returns (+-)(inf).
21822 <!--page 477 -->
21823 </ul>
21828 <p><!--para 1 -->
21829 <ul>
21830 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
21831 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
21832 infinite or y zero.
21833 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
21834 </ul>
21835 <p><!--para 2 -->
21836 The double version of fmod behaves as though implemented by
21837 <pre>
21840 #pragma STDC FENV_ACCESS ON
21841 double fmod(double x, double y)
21842 {
21843 double result;
21844 result = remainder(fabs(x), (y = fabs(y)));
21845 if (signbit(result)) result += y;
21846 return copysign(result, x);
21847 }</pre>
21850 <p><!--para 1 -->
21851 The remainder functions are fully specified as a basic arithmetic operation in
21852 IEC 60559.
21855 <p><!--para 1 -->
21856 The remquo functions follow the specifications for the remainder functions. They
21857 have no further specifications special to IEC 60559 implementations.
21862 <p><!--para 1 -->
21863 copysign is specified in the Appendix to IEC 60559.
21866 <p><!--para 1 -->
21867 All IEC 60559 implementations support quiet NaNs, in all floating formats.
21868 <!--page 478 -->
21871 <p><!--para 1 -->
21872 <ul>
21873 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
21874 for x finite and the function value infinite.
21875 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
21876 exceptions for the function value subnormal or zero and x != y.
21877 </ul>
21880 <p><!--para 1 -->
21881 No additional requirements beyond those on nextafter.
21883 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
21886 <p><!--para 1 -->
21887 No additional requirements.
21890 <p><!--para 1 -->
21891 If just one argument is a NaN, the fmax functions return the other argument (if both
21892 arguments are NaNs, the functions return a NaN).
21893 <p><!--para 2 -->
21895 <pre>
21896 { return (isgreaterequal(x, y) ||
21897 isnan(y)) ? x : y; }</pre>
21899 <h6>footnotes</h6>
21900 <p><small><a name="note323" href="#note323">323)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
21901 return +0; however, implementation in software might be impractical.
21902 </small>
21905 <p><!--para 1 -->
21911 <p><!--para 1 -->
21912 <ul>
21913 <li> fma(x, y, z) computes xy + z, correctly rounded once.
21914 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
21915 exception if one of x and y is infinite, the other is zero, and z is a NaN.
21916 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
21917 one of x and y is infinite, the other is zero, and z is not a NaN.
21918 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
21919 times y is an exact infinity and z is also an infinity but with the opposite sign.
21924 <!--page 479 -->
21925 </ul>
21928 <pre>
21929 (informative)
21930 IEC 60559-compatible complex arithmetic</pre>
21933 <p><!--para 1 -->
21934 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
21935 IEC 60559 real floating-point arithmetic. Although these specifications have been
21936 carefully designed, there is little existing practice to validate the design decisions.
21937 Therefore, these specifications are not normative, but should be viewed more as
21938 recommended practice. An implementation that defines
21939 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
21942 <p><!--para 1 -->
21943 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
21944 used as a type specifier within declaration specifiers in the same way as _Complex is
21945 (thus, _Imaginary float is a valid type name).
21946 <p><!--para 2 -->
21947 There are three imaginary types, designated as float _Imaginary, double
21948 _Imaginary, and long double _Imaginary. The imaginary types (along with
21949 the real floating and complex types) are floating types.
21950 <p><!--para 3 -->
21951 For imaginary types, the corresponding real type is given by deleting the keyword
21952 _Imaginary from the type name.
21953 <p><!--para 4 -->
21954 Each imaginary type has the same representation and alignment requirements as the
21955 corresponding real type. The value of an object of imaginary type is the value of the real
21956 representation times the imaginary unit.
21957 <p><!--para 5 -->
21958 The imaginary type domain comprises the imaginary types.
21961 <p><!--para 1 -->
21962 A complex or imaginary value with at least one infinite part is regarded as an infinity
21963 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
21964 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
21965 a zero if each of its parts is a zero.
21966 <!--page 480 -->
21971 <p><!--para 1 -->
21972 Conversions among imaginary types follow rules analogous to those for real floating
21973 types.
21976 <p><!--para 1 -->
21977 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note324"><b>324)</b></a></sup> the
21978 result is a positive zero.
21979 <p><!--para 2 -->
21980 When a value of real type is converted to an imaginary type, the result is a positive
21981 imaginary zero.
21983 <h6>footnotes</h6>
21985 </small>
21988 <p><!--para 1 -->
21989 When a value of imaginary type is converted to a complex type, the real part of the
21990 complex result value is a positive zero and the imaginary part of the complex result value
21991 is determined by the conversion rules for the corresponding real types.
21992 <p><!--para 2 -->
21993 When a value of complex type is converted to an imaginary type, the real part of the
21994 complex value is discarded and the value of the imaginary part is converted according to
21995 the conversion rules for the corresponding real types.
21998 <p><!--para 1 -->
21999 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
22000 operation with an imaginary operand.
22001 <p><!--para 2 -->
22002 For most operand types, the value of the result of a binary operator with an imaginary or
22003 complex operand is completely determined, with reference to real arithmetic, by the usual
22004 mathematical formula. For some operand types, the usual mathematical formula is
22005 problematic because of its treatment of infinities and because of undue overflow or
22006 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
22007 not completely determined.
22012 <!--page 481 -->
22015 <h6>Semantics</h6>
22016 <p><!--para 1 -->
22017 If one operand has real type and the other operand has imaginary type, then the result has
22018 imaginary type. If both operands have imaginary type, then the result has real type. (If
22019 either operand has complex type, then the result has complex type.)
22020 <p><!--para 2 -->
22021 If the operands are not both complex, then the result and floating-point exception
22022 behavior of the * operator is defined by the usual mathematical formula:
22023 <pre>
22024 * u iv u + iv</pre>
22026 <pre>
22027 x xu i(xv) (xu) + i(xv)</pre>
22029 <pre>
22030 iy i(yu) -yv (-yv) + i(yu)</pre>
22032 <p><!--para 3 -->
22033 <pre>
22034 x + iy (xu) + i(yu) (-yv) + i(xv)</pre>
22035 If the second operand is not complex, then the result and floating-point exception
22036 behavior of the / operator is defined by the usual mathematical formula:
22037 <pre>
22038 / u iv</pre>
22040 <pre>
22041 x x/u i(-x/v)</pre>
22043 <pre>
22044 iy i(y/u) y/v</pre>
22046 <p><!--para 4 -->
22047 <pre>
22048 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)</pre>
22049 The * and / operators satisfy the following infinity properties for all real, imaginary, and
22051 <ul>
22052 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
22053 infinity, then the result of the * operator is an infinity;
22054 <li> if the first operand is an infinity and the second operand is a finite number, then the
22055 result of the / operator is an infinity;
22056 <li> if the first operand is a finite number and the second operand is an infinity, then the
22057 result of the / operator is a zero;
22062 <!--page 482 -->
22063 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
22064 a zero, then the result of the / operator is an infinity.
22065 </ul>
22066 <p><!--para 5 -->
22067 If both operands of the * operator are complex or if the second operand of the / operator
22068 is complex, the operator raises floating-point exceptions if appropriate for the calculation
22069 of the parts of the result, and may raise spurious floating-point exceptions.
22070 <p><!--para 6 -->
22071 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
22073 <!--page 483 -->
22074 <p><!--para 7 -->
22075 <pre>
22078 /* Multiply z * w ... */
22079 double complex _Cmultd(double complex z, double complex w)
22080 {
22081 #pragma STDC FP_CONTRACT OFF
22082 double a, b, c, d, ac, bd, ad, bc, x, y;
22083 a = creal(z); b = cimag(z);
22084 c = creal(w); d = cimag(w);
22085 ac = a * c; bd = b * d;
22086 ad = a * d; bc = b * c;
22087 x = ac - bd; y = ad + bc;
22088 if (isnan(x) && isnan(y)) {
22089 /* Recover infinities that computed as NaN+iNaN ... */
22090 int recalc = 0;
22091 if ( isinf(a) || isinf(b) ) { // z is infinite
22093 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22094 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22095 if (isnan(c)) c = copysign(0.0, c);
22096 if (isnan(d)) d = copysign(0.0, d);
22097 recalc = 1;
22098 }
22099 if ( isinf(c) || isinf(d) ) { // w is infinite
22101 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22102 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22103 if (isnan(a)) a = copysign(0.0, a);
22104 if (isnan(b)) b = copysign(0.0, b);
22105 recalc = 1;
22106 }
22107 if (!recalc && (isinf(ac) || isinf(bd) ||
22108 isinf(ad) || isinf(bc))) {
22109 /* Recover infinities from overflow by changing NaNs to 0 ... */
22110 if (isnan(a)) a = copysign(0.0, a);
22111 if (isnan(b)) b = copysign(0.0, b);
22112 if (isnan(c)) c = copysign(0.0, c);
22113 if (isnan(d)) d = copysign(0.0, d);
22114 recalc = 1;
22115 }
22116 if (recalc) {
22117 x = INFINITY * ( a * c - b * d );
22118 y = INFINITY * ( a * d + b * c );
22119 }
22120 }
22121 return x + I * y;
22122 }</pre>
22123 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
22124 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
22126 <p><!--para 8 -->
22127 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
22128 <!--page 484 -->
22129 <p><!--para 9 -->
22130 <pre>
22133 /* Divide z / w ... */
22134 double complex _Cdivd(double complex z, double complex w)
22135 {
22136 #pragma STDC FP_CONTRACT OFF
22137 double a, b, c, d, logbw, denom, x, y;
22138 int ilogbw = 0;
22139 a = creal(z); b = cimag(z);
22140 c = creal(w); d = cimag(w);
22141 logbw = logb(fmax(fabs(c), fabs(d)));
22142 if (isfinite(logbw)) {
22143 ilogbw = (int)logbw;
22144 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
22145 }
22146 denom = c * c + d * d;
22147 x = scalbn((a * c + b * d) / denom, -ilogbw);
22148 y = scalbn((b * c - a * d) / denom, -ilogbw);
22149 /* Recover infinities and zeros that computed as NaN+iNaN; */
22150 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
22151 if (isnan(x) && isnan(y)) {
22152 if ((denom == 0.0) &&
22153 (!isnan(a) || !isnan(b))) {
22154 x = copysign(INFINITY, c) * a;
22155 y = copysign(INFINITY, c) * b;
22156 }
22157 else if ((isinf(a) || isinf(b)) &&
22158 isfinite(c) && isfinite(d)) {
22159 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22160 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22161 x = INFINITY * ( a * c + b * d );
22162 y = INFINITY * ( b * c - a * d );
22163 }
22164 else if (isinf(logbw) &&
22165 isfinite(a) && isfinite(b)) {
22166 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22167 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22168 x = 0.0 * ( a * c + b * d );
22169 y = 0.0 * ( b * c - a * d );
22170 }
22171 }
22172 return x + I * y;
22173 }</pre>
22174 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
22175 for multiplication. In the spirit of the multiplication example above, this code does not defend against
22176 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
22177 with division, provides better roundoff characteristics.
22180 <h6>footnotes</h6>
22181 <p><small><a name="note325" href="#note325">325)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
22182 (at least where the state for CX_LIMITED_RANGE is ''off'').
22183 </small>
22186 <h6>Semantics</h6>
22187 <p><!--para 1 -->
22188 If both operands have imaginary type, then the result has imaginary type. (If one operand
22189 has real type and the other operand has imaginary type, or if either operand has complex
22190 type, then the result has complex type.)
22191 <p><!--para 2 -->
22192 In all cases the result and floating-point exception behavior of a + or - operator is defined
22193 by the usual mathematical formula:
22194 <pre>
22195 + or - u iv u + iv</pre>
22197 <pre>
22198 x x(+-)u x (+-) iv (x (+-) u) (+-) iv</pre>
22200 <pre>
22201 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)</pre>
22203 <pre>
22204 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)</pre>
22207 <p><!--para 1 -->
22208 The macros
22209 <pre>
22210 imaginary</pre>
22211 and
22212 <pre>
22213 _Imaginary_I</pre>
22214 are defined, respectively, as _Imaginary and a constant expression of type const
22215 float _Imaginary with the value of the imaginary unit. The macro
22216 <pre>
22217 I</pre>
22218 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
22219 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
22220 imaginary.
22221 <p><!--para 2 -->
22222 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
22223 particularly suited to IEC 60559 implementations. For families of functions, the
22224 specifications apply to all of the functions even though only the principal function is
22225 <!--page 485 -->
22226 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
22227 and the result, the result has the same sign as the argument.
22228 <p><!--para 3 -->
22229 The functions are continuous onto both sides of their branch cuts, taking into account the
22230 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
22231 <p><!--para 4 -->
22232 Since complex and imaginary values are composed of real values, each function may be
22233 regarded as computing real values from real values. Except as noted, the functions treat
22234 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
22235 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
22236 <p><!--para 5 -->
22237 The functions cimag, conj, cproj, and creal are fully specified for all
22238 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
22239 point exceptions.
22240 <p><!--para 6 -->
22241 Each of the functions cabs and carg is specified by a formula in terms of a real
22243 <p><!--para 7 -->
22244 <pre>
22245 cabs(x + iy) = hypot(x, y)
22246 carg(x + iy) = atan2(y, x)</pre>
22247 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
22248 a formula in terms of other complex functions (whose special cases are specified below):
22249 <p><!--para 8 -->
22250 <pre>
22251 casin(z) = -i casinh(iz)
22252 catan(z) = -i catanh(iz)
22253 ccos(z) = ccosh(iz)
22254 csin(z) = -i csinh(iz)
22255 ctan(z) = -i ctanh(iz)</pre>
22256 For the other functions, the following subclauses specify behavior for special cases,
22257 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
22258 families of functions, the specifications apply to all of the functions even though only the
22259 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
22260 specifications for the upper half-plane imply the specifications for the lower half-plane; if
22261 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
22262 specifications for the first quadrant imply the specifications for the other three quadrants.
22263 <p><!--para 9 -->
22264 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
22269 <!--page 486 -->
22271 <h6>footnotes</h6>
22272 <p><small><a name="note326" href="#note326">326)</a> As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
22273 other part is a NaN.
22274 </small>
22279 <p><!--para 1 -->
22280 <ul>
22281 <li> cacos(conj(z)) = conj(cacos(z)).
22282 <li> cacos((+-)0 + i0) returns pi /2 - i0.
22283 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
22284 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
22285 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22286 point exception, for nonzero finite x.
22287 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
22288 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
22289 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
22290 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
22291 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22292 result is unspecified).
22293 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22294 point exception, for finite y.
22295 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
22296 <li> cacos(NaN + iNaN) returns NaN + iNaN.
22297 </ul>
22302 <p><!--para 1 -->
22303 <ul>
22304 <li> cacosh(conj(z)) = conj(cacosh(z)).
22305 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
22306 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22307 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22308 floating-point exception, for finite x.
22309 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
22310 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
22311 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22312 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22313 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
22314 <!--page 487 -->
22315 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22316 floating-point exception, for finite y.
22317 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
22318 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
22319 </ul>
22322 <p><!--para 1 -->
22323 <ul>
22324 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
22325 <li> casinh(+0 + i0) returns 0 + i0.
22326 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
22327 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22328 floating-point exception, for finite x.
22329 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
22330 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22331 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
22332 <li> casinh(NaN + i0) returns NaN + i0.
22333 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22334 floating-point exception, for finite nonzero y.
22335 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22336 is unspecified).
22337 <li> casinh(NaN + iNaN) returns NaN + iNaN.
22338 </ul>
22341 <p><!--para 1 -->
22342 <ul>
22343 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
22344 <li> catanh(+0 + i0) returns +0 + i0.
22345 <li> catanh(+0 + iNaN) returns +0 + iNaN.
22346 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
22347 exception.
22348 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
22349 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22350 floating-point exception, for nonzero finite x.
22351 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
22352 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
22353 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
22354 <!--page 488 -->
22355 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22356 floating-point exception, for finite y.
22357 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
22358 unspecified).
22359 <li> catanh(NaN + iNaN) returns NaN + iNaN.
22360 </ul>
22363 <p><!--para 1 -->
22364 <ul>
22365 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
22366 <li> ccosh(+0 + i0) returns 1 + i0.
22367 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
22368 result is unspecified) and raises the ''invalid'' floating-point exception.
22369 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
22370 result is unspecified).
22371 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22372 exception, for finite nonzero x.
22373 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22374 point exception, for finite nonzero x.
22375 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
22376 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22377 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22378 unspecified) and raises the ''invalid'' floating-point exception.
22379 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
22380 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
22381 result is unspecified).
22382 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22383 point exception, for all nonzero numbers y.
22384 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
22385 </ul>
22388 <p><!--para 1 -->
22389 <ul>
22390 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
22391 <li> csinh(+0 + i0) returns +0 + i0.
22392 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
22393 unspecified) and raises the ''invalid'' floating-point exception.
22394 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
22395 unspecified).
22396 <!--page 489 -->
22397 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22398 exception, for positive finite x.
22399 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22400 point exception, for finite nonzero x.
22401 <li> csinh(+(inf) + i0) returns +(inf) + i0.
22402 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
22403 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22404 unspecified) and raises the ''invalid'' floating-point exception.
22405 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22406 is unspecified).
22407 <li> csinh(NaN + i0) returns NaN + i0.
22408 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22409 point exception, for all nonzero numbers y.
22410 <li> csinh(NaN + iNaN) returns NaN + iNaN.
22411 </ul>
22414 <p><!--para 1 -->
22415 <ul>
22416 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
22417 <li> ctanh(+0 + i0) returns +0 + i0.
22418 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22419 exception, for finite x.
22420 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22421 point exception, for finite x.
22422 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
22423 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
22424 is unspecified).
22425 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
22426 result is unspecified).
22427 <li> ctanh(NaN + i0) returns NaN + i0.
22428 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22429 point exception, for all nonzero numbers y.
22430 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
22431 <!--page 490 -->
22432 </ul>
22437 <p><!--para 1 -->
22438 <ul>
22439 <li> cexp(conj(z)) = conj(cexp(z)).
22440 <li> cexp((+-)0 + i0) returns 1 + i0.
22441 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22442 exception, for finite x.
22443 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22444 point exception, for finite x.
22445 <li> cexp(+(inf) + i0) returns +(inf) + i0.
22446 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
22447 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22448 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
22449 the result are unspecified).
22450 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
22451 exception (where the sign of the real part of the result is unspecified).
22452 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
22453 of the result are unspecified).
22454 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22455 is unspecified).
22456 <li> cexp(NaN + i0) returns NaN + i0.
22457 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22458 point exception, for all nonzero numbers y.
22459 <li> cexp(NaN + iNaN) returns NaN + iNaN.
22460 </ul>
22463 <p><!--para 1 -->
22464 <ul>
22465 <li> clog(conj(z)) = conj(clog(z)).
22466 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
22467 exception.
22468 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
22469 exception.
22470 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22471 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22472 point exception, for finite x.
22473 <!--page 491 -->
22474 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
22475 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22476 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22477 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
22478 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
22479 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22480 point exception, for finite y.
22481 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
22482 <li> clog(NaN + iNaN) returns NaN + iNaN.
22483 </ul>
22488 <p><!--para 1 -->
22489 The cpow functions raise floating-point exceptions if appropriate for the calculation of
22490 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
22492 <h6>footnotes</h6>
22493 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
22494 implementations that treat special cases more carefully.
22495 </small>
22498 <p><!--para 1 -->
22499 <ul>
22500 <li> csqrt(conj(z)) = conj(csqrt(z)).
22501 <li> csqrt((+-)0 + i0) returns +0 + i0.
22502 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
22503 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22504 point exception, for finite x.
22505 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
22506 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22507 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22508 result is unspecified).
22509 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
22510 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22511 point exception, for finite y.
22512 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
22517 <!--page 492 -->
22518 </ul>
22521 <p><!--para 1 -->
22522 Type-generic macros that accept complex arguments also accept imaginary arguments. If
22523 an argument is imaginary, the macro expands to an expression whose type is real,
22524 imaginary, or complex, as appropriate for the particular function: if the argument is
22525 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
22526 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
22527 the types of the others are complex.
22528 <p><!--para 2 -->
22529 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
22530 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
22531 functions:
22532 <!--page 493 -->
22533 <pre>
22534 cos(iy) = cosh(y)
22535 sin(iy) = i sinh(y)
22536 tan(iy) = i tanh(y)
22537 cosh(iy) = cos(y)
22538 sinh(iy) = i sin(y)
22539 tanh(iy) = i tan(y)
22540 asin(iy) = i asinh(y)
22541 atan(iy) = i atanh(y)
22542 asinh(iy) = i asin(y)
22543 atanh(iy) = i atan(y)</pre>
22546 <pre>
22547 (informative)
22548 Language independent arithmetic</pre>
22551 <p><!--para 1 -->
22552 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
22553 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
22554 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
22557 <p><!--para 1 -->
22558 The relevant C arithmetic types meet the requirements of LIA-1 types if an
22559 implementation adds notification of exceptional arithmetic operations and meets the 1
22560 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
22563 <p><!--para 1 -->
22564 The LIA-1 data type Boolean is implemented by the C data type bool with values of
22568 <p><!--para 1 -->
22569 The signed C integer types int, long int, long long int, and the corresponding
22570 unsigned types are compatible with LIA-1. If an implementation adds support for the
22571 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
22572 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
22573 in that overflows or out-of-bounds results silently wrap. An implementation that defines
22574 signed integer types as also being modulo need not detect integer overflow, in which case,
22575 only integer divide-by-zero need be detected.
22576 <p><!--para 2 -->
22577 The parameters for the integer data types can be accessed by the following:
22578 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
22579 <pre>
22580 ULLONG_MAX</pre>
22581 minint INT_MIN, LONG_MIN, LLONG_MIN
22582 <p><!--para 3 -->
22583 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
22584 is always 0 for the unsigned types, and is not provided for those types.
22585 <!--page 494 -->
22588 <p><!--para 1 -->
22589 The integer operations on integer types are the following:
22590 addI x + y
22591 subI x - y
22592 mulI x * y
22593 divI, divtI x / y
22594 remI, remtI x % y
22595 negI -x
22596 absI abs(x), labs(x), llabs(x)
22597 eqI x == y
22598 neqI x != y
22599 lssI x < y
22600 leqI x <= y
22601 gtrI x > y
22602 geqI x >= y
22603 where x and y are expressions of the same integer type.
22606 <p><!--para 1 -->
22607 The C floating-point types float, double, and long double are compatible with
22608 LIA-1. If an implementation adds support for the LIA-1 exceptional values
22609 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
22611 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
22612 conformant types.
22616 The parameters for a floating point data type can be accessed by the following:
22617 r FLT_RADIX
22618 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
22619 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
22620 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
22622 The derived constants for the floating point types are accessed by the following:
22623 <!--page 495 -->
22624 fmax FLT_MAX, DBL_MAX, LDBL_MAX
22625 fminN FLT_MIN, DBL_MIN, LDBL_MIN
22626 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
22627 rnd_style FLT_ROUNDS
22631 The floating-point operations on floating-point types are the following:
22632 addF x + y
22633 subF x - y
22634 mulF x * y
22635 divF x / y
22636 negF -x
22637 absF fabsf(x), fabs(x), fabsl(x)
22639 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
22640 <pre>
22641 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)</pre>
22644 eqF x == y
22645 neqF x != y
22646 lssF x < y
22647 leqF x <= y
22648 gtrF x > y
22649 geqF x >= y
22650 where x and y are expressions of the same floating point type, n is of type int, and li
22651 is of type long int.
22655 The C Standard requires all floating types to use the same radix and rounding style, so
22656 that only one identifier for each is provided to map to LIA-1.
22658 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
22659 truncate FLT_ROUNDS == 0
22660 <!--page 496 -->
22661 nearest FLT_ROUNDS == 1
22663 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
22664 in all relevant LIA-1 operations, not just addition as in C.
22668 The LIA-1 type conversions are the following type casts:
22669 cvtI' -> I (int)i, (long int)i, (long long int)i,
22670 <pre>
22671 (unsigned int)i, (unsigned long int)i,
22672 (unsigned long long int)i</pre>
22673 cvtF -> I (int)x, (long int)x, (long long int)x,
22674 <pre>
22675 (unsigned int)x, (unsigned long int)x,
22676 (unsigned long long int)x</pre>
22677 cvtI -> F (float)i, (double)i, (long double)i
22678 cvtF' -> F (float)x, (double)x, (long double)x
22680 In the above conversions from floating to integer, the use of (cast)x can be replaced with
22681 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
22682 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
22683 conversion functions, lrint(), llrint(), lround(), and llround(), can be
22684 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
22685 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
22687 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
22690 to 65535.0 which can then be cast to unsigned short int. But, the
22691 remainder() function is not useful for doing silent wrapping to signed integer types,
22692 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
22694 int.
22696 C's conversions (casts) from floating-point to floating-point can meet LIA-1
22697 requirements if an implementation uses round-to-nearest (IEC 60559 default).
22699 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
22700 implementation uses round-to-nearest.
22701 <!--page 497 -->
22705 Notification is the process by which a user or program is informed that an exceptional
22706 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
22707 allows an implementation to cause a notification to occur when any arithmetic operation
22712 LIA-1 requires at least the following two alternatives for handling of notifications:
22713 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
22714 resume.
22716 An implementation need only support a given notification alternative for the entire
22717 program. An implementation may support the ability to switch between notification
22718 alternatives during execution, but is not required to do so. An implementation can
22719 provide separate selection for each kind of notification, but this is not required.
22721 C allows an implementation to provide notification. C's SIGFPE (for traps) and
22722 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
22723 can provide LIA-1 notification.
22725 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
22726 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
22727 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
22728 and-resume behavior with the same constraint.
22734 The following mapping is for floating-point types:
22735 undefined FE_INVALID, FE_DIVBYZERO
22736 floating_overflow FE_OVERFLOW
22737 underflow FE_UNDERFLOW
22739 The floating-point indicator interrogation and manipulation operations are:
22740 set_indicators feraiseexcept(i)
22741 clear_indicators feclearexcept(i)
22742 test_indicators fetestexcept(i)
22743 current_indicators fetestexcept(FE_ALL_EXCEPT)
22744 where i is an expression of type int representing a subset of the LIA-1 indicators.
22746 C allows an implementation to provide the following LIA-1 required behavior: at
22747 program termination if any indicator is set the implementation shall send an unambiguous
22748 <!--page 498 -->
22751 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
22752 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
22753 point indicators.
22757 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
22758 math library functions (which are not permitted to generate any externally visible
22759 exceptional conditions). An implementation can provide an alternative of notification
22760 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
22762 LIA-1 does not require that traps be precise.
22764 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
22765 is any signal raised for them.
22767 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
22768 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
22769 terminate (either default implementation behavior or user replacement for it) or trap-and-
22770 resume, at the programmer's option.
22771 <!--page 499 -->
22775 <pre>
22776 (informative)
22777 Common warnings</pre>
22778 An implementation may generate warnings in many situations, none of which are
22779 specified as part of this International Standard. The following are a few of the more
22780 common situations.
22782 <ul>
22783 <li> A new struct or union type appears in a function prototype (<a href="#6.2.1">6.2.1</a>, <a href="#6.7.2.3">6.7.2.3</a>).
22784 <li> A block with initialization of an object that has automatic storage duration is jumped
22786 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
22787 int or a double to an int, or a pointer to void to a pointer to any type other than
22789 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
22791 <li> An integer character constant includes more than one character or a wide character
22794 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
22795 lvalue in one operand, and a side effect to, or an access to the value of, the identical
22797 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
22798 <li> The arguments in a function call do not agree in number and type with those of the
22801 <li> A value is given to an object of an enumerated type other than by assignment of an
22802 enumeration constant that is a member of that type, or an enumeration object that has
22803 the same type, or the value of a function that returns the same enumerated type
22808 <li> A constant expression is used as the controlling expression of a selection statement
22810 <!--page 500 -->
22811 <li> An incorrectly formed preprocessing group is encountered while skipping a
22814 <!--page 501 -->
22815 </ul>
22819 <pre>
22820 (informative)
22821 Portability issues</pre>
22822 This annex collects some information about portability that appears in this International
22823 Standard.
22827 The following are unspecified:
22828 <ul>
22830 <li> The termination status returned to the hosted environment if the return type of main
22832 <li> The behavior of the display device if a printing character is written when the active
22834 <li> The behavior of the display device if a backspace character is written when the active
22836 <li> The behavior of the display device if a horizontal tab character is written when the
22837 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
22838 <li> The behavior of the display device if a vertical tab character is written when the active
22839 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
22840 <li> How an extended source character that does not correspond to a universal character
22841 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
22843 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
22844 <li> The value of a union member other than the last one stored into (<a href="#6.2.6.1">6.2.6.1</a>).
22845 <li> The representation used when storing a value in an object that has more than one
22847 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
22848 <li> Whether certain operators can generate negative zeros and whether a negative zero
22851 <li> The order in which subexpressions are evaluated and the order in which side effects
22852 take place, except as specified for the function-call (), &&, ||, ?:, and comma
22854 <!--page 502 -->
22855 <li> The order in which the function designator, arguments, and subexpressions within the
22857 <li> The order of side effects among compound literal initialization list expressions
22859 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
22860 <li> The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
22861 <li> Whether a call to an inline function uses the inline definition or the external definition
22863 <li> Whether or not a size expression is evaluated when it is part of the operand of a
22864 sizeof operator and changing the value of the size expression would not affect the
22866 <li> The order in which any side effects occur among the initialization list expressions in
22869 <li> When a fully expanded macro replacement list contains a function-like macro name
22870 as its last preprocessing token and the next preprocessing token from the source file is
22871 a (, and the fully expanded replacement of that macro ends with the name of the first
22872 macro and the next preprocessing token from the source file is again a (, whether that
22874 <li> The order in which # and ## operations are evaluated during macro substitution
22876 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
22877 <li> The state of the floating-point status flags when execution passes from a part of the
22878 program translated with FENV_ACCESS ''off'' to a part translated with
22880 <li> The order in which feraiseexcept raises floating-point exceptions, except as
22882 <li> Whether math_errhandling is a macro or an identifier with external linkage
22884 <li> The results of the frexp functions when the specified value is not a floating-point
22886 <li> The numeric result of the ilogb functions when the correct value is outside the
22888 <li> The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.5">F.9.6.5</a>).
22889 <!--page 503 -->
22890 <li> The value stored by the remquo functions in the object pointed to by quo when y is
22892 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
22893 <li> Whether va_copy and va_end are macros or identifiers with external linkage
22895 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
22896 number is printed with an a or A conversion specifier (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
22897 <li> The value of the file position indicator after a successful call to the ungetc function
22898 for a text stream, or the ungetwc function for any stream, until all pushed-back
22899 characters are read or discarded (<a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.3.10">7.24.3.10</a>).
22900 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
22901 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.19.9.4">7.19.9.4</a>).
22902 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
22903 functions convert a minus-signed sequence to a negative number directly or by
22904 negating the value resulting from converting the corresponding unsigned sequence
22906 <li> The order and contiguity of storage allocated by successive calls to the calloc,
22908 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
22910 <li> Which of two elements that compare as equal is matched by the bsearch function
22912 <li> The order of two elements that compare as equal in an array sorted by the qsort
22914 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
22915 <li> The characters stored by the strftime or wcsftime function if any of the time
22916 values being converted is outside the normal range (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
22917 <li> The conversion state after an encoding error occurs (<a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>,
22919 <li> The resulting value when the ''invalid'' floating-point exception is raised during
22923 <!--page 504 -->
22924 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
22926 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
22928 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
22929 <li> The numeric result returned by the lrint, llrint, lround, and llround
22930 functions if the rounded value is outside the range of the return type (<a href="#F.9.6.5">F.9.6.5</a>, <a href="#F.9.6.7">F.9.6.7</a>).
22931 <li> The sign of one part of the complex result of several math functions for certain
22932 exceptional values in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>,
22933 <a href="#G.6.2.3">G.6.2.3</a>, <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
22934 </ul>
22938 The behavior is undefined in the following circumstances:
22939 <ul>
22940 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
22941 (clause 4).
22942 <li> A nonempty source file does not end in a new-line character which is not immediately
22943 preceded by a backslash character or ends in a partial preprocessing token or
22945 <li> Token concatenation produces a character sequence matching the syntax of a
22947 <li> A program in a hosted environment does not define a function named main using one
22949 <li> A character not in the basic source character set is encountered in a source file, except
22950 in an identifier, a character constant, a string literal, a header name, a comment, or a
22952 <li> An identifier, comment, string literal, character constant, or header name contains an
22953 invalid multibyte character or does not begin and end in the initial shift state (<a href="#5.2.1.2">5.2.1.2</a>).
22954 <li> The same identifier has both internal and external linkage in the same translation unit
22957 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
22958 <li> The value of an object with automatic storage duration is used while it is
22959 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.8">6.7.8</a>, <a href="#6.8">6.8</a>).
22960 <li> A trap representation is read by an lvalue expression that does not have character type
22962 <!--page 505 -->
22963 <li> A trap representation is produced by a side effect that modifies any part of the object
22964 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
22965 <li> The arguments to certain operators are such that could produce a negative zero result,
22967 <li> Two declarations of the same object or function specify types that are not compatible
22969 <li> Conversion to or from an integer type produces a value outside the range that can be
22971 <li> Demotion of one real floating type to another produces a value outside the range that
22974 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
22976 <li> An lvalue having array type is converted to a pointer to the initial element of the
22978 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
22980 <li> Conversion of a pointer to an integer type produces a value outside the range that can
22982 <li> Conversion between two pointer types produces a result that is incorrectly aligned
22984 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
22988 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
22990 <li> A universal character name in an identifier does not designate a character whose
22992 <li> The initial character of an identifier is a universal character name designating a digit
22994 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
22996 <!--page 506 -->
22999 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
23001 <li> Between two sequence points, an object is modified more than once, or is modified
23002 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
23003 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
23004 <li> An object has its stored value accessed other than by an lvalue of an allowable type
23006 <li> An attempt is made to modify the result of a function call, a conditional operator, an
23007 assignment operator, or a comma operator, or to access it after the next sequence
23008 point (<a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.15">6.5.15</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.17">6.5.17</a>).
23009 <li> For a call to a function without a function prototype in scope, the number of
23011 <li> For call to a function without a function prototype in scope where the function is
23012 defined with a function prototype, either the prototype ends with an ellipsis or the
23013 types of the arguments after promotion are not compatible with the types of the
23015 <li> For a call to a function without a function prototype in scope where the function is not
23016 defined with a function prototype, the types of the arguments after promotion are not
23017 compatible with those of the parameters after promotion (with certain exceptions)
23019 <li> A function is defined with a type that is not compatible with the type (of the
23020 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
23021 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
23022 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
23023 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
23024 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23025 integer type produces a result that does not point into, or just beyond, the same array
23027 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23028 integer type produces a result that points just beyond the array object and is used as
23030 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
23032 <!--page 507 -->
23033 <li> An array subscript is out of range, even if an object is apparently accessible with the
23034 given subscript (as in the lvalue expression a[1][7] given the declaration int
23036 <li> The result of subtracting two pointers is not representable in an object of type
23038 <li> An expression is shifted by a negative number or by an amount greater than or equal
23040 <li> An expression having signed promoted type is left-shifted and either the value of the
23041 expression is negative or the result of shifting would be not be representable in the
23043 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
23045 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
23047 <li> An expression that is required to be an integer constant expression does not have an
23048 integer type; has operands that are not integer constants, enumeration constants,
23049 character constants, sizeof expressions whose results are integer constants, or
23050 immediately-cast floating constants; or contains casts (outside operands to sizeof
23051 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
23052 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
23053 following: an arithmetic constant expression, a null pointer constant, an address
23054 constant, or an address constant for an object type plus or minus an integer constant
23056 <li> An arithmetic constant expression does not have arithmetic type; has operands that
23057 are not integer constants, floating constants, enumeration constants, character
23058 constants, or sizeof expressions; or contains casts (outside operands to sizeof
23059 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
23060 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
23061 address &, or indirection * operator or a pointer cast in creating an address constant
23063 <li> An identifier for an object is declared with no linkage and the type of the object is
23064 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
23065 <li> A function is declared at block scope with an explicit storage-class specifier other
23067 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
23068 <!--page 508 -->
23069 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
23070 member of a structure when the referenced object provides no elements for that array
23072 <li> When the complete type is needed, an incomplete structure or union type is not
23073 completed in the same scope by another declaration of the tag that defines the content
23075 <li> An attempt is made to modify an object defined with a const-qualified type through
23077 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
23079 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
23080 <li> Two qualified types that are required to be compatible do not have the identically
23082 <li> An object which has been modified is accessed through a restrict-qualified pointer to
23083 a const-qualified type, or through a restrict-qualified pointer and another pointer that
23085 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
23086 whose associated block neither began execution before the block associated with this
23088 <li> A function with external linkage is declared with an inline function specifier, but is
23090 <li> Two pointer types that are required to be compatible are not identically qualified, or
23092 <li> The size expression in an array declaration is not a constant expression and evaluates
23094 <li> In a context requiring two array types to be compatible, they do not have compatible
23095 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
23096 <li> A declaration of an array parameter includes the keyword static within the [ and
23097 ] and the corresponding argument does not provide access to the first element of an
23099 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
23101 <li> In a context requiring two function types to be compatible, they do not have
23102 compatible return types, or their parameters disagree in use of the ellipsis terminator
23103 or the number and type of parameters (after default argument promotion, when there
23104 is no parameter type list or when one type is specified by a function definition with an
23105 <!--page 509 -->
23107 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
23108 <li> The initializer for a scalar is neither a single expression nor a single expression
23110 <li> The initializer for a structure or union object that has automatic storage duration is
23111 neither an initializer list nor a single expression that has compatible structure or union
23113 <li> The initializer for an aggregate or union, other than an array initialized by a string
23114 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
23115 <li> An identifier with external linkage is used, but in the program there does not exist
23116 exactly one external definition for the identifier, or the identifier is not used and there
23118 <li> A function definition includes an identifier list, but the types of the parameters are not
23120 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
23121 <li> A function that accepts a variable number of arguments is defined without a
23123 <li> The } that terminates a function is reached, and the value of the function call is used
23125 <li> An identifier for an object with internal linkage and an incomplete type is declared
23127 <li> The token defined is generated during the expansion of a #if or #elif
23128 preprocessing directive, or the use of the defined unary operator does not match
23130 <li> The #include preprocessing directive that results after expansion does not match
23132 <li> The character sequence in an #include preprocessing directive does not start with a
23134 <li> There are sequences of preprocessing tokens within the list of macro arguments that
23136 <li> The result of the preprocessing operator # is not a valid character string literal
23138 <li> The result of the preprocessing operator ## is not a valid preprocessing token
23140 <!--page 510 -->
23141 <li> The #line preprocessing directive that results after expansion does not match one of
23142 the two well-defined forms, or its digit sequence specifies zero or a number greater
23144 <li> A non-STDC #pragma preprocessing directive that is documented as causing
23145 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
23146 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
23148 <li> The name of a predefined macro, or the identifier defined, is the subject of a
23150 <li> An attempt is made to copy an object to an overlapping object by use of a library
23151 function, other than as explicitly allowed (e.g., memmove) (clause 7).
23152 <li> A file with the same name as one of the standard headers, not provided as part of the
23153 implementation, is placed in any of the standard places that are searched for included
23155 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
23156 <li> A function, object, type, or macro that is specified as being declared or defined by
23157 some standard header is used before any header that declares or defines it is included
23159 <li> A standard header is included while a macro is defined with the same name as a
23161 <li> The program attempts to declare a library function itself, rather than via a standard
23163 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
23165 <li> The program removes the definition of a macro whose name begins with an
23167 <li> An argument to a library function has an invalid value or a type not expected by a
23169 <li> The pointer passed to a library function array parameter does not have a value such
23171 <li> The macro definition of assert is suppressed in order to access an actual function
23174 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
23175 any context other than outside all external declarations or preceding all explicit
23176 <!--page 511 -->
23177 declarations and statements inside a compound statement (<a href="#7.3.4">7.3.4</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.12.2">7.12.2</a>).
23178 <li> The value of an argument to a character handling function is neither equal to the value
23180 <li> A macro definition of errno is suppressed in order to access an actual object, or the
23182 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
23183 or runs under non-default mode settings, but was translated with the state for the
23185 <li> The exception-mask argument for one of the functions that provide access to the
23186 floating-point status flags has a nonzero value not obtained by bitwise OR of the
23188 <li> The fesetexceptflag function is used to set floating-point status flags that were
23189 not specified in the call to the fegetexceptflag function that provided the value
23191 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
23192 fegetenv or feholdexcept, nor is it an environment macro (<a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>).
23193 <li> The value of the result of an integer arithmetic or conversion function cannot be
23194 represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.6.1">7.20.6.1</a>, <a href="#7.20.6.2">7.20.6.2</a>, <a href="#7.20.1">7.20.1</a>).
23195 <li> The program modifies the string pointed to by the value returned by the setlocale
23197 <li> The program modifies the structure pointed to by the value returned by the
23199 <li> A macro definition of math_errhandling is suppressed or the program defines
23201 <li> An argument to a floating-point classification or comparison macro is not of real
23203 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
23205 <li> An invocation of the setjmp macro occurs other than in an allowed context
23207 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
23208 <li> After a longjmp, there is an attempt to access the value of an object of automatic
23209 storage class with non-volatile-qualified type, local to the function containing the
23210 invocation of the corresponding setjmp macro, that was changed between the
23212 <!--page 512 -->
23213 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
23214 <li> A signal handler returns when the signal corresponded to a computational exception
23216 <li> A signal occurs as the result of calling the abort or raise function, and the signal
23218 <li> A signal occurs other than as the result of calling the abort or raise function, and
23219 the signal handler refers to an object with static storage duration other than by
23220 assigning a value to an object declared as volatile sig_atomic_t, or calls any
23221 function in the standard library other than the abort function, the _Exit function,
23223 <li> The value of errno is referred to after a signal occurred other than as the result of
23224 calling the abort or raise function and the corresponding signal handler obtained
23226 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
23227 <li> A function with a variable number of arguments attempts to access its varying
23228 arguments other than through a properly declared and initialized va_list object, or
23229 before the va_start macro is invoked (<a href="#7.15">7.15</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23230 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
23232 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
23233 order to access an actual function, or the program defines an external identifier with
23235 <li> The va_start or va_copy macro is invoked without a corresponding invocation
23236 of the va_end macro in the same function, or vice versa (<a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>,
23238 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
23240 <li> The va_arg macro is invoked when there is no actual next argument, or with a
23241 specified type that is not compatible with the promoted type of the actual next
23243 <li> The va_copy or va_start macro is called to initialize a va_list that was
23244 previously initialized by either macro without an intervening invocation of the
23245 va_end macro for the same va_list (<a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23246 <li> The parameter parmN of a va_start macro is declared with the register
23247 storage class, with a function or array type, or with a type that is not compatible with
23248 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
23249 <!--page 513 -->
23250 <li> The member designator parameter of an offsetof macro is an invalid right
23251 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
23252 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
23253 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
23255 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
23257 <li> Use is made of any portion of a file beyond the most recent wide character written to
23259 <li> The value of a pointer to a FILE object is used after the associated file is closed
23261 <li> The stream for the fflush function points to an input stream or to an update stream
23263 <li> The string pointed to by the mode argument in a call to the fopen function does not
23265 <li> An output operation on an update stream is followed by an input operation without an
23266 intervening call to the fflush function or a file positioning function, or an input
23267 operation on an update stream is followed by an output operation with an intervening
23269 <li> An attempt is made to use the contents of the array that was supplied in a call to the
23271 <li> There are insufficient arguments for the format in a call to one of the formatted
23272 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
23273 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23274 <li> The format in a call to one of the formatted input/output functions or to the
23275 strftime or wcsftime function is not a valid multibyte character sequence that
23276 begins and ends in its initial shift state (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
23278 <li> In a call to one of the formatted output functions, a precision appears with a
23279 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23280 <li> A conversion specification for a formatted output function uses an asterisk to denote
23281 an argument-supplied field width or precision, but the corresponding argument is not
23283 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
23284 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23285 <!--page 514 -->
23286 <li> A conversion specification for one of the formatted input/output functions uses a
23287 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
23288 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23289 <li> An s conversion specifier is encountered by one of the formatted output functions,
23290 and the argument is missing the null terminator (unless a precision is specified that
23291 does not require null termination) (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23292 <li> An n conversion specification for one of the formatted input/output functions includes
23293 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
23294 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23295 <li> A % conversion specifier is encountered by one of the formatted input/output
23296 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
23297 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23298 <li> An invalid conversion specification is found in the format for one of the formatted
23299 input/output functions, or the strftime or wcsftime function (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
23300 <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23301 <li> The number of characters transmitted by a formatted output function is greater than
23302 INT_MAX (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>).
23303 <li> The result of a conversion by one of the formatted input functions cannot be
23304 represented in the corresponding object, or the receiving object does not have an
23306 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
23307 functions, and the array pointed to by the corresponding argument is not large enough
23308 to accept the input sequence (and a null terminator if the conversion specifier is s or
23310 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
23311 formatted input functions, but the input is not a valid multibyte character sequence
23312 that begins in the initial shift state (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23313 <li> The input item for a %p conversion by one of the formatted input functions is not a
23314 value converted earlier during the same program execution (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23315 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
23316 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
23317 vwscanf function is called with an improperly initialized va_list argument, or
23318 the argument is used (other than in an invocation of va_end) after the function
23319 returns (<a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
23320 <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>).
23321 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
23322 are used after a read error occurred (<a href="#7.19.7.2">7.19.7.2</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.3.2">7.24.3.2</a>).
23323 <!--page 515 -->
23324 <li> The file position indicator for a binary stream is used after a call to the ungetc
23326 <li> The file position indicator for a stream is used after an error occurred during a call to
23327 the fread or fwrite function (<a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>).
23328 <li> A partial element read by a call to the fread function is used (<a href="#7.19.8.1">7.19.8.1</a>).
23329 <li> The fseek function is called for a text stream with a nonzero offset and either the
23330 offset was not returned by a previous successful call to the ftell function on a
23331 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
23332 <li> The fsetpos function is called to set a position that was not returned by a previous
23333 successful call to the fgetpos function on a stream associated with the same file
23335 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
23337 <li> The value of a pointer that refers to space deallocated by a call to the free or
23339 <li> The pointer argument to the free or realloc function does not match a pointer
23340 earlier returned by calloc, malloc, or realloc, or the space has been
23341 deallocated by a call to free or realloc (<a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a>).
23342 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
23343 <li> The value of any bytes in a new object allocated by the realloc function beyond
23345 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
23346 <li> During the call to a function registered with the atexit function, a call is made to
23347 the longjmp function that would terminate the call to the registered function
23349 <li> The string set up by the getenv or strerror function is modified by the program
23351 <li> A command is executed through the system function in a way that is documented as
23352 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
23353 <li> A searching or sorting utility function is called with an invalid pointer argument, even
23355 <li> The comparison function called by a searching or sorting utility function alters the
23356 contents of the array being searched or sorted, or returns ordering values
23358 <!--page 516 -->
23359 <li> The array being searched by the bsearch function does not have its elements in
23361 <li> The current conversion state is used by a multibyte/wide character conversion
23363 <li> A string or wide string utility function is instructed to access an array beyond the end
23365 <li> A string or wide string utility function is called with an invalid pointer argument, even
23367 <li> The contents of the destination array are used after a call to the strxfrm,
23368 strftime, wcsxfrm, or wcsftime function in which the specified length was
23369 too small to hold the entire null-terminated result (<a href="#7.21.4.5">7.21.4.5</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a>,
23371 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
23373 <li> The type of an argument to a type-generic macro is not compatible with the type of
23375 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
23377 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
23378 fwprintf function does not point to a valid multibyte character sequence that
23380 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
23381 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
23383 <li> The value of an argument of type wint_t to a wide character classification or case
23384 mapping function is neither equal to the value of WEOF nor representable as a
23386 <li> The iswctype function is called using a different LC_CTYPE category from the
23387 one in effect for the call to the wctype function that returned the description
23389 <li> The towctrans function is called using a different LC_CTYPE category from the
23390 one in effect for the call to the wctrans function that returned the description
23392 <!--page 517 -->
23393 </ul>
23396 <p><!--para 1 -->
23397 A conforming implementation is required to document its choice of behavior in each of
23398 the areas listed in this subclause. The following are implementation-defined:
23401 <p><!--para 1 -->
23402 <ul>
23403 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
23404 <li> Whether each nonempty sequence of white-space characters other than new-line is
23405 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
23406 </ul>
23409 <p><!--para 1 -->
23410 <ul>
23411 <li> The mapping between physical source file multibyte characters and the source
23413 <li> The name and type of the function called at program startup in a freestanding
23415 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
23416 <li> An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23417 <li> The values given to the strings pointed to by the argv argument to main (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23419 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
23420 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
23422 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
23424 <li> The set of environment names and the method for altering the environment list used
23426 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
23427 </ul>
23430 <p><!--para 1 -->
23431 <ul>
23432 <li> Which additional multibyte characters may appear in identifiers and their
23434 <li> The number of significant initial characters in an identifier (<a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2">6.4.2</a>).
23435 <!--page 518 -->
23436 </ul>
23439 <p><!--para 1 -->
23440 <ul>
23443 <li> The unique value of the member of the execution character set produced for each of
23445 <li> The value of a char object into which has been stored any character other than a
23447 <li> Which of signed char or unsigned char has the same range, representation,
23449 <li> The mapping of members of the source character set (in character constants and string
23450 literals) to members of the execution character set (<a href="#6.4.4.4">6.4.4.4</a>, <a href="#5.1.1.2">5.1.1.2</a>).
23451 <li> The value of an integer character constant containing more than one character or
23452 containing a character or escape sequence that does not map to a single-byte
23454 <li> The value of a wide character constant containing more than one multibyte character,
23455 or containing a multibyte character or escape sequence not represented in the
23457 <li> The current locale used to convert a wide character constant consisting of a single
23458 multibyte character that maps to a member of the extended execution character set
23460 <li> The current locale used to convert a wide string literal into corresponding wide
23462 <li> The value of a string literal containing a multibyte character or escape sequence not
23464 </ul>
23467 <p><!--para 1 -->
23468 <ul>
23469 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
23470 <li> Whether signed integer types are represented using sign and magnitude, two's
23471 complement, or ones' complement, and whether the extraordinary value is a trap
23473 <li> The rank of any extended integer type relative to another extended integer type with
23475 <li> The result of, or the signal raised by, converting an integer to a signed integer type
23476 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
23477 <!--page 519 -->
23479 </ul>
23482 <p><!--para 1 -->
23483 <ul>
23484 <li> The accuracy of the floating-point operations and of the library functions in
23485 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23486 <li> The accuracy of the conversions between floating-point internal representations and
23487 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
23488 <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23489 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
23491 <li> The evaluation methods characterized by non-standard negative values of
23493 <li> The direction of rounding when an integer is converted to a floating-point number that
23495 <li> The direction of rounding when a floating-point number is converted to a narrower
23497 <li> How the nearest representable value or the larger or smaller representable value
23498 immediately adjacent to the nearest representable value is chosen for certain floating
23500 <li> Whether and how floating expressions are contracted when not disallowed by the
23503 <li> Additional floating-point exceptions, rounding modes, environments, and
23506 </ul>
23509 <p><!--para 1 -->
23510 <ul>
23511 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
23512 <li> The size of the result of subtracting two pointers to elements of the same array
23514 <!--page 520 -->
23515 </ul>
23518 <p><!--para 1 -->
23519 <ul>
23520 <li> The extent to which suggestions made by using the register storage-class
23522 <li> The extent to which suggestions made by using the inline function specifier are
23524 </ul>
23526 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
23527 <p><!--para 1 -->
23528 <ul>
23529 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
23531 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
23533 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
23535 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
23536 no problem unless binary data written by one implementation is read by another.
23538 </ul>
23541 <p><!--para 1 -->
23542 <ul>
23543 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23544 </ul>
23547 <p><!--para 1 -->
23548 <ul>
23549 <li> The locations within #pragma directives where header name preprocessing tokens
23551 <li> How sequences in both forms of header names are mapped to headers or external
23553 <li> Whether the value of a character constant in a constant expression that controls
23554 conditional inclusion matches the value of the same character constant in the
23556 <li> Whether the value of a single-character character constant in a constant expression
23558 <li> The places that are searched for an included < > delimited header, and how the places
23562 <li> The method by which preprocessing tokens (possibly resulting from macro
23563 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
23564 <!--page 521 -->
23566 <li> Whether the # operator inserts a \ character before the \ character that begins a
23567 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
23568 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
23569 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
23571 </ul>
23574 <p><!--para 1 -->
23575 <ul>
23576 <li> Any library facilities available to a freestanding program, other than the minimal set
23578 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
23579 <li> The representation of the floating-point status flags stored by the
23581 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
23582 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
23586 <li> The types defined for float_t and double_t when the value of the
23588 <li> Domain errors for the mathematics functions, other than those required by this
23590 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
23591 <li> The values returned by the mathematics functions on underflow range errors, whether
23592 errno is set to the value of the macro ERANGE when the integer expression
23593 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
23594 floating-point exception is raised when the integer expression math_errhandling
23596 <li> Whether a domain error occurs or zero is returned when an fmod function has a
23598 <li> Whether a domain error occurs or zero is returned when a remainder function has
23600 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
23602 <!--page 522 -->
23603 <li> Whether a domain error occurs or zero is returned when a remquo function has a
23605 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
23606 of a signal handler, and, if not, the blocking of signals that is performed (<a href="#7.14.1.1">7.14.1.1</a>).
23608 <li> Whether the last line of a text stream requires a terminating new-line character
23610 <li> Whether space characters that are written out to a text stream immediately before a
23612 <li> The number of null characters that may be appended to data written to a binary
23614 <li> Whether the file position indicator of an append-mode stream is initially positioned at
23616 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
23621 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
23622 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
23624 <li> The effect if a file with the new name exists prior to a call to the rename function
23626 <li> Whether an open temporary file is removed upon abnormal program termination
23628 <li> Which changes of mode are permitted (if any), and under what circumstances
23630 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
23631 sequence printed for a NaN (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23632 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
23634 <li> The interpretation of a - character that is neither the first nor the last character, nor
23635 the second where a ^ character is the first, in the scanlist for %[ conversion in the
23636 fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23637 <!--page 523 -->
23638 <li> The set of sequences matched by a %p conversion and the interpretation of the
23639 corresponding input item in the fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23640 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
23641 functions on failure (<a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>).
23642 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
23643 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23645 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23646 function sets errno to ERANGE when underflow occurs (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23647 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
23648 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
23649 <li> Whether open streams with unwritten buffered data are flushed, open streams are
23650 closed, or temporary files are removed when the abort or _Exit function is called
23652 <li> The termination status returned to the host environment by the abort, exit, or
23653 _Exit function (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23654 <li> The value returned by the system function when its argument is not a null pointer
23657 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
23659 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
23660 functions in the "C" locale (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23661 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
23662 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
23663 </ul>
23666 <p><!--para 1 -->
23667 <ul>
23668 <li> The values or expressions assigned to the macros specified in the headers
23669 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.18"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>).
23670 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
23673 <!--page 524 -->
23674 </ul>
23677 <p><!--para 1 -->
23678 The following characteristics of a hosted environment are locale-specific and are required
23679 to be documented by the implementation:
23680 <ul>
23681 <li> Additional members of the source and execution character sets beyond the basic
23683 <li> The presence, meaning, and representation of additional multibyte characters in the
23685 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
23690 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
23691 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
23692 iswspace, or iswupper functions (<a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>,
23693 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>).
23695 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
23697 <li> The collation sequence of the execution character set (<a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>).
23698 <li> The contents of the error message strings set up by the strerror function
23700 <li> The formats for time and date (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23701 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
23702 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
23703 <!--page 525 -->
23704 </ul>
23707 <p><!--para 1 -->
23708 The following extensions are widely used in many systems, but are not portable to all
23709 implementations. The inclusion of any extension that may cause a strictly conforming
23710 program to become invalid renders an implementation nonconforming. Examples of such
23711 extensions are new keywords, extra library functions declared in standard headers, or
23712 predefined macros with names that do not begin with an underscore.
23715 <p><!--para 1 -->
23716 In a hosted environment, the main function receives a third argument, char *envp[],
23717 that points to a null-terminated array of pointers to char, each of which points to a string
23718 that provides information about the environment for this execution of the program
23722 <p><!--para 1 -->
23723 Characters other than the underscore _, letters, and digits, that are not part of the basic
23724 source character set (such as the dollar sign $, or characters in national character sets)
23728 <p><!--para 1 -->
23729 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
23732 <p><!--para 1 -->
23733 A function identifier, or the identifier of an object the declaration of which contains the
23737 <p><!--para 1 -->
23738 String literals are modifiable (in which case, identical string literals should denote distinct
23742 <p><!--para 1 -->
23743 Additional arithmetic types, such as __int128 or double double, and their
23744 appropriate conversions are defined (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1">6.3.1</a>). Additional floating types may have
23745 more range or precision than long double, may be used for evaluating expressions of
23746 other floating types, and may be used to define float_t or double_t.
23747 <!--page 526 -->
23750 <p><!--para 1 -->
23751 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
23753 <p><!--para 2 -->
23754 A pointer to a function may be cast to a pointer to an object or to void, allowing a
23755 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
23758 <p><!--para 1 -->
23759 A bit-field may be declared with a type other than _Bool, unsigned int, or
23763 <p><!--para 1 -->
23764 The fortran function specifier may be used in a function declaration to indicate that
23765 calls suitable for FORTRAN should be generated, or that a different representation for the
23769 <p><!--para 1 -->
23770 The asm keyword may be used to insert assembly language directly into the translator
23771 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
23772 <pre>
23773 asm ( character-string-literal );</pre>
23776 <p><!--para 1 -->
23777 There may be more than one external definition for the identifier of an object, with or
23778 without the explicit use of the keyword extern; if the definitions disagree, or more than
23782 <p><!--para 1 -->
23783 Macro names that do not begin with an underscore, describing the translation and
23784 execution environments, are defined by the implementation before translation begins
23788 <p><!--para 1 -->
23789 If any floating-point status flags are set on normal termination after all calls to functions
23790 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
23791 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
23792 <!--page 527 -->
23795 <p><!--para 1 -->
23796 Handlers for specific signals are called with extra arguments in addition to the signal
23799 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
23800 <p><!--para 1 -->
23802 <p><!--para 2 -->
23803 Additional file-opening modes may be specified by characters appended to the mode
23807 <p><!--para 1 -->
23808 The file position indicator is decremented by each successful call to the ungetc or
23809 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.19.7.11">7.19.7.11</a>,
23813 <p><!--para 1 -->
23814 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
23815 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
23817 <!--page 528 -->
23820 <ol>
23821 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
23822 published in The C Programming Language by Brian W. Kernighan and Dennis
23823 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
23824 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
23825 California, USA, November 1984.
23826 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
23827 Processing Systems, Information Processing Systems Technical Report.
23828 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
23829 Arithmetic.
23830 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
23831 Floating-Point Arithmetic.
23832 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
23833 second edition (previously designated IEC 559:1989).
23834 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
23835 symbols for use in the physical sciences and technology.
23836 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
23837 information interchange.
23838 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
23839 Fundamental terms.
23840 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
23841 <li> ISO 8601:1988, Data elements and interchange formats -- Information
23842 interchange -- Representation of dates and times.
23843 <li> ISO/IEC 9899:1990, Programming languages -- C.
23844 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
23845 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
23846 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
23847 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
23848 Interface (POSIX) -- Part 2: Shell and Utilities.
23849 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
23850 preparation of programming language standards.
23851 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
23852 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
23853 <!--page 529 -->
23854 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
23855 ISO/IEC 10646-1:1993.
23856 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
23857 ISO/IEC 10646-1:1993.
23858 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
23859 Transformation Format for 16 planes of group 00 (UTF-16).
23860 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
23861 Transformation Format 8 (UTF-8).
23862 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
23863 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
23864 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
23865 syllables.
23866 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
23867 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
23868 additional characters.
23869 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
23870 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
23871 Identifiers for characters.
23872 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
23873 Ethiopic.
23874 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
23875 Unified Canadian Aboriginal Syllabics.
23876 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
23877 Cherokee.
23878 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
23879 arithmetic -- Part 1: Integer and floating point arithmetic.
23880 <!--page 530 -->
23881 <!--page 531 -->
23882 </ol>
23885 <pre>
23886 ??? x ???, <a href="#3.18">3.18</a> , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
23888 ??? x ???, <a href="#3.19">3.19</a> - (subtraction operator), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
23889 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
23890 != (inequality operator), <a href="#6.5.9">6.5.9</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
23891 # operator, <a href="#6.10.3.2">6.10.3.2</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
23892 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
23893 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
23894 ## operator, <a href="#6.10.3.3">6.10.3.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
23896 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
23897 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
23898 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> / (division operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
23899 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
23900 #if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, // (comment delimiter), <a href="#6.4.9">6.4.9</a>
23901 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
23902 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
23903 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
23904 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
23906 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
23907 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
23908 #undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
23910 % (remainder operator), <a href="#6.5.5">6.5.5</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
23911 %: (alternative spelling of #), <a href="#6.4.6">6.4.6</a> <= (less-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a>
23912 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
23913 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>,
23914 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.26.1">7.26.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
23915 & (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
23916 & (bitwise AND operator), <a href="#6.5.10">6.5.10</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
23917 && (logical AND operator), <a href="#6.5.13">6.5.13</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>,
23919 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
23920 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
23921 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
23922 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
23923 ( ) (parentheses punctuator), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
23924 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
23925 * (asterisk punctuator), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>,
23926 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.9">F.9</a>, <a href="#J.5.17">J.5.17</a>
23927 * (multiplication operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
23928 *= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
23929 + (addition operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#7.15"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
23930 <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
23931 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
23932 ++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
23933 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>,
23934 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.18">7.18</a>, <a href="#7.26.8">7.26.8</a>
23936 <!--page 532 -->
23937 <a href="#7.19"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
23938 <a href="#7.20"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> __DATE__ macro, <a href="#6.10.8">6.10.8</a>
23939 <a href="#7.21"><string.h></a> header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a> __FILE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
23940 <a href="#7.22"><tgmath.h></a> header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
23941 <a href="#7.23"><time.h></a> header, <a href="#7.23">7.23</a> __LINE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
23942 <a href="#7.24"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, __STDC_, <a href="#6.11.9">6.11.9</a>
23943 <a href="#7.26.12">7.26.12</a>, <a href="#F">F</a> __STDC__ macro, <a href="#6.10.8">6.10.8</a>
23944 <a href="#7.25"><wctype.h></a> header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a> __STDC_CONSTANT_MACROS macro, <a href="#7.18.4">7.18.4</a>
23945 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_FORMAT_MACROS macro, <a href="#7.8.1">7.8.1</a>
23946 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8">6.10.8</a>
23947 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#F.1">F.1</a>
23949 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8">6.10.8</a>, <a href="#G.1">G.1</a>
23950 >> (right-shift operator), <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8">6.10.8</a>
23951 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIMIT_MACROS macro, <a href="#7.18.2">7.18.2</a>,
23954 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>
23955 [ ] (brackets punctuator), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_VERSION__ macro, <a href="#6.10.8">6.10.8</a>
23956 \ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> __TIME__ macro, <a href="#6.10.8">6.10.8</a>
23957 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
23958 \" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>
23959 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
23960 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
23961 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Complex_I macro, <a href="#7.3.1">7.3.1</a>
23962 \0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Exit function, <a href="#7.20.4.4">7.20.4.4</a>
23963 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
23964 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
23965 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
23966 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _IOFBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
23967 \f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _IOLBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.6">7.19.5.6</a>
23968 <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
23969 \n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
23970 <a href="#7.4.1.10">7.4.1.10</a> { } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>,
23972 <a href="#6.4.4.4">6.4.4.4</a> { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a>
23973 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, | (bitwise inclusive OR operator), <a href="#6.5.12">6.5.12</a>
23974 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> |= (bitwise inclusive OR assignment operator),
23975 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.5.16.2">6.5.16.2</a>
23976 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> || (logical OR operator), <a href="#6.5.14">6.5.14</a>
23977 \U (universal character names), <a href="#6.4.3">6.4.3</a> ~ (bitwise complement operator), <a href="#6.5.3.3">6.5.3.3</a>
23979 \v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>,
23983 ^ (bitwise exclusive OR operator), <a href="#6.5.11">6.5.11</a> complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
23984 ^= (bitwise exclusive OR assignment operator), integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.20.6.1">7.20.6.1</a>
23985 <a href="#6.5.16.2">6.5.16.2</a> real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a>
23988 <!--page 533 -->
23991 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.9.1.1">F.9.1.1</a> declarator, <a href="#6.7.5.2">6.7.5.2</a>
23993 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.9.2.1">F.9.2.1</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
23996 actual argument, <a href="#3.3">3.3</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
23997 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
23998 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
23999 addition operator (+), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
24000 <a href="#G.5.2">G.5.2</a> variable length, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24001 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24003 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
24004 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
24005 aggregate types, <a href="#6.2.5">6.2.5</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.9.1.2">F.9.1.2</a>
24006 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> asin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24007 aliasing, <a href="#6.5">6.5</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.9.2.2">F.9.2.2</a>
24008 alignment, <a href="#3.2">3.2</a> asinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24009 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asm keyword, <a href="#J.5.10">J.5.10</a>
24010 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> assert macro, <a href="#7.2.1.1">7.2.1.1</a>
24011 allocated storage, order and contiguity, <a href="#7.20.3">7.20.3</a> assert.h header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24015 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
24016 logical (&&), <a href="#6.5.13">6.5.13</a> operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>
24019 ANSI/IEEE 854, <a href="#F.1">F.1</a> asterisk punctuator (*), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a>
24020 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.9.1.3">F.9.1.3</a>
24021 argument, <a href="#3.3">3.3</a> atan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24022 array, <a href="#6.9.1">6.9.1</a> atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.9.1.4">F.9.1.4</a>
24023 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
24024 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.9.2.3">F.9.2.3</a>
24025 macro, substitution, <a href="#6.10.3.1">6.10.3.1</a> atanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24026 argument, complex, <a href="#7.3.9.1">7.3.9.1</a> atexit function, <a href="#7.20.4.2">7.20.4.2</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>,
24027 argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> <a href="#J.5.13">J.5.13</a>
24028 arithmetic constant expression, <a href="#6.6">6.6</a> atof function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.1">7.20.1.1</a>
24029 arithmetic conversions, usual, see usual arithmetic atoi function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24031 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24032 additive, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
24033 bitwise, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
24035 multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24036 shift, <a href="#6.5.7">6.5.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
24037 unary, <a href="#6.5.3.3">6.5.3.3</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24038 arithmetic types, <a href="#6.2.5">6.2.5</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
24040 <!--page 534 -->
24042 binary streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, calloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.1">7.20.3.1</a>, <a href="#7.20.3.2">7.20.3.2</a>,
24044 bit, <a href="#3.5">3.5</a> carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a>
24045 high order, <a href="#3.6">3.6</a> carg type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24046 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
24047 bit-field, <a href="#6.7.2.1">6.7.2.1</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a>
24048 bitand macro, <a href="#7.9">7.9</a> case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24052 AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24053 complement (~), <a href="#6.5.3.3">6.5.3.3</a> casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a>
24055 exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a>
24057 inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> cast expression, <a href="#6.5.4">6.5.4</a>
24059 blank character, <a href="#7.4.1.3">7.4.1.3</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
24060 block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24061 block scope, <a href="#6.2.1">6.2.1</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
24063 bold type convention, <a href="#6.1">6.1</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.9.4.1">F.9.4.1</a>
24065 boolean type, <a href="#6.3.1.2">6.3.1.2</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
24066 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24067 braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>, ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
24069 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.9.6.1">F.9.6.1</a>
24070 brackets punctuator ([ ]), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> ceil type-generic macro, <a href="#7.22">7.22</a>
24073 broken-down time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
24074 <a href="#7.23.3.1">7.23.3.1</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24075 bsearch function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a> cexp2 function, <a href="#7.26.1">7.26.1</a>
24076 btowc function, <a href="#7.24.6.1.1">7.24.6.1.1</a> cexpm1 function, <a href="#7.26.1">7.26.1</a>
24077 BUFSIZ macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.5">7.19.5.5</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>
24078 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24080 byte-oriented stream, <a href="#7.19.2">7.19.2</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24082 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24083 <a href="#C">C</a>++, <a href="#7.8.1">7.8.1</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.18.4">7.18.4</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
24084 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> character array initialization, <a href="#6.7.8">6.7.8</a>
24085 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
24086 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24088 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> character classification functions, <a href="#7.4.1">7.4.1</a>
24089 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
24090 calendar time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
24091 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24092 <!--page 535 -->
24093 character display semantics, <a href="#5.2.2">5.2.2</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24094 character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24098 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
24099 character type conversion, <a href="#6.3.1.1">6.3.1.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
24100 character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.8">6.7.8</a> compound statement, <a href="#6.8.2">6.8.2</a>
24101 cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
24102 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
24108 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
24109 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
24111 clock function, <a href="#7.23.2.1">7.23.2.1</a> conj functions, <a href="#7.3.9.3">7.3.9.3</a>, <a href="#G.6">G.6</a>
24112 clock_t type, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> conj type-generic macro, <a href="#7.22">7.22</a>
24113 CLOCKS_PER_SEC macro, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
24114 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
24115 type-generic macro for, <a href="#7.22">7.22</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.7.4">F.7.4</a>
24117 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
24119 collating sequences, <a href="#5.2.1">5.2.1</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24122 comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, integer, <a href="#6.4.4.1">6.4.4.1</a>
24123 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
24124 command processor, <a href="#7.20.4.6">7.20.4.6</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
24125 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
24126 comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> contiguity of allocated storage, <a href="#7.20.3">7.20.3</a>
24128 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.6">F.6</a>
24129 common real type, <a href="#6.3.1.8">6.3.1.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
24131 comparison functions, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a>, <a href="#7.20.5.2">7.20.5.2</a> conversion, <a href="#6.3">6.3</a>
24136 compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
24137 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
24138 complement operator (~), <a href="#6.5.3.3">6.5.3.3</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
24140 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
24141 complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a> explicit, <a href="#6.3">6.3</a>
24143 complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#G">G</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
24144 <!--page 536 -->
24145 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24146 function parameter, <a href="#6.9.1">6.9.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
24148 imaginary and complex, <a href="#G.4.3">G.4.3</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
24150 lvalues, <a href="#6.3.2.1">6.3.2.1</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
24151 pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24152 real and complex, <a href="#6.3.1.7">6.3.1.7</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
24153 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24154 real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctgamma function, <a href="#7.26.1">7.26.1</a>
24155 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> ctime function, <a href="#7.23.3.2">7.23.3.2</a>
24156 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24160 conversion functions data stream, see streams
24161 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
24163 restartable, <a href="#7.24.6.3">7.24.6.3</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24164 multibyte/wide string, <a href="#7.20.8">7.20.8</a> DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24165 restartable, <a href="#7.24.6.4">7.24.6.4</a> DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24166 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24167 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24168 single byte/wide character, <a href="#7.24.6.1">7.24.6.1</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24170 wide character, <a href="#7.24.5">7.24.5</a> DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24171 conversion specifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24173 conversion state, <a href="#7.20.7">7.20.7</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.24.6.2.1">7.24.6.2.1</a>, decimal digit, <a href="#5.2.1">5.2.1</a>
24174 <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4">7.24.6.4</a>, decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24175 <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24176 conversion state functions, <a href="#7.24.6.2">7.24.6.2</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.5">F.5</a>
24180 copysign functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, pointer, <a href="#6.7.5.1">6.7.5.1</a>
24185 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.9.1.5">F.9.1.5</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.5">6.7.5</a>
24186 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
24187 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.9.2.4">F.9.2.4</a> increment and decrement
24188 cosh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
24189 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> default initialization, <a href="#6.7.8">6.7.8</a>
24190 type-generic macro for, <a href="#7.22">7.22</a> default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24191 cproj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> define preprocessing directive, <a href="#6.10.3">6.10.3</a>
24192 cproj type-generic macro, <a href="#7.22">7.22</a> defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a>
24193 creal functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> definition, <a href="#6.7">6.7</a>
24194 creal type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> function, <a href="#6.9.1">6.9.1</a>
24195 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> derived declarator types, <a href="#6.2.5">6.2.5</a>
24196 <!--page 537 -->
24197 derived types, <a href="#6.2.5">6.2.5</a> end-of-file indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>,
24198 designated initializer, <a href="#6.7.8">6.7.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>,
24199 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.2">7.19.10.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24201 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file macro, see EOF macro
24203 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
24204 difftime function, <a href="#7.23.2.2">7.23.2.2</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
24205 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> enumerated type, <a href="#6.2.5">6.2.5</a>
24206 digraphs, <a href="#6.4.6">6.4.6</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
24207 direct input/output functions, <a href="#7.19.8">7.19.8</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24208 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
24209 div function, <a href="#7.20.6.2">7.20.6.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
24211 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24212 division operator (/), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
24214 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
24215 domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, environment list, <a href="#7.20.4.5">7.20.4.5</a>
24216 <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, environmental considerations, <a href="#5.2">5.2</a>
24217 <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.19.2">7.19.2</a>,
24218 <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.4">7.19.4.4</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.4.2">7.20.4.2</a>,
24219 <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> <a href="#7.24.2.1">7.24.2.1</a>
24220 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.2">7.19.5.2</a>,
24221 double _Complex type, <a href="#6.2.5">6.2.5</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.11">7.19.6.11</a>,
24222 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.4">7.19.7.4</a>,
24223 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>,
24224 double _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.4">7.24.2.4</a>,
24225 double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
24226 <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.24.3.4">7.24.3.4</a>, <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.24.6.1.2">7.24.6.1.2</a>
24227 double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a>
24229 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> equality expressions, <a href="#6.5.9">6.5.9</a>
24230 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
24231 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>,
24232 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, see
24233 also range error
24234 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.9.5.1">F.9.5.1</a>
24236 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.9.5.2">F.9.5.2</a>
24237 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, erfc type-generic macro, <a href="#7.22">7.22</a>
24238 see also encoding error errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>,
24239 element type, <a href="#6.2.5">6.2.5</a> <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.4">7.19.10.4</a>,
24240 elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24241 ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a> <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>,
24242 else preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, <a href="#J.5.17">J.5.17</a>
24243 else statement, <a href="#6.8.4.1">6.8.4.1</a> errno.h header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24245 encoding error, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, domain, see domain error
24246 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> encoding, see encoding error
24248 <!--page 538 -->
24249 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
24250 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
24251 error indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.18">7.18</a>
24252 <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.8">7.19.7.8</a>, extended multibyte/wide character conversion
24253 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.3">7.19.10.3</a>, utilities, <a href="#7.24.6">7.24.6</a>
24254 <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a> extensible wide character case mapping functions,
24255 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.25.3.2">7.25.3.2</a>
24256 error-handling functions, <a href="#7.19.10">7.19.10</a>, <a href="#7.21.6.2">7.21.6.2</a> extensible wide character classification functions,
24258 escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
24259 evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a> external definition, <a href="#6.9">6.9</a>
24260 evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.7.5">F.7.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
24262 exceptional condition, <a href="#6.5">6.5</a>, <a href="#7.12.1">7.12.1</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
24263 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external object definitions, <a href="#6.9.2">6.9.2</a>
24265 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.9.4.2">F.9.4.2</a>
24266 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24268 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fclose function, <a href="#7.19.5.1">7.19.5.1</a>
24269 executable program, <a href="#5.1.1.1">5.1.1.1</a> fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.9.9.1">F.9.9.1</a>
24270 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
24271 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
24273 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a> FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24274 exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a>, FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24275 <a href="#7.20.4.4">7.20.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24276 EXIT_FAILURE macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24277 EXIT_SUCCESS macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24278 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.9.3.1">F.9.3.1</a> FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24279 exp type-generic macro, <a href="#7.22">7.22</a> FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24280 exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.9.3.2">F.9.3.2</a> FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24281 exp2 type-generic macro, <a href="#7.22">7.22</a> FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24282 explicit conversion, <a href="#6.3">6.3</a> feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a>
24283 expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.9.3.3">F.9.3.3</a> fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24284 expm1 type-generic macro, <a href="#7.22">7.22</a> fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a>
24285 exponent part, <a href="#6.4.4.2">6.4.4.2</a> fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a>
24286 exponential functions feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>,
24287 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24288 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a> fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24289 expression, <a href="#6.5">6.5</a> FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.7">F.7</a>, <a href="#F.8">F.8</a>,
24293 full, <a href="#6.8">6.8</a> feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a>
24294 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
24295 parenthesized, <a href="#6.5.1">6.5.1</a> fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a>
24296 primary, <a href="#6.5.1">6.5.1</a> fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a>
24297 unary, <a href="#6.5.3">6.5.3</a> fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a>
24298 expression statement, <a href="#6.8.3">6.8.3</a> fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a>
24299 extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a> feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24300 <!--page 539 -->
24301 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a>
24302 fflush function, <a href="#7.19.5.2">7.19.5.2</a>, <a href="#7.19.5.3">7.19.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.9.6.2">F.9.6.2</a>
24303 fgetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, floor type-generic macro, <a href="#7.22">7.22</a>
24304 <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.8.1">7.19.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24305 fgetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24306 fgets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.2">7.19.7.2</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.8.6.4">6.8.6.4</a>,
24307 fgetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.12">7.12</a>
24309 fgetws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.2">7.24.3.2</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24310 field width, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24312 access functions, <a href="#7.19.5">7.19.5</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24314 operations, <a href="#7.19.4">7.19.4</a> FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24315 position indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24316 <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24317 <a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.2">7.19.9.2</a>, FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24318 <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.1">7.24.3.1</a>, fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.9.10.1">F.9.10.1</a>
24319 <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.10">7.24.3.10</a> fma type-generic macro, <a href="#7.22">7.22</a>
24320 positioning functions, <a href="#7.19.9">7.19.9</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.9.9.2">F.9.9.2</a>
24321 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fmax type-generic macro, <a href="#7.22">7.22</a>
24322 FILE type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.9.9.3">F.9.9.3</a>
24323 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
24324 flags, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.9.7.1">F.9.7.1</a>
24325 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
24327 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> FOPEN_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.3">7.19.4.3</a>
24328 float _Complex type, <a href="#6.2.5">6.2.5</a> for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a>
24329 float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24330 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24332 float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a> formal argument (deprecated), <a href="#3.15">3.15</a>
24333 float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, formal parameter, <a href="#3.15">3.15</a>
24334 <a href="#6.3.1.8">6.3.1.8</a> formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.19.6">7.19.6</a>
24335 float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>, wide character, <a href="#7.24.2">7.24.2</a>
24337 float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> forward reference, <a href="#3.11">3.11</a>
24338 floating constant, <a href="#6.4.4.2">6.4.4.2</a> FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see
24339 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
24340 floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, FP_FAST_FMA macro, <a href="#7.12">7.12</a>
24342 floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a> FP_FAST_FMAL macro, <a href="#7.12">7.12</a>
24343 floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>, FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24344 <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24345 floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24346 floating-point classification functions, <a href="#7.12.3">7.12.3</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24347 floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24348 floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.7">F.7</a>, <a href="#F.7.6">F.7.6</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24349 floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.9">F.9</a> FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24350 floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
24351 floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>
24352 <!--page 540 -->
24353 fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, language, <a href="#6.11">6.11</a>
24354 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.6">7.19.6.6</a>, library, <a href="#7.26">7.26</a>
24355 <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a> fwide function, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24356 fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.3">7.19.7.3</a>, fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
24357 <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.8.2">7.19.8.2</a> <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.5">7.24.2.5</a>,
24358 fputs function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.4">7.19.7.4</a> <a href="#7.24.2.11">7.24.2.11</a>
24359 fputwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.3">7.24.3.3</a>, fwrite function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.2">7.19.8.2</a>
24360 <a href="#7.24.3.8">7.24.3.8</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24361 fputws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.4">7.24.3.4</a> <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.10">7.24.3.10</a>
24363 free function, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a>
24364 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, general utilities, <a href="#7.20">7.20</a>
24366 freopen function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.4">7.19.5.4</a> general wide string utilities, <a href="#7.24.4">7.24.4</a>
24367 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.9.3.4">F.9.3.4</a> generic parameters, <a href="#7.22">7.22</a>
24368 frexp type-generic macro, <a href="#7.22">7.22</a> getc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>
24369 fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, getchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.6">7.19.7.6</a>
24370 <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#F.3">F.3</a> getenv function, <a href="#7.20.4.5">7.20.4.5</a>
24371 fseek function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, gets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.26.9">7.26.9</a>
24372 <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.10">7.24.3.10</a> getwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.6">7.24.3.6</a>, <a href="#7.24.3.7">7.24.3.7</a>
24373 fsetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, getwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.7">7.24.3.7</a>
24374 <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.24.3.10">7.24.3.10</a> gmtime function, <a href="#7.23.3.3">7.23.3.3</a>
24375 ftell function, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a>
24377 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
24378 fully buffered stream, <a href="#7.19.3">7.19.3</a> greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a>
24379 function
24380 argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
24381 body, <a href="#6.9.1">6.9.1</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
24383 library, <a href="#7.1.4">7.1.4</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24384 declarator, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.11.6">6.11.6</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
24385 definition, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a> hexadecimal-character escape sequence
24386 designator, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
24388 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24389 name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> horizontal-tab escape sequence (\r), <a href="#7.25.2.1.3">7.25.2.1.3</a>
24390 parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
24391 prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>
24392 <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a> hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a>
24393 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.5.2">6.7.5.2</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24394 recursive call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24395 return, <a href="#6.8.6.4">6.8.6.4</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24396 scope, <a href="#6.2.1">6.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24397 type, <a href="#6.2.5">6.2.5</a> HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24398 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24400 function type, <a href="#6.2.5">6.2.5</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
24401 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> real, <a href="#7.12.5">7.12.5</a>, <a href="#F.9.2">F.9.2</a>
24402 function-like macro, <a href="#6.10.3">6.10.3</a> hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.9.4.3">F.9.4.3</a>
24404 <!--page 541 -->
24405 <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> initial position, <a href="#5.2.2">5.2.2</a>
24406 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> initial shift state, <a href="#5.2.1.2">5.2.1.2</a>
24407 linkage, see linkage initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.8">6.7.8</a>,
24410 reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> initializer, <a href="#6.7.8">6.7.8</a>
24415 IEC 559, <a href="#F.1">F.1</a> input failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>
24416 IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8">6.10.8</a>, <a href="#7.3.3">7.3.3</a>, <a href="#7.6">7.6</a>, input/output functions
24417 <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>, <a href="#H.1">H.1</a> character, <a href="#7.19.7">7.19.7</a>
24423 if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, input/output header, <a href="#7.19">7.19</a>
24424 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
24425 if statement, <a href="#6.8.4.1">6.8.4.1</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
24426 ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24428 ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a> INT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
24429 ilogb type-generic macro, <a href="#7.22">7.22</a> INT_FASTN_MIN macros, <a href="#7.18.2.3">7.18.2.3</a>
24430 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> int_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
24432 imaginary type domain, <a href="#G.2">G.2</a> INT_LEASTN_MIN macros, <a href="#7.18.2.2">7.18.2.2</a>
24434 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24435 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
24436 imaxdiv_t type, <a href="#7.8">7.8</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
24438 implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>, integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
24439 <a href="#6.7.5">6.7.5</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental integer constant, <a href="#6.4.4.1">6.4.4.1</a>
24441 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
24442 implementation-defined value, <a href="#3.17.1">3.17.1</a> integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
24443 implicit conversion, <a href="#6.3">6.3</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>,
24444 implicit initialization, <a href="#6.7.8">6.7.8</a> <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>
24445 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
24446 inclusive OR operators integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24448 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.18">7.18</a>
24449 incomplete type, <a href="#6.2.5">6.2.5</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.18">7.18</a>
24450 increment operators, see arithmetic operators, interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24452 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
24453 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> interrupt, <a href="#5.2.3">5.2.3</a>
24454 inequality operator (!=), <a href="#6.5.9">6.5.9</a> INTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
24455 INFINITY macro, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
24456 <!--page 542 -->
24457 INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a> iswalpha function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24458 intmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24459 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> iswblank function, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24460 INTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> iswcntrl function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.4">7.25.2.1.4</a>,
24461 INTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24462 INTN_MIN macros, <a href="#7.18.2.1">7.18.2.1</a> iswctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
24463 intN_t types, <a href="#7.18.1.1">7.18.1.1</a> iswdigit function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24464 INTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a> <a href="#7.25.2.1.5">7.25.2.1.5</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24465 INTPTR_MIN macro, <a href="#7.18.2.4">7.18.2.4</a> iswgraph function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24466 intptr_t type, <a href="#7.18.1.4">7.18.1.4</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24467 inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a> iswlower function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>,
24468 isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24469 isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a> iswprint function, <a href="#7.25.2.1.6">7.25.2.1.6</a>, <a href="#7.25.2.1.8">7.25.2.1.8</a>,
24471 iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>, iswpunct function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24472 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24473 isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24474 <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a> iswspace function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24475 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24476 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24477 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24478 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>,
24479 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24480 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> iswxdigit function, <a href="#7.25.2.1.12">7.25.2.1.12</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24481 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
24482 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
24483 islower function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.2.1">7.4.2.1</a>, iteration statements, <a href="#6.8.5">6.8.5</a>
24485 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jmp_buf type, <a href="#7.13">7.13</a>
24488 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
24489 ISO 8601, <a href="#2">2</a>, <a href="#7.23.3.5">7.23.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
24490 ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8">6.10.8</a>
24491 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.4">7.19.4.4</a>
24492 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
24493 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> labeled statement, <a href="#6.8.1">6.8.1</a>
24496 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
24497 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> syntax summary, <a href="#A">A</a>
24498 ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24499 <a href="#7.4.1.11">7.4.1.11</a> LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24500 isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>,
24501 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>
24502 <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a> LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7">7.20.7</a>,
24503 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.20.8">7.20.8</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>,
24504 isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24505 <a href="#7.4.2.2">7.4.2.2</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24506 iswalnum function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24507 <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3.5">7.23.3.5</a>
24508 <!--page 543 -->
24509 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
24510 LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv function, <a href="#7.20.6.2">7.20.6.2</a>
24512 LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24514 LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24516 LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a>
24517 LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint type-generic macro, <a href="#7.22">7.22</a>
24518 LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a>
24519 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.9.3.6">F.9.3.6</a> llround type-generic macro, <a href="#7.22">7.22</a>
24522 ldiv_t type, <a href="#7.20">7.20</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
24523 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24524 left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a> localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24525 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
24527 external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.9.3.7">F.9.3.7</a>
24528 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log type-generic macro, <a href="#7.22">7.22</a>
24529 identifier, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.9.3.8">F.9.3.8</a>
24530 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 type-generic macro, <a href="#7.22">7.22</a>
24531 length function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.24.4.6.1">7.24.4.6.1</a>, log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.9.3.9">F.9.3.9</a>
24533 length modifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.9.3.10">F.9.3.10</a>
24536 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
24537 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a>
24538 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.11">F.9.3.11</a>
24539 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.9.5.3">F.9.5.3</a> logb type-generic macro, <a href="#7.22">7.22</a>
24541 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a> AND (&&), <a href="#6.5.13">6.5.13</a>
24545 use of functions, <a href="#7.1.4">7.1.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
24547 limits <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24549 implementation, see implementation limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
24550 numerical, see numerical limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
24551 translation, see translation limits <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a>
24552 limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
24553 line buffered stream, <a href="#7.19.3">7.19.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24554 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24555 line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24556 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.19.2">7.19.2</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24557 preprocessing directive, <a href="#6.10">6.10</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24558 linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
24559 <a href="#6.11.2">6.11.2</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
24560 <!--page 544 -->
24561 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> mbsinit function, <a href="#7.24.6.2.1">7.24.6.2.1</a>
24562 long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, mbsrtowcs function, <a href="#7.24.6.4.1">7.24.6.4.1</a>
24563 <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> mbstate_t type, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24564 long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6">7.24.6</a>,
24565 LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.6.2.1">7.24.6.2.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24566 LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.20.8.1">7.20.8.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24567 longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.20.4.3">7.20.4.3</a> mbtowc function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.20.7.2">7.20.7.2</a>, <a href="#7.20.8.1">7.20.8.1</a>,
24569 low-order bit, <a href="#3.6">3.6</a> member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
24571 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a> memchr function, <a href="#7.21.5.1">7.21.5.1</a>
24572 lrint type-generic macro, <a href="#7.22">7.22</a> memcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.1">7.21.4.1</a>
24573 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a> memcpy function, <a href="#7.21.2.1">7.21.2.1</a>
24574 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
24575 lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a> memory management functions, <a href="#7.20.3">7.20.3</a>
24577 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a>
24583 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.9.3.12">F.9.3.12</a>
24586 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
24587 macro preprocessor, <a href="#6.10">6.10</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24589 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
24590 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>, extended, <a href="#7.24.6">7.24.6</a>
24592 malloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.3">7.20.3.3</a>, wide string, <a href="#7.20.8">7.20.8</a>
24597 matching failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a> extended, <a href="#7.24.6">7.24.6</a>
24598 math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>, restartable, <a href="#7.24.6.3">7.24.6.3</a>
24599 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
24600 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24601 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
24602 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
24603 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> multiplication operator (*), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
24604 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7.2">7.20.7.2</a>, multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24606 MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a> n-char sequence, <a href="#7.20.1.3">7.20.1.3</a>
24607 mblen function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a> n-wchar sequence, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24609 mbrtowc function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
24610 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, file, <a href="#7.19.3">7.19.3</a>
24611 <a href="#7.24.6.4.1">7.24.6.4.1</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24612 <!--page 545 -->
24618 nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.9.8.2">F.9.8.2</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
24619 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.20.4.6">7.20.4.6</a>
24621 nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, operator, <a href="#6.4.6">6.4.6</a>
24623 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
24624 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.9.6">F.9.6</a> associativity, <a href="#6.5">6.5</a>
24626 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24627 new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> postfix, <a href="#6.5.2">6.5.2</a>
24628 new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, precedence, <a href="#6.5">6.5</a>
24629 <a href="#7.4.1.10">7.4.1.10</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
24630 nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, relational, <a href="#6.5.8">6.5.8</a>
24633 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.8.4">F.9.8.4</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
24636 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> bitwise exclusive (^), <a href="#6.5.11">6.5.11</a>
24637 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
24638 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
24639 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
24643 null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> order of evaluation, <a href="#6.5">6.5</a>
24644 padding of binary stream, <a href="#7.19.2">7.19.2</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
24645 NULL macro, <a href="#7.11">7.11</a>, <a href="#7.17">7.17</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, orientation of stream, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24646 <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> outer scope, <a href="#6.2.1">6.2.1</a>
24649 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
24650 null statement, <a href="#6.8.3">6.8.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
24651 null wide character, <a href="#7.1.1">7.1.1</a> structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
24652 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> parameter, <a href="#3.15">3.15</a>
24653 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> array, <a href="#6.9.1">6.9.1</a>
24654 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> ellipsis, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24655 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
24658 object representation, <a href="#6.2.6.1">6.2.6.1</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24660 object-like macro, <a href="#6.10.3">6.10.3</a> parentheses punctuator (( )), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
24661 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.26">7.26</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
24663 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> permitted form of initializer, <a href="#6.6">6.6</a>
24664 <!--page 546 -->
24665 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
24666 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> primary expression, <a href="#6.5.1">6.5.1</a>
24667 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> printf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.10">7.19.6.10</a>
24668 placemarker, <a href="#6.10.3.3">6.10.3.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
24669 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> printing wide character, <a href="#7.25.2">7.25.2</a>
24670 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
24671 pointer comparison, <a href="#6.5.8">6.5.8</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
24672 pointer declarator, <a href="#6.7.5.1">6.7.5.1</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
24673 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> program image, <a href="#5.1.1.2">5.1.1.2</a>
24674 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
24675 pointer type, <a href="#6.2.5">6.2.5</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24676 pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24677 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program structure, <a href="#5.1.1.1">5.1.1.1</a>
24678 portability, <a href="#4">4</a>, <a href="#J">J</a> program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>,
24680 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
24681 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> program, strictly conforming, <a href="#4">4</a>
24682 postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> promotions
24683 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
24684 postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
24685 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.9.4.4">F.9.4.4</a> prototype, see function prototype
24686 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
24688 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> PTRDIFF_MIN macro, <a href="#7.18.3">7.18.3</a>
24689 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a> ptrdiff_t type, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24690 pp-number, <a href="#6.4.8">6.4.8</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24692 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> putc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.7.9">7.19.7.9</a>
24693 precedence of operators, <a href="#6.5">6.5</a> putchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.9">7.19.7.9</a>
24694 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> puts function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.10">7.19.7.10</a>
24695 precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> putwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>
24696 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> putwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.9">7.24.3.9</a>
24698 prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qsort function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.2">7.20.5.2</a>
24699 prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qualified types, <a href="#6.2.5">6.2.5</a>
24700 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
24701 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
24702 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24704 preprocessing operators raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.20.4.1">7.20.4.1</a>
24705 #, <a href="#6.10.3.2">6.10.3.2</a> rand function, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.2.2">7.20.2.2</a>
24706 ##, <a href="#6.10.3.3">6.10.3.3</a> RAND_MAX macro, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>
24708 defined, <a href="#6.10.1">6.10.1</a> excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
24709 preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a> range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>,
24710 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>,
24711 preprocessor, <a href="#6.10">6.10</a> <a href="#7.12.6.6">7.12.6.6</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>,
24712 PRIcFASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>,
24713 PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>,
24714 PRIcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>,
24716 <!--page 547 -->
24718 real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, save calling environment function, <a href="#7.13.1">7.13.1</a>
24719 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> scalar types, <a href="#6.2.5">6.2.5</a>
24720 real floating types, <a href="#6.2.5">6.2.5</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24721 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
24722 real types, <a href="#6.2.5">6.2.5</a> scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24723 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
24724 realloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> scanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.11">7.19.6.11</a>
24725 recommended practice, <a href="#3.16">3.16</a> scanlist, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24726 recursion, <a href="#6.5.2.2">6.5.2.2</a> scanset, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24727 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24728 redefinition of macro, <a href="#6.10.3">6.10.3</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24729 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
24732 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
24734 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
24736 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.9.7">F.9.7</a> string, <a href="#7.21.5">7.21.5</a>
24737 remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, utility, <a href="#7.20.5">7.20.5</a>
24739 remainder operator (%), <a href="#6.5.5">6.5.5</a> SEEK_CUR macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24740 remainder type-generic macro, <a href="#7.22">7.22</a> SEEK_END macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24741 remove function, <a href="#7.19.4.1">7.19.4.1</a>, <a href="#7.19.4.4">7.19.4.4</a> SEEK_SET macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24742 remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.9.7.3">F.9.7.3</a> selection statements, <a href="#6.8.4">6.8.4</a>
24743 remquo type-generic macro, <a href="#7.22">7.22</a> self-referential structure, <a href="#6.7.2.3">6.7.2.3</a>
24744 rename function, <a href="#7.19.4.2">7.19.4.2</a> semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
24745 representations of types, <a href="#6.2.6">6.2.6</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24747 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> separate translation, <a href="#5.1.1.1">5.1.1.1</a>
24748 reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.8">6.8</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.19.6">7.19.6</a>,
24749 restartable multibyte/wide character conversion <a href="#7.20.5">7.20.5</a>, <a href="#7.24.2">7.24.2</a>, <a href="#C">C</a>
24751 restartable multibyte/wide string conversion setbuf function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.5">7.19.5.5</a>
24752 functions, <a href="#7.24.6.4">7.24.6.4</a> setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
24753 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
24754 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24755 restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> setvbuf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>,
24756 return statement, <a href="#6.8.6.4">6.8.6.4</a> <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24757 rewind function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.5">7.19.9.5</a>, shall, <a href="#4">4</a>
24759 right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a> shift sequence, <a href="#7.1.1">7.1.1</a>
24760 right-shift operator (>>), <a href="#6.5.7">6.5.7</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
24761 rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.4">F.9.6.4</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
24762 rint type-generic macro, <a href="#7.22">7.22</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24763 round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.9.6.6">F.9.6.6</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24764 round type-generic macro, <a href="#7.22">7.22</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24765 rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24768 <!--page 548 -->
24769 side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
24770 SIG_ATOMIC_MAX macro, <a href="#7.18.3">7.18.3</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
24771 SIG_ATOMIC_MIN macro, <a href="#7.18.3">7.18.3</a> space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>,
24772 sig_atomic_t type, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.18.3">7.18.3</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>
24773 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.19.6.6">7.19.6.6</a>, <a href="#7.19.6.13">7.19.6.13</a>
24774 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.4.5">F.9.4.5</a>
24775 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt type-generic macro, <a href="#7.22">7.22</a>
24776 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.20.4.1">7.20.4.1</a> srand function, <a href="#7.20.2.2">7.20.2.2</a>
24777 SIGFPE macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.5.17">J.5.17</a> sscanf function, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.14">7.19.6.14</a>
24778 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> standard error stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.10.4">7.19.10.4</a>
24779 SIGINT macro, <a href="#7.14">7.14</a> standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a>
24780 sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24781 sign bit, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24782 signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.20.4.4">7.20.4.4</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24783 signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a> <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24784 signal handling functions, <a href="#7.14.1">7.14.1</a> <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24785 signal.h header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a> <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24786 signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a> <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24787 signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24788 signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24789 signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24790 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24791 signed character, <a href="#6.3.1.1">6.3.1.1</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24792 signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>,
24793 signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#J.5.17">J.5.17</a>
24795 signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24796 significand part, <a href="#6.4.4.2">6.4.4.2</a> <a href="#7.15"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24797 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> <a href="#7.16"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24798 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.17"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24799 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
24800 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.9.1.6">F.9.1.6</a> <a href="#7.18"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>,
24801 sin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#7.26.8">7.26.8</a>
24802 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#7.19"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a>
24803 single-byte/wide character conversion functions, <a href="#7.20"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a>
24804 <a href="#7.24.6.1">7.24.6.1</a> <a href="#7.21"><string.h></a>, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24805 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.22"><tgmath.h></a>, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24806 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.23"><time.h></a>, <a href="#7.23">7.23</a>
24807 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.9.2.5">F.9.2.5</a> <a href="#7.24"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>,
24809 SIZE_MAX macro, <a href="#7.18.3">7.18.3</a> <a href="#7.25"><wctype.h></a>, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
24810 size_t type, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.1">7.19.1</a>, standard input stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24811 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.23.1">7.23.1</a>, standard integer types, <a href="#6.2.5">6.2.5</a>
24812 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> standard output stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24813 sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> standard signed integer types, <a href="#6.2.5">6.2.5</a>
24814 snprintf function, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.12">7.19.6.12</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.20.7">7.20.7</a>
24816 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> break, <a href="#6.8.6.3">6.8.6.3</a>
24818 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
24820 <!--page 549 -->
24828 labeled, <a href="#6.8.1">6.8.1</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.8">6.7.8</a>
24830 return, <a href="#6.8.6.4">6.8.6.4</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a>
24833 switch, <a href="#6.8.4.2">6.8.4.2</a> string.h header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24834 while, <a href="#6.8.5.1">6.8.5.1</a> stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
24835 static storage duration, <a href="#6.2.4">6.2.4</a> strlen function, <a href="#7.21.6.3">7.21.6.3</a>
24836 static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a> strncat function, <a href="#7.21.3.2">7.21.3.2</a>
24837 static, in array declarators, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.5.3">6.7.5.3</a> strncmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.4">7.21.4.4</a>
24838 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a> strncpy function, <a href="#7.21.2.4">7.21.2.4</a>
24839 stdbool.h header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a> strpbrk function, <a href="#7.21.5.4">7.21.5.4</a>
24840 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> strrchr function, <a href="#7.21.5.5">7.21.5.5</a>
24841 stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, strspn function, <a href="#7.21.5.6">7.21.5.6</a>
24842 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a> strstr function, <a href="#7.21.5.7">7.21.5.7</a>
24843 stderr macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24844 stdin macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a>
24845 <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.7">7.24.3.7</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24846 stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>, strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
24848 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24849 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24850 stdout macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.3">7.19.6.3</a>, strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24851 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>, <a href="#7.24.2.11">7.24.2.11</a>, <a href="#7.24.3.9">7.24.3.9</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24852 storage duration, <a href="#6.2.4">6.2.4</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24853 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24854 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24855 strcat function, <a href="#7.21.3.1">7.21.3.1</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
24858 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.5">7.21.4.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24860 strcspn function, <a href="#7.21.5.3">7.21.5.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
24861 streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.20.4.3">7.20.4.3</a> initialization, <a href="#6.7.8">6.7.8</a>
24864 orientation, <a href="#7.19.2">7.19.2</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
24865 standard error, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24866 standard input, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
24867 standard output, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24868 unbuffered, <a href="#7.19.3">7.19.3</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
24869 strerror function, <a href="#7.19.10.4">7.19.10.4</a>, <a href="#7.21.6.2">7.21.6.2</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.5">7.21.4.5</a>
24870 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.5">7.23.3.5</a>, subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24871 <a href="#7.24.5.1">7.24.5.1</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
24872 <!--page 550 -->
24873 subtraction operator (-), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
24875 floating constant, <a href="#6.4.4.2">6.4.4.2</a> towctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24876 integer constant, <a href="#6.4.4.1">6.4.4.1</a> towlower function, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24877 switch body, <a href="#6.8.4.2">6.8.4.2</a> towupper function, <a href="#7.25.3.1.2">7.25.3.1.2</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24878 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
24879 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
24880 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
24881 swprintf function, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.7">7.24.2.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
24882 swscanf function, <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.8">7.24.2.8</a> trap representation, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.2.3">6.3.2.3</a>,
24885 syntax notation, <a href="#6.1">6.1</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
24886 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.9.1">F.9.1</a>
24887 syntax summary, language, <a href="#A">A</a> trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a>
24890 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> trunc type-generic macro, <a href="#7.22">7.22</a>
24891 tag compatibility, <a href="#6.2.7">6.2.7</a> truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24893 tags, <a href="#6.7.2.3">6.7.2.3</a> two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
24894 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.9.1.7">F.9.1.7</a> type category, <a href="#6.2.5">6.2.5</a>
24895 tan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type conversion, <a href="#6.3">6.3</a>
24896 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.9.2.6">F.9.2.6</a> type definitions, <a href="#6.7.7">6.7.7</a>
24897 tanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
24900 text streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
24901 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.9.5.4">F.9.5.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
24902 tgamma type-generic macro, <a href="#7.22">7.22</a> type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24903 tgmath.h header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> typedef declaration, <a href="#6.7.7">6.7.7</a>
24905 broken down, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.1">7.23.3.1</a>, types, <a href="#6.2.5">6.2.5</a>
24906 <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> character, <a href="#6.7.8">6.7.8</a>
24907 calendar, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a>
24908 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
24910 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
24913 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
24914 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
24917 tm structure type, <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> UINT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
24918 TMP_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
24919 tmpfile function, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.20.4.3">7.20.4.3</a> UINT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
24920 tmpnam function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
24921 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24922 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
24923 token pasting, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
24924 <!--page 551 -->
24925 uintmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24926 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>,
24927 UINTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a>
24928 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
24931 uintptr_t type, <a href="#7.18.1.4">7.18.1.4</a> va_arg macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
24932 ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
24933 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
24934 ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
24935 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
24936 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> va_copy macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
24938 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.3">7.15.1.3</a>,
24939 unary operators, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
24940 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
24941 unbuffered stream, <a href="#7.19.3">7.19.3</a> <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
24942 undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
24943 <a href="#7.1.4">7.1.4</a> va_list type, <a href="#7.15">7.15</a>, <a href="#7.15.1.3">7.15.1.3</a>
24944 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> va_start macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>,
24945 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>,
24946 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>,
24947 ungetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>,
24948 <a href="#7.19.9.3">7.19.9.3</a> <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
24949 ungetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.10">7.24.3.10</a> value, <a href="#3.17">3.17</a>
24952 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
24953 content, <a href="#6.7.2.3">6.7.2.3</a> variable length array, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24954 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> variably modified type, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24955 initialization, <a href="#6.7.8">6.7.8</a> vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24956 member alignment, <a href="#6.7.2.1">6.7.2.1</a> vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24958 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> vfprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>
24959 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> vfscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>
24960 specifier, <a href="#6.7.2.1">6.7.2.1</a> vfwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.5">7.24.2.5</a>
24961 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> vfwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.3.10">7.24.3.10</a>
24962 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
24965 unqualified version of type, <a href="#6.2.5">6.2.5</a> void function parameter, <a href="#6.7.5.3">6.7.5.3</a>
24966 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>
24967 unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
24968 unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
24969 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> volatile type qualifier, <a href="#6.7.3">6.7.3</a>
24970 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
24971 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> vprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>
24972 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.11">7.19.6.11</a>
24973 unspecified value, <a href="#3.17.3">3.17.3</a> vsnprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.12">7.19.6.12</a>
24974 uppercase letter, <a href="#5.2.1">5.2.1</a> vsprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.13">7.19.6.13</a>
24975 use of library functions, <a href="#7.1.4">7.1.4</a> vsscanf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.14">7.19.6.14</a>
24976 <!--page 552 -->
24977 vswprintf function, <a href="#7.24.2.7">7.24.2.7</a> wctype.h header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
24978 vswscanf function, <a href="#7.24.2.8">7.24.2.8</a> wctype_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
24979 vwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a> WEOF macro, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.6">7.24.3.6</a>,
24980 vwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.3.10">7.24.3.10</a> <a href="#7.24.3.7">7.24.3.7</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>, <a href="#7.24.3.10">7.24.3.10</a>,
24983 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>, white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
24985 WCHAR_MAX macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> white-space characters, <a href="#6.4">6.4</a>
24986 WCHAR_MIN macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> wide character, <a href="#3.7.3">3.7.3</a>
24987 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.8">6.7.8</a>, case mapping functions, <a href="#7.25.3.1">7.25.3.1</a>
24988 <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, extensible, <a href="#7.25.3.2">7.25.3.2</a>
24989 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> classification functions, <a href="#7.25.2.1">7.25.2.1</a>
24990 wcrtomb function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
24991 <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
24992 wcscat function, <a href="#7.24.4.3.1">7.24.4.3.1</a> formatted input/output functions, <a href="#7.24.2">7.24.2</a>
24993 wcschr function, <a href="#7.24.4.5.1">7.24.4.5.1</a> input functions, <a href="#7.19.1">7.19.1</a>
24994 wcscmp function, <a href="#7.24.4.4.1">7.24.4.4.1</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> input/output functions, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3">7.24.3</a>
24995 wcscoll function, <a href="#7.24.4.4.2">7.24.4.4.2</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> output functions, <a href="#7.19.1">7.19.1</a>
24996 wcscpy function, <a href="#7.24.4.2.1">7.24.4.2.1</a> single-byte conversion functions, <a href="#7.24.6.1">7.24.6.1</a>
24997 wcscspn function, <a href="#7.24.4.5.2">7.24.4.5.2</a> wide string, <a href="#7.1.1">7.1.1</a>
24998 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.5.1">7.24.5.1</a> wide string comparison functions, <a href="#7.24.4.4">7.24.4.4</a>
24999 wcslen function, <a href="#7.24.4.6.1">7.24.4.6.1</a> wide string concatenation functions, <a href="#7.24.4.3">7.24.4.3</a>
25000 wcsncat function, <a href="#7.24.4.3.2">7.24.4.3.2</a> wide string copying functions, <a href="#7.24.4.2">7.24.4.2</a>
25001 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
25002 wcsncpy function, <a href="#7.24.4.2.2">7.24.4.2.2</a> wide string miscellaneous functions, <a href="#7.24.4.6">7.24.4.6</a>
25003 wcspbrk function, <a href="#7.24.4.5.3">7.24.4.5.3</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
25005 wcsrtombs function, <a href="#7.24.6.4.2">7.24.6.4.2</a> wide string search functions, <a href="#7.24.4.5">7.24.4.5</a>
25006 wcsspn function, <a href="#7.24.4.5.5">7.24.4.5.5</a> wide-oriented stream, <a href="#7.19.2">7.19.2</a>
25008 wcstod function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a> WINT_MAX macro, <a href="#7.18.3">7.18.3</a>
25009 wcstod function, <a href="#7.24.4.1.1">7.24.4.1.1</a> WINT_MIN macro, <a href="#7.18.3">7.18.3</a>
25010 wcstof function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wint_t type, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>,
25012 wcstok function, <a href="#7.24.4.5.7">7.24.4.5.7</a> wmemchr function, <a href="#7.24.4.5.8">7.24.4.5.8</a>
25013 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wmemcmp function, <a href="#7.24.4.4.5">7.24.4.4.5</a>
25015 wcstold function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wmemmove function, <a href="#7.24.4.2.4">7.24.4.2.4</a>
25016 wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemset function, <a href="#7.24.4.6.2">7.24.4.6.2</a>
25017 wcstombs function, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.4">7.24.6.4</a> wprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.11">7.24.2.11</a>
25018 wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
25024 wctomb function, <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.3">7.24.6.3</a>
25028 </pre>
25029 </body></html>