1stddef.h(0P) POSIX Programmer's Manual stddef.h(0P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 stddef.h — standard type definitions
14
16 #include <stddef.h>
17
19 The functionality described on this reference page is aligned with the
20 ISO C standard. Any conflict between the requirements described here
21 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
22 defers to the ISO C standard.
23 The <stddef.h> header shall define the following macros:
25 NULL Null pointer constant. The macro shall expand to an integer
27 constant expression with the value 0 cast to type void *.
28 offsetof(type, member-designator)
30 Integer constant expression of type size_t, the value of
31 which is the offset in bytes to the structure member (member-
32 designator), from the beginning of its structure (type).
33 The <stddef.h> header shall define the following types:
35 ptrdiff_t Signed integer type of the result of subtracting two point‐
37 ers.
38 wchar_t Integer type whose range of values can represent distinct
40 codes for all members of the largest extended character set
41 specified among the supported locales; the null character
42 shall have the code value zero. Each member of the basic
43 character set shall have a code value equal to its value when
44 used as the lone character in an integer character constant
45 if an implementation does not define
46 __STDC_MB_MIGHT_NEQ_WC__.
47 size_t Unsigned integer type of the result of the sizeof operator.
49 The implementation shall support one or more programming environments
51 in which the widths of ptrdiff_t, size_t, and wchar_t are no greater
52 than the width of type long. The names of these programming environ‐
53 ments can be obtained using the confstr() function or the getconf util‐
54 ity.
55 The following sections are informative.
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59 None.
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62 The ISO C standard does not require the NULL macro to include the cast
63 to type void * and specifies that the NULL macro be implementation-
64 defined. POSIX.1‐2008 requires the cast and therefore need not be
65 implementation-defined.
66
68 None.
69
71 <sys_types.h>, <wchar.h>
72 The System Interfaces volume of POSIX.1‐2008, confstr()
74 The Shell and Utilities volume of POSIX.1‐2008, getconf
76
78 Portions of this text are reprinted and reproduced in electronic form
79 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
80 -- Portable Operating System Interface (POSIX), The Open Group Base
81 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
82 cal and Electronics Engineers, Inc and The Open Group. (This is
83 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
84 event of any discrepancy between this version and the original IEEE and
85 The Open Group Standard, the original IEEE and The Open Group Standard
86 is the referee document. The original Standard can be obtained online
87 at http://www.unix.org/online.html .
88 Any typographical or formatting errors that appear in this page are
90 most likely to have been introduced during the conversion of the source
91 files to man page format. To report such errors, see https://www.ker‐
92 nel.org/doc/man-pages/reporting_bugs.html .
93IEEE/The Open Group 2013 stddef.h(0P)