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PROLOG | NAME | SYNOPSIS | DESCRIPTION | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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stddef.h(0P) POSIX Programmer's Manual stddef.h(0P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
stddef.h — standard type definitions
#include <stddef.h>
The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The <stddef.h> header shall define the following macros:
NULL Null pointer constant. The macro shall expand to an
integer constant expression with the value 0 cast to
type void *.
offsetof(type, member-designator)
Integer constant expression of type size_t, the value of
which is the offset in bytes to the structure member
(member-designator), from the beginning of its structure
(type).
The <stddef.h> header shall define the following types:
ptrdiff_t Signed integer type of the result of subtracting two
pointers.
wchar_t Integer type whose range of values can represent
distinct codes for all members of the largest extended
character set specified among the supported locales; the
null character shall have the code value zero. Each
member of the basic character set shall have a code
value equal to its value when used as the lone character
in an integer character constant if an implementation
does not define __STDC_MB_MIGHT_NEQ_WC__.
size_t Unsigned integer type of the result of the sizeof
operator.
The implementation shall support one or more programming
environments in which the widths of ptrdiff_t, size_t, and wchar_t
are no greater than the width of type long. The names of these
programming environments can be obtained using the confstr()
function or the getconf utility.
The following sections are informative.
None.
The ISO C standard does not require the NULL macro to include the
cast to type void * and specifies that the NULL macro be
implementation-defined. POSIX.1‐2008 requires the cast and
therefore need not be implementation-defined.
None.
sys_types.h(0p), wchar.h(0p)
The System Interfaces volume of POSIX.1‐2017, confstr(3p)
The Shell and Utilities volume of POSIX.1‐2017, getconf(1p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 stddef.h(0P)
Pages that refer to this page: inttypes.h(0p), locale.h(0p), math.h(0p), monetary.h(0p), ndbm.h(0p), stdint.h(0p), stdio.h(0p), stdlib.h(0p), string.h(0p), time.h(0p), unistd.h(0p), wchar.h(0p), wctype.h(0p), wordexp.h(0p), wcstoimax(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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