stddef.h(0p) — Linux manual page

stddef.h(0P)            POSIX Programmer's Manual           stddef.h(0P)

PROLOG

       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.

NAME

       stddef.h — standard type definitions

SYNOPSIS

       #include <stddef.h>

DESCRIPTION

       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.

APPLICATION USAGE

       None.

RATIONALE

       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.

FUTURE DIRECTIONS

       None.

SEE ALSO

       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)

COPYRIGHT

       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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