xenial (7) stddef.h.7posix.gz

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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.1‐2008 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>, <wchar.h>

       The System Interfaces volume of POSIX.1‐2008, confstr()

       The Shell and Utilities volume of POSIX.1‐2008, getconf


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .