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



NAME
       stddef.h - standard type definitions

SYNOPSIS
       #include <stddef.h>

DESCRIPTION
       The <stddef.h> header shall define the following macros:

       NULL   Null pointer constant.

       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 wide-character codes for  all  members  of  the  largest
              character  set  specified  among  the locales supported by the compilation environment: the null character has the
              code value 0 and each member of the portable character set has a code value equal to its value when  used  as  the
              lone character in an integer character constant.

       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
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <wchar.h>, <sys/types.h>, the System Interfaces volume of IEEE Std 1003.1-2001, confstr(), the Shell and Utilities volume
       of IEEE Std 1003.1-2001, getconf

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                <stddef.h>(0P)