The <stddef.h> header shall define the following macros:
Null pointer constant.
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:
Signed integer type of the result of subtracting two
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.
Unsigned integer type of the result of the sizeof
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
The following sections are informative.
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, Copyright (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.opengroup.org/unix/online.html