стандартные определения типов (standard type definitions)
Пролог (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.
Имя (Name)
stddef.h — standard type definitions
Синопсис (Synopsis)
#include <stddef.h>
Описание (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.
Использование в приложениях (Application usage)
None.
Обоснование (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.
Будущие направления (Future directions)
None.
Смотри также (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)
