Standard library header <stddef.h>

 

C

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Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Strings library

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Numerics

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

Standard Library headers

<assert.h> <complex.h> (C99) <ctype.h> <errno.h> <fenv.h> (C99) <float.h> <inttypes.h> (C99)     <iso646.h> (C95) <limits.h> <locale.h> <math.h>

<setjmp.h> <signal.h> <stdalign.h> (C11*) <stdarg.h> <stdatomic.h> (C11)     <stdbit.h> (C23) <stdbool.h> (C99*) <stdckdint.h> (C23) <stddef.h> <stdint.h> (C99) <stdio.h>

<stdlib.h> <stdmchar.h> (C29) <stdnoreturn.h> (C11*) <string.h> <tgmath.h> (C99) <threads.h> (C11) <time.h> <uchar.h> (C11) <wchar.h> (C95) <wctype.h> (C95)

 

This header is part of types support library, in particular, it provides additional basic types and convenience macros.

Types
ptrdiff_t	signed integer type returned when subtracting two pointers (typedef)
nullptr_t (C23)	the type of the predefined null pointer constant nullptr (typedef)
max_align_t (C11)	a type with alignment requirement as great as any other scalar type (typedef)
size_t	unsigned integer type returned by the sizeof operator (typedef)
Constants
NULL	implementation-defined null pointer constant (macro constant)
Macros
offsetof	byte offset from the beginning of a struct type to specified member (function macro)

Synopsis

#define __STDC_VERSION_STDDEF_H__ 202311L
 
typedef /* see description */ ptrdiff_t;
typedef /* see description */ nullptr_t;
typedef /* see description */ max_align_t;
typedef /* see description */ wchar_t;
typedef /* see description */ size_t;
 
#define NULL /* see description */
#define unreachable() /* see description */
#define offsetof(P, D) /* see description */

Only if the implementation defines __STDC_LIB_EXT1__ and additionally the user code defines __STDC_WANT_LIB_EXT1__ before any inclusion of <stddef.h>:

#if defined(__STDC_WANT_LIB_EXT1__)
typedef /* see description */ rsize_t;
#endif