Type support

 

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

 

Type support

size_t

ptrdiff_t

NULL

max_align_t (C11)

offsetof

Numeric limits

Fixed width integer types (C99)

 

Basic types

Additional basic types and convenience macros

Defined in header <stddef.h>
size_t	unsigned integer type returned by the sizeof operator (typedef)
ptrdiff_t	signed integer type returned when subtracting two pointers (typedef)
NULL	implementation-defined null pointer constant (macro constant)
max_align_t (C11)	a type with alignment requirement as great as any other scalar type (typedef)
offsetof	byte offset from the beginning of a struct type to specified member (function macro)
Defined in header <stdbool.h>
bool (C99)	convenience macro, expands to _Bool (keyword macro)
true (C99)	expands to integer constant 1 (until C23)((_Bool)+1u) (since C23) (macro constant)
false (C99)	expands to integer constant 0 (until C23)((_Bool)+0u) (since C23) (macro constant)
__bool_true_false_are_defined (C99)	expands to integer constant 1 (macro constant)
Defined in header <stdalign.h>
alignas (C11)	convenience macro, expands to keyword _Alignas (keyword macro)
alignof (C11)	convenience macro, expands to keyword _Alignof (keyword macro)
__alignas_is_defined (C11)	expands to integer constant 1 (macro constant)
__alignof_is_defined (C11)	expands to integer constant 1 (macro constant)
Defined in header <stdnoreturn.h>
noreturn (C11)	convenience macro, expands to _Noreturn (keyword macro)

Notes

The type of true and false is int rather than _Bool.

(since C99) (until C23)

A program may undefine and perhaps then redefine the macros bool, true and false. However, such ability is a deprecated feature.

(since C99)

Example

Run this code

#include <stdio.h>
#include <stdbool.h>
#include <stdalign.h>
 
int main(void)
{
    printf("%d %d %d\n", true && false, true || false, !false);
    printf("%zu\n", alignof(char));
}

Output:

0 1 1
1

References

• C17 standard (ISO/IEC 9899:2018):

• 7.15 Alignment <stdalign.h> (p: 196)

• 7.18 Boolean type and values <stdbool.h> (p: 210)

• 7.19 Common definitions <stddef.h> (p: 211)

• 7.23 _Noreturn <stdnoreturn.h> (p: 263)

• 7.31.9 Boolean type and values <stdbool.h> (p: 332)

• C11 standard (ISO/IEC 9899:2011):

• 7.15 Alignment <stdalign.h> (p: 268)

• 7.18 Boolean type and values <stdbool.h> (p: 287)

• 7.19 Common definitions <stddef.h> (p: 288)

• 7.23 _Noreturn <stdnoreturn.h> (p: 361)

• 7.31.9 Boolean type and values <stdbool.h> (p: 456)

• C99 standard (ISO/IEC 9899:1999):

• 7.18 Boolean type and values <stdbool.h> (p: 253)

• 7.19 Common definitions <stddef.h> (p: 254)

• 7.26.7 Boolean type and values <stdbool.h> (p: 401)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.1.5 Common definitions <stddef.h>