9.10 Common Definitions (<stddef.h>)

The <stddef.h> header file defines several types and macros, some of which are also defined in other header files.

ptrdiff

A signed integral type of the result of subtracting two pointers.

size_t

An unsigned integral type of the result of the sizeof operator.

wchar_t

An integral type whose range of values can represent distinct codes for all members of the largest extended character set specified among the supported locales.

Macros

NULL

Expands to an implementation-defined null pointer constant.

offsetof(type, member-designator)

Expands to an integral constant expression that has type size_t and a value that is the offset, in bytes, to the structure member (specified by member-designator) from the beginning of its structure (specified by type). The member-designator is such that the expression &(t.member-designator) evaluates to an address constant given the following:

static type t;

If the specified member is a bit field, the behavior is undefined.

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