C standard library stddef.h

The stddef.h header defines various variable types and macros. Many of these definitions also appear in other headers.

Library Variables

ptrdiff_t

This is the signed integral type and is the result of subtracting two pointers.

size_t

This is the unsigned integral type and is the result of the sizeofkeyword.

wchar_t

This is an integral type of the size of a wide character constant.

Library Macros

NULL

This macro is the value of a null pointer constant.

offsetof(type, member-designator)

This results in a constant integer of type size_t which is the offset in bytes of a structure member from the beginning of the structure. The member is given bymember-designator, and the name of the structure is given in type.