C Library - <stddef.h>


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

Library Variables

Following are the variable types defined in the header stddef.h −

S.N. Variable & Description
1 ptrdiff_t

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

2 size_t

This is the unsigned integral type and is the result of the sizeof keyword.

3 wchar_t

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

Library Macros

Following are the macros defined in the header stddef.h −

S.N. Macro & Description
1

NULL

This macro is the value of a null pointer constant.

2

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 by member-designator, and the name of the structure is given in type.



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