C Library - <stddef.h>-alljchome-开发者的教程家园

The C Standard Library

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C Library - <stddef.h>

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 −

Sr.No.	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.

Sr.No.

Variable & Description

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 sizeof keyword.

wchar_t

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

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

Sr.No.	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.