C Library - <stddef.h>

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Introduction

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
1ptrdiff_t
This is the signed integral type and is the result of subtracting two pointers.
2size_t
This is the unsigned integral type and is the result of the sizeof keyword.
3wchar_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
1NULL
This macro is the value of a null pointer constant.
2offsetof(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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