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.
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| 2 |
size_t
This is the unsigned integral type and is the result of the sizeof keyword.
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| 3 |
wchar_t
This is an integral type of the size of a wide character constant.
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Library Macros
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.
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| 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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