Miscellaneous types and constants

Names specified for `<stddef.h>`, “Miscellaneous types and constants”
Name	Description	Notes				Source	Availability
`max_align_t`	Type with maximum alignment requirement	L			T	`<stddef.h>`					C11
`NULL`	Null pointer constant	L		M		Headers	C89	C90	C95	C99	C11
`offsetof()`	Determine structure-member position	L		M	(·)	`<stddef.h>`	C89	C90	C95	C99	C11
`ptrdiff_t`	Implementation-defined pointer-difference type	H			T	`<stddef.h>`	C89	C90	C95	C99	C11
`rsize_t`	Implementation-defined size type with implied run-time constraints	L	?		T	Headers					C11
`size_t`	Implementation-defined size type	H			T	Headers	C89	C90	C95	C99	C11
`wchar_t`	Wide-character type	H			T	Headers			C95	C99	C11

This header is available in C89, C90, C95, C99 and C11.

The header <stddef.h> declares a few miscellaneous types and constants used by other headers.