Visual Studio 6.0

Retrieves the offset of a member from the beginning of its parent structure.

size_t offsetof( structName, memberName );

Routine Required Header Compatibility
offsetof <stddef.h> ANSI, Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.


LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version

Return Value

offsetof returns the offset in bytes of the specified member from the beginning of its parent data structure. It is undefined for bit fields.



Name of the parent data structure


Name of the member in the parent data structure for which to determine the offset


The offsetof macro returns the offset in bytes of memberName from the beginning of the structure specified by structName. You can specify types with the struct keyword.

Note   offsetof is not a function and cannot be described using a C prototype.