#### A.5.4 Structure Field Offset Measurement

You can use `offsetof` to measure the location within a structure type of a particular structure member.

— Macro: size_t offsetof (type, member)

> Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

> This expands to an integer constant expression that is the offset of the structure member named member in the structure type type. For example, `offsetof (struct s, elem)` is the offset, in bytes, of the member `elem` in a `struct s`.

> This macro won't work if member is a bit field; you get an error from the C compiler in that case.