OFFSETOF(3)            FreeBSD Library Functions Manual            OFFSETOF(3)

NAME
     offsetof - offset of a structure member

SYNOPSIS
     #include <stddef.h>

     size_t
     offsetof(type, member);

DESCRIPTION
     The offsetof() macro expands to an integer constant expression of type
     size_t and yields the offset, in bytes, of the field member from the
     start of the structure type.

     A compiler error will result if member is not aligned to a byte boundary
     (i.e. it is a bit-field).

STANDARDS
     The offsetof() macro conforms to ANSI X3.159-1989 ("ANSI C89").

FreeBSD 13.1-RELEASE-p6        February 18, 2010       FreeBSD 13.1-RELEASE-p6