Gcc/10.2.0/gcc/Offsetof
From Get docs
Next: __sync Builtins, Previous: Vector Extensions, Up: C Extensions [Contents][Index]
6.53 Support for offsetof
GCC implements for both C and C++ a syntactic extension to implement
the offsetof
macro.
primary: "__builtin_offsetof" "(" typename "," offsetof_member_designator ")" offsetof_member_designator: identifier | offsetof_member_designator "." identifier | offsetof_member_designator "[" expr "]"
This extension is sufficient such that
#define offsetof(type, member) __builtin_offsetof (type, member)
is a suitable definition of the offsetof
macro. In C++, type
may be dependent. In either case, member
may consist of a single
identifier, or a sequence of member accesses and array references.