offsetof
# define offsetof(type, member) ((size_t) &((type *)0)->member)
#define offsetof(type, member) __offsetof(type, member)
#define offsetof(type, field) ((size_t)(&((type *)0)->field))
#define offsetof(type, member) ((size_t)(&((type *)0)->member))
#define offsetof(TYPE, MEM) ((size_t)&((TYPE*)0)->MEM)
#define offsetof(type, field) __offsetof(type, field)
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)