#define pb_arraysize(st, m) (pb_membersize(st, m) / pb_membersize(st, m[0]))
#define pb_delta(st, m1, m2) ((int)offsetof(st, m1) - (int)offsetof(st, m2))
#define pb_delta_end(st, m1, m2) (offsetof(st, m1) - offsetof(st, m2) - pb_membersize(st, m2))
#define pb_arraysize(st, m) (pb_membersize(st, m) / pb_membersize(st, m[0]))
#define pb_delta(st, m1, m2) ((int)offsetof(st, m1) - (int)offsetof(st, m2))
#define pb_delta_end(st, m1, m2) (offsetof(st, m1) - offsetof(st, m2) - pb_membersize(st, m2))