MARK
#define MARK(F, M) (((F)->mark |= M), (F)->level = our_tag)
#define MARK 258
#define MARK 0x80000000
#define MARK 0x020 /* this message is a mark */
#define MARK(K) {}
#undef MARK
#define MARK(K) {\
#define MARK(K) {\