return tracebackPCs(&u, 0, stk)
	}
	n := 0
	systemstack(func() {
		n = TracebackSystemstack(stk, i-1)
	})
	return n
}

func KeepNArenaHints(n int) {
	hint := mheap_.arenaHints
	for i := 1; i < n; i++ {
		hint = hint.next
		if hint == nil {
			return
		}
	}
	hint.next = nil
}