// Use a new goroutine so that we get a small stack.
	c := make(chan int)
	go func() {
		c <- int(C.returnAfterGrowFromGo())
	}()
	if got, want := <-c, 129*128/2; got != want {
		t.Errorf("got %d want %d", got, want)
	}
}

//export goReturnVal
func goReturnVal() (r C.int) {
	// Force a stack copy.
	var f func(int) int
	f = func(i int) int {
		var buf [256]byte
		use(buf[:])
		if i == 0 {