and is not guaranteed to be the same from one iteration to the next.
If a map entry that has not yet been reached is removed during iteration,
the corresponding iteration value will not be produced. If a map entry is
created during iteration, that entry may be produced during the iteration or
may be skipped. The choice may vary for each entry created and from one
iteration to the next.

func testCallbackGC(t *testing.T) {
	nestedCall(runtime.GC)
}

func testCallbackPanic(t *testing.T) {
	// Make sure panic during callback unwinds properly.
	if lockedOSThread() {
		t.Fatal("locked OS thread on entry to TestCallbackPanic")
	}
	defer func() {
		s := recover()
		if s == nil {
			t.Fatal("did not panic")
		}
		if s.(string) != "callback panic" {
			t.Fatal("wrong panic:", s)
		}
		if lockedOSThread() {

pkg debug/plan9obj, type File struct, embedded FileHeader
pkg debug/plan9obj, type FileHeader struct
pkg debug/plan9obj, type FileHeader struct, Bss uint32
pkg debug/plan9obj, type FileHeader struct, Entry uint64
pkg debug/plan9obj, type FileHeader struct, Magic uint32
pkg debug/plan9obj, type FileHeader struct, PtrSize int
pkg debug/plan9obj, type Section struct
pkg debug/plan9obj, type Section struct, embedded SectionHeader