Matthew Dempsky <******@****.***> 1646087539 -0800

import (
	"sync/atomic"
	"unsafe"
)

var one interface{} = 1

type eface struct {
	typ  unsafe.Pointer
	data unsafe.Pointer
}

func f(c chan struct{}) {
	var x atomic.Value

	go func() {
		x.Swap(one) // writing using the old marker
	}()
	for i := 0; i < 100000; i++ {
		v := x.Load() // reading using the new marker

		p := (*eface)(unsafe.Pointer(&v)).typ
		if uintptr(p) == ^uintptr(0) {

	// otherwise. A slot is still in use until *both* the tail
	// index has moved beyond it and typ has been set to nil. This
	// is set to nil atomically by the consumer and read
	// atomically by the producer.
	vals []eface
}

type eface struct {
	typ, val unsafe.Pointer
}

const dequeueBits = 32

// dequeueLimit is the maximum size of a poolDequeue.
//
// This must be at most (1<<dequeueBits)/2 because detecting fullness

	verifyGCInfo(t, "bss BigStruct", &bssBigStruct, infoBigStruct())
	verifyGCInfo(t, "bss string", &bssString, infoString)
	verifyGCInfo(t, "bss slice", &bssSlice, infoSlice)
	verifyGCInfo(t, "bss eface", &bssEface, infoEface)
	verifyGCInfo(t, "bss iface", &bssIface, infoIface)

	verifyGCInfo(t, "data Ptr", &dataPtr, infoPtr)
	verifyGCInfo(t, "data ScalarPtr", &dataScalarPtr, infoScalarPtr)

func TestEmbeddedMethod(t *testing.T) {
	const src = `package p; type I interface { error }`
	pkg := mustTypecheck(src, nil, nil)

	// get original error.Error method
	eface := Universe.Lookup("error")
	orig, _, _ := LookupFieldOrMethod(eface.Type(), false, nil, "Error")
	if orig == nil {
		t.Fatalf("original error.Error not found")
	}

	// get embedded error.Error method
	iface := pkg.Scope().Lookup("I")

// poolDequeue testing.
type PoolDequeue interface {
	PushHead(val any) bool
	PopHead() (any, bool)
	PopTail() (any, bool)
}

func NewPoolDequeue(n int) PoolDequeue {
	d := &poolDequeue{
		vals: make([]eface, n),
	}
	// For testing purposes, set the head and tail indexes close
	// to wrapping around.
	d.headTail.Store(d.pack(1<<dequeueBits-500, 1<<dequeueBits-500))
	return d
}

func TestEmbeddedMethod(t *testing.T) {
	const src = `package p; type I interface { error }`
	pkg := mustTypecheck(src, nil, nil)

	// get original error.Error method
	eface := Universe.Lookup("error")
	orig, _, _ := LookupFieldOrMethod(eface.Type(), false, nil, "Error")
	if orig == nil {
		t.Fatalf("original error.Error not found")
	}

	// get embedded error.Error method
	iface := pkg.Scope().Lookup("I")

		# "0x429d6c <runtime.gopark+284>", so
		# chop at first space.
		pc = int(str(pc).split(None, 1)[0], 16)
	return pc


#
#  For reference, this is what we're trying to do:
#  eface: p *(*(struct 'runtime.rtype'*)'main.e'->type_->data)->string
#  iface: p *(*(struct 'runtime.rtype'*)'main.s'->tab->Type->data)->string
#
# interface types can't be recognized by their name, instead we check

// It returns the zero Value if v is nil.
func (v Value) Elem() Value {
	k := v.kind()
	switch k {
	case abi.Interface:
		var eface any
		if v.typ().NumMethod() == 0 {
			eface = *(*any)(v.ptr)
		} else {
			eface = (any)(*(*interface {
				M()
			})(v.ptr))
		}
		x := unpackEface(eface)
		if x.flag != 0 {
			x.flag |= v.flag.ro()
		}
		return x
	case abi.Pointer:
		ptr := v.ptr

	{"runtime.panicdottypeE", 1},
	{"runtime.panicdottypeI", 1},
	{"runtime.panicnildottype", 1},
	{"runtime.typeAssert", 1},
	{"runtime.interfaceSwitch", 1},
	{"runtime.ifaceeq", 1},
	{"runtime.efaceeq", 1},
	{"runtime.panicrangestate", 1},
	{"runtime.deferrangefunc", 1},
	{"runtime.rand32", 1},
	{"runtime.makemap64", 1},
	{"runtime.makemap", 1},
	{"runtime.makemap_small", 1},
	{"runtime.mapaccess1", 1},