func createStackTraceElements(tObj *heap.Object, frame *rtda.Frame) []*StackTraceElement {
	thread := frame.Thread()
	depth := thread.StackDepth()

	// skip unrelated frames
	i := uint(1)
	for k := tObj.Class(); k != nil; k = k.SuperClass() {
		i++
	}
	if thread.TopFrameN(i).Method().Name() == "<athrow>" {
		i++
	}

	stes := make([]*StackTraceElement, 0, depth)
	for ; i < depth; i++ {
		frameN := thread.TopFrameN(i)
		methodN := frameN.Method()
		classN := methodN.Class()
		if classN.Name() != "~shim" { // skip shim frame
			lineNumber := methodN.GetLineNumber(frameN.NextPC() - 1)
			ste := &StackTraceElement{
				declaringClass: classN.NameJlsFormat(),
				methodName:     methodN.Name(),
				fileName:       classN.SourceFile(),
				lineNumber:     lineNumber,
			}
			stes = append(stes, ste)
		}
	}

	return stes
}

// Object[] -> []interface{}
func convertArgs(this, argArr *heap.Object, method *heap.Method) []interface{} {
	if method.ArgSlotCount() == 0 {
		return nil
	}
	if method.ArgSlotCount() == 1 && !method.IsStatic() {
		return []interface{}{this}
	}

	argObjs := argArr.Refs()
	argTypes := method.ParsedDescriptor().ParameterTypes()

	args := make([]interface{}, method.ArgSlotCount())
	j := 0
	if !method.IsStatic() {
		args[0] = this
		j = 1
	}

	for i, argType := range argTypes {
		argObj := argObjs[i]

		if argType.IsBaseType() {
			// todo
			unboxed := box.Unbox(argObj, argType.Descriptor())
			args[i+j] = unboxed
			if argType.IsLongOrDouble() {
				j++
			}
		} else {
			args[i+j] = argObj
		}
	}

	return args
}

func _getGoField(fieldObj *heap.Object) *heap.Field {
	extra := fieldObj.Extra()
	if extra != nil {
		return extra.(*heap.Field)
	}

	root := fieldObj.GetFieldValue("root", "Ljava/lang/reflect/Field;").(*heap.Object)
	return root.Extra().(*heap.Field)
}

func checkArrayCopy(src, dest *heap.Object) bool {
	srcClass := src.Class()
	destClass := dest.Class()

	if !srcClass.IsArray() || !destClass.IsArray() {
		return false
	}
	if srcClass.IsPrimitiveArray() || destClass.IsPrimitiveArray() {
		return srcClass == destClass
	}
	return true
}

func _casObj(obj *heap.Object, fields []interface{}, offset int64, expected, newVal *heap.Object) bool {
	// todo
	obj.LockState()
	defer obj.UnlockState()

	current := _getObj(fields, offset)
	if current == expected {
		fields[offset] = newVal
		return true
	} else {
		return false
	}
}

func (self *Thread) HandleUncaughtException(ex *heap.Object) {
	self.stack.clear()
	sysClass := heap.BootLoader().LoadClass("java/lang/System")
	sysErr := sysClass.GetStaticValue("out", "Ljava/io/PrintStream;").(*heap.Object)
	printStackTrace := ex.Class().GetInstanceMethod("printStackTrace", "(Ljava/io/PrintStream;)V")

	// call ex.printStackTrace(System.err)
	newFrame := self.NewFrame(printStackTrace)
	vars := newFrame.localVars
	vars.SetRef(0, ex)
	vars.SetRef(1, sysErr)
	self.PushFrame(newFrame)

	//
	// printString := sysErr.Class().GetInstanceMethod("print", "(Ljava/lang/String;)V")
	// newFrame = self.NewFrame(printString)
	// vars = newFrame.localVars
	// vars.SetRef(0, sysErr)
	// vars.SetRef(1, JString("Exception in thread \"main\" ", newFrame))
	// self.PushFrame(newFrame)
}

func _extraThread(threadObj *heap.Object) *rtda.Thread {
	threadObj.RLockState()
	defer threadObj.RUnlockState()

	extra := threadObj.Extra()
	if extra == nil {
		return nil
	} else {
		return extra.(*rtda.Thread)
	}
}

func _getGoMethod(methodObj *heap.Object, isConstructor bool) *heap.Method {
	extra := methodObj.Extra()
	if extra != nil {
		return extra.(*heap.Method)
	}

	if isConstructor {
		root := methodObj.GetFieldValue("root", "Ljava/lang/reflect/Constructor;").(*heap.Object)
		return root.Extra().(*heap.Method)
	} else {
		root := methodObj.GetFieldValue("root", "Ljava/lang/reflect/Method;").(*heap.Object)
		return root.Extra().(*heap.Method)
	}
}

func Unbox(obj *heap.Object, primitiveDescriptor string) interface{} {
	return obj.GetFieldValue("value", primitiveDescriptor)
}

func _getPath(fileObj *heap.Object) string {
	pathStr := fileObj.GetFieldValue("path", "Ljava/lang/String;").(*heap.Object)
	return rtda.GoString(pathStr)
}

// todo
func isAppClassLoader(loader *heap.Object) bool {
	return loader.Class().Name() == "sun/misc/Launcher$AppClassLoader"
}

// java.lang.String -> go string
func GoString(jStr *heap.Object) string {
	charArr := jStr.GetFieldValue("value", "[C").(*heap.Object)
	return _utf16ToString(charArr.Chars())
}