1// run
2
3// Copyright 2018 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// Make sure return values are always scanned, when
8// calling methods (+functions, TODO) with reflect.
9
10package main
11
12import (
13	"reflect"
14	"runtime/debug"
15	"sync"
16)
17
18func main() {
19	debug.SetGCPercent(1) // run GC frequently
20	var wg sync.WaitGroup
21	for i := 0; i < 20; i++ {
22		wg.Add(1)
23		go func() {
24			defer wg.Done()
25			for i := 0; i < 2000; i++ {
26				_test()
27			}
28		}()
29	}
30	wg.Wait()
31}
32
33type Stt struct {
34	Data interface{}
35}
36
37type My struct {
38	b byte
39}
40
41func (this *My) Run(rawData []byte) (Stt, error) {
42	var data string = "hello"
43	stt := Stt{
44		Data: data,
45	}
46	return stt, nil
47}
48
49func _test() (interface{}, error) {
50	f := reflect.ValueOf(&My{}).MethodByName("Run")
51	if method, ok := f.Interface().(func([]byte) (Stt, error)); ok {
52		s, e := method(nil)
53		// The bug in issue27695 happens here, during the return
54		// from the above call (at the end of reflect.callMethod
55		// when preparing to return). The result value that
56		// is assigned to s was not being scanned if GC happens
57		// to occur there.
58		i := interface{}(s)
59		return i, e
60	}
61	return nil, nil
62}
63