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 aren't scanned until they
8// are initialized, when calling functions and methods
9// via reflect.
10
11package main
12
13import (
14	"io"
15	"reflect"
16	"runtime"
17	"unsafe"
18)
19
20var badPtr uintptr
21
22var sink []byte
23
24func init() {
25	// Allocate large enough to use largeAlloc.
26	b := make([]byte, 1<<16-1)
27	sink = b // force heap allocation
28	//  Any space between the object and the end of page is invalid to point to.
29	badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1
30}
31
32func f(d func(error) error) error {
33	// Initialize callee args section with a bad pointer.
34	g(badPtr, badPtr, badPtr, badPtr)
35
36	// Then call a function which returns a pointer.
37	// That return slot starts out holding a bad pointer.
38	return d(io.EOF)
39}
40
41//go:noinline
42func g(x, y, z, w uintptr) {
43}
44
45type T struct {
46}
47
48func (t *T) Foo(e error) error {
49	runtime.GC()
50	return e
51}
52
53func main() {
54	// Functions
55	d := reflect.MakeFunc(reflect.TypeOf(func(e error) error { return e }),
56		func(args []reflect.Value) []reflect.Value {
57			runtime.GC()
58			return args
59		}).Interface().(func(error) error)
60	f(d)
61
62	// Methods
63	x := reflect.ValueOf(&T{}).Method(0).Interface().(func(error) error)
64	f(x)
65}
66