1// errorcheck -0 -m
2
3//go:build !gcflags_noopt && !goexperiment.newinliner
4
5// Copyright 2018 The Go Authors. All rights reserved.
6// Use of this source code is governed by a BSD-style
7// license that can be found in the LICENSE file.
8
9package foo
10
11import "bytes"
12
13// In order to get desired results, we need a combination of
14// both escape analysis and inlining.
15
16func bufferNotEscape() string {
17	// b itself does not escape, only its buf field will be
18	// copied during String() call, but object "handle" itself
19	// can be stack-allocated.
20	var b bytes.Buffer
21	b.WriteString("123")
22	b.Write([]byte{'4'}) // ERROR "\[\]byte{...} does not escape$"
23	return b.String()    // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
24}
25
26func bufferNoEscape2(xs []string) int { // ERROR "xs does not escape$"
27	b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
28	for _, x := range xs {
29		b.WriteString(x)
30	}
31	return b.Len() // ERROR "inlining call to bytes.\(\*Buffer\).Len$"
32}
33
34func bufferNoEscape3(xs []string) string { // ERROR "xs does not escape$"
35	b := bytes.NewBuffer(make([]byte, 0, 64)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 64\) does not escape$" "inlining call to bytes.NewBuffer$"
36	for _, x := range xs {
37		b.WriteString(x)
38		b.WriteByte(',')
39	}
40	return b.String() // ERROR "inlining call to bytes.\(\*Buffer\).String$" "string\(bytes.b.buf\[bytes.b.off:\]\) escapes to heap$"
41}
42
43func bufferNoEscape4() []byte {
44	var b bytes.Buffer
45	b.Grow(64) // ERROR "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m\]$" "inlining call to bytes.\(\*Buffer\).Grow$" `".+" escapes to heap`
46	useBuffer(&b)
47	return b.Bytes() // ERROR "inlining call to bytes.\(\*Buffer\).Bytes$"
48}
49
50func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5$"
51	b := bytes.NewBuffer(make([]byte, 0, 128)) // ERROR "&bytes.Buffer{...} does not escape$" "make\(\[\]byte, 0, 128\) does not escape$" "inlining call to bytes.NewBuffer$"
52	useBuffer(b)
53}
54
55//go:noinline
56func useBuffer(b *bytes.Buffer) { // ERROR "b does not escape$"
57	b.WriteString("1234")
58}
59