issue7921.go

     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  
     9  package foo
    10  
    11  import "bytes"
    12  
    13  // In order to get desired results, we need a combination of
    14  // both escape analysis and inlining.
    15  
    16  func 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$"
    24  }
    25  
    26  func bufferNoEscape2(xs []string) int { // ERROR "xs does not escape$"
    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$"
    32  }
    33  
    34  func bufferNoEscape3(xs []string) string { // ERROR "xs does not escape$"
    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  
    43  func 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$"
    48  }
    49  
    50  func bufferNoEscape5() { // ERROR "can inline bufferNoEscape5$"
    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
    56  func useBuffer(b *bytes.Buffer) { // ERROR "b does not escape$"
    57  	b.WriteString("1234")
    58  }
    59
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