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cmd/compile: added special case for reflect header fields to esc
The uintptr-typed Data field in reflect.SliceHeader and reflect.StringHeader needs special treatment because it is really a pointer. Add the special treatment in walk for bug #19168 to escape analysis. Includes extra debugging that was helpful. Fixes #19743. Change-Id: I6dab5002f0d436c3b2a7cdc0156e4fc48a43d6fe Reviewed-on: https://go-review.googlesource.com/38738 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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@ -477,6 +477,10 @@ func escAnalyze(all []*Node, recursive bool) {
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for _, n := range all {
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if n.Op == ODCLFUNC {
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n.Esc = EscFuncPlanned
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if Debug['m'] > 3 {
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Dump("escAnalyze", n)
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}
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}
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}
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@ -1682,7 +1686,10 @@ func (e *EscState) escflows(dst, src *Node, why *EscStep) {
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}
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// Don't bother building a graph for scalars.
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if src.Type != nil && !haspointers(src.Type) {
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if src.Type != nil && !haspointers(src.Type) && !isReflectHeaderDataField(src) {
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if Debug['m'] > 3 {
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fmt.Printf("%v::NOT flows:: %S <- %S\n", linestr(lineno), dst, src)
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}
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return
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}
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31
test/fixedbugs/issue19743.go
Normal file
31
test/fixedbugs/issue19743.go
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@ -0,0 +1,31 @@
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// errorcheck -0 -m -l
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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package foo
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// Escape analysis needs to treat the uintptr-typed reflect.*Header fields as pointers.
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import (
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"reflect"
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"unsafe"
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)
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type immutableBytes []byte
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// Bug was failure to leak param b.
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func toString(b immutableBytes) string { // ERROR "leaking param: b$"
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var s string
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if len(b) == 0 {
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return s
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}
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strHeader := (*reflect.StringHeader)(unsafe.Pointer(&s)) // ERROR "toString &s does not escape$"
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strHeader.Data = (*reflect.SliceHeader)(unsafe.Pointer(&b)).Data // ERROR "toString &b does not escape$"
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l := len(b)
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strHeader.Len = l
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return s
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}
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