Commit 95a5b80e authored by David Chase's avatar David Chase Committed by Matthew Dempsky

[release-branch.go1.8] 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/39616
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: 's avatarAustin Clements <austin@google.com>
parent fe79c752
......@@ -477,6 +477,10 @@ func escAnalyze(all []*Node, recursive bool) {
for _, n := range all {
if n.Op == ODCLFUNC {
n.Esc = EscFuncPlanned
if Debug['m'] > 3 {
Dump("escAnalyze", n)
}
}
}
......@@ -1675,7 +1679,10 @@ func (e *EscState) escflows(dst, src *Node, why *EscStep) {
}
// Don't bother building a graph for scalars.
if src.Type != nil && !haspointers(src.Type) {
if src.Type != nil && !haspointers(src.Type) && !isReflectHeaderDataField(src) {
if Debug['m'] > 3 {
fmt.Printf("%v::NOT flows:: %S <- %S\n", linestr(lineno), dst, src)
}
return
}
......
// errorcheck -0 -m -l
// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package foo
// Escape analysis needs to treat the uintptr-typed reflect.*Header fields as pointers.
import (
"reflect"
"unsafe"
)
type immutableBytes []byte
// Bug was failure to leak param b.
func toString(b immutableBytes) string { // ERROR "leaking param: b$"
var s string
if len(b) == 0 {
return s
}
strHeader := (*reflect.StringHeader)(unsafe.Pointer(&s)) // ERROR "toString &s does not escape$"
strHeader.Data = (*reflect.SliceHeader)(unsafe.Pointer(&b)).Data // ERROR "toString &b does not escape$"
l := len(b)
strHeader.Len = l
return s
}
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