cmd/gc: fix escape analysis bug.

It used to not mark parameters as escaping if only one of the
fields it points to leaks out of the function. This causes
problems when importing from another package.

Fixes #4964.

R=rsc, lvd, dvyukov, daniel.morsing
CC=golang-dev
https://golang.org/cl/7648045

diff --git a/src/cmd/gc/esc.c b/src/cmd/gc/esc.c
index 46c06d10e458c174b96c9631eff06fdbfc3da034..7be7b534139c2cbfa39e221f9605e001398e611c 100644 (file)
--- a/src/cmd/gc/esc.c
+++ b/src/cmd/gc/esc.c
@@ -1033,7 +1033,7 @@ escwalk(EscState *e, int level, Node *dst, Node *src)
 
        switch(src->op) {
        case ONAME:
-               if(src->class == PPARAM && leaks && src->esc != EscHeap) {
+               if(src->class == PPARAM && (leaks || dst->escloopdepth < 0) && src->esc != EscHeap) {
                        src->esc = EscScope;
                        if(debug['m'])
                                warnl(src->lineno, "leaking param: %hN", src);

diff --git a/test/escape2.go b/test/escape2.go
index 94816193385cceb9d7f10acf6d87de9573ff1d24..3473e4fa450779074912d478d4cf64296c8c56f3 100644 (file)
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -80,7 +80,9 @@ func foo12(yyy **int) { // ERROR "leaking param: yyy"
        xxx = yyy
 }
 
-func foo13(yyy **int) { // ERROR "yyy does not escape"
+// Must treat yyy as leaking because *yyy leaks, and the escape analysis 
+// summaries in exported metadata do not distinguish these two cases.
+func foo13(yyy **int) { // ERROR "leaking param: yyy"
        *xxx = *yyy
 }
 
@@ -299,7 +301,8 @@ func (f *Foo) foo45() { // ERROR "f does not escape"
        F.x = f.x
 }
 
-func (f *Foo) foo46() { // ERROR "f does not escape"
+// See foo13 above for explanation of why f leaks.
+func (f *Foo) foo46() { // ERROR "leaking param: f"
        F.xx = f.xx
 }
 

diff --git a/test/fixedbugs/issue4964.dir/a.go b/test/fixedbugs/issue4964.dir/a.go
new file mode 100644 (file)
index 0000000..2b9e44e
--- /dev/null
+++ b/test/fixedbugs/issue4964.dir/a.go
@@ -0,0 +1,27 @@
+// Copyright 2013 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 a
+
+var global, global2 *int
+
+type T struct {
+       Pointer *int
+}
+
+func dontinline() {}
+
+func Store(t *T) {
+       global = t.Pointer
+       dontinline()
+}
+
+func Store2(t *T) {
+       global2 = t.Pointer
+       dontinline()
+}
+
+func Get() *int {
+       return global
+}

diff --git a/test/fixedbugs/issue4964.dir/b.go b/test/fixedbugs/issue4964.dir/b.go
new file mode 100644 (file)
index 0000000..42a6f1d
--- /dev/null
+++ b/test/fixedbugs/issue4964.dir/b.go
@@ -0,0 +1,34 @@
+// Copyright 2013 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 main
+
+import "./a"
+
+func F() {
+       // store 1 in a.global
+       x, y := 1, 2
+       t := a.T{Pointer: &x}
+       a.Store(&t)
+       _ = y
+}
+
+func G() {
+       // store 4 in a.global2
+       x, y := 3, 4
+       t := a.T{Pointer: &y}
+       a.Store2(&t)
+       _ = x
+}
+
+func main() {
+       F()
+       G()
+       p := a.Get()
+       n := *p
+       if n != 1 {
+               println(n, "!= 1")
+               panic("n != 1")
+       }
+}

diff --git a/test/fixedbugs/issue4964.go b/test/fixedbugs/issue4964.go
new file mode 100644 (file)
index 0000000..8291d1b
--- /dev/null
+++ b/test/fixedbugs/issue4964.go
@@ -0,0 +1,10 @@
+// rundir
+
+// Copyright 2013 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.
+
+// Issue 4964: exported escape analysis result is not enough
+// for cross package analysis.
+
+package ignored