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gc: select receive bug fix

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Affects receive using := when new variable escapes to heap.

Fixes #1468.

R=ken2
CC=golang-dev
https://golang.org/cl/4119052
This commit is contained in:
Russ Cox 2011-02-02 18:34:09 -05:00
parent c5fc3b6972
commit 8a2891fc56
2 changed files with 47 additions and 2 deletions
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4
src/cmd/gc/select.c
View File

@ -157,7 +157,7 @@ walkselect(Node *sel)
if(n->left == N || isblank(n->left))
n->left = nodnil();
else if(n->left->op == ONAME &&
(!n->colas || (n->class&PHEAP) == 0) &&
(!n->colas || (n->left->class&PHEAP) == 0) &&
convertop(ch->type->type, n->left->type, nil) == OCONVNOP) {
n->left = nod(OADDR, n->left, N);
n->left->etype = 1; // pointer does not escape
@ -170,9 +170,9 @@ walkselect(Node *sel)
typecheck(&a, Erv);
r = nod(OAS, n->left, tmp);
typecheck(&r, Etop);
cas->nbody = concat(list1(r), cas->nbody);
cas->nbody = concat(n->ninit, cas->nbody);
n->ninit = nil;
cas->nbody = concat(list1(r), cas->nbody);
n->left = a;
}
}

45
test/fixedbugs/bug320.go Normal file
View File

@ -0,0 +1,45 @@
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2011 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
func main() {
c := make(chan int, 1)
dummy := make(chan int)
v := 0x12345678
for i := 0; i < 10; i++ {
// 6g had a bug that caused select to pass &t to
// selectrecv before allocating the memory for t,
// which caused non-deterministic crashes.
// This test looks for the bug by checking that the
// value received actually ends up in t.
// If the allocation happens after storing through
// whatever garbage &t holds, the later reference
// to t in the case body will use the new pointer and
// not see the received value.
v += 0x1020304
c <- v
select {
case t := <-c:
go func() {
f(t)
}()
escape(&t)
if t != v {
println(i, v, t)
panic("wrong values")
}
case dummy <- 1:
}
}
}
func escape(*int) {
}
func f(int) {
}