runtime: check for nil value pointer in select syncsend case

Fixes #2309.

R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/5128053

diff --git a/src/pkg/runtime/chan.c b/src/pkg/runtime/chan.c
index eac2098c396dac1bc14d24066cea57ec05dad0c9..cc056f65f10f52b4ecddc6d3352b670b2e7ef147 100644 (file)
--- a/src/pkg/runtime/chan.c
+++ b/src/pkg/runtime/chan.c
@@ -1024,7 +1024,8 @@ syncsend:
        selunlock(sel);
        if(debug)
                runtime·printf("syncsend: sel=%p c=%p o=%d\n", sel, c, o);
-       c->elemalg->copy(c->elemsize, sg->elem, cas->sg.elem);
+       if(sg->elem != nil)
+               c->elemalg->copy(c->elemsize, sg->elem, cas->sg.elem);
        gp = sg->g;
        gp->param = sg;
        runtime·ready(gp);

diff --git a/test/chan/select7.go b/test/chan/select7.go
new file mode 100644 (file)
index 0000000..5fed6cb
--- /dev/null
+++ b/test/chan/select7.go
@@ -0,0 +1,68 @@
+// $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.
+
+// Test select when discarding a value.
+
+package main
+
+import "runtime"
+
+func recv1(c <-chan int) {
+       <-c
+}
+
+func recv2(c <-chan int) {
+       select {
+       case <-c:
+       }
+}
+
+func recv3(c <-chan int) {
+       c2 := make(chan int)
+       select {
+       case <-c:
+       case <-c2:
+       }
+}
+
+func send1(recv func(<-chan int)) {
+       c := make(chan int)
+       go recv(c)
+       runtime.Gosched()
+       c <- 1
+}
+
+func send2(recv func(<-chan int)) {
+       c := make(chan int)
+       go recv(c)
+       runtime.Gosched()
+       select {
+       case c <- 1:
+       }
+}
+
+func send3(recv func(<-chan int)) {
+       c := make(chan int)
+       go recv(c)
+       runtime.Gosched()
+       c2 := make(chan int)
+       select {
+       case c <- 1:
+       case c2 <- 1:
+       }
+}
+
+func main() {
+       send1(recv1)
+       send2(recv1)
+       send3(recv1)
+       send1(recv2)
+       send2(recv2)
+       send3(recv2)
+       send1(recv3)
+       send2(recv3)
+       send3(recv3)
+}