runtime: don't crash in SetFinalizer if sizeof *x is zero
And document it explicitly, even though it already said
it wasn't guaranteed.
Fixes #6857
R=golang-dev, khr
CC=golang-dev
https://golang.org/cl/43580043
diff --git a/src/pkg/runtime/mfinal_test.go b/src/pkg/runtime/mfinal_test.go
index 6efef9b..4a34cd6 100644
--- a/src/pkg/runtime/mfinal_test.go
+++ b/src/pkg/runtime/mfinal_test.go
@@ -100,6 +100,13 @@
func fin(v *int) {
}
+// Verify we don't crash at least. golang.org/issue/6857
+func TestFinalizerZeroSizedStruct(t *testing.T) {
+ type Z struct{}
+ z := new(Z)
+ runtime.SetFinalizer(z, func(*Z) {})
+}
+
func BenchmarkFinalizer(b *testing.B) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
