runtime: better error from TestGcSys when gc is disabled

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7390047

diff --git a/src/pkg/runtime/gc_test.go b/src/pkg/runtime/gc_test.go
index 283a6812e95f3d270920ff526cfffe45d50ecdd1..0215ff2cf435059eb3a8da7dcc042a5c6decad83 100644 (file)
--- a/src/pkg/runtime/gc_test.go
+++ b/src/pkg/runtime/gc_test.go
@@ -5,11 +5,15 @@
 package runtime_test
 
 import (
+       "os"
        "runtime"
        "testing"
 )
 
 func TestGcSys(t *testing.T) {
+       if os.Getenv("GOGC") == "off" {
+               t.Fatalf("GOGC=off in environment; test cannot pass")
+       }
        defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
        memstats := new(runtime.MemStats)
        runtime.GC()