misc/cgo/test: fail issue 7978 with clearer error when GOTRACEBACK != 2

The test doesn't work with GOTRACEBACK != 2.
Diagnose that failure mode.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews, r
https://golang.org/cl/152970043

diff --git a/misc/cgo/test/issue7978.go b/misc/cgo/test/issue7978.go
index 39864476ceb39327e2d2d00ffc68e6a821224a8d..5feed07b957c452b8377e0f74c2445623688d803 100644 (file)
--- a/misc/cgo/test/issue7978.go
+++ b/misc/cgo/test/issue7978.go
@@ -29,6 +29,7 @@ static void issue7978c(uint32_t *sync) {
 import "C"
 
 import (
+       "os"
        "runtime"
        "strings"
        "sync/atomic"
@@ -81,6 +82,9 @@ func issue7978go() {
 }
 
 func test7978(t *testing.T) {
+       if os.Getenv("GOTRACEBACK") != "2" {
+               t.Fatalf("GOTRACEBACK must be 2")
+       }
        issue7978sync = 0
        go issue7978go()
        // test in c code, before callback