runtime: avoid endless loop if printing the panic value panics

Change-Id: I56de359a5ccdc0a10925cd372fa86534353c6ca0
Reviewed-on: https://go-review.googlesource.com/30358
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprog/deadlock.go b/src/runtime/testdata/testprog/deadlock.go
index c938fcfb56..ca2be57911 100644
--- a/src/runtime/testdata/testprog/deadlock.go
+++ b/src/runtime/testdata/testprog/deadlock.go
@@ -32,6 +32,7 @@ func init() {
 	register("PanicTraceback", PanicTraceback)
 	register("GoschedInPanic", GoschedInPanic)
 	register("SyscallInPanic", SyscallInPanic)
+	register("PanicLoop", PanicLoop)
 }
 
 func SimpleDeadlock() {
@@ -214,3 +215,13 @@ func pt2() {
 	}()
 	panic("hello")
 }
+
+type panicError struct{}
+
+func (*panicError) Error() string {
+	panic("double error")
+}
+
+func PanicLoop() {
+	panic(&panicError{})
+}