diff -r 000000000000 -r 6474c204b198 ipc/ipdl/test/cxx/TestSyncHang.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/ipdl/test/cxx/TestSyncHang.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,71 @@
+#include "TestSyncHang.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+
+#include "IPDLUnitTests.h"      // fail etc.
+
+using std::vector;
+using std::string;
+
+namespace mozilla {
+namespace _ipdltest {
+
+//-----------------------------------------------------------------------------
+// parent
+
+mozilla::ipc::GeckoChildProcessHost* gSyncHangSubprocess;
+
+TestSyncHangParent::TestSyncHangParent()
+{
+    MOZ_COUNT_CTOR(TestSyncHangParent);
+}
+
+TestSyncHangParent::~TestSyncHangParent()
+{
+    MOZ_COUNT_DTOR(TestSyncHangParent);
+}
+
+void
+DeleteSyncHangSubprocess(MessageLoop* uiLoop)
+{
+  delete gSyncHangSubprocess;
+}
+
+void
+DeferredSyncHangParentShutdown()
+{
+  // ping to DeleteSubprocess
+  XRE_GetIOMessageLoop()->PostTask(
+      FROM_HERE,
+      NewRunnableFunction(DeleteSyncHangSubprocess, MessageLoop::current()));
+}
+
+void
+TestSyncHangParent::Main()
+{
+  vector<string> args;
+  args.push_back("fake/path");
+  gSyncHangSubprocess = new mozilla::ipc::GeckoChildProcessHost(GeckoProcessType_Plugin);
+  bool launched = gSyncHangSubprocess->SyncLaunch(args, 2);
+  if (launched)
+    fail("Calling SyncLaunch with an invalid path should return false");
+
+  MessageLoop::current()->PostTask(
+  				   FROM_HERE, NewRunnableFunction(DeferredSyncHangParentShutdown));
+  Close();
+}
+
+//-----------------------------------------------------------------------------
+// child
+
+TestSyncHangChild::TestSyncHangChild()
+{
+    MOZ_COUNT_CTOR(TestSyncHangChild);
+}
+
+TestSyncHangChild::~TestSyncHangChild()
+{
+    MOZ_COUNT_DTOR(TestSyncHangChild);
+}
+
+} // namespace _ipdltest
+} // namespace mozilla