Fix crash in ScriptDebugServer::wrapCallFrames

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 5bdf53f058e528ff7faf9760f36f45b54a7685a8..46917380d93be7bde33319dbf200e7db87220110 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2505,8 +2505,13 @@ MaybeHandle<Object> Debug::MakeAsyncTaskEvent(Handle<JSObject> task_event) {
 
 void Debug::OnThrow(Handle<Object> exception, bool uncaught) {
   if (in_debug_scope() || ignore_events()) return;
+  // Temporarily clear any scheduled_exception to allow evaluating
+  // JavaScript from the debug event handler.
   HandleScope scope(isolate_);
+  Object* scheduled_exception = isolate_->scheduled_exception();

[Yang, 2014/09/11 07:26:05]

I just realized that this is not GC-safe. You have to put this into a handle.

[aandrey, 2014/09/11 08:20:24]

But isolate_->thread_local_top()->scheduled_exception_ stores it as Object*. How
does it tolerate GC?

[Yang, 2014/09/11 08:26:21]

Also, this getter asserts that we have a scheduled exception. We should access
it directly through isolate_->thread_local_top()->scheduled_exception_.

[aandrey, 2014/09/11 08:47:22]

Done.

+  isolate_->clear_scheduled_exception();
   OnException(exception, uncaught, isolate_->GetPromiseOnStackOnThrow());
+  isolate_->thread_local_top()->scheduled_exception_ = scheduled_exception;
 }