Fix crash in ScriptDebugServer::wrapCallFrames

src/debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2487 matching lines @@
 
 MaybeHandle<Object> Debug::MakeAsyncTaskEvent(Handle<JSObject> task_event) {
   // Create the async task event object.
   Handle<Object> argv[] = { task_event };
   return MakeJSObject("MakeAsyncTaskEvent", arraysize(argv), argv);
 }
 
 
 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;
 }
 
 
 void Debug::OnPromiseReject(Handle<JSObject> promise, Handle<Object> value) {
   if (in_debug_scope() || ignore_events()) return;
   HandleScope scope(isolate_);
   OnException(value, false, promise);
 }
 
 
@@ skipping 842 matching lines @@
   logger_->DebugEvent("Put", message.text());
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 } }  // namespace v8::internal