ReturnValue::Set needs to check for empty handles

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/16073010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14898 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -5665,14 +5665,22 @@ template<typename T>
 template<typename S>
 void ReturnValue<T>::Set(const Persistent<S>& handle) {
   TYPE_CHECK(T, S);
-  *value_ = *reinterpret_cast<internal::Object**>(*handle);
+  if (V8_UNLIKELY(handle.IsEmpty())) {
+    SetUndefined();
+  } else {
+    *value_ = *reinterpret_cast<internal::Object**>(*handle);
+  }
 }
 
 template<typename T>
 template<typename S>
 void ReturnValue<T>::Set(const Handle<S> handle) {
   TYPE_CHECK(T, S);
-  *value_ = *reinterpret_cast<internal::Object**>(*handle);
+  if (V8_UNLIKELY(handle.IsEmpty())) {
+    SetUndefined();
+  } else {
+    *value_ = *reinterpret_cast<internal::Object**>(*handle);
+  }
 }
 
 template<typename T>

test/cctest/test-api.cc

@@ -1029,6 +1029,7 @@ static const double kFastReturnValueDouble = 2.7;
 // variable return values
 static bool fast_return_value_bool = false;
 static bool fast_return_value_void_is_null = false;
+static bool fast_return_value_object_is_empty = false;
 
 template<>
 void FastReturnValueCallback<int32_t>(
@@ -1072,7 +1073,9 @@ void FastReturnValueCallback<void>(
 template<>
 void FastReturnValueCallback<Object>(
     const v8::FunctionCallbackInfo<v8::Value>& info) {
-  info.GetReturnValue().Set(Object::New());
+  v8::Handle<v8::Object> object;
+  if (!fast_return_value_object_is_empty) object = Object::New();
+  info.GetReturnValue().Set(object);
 }
 
 template<typename T>
@@ -1119,8 +1122,13 @@ THREADED_TEST(FastReturnValues) {
       CHECK(value->IsUndefined());
     }
   }
+  // check handles
+  fast_return_value_object_is_empty = false;
   value = TestFastReturnValues<Object>();
   CHECK(value->IsObject());
+  fast_return_value_object_is_empty = true;
+  value = TestFastReturnValues<Object>();
+  CHECK(value->IsUndefined());
 }