Make object groups and implicit references a bit more lightweight.

test/cctest/test-mark-compact.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 281 matching lines @@
 
 
 static int NumberOfWeakCalls = 0;
 static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
   ASSERT(id == reinterpret_cast<void*>(1234));
   NumberOfWeakCalls++;
   handle.Dispose();
 }
 
 TEST(ObjectGroups) {
+  InitializeVM();
   GlobalHandles* global_handles = Isolate::Current()->global_handles();
-  InitializeVM();
 
   NumberOfWeakCalls = 0;
   v8::HandleScope handle_scope;
 
   Handle<Object> g1s1 =
       global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g1s2 =
-    global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
+      global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g1c1 =
-    global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
+      global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   global_handles->MakeWeak(g1s1.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
   global_handles->MakeWeak(g1s2.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
   global_handles->MakeWeak(g1c1.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
 
@@ skipping 18 matching lines @@
   // Connect group 1 and 2, make a cycle.
   Handle<FixedArray>::cast(g1s2)->set(0, *g2s2);
   Handle<FixedArray>::cast(g2s1)->set(0, *g1s1);
 
   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
     Object** g1_children[] = { g1c1.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     Object** g2_children[] = { g2c1.location() };
     global_handles->AddObjectGroup(g1_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g1s1),
-                                          g1_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g1s1).location(), g1_children, 1);
     global_handles->AddObjectGroup(g2_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g2s2),
-                                          g2_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g2s2).location(), g2_children, 1);
   }
   // Do a full GC
   HEAP->CollectGarbage(OLD_POINTER_SPACE);
 
   // All object should be alive.
   CHECK_EQ(0, NumberOfWeakCalls);
 
   // Weaken the root.
   global_handles->MakeWeak(root.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
   // But make children strong roots---all the objects (except for children)
   // should be collectable now.
   global_handles->ClearWeakness(g1c1.location());
   global_handles->ClearWeakness(g2c1.location());
 
   // Groups are deleted, rebuild groups.
   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
     Object** g1_children[] = { g1c1.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     Object** g2_children[] = { g2c1.location() };
     global_handles->AddObjectGroup(g1_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g1s1),
-                                         g1_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g1s1).location(), g1_children, 1);
     global_handles->AddObjectGroup(g2_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g2s2),
-                                         g2_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g2s2).location(), g2_children, 1);
   }
 
   HEAP->CollectGarbage(OLD_POINTER_SPACE);
 
   // All objects should be gone. 5 global handles in total.
   CHECK_EQ(5, NumberOfWeakCalls);
 
   // And now make children weak again and collect them.
   global_handles->MakeWeak(g1c1.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
   global_handles->MakeWeak(g2c1.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
 
   HEAP->CollectGarbage(OLD_POINTER_SPACE);
   CHECK_EQ(7, NumberOfWeakCalls);
 }
+
+
+class TestRetainedObjectInfo : public v8::RetainedObjectInfo {
+ public:
+  TestRetainedObjectInfo() : has_been_disposed_(false) {}
+
+  bool has_been_disposed() { return has_been_disposed_; }
+
+  virtual void Dispose() {
+    ASSERT(!has_been_disposed_);
+    has_been_disposed_ = true;
+  }
+
+  virtual bool IsEquivalent(v8::RetainedObjectInfo* other) {
+    return other == this;
+  }
+
+  virtual intptr_t GetHash() { return 0; };
+
+  virtual const char* GetLabel() { return "whatever"; }
+
+ private:
+  bool has_been_disposed_;
+};
+
+
+TEST(EmptyObjectGroups) {
+  InitializeVM();
+  GlobalHandles* global_handles = Isolate::Current()->global_handles();
+
+  v8::HandleScope handle_scope;
+
+  Handle<Object> object =
+      global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
+
+  TestRetainedObjectInfo info;
+  global_handles->AddObjectGroup(NULL, 0, &info);
+  ASSERT(info.has_been_disposed());
+
+  global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(object).location(), NULL, 0);
+}