Fix ThreadHeap::isHeapObjectAlive(const T*& ptr) stack overflow.

third_party/WebKit/Source/platform/heap/HeapTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 3904 matching lines @@
 }
 
 TEST(HeapTest, Comparisons) {
   Persistent<Bar> barPersistent = Bar::create();
   Persistent<Foo> fooPersistent = Foo::create(barPersistent);
   EXPECT_TRUE(barPersistent != fooPersistent);
   barPersistent = fooPersistent;
   EXPECT_TRUE(barPersistent == fooPersistent);
 }
 
+TEST(HeapTest, CheckConstObjectAlive) {
+  SimpleObject* object = SimpleObject::create();
+  const SimpleObject* constObject = object;
+
+  EXPECT_FALSE(ThreadHeap::isHeapObjectAlive(object));
+  EXPECT_FALSE(ThreadHeap::isHeapObjectAlive(constObject));
+
+  // {
+  //   TestGCScope scope(BlinkGC::HeapPointersOnStack);
+  //   ThreadHeap& heap = ThreadState::current()->heap();
+  //   CountingVisitor visitor(ThreadState::current());
+
+  //   Address objectAddress = reinterpret_cast<Address>(object);
+  //   EXPECT_TRUE(heap.checkAndMarkPointer(&visitor, objectAddress));
+
+  //   EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(object));
+  //   EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(constObject));
+  // }

[haraken, 2016/11/02 01:12:47]

Can we remove this comment? It's not worth adding comment-outed code.

[chcunningham, 2016/11/02 01:19:06]

Sorry, I mean to uncomment it actually, but it doesn't pass. The stack overflow
problem is definitely solved, but for some reason the checkAndMarkPointer does
not cause the later isHeapObjectAlive calls to return true. Can you point out
what I'm missing? Is there some better way to mark the object alive?

[haraken, 2016/11/02 01:22:30]

Ah, actually this test doesn't make sense in the first place because
isHeapObjectAlive can be used only during a GC phase.

Instead of adding this test, can you add EXPECT_TRUE/FALSE to ClassWithMember?

+}
+
 TEST(HeapTest, CheckAndMarkPointer) {
   ThreadHeap& heap = ThreadState::current()->heap();
   clearOutOldGarbage();
 
   Vector<Address> objectAddresses;
   Vector<Address> endAddresses;
   Address largeObjectAddress;
   Address largeObjectEndAddress;
   for (int i = 0; i < 10; i++) {
     SimpleObject* object = SimpleObject::create();
@@ skipping 2866 matching lines @@
       "HeapVector");
   static_assert(
       WTF::IsGarbageCollectedType<HeapDeque<Member<IntWrapper>>>::value,
       "HeapDeque");
   static_assert(WTF::IsGarbageCollectedType<
                     HeapTerminatedArray<Member<IntWrapper>>>::value,
                 "HeapTerminatedArray");
 }
 
 }  // namespace blink