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

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

Index: third_party/WebKit/Source/platform/heap/HeapTest.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapTest.cpp b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
index c3d0aa58ecde03ca0c071339ef8076e59a984131..10bcac901bb2204a7d9acabe1f56e30a9a8f49b3 100644
--- a/third_party/WebKit/Source/platform/heap/HeapTest.cpp
+++ b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
@@ -3922,6 +3922,26 @@ TEST(HeapTest, Comparisons) {
   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();