Implement HeapIterator that skips over unreachable objects.

test/cctest/test-heap.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 
 #include <stdlib.h>
 
 #include "v8.h"
 
 #include "execution.h"
 #include "factory.h"
 #include "macro-assembler.h"
 #include "global-handles.h"
@@ skipping 1198 matching lines @@
   CHECK_EQ(opt ? 5 : 0, CountOptimizedUserFunctions(ctx[0]));
   CHECK_EQ(opt ? 5 : 0, CountOptimizedUserFunctionsWithGC(ctx[0], 4));
 
   ctx[0]->Exit();
 }
 
 
 TEST(TestSizeOfObjectsVsHeapIteratorPrecision) {
   InitializeVM();
   intptr_t size_of_objects_1 = Heap::SizeOfObjects();
-  HeapIterator iterator(HeapIterator::kPreciseFiltering);
+  HeapIterator iterator(HeapIterator::kFilterFreeListNodes);
   intptr_t size_of_objects_2 = 0;
   for (HeapObject* obj = iterator.next();
        obj != NULL;
        obj = iterator.next()) {
     size_of_objects_2 += obj->Size();
   }
   // Delta must be within 1% of the larger result.
   if (size_of_objects_1 > size_of_objects_2) {
     intptr_t delta = size_of_objects_1 - size_of_objects_2;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "
            "Iterator: %" V8_PTR_PREFIX "d, "
            "delta: %" V8_PTR_PREFIX "d\n",
            size_of_objects_1, size_of_objects_2, delta);
     CHECK_GT(size_of_objects_1 / 100, delta);
   } else {
     intptr_t delta = size_of_objects_2 - size_of_objects_1;
     PrintF("Heap::SizeOfObjects: %" V8_PTR_PREFIX "d, "
            "Iterator: %" V8_PTR_PREFIX "d, "
            "delta: %" V8_PTR_PREFIX "d\n",
            size_of_objects_1, size_of_objects_2, delta);
     CHECK_GT(size_of_objects_2 / 100, delta);
   }
 }
+
+
+class HeapIteratorTestHelper {
+ public:
+  HeapIteratorTestHelper(Object* a, Object* b)
+      : a_(a), b_(b), a_found_(false), b_found_(false) {}
+  bool a_found() { return a_found_; }
+  bool b_found() { return b_found_; }
+  void IterateHeap(HeapIterator::HeapObjectsFiltering mode) {
+    HeapIterator iterator(mode);
+    for (HeapObject* obj = iterator.next();
+         obj != NULL;
+         obj = iterator.next()) {
+      if (obj == a_)
+        a_found_ = true;
+      else if (obj == b_)
+        b_found_ = true;
+    }
+  }
+ private:
+  Object* a_;
+  Object* b_;
+  bool a_found_;
+  bool b_found_;
+};
+
+TEST(HeapIteratorFilterUnreachable) {
+  InitializeVM();
+  v8::HandleScope scope;
+  CompileRun("a = {}; b = {};");
+  v8::Handle<Object> a(Top::context()->global()->GetProperty(
+      *Factory::LookupAsciiSymbol("a"))->ToObjectChecked());
+  v8::Handle<Object> b(Top::context()->global()->GetProperty(
+      *Factory::LookupAsciiSymbol("b"))->ToObjectChecked());
+  CHECK_NE(*a, *b);
+  {
+    HeapIteratorTestHelper helper(*a, *b);
+    helper.IterateHeap(HeapIterator::kFilterUnreachable);
+    CHECK(helper.a_found());
+    CHECK(helper.b_found());
+  }
+  CHECK(Top::context()->global()->DeleteProperty(
+      *Factory::LookupAsciiSymbol("a"), JSObject::FORCE_DELETION));
+  // We ensure that GC will not happen, so our raw pointer stays valid.
+  AssertNoAllocation no_alloc;
+  Object* a_saved = *a;
+  a.Clear();
+  // Verify that "a" object still resides in the heap...
+  {
+    HeapIteratorTestHelper helper(a_saved, *b);
+    helper.IterateHeap(HeapIterator::kNoFiltering);
+    CHECK(helper.a_found());
+    CHECK(helper.b_found());
+  }
+  // ...but is now unreachable.
+  {
+    HeapIteratorTestHelper helper(a_saved, *b);
+    helper.IterateHeap(HeapIterator::kFilterUnreachable);
+    CHECK(!helper.a_found());
+    CHECK(helper.b_found());
+  }
+}