cppgc: Remove object during sweep

The dummy sweeping algorithm didn't actually remove objects from the
internal list.

Bug: chromium:1056170
Change-Id: I29a93a2ac7fc36ca95125805076ff5ce257de8a4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2138433
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67033}

src/heap/cppgc/heap.cc

@@ -50,20 +50,22 @@ Heap::Heap()
     : stack_(std::make_unique<Stack>(v8::base::Stack::GetStackStart())) {}
 
 void Heap::CollectGarbage(GCConfig config) {
-  current_config_ = config;
   // TODO(chromium:1056170): Replace with proper mark-sweep algorithm.
   // "Marking".
-  if (NeedsConservativeStackScan(current_config_)) {
+  if (NeedsConservativeStackScan(config)) {
     StackMarker marker(objects_);
     stack_->IteratePointers(&marker);
   }
   // "Sweeping and finalization".
-  for (HeapObjectHeader* header : objects_) {
+  for (auto it = objects_.begin(); it != objects_.end();) {
+    HeapObjectHeader* header = *it;
     if (header->IsMarked()) {
       header->Unmark();
+      ++it;
     } else {
       header->Finalize();
       free(header);
+      it = objects_.erase(it);
     }
   }
 }

src/heap/cppgc/heap.h

@@ -40,8 +40,6 @@ class V8_EXPORT_PRIVATE Heap final : public cppgc::Heap {
   void CollectGarbage(GCConfig config = GCConfig::Default());
 
  private:
-  GCConfig current_config_;
-
   std::unique_ptr<Stack> stack_;
   std::vector<HeapObjectHeader*> objects_;
 };

test/unittests/heap/cppgc/heap_unittest.cc

@@ -39,21 +39,25 @@ size_t Foo::destructor_callcount;
 }  // namespace
 
 TEST_F(GCHeapTest, PreciseGCReclaimsObjectOnStack) {
-  Foo* volatile do_not_acces = MakeGarbageCollected<Foo>(GetHeap());
-  USE(do_not_acces);
+  Foo* volatile do_not_access = MakeGarbageCollected<Foo>(GetHeap());
+  USE(do_not_access);
   EXPECT_EQ(0u, Foo::destructor_callcount);
   PreciseGC();
   EXPECT_EQ(1u, Foo::destructor_callcount);
+  PreciseGC();
+  EXPECT_EQ(1u, Foo::destructor_callcount);
 }
 
 TEST_F(GCHeapTest, ConservaitveGCRetainsObjectOnStack) {
-  Foo* volatile do_not_acces = MakeGarbageCollected<Foo>(GetHeap());
-  USE(do_not_acces);
+  Foo* volatile do_not_access = MakeGarbageCollected<Foo>(GetHeap());
+  USE(do_not_access);
   EXPECT_EQ(0u, Foo::destructor_callcount);
   ConservativeGC();
   EXPECT_EQ(0u, Foo::destructor_callcount);
   PreciseGC();
   EXPECT_EQ(1u, Foo::destructor_callcount);
+  PreciseGC();
+  EXPECT_EQ(1u, Foo::destructor_callcount);
 }
 
 }  // namespace internal