[api] Prototype WeakRef implementation

src/heap/objects-visiting-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_VISITING_INL_H_
 #define V8_OBJECTS_VISITING_INL_H_
 
 #include "src/heap/array-buffer-tracker.h"
 #include "src/heap/mark-compact.h"
 #include "src/heap/objects-visiting.h"
@@ skipping 146 matching lines @@
   table_.Register(kVisitBytecodeArray, &VisitBytecodeArray);
 
   table_.Register(kVisitFreeSpace, &DataObjectVisitor::Visit);
 
   table_.Register(kVisitSeqOneByteString, &DataObjectVisitor::Visit);
 
   table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit);
 
   table_.Register(kVisitJSWeakCollection, &VisitWeakCollection);
 
+  table_.Register(kVisitJSWeakRef, &VisitWeakRef);
+
   table_.Register(
       kVisitOddball,
       &FixedBodyVisitor<StaticVisitor, Oddball::BodyDescriptor, void>::Visit);
 
   table_.Register(kVisitMap, &VisitMap);
 
   table_.Register(kVisitCode, &VisitCode);
 
   table_.Register(kVisitSharedFunctionInfo, &VisitSharedFunctionInfo);
 
@@ skipping 215 matching lines @@
   // Partially initialized weak collection is enqueued, but table is ignored.
   if (!weak_collection->table()->IsHashTable()) return;
 
   // Mark the backing hash table without pushing it on the marking stack.
   Object** slot = HeapObject::RawField(object, JSWeakCollection::kTableOffset);
   HeapObject* obj = HeapObject::cast(*slot);
   heap->mark_compact_collector()->RecordSlot(object, slot, obj);
   StaticVisitor::MarkObjectWithoutPush(heap, obj);
 }
 
+template <typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitWeakRef(
+    Map* map, HeapObject* object) {
+  Heap* heap = map->GetHeap();
+  JSWeakRef* weak_ref =
+      reinterpret_cast<JSWeakRef*>(object);
+
+  if (weak_ref->executor() != nullptr) {
+    StaticVisitor::MarkObject(heap, weak_ref->executor());
+  }
+  if (weak_ref->holdings() != nullptr && weak_ref->holdings()->IsHeapObject()) {
+    StaticVisitor::MarkObject(heap,
+        reinterpret_cast<HeapObject*>(weak_ref->holdings()));
+  }
+  if (weak_ref->target() != nullptr) {
+    StaticVisitor::MarkObject(heap, weak_ref->target());
+    if (weak_ref->held()) {
+      if (!weak_ref->target()->cleared()) {
+        StaticVisitor::MarkObject(heap,
+          reinterpret_cast<JSObject*>(weak_ref->target()->value()));
+      }
+    } else if (weak_ref->target()->cleared()) {
+      weak_ref->set_target(nullptr);
+      weak_ref->set_held(false);
+      weak_ref->set_queued(true);
+    }
+  }
+}
+
 
 template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitCode(Map* map,
                                                     HeapObject* object) {
   typedef FlexibleBodyVisitor<StaticVisitor, Code::BodyDescriptor, void>
       CodeBodyVisitor;
   Heap* heap = map->GetHeap();
   Code* code = Code::cast(object);
   if (FLAG_age_code && !heap->isolate()->serializer_enabled()) {
     code->MakeOlder();
@@ skipping 223 matching lines @@
   typedef FlexibleBodyVisitor<StaticVisitor, JSFunction::BodyDescriptorWeakCode,
                               void> JSFunctionWeakCodeBodyVisitor;
   JSFunctionWeakCodeBodyVisitor::Visit(map, object);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_VISITING_INL_H_