Weak Cells

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index cff5b61b527bec83db46b2efbc99d85898e0a1ae..9858552dcf0cc7c04a9607386256507181629c44 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -786,6 +786,7 @@ TYPE_CHECKER(Code, CODE_TYPE)
 TYPE_CHECKER(Oddball, ODDBALL_TYPE)
 TYPE_CHECKER(Cell, CELL_TYPE)
 TYPE_CHECKER(PropertyCell, PROPERTY_CELL_TYPE)
+TYPE_CHECKER(WeakCell, WEAK_CELL_TYPE)
 TYPE_CHECKER(SharedFunctionInfo, SHARED_FUNCTION_INFO_TYPE)
 TYPE_CHECKER(JSGeneratorObject, JS_GENERATOR_OBJECT_TYPE)
 TYPE_CHECKER(JSModule, JS_MODULE_TYPE)
@@ -1929,6 +1930,28 @@ void PropertyCell::set_type_raw(Object* val, WriteBarrierMode ignored) {
 }
 
 
+HeapObject* WeakCell::value() const {
+  return HeapObject::cast(READ_FIELD(this, kValueOffset));
+}
+
+
+void WeakCell::update_value_from_gc(HeapObject* val) {
+  WRITE_FIELD(this, kValueOffset, val);
+  WRITE_BARRIER(GetHeap(), this, kValueOffset, val);

[Erik Corry, 2014/10/13 15:56:17]

If we are in GC, do we need the write barrier?  I think this is only
legitimately used to set the value to 'undefined', so pehaps it should be
renamed clear_value_from_gc and it should not take an argument.

[ulan, 2014/10/14 10:17:22]

Yes, we need write barrier for the first initialization. All other usages are
indeed "set to undefined" that don't need write barrier. I introduced two
functions: initialize and clear.

+}
+
+
+Object* WeakCell::next() const { return READ_FIELD(this, kNextOffset); }
+
+
+void WeakCell::set_next(Object* val, WriteBarrierMode mode) {
+  WRITE_FIELD(this, kNextOffset, val);
+  if (mode == UPDATE_WRITE_BARRIER) {
+    WRITE_BARRIER(GetHeap(), this, kNextOffset, val);
+  }
+}
+
+
 int JSObject::GetHeaderSize() {
   InstanceType type = map()->instance_type();
   // Check for the most common kind of JavaScript object before
@@ -3253,6 +3276,7 @@ CAST_ACCESSOR(StringTable)
 CAST_ACCESSOR(Struct)
 CAST_ACCESSOR(Symbol)
 CAST_ACCESSOR(UnseededNumberDictionary)
+CAST_ACCESSOR(WeakCell)
 CAST_ACCESSOR(WeakHashTable)