two pass phantom collection

include/v8-util.h

 // Copyright 2014 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_UTIL_H_
 #define V8_UTIL_H_
 
 #include "v8.h"
 #include <map>
 #include <vector>
@@ skipping 304 matching lines @@
   static Global<V> Release(PersistentContainerValue v) {
     Global<V> p;
     p.val_ = FromVal(v);
     if (Traits::kCallbackType != kNotWeak && p.IsWeak()) {
       Traits::DisposeCallbackData(
           p.template ClearWeak<typename Traits::WeakCallbackDataType>());
     }
     return p.Pass();
   }
 
-  void RemoveWeak(const K& key) { Traits::Remove(&impl_, key); }
+  void RemoveWeak(const K& key) {
+    Global<V> p;
+    p.val_ = FromVal(Traits::Remove(&impl_, key));
+    p.Reset();

[Erik Corry, 2015/03/26 10:07:10]

Why do we have to create a Global, then immediately reset it?

[dcarney, 2015/03/26 10:26:56]

here nothing is being created.  we're just releasing the cell

+  }
 
  private:
   PersistentValueMapBase(PersistentValueMapBase&);
   void operator=(PersistentValueMapBase&);
 
   static bool SetReturnValueFromVal(ReturnValue<Value>* returnValue,
                                     PersistentContainerValue value) {
     bool hasValue = value != kPersistentContainerNotFound;
     if (hasValue) {
       returnValue->SetInternal(
@@ skipping 133 matching lines @@
 
  private:
   static void WeakCallback(
       const WeakCallbackInfo<typename Traits::WeakCallbackDataType>& data) {
     if (Traits::kCallbackType != kNotWeak) {
       GlobalValueMap<K, V, Traits>* persistentValueMap =
           Traits::MapFromWeakCallbackInfo(data);
       K key = Traits::KeyFromWeakCallbackInfo(data);
       persistentValueMap->RemoveWeak(key);
       Traits::DisposeWeak(data.GetIsolate(), data, key);
-      Traits::DisposeCallbackData(data.GetParameter());
     }
   }
 };
 
 
 /**
  * A map that uses Global as value and std::map as the backing
  * implementation. Persistents are held non-weak.
  *
  * C++11 embedders don't need this class, as they can use
@@ skipping 119 matching lines @@
     return reinterpret_cast<V*>(v);
   }
 
   Isolate* isolate_;
   typename Traits::Impl impl_;
 };
 
 }  // namespace v8
 
 #endif  // V8_UTIL_H