Add defensive assert for having a weak, empty presistent in a

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 265 matching lines @@
  private:
   PersistentValueMap(PersistentValueMap&);
   void operator=(PersistentValueMap&);
 
   /**
    * Put the value into the map, and set the 'weak' callback when demanded
    * by the Traits class.
    */
   UniquePersistent<V> SetUnique(const K& key, UniquePersistent<V>* persistent) {
     if (Traits::kCallbackType != kNotWeak) {
+      // If the persistent is empty, the weak callback will actually never
+      // happen since there's no object to be garbage collected.
+      RELEASE_ASSERT(!persistent->IsEmpty());

[jochen (gone - plz use gerrit), 2014/05/05 17:42:46]

the v8 equivalent to RELEASE_ASSERT() is CHECK(), however, it's not available in
the header :-/

I'd add the CHECK in GlobalHandles::MakeWeak()

+
       Local<V> value(Local<V>::New(isolate_, *persistent));
       persistent->template SetWeak<typename Traits::WeakCallbackDataType>(
         Traits::WeakCallbackParameter(this, key, value), WeakCallback);
     }
     PersistentContainerValue old_value =
         Traits::Set(&impl_, key, ClearAndLeak(persistent));
     return Release(old_value).Pass();
   }
 
   static void WeakCallback(
@@ skipping 181 matching lines @@
     return reinterpret_cast<V*>(v);
   }
 
   Isolate* isolate_;
   typename Traits::Impl impl_;
 };
 
 }  // namespace v8
 
 #endif  // V8_UTIL_H_