Disallow dereferencing deferred handles when generating optimized code.

src/handles.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 55 matching lines @@
   // Check if this handle refers to the exact same object as the other handle.
   INLINE(bool is_identical_to(const Handle<T> other) const);
 
   // Provides the C++ dereference operator.
   INLINE(T* operator*() const);
 
   // Returns the address to where the raw pointer is stored.
   INLINE(T** location() const);
 
   template <class S> static Handle<T> cast(Handle<S> that) {
-    T::cast(*that);
-    return Handle<T>(reinterpret_cast<T**>(that.location()));
+    T::cast(*reinterpret_cast<T**>(that.location_));
+    return Handle<T>(reinterpret_cast<T**>(that.location_));
   }
 
   static Handle<T> null() { return Handle<T>(); }
   bool is_null() const { return location_ == NULL; }
 
   // Closes the given scope, but lets this handle escape. See
   // implementation in api.h.
   inline Handle<T> EscapeFrom(v8::HandleScope* scope);
 
+#ifdef DEBUG
+  bool IsDereferenceAllowed(bool allow_deferred) const;
+#endif  // DEBUG
+
  private:
   T** location_;
 
   // Handles of different classes are allowed to access each other's location_.
   template<class S> friend class Handle;
 };
 
 
 // Convenience wrapper.
 template<class T>
@@ skipping 237 matching lines @@
  private:
   Isolate* isolate_;
   int level_;
   bool active_;
 #endif
 };
 
 
 class HandleDereferenceGuard BASE_EMBEDDED {
  public:
-  enum State { ALLOW, DISALLOW };
+  enum State { ALLOW, DISALLOW, DISALLOW_DEFERRED };
 #ifndef DEBUG
   HandleDereferenceGuard(Isolate* isolate, State state) { }
   ~HandleDereferenceGuard() { }
 #else
   inline HandleDereferenceGuard(Isolate* isolate,  State state);
   inline ~HandleDereferenceGuard();
  private:
   Isolate* isolate_;
-  bool old_state_;
+  State old_state_;
 #endif
 };
 
+#ifdef DEBUG
+#define ALLOW_HANDLE_DEREF(isolate, why_this_is_safe)                          \
+  HandleDereferenceGuard allow_deref(isolate,                                  \
+                                     HandleDereferenceGuard::ALLOW);
+#else
+#define ALLOW_HANDLE_DEREF(isolate, why_this_is_safe)
+#endif  // DEBUG
+
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_