give UniquePersistent full move semantics

include/v8.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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 647 matching lines @@
   template<class F1, class F2> friend class Persistent;
   template<class F> friend class UniquePersistent;
   template<class F> friend class PersistentBase;
   template<class F> friend class ReturnValue;
   template <class F1, class F2, class F3>
   friend class PersistentValueMapBase;
   template<class F1, class F2> friend class PersistentValueVector;
   friend class Object;
 
   explicit V8_INLINE PersistentBase(T* val) : val_(val) {}
-  PersistentBase(PersistentBase& other); // NOLINT
-  void operator=(PersistentBase&);
+  PersistentBase(PersistentBase& other) = delete;  // NOLINT
+  void operator=(PersistentBase&) = delete;
   V8_INLINE static T* New(Isolate* isolate, T* that);
 
   T* val_;
 };
 
 
 /**
  * Default traits for Persistent. This class does not allow
  * use of the copy constructor or assignment operator.
  * At present kResetInDestructor is not set, but that will change in a future
@@ skipping 127 matching lines @@
 };
 
 
 /**
  * A PersistentBase which has move semantics.
  *
  * Note: Persistent class hierarchy is subject to future changes.
  */
 template<class T>
 class UniquePersistent : public PersistentBase<T> {
-  struct RValue {
-    V8_INLINE explicit RValue(UniquePersistent* obj) : object(obj) {}
-    UniquePersistent* object;
-  };
-
  public:
   /**
    * A UniquePersistent with no storage cell.
    */
-  V8_INLINE UniquePersistent() : PersistentBase<T>(0) { }
+  V8_INLINE UniquePersistent() : PersistentBase<T>(nullptr) {}
   /**
    * Construct a UniquePersistent from a Handle.
    * When the Handle is non-empty, a new storage cell is created
    * pointing to the same object, and no flags are set.
    */
   template <class S>
   V8_INLINE UniquePersistent(Isolate* isolate, Handle<S> that)
       : PersistentBase<T>(PersistentBase<T>::New(isolate, *that)) {
     TYPE_CHECK(T, S);
   }
   /**
    * Construct a UniquePersistent from a PersistentBase.
    * When the Persistent is non-empty, a new storage cell is created
    * pointing to the same object, and no flags are set.
    */
   template <class S>
   V8_INLINE UniquePersistent(Isolate* isolate, const PersistentBase<S>& that)
     : PersistentBase<T>(PersistentBase<T>::New(isolate, that.val_)) {
     TYPE_CHECK(T, S);
   }
   /**
    * Move constructor.
    */
-  V8_INLINE UniquePersistent(RValue rvalue)
-    : PersistentBase<T>(rvalue.object->val_) {
-    rvalue.object->val_ = 0;
+  V8_INLINE UniquePersistent(UniquePersistent&& other)
+      : PersistentBase<T>(other.val_) {
+    other.val_ = nullptr;
   }
   V8_INLINE ~UniquePersistent() { this->Reset(); }
   /**
    * Move via assignment.
    */
-  template<class S>
-  V8_INLINE UniquePersistent& operator=(UniquePersistent<S> rhs) {
+  template <class S>
+  V8_INLINE UniquePersistent& operator=(UniquePersistent<S>&& rhs) {

[jamesr, 2015/03/04 18:52:37]

operator=(T&&)s should support self assignment, but this appears to blow away
the object if |*this| == |rhs|. a safer way to write this would be

if (this != &rhs) {
  TYPE_CHECK
  ..
}

return *this

[dcarney, 2015/03/04 19:40:24]

good catch, thanks

     TYPE_CHECK(T, S);
     this->Reset();
     this->val_ = rhs.val_;
-    rhs.val_ = 0;
+    rhs.val_ = nullptr;
     return *this;
   }
   /**
-   * Cast operator for moves.
-   */
-  V8_INLINE operator RValue() { return RValue(this); }
-  /**
    * Pass allows returning uniques from functions, etc.
    */
-  UniquePersistent Pass() { return UniquePersistent(RValue(this)); }
+  // TODO(dcarney): deprecate, this is just std::move
+  UniquePersistent Pass() { return static_cast<UniquePersistent&&>(*this); }
 
  private:
-  UniquePersistent(UniquePersistent&);
-  void operator=(UniquePersistent&);
+  UniquePersistent(UniquePersistent&) = delete;
+  void operator=(UniquePersistent&) = delete;
 };
 
 
  /**
  * A stack-allocated class that governs a number of local handles.
  * After a handle scope has been created, all local handles will be
  * allocated within that handle scope until either the handle scope is
  * deleted or another handle scope is created.  If there is already a
  * handle scope and a new one is created, all allocations will take
  * place in the new handle scope until it is deleted.  After that,
@@ skipping 6828 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_