Move CallbackBase::polymorphic_invoke_ into BindStateBase

base/callback_internal.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains utility functions and classes that help the
 // implementation, and management of the Callback objects.
 
 #ifndef BASE_CALLBACK_INTERNAL_H_
 #define BASE_CALLBACK_INTERNAL_H_
 
@@ skipping 13 matching lines @@
 // behaves as an existential type that is used by a corresponding
 // DoInvoke function to perform the function execution.  This allows
 // us to shield the Callback class from the types of the bound argument via
 // "type erasure."
 // At the base level, the only task is to add reference counting data. Don't use
 // RefCountedThreadSafe since it requires the destructor to be a virtual method.
 // Creating a vtable for every BindState template instantiation results in a lot
 // of bloat. Its only task is to call the destructor which can be done with a
 // function pointer.
 class BindStateBase {
+ public:
+  using InvokeFuncStorage = void(*)();
+
  protected:
-  explicit BindStateBase(void (*destructor)(BindStateBase*))
-      : ref_count_(0), destructor_(destructor) {}
+  BindStateBase(InvokeFuncStorage polymorphic_invoke,
+                void (*destructor)(BindStateBase*))
+      : polymorphic_invoke_(polymorphic_invoke),
+        ref_count_(0), destructor_(destructor) {}
   ~BindStateBase() = default;
 
  private:
   friend class scoped_refptr<BindStateBase>;
   template <CopyMode copy_mode>
   friend class CallbackBase;
 
   void AddRef();
   void Release();
 
+  // In C++, it is safe to cast function pointers to function pointers of
+  // another type. It is not okay to use void*. We create a InvokeFuncStorage
+  // that that can store our function pointer, and then cast it back to
+  // the original type on usage.
+  InvokeFuncStorage polymorphic_invoke_;
+
   AtomicRefCount ref_count_;
 
   // Pointer to a function that will properly destroy |this|.
   void (*destructor_)(BindStateBase*);
 
   DISALLOW_COPY_AND_ASSIGN(BindStateBase);
 };
 
 // Holds the Callback methods that don't require specialization to reduce
 // template bloat.
 // CallbackBase<MoveOnly> is a direct base class of MoveOnly callbacks, and
 // CallbackBase<Copyable> uses CallbackBase<MoveOnly> for its implementation.
 template <>
 class BASE_EXPORT CallbackBase<CopyMode::MoveOnly> {
  public:
   CallbackBase(CallbackBase&& c);
   CallbackBase& operator=(CallbackBase&& c);
 
   // Returns true if Callback is null (doesn't refer to anything).
   bool is_null() const { return bind_state_.get() == NULL; }
   explicit operator bool() const { return !is_null(); }
 
   // Returns the Callback into an uninitialized state.
   void Reset();
 
  protected:
-  // In C++, it is safe to cast function pointers to function pointers of
-  // another type. It is not okay to use void*. We create a InvokeFuncStorage
-  // that that can store our function pointer, and then cast it back to
-  // the original type on usage.
-  using InvokeFuncStorage = void(*)();
+  using InvokeFuncStorage = BindStateBase::InvokeFuncStorage;
 
   // Returns true if this callback equals |other|. |other| may be null.
   bool EqualsInternal(const CallbackBase& other) const;
 
   // Allow initializing of |bind_state_| via the constructor to avoid default
-  // initialization of the scoped_refptr.  We do not also initialize
-  // |polymorphic_invoke_| here because doing a normal assignment in the
-  // derived Callback templates makes for much nicer compiler errors.
+  // initialization of the scoped_refptr.
   explicit CallbackBase(BindStateBase* bind_state);
 
+  InvokeFuncStorage polymorphic_invoke() const {
+    return bind_state_->polymorphic_invoke_;
+  }
+
   // Force the destructor to be instantiated inside this translation unit so
   // that our subclasses will not get inlined versions.  Avoids more template
   // bloat.
   ~CallbackBase();
 
   scoped_refptr<BindStateBase> bind_state_;
-  InvokeFuncStorage polymorphic_invoke_ = nullptr;
 };
 
 // CallbackBase<Copyable> is a direct base class of Copyable Callbacks.
 template <>
 class BASE_EXPORT CallbackBase<CopyMode::Copyable>
     : public CallbackBase<CopyMode::MoveOnly> {
  public:
   CallbackBase(const CallbackBase& c);
   CallbackBase(CallbackBase&& c);
   CallbackBase& operator=(const CallbackBase& c);
   CallbackBase& operator=(CallbackBase&& c);
  protected:
   explicit CallbackBase(BindStateBase* bind_state)
       : CallbackBase<CopyMode::MoveOnly>(bind_state) {}
   ~CallbackBase() {}
 };
 
 extern template class CallbackBase<CopyMode::MoveOnly>;
 extern template class CallbackBase<CopyMode::Copyable>;
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_INTERNAL_H_