Clean up base::Callback stuff

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 49 matching lines @@
  public:
   CallbackBase(const CallbackBase& c);
   CallbackBase& operator=(const CallbackBase& c);
 
   // Returns true if Callback is null (doesn't refer to anything).
   bool is_null() const { return bind_state_.get() == NULL; }
 
   // Returns the Callback into an uninitialized state.
   void Reset();
 
+  // Returns true if this callback equals |other|. |other| may be null.
+  bool Equals(const CallbackBase& other) const;

[dcheng, 2015/12/08 20:16:46]

I'm curious: do you know why we didn't just do this to begin with?

[danakj, 2015/12/08 22:12:59]

Does this allow comparison of

Callback<void(int)> and Callback<void(int, int)> to compile because they both
upcast to CallbackBase?

[tzik, 2015/12/09 07:03:15]

Ah, yes. Let me revert this part, that is an unintended side effect of the clean
up.

+
  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.
   typedef void(*InvokeFuncStorage)(void);
 
-  // Returns true if this callback equals |other|. |other| may be null.
-  bool Equals(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.
   explicit CallbackBase(BindStateBase* bind_state);
 
   // Force the destructor to be instantiated inside this translation unit so
   // that our subclasses will not get inlined versions.  Avoids more template
   // bloat.
   ~CallbackBase();
@@ skipping 123 matching lines @@
 template <typename T>
 typename std::enable_if<IsMoveOnlyType<T>::value, T>::type CallbackForward(
     T& t) {
   return std::move(t);
 }
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_INTERNAL_H_