// Copyright 2018 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. #ifndef BASE_OBSERVER_LIST_TYPES_H_ #define BASE_OBSERVER_LIST_TYPES_H_ #include "base/base_export.h" #include "base/memory/weak_ptr.h" namespace base { namespace internal { class CheckedObserverAdapter; } // A CheckedObserver serves as a base class for an observer interface designed // to be used with base::ObserverList. It helps detect potential use-after-free // issues that can occur when observers fail to remove themselves from an // observer list upon destruction. // // A CheckedObserver will CHECK() if an ObserverList iteration is attempted over // a destroyed Observer. // // Note that a CheckedObserver subclass must be deleted on the same thread as // the ObserverList(s) it is added to. This is DCHECK()ed via WeakPtr. class BASE_EXPORT CheckedObserver { public: CheckedObserver(); CheckedObserver(const CheckedObserver&) = delete; CheckedObserver& operator=(const CheckedObserver&) = delete; virtual ~CheckedObserver(); // Returns whether |this| is in any ObserverList. Subclasses can CHECK() this // in their destructor to obtain a nicer stacktrace. bool IsInObserverList() const; private: friend class internal::CheckedObserverAdapter; // Must be mutable to allow ObserverList. mutable WeakPtrFactory factory_{this}; }; } // namespace base #endif // BASE_OBSERVER_LIST_TYPES_H_