pjs/xpcom/base/ClearOnShutdown.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=8 et ft=cpp : */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at:
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Justin Lebar <justin.lebar@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef mozilla_ClearOnShutdown_h
#define mozilla_ClearOnShutdown_h
#include "mozilla/LinkedList.h"
#include "nsThreadUtils.h"
/*
* This header exports one public method in the mozilla namespace:
*
* template<class SmartPtr>
* void ClearOnShutdown(SmartPtr *aPtr)
*
* This function takes a pointer to a smart pointer (i.e., nsCOMPtr<T>*,
* nsRefPtr<T>*, or nsAutoPtr<T>*) and nulls the smart pointer on shutdown.
*
* This is useful if you have a global smart pointer object which you don't
* want to "leak" on shutdown.
*
* There is no way to undo a call to ClearOnShutdown, so you can call it only
* on smart pointers which you know will live until the program shuts down.
*
* ClearOnShutdown is currently main-thread only because we don't want to
* accidentally free an object from a different thread than the one it was
* created on.
*/
namespace mozilla {
namespace ClearOnShutdown_Internal {
class ShutdownObserver : public LinkedListElement<ShutdownObserver>
{
public:
virtual void Shutdown() = 0;
};
template<class SmartPtr>
class PointerClearer : public ShutdownObserver
{
public:
PointerClearer(SmartPtr *aPtr)
: mPtr(aPtr)
{}
virtual void Shutdown()
{
if (mPtr) {
*mPtr = NULL;
}
}
private:
SmartPtr *mPtr;
};
extern bool sHasShutDown;
extern LinkedList<ShutdownObserver> sShutdownObservers;
} // namespace ClearOnShutdown_Internal
template<class SmartPtr>
inline void ClearOnShutdown(SmartPtr *aPtr)
{
using namespace ClearOnShutdown_Internal;
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(!sHasShutDown);
ShutdownObserver *observer = new PointerClearer<SmartPtr>(aPtr);
sShutdownObservers.insertBack(observer);
}
// Called when XPCOM is shutting down, after all shutdown notifications have
// been sent and after all threads' event loops have been purged.
inline void KillClearOnShutdown()
{
using namespace ClearOnShutdown_Internal;
MOZ_ASSERT(NS_IsMainThread());
ShutdownObserver *observer;
while ((observer = sShutdownObservers.popFirst())) {
observer->Shutdown();
delete observer;
}
sHasShutDown = true;
}
} // namespace mozilla
#endif