1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/base/ClearOnShutdown.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,108 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set sw=2 ts=8 et ft=cpp : */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef mozilla_ClearOnShutdown_h
1.11 +#define mozilla_ClearOnShutdown_h
1.12 +
1.13 +#include "mozilla/LinkedList.h"
1.14 +#include "mozilla/StaticPtr.h"
1.15 +#include "MainThreadUtils.h"
1.16 +
1.17 +/*
1.18 + * This header exports one public method in the mozilla namespace:
1.19 + *
1.20 + * template<class SmartPtr>
1.21 + * void ClearOnShutdown(SmartPtr *aPtr)
1.22 + *
1.23 + * This function takes a pointer to a smart pointer and nulls the smart pointer
1.24 + * on shutdown.
1.25 + *
1.26 + * This is useful if you have a global smart pointer object which you don't
1.27 + * want to "leak" on shutdown.
1.28 + *
1.29 + * Although ClearOnShutdown will work with any smart pointer (i.e., nsCOMPtr,
1.30 + * nsRefPtr, nsAutoPtr, StaticRefPtr, and StaticAutoPtr), you probably want to
1.31 + * use it only with StaticRefPtr and StaticAutoPtr. There is no way to undo a
1.32 + * call to ClearOnShutdown, so you can call it only on smart pointers which you
1.33 + * know will live until the program shuts down. In practice, these are likely
1.34 + * global variables, which should be Static{Ref,Auto}Ptr.
1.35 + *
1.36 + * ClearOnShutdown is currently main-thread only because we don't want to
1.37 + * accidentally free an object from a different thread than the one it was
1.38 + * created on.
1.39 + */
1.40 +
1.41 +namespace mozilla {
1.42 +namespace ClearOnShutdown_Internal {
1.43 +
1.44 +class ShutdownObserver : public LinkedListElement<ShutdownObserver>
1.45 +{
1.46 +public:
1.47 + virtual void Shutdown() = 0;
1.48 + virtual ~ShutdownObserver() {}
1.49 +};
1.50 +
1.51 +template<class SmartPtr>
1.52 +class PointerClearer : public ShutdownObserver
1.53 +{
1.54 +public:
1.55 + PointerClearer(SmartPtr *aPtr)
1.56 + : mPtr(aPtr)
1.57 + {}
1.58 +
1.59 + virtual void Shutdown()
1.60 + {
1.61 + if (mPtr) {
1.62 + *mPtr = nullptr;
1.63 + }
1.64 + }
1.65 +
1.66 +private:
1.67 + SmartPtr *mPtr;
1.68 +};
1.69 +
1.70 +extern bool sHasShutDown;
1.71 +extern StaticAutoPtr<LinkedList<ShutdownObserver> > sShutdownObservers;
1.72 +
1.73 +} // namespace ClearOnShutdown_Internal
1.74 +
1.75 +template<class SmartPtr>
1.76 +inline void ClearOnShutdown(SmartPtr *aPtr)
1.77 +{
1.78 + using namespace ClearOnShutdown_Internal;
1.79 +
1.80 + MOZ_ASSERT(NS_IsMainThread());
1.81 + MOZ_ASSERT(!sHasShutDown);
1.82 +
1.83 + if (!sShutdownObservers) {
1.84 + sShutdownObservers = new LinkedList<ShutdownObserver>();
1.85 + }
1.86 + sShutdownObservers->insertBack(new PointerClearer<SmartPtr>(aPtr));
1.87 +}
1.88 +
1.89 +// Called when XPCOM is shutting down, after all shutdown notifications have
1.90 +// been sent and after all threads' event loops have been purged.
1.91 +inline void KillClearOnShutdown()
1.92 +{
1.93 + using namespace ClearOnShutdown_Internal;
1.94 +
1.95 + MOZ_ASSERT(NS_IsMainThread());
1.96 +
1.97 + if (sShutdownObservers) {
1.98 + ShutdownObserver *observer;
1.99 + while ((observer = sShutdownObservers->popFirst())) {
1.100 + observer->Shutdown();
1.101 + delete observer;
1.102 + }
1.103 + }
1.104 +
1.105 + sShutdownObservers = nullptr;
1.106 + sHasShutDown = true;
1.107 +}
1.108 +
1.109 +} // namespace mozilla
1.110 +
1.111 +#endif
