113 lines
2.9 KiB
C++
113 lines
2.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_ClearOnShutdown_h
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#define mozilla_ClearOnShutdown_h
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#include "mozilla/LinkedList.h"
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#include "mozilla/StaticPtr.h"
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#include "MainThreadUtils.h"
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/*
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* This header exports one public method in the mozilla namespace:
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*
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* template<class SmartPtr>
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* void ClearOnShutdown(SmartPtr *aPtr)
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*
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* This function takes a pointer to a smart pointer and nulls the smart pointer
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* on shutdown.
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*
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* This is useful if you have a global smart pointer object which you don't
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* want to "leak" on shutdown.
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*
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* Although ClearOnShutdown will work with any smart pointer (i.e., nsCOMPtr,
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* nsRefPtr, nsAutoPtr, StaticRefPtr, and StaticAutoPtr), you probably want to
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* use it only with StaticRefPtr and StaticAutoPtr. There is no way to undo a
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* call to ClearOnShutdown, so you can call it only on smart pointers which you
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* know will live until the program shuts down. In practice, these are likely
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* global variables, which should be Static{Ref,Auto}Ptr.
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*
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* ClearOnShutdown is currently main-thread only because we don't want to
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* accidentally free an object from a different thread than the one it was
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* created on.
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*/
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namespace mozilla {
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namespace ClearOnShutdown_Internal {
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class ShutdownObserver : public LinkedListElement<ShutdownObserver>
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{
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public:
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virtual void Shutdown() = 0;
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virtual ~ShutdownObserver()
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{
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}
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};
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template<class SmartPtr>
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class PointerClearer : public ShutdownObserver
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{
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public:
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explicit PointerClearer(SmartPtr* aPtr)
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: mPtr(aPtr)
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{
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}
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virtual void Shutdown() override
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{
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if (mPtr) {
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*mPtr = nullptr;
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}
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}
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private:
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SmartPtr* mPtr;
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};
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extern bool sHasShutDown;
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extern StaticAutoPtr<LinkedList<ShutdownObserver>> sShutdownObservers;
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} // namespace ClearOnShutdown_Internal
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template<class SmartPtr>
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inline void
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ClearOnShutdown(SmartPtr* aPtr)
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{
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using namespace ClearOnShutdown_Internal;
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MOZ_ASSERT(NS_IsMainThread());
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MOZ_ASSERT(!sHasShutDown);
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if (!sShutdownObservers) {
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sShutdownObservers = new LinkedList<ShutdownObserver>();
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}
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sShutdownObservers->insertBack(new PointerClearer<SmartPtr>(aPtr));
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}
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// Called when XPCOM is shutting down, after all shutdown notifications have
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// been sent and after all threads' event loops have been purged.
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inline void
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KillClearOnShutdown()
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{
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using namespace ClearOnShutdown_Internal;
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MOZ_ASSERT(NS_IsMainThread());
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if (sShutdownObservers) {
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while (ShutdownObserver* observer = sShutdownObservers->popFirst()) {
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observer->Shutdown();
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delete observer;
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}
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}
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sShutdownObservers = nullptr;
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sHasShutDown = true;
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}
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} // namespace mozilla
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#endif
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