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comparison: xpcom/base/ClearOnShutdown.h
xpcom/base/ClearOnShutdown.h
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* vim: set sw=2 ts=8 et ft=cpp : */ | |
| 3 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 #ifndef mozilla_ClearOnShutdown_h | |
| 8 #define mozilla_ClearOnShutdown_h | |
| 9 | |
| 10 #include "mozilla/LinkedList.h" | |
| 11 #include "mozilla/StaticPtr.h" | |
| 12 #include "MainThreadUtils.h" | |
| 13 | |
| 14 /* | |
| 15 * This header exports one public method in the mozilla namespace: | |
| 16 * | |
| 17 * template<class SmartPtr> | |
| 18 * void ClearOnShutdown(SmartPtr *aPtr) | |
| 19 * | |
| 20 * This function takes a pointer to a smart pointer and nulls the smart pointer | |
| 21 * on shutdown. | |
| 22 * | |
| 23 * This is useful if you have a global smart pointer object which you don't | |
| 24 * want to "leak" on shutdown. | |
| 25 * | |
| 26 * Although ClearOnShutdown will work with any smart pointer (i.e., nsCOMPtr, | |
| 27 * nsRefPtr, nsAutoPtr, StaticRefPtr, and StaticAutoPtr), you probably want to | |
| 28 * use it only with StaticRefPtr and StaticAutoPtr. There is no way to undo a | |
| 29 * call to ClearOnShutdown, so you can call it only on smart pointers which you | |
| 30 * know will live until the program shuts down. In practice, these are likely | |
| 31 * global variables, which should be Static{Ref,Auto}Ptr. | |
| 32 * | |
| 33 * ClearOnShutdown is currently main-thread only because we don't want to | |
| 34 * accidentally free an object from a different thread than the one it was | |
| 35 * created on. | |
| 36 */ | |
| 37 | |
| 38 namespace mozilla { | |
| 39 namespace ClearOnShutdown_Internal { | |
| 40 | |
| 41 class ShutdownObserver : public LinkedListElement<ShutdownObserver> | |
| 42 { | |
| 43 public: | |
| 44 virtual void Shutdown() = 0; | |
| 45 virtual ~ShutdownObserver() {} | |
| 46 }; | |
| 47 | |
| 48 template<class SmartPtr> | |
| 49 class PointerClearer : public ShutdownObserver | |
| 50 { | |
| 51 public: | |
| 52 PointerClearer(SmartPtr *aPtr) | |
| 53 : mPtr(aPtr) | |
| 54 {} | |
| 55 | |
| 56 virtual void Shutdown() | |
| 57 { | |
| 58 if (mPtr) { | |
| 59 *mPtr = nullptr; | |
| 60 } | |
| 61 } | |
| 62 | |
| 63 private: | |
| 64 SmartPtr *mPtr; | |
| 65 }; | |
| 66 | |
| 67 extern bool sHasShutDown; | |
| 68 extern StaticAutoPtr<LinkedList<ShutdownObserver> > sShutdownObservers; | |
| 69 | |
| 70 } // namespace ClearOnShutdown_Internal | |
| 71 | |
| 72 template<class SmartPtr> | |
| 73 inline void ClearOnShutdown(SmartPtr *aPtr) | |
| 74 { | |
| 75 using namespace ClearOnShutdown_Internal; | |
| 76 | |
| 77 MOZ_ASSERT(NS_IsMainThread()); | |
| 78 MOZ_ASSERT(!sHasShutDown); | |
| 79 | |
| 80 if (!sShutdownObservers) { | |
| 81 sShutdownObservers = new LinkedList<ShutdownObserver>(); | |
| 82 } | |
| 83 sShutdownObservers->insertBack(new PointerClearer<SmartPtr>(aPtr)); | |
| 84 } | |
| 85 | |
| 86 // Called when XPCOM is shutting down, after all shutdown notifications have | |
| 87 // been sent and after all threads' event loops have been purged. | |
| 88 inline void KillClearOnShutdown() | |
| 89 { | |
| 90 using namespace ClearOnShutdown_Internal; | |
| 91 | |
| 92 MOZ_ASSERT(NS_IsMainThread()); | |
| 93 | |
| 94 if (sShutdownObservers) { | |
| 95 ShutdownObserver *observer; | |
| 96 while ((observer = sShutdownObservers->popFirst())) { | |
| 97 observer->Shutdown(); | |
| 98 delete observer; | |
| 99 } | |
| 100 } | |
| 101 | |
| 102 sShutdownObservers = nullptr; | |
| 103 sHasShutDown = true; | |
| 104 } | |
| 105 | |
| 106 } // namespace mozilla | |
| 107 | |
| 108 #endif |
