/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_ClearOnShutdown_h

#define mozilla_ClearOnShutdown_h

#include "mozilla/LinkedList.h"

#include "mozilla/StaticPtr.h"

#include "mozilla/Array.h"

#include "MainThreadUtils.h"

/*

 * This header exports one public method in the mozilla namespace:

 *

 *   template<class SmartPtr>

 *   void ClearOnShutdown(SmartPtr *aPtr, aPhase=ShutdownPhase::ShutdownFinal)

 *

 * This function takes a pointer to a smart pointer and nulls the smart pointer

 * on shutdown (and a particular phase of shutdown as needed).  If a phase

 * is specified, the ptr will be cleared at the start of that phase.  Also,

 * if a phase has already occurred when ClearOnShutdown() is called it will

 * cause a MOZ_ASSERT.  In case a phase is not explicitly cleared we will

 * clear it on the next phase that occurs.

 *

 * This is useful if you have a global smart pointer object which you don't

 * want to "leak" on shutdown.

 *

 * Although ClearOnShutdown will work with any smart pointer (i.e., nsCOMPtr,

 * nsRefPtr, nsAutoPtr, StaticRefPtr, and StaticAutoPtr), you probably want to

 * use it only with StaticRefPtr and StaticAutoPtr.  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.  In practice, these are likely

 * global variables, which should be Static{Ref,Auto}Ptr.

 *

 * 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 {

// Must be contiguous starting at 0

enum class ShutdownPhase {

  NotInShutdown = 0,

  WillShutdown,

  Shutdown,

  ShutdownThreads,

  ShutdownLoaders,

  ShutdownFinal,

  ShutdownPhase_Length, // never pass this value

  First = WillShutdown, // for iteration

  Last = ShutdownFinal

};

namespace ClearOnShutdown_Internal {

class ShutdownObserver : public LinkedListElement<ShutdownObserver>

{

public:

  virtual void Shutdown() = 0;

  virtual ~ShutdownObserver()

  {

  }

};

template<class SmartPtr>

class PointerClearer : public ShutdownObserver

{

public:

  explicit PointerClearer(SmartPtr* aPtr)

    : mPtr(aPtr)

  {

  }

Unexecuted instantiation: mozilla::ClearOnShutdown_Internal::PointerClearer<mozilla::StaticAutoPtr<mozilla::plugins::FunctionHookArray> >::PointerClearer(mozilla::StaticAutoPtr<mozilla::plugins::FunctionHookArray>*)

Unexecuted instantiation: mozilla::ClearOnShutdown_Internal::PointerClearer<mozilla::StaticAutoPtr<mozilla::dom::ContentChild::ShutdownCanary> >::PointerClearer(mozilla::StaticAutoPtr<mozilla::dom::ContentChild::ShutdownCanary>*)

  virtual void Shutdown() override

  {

    if (mPtr) {

      *mPtr = nullptr;

    }

  }

Unexecuted instantiation: mozilla::ClearOnShutdown_Internal::PointerClearer<mozilla::StaticAutoPtr<mozilla::plugins::FunctionHookArray> >::Shutdown()

Unexecuted instantiation: mozilla::ClearOnShutdown_Internal::PointerClearer<mozilla::StaticAutoPtr<mozilla::dom::ContentChild::ShutdownCanary> >::Shutdown()

private:

  SmartPtr* mPtr;

};

typedef LinkedList<ShutdownObserver> ShutdownList;

extern Array<StaticAutoPtr<ShutdownList>,

             static_cast<size_t>(ShutdownPhase::ShutdownPhase_Length)> sShutdownObservers;

extern ShutdownPhase sCurrentShutdownPhase;

} // namespace ClearOnShutdown_Internal

template<class SmartPtr>

inline void

ClearOnShutdown(SmartPtr* aPtr, ShutdownPhase aPhase = ShutdownPhase::ShutdownFinal)

{

  using namespace ClearOnShutdown_Internal;

  MOZ_ASSERT(NS_IsMainThread());

  MOZ_ASSERT(aPhase != ShutdownPhase::ShutdownPhase_Length);

  // Adding a ClearOnShutdown for a "past" phase is an error.

  if (!(static_cast<size_t>(sCurrentShutdownPhase) < static_cast<size_t>(aPhase))) {

    MOZ_ASSERT(false, "ClearOnShutdown for phase that already was cleared");

    *aPtr = nullptr;

    return;

  }

  if (!(sShutdownObservers[static_cast<size_t>(aPhase)])) {

    sShutdownObservers[static_cast<size_t>(aPhase)] = new ShutdownList();

  }

  sShutdownObservers[static_cast<size_t>(aPhase)]->insertBack(new PointerClearer<SmartPtr>(aPtr));

}

Unexecuted instantiation: void mozilla::ClearOnShutdown<mozilla::StaticAutoPtr<mozilla::plugins::FunctionHookArray> >(mozilla::StaticAutoPtr<mozilla::plugins::FunctionHookArray>*, mozilla::ShutdownPhase)

Unexecuted instantiation: void mozilla::ClearOnShutdown<mozilla::StaticAutoPtr<mozilla::dom::ContentChild::ShutdownCanary> >(mozilla::StaticAutoPtr<mozilla::dom::ContentChild::ShutdownCanary>*, mozilla::ShutdownPhase)

// Called when XPCOM is shutting down, after all shutdown notifications have

// been sent and after all threads' event loops have been purged.

void KillClearOnShutdown(ShutdownPhase aPhase);

} // namespace mozilla

#endif