POSIX: allow WaitableEvents to be deleted while watching them.

base/waitable_event_watcher.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_WAITABLE_EVENT_WATCHER_H_
 #define BASE_WAITABLE_EVENT_WATCHER_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include "base/object_watcher.h"
 #else
 #include "base/message_loop.h"
+#include "base/waitable_event.h"
 #endif
 
 namespace base {
 
-class WaitableEvent;
 class Flag;
 class AsyncWaiter;
 class AsyncCallbackTask;
 
 // -----------------------------------------------------------------------------
 // This class provides a way to wait on a WaitableEvent asynchronously.
 //
 // Each instance of this object can be waiting on a single WaitableEvent. When
 // the waitable event is signaled, a callback is made in the thread of a given
 // MessageLoop. This callback can be deleted by deleting the waiter.
@@ skipping 15 matching lines @@
 // In the above example, MyClass wants to "do stuff" when waitable_event
 // becomes signaled. WaitableEventWatcher makes this task easy. When MyClass
 // goes out of scope, the watcher_ will be destroyed, and there is no need to
 // worry about OnWaitableEventSignaled being called on a deleted MyClass
 // pointer.
 //
 // BEWARE: With automatically reset WaitableEvents, a signal may be lost if it
 // occurs just before a WaitableEventWatcher is deleted. There is currently no
 // safe way to stop watching an automatic reset WaitableEvent without possibly
 // missing a signal.
+//
+// NOTE: you /are/ allowed to delete the WaitableEvent while still waiting on
+// it with a Watcher. It will act as if the event was never signaled.
 // -----------------------------------------------------------------------------
 
 class WaitableEventWatcher
 #if defined(OS_POSIX)
     : public MessageLoop::DestructionObserver
 #endif
 {
  public:
 
   WaitableEventWatcher();
@@ skipping 69 matching lines @@
 #else
   // ---------------------------------------------------------------------------
   // Implementation of MessageLoop::DestructionObserver
   // ---------------------------------------------------------------------------
   void WillDestroyCurrentMessageLoop();
 
   MessageLoop* message_loop_;
   scoped_refptr<Flag> cancel_flag_;
   AsyncWaiter* waiter_;
   AsyncCallbackTask* callback_task_;
+  scoped_refptr<WaitableEvent::WaitableEventKernel> kernel_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_WAITABLE_EVENT_WATCHER_H_