Fix race between Thread ctor/dtor and MessageQueueManager registrations.

webrtc/base/thread.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 76 matching lines @@
   Runnable() {}
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(Runnable);
 };
 
 // WARNING! SUBCLASSES MUST CALL Stop() IN THEIR DESTRUCTORS!  See ~Thread().
 
 class Thread : public MessageQueue {
  public:
-  explicit Thread(SocketServer* ss = NULL);
+  // Create a new Thread and optionally assign it to the passed SocketServer.
+  // Subclasses that override Clear should pass false for init_queue and call
+  // DoInit() from their constructor to prevent races with the
+  // MessageQueueManager already using the object while the vtable is still
+  // being created.
+  explicit Thread(SocketServer* ss = nullptr, bool init_queue = true);
+
   // NOTE: ALL SUBCLASSES OF Thread MUST CALL Stop() IN THEIR DESTRUCTORS (or
   // guarantee Stop() is explicitly called before the subclass is destroyed).
   // This is required to avoid a data race between the destructor modifying the
   // vtable, and the Thread::PreRun calling the virtual method Run().
   ~Thread() override;
 
   static Thread* Current();
 
   // Used to catch performance regressions. Use this to disallow blocking calls
   // (Invoke) for a given scope.  If a synchronous call is made while this is in
@@ skipping 170 matching lines @@
 
   RTC_DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 // AutoThread automatically installs itself at construction
 // uninstalls at destruction, if a Thread object is
 // _not already_ associated with the current OS thread.
 
 class AutoThread : public Thread {
  public:
-  explicit AutoThread(SocketServer* ss = 0);
+  explicit AutoThread(SocketServer* ss = nullptr);
   ~AutoThread() override;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(AutoThread);
 };
 
 // Win32 extension for threads that need to use COM
 #if defined(WEBRTC_WIN)
 class ComThread : public Thread {
  public:
   ComThread() {}
-  virtual ~ComThread() { Stop(); }
+  ~ComThread() override { Stop(); }
 
  protected:
-  virtual void Run();
+  void Run() override;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(ComThread);
 };
 #endif
 
 // Provides an easy way to install/uninstall a socketserver on a thread.
 class SocketServerScope {
  public:
   explicit SocketServerScope(SocketServer* ss) {
     old_ss_ = Thread::Current()->socketserver();
     Thread::Current()->set_socketserver(ss);
   }
   ~SocketServerScope() {
     Thread::Current()->set_socketserver(old_ss_);
   }
 
  private:
   SocketServer* old_ss_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(SocketServerScope);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_THREAD_H_