Question

I have a few singleton classes with some extra functions which are run in separate thread. The structure looks like:

class Singleton
{
   private:
      boost::mutex mMutex;
      std::vector<std::string> mMessages;

   public:
      void AddMessage(const std::string &msg)
      {
         mMutex.lock();
         mMessages.push_back(msg);
         mMutex.unlock();
      }

      void Sender()
      {
          while (true) {
             mMutex.lock();
             for (size_t i = 0; i < mMessages.size(); ++i)
             {
                 // Do something with mMessages[i]
             }
             mMutex.unlock();
          }
      }
};

...

int main()
{
   Singleton *handle;
   handle = Singleton::instance();
   boost::thread sender(boost::bind(&Singleton::Sender, handle));

   ... app cycle ...
}

Sometimes it fails with error:

terminate called after throwing an instance of

'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::lock_error> >'
  what():  boost::lock_error
Aborted

What could it be and what’s the best why to find out the reason of assert?

Answer 1

May be that you did not create the object Singleton! So the mutex is not created either.

Try:

int main()
{
   Singleton handle; //object, not pointer
   boost::thread sender(boost::bind(&Singleton::Sender, &handle));
   ...
}