Assertion failure causing immediate app exit in the debug mode when adding a connection

[yurrig]

Hi there,

Thanks for the great library!

Now, the issue.

I have just got an assertion failure in the QToolBar constructor that prevents my app to start in the debug mode. A closer look shows that it is caused by broken mutex in a libguarded::SharedList<ConnectStruct>::write_handle instance in QObject::connect(). This happens when the senderListHandle is passed by value to sender.addConnection in cs_signal.h line 332, and then unlock() call when destructing the copy corrupts the mutex in the original write_handle.

I fixed the issue locally by passing the write_handle to sender.addConnection() by reference. However, the problem with copying of write_handle objects looks more general. Here is a little repro example:

Code: Select all

      libguarded::SharedList<ConnectStruct> connectList;
      {
         auto senderListHandle = connectList.lock_write();
         *senderListHandle; // access the handle - important!
         {
            auto senderListHandle2 = senderListHandle; // make a local copy that is immediately destructed
         }
      } // <-- assertion failure in the senderListHandle destructor, as both senderListHandle and senderListHandle2 share the same mutex instance

Would it make sense to make the class movable-only? Or maybe use a reference counting to make sure the unlock happens only when the last copy of a write_handle object is destroyed?

Best Regards,
Yuri