With the introduction of Qt 6 we encountered a memory leak which seems to be caused by sending queued signals.

I attached an example project along with a  heaptrack summary that points to some QByteArray reallocation when queued_activate for a signal is called.

The sample project is quite simple: A producer generates some signals in a thread. These signals are connected as Qt::QueuedConnections to a slot of an object in the main thread.

If I do something wrong in connection the thread please let me know

Btw, I made the same test with Qt 5.15 and the memory usage was stable.