without Qt::QueuedConnection will crash

[hashb]

Hi tbscope,you mean the slot of the thread executed in the main thread ?

Here the big problem is that you're dealing with two distinct event loops.
Even with a queued connection, the logic is still wrong as the slot of the thread is not executed in the thread itself but in the main thread resulting in possible crashes.

Edit: never mind, the connection is made in the main thread. Just ignore this post.

Thanks a lot for you explanation,
it was just a test in order to produce a loop

Because without Qt::QueuedConnection emmiting signal is like a calling slot function. So You call onDoComm() BEFORE ending this method that is to say "classic stack overflow".
With Qt::QueuedConnection slot function is calling by signal dispatcher in idle time.

Question is : why You emit StartSignal() in onDoComm() ?