signal/slot mechanism is totally independent of any GUI event loop

[Codepoet]

It means that this mechanism will work even if you don't have a running event loop.

At least if you have multiple threads with queued connections this is wrong: Queued connections are only processed in the event loop: QThread::exec
But all this works without a GUI, use QCoreApplication instead of QApplication.

[jacek]

At least if you have multiple threads with queued connections this is wrong:

Provided that you use Qt4, unlike the author of this thread.