app.exec() never returns?

[marcel]

Do you create any widget?I mean, a widget that is displayed.
Because exec() is actually a loop that exits when you call quit or exit.
When you press the close("x") button in a window, then exit(0) is called. Therefore the event loop exits.

So, most likely you did not create a main widget.

If you did, then check your code in other parts of the application. Maybe an infinite loop ?

Regards