When you call hide() on a QDialog, it breaks the exec() loop, even if you subsequently call show(). According to the documentation, the loop should remain active until the dialog is closed. Calling hide() does not close the dialog; it simply makes it invisible while the dialog still exists.

I have attached a simple example (without a main loop) featuring two buttons: one for hiding the dialog and another for closing it. The button for hiding should not exit the exec() loop.