Comment 7 for bug 1497179

I think the bug is related to https://bugreports.qt.io/browse/QTBUG-48709
It happens when a QApplication has been instantiated but its destructor is not called before the atexit() handlers, i.e. the code terminates through exit() without cleaning up.
In the core file, the call stack is smashed.

I don't know what particular program does that in a KUbuntu login sequence, though. If dmesg doesn't tell, maybe core files should be activated and inspected after the fact, just to get the name of the executable.