Restore the GUI to previous state when System signal occurs

[wysota]

You don't need to sync() in this situation, because the object gets synced when it's deleted. Does the signal handler actually get called?

[jpn]

Also, looks like you create a new MainWindow object in sighandler(). It's not the original window you have shown but another object..

[arunvv]

It worked now, it was just the way I was calling the writeSettings function.

Here is the way I handled the signal for MainWindow.
signal(SIGTERM, MainWindow::writeSettings);

And declared static void writeSettings(int sigNum); in header file under public.
And thus this function has been called when SIGTERM signal is caught.

Thanks to all who supported me in correcting me from doing faults.