title: Correct way to quit a Qt program?
body: <p>How should I quit a Qt Program, e.g when loading a data file, and discovered file corruption, and user need to quit this app or re-initiate data file?</p>
  
  <p>Should I:</p>
  
  <ol>
  <li>call <code>exit(EXIT_FAILURE)</code></li>
  <li>call <code>QApplication::quit()</code></li>
  <li>call <code>QCoreApplication::quit()</code></li>
  </ol>
  
  <p>And difference between (2) and (3)?</p>