title: Delete on already deleted object : behavior?
body: <p>I am wondering what will hapen if I try to do a <code>delete</code> on a pointer that is already deleted, or may have not been allocated ? I've read two things : first, that <code>delete</code> operator will do some checkings and we do not need to check if the pointer is null ; and then, I read that it can lead to unknown behaviors..</p>
  
  <p>I'm asking it, because I use some personal objects that contains Qt objects attributes ; I think that Qt delete all widgets associated when we close the window, but I'm not pretty sure and still : if the soft crash before the window's close, we have to delete all objects manually.</p>
  
  <p>So, what would be the best solution ? Something like that ?</p>
  
  <pre><code>if( my_object )
      delete my_object;
  </code></pre>
  
  <p>Can it avoid dangerous behaviours ?</p>