title: Passing an auto_ptr to a function effectively makes it a sink. Why?
body: <p>I'm reading some notes about shared pointers.
  They say the first attempt by STL with the auto_ptr had the following major drawbacks:</p>
  
  <ul>
  <li>They can't be used in STL containers</li>
  <li>Copying the auto_ptr transfers ownership</li>
  <li>Passing an auto_ptr to a function effectively makes it a sink</li>
  </ul>
  
  <p>I understand the first two, but am unsure what the last one means. </p>
  
  <p>Could someone please explain this.</p>
  
  <p>Thanks.</p>