title: How can i get xml line number from ptree exception
body: <p>I am using boost ptree to read an xml file like this:</p>
  
  <pre><code>ptree myTree;
  ... /*open xml file*/
  try{
      myTree.get&lt;string&gt;(s);
  }
  catch(boost::exception const&amp;  ex)
  {
  /*get useful info!*/
  }
  </code></pre>
  
  <p>I know I can use the <code>what()</code> function, but it produces an error and the strings I just sent.</p>
  
  <p>Is there a way to get more useful information like the line numbers in the xml that are relevant to the call?</p>