title: How to send a string via PostMessage?
body: <p>Inside my app, I want to send a message to a dialog from a different thread.
  I want to pass an std::exception derived class reference to the dialog. </p>
  
  <p>Something like this:</p>
  
  <pre><code>try {
         //do stuff
  }
  catch (MyException&amp; the_exception) {
      PostMessage(MyhWnd, CWM_SOME_ERROR, 0, 0); //send the_exception or the_exception.error_string() here
  }
  </code></pre>
  
  <p>I want to receive the message in my dialog and show the error that is in    <code>the_exception.error_string()</code></p>
  
  <pre><code>LPARAM CMyDlg::SomeError(WPARAM, LPARAM)
  {
      show_error( ?????
      return 0;
  }
  </code></pre>
  
  <p>passing the <code>std::string the_exception.error_string()</code> using PostMessage would also be ok, I guess.</p>