title: QLineEdit password safety
body: <p>In my application user types his password in <code>QLineEdit</code>.
  <code>QLineEdit</code> works in Password echo mode.</p>
  
  <p>Application must clear password from memory when it is no longer needed.</p>
  
  <p>Does <code>QLineEdit</code> make sure that it clears all its internal memory buffers before they are freed? I cannot found such information in documentation.</p>
  
  <p>If <code>QLineEdit</code> does not clear its content then what is the simplest way to implement such behavior? I want to reuse <code>QLineEdit</code> functionality as much as possible and do not want to implement my own password edit control from scratch. Is it possible?</p>