title: Use std::vector::data after reserve
body: <p>I have a <code>std::vector</code> on which I call <code>reserve</code> with a large value. Afterwards I retrieve <code>data()</code>.</p>
  
  <p>Since iterating <code>data</code> is then crashing I am wondering whether this is even allowed. Is <code>reserve</code> forced to update <code>data</code> to the allocated memory range?</p>