class="code">std::list</code>, adding additional semantic
  checks and then forwarding operations to the
  real <code class="code">std::list</code> (a public base class of the debugging
  version) as appropriate. However, all safe containers inherit from
  the class template <code class="code">__gnu_debug::_Safe_sequence</code>,
  instantiated with the type of the safe container itself (an instance
  of the curiously recurring template pattern).</p><p>The iterators of a container wrapper will be
  <a class=