 invokes undefined
    behavior) is not required to behave similarly, although the debug
    mode will abort with a diagnostic when it detects undefined
    behavior.</p></li><li class="listitem"><p><span class="emphasis"><em>Performance</em></span>: the additional of the libstdc++ debug mode
    must not affect the performance of the library when it is compiled
    in release mode. Performance of the libstdc++ debug mode is
    secondary (and, in fact, will be worse than the release
    mode).</p></li><li 