code class="code">_GLIBCXX_DEBUG</code> could decide whether the
  default <code class="code">Debug</code> argument is <code class="code">true</code>
  or <code class="code">false</code>. This option would break conformance with the
  C++ standard in both debug <span class="emphasis"><em>and</em></span> release modes. This would
  not meet our <span class="emphasis"><em>correctness</em></span> criteria. </p></li><li class="listitem"><p><span class="emphasis"><em>Packaging a debug flag in the allocators</em>