 and STL: <span class="quote">&#8220;<span class="quote"><span class="emphasis"><em>17.6.4.8
      Other functions (...) 2. the effects are undefined in the following cases:
      (...) In particular - if an incomplete type (3.9) is used as a template argument
      when instantiating a template component, unless specifically allowed for that
      component</em></span></span>&#8221;</span>. Fortunately <span class="bold"><strong>Boost.Container</strong></span>
      containers are designed to support type 