">chanp</span><span class="special">-&gt;</span><span class="identifier">value_pop</span><span class="special">()</span> <span class="special">);</span>
        <span class="comment">// retrieve exception_ptr if any</span>
        <span class="identifier">std</span><span class="special">::</span><span class="identifier">exception_ptr</span> <span class="identifier">error</span><span class="special">(</span> <span class="identifier">future</span><span class="special">.</span><span class="identifier">get_exce