end of each line no backtracking can</span>
    <span class="comment">// occur anymore so that it's safe to clear all internal buffers in the </span>
    <span class="comment">// multi_pass.</span>
    <span class="identifier">preprocessor</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">preprocessor</span><span class="special">::</span><span class="identifier">base_type</span><span class="special">(</span><span class="identifier">file</span><span class="special"