chSource</span> <span class="k">is</span> <span class="n">used</span>
<span class="mi">3</span><span class="o">.</span> <span class="kt">On</span> <span class="kt">Linux</span><span class="p">,</span> <span class="k">if</span> <span class="n">the</span> <span class="n">compile</span> <span class="n">time</span> <span class="n">option</span> <span class="o">-</span><span class="kt">Xswiftc</span> <span class="o">-</span><span class="kt">DGCD_ASYNCH</span> <span class="k">is</span> <span class="n">specified</