ccess and non-zero return
value will invoke <code>usage_with_options()</code> and, thus, die.</p>
</li>
<li>
<p>If the user negates the option, <code>arg</code> is <code>NULL</code> and <code>unset</code> is 1.</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_sophisticated_option_parsing">Sophisticated option parsing</h2>
<div class="sectionbody">
<div class="paragraph">
<p>If you need, for example, option callbacks with optional arguments
or without arguments at all, or if you need other s