aragraph regarding how to treat it.</li>
</ul>
</li>
<li>If any async API reports errors, then its handler function shall take a <code>const Error_code&amp;</code> argument. When the handler function is invoked, the <code>Error_code</code> shall be falsy on success, truthy on Error. In the latter case see preceding bullet point regarding how to treat it.</li>
</ul>
<p >Informally we recommend, when invoking a synchronous API:</p><ul>
<li>When prototyping just pass-in null <code>Error_code*</code>. It'll thr