ystem error).
                </p></dd>
<dt><span class="term">ec</span></dt>
<dd><p>
                  Set to indicate what error occurred, if any. If the <code class="computeroutput">mode</code>
                  is <code class="computeroutput">false</code>, but the current value of <code class="computeroutput">non_blocking()</code>
                  is <code class="computeroutput">true</code>, this function fails with <code class="computeroutput">boost::asio::error::invalid_argument</code>,
             