title: Updateing code to swift 4 results in an error message
body: <p>I wan to update this code to swift 4:</p>
  
  <pre><code>rc = select(socket_fd + 1, readfd, writefd, NULL, &amp;timeout);
  
  return rc;
    }
  </code></pre>
  
  <p>But I get two errors:</p>
  
  <blockquote>
    <p>Declaration of 'select' must be imported from module 'Darwin.POSIX.sys.time' before it is required<br>
    Implicit declaration of function 'select' is invalid in C99</p>
  </blockquote>
  
  <p>How can I can fix this?</p>