title: What is the function of Macro definition "__P" in getopt_long.c
body: <p>As stated in the title, the source code site:<a href="https://github.com/libevent/libevent/blob/master/WIN32-Code/getopt_long.c" rel="nofollow noreferrer">libevent/WIN32-Code/getopt_long.c</a>:</p>
  <pre><code>#define __P(x) x
  </code></pre>