title: How #if 0 && defined(_LP64) be true?
body: <p>From the header file ncurses.h, what is the use of <code>#if</code> as I think <code>#if 0</code> will always return  false and control will always go the <code>#else</code> part?</p>
  
  <pre><code>#if 0 &amp;&amp; defined(_LP64)
  typedef unsigned chtype;
  typedef unsigned mmask_t;
  #else
  typedef unsigned long chtype;
  typedef unsigned long mmask_t;
  #endif
  </code></pre>