title: Why does this .c file #include itself?
body: <p>Why does this <code>.c</code> file <code>#include</code> itself?</p>
  <ul>
  <li><a href="https://github.com/powturbo/TurboPFor-Integer-Compression" rel="noreferrer">https://github.com/powturbo/TurboPFor-Integer-Compression</a></li>
  </ul>
  <p><strong>vsimple.c</strong></p>
  <pre><code>#define USIZE 8
  #include &quot;vsimple.c&quot;
  #undef USIZE
  
  #define USIZE 16
  #include &quot;vsimple.c&quot;
  #undef USIZE
  
  #define USIZE 32
  #include &quot;vsimple.c&quot;
  #undef USIZE
  
  #define USIZE 64
  #include &quot;vsimple.c&quot;
  #undef USIZE
  </code></pre>