title: ifdef & solaris
body: <p>I want to undefine variable when compiling on SunOS. Therefore, i tried to put</p>
  
  <pre><code>#ifdef SunOS
  #undef FOO
  #endif
  </code></pre>
  
  <p>but it does not work. The problem is in #ifdef sunos ? Should i declarate it, or complier do it by itself ? </p>
  
  <p>regards
  S.</p>