title: #ifdef not working properly?
body: <p>I am facing issues with Xcode 5.1. Everything works fine if I do this:</p>
  
  <pre><code>#include "glew.h"
  </code></pre>
  
  <p>But as soon as I try to make it cross-platform, it starts giving the compilation error.</p>
  
  <pre><code>#if defined(_APPLE_) || defined(_MACH_)
  #define OS_MACOSX
  #endif
  
  #ifdef OS_MACOSX
  #include "glew.h"
  #else
  #include &lt;GL/glew.h&gt;
  #endif
  </code></pre>
  
  <p>Please help me to understand this.</p>