title: #warning in Visual Studio
body: <p>In gcc I can do compile-time warnings like this:</p>
  
  <pre><code>#if !defined(_SOME_FEATURE_)
     #warning _SOME_FEATURE_ not defined-- be careful!
  #endif
  </code></pre>
  
  <p>But in Visual Studio this doesn't work.  Is there an alternative syntax for #warning?</p>