title: M_PI in VS2010: working in Debug conf but not in Release
body: <p>In my unmanaged C++ source i have:</p>
  
  <pre><code>#define _USE_MATH_DEFINES
  #include &lt;cmath&gt;
  </code></pre>
  
  <p>and then I use M_PI a couple of times.
  Compiling in Debug configuration works flawlessly but in Release it gives:</p>
  
  <blockquote>
    <p>error C2065: 'M_PI' : undeclared identifier</p>
  </blockquote>
  
  <p>What could be the configuration property causing this?</p>