title: Check if a value is defined in an C enum?
body: <p>Assuming that I have this: </p>
  
  <p><code>enum { A = 0x2E, B = 0x23, C = 0x40 }</code></p>
  
  <p>it's possible check if <code>x</code> is defined into <code>enum</code>?</p>
  
  <p>I'm doing it manually: <code>int isdef = (x == A || x == B || x == C);</code> But I want to something more dynamic. <code>GCC-extensions</code> are welcome too.</p>