title: How to test if defined macro is empty at compile time (Cbjective-C / c)?
body: <p>Is it possible to do check if I've got an empty define? IS_EMPTY_OR_UNDEFINED is a fictive macro I just came up with.</p>
  
  <pre><code>#define constantA 0
  #define constantB 1
  #define constantC null
  #define constantF ""
  #define constantH 
  
  #if IS_EMPTY_OR_UNDEFINED(constantA)
  # error constantA is defined 0 and the above if should not be true - this line should not run
  #endif
  
  #if IS_EMPTY_OR_UNDEFINED(constantB)
  # error constantB is defined 1 and the above if should not be true - this line should not run
  #endif
  
  #if IS_EMPTY_OR_UNDEFINED(constantC)
  # error constantC is defined null and the above if should not be true - this line should not run
  #endif
  
  #if IS_EMPTY_OR_UNDEFINED(constantF)
  # error constantF is defined "" and the above if should not be true - this line should not run
  #endif
  
  #if ! IS_EMPTY_OR_UNDEFINED(constantH)
  # error constantH is defined empty and the above if should not be true - this line should not run
  #endif
  
  #if defined(undefinedConstant) &amp;&amp; ! IS_EMPTY_OR_UNDEFINED(undefinedConstant)
  # error undefinedConstant is not defined and the above if should not be true - this line should not run
  #endif
  </code></pre>