title: How to make a Macro parser in C++ project
body: <p>in the project, there are a lot of macros
  such as</p>
  
  <pre><code>#define a (b+c)
  #define b (e+d)
  </code></pre>
  
  <p>sometimes you need to decide the actual value of a .
  so i am wondering if there are any tools for doing that, calculating all the macros and give the actual value as comment: (like below)</p>
  
  <pre><code>#define a (b+c)  //a = 5
  </code></pre>
  
  <p>Are there any opensource project related on this macro parsing job?
  thanx</p>