title: How to get abstract syntax tree of a `c` program in `GCC`
body: <p>How can I  get the  abstract syntax tree of a c program in gcc?<br>
  I'm trying to automatically insert OpenMP pragmas to the input c program.<br>
  I need to analyze nested <code>for</code> loops for finding dependencies so that I can insert appropriate OpenMP pragmas.<br>
  So basically what I want to do is traverse and analyze the abstract syntax tree of the input c program.<br>
  How do I achieve this?  </p>