title: Custom gcc preprocessor
body: <p>Could you please give me an example of writing a custom gcc preprocessor? </p>
  
  <p>My goal is to replace SID("foo") alike macros with appropriate CRC32 computed values. For any other macro I'd like to use the standard cpp preprocessor.</p>
  
  <p>It looks like it's possible to achieve this goal using <code>-no-integrated-cpp -B</code> options, however I can't find any simple example of their usage.</p>