title: FFI in Haskell, question about the LANGUAGE CPP and how to use a c struct with the FFI
body: <p>I have some questions about the FFI in Haskell</p>
  
  <ol>
  <li>I know i must use the language pragma <code>{-# LANGUAGE ForeignFunctionInterface #-}</code> but what is the difference when i use <code>{-# LANGUAGE CPP, ForeignFunctionInterface #-}</code> what can i do "more" with the CPP</li>
  <li>i use a function in c which use a <code>struct</code>, how can i handle this in the FFI?</li>
  <li>when i have to use <code>CInt</code> and when just <code>Int</code>?</li>
  </ol>