[Haskell-cafe] Mixing C and Haskell code in the same file

Is it possible to insert C code directly to, say, .hsc files? I see this construct in ghc user docs: #def ... which should insert definitions, but I could not find examples of usage in Hackage. My goal is to write some cpp macros that build both a C function and its 'foreign import ccall' wrapper in the same file. Thanks for your help, Maurício