Use of cpp

Hello, I've just modified some Haskell code from the AVL library to explicitly use ghc unboxed Ints in some routines. Unfortunately, I've broken portability by doing this and was considering some cpp magic to restore portability. But IIRC, the use of cpp is discouraged for Haskell library infrastructure. Is that so? If so, what should I use instead? Is cpphs the way to go? Thanks -- Adrian Hey