Hi Malcolm: cpphs is under consideration as a replacement for GCC's C preprocessor in the GHC toolchain: https://ghc.haskell.org/trac/ghc/wiki/Proposal/NativeCpp GHC 7.10.3's build fails when cpphs is used as the C preprocessor (--with-hs-cpp=cpphs --with-hs-cpp-flags="--cpp"). It runs into this error when preprocessing libraries/base/GHC/Natural.hs: cpphs: macro MIN_VERSION_integer_gmp expected 3 arguments, but was given 0 I've reproduced this issue on Ubuntu 14.04 x86-64 and SmartOS 15.3.0 x86-64. Interestingly the error seems to arise only when preprocessing Natural.hs while the autogenerated cabal-macros.h is present. Removing that include from the cpphs flags leads to a clean preprocessing run. I have more details of this investigation here: https://gist.github.com/AlainODea/bd5b3e0e6f7c4227f009 Is this a bug? Best, Alain