RE: Can Cabal use GHC's preprocessor?

On 11 July 2005 06:37, Isaac Jones wrote:

Brian Smith writes:

...

I have some source files which need CPP style preprocessing. Since I am using GHC, I would like to automatically use GHC's preprocessor instead of having to download and install cpphs. For example, I want to "runghc ./Setup.hs haddock" without cpphs installed. However, references to cpphs are hard-coded into Cabal. What is the best way to go about accomplishing this?

I believe that if you say "ghc-options: -cpp" or whatever it is, then it should use the "built-in" one for building. Don't list CPP as an extension in this case. This may mess up the preprocessing during the haddock command, fwiw.

I'd recommend against doing this, though. The "built-in" one actually just calls cpp, which does not accept all legal Haskell code. Sticking to hscpp will help your code to be more portable as well.

Another option is to patch the PreProcess.hs module to check to see if cpphs exists and if not, to use "raw" cpp, or cpp through ghc or something. If someone does this, they should also patch the sanity checker to add a warning.

I've fixed this now (as per your last paragraph above), and done some rudimentary testing. I didn't add a warning though; perhaps we should, but since it's using the same preprocessor that will be used when compiling with GHC anyway, I'm not sure a warning will be terribly helpful. I hope this can sneak into the Cabal release, but don't worry if not. Cheers, Simon