[C2hs] Re: [Haskell] building c2hs on winows

[Duncan Coutts]

On Thu, 2006-07-06 at 11:35 -0400, Manuel M T Chakravarty wrote:
> Duncan Coutts:
> > On Thu, 2006-07-06 at 10:30 +0100, Duncan Coutts wrote:
> > > On Wed, 2006-07-05 at 20:58 -0700, Anatoly Yakovenko wrote:
> > > > On 7/4/06, Arjan Oosting <arjanoosting at home.nl> wrote:
> > > > > Op di, 04-07-2006 te 09:09 -0700, schreef Anatoly Yakovenko:
> > > > > > I can't get c2hs to build on windows with ghc-6.4.2
> > > > > >
> > > > I get a little farther, but it still doesn't work:
> > > 
> > > Actually, c2hs's setup is doing something that only works on unix. In
> > > fact it doesn't even always work on unix. For the Gentoo ebuild we
> > > changed it because it doesn't work in the context of installing into a
> > > temp dir.
> > > 
> > > A temporary hack is to change the Setup.hs to be just:
> > > 
> > > import Distribution.Simple
> > > main = defaultMain
> > > 
> > > it means that c2hs's --copy-library feature will not work but everything
> > > else should. We'll have to look into doing that in a more portable way.
> 
> With the latest Cabal (as included in recent GHC), the postInst.sh
> (which is the problem) can be rewritten in Haskell and added to Setup.hs
> directly.  That should remove this particular problem (but will of
> course mean that c2hs doesn't work anymore with earlier versions of
> Cabal, but that is probably secondary).
> 
> > Actually it turns out the c2hs is doing a lot of things that are not
> > portable to windows. It'll need some effort to fix. Any helpers?
> 
> What else apart from pathname separators?  It'd be great if somebody
> could look into that.  

The use of configure(.in) is the main problem. Most Windows users do not
have mingw/cygwin.

I've been looking through what c2hs uses configure for and what portable
replacements there are:

      * for finding the os and arch in c2hs/toplevel/C2HSConfig.hs.in
        for the platform spec system. Perhaps this could be replaced
        with System.Info.{os,arch} ?
      * finding the temp dir. this is not actually used anywhere.
      * substituting the c2hs version into the Version.hs module. This
        can be replaced with Cabal's new Path_c2hs.hs feature.

The postinst.sh could be eliminated entirely. All it's used for is
finding the location where a data file was installed. This can now be
found using Cabal's new Path_c2hs.hs feature. Cabal generates that
module which provides a portable way of finding the location of data
files. Also the field 'Data-Files:' can be added to the c2hs.cabal file
to specify extra data files that need to be installed.

So I think the only things left are finding the copyright notice and a
couple other items that are kept centrally in the c2hs.cabal file. For
the moment they could perhaps just be duplicated. I've got a suggestion
for how to deal with that case better in future which I posted to the
cabal-devel list:
http://www.haskell.org//pipermail/cabal-devel/2006-July/000027.html

The configure script is also used for the the makefile in the docs
directory and the rpm spec file. I'm not sure how to deal with those,
but perhaps they're not so important and we could live with those using
a unix-specific mechanism (since they need rpm or latex anyway).

Duncan