Re: Cabal and c2hs

On Saturday 30 Apr 2005 6:51 pm, Isaac Jones wrote:

Dominic Steinitz writes:

...

Isaac,

Thanks for your prompt response. I did have a look at these references before I posted and didn't find them very enlightening.

Was the example test case I gave you helpful?

Not really. I needed a simple example like the one I eventually came up with.

We sorta didn't put the UserHooks in the docs too much because they are a feature that we're not as sure about in the long-term; they're trying to support a lot of different kinds of things, and it'll take time to make sure we get them right. In the meantime, maybe I'll add a little documentation with the warning that things might change.

I thought there already was a warning that things might change.

...

BTW I discovered a bug in the .chs handler. You have "-o " rather than "-o". I can try and send a patch but it might be easier if you edit the file yourself.

Does "-o " not work? According to the help output, it's correct:

I don't understand why but it produced a file called " IP_ICMP.hs". If you run it at the command line c2hs -o IP_ICMP.hs ip_icmp.h IP_ICMP.chs then you get "IP_ICMP.hs" as required. Perhaps something is taking the extra space to be part of the filename?

Usage: c2hs [ option... ] [header-file] binding-file

-C CPPOPTS --cppopts=CPPOPTS pass CPPOPTS to the C preprocessor -c CPP --cpp=CPP use executable CPP to invoke C preprocessor -d TYPE --dump=TYPE dump internal information (for debugging) -h, -? --help brief help (the present message) -i INCLUDE --include=INCLUDE include paths for .chi files -k --keep keep pre-processed C header -o FILE --output=FILE output result to FILE (should end in .hs) -v --version show version information --old-ffi[=OLDFFI] use the FFI without `Ptr a'

...

import Distribution.Simple import Distribution.Simple.Utils(rawSystemPath)

main = defaultMainWithHooks defaultUserHooks { hookedPreProcessors = [("chs", \_ _ -> myPpC2hs)] }

myPpC2hs inFile outFile verbose = rawSystemPath verbose "c2hs" ["-o" ++ outFile, "ip_icmp.h", inFile]

That looks fine. You could just use "system" instead of rawSystemPath, but since you found it, that's cool.

I don't use c2hs myself; is there any pattern to the .h files we might want to preprocess? Any way to derive it from the sources or the module names? I'm not sure how better to support the kind of thing you need.

I'm not an expert so I really don't know. The author and other users are probably your best bet. My requirement here was to take a system file with a lot of values and use it in Haskell. The c file was called ip_icmp.h so I called the module IP_ICMP. The only other file I have used is in.h and I called the the module IN. I recall that c2hs at that time couldn't swallow netinet/ip_icmp.h and netinet/in.h so I copied them and deleted the offending parts (which I didn't need). Perhaps the modules should have been called Netinet.ICMP and Netinet.IN? I've no idea about Windows. I'm about to recommence work in this area so I'll let you know if anything occurs to me. Dominic.