Cabal

The Haskell Cabal:

The Common Architecture for Building Applications and Libraries

http://www.haskell.org/cabal/

Information for users

• How to install a Cabal package
• FAQ: Frequently Asked Questions
• Cabal-Install - tool that greatly simplifies installation of Cabal packages

Information for developers

• How to write a Haskell program
• Upgrading packages
• Package versioning policy
• Creating Debian packages from Cabal package

Related contributed tools

• CabalFind - finding Cabal packages on the web (now superseded by Hackage)
• Cabal-make - automation based on makefiles

Building Dlls on Windows with Cabal

Cabal does not currently support building dlls on windows out of the box. Some details about why can be found here: http://www.haskell.org/ghc/docs/6.4.2/html/users_guide/packages.html http://www.haskell.org/ghc/docs/6.4.2/html/users_guide/win32-dlls.html

This means that we have to do a bit of hackery to get Cabal to build a dll from a library. As long as we build a single DLL from the entire project the dll should behave as expected. Using the Setup.lhs listed below and following the directions listed above (the second link) I was able to use Visual Haskell to build a dll which I could load into Visual Basic for testing.

The following Setup.lhs should do the trick for most projects which consist of a single library which needs to be built as a dll. If you need to specify a dll export file you'll need to modify the function cmd to take this into account. Another possible addition is specifying a static dll. Check the ghc manual above.

#! /usr/bin/runghc

> import Distribution.Simple
> import Distribution.Simple.LocalBuildInfo
> import Distribution.PackageDescription
> import System.Cmd
> import System.Directory
> import Data.List
>
>
> main = defaultMainWithHooks (defaultUserHooks { postBuild = buildDll })
>   where
>   buildDll _ _ pkg info = do putStrLn "Building Dll..."
>                              setCurrentDirectory (buildDir info)
>                              let buildCmd = cmd pkg info
>                              putStrLn buildCmd
>                              system buildCmd
>                              let dll = dllFile pkg
>                              let cpDllCmd = "cp " ++ dll ++ " " ++ (name pkg) ++ "\\" ++ dll
>                              putStrLn cpDllCmd
>                              system cpDllCmd
>   ghcExe :: LocalBuildInfo -> String
>   ghcExe info = "\"" ++ (compilerPath (compiler info)) ++ "\""
>   mainOFile :: PackageDescription -> String
>   mainOFile pd = "HS" ++ (name pd) ++ "-" ++ (showVersion (pkgVersion (package pd))) ++ ".o"
>   cmd :: PackageDescription -> LocalBuildInfo -> String
>   cmd pd i = (ghcExe i) ++ " --mk-dll -o " ++ (dllFile pd) ++ " " ++ (mainOFile pd) ++ " " ++ (packages i)
>   packages :: LocalBuildInfo -> String
>   packages i = foldl1 (\x y -> x ++ " " ++ y) (map showPackage (packageDeps i))
>   showPackage :: PackageIdentifier -> String
>   showPackage pi = "-package " ++ showPackageId pi
>   name :: PackageDescription -> String
>   name = pkgName . package 
>   dllFile :: PackageDescription -> String
>   dllFile pd = (name pd) ++ ".dll"