Hi all, I'd like to share my experiences packaging a Haskell program so that it can be used as a library by a non-Haskell application. I hope somebody might be able to (A) confirm that I'm doing the right thing or better still (B) suggest some corrections and/or simplifications. My objectives are: 1. For the non-Haskell application to use my library 2. ... without any Haskell infrastructure on the machine I think this means I want a shared library [1,2] although I'm a little bit fuzzy on the issue. I am not particularly concerned about the size of my executable or libraries. Including the Haskell RTS and my package deps is acceptable if that's what it takes to meet my primary and secondary objectives. I am targeting Windows and MacOS X. For Windows, my approach is to build a giant DLL with all the Haskell stuff statically linked in. For MacOS X I am using the `-dynamic` flag to compile all my dependencies (actually, I just set shared: True in cabal config) as well as the `-shared` flag. I am also now using GHC 7.0.3 with the latest (at the time of this writing) Haskell Platform (2011.2.0.1) [1] http://hackage.haskell.org/trac/ghc/wiki/SharedLibraries [2] http://www.haskell.org/ghc/docs/latest/html/users_guide/using-shared-libs.ht... The whole thing ---------------------------------------------------------------------- You can see my efforts so far with darcs get --lazy http://code.haskell.org/GenI cd GenI cabal install cd geniwrapper make MacOS X users should be able to download http://erickow.com/tmp/MinimalGenI-OSX.tar.gz and run a test-mac.sh script which compiles a program with GCC using GenI, runs it and outputs some JSON string. Exposing some C functions and using them ---------------------------------------------------------------------- So far, I think I know how to expose some of library as C functions and to compile a little program written in C that uses this library. ghc --make -fvia-C MinimalGenI # provides some C functions via FFI exports ghc -c StartEnd.c # http://www.haskell.org/ghc/docs/latest/html/users_guide/win32-dlls.html ghc test-c.c MinimalGenI.o MinimalGenI_stub.o StartEnd.o\ -package GenI -package utf8-string\ -o test-c.o I notice that -fvia-C is going away, but I'm going to ignore this fact for now and assume/hope that doing without it will be easy Building a Windows shared library ---------------------------------------------------------------------- As I understand it, it is possible to build a Windows DLL, albeit one containing the Haskell RTS and all my Haskell libraries statically linked in. Users can download the DLL and link it to their Visual Basic programs without having to touch GHC. The extra work involved looks like this: ghc MinimalGenI.o MinimalGenI_stub.o StartEnd.o\ -package GenI -package utf8-string\ -shared -o MinimalGenI.dll ghc test-c.c MinimalGenI.dll -o test-c2 Note that building test-c.c with ghc does not meet my second objective of being able to combine Haskell lib with non-Haskell program sans Haskell infrastructure. However, I think I know how to do it for MacOS X and that the procedure would be more or less the same. I have not looked into it. [3] http://www.haskell.org/ghc/docs/latest/html/users_guide/win32-dlls.html Building a MacOS X shared library ---------------------------------------------------------------------- For MacOS X, I would almost like to generate a gigantic file like the Windows DLL. But maybe that's the wrong thing to want. I do almost exactly the same thing, except that instead of distributing a single giant file, I track down a whole bunch of dependencies and copy over the dylib files for them. Note that as a prerequisite, this requires reinstalling a lot of packages with --enable-shared (I just edit ~/.cabal/config and set shared to True). ghc MinimalGenI.o MinimalGenI_stub.o StartEnd.o\ -package GenI -package utf8-string\ -dynamic -shared -o MinimalGenI.dylib ghc test-c.c MinimalGenI.dylib -o test-c2 As an alternative to building with GHC, I can compile test-c.c and link with MinimalGenI.dylib directly with GCC. It's a little bit hairy. What I did was to run ghc with -v3 to see what gcc commands it was running, clean them up and package them in a script (test-mac.sh attached). It's a little bit voodoo-ish, a lot of flags that I don't really understand the significance of, and some libraries I'm not 100% clear on why I need the static versions for. Also I find it slightly odd that I can't seem to just merge the first two steps of the process, producing/assembling assembly code for test.c. In any case, it seems to work... Packaging the MacOS X shared library ---------------------------------------------------------------------- I'm trying to distribute my Haskell library in a way that does not require the user to install anything beyond XCode. To do this, I track down the dynamic libraries for all the packages I'm using and their dependencies. Unfortunately, the way I did it was basically trial and error (find all dylib and hand remove the ones that seem totally irrelevant; get a friend to test it on a raw machine). Rather than the dumb approach used in the attached dist-mac.sh, it should be relatively easy to write a small Haskell script to recurse down the package dependency tree and tell me exactly which files I need to copy. Maybe such a tool exists already. If this procedure is right, and if somebody should write such a script (maybe already part of the cabal-macosx package?) then I bet creating app bundles for your MacOS X Haskell GUI tools should be quite straightforward as well. Thanks for reading! -- Eric Kow http://erickow.com