A simple example of calling a function in a shared library from Haskell
To build the C library CMake must be installed.
To build the C library on Windows you'll need to have the Visual Studio compiler installed.
You'll need stack installed to build the Haskell side of things. If you'd rather use cabal then replace stack build in build.{bat,sh} with cabal sandbox init; cabal install --extra-lib-dirs=. --extra-include-dirs=.
Run build.sh on a Unix system or build.bat on a Windows system.
You can run the executable with stack exec executable.
You should expect to see '5' printed.
If you built the executable with Cabal it will be located at executable/.cabal-sandbox/bin/executable[.exe]
In order to find libadd.so on Linux it's sufficient to add the directory containing libadd.so to LD_LIBRARY_PATH.
In order to find add.dll on Windows it's sufficient for it to be in either the current directory or the same directory as the executable.
There are a number of things which can go wrong when building on Windows.
Make sure that that add.lib isn't in the GHC's library search directories. GHC will try to link against this instead of add.dll which isn't just an interface.
This will lead to a segmentation fault when running executable.exe.
The RUNTIME modifier in the install command in CMakeLists.txt ensures that add.lib installed installed.
It's possible to build the shared library using Mingw's gcc on Windows, follow the commands in build.bat but replace the first cmake command with cmake ../ -G "Unix Makefiles" -DCMAKE_C_COMPILER=/path/to/mingw/gcc -DCMAKE_INSTALL_PREFIX=../../executable
Using cygwin's gcc doesn't work very well with a ghc using mingw's gcc for obvious reasons
If you can get this to build on any other platforms it would be super to add that know-how to this repo.
Please feel free to submit any issues or pull requests.
I can be reached as 'jophish' on freenode if you have any questions.