5.4 Using Hugs

When compiling with the --hugs option on, a .c file is generated, as well as a .hs file. Before the Haskell stubs can be loaded by Hugs, you'll have to compile up the .c stubs into a dynamically loadable library.

The details of how this is done differs from platform to platform, but here's an outline of how to do it on platforms using ELF (e.g., modern versions of Linux) and Win32. Under ELF, it's just a matter of generating a little bit of position-independent code:

 gcc -fPIC -shared -o MyModule.so MyModule.c -Ihdirect/dir

A couple of things to note about this:

• Use the options -fPIC -shared to generate a dynamically loadable library - standard stuff, really.
• The generated stub contain a #include of the header file HDirect.h, which is supplied with the HaskellDirect distribution. So, you'll need to use the -I option to tell the C compiler where to find it.
• It is very likely that you will need to augment the above command line with some -l and -L options to satisfy the linker ; exactly which ones depend on what library the generated stubs help you interface to.

On the Win32 side, the extension module can be created using Microsoft Visual C++

  cl /nologo /LD /MD -o MyModule.dll MyModule.c -Ihdirect/dir

which also needs to be pointed at the directory containing the HDirect.h header file.

Alternatively on Win32 platforms, you can use mingw32 as supplied by the Cygwin toolchain distribution, for example:

 c:\example> gcc -mno-cygwin -o MyModule.o MyModule.c -Ihdirect/dir
 c:\example> dllwrap -mno-cygwin --target=i386-mingw32 \
             --def HugsExt.def MyModule.o -o MyModule.dll

HugsExt.def is the module definition file, and contains the following two lines:

EXPORTS
initModule

This .def file isn't supplied, so you'll have to type it all in yourself.

As in the ELF case, both the VC++ and mingw32 route will in all likelihood require you to augment the command-lines in order to satisfy the linker.