Using GHC and FFI

[Bayley, Alistair]

> After that I wrote ghc -fffi -c test.lhs. But when I call 
> blah from ghci I get the error message: "test.o unknown symbol '_test'
> 
> I think ghc doen't link test.o to projekt.obj. What do I have to do? 


I don't know about linking object files I've created myself, but to link an
existing library (a .dll on my Windows system) I use these options:
  -L/path/to/library/file -lprojekt
-I/path/to/header/include/directory/if/it/exists

If the object file is in the same dir as test.lhs then you might get away
with just the -l option. Also, you might have to rename projekt.obj to
projekt.o (I don't know if this matters or not).


See GHC Users Guide "4.10.7. Options affecting linking", for -L and -l:
 
http://www.haskell.org/ghc/docs/latest/html/users_guide/options-phases.html#
OPTIONS-LINKER

And see "4.10.3 Options affecting the C pre-processor", for -I:
 
http://www.haskell.org/ghc/docs/latest/html/users_guide/options-phases.html#
C-PRE-PROCESSOR

I believe you only need to use -I if you're compiling via-c (which happens
if you use -O).

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