I made a Delphi dll (32 bits windows). This dll exports a function named getPngVersion. This is a function with no arguments that returns a pointer to a array of chars.

If I examine the dll with a tools like tdump, I can see the function getPngVersion on index 1.

Now I want to use this dll in Haskell:

 

{-# LANGUAGE ForeignFunctionInterface #-}

module Main(

main

)

 

where

import Control.Monad

import Foreign.C

import Foreign.Marshal.Alloc

import Foreign.Marshal.Array

import System.Win32.Types

 

foreign import stdcall "glasPng getPngVersion"  getPngDllVersion :: IO CString

 

main :: IO ()

main = do

         s <- getPngDllVersion

         putStrLn (show s)

 

Compiling this with ghc --make glasPng.hs gives:

GlasPng.o: fake: (.text +0x82): undefined reference to  ‘getPngVersion@0’ collect2 : Id returned 1 exit status

 

I wonder what went wrong. In the foreign import line I use “glasPng…. “ to tell ghc, it has to searh in glasPng.dll (changing glasPng to glasPng.dll doesn’t help). I’ve changed the name of the function in  the dll to getPngVersion@0 but no luck.  I’ve read and tested the last example at http://stackoverflow.com/questions/1027246/haskell-foreign-import-stdcall-on-dll-function  (win32_getComputername,  this works!). I wonder how  haskell knows which dll to use in this example?)

Probably I’am doing something wrong with the way I tell ghc which dll to link or….

 

Any ideas?

 

Kees

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