[Haskell-cafe] Use Haskell shared library with foreign exports with dlopen/dlsym

8 Sep 2014

      Hello Cafe,

I am trying to use a Haskell shared library with foreign exports from 
Haskell again via dlopen/dlsym. Sadly it segfaults, and the segfaults 
happen on dlclose during garbage collection points (as figured out by 
monochrom in #haskell). So right now I can only open a library once and 
may not dlclose it. Can someone point me to a mistake I made, or is this 
rather a ghc (7.8.3) bug? Please see attached minimal example.

Regards, Tobias

test.hs:
module Main where

import qualified System.Posix.DynamicLinker as DL
import Foreign

foreign import ccall "dynamic"
    mkTest :: FunPtr Int -> Int

main = do
    DL.withDL ("./libtest.so") [DL.RTLD_NOW] $ \dl -> do
        dimPtr <- DL.dlsym dl "test"
        let test = mkTest dimPtr
        print test

libtest.hs:
module Test() where

import Foreign

foreign export ccall test :: Int

test :: Int
test = 124

build with:
	ghc --make -shared -dynamic -fPIC libtest.hs -o libtest.so
	ghc --make -dynamic test.hs

[Haskell-cafe] Use Haskell shared library with foreign exports with dlopen/dlsym

Tobias Neumann