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

[Carter Schonwald]

what OS and other things?
what does ghc --info say?
Also, when calling haskell code as if it were C code, you need to init the
RTS its using, its not going to magically know you're linking to it from
haskell.(though maybe you can arrange things to use the pre inited hs
runtime, but i'm not familiar with how to do so)
http://www.haskell.org/haskellwiki/Calling_Haskell_from_C

On Mon, Sep 8, 2014 at 10:05 AM, Tobias Neumann <mail at tobias-neumann.eu>
wrote:

> 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
>
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