Fwd: FFI and ghci

[Simon Marlow]

On 05/12/2009 13:53, Patrick LeBoutillier wrote:
> Hi,
>
> I sent this question to haskell-cafe, realizing later that perhaps
> this list is a better place for it.
>
> Patrick
>
> ---------- Forwarded message ----------
> From: Patrick LeBoutillier<patrick.leboutillier at gmail.com>
> Date: Fri, Dec 4, 2009 at 2:09 PM
> Subject: FFI and ghci
> To: Haskell Cafe<haskell-cafe at haskell.org>
>
>
> Hi all,
>
> I have a small FFI-based library that I like to test like this:
>
>   $ ghci -I../c -L../c/.libs -lmlp t.hs
>   GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help

Please upgrade to 6.10.4, lots of bugs were fixed.

>   Loading package ghc-prim ... linking ... done.
>   Loading package integer ... linking ... done.
>   Loading package base ... linking ... done.
>   Loading object (dynamic) mlp ... done
>   final link ... done
>   [1 of 9] Compiling MLP              ( MLP.hs, interpreted )
>   [2 of 9] Compiling MLP.Error        ( MLP/Error.hs, interpreted )
>   [3 of 9] Compiling MLP.Context      ( MLP/Context.hs, interpreted )
>   [4 of 9] Compiling MLP.Runtime      ( MLP/Runtime.hs, interpreted )
>   [5 of 9] Compiling MLP.Object       ( MLP/Object.hs, interpreted )
>   [6 of 9] Compiling MLP.Type         ( MLP/Type.hs, interpreted )
>   [7 of 9] Compiling MLP.Value        ( MLP/Value.hs, interpreted )
>   [8 of 9] Compiling MLP.Language     ( MLP/Language.hs, interpreted )
>   [9 of 9] Compiling Main             ( t.hs, interpreted )
>   Ok, modules loaded: MLP, MLP.Object, Main, MLP.Runtime, MLP.Context,
> MLP.Error, MLP.Value, MLP.Type, MLP.Language.
>   *Main>  main
>
> Note: Inside libmlp.so, another shared object is loaded using dlopen().
>
> When running this test program I get some sporadic segmentation
> faults, which seem to always occur at entrypoint to the
> shared object that is loaded with dlopen().
>
>
> But when I compile it with ghc, i.e.
>
> $ ghc --make -I../c -L../c/.libs -lmlp t.hs
>
> I can't reproduce crash.
>
> Can anyone see why this could be happening? It's quite possible that
> there is really a bug in the C code,
> but if someone knows about a bug or something in ghci that can cause
> this behaviour I can stop looking...

This one might apply if you're on x86-64:

http://hackage.haskell.org/trac/ghc/ticket/781

other than that, nothing springs to mind.  If you can narrow it down to 
a small(er) test case and submit a bug report, we'll try to take a look.

Cheers,
	Simon