Sorry for the double post, but I forgot to mention I'm using GHC 7.4 and gcc/libstdc++ 4.5.2. (Running Ubuntu 11.04 Natty Narwhal). 2012/3/7 Yves Parès <yves.pares@gmail.com>

Hi, I'm trying to have GHCi load a haskell file that depends on a C++ object file, which causes GHCi to fail because of an unknown symbol (*and I did link with **libstdc++*), whereas the link into an executable with ghc works and runs perfectly.

I've reduced my code to the smallest one that produces the problem: The C++ part defines a mere class and C externals that enable communication with Haskell:

// Header Stuff.hpp class Base { public: Base(); ~Base(); }

extern "C" { Base* mkthing(); void delthing(Base*); }

-----------

// Source Stuff.cpp #include <iostream> #include "Stuff.hpp" using namespace std;

Base::Base() { cout << "Base created" << endl; }

Base::~Base() { cout << "Base deleted" << endl; }

extern "C" { Base* mkthing() { return new Base(); }

void delthing(Base* b) { delete b; } }

Haskell code (just for reference, but I'm not sure it's relevant), Main.hs:

{-# LANGUAGE ForeignFunctionInterface #-} import Foreign import Foreign.C

foreign import ccall unsafe "mkthing" mkthing :: IO (Ptr ())

foreign import ccall unsafe "delthing" delthing :: Ptr () -> IO ()

main = do p <- mkthing delthing p

I then compile it with: g++ -c Stuff.cpp ghci Main.hs Stuff.o -lstdc++

And then the error is: Loading object (static) Stuff.o ... done Loading object (dynamic) /usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5.2/libstdc++.so ... done final link ... ghc: Stuff.o: unknown symbol `__dso_handle' linking extra libraries/objects failed

Whereas 'ghc Main.hs Stuff.o -lstdc++' works just fine. Does GHCi lacks a link directive that regular GHC has?