I wrotted some messages on fa.haskell newsgroup but then I've figured that people actually read mailing lists :) So this is digest of mine recent messages on this newsgroup. First I want to say about OpenSSL thread safety. It is not thread safe by default. Who wants to import and use OpenSLL functions with FFI, have to set locking hooks for it, or else spurious crashes with useless stack trace will result. Higher level of concurrency, more likely crash will happen. Since this hooks are called by C, it is easer to setup mutexes in C module, then call Haskell main function from it. details: http://www.openssl.org/docs/crypto/threads.html Second I've successfully linked Haskell and C++ with threaded run time. Well, I'm planning to use Haskell in C++ programs and to call Haskell functions from C++ and vice versa. So far I've tried some small test programs and it seems works ok. If I launch threads from C++ then call Haskell I have to link with -threaded flag as Haskell run time complains about entering functions unsafelly without it. Also I have another question about hs_add_root. Is this neccessary? I've tried with and without call to this function and everything seems to work same way. That means I don't notice any difference. I ask this because if for example I have lot of Haskell modules do I need to call hs_add_root for every and each one? This is just a small example that works both on linux and windows, (I have different C++ versions but Haskell module is same). Haskell makes and frees array of pointers to CStrings (char**) from argument that is CString(char*). Error checking and handling is intentionally left out for now. I would appreciate any critics about it, as I've started to learn language one month ago, but have professional experience since 92 in other languages, specially C++. -- Haskell module module MakeWords where import Foreign import Foreign.C.String import Foreign.Storable import Foreign.Ptr import Foreign.Marshal.Array foreign export ccall makeWords :: CString -> IO (Ptr CString) foreign export ccall freeWords :: Ptr CString -> IO () makeWords :: CString -> IO (Ptr CString) makeWords cs = do let lst = words $ unsafePerformIO $ peekCString cs p <- mallocArray0 $ length lst makeWords' lst p return (p) makeWords' :: [String] -> Ptr CString -> IO () makeWords' [] p = do poke p nullPtr makeWords' (s:strs) p = do poke p $ unsafePerformIO $ newCString s makeWords' strs (plusPtr p $ sizeOf p) freeWords :: Ptr CString -> IO () freeWords p = do freeWords' p free p freeWords' :: Ptr CString -> IO () freeWords' p = if nullPtr /= (unsafePerformIO $ peek p) then do free $ unsafePerformIO $ peek p freeWords' $ plusPtr p $ sizeOf p else return () -- end Haskell module // C++, windows version #include #ifdef __GLASGOW_HASKELL__ #include "makeWords_stub.h" #endif #include <iostream> #include <ostream> #include using namespace std; class Mutex{ public: Mutex(){ InitializeCriticalSection(&s); } ~Mutex(){ DeleteCriticalSection(&s); } void acquire(){ EnterCriticalSection(&s); } void release(){ LeaveCriticalSection(&s); } private: Mutex(const Mutex&); Mutex& operator=(const Mutex&); CRITICAL_SECTION s; }m; DWORD WINAPI tf(LPVOID arg) { for(int i=0;i<100000;++i) { const char** p = (const char**)makeWords(arg?arg:(void*)"boring default"); const char** q = p; if(!(i%10000)) { m.acquire(); while(*q){ cout<<*q++<<' '; } cout<http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/