Re: [Haskell-cafe] ffi call works fine in ghci but not as ghc compiledsegfault

what version of ghc and cabal? have you tried cabalizing the code and seeing what flags its passing? is it possible you're passing the wrong flags? On Sun, Mar 16, 2014 at 5:21 PM, Miro Karpis wrote:

thanks. Have tried with safe - still seg-fault.

On Sun, Mar 16, 2014 at 5:09 PM, Vagif Verdi wrote:

...

Notice that i have "safe" in my foreign import ccall. This makes it safe to run in threaded mode. Did you try that?

Are you on windows?

On Sunday, March 16, 2014 1:40:48 AM UTC-7, Miro Karpis wrote:

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thank you very much - I have tried also that but got the the same behaviour (seg fault)

cheers, m.

On Sun, Mar 16, 2014 at 7:45 AM, Vagif Verdi wrote:

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I do not think i can help you, but my FFi to functions with similar signature looks like this:

C definition:

PDFLIB_API int PDFLIB_CALL PDF_begin_document(PDF *p, const char *filename, int len, const char *optlist);

haskell FFI:

c_beginDocument :: Pdf -> String -> String -> IO Int c_beginDocument pdf a2 a3 = withCString a2 $ \a2' -> withCString a3 $ c_beginDocument'_ pdf a2' 0

foreign import ccall safe "Pdflib.chs.h PDF_begin_document" c_beginDocument'_ :: Pdf -> Ptr CChar -> CInt -> Ptr CChar -> IO Int

The difference as you see, i'm using withCString to convert from ahskell to C and i'm passing 0 as the string size.

On Friday, March 14, 2014 3:24:23 PM UTC-7, Miroslav Karpis wrote:

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Hi, please can you help me with following?

I have a call to an external dll (via ffi) which if executed from ghci works fine. If I compile my code with 'ghc -o fm Mycode.hs -L. -lextdll' and run it I get 'Segmentation fault/access violation in generated code'.

main = do let param = "FilePath" let value = "C:/dev/misc/haskell/services/FM" result <- liftIO $ FM.setmodulestring param value return "done"

setmodulestring :: String -> String -> IO CInt setmodulestring param value = do let cParamLength = fromIntegral $ length param ::CInt cValueLength = fromIntegral $ length value ::CInt setVarInArray = (-1)::CInt alloca $ \cParam -> do alloca $ \cValue -> do result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray return result

If I try also with following, the behaviour is the same:

setmodulestring2 :: String -> String -> IO CInt setmodulestring2 param value = do cParam <- newCWString param cValue <- newCWString value let cParamLength = fromIntegral $ length param ::CInt cValueLength = fromIntegral $ length value ::CInt setVarInArray = (-1)::CInt result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray free cParam free cValue return res

Any comments/ideas more than appreciated.

Cheers, Miro

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