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

[Miro Karpis]

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


On Sun, Mar 16, 2014 at 5:09 PM, Vagif Verdi <vagif.verdi at gmail.com> 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:
>
>> 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 <vagif... at gmail.com> wrote:
>>
>>> 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:
>>>>
>>>> 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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