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

[Vagif Verdi]

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<javascript:>
> > 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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20140316/9b96a737/attachment.html>