ffi call works fine in ghci but not as ghc compiledsegfault

Miroslav Karpis

14 Mar 2014 14 Mar '14

6:24 p.m.

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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Branimir Maksimovic

14 Mar 14 Mar

7:14 p.m.

On 03/14/2014 11:24 PM, 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

This does not seems correct (or incomplete).

...

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

This one may be correct but without, seeing C code (where it probably segfaults) I cannot say anything further. exact ffi declaration of c_setmodulestring would be usefull, too, to compare with C function.

Miro Karpis

7:23 p.m.

here comes the c definition: int setmodulestring(char* parameter, int parameterLength, char* value, int valueLength, int setVarInArray); In ghci the main and setmodulestring functions works fine On Sat, Mar 15, 2014 at 12:14 AM, Branimir Maksimovic < branimir.maksimovic@gmail.com> wrote:

...

On 03/14/2014 11:24 PM, 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

This does not seems correct (or incomplete).

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

This one may be correct but without, seeing C code (where it probably segfaults) I cannot say anything further. exact ffi declaration of c_setmodulestring would be usefull, too, to compare with C function.

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Branimir Maksimovic

7:29 p.m.

You are passing wchar_t* and function expects char*. On 03/15/2014 12:23 AM, Miro Karpis wrote:

...

here comes the c definition:

int setmodulestring(char* parameter, int parameterLength, char* value, int valueLength, int setVarInArray);

In ghci the main and setmodulestring functions works fine

On Sat, Mar 15, 2014 at 12:14 AM, Branimir Maksimovic mailto:branimir.maksimovic@gmail.com> wrote:

On 03/14/2014 11:24 PM, 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

This does not seems correct (or incomplete).

...
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

This one may be correct but without, seeing C code (where it probably segfaults) I cannot say anything further. exact ffi declaration of c_setmodulestring would be usefull, too, to compare with C function.

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org mailto:Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Brandon Allbery

10:32 p.m.

On Fri, Mar 14, 2014 at 7:29 PM, Branimir Maksimovic < branimir.maksimovic@gmail.com> wrote:

...

You are passing wchar_t* and function expects char*.

FWIW they asked this before (possibly on a different list) and, absent the C information, I pointed out that Win32 API functions use CWString. This was apparently taken to mean that CWString was the only option.... Some awareness of one's platform conventions tends to be helpful when doing FFI. It seems to be absent here. :/ -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

Brandon Allbery

10:30 p.m.

On Fri, Mar 14, 2014 at 7:23 PM, Miro Karpis wrote:

...

here comes the c definition:

int setmodulestring(char* parameter, int parameterLength, char* value, int valueLength, int setVarInArray);

If you had included this before (or perhaps noted that I specified Win32 API, not general C function) then I wouldn't have raised the CWString issue. This declaration is not Win32 API and the original CString was correct for it. If you're still having issues... does this by any chance have any association with threads? ghci uses the threaded runtime *and* handles threads slightly differently from compiled code with -threaded (if it core dumps in ghci with -no-ghci-sandbox then this may be the issue)? -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

Vagif Verdi

16 Mar 16 Mar

2:45 a.m.

New subject: ffi call works fine in ghci but not as ghc compiledsegfault

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

Miro Karpis

4:40 a.m.

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:

...

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

Vagif Verdi

12:09 p.m.

New subject: ffi call works fine in ghci but not as ghc compiledsegfault

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 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

Miro Karpis

5:21 p.m.

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:

...
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:

...
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

Carter Schonwald

6:20 p.m.

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:

...
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:

...
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

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Miro Karpis

6:38 p.m.

Hi, sorry, but not sure what you mean with 'cabalizing the code and seeing the flags its passing'. cabal-install version 1.16.0.2 using version 1.16.0 of the Cabal library ghc: version 7.6.3 after looking a bit more I can see that the ffi call does what it should do, but it crashes right after that. As mentioned before in ghci everything runs fine. On Sun, Mar 16, 2014 at 11:20 PM, Carter Schonwald < carter.schonwald@gmail.com> wrote:

...

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:

...
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:

...
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

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Brandon Allbery

6:47 p.m.

On Sun, Mar 16, 2014 at 6:38 PM, Miro Karpis wrote:

...

after looking a bit more I can see that the ffi call does what it should do, but it crashes right after that. As mentioned before in ghci everything runs fine.

I don't think I got an answer to this before: does it still work in ghci if you run it with ghci -fno-ghci-sandbox ? -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

Miro Karpis

6:57 p.m.

sorry,...yes it works with -fno-ghci-sandbox (no seg.fault) On Sun, Mar 16, 2014 at 11:47 PM, Brandon Allbery wrote:

...

On Sun, Mar 16, 2014 at 6:38 PM, Miro Karpis wrote:

...
after looking a bit more I can see that the ffi call does what it should do, but it crashes right after that. As mentioned before in ghci everything runs fine.

I don't think I got an answer to this before: does it still work in ghci if you run it with

ghci -fno-ghci-sandbox

?

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

Miro Karpis

17 Mar 17 Mar

5:50 a.m.

I finally managed to fix the seg-fault. Brandon and Branimir you were as always right ;-) . Problem was in the external function definition. After changing it to 'stdcall' everything works fine. for further reference working code below: foreign import stdcall safe "setmodulestring" c_setmodulestring :: CString -> CUInt -> CString -> CUInt -> CInt -> IO CInt --all 3 versions work fine: setmodulestring param value = do cParam <- newCString param cValue <- newCString value let cParamLength = fromIntegral $ length param ::CUInt cValueLength = fromIntegral $ length value ::CUInt setVarInArray = (-1)::CInt result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray free cParam free cValue return result setmodulestring2 param value = do let cParamLength = fromIntegral $ length param ::CUInt cValueLength = fromIntegral $ length value ::CUInt setVarInArray = (-1)::CInt B.useAsCString (B.pack param) $ \cParam -> do B.useAsCString (B.pack value) $ \cValue -> do result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray return result setmodulestring3 param value = withCString param $ \cParam -> do withCString value $ \cValue -> do result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray return result where cParamLength = fromIntegral $ length param ::CUInt cValueLength = fromIntegral $ length value ::CUInt setVarInArray = (-1)::CInt thank you cafe, for helping me along this ;-) On Sun, Mar 16, 2014 at 11:57 PM, Miro Karpis wrote:

...

sorry,...yes it works with -fno-ghci-sandbox (no seg.fault)

On Sun, Mar 16, 2014 at 11:47 PM, Brandon Allbery wrote:

...
On Sun, Mar 16, 2014 at 6:38 PM, Miro Karpis wrote:

...
after looking a bit more I can see that the ffi call does what it should do, but it crashes right after that. As mentioned before in ghci everything runs fine.

I don't think I got an answer to this before: does it still work in ghci if you run it with

ghci -fno-ghci-sandbox

?

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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participants (6)

Brandon Allbery
Branimir Maksimovic
Carter Schonwald
Miro Karpis
Miroslav Karpis
Vagif Verdi