Re: allocate memory to Char **

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Hi,

"varnames" is an array of pointers, you cannot allocate it with mallocBytes
(n*100).

Try something like this (not tested):

mallocList :: [String] -> IO (Ptr CString)
mallocList xs = newArray =<< forM xs g
  where
    g x = do
       b <- mallocBytes 100
       pokeCString b x 99
       return b

pokeCString :: CString -> String -> Int -> IO ()
pokeCString dst value maxLen = withCStringLen (take maxLen value) $ uncurry
(copyArray dst)

-Sylvain


2014-04-29 13:11 GMT+02:00 Lamine <[email protected]>:

>
> Hi,
>
> I want to do write this C code in haskell code, but i have some pb:
>
> int w ;
> char **varnames = ccl_new_array (char *, w);
>
> int i;
>           for (i = 0; i < w; i++)
>             {
>               varnames[i] = ccl_new_array (char, 100);
>               sprintf (varnames[i], "x%d", i);
>             }
>
> I try this code unsing mallocList to (http://lpaste.net/report/712):
> mallocList :: [CString] -> IO (Ptr CString)
> mallocList xs = do let n = Prelude.length xs
>                    p <- mallocBytes (n*100)
>                    forM_ (Prelude.zip [0..] xs)
>                     (uncurry (pokeByteOff p))
>                    return p
>
> let n = sizeOf(undefined :: CString)
>            allocaArray w $ \var -> do
>                   xs <- peekArray (w*n) var
>                   varnames <- mallocList xs
>
> I have an error "segmentation fault(core dumped)".
> can someone please help me? Thank you.
>
> Lamine
> _______________________________________________
> FFI mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/ffi
>

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<div dir=3D"ltr">Hi,<br><br>&quot;varnames&quot; is an array of pointers, y=
ou cannot allocate it with mallocBytes (n*100).<br><br>Try something like t=
his (not tested):<br><br>mallocList :: [String] -&gt; IO (Ptr CString)<br>
mallocList xs =3D newArray =3D&lt;&lt; forM xs g<br>=C2=A0 where<br>=C2=A0=
=C2=A0=C2=A0 g x =3D do<br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 b &lt;- mal=
locBytes 100<br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pokeCString b x 99<br>=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return b<br><br>pokeCString :: CString=
 -&gt; String -&gt; Int -&gt; IO () <br>
pokeCString dst value maxLen =3D withCStringLen (take maxLen value) $ uncur=
ry (copyArray dst)<br><br>-Sylvain<br></div><div class=3D"gmail_extra"><br>=
<br><div class=3D"gmail_quote">2014-04-29 13:11 GMT+02:00 Lamine <span dir=
=3D"ltr">&lt;<a href=3D"mailto:[email protected]" target=3D"_blank"=
>[email protected]</a>&gt;</span>:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><br>
Hi,<br>
<br>
I want to do write this C code in haskell code, but i have some pb:<br>
<br>
int w ;<br>
char **varnames =3D ccl_new_array (char *, w);<br>
<br>
int i;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 for (i =3D 0; i &lt; w; i++)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 varnames[i] =3D ccl_new_ar=
ray (char, 100);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 sprintf (varnames[i], &quo=
t;x%d&quot;, i);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 }<br>
<br>
I try this code unsing mallocList to (<a href=3D"http://lpaste.net/report/7=
12" target=3D"_blank">http://lpaste.net/report/712</a>)<u></u>:<br>
mallocList :: [CString] -&gt; IO (Ptr CString)<br>
mallocList xs =3D do let n =3D Prelude.length xs<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0p &lt;=
- mallocBytes (n*100)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0forM_ =
(Prelude.zip [0..] xs)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (uncu=
rry (pokeByteOff p))<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return=
 p<br>
<br>
let n =3D sizeOf(undefined :: CString)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0allocaArray w $ \var -&gt; do<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 xs &lt;- pee=
kArray (w*n) var<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 varnames &lt=
;- mallocList xs<br>
<br>
I have an error &quot;segmentation fault(core dumped)&quot;.<br>
can someone please help me? Thank you.<span class=3D"HOEnZb"><font color=3D=
"#888888"><br>
<br>
Lamine<br>
______________________________<u></u>_________________<br>
FFI mailing list<br>
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>
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ttp://www.haskell.org/<u></u>mailman/listinfo/ffi</a><br>
</font></span></blockquote></div><br></div>

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