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Re: [Swig-user] 64-bit Segmentation Fault with Swig 1.3.36
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From: Brian B. <Bri...@se...> - 2008-08-13 14:56:20
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Thanks! That seems to work perfectly.
Now I just need to look into prototyping to find out *why* that works!
:)
> -----Original Message-----
> From: Matthew O'Meara [mailto:mat...@gm...]
> Sent: 13 August 2008 14:29
> To: Brian Bird; swi...@li...
> Subject: Re: [Swig-user] 64-bit Segmentation Fault with Swig 1.3.36
>
> Try using this interface file--
>
>
>
> /* file /tmp/example.i */
>
> %module example
>
> %{
> extern char *test(char *, char *);
>
> %}
>
> extern char *test(char *, char *);
>
>
> Best,
> Matt
>
>
> On Wed, Aug 13, 2008 at 9:13 AM, Brian Bird
> <Bri...@se...> wrote:
> >
> > The function in example_wrap is below (I've added // ** LINE 2631
** to
> > highlight the line showing the warning during compilation):
> >
> > example_wrap.c: In function '_wrap_test':
> > example_wrap.c:2631: warning: cast to pointer from integer of
different
> > size
> >
> > I tried attaching the complete example_wrap files generated by both
Swig
> > versions 1.3.36 and 1.3.16 but they were too large and the mailing
list
> > doesn't accept zip attachments. If they're any use I could send them
to
> > you directly?
> >
> > Version 1.3.16 generates a much smaller function (also reproduced
below)
> > and works successfully, but it has an identical line to cast the
result
> > to a (char *), so I've no idea what's going wrong. As far as I can
tell
> > the same *_wrap.c files are generated on a 32 bit machine.
> >
> > Thanks!
> > Brian
> >
> >
> > /* Output in example_wrap.c from SWIG 1.3.36 */
> > SWIGINTERN PyObject *_wrap_test(PyObject *SWIGUNUSEDPARM(self),
PyObject
> > *args) {
> > PyObject *resultobj = 0;
> > char *arg1 = (char *) 0 ;
> > char *arg2 = (char *) 0 ;
> > int res1 ;
> > char *buf1 = 0 ;
> > int alloc1 = 0 ;
> > int res2 ;
> > char *buf2 = 0 ;
> > int alloc2 = 0 ;
> > PyObject * obj0 = 0 ;
> > PyObject * obj1 = 0 ;
> > char *result = 0 ;
> >
> > if (!PyArg_ParseTuple(args,(char *)"OO:test",&obj0,&obj1))
SWIG_fail;
> > res1 = SWIG_AsCharPtrAndSize(obj0, &buf1, NULL, &alloc1);
> > if (!SWIG_IsOK(res1)) {
> > SWIG_exception_fail(SWIG_ArgError(res1), "in method '" "test" "',
> > argument " "1"" of type '" "char *""'");
> > }
> > arg1 = (char *)(buf1);
> > res2 = SWIG_AsCharPtrAndSize(obj1, &buf2, NULL, &alloc2);
> > if (!SWIG_IsOK(res2)) {
> > SWIG_exception_fail(SWIG_ArgError(res2), "in method '" "test" "',
> > argument " "2"" of type '" "char *""'");
> > }
> > arg2 = (char *)(buf2);
> > result = (char *)test(arg1,arg2); // ** LINE 2631 **
> > resultobj = SWIG_FromCharPtr((const char *)result);
> > if (alloc1 == SWIG_NEWOBJ) free((char*)buf1);
> > if (alloc2 == SWIG_NEWOBJ) free((char*)buf2);
> > return resultobj;
> > fail:
> > if (alloc1 == SWIG_NEWOBJ) free((char*)buf1);
> > if (alloc2 == SWIG_NEWOBJ) free((char*)buf2);
> > return NULL;
> > }
> >
> >
> >
> >
> >
> >
> >
> > /* Output in example_wrap.c from SWIG 1.3.16 */
> > static PyObject *_wrap_test(PyObject *self, PyObject *args) {
> > PyObject *resultobj;
> > char *arg1 ;
> > char *arg2 ;
> > char *result;
> >
> > if(!PyArg_ParseTuple(args,(char *)"ss:test",&arg1,&arg2)) goto
fail;
> > result = (char *)test(arg1,arg2);
> >
> > resultobj = result ? PyString_FromString(result) :
> > Py_BuildValue((char*)"");
> > return resultobj;
> > fail:
> > return NULL;
> > }
> >
> >
> >
> >> -----Original Message-----
> >> From: Haoyu Bai [mailto:div...@gm...]
> >> Sent: 13 August 2008 13:23
> >> To: Brian Bird
> >> Cc: swi...@li...
> >> Subject: Re: [Swig-user] 64-bit Segmentation Fault with Swig 1.3.36
> >>
> >> On Wed, Aug 13, 2008 at 7:08 PM, Brian Bird
> >> <Bri...@se...> wrote:
> >> > I'm getting a Segmentation fault on a 64-bit Ubuntu machine when
> > using
> >> > Swig1.3.36 and Python2.5.
> >> >
> >> >
> >> >
> >> > When compiling my example_wrap.c I get a warning about "casting
to
> >> pointer
> >> > from integer of different size". I assume this is the cause of
the
> >> segfault.
> >> >
> >> >
> >> >
> >> > Everything works on a 32-bit machine. There is no warning (since
> >> pointers
> >> > and integers are the same size).
> >> >
> >> >
> >> >
> >> > However the wrapper works fine when generated from swig version
> > 1.3.16
> >> (on
> >> > both 32-bit and 64-bit machines).
> >> >
> >> >
> >> >
> >> > I tried Swig1.3.33 and it fails in the same way. Has something
> > broken in
> >> > Swig since version 1.3.16 when returning strings (char *) to
Python?
> > Or
> >> is
> >> > there a better way to return a string from a C function to python
> > which
> >> will
> >> > ensure the latest versions of swig will generate wrappers which
work
> > on
> >> > 64-bit machines? Most of the documentation/forums I've read seem
to
> > be
> >> aimed
> >> > either at Swig1.1 or using typedefs/structs which seems (IMHO) to
be
> >> > overcomplicated just to return a string to Python - isn't it?
> >> >
> >> >
> >> >
> >> > Any suggestions would be appreciated!
> >> >
> >> >
> >> >
> >> > Below is the simplest example I could create which shows the
> > problem.
> >> > Thanks!
> >> >
> >> >
> >> >
> >> > /* file /tmp/example.i */
> >> >
> >> > %module example
> >> >
> >> > extern char *test(char *, char *);
> >> >
> >> >
> >> >
> >> > /* file /tmp/example.c */
> >> >
> >> > char *test(char *param1, char *param2) {
> >> >
> >> > return param2;
> >> >
> >> > }
> >> >
> >> >
> >> >
> >> > % cd /tmp
> >> >
> >> > % tar -xzf swig-1.3.36.tar.gz
> >> >
> >> > % cd swig-1.3.36/
> >> >
> >> > % ./configure --with-python=/usr/bin/python2.5 --prefix=/tmp/swig
&&
> >> make &&
> >> > make install
> >> >
> >> > % cd ..
> >> >
> >> > % /tmp/swig/bin/swig -python example.i # Creates example_wrap.c
and
> >> > example.py
> >> >
> >> > % gcc -c -fpic example_wrap.c example.c -I/usr/include/python2.5
> >> >
> >> > example_wrap.c: In function '_wrap_test':
> >> >
> >> > example_wrap.c:2631: warning: cast to pointer from integer of
> > different
> >> size
> >> >
> >> > % gcc -shared example.o example_wrap.o -o _example.so # Creates
> >> _example.so
> >> >
> >> > % python
> >> >
> >> > Python 2.5.2 (r252:60911, Apr 21 2008, 11:17:30)
> >> >
> >> > [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
> >> >
> >> > Type "help", "copyright", "credits" or "license" for more
> > information.
> >> >
> >> >>>> import example
> >> >
> >> >>>> print example.test("Hello","World") # Should print "World" on
the
> >> >>>> screen. It works on 32-bit machines and with SWIG-1.3.16
> >> >
> >> > Segmentation fault
> >> >
> >>
> >> Could you provide more information likes the line of the code
> >> generated the compile warning, or the trace back of the
segmentation
> >> fault? I havn't a 64-bit Linux so I can't debug it.However, I
believe
> >> it is somewhere the pointer of a 32-bit int casted to a 64-bit
size_t.
> >>
> >> --
> >> Haoyu Bai
> >
> >
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