Thank you Anthony and Joe. I thought that all arguments should be passed into pointers. The introductary example in the python reference documentation about Python extension confused me. I hope that the mentioned example will be changed to something simpler.

On Tue, 14 Aug 2007 17:34:28 +0200, Anthony Tuininga <anthony.tuininga@gmail.com> wrote:

I suspect the problem is the following:

double *min_eps;

if (!PyArg_ParseTuple(args, "d", &min_eps)) return NULL;

That should be

double min_eps;

as Python is expecting a double, not a pointer to a double! And since the difference is about 4 bytes, that would explain the segfault. :-)

Anthony

On 8/14/07, Ali Alhakim <alika@spray.se> wrote:

...

Hello!

I'm quite new to Python and definitely a beginner in implementing Python extensions in C/C++. I've followed the structure given in the formal
Python documentation to write the following code block:

//cmatmod.c

#include

static unsigned int eigenvect_calc(double *min_eps) { return 5; }

static PyObject *cmat_eigv(PyObject *self, PyObject *args) { double *min_eps; unsigned int m; if(!PyArg_ParseTuple(args, "d", &min_eps)) return NULL; m=eigenvect_calc(min_eps); return Py_BuildValue("I", m); } static PyMethodDef cmat_methods[]= { { "eigenvect", cmat_eigv, METH_VARARGS, "Comment"},{NULL, NULL, 0,
NULL} };

void initcmat(void) { (void) Py_InitModule("cmat", cmat_methods); }

===========

I have succeeded to build and install this extension using disutils
package in the setup.py file below:

from distutils.core import setup from distutils.extension import Extension setup(name='eigenvect', version='1.0', ext_modules=[Extension('cmat', ['cmatmod.c'])], )

========== But when I try to call eigenvect(3.0) from Python I would receive a core dump:

6 [main] python 2336 _cygtls::handle_exceptions: Error while dumping
state (probably corrupted stack) Segmentation fault (core dumped)

========== My question is what is wrong with the extension code above? Is it
something with reference counting? I don't know which method is suitable for debugging extension codes.
I've tried gdb but I didn't understand the debug information:

(gdb) >>> eigenvect(4.0)

Program received signal SIGSEGV, Segmentation fault. ---Type to continue, or q to quit--- 0x6abb248e in libpython2!PyEval_EvalFrameEx () from /usr/bin/libpython2.5dll (gdb)

========== /best regards

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