On 3/06/2006 9:51 AM, Luke Miller wrote:
> Hello,
>
> I am working on my first python module based on a c program. The
> module builds and installs OK using dist-utils, and imports fine into
> python. However, when I try and use the one wrapper
> ("modgl.glVertex4f(1, 2, 3, 1)") in the module, it seg faults.
>
> Can anyone spot why this isn't working, or recommend a way to debug
> these things.
>
> Thanks,
> Luke
>
> #include <Python.h>
>
> static PyObject *_wrap_glVertex4f(PyObject *self, PyObject *args) {
> PyObject *resultobj = NULL;
> float arg1 ;
> float arg2 ;
> float arg3 ;
> float arg4 ;
> PyObject * obj0 = 0 ;
> PyObject * obj1 = 0 ;
> PyObject * obj2 = 0 ;
> PyObject * obj3 = 0 ;
>
> if(!PyArg_ParseTuple(args,(char
> *)"OOOO:glVertex4f",&obj0,&obj1,&obj2,&obj3)) goto fail;
> {
> arg1 = (float)(PyFloat_AsDouble(obj0));
Not testing for an error after an API call is just asking for trouble.
> }
> {
> arg2 = (float)(PyFloat_AsDouble(obj1));
> }
> {
> arg3 = (float)(PyFloat_AsDouble(obj2));
> }
> {
> arg4 = (float)(PyFloat_AsDouble(obj3));
> }
You are making it really hard for yourself. Try this:
if(!PyArg_ParseTuple(args,"ffff:glVertex4f",&arg1,&arg2 etc etc
The batteries are already included. Using the code for the precise type
that you want gives you checking for type mismatches, a with sensible
error message.
> glVertex4f(arg1,arg2,arg3,arg4);
You don't declare this function before calling it. That's dangerous.
>
> Py_INCREF(Py_None); resultobj = Py_None;
> return resultobj;
> fail:
> return NULL;
> };
>
>
> static PyMethodDef modglMethods[] = {
> { (char *)"glVertex4f", _wrap_glVertex4f, METH_VARARGS, NULL},
> { NULL, NULL, 0, NULL }
> };
>
>
> PyMODINIT_FUNC modgl(void)
I can't see how you were able to import the module. For "import modgl"
to work, your initialisation function should be called "initmodgl".
> {
> (void) Py_InitModule("modgl", modglMethods);
> };
>
>
You are writing an extension, not embedding Python. You don't need a
main(). Lose it.
> int
> main(int argc, char *argv[])
> {
> /* Pass argv[0] to the Python interpreter */
> Py_SetProgramName(argv[0]);
>
> /* Initialize the Python interpreter. Required. */
> Py_Initialize();
>
> /* Add a static module */
> initmodgl();
> return 0;
> };
Below is a cutdown version of your module, that returns a value so that
you can see that it is working. You might like to use that as a base.
Here it is working:
|>>> import modgl
|>>> modgl.glVertex4f(1, 2, 3, 4)
10.0
|>>> modgl.glVertex4f(1, 2, "three", 4)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: a float is required
|>>>
HTH,
John
8<---
#include <Python.h>
static PyObject *
_wrap_glVertex4f(PyObject *self, PyObject *args) {
PyObject *resultobj = NULL;
float arg1, arg2, arg3, arg4;
if(!PyArg_ParseTuple(args,"ffff:glVertex4f",&arg1,&arg2,&arg3,&arg4))
goto fail;
/* glVertex4f(arg1,arg2,arg3,arg4); */
/* Py_INCREF(Py_None); resultobj = Py_None; */
resultobj = Py_BuildValue("d", (double)(arg1 + arg2 + arg3 + arg4));
return resultobj;
fail:
return NULL;
};
static PyMethodDef modglMethods[] = {
{ (char *)"glVertex4f", _wrap_glVertex4f, METH_VARARGS, NULL},
{ NULL, NULL, 0, NULL }
};
PyMODINIT_FUNC
initmodgl(void)
{
(void) Py_InitModule("modgl", modglMethods);
};
8<---
--
http://mail.python.org/mailman/listinfo/python-list
