[Numpy-discussion] Segfault with simplest operation on extension module using numpy

Glen W. Mabey Glen.Mabey at swri.org
Fri Jun 16 12:23:58 EDT 2006


I am writing a python extension module to create an interface to some C
code, and am using numpy array as the object type for transferring data
back and forth.

Using either the numpy svn from yesterday, or 0.9.6 or 0.9.8, with or 
without optimized ATLAS installation, I get a segfault at what should be
the most straightforward of all operations: PyArray_Check() on the input

That is, when I run:
    import DFALG
    DFALG.bsvmdf( 3 )
after compiling the below code, it always segfaults, regardless of the
type of the argument given.  Just as a sanity check (it's been a little
while since I have written an extension module for Python) I changed the
line containing PyArray_Check() to one that calls PyInt_Check(), which
does perform exactly how I would expect it to.

Is there something I'm missing?

Thank you!
Glen Mabey

#include <Python.h>
#include <arrayobject.h>

static PyObject *
DFALG_bsvmdf(PyObject *self, PyObject *args);

static PyMethodDef DFALGMethods[] = {
	{"bsvmdf",  DFALG_bsvmdf, METH_VARARGS, "This should be a docstring, really."},
	{NULL, NULL, 0, NULL}        /* Sentinel */

	(void) Py_InitModule("DFALG", DFALGMethods);

static PyObject *
DFALG_bsvmdf(PyObject *self, PyObject *args)
    PyObject *inputarray;
    //printf( "Hello, Python!" );
	//return Py_None;

    if ( !PyArg_ParseTuple( args, "O", &inputarray ) )
        return NULL;

    if ( PyArray_Check( inputarray ) ) {
    //if ( PyInt_Check( inputarray ) ) {
        printf( "DFALG_bsvmdf() was passed a PyArray.()\n" );
    } else {
        printf( "DFALG_bsvmdf() was NOT passed a PyArray.()\n" );
	return Py_BuildValue( "ss", "Thing 1", "Thing 2" );

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