Yet another Numeric Swig core dump problem

[Travis Oliphant]

Edward C. Jones wrote:

> The following Python / SWIG / Numeric program dumps core. I use RedHat
> Linux on a PC. Python 2.1, Numeric 20.0.0, SWIG 1.1 build 883, gcc 2.96.
> 
> The output looks like:
> 
>  > testdb.py
> called import_array
> L11
> Segmentation fault (core dumped)
>  >KLTfeatures.KLTSelectGoodFeatures()
>  >
> 
> The program files are:
> 
> -----------
> testdb.py:
> 
> #! /usr/bin/python
> 
> import Numeric, KLTfeatures
> 
> KLTfeatures.KLTSelectGoodFeatures()
> 
> -----------
> KLTfeatures.h:
> 
> #include "Python.h"
> #include "/usr/include/python2.1/Numeric/arrayobject.h"
> 
> void KLTSelectGoodFeatures(void);
> 
> -----------
> KLTfeatures.i:
> 
> %module KLTfeatures
> 
> %{
> #include "KLTfeatures.h"
> %}
> 
> %init %{
>      import_array();
>      printf("called import_array\n");
> 
> %}
> 
> void KLTSelectGoodFeatures(void);
> 
> -----------
> KLTfeaturesmodule.c:
> 
> #include "KLTfeatures.h"
> 
> void KLTSelectGoodFeatures()
> {    PyArrayObject *pao;
>      int dims[2];
> 
>      dims[0] = 100;
>      dims[1] = 200;
>      printf("L11\n");
>      pao = (PyArrayObject*) PyArray_FromDims(2, dims, PyArray_UBYTE);
>      printf("L17\n");
>      Py_DECREF(pao);
> }
> 
> ----------
> How to compile:
> 
> swig -python KLTfeatures.i
> gcc -c -Wall KLTfeaturesmodule.c KLTfeatures_wrap.c
> -I/usr/include/python2.1 ld -shared KLTfeaturesmodule.o KLTfeatures_wrap.o
> -o KLTfeatures.so
> 


import_array must be in the file that is accessing the C-API for Numeric.

You are using PyArray_FromDims in a file without the import_array statement.

A quick hack is to place import_array in the KLTfeatures file.

A better way is to use some defines appropriately as described by Paul 
Dubois (I'm not sure exactly how to do it).  

-Travis