[Numpy-discussion] SWIG, numpy.i and errno: comments?

[Egor Zindy]

Bill,

thank you for your comment. Would this do instead? (replacing the
return NULL with SWIG_fail):

%exception
{
    errno = 0;
    $action

    if (errno != 0)
    {
        switch(errno)
        {
            case EPERM:
                PyErr_Format(PyExc_IndexError, "Index out of range");
                break;
            case ENOMEM:
                PyErr_Format(PyExc_MemoryError, "failed malloc()");
                break;
            default:
                PyErr_Format(PyExc_Exception, "Unknown exception");
        }
        SWIG_fail;
    }
}

Cheers,
Egor

On Sun, Aug 9, 2009 at 2:30 PM, Bill Spotz<wfspotz at sandia.gov> wrote:
> Egor,
>
> This looks about right.  However, it is customary to invoke the SWIG macro
> "SWIG_fail;" instead of "break;".  (This translates into a "goto" to the
> failure label, and is better in case there is any other cleanup code to
> execute.)
>
> On Aug 9, 2009, at 6:17 AM, Egor Zindy wrote:
>
>> Hello list,
>>
>> this is my attempt at generating python exceptions in SWIG/C using the
>> errno mechanism:
>>
>> http://www.scipy.org/Cookbook/SWIG_NumPy_examples#head-10f49a0f5ea6b313127d2ec5ffa1eaf1c133cb22
>>
>> Used together with numpy.i, this has been useful for notifying (in a
>> pythonic way) memory allocation errors or array index problems.
>>
>> A change in the errno global variable is detected in the %exception
>> part of the SWIG interface file, and Python exceptions are generated
>> after $action depending on the errno error code value.
>>
>> %exception
>> {
>>   errno = 0;
>>   $action
>>
>>   if (errno != 0)
>>   {
>>       switch(errno)
>>       {
>>           case EPERM:
>>               PyErr_Format(PyExc_IndexError, "Index out of range");
>>               break;
>>           case ENOMEM:
>>               PyErr_Format(PyExc_MemoryError, "Failed malloc()");
>>               break;
>>           default:
>>               PyErr_Format(PyExc_Exception, "Unknown exception");
>>       }
>>       return NULL;
>>   }
>> }
>>
>> If there's a better way of doing this, I'll update the cookbook recipe.
>>
>> Regards,
>> Egor
>
> ** Bill Spotz                                              **
> ** Sandia National Laboratories  Voice: (505)845-0170      **
> ** P.O. Box 5800                 Fax:   (505)284-0154      **
> ** Albuquerque, NM 87185-0370    Email: wfspotz at sandia.gov **
>
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