Extension types as exceptions (Wrapup)

[Daniel Dittmar]

My code creates an actual instance of the exception class, which might
be a bit more self documenting (as the attributes have names) and is
easier to handle when there are many attributes.

This has the one disadvantage that you have to create a __str__ method
for the class (that's what the exceptionCode parameter in
createExceptionKind is for), because without it, a traceback will show
only the class name.

Actually, my current code first tries to create the instance. If this
fails, it will try to create the tuple.

There is a reference counting error in my raiseError routine:
PyInt_FromLong  (code) will set the ref count to 1,
PyObject_SetAttrString will set it to 2, so the object can never be
reclaimed.

The hopefully correct version is:

static PyObject*
 raiseCommunicationError (
    int code,
    const char * msg)
{
    PyObject * exception = PyInstance_New (CommunicationErrorType,
NULL, NULL);
    PyObject * pycode = NULL;
    PyObject * pymsg = NULL;

    pycode = PyInt_FromLong  (code);
    pymsg = PyString_FromString  (msg);
    if (exception != NULL) {
        PyObject_SetAttrString (exception, "errorCode", pycode) ;
        PyObject_SetAttrString (exception, "message", pymsg);
        Py_XDECREF (pycode);
        Py_XDECREF (pymsg);
    }
    else {
        exception = Py_BuildValue ("NN", pycode, pymsg);
    }
    PyErr_SetObject (CommunicationErrorType, exception);
    return NULL;
}


Daniel Dittmar
daniel.dittmar at sap-ag.de
SAP AG, Basis Entwicklung Berlin