PyErr_Warn

[Jane Austine]

Please someone demystify PyErr_Warn...

First the context of the problem:

I'm using bsddb module with Python2.3a2.

I run the script with -Wi arg so that no warnings show up. However, I
found some warning messages recorded in my log:

warning: DB_INCOMPLETE: Cache flush was unable to complete

Tracking down the source code, I noticed that I came from the
following
code in _bsddb.c file:
----
#if PYTHON_API_VERSION >= 1010
            exceptionRaised = PyErr_Warn(PyExc_RuntimeWarning,
errTxt);
#else
            fprintf(stderr, errTxt);
            fprintf(stderr, "\n");
#endif
----

Since the api version is higher than 1010, PyErr_Warn must have been
called.

In errors.c file:
----
int
PyErr_Warn(PyObject *category, char *message)
{
        PyObject *dict, *func = NULL;
        
        if (PyModule_WarningsModule != NULL) {
                dict = PyModule_GetDict(PyModule_WarningsModule);
                func = PyDict_GetItemString(dict, "warn");
        }       
        if (func == NULL) {
                PySys_WriteStderr("warning: %s\n", message);
                return 0;       
        }                       
        else {          
                PyObject *args, *res;
                
                if (category == NULL)
                        category = PyExc_RuntimeWarning;
                args = Py_BuildValue("(sO)", message, category);
                if (args == NULL)
                        return -1;
                res = PyEval_CallObject(func, args);
                Py_DECREF(args);
                if (res == NULL)
----

It seems like "func == NULL" is true and the message is thrown to the
stderr at the time.

Now the question:

Why is the func(warnings.warn) NULL in this case? What does that mean?
When is it supposed to be NULL?

Thank you in advance,

Jane.