[ZODB-Dev] Re: raising ConflictError from C (was: Latest news: core dump ...)

[Greg Ward]

On 04 October 2001, I said:
> I'm not sure of the best way to fix this.  The most obvious is to do the
> C equivalent of this:
>   except:
>     (error, value, traceback) = sys.excinfo()
>     raise ConflictError(str(value)), traceback
> 
> -- ie. don't pass an arbitrary exception object to the ConflictError
> constructor, instead use its stringification as the ConflictError's
> message.

OK, I've coded this in C, added it to BTreeBucket.c
(BTree__p_resolveConflict()) and BucketTemplate.c
(_bucket__p_resolveConflict()), and now the testConflict test passes
with flying colours.  Here's the code:

err:

  if (r) {
  	ASSIGN(r, Py_BuildValue("((O))", r));
  } else {
  	PyObject *error;
	PyObject *value;
	PyObject *traceback;
        PyObject *args;
        PyObject *str_value;
  	/* Change any errors to ConflictErrors */

	PyErr_Fetch(&error, &value, &traceback);

        /* XXX error-checking! */
        if (value != NULL) {
           args = PyTuple_New(1);
           str_value = PyObject_Str(value);
           PyTuple_SET_ITEM(args, 0, str_value);
           Py_DECREF(value);
        } else {
           args = PyTuple_New(0);
        }
        value = PyInstance_New(ConflictError, args, NULL);
        Py_DECREF(args);

	Py_INCREF(ConflictError);
	Py_XDECREF(error);
        PyErr_Restore(ConflictError, value, traceback);
  }

Yes, I know there's no error-checking there.  I wanted to make sure it
works first.  Another problem: previously, there were 7 lines of
duplicate code between BTree__p_resolveConflict() and
_bucket__p_resolveConflict(), which is probably acceptable.  Now the
duplication is 18 lines; after I've added error-checking, it'll be even
more.  That makes me nervous; I really don't like copy 'n paste code
reuse.  So where should a mythical
convert_arbitrary_exception_to_ConflictError() function live?

        Greg
-- 
Greg Ward - software developer                gward@mems-exchange.org
MEMS Exchange                            http://www.mems-exchange.org