I'm working on issue 1615 [1] and came up with this tidbit, which works [2],
but not well enough:
slot_tp_getattr_hook(PyObject *self, PyObject *name)
{
...
+ PyObject *error_type, *error_value, *error_traceback;
...
+ /* if an AttributeError is set, save it and call getattr; if getattr
+ sets an AttributeError, discard it and return the original
+ AttributeError */
if (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
+ PyErr_Fetch(&error_type, &error_value, &error_traceback);
res = call_attribute(self, getattr, name);
+ if (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError))
+ PyErr_Restore(error_type, error_value, error_traceback);
}
So I tried adding in a second call to PyErr_Fetch and adding the original error
as context, like so:
if (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
PyErr_Fetch(&ctx_error_type, &ctx_error_value, &ctx_error_traceback);
res = call_attribute(self, getattr, name);
if (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
PyErr_Fetch(&error_type, &error_value, &error_traceback);
PyException_SetContext(error_value, ctx_error_value);
PyErr_Restore(error_type, error_value, error_traceback);
} else {
Py_DECREF(ctx_error_value);
}
Py_DECREF(ctx_error_type);
Py_DECREF(ctx_error_traceback);
}
This bit of code won't even finish compiling. I am not sure if my understanding of references (and how these functions
create/consume them) or my understanding of when and where to call PyErr_Fetch|Restore or PyException_SetContext is at
fault, but I would greatly appreciate somebody correcting my understanding. :)
--
~Ethan~
[1] http://http://bugs.python.org/issue1615
[2] works as in everything compiles, but the resulting behavior introduces a new bug (the message of a 'raise
AttributeError' in a __getattr__ is ignored).
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