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type_new(): only defer to the winning metatype if it's different from 

the metatype passed in as an argument.  This prevents infinite
recursion when a metatype written in Python calls type.__new__() as a
"super" call.

Also tweaked some comments.
This commit is contained in:
Guido van Rossum 2001-08-17 11:18:38 +00:00
parent 4b046c252e
commit 8d32c8b59f
1 changed files with 12 additions and 8 deletions
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20
Objects/typeobject.c
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@ -497,21 +497,21 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
PyObject *name, *bases, *dict;
static char *kwlist[] = {"name", "bases", "dict", 0};
PyObject *slots, *tmp;
PyTypeObject *type, *base, *tmptype;
PyTypeObject *type, *base, *tmptype, *winner;
etype *et;
struct memberlist *mp;
int i, nbases, nslots, slotoffset, dynamic;
/* Special case: type(x) should return x->ob_type */
if (metatype == &PyType_Type &&
PyTuple_Check(args) && PyTuple_GET_SIZE(args) == 1 &&
(kwds == NULL || (PyDict_Check(kwds) && PyDict_Size(kwds) == 0))) {
/* type(x) -> x.__class__ */
PyObject *x = PyTuple_GET_ITEM(args, 0);
Py_INCREF(x->ob_type);
return (PyObject *) x->ob_type;
}
/* Check arguments */
/* Check arguments: (name, bases, dict) */
if (!PyArg_ParseTupleAndKeywords(args, kwds, "SO!O!:type", kwlist,
&name,
&PyTuple_Type, &bases,
@ -523,21 +523,25 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
Note that if some other metatype wins to contract,
it's possible that its instances are not types. */
nbases = PyTuple_GET_SIZE(bases);
winner = metatype;
for (i = 0; i < nbases; i++) {
tmp = PyTuple_GET_ITEM(bases, i);
tmptype = tmp->ob_type;
if (PyType_IsSubtype(metatype, tmptype))
if (PyType_IsSubtype(winner, tmptype))
continue;
if (PyType_IsSubtype(tmptype, metatype)) {
metatype = tmptype;
if (PyType_IsSubtype(tmptype, winner)) {
winner = tmptype;
continue;
}
PyErr_SetString(PyExc_TypeError,
"metatype conflict among bases");
return NULL;
}
if (metatype->tp_new != type_new) /* Pass it to the winner */
return metatype->tp_new(metatype, args, kwds);
if (winner != metatype) {
if (winner->tp_new != type_new) /* Pass it to the winner */
return winner->tp_new(winner, args, kwds);
metatype = winner;
}
/* Adjust for empty tuple bases */
if (nbases == 0) {