Patch #1623563: allow __class__ assignment for classes with __slots__.
The old and the new class are still required to have the same slot
names, but the order in which they are specified is not relevant.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 64abe5a..64003fc 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1844,8 +1844,11 @@
}
}
- /* Copy slots into yet another tuple, demangling names */
- newslots = PyTuple_New(nslots - add_dict - add_weak);
+ /* Copy slots into a list, mangle names and sort them.
+ Sorted names are needed for __class__ assignment.
+ Convert them back to tuple at the end.
+ */
+ newslots = PyList_New(nslots - add_dict - add_weak);
if (newslots == NULL)
goto bad_slots;
for (i = j = 0; i < nslots; i++) {
@@ -1858,13 +1861,23 @@
tmp =_Py_Mangle(name, tmp);
if (!tmp)
goto bad_slots;
- PyTuple_SET_ITEM(newslots, j, tmp);
+ PyList_SET_ITEM(newslots, j, tmp);
j++;
}
assert(j == nslots - add_dict - add_weak);
nslots = j;
Py_DECREF(slots);
- slots = newslots;
+ if (PyList_Sort(newslots) == -1) {
+ Py_DECREF(bases);
+ Py_DECREF(newslots);
+ return NULL;
+ }
+ slots = PyList_AsTuple(newslots);
+ Py_DECREF(newslots);
+ if (slots == NULL) {
+ Py_DECREF(bases);
+ return NULL;
+ }
/* Secondary bases may provide weakrefs or dict */
if (nbases > 1 &&
@@ -2481,6 +2494,7 @@
{
PyTypeObject *base = a->tp_base;
Py_ssize_t size;
+ PyObject *slots_a, *slots_b;
if (base != b->tp_base)
return 0;
@@ -2491,6 +2505,15 @@
size += sizeof(PyObject *);
if (a->tp_weaklistoffset == size && b->tp_weaklistoffset == size)
size += sizeof(PyObject *);
+
+ /* Check slots compliance */
+ slots_a = ((PyHeapTypeObject *)a)->ht_slots;
+ slots_b = ((PyHeapTypeObject *)b)->ht_slots;
+ if (slots_a && slots_b) {
+ if (PyObject_Compare(slots_a, slots_b) != 0)
+ return 0;
+ size += sizeof(PyObject *) * PyTuple_GET_SIZE(slots_a);
+ }
return size == a->tp_basicsize && size == b->tp_basicsize;
}