prevent unacceptable bases from becoming bases through multiple inheritance (#24806)
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 0ac458f..25f65c5 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4065,6 +4065,37 @@
else:
assert 0, "best_base calculation found wanting"
+ def test_unsubclassable_types(self):
+ with self.assertRaises(TypeError):
+ class X(types.NoneType):
+ pass
+ with self.assertRaises(TypeError):
+ class X(object, types.NoneType):
+ pass
+ with self.assertRaises(TypeError):
+ class X(types.NoneType, object):
+ pass
+ class O(object):
+ pass
+ with self.assertRaises(TypeError):
+ class X(O, types.NoneType):
+ pass
+ with self.assertRaises(TypeError):
+ class X(types.NoneType, O):
+ pass
+
+ class X(object):
+ pass
+ with self.assertRaises(TypeError):
+ X.__bases__ = types.NoneType,
+ with self.assertRaises(TypeError):
+ X.__bases__ = object, types.NoneType
+ with self.assertRaises(TypeError):
+ X.__bases__ = types.NoneType, object
+ with self.assertRaises(TypeError):
+ X.__bases__ = O, types.NoneType
+ with self.assertRaises(TypeError):
+ X.__bases__ = types.NoneType, O
def test_mutable_bases_with_failing_mro(self):
# Testing mutable bases with failing mro...
diff --git a/Misc/NEWS b/Misc/NEWS
index eb43f1f..60dfbf0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
Core and Builtins
-----------------
+- Issue #24806: Prevent builtin types that are not allowed to be subclassed from
+ being subclassed through multiple inheritance.
+
- Issue #24848: Fixed a number of bugs in UTF-7 decoding of misformed data.
- Issue #25003: os.urandom() doesn't use getentropy() on Solaris because
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 9a221b3..d3e5384 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1724,6 +1724,12 @@
if (PyType_Ready(base_i) < 0)
return NULL;
}
+ if (!PyType_HasFeature(base_i, Py_TPFLAGS_BASETYPE)) {
+ PyErr_Format(PyExc_TypeError,
+ "type '%.100s' is not an acceptable base type",
+ base_i->tp_name);
+ return NULL;
+ }
candidate = solid_base(base_i);
if (winner == NULL) {
winner = candidate;
@@ -2148,13 +2154,6 @@
Py_DECREF(bases);
return NULL;
}
- if (!PyType_HasFeature(base, Py_TPFLAGS_BASETYPE)) {
- PyErr_Format(PyExc_TypeError,
- "type '%.100s' is not an acceptable base type",
- base->tp_name);
- Py_DECREF(bases);
- return NULL;
- }
/* Check for a __slots__ sequence variable in dict, and count it */
slots = PyDict_GetItemString(dict, "__slots__");