https://github.com/python/cpython/commit/e7eaed56149aa08f7fd5012784cc1deef8e483de
commit: e7eaed56149aa08f7fd5012784cc1deef8e483de
branch: main
author: Hai Zhu <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-05-23T13:55:44+05:30
summary:
gh-148450: `abc.register` needs to update `type_version` when `tp_flags` is
changed (#148623)
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-04-15-15-48-04.gh-issue-148450.2MEVqH.rst
M Lib/test/test_type_cache.py
M Objects/typeobject.c
diff --git a/Lib/test/test_type_cache.py b/Lib/test/test_type_cache.py
index 22ad9f6243eda91..849a2afd8ed7986 100644
--- a/Lib/test/test_type_cache.py
+++ b/Lib/test/test_type_cache.py
@@ -1,4 +1,5 @@
""" Tests for the internal type cache in CPython. """
+import collections.abc
import dis
import unittest
import warnings
@@ -114,6 +115,25 @@ class HolderSub(Holder):
Holder.set_value()
HolderSub.value
+ def test_abc_register_invalidates_subclass_versions(self):
+ class Parent:
+ pass
+
+ class Child(Parent):
+ pass
+
+ type_assign_version(Parent)
+ type_assign_version(Child)
+ parent_version = type_get_version(Parent)
+ child_version = type_get_version(Child)
+ if parent_version == 0 or child_version == 0:
+ self.skipTest("Could not assign valid type versions")
+
+ collections.abc.Mapping.register(Parent)
+
+ self.assertEqual(type_get_version(Parent), 0)
+ self.assertEqual(type_get_version(Child), 0)
+
@support.cpython_only
class TypeCacheWithSpecializationTests(unittest.TestCase):
def tearDown(self):
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-15-15-48-04.gh-issue-148450.2MEVqH.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-15-15-48-04.gh-issue-148450.2MEVqH.rst
new file mode 100644
index 000000000000000..2a7d0d9bb3a7f7e
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-15-15-48-04.gh-issue-148450.2MEVqH.rst
@@ -0,0 +1 @@
+Fix ``abc.register()`` so it invalidates type version tags for registered
classes.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 7cca137f74be58f..fc679ef747e8567 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -6490,9 +6490,25 @@ set_flags_recursive(PyTypeObject *self, unsigned long
mask, unsigned long flags)
void
_PyType_SetFlagsRecursive(PyTypeObject *self, unsigned long mask, unsigned
long flags)
{
+ BEGIN_TYPE_LOCK();
+ /* Ideally, changing flags and invalidating the old version tag would
+ happen in one step. But type_modified_unlocked() is re-entrant and
+ cannot run with the world stopped, so we must invalidate first.
+ Immutable/static-builtin types are skipped because
+ set_flags_recursive() does not modify them. */
+ if (!PyType_HasFeature(self, Py_TPFLAGS_IMMUTABLETYPE) &&
+ (self->tp_flags & mask) != flags)
+ {
+ type_modified_unlocked(self);
+ }
+ /* Keep TYPE_LOCK held while waiting for stop-the-world so no thread
+ can reassign a version tag before the flag update. */
+ type_lock_prevent_release();
types_stop_world();
set_flags_recursive(self, mask, flags);
types_start_world();
+ type_lock_allow_release();
+ END_TYPE_LOCK();
}
/* This is similar to PyObject_GenericGetAttr(),
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