https://github.com/python/cpython/commit/08d7bd28fecca524c648dda240022add704b8f8a commit: 08d7bd28fecca524c648dda240022add704b8f8a branch: main author: Pieter Eendebak <[email protected]> committer: vstinner <[email protected]> date: 2026-01-28T11:27:37+01:00 summary:
gh-140232: Do not track frozenset objects with immutables (#140234) Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com> Co-authored-by: Mikhail Efimov <[email protected]> Co-authored-by: Victor Stinner <[email protected]> files: A Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-22-36-05.gh-issue-140232.u3srgv.rst M Lib/test/test_capi/test_set.py M Lib/test/test_sys.py M Modules/_testlimitedcapi/set.c M Objects/setobject.c diff --git a/Lib/test/test_capi/test_set.py b/Lib/test/test_capi/test_set.py index 62d90a3f94326d..a41c2fcaf12270 100644 --- a/Lib/test/test_capi/test_set.py +++ b/Lib/test/test_capi/test_set.py @@ -166,6 +166,12 @@ def test_add(self): # CRASHES: add(instance, NULL) # CRASHES: add(NULL, NULL) + def test_add_frozenset(self): + add = _testlimitedcapi.set_add + frozen_set = frozenset() + # test adding an element to a non-uniquely referenced frozenset throws an exception + self.assertRaises(SystemError, add, frozen_set, 1) + def test_discard(self): discard = _testlimitedcapi.set_discard for cls in (set, set_subclass): diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py index a5708b298c84a5..b44e0c9779aa59 100644 --- a/Lib/test/test_sys.py +++ b/Lib/test/test_sys.py @@ -1880,7 +1880,10 @@ class S(set): check(S(), set(), '3P') class FS(frozenset): __slots__ = 'a', 'b', 'c' - check(FS(), frozenset(), '3P') + + class mytuple(tuple): + pass + check(FS([mytuple()]), frozenset([mytuple()]), '3P') from collections import OrderedDict class OD(OrderedDict): __slots__ = 'a', 'b', 'c' diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-22-36-05.gh-issue-140232.u3srgv.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-22-36-05.gh-issue-140232.u3srgv.rst new file mode 100644 index 00000000000000..e40daacbc45b7b --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-16-22-36-05.gh-issue-140232.u3srgv.rst @@ -0,0 +1 @@ +Frozenset objects with immutable elements are no longer tracked by the garbage collector. diff --git a/Modules/_testlimitedcapi/set.c b/Modules/_testlimitedcapi/set.c index 34ed6b1d60b5a4..8aade9502b6182 100644 --- a/Modules/_testlimitedcapi/set.c +++ b/Modules/_testlimitedcapi/set.c @@ -155,6 +155,72 @@ test_frozenset_add_in_capi(PyObject *self, PyObject *Py_UNUSED(obj)) return NULL; } +static PyObject * +raiseTestError(const char* test_name, const char* msg) +{ + PyErr_Format(PyExc_AssertionError, "%s: %s", test_name, msg); + return NULL; +} + +static PyObject * +test_frozenset_add_in_capi_tracking_immutable(PyObject *self, PyObject *Py_UNUSED(ignored)) +{ + // Test: GC tracking - frozenset with only immutable items should not be tracked + PyObject *frozenset = PyFrozenSet_New(NULL); + if (frozenset == NULL) { + return NULL; + } + if (PySet_Add(frozenset, Py_True) < 0) { + Py_DECREF(frozenset); + return NULL; + } + if (PyObject_GC_IsTracked(frozenset)) { + Py_DECREF(frozenset); + return raiseTestError("test_frozenset_add_in_capi_tracking_immutable", + "frozenset with only bool should not be GC tracked"); + } + Py_DECREF(frozenset); + Py_RETURN_NONE; +} + +static PyObject * +test_frozenset_add_in_capi_tracking(PyObject *self, PyObject *Py_UNUSED(ignored)) +{ + // Test: GC tracking - frozenset with tracked object should be tracked + PyObject *frozenset = PyFrozenSet_New(NULL); + if (frozenset == NULL) { + return NULL; + } + + PyObject *tracked_obj = PyErr_NewException("_testlimitedcapi.py_set_add", NULL, NULL); + if (tracked_obj == NULL) { + goto error; + } + if (!PyObject_GC_IsTracked(tracked_obj)) { + Py_DECREF(frozenset); + Py_DECREF(tracked_obj); + return raiseTestError("test_frozenset_add_in_capi_tracking", + "test object should be tracked"); + } + if (PySet_Add(frozenset, tracked_obj) < 0) { + goto error; + } + Py_DECREF(tracked_obj); + if (!PyObject_GC_IsTracked(frozenset)) { + Py_DECREF(frozenset); + return raiseTestError("test_frozenset_add_in_capi_tracking", + "frozenset with with GC tracked object should be tracked"); + } + Py_DECREF(frozenset); + Py_RETURN_NONE; + +error: + Py_DECREF(frozenset); + Py_XDECREF(tracked_obj); + return NULL; +} + + static PyObject * test_set_contains_does_not_convert_unhashable_key(PyObject *self, PyObject *Py_UNUSED(obj)) { @@ -219,6 +285,8 @@ static PyMethodDef test_methods[] = { {"set_clear", set_clear, METH_O}, {"test_frozenset_add_in_capi", test_frozenset_add_in_capi, METH_NOARGS}, + {"test_frozenset_add_in_capi_tracking", test_frozenset_add_in_capi_tracking, METH_NOARGS}, + {"test_frozenset_add_in_capi_tracking_immutable", test_frozenset_add_in_capi_tracking_immutable, METH_NOARGS}, {"test_set_contains_does_not_convert_unhashable_key", test_set_contains_does_not_convert_unhashable_key, METH_NOARGS}, diff --git a/Objects/setobject.c b/Objects/setobject.c index 378f221bcfd1e1..5d4d1812282eed 100644 --- a/Objects/setobject.c +++ b/Objects/setobject.c @@ -1368,6 +1368,26 @@ make_new_set_basetype(PyTypeObject *type, PyObject *iterable) return make_new_set(type, iterable); } +// gh-140232: check whether a frozenset can be untracked from the GC +static void +_PyFrozenSet_MaybeUntrack(PyObject *op) +{ + assert(op != NULL); + // subclasses of a frozenset can generate reference cycles, so do not untrack + if (!PyFrozenSet_CheckExact(op)) { + return; + } + // if no elements of a frozenset are tracked by the GC, we untrack the object + Py_ssize_t pos = 0; + setentry *entry; + while (set_next((PySetObject *)op, &pos, &entry)) { + if (_PyObject_GC_MAY_BE_TRACKED(entry->key)) { + return; + } + } + _PyObject_GC_UNTRACK(op); +} + static PyObject * make_new_frozenset(PyTypeObject *type, PyObject *iterable) { @@ -1379,7 +1399,11 @@ make_new_frozenset(PyTypeObject *type, PyObject *iterable) /* frozenset(f) is idempotent */ return Py_NewRef(iterable); } - return make_new_set(type, iterable); + PyObject *obj = make_new_set(type, iterable); + if (obj != NULL) { + _PyFrozenSet_MaybeUntrack(obj); + } + return obj; } static PyObject * @@ -2932,7 +2956,11 @@ PySet_New(PyObject *iterable) PyObject * PyFrozenSet_New(PyObject *iterable) { - return make_new_set(&PyFrozenSet_Type, iterable); + PyObject *result = make_new_set(&PyFrozenSet_Type, iterable); + if (result != NULL) { + _PyFrozenSet_MaybeUntrack(result); + } + return result; } Py_ssize_t @@ -3010,6 +3038,11 @@ PySet_Add(PyObject *anyset, PyObject *key) // API limits the usage of `PySet_Add` to "fill in the values of brand // new frozensets before they are exposed to other code". In this case, // this can be done without a lock. + // Since another key is added to the set, we must track the frozenset + // if needed. + if (PyFrozenSet_CheckExact(anyset) && !PyObject_GC_IsTracked(anyset) && PyObject_GC_IsTracked(key)) { + _PyObject_GC_TRACK(anyset); + } return set_add_key((PySetObject *)anyset, key); } _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
