From ab3f7bad99edffcab88d0c3876bcdf5bac07acc3 Mon Sep 17 00:00:00 2001
From: An Long <aisk1988@gmail.com>
Date: Wed, 5 Aug 2026 01:10:41 +0900
Subject: [PATCH] gh-155181: Untrack frozensets created from set literals when
 possible

---
 Lib/test/test_set.py                                  | 11 +++++++++++
 .../2026-08-05-01-10-20.gh-issue-155181.jj8jhk.rst    |  3 +++
 Objects/setobject.c                                   |  1 +
 3 files changed, 15 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-08-05-01-10-20.gh-issue-155181.jj8jhk.rst

diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 9bfd4bc7d636699..54d229b71def9a7 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -762,6 +762,17 @@ def test_constructor_identity(self):
         t = self.thetype(s)
         self.assertEqual(id(s), id(t))
 
+    def test_gc_tracking(self):
+        # gh-140232: frozensets whose elements can never be tracked by the
+        # GC are not tracked, including the compiled frozenset({...}) form
+        s = {1, 2}
+        self.assertFalse(gc.is_tracked(frozenset(s)))
+        self.assertFalse(gc.is_tracked(frozenset({1, 2})))
+        self.assertFalse(gc.is_tracked(frozenset({x for x in range(2)})))
+        class C:
+            pass
+        self.assertTrue(gc.is_tracked(frozenset({C()})))
+
     def test_hash(self):
         self.assertEqual(hash(self.thetype('abcdeb')),
                          hash(self.thetype('ebecda')))
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-08-05-01-10-20.gh-issue-155181.jj8jhk.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-05-01-10-20.gh-issue-155181.jj8jhk.rst
new file mode 100644
index 000000000000000..1acf8fda95e4652
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-05-01-10-20.gh-issue-155181.jj8jhk.rst
@@ -0,0 +1,3 @@
+:class:`frozenset` objects created from a set literal or a set comprehension
+are now untracked by the garbage collector when none of their elements can
+be tracked.
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 8fdd1eb26118c0a..2b7fce6be3c1bd2 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1574,6 +1574,7 @@ _PySet_Freeze(PyObject *set)
     assert(PySet_CheckExact(set));
     assert(_PyObject_IsUniquelyReferenced(set));
     set->ob_type = &PyFrozenSet_Type;
+    _PyFrozenSet_MaybeUntrack(set);
     return Py_NewRef(set);
 }