[3.8] bpo-39492: Fix a reference cycle between reducer_override and a Pickler instance (GH-18266) (#18316)
https://bugs.python.org/issue39492
Automerge-Triggered-By: @pitrou
(cherry picked from commit 0f2f35e)
Co-authored-by: Pierre Glaser <pierreglaser@msn.com>
diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index c9f3746..3a8aee4 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -3497,6 +3497,30 @@
ValueError, 'The reducer just failed'):
p.dump(h)
+ @support.cpython_only
+ def test_reducer_override_no_reference_cycle(self):
+ # bpo-39492: reducer_override used to induce a spurious reference cycle
+ # inside the Pickler object, that could prevent all serialized objects
+ # from being garbage-collected without explicity invoking gc.collect.
+
+ for proto in range(0, pickle.HIGHEST_PROTOCOL + 1):
+ with self.subTest(proto=proto):
+ def f():
+ pass
+
+ wr = weakref.ref(f)
+
+ bio = io.BytesIO()
+ p = self.pickler_class(bio, proto)
+ p.dump(f)
+ new_f = pickle.loads(bio.getvalue())
+ assert new_f == 5
+
+ del p
+ del f
+
+ self.assertIsNone(wr())
+
class AbstractDispatchTableTests(unittest.TestCase):