Fix a memory leak in split-table dictionaries

Issue #28147: Fix a memory leak in split-table dictionaries: setattr() must not
convert combined table into split table.

Patch written by INADA Naoki.
(grafted from 85be9dcc16a81d3ccd1f67b056255a7f206edd47)

1 files changed, 30 insertions, 0 deletions

diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index cd077ff..832bb9c 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -933,6 +933,36 @@ class DictTest(unittest.TestCase):
         self.assertEqual(list(a), ['x', 'y'])
         self.assertEqual(list(b), ['x', 'y', 'z'])
 
+    @support.cpython_only
+    def test_splittable_setattr_after_pop(self):
+        """setattr() must not convert combined table into split table."""
+        # Issue 28147
+        import _testcapi
+
+        class C:
+            pass
+        a = C()
+
+        a.a = 1
+        self.assertTrue(_testcapi.dict_hassplittable(a.__dict__))
+
+        # dict.pop() convert it to combined table
+        a.__dict__.pop('a')
+        self.assertFalse(_testcapi.dict_hassplittable(a.__dict__))
+
+        # But C should not convert a.__dict__ to split table again.
+        a.a = 1
+        self.assertFalse(_testcapi.dict_hassplittable(a.__dict__))
+
+        # Same for popitem()
+        a = C()
+        a.a = 2
+        self.assertTrue(_testcapi.dict_hassplittable(a.__dict__))
+        a.__dict__.popitem()
+        self.assertFalse(_testcapi.dict_hassplittable(a.__dict__))
+        a.a = 3
+        self.assertFalse(_testcapi.dict_hassplittable(a.__dict__))
+
     def test_iterator_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             data = {1:"a", 2:"b", 3:"c"}