Issue #23726: Don't enable GC for user subclasses of non-GC types that don't add any new fields.

Patch by Eugene Toder.

2 files changed, 20 insertions, 2 deletions

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index cdaae0a..9f3d34d 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -3020,8 +3020,6 @@ order (MRO) for bases """
         cant(object(), list)
         cant(list(), object)
         class Int(int): __slots__ = []
-        cant(2, Int)
-        cant(Int(), int)
         cant(True, int)
         cant(2, bool)
         o = object()
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 2ac1d4b..254f64b 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -546,11 +546,31 @@ class GCTests(unittest.TestCase):
 
         class UserClass:
             pass
+
+        class UserInt(int):
+            pass
+
+        # Base class is object; no extra fields.
+        class UserClassSlots:
+            __slots__ = ()
+
+        # Base class is fixed size larger than object; no extra fields.
+        class UserFloatSlots(float):
+            __slots__ = ()
+
+        # Base class is variable size; no extra fields.
+        class UserIntSlots(int):
+            __slots__ = ()
+
         self.assertTrue(gc.is_tracked(gc))
         self.assertTrue(gc.is_tracked(UserClass))
         self.assertTrue(gc.is_tracked(UserClass()))
+        self.assertTrue(gc.is_tracked(UserInt()))
         self.assertTrue(gc.is_tracked([]))
         self.assertTrue(gc.is_tracked(set()))
+        self.assertFalse(gc.is_tracked(UserClassSlots()))
+        self.assertFalse(gc.is_tracked(UserFloatSlots()))
+        self.assertFalse(gc.is_tracked(UserIntSlots()))
 
     def test_bug1055820b(self):
         # Corresponds to temp2b.py in the bug report.