bpo-38140: Make dict and weakref offsets opaque for C heap types (#16076)

* Make dict and weakref offsets opaque for C heap types

* Add news

1 files changed, 27 insertions, 0 deletions

diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index b1d045c..79059bc 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -12,6 +12,7 @@ import textwrap
 import threading
 import time
 import unittest
+import weakref
 from test import support
 from test.support import MISSING_C_DOCSTRINGS
 from test.support.script_helper import assert_python_failure, assert_python_ok
@@ -437,6 +438,32 @@ class CAPITest(unittest.TestCase):
         # Test that subtype_dealloc decref the newly assigned __class__ only once
         self.assertEqual(new_type_refcnt, sys.getrefcount(A))
 
+    def test_heaptype_with_dict(self):
+        inst = _testcapi.HeapCTypeWithDict()
+        inst.foo = 42
+        self.assertEqual(inst.foo, 42)
+        self.assertEqual(inst.dictobj, inst.__dict__)
+        self.assertEqual(inst.dictobj, {"foo": 42})
+
+        inst = _testcapi.HeapCTypeWithDict()
+        self.assertEqual({}, inst.__dict__)
+
+    def test_heaptype_with_negative_dict(self):
+        inst = _testcapi.HeapCTypeWithNegativeDict()
+        inst.foo = 42
+        self.assertEqual(inst.foo, 42)
+        self.assertEqual(inst.dictobj, inst.__dict__)
+        self.assertEqual(inst.dictobj, {"foo": 42})
+
+        inst = _testcapi.HeapCTypeWithNegativeDict()
+        self.assertEqual({}, inst.__dict__)
+
+    def test_heaptype_with_weakref(self):
+        inst = _testcapi.HeapCTypeWithWeakref()
+        ref = weakref.ref(inst)
+        self.assertEqual(ref(), inst)
+        self.assertEqual(inst.weakreflist, ref)
+
     def test_c_subclass_of_heap_ctype_with_tpdealloc_decrefs_once(self):
         subclass_instance = _testcapi.HeapCTypeSubclass()
         type_refcnt = sys.getrefcount(_testcapi.HeapCTypeSubclass)