GH-92678: Fix tp_dictoffset inheritance. (GH-95596) (GH-95604)

* Add test for inheriting explicit __dict__ and weakref.

* Restore 3.10 behavior for multiple inheritance of C extension classes that store their dictionary at the end of the struct.

1 files changed, 28 insertions, 0 deletions

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 9022ee4..a394f46 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -7321,6 +7321,14 @@ static PyType_Spec HeapCTypeWithDict_spec = {
     HeapCTypeWithDict_slots
 };
 
+static PyType_Spec HeapCTypeWithDict2_spec = {
+    "_testcapi.HeapCTypeWithDict2",
+    sizeof(HeapCTypeWithDictObject),
+    0,
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    HeapCTypeWithDict_slots
+};
+
 static struct PyMemberDef heapctypewithnegativedict_members[] = {
     {"dictobj", T_OBJECT, offsetof(HeapCTypeWithDictObject, dict)},
     {"__dictoffset__", T_PYSSIZET, -(Py_ssize_t)sizeof(void*), READONLY},
@@ -7380,6 +7388,14 @@ static PyType_Spec HeapCTypeWithWeakref_spec = {
     HeapCTypeWithWeakref_slots
 };
 
+static PyType_Spec HeapCTypeWithWeakref2_spec = {
+    "_testcapi.HeapCTypeWithWeakref2",
+    sizeof(HeapCTypeWithWeakrefObject),
+    0,
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    HeapCTypeWithWeakref_slots
+};
+
 PyDoc_STRVAR(heapctypesetattr__doc__,
 "A heap type without GC, but with overridden __setattr__.\n\n"
 "The 'value' attribute is set to 10 in __init__ and updated via attribute setting.");
@@ -7757,6 +7773,12 @@ PyInit__testcapi(void)
     }
     PyModule_AddObject(m, "HeapCTypeWithDict", HeapCTypeWithDict);
 
+    PyObject *HeapCTypeWithDict2 = PyType_FromSpec(&HeapCTypeWithDict2_spec);
+    if (HeapCTypeWithDict2 == NULL) {
+        return -1;
+    }
+    PyModule_AddObject(m, "HeapCTypeWithDict2", HeapCTypeWithDict2);
+
     PyObject *HeapCTypeWithNegativeDict = PyType_FromSpec(&HeapCTypeWithNegativeDict_spec);
     if (HeapCTypeWithNegativeDict == NULL) {
         return NULL;
@@ -7775,6 +7797,12 @@ PyInit__testcapi(void)
     }
     PyModule_AddObject(m, "HeapCTypeWithBuffer", HeapCTypeWithBuffer);
 
+    PyObject *HeapCTypeWithWeakref2 = PyType_FromSpec(&HeapCTypeWithWeakref2_spec);
+    if (HeapCTypeWithWeakref2 == NULL) {
+        return -1;
+    }
+    PyModule_AddObject(m, "HeapCTypeWithWeakref2", HeapCTypeWithWeakref2);
+
     PyObject *HeapCTypeSetattr = PyType_FromSpec(&HeapCTypeSetattr_spec);
     if (HeapCTypeSetattr == NULL) {
         return NULL;