From 97e36b55ed62d95574c00ef5afd12943f9cad9a2 Mon Sep 17 00:00:00 2001
From: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Mon, 25 Jul 2022 20:09:55 +0800
Subject: [PATCH] Fix MRO calculation for types with manual __dict__

---
 .../2022-07-25-20-09-21.gh-issue-92678.8IfNdU.rst           | 2 ++
 Objects/typeobject.c                                        | 6 ++++++
 2 files changed, 8 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-07-25-20-09-21.gh-issue-92678.8IfNdU.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-25-20-09-21.gh-issue-92678.8IfNdU.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-25-20-09-21.gh-issue-92678.8IfNdU.rst
new file mode 100644
index 00000000000000..636ef4b1492da6
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-07-25-20-09-21.gh-issue-92678.8IfNdU.rst	
@@ -0,0 +1,2 @@
+Fix MRO calculation issue which caused C extension types manually managing
+their own ``__dict__`` to fail in Python 3.11.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 5ebff6084f4a97..fdf5014cc4edcf 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2241,6 +2241,12 @@ extra_ivars(PyTypeObject *type, PyTypeObject *base)
         type->tp_weaklistoffset + sizeof(PyObject *) == t_size &&
         type->tp_flags & Py_TPFLAGS_HEAPTYPE)
         t_size -= sizeof(PyObject *);
+    if (!(type->tp_flags & Py_TPFLAGS_MANAGED_DICT) &&
+        type->tp_dictoffset && base->tp_dictoffset == 0 &&
+        type->tp_dictoffset + sizeof(PyObject *) == t_size &&
+        type->tp_flags & Py_TPFLAGS_HEAPTYPE) {
+        t_size -= sizeof(PyObject *);
+    }
     return t_size != b_size;
 }