From 171947e68f2848b845b4b248dc0298c8a592d885 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Tue, 25 May 2021 23:55:19 +0800
Subject: [PATCH] Fix type_new crash

---
 Lib/test/test_builtin.py                        | 17 ++++++++++++++++-
 .../2021-05-25-23-55-02.bpo-44232.KEDM_e.rst    |  2 ++
 Objects/typeobject.c                            |  1 -
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2021-05-25-23-55-02.bpo-44232.KEDM_e.rst

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index bd8353d038b6fea..efe1fa0911eddb9 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -19,7 +19,7 @@
 import types
 import unittest
 import warnings
-from contextlib import ExitStack
+from contextlib import ExitStack, suppress
 from functools import partial
 from inspect import CO_COROUTINE
 from itertools import product
@@ -2343,6 +2343,21 @@ def test_namespace_order(self):
         C = type('C', (), od)
         self.assertEqual(list(C.__dict__.items())[:2], [('b', 2), ('a', 1)])
 
+    def test_new_type_bad_tp_new(self):
+        # bpo-44232: Bad tp_new in bases tuple should just return NULL
+        # instead of causing an interpreter crash in debug mode.
+        class XBase(type):
+            def __new__(cls, name, bases, attrs, **kwargs):
+                attrs.pop('__module__')
+                return super().__new__(cls, name, bases, attrs, **kwargs)
+
+        class X(metaclass=XBase): ...
+
+        # The actual error here doesn't matter.  As long as the interpreter
+        # doesn't crash.
+        with suppress(Exception):
+            type('A', (X,), {})
+
 
 def load_tests(loader, tests, pattern):
     from doctest import DocTestSuite
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-05-25-23-55-02.bpo-44232.KEDM_e.rst b/Misc/NEWS.d/next/Core and Builtins/2021-05-25-23-55-02.bpo-44232.KEDM_e.rst
new file mode 100644
index 000000000000000..463c764cecad9e2
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-05-25-23-55-02.bpo-44232.KEDM_e.rst	
@@ -0,0 +1,2 @@
+Fixed a crash caused by bad metaclass bases being passed into :func:`type`.
+This only affected debug builds of Python -- release builds are unaffected.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index af99ab79d14ade8..d8aff7ac07580a0 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -3310,7 +3310,6 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
         return NULL;
     }
     if (res == 1) {
-        assert(type != NULL);
         return type;
     }
     assert(ctx.base != NULL);