From 7c2efccfe0b0bb683fbbda0e7881bd03ca8dcdd6 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Mon, 18 Mar 2024 08:57:27 +0100
Subject: [PATCH] gh-116946: Emit RuntimeError if a heap does not implement
 traverse

---
 Objects/typeobject.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 24f31492985164..c462ebd0f6339e 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -4709,6 +4709,15 @@ _PyType_FromMetaclass_impl(
         }
     }
 
+    if (!(type->tp_flags & Py_TPFLAGS_HAVE_GC)
+        || type->tp_traverse == NULL)
+    {
+        if (PyErr_WarnFormat(PyExc_RuntimeError, 1,
+                "heap type %N should implement tp_traverse and visit their type",
+                type)) {
+            goto finally;
+        }
+    }
     assert(_PyType_CheckConsistency(type));
 
  finally: