From 9b5df8b940deb27f18f0c4ec71e2a471be293077 Mon Sep 17 00:00:00 2001
From: AN Long <aisk1988@gmail.com>
Date: Sat, 27 Dec 2025 16:57:51 +0900
Subject: [PATCH 1/2] Add test for Py_tp_bases

---
 Lib/test/test_capi/test_misc.py | 12 ++++++++++
 Modules/_testcapi/heaptype.c    | 41 +++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
index 3997acbdf84695..363768b793ae03 100644
--- a/Lib/test/test_capi/test_misc.py
+++ b/Lib/test/test_capi/test_misc.py
@@ -916,6 +916,18 @@ def genf(): yield
         gen = genf()
         self.assertEqual(_testcapi.gen_get_code(gen), gen.gi_code)
 
+    def test_tp_bases_slot(self):
+        cls = _testcapi.HeapCTypeWithBasesSlot
+        self.assertEqual(cls.__bases__, (int,))
+        self.assertEqual(cls.__base__, int)
+
+    def test_tp_bases_slot_invalid(self):
+        self.assertRaisesRegex(
+            SystemError,
+            "Py_tp_bases is not a tuple",
+            _testcapi.create_heapctype_with_invalid_bases_slot
+        )
+
 
 @requires_limited_api
 class TestHeapTypeRelative(unittest.TestCase):
diff --git a/Modules/_testcapi/heaptype.c b/Modules/_testcapi/heaptype.c
index 4fdcc850a339b4..3663a7a44cc0c4 100644
--- a/Modules/_testcapi/heaptype.c
+++ b/Modules/_testcapi/heaptype.c
@@ -543,6 +543,24 @@ pytype_getmodulebytoken(PyObject *self, PyObject *args)
     return PyType_GetModuleByToken((PyTypeObject *)type, token);
 }
 
+static PyType_Slot HeapCTypeWithBasesSlotInvalid_slots[] = {
+    {Py_tp_bases, Py_None},  /* Not a tuple - should raise SystemError */
+    {0, 0},
+};
+
+static PyType_Spec HeapCTypeWithBasesSlotInvalid_spec = {
+    .name = "_testcapi.HeapCTypeWithBasesSlotInvalid",
+    .basicsize = sizeof(PyObject),
+    .flags = Py_TPFLAGS_DEFAULT,
+    .slots = HeapCTypeWithBasesSlotInvalid_slots
+};
+
+static PyObject *
+create_heapctype_with_invalid_bases_slot(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    return PyType_FromSpec(&HeapCTypeWithBasesSlotInvalid_spec);
+}
+
 
 static PyMethodDef TestMethods[] = {
     {"pytype_fromspec_meta",    pytype_fromspec_meta,            METH_O},
@@ -562,6 +580,8 @@ static PyMethodDef TestMethods[] = {
     {"pytype_getbasebytoken", pytype_getbasebytoken, METH_VARARGS},
     {"pytype_getmodulebydef", pytype_getmodulebydef, METH_O},
     {"pytype_getmodulebytoken", pytype_getmodulebytoken, METH_VARARGS},
+    {"create_heapctype_with_invalid_bases_slot",
+        create_heapctype_with_invalid_bases_slot, METH_NOARGS},
     {NULL},
 };
 
@@ -892,6 +912,18 @@ static PyType_Spec HeapCTypeMetaclassNullNew_spec = {
     .slots = empty_type_slots
 };
 
+static PyType_Slot HeapCTypeWithBasesSlot_slots[] = {
+    {Py_tp_bases, NULL},  /* filled out in module init function */
+    {0, 0},
+};
+
+static PyType_Spec HeapCTypeWithBasesSlot_spec = {
+    .name = "_testcapi.HeapCTypeWithBasesSlot",
+    .basicsize = sizeof(PyLongObject),
+    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    .slots = HeapCTypeWithBasesSlot_slots
+};
+
 
 typedef struct {
     PyObject_HEAD
@@ -1432,6 +1464,15 @@ _PyTestCapi_Init_Heaptype(PyObject *m) {
         &PyType_Type, m, &HeapCTypeMetaclassNullNew_spec, (PyObject *) &PyType_Type);
     ADD("HeapCTypeMetaclassNullNew", HeapCTypeMetaclassNullNew);
 
+    PyObject *bases = PyTuple_Pack(1, &PyLong_Type);
+    if (bases == NULL) {
+        return -1;
+    }
+    HeapCTypeWithBasesSlot_slots[0].pfunc = bases;
+    PyObject *HeapCTypeWithBasesSlot = PyType_FromSpec(&HeapCTypeWithBasesSlot_spec);
+    Py_DECREF(bases);
+    ADD("HeapCTypeWithBasesSlot", HeapCTypeWithBasesSlot);
+
     ADD("Py_TP_USE_SPEC", PyLong_FromVoidPtr(Py_TP_USE_SPEC));
 
     PyObject *HeapCCollection = PyType_FromMetaclass(

From e592491984f189f08b0cb97569c08013e41cd3bb Mon Sep 17 00:00:00 2001
From: AN Long <aisk1988@gmail.com>
Date: Sat, 27 Dec 2025 17:34:20 +0900
Subject: [PATCH 2/2] Fix test on Windows

---
 Modules/_testcapi/heaptype.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Modules/_testcapi/heaptype.c b/Modules/_testcapi/heaptype.c
index 3663a7a44cc0c4..0ffed2e32a52ec 100644
--- a/Modules/_testcapi/heaptype.c
+++ b/Modules/_testcapi/heaptype.c
@@ -544,7 +544,7 @@ pytype_getmodulebytoken(PyObject *self, PyObject *args)
 }
 
 static PyType_Slot HeapCTypeWithBasesSlotInvalid_slots[] = {
-    {Py_tp_bases, Py_None},  /* Not a tuple - should raise SystemError */
+    {Py_tp_bases, NULL},  /* filled out with Py_None in runtime */
     {0, 0},
 };
 
@@ -558,6 +558,7 @@ static PyType_Spec HeapCTypeWithBasesSlotInvalid_spec = {
 static PyObject *
 create_heapctype_with_invalid_bases_slot(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
+    HeapCTypeWithBasesSlotInvalid_slots[0].pfunc = Py_None;
     return PyType_FromSpec(&HeapCTypeWithBasesSlotInvalid_spec);
 }