gh-144330: Initialize staticmethod/classmethod callables in tp_new

Lib/test/test_descr.py

@@ -1831,6 +1831,24 @@ def test_refleaks_in_staticmethod___init__(self):
             sm.__init__(None)
         self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
 
+    def test_staticmethod_new(self):
+        sm = staticmethod.__new__(staticmethod, None)
+        self.assertEqual(repr(sm), '<staticmethod(None)>')
+
+    def test_classmethod_new(self):
+        cm = classmethod.__new__(classmethod, None)
+        self.assertEqual(repr(cm), '<classmethod(None)>')
+
+    def test_staticmethod_func_readonly(self):
+        sm = staticmethod(lambda x: x)
+        with self.assertRaises(AttributeError):
+            sm.__func__ = None
+
+    def test_classmethod_func_readonly(self):
+        cm = classmethod(lambda x: x)
+        with self.assertRaises(AttributeError):
+            cm.__func__ = None
+
     @support.impl_detail("the module 'xxsubtype' is internal")
     @unittest.skipIf(xxsubtype is None, "requires xxsubtype module")
     def test_staticmethods_in_c(self):

Objects/funcobject.c

@@ -1555,11 +1555,15 @@ static PyMethodDef cm_methodlist[] = {
     {NULL} /* Sentinel */
 };
 
+static PyObject *cm_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
+static PyObject *sm_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
+
 static PyObject*
 cm_repr(PyObject *self)
 {
     classmethod *cm = _PyClassMethod_CAST(self);
-    return PyUnicode_FromFormat("<classmethod(%R)>", cm->cm_callable);
+    PyObject *callable = cm->cm_callable != NULL ? cm->cm_callable : Py_None;
+    return PyUnicode_FromFormat("<classmethod(%R)>", callable);
 }
 
 PyDoc_STRVAR(classmethod_doc,
@@ -1623,7 +1627,7 @@ PyTypeObject PyClassMethod_Type = {
     offsetof(classmethod, cm_dict),             /* tp_dictoffset */
     cm_init,                                    /* tp_init */
     PyType_GenericAlloc,                        /* tp_alloc */
-    PyType_GenericNew,                          /* tp_new */
+    cm_new,                                     /* tp_new */
     PyObject_GC_Del,                            /* tp_free */
 };
 
@@ -1638,6 +1642,18 @@ PyClassMethod_New(PyObject *callable)
     return (PyObject *)cm;
 }
 
+static PyObject *
+cm_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    classmethod *cm = (classmethod *)PyType_GenericAlloc(type, 0);
+    if (cm == NULL) {
+        return NULL;
+    }
+    cm->cm_callable = Py_None;
+    cm->cm_dict = NULL;
+    return (PyObject *)cm;
+}
+
 
 /* Static method object */
 
@@ -1796,7 +1812,8 @@ static PyObject*
 sm_repr(PyObject *self)
 {
     staticmethod *sm = _PyStaticMethod_CAST(self);
-    return PyUnicode_FromFormat("<staticmethod(%R)>", sm->sm_callable);
+    PyObject *callable = sm->sm_callable != NULL ? sm->sm_callable : Py_None;
+    return PyUnicode_FromFormat("<staticmethod(%R)>", callable);
 }
 
 PyDoc_STRVAR(staticmethod_doc,
@@ -1858,7 +1875,7 @@ PyTypeObject PyStaticMethod_Type = {
     offsetof(staticmethod, sm_dict),            /* tp_dictoffset */
     sm_init,                                    /* tp_init */
     PyType_GenericAlloc,                        /* tp_alloc */
-    PyType_GenericNew,                          /* tp_new */
+    sm_new,                                     /* tp_new */
     PyObject_GC_Del,                            /* tp_free */
 };
 
@@ -1872,3 +1889,14 @@ PyStaticMethod_New(PyObject *callable)
     }
     return (PyObject *)sm;
 }
+
+static PyObject *
+sm_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    staticmethod *sm = (staticmethod *)PyType_GenericAlloc(type, 0);
+    if (sm == NULL)
+        return NULL;
+    sm->sm_callable = Py_NewRef(Py_None);
+    sm->sm_dict = NULL;
+    return (PyObject *)sm;
+}