Issue #24257: Fixed incorrect uses of PyObject_IsInstance().

Fixed segmentation fault in sqlite3.Row constructor with faked cursor type.
Fixed system error in the comparison of faked types.SimpleNamespace.

2 files changed, 5 insertions, 7 deletions

diff --git a/Objects/genobject.c b/Objects/genobject.c
index 3c32e7b..555e4fd 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -442,8 +442,7 @@ _PyGen_FetchStopIterationValue(PyObject **pvalue) {
         PyErr_Fetch(&et, &ev, &tb);
         if (ev) {
             /* exception will usually be normalised already */
-            if (Py_TYPE(ev) == (PyTypeObject *) et
-                || PyObject_IsInstance(ev, PyExc_StopIteration)) {
+            if (PyObject_TypeCheck(ev, (PyTypeObject *) et)) {
                 value = ((PyStopIterationObject *)ev)->value;
                 Py_INCREF(value);
                 Py_DECREF(ev);
@@ -453,7 +452,7 @@ _PyGen_FetchStopIterationValue(PyObject **pvalue) {
             } else {
                 /* normalisation required */
                 PyErr_NormalizeException(&et, &ev, &tb);
-                if (!PyObject_IsInstance(ev, PyExc_StopIteration)) {
+                if (!PyObject_TypeCheck(ev, (PyTypeObject *)PyExc_StopIteration)) {
                     PyErr_Restore(et, ev, tb);
                     return -1;
                 }
diff --git a/Objects/namespaceobject.c b/Objects/namespaceobject.c
index 720ac0d..3d27a95 100644
--- a/Objects/namespaceobject.c
+++ b/Objects/namespaceobject.c
@@ -164,12 +164,11 @@ namespace_clear(_PyNamespaceObject *ns)
 static PyObject *
 namespace_richcompare(PyObject *self, PyObject *other, int op)
 {
-    if (PyObject_IsInstance(self, (PyObject *)&_PyNamespace_Type) &&
-            PyObject_IsInstance(other, (PyObject *)&_PyNamespace_Type))
+    if (PyObject_TypeCheck(self, &_PyNamespace_Type) &&
+        PyObject_TypeCheck(other, &_PyNamespace_Type))
         return PyObject_RichCompare(((_PyNamespaceObject *)self)->ns_dict,
                                    ((_PyNamespaceObject *)other)->ns_dict, op);
-    Py_INCREF(Py_NotImplemented);
-    return Py_NotImplemented;
+    Py_RETURN_NOTIMPLEMENTED;
 }