bpo-32571: Avoid raising unneeded AttributeError and silencing it in C code (GH-5222)

Add two new private APIs: _PyObject_LookupAttr() and _PyObject_LookupAttrId()

1 files changed, 9 insertions, 18 deletions

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 0c8f0adfb78..a22173878e8 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2403,7 +2403,9 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
             if (PyType_Check(tmp)) {
                 continue;
             }
-            tmp = _PyObject_GetAttrId(tmp, &PyId___mro_entries__);
+            if (_PyObject_LookupAttrId(tmp, &PyId___mro_entries__, &tmp) < 0) {
+                return NULL;
+            }
             if (tmp != NULL) {
                 PyErr_SetString(PyExc_TypeError,
                                 "type() doesn't support MRO entry resolution; "
@@ -2411,12 +2413,6 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
                 Py_DECREF(tmp);
                 return NULL;
             }
-            else if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
-                PyErr_Clear();
-            }
-            else {
-                return NULL;
-            }
         }
         /* Search the bases for the proper metatype to deal with this: */
         winner = _PyType_CalculateMetaclass(metatype, bases);
@@ -4099,15 +4095,12 @@ _PyObject_GetState(PyObject *obj, int required)
     PyObject *getstate;
     _Py_IDENTIFIER(__getstate__);
 
-    getstate = _PyObject_GetAttrId(obj, &PyId___getstate__);
+    if (_PyObject_LookupAttrId(obj, &PyId___getstate__, &getstate) < 0) {
+        return NULL;
+    }
     if (getstate == NULL) {
         PyObject *slotnames;
 
-        if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
-            return NULL;
-        }
-        PyErr_Clear();
-
         if (required && obj->ob_type->tp_itemsize) {
             PyErr_Format(PyExc_TypeError,
                          "can't pickle %.200s objects",
@@ -4174,14 +4167,12 @@ _PyObject_GetState(PyObject *obj, int required)
 
                 name = PyList_GET_ITEM(slotnames, i);
                 Py_INCREF(name);
-                value = PyObject_GetAttr(obj, name);
+                if (_PyObject_LookupAttr(obj, name, &value) < 0) {
+                    goto error;
+                }
                 if (value == NULL) {
                     Py_DECREF(name);
-                    if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
-                        goto error;
-                    }
                     /* It is not an error if the attribute is not present. */
-                    PyErr_Clear();
                 }
                 else {
                     int err = PyDict_SetItem(slots, name, value);