gh-135878: Fix crash in types.SimpleNamespace.__repr__

Author: sobolevn

Misc/NEWS.d/next/Library/2025-06-24-14-43-24.gh-issue-135878.Db4roX.rst

@@ -0,0 +1,3 @@
+Fixes a crash of :class:`types.SimpleNamespace` on free-threading builds,
+when several threads were calling its :meth:`~object.__repr__` method at the
+same time.

Objects/namespaceobject.c

@@ -124,8 +124,7 @@ namespace_repr(PyObject *ns)
         if (PyUnicode_Check(key) && PyUnicode_GET_LENGTH(key) > 0) {
             PyObject *value, *item;
 
-            value = PyDict_GetItemWithError(d, key);
-            if (value != NULL) {
+            if (PyDict_GetItemRef(d, key, &value) == 1) {
                 item = PyUnicode_FromFormat("%U=%R", key, value);
                 if (item == NULL) {
                     loop_error = 1;
@@ -135,7 +134,7 @@ namespace_repr(PyObject *ns)
                     Py_DECREF(item);
                 }
             }
-            else if (PyErr_Occurred()) {
+            else {
                 loop_error = 1;
             }
         }