[3.10] gh-101765: Fix SystemError / segmentation fault in iter `__reduce__` when internal access of `builtins.__dict__` exhausts the iterator (GH-101769) (#102229)

(cherry picked from commit 54dfa14c5a94b893b67a4d9e9e403ff538ce9023)

1 files changed, 8 insertions, 3 deletions

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index b7ec1f2..5a1865f 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -16070,14 +16070,19 @@ static PyObject *
 unicodeiter_reduce(unicodeiterobject *it, PyObject *Py_UNUSED(ignored))
 {
     _Py_IDENTIFIER(iter);
+    PyObject *iter = _PyEval_GetBuiltinId(&PyId_iter);
+
+    /* _PyEval_GetBuiltinId can invoke arbitrary code,
+     * call must be before access of iterator pointers.
+     * see issue #101765 */
+
     if (it->it_seq != NULL) {
-        return Py_BuildValue("N(O)n", _PyEval_GetBuiltinId(&PyId_iter),
-                             it->it_seq, it->it_index);
+        return Py_BuildValue("N(O)n", iter, it->it_seq, it->it_index);
     } else {
         PyObject *u = (PyObject *)_PyUnicode_New(0);
         if (u == NULL)
             return NULL;
-        return Py_BuildValue("N(N)", _PyEval_GetBuiltinId(&PyId_iter), u);
+        return Py_BuildValue("N(N)", iter, u);
     }
 }