Issue #26494: Fixed crash on iterating exhausting iterators.
Affected classes are generic sequence iterators, iterators of str, bytes,
bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding
views and os.scandir() iterator.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index eee7c68..d688179 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2782,8 +2782,8 @@
return item;
}
- Py_DECREF(seq);
it->it_seq = NULL;
+ Py_DECREF(seq);
return NULL;
}
@@ -2912,9 +2912,17 @@
listreviter_next(listreviterobject *it)
{
PyObject *item;
- Py_ssize_t index = it->it_index;
- PyListObject *seq = it->it_seq;
+ Py_ssize_t index;
+ PyListObject *seq;
+ assert(it != NULL);
+ seq = it->it_seq;
+ if (seq == NULL) {
+ return NULL;
+ }
+ assert(PyList_Check(seq));
+
+ index = it->it_index;
if (index>=0 && index < PyList_GET_SIZE(seq)) {
item = PyList_GET_ITEM(seq, index);
it->it_index--;
@@ -2922,10 +2930,8 @@
return item;
}
it->it_index = -1;
- if (seq != NULL) {
- it->it_seq = NULL;
- Py_DECREF(seq);
- }
+ it->it_seq = NULL;
+ Py_DECREF(seq);
return NULL;
}