gh-128961: Fix exhausted array iterator crash in __setstate__() (GH-128962)

(cherry picked from commit 4dade05)

Co-authored-by: Tomasz Pytel <[email protected]>

Author: tom-pytel

Lib/test/test_array.py

@@ -1609,5 +1609,13 @@ def test_tolist(self, size):
         self.assertEqual(ls[:8], list(example[:8]))
         self.assertEqual(ls[-8:], list(example[-8:]))
 
+    def test_gh_128961(self):
+        a = array.array('i')
+        it = iter(a)
+        list(it)
+        it.__setstate__(0)
+        self.assertRaises(StopIteration, next, it)
+
+
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Library/2025-01-17-21-33-11.gh-issue-128961.XwvyIZ.rst

@@ -0,0 +1 @@
+Fix a crash when setting state on an exhausted :class:`array.array` iterator.

Modules/arraymodule.c

@@ -2966,11 +2966,16 @@ array_arrayiterator___setstate__(arrayiterobject *self, PyObject *state)
     Py_ssize_t index = PyLong_AsSsize_t(state);
     if (index == -1 && PyErr_Occurred())
         return NULL;
-    if (index < 0)
-        index = 0;
-    else if (index > Py_SIZE(self->ao))
-        index = Py_SIZE(self->ao); /* iterator exhausted */
-    self->index = index;
+    arrayobject *ao = self->ao;
+    if (ao != NULL) {
+        if (index < 0) {
+            index = 0;
+        }
+        else if (index > Py_SIZE(ao)) {
+            index = Py_SIZE(ao); /* iterator exhausted */
+        }
+        self->index = index;
+    }
     Py_RETURN_NONE;
 }