GH-141312: Allow only integers to longrangeiter_setstate state (GH-141317)

This fixes an assertion error when the new computed start is not an integer.

Lib/test/test_range.py

@@ -470,6 +470,16 @@ class RangeTest(unittest.TestCase):
         it.__setstate__(2**64 - 7)
         self.assertEqual(list(it), [12, 10])
 
+    def test_iterator_invalid_setstate(self):
+        for invalid_value in (1.0, ""):
+            ranges = (('rangeiter', range(10, 100, 2)),
+                      ('longrangeiter', range(10, 2**65, 2)))
+            for rng_name, rng in ranges:
+                with self.subTest(invalid_value=invalid_value, range=rng_name):
+                    it = iter(rng)
+                    with self.assertRaises(TypeError):
+                        it.__setstate__(invalid_value)
+
     def test_odd_bug(self):
         # This used to raise a "SystemError: NULL result without error"
         # because the range validation step was eating the exception

Misc/NEWS.d/next/Core_and_Builtins/2025-11-10-23-07-06.gh-issue-141312.H-58GB.rst

@@ -0,0 +1,2 @@
+Fix the assertion failure in the ``__setstate__`` method of the range iterator
+when a non-integer argument is passed. Patch by Sergey Miryanov.

Objects/rangeobject.c

@@ -1042,6 +1042,11 @@ longrangeiter_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))
 static PyObject *
 longrangeiter_setstate(PyObject *op, PyObject *state)
 {
+    if (!PyLong_CheckExact(state)) {
+        PyErr_Format(PyExc_TypeError, "state must be an int, not %T", state);
+        return NULL;
+    }
+
     longrangeiterobject *r = (longrangeiterobject*)op;
     PyObject *zero = _PyLong_GetZero();  // borrowed reference
     int cmp;