bpo-45018: Fix rangeiter_reduce in rangeobject.c (GH-27938)

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

Lib/test/test_range.py

@@ -374,10 +374,12 @@ class RangeTest(unittest.TestCase):
                                      list(r))
 
     def test_iterator_pickling(self):
-        testcases = [(13,), (0, 11), (-22, 10), (20, 3, -1),
+        testcases = [(13,), (0, 11), (-22, 10), (20, 3, -1), (13, 21, 3),
-                     (13, 21, 3), (-2, 2, 2), (2**65, 2**65+2)]
+                     (-2, 2, 2), (2**31-3, 2**31-1), (2**33, 2**33+2),
+                     (2**63-3, 2**63-1), (2**65, 2**65+2)]
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             for t in testcases:
+                with self.subTest(proto=proto, t=t):
                     it = itorg = iter(range(*t))
                     data = list(range(*t))
 
@@ -395,6 +397,19 @@ class RangeTest(unittest.TestCase):
                     it = pickle.loads(d)
                     self.assertEqual(list(it), data[1:])
 
+    def test_iterator_pickling_overflowing_index(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(proto=proto):
+                it = iter(range(2**32 + 2))
+                _, _, idx = it.__reduce__()
+                self.assertEqual(idx, 0)
+                it.__setstate__(2**32 + 1)  # undocumented way to set r->index
+                _, _, idx = it.__reduce__()
+                self.assertEqual(idx, 2**32 + 1)
+                d = pickle.dumps(it, proto)
+                it = pickle.loads(d)
+                self.assertEqual(next(it), 2**32 + 1)
+
     def test_exhausted_iterator_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             r = range(2**65, 2**65+2)

Misc/NEWS.d/next/Core and Builtins/2021-08-26-18-44-03.bpo-45018.pu8H9L.rst

@@ -0,0 +1 @@
+Fixed pickling of range iterators that iterated for over 2**32 times.

Objects/rangeobject.c

@@ -813,7 +813,7 @@ rangeiter_reduce(rangeiterobject *r, PyObject *Py_UNUSED(ignored))
     if (range == NULL)
         goto err;
     /* return the result */
-    return Py_BuildValue("N(N)i", _PyEval_GetBuiltinId(&PyId_iter),
+    return Py_BuildValue("N(N)l", _PyEval_GetBuiltinId(&PyId_iter),
                          range, r->index);
 err:
     Py_XDECREF(start);