Issue #28376: The constructor of range_iterator now checks that step is not 0.

Patch by Oren Milman.

Lib/test/test_range.py

@@ -493,6 +493,35 @@ class RangeTest(unittest.TestCase):
             test_id = "reversed(range({}, {}, {}))".format(start, end, step)
             self.assert_iterators_equal(iter1, iter2, test_id, limit=100)
 
+    @test.support.cpython_only
+    def test_range_iterator_invocation(self):
+        import _testcapi
+        rangeiter_type = type(iter(range(0)))
+
+        # rangeiter_new doesn't take keyword arguments
+        with self.assertRaises(TypeError):
+            rangeiter_type(a=1)
+
+        # rangeiter_new takes exactly 3 arguments
+        self.assertRaises(TypeError, rangeiter_type)
+        self.assertRaises(TypeError, rangeiter_type, 1)
+        self.assertRaises(TypeError, rangeiter_type, 1, 1)
+        self.assertRaises(TypeError, rangeiter_type, 1, 1, 1, 1)
+
+        # start, stop and stop must fit in C long
+        for good_val in [_testcapi.LONG_MAX, _testcapi.LONG_MIN]:
+            rangeiter_type(good_val, good_val, good_val)
+        for bad_val in [_testcapi.LONG_MAX + 1, _testcapi.LONG_MIN - 1]:
+            self.assertRaises(OverflowError,
+                              rangeiter_type, bad_val, 1, 1)
+            self.assertRaises(OverflowError,
+                              rangeiter_type, 1, bad_val, 1)
+            self.assertRaises(OverflowError,
+                              rangeiter_type, 1, 1, bad_val)
+
+        # step mustn't be zero
+        self.assertRaises(ValueError, rangeiter_type, 1, 1, 0)
+
     def test_slice(self):
         def check(start, stop, step=None):
             i = slice(start, stop, step)

Misc/NEWS

@@ -10,6 +10,9 @@ Release date: TBA
 Core and Builtins
 -----------------
 
+- Issue #28376: The constructor of range_iterator now checks that step is not 0.
+  Patch by Oren Milman.
+
 - Issue #26906: Resolving special methods of uninitialized type now causes
   implicit initialization of the type instead of a fail.
 

Objects/rangeobject.c

@@ -937,12 +937,20 @@ rangeiter_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 {
     long start, stop, step;
 
-    if (!_PyArg_NoKeywords("rangeiter()", kw))
+    if (!_PyArg_NoKeywords("range_iterator()", kw)) {
         return NULL;
+    }
 
-    if (!PyArg_ParseTuple(args, "lll;rangeiter() requires 3 int arguments",
-                          &start, &stop, &step))
+    if (!PyArg_ParseTuple(args,
+                          "lll;range_iterator() requires 3 int arguments",
+                          &start, &stop, &step)) {
+        return NULL;
+    }
+    if (step == 0) {
+        PyErr_SetString(PyExc_ValueError,
+                        "range_iterator() arg 3 must not be zero");
         return NULL;
+    }
 
     return fast_range_iter(start, stop, step);
 }