bpo-26423: Fix possible overflow in wrap_lenfunc() (GH-13606)

Fix possible overflow in wrap_lenfunc() when
sizeof(long) < sizeof(Py_ssize_t) (e.g., 64-bit Windows).

Lib/test/test_descr.py

@@ -389,6 +389,10 @@ class OperatorsTest(unittest.TestCase):
         a.setstate(100)
         self.assertEqual(a.getstate(), 100)
 
+    def test_wrap_lenfunc_bad_cast(self):
+        self.assertEqual(range(sys.maxsize).__len__(), sys.maxsize)
+
+
 class ClassPropertiesAndMethods(unittest.TestCase):
 
     def assertHasAttr(self, obj, name):

Misc/NEWS.d/next/Core and Builtins/2019-05-27-18-00-19.bpo-26423.RgUOE8.rst

+Fix possible overflow in ``wrap_lenfunc()`` when
+``sizeof(long) < sizeof(Py_ssize_t)`` (e.g., 64-bit Windows).

Objects/typeobject.c

@@ -5536,7 +5536,7 @@ wrap_lenfunc(PyObject *self, PyObject *args, void *wrapped)
     res = (*func)(self);
     if (res == -1 && PyErr_Occurred())
         return NULL;
-    return PyLong_FromLong((long)res);
+    return PyLong_FromSsize_t(res);
 }
 
 static PyObject *