Backport fix for SF bug #1550714, itertools.tee raises SystemError

Lib/test/test_itertools.py

@@ -371,6 +371,7 @@ class TestBasicOps(unittest.TestCase):
 
         # test values of n
         self.assertRaises(TypeError, tee, 'abc', 'invalid')
+        self.assertRaises(ValueError, tee, [], -1)
         for n in xrange(5):
             result = tee('abc', n)
             self.assertEqual(type(result), tuple)

Misc/NEWS

@@ -43,6 +43,12 @@ Library
 - Bug #1543303, patch #1543897: remove NUL padding from tarfiles.
 
 
+Extension Modules
+-----------------
+
+- Bug #1550714: fix SystemError from itertools.tee on negative value for n.
+
+
 Tests
 -----
 

Modules/itertoolsmodule.c

@@ -618,11 +618,15 @@ static PyTypeObject tee_type = {
 static PyObject *
 tee(PyObject *self, PyObject *args)
 {
-	int i, n=2;
+	Py_ssize_t i, n=2;
 	PyObject *it, *iterable, *copyable, *result;
 
-	if (!PyArg_ParseTuple(args, "O|i", &iterable, &n))
+	if (!PyArg_ParseTuple(args, "O|n", &iterable, &n))
 		return NULL;
+	if (n < 0) {
+		PyErr_SetString(PyExc_ValueError, "n must be >= 0");
+		return NULL;
+	}
 	result = PyTuple_New(n);
 	if (result == NULL)
 		return NULL;