From 9f0e1ea96402bf6fa72560640777bf8c3bd186fb Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Wed, 7 Feb 2007 23:57:05 +0000
Subject: [PATCH] Do not let overflows in enumerate() and count() pass
 silently.

---
 Lib/test/test_itertools.py | 3 +--
 Misc/NEWS                  | 4 ++++
 Modules/itertoolsmodule.c  | 5 +++++
 Objects/enumobject.c       | 6 ++++++
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 5e375c9b526..c965d4c14ef 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -52,8 +52,7 @@ class TestBasicOps(unittest.TestCase):
         self.assertEqual(take(2, zip('abc',count(3))), [('a', 3), ('b', 4)])
         self.assertRaises(TypeError, count, 2, 3)
         self.assertRaises(TypeError, count, 'a')
-        c = count(sys.maxint-2)   # verify that rollover doesn't crash
-        c.next(); c.next(); c.next(); c.next(); c.next()
+        self.assertRaises(OverflowError, list, islice(count(sys.maxint-5), 10))
         c = count(3)
         self.assertEqual(repr(c), 'count(3)')
         c.next()
diff --git a/Misc/NEWS b/Misc/NEWS
index a24ec2675b4..8f15724b39f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@ What's New in Python 2.5.1c1?
 Core and builtins
 -----------------
 
+- SF #151204:  enumerate() now raises an Overflow error at sys.maxint items.
+
 - Bug #1377858: Fix the segfaulting of the interpreter when an object created
   a weakref on itself during a __del__ call for new-style classes (classic
   classes still have the bug).
@@ -103,6 +105,8 @@ Core and builtins
 Extension Modules
 -----------------
 
+- operator.count() now raises an OverflowError when the count reaches sys.maxint.
+
 - Bug #1575169: operator.isSequenceType() now returns False for subclasses of dict.
 
 - collections.defaultdict() now verifies that the factory function is callable.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 7896143b084..70f787f784b 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -2073,6 +2073,11 @@ count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static PyObject *
 count_next(countobject *lz)
 {
+        if (lz->cnt == LONG_MAX) {
+                PyErr_SetString(PyExc_OverflowError,
+                        "cannot count beyond LONG_MAX");                
+                return NULL;         
+        }
 	return PyInt_FromSsize_t(lz->cnt++);
 }
 
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index a8f43e07386..a456c9dafd7 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -62,6 +62,12 @@ enum_next(enumobject *en)
 	PyObject *result = en->en_result;
 	PyObject *it = en->en_sit;
 
+	if (en->en_index == LONG_MAX) {
+		PyErr_SetString(PyExc_OverflowError,
+			"enumerate() is limited to LONG_MAX items");                
+		return NULL;         
+	}
+
 	next_item = (*it->ob_type->tp_iternext)(it);
 	if (next_item == NULL)
 		return NULL;