From 001f228f369d5c3e9fc28ae7a9815e1317bbe72f Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Sat, 8 Nov 2003 11:58:44 +0000
Subject: [PATCH] Improve the reverse list iterator to free memory as soon as
 the iterator is exhausted.

---
 Objects/listobject.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 7198e3481af..3782c3baacf 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2771,7 +2771,7 @@ PyTypeObject PyListIter_Type = {
 typedef struct {
 	PyObject_HEAD
 	long it_index;
-	PyListObject *it_seq;
+	PyListObject *it_seq; /* Set to NULL when iterator is exhausted */
 } listreviterobject;
 
 PyTypeObject PyListRevIter_Type;
@@ -2819,6 +2819,9 @@ listreviter_next(listreviterobject *it)
 		item = PyList_GET_ITEM(it->it_seq, it->it_index);
 		it->it_index--;
 		Py_INCREF(item);
+	} else if (it->it_seq != NULL) {
+		Py_DECREF(it->it_seq);
+		it->it_seq = NULL;
 	}
 	return item;
 }