From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Fri, 3 Jul 2026 18:08:00 +0000 (+0200)
Subject: [3.13] gh-152951 - Fix double DECREF when `newblock` fails during deque.extend calls... 
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=584a46491aca20c9211f54a85efff429e5d564fc;p=thirdparty%2FPython%2Fcpython.git

[3.13] gh-152951 - Fix double DECREF when `newblock` fails during deque.extend calls (GH-152961) (#152973)

gh-152951 - Fix double DECREF when `newblock` fails during deque.extend calls (GH-152961)
(cherry picked from commit a90576d72c8a409f7c3ffcaefafb13945e3405ab)

Co-authored-by: Steve Stagg <stestagg@gmail.com>
---

diff --git a/Misc/NEWS.d/next/Library/2026-07-03-14-54-33.gh-issue-152951.u8tPCI.rst b/Misc/NEWS.d/next/Library/2026-07-03-14-54-33.gh-issue-152951.u8tPCI.rst
new file mode 100644
index 000000000000..c3d56c6d59c9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-03-14-54-33.gh-issue-152951.u8tPCI.rst
@@ -0,0 +1,2 @@
+:class:`collections.deque` prevent rare crash when calling ``extend`` under
+high memory pressure conditions.
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index daf62c940b3e..9e3d77c8e465 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -506,7 +506,6 @@ deque_extend_impl(dequeobject *deque, PyObject *iterable)
     iternext = *Py_TYPE(it)->tp_iternext;
     while ((item = iternext(it)) != NULL) {
         if (deque_append_lock_held(deque, item, maxlen) == -1) {
-            Py_DECREF(item);
             Py_DECREF(it);
             return NULL;
         }