From 7c08f0162cf6254d101e5f04dd58993ae05fa97e Mon Sep 17 00:00:00 2001
From: Thomas Kowalski <thom.kowa@gmail.com>
Date: Sun, 23 Aug 2026 16:35:21 +0200
Subject: [PATCH] gh-151126: Check strdup result in readline on_completion

Add a NULL check and an explicit PyErr_NoMemory() before goto
error.
---
 .../Library/2026-08-23-16-36-00.gh-issue-151126.m3YbXU.rst    | 2 ++
 Modules/readline.c                                            | 4 ++++
 2 files changed, 6 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-08-23-16-36-00.gh-issue-151126.m3YbXU.rst

diff --git a/Misc/NEWS.d/next/Library/2026-08-23-16-36-00.gh-issue-151126.m3YbXU.rst b/Misc/NEWS.d/next/Library/2026-08-23-16-36-00.gh-issue-151126.m3YbXU.rst
new file mode 100644
index 000000000000000..4a17834c7f2a907
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-23-16-36-00.gh-issue-151126.m3YbXU.rst
@@ -0,0 +1,2 @@
+Raise :exc:`MemoryError` on allocation failure in the :mod:`!readline`
+completion callback.
diff --git a/Modules/readline.c b/Modules/readline.c
index fc79a5866dfd38c..cbc8c872e7b3d64 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -1272,6 +1272,10 @@ on_completion(const char *text, int state)
                 goto error;
             result = strdup(PyBytes_AS_STRING(encoded));
             Py_DECREF(encoded);
+            if (result == NULL) {
+                PyErr_NoMemory();
+                goto error;
+            }
         }
         Py_DECREF(r);
         goto done;