From 7c6efc3a4f41f527ec40b5f5fd0ee1fb7af7c82f Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Mon, 15 Sep 2025 15:23:11 +0100
Subject: [PATCH] gh-129813, PEP 782: Init small_buffer in
 PyBytesWriter_Create() (#138924)

Fill small_buffer with 0xFF byte pattern to detect the usage of
uninitialized bytes in debug build.
---
 Objects/bytesobject.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 3de57fe4e99e..ee10f13b7bb0 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -3861,6 +3861,9 @@ byteswriter_create(Py_ssize_t size, int use_bytearray)
             return NULL;
         }
     }
+#ifdef Py_DEBUG
+    memset(writer->small_buffer, 0xff, sizeof(writer->small_buffer));
+#endif
     writer->obj = NULL;
     writer->size = 0;
     writer->use_bytearray = use_bytearray;
-- 
2.47.3