From: Victor Stinner <vstinner@python.org>
Date: Mon, 15 Sep 2025 14:23:11 +0000 (+0100)
Subject: gh-129813, PEP 782: Init small_buffer in PyBytesWriter_Create() (#138924)
X-Git-Tag: v3.15.0a1~365
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7c6efc3a4f41f527ec40b5f5fd0ee1fb7af7c82f;p=thirdparty%2FPython%2Fcpython.git

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.
---

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;