gh-129813, PEP 782: Init small_buffer in PyBytesWriter_Create() (#138924)

vstinner · web-flow · commit 7c6efc3a4f41 · 2025-09-15T16:23:11.000+02:00
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
@@ -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;

Original file line number	Diff line number	Diff line change
`@@ -3861,6 +3861,9 @@ byteswriter_create(Py_ssize_t size, int use_bytearray)`
`3861`	`3861`	`return NULL;`
`3862`	`3862`	`}`
`3863`	`3863`	`}`
	`3864`	`+#ifdef Py_DEBUG`
	`3865`	`+ memset(writer->small_buffer, 0xff, sizeof(writer->small_buffer));`
	`3866`	`+#endif`
`3864`	`3867`	`writer->obj = NULL;`
`3865`	`3868`	`writer->size = 0;`
`3866`	`3869`	`writer->use_bytearray = use_bytearray;`