Use the correct sizeof() in BufFileLoadBuffer

tvondra · tvondra · commit 38273b5f831b · 2025-01-25T02:12:59.000+01:00
The sizeof() call should reference buffer.data, because that's the buffer we're reading data into, not the whole PGAlignedBuffer union. This was introduced by 44cac93, which replaced the simple buffer with a PGAlignedBuffer field. It's benign, because the buffer is the largest field of the union, so the sizes are the same. But it's easy to trip over this in a patch, so fix and backpatch. Commit 44cac93 went into 12, but that's EOL. Backpatch-through: 13 Discussion: https://postgr.es/m/928bdab1-6567-449f-98c4-339cd2203b87@vondra.me
diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
@@ -459,7 +459,7 @@ BufFileLoadBuffer(BufFile *file)
 	 */
 	file->nbytes = FileRead(thisfile,
 							file->buffer.data,
-							sizeof(file->buffer),
+							sizeof(file->buffer.data),
 							file->curOffset,
 							WAIT_EVENT_BUFFILE_READ);
 	if (file->nbytes < 0)
