Add parens to ConvertToXSegs macro

alvherre · alvherre · commit 5c215c941c3f · 2020-06-24T13:57:21.000-04:00
The current definition (introduced in 9a32150) is dangerous. No bugs exist in our code at present, but backpatch to 11 nonetheless, where that commit debuted. Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -738,9 +738,12 @@ static ControlFileData *ControlFile = NULL;
  */
 #define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD)
 
-/* Convert min_wal_size_mb and max wal_size_mb to equivalent segment count */
+/*
+ * Convert min_wal_size_mb and max wal_size_mb to equivalent segment count.
+ * Rounds down.
+ */
 #define ConvertToXSegs(x, segsize)	\
-	(x / ((segsize) / (1024 * 1024)))
+	((x) / ((segsize) / (1024 * 1024)))
 
 /* The number of bytes in a WAL segment usable for WAL data. */
 static int	UsableBytesInSegment;
