Add parens to ConvertToXSegs macro

The current definition (introduced in 9a3215026bd6) 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
index bceef897d6eb5f32f6d8a424c086a6476924175b..28292393d199c64714ce8548b284054187eb6cb4 100644 (file)
--- 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;