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commit    368d7f3297e7e1304da03904d2e1310d79fa82a9
Author:   Alvaro Herrera <alvherre@alvh.no-ip.org>
Date:     Wed Jun 24 18:00:37 2020 +0000
First released in: 14.0, 11.9, 12.4, 13.0

    Add parens to ConvertToXSegs macro
    
    The current definition is dangerous.  No bugs exist in our code at
    present, but backpatch to 11 nonetheless where it was introduced.
    
    Author: Álvaro Herrera <alvherre@alvh.no-ip.org>


 src/backend/access/transam/xlog.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a1256a103b6..34ede80c44f 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -760,9 +760,12 @@ static ControlFileData *ControlFile = NULL;
  */
 #define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD)
 
-/* Convert values of GUCs measured in megabytes to equiv. segment count */
+/*
+ * Convert values of GUCs measured in megabytes to equiv. 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;


[parent: a3554b2d7185]