Fix assert in logicalmsg_desc

The assert, introduced by 9f1cf97bb5, is intended to check if the prefix
is terminated by a \0 byte, but it has two flaws. Firstly, prefix_size
includes the \0 byte, so prefix[prefix_size] points to the byte after
the null byte. Secondly, the check ensures the byte is not equal \0,
while it should be checking the opposite.

Backpatch-through: 14
Discussion: https://postgr.es/m/b99b6101-2f14-3796-3dfa-4a6cd7d4326d@enterprisedb.com

diff --git a/src/backend/access/rmgrdesc/logicalmsgdesc.c b/src/backend/access/rmgrdesc/logicalmsgdesc.c
index 099e11a84e7796c0e73e8c8eb21c4bff1921b902..08e03aa30d13f15557a3c10ccf7c71bcf0c9f19a 100644 (file)
--- a/src/backend/access/rmgrdesc/logicalmsgdesc.c
+++ b/src/backend/access/rmgrdesc/logicalmsgdesc.c
@@ -28,7 +28,7 @@ logicalmsg_desc(StringInfo buf, XLogReaderState *record)
                char       *message = xlrec->message + xlrec->prefix_size;
                char       *sep = "";
 
-               Assert(prefix[xlrec->prefix_size] != '\0');
+               Assert(prefix[xlrec->prefix_size - 1] == '\0');
 
                appendStringInfo(buf, "%s, prefix \"%s\"; payload (%zu bytes): ",
                                                 xlrec->transactional ? "transactional" : "non-transactional",