Remember to reset yy_start state when firing up repl_scanner.l.

Without this, we get odd behavior when the previous cycle of
lexing exited in a non-default exclusive state.  Every other
copy of this code is aware that it has to do BEGIN(INITIAL),
but repl_scanner.l did not get that memo.

The real-world impact of this is probably limited, since most
replication clients would abandon their connection after getting
a syntax error.  Still, it's a bug.

This mistake is old, so back-patch to all supported branches.

Discussion: https://postgr.es/m/1874781.1643035952@sss.pgh.pa.us

diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index c80f158095b533d2c395ccc05c0cb4b95aabffcf..81ac41e9d451f71909fb9710b1fa7d1aac5ad944 100644 (file)
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -247,6 +247,9 @@ replication_scanner_init(const char *str)
        memcpy(scanbuf, str, slen);
        scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
        scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+       /* Make sure we start in proper state */
+       BEGIN(INITIAL);
 }
 
 void