From 49d65d0b063f1bdca9276caa511c177fef5953fd Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Date: Tue, 20 Oct 2026 20:01:11 +0900
Subject: [PATCH v4 4/4] Use pg_parse_lsn() for reading backup label

read_backup_label() parsed several WAL positions on the label file with
fscanf("%X/%08X"). This commit convert to use the common LSN parser.
---
 src/backend/access/transam/xlogrecovery.c | 23 ++++++++++++++---------
 src/backend/utils/adt/pg_lsn.c            |  2 --
 src/include/common/pg_parse_lsn.h         |  2 ++
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 20be788da78..7c9c6acf1d2 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_control.h"
 #include "commands/tablespace.h"
 #include "common/file_utils.h"
+#include "common/pg_parse_lsn.h"
 #include "miscadmin.h"
 #include "nodes/miscnodes.h"
 #include "pgstat.h"
@@ -1190,8 +1191,7 @@ read_backup_label(XLogRecPtr *checkPointLoc, TimeLineID *backupLabelTLI,
 	char		backupfrom[20];
 	char		backuplabel[MAXPGPATH];
 	char		backuptime[128];
-	uint32		hi,
-				lo;
+	char		lsn[MAXPG_LSNLEN + 1];
 
 	/* suppress possible uninitialized-variable warnings */
 	*checkPointLoc = InvalidXLogRecPtr;
@@ -1218,19 +1218,23 @@ read_backup_label(XLogRecPtr *checkPointLoc, TimeLineID *backupLabelTLI,
 	 * is pretty crude, but we are not expecting any variability in the file
 	 * format).
 	 */
-	if (fscanf(lfp, "START WAL LOCATION: %X/%08X (file %08X%16s)%c",
-			   &hi, &lo, &tli_from_walseg, startxlogfilename, &ch) != 5 || ch != '\n')
+	if (fscanf(lfp,
+			   "START WAL LOCATION: %" CppAsString2(MAXPG_LSNLEN) "s (file %08X%16s)%c",
+			   lsn, &tli_from_walseg, startxlogfilename, &ch) != 4 ||
+		ch != '\n' ||
+		!pg_parse_lsn(lsn, &RedoStartLSN))
 		ereport(FATAL,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE)));
-	RedoStartLSN = ((uint64) hi) << 32 | lo;
 	RedoStartTLI = tli_from_walseg;
-	if (fscanf(lfp, "CHECKPOINT LOCATION: %X/%08X%c",
-			   &hi, &lo, &ch) != 3 || ch != '\n')
+	if (fscanf(lfp,
+			   "CHECKPOINT LOCATION: %" CppAsString2(MAXPG_LSNLEN) "s%c", lsn,
+			   &ch) != 2 ||
+		ch != '\n' ||
+		!pg_parse_lsn(lsn, checkPointLoc))
 		ereport(FATAL,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE)));
-	*checkPointLoc = ((uint64) hi) << 32 | lo;
 	*backupLabelTLI = tli_from_walseg;
 
 	/*
@@ -1297,7 +1301,8 @@ read_backup_label(XLogRecPtr *checkPointLoc, TimeLineID *backupLabelTLI,
 								 tli_from_file, BACKUP_LABEL_FILE)));
 	}
 
-	if (fscanf(lfp, "INCREMENTAL FROM LSN: %X/%08X\n", &hi, &lo) > 0)
+	if (fscanf(lfp, "INCREMENTAL FROM LSN: %" CppAsString2(MAXPG_LSNLEN) "s\n",
+			   lsn) > 0)
 		ereport(FATAL,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("this is an incremental backup, not a data directory"),
diff --git a/src/backend/utils/adt/pg_lsn.c b/src/backend/utils/adt/pg_lsn.c
index 7886e9b83e8..3ec2c2b650e 100644
--- a/src/backend/utils/adt/pg_lsn.c
+++ b/src/backend/utils/adt/pg_lsn.c
@@ -19,8 +19,6 @@
 #include "utils/numeric.h"
 #include "utils/pg_lsn.h"
 
-#define MAXPG_LSNLEN			17
-
 /*----------------------------------------------------------
  * Formatting and conversion routines.
  *---------------------------------------------------------*/
diff --git a/src/include/common/pg_parse_lsn.h b/src/include/common/pg_parse_lsn.h
index 0a80785a4e9..85cda67bce9 100644
--- a/src/include/common/pg_parse_lsn.h
+++ b/src/include/common/pg_parse_lsn.h
@@ -15,6 +15,8 @@
 
 #include "access/xlogdefs.h"
 
+#define MAXPG_LSNLEN			17
+
 extern bool pg_parse_lsn(const char *str, XLogRecPtr *result);
 
 #endif							/* PG_PARSE_LSN_H */
-- 
2.52.0