Executing pg_createsubscriber with a non-compatible control file

From b856d200e52ccb3d841ba05df149173cb7cd8772 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 10 Oct 2025 15:01:57 +0900
Subject: [PATCH v1 1/5] Introduce API able to retrieve contents of PG_VERSION

This will be used by a set of follow-up patches, to be consumed in
various frontend tools.
---
 src/include/fe_utils/version.h | 23 ++++++++++
 src/fe_utils/Makefile          |  3 +-
 src/fe_utils/meson.build       |  1 +
 src/fe_utils/version.c         | 81 ++++++++++++++++++++++++++++++++++
 4 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 src/include/fe_utils/version.h
 create mode 100644 src/fe_utils/version.c

diff --git a/src/include/fe_utils/version.h b/src/include/fe_utils/version.h
new file mode 100644
index 000000000000..3b8c1884de5f
--- /dev/null
+++ b/src/include/fe_utils/version.h
@@ -0,0 +1,23 @@
+/*-------------------------------------------------------------------------
+ *
+ * Routines to retrieve information of PG_VERSION
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/fe_utils/version.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef VERSION_H
+#define VERSION_H
+
+/*
+ * Retrieve the version major number, useful for major version checks
+ * based on PG_MAJORVERSION_NUM.
+ */
+#define GET_PG_MAJORVERSION_NUM(v)	((v) / 10000)
+
+extern uint32 get_pg_version(const char *datadir, char **version_str);
+
+#endif							/* VERSION_H */
diff --git a/src/fe_utils/Makefile b/src/fe_utils/Makefile
index 28196ce0f6ae..b9fd566ff873 100644
--- a/src/fe_utils/Makefile
+++ b/src/fe_utils/Makefile
@@ -37,7 +37,8 @@ OBJS = \
 	query_utils.o \
 	recovery_gen.o \
 	simple_list.o \
-	string_utils.o
+	string_utils.o \
+	version.o
 
 ifeq ($(PORTNAME), win32)
 override CPPFLAGS += -DFD_SETSIZE=1024
diff --git a/src/fe_utils/meson.build b/src/fe_utils/meson.build
index 5a9ddb73463e..ddac3c3a6584 100644
--- a/src/fe_utils/meson.build
+++ b/src/fe_utils/meson.build
@@ -18,6 +18,7 @@ fe_utils_sources = files(
   'recovery_gen.c',
   'simple_list.c',
   'string_utils.c',
+  'version.c',
 )
 
 psqlscan = custom_target('psqlscan',
diff --git a/src/fe_utils/version.c b/src/fe_utils/version.c
new file mode 100644
index 000000000000..8c06bb84b4d6
--- /dev/null
+++ b/src/fe_utils/version.c
@@ -0,0 +1,81 @@
+/*-------------------------------------------------------------------------
+ *
+ * version.c
+ *		Routine to retrieve information of PG_VERSION
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <sys/stat.h>
+
+#include "common/logging.h"
+#include "fe_utils/version.h"
+
+/*
+ * Assumed maximum size of PG_VERSION.  This should be more than enough for
+ * any version numbers that need to be handled.
+ */
+#define PG_VERSION_MAX_SIZE	64
+
+/*
+ * get_major_version
+ *
+ * Retrieve the major version number of the given data folder, from
+ * PG_VERSION.  The result returned is a version number, that can be used
+ * for comparisons based on PG_VERSION_NUM.  For example, if PG_VERSION
+ * contains "18\n", this function returns 180000.
+ *
+ * This supports both the pre-v10 and the post-v10 version numbering.
+ * Optionally. "version_str" can be specified to store the contents
+ * retrieved from PG_VERSION.  It is allocated by this routine; the
+ * caller is responsible for pg_free()-ing it.
+ */
+uint32
+get_pg_version(const char *datadir, char **version_str)
+{
+	FILE	   *version_fd;
+	char		ver_filename[MAXPGPATH];
+	char		buf[PG_VERSION_MAX_SIZE];
+	int			v1 = 0,
+				v2 = 0;
+	struct stat st;
+
+	snprintf(ver_filename, sizeof(ver_filename), "%s/PG_VERSION",
+			 datadir);
+
+	if ((version_fd = fopen(ver_filename, "r")) == NULL)
+		pg_fatal("could not open version file \"%s\": %m", ver_filename);
+
+	if (fstat(fileno(version_fd), &st) != 0)
+		pg_fatal("could not stat file \"%s\": %m", ver_filename);
+	if (st.st_size > PG_VERSION_MAX_SIZE)
+		pg_fatal("file \"%s\" is too large", ver_filename);
+
+	if (fscanf(version_fd, "%63s", buf) == 0 ||
+		sscanf(buf, "%d.%d", &v1, &v2) < 1)
+		pg_fatal("could not parse version file \"%s\"", ver_filename);
+
+	fclose(version_fd);
+
+	if (version_str)
+	{
+		*version_str = pg_malloc(PG_VERSION_MAX_SIZE);
+		memcpy(*version_str, buf, st.st_size);
+	}
+
+	if (v1 < 10)
+	{
+		/* pre-v10 style, e.g. 9.6.1 */
+		return v1 * 10000 + v2 * 100;
+	}
+	else
+	{
+		/* post-v10 style, e.g. 10.1 */
+		return v1 * 10000;
+	}
+}
-- 
2.51.0

From 80fe5aa1bcc36a12969a3936e4c18cf374ab5b90 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 10 Oct 2025 15:03:32 +0900
Subject: [PATCH v1 2/5] pg_upgrade: Use PG_VERSION generic routine

---
 src/bin/pg_upgrade/exec.c       |  5 +++--
 src/bin/pg_upgrade/pg_upgrade.h |  3 +--
 src/bin/pg_upgrade/server.c     | 39 ---------------------------------
 3 files changed, 4 insertions(+), 43 deletions(-)

diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 63f2815a7cd1..c045633d0c2a 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -12,6 +12,7 @@
 #include <fcntl.h>
 
 #include "common/string.h"
+#include "fe_utils/version.h"
 #include "pg_upgrade.h"
 
 static void check_data_dir(ClusterInfo *cluster);
@@ -343,8 +344,8 @@ check_data_dir(ClusterInfo *cluster)
 	const char *pg_data = cluster->pgdata;
 
 	/* get the cluster version */
-	cluster->major_version = get_major_server_version(cluster);
-
+	cluster->major_version = get_pg_version(cluster->pgdata,
+											&cluster->major_version_str);
 	check_single_dir(pg_data, "");
 	check_single_dir(pg_data, "base");
 	check_single_dir(pg_data, "global");
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h
index 0ef47be0dc19..e86336f4be95 100644
--- a/src/bin/pg_upgrade/pg_upgrade.h
+++ b/src/bin/pg_upgrade/pg_upgrade.h
@@ -298,7 +298,7 @@ typedef struct
 	char	   *sockdir;		/* directory for Unix Domain socket, if any */
 	unsigned short port;		/* port number where postmaster is waiting */
 	uint32		major_version;	/* PG_VERSION of cluster */
-	char		major_version_str[64];	/* string PG_VERSION of cluster */
+	char	   *major_version_str;	/* string PG_VERSION of cluster */
 	uint32		bin_version;	/* version returned from pg_ctl */
 	char	  **tablespaces;	/* tablespace directories */
 	int			num_tablespaces;
@@ -473,7 +473,6 @@ char	   *cluster_conn_opts(ClusterInfo *cluster);
 
 bool		start_postmaster(ClusterInfo *cluster, bool report_and_exit_on_error);
 void		stop_postmaster(bool in_atexit);
-uint32		get_major_server_version(ClusterInfo *cluster);
 void		check_pghost_envvar(void);
 
 
diff --git a/src/bin/pg_upgrade/server.c b/src/bin/pg_upgrade/server.c
index 7eb15bc7d5ac..d51bee885b82 100644
--- a/src/bin/pg_upgrade/server.c
+++ b/src/bin/pg_upgrade/server.c
@@ -148,45 +148,6 @@ executeQueryOrDie(PGconn *conn, const char *fmt,...)
 }
 
 
-/*
- * get_major_server_version()
- *
- * gets the version (in unsigned int form) for the given datadir. Assumes
- * that datadir is an absolute path to a valid pgdata directory. The version
- * is retrieved by reading the PG_VERSION file.
- */
-uint32
-get_major_server_version(ClusterInfo *cluster)
-{
-	FILE	   *version_fd;
-	char		ver_filename[MAXPGPATH];
-	int			v1 = 0,
-				v2 = 0;
-
-	snprintf(ver_filename, sizeof(ver_filename), "%s/PG_VERSION",
-			 cluster->pgdata);
-	if ((version_fd = fopen(ver_filename, "r")) == NULL)
-		pg_fatal("could not open version file \"%s\": %m", ver_filename);
-
-	if (fscanf(version_fd, "%63s", cluster->major_version_str) == 0 ||
-		sscanf(cluster->major_version_str, "%d.%d", &v1, &v2) < 1)
-		pg_fatal("could not parse version file \"%s\"", ver_filename);
-
-	fclose(version_fd);
-
-	if (v1 < 10)
-	{
-		/* old style, e.g. 9.6.1 */
-		return v1 * 10000 + v2 * 100;
-	}
-	else
-	{
-		/* new style, e.g. 10.1 */
-		return v1 * 10000;
-	}
-}
-
-
 static void
 stop_postmaster_atexit(void)
 {
-- 
2.51.0

From 2cd799e94b8453f7fae4134e37de78328719d411 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 10 Oct 2025 15:04:03 +0900
Subject: [PATCH v1 3/5] pg_createsubscriber: Use PG_VERSION generic routine

---
 src/bin/pg_basebackup/pg_createsubscriber.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/bin/pg_basebackup/pg_createsubscriber.c b/src/bin/pg_basebackup/pg_createsubscriber.c
index d29407413d96..c3732adabc86 100644
--- a/src/bin/pg_basebackup/pg_createsubscriber.c
+++ b/src/bin/pg_basebackup/pg_createsubscriber.c
@@ -26,6 +26,7 @@
 #include "fe_utils/recovery_gen.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 
 #define	DEFAULT_SUB_PORT	"50432"
@@ -407,7 +408,7 @@ static void
 check_data_directory(const char *datadir)
 {
 	struct stat statbuf;
-	char		versionfile[MAXPGPATH];
+	uint32		major_version;
 
 	pg_log_info("checking if directory \"%s\" is a cluster data directory",
 				datadir);
@@ -420,11 +421,18 @@ check_data_directory(const char *datadir)
 			pg_fatal("could not access directory \"%s\": %m", datadir);
 	}
 
-	snprintf(versionfile, MAXPGPATH, "%s/PG_VERSION", datadir);
-	if (stat(versionfile, &statbuf) != 0 && errno == ENOENT)
+	/*
+	 * Retrieve the contents of this cluster's PG_VERSION.  We require
+	 * compatibility with the same major version as the one this tool is
+	 * compiled with.
+	 */
+	major_version = GET_PG_MAJORVERSION_NUM(get_pg_version(datadir, NULL));
+	if (major_version != PG_MAJORVERSION_NUM)
 	{
-		pg_fatal("directory \"%s\" is not a database cluster directory",
-				 datadir);
+		pg_log_error("data directory is of wrong version");
+		pg_log_error_detail("File \"%s\" contains \"%u\", which is not compatible with this program's version \"%u\".",
+							"PG_VERSION", major_version, PG_MAJORVERSION_NUM);
+		exit(1);
 	}
 }
 
-- 
2.51.0

From 241106d3f694403c75ae922446a2eb99e91a63f2 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 10 Oct 2025 15:04:29 +0900
Subject: [PATCH v1 4/5] pg_combinebackup: use PG_VERSION generic routine

---
 src/bin/pg_combinebackup/pg_combinebackup.c | 63 +++------------------
 1 file changed, 7 insertions(+), 56 deletions(-)

diff --git a/src/bin/pg_combinebackup/pg_combinebackup.c b/src/bin/pg_combinebackup/pg_combinebackup.c
index f5cef99f6273..1f0531154b1d 100644
--- a/src/bin/pg_combinebackup/pg_combinebackup.c
+++ b/src/bin/pg_combinebackup/pg_combinebackup.c
@@ -34,6 +34,7 @@
 #include "common/relpath.h"
 #include "copy_file.h"
 #include "fe_utils/option_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 #include "lib/stringinfo.h"
 #include "load_manifest.h"
@@ -117,7 +118,6 @@ static void process_directory_recursively(Oid tsoid,
 										  manifest_data **manifests,
 										  manifest_writer *mwriter,
 										  cb_options *opt);
-static int	read_pg_version_file(char *directory);
 static void remember_to_cleanup_directory(char *target_path, bool rmtopdir);
 static void reset_directory_cleanup_list(void);
 static cb_tablespace *scan_for_existing_tablespaces(char *pathname,
@@ -153,7 +153,7 @@ main(int argc, char *argv[])
 	int			c;
 	int			n_backups;
 	int			n_prior_backups;
-	int			version;
+	uint32		version;
 	uint64		system_identifier;
 	char	  **prior_backup_dirs;
 	cb_options	opt;
@@ -271,7 +271,11 @@ main(int argc, char *argv[])
 	}
 
 	/* Read the server version from the final backup. */
-	version = read_pg_version_file(argv[argc - 1]);
+	version = get_pg_version(argv[argc - 1], NULL);
+	if (GET_PG_MAJORVERSION_NUM(version) < 10)
+		pg_fatal("server version too old");
+	pg_log_debug("read server version %u from file \"%s\"",
+				 GET_PG_MAJORVERSION_NUM(version), "PG_VERSION");
 
 	/* Sanity-check control files. */
 	n_backups = argc - optind;
@@ -1155,59 +1159,6 @@ process_directory_recursively(Oid tsoid,
 	closedir(dir);
 }
 
-/*
- * Read the version number from PG_VERSION and convert it to the usual server
- * version number format. (e.g. If PG_VERSION contains "14\n" this function
- * will return 140000)
- */
-static int
-read_pg_version_file(char *directory)
-{
-	char		filename[MAXPGPATH];
-	StringInfoData buf;
-	int			fd;
-	int			version;
-	char	   *ep;
-
-	/* Construct pathname. */
-	snprintf(filename, MAXPGPATH, "%s/PG_VERSION", directory);
-
-	/* Open file. */
-	if ((fd = open(filename, O_RDONLY, 0)) < 0)
-		pg_fatal("could not open file \"%s\": %m", filename);
-
-	/* Read into memory. Length limit of 128 should be more than generous. */
-	initStringInfo(&buf);
-	slurp_file(fd, filename, &buf, 128);
-
-	/* Close the file. */
-	if (close(fd) != 0)
-		pg_fatal("could not close file \"%s\": %m", filename);
-
-	/* Convert to integer. */
-	errno = 0;
-	version = strtoul(buf.data, &ep, 10);
-	if (errno != 0 || *ep != '\n')
-	{
-		/*
-		 * Incremental backup is not relevant to very old server versions that
-		 * used multi-part version number (e.g. 9.6, or 8.4). So if we see
-		 * what looks like the beginning of such a version number, just bail
-		 * out.
-		 */
-		if (version < 10 && *ep == '.')
-			pg_fatal("%s: server version too old", filename);
-		pg_fatal("%s: could not parse version number", filename);
-	}
-
-	/* Debugging output. */
-	pg_log_debug("read server version %d from file \"%s\"", version, filename);
-
-	/* Release memory and return result. */
-	pfree(buf.data);
-	return version * 10000;
-}
-
 /*
  * Add a directory to the list of output directories to clean up.
  */
-- 
2.51.0

From d5bd304ee6a0c236ff323cc5d43713f10c1b20e8 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 10 Oct 2025 15:04:47 +0900
Subject: [PATCH v1 5/5] pg_resetwal: use PG_VERSION generic routine

---
 src/bin/pg_resetwal/pg_resetwal.c | 36 +++++++++----------------------
 1 file changed, 10 insertions(+), 26 deletions(-)

diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 7a4e4eb95706..42d15a2612d8 100644
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -55,6 +55,7 @@
 #include "common/restricted_token.h"
 #include "common/string.h"
 #include "fe_utils/option_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 #include "pg_getopt.h"
 #include "storage/large_object.h"
@@ -77,7 +78,7 @@ static int	WalSegSz;
 static int	set_wal_segsize;
 static int	set_char_signedness = -1;
 
-static void CheckDataVersion(void);
+static void CheckDataVersion(const char *datadir);
 static bool read_controlfile(void);
 static void GuessControlValues(void);
 static void PrintControlValues(bool guessed);
@@ -377,7 +378,7 @@ main(int argc, char *argv[])
 				 DataDir);
 
 	/* Check that data directory matches our server version */
-	CheckDataVersion();
+	CheckDataVersion(DataDir);
 
 	/*
 	 * Check for a postmaster lock file --- if there is one, refuse to
@@ -537,37 +538,20 @@ main(int argc, char *argv[])
  * to prevent simple user errors.
  */
 static void
-CheckDataVersion(void)
+CheckDataVersion(const char *datadir)
 {
-	const char *ver_file = "PG_VERSION";
-	FILE	   *ver_fd;
-	char		rawline[64];
+	char	   *version_str;
+	uint32		version = get_pg_version(datadir, &version_str);
 
-	if ((ver_fd = fopen(ver_file, "r")) == NULL)
-		pg_fatal("could not open file \"%s\" for reading: %m",
-				 ver_file);
-
-	/* version number has to be the first line read */
-	if (!fgets(rawline, sizeof(rawline), ver_fd))
-	{
-		if (!ferror(ver_fd))
-			pg_fatal("unexpected empty file \"%s\"", ver_file);
-		else
-			pg_fatal("could not read file \"%s\": %m", ver_file);
-	}
-
-	/* strip trailing newline and carriage return */
-	(void) pg_strip_crlf(rawline);
-
-	if (strcmp(rawline, PG_MAJORVERSION) != 0)
+	if (GET_PG_MAJORVERSION_NUM(version) != PG_MAJORVERSION_NUM)
 	{
 		pg_log_error("data directory is of wrong version");
 		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
-							ver_file, rawline, PG_MAJORVERSION);
+							"PG_VERSION",
+							version_str,
+							PG_MAJORVERSION);
 		exit(1);
 	}
-
-	fclose(ver_fd);
 }
 
 
-- 
2.51.0

From 1446b30bea9786432dcd9029ce61958ae334e46b Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 14 Oct 2025 16:41:19 +0900
Subject: [PATCH v2 1/3] pg_createsubscriber: Use PG_VERSION generic routine

---
 src/bin/pg_basebackup/pg_createsubscriber.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/bin/pg_basebackup/pg_createsubscriber.c b/src/bin/pg_basebackup/pg_createsubscriber.c
index d29407413d96..9fa5caaf91d6 100644
--- a/src/bin/pg_basebackup/pg_createsubscriber.c
+++ b/src/bin/pg_basebackup/pg_createsubscriber.c
@@ -26,6 +26,7 @@
 #include "fe_utils/recovery_gen.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 
 #define	DEFAULT_SUB_PORT	"50432"
@@ -407,7 +408,8 @@ static void
 check_data_directory(const char *datadir)
 {
 	struct stat statbuf;
-	char		versionfile[MAXPGPATH];
+	uint32		major_version;
+	char	   *version_str;
 
 	pg_log_info("checking if directory \"%s\" is a cluster data directory",
 				datadir);
@@ -420,11 +422,18 @@ check_data_directory(const char *datadir)
 			pg_fatal("could not access directory \"%s\": %m", datadir);
 	}
 
-	snprintf(versionfile, MAXPGPATH, "%s/PG_VERSION", datadir);
-	if (stat(versionfile, &statbuf) != 0 && errno == ENOENT)
+	/*
+	 * Retrieve the contents of this cluster's PG_VERSION.  We require
+	 * compatibility with the same major version as the one this tool is
+	 * compiled with.
+	 */
+	major_version = GET_PG_MAJORVERSION_NUM(get_pg_version(datadir, &version_str));
+	if (major_version != PG_MAJORVERSION_NUM)
 	{
-		pg_fatal("directory \"%s\" is not a database cluster directory",
-				 datadir);
+		pg_log_error("data directory is of wrong version");
+		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
+							"PG_VERSION", version_str, PG_MAJORVERSION);
+		exit(1);
 	}
 }
 
-- 
2.51.0

From 7185c5d6eb3ce0afb22d7be197e6901f2cab55c4 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 14 Oct 2025 16:47:03 +0900
Subject: [PATCH v2 2/3] pg_combinebackup: use PG_VERSION generic routine

---
 src/bin/pg_combinebackup/pg_combinebackup.c | 65 +++------------------
 1 file changed, 9 insertions(+), 56 deletions(-)

diff --git a/src/bin/pg_combinebackup/pg_combinebackup.c b/src/bin/pg_combinebackup/pg_combinebackup.c
index a330c09d939d..3a3251272092 100644
--- a/src/bin/pg_combinebackup/pg_combinebackup.c
+++ b/src/bin/pg_combinebackup/pg_combinebackup.c
@@ -34,6 +34,7 @@
 #include "common/relpath.h"
 #include "copy_file.h"
 #include "fe_utils/option_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 #include "lib/stringinfo.h"
 #include "load_manifest.h"
@@ -117,7 +118,6 @@ static void process_directory_recursively(Oid tsoid,
 										  manifest_data **manifests,
 										  manifest_writer *mwriter,
 										  cb_options *opt);
-static int	read_pg_version_file(char *directory);
 static void remember_to_cleanup_directory(char *target_path, bool rmtopdir);
 static void reset_directory_cleanup_list(void);
 static cb_tablespace *scan_for_existing_tablespaces(char *pathname,
@@ -153,7 +153,7 @@ main(int argc, char *argv[])
 	int			c;
 	int			n_backups;
 	int			n_prior_backups;
-	int			version;
+	uint32		version;
 	uint64		system_identifier;
 	char	  **prior_backup_dirs;
 	cb_options	opt;
@@ -162,6 +162,7 @@ main(int argc, char *argv[])
 	StringInfo	last_backup_label;
 	manifest_data **manifests;
 	manifest_writer *mwriter;
+	char	   *pgdata;
 
 	pg_logging_init(argv[0]);
 	progname = get_progname(argv[0]);
@@ -271,7 +272,12 @@ main(int argc, char *argv[])
 	}
 
 	/* Read the server version from the final backup. */
-	version = read_pg_version_file(argv[argc - 1]);
+	pgdata = argv[argc - 1];
+	version = get_pg_version(pgdata, NULL);
+	if (GET_PG_MAJORVERSION_NUM(version) < 10)
+		pg_fatal("server version too old");
+	pg_log_debug("read server version %u from file \"%s/%s\"",
+				 GET_PG_MAJORVERSION_NUM(version), pgdata, "PG_VERSION");
 
 	/* Sanity-check control files. */
 	n_backups = argc - optind;
@@ -1155,59 +1161,6 @@ process_directory_recursively(Oid tsoid,
 	closedir(dir);
 }
 
-/*
- * Read the version number from PG_VERSION and convert it to the usual server
- * version number format. (e.g. If PG_VERSION contains "14\n" this function
- * will return 140000)
- */
-static int
-read_pg_version_file(char *directory)
-{
-	char		filename[MAXPGPATH];
-	StringInfoData buf;
-	int			fd;
-	int			version;
-	char	   *ep;
-
-	/* Construct pathname. */
-	snprintf(filename, MAXPGPATH, "%s/PG_VERSION", directory);
-
-	/* Open file. */
-	if ((fd = open(filename, O_RDONLY, 0)) < 0)
-		pg_fatal("could not open file \"%s\": %m", filename);
-
-	/* Read into memory. Length limit of 128 should be more than generous. */
-	initStringInfo(&buf);
-	slurp_file(fd, filename, &buf, 128);
-
-	/* Close the file. */
-	if (close(fd) != 0)
-		pg_fatal("could not close file \"%s\": %m", filename);
-
-	/* Convert to integer. */
-	errno = 0;
-	version = strtoul(buf.data, &ep, 10);
-	if (errno != 0 || *ep != '\n')
-	{
-		/*
-		 * Incremental backup is not relevant to very old server versions that
-		 * used multi-part version number (e.g. 9.6, or 8.4). So if we see
-		 * what looks like the beginning of such a version number, just bail
-		 * out.
-		 */
-		if (version < 10 && *ep == '.')
-			pg_fatal("%s: server version too old", filename);
-		pg_fatal("%s: could not parse version number", filename);
-	}
-
-	/* Debugging output. */
-	pg_log_debug("read server version %d from file \"%s\"", version, filename);
-
-	/* Release memory and return result. */
-	pfree(buf.data);
-	return version * 10000;
-}
-
 /*
  * Add a directory to the list of output directories to clean up.
  */
-- 
2.51.0

From 5ab7579870f9d2dee1b707c0914308823479f51c Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 14 Oct 2025 16:55:04 +0900
Subject: [PATCH v2 3/3] pg_resetwal: use PG_VERSION generic routine

---
 src/bin/pg_resetwal/pg_resetwal.c | 30 +++++++-----------------------
 1 file changed, 7 insertions(+), 23 deletions(-)

diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 7a4e4eb95706..a89d72fc5cfe 100644
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -55,6 +55,7 @@
 #include "common/restricted_token.h"
 #include "common/string.h"
 #include "fe_utils/option_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 #include "pg_getopt.h"
 #include "storage/large_object.h"
@@ -539,35 +540,18 @@ main(int argc, char *argv[])
 static void
 CheckDataVersion(void)
 {
-	const char *ver_file = "PG_VERSION";
-	FILE	   *ver_fd;
-	char		rawline[64];
+	char	   *version_str;
+	uint32		version = get_pg_version(".", &version_str);
 
-	if ((ver_fd = fopen(ver_file, "r")) == NULL)
-		pg_fatal("could not open file \"%s\" for reading: %m",
-				 ver_file);
-
-	/* version number has to be the first line read */
-	if (!fgets(rawline, sizeof(rawline), ver_fd))
-	{
-		if (!ferror(ver_fd))
-			pg_fatal("unexpected empty file \"%s\"", ver_file);
-		else
-			pg_fatal("could not read file \"%s\": %m", ver_file);
-	}
-
-	/* strip trailing newline and carriage return */
-	(void) pg_strip_crlf(rawline);
-
-	if (strcmp(rawline, PG_MAJORVERSION) != 0)
+	if (GET_PG_MAJORVERSION_NUM(version) != PG_MAJORVERSION_NUM)
 	{
 		pg_log_error("data directory is of wrong version");
 		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
-							ver_file, rawline, PG_MAJORVERSION);
+							"PG_VERSION",
+							version_str,
+							PG_MAJORVERSION);
 		exit(1);
 	}
-
-	fclose(ver_fd);
 }
 
 
-- 
2.51.0

From 8b9f720854c8c4f9be7fb0e7ff186ddf1cfdcbf1 Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.banck@credativ.de>
Date: Fri, 17 Oct 2025 10:22:20 +0200
Subject: [PATCH] pg_checksums: Use new routine to retrieve data of PG_VERSION

pg_checksums currently refuses to work with clusters of a different version.
Until this limitation is lifted, running it on a cluster with a different major
version errors out either with a "pg_control CRC value is incorrect" message,
or, if that works, with a "cluster is not compatible with this version of
pg_checksums" message in case the control file is different.

The former is confusing as the control file is correct: only the expected
version does not match.  This commit integrates pg_checksums with the facility
added by cd0be131ba6f, where the contents of PG_VERSION are read and compared
with the value of PG_MAJORVERSION_NUM expected by the tool.
---
 src/bin/pg_checksums/pg_checksums.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
index f20be82862a..46cb2f36efa 100644
--- a/src/bin/pg_checksums/pg_checksums.c
+++ b/src/bin/pg_checksums/pg_checksums.c
@@ -25,6 +25,7 @@
 #include "common/logging.h"
 #include "common/relpath.h"
 #include "fe_utils/option_utils.h"
+#include "fe_utils/version.h"
 #include "getopt_long.h"
 #include "pg_getopt.h"
 #include "storage/bufpage.h"
@@ -448,6 +449,8 @@ main(int argc, char *argv[])
 	int			c;
 	int			option_index;
 	bool		crc_ok;
+	uint32		major_version;
+	char	   *version_str;
 
 	pg_logging_init(argv[0]);
 	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_checksums"));
@@ -543,6 +546,20 @@ main(int argc, char *argv[])
 		exit(1);
 	}
 
+	/*
+	 * Retrieve the contents of this cluster's PG_VERSION.  We require
+	 * compatibility with the same major version as the one this tool is
+	 * compiled with.
+	 */
+	major_version = GET_PG_MAJORVERSION_NUM(get_pg_version(DataDir, &version_str));
+	if (major_version != PG_MAJORVERSION_NUM)
+	{
+		pg_log_error("data directory is of wrong version");
+		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
+							"PG_VERSION", version_str, PG_MAJORVERSION);
+		exit(1);
+	}
+
 	/* Read the control file and check compatibility */
 	ControlFile = get_controlfile(DataDir, &crc_ok);
 	if (!crc_ok)
-- 
2.39.5