From 9b6bc4e0fdbb3d6c7e7f19ebb267ae28549b5076 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 16 Jan 2026 08:35:14 -0500
Subject: [PATCH v1] Remove file-level global WalSegSz.

It's better style to pass the value around to just the places that
need it. This makes it easier to determine whether the value is
always properly initialized before use.
---
 src/bin/pg_waldump/pg_waldump.c | 37 +++++++++++++++++----------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index aae655966ef..f3446385d6a 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -39,7 +39,6 @@
 
 static const char *progname;
 
-static int	WalSegSz;
 static volatile sig_atomic_t time_to_stop = false;
 
 static const RelFileLocator emptyRelFileLocator = {0, 0, 0};
@@ -203,11 +202,11 @@ open_file_in_directory(const char *directory, const char *fname)
 /*
  * Try to find fname in the given directory. Returns true if it is found,
  * false otherwise. If fname is NULL, search the complete directory for any
- * file with a valid WAL file name. If file is successfully opened, set the
- * wal segment size.
+ * file with a valid WAL file name. If file is successfully opened, set
+ * *WaSegSz to the WAL segment size.
  */
 static bool
-search_directory(const char *directory, const char *fname)
+search_directory(const char *directory, const char *fname, int *WalSegSz)
 {
 	int			fd = -1;
 	DIR		   *xldir;
@@ -249,17 +248,17 @@ search_directory(const char *directory, const char *fname)
 		{
 			XLogLongPageHeader longhdr = (XLogLongPageHeader) buf.data;
 
-			WalSegSz = longhdr->xlp_seg_size;
-
-			if (!IsValidWalSegSize(WalSegSz))
+			if (!IsValidWalSegSize(longhdr->xlp_seg_size))
 			{
 				pg_log_error(ngettext("invalid WAL segment size in WAL file \"%s\" (%d byte)",
 									  "invalid WAL segment size in WAL file \"%s\" (%d bytes)",
-									  WalSegSz),
-							 fname, WalSegSz);
+									  longhdr->xlp_seg_size),
+							 fname, longhdr->xlp_seg_size);
 				pg_log_error_detail("The WAL segment size must be a power of two between 1 MB and 1 GB.");
 				exit(1);
 			}
+
+			*WalSegSz = longhdr->xlp_seg_size;
 		}
 		else if (r < 0)
 			pg_fatal("could not read file \"%s\": %m",
@@ -286,21 +285,22 @@ search_directory(const char *directory, const char *fname)
  *	 XLOGDIR /
  *	 $PGDATA / XLOGDIR /
  *
- * The valid target directory is returned.
+ * The valid target directory is returned, and *WalSegSz is set to the
+ * size of the WAL segment found in that directory.
  */
 static char *
-identify_target_directory(char *directory, char *fname)
+identify_target_directory(char *directory, char *fname, int *WalSegSz)
 {
 	char		fpath[MAXPGPATH];
 
 	if (directory != NULL)
 	{
-		if (search_directory(directory, fname))
+		if (search_directory(directory, fname, WalSegSz))
 			return pg_strdup(directory);
 
 		/* directory / XLOGDIR */
 		snprintf(fpath, MAXPGPATH, "%s/%s", directory, XLOGDIR);
-		if (search_directory(fpath, fname))
+		if (search_directory(fpath, fname, WalSegSz))
 			return pg_strdup(fpath);
 	}
 	else
@@ -308,10 +308,10 @@ identify_target_directory(char *directory, char *fname)
 		const char *datadir;
 
 		/* current directory */
-		if (search_directory(".", fname))
+		if (search_directory(".", fname, WalSegSz))
 			return pg_strdup(".");
 		/* XLOGDIR */
-		if (search_directory(XLOGDIR, fname))
+		if (search_directory(XLOGDIR, fname, WalSegSz))
 			return pg_strdup(XLOGDIR);
 
 		datadir = getenv("PGDATA");
@@ -319,7 +319,7 @@ identify_target_directory(char *directory, char *fname)
 		if (datadir != NULL)
 		{
 			snprintf(fpath, MAXPGPATH, "%s/%s", datadir, XLOGDIR);
-			if (search_directory(fpath, fname))
+			if (search_directory(fpath, fname, WalSegSz))
 				return pg_strdup(fpath);
 		}
 	}
@@ -801,6 +801,7 @@ main(int argc, char **argv)
 	XLogRecPtr	first_record;
 	char	   *waldir = NULL;
 	char	   *errormsg;
+	int			WalSegSz;
 
 	static struct option long_options[] = {
 		{"bkp-details", no_argument, NULL, 'b'},
@@ -1127,7 +1128,7 @@ main(int argc, char **argv)
 				pg_fatal("could not open directory \"%s\": %m", waldir);
 		}
 
-		waldir = identify_target_directory(waldir, fname);
+		waldir = identify_target_directory(waldir, fname, &WalSegSz);
 		fd = open_file_in_directory(waldir, fname);
 		if (fd < 0)
 			pg_fatal("could not open file \"%s\"", fname);
@@ -1189,7 +1190,7 @@ main(int argc, char **argv)
 		}
 	}
 	else
-		waldir = identify_target_directory(waldir, NULL);
+		waldir = identify_target_directory(waldir, NULL, &WalSegSz);
 
 	/* we don't know what to print */
 	if (!XLogRecPtrIsValid(private.startptr))
-- 
2.51.0