Provide a clearer error message if the pg_control version number looks

wrong because of mismatched byte ordering.

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.291 2008/01/01 19:45:48 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.292 2008/01/21 11:17:46 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3888,6 +3888,16 @@ ReadControlFile(void)
 	 * of bytes.  Complaining about wrong version will probably be more
 	 * enlightening than complaining about wrong CRC.
 	 */
+
+	if (ControlFile->pg_control_version != PG_CONTROL_VERSION && ControlFile->pg_control_version % 65536 == 0 && ControlFile->pg_control_version / 65536 != 0)
+		ereport(FATAL,
+				(errmsg("database files are incompatible with server"),
+				 errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d (0x%08x),"
+						   " but the server was compiled with PG_CONTROL_VERSION %d (0x%08x).",
+						   ControlFile->pg_control_version, ControlFile->pg_control_version,
+						   PG_CONTROL_VERSION, PG_CONTROL_VERSION),
+				 errhint("This could be a problem of mismatched byte ordering.  It looks like you need to initdb.")));
+
 	if (ControlFile->pg_control_version != PG_CONTROL_VERSION)
 		ereport(FATAL,
 				(errmsg("database files are incompatible with server"),
@@ -3895,6 +3905,7 @@ ReadControlFile(void)
 				  " but the server was compiled with PG_CONTROL_VERSION %d.",
 						ControlFile->pg_control_version, PG_CONTROL_VERSION),
 				 errhint("It looks like you need to initdb.")));
+
 	/* Now check the CRC. */
 	INIT_CRC32(crc);
 	COMP_CRC32(crc,

src/bin/pg_controldata/pg_controldata.c

@@ -6,7 +6,7 @@
  * copyright (c) Oliver Elphick <olly@lfix.co.uk>, 2001;
  * licence: BSD
  *
- * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.35 2007/04/03 04:14:26 tgl Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.36 2008/01/21 11:17:46 petere Exp $
  */
 #include "postgres.h"
 
@@ -151,6 +151,11 @@ main(int argc, char *argv[])
 
 	printf(_("pg_control version number:            %u\n"),
 		   ControlFile.pg_control_version);
+	if (ControlFile.pg_control_version % 65536 == 0 && ControlFile.pg_control_version / 65536 != 0)
+		printf(_("WARNING: possible byte ordering mismatch\n"
+				 "The byte ordering used to store the pg_control file might not match the one\n"
+				 "used by this program.  In that case the results below would be incorrect, and\n"
+				 "the PostgreSQL installation would be incompatible with this data directory.\n"));
 	printf(_("Catalog version number:               %u\n"),
 		   ControlFile.catalog_version_no);
 	printf(_("Database system identifier:           %s\n"),