--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,25 @@
 2012-06-26  Paul Eggert  <eggert@cs.ucla.edu>
 
+	root-uid: new module
+	This is for portability to Tandem's NonStop Kernel.
+	* lib/root-uid.h, modules/root-uid: New files.
+	* lib/euidaccess.c, lib/pt_chown.c, lib/unlinkdir.c:
+	* lib/write-any-file.c, tests/test-sethostname2.c:
+	Include "root-uid.h".
+	* lib/euidaccess.c (euidaccess):
+	* lib/pt_chown.c (main):
+	* lib/unlinkdir.c (cannot_unlink_dir):
+	* lib/write-any-file.c (can_write_any_file):
+	* m4/mknod.m4 (gl_FUNC_MKNOD):
+	* tests/test-sethostname2.c (geteuid, main):
+	Don't assume ROOT_UID == 0.
+	* modules/euidaccess (Depends-on):
+	* modules/pt_chown (Depends-on):
+	* modules/sethostname-tests (Depends-on):
+	* modules/unlinkdir (Depends-on):
+	* modules/write-any-file (Depends-on):
+	Add root-uid.
+
 	regex: use locale-independent comparison for codeset name
 	See Bruno Haible's comment in <http://bugs.gnu.org/10305#120>.
 	* lib/regcomp.c (init_dfa): Use just ASCII case comparison

--- a/lib/euidaccess.c
+++ b/lib/euidaccess.c
@@ -30,6 +30,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "root-uid.h"
+
 #if HAVE_LIBGEN_H
 # include <libgen.h>
 #endif
@@ -140,8 +142,9 @@
 
   /* The super-user can read and write any file, and execute any file
      that anyone can execute.  */
-  if (euid == 0 && ((mode & X_OK) == 0
-                    || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
+  if (euid == ROOT_UID
+      && ((mode & X_OK) == 0
+          || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
     return 0;
 
   /* Convert the mode to traditional form, clearing any bogus bits.  */

--- a/lib/pt_chown.c
+++ b/lib/pt_chown.c
@@ -25,6 +25,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "root-uid.h"
+
 #include "pty-private.h"
 
 /* For security reasons, we try to minimize the dependencies on libraries
@@ -75,7 +77,7 @@
 {
   uid_t euid = geteuid ();
 
-  if (argc == 1 && euid == 0)
+  if (argc == 1 && euid == ROOT_UID)
     {
       /* Normal invocation of this program is with no arguments and
          with privileges.  */
@@ -152,7 +154,7 @@
   }
 
   /* Check if we are properly installed.  */
-  if (euid != 0)
+  if (euid != ROOT_UID)
     {
       fprintf (stderr, "pt_chown: needs to be installed setuid 'root'\n");
       return FAIL_EXEC;

new file mode 100644
--- /dev/null
+++ b/lib/root-uid.h
@@ -0,0 +1,30 @@
+/* The user ID that always has appropriate privileges in the POSIX sense.
+
+   Copyright 2012 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+   Written by Paul Eggert.  */
+
+#ifndef ROOT_UID_H_
+#define ROOT_UID_H_
+
+/* The user ID that always has appropriate privileges in the POSIX sense.  */
+#ifdef __TANDEM
+# define ROOT_UID 65535
+#else
+# define ROOT_UID 0
+#endif
+
+#endif

--- a/lib/unlinkdir.c
+++ b/lib/unlinkdir.c
@@ -21,6 +21,7 @@
 
 #include "unlinkdir.h"
 #include "priv-set.h"
+#include "root-uid.h"
 #include <unistd.h>
 
 #if ! UNLINK_CANNOT_UNLINK_DIR
@@ -43,7 +44,7 @@
       cannot = (priv_set_ismember (PRIV_SYS_LINKDIR) == 0);
 # else
       /* In traditional Unix, only root can unlink directories.  */
-      cannot = (geteuid () != 0);
+      cannot = (geteuid () != ROOT_UID);
 # endif
       initialized = true;
     }

--- a/lib/write-any-file.c
+++ b/lib/write-any-file.c
@@ -21,6 +21,7 @@
 
 #include "write-any-file.h"
 #include "priv-set.h"
+#include "root-uid.h"
 
 #include <unistd.h>
 
@@ -40,7 +41,7 @@
       can = (priv_set_ismember (PRIV_FILE_DAC_WRITE) == 1);
 #else
       /* In traditional Unix, only root can unlink directories.  */
-      can = (geteuid () == 0);
+      can = (geteuid () == ROOT_UID);
 #endif
       can_write = can;
       initialized = true;

--- a/m4/mknod.m4
+++ b/m4/mknod.m4
@@ -25,9 +25,16 @@
          [AC_LANG_PROGRAM(
            [[#include <sys/stat.h>
              #include <unistd.h>
+
+             /* Copied from root-uid.h.  FIXME: Just use root-uid.h.  */
+             #ifdef __TANDEM
+             # define ROOT_UID 65535
+             #else
+             # define ROOT_UID 0
+             #endif
 ]], [[/* Indeterminate for super-user, assume no.  Why are you running
          configure as root, anyway?  */
-      if (!geteuid ()) return 99;
+      if (geteuid () == ROOT_UID) return 99;
       if (mknod ("conftest.fifo", S_IFIFO | 0600, 0)) return 2;]])],
          [gl_cv_func_mknod_works=yes],
          [if test $? = 99 && test x"$FORCE_UNSAFE_CONFIGURE" = x; then

--- a/modules/euidaccess
+++ b/modules/euidaccess
@@ -8,6 +8,7 @@
 Depends-on:
 unistd
 extensions
+root-uid
 group-member    [test $HAVE_EUIDACCESS = 0]
 stat            [test $HAVE_EUIDACCESS = 0]
 sys_stat        [test $HAVE_EUIDACCESS = 0]

--- a/modules/pt_chown
+++ b/modules/pt_chown
@@ -7,6 +7,7 @@
 
 Depends-on:
 ptsname
+root-uid
 stdlib
 configmake
 

new file mode 100644
--- /dev/null
+++ b/modules/root-uid
@@ -0,0 +1,20 @@
+Description:
+ROOT_UID macro: superuser's user ID
+
+Files:
+lib/root-uid.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+
+Include:
+"root-uid.h"
+
+License:
+LGPLv2+
+
+Maintainer:
+all

--- a/modules/sethostname-tests
+++ b/modules/sethostname-tests
@@ -6,6 +6,7 @@
 
 Depends-on:
 gethostname
+root-uid
 
 configure.ac:
 AC_CHECK_FUNCS_ONCE([geteuid])

--- a/modules/unlinkdir
+++ b/modules/unlinkdir
@@ -9,6 +9,7 @@
 Depends-on:
 stdbool
 priv-set
+root-uid
 
 configure.ac:
 gl_UNLINKDIR

--- a/modules/write-any-file
+++ b/modules/write-any-file
@@ -9,6 +9,7 @@
 Depends-on:
 stdbool
 priv-set
+root-uid
 
 configure.ac:
 gl_WRITE_ANY_FILE

--- a/tests/test-sethostname2.c
+++ b/tests/test-sethostname2.c
@@ -27,6 +27,8 @@
 #include <errno.h>
 #include <stdio.h>
 
+#include "root-uid.h"
+
 #include "macros.h"
 
 #define TESTHOSTNAME "gnulib-hostname"
@@ -35,7 +37,7 @@
    On Cygwin, geteuid() may return non-zero even for user accounts with
    administrator privileges, so use a dummy value as well.  */
 #if !HAVE_GETEUID || defined __CYGWIN__
-# define geteuid() 0
+# define geteuid() ROOT_UID
 #endif
 
 int
@@ -50,7 +52,7 @@
      consider things like CAP_SYS_ADMIN (linux) or PRIV_SYS_ADMIN
      (solaris), etc.  systems without a working geteuid (mingw, MSVC
      9) will always skip this test. */
-  if (geteuid () != 0)
+  if (geteuid () != ROOT_UID)
     {
       fprintf (stderr, "Skipping test: insufficient permissions.\n");
       return 77;