--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2009-11-17  Eric Blake  <ebb9@byu.net>
 
+	chown: work around OpenBSD bug
+	* lib/chown.c (rpl_chown): Work around the bug.
+	* lib/lchown.c (rpl_lchown): Attempt to do likewise.
+	* m4/chown.m4 (gl_FUNC_CHOWN): Test for ctime bug.
+	* m4/lchown.m4 (gl_FUNC_LCHOWN): Check for lchmod.
+	* modules/chown (Depends-on): Add stdbool.
+	* modules/lchown (Depends-on): Likewise.
+	* doc/posix-functions/chown.texi (chown): Document the bug.
+	* doc/posix-functions/lchown.texi (lchown): Likewise.
+	* tests/test-lchown.h (test_chown): Relax test.
+
 	mkstemp: avoid conflict with C++ keyword template
 	* lib/mkdtemp.c (mkdtemp): Change spelling of template.
 	* lib/mkostemp.c (mkostemp): Likewise.

--- a/doc/posix-functions/chown.texi
+++ b/doc/posix-functions/chown.texi
@@ -13,6 +13,10 @@
 @code{chown("link-to-file/",uid,gid)}:
 FreeBSD 7.2, Solaris 9.
 @item
+Some platforms fail to update the change time when at least one
+argument was not -1, but no ownership changes resulted:
+OpenBSD 4.0.
+@item
 When passed an argument of -1, some implementations really set the owner
 user/group id of the file to this value, rather than leaving that id of the
 file alone.

--- a/doc/posix-functions/lchown.texi
+++ b/doc/posix-functions/lchown.texi
@@ -13,6 +13,11 @@
 @code{lchown("link-to-file/",uid,gid)}:
 FreeBSD 7.2, Solaris 9.
 @item
+Some platforms fail to update the change time when at least one
+argument was not -1, but no ownership changes resulted.  However,
+without @code{lchmod}, the replacement only fixes this for non-symlinks:
+OpenBSD 4.0.
+@item
 This function is missing on some platforms; however, the replacement
 fails on symlinks if @code{chown} is supported, and fails altogether
 with @code{ENOSYS} otherwise:

--- a/lib/chown.c
+++ b/lib/chown.c
@@ -59,20 +59,29 @@
 int
 rpl_chown (const char *file, uid_t uid, gid_t gid)
 {
+  struct stat st;
+  bool stat_valid = false;
+  int result;
+
+# if CHOWN_CHANGE_TIME_BUG
+  if (gid != (gid_t) -1 || uid != (uid_t) -1)
+    {
+      if (stat (file, &st))
+        return -1;
+      stat_valid = true;
+    }
+# endif
+
 # if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
   if (gid == (gid_t) -1 || uid == (uid_t) -1)
     {
-      struct stat file_stats;
-
       /* Stat file to get id(s) that should remain unchanged.  */
-      if (stat (file, &file_stats))
+      if (!stat_valid && stat (file, &st))
         return -1;
-
       if (gid == (gid_t) -1)
-        gid = file_stats.st_gid;
-
+        gid = st.st_gid;
       if (uid == (uid_t) -1)
-        uid = file_stats.st_uid;
+        uid = st.st_uid;
     }
 # endif
 
@@ -89,15 +98,18 @@
         || (errno == EACCES
             && 0 <= (fd = open (file, O_WRONLY | open_flags))))
       {
-        int result = fchown (fd, uid, gid);
-        int saved_errno = errno;
+        int saved_errno;
+        bool fchown_socket_failure;
+
+        result = fchown (fd, uid, gid);
+        saved_errno = errno;
 
-        /* POSIX says fchown can fail with errno == EINVAL on sockets,
-           so fall back on chown in that case.  */
-        struct stat sb;
-        bool fchown_socket_failure =
+        /* POSIX says fchown can fail with errno == EINVAL on sockets
+           and pipes, so fall back on chown in that case.  */
+        fchown_socket_failure =
           (result != 0 && saved_errno == EINVAL
-           && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
+           && fstat (fd, &st) == 0
+           && (S_ISFIFO (st.st_mode) || S_ISSOCK (st.st_mode)));
 
         close (fd);
 
@@ -113,15 +125,32 @@
 # endif
 
 # if CHOWN_TRAILING_SLASH_BUG
-  {
-    size_t len = strlen (file);
-    struct stat st;
-    if (len && file[len - 1] == '/' && stat (file, &st))
-      return -1;
-  }
+  if (!stat_valid)
+    {
+      size_t len = strlen (file);
+      if (len && file[len - 1] == '/' && stat (file, &st))
+        return -1;
+    }
 # endif
 
-  return chown (file, uid, gid);
+  result = chown (file, uid, gid);
+
+# if CHOWN_CHANGE_TIME_BUG
+  if (result == 0 && stat_valid
+      && (uid == st.st_uid || uid == (uid_t) -1)
+      && (gid == st.st_gid || gid == (gid_t) -1))
+    {
+      /* No change in ownership, but at least one argument was not -1,
+         so we are required to update ctime.  Since chown succeeded,
+         we assume that chmod will do likewise.  Fortunately, on all
+         known systems where a 'no-op' chown skips the ctime update, a
+         'no-op' chmod still does the trick.  */
+      result = chmod (file, st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO
+                                          | S_ISUID | S_ISGID | S_ISVTX));
+    }
+# endif
+
+  return result;
 }
 
 #endif /* HAVE_CHOWN */

--- a/lib/lchown.c
+++ b/lib/lchown.c
@@ -23,6 +23,7 @@
 #include <unistd.h>
 
 #include <errno.h>
+#include <stdbool.h>
 #include <string.h>
 #include <sys/stat.h>
 
@@ -69,10 +70,47 @@
 int
 rpl_lchown (const char *file, uid_t uid, gid_t gid)
 {
-  size_t len = strlen (file);
-  if (len && file[len - 1] == '/')
-    return chown (file, uid, gid);
-  return lchown (file, uid, gid);
+  struct stat st;
+  bool stat_valid = false;
+  int result;
+
+# if CHOWN_CHANGE_TIME_BUG
+  if (gid != (gid_t) -1 || uid != (uid_t) -1)
+    {
+      if (lstat (file, &st))
+        return -1;
+      stat_valid = true;
+      if (!S_ISLNK (st.st_mode))
+        return chown (file, uid, gid);
+    }
+# endif
+
+# if CHOWN_TRAILING_SLASH_BUG
+  if (!stat_valid)
+    {
+      size_t len = strlen (file);
+      if (len && file[len - 1] == '/')
+        return chown (file, uid, gid);
+    }
+# endif
+
+  result = lchown (file, uid, gid);
+
+# if CHOWN_CHANGE_TIME_BUG && HAVE_LCHMOD
+  if (result == 0 && stat_valid
+      && (uid == st.st_uid || uid == (uid_t) -1)
+      && (gid == st.st_gid || gid == (gid_t) -1))
+    {
+      /* No change in ownership, but at least one argument was not -1,
+         so we are required to update ctime.  Since lchown succeeded,
+         we assume that lchmod will do likewise.  But if the system
+         lacks lchmod and lutimes, we are out of luck.  Oh well.  */
+      result = lchmod (file, st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO
+                                           | S_ISUID | S_ISGID | S_ISVTX));
+    }
+# endif
+
+  return result;
 }
 
 #endif /* HAVE_LCHOWN */

--- a/m4/chown.m4
+++ b/m4/chown.m4
@@ -1,4 +1,4 @@
-# serial 21
+# serial 22
 # Determine whether we need the chown wrapper.
 
 dnl Copyright (C) 1997-2001, 2003-2005, 2007, 2009
@@ -22,20 +22,27 @@
   AC_REQUIRE([gl_FUNC_CHOWN_FOLLOWS_SYMLINK])
   AC_CHECK_FUNCS_ONCE([chown fchown])
 
+  dnl mingw lacks chown altogether.
   if test $ac_cv_func_chown = no; then
     HAVE_CHOWN=0
     AC_LIBOBJ([chown])
   else
+    dnl Some old systems treated chown like lchown.
     if test $gl_cv_func_chown_follows_symlink = no; then
       REPLACE_CHOWN=1
       AC_LIBOBJ([chown])
     fi
+
+    dnl Some old systems tried to use uid/gid -1 literally.
     if test $ac_cv_func_chown_works = no; then
       AC_DEFINE([CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE], [1],
         [Define if chown is not POSIX compliant regarding IDs of -1.])
       REPLACE_CHOWN=1
       AC_LIBOBJ([chown])
     fi
+
+    dnl Solaris 9 ignores trailing slash.
+    dnl FreeBSD 7.2 mishandles trailing slash on symlinks.
     AC_CACHE_CHECK([whether chown honors trailing slash],
       [gl_cv_func_chown_slash_works],
       [touch conftest.file && rm -f conftest.link
@@ -52,10 +59,39 @@
       rm -f conftest.link conftest.file])
     if test "$gl_cv_func_chown_slash_works" != yes; then
       AC_DEFINE([CHOWN_TRAILING_SLASH_BUG], [1],
-        [Define if chown mishandles trailing slash.])
+        [Define to 1 if chown mishandles trailing slash.])
       REPLACE_CHOWN=1
       AC_LIBOBJ([chown])
     fi
+
+    dnl OpenBSD fails to update ctime if ownership does not change.
+    AC_CACHE_CHECK([whether chown always updates ctime],
+      [gl_cv_func_chown_ctime_works],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+]], [[    struct stat st1, st2;
+          if (close (creat ("conftest.file", 0600))) return 1;
+          if (stat ("conftest.file", &st1)) return 2;
+          sleep (1);
+          if (chown ("conftest.file", st1.st_uid, st1.st_gid)) return 3;
+          if (stat ("conftest.file", &st2)) return 4;
+          if (st2.st_ctime <= st1.st_ctime) return 5;
+        ]])],
+        [gl_cv_func_chown_ctime_works=yes],
+        [gl_cv_func_chown_ctime_works=no],
+        [gl_cv_func_chown_ctime_works="guessing no"])
+      rm -f conftest.file])
+    if test "$gl_cv_func_chown_ctime_works" != yes; then
+      AC_DEFINE([CHOWN_CHANGE_TIME_BUG], [1], [Define to 1 if chown fails
+        to change ctime when at least one argument was not -1.])
+      REPLACE_CHOWN=1
+      AC_LIBOBJ([chown])
+    fi
+
     if test $REPLACE_CHOWN = 1 && test $ac_cv_func_fchown = no; then
       AC_LIBOBJ([fchown-stub])
     fi

--- a/m4/lchown.m4
+++ b/m4/lchown.m4
@@ -1,4 +1,4 @@
-# serial 14
+# serial 15
 # Determine whether we need the lchown wrapper.
 
 dnl Copyright (C) 1998, 2001, 2003-2007, 2009 Free Software
@@ -9,18 +9,20 @@
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Jim Meyering.
-dnl Provide lchown on systems that lack it, and work around trailing
-dnl slash bugs on systems that have it.
+dnl Provide lchown on systems that lack it, and work around bugs
+dnl on systems that have it.
 
 AC_DEFUN([gl_FUNC_LCHOWN],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_CHOWN])
+  AC_CHECK_FUNCS_ONCE([lchmod])
   AC_REPLACE_FUNCS([lchown])
   if test $ac_cv_func_lchown = no; then
     HAVE_LCHOWN=0
-  elif test "$gl_cv_func_chown_slash_works" != yes; then
-    dnl Trailing slash bugs in chown also occur in lchown.
+  elif test "$gl_cv_func_chown_slash_works" != yes \
+      || test "$gl_cv_func_chown_ctime_works" != yes; then
+    dnl Trailing slash and ctime bugs in chown also occur in lchown.
     AC_LIBOBJ([lchown])
     REPLACE_LCHOWN=1
   fi

--- a/modules/chown
+++ b/modules/chown
@@ -8,9 +8,10 @@
 
 Depends-on:
 open
+stat
+stdbool
+sys_stat
 unistd
-stat
-sys_stat
 
 configure.ac:
 gl_FUNC_CHOWN

--- a/modules/lchown
+++ b/modules/lchown
@@ -9,6 +9,7 @@
 chown
 errno
 lstat
+stdbool
 sys_stat
 unistd
 

--- a/tests/test-lchown.h
+++ b/tests/test-lchown.h
@@ -75,6 +75,14 @@
 # define getegid() (-1)
 #endif
 
+#ifndef HAVE_LCHMOD
+# define HAVE_LCHMOD 0
+#endif
+
+#ifndef CHOWN_CHANGE_TIME_BUG
+# define CHOWN_CHANGE_TIME_BUG 0
+#endif
+
 /* This file is designed to test lchown(n,o,g) and
    chownat(AT_FDCWD,n,o,g,AT_SYMLINK_NOFOLLOW).  FUNC is the function
    to test.  Assumes that BASE and ASSERT are already defined, and
@@ -251,8 +259,10 @@
       ASSERT (st1.st_uid == st2.st_uid);
       ASSERT (gids[0] == st2.st_gid);
     }
-  else
+  else if (!CHOWN_CHANGE_TIME_BUG || HAVE_LCHMOD)
     {
+      /* If we don't have lchmod, and lchown fails to change ctime,
+         then we can't test this part of lchown.  */
       struct stat l1;
       struct stat l2;
       ASSERT (stat (BASE "dir/file", &st1) == 0);