X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fchown.c;h=1301aa6ad7a63185baed7bba77c402c3c5c29d58;hb=76cfe20c721a2dcefaabf27de32082458b51b281;hp=2b3fc9a69656490a59cb5d02134b235d9d69d7ac;hpb=d349992d82f97d614404565ff66e3f8a47b4a568;p=gnulib.git

diff --git a/lib/chown.c b/lib/chown.c
index 2b3fc9a69..1301aa6ad 100644
--- a/lib/chown.c
+++ b/lib/chown.c
@@ -1,6 +1,7 @@
 /* provide consistent interface to chown for systems that don't interpret
    an ID of -1 as meaning `don't change the corresponding ID'.
-   Copyright (C) 1997, 2000 Free Software Foundation, Inc.
+
+   Copyright (C) 1997, 2004, 2005, 2006 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
@@ -14,7 +15,7 @@
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software Foundation,
-   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
 
 /* written by Jim Meyering */
 
@@ -25,24 +26,30 @@
    most systems.  */
 #undef chown
 
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#if HAVE_UNISTD_H
-# include <unistd.h>
-#endif
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
 
-/* FIXME: describe.  */
+/* Provide a more-closely POSIX-conforming version of chown on
+   systems with one or both of the following problems:
+   - chown doesn't treat an ID of -1 as meaning
+   `don't change the corresponding ID'.
+   - chown doesn't dereference symlinks.  */
 
 int
 rpl_chown (const char *file, uid_t uid, gid_t gid)
 {
+#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))
-	return 1;
+	return -1;
 
       if (gid == (gid_t) -1)
 	gid = file_stats.st_gid;
@@ -50,6 +57,43 @@ rpl_chown (const char *file, uid_t uid, gid_t gid)
       if (uid == (uid_t) -1)
 	uid = file_stats.st_uid;
     }
+#endif
+
+#if CHOWN_MODIFIES_SYMLINK
+  {
+    /* Handle the case in which the system-supplied chown function
+       does *not* follow symlinks.  Instead, it changes permissions
+       on the symlink itself.  To work around that, we open the
+       file (but this can fail due to lack of read or write permission) and
+       use fchown on the resulting descriptor.  */
+    int open_flags = O_NONBLOCK | O_NOCTTY;
+    int fd = open (file, O_RDONLY | open_flags);
+    if (0 <= fd
+	|| (errno == EACCES
+	    && 0 <= (fd = open (file, O_WRONLY | open_flags))))
+      {
+	int result = fchown (fd, uid, gid);
+	int 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 =
+	  (result != 0 && saved_errno == EINVAL
+	   && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
+
+	close (fd);
+
+	if (! fchown_socket_failure)
+	  {
+	    errno = saved_errno;
+	    return result;
+	  }
+      }
+    else if (errno != EACCES)
+      return -1;
+  }
+#endif
 
   return chown (file, uid, gid);
 }