chown: Update doc regarding AIX.

[gnulib.git] / lib / openat-proc.c

diff --git a/lib/openat-proc.c b/lib/openat-proc.c
index 87293a4..2538412 100644 (file)
--- a/lib/openat-proc.c
+++ b/lib/openat-proc.c
@@ -1,11 +1,11 @@
 /* Create /proc/self/fd-related names for subfiles of open directories.
 
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006, 2009-2010 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   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 2, or (at your option)
-   any later version.
+   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
@@ -13,8 +13,7 @@
    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, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Written by Paul Eggert.  */
 
@@ -28,12 +27,21 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "dirname.h"
 #include "intprops.h"
 #include "same-inode.h"
 #include "xalloc.h"
 
+/* The results of open() in this file are not used with fchdir,
+   and we do not leak fds to any single-threaded code that could use stdio,
+   therefore save some unnecessary work in fchdir.c.
+   FIXME - if the kernel ever adds support for multi-thread safety for
+   avoiding standard fds, then we should use open_safer.  */
+#undef open
+#undef close
+
 #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
 
 #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
@@ -50,32 +58,39 @@ openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
 {
   static int proc_status = 0;
 
+  /* Make sure the caller gets ENOENT when appropriate.  */
+  if (!*file)
+    {
+      buf[0] = '\0';
+      return buf;
+    }
+
   if (! proc_status)
     {
       /* Set PROC_STATUS to a positive value if /proc/self/fd is
-        reliable, and a negative value otherwise.  Solaris 10
-        /proc/self/fd mishandles "..", and any file name might expand
-        to ".." after symbolic link expansion, so avoid /proc/self/fd
-        if it mishandles "..".  Solaris 10 has openat, but this
-        problem is exhibited on code that built on Solaris 8 and
-        running on Solaris 10.  */
+         reliable, and a negative value otherwise.  Solaris 10
+         /proc/self/fd mishandles "..", and any file name might expand
+         to ".." after symbolic link expansion, so avoid /proc/self/fd
+         if it mishandles "..".  Solaris 10 has openat, but this
+         problem is exhibited on code that built on Solaris 8 and
+         running on Solaris 10.  */
 
       int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
       if (proc_self_fd < 0)
-       proc_status = -1;
+        proc_status = -1;
       else
-       {
-         struct stat proc_self_fd_dotdot_st;
-         struct stat proc_self_st;
-         char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
-         sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
-         proc_status =
-           ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
-             && stat ("/proc/self", &proc_self_st) == 0
-             && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
-            ? 1 : -1);
-         close (proc_self_fd);
-       }
+        {
+          struct stat proc_self_fd_dotdot_st;
+          struct stat proc_self_st;
+          char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
+          sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
+          proc_status =
+            ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
+              && stat ("/proc/self", &proc_self_st) == 0
+              && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
+             ? 1 : -1);
+          close (proc_self_fd);
+        }
     }
 
   if (proc_status < 0)