+2014-08-10 Paul Eggert <eggert@cs.ucla.edu>
+
+ Don't prevent random file systems from being unmounted (Bug#18232).
+ This fix relies on having the 'fchdir' function, and on having
+ "." be searchable (or at least readable, on platforms lacking O_SEARCH),
+ but that's good enough to handle the vast majority of cases and the
+ remaining folks can just live with the annoyance of file systems
+ that occasionally can't be unmounted.
+ * configure.ac (fchdir): New function to check for.
+ * lib/save-cwd.c: Copy from gnulib, except omit the part that
+ allocates memory, since that can cause problems in Emacs.
+ * lib/save-cwd.h: Copy from gnulib.
+
2014-07-11 Paul Eggert <eggert@cs.ucla.edu>
* Makefile.in (install-arch-indep): Avoid readdir race (Bug#17971).
+/* save-cwd.c -- Save and restore current working directory.
+
+ Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2014 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/>. */
+
+/* Gnulib needs to save and restore the current working directory to
+ fully emulate functions like fstatat. But Emacs doesn't care what
+ the current working directory is; it always uses absolute file
+ names. This module replaces the Gnulib module by omitting the code
+ that Emacs does not need. */
+
#include <config.h>
-#define SAVE_CWD_INLINE _GL_EXTERN_INLINE
+
#include "save-cwd.h"
+
+#include <fcntl.h>
+#include <unistd.h>
+
+/* Record the location of the current working directory in CWD so that
+ the program may change to other directories and later use restore_cwd
+ to return to the recorded location. This function may allocate
+ space using malloc (via getcwd) or leave a file descriptor open;
+ use free_cwd to perform the necessary free or close. Upon failure,
+ no memory is allocated, any locally opened file descriptors are
+ closed; return non-zero -- in that case, free_cwd need not be
+ called, but doing so is ok. Otherwise, return zero.
+
+ The _raison d'etre_ for this interface is that the working directory
+ is sometimes inaccessible, and getcwd is not robust or as efficient.
+ So, we prefer to use the open/fchdir approach, but fall back on
+ getcwd if necessary. This module works for most cases with just
+ the getcwd-lgpl module, but to be truly robust, use the getcwd module.
+
+ Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin,
+ SCO Xenix. Also, SunOS 4 and Irix 5.3 provide the function, yet it
+ doesn't work for partitions on which auditing is enabled. If
+ you're still using an obsolete system with these problems, please
+ send email to the maintainer of this code. */
+
+int
+save_cwd (struct saved_cwd *cwd)
+{
+#ifdef HAVE_FCHDIR
+ cwd->desc = open (".", O_SEARCH | O_CLOEXEC);
+#else
+ cwd->desc = -1;
+#endif
+ /* The 'name' member is present only to minimize differences from
+ gnulib. Initialize it to zero, if only to simplify debugging. */
+ cwd->name = 0;
+ return 0;
+}
+
+/* Change to recorded location, CWD, in directory hierarchy.
+ Upon failure, return -1 (errno is set by chdir or fchdir).
+ Upon success, return zero. */
+
+int
+restore_cwd (const struct saved_cwd *cwd)
+{
+#ifdef HAVE_FCHDIR
+ /* Restore the previous directory if possible, to avoid tying down
+ the file system of the new directory (Bug#18232). */
+ if (fchdir (cwd->desc) == 0)
+ return 0;
+
+ /* Don't worry if fchdir fails, as Emacs doesn't care what the
+ working directory is. The fchdir call is inside an 'if' merely to
+ pacify compilers that complain if fchdir's return value is ignored. */
+#endif
+ return 0;
+}
+
+void
+free_cwd (struct saved_cwd *cwd)
+{
+ close (cwd->desc);
+}
-/* Do not save and restore the current working directory.
+/* Save and restore current working directory.
- Copyright 2013-2014 Free Software Foundation, Inc.
+ Copyright (C) 1995, 1997-1998, 2003, 2009-2014 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
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
-/* Gnulib needs to save and restore the current working directory to
- fully emulate functions like fstatat. But Emacs doesn't care what
- the current working directory is; it always uses absolute file
- names. This module replaces the Gnulib module by omitting the code
- that Emacs does not need. */
+/* Written by Jim Meyering. */
#ifndef SAVE_CWD_H
-#define SAVE_CWD_H 1
+# define SAVE_CWD_H 1
-_GL_INLINE_HEADER_BEGIN
-#ifndef SAVE_CWD_INLINE
-# define SAVE_CWD_INLINE _GL_INLINE
-#endif
+struct saved_cwd
+ {
+ int desc;
+ char *name;
+ };
-struct saved_cwd { int desc; };
+int save_cwd (struct saved_cwd *cwd);
+int restore_cwd (const struct saved_cwd *cwd);
+void free_cwd (struct saved_cwd *cwd);
-SAVE_CWD_INLINE int
-save_cwd (struct saved_cwd *cwd)
-{
- cwd->desc = -1;
- return 0;
-}
-
-SAVE_CWD_INLINE int restore_cwd (struct saved_cwd const *cwd) { return 0; }
-SAVE_CWD_INLINE void free_cwd (struct saved_cwd *cwd) { }
-
-_GL_INLINE_HEADER_END
-
-#endif
+#endif /* SAVE_CWD_H */