+/* save-cwd.c -- Save and restore current working directory.
+
+ Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2016 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. */
+
+#if !defined HAVE_FCHDIR && !defined fchdir
+# define fchdir(fd) (-1)
+#endif
+
+int
+save_cwd (struct saved_cwd *cwd)
+{
+ cwd->desc = open (".", O_SEARCH | O_CLOEXEC);
+ /* 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)
+{
+ /* Restore the previous directory if possible, to avoid tying down
+ the file system of the new directory (Bug#18232).
+ 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. */
+ if (fchdir (cwd->desc) == 0)
+ return 0;
+
+ return 0;
+}
+
+void
+free_cwd (struct saved_cwd *cwd)
+{
+ close (cwd->desc);
+}