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41bdb6e20c
2001-07-06 Paul Eggert <eggert@twinsun.com> * manual/argp.texi: Remove ignored LGPL copyright notice; it's not appropriate for documentation anyway. * manual/libc-texinfo.sh: "Library General Public License" -> "Lesser General Public License". 2001-07-06 Andreas Jaeger <aj@suse.de> * All files under GPL/LGPL version 2: Place under LGPL version 2.1.
240 lines
6.3 KiB
C
240 lines
6.3 KiB
C
/* Copyright (C) 2000, 2001 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <errno.h>
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#include <fcntl.h>
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#include <mntent.h>
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#include <paths.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/statfs.h>
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#include <bits/libc-lock.h>
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#include "linux_fsinfo.h"
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/* Mount point of the shared memory filesystem. */
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static struct
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{
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char *dir;
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size_t dirlen;
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} mountpoint;
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/* This is the default directory. */
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static const char defaultdir[] = "/dev/shm/";
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/* Protect the `mountpoint' variable above. */
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__libc_once_define (static, once);
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/* Determine where the shmfs is mounted (if at all). */
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static void
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where_is_shmfs (void)
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{
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char buf[512];
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struct statfs f;
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struct mntent resmem;
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struct mntent *mp;
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FILE *fp;
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/* The canonical place is /dev/shm. This is at least what the
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documentation tells everybody to do. */
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if (__statfs (defaultdir, &f) == 0 && f.f_type == SHMFS_SUPER_MAGIC)
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{
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/* It is in the normal place. */
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mountpoint.dir = (char *) defaultdir;
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mountpoint.dirlen = sizeof (defaultdir) - 1;
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return;
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}
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/* OK, do it the hard way. Look through the /proc/mounts file and if
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this does not exist through /etc/fstab to find the mount point. */
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fp = __setmntent ("/proc/mounts", "r");
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if (__builtin_expect (fp == NULL, 0))
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{
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fp = __setmntent (_PATH_MNTTAB, "r");
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if (__builtin_expect (fp == NULL, 0))
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/* There is nothing we can do. Blind guesses are not helpful. */
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return;
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}
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/* Now read the entries. */
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while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
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/* The original name is "shm" but this got changed in early Linux
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2.4.x to "tmpfs". */
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if ((strcmp (mp->mnt_type, "tmpfs") == 0)
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|| (strcmp (mp->mnt_type, "shm")))
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{
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/* Found it. There might be more than one place where the
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filesystem is mounted but one is enough for us. */
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size_t namelen;
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/* First make sure this really is the correct entry. At least
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some versions of the kernel give wrong information because
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of the implicit mount of the shmfs for SysV IPC. */
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if (__statfs (mp->mnt_dir, &f) != 0 || f.f_type != SHMFS_SUPER_MAGIC)
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continue;
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namelen = strlen (mp->mnt_dir);
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if (namelen == 0)
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/* Hum, maybe some crippled entry. Keep on searching. */
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continue;
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mountpoint.dir = (char *) malloc (namelen + 2);
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if (mountpoint.dir != NULL)
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{
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char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
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if (cp[-1] != '/')
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*cp++ = '/';
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*cp = '\0';
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mountpoint.dirlen = cp - mountpoint.dir;
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}
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break;
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}
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/* Close the stream. */
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__endmntent (fp);
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}
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/* Open shared memory object. This implementation assumes the shmfs
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implementation introduced in the late 2.3.x kernel series to be
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available. Normally the filesystem will be mounted at /dev/shm but
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we fall back on searching for the actual mount point should opening
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such a file fail. */
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int
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shm_open (const char *name, int oflag, mode_t mode)
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{
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size_t namelen;
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char *fname;
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int fd;
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/* Determine where the shmfs is mounted. */
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__libc_once (once, where_is_shmfs);
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/* If we don't know the mount points there is nothing we can do. Ever. */
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if (mountpoint.dir == NULL)
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{
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__set_errno (ENOSYS);
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return -1;
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}
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/* Construct the filename. */
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while (name[0] == '/')
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++name;
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if (name[0] == '\0')
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{
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/* The name "/" is not supported. */
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__set_errno (EINVAL);
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return -1;
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}
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namelen = strlen (name);
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fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
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__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
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name, namelen + 1);
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/* And get the file descriptor.
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XXX Maybe we should test each descriptor whether it really is for a
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file on the shmfs. If this is what should be done the whole function
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should be revamped since we can determine whether shmfs is available
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while trying to open the file, all in one turn. */
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fd = open (fname, oflag | O_NOFOLLOW, mode);
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if (fd != -1)
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{
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/* We got a descriptor. Now set the FD_CLOEXEC bit. */
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int flags = fcntl (fd, F_GETFD, 0);
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if (__builtin_expect (flags, 0) >= 0)
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{
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flags |= FD_CLOEXEC;
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flags = fcntl (fd, F_SETFD, flags);
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}
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if (flags == -1)
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{
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/* Something went wrong. We cannot return the descriptor. */
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int save_errno = errno;
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close (fd);
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fd = -1;
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__set_errno (save_errno);
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}
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}
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return fd;
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}
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/* Unlink a shared memory object. */
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int
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shm_unlink (const char *name)
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{
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size_t namelen;
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char *fname;
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/* Determine where the shmfs is mounted. */
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__libc_once (once, where_is_shmfs);
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if (mountpoint.dir == NULL)
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{
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/* We cannot find the shmfs. If `name' is really a shared
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memory object it must have been created by another process
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and we have no idea where that process found the mountpoint. */
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__set_errno (ENOENT);
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return -1;
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}
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/* Construct the filename. */
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while (name[0] == '/')
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++name;
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if (name[0] == '\0')
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{
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/* The name "/" is not supported. */
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__set_errno (ENOENT);
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return -1;
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}
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namelen = strlen (name);
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fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
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__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
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name, namelen + 1);
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/* And remove the file. */
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return unlink (fname);
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}
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static void __attribute__ ((unused))
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freeit (void)
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{
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if (mountpoint.dir != defaultdir)
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free (mountpoint.dir);
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}
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/* Make sure the table is freed if we want to free everything before
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exiting. */
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text_set_element (__libc_subfreeres, freeit);
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