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/* Define at-style functions like fstatat, unlinkat, fchownat, etc.
Copyright (C) 2006, 2009-2026 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 <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include "filename.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
# include <errno.h>
# ifndef ENOTSUP
# define ENOTSUP EINVAL
# endif
#else
# include "openat.h"
# include "openat-priv.h"
# include "save-cwd.h"
#endif
#ifdef AT_FUNC_USE_F1_COND
# define CALL_FUNC(F) \
(flag == AT_FUNC_USE_F1_COND \
? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS) \
: AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS))
# define VALIDATE_FLAG(F) \
if (flag & ~AT_FUNC_USE_F1_COND) \
{ \
errno = EINVAL; \
return FUNC_FAIL; \
}
#else
# define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS))
# define VALIDATE_FLAG(F) /* empty */
#endif
#ifdef AT_FUNC_RESULT
# define FUNC_RESULT AT_FUNC_RESULT
#else
# define FUNC_RESULT int
#endif
#ifdef AT_FUNC_FAIL
# define FUNC_FAIL AT_FUNC_FAIL
#else
# define FUNC_FAIL -1
#endif
/* Call AT_FUNC_F1 to operate on FILE, which is in the directory
open on descriptor FD. If AT_FUNC_USE_F1_COND is defined to a value,
AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag;
call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than
AT_FUNC_USE_F1_COND. Return int and fail with -1 unless AT_FUNC_RESULT
or AT_FUNC_FAIL are defined. If possible, do it without changing the
working directory. Otherwise, resort to using save_cwd/fchdir,
then AT_FUNC_F?/restore_cwd. If either the save_cwd or the restore_cwd
fails, then give a diagnostic and exit nonzero. */
FUNC_RESULT
AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS)
{
VALIDATE_FLAG (flag);
if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
return CALL_FUNC (file);
#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
errno = ENOTSUP;
return FUNC_FAIL;
#else
/* Be careful to choose variable names unlikely to conflict with
AT_FUNC_POST_FILE_PARAM_DECLS. */
{
char proc_buf[OPENAT_BUFFER_SIZE];
char *proc_file = openat_proc_name (proc_buf, fd, file);
if (proc_file)
{
FUNC_RESULT proc_result = CALL_FUNC (proc_file);
int proc_errno = errno;
if (proc_file != proc_buf)
free (proc_file);
/* If the syscall succeeds, or if it fails with an unexpected
errno value, then return right away. Otherwise, fall through
and resort to using save_cwd/restore_cwd. */
if (FUNC_FAIL != proc_result)
return proc_result;
if (! EXPECTED_ERRNO (proc_errno))
{
errno = proc_errno;
return proc_result;
}
}
}
struct saved_cwd saved_cwd;
if (save_cwd (&saved_cwd) != 0)
openat_save_fail (errno);
if (0 <= fd && fd == saved_cwd.desc)
{
/* If saving the working directory collides with the user's
requested fd, then the user's fd must have been closed to
begin with. */
free_cwd (&saved_cwd);
errno = EBADF;
return FUNC_FAIL;
}
if (fchdir (fd) != 0)
{
int saved_errno = errno;
free_cwd (&saved_cwd);
errno = saved_errno;
return FUNC_FAIL;
}
FUNC_RESULT err = CALL_FUNC (file);
int saved_errno = (err == FUNC_FAIL ? errno : 0);
if (restore_cwd (&saved_cwd) != 0)
openat_restore_fail (errno);
free_cwd (&saved_cwd);
if (saved_errno)
errno = saved_errno;
return err;
#endif
}
#undef CALL_FUNC
#undef FUNC_RESULT
#undef FUNC_FAIL
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