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/* Internals for openat-like functions.
Copyright (C) 2005-2006, 2009-2020 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 */
#ifndef _GL_HEADER_OPENAT_PRIV
#define _GL_HEADER_OPENAT_PRIV
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
/* Maximum number of bytes that it is safe to allocate as a single
array on the stack, and that is known as a compile-time constant.
The assumption is that we'll touch the array very quickly, or a
temporary very near the array, provoking an out-of-memory trap. On
some operating systems, there is only one guard page for the stack,
and a page size can be as small as 4096 bytes. Subtract 64 in the
hope that this will let the compiler touch a nearby temporary and
provoke a trap. */
#define SAFER_ALLOCA_MAX (4096 - 64)
#define SAFER_ALLOCA(m) ((m) < SAFER_ALLOCA_MAX ? (m) : SAFER_ALLOCA_MAX)
#if defined PATH_MAX
# define OPENAT_BUFFER_SIZE SAFER_ALLOCA (PATH_MAX)
#elif defined _XOPEN_PATH_MAX
# define OPENAT_BUFFER_SIZE SAFER_ALLOCA (_XOPEN_PATH_MAX)
#else
# define OPENAT_BUFFER_SIZE SAFER_ALLOCA (1024)
#endif
char *openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file);
/* Trying to access a BUILD_PROC_NAME file will fail on systems without
/proc support, and even on systems *with* ProcFS support. Return
nonzero if the failure may be legitimate, e.g., because /proc is not
readable, or the particular .../fd/N directory is not present. */
#define EXPECTED_ERRNO(Errno) \
((Errno) == ENOTDIR || (Errno) == ENOENT \
|| (Errno) == EPERM || (Errno) == EACCES \
|| (Errno) == ENOSYS /* Solaris 8 */ \
|| (Errno) == EOPNOTSUPP /* FreeBSD */)
/* Wrapper function shared among linkat and renameat. */
int at_func2 (int fd1, char const *file1,
int fd2, char const *file2,
int (*func) (char const *file1, char const *file2));
#endif /* _GL_HEADER_OPENAT_PRIV */
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