--- /dev/null
+/* Internals for openat-like functions.
+
+ Copyright (C) 2005-2006, 2009-2013 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/>. */
+
+/* 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 */