emacs/lib/pathmax.h

/* Define PATH_MAX somehow.  Requires sys/types.h.
   Copyright (C) 1992, 1999, 2001, 2003, 2005, 2009-2023 Free Software
   Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#ifndef _PATHMAX_H
# define _PATHMAX_H

/* POSIX:2008 defines PATH_MAX to be the maximum number of bytes in a filename,
   including the terminating NUL byte.
   <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html>
   PATH_MAX is not defined on systems which have no limit on filename length,
   such as GNU/Hurd.

   This file does *not* define PATH_MAX always.  Programs that use this file
   can handle the GNU/Hurd case in several ways:
     - Either with a package-wide handling, or with a per-file handling,
     - Either through a
         #ifdef PATH_MAX
       or through a fallback like
         #ifndef PATH_MAX
         # define PATH_MAX 8192
         #endif
       or through a fallback like
         #ifndef PATH_MAX
         # define PATH_MAX pathconf ("/", _PC_PATH_MAX)
         #endif
 */

# include <unistd.h>

# include <limits.h>

# ifndef _POSIX_PATH_MAX
#  define _POSIX_PATH_MAX 256
# endif

/* Don't include sys/param.h if it already has been.  */
# if defined HAVE_SYS_PARAM_H && !defined PATH_MAX && !defined MAXPATHLEN
#  include <sys/param.h>
# endif

# if !defined PATH_MAX && defined MAXPATHLEN
#  define PATH_MAX MAXPATHLEN
# endif

# ifdef __hpux
/* On HP-UX, PATH_MAX designates the maximum number of bytes in a filename,
   *not* including the terminating NUL byte, and is set to 1023.
   Additionally, when _XOPEN_SOURCE is defined to 500 or more, PATH_MAX is
   not defined at all any more.  */
#  undef PATH_MAX
#  define PATH_MAX 1024
# endif

# if defined _WIN32 && ! defined __CYGWIN__
/* The page "Naming Files, Paths, and Namespaces" on msdn.microsoft.com,
   section "Maximum Path Length Limitation",
   <https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#maximum-path-length-limitation>
   explains that the maximum size of a filename, including the terminating
   NUL byte, is 260 = 3 + 256 + 1.
   This is the same value as
     - FILENAME_MAX in <stdio.h>,
     - _MAX_PATH in <stdlib.h>,
     - MAX_PATH in <windef.h>.
   Undefine the original value, because mingw's <limits.h> gets it wrong.  */
#  undef PATH_MAX
#  define PATH_MAX 260
# endif

#endif /* _PATHMAX_H */