##### http://autoconf-archive.cryp.to/ac_sys_largefile_sensitive.html
#
# SYNOPSIS
#
#   AC_SYS_LARGEFILE_SENSITIVE
#
# DESCRIPTION
#
#   Check whether the current system is sensitive to -Ddefines making
#   off_t having different types/sizes. Automatically define a config.h
#   symbol LARGEFILE_SENSITIVE if that is the case, otherwise leave
#   everything as is.
#
#   This macro builds on top of AC_SYS_LARGEFILE to detect whether
#   special options are neede to make the code use 64bit off_t - in
#   many setups this will also make the code use 64bit off_t
#   immediatly.
#
#   The common use of a LARGEFILE_SENSITIVE config.h-define is to
#   rename exported functions, usually adding a 64 to the original
#   function name. Such renamings are only needed on systems being both
#   (a) 32bit off_t by default and (b) implementing large.file
#   extensions (as for unix98).
#
#   a renaming section could look like this:
#
#    #if defined LARGEFILE_SENSITIVE && _FILE_OFFSET_BITS+0 == 64
#    #define zzip_open zzip_open64
#    #define zzip_seek zzip_seek64
#    #endif
#
#   for libraries, it is best to take advantage of the prefix-config.h
#   macro, otherwise you want to export a renamed LARGEFILE_SENSITIVE
#   in an installed header file. -> see AX_PREFIX_CONFIG_H
#
# LAST MODIFICATION
#
#   2006-10-13
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
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#
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#   General Public License for more details.
#
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AC_DEFUN([AC_SYS_LARGEFILE_SENSITIVE],[dnl
AC_REQUIRE([AC_SYS_LARGEFILE])dnl
# we know about some internals of ac_sys_largefile here...
AC_MSG_CHECKING(whether system differentiates 64bit off_t by defines)
ac_cv_sys_largefile_sensitive="no"
if test ".$ac_cv_sys_file_offset_bits$ac_cv_sys_large_files" != ".nono"
then ac_cv_sys_largefile_sensitive="yes"
  AC_DEFINE(LARGEFILE_SENSITIVE, 1,
  [whether the system defaults to 32bit off_t but can do 64bit when requested])
fi
AC_MSG_RESULT([$ac_cv_sys_largefile_sensitive])
])