##### http://autoconf-archive.cryp.to/ac_c_bigendian_cross.html
#
# SYNOPSIS
#
#   AC_C_BIGENDIAN_CROSS
#
# DESCRIPTION
#
#   Check endianess even when crosscompiling (partially based on the
#   original AC_C_BIGENDIAN).
#
#   The implementation will create a binary, but instead of running the
#   binary it will be grep'ed for some symbols that differ for
#   different endianess of the binary.
#
#   NOTE: The upcoming autoconf 2.53 does include the idea of this
#   macro, what makes it superfluous by then.
#
# LAST MODIFICATION
#
#   2006-10-13
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
#   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 2 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, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
#   As a special exception, the respective Autoconf Macro's copyright
#   owner gives unlimited permission to copy, distribute and modify the
#   configure scripts that are the output of Autoconf when processing
#   the Macro. You need not follow the terms of the GNU General Public
#   License when using or distributing such scripts, even though
#   portions of the text of the Macro appear in them. The GNU General
#   Public License (GPL) does govern all other use of the material that
#   constitutes the Autoconf Macro.
#
#   This special exception to the GPL applies to versions of the
#   Autoconf Macro released by the Autoconf Macro Archive. When you
#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([AC_C_BIGENDIAN_CROSS],
[AC_CACHE_CHECK(whether byte ordering is bigendian, ac_cv_c_bigendian,
[ac_cv_c_bigendian=unknown
# See if sys/param.h defines the BYTE_ORDER macro.
AC_TRY_COMPILE([#include <sys/types.h>
#include <sys/param.h>], [
#if !BYTE_ORDER || !BIG_ENDIAN || !LITTLE_ENDIAN
 bogus endian macros
#endif], [# It does; now see whether it defined to BIG_ENDIAN or not.
AC_TRY_COMPILE([#include <sys/types.h>
#include <sys/param.h>], [
#if BYTE_ORDER != BIG_ENDIAN
 not big endian
#endif], ac_cv_c_bigendian=yes, ac_cv_c_bigendian=no)])
if test $ac_cv_c_bigendian = unknown; then
AC_TRY_RUN([main () {
  /* Are we little or big endian?  From Harbison&Steele.  */
  union
  {
    long l;
    char c[sizeof (long)];
  } u;
  u.l = 1;
  exit (u.c[sizeof (long) - 1] == 1);
}], ac_cv_c_bigendian=no, ac_cv_c_bigendian=yes,
[ echo $ac_n "cross-compiling... " 2>&AC_FD_MSG ])
fi])
if test $ac_cv_c_bigendian = unknown; then
AC_MSG_CHECKING(to probe for byte ordering)
[
cat >conftest.c <<EOF
short ascii_mm[] = { 0x4249, 0x4765, 0x6E44, 0x6961, 0x6E53, 0x7953, 0 };
short ascii_ii[] = { 0x694C, 0x5454, 0x656C, 0x6E45, 0x6944, 0x6E61, 0 };
void _ascii() { char* s = (char*) ascii_mm; s = (char*) ascii_ii; }
short ebcdic_ii[] = { 0x89D3, 0xE3E3, 0x8593, 0x95C5, 0x89C4, 0x9581, 0 };
short ebcdic_mm[] = { 0xC2C9, 0xC785, 0x95C4, 0x8981, 0x95E2, 0xA8E2, 0 };
void _ebcdic() { char* s = (char*) ebcdic_mm; s = (char*) ebcdic_ii; }
int main() { _ascii (); _ebcdic (); return 0; }
EOF
] if test -f conftest.c ; then
     if ${CC-cc} -c conftest.c -o conftest.o && test -f conftest.o ; then
        if test `grep -l BIGenDianSyS conftest.o` ; then
           echo $ac_n ' big endian probe OK, ' 1>&AC_FD_MSG
	   ac_cv_c_bigendian=yes
        fi
        if test `grep -l LiTTleEnDian conftest.o` ; then
           echo $ac_n ' little endian probe OK, ' 1>&AC_FD_MSG
	   if test $ac_cv_c_bigendian = yes ; then
	    ac_cv_c_bigendian=unknown;
           else
            ac_cv_c_bigendian=no
           fi
        fi
	echo $ac_n 'guessing bigendian ...  ' >&AC_FD_MSG
     fi
  fi
AC_MSG_RESULT($ac_cv_c_bigendian)
fi
if test $ac_cv_c_bigendian = yes; then
  AC_DEFINE(WORDS_BIGENDIAN, 1, [whether byteorder is bigendian])
  BYTEORDER=4321
else
  BYTEORDER=1234
fi
AC_DEFINE_UNQUOTED(BYTEORDER, $BYTEORDER, [1234 = LIL_ENDIAN, 4321 = BIGENDIAN])
if test $ac_cv_c_bigendian = unknown; then
  AC_MSG_ERROR(unknown endianess - sorry, please pre-set ac_cv_c_bigendian)
fi
])