AC_C_BIGENDIAN_CROSS
, 

2002-03-18

Guido U. Draheim <guidod@gmx.de>

GPLWithACException
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. 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

guidod's Cross Compilation (released)

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.

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
])