Macro: ac_c_bigendian_cross

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# ac_c_bigendian_cross

## Synopsis

`AC_C_BIGENDIAN_CROSS`

## Version

1.2 (2001/08/25) Cross_Compilation @ ac-archive-0.5.32

## Author

Guido Draheim <guidod@gmx.de>

## Description

check endianess even when crosscompiling (partially based on the original AC_C_BIGENDIAN)

the implementation will create a binary, and instead of running the binary it will be grep'ed for some symbols that will look different for different endianess of the binary.

## M4 Source Code

    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} 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
    ])