Macro: ac_c_bigendian_cross

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Synopsis

  `AC_C_BIGENDIAN_CROSS`

Version

  1.3 (2002/09/12) guidod @ ac-archive-0.5.39

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, 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.

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} -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
      ])