src/expat/conftools/ac_c_bigendian_cross.m4

   1 dnl @synopsis AC_C_BIGENDIAN_CROSS
   2 dnl
   3 dnl Check endianess even when crosscompiling
   4 dnl (partially based on the original AC_C_BIGENDIAN).
   5 dnl
   6 dnl The implementation will create a binary, and instead of running
   7 dnl the binary it will be grep'ed for some symbols that will look
   8 dnl different for different endianess of the binary.
   9 dnl
  10 dnl @version $Id$
  11 dnl @author Guido Draheim <guidod@gmx.de>
  12 dnl
  13 AC_DEFUN([AC_C_BIGENDIAN_CROSS],
  14 [AC_CACHE_CHECK(whether byte ordering is bigendian, ac_cv_c_bigendian,
  15 [ac_cv_c_bigendian=unknown
  16 # See if sys/param.h defines the BYTE_ORDER macro.
  17 AC_TRY_COMPILE([#include <sys/types.h>
  18 #include <sys/param.h>], [
  19 #if !BYTE_ORDER || !BIG_ENDIAN || !LITTLE_ENDIAN
  20  bogus endian macros
  21 #endif], [# It does; now see whether it defined to BIG_ENDIAN or not.
  22 AC_TRY_COMPILE([#include <sys/types.h>
  23 #include <sys/param.h>], [
  24 #if BYTE_ORDER != BIG_ENDIAN
  25  not big endian
  26 #endif], ac_cv_c_bigendian=yes, ac_cv_c_bigendian=no)])
  27 if test $ac_cv_c_bigendian = unknown; then
  28 AC_TRY_RUN([main () {
  29   /* Are we little or big endian?  From Harbison&Steele.  */
  30   union
  31   {
  32     long l;
  33     char c[sizeof (long)];
  34   } u;
  35   u.l = 1;
  36   exit (u.c[sizeof (long) - 1] == 1);
  37 }], ac_cv_c_bigendian=no, ac_cv_c_bigendian=yes,
  38 [ echo $ac_n "cross-compiling... " 2>&AC_FD_MSG ])
  39 fi])
  40 if test $ac_cv_c_bigendian = unknown; then
  41 AC_MSG_CHECKING(to probe for byte ordering)
  42 [
  43 cat >conftest.c <<EOF
  44 short ascii_mm[] = { 0x4249, 0x4765, 0x6E44, 0x6961, 0x6E53, 0x7953, 0 };
  45 short ascii_ii[] = { 0x694C, 0x5454, 0x656C, 0x6E45, 0x6944, 0x6E61, 0 };
  46 void _ascii() { char* s = (char*) ascii_mm; s = (char*) ascii_ii; }
  47 short ebcdic_ii[] = { 0x89D3, 0xE3E3, 0x8593, 0x95C5, 0x89C4, 0x9581, 0 };
  48 short ebcdic_mm[] = { 0xC2C9, 0xC785, 0x95C4, 0x8981, 0x95E2, 0xA8E2, 0 };
  49 void _ebcdic() { char* s = (char*) ebcdic_mm; s = (char*) ebcdic_ii; }
  50 int main() { _ascii (); _ebcdic (); return 0; }
  51 EOF
  52 ] if test -f conftest.c ; then
  53      if ${CC-cc} -c conftest.c -o conftest.o && test -f conftest.o ; then
  54         if test `grep -l BIGenDianSyS conftest.o` ; then
  55            echo $ac_n ' big endian probe OK, ' 1>&AC_FD_MSG
  56            ac_cv_c_bigendian=yes
  57         fi
  58         if test `grep -l LiTTleEnDian conftest.o` ; then
  59            echo $ac_n ' little endian probe OK, ' 1>&AC_FD_MSG
  60            if test $ac_cv_c_bigendian = yes ; then
  61             ac_cv_c_bigendian=unknown;
  62            else
  63             ac_cv_c_bigendian=no
  64            fi
  65         fi
  66         echo $ac_n 'guessing bigendian ...  ' >&AC_FD_MSG
  67      fi
  68   fi
  69 AC_MSG_RESULT($ac_cv_c_bigendian)
  70 fi
  71 if test $ac_cv_c_bigendian = yes; then
  72   AC_DEFINE(WORDS_BIGENDIAN, 1, [whether byteorder is bigendian])
  73   BYTEORDER=4321
  74 else
  75   BYTEORDER=1234
  76 fi
  77 AC_DEFINE_UNQUOTED(BYTEORDER, $BYTEORDER, [1234 = LIL_ENDIAN, 4321 = BIGENDIAN])
  78 if test $ac_cv_c_bigendian = unknown; then
  79   AC_MSG_ERROR(unknown endianess - sorry, please pre-set ac_cv_c_bigendian)
  80 fi
  81 ])