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