tools/missing-macros/src/m4/as-unaligned-access.m4

   1 dnl AS_UNALIGNED_ACCESS
   2
   3 dnl check if unaligned memory access works correctly
   4 AC_DEFUN([AS_UNALIGNED_ACCESS], [
   5   AC_MSG_CHECKING([if unaligned memory access works correctly])
   6   if test x"$as_cv_unaligned_access" = x ; then
   7     case $host in
   8       alpha*|arm*|hp*|mips*|sh*|sparc*|ia64*)
   9         _AS_ECHO_N([(blacklisted) ])
  10         as_cv_unaligned_access=no
  11         ;;
  12       i?86*|x86_64|amd64|powerpc*|m68k*|cris*)
  13         _AS_ECHO_N([(whitelisted) ])
  14         as_cv_unaligned_access=yes
  15         ;;
  16     esac
  17   else
  18     _AS_ECHO_N([(cached) ])
  19   fi
  20   if test x"$as_cv_unaligned_access" = x ; then
  21     AC_TRY_RUN([
  22 int main(int argc, char **argv)
  23 {
  24   char array[] = "ABCDEFGH";
  25   unsigned int iarray[2];
  26   memcpy(iarray,array,8);
  27 #define GET(x) (*(unsigned int *)((char *)iarray + (x)))
  28   if(GET(0) != 0x41424344 && GET(0) != 0x44434241) return 1;
  29   if(GET(1) != 0x42434445 && GET(1) != 0x45444342) return 1;
  30   if(GET(2) != 0x43444546 && GET(2) != 0x46454443) return 1;
  31   if(GET(3) != 0x44454647 && GET(3) != 0x47464544) return 1;
  32   return 0;
  33 }
  34     ], as_cv_unaligned_access="yes", as_cv_unaligned_access="no")
  35   fi
  36   AC_MSG_RESULT($as_cv_unaligned_access)
  37   if test "$as_cv_unaligned_access" = "yes"; then
  38     AC_DEFINE_UNQUOTED(HAVE_UNALIGNED_ACCESS, 1,
  39       [defined if unaligned memory access works correctly])
  40   fi
  41 ])