| # AX_C_FLOAT_WORDS_BIGENDIAN ([ACTION-IF-TRUE], [ACTION-IF-FALSE], |
| # [ACTION-IF-UNKNOWN]) |
| # |
| # Checks the ordering of words within a multi-word float. This check |
| # is necessary because on some systems (e.g. certain ARM systems), the |
| # float word ordering can be different from the byte ordering. In a |
| # multi-word float context, "big-endian" implies that the word containing |
| # the sign bit is found in the memory location with the lowest address. |
| # This implemenation was inspired by the AC_C_BIGENDIAN macro in autoconf. |
| # ------------------------------------------------------------------------- |
| AC_DEFUN([AX_C_FLOAT_WORDS_BIGENDIAN], |
| [AC_CACHE_CHECK(whether float word ordering is bigendian, |
| ax_cv_c_float_words_bigendian, [ |
| |
| # The endianess is detected by first compiling C code that contains a special |
| # double float value, then grepping the resulting object file for certain |
| # strings of ascii values. The double is specially crafted to have a |
| # binary representation that corresponds with a simple string. In this |
| # implementation, the string "noonsees" was selected because the individual |
| # word values ("noon" and "sees") are palindromes, thus making this test |
| # byte-order agnostic. If grep finds the string "noonsees" in the object |
| # file, the target platform stores float words in big-endian order. If grep |
| # finds "seesnoon", float words are in little-endian order. If neither value |
| # is found, the user is instructed to specify the ordering. |
| |
| ax_cv_c_float_words_bigendian=unknown |
| AC_LINK_IFELSE([AC_LANG_SOURCE([[ |
| |
| double d __attribute__((used)) = 90904234967036810337470478905505011476211692735615632014797120844053488865816695273723469097858056257517020191247487429516932130503560650002327564517570778480236724525140520121371739201496540132640109977779420565776568942592.0; |
| int main() { return 0; } |
| |
| ]])], [ |
| |
| if strings -a conftest$ac_exeext | grep noonsees >/dev/null ; then |
| ax_cv_c_float_words_bigendian=yes |
| fi |
| if strings -a conftest$ac_exeext | grep seesnoon >/dev/null ; then |
| if test "$ax_cv_c_float_words_bigendian" = unknown; then |
| ax_cv_c_float_words_bigendian=no |
| else |
| ax_cv_c_float_words_bigendian=unknown |
| fi |
| fi |
| |
| ])]) |
| |
| case $ax_cv_c_float_words_bigendian in |
| yes) |
| m4_default([$1], |
| [AC_DEFINE([FLOAT_WORDS_BIGENDIAN], 1, |
| [Define to 1 if your system stores words within floats |
| with the most significant word first])]) ;; |
| no) |
| $2 ;; |
| *) |
| m4_default([$3], |
| [AC_MSG_ERROR([ |
| |
| Unknown float word ordering. You need to manually preset |
| ax_cv_c_float_words_bigendian=no (or yes) according to your system. |
| |
| ])]) ;; |
| esac |
| |
| ])# AX_C_FLOAT_WORDS_BIGENDIAN |