| # =============================================================================== |
| # https://www.gnu.org/software/autoconf-archive/ax_c_float_words_bigendian.html |
| # =============================================================================== |
| # |
| # SYNOPSIS |
| # |
| # AX_C_FLOAT_WORDS_BIGENDIAN([ACTION-IF-TRUE], [ACTION-IF-FALSE], [ACTION-IF-UNKNOWN]) |
| # |
| # DESCRIPTION |
| # |
| # 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 |
| # implementation was inspired by the AC_C_BIGENDIAN macro in autoconf. |
| # |
| # The endianness 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. |
| # |
| # LICENSE |
| # |
| # Copyright (c) 2008 Daniel Amelang <dan@amelang.net> |
| # |
| # Copying and distribution of this file, with or without modification, are |
| # permitted in any medium without royalty provided the copyright notice |
| # and this notice are preserved. This file is offered as-is, without any |
| # warranty. |
| |
| #serial 11 |
| |
| AC_DEFUN([AX_C_FLOAT_WORDS_BIGENDIAN], |
| [AC_CACHE_CHECK(whether float word ordering is bigendian, |
| ax_cv_c_float_words_bigendian, [ |
| |
| ax_cv_c_float_words_bigendian=unknown |
| AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ |
| |
| double d = 90904234967036810337470478905505011476211692735615632014797120844053488865816695273723469097858056257517020191247487429516932130503560650002327564517570778480236724525140520121371739201496540132640109977779420565776568942592.0; |
| |
| ]])], [ |
| |
| if grep noonsees conftest.$ac_objext >/dev/null ; then |
| ax_cv_c_float_words_bigendian=yes |
| fi |
| if grep seesnoon conftest.$ac_objext >/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 |