mirror of https://github.com/python/cpython
84 lines
3.1 KiB
Plaintext
84 lines
3.1 KiB
Plaintext
# ===============================================================================
|
|
# 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
|