# * Check for various properties of floating point *
# **************************************************
-AC_MSG_CHECKING(whether C doubles are little-endian IEEE 754 binary64)
-AC_CACHE_VAL(ac_cv_little_endian_double, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <string.h>
-int main() {
- double x = 9006104071832581.0;
- if (memcmp(&x, "\x05\x04\x03\x02\x01\xff\x3f\x43", 8) == 0)
- return 0;
- else
- return 1;
-}
-]])],
-[ac_cv_little_endian_double=yes],
-[ac_cv_little_endian_double=no],
-[ac_cv_little_endian_double=no])])
-AC_MSG_RESULT($ac_cv_little_endian_double)
-if test "$ac_cv_little_endian_double" = yes
-then
- AC_DEFINE(DOUBLE_IS_LITTLE_ENDIAN_IEEE754, 1,
- [Define if C doubles are 64-bit IEEE 754 binary format, stored
- with the least significant byte first])
-fi
-
-AC_MSG_CHECKING(whether C doubles are big-endian IEEE 754 binary64)
-AC_CACHE_VAL(ac_cv_big_endian_double, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <string.h>
-int main() {
- double x = 9006104071832581.0;
- if (memcmp(&x, "\x43\x3f\xff\x01\x02\x03\x04\x05", 8) == 0)
- return 0;
- else
- return 1;
-}
-]])],
-[ac_cv_big_endian_double=yes],
-[ac_cv_big_endian_double=no],
-[ac_cv_big_endian_double=no])])
-AC_MSG_RESULT($ac_cv_big_endian_double)
-if test "$ac_cv_big_endian_double" = yes
+AX_C_FLOAT_WORDS_BIGENDIAN
+if test "$ax_cv_c_float_words_bigendian" = "yes"
then
AC_DEFINE(DOUBLE_IS_BIG_ENDIAN_IEEE754, 1,
[Define if C doubles are 64-bit IEEE 754 binary format, stored
with the most significant byte first])
-fi
-
-# Some ARM platforms use a mixed-endian representation for doubles.
-# While Python doesn't currently have full support for these platforms
-# (see e.g., issue 1762561), we can at least make sure that float <-> string
-# conversions work.
-AC_MSG_CHECKING(whether C doubles are ARM mixed-endian IEEE 754 binary64)
-AC_CACHE_VAL(ac_cv_mixed_endian_double, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <string.h>
-int main() {
- double x = 9006104071832581.0;
- if (memcmp(&x, "\x01\xff\x3f\x43\x05\x04\x03\x02", 8) == 0)
- return 0;
- else
- return 1;
-}
-]])],
-[ac_cv_mixed_endian_double=yes],
-[ac_cv_mixed_endian_double=no],
-[ac_cv_mixed_endian_double=no])])
-AC_MSG_RESULT($ac_cv_mixed_endian_double)
-if test "$ac_cv_mixed_endian_double" = yes
+elif test "$ax_cv_c_float_words_bigendian" = "no"
then
+ AC_DEFINE(DOUBLE_IS_LITTLE_ENDIAN_IEEE754, 1,
+ [Define if C doubles are 64-bit IEEE 754 binary format, stored
+ with the least significant byte first])
+else
+ # Some ARM platforms use a mixed-endian representation for doubles.
+ # While Python doesn't currently have full support for these platforms
+ # (see e.g., issue 1762561), we can at least make sure that float <-> string
+ # conversions work.
+ # FLOAT_WORDS_BIGENDIAN doesnt actually detect this case, but if it's not big
+ # or little, then it must be this?
AC_DEFINE(DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754, 1,
[Define if C doubles are 64-bit IEEE 754 binary format, stored
in ARM mixed-endian order (byte order 45670123)])
--- /dev/null
+# ===============================================================================
+# 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
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