From e270b13cb98d39b175f04d5b3a53df723b19703c Mon Sep 17 00:00:00 2001
From: vlefevre <vlefevre@280ebfd0-de03-0410-8827-d642c229c3f4>
Date: Thu, 9 Jan 2020 14:37:48 +0000
Subject: [acinclude.m4,configure.ac]   * Moved the code that tries to
 determine the format of double from     configure.ac to acinclude.m4 in
 MPFR_CONFIGS (as required), just     before the one for long double.   *
 Added a FIXME comment: This code uses AC_RUN_IFELSE, which cannot     run the
 test when cross-compiling; use a test like for long double     instead.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@13663 280ebfd0-de03-0410-8827-d642c229c3f4
---
 acinclude.m4 | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

(limited to 'acinclude.m4')

diff --git a/acinclude.m4 b/acinclude.m4
index 437923dd3..fc98848f9 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -526,7 +526,44 @@ AC_RUN_IFELSE([AC_LANG_PROGRAM([[
 
 LIBS="$saved_LIBS"
 
-dnl Now try to check the long double format
+dnl Try to determine the format of double
+dnl FIXME: Use a test like for long double instead of AC_RUN_IFELSE,
+dnl        which cannot run the test when cross-compiling.
+AC_MSG_CHECKING(format of floating-point type `double')
+AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+]], [[
+union ieee_double_extract
+{
+  double d;
+  unsigned char x[8];
+} t;
+t.d = 2.877939254133025759330166692961938679218292236328125; /* exact */
+if (sizeof (double) != 8)
+   return 0;
+if (sizeof (unsigned char) != 1)
+   return 0;
+if (t.x[0] == 1 && t.x[1] == 2 && t.x[2] == 3 && t.x[3] == 4 &&
+    t.x[4] == 5 && t.x[5] == 6 && t.x[6] == 7 && t.x[7] == 64)
+   return 1; /* little endian */
+else if (t.x[7] == 1 && t.x[6] == 2 && t.x[5] == 3 && t.x[4] == 4 &&
+    t.x[3] == 5 && t.x[2] == 6 && t.x[1] == 7 && t.x[0] == 64)
+   return 2; /* big endian */
+else
+   return 0; /* unknown */
+]])],
+   [mpfr_ieee_double=$?],
+   [mpfr_ieee_double=$?],
+   [mpfr_ieee_double=0])
+case "$mpfr_ieee_double" in
+  1) AC_MSG_RESULT([IEEE little endian])
+     AC_DEFINE(HAVE_DOUBLE_IEEE_LITTLE_ENDIAN) ;;
+  2) AC_MSG_RESULT([IEEE big endian])
+     AC_DEFINE(HAVE_DOUBLE_IEEE_BIG_ENDIAN) ;;
+  *) AC_MSG_RESULT([unknown])
+     AC_MSG_WARN([format of `double' not recognized]) ;;
+esac
+
+dnl Now try to determine the format of long double
 MPFR_C_LONG_DOUBLE_FORMAT
 
 dnl Check if thread-local variables are supported.
-- 
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