From cabfe198fd954fbf1c2afd839fd36eb20a803baf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Mon, 11 May 2009 22:11:25 +0200
Subject: [PATCH] Ask for IEEE floating point behavior on Alpha and SH.

* configure.in (CPPFLAGS): Add `-mieee' or `-ieee' on Alpha and SH.

* libguile/numbers.c (guile_ieee_init): Make sure `-mieee' was passed
  when using GCC on Alpha.

* NEWS: Update.
---
 NEWS               |  1 +
 configure.in       | 34 ++++++++++++++++++++++++++++++++++
 libguile/numbers.c |  7 +++++++
 3 files changed, 42 insertions(+)

diff --git a/NEWS b/NEWS
index a65a81361..fa92e327b 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,7 @@ Changes in 1.8.7 (since 1.8.6)
 ** Fix build problem when scm_t_timespec is different from struct timespec
 ** Fix build when compiled with -Wundef -Werror
 ** More build fixes for `alphaev56-dec-osf5.1b' (Tru64)
+** With GCC, always compile with `-mieee' on `alpha*' and `sh*'
 
 ** Allow @ macro to work with (ice-9 syncase)
 
diff --git a/configure.in b/configure.in
index b53b862e7..721394b1c 100644
--- a/configure.in
+++ b/configure.in
@@ -222,6 +222,40 @@ case "$use_64_calls" in
     ;;
 esac
 
+AC_MSG_CHECKING([whether the compiler defaults to IEEE floating point behavior])
+# The following snippet was taken from Gnulib's `fpieee'.  See also the definition
+# of `guile_NaN' in `numbers.c'.
+
+# IEEE behaviour is the default on all CPUs except Alpha and SH
+# (according to the test results of Bruno Haible's ieeefp/fenv_default.m4
+# and the GCC 4.1.2 manual).
+case "$host_cpu" in
+alpha*)
+  # On Alpha systems, a compiler option provides the behaviour.
+  # See the ieee(3) manual page, also available at
+  # <http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/V51B_HTML/MAN/MAN3/0600____.HTM>
+  AC_MSG_RESULT([no])
+  if test -n "$GCC"; then
+    # GCC has the option -mieee.
+    CPPFLAGS="$CPPFLAGS -mieee"
+  else
+    # Compaq (ex-DEC) C has the option -ieee.
+    CPPFLAGS="$CPPFLAGS -ieee"
+  fi
+  ;;
+sh*)
+  AC_MSG_RESULT([no])
+  if test -n "$GCC"; then
+    # GCC has the option -mieee.
+    CPPFLAGS="$CPPFLAGS -mieee"
+  fi
+  ;;
+*)
+  AC_MSG_RESULT([yes])
+  ;;
+esac
+
+
 #--------------------------------------------------------------------
 
 dnl Check for dynamic linking
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 37435b50b..25b0c1a62 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -637,6 +637,13 @@ guile_ieee_init (void)
 
 #if defined (HAVE_ISNAN)
 
+#if defined __GNUC__ && defined __alpha__ && !defined _IEEE_FP
+  /* On Alpha GCC must be passed `-mieee' to provide proper NaN handling.
+     See http://lists.gnu.org/archive/html/bug-gnulib/2009-05/msg00010.html
+     for more details.  */
+# error NaN handling will not work when compiling without -mieee
+#endif
+
 #ifdef NAN
   /* C99 NAN, when available */
   guile_NaN = NAN;