--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2010-12-21  Bruno Haible  <bruno@clisp.org>
+
+	New module 'roundl-ieee'.
+	* modules/roundl-ieee: New file.
+	* m4/roundl.m4 (gl_FUNC_ROUNDL): If gl_FUNC_ROUNDL_IEEE is also used,
+	test whether roundl works according to ISO C 99 with IEC 60559.
+	* m4/roundl-ieee.m4: New file.
+	* modules/roundl-ieee-tests: New file.
+	* tests/test-roundl-ieee.c: New file, based on tests/test-roundl.c.
+	* tests/test-roundl.c (main): Remove signbit tests.
+	* modules/roundl-tests (Depends-on): Remove signbit.
+	* doc/posix-functions/roundl.texi: Mention the new module.
+
 2010-12-21  Bruno Haible  <bruno@clisp.org>
 
 	New module 'truncl-ieee'.

--- a/doc/posix-functions/roundl.texi
+++ b/doc/posix-functions/roundl.texi
@@ -4,9 +4,9 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/roundl.html}
 
-Gnulib module: roundl
+Gnulib module: roundl or roundl-ieee
 
-Portability problems fixed by Gnulib:
+Portability problems fixed by either Gnulib module @code{roundl} or @code{roundl-ieee}:
 @itemize
 @item
 This function is missing on some platforms:
@@ -16,6 +16,14 @@
 glibc 2.8, OSF/1 5.1.
 @end itemize
 
+Portability problems fixed by Gnulib module @code{roundl-ieee}:
+@itemize
+@item
+This function returns a positive zero for a minus zero argument
+on some platforms:
+OSF/1 5.1.
+@end itemize
+
 Portability problems not fixed by Gnulib:
 @itemize
 @end itemize

new file mode 100644
--- /dev/null
+++ b/m4/roundl-ieee.m4
@@ -0,0 +1,15 @@
+# roundl-ieee.m4 serial 1
+dnl Copyright (C) 2010 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl This macro is in a separate file (not in roundl.m4 and not inlined in the
+dnl module description), so that gl_FUNC_ROUNDL can test whether 'aclocal' has
+dnl found uses of this macro.
+
+AC_DEFUN([gl_FUNC_ROUNDL_IEEE],
+[
+  m4_divert_text([INIT_PREPARE], [gl_roundl_required=ieee])
+  AC_REQUIRE([gl_FUNC_ROUNDL])
+])

--- a/m4/roundl.m4
+++ b/m4/roundl.m4
@@ -1,4 +1,4 @@
-# roundl.m4 serial 7
+# roundl.m4 serial 8
 dnl Copyright (C) 2007, 2009-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,7 @@
 
 AC_DEFUN([gl_FUNC_ROUNDL],
 [
+  m4_divert_text([DEFAULTS], [gl_roundl_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   dnl Persuade glibc <math.h> to declare roundl().
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
@@ -15,6 +16,40 @@
     if test "$ROUNDL_LIBM" = missing; then
       REPLACE_ROUNDL=1
     fi
+    m4_ifdef([gl_FUNC_ROUNDL_IEEE], [
+      if test $gl_roundl_required = ieee && test $REPLACE_ROUNDL = 0; then
+        AC_CACHE_CHECK([whether roundl works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_roundl_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $ROUNDL_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_LONG_DOUBLE_MINUS_ZERO_CODE[
+]gl_LONG_DOUBLE_SIGNBIT_CODE[
+int main()
+{
+  /* Test whether roundl (-0.0L) is -0.0L.  */
+  if (signbitl (minus_zerol) && !signbitl (roundl (minus_zerol)))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_roundl_ieee=yes],
+              [gl_cv_func_roundl_ieee=no],
+              [gl_cv_func_roundl_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_roundl_ieee" in
+          *yes) ;;
+          *) REPLACE_ROUNDL=1 ;;
+        esac
+      fi
+    ])
   else
     HAVE_DECL_ROUNDL=0
   fi

new file mode 100644
--- /dev/null
+++ b/modules/roundl-ieee
@@ -0,0 +1,27 @@
+Description:
+roundl() function according to ISO C 99 with IEC 60559.
+
+Files:
+m4/roundl-ieee.m4
+m4/minus-zero.m4
+m4/signbit.m4
+
+Depends-on:
+roundl
+
+configure.ac:
+gl_FUNC_ROUNDL_IEEE
+
+Makefile.am:
+
+Include:
+<math.h>
+
+Link:
+$(ROUNDL_LIBM)
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible

new file mode 100644
--- /dev/null
+++ b/modules/roundl-ieee-tests
@@ -0,0 +1,15 @@
+Files:
+tests/test-roundl-ieee.c
+tests/minus-zero.h
+tests/macros.h
+
+Depends-on:
+float
+signbit
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-roundl-ieee
+check_PROGRAMS += test-roundl-ieee
+test_roundl_ieee_LDADD = $(LDADD) @ROUNDL_LIBM@

--- a/modules/roundl-tests
+++ b/modules/roundl-tests
@@ -9,7 +9,6 @@
 fpucw
 isnanl-nolibm
 float
-signbit
 
 configure.ac:
 

new file mode 100644
--- /dev/null
+++ b/tests/test-roundl-ieee.c
@@ -0,0 +1,38 @@
+/* Test of rounding to nearest, breaking ties away from zero.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#include <config.h>
+
+#include <math.h>
+
+#include "fpucw.h"
+#include "minus-zero.h"
+#include "macros.h"
+
+int
+main ()
+{
+  DECL_LONG_DOUBLE_ROUNDING
+
+  BEGIN_LONG_DOUBLE_ROUNDING ();
+
+  /* Zero.  */
+  ASSERT (!signbit (roundl (0.0L)));
+  ASSERT (!!signbit (roundl (minus_zerol)) == !!signbit (minus_zerol));
+
+  return 0;
+}

--- a/tests/test-roundl.c
+++ b/tests/test-roundl.c
@@ -42,9 +42,7 @@
 
   /* Zero.  */
   ASSERT (roundl (0.0L) == 0.0L);
-  ASSERT (!signbit (roundl (0.0L)));
   ASSERT (roundl (minus_zerol) == 0.0L);
-  ASSERT (!!signbit (minus_zerol) == !!signbit (roundl (minus_zerol)));
   /* Positive numbers.  */
   ASSERT (roundl (0.3L) == 0.0L);
   ASSERT (roundl (0.5L) == 1.0L);