--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,23 @@
+2010-12-21  Bruno Haible  <bruno@clisp.org>
+
+	New module 'floor-ieee'.
+	* modules/floor-ieee: New file.
+	* m4/floor.m4 (gl_FUNC_FLOOR): Require gl_MATH_H_DEFAULTS. If
+	gl_FUNC_FLOOR_IEEE is also used, test whether floor works according to
+	ISO C 99 with IEC 60559.
+	* m4/floor-ieee.m4: New file.
+	* modules/floor (Files): Add lib/floor.c.
+	(Depends-on): Add 'float'.
+	(configure.ac): Invoke gl_MATH_MODULE_INDICATOR.
+	* lib/math.in.h (floor): New declaration.
+	* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize GNULIB_FLOOR,
+	REPLACE_FLOOR.
+	* modules/math (Makefile.am): Substitute GNULIB_FLOOR, REPLACE_FLOOR.
+	* modules/floor-ieee-tests: New file.
+	* tests/test-floor-ieee.c: New file, based on tests/test-floorf-ieee.c.
+	* tests/test-math-c++.cc: Check the signature of 'floor'.
+	* doc/posix-functions/floor.texi: Mention the new module.
+
 2010-12-21  Bruno Haible  <bruno@clisp.org>
 
 	New module 'roundf-ieee'.

--- a/doc/posix-functions/floor.texi
+++ b/doc/posix-functions/floor.texi
@@ -4,10 +4,18 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/floor.html}
 
-Gnulib module: floor
+Gnulib module: floor or floor-ieee
+
+Portability problems fixed by either Gnulib module @code{floor} or @code{floor-ieee}:
+@itemize
+@end itemize
 
-Portability problems fixed by Gnulib:
+Portability problems fixed by Gnulib module @code{floor-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:

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -277,6 +277,19 @@
 # endif
 #endif
 
+#if @GNULIB_FLOOR@
+# if @REPLACE_FLOOR@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   define floor rpl_floor
+#  endif
+_GL_FUNCDECL_RPL (floor, double, (double x));
+_GL_CXXALIAS_RPL (floor, double, (double x));
+# else
+_GL_CXXALIAS_SYS (floor, double, (double x));
+# endif
+_GL_CXXALIASWARN (floor);
+#endif
+
 #if @GNULIB_FLOORL@
 # if @REPLACE_FLOORL@
 #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)

new file mode 100644
--- /dev/null
+++ b/m4/floor-ieee.m4
@@ -0,0 +1,15 @@
+# floor-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 floor.m4 and not inlined in the
+dnl module description), so that gl_FUNC_FLOOR can test whether 'aclocal' has
+dnl found uses of this macro.
+
+AC_DEFUN([gl_FUNC_FLOOR_IEEE],
+[
+  m4_divert_text([INIT_PREPARE], [gl_floor_required=ieee])
+  AC_REQUIRE([gl_FUNC_FLOOR])
+])

--- a/m4/floor.m4
+++ b/m4/floor.m4
@@ -1,16 +1,56 @@
-# floor.m4 serial 4
-dnl Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc.
+# floor.m4 serial 5
+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,
 dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_FLOOR],
 [
+  m4_divert_text([DEFAULTS], [gl_floor_required=plain])
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
   dnl Test whether floor() can be used without libm.
   gl_FUNC_FLOOR_LIBS
   if test "$FLOOR_LIBM" = "?"; then
     FLOOR_LIBM=
   fi
+  m4_ifdef([gl_FUNC_FLOOR_IEEE], [
+    if test $gl_floor_required = ieee && test $REPLACE_FLOOR = 0; then
+      AC_CACHE_CHECK([whether floor works according to ISO C 99 with IEC 60559],
+        [gl_cv_func_floor_ieee],
+        [
+          save_LIBS="$LIBS"
+          LIBS="$LIBS $FLOOR_LIBM"
+          AC_RUN_IFELSE(
+            [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+int main()
+{
+  /* Test whether floor (-0.0) is -0.0.  */
+  if (signbitd (minus_zerod) && !signbitd (floor (minus_zerod)))
+    return 1;
+  return 0;
+}
+            ]])],
+            [gl_cv_func_floor_ieee=yes],
+            [gl_cv_func_floor_ieee=no],
+            [gl_cv_func_floor_ieee="guessing no"])
+          LIBS="$save_LIBS"
+        ])
+      case "$gl_cv_func_floor_ieee" in
+        *yes) ;;
+        *) REPLACE_FLOOR=1 ;;
+      esac
+    fi
+  ])
+  if test $REPLACE_FLOOR = 1; then
+    AC_LIBOBJ([floor])
+    FLOOR_LIBM=
+  fi
   AC_SUBST([FLOOR_LIBM])
 ])
 

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 22
+# math_h.m4 serial 23
 dnl Copyright (C) 2007-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -61,6 +61,7 @@
   GNULIB_CEILL=0;    AC_SUBST([GNULIB_CEILL])
   GNULIB_COSL=0;     AC_SUBST([GNULIB_COSL])
   GNULIB_EXPL=0;     AC_SUBST([GNULIB_EXPL])
+  GNULIB_FLOOR=0;    AC_SUBST([GNULIB_FLOOR])
   GNULIB_FLOORF=0;   AC_SUBST([GNULIB_FLOORF])
   GNULIB_FLOORL=0;   AC_SUBST([GNULIB_FLOORL])
   GNULIB_FREXP=0;    AC_SUBST([GNULIB_FREXP])
@@ -121,6 +122,7 @@
   HAVE_DECL_TRUNCL=1;          AC_SUBST([HAVE_DECL_TRUNCL])
   REPLACE_CEILF=0;             AC_SUBST([REPLACE_CEILF])
   REPLACE_CEILL=0;             AC_SUBST([REPLACE_CEILL])
+  REPLACE_FLOOR=0;             AC_SUBST([REPLACE_FLOOR])
   REPLACE_FLOORF=0;            AC_SUBST([REPLACE_FLOORF])
   REPLACE_FLOORL=0;            AC_SUBST([REPLACE_FLOORL])
   REPLACE_FREXP=0;             AC_SUBST([REPLACE_FREXP])

--- a/modules/floor
+++ b/modules/floor
@@ -2,13 +2,16 @@
 floor() function: round towards negative infinity.
 
 Files:
+lib/floor.c
 m4/floor.m4
 
 Depends-on:
 math
+float
 
 configure.ac:
 gl_FUNC_FLOOR
+gl_MATH_MODULE_INDICATOR([floor])
 
 Makefile.am:
 

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

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

--- a/modules/math
+++ b/modules/math
@@ -33,6 +33,7 @@
 	      -e 's|@''GNULIB_CEILL''@|$(GNULIB_CEILL)|g' \
 	      -e 's|@''GNULIB_COSL''@|$(GNULIB_COSL)|g' \
 	      -e 's|@''GNULIB_EXPL''@|$(GNULIB_EXPL)|g' \
+	      -e 's|@''GNULIB_FLOOR''@|$(GNULIB_FLOOR)|g' \
 	      -e 's|@''GNULIB_FLOORF''@|$(GNULIB_FLOORF)|g' \
 	      -e 's|@''GNULIB_FLOORL''@|$(GNULIB_FLOORL)|g' \
 	      -e 's|@''GNULIB_FREXP''@|$(GNULIB_FREXP)|g' \
@@ -92,6 +93,7 @@
 	      -e 's|@''HAVE_DECL_TRUNCL''@|$(HAVE_DECL_TRUNCL)|g' \
 	      -e 's|@''REPLACE_CEILF''@|$(REPLACE_CEILF)|g' \
 	      -e 's|@''REPLACE_CEILL''@|$(REPLACE_CEILL)|g' \
+	      -e 's|@''REPLACE_FLOOR''@|$(REPLACE_FLOOR)|g' \
 	      -e 's|@''REPLACE_FLOORF''@|$(REPLACE_FLOORF)|g' \
 	      -e 's|@''REPLACE_FLOORL''@|$(REPLACE_FLOORL)|g' \
 	      -e 's|@''REPLACE_FREXP''@|$(REPLACE_FREXP)|g' \

new file mode 100644
--- /dev/null
+++ b/tests/test-floor-ieee.c
@@ -0,0 +1,32 @@
+/* Test of rounding towards negative infinity.
+   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 of the License, 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, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <math.h>
+
+#include "minus-zero.h"
+#include "macros.h"
+
+int
+main ()
+{
+  /* Zero.  */
+  ASSERT (!signbit (floor (0.0)));
+  ASSERT (!!signbit (floor (minus_zerod)) == !!signbit (minus_zerod));
+
+  return 0;
+}

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -96,6 +96,10 @@
 SIGNATURE_CHECK (GNULIB_NAMESPACE::floorf, float, (float));
 #endif
 
+#if GNULIB_TEST_FLOOR
+SIGNATURE_CHECK (GNULIB_NAMESPACE::floor, double, (double));
+#endif
+
 #if GNULIB_TEST_FLOORL
 SIGNATURE_CHECK (GNULIB_NAMESPACE::floorl, long double, (long double));
 #endif