--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,23 @@
 2012-02-27  Bruno Haible  <bruno@clisp.org>
 
+	fmod-ieee: Work around test failures on OSF/1, mingw.
+	* m4/fmod-ieee.m4: New file.
+	* m4/fmod.m4 (gl_FUNC_FMOD): If gl_FUNC_FMOD_IEEE is present, test
+	whether fmod works with zero arguments. Replace it if not.
+	* lib/math.in.h (fmod): New declaration.
+	* lib/fmod.c: New file.
+	* m4/math_h.m4 (gl_MATH_H): Test whether fmod is declared.
+	(gl_MATH_H_DEFAULTS): Initialize GNULIB_FMOD, REPLACE_FMOD.
+	* modules/math (Makefile.am): Substitute GNULIB_FMOD, REPLACE_FMOD.
+	* modules/fmod (Files): Add lib/fmod.c.
+	(Depends-on): Add math, isinf, trunc, fma.
+	(configure.ac): Arrange to compile lib/fmod.c if needed.
+	* modules/fmod-ieee (Files): Add m4/fmod-ieee.m4, m4/minus-zero.m4,
+	m4/signbit.m4.
+	(configure.ac): Invoke gl_FUNC_FMOD_IEEE.
+	* tests/test-math-c++.cc: Check the declaration of fmod.
+	* doc/posix-functions/fmod.texi: Mention the fmod-ieee module.
+
 	fmodl-ieee: Fix test failures.
 	* lib/fmodl.c (fmodl): Treat Inf specially.
 	* modules/fmodl (Depends-on): Add isinf.

--- a/doc/posix-functions/fmod.texi
+++ b/doc/posix-functions/fmod.texi
@@ -4,10 +4,21 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/fmod.html}
 
-Gnulib module: fmod
+Gnulib module: fmod or fmod-ieee
+
+Portability problems fixed by either Gnulib module @code{fmod} or @code{fmod-ieee}:
+@itemize
+@end itemize
 
-Portability problems fixed by Gnulib:
+Portability problems fixed by Gnulib module @code{fmod-ieee}:
 @itemize
+@item
+This function has problems when the second argument is zero on some platforms:
+OSF/1 5.1.
+@item
+This function has problems when the first argument is minus zero on some
+platforms:
+mingw, MSVC 9.
 @end itemize
 
 Portability problems not fixed by Gnulib:

new file mode 100644
--- /dev/null
+++ b/lib/fmod.c
@@ -0,0 +1,72 @@
+/* Remainder.
+   Copyright (C) 2011-2012 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>
+
+/* Specification.  */
+#include <math.h>
+
+double
+fmod (double x, double y)
+{
+  if (isinf (y))
+    return x;
+  else
+    {
+      double q = - trunc (x / y);
+      double r = fma (q, y, x); /* = x + q * y, computed in one step */
+      /* Correct possible rounding errors in the quotient x / y.  */
+      if (y >= 0)
+        {
+          if (x >= 0)
+            {
+              /* Expect 0 <= r < y.  */
+              if (r < 0)
+                q += 1, r = fma (q, y, x);
+              else if (r >= y)
+                q -= 1, r = fma (q, y, x);
+            }
+          else
+            {
+              /* Expect - y < r <= 0.  */
+              if (r > 0)
+                q -= 1, r = fma (q, y, x);
+              else if (r <= - y)
+                q += 1, r = fma (q, y, x);
+            }
+        }
+      else
+        {
+          if (x >= 0)
+            {
+              /* Expect 0 <= r < - y.  */
+              if (r < 0)
+                q -= 1, r = fma (q, y, x);
+              else if (r >= - y)
+                q += 1, r = fma (q, y, x);
+            }
+          else
+            {
+              /* Expect y < r <= 0.  */
+              if (r > 0)
+                q += 1, r = fma (q, y, x);
+              else if (r <= y)
+                q -= 1, r = fma (q, y, x);
+            }
+        }
+      return r;
+    }
+}

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -629,6 +629,26 @@
 # endif
 #endif
 
+#if @GNULIB_FMOD@
+# if @REPLACE_FMOD@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef fmod
+#   define fmod rpl_fmod
+#  endif
+_GL_FUNCDECL_RPL (fmod, double, (double x, double y));
+_GL_CXXALIAS_RPL (fmod, double, (double x, double y));
+# else
+_GL_CXXALIAS_SYS (fmod, double, (double x, double y));
+# endif
+_GL_CXXALIASWARN (fmod);
+#elif defined GNULIB_POSIXCHECK
+# undef fmod
+# if HAVE_RAW_DECL_FMOD
+_GL_WARN_ON_USE (fmod, "fmod has portability problems - "
+                 "use gnulib module fmod for portability");
+# endif
+#endif
+
 #if @GNULIB_FMODL@
 # if @REPLACE_FMODL@
 #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)

new file mode 100644
--- /dev/null
+++ b/m4/fmod-ieee.m4
@@ -0,0 +1,15 @@
+# fmod-ieee.m4 serial 1
+dnl Copyright (C) 2012 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 fmod.m4 and not inlined in the
+dnl module description), so that gl_FUNC_FMOD can test whether 'aclocal' has
+dnl found uses of this macro.
+
+AC_DEFUN([gl_FUNC_FMOD_IEEE],
+[
+  m4_divert_text([INIT_PREPARE], [gl_fmod_required=ieee])
+  AC_REQUIRE([gl_FUNC_FMOD])
+])

--- a/m4/fmod.m4
+++ b/m4/fmod.m4
@@ -1,4 +1,4 @@
-# fmod.m4 serial 1
+# fmod.m4 serial 2
 dnl Copyright (C) 2011-2012 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 +6,80 @@
 
 AC_DEFUN([gl_FUNC_FMOD],
 [
+  m4_divert_text([DEFAULTS], [gl_fmod_required=plain])
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
   dnl Determine FMOD_LIBM.
   gl_COMMON_DOUBLE_MATHFUNC([fmod])
+
+  m4_ifdef([gl_FUNC_FMOD_IEEE], [
+    if test $gl_fmod_required = ieee && test $REPLACE_FMOD = 0; then
+      AC_CACHE_CHECK([whether fmod works according to ISO C 99 with IEC 60559],
+        [gl_cv_func_fmod_ieee],
+        [
+          save_LIBS="$LIBS"
+          LIBS="$LIBS $FMOD_LIBM"
+          AC_RUN_IFELSE(
+            [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+/* Compare two numbers with ==.
+   This is a separate function because IRIX 6.5 "cc -O" miscompiles an
+   'x == x' test.  */
+static int
+numeric_equal (double x, double y)
+{
+  return x == y;
+}
+static double dummy (double x, double y) { return 0; }
+int main (int argc, char *argv[])
+{
+  double (*my_fmod) (double, double) = argc ? fmod : dummy;
+  int result = 0;
+  double i;
+  double f;
+  /* Test fmod(...,0.0).
+     This test fails on OSF/1 5.1.  */
+  f = my_fmod (2.0, 0.0);
+  if (numeric_equal (f, f))
+    result |= 1;
+  /* Test fmod(-0.0,...).
+     This test fails on native Windows.  */
+  f = my_fmod (minus_zerod, 2.0);
+  if (!(f == 0.0) || (signbitd (minus_zerod) && !signbitd (f)))
+    result |= 2;
+  return result;
+}
+            ]])],
+            [gl_cv_func_fmod_ieee=yes],
+            [gl_cv_func_fmod_ieee=no],
+            [gl_cv_func_fmod_ieee="guessing no"])
+          LIBS="$save_LIBS"
+        ])
+      case "$gl_cv_func_fmod_ieee" in
+        *yes) ;;
+        *) REPLACE_FMOD=1 ;;
+      esac
+    fi
+  ])
+  if test $REPLACE_FMOD = 1; then
+    dnl Find libraries needed to link lib/fmod.c.
+    AC_REQUIRE([gl_FUNC_TRUNC])
+    AC_REQUIRE([gl_FUNC_FMA])
+    FMOD_LIBM=
+    dnl Append $TRUNC_LIBM to FMOD_LIBM, avoiding gratuitous duplicates.
+    case " $FMOD_LIBM " in
+      *" $TRUNC_LIBM "*) ;;
+      *) FMOD_LIBM="$FMOD_LIBM $TRUNC_LIBM" ;;
+    esac
+    dnl Append $FMA_LIBM to FMOD_LIBM, avoiding gratuitous duplicates.
+    case " $FMOD_LIBM " in
+      *" $FMA_LIBM "*) ;;
+      *) FMOD_LIBM="$FMOD_LIBM $FMA_LIBM" ;;
+    esac
+  fi
 ])

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 66
+# math_h.m4 serial 67
 dnl Copyright (C) 2007-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -41,7 +41,8 @@
   gl_WARN_ON_USE_PREPARE([[#include <math.h>]],
     [acosf acosl asinf asinl atanf atanl
      ceilf ceill copysign copysignf copysignl cosf cosl coshf
-     expf expl fabsf fabsl floorf floorl fma fmaf fmal fmodf fmodl frexpf frexpl
+     expf expl fabsf fabsl floorf floorl fma fmaf fmal
+     fmod fmodf fmodl frexpf frexpl
      ldexpf ldexpl logb logf logl log10f log10l modf modff modfl powf
      remainder remainderf remainderl
      rint rintf rintl round roundf roundl sinf sinl sinhf sqrtf sqrtl
@@ -85,6 +86,7 @@
   GNULIB_FMA=0;        AC_SUBST([GNULIB_FMA])
   GNULIB_FMAF=0;       AC_SUBST([GNULIB_FMAF])
   GNULIB_FMAL=0;       AC_SUBST([GNULIB_FMAL])
+  GNULIB_FMOD=0;       AC_SUBST([GNULIB_FMOD])
   GNULIB_FMODF=0;      AC_SUBST([GNULIB_FMODF])
   GNULIB_FMODL=0;      AC_SUBST([GNULIB_FMODL])
   GNULIB_FREXPF=0;     AC_SUBST([GNULIB_FREXPF])
@@ -211,6 +213,7 @@
   REPLACE_FMA=0;               AC_SUBST([REPLACE_FMA])
   REPLACE_FMAF=0;              AC_SUBST([REPLACE_FMAF])
   REPLACE_FMAL=0;              AC_SUBST([REPLACE_FMAL])
+  REPLACE_FMOD=0;              AC_SUBST([REPLACE_FMOD])
   REPLACE_FMODL=0;             AC_SUBST([REPLACE_FMODL])
   REPLACE_FREXPF=0;            AC_SUBST([REPLACE_FREXPF])
   REPLACE_FREXP=0;             AC_SUBST([REPLACE_FREXP])

--- a/modules/fmod
+++ b/modules/fmod
@@ -2,13 +2,22 @@
 fmod() function: floating-point remainder function.
 
 Files:
+lib/fmod.c
 m4/fmod.m4
 m4/mathfunc.m4
 
 Depends-on:
+math
+isinf           [test $REPLACE_FMOD = 1]
+trunc           [test $REPLACE_FMOD = 1]
+fma             [test $REPLACE_FMOD = 1]
 
 configure.ac:
 gl_FUNC_FMOD
+if test $REPLACE_FMOD = 1; then
+  AC_LIBOBJ([fmod])
+fi
+gl_MATH_MODULE_INDICATOR([fmod])
 
 Makefile.am:
 

--- a/modules/fmod-ieee
+++ b/modules/fmod-ieee
@@ -2,12 +2,16 @@
 fmod() function according to ISO C 99 with IEC 60559.
 
 Files:
+m4/fmod-ieee.m4
+m4/minus-zero.m4
+m4/signbit.m4
 
 Depends-on:
 fmod
 fpieee
 
 configure.ac:
+gl_FUNC_FMOD_IEEE
 
 Makefile.am:
 

--- a/modules/math
+++ b/modules/math
@@ -54,6 +54,7 @@
 	      -e 's/@''GNULIB_FMA''@/$(GNULIB_FMA)/g' \
 	      -e 's/@''GNULIB_FMAF''@/$(GNULIB_FMAF)/g' \
 	      -e 's/@''GNULIB_FMAL''@/$(GNULIB_FMAL)/g' \
+	      -e 's/@''GNULIB_FMOD''@/$(GNULIB_FMOD)/g' \
 	      -e 's/@''GNULIB_FMODF''@/$(GNULIB_FMODF)/g' \
 	      -e 's/@''GNULIB_FMODL''@/$(GNULIB_FMODL)/g' \
 	      -e 's/@''GNULIB_FREXPF''@/$(GNULIB_FREXPF)/g' \
@@ -181,6 +182,7 @@
 	      -e 's|@''REPLACE_FMA''@|$(REPLACE_FMA)|g' \
 	      -e 's|@''REPLACE_FMAF''@|$(REPLACE_FMAF)|g' \
 	      -e 's|@''REPLACE_FMAL''@|$(REPLACE_FMAL)|g' \
+	      -e 's|@''REPLACE_FMOD''@|$(REPLACE_FMOD)|g' \
 	      -e 's|@''REPLACE_FMODL''@|$(REPLACE_FMODL)|g' \
 	      -e 's|@''REPLACE_FREXPF''@|$(REPLACE_FREXPF)|g' \
 	      -e 's|@''REPLACE_FREXP''@|$(REPLACE_FREXP)|g' \

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -137,7 +137,9 @@
 #if GNULIB_TEST_FMODF
 SIGNATURE_CHECK (GNULIB_NAMESPACE::fmodf, float, (float, float));
 #endif
-//SIGNATURE_CHECK (GNULIB_NAMESPACE::fmod, double, (double, double));
+#if GNULIB_TEST_FMOD
+SIGNATURE_CHECK (GNULIB_NAMESPACE::fmod, double, (double, double));
+#endif
 #if GNULIB_TEST_FMODL
 SIGNATURE_CHECK (GNULIB_NAMESPACE::fmodl, long double,
                  (long double, long double));