--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2011-10-09  Bruno Haible  <bruno@clisp.org>
+
+	New module 'copysignl'.
+	* lib/math.in.h (copysignl): New declaration.
+	* lib/copysignl.c: New file.
+	* m4/copysignl.m4: New file.
+	* m4/math_h.m4 (gl_MATH_H): Test whether copysignl is declared.
+	(gl_MATH_H_DEFAULTS): Initialize GNULIB_COPYSIGNL, HAVE_COPYSIGNL.
+	* modules/math (Makefile.am): Substitute GNULIB_COPYSIGNL,
+	HAVE_COPYSIGNL.
+	* modules/copysignl: New file.
+	* tests/test-math-c++.cc: Check the declaration of copysignl.
+	* modules/math-c++-tests (Makefile.am): Link test-math-c++ against
+	$(COPYSIGNL_LIBM). Needed on IRIX 6.5 with cc.
+	* doc/posix-functions/copysignl.texi: Mention the new module.
+
 2011-10-09  Bruno Haible  <bruno@clisp.org>
 
 	Tests for module 'copysignf'.

--- a/doc/posix-functions/copysignl.texi
+++ b/doc/posix-functions/copysignl.texi
@@ -4,15 +4,15 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/copysignl.html}
 
-Gnulib module: ---
+Gnulib module: copysignl
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+This function is missing on some platforms:
+FreeBSD 5.2.1, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, older IRIX 6.5, Solaris 9, Cygwin, MSVC 9, Interix 3.5.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
-@item
-This function is missing on some platforms:
-FreeBSD 5.2.1, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 9, Cygwin, MSVC 9, Interix 3.5.
 @end itemize

new file mode 100644
--- /dev/null
+++ b/lib/copysignl.c
@@ -0,0 +1,26 @@
+/* Copy sign into another 'long double' number.
+   Copyright (C) 2011 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>
+
+long double
+copysignl (long double x, long double y)
+{
+  return (signbit (x) != signbit (y) ? - x : x);
+}

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -302,6 +302,20 @@
 # endif
 #endif
 
+#if @GNULIB_COPYSIGNL@
+# if !@HAVE_COPYSIGNL@
+_GL_FUNCDECL_SYS (copysignl, long double, (long double x, long double y));
+# endif
+_GL_CXXALIAS_SYS (copysignl, long double, (long double x, long double y));
+_GL_CXXALIASWARN (copysignl);
+#elif defined GNULIB_POSIXCHECK
+# undef copysignl
+# if HAVE_RAW_DECL_COPYSIGNL
+_GL_WARN_ON_USE (copysign, "copysignl is unportable - "
+                 "use gnulib module copysignl for portability");
+# endif
+#endif
+
 
 #if @GNULIB_COSF@
 # if !@HAVE_COSF@

new file mode 100644
--- /dev/null
+++ b/m4/copysignl.m4
@@ -0,0 +1,19 @@
+# copysignl.m4 serial 1
+dnl Copyright (C) 2011 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_COPYSIGNL],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
+  dnl Determine COPYSIGNL_LIBM.
+  gl_MATHFUNC([copysignl], [long double], [(long double, long double)])
+  if test $gl_cv_func_copysignl_no_libm = no \
+     && test $gl_cv_func_copysignl_in_libm = no; then
+    HAVE_COPYSIGNL=0
+    COPYSIGNL_LIBM=
+  fi
+  AC_SUBST([COPYSIGNL_LIBM])
+])

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 49
+# math_h.m4 serial 50
 dnl Copyright (C) 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -40,7 +40,7 @@
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[#include <math.h>]],
     [acosf acosl asinf asinl atanf atanl
-     ceilf ceill copysign copysignf cosf cosl coshf
+     ceilf ceill copysign copysignf copysignl cosf cosl coshf
      expf expl fabsf floorf floorl fmodf frexpf frexpl
      ldexpf ldexpl logb logf logl log10f modff powf
      round roundf roundl sinf sinl sinhf sqrtf sqrtl
@@ -70,6 +70,7 @@
   GNULIB_CEILL=0;     AC_SUBST([GNULIB_CEILL])
   GNULIB_COPYSIGN=0;  AC_SUBST([GNULIB_COPYSIGN])
   GNULIB_COPYSIGNF=0; AC_SUBST([GNULIB_COPYSIGNF])
+  GNULIB_COPYSIGNL=0; AC_SUBST([GNULIB_COPYSIGNL])
   GNULIB_COSF=0;      AC_SUBST([GNULIB_COSF])
   GNULIB_COSL=0;      AC_SUBST([GNULIB_COSL])
   GNULIB_COSHF=0;     AC_SUBST([GNULIB_COSHF])
@@ -122,6 +123,7 @@
   HAVE_ATAN2F=1;               AC_SUBST([HAVE_ATAN2F])
   HAVE_COPYSIGN=1;             AC_SUBST([HAVE_COPYSIGN])
   HAVE_COPYSIGNF=1;            AC_SUBST([HAVE_COPYSIGNF])
+  HAVE_COPYSIGNL=1;            AC_SUBST([HAVE_COPYSIGNL])
   HAVE_COSF=1;                 AC_SUBST([HAVE_COSF])
   HAVE_COSL=1;                 AC_SUBST([HAVE_COSL])
   HAVE_COSHF=1;                AC_SUBST([HAVE_COSHF])

new file mode 100644
--- /dev/null
+++ b/modules/copysignl
@@ -0,0 +1,32 @@
+Description:
+copysignl() function: copy sign into another 'long double' number.
+
+Files:
+lib/copysignl.c
+m4/copysignl.m4
+m4/mathfunc.m4
+
+Depends-on:
+math
+signbit         [test $HAVE_COPYSIGNL = 0]
+
+configure.ac:
+gl_FUNC_COPYSIGNL
+if test $HAVE_COPYSIGNL = 0; then
+  AC_LIBOBJ([copysignl])
+fi
+gl_MATH_MODULE_INDICATOR([copysignl])
+
+Makefile.am:
+
+Include:
+<math.h>
+
+Link:
+$(COPYSIGNL_LIBM)
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible

--- a/modules/math
+++ b/modules/math
@@ -40,6 +40,7 @@
 	      -e 's/@''GNULIB_CEILL''@/$(GNULIB_CEILL)/g' \
 	      -e 's/@''GNULIB_COPYSIGN''@/$(GNULIB_COPYSIGN)/g' \
 	      -e 's/@''GNULIB_COPYSIGNF''@/$(GNULIB_COPYSIGNF)/g' \
+	      -e 's/@''GNULIB_COPYSIGNL''@/$(GNULIB_COPYSIGNL)/g' \
 	      -e 's/@''GNULIB_COSF''@/$(GNULIB_COSF)/g' \
 	      -e 's/@''GNULIB_COSL''@/$(GNULIB_COSL)/g' \
 	      -e 's/@''GNULIB_COSHF''@/$(GNULIB_COSHF)/g' \
@@ -92,6 +93,7 @@
 	      -e 's|@''HAVE_ATAN2F''@|$(HAVE_ATAN2F)|g' \
 	      -e 's|@''HAVE_COPYSIGN''@|$(HAVE_COPYSIGN)|g' \
 	      -e 's|@''HAVE_COPYSIGNF''@|$(HAVE_COPYSIGNF)|g' \
+	      -e 's|@''HAVE_COPYSIGNL''@|$(HAVE_COPYSIGNL)|g' \
 	      -e 's|@''HAVE_COSF''@|$(HAVE_COSF)|g' \
 	      -e 's|@''HAVE_COSL''@|$(HAVE_COSL)|g' \
 	      -e 's|@''HAVE_COSHF''@|$(HAVE_COSHF)|g' \

--- a/modules/math-c++-tests
+++ b/modules/math-c++-tests
@@ -16,4 +16,5 @@
 TESTS += test-math-c++
 check_PROGRAMS += test-math-c++
 test_math_c___SOURCES = test-math-c++.cc test-math-c++2.cc
+test_math_c___LDADD = $(LDADD) $(COPYSIGNL_LIBM)
 endif

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -153,6 +153,11 @@
 SIGNATURE_CHECK (GNULIB_NAMESPACE::ceill, long double, (long double));
 #endif
 
+#if GNULIB_TEST_COPYSIGNL
+SIGNATURE_CHECK (GNULIB_NAMESPACE::copysignl, long double,
+                 (long double, long double));
+#endif
+
 #if GNULIB_TEST_COSL
 SIGNATURE_CHECK (GNULIB_NAMESPACE::cosl, long double, (long double));
 #endif