--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2011-10-08  Bruno Haible  <bruno@clisp.org>
 
+	New module 'log10f'.
+	* lib/math.in.h (log10f): New declaration.
+	* lib/log10f.c: New file.
+	* m4/log10f.m4: New file.
+	* m4/math_h.m4 (gl_MATH_H): Test whether log10f is declared.
+	(gl_MATH_H_DEFAULTS): Initialize GNULIB_LOG10F, HAVE_LOG10F.
+	* modules/math (Makefile.am): Substitute GNULIB_LOG10F, HAVE_LOG10F.
+	* modules/log10f: New file.
+	* tests/test-math-c++.cc: Check the declaration of log10f.
+	* doc/posix-functions/log10f.texi: Mention the new module.
+
 	log10: Use a .m4 file.
 	* m4/log10.m4: New file.
 	* modules/log10 (Files): Add it.

--- a/doc/posix-functions/log10f.texi
+++ b/doc/posix-functions/log10f.texi
@@ -4,14 +4,10 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/log10f.html}
 
-Gnulib module: ---
+Gnulib module: log10f
 
 Portability problems fixed by Gnulib:
 @itemize
-@end itemize
-
-Portability problems not fixed by Gnulib:
-@itemize
 @item
 This function is missing on some platforms:
 Minix 3.1.8, AIX 5.1, Solaris 9.
@@ -19,3 +15,7 @@
 This function is only defined as a macro with arguments on some platforms:
 MSVC 9.
 @end itemize
+
+Portability problems not fixed by Gnulib:
+@itemize
+@end itemize

new file mode 100644
--- /dev/null
+++ b/lib/log10f.c
@@ -0,0 +1,26 @@
+/* Base 10 logarithmic function.
+   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>
+
+float
+log10f (float x)
+{
+  return (float) log10 ((double) x);
+}

--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -529,6 +529,22 @@
 #endif
 
 
+#if @GNULIB_LOG10F@
+# if !@HAVE_LOG10F@
+#  undef log10f
+_GL_FUNCDECL_SYS (log10f, float, (float x));
+# endif
+_GL_CXXALIAS_SYS (log10f, float, (float x));
+_GL_CXXALIASWARN (log10f);
+#elif defined GNULIB_POSIXCHECK
+# undef log10f
+# if HAVE_RAW_DECL_LOG10F
+_GL_WARN_ON_USE (log10f, "log10f is unportable - "
+                 "use gnulib module log10f for portability");
+# endif
+#endif
+
+
 #if @GNULIB_MODFF@
 # if !@HAVE_MODFF@
 #  undef modff

new file mode 100644
--- /dev/null
+++ b/m4/log10f.m4
@@ -0,0 +1,25 @@
+# log10f.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_LOG10F],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_LOG10])
+
+  dnl Test whether log10f() exists. Assume that log10f(), if it exists, is
+  dnl defined in the same library as log10().
+  save_LIBS="$LIBS"
+  LIBS="$LIBS $LOG10_LIBM"
+  AC_CHECK_FUNCS([log10f])
+  LIBS="$save_LIBS"
+  if test $ac_cv_func_log10f = yes; then
+    LOG10F_LIBM="$LOG10_LIBM"
+  else
+    HAVE_LOG10F=0
+    LOG10F_LIBM="$LOG10_LIBM"
+  fi
+  AC_SUBST([LOG10F_LIBM])
+])

--- a/m4/math_h.m4
+++ b/m4/math_h.m4
@@ -1,4 +1,4 @@
-# math_h.m4 serial 34
+# math_h.m4 serial 35
 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,
@@ -41,7 +41,8 @@
   gl_WARN_ON_USE_PREPARE([[#include <math.h>]],
     [acosl asinl atanl ceilf ceill cosl expf expl fabsf floorf floorl fmodf
      frexpf frexpl
-     ldexpf ldexpl logb logf logl modff round roundf roundl sinl sqrtf sqrtl
+     ldexpf ldexpl logb logf logl log10f modff
+     round roundf roundl sinl sqrtf sqrtl
      tanl trunc truncf truncl])
 ])
 
@@ -84,6 +85,7 @@
   GNULIB_LOGB=0;     AC_SUBST([GNULIB_LOGB])
   GNULIB_LOGF=0;     AC_SUBST([GNULIB_LOGF])
   GNULIB_LOGL=0;     AC_SUBST([GNULIB_LOGL])
+  GNULIB_LOG10F=0;   AC_SUBST([GNULIB_LOG10F])
   GNULIB_MODFF=0;    AC_SUBST([GNULIB_MODFF])
   GNULIB_ROUND=0;    AC_SUBST([GNULIB_ROUND])
   GNULIB_ROUNDF=0;   AC_SUBST([GNULIB_ROUNDF])
@@ -112,6 +114,7 @@
   HAVE_LDEXPF=1;               AC_SUBST([HAVE_LDEXPF])
   HAVE_LOGF=1;                 AC_SUBST([HAVE_LOGF])
   HAVE_LOGL=1;                 AC_SUBST([HAVE_LOGL])
+  HAVE_LOG10F=1;               AC_SUBST([HAVE_LOG10F])
   HAVE_MODFF=1;                AC_SUBST([HAVE_MODFF])
   HAVE_SINL=1;                 AC_SUBST([HAVE_SINL])
   HAVE_SQRTF=1;                AC_SUBST([HAVE_SQRTF])

new file mode 100644
--- /dev/null
+++ b/modules/log10f
@@ -0,0 +1,31 @@
+Description:
+log10f() function: base 10 logarithmic function.
+
+Files:
+lib/log10f.c
+m4/log10f.m4
+
+Depends-on:
+math
+log10           [test $HAVE_LOG10F = 0]
+
+configure.ac:
+gl_FUNC_LOG10F
+if test $HAVE_LOG10F = 0; then
+  AC_LIBOBJ([log10f])
+fi
+gl_MATH_MODULE_INDICATOR([log10f])
+
+Makefile.am:
+
+Include:
+<math.h>
+
+Link:
+$(LOG10F_LIBM)
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible

--- a/modules/math
+++ b/modules/math
@@ -56,6 +56,7 @@
 	      -e 's/@''GNULIB_LOGB''@/$(GNULIB_LOGB)/g' \
 	      -e 's/@''GNULIB_LOGF''@/$(GNULIB_LOGF)/g' \
 	      -e 's/@''GNULIB_LOGL''@/$(GNULIB_LOGL)/g' \
+	      -e 's/@''GNULIB_LOG10F''@/$(GNULIB_LOG10F)/g' \
 	      -e 's/@''GNULIB_MODFF''@/$(GNULIB_MODFF)/g' \
 	      -e 's/@''GNULIB_ROUND''@/$(GNULIB_ROUND)/g' \
 	      -e 's/@''GNULIB_ROUNDF''@/$(GNULIB_ROUNDF)/g' \
@@ -84,6 +85,7 @@
 	      -e 's|@''HAVE_LDEXPF''@|$(HAVE_LDEXPF)|g' \
 	      -e 's|@''HAVE_LOGF''@|$(HAVE_LOGF)|g' \
 	      -e 's|@''HAVE_LOGL''@|$(HAVE_LOGL)|g' \
+	      -e 's|@''HAVE_LOG10F''@|$(HAVE_LOG10F)|g' \
 	      -e 's|@''HAVE_MODFF''@|$(HAVE_MODFF)|g' \
 	      -e 's|@''HAVE_SINL''@|$(HAVE_SINL)|g' \
 	      -e 's|@''HAVE_SQRTF''@|$(HAVE_SQRTF)|g' \

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -68,6 +68,9 @@
 SIGNATURE_CHECK (GNULIB_NAMESPACE::logf, float, (float));
 #endif
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::log, double, (double));
+#if GNULIB_TEST_LOG10F
+SIGNATURE_CHECK (GNULIB_NAMESPACE::log10f, float, (float));
+#endif
 #if GNULIB_TEST_MODFF
 SIGNATURE_CHECK (GNULIB_NAMESPACE::modff, float, (float, float *));
 #endif