--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2012-03-31  Bruno Haible  <bruno@clisp.org>
+
+	log10 tests: More tests.
+	* tests/test-log10.h: New file.
+	* modules/log10-tests (Files): Add tests/test-log10.h,
+	tests/minus-zero.h, tests/randomd.c.
+	(Makefile.am): Add randomd.c to test_log10_SOURCES.
+	* tests/test-log10.c: Include <float.h>, minus-zero.h, test-log10.h.
+	(main): Invoke test_function.
+
 2012-03-31  Simon Josefsson  <simon@josefsson.org>
 
 	fflush: Fix syntax error.

--- a/modules/log10-tests
+++ b/modules/log10-tests
@@ -1,7 +1,10 @@
 Files:
 tests/test-log10.c
+tests/test-log10.h
+tests/minus-zero.h
 tests/signature.h
 tests/macros.h
+tests/randomd.c
 
 Depends-on:
 
@@ -10,4 +13,5 @@
 Makefile.am:
 TESTS += test-log10
 check_PROGRAMS += test-log10
+test_log10_SOURCES = test-log10.c randomd.c
 test_log10_LDADD = $(LDADD) @LOG10_LIBM@

--- a/tests/test-log10.c
+++ b/tests/test-log10.c
@@ -23,10 +23,19 @@
 #include "signature.h"
 SIGNATURE_CHECK (log10, double, (double));
 
+#include <float.h>
+
+#include "minus-zero.h"
 #include "macros.h"
 
-volatile double x;
-double y;
+#define DOUBLE double
+#define HUGEVAL HUGE_VAL
+#define L_(literal) literal
+#define MANT_DIG DBL_MANT_DIG
+#define MINUS_ZERO minus_zerod
+#define LOG10 log10
+#define RANDOM randomd
+#include "test-log10.h"
 
 int
 main ()
@@ -36,5 +45,7 @@
   y = log10 (x);
   ASSERT (y >= -0.2218487497 && y <= -0.2218487496);
 
+  test_function ();
+
   return 0;
 }

new file mode 100644
--- /dev/null
+++ b/tests/test-log10.h
@@ -0,0 +1,104 @@
+/* Test of log10*() function family.
+   Copyright (C) 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/>.  */
+
+static void
+test_function (void)
+{
+  int i;
+  int j;
+  const DOUBLE TWO_MANT_DIG =
+    /* Assume MANT_DIG <= 5 * 31.
+       Use the identity
+         n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
+    (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
+
+  /* Pole.  */
+  {
+    DOUBLE z = LOG10 (L_(0.0));
+    ASSERT (z == - HUGEVAL);
+  }
+  {
+    DOUBLE z = LOG10 (MINUS_ZERO);
+    ASSERT (z == - HUGEVAL);
+  }
+
+  /* Randomized tests.  */
+  {
+    /* Error bound, in ulps.  */
+    const DOUBLE err_bound =
+      (sizeof (DOUBLE) > sizeof (double) ?
+#if defined __i386__ && defined __FreeBSD__
+       /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
+          precision in the compiler but 64 bits of precision at runtime.  See
+          <http://lists.gnu.org/archive/html/bug-gnulib/2008-07/msg00063.html>.
+          The compiler has truncated all 'long double' literals in log10l.c to
+          53 bits of precision.  */
+       L_(18.0)
+#else
+       L_(3.0)
+#endif
+       : L_(3.0));
+
+    for (i = 0; i < SIZEOF (RANDOM); i++)
+      {
+        DOUBLE x = L_(16.0) * RANDOM[i] + L_(1.0); /* 1.0 <= x <= 17.0 */
+        DOUBLE y = LOG10 (x);
+        DOUBLE z = LOG10 (L_(1.0) / x);
+        DOUBLE err = y + z;
+        ASSERT (y >= L_(0.0));
+        ASSERT (z <= L_(0.0));
+        ASSERT (err > - err_bound / TWO_MANT_DIG
+                && err < err_bound / TWO_MANT_DIG);
+      }
+  }
+
+  {
+    /* Error bound, in ulps.  */
+    const DOUBLE err_bound =
+      (sizeof (DOUBLE) > sizeof (double) ?
+#if defined __i386__ && defined __FreeBSD__
+       /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
+          precision in the compiler but 64 bits of precision at runtime.  See
+          <http://lists.gnu.org/archive/html/bug-gnulib/2008-07/msg00063.html>.
+          The compiler has truncated all 'long double' literals in log10l.c to
+          53 bits of precision.  */
+       L_(38.0)
+#else
+       L_(5.0)
+#endif
+       : L_(5.0));
+
+    for (i = 0; i < SIZEOF (RANDOM); i++)
+      for (j = 0; j < SIZEOF (RANDOM); j++)
+        {
+          DOUBLE x = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[i]) - L_(1.0);
+          DOUBLE y = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[j]) - L_(1.0);
+          /* 1/16 <= x,y <= 16 */
+          DOUBLE z = L_(1.0) / (x * y);
+          /* Approximately  x * y * z = 1.  */
+          DOUBLE err = LOG10 (x) + LOG10 (y) + LOG10 (z);
+          ASSERT (err > - err_bound / TWO_MANT_DIG
+                  && err < err_bound / TWO_MANT_DIG);
+        }
+  }
+}
+
+volatile DOUBLE x;
+DOUBLE y;