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changeset 40115:d53c98a8c061

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log10l: Work around inaccurate implementation on NetBSD. * m4/log10l.m4 (gl_FUNC_LOG10L_WORKS): Add test for a certain accuracy. * lib/log10l.c: Comment out too simplistic override. * doc/posix-functions/log10l.texi: Mention the NetBSD bug.
author Bruno Haible <bruno@clisp.org>
date Sun, 20 Jan 2019 23:48:18 +0100
parents d871c219134f
children 54732a1c637e
files ChangeLog doc/posix-functions/log10l.texi lib/log10l.c m4/log10l.m4
diffstat 4 files changed, 82 insertions(+), 18 deletions(-) [+]
line wrap: on
line diff
--- a/ChangeLog	Sun Jan 20 22:57:41 2019 +0100
+++ b/ChangeLog	Sun Jan 20 23:48:18 2019 +0100
@@ -1,3 +1,10 @@
+2019-01-20  Bruno Haible  <bruno@clisp.org>
+
+	log10l: Work around inaccurate implementation on NetBSD.
+	* m4/log10l.m4 (gl_FUNC_LOG10L_WORKS): Add test for a certain accuracy.
+	* lib/log10l.c: Comment out too simplistic override.
+	* doc/posix-functions/log10l.texi: Mention the NetBSD bug.
+
 2019-01-20  Bruno Haible  <bruno@clisp.org>
 
 	logl: Work around inaccurate implementation on NetBSD.
--- a/doc/posix-functions/log10l.texi	Sun Jan 20 22:57:41 2019 +0100
+++ b/doc/posix-functions/log10l.texi	Sun Jan 20 23:48:18 2019 +0100
@@ -26,6 +26,10 @@
 @item
 This function returns an unnormalized positive infinity for a positive infinite argument on some platforms:
 IRIX 6.5.
+@item
+This function produces results which are accurate to only 16 digits on some
+platforms:
+NetBSD 8.0.
 @end itemize
 
 Portability problems not fixed by Gnulib:
--- a/lib/log10l.c	Sun Jan 20 22:57:41 2019 +0100
+++ b/lib/log10l.c	Sun Jan 20 23:48:18 2019 +0100
@@ -27,7 +27,7 @@
   return log10 (x);
 }
 
-#elif HAVE_LOG10L
+#elif 0 /* was: HAVE_LOG10L */
 
 # include <float.h>
 
--- a/m4/log10l.m4	Sun Jan 20 22:57:41 2019 +0100
+++ b/m4/log10l.m4	Sun Jan 20 23:48:18 2019 +0100
@@ -1,4 +1,4 @@
-# log10l.m4 serial 5
+# log10l.m4 serial 6
 dnl Copyright (C) 2011-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -60,6 +60,7 @@
 dnl 0xFFF00000000000000000000000000000.
 dnl On AIX 5.1, log10l(-0.0L) is finite if it's not the first log10l call
 dnl in the program.
+dnl On NetBSD 8.0, the result is accurate to only 16 digits.
 AC_DEFUN([gl_FUNC_LOG10L_WORKS],
 [
   AC_REQUIRE([AC_PROG_CC])
@@ -68,36 +69,88 @@
     [
       AC_RUN_IFELSE(
         [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <float.h>
 #include <math.h>
-#ifndef log10l /* for AIX */
+/* Override the values of <float.h>, like done in float.in.h.  */
+#if defined __i386__ && (defined __BEOS__ || defined __OpenBSD__)
+# undef LDBL_MANT_DIG
+# define LDBL_MANT_DIG   64
+# undef LDBL_MIN_EXP
+# define LDBL_MIN_EXP    (-16381)
+# undef LDBL_MAX_EXP
+# define LDBL_MAX_EXP    16384
+#endif
+#if defined __i386__ && (defined __FreeBSD__ || defined __DragonFly__)
+# undef LDBL_MANT_DIG
+# define LDBL_MANT_DIG   64
+# undef LDBL_MIN_EXP
+# define LDBL_MIN_EXP    (-16381)
+# undef LDBL_MAX_EXP
+# define LDBL_MAX_EXP    16384
+#endif
+#if (defined _ARCH_PPC || defined _POWER) && defined _AIX && (LDBL_MANT_DIG == 106) && defined __GNUC__
+# undef LDBL_MIN_EXP
+# define LDBL_MIN_EXP DBL_MIN_EXP
+#endif
+#if defined __sgi && (LDBL_MANT_DIG >= 106)
+# undef LDBL_MANT_DIG
+# define LDBL_MANT_DIG 106
+# if defined __GNUC__
+#  undef LDBL_MIN_EXP
+#  define LDBL_MIN_EXP DBL_MIN_EXP
+# endif
+#endif
+#undef log10l /* for AIX */
 extern
 #ifdef __cplusplus
 "C"
 #endif
 long double log10l (long double);
-#endif
-volatile long double x;
-long double y;
-int main ()
+static long double dummy (long double x) { return 0; }
+volatile long double gx;
+long double gy;
+int main (int argc, char *argv[])
 {
+  long double (* volatile my_log10l) (long double) = argc ? log10l : dummy;
+  int result = 0;
   /* Dummy call, to trigger the AIX 5.1 bug.  */
-  x = 0.6L;
-  y = log10l (x);
+  gx = 0.6L;
+  gy = log10l (gx);
   /* This test fails on AIX 5.1, IRIX 6.5, OSF/1 5.1.  */
-  x = -0.0L;
-  y = log10l (x);
-  if (!(y + y == y))
-    return 1;
-  return 0;
+  {
+    gx = -0.0L;
+    gy = log10l (gx);
+    if (!(gy + gy == gy))
+      result |= 1;
+  }
+  /* This test fails on NetBSD 8.0.  */
+  {
+    const long double TWO_LDBL_MANT_DIG = /* 2^LDBL_MANT_DIG */
+      (long double) (1U << ((LDBL_MANT_DIG - 1) / 5))
+      * (long double) (1U << ((LDBL_MANT_DIG - 1 + 1) / 5))
+      * (long double) (1U << ((LDBL_MANT_DIG - 1 + 2) / 5))
+      * (long double) (1U << ((LDBL_MANT_DIG - 1 + 3) / 5))
+      * (long double) (1U << ((LDBL_MANT_DIG - 1 + 4) / 5));
+    long double x = 7.90097792256024576L;
+    long double err = (my_log10l (x) + my_log10l (1.0L / x)) * TWO_LDBL_MANT_DIG;
+    if (!(err >= -100.0L && err <= 100.0L))
+      result |= 2;
+  }
+  return result;
 }
 ]])],
         [gl_cv_func_log10l_works=yes],
         [gl_cv_func_log10l_works=no],
         [case "$host_os" in
-           aix* | irix* | osf*) gl_cv_func_log10l_works="guessing no" ;;
-                                # Guess yes on native Windows.
-           mingw*)              gl_cv_func_log10l_works="guessing yes" ;;
-           *)                   gl_cv_func_log10l_works="guessing yes" ;;
+                          # Guess yes on glibc systems.
+           *-gnu* | gnu*) gl_cv_func_log10l_works="guessing yes" ;;
+                          # Guess yes on native Windows.
+           mingw*)        gl_cv_func_log10l_works="guessing yes" ;;
+                          # If we don't know, assume the worst.
+           *)             gl_cv_func_log10l_works="guessing no" ;;
          esac
         ])
     ])