cbrt portability

[Bruno Haible]

This patch provides a replacement for platforms without the cbrt() function.


2012-02-29  Bruno Haible  <address@hidden>

        cbrt: Provide replacement on MSVC and Minix.
        * lib/math.in.h (cbrt): New declaration.
        * lib/cbrt.c: New file.
        * m4/cbrt.m4: New file.
        * m4/math_h.m4 (gl_MATH_H): Test whether cbrt is declared.
        (gl_MATH_H_DEFAULTS): Initialize GNULIB_CBRT, HAVE_CBRT.
        * modules/math (Makefile.am): Substitute GNULIB_CBRT, HAVE_CBRT.
        * modules/cbrt (Files): Add lib/cbrt.c, m4/cbrt.m4.
        (Depends-on): Add dependencies.
        (configure.ac): Arrange to compile replacement if HAVE_CBRT is 0.
        * tests/test-math-c++.cc: Check the declaration of cbrt.
        * doc/posix-functions/cbrt.texi: Mention that the module provides a
        replacement.

================================= lib/cbrt.c =================================
/* Compute cubic root of double value.
   Copyright (C) 1997, 2012 Free Software Foundation, Inc.

   Contributed by Dirk Alboth <address@hidden> and
   Ulrich Drepper <address@hidden>, 1997.

   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>

/* Code based on glibc/sysdeps/ieee754/dbl-64/s_cbrt.c.  */

#define CBRT2 1.2599210498948731648             /* 2^(1/3) */
#define SQR_CBRT2 1.5874010519681994748         /* 2^(2/3) */

static const double factor[5] =
{
  1.0 / SQR_CBRT2,
  1.0 / CBRT2,
  1.0,
  CBRT2,
  SQR_CBRT2
};


double
cbrt (double x)
{
  if (isfinite (x) && x != 0.0)
    {
      double xm, ym, u, t2;
      int xe;

      /* Reduce X.  XM now is an range 1.0 to 0.5.  */
      xm = frexp (fabs (x), &xe);

      u = (0.354895765043919860
           + ((1.50819193781584896
               + ((-2.11499494167371287
                   + ((2.44693122563534430
                       + ((-1.83469277483613086
                           + (0.784932344976639262 - 0.145263899385486377 * xm)
                             * xm)
                          * xm))
                      * xm))
                  * xm))
              * xm));

      t2 = u * u * u;

      ym = u * (t2 + 2.0 * xm) / (2.0 * t2 + xm) * factor[2 + xe % 3];

      return ldexp (x > 0.0 ? ym : -ym, xe / 3);
    }
  else
    return x + x;
}
================================= m4/cbrt.m4 =================================
# cbrt.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.

AC_DEFUN([gl_FUNC_CBRT],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])

  dnl Determine CBRT_LIBM.
  gl_COMMON_DOUBLE_MATHFUNC([cbrt])

  dnl Test whether cbrt() exists.
  save_LIBS="$LIBS"
  LIBS="$LIBS $CBRT_LIBM"
  AC_CHECK_FUNCS([cbrt])
  LIBS="$save_LIBS"
  if test $ac_cv_func_cbrt = no; then
    HAVE_CBRT=0
    dnl Find libraries needed to link lib/cbrt.c.
    AC_REQUIRE([gl_FUNC_FABS])
    AC_REQUIRE([gl_FUNC_FREXP])
    AC_REQUIRE([gl_FUNC_LDEXP])
    CBRT_LIBM=
    dnl Append $FABS_LIBM to CBRT_LIBM, avoiding gratuitous duplicates.
    case " $CBRT_LIBM " in
      *" $FABS_LIBM "*) ;;
      *) CBRT_LIBM="$CBRT_LIBM $FABS_LIBM" ;;
    esac
    dnl Append $FREXP_LIBM to CBRT_LIBM, avoiding gratuitous duplicates.
    case " $CBRT_LIBM " in
      *" $FREXP_LIBM "*) ;;
      *) CBRT_LIBM="$CBRT_LIBM $FREXP_LIBM" ;;
    esac
    dnl Append $LDEXP_LIBM to CBRT_LIBM, avoiding gratuitous duplicates.
    case " $CBRT_LIBM " in
      *" $LDEXP_LIBM "*) ;;
      *) CBRT_LIBM="$CBRT_LIBM $LDEXP_LIBM" ;;
    esac
  fi
])
==============================================================================
--- doc/posix-functions/cbrt.texi.orig  Wed Feb 29 23:42:05 2012
+++ doc/posix-functions/cbrt.texi       Wed Feb 29 23:08:54 2012
@@ -8,11 +8,11 @@
 
 Portability problems fixed by Gnulib:
 @itemize
address@hidden
+This function is missing on some platforms:
+Minix 3.1.8, MSVC 9.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
address@hidden
-This function is missing on some platforms:
-Minix 3.1.8, MSVC 9.
 @end itemize
--- lib/math.in.h.orig  Wed Feb 29 23:42:05 2012
+++ lib/math.in.h       Wed Feb 29 23:07:01 2012
@@ -288,6 +288,21 @@
 #endif
 
 
+#if @GNULIB_CBRT@
+# if address@hidden@
+_GL_FUNCDECL_SYS (cbrt, double, (double x));
+# endif
+_GL_CXXALIAS_SYS (cbrt, double, (double x));
+_GL_CXXALIASWARN (cbrt);
+#elif defined GNULIB_POSIXCHECK
+# undef cbrt
+# if HAVE_RAW_DECL_CBRT
+_GL_WARN_ON_USE (cbrt, "cbrt is unportable - "
+                 "use gnulib module cbrt for portability");
+# endif
+#endif
+
+
 #if @GNULIB_CEILF@
 # if @REPLACE_CEILF@
 #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
--- m4/math_h.m4.orig   Wed Feb 29 23:42:05 2012
+++ m4/math_h.m4        Wed Feb 29 23:08:38 2012
@@ -1,4 +1,4 @@
-# math_h.m4 serial 75
+# math_h.m4 serial 76
 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,
@@ -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 copysignl cosf cosl coshf
+     cbrt ceilf ceill copysign copysignf copysignl cosf cosl coshf
      expf expl fabsf fabsl floorf floorl fma fmaf fmal
      fmod fmodf fmodl frexpf frexpl hypotf hypotl
      ldexpf ldexpl logb logf logl log10f log10l modf modff modfl powf
@@ -67,6 +67,7 @@
   GNULIB_ATANF=0;      AC_SUBST([GNULIB_ATANF])
   GNULIB_ATANL=0;      AC_SUBST([GNULIB_ATANL])
   GNULIB_ATAN2F=0;     AC_SUBST([GNULIB_ATAN2F])
+  GNULIB_CBRT=0;       AC_SUBST([GNULIB_CBRT])
   GNULIB_CEIL=0;       AC_SUBST([GNULIB_CEIL])
   GNULIB_CEILF=0;      AC_SUBST([GNULIB_CEILF])
   GNULIB_CEILL=0;      AC_SUBST([GNULIB_CEILL])
@@ -141,6 +142,7 @@
   HAVE_ATANF=1;                AC_SUBST([HAVE_ATANF])
   HAVE_ATANL=1;                AC_SUBST([HAVE_ATANL])
   HAVE_ATAN2F=1;               AC_SUBST([HAVE_ATAN2F])
+  HAVE_CBRT=1;                 AC_SUBST([HAVE_CBRT])
   HAVE_COPYSIGN=1;             AC_SUBST([HAVE_COPYSIGN])
   HAVE_COPYSIGNF=1;            AC_SUBST([HAVE_COPYSIGNF])
   HAVE_COPYSIGNL=1;            AC_SUBST([HAVE_COPYSIGNL])
--- modules/cbrt.orig   Wed Feb 29 23:42:05 2012
+++ modules/cbrt        Wed Feb 29 23:40:20 2012
@@ -2,12 +2,23 @@
 cbrt() function: cube root.
 
 Files:
+lib/cbrt.c
+m4/cbrt.m4
 m4/mathfunc.m4
 
 Depends-on:
+math
+isfinite        [test $HAVE_CBRT = 0]
+fabs            [test $HAVE_CBRT = 0]
+frexp           [test $HAVE_CBRT = 0]
+ldexp           [test $HAVE_CBRT = 0]
 
 configure.ac:
-gl_COMMON_DOUBLE_MATHFUNC([cbrt])
+gl_FUNC_CBRT
+if test $HAVE_CBRT = 0; then
+  AC_LIBOBJ([cbrt])
+fi
+gl_MATH_MODULE_INDICATOR([cbrt])
 
 Makefile.am:
 
--- modules/math.orig   Wed Feb 29 23:42:05 2012
+++ modules/math        Wed Feb 29 23:07:43 2012
@@ -35,6 +35,7 @@
              -e 's/@''GNULIB_ATANF''@/$(GNULIB_ATANF)/g' \
              -e 's/@''GNULIB_ATANL''@/$(GNULIB_ATANL)/g' \
              -e 's/@''GNULIB_ATAN2F''@/$(GNULIB_ATAN2F)/g' \
+             -e 's/@''GNULIB_CBRT''@/$(GNULIB_CBRT)/g' \
              -e 's/@''GNULIB_CEIL''@/$(GNULIB_CEIL)/g' \
              -e 's/@''GNULIB_CEILF''@/$(GNULIB_CEILF)/g' \
              -e 's/@''GNULIB_CEILL''@/$(GNULIB_CEILL)/g' \
@@ -109,6 +110,7 @@
              -e 's|@''HAVE_ATANF''@|$(HAVE_ATANF)|g' \
              -e 's|@''HAVE_ATANL''@|$(HAVE_ATANL)|g' \
              -e 's|@''HAVE_ATAN2F''@|$(HAVE_ATAN2F)|g' \
+             -e 's|@''HAVE_CBRT''@|$(HAVE_CBRT)|g' \
              -e 's|@''HAVE_COPYSIGN''@|$(HAVE_COPYSIGN)|g' \
              -e 's|@''HAVE_COPYSIGNF''@|$(HAVE_COPYSIGNF)|g' \
              -e 's|@''HAVE_COPYSIGNL''@|$(HAVE_COPYSIGNL)|g' \
--- tests/test-math-c++.cc.orig Wed Feb 29 23:42:05 2012
+++ tests/test-math-c++.cc      Wed Feb 29 23:11:46 2012
@@ -68,7 +68,9 @@
 #endif
 //SIGNATURE_CHECK (GNULIB_NAMESPACE::atan2, double, (double, double));
 
-//SIGNATURE_CHECK (GNULIB_NAMESPACE::cbrt, double, (double));
+#if GNULIB_TEST_CBRT
+SIGNATURE_CHECK (GNULIB_NAMESPACE::cbrt, double, (double));
+#endif
 
 #if GNULIB_TEST_CEILF
 SIGNATURE_CHECK (GNULIB_NAMESPACE::ceilf, float, (float));