# log10f.m4 serial 3
dnl Copyright (C) 2011-2012 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_LOG10F],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  AC_REQUIRE([gl_FUNC_LOG10])

  dnl Persuade glibc <math.h> to declare log10f().
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])

  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"

    save_LIBS="$LIBS"
    LIBS="$LIBS $LOG10F_LIBM"
    gl_FUNC_LOG10F_WORKS
    LIBS="$save_LIBS"
    case "$gl_cv_func_log10f_works" in
      *yes) ;;
      *) REPLACE_LOG10F=1 ;;
    esac
  else
    HAVE_LOG10F=0
  fi
  if test $HAVE_LOG10F = 0 || test $REPLACE_LOG10F = 1; then
    dnl Find libraries needed to link lib/log10f.c.
    if test $HAVE_LOG10F = 0; then
      LOG10F_LIBM="$LOG10_LIBM"
    fi
  fi
  AC_SUBST([LOG10F_LIBM])
])

dnl Test whether log10f() works.
dnl On OSF/1 5.1, log10f(-0.0f) is NaN.
AC_DEFUN([gl_FUNC_LOG10F_WORKS],
[
  AC_REQUIRE([AC_PROG_CC])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  AC_CACHE_CHECK([whether log10f works], [gl_cv_func_log10f_works],
    [
      AC_RUN_IFELSE(
        [AC_LANG_SOURCE([[
#include <math.h>
volatile float x;
float y;
int main ()
{
  x = -0.0f;
  y = log10f (x);
  if (!(y + y == y))
    return 1;
  return 0;
}
]])],
        [gl_cv_func_log10f_works=yes],
        [gl_cv_func_log10f_works=no],
        [case "$host_os" in
           osf*) gl_cv_func_log10f_works="guessing no";;
           *)    gl_cv_func_log10f_works="guessing yes";;
         esac
        ])
    ])
])