# log1pf.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_LOG1PF],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  AC_REQUIRE([gl_FUNC_LOG1P])

  dnl Persuade glibc <math.h> to declare log1pf().
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])

  dnl Test whether log1pf() exists. Assume that log1pf(), if it exists, is
  dnl defined in the same library as log1p().
  save_LIBS="$LIBS"
  LIBS="$LIBS $LOG1P_LIBM"
  AC_CHECK_FUNCS([log1pf])
  LIBS="$save_LIBS"
  if test $ac_cv_func_log1pf = yes; then
    LOG1PF_LIBM="$LOG1P_LIBM"

    save_LIBS="$LIBS"
    LIBS="$LIBS $LOG1PF_LIBM"
    gl_FUNC_LOG1PF_WORKS
    LIBS="$save_LIBS"
    case "$gl_cv_func_log1pf_works" in
      *yes) ;;
      *) REPLACE_LOG1PF=1 ;;
    esac
  else
    HAVE_LOG1PF=0
  fi
  if test $HAVE_LOG1PF = 0 || test $REPLACE_LOG1PF = 1; then
    dnl Find libraries needed to link lib/log1pf.c.
    LOG1PF_LIBM="$LOG1P_LIBM"
  fi
  AC_SUBST([LOG1PF_LIBM])
])

dnl Test whether log1pf() works.
dnl On IRIX 6.5, log1pf(-1.0f) returns +Infinity instead of -Infinity.
AC_DEFUN([gl_FUNC_LOG1PF_WORKS],
[
  AC_REQUIRE([AC_PROG_CC])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  AC_CACHE_CHECK([whether log1pf works], [gl_cv_func_log1pf_works],
    [
      AC_RUN_IFELSE(
        [AC_LANG_SOURCE([[
#include <math.h>
volatile float x;
float y;
int main ()
{
  x = -1.0f;
  y = log1pf (x);
  if (!(y + y == y && y < 0.0f))
    return 1;
  return 0;
}
]])],
        [gl_cv_func_log1pf_works=yes],
        [gl_cv_func_log1pf_works=no],
        [case "$host_os" in
           irix*) gl_cv_func_log1pf_works="guessing no";;
           *)     gl_cv_func_log1pf_works="guessing yes";;
         esac
        ])
    ])
])