# expl.m4 serial 11
dnl Copyright (C) 2010-2019 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_EXPL],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles

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

  EXPL_LIBM=
  AC_CACHE_CHECK([whether expl() can be used without linking with libm],
    [gl_cv_func_expl_no_libm],
    [
      AC_LINK_IFELSE(
        [AC_LANG_PROGRAM(
           [[#ifndef __NO_MATH_INLINES
             # define __NO_MATH_INLINES 1 /* for glibc */
             #endif
             #include <math.h>
             long double (*funcptr) (long double) = expl;
             long double x;]],
           [[return funcptr (x) > 1.5
                    || expl (x) > 1.5;]])],
        [gl_cv_func_expl_no_libm=yes],
        [gl_cv_func_expl_no_libm=no])
    ])
  if test $gl_cv_func_expl_no_libm = no; then
    AC_CACHE_CHECK([whether expl() can be used with libm],
      [gl_cv_func_expl_in_libm],
      [
        save_LIBS="$LIBS"
        LIBS="$LIBS -lm"
        AC_LINK_IFELSE(
          [AC_LANG_PROGRAM(
             [[#ifndef __NO_MATH_INLINES
               # define __NO_MATH_INLINES 1 /* for glibc */
               #endif
               #include <math.h>
               long double (*funcptr) (long double) = expl;
               long double x;]],
             [[return funcptr (x) > 1.5
                      || expl (x) > 1.5;]])],
          [gl_cv_func_expl_in_libm=yes],
          [gl_cv_func_expl_in_libm=no])
        LIBS="$save_LIBS"
      ])
    if test $gl_cv_func_expl_in_libm = yes; then
      EXPL_LIBM=-lm
    fi
  fi
  dnl On Haiku 2017 the system's native expl() is just a stub: it returns 0.0
  dnl and prints "__expl not implemented" for all arguments.
  dnl On OpenBSD 5.4 the system's native expl() is buggy:
  dnl it returns 'nan' for small values. Test for this anomaly.
  if test $gl_cv_func_expl_no_libm = yes \
     || test $gl_cv_func_expl_in_libm = yes; then
    AC_CACHE_CHECK([whether expl() breaks with small values],
      [gl_cv_func_expl_buggy],
      [save_LIBS="$LIBS"
       LIBS="$EXPL_LIBM"
       AC_RUN_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <math.h>]],
            [[volatile long double x1 = -1.0;
              volatile long double x2 = -0.8;
              volatile long double x3 = -0.4;
              return expl(x1) == 0.0 || isnan(expl(x1))
                     || isnan(expl(x2)) || isnan(expl(x3));
            ]])
         ],
         [gl_cv_func_expl_buggy=no], [gl_cv_func_expl_buggy=yes],
         [case $host_os in
            haiku* | openbsd*)
                      gl_cv_func_expl_buggy="guessing yes" ;;
                      # Guess no on native Windows.
            mingw*)   gl_cv_func_expl_buggy="guessing no" ;;
            *)        gl_cv_func_expl_buggy="guessing no" ;;
          esac
         ])
       LIBS="$save_LIBS"
      ])
    case "$gl_cv_func_expl_buggy" in
      *yes)
        gl_cv_func_expl_in_libm=no
        gl_cv_func_expl_no_libm=no ;;
    esac
  fi
  if test $gl_cv_func_expl_no_libm = yes \
     || test $gl_cv_func_expl_in_libm = yes; then
    dnl Also check whether it's declared.
    dnl Mac OS X 10.3 has expl() in libc but doesn't declare it in <math.h>.
    AC_CHECK_DECL([expl], , [HAVE_DECL_EXPL=0], [[#include <math.h>]])
  else
    HAVE_DECL_EXPL=0
    HAVE_EXPL=0
    dnl Find libraries needed to link lib/expl.c.
    if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
      AC_REQUIRE([gl_FUNC_EXP])
      EXPL_LIBM="$EXP_LIBM"
    else
      AC_REQUIRE([gl_FUNC_ISNANL])
      AC_REQUIRE([gl_FUNC_ROUNDL])
      AC_REQUIRE([gl_FUNC_LDEXPL])
      EXPL_LIBM=
      dnl Append $ISNANL_LIBM to EXPL_LIBM, avoiding gratuitous duplicates.
      case " $EXPL_LIBM " in
        *" $ISNANL_LIBM "*) ;;
        *) EXPL_LIBM="$EXPL_LIBM $ISNANL_LIBM" ;;
      esac
      dnl Append $ROUNDL_LIBM to EXPL_LIBM, avoiding gratuitous duplicates.
      case " $EXPL_LIBM " in
        *" $ROUNDL_LIBM "*) ;;
        *) EXPL_LIBM="$EXPL_LIBM $ROUNDL_LIBM" ;;
      esac
      dnl Append $LDEXPL_LIBM to EXPL_LIBM, avoiding gratuitous duplicates.
      case " $EXPL_LIBM " in
        *" $LDEXPL_LIBM "*) ;;
        *) EXPL_LIBM="$EXPL_LIBM $LDEXPL_LIBM" ;;
      esac
    fi
  fi
  AC_SUBST([EXPL_LIBM])
])