acinclude.m4

dnl
dnl $Source$
dnl $Date$
dnl $Revision$
dnl
dnl DESCRIPTION:
dnl Local macro definitions for Gambit configure.in
dnl

dnl ---------------------------------------------------------------------------
dnl Macros for wxWidgets detection. Typically used in configure.in as:
dnl
dnl     AC_ARG_ENABLE(...)
dnl     AC_ARG_WITH(...)
dnl        ...
dnl     AM_OPTIONS_WXCONFIG
dnl        ...
dnl        ...
dnl     AM_PATH_WXCONFIG(2.6.0, wxWin=1)
dnl     if test "$wxWin" != 1; then
dnl        AC_MSG_ERROR([
dnl                wxWidgets must be installed on your system
dnl                but wx-config script couldn't be found.
dnl
dnl                Please check that wx-config is in path, the directory
dnl                where wxWidgets libraries are installed (returned by
dnl                'wx-config --libs' command) is in LD_LIBRARY_PATH or
dnl                equivalent variable and wxWidgets version is 2.3.4 or above.
dnl        ])
dnl     fi
dnl     CPPFLAGS="$CPPFLAGS $WX_CPPFLAGS"
dnl     CXXFLAGS="$CXXFLAGS $WX_CXXFLAGS_ONLY"
dnl     CFLAGS="$CFLAGS $WX_CFLAGS_ONLY"
dnl
dnl     LIBS="$LIBS $WX_LIBS"
dnl ---------------------------------------------------------------------------

dnl ---------------------------------------------------------------------------
dnl AM_OPTIONS_WXCONFIG
dnl
dnl adds support for --wx-prefix, --wx-exec-prefix, --with-wxdir and
dnl --wx-config command line options
dnl ---------------------------------------------------------------------------

AC_DEFUN([AM_OPTIONS_WXCONFIG],
[
    AC_ARG_WITH(wxdir,
                [  --with-wxdir=PATH       Use uninstalled version of wxWidgets in PATH],
                [ wx_config_name="$withval/wx-config"
                  wx_config_args="--inplace"])
    AC_ARG_WITH(wx-config,
                [  --with-wx-config=CONFIG wx-config script to use (optional)],
                wx_config_name="$withval" )
    AC_ARG_WITH(wx-prefix,
                [  --with-wx-prefix=PREFIX Prefix where wxWidgets is installed (optional)],
                wx_config_prefix="$withval", wx_config_prefix="")
    AC_ARG_WITH(wx-exec-prefix,
                [  --with-wx-exec-prefix=PREFIX
                          Exec prefix where wxWidgets is installed (optional)],
                wx_config_exec_prefix="$withval", wx_config_exec_prefix="")
])

dnl Helper macro for checking if wx version is at least $1.$2.$3, set's
dnl wx_ver_ok=yes if it is:
AC_DEFUN([_WX_PRIVATE_CHECK_VERSION],
[
    wx_ver_ok=""
    if test "x$WX_VERSION" != x ; then
      if test $wx_config_major_version -gt $1; then
        wx_ver_ok=yes
      else
        if test $wx_config_major_version -eq $1; then
           if test $wx_config_minor_version -gt $2; then
              wx_ver_ok=yes
           else
              if test $wx_config_minor_version -eq $2; then
                 if test $wx_config_micro_version -ge $3; then
                    wx_ver_ok=yes
                 fi
              fi
           fi
        fi
      fi
    fi
])

dnl ---------------------------------------------------------------------------
dnl AM_PATH_WXCONFIG(VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND
dnl                  [, WX-LIBS [, ADDITIONAL-WX-CONFIG-FLAGS]]]])
dnl
dnl Test for wxWidgets, and define WX_C*FLAGS, WX_LIBS and WX_LIBS_STATIC
dnl (the latter is for static linking against wxWidgets). Set WX_CONFIG_NAME
dnl environment variable to override the default name of the wx-config script
dnl to use. Set WX_CONFIG_PATH to specify the full path to wx-config - in this
dnl case the macro won't even waste time on tests for its existence.
dnl
dnl Optional WX-LIBS argument contains comma- or space-separated list of
dnl wxWidgets libraries to link against (it may include contrib libraries). If
dnl it is not specified then WX_LIBS and WX_LIBS_STATIC will contain flags to
dnl link with all of the core wxWidgets libraries.
dnl
dnl Optional ADDITIONAL-WX-CONFIG-FLAGS argument is appended to wx-config
dnl invocation command in present. It can be used to fine-tune lookup of
dnl best wxWidgets build available.
dnl
dnl Example use:
dnl   AM_PATH_WXCONFIG([2.6.0], [wxWin=1], [wxWin=0], [html,core,net]
dnl                    [--unicode --debug])
dnl ---------------------------------------------------------------------------

dnl
dnl Get the cflags and libraries from the wx-config script
dnl
AC_DEFUN([AM_PATH_WXCONFIG],
[
  dnl do we have wx-config name: it can be wx-config or wxd-config or ...
  if test x${WX_CONFIG_NAME+set} != xset ; then
     WX_CONFIG_NAME=wx-config
  fi

  if test "x$wx_config_name" != x ; then
     WX_CONFIG_NAME="$wx_config_name"
  fi

  dnl deal with optional prefixes
  if test x$wx_config_exec_prefix != x ; then
     wx_config_args="$wx_config_args --exec-prefix=$wx_config_exec_prefix"
     WX_LOOKUP_PATH="$wx_config_exec_prefix/bin"
  fi
  if test x$wx_config_prefix != x ; then
     wx_config_args="$wx_config_args --prefix=$wx_config_prefix"
     WX_LOOKUP_PATH="$WX_LOOKUP_PATH:$wx_config_prefix/bin"
  fi
  if test "$cross_compiling" = "yes"; then
     wx_config_args="$wx_config_args --host=$host_alias"
  fi

  dnl don't search the PATH if WX_CONFIG_NAME is absolute filename
  if test -x "$WX_CONFIG_NAME" ; then
     AC_MSG_CHECKING(for wx-config)
     WX_CONFIG_PATH="$WX_CONFIG_NAME"
     AC_MSG_RESULT($WX_CONFIG_PATH)
  else
     AC_PATH_PROG(WX_CONFIG_PATH, $WX_CONFIG_NAME, no, "$WX_LOOKUP_PATH:$PATH")
  fi

  if test "$WX_CONFIG_PATH" != "no" ; then
    WX_VERSION=""

    min_wx_version=ifelse([$1], ,2.2.1,$1)
    if test -z "$5" ; then
      AC_MSG_CHECKING([for wxWidgets version >= $min_wx_version])
    else
      AC_MSG_CHECKING([for wxWidgets version >= $min_wx_version ($5)])
    fi

    WX_CONFIG_WITH_ARGS="$WX_CONFIG_PATH $wx_config_args $5 $4"

    WX_VERSION=`$WX_CONFIG_WITH_ARGS --version 2>/dev/null`
    wx_config_major_version=`echo $WX_VERSION | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\1/'`
    wx_config_minor_version=`echo $WX_VERSION | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\2/'`
    wx_config_micro_version=`echo $WX_VERSION | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\3/'`

    wx_requested_major_version=`echo $min_wx_version | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\1/'`
    wx_requested_minor_version=`echo $min_wx_version | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\2/'`
    wx_requested_micro_version=`echo $min_wx_version | \
           sed 's/\([[0-9]]*\).\([[0-9]]*\).\([[0-9]]*\)/\3/'`

    _WX_PRIVATE_CHECK_VERSION([$wx_requested_major_version],
                              [$wx_requested_minor_version],
                              [$wx_requested_micro_version])

    if test -n "$wx_ver_ok"; then

      AC_MSG_RESULT(yes (version $WX_VERSION))
      WX_LIBS=`$WX_CONFIG_WITH_ARGS --libs`

      dnl is this even still appropriate?  --static is a real option now
      dnl and WX_CONFIG_WITH_ARGS is likely to contain it if that is
      dnl what the user actually wants, making this redundant at best.
      dnl For now keep it in case anyone actually used it in the past.
      AC_MSG_CHECKING([for wxWidgets static library])
      WX_LIBS_STATIC=`$WX_CONFIG_WITH_ARGS --static --libs 2>/dev/null`
      if test "x$WX_LIBS_STATIC" = "x"; then
        AC_MSG_RESULT(no)
      else
        AC_MSG_RESULT(yes)
      fi

      dnl starting with version 2.2.6 wx-config has --cppflags argument
      wx_has_cppflags=""
      if test $wx_config_major_version -gt 2; then
        wx_has_cppflags=yes
      else
        if test $wx_config_major_version -eq 2; then
           if test $wx_config_minor_version -gt 2; then
              wx_has_cppflags=yes
           else
              if test $wx_config_minor_version -eq 2; then
                 if test $wx_config_micro_version -ge 6; then
                    wx_has_cppflags=yes
                 fi
              fi
           fi
        fi
      fi

      dnl starting with version 2.7.0 wx-config has --rescomp option
      wx_has_rescomp=""
      if test $wx_config_major_version -gt 2; then
        wx_has_rescomp=yes
      else
        if test $wx_config_major_version -eq 2; then
           if test $wx_config_minor_version -ge 7; then
              wx_has_rescomp=yes
           fi
        fi
      fi
      if test "x$wx_has_rescomp" = x ; then
         dnl cannot give any useful info for resource compiler
         WX_RESCOMP=
      else
         WX_RESCOMP=`$WX_CONFIG_WITH_ARGS --rescomp`
      fi

      if test "x$wx_has_cppflags" = x ; then
         dnl no choice but to define all flags like CFLAGS
         WX_CFLAGS=`$WX_CONFIG_WITH_ARGS --cflags`
         WX_CPPFLAGS=$WX_CFLAGS
         WX_CXXFLAGS=$WX_CFLAGS

         WX_CFLAGS_ONLY=$WX_CFLAGS
         WX_CXXFLAGS_ONLY=$WX_CFLAGS
      else
         dnl we have CPPFLAGS included in CFLAGS included in CXXFLAGS
         WX_CPPFLAGS=`$WX_CONFIG_WITH_ARGS --cppflags`
         WX_CXXFLAGS=`$WX_CONFIG_WITH_ARGS --cxxflags`
         WX_CFLAGS=`$WX_CONFIG_WITH_ARGS --cflags`

         WX_CFLAGS_ONLY=`echo $WX_CFLAGS | sed "s@^$WX_CPPFLAGS *@@"`
         WX_CXXFLAGS_ONLY=`echo $WX_CXXFLAGS | sed "s@^$WX_CFLAGS *@@"`
      fi

      ifelse([$2], , :, [$2])

    else

       if test "x$WX_VERSION" = x; then
          dnl no wx-config at all
          AC_MSG_RESULT(no)
       else
          AC_MSG_RESULT(no (version $WX_VERSION is not new enough))
       fi

       WX_CFLAGS=""
       WX_CPPFLAGS=""
       WX_CXXFLAGS=""
       WX_LIBS=""
       WX_LIBS_STATIC=""
       WX_RESCOMP=""
       ifelse([$3], , :, [$3])

    fi
  else

    WX_CFLAGS=""
    WX_CPPFLAGS=""
    WX_CXXFLAGS=""
    WX_LIBS=""
    WX_LIBS_STATIC=""
    WX_RESCOMP=""

    ifelse([$3], , :, [$3])

  fi

  AC_SUBST(WX_CPPFLAGS)
  AC_SUBST(WX_CFLAGS)
  AC_SUBST(WX_CXXFLAGS)
  AC_SUBST(WX_CFLAGS_ONLY)
  AC_SUBST(WX_CXXFLAGS_ONLY)
  AC_SUBST(WX_LIBS)
  AC_SUBST(WX_LIBS_STATIC)
  AC_SUBST(WX_VERSION)
  AC_SUBST(WX_RESCOMP)
])

dnl ---------------------------------------------------------------------------
dnl Get information on the wxrc program for making C++, Python and xrs
dnl resource files.
dnl
dnl     AC_ARG_ENABLE(...)
dnl     AC_ARG_WITH(...)
dnl        ...
dnl     AM_OPTIONS_WXCONFIG
dnl        ...
dnl     AM_PATH_WXCONFIG(2.6.0, wxWin=1)
dnl     if test "$wxWin" != 1; then
dnl        AC_MSG_ERROR([
dnl                wxWidgets must be installed on your system
dnl                but wx-config script couldn't be found.
dnl
dnl                Please check that wx-config is in path, the directory
dnl                where wxWidgets libraries are installed (returned by
dnl                'wx-config --libs' command) is in LD_LIBRARY_PATH or
dnl                equivalent variable and wxWidgets version is 2.6.0 or above.
dnl        ])
dnl     fi
dnl
dnl     AM_PATH_WXRC([HAVE_WXRC=1], [HAVE_WXRC=0])
dnl     if test "x$HAVE_WXRC" != x1; then
dnl         AC_MSG_ERROR([
dnl                The wxrc program was not installed or not found.
dnl
dnl                Please check the wxWidgets installation.
dnl         ])
dnl     fi
dnl
dnl     CPPFLAGS="$CPPFLAGS $WX_CPPFLAGS"
dnl     CXXFLAGS="$CXXFLAGS $WX_CXXFLAGS_ONLY"
dnl     CFLAGS="$CFLAGS $WX_CFLAGS_ONLY"
dnl
dnl     LDFLAGS="$LDFLAGS $WX_LIBS"
dnl ---------------------------------------------------------------------------



dnl ---------------------------------------------------------------------------
dnl AM_PATH_WXRC([ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]])
dnl
dnl Test for wxWidgets' wxrc program for creating either C++, Python or XRS
dnl resources.  The variable WXRC will be set and substituted in the configure
dnl script and Makefiles.
dnl
dnl Example use:
dnl   AM_PATH_WXRC([wxrc=1], [wxrc=0])
dnl ---------------------------------------------------------------------------

dnl
dnl wxrc program from the wx-config script
dnl
AC_DEFUN([AM_PATH_WXRC],
[
  AC_ARG_VAR([WXRC], [Path to wxWidget's wxrc resource compiler])

  if test "x$WX_CONFIG_NAME" = x; then
    AC_MSG_ERROR([The wxrc tests must run after wxWidgets test.])
  else

    AC_MSG_CHECKING([for wxrc])

    if test "x$WXRC" = x ; then
      dnl wx-config --utility is a new addition to wxWidgets:
      _WX_PRIVATE_CHECK_VERSION(2,5,3)
      if test -n "$wx_ver_ok"; then
        WXRC=`$WX_CONFIG_WITH_ARGS --utility=wxrc`
      fi
    fi

    if test "x$WXRC" = x ; then
      AC_MSG_RESULT([not found])
      ifelse([$2], , :, [$2])
    else
      AC_MSG_RESULT([$WXRC])
      ifelse([$1], , :, [$1])
    fi

    AC_SUBST(WXRC)
  fi
])


# ===========================================================================
#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional])
#
# DESCRIPTION
#
#   Check for baseline language coverage in the compiler for the specified
#   version of the C++ standard.  If necessary, add switches to CXX and
#   CXXCPP to enable support.  VERSION may be '11', '14', '17', or '20' for
#   the respective C++ standard version.
#
#   The second argument, if specified, indicates whether you insist on an
#   extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
#   -std=c++11).  If neither is specified, you get whatever works, with
#   preference for no added switch, and then for an extended mode.
#
#   The third argument, if specified 'mandatory' or if left unspecified,
#   indicates that baseline support for the specified C++ standard is
#   required and that the macro should error out if no mode with that
#   support is found.  If specified 'optional', then configuration proceeds
#   regardless, after defining HAVE_CXX${VERSION} if and only if a
#   supporting mode is found.
#
# LICENSE
#
#   Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
#   Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
#   Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
#   Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
#   Copyright (c) 2015 Paul Norman <penorman@mac.com>
#   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
#   Copyright (c) 2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
#   Copyright (c) 2019 Enji Cooper <yaneurabeya@gmail.com>
#   Copyright (c) 2020 Jason Merrill <jason@redhat.com>
#   Copyright (c) 2021 Jörn Heusipp <osmanx@problemloesungsmaschine.de>
#
#   Copying and distribution of this file, with or without modification, are
#   permitted in any medium without royalty provided the copyright notice
#   and this notice are preserved.  This file is offered as-is, without any
#   warranty.

dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
dnl  (serial version number 13).

AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
  m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
        [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
        [$1], [17], [ax_cxx_compile_alternatives="17 1z"],
        [$1], [20], [ax_cxx_compile_alternatives="20"],
        [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
  m4_if([$2], [], [],
        [$2], [ext], [],
        [$2], [noext], [],
        [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
  m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
        [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
        [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
        [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
  AC_LANG_PUSH([C++])dnl
  ac_success=no

  m4_if([$2], [], [dnl
    AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
		   ax_cv_cxx_compile_cxx$1,
      [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
        [ax_cv_cxx_compile_cxx$1=yes],
        [ax_cv_cxx_compile_cxx$1=no])])
    if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
      ac_success=yes
    fi])

  m4_if([$2], [noext], [], [dnl
  if test x$ac_success = xno; then
    for alternative in ${ax_cxx_compile_alternatives}; do
      switch="-std=gnu++${alternative}"
      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
                     $cachevar,
        [ac_save_CXX="$CXX"
         CXX="$CXX $switch"
         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
          [eval $cachevar=yes],
          [eval $cachevar=no])
         CXX="$ac_save_CXX"])
      if eval test x\$$cachevar = xyes; then
        CXX="$CXX $switch"
        if test -n "$CXXCPP" ; then
          CXXCPP="$CXXCPP $switch"
        fi
        ac_success=yes
        break
      fi
    done
  fi])

  m4_if([$2], [ext], [], [dnl
  if test x$ac_success = xno; then
    dnl HP's aCC needs +std=c++11 according to:
    dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
    dnl Cray's crayCC needs "-h std=c++11"
    dnl MSVC needs -std:c++NN for C++17 and later (default is C++14)
    for alternative in ${ax_cxx_compile_alternatives}; do
      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}" MSVC; do
        if test x"$switch" = xMSVC; then
          dnl AS_TR_SH maps both `:` and `=` to `_` so -std:c++17 would collide
          dnl with -std=c++17.  We suffix the cache variable name with _MSVC to
          dnl avoid this.
          switch=-std:c++${alternative}
          cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_${switch}_MSVC])
        else
          cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
        fi
        AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
                       $cachevar,
          [ac_save_CXX="$CXX"
           CXX="$CXX $switch"
           AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
            [eval $cachevar=yes],
            [eval $cachevar=no])
           CXX="$ac_save_CXX"])
        if eval test x\$$cachevar = xyes; then
          CXX="$CXX $switch"
          if test -n "$CXXCPP" ; then
            CXXCPP="$CXXCPP $switch"
          fi
          ac_success=yes
          break
        fi
      done
      if test x$ac_success = xyes; then
        break
      fi
    done
  fi])
  AC_LANG_POP([C++])
  if test x$ax_cxx_compile_cxx$1_required = xtrue; then
    if test x$ac_success = xno; then
      AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
    fi
  fi
  if test x$ac_success = xno; then
    HAVE_CXX$1=0
    AC_MSG_NOTICE([No compiler with C++$1 support was found])
  else
    HAVE_CXX$1=1
    AC_DEFINE(HAVE_CXX$1,1,
              [define if the compiler supports basic C++$1 syntax])
  fi
  AC_SUBST(HAVE_CXX$1)
])


dnl  Test body for checking C++11 support

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
)

dnl  Test body for checking C++14 support

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
)

dnl  Test body for checking C++17 support

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
)

dnl  Test body for checking C++20 support

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_20],
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
  _AX_CXX_COMPILE_STDCXX_testbody_new_in_20
)


dnl  Tests for new features in C++11

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[

// If the compiler admits that it is not ready for C++11, why torture it?
// Hopefully, this will speed up the test.

#ifndef __cplusplus

#error "This is not a C++ compiler"

// MSVC always sets __cplusplus to 199711L in older versions; newer versions
// only set it correctly if /Zc:__cplusplus is specified as well as a
// /std:c++NN switch:
// https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
#elif __cplusplus < 201103L && !defined _MSC_VER

#error "This is not a C++11 compiler"

#else

namespace cxx11
{

  namespace test_static_assert
  {

    template <typename T>
    struct check
    {
      static_assert(sizeof(int) <= sizeof(T), "not big enough");
    };

  }

  namespace test_final_override
  {

    struct Base
    {
      virtual ~Base() {}
      virtual void f() {}
    };

    struct Derived : public Base
    {
      virtual ~Derived() override {}
      virtual void f() override {}
    };

  }

  namespace test_double_right_angle_brackets
  {

    template < typename T >
    struct check {};

    typedef check<void> single_type;
    typedef check<check<void>> double_type;
    typedef check<check<check<void>>> triple_type;
    typedef check<check<check<check<void>>>> quadruple_type;

  }

  namespace test_decltype
  {

    int
    f()
    {
      int a = 1;
      decltype(a) b = 2;
      return a + b;
    }

  }

  namespace test_type_deduction
  {

    template < typename T1, typename T2 >
    struct is_same
    {
      static const bool value = false;
    };

    template < typename T >
    struct is_same<T, T>
    {
      static const bool value = true;
    };

    template < typename T1, typename T2 >
    auto
    add(T1 a1, T2 a2) -> decltype(a1 + a2)
    {
      return a1 + a2;
    }

    int
    test(const int c, volatile int v)
    {
      static_assert(is_same<int, decltype(0)>::value == true, "");
      static_assert(is_same<int, decltype(c)>::value == false, "");
      static_assert(is_same<int, decltype(v)>::value == false, "");
      auto ac = c;
      auto av = v;
      auto sumi = ac + av + 'x';
      auto sumf = ac + av + 1.0;
      static_assert(is_same<int, decltype(ac)>::value == true, "");
      static_assert(is_same<int, decltype(av)>::value == true, "");
      static_assert(is_same<int, decltype(sumi)>::value == true, "");
      static_assert(is_same<int, decltype(sumf)>::value == false, "");
      static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
      return (sumf > 0.0) ? sumi : add(c, v);
    }

  }

  namespace test_noexcept
  {

    int f() { return 0; }
    int g() noexcept { return 0; }

    static_assert(noexcept(f()) == false, "");
    static_assert(noexcept(g()) == true, "");

  }

  namespace test_constexpr
  {

    template < typename CharT >
    unsigned long constexpr
    strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
    {
      return *s ? strlen_c_r(s + 1, acc + 1) : acc;
    }

    template < typename CharT >
    unsigned long constexpr
    strlen_c(const CharT *const s) noexcept
    {
      return strlen_c_r(s, 0UL);
    }

    static_assert(strlen_c("") == 0UL, "");
    static_assert(strlen_c("1") == 1UL, "");
    static_assert(strlen_c("example") == 7UL, "");
    static_assert(strlen_c("another\0example") == 7UL, "");

  }

  namespace test_rvalue_references
  {

    template < int N >
    struct answer
    {
      static constexpr int value = N;
    };

    answer<1> f(int&)       { return answer<1>(); }
    answer<2> f(const int&) { return answer<2>(); }
    answer<3> f(int&&)      { return answer<3>(); }

    void
    test()
    {
      int i = 0;
      const int c = 0;
      static_assert(decltype(f(i))::value == 1, "");
      static_assert(decltype(f(c))::value == 2, "");
      static_assert(decltype(f(0))::value == 3, "");
    }

  }

  namespace test_uniform_initialization
  {

    struct test
    {
      static const int zero {};
      static const int one {1};
    };

    static_assert(test::zero == 0, "");
    static_assert(test::one == 1, "");

  }

  namespace test_lambdas
  {

    void
    test1()
    {
      auto lambda1 = [](){};
      auto lambda2 = lambda1;
      lambda1();
      lambda2();
    }

    int
    test2()
    {
      auto a = [](int i, int j){ return i + j; }(1, 2);
      auto b = []() -> int { return '0'; }();
      auto c = [=](){ return a + b; }();
      auto d = [&](){ return c; }();
      auto e = [a, &b](int x) mutable {
        const auto identity = [](int y){ return y; };
        for (auto i = 0; i < a; ++i)
          a += b--;
        return x + identity(a + b);
      }(0);
      return a + b + c + d + e;
    }

    int
    test3()
    {
      const auto nullary = [](){ return 0; };
      const auto unary = [](int x){ return x; };
      using nullary_t = decltype(nullary);
      using unary_t = decltype(unary);
      const auto higher1st = [](nullary_t f){ return f(); };
      const auto higher2nd = [unary](nullary_t f1){
        return [unary, f1](unary_t f2){ return f2(unary(f1())); };
      };
      return higher1st(nullary) + higher2nd(nullary)(unary);
    }

  }

  namespace test_variadic_templates
  {

    template <int...>
    struct sum;

    template <int N0, int... N1toN>
    struct sum<N0, N1toN...>
    {
      static constexpr auto value = N0 + sum<N1toN...>::value;
    };

    template <>
    struct sum<>
    {
      static constexpr auto value = 0;
    };

    static_assert(sum<>::value == 0, "");
    static_assert(sum<1>::value == 1, "");
    static_assert(sum<23>::value == 23, "");
    static_assert(sum<1, 2>::value == 3, "");
    static_assert(sum<5, 5, 11>::value == 21, "");
    static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");

  }

  // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
  // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
  // because of this.
  namespace test_template_alias_sfinae
  {

    struct foo {};

    template<typename T>
    using member = typename T::member_type;

    template<typename T>
    void func(...) {}

    template<typename T>
    void func(member<T>*) {}

    void test();

    void test() { func<foo>(0); }

  }

}  // namespace cxx11

#endif  // __cplusplus >= 201103L

]])


dnl  Tests for new features in C++14

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[

// If the compiler admits that it is not ready for C++14, why torture it?
// Hopefully, this will speed up the test.

#ifndef __cplusplus

#error "This is not a C++ compiler"

#elif __cplusplus < 201402L && !defined _MSC_VER

#error "This is not a C++14 compiler"

#else

namespace cxx14
{

  namespace test_polymorphic_lambdas
  {

    int
    test()
    {
      const auto lambda = [](auto&&... args){
        const auto istiny = [](auto x){
          return (sizeof(x) == 1UL) ? 1 : 0;
        };
        const int aretiny[] = { istiny(args)... };
        return aretiny[0];
      };
      return lambda(1, 1L, 1.0f, '1');
    }

  }

  namespace test_binary_literals
  {

    constexpr auto ivii = 0b0000000000101010;
    static_assert(ivii == 42, "wrong value");

  }

  namespace test_generalized_constexpr
  {

    template < typename CharT >
    constexpr unsigned long
    strlen_c(const CharT *const s) noexcept
    {
      auto length = 0UL;
      for (auto p = s; *p; ++p)
        ++length;
      return length;
    }

    static_assert(strlen_c("") == 0UL, "");
    static_assert(strlen_c("x") == 1UL, "");
    static_assert(strlen_c("test") == 4UL, "");
    static_assert(strlen_c("another\0test") == 7UL, "");

  }

  namespace test_lambda_init_capture
  {

    int
    test()
    {
      auto x = 0;
      const auto lambda1 = [a = x](int b){ return a + b; };
      const auto lambda2 = [a = lambda1(x)](){ return a; };
      return lambda2();
    }

  }

  namespace test_digit_separators
  {

    constexpr auto ten_million = 100'000'000;
    static_assert(ten_million == 100000000, "");

  }

  namespace test_return_type_deduction
  {

    auto f(int& x) { return x; }
    decltype(auto) g(int& x) { return x; }

    template < typename T1, typename T2 >
    struct is_same
    {
      static constexpr auto value = false;
    };

    template < typename T >
    struct is_same<T, T>
    {
      static constexpr auto value = true;
    };

    int
    test()
    {
      auto x = 0;
      static_assert(is_same<int, decltype(f(x))>::value, "");
      static_assert(is_same<int&, decltype(g(x))>::value, "");
      return x;
    }

  }

}  // namespace cxx14

#endif  // __cplusplus >= 201402L

]])


dnl  Tests for new features in C++17

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[

// If the compiler admits that it is not ready for C++17, why torture it?
// Hopefully, this will speed up the test.

#ifndef __cplusplus

#error "This is not a C++ compiler"

#elif __cplusplus < 201703L && !defined _MSC_VER

#error "This is not a C++17 compiler"

#else

#include <initializer_list>
#include <utility>
#include <type_traits>

namespace cxx17
{

  namespace test_constexpr_lambdas
  {

    constexpr int foo = [](){return 42;}();

  }

  namespace test::nested_namespace::definitions
  {

  }

  namespace test_fold_expression
  {

    template<typename... Args>
    int multiply(Args... args)
    {
      return (args * ... * 1);
    }

    template<typename... Args>
    bool all(Args... args)
    {
      return (args && ...);
    }

  }

  namespace test_extended_static_assert
  {

    static_assert (true);

  }

  namespace test_auto_brace_init_list
  {

    auto foo = {5};
    auto bar {5};

    static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
    static_assert(std::is_same<int, decltype(bar)>::value);
  }

  namespace test_typename_in_template_template_parameter
  {

    template<template<typename> typename X> struct D;

  }

  namespace test_fallthrough_nodiscard_maybe_unused_attributes
  {

    int f1()
    {
      return 42;
    }

    [[nodiscard]] int f2()
    {
      [[maybe_unused]] auto unused = f1();

      switch (f1())
      {
      case 17:
        f1();
        [[fallthrough]];
      case 42:
        f1();
      }
      return f1();
    }

  }

  namespace test_extended_aggregate_initialization
  {

    struct base1
    {
      int b1, b2 = 42;
    };

    struct base2
    {
      base2() {
        b3 = 42;
      }
      int b3;
    };

    struct derived : base1, base2
    {
        int d;
    };

    derived d1 {{1, 2}, {}, 4};  // full initialization
    derived d2 {{}, {}, 4};      // value-initialized bases

  }

  namespace test_general_range_based_for_loop
  {

    struct iter
    {
      int i;

      int& operator* ()
      {
        return i;
      }

      const int& operator* () const
      {
        return i;
      }

      iter& operator++()
      {
        ++i;
        return *this;
      }
    };

    struct sentinel
    {
      int i;
    };

    bool operator== (const iter& i, const sentinel& s)
    {
      return i.i == s.i;
    }

    bool operator!= (const iter& i, const sentinel& s)
    {
      return !(i == s);
    }

    struct range
    {
      iter begin() const
      {
        return {0};
      }

      sentinel end() const
      {
        return {5};
      }
    };

    void f()
    {
      range r {};

      for (auto i : r)
      {
        [[maybe_unused]] auto v = i;
      }
    }

  }

  namespace test_lambda_capture_asterisk_this_by_value
  {

    struct t
    {
      int i;
      int foo()
      {
        return [*this]()
        {
          return i;
        }();
      }
    };

  }

  namespace test_enum_class_construction
  {

    enum class byte : unsigned char
    {};

    byte foo {42};

  }

  namespace test_constexpr_if
  {

    template <bool cond>
    int f ()
    {
      if constexpr(cond)
      {
        return 13;
      }
      else
      {
        return 42;
      }
    }

  }

  namespace test_selection_statement_with_initializer
  {

    int f()
    {
      return 13;
    }

    int f2()
    {
      if (auto i = f(); i > 0)
      {
        return 3;
      }

      switch (auto i = f(); i + 4)
      {
      case 17:
        return 2;

      default:
        return 1;
      }
    }

  }

  namespace test_template_argument_deduction_for_class_templates
  {

    template <typename T1, typename T2>
    struct pair
    {
      pair (T1 p1, T2 p2)
        : m1 {p1},
          m2 {p2}
      {}

      T1 m1;
      T2 m2;
    };

    void f()
    {
      [[maybe_unused]] auto p = pair{13, 42u};
    }

  }

  namespace test_non_type_auto_template_parameters
  {

    template <auto n>
    struct B
    {};

    B<5> b1;
    B<'a'> b2;

  }

  namespace test_structured_bindings
  {

    int arr[2] = { 1, 2 };
    std::pair<int, int> pr = { 1, 2 };

    auto f1() -> int(&)[2]
    {
      return arr;
    }

    auto f2() -> std::pair<int, int>&
    {
      return pr;
    }

    struct S
    {
      int x1 : 2;
      volatile double y1;
    };

    S f3()
    {
      return {};
    }

    auto [ x1, y1 ] = f1();
    auto& [ xr1, yr1 ] = f1();
    auto [ x2, y2 ] = f2();
    auto& [ xr2, yr2 ] = f2();
    const auto [ x3, y3 ] = f3();

  }

  namespace test_exception_spec_type_system
  {

    struct Good {};
    struct Bad {};

    void g1() noexcept;
    void g2();

    template<typename T>
    Bad
    f(T*, T*);

    template<typename T1, typename T2>
    Good
    f(T1*, T2*);

    static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);

  }

  namespace test_inline_variables
  {

    template<class T> void f(T)
    {}

    template<class T> inline T g(T)
    {
      return T{};
    }

    template<> inline void f<>(int)
    {}

    template<> int g<>(int)
    {
      return 5;
    }

  }

}  // namespace cxx17

#endif  // __cplusplus < 201703L && !defined _MSC_VER

]])


dnl  Tests for new features in C++20

m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_20], [[

#ifndef __cplusplus

#error "This is not a C++ compiler"

#elif __cplusplus < 202002L && !defined _MSC_VER

#error "This is not a C++20 compiler"

#else

#include <version>

namespace cxx20
{

// As C++20 supports feature test macros in the standard, there is no
// immediate need to actually test for feature availability on the
// Autoconf side.

}  // namespace cxx20

#endif  // __cplusplus < 202002L && !defined _MSC_VER

]])