trunk/m4/ax_cxx_compile_stdcxx.m4

# ===========================================================================
#  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' (for the C++11 standard)
#   or '14' (for the C++14 standard).
#
#   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 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>
#
#   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.

#serial 11

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"],
        [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([$2], [noext], [], [dnl
  if test x$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"
    for alternative in ${ax_cxx_compile_alternatives}; do
      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
        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 $switch"
          fi
          ac_success=yes
          break
        fi
      done
      if test x$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
)

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  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"

#elif __cplusplus < 201103L

#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

#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

#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

]])
1	# ===========================================================================
2	# https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html
3	# ===========================================================================
4	#
5	# SYNOPSIS
6	#
7	# AX_CXX_COMPILE_STDCXX(VERSION, [ext\|noext], [mandatory\|optional])
8	#
9	# DESCRIPTION
10	#
11	# Check for baseline language coverage in the compiler for the specified
12	# version of the C++ standard. If necessary, add switches to CXX and
13	# CXXCPP to enable support. VERSION may be '11' (for the C++11 standard)
14	# or '14' (for the C++14 standard).
15	#
16	# The second argument, if specified, indicates whether you insist on an
17	# extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
18	# -std=c++11). If neither is specified, you get whatever works, with
19	# preference for an extended mode.
20	#
21	# The third argument, if specified 'mandatory' or if left unspecified,
22	# indicates that baseline support for the specified C++ standard is
23	# required and that the macro should error out if no mode with that
24	# support is found. If specified 'optional', then configuration proceeds
25	# regardless, after defining HAVE_CXX${VERSION} if and only if a
26	# supporting mode is found.
27	#
28	# LICENSE
29	#
30	# Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
31	# Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
32	# Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
33	# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
34	# Copyright (c) 2015 Paul Norman <penorman@mac.com>
35	# Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
36	# Copyright (c) 2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
37	# Copyright (c) 2019 Enji Cooper <yaneurabeya@gmail.com>
38	#
39	# Copying and distribution of this file, with or without modification, are
40	# permitted in any medium without royalty provided the copyright notice
41	# and this notice are preserved. This file is offered as-is, without any
42	# warranty.
43
44	#serial 11
45
46	dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
47	dnl (serial version number 13).
48
49	AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
50	m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
51	[$1], [14], [ax_cxx_compile_alternatives="14 1y"],
52	[$1], [17], [ax_cxx_compile_alternatives="17 1z"],
53	[m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
54	m4_if([$2], [], [],
55	[$2], [ext], [],
56	[$2], [noext], [],
57	[m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
58	m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
59	[$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
60	[$3], [optional], [ax_cxx_compile_cxx$1_required=false],
61	[m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
62	AC_LANG_PUSH([C++])dnl
63	ac_success=no
64
65	m4_if([$2], [noext], [], [dnl
66	if test x$ac_success = xno; then
67	for alternative in ${ax_cxx_compile_alternatives}; do
68	switch="-std=gnu++${alternative}"
69	cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
70	AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
71	$cachevar,
72	[ac_save_CXX="$CXX"
73	CXX="$CXX $switch"
74	AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
75	[eval $cachevar=yes],
76	[eval $cachevar=no])
77	CXX="$ac_save_CXX"])
78	if eval test x\$$cachevar = xyes; then
79	CXX="$CXX $switch"
80	if test -n "$CXXCPP" ; then
81	CXXCPP="$CXXCPP $switch"
82	fi
83	ac_success=yes
84	break
85	fi
86	done
87	fi])
88
89	m4_if([$2], [ext], [], [dnl
90	if test x$ac_success = xno; then
91	dnl HP's aCC needs +std=c++11 according to:
92	dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
93	dnl Cray's crayCC needs "-h std=c++11"
94	for alternative in ${ax_cxx_compile_alternatives}; do
95	for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
96	cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
97	AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
98	$cachevar,
99	[ac_save_CXX="$CXX"
100	CXX="$CXX $switch"
101	AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
102	[eval $cachevar=yes],
103	[eval $cachevar=no])
104	CXX="$ac_save_CXX"])
105	if eval test x\$$cachevar = xyes; then
106	CXX="$CXX $switch"
107	if test -n "$CXXCPP" ; then
108	CXXCPP="$CXXCPP $switch"
109	fi
110	ac_success=yes
111	break
112	fi
113	done
114	if test x$ac_success = xyes; then
115	break
116	fi
117	done
118	fi])
119	AC_LANG_POP([C++])
120	if test x$ax_cxx_compile_cxx$1_required = xtrue; then
121	if test x$ac_success = xno; then
122	AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
123	fi
124	fi
125	if test x$ac_success = xno; then
126	HAVE_CXX$1=0
127	AC_MSG_NOTICE([No compiler with C++$1 support was found])
128	else
129	HAVE_CXX$1=1
130	AC_DEFINE(HAVE_CXX$1,1,
131	[define if the compiler supports basic C++$1 syntax])
132	fi
133	AC_SUBST(HAVE_CXX$1)
134	])
135
136
137	dnl Test body for checking C++11 support
138
139	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
140	_AX_CXX_COMPILE_STDCXX_testbody_new_in_11
141	)
142
143
144	dnl Test body for checking C++14 support
145
146	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
147	_AX_CXX_COMPILE_STDCXX_testbody_new_in_11
148	_AX_CXX_COMPILE_STDCXX_testbody_new_in_14
149	)
150
151	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
152	_AX_CXX_COMPILE_STDCXX_testbody_new_in_11
153	_AX_CXX_COMPILE_STDCXX_testbody_new_in_14
154	_AX_CXX_COMPILE_STDCXX_testbody_new_in_17
155	)
156
157	dnl Tests for new features in C++11
158
159	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
160
161	// If the compiler admits that it is not ready for C++11, why torture it?
162	// Hopefully, this will speed up the test.
163
164	#ifndef __cplusplus
165
166	#error "This is not a C++ compiler"
167
168	#elif __cplusplus < 201103L
169
170	#error "This is not a C++11 compiler"
171
172	#else
173
174	namespace cxx11
175	{
176
177	namespace test_static_assert
178	{
179
180	template <typename T>
181	struct check
182	{
183	static_assert(sizeof(int) <= sizeof(T), "not big enough");
184	};
185
186	}
187
188	namespace test_final_override
189	{
190
191	struct Base
192	{
193	virtual ~Base() {}
194	virtual void f() {}
195	};
196
197	struct Derived : public Base
198	{
199	virtual ~Derived() override {}
200	virtual void f() override {}
201	};
202
203	}
204
205	namespace test_double_right_angle_brackets
206	{
207
208	template < typename T >
209	struct check {};
210
211	typedef check<void> single_type;
212	typedef check<check<void>> double_type;
213	typedef check<check<check<void>>> triple_type;
214	typedef check<check<check<check<void>>>> quadruple_type;
215
216	}
217
218	namespace test_decltype
219	{
220
221	int
222	f()
223	{
224	int a = 1;
225	decltype(a) b = 2;
226	return a + b;
227	}
228
229	}
230
231	namespace test_type_deduction
232	{
233
234	template < typename T1, typename T2 >
235	struct is_same
236	{
237	static const bool value = false;
238	};
239
240	template < typename T >
241	struct is_same<T, T>
242	{
243	static const bool value = true;
244	};
245
246	template < typename T1, typename T2 >
247	auto
248	add(T1 a1, T2 a2) -> decltype(a1 + a2)
249	{
250	return a1 + a2;
251	}
252
253	int
254	test(const int c, volatile int v)
255	{
256	static_assert(is_same<int, decltype(0)>::value == true, "");
257	static_assert(is_same<int, decltype(c)>::value == false, "");
258	static_assert(is_same<int, decltype(v)>::value == false, "");
259	auto ac = c;
260	auto av = v;
261	auto sumi = ac + av + 'x';
262	auto sumf = ac + av + 1.0;
263	static_assert(is_same<int, decltype(ac)>::value == true, "");
264	static_assert(is_same<int, decltype(av)>::value == true, "");
265	static_assert(is_same<int, decltype(sumi)>::value == true, "");
266	static_assert(is_same<int, decltype(sumf)>::value == false, "");
267	static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
268	return (sumf > 0.0) ? sumi : add(c, v);
269	}
270
271	}
272
273	namespace test_noexcept
274	{
275
276	int f() { return 0; }
277	int g() noexcept { return 0; }
278
279	static_assert(noexcept(f()) == false, "");
280	static_assert(noexcept(g()) == true, "");
281
282	}
283
284	namespace test_constexpr
285	{
286
287	template < typename CharT >
288	unsigned long constexpr
289	strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
290	{
291	return *s ? strlen_c_r(s + 1, acc + 1) : acc;
292	}
293
294	template < typename CharT >
295	unsigned long constexpr
296	strlen_c(const CharT *const s) noexcept
297	{
298	return strlen_c_r(s, 0UL);
299	}
300
301	static_assert(strlen_c("") == 0UL, "");
302	static_assert(strlen_c("1") == 1UL, "");
303	static_assert(strlen_c("example") == 7UL, "");
304	static_assert(strlen_c("another\0example") == 7UL, "");
305
306	}
307
308	namespace test_rvalue_references
309	{
310
311	template < int N >
312	struct answer
313	{
314	static constexpr int value = N;
315	};
316
317	answer<1> f(int&) { return answer<1>(); }
318	answer<2> f(const int&) { return answer<2>(); }
319	answer<3> f(int&&) { return answer<3>(); }
320
321	void
322	test()
323	{
324	int i = 0;
325	const int c = 0;
326	static_assert(decltype(f(i))::value == 1, "");
327	static_assert(decltype(f(c))::value == 2, "");
328	static_assert(decltype(f(0))::value == 3, "");
329	}
330
331	}
332
333	namespace test_uniform_initialization
334	{
335
336	struct test
337	{
338	static const int zero {};
339	static const int one {1};
340	};
341
342	static_assert(test::zero == 0, "");
343	static_assert(test::one == 1, "");
344
345	}
346
347	namespace test_lambdas
348	{
349
350	void
351	test1()
352	{
353	auto lambda1 = [](){};
354	auto lambda2 = lambda1;
355	lambda1();
356	lambda2();
357	}
358
359	int
360	test2()
361	{
362	auto a = [](int i, int j){ return i + j; }(1, 2);
363	auto b = []() -> int { return '0'; }();
364	auto c = [=](){ return a + b; }();
365	auto d = [&](){ return c; }();
366	auto e = [a, &b](int x) mutable {
367	const auto identity = [](int y){ return y; };
368	for (auto i = 0; i < a; ++i)
369	a += b--;
370	return x + identity(a + b);
371	}(0);
372	return a + b + c + d + e;
373	}
374
375	int
376	test3()
377	{
378	const auto nullary = [](){ return 0; };
379	const auto unary = [](int x){ return x; };
380	using nullary_t = decltype(nullary);
381	using unary_t = decltype(unary);
382	const auto higher1st = [](nullary_t f){ return f(); };
383	const auto higher2nd = [unary](nullary_t f1){
384	return [unary, f1](unary_t f2){ return f2(unary(f1())); };
385	};
386	return higher1st(nullary) + higher2nd(nullary)(unary);
387	}
388
389	}
390
391	namespace test_variadic_templates
392	{
393
394	template <int...>
395	struct sum;
396
397	template <int N0, int... N1toN>
398	struct sum<N0, N1toN...>
399	{
400	static constexpr auto value = N0 + sum<N1toN...>::value;
401	};
402
403	template <>
404	struct sum<>
405	{
406	static constexpr auto value = 0;
407	};
408
409	static_assert(sum<>::value == 0, "");
410	static_assert(sum<1>::value == 1, "");
411	static_assert(sum<23>::value == 23, "");
412	static_assert(sum<1, 2>::value == 3, "");
413	static_assert(sum<5, 5, 11>::value == 21, "");
414	static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
415
416	}
417
418	// http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
419	// Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
420	// because of this.
421	namespace test_template_alias_sfinae
422	{
423
424	struct foo {};
425
426	template<typename T>
427	using member = typename T::member_type;
428
429	template<typename T>
430	void func(...) {}
431
432	template<typename T>
433	void func(member<T>*) {}
434
435	void test();
436
437	void test() { func<foo>(0); }
438
439	}
440
441	} // namespace cxx11
442
443	#endif // __cplusplus >= 201103L
444
445	]])
446
447
448	dnl Tests for new features in C++14
449
450	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
451
452	// If the compiler admits that it is not ready for C++14, why torture it?
453	// Hopefully, this will speed up the test.
454
455	#ifndef __cplusplus
456
457	#error "This is not a C++ compiler"
458
459	#elif __cplusplus < 201402L
460
461	#error "This is not a C++14 compiler"
462
463	#else
464
465	namespace cxx14
466	{
467
468	namespace test_polymorphic_lambdas
469	{
470
471	int
472	test()
473	{
474	const auto lambda = [](auto&&... args){
475	const auto istiny = [](auto x){
476	return (sizeof(x) == 1UL) ? 1 : 0;
477	};
478	const int aretiny[] = { istiny(args)... };
479	return aretiny[0];
480	};
481	return lambda(1, 1L, 1.0f, '1');
482	}
483
484	}
485
486	namespace test_binary_literals
487	{
488
489	constexpr auto ivii = 0b0000000000101010;
490	static_assert(ivii == 42, "wrong value");
491
492	}
493
494	namespace test_generalized_constexpr
495	{
496
497	template < typename CharT >
498	constexpr unsigned long
499	strlen_c(const CharT *const s) noexcept
500	{
501	auto length = 0UL;
502	for (auto p = s; *p; ++p)
503	++length;
504	return length;
505	}
506
507	static_assert(strlen_c("") == 0UL, "");
508	static_assert(strlen_c("x") == 1UL, "");
509	static_assert(strlen_c("test") == 4UL, "");
510	static_assert(strlen_c("another\0test") == 7UL, "");
511
512	}
513
514	namespace test_lambda_init_capture
515	{
516
517	int
518	test()
519	{
520	auto x = 0;
521	const auto lambda1 = [a = x](int b){ return a + b; };
522	const auto lambda2 = [a = lambda1(x)](){ return a; };
523	return lambda2();
524	}
525
526	}
527
528	namespace test_digit_separators
529	{
530
531	constexpr auto ten_million = 100'000'000;
532	static_assert(ten_million == 100000000, "");
533
534	}
535
536	namespace test_return_type_deduction
537	{
538
539	auto f(int& x) { return x; }
540	decltype(auto) g(int& x) { return x; }
541
542	template < typename T1, typename T2 >
543	struct is_same
544	{
545	static constexpr auto value = false;
546	};
547
548	template < typename T >
549	struct is_same<T, T>
550	{
551	static constexpr auto value = true;
552	};
553
554	int
555	test()
556	{
557	auto x = 0;
558	static_assert(is_same<int, decltype(f(x))>::value, "");
559	static_assert(is_same<int&, decltype(g(x))>::value, "");
560	return x;
561	}
562
563	}
564
565	} // namespace cxx14
566
567	#endif // __cplusplus >= 201402L
568
569	]])
570
571
572	dnl Tests for new features in C++17
573
574	m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
575
576	// If the compiler admits that it is not ready for C++17, why torture it?
577	// Hopefully, this will speed up the test.
578
579	#ifndef __cplusplus
580
581	#error "This is not a C++ compiler"
582
583	#elif __cplusplus < 201703L
584
585	#error "This is not a C++17 compiler"
586
587	#else
588
589	#include <initializer_list>
590	#include <utility>
591	#include <type_traits>
592
593	namespace cxx17
594	{
595
596	namespace test_constexpr_lambdas
597	{
598
599	constexpr int foo = [](){return 42;}();
600
601	}
602
603	namespace test::nested_namespace::definitions
604	{
605
606	}
607
608	namespace test_fold_expression
609	{
610
611	template<typename... Args>
612	int multiply(Args... args)
613	{
614	return (args * ... * 1);
615	}
616
617	template<typename... Args>
618	bool all(Args... args)
619	{
620	return (args && ...);
621	}
622
623	}
624
625	namespace test_extended_static_assert
626	{
627
628	static_assert (true);
629
630	}
631
632	namespace test_auto_brace_init_list
633	{
634
635	auto foo = {5};
636	auto bar {5};
637
638	static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
639	static_assert(std::is_same<int, decltype(bar)>::value);
640	}
641
642	namespace test_typename_in_template_template_parameter
643	{
644
645	template<template<typename> typename X> struct D;
646
647	}
648
649	namespace test_fallthrough_nodiscard_maybe_unused_attributes
650	{
651
652	int f1()
653	{
654	return 42;
655	}
656
657	[[nodiscard]] int f2()
658	{
659	[[maybe_unused]] auto unused = f1();
660
661	switch (f1())
662	{
663	case 17:
664	f1();
665	[[fallthrough]];
666	case 42:
667	f1();
668	}
669	return f1();
670	}
671
672	}
673
674	namespace test_extended_aggregate_initialization
675	{
676
677	struct base1
678	{
679	int b1, b2 = 42;
680	};
681
682	struct base2
683	{
684	base2() {
685	b3 = 42;
686	}
687	int b3;
688	};
689
690	struct derived : base1, base2
691	{
692	int d;
693	};
694
695	derived d1 {{1, 2}, {}, 4}; // full initialization
696	derived d2 {{}, {}, 4}; // value-initialized bases
697
698	}
699
700	namespace test_general_range_based_for_loop
701	{
702
703	struct iter
704	{
705	int i;
706
707	int& operator* ()
708	{
709	return i;
710	}
711
712	const int& operator* () const
713	{
714	return i;
715	}
716
717	iter& operator++()
718	{
719	++i;
720	return *this;
721	}
722	};
723
724	struct sentinel
725	{
726	int i;
727	};
728
729	bool operator== (const iter& i, const sentinel& s)
730	{
731	return i.i == s.i;
732	}
733
734	bool operator!= (const iter& i, const sentinel& s)
735	{
736	return !(i == s);
737	}
738
739	struct range
740	{
741	iter begin() const
742	{
743	return {0};
744	}
745
746	sentinel end() const
747	{
748	return {5};
749	}
750	};
751
752	void f()
753	{
754	range r {};
755
756	for (auto i : r)
757	{
758	[[maybe_unused]] auto v = i;
759	}
760	}
761
762	}
763
764	namespace test_lambda_capture_asterisk_this_by_value
765	{
766
767	struct t
768	{
769	int i;
770	int foo()
771	{
772	return [*this]()
773	{
774	return i;
775	}();
776	}
777	};
778
779	}
780
781	namespace test_enum_class_construction
782	{
783
784	enum class byte : unsigned char
785	{};
786
787	byte foo {42};
788
789	}
790
791	namespace test_constexpr_if
792	{
793
794	template <bool cond>
795	int f ()
796	{
797	if constexpr(cond)
798	{
799	return 13;
800	}
801	else
802	{
803	return 42;
804	}
805	}
806
807	}
808
809	namespace test_selection_statement_with_initializer
810	{
811
812	int f()
813	{
814	return 13;
815	}
816
817	int f2()
818	{
819	if (auto i = f(); i > 0)
820	{
821	return 3;
822	}
823
824	switch (auto i = f(); i + 4)
825	{
826	case 17:
827	return 2;
828
829	default:
830	return 1;
831	}
832	}
833
834	}
835
836	namespace test_template_argument_deduction_for_class_templates
837	{
838
839	template <typename T1, typename T2>
840	struct pair
841	{
842	pair (T1 p1, T2 p2)
843	: m1 {p1},
844	m2 {p2}
845	{}
846
847	T1 m1;
848	T2 m2;
849	};
850
851	void f()
852	{
853	[[maybe_unused]] auto p = pair{13, 42u};
854	}
855
856	}
857
858	namespace test_non_type_auto_template_parameters
859	{
860
861	template <auto n>
862	struct B
863	{};
864
865	B<5> b1;
866	B<'a'> b2;
867
868	}
869
870	namespace test_structured_bindings
871	{
872
873	int arr[2] = { 1, 2 };
874	std::pair<int, int> pr = { 1, 2 };
875
876	auto f1() -> int(&)[2]
877	{
878	return arr;
879	}
880
881	auto f2() -> std::pair<int, int>&
882	{
883	return pr;
884	}
885
886	struct S
887	{
888	int x1 : 2;
889	volatile double y1;
890	};
891
892	S f3()
893	{
894	return {};
895	}
896
897	auto [ x1, y1 ] = f1();
898	auto& [ xr1, yr1 ] = f1();
899	auto [ x2, y2 ] = f2();
900	auto& [ xr2, yr2 ] = f2();
901	const auto [ x3, y3 ] = f3();
902
903	}
904
905	namespace test_exception_spec_type_system
906	{
907
908	struct Good {};
909	struct Bad {};
910
911	void g1() noexcept;
912	void g2();
913
914	template<typename T>
915	Bad
916	f(T, T);
917
918	template<typename T1, typename T2>
919	Good
920	f(T1, T2);
921
922	static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
923
924	}
925
926	namespace test_inline_variables
927	{
928
929	template<class T> void f(T)
930	{}
931
932	template<class T> inline T g(T)
933	{
934	return T{};
935	}
936
937	template<> inline void f<>(int)
938	{}
939
940	template<> int g<>(int)
941	{
942	return 5;
943	}
944
945	}
946
947	} // namespace cxx17
948
949	#endif // __cplusplus < 201703L
950
951	]])