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	schoenebeck	3619	# ===========================================================================
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			]])