1 # ===========================================================================
2 # https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html
3 # ===========================================================================
7 # AX_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional])
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).
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.
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.
30 # SPDX-License-Identifier: FSFAP
32 # Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
33 # Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
34 # Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
35 # Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
36 # Copyright (c) 2015 Paul Norman <penorman@mac.com>
37 # Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
38 # Copyright (c) 2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
39 # Copyright (c) 2019 Enji Cooper <yaneurabeya@gmail.com>
41 # Copying and distribution of this file, with or without modification, are
42 # permitted in any medium without royalty provided the copyright notice
43 # and this notice are preserved. This file is offered as-is, without any
48 dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
49 dnl (serial version number 13).
51 AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
52 m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
53 [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
54 [$1], [17], [ax_cxx_compile_alternatives="17 1z"],
55 [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
59 [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
60 m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
61 [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
62 [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
63 [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
64 AC_LANG_PUSH([C++])dnl
67 m4_if([$2], [noext], [], [dnl
68 if test x$ac_success = xno; then
69 for alternative in ${ax_cxx_compile_alternatives}; do
70 switch="-std=gnu++${alternative}"
71 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
72 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
76 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
80 if eval test x\$$cachevar = xyes; then
82 if test -n "$CXXCPP" ; then
83 CXXCPP="$CXXCPP $switch"
91 m4_if([$2], [ext], [], [dnl
92 if test x$ac_success = xno; then
93 dnl HP's aCC needs +std=c++11 according to:
94 dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
95 dnl Cray's crayCC needs "-h std=c++11"
96 for alternative in ${ax_cxx_compile_alternatives}; do
97 for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
98 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
99 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
103 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
104 [eval $cachevar=yes],
107 if eval test x\$$cachevar = xyes; then
109 if test -n "$CXXCPP" ; then
110 CXXCPP="$CXXCPP $switch"
116 if test x$ac_success = xyes; then
122 if test x$ax_cxx_compile_cxx$1_required = xtrue; then
123 if test x$ac_success = xno; then
124 AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
127 if test x$ac_success = xno; then
129 AC_MSG_NOTICE([No compiler with C++$1 support was found])
132 AC_DEFINE(HAVE_CXX$1,1,
133 [define if the compiler supports basic C++$1 syntax])
139 dnl Test body for checking C++11 support
141 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
142 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
146 dnl Test body for checking C++14 support
148 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
149 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
150 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
153 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
154 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
155 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
156 _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
159 dnl Tests for new features in C++11
161 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
163 // If the compiler admits that it is not ready for C++11, why torture it?
164 // Hopefully, this will speed up the test.
168 #error "This is not a C++ compiler"
170 #elif __cplusplus < 201103L
172 #error "This is not a C++11 compiler"
179 namespace test_static_assert
182 template <typename T>
185 static_assert(sizeof(int) <= sizeof(T), "not big enough");
190 namespace test_final_override
199 struct Derived : public Base
201 virtual ~Derived() override {}
202 virtual void f() override {}
207 namespace test_double_right_angle_brackets
210 template < typename T >
213 typedef check<void> single_type;
214 typedef check<check<void>> double_type;
215 typedef check<check<check<void>>> triple_type;
216 typedef check<check<check<check<void>>>> quadruple_type;
220 namespace test_decltype
233 namespace test_type_deduction
236 template < typename T1, typename T2 >
239 static const bool value = false;
242 template < typename T >
245 static const bool value = true;
248 template < typename T1, typename T2 >
250 add(T1 a1, T2 a2) -> decltype(a1 + a2)
256 test(const int c, volatile int v)
258 static_assert(is_same<int, decltype(0)>::value == true, "");
259 static_assert(is_same<int, decltype(c)>::value == false, "");
260 static_assert(is_same<int, decltype(v)>::value == false, "");
263 auto sumi = ac + av + 'x';
264 auto sumf = ac + av + 1.0;
265 static_assert(is_same<int, decltype(ac)>::value == true, "");
266 static_assert(is_same<int, decltype(av)>::value == true, "");
267 static_assert(is_same<int, decltype(sumi)>::value == true, "");
268 static_assert(is_same<int, decltype(sumf)>::value == false, "");
269 static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
270 return (sumf > 0.0) ? sumi : add(c, v);
275 namespace test_noexcept
278 int f() { return 0; }
279 int g() noexcept { return 0; }
281 static_assert(noexcept(f()) == false, "");
282 static_assert(noexcept(g()) == true, "");
286 namespace test_constexpr
289 template < typename CharT >
290 unsigned long constexpr
291 strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
293 return *s ? strlen_c_r(s + 1, acc + 1) : acc;
296 template < typename CharT >
297 unsigned long constexpr
298 strlen_c(const CharT *const s) noexcept
300 return strlen_c_r(s, 0UL);
303 static_assert(strlen_c("") == 0UL, "");
304 static_assert(strlen_c("1") == 1UL, "");
305 static_assert(strlen_c("example") == 7UL, "");
306 static_assert(strlen_c("another\0example") == 7UL, "");
310 namespace test_rvalue_references
316 static constexpr int value = N;
319 answer<1> f(int&) { return answer<1>(); }
320 answer<2> f(const int&) { return answer<2>(); }
321 answer<3> f(int&&) { return answer<3>(); }
328 static_assert(decltype(f(i))::value == 1, "");
329 static_assert(decltype(f(c))::value == 2, "");
330 static_assert(decltype(f(0))::value == 3, "");
335 namespace test_uniform_initialization
340 static const int zero {};
341 static const int one {1};
344 static_assert(test::zero == 0, "");
345 static_assert(test::one == 1, "");
349 namespace test_lambdas
355 auto lambda1 = [](){};
356 auto lambda2 = lambda1;
364 auto a = [](int i, int j){ return i + j; }(1, 2);
365 auto b = []() -> int { return '0'; }();
366 auto c = [=](){ return a + b; }();
367 auto d = [&](){ return c; }();
368 auto e = [a, &b](int x) mutable {
369 const auto identity = [](int y){ return y; };
370 for (auto i = 0; i < a; ++i)
372 return x + identity(a + b);
374 return a + b + c + d + e;
380 const auto nullary = [](){ return 0; };
381 const auto unary = [](int x){ return x; };
382 using nullary_t = decltype(nullary);
383 using unary_t = decltype(unary);
384 const auto higher1st = [](nullary_t f){ return f(); };
385 const auto higher2nd = [unary](nullary_t f1){
386 return [unary, f1](unary_t f2){ return f2(unary(f1())); };
388 return higher1st(nullary) + higher2nd(nullary)(unary);
393 namespace test_variadic_templates
399 template <int N0, int... N1toN>
400 struct sum<N0, N1toN...>
402 static constexpr auto value = N0 + sum<N1toN...>::value;
408 static constexpr auto value = 0;
411 static_assert(sum<>::value == 0, "");
412 static_assert(sum<1>::value == 1, "");
413 static_assert(sum<23>::value == 23, "");
414 static_assert(sum<1, 2>::value == 3, "");
415 static_assert(sum<5, 5, 11>::value == 21, "");
416 static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
420 // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
421 // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
423 namespace test_template_alias_sfinae
429 using member = typename T::member_type;
435 void func(member<T>*) {}
439 void test() { func<foo>(0); }
445 #endif // __cplusplus >= 201103L
450 dnl Tests for new features in C++14
452 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
454 // If the compiler admits that it is not ready for C++14, why torture it?
455 // Hopefully, this will speed up the test.
459 #error "This is not a C++ compiler"
461 #elif __cplusplus < 201402L
463 #error "This is not a C++14 compiler"
470 namespace test_polymorphic_lambdas
476 const auto lambda = [](auto&&... args){
477 const auto istiny = [](auto x){
478 return (sizeof(x) == 1UL) ? 1 : 0;
480 const int aretiny[] = { istiny(args)... };
483 return lambda(1, 1L, 1.0f, '1');
488 namespace test_binary_literals
491 constexpr auto ivii = 0b0000000000101010;
492 static_assert(ivii == 42, "wrong value");
496 namespace test_generalized_constexpr
499 template < typename CharT >
500 constexpr unsigned long
501 strlen_c(const CharT *const s) noexcept
504 for (auto p = s; *p; ++p)
509 static_assert(strlen_c("") == 0UL, "");
510 static_assert(strlen_c("x") == 1UL, "");
511 static_assert(strlen_c("test") == 4UL, "");
512 static_assert(strlen_c("another\0test") == 7UL, "");
516 namespace test_lambda_init_capture
523 const auto lambda1 = [a = x](int b){ return a + b; };
524 const auto lambda2 = [a = lambda1(x)](){ return a; };
530 namespace test_digit_separators
533 constexpr auto ten_million = 100'000'000;
534 static_assert(ten_million == 100000000, "");
538 namespace test_return_type_deduction
541 auto f(int& x) { return x; }
542 decltype(auto) g(int& x) { return x; }
544 template < typename T1, typename T2 >
547 static constexpr auto value = false;
550 template < typename T >
553 static constexpr auto value = true;
560 static_assert(is_same<int, decltype(f(x))>::value, "");
561 static_assert(is_same<int&, decltype(g(x))>::value, "");
569 #endif // __cplusplus >= 201402L
574 dnl Tests for new features in C++17
576 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
578 // If the compiler admits that it is not ready for C++17, why torture it?
579 // Hopefully, this will speed up the test.
583 #error "This is not a C++ compiler"
585 #elif __cplusplus < 201703L
587 #error "This is not a C++17 compiler"
591 #include <initializer_list>
593 #include <type_traits>
598 namespace test_constexpr_lambdas
601 constexpr int foo = [](){return 42;}();
605 namespace test::nested_namespace::definitions
610 namespace test_fold_expression
613 template<typename... Args>
614 int multiply(Args... args)
616 return (args * ... * 1);
619 template<typename... Args>
620 bool all(Args... args)
622 return (args && ...);
627 namespace test_extended_static_assert
630 static_assert (true);
634 namespace test_auto_brace_init_list
640 static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
641 static_assert(std::is_same<int, decltype(bar)>::value);
644 namespace test_typename_in_template_template_parameter
647 template<template<typename> typename X> struct D;
651 namespace test_fallthrough_nodiscard_maybe_unused_attributes
659 [[nodiscard]] int f2()
661 [[maybe_unused]] auto unused = f1();
676 namespace test_extended_aggregate_initialization
692 struct derived : base1, base2
697 derived d1 {{1, 2}, {}, 4}; // full initialization
698 derived d2 {{}, {}, 4}; // value-initialized bases
702 namespace test_general_range_based_for_loop
714 const int& operator* () const
731 bool operator== (const iter& i, const sentinel& s)
736 bool operator!= (const iter& i, const sentinel& s)
760 [[maybe_unused]] auto v = i;
766 namespace test_lambda_capture_asterisk_this_by_value
783 namespace test_enum_class_construction
786 enum class byte : unsigned char
793 namespace test_constexpr_if
811 namespace test_selection_statement_with_initializer
821 if (auto i = f(); i > 0)
826 switch (auto i = f(); i + 4)
838 namespace test_template_argument_deduction_for_class_templates
841 template <typename T1, typename T2>
855 [[maybe_unused]] auto p = pair{13, 42u};
860 namespace test_non_type_auto_template_parameters
872 namespace test_structured_bindings
875 int arr[2] = { 1, 2 };
876 std::pair<int, int> pr = { 1, 2 };
878 auto f1() -> int(&)[2]
883 auto f2() -> std::pair<int, int>&
899 auto [ x1, y1 ] = f1();
900 auto& [ xr1, yr1 ] = f1();
901 auto [ x2, y2 ] = f2();
902 auto& [ xr2, yr2 ] = f2();
903 const auto [ x3, y3 ] = f3();
907 namespace test_exception_spec_type_system
920 template<typename T1, typename T2>
924 static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
928 namespace test_inline_variables
931 template<class T> void f(T)
934 template<class T> inline T g(T)
939 template<> inline void f<>(int)
942 template<> int g<>(int)
951 #endif // __cplusplus < 201703L