ax_cxx_compile_stdcxx.m4 raw
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 no added switch, and then 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 # Copyright (c) 2020 Jason Merrill <jason@redhat.com>
39 #
40 # Copying and distribution of this file, with or without modification, are
41 # permitted in any medium without royalty provided the copyright notice
42 # and this notice are preserved. This file is offered as-is, without any
43 # warranty.
44
45 #serial 12
46
47 dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
48 dnl (serial version number 13).
49
50 AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
51 m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
52 [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
53 [$1], [17], [ax_cxx_compile_alternatives="17 1z"],
54 [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
55 m4_if([$2], [], [],
56 [$2], [ext], [],
57 [$2], [noext], [],
58 [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
59 m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
60 [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
61 [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
62 [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
63 AC_LANG_PUSH([C++])dnl
64 ac_success=no
65
66 m4_if([$2], [], [dnl
67 AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
68 ax_cv_cxx_compile_cxx$1,
69 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
70 [ax_cv_cxx_compile_cxx$1=yes],
71 [ax_cv_cxx_compile_cxx$1=no])])
72 if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
73 ac_success=yes
74 fi])
75
76 m4_if([$2], [noext], [], [dnl
77 if test x$ac_success = xno; then
78 for alternative in ${ax_cxx_compile_alternatives}; do
79 switch="-std=gnu++${alternative}"
80 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
81 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
82 $cachevar,
83 [ac_save_CXX="$CXX"
84 CXX="$CXX $switch"
85 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
86 [eval $cachevar=yes],
87 [eval $cachevar=no])
88 CXX="$ac_save_CXX"])
89 if eval test x\$$cachevar = xyes; then
90 CXX="$CXX $switch"
91 if test -n "$CXXCPP" ; then
92 CXXCPP="$CXXCPP $switch"
93 fi
94 ac_success=yes
95 break
96 fi
97 done
98 fi])
99
100 m4_if([$2], [ext], [], [dnl
101 if test x$ac_success = xno; then
102 dnl HP's aCC needs +std=c++11 according to:
103 dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
104 dnl Cray's crayCC needs "-h std=c++11"
105 for alternative in ${ax_cxx_compile_alternatives}; do
106 for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
107 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
108 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
109 $cachevar,
110 [ac_save_CXX="$CXX"
111 CXX="$CXX $switch"
112 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
113 [eval $cachevar=yes],
114 [eval $cachevar=no])
115 CXX="$ac_save_CXX"])
116 if eval test x\$$cachevar = xyes; then
117 CXX="$CXX $switch"
118 if test -n "$CXXCPP" ; then
119 CXXCPP="$CXXCPP $switch"
120 fi
121 ac_success=yes
122 break
123 fi
124 done
125 if test x$ac_success = xyes; then
126 break
127 fi
128 done
129 fi])
130 AC_LANG_POP([C++])
131 if test x$ax_cxx_compile_cxx$1_required = xtrue; then
132 if test x$ac_success = xno; then
133 AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
134 fi
135 fi
136 if test x$ac_success = xno; then
137 HAVE_CXX$1=0
138 AC_MSG_NOTICE([No compiler with C++$1 support was found])
139 else
140 HAVE_CXX$1=1
141 AC_DEFINE(HAVE_CXX$1,1,
142 [define if the compiler supports basic C++$1 syntax])
143 fi
144 AC_SUBST(HAVE_CXX$1)
145 ])
146
147
148 dnl Test body for checking C++11 support
149
150 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
151 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
152 )
153
154
155 dnl Test body for checking C++14 support
156
157 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
158 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
159 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
160 )
161
162 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
163 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
164 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
165 _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
166 )
167
168 dnl Tests for new features in C++11
169
170 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
171
172 // If the compiler admits that it is not ready for C++11, why torture it?
173 // Hopefully, this will speed up the test.
174
175 #ifndef __cplusplus
176
177 #error "This is not a C++ compiler"
178
179 #elif __cplusplus < 201103L
180
181 #error "This is not a C++11 compiler"
182
183 #else
184
185 namespace cxx11
186 {
187
188 namespace test_static_assert
189 {
190
191 template <typename T>
192 struct check
193 {
194 static_assert(sizeof(int) <= sizeof(T), "not big enough");
195 };
196
197 }
198
199 namespace test_final_override
200 {
201
202 struct Base
203 {
204 virtual ~Base() {}
205 virtual void f() {}
206 };
207
208 struct Derived : public Base
209 {
210 virtual ~Derived() override {}
211 virtual void f() override {}
212 };
213
214 }
215
216 namespace test_double_right_angle_brackets
217 {
218
219 template < typename T >
220 struct check {};
221
222 typedef check<void> single_type;
223 typedef check<check<void>> double_type;
224 typedef check<check<check<void>>> triple_type;
225 typedef check<check<check<check<void>>>> quadruple_type;
226
227 }
228
229 namespace test_decltype
230 {
231
232 int
233 f()
234 {
235 int a = 1;
236 decltype(a) b = 2;
237 return a + b;
238 }
239
240 }
241
242 namespace test_type_deduction
243 {
244
245 template < typename T1, typename T2 >
246 struct is_same
247 {
248 static const bool value = false;
249 };
250
251 template < typename T >
252 struct is_same<T, T>
253 {
254 static const bool value = true;
255 };
256
257 template < typename T1, typename T2 >
258 auto
259 add(T1 a1, T2 a2) -> decltype(a1 + a2)
260 {
261 return a1 + a2;
262 }
263
264 int
265 test(const int c, volatile int v)
266 {
267 static_assert(is_same<int, decltype(0)>::value == true, "");
268 static_assert(is_same<int, decltype(c)>::value == false, "");
269 static_assert(is_same<int, decltype(v)>::value == false, "");
270 auto ac = c;
271 auto av = v;
272 auto sumi = ac + av + 'x';
273 auto sumf = ac + av + 1.0;
274 static_assert(is_same<int, decltype(ac)>::value == true, "");
275 static_assert(is_same<int, decltype(av)>::value == true, "");
276 static_assert(is_same<int, decltype(sumi)>::value == true, "");
277 static_assert(is_same<int, decltype(sumf)>::value == false, "");
278 static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
279 return (sumf > 0.0) ? sumi : add(c, v);
280 }
281
282 }
283
284 namespace test_noexcept
285 {
286
287 int f() { return 0; }
288 int g() noexcept { return 0; }
289
290 static_assert(noexcept(f()) == false, "");
291 static_assert(noexcept(g()) == true, "");
292
293 }
294
295 namespace test_constexpr
296 {
297
298 template < typename CharT >
299 unsigned long constexpr
300 strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
301 {
302 return *s ? strlen_c_r(s + 1, acc + 1) : acc;
303 }
304
305 template < typename CharT >
306 unsigned long constexpr
307 strlen_c(const CharT *const s) noexcept
308 {
309 return strlen_c_r(s, 0UL);
310 }
311
312 static_assert(strlen_c("") == 0UL, "");
313 static_assert(strlen_c("1") == 1UL, "");
314 static_assert(strlen_c("example") == 7UL, "");
315 static_assert(strlen_c("another\0example") == 7UL, "");
316
317 }
318
319 namespace test_rvalue_references
320 {
321
322 template < int N >
323 struct answer
324 {
325 static constexpr int value = N;
326 };
327
328 answer<1> f(int&) { return answer<1>(); }
329 answer<2> f(const int&) { return answer<2>(); }
330 answer<3> f(int&&) { return answer<3>(); }
331
332 void
333 test()
334 {
335 int i = 0;
336 const int c = 0;
337 static_assert(decltype(f(i))::value == 1, "");
338 static_assert(decltype(f(c))::value == 2, "");
339 static_assert(decltype(f(0))::value == 3, "");
340 }
341
342 }
343
344 namespace test_uniform_initialization
345 {
346
347 struct test
348 {
349 static const int zero {};
350 static const int one {1};
351 };
352
353 static_assert(test::zero == 0, "");
354 static_assert(test::one == 1, "");
355
356 }
357
358 namespace test_lambdas
359 {
360
361 void
362 test1()
363 {
364 auto lambda1 = [](){};
365 auto lambda2 = lambda1;
366 lambda1();
367 lambda2();
368 }
369
370 int
371 test2()
372 {
373 auto a = [](int i, int j){ return i + j; }(1, 2);
374 auto b = []() -> int { return '0'; }();
375 auto c = [=](){ return a + b; }();
376 auto d = [&](){ return c; }();
377 auto e = [a, &b](int x) mutable {
378 const auto identity = [](int y){ return y; };
379 for (auto i = 0; i < a; ++i)
380 a += b--;
381 return x + identity(a + b);
382 }(0);
383 return a + b + c + d + e;
384 }
385
386 int
387 test3()
388 {
389 const auto nullary = [](){ return 0; };
390 const auto unary = [](int x){ return x; };
391 using nullary_t = decltype(nullary);
392 using unary_t = decltype(unary);
393 const auto higher1st = [](nullary_t f){ return f(); };
394 const auto higher2nd = [unary](nullary_t f1){
395 return [unary, f1](unary_t f2){ return f2(unary(f1())); };
396 };
397 return higher1st(nullary) + higher2nd(nullary)(unary);
398 }
399
400 }
401
402 namespace test_variadic_templates
403 {
404
405 template <int...>
406 struct sum;
407
408 template <int N0, int... N1toN>
409 struct sum<N0, N1toN...>
410 {
411 static constexpr auto value = N0 + sum<N1toN...>::value;
412 };
413
414 template <>
415 struct sum<>
416 {
417 static constexpr auto value = 0;
418 };
419
420 static_assert(sum<>::value == 0, "");
421 static_assert(sum<1>::value == 1, "");
422 static_assert(sum<23>::value == 23, "");
423 static_assert(sum<1, 2>::value == 3, "");
424 static_assert(sum<5, 5, 11>::value == 21, "");
425 static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
426
427 }
428
429 // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
430 // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
431 // because of this.
432 namespace test_template_alias_sfinae
433 {
434
435 struct foo {};
436
437 template<typename T>
438 using member = typename T::member_type;
439
440 template<typename T>
441 void func(...) {}
442
443 template<typename T>
444 void func(member<T>*) {}
445
446 void test();
447
448 void test() { func<foo>(0); }
449
450 }
451
452 } // namespace cxx11
453
454 #endif // __cplusplus >= 201103L
455
456 ]])
457
458
459 dnl Tests for new features in C++14
460
461 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
462
463 // If the compiler admits that it is not ready for C++14, why torture it?
464 // Hopefully, this will speed up the test.
465
466 #ifndef __cplusplus
467
468 #error "This is not a C++ compiler"
469
470 #elif __cplusplus < 201402L
471
472 #error "This is not a C++14 compiler"
473
474 #else
475
476 namespace cxx14
477 {
478
479 namespace test_polymorphic_lambdas
480 {
481
482 int
483 test()
484 {
485 const auto lambda = [](auto&&... args){
486 const auto istiny = [](auto x){
487 return (sizeof(x) == 1UL) ? 1 : 0;
488 };
489 const int aretiny[] = { istiny(args)... };
490 return aretiny[0];
491 };
492 return lambda(1, 1L, 1.0f, '1');
493 }
494
495 }
496
497 namespace test_binary_literals
498 {
499
500 constexpr auto ivii = 0b0000000000101010;
501 static_assert(ivii == 42, "wrong value");
502
503 }
504
505 namespace test_generalized_constexpr
506 {
507
508 template < typename CharT >
509 constexpr unsigned long
510 strlen_c(const CharT *const s) noexcept
511 {
512 auto length = 0UL;
513 for (auto p = s; *p; ++p)
514 ++length;
515 return length;
516 }
517
518 static_assert(strlen_c("") == 0UL, "");
519 static_assert(strlen_c("x") == 1UL, "");
520 static_assert(strlen_c("test") == 4UL, "");
521 static_assert(strlen_c("another\0test") == 7UL, "");
522
523 }
524
525 namespace test_lambda_init_capture
526 {
527
528 int
529 test()
530 {
531 auto x = 0;
532 const auto lambda1 = [a = x](int b){ return a + b; };
533 const auto lambda2 = [a = lambda1(x)](){ return a; };
534 return lambda2();
535 }
536
537 }
538
539 namespace test_digit_separators
540 {
541
542 constexpr auto ten_million = 100'000'000;
543 static_assert(ten_million == 100000000, "");
544
545 }
546
547 namespace test_return_type_deduction
548 {
549
550 auto f(int& x) { return x; }
551 decltype(auto) g(int& x) { return x; }
552
553 template < typename T1, typename T2 >
554 struct is_same
555 {
556 static constexpr auto value = false;
557 };
558
559 template < typename T >
560 struct is_same<T, T>
561 {
562 static constexpr auto value = true;
563 };
564
565 int
566 test()
567 {
568 auto x = 0;
569 static_assert(is_same<int, decltype(f(x))>::value, "");
570 static_assert(is_same<int&, decltype(g(x))>::value, "");
571 return x;
572 }
573
574 }
575
576 } // namespace cxx14
577
578 #endif // __cplusplus >= 201402L
579
580 ]])
581
582
583 dnl Tests for new features in C++17
584
585 m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
586
587 // If the compiler admits that it is not ready for C++17, why torture it?
588 // Hopefully, this will speed up the test.
589
590 #ifndef __cplusplus
591
592 #error "This is not a C++ compiler"
593
594 #elif __cplusplus < 201703L
595
596 #error "This is not a C++17 compiler"
597
598 #else
599
600 #include <initializer_list>
601 #include <utility>
602 #include <type_traits>
603
604 namespace cxx17
605 {
606
607 namespace test_constexpr_lambdas
608 {
609
610 constexpr int foo = [](){return 42;}();
611
612 }
613
614 namespace test::nested_namespace::definitions
615 {
616
617 }
618
619 namespace test_fold_expression
620 {
621
622 template<typename... Args>
623 int multiply(Args... args)
624 {
625 return (args * ... * 1);
626 }
627
628 template<typename... Args>
629 bool all(Args... args)
630 {
631 return (args && ...);
632 }
633
634 }
635
636 namespace test_extended_static_assert
637 {
638
639 static_assert (true);
640
641 }
642
643 namespace test_auto_brace_init_list
644 {
645
646 auto foo = {5};
647 auto bar {5};
648
649 static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
650 static_assert(std::is_same<int, decltype(bar)>::value);
651 }
652
653 namespace test_typename_in_template_template_parameter
654 {
655
656 template<template<typename> typename X> struct D;
657
658 }
659
660 namespace test_fallthrough_nodiscard_maybe_unused_attributes
661 {
662
663 int f1()
664 {
665 return 42;
666 }
667
668 [[nodiscard]] int f2()
669 {
670 [[maybe_unused]] auto unused = f1();
671
672 switch (f1())
673 {
674 case 17:
675 f1();
676 [[fallthrough]];
677 case 42:
678 f1();
679 }
680 return f1();
681 }
682
683 }
684
685 namespace test_extended_aggregate_initialization
686 {
687
688 struct base1
689 {
690 int b1, b2 = 42;
691 };
692
693 struct base2
694 {
695 base2() {
696 b3 = 42;
697 }
698 int b3;
699 };
700
701 struct derived : base1, base2
702 {
703 int d;
704 };
705
706 derived d1 {{1, 2}, {}, 4}; // full initialization
707 derived d2 {{}, {}, 4}; // value-initialized bases
708
709 }
710
711 namespace test_general_range_based_for_loop
712 {
713
714 struct iter
715 {
716 int i;
717
718 int& operator* ()
719 {
720 return i;
721 }
722
723 const int& operator* () const
724 {
725 return i;
726 }
727
728 iter& operator++()
729 {
730 ++i;
731 return *this;
732 }
733 };
734
735 struct sentinel
736 {
737 int i;
738 };
739
740 bool operator== (const iter& i, const sentinel& s)
741 {
742 return i.i == s.i;
743 }
744
745 bool operator!= (const iter& i, const sentinel& s)
746 {
747 return !(i == s);
748 }
749
750 struct range
751 {
752 iter begin() const
753 {
754 return {0};
755 }
756
757 sentinel end() const
758 {
759 return {5};
760 }
761 };
762
763 void f()
764 {
765 range r {};
766
767 for (auto i : r)
768 {
769 [[maybe_unused]] auto v = i;
770 }
771 }
772
773 }
774
775 namespace test_lambda_capture_asterisk_this_by_value
776 {
777
778 struct t
779 {
780 int i;
781 int foo()
782 {
783 return [*this]()
784 {
785 return i;
786 }();
787 }
788 };
789
790 }
791
792 namespace test_enum_class_construction
793 {
794
795 enum class byte : unsigned char
796 {};
797
798 byte foo {42};
799
800 }
801
802 namespace test_constexpr_if
803 {
804
805 template <bool cond>
806 int f ()
807 {
808 if constexpr(cond)
809 {
810 return 13;
811 }
812 else
813 {
814 return 42;
815 }
816 }
817
818 }
819
820 namespace test_selection_statement_with_initializer
821 {
822
823 int f()
824 {
825 return 13;
826 }
827
828 int f2()
829 {
830 if (auto i = f(); i > 0)
831 {
832 return 3;
833 }
834
835 switch (auto i = f(); i + 4)
836 {
837 case 17:
838 return 2;
839
840 default:
841 return 1;
842 }
843 }
844
845 }
846
847 namespace test_template_argument_deduction_for_class_templates
848 {
849
850 template <typename T1, typename T2>
851 struct pair
852 {
853 pair (T1 p1, T2 p2)
854 : m1 {p1},
855 m2 {p2}
856 {}
857
858 T1 m1;
859 T2 m2;
860 };
861
862 void f()
863 {
864 [[maybe_unused]] auto p = pair{13, 42u};
865 }
866
867 }
868
869 namespace test_non_type_auto_template_parameters
870 {
871
872 template <auto n>
873 struct B
874 {};
875
876 B<5> b1;
877 B<'a'> b2;
878
879 }
880
881 namespace test_structured_bindings
882 {
883
884 int arr[2] = { 1, 2 };
885 std::pair<int, int> pr = { 1, 2 };
886
887 auto f1() -> int(&)[2]
888 {
889 return arr;
890 }
891
892 auto f2() -> std::pair<int, int>&
893 {
894 return pr;
895 }
896
897 struct S
898 {
899 int x1 : 2;
900 volatile double y1;
901 };
902
903 S f3()
904 {
905 return {};
906 }
907
908 auto [ x1, y1 ] = f1();
909 auto& [ xr1, yr1 ] = f1();
910 auto [ x2, y2 ] = f2();
911 auto& [ xr2, yr2 ] = f2();
912 const auto [ x3, y3 ] = f3();
913
914 }
915
916 namespace test_exception_spec_type_system
917 {
918
919 struct Good {};
920 struct Bad {};
921
922 void g1() noexcept;
923 void g2();
924
925 template<typename T>
926 Bad
927 f(T*, T*);
928
929 template<typename T1, typename T2>
930 Good
931 f(T1*, T2*);
932
933 static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
934
935 }
936
937 namespace test_inline_variables
938 {
939
940 template<class T> void f(T)
941 {}
942
943 template<class T> inline T g(T)
944 {
945 return T{};
946 }
947
948 template<> inline void f<>(int)
949 {}
950
951 template<> int g<>(int)
952 {
953 return 5;
954 }
955
956 }
957
958 } // namespace cxx17
959
960 #endif // __cplusplus < 201703L
961
962 ]])
963