xref: /freebsd/contrib/kyua/m4/ax_cxx_compile_stdcxx.m4 (revision d65cd7a57bf0600b722afc770838a5d0c1c3a8e1) 
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
46dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
47dnl  (serial version number 13).
48
49AC_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
137dnl  Test body for checking C++11 support
138
139m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
140  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
141)
142
143
144dnl  Test body for checking C++14 support
145
146m4_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
151m4_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
157dnl  Tests for new features in C++11
158
159m4_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
174namespace 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
448dnl  Tests for new features in C++14
449
450m4_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
465namespace 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
572dnl  Tests for new features in C++17
573
574m4_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
593namespace 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]])
952