source: trunk/m4/ax_cxx_compile_stdcxx.m4

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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
47dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
48dnl  (serial version number 13).
49
50AC_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
148dnl  Test body for checking C++11 support
149
150m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
151  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
152)
153
154
155dnl  Test body for checking C++14 support
156
157m4_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
162m4_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
168dnl  Tests for new features in C++11
169
170m4_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
185namespace 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
459dnl  Tests for new features in C++14
460
461m4_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
476namespace 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
583dnl  Tests for new features in C++17
584
585m4_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
604namespace 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]])
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