1# ===========================================================================
2#   http://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#
37#   Copying and distribution of this file, with or without modification, are
38#   permitted in any medium without royalty provided the copyright notice
39#   and this notice are preserved.  This file is offered as-is, without any
40#   warranty.
41
42#serial 4
43
44dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
45dnl  (serial version number 13).
46
47AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
48  m4_if([$1], [11], [],
49        [$1], [14], [],
50        [$1], [17], [m4_fatal([support for C++17 not yet implemented in AX_CXX_COMPILE_STDCXX])],
51        [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
52  m4_if([$2], [], [],
53        [$2], [ext], [],
54        [$2], [noext], [],
55        [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
56  m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
57        [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
58        [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
59        [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
60  AC_LANG_PUSH([C++])dnl
61  ac_success=no
62  AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
63  ax_cv_cxx_compile_cxx$1,
64  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
65    [ax_cv_cxx_compile_cxx$1=yes],
66    [ax_cv_cxx_compile_cxx$1=no])])
67  if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
68    ac_success=yes
69  fi
70
71  m4_if([$2], [noext], [], [dnl
72  if test x$ac_success = xno; then
73    for switch in -std=gnu++$1 -std=gnu++0x; do
74      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
75      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
76                     $cachevar,
77        [ac_save_CXX="$CXX"
78         CXX="$CXX $switch"
79         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
80          [eval $cachevar=yes],
81          [eval $cachevar=no])
82         CXX="$ac_save_CXX"])
83      if eval test x\$$cachevar = xyes; then
84        CXX="$CXX $switch"
85        if test -n "$CXXCPP" ; then
86          CXXCPP="$CXXCPP $switch"
87        fi
88        ac_success=yes
89        break
90      fi
91    done
92  fi])
93
94  m4_if([$2], [ext], [], [dnl
95  if test x$ac_success = xno; then
96    dnl HP's aCC needs +std=c++11 according to:
97    dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
98    dnl Cray's crayCC needs "-h std=c++11"
99    for switch in -std=c++$1 -std=c++0x +std=c++$1 "-h std=c++$1"; do
100      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
101      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
102                     $cachevar,
103        [ac_save_CXX="$CXX"
104         CXX="$CXX $switch"
105         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
106          [eval $cachevar=yes],
107          [eval $cachevar=no])
108         CXX="$ac_save_CXX"])
109      if eval test x\$$cachevar = xyes; then
110        CXX="$CXX $switch"
111        if test -n "$CXXCPP" ; then
112          CXXCPP="$CXXCPP $switch"
113        fi
114        ac_success=yes
115        break
116      fi
117    done
118  fi])
119  AC_LANG_POP([C++])
120  if test x$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
151
152dnl  Tests for new features in C++11
153
154m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
155
156// If the compiler admits that it is not ready for C++11, why torture it?
157// Hopefully, this will speed up the test.
158
159#ifndef __cplusplus
160
161#error "This is not a C++ compiler"
162
163#elif __cplusplus < 201103L
164
165#error "This is not a C++11 compiler"
166
167#else
168
169namespace cxx11
170{
171
172  namespace test_static_assert
173  {
174
175    template <typename T>
176    struct check
177    {
178      static_assert(sizeof(int) <= sizeof(T), "not big enough");
179    };
180
181  }
182
183  namespace test_final_override
184  {
185
186    struct Base
187    {
188      virtual void f() {}
189    };
190
191    struct Derived : public Base
192    {
193      virtual void f() override {}
194    };
195
196  }
197
198  namespace test_double_right_angle_brackets
199  {
200
201    template < typename T >
202    struct check {};
203
204    typedef check<void> single_type;
205    typedef check<check<void>> double_type;
206    typedef check<check<check<void>>> triple_type;
207    typedef check<check<check<check<void>>>> quadruple_type;
208
209  }
210
211  namespace test_decltype
212  {
213
214    int
215    f()
216    {
217      int a = 1;
218      decltype(a) b = 2;
219      return a + b;
220    }
221
222  }
223
224  namespace test_type_deduction
225  {
226
227    template < typename T1, typename T2 >
228    struct is_same
229    {
230      static const bool value = false;
231    };
232
233    template < typename T >
234    struct is_same<T, T>
235    {
236      static const bool value = true;
237    };
238
239    template < typename T1, typename T2 >
240    auto
241    add(T1 a1, T2 a2) -> decltype(a1 + a2)
242    {
243      return a1 + a2;
244    }
245
246    int
247    test(const int c, volatile int v)
248    {
249      static_assert(is_same<int, decltype(0)>::value == true, "");
250      static_assert(is_same<int, decltype(c)>::value == false, "");
251      static_assert(is_same<int, decltype(v)>::value == false, "");
252      auto ac = c;
253      auto av = v;
254      auto sumi = ac + av + 'x';
255      auto sumf = ac + av + 1.0;
256      static_assert(is_same<int, decltype(ac)>::value == true, "");
257      static_assert(is_same<int, decltype(av)>::value == true, "");
258      static_assert(is_same<int, decltype(sumi)>::value == true, "");
259      static_assert(is_same<int, decltype(sumf)>::value == false, "");
260      static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
261      return (sumf > 0.0) ? sumi : add(c, v);
262    }
263
264  }
265
266  namespace test_noexcept
267  {
268
269    int f() { return 0; }
270    int g() noexcept { return 0; }
271
272    static_assert(noexcept(f()) == false, "");
273    static_assert(noexcept(g()) == true, "");
274
275  }
276
277  namespace test_constexpr
278  {
279
280    template < typename CharT >
281    unsigned long constexpr
282    strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
283    {
284      return *s ? strlen_c_r(s + 1, acc + 1) : acc;
285    }
286
287    template < typename CharT >
288    unsigned long constexpr
289    strlen_c(const CharT *const s) noexcept
290    {
291      return strlen_c_r(s, 0UL);
292    }
293
294    static_assert(strlen_c("") == 0UL, "");
295    static_assert(strlen_c("1") == 1UL, "");
296    static_assert(strlen_c("example") == 7UL, "");
297    static_assert(strlen_c("another\0example") == 7UL, "");
298
299  }
300
301  namespace test_rvalue_references
302  {
303
304    template < int N >
305    struct answer
306    {
307      static constexpr int value = N;
308    };
309
310    answer<1> f(int&)       { return answer<1>(); }
311    answer<2> f(const int&) { return answer<2>(); }
312    answer<3> f(int&&)      { return answer<3>(); }
313
314    void
315    test()
316    {
317      int i = 0;
318      const int c = 0;
319      static_assert(decltype(f(i))::value == 1, "");
320      static_assert(decltype(f(c))::value == 2, "");
321      static_assert(decltype(f(0))::value == 3, "");
322    }
323
324  }
325
326  namespace test_uniform_initialization
327  {
328
329    struct test
330    {
331      static const int zero {};
332      static const int one {1};
333    };
334
335    static_assert(test::zero == 0, "");
336    static_assert(test::one == 1, "");
337
338  }
339
340  namespace test_lambdas
341  {
342
343    void
344    test1()
345    {
346      auto lambda1 = [](){};
347      auto lambda2 = lambda1;
348      lambda1();
349      lambda2();
350    }
351
352    int
353    test2()
354    {
355      auto a = [](int i, int j){ return i + j; }(1, 2);
356      auto b = []() -> int { return '0'; }();
357      auto c = [=](){ return a + b; }();
358      auto d = [&](){ return c; }();
359      auto e = [a, &b](int x) mutable {
360        const auto identity = [](int y){ return y; };
361        for (auto i = 0; i < a; ++i)
362          a += b--;
363        return x + identity(a + b);
364      }(0);
365      return a + b + c + d + e;
366    }
367
368    int
369    test3()
370    {
371      const auto nullary = [](){ return 0; };
372      const auto unary = [](int x){ return x; };
373      using nullary_t = decltype(nullary);
374      using unary_t = decltype(unary);
375      const auto higher1st = [](nullary_t f){ return f(); };
376      const auto higher2nd = [unary](nullary_t f1){
377        return [unary, f1](unary_t f2){ return f2(unary(f1())); };
378      };
379      return higher1st(nullary) + higher2nd(nullary)(unary);
380    }
381
382  }
383
384  namespace test_variadic_templates
385  {
386
387    template <int...>
388    struct sum;
389
390    template <int N0, int... N1toN>
391    struct sum<N0, N1toN...>
392    {
393      static constexpr auto value = N0 + sum<N1toN...>::value;
394    };
395
396    template <>
397    struct sum<>
398    {
399      static constexpr auto value = 0;
400    };
401
402    static_assert(sum<>::value == 0, "");
403    static_assert(sum<1>::value == 1, "");
404    static_assert(sum<23>::value == 23, "");
405    static_assert(sum<1, 2>::value == 3, "");
406    static_assert(sum<5, 5, 11>::value == 21, "");
407    static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
408
409  }
410
411  // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
412  // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
413  // because of this.
414  namespace test_template_alias_sfinae
415  {
416
417    struct foo {};
418
419    template<typename T>
420    using member = typename T::member_type;
421
422    template<typename T>
423    void func(...) {}
424
425    template<typename T>
426    void func(member<T>*) {}
427
428    void test();
429
430    void test() { func<foo>(0); }
431
432  }
433
434}  // namespace cxx11
435
436#endif  // __cplusplus >= 201103L
437
438]])
439
440
441dnl  Tests for new features in C++14
442
443m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
444
445// If the compiler admits that it is not ready for C++14, why torture it?
446// Hopefully, this will speed up the test.
447
448#ifndef __cplusplus
449
450#error "This is not a C++ compiler"
451
452#elif __cplusplus < 201402L
453
454#error "This is not a C++14 compiler"
455
456#else
457
458namespace cxx14
459{
460
461  namespace test_polymorphic_lambdas
462  {
463
464    int
465    test()
466    {
467      const auto lambda = [](auto&&... args){
468        const auto istiny = [](auto x){
469          return (sizeof(x) == 1UL) ? 1 : 0;
470        };
471        const int aretiny[] = { istiny(args)... };
472        return aretiny[0];
473      };
474      return lambda(1, 1L, 1.0f, '1');
475    }
476
477  }
478
479  namespace test_binary_literals
480  {
481
482    constexpr auto ivii = 0b0000000000101010;
483    static_assert(ivii == 42, "wrong value");
484
485  }
486
487  namespace test_generalized_constexpr
488  {
489
490    template < typename CharT >
491    constexpr unsigned long
492    strlen_c(const CharT *const s) noexcept
493    {
494      auto length = 0UL;
495      for (auto p = s; *p; ++p)
496        ++length;
497      return length;
498    }
499
500    static_assert(strlen_c("") == 0UL, "");
501    static_assert(strlen_c("x") == 1UL, "");
502    static_assert(strlen_c("test") == 4UL, "");
503    static_assert(strlen_c("another\0test") == 7UL, "");
504
505  }
506
507  namespace test_lambda_init_capture
508  {
509
510    int
511    test()
512    {
513      auto x = 0;
514      const auto lambda1 = [a = x](int b){ return a + b; };
515      const auto lambda2 = [a = lambda1(x)](){ return a; };
516      return lambda2();
517    }
518
519  }
520
521  namespace test_digit_seperators
522  {
523
524    constexpr auto ten_million = 100'000'000;
525    static_assert(ten_million == 100000000, "");
526
527  }
528
529  namespace test_return_type_deduction
530  {
531
532    auto f(int& x) { return x; }
533    decltype(auto) g(int& x) { return x; }
534
535    template < typename T1, typename T2 >
536    struct is_same
537    {
538      static constexpr auto value = false;
539    };
540
541    template < typename T >
542    struct is_same<T, T>
543    {
544      static constexpr auto value = true;
545    };
546
547    int
548    test()
549    {
550      auto x = 0;
551      static_assert(is_same<int, decltype(f(x))>::value, "");
552      static_assert(is_same<int&, decltype(g(x))>::value, "");
553      return x;
554    }
555
556  }
557
558}  // namespace cxx14
559
560#endif  // __cplusplus >= 201402L
561
562]])
563