1# Copyright (c) 2016-2020 Free Software Foundation, Inc. 2# 3# Originally based on the AX_CXX_COMPILE_STDCXX macro found at the url 4# below. 5# 6# Local GDB customizations: 7# 8# - AC_SUBST CXX_DIALECT instead of changing CXX/CXXCPP. 9# 10# =========================================================================== 11# https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html 12# =========================================================================== 13# 14# SYNOPSIS 15# 16# AX_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional]) 17# 18# DESCRIPTION 19# 20# Check for baseline language coverage in the compiler for the specified 21# version of the C++ standard. If necessary, add switches to CXX and 22# CXXCPP to enable support. VERSION may be '11' (for the C++11 standard) 23# or '14' (for the C++14 standard). 24# 25# The second argument, if specified, indicates whether you insist on an 26# extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g. 27# -std=c++11). If neither is specified, you get whatever works, with 28# preference for an extended mode. 29# 30# The third argument, if specified 'mandatory' or if left unspecified, 31# indicates that baseline support for the specified C++ standard is 32# required and that the macro should error out if no mode with that 33# support is found. If specified 'optional', then configuration proceeds 34# regardless, after defining HAVE_CXX${VERSION} if and only if a 35# supporting mode is found. 36# 37# LICENSE 38# 39# Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com> 40# Copyright (c) 2012 Zack Weinberg <zackw@panix.com> 41# Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu> 42# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com> 43# Copyright (c) 2015 Paul Norman <penorman@mac.com> 44# Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu> 45# Copyright (c) 2016 Krzesimir Nowak <qdlacz@gmail.com> 46# 47# Copying and distribution of this file, with or without modification, are 48# permitted in any medium without royalty provided the copyright notice 49# and this notice are preserved. This file is offered as-is, without any 50# warranty. 51 52#serial 8 53 54dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro 55dnl (serial version number 13). 56 57AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl 58 m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"], 59 [$1], [14], [ax_cxx_compile_alternatives="14 1y"], 60 [$1], [17], [ax_cxx_compile_alternatives="17 1z"], 61 [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl 62 m4_if([$2], [], [], 63 [$2], [ext], [], 64 [$2], [noext], [], 65 [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl 66 m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true], 67 [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true], 68 [$3], [optional], [ax_cxx_compile_cxx$1_required=false], 69 [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])]) 70 AC_LANG_PUSH([C++])dnl 71 CXX_DIALECT="" 72 ac_success=no 73 AC_CACHE_CHECK(whether $CXX supports C++$1 features by default, 74 ax_cv_cxx_compile_cxx$1, 75 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])], 76 [ax_cv_cxx_compile_cxx$1=yes], 77 [ax_cv_cxx_compile_cxx$1=no])]) 78 if test x$ax_cv_cxx_compile_cxx$1 = xyes; then 79 ac_success=yes 80 fi 81 82 m4_if([$2], [noext], [], [dnl 83 if test x$ac_success = xno; then 84 for alternative in ${ax_cxx_compile_alternatives}; do 85 switch="-std=gnu++${alternative}" 86 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch]) 87 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch, 88 $cachevar, 89 [ac_save_CXX="$CXX" 90 CXX="$CXX $switch" 91 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])], 92 [eval $cachevar=yes], 93 [eval $cachevar=no]) 94 CXX="$ac_save_CXX"]) 95 if eval test x\$$cachevar = xyes; then 96 CXX_DIALECT="$switch" 97 ac_success=yes 98 break 99 fi 100 done 101 fi]) 102 103 m4_if([$2], [ext], [], [dnl 104 if test x$ac_success = xno; then 105 dnl HP's aCC needs +std=c++11 according to: 106 dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf 107 dnl Cray's crayCC needs "-h std=c++11" 108 for alternative in ${ax_cxx_compile_alternatives}; do 109 for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do 110 cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch]) 111 AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch, 112 $cachevar, 113 [ac_save_CXX="$CXX" 114 CXX="$CXX $switch" 115 AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])], 116 [eval $cachevar=yes], 117 [eval $cachevar=no]) 118 CXX="$ac_save_CXX"]) 119 if eval test x\$$cachevar = xyes; then 120 CXX_DIALECT="$switch" 121 ac_success=yes 122 break 123 fi 124 done 125 if test x$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 AC_SUBST(CXX_DIALECT) 146]) 147 148 149dnl Test body for checking C++11 support 150 151m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11], 152 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11 153) 154 155 156dnl Test body for checking C++14 support 157 158m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14], 159 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11 160 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14 161) 162 163m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17], 164 _AX_CXX_COMPILE_STDCXX_testbody_new_in_11 165 _AX_CXX_COMPILE_STDCXX_testbody_new_in_14 166 _AX_CXX_COMPILE_STDCXX_testbody_new_in_17 167) 168 169dnl Tests for new features in C++11 170 171m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[ 172 173// If the compiler admits that it is not ready for C++11, why torture it? 174// Hopefully, this will speed up the test. 175 176#ifndef __cplusplus 177 178#error "This is not a C++ compiler" 179 180#elif __cplusplus < 201103L 181 182#error "This is not a C++11 compiler" 183 184#else 185 186namespace cxx11 187{ 188 189 namespace test_static_assert 190 { 191 192 template <typename T> 193 struct check 194 { 195 static_assert(sizeof(int) <= sizeof(T), "not big enough"); 196 }; 197 198 } 199 200 namespace test_final_override 201 { 202 203 struct Base 204 { 205 virtual void f() {} 206 }; 207 208 struct Derived : public Base 209 { 210 virtual void f() override {} 211 }; 212 213 } 214 215 namespace test_double_right_angle_brackets 216 { 217 218 template < typename T > 219 struct check {}; 220 221 typedef check<void> single_type; 222 typedef check<check<void>> double_type; 223 typedef check<check<check<void>>> triple_type; 224 typedef check<check<check<check<void>>>> quadruple_type; 225 226 } 227 228 namespace test_decltype 229 { 230 231 int 232 f() 233 { 234 int a = 1; 235 decltype(a) b = 2; 236 return a + b; 237 } 238 239 } 240 241 namespace test_type_deduction 242 { 243 244 template < typename T1, typename T2 > 245 struct is_same 246 { 247 static const bool value = false; 248 }; 249 250 template < typename T > 251 struct is_same<T, T> 252 { 253 static const bool value = true; 254 }; 255 256 template < typename T1, typename T2 > 257 auto 258 add(T1 a1, T2 a2) -> decltype(a1 + a2) 259 { 260 return a1 + a2; 261 } 262 263 int 264 test(const int c, volatile int v) 265 { 266 static_assert(is_same<int, decltype(0)>::value == true, ""); 267 static_assert(is_same<int, decltype(c)>::value == false, ""); 268 static_assert(is_same<int, decltype(v)>::value == false, ""); 269 auto ac = c; 270 auto av = v; 271 auto sumi = ac + av + 'x'; 272 auto sumf = ac + av + 1.0; 273 static_assert(is_same<int, decltype(ac)>::value == true, ""); 274 static_assert(is_same<int, decltype(av)>::value == true, ""); 275 static_assert(is_same<int, decltype(sumi)>::value == true, ""); 276 static_assert(is_same<int, decltype(sumf)>::value == false, ""); 277 static_assert(is_same<int, decltype(add(c, v))>::value == true, ""); 278 return (sumf > 0.0) ? sumi : add(c, v); 279 } 280 281 } 282 283 namespace test_noexcept 284 { 285 286 int f() { return 0; } 287 int g() noexcept { return 0; } 288 289 static_assert(noexcept(f()) == false, ""); 290 static_assert(noexcept(g()) == true, ""); 291 292 } 293 294 namespace test_constexpr 295 { 296 297 template < typename CharT > 298 unsigned long constexpr 299 strlen_c_r(const CharT *const s, const unsigned long acc) noexcept 300 { 301 return *s ? strlen_c_r(s + 1, acc + 1) : acc; 302 } 303 304 template < typename CharT > 305 unsigned long constexpr 306 strlen_c(const CharT *const s) noexcept 307 { 308 return strlen_c_r(s, 0UL); 309 } 310 311 static_assert(strlen_c("") == 0UL, ""); 312 static_assert(strlen_c("1") == 1UL, ""); 313 static_assert(strlen_c("example") == 7UL, ""); 314 static_assert(strlen_c("another\0example") == 7UL, ""); 315 316 } 317 318 namespace test_rvalue_references 319 { 320 321 template < int N > 322 struct answer 323 { 324 static constexpr int value = N; 325 }; 326 327 answer<1> f(int&) { return answer<1>(); } 328 answer<2> f(const int&) { return answer<2>(); } 329 answer<3> f(int&&) { return answer<3>(); } 330 331 void 332 test() 333 { 334 int i = 0; 335 const int c = 0; 336 static_assert(decltype(f(i))::value == 1, ""); 337 static_assert(decltype(f(c))::value == 2, ""); 338 static_assert(decltype(f(0))::value == 3, ""); 339 } 340 341 } 342 343 namespace test_uniform_initialization 344 { 345 346 struct test 347 { 348 static const int zero {}; 349 static const int one {1}; 350 }; 351 352 static_assert(test::zero == 0, ""); 353 static_assert(test::one == 1, ""); 354 355 } 356 357 namespace test_lambdas 358 { 359 360 void 361 test1() 362 { 363 auto lambda1 = [](){}; 364 auto lambda2 = lambda1; 365 lambda1(); 366 lambda2(); 367 } 368 369 int 370 test2() 371 { 372 auto a = [](int i, int j){ return i + j; }(1, 2); 373 auto b = []() -> int { return '0'; }(); 374 auto c = [=](){ return a + b; }(); 375 auto d = [&](){ return c; }(); 376 auto e = [a, &b](int x) mutable { 377 const auto identity = [](int y){ return y; }; 378 for (auto i = 0; i < a; ++i) 379 a += b--; 380 return x + identity(a + b); 381 }(0); 382 return a + b + c + d + e; 383 } 384 385 int 386 test3() 387 { 388 const auto nullary = [](){ return 0; }; 389 const auto unary = [](int x){ return x; }; 390 using nullary_t = decltype(nullary); 391 using unary_t = decltype(unary); 392 const auto higher1st = [](nullary_t f){ return f(); }; 393 const auto higher2nd = [unary](nullary_t f1){ 394 return [unary, f1](unary_t f2){ return f2(unary(f1())); }; 395 }; 396 return higher1st(nullary) + higher2nd(nullary)(unary); 397 } 398 399 } 400 401 namespace test_variadic_templates 402 { 403 404 template <int...> 405 struct sum; 406 407 template <int N0, int... N1toN> 408 struct sum<N0, N1toN...> 409 { 410 static constexpr auto value = N0 + sum<N1toN...>::value; 411 }; 412 413 template <> 414 struct sum<> 415 { 416 static constexpr auto value = 0; 417 }; 418 419 static_assert(sum<>::value == 0, ""); 420 static_assert(sum<1>::value == 1, ""); 421 static_assert(sum<23>::value == 23, ""); 422 static_assert(sum<1, 2>::value == 3, ""); 423 static_assert(sum<5, 5, 11>::value == 21, ""); 424 static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, ""); 425 426 } 427 428 // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae 429 // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function 430 // because of this. 431 namespace test_template_alias_sfinae 432 { 433 434 struct foo {}; 435 436 template<typename T> 437 using member = typename T::member_type; 438 439 template<typename T> 440 void func(...) {} 441 442 template<typename T> 443 void func(member<T>*) {} 444 445 void test(); 446 447 void test() { func<foo>(0); } 448 449 } 450 451} // namespace cxx11 452 453#endif // __cplusplus >= 201103L 454 455]]) 456 457 458dnl Tests for new features in C++14 459 460m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[ 461 462// If the compiler admits that it is not ready for C++14, why torture it? 463// Hopefully, this will speed up the test. 464 465#ifndef __cplusplus 466 467#error "This is not a C++ compiler" 468 469#elif __cplusplus < 201402L 470 471#error "This is not a C++14 compiler" 472 473#else 474 475namespace cxx14 476{ 477 478 namespace test_polymorphic_lambdas 479 { 480 481 int 482 test() 483 { 484 const auto lambda = [](auto&&... args){ 485 const auto istiny = [](auto x){ 486 return (sizeof(x) == 1UL) ? 1 : 0; 487 }; 488 const int aretiny[] = { istiny(args)... }; 489 return aretiny[0]; 490 }; 491 return lambda(1, 1L, 1.0f, '1'); 492 } 493 494 } 495 496 namespace test_binary_literals 497 { 498 499 constexpr auto ivii = 0b0000000000101010; 500 static_assert(ivii == 42, "wrong value"); 501 502 } 503 504 namespace test_generalized_constexpr 505 { 506 507 template < typename CharT > 508 constexpr unsigned long 509 strlen_c(const CharT *const s) noexcept 510 { 511 auto length = 0UL; 512 for (auto p = s; *p; ++p) 513 ++length; 514 return length; 515 } 516 517 static_assert(strlen_c("") == 0UL, ""); 518 static_assert(strlen_c("x") == 1UL, ""); 519 static_assert(strlen_c("test") == 4UL, ""); 520 static_assert(strlen_c("another\0test") == 7UL, ""); 521 522 } 523 524 namespace test_lambda_init_capture 525 { 526 527 int 528 test() 529 { 530 auto x = 0; 531 const auto lambda1 = [a = x](int b){ return a + b; }; 532 const auto lambda2 = [a = lambda1(x)](){ return a; }; 533 return lambda2(); 534 } 535 536 } 537 538 namespace test_digit_separators 539 { 540 541 constexpr auto ten_million = 100'000'000; 542 static_assert(ten_million == 100000000, ""); 543 544 } 545 546 namespace test_return_type_deduction 547 { 548 549 auto f(int& x) { return x; } 550 decltype(auto) g(int& x) { return x; } 551 552 template < typename T1, typename T2 > 553 struct is_same 554 { 555 static constexpr auto value = false; 556 }; 557 558 template < typename T > 559 struct is_same<T, T> 560 { 561 static constexpr auto value = true; 562 }; 563 564 int 565 test() 566 { 567 auto x = 0; 568 static_assert(is_same<int, decltype(f(x))>::value, ""); 569 static_assert(is_same<int&, decltype(g(x))>::value, ""); 570 return x; 571 } 572 573 } 574 575} // namespace cxx14 576 577#endif // __cplusplus >= 201402L 578 579]]) 580 581 582dnl Tests for new features in C++17 583 584m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[ 585 586// If the compiler admits that it is not ready for C++17, why torture it? 587// Hopefully, this will speed up the test. 588 589#ifndef __cplusplus 590 591#error "This is not a C++ compiler" 592 593#elif __cplusplus <= 201402L 594 595#error "This is not a C++17 compiler" 596 597#else 598 599#if defined(__clang__) 600 #define REALLY_CLANG 601#else 602 #if defined(__GNUC__) 603 #define REALLY_GCC 604 #endif 605#endif 606 607#include <initializer_list> 608#include <utility> 609#include <type_traits> 610 611namespace cxx17 612{ 613 614#if !defined(REALLY_CLANG) 615 namespace test_constexpr_lambdas 616 { 617 618 // TODO: test it with clang++ from git 619 620 constexpr int foo = [](){return 42;}(); 621 622 } 623#endif // !defined(REALLY_CLANG) 624 625 namespace test::nested_namespace::definitions 626 { 627 628 } 629 630 namespace test_fold_expression 631 { 632 633 template<typename... Args> 634 int multiply(Args... args) 635 { 636 return (args * ... * 1); 637 } 638 639 template<typename... Args> 640 bool all(Args... args) 641 { 642 return (args && ...); 643 } 644 645 } 646 647 namespace test_extended_static_assert 648 { 649 650 static_assert (true); 651 652 } 653 654 namespace test_auto_brace_init_list 655 { 656 657 auto foo = {5}; 658 auto bar {5}; 659 660 static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value); 661 static_assert(std::is_same<int, decltype(bar)>::value); 662 } 663 664 namespace test_typename_in_template_template_parameter 665 { 666 667 template<template<typename> typename X> struct D; 668 669 } 670 671 namespace test_fallthrough_nodiscard_maybe_unused_attributes 672 { 673 674 int f1() 675 { 676 return 42; 677 } 678 679 [[nodiscard]] int f2() 680 { 681 [[maybe_unused]] auto unused = f1(); 682 683 switch (f1()) 684 { 685 case 17: 686 f1(); 687 [[fallthrough]]; 688 case 42: 689 f1(); 690 } 691 return f1(); 692 } 693 694 } 695 696 namespace test_extended_aggregate_initialization 697 { 698 699 struct base1 700 { 701 int b1, b2 = 42; 702 }; 703 704 struct base2 705 { 706 base2() { 707 b3 = 42; 708 } 709 int b3; 710 }; 711 712 struct derived : base1, base2 713 { 714 int d; 715 }; 716 717 derived d1 {{1, 2}, {}, 4}; // full initialization 718 derived d2 {{}, {}, 4}; // value-initialized bases 719 720 } 721 722 namespace test_general_range_based_for_loop 723 { 724 725 struct iter 726 { 727 int i; 728 729 int& operator* () 730 { 731 return i; 732 } 733 734 const int& operator* () const 735 { 736 return i; 737 } 738 739 iter& operator++() 740 { 741 ++i; 742 return *this; 743 } 744 }; 745 746 struct sentinel 747 { 748 int i; 749 }; 750 751 bool operator== (const iter& i, const sentinel& s) 752 { 753 return i.i == s.i; 754 } 755 756 bool operator!= (const iter& i, const sentinel& s) 757 { 758 return !(i == s); 759 } 760 761 struct range 762 { 763 iter begin() const 764 { 765 return {0}; 766 } 767 768 sentinel end() const 769 { 770 return {5}; 771 } 772 }; 773 774 void f() 775 { 776 range r {}; 777 778 for (auto i : r) 779 { 780 [[maybe_unused]] auto v = i; 781 } 782 } 783 784 } 785 786 namespace test_lambda_capture_asterisk_this_by_value 787 { 788 789 struct t 790 { 791 int i; 792 int foo() 793 { 794 return [*this]() 795 { 796 return i; 797 }(); 798 } 799 }; 800 801 } 802 803 namespace test_enum_class_construction 804 { 805 806 enum class byte : unsigned char 807 {}; 808 809 byte foo {42}; 810 811 } 812 813 namespace test_constexpr_if 814 { 815 816 template <bool cond> 817 int f () 818 { 819 if constexpr(cond) 820 { 821 return 13; 822 } 823 else 824 { 825 return 42; 826 } 827 } 828 829 } 830 831 namespace test_selection_statement_with_initializer 832 { 833 834 int f() 835 { 836 return 13; 837 } 838 839 int f2() 840 { 841 if (auto i = f(); i > 0) 842 { 843 return 3; 844 } 845 846 switch (auto i = f(); i + 4) 847 { 848 case 17: 849 return 2; 850 851 default: 852 return 1; 853 } 854 } 855 856 } 857 858#if !defined(REALLY_CLANG) 859 namespace test_template_argument_deduction_for_class_templates 860 { 861 862 // TODO: test it with clang++ from git 863 864 template <typename T1, typename T2> 865 struct pair 866 { 867 pair (T1 p1, T2 p2) 868 : m1 {p1}, 869 m2 {p2} 870 {} 871 872 T1 m1; 873 T2 m2; 874 }; 875 876 void f() 877 { 878 [[maybe_unused]] auto p = pair{13, 42u}; 879 } 880 881 } 882#endif // !defined(REALLY_CLANG) 883 884 namespace test_non_type_auto_template_parameters 885 { 886 887 template <auto n> 888 struct B 889 {}; 890 891 B<5> b1; 892 B<'a'> b2; 893 894 } 895 896#if !defined(REALLY_CLANG) 897 namespace test_structured_bindings 898 { 899 900 // TODO: test it with clang++ from git 901 902 int arr[2] = { 1, 2 }; 903 std::pair<int, int> pr = { 1, 2 }; 904 905 auto f1() -> int(&)[2] 906 { 907 return arr; 908 } 909 910 auto f2() -> std::pair<int, int>& 911 { 912 return pr; 913 } 914 915 struct S 916 { 917 int x1 : 2; 918 volatile double y1; 919 }; 920 921 S f3() 922 { 923 return {}; 924 } 925 926 auto [ x1, y1 ] = f1(); 927 auto& [ xr1, yr1 ] = f1(); 928 auto [ x2, y2 ] = f2(); 929 auto& [ xr2, yr2 ] = f2(); 930 const auto [ x3, y3 ] = f3(); 931 932 } 933#endif // !defined(REALLY_CLANG) 934 935#if !defined(REALLY_CLANG) 936 namespace test_exception_spec_type_system 937 { 938 939 // TODO: test it with clang++ from git 940 941 struct Good {}; 942 struct Bad {}; 943 944 void g1() noexcept; 945 void g2(); 946 947 template<typename T> 948 Bad 949 f(T*, T*); 950 951 template<typename T1, typename T2> 952 Good 953 f(T1*, T2*); 954 955 static_assert (std::is_same_v<Good, decltype(f(g1, g2))>); 956 957 } 958#endif // !defined(REALLY_CLANG) 959 960 namespace test_inline_variables 961 { 962 963 template<class T> void f(T) 964 {} 965 966 template<class T> inline T g(T) 967 { 968 return T{}; 969 } 970 971 template<> inline void f<>(int) 972 {} 973 974 template<> int g<>(int) 975 { 976 return 5; 977 } 978 979 } 980 981} // namespace cxx17 982 983#endif // __cplusplus <= 201402L 984 985]]) 986