libstdc++-v3/testsuite/20_util/tuple/cv_tuple_size.cc

   1 // { dg-do run { target c++11 } }
   2
   3 // Copyright (C) 2011-2022 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20 // Tuple
  21
  22 #include <tuple>
  23 #include <testsuite_hooks.h>
  24
  25 void
  26 test01()
  27 {
  28   using namespace std;
  29
  30   VERIFY( tuple_size<const tuple<> >::value == 0 );
  31   VERIFY( tuple_size<volatile tuple<int> >::value == 1 );
  32   VERIFY( tuple_size<const volatile tuple<void> >::value == 1 );
  33
  34   typedef tuple<int, const int&, void> test_tuple1;
  35   VERIFY( tuple_size<const test_tuple1>::value == 3 );
  36   VERIFY( tuple_size<const volatile test_tuple1>::value == 3 );
  37   VERIFY( tuple_size<volatile tuple<tuple<void> > >::value == 1 );
  38 }
  39
  40 int main()
  41 {
  42   test01();
  43   return 0;
  44 }
  45
  46 // LWG DR 2770. tuple_size<const T> specialization is not SFINAE compatible
  47 template<typename T, typename = void>
  48 struct has_value : std::false_type { };
  49
  50 template<typename T>
  51 struct has_value<T, std::__void_t<decltype(T::value)>> : std::true_type { };
  52
  53 static_assert( !has_value<std::tuple_size<int>>::value, "" );
  54 static_assert( !has_value<std::tuple_size<const int>>::value, "" );