libstdc++-v3/testsuite/20_util/tuple/77802.cc

   1 // { dg-do compile { target c++11 } }
   2
   3 // Copyright (C) 2016-2022 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 #include <tuple>
  21
  22 // This testcase instantiates a tuple with an incomplete type.
  23 // That is undefined behavior, but our tuple implementation manages
  24 // to cope with this particular case. The attempt to provide
  25 // a tuple implementation that yields the right result for
  26 // traits like is_copy_constructible and is_move_constructible as
  27 // per LWG 2729 results in ill-formed copy/move constructors being
  28 // generated for a tuple that contains an incomplete type.
  29 // Once we get concepts, we can solve that problem much easier.
  30
  31 template <typename... Args> struct execution_context
  32 {
  33   typedef std::tuple<Args...> args_tpl_t;
  34   typedef std::tuple<execution_context, typename std::decay<Args>::type...>
  35   ret_tpl_t;
  36   execution_context();
  37   execution_context(execution_context &&);
  38   ret_tpl_t operator()() {
  39     args_tpl_t data;
  40     return tuple_cat(std::forward_as_tuple(execution_context()), data);
  41   }
  42 };
  43
  44 void fn1()
  45 {
  46   execution_context<int> cc;
  47   cc();
  48 }
  49