libstdc++-v3/testsuite/20_util/forward/b.cc

   1 // { dg-do run { target c++11 } }
   2
   3 // Copyright (C) 2010-2020 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 <list>
  21 #include <testsuite_hooks.h>
  22
  23 template <class T>
  24   struct C
  25   {
  26     T t_;
  27
  28     template <class U,
  29               class = typename std::enable_if
  30                     <
  31                         !std::is_lvalue_reference<U>::value
  32                     >::type>
  33       C(U&& u) : t_(std::forward<T>(std::move(u).get())) {}
  34   };
  35
  36 class A
  37 {
  38   int data_;
  39 public:
  40   explicit
  41   A(int data = 1)
  42   : data_(data) { }
  43
  44   ~A() { data_ = -1; }
  45
  46   void test() const
  47   {
  48     VERIFY( data_ == 3 );
  49   }
  50 };
  51
  52 class Awrap
  53 {
  54   A a_;
  55 public:
  56   explicit Awrap(const A& a) : a_(a) { }
  57   A get() const { return a_; }
  58 };
  59
  60 template <class C>
  61 void test(C c)
  62 {
  63   c.t_.test();
  64 }
  65
  66 // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
  67 // Test B.
  68 int main()
  69 {
  70   std::list<C<A> > list;
  71   A a(3);
  72   C<A> c((Awrap(a)));
  73   list.push_back(c);
  74   test(c);
  75   test(list.front());
  76 }