libstdc++-v3/testsuite/20_util/exchange/constexpr.cc

   1 // Copyright (C) 2019-2023 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <utility>
  22
  23 constexpr bool
  24 test()
  25 {
  26   constexpr double e_v = 2.71828182846;
  27   double e = e_v;
  28   constexpr double pi_v = 3.14159265359;
  29   const auto x = std::exchange(e, pi_v);
  30
  31   return x == e_v && e == pi_v;
  32 }
  33
  34 static_assert(test());