libstdc++-v3/testsuite/20_util/exchange/1.cc

   1 // { dg-do run { target c++14 } }
   2
   3 // Copyright (C) 2013-2020 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 // 20.2.3 exchange [utility.exchange]
  21
  22 #include <utility>
  23 #include <type_traits>
  24 #include <testsuite_hooks.h>
  25
  26 void
  27 test01()
  28 {
  29   const unsigned val = 4;
  30   int i = 1;
  31   auto prev = std::exchange(i, val);
  32   static_assert( std::is_same<decltype(prev), int>::value, "return type" );
  33   VERIFY( i == 4 );
  34   VERIFY( prev == 1 );
  35   prev = std::exchange(i, 3);
  36   VERIFY( i == 3 );
  37   VERIFY( prev == 4 );
  38 }
  39
  40 // Default construction from empty braces
  41 void
  42 test02()
  43 {
  44   struct DefaultConstructible
  45   {
  46     DefaultConstructible(int i = 0) : value(i) { }
  47     int value;
  48   };
  49
  50   DefaultConstructible x = 1;
  51   auto old = std::exchange(x, {});
  52   VERIFY( x.value == 0 );
  53   VERIFY( old.value == 1 );
  54 }
  55
  56 int f(int) { return 0; }
  57
  58 double f(double) { return 0; }
  59
  60 // Deduce type of overloaded function
  61 void
  62 test03()
  63 {
  64   int (*fp)(int);
  65   std::exchange(fp, &f);
  66   VERIFY( fp != nullptr );
  67 }
  68
  69 void test04()
  70 {
  71   struct From { };
  72   struct To {
  73     int value = 0;
  74     To() = default;
  75     To(const To&) = default;
  76     To(const From&) = delete;
  77     To& operator=(const From&) { value = 1; return *this; }
  78     To& operator=(From&&) { value = 2; return *this; }
  79   };
  80
  81   To t;
  82   From f;
  83
  84   auto prev = std::exchange(t, f);
  85   VERIFY( t.value == 1 );
  86   VERIFY( prev.value == 0 );
  87
  88   prev = std::exchange(t, From{});
  89   VERIFY( t.value == 2 );
  90   VERIFY( prev.value == 1 );
  91 }
  92
  93 int
  94 main()
  95 {
  96   test01();
  97   test02();
  98   test03();
  99   test04();
 100   return 0;
 101 }