libcxx/test/std/utilities/utility/exchange/exchange.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11
  10 // <utility>
  11
  12 // exchange
  13
  14 // template<class T, class U=T>
  15 //    constexpr T            // constexpr after C++17
  16 //    exchange(T& obj, U&& new_value)
  17 //      noexcept(is_nothrow_move_constructible<T>::value && is_nothrow_assignable<T&, U>::value);
  18
  19 #include <utility>
  20 #include <cassert>
  21 #include <string>
  22
  23 #include "test_macros.h"
  24
  25 #if TEST_STD_VER > 17
  26 TEST_CONSTEXPR bool test_constexpr() {
  27     int v = 12;
  28
  29     if (12 != std::exchange(v,23) || v != 23)
  30         return false;
  31
  32     if (23 != std::exchange(v,static_cast<short>(67)) || v != 67)
  33         return false;
  34
  35     if (67 != std::exchange<int, short>(v, {}) || v != 0)
  36         return false;
  37     return true;
  38     }
  39 #endif
  40
  41 template<bool Move, bool Assign>
  42 struct TestNoexcept {
  43     TestNoexcept() = default;
  44     TestNoexcept(const TestNoexcept&);
  45     TestNoexcept(TestNoexcept&&) noexcept(Move);
  46     TestNoexcept& operator=(const TestNoexcept&);
  47     TestNoexcept& operator=(TestNoexcept&&) noexcept(Assign);
  48 };
  49
  50 constexpr bool test_noexcept() {
  51   {
  52     int x = 42;
  53     ASSERT_NOEXCEPT(std::exchange(x, 42));
  54   }
  55   {
  56     TestNoexcept<true, true> x;
  57     ASSERT_NOEXCEPT(std::exchange(x, std::move(x)));
  58     ASSERT_NOT_NOEXCEPT(std::exchange(x, x)); // copy-assignment is not noexcept
  59   }
  60   {
  61     TestNoexcept<true, false> x;
  62     ASSERT_NOT_NOEXCEPT(std::exchange(x, std::move(x)));
  63   }
  64   {
  65     TestNoexcept<false, true> x;
  66     ASSERT_NOT_NOEXCEPT(std::exchange(x, std::move(x)));
  67   }
  68
  69   return true;
  70 }
  71
  72 int main(int, char**)
  73 {
  74     {
  75     int v = 12;
  76     assert ( std::exchange ( v, 23 ) == 12 );
  77     assert ( v == 23 );
  78     assert ( std::exchange ( v, static_cast<short>(67) ) == 23 );
  79     assert ( v == 67 );
  80
  81     assert ((std::exchange<int, short> ( v, {} )) == 67 );
  82     assert ( v == 0 );
  83
  84     }
  85
  86     {
  87     bool b = false;
  88     assert ( !std::exchange ( b, true ));
  89     assert ( b );
  90     }
  91
  92     {
  93     const std::string s1 ( "Hi Mom!" );
  94     const std::string s2 ( "Yo Dad!" );
  95     std::string s3 = s1; // Mom
  96     assert ( std::exchange ( s3, s2 ) == s1 );
  97     assert ( s3 == s2 );
  98     assert ( std::exchange ( s3, "Hi Mom!" ) == s2 );
  99     assert ( s3 == s1 );
 100
 101     s3 = s2; // Dad
 102     assert ( std::exchange ( s3, {} ) == s2 );
 103     assert ( s3.size () == 0 );
 104
 105     s3 = s2; // Dad
 106     assert ( std::exchange ( s3, "" ) == s2 );
 107     assert ( s3.size () == 0 );
 108     }
 109
 110 #if TEST_STD_VER > 17
 111     static_assert(test_constexpr());
 112 #endif
 113
 114     static_assert(test_noexcept(), "");
 115
 116   return 0;
 117 }