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
26TEST_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
41template<bool Move, bool Assign>
42struct 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
50constexpr bool test_noexcept() {
51 {
52 int x = 42;
53 ASSERT_NOEXCEPT(std::exchange(obj&: x, new_val: 42));
54 }
55 {
56 TestNoexcept<true, true> x;
57 ASSERT_NOEXCEPT(std::exchange(obj&: x, new_val: std::move(x)));
58 ASSERT_NOT_NOEXCEPT(std::exchange(obj&: x, new_val&: x)); // copy-assignment is not noexcept
59 }
60 {
61 TestNoexcept<true, false> x;
62 ASSERT_NOT_NOEXCEPT(std::exchange(obj&: x, new_val: std::move(x)));
63 }
64 {
65 TestNoexcept<false, true> x;
66 ASSERT_NOT_NOEXCEPT(std::exchange(obj&: x, new_val: std::move(x)));
67 }
68
69 return true;
70}
71
72int 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}
118

source code of libcxx/test/std/utilities/utility/exchange/exchange.pass.cpp