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
10
11// <string>
12
13// void swap(basic_string& c)
14// noexcept(!allocator_type::propagate_on_container_swap::value ||
15// __is_nothrow_swappable<allocator_type>::value); // constexpr since C++20
16//
17// In C++17, the standard says that swap shall have:
18// noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
19// allocator_traits<Allocator>::is_always_equal::value); // constexpr since C++20
20
21// This tests a conforming extension
22
23#include <string>
24#include <utility>
25#include <cassert>
26
27#include "test_macros.h"
28#include "test_allocator.h"
29
30template <class T>
31struct some_alloc {
32 typedef T value_type;
33
34 some_alloc() {}
35 some_alloc(const some_alloc&);
36 T* allocate(std::size_t);
37 void deallocate(void*, unsigned) {}
38 typedef std::true_type propagate_on_container_swap;
39};
40
41template <class T>
42struct some_alloc2 {
43 typedef T value_type;
44
45 some_alloc2() {}
46 some_alloc2(const some_alloc2&);
47 T* allocate(std::size_t);
48 void deallocate(void*, unsigned) {}
49
50 typedef std::false_type propagate_on_container_swap;
51 typedef std::true_type is_always_equal;
52};
53
54int main(int, char**) {
55 {
56 typedef std::string C;
57 static_assert(noexcept(swap(lhs&: std::declval<C&>(), rhs&: std::declval<C&>())), "");
58 }
59#if defined(_LIBCPP_VERSION)
60 {
61 typedef std::basic_string<char, std::char_traits<char>, test_allocator<char>> C;
62 static_assert(noexcept(swap(std::declval<C&>(), std::declval<C&>())), "");
63 }
64#endif // _LIBCPP_VERSION
65 {
66 typedef std::basic_string<char, std::char_traits<char>, some_alloc<char>> C;
67#if TEST_STD_VER >= 14
68 // In C++14, if POCS is set, swapping the allocator is required not to throw
69 static_assert(noexcept(swap(std::declval<C&>(), std::declval<C&>())), "");
70#else
71 static_assert(!noexcept(swap(lhs&: std::declval<C&>(), rhs&: std::declval<C&>())), "");
72#endif
73 }
74#if TEST_STD_VER >= 14
75 {
76 typedef std::basic_string<char, std::char_traits<char>, some_alloc2<char>> C;
77 // if the allocators are always equal, then the swap can be noexcept
78 static_assert(noexcept(swap(std::declval<C&>(), std::declval<C&>())), "");
79 }
80#endif
81
82 return 0;
83}
84

source code of libcxx/test/std/strings/basic.string/string.nonmembers/string.special/swap_noexcept.pass.cpp