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
30 template <class T>
31 struct some_alloc {
32 typedef T value_type;
33
some_allocsome_alloc34 some_alloc() {}
35 some_alloc(const some_alloc&);
36 T* allocate(std::size_t);
deallocatesome_alloc37 void deallocate(void*, unsigned) {}
38 typedef std::true_type propagate_on_container_swap;
39 };
40
41 template <class T>
42 struct some_alloc2 {
43 typedef T value_type;
44
some_alloc2some_alloc245 some_alloc2() {}
46 some_alloc2(const some_alloc2&);
47 T* allocate(std::size_t);
deallocatesome_alloc248 void deallocate(void*, unsigned) {}
49
50 typedef std::false_type propagate_on_container_swap;
51 typedef std::true_type is_always_equal;
52 };
53
main(int,char **)54 int main(int, char**) {
55 {
56 typedef std::string C;
57 static_assert(noexcept(swap(std::declval<C&>(), 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(std::declval<C&>(), 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