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// UNSUPPORTED: c++03, c++11, c++14, c++17
9// XFAIL: !has-64-bit-atomics
10
11// T exchange(T, memory_order = memory_order::seq_cst) volatile noexcept;
12// T exchange(T, memory_order = memory_order::seq_cst) noexcept;
13
14#include <atomic>
15#include <cassert>
16#include <concepts>
17#include <type_traits>
18
19#include "test_helper.h"
20#include "test_macros.h"
21
22template <class T>
23concept HasVolatileExchange = requires(volatile std::atomic<T>& a, T t) { a.exchange(t); };
24
25template <class T, template <class> class MaybeVolatile = std::type_identity_t>
26void test_impl() {
27 // Uncomment the test after P1831R1 is implemented
28 // static_assert(HasVolatileExchange<T> == std::atomic<T>::is_always_lock_free);
29 static_assert(noexcept(std::declval<MaybeVolatile<std::atomic<T>>&>() = (T(0))));
30
31 // exchange
32 {
33 MaybeVolatile<std::atomic<T>> a(T(3.1));
34 std::same_as<T> decltype(auto) r = a.exchange(T(1.2), std::memory_order::relaxed);
35 assert(a.load() == T(1.2));
36 assert(r == T(3.1));
37 }
38
39 // memory_order::release
40 {
41 auto exchange = [](MaybeVolatile<std::atomic<T>>& x, T, T new_val) {
42 x.exchange(new_val, std::memory_order::release);
43 };
44 auto load = [](MaybeVolatile<std::atomic<T>>& x) { return x.load(std::memory_order::acquire); };
45 test_acquire_release<T, MaybeVolatile>(exchange, load);
46 }
47
48 // memory_order::seq_cst
49 {
50 auto exchange_no_arg = [](MaybeVolatile<std::atomic<T>>& x, T, T new_val) { x.exchange(new_val); };
51 auto exchange_with_order = [](MaybeVolatile<std::atomic<T>>& x, T, T new_val) {
52 x.exchange(new_val, std::memory_order::seq_cst);
53 };
54 auto load = [](MaybeVolatile<std::atomic<T>>& x) { return x.load(); };
55 test_seq_cst<T, MaybeVolatile>(exchange_no_arg, load);
56 test_seq_cst<T, MaybeVolatile>(exchange_with_order, load);
57 }
58}
59
60template <class T>
61void test() {
62 test_impl<T>();
63 if constexpr (std::atomic<T>::is_always_lock_free) {
64 test_impl<T, std::add_volatile_t>();
65 }
66}
67
68int main(int, char**) {
69 test<float>();
70 test<double>();
71 // TODO https://github.com/llvm/llvm-project/issues/47978
72 // test<long double>();
73
74 return 0;
75}
76

source code of libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/exchange.pass.cpp