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: no-threads
10// UNSUPPORTED: c++03, c++11, c++14, c++17
11// XFAIL: availability-synchronization_library-missing
12
13// void join();
14
15#include <atomic>
16#include <cassert>
17#include <chrono>
18#include <concepts>
19#include <functional>
20#include <system_error>
21#include <thread>
22#include <type_traits>
23#include <vector>
24
25#include "make_test_thread.h"
26#include "test_macros.h"
27
28int main(int, char**) {
29 // Effects: Blocks until the thread represented by *this has completed.
30 {
31 std::atomic_int calledTimes = 0;
32 std::vector<std::jthread> jts;
33 constexpr auto numberOfThreads = 10u;
34 jts.reserve(numberOfThreads);
35 for (auto i = 0u; i < numberOfThreads; ++i) {
36 jts.emplace_back(support::make_test_jthread([&] {
37 std::this_thread::sleep_for(std::chrono::milliseconds(2));
38 calledTimes.fetch_add(1, std::memory_order_relaxed);
39 }));
40 }
41
42 for (auto i = 0u; i < numberOfThreads; ++i) {
43 jts[i].join();
44 }
45
46 // If join did block, calledTimes must equal to numberOfThreads
47 // If join did not block, there is a chance that the check below happened
48 // before test threads incrementing the counter, thus calledTimed would
49 // be less than numberOfThreads.
50 // This is not going to catch issues 100%. Creating more threads to increase
51 // the probability of catching the issue
52 assert(calledTimes.load(std::memory_order_relaxed) == numberOfThreads);
53 }
54
55 // Synchronization: The completion of the thread represented by *this synchronizes with
56 // ([intro.multithread]) the corresponding successful join() return.
57 {
58 bool flag = false;
59 std::jthread jt = support::make_test_jthread([&] { flag = true; });
60 jt.join();
61 assert(flag); // non atomic write is visible to the current thread
62 }
63
64 // Postconditions: The thread represented by *this has completed. get_id() == id().
65 {
66 std::jthread jt = support::make_test_jthread([] {});
67 assert(jt.get_id() != std::jthread::id());
68 jt.join();
69 assert(jt.get_id() == std::jthread::id());
70 }
71
72#if !defined(TEST_HAS_NO_EXCEPTIONS)
73 // Throws: system_error when an exception is required ([thread.req.exception]).
74 // invalid_argument - if the thread is not joinable.
75 {
76 std::jthread jt;
77 try {
78 jt.join();
79 assert(false);
80 } catch (const std::system_error& err) {
81 assert(err.code() == std::errc::invalid_argument);
82 }
83 }
84
85#endif
86
87 return 0;
88}
89

source code of libcxx/test/std/thread/thread.jthread/join.pass.cpp