libcxx/test/std/thread/thread.jthread/join.pass.cpp

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