c++ - 如何使类静态变量线程安全

Question

我有这样一个类:

class Test
{
private:
    Test() {}
    static bool is_done;
    static void ThreadFunction();
public:
    static void DoSomething();
}


bool Test::is_done = true;

void Test::DoSomething()
{
    std::thread t_thread(Test::ThreadFunction);

    while (true) {
        if (is_done) {
            //do something else
            is_done = false;
        }

        if (/*something happened*/) { break; }
    }

    // Finish thread.
    t_thread.join();
}

void Test::ThreadFunction()
{
    while (true) {
        if (/*something happened*/) {
            is_done = true;
        }
    }
}

然后在 main 中我只调用 Test::DoSomething();在这种情况下变量'is_done'是线程安全的吗？如果不是，我怎样才能保证阅读安全？

Answer 1

Is global variable 'is_done' in this case thread safe?

没有。 static并不意味着线程安全。

---

If its not how can I make reading it safe?

你应该使用 std::atomic<bool> :

class Test
{
private:
    Test() {}
    static std::atomic<bool> is_done;
    static void ThreadFunction();
public:
    static void DoSomething();
}

std::atomic<bool> Test::is_done{true};