在c ++ 11中使用带std :: thread的atomics [英] Using atomics with std::thread in c++11

问题描述

我有一个线程，我想坐在一个循环，直到我准备好退出程序，在这一点，我想它打破循环，退出，所以我可以调用 std :: thread :: join 就可以了。在c ++ 03的日子里，我只是使用一个bool保护锁，以告诉线程何时退出。这一次我想我会利用新的原子库（特别是 std :: atomic_bool ），但我有麻烦。下面是我的测试用例：

I have a thread that I want to sit in a loop until I'm ready to exit the program, at which point I want it to break out of the loop and exit so I can call std::thread::join on it. In the days of c++03, I would just use a bool protected by a lock in order to tell the thread when to exit. This time I thought I would take advantage of the new atomics library (specifically std::atomic_bool), but I'm having trouble. Below is my test case:

#include <atomic>
#include <thread>
#include <cstdio>

using namespace std;

void setBool(atomic_bool& ab)
{
    ab = true;
}

int main()
{
    atomic_bool b;
    b = false;
    thread t(setBool, b);
    t.join();
    printf("Atomic bool value: %d\n", b.load());
    return 0;
}

线程t 当我尝试编译时，会出现此怪物。错误的中心部分似乎是：

The declaration of thread t spits out this monstrosity when I try to compile. The central part of the error seems to be:

无法初始化类型为'std :: atomic_bool&'的非const引用为什么我不能得到 atomic_bool

invalid initialization of non-const reference of type ‘std::atomic_bool&’ from an rvalue of type ‘std::atomic_bool’

？我应该怎么办？

Why can I not get a reference to an atomic_bool? What should I do instead?

推荐答案

你必须明确传递一个ref到你的线程。使用 std :: ref 将创建一个 std :: reference_wrapper ，它是可复制的，

You have to explicitly pass a ref to your thread. Using std::ref will create a std::reference_wrapper which is copyable and will carry the ref to your function.

thread t(setBool, std::ref(b));

否则会尝试复制原子，这是不可复制的。

Otherwise it will try to copy your atomic, which is uncopyable.

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