boost::scoped_lock 似乎没有锁定 std::cout

Question

我使用的是 boost 1.54.0 和 Visual Studio 2010。对于代码：

#include <iostream>
#include "boost/thread/thread.hpp"
#include "boost/thread/mutex.hpp"

boost::mutex mx1;

void func1()
{
    {
        boost::mutex::scoped_lock(mx1);
        std::cout << "Thread " << boost::this_thread::get_id() << " starting work." << std::endl;
    }
    int x = 0;
    for (int i=0; i<100; i++)
        x++;
    {
        boost::mutex::scoped_lock(mx1);
        std::cout << "Thread " << boost::this_thread::get_id() << " finished." << std::endl;
    }
}

int main(void)
{
    boost::thread thread1(&func1);
    boost::thread thread2(&func1);
    thread1.join();
    thread2.join();
    return 0;
}

大约一半的时间我得到以下结果（显然有不同的线程 ID 和执行顺序）：

Thread Thread 15b0 starting work.
1a18 starting work.
Thread 15b0 finished.
Thread 1a18 finished.

...而不是这个（这是我所期望的）：

Thread 15b0 starting work.
Thread 1a18 starting work.
Thread 15b0 finished.
Thread 1a18 finished.

但是，使用

mx1.lock();
std::cout << "Thread " << boost::this_thread::get_id() << " starting work." << std::endl;
mx1.unlock();

...似乎工作没有问题。

输出似乎总是遵循相同的模式。我是否错误地使用了互斥锁，或者它与 std::cout?

有关

Answer 1

替换

    boost::mutex::scoped_lock(mx1);

和

    boost::mutex::scoped_lock lock(mx1);

你成为了范围锁最常出现的拼写错误的受害者:-)

boost::scoped_lock 似乎没有锁定 std::cout

boost::scoped_lock appears not to lock std::cout

c++

multithreading

boost

mutex

boost-mutex