VC ++中的MultiThread程序

Question

I am trying to do a threaded application to infinitely print a set of numbers after enqueing them. I get this error:

Error 1 error C3867: 'Test::ThreadFunc': function call missing argument list; use '&Test::ThreadFunc' to create a pointer to member.

What am I doing wrong? What is the mistake ?

#include "stdafx.h"

#include <chrono>
#include <mutex>
#include <thread>
#include <list>

class Test {
    std::list<int> queue;
    std::mutex m;

public:
    void ThreadFunc()
    {
        // Loop is required, otherwise thread will exit
        for (;;)
        {
            bool read = false;
            int value;
            {
                std::lock_guard<std::mutex> lock(m);

                if (queue.size())
                {
                    value = queue.front();
                    read = true;
                    queue.pop_back();
                }
            }

            if (read)
            {
                // send(header.data(), header.dataSize());
                // send(proto.data(), proto.dataSize());
                printf("Hello %d\n", value);
            }

            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }

    void TestFunc()
    {
        std::thread thread(ThreadFunc);
        thread.detach();

        int i = 0;
        // Loops only as a test example
        for (;;)
        {
            std::lock_guard<std::mutex> lock(m);
            std::this_thread::sleep_for(std::chrono::milliseconds(2000));
            queue.push_back(i++);
            // Queue Message(header, payload);
        }
    }

};

int main()
{
    Test test;
    test.TestFunc();
}

Answer 1

You're attempting to pass a pointer to a member function of a class. When you do this, there's an argument added to the function, tacitly, that is a pointer to the instance of the class that you're invoking the function on. In your case, the pointer to the class will be the this pointer.

See this for syntax reference: Start thread with member function

To answer your comment, why isn't it passed implicitly? You're not calling the function as a member of a class, you're passing the member function by pointer. This is a different, unique, situation, see this reference: Passing a member function as an argument in C++

Also, to save a little future headache, the next problem that comes up is that std::thread's constructor takes its arguments by value, so if you need to pass any arguments by reference, take a look at std::ref.

Answer 2

Here's the fix. This works. Thank you @mock_blatt

#include "stdafx.h"

#include <chrono>
#include <mutex>
#include <thread>
#include <list>



class Test {
std::list<int> queue;
std::mutex m;

public:
    void ThreadFunc()
    {
        // Loop is required, otherwise thread will exit
        for (;;)
            {
                bool read = false;
                int value;
                {
                    std::lock_guard<std::mutex> lock(m);

                    if (queue.size())
                    {
                        value = queue.front();
                        read = true;
                        queue.pop_back();
                    }
                }

        if (read)
        {
        // send(header.data(), header.dataSize());
        // send(proto.data(), proto.dataSize());
            printf("Hello %d\n", value);
        }

        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
}

 void TestFunc()
 {
    std::thread thread(std::bind(&Test::ThreadFunc, this));
    thread.detach();

    int i = 0;
    // Loops only as a test example
    for (;;)
    {
        std::lock_guard<std::mutex> lock(m);
        std::this_thread::sleep_for(std::chrono::milliseconds(2000));
        queue.push_back(i++);
        // Queue Message(header, payload);
    }
}

};

int main()
{
 Test test;
test.TestFunc();
}

Answer 3

Change std::thread thread(ThreadFunc); to std::thread thread(Test::ThreadFunc, this);