如何为成员对象的过程启动新线程

Question

我正在尝试从我的 main() 开始一个方法，作为一个带有 pthread 的新线程：

int main(int argc, char** argv) {
    pthread_t shipGeneratorThread;
    Port portMelbourne;

    pthread_create(&shipGeneratorThread, NULL, portMelbourne.generateShips(), NULL);

    return (EXIT_SUCCESS);
}

Port 类有一个生成船的函数：

void Port::generateShips() {
    //Generate 1 cargo ship every 2.5 hours
    bool stop = false;

    while(!stop) {
        if(numberOfShipsInBay < 20) {
            Ship ship;
            ship.setTicket(numberOfShipsInBay);
            shipsWaitingToDock[numberOfShipsInBay] = ship;
            term.displayMessage("A new ship has entered the port");
            numberOfShipsInBay++;
        } else {
            term.displayMessage("A ship has been sent to another port");
        }
        usleep(FIVE_MINUTES * 30); //2.5 hours simulated time
    }
}

但是编译器给了我一个错误，“无效使用无效表达式”用于 pthread 创建函数。

我是 C++ 和线程的新手，有什么想法吗？

Answer 1

在这种情况下您应该使用静态方法，是的，请查看 man pthread_create。 函数的签名很重要。

此外，如果您创建线程方式，您的代码将在 main() 退出后立即终止。 您需要等待线程完成。我在下面举个例子。它并不理想，但似乎足以用于演示。

在处理线程启动时，请注意静态 -> 非静态方法转换。这是常见的方法（尽管不是唯一可能的方法）。

#include <stdio.h>
#include <pthread.h>

class Test {
    public:
        static void* Run(void* me) {
            static_cast<Test*>(me)->RunMe();
            return NULL;
        }

    private:
        void RunMe() {
            printf("%p: %p is running.\n", pthread_self(), this);
        }
};

int main() {

    pthread_t tid;
    Test test;

    printf("%p: creating thread for %p is running.\n", pthread_self(), &test);
    pthread_create(&tid, NULL, Test::Run, &test);
    printf("%p: waiting %p to finish.\n", pthread_self(), &test);

    // In real code you should check 'create' operation result.
    pthread_join(tid, NULL);
    printf("%p: OK, exiting\n", pthread_self());

    return 0;
}

Answer 2

你需要 "static void* generateShips(void*)" 并使用 "pthread_create(&shipGeneratorThread, NULL, Port::generateShips, NULL); ”。

问候。

Answer 3

/* you need a wrapper function like this, it can be also a static method of some class */
void *GenerateShipsThread(void *port)
{
    /* do desired action */
    reinterpret_cast<Port*>(port)->generateShips();

    /* destroy Port object here or somewhere else */
    delete reinterpret_cast<Port*>(port);

    return NULL;
}

int main(int argc, char** argv) {
    pthread_t shipGeneratorThread;

    /* Port object is passed to the thread so you don't want it to be
     * destoyed when this function returns - create it on the heap */
    Port *portMelbourne = new Port();

    pthread_create(&shipGeneratorThread, NULL, GenerateShipsWrapper, portMelbourne);

    return (EXIT_SUCCESS);
}