c++ - 使用 pthread_create 从线程调用类成员函数

Question

下面是代码

#include <iostream>
#include <pthread.h>

using namespace std;

class Base

{
    private:
    public:

        void *threadCall1( void * value)
        {
            cout<<"inside threadCall1"<<endl;

        }

    protected:

};

class Derived
{
    private:
    public:
        void  *threadCall2 ();
    protected:



};


 void *Derived::threadCall2()
{
    cout<<"inside threadCall2"<<endl;

}
int main ()
{
    int k = 2;
    pthread_t t1;
    cout<<"inside main"<<endl;
    Base *b = new Base();

    pthread_create(&t1,NULL,&b->threadCall1,(void *)k);

    return 0;
}

错误

main.cc: In function int main()': main.cc:46: error: ISO C++ forbids
taking the address of a bound member function to form a pointer to
member function. Say&Base::threadCall1' main.cc:46: error: cannot convert void*(Base::*)(void*)' tovoid*()(void)' for argument 3'
toint pthread_create(pthread_t*, const pthread_attr_t*, void*()(void), void*)'

我同意 C++ 禁止此调用，但有什么方法可以使用 posix 线程调用类成员函数

Answer 1

您可以通过相应地分派(dispatch)工作的函数来执行此操作:

#include <iostream>
#include <pthread.h>

struct Base {
    virtual void work() {
        std::cout << "Base::work()\n";
    }

    virtual ~Base() {}
};

struct Derived : public Base {
    void work() override {
        std::cout << "Derived::work()\n";
    }
};

void* thread_adapter(void* obj) {
    Base* p = static_cast<Base*>(obj);
    p->work();
    return nullptr;
}

int main() {
    Derived d;
    pthread_t thread;
    pthread_create(&thread, nullptr, thread_adapter, &d);
    pthread_join(thread, nullptr);
}

Live example

pthread_create 接受指向线程函数的任意数据的指针。传递对象的地址，并使用转发函数，例如上面定义的 thread_adapter。在适配器函数内部，您可以将参数 static_cast 返回到线程函数内部的 Base* 并根据需要调用成员函数。

但是，您可能需要查看 std::thread库，以更自然的方式支持此类操作:

#include <iostream>
#include <thread>

struct Base {
    virtual void work() {
        std::cout << "Base::work()\n";
    }

    virtual ~Base() {}
};

struct Derived : public Base {
    void work() override {
        std::cout << "Derived::work()\n";
    }
};

int main() {
    Derived d;
    std::thread t(&Base::work, d);
    t.join();
}

Live example