c++ - 将函数传递给新线程时编译器错误？

Question

有人可以帮我解决我在下面的 main 中创建线程时遇到的错误吗？

#include "lock_free_queue.h"
#include "Consumer.h"
#include <thread>

int main(){
    lock_free_queue* my_queue = new lock_free_queue();
    Consumer* c = new Consumer(my_queue);

    //Error occurs here I think
    std::thread t3(&Consumer::start);
    ...
    t3.join();

Consumer.h(它都在标题中，因为最初要使用模板):

#ifndef CONSUMER_H
#define CONSUMER_H

#include "lock_free_queue.h"
#include <iostream>

class Consumer{
public:

    Consumer(lock_free_queue* queue) : the_queue(queue){}

    void start(){
        consume = true;
        while(consume){
            while(the_queue->getSize()==0){}
            process();
        }
    }

我收到这个错误(看起来很可怕):

1>C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\functional(1152): error C2064: term does not evaluate to a function taking 0 arguments
1>          class does not define an 'operator()' or a user defined conversion operator to a pointer-to-function or reference-to-function that takes appropriate number of arguments
1>          C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\functional(1152) : while compiling class template member function 'void std::_Bind<_Forced,_Ret,_Fun,_V0_t,_V1_t,_V2_t,_V3_t,_V4_t,_V5_t,<unnamed-symbol>>::operator ()(void)'
1>          with
1>          [
1>              _Forced=true,
1>              _Ret=void,
1>              _Fun=std::_Pmf_wrap<void (__cdecl Consumer::* )(void),void,Consumer,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil>,
1>              _V0_t=std::_Nil,
1>              _V1_t=std::_Nil,
1>              _V2_t=std::_Nil,
1>              _V3_t=std::_Nil,
1>              _V4_t=std::_Nil,
1>              _V5_t=std::_Nil,
1>              <unnamed-symbol>=std::_Nil
1>          ]
1>          C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\thr/xthread(195) : see reference to function template instantiation 'void std::_Bind<_Forced,_Ret,_Fun,_V0_t,_V1_t,_V2_t,_V3_t,_V4_t,_V5_t,<unnamed-symbol>>::operator ()(void)' being compiled
1>          with
1>          [
1>              _Forced=true,
1>              _Ret=void,
1>              _Fun=std::_Pmf_wrap<void (__cdecl Consumer::* )(void),void,Consumer,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil>,
1>              _V0_t=std::_Nil,
1>              _V1_t=std::_Nil,
1>              _V2_t=std::_Nil,
1>              _V3_t=std::_Nil,
1>              _V4_t=std::_Nil,
1>              _V5_t=std::_Nil,
1>              <unnamed-symbol>=std::_Nil
1>          ]
1>          C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\thread(52) : see reference to class template instantiation 'std::_Bind<_Forced,_Ret,_Fun,_V0_t,_V1_t,_V2_t,_V3_t,_V4_t,_V5_t,<unnamed-symbol>>' being compiled
1>          with
1>          [
1>              _Forced=true,
1>              _Ret=void,
1>              _Fun=std::_Pmf_wrap<void (__cdecl Consumer::* )(void),void,Consumer,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil,std::_Nil>,
1>              _V0_t=std::_Nil,
1>              _V1_t=std::_Nil,
1>              _V2_t=std::_Nil,
1>              _V3_t=std::_Nil,
1>              _V4_t=std::_Nil,
1>              _V5_t=std::_Nil,
1>              <unnamed-symbol>=std::_Nil
1>          ]
1>          Main.cpp(10) : see reference to function template instantiation 'std::thread::thread<void(__cdecl Consumer::* )(void)>(_Fn)' being compiled
1>          with
1>          [
1>              _Fn=void (__cdecl Consumer::* )(void)
1>          ]

Answer 1

Consumer::start 是一个非静态成员函数。这意味着它需要一个 Consumer 实例来执行。形式上，这是通过为非静态成员函数提供 this 的隐式第一个参数来完成的。 std::thread 希望您传递一些东西，它可以用作第一个参数的参数。

因此，您需要传递一个 Consumer 实例或一个指向实例的指针，以便成员函数作用于:

std::thread t3(&Consumer::start, c);