error when use std::thread in Class

Question

I tried to use std::thread in Visual Studio 2013. It works all right like this.

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <chrono>    // std::chrono::seconds
#include <iostream>  // std::cout
#include <thread>    // std::thread, std::this_thread::sleep_for
#include <vector>
void thread_task(int n) {
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "hello thread "
        << std::this_thread::get_id()
        << " paused " << n << " seconds" << std::endl;
}
int _tmain(int argc, _TCHAR* argv[])
{
    std::vector<std::thread> threads;
    std::cout << "Spawning 5 threads...\n";
    for (int i = 0; i < 5; i++) {
        threads.emplace_back( std::thread(thread_task, i + 1));
    }
    std::cout << "Done spawning threads! Now wait for them to join\n";
    for (auto& t : threads) {
        t.join();
    }
    std::cout << "All threads joined.\n";
    return 0;
}

but when I tried to make thread in a Class, I met some compiling errors.

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <chrono>    // std::chrono::seconds
#include <iostream>  // std::cout
#include <thread>    // std::thread, std::this_thread::sleep_for
#include <vector>
class MyClass
{
public:
    MyClass();
    void thread_task(int n);
    ~MyClass();
private:
};
MyClass::MyClass()
{
    std::vector<std::thread> threads;
    std::cout << "Spawning 5 threads...\n";
    for (int i = 0; i < 5; i++) {
        threads.emplace_back(std::thread(&MyClass::thread_task, i + 1));
    }
    std::cout << "Done spawning threads! Now wait for them to join\n";
    for (auto& t : threads) {
        t.join();
    }
    std::cout << "All threads joined.\n";
}
void MyClass::thread_task(int n) {
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "hello thread "
        << std::this_thread::get_id()
        << " paused " << n << " seconds" << std::endl;
}
MyClass::~MyClass(){}
int _tmain(int argc, _TCHAR* argv[])
{   
    MyClass test();
    return 0;
}

The error messages are copied below.

1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\functional(1149): error C2064: term does not evaluate to a function taking 1 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 12.0\vc\include\functional(1137) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>::_Do_call<,0>(std::tuple<>,std::_Arg_idx<0>)' being compiled
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\functional(1137) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>::_Do_call<,0>(std::tuple<>,std::_Arg_idx<0>)' being compiled
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thr\xthread(195) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>::operator ()<>(void)' being compiled
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thr\xthread(195) : see reference to function template instantiation 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>::operator ()<>(void)' being compiled
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thr\xthread(192) : while compiling class template member function 'unsigned int std::_LaunchPad<_Target>::_Run(std::_LaunchPad<_Target> *)'
1>          with
1>          [
1>              _Target=std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thr\xthread(187) : see reference to function template instantiation 'unsigned int std::_LaunchPad<_Target>::_Run(std::_LaunchPad<_Target> *)' being compiled
1>          with
1>          [
1>              _Target=std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thr\xthread(205) : see reference to class template instantiation 'std::_LaunchPad<_Target>' being compiled
1>          with
1>          [
1>              _Target=std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>
1>          ]
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\thread(49) : see reference to function template instantiation 'void std::_Launch<std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>>(_Thrd_t *,_Target &&)' being compiled
1>          with
1>          [
1>              _Target=std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall MyClass::* )(int),void,MyClass,int>,int>
1>          ]
1>          d:\projects\consoleapplication2\consoleapplication2\consoleapplication2.cpp(29) : see reference to function template instantiation 'std::thread::thread<void(__thiscall MyClass::* )(int),int>(_Fn &&,int &&)' being compiled
1>          with
1>          [
1>              _Fn=void (__thiscall MyClass::* )(int)
1>          ]
1>

What cause the problem?

Thanks @malchemist, when add this solve the problem. But it makes me confused this piece of codecode error still got some compiling errors even written just like the answer shows.

Can anyone help me? Thanks a lot.

Possible duplicate of [Start thread with member function](http://stackoverflow.com/questions/10673585/start-thread-with-member-function) — Peter K, Aug 18 '16 at 11:02

score 2 · Accepted Answer · answered Aug 18 '16 at 11:11

2

You have to specify an object to call function inside new thread. Try this:

threads.emplace_back(std::thread(&MyClass::thread_task,this, i + 1));

answered Aug 18 '16 at 11:11

malchemist

434
2
13

Thanks a lot, It definitely solve this problem. is it possible to run on a gpu like this? I met some code written just like you answer, but I still got errors when compiling.[link to the project](https://github.com/btgraham/SparseConvNet/issues/7) – wanglinski Aug 18 '16 at 11:23

error when use std::thread in Class

What cause the problem?

1 Answers1