multithreading - Asynchronous threads in class

Question

I've got a class Foo, which have a main function and execute function. I want to start an unknown number of threads with the execute function, but when I try to compile the code I always get error C2064: term does not evaluate to a function taking 1 arguments.

foo.h

#ifndef BOT_H
#define BOT_H

#pragma once
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <string>
class foo
{
public:
    foo(char *_server, char *_port);
    ~foo(void);
private:
    char *server;
    char *port;

    void execute(char *cmd);
    void main();
};

#endif

foo.c

#include <thread>
#include "bot.h"
#include "definitions.h"

using namespace std;
foo::foo(char *_server, char *_port){
        ...
}

bot::~bot(void) {
        ...
}
void bot::execute(char *command){
    ...
}
    void bot::main(){
        thread(&bot::execute, (char*)commanda.c_str()).detach();
    }

How should I create threads from class member functions?

Thanks for any answer

Mike Seymour · Accepted Answer · 2014-01-09 16:53:31Z

5

You need a bot object to call the member function on:

thread(&bot::execute, this, (char*)commanda.c_str())
                      ^^^^

although you really should either change the function to take either std::string or const char*. You have a minefield of undefined behaviour here, if either the function tries to modify the string, or commanda is destroyed while the thread is still using it.

A lambda may be more readable; and would also fix the lifetime fiasco by capturing a copy of the string:

thread([=]{execute((char*)commanda.c_str();})

answered Jan 9, 2014 at 16:53

Mike Seymour

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