How does std::bind differentiate between arguments and pointer to an object?

[u/CommandShot1398]

Hi everyone,

I have difficulties understanding something:

class HttpServer {
    public:
        HttpServer(std::string_view address, uint16_t port):ioc{1},endpoint{boost::asio::ip::make_address(address)},
        acceptor{ioc,{endpoint,port}} {
        };
        ~HttpServer()=default;


        void handle_request() {
            for (;;) {
                tcp::socket socket{ioc};


                // Block until we get a connection
                acceptor.accept(socket);
                std::cout<<"connection accepted"<<std::endl;
                std::thread{std::bind(
                &HttpServer::do_session,this,
                std::move(socket))}.detach();
            }

        }

        void do_session(tcp::socket& socket) {
            //handle request



        }

    private:
        const boost::asio::ip::address endpoint;
        uint16_t port;
        boost::asio::io_context ioc;
        tcp::acceptor acceptor;

    };

In this piece of code, how does std::bind understand that it should infer this as a pointer to the object which own the function pointer (I'm not even sure if I stated it correctly)?

according to chatgpt

std::bind( function, argument1, argument2, argument3 )
is a template that takes a pointer to the function that it should return the wrapper for, along with the arguments and their placeholders. What I don't understand is how it differentiates between the "this" pointer and an argument? How does it know it should take the non-static member function and dereference it based on the address (or reference) of the object that owns it, rather than just using "this" pointer as another argument?

[u/Dan13l_N]

This is likely done by template specialization. If the first argument of std::bind is a non-static member function, the second argument must be a pointer to object you'll call the function on.

[u/CommandShot1398 → u/Dan13l_N]

This makes sense.