Boost:asio getting exception

Question

I am writing a client server demo using boost.asio. I went through the http demo and wrote my own code from scratch. But, I am getting an exception (most probably) while acceptor is getting initialized. I ma not sure why I am getting this exception and my example http code (from boost site) is doing same thing and running fine.

Here is my server.h code sample,

 #include <boost/asio.hpp>
 #include <boost/noncopyable.hpp>
 #include "Connection.h"
 #include <iostream>

 using boost::asio::ip::tcp;

 class Server : private boost::noncopyable
 {
   public:
   explicit Server(const std::string& address, const std::string& port);

   void run();

   private:
   boost::asio::ip::tcp::acceptor   _acceptor;
   boost::asio::io_service          _ioService;
   CONNECTION_SHARED_POINTER        _connection;

   void start_accept();
   void handle_accept(const boost::system::error_code& e);
   void handle_stop();
 };

server.cpp code

#include "Server.h"
#include <boost/bind.hpp>


Server::Server(const std::string& address, const std::string& port)
    :_acceptor(_ioService),
     _connection()
{

    boost::asio::ip::tcp::resolver resolver(_ioService);
    boost::asio::ip::tcp::resolver::query query(address, port);
    boost::asio::ip::tcp::endpoint endpoint = *resolver.resolve(query);

    _acceptor.open(endpoint.protocol());
    _acceptor.set_option(
                boost::asio::ip::tcp::acceptor::reuse_address(true));
   _acceptor.bind(endpoint);
   _acceptor.listen();


   //Starting the acceptor
   start_accept();
 }

void Server::run()
{
   std::cout<< "Running ioService" <<std::endl;
   _ioService.run();
}

void Server::start_accept()
{
    _connection.reset(new Connection(_ioService));

    std::cout<< "Accept connection" <<std::endl;
    _acceptor.async_accept( _connection->socket(),
                        boost::bind(    &Server::handle_accept, this,
                                        boost::asio::placeholders::error));


}

void Server::handle_accept(const boost::system::error_code& e)
{

   if (!e)
   {
      _connection->start();
    }

   start_accept();
 } 

And my main.cpp

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

int main(int argc, char* argv[])
{
  try
     {
        Server s("0.0.0.0", "7000");
        s.run();
   }
   catch (std::exception& e)
   {
       std::cerr << "exception: " << e.what() << "\n";
   }

    return 0;
 }

Now my code is getting an excpetion inside Server CTOR, while tryig to init _acceptor. The error message is as follows:

Unhandled exception at 0x7747d7f6 in VrfServer.exe: 0xC0000005: Access violation reading location 0xffffffffffffffff.

Stack dump is as follows:

 ntdll.dll!000000007747d7f6()   
 [Frames below may be incorrect and/or missing, no symbols loaded for ntdll.dll]
 VrfServer.exe!boost::asio::detail::win_mutex::lock()  Line 51  C++
 VrfServer.exe!boost::asio::detail::scoped_lock<boost::asio::detail::win_mutex>::scoped_lock<boost::asio::detail::win_mutex>(boost::asio::detail::win_mutex & m)  Line 47   C++
VrfServer.exe!boost::asio::detail::service_registry::do_use_service(const boost::asio::io_service::service::key & key, boost::asio::io_service::service * (boost::asio::io_service &)* factory)  Line 108 + 0x12 bytes  C++
VrfServer.exe!boost::asio::detail::service_registry::use_service<boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >()  Line 49    C++
VrfServer.exe!boost::asio::use_service<boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >(boost::asio::io_service & ios)  Line 34 C++
VrfServer.exe!boost::asio::basic_io_object<boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >::basic_io_object<boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >(boost::asio::io_service & io_service)  Line 91 + 0x36 bytes   C++
VrfServer.exe!boost::asio::basic_socket_acceptor<boost::asio::ip::tcp,boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >::basic_socket_acceptor<boost::asio::ip::tcp,boost::asio::socket_acceptor_service<boost::asio::ip::tcp> >(boost::asio::io_service & io_service)  Line 86  C++
VrfServer.exe!Server::Server(const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & address, const std::basic_string<char,std::char_traits<char>,std::allocator<char> > & port)  Line 8 + 0x76 bytes  C++
VrfServer.exe!main(int argc, char * * argv)  Line 8 + 0x52 bytes    C++
VrfServer.exe!__tmainCRTStartup()  Line 555 + 0x19 bytes    C
VrfServer.exe!mainCRTStartup()  Line 371    C
kernel32.dll!00000000772259bd()     
ntdll.dll!000000007745a2e1()    

Can anyone shed any light?

Answer 1

The problem has nothing to do with asio, it's just how C++ works

In your Server class you declare:

   private:
   boost::asio::ip::tcp::acceptor   _acceptor;
   boost::asio::io_service          _ioService;
   CONNECTION_SHARED_POINTER        _connection;

And then you initialize it as follows:

Server::Server(const std::string& address, const std::string& port)
    :_acceptor(_ioService),
     _connection()

When you initialize _acceptor, _ioService has not yet been initialized, due to how the order of declaration in the class.

   boost::asio::io_service          _ioService;
   boost::asio::ip::tcp::acceptor   _acceptor;
   CONNECTION_SHARED_POINTER        _connection;

Should solve the problem.