c++ - Boost:asio 获取异常

Question

我正在使用 boost.asio 编写客户端服务器演示。我浏览了 http 演示并从头开始编写了自己的代码。但是，我在接受器初始化时遇到了一个异常(很可能)。我不确定为什么我会收到此异常，而我的示例 http 代码(来自 boost 站点)正在做同样的事情并且运行良好。

这是我的 server.h 代码示例，

 #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代码

#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();
 } 

还有我的 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;
 }

现在我的代码在服务器 CTOR 中得到一个异常，同时尝试初始化 _acceptor。错误信息如下:

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

堆栈转储如下:

 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()    

任何人都可以阐明吗？

Answer 1

问题与 asio 无关，这只是 C++ 的工作方式

在您的 Server 类中声明:

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

然后按如下方式初始化它:

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

当你初始化_acceptor时，_ioService还没有被初始化，因为在类中声明的顺序。

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

应该可以解决问题。