Boost：asio得到异常

Question

我正在使用boost.asio编写客户端服务器演示。 我经历了http演示，并从头开始编写自己的代码。 但是，我收到一个异常（最有可能），而接受者正在初始化。我不知道为什么我得到这个异常和我的示例http代码（来自boost网站）做同样的事情，运行良好。

这里是我的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(); 
} 

而且我的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，我的代码得到一个错误时抛出在服务器CTOR内部，同时尝试初始化_acceptor。该错误消息如下：

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()  

谁能有何启示？

Answer 1

问题无关与ASIO，它只是如何C++工作

在你Server类声明：

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

然后你如下初始化：

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

当初始化_acceptor时，_ioService尚未初始化，由于声明的顺序如何在t他上课。

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

应该解决问题。