再次调用async_read会抛出异常

calling async_read again is throwing exception

本文关键字：read 抛出异常 async 调用更新时间：2023-10-16

我有以下代码:

 void GnutellaApp::HandleRead (boost::asio::ip::tcp::socket& socket)
{
     char buf[128];
     try {
     boost::asio::async_read(   socket,
                                boost::asio::buffer(buf),
                                boost::asio::transfer_all(),
                                boost::bind(&GnutellaApp::HandleRead,
                                            this,
                                            boost::ref(socket)
                                            )
                            );
     }
        catch (boost::system::system_error const& e)
        {
            std::cout << "Warning:  " << e.what() << std::endl;
        }
}

当HandleRead被调用并且async_read被执行时，它抛出一个异常。为了异步等待下一个请求，我们需要再次调用async_read，对吗?第一次呼叫async_read成功。

我得到以下异常

Gnutella.exe!std::_Ref_count_base::_Incwref() Line 113  C++
    Gnutella.exe!std::_Ptr_base<void>::_Resetw<void>(void * _Other_ptr, std::_Ref_count_base * _Other_rep) Line 458 C++
    Gnutella.exe!std::_Ptr_base<void>::_Resetw<void>(const std::_Ptr_base<void> & _Other) Line 445  C++
    Gnutella.exe!std::weak_ptr<void>::weak_ptr<void><void>(const std::shared_ptr<void> & _Other, void * * __formal) Line 994    C++
    Gnutella.exe!boost::asio::detail::win_iocp_socket_service_base::async_receive<boost::asio::mutable_buffers_1,boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > >(boost::asio::detail::win_iocp_socket_service_base::base_implementation_type & impl, const boost::asio::mutable_buffers_1 & buffers, int flags, boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > & handler) Line 292   C++
    Gnutella.exe!boost::asio::stream_socket_service<boost::asio::ip::tcp>::async_receive<boost::asio::mutable_buffers_1,boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > >(boost::asio::detail::win_iocp_socket_service<boost::asio::ip::tcp>::implementation_type & impl, const boost::asio::mutable_buffers_1 & buffers, int flags, boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > && handler) Line 359   C++
    Gnutella.exe!boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >::async_read_some<boost::asio::mutable_buffers_1,boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > >(const boost::asio::mutable_buffers_1 & buffers, boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > > && handler) Line 846    C++
    Gnutella.exe!boost::asio::detail::read_op<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > >::operator()(const boost::system::error_code & ec, unsigned int bytes_transferred, int start) Line 273  C++
    Gnutella.exe!boost::asio::async_read<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> >,boost::asio::mutable_buffers_1,boost::asio::detail::transfer_all_t,boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > >(boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > & s, const boost::asio::mutable_buffers_1 & buffers, boost::asio::detail::transfer_all_t completion_condition, boost::_bi::bind_t<void,boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>,boost::_bi::list2<boost::_bi::value<GnutellaApp *>,boost::reference_wrapper<boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > > > > && handler) Line 535   C++
    Gnutella.exe!GnutellaApp::HandleRead(boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > & socket) Line 232    C++
>   Gnutella.exe!boost::_mfi::mf1<void,GnutellaApp,boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > &>::operator()(GnutellaApp * p, boost::asio::basic_stream_socket<boost::asio::ip::tcp,boost::asio::stream_socket_service<boost::asio::ip::tcp> > & a1) Line 165 C++
    Gnutella.exe!boost::_bi::list2<boost::_bi::value

这会使您看起来好像持有一个过时的引用。

此外，boost::asio::buffer(buf)是一个明显的冒犯，因为buf是堆栈局部的，但async_read是…好异步。

常见的模式是

使buf和socket类成为成员(这样它们就可以确保比异步请求活得更长)
使buf和socket共享(boost::shared_ptr<boost::asio::ip::tcp::socket>)，您可以通过值传递/绑定:
```
   boost::bind(&GnutellaApp::HandleRead,
                this,
                socket
             )
```
根据shared_ptr

将使套接字保持活动状态。