Question

当我以字符串作为缓冲区开始async_write（）时，我不确定为什么会出现分段错误。我过去成功使用过这个功能。

以下是我获得分段错误的方法：

void StringSocket::sendLine(const string& toWrite)
{
    try
    {
    std::cout << "in StringSocket::sendLine()\n";
    std::cout << "is the socket alive?: " << (bool)s->is_open() << "\n";
    std::cout << "toWrite: " << toWrite;

     //s = asio::ip::tcp::socket* 
     asio::async_write(*this->s,
           asio::buffer(toWrite),
           boost::bind(&StringSocket::MessageSent,
                   this,
                   asio::placeholders::error));
  std::cout << "AFTER: asio::async_write()\n";

    }
    catch (int e)
    {
        std::cout << "ERROR: " << e << "\n";
    }
}

这是编译器所说的：

in main()
in serverTCP::serverTCP()!
in spreadsheet::spreadsheet()
in serverTCP::start_accept()!
in client::client(asio::io_service& io_service, std::string name)
in StringSocket::StringSocket(asio::ip::tcp::socket *_socket)
in client::getSocket()
in StringSocket::underSoc()
in serverTCP::pickSpreadsheet()!
in client::getClientName()
in client::sendToGui(std::string mess)
in StringSocket::beginSend(const string& toWrite, sendCallback callBack, void* payload)
toWrite: Welcome to SS! user: user0000
in StringSocket::ProcessSend()
TextToSend: Welcome to SS! user: user0000
in StringSocket::sendLine()
is the socket alive?: 1
toWrite: Welcome to SS! user: user0000
Segmentation fault

Answer 1

asio::async_write(*this->s, asio::buffer(toWrite),...

请注意，asio::buffer只是一个不会复制其参数的适配器。因此，在上面的行中，您实际上将 local 对象作为缓冲区传递给async。操作。因此，toWrite寿命和异步之间存在竞争条件。操作

Answer 2

如果检查async_write的引用（所有重载在此主题上都表示相同），它将告诉您处理函数有两个参数，首先是错误代码，然后是发送数据的长度。

您的boost::bind来电仅提供一个参数。您仍然必须告诉boost::bind有一个额外的参数将在稍后填写。您可以使用占位符参数boost::asio::placeholders::bytes_transferred：

来实现

所以把它改成例如。

boost::bind(&StringSocket::MessageSent,
            this,
            asio::placeholders::error,
            asio::placeholders::bytes_transferred)

asio :: async_write SEG FAULT

2 个答案: