Beginning on boost::asio : Having problems using io_context

Question

I've been coding in c++ and wanted to try out boost asio to create a TCP asynchronous server.

I read the documentation that boost provides and I used boost 1.75 to try and code this server.

However, I don't seem to understand how to use the io_context from the documentation.

When I am compiling the code for the Day 3: Asynchronous TCP daytime server ( this link which is in boost 1.78 but doesn't seem to differ a lot from 1.75) I constantly get the error that io_context cannot be copied due to their inheritance from execution_context, which inherits from noncopyable .

So I don't understand how to write and compile the documentation code since it tries to make a copy of an io_context in it.

Thanks in advance for any replies.

Edit: I've been compiling the code on C++ 17 and used conan to manage boost, the problem I am having comes from the constructor where I try to copy an io_context to an attribute of my class:

   class Server {
    public:
        Server(boost::asio::io_context& io_context) : _io_context(io_context), _acceptor(io_context, boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), 13))
        {
            startAccept();
        }
        ~Server();
    private:
        void startAccept();
        void handleAccept(ConnectionHandler::pointer new_connection, const boost::system::error_code &error);
        boost::asio::io_context _io_context;
        boost::asio::ip::tcp::acceptor _acceptor;
};

And here are the compilation error I was getting with the example:

    error: use of deleted function 
    ‘boost::asio::io_context::io_context(const boost::asio::io_context&)’17 | Server(boost::asio::io_context& io_context) : 
    _io_context(io_context), _acceptor(io_context, 
    boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), 13))

/home/romsnouk/.conan/data/boost/1.75.0/_/_/package/634391908be52704fdd5c332658475fe91ab3b1d/include/boost/asio/io_context.hpp:639:3: note: declared here
  639 |   io_context(const io_context&) BOOST_ASIO_DELETED;

Answer 1

The problem? When you try to initialize the _io_context member you copy the un-copyable io_context object.

The _io_context member needs to be a reference:

boost::asio::io_context& _io_context;
//                     ^
// Note ampersand, to make it a reference

This is what's done in the full example .

---

Of course make sure that the life-time of the original io_context object is at least as long as the Server object you create.