Question

I have the following code :

try
{
    HAS::TCPServerSocket servSock(echoServPort);    // Socket descriptor for server
    std::vector<HAS::TCPSocket*> sockets(MAXCONN);
    for (;;)
    {
        try
        {
            if (socketCount < MAXCONN)
            {
                HAS::TCPSocket* sock(servSock.accept());
                sockets.push_back(sock);
                std::thread handler(handleTCPClient, std::ref(sockets[socketCount++]));
                handler.detach();
            }
        }
        catch (...)
        {
            cerr << "Unable to create thread" << endl;
            exit(1);
        }
    }
}

I want to keep track of a limited number of connections (MAXCONN=4) and would like to keep track of opened sockets using a std::vector. Somehow, when I use the above code the sock variable gets properly set to the current socket as accepted by servSock.accept(). However, when I try to push the sock variable onto the std::vector I loose the sock object.

I have a feeling it has to do with properly specifying a copy and/or move constructor but I have defined both (and used breakpoints to see when the would be called) but they don’t seem to get called at all.

Answer 1

References to vector elements are invalidated when you say push_back. You can’t use the code the way you have. You must first populate the entire vector and then never touch it again. Alternatively, use a container whose element references aren’t invalidated by container mutations (list or multiset or unordered_multiset for general purpose, deque for insertion/deletion at the ends).

Or just pass a copy of the pointer to the thread?!