cppzmq docs for poll are wrong

[TobiSchluter]

The example does the following to initialize the poller:

    zmq::pollitem_t items [] = {
        { static_cast<void*>(receiver), 0, ZMQ_POLLIN, 0 },
        { static_cast<void*>(subscriber), 0, ZMQ_POLLIN, 0 }
    };

The correct way to do this is to use the implicit conversion of zmq::socket_t to void*, i.e.

    zmq::pollitem_t items [] = {
        { receiver, 0, ZMQ_POLLIN, 0 },
        { subscriber, 0, ZMQ_POLLIN, 0 }
    };

I needed StackOverflow to figure out this issue https://stackoverflow.com/questions/16429907/zmq-poll-not-working

To be frank, I don't really understand the failure mode (I'm using references ìn the place of receiver and subscriber, and I'm getting ERRNOSOCK when calling zmq_poll), but it's clear that the intent of zmq::socket_t is that it be used without the static_cast.

[sappo]

Hi @TobiSchluter, thanks for reporting the bug. It would be great if you could fix the example and send a PR :)

[TobiSchluter]

Well, I'm no longer sure what the intended way to do this is given this comment in zmq.hpp:

// note: non-const operator bool can be removed once
// operator void* is removed from socket_t
ZMQ_EXPLICIT operator bool() ZMQ_NOTHROW { return _handle != ZMQ_NULLPTR; }

It certainly seems to suggest that operator void * is not the proper interface to use.

But sure, PR coming. It's always easier for people "in the know" to step up when there's an actual change :)

[aviallon]

Shouldn't this be closed?