[zeromq-dev] Can zmq_pollitem_t contain an item with a NULL socket ?

[Laurent Alebarde]

IMHO, it is a bad design of zmq_pollitem_t. It should not have one 
attribute for socket and another one for file-descriptor with this 
unrobust behaviour to use the second one when the first one is NULL, but 
one for the type (socket or fd), and a union containing one or the other.

Implemented:
typedef struct
{
     void *socket;
#if defined _WIN32
     SOCKET fd;
#else
     int fd;
#endif
     short events;
     short revents;
} zmq_pollitem_t;

Should be:

typedef struct
{
     int type; // ZMQ_SOCKET | ZMQ_FD
     union {
         void *socket;
#if defined _WIN32
         SOCKET fd;
#else
         int fd;
#endif
     } dev;
     short events;
     short revents;
} zmq_pollitem_t;

But it would break the ABI to change it, isn't it ?


Le 30/01/2014 10:56, Laurent Alebarde a écrit :
> In fact, it is in src/zmq.cpp / "int zmq_poll (zmq_pollitem_t *items_, 
> int nitems_, long timeout_)"
>
> When the socket is NULL, zmq_poll takes the second attribute of the 
> zmq_pollitem_t structure which is a file descriptor. So, I cannot do 
> anything here, as "socket == NULL and fd == 0" is legitimate.
>
> Conclusion: I have to deal myself with the complexity of not having 
> NULL sockets in my zmq_pollitem_t array.
>
> Le 30/01/2014 09:23, Laurent Alebarde a écrit :
>> Thanks Pieter.
>>
>> Personnaly, I would prefer "ignore", in order to build zmq_pollitem_t 
>> arrays with more ease, when they are built by the application itself, 
>> and not hardwritten in the code.
>>
>> Any objection ?
>>
>> Le 29/01/2014 20:20, Pieter Hintjens a écrit :
>>> Undefined, by the man page. It should probably assert in such a case.
>>>
>>> On Wed, Jan 29, 2014 at 12:07 PM, Laurent Alebarde<l.alebarde at free.fr>  wrote:
>>>> Hi Devs,
>>>>
>>>> What is the zmq_poll behaviour when the zmq_pollitem_t array contains an
>>>> item with a NULL socket ? ignored, undefined, error ?
>>>>
>>>> If it is in src/poll.cpp / "void zmq::poll_t::loop ()" / "for
>>>> (pollset_t::size_type i = 0; i != pollset.size (); i++)", it seems there is
>>>> no NULL test with a continue.
>>>>
>>>> Cheers,
>>>>
>>>>
>>>> Laurent
>>>>
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