Re: [Boost-bugs] [Boost C++ Libraries] #2832: Asio sync IO functions need timeout parameters

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #2832: Asio sync IO functions need timeout parameters
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-01-13 08:54:01

#2832: Asio sync IO functions need timeout parameters
-----------------------------------------------------+----------------------
  Reporter:  Stephan Menzel <stephan.menzel@…>       |       Owner:  chris_kohlhoff
      Type:  Bugs                                    |      Status:  reopened      
 Milestone:  Boost 1.39.0                            |   Component:  asio          
   Version:  Boost 1.38.0                            |    Severity:  Problem       
Resolution:                                          |    Keywords:                
-----------------------------------------------------+----------------------
Changes (by stephan.menzel@…):

  * status:  closed => reopened
  * resolution:  wontfix =>

Comment:

 Hi Chris,

 I guess I have to work through this disappointment then.... And yet, if
 there are no use cases and the situation is good as it is, how come the
 topic pops up in both asio and boost mailing list with such a regularity?

 My code has now several unportable spots in one lib caused entirely by
 this. Whenever things have to go synchronous, I have to workaround that
 way:

 Example snippet UDP request/answer:

    asio::ip::udp::endpoint sender_endpoint;

    asio::ip::udp::socket socket(m_iosrv, asio::ip::udp::v4());
    socket.send_to(asio::buffer(requeststring), m_pwh_master_ep);

    asio::ip::udp::socket::native_type native_sock = socket.native();
    fd_set rfds;
    FD_ZERO(&rfds);
    FD_SET(native_sock, &rfds);

    struct timeval tv;
    tv.tv_sec = 42;
    tv.tv_usec = 0;
    if (!select(native_sock + 1, &rfds, NULL, NULL, &tv)) {
        THROW(net_error, "timeout reading from socket");
    }

    size_t reply_length =
         socket.receive_from(asio::buffer(reply, udp_max_length),
 sender_endpoint);

 ...and so forth and suchlike.
 Is that really what you want asio code to look like?

 Realizing this with a timer would be OK for me and I tried but this
 doesn't work because the timers cannot cancel syncronous operations.
 Behold your very own docs:
 http://www.boost.org/doc/libs/1_41_0/doc/html/boost_asio/reference/basic_datagram_socket/cancel.html


 It clearly says "cancel all asynchronous operations" so I can't timeout a
 sync_read with it.

 Once I go in these synchronous functions asio appears not to offer any
 kind of defined way out of it. Please correct me if I'm wrong but all the
 answers to all the questions on the lists always boiled down to this.

 If the given solutions are not viable, well that's alright with me. Just
 tried to help. But in any case the topic needs to be addressed.

 By the way, If you say "They're in POSIX this way so they're staying in
 asio this way.", can you clearify that? In my example I have to go down to
 select, which has a timeout and solves the problem. Besides, I doubt very
 much this is a valid point. The whole boost is about offering stuff that
 should be cross platform standard but is not yet. Does POSIX offer
 regexes, time localisation, string formatting or parsing? Boost offers
 lots of such things and if plain POSIX is enough and everything on top of
 it is unnecessary, what's the point of having asio or indeed boost anyway?

 Sorry for being so stubborn and verbose but I urge you to reconsider this.
 I'm sure there must be a way.

 Cheers,
 Stephan

 BTW:
 Milestone 1.39, so take your time, no rush ;-)

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/2832#comment:3>
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