April 2017 - Boost-users - lists.preview.boost.org

What is the effective way to use boost::asio::deadline_timer for udp socket receive_from?
by jupiter 14 Apr '17

14 Apr '17

Hi, My program needs a sync udp socket send / receiver so I use the deadline_timer as timeout for udp socket receive_from on Debian Jessie: boost::asio::deadline_timer deadline(io_service, boost::posix_time::seconds(2)); In checkDeadline function, when the timer expires, it calls socket.cancel, otherwise calls the deadline.async_wait(checkDeadline); again. Apparently when the program runs to socket.receive_from(), it is blocked and the timer is never called because both socket.receive_from and the timer in the same thread. I've been thinking to run the timer in another thread, but I checked Internet, there are comments said deadline_timer is not thread safe, please correct me if I am wrong here. It will be a simple solution for me if I can run timer on another thread. Anyone has other ideas to run the timer effectively? Appreciate your comments. Thank you.

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Re: [Boost-users] udp::endpoint listen_endpoint invalid argument
by Bjorn Reese 12 Apr '17

12 Apr '17

On 04/11/2017 07:32 AM, jupiter via Boost-users wrote: > To simplify it, I changed to: > udp::endpoint listen_endpoint( > boost::asio::ip::address::from_string("localhost"), 15555); Quoting the documentation: "from_string Create an address from an IPv4 address string in dotted decimal form, or from an IPv6 address in hexadecimal notation." You need to resolve "localhost" first.

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udp::endpoint listen_endpoint invalid argument
by jupiter 11 Apr '17

11 Apr '17

Hi, I built doc/html/boost_asio/example/timeouts/blocking_udp_client.cpp on Debian Jessie, but when I run it, I got Invalid argument on the statement of udp::endpoint listen_endpoint( boost::asio::ip::address::from_string(argv[1]), std::atoi(argv[2])); To simplify it, I changed to: udp::endpoint listen_endpoint( boost::asio::ip::address::from_string("localhost"), 15555); Appreciate any clues what's wrong with that statement and why it caused invalid argument? Thank you.

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Thread Pool example
by Gonzalo Garramuño 10 Apr '17

10 Apr '17

Hi, I currently use boost (1.60) for my program and would like to have a part of it multithreaded (the creation of icons in a file requester). I would like to create those with a thread pool. I am currently using gcc 4.6.3, which is not yet c++11 compatible. I found no documentation on the usage of boost/thread/thread_pool.hpp so I turn to the list. Does anyone have an example of a thread pool with boost threads. Thanks in advance, -- Gonzalo Garramuño

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Boost.Pool: singleton_pool - thread safe for any kind of threads?
by Igor Yakushin 07 Apr '17

07 Apr '17

Hi All, singleton_pool documentation claims that it is thread safe. It is not clear too me if this is applied to all kinds of threads or only the ones from Boost library. For example, I am using OpenMP which is external to Boost. Would singleton_pool still be thread safe or do I need to redefine Mutex? What if I later decide to use some other kind of threads like Intel Cilk Plus or TBB? Thank you, Igor

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Boost Asio not built
by Balázs Bámer 07 Apr '17

07 Apr '17

Hi All, I have downloaded Boost 1.63 the second time. On my home computer, building it yielded all libraries. However, I do similar now at work, and it won't build Asio. First I do ./bootstrap.sh --with-libraries=all Then I build, but these are the results: balazs@bamer-debian:/opt/boost-1.63$ ls stage/lib/ |grep asio|wc 0 0 0 Although there are cpp files, that should be turned into a linbrary: balazs@bamer-debian:/opt/boost-1.63$ find |grep asio |grep cpp$|wc 214 214 9862 Asking bootstrap about what it would do shows it is not willing to build Asio: balazs@bamer-debian:/opt/boost-1.63$ ./b2 --show-libraries The following libraries require building: - atomic - chrono - container - context - coroutine - coroutine2 - date_time - exception - fiber - filesystem - graph - graph_parallel - iostreams - locale - log - math - metaparse - mpi - program_options - python - random - regex - serialization - signals - system - test - thread - timer - type_erasure - wave What should I do? Is there a dependency missing? Thank you in advance. Best regards: Balazs

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How to design proper release of a boost::asio socket or wrapper thereof
by Christopher Pisz 06 Apr '17

06 Apr '17

I am making a few attempts at making my own simple asynch TCP server using boost::asio after not having touched it for several years. The latest example listing I can find is: http://www.boost.org/doc/libs/1_54_0/doc/html/boost_asio/tutorial/tutdaytim… The problem I have with this example listing is that it cheats and it cheats big, by making the tcp_connection a shared_ptr, such that it doesn't worry about the lifetime management of each connection. I am worried about the lifetime management of each connection. I figure the natural thing to do would be to keep some collection of tcp_connection objects or pointers to them inside tcp_server. Adding to that collection from the OnConnect callback and removing from that collection OnDisconnect. Note that OnDisconnect would most likely be called from an actual Disconnect method, which in turn would be called from OnReceive callback or OnSend callback, in the case of an error. Well, therein lies the problem. Consider we'd have a callstack that looked something like this: tcp_connection::~tcp_connection tcp_server::OnDisconnect tcp_connection::OnDisconnect tcp_connection::Disconnect tcp_connection::OnReceive This would cause errors as the call stack unwinds and we are executing code in a object that has had its destructor called...I think, right? I then thought to myself, well I could flag the tcp_connection as disconnected when it disconnects and then on some timer on the tcp_server, go through its collection and start deleting disconnected tcp_connection objects, but then the timer could fire after the flag is set, but before it returns from a OnReceive where an error occurred and I Disconnected as a response. I imagine everyone doing server programming comes across this scenario in some fashion. What is a strategy for handling it? I hope the explanation is good enough to follow. If not let me know and I will create my own source listing, but it will be very large. -- View this message in context: http://boost.2283326.n4.nabble.com/How-to-design-proper-release-of-a-boost-… Sent from the Boost - Users mailing list archive at Nabble.com.

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Re: [Boost-users] How to design proper release of a boost::asio socket or wrapper thereof
by Bjorn Reese 06 Apr '17

06 Apr '17

On 04/05/2017 10:32 PM, Christopher Pisz via Boost-users wrote: > The problem I have with this example listing is that it cheats and it cheats > big, by making the tcp_connection a shared_ptr, such that it doesn't worry > about the lifetime management of each connection. That is not cheating. > Consider we'd have a callstack that looked something like this: > tcp_connection::~tcp_connection > tcp_server::OnDisconnect > tcp_connection::OnDisconnect > tcp_connection::Disconnect If Disconnect is an asynchronous operation, then it should not call OnDisconnect directly. You can post it on the io_service instead. > I imagine everyone doing server programming comes across this scenario in > some fashion. What is a strategy for handling it? Preferably shared_ptr, or io_service::post() if for some reason you cannot use shared_ptr, e.g. if the object has to be destroyed by a a specific thread.

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[gsoc17] Help review Google Summer of Code proposals
by Niall Douglas 05 Apr '17

05 Apr '17

Dear Boost, Student proposals for Google Summer of Code are submitted, please help us decide which have the most merit. I have reduced the fifty something proposals submitted down to twenty seven which have some chance. To be able to view and rank the student proposals, please do the following: 1. Send to gsoc-admin(a)boost.org your Google login. We will invite you to view the student proposals on the Boost Google Drive. Until you receive the invitation email, you won't be able to view the proposals. 2. Go to https://goo.gl/forms/EVppdHsHMnjkcUoD3 which is a Google form where you can score the proposals. We have linked each proposal there to the Google Drive item and there you can rank a proposal between 1 and 5. Make sure you use the same email as your Google login in the form, otherwise we will ignore any forms submitted to prevent gaming the results. 3. Even if you can't rank all twenty seven proposals, try to do as many as you can and then PRESS SUBMIT at the end of the form (forgetting to press SUBMIT means we never get your rankings). The proposals are presented in random order per person so any work you do will be useful. 4. Please try to have your rankings done by Monday 10th. You may find reviewing the page at https://svn.boost.org/trac/boost/wiki/SoC2017 useful. 5. Finally, if you'd like to mentor any of the proposals, send to gsoc-admin(a)boost.org your Google login so we may invite you onto the Google website as a mentor. Many thanks in advance. Niall & Bryce

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[Fusion] wide-char output
by Leo Cacciari 05 Apr '17

05 Apr '17

Hi, the documentation of the Boost.Fusion library (1.63.0) at http://www.boost.org/doc/libs/1_63_0/libs/fusion/doc/html/fusion/sequence/o… affirms that operator<< is defined in the boost::fusion namespace with the following synopsis: template <typename OStream, typename Sequence> OStream& operator<<(OStream& os, Sequence& seq); where the template parameter OStream is defined as "An output stream". Accordingly, I thought that the following would work: using boost::fusion::operator<<; fusion::vector<int, double, const char *> v = fusion::make_vector(42, 3.1415, "foobar"); std::wcout << "v = " << v << std::endl; However, the compiler (MSVC 9) complains that it has: "found no defined operator << taking a right-hand argument of type boost::fusion::vector<T0,T1,T2> with T0 = int, T1 = double, T2 = char *" If I replace std::wcout with its narrow-char sibling std::cout, everything works as expected; i.e. the code compiles and when run prints (42,3.1415, foobar). Looking into the source (file boost/fusion/sequence/io/out.hpp) it seems that the operator<< is only defined for left-hand argument of type std::ostream. Thus the questions: 1. Is this a bug and should I post a ticket about it? (I looked in the bugs database but I couldn't find it) 2. If it's a bug, are there any plan to patch it soon? 3. If not, does exist any reason why it shouldn't be patched nevertheless? If needed, I could volunteer for writing a patch. Thank for your attention -- Leo Cacciari Aliae nationes servitutem pati possunt. Populi Romani est propria libertas.

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