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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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Query regarding Boost.Log
by Leo Carreon 02 Apr '17

02 Apr '17

Hi, Does Boost.Log require synchronization when multiple processes log to the same log file? Kind regards, Leo

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[Stacktrace] Review 2 Manager report
by Niall Douglas 31 Mar '17

31 Mar '17

Many thanks to all those who participated in the second review of proposed Boost.Stacktrace. I received the following formal reviews: 1. Peter Dimov (ACCEPT) 2. Vladimir Batov (ACCEPT) 3. Artyom Bellis (CONDITIONAL ACCEPT) 4. Bjorn Reese (ACCEPT) 5. Edward Diener (ACCEPT) Extensive comments without a formal recommendation were also made by: 1. Mark Bartosik 2. Florian Weimer Some of the more important conditions for acceptance as judged by the review manager are: * Problems on FreeBSD (and by inference OS X?). * Per frame execution of addr2line rather than calling it once. * Throw-with-trace was asked for by a lot of people. * One reviewer suggested that the addr2line backend was async signal unsafe. My reading of the code is that it is async signal unsafe to parse a stacktrace (and unavoidably so on any platform), but the capture of backtraces is now fully async signal safe. * Some disliked the bringing in of windows.h and the COM headers on Windows. For a header only library I consider this acceptable, Stacktrace when configured in non-header only mode does not inject windows.h into everything including stacktrace. Congratulations to Antony on getting yet another library of his into Boost! Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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Problem statically linking Boost 1.63
by Balázs Bámer 31 Mar '17

31 Mar '17

Hi All, I have asked it on Stackoverflow, but know one seems to know the answer who saw it. I post it here, too, because 1.55 (which works for me) is quite old and has problems in logging: writing logfiles stops whithin a day every time. So 1.63 would be important for me to try. Link to the Stackoverflow post: http://stackoverflow.com/questions/42978843/boost-inner-function-argument-m… Thank you in advance. Best regards: Balazs PS: I copy the post here, but its formatting will break in plain text. I have a strange problem during linking Boost 1.63.0. I use the following cmake lines to configure Boost: add_compile_options(-std=c++14 -DBOOST_LOG_DYN_LINK)set(BOOST_ROOT "/usr/local/alk/boost_1_63_0/") SET(Boost_USE_STATIC_LIBS OFF) find_package(Boost 1.63 REQUIRED COMPONENTS log_setup log regex thread date_time filesystem system) Then the sources compile, and the linker tells me similar messages: CMakeFiles/dsmip.dir/main.cpp.o: In function `boost::log::v2_mt_posix::sources::aux::logger_singleton<dataLogger>::init_instance()': /home/balazs/munka/neovoltaic/aufgaben/dsmip/main.cpp:(.text._ZN5boost3log11v2_mt_posix7sources3aux16logger_singletonI10dataLoggerE13init_instanceEv[_ZN5boost3log11v2_mt_posix7sources3aux16logger_singletonI10dataLoggerE13init_instanceEv]+0x2d): undefined reference to `boost::log::v2_mt_posix::sources::aux::global_storage::get_or_init(std::type_info const&, boost::shared_ptr<boost::log::v2_mt_posix::sources::aux::logger_holder_base> (*)())' Here the following function is missing: *boost::log::v2_mt_posix::sources::aux::global_storage::get_or_init(std::type_info const&, boost::shared_ptr (*)())* Going into the freshly compiled Boost stage directory: balazs@balazs:/usr/local/alk/boost_1_63_0/stage/lib$ grep get_or_init *Binary file libboost_log.so matchesBinary file libboost_log.so.1.63.0 matches balazs@balazs:/usr/local/alk/boost_1_63_0/stage/lib$ strings libboost_log.so |grep get_or_init _ZN5boost3log11v2_mt_posix7sources3aux14global_storage11get_or_initENS_9typeindex14stl_type_indexEPFNS_10shared_ptrINS3_18logger_holder_baseEEEvE Demangling it yields: *boost::log::v2_mt_posix::sources::aux::global_storage::get_or_init(boost::typeindex::stl_type_index, boost::shared_ptr (*)())* which are not identical, the first function argument type differs. I used these commands to compile Boost: ./bootstrap.sh --with-toolset=clang./b2 --build-type=minimal --layout=system toolset=clang variant=release link=shared threading=multi runtime-link=shared stage How can this happen? Actually, this dynamically linked Boost is my second experiment. Originally I wanted to link it statically. Thank you in advance. Best regards: Balázs Bámer EDIT Now I have tried the Boost libraries I get with apt-get, and the situation is the same. However, I have found my old settings. They do work: add_compile_options(-std=c++14) SET(Boost_USE_STATIC_LIBS ON) find_package(Boost 1.55 REQUIRED COMPONENTS log_setup log thread date_time filesystem system) find_package(Threads REQUIRED)

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