February 2015 - Boost-users - lists.preview.boost.org

[msm] multi thread access
by Sam Fisher 05 Feb '15

05 Feb '15

Hi Christophe, Did you consider adding build-in multi-thread support? (via policies maybe?) For example, I can guaranteed that all access to sub-fsm within its handlers (process_event()) will be synchronized. The problem is, sub-fsm "knows" about its parent and internally communicates with it (forwarding events etc). I can't control it from my side. typical scenario: an action from sub-fsm struct A_Init { template <typename Evt, typename FSM, typename SourceState, typename TargetState> void operator()(Evt&, FSM& fsm, SourceState&, TargetState&) const { std::thread([=]() mutable { std::lock_guard<std::mutex> l(access); fsm.process_event(some_event()); }).detach(); } }; locking proccess_event() in sub-fsm doesn't help if it alters the root.

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Using io_service for synchronous tcp accept + custom tasks
by Aaron Levy 04 Feb '15

04 Feb '15

I've written code of the form: Code: io_service svc; io_service::work work(svc); thread t1( [&svc]() { svc.run(); } ); thread t2( [&svc]() { svc.run(); } ); thread t3( [&svc]() { svc.run(); } ); endpoint ep(ip::tcp::v4(), port); acceptor acceptor(svc, ep); while (true) { shared_ptr<socket> sock(new socket(svc)); acceptor.accept(*sock); svc.post( [sock]() { /* do stuff on sock here */ }); } Is this way of using io_service for accepting tcp connections and also as a thread pool for serving connected clients valid or could I hit some undefined behavior. -- Aaron Levy aaron.levy(a)yandex.com

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joining boost ranges in loop
by Ernest Zaslavsky 04 Feb '15

04 Feb '15

Actually the question is how to achieve it? The use of boost::any_range is possible but undesirable (performance considerations) Sample code: typedef boost::multi_index_container< int, bmi::indexed_by<bmi::hashed_unique<bmi::tag<struct someTag>, bmi::identity<int>>>> Datum; class bar { public: auto foo() const; private: Datum m_someDataContainer; }; SomeType bar::foo() const { SomeType retVal; for (auto i = 0u; i < 10; ++i) { retVal = boost::range::join(retVal, m_someDataContainer.equal_range(i)); } return retVal; } Here we can observe several problems. The return type cannot be easily deduced. The join would create joined_range<joined_range<joined_range and so on of nested types. The above can be achieved by using any_range like typedef boost::any_range<int, boost::random_access_traversal_tag, int&, std::ptrdiff_t> VersionRange; but above will create nested joined_range of any_range which, when the number of iterations is big enough, has tremendous impact on performance. So, what can be done here?

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boost serialization + boost variant + boost blank
by Merrill Cornish 04 Feb '15

04 Feb '15

I'm running Boost 1.57.0 using serialization, variant, and boost::blank with that variant. I found that when compiled, serialization complains that blank does not contain a serialize method, which is true. I made a copy of blank.hpp, called it blank.h, and added template< class Archive > void serialize(Archive& ar, const unsigned int version) {} to the body of struct blank. That made the compiler happy, but is it a fix in general?

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[statechart] fifo_scheduler<>::operator() in state constructor
by Andrew C 04 Feb '15

04 Feb '15

Hi, is it allowed to call fifo_scheduler<>::operator() from state constructor? If yes, then let's assume "scheduler" and "processor" are objects of "fifo_scheduler<>" and "fifo_scheduler<>::processor_handle" types respectively in the some state constructor code below: State(my_context ctx): my_base(ctx) { boost::intrusive_ptr<Event> pEvent(new Event()); // If both lines [A] and [B] are uncommented // then "unconsumed_event" method is called twice. // If just line [A] is uncommented then "unconsumed_event" method is called. // If just line [B] is uncommented then certain "react" method is called. // scheduler.queue_event(processor, pEvent); // [A] // this->post_event(Event()); // [B] scheduler(); } Note constructor calls "scheduler()" at the end. Other questions: Is this code correct and runs expectedly as described in comments? Why "unconsumed_event" is called if use "queue_event" instead of "post_event"? Thanks, Andrew.

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Crashing Issue
by swati upadhyaya 03 Feb '15

03 Feb '15

In my code join() timed_joined() is crashing, I am using these API after interrupt(),Same piece of code is working for others but in my system its crashing, Is there some dependency problem I am using Boost version: 1.55.0 OS: Windows 8 IDE: Visual Studio 2010

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[Variant] Assertion fails at variant/detail/visitation_impl.hpp:207
by Attila Rajmund Nohl 02 Feb '15

02 Feb '15

Hello! I'm using boost-1.55 on Linux. When I run a specific testcase, I get an abort at line 207 in the visitation_impl.hpp file. The comment says that "should never be here at runtime". Unfortunately I don't really understand under what circumstances could runtime end up here - could someone explain how? The variant has a recursive element, i.e. looks something like this: struct Resp; struct SR { } struct AR { std::vector<Resp> resp; } typedef variant< SR, recursive_wrapper<AR> > RMType; struct Resp { RMType rm; }

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boost::ptr_container library question ?
by Danny K 02 Feb '15

02 Feb '15

The ptr_container supports an overload for std::auto_ptr<U>. I was curious if there was a way to add the same functionality for std::unique_ptr<U>. ie an overload that allows a std::unique_ptr to be added to a ptr_vector for example?

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