January 2012 - Boost-users - lists.preview.boost.org

[BGL] Serialize boost::labeled_graph
by Alper Aydemir 15 Jan '12

15 Jan '12

Hi, Is there anyway to easily serialize labeled_graphs ? I can see that <boost/graph/adj_list_serialize.hpp> does it for adjacency lists, however no such header seem to exist for labeled graph type. -- Alper Aydemir

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Multi Threaded Server with boost asio
by mark pashley 15 Jan '12

15 Jan '12

I am looking at writing a multithreaded tcp server using boost ASIO. I have read through the tutorials and had a look at some of the examples and just want to check that my understanding is correct. The server will accept connections then service requests from multiple clients. My understanding is as follows: 1 The server uses "a single io_service and a thread pool calling io_service::run()" 2 All threads call io_service::run(). 3 The calls to io_service::run() are not within a strand, ergo completion handlers can run simultaneously. 4 When a request arrives one of the threads is chosen, it's read handler will be called 5 Another request may arrive,starting the read handler on a second thread 6 When one of the threads has finished handling the request it calls async_write, from within a strand 7 Another thread also finishes processing its request, it also calls async_write, from within a strand 8 The writes to the io_service are serialised via the strand, ergo they are thread safe. 9 When the write operation completes the thread calls async_read() 10 This call is not protected by a strand and the thread will be used for handling requests Is my understanding correct? -- View this message in context: http://boost.2283326.n4.nabble.com/Multi-Threaded-Server-with-boost-asio-tp… Sent from the Boost - Users mailing list archive at Nabble.com.

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What's the execution sequence of phoenix::lambda function?
by 饭桶 15 Jan '12

15 Jan '12

I'm a newbie for boost phoenix, I wrote a small piece of code but it totally confuses me about the execution sequence, you can check the code ------------------clip----------------- std::vector<int> v; v.push_back(1); ph::for_each(v, ph::lambda[ph::ref(cout)<<"a", ph::ref(cout)<<"b" ])(v); ph::for_each(arg1, ph::lambda[ph::ref(cout)<<"a", ph::for_each(v, ph::lambda[ph::ref(cout)<<"b", ph::ref(cout)<<"c" ]), ph::ref(cout)<<"d" ])(v); ------------------------clap-------------------------- The first output is "ab" but the second output is "dbca". It seams ph::for_each is lazy evaluate , but what is the correct one to make it execute from left to right? thanks -- 半亩薄田一头牛老婆孩子热炕头

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[asio] usb howto
by László Veréb 15 Jan '12

15 Jan '12

Hi All! I would like to use the asio library to communicate through usb with some devices. I looked the documentation, and searched the internet. It was said that it can be done, but I could not find any specific information. I found a code for (old) serial ports, it mentioned the usb, but nothing more. I think the important parts were: boost::asio::serial_port port; port.open(devname); port.set_option(***); where one can set these options boost::asio::serial_port_base::baud_rate, parity, character_size, flow_control, stop_bits Are these option also available for usb ports? For example the data flows (found by be) are not the same. Thanks beforehand for your reply and help. Laci

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Boost interprocess vector, creating multiple vector pointers
by Prasanth Madhavan 15 Jan '12

15 Jan '12

I want to insert a shared vector into a shared map using the following code: managed_shared_memory segment(create_only ,"MySharedMemory" ,65536); typedef allocator<int, managed_shared_memory::segment_manager> vecAllocator;typedef vector<int, vecAllocator> vec;typedef std::pair<int, vec* > ValueType;typedef allocator<ValueType, managed_shared_memory::segment_manager> ShmemAllocator;typedef multimap<int, vec*, std::less<int>, ShmemAllocator> MyMap; ShmemAllocator alloc_inst (segment.get_segment_manager());vecAllocator vectorallocator (segment.get_segment_manager()); MyMap *mymap = segment.construct<MyMap>("MyMap")(std::less<int>(),alloc_inst);vec *myvec = segment.construct<vec>("myvec")(vectorallocator);vec *myvec1 = segment.construct<vec>("myvec1")(vectorallocator); myvec->push_back(10);myvec->push_back(9);myvec->push_back(8);myvec1->push_back(987);myvec1->push_back(123);myvec1->push_back(456); for(int i = 0; i < 6; ++i){ for(int j = 0; j<6; j++) mymap->insert(std::pair<int, vec*>(i, myvec));}for(int i = 0; i < 6; ++i){ for(int j = 0; j<6; j++) mymap->insert(std::pair<int, vec*>(i, myvec1));}the code works.. but what i want to do is construct a vector without a name. that is do something like this vec *myvec = segment.construct<vec>(vectorallocator);vec *myvec1 = segment.construct<vec>(vectorallocator);so that if i put it inside a loop and there is no problem with naming them differently every loop. Is there a way to do so? Or atleast is there an automatic way to name them differently every loop? -- Prasanth Madhavan

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[xpressive] sporadic crashes in multi-threaded code
by Ovanes Markarian 14 Jan '12

14 Jan '12

Hello *, I face some issue with sporadic crashes in xpressive which I think a result of a race condition. The use case is: a function which needs to parse smth create local regex objects: const sregex any_char = _; sregex const& rdelim = parser_->delimiter(); //some dynamic delimiter token const sregex re_prefix = bos >> (s1=-*by_ref(any_char)) >> *(s2=by_ref(rdelim)) >> eos ; calling this function from multiple threads results in a crash with (boost 1.42, gcc 4.3.5 on debian linux). I previously had more crashes, but moved all regex objects to global space as const objects and they seem to be fine now. This is the only place I left with a local regex. In the stack trace it seems like internals of the local object regex are freed via boost weak_ptr with possible double delete attempt. The stack-trace of the created core-dump during the crash can be accessed via: https://docs.google.com/open?id=0BzJl1eEH-CCGODU5N2JhOTAtNWMxMy00OGNhLThhNz… (Did not want to send addional 200k to the mailing list.) Many thanks for help, Ovanes

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boost::interprocess and synchronization
by Juan Ramírez 13 Jan '12

13 Jan '12

Hi, I've been working a lot with interprocess communication, but using plain windows API. Now I'm thinking about changing the implementation to boost::interprocess, but a simple question arises: Does boost::interprocess provide any kind of synchronization? On past projects I used to create a global mutex and an avent (or semaphore) object, the global mutex makes sure that only one process is writing at the same time, and the event indicates that there is new data to read.. Does boost:.interprocess provide those objects under the hood or I have to use my own named mutex and conditions? Thanks a lot :) Saludos! Juan

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Problems using boost::mpl::for_each
by Allan Nielsen 13 Jan '12

13 Jan '12

Hi, I have a function where I think mpl::for_each might be use full, but I can not get it to work: template<typename SYM> BaseGamePlateHash holdClear(const BaseGamePlateHash& h) { struct ClearSymbol { ClearSymbol(BaseGamePlateHash& h) : hash(h) { } template <typename _SYM> void operator()(_SYM) { hash.clear<_SYM>(); } BaseGamePlateHash& hash; }; BaseGamePlateHash new_hash = h; typedef typename boost::mpl::remove< SymbolCounts, SYM>::type ClearSymbols; ClearSymbol clearsymbol(new_hash); clearsymbol(SYM()); // this is working //boost::mpl::for_each< boost::mpl::vector<SYM> >( clearsymbol ); // not compiling, this is just a simple test //boost::mpl::for_each< ClearSymbols >( clearsymbol ); // not compiling, this is what I want to do... return new_hash; } I had the impression that the following two statements would do the same: clearsymbol(SYM()); // this is working should be equal to: boost::mpl::for_each< boost::mpl::vector<SYM> >( clearsymbol ); // not compiling But this does not seems to be the case... This is the compile error I get when enabling: boost::mpl::for_each< boost::mpl::vector<SYM> >( clearsymbol ); test7.cxx:303:13: error: 'holdClear(const BaseGamePlateHash &)::ClearSymbol::operator()(SymbolCntDice)::ClearSymbol::hash' is not a member of class 'ClearSymbol' hash.clear<_SYM>(); ^ /usr/local/include/boost/mpl/for_each.hpp:75:9: note: in instantiation of function template specialization 'holdClear(const BaseGamePlateHash &)::ClearSymbol::operator()<SymbolCntDice>' requested here aux::unwrap(f, 0)(boost::get(x)); ^ /usr/local/include/boost/mpl/for_each.hpp:100:5: note: in instantiation of function template specialization 'boost::mpl::aux::for_each_impl<false>::execute<boost::mpl::v_iter<boost::mpl::vector<SymbolCntDice, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, 0>, boost::mpl::v_iter<boost::mpl::vector<SymbolCntDice, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, 1>, boost::mpl::identity<mpl_::na>, ClearSymbol>' requested here aux::for_each_impl< boost::is_same<first,last>::value > ^ /usr/local/include/boost/mpl/for_each.hpp:111:5: note: in instantiation of function template specialization 'boost::mpl::for_each<boost::mpl::vector<SymbolCntDice, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, boost::mpl::identity<mpl_::na>, ClearSymbol>' requested here for_each<Sequence, identity<> >(f); ^ test7.cxx:313:5: note: in instantiation of function template specialization 'boost::mpl::for_each<boost::mpl::vector<SymbolCntDice, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, ClearSymbol>' requested here boost::mpl::for_each< boost::mpl::vector<SYM> >( clearsymbol ); ^ test7.cxx:437:36: note: in instantiation of function template specialization 'holdClear<SymbolCntDice>' requested here BaseGamePlateHash hh = holdClear<SYM>( h ); ^ test7.cxx:386:13: note: in instantiation of function template specialization 'BaseGamePreCalc::create_hold_actions<SymbolCntDice>' requested here create_hold_actions<SymbolCntDice>(hash_enum.first); ^ 1 error generated. So, what have I done wrong? Best regards Allan W. Nielsen

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Get fields from struct
by Matthijs Möhlmann 13 Jan '12

13 Jan '12

Hello all, I'm currently busy to get things like this working: struct person { std::string name; int age; }; int main(int argc, char **argv) { person p; p.name = "Matthijs" p.age = 1234; std::string key = "name"; // Now try to fetch the value based on the key string. std::cout << p.{key} << std::endl; // does not compile return 0; } Of course above doesn't work for obvious reasons. The closest I get is: struct person { std::string name; int age; }; namespace keys { struct name; struct age; } BOOST_FUSION_ADAPT_ASSOC_STRUCT( person, (std::string, name, keys::name) (int, age, keys::age) ); int main(int argc, char **argv) { person x; x.name = "Matthijs"; x.age = 1234; std::cout << "Name: " << boost::fusion::at_key<keys::name>(x) << std::endl; std::cout << "Age: " << boost::fusion::at_key<keys::age>(x) << std::endl; return 0; } Now my question, is there maybe another way to achieve this? Regards, Matthijs Möhlmann Cacholong

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boost::date_time with BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG on MinGW: segfault on multithreading
by Yana A Kireyonok (aka Iron Bug) 13 Jan '12

13 Jan '12

Hello, everybody. Looks like I found a bug in date_time library when building with MinGW. I've built static boost 1.48.0 libraries under windows (Win7 64) with MinGW 3.20 (32 bit, GCC 4.6.1) with BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG option and threading=multi link=static runtime-link=static address-model=32 In this case, when using threads (-mthreads) simple operations with timings fail. I simply created a thread that slept for some milliseconds ten times next and it fails. I traced a little, it fails inside date_time functions, called from this_thread::sleep() with SIGSEGV, segmentation fault. That happens in ctor of structure simple_time_rep, out of reasons, at first glance. Looks like this structure or maybe standard time functions of MinGW are not reentrant (this is my guess, I did not dig too deep in the causes of segfault). Without flag BOOST_DATE_TIME_POSIX_TIME_STD_CONFIG it's going all right with timings and threads. But when using precise timings and threading it fails. I also tried flags BOOST_HAS_WINTHREADS and _REENTRANT - that does not affect the case. BOOST_THREAD_USE_LIB was defined (to let it work with static libs). Is this a bug or problem of MinGW of certain version? I haven't found anything similar in bugtracker. Sincerely, Yana A. Kireyonok

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