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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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const char* in shared memory object
by Sabine B 13 Jan '12

13 Jan '12

Hi all! I'm a newbie with boost and I'm struggling with objects in shared memory. The following struct is given: struct MyType{ int id; const char* name; const char* rep; MyType(){}; MyType(MyType* const& type){ id = type->id; name = type->name; rep = type->rep; }; Objects of MyType should be shared between processes in shared memory. I have no problem to put and extract the objects from shared space. But I'm struggling with the const char* pointers. I know that pointers are not allowed in shared memory, thats why I tried to realize with boost string by doing the following: typedef boost::interprocess::allocator<char,boost::interprocess::managed_shared_memory::segment_manager> CharAllocator; typedef boost::interprocess::basic_string<char, std::char_traits<char>, CharAllocator> MyString; boost::interprocess::managed_shared_memory segment(boost::interprocess::open_only, "MySharedMemory"); CharAllocator charallocator(segment.get_segment_manager()); struct MyType{ int id; MyString name; MyString rep; MyType(){}; MyType(MyType* const& type){ id = type->id; name = type->name; rep = type->rep; }; But this is not working because the segment and charallocator are not recognized in the struct and if I put boost::interprocess::managed_shared_memory segment(boost::interprocess::open_only, "MySharedMemory"); CharAllocator charallocator(segment.get_segment_manager()); In the struct I get compiler errors. Could anybody help me how I can realize const char* in an object that should be shared? Please help me! Thank you very much! Best regards, Sabine

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Boost.Move template-function parameter
by Luke J. West 12 Jan '12

12 Jan '12

Hi. I'm trying to implement a template function that 'moves' it's parameter. Here's a simple moveable class... struct my_class { my_class() {} my_class(BOOST_RV_REF(my_class)) {} my_class& operator=(BOOST_COPY_ASSIGN_REF(my_class) c) {return *this;} BOOST_COPYABLE_AND_MOVABLE(my_class); }; And here is the function... template<typename T > void steal(BOOST_COPY_ASSIGN_REF(T) c) {} so it works fine when I do this... int main() { my_class c; steal<my_class >(c); } but not when I do this... int main() { int c; steal<int >(c); } It's as if 'int' is not a movable type which of course it trivially is. I read that Boost.Container classes are 'move aware' and I assume boost::vector<int > works, so what am I doing wrong - how to write my 'steal' function capable of moving it's argument when it's moveable class, but not breaking for primitives? Thanks, Luke (hopeful newbie!)

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Question regarding boost::program_options
by Ankur Sinha 12 Jan '12

12 Jan '12

Hello, I've just started using boost. I'm making use of the program_options to take arguments for my tool. I've written the following: > mDesc.add_options() > ("help,h", "Print this usage message.") > ... > .... > .. > ("v-level,v",boost::program_options::value<int>(&mVerboseLevel),"Debug level: 1,2,3\n(default: 0)") > ("version",boost::program_options::value<std::string>()->zero_tokens(),"Package information: version etc.") > and then, I have a method, which I call in main(int argc, char **argv): > /* > *-------------------------------------------------------------------------------------- > * Class: Session > * Method: Session :: ParseCommandLine > * Description: Parse the command line > *-------------------------------------------------------------------------------------- > */ > int > Session::ParseCommandLine (int argc, char **argv) > { > boost::program_options::store(boost::program_options::parse_command_line(argc, argv, mDesc), mVariableMap); > /* notify required to save the values into my variables. */ > /* TODO: confirm this behaviour */ > boost::program_options::notify(mVariableMap); > > if (mVariableMap.count("help")) > { > std::cout << mDesc << std::endl; > return -1; > } > return 0; > } /* ----- end of method Session::ParseCommandLine ----- */ > However, when I invoke my tool, I get an exception (which I admit I haven't handled yet): > [ankur@ankur dump]$ ./src/test --version > terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::program_options::validation_error> >' > what(): in option 'version': at least one value required > Aborted (core dumped) > [ankur@ankur dump]$ > I'm referring this document[1] which says that zero_tokens() implies an argument may or may not be provided. Why is the exception coming up saying I need "at least one value"? What am I missing? Another query: is notify() necessary to save the values provided on the command line to the variables I pass in the add_options() from the variable map (to mVerboseLevel for instance)? [1] http://www.boost.org/doc/libs/1_42_0/doc/html/program_options/overview.html -- Thanks, Regards, Ankur: "FranciscoD" http://fedoraproject.org/wiki/User:Ankursinha http://dodoincfedora.wordpress.com/

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[BGL] creating a single vertex for the loop in a graph
by srinivas boppu 12 Jan '12

12 Jan '12

Hello All, I am looking for the following in boost graph. I have a graph in which I am able to find out the loops. Now, I wanted to replace the whole loop with a single vertex in the same Graph. Is that possible ? if it is, can you suggest me how do it. Alternate way could be, I copy the loop and make another graph and add this whole graph as a "vertex" in initial graph. Can I add a "graph" as a vertex to existing graph? Thanks and regards, Srinivas Boppu

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Boost, git or svn?
by Robert Jones 12 Jan '12

12 Jan '12

I'm confused about the current status of the svn -> git transition,if indeed any such transition is occuring. Boost main page still seems refer to the old SVN repository, but vault references are to a git-hub server. Can someone supply a few sentences of explanation. Thx. - Rob.

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