March 2011 - Boost-users - lists.preview.boost.org

issue with make_shared
by Sean Farrow 21 Mar '11

21 Mar '11

Hi: Ok, having got to grips with fusion, and thought it was working. I now have an issue whereby when using make_shared, it is working in one case, and not in the other. I've got the following definition:P typedef boost::fusion::vector<PmStream*, MIDIInputThread, boost::shared_ptr<boost::asio::io_service> , boost::shared_ptr<boost::thread> > InputType; and when I use: InputType NewInput =InputType(Port, cl, boost::make_shared<boost::asio::io_service> , boost::make_shared<boost::thread>(boost::bind(&boost::asio::io_service::run, io.get()))); Replacing the asio::io declaration with an actual variable of type boost::shared_ptr<boost::asio::io_service> seems to work fine. Is ther anything I'm doing wrong that's not allowing me to use boost::make_shared? Any help appreciated. Regards Sean.

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refering to objects when constructing a boost::fusion::vector
by Sean Farrow 21 Mar '11

21 Mar '11

Hi list: I'm in the process of using boost::fusion::vector, with the following definition: typedef boost::fusion::vector<PmStream*, MIDIInputThread, boost::shared_ptr<boost::asio::io_service>, boost::shared_ptr<boost::thread> > InputType; I'm then constructing this using the following code: PmStream* Port; MIDIInputThread cl; InputType NewInput =InputType(Port, cl, boost::make_shared<boost::asio::io_service>, boost::make_shared<boost::thread>(boost::bind(&boost::asio::io_service::run, io.get()))); What I'm wondering is is there a way to refer to a previously declared argument in this case, I'd like to refer to the shared pointer containing the boost::asio::io_service. Given that I've not actually named this argument, could I use anything from either boost.fusion or boost.mpl to do what I require. Any help appreciated. Regards Sean.

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storing a boost.thread in a boost shared ptr
by Sean Farrow 21 Mar '11

21 Mar '11

Hi: I'm trying to store a boost.thread in a boost::fusion::vector, and need to use a shared ptr, due to boost.thrad being non-copyable I'm using Microsoft visual c++ 2010. I get the following error: 1>d:\devexpress\mdrlite\mdrlite\mdrlite\midiwidget.cpp(21): error C2664: 'boost::shared_ptr<T>::shared_ptr(boost::shared_ptr<T> &&)' : cannot convert parameter 1 from 'boost::_bi::bind_t<R,F,L>' to 'boost::shared_ptr<T> &&' with [ T=boost::thread ] and [ R=size_t, F=boost::_mfi::mf0<size_t,boost::asio::io_service>, L=boost::_bi::list1<boost::_bi::value<boost::asio::io_service *>> ] and [ T=boost::thread ] Reason: cannot convert from 'boost::_bi::bind_t<R,F,L>' to 'boost::shared_ptr<T>' with [ R=size_t, F=boost::_mfi::mf0<size_t,boost::asio::io_service>, L=boost::_bi::list1<boost::_bi::value<boost::asio::io_service *>> ] and [ T=boost::thread ] No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called My boost thread is defined as: boost::thread t(boost::bind(&boost::asio::io_service::run, io.get())); and io is defined as: boost::shared_ptr<boost::asio::io_service> io; I'm obviously overlooking something, I just carn't work out what? Any help appreciated. Regards Sean.

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[context review] Review starts today, Mars 21st 2011
by Vicente BOTET 21 Mar '11

21 Mar '11

Hi all, The review of Oliver Kowalke Context library starts today Mars 21st 2011, and will end on Mars 30th. Boost.Context is a basic building block library that is used for more higher abstractions. It is used by Boost.Fiber, Boost.Tasklet and Boost.Task from the same author. I really hope to see your vote and your participation in the discussions on the Boost DEVELOPMENT mailing lists! WARNING !!!!!!!!!!!!! Only on the Boost DEVELOPMENT mailing lists Please use [context review] as prefix of your post to make easier the review follow up. You can download a frozen version for the review from the Vault, TinyURL: http://tinyurl.com/5r77rel or The documentation is available directly here: http://ok73.ok.funpic.de/boost/libs/context/doc/html/ --------------------------------------------------- About the library: Boost.Context provides a possibility to switch between different user-level context and is intended to be the basis for a higher abstraction like coroutine and fiber. A user-level context represents the current execution state, including all registers and CPU flags, the instruction pointer, the stack pointer. boost::context encapsulates such a user-level context and is able to store/restore its associated user-level context. This allows multiple execution paths running on a single thread using a sort of cooperative scheduling (in contrast a thread is preemptively scheduled) - the running boost::context decides explicitly when its yields to allow another boost::context to run (user-level context switching). A context can only run on a single thread at any point in time but may be migrated between thread. A context switch between threads costs usually thousands of CPU cycles on x86 compared to a user-level context switch with few hundreds of cycles. Boost.Context differes to setjmp()/longjmp() in the fact that the C99 standard does not require that longjmp() preserves the current stack frame, e. g. jumping into a function which was exited via a call to longjmp() is undefined. Boost.Context allows to select the mechanism provided by the operating system (ucontext on UNIX, Windows Fibers on Windows) or a faster implementation provided by this library (fcontext using assembler). --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Have a good review, Vicente Review Manager

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[Fusion] value_at_c and its relatives not applicable to Associative Sequence?
by TONGARI 21 Mar '11

21 Mar '11

Hi, the document says that 'value_at_c' accepts a Forward Sequence, and set/map, which is of Associative Sequence as well as Forward Sequence, why the following does not work? #include <boost/fusion/include/value_at.hpp> #include <boost/fusion/include/set.hpp> int main() { namespace fs = boost::fusion; typedef fs::result_of::value_at_c<fs::set<int>, 0> >::type type; return 0; }

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Re: [Boost-users] using boost.asio with wx widgets
by Marat Abrarov 21 Mar '11

21 Mar '11

Hi, Sean Farrow. I use Boost.Asio with Qt. I don't use the default MSVS C++ project structure with additional header, where MSVS adds some preprocessor directives by default. So I moved those directives (preprocessor defines) to project settings: WIN32 WIN32_LEAN_AND_MEAN WINVER=0x0500 _WIN32_WINNT=0x0500 _WIN32_WINDOWS=0x0410 _WIN32_IE=0x0600 May be would solve your problem? Regards, Marat Abrarov.

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Thread Interruption Best Practice
by Dom Driver 21 Mar '11

21 Mar '11

Hi List, I'm fairly new to boost, and have recently started to use the threading system from v1.46 in an app I'm writing targeting Linux. This was primarily to enable execution of threads to be blocked until a condition variable is set, at which point the thread is kicked awake and actions whatever is waiting to be done. All good, and all working as expected. However, I've got another thread which sits listening for data on a socket using a Linux select() call. This blocks until data is available for reading, at which point it is read from the socket as expected. This also works fine, except on termination of the application. Using native Linux implementations, a signal can be sent to the thread that is blocking on the select() call, at which point the call returns, and the EINTR error is set. I can therefore check for this condition and handle appropriately. Is there a way to send a Linux signal (or boost equivalent) to a specific boost thread to emulate this behaviour? Failing that, is there an alternative implementation of the classic Linux select()/read() functionality using boost classes? I had a look at the async I/O library and it seems a bit convoluted. TIA, Dom

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Re: [Boost-users] [boost::thread] interrupt a future get boost::unknown_exception
by 乔志强 21 Mar '11

21 Mar '11

It may be a bug of the thread or future. in boost_1_46_0/doc/html/thread/synchronization.html these Member functions: shared_future class template: Member function get() Member function wait() Member function timed_wait() and unique_future class template: Member function get() Member function wait() Member function timed_wait() Throws: ........ boost::thread_interrupted if the result associated with *this is not ready at the point of the call, and the [current] thread is interrupted. ............ the [current] thread is interrupted. Should be the [working] thread is interrupted ? > > [Windows XP, VC++ 10, boost 1.46] > > When interrupt a future, the future.get() throw boost::unknown_exception, > > Not boost::thread_interrupted. > > > > Class boost::thread_interrupted should have a base class for > > current_exception_impl() to catch it ? or use BOOST_THROW_EXCEPTION to throw ? ////////// namespace boost { class thread_interrupted {}; } These function use [ throw thread_interrupted(); ] : this_thread ::interruption_point() // pthread / win32 this_thread::interruptible_wait() // win32 interruption_checker:: check_for_interruption()// pthread ///////////// // [Windows XP, VC++ 10, boost 1.46] #include <boost/thread.hpp> #include <boost/date_time/posix_time/posix_time_types.hpp> #include <boost/thread/future.hpp> using namespace boost::posix_time; using namespace boost; int foo() { this_thread::sleep(seconds(1000)); return 0; } int main(int argc, char** argv) { boost::packaged_task<int> pt(&foo); boost::unique_future<int> fi = pt.get_future(); boost::thread task(std::move(pt)); // launch task on a thread task.interrupt(); try { int v = fi.get(); } catch (boost::exception& exc) { std::cerr << "ERROR: " << boost::diagnostic_information(exc) << std::endl; } } > > > > // unknown_exception////////////////// > > ERROR: Throw in function (unknown) > > Dynamic exception type: class boost::exception_detail::clone_impl<class > > boost::unknown_exception> > > std::exception::what: Unknown exception

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[function] Compiler error with Boost 1.46.1
by Boris Schaeling 20 Mar '11

20 Mar '11

The sample program at http://en.highscore.de/cpp/boost/src/3.4.3/main.cpp can't be compiled anymore with Boost 1.46.1 (using VC++ 2010). Is this a known problem? 1>------ Rebuild All started: Project: Test, Configuration: Debug Win32 ------ 1> main.cpp 1>c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(539): error C2668: 'boost::mem_fn' : ambiguous call to overloaded function 1> c:\boost\include\boost-1_46_1\boost\bind\mem_fn_cc.hpp(25): could be 'boost::_mfi::mf1<R,T,A1> boost::mem_fn<void,world,std::ostream&>(R (__thiscall world::* )(A1))' 1> with 1> [ 1> R=void, 1> T=world, 1> A1=std::ostream & 1> ] 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\xxmem_fn(32): or 'std::tr1::_Mem_fn2<_Rx,_Pmf,_Arg0,_Arg1> std::tr1::mem_fn<void,world,std::ostream&>(_Rx (__thiscall world::* )(_Arg1))' [found using argument-dependent lookup] 1> with 1> [ 1> _Rx=void, 1> _Pmf=void (__thiscall world::* )(std::ostream &), 1> _Arg0=world, 1> _Arg1=std::ostream & 1> ] 1> while trying to match the argument list '(void (__thiscall world::* )(std::ostream &))' 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(492) : see reference to function template instantiation 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to<F>(MemberPtr,boost::detail::function::function_buffer &,boost::detail::function::member_ptr_tag)' being compiled 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> &, 1> F=void (__thiscall world::* )(std::ostream &), 1> MemberPtr=void (__thiscall world::* )(std::ostream &) 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(915) : see reference to function template instantiation 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to<Functor>(F,boost::detail::function::function_buffer &)' being compiled 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> &, 1> Functor=void (__thiscall world::* )(std::ostream &), 1> F=void (__thiscall world::* )(std::ostream &) 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(722) : see reference to function template instantiation 'void boost::function2<R,T0,T1>::assign_to<Functor>(Functor)' being compiled 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> &, 1> Functor=void (__thiscall world::* )(std::ostream &) 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(1065) : see reference to function template instantiation 'boost::function2<R,T0,T1>::function2<void(__thiscall world::* )(std::ostream &)>(Functor,int)' being compiled 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> &, 1> Functor=void (__thiscall world::* )(std::ostream &) 1> ] 1> c:\users\boris\documents\visual studio 2010\projects\test\main.cpp(14) : see reference to function template instantiation 'boost::function<Signature>::function<void(__thiscall world::* )(std::ostream &)>(Functor,int)' being compiled 1> with 1> [ 1> Signature=void (world *,std::ostream &), 1> Functor=void (__thiscall world::* )(std::ostream &) 1> ] 1>c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(539): error C2780: 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to(const boost::reference_wrapper<FunctionObj> &,boost::detail::function::function_buffer &,boost::detail::function::function_obj_ref_tag)' : expects 3 arguments - 2 provided 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(625) : see declaration of 'boost::detail::function::basic_vtable2<R,T0,T1>::assign_to' 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1>c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(539): error C2780: 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to(FunctionObj,boost::detail::function::function_buffer &,boost::detail::function::function_obj_tag)' : expects 3 arguments - 2 provided 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(599) : see declaration of 'boost::detail::function::basic_vtable2<R,T0,T1>::assign_to' 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1>c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(539): error C2780: 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to(MemberPtr,boost::detail::function::function_buffer &,boost::detail::function::member_ptr_tag)' : expects 3 arguments - 2 provided 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(533) : see declaration of 'boost::detail::function::basic_vtable2<R,T0,T1>::assign_to' 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1>c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(539): error C2780: 'bool boost::detail::function::basic_vtable2<R,T0,T1>::assign_to(FunctionPtr,boost::detail::function::function_buffer &,boost::detail::function::function_ptr_tag)' : expects 3 arguments - 2 provided 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] 1> c:\boost\include\boost-1_46_1\boost\function\function_template.hpp(511) : see declaration of 'boost::detail::function::basic_vtable2<R,T0,T1>::assign_to' 1> with 1> [ 1> R=void, 1> T0=world *, 1> T1=std::basic_ostream<char,std::char_traits<char>> & 1> ] ========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ========== Boris

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plus<boost::gregorian::date> - how to?
by qplace 20 Mar '11

20 Mar '11

I need to be able to either add or substruct boost::gregorian::days from boost::gregorian::date. As far as I understand I have to define plus<boost::gregorian::date> and minius<boost::gregorian::date> and provide function operators for them. My question is: Function operator required in plus and minus template has a form of T operator()(const T& x, const T& y) , but I need to use not only gregorian::date, but gregorian::days as well. Any advise is greatly appreciated.

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