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Re: [Boost-users] [bind] Dereferencing placeholder argument
by Ivan Le Lann 09 Sep '11

09 Sep '11

----- "Szymon Gatner" <szymon.gatner(a)gmail.com> a écrit : > Hi, > > Is there a way of automatic placeholder argument dereferencing when > using bind()? I mean: > > struct SomePredicate > { > bool operator()(int num, const Foo& foo) const > { > return SomeTestOnFoo(num, foo); > } > } > > std::vector<Foo*> foos; > > // line below gives compilation error because second argument passed > // to functor is Foo* and not Foo. > > std::for_each(foos.begin(), foos.end(), bind(SomePredicate(), 123, > _1); >From http://www.boost.org/doc/libs/1_47_0/doc/html/lambda/le_in_details.html#id2… (section "Sizeof and typeid") for_each(a.begin(), a.end(), cout << bind(&type_info::name, ll_typeid(*_1))); Have you tried *_1 ? Regards, Ivan

3 2

memory lost using cyclic pointers (shared_ptr)
by Peng Yu 09 Sep '11

09 Sep '11

Hi, I think that it is expected that shared_ptr cannot handle points that have cyclic references. In the following example, "a" points to "b" and "b" points to "a". There is a memory leak. I then modified it to remove the dependence using bare pointers, then the leak is resolved. But this is not a very satisfactory solution, as the programmer has to know whether to use bare point or shared_ptr. For very complexity program, it may not be possible to figure out it correctly. Does anybody know what is the best strategy for handing cyclic pointers? ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ cat main.cpp #include <tr1/memory> #include <iostream> struct B; struct A { std::tr1::shared_ptr<B> p; void print() { std::cout << "A" << std::endl; } }; struct B { std::tr1::shared_ptr<A> p; void print() { std::cout << "B" << std::endl; } }; int main () { std::tr1::shared_ptr<A> a(new A); std::tr1::shared_ptr<B> b(new B); a->p=b; b->p=a; a->p->print(); b->p->print(); } ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ valgrind ./main.exe ==75090== Memcheck, a memory error detector ==75090== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al. ==75090== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info ==75090== Command: ./main.exe ==75090== --75090-- ./main.exe: --75090-- dSYM directory is missing; consider using --dsymutil=yes B A ==75090== ==75090== HEAP SUMMARY: ==75090== in use at exit: 4,280 bytes in 6 blocks ==75090== total heap usage: 6 allocs, 0 frees, 4,280 bytes allocated ==75090== ==75090== LEAK SUMMARY: ==75090== definitely lost: 16 bytes in 1 blocks ==75090== indirectly lost: 80 bytes in 3 blocks ==75090== possibly lost: 0 bytes in 0 blocks ==75090== still reachable: 4,184 bytes in 2 blocks ==75090== suppressed: 0 bytes in 0 blocks ==75090== Rerun with --leak-check=full to see details of leaked memory ==75090== ==75090== For counts of detected and suppressed errors, rerun with: -v ==75090== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) #removing cyclic reference by using bare pointer. ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ cat main.cpp #include <tr1/memory> #include <iostream> struct B; struct A { std::tr1::shared_ptr<B> p; void print() { std::cout << "A" << std::endl; } }; struct B { std::tr1::shared_ptr<A> p; void print() { std::cout << "B" << std::endl; } }; int main () { std::tr1::shared_ptr<A> a(new A); std::tr1::shared_ptr<B> b(new B); a->p=b; b->p=a; a->p->print(); b->p->print(); } ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ vim main.cpp ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ make g++ -o main.exe main.cpp ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ valgrind main.exe valgrind: main.exe: command not found ~/linux/test/cpp/library/std/tr1/shared_ptr/loop$ valgrind ./main.exe ==75167== Memcheck, a memory error detector ==75167== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al. ==75167== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info ==75167== Command: ./main.exe ==75167== --75167-- ./main.exe: --75167-- dSYM directory is missing; consider using --dsymutil=yes B A ==75167== ==75167== HEAP SUMMARY: ==75167== in use at exit: 4,184 bytes in 2 blocks ==75167== total heap usage: 6 allocs, 4 frees, 4,272 bytes allocated ==75167== ==75167== LEAK SUMMARY: ==75167== definitely lost: 0 bytes in 0 blocks ==75167== indirectly lost: 0 bytes in 0 blocks ==75167== possibly lost: 0 bytes in 0 blocks ==75167== still reachable: 4,184 bytes in 2 blocks ==75167== suppressed: 0 bytes in 0 blocks ==75167== Rerun with --leak-check=full to see details of leaked memory ==75167== ==75167== For counts of detected and suppressed errors, rerun with: -v ==75167== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) -- Regards, Peng

4 3

[bind] Dereferencing placeholder argument
by Szymon Gatner 09 Sep '11

09 Sep '11

Hi, Is there a way of automatic placeholder argument dereferencing when using bind()? I mean: struct SomePredicate { bool operator()(int num, const Foo& foo) const { return SomeTestOnFoo(num, foo); } } std::vector<Foo*> foos; // line below gives compilation error because second argument passed // to functor is Foo* and not Foo. std::for_each(foos.begin(), foos.end(), bind(SomePredicate(), 123, _1); I don't want to use indirect() adaptor from boost.range because I want final output range to still have Foo* as value_type so that it can still be copied to another std::vector<Foo*> etc. So: is there a way of telling bind() that is should dereference a placeholder argument before passing it to underlying bound functor? Regards, Simon -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

1 0

[container] Initialization from transformed_range compilation error
by Szymon Gatner 09 Sep '11

09 Sep '11

Hi, snipped below gives this error in VS 2008 SP1: Error 1 error C2664: 'void boost::container::vector<T>::priv_range_insert<InIt>(Object **,FwdIt,FwdIt,std::forward_iterator_tag)' : cannot convert parameter 4 from 'boost::detail::iterator_category_with_traversal<Category,Traversal>' to 'std::forward_iterator_tag' c:\devel\boost_1_47_0\boost\container\vector.hpp 1908 copy_range code: #include <boost/container/vector.hpp> #include <boost/range/adaptor/transformed.hpp> #include <functional> class Object; struct DecodeID : public std::unary_function<int, Object*> { Object* operator() (int id) const { return 0; } }; int main() { using namespace boost; using namespace boost::container; using namespace boost::range; vector<int> ids; vector<Object*> objects = copy_range<vector<Object*> >(adaptors::transform(ids, DecodeID())); } Am I missing something obvious here? Regards, Szymon P.S. full build log: 1>------ Build started: Project: copy_range, Configuration: Debug Win32 ------ 1>Compiling... 1>main.cpp 1>c:\devel\boost_1_47_0\boost\container\vector.hpp(1908) : error C2664: 'void boost::container::vector<T>::priv_range_insert<InIt>(Object **,FwdIt,FwdIt,std::forward_iterator_tag)' : cannot convert parameter 4 from 'boost::detail::iterator_category_with_traversal<Category,Traversal>' to 'std::forward_iterator_tag' 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>>, 1> FwdIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>> 1> ] 1> and 1> [ 1> Category=std::input_iterator_tag, 1> Traversal=boost::random_access_traversal_tag 1> ] 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1> c:\devel\boost_1_47_0\boost\container\vector.hpp(1093) : see reference to function template instantiation 'void boost::container::vector<T>::priv_insert_dispatch<InIt>(boost::container::containers_detail::vector_const_iterator<Pointer>,InIt,InIt,boost::container::containers_detail::false_)' being compiled 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>>, 1> Pointer=Object ** 1> ] 1> c:\devel\boost_1_47_0\boost\container\vector.hpp(1761) : see reference to function template instantiation 'void boost::container::vector<T>::insert<InIt>(boost::container::containers_detail::vector_const_iterator<Pointer>,InIt,InIt)' being compiled 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>>, 1> Pointer=Object ** 1> ] 1> c:\devel\boost_1_47_0\boost\container\vector.hpp(1895) : see reference to function template instantiation 'void boost::container::vector<T>::priv_assign_aux<InIt>(InIt,InIt,std::input_iterator_tag)' being compiled 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>> 1> ] 1> c:\devel\boost_1_47_0\boost\container\vector.hpp(867) : see reference to function template instantiation 'void boost::container::vector<T>::priv_assign_dispatch<InIt>(InIt,InIt,boost::container::containers_detail::false_)' being compiled 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>> 1> ] 1> c:\devel\boost_1_47_0\boost\container\vector.hpp(487) : see reference to function template instantiation 'void boost::container::vector<T>::assign<InIt>(InIt,InIt)' being compiled 1> with 1> [ 1> T=Object *, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>> 1> ] 1> c:\devel\boost_1_47_0\boost\range\iterator_range_core.hpp(640) : see reference to function template instantiation 'boost::container::vector<T>::vector<boost::transform_iterator<UnaryFunc,Iterator>>(InIt,InIt,const std::allocator<_Ty> &)' being compiled 1> with 1> [ 1> T=Object *, 1> UnaryFunc=DecodeID, 1> Iterator=boost::container::containers_detail::vector_iterator<int *>, 1> InIt=boost::transform_iterator<DecodeID,boost::container::containers_detail::vector_iterator<int *>>, 1> _Ty=Object * 1> ] 1> c:\users\bravo\documents\visual studio 2008\projects\copy_range\copy_range\main.cpp(23) : see reference to function template instantiation 'SeqT boost::copy_range<boost::container::vector<T>,boost::range_detail::transformed_range<F,R>>(const Range &)' being compiled 1> with 1> [ 1> SeqT=boost::container::vector<Object *>, 1> T=Object *, 1> F=DecodeID, 1> R=boost::container::vector<int>, 1> Range=boost::range_detail::transformed_range<DecodeID,boost::container::vector<int>> 1> ] 1>Build log was saved at "file://c:\Users\bravo\Documents\Visual Studio 2008\Projects\copy_range\copy_range\Debug\BuildLog.htm" 1>copy_range - 1 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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asio::io_service as a thread-pool executor
by aiooua 08 Sep '11

08 Sep '11

I'm trying to use boost::asio::io_service as a thread pool executor. Here's my attempt: ---- using std::vector; using boost::bind; using boost::thread; using boost::shared_ptr; using boost::asio::io_service; class executor { public: executor(size_t n): service_(n), work_(service_) { for (size_t i = 0; i < n; i++) { shared_ptr<thread> worker(new thread(bind(&io_service::run, &service_))); pool_.push_back(worker); } } ~executor() { service_.stop(); for (auto i = pool_.begin(); i != pool_.end(); ++i) { (*i)->join(); } } template<typename F> void submit(F task) { service_.post(task); } private: io_service service_; io_service::work work_; vector<shared_ptr<thread> > pool_; }; void work() {} void other_work(const char *c) {} struct functor_work { void operator()() {} }; auto lambda = [] {}; int main() { executor e(4); e.submit(work); e.submit(boost::bind(other_work, "input")); e.submit(functor_work()); e.submit(lambda); } ---- Is this usage correct or am I missing anything here? The bit I'm not sure about in particular is this: Is it guaranteed that the io_service::run will wait for the completion of the posted jobs (via io_service::post) after I have called io_service::stop? In other words, do I have to explicitly ensure that my executor instance lives at least as long as the last submitted job has finished? Or can I assume that io_service::run will only return after all its posted jobs have had a chance to finish? Thanks!

1 0

[Units] defining a derived dimension
by Michael Powell 08 Sep '11

08 Sep '11

I want to define a dimension stroke_rate, or flow_rate, for that matter. Not too out of the ordinary for our application. So I am starting with something like this for my dimensions. #include <boost/units/derived_dimension.hpp> #include <boost/units/physical_dimensions/length.hpp> #include <boost/units/physical_dimensions/time.hpp> typedef boost::units::derived_dimension<boost::units::dimensionless_type,1,boost::units::time_base_dimension,-1>::type stroke_rate_dimension; typedef boost::units::derived_dimension<boost::units::length_dimension,3,boost::units::time_dimension,-1>::type flow_rate_dimension; typedef boost::units::unit<ourns::units::stroke_rate_dimension,boost::units::si::system> stroke_rate; typedef boost::units::unit<ourns::units::flow_rate_dimension,boost::units::si::system> flow_rate; However, I am receiving compiler errors when I try and include the units, Error 1 error C2039: 'value' : is not a member of 'boost::units::detail::dimension_list_tag' C:\Source\Simulations\tools\boost-msvc90-pro\boost\mpl\aux_\preprocessed\plain\less.hpp 20 CS.Calculations.Managed Error 2 error C2065: 'value' : undeclared identifier C:\Source\Simulations\tools\boost-msvc90-pro\boost\mpl\aux_\preprocessed\plain\less.hpp 21 CS.Calculations.Managed Error 3 error C2039: 'value' : is not a member of 'boost::units::detail::dimension_list_tag' C:\Source\Simulations\tools\boost-msvc90-pro\boost\mpl\aux_\preprocessed\plain\less.hpp 21 CS.Calculations.Managed Error 4 error C2065: 'value' : undeclared identifier C:\Source\Simulations\tools\boost-msvc90-pro\boost\mpl\aux_\preprocessed\plain\less.hpp 22 CS.Calculations.Managed And so on along these lines. What am I doing wrong with the units and/or dimensions? This is quite similar to energy_density_dimension, for example. typedef derived_dimension<length_base_dimension,-1,mass_base_dimension,1,time_base_dimension,-2>::type energy_density_dimension; However, I am failing to see any appreciable difference. Any thoughts? Thanks, Michael

2 4

units length operator * / area
by Michael Powell 08 Sep '11

08 Sep '11

Units users, How do I define an operator* which takes a quantity<length>,quantity<length> and returns a quantity<area>? This doesn't seem to be defined in the boost::units, which somewhat surprises me. How do we make something like that part of the core definition? Thanks, Michael

1 1

Unicode support in boost?
by code 08 Sep '11

08 Sep '11

Hi, Can someone tell me how much Boost supports Uincode? Thank you

5 10

Wave Linker Error
by Alexander Feldman 08 Sep '11

08 Sep '11

Gentlemen, I'm getting the following linker error: /tmp/ccTiqxQC.o: In function `boost::wave::cpplexer::lex_input_interface<boost::wave::cpplexer::lex_token<boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > > >* boost::wave::cpplexer::lex_input_interface_generator<boost::wave::cpplexer::lex_token<boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > > >::new_lexer<boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> >(boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > const&, boost::wave::language_support)': wave+spirit.cpp:(.text._ZN5boost4wave8cpplexer29lex_input_interface_generatorINS1_9lex_tokenINS0_4util13file_positionINS4_11flex_stringIcSt11char_traitsIcESaIcENS4_9CowStringINS4_22AllocatorStringStorageIcS9_EEPcEEEEEEEEE9new_lexerINS_6spirit7classic17position_iteratorINSK_22basic_istream_iteratorIcS8_EENSL_18file_position_baseISsEENSL_5nil_tEEEEEPNS1_19lex_input_interfaceISH_EERKT_SY_RKSG_NS0_16language_supportE[boost::wave::cpplexer::lex_input_interface<boost::wave::cpplexer::lex_token<boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > > >* boost::wave::cpplexer::lex_input_interface_generator<boost::wave::cpplexer::lex_token<boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > > >::new_lexer<boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> >(boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > const&, boost::wave::language_support)]+0x13): undefined reference to `boost::wave::cpplexer::new_lexer_gen<boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t>, boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > >, boost::wave::cpplexer::lex_token<boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > > >::new_lexer(boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::spirit::classic::position_iterator<boost::spirit::basic_istream_iterator<char, std::char_traits<char> >, boost::spirit::classic::file_position_base<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::classic::nil_t> const&, boost::wave::util::file_position<boost::wave::util::flex_string<char, std::char_traits<char>, std::allocator<char>, boost::wave::util::CowString<boost::wave::util::AllocatorStringStorage<char, std::allocator<char> >, char*> > > const&, boost::wave::language_support)' collect2: ld returned 1 exit status -------------------------- Trying to link: std::ifstream instream(argv[1]); std::string instring; if (!instream.is_open()) { std::cerr << "Could not open input file: " << argv[1] << std::endl; return -2; } instream.unsetf(std::ios::skipws); typedef boost::spirit::classic::position_iterator<boost::spirit::istream_iterator> pos_iterator; boost::spirit::istream_iterator begin1(instream); boost::spirit::istream_iterator end1; pos_iterator begin(begin1, end1, argv[1]); pos_iterator end; typedef boost::wave::cpplexer::lex_token<> token_type; typedef boost::wave::cpplexer::lex_iterator<token_type> lex_iterator_type; typedef boost::wave::context<pos_iterator, lex_iterator_type> context_type; context_type ctx(begin, end, argv[1]); context_type::iterator_type preprocessedInputBegin = ctx.begin(); context_type::iterator_type preprocessedInputEnd = ctx.end(); --------------- Any ideas what am I missing? Thanks, -- Alex

2 2

[Serialization]Serialization of pointer to pointers
by Kangkook Jee 08 Sep '11

08 Sep '11

Hi, all I'm trying to use boost library for serialization of my program which contains many custom class definitions. However, I can't figure out how to handle a class member which is *pointer to pointers* such as 'a' from the following code snippet. class B { A** a; friend class boost::serialization::access; … template<class Archive> void serialize(Archive &ar, const unsigned int version) { ar & a: …. Above code fails to be compiled with the following error message. … /usr/include/boost/archive/detail/oserializer.hpp:148:5: instantiated from ‘void boost::archive::detail::oserializer<Archive, T>::save_object_data(boost::archive::detail::basic_oarchive&, const void*) const [with Archive = boost::archive::text_oarchive, T = A*]’ serial0.cpp:118:1: instantiated from here /usr/include/boost/serialization/access.hpp:118:9: error: request for member ‘serialize’ in ‘t’, which is of non-class type ‘A*’ Do we have a typical way to handle a such case? I spend some time to find a solution from the web and tutorials but I couldn't. I'm new to the boost library and your helps will be greatly appreciated. Thanks, Kangkook

2 1