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Several novice questions concerning threading
by Master 12 Apr '12

12 Apr '12

Hello all . i am a newbie to the boost community . i recently started learning about threads in boost . now there are some questions i would like to ask : 1.where can i find examples showing practical uses of boost::thread features? 2.how can i get all threads ID issued by me in my app? 3.how can i iterate through running threads in my app ? 4.is there any kind of means to get all the running threads using boost library? if it does whats the calss? if it doesnt how can i do that? 5.can i resume a thread after pausing it ? ( how can i pause a thread? ) 6. how can i share a variable between two or more threads , suppose i have a loop , i want two threads to simultaneously iterate through it , if thread1 counted to 3, thread2 continues it from 4 and so on . ? i already tried ------ > what is wrong with my sample app ? > #include <iostream> > #include <boost/thread.hpp> > using namespace std; > using namespace boost; > > mutex bmutex; > int i=0; > int sum=0; > void IteratorFunc(int threadid) > { > for ( ; i<25 ; i++) > { > lock_guard<mutex> locker(bmutex); > > cout<<"\t"<<threadid<<"\t"<<this_thread::get_id()<<"\t"<<i<<"\n"; > sum+=i; > } > } > > int main() > { > //boost::posix_time::ptime start = > boost::posix_time::microsec_clock::local_time(); > > thread thrd(IteratorFunc,1); > thread thrd2(IteratorFunc,2); > > cout<<sum; > thrd.join(); > thrd2.join(); > } > Thank you in advance

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[BLL] Problem with print vector elements.
by mik 12 Apr '12

12 Apr '12

Hi, I'm trying to use thew BLL for the first time and I've the following program: class Date { public: Date(long d): _lDate(d) {} long getDate() const { return _lDate; } [...] private: long _lDate; }; std::ostream& operator<<(std::ostream &s, const Date &x) { [...] } struct C { C(long d): date(d) {} Date date; }; int main() { const C c(46000); std::cout << boost::bind(&C::date, boost::lambda::_1)(c) << std::endl; std::vector<C> cont(1, C(46000)); std::for_each(cont.begin(), cont.end(), std::cout << boost::bind(&C::date, boost::lambda::_1)); return 0; } The first std::cout is ok. But for the second one nested int the for_each I get this message error: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'boost::_bi::bind_t<R,F,L>' (or there is no acceptable conversion) with [ R=const Date &, F=boost::_mfi::dm<Date,C>, L=boost::_bi::list1<boost::arg<1>> ] C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\ostream(653): could be 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const char *)' [found using argument-dependent lookup] with [ _Elem=char, _Traits=std::char_traits<char> ] Can you help me? Thank you, Mirko **

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boost arm compilation
by Bisegni Claudio 12 Apr '12

12 Apr '12

Hi all, i have some problem compiling boost on arm. i can compile package individually but when i use "install" i go segmentation fault after a some times. So i have compiled by every library and i have installed by handle all file. after that compiling my code with boost i got this error: /usr/local/include/boost/cstdint.hpp:104: error: '::int_least8_t' has not been declared /usr/local/include/boost/cstdint.hpp:105: error: '::int_fast8_t' has not been declared /usr/local/include/boost/cstdint.hpp:106: error: '::uint8_t' has not been declared /usr/local/include/boost/cstdint.hpp:107: error: '::uint_least8_t' has not been declared /usr/local/include/boost/cstdint.hpp:108: error: '::uint_fast8_t' has not been declared /usr/local/include/boost/cstdint.hpp:111: error: '::int_least16_t' has not been declared /usr/local/include/boost/cstdint.hpp:112: error: '::int_fast16_t' has not been declared /usr/local/include/boost/cstdint.hpp:113: error: '::uint16_t' has not been declared /usr/local/include/boost/cstdint.hpp:114: error: '::uint_least16_t' has not been declared /usr/local/include/boost/cstdint.hpp:115: error: '::uint_fast16_t' has not been declared /usr/local/include/boost/cstdint.hpp:118: error: '::int_least32_t' has not been declared /usr/local/include/boost/cstdint.hpp:119: error: '::int_fast32_t' has not been declared /usr/local/include/boost/cstdint.hpp:120: error: '::uint32_t' has not been declared /usr/local/include/boost/cstdint.hpp:121: error: '::uint_least32_t' has not been declared /usr/local/include/boost/cstdint.hpp:122: error: '::uint_fast32_t' has not been declared /usr/local/include/boost/cstdint.hpp:127: error: '::int_least64_t' has not been declared /usr/local/include/boost/cstdint.hpp:128: error: '::int_fast64_t' has not been declared /usr/local/include/boost/cstdint.hpp:129: error: '::uint64_t' has not been declared /usr/local/include/boost/cstdint.hpp:130: error: '::uint_least64_t' has not been declared /usr/local/include/boost/cstdint.hpp:131: error: '::uint_fast64_t' has not been declared /usr/local/include/boost/cstdint.hpp:135: error: '::intmax_t' has not been declared /usr/local/include/boost/cstdint.hpp:136: error: '::uintmax_t' has not been declared someone has some idea on how resolve this issue? thank in advanced

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Prim's algorithm with custom weights?
by John asdf 11 Apr '12

11 Apr '12

I feel like I explain the problem well with my question on stackoverflow but it's not getting much response. http://stackoverflow.com/questions/10098437/c-boost-prims-algorithm-with-cu… If anyone can help I would greatly appreciate it.

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[Variant] recursive_wrapper and ambiguous convert_construct()
by Florian Goujeon 11 Apr '12

11 Apr '12

Hello, I'm modelizing a syntax tree using boost::variant, std::tuple and std::vector. This syntax tree has a lot of cyclic dependencies, so I have to use boost::recursive_wrapper along with forward declarations. I've encountered a case that my compiler (GCC 4.7) refuses to build. Here is the source code: http://pastebin.com/3a5xU06x (it's pretty short) Here is the compilation error message: http://pastebin.com/Zpa3TCp2 (Of course, reordering the declarations would solve the problem in this example, but it's not the point. This is a constraint I can't get rid of in my whole project.) The compiler complains about an ambiguous call of convert_construct() in Boost's source code, where a comment says: NOTE TO USER : Compile error here indicates that the given type is not unambiguously convertible to one of the variant's types (or that no conversion exists). c can be converted to boost::recursive_wrapper<c_fwd> though. Where is the ambiguity? I really don't know what to do. Help would be appreciated. Thank you.

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Two days left to save on BoostCon / C++Now! 2012
by Dave Abrahams 11 Apr '12

11 Apr '12

Just a quick reminder to everyone that early-bird registration closes at the end of this week. After Friday, the price goes up by $100. Spots are limited and registrations have been coming in faster than in past years. http://cppnow.org Cheers! -- Dave Abrahams BoostPro Computing http://www.boostpro.com

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Boost.Locale: normalized concatenation?
by Narcoleptic Electron 11 Apr '12

11 Apr '12

I'm a happy user of boost.locale, but there is a use case that I can't see a solution for. I would like to concatenate two long, canonically normalized (NFC) UTF-8 strings. It seems that the only way to currently do this is by calling boost::locale::normalize on the resulting string. This is wasteful, as it requires walking the entire string when only a well-defined substring of each (at the boundary) can possibly require modification. The ideal solution would be for boost.locale to expose something like ICU's unorm2_normalizeSecondAndAppend, which takes advantage of normalization guarantees in the Unicode standard to only normalize the boundary where it is required. Does this capability already exist in boost.locale? Thanks.

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Best practice for singletons?
by Chris Cleeland 11 Apr '12

11 Apr '12

There are many ways to skin the singleton cat. In fact, boost itself sports several--some publicly exposed, some in "detail". I'm wondering if any one or two of these might be considered to be the current state-of-the-art with regard to implementing a singleton. I can certainly "roll my own" as I've done in the past, but if I can stand on the shoulders of giants and since I already have an accepted dependency on boost, I definitely prefer that. I do not wish to engage in any religious wars regarding singletons--I'm aware that they have their evils. Thanks much! -- Chris Cleeland

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memory leak with boost asio and openssl
by Paul Bergen 11 Apr '12

11 Apr '12

I've written an HTTP daemon (like Apache) with Boost that takes https connections with openssl. Everything is working fine, except that it's leaking memory. Valgrind shows the leak is always in the openssl functions, and the backtrace shows it always starts inside boosts architecture. The backtraces are something like (this is heavily cleaned up since they're huge): CRYPTO_malloc openssl_stream_service::ssl_wrap openssl_operation::async_read_handler boost_asio_handler_invoke_helpers::invoke strand_service::dispatch asio_handler_invoke task_io_service::do_one io_service::run thread_proxy start_thread clone In my code I have a single 'server' class, I have a single instance of boost::asio::ssl::context(_io_service,boost::asio::ssl::context::sslv23) which I setup one time in my server's constructor (setting use_certificate_chain_file, etc). I also have an boost::asio::io_service and a boost::asio::ip::tcp::acceptor. An instance of my Connection class is created for each inbound connection, and it has a boost ssl_socket, which gets the io_service and context (by reference). Naturally lots and lots of other code too, and it's all working. My Connection objects are properly deleted when the connection is done, and so is the boost ssl_socket. And I call ssl_socket::shutdown(ip::tcp::socket::shutdown_both, ec) before deleting the socket. But it seems that's not enough to free all the memory. Valgrind shows there are no stray copies of any of my objects or of any boost objects that I created. Just all these openssl calls that originate within the boost framework. What's very strange is that the number of allocations leaked doesn't correspond to the number of connections. If my app starts and exits with no connections, there are only some leaks in static constructors, which, from what I read, is a known bug in openssl. But after there is 1 connection, there are about 6 new leaks similar to that stack trace above. After there are 10 connections, there are 16 leaks. But after 40 connections, there are only 18 leaks. So the leaks grows gradually, but over time it does keep growing until my app runs out of memory. Anybody know what cleanup functions I might not be calling to free up the memory? Thanks.

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[Interprocess] Collection of base shared_ptr
by Aaron_Wright＠selinc.com 11 Apr '12

11 Apr '12

I'm using Boost 1.49, and Visual Studio 10. I'm having a hard time figuring out how to store a shared_ptr to a derived class in a collection of shared_ptr to the base class. This is something I do all the time with normal shared pointers. This is my code: { struct Base {}; struct Derived : public Base {}; typedef boost::interprocess::managed_shared_ptr < Base, boost::interprocess::managed_shared_memory >::type Base_ptr; typedef boost::interprocess::deque < Base_ptr, boost::interprocess::managed_shared_memory::allocator< Base_ptr >::type > Queue; struct shm_remove { shm_remove() { boost::interprocess::shared_memory_object::remove("testing"); } ~shm_remove() { boost::interprocess::shared_memory_object::remove("testing"); } } remover; boost::interprocess::managed_shared_memory shared_memory( boost::interprocess::create_only, "testing", 65536); Queue* queue = shared_memory.construct< Queue >(boost::interprocess::anonymous_instance)( shared_memory.get_allocator< Base_ptr >()); queue->push_back( bi::make_managed_shared_ptr< Derived >( shared_memory.construct< Derived >(bi::anonymous_instance)(), shared_memory)); } The compiler tells me a bunch of cryptic stuff, I think it has to do with the different deleter types: boost/container/deque.hpp(1040): error C2664: 'boost::interprocess::shared_ptr<T,VoidAllocator,Deleter>::shared_ptr(const boost::interprocess::offset_ptr<PointedType,DifferenceType,OffsetType,OffsetAlignment> &,const VoidAllocator &,const Deleter &)' : cannot convert parameter 1 from 'const boost::interprocess::shared_ptr<T,VoidAllocator,Deleter>' to 'const boost::interprocess::offset_ptr<PointedType,DifferenceType,OffsetType,OffsetAlignment> &' 5> with 5> [ 5> T=Base, 5> VoidAllocator=boost::interprocess::allocator<void,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> Deleter=boost::interprocess::deleter<Base,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> PointedType=Base, 5> DifferenceType=ptrdiff_t, 5> OffsetType=size_t, 5> OffsetAlignment=0 5> ] 5> and 5> [ 5> T=Derived, 5> VoidAllocator=boost::interprocess::allocator<void,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> Deleter=boost::interprocess::deleter<Derived,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> 5> ] 5> and 5> [ 5> PointedType=Base, 5> DifferenceType=ptrdiff_t, 5> OffsetType=size_t, 5> OffsetAlignment=0 5> ] 5> Reason: cannot convert from 'const boost::interprocess::shared_ptr<T,VoidAllocator,Deleter>' to 'const boost::interprocess::offset_ptr<PointedType,DifferenceType,OffsetType,OffsetAlignment>' 5> with 5> [ 5> T=Derived, 5> VoidAllocator=boost::interprocess::allocator<void,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> Deleter=boost::interprocess::deleter<Derived,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> 5> ] 5> and 5> [ 5> PointedType=Base, 5> DifferenceType=ptrdiff_t, 5> OffsetType=size_t, 5> OffsetAlignment=0 5> ] 5> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 5> test.cpp(94) : see reference to function template instantiation 'void boost::container::deque<T,A>::push_back<boost::interprocess::shared_ptr<Derived,VoidAllocator,Deleter>>(const BOOST_MOVE_TEMPL_PARAM &)' being compiled 5> with 5> [ 5> T=Base_ptr, 5> A=boost::interprocess::allocator<Base_ptr,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> VoidAllocator=boost::interprocess::allocator<void,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> Deleter=boost::interprocess::deleter<Derived,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>, 5> BOOST_MOVE_TEMPL_PARAM=boost::interprocess::shared_ptr<Derived,boost::interprocess::allocator<void,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>,boost::interprocess::deleter<Derived,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>> 5> ] --- Aaron Wright

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