December 2009 - Boost-users - lists.preview.boost.org

boost::variant and SFINAE
by Jonathan Chambers` 03 Dec '09

03 Dec '09

I'm using boost::variant in the following manner struct Visitor : boost::static_visitor<> { void operator()(int &i) const { i = 1; } }; boost::variant<int, char> var = 0; boost::apply_visitor(Visitor(), 0); I'm trying to get the program to compile if the variant takes on the guise of an int (because I've implemented void operator()(int &i) const, but not compile if I make the variant take the guise of a char e.g. boost::variant<int, char> var = 'a'; because I've not implemented the void operator()(char &c) const Can anyone think of a way of doing this, maybe using SFINAE (Substitution Failure Is Not An Error) I'm thinking of doing something along the lines of : template <typename T> struct SetObj; template <> struct SetObj<int> { void operator()(int &obj) const { obj = 1; } } struct Visitor : boost::static_visitor<> { template <typename T> void operator()(T& obj) const { SetObj<T>()(obj); } }; But not sure how to take it to the next level to get the desired behaviour. _________________________________________________________________ Have more than one Hotmail account? Link them together to easily access both http://clk.atdmt.com/UKM/go/186394591/direct/01/

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Problem using enable_if with gcc 3.4.4
by gao_bolin＠voila.fr 03 Dec '09

03 Dec '09

Hi, I am having some trouble using enable_if with gcc 3.4.4 (code below). Basically it is working as expected with functions ("bar"), but using it on member functions of a class ("Foo"), I am getting the error that this member function cannot be overloaded. Visual 2008 and gcc4 seem to be ok with it though. Any explanation and work around appreciated. B. -- #include <iostream> #include <boost/type_traits.hpp> #include <boost/utility/enable_if.hpp> // This won't compile with gcc 3.4.4 class Foo { public: template < typename T > typename boost::enable_if<boost::is_same<T, int>, T>::type bar(int x) { std::cout << "A" << std::endl; return x; } template < typename T > typename boost::disable_if<boost::is_same<T, int>, T>::type bar(int x) { std::cout << "B" << std::endl; return x; } }; // this would. template < typename T > typename boost::enable_if<boost::is_same<T, int>, T>::type bar(int x) { std::cout << "A" << std::endl; return x; } template < typename T > typename boost::disable_if<boost::is_same<T, int>, T>::type bar(int x) { std::cout << "B" << std::endl; return x; } int main() { bar<int>(1); bar<double>(1); Foo f; f.bar<int>(1); f.bar<double>(1); return 0; } ____________________________________________________ Michael Jackson, Susan Boyle, Black Eyed Peas ... Retrouvez leurs derniers titres sur http://musiline.voila.fr

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xpressive compilation error
by Pablo Hernández Valdés 03 Dec '09

03 Dec '09

Hello, I used to had an old version of boost (I don't remember exactly which) and my code worked fine. Now I updated to the last version and I started to receive compilation errors in linux when using a std::vector with regular expressions from boost::xpressive, in windows it compiles fine. This code doesn't compile: #include <vector> #include <boost/xpressive/xpressive.hpp> typedef boost::xpressive::basic_regex<std::string::const_iterator> regex_t; int main(int argc, char* argv[]) { std::vector<regex_t> vector; vect.push_back(regex_t()); return 0; } Compiler output: cd '/home/segurmatica/console_filter/debug' && WANT_AUTOCONF_2_5="1" WANT_AUTOMAKE_1_6="1" LC_MESSAGES="C" LC_CTYPE="C" gmake -k gmake all-recursive Making all in src compiling console_filter.cpp (g++) In file included from /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/vector:63, from /home/segurmatica/console_filter/src/console_filter.cpp:1: /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/bits/stl_construct.h: In static member function 'static void std::_Destroy_aux<<anonymous> >::__destroy(_ForwardIterator, _ForwardIterator) [with _ForwardIterator = boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >*, bool <anonymous> = false]': /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/bits/stl_construct.h:116: instantiated from 'void std::_Destroy(_ForwardIterator, _ForwardIterator) [with _ForwardIterator = boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >*]' /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/bits/stl_construct.h:142: instantiated from 'void std::_Destroy(_ForwardIterator, _ForwardIterator, std::allocator<_T2>&) [with _ForwardIterator = boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >*, _Tp = boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]' /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/bits/stl_vector.h:313: instantiated from 'std::vector<_Tp, _Alloc>::~vector() [with _Tp = boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, _Alloc = std::allocator<boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >]' /home/segurmatica/console_filter/src/console_filter.cpp:8: instantiated from here /usr/local/lib/gcc/i686-pc-linux-gnu/4.4.2/../../../../include/c++/4.4.2/bits/stl_construct.h:93: error: no matching function for call to '_Destroy(const boost::proto::exprns_::expr<boost::proto::tag::address_of, boost::proto::argsns_::list1<boost::xpressive::basic_regex<__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&>, 1l>)' gmake[2]: *** [console_filter.o] Error 1 gmake[2]: Target `all' not remade because of errors. gmake[2]: Nothing to be done for `all-am'. gmake[1]: *** [all-recursive] Error 1 gmake: *** [all] Error 2 *** Exited with status: 2 *** I'm using gcc 4.4.2 and boost 1.41 Thanks in advance, Pablo -- View this message in context: http://old.nabble.com/xpressive-compilation-error-tp26609113p26609113.html Sent from the Boost - Users mailing list archive at Nabble.com.

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problems with boost::thread::native_handle()
by Carlos Casado Cascado 03 Dec '09

03 Dec '09

Hello, my name is Carlos Casado, i work at the Malaga univeristy in Spain. I´m working with a robotic arm and we use boost thread library. We need give some thread priority, we want use the thread's original handle (pthread) because we can manage priority with pthread_setschedparam () . The problem is that we can´t use native_handle() because it is not defined. We have a RT ubuntu machine with boost thread 1.35 version Forgive my english errors. And thanks for your help

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[Serialization] Does it leak memory when applied to shared_ptr?
by Peng.Huang 03 Dec '09

03 Dec '09

When used for serialize the shared pointer, memory leak occurs. I am not sure that is due to the internal bug or the wrong use of serialization library. The following is test code: ============================================================================ ====== #include <iostream> #include <cstddef> #include <fstream> #include <string> #include <cstdio> #include <boost/config.hpp> #include <boost/archive/tmpdir.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/shared_ptr.hpp> class A{ private: friend class boost::serialization::access; int x; template<class Archive> void serialize(Archive& ar, const unsigned int /* file version */) { ar & x; } public: static int count; A(){++count; std::cout<<"A ctor"<<std::endl;} virtual ~A(){--count;std::cout<<"A dtro"<<std::endl;} }; int A::count = 0; int main(int /* argc */, char /*argv[] */){ std::string filename(boost::archive::tmpdir()); filename += "/testfile"; boost::shared_ptr<A> spa(new A); { std::ofstream ofs(filename.c_str()); boost::archive::text_oarchive oa(ofs); oa << spa; } spa.reset(); { std::ifstream ifs(filename.c_str()); boost::archive::text_iarchive ia(ifs); ia >> spa; } spa.reset(); std::cout << std::endl; return 0; } ============================================================================ ====== The output is: A ctor A dtor A ctor Valgrind report memory leak of 8 bytes, just the size of class A.

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compare strings??
by pedro chaparro 03 Dec '09

03 Dec '09

hi, i need to know how to compare two strings S1 and S2 , i've found fuction is_iequal and is_equal but i dont understand how use it =(, can anyone give me a example? thanks <http://www.boost.org/doc/libs/1_41_0/doc/html/boost/algorithm/is_iequal.html> -- Ing Pedro Alonso Chaparro Valero Ciudad Politecnica de la Innovación iTEAM - Mobile Communications Group Polytechnic University of Valencia C\ Camino de Vera S/N, Edificio 8G 46022 Valencia, Spain

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boost::thread and SunStudio
by Frank Meerkötter 03 Dec '09

03 Dec '09

Hi, i was trying to compile boost (1.40) with SunStudio11 but failed. By searching around a little bit i found this mail by Steven Watanabe http://article.gmane.org/gmane.comp.lib.boost.user/48995 The patch mentioned in the mail fixes my problem but i am wondering why it was not applied to the 1.40 release? KR, Frank

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boost asio - async_read and deadline_timer don't call their handler functions
by Gözde Bahar KOŞ 03 Dec '09

03 Dec '09

Hello, I want to use asio library for my serial communication module but I'm having trouble on asynchronous functionality. In the following code block, I wanted to read 5 bytes from the first serial port of my computer in 10 seconds. But none of the handler functions were called. Firstly I waited not inputing any bytes but timer did not call wait_handler. Secondly I sent 5 bytes in 10 seconds from the other computer but read_handler was not called. I could read the bytes using synchronous functions like read function, I mean there is nothing wrong with the communication. I tried this code both on a Windows and a Linux host but results were the same.. Can you please check what can be wrong with the following code? ************************************************************** #include <iostream> #include <boost/asio.hpp> #include <boost/asio/buffer.hpp> #include <boost/asio/deadline_timer.hpp> using namespace std; using namespace boost::asio; using namespace boost::system; using namespace boost::posix_time; struct wait_handler { void operator()(const error_code& ec){ cout << "Timeout!" << endl; } }; struct read_handler { void operator()(const error_code& ec, size_t bytes_transferred) { cout << "Data read!" << endl; } }; int main(int argc, char* argv[]) { char read_msg_[5]; io_service io; serial_port theport(io, "com1"); deadline_timer * timer = new deadline_timer(io); timer->expires_from_now(seconds(10)); wait_handler whandler; timer->async_wait(whandler); read_handler rhandler; async_read(theport, buffer(read_msg_, 5), rhandler); Sleep(30000); //30 seconds return 0; } ************************************************************** Best Regards, Gözde Bahar Koş ###################################################################### Dikkat: Bu elektronik posta mesaji kisisel ve ozeldir. Eger size gonderilmediyse lutfen gondericiyi bilgilendirip mesaji siliniz. Firmamiza gelen ve giden mesajlar virus taramasindan gecirilmekte, guvenlik nedeni ile kontrol edilerek saklanmaktadir. Mesajdaki gorusler ve bakis acisi gondericiye ait olup Aselsan A.S. resmi gorusu olmak zorunda degildir. ###################################################################### Attention: This e-mail message is privileged and confidential. If you are not the intended recipient please delete the message and notify the sender. E-mails to and from the company are monitored for operational reasons and in accordance with lawful business practices. Any views or opinions presented are solely those of the author and do not necessarily represent the views of the company. ######################################################################

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autolinking problem with iostream bzip2 and zlib filters -- DLLs needed for some reason? (updated)
by ChristinaGE 03 Dec '09

03 Dec '09

Hello, I am using the boost iostreams with the bzip2 qnd zlib filters. I built boost according to the directions here: http://www.boost.org/doc/libs/1_40_0/libs/iostreams/doc/installation.html This created the following libraries in the boost/stage/lib directory: libboost_bzip2-vc90-mt libboost_bzip2-vc90-mt-1_40 libboost_bzip2-vc90-mt-gd libboost_bzip2-vc90-mt-gd-1_40 libboost_zlib-vc90-mt libboost_zlib-vc90-mt-1_40 libboost_zlib-vc90-mt-gd libboost_zlib-vc90-mt-gd-1_40 now, here is the problem.. on every machien I usually do this on, it "autolinks" these libraries.. I have just started to build my code on a new machine, and for some reason it is not autolinking them. So to get my code to work I have to manually add them to my dependencies list and also add the directory where they are located. >From the link above it seems not to autolink of you have the preprocessor variable BOOST_IOSTREAMS_NO_LIB defined, but I dont seem to have that defined anywhere. Does anyone know why these libraries may not be autolinked? Also, I just now noticed that I am required to have the bzip2 and zlib DLLs to run my application, when before I never needed them. Thanks! Christy

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boost::any and const pointers
by James C. Sutherland 02 Dec '09

02 Dec '09

I have a map<string,any> that I would like to control access to so that if a pointer is put in the map, only a const pointer can be extracted. The following simple code illustrates the situation. //-------------------- <snip> -------------------------- typedef std::map<std::string,boost::any> Properties; template<typename T> void set( Properties& p, const std::string name, const T t ) { p[name] = t; } template<typename T> const T get( const Properties& p, const std::string name ) { const Properties::const_iterator iprop=p.find(name); try{ const T t = boost::any_cast<const T>(iprop->second); return t; } catch(const boost::bad_any_cast &){ throw std::runtime_error("bad cast"); } } int main() { Properties p; int i=1; set(p,"int",i); set(p,"int*",&i); int* j = get<int*>(p,"int*"); // I don't want this to compile const int* k = get<int*>(p,"int*"); // I want this to compile fine. } //-------------------- </snip> ------------------------- Currently this whole code compiles without trouble, but I don't want to allow a non-const pointer to be extracted. Any ideas of how to accomplish this? Thanks for any tips!

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