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

Portable Approach to get System Time
by Wong Peter 15 Jul '09

15 Jul '09

Hello to all, What is the portable approach to get the current system time ? Thanks. -- Linux

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Boost Function
by Wong Peter 15 Jul '09

15 Jul '09

What is Boost::function ? I read the documentation but cann;t find any clear explanation. -- Linux

5 7

boost bind example does not compile with member template function on gcc 4.0
by James Pritts 15 Jul '09

15 Jul '09

Unfortunately I cannot grok boost::bind error, but this code seems really simple. If I change the code so that an int is passed to async_discovery, the program compiles. The problem seems to be centered around passing a boost::bind as a template argument. Any help would be appreciated. Here is the code... #include <boost/bind.hpp> class antix_discovery_service { public: template <typename Handler> void start_async_discovery(Handler handler) { } /// Asynchronously resolve a query to a list of entries. template <typename Handler> void async_discovery(Handler handler) { boost::bind(&antix_discovery_service::template start_async_discovery<Handler>, this, handler)(); } private: int ttt; }; class test { public: void do_it() { } }; int main() { antix_discovery_service ads; test t; ads.async_discovery(boost::bind<void>(&test::do_it, t)); return 0; } and here is the error... main.cpp: In function 'int main()': main.cpp:33: warning: unused variable 'jjj' ../vendor/boost/boost/bind/bind.hpp: In member function 'void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = boost::_mfi::mf1<void, antix_discovery_service, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >, A = boost::_bi::list0, A1 = boost::_bi::value<antix_discovery_service*>, A2 = boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > >]': ../vendor/boost/boost/bind/bind_template.hpp:20: instantiated from 'typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()() [with R = void, F = boost::_mfi::mf1<void, antix_discovery_service, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >, L = boost::_bi::list2<boost::_bi::value<antix_discovery_service*>, boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > > >]' main.cpp:14: instantiated from 'void antix_discovery_service::async_discovery(Handler) [with Handler = boost::_bi::bind_t<void, boost::_mfi::mf0<void, test>, boost::_bi::list1<boost::_bi::value<test> > >]' main.cpp:35: instantiated from here ../vendor/boost/boost/bind/bind.hpp:306: error: invalid use of void expression ...failed gcc.compile.c++ ..\.bin\test_bind\gcc-4.0\debug\main.o... ...skipped <p..\.bin\test_bind\gcc-4.0\debug>test_bind.avc for lack of <p..\.bin\test_bind\gcc-4.0\debug>main.o... ...skipped <p..\.bin\test_bind\gcc-4.0\debug>test_bind.ix86-win32.elf for lack of <p..\.bin\test_bind\gcc-4.0\debug>test_bind.avc... ...skipped <pinstall>test_bind.ix86-win32.elf for lack of <p..\.bin\test_bind\gcc-4.0\debug>test_bind.ix86-win32.elf... ...failed updating 1 target... ...skipped 3 targets... Compilation exited abnormally with code 1 at Tue Jul 14 14:27:58 -Jimmy.

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Re: [Boost-users] [statechart] friend state can't call overloaded member functions in machine class
by David Matz 15 Jul '09

15 Jul '09

Hello Andreas, [snip] Replace with the following lines and everything should work: > > sc::in_state_reaction< EvBack, CoreApp, (void (CoreApp::*)(const EvBack &)) > &CoreApp::doInStateReaction >, > sc::in_state_reaction< EvNext, CoreApp, (void (CoreApp::*)(const EvNext &)) > &CoreApp::doInStateReaction > Yes, thats what I'm looking for. Now it compiles. Thanks a lot :-) David

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[program options] vectro from config file
by Diederick C. Niehorster 15 Jul '09

15 Jul '09

Hi All, I can't find an answer to this before, so I'll ask here. I would like to read a vector from a config file using program_options. example definition of option: ("Expt.ControlOrd", po::value<vector<int>>(&_pcData->SetExptOrders()), "Expt.ControlOrd") In the config file, the following works: ControlOrd = 1 ControlOrd = 2 But i would much prefer to use: ControlOrd = 1 2 or ControlOrd = (1 2) or something like that. I have made this work by editing the sourcecode, diff: ---- Index: config_file.cpp =================================================================== --- config_file.cpp (revision 54915) +++ config_file.cpp (working copy) @@ -12,6 +12,8 @@ #include <boost/program_options/detail/convert.hpp> #include <boost/throw_exception.hpp> +#include <boost/algorithm/string.hpp> + #include <iostream> #include <fstream> #include <cassert> @@ -112,8 +114,17 @@ found = true; this->value().string_key = name; this->value().value.clear(); - this->value().value.push_back(value); this->value().unregistered = !registered; + + if (*value.begin() == '(' && *value.rbegin() == ')') + { + value = value.substr(1, value.size()-2); + vector<string> SplitVec; + split( SplitVec, value, is_any_of(" ") ); + this->value().value.swap(SplitVec); + } + else + this->value().value.push_back(value); break; } else { ---- Of course, this is not a great solution as it doesn't allow you to read strings starting with ( and ending with ). Well, it is missing one thing. If we could somehow check that the datatype requested for this options is a vector, we could add that check to the if. I think that leaves only one problem, that of reading a vector of strings. Please tell me if it is possible to check for the requested type at this point in the code and how to do it. Any other comments also very welcome! I'll suggest it to the author once it works well. Thank you, Diederick

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Re: [Boost-users] Unable to catch exception using boost::asio
by Alex Black 15 Jul '09

15 Jul '09

>> I'm using boost::asio for sockets, writing a response out to a client. >> >> If the client stops part way through getting the response, then my >> server process dies: >> >> terminate called after throwing an instance of >> 'boost::exception_detail::clone_impl<boost::exception_detail::error_in >> fo_injector<boost::system::system_error> >>>' >> ? what():? Broken pipe >> >> The code though is surrounded by try catch like this: >> >> try >> { >> ??? ... >> } >> catch ( std::exception& e ) >> { >> ??? cout << e.what() << endl; >> } >> catch ( ... ) >> { >> ???? cout << "unexpected exception" << endl; } >> >> How do I prevent my process from aborting/terminating like this? v >Have you verified that the code inside the try block executes on the same thread that the exception is occuring in? Not explicitly, how would I do that? thx - Alex

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[mpl] BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF
by Hicham Mouline 15 Jul '09

15 Jul '09

#include <iostream> #include <boost/mpl/has_xxx.hpp> #include <boost/mpl/bool.hpp> BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_xxx, xxx, false) struct test1 { int xxx; }; using namespace boost::mpl; int main() { std::cout<< has_xxx<test1>::value <<std::endl; return 0; } The output is 0, while it should be 1, shouldn't it? Rds,

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Re: [Boost-users] Unable to catch exception using boost::asio
by Alex Black 15 Jul '09

15 Jul '09

>> The code though is surrounded by try catch like this: >> >> try >> { >> ??? ... >> } > What code resides in the protected block? Do you run io_service in multiple threads? What exception-related compiler options do you use? I do call io_service.run, on a thread on startup. I call async_accept, and accept connections one at a time. So basically I a my accept_handler gets called, I enter the try, then its just business logic and writing results out onto a socket. Exception-related compiler options? Not sure. This is happening in debug (and release). In release I have march=native and O-O3 set.

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Unable to catch exception using boost::asio (boost::exception_detail::clone_imple<.....
by Alex Black 14 Jul '09

14 Jul '09

I'm using boost::asio for sockets, writing a response out to a client. If the client stops part way through getting the response, then my server process dies: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info _injector<boost::system::system_error> >' what(): Broken pipe The code though is surrounded by try catch like this: try { ... } catch ( std::exception& e ) { cout << e.what() << endl; } catch ( ... ) { cout << "unexpected exception" << endl; } How do I prevent my process from aborting/terminating like this? thx - Alex

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[statechart] friend state can't call overloaded member functions in machine class
by David Matz 14 Jul '09

14 Jul '09

Hi, if one want to centralize all transition callbacks into the machine itself it's a good way to declare the states as friends and call the machine member functions which should (of course) private. But boost::statechart has problems if the member functions in the machine class are overloaded. Then the friend declaration is ignored by the compiler. Here is a snippet to reproduce the error: struct Active; class CoreApp : public boost::statechart::state_machine< CoreApp, Active > { friend struct Active; public: CoreApp() { initiate(); } private: void doInStateReaction(const EvNext &) {} void doInStateReaction(const EvBack &) {} ///< uncomment this line to resolve the error }; struct Active : boost::statechart::simple_state< Active, CoreApp > { typedef boost::mpl::list < //sc::in_state_reaction < EvBack, CoreApp, &CoreApp::doInStateReaction >, sc::in_state_reaction < EvNext, CoreApp, &CoreApp::doInStateReaction > > reactions; }; As one can see two functions doInStateReaction() are defined in the state machine class. Comment the second one out and it compiles. This problem occurs too if one uses a templated event which calls a templated function. A easy solution to this problem is to rename the functions slightly but I hope there is a better way. Has anyone an idea to catch this? David

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