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[1.33] [signals] auto_ptr and boost::signals
by Seweryn Habdank-Wojewódzki 26 Aug '07

26 Aug '07

Dears I have question. Why there are problems to connect function that returns auto_ptr to the signal? Below there is a code which won't compile i line where is comment. Regards. #include <iostream> #include <boost/signals.hpp> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> #include <memory> #include <vector> #include <iterator> #include <algorithm> class some_class { public: ::std::vector <int> func1() { using ::std::vector; typedef vector <int> Res; Res res (2); res.at(0) = 13; res.at(1) = 14; return res; } ::boost::shared_ptr < ::std::vector <int> > func2() { using ::std::vector; using ::boost::shared_ptr; typedef shared_ptr < vector <int> > Res; Res res (new vector<int> (2)); res->at(0) = 23; res->at(1) = 24; return res; } ::std::auto_ptr < ::std::vector <int> > func3() { using ::std::vector; using ::std::auto_ptr; typedef auto_ptr < vector <int> > Res; Res res (new vector<int> (2)); res->at(0) = 33; res->at(1) = 34; return res; } }; int main() { using ::boost::signal; using ::std::vector; using ::std::auto_ptr; using ::boost::shared_ptr; using ::boost::bind; some_class sc; signal < vector <int> (void) > sig1; signal < shared_ptr < vector <int> > (void) > sig2; signal < auto_ptr < vector <int> > (void) > sig3; sig1.connect (bind (&some_class::func1,&sc)); vector <int> ret1 (sig1()); ::std::copy (ret1.begin(), ret1.end(), ::std::ostream_iterator<int> (::std::cout, "\n")); sig2.connect (bind (&some_class::func2,&sc)); vector <int> ret2 (*sig2()); ::std::copy (ret2.begin(), ret2.end(), ::std::ostream_iterator<int> (::std::cout, "\n")); sig3.connect (bind (&some_class::func3,&sc)); //sig3(); // <- ERROR } -- |\/\/| Seweryn Habdank-Wojewódzki \/\/

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Boost Unit Test Undefined Reference
by cmicel1＠cct.lsu.edu 26 Aug '07

26 Aug '07

Am I missing something when I get undefined references to main using boost 1.34.1. Here is a minimal example #include <iostream> #include <boost/test/unit_test.hpp> void my_test_function() { std::cout << "hi there" << std::endl; } boost::unit_test::test_suite* init_unit_test_suite( int , char*[] ) { boost::unit_test::test_suite* test = BOOST_TEST_SUITE( "Master test suite" ); test->add( BOOST_TEST_CASE( &my_test_function ) ); return test; } This is copied off of the main page. Here is the compilation line g++ test.cpp -o test -lboost_unit_test_framework-gcc41 With gcc version 4.1.2 Here is the error message: /usr/lib/gcc/i486-linux-gnu/4.1.2/../../../../lib/crt1.o: In function `_start': (.text+0x18): undefined reference to `main' collect2: ld returned 1 exit status Any insight? Chris Miceli

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Re: [Boost-users] boost::thread Destructor being called multiple times
by Nat Goodspeed 26 Aug '07

26 Aug '07

At 09:51 AM 8/25/2007, kaliwanagan wrote: >I was just curious as to why the class destructor are (apparently) >being called multiple times. I have tried searching the archives to no >avail (which prompted me to register and post to the mailinglist). Try defining an explicit copy constructor with a message like the others. I believe the issue is that your object is being passed by value, and being copied a few times along the way. You're not seeing your no-args constructor message because the other new instances are invoking the copy constructor.

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Unable to work out a Composite predicate.
by PJ Durai 25 Aug '07

25 Aug '07

Hello everyone, I am not able to figure out the correct syntax for something I am trying to do. The following works as expected. It filters all the 'new' events into a new vector. remove_copy_if ( myEvents.begin(), myEvents.end(), back_inserter(newEvents), !(boost::bind(&Event::GetEventType, _1) == EventType_New)); I cant figure out how to get a complex conditional working as the predicate. e.g. remove_copy_if ( myEvents.begin(), myEvents.end(), back_inserter(newEvents), (boost::bind(&Event::GetEventType, _1) == NotesEventType_New) && (boost::bind(&Event::GetEventID, _1) == 1000 ) ); I have tried various ways of putting parens around this expression. I just couldn't get it to compile. Is that even possible ? Please Advise. I am using Visual C++ 2005 SP1 on Windows XP SP2. Appreciate your time. thanks pj

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Re: [Boost-users] Serialization newbie needs help
by Dominick Layfield 25 Aug '07

25 Aug '07

"Robert Ramey" <ramey(a)rrsd.com> wrote: >> goes away. Any chance this could be added to a boost::serialization >> FAQ? > > you mean change the section named "rationale" to "FAQ"? Ermm... Yes, I suppose so. There ought to be some section that a newbie who is having problems would immediately look to see if this is a common problem. In my browser, the "Rationale" section of the documentation appears unexpanded by default. And even when I expand it, "Compile time trap when saving a non-const value" doesn't seem (when skimming the docs) relevant to the static assertion error. It also didn't appear in my Google search for the cryptic error message that the compiler produced. >> The "Compile time trap" section of the documentation doesn't actually >> explain what "object tracking" is all about. Neither (amusingly) >> does the Boost->Serialization->Reference->Special >> Considerations->Object Tracking section! > > Hmmm - well it's intended to. Maybe I just thought the meaning of the > term "Object Tracking" obvious. As a newbie, I can tell you that it wasn't obvious to me! :-) As I said, I wouldn't have expected the serialization library to do any automagical pointer stuff, so from this perspective, it's very hard to see what object tracking is, and why it would be necessary. >> What on earth does it actually mean to serialize a pointer? > > Exactly what you think it means - see above. Well, once you've got an idea in your head about what should happen when a pointer is serialized (and had that concept for years, and written a whole library to implement it!), it probably seems obvious and "natural" that it should work that way. But to a newbie (to boost::serialization, not to C++), this behavior is rather surprising. For example if I do: my_class mc; my_class* mc_ptr = &mc; cout << mc_ptr; I don't get the my_class object sent to stdout. I get the value of the pointer itself. If I wanted the actual object displayed, I would dereference the pointer. So my intuition would be that boost::serialization would work in a similar way: if I wanted the object itself output/input, I would do it explicitly. I'm not trying to say that your approach is wrong. All I'm attempting to point out is that other people may have very different (and quite reasonable) expectations about what should happen. >> And why would I want to do such a thing, anyway? > > I don't know what your application is. Sorry. What I meant was "Why would someone want this?" or "Why is this a useful feature?" Fundamentally, there are two approaches to dealing with pointer serialization: (1) disallow it altogether; or (2) serialize the pointed-to object, and do all the clever object-tracking stuff. The first approach has the benefit of simplicity . So the only reason to take the second approach would be if automagic pointer serialization is really useful. However, I can't think of an example of when this would be really useful. Hence my question. But if you could provide me an example of when pointer serialization shines, then I would say "Aha! Now I understand why Robert went to so much trouble to make this work.", and I could be at peace with the world again! :-) BTW, I don't want to sound like I'm bashing your library, so let me end with a compliment. I think the symmetric design of serialize(), with the same function used for both input and output, is one of the prettiest idioms I've seen in years. -- Dominick

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[boost::multi-index] improvement suggestion
by Ovanes Markarian 24 Aug '07

24 Aug '07

Hello all, working with boost multi-index container requires sometimes some effort in regards of correct tagging (or at least some typing work ;). I found the following approach to be useful and may be it can be integrated in the multi-index library. First of all the dealing with searchable collections (STL collections are no exception) can be really nasty in regards of finding an iterator and comparing it with the end iterator. The following function can really be of help: /// template function to dermine if the container contains the key specified /// @param T - container type /// @param K - key type /// @param container - container to search for a key /// @param key - key to be found in the container /// \return iterator_range containing the begin and end iterator of the found key. begin iterator equals end iterator the range is empty => nothing found template<class T, class K> inline boost::iterator_range<typename T::const_iterator> find_range(T const& container, K const& key) { return boost::make_iterator_range(container.find(key),container.end ()); } //non-const version follows as well ... Actually iterator_range defines a "bool"- and "!"- (NOT) operators. iterator_range is returned by this function. Therefore constructs like: std::set<std::string> some_set; if(!find_range(some_set, "my_key")) some_set.insert("my_key"); are possible without the need of accesing the underlying iterator types or explicitly comparing the found iterator with the end iterator. The next step dealing with Multi-Index container turned out in multiple typedefs for every tagged type. The main disadvantage in this approach was to constantly retrieve the required container view and related iterator, so I came up the the following class: /// helper class used to retrieve multi-index values dependent on the view tag template<class Tag_, class MultiIndex_> struct value_retrieval { /// type definition used to produce tag dependent view typedef typename MultiIndex_::index<Tag_>::type view_type; /// type definition for the const iterator through the view typedef typename view_type::const_iterator citer_type; /// iterator range used to represent the result typedef boost::iterator_range<citer_type> result_type; /// initializing ctor /// initializes the contained view by using the specified Tag_ type value_retrieval(MultiIndex_ const& mi) : view_(mi.get<Tag_>()) {} /// find a type at the key specified /// @param LookUpType_ - key type /// @param key - key instance to be found template<class LookUpType_> result_type at(LookUpType_ const& key)const { return find_range(view_, key); } private: /// view reference view_type const& view_; }; This class deals with constant views, since I did not require changeable ones, but as one can see the "at"-function can either be used to identify the found iterator range or just to make a check if such a key exists. Dealing with this type is more easier, as to define multi-index accessed view and iterator types. Sample typedef multi_index_container < some_type , indexed_by < .... > > my_container; typedef value_retrieval<my_container, tag_name> by_name; typedef value_retrieval<my_container, tag_value> by_value; //somewhere in code by_name value_by_name(some_container_inst); //if typename is required prefix it... by_name::result_type r = value_by_name.at("some key"); if(r) /// do smth with r Best Regards, Ovanes

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Serializeable Boost hashmap with vector<long> as key
by Oliver Kania 24 Aug '07

24 Aug '07

Hello ! I am looking for a hashmap that is boost::serializeable, has good performance and is implemented by boost-means. Furthermore, it must have vector<long> as key type. I tried multiindex, but it seems one cannot have keys that are not members of the value type. Boost Bimap is not serializeabel and i do not need the bimap functionality. regards, Oliver

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boost program_options "count" question
by F David Sacerdoti 24 Aug '07

24 Aug '07

As per Volodya's suggestion, posting this question here. He mentioned it had been discussed, but I was unable to find anything appropriate using search engines. I apologize in advance if this is a repeat question. Hi, I am trying to do a simple thing with your program_options boost library: I have a program foo, and I want to invoke it like this: foo -d -d -d I want foo to know "I have counted three -d". I followed your tutorial and tried this: desc.add_options() ("debug,d",po::value< vector<int> >()->default_value(1), "Debug level") ; po::variables_map vm; po::store(po::parse_command_line(argc, argv, desc), vm); po::notify(vm); if (vm.count("debug")) { cout << "Running, debug level: " << vm["debug"].as< vector<int> >().size() << "\n"; } But it did not work, always prints "debug level: 0". For background, this is to make the program compatible with a Python implementation which uses optparse. I have an extensive testing framework that assumes this behavior and it would be nice to implement the same with program_options. Thanks, Federico

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error C2976 in python tutorial?
by Guido Ziliotti 24 Aug '07

24 Aug '07

Probably Has anybody faced error C2976: 'boost::python::class_' : too few template arguments? Compiler msvc-8.0. BOOST_PYTHON_MODULE(hello){ class_<World>("World") .def("greet", &World::greet) .def("set", &World::set) ; } produced that. Source code follows. #include <string> char const* greet() { return "hello, world"; } struct World { void set(std::string msg) { this->msg = msg; } std::string greet() { return msg; } std::string msg; }; #include <boost/python/module.hpp> #include <boost/python/def.hpp> using namespace boost::python; //nota che la funzione globale va prima BOOST_PYTHON_MODULE(hello) { def("greet", greet); class_<World>("World") .def("greet", &World::greet) .def("set", &World::set) ; }

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[test] Uncaught exception in BOOST_CHECK_THROW() causing SIGABRT
by Richard Dingwall 24 Aug '07

24 Aug '07

Hi there, I thought I'd post this because A) it might save someone a lot of head-scratching and B) there aren't any posts on it already. The short of it is, that if you have a setup similar to the following (i.e., an empty throw() clause on a template specialisation): template<class output_type> output_type do_something(int input_value) throw(std::invalid_argument); template<> int do_something(int input_value) throw(std::invalid_argument); template<> long do_something(int input_value) throw(); And attempt to test throwing a std::invalid_argument from within the long specialised function, e.g.: // note: an argument less than zero will throw a std::invalid_argument BOOST_CHECK_THROW(do_something<long>(-1), std::invalid_argument); You will see something the following: Running 4 test cases... terminate called after throwing an instance of 'std::invalid_argument' what(): Input value too low. unknown location(0): fatal error in "long_throw": signal: SIGABRT (application abort requested) sigabrt_test_suite.cpp(58): last checkpoint *** 1 failure detected in test suite "sigabrt tests" My function is throwing a std::invalid_argument and my test case been programmed to catch it. But it doesn't. This had me scratching my head for a few days, until I noticed the empty throw() clause. Completing it resolved the problem immediately. I'm not sure if this is expected behaviour, but if anyone's interested, a test case is attached. I'm using gcc version 4.0.1 (Apple Computer, Inc. build 5367) on a G4 Powerbook with whatever was in Boost's SVN trunk on August 6. Cheers, Richard

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