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

Recommended linker order
by Michael Powell 19 Apr '13

19 Apr '13

Hello, So I am reading the article: http://www.boost.org/boost-build2/doc/html/bbv2/faq/liborder.html But I am not clear what this means? For instance, I'd like to put filesystem to use, but was finding linker errors there. Either could use filesystem issues, or std::string issues (<string>), but not both, for instance. No clue how that could even be possible. Build was also failing along similar lines, semantic and/or what I gather are linker failures. So... I get to specify the order CodeBench for Linux targeting ARM, wants to link libraries. Is there a specific order to include boost static libs that keeps the system happy? If so, what? Thank you... Regards, Michael Powell

2 1

heap handle invalidation
by ☂Josh Chia (谢任中) 19 Apr '13

19 Apr '13

Hi, I'm using a mutable heap, in particular a mutable d_ary_heap, for the priority queue in Djikstra's algorithm. When does a handle become invalid? I don't know how a d_ary_heap is implemented, but if it's like the standard array-backed binary heap, then I would expect invalidation of many handles whenever an item gets popped or an item gets increased or decreased. I need references to the elements in order to update them, so if the invalidation I expect does happen as I describe, how can I get permanent references/pointers/iterators to the elements? Perhaps another implementation besides d_ary_heap? Although I haven't profiled the performance, I think even though something like the fibonacci heap may have permanent handles, pointer chasing, more frequent cache misses and frequent dynamic memory allocation may be detrimental to performance. Which heap implementation supports key increase without handle invalidation? Josh

1 0

boost.log: update filters at runtime
by Jonathan Walker 18 Apr '13

18 Apr '13

Hello, I've been working on integrating the boost logger into my application for the past few days now. I'm looking for the ability to update filters at runtime based on settings from a file or other source. A specific use-case would be the ability to decrease a severity level during a debugging session for more detailed log reports without having to restart the application. Is there anything like this available in the current release? Is there any plan to incorporate this kind of functionality in future releases? Thanks, Jonathan ________________________________ This e-mail and any attachments are confidential. If it is not intended for you, please notify the sender, and please erase and ignore the contents.

1 0

[Range] size and list, for example.
by Robert Jones 17 Apr '13

17 Apr '13

I know this has come up before, so I'm really seeking to discover the current situation. boost::size( std::list<...> ) fails because the implementation of size is end - begin. I know I could use distance, but am surprised size(list) doesn't work out of the box. * So, is it correct that size(list) doesn't work? * Does distance(begin, end) specialise for random access iterators to O(n) performance? * Why doesn't size similarly specialise? Thx, Rob.

3 2

[filesystem] Using filesystem with std::string
by Michael Powell 17 Apr '13

17 Apr '13

Hello, Or vice versa. When I include <boost/filesystem.hpp> and <string>, uses of std::string fall over it seems. As long as I do not include filesystem.hpp, it's okay. Would like to use the filesystem features if possible, but I also want to keep track of some strings, possible override operator<< for various requirements (TBD). Is this a boost bug? Or what do I need to do to make it work? I am building against a static library, multithreading AFAIK, targeting ArchLinux ARM. Building against a GCC 4.7.2 toolchain (CodeBench). Thank you... Regards, Michael Powell

3 3

Re: [Boost-users] [graph] dijkstra additional constrains that will stop the search (ex. distance from source)
by a.hagen-zanker＠surrey.ac.uk 17 Apr '13

17 Apr '13

From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of The Maschine boost::dijkstra_shortest_paths(m_ugraph, *vertex_iterator_begin, boost::predecessor_map(predecessorMap).distance_map(distanceMap)); currently works ok. Finds the shortest path based on the "edge_weight" (this is what I need). The addition I need: I need the search for the shortest path to stop if outside a radius. (my graph is a street network). lets say max "travel distance" = 4 Source -> V1(length=1) -> V2(length=3) -> V3(length=2) -> V4(length=1) -> V5(length=1) ->VEnd The search should end on V3 and V3 should be "unreachable" from the source (V4,V5 and Vend should be unreachable too) The distance_map should have the distances for V1 and V2 based on the "edge_weight". This explanation seems to be better. Thanks Tasos Hi Tasos, You could consider that "unreachable" is the same as "d = travel distance". You could use a closed plus and a custom value for infinite distance. You would need to create a closed plus that is a bit more robust than the closed_plus currently in BGL, e.g.: struct robust_closed_plus { robust_closed_plus (double d) : d(d) {} double operator(double a, double b){ return (d-a < b) >? d : a+b; } double d; }; Then you can use dijkstra_shortest_path, using your travel distance as infinity. robust_closed_plus plusser(travel_distance); boost::dijkstra_shortest_paths(m_ugraph, *vertex_iterator_begin , boost::predecessor_map(predecessorMap) .distance_map(distanceMap) .distance_compare(plusser) .distane_inf(travel_distance); This should already give you the correct result, but will also make you visit more vertices than necessary. Still combine with a visitor like Jeremiah suggested before: struct hit_inf{}; template<typename DistanceMap> struct inf_quit_visitor: boost::default_dijkstra_visitor { inf_quit_visitor (DistanceMap dm, double inf) : dm(dm), inf(inf) {} template<typename V, typename G> void examine_vertex(V v, const G& g) { if (get(dm, v) == inf) throw hit_inf(); } DistanceMap dm; double inf; }; robust_closed_plus plusser(travel_distance); inf_quit_visitor<DistanceMap> quitter(distanceMap, travel_distance); try { boost::dijkstra_shortest_paths(m_ugraph, *vertex_iterator_begin, boost::predecessor_map(predecessorMap) .distance_map(distanceMap) .distance_compare(plusser) .distane_inf(travel_distance) .visitor(quitter) ); } catch(hit_inf&) { } Hope this helps, Alex

1 0

Boost for GPUs
by Blesson Varghese 17 Apr '13

17 Apr '13

Hi All I am new to using Boost libraries. I have written a function that makes use of the boost for computing the inverse of the cummulative distribution function of the beta distribution (quantile) in C++ which works fine. Now I would like to use the same function on the GPU, but I cannot call a host function from device. Are there any alternatives to use boost functions on GPU? Looking forward to your reply. Many thanks and kind regards Blesson

4 5

[timer] Error linking boost::chrono::steady_clock::now
by Michael Powell 16 Apr '13

16 Apr '13

Hello, I get the following linker error. Description Resource Path Location Type undefined reference to `boost::chrono::steady_clock::now()' detector line 0 C/C++ Problem I am using Boost 1.53. A little unclear what the docs are talking about. If I can go header only, and if it is advantageous to do so, I'd like to. http://www.boost.org/doc/libs/1_53_0/doc/html/chrono/users_guide.html#chron… However, not sure what else we're talking about here, when it talks about building boost with buggy header only support (?). Regards, Michael Powell

3 4

Re: [Boost-users] [graph] dijkstra additional constrains that will stop the search (ex. distance from source)
by The Maschine 16 Apr '13

16 Apr '13

:) My description of the problem is hopeless. The boost::dijkstra_shortest_paths(m_ugraph, *vertex_iterator_begin, boost:: predecessor_map(predecessorMap).distance_map(distanceMap)); currently works ok. Finds the shortest path based on the "edge_weight" (this is what I need). The addition I need: I need the search for the shortest path to stop if outside a radius. (my graph is a street network). lets say max "travel distance" = 4 Source -> V1(length=1) -> V2(length=3) -> V3(length=2) -> V4(length=1) -> V5 (length=1) ->VEnd The search should end on V3 and V3 should be "unreachable" from the source (V4,V5 and Vend should be unreachable too) The distance_map should have the distances for V1 and V2 based on the "edge_weight". This explanation seems to be better. Thanks Tasos

2 1

How to print boost::exceptions to ostream
by Michael Powell 16 Apr '13

16 Apr '13

Hello, Basically like the subject says. I need a way to print boost::exceptions through an ostream. Or std::exception if that's a better more portable route to take. Suggestions? Regards, Michael Powell

2 1

Need good semi-high-res timer
by Michael Powell 16 Apr '13

16 Apr '13

Hello, I am looking for a semi-high-res timer solution. Ideally, should be clock-agnostic, shouldn't see non-deterministic behavior in the face of NTP or GPS system or local time updates. Thus far attempts to use boost/timer/timer.hpp have been frustrated by what seems like the common occurrence linker issues. I've defined to use header only, but that doesn't seem to have fixed it. Or possibly I need to rebuild boost with that option? Or something along these lines. I'd like to use boost if that feature is available, and avoid clock-bound timers if at all possible. Recommendations? Thanks much. Regards, Michael Powell

1 0

Re: [Boost-users] boost asio daemon
by Marat Abrarov 16 Apr '13

16 Apr '13

Hi, Philipp. > io::io_service l_ioservice; > io::signal_set l_signals(l_ioservice, SIGINT, SIGTERM); > l_signals.async_wait(daemonhandler); // * > l_ioservice.run(); // ** > > void daemonhandler( const boost::system::Error_code& err ) { > if (!err) > do some log > else > do daemon work > } > > My question is, is the daemonhandler function a function that is called > only if the daemon is stopped or that is run during the daemon is active / > working? According to Boost.Asio docs (http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/core/basi cs.html) all callbacks (handlers) are executed (handler::operator() is called) within the threads running asio::io_service::run() (run_one/poll/poll_one). So at the execution point of the daemonhandler function at least one thread of daemon (thread of the daemon's process) runs. If the above code is the only place that executes asio::io_service::run() (see **) then daemonhandler function will be called within the same thread. And if (*) is the only pending async operation then continuation of execution of asio::io_service::run() depends on daemonhandler starting additional async operations on the same instance of asio::io_service (on l_ioservice). Regards, Marat Abrarov.

2 1

[timer] Examples do not compile
by Michael Powell 16 Apr '13

16 Apr '13

Hello, I am trying to setup a "simple" elapsed timer abstraction to hide the boost::timer::cpu_timer concern. However, I am finding that the usage example illustrated here does not compile, or I am not including something I need to include (more likely). http://www.boost.org/doc/libs/1_53_0/libs/timer/doc/cpu_timers.html#using-c… Might there be more complete working examples I can draw from? Thank you... Regards, Michael Powell

1 1

Re: [Boost-users] [graph] dijkstra additional constrains that will stop the search (ex. distance from source)
by The Maschine 16 Apr '13

16 Apr '13

Hi, Not really! (Im not that advance yet) Let me explain. 1) Every vertex in the graph has each own m_length value which is the 'length' of that node only. 2) from the "source" of the search, I want the search to extent to only the node in the radius from the source. So that "radius" cutoff should by something like adding all "m_length" of the route to the current node. At the moment my search only has a weight_map of the "Edge Weights" not some sort of "Vertex Weight". How should I proceed? Is this clear? Sorry for the confusion. Thanks Tasos > I had assumed you were using m_length as the distance map in Dijkstra's > algorithm, and so that would be the total distance you want to compare to. > Is that what you intended? If not, what are you using as your distance > map? > > -- Jeremiah Willcock > >

2 1

program_options allow_unregistered and *nix style
by Michael Powell 16 Apr '13

16 Apr '13

Hello, I would like to find a way to allow_unregistered program_options, as well as specify cls::unix_style ^ cls::allow_short, where cls is po::command_line_style. The code I've got here doesn't seem to like unrecognized ones: //vis_ are my visible options, vars_ is my variable map. po::store(parse_command_line(argc, argv, vis_, cls::unix_style ^ cls::allow_short), vars_); po::notify(vars_); And then a slight variation with apparently a way to do this (untested), how to specify that cls? // http://stackoverflow.com/questions/10178525/how-to-handle-unsolicited-param… po::parsed_options parsed_ = po::command_line_parser(argc, argv) .options(vis_).allow_unregistered().run(); Possible? Thank ye... Regards, Michael Powell

2 4

Re: [Boost-users] [graph] dijkstra additional constrains that will stop the search (ex. distance from source)
by The Maschine 16 Apr '13

16 Apr '13

Hi Jeremiah, As far as I understand this will examine only the "local" value (node length for example) against the threshold. In my path search I need to be able to find the "total length/distance" from the source to the vertex in question. Adding up the lengths (of the nodes that the path is passing) from source to current vertex and then tested against the threshold. Am I clear or my description is wrong? Thanks a lot, Tasos > Here's the basic idea (not tested); use this as your Dijkstra visitor, and > change the part labeled "threshold" to your threshold computation: > > struct threshold_visitor: boost::default_dijkstra_visitor { > double threshold; > > threshold_visitor(double threshold): threshold(threshold) {} > > struct hit_threshold {}; > > void examine_vertex(vertex_descriptor v, const unGraph& g) { > if (get(&VertexProperties::m_ref, g, v) > threshold) > throw hit_threshold(); > } > }; > > Remember to wrap your call to Dijkstra's algorithm in a try-catch block > for threshold_visitor::hit_threshold. > > -- Jeremiah Willcock > >

2 1

[graph] dijkstra additional constrains that will stop the search (ex. distance from source)
by The Maschine 16 Apr '13

16 Apr '13

Hi all, I've been reading around the list (Ill post examples below) but I dont really know how to implement the thing below. I want the search to be able to stop based on some "value" or "result of a function". For example, every node has a "length" value in a custom "struct VertexProperties". How is it possible for dijkstra_shortest_paths to only consider nodes that are inside a radius from the source? Everything else should be considered as 'unconnected'. I have checked a couple of posts form the list but I dont know what do really do. (function property map, exceptions in visitors etc) http://thread.gmane.org/gmane.comp.lib.boost.user/54392/focus=54397 http://thread.gmane.org/gmane.comp.lib.boost.user/72072/focus=72074 http://thread.gmane.org/gmane.comp.lib.boost.user/73358/focus=73384 I havent found any example or source online that deals with something similar. Any ideas? code example or tutorials? Best, Tasos my graph for example: struct VertexProperties { double m_length; int m_ref; }; typedef double Weight; typedef boost::property<boost::edge_weight_t, double> EdgeWeightProperty; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, VertexProperties, EdgeWeightProperty> unGraph;

2 1

Re: [Boost-users] [Graph] dijkstra_shortest_paths: weird distance to vertex (1.79769e+308)
by The Maschine 16 Apr '13

16 Apr '13

Hi Jeremiah, How do I eliminate cases like this? (not connected vertex) For you post I think you cannot use "isnan" or "isinfinate" right? My only option is colormap or predecessors? (I havent use them yet) Best, Tasos

2 1

boost asio daemon
by Philipp Kraus 16 Apr '13

16 Apr '13

Hello, I use boost::asio for creating a daemon, I do this: io::io_service l_ioservice; io::signal_set l_signals(l_ioservice, SIGINT, SIGTERM); l_signals.async_wait(daemonhandler); l_ioservice.run(); my daemonhandler shows: void daemonhandler( const boost::system::Error_code& err ) { if (!err) do some log } The daemon handler function is a function, that runs in a thread loop, does it? Can I create something like: void daemonhandler( const boost::system::Error_code& err ) { if (!err) do some log else do daemon work } My question is, is the daemonhandler function a function that is called only if the daemon is stopped or that is run during the daemon is active / working? Thanks Phil

1 0

Re: [Boost-users] [CMake] [boost][b2] Differenciate 32bit and 64 bit binaries when using CMake.
by Klaim - Joël Lamotte 16 Apr '13

16 Apr '13

Júlio Hoffimann said: > > I don't know if i understood correctly, but you can set the library > directory by hand, please refer to > /usr/share/cmake-<version>/Modules/FindBoost.cmake, in particular the > variable BOOST_LIBRARYDIR. On Thu, Oct 11, 2012 at 1:29 PM, Miller, Frank <FMiller(a)sjm.com> wrote: > A simple solution would be to install only the 64bit version of boost > into a new directory and change the environment variable to point there. > Then FindBoost will only be able to see the version you want. > Thanks, this will solve my immediate problem, but it don't solve it in general. (I will use it though, so thanks) I can't guarantee where the boost libraries are installed, that's why I use FindBoost. My current understanding is that boost don't have a specific default lib dir for different address models, which is the source of the problem as FindBoost script can't rely on a protocol to find these lib files. Am I correct? Joel Lamotte

3 8

PBGL Dijkstra's Single Source Shortest Path
by claire eisner 15 Apr '13

15 Apr '13

Is there a way to access the shortest path from source to target? The issue I am having is that only the local portions of the predecessor maps are written. Claire

1 0

MSM: Initialize inner state machine from outer state machine
by Dan Schatzberg 15 Apr '13

15 Apr '13

Hi, I have shared data between states which are state machines themselves. I've stored the shared data in the outer state machine and wish to initialize each of the inner state machines with a reference to the shared data. Is this the "right way" to do this? How would I do this? Here's an example of what I'm doing: struct Outer_ : state_machine_def<Outer_> { int foo; struct Inner_ : state_machine_def<Inner_> { int& foo; Inner_(int& f) : foo(f) {} ... } ... } How do I get the inner state machines constructor called with data from the outer state machine? Or is this just the wrong way to do things? Thanks

2 1

[serialization] EOF marker?
by Ramey, Larry 15 Apr '13

15 Apr '13

Is there a way to serialize an unknown number of items and then read them back? In essence, I'd like to do this: Ignore the variables being serialized, these are pointers to base classes, they go in and out just fine. try { ofstream ofs(fileName.c_str(),ios::binary); portable_binary_oarchive oa(ofs); //boost::archive::text_oarchive oa(ofs); oa<<qdc <<qdf <<qdenv <<qdmsg <<qsd <<qdfc <<qdce; } catch(boost::archive::archive_exception& ae) { cout<<ae.what(); } try { ifstream ifs(fileName.c_str(),ios::binary); portable_binary_iarchive ia(ifs); //boost::archive::text_iarchive ia(ifs); while( true ) { ia>>qdc2; cout<<qdc2->GetElementDebugType()<<endl; delete qdc2; qdc2=NULL; } } catch(boost::archive::archive_exception& ae) { cout<<ae.what(); } catch( std::exception& e) { cout<<e.what(); } What happens is that an exception gets tossed with this message: 5 2 14 1 3 18 Access violation - no RTTI data! The numbers are correct, those are the elements that got serialized. I'd like to do something like: while( ia ) { Ia>>qdc2; } But there is no () operator on an portable_binary_iarchive . I tried to do the test on the input stream, but that didn't work either. I don't know how many elements there are because I'm writing them as I go, I don't want to catch that exception as the EOF marker, because it really isn't the correct exception for that. I tried walking through the serialization code to see where it actually reads a byte stream form the file... but I'm apparently not smart enough to unravel that much templated Macro awesomeness. :) Larry E. Ramey

2 3

Compile error in boost atomic on iOS
by Olivier Tristan 15 Apr '13

15 Apr '13

Hi Guys, I'm trying to use boost lockfree and a fixed size queue on iOS and I got some compile issue. The target is an armV7 compiled with clang in c++11 mode from Xcode 4.6 Does this ring a bell to someone ? Thanks, In file included from /usr/local/include/boost/lockfree/queue.hpp:22: In file included from /usr/local/include/boost/lockfree/detail/atomic.hpp:39: In file included from /usr/local/include/boost/atomic.hpp:12: In file included from /usr/local/include/boost/atomic/atomic.hpp:16: In file included from /usr/local/include/boost/atomic/detail/platform.hpp:37: In file included from /usr/local/include/boost/atomic/detail/gcc-armv6plus.hpp:245: /usr/local/include/boost/atomic/detail/cas32weak.hpp:892:21: error: invalid operands to binary expression ('value_type' (aka 'boost::lockfree::detail::tagged_index') and 'value_type') if (tmp != expected) { ~~~ ^ ~~~~~~~~ /usr/local/include/boost/atomic/detail/cas32weak.hpp:905:5: note: in instantiation of member function 'boost::atomics::detail::base_atomic<boost::lockfree::detail::tagged_index, void, 4, false>::compare_exchange_strong' requested here BOOST_ATOMIC_DECLARE_BASE_OPERATORS ^ /usr/local/include/boost/atomic/detail/base.hpp:44:16: note: expanded from macro 'BOOST_ATOMIC_DECLARE_BASE_OPERATORS' return compare_exchange_strong(expected, desired, order, calculate_failure_order(order)); \ ^ /usr/local/include/boost/lockfree/queue.hpp:290:31: note: in instantiation of member function 'boost::atomics::detail::base_atomic<boost::lockfree::detail::tagged_index, void, 4, false>::compare_exchange_strong' requested here tail_.compare_exchange_strong(tail, new_tail); ^ /usr/local/include/boost/lockfree/queue.hpp:261:16: note: in instantiation of function template specialization 'boost::lockfree::queue<StreamingCommand, boost::lockfree::fixed_sized<true>, boost::lockfree::capacity<1024>, boost::parameter::void_>::do_push<true>' requested here return do_push<true>(t); -- Olivier Tristan

1 0

[preprocessor] Is there an equivalent of "delayed expansion"?
by Mostafa 15 Apr '13

15 Apr '13

Is there an equivalent in boost for delaying the expansion of a macro? For example, I want EAT to act on TSEQ2, so I have to use trick on line 4. #define TSEQ2 (w)(x)(y)(z)(a)(b)(c)(d 2) #define IDENTITY(x) x #define EAT(x) IDENTITY(IDENTITY(EAT)TSEQ2) Thanks, Mostafa

2 2

[Graph] dijkstra_shortest_paths: weird distance to vertex (1.79769e+308)
by The Maschine 15 Apr '13

15 Apr '13

Hi all, Might be something really stupid but I cant think of a problem. (maybe its my limited experience with BGL common pitfalls) for (boost::tie(vi, vi_end) = boost::vertices(m_ugraph); vi != vi_end; ++vi) { depth += distances[*vi]; ..... path to:51886 distance to that node: 16.2 current total: 437998 path to:51887 distance to that node: 16.3 current total: 438014 path to:51888 distance to that node: 16.2 current total: 438031 path to:51889 distance to that node: 16.2 current total: 438047 path to:51890 distance to that node: 16.1 current total: 438063 path to:51891 distance to that node: 16.2 current total: 438079 path to:51892 distance to that node: 1.79769e+308 current total: 1.79769e+308 path to:51893 distance to that node: 16.3 current total: 1.79769e+308 path to:51894 distance to that node: 13.8 current total: 1.79769e+308 path to:51895 distance to that node: 13.9 current total: 1.79769e+308 I have checked my weights: if(edge_w<=0.0) edge_w = 0.1; if(edge_w >2.0) edge_w = 2.0; if( !(std::isnan(edge_w)) ) edge_w = 0.1; if( !(std::isfinite(edge_w)) ) edge_w = 0.1; boost::dijkstra_shortest_paths(m_ugraph, *vertex_iterator_begin, boost::distance_map(distanceMap)); typedef double Weight; typedef boost::property<boost::edge_weight_t, double> EdgeWeightProperty; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, VertexProperties, EdgeWeightProperty> unGraph; Any ideas? Thanks a lot Tasos

2 1

Re: [Boost-users] [Graph] dijkstra_shortest_paths: weird distance to vertex (1.79769e+308)
by The Maschine 15 Apr '13

15 Apr '13

This is not in my actual code! and not risponsible for my problem. Its incorrect from the copy/paste. !(std::isnan(edge_w)) its: std::isnan() Tasos

1 0

Accessing members from a shared pointer passed as argument to a function gives incorrect results without typecast
by Deepak Gunjal 15 Apr '13

15 Apr '13

Hi, class A; class B; typedef boost::shared_ptr<A> pSharedPtrA; typedef boost::shared_ptr<B> pSharedPtrB; class B { public: int memberB; }; Class A { public: pSharedPtrB pMember; }; Suppose i have one shared pointer of type pSharedPtrA pointing to an object of class A and the member variable pMember pinging to a valid object of class B. Now if i pass the shared pointer of type pSharedPtrA to a function suppose Test_Func(pSharedPtrA): void Test_Func(pSharedPtrA pLocalA) { pSharedPtrA ptrA = boost::static_pointer_cast<A> (pLocalA) pSharedPtrB tmpB = boost::static_pointer_cast<B>(ptrA->pMember) Another_Func(tmpB) } Another_Func(pSharedPtrB pLocalB) { int x = pLocalB->memberB; //Gives WRONG value pSharedPtrB ptmp = boost::static_pointer_cast<B> (pLocalB) x = ptmp ->memberB; //Gives CORRECT Value } The problem is when typecast is not used then in function Another_Func(pSharedPtrB pLocalB), pLocalB->memberB is not giving the correct result but after typecast it is giving the correct results. The inference is that in function Another_Func() data is preserved in the pLocalB but without typecast i am not able to access it. Though i have not declared any virtual functions in above code but where we are having problem does contain the vritual functions. I dont know if it has any bearing on behavior observed. I want to know why typecasting is required to get the correct result and why cant i access the members without typecasting. Thanks and Regards Deepak

2 1

unit test on vc++ 64 bit application
by young 15 Apr '13

15 Apr '13

I try to use boost 1.51 for my vc++ 64 bit application on windows 7 enterprise. In short, if I set config to 32 bit, everything is OK. I mean build successfully. But if I changed to 64 bit, I get build error. I am sure I include the 64 bit header and the lib path is 64 bit lib. My test application is win32 console application. The error I got: Error 1 error LNK2019: unresolved external symbol main referenced in function __tmainCRTStartup D:\Temp\test\test\MSVCRTD.lib(crtexe.obj) test My test.cpp: #define BOOST_TEST_MAIN #include <boost/test/unit_test.hpp> Why 32 bit build and 64 bit would not? The library I used is from www.boostpro.com. -- View this message in context: http://boost.2283326.n4.nabble.com/unit-test-on-vc-64-bit-application-tp464… Sent from the Boost - Users mailing list archive at Nabble.com.

3 7

Unit Test for vc++ exe project possible?
by young 15 Apr '13

15 Apr '13

I see a good tutorial for Boost Test using Visual Studio. (http://legalizeadulthood.wordpress.com/2009/07/04/c-unit-tests-with-boost-t…) But it looks like only forstatic or dynamic library. Is that possible to unit test the exe production project using Boost Test? If yes, how? Any link for tutorial, etc? -- View this message in context: http://boost.2283326.n4.nabble.com/Unit-Test-for-vc-exe-project-possible-tp… Sent from the Boost - Users mailing list archive at Nabble.com.

2 1

Boost.Test : Project setting in Visual 2010
by Oodini 15 Apr '13

15 Apr '13

Hello, I am trying to setup in Visual C++ 2010 some projects to use Boost.Test. I have a project with some classes I want to test. This project builds a static library. I put in this project a test file ; here is its content : #define BOOST_TEST_MODULE MyTest #include <boost/test/unit_test.hpp> BOOST_AUTO_TEST_CASE(Test1) { BOOST_REQUIRE(false); } I created an other project (a console program). Its content is : #define BOOST_TEST_MAIN #include <boost/test/unit_test.hpp> In its properties, I linked it to the first project, trough Common Properties -> Framework and references. When I execute this program, I get the message "test tree is empty". How should I setup me projects ? I can't find clear documentation about this subject. Thanks a lot.

5 11

Re: [Boost-users] [boost][thread] Future returning 0xfeeefeee
by Stefan Strasser 14 Apr '13

14 Apr '13

Zitat von Klaim - Joël Lamotte <mjklaim(a)gmail.com>: > On Sun, Apr 7, 2013 at 1:02 AM, Klaim - Joël Lamotte > <mjklaim(a)gmail.com>wrote: > >> So the promise is destroyed before setting the value to the future. > > > Sorry, I meant: the promise is (a priori) guaranteed to be destroyed AFTER > having set the value to the future. > > Joel Lamotte > I was under the impression that the promise object itself has to be alive when the future result is used. and since you're emptying your queue on execution it's not. but considering that the promise object could be in another thread that was probably a false impression. Which compiler does this even work with yet? Both gcc and clang fail. clang on compilation, gcc compiles it but fails at runtime with a system_error exception and an invalid error code. so you might wanna consider compiler and library bugs, too.

4 19

Re: [Boost-users] Can I implement asynchronous and non-blocking socket IO with boost.asio on LINUX?
by Marat Abrarov 14 Apr '13

14 Apr '13

> I think this implementation looks similar to ACE. The proactor > implementation varies depends on platforms. ACE uses native asynch IO > features for Windows, Solaris but not for LINUX. > I wanted to know if boost.asio implements asynch IO for LINUX not like > ACE. RTFM? http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/overview/implementa tion.html > Then does proactor of boost.asio on LINUX work well? If it is portable I > guess it should though. > > Do people use proactor of boost.asio on LINUX? http://think-async.com/Asio/WhoIsUsingAsio As far as I know, the best performance at Linux can be achieved using "io_service-per-CPU design": http://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/examples.html#boost _asio.examples.http_server_2 Regards, Marat Abrarov.

2 1

Can I implement asynchronous and non-blocking socket IO with boost.asio on LINUX?
by Journeyer J. Joh 14 Apr '13

14 Apr '13

Can I implement asynchronous and non-blocking (overlapped) socket IO with boost.asio on LINUX? If so please provide me some information for that. Thank you in advance! Best regards ---------------------------------------- Journeyer J. Joh o o s a p r o g r a m m e r a t g m a i l d o t c o m ----------------------------------------

3 3

C++ and/or boost analog to .NET System.Version
by Michael Powell 13 Apr '13

13 Apr '13

Hello, I am curious is there an analog to System.Version in .NET? http://msdn.microsoft.com/en-us/library/system.version.aspx Basically a cloneable, comparable, equatable version composed of major, minor, build, revision. Or patch, build, or however you'd like to decompose the fields. I don't think it'd be hard to cook one up using say tuple<int, int, int, int> for instance, but if one already exists I'd like to save the effort. Thanks! Regards, Michael Powell

3 2

Issue with asio::serial_port - async_write_some handler isn't firing
by Alex McClung 13 Apr '13

13 Apr '13

Hi, I'm trying to get a simple application up and running that sends and receives simple commands through a COM port to an Arduino hooked up to some sensors. Right now, I'm just trying to send the Arduino a simple command through a boost::asio::serial_port instance, although at some point I'll need to start reading from it as well. At any rate, I think I've got the basic premise down, but for some reason the WriteComplete function (see code below) isn't being called. After running the program, the output is: Open Sending command '.' Press any key to continue. I'm not 100% sure what's going on. The only thing I can think of is that the boost::asio::buffer(&command, sizeof(command)) statement is wrong. I'm not very familiar with these libraries, though, so I don't know what I would replace it with. I've included the code I'm using in case anyone can help me out. Thanks, -Alex --- #include "stdafx.h" #include <iostream> #include <boost\bind.hpp> #include <boost\asio.hpp> using namespace std; boost::asio::io_service gService; boost::asio::serial_port gPort(gService); void WriteComplete(const boost::system::error_code& error, std::size_t bytes_transferred) { cout << "Write complete." << endl; gPort.close(); } int _tmain(int argc, _TCHAR* argv[]) { gPort.open("COM3"); if(!gPort.is_open()) { cout << "Could not open com port." << endl; return 0; } cout << "Open" << endl; typedef boost::asio::serial_port_base asio_serial; gPort.set_option( asio_serial::baud_rate( 9600 ) ); gPort.set_option( asio_serial::flow_control( asio_serial::flow_control::none ) ); gPort.set_option( asio_serial::parity( asio_serial::parity::none ) ); gPort.set_option( asio_serial::stop_bits( asio_serial::stop_bits::one ) ); gPort.set_option( asio_serial::character_size( 8 ) ); char command = '.'; cout << "Sending command '" << command << "'" << endl; gPort.async_write_some( boost::asio::buffer(&command, sizeof(command)), boost::bind( &WriteComplete, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred ) ); cout << "Press any key to continue."; cin.ignore(); cin.get(); return 0; }

2 1

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 13 Apr '13

13 Apr '13

> > Actually, I try to use template variadic functions which can contains references, pointers and/or values which must be converted to boost::function0<void>. > > I tried to use forward() but I lose references with it. I tried ref() to but it make values interpreted as references (so ints are broken). So I'm looking for a magic way to use ref() only when needed by the arguments. > What do you mean by "when needed by the arguments?" How do you specify what should have ref added and what shouldn't? Well, I tried to make a template pseudo-code to determine which function it needs to use. Like this code that does not work: ///// Big code to make it working template<typename W,typename T> struct SignalArgumentValueConverter { }; template<typename T> struct SignalArgumentValueConverter<const boost::reference_wrapper<T>,T> { static const boost::reference_wrapper<T> convert(T&& t) { return boost::ref<T>(t); } }; template<typename T> struct SignalArgumentValueConverter<T&&,T> { static T&& convert(T&& t) { return std::forward<T&&>(t); } }; template<typename T> struct SignalArgumentTypeConverter { typedef typename std::conditional<std::is_reference<T>::value,const boost::reference_wrapper<T>,T&&>::type type; static type convert(T&& t) { return SignalArgumentValueConverter<type,T>::convert(std::forward<T&&>(t)); } }; ////// Little code to use it // Note: current is an iterator on a std::vector< boost::function<void(Args…)> > (*current)( SignalArgumentTypeConverter<Args>::convert(boost::forward<Args>(args))... ); This code does not compile and I think that I may break its code while I made some tests. Any idea to create something lile that (or even better) ? Regards, Yannick POTIN

1 0

[program_options] Possible to compose notifier to void void function?
by Michael Powell 13 Apr '13

13 Apr '13

Hello, Is it possible? Something like the example identified here: http://stackoverflow.com/questions/7125666/what-is-boostprogram-optionsnoti… Except I'd like to hook up a void(void) notifier handler instead of the parameter. Thank ye... Regards, Michael Powell

2 1

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

> > >> template<class ...classes> >> boost::function0<void> call_something(classes&... c) > > Thank you, It actually allows me to use references in these functions. > I just tried and g++ is waiting for only references but I need to use pointers and/or values too. > There is a way to use mixed types in template variadic functions ? > For perfect forwarding use: template<class... T> void call(T&&... t) { foo(std::forward<T>(t)...); } I tried this one too and it works fine thank you. However, I use these functions with boost::bind library and actually references are lost when I use it (and I need to). After some google searches, it seems that boost::bind officially does not support this use (due to internal references). So I tried with std::bind because I read somewhere the problem was fixed with its C++11 version. The problem is the same : with std::bind too, references are lost using std::forward. Does anyone made this duo bind/template variadic functions working together ? And if someone did, how did you do ? Sorry, I lost context with what you're trying to do, but maybe you want to use boost::ref / std::ref in conjunction with boost::bind / std::bind, respectively? I think that should indicate to the binding framework to hold the bound values by reference rather than by value (if that's what you want). - Jeff Actually, I try to use template variadic functions which can contains references, pointers and/or values which must be converted to boost::function0<void>. I tried to use forward() but I lose references with it. I tried ref() to but it make values interpreted as references (so ints are broken). So I'm looking for a magic way to use ref() only when needed by the arguments. Regards, Yannick POTIN

2 1

Difficulty using promises and futures
by Michael Powell 12 Apr '13

12 Apr '13

Hello, I would like to use promises and futures in our embedded app. We're targeting ArchLinux ARM. I believe we can build against a GCC 4.7.2 toolchain which has either C++0x or possibly even C++11 (somewhat) support. I am trying to setup a couple of simple issues to make it even compile, but am having trouble. boost::packaged_task<vector<int> > int_vect_pt_(simple_vector_getter); boost::unique_future<vector<int> > int_vect_f_ = int_vect_pt_.get_future(); boost::thread task(boost::move(int_vect_pt_)); boost::packaged_task<int> int_pt_(simple_getter); boost::unique_future<int> int_f_ = int_pt_.get_future(); boost::thread task(boost::move(int_pt_)); Error(s): Description Resource Path Location Type 'boost::move' is ambiguous ' Candidates are: boost::type move(boost::packaged_task<int> &) ' optics.cpp /detector/devices line 156 Semantic Error Description Resource Path Location Type 'boost::move' is ambiguous ' Candidates are: boost::type move(boost::packaged_task<std::vector<int,std::allocator<int>>> &) ' optics.cpp /detector/devices line 152 Semantic Error Can anyone help or otherwise advise? I've even got a "crude" future implementation in C# .NETCF for pity's sake... Anyway, if necessary, what did we do before promises/futures? ;-) Thank you... Regards, Michael Powell

2 3

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

> >> template<class ...classes> >> boost::function0<void> call_something(classes&... c) > > Thank you, It actually allows me to use references in these functions. > I just tried and g++ is waiting for only references but I need to use pointers and/or values too. > There is a way to use mixed types in template variadic functions ? > For perfect forwarding use: template<class... T> void call(T&&... t) { foo(std::forward<T>(t)...); } I tried this one too and it works fine thank you. However, I use these functions with boost::bind library and actually references are lost when I use it (and I need to). After some google searches, it seems that boost::bind officially does not support this use (due to internal references). So I tried with std::bind because I read somewhere the problem was fixed with its C++11 version. The problem is the same : with std::bind too, references are lost using std::forward. Does anyone made this duo bind/template variadic functions working together ? And if someone did, how did you do ? Regards, Yannick POTIN

2 1

Document for static / dynamic library?
by young 12 Apr '13

12 Apr '13

How do I know which library have both dynamically linked library and static linked library? I heard of there may be some libraries that can only be statically linked (Boost.Test for example) and others which may only be dynamically linked (Boost.Threads for example), Does any document has the list for available library? Or I have to look at each library individually? -- View this message in context: http://boost.2283326.n4.nabble.com/Document-for-static-dynamic-library-tp46… Sent from the Boost - Users mailing list archive at Nabble.com.

1 0

boost_thread-vc100-mt-1_53.lib vs libboost_thread-vc100-mt-1_53.lib
by young 12 Apr '13

12 Apr '13

I try to use boost library in VC++ application, I am wondering which library to use. For example, for boost thread, should I use boost_thread-vc100-mt-1_53.lib or libboost_thread-vc100-mt-1_53.lib? What is difference between them? or in more general, what is difference between boost_xxx_vc100-mt-1_53.lib and libboost_xxx_vc100-mt-1_53.lib? -- View this message in context: http://boost.2283326.n4.nabble.com/boost-thread-vc100-mt-1-53-lib-vs-libboo… Sent from the Boost - Users mailing list archive at Nabble.com.

5 12

Re: [Boost-users] Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

AMDG On 04/11/2013 01:57 PM, Yannick POTIN wrote: > > <snip> > > // A template variadic function... > template<class ...classes> > boost::function0<void> call_something(classes... c) { > // ... here we are: > return boost::bind(call_a,boost::ref(c...)); > } > > <snip> > ---------------------------------------------- > After compilation, I get this output (watch the memory addresses): > 0xbfc8f994::operator()(): 1 > 0xbfc8f990::operator()(): 2 > 0xbfc8f984::operator()(): 1 > 0xbfc8f984::operator()(): 2 > I really don't know what happened (even if I can imagine). > But references are just lost and this is not good. > > So, here is my question: How can I make this working ? > The arguments of call_something are passed by value. Try: template<class ...classes> boost::function0<void> call_something(classes&... c) In Christ, Steven Watanabe Thank you, It actually allows me to use references in these functions. I just tried and g++ is waiting for only references but I need to use pointers and/or values too. There is a way to use mixed types in template variadic functions ? Regards, Yannick POTIN

2 1

[preprocessor] How to transform sequence into sequence of tuples.
by Mostafa 12 Apr '13

12 Apr '13

How would I go about doing the following transformation: (a)(b)(c)(d) -> (a, b)(c, d) Thanks, Mostafa

3 5

Asio Serial ports: enumerating all the devices
by Vincent Boucher 12 Apr '13

12 Apr '13

Hello, Are there cross-platform methods to discover all the devices currently connected through serial ports with Boost? The idea is to have a function returning a list of device objects, each containing a handle, the related vendor id, product id and the baud rate at which the device was able to communicate. My knowledge of serial communication is very limited, may be it is technically infeasible. Do you have any thoughts for Boost or other libs? Analog enumerate method for HID devices: http://www.signal11.us/oss/hidapi/ Thanks, Vincent

5 13

Bind/Function: use reference arguments in template variadic functions
by Yannick POTIN 12 Apr '13

12 Apr '13

Hello, I'm working on a little project which use the template variadic technology. I use them with boost::bind and boost::function and found a very annoying bug. Because I have a lot of files very long and (sorry :-( ) uncommented. I made a simple but explicit example like this one : ---------------------------------------------- #include <boost/function.hpp> #include <boost/bind.hpp> #include <iostream> // A classic class... class A { public: // ... with a constructor A(int a) : a(a) { } // ... an operator void operator()() { std::cout << (void*)this << "::" << __func__ << "(): " << a << std::endl; } // ... and a member int a; }; // A stupid function... void call_a(A &a) { // ... which do something usefull // please not that this function NEEDs a reference a(); } // A template variadic function... template<class ...classes> boost::function0<void> call_something(classes... c) { // ... here we are: return boost::bind(call_a,boost::ref(c...)); } // Ok, this one, I think you know it more than I do int main(void) { // Let's create some objets A a1(1); A a2(2); // Call them to print the memory // position (see A::operator()()) a1(); a2(); // Create a boost::function0<void> and call it call_something<A>(boost::ref(a1))(); // Again call_something<A>(boost::ref(a2))(); return 0; } ---------------------------------------------- After compilation, I get this output (watch the memory addresses): 0xbfc8f994::operator()(): 1 0xbfc8f990::operator()(): 2 0xbfc8f984::operator()(): 1 0xbfc8f984::operator()(): 2 I really don't know what happened (even if I can imagine). But references are just lost and this is not good. So, here is my question: How can I make this working ? May I precise that this example only use one argument but my project actually use at most five so the boost::ref() call like in the call_something function is impossible (and does not work anyway). Before someone ask me if I can use pointer instead, I answer: Yes I can, but it will take a lot of time and if I can avoid this, I will. Thank you for reading, for your patience and for your answers ;-) Regards, Yannick POTIN

2 1

Re: [Boost-users] [multiprecision] radix-2
by Lucas Sousa de Oliveira 12 Apr '13

12 Apr '13

Hey Paul, First of all, thanks for the tips, it did help a lot. But would you mind if I use you a little more to get up to speed with this project? Answering your first question, yes, I'm studying to the best of my capacities and time-constrains. I found the PDF a little too succint though. If you had some more recommended literature, I'd be very happy to read it. I took a brief look at the present library's code but I must confess I got a little confused. Probably because I was too unprepared. I'll do that again when I experiment a little more with the examples and know exactly what to look for. I did a couple of quick tests to see if my setup is working fine (it is). I tested it using some Boost.Math functions as suggested, but I reckon the test was not solid enough yet. I'll search for a few known big numbers and way to compute them tomorrow. I think it's more convenient (not to overuse the list) to put my files here (https://bitbucket.org/luk51000/multiprecision) It's currently empty since I my git broke today and I didn't have time to fix it, but I should be pushing code as soon as tomorrow. -- Lucas Oliveira On Wed, Apr 10, 2013 at 2:01 PM, <boost-users-request(a)lists.boost.org>wrote: > Send Boost-users mailing list submissions to > boost-users(a)lists.boost.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.boost.org/mailman/listinfo.cgi/boost-users > or, via email, send a message with subject or body 'help' to > boost-users-request(a)lists.boost.org > > You can reach the person managing the list at > boost-users-owner(a)lists.boost.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Boost-users digest..." > > > Today's Topics: > > 1. Re: Asio Serial ports: enumerating all the devices > (Kerry, Richard) > 2. Re: [BGL] Error using breadth_first_search with labeled_graph > (Jeremiah Willcock) > 3. Re: [multiprecision] radix-2 (Paul A. Bristow) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 10 Apr 2013 13:22:14 +0000 > From: "Kerry, Richard" <richard.kerry(a)atos.net> > To: "boost-users(a)lists.boost.org" <boost-users(a)lists.boost.org> > Subject: Re: [Boost-users] Asio Serial ports: enumerating all the > devices > Message-ID: > < > 61C67DC73308BD49B2D4B65072480DBA15397181(a)DEFTHW99EZ1MSX.ww931.my-it-solutions.net > > > > Content-Type: text/plain; charset="us-ascii" > > > "vendor id, product id " > What's that ? > I mean for a serial device. If they are present in the device protocol > then fine, but that depends on the individual devices and their protocols. > You can check whether there has been any traffic, which might be useful, > but serial connections are just streams of bytes. > > > Unhelpfully, > Richard. > > > PS > I do recognize "vendor id, product id " for SNMP and for other protocols > working at a higher level than "serial". > > > > > > ________________________________ > From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf > Of Vincent Boucher > Sent: 10 April 2013 13:40 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] Asio Serial ports: enumerating all the devices > > Hello, > > Are there cross-platform methods to discover all the devices currently > connected through serial ports with Boost? > > The idea is to have a function returning a list of device objects, each > containing a handle, the related vendor id, product id and the baud rate at > which the device was able to communicate. > > My knowledge of serial communication is very limited, may be it is > technically infeasible. Do you have any thoughts for Boost or other libs? > > > Analog enumerate method for HID devices: > http://www.signal11.us/oss/hidapi/ > > Thanks, > > Vincent >

1 0

"Simple" graceful stop of boost thread
by Michael Powell 11 Apr '13

11 Apr '13

Hello, I know this is possible, just don't have all the templates at the ready. Graceful way of stopping a boost worker thread from running. I am familiar with C# .NET threading, I can fairly simply signal an AutoResetEvent, for instance, and wait a nominal period for it to be set. Afterwards, this tells the thread to stop what it's doing at an opportune moment. Meanwhile the parent thread is joining the worker thread(s) back up. Something like that. I just need a few tips what concept to link up: i.e. mutex? shared_mutex? lock? shared_lock? I'll have a start_work, stop_work, and working type motif going on. I call start_work to start the working thread going. Simple enough. I will call stop_work to signal the worker thread(s) to stop and join up with the worker threads. Somewhere in between the worker thread is polling the lock does it need to stop, do it's work, then back around again. And so on... Thank you... Regards, Michael Powell

3 3

Confirm required libs for boost
by Michael Powell 11 Apr '13

11 Apr '13

Hello, I believe I've identified them, but wanted to make sure. We're targeting ArchLinux ARM. Thus far, I am using boost for chrono (date/time) and threading are the two major features needing special attention in my build settings. I've identified libraries to link against: rt, pthread (from my toolchain), boost_system, boost_date_time, and boost_thread. Build seems satisfied with those issues at the moment, 'course I haven't run anything on our target. That I know of, most everything is statically linked, except rt and the pthread issue, which probably need a package for deployment, or to manually copy to target. Sounds about right? Regards, Michael Powell

2 1

Error messages during configuration checks
by Braden McDaniel 11 Apr '13

11 Apr '13

I'm seeing these error messages interspersed with the normal output of the Boost build's configuration checks: > Performing configuration checks > - x86 : yes > has_icu_test.cpp > libs\regex\build\has_icu_test.cpp(12) : fatal error C1083: Cannot open include file: 'unicode/uversion.h': No such file or directory > - has_icu builds : no > warning: Graph library does not contain MPI-based parallel components. > note: to enable them, add "using mpi ;" to your user-config.jam > has_iconv.cpp > libs\locale\src\..\build\has_iconv.cpp(8) : fatal error C1083: Cannot open include file: 'iconv.h': No such file or directory > - iconv (libc) : no > has_iconv.cpp > libs\locale\src\..\build\has_iconv.cpp(8) : fatal error C1083: Cannot open include file: 'iconv.h': No such file or directory > - iconv (separate) : no > has_icu_test.cpp > libs\locale\src\..\build\has_icu_test.cpp(12) : fatal error C1083: Cannot open include file: 'unicode/uversion.h': No such file or directory > - icu : no > has_icu_test.cpp > libs\locale\src\..\build\has_icu_test.cpp(12) : fatal error C1083: Cannot open include file: 'unicode/uversion.h': No such file or directory > - icu (lib64) : no > has_gcc_visibility.cpp > libs\math\config\has_gcc_visibility.cpp(7) : fatal error C1189: #error : "This is a GCC specific test case". > - gcc visibility : no > - long double support : yes I don't recall seeing these when building Boost previously (using the same compiler, Visual C++ 2008); though it's possible I'm misremembering and they're just sticking out more now. What I have started doing differently is that I'm now calling b2 from a CMake script (via execute_process); but if that's what's triggering this, I don't understand how. Has anyone here seen this before? How might these error messages be suppressed? -- Braden McDaniel braden(a)endoframe.com

2 2

ASIO file monitoring help
by SRD 11 Apr '13

11 Apr '13

I'm using an ASIO extention that was suggested for file monitoring. I've added this to my project and though I see a change when I add a file to the directory being monitored, I see no futher changes thereafter. Can anyone offer some insight as to how this should work? Any help much appreciated. void create_file_handler(const boost::system:error_code &ec, const boost::asio::dir_monitor_event &ev) { cout << "file name: " << ev.filename << endl; cout << " type : " << ev.type << endl; // now edit file ... } // from within main() boost::thread t; { boost::asio::io_service io_service; boost::asio::dir_monitor dm(io_service); dm.add_directory("C:\\Users\\SRD\\DirA"); boost::asio::dir_monitor_event ev = dm.monitor(); dm.async_monitor(create_file_handler); t = boost::thread(boost::bind(&boost::asio::io_service::run, boost::refio_service))); boost::system_time time = boost::get_system_time(); time += boost::posix_time::time_duration(0, 0, 1); boost::thread::sleep(time); } t.join(); io_service.reset(); // now do app stuff ..

3 2

How is the proactor pattern of boost.asio implemented in linux?
by Journeyer J. Joh 11 Apr '13

11 Apr '13

Hi list, I am wondering about boost.asio. Boost.asio must have a proactor implementation on Linux, I guess. How does the proactor of boost.asio work? Does it use epoll? Is it edge-triggered? What about real-time signal? Doesn't boost.asio use real-time signal on Linux? What is the recommended implementation of boost.asio for asynchronous and non-blocking overlapped IO on Linux? Thank you in advance! ---------------------------------------- Journeyer J. Joh o o s a p r o g r a m m e r a t g m a i l d o t c o m ----------------------------------------

1 0

[BGL] Error using breadth_first_search with labeled_graph
by Julio Cezar Novais Raffaine 10 Apr '13

10 Apr '13

Hi, I'm having the above (end of email) error message when compiling my source using breadth_first_search in a labeled_graph, here are some of my definitions: I'm using boost 1.51.0. struct VertexProperty { string x; }; typedef boost::property<boost::edge_weight_t, double> IndexProperty; typedef boost::labeled_graph< boost::adjacency_list<boost::vecS, boost::setS, boost::bidirectionalS, VertexProperty, IndexProperty>, std::string> GraphT; I also created the following visitor: class recurrence_bfs_visitor : public boost::default_bfs_visitor { public: GraphT::vertex_descriptor check_node; recurrence_bfs_visitor(GraphT::vertex_descriptor node) : boost::default_bfs_visitor(), check_node(node) {} template < typename Vertex, typename Graph > void discover_vertex(Vertex u, const Graph & g) const { if( u == check_node ) throw std::runtime_error(""); } }; Then I call my functions in this way: auto v1 = g.vertex(e1); auto v2 = g.vertex(e2); recurrence_bfs_visitor vis(v2); boost::breadth_first_search(g.graph(), v1, boost::visitor(vis)); Where g is my GraphT and e1,e2 are strings that I receive as parameters. Here are the error message: 1>d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2499): error C2039: 'type' : is not a member of 'boost::property_value<PropertyList,Tag>' 1> with 1> [ 1> PropertyList=VertexProperty, 1> Tag=boost::vertex_index_t 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2576) : see reference to class template instantiation 'boost::adj_list_any_vertex_pa::bind_<Tag,Graph,Property>' being compiled 1> with 1> [ 1> Tag=boost::vertex_index_t, 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> Property=VertexProperty 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2709) : see reference to class template instantiation 'boost::detail::adj_list_choose_vertex_pa<Tag,Graph,Property>' being compiled 1> with 1> [ 1> Tag=boost::vertex_index_t, 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> Property=VertexProperty 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\properties.hpp(224) : see reference to class template instantiation 'boost::adj_list_vertex_property_selector::bind_<Graph,Property,Tag>' being compiled 1> with 1> [ 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> Property=VertexProperty, 1> Tag=boost::vertex_index_t 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\properties.hpp(233) : see reference to class template instantiation 'boost::detail::vertex_property_map<Graph,PropertyTag>' being compiled 1> with 1> [ 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> PropertyTag=boost::vertex_index_t 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\named_function_params.hpp(259) : see reference to class template instantiation 'boost::property_map<Graph,Property>' being compiled 1> with 1> [ 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> Property=boost::vertex_index_t 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\mpl\eval_if.hpp(41) : see reference to class template instantiation 'boost::detail::const_type_as_type<T>' being compiled 1> with 1> [ 1> T=boost::property_map<boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>,boost::vertex_index_t> 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\mpl\eval_if.hpp(41) : see reference to class template instantiation 'boost::mpl::eval_if<C,F1,F2>' being compiled 1> with 1> [ 1> C=boost::mpl::true_, 1> F1=boost::detail::const_type_as_type<boost::property_map<boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>,boost::vertex_index_t>>, 1> F2=boost::property_map<boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>,boost::vertex_index_t> 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\named_function_params.hpp(274) : see reference to class template instantiation 'boost::mpl::eval_if<C,F1,F2>' being compiled 1> with 1> [ 1> C=boost::is_same<boost::param_not_found,boost::param_not_found>, 1> F1=boost::mpl::eval_if<boost::mpl::true_,boost::detail::const_type_as_type<boost::property_map<boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>,boost::vertex_index_t>>,boost::property_map<boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>,boost::vertex_index_t>>, 1> F2=boost::mpl::identity<boost::param_not_found> 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\breadth_first_search.hpp(316) : see reference to class template instantiation 'boost::detail::choose_impl_result<GraphIsConst,Graph,Param,Tag>' being compiled 1> with 1> [ 1> GraphIsConst=boost::mpl::true_, 1> Graph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> Param=boost::param_not_found, 1> Tag=boost::vertex_index_t 1> ] 1> d:\projects\cprojects\boost_1_51_0\boost\graph\breadth_first_search.hpp(340) : see reference to function template instantiation 'void boost::detail::bfs_dispatch<boost::param_not_found>::apply<VertexListGraph,recurrence_bfs_visitor,boost::graph_visitor_t,boost::no_property>(VertexListGraph &,void *,const boost::bgl_named_params<T,Tag,Base> &,boost::param_not_found)' being compiled 1> with 1> [ 1> VertexListGraph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> T=recurrence_bfs_visitor, 1> Tag=boost::graph_visitor_t, 1> Base=boost::no_property 1> ] 1> d:\novosprojetos\experiments\orcgraph\graphlib\graph.cpp(124) : see reference to function template instantiation 'void boost::breadth_first_search<boost::adjacency_list<OutEdgeListS,VertexListS,DirectedS,VertexProperty,EdgeProperty>,recurrence_bfs_visitor,boost::graph_visitor_t,boost::no_property>(const VertexListGraph &,void *,const boost::bgl_named_params<T,Tag,Base> &)' being compiled 1> with 1> [ 1> OutEdgeListS=boost::vecS, 1> VertexListS=boost::setS, 1> DirectedS=boost::bidirectionalS, 1> VertexProperty=VertexProperty, 1> EdgeProperty=IndexProperty, 1> VertexListGraph=boost::adjacency_list<boost::vecS,boost::setS,boost::bidirectionalS,VertexProperty,IndexProperty>, 1> T=recurrence_bfs_visitor, 1> Tag=boost::graph_visitor_t, 1> Base=boost::no_property 1> ] 1>d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2504): error C3203: 'type' : unspecialized class template can't be used as a template argument for template parameter 'ValueType', expected a real type 1>d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2504): error C2955: 'boost::type' : use of class template requires template argument list 1> d:\projects\cprojects\boost_1_51_0\boost\type.hpp(14) : see declaration of 'boost::type' 1> d:\projects\cprojects\boost_1_51_0\boost\type.hpp(14) : see declaration of 'boost::type' 1>d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2506): error C3203: 'type' : unspecialized class template can't be used as a template argument for template parameter 'ValueType', expected a real type 1>d:\projects\cprojects\boost_1_51_0\boost\graph\detail\adjacency_list.hpp(2506): error C2955: 'boost::type' : use of class template requires template argument list 1> d:\projects\cprojects\boost_1_51_0\boost\type.hpp(14) : see declaration of 'boost::type' 1> d:\projects\cprojects\boost_1_51_0\boost\type.hpp(14) : see declaration of 'boost::type' 1>d:\projects\cprojects\boost_1_51_0\boost\graph\breadth_first_search.hpp(316): error C2893: Failed to specialize function template 'boost::two_bit_color_map<IndexMap> boost::make_two_bit_color_map(size_t,const IndexMap &)' 1> With the following template arguments: 1> 'boost::adj_list_vertex_property_map' -- Julio Cezar Novais Raffaine Sistemas de Engenharia, Odebrecht SA São Paulo, SP http://elloxas.blogspot.com/

2 2

[multiprecision] radix-2
by Lucas Sousa de Oliveira 10 Apr '13

10 Apr '13

Hey guys, I'm considering participating in this year's GSoC 2013 with Boost. I think the multiprecision problem is very interesting and I'll give my best to implement it But first, what would you think is the challenge here? What would make this problem very complex? I'm studying the general radix algorithm and it doesn't seem to be that bad. Am I being misled? All the best, -- Lucas Oliveira

2 1

Re: [Boost-users] ASIO with std::thread
by Marat Abrarov 10 Apr '13

10 Apr '13

> Are there any implications of using std::thread and std::future, etc. with > boost.asio (instead of boost.thread, etc.)? I'd be thankful if you could > provide me the answer in detail and give me helpful pointers to online > links and provide examples. Specifically, I'm very interested in using > std::future and promise with std::thread but I want future with ASIO based > sockets. > > In addition, it'd be just great if you could also provide me an example of > using boost's chrono based stead clock for setting up interval timers to, > for example, get an event after every 10 seconds. As short example: #if defined(WIN32) #include <tchar.h> #include <windows.h> #endif #include <cstdlib> #include <cstddef> #include <utility> #include <iostream> #include <exception> #include <thread> #include <future> #include <vector> #include <memory> #include <algorithm> #include <functional> #include <boost/asio.hpp> #include <boost/optional.hpp> #include <boost/utility/in_place_factory.hpp> namespace ma { namespace test { namespace asio_future { class connect_task { public: typedef boost::system::error_code result; typedef std::future<result> future; private: typedef connect_task this_type; typedef std::promise<result> promise; this_type& operator=(const this_type&); public: connect_task() : promise_(std::make_shared<promise>()) { } connect_task(const this_type& other) : promise_(other.promise_) { } connect_task(this_type&& other) : promise_(std::move(other.promise_)) { } void operator()(const boost::system::error_code& error) { promise_->set_value(error); } future get_future() { return promise_->get_future(); }; private: std::shared_ptr<promise> promise_; }; // connect_task class io_task { public: typedef std::pair<boost::system::error_code, std::size_t> result; typedef std::future<result> future; private: typedef io_task this_type; typedef std::promise<result> promise; this_type& operator=(const this_type&); public: io_task() : promise_(std::make_shared<promise>()) { } io_task(const this_type& other) : promise_(other.promise_) { } io_task(this_type&& other) : promise_(std::move(other.promise_)) { } void operator()(const boost::system::error_code& error, std::size_t bytes_transferred) { promise_->set_value(std::make_pair(error, bytes_transferred)); } future get_future() { return promise_->get_future(); }; private: std::shared_ptr<promise> promise_; }; // io_task class io_service_pool { private: typedef io_service_pool this_type; io_service_pool(const this_type&); this_type& operator=(const this_type&); public: io_service_pool(boost::asio::io_service& io_service, std::size_t size) : work_guard_(boost::in_place(std::ref(io_service))) { for (; size; --size) { threads_.emplace_back([&io_service]() { io_service.run(); }); } } ~io_service_pool() { work_guard_ = boost::none; std::for_each(threads_.begin(), threads_.end(), [](std::thread& thread) { thread.join(); }); } private: boost::optional<boost::asio::io_service::work> work_guard_; std::vector<std::thread> threads_; }; // io_service_pool void run_test() { const boost::asio::ip::tcp::endpoint endpoint( boost::asio::ip::address_v4::loopback(), 7); const std::size_t cpu_count = std::thread::hardware_concurrency(); const std::size_t io_threadpool_size = cpu_count < 2 ? 2 : cpu_count; boost::asio::io_service io_service(io_threadpool_size); io_service_pool io_threadpool(io_service, io_threadpool_size); boost::asio::ip::tcp::socket socket(io_service); { // Connect to localhost:7 connect_task handler; connect_task::future future = handler.get_future(); socket.async_connect(endpoint, std::move(handler)); if (connect_task::result result = future.get()) { std::cout << "Failed to connect: " << result << std::endl; return; } std::cout << "Connected" << std::endl; } { // Send some data const std::string data = "Hello from Boost.Asio!"; io_task handler; io_task::future future = handler.get_future(); boost::asio::async_write( socket, boost::asio::buffer(data), std::move(handler)); io_task::result result = future.get(); if (result.first) { std::cout << "Failed to send: " << result.first << std::endl; return; } std::cout << "Sent: " << data << std::endl; } } // run_test } // namespace asio_future } // namespace test } // namespace ma #if defined(WIN32) int _tmain(int /*argc*/, _TCHAR* /*argv*/[]) #else int main(int /*argc*/, char* /*argv*/[]) #endif { try { ma::test::asio_future::run_test(); return EXIT_SUCCESS; } catch (const std::exception& e) { std::cerr << "Unexpected exception: " << e.what() << std::endl; } catch (...) { std::cerr << "Unknown exception" << std::endl; } return EXIT_FAILURE; } Regards, Marat Abrarov.

1 0

How is the proactor pattern of boost.asio implemented in linux?
by Journeyer J. Joh 10 Apr '13

10 Apr '13

Hello list, In ACE and on Linux the Proactor pattern is not recommended. Instead of this, ACE_Dev_Poll_Reactor seems to be recommended. It is one of Reactor implementation. ACE_Dev_Poll_Reactor uses epoll in a level-trigger method. But, I am not sure of this information.... I just found some blog essays on internet. Now I wonder about boost.asio. boost.asio must have a proactor implementation on Linux, I guess. How does the proactor of boost.asio work? Does it use epoll? Is it edge-triggered? What about real-time signal? Doesn't boost.asio use real-time signal on Linux? What is the recommended implementation of boost.asio for asynchronous and non-blocking overlapped IO on Linux? Thank you in advance! ---------------------------------------- Journeyer J. Joh o o s a p r o g r a m m e r a t g m a i l d o t c o m ----------------------------------------

1 0

ASIO with std::thread
by asif saeed 10 Apr '13

10 Apr '13

Hi, I am a newbie to both boost.asio and std::thread and std::future and so on and am just learning and trying to develop a messaging library. Are there any implications of using std::thread and std::future, etc. with boost.asio (instead of boost.thread, etc.)? I'd be thankful if you could provide me the answer in detail and give me helpful pointers to online links and provide examples. Specifically, I'm very interested in using std::future and promise with std::thread but I want future with ASIO based sockets. In addition, it'd be just great if you could also provide me an example of using boost's chrono based stead clock for setting up interval timers to, for example, get an event after every 10 seconds. Best regards, -Asif

1 0

Efficient "[][]" operator overloading (encapsulating a MultiArray)
by Jiří Vyskočil 09 Apr '13

09 Apr '13

Hello, I need to encapsulate a 3D MultiArray inside another class "GridArray". The reason is that GridArray will have another implementation not using MultiArray and it seems much easier to provide an abstration over MultiArray, than to reimplement its interface for the other implementation. I need to keep the [][][] operator access to the structure. I created a class like this, but it is slow: template<class T> class GridArray<T,3> { public: GridArray(int x, int y, int z): _array(boost::extents[x][y][z]) { } boost::multi_array<T, 3> _array; struct SliceRef { struct ColRef { SliceRef &_parent; int _x, _y; ColRef(SliceRef &p, const int x, const int y): _parent(p), _x(x), _y(y) {} T& operator[](const int z) { return _parent._parent._array[_x][_y][z]; } }; GridArray<T,3> &_parent; int _x; SliceRef(GridArray<T,3> &p, const int x): _parent(p), _x(x) {} ColRef operator[](const int y) { return ColRef(*this,_x,y); } }; SliceRef operator[](const int x){ return SliceRef(*this,x); } }; I am unable to write a minimal test case - if I compare using multi_array directly vs. using this GridArray class in a simple test program (compiled with -O2), the performance is the same. But the real code shows about 20% slowdown - it's a numerical simulaiton, I create several arrays at the beginning and then do computations with them. The rest of the code hasn't been touched - I only chanded the constructors for the arrays and replaced a header which contained some typedefs with a header containing this class. Do you have any idea what might be going on? Is there a better way to write an interface for successive [] operators? Thanks, Jiri

4 3

message_queue memory leak in Boost::test
by John Davies 09 Apr '13

09 Apr '13

I have this simple test case: BOOST_AUTO_TEST_CASE(TestLogin) { message_queue inQueue(open_or_create, "InQueue", 100, 100); remove("InQueue"); } And Boost::test reports a memory leak: Running 1 test case... *** No errors detected Detected memory leaks! Dumping objects -> {668} normal block at 0x0039DE78, 57 bytes long. Data: <struct boost::in> 73 74 72 75 63 74 20 62 6F 6F 73 74 3A 3A 69 6E {667} normal block at 0x0039DE40, 8 bytes long. Data: <x 9 > 78 DE 39 00 00 00 00 00 Object dump complete. Press any key to continue . . . If I comment out the two lines of code there is no memory leak. Is this something I have to live with? In my real code the message_queue is alive the whole time the program is running.

3 4

[Boost.Test + Turtle] Suggestion how to test async events.
by Daniele Barzotti 09 Apr '13

09 Apr '13

Hi, I'm trying to take a first touch with Boost.Test and Turtle. I have some objects for network communication with async notifications. class ServerHandler : public MessageEventHandler { public: ServerHandler() { // Register the messages I want to manage this->RegisterMsg(E_MSG_METHOD_CONNECT, Poco::delegate(this, &ServerHandler::OnMsgMethodConnect)); } // Messages Handlers virtual void OnMsgMethodConnect(const void* pSender, TArgs& args) { cout << "ServerHandler receive E_MSG_METHOD_CONNECT" << endl; MSG_METHOD_CONNECT& msg = RetrieveMessage<MSG_METHOD_CONNECT>(args.msg); }; }; This class is an observer which handle the notification through the OnMsgMethodConnect method. The test body I wrote is: // declare a 'mockServerHandler' class implementing 'ServerHandler' MOCK_BASE_CLASS( mockServerHandler, ServerHandler ) { MOCK_METHOD( OnMsgMethodConnect, 2 ); }; BOOST_AUTO_TEST_SUITE(NetMessageDispatcherTest) BOOST_AUTO_TEST_CASE(Test1) { mockServerHandler mockSvr; SessionFactory* sf = new SessionFactory( &mockSvr ); IMessageFactory* mf = new PBMessageFactory(); NetMessageDispatcher* server = new NetMessageDispatcher(sf, mf, NULL, E_DISP_SERVER); NetMessageDispatcher* client = new NetMessageDispatcher(sf, mf, NULL, E_DISP_CLIENT); BOOST_CHECK( server->Init("LOCALHOST", "TestServer") == 0 ); BOOST_CHECK( server->Connect(8000, "127.0.0.1") == 0 ); BOOST_CHECK( client->Init("LOCALHOST", "TestClient") == 0 ); BOOST_CHECK( client->Connect(8000, "127.0.0.1") == 0 ); MOCK_EXPECT( mockSvr.OnMsgMethodConnect ).once().with(????) } BOOST_AUTO_TEST_SUITE_END() Now, I have to test if into the ServerHandler::OnMsgMethodConnect() the argument args.msg (which is a message class) has the correct values. EG. if (msg.station_type() == EStationType::ST_CLIENT) => OK Which is the correct way to do it? Regards, Daniele.

2 2

file monitoring
by SRD 08 Apr '13

08 Apr '13

I'm looking for a way to get notified as soon as a new file has been created. So I was wondering if boost has a way of monitoring files so I can send them off as soon as I receive them. This would have to work for Linux and windows. I saw a few posts which seem to indicate that its not there yet, but that was some time ago. Thanks,

4 4

[boost::asio] how should I use accept and io_service?
by Shenyu Yao 08 Apr '13

08 Apr '13

Hi guys, this is my first post to this mail list. Forgive my noob questions, I am new to boost. I have read some documentations but still dont understand how io_service works. My problem is that I need two functions in my server class, listen() and handle() listen() is to accept all incoming connections and bind them with a handler function which accept a socket as argument. and handler will simply call io_service.run() ========================= class Server { io_service IOService; std::vector<boost:: ... :: socket> SocketVector; listen() { //blocking accept all incoming connection and bind socket with handleSocket } HandleRequest() { //io_service.run(); } } ============================ handleSocket(*Socket) { //handleSocket; } ============================== main() { boost::thread t1(&Server::listen, &myServer); boost::thread t2(&Server::HandleRequest, &myServer); } ==================================== my understanding is that everytime you instantiate a new socket object with a constructor including a io_service object, this socket object is associated with the io_service object, since I only have one io_service object, these socket object will be executed when I call io_service.run()but, the question is, how do i assign handle_function to those socket, I saw people use acceptor.async_accept(socket, boost::bind(handler, &socket)) like this, But I want to use accept rather than async_accept(), but the accept() function cant be used to bind a handler function to this socket Thank you

2 1

c++ Bit Fields
by Chris Gem 08 Apr '13

08 Apr '13

Please forgive me if this question has been answered but I've searched for days now and cannot find it. How do I expose a c++ struct with a bit field to python using boost::python? When I try I get this error. error: invalid pointer to bit-field ‘frameHdr_s::hdrSize’ Here is the struct: #define DATA_SIZE 0x100 typedef struct frameHdr_s { #define USE_BIT_FIELDS #ifdef USE_BIT_FIELDS // Longword 0 uint32_t hdrSize : 16; ///< Size of the header uint32_t revMin : 8; ///< Frame Minor Version uint32_t revMaj : 8; ///< Frame Major Version #else // Longword 0 uint32_t hdrSize; ///< Size of the header uint32_t revMin ; ///< Frame Minor Version uint32_t revMaj ; ///< Frame Major Version #endif } frameHdr_t; typedef struct frame_t { frameHdr_t frame_header; ///< frame header uint8_t data[DATA_SIZE]; ///< Byte array of data } frame_t; Here is boost code to expose it: using namespace boost::python; BOOST_PYTHON_MODULE(api) { class_<frameHdr_t>("frameHdr_t") .def_readwrite("hdrSize", &frameHdr_t::hdrSize) ; class_<frame_t>("frame_t") .def_readwrite("frame_header", &frame_t::frame_header) ; class_<myClass>("myClass") .def("register_callback", &myClass::register_callback) .def("boo", &myClass::boo) .def("crap", &myClass::crap) ; } I know that with ctypes I can create the same struct as in c++: from ctypes import * class frameHdr_t(Structure): _pack_ = 1 _fields_=[ # Longword 0 ("hdrSize",c_uint32, 16), ("revMin",c_uint32, 8), ("revMaj",c_uint32, 8), ] DATA_SIZE = 0x100 class frame_t(Structure): _pack_ = 1 _fields_=[ ("frame_header",frameHdr_t), ("data",c_uint8 * DATA_SIZE), ] But how do I translate from the Python version of frame_t to the c++ version of frame_t? In summary, * How do I tell boost to expose a bitfield? * If that is not possible, how do I translate from Python frame_t to C++ frame_t using boot? (I don't want to wrap in C because I need to preserve the C++ness of the interface.) The code is attached. Thank you for your time, Chris

4 4

type_erasure question
by Aleksandar Fabijanic 07 Apr '13

07 Apr '13

Looking at the type_erasure example: typedef any<boost::mpl::vector<copy_constructible<>, typeid_<>, addable<>> > any_type; any_type x(1.1); any_type y(1); any_type z(x + y); Apparently, without placeholders for x and y, this is undefined behavior. Am I interpreting it right? If so, shouldn't it fail to compile or at least throw an exception at runtime? Thanks, Alex

3 3

publish/subscribe/message architecture using boost
by Sean Farrow 07 Apr '13

07 Apr '13

Hi all, I 'm currently looking at redesigning an application and changing to boost/c++11 library components. The application reads data from an input, processes the data and then send it to an output. The current architecture is one thread per "device" where a device is a pair of input/output ports and one processing stage. What I'd like to do is move this to either a publish/subscribe model or some form of message-based system where an input comes in and a message is then sent to the next stage of the process. All stages will happen on the same physical/virtual machine. Are there any good pub/subscribe or message-based components using the boost architecture that works on mac osx/win32. Any help appreciated. Regards Sean.

3 3

Re: [Boost-users] [boost][thread] Future returning 0xfeeefeee
by Stefan Strasser 06 Apr '13

06 Apr '13

Zitat von Klaim - Joël Lamotte <mjklaim(a)gmail.com>: > My current suspicion: maybe I do something wrong with the lifetime of the > promise? > I don't see what unfortunately. your example is not easy to read. IIUC, after execute(), the work queue is emptied and the last shared_ptr to struct K goes out of scope. K contains your promise and the future associated with it is accessed after the promise has been destroyed. try a breakpoint in the destructor of K to make sure, I don't have tbb installed to test.

2 2

[boost][thread] Future returning 0xfeeefeee
by Klaim - Joël Lamotte 06 Apr '13

06 Apr '13

I'm stuck with a problem I quite don't understand and that involve either boost::future/promise or tbb::concurrent_queue, or my understanding of using both. I think there is a high probability that someone here will point to the problem, but I will report too to the tbb forum Some context: - I'm using VS2012 Update 2 - it's 32 bit DEBUG mode - I use Boost.Thread V4 (in CMake I set "add_definitions( -DBOOST_THREAD_VERSION=4 )" to force it ) - I use TBB 4.1 Update 2 I've setup a test (using GTest) which reproduce the problem: ############ int TRUC = 42; TEST( Test_WorkQueue, future_promise_shared_work ) { WorkQueue work_queue; // I'm doing this like that because it reflect the use case I have, // I didn't find another way to have the promise alive in a container which don't allow move semantic auto do_some_work = [&]()-> boost::future<int*> { struct K { boost::promise<int*> promise; void foo() { promise.set_value( &TRUC ); } }; auto object_ptr = std::make_shared<K>(); // D: work_queue.push( [=] { object_ptr->foo(); }); return object_ptr->promise.get_future(); }; auto ft_value = do_some_work(); work_queue.execute(); auto value = ft_value.get(); ASSERT_EQ( &TRUC, value ); // this fails, value == 0xfeeefeee } ########## My WorkQueue type use tbb::concurrent_queue and is defined as: ########## class WorkQueue { public: template< class WorkTask > void push( WorkTask&& task ) { m_task_queue.push( std::forward<WorkTask>( task ) ); } /** Execute all the work queued until now. */ void execute() { if( m_task_queue.empty() ) return; bool end_of_work = false; m_task_queue.push( [&]{ end_of_work = true; } ); std::function<void()> work; while( !end_of_work && m_task_queue.try_pop( work ) ) { work(); } } private: mutable tbb::concurrent_queue< std::function<void()> > m_task_queue; }; ############ It's basically a simple wrapper around the concurrent_queue, but maybe the execute() code have an impact. THE PROBLEM: The test fails. value == 0xfeeefeee as soon as the get() call is done. Using the debugger, I can't figure where the data is lost. It seem that everything is correct until when all the hierarchy of function call returns the result...which is different and wrong once out of the function. I first wrote this test with std::vector< std::function<void()> > instead of the concurrent queue to check if it was boost::future/promise which was not working well with Boost.Thread V4. With the vector instead of concurrent_queue, the code works perfectly. Does someone have an idea what is going on? Joel Lamotte

1 2

Re: [Boost-users] Boost-users] publish/subscribe/message architecture using boost
by Brian Wood 06 Apr '13

06 Apr '13

Sean Farrow writes: > Hi all, > I''m currently looking at redesigning an application and changing to > boost/c++11 library components. The application reads data from an input, > processes the data and then send it to an output. The C++ Middelware Writer (CMW) may be of interest. The application you mention sounds similar to the middle tier of the CMW -- http://webEbenezer.net/build_integration.html http://webEbenezer.net/misc/cmwAmbassador.hh http://webEbenezer.net/misc/cmwAmbassador.cc > The current architecture is one thread per "device" where a device is a > pair of input/output ports and one processing stage. What I'd like to > do is move this to either a publish/subscribe model or some form of > message-based system where an input comes in and a message is then > sent to the next stage of the process. All stages will happen on the same > physical/virtual machine. Are there any good pub/subscribe or > message-based components using the boost architecture that works > on mac osx/win32. We don't have pub/subscribe support, but the CMW is a message-based middleware. -- Brian Wood Ebenezer Enterprises - in G-d we trust. http://webEbenezer.net (651) 251-9384

1 0

Scope Tracer or General Scope Function with parameter or variable values
by Anlin Zhang 05 Apr '13

05 Apr '13

Hi, I'm wondering if a "Scope Tracer" or a "General Scope Function" can be easily implemented with existing boost libraries now. One example use case is to log variable or parameter values or any program state when entering or leaving a scope, but it can do more than just logging, it can, for example, lock/unlock mutex, or prepare/teardown test cases, etc. For logging requirement, to give you an idea, the expected log message looks like this: >04/10/09 05:29:12:210257 entering func foo with parameter a=10, b=1.5, d.x=10, d.y=[string], global d=2, filename:test.cpp>04/10/09 05:29:12:210257 entering while() a=10, b=1.5, d.x=10>04/10/09 05:29:12:210257 leaving while() a=9, b=1.5, d.x=9>04/10/09 05:29:12:210257 entering while() a=9, b=1.5, d.x=9>04/10/09 05:29:12:210257 leaving while() a=8, b=1.5, d.x=8>...>04/10/09 05:29:12:210257 entering while() a=2, b=1.5, d.x=2>04/10/09 05:29:12:210257 leaving while() a=1, b=1.5, d.x=1>04/10/09 05:29:12:210257 entering while() a=1, b=1.5, d.x=1>04/10/09 05:29:12:210257 leaving while() a=0, b=1.5, d.x=0>04/10/09 05:29:12:210257 leaving function foo with parameter a=0, b=1.5, d.x=0, d.y=[string], global d=2, filename:test.cpp It does not have to be logging, it can do any general processing when entering/leaving a scope. I implemented a small library to do so in 2008 mainly for tracing, it worked fine for me and I never revisited it again until recently. Wondering if boost has libraries to support such a requirment. My implementation has a template class logger_class which can manage the log-level at runtime and send the log message to standard-output or other places. Application code use a macro to invoke the library, the macro can be disabled at compile time, or weakened to only log scope without variables. Example of the macro definition: #ifdef ENABLE_ONLY_SCOPE_TRACER #define SCOPE_TRACER(logger_class, logger, args, level, scope) \ scope_tracer<logger_class> tracer_obj(logger, __FUNCTION__, __FILE__, __LINE__); \ if (logger.get_level() >= level){ \ tracer_obj.init(level, scope).noMore(); \ } #else #ifdef DISABLE_SCOPE_VAR_TRACER #define SCOPE_TRACER(logger_class, logger, args, level, scope) #else #define SCOPE_TRACER(logger_class, logger, args, level, scope) \ scope_tracer<loggerClass> tracer_obj(logger, __FUNCTION__, __FILE__, __LINE__); \ if (logger.get_level() >= level){ \ tracer_obj.init(level, scope) << args; \ tracer_obj.noMore(); \ } #endif#endif Application code example: int globalVar; void MyClass::func1( A a, B&b, C* c, int d, std::string & s){ SCOPE_TRACER(MyLogger, test_logger, a<<b<<c<<d<<s<<globalVar, LOG_LEVEL_TRACE, "func1"); ... int localVar; while(x){ SCOPE_TRACER(MyLogger, test_logger, x<<a<<b<<c<<d<<s<<globalVar<<localVar, LOG_LEVEL_TRACE, "while(x)"); ... } ... } As you see, "<<" operator is being used. But it does not have to be only "<<" operator. Basically any C++ operator can be supported between the logger class and logged type. And the logger_class is not limited to just do tracing, it can virtuall do anything. I can attach the code if needed. The code was compiled with GCC on linux and VisualStudio on Windows. If the above functionality can be easily achieved using existing boot library, please advise how. Otherwise is it worth to request such a feature in boost? Thanks,Anlin

1 0

Visual C++ 11 cannot find Boost unit_test_framework library in CMake generated project
by Emre Şahin 05 Apr '13

05 Apr '13

I have a C++ project using CMake and Boost that compiles/links under Linux without any problems. I'm working towards porting this to Windows via Visual C++ 2012. My CMake configuration is as follows: set(BOOST_ROOT ${DEPENDENCY_DIR}/boost/) set(Boost_USE_STATIC_LIBS ON) set(Boost_USE_MULTITHREADED ON) set(Boost_USE_STATIC_RUNTIME OFF) find_package(Boost 1.53 COMPONENTS system date_time chrono serialization filesystem program_options random thread regex unit_test_framework) message(STATUS "Boost Version:" ${Boost_VERSION}) message(STATUS "Boost Include Dirs:" ${Boost_INCLUDE_DIR}) message(STATUS "Boost Libraries:") foreach(lib ${Boost_LIBRARIES}) message(STATUS ${lib}) endforeach() include_directories(${Boost_INCLUDE_DIR}) and I'm using `target_link_libraries` with `${Boost_LIBRARIES}` in my targets. Also above `message` commands show all found files without any problem. Moreover required libraries show `libboost_unit_test_framework-vc110-mt-gd-1_53.lib` as it should be. (Screenshot: http://i.stack.imgur.com/UgPTG.png) However, when I build one of the targets, I get 2>LINK : fatal error LNK1104: cannot open file 'boost_unit_test_framework-vc110-mt-gd-1_53.lib' I removed another Boost library and from the error it seems the linker is able to find others. (like `chrono` or `serialization`.) But the error message is a bit different. The filename has _lib_ in front of it. 2>LINK : fatal error LNK1104: cannot open file 'libboost_serialization-vc110-mt-gd-1_53.lib' Why does VC++ looks for a file prefixed with **boost** and not **libboost** for unit_test_framework? Best Regards, Emre PS: This is crossposted to http://stackoverflow.com/questions/15815467/ if you like to answer there.

3 2

Boost-enabled loosely coupled ORM serialization
by Michael Powell 05 Apr '13

05 Apr '13

Hello, I am coming up on a decision in the architecture I am working on. I want to serialize some domain data to a data store. I'm aware boost has serialization features, which I'd like to explore further. I'm coming at this first from a boost standpoint because I am successfully building upon it for other parts of the engine and domain model, so boost is available right now. I am expecting I might go with a third-party library like ODB, Wt::Dbo, or something like that. Also, background, I am no stranger to ORM concepts. I was first exposed to them through Java, C# .NET, and have dealt with Hibernate, NHibernate, Fluent NHibernate, and so on. So vocabulary-wise, grammar-wise, we're talking the same language. Also, I'll defer backend decisions until later. Probably that will be somewhat determined by target platform support and so on: landing on ArchLinux ARM. For now, my focus for now is on keeping ORM intersection with my domain as loosely coupled as possible. For anyone versed in ORM nuances, for obvious reasons, I want for the ORM to be as transparent through the domain model as possible. I want to steer clear of the active record anti-pattern whenever possible. I'd like to gear up for a repository pattern whenever feasible. No time to get into that discussion why I believe these are patterns or anti-patterns. That's a separate blog for another time. Wrappers like smart pointers, smart collections, are understandable, and may be the way to go, but put opaqueness layers between end-users of the domain objects and the rest of the model. Will use them if I must, but I'd like to avoid them if possible. Additionally, given some language "features", perhaps "limitations" if you will, of C++11, as contrasted with a C# let's say, I also want for any ORM code, whether meta-programmed or not, to be as non-intrusive to the domain model as possible. I've seen a ton of code that have persist methods, friend access, macros, and such. Sounds like a tall order I know. Call me spoiled on the "niceness" of .NET, Reflection, and so on. More likely I'm getting reacquainted with the practicalities of using a paradigm-rich language like C++11. Now back to the "real world" what the rest of us deal with. Realistically, a sober look at it, I believe there will be tradeoffs: SOLID is my goal, sufficiently extensible to meet the seams we'll need to meet, yet maintainable at the end of the day. Regards, Michael Powell

3 2

Signals2 event broker framework
by Michael Powell 05 Apr '13

05 Apr '13

Hello, I am interested to put an event broker system into practice in our architecture. Since we're using boost successfully already, Signals2 seems like the most likely candidate. At the moment, this is intra-process, most likely inter-thread but for now that's not the concern. Just getting event signals from point A to points B, C, D in pub/sub manner, however, is. http://www.boost.org/doc/libs/1_53_0/doc/html/signals2.html If I can abstract that out further, for instance I noticed there was an C# event-like abstraction someone published as an add-on feature to boost a little while back, handled subscriptions through +=, -= operator overloads, that sort of thing, would be helpful, but probably not completely necessary. If I can loosely couple subscribers from publishers is also desired. Something like bbv EventBroker ( http://code.google.com/p/bbvcommon/wiki/EventBroker) is to C#. That'll keep things nice and loosely coupled, so that if we ever need to get more distributed (i.e. via a CORBA or ZeroC) we can potentially do so. Regards, Michael Powell

1 0

dynamic_bitset get block_type not ulong
by Michael Powell 05 Apr '13

05 Apr '13

Hello, How do I get at the block_type value itself, not an unsigned long, from a dynamic_bitset (or std::bitset for that matter). For instance, can I do something like this? typedef unsigned char byte; boost::dynamic_bitset<byte> my_bitset(static_cast<byte>(0x00)); //Do some bit twiddling... byte my_value = static_cast<byte>(my_bitset); Or something like that. Basically I want to avoid any to_ulong() mumbo jumbo if I can just get at the underlying block_type value. Thank you... Regards, Michael Powell

1 3

Problem with Serialization: invalid signature
by Alexander Striffeler 04 Apr '13

04 Apr '13

Hi all I have some trouble with the serialization of objects in C++ using boost. Since there was some strange behaviour in the code, I tried to serialize and deserialize a sample object isolated trying two versions: |deSerialize(Packet p1, Packet p2){ // Version 1 using stringstreams std::ostringstream *serialized = new std::ostringstream[2];|| ||serialized[0]=std::ostringstream(std::ios_base::binary);|| ||serialized[1]=std::ostringstream(std::ios_base::binary);|| || || boost::archive::text_oarchive oa(serialized[0]);|| || oa << p1;|| || || boost::archive::text_oarchive oa2(serialized[1]);|| || oa2 << p2;|| || || std::string s1, s2;|| || || s1 = serialized[0].str();|| || s2 = serialized[1].str();|| || || //deserialize CCNDataPkt newPacket; std::istringstream inputStream(s2, std::ios_base::binary); boost::archive::text_iarchive ia(inputStream); | | ia >> newPacket;| // throws boost::archive::archive_exception: invalid signature. } and |deSerialize(Packet p1, Packet p2){ // Version 2 using ofstreams ||std::ofstream of("deleteme",std::ios_base::binary);|| || boost::archive::binary_oarchive oa(of);|| || oa << p1;|| || || std::ifstream ifstr("deleteme", std::ios_base::binary);|| || CCNDataPkt newp;|| || boost::archive::binary_iarchive ia(ifstr);|| | | ia >> newp;| // boost::archive::archive_exception: invalid signature. } However, both variants returned an invalid signature exception even though I haven't changed anything on the serialized data. Does anyone know what is wrong in either of the examples above? The methods for serializing the custom object 'Packet' are implemented according to the boost serialization tutorial (non-intrusive version splitted) Any hints are very much appreciated - TIA! Cheers, Alex

4 5

[Parallel BGL] Error during building library
by Nikos Kyrtatas 04 Apr '13

04 Apr '13

In order to build Parallel BGL 0.7.0 beta, I first used cmake: ~/project/lib> cmake parallel-bgl-0.7.0/ -- The C compiler identification is GNU -- The CXX compiler identification is GNU -- Check for working C compiler: /usr/bin/cc -- Check for working C compiler: /usr/bin/cc -- works -- Detecting C compiler ABI info -- Detecting C compiler ABI info - done -- Check for working CXX compiler: /usr/bin/c++ -- Check for working CXX compiler: /usr/bin/c++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Configuring done -- Generating done -- Build files have been written to: /home/nkyrtata/project/lib and then make: ~/project/lib> make -- Configuring done -- Generating done -- Build files have been written to: /home/nkyrtata/project/lib Scanning dependencies of target boost_graph_mpi [ 2%] Building CXX object libs/graph_parallel/src/CMakeFiles/boost_graph_mpi.dir/mpi_process_group.cpp.o [ 5%] Building CXX object libs/graph_parallel/src/CMakeFiles/boost_graph_mpi.dir/tag_allocator.cpp.o Linking CXX static library ../../../lib/libboost_graph_mpi.a [ 5%] Built target boost_graph_mpi Scanning dependencies of target adjlist_build_test [ 8%] Building CXX object libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/adjlist_build_test.cpp.o In file included from /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjacency_list.hpp:3961:0, from /home/nkyrtata/project/lib/parallel-bgl-0.7.0/libs/graph_parallel/test/adjlist_build_test.cpp:10: /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjlist/serialization.hpp: In function ‘std::vector<int> boost::detail::parallel::available_process_files(const string&)’: /home/nkyrtata/project/lib/parallel-bgl-0.7.0/boost/graph/distributed/adjlist/serialization.hpp:97:61: error: conversion from ‘boost::filesystem3::path’ to non-scalar type ‘std::string {aka std::basic_string<char>}’ requested make[2]: *** [libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/adjlist_build_test.cpp.o] Error 1 make[1]: *** [libs/graph_parallel/test/CMakeFiles/adjlist_build_test.dir/all] Error 2 make: *** [all] Error 2 I am using Ubuntu 11.10, gcc 4.6.1 and boost 1.52. Any help would be greatly appreciated.

2 1

[program options] compile error if BOOST_NO_EXCEPTIONS defined
by Olaf Krzikalla 04 Apr '13

04 Apr '13

Hi, MSVC 2008, program_options/variables_map.cpp: try without catch error, if BOOST_NO_EXCEPTIONS is defined. Fixable by wrapping the try on line 46: + #ifndef BOOST_NO_EXCEPTIONS try + #endif Best Olaf

1 0

[Boost.Coroutine] Problem compiling simple code with c++98 compiler
by Lukas Czaja 03 Apr '13

03 Apr '13

Hi, i was checking if my code is compatible with c++98 standard and i've encounterd compile error. With -std c++11 option everything works fine. Below i've written code causing same problem. #include <boost/coroutine/coroutine.hpp> #include <boost/coroutine/attributes.hpp> typedef boost::coroutines::coroutine<void( boost::system::error_code , std::size_t)> coro_t; struct coro_test{ coro_test() {} void coro_fun(typename coro_t::caller_type& ca)const{ boost::system::error_code ec; boost::tie(ec, boost::tuples::ignore) = ca.get(); ca(); } coro_t coro; }; int main(int argc, char *argv[]) { { boost::system::error_code ec; coro_t coro2; //default construction is ok coro_test ctest; //compile error , why ??? coro_t coro( boost::bind(&coro_test::coro_fun, &ctest, _1),coro_t::arguments( ec, 7)); coro = coro_t(boost::bind(&coro_test::coro_fun, &ctest, _1),coro_t::arguments( ec, 7)); } ... /usr/local/include/boost/type_traits/is_function.hpp:50: błąd:forming pointer to reference type 'boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&' /usr/local/include/boost/type_traits/is_function.hpp:102: błąd:'value' is not a member of 'boost::detail::is_function_impl<boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' /usr/local/include/boost/type_traits/is_convertible.hpp:354: błąd:'value' is not a member of 'boost::is_function<boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' /usr/local/include/boost/utility/enable_if.hpp:59: błąd:'value' is not a member of 'boost::is_convertible<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)>&, boost::rv<boost::coroutines::coroutine<void(boost::system::error_code, long unsigned int)> >&>' I work with Qt, g++ compiler on ubuntu 12.10 Is this library bug ?

2 3

[serialization] serializing a pointer without causing object tracking
by Stefan Strasser 02 Apr '13

02 Apr '13

Hi everyone, Hi Robert, in case you'd like to answer this one, because I have a rather specific question about your library. Thank you in advance! I'd like to serialize an object and later reconstruct it from the serialized data: void save(T const &t){ ar << t; } T* load(){ T *t=new T(); //error ar >> *t; } T might not have a default constructor. so load_construct_data should be used. apparently the way to do this is to serialize through a pointer: void save(T const *t){ ar << t; } T *load(){ T *t; ar >> t; } this works, but it causes the type T to be tracked, if its object tracking is set to track_selectively. I don't want that. but I can't set it to track_never either, because if the type is serialized at another point in the program through a pointer, the type should be tracked. is there a solution to this? is there a serialization wrapper that says "don't track this type just because of this pointer"? what comes to mind as a solution is serializing as an object, and calling load/save_construct_data manually. but then there is another problem: void save(T const &t){ save_construct_data(t,version<T>::value); ar << t; } void load(T *unconstructed_t){ load_construct_data(unconstructed_t, ??? ); ar >> *t; } if the implementation level of T is object_class_info, the object version is loaded from the preamble when the object itself is loaded. there is no in between loading the version and loading the object, it's entirely handled in the non-header part of the library. so basically I have a solution when the implementation level is object_serializable (no version info, call load_construct_data manually), and when tracking is set to track_never (serialize as a pointer). but not for the default case, object_class_info with track_selectively. am I missing something? Stefan

3 6

Problems with stl::map
by Michael Powell 02 Apr '13

02 Apr '13

Hello, Perhaps there is a boost answer for this, I don't know. I have a typedef unsigned char byte defined in global scope. Then a typedef byte address_type defined in the scope of a class. I'd like to setup a std::map<address_type, byte> if at all possible. Or just in general, use std::map, but it doesn't seem to like anything I give it. I am building using GCC 4.7.2 cross compiling to ARM through Sourcery CodeBench for ARM. Kind of at a loss. Regards, Michael Powell

4 5

safe check if lockfree::queue is empty
by niXman 02 Apr '13

02 Apr '13

Hi, I read the docs about lockfree::queue::empty() and understang what this way is not safe in multithreaded program. The question is, how can I verify that the queue is empty? Will it be correct the following code? bool empty() { T *tmp = 0; if ( queue.pop(tmp) ) { queue.push(tmp); return false; } return true; } Thanks. -- Regards, niXman ___________________________________________________ Dual-target(32 & 64-bit) MinGW compilers for 32 and 64-bit Windows: http://sourceforge.net/projects/mingwbuilds/ ___________________________________________________ Another online IDE: http://liveworkspace.org/

2 2

Good lock_guard<mytype> example
by Michael Powell 02 Apr '13

02 Apr '13

Hello, The pattern goes something like this: boost::lock_guard<mytype> guard(*this). However, compiler is asking for a lock or unlock. I don't know what this is, or what it should be. Thank you... Regards, Michael Powell

4 4

Newbie Interprocess message_thread user
by John Davies 01 Apr '13

01 Apr '13

I'm new to Boost and new to Linux. But old to Windows. So I'm doing some initial development in Windows XP. I have two executables made in different projects. I planned on using a message_queue to communicate between the two applications. But sending a message from one app does not make it to the other. I can add and handle messages from one thread to another within the same application. SO I know I have things partially setup correctly. But now I'm at a complete loss. Should two exe files be able to communicate through Boost message_queues? Or am I misunderstanding the whole thing?

2 2

[Boost.Container] missing image in the documentation
by ilya shlyakhter 01 Apr '13

01 Apr '13

At the URL http://www.boost.org/doc/libs/1_53_0/doc/html/container/non_standard_contai… the illustration of stable vector is missing.

2 1

How should I define a wchar_t type for use in mbtowc? [Android] [Serialization]
by Wesley Paugh 01 Apr '13

01 Apr '13

I'm attempting to port Serialization code to Android. Android-ndk-r8d does not have mbtowc implemented, which Serialization apparently uses, somewhere. I would like to recreate this function myself, rather than find another Serialization library entirely or write one myself. The function leverages the wchar_t type, which also does not appear to built into android-ndk-r8d. What is boost serialization expecting this type to be? Can I grab an implementation of it from off of a shelf somewhere?

2 1

Problems using for_each
by Michael Powell 31 Mar '13

31 Mar '13

Hello, I am struggling making for_each work right. I am using Sourcery targeting ARM. AFAIK, GCC is actually 4.7.2, and I am flagging -std=c++11. I'm not really picky how we get for_each done (or constructs like it). I'd like to avoid "macro-expansion" for obvious reasons (i.e. debug), and the always-infamous verbosity of a for loop, if possible. I've got the following: vector<rgb_type*> all; rgb_type rgb; rgb_type rgb2 = rgb.clone(); for_each(all.begin(), all.end(), cout << _1->r() << endl); With errors: _1 was not declared in this scope. (C++ Problem) That or, void rgb_printer_func(rgb_type* prgb) { cout << prgb->r() << endl; } for_each(all.begin(), all.end(), rgb_printer_func); With errors: Invalid arguments Candidates are: #1 for_each(#0, #0, #1) (Semantic Error) Thank you. Regards, Michael Powell

2 4

Building Boost 1.53
by Michael Powell 30 Mar '13

30 Mar '13

Hello, I believe we're on the home stretch building boost and getting productive with it. But I have a couple of questions. When we run ./b2 to build boost with the PREFIX option, what actually lands there? I'm thinking we just locate that in our /path/to/boost/, which ends up being ./tools/boost_1_53_0 from our project workspace perspective. But, there are other insights I don't know about I am certain. Thanks much. Regards, Michael Powell

3 5

[lockfree] Queue with shared_ptr as elements
by sguazt 30 Mar '13

30 Mar '13

Hello, Is it possible to use lockfree::queue with shared_ptr as element types? For instance, ---[code]--- #include <boost/lockfree/queue.hpp> #include <boost/smart_ptr.hpp> class foobar { }; int main() { typedef boost::shared_ptr<foobar> element_type; typedef boost::lockfree::queue<element_type> queue_type; queue_type queue; } ---[/code]--- If I compile the above code I get the following error: ---[error]--- boost_lockfree_mwmr_queue.cpp:13:13: required from here ~/projects/svn/boost-trunk/boost/lockfree/queue.hpp:81:5: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’ ~/projects/svn/boost-trunk/boost/lockfree/queue.hpp:85:5: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’ ---[/error]--- If I use "foobar" or "foobar*" as element_type, it works. I'm using - GCC 4.7.2 with the following options enabled: -Wextra -Wall -ansi -pedantic - boost SVN trunk version Thank you very much for helping. Best, -- Marco

2 1

[fusion] [mpl] binary mpl::transform on empty std::tuple
by Nathan Ridge 30 Mar '13

30 Mar '13

Hello, Fusion provides adaptation code for treating an std::tuple as a Fusion sequence, and adaptation code for treating Fusion sequences as MPL sequences, but it seems that in the case of a binary mpl::transform on an empty std::tuple, the two do not work well together. When trying to compile the following code: #include <boost/mpl/transform.hpp> #include <boost/mpl/back_inserter.hpp> #include <boost/mpl/vector.hpp> #include <boost/fusion/adapted/std_tuple.hpp> #include <boost/fusion/adapted/mpl.hpp> #include <boost/fusion/mpl.hpp> struct first { template <typename T, typename U> struct apply { typedef T type; }; }; int main() { typedef std::tuple<> fusion_sequence1_type; typedef std::tuple<> fusion_sequence2_type; typedef boost::mpl::transform<fusion_sequence1_type, fusion_sequence2_type, first, boost::mpl::back_inserter<boost::mpl::vector<>> >::type result_type; } I get the following errors: In file included from test.cpp:4: In file included from boost/fusion/adapted/std_tuple.hpp:13: In file included from boost/fusion/adapted/std_tuple/detail/begin_impl.hpp:10: boost/fusion/adapted/std_tuple/std_tuple_iterator.hpp:45:13: error: implicit instantiation of undefined template 'std::tuple_element<0, std::tuple<> >' : std::tuple_element<Iterator::index, ^ boost/fusion/iterator/value_of.hpp:34:28: note: in instantiation of template class 'boost::fusion::std_tuple_iterator<std::tuple<>, 0>::value_of<boost::fusion::std_tuple_iterator<std::tuple<>, 0> >' requested here struct apply : Iterator::template value_of<Iterator> {}; ^ boost/fusion/iterator/value_of.hpp:51:15: note: in instantiation of template class 'boost::fusion::extension::value_of_impl<boost::fusion::iterator_facade_tag>::apply<boost::fusion::std_tuple_iterator<std::tuple<>, 0> >' requested here : extension::value_of_impl<typename detail::tag_of<Iterator>::type>:: ^ boost/fusion/iterator/mpl/fusion_iterator.hpp:46:45: note: in instantiation of template class 'boost::fusion::result_of::value_of<boost::fusion::std_tuple_iterator<std::tuple<>, 0> >' requested here typedef typename fusion::result_of::value_of<Iterator>::type type; ^ boost/mpl/iterator_category.hpp:27:22: note: in instantiation of template class 'boost::mpl::fusion_iterator<boost::fusion::std_tuple_iterator<std::tuple<>, 0> >' requested here typedef typename Iterator::category type; ^ boost/mpl/pair_view.hpp:152:20: note: in instantiation of template class 'boost::mpl::iterator_category<boost::mpl::fusion_iterator<boost::fusion::std_tuple_iterator<std::tuple<>, 0> > >' requested here typename iterator_category<iter1_>::type ^ boost/mpl/aux_/has_tag.hpp:20:1: note: (skipping 5 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all) BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_tag, tag, false) ^ boost/mpl/has_xxx.hpp:244:65: note: expanded from macro 'BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF' , boost::mpl::aux::type_wrapper<BOOST_MSVC_TYPENAME U::name>* = 0 \ ^ boost/mpl/transform.hpp:75:7: note: in instantiation of template class 'boost::mpl::fold<boost::mpl::pair_view<std::tuple<>, std::tuple<> >, boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, boost::mpl::bind2<boost::mpl::push_back<mpl_::na, mpl_::na>, mpl_::arg<1>, boost::mpl::bind2<first, boost::mpl::bind1<boost::mpl::first<mpl_::na>, mpl_::arg<2> >, boost::mpl::bind1<boost::mpl::second<mpl_::na>, mpl_::arg<2> > > > >' requested here : fold< ^ boost/mpl/transform.hpp:114:1: note: in instantiation of template class 'boost::mpl::aux::transform2_impl<std::tuple<>, std::tuple<>, first, boost::mpl::back_inserter<boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na> > >' requested here BOOST_MPL_AUX_INSERTER_ALGORITHM_DEF(4, transform2) ^ boost/mpl/aux_/inserter_algorithm.hpp:44:7: note: expanded from macro 'BOOST_MPL_AUX_INSERTER_ALGORITHM_DEF' : aux::name##_impl<BOOST_MPL_PP_PARAMS(arity, P)> \ ^ boost/mpl/eval_if.hpp:38:22: note: in instantiation of template class 'boost::mpl::transform2<std::tuple<>, std::tuple<>, first, boost::mpl::back_inserter<boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na> > >' requested here typedef typename f_::type type; ^ boost/mpl/transform.hpp:138:1: note: in instantiation of template class 'boost::mpl::eval_if<boost::mpl::or_<boost::mpl::is_na<first>, boost::mpl::is_lambda_expression<std::tuple<> >, boost::mpl::not_<boost::mpl::is_sequence<std::tuple<> > >, mpl_::bool_<false>, mpl_::bool_<false> >, boost::mpl::transform1<std::tuple<>, std::tuple<>, first>, boost::mpl::transform2<std::tuple<>, std::tuple<>, first, boost::mpl::back_inserter<boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na> > > >' requested here AUX778076_TRANSFORM_DEF(transform) ^ boost/mpl/transform.hpp:125:22: note: expanded from macro 'AUX778076_TRANSFORM_DEF' typedef typename eval_if< \ ^ test.cpp:21:25: note: in instantiation of template class 'boost::mpl::transform<std::tuple<>, std::tuple<>, first, boost::mpl::back_inserter<boost::mpl::vector<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na> > >' requested here typedef boost::mpl::transform<fusion_sequence1_type, ^ c++/4.8.0/tuple:672:12: note: template is declared here struct tuple_element; ^ 1 error generated. Seems like something is trying to call value_of on the begin iterator of the tuple, which in the case of an empty tuple is a past-the-end iterator. If I use non-empty tuples instead: typedef std::tuple<int> fusion_sequence1_type; typedef std::tuple<int> fusion_sequence2_type; It works fine. Unary mpl::transform works fine in either case. Am I doing something wrong, or is this a bug? Thanks, Nate

1 0

Elegant solution to interview question about boost::fusion::vector
by Stuart 29 Mar '13

29 Mar '13

Hello everyone, I have stumbled over m2pq36bk97.fsf(a)boostpro.com in comp.lang.c++.moderated. I had never used boost before but I always try to solve interview questions. I found a solution that works, but I have the feeling that there must be a more elegant solution. The problem that was presented in the interview was the following: typedef boost::fusion::vector<int, double, float> row; std::vector<row> M; template <typename T> typename T::value_type Accumulate (T const &t) { typedef typename T::value_type value_type; return std::accumulate (t.begin (), t.end (), value_type ()); } Provide a function fun so that Accumulate (fun<0>(M)); computes the sum of the first column of M, or more generally Accumulate (fun<x>(M)); computes the sum of the xth column of M. The solution that was provided in m2pq36bk97.fsf(a)boostpro.com did not work out of the box, but I was able to fix it into the following solution: // Functor that extracts nth element of row vector. template <unsigned N> struct tuple_at { template <class Vector> typename boost::fusion::result_of::at_c<const Vector,N>::type operator()(Vector const& t) const { return boost::fusion::at_c<N, Vector>(t); } }; template <unsigned N, class M> auto fun(M const& x) -> decltype(x | boost::adaptors::transformed(tuple_at<N>())) { return x | boost::adaptors::transformed(tuple_at<N>()); } so that int main () { M.push_back(row (1, 1.0, 2.8)); M.push_back(row (2, 0.1, 2.8)); M.push_back(row (3, 0.01, 2.8)); std::cout << Accumulate(fun<1> (M)); } prints 1.11 as expected. However, I think that I should be able to achieve the same without the template tuple_at. I tried using a lambda: template <unsigned N, class M> auto fun(M const& x) -> decltype(x | boost::adaptors::transformed( [] (typename M::value_type const& x ) { return boost::fusion::at_c<N> (x); })) { auto retval = x | boost::adaptors::transformed( [] (typename M::value_type const& x ) { return boost::fusion::at_c<N> (x); }); return retval; } Unfortunately, this does not compile ("Lambda expression in an unevaluated operand"). I'm also not sure whether boost::adaptor::transformed can work with lambdas. I also tried to generate a functor object from boost::fusion::at_c using the following code from the internet: template<typename T> std::function<T> make_function (T* t) { return { t }; } template <unsigned N, class M> auto fun (M const& x) -> decltype(make_function(&boost::fusion::at_c<N, const M>)) { auto retval = make_function(&boost::fusion::at_c<N, const M> ); return retval } but this yields an error that I can't decipher yet: at.hpp:62:15: Implicit instantiation of undefined template 'boost::fusion::extension::at_impl<boost::fusion::non_fusion_tag>::apply<const std::__1::vector<boost::fusion::vector<int, double, float, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>, std::__1::allocator<boost::fusion::vector<int, double, float, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>>>, mpl_::int_<2>>' The ideal solution would be one where I don't have to write the functor object manually. Even more elegantly, I should be able to leave out the return type and let the compiler figure it out automatically. Unfortunately, I use llvm gcc 4.2, so the automatic return type evaluation is out of reach (although boost without this feature seems to be quite cumbersome). Can anyone provide some insights? Thanks in advance, Stuart

2 2

[chrono][thread] Best way to wait?
by Klaim - Joël Lamotte 29 Mar '13

29 Mar '13

Hi, can someone clarify: 1. what is the difference between: const auto wait_time = boost::chrono::miliseconds( 8 ); boost::mutex mutex; boost::unique_lock<boost::mutex> lock( mutex ); boost::condition_variable wait_condition; wait_condition.wait_for( lock, wait_time ); and const auto wait_time = boost::chrono::miliseconds( 8 ); boost::this_thread::sleep_for( wait_time ); 2. are there other ways to wait? (I mean make the thread sleep, not looping until it's time) Joel Lamotte

2 4

Some questions about vertex removal in subgraph
by Nicholas Mario Wardhana 29 Mar '13

29 Mar '13

Hi all, In the last few days I have been implementing partial I/O for a subgraph by saving and loading a subgraph (although actually it is only partial if we see it from the parent graph's point of view). So far, by modifying some code in Boost, I managed to save a child graph to a file, and also load two subgraphs which share a vertex without having that vertex duplicated. However, in addition to save and load, I also need to clear (i.e. remove all nodes and edges from) a subgraph, and I found that remove_vertex is not implemented; only remove_edge is. I noticed that as of now (March 2013) there is no plan to implement it [1]. I cannot use Jeremiah's suggestion there (and also in [2]) to use filtered_graph, because I need to physically remove the nodes and edges from memory, so I am thinking to implement it myself. I have a few questions about this. 1) Jeremiah said that "In particular, local vertex descriptors in subgraphs are indices into an std::vector, and so removing a vertex would invalidate many other vertex descriptors." [1] Am I right to assume that this statement is about m_global_vertex, which is of std::vector<vertex_descriptor> type? 2) Removing a vertex from a regular graph involves calling g.m_vertices.erase(..) (adjacency_list.hpp, line 1951). I found that m_vertices is also of type std::vector. So why does vertex removal work for regular graph, but supposedly not for subgraph? I use Boost version 1.53.0, and my subgraph configuration is typedef adjacency_list<vecS, vecS, undirectedS, property<vertex_index_t, int, VertexProperty>, property<edge_index_t, int, EdgeProperty> > RegularGraph; typedef subgraph<RegularGraph> Subgraph; where VertexProperty and EdgeProperty are respectively bundled properties for vertex and edge. Thank you very much! Best regards, Nicholas Mario Wardhana References: [1] https://svn.boost.org/trac/boost/ticket/4752 [2] http://boost.2283326.n4.nabble.com/Can-t-link-subgraphs-because-remove-vert…

1 0

Re: [Boost-users] header-only libraries
by dib 27 Mar '13

27 Mar '13

> > >> I'd like to use the program_options library, but am reluctant to > >> require my users to build parts of Boost. Is there a strong > >> reason that this library cannot be header-only? > > You can build the necessary Boost CPP files as part of your own > build. > Asio (which is header-only) offers the possibility for "optional separate compilation" by including some ".../impl/src.hpp" in a source file and defining either "BOOST_ASIO_SEPARATE_COMPILATION" or "BOOST_ASIO_DYN_LINK", which very nicely lets the user choose which one suits best for his needs. Is there a reason why this isn't done for other libs like program_options, regex, etc., or has it (at least sometimes) just not been done because nobody wanted to do this extra-work? It is a very frequently asked question if/why not there is a header-only version, and although it is sometimes really not possible to make it header-only, most libs should work that way. Furthermore, in my experience specially commercial projects are reluctant to use libraries that have to be shipped with the own product, whereas it is no problem as long as they are "hidden" inside the binary.. Of course there are some disadvantages as shown in the discussion on stackoverflow, but giving the user a choice where possible should hugely increase acceptance and usage of those libraries. Greetings, dib PS: I just tried it with program_options and at least with my programs on linux it works fine, don't know how it is on other platforms or if I was just lucky: copy the src-files from libs/program_options/src to the include/boost/program_options/impl and do it "the asio-way", including the source files in a separate .cpp in my projects.. works fine and no linking is required any more.

3 4

header-only libraries
by ilya shlyakhter 26 Mar '13

26 Mar '13

Dear Boost experts, I'd like to use the program_options library, but am reluctant to require my users to build parts of Boost. Is there a strong reason that this library cannot be header-only? Or perhaps, it's possible to create a header-only version of this library? I have the same question for regex. Thanks, ilya

3 2

[MSM] "favor_compile_time" policy disables "kleene" events. (Bug?)
by Deniz Bahadir 25 Mar '13

25 Mar '13

Hi everyone, Hi Christophe, While trying to speedup compilation of my MSM/eUML-based state machine, I seem to have found a bug. I added the "favor_compile_time" policy to the type-definition of my state-machine as the documentation suggests. I did not use the macro "BOOST_MSM_BACK_GENERATE_PROCESS_EVENT" because I do not have any sub-statemachines. This did speed up compilation, however obviously by changing my transition-table: All "kleene"-events in my transition-table are ignored, when defining the state-machine with the "favor_compile_time" policy. Can anyone confirm this or am I using it wrong? (Was this policy supposed to work with eUML in the first place?) Thanks, Deniz PS: I am using GCC 4.7.2 with Boost 1.53.

3 6

Broken Links?
by Hei Chan 25 Mar '13

25 Mar '13

Hi, On http://www.boost.org/doc/libs/1_53_0/libs/pool/doc/html/boost_pool/pool/poo…, all the graphs there seem broken. Anyone fixing it? Thanks in advance. Cheers, Hei

2 1

[boost::Statechart] posting a "serial timeout" event
by Andre de Jong 25 Mar '13

25 Mar '13

I've been using boost's asynchronous statechart to write a program. In this program I communicate with another device using an asynchronous serial port. I have a state that waits for a confirmation from the device over the serial port and then posts a "confirmation received" event. This works well but, I would also like to implement a "timeout" event. In previous programs I had been using switch case statements for my state machines where I had code that could be run each time the loop was run. This meant I could run code and check if I should change state due to something timing out. Like this: while(1){ switch (state){ case 0:{ sendMessage(); state = 1; sendTime = boost::chrono::steady_clock::now(); } break; case 1:{ if (isConfirmationReceived()){ // do something state = 2; } else if (boost::chrono::steady_clock::now() > start + boost::chrono::duration<double>(WAIT_LENGTH)){ //do something state = 3; } } break; // etc etc } } How would I implement something like this using boost::StateChart? Or, should i be thinking about this a completely different way?

1 0

Re: [Boost-users] Broken Links?
by Boost_mailinglist＠gmx.de 25 Mar '13

25 Mar '13

Hello, you can see the directory listing of the pictures under http://www.boost.org/doc/libs/1_53_0/libs/pool/doc/images/ -----Ursprüngliche Nachricht----- Gesendet: Montag, 25 März 2013 um 06:32:27 Uhr Von: "Hei Chan" <structurechart(a)yahoo.com> An: "boost-users(a)lists.boost.org" <boost-users(a)lists.boost.org> Betreff: [Boost-users] Broken Links? Hi, On�http://www.boost.org/doc/libs/1_53_0/libs/pool/doc/html/boost_pool/pool/…, all the graphs there seem broken. Anyone fixing it? Thanks in advance. Cheers, Hei _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

1 0

bad reloc address when compiling with mingw
by Leonardo Sá 24 Mar '13

24 Mar '13

Hi all, I have been trying to create an .exe that links to several boost libraries (date-time, python, etc.) using MinGW, cross compiling for windows on linux. I compiled boost using mingw without problems. When linking the exe, I am receiving the following error: CMakeFiles/fp_core_test.dir/objects.a(MockEnvironment.cpp.obj):MockEnvironment.cpp:(.text+0x381): undefined reference to `fp_core::Window::init(int, int, boost::shared_ptr<fp_core::Renderer>)' /usr/bin/i686-w64-mingw32-ld: CMakeFiles/fp_core_test.dir/objects.a(MockEnvironment.cpp.obj): bad reloc address 0x8 in section `.text$_ZN5boost6detail15sp_counted_baseC2Ev[boost::detail::sp_counted_base::sp_counted_base()] I have no idea what "bad reloc address" means. Googling wasn't much help. Anyone can give me a pointer in the right direction? Thanks!

1 0

newbie problem with Program Option string value
by Neil Sutton 24 Mar '13

24 Mar '13

I am having problems getting a program option to work. The option should enable a user to enter a location when they select the '--location' option. so, if you type --location canada, the code should store the supplied string - canada and pass it on to the program. This is a typical program option with nothing special. But I cannot seem to get it to work! Please look at this: ---------------------------------------------------- std::string place_option; // a global variable po::options_description general("General options"); general.add_options() ("location", po::value<std::string>(), "location of your home"); // there are other non string options po::variables_map vm; po::store(po::parse_command_line(ac,av, general),vm); po::notify(vm); if(vm.count("help")) { std::cout << general << "\n"; return 0; } if(vm.count("version, v")) { std::cout << "version aplha\n"; } if(vm.count("location")) { place_option = vm["location"].as<std::string>(); // should pass the string value entered at command line to std::string place. } If i run my program with eg 'myprogram --location disney' I get: terminate called after throwing an instance of 'std::logic_error' what(): basic_string::_S_construct NULL not valid Aborted ------------------------------ Now I have tried a few variations of the code. The examples show where an int value is supplied and retrieved. I cannot work out how to do - what should be very trivial. I simply want to recover the value associated with 'location' i.e a std::string entered at the command line. I then want to pass that value on to my program to do something with it. I do not understand the error. Can someone kindly show me the correct syntax to accomplish this please? Kind regards.

3 2