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

Problem with 'cannot instantiate abstract class' after switching from BOOST 1.33.0 to 1.34.1 (also VS2005 -> VS2008)
by Tobias Alte 18 Mar '09

18 Mar '09

Hi everyone, After switching from BOOST 1.33.0 to 1.34.1 (and also from VS2005 -> VS2008) we got a couple of problems with "cannot instantiate abstract class" errors. The application compiles fine in the setup VS2005 + BOOST 1.33.0 but suddenly started to throw a couple of "cannot instantiate abstract class" errors when using VS2008 + BOOST 1.34.1 . The errors itself get reported for 'concept_check.hpp' but that header did not change between the two BOOST releases (as far as I know - I think I made a diff with no results). I believe that the issue is most likely related to the boost::shared_ptr's to templated classes in our code. I already solved a few of these errors that arose thanks to slightly different types in the method definitions thanks to VS2008 having more built in types. However, the current "cannot instantiate abstract class" errors are persistently eluding my grasp. And the compiler is not helpful with just reporting the error in 'concept_check.hpp' and not where it really is. Questions: Can anyone of you think of additional (compiler) switches for BOOST (or even VS2008) that could help track down these kind of the issues? Did anyone experience similar problems when switching between BOOST versions (in general)? Thanks a lot for reading this and for any advice. T

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Passing arguments to threads
by r ottmanj 18 Mar '09

18 Mar '09

I am working on an application that takes use of boost::thread. During the initial method of my application I need to pass one argument to the method. As per the api documentation for boost::thread I am using the following: boost::thread dataThread(dparse.dataMain,instUUID); dataThread.join(); However, when I attempt to use this, I get the following exception from my compiler. Is there something that I am missing? I do not see how my thread constructor is any different from the constructor in the api documentation. Any help with this is greatly appreciated. error: no matching function for call to ‘boost::thread::thread(<unresolved overloaded function type>, std::string&)’ /usr/include/boost/thread/thread.hpp:38: note: candidates are: boost::thread::thread(const boost::function0<void, std::allocator<boost::function_base> >&) /usr/include/boost/thread/thread.hpp:37: note: boost::thread::thread() /usr/include/boost/thread/thread.hpp:35: note: boost::thread::thread(const boost::thread&)

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[Lexical Cast] Strange behaviour
by Robert Jones 18 Mar '09

18 Mar '09

I know this is not new, but I've just bumped into it.... This code #include <iostream> #include <boost/lexical_cast.hpp> int main(int argc, char* argv[]) { try { ulong u = boost::lexical_cast<ulong>("-1"); cout<<"Conversion"< } catch(const std::exception&) { cout<<"Exception"< } } Silently returns ULONG_MAX under MSVC7, though not under GCC. It's an accuate reflection of how the underlying C library handles it, but do we want to propogate this strangeness? Rob.

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[asio] io_service threadpool performance
by Rutger ter Borg 18 Mar '09

18 Mar '09

Dear all, I have been testing asio's io_service in a threadpool setup for job dispatching. However, it seems as if adding threads doesn't improve performance; perhaps even the opposite with 1 thread having the best performance. See below for some results of a simple test I'm doing, posting 10 M jobs to the io_service, and starting N threads at io_service::run after that. Timings below are measured on an 8-core machine, I would expect the execution performance to improve (not to get worse) for execution by more threads. Posting to the io_service is done single-threaded, so these timings should remain approx. the same. Please find attached the test program. Is there something I've missed and/or should tweak to get the desired improvement per added thread? Many thanks, Kind regards, Rutger ter Borg Concurrency = 1 Finished posting after: 3.15 Finished execution after: 5.44 Execs / sec: 1e+07/2.29=4.36681e+06 Concurrency = 2 Finished posting after: 2.85 Finished execution after: 5.47 Execs / sec: 1e+07/2.62=3.81679e+06 Concurrency = 3 Finished posting after: 3.15 Finished execution after: 11.65 Execs / sec: 1e+07/8.5=1.17647e+06 Concurrency = 4 Finished posting after: 3.15 Finished execution after: 9.8 Execs / sec: 1e+07/6.65=1.50376e+06 Concurrency = 5 Finished posting after: 3.28 Finished execution after: 12.45 Execs / sec: 1e+07/9.17=1.09051e+06 Concurrency = 6 Finished posting after: 3.29 Finished execution after: 8.84 Execs / sec: 1e+07/5.55=1.8018e+06 Concurrency = 7 Finished posting after: 3.51 Finished execution after: 10.09 Execs / sec: 1e+07/6.58=1.51976e+06 Concurrency = 8 Finished posting after: 3.38 Finished execution after: 12.54 Execs / sec: 1e+07/9.16=1.0917e+06

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Range_Ex and Multi-Index: conflicting mpl::begin and boost::begin
by Sandeep Gupta 18 Mar '09

18 Mar '09

Hi, I am under-impression that for_each construct of range_ex for all container concepts. However when I tried with multi-index it gave conflicting errors. Attached below is the code and corresponding errors. code: typedef multi_index_container< std::pair<value_type,int>, indexed_by< ordered_unique<member<pair<value_type,int>, value_type, &pair<value_type, int>::first> >, ordered_unique<member<pair<value_type,int>, int, &pair<value_type, int>::second> > > > mic; mic serialStore; for_each(serialStore, std::cout<<boost::lambda::_1<<' '); error: /home/sandeep/Computing/boost_1_38_0/boost/mpl/begin_end_fwd.hpp:22: error: ‘template<class Sequence> struct boost::mpl::begin’ is not a function, /home/sandeep/Computing/boost_1_38_0/boost/range/begin.hpp:96: error: conflict with ‘template<class T> typename boost::range_iterator::type boost::begin(T&)’ /home/sandeep/Computing/boost_1_38_0/boost/range_ex/./detail/adl_begin_end.hpp:27: error: in call to ‘begin’ /home/sandeep/Computing/boost_1_38_0/boost/mpl/begin_end_fwd.hpp:23: error: ‘template<class Sequence> struct boost::mpl::end’ is not a function, /home/sandeep/Computing/boost_1_38_0/boost/range/end.hpp:92: error: conflict with ‘template<class T> typename boost::range_iterator::type boost::end(T&)’ /home/sandeep/Computing/boost_1_38_0/boost/range_ex/./detail/adl_begin_end.hpp:35: error: in call to ‘end’ I apologies in advance if this is due to trivial omission. Thanks -sandeep

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[xpressive] is regex_match threadsafe?
by Sergey Skorokhodov 18 Mar '09

18 Mar '09

Hi, Is it safe to call regex_match with the same cregex|sregex object from different threads? Or should each thread use its own cregex|sregex object? TIA -- Sergey Skorokhodov

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[program options] allow unregistered options for config file
by Deane Yang 18 Mar '09

18 Mar '09

Instructions for how to allow unregistered options on the command-line are given here: http://www.boost.org/doc/libs/1_38_0/doc/html/program_options/howto.html#id… Is there any way to allow unregistered options for a configuration file, too?

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[boost-users][python]
by Germán Diago 18 Mar '09

18 Mar '09

Hello. I have a library which exposes the following function: namespace ftr { Player & getPlayer(int num); } and it's exposed to python by: def("getPlayer", &ftr::getPlayer, return_value_policy<reference_existing_object>()); This code used to work, but now I compile it and get this error when using it from the python module, under ubuntu 9.04: Traceback (most recent call last): File "/usr/lib/python2.5/site-packages/apport_python_hook.py", line 77, in apport_excepthook pr['PythonArgs'] = '%r' % sys.argv AttributeError: 'module' object has no attribute 'argv' Original exception was: Traceback (most recent call last): File "<string>", line 1, in <module> Boost.Python.ArgumentError: Python argument types in ftr.getPlayer(int) did not match C++ signature: getPlayer(int) Any help here, please? I don't know why this should happen.

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Re: [Boost-users] [graph] set of edges
by Michael Fawcett 18 Mar '09

18 Mar '09

On Mon, Mar 16, 2009 at 5:30 PM, Michael Fawcett <michael.fawcett(a)gmail.com> wrote: > On Mon, Mar 16, 2009 at 5:15 PM, Juan Antonio Farré Basurte > <jafb(a)tinet.org> wrote: > > Please try not to top post per guidelines. I've lost the attributions > unfortunately, but fixed the formatting a little. > >>> I meant for OutEdgeList, however I went back and tried vecS for >>> EdgeList as well and all my tests still passed and my program output >>> was still correct. Perhaps this was corrected in code but the docs >>> weren't updated? >> >> I don't think so... I'm working with version 1.38 and I had a std::map with >> edge_descriptor keys. >> I passed this map, wrapped as an associative_property_map, and added to a >> dynamic_properties object, to graph-reading functions. >> When I traversed the map contents to do something useful with it, looks like >> the descriptors where invalid. In some cases it just looked to do nothing. >> In other cases I got segmentation fault. When I changed to listS, everything >> worked all right. >> In the documentation it just says that it's "not guarranted" to work. And >> looks to be true. Works in some cases and not in others. > > It sounds like something assumes that those descriptors will not be > invalidated unless removed. Maybe Andrew can chime in? > > I would guess it's working for me by accident since I'm never removing > anything from the graphs I create. I'll make sure to keep my usage to > listS for now. Reposting with subject line changed. --Michael Fawcett

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factorial function
by agascon＠correo.ugr.es 18 Mar '09

18 Mar '09

Hi everyone, I'm new to boost (and not so new but not very experienced to c++) and I'm having problems with functions defined with a template, as factorial (http://www.boost.org/doc/libs/1_38_0/libs/math/doc/sf_and_dist/html/math_to…). My questions is, how do I call the funtion factorial? Why isn't it enough calling factorial(n) where n is an unsigned integer? Does one need to define the function specifying the result type before? If so, how? Thanks in advance. Greetings, Alberto.

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