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C4251 needs to have dll-interface
by Christopher Pisz 28 Sep '11

28 Sep '11

This might be more of a windows question, but... Everytime I use a boost template as part of a class interface that is exported from a dll, I get this compiler warning. For example I just cut and paste the TcpServer example from boost::asio::ip::tcp into a test project dll. I get: warning C3251: 'boost_enable_shared_from_this<T>::weak_this_':class 'boost::weak_ptr<T> ' needs to have a dll-interface to be used by clients of class 'boost::enable_shared_from_this<T>' It comes from the line: class __declspec(dllexport) TcpConnection : public boost::enable_shared_from_this<TcpConnection> { public: typedef boost::shared_ptr<TcpConnection> SmartPtr; . . . }; How do I solve these types of errors? Currently, I just include the correspnding boost header in the client project and igore the warnings, but I'd really like to get rid of them. Should I be including the boost headers and library in the client project? Doesn't the client project get what it needs from the dll, when the dll includes the headers and library?

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[boost-newbie] Compiler Error on OS X 10.7.1 (Lion)
by Rob Jones 28 Sep '11

28 Sep '11

Trying to use BOOST_FOREACH() in some code and I'm getting the following errors: /Developer/SDKs/MacOSX10.7.sdk/usr/include/c++/4.2.1/bits/ios_base.h:779: error: 'std::ios_base::ios_base(const std::ios_base&)' is private /Developer/SDKs/MacOSX10.7.sdk/usr/include/c++/4.2.1/streambuf:802: error: 'std::basic_streambuf<_CharT, _Traits>& std::basic_streambuf<_CharT, _Traits>::operator=(const std::basic_streambuf<_CharT, _Traits>&) [with _CharT = char, _Traits = std::char_traits<char>]' is private The compiler is: GCC 4.2 O/S is: OS X 1.7.1 Boost 1.47.0 was installed using MacPorts. Any help / pointers here would be useful. Thanks in advance. Rob

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Problem with the filesystem::exists()
by Danilo da Silveira Figueira 27 Sep '11

27 Sep '11

Hi folks, I´m stuck with an problem, when i try pass an accentued string to exists method: When i wrote in the code "C:\\ó.txt" and the file is under ANSI codification the function exists return true. But when i ask the input to the user the function return false. Ps: wstring in the basic_path template dont fix this. If someone know how and have a time to help me i will be very grateful

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How do I print a standard pair?
by Krzysztof Żelechowski 27 Sep '11

27 Sep '11

The expression (cout << make_pair (0, 1)) gives me an error. Does Boost offer me a way to print a (rvalue) pair, as within an expression?

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Compilation Error in Boost::unordered_detail::hash_table on boost 1_46_1
by Shinil Gangadharan 27 Sep '11

27 Sep '11

Hi, I am using Sun CC v5.9 compiler to compile boost 1_46_1. We are getting the following error. Is there a way to get around with this error? "/dvobs/a-ThirdParty/Boost/boost_1_46_1/boost/unordered/detail/table.hpp", line 595: Error: Could not find a match for boost::unordered_detail::hash_table<boost::unordered_detail::T>::find(const boost::unordered_detail::Key&, const boost::unordered_detail::Hash&, const boost::unordered_detail::Pred&) const. "/dvobs/a-ThirdParty/Boost/boost_1_46_1/boost/unordered/detail/table.hpp", line 595: Error: Too many args in template, from boost::unordered_detail::Hash on ignored. Regards, Shinil V.G.

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boost thread / condition_variable / old patch not applied to 1.47.0
by Julien Nitard 27 Sep '11

27 Sep '11

Hi All, I have a warning when compiling some code using a condition variable (unused variable in boost/thread/pthread/condition_variable.hpp on line 53). It seems there is a patch for it but it has not been applied to 1.47.0 despite being quite old: https://svn.boost.org/trac/boost/attachment/ticket/4818/boost-thread-pthrea… I have tested the patch it works for me (Ubuntu / GCC 4.5 / -Wall). Hoping this helps, Best regards, Julien

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[BGL] Distributed adiacency_list memory allocation
by Cosimo Calabrese 27 Sep '11

27 Sep '11

Hi to all, I'm working on WinXP, VS2010, Boost 1.46.1. I've writed this short program: //---------------------------------- #include <boost/graph/use_mpi.hpp> #include <boost/graph/distributed/mpi_process_group.hpp> #include <boost/graph/distributed/adjacency_list.hpp> using boost::graph::distributed::mpi_process_group; typedef boost::property<boost::vertex_distance_t, long, boost::property<boost::vertex_name_t, std::string > > vertex_prop; typedef boost::property<boost::edge_weight_t, long > edge_prop; typedef boost::adjacency_list< boost::vecS, boost::distributedS<mpi_process_group, boost::vecS>, boost::directedS, vertex_prop, edge_prop > Graph; typedef boost::graph_traits<Graph>::edge_descriptor EdgeDescriptor; typedef boost::graph_traits<Graph>::vertex_descriptor VertexDescriptor; int main(int argc, char* argv[]) { boost::mpi::environment env(argc,argv); Graph g( 10 ); return 0; } //---------------------------------- When I launch it, every process allocates about 1 GB of memory. Why it allocates all that memory? Is it normal? Is there any tuning to the PBGL framework that I must made? I use it on a 2-core machine, and the command that I use is: mpiexec -n 2 .\test.exe I've tried with openMPI 1.4.3 and Microsoft HPC Pack 2008, but it seems irrilevant. Thanks in advance, Cosimo Calabrese.

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Class version exception during load
by Andrew Swerlick 27 Sep '11

27 Sep '11

Hi all, I'm trying to create a class with built in save and load methods that handles serializing and deserializing data to disk to persist the class. I've been able to get the save working, but I'm having some trouble with the load. I getting the below error. error: Failure in UserObjectSerialization: Unhandled exception: class version I've done some googling on it and can't find any documentation that seems to apply in my situation. I'm not using any of the versioning features built into boost, as this is mostly an experiment to get familar with the library. The error is happening inside of a basic c++ Unit Test, copied below TEST(UserObjectSerialization) { UserObjects::UserObject userobj; boost::posix_time::ptime time = userobj.GetCreatedOn(); userobj.SetName("TestObj"); userobj.Save(); sleep(5); UserObjects::UserObject loadedUserObj; { std::ifstream ifs("TestObj"); boost::archive::text_iarchive ia(ifs); ia >> loadedUserObj; } The save method of the user object looks like this void UserObject::Save() { std::ofstream ofs(_name.c_str()); { boost::archive::text_oarchive oa(ofs); // write class instance to archive oa << this; // archive and stream closed when destructors are called } } The error is being thrown on the line "ia >> loadedUserObj" of the test method. I can provide the full include and class definition file for the UserObject class if needed, but I didn't want to clutter up my message if it wasn't necessary. I can also post the contents of one of the files created during a sucessful save. Does anyone have any advice on how to deal with this error? Thanks for your help. ~Andrew S.

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Re: [Boost-users] Boost.Units documentation
by Matthias Schabel 26 Sep '11

26 Sep '11

> I am afraid I have yet another question for you. I am trying to define a > polynomial in what boost.units calls 'absolute temperature', something along > the lines of > > (0.015/kelvin_squared)*T_abs*T_abs + (0.014/kelvin)*T_abs > > The temperature involved is simply the temperature of the atmosphere, which > seems best represented by an absolute temperature. As I understand things > now this is not possible and I would need to user 'relative temperatures' to > be able to use multiplications etcetera. In the case at hand, that would > mean that I should use T_rel = T_abs - 0.0*kelvin which just doesn't feel > right I am afraid and does not allow conversion to a Celsius scale (which > needs to be based on the 'absolute temperature'). It seems to me that > 'scaling by a factor 0.015' is just as meaningful for absolute temperatures > as it is for relative temperatures... > > I understand that the relation between (absolute) temperature scales is > affine instead of linear and that this has triggered the need to make the > distinction (as for the relation between linear scales it does not really > matter whether measurements are relative or absolute (which is just > 'relative to zero' as indicated above)). Pieter, In general, equations like these have an implicit offset, so what you really want is T_rel = T_abs - T_offs, as you have written. Especially if it is empirically-derived, polynomial expansions are often used implicitly - that is, the model equations are essentially intended to represent a Taylor (or some other) series expansion. As Steven pointed out, Kelvin is a special case because the offset is defined as zero. These expansions are always done around a specific point and, if you look at the equations for the expansions themselves you will see that they are dimensionally consistent : f(T-T_offs) ~ f(T_offs) + f'(T_offs) (T-T_offs)/1! + f''(T_offs)(T-T_offs)/2! + … -> Unit ~ Unit + Unit/Kelvin (Kelvin) + Unit/Kelvin^2 (Kelvin)^2 + … should also make sense if you change the unit of temperature to something else, which is what you would be doing if you wanted to scale by 0.015...this is only possible if you use relative temperatures. One way to think about it is to try to rewrite the equation so it works correctly if temperatures are specified in Celsius - clearly, you will have to introduce both an offset and a scale factor to get the correct behavior... Matthias

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BGL: How to get add_edge work with adjacency_list graph
by Christoph 26 Sep '11

26 Sep '11

Dear List, i just started learning about The Boost Graph Library. Here is my Problem in a minimal example: #include <iostream> #include <boost/graph/adjacency_list.hpp> typedef boost::adjacency_list < boost::listS, boost::listS, boost::bidirectionalS> Map; int main() { Map map; std::cout << "number of vertices: " << num_vertices(map) << std::endl; Map::vertex_descriptor u = boost::add_vertex (map);; Map::vertex_descriptor v = boost::add_vertex (map);; std::cout << "number of vertices: " << num_vertices(map) << std::endl; Map::add_edge (u, v, map); // <- problem return 0; } The compiler tells me that ‘add_edge’ is not a member of ‘Map’. I would like to know why and what am i doing wrong by writing "Map::add_edge (u, v, map);" best regards Christoph

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