June 2011 - Boost-users - lists.preview.boost.org

[Serialization] [Ptr_container] Serializing a boost::ptr_vector fails
by Philipp Münzel 17 Jun '11

17 Jun '11

Dear list, I want to use boost::ptr_vector<> in conjunction with boost::serialization. The ptr_cotainer documentation says: > As of version 1.34.0 of Boost, the library supports serialization via Boost.Serialization. > Of course, for serialization to work it is required that the stored type itself is serializable. For maps, both the key type and the mapped type must be serializable. However, when I create a class like this: #include <boost/ptr_container/ptr_vector.hpp> #include <boost/serialization/access.hpp> class Foo { boost::ptr_vector<int> the_vector_ friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int) { ar & the_vector_; } } and then try to serialize it: std::ofstream ofs("filename"); Foo f; boost::archive::text_oarchive oa(ofs); oa << f; I'm getting the following error, using gcc 4.2.1 and boost 1.46.1: /usr/local/include/boost/serialization/access.hpp:118: error: 'class boost::ptr_vector<Waypoint, boost::heap_clone_allocator, std::allocator<void*> >' has no member named 'serialize' How can I serialize a boost::ptr_container ? Regards, Philipp

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[Threads] How to keep number of running thread constant, performing different operations
by Alessandro Candini 17 Jun '11

17 Jun '11

I have a problem in organizing concurrent thread launch. My program structure is the following: #include <iostream> #include <boost/thread.hpp> using namespace std; class Worker { private: boost::thread m_Thread; public: Worker() { /* the thread is not-a-thread until we call start() */ } void start(int N) { m_Thread = boost::thread(&Worker::processQueue, this, N); } void join() { m_Thread.join(); } void processQueue(unsigned N) { /* Do some long long stuff... */ } }; int main(int argc, char* argv[]) { Worker worker_1, worker_2, worker_3, worker_4; // How to start threads and join them in order // to make constantly two of them running? return 0; } I have different threads which have to work on completely different input and output data (non critical sections): an atomic operation per thread, each one with different time execution but everyone with an intense use of the CPU. Let's say I have 10 operations to perform (10 threads): I would like to run concurrently only 2 threads because of resource consumption. My problem is that when a threads ends its execution, I would like to suddenly start another thread performing operation 3, in order to have constantly 2 threads working, and so on until the end of operations. How can I achieve this? I thought to insert my threads into a vector...but I have no idea on how start and join them in order to obtain what described above. Can anyone post me a little example? Thanks in advance. -- Alessandro Candini MEEO S.r.l. Via Saragat 9 I-44122 Ferrara, Italy Tel: +39 0532 1861501 Fax: +39 0532 1861637 http://www.meeo.it ======================================== "ATTENZIONE:le informazioni contenute in questo messaggio sono da considerarsi confidenziali ed il loro utilizzo è riservato unicamente al destinatario sopra indicato. Chi dovesse ricevere questo messaggio per errore è tenuto ad informare il mittente ed a rimuoverlo definitivamente da ogni supporto elettronico o cartaceo." "WARNING:This message contains confidential and/or proprietary information which may be subject to privilege or immunity and which is intended for use of its addressee only. Should you receive this message in error, you are kindly requested to inform the sender and to definitively remove it from any paper or electronic format."

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[Python] Undefined symbol in extension library with python 3
by Vivek 17 Jun '11

17 Jun '11

I compiled and installed boost 1.46.1 from source recently using: $ ./bootstrap.sh --with-python-version=3.1 $ sudo ./bjam -j4 install I then created the following trivial python extension: #include <boost/python.hpp> struct mystruct { int i; }; BOOST_PYTHON_MODULE(test) { using namespace boost::python; class_<mystruct>("Mystruct") .def_readwrite("i", &mystruct::i) ; } and compiled and ran it, but got an undefined symbol error: $ g++ -shared question.cpp -I/usr/include/python3.1 -lboost_python3 -otest.so $ python3 Python 3.1.2 (release31-maint, Sep 17 2010, 20:34:23) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import test Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: ./test.so: undefined symbol: _ZN5boost6python6detail11init_moduleEPKcPFvvE ldd confirms the missing symbol: $ ldd -r test.so linux-gate.so.1 => (0x00221000) libboost_python3.so.1.46.1 => /usr/local/lib/libboost_python3.so.1.46.1 (0x00a3d000) libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x0022b000) libm.so.6 => /lib/libm.so.6 (0x00960000) libc.so.6 => /lib/libc.so.6 (0x00316000) libutil.so.1 => /lib/libutil.so.1 (0x004b8000) libpthread.so.0 => /lib/libpthread.so.0 (0x00cf2000) libdl.so.2 => /lib/libdl.so.2 (0x00be4000) librt.so.1 => /lib/librt.so.1 (0x005d3000) libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00489000) /lib/ld-linux.so.2 (0x00fd5000) undefined symbol: PyExc_ImportError (/usr/local/lib/libboost_python3.so.1.46.1) undefined symbol: PyProperty_Type (/usr/local/lib/libboost_python3.so.1.46.1) ... snip ... *undefined symbol: _ZN5boost6python6detail11init_moduleEPKcPFvvE (./test.so) * undefined symbol: _Py_NoneStruct (./test.so) undefined symbol: PyLong_FromLong (./test.so) undefined symbol: PyLong_Type (./test.so) However nm confirms that the symbol exists in /usr/local/lib/libboost_python3.so.1.46.1: $ nm /usr/local/lib/libboost_python3.so.1.46.1 | c++filt | grep init_module 00031a00 T boost::python::detail::init_module(PyModuleDef&, void (*)()) I've tried running ldconfig to update the library cache, as well as compiling the extension with -lpython3.1, but no luck. Ideas appreciated, Vivek

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[review][assign] Formal review of Assign v2 ongoing
by John Bytheway 16 Jun '11

16 Jun '11

For those who did not see the notices elsewhere, note that the formal review of the Assign v2 library upgrade by Erwann Rogard is ongoing, and is scheduled to continue until June 24th. Please consider looking at the library and submitting a review to the developer list (boost(a)lists.boost.org) or directly to me (in which case let me know whether you would like the review forwarded to the developer list). About Assign v2 =============== Assign v2 is an upgrade of Boost.Assign (1.0) that redefines its functionality, with optional C++0x support and new features. It is a compact interface for executing the repetitive tasks of assigning or inserting container elements. For example, std::map<std::string, int> map; // Inserts each pair ("jan", 31),...,("may", 31) in map: csv_put<2>(map, "jan", 31, "feb", 28, "mar", 31, "apr", 30, "may", 31); Please see the change log (linked below) for more detail on the motivation for this library and pointers for navigating the documentation. Where to get it =============== The documentation is online at: <http://svn.boost.org/svn/boost/sandbox/assign_v2/libs/assign/v2/doc/html/in…> With the change log at: <http://svn.boost.org/svn/boost/sandbox/assign_v2/libs/assign/v2/doc/html/bo…> The Assign v2 source can be found in the Boost sandbox at: <http://svn.boost.org/svn/boost/sandbox/assign_v2/> or downloaded from: <http://www.boostpro.com/vault/index.php?action=downloadfile&filename=assign…> Review guidelines ================= Reviews should be submitted to the developer list (boost(a)lists.boost.org) with '[assign]' in the subject. Or if you don't wish to for some reason, you can send them privately to me. If so, please let me know whether or not you'd like your review to be forwarded to the list. All reviews are appreciated, even if you don't have time for an in-depth study. The Assign v2 library consists of several largely independent components: Reference containers and chaining, container modification and generation, and conversion of ranges to containers. If you wish, feel free to review and even vote on these separately. For your review you may wish to consider the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. More detail on the review process is available at: http://www.boost.org/community/reviews.html John Bytheway Review Manager

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Since which boost-version is linking against boost-system required?
by Cedric Laczny 16 Jun '11

16 Jun '11

Hi, I have an application which compiles fine with boost-1.40 and 1.41 (global installation). When I try to compile that application on a system with a local (staged) installation of boost-1.46.0, it complains about undefined reference to `boost::system::get_system_category()' etc. So, now, it has to be linked also to boost-system via -lboost-system. Linking against boost_filesystem and boost_regex ist already specified. So far, so good. My question is now, since when is this required? Thank you. Best, Cedric

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Re: [Boost-users] [statechart] Is it possible to have nested (sub)states in an asynchronous state machine?
by Gurcan Gulesir 16 Jun '11

16 Jun '11

> I don't know what compiler you used and what your real code looked > like, but when I tried to compile some portions of your sample code > with VC10, I got a lot of "use of undefined type" errors. I am using Eclipse IDE for C/C++ Helios Service Release 2 and Ubuntu 10.04 LTS with its built-in GCC C++ compiler and linker. My software uses Linux-specific libraries, so VC10 is currently not an option for me. If I encounter any additional problems, then I will first compile the "skeleton code" of my state machines in VC10, find and solve the problem there, and then port the solution to Eclipse in Ubuntu. So, thanks for the tip!

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Serialize a vector of lists with boost
by Alessandro Candini 16 Jun '11

16 Jun '11

Hi all. I have a program, simplified as follows: |#include<vector> #include<list> #include<fstream> using namespace std; class MyObj { int val; public: MyObj(int v){ val = v; }; ~MyObj(){}; }; int main (int argc,char *argv[]) { int i, j; vector< list<MyObj*> > layers; for(i=0; i<5; i++) { list<MyObj*> tmp; for(j=0; j<10; j++) tmp.push_back(new MyObj(j) ); layers.push_back(tmp); } return 0; }| I need to serialize/deserialize the object "layers". Can anyone give me an example on how to do this with boost serialization library? Thanks in advance. -- Alessandro Candini MEEO S.r.l. Via Saragat 9 I-44122 Ferrara, Italy Tel: +39 0532 1861501 Fax: +39 0532 1861637 http://www.meeo.it ======================================== "ATTENZIONE:le informazioni contenute in questo messaggio sono da considerarsi confidenziali ed il loro utilizzo è riservato unicamente al destinatario sopra indicato. Chi dovesse ricevere questo messaggio per errore è tenuto ad informare il mittente ed a rimuoverlo definitivamente da ogni supporto elettronico o cartaceo." "WARNING:This message contains confidential and/or proprietary information which may be subject to privilege or immunity and which is intended for use of its addressee only. Should you receive this message in error, you are kindly requested to inform the sender and to definitively remove it from any paper or electronic format."

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A doubt in Boost Format
by Gokulakannan Somasundaram 16 Jun '11

16 Jun '11

Hi, We are using Boost format in our project. We want to replace the normal allocator with a special allocator and we don't want any allocation be made with normal new. I was looking at the Boost fusion reference. format_class.hpp The class accepts a allocator and indeed uses it to instantiate the std::string inside. But there are two vectors inside - std::vector<format_item_t> items_; // each '%..' directive leads to a format_item std::vector<bool> bound_; // stores which arguments were bound. size() == 0 || num_args I am seeing that the vectors are not using the allocators. Is this the intended behavior? Is it right, to try to make an application not to use the normal new/delete completely? Thanks, Gokul.

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Exception: adding diagnostic information from a dtor?
by Michael Schuerig 16 Jun '11

16 Jun '11

The FAQ for boost exception contain this example snippet for adding further information to an exception while the call stack is unwound catch( boost::exception & e ) { e << foo_info(foo); throw; //Okay, re-throwing the original exception object. } I like that this possible, but I think the resulting code is somewhat tedious: void foo(const string& file_name) { try { do_something_fallible(file_name); } catch( boost::exception & e ) { e << boost::errinfo_file_name(file_name); throw; } } I'd rather write it like this: void foo(const string& file_name) { diagnostic<errinfo_file_name>(file_name); do_something_fallible(file_name); } My first, non-generic attempt fails: class diagnostic { public: explicit diagnostic(const string& file_name) : file_name_(file_name) {} ~diagnostic() { if ( boost::exception_ptr e = boost::current_exception() ) { *e << boost::errinfo_file_name(file_name_.c_str()); } } private: const string file_name_; }; The requirements for boost::current_exception() state that it may only be called inside a catch block, therefore the code above is illegal to begin with. Ignoring that, operator<< doesn't appear to be suitably overloaded for this use, anyway. Now, I'm wondering, is what I'm trying to achieve a bad idea? If not, is there another way to do it? Michael -- Michael Schuerig mailto:michael@schuerig.de http://www.schuerig.de/michael/

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[linking] simplifying compilation line with many boost libs
by alfC 16 Jun '11

16 Jun '11

This post is mainly about the linux distribution of boost, oriented to gcc. Given the lack of pgk-config for linux and the lack of linking pragmas in g++ I am wondering if somebody investigated the possibility of having all boost binary libraries in one file or something like that. Such that compilation line c++ -lboost_regex -lboost_system -lboost_filesystem -lboost_mpi - lboost_serialization ... can be simplified into c++ -lboost_all or simply c++ -lboost where boost_all.so have the contents of all boost libraries or references to the other boost_*.so the idea is to simplify sharing short code with other people not familiar with boost itself. Thanks, Alfredo

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