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[boost][Serialization] - xml-stylesheet tag not recognized
by girish hilage 08 Jan '11

08 Jan '11

Hi, I am trying to learn how to read an XML file using boost-serialization. The code snippet of a sample program is as follows : void restore_schedule(bus_schedule &s, const char * filename) { // open the archive std::ifstream ifs(filename); assert(ifs.good()); boost::archive::xml_iarchive ia(ifs); // restore the schedule from the archive ia >> BOOST_SERIALIZATION_NVP(s); } First few lines of demo.xml are as follows : <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <?xml-stylesheet type="text/xsl" href="XSLTFile.xsl"?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="6"> But this gives me below error : $ ./a.out terminate called after throwing an instance of 'boost::archive::xml_archive_exception' what(): unrecognized XML syntax If I remove the line : <?xml-stylesheet type="text/xsl" href="XSLTFile.xsl"?> from demo.xml then it works fine. Can you please let me know if there is any workaround for this problem? Currently I am using Fedora Core 13 with boost-serialization-1.41.0-7.fc13.i686. Is this case handled in latest boost release? Regards, Girish

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[signals vs. signals2] Slot connecting another slot to invoking signal
by Boris Schaeling 08 Jan '11

08 Jan '11

The Boost.Signals2 documentation at http://www.boost.org/doc/libs/1_45_0/doc/html/signals2/thread-safety.html says: "Suppose a user writes a slot which connects another slot to the invoking signal. Will the newly connected slot be run during the same signal invocation in which the new connection was made? The answer is no." I'm trying to find out what Boost.Signals has to say about it. A quick test program shows that Boost.Signals does call the newly connected slot. I'm not sure though if this is undefined behavior as connecting another slot might invalidate the iterators used by the combiner? Boris

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[serialization] polymorphic archives in dlls and pointer to derived problems
by Kolb, Jeremy 07 Jan '11

07 Jan '11

I'm having a lot of trouble getting serialization of derived classes through a base pointer working across dlls. I have the following: DLL (data_types.dll) code: stdafx.h: #pragma once #include "targetver.h" #define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers // Windows Header Files: #include <windows.h> #pragma warning(disable: 4308) #include "boost/archive/polymorphic_iarchive.hpp" #include "boost/archive/polymorphic_oarchive.hpp" #include "boost/serialization/nvp.hpp" Base.h: #pragma once #include "boost/serialization/export.hpp" class __declspec(dllexport) Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Base() {} virtual ~Base() {} int i; }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(Base); // Doesn't make a difference. BOOST_CLASS_EXPORT_KEY(Base); Base.cpp: #include "stdafx.h" #include "Base.h" template<class Archive> void Base::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(i); } BOOST_CLASS_EXPORT_IMPLEMENT(Base); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); Derived.h: #include "Base.h" class __declspec(dllexport) Derived : public Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Derived() {} Derived(int num) : j(num) {} int j; }; BOOST_CLASS_EXPORT_KEY(Derived); Derived.cpp: #include "stdafx.h" #include "Derived.h" template<class Archive> void Derived::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base); ar & BOOST_SERIALIZATION_NVP(j); } BOOST_CLASS_EXPORT_IMPLEMENT(Derived); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); My exe links against the DLL and contains the following: #include "stdafx.h" #include "boost/archive/polymorphic_xml_iarchive.hpp" #include "boost/archive/polymorphic_xml_oarchive.hpp" #include "data_types/Derived.h" #include <fstream> int _tmain(int argc, _TCHAR* argv[]) { std::ofstream f("c:\\test.xml"); boost::archive::polymorphic_xml_oarchive xml(f); Base* b = new Derived(123); xml & BOOST_SERIALIZATION_NVP(b); delete b; return 0; } When serializing this fails with unregistered_class even though I export both Base and Derived. Jeremy

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How to get bug reports addressed
by Geoffrey Romer 07 Jan '11

07 Jan '11

I'm responsible for maintaining the local Boost install for a large group of developers, and I find myself spending an inordinate amount of time reapplying our local patches for Boost bugs every time a new version comes out, seemingly with no end in sight. One obvious example is https://svn.boost.org/trac/boost/ticket/3645: the report is clear and specific, documents a real bug, and provides a trivial patch which completely resolves the issue. It's everything one could possibly want in a bug report, and it has been utterly ignored for over a year. In my experience this has been the rule rather than the exception; other examples that I've been personally acquainted with include http://lists.boost.org/Archives/boost/2009/06/153214.php, https://svn.boost.org/trac/boost/ticket/4918, and https://svn.boost.org/trac/boost/ticket/4919. In every case the reporters have done everything they could to provide a useful bug report, up to and including providing patches, but have been met with profound silence. Does anyone have any suggestions for how to get action in these situations?

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[DateTime] Daily Schedules
by John Rocha 07 Jan '11

07 Jan '11

I was looking at the DateTime library for a scheduling module in my application. I was very excited to see time periods (time_period) and its method contains(). I could set up a time_period for say 8:00-17:00, and then when something happened I could create a ptime and see if the time_period contains my ptime. (i.e. did my action happen between 8:00 and 17:00.) However, I realized that a time period is much more specific than I want. A time_period is tied to a specific date, i.e. 8:00-17:00 on Sep. 20 1999. I read the documentation, and I didn't see (or missed) anything that might be what I would call an hour period -- a range of time that is independent of the date. I don't think it's a duration, because I understood that to mean the amount of time between two time points (i.e. +/- 5 hours). I have some ideas on how I might extend this to achieve what I want, but before going that route, I wanted to double check if others have encountered this and if so how they resolved it. Was it done with a bit of the library that I'm overlooking? Or did you have to extend the class to achieve the desired results? Thanks in advance, -=John

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[boost][Serialization] - about macro BOOST_CLASS_VERSION
by girish hilage 07 Jan '11

07 Jan '11

Hi, I have a query regarding macro BOOST_CLASS_VERSION(). I am running following code : class testRep { friend std::ostream & operator<<(std::ostream &os, const testRep &tr); public : template<class Archive> void serialize(Archive &ar, const unsigned int version) { if(version >= 2) ar & BOOST_SERIALIZATION_NVP(Site); } private : string Site; }; BOOST_CLASS_VERSION(testRep, 2) std::ostream & operator<<(std::ostream &os, const testRep &tr) { return os << '\n' << tr.Site << endl; } void read_file (testRep &s, const char * filename) { std::ifstream ifs(filename); assert (ifs.good()); boost::archive::xml_iarchive ia(ifs); ia >> BOOST_SERIALIZATION_NVP(s); } int main (void) { testRep tr; read_file (tr, "Test.xml"); cout << tr << endl; return 0; } This code runs fine. But, if I remove the statement : BOOST_CLASS_VERSION(testRep, 2) then I get following error : terminate called after throwing an instance of 'boost::archive::archive_exception' what(): class version Aborted (core dumped) So, want to ask if it is mandatory to declare a macro BOOST_CLASS_VERSION()? and if not then how do I prevent this runtime error from happening? Regards, Girish

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[Off topic] Strict Aliasing white paper redux
by Patrick Horgan 07 Jan '11

07 Jan '11

Some time ago, I posted a link here to my (then new) white paper on strict-aliasing. I wrote it because people keep posting, on this and on other lists, questions that show a basic misunderstanding of aliasing and what the rules in C and C++ standards on aliasing are intended to communicate. I got some great feedback and have posted a new revision, http://dbp-consulting.com/StrictAliasing.pdf. I'm hoping that people on this list will review the paper and tell me some more ways of improving it. My intention is to write a paper that will make it so that I won't have to keep answering the same questions over and over again;) I'll just point people at the paper. Best regards, Patrick

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1.45: thread/condition_variable.hpp: unused variable 'res' warning, gcc 4.2
by Hicham Mouline 06 Jan '11

06 Jan '11

hello, in Release build in Xcode, gcc 4.2.1, inline void condition_variable::wait(unique_lock<mutex>& m) { ... int const res = pthread_cond_wait(&cond, &internal_mutex); BOOST_ASSERT(!res); ... } Unused variable 'res' is gcc mistaken? regards,

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Re: [Boost-users] [FunctionTypes] function_arity for non-built-ins
by Hossein Haeri 06 Jan '11

06 Jan '11

Hi Roman, > This is actually possible in most cases. Check this nice article by Eric > Niebler: http://www.boost.org/doc/libs/1_45_0/doc/html/proto/appendices.html#boost_p… This is beautiful, thanks! :) So, from the description, it seems like this can_be_called guy (or its siblings) is in heavy use for Proto. Does Proto then also port this as a part of its toolbox? Or, is it only for internal use and I'll need to craft my own version of it? TIA, --Hossein

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Re: [Boost-users] [ asio ] how to determine if a server is overloaded ?
by Avi Bahra 06 Jan '11

06 Jan '11

ecyrb wrote> >Server overload does not come from network overload, but from service >overload. If you can't serve (compute) more requests/s than the network >load, your server is overloaded... >You can compute your server overload by queuing requests. If your queue >becomes too big, you can consider that your server is under heavy pressure >and take appropriate measures to circumvent the flow of requests (load >balancing etc...) Is there any asio example in the docs, which demostrate this Does the io_service expose the queue of request/connections as I have not seen such an api ? or do you mean that server should be structured to maintain its _own_ queue.( as apposed to the queue in io_service) Request are then handled from this internal queue? Best regards, Ta, Avi

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