October 2010 - Boost-users - lists.preview.boost.org

[date_time] POSIX time zones
by david.mcminn＠intelligentwellcontrols.com 28 Oct '10

28 Oct '10

Hi, I'm looking at using the Boost date_time library in an upcoming project and found a few inconsistencies when handling POSIX timezones. The date_time library seems to interpret the offset in a POSIX timezone string using the opposite sign as given in the standards. It also appears to use the DST offset as an offset from it's own local time, rather than the offset from UTC as specified in the standard. And obviously when calling to_string() will output the string with the incorrect values, even if you do fudge the values before creating the object. There was another query about this previously that went unanswered: http://lists.boost.org/boost-users/2009/11/53828.php Is there anyone maintaining the library, or somewhere to report bugs? Or is it just left as an exercise to the user to change? Thanks.

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[regex] BOOST_REGEX_MATCH_EXTRA not working?
by Christian Henning 28 Oct '10

28 Oct '10

Hi there, pretty new to boost::regex and though I'm just toying around with the documentation and some basic test code. The following code crashes when setting the BOOST_REGEX_MATCH_EXTRA symbol. #include <iostream> #include <boost/regex.hpp> void print_captures( const std::string& regx , const std::string& text ) { boost::regex e( regx ); boost::smatch what; std::cout << "Expression: \"" << regx << "\"\n"; std::cout << "Text: \"" << text << "\"\n"; // crash occurs in the next statement if( boost::regex_match( text, what, e, boost::match_extra )) { unsigned int i,j; std::cout << "**Match found ** \n Sub-Expressions:\n"; for( i = 0; i < what.size(); ++i ) { std::cout << " $" << i << " = \"" << what[i] << "\"\n"; } std::cout << " Captures:\n"; for( i = 0; i < what.size(); ++i ) { std::cout << " $" << i << " = {"; for( j = 0; j < what.captures(i).size(); ++j ) { } } } } int _tmain(int argc, _TCHAR* argv[]) { print_captures( "(.*)bar|(.*)bah", "abcbar" ); return 0; } I'm using MSVC10 express. Am I doing something wrong? Regards, Christian

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Are memory leaks reported by Boost.Test Microsoft Memory Leak Detection Enabling spurious or real?
by Paul A. Bristow 28 Oct '10

28 Oct '10

I've just added some code (ready for Inverse Gaussian distribution in preparation for Boost.Math). When I added one new section of kosher-looking C++ code, I started to see memory leaks reported: For example: *** No errors detected Detected memory leaks! Dumping objects -> {3485} normal block at 0x003611B0, 42 bytes long. Data: <class boost::mat> 63 6C 61 73 73 20 62 6F 6F 73 74 3A 3A 6D 61 74 {3484} normal block at 0x003635A0, 8 bytes long. Data: < 6 46 > B0 11 36 00 F8 34 36 00 ... But no filename is given as promised by http://msdn.microsoft.com/en-us/library/e5ewb1h3%28v=VS.80%29.aspx So I'm puzzled if/where I should look for a problem. (occurs for both debug and release) Or is this spurious? Should I just suppress the warnings? Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow(a)hetp.u-net.com

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Checking if a stand-alone function exists
by Ioannis Papadopoulos 28 Oct '10

28 Oct '10

Hi, Is there a way of checking if a stand-alone function exists? Thanks

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Serialization to human-readable formats
by Mateusz Loskot 28 Oct '10

28 Oct '10

Hi, I have a library reading/writing data from binary files. The library defines collection of type representing schema and data stored in the files. Definition of those elements is versioned, so one file can be slightly different than other. The de-/serialization from/to those files is implemented, so it's not part of my problem. I'm looking for recommendation of tools to based implementation of serialization of those objects to/from human-readable format like XML, JSON, other text-based formats. I'm looking for non-intrusive solution with degree of extensibility, so new formats can be added if needed. Ideally, if the mechanism could be aware of the versions of objects being serialized. I have never used the Boost Serialization library, but reading its documentation suggests it may fit the problem well. UDT can be instrumented with serialization mechanism in non-intrusive way. There are some archivers provided and, as far as I understand, new can be added. There are also other tools like Boost Property Tree or even Spirit Qi/Karma which technically could do the job, I think. There is also this naive option dangling around, which is implementation of << and >> operators for my types. Hoping I've described what I need fairly well, I'd like to ask for some suggestions which option sounds better. Perhaps I've missed some details or possibilities, thus any brainstorming is welcome. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org Member of ACCU, http://accu.org

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[serialization] compile error on Mac OSX Tiger
by Philipp Münzel 27 Oct '10

27 Oct '10

Hi folks, after successfully deploying boost 1.44 on Windows and Linux, I now fail bitterly on Mac OSX. It is a Power PC with OSX 10.4 and gcc 4.0.1 When building boost with the following command: ./bjam --layout=system --with-serialization link=static variant=release threading=multi I get the following error: darwin.compile.c++ bin.v2/libs/serialization/build/darwin-4.0.1/release/link-static/threading- multi/basic_xml_archive.o darwin.compile.c++ bin.v2/libs/serialization/build/darwin-4.0.1/release/link-static/threading- multi/binary_iarchive.o ./boost/archive/basic_binary_iarchive.hpp:74: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>' "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -no-cpp-precomp -gdwarf-2 -Wno-long-double -DBOOST_ALL_NO_LIB=1 -DNDEBUG -I"." -c -o "bin.v2/libs/serialization/build/darwin-4.0.1/release/link-static/threading- multi/binary_iarchive.o" "libs/serialization/src/binary_iarchive.cpp" ...failed darwin.compile.c++ bin.v2/libs/serialization/build/darwin-4.0.1/release/link-static/threading- multi/binary_iarchive.o... ...failed updating 1 target... ...updated 74 targets... I did NOT set architecture=combined. I want a PPC only build. Any help is greatly appreciated. Regards Philipp

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[mpl] Accessing the nested value of an invoked placeholder
by Nathan Crookston 27 Oct '10

27 Oct '10

All, I'm writing some code to filter a vector_c of enum values. I have some existing structs which are templatized on those enum types and I'm having some trouble accessing those structs using placeholders. Following is code which hopefully clarifies: #include <boost/cstdint.hpp> #include <boost/mpl/assert.hpp> #include <boost/mpl/copy_if.hpp> #include <boost/mpl/vector_c.hpp> #include <boost/type_traits.hpp> #include <iostream> using boost::mpl::placeholders::_; enum MyEnum { val1, val2, }; template <MyEnum me> struct trait; template <> struct trait<val1> { typedef boost::uint16_t type; }; template <> struct trait<val2> { typedef boost::uint8_t type; }; //PROBLEM: The 'T' passed in is _, not what it substitutes for. template <typename T> struct traitMeta : trait<T::value> {}; typedef boost::mpl::vector_c<MyEnum, val1, val2> Vec; //For each item in Vec, determine if trait<_>::type matches T. If so, add it. template <typename T> struct TypeIs : boost::mpl::copy_if<Vec, boost::is_same<typename traitMeta<_>::type, T> > {}; BOOST_MPL_ASSERT((TypeIs<boost::uint16_t>::type, boost::mpl::vector_c<MyEnum, val1>)); int main() { return 0; } //END CODE I would assume from reading the book and documentation that mpl::apply or mpl::lambda would be best to use here, but my attempts to do so haven't been successful. I'd appreciate any guidance. Thanks, Nate

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[thread] recursive shared mutex
by JOAQUIN M. LOPEZ MUÑOZ 27 Oct '10

27 Oct '10

Hi, Boost.Threads provides a recursive mutex and a shared mutex, but no recursive *and* shared mutex. Would it be a good idea to add this to the library? How hard is it to construct a recursive shared mutex from boost::sahred_mutex (i.e. adding reentrancy to boost::shared_mutex)? Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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load a serialized object into Matlab?
by James C. Sutherland 27 Oct '10

27 Oct '10

I am just looking into the serialization library. It seems really nice for archiving using C++. Is there a way to import an archive generated by that library into another language (e.g. matlab)? I guess that one would need the rules for IO that the serialization archives use? Thanks, James

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Boost::Log named_scope issue
by Kieran Parsons 27 Oct '10

27 Oct '10

Can someone give me a working example of using named_scope for Boost::Log? I have tried something like: boost::shared_ptr< boost::log::core > logCore = boost::log::core::get(); logCore->add_global_attribute("Scope", boost::make_shared< boost::log::attributes::named_scope >()); boost::shared_ptr< boost::log::sinks::synchronous_sink< boost::log::sinks::text_file_backend > > sink = boost::log::init_log_to_file("myfile.txt"); sink->locked_backend()->set_formatter ( boost::log::formatters::stream << boost::log::formatters::named_scope( "Scope", keywords::iteration = boost::log::formatters::reverse, keywords::delimiter = " | ") ); logCore->add_sink(sink); BOOST_LOG_FUNCTION(); BOOST_LOG_NAMED_SCOPE("MyScope"); boost::log::sources::logger lg; BOOST_LOG(lg) << "TEST"; But it fails with an exception during the BOOST_LOG (I think due to missing attribute). As a general comment, the fact that none of the tutorial examples in the documentation work as-is makes it extremely difficult for a newbie to use (namespaces undefined, lack of include files etc). Thanks for your help.

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