December 2013 - Boost-users

Re: [Boost-users] [boost] [variant] Warning: variadic templates in boost::variant
by Igor R 09 Dec '13

09 Dec '13

> Development version of Boost.Variant library now uses C++11 variadic > templates when possible. > This leads to more compact binaries, more readable compiler error messages > and faster compilation times. Will it support MSVC12 (i.e. VS2013)? In particular, won't it be affected by the following bug: http://tinyurl.com/o2psdj5 ?

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[boost] [variant] Warning: variadic templates in boost::variant
by Antony Polukhin 09 Dec '13

09 Dec '13

Development version of Boost.Variant library now uses C++11 variadic templates when possible. This leads to more compact binaries, more readable compiler error messages and faster compilation times. However this: * breaks ABI (now variant is declared as `template <typename T0, typename... TN> class variant`) * breaks user code that was explicitly using BOOST_VARIANT_LIMIT_TYPES Code that was using BOOST_VARIANT_ENUM_PARAMS and BOOST_VARIANT_ENUM_SHIFTED_PARAMS macro *must* work correctly without any modifications. To disable variadic templates usage in variant define BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES. When all the tests will pass successfully changes will be merged to master branch, so there is a high chance that variadic templates will be supported by Boost 1.56. In case of appearance of hard to fix variadic templates errors in Boost libraries dependent on Boost.Variant - report them in this letter and I'll help in resolving issues. -- Best regards, Antony Polukhin

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C++Now 2014: Call for Submissions, Updated deadlines
by Hartmut Kaiser 08 Dec '13

08 Dec '13

Updated submission dates! Please see below! ============================================== C++ Now Conference 2014 Aspen CO, USA, May 12-17, 2014, www.cppnow.org ============================================== For the full announcement online, please see here: http://cppnow.org/2013/10/21/2014-call-for-submissions/ Call for Submissions -------------------- We invite you to submit session proposals to the 3rd annual C++Now Conference (Aspen CO, USA, May 12-17, 2014). Building upon the resounding success of C++Now 2013 and five years of BoostCon, C++Now 2014 will present leading speakers from the whole C++ community. The C++Now Conference is dedicated to discussion and education about C++, an open and free language and standard. Our Conference will focus on discussion and education about open source software usage and developments in the C++ developer and user community. To reflect the breadth of the C++ and Boost communities, the conference includes sessions aimed at three constituencies: C++ and Boost end-users, hard-core Boost library and tool developers, and researchers pushing the boundaries of computation. The program fosters interaction and engagement within and across those groups, with an emphasis on hands-on, participatory sessions. As a multi-paradigm language, C++ is a melting pot where the most compelling ideas from other programming communities are blended in powerful ways. Historically, some of the most popular sessions at C++Now have highlighted these concepts, from DSLs to functional programming to transactional memory and more. Bring your C#, Python, Ruby or Haskell influences to bear in an environment that will broaden their exposure. At C++Now 2014 we would like to focus on the now established C++11 standard and the new, upcoming C++14 and how those standards are and will shape C++'s future. However, by no means is this intended to restrict the topics of proposals we hope to see. Any other topic related to C++ as outlined below is perfectly fine for submission. Important dates --------------- New proposal submissions due: December 22th, 2013. Proposals decisions sent (tentative program available): February 15th, 2014. Fully scheduled program available: February 28th, 2014. Best Presentation Awards ------------------------ We know how much effort it takes to prepare talks for our conference. For this reason we will award the best The awards will be given based on the audience's voting. Each award will include the author's name listed on the cover of the C++Now website for that year and a plaque containing all the C++Now conference information. Session topics -------------- Topics of interest include, but are not restricted to, the following: * C++11/14 and how it changes life for users and library writers * General tutorial sessions on C++11/14, the C++11/14 Standards library, and one or more Boost libraries * Parallelism in the new C++11/14 standard * Parallel, distributed and GPGPU topics relating to C++ * In-depth sessions on using specific Boost libraries * Case studies on using Boost * Experts panels * Advanced sessions on implementation techniques used within Boost libraries * Development workshops to extend or enhance existing Boost libraries * Workshops on design process * Infrastructure workshops such as Build tools, Website, Testing * Concepts and Generic Programming * Hardware and infrastructure presentations focused on how libraries can make better use of the technology * Software development tools and their application to C++ and or Boost * Other topics likely to be of great interest to C++ users and developers Interactive and collaborative sessions are encouraged, as this is the style of learning and participation that has proven most successful at such events. Sessions can be tutorial based, with an emphasis on interaction and participant involvement, or workshop based, whether hands-on programming or paper-based, discussion-driven collaborative work. Session formats --------------- Presentations Presentations focus on a practitioner's ideas and experience with anything relevant to C++11 or C++14, Boost and users. Panels Panels feature three or four people presenting their ideas and experiences relating to C++11 or C++14 and Boost's relevant, controversial, emerging, or unresolved issues. Panels may be conducted in several ways, such as comparative, analytic, or historic. Tutorials Tutorials are sessions at which instructors teach conference participants specific skills relevant to C++11 or C++14 and Boost. Workshops Workshops provide an active arena for advancements in Boost-relevant topics. Workshops provide the opportunity for experienced practitioners to develop new ideas about a topic of common interest and experience. Author's Corner Presentations These were introduced at BoostCon 2008, and were a great success. They are short (30 minute) sessions, focusing on tips on usage and design. In addition, we're looking to uncover the hidden design gems in Boost libraries. Tool Vendors Presentations We actively encourage tool vendors and ISP's to submit proposals for a special Tool Vendors Session Track aimed at products related to Boost and C++ (compilers, libraries, tools, etc.). Other formats may also be of interest. Don't hold back a proposal just because it doesn't fit into a pigeonhole. Submitting a proposal --------------------- Standard sessions are 90 minutes. You may submit a proposal for fractions or multiples of 90-minutes. Fractional proposals will be grouped into 90 minute sessions covering related topics. Longer sessions, such as tutorials and classes, will be assigned three hour (i.e. half day), or six hour (i.e. full day) time slots. Please include: * The working title. * Type of session: presentation, panel, tutorial, workshop, authors corner, vendor track, other. * A paragraph or two describing the topic covered, suitable for the conference web site. * Proposed length: 10-20 minute short talks, 45 minutes, 90 minutes, half day, full day. * Alternate lengths, if you are willing to make adjustments: 10-20 minute short-talks, 45 minutes, 90 minutes, half-day, full day. * Audience: users, developers, both. * Level: basic, intermediate, advanced. * A biography, suitable for the conference web site. * A photo of about 150 x 150 * Your public contact information (twitter handle, blog, website, google plus, etc.) * Your contact information (will not be made public). Submission details ------------------ All submissions should be made through the EasyChair conference management system: http://www.easychair.org/conferences/?conf=cppnow2014. If you have not already registered at EasyChair, you will need to do so in order to submit your proposal. All submissions will go through a peer review process. Authors are invited (but are not required) to submit PDF versions of full papers of up to 10 pages in ACM conference proceedings format (see http://www.acm.org/sigs/publications/proceedings-templates) The full papers are not required unless you want them published in the proceedings. All accepted proposals will be made available in the Association for Computing Machinery (ACM) Digital Library (approval pending). Best papers, after further reviews, will be considered to be book chapters or journal articles in a renowned journal. The session materials go on the C++ Now website and will be available to attendees. For general information on the C++ Now 2014 paper submission or the scope of technical papers solicited; please refer to the conference website at www.cppnow.org. For any other questions about the submission process or paper format, please contact the Program Committee at cppnow2014(a)easychair.com. If you have any technical problems with EasyChair, please contact EasyChair for help. Note: Presenters must agree to grant a non-exclusive perpetual license to publish submitted materials, either electronically or in print, in any media related to C++ Now. Hartmut Kaiser, email: hartmut.kaiser(a)gmail.com (Program Committee Chair) Joel Falcou, email: joel.falcou(a)lri.fr (Program Committee Co-Chair) Jon Kalb, , email: jon(a)kalbweb.com (Conference Chair) Dave Abrahams, dave(a)boostpro.com (Conference Chair) On behalf of the conference organizers

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Thread synchronization
by Gonzalo Garramuno 08 Dec '13

08 Dec '13

I have an application (a video player), that uses three threads to play videos (one thread handles decoding, another video display, and another audio). These threads have a thread barrier to wait until all 3 threads finish. This works fine. Now, my video player supports playing back two movies at the same time (to have one as a background and one as a foreground). Currently this is done with the same code for both. My problem is that there's no sync between the two movies and I am puzzled on how to achieve synchronism. I am unsure whether a thread barrier can be waited twice by two threads or whether I should have a single barrier that waits on the 6 threads ( 2 decode, 2 video, 2 audio ). If someone has any insight, it would be appreciated.

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boost::iostreams::copy - sink - ENOSPC (No space left on device) error handling
by Dino Korah 06 Dec '13

06 Dec '13

Platform: GCC on Linux; boost 1.55. In the code fragment below, is there a way to handle ENOSPC? #include <fstream> #include <iostream> #include <boost/iostreams/filtering_streambuf.hpp> #include <boost/iostreams/copy.hpp> #include <boost/iostreams/filter/bzip2.hpp> // open input file stream of the bzip2 file std::ifstream ifs("file.bz2"); // open output stream to the "full" device // full device is a "utility-device" to check how applications handle ENOSPC // more details in "man full" std::ofstream ofs("/dev/full"); // Setup the iostreams filter boost::iostreams::filtering_streambuf<boost::iostreams::output> filters; filters.push(boost::iostreams::bzip2_decompressor()); filters.push(ofs); // "run" the filter boost::iostreams::copy(ifs, filters); If I do strace of the compiled binary, the code seem to infinitely call writev() with the same data and returns ENOSPC error. writev(4, [{NULL, 0}, {"DATA DATA "..., 4096}], 2) = -1 ENOSPC (No space left on device) How can this error be handled or made thrown as an error from boost::iostreams::copy() Is it possible to set appropriate exceptions() on the ofstream object? I tried ofs.exceptions(std::ios::badbit | std::ios::failbit) but it didn't make any difference.

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one memory leak
by XIN LI 06 Dec '13

06 Dec '13

Hi there, I use boost version 1.49.0. I meet a memory leak for below sentences: boost::filesystem::path tmp = input.stem(); string strDir = tmp.normalize().string(); Valgrind report memory leak as below: ==18299== 56 bytes in 1 blocks are still reachable in loss record 26 of 61 ==18299== at 0x16DF68B8: malloc (vg_replace_malloc.c:270) ==18299== by 0x3F64FEC: operator new(unsigned long) (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x3F5B8F1: stlp_std::priv::__acquire_category(char const*&, char*, _Locale_name_hint*, char const* (*)(char const*, char*, _Locale_name_hint*, int*), void* (*)(char const*, _Locale_name_hint*, int*), char const* (*)(char*), stlp_std::hash_map<stlp_std::basic_string<char, stlp_std::char_traits<char>, stlp_std::allocator<char> >, stlp_std::pair<void*, unsigned long>, stlp_std::hash<stlp_std::basic_string<char, stlp_std::char_traits<char>, stlp_std::allocator<char> > >, stlp_std::equal_to<stlp_std::basic_string<char, stlp_std::char_traits<char>, stlp_std::allocator<char> > >, stlp_std::allocator<stlp_std::pair<stlp_std::basic_string<char, stlp_std::char_traits<char>, stlp_std::allocator<char> > const, stlp_std::pair<void*, unsigned long> > > >**, int*) (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x3F5BD04: stlp_std::priv::__acquire_ctype(char const*&, char*, _Locale_name_hint*, int*) (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x3F3F502: stlp_std::_Locale_impl::insert_ctype_facets(char const*&, char*, _Locale_name_hint*) (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x3F3DC3C: stlp_std::locale::locale(char const*) (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x458FFFE: boost::filesystem3::path::wchar_t_codecvt_facet() (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x4591806: boost::filesystem3::path::begin() const (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x4592844: boost::filesystem3::path::m_normalize() (in /home/lixin/work/prj/hotfix/13q2_ehf1/src/prosim/dist/Debug_64/GNU-Linux-x86/nanospice) ==18299== by 0x21019EB: boost::filesystem3::path::normalize() (path.hpp:430) Because my program need run thousands of time and very sensitive for the memory leak. Could anyone help to suggest one way to avoid such memory leak? Thanks a lot! Best wishes, Andy Li

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[log] Sink format is ignored
by Igor R 06 Dec '13

06 Dec '13

Hello, I'm setting up a sink like this: boost::shared_ptr<sinks::text_file_backend> backend = boost::make_shared<sinks::text_file_backend> ( keywords::file_name = fileName, keywords::rotation_size = maxSize, keywords::format = "[%TimeStamp%][%LineID%]: %Message%", keywords::auto_flush = true ); typedef sinks::synchronous_sink<sinks::text_file_backend> file_sink; boost::shared_ptr<file_sink> sink = boost::make_shared<file_sink>(backend); sink->set_filter(!expr::has_attr(serv_attr)); logging::core::get()->add_sink(sink); logging::add_common_attributes(); However, it seems that keywords::format parameter is just ignored. What am I doing wrong?

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Re: [Boost-users] [graph] Compilation problem using depth_first_visit with a listS as a VertexListS
by Simon Bozonnet 06 Dec '13

06 Dec '13

Thanks Alex, I finally understood that using std::vec and std::list is different in the way that we need to specify an index for the edges/nodes while using such a routine like depth_first_visit. Thanks for your help! Simon > From that I isolated the following code which compiles without any problem: > > typedef adjacency_list < vecS, vecS, bidirectionalS, GraphvizVertexProperty,GraphvizEdgeProperty, GraphvizGraphProperty > Graph; > ... > depth_first_visit(_graph2, loop_head, default_dfs_visitor(), make_iterator_property_map(reachable_from_head.begin(),get(vertex_index, _graph2), c)); > So this works fine! > Then, I would like to change the type of graph, so more precisely, to use a std::list (or listS) instead of a std..vector (vecS) for the VertexListS > So the first line declaration becomes: > typedef adjacency_list < vecS, listS, bidirectionalS,GraphvizVertexProperty,GraphvizEdgeProperty, GraphvizGraphProperty > Graph; > //only the 2nd argument changes > But then when I compile the code, I get 1 error during the compilation as described hereafter. "If the VertexList of the graph is vecS, then the graph has a builtin vertex indices accessed via the property map for the vertex_index_t property." (http://www.boost.org/doc/libs/1_55_0/libs/graph/doc/adjacency_list.html <http://www.boost.org/doc/libs/1_55_0/libs/graph/doc/adjacency_list.html>) So when you use listS instead you have to supply your own vertex index map.

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Fwd: support for bjam projects in IDE
by Witold E Wolski 05 Dec '13

05 Dec '13

Hi, I will have to work on bjam based project (rather big). I normally use QT Creator for programming and work with cmake based project. I could't find any hint how to set up an bjam project to work with QT neither information about any IDE which supports bjam. Do boost developer use vim and debug using gdb only? Actually the other guys on the project wrote some python scripts which parse bjam output to generated vcproj files :-@ I would be happy to hear from someone who are happy using bjam with qtcreator or any other IDE for larger projects and how to set this up. All my searches so far regarding bjam return almost exclusively FUD (http://en.wikipedia.org/wiki/Fear,_uncertainty_and_doubt) but looking at the Jamroot.jam file of the project (more than 1000 lines) I am inclinded to believe it. ;-( -- Witold Eryk Wolski -- Witold Eryk Wolski

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Await the result of several futures to chain another task
by Kaspar Fischer 05 Dec '13

05 Dec '13

Hi, If I have two futures f1 and f2, can I compose them to a future that completes with the result of f1 and f2 when both f1 and f2 have finished? I'd like to have a future so that I can use the then()<http://www.boost.org/doc/libs/1_55_0/doc/html/thread/synchronization.html#t…>method to run another transformation. I see method wait_for_all()<http://www.boost.org/doc/libs/1_55_0/doc/html/thread/synchronization.html#t…>but this method blocks. Best, Kaspar

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