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Linker error when using time_from_string
by nick.snels＠telenet.be 02 Jun '16

02 Jun '16

The following code gives an error for the time_from_string function (from_time_t works just fine): using namespace boost::posix_time; ptime epoch = from_time_t(0); ptime other = time_from_string("2011-08-09 17:27:00.000000"); The error is: main.obj:-1: error: LNK2019: unresolved external symbol "public: static class boost::shared_ptr<class std::map<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,unsigned short,struct std::less<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class std::allocator<struct std::pair<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const ,unsigned short> > > > __cdecl boost::gregorian::greg_month::get_month_map_ptr(void)" (?get_month_map_ptr@greg_month@gregorian@boost@@SA?AV?$shared_ptr@V?$map@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@GU?$less@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@V?$allocator@U?$pair@$$CBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@G@std@@@2@@std@@@3@XZ) referenced in function "unsigned short __cdecl boost::date_time::month_str_to_ushort<class boost::gregorian::greg_month>(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??$month_str_to_ushort@Vgreg_month@gregorian@boost@@@date_time@boost@@YAGAEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) I’m using Qt Creator, along with Visual Studio 2015. I have the installed the windows binary of boost 1.61.1 .

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installing on a local 2 core system
by Salvador Aguiñaga 30 May '16

30 May '16

> Installing on small system I want to use for temporary development, I get the following error. > > >parallel-bgl-0.7.0/boost/property_map/property_map.hpp:16:37: fatal error: boost/pending/cstddef.hpp: No such file or directory > compilation terminated > > I've configured the system: > >"sudo apt-get install build-essential" > > And successfully installed the openmpi: "openmpi-1.10.2.tar.bz2" > > But when I get to: > /parallel-bgl-0.7.0/build/cmake .. > > I can't find a good solution online to this cstddef.hpp error. > > Any suggestions? > > > My system: uname -a > > Linux atomix 4.2.0-16-generic #19-Ubuntu SMP Thu Oct 8 14:46:51 UTC 2015 i686 i686 i686 GNU/Linux

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[proto] non-proto objects as terminals
by Igor R 30 May '16

30 May '16

I would like to use instances of a non-proto class as proto terminals for all purposes. To enable this functionality, I use is_terminal metafunction that I pass to BOOST_PROTO_DEFINE_OPERATORS(). This actually defines the operators, so the following expression makes an expression tree, as expected: non_proto_obj * proto_obj; However, I cannot do this: non_proto_obj = proto_obj; Or this: non_proto_obj[proto_obj]; While the opposite does compile: proto_obj = non_proto_obj; proto_obj[non_proto_obj]; How to solve this issue? Thanks! P.S.: here is an sscce: /////////////////// #include <iostream> #include <boost/proto/proto.hpp> #include <boost/mpl/int.hpp> namespace mpl = boost::mpl; namespace proto = boost::proto; using proto::_; template<typename Expr> struct my_expression; struct my_domain : proto::domain<proto::generator<my_expression> > {}; template<int I> struct placeholder {}; template<typename Expr> struct my_expression : proto::extends<Expr, my_expression<Expr>, my_domain> { explicit my_expression(Expr const &expr = Expr()) : my_expression::proto_extends(expr) {} BOOST_PROTO_EXTENDS_USING_ASSIGN(my_expression<Expr>) }; const my_expression<proto::terminal<placeholder<1>>::type> _1; namespace app { struct non_proto_type {}; template <typename T> struct is_terminal : mpl::false_ {}; template<> struct is_terminal<non_proto_type> : mpl::true_ {}; BOOST_PROTO_DEFINE_OPERATORS(is_terminal, my_domain) non_proto_type non_proto; } int main() { _1 = app::non_proto; // ok, builds temporary proto expression //app::non_proto = _1; // does not compile! no operator= _1[app::non_proto]; // ok //app::non_proto[_1]; // does not compile! no operator[] (+app::non_proto)[_1]; // ok! applying unary + to make a proto expression first, then operator[] is available }

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Boost.Fiber mini-review May 23 - June 1
by Nat Goodspeed 30 May '16

30 May '16

Hi all, The Boost.Fiber candidate library by Oliver Kowalke begins a mini-review today, Monday May 23, which will close Wednesday June 1. It was last reviewed in September 2015; the verdict at that time was "not yet." Oliver has been working steadily to address review comments and to improve the library in other ways, and has brought the library back for mini-review. The updated documentation is here: http://olk.github.io/libs/fiber/doc/html/index.html The code is on the master branch of this repository: https://github.com/olk/boost-fiber/tree/master I believe it is Oliver's intention to respond to review feedback on the develop branch, leaving the master branch stable during the review. I will monitor reviews and discussion on both the boost-users@ list and the boost@ developers' list. Please include at least "fiber" and "review" in the subject line of your mail, e.g. by replying to this message. (Please reply to only ONE list, however.) I will also check the Boost Library Incubator for Fiber reviews: http://rrsd.com/blincubator.com/bi_library/fiber/?gform_post_id=859 though I check that less frequently than email. Please do remember to state in your review whether you think the library should be accepted as a Boost library. Thank you for your interest and your feedback! ----------------------------------------------------- Here follows a synopsis of issues raised during the September 2015 review: Cross-thread fiber migration: Evidently the community strongly desires the ability to transfer a suspended fiber from one thread to another. Now supported, with documentation. Cross-thread migration support implies a requirement to document the thread safety requirements of the customization API. Addressed. Standard required timing specifications: meet (30.2.4 Timing specifications [thread.req.timing]). Addressed. Adapt one or more existing test suites for thread facilities to validate the correctness of the Fiber library's synchronization constructs. The requester clarified in private mail that I misstated his suggestion: he wanted Oliver to review one or more such test suites to discover the kinds of issues that can arise with thread synchronization constructs. He has professed himself satisfied with the current state of the Fiber library's synchronization constructs. std::chrono support: ensure that wait_until() can accept any supported time_point specialization. Addressed. C++11 compatibility. Addressed. Document that this_fiber::yield() (et al.) are valid from main(), or in general from a thread function, as well as from explicitly-launched fibers. Addressed. Make shared_state lock requirements explicit: for example, make mark_ready_and_notify_() accept a std::unique_lock<>& (or &&) to force its caller to provide one. Addressed. Avoid holding mutex during condition_variable::notify_*() calls. Addressed. packaged_task must not decay-copy its task arguments. Addressed. Align fibers::async() signature, result description and invoke_helper implementation with std::async(). Avoid returning std::move(...). Addressed. Wait list implementation: try an intrusive linked list of fiber_context objects. Addressed. Avoid sleeping thread when no fibers are ready -- block on external event. Better handling of waiting tasks (decentralized wait queues?). Addressed. Optimization to resume awakened fiber on the thread that awakens it. Hooks provided. Template redundancy: eliminate duplication between specializations for T, T& and void. The future, shared_future, shared_state, promise and task_object templates were specifically cited. Addressed. Leverage predicate-based condition::wait() overload internally. Addressed. Nested schedulers: make schedulers be schedulable entities themselves. Not implemented. Improve robustness of `promise' handling in Asynchronous Callbacks documentation. Avoid overconfident remarks about it. Addressed. Fix Note overstating the requirements on condition_variable::wait(). Addressed.

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[test] how to test std::pair with BOOST_TEST
by Tan, Tom (Shanghai) 29 May '16

29 May '16

The following snippet does not compile with VS2015 and boost 1.61. What should the correct way to do it? Thanks. // compile with cl.exe /EHSc #define BOOST_TEST_MODULE pair #include <boost/test/included/unit_test.hpp> std::pair<uint32_t, uint32_t> v() { return std::make_pair(0, 0); } BOOST_AUTO_TEST_CASE(range) { BOOST_TEST(std::make_pair(0, 0) == v()); } Here's the error message: C:\3rd\boost_1_61_0\boost/test/tools/assertion.hpp(163): error C2678: binary '==': no operator found which takes a left-hand operand of type 'std::pair<int,int>' (or there is no acceptable conversion) C:\3rd\boost_1_61_0\boost/function/function_base.hpp(740): note: could be 'bool boost::operator ==(boost::detail::function::useless_clear_type *,const boost::function_base &)' C:\3rd\boost_1_61_0\boost/function/function_base.hpp(728): note: or 'bool boost::operator ==(const boost::function_base &,boost::detail::function::useless_clear_type *)' C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\exception(329): note: or 'bool std::operator ==(const std::exception_ptr &,const std::exception_ptr &) throw()' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\exception(334): note: or 'bool std::operator ==(std::nullptr_t,const std::exception_ptr &) throw()' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\exception(339): note: or 'bool std::operator ==(const std::exception_ptr &,std::nullptr_t) throw()' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\system_error(365): note: or 'bool std::operator ==(const std::error_code &,const std::error_code &) noexcept' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\system_error(373): note: or 'bool std::operator ==(const std::error_code &,const std::error_condition &) noexcept' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\system_error(381): note: or 'bool std::operator ==(const std::error_condition &,const std::error_code &) noexcept' [found using argument-dependent lookup] C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\system_error(389): note: or 'bool std::operator ==(const std::error_condition &,const std::error_condition &) noexcept' [found using argument-dependent lookup] C:\3rd\boost_1_61_0\boost/function/function_base.hpp(799): note: or 'bool boost::operator ==<T>(Functor,const boost::function_base &)' with [ T=std::pair<int,int>, Functor=std::pair<int,int> ] C:\3rd\boost_1_61_0\boost/function/function_base.hpp(790): note: or 'bool boost::operator ==<T>(const boost::function_base &,Functor)' with [ T=std::pair<uint32_t,uint32_t>, Functor=std::pair<uint32_t,uint32_t> ] C:\3rd\boost_1_61_0\boost/test/tools/assertion.hpp(163): note: while trying to match the argument list '(std::pair<int,int>, std::pair<uint32_t,uint32_t>)' C:\3rd\boost_1_61_0\boost/test/tools/assertion.hpp(326): note: see reference to class template instantiation 'boost::test_tools::assertion::op::EQ<ValType,T,void>' being compiled with [ ValType=std::pair<int,int>, T=std::pair<uint32_t,uint32_t> ] s.cpp(14): note: see reference to class template instantiation 'boost::test_tools::assertion::binary_expr<ExprType,std::pair<uint32_t,uint32_t>,boost::test_tools::assertion::op::EQ<ValType,T,void>>' being compiled with [ ExprType=boost::test_tools::assertion::value_expr<std::pair<int,int>>, ValType=std::pair<int,int>, T=std::pair<uint32_t,uint32_t> ] C:\3rd\boost_1_61_0\boost/test/tools/assertion.hpp(377): warning C4624: 'boost::test_tools::assertion::binary_expr<ExprType,std::pair<uint32_t,uint32_t>,boost::test_tools::assertion::op::EQ<ValType,T,void>>': destructor was implicitly defined as deleted with [ ExprType=boost::test_tools::assertion::value_expr<std::pair<int,int>>, ValType=std::pair<int,int>, T=std::pair<uint32_t,uint32_t> ]

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Call for Papers for Meeting C++ 2016 ends on Friday night!
by Jens Weller 25 May '16

25 May '16

Hello Boost Community! a short reminder, that the deadline is coming up for submitting your talk to this years Meeting C++ conference! Meeting C++ 2016 Page: http://meetingcpp.com/index.php/mcpp2016.html Talk submission page: https://meetingcpp.com/mcpp/submittalk/ thanks, Jens Weller

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File-mapped shared memory access through Boost interprocess is slow on some HPC file-systems due to mmap
by Scott Ritchie 24 May '16

24 May '16

Hi all, I'm wondering if there is some way to use the Boost interprocess library without the use of mmap for file I/O? I have developed an R-language package that uses another third party package (bigmemory) to access objects in shared memory when parallelising R across multiple cores. This third party package uses the Boost interprocess library to make these file-backed shared memory objects available to R. This worked perfectly, until I tested my package on a multi-node cluster. After some digging I found that the code calling these shared memory objects was extremely slow, and had hugely variable runtimes. Accessing these shared memory objects became exponentially slower as I parallelised over more and more cores. After talking to the authors of the bigmemory library and the administrators of the cluster, we have determined the route cause to be the use of mmap() on that particular filesystem (GPFS). On this filesystem, mmap() performs concurrency checking on every read and write since the filesystem is shared across multiple physical nodes. Marking the shared memory segments as read_only did not solve the issue. The advice of the cluster administrators is to not use mmap() for file I/O. I'm hoping there is a simple fix, such as a compilation flag I can provide to boost to use some alternative file I/O function/library? If not I will need to rewrite my code so that it is multi-threaded instead of multi-process without the use of Boost. Kind regards, --- Scott Ritchie, Ph.D. Student | Integrative Systems Biology | Pathology | http://www.inouyelab.org The University of Melbourne ---

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[Parallel Boost Graph Library] General Questions and Redistribution Questions
by Jun Kudo 24 May '16

24 May '16

Hi everyone, I've been playing around with the Parallel Boost Graph Library in hopes of using it for a distributed mesh with redistribution capabilities. Unfortunately, I've been having a lot of issues and I was hoping to get some clarification from the community on some points. I am trying to construct a distributed graph that represents a mesh. The idealized plan is to use this library to create a mesh class that allows for the easy introduction of new vertices and edges as well as repartitioning/data migration capabilities. For this effort, I created a simple struct called Cell that is attached as an interior vertex property and identified the cell id value as the key for indexing. I've attached a short program to really quickly demonstrate what I've been trying to prototype. At this point, I have some questions regarding some things about the library that I can't seem to figure out. 1. How do you control the initial distribution of the names? That is, how do you control which processes own what vertex names when you dynamically add named vertices? 2. How do you create a VertexProcessorMap to use with the redistribution function? The test adjlist_redist_test.cpp looks like it creates a property_map of the vertex_rank but I'm not sure how to do something similar when I have named graph. 3. Is there any way and any point to accomplish what I'm trying to do without using named graphs? I started down this route because the referenced test did not use named graphs. I quickly ran into a situation where I did not know how to grab a vertex descriptor for an off-process vertex without using the vertex(vertices_size_type n, const adjacency_list& g) function or without knowing a priori where that vertex lived. Similar to the named graph situation, I want to be able to dynamically add numbered vertices (which according to the documentation invalidates the use of vertex()) on different processes and then define edges between them based on these numbers. Does the fact that I'm trying to use a global numbering system as a name convention make this question silly? Sorry about the wall of text and I hope my questions are not too nonsensical! Thanks in advance for all the help. Sincerely, Jun

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Rebooting Boost: Call for Lightning Talks @ CppCon
by Niall Douglas 23 May '16

23 May '16

At C++ Now a number of informal meetings showed there to be frustrations with the current ecosystem around the Boost C++ Libraries (to paraphrase a founder of Boost, "Boost is supposed to serve *the entire C++ community; it isn't Boost's goal to serve Boost's community*". Recent and recurrent boost-dev discussions have raised the lack of cmake based tooling; lack of ABI management and the consequent ODR violation when mixing Boost versions in the same process; the anti-social behaviour of Boost towards library end users, new ideas, new blood and the wider C++ community; and the chronic lack of maintenance of up to half the Boost libraries. One question which needs to be answered is whether a clean reboot of Boost from the first principles of proving high quality C++ libraries well suited for use with the latest C++ standard is viable. This new collection of C++ libraries would be started completely from scratch (even if some existing libraries were ported into the new organisation), so ANYTHING is possible. All we need is a critical mass of library developers willing to collaborate on developing a shared infrastructure mutually beneficial to all participants, whether library developer or library end user. To that end of discovering if this critical mass is there, five minute lightning talk topics are requested for CppCon this September on this topic: "What design pattern, practice or idiom should a standards aspiring collection of C++ 14/17 libraries share?" Please keep each talk topic focused on a single design pattern, practice or idiom (see suggested talk format below). Each speaker may submit up to THREE talk topics (not all may be accepted if there are a lack of slots, so please rank them in order of preference). Please send your talk topics to me privately by email, only if sufficient numbers present to fill a session will your name and your talk topic be shared with the CppCon Programme Committee. We'll try to arrange a short panel session at the end so attendees can ask questions of the speakers. After the lightning talk we'll arrange a restaurant so all the speakers and any interested attendees can dine together, followed by a night in a Bellevue bar. If after the dust has settled it is felt there is a critical mass sufficient to reboot a brand shiny new edition of Boost, we'll start development! I should *stress* that it is up to the CppCon Programme Committee whether these lightning talks are approved or not. I'll just copy and paste your proposed talk to the CppCon PC as-is. If insufficient lightning talk topics are received by me to fill a 60 minute session, I'll withdraw this talk proposal from CppCon. Suggested talk format ================ Five minutes is not much time, so here is a suggested lightning talk outline: 1. A current widely practiced library design pattern (show example). 2. The problems it generates for library users or maintainers. 3. Your proposed alternative design pattern (show example). 4. The problems the alternative design pattern fixes. 5. Any mockup, prototype or even live demo (!) of the alternative design pattern in action. Suggested talk themes might be documentation, packaging, distribution, testing, tooling, quality assessment, barriers to entry, governance, strategy, important gaps in the standard libraries, automation and deprecation/removal policies. Here is an example of such a lightning talk: 1. Current design pattern: Library v1.00: namespace boost { namespace lib { void foo(size_t, char); } } User code: boost::lib::foo(100, 'n'); 2. Problem: Library v1.01: namespace boost { namespace lib { void foo(char, size_t); } } User code: boost::lib::foo(100, 'n'); // oh oh! 3. Alternative: Library v1.00: namespace boost { namespace lib { inline namespace v100 { void foo(size_t, char); } } } #define BOOST_LIB_NAMESPACE_V100 boost::lib::v100 Library v1.01: namespace boost { namespace lib { inline namespace v101 { void foo(char, size_t); } } } #define BOOST_LIB_NAMESPACE_V101 boost::lib::v101 User code: // Mount v100 of Boost.Lib into "lib" namespace lib=BOOST_LIB_NAMESPACE_V100; lib::foo(100, 'n'); // ABI stable! No ODR violation possible! 4. Problems fixed: a) Mixing incompatible versions of individual Boost libraries in the same process (or even translation unit) is now safe. b) Libraries can now depend on other libraries without worrying about breaking code which depends on them which uses a different version of the same dependency. This greatly helps reduce change ripple effects. c) Forward compatibility or alternative implementation shims are now very easy to implement e.g. library users can externally configure either Boost.Filesystem or std::experimental::filesystem for your library to use, your code simply refers to _some_ Filesystem TS implementation e.g. namespace filesystem = FILESYSTEM_TS_IMPLEMENTATION; filesystem::path mypath; -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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How to write one property page .props to select the right x86 or x64 Boost libraries folder automatically using Visual Studio
by Paul A. Bristow 22 May '16

22 May '16

I have downloaded the shiny new release boost_1_61_0_b1 and am trying to set up so that I can test a lot of Boost-ish console applications using both 32 and 64-bit. This is easier with bjam, but I'd like to use the Visual studio IDE too. I'd like a single property page that can be placed in the same folder as my .sln file and added to each and every project. (or better, made the default for all projects). I have a I:\boost_1_61_0_b1; as the include directory, and that is common to all configurations and platforms. But the libraries files are in two separate folders because the name does not yet include the platform :-( Linking to lib file: libboost_chrono-vc140-mt-gd-1_61.lib lib32-msvc-14.0 and lib64-msvc-14.0 Googling gives some suggestions to select the right folder for libraries, but I wonder if anyone has found a slick solution? (I'll edit the property xml if necessary - it would seem that the IDE GUI tool isn't up to the job?) Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830

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