October 2018 - Boost - lists.preview.boost.org

[concept_check] CopyConstructible Concept Does Not Accept Lvalue Reference
by Qu Xing 11 Oct '18

11 Oct '18

Boost version: 1.67.0 Compiler: GCC 7.3.0 Environment: Cygwin on Windows 10 version 1709 In the Boost Concept Check library, CopyConstructible concept requires operator & applicable to the type being checked, and the return value is required to be convertible to pointer to the type. However, pointer to reference is not allowed in C++. This concept check fails to compile if applying to a lvalue reference type. On the other hand, is_copy_constructible<T> type trait class in the Boost Type Traits library and the standard C++ library both give positive result on lvalue reference types. For example, the following code snippet will fail to compile if T is a lvalue reference: #include <type_traits> #include <boost/static_assert.hpp> #include <boost/type_traits/is_copy_constructible.hpp> #include <boost/concept_check.hpp> #include <boost/concept/assert.hpp> template <typename T> void RequireCopyConstructible() { BOOST_STATIC_ASSERT(boost::is_copy_constructible<T>::value); // PASS on lvalue reference BOOST_STATIC_ASSERT(std::is_copy_constructible<T>::value); // PASS on lvalue reference BOOST_CONCEPT_ASSERT((boost::CopyConstructible<T>)); // FAIL on lvalue reference } void TestReference() { RequireCopyConstructible<int&>(); } Diagnosis message is generated as: "error: forming pointer to reference type ‘int&’". I think the operator & applicable requirement should be removed for CopyConstructible concept. Alternatively, adding a template specialization on lvalue reference type for CopyConstructible concept may work as well.

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[config] really, really sticky issue with BOOST_SYMBOL_IMPORT
by Robert Ramey 10 Oct '18

10 Oct '18

For many, many years we've built the Boost serialization library with the macros for BOOST_SYMBOL_IMPORT and BOOST_SYMBOL_EXPORT set according to the instructions included in the boost/config documentation written by John Maddock. These set attributes for creating and using DLLS for windows and (used to) resolve to nothing on other systems. So far so good. At some point things changed for gcc compilers. Now it seems that BOOST_SYMBOL_IMPORT resolves to nothing and BOOST_SYMBOL_EXPORT resolves to : __attribute__ ((visibility("default"))) and BOOST_SYMBOL_IMPORT still resolves to nothing. OK - this has never been a problem. Now we have an extremely subtle issue which appears on linux systems with gcc. It's related to sequence of shared library loading and unloading. It shows up as a bunch of test failures for the test named test_exported_dll. A very astute user has determined that this can be "fixed" by defining BOOST_SYMBOL_IMPORT as __attribute__ ((visibility("default"))) as well. Question. should config/gcc be updated in this way? Also is it possible that this "fix" is just a fluke unrelated to the real source of the problem? Note that this issue predates the recent change to make -visibility=default which has, as one might expect, caused some issues. I believe that this situation is unrelated. Any help appreciated Robert Ramey reference: https://github.com/boostorg/serialization/issues/104#issuecomment-416948110

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Tools to manage multiple repositories effectively?
by James E. King III 09 Oct '18

09 Oct '18

Hello, I am looking for tools that would allow me to create a portal and/or monitor the following properties of boost repositories. I am in the CMT and at least one fix that was in develop never made it into master for the 1.68.0 release, so I want to be able to see, at a glance, information about the boost repositories I care about in one place. There are about 20 repositories I regularly participate in now so a portal to show what I need to worry about would be useful. 1. How far behind is master (with respect to develop)? This would help identify which repositories are behind develop. Useful for ensuring things get into a release. 2. How many open pull requests? 3. How many new pull requests (within the last week)? 4. How many updated pull requests (within the last week)? 5. How many open issues? 6. How many new issues (within the last week)? 7. How many updated issues (within the last week)? "week" could be configured, perhaps month, or "since I last visited". Anybody know of any good tools or perhaps an existing site that can do this for a multi-repository solution? Thanks, Jim

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[system] The new Boost.System is now ready
by Peter Dimov 09 Oct '18

09 Oct '18

The new Boost.System is now complete, on the develop branch: https://www.boost.org/doc/libs/develop/libs/system/ - header-only - even more constexpr than 1.68 - identifier-based category comparison - message() into a caller-supplied buffer - failed() The plan is to merge it to master at some point if no breakage is encountered on develop, so that it can go into the next release.

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Export control classification number for boost
by DEMIAN, Beatrice (SOPRA STERIA GROUP SA) 08 Oct '18

08 Oct '18

Hi, We are using boost in one of our products, and are now in the process of collecting the information needed to export it. Can you tell me what the U.S. Export Control Classification Number (ECCN) for boost is, and whether a license exception may be used for it? Béatrice Demian On behalf of SOPRA STERIA Subcontractor for EYYW6 (AIRBUS France) The information in this e-mail is confidential. The contents may not be disclosed or used by anyone other than the addressee. Access to this e-mail by anyone else is unauthorised. If you are not the intended recipient, please notify Airbus immediately and delete this e-mail. Airbus cannot accept any responsibility for the accuracy or completeness of this e-mail as it has been sent over public networks. If you have any concerns over the content of this message or its Accuracy or Integrity, please contact Airbus immediately. All outgoing e-mails from Airbus are checked using regularly updated virus scanning software but you should take whatever measures you deem to be appropriate to ensure that this message and any attachments are virus free.

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[graph_parallel] property_serialize.hpp
by Peter Dimov 06 Oct '18

06 Oct '18

I'm looking at boost/pending/property_serialize.hpp, with the intent of moving it from Graph Parallel to Graph as it's included from a Graph header, and I see this: https://github.com/boostorg/graph_parallel/blob/develop/include/boost/pendi… #ifdef BOOST_GRAPH_USE_MPI namespace boost { namespace mpi { template<> struct is_mpi_datatype<boost::no_property> : mpl::true_ { }; } } // end namespace boost::mpi BOOST_IS_BITWISE_SERIALIZABLE(boost::no_property) BOOST_CLASS_IMPLEMENTATION(boost::no_property,object_serializable) BOOST_CLASS_TRACKING(boost::no_property,track_never) #endif // BOOST_GRAPH_USE_MPI What this does is, when BOOST_GRAPH_MPI is defined, it sets certain serialization properties for boost::no_property (is bitwise serializable, use object level versioning, never track address), but when BOOST_GRAPH_MPI is not defined, it doesn't. That is, the serialization format of boost::no_property changes on the basis of whether BOOST_GRAPH_MPI is defined. (It's the same for boost::property<>, above in the same file.) This does not seem correct to me. I would expect these serialization properties to be applied consistently regardless of whether MPI is used or not. But fixing this could conceivably break existing code that serializes and deserializes non-parallel graphs and relies on a certain format on disk. So... should we fix this or not?

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Cycle between Graph and GraphParallel
by Peter Dimov 06 Oct '18

06 Oct '18

Currently we have a dependency cycle between `graph` and `graph_parallel`. It's not the only one, but it's notable with the fact that both libraries are buildable and we therefore can't ignore it as we can ignore cycles between header-only libraries that at release time become a single directory. In the particular, this impedes efforts to generate CMake config files. Under one scheme I'm currently working on, for instance, Boost.Python can't be installed because it tries to install Graph, which tries to install GraphParallel, which tries to install Graph. The cycle between these two is an interesting one. boost/graph/breadth_first_search.hpp does: #ifdef BOOST_GRAPH_USE_MPI # include <boost/graph/distributed/breadth_first_search.hpp> #endif at its end, and boost/graph/distributed/breadth_first_search.hpp does: #ifndef BOOST_GRAPH_USE_MPI #error "Parallel BGL files should not be included unless <boost/graph/use_mpi.hpp> has been included" #endif #include <boost/graph/breadth_first_search.hpp> at its very start. So these headers include each other. One would naively think that only the parallel header should include the normal one, but one is not well versed in graph library architectures, so one might quite possibly be missing something, or a lot. Comments?

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Formal Review of Proposed Boost.Histogram Library is FINISHED
by Mateusz Loskot 05 Oct '18

05 Oct '18

Dear Boost Community, The formal review of Hans Dembinski's Histogram library has been completed. Here is the quantitative summary of feedback received: * Reviews: 1. Klemens David Morgenstern 2. Jim Pivarski (off-list via e-mail to Hans) 3. Björn Reese 4. Steven Watanabe 5. Alex Hagen-Zanker * Non-review participations: 1. degski 2. Gavin Lambert 3. Seth 4. Mateusz Loskot I believe I've collected the names/numbers right, but please let me know ASAP if you think otherwise. I'd like to thank all the participants for their time and efforts. I'm sure Hans received lots of valuable comments and suggestions. FYI, the discussion threads are still open for new posts. Those won't be taken into consideration towards the review result though. I will do my best to announce the review results next week. Mateusz Review Manager for the proposed Boost.Histogram -- Mateusz Loskot, http://mateusz.loskot.net

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Twenty years and time to retire
by Beman Dawes 04 Oct '18

04 Oct '18

The idea behind Boost was hatched in March, 1998, and the proposal document <https://www.boost.org/users/proposal.pdf> was released May 6, 1998. That makes Boost twenty years old, and makes me twenty years older. It is high time I retire from Boost; I haven't been able to contribute for some time now. Thanks to all of you who made Boost such an overwhelming success in the past and will drive Boost forward into a bright future! --Beman

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Release notes for release 1.69
by Paul A. Bristow 02 Oct '18

02 Oct '18

To avoid forgetting to do it when release time comes, I would like to add some Math and Multiprecision library release notes for the next release 1.69 Is providing a PR for this file that way to do this? ( I speak Quickbook ;-) ) https://github.com/boostorg/website/blob/master/feed/history/boost_1_69_0.q… (but it doesn't exist yet!) Thanks. Paul --- Paul A. Bristow Prizet Farmhouse Kendal UK LA8 8AB +44 (0) 1539 561830

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