October 2015 - Boost - lists.preview.boost.org

[python] Merging pull request #25
by Edward Diener 17 Oct '15

17 Oct '15

The PR is necessary so that user's of Python to not see a deprecated warning coming from the updated type_traits whenever they use Boost python. Would the maintainer of Boost Python please take a look at this simple PR so we can get this in the upcoming release. Thanks !

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[Build] Specify compiler on the command line
by Louis Dionne 17 Oct '15

17 Oct '15

Hi, Still attempting to setup Boost.Build for Hana, I find myself unable to specify the compiler to be used by `b2` on the command line. The system compiler is then used by default, which does not work because I need to test on recent compilers. This can be handled by writing a project-config.jam file with the following in it: import feature ; if ! clang in [ feature.values <toolset> ] { using clang : : /path/to/clang ; } However, this is not very script-friendly, and I wonder whether there's a way to specify it on the command-line instead. Regards, Louis

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[iterator][range] Synchronization on 'master'
by Edward Diener 16 Oct '15

16 Oct '15

I have pushed a number of changes to iterator from 'develop' to 'master' for the next release. A series of these changes on 'develop', by Marcel Raad, is an attempt to remove from 'iterator' the use of the deprecated headers 'boost/iterator.hpp' and 'boost/detail/iterator.hpp' in favor of using 'std::iterator' directly instead of 'boost::iterator' and 'std::iterator_traits' and 'std::distance' directly instead of 'boost::detail::iterator_traits' and 'boost::detail::distance'. Essentially these changes mean that any other library using 'iterator' classes would fail if they attempted to refer to 'boost::iterator', 'boost::detail::iterator_traits', or 'boost::detail::distance'. After I had pushed these changes to 'master' I noticed that it broke 'range' on 'master' and reverted these specific pushed commits on iterator 'master'. On 'develop' the 'range' library ( and possibly other libraries using 'iterator' ) had been changed so that it correctly used the 'std::iterator' terminology rather than the deprecated 'boost::iterator' terminology. If we are going to make this change to 'iterator' on 'master' it needs to be co-ordinated with the same set of changes for other libraries which now work with these changes on 'develop'. I noticed quite a few changes for 'range' on 'develop' which have not been pushed to 'master' for the upcoming release. I will assume that the maintainer of 'range' will want to push these changes to 'master' for the upcoming release so this is a heads up that the changes ( actually the last 'develop' commit for 'range' ) need to be co-ordinated with 'iterator' if it is done. Similarly if any other library depending on 'iterator' needs these changes on 'master' it needs to be co-ordinated with 'iterator'. I will NOT be re-pushing these changes on 'iterator' until this co-ordination is in place as I do not want to break 'master' in the interim. I am also fine with waiting until after this upcoming release to re-push these 'iterator' change to 'master' if that is what is desired by others, but any library currently depending on these changes in 'develop' must be aware of what the decision end up to be.

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[serialization] Test runners being stopped
by Tom Kent 16 Oct '15

16 Oct '15

I think there is a bug in the serialization library that is breaking out of the test harness and causing window's error handling to kick in (when running on Windows, obviously). Usually when this happens the test runner application eventually (I believe) times out the test and marks it as failed. However, there are an incredible number of failures happening (since late last week) and they are bogging down the entire test run. Most of the runs I have attempted in the last week on windows have failed...the ones that have succeeded have taken ~12hrs up from the normal 3-4hrs. I was able to capture a stack trace of one of these random failures: msvcp140d.dll!00007ff9cfffb968() Unknown msvcp140d.dll!00007ff9cff73005() Unknown > test_list_ptrs_text_warchive.exe!std::basic_filebuf<wchar_t,std::char_traits<wchar_t> >::_Endwrite() Line 649 C++ test_list_ptrs_text_warchive.exe!std::basic_filebuf<wchar_t,std::char_traits<wchar_t> >::close() Line 341 C++ test_list_ptrs_text_warchive.exe!std::basic_filebuf<wchar_t,std::char_traits<wchar_t> >::~basic_filebuf<wchar_t,std::char_traits<wchar_t> >() Line 155 C++ test_list_ptrs_text_warchive.exe!std::basic_ofstream<wchar_t,std::char_traits<wchar_t> >::~basic_ofstream<wchar_t,std::char_traits<wchar_t> >() Line 1068 C++ test_list_ptrs_text_warchive.exe!std::basic_ofstream<wchar_t,std::char_traits<wchar_t> >::`vbase destructor'() C++ test_list_ptrs_text_warchive.exe!test_list() Line 65 C++ test_list_ptrs_text_warchive.exe!test_main(int __formal, char * * __formal) Line 176 C++ test_list_ptrs_text_warchive.exe!main(int argc, char * * argv) Line 203 C++ [External Code] I'd be happy to help get to the bottom of this, if you can give me any more diagnostic steps to take. We need to resolve this ASAP because it is preventing the windows test runners from producing timely results and we have a release coming up. Thanks, Tom

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[test] BOOST_PP_VARIADICS is defined twice
by Andrey Semashev 16 Oct '15

16 Oct '15

Hi, For some reason Boost.Test defines the BOOST_PP_VARIADICS macro, which, I believe, is a macro defined by Boost.Preprocessor. This results in build errors as can be seen here: http://www.boost.org/development/tests/develop/developer/output/teeks99-01b… I think Boost.Test should not define BOOST_PP_VARIADICS and rely on Boost.PP for that. In any case, BOOST_PP* is not the namespace of Boost.Test.

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[fusion] result_of_with_decltype is missing
by Andrey Semashev 16 Oct '15

16 Oct '15

Hi, I can see many of my tests are failing like this: http://www.boost.org/development/tests/develop/developer/output/teeks99-01b… Basically, it complains that fusion::detail::result_of_with_decltype is missing and indeed I cannot find it defined in Boost.Fusion anywhere.

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Valgrind reports use of uninitialized value in any_range
by Auer, Jens 16 Oct '15

16 Oct '15

Hi, I am using an any_range of std::unique_ptr values in one of my programs. When I analyse this with valgrind, it reports many uninitialized value usages in any_range, and I cannot explain this from my code. I managed to produce a small example to reproduce this. I would like to know if that is a real issue, or if can just create a valgrind suppression rule. #include <iostream> #include <boost/range.hpp> #include <boost/range/any_range.hpp> #include <boost/range/adaptors.hpp> struct Int { Int(int i): x(i) {} int x; }; int main( int argc, char* argv[] ) { typedef boost::any_range<Int*, boost::forward_traversal_tag, Int*, std::ptrdiff_t> R; std::vector<std::unique_ptr<Int>> v; v.push_back( std::make_unique<Int>(42) ); auto f = [](std::unique_ptr<Int> const& p) {return p.get();}; R r = v | boost::adaptors::transformed(f); auto x = (*boost::begin(r))->x; std::cout << x << std::endl; return 0; } Running this, valgrind reports a "Use of uninitialized value of size 8": # g++ --version g++ (GCC) 5.2.0 # g++ -std=c++1y -o test test.cpp # valgrind --version valgrind-3.11.0 # valgrind --track-origins=yes ./test ==8119== Memcheck, a memory error detector ==8119== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. ==8119== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info ==8119== Command: ./test ==8119== ==8119== Use of uninitialised value of size 8 ==8119== at 0x4010B8: main (in /tmp/test) ==8119== Uninitialised value was created by a stack allocation ==8119== at 0x40315D: boost::range_detail::any_iterator<Int*, boost::iterators::forward_traversal_tag, Int*, long, boost::any_iterator_buffer<64ul> >::dereference() const (in /tmp/test) ==8119== 42 ==8119== ==8119== HEAP SUMMARY: ==8119== in use at exit: 72,704 bytes in 1 blocks ==8119== total heap usage: 3 allocs, 2 frees, 72,716 bytes allocated ==8119== ==8119== LEAK SUMMARY: ==8119== definitely lost: 0 bytes in 0 blocks ==8119== indirectly lost: 0 bytes in 0 blocks ==8119== possibly lost: 0 bytes in 0 blocks ==8119== still reachable: 72,704 bytes in 1 blocks ==8119== suppressed: 0 bytes in 0 blocks ==8119== Rerun with --leak-check=full to see details of leaked memory ==8119== ==8119== For counts of detected and suppressed errors, rerun with: -v ==8119== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 1 from 1) Best wishes, Jens PS: I've sent this to boost-users yesterday, but I now think that boost-devel is a better match. -- Dr. Jens Auer | CGI | Software Engineer CGI Deutschland Ltd. & Co. KG Rheinstraße 95 | 64295 Darmstadt | Germany T: +49 6151 36860 154 jens.auer(a)cgi.com Unsere Pflichtangaben gemäß § 35a GmbHG / §§ 161, 125a HGB finden Sie unter de.cgi.com/pflichtangaben. CONFIDENTIALITY NOTICE: Proprietary/Confidential information belonging to CGI Group Inc. and its affiliates may be contained in this message. If you are not a recipient indicated or intended in this message (or responsible for delivery of this message to such person), or you think for any reason that this message may have been addressed to you in error, you may not use or copy or deliver this message to anyone else. In such case, you should destroy this message and are asked to notify the sender by reply e-mail.

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Beginner Request for Contributing to Boost Library
by Arafat Khan 16 Oct '15

16 Oct '15

Hi Respected Sir/ Mam, I am Arafat Dad Khan, an undergraduate student at Indian Institute of Technology, Kharagpur. I wish to contribute to the Boost Library (Specifically Graph and Data Structures). I have decent knowledge of Algorithms and Data Structures and have consistently taken part in algorithmic competitions on websites such as Codechef and Spoj(Sphere online Judge ) you can view my profile here http://www.spoj.com/SPOJ/users/adk/ I am very new to open source, And i just need someone to guide me so that i could focus on the right areas to contribute. I am very comfortable with C++ language and learning complicated algorithms is great fun to me. Can anyone please tell me the ways in which i could contribute? If this is not the right place to ask newbie questions please tell me where i could ask the my questions. Thanks Arafat Dad Khan Indian Institute of Technology Kharagpur

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We need a coherent higher level parallelization story for C++ (was [thread] Is there a non-blocking future-destructor?)
by Hartmut Kaiser 16 Oct '15

16 Oct '15

Sorry for cross-posting. > Vicente J. Botet Escriba wrote: > > I have a branch > (https://github.com/boostorg/thread/tree/feature/non_blocking_futures) > that don't blocks on any future, but this will break async. FWIW, the design decision to let those (and only those) futures block on destruction which are returned from async was one of the really bad decisions made for C++11, however that's just my opinion (others agree, but yet others disagree). This flaw essentially caused us to spend many committee hours on discussions how to mitigate the situation, with proposed solutions ranging from 'leave it be as is' to as extreme as 'deprecate it now'. There seems to be a growing consensus however to develop other constructs which eventually could replace async, such as executors, etc. I'm a proponent of following that path. More generally, I strongly believe that we have to come up with a _coherent story_ for all kinds of (higher-level) parallelism in C++: task-based parallelism, asynchronous, continuation style programming, fork-join parallelism of heterogeneous tasks, simple fork-join (iteration based) parallelism, etc. All of this has to go hand in hand with a (orthogonal) vectorization story. We also need to think about integrating GPUs. The goal has to be to make parallelism in C++ independent of any external solutions such as OpenMP, OpenACC, etc. Many of the building blocks for this are already being discussed: executors and executor_traits for customizing the 'how and where' of task execution, executor parameters for grain-size control, and execution policies as the higher level facility allowing to tie everything together (see for instance HPX [7]). We (as a committee) already allow for passing execution policies as the first argument to parallel algorithms (Parallelism TS, N4505 [2]). We already have some facilities for task-based, asynchronous, and continuation style parallelism in place (Concurrency TS, N4501 [3]). We have a paper proposing task_blocks for fork-join parallelism of heterogeneous tasks (N4411 [4]). We have two competing (but converging) efforts for defining an executor concept (N4406 [5], PR0008R0 [6]). We have a (strong) proposal for simplifying continuation based programming (await, PR0057R0 [8]). We have attempts on integrating executors with existing facilities (Boost, HPX). We miss work on parallel ranges. We miss work on integrating data structures with data placement policies in conjunction with executors. We miss work on extending all of this to many-core, distributed, and high-performance computing. Etc. We (as a community) really need a higher level, over-arching approach which ties all of the above together! My plan is to work on a corresponding concept paper by the time of the committee meeting end of February 2016. Our group has outlined our current understanding and a possible approach to this here [1]. I'd like for this to be understood as a seed for a wider discussion. Needless to say, I'd very much like to collaborate on this with anybody interested in joining the effort. Regards Hartmut --------------- http://boost-spirit.com http://stellar.cct.lsu.edu [1] http://stellar.cct.lsu.edu/pubs/executors_espm2_2015.pdf [2] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4505.pdf [3] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4501.html [4] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4411.pdf [5] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4406.pdf [6] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0008r0.pdf [7] http://stellar-group.github.io/hpx/docs/html/hpx/manual/parallel.html [8] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0057r0.pdf

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[WG21 mailing] N4453 Resumable expressions
by Niall Douglas 15 Oct '15

15 Oct '15

I'm finding Chris' paper on resumable expressions instead of compiler magic created resumable functions awfully compelling: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4453.pdf I essentially proposed the same with my functionally composed constexpr basic_future design some months ago. Would anyone else like to comment on this library based instead of compiler based resumable execution? I'm not against some compiler support for resumable execution, but I am finding the await based proposal highly problematic, and Chris does an excellent job in summarising my own thoughts on what's wrong with it. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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