October 2022 - Boost - lists.preview.boost.org

Library proposal - indexed_array
by Julien Blanc 12 Oct '23

12 Oct '23

Hi, I've written and released a (rather small) library which allows defining arrays with arbitrary index mechanisms (hence the name, indexed_array). This especially allows indexing with scoped enums, use non zero-starting indexes, or use sparse indexes. This is not a view, but an array in the sense that it owns the data, and provides the same guarantees and functionalities as std::array, such as triviality propagation, being able to reside in read-only program sections, etc. It also supports multidimensional indexing, and provides an indexed_span template class to access lower dimension content (which can be used outside indexed_array). Finally, it provides an opt-in safer way to initialize the array content, which is especially useful when using complex and/or changing indexing schemes (like based on externally generated files). The library is available here: https://github.com/Julien-Blanc-tgcm/indexed_array And the doc is here: https://julien-blanc-tgcm.github.io/indexed_array/ It requires C++17 and mp11, and has first-class support for describe-d enums. If there is some interest, i'd like to propose it for inclusion in boost. So i'm looking for people who would endorse it. Thanks and best regards, Julien

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Decommissioning Trac (svn.boost.org)
by Glen Fernandes 31 Jan '23

31 Jan '23

We have Trac in read-only mode after we migrated to Git, but we're still paying for the server. Do people still want to preserve any part of the content in some way? The wiki aside, there are old issues, with comments, and some of them have patches attached. Peter had the idea of generating static HTML content from Trac and hosting that on an archive section on boost.org. (I don't know how difficult this is to do). Thoughts? Suggestions? Glen

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Regression Results Not Updating
by Tom Kent 15 Jan '23

15 Jan '23

The results from the pages at: https://www.boost.org/development/tests/develop/developer/summary.html https://www.boost.org/development/tests/master/developer/summary.html Have not updated in almost a month. Can someone check on the process that manages this? Thanks, Tom

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Boost.Text is looking for a (mini-)review manager
by Zach Laine 07 Dec '22

07 Dec '22

I've made all the recommended changes to Boost.Text that came up in the review. Glen, the previous review manager, recommended a mini review of Boost.Text once I'd made those changes. If you'd like to manage the mini-review, please let me know. For everyone, including potential reviewers and review managers, here are the major changes: * All the specific review feedback issues have been addressed. * The string layer is now gone. * The text layer got a major re-work. It is now a set of template-based adaptors (basic_text<>, vs. a text typedef. etc.), which lets everyone get what they want. You can change the underlying storage type (including whatever allocator you prefer), select UTF-8 or UTF-16, and change the normalization form. Glen recommended I drop this layer, but the library is way less useful without this stuff, and these changes address all the concerns raised about the text layer in the review. The updated docs can be found here: https://tzlaine.github.io/text/doc/html/index.html Oh yeah, and I added concept constraints to the whole library when you build in C++20 mode. Zach

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Build Issue - URL - msvc-14.0
by Tom Kent 05 Nov '22

05 Nov '22

In preparation for the upcoming lockdown and release, I just grabbed the latest snapshot from here: https://boostorg.jfrog.io/artifactory/main/master/boost_1_81_0-snapshot.tar… I ran it through the build process and got some issues with boost::url running on msvc-14.0. Some examples of them are: D:\RB\boost_1_81_0\boost/url/param.hpp(886): error C2134: 'boost::urls::grammar::string_view_base::string_view_base': call does not result in a constant expression D:\RB\boost_1_81_0\boost/url/param.hpp(886): note: failure was caused by call of undefined function or one not declared 'constexpr' The full output log is here: https://gist.github.com/teeks99/8d14da5b50cffda13f9ad5e23a8d80aa Tom

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Does ASIO really still uses reactor instead of proactor on some OSes or is documentation just outdated?
by Ivan Matek 29 Oct '22

29 Oct '22

If you go to https://www.boost.org/doc/libs/1_80_0/doc/html/boost_asio/overview/core/asy… you will see that it says: * On many platforms, Boost.Asio implements the Proactor design pattern in terms of a Reactor, such as select, epoll or kqueue. This implementation approach corresponds to the Proactor design pattern as follows: * *[...]* * On Windows NT, 2000 and XP, Boost.Asio takes advantage of overlapped I/O to provide an efficient implementation of the Proactor design pattern. This implementation approach corresponds to the Proactor design pattern as follows: * I am unfortunately not a pattern or OS expert, but I would expect that on every modern OS proactor can be implemented without using reactor, e.g. see *https://stackoverflow.com/a/57451551/700825 <https://stackoverflow.com/a/57451551/700825>* The fact that mentioned Windows are NT, XP and 2000 also furthers my suspicion that docs are outdated.

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Boost.StaticString
by Vinnie Falco 29 Oct '22

29 Oct '22

Alan de Freitas has generously stepped up to maintain Boost.StaticString in the absence of Krystian. -- Regards, Vinnie Follow me on GitHub: https://github.com/vinniefalco

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1.81.0 closed for new libraries and breaking changes
by Glen Fernandes 28 Oct '22

28 Oct '22

Next deadline: On 2022-11-02 Boost 1.81.0 closes for major code changes. Still open for serious problem fixes and docs changes without release manager review. - Boost release team

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Wants to start contributing to boost libraries
by Shivam Rajput 28 Oct '22

28 Oct '22

Hey, I'm really interested to start contributing to boost, it would be really great if any of you could suggest which libraries that i can start with? Maybe any of the gsoc projects that need maintenance and more work? Currently I'm more interested in c++23 features and trying to implement some of them into libcxx. Thanks and regards Shivam

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Reminder: Oct 26, 1.81.0 closed for new libraries and breaking changes
by Glen Fernandes 18 Oct '22

18 Oct '22

1.81.0 closes for new libraries and breaking changes next Wednesday (2022-10-26). We have two new accepted libraries: MySQL and URL, but only URL has been imported into the organization and has a submodule right now. Glen

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New Library Proposal: xvec/simd
by Towner, Daniel 17 Oct '22

17 Oct '22

I would like to propose a SIMD/data-parallel header-only library for inclusion in boost. The library is an example implementation already developed by Intel of a C++ TS proposal called std::experimental::parallelism_v2::simd [1]. The library is styled as a data-parallel library where the programmer specifies the data parallelism available in the source program, and the compiler will generate the appropriate simd instruction sequences. The library is agnostic of simd element type and length, and within reason, should be able to target any processor with simd capabilities. Intel has added further generic extensions to the proposal, such as permutation operations and support for complex numbers [2]. Motivation: The concept of simd needs little introduction as the technique is widely used in high performance software and there are many libraries providing varying level of abstraction and portability. In [1], Matthias Kretz made a proposal to provide a standard C++ library which implements many data-parallel concepts in a portable, vendor-neutral style, and with tight integration with C++ (e.g., operator overloading, overloads for all appropriate standard library functions). That proposal and the feedback on it have been discussed in WG21 and Intel supports the proposal. There was an attempt to add a boost.simd library in the past but that was abandoned after its authors decided to commercialise it. Despite the availability of other simd or data-parallel libraries in the wider community there is still a gap for a data-parallel, width-agnostic, vendor neutral library with close integration into C++. The std::simd library proposal and its example implementation from Intel seem to fill this gap. The existence of an example implementation in boost will also make it easier to get users to adopt the TS and provide feedback to improve its API and feature set for real-world code. History: There are two strands of history that come together in this proposal: Intel's own vector libraries, and the C++ std::simd proposal. Intel has a long history of developing simd-capable processors and has its own libraries for accessing simd features [3]. A recent Intel project to refresh those libraries resulted in a new library called `xvec' which incorporates many modern C++ features and is deliberately vendor and target neutral, with the target being selected at compile-time. In 2013 the proposal was started, and then a C++ TS was published in 2018 [1] and discussed in WG21. Due to the similarities of the two libraries and their common goals, myself and Matthias Kretz are now working together on merging the simd specification from the Parallelism TS 2 into the IS for C++26. Status and Implementation: The `xvec' example library implemented by Intel supports most of the features of the std::simd proposal [1], along with a number of extensions to add some capabilities (e.g., generic permutation, complex number support) [2]. The library works in Linux and Windows, and can be compiled with GCC 12, LLVM 14 and Intel's oneAPI 2022. It is currently tested using googletest. Most of the library is implemented on top of the LLVM and GCC vector extensions [4], which makes it compilable on any target supported by those extensions. In a limited number of places intrinsics are used to access specific Intel instructions, but efficient generic fall-backs are also provided for simd targets which don't have those instructions (and this can included unsupported Intel processors too). Request: I would welcome any comments, questions or ideas on how to proceed with this proposal. [1] ISO/IEC TS 19570:2018, Programming Languages - Technical Specification for C++ Extensions for Parallelism, by Matthias Kretz. http://open-std.org/JTC1/SC22/WG21/docs/papers/2019/n4808.pdf [2] P2638R0: Intel's response to P1915R0 for std::simd parallelism in TS 2. https://wg21.link/p2638r0 [3] https://www.intel.com/content/www/us/en/develop/documentation/cpp-compiler-… [4] https://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-ve…

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Github Actions slow
by Sam Darwin 12 Oct '22

12 Oct '22

On https://github.com/boostorg/json we have noticed very slow Github Actions times such as "Total duration: 6h 8m 47s" This is very likely caused by Github throttling jobs. https://docs.github.com/en/actions/learn-github-actions/usage-limits-billin… mentions limits of between 20 and 180 which would apply to the entire boostorg account. A reminder to any boost developers who are seeing slow processing time that they may use Drone CI, instructions at https://github.com/boostorg/boost-ci

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Boost.URL examples
by Alan de Freitas 10 Oct '22

10 Oct '22

Hi, Would anyone like to suggest examples you'd like to see in Boost.URL? Best, -- Alan Freitas https://alandefreitas.github.io/alandefreitas/ <https://github.com/alandefreitas>

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[checking interest] boost.tcl
by Klemens Morgenstern 01 Oct '22

01 Oct '22

Is there any interest in C++ Tcl bindings? I wanted to find out how far I can push boost.describe so I create C++ tcl binding based on it, PoC is here https://github.com/klemens-morgenstern/boost.tcl It's currently a rough PoC so it'd be a lot of work to make this a proper boost library, hence the question if there's some actual interest, otherwise it's a nice toy project. All you need to do is to use boost.describe for your enum or class and then you can use them in tcl: // C++ enum test_enum {foo = 1}; BOOST_DESCRIBE_ENUM(test_enum, foo); struct my_class { double foo; void bar(int); }; BOOST_DESCRIBE_STRUCT(my_class, (), (foo, bar)); BOOST_TCL_PACKAGE(Test_module, "1.0", mod) { auto & cmd = boost::tcl::create_command(mod, "test"); auto & enm = cmd.add_subcommand("enum"); enm.add_enum<test_enum>(); auto & fun = cmd.add_subcommand("add").add_function(+[](int i, int j) {return i + j;); auto & cl = cmd.add_subcommand("add") .add_class<my_class>() // adds all the members based on boost.describe .add_constructor<my_class(int, std::string)>(); } # TCL # create `test_enum` from it's int valid set e1 [test enum 1] # create test_enum from it's name set e2 [test enum foo] # call the function - overloading is supported [test add 1 2] # create an instance of my_class set mc [my_class new 1 test-string] # get a data-member puts [ *$mc .get foo ] # call a method *$mc bar 42

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