May 2022 - Boost-users - lists.preview.boost.org

Any objections to making C++14 the current baseline for Boost support and testing?
by John Maddock 10 Jun '22

10 Jun '22

Pursuant of discussion elsewhere: Does anyone have any concrete objections to Boost moving to a C++14 baseline? This would mean: * Library authors can drop and remove all support for pre-C++14 compilers after a suitable deprecation notice in place for say 3 releases. * The community maintenance team can likewise drop pre-C++14 support from community maintained / orphan libaries. * CI tests no longer need report pre-C++14 results. * From the next release onward, the boost super-project should clearly announce in our release notes, that C++11 and earlier support may no longer be available from the start of 2023. Thoughts? Thanks, John Maddock.

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[thread] attribute constructor failing to compile
by Jeanette C. 07 Jun '22

07 Jun '22

Hey hey, using boost 1.78 from the Archlinux repository, using the thread constructor with boost::thread::attributes as first argument fails to compile. The relevant code from the small test program is this: void work(bool& done) // simple main function for the thread int main() { bool done = false; boost::thread::attributes attr; // all changes commented out in the program boost::thread th1(attr, work, std::ref(done)); // some code, sleep and set done to true th1.join(); return 0; } g++ 11.2.0 reports the following error: In file included from /usr/include/boost/thread/detail/thread.hpp:33, from /usr/include/boost/thread/thread_only.hpp:22, from /usr/include/boost/thread/thread.hpp:12, from thread_prio.cpp:1: /usr/include/boost/bind/bind.hpp: In instantiation of 'void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = boost::thread_attributes; A = boost::_bi::list0; A1 = boost::_bi::value<int (*)(bool&)>; A2 = boost::_bi::value<std::reference_wrapper<bool> >]': /usr/include/boost/bind/bind.hpp:1273:18: required from 'boost::_bi::bind_t<R, F, L>::result_type boost::_bi::bind_t<R, F, L>::operator()() [with R = void; F = boost::thread_attributes; L = boost::_bi::list2<boost::_bi::value<int (*)(bool&)>, boost::_bi::value<std::reference_wrapper<bool> > >; boost::_bi::bind_t<R, F, L>::result_type = void]' /usr/include/boost/thread/detail/thread.hpp:120:18: required from 'void boost::detail::thread_data<F>::run() [with F = boost::_bi::bind_t<void, boost::thread_attributes, boost::_bi::list2<boost::_bi::value<int (*)(bool&)>, boost::_bi::value<std::reference_wrapper<bool> > > >]' /usr/include/boost/thread/detail/thread.hpp:118:18: required from here /usr/include/boost/bind/bind.hpp:298:35: error: no match for call to '(boost::thread_attributes) (int (*&)(bool&), std::reference_wrapper<bool>&)' 298 | unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); | ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The syntax is based on this part of the manual: https://www.boost.org/doc/libs/1_79_0/doc/html/thread/thread_management.htm… Is that perhaps a feature only introduced in version 1.79 of the Boost libraries? Best wishes and thanks for any pointers, Jeanette -- * Website: http://juliencoder.de - for summer is a state of sound * Youtube: https://www.youtube.com/channel/UCMS4rfGrTwz8W7jhC1Jnv7g * Audiobombs: https://www.audiobombs.com/users/jeanette_c * GitHub: https://github.com/jeanette-c Don't care about money It doesn't give me half the thrill <3 (Britney Spears)

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[Compute] Auto-determine work group size
by Stephan Menzel 12 May '22

12 May '22

Hi everyone, perhaps someone can answer a question about Boost.Compute. I have recently switched to it from using native OpenCL. Most of the things work fine except for one quirk: OpenCL allows for auto-determining the work group size when using enqueue_kernel(). As the correct work group size is still a mystery to me after using OpenCl for almost a year now I normally left this parameter to 0 to let OpenCL figure it out. With Boost.Compute and the equivalent function enqueue_nd_range_kernel() this doesn't seem to be possible. I have to use a parameter like boost::compute::extents<2>{ 8, 2 } as local_work_size. Leaving it 0 or using extents<2>{ 0, 0 } doesn't do the trick and I'm getting "Invalid work group size". This forces me to guess values until one works, which is extremely error prone and breaks all the time with images of different resolutions. Does anyone know how I can use OpenCL's auto-work-group-size feature in Boost.Compute? Cheers, Stephan

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Iterating over each point within a geometry::box
by Keith Bennett 11 May '22

11 May '22

I want to iterate over every point within a geometry::model::box<point>. I want to be able to do that with iterators so that I can also use all (or most of) the standard algorithms like for_each or all_of or etc. Initially my code used several loops, one for each axis, like so for a 2d point: for (int x = box.min_corner().template get<0>(); x <= box.max_corner().template get<0>(); ++x) { for (int y = box.min_corner().template get<1>(); y <= box.max_corner().template get<1>(); ++y) { callback(point(x,y)) } } There are several places where this occurs. Some loops have the x axis first, others the y axis first -- and this has performance issues when translating the point to a container. Some loops were erroneously considering right-open intervals with less-than instead of less-than-or-equal-to comparisons. So I've had to fix bounding bugs and performance issues in multiple places that are caused by these manual loops. I've gone and unified a lot of that to use templated functions that basically duplicate some of the functionality in the standard. But that's not tractable and still doesn't use iterators so most of <algorithm> is still off-limits: namespace mynamespace { template <class box, enable_if vomit, blah blah> void for_each(const box& b, const std::function<void(const typename box::point_type&)> callback) { // the manual loops here, not repeated for brevity } } Then I've replaced most of those manual loops with calls to: mynamespace::for_each(box, [](const point& p){ // do some work here }); So I want to instead do: for (const auto& point : box) { callback(point); } Satisfying that would make a lot of places simpler and easier to read. I think it should also help to enable use of a lot of the stuff in the standard <algorithm> I understand that it might be difficult for, eg, a box containing a point with floating point types. But that's fine ... I'm only looping over integral points anyway. I'd also prefer to have the ability to control the axis order ... eg do I want x or y on the inner/outer loop? Do I want to only iterate over the y axis? I'm using C++14 and boost 1.70 at the moment. There's some friction against upgrading. But if this problem is solved in a future version -- like with C++20 ranges -- then that would be a strong point for me to convince my team to upgrade. I could go and write up some iterators myself of course. But before I do that I wondered if someone else has already solved this problem and I just haven't found the solution. Thoughts? -- Keith Bennett

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Fwd: [boost] Boost MySQL Review Starts Today
by Mateusz Loskot 10 May '22

10 May '22

FYI ---------- Forwarded message --------- From: Richard Hodges via Boost <boost(a)lists.boost.org> Date: Tue, 10 May 2022 at 09:14 Subject: [boost] Boost MySQL Review Starts Today To: boost(a)lists.boost.org List <boost(a)lists.boost.org>, <boost-announce(a)lists.boost.org> Cc: Richard Hodges <hodges.r(a)gmail.com> Dear All, The Boost formal review of the MySQL library starts Today, taking place from May 10th, 2022 to May 19th, 2022 (inclusive) - We are starting one day after the announced date and extending the period by one day to compensate. The library is authored by Rubén Pérez Hidalgo (@anarthal in the CppLang slack). Documentation: https://anarthal.github.io/mysql/index.html Source: https://github.com/anarthal/mysql/ The library is built on the bedrock of Boost.Asio and provides both synchronous and asynchronous client connectors for the MySQL database system. Boost.MySQL is written from the ground up, implementing the entire protocol with no external dependencies beyond the Boost library. It is compatible with MariaDB. Connectivity options include TCP, SSL and Unix Sockets. For async interfaces, examples in the documentation demonstrate full compatibility with all Asio completion handler styles, including: Callbacks:- https://anarthal.github.io/mysql/mysql/examples/query_async_callbacks.html Futures :- https://anarthal.github.io/mysql/mysql/examples/query_async_futures.html Boost.Coroutine :- https://anarthal.github.io/mysql/mysql/examples/query_async_coroutines.html C++20 Coroutines :- https://anarthal.github.io/mysql/mysql/examples/query_async_coroutinescpp20… Rubén has also implemented the Asio protocols for deducing default completion token types :- https://anarthal.github.io/mysql/mysql/examples/default_completion_tokens.h… Reviewing a database connector in depth will require setting up an instance of a MySQL database. Fortunately most (all?) Linux distributions carry a MySQL and/or MariaDB package. MySQL community edition is available for download on all platforms here: https://dev.mysql.com/downloads/ Rubén has spent quite some time in order to bring us this library candidate. The development process has no doubt been a journey of discovery into Asio, its concepts and inner workings. I am sure he has become a fount of knowledge along the way. >From a personal perspective, I was very happy to be asked to manage this review. I hope it will be the first of many more reviews of libraries that tackle business connectivity problems without further dependencies beyond Boost, arguably one of the most trusted foundation libraries available. Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including Describe as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - Will the library bring additional out-of-the-box utility to Boost? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - Will the choice of API abstraction model ease the development of software that must talk to a MySQL database? - Are there any immediate improvements that could be made after acceptance, if acceptance should happen? - Did you try to use the library? With which compiler(s)? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? More information about the Boost Formal Review Process can be found at: http://www.boost.org/community/reviews.html The review is open to anyone who is prepared to put in the work of evaluating and reviewing the library. Prior experience in contributing to Boost reviews is not a requirement. Thank you for your efforts in the Boost community. They are very much appreciated. Richard Hodges - review manager of the proposed Boost.MySQL library Rubén is often available on CppLang Slack and of course by email should you require any clarification not covered by the documentation, as am I. -- Richard Hodges hodges.r(a)gmail.com tg: @rhodges office: +44 2032 898 513 mobile: +376 380 212 _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost -- Mateusz Loskot, http://mateusz.loskot.net

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[Boost.Asio] [SSL] Can I set the host name before performing a handshake?
by B Aleck 04 May '22

04 May '22

In openssl you call SSL_set_tlsext_host_name to set that Can I do that in boost?

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boost.org domain expired?
by Warren Weckesser 03 May '22

03 May '22

(Hit enter too soon in my last email.) FYI: Attempting to visit https://www.boost.org results in a Network Solutions page, with links for "Renew Now" and "Backorder Domain". Warren

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Re: [Boost-users] boost.org domain expired?
by Kenneth Porter 03 May '22

03 May '22

Confirmed. Here's a site snapshot from yesterday in case someone needs it: https://web.archive.org/web/20220502193202/https://www.boost.org/

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boost.org domain expired?
by Warren Weckesser 03 May '22

03 May '22

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[Math / Distributions] How do mean, variance, etc end up in scope?
by Warren Weckesser 02 May '22

02 May '22

This is probably more of a C++ question than a Boost/Math question. I think the answer comes down to a (surprising?) Boost namespace convention. In a program like this: ``` #include <boost/math/distributions/beta.hpp> using boost::math::beta_distribution; int main() { float a = 1.5f; float b = 3.0f; beta_distribution<float> dist(a, b); auto m = mean(dist); } ``` how does the name 'mean' end up in scope in 'main()'? I would have expected (and preferred!) something like 'using boost::math::mean;' to be required. Warren

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