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xpressive: How to combine vector of regex to one?
by Anton Sergunov 08 Jul '22

08 Jul '22

Hello Boost Users! I'm seeking some help from the community because can't see answer in documentation or in source code. I need to find which regex of N my string matches. I don't like to compare them one by one, to speed up the process. It's easy to implement if I have them compile time: ```cpp sregex re = (s1 = re1)|(s2 = re2)|(s3=re3); ... std::set<int> foo(const std::string& str) { std::set<int> result; smatch match; if(regex_match(str, match, re)) { for(int i = 0; i<3; ++i) if(match[i+1]) result.insert(i); } return result; } ``` But I have a vector: ```cpp std::set<int> foo(const std::string& str, const std::vector<sregex>& reVector) { sregex re; int index = 1; for(auto&& item : reVector) { re |= (mark_tag(index++) = item); // (1) } std::set<int> result; smatch match; if(regex_match(str, match, re)) { for(int i = 0; i<reVector; ++i) if(match[i+1]) result.insert(i); } } return result; } ``` There at (1) `|=` doesn't work as I expect for some reson, It didn't catch some values. If I replace it with ```cpp re = re | (mark_tag(index++) = item); ``` it just crashes. If I replace with: ```cpp auto t = re; re = t | (mark_tag(index++) = item); ``` it making captures of previous tags to be subexpresions matches. So code doesn't work as I want. Is it any way to prevent sub-expression capture isolation? As I understand it should be some intermediate type before sregex to express expression under construction. So it will not isolate matches of existing part. I'm using v1.65.1 https://github.com/boostorg/xpressive/issues/24

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Embedded install paths in CMake files for Boost 1.79
by Alex 05 Jul '22

05 Jul '22

Apologies if this is the wrong list. I tried boost-build but I'm not sure if my message was verified (I don't see it in the archive). I'm trying to make a build of Boost that includes the generated CMake files. For my case, I need to install the files to a staging area before packaging them up for installation in the target environment. I've tried "b2 --stagedir <dir> stage" but the generated CMake files still include the stagedir path in them, instead of the install prefix specified during bootstrap, which triggers errors in the packaging system I need to use. I'm also not sure if it's then possible to just install the headers to the same staging location. Is there a way to install to a staging location while the CMake files have the paths to the final install location? CMake uses CMAKE_STAGING_PREFIX for this but I can't find an equivalent for b2. I guess it must be required for cross-compiling though, if you want to support CMake on the target? Regards, Alex

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Excessive dynamic allocation when using boost::split(..., boost::is_any_of(", "))?
by Dominique Pellé 05 Jul '22

05 Jul '22

Hi This following program shows many allocations coming from boost::split(..., boost::is_any_of(",")): ``` $ cat split.cpp #include <string> #include <cstdio> #include <boost/algorithm/string.hpp> #include <boost/container/small_vector.hpp> int main() { std::string str = "foo,bar,foobar,quux"; std::size_t s = 0; for (int i = 0; i < 100; ++i) { boost::container::small_vector<std::string, 4> v; #ifdef USE_IS_ANY_OF boost::split(v, str, boost::is_any_of(",")); #else boost::split(v, str, [](const char c) { return c == ',';}); #endif s += v.size(); } fprintf(stderr, "%zu\n", s); } ``` When using boost::is_any_of(","), there are 7 dynamic allocations per loop iteration whereas when using the lambda predicate, there are 0 dynamic allocation per loop as shown below: ``` $ clang++ -std=c++14 -DUSE_IS_ANY_OF split.cpp $ heaptrack ./a.out ... allocations: 702 $ clang++ -std=c++14 split.cpp $ heaptrack ./a.out ... allocations: 2 ``` I suspect that there are potential optimizations in Boost here to avoid so many allocations when boost::is_any_of(",") is used. Regards Dominique

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Boost.URL review planned for 13-22 August 2022
by Mateusz Loskot 29 Jun '22

29 Jun '22

Folks, Klemens Morgenstern kindly volunteered [1] as the Review Manager (thanks Klemens!) for the Boost.URL [2], so we have planned the review shortly after the upcoming release of the Boost 1.80. Check the Review Schedule [3] for details! [1] https://lists.boost.org/Archives/boost/2022/06/253225.php [2] https://lists.boost.org/Archives/boost/2022/04/252814.php [3] https://www.boost.org/community/review_schedule.html Best regards, -- The Boost Review Wizards Mateusz Loskot

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Boost Twitter is Blowing Up!!!
by Vinnie Falco 21 Jun '22

21 Jun '22

Greetings fellow users, library authors, maintainers, review wizards, release wizards, and Boost Foundation Board members! As part of our ongoing effort to continue the revitalization of Boost, a handful of us have taken the reins to post about Boost on social media. We have postings on Reddit and Hacker news, blog posts about the new efforts in Boost.Unordered, and new tweets. However, we could use your help! Right now the Boost Twitter account has a measly 957 followers. It would be great to increase our reach, so I'm asking everyone if they could be so kind as to Follow the official Boost Twitter account here: <https://twitter.com/Boost_Libraries> and then amplify our messages by Liking and Retweeting. Starting with this pinned tweet, which everyone will see when they visit the Boost Libraries Twittter profile page: <https://twitter.com/Boost_Libraries/status/1539003321939202048> Following the Boost Twitter account will give you up-to-date information about what is going on with Boost, including articles and mentions on other social media sites. Here is what we have so far: <https://www.reddit.com/r/cpp/comments/vfdcrz/advancing_the_state_of_the_art…> <https://www.reddit.com/r/cpp/comments/vbdr3z/new_boostunordered_containers_…> <https://twitter.com/hackernewstop10/status/1538622706035343364> <https://news.ycombinator.com/item?id=31801814> To summarize, engaging with Boost related content on social media will enhance our profile - any help is appreciated! -- Regards, Vinnie Follow me on GitHub: https://github.com/vinniefalco

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[JSON] Vote for Boost.JSON in this poll!
by Vinnie Falco 21 Jun '22

21 Jun '22

There's an online poll asking about which JSON library you use. If you use Boost.JSON consider voting for it: <https://meetingcpp.com/mcpp/survey/?q=2> Also, consider voting for it if you _don't_ use Boost.JSON, but you want to. -- Regards, Vinnie Follow me on GitHub: https://github.com/vinniefalco

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[Locale] IBM437 encoding not supported in wconv
by Arnold, Stefan 14 Jun '22

14 Jun '22

Why is the IBM437 encoding not supported in boost::locale with the Win32 API ("wconv") backend? The following call will fail with a boost::locale::conv::invalid_charset_error when using the Win32 API backend: boost::locale::conv::to_utf<char>("abc", "IBM437") This is because "ibm437" is not contained in the all_windows_encodings variable in wconv_codepage.ipp (nor is "cp437" or another alias). As per Win32 API documentation (https://docs.microsoft.com/en-us/windows/win32/api/stringapiset/nf-stringap…, https://docs.microsoft.com/en-us/windows/win32/intl/code-page-identifiers) this encoding is supported in Win32 API. Furthermore, IBM437 is the legacy encoding of filenames in ZIP files, so it should be quite common.

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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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