October 2025 - Boost - lists.boost.org

utility::string_view and core::detail::string_view
by Vinnie Falco 14 Dec '25

14 Dec '25

On Thu, Oct 23, 2025 at 4:17 AM Dmitry Arkhipov via Boost < boost(a)lists.boost.org> wrote: > Url's and Charconv's maintainers decided > to not play along with the charade and reference boost::core::string_view > directly with the obvious drawback that that type is not documented > anywhere. > core::detail::string_view was added because this pull request FROM 2018 (seven years ago) was rejected: https://github.com/boostorg/utility/pull/51 We really need to fix this properly. In my opinion the maintainer of utility::string_view made the wrong choice when they rejected the pull request to make the constructors more useful. The consequence is that several Boost authors now use core::detail::string_view because it better satisfies user needs. At a time when people complain that Boost has its own version of std types, it would be best if we could come together and sort this. I would like to see the change which motivated core::detail::string view get applied to utility::string_view. Then we can change core::detail::string_view to be a deprecated alias, and after one release we can remove it. This solves everyone's problem: 1. Users get a type that works 2. Folks are not triggered by having two string views 3. Every library doesn't have to lift string_view into its own namespace 4. Cross-linking in documentation becomes possible With each new version of C++ we are asking more and more of Boost users. We are asking them to opt-in to our ecosystem which includes its own types similar yet sometimes incompatible with the standard types. It is our responsibility to make sure that we respect the user's trust, and deliver types which work for them. boost::utility::string_view breaks that trust at a time when we cannot afford to alienate. The consequence of the decision not to be flexible with the utility::string_view API is that now we have two string views. We have documentation issues. We have discovery issues. There is strife within the community. Yet more and more libraries are choosing core/detail/string_view.hpp instead of utility/string_view.hpp, simply because the core version works better. It is in the project's best interest to show the C++ community writ large that we can adapt and satisfy user needs. Lets do that by resolving the two string views. Thanks

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A proposal for a modern build-system
by Hassan Sajjad 08 Dec '25

08 Dec '25

Hi. I compiled 25 Boost libraries with C++20 header-units, including examples and Tests of a few. This resulted in a 1.44x speed-up if we exclude the scanning. Scanning was as slow as the header-unit build. I have a solution for that. I am sending this paper (Making some final edits) https://htmlpreview.github.io/?https://github.com/HassanSajjad-302/iso-pape… , which allows for a build-system to use a scanning-less approach to build header-units.This method requires only minimal modifications to the compiler and enables memory-mapped file sharing, which significantly reduces filesystem overhead and further boosts speed. My proposal for a scanning-less approach will allow HMake to have another amazing feature, monolithic Big header-units. BigHu will allow you to map all the headers from a directory to a single header-unit. This header-unit includes all these header-files and consumes them as header-files. Now, whenever the compiler requests a header-unit from this directory, the build-system instead sends this consolidated BigHu. This will not only improve the clean build speed, because of fewer process launches. But also massively boosts the rebuild speed as few header-units need to be read instead of lots of files. No source-code editing will be needed to use this feature. And you will have the option to either build a library as BigHu (if you don't mean to edit it) or as small header-units (if you are working on it). HMake will soon support compile_commands.json, which I guess can work fine with header-units. Thus you can benefit from both, faster compilation and working intelliscence. The API shown in hmake.cpp is a work in progress. HMake build-system benefits are numerous, even if we leave out the header-units support. This makes it a perfect replacement for B2. I believe we can complete the switch in the next 2 months. And if some compiler supports my paper, we get >3x faster compilation as well. Best, Hassan Sajjad

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[release] New procedure for Boost 1.90 release notes
by Joaquin M López Muñoz 03 Dec '25

03 Dec '25

Hi everybody, As part of the evolution of the new website, the release notes procedure for the upcoming Boost 1.90 release is changing: BEFORE * Authors contributed their release notes as PRs to the file https://github.com/boostorg/website/blob/master/feed/history/boost_1_89_0.q… whose format was **Quickbook**. NOW * Authors should contribute their release notes as PRs to the file https://github.com/boostorg/website-v2-docs/blob/develop/release-notes/boos… whose format is **Asciidoc**. The procedure should be as straightforward as always. Asciidoc is in essence a Markdown variant, and the file already has some entry examples you can copy, adapt and paste. The following Asciidoc macros are available as a replacement to similarly-called Quickbook macros used before: https://github.com/cppalliance/asciidoctor-boost?tab=readme-ov-file#macros Currently there's no easy way to obtain a preview of the upcoming release notes, but I know the team in charge is working on this. Allow me to remind authors and contributors that now is an excellent time to add your entries to the release notes. If you have any doubts please post them here, or ask at the #boost Slack group. Thank you! Best, Joaquín M López Muñoz

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Boost interprocess library using in python
by Murali Kishore 31 Oct '25

31 Oct '25

Hi, trying interprocess applications where Process A is cpp based and creates a shared memory segment and Process B from Python reads this shared memory. Is the boost interprocess library used in python ? If yes , share with me details on how to use it. -- Regards, Murali Kishore

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Boost.CI: Test with minimum CMake version
by Alexander Grund 30 Oct '25

30 Oct '25

Hi all, recently there were issues where the CMake build of individual libraries failed because features from a newer version than the requested minimum CMake version (`cmake_minimum_required(...)` in CMakeLists.txt) were used. This would be a bad UX in releases as the error in that case isn't really helpful. There was a recent discussion [3] about that. For that I introduced a new option for the Boost.CI "reusable" workflow: `min_cmake_version` [1] So additionally to running the CMake build with the "ubuntu-latest" runner and whatever CMake version is installed there (supposed to be "quite new") there is now an extra job that uses the CMake version specified in `min_cmake_version`. The default is CMake 3.16, which is the system CMake of Ubuntu 20. If you want to test against another CMake version, just add `min_cmake_version: x.y[.z]` to the `with:` key/section of the boost-ci call in your ci.yml A good idea is to use what you specified by `cmake_minimum_required` but you might need a higher version if a dependency requires a higher version. This is similar to the C++ standard: The minimum "propagates" to the dependents. In the boostorg/cmake repo there is a recently added workflow that tests the successful configuration of the Boost superproject with 26 different CMake versions. [2] Besides the usual trigger on commits and tags (important here e.g. the -beta tags prior to releases) a maintainer of this repo can trigger it manually for the master or develop branch of the super-project. This allows to check compatibility at any point in time. IIRC currently Peter is the (only?) maintainer of that repo, so you'd got to ask him to trigger this pipeline when necessary. Best Regards, Alex [1] https://github.com/boostorg/boost-ci/blob/96d19ca968a8ec530a656b50d0dbef4bb… [2] https://github.com/boostorg/cmake/blob/1b3a785d348420996c5cd5c9efe310aa2e9a… [3] https://github.com/boostorg/boost/pull/1081

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Boost.Log Missed Performance Optmization ? Recursion unrolling in Attributes visitation
by Damien Buhl 28 Oct '25

28 Oct '25

Hello, I'm unsure if Andrey is reading the mailing list nowadays as it's been a while I didn't write here. But as I explained in my recent blog post, I discovered a missed optimization in Boost.Log, it seems the code implementing the attribute value visitation which is supposed to unroll up to 8 recursion, never unrolls them because nobody defines BOOST_LOG_VALUE_REF_VISITATION_VTABLE_SIZE : - https://tipi.build/blog/20250528-distributed#-meet-the-whistleblower-boostl… See https://github.com/boostorg/log/blob/2d932ddcb5b05a9b2cc0a9df2d8a6ff88883f2… I haven't an application on Boost.Log with enough hot code path to measure the performance impact of the unrolling, but I thought I would post it here, possibly this could improve the performance of some application. A workaround is to pass -DBOOST_LOG_VALUE_REF_VISITATION_VTABLE_SIZE=8 to get the unrolling to do what it was supposed to. Best Damien Buhl (alias daminetreg)

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BOOST_STATIC_ASSERT frowned up by core users
by Vinnie Falco 24 Oct '25

24 Oct '25

If you use BOOST_STATIC_ASSERT and you also use Boost.Core, you can use BOOST_CORE_STATIC_ASSERT instead and save one dependency. Thanks

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[static_string] Desired behavior of to_static_[w]string() for floating point values
by Gennaro Prota 23 Oct '25

23 Oct '25

Hi everyone, I'd like to gather your input on the desired behavior of to_static_string() and to_static_wstring() when formatting floating point values. Currently, both functions mimic std::to_string() / std::to_wstring() as long as the result fits within the static string's capacity. If not, they fall back to scientific notation. However, C++26 introduces a breaking change: std::to_string() and std::to_wstring() will behave as if implemented via std::format() rather than s[w]printf(). For example, std::to_string( 0.1 ) will yield "0.1" instead of "0.100000". Given this shift, what behavior would you prefer for to_static_[w]string()? a) Match std::to_[w]string() and adopt the new behavior when compiling under C++26. b) Preserve the legacy behavior with fixed precision (6 digits) across all standard versions. c) Always behave as if using std::format(), even in pre-C++26 builds (breaking change). d) Other. Please let me know what you think. Thanks. -- Gennaro Prota <https://prota.dev>

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Re: New depinst feature
by Dmitry Arkhipov 23 Oct '25

23 Oct '25

I just found out that the original email was mangled by my email client, so I am sending it again. You might know that recently we discovered a circular dependency between Graph and Geometry. Because of this I added a flag to depinst that causes it to detect dependency cycles and exit with an error. E.g. localy I get: $ python tools/boostdep/depinst/depinst.py graph -C Installing: config, headers, ../tools/boost_install, ../tools/build, ../tools/ cmake Installing: config, property_map, serialization, concept_check, iterator, unordered, optional, mpl, core, type_traits, static_assert, smart_ptr, assert, random, tuple, range, throw_exception, parameter, detail, foreach, move, utility, preprocessor, integer, container_hash, typeof, geometry, numeric/ conversion, multi_index, algorithm, bimap, array, math, spirit, lexical_cast, xpressive, any, property_tree, conversion, tti, function, regex Error: Dependency cycle detected: graph -> geometry -> graph I suggest we add jobs to our CI workflows that use the flag. Note that it's probably not a good idea to always use the flag, because then a cycle created by your dependency can break your CI jobs. If you are using boost-ci's common_install, the flag can be enabled by setting the environment variable DEPINST to "-C" or "--reject-cycles".

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[release] Deadline for New Libraries and Breaking Changes is today!
by Marshall Clow 22 Oct '25

22 Oct '25

We’re starting the 1.90.0 release cycle. Upcoming milestones: 22-Oct - Boost 1.90.0 closed for new libraries and breaking changes 29-Oct - Boost 1.90.0 closed for major changes 05 -Nov- Boost 1.90.0 closed for beta As always, you can find the calendar here: https://www.boost.org/calendar/ — The release managers

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