- Boost - lists.boost.org

moving TypeTraits to the boost::type_traits namespace
by Gero Peterhoff 05 Nov '25

05 Nov '25

I think we should finally move TypeTraits to the boost::type_traits namespace. This has only advantages: - clear separation from other boost libraries - the boost namespace is no longer contaminated - when providing additional TypeTraits, it is immediately clear in which namespace they must be implemented These changes would of course be elaborate, but they would bring advantages: consolidation + general review of existing TypeTraits: - are they still necessary / could they be removed? better to use std::TypeTraits - could they be implemented in a more contemporary way? Gero

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boost.parser: Hitting the wall; what am I doing wrong?
by Richard 03 Nov '25

03 Nov '25

Hi Boosters, I've hit a wall while using boost.parser to parse a fractal formula file format. At this point, when I attempt to add a new rule to my grammar, msvc goes to compile the file and just sits there. It isn't hammering CPU, memory or disk, just sitting there. I let it run for like 30 minutes before I aborted it. There's no error or warning diagnostic. The details are in this issue on boost.parser: <https://github.com/boostorg/parser/issues/288> I believe separate compilation of the rules implementing my grammar would work around this problem (and give me better turnaround time on edits as I'm not changing the entire grammar as I improve it), but I was unable to get separate compilation of rules to work with boost.parser. Is separate compilation even possible? -- Richard -- "The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline> The Terminals Wiki <http://terminals-wiki.org> The Computer Graphics Museum <http://ComputerGraphicsMuseum.org> Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>

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The Master branch will be closing for the 1.90.0 beta release on Wednesday (5-Nov)
by Marshall Clow 02 Nov '25

02 Nov '25

As always, you can find the calendar here: https://www.boost.org/calendar/ — The release managers

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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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