Dear Boost Community, I am very happy to open the Formal Review period for Candidate Boost.Int128 authored by Matt Borland, running from today, July 22nd to July 31st 2026. Int128 is a portable C++14 implementation of signed and unsigned 128-bit integers. It has no dependencies, is header-only, and can be consumed as a module in C++20. You can find the library and its documentation here: - https://github.com/cppalliance/int128/tree/boost_review - https://develop.int128.cpp.al/overview.html I could make examples work in Compiler Explorer: https://godbolt.org/z/5aM6K9b4r Although possibly not faithful to Matt's implementation, this CE link will be handy if you are in a rush but want to play with the library. Candidate Boost.Int128 serves as a practical solution to the partial (resp. absent) support of 128-bit integers by gcc/clang (resp. msvc), and as an alternative to projects with a heavy dependency footprint. For example Boost.Multiprecision offers 128-bit integers but drags 25 Boost modules which may not be acceptable when only a single type is required. We can expect this new lightweight library to interest anyone manipulating integers beyond the 64bit numeric range, for simple problems like when summing many 64-bits integers in an accumulator, computing a*b/c where the intermediate product overflows 64 bits, or in complex fields like cryptography, hashing, random number generation, precision arithmetic... Note: Due to the Boost release cycle, the master branch is frozen on all Boost projects. This had the inconvenient effect of preventing Matt from operating a cross-repo PR to enable GPU support with Boost.Charconv. Due to the lack of a practical solution, the CI on master will remain red until 1.92 ships. We kindly ask reviewers to focus on the boost_review branch. As always, we welcome all reviews, from quick impressions to detailed analysis. Your feedback helps ensure that the library meets Boost's high standards for correctness, performance, documentation, and design. If you’re interested in contributing a review, please post to the Boost mailing list during the review period. In your review please state whether you recommend to REJECT or ACCEPT the library into Boost, and whether you suggest any conditions for acceptance. Other questions you might want to answer in your review are: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? 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 problems tackled by the library? Thank you for your time, Have a wonderful week, Arnaud Becheler, Review Manager Boost.Int128