added Joaquín's 2025Q4 update

Author: joaquintides

_posts/2026-01-18-Joaquins2025Q4Update.md

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+---
+layout: post
+nav-class: dark
+categories: joaquin
+title: Containers galore
+author-id: joaquin
+author-name: Joaquín M López Muñoz
+---
+
+During Q4 2025, I've been working in the following areas:
+
+### Boost.Bloom
+
+* Written [an article](https://bannalia.blogspot.com/2025/10/bulk-operations-in-boostbloom.html) explaining
+the usage and implementation of the recently introduced bulk operations.
+
+### Boost.Unordered
+
+* Written maintenance fixes
+[PR#320](https://github.com/boostorg/unordered/pull/320),
+[PR#321](https://github.com/boostorg/unordered/pull/321),
+[PR#326](https://github.com/boostorg/unordered/pull/326),
+[PR#327](https://github.com/boostorg/unordered/pull/327),
+[PR#328](https://github.com/boostorg/unordered/pull/328),
+[PR#335](https://github.com/boostorg/unordered/pull/335).
+
+### Boost.MultiIndex
+
+* Refactored the library to use Boost.Mp11 instead of Boost.MPL ([PR#87](https://github.com/boostorg/multi_index/pull/87)),
+remove pre-C++11 variadic argument emulation ([PR#88](https://github.com/boostorg/multi_index/pull/88))
+and remove all sorts of pre-C++11 polyfills ([PR#90](https://github.com/boostorg/multi_index/pull/90)).
+These changes are explained in [an article](https://bannalia.blogspot.com/2025/12/boostmultiindex-refactored.html)
+and will be shipped in Boost 1.91. Transition is expected to be mostly backwards
+compatible, though two Boost libraries needed adjustments as they use MultiIndex
+in rather advanced ways (see below).
+
+### Boost.Flyweight
+
+* Adapted the library to work with Boost.MultiIndex 1.91
+([PR#25](https://github.com/boostorg/flyweight/pull/25)).
+
+### Boost.Bimap
+
+* Adapted the library to work with Boost.MultiIndex 1.91
+([PR#50](https://github.com/boostorg/bimap/pull/50)).
+
+### Other Boost libraries
+
+* Helped set up the Antora-based doc build chain for DynamicBitset
+([PR#96](https://github.com/boostorg/dynamic_bitset/pull/96),
+[PR#97](https://github.com/boostorg/dynamic_bitset/pull/97),
+[PR#98](https://github.com/boostorg/dynamic_bitset/pull/98)).
+* Same with OpenMethod
+([PR#40](https://github.com/boostorg/openmethod/pull/40)).
+* Fixed concept compliance of iterators provided by Spirit
+([PR#840](https://github.com/boostorg/spirit/pull/840),
+[PR#841](https://github.com/boostorg/spirit/pull/841)).
+
+### Experiments with Fil-C
+
+[Fil-C](https://fil-c.org/) is a C and C++ compiler built on top of LLVM that adds run-time
+memory-safety mechanisms preventing out-of-bounds and use-after-free accesses. 
+I've been experimenting with compiling Boost.Unordered test suite with Fil-C and running
+some benchmarks to measure the resulting degradation in execution times and memory usage.
+Results follow:
+
+* Articles
+  *  [Some experiments with Boost.Unordered on Fil-C](https://bannalia.blogspot.com/2025/11/some-experiments-with-boostunordered-on.html)
+  *  [Comparing the run-time performance of Fil-C and ASAN](https://bannalia.blogspot.com/2025/11/comparing-run-time-performance-of-fil-c.html)
+* Repos
+  *  [Compiling Boost.Unordered test suite with Fil-C](https://github.com/joaquintides/fil-c_boost_unordered)
+  *  [Benchmarks of Fil-C and ASAN against baseline](https://github.com/boostorg/boost_unordered_benchmarks/tree/boost_unordered_flat_map_fil-c)
+  *  [Memory consumption of Fil-C and ASAN with respect to baseline](https://github.com/boostorg/boost_unordered_benchmarks/tree/boost_unordered_flat_map_fil-c_memory)
+
+### Proof of concept of a semistable vector
+
+By "semistable vector" I mean that pointers to the elements may be invalidated
+upon isertion and erasure (just like a regular `std::vector`) but iterators
+to non-erased elements remain valid throughout.
+I've written a small [proof of concept](https://github.com/joaquintides/semistable_vector/)
+of this idea and measured its performance against non-stable `std::vector` and fully
+stable `std::list`. It is dubious that such container could be of interest for production
+use, but the techniques explored are mildly interesting and could be adapted, for
+instance, to write powerful safe iterator facilities.
+
+### Teaser: exploring the `std::hive` space
+
+In short, `std::hive` (coming in C++26) is a container with stable references/iterators
+and fast insertion and erasure. The [reference implementation](https://github.com/mattreecebentley/plf_hive)
+for this container relies on a rather convoluted data structure, and I started to wonder
+if something simpler could deliver superior performance. Expect to see the results of
+my experiments in Q1 2026.
+
+### Website
+
+* Filed issues
+[#1936](https://github.com/boostorg/website-v2/issues/1936),
+[#1937](https://github.com/boostorg/website-v2/issues/1937),
+[#1984](https://github.com/boostorg/website-v2/issues/1984).
+
+### Support to the community
+
+* I've been part of a task force with the C++ Alliance to review the entire
+catalog of Boost libraries (170+) and categorize them according to their
+maintainance status and relevance in light of additions to the C++
+standard library over the years.
+* Supporting the community as a member of the Fiscal Sponsorhip Committee (FSC).