First version of Ion's 2026Q1Update

_posts/2026-04-20-Ions2026Q1Update.md

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+---
+layout: post
+nav-class: dark
+categories: ion
+title: Deque rewrite, segtor, segmented algorithms and a hub review ahead
+author-id: ion
+
+---
+
+During Q1 2026, I've been working in the following areas:
+
+### Boost.Container
+
+The rewritten `boost::container::deque` shipped in 1.90. Leaner container
+and iterators. Details and benchmarks against libstdc++, libc++ and
+MSVC STL on my blog:
+[Inside Boost.Container: comparing different deque implementations](https://boostedcpp.net/2026/03/30/deque/).
+
+The deque implementation was refactored into a reusable `deque_impl` so it
+could back a new **`segtor`** container: a single-ended counterpart to
+`deque` (same segmented storage, `push_back`/`pop_back` only) for the
+common case of stable references plus append-only growth. Ships in 1.91.
+
+For the upcoming `hub` review I also added an experimental **`nest`**
+container as a neutral reference point for benchmarking against Joaquín's
+`hub` and Matthew Bentley's `plf::hive`.
+
+The largest piece of work was a family of experimental **segmented algorithms**
+(`segmented_find_if`, `segmented_mismatch`, `segmented_copy`,
+`segmented_partition`, `segmented_set_union`, … around 30 in total) that
+understand the block layout of `deque` / `segtor` / `nest` and recurse
+into segments instead of walking iterators one element at a time.
+Experimented also with loop unrolling in STL-like algorithms.
+
+Other additions: C++20 `starts_with` / `ends_with` and C++23 `contains`
+on `basic_string`; new `inline_chars`, `stored_size` and `growth_factor`
+options for `basic_string`; overalignment support across the pool
+allocator family (`adaptive_pool`, `private_node_pool`, `shared_node_pool`
+and friends); `unchecked_push_back` / `unchecked_emplace_back` on
+`vector` / `small_vector` / `static_vector`; a `prefetch` option.
+
+Fixes:
+[#328](https://github.com/boostorg/container/issues/328) (redundant
+allocator copy in `deque`, resolved by the rewrite),
+[#330](https://github.com/boostorg/container/issues/330)
+(`detail/pair.hpp` partial specializations for `std::pair`),
+[#332](https://github.com/boostorg/container/issues/332)
+(`aligned_alloc` on XCode 12),
+[#334](https://github.com/boostorg/container/issues/334) (overload
+resolution in the P2363R5 implementation).
+
+### Boost.Intrusive
+
+Changed the return type of `list` / `slist` `remove`, `remove_if` and
+`unique` from `void` to `size_type` following C++20 (LWG 2959 / P0646).
+Merged [PR#104](https://github.com/boostorg/intrusive/pull/104) and
+[PR#105](https://github.com/boostorg/intrusive/pull/105), both from
+@nkolotov — the first fixes a `noexcept`-specifier bug that broke
+`ebo_function_holder_traits` under C++17, the second simplifies
+`ebo_functor_holder` by removing custom type-traits machinery. Many
+thanks. Also removed MSVC C4180 and switched several constant-condition
+branches to `BOOST_IF_CONSTEXPR`.
+
+### Boost.Move
+
+Merged [PR#63](https://github.com/boostorg/move/pull/63) by @Lastique
+removing Boost.StaticAssert dependencies, addressed
+[#64](https://github.com/boostorg/move/pull/64) (`std::pair`
+specializations for the trivial type traits), and marked the
+conversion-aware helpers `forceinline`.
+
+### Boost.Interprocess
+
+Added OS-native **systemwide thread IDs** with backends for Linux,
+FreeBSD, macOS, Cygwin (via WinAPI) and Windows. This unblocks
+process-shared mutex ownership tracking on systems where
+`_POSIX_THREAD_PROCESS_SHARED` is buggy (notably FreeBSD).
+
+Reworked the allocator stack for **overaligned types** end-to-end:
+`segment_manager`, `allocator`, `node_allocator`, `private_node_allocator`,
+`cached_node_allocator`, `adaptive_pool` and friends now carry explicit
+alignment and use `allocate_aligned` internally.
+
+Fixes:
+[#252](https://github.com/boostorg/interprocess/issues/252) (`offset_ptr`
+construction regression with clang since 1.87.0),
+[#276](https://github.com/boostorg/interprocess/issues/276) and
+[#277](https://github.com/boostorg/interprocess/issues/277) (`-Wundef`
+warnings). Windows MSVC 14.5, Windows-ARM64 and Linux-ARM64 were added to
+the CI matrix across all four libraries.
+
+### Review manager for `boost::container::hub`
+
+I'll be serving as review manager for Joaquín's
+[`boost::container::hub`](https://github.com/joaquintides/hub), a
+drop-in replacement for C++26 `std::hive`, formally reviewed April 16-26.
+Late Q1 went into reading the proposal, running the benchmarks and
+putting the reviewer materials together.
+
+### Support to the community
+
+Ongoing maintenance and review of community contributions across Move,
+Container, Intrusive and Interprocess.