Add Gennaro's 2025 Q3 update

Author: gennaroprota

_posts/2025-10-14-Gennaros2025Q3Update.md

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+---
+layout: post
+nav-class: dark
+categories: gennaro
+title: "DynamicBitset Reimagined: A Quarter of Flexibility, Cleanup, and Modern C++"
+author-id: gennaro
+author-name: Gennaro Prota
+---
+
+Over the past three months, I've been immersed in a deep and wide-ranging
+overhaul of the Boost.DynamicBitset library. What started as a few targeted
+improvements quickly evolved into a full-scale modernization effort—touching
+everything from the underlying container to iterator concepts, from test
+coverage to documentation style. More than 170 commits later, the library is
+leaner, more flexible, and better aligned with modern C++ practices.
+
+## Making the core more flexible
+
+The most transformative change this quarter was allowing users to choose the
+underlying container type for `dynamic_bitset`. Until now, the implementation
+assumed `std::vector`, which limited optimization opportunities and imposed
+certain behaviors. By lifting that restriction, developers can now use
+alternatives like `boost::container::small_vector`, enabling small buffer
+optimization and more control over memory layout.
+
+This change had ripple effects throughout the codebase. I had to revisit
+assumptions about contiguous storage, update operators like `<<=`, `>>=`, and
+ensure that reference stability and iterator behavior were correctly handled.
+
+## Introducing C++20 iterators
+
+One of the more exciting additions this quarter was support for C++20-style
+iterators. These new iterators conform to the standard iterator concepts, making
+`dynamic_bitset` more interoperable with modern algorithms and range-based
+utilities.
+
+I added assertions to ensure that both the underlying container and
+`dynamic_bitset` itself meet the requirements for bidirectional iteration. These
+checks are enabled only when compiling with C++20 or later, and they help catch
+subtle mismatches early—especially when users plug in custom containers.
+
+## Saying goodbye to legacy workarounds
+
+With modern compilers and standard libraries, many old workarounds are no longer
+needed. I removed the `max_size_workaround()` after confirming that major
+implementations now correctly account for allocators in `max_size()`. I also
+dropped support for obsolete compilers like MSVC 6 and CodeWarrior 8.3, and for
+pre-standard iostreams, cleaned up outdated macros, and removed compatibility
+layers for pre-C++11 environments.
+
+These removals weren't just cosmetic—they simplified the code and made it easier
+to reason about. In many places, I replaced legacy constructs with standard
+features like `noexcept` and `std::move()`.
+
+## constexpr support
+
+When it is compiled as C++20 or later, almost all functions in DynamicBitset are
+now `constexpr`.
+
+## Dropping obsolete dependencies
+
+As part of the cleanup effort, I also removed several outdated dependencies that
+were no longer justified. These included Boost.Integer (previously used by
+`lowest_bit()`), `core/allocator_access.hpp`, and various compatibility headers
+tied to pre-C++11 environments. This not only reduces compile-time overhead and
+cognitive load, but also makes the library easier to audit and maintain.
+
+
+## Strengthening the test suite
+
+A part of this quarter's work was expanding and refining the test coverage. I
+added new tests for `flip()`, `resize()`, `swap()`, and `operator!=()`. I also
+ensured that input iterators are properly supported in `append()`, and verified
+that `std::hash` behaves correctly even when two bitsets share the same
+underlying container but differ in size.
+
+Along the way, I cleaned up misleading comments, shortened overly complex
+conditions, and removed legacy test code that no longer reflected the current
+behavior of the library. The result is a test suite that's more robust, more
+meaningful, and easier to maintain.
+
+## Documentation that speaks clearly
+
+I've always believed that documentation should be treated as part of the design,
+not an afterthought. This quarter, I ported the existing documentation to MrDocs
+and Antora, while fixing and improving a few bits in the process. This uncovered
+a few MrDocs bugs, some of which remain—but I'm hopeful.
+
+I also spent time harmonizing the style and structure of the library's comments
+and docstrings.
+
+I chose to document iterator categories rather than exposing concrete types,
+which keeps the interface clean and focused on behavior rather than
+implementation details.
+
+## New member functions and smarter implementations
+
+This quarter also introduced several new member functions that expand the
+expressiveness and utility of `dynamic_bitset`:
+
+- `push_front()` and `pop_front()` allow bit-level manipulation at the front of
+  the bitset, complementing the existing back-oriented operations.
+- `find_first_off()` and `find_next_off()` provide symmetric functionality to
+  their `find_first()` counterparts, making it easier to locate unset bits.
+- A constructor from `basic_string_view` was added for C++17 and later,
+  improving interoperability with modern string APIs.
+
+Alongside these additions, I revisited the implementation of several existing
+members to improve performance and clarity:
+
+- `push_back()` and `pop_back()` were streamlined for better efficiency.
+- `all()` and `lowest_bit()` were simplified and optimized, with the latter also
+  shedding its dependency on Boost.Integer.
+- `append()` was fixed to properly support input iterators and avoid redundant
+  checks.
+
+## Minor but impactful cleanups
+
+A large number of small edits improved correctness, readability, and
+maintainability:
+
+- Fixed the stream inserter to set `badbit` if an exception is thrown during
+  output.
+- Changed the stream extractor to rethrow any exceptions coming from the
+  underlying container.
+- Reordered and cleaned up all #include sections to use the "" form for Boost
+  includes where appropriate and to keep include groups sorted.
+- Removed an example timing benchmark that was misleading and a number of
+  unneeded comments and minor typos across code and docs.
+
+These edits reduce noise and make code reviews and maintenance more pleasant.
+
+## Reflections
+
+Looking back, this quarter reminded me of the value of revisiting assumptions.
+Many of the workarounds and constraints that once made sense are now obsolete.
+By embracing modern C++ features and simplifying where possible, we can make
+libraries like `dynamic_bitset` more powerful and more approachable.
+
+It also reinforced the importance of clarity—both in code and in documentation.
+Whether it's a test case, a comment, or a public API, precision and consistency
+go a long way.
+
+The work continues, but the foundation is stronger than ever. If you're using
+`dynamic_bitset` or thinking about integrating it into your project, I'd love to
+hear your feedback.