# Changelog

## v2.1.1 — 2026-08-18

**`make test` graded a different library depending on what you had built.**
The test rule depended on the static archive but linked `-L$(BUILDDIR)
-lmembus`. That flag finds `build/libmembus.so` once `make all` has run, and
pins nothing at run time — so `make clean && make test` linked the archive and
graded this tree, while `make clean && make all && make test` resolved
`/usr/local/lib/libmembus.so`, an installed copy from 2026-06-05. Both orders
printed `45/45 passed` and nothing distinguished them.

It was harmless only by coincidence: the installed copy was byte-identical to a
fresh build because the source had not changed since April. The first source
change would have made the two orders disagree, silently, in a green suite.

The test now links the archive the rule already named, so the dependency and the
link are the same file in both orders and no runtime search can shadow either.

**The README documented five of the six public methods.** `set_reader_name` was
absent from it entirely, while the specification gives it §8.7, §7 references it,
the header documents it inline, it has a dedicated public constant
(`READER_NAME_LEN`), and two tests exercise it. The spec was complete and the
tests were complete; the one document a reader meets first was not.

The API tour now shows all six, notes the truncation at `READER_NAME_LEN - 1`,
and stops writing `65536` as a bare literal — it is `membus::DEFAULT_SIZE` and
the parameter is defaulted, so a reader was learning a magic number instead of
the constant. Both forms are shown, defaulted first.

## v2.1.0 — 2026-04-03

Open-source release under MIT license.

- MIT license (was proprietary)
- SPDX-License-Identifier headers in source files
- CONTRIBUTING.md
- 45 tests across full API surface

## v2.0.0 — 2026-03-16

Full C++17 rewrite. Native `membus::Bus` class replaces C11 API.

### Changed

- **Language**: C11 → C++17. Single public header `membus.hpp`.
- **API**: RAII `Bus` class, `std::system_error` exceptions, pimpl.
- **Build output**: `libmembus.a` (static) replaces `libmembus.so` (shared).
- **Tests**: 19 tests (16 ported from C11 + 3 C++ specific).

### Preserved

- SHM layout (version 3) — binary compatible with v1.x.
- All v1.1.0 features: robust mutexes, futex, dead-slot reclamation, lossy writes.

---

## v1.1.0 — 2026-03-16

Complete rewrite of synchronization and buffer management (v3 architecture).

### Changed

- **Robust mutexes** replace semaphores — `PTHREAD_PROCESS_SHARED` +
  `PTHREAD_MUTEX_ROBUST` embedded in shared memory. Handles crashed process
  recovery via `EOWNERDEAD` → `pthread_mutex_consistent()`.
- **Futex wakeup** replaces polling — `write_seq` atomic counter with
  `FUTEX_WAKE` broadcast. New `membus_read_wait()` for efficient blocking reads.
- **Slow reader advance** — `membus_write()` advances slow readers instead of
  returning `EAGAIN`. Bus is lossy for unpumped handles, never blocking.
- **Dead-slot reclamation** — `membus_open()` proactively reclaims dead process
  reader slots via `kill(pid, 0)`. Also checked inline during writes.
- **Magic + version validation** — header contains `0x4D425553` ("MBUS") +
  version 3, validated on every `membus_open()`.
- **Shared library output** — builds as `libmembus.so` instead of static binaries.
- **Simplified Makefile** — library + test only; no server/writer/reader binaries.

### Fixed

- **MEMBUS-01:** Reader slot leak — slots not released on close.
- **MEMBUS-02:** Slow live readers block writes — writer returned `EAGAIN` instead
  of advancing the slow reader.
- **BOOT-01:** Stale shared memory after hard reboot — semaphore files left in
  `/dev/shm`. Eliminated by moving to embedded robust mutexes (no external
  semaphore files).

### Removed

- `membus_server` binary (bus creation is now just `membus_create()`).
- `membus_writer` / `membus_reader` test binaries (replaced by unit tests).
- Example programs (echo server, log aggregator, pubsub, benchmark).
- Named semaphore files — synchronization is fully embedded in shared memory.

## v1.0.0 — 2025-12-01

Initial release. Semaphore-based synchronization, server/writer/reader binaries.