nim-ffi/CHANGELOG.md

# Changelog

All notable changes to this project are documented in this file.

## [Unreleased]

### Changed
- User event callbacks now run on a dedicated event thread fed by a
  bounded SPSC queue (default capacity 1024), so a slow listener can no
  longer block the FFI thread or concurrent `add_event_listener` /
  `remove_event_listener` calls
  ([#6](https://github.com/logos-messaging/nim-ffi/issues/6)).
- Replaced the dedicated watchdog thread with a heartbeat check that
  runs on the event thread. The FFI thread advances an atomic heartbeat
  each loop iteration; if it stalls for more than 1s past the start-up
  grace window, the event thread emits the `not_responding` event.
- `declareLibrary` no longer emits the shared-library `soname` /
  `install_name` linker flags when building as an executable (`--app:lib`
  guard), so FFI code can be unit-tested as a plain binary — fatal on macOS,
  where `-install_name` requires `-dynamiclib`.

### Added
- `{.ffiEvent.}` no longer requires an explicit wire-name string: when omitted
  it is derived from the proc name via `camelToSnakeCase`
  (`onPeerConnected` → `on_peer_connected`), matching how `{.ffi.}` derives its
  C export symbol. Pass a string literal only to override it.
- FFI annotations (`{.ffi.}`, `{.ffiCtor.}`, `{.ffiDtor.}`, `{.ffiEvent.}`,
  `{.ffiHandle.}`, `{.ffiRaw.}`) that expand after `genBindings()` now produce a
  loud compile error instead of being silently dropped from the generated
  bindings.
- **C binding generator** (`-d:targetLang=c`): emits a header-only C binding
  (`<lib>.h`) plus a `CMakeLists.txt`, alongside the existing Rust / C++ / CDDL
  backends. Requests/responses travel as CBOR using the same vendored TinyCBOR
  the C++ backend uses. C has no generics or overloading, so each `seq[T]` /
  `Option[T]` is monomorphised into its own struct + encode/decode/free triple.
  The high-level `<lib>_ctx_*` API is asynchronous: each method/constructor
  takes a typed result callback and the binding owns and reclaims all reply
  data and error strings (valid only for the duration of the callback), so the
  caller never frees anything — there is no blocking wait and no manual-free
  contract. Shared codegen helpers were extracted
  into `ffi/codegen/common.nim` (used by both the C and C++ backends). New
  `nimble genbindings_c` / `genbindings_c_echo` / `check_bindings_c` /
  `test_c_e2e` tasks, a `tests/e2e/c` ctest harness, and a
  `tests/unit/test_c_codegen.nim` unit suite.
- Configurable per-request handler timeout with a finite default: each
  `FFIContext` now carries a `defaultRequestTimeout` (5s) applied to every
  handler, replacing the previous unbounded wait so a wedged handler can no
  longer hang a foreign caller forever. On trip the caller is unblocked with an
  `ffi request timed out after <n>ms` err; the handler is left running (not
  cancelled, since a hard-cancel mid-call into the underlying library can leave
  it partial), and the callback still fires exactly once. Override per proc with
  a `"timeout = <ms>"` spec (e.g. `{.ffi: "timeout = 30000".}`), parsed like the
  `abi = ...` spec; runtime-only, codegen ignores it
  ([#93](https://github.com/logos-messaging/nim-ffi/issues/93)).
- Per-interaction ABI-format annotations: `declareLibrary` now takes an
  optional `defaultABIFormat` (`"cbor"` default, or `"c"`) that every
  `{.ffi.}` / `{.ffiCtor.}` / `{.ffiDtor.}` / `{.ffiRaw.}` / `{.ffiEvent.}`
  inherits, and each annotation can override it with an `"abi = c"` /
  `"abi = cbor"` spec (e.g. `{.ffi: "abi = cbor".}`). `declareLibrary` is now
  required before any FFI annotation
  ([#78](https://github.com/logos-messaging/nim-ffi/issues/78)).
- `c` (flat C-struct) ABI **codec**: every `{.ffi: "abi = c".}` type gets a
  `<T>_CWire` companion plus `cwirePack` / `cwireUnpack` / `cwireFree`. This
  first slice covers the flat path — POD scalars and `string` (as `cstring`);
  composite fields follow. The `c` proc-dispatch path and the foreign (C++ /
  Rust) generators are still pending, so `c` remains rejected on
  proc/ctor/dtor/event annotations for now.
- `tests/bench/bench_codec.nim` (+ `nimble bench_codec`): a single-process
  microbenchmark comparing the `cbor` and `c` codecs across payload shapes,
  isolating codec cost from the (identical) thread/callback round-trip.
- Queue-overflow handling: when the bounded event queue is full, the
  library sets a sticky "stuck" flag, logs an error, fires
  `not_responding` from the event thread, and rejects subsequent
  `sendRequestToFFIThread` calls with `event queue stuck - library
  cannot accept new requests`.

## [0.2.0] - 2026-06-04

Major release introducing the CBOR-based wire format, CBOR-backed FFI events
with a multi-listener registry, multi-language binding generation (C++, Rust,
CDDL), CI hardening with sanitizers, and several robustness fixes around
context lifetime and memory safety.

### Added
- **CBOR serialization** as the FFI wire format, replacing the previous
  JSON/string-based `serial.nim`
  ([#23](https://github.com/logos-messaging/nim-ffi/pull/23)).
- **CBOR-backed FFI events**: event payloads are now serialized with CBOR
  ([#39](https://github.com/logos-messaging/nim-ffi/pull/39)).
- **Multi-listener event registry** (`FFIEventRegistry`) and its wiring into
  `FFIContext`
  ([#45](https://github.com/logos-messaging/nim-ffi/pull/45),
  [#49](https://github.com/logos-messaging/nim-ffi/pull/49)).
- **Event-listener ABI** with per-event typed listeners
  ([#50](https://github.com/logos-messaging/nim-ffi/pull/50)).
- **C++ typed per-event listeners** in the generated bindings
  ([#51](https://github.com/logos-messaging/nim-ffi/pull/51)).
- **Rust per-event typed listeners** (`add_on_<x>_listener` + wildcard
  `add_event_listener`)
  ([#52](https://github.com/logos-messaging/nim-ffi/pull/52)) and Rust event
  example bindings/clients
  ([#53](https://github.com/logos-messaging/nim-ffi/pull/53)).
- **C++ binding generator** with end-to-end tests driven by CMake/CTest
  ([#27](https://github.com/logos-messaging/nim-ffi/pull/27)), later expanded
  with multi-context, cross-library, pipeline, and stress tests
  ([#42](https://github.com/logos-messaging/nim-ffi/pull/42)).
- **CDDL schema generator** for the FFI types
  ([#24](https://github.com/logos-messaging/nim-ffi/pull/24)).
- **CI pipeline**: parallel test execution
  ([#26](https://github.com/logos-messaging/nim-ffi/pull/26)),
  AddressSanitizer / UndefinedBehaviorSanitizer / ThreadSanitizer jobs
  ([#34](https://github.com/logos-messaging/nim-ffi/pull/34)), and a
  cross-platform OS matrix for the C++ e2e suite
  ([#38](https://github.com/logos-messaging/nim-ffi/pull/38)).
- CBOR type-coverage tests
  ([#41](https://github.com/logos-messaging/nim-ffi/pull/41)).

### Changed
- Removed the redundant `ffiType` macro; the `ffi` macro is now the single
  authoring entry point
  ([#22](https://github.com/logos-messaging/nim-ffi/pull/22)).
- Generated C++ avoids move constructors and assignment operators
  ([#36](https://github.com/logos-messaging/nim-ffi/pull/36)) and no longer
  throws exceptions across the binding boundary
  ([#46](https://github.com/logos-messaging/nim-ffi/pull/46)).
- Removed the wildcard event listener; event dispatch is now strictly
  per-event ([#70](https://github.com/logos-messaging/nim-ffi/pull/70)).

### Fixed
- Use-after-free in the event/context lifetime path
  ([#47](https://github.com/logos-messaging/nim-ffi/pull/47)).

## [0.1.4] - 2026-05-13

[Full changelog](https://github.com/logos-messaging/nim-ffi/compare/v0.1.3...v0.1.4)

### Added

- Simplified FFI authoring with auto-generated C++ and Rust language bindings,
  including new `ffi/codegen/cpp.nim`, `ffi/codegen/rust.nim` and shared
  `ffi/codegen/meta.nim` helpers (#15).
- Rust example bindings and clients under `examples/nim_timer/` (`rust_bindings`
  and `rust_client`, the latter with a Tokio async variant) (#15).
- JSON/string-based FFI (de)serialization via `ffi/serial.nim`
  (`ffiSerialize`/`ffiDeserialize`), with `tests/test_serial.nim` coverage.
  (CBOR replaced this layer later, in 0.2.0.)
- FFI context pool (`ffi/ffi_context_pool.nim`) using a fixed array of contexts.
- Test suite expansion: `test_alloc.nim`, `test_ctx_validation.nim`,
  `test_ffi_context.nim`, `test_gc_compat.nim`.
- Continuous integration pipeline (#12).

### Fixed

- Context buffer overflow (#21).
- Use a fixed array of contexts to avoid consuming all file descriptors (#14).
- Memory leaks (#11).
- Add `install_name` for macOS shared libraries (#8).

### Changed

- Run tests with the `refc` garbage collector (#20).
- Remove `CatchableError` usage (#19).
- Update license files to comply with Logos licensing requirements.

## [0.1.3] - 2026-01-23

### Fixed
- Properly import and re-export `chronicles` so downstream packages get the
  logging macros transitively.

## [0.1.2] - 2026-01-23

### Fixed
- Re-export `chronicles` and `std/tables` when the `ffi` module is imported,
  so generated code resolves these symbols at the call site.

## [0.1.1] - 2026-01-23

Initial tagged release.

### Added
- Core `ffi` macro for declaring procs exposed across the FFI boundary.
- `FFIContext` with a dedicated worker thread, request dispatch, and a
  watchdog with configurable timeout
  ([#7](https://github.com/logos-messaging/nim-ffi/pull/7)).
- License files updated to comply with Logos licensing requirements.