# libmultiprocess Versions Library versions are tracked with simple [tags](https://github.com/bitcoin-core/libmultiprocess/tags) and [branches](https://github.com/bitcoin-core/libmultiprocess/branches). Versioning policy is described in the [version.h](../include/mp/version.h) include. ## v12 - Current unstable version. - Adds an optional per-listener `max_connections` parameter to `ListenConnections()` so servers can stop accepting new connections when a local connection cap is reached, and resume accepting after existing connections disconnect. ## [v11.0](https://github.com/bitcoin-core/libmultiprocess/commits/v11.0) - Adds `makePool` method on `ThreadMap` to support thread pool routing, allowing requests without a specific client thread to be dispatched to a pool using a shortest-queue strategy ([#283](https://github.com/bitcoin-core/libmultiprocess/pull/283)). - Adds `std::unordered_set` support, a `BuildList` helper, and a `ReadList` helper to reduce duplication in list build and read handlers ([#277](https://github.com/bitcoin-core/libmultiprocess/pull/277), [#285](https://github.com/bitcoin-core/libmultiprocess/pull/285)). - Adds support for translating C++ `std::optional` struct fields to pairs of `T` + `hasT :Bool` Cap'n Proto struct fields, allowing unset optional primitive fields to be represented ([#243](https://github.com/bitcoin-core/libmultiprocess/pull/243)). - Produces more readable log output for Proxy object lifecycle events and IPC server-side failures ([#218](https://github.com/bitcoin-core/libmultiprocess/pull/218)). - Handles exceptions thrown by `destroy` methods by logging instead of aborting ([#273](https://github.com/bitcoin-core/libmultiprocess/pull/273)). This can prevent server crashes when non-libmultiprocess clients disconnect without destroying objects, in the case where a server object owns client objects and the server destructor tries to call the disconnected client to free them ([#219](https://github.com/bitcoin-core/libmultiprocess/issues/219)). - Handles unexpected exceptions thrown by callbacks (that should never happen) by logging errors instead of deadlocking ([#260](https://github.com/bitcoin-core/libmultiprocess/pull/260)). - Fixes a rare mptest hang on musl builds caused by a lost wakeup bug in `Waiter` ([#295](https://github.com/bitcoin-core/libmultiprocess/pull/295)). - Fixes a race condition in a log print detected by TSan ([#286](https://github.com/bitcoin-core/libmultiprocess/pull/286)). - Build improvements: makes `target_capnp_sources` work correctly when libmultiprocess is used as a CMake subproject ([#289](https://github.com/bitcoin-core/libmultiprocess/pull/289)), adds `mp_headers` target for better lint tool support ([#291](https://github.com/bitcoin-core/libmultiprocess/pull/291)), and fixes compatibility with recent Nix and CMake 4.0 ([#238](https://github.com/bitcoin-core/libmultiprocess/pull/238)). - Test, CI, documentation, and minor code improvements: design document corrections ([#278](https://github.com/bitcoin-core/libmultiprocess/pull/278)), field constant comments ([#279](https://github.com/bitcoin-core/libmultiprocess/pull/279)), clang-tidy fix ([#292](https://github.com/bitcoin-core/libmultiprocess/pull/292)), new smoke test for double-precision float values ([#294](https://github.com/bitcoin-core/libmultiprocess/pull/294)), new test for recursive async IPC calls ([#301](https://github.com/bitcoin-core/libmultiprocess/pull/301)), removal of libevent from Core CI builds ([#299](https://github.com/bitcoin-core/libmultiprocess/pull/299)), and rename of `EventLoop::m_num_clients` to `m_num_refs` ([#302](https://github.com/bitcoin-core/libmultiprocess/pull/302)). - Used in Bitcoin Core master branch, pulled in by [#35661](https://github.com/bitcoin/bitcoin/pull/35661). ## [v10.0](https://github.com/bitcoin-core/libmultiprocess/commits/v10.0) - Increases spawn test timeout to avoid spurious failures. - Uses `throwRecoverableException` instead of raw `throw` to improve runtime error messages in macOS builds. - Used in Bitcoin Core master branch, pulled in by [#34977](https://github.com/bitcoin/bitcoin/pull/34977). Also pulled into Bitcoin Core 31.x stable branch by [#35028](https://github.com/bitcoin/bitcoin/pull/35028). ## [v9.0](https://github.com/bitcoin-core/libmultiprocess/commits/v9.0) - Fixes race conditions where worker thread could be used after destruction, where getParams() could be called after request cancel, and where m_on_cancel could be called after request finishes. - Adds `CustomHasField` hook to map Cap'n Proto null values to C++ null values. - Improves `CustomBuildField` for `std::optional` to use move semantics. - Adds LLVM 22 compatibility fix in type-map. - Used in Bitcoin Core master branch, pulled in by [#34804](https://github.com/bitcoin/bitcoin/pull/34804). Also pulled into Bitcoin Core 31.x stable branch by [#34952](https://github.com/bitcoin/bitcoin/pull/34952). ## [v8.0](https://github.com/bitcoin-core/libmultiprocess/commits/v8.0) - Better support for non-libmultiprocess IPC clients: avoiding errors on unclean disconnects, and allowing simultaneous requests to worker threads which previously triggered "thread busy" errors. - Intermediate version used in Bitcoin Core master branch between 30.x and 31.x branches, pulled in by [#34422](https://github.com/bitcoin/bitcoin/pull/34422). ## [v7.0](https://github.com/bitcoin-core/libmultiprocess/commits/v7.0) - Adds SpawnProcess race fix, cmake `target_capnp_sources` option, ci and documentation improvements. Adds `version.h` header declaring major and minor version numbers. - Intermediate version used in Bitcoin Core master branch between 30.x and 31.x branches, pulled in by [#34363](https://github.com/bitcoin/bitcoin/pull/34363). ## [v7.0-pre2](https://github.com/bitcoin-core/libmultiprocess/commits/v7.0-pre2) - Fixes intermittent mptest hang and makes other minor improvements. - Used in Bitcoin Core 30.1 and 30.2 releases and 30.x branch, pulled in by [#33518](https://github.com/bitcoin/bitcoin/pull/33518) and [#33519](https://github.com/bitcoin/bitcoin/pull/33519). ## [v7.0-pre1](https://github.com/bitcoin-core/libmultiprocess/commits/v7.0-pre1) - Adds support for log levels to reduce logging and "thread busy" error to avoid a crash on misuse. - Minimum required version since Bitcoin Core 30.1, pulled in by [#33412](https://github.com/bitcoin/bitcoin/pull/33412), [#33518](https://github.com/bitcoin/bitcoin/pull/33518), and [#33519](https://github.com/bitcoin/bitcoin/pull/33519). ## [v6.0](https://github.com/bitcoin-core/libmultiprocess/commits/v6.0) - Adds CI scripts and build and test fixes. - Used in Bitcoin Core 30.0 release, pulled in by [#32345](https://github.com/bitcoin/bitcoin/pull/32345), [#33241](https://github.com/bitcoin/bitcoin/pull/33241), and [#33322](https://github.com/bitcoin/bitcoin/pull/33322). ## [v6.0-pre1](https://github.com/bitcoin-core/libmultiprocess/commits/v6.0-pre1) - Adds fixes for unclean shutdowns and thread sanitizer issues. - Drops `EventLoop::addClient` and `EventLoop::removeClient` methods, requiring clients to use new `EventLoopRef` class instead. - Minimum required version for Bitcoin Core 30.0 release, pulled in by [#31741](https://github.com/bitcoin/bitcoin/pull/31741), [#32641](https://github.com/bitcoin/bitcoin/pull/32641), and [#32345](https://github.com/bitcoin/bitcoin/pull/32345). ## [v5.0](https://github.com/bitcoin-core/libmultiprocess/commits/v5.0) - Adds build improvements and tidy/warning fixes. - Used in Bitcoin Core 29 releases, pulled in by [#31945](https://github.com/bitcoin/bitcoin/pull/31945). ## [v5.0-pre1](https://github.com/bitcoin-core/libmultiprocess/commits/v5.0-pre1) - Adds many improvements to Bitcoin Core mining interface: splitting up type headers, fixing shutdown bugs, adding subtree build support. - Broke up `proxy-types.h` into `type-*.h` files requiring clients to explicitly include overloads needed for C++ ↔️ Cap'n Proto type conversions. - Now requires C++ 20 support. - Minimum required version for Bitcoin Core 29 releases, pulled in by [#30509](https://github.com/bitcoin/bitcoin/pull/30509), [#30510](https://github.com/bitcoin/bitcoin/pull/30510), [#31105](https://github.com/bitcoin/bitcoin/pull/31105), [#31740](https://github.com/bitcoin/bitcoin/pull/31740). ## [v4.0](https://github.com/bitcoin-core/libmultiprocess/commits/v4.0) - Added better cmake support, installing cmake package files so clients do not need to use pkgconfig. - Used in Bitcoin Core 28 releases, pulled in by [#30490](https://github.com/bitcoin/bitcoin/pull/30490) and [#30513](https://github.com/bitcoin/bitcoin/pull/30513). ## [v3.0](https://github.com/bitcoin-core/libmultiprocess/commits/v3.0) - Dropped compatibility with Cap'n Proto versions before 0.7. - Used in Bitcoin Core 27 releases, pulled in by [#28735](https://github.com/bitcoin/bitcoin/pull/28735), [#28907](https://github.com/bitcoin/bitcoin/pull/28907), and [#29276](https://github.com/bitcoin/bitcoin/pull/29276). ## [v2.0](https://github.com/bitcoin-core/libmultiprocess/commits/v2.0) - Changed `PassField` function signature. - Now requires C++17 support. - Used in Bitcoin Core 25 and 26 releases, pulled in by [#26672](https://github.com/bitcoin/bitcoin/pull/26672). ## [v1.0](https://github.com/bitcoin-core/libmultiprocess/commits/v1.0) - Dropped hardcoded includes in generated files, now requiring `include` and `includeTypes` annotations. - Used in Bitcoin Core 22, 23, and 24 releases, pulled in by [#19160](https://github.com/bitcoin/bitcoin/pull/19160). ## [v0.0](https://github.com/bitcoin-core/libmultiprocess/commits/v0.0) - Initial version used in a downstream release. - Used in Bitcoin Core 21 releases, pulled in by [#16367](https://github.com/bitcoin/bitcoin/pull/16367), [#18588](https://github.com/bitcoin/bitcoin/pull/18588), and [#18677](https://github.com/bitcoin/bitcoin/pull/18677).