babashka.ffi

Call C libraries from Clojure and babashka.

This library is the babashka.ffi namespace that ships inside babashka, extracted so that JVM Clojure programs can use it too. Babashka consumes this repository as a submodule.

Status: work in progress, not yet released.

Requirements

On the JVM:

• JDK 22 or newer. The library uses the Java FFM API.
• Start the JVM with --enable-native-access=ALL-UNNAMED, or set the Enable-Native-Access manifest attribute in an uberjar. Without the flag, modern JDKs warn, and a future JDK release refuses the calls.

In babashka the namespace is built in: (require '[babashka.ffi :as ffi]).

Libraries built on it

• babashka.sqlite: SQLite
• babashka.postgres: PostgreSQL through libpq
• babashka.duckdb: DuckDB
• filewatcher: file watching through FSEvents, inotify and ReadDirectoryChangesW

None of them expose an arena, a pointer, or a layout: the FFI stays inside the library.

Documentation

doc/guide.md documents the API: library loading, function binding, memory, arenas, structs, callbacks, and performance limits for each host.

API.md lists every public var with its arities and docstring. Regenerate it with bb quickdoc.

clj-kondo

The library exports a clj-kondo hook for defcfn. Copy the config with:

clj-kondo --lint "$(clojure -Spath)" --copy-configs --skip-lint

In a babashka project, use the built-in classpath:

clj-kondo --lint "$(bb print-deps --format classpath)" --copy-configs --skip-lint

License

Copyright © 2026 Michiel Borkent

Distributed under the MIT License. See LICENSE.

Babashka embeds this library and is itself EPL licensed. The two licenses apply to their own repositories.