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: experimental. The API can still change.

org.babashka/ffi {:mvn/version "0.1.2"}

Platforms

Platform	Requirement	Notes
JVM	JDK 25 or newer	Uses the Java FFM API.
babashka	1.13.220 or newer	Built in, no dependency needed.
GraalVM native image	GraalVM 25 or newer	See Build your own native image.
Node.js	26.1 or newer	Works with nbb, ClojureScript and shadow-cljs through node:ffi. See On Node.js.

Bun and Deno are not supported.

On the JVM, start 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.