A JIT compiler and Java runtime in Common Lisp.
OpenLDK runs Java libraries inside SBCL. It translates Java bytecode into Common Lisp, which SBCL compiles to native machine code, and maps Java classes to CLOS classes. Java and Lisp code share a process.
It's for when you want to write Common Lisp but need a Java library. See cl-log4j for an example. Clojure, Scheme, Scala, Kotlin, Groovy, and ABCL can also be embedded through OpenLDK's language interop systems.
Development targets SBCL on Linux and JDK 25. Install SBCL,
ocicl, JDK 25, a C compiler, Python 3, and
the libffi development package. Set JAVA_HOME before building:
git clone https://github.com/atgreen/openldk.git
cd openldk
export JAVA_HOME=/path/to/jdk-25
export PATH="$JAVA_HOME/bin:$PATH"
ocicl install
make
./openldk -cp classes:lib/foo.jar com.example.Main
./openldk -jar app.jar
./openldk Hello.javamake builds openldk, the JNI bridge, and javacl, a saved executable
of the Java compiler running on OpenLDK. The default image heap is 32 GB;
use make DYNAMIC_SPACE_SIZE=4096 for a 4 GB heap.
See Building and Running for JDK discovery, offline setup, launcher options, source-file execution, and the code cache.
Load the interop system and enable its reader syntax. #[ ... ] accepts
Clojure source, and Clojure functions can be called with Lisp's funcall
and mapcar:
CL-USER> (asdf:load-system :openldk/clojure)
CL-USER> (openldk.clojure:enable-syntax)
CL-USER> (funcall #[(fn [x] (+ x 4))] 4)
8
CL-USER> (mapcar #[#(* % %)] '(1 2 3 4))
(1 4 9 16)Similar interop is available for Scheme (Kawa and JScheme), Scala, Kotlin, Groovy, and Common Lisp through ABCL. See Language interop for setup and more examples.
OpenLDK targets Java 25 and can run applications including javac, JVM language compilers and REPLs, Spring Boot, and Quarkus. It supports ordinary JNI libraries and FFM through its own libffi bridge. See Applications for examples and Java Compatibility for tested features and limits.
OpenLDK is under development and is not performance-competitive with modern JVMs. Bytecode verification is incomplete, so it is not a security boundary for untrusted class files. Java finalization and object resurrection are not implemented.
- Language interop: call Java and JVM languages from Lisp.
- Executable images: save applications and warmed runtimes.
- Native libraries: JNI, FFM, and native-access policy.
- Eclipse runner: try the GUI or headless checks.
- Hacking guide: compiler internals, debugging, and tests.
For development, run ocicl lint openldk.asd and
make check-regression. See the hacking guide for additional checks.
Written by Anthony Green. Distributed under the GNU GPL, version 3 or later, with the Classpath exception. See COPYING.