Clobits — Clojure ❤️ C

Use C inside Clojure, then run it on the JVM or compile a native binary.

Features

• One source to rule them all — write code once, run it on both jvm and native binary

(ns clobits.examples.ncurses.hello-world
  (:require [clobits.native-interop :refer [*native-image*]]
            [clobits.c :as c])
  (:gen-class))

(if *native-image*
  (do (println "In native image context")
      (require '[clobits.ncurses.ni :as ncurses]))
  (do (println "In polyglot context")
      (require '[clobits.ncurses.poly :as ncurses])))

(defn -main [& args]
  (let [w (ncurses/initscr)]
    
    (ncurses/printw (c/str* "hello"))
    (ncurses/curs-set 0)
    (ncurses/refresh)
    (Thread/sleep 1000)
    
    (ncurses/endwin)))

For a bigger example, check out wasd_rect.clj

Misc. features

• Parse C function prototypes to Clojure maps
• Generate .h/.c-files and Clojure namespaces based off of C function prototypes or using Clojure maps
• Generate wrapper classes for easier use of c functions / structs in clojure

Project status

This project is a work in progress. I wanted to share this mostly to add another example of how to use Clojure + C using GraalVM.

I'd be very happy if you tried to use it and have questions. If you have a specific C library you want to get working, let me know. Since the generated code can be reused, it'd be nice if we could host the bits required for various C libraries at clojars. :)

Known unknowns and possible solutions

• Calling variadic C functions that do not have a va_args variation (see printf vs vprintf)

If you know how to solve the problems above, please tell me how! :) Either through an issue, or @Saikyun on twitter.

Prerequisites

• graalvm -- tested with graalvm-ce-java11-20.2.0-dev: https://github.com/graalvm/graalvm-ce-dev-builds/releases
  • download, then add the following to e.g. .zprofile
  • export GRAALVM_HOME="/path/to/graalvm-ce-java11-20.2.0-dev/Contents/Home/"
• install native-image: $GRAALVM_HOME/bin/gu install native-image (will be installed by ./compile otherwise)
• install llvm toolchain: $GRAALVM_HOME/bin/gu install llvm-toolchain
• leiningen -- https://leiningen.org/

Tested on macos and linux.

Get the source

git clone https://github.com/Saikyun/clobits
cd clobits

ncurses hello-world example

Displays hello for a second.

Run on JVM using Polyglot

make ncurses-poly

Compile and run a native binary using native-image

make clean ncurses-ni

ncurses bounce example

Displays hello for a second.

Run on JVM using Polyglot

make bounce-poly

Compile and run a native binary using native-image

make bounce-ni

SDL wasd-rect example

Get libSDL2

You need libSDL2 on your path, and possibly added to "-Djava.library.path=<LIB_PATH_HERE>" under your OS profile in project.clj. I've put some defaults there, but I'm not sure they're universal.

Run on JVM using Polyglot

make sdl-poly

Compile and run a native binary using native-image

make sdl-ni

You should see a red square, that you can control with wasd

Examples

The examples contain source code and more information about the examples.

Play around

If you start one of the examples in polyglot-mode you can connect to it using a repl. I usually go with a socket repl on port 5555, which is automatically started when you use the makefile.

Thanks

• sogaiu -- support, testing and helpful discussion
• cornerwings -- java + native image example: https://github.com/cornerwings/graal-native-interaction
• u/duhace -- java + polyglot example: https://www.reddit.com/r/java/comments/8s7sr8/interacting_with_c_using_graalvm/
• borkdude -- help, project setup for clojure / native image compilation: https://github.com/borkdude/clj-kondo

License

Copyright © 2020 Jona Ekenberg

Distributed under the EPL License. See LICENSE.

This project contains code from:

• Clojure, which is licensed under the same EPL License.
• clj-kondo, which is licensed under the same EPL License.