calling c from clojure using graalvm

readme

// tested using graalvm 20.2 dev
// https://github.com/graalvm/graalvm-ce-dev-builds/releases
// thanks u/duhace for https://www.reddit.com/r/java/comments/8s7sr8/interacting_with_c_using_graalvm/

main.c
====
#include <stdio.h>

void printHello() {
  FILE *f = fopen("file.txt", "w");
  if (f == NULL)
    {
      printf("Error opening file!\n");
    } else {
    const char *text = "world";
    fprintf(f, "Hello: %s\n", text);
    fclose(f);
  }
}

===
compile
$ clang -g -O1 -c -emit-llvm main.c 
===

saik/test.clj
===
(ns saik.test
  (:require [clojure.java.io :as io])
  (:import org.graalvm.polyglot.Context
           org.graalvm.polyglot.Source))

(let [s (-> (Source/newBuilder "llvm" (io/file "main.bc"))
            (.build))
      c (-> (Context/newBuilder (into-array ["llvm"]))
            (.allowIO true)
            (.allowNativeAccess true)
            (.build))
      lib (.eval c s)
      f (.getMember lib "printHello")]
  (.executeVoid f (into-array [""]))) ;; for some reason I was unable to call this without an array -- no clue why