GraalVM shared library example which receives String arguments called from C

commands

$ javac org/komamitsu/foobar/SharedStringMethod.java
$ native-image --shared -H:Name=libfoobar
$ cc -Wall '-Wl,-rpath,$ORIGIN' -I. -L. -lfoobar main.c
$ ./a.out
result: hello world

main.c

#include <stdio.h>
#include <stdlib.h>
#include <libfoobar.h>

int main(void) {
    int ret;
    graal_isolatethread_t *isolate_thread = NULL;

    ret = graal_create_isolate(NULL, NULL, &isolate_thread);
    if (ret != 0) {
        fprintf(stderr, "graal_create_isolate: %d\n", ret);
        return 1;
    }

    char *result = NULL;
    result = add(isolate_thread, "hello ", "world");
    if (result == NULL) {
        fprintf(stderr, "add() returned NULL\n");
        return 1;
    }
    printf("result: %s\n", result);

    ret = graal_tear_down_isolate(isolate_thread);
    if (ret != 0) {
        fprintf(stderr, "graal_tear_down_isolate: %d\n", ret);
        return 1;
    }

    return 0;
}

SharedStringMethod.java

package org.komamitsu.foobar;

import org.graalvm.nativeimage.IsolateThread;
import org.graalvm.nativeimage.c.function.CEntryPoint;
import org.graalvm.nativeimage.c.type.CCharPointer;
import org.graalvm.nativeimage.c.type.CTypeConversion;

public class SharedStringMethod
{
    @CEntryPoint(name = "add")
    public static CCharPointer add(
            IsolateThread isolateThread,
            CCharPointer rawA,
            CCharPointer rawB
    ) {
        String a = CTypeConversion.toJavaString(rawA);
        String b = CTypeConversion.toJavaString(rawB);
        try (CTypeConversion.CCharPointerHolder pointerHolder = CTypeConversion.toCString(a + b)) {
            return pointerHolder.get();
        }
    }
}