Returning an int from native function(c++, jni) crashes application

Question

Trying to figure out why c++ function call returning an int crashes the whole application without any errors/warnings.

Here is working code:

    jint Java_org_ntorrent_DummyTorrentInfoProvider_next(
            JNIEnv * env, jobject obj, jint number)
    {
        jint test = rand();
        __android_log_print(ANDROID_LOG_DEBUG, "HelloNDK!", "rand() = %d", test);

        return number;
    }

And this code crashes application without warnings:

    jint Java_org_ntorrent_DummyTorrentInfoProvider_next(
            JNIEnv * env, jobject obj, jint number)
    {
        jint test = rand();
        __android_log_print(ANDROID_LOG_DEBUG, "HelloNDK!", "rand() = %d", test);

        return number + test;
    }

Before the application crashes i can see my log message(__android_log_print) in log cat

EDIT: Even if I replace "number + test" with "1" the application still crashing... It only works if I return "number"...

EDIT#2: Java-side code:

package org.ntorrent;

import java.util.ArrayList;
import java.util.Random;

public class DummyTorrentInfoProvider implements TorrentInfoProvider {

    public native Integer next(Integer number);

    //public Integer next() { return _random.nextInt(); }

    public native void test();

    private Random _random = new Random(100);

    @Override
    public ArrayList getTorrents() {
        test();
        ArrayList torrents = new ArrayList();
        torrents.add(
                new TorrentInfo("test torrent number 1", next(1),  3f, 5f));
        torrents.add(
                new TorrentInfo("test torrent number 2", next(2), 4f, 15f));
        torrents.add(
                new TorrentInfo("test torrent number 555"));
        torrents.add(
                new TorrentInfo("test torrent number 3", next(3), 13f, 5f));
        return torrents;
    }

    static {
        System.loadLibrary("test");
    }
}

Answer 1

jint Java_org_ntorrent_DummyTorrentInfoProvider_next(
    JNIEnv * env, jobject obj, jint number)

and

public native Integer next(Integer number);

Do not match. An Integer is an Object, while an int is a primitive.

If your native code uses jint , your java code should use int in the declaration of the native method.

(If you wish to pass an Integer, you'll need to treat it as a jobject on the native side, and jump through hoops to access it - it's probably easier to use int/jint and do any necessary conversion to from Integer in the java side)