Building an Android library out of a JVM project using GraalJS

[brocollie08]

Follow up from https://graalvm.slack.com/archives/CN9L59P61/p1634770859026100

A bit more background, I'm not using native image.
I've taken a look at Gluon maven plugin as suggested here, I'm not sure this is what I need.
I'm not trying to create an APK to run on Android, but a JAR for an existing Android app to consume.

I've tried to get the minimal reproducible steps, I was able to get the same stack trace by just trying to build a Context in a vanilla Android app.

MainActivity.kt:

override fun onCreate(savedInstanceState: Bundle?) {
  super.onCreate(savedInstanceState)

  Context
    .newBuilder(JS)
    .allowAllAccess(true)
    .allowExperimentalOptions(true)
    .option("js.experimental-foreign-object-prototype", "true")
    .build()
}

Producing

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.demo, PID: 9622
    java.lang.NoSuchMethodError: No virtual method ensureClassInitialized(Ljava/lang/Class;)V in class Lsun/misc/Unsafe; or its super classes (declaration of 'sun.misc.Unsafe' appears in /apex/com.android.runtime/javalib/core-oj.jar)
        at com.oracle.truffle.api.library.LibraryFactory.ensureLibraryInitialized(LibraryFactory.java:384)
        at com.oracle.truffle.api.library.LibraryFactory.getUncached(LibraryFactory.java:364)
        at com.oracle.truffle.api.library.LibraryFactory.<init>(LibraryFactory.java:210)
        at com.oracle.truffle.api.interop.InteropLibraryGen.<init>(InteropLibraryGen.java:170)
        at com.oracle.truffle.api.interop.InteropLibraryGen.<clinit>(InteropLibraryGen.java:161)
        at java.lang.Class.classForName(Native Method)
        at java.lang.Class.forName(Class.java:454)
        at com.oracle.truffle.api.library.LibraryFactory.loadGeneratedClass(LibraryFactory.java:771)
        at com.oracle.truffle.api.library.LibraryFactory.resolveImpl(LibraryFactory.java:734)
        at com.oracle.truffle.api.library.LibraryFactory.resolve(LibraryFactory.java:727)
        at com.oracle.truffle.api.interop.InteropLibrary.<clinit>(InteropLibrary.java:2875)
        at com.oracle.truffle.api.interop.InteropLibrary.getFactory(InteropLibrary.java:2839)
        at com.oracle.truffle.polyglot.PolyglotValueDispatch.<clinit>(PolyglotValueDispatch.java:156)
        at com.oracle.truffle.polyglot.PolyglotValueDispatch.createHostNull(PolyglotValueDispatch.java:1604)
        at com.oracle.truffle.polyglot.PolyglotImpl.initialize(PolyglotImpl.java:143)
        at org.graalvm.polyglot.impl.AbstractPolyglotImpl.setConstructors(AbstractPolyglotImpl.java:233)
        at org.graalvm.polyglot.Engine$1.loadAndValidateProviders(Engine.java:821)
        at org.graalvm.polyglot.Engine$1.run(Engine.java:794)
        at org.graalvm.polyglot.Engine$1.run(Engine.java:768)
        at java.security.AccessController.doPrivileged(AccessController.java:43)
        at org.graalvm.polyglot.Engine.initEngineImpl(Engine.java:768)
        at org.graalvm.polyglot.Engine.access$000(Engine.java:109)
        at org.graalvm.polyglot.Engine$ImplHolder.<clinit>(Engine.java:133)
        at org.graalvm.polyglot.Engine$ImplHolder.access$100(Engine.java:132)
        at org.graalvm.polyglot.Engine.getImpl(Engine.java:320)
        at org.graalvm.polyglot.Engine$Builder.build(Engine.java:559)
        at org.graalvm.polyglot.Context$Builder.build(Context.java:1725)

Which suggests GraalJS can't be used on the Android VM

These are my dependencies in the Android app/JVM project if relevant

implementation("org.graalvm.js", "js", "21.2.0")
implementation("org.graalvm.js", "js-scriptengine", "21.2.0")
implementation("org.graalvm.sdk", "graal-sdk", "21.2.0")

[wirthi]

Hi,

Graal.js should be runnable on every compatible Java platform. In the error message you can see that we rely on e.g. sun.misc.Unsafe - which seems not be (fully) supported on Android. We have also heard before that other relevant features are missing from Android that Graal.js and Truffle rely on.

I don't believe this is easily supportable on Android without a major rework of Graal.js and the Truffle Framework. I don't have any experience on Android though and might miss an easy workaround. CC @chumer

Best,
Christian

[caoccao]

I wonder if you mind trying the dog food from Javet (Java + V8). Its first Android snapshot build is under community test.

[wirthi]

Hi,

I don't believe Javet is in any way related. We simply use Java infrastructure (e.g. sun.misc.Unsafe) that is available on compatible JREs, but not on Android. Of course there is a way around that, but this would require major changes to make sure we only use features also available on Android.

Christian

[caoccao]

I don't believe Javet is in any way related. We simply use Java infrastructure (e.g. sun.misc.Unsafe) that is available on compatible JREs, but not on Android.

No problem. Actually, in Javet I polyfill some missing internal API to allow modern Java code to run in legacy environment like Android. Javet has a JNI library, so polyfilling Unsafe is only a matter of time.

[wirthi]

Ok, if it can polyfill Unsafe and other JDK9+ feature (Method handles, etc.) then it might be an option to go that route.

[caoccao]

Ok, if it can polyfill Unsafe and other JDK9+ feature (Method handles, etc.) then it might be an option to go that route.

For now, in the dev branch, under /android/javet-android/src/main/java/ I polyfilled:

• java.lang.management.*
• javax.management.*

Later next week, changes will be merged to main branch.

The idea here is: The community get a fully functional and genuine V8 for free (99.99%), but only need to polyfill what they want (0.01%). I might not prioritize some of the API polifill work, but I encourage the community to submit pull requests for what they need.

[frank-dspeed]

@caoccao i 100% support your effort it sounds like i do able thing and is the right way to do it we need to be able to pollyfill the env thats it thats the missing keypart i have also some android expirence and also vm expirence but i am not as deep into the java core language implementation while i am familar with the v8 implementation on all platforms and chipsets.

but you need to be also aware of the core fact why this api's are missing they are missing because google does not want that you run a JIT on it.

• So everything we do here that uses or enables JIT will only be deploy able via Enterprise Policys of Android or InSecure Apk app install which needs user interactions and so on

• it will also never get published on the android store.

• to get for example nodejs running on Android and Ios we do the following we fork it and then we replace v8 with the OS engine after that we build it as LIB without the JIT Memory Features https://v8.dev/blog/jitless

  • What’s the difference between --jitless and --no-opt? --no-opt disables the TurboFan optimizing compiler. --jitless disables all runtime allocation of executable memory.
  • yes nodejs It is only available since Node.js 12.0.0 node --jitless emscripten-compiled.js

https://github.com/nodejs-mobile/nodejs-mobile the project now got a community project you can look into it

[caoccao]

@frank-dspeed Thank you for the info and suggestions.

Regarding JIT, the V8 in Javet is JIT enabled. So far, there's no user complaining it's blocked by Google Play or other app stores. Of course, most Javet Android users publish their apps in China where there's no Google Play.