RFR(S): JDK-8033126 : Can't call default methods from JNI

[Staffan Larsen]

On 30 jan 2014, at 01:51, David Holmes <david.holmes at oracle.com> wrote:

> Hi Staffan,
> 
> On 29/01/2014 11:17 PM, Staffan Larsen wrote:
>> This is a more formal review request for the patch proposed in [0]
>> 
>> webrev: http://cr.openjdk.java.net/~sla/8033126/webrev.00/
>> bug: https://bugs.openjdk.java.net/browse/JDK-8033126
>> 
>> The bug report has a reproducer/testcase that I have used to verify the fix. I have also run the vm/jni tests in the JCK.
> 
> This whole scenario doesn't look right to me. You can't arbitrarily invoke default methods in a class hierarchy. Given the testcase:
> 
> interface A {
>    default int getOne() {
>        return 1;
>    }
> }
> 
> interface B extends A {
>    default int getOne() {
>        return 2;
>    }
> }
> 
> abstract class Abstract implements B {
> }
> 
> class Impl extends Abstract {
>    public int getOne() {
>        return 3;
>    }
> }
> 
> class Impl2 extends Impl {
>    public int getOne() {
>        return 4;
>    }
> }
> 
> public class ImplTest {
>    public static void main(String[] args) {
>        System.loadLibrary("impl");
>        Impl2 i = new Impl2();
>        test(i);
>    }
>    static native void test(Impl i);
> }
> 
> The only legitimate call is Impl2.getOne() which should return 4.

What I am trying to mimic here (and which must be possible to do from JNI because debuggers need to do it) is the Java construct "B.super.getOne()” which you can call from anywhere B is implemented to actually call getOne() in B.

I think the CallNonvirtual<Type>Method()s are supposed to disregard the “normal” virtual lookup of methods and allow the caller to pick and choose. 

"The CallNonvirtual<type>Method families of routines and the Call<type>Method families of routines are different. Call<type>Method routines invoke the method based on the class of the object, whileCallNonvirtual<type>Method routines invoke the method based on the class, designated by the clazz parameter, from which the method ID is obtained. The method ID must be obtained from the real class of the object or from one of its superclasses.”

Thanks,
/Staffan


> 
> David
> -----
> 
> 
>> Thanks,
>> /Staffan
>> 
>> [0] http://mail.openjdk.java.net/pipermail/hotspot-dev/2014-January/012325.html
>>