Issue2403

Systematically an exception pops up when declaring a Python class implementing a Java interface containing default methods, even if all methods are overriden:
-  java.lang.VerifyError... Illegal use of nonvirtual function call in listener.py at line number ...

Workaround: start JVM with option Xverify:none

Can you provide more details? Java version, code you're executing, ideally repro example.

Thanks!

Below an example - I use Jython 2.7.0. Java 1.8.0_11 and Java 1.8.0_51. The exception throws a VerifyError when declaring the class "MyClass" overriding get().


package test;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class Test {

    public static interface TestInterface {

        default String get() {
            return "Unknown";
        }
    }

    public static class TestClass implements TestInterface {

        public String get() {
            return "Value";
        }
    }

    public static void main(String[] args) throws Exception {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("python");

        engine.eval("import test.Test.TestClass");
        engine.eval("o = test.Test.TestClass()");
        engine.eval("print o.get()"); //This is ok

        engine.eval("import test.Test.TestInterface");
        engine.eval("class MyClass(test.Test.TestInterface):\n"
                + "   def get(self):\n"
                + "       return 'value'");
        engine.eval("o = MyClass()");
        engine.eval("print o.get()");

    }
}

The problem specifically occurs when a default method is overridden.

This appears to be caused by the use of v1.5 class files when generating code.  Updating "Opcodes.V1_5" in org.python.compiler.ClassFile to any newer version -- even just V1_6! -- seems to work, at least for a toy example.

Thanks for the tip about Opcodes I have investigated this slightly and have a pull request to discuss this https://github.com/jythontools/jython/pull/91

Switching from Opcodes.V1_5 to Opcodes.V1_6 does appear to resolve this issue, i'm not really sure why though. I have added a test for this in the pull request unfortunately I don't think it can be merged as it would require a source level of 1.8

Increasing to Opcodes higher than 1.6 cause things to break.

I would like to see this one make it into 2.7.2

Now committed at https://hg.python.org/jython/rev/f842e0a9d903, which makes Alex's program run for me. Thanks Alex, Darjus, Andy, and James.