Isolated Methods JEP

[Peter Levart]

Hi Michael,

In the JEP's description you write:

    /"The loadCode method creates a method from the passed bytecode
    instructions and constants and returns a MethodHandle that can be
    used to call the method. The implementation of loadCode will take
    care of verification of the code to load.//"/

//
That's clear.

//

    /"This method is isolated from any class and behaves largely like a
    static method. The method handle resulting from a loadCode
    invocation is of the REF_static kind. It cannot be cracked via
    MethodHandles.Lookup.revealDirect().//"/


So there will be no class hosting this method? Not even the "caller" 
class of the Lookup instance that loadCode was invoked upon? What will 
be reported by Reflection.getCallerClass() invoked in a @CallerSensitive 
method invoked from the isolated method? Perhaps the following is a hint...

//

    /"The context for a method defined in this way is determined by the
    Lookup instance receiving the loadCode call. In case the lookup
    privileges are not sufficient, an exception will be thrown.//"

    /

The "context" meaning the caller context, including the caller class 
that appears in the stack trace of a call originating from an isolated 
method and is important for security decisions?

In which case would lookup privileges be insufficient to define an 
isolated method? I would expect the privileges of the code in the 
isolated method to be checked when such method is executed and not when 
defining such method - lazily, like for normal methods. In which case it 
is important which "caller" class the privileges are check against. This 
would most naturally be the "caller" class of the Lookup instance used 
to define the method. In all respects the code of such isolated method 
would appear to be defined in the lookup class except it would not be 
denotable symbolically - only through a MethodHandle. Analogous to 
VM-anonymous classes. So why not call such methods "anonymous methods" 
instead of isolated methods?


Regards, Peter


On 08/05/2016 06:33 PM, Michael Haupt wrote:
> Dear all,
>
> during the Indy workshop at JVMLS, a JEP draft supposed to enable the 
> loading of methods in isolation was mentioned and discussed. This JEP 
> draft is now public, and I'd like to invite The Interested Parties 
> (you know who you are) to tear it apart in a constructive manner. :-)
>
> https://bugs.openjdk.java.net/browse/JDK-8158765
>
> Thanks,
>
> Michael
>
> -- 
>
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