Multiple this$1 fields when mixing subclassing and inner classes

[Stefan Reich]

Oh, because it doesn't affect the Java source level, right? Got it. Thanks

On Wed, 11 Sep 2019 at 14:42, David Holmes <david.holmes at oracle.com> wrote:

> On 11/09/2019 10:30 pm, Stefan Reich wrote:
> > I'm thinking about becoming a JCP member to turn this idea (merging
> > this$x fields) into a JSR.
>
> This doesn't require a JSR, nor do you need to become a JCP member.
>
> This is just an enhancement request for the hotspot implementation
> (assuming it is actually valid, viable and worthwhile).
>
> To work on this all you need to do is become an OpenJDK contributor:
>
> http://openjdk.java.net/contribute/
>
> If the issue is large enough then it may warrant a Java Enhancement
> Proposal (JEP):
>
> https://openjdk.java.net/jeps/1
>
> David
> -----
>
> > The JCP paperwork seems scary though, and I don't speak their
> > programming language (legalese) enough to really get what is demanded...
> > https://jcp.org/aboutJava/communityprocess/JSPA2.pdf
> >
> > It seems I could become a JCP member as an individual without having to
> > pay a fee. Not sure what all the "IP" fuss is about. "Are you willing
> > and able to sign the JSPA and license IP"? License MY IP to Oracle? Or
> > the other way around? Who can help me out there?
> >
> > Greetings
> >
> > On Tue, 10 Sep 2019 at 01:30, Stefan Reich
> > <stefan.reich.maker.of.eye at googlemail.com
> > <mailto:stefan.reich.maker.of.eye at googlemail.com>> wrote:
> >
> >     Oh, I didn't know about those JDK 11 changes. That may in fact break
> >     the idea of merging the references. I'm sure it can still be done,
> >     but might require a spec change. And who's gonna pay for that?
> >
> >     :-D
> >
> >     Thanks
> >
> >     On Tue, 10 Sep 2019 at 01:17, David Holmes <david.holmes at oracle.com
> >     <mailto:david.holmes at oracle.com>> wrote:
> >
> >         On 10/09/2019 9:09 am, Stefan Reich wrote:
> >          >     But you're not talking about bytecode here you're talking
> >         about inside
> >          >     the VM. If there is an invokespecial on this$1 of type A
> >         then the
> >          >     constant pool lookup of its type will be A and we will
> >         resolve the call
> >          >     based on A's methods. If it were of type B then the
> >         resolution process
> >          >     would be different. There's nowhere to "insert a cast"
> here.
> >          >
> >          >
> >          > Can invokespecials on this$0/this$1 happen? I'm struggling to
> >         imagine a
> >          > case for this.
> >          >
> >          > invokespecial invokes private instance methods, superclass
> >         methods or
> >          > constructors. Superclass methods don't apply, neither do
> >         constructors.
> >          > And calls to private methods happen through bridges (just
> >         verified this
> >          > for myself again :):
> >          >
> >          >        13: aload_0
> >          >        14: getfield      #1                  // Field
> >         this$0:Lbla;
> >          >        17: invokestatic  #4                  // Method
> >          > bla.access$000:(Lbla;)V
> >          >
> >          > So what remains?
> >
> >         This changed in JDK 11 with the addition of nestmates. Now inner
> >         classes
> >         have direct private access, no bridges needed, and we use
> >         invokespecial
> >         or invokevirtual as appropriate. For private methods
> >         invokevirtual is
> >         mainly used now, but of course we don't do virtual dispatch -
> >         there are
> >         special rules for private method resolution and selection.
> >
> >         class A {
> >             void m() {}
> >             class InnerA {
> >               void callM() { m(); }
> >             }
> >         }
> >
> >            void callM();
> >               descriptor: ()V
> >               flags: (0x0000)
> >               Code:
> >                 stack=1, locals=1, args_size=1
> >                    0: aload_0
> >                    1: getfield      #1                  // Field
> this$0:LA;
> >                    4: invokevirtual #13                 // Method A.m:()V
> >                    7: return
> >                 LineNumberTable:
> >                   line 4: 0
> >
> >          >     BTW what introspection tool did you use to show this?
> >          >
> >          > My own tools ("JavaX")... here's the example program:
> >          > http://code.botcompany.de/1025166
> >
> >         Thanks for the pointer.
> >
> >         Cheers,
> >         David
> >
> >          > Many greetings :)
> >
> >
> >
> >     --
> >     Stefan Reich
> >     BotCompany.de // Java-based operating systems
> >
> >
> >
> > --
> > Stefan Reich
> > BotCompany.de // Java-based operating systems
>


-- 
Stefan Reich
BotCompany.de // Java-based operating systems