Source Code to Build invokedynamic.jar

[John Rose]

On Dec 10, 2008, at 2:50 AM, BGB wrote:

> pardon my ignorance, but is there any plan to allow dynamic slot/ 
> field access?...

Yes, but not directly in this project.  The dynalang.org project  
builds such things on top of Java.  Invokedynamic (and later  
interface injection) will allow such things to be treated almost as  
if they were built into the JVM.

> ok, I am starting out just implementing my own VM with little  
> familiarity with this framework in general (at this point I have  
> little idea if it will actually be compatible), my tweak was partly  
> to add the ability to have usable fields in interfaces (AFAIK, this  
> is not allowed in standard JVMs).

No.  Because you can build that on top of Java with getters and  
setters, JVM users do not (usually) feel that the JVM is missing  
anything on this score.

> ok, from what info I can find, interfaces in my case work a little  
> differently. there is actually almost no structural coupling  
> between interfaces and object methods. instead, a set of hash  
> tables is used, and the slot/method handle from the interface is  
> used to lookup the appropriate method in the object via the hash  
> tables (actually, a set of single largish hash tables is used for  
> managing the entire object system)....

There are technical advantages to having slots as first-class objects  
in a VM, but most designs happily use coordinated pairs (get/set) of  
access functions.

If you do reify slots, you might consider making them anonymous and  
composable in the same way that Lisp or JavaScript functions are  
anonymous and composable.  I don't think it's enough of a win to  
reify them but restrict their use to implementing object (and  
interface) attributes.  Perhaps you could unify them with local  
variables.

But this has little to do with what we are currently aiming at on the  
JVM.

Best wishes,
-- John