jdk7 b58, VM doesn't smell good

[John Rose]

On May 12, 2009, at 4:55 PM, Rémi Forax wrote:

> Ok, that why I haven't found that bug before b58 because
> my old tests was also on the boot class path.

Yep, I'm in the same boat; I've been living out of incremental builds  
and -Xbcp options for a long time.  It has been a scramble for me in  
M3 (b58 and b59) to recover from the unforeseen effects of "hatching"  
out of the BCP and into a real class loader.

> So this is a another workaround, put all your app on the boot class  
> path.

Yep, for now it is.

>> I don't see that there's a cleanup to be done at this point in the  
>> API.\
>
> The VM doesn't differentiate a Java anonymous class from a standard  
> class,
> so it seems there is no way to improve the API.

Yes, unless there's a way to express the programmer's intention about  
the class.  That's the main reason why MHs.bind is there.

Or, I keep thinking there's room for a feature in the API which takes  
a class (maybe a concrete anonymous class) and walks up the supertype  
lattice looking for a supertype which is accessible to the guy doing  
the lookup.

>
>> ... it would be a long stretch to call these conversions subtype
>> relations.
>>
>
> The downside of that is that the only way to implement Neal's closure
> type system with the current spec is to erase all Method handle type
> (with convert) just after the creation of a method handle.

Yes, but he was expecting to do that anyway.  I've had some  
interesting 1-1 conversations with Neal lately about MHs and closures;  
the semantic gap is not as bad as I thought it might be.

> About the slow down effect, It can be removed by allowing the two way
> (John's one and Fredrik's one) to call a method handle:
>  MethodHandle.invoke() that performs a single pointer check and
>  MethodHandle.apply() that performs a less restrictive/more expensive
> check.

Well, that's what MHs.invoke is for!  See the latest javadoc, which I  
just posted:
   http://cr.openjdk.java.net/~jrose/pres/indy-javadoc-b59/

(And, I've taken some pains to make it reasonably fast.)

-- John