draft of classfile spec changes for JDK 1.6 available

[Martin Zaun <Ma...@Sun.COM>]

Craig,
just FYI, I've seen that JSR202 (Class File spec for 1.6)
now has a downloadable draft for public review.

The major change is a new classfile verification scheme
based on 'type checking' rather than 'type inference',
mainly for performance (and slightly stricter enforcement)
reasons:

- The consistency rules are given in Prolog-like rules :)

- There's a new, complex StackMapTable attribute to be
   generated, which is mandatory with verson 50.0 (1.6);
   but a JVM is (still) allowed to fall back to type-
   inference, if type-checking fails.

- Byte-code manipulation tools are explicitely addressed!

- I expected but couldn't find any references of the new
   type-checking towards generics/signatures.  Only
   descriptors seem to be used.  So, I assume no changes
   with respect to omitting checkcasts (and breaking
   legacy code) in 1.6.

Martin