method handle cracking API

[John Rose]

On Apr 24, 2013, at 7:45 PM, Mark Roos <mroos at roos.com> wrote:

> Any chance that one could walk the GWT chain from a call site in order to build 
> a different look up structure or maybe even some specialized code?  Currently I 
> keep this in the call site but it seems redundant. 

Sorry, not in this go-around.  We are aiming at cracking CONSTANT_MethodHandle constants.

Cracking transforms like GWT is a harder problem, which we need to think about more.

Simple example:  Suppose you have a tree of GWTs that a clever implementation compiles into a big hunk of bytecode.  How do you recover the original GWT chain from the bytecode?  Answer is, you can't, not unambiguously.  And a testable public API requires reproducible results.  So now implementations will have to keep extra information about the genesis of each MH, in case someone cracks it.  That will be a large and mostly-useless expense.

— John
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