Proposal: Large arrays (original) (raw)

james lowden jl0235 at yahoo.com
Tue Mar 24 11:03:02 PDT 2009

I don't think the source compatibility impact is that large actually. Let's say all arrays can potentially be 64-bit now. The existing code that uses an int expression to index into the array will still index into the same element and negative indexes will still cause an exception. Now, how should the length field be set? I'd guess it should saturate to Integer.MAXVALUE for oversize arrays and a new "long size()" method could be added to return the full length.

This I'd actually prefer over what I proposed (and, based on the response so far and the previous bug, what others would probably like as well); my main concern was not breaking the int "length" field; I'd slightly prefer the long size to be a field rather than a method, but that may just be due to that being how I'm used to obtaining the array size; if there's a compelling reason to use a method rather than a field for this, I'd be curious to hear it.

The JVM would need to be modified to handle the long indexes of course; perhaps the wide bytecode prefix could be put to use here.

Looking at wide, it looks like applying it to the existing array instructions would be an option; I would favor that approach over my original idea, which chews up a whole slew of opcodes.

I'll probably stew on the various suggestions for a while, and send out a revised version of the proposal.

-JL-

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