typed array strawman proposal

Brendan Eich brendan at mozilla.com
Wed Jan 27 10:46:55 PST 2010


On Jan 27, 2010, at 10:41 AM, Brendan Eich wrote:

> Only native code can do this currently, whether generated by a C++  
> compiler or even a crazy pattern-matching compiler that tries to  
> recognize bitwise ops clamping doubles stored in JS Arrays. The  
> latter, besides being crazy, does not prevent the doubles from  
> leaking, and again it is not something the spec should cater to, let  
> alone mandate.

To avoid confusion, I mean "leak" as in "abstraction leak", not  
"memory leak".

So long as some crazy JIT pattern matches clichés involving bitwise  
ops before stores and after loads involving certain Array instances  
(ahem, TraceMonkey does a bit of this for crypto code clichés), you  
could argue that you can desugar ("sour") to closures plus bitwise ops  
and plain old Arrays. But as noted, nothing guarantees that someone  
won't write double into such an Array,  and read it back.

This rules out such implementations as conforming to any spec such as  
the WebGL "typed arrays" spec. We cannot allow such abstraction leaks.

/be


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