It is native code, all ECMAScript based solutions would leak as of right now.
I am also unsure you could tell what has been collected since you would need to maintains a reference to that object, you could however tell how many objects are left for possible collection. You could do a complex reverse hashing possibly on a WeakMap an attacker creates, but then, if that information was privy, why make the WeakMap key exposed outside of a closure? A last point I would make on this if an Object used as a key is near death (available for collection but 1 reference), if that reference were in a non-key WeakMap, it would be possible to find out this information anyway if i understand the gc algorithm. All you would need is to set a map to contain the first object and have the second object point to the first weakly. All in all I wanted to point out some valid uses of the keys that I currently use. Both of which would leak terribly / not work if using anything else. On Thu, Aug 26, 2010 at 11:03 PM, Brendan Eich <[email protected]> wrote: > On Aug 26, 2010, at 8:19 PM, Bradley Meck wrote: > > I am not sure that would make it a regular map. Having the keys available > does not ensure that the keys will not be collected. > > > That's the crux of the matter. Mark Miller should weigh in, since he has > argued this point in the past with some good arguments. > > The issue is that enumeration or even a weakmap.length property would > convey what has been collected as garbage, and what has not yet been > collected even though weakly referenced by a map entry. There could be > strong refs elsewhere, or the GC might just not have gotten around to > collecting the still-enumerated or counted-by-length entry. > > This makes a covert channel from the implementation's garbage collector, > and it can be abused. The GC schedule may be deterministic, so as I > understand it the issue is not non-determinism (or it's more than ND vs. D > -- it's really the ability of attackers to tell what the GC considers live > still). > > > I personally use the keys on a personal implementation to check and see > what callbacks may be outstanding, and if I need to reference all the > Objects of a given type at once. > > > How does your implementation work (or is it native code)? > > /be > > > On Thu, Aug 26, 2010 at 8:14 PM, Waldemar Horwat <[email protected]>wrote: > >> Erik Arvidsson wrote: >> >>> 3. Why isn't there a way to iterate over the keys? >>> >> >> Because then it would be a regular map, not a weak map. This is something >> that only a debugger should be able to do. >> >> Waldemar >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > >
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