On Oct 15, 2014, at 12:14 PM, Boris Zbarsky wrote: > On 10/15/14, 3:05 PM, Allen Wirfs-Brock wrote: >> ... > >> So, the basic question becomes one how the browser maps web pages to >> Vats. If each pages get a separate Vat > > They don't. Basically, same-origin web pages correspond to multiple Realms > within a single Vat, since from their point of view direct object references > exist between them. > > Worse yet, different-origin web pages might be able to become same-origin > (due to document.domain). > > So in practice in a web browser a bunch of different web pages are all > separate Realms in the same Vat.
Right, but in practice, for different-origin pages, don't you use various forms of serialization/proxying to provide Vat-like object reference isolation? If you do that, then it feels like multiple Vats that share a single execution thread. We didn't current have that concept in ES, but we probably could. Don't multi-process (eg, process per tab, etc.) browsers in fact have multiple execution threads? > >> If the entire browser environment was represent >> as one vat then the loop continues as long as the browser is running. > > Yes, this is precisely the failure mode in Firefox right now. > >> For example, perhaps it could purge all Jn jobs if Realm R is destroyed. > > You can't really "destroy" a realm while someone is holding references to > functions from that realm, yes? > > What Gecko does do is mark a realm that corresponds to a navigated-away-from > web page (but NOT a web page loaded in an <iframe> that is then removed from > the DOM, for web compat reasons) as "inactive", and Web IDL callbacks that > are backed by functions from such a Realm become no-ops. Functions in that > Realm can still be called directly, but not via a Web IDL callback. I intentionally used "destroy" as a ill defined, non-technical terms. What you describe above is along the lines of what I was thinking. A PromiseReactionJob that is associated with a marked Realm might plausibly by purged (perhaps by replacing its reaction function with a "Thrower", which would break the loop). Regardless, it seems desirable to be able to describe what happens in terms of the specified Promise/Realm/Job semantics. Allen _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
