Specification doesn't guarantee any optimization, not even garbage collection, so conforming implementation can allocate objects until OOM.
On Sat, Aug 6, 2016 at 5:57 AM, /#!/JoePea <[email protected]> wrote: > Ah, interesting to know. Is such an optimization guaranteed? > > */#!/*JoePea > > On Tue, Aug 2, 2016 at 1:59 PM, Jason Orendorff <[email protected] > > wrote: > >> On Tue, Aug 2, 2016 at 3:09 PM, Bergi <[email protected]> wrote: >> >>> Why would `tmp` be stored as the [[HomeObject]] when the function >>> doesn't use `super`? In that case a [[HomeObject]] is not needed at all. >>> >> >> To clarify this: of course the JS engine knows whether the code uses >> `super` or not and can decide to retain the [[HomeObject]] only when >> there's some danger of its actually being needed. But do implementations >> actually do this optimization in practice? >> >> SpiderMonkey has a findPath() primitive that searches the GC heap for >> paths from one object to another, handy for answering questions like this >> one: >> >> js> function SomeFactory(name) { >> let tmp = { >> [name]() { /* this doesn't use `super` */ } >> } >> return findPath(tmp[name], tmp); >> } >> js> SomeFactory("foo") === undefined >> true >> >> That is, there is no GC-path from the method back to the object; >> apparently [[HomeObject]] is not being retained. What if we change the >> method to use `super`? >> >> js> function SomeFactory2(name) { >> let tmp = { >> [name]() { return super[name](); } >> }; >> return findPath(tmp[name], tmp); >> } >> js> typeof SomeFactory2("foo") >> "object" >> js> SomeFactory2("foo").length >> 1 >> >> Now there is a direct GC-reference from the method to its home object, as >> expected. >> >> -j >> >> >> _______________________________________________ >> 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 > >
_______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
