Multiple finalizers per single object
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Re: New finalization support code is in the Trunk now (was: Re: [squeak-dev] Re: Multiple finalizers per single object)
 
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On Mon, 27 Sep 2010, Igor Stasenko wrote:
> Tested on both Squeak & Cog VMs. > WeakRegistryTest and WeakFinalizersTests are all green. Great, thanks. Levente > > Now all is left is release new VMs with finalization. > > On 26 September 2010 06:26, Levente Uzonyi <[hidden email]> wrote: >> On Sun, 26 Sep 2010, Igor Stasenko wrote: >> >>> Great news! Thanks Levente. >>> I will test if everything ok on my VM(s), since i have Squeak&Cog with >>> new finalization both :) >> >> Thanks. >> >> >> Levente >> >>> >>> On 26 September 2010 04:29, Levente Uzonyi <[hidden email]> wrote: >>>> >>>> On Fri, 24 Sep 2010, Igor Stasenko wrote: >>>> >>>>> 2010/9/24 Levente Uzonyi <[hidden email]>: >>>> >>>> snip >>>> >>>>>> >>>>>> Today or tomorrow I'll check the code more in-depth and prepare mczs >>>>>> from >>>>>> your changesets (if noone else does it before me). >>>>>> >>>>> Please, do :) >>>> >>>> It's in the Trunk now. I did the following changes: >>>> - there was a bug in the evaluated code in WeakFinalizationRegistry class >>>>>> >>>> #migrateOldRegistries, the first argument of forgetClass:logged: was a >>>> Symbol instead of a Class, so WeakFinalizationRegistry was still around. >>>> - WeakRegistry >> #keys is now protected >>>> - I merged the old comment of WeakRegistry with the new one >>>> = I merged phase-0 with phase-1 >>>> - I omitted phase-3, because I added the migration code to phase-2 >>>> - I omitted phase-4 because those tests are already in the Trunk >>>> >>>> What I didn't do so far, is that I didn't build a VM with the new >>>> finalization support, so someone should check if it works as expected. >>>> >>>> >>>> Levente >>>> >>>> P.S.: Seems like the MC postscript is evaluated before the class >>>> initializers which is a bit surprising. This is why I couldn't merge >>>> phase-2 >>>> into phase-1. >>>> >>>> >>> >>> >>> >>> -- >>> Best regards, >>> Igor Stasenko AKA sig. >>> >>> >> >> > > > > -- > Best regards, > Igor Stasenko AKA sig. > > |
Re: [Pharo-project] [squeak-dev] Multiple finalizers per single object
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In reply to this post by Chris Muller-3
I sort of disagree, in that it's neat to have a way for objects to be notified when other objects die, without that object necessarily having to know about all objects that may be interested in its death.
(Like, in Leventes case which triggered their creation in the first place, objects which are weakly registered to one or more announcers) I don't really see the benefit in constraining an existing, flexible mechanic to only cover the common use case. If multiple finalizers are removed, at least so should Object>>toFinalizeSend:to:with: (and potentially other spots, I haven't checked exactly) leaving Object >> finalize as the only place where finalization actions take place. (Which is where the actions Igor are talking about should be happening in the first place) Cheers, Henry On Sep 23, 2010, at 10:36 27PM, Chris Muller wrote: > I agree that multiple finalizers per object seems unnecessary and, as > you pointed out, potentially confusing, if not also conflicting. > TSTTCPW seems appropriate in this case. > > On Thu, Sep 23, 2010 at 3:23 PM, Igor Stasenko <[hidden email]> wrote: >> Hello, >> >> i'd like to raise this subject once more, because i don't like it (or >> don't understand?). >> >> In all scenarios, where i met the need to use finalization, a single >> finalizer is sufficient. >> Moreover, there is always a single object who controls a weak >> reference, and it never leaks it out, to prevent >> the case, when some other object may obtain a strong reference on it, >> making it permanently held in object memory. >> >> Multiple different finalizers for single object, from design point of >> view, means that you having two different, not related frameworks, >> which using same object, and want to do something when it dies. >> A scenario, where its possible and userful, still don't comes into my mind. >> In contrary, whenever i see a use of finalizers, its in most cases >> about graceful control over external resource, such as: >> - file >> - socket >> - external memory >> >> and i really don't see how multiple finalizers per single resource >> could do any good. >> >> Suppose one finalizer closing a file handle, while another one >> flushing it buffer cache. >> Now, how you going to ensure, that one finalizer will execute first, >> before another one? >> And what if third framework comes into play and wants to add another >> finalizer on top of that, which should do something in the middle >> between flushing a cache and closing file handle? >> >>> From the above, the only conclusion can be made: use a single >> finalizer, and put all logic & operation ordering into it. >> And also, prevent leakage of object pointer (such as file handle) >> outside of your model, otherwise it may cause harm. >> >> That's why i think a current WeakRegistry model provoking bad design practices. >> I think a better behavior would be to raise an error, if something >> wants to register finalizer twice for a single object. >> >> >> -- >> Best regards, >> Igor Stasenko AKA sig. >> >> > > > _______________________________________________ > Pharo-project mailing list > [hidden email] > http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project |
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