DIP74 & GC Destructors

[rsw0x via Digitalmars-d]

On Monday, 15 June 2015 at 16:20:56 UTC, Marc Schütz wrote:
> I hope we won't get builtin RC, but that's off-topic.

I disagree, that's entirely on topic. I believe every modern 
implementation of Ada relies solely on RC(while having GC hooks.) 
Nobody really seems to have an issue with RC there. I personally 
believe that immediate RC and GC solve completely different 
issues of deterministic vs non-deterministic resource management. 
Trying to shoehorn them into the same thing gets you a broken, 
slow implementation(see: C++'s shared_ptr. It's dog slow and 
_way_ overused IMO.)

>
> In any case, there has been talk about introducing finalizers 
> instead of destructors for GC managed objects. 
> rt_attachDisposeEvent() already exists and is used by 
> std.signal for weak references, but it's a hack, it needs to be 
> formalized.
>
> These finalizers can then have much more restricted semantics 
> than destructors, e.g. they must be callable on any thread, are 
> generally un- at safe if they access members with indirections, 
> and so on.

I'm honestly curious of examples where finalizers are needed. The 
one exception I can think of is managing non-GC objects, as in 
C#. But that *still* seems like a bad idea because there's zero 
guarantee the destructor will ever run - i.e, a GC implementation 
that decides to just never call destructors is a valid 
implementation.

http://dlang.org/class.html#destructors
"The garbage collector is not guaranteed to run the destructor 
for all unreferenced objects. "

D has more than one issue here, from combining "finalizer" and 
"destructor" into the same term to destructors being incredibly 
bug-prone and almost useless as defined by the standard.

I hope this gets looked at.

Bye.