On 7/27/17 4:23 AM, Guillaume Piolat wrote:
On Wednesday, 26 July 2017 at 22:29:50 UTC, Steven Schveighoffer wrote:
Today, the finalizer is essentially a last-effort to clean up
resources that would otherwise leak.
My point is that this "last chance" to clean up resources should only be
used to tell deterministic destruction wasn't acheived (for reasons
given in my former post: it's _too hard to explain_ how to do resource
management else).
Consider reference counting with cycles. The proposal from Walter/Andrei
is to do reference counting to clean up everything but cycles. For
cycles, the GC will take care of it.
So how do you do this correctly without having two separate mechanisms?
The reason deterministic destruction sucks today is because once you
go 2 levels deep, the only tool available (~this) cannot release any
resources (because it's not legal to access GC-allocated members
inside ~this).
You already know it, but if you commit to not doing anything in the
finalizer case, then ~this doesn't suck, it works as a destructor and
the restrictions lift.
So "suck" is a bit strong.
This is an unworkable solution. One simple time you forget to clean up
deterministically and then you corrupt memory by using members that are
already cleaned up.
Or, you disable calling destructors in the GC, and instead leak resources.
Or I suppose you could crash your application. This would be a fun bug
to figure out...
-Steve
