Finalizers, Destructors, RAII, GC

[sighoya]

On Wednesday, 28 April 2021 at 10:04:20 UTC, Ola Fosheim Grøstad 
wrote:
> It is currently an issue that people might write a class for 
> RAII and then allocate in on the GC heap, that means that 
> destructors can be called in the wrong order.
>
> If D adds a finalizer() method, this could be resolved the 
> following way:
>
> Objects with non-empty destructors cannot be GC allocated.
>
> The finalizer() method should be used for releasing all non-GC 
> resources accessible from non-GC pointers/identifiers, but one 
> should not follow pointers to GC-memory from a finalizer as 
> they may not exist.

Doesn't suffice ownership here? I mean you surely talk about 
owned manually allocated memory inside a class.
But why the need at all for a finalizer and instead allow 
non-empty destructors for gc allocated classes?
Having both is confusing.

> Or would it be better to simply forbid any cleanup in the GC? I 
> kinda think so, but I also think many D users are used to 
> letting the GC trigger cleanup on collection.
>
> What do you think?

Probably not for gc managed resources, but what about making 
class members reference counted or owned instead. Owned resources 
should be deleted automatically when a class object is destructed 
and reference counted resources are deleted if refcount goes to 
zero, which may occurs after destruction but at least not before.

Btw, I don't know how much is currently possible in D.