Why is the class ._dtor symbol not virtual?

[Jonathan M Davis]

On Wednesday, March 28, 2018 20:17:28 12345swordy via Digitalmars-d wrote:
> I quite curious on the rational behind the decision, as currently
> it's not very attribute friendly, which makes destroy function
> @nogc for certain classes downright near impossible. From the
> time that I have looked into this issue(and from frequent
> discussions) many of the issues and bugs is the result of this
> bizarre design decision.

I think that this is the first that I've heard of them not being virtual,
but if I had to guess, the reason is that class finalizers are called by the
GC, and their TypeInfo is probably used, which would make it unnecessary for
the finalizer to be virtual, because it would always be called directly
rather than through a base class reference. But that's just a guess.

However, I don't understand why that would make the finalizer interact badly
with attributes. If the finalizer is not virtual, then the attributes for
each finalizer should be independent of one another. The reason that
attributes and classes are normally a problem is because you're restricted
by the attributes that were chosen for the base class function, and your
options for choosing different attributes for the function in a derived
class are limited.

As for issues with destroy in particular, remember that classes were
designed to be constructed and allocated using the GC and then destroyed and
freed by the GC. All of the stuff that tries to deal with any of that
without the GC came later - including using destroy to destroy an object
rather than waiting for the GC to do it. So, it's not exactly surprising if
there were design decisions made that don't play well with something like
destroy. Hopefully, any such problems can be fixed, but stuff like destroy
is trying to work around how classes were designed to be used.

- Jonathan M Davis