On Wednesday, 11 February 2015 at 21:34:00 UTC, Andrey Derzhavin
wrote:
If we are using a DMD realization of destroying of
objects, happens the following: at the calling the «destroy»
method the calling of dtor takes place always, and then the
object which is being destroyed is initialized by the default
state. In other words, after calling «destroy» method, there is
no way of getting an access to the members of the object that
is being destroyed (it is meant, that the members are the
references). GC works the same way.
This approach in case of manual calling of «destroy» method
has predictable and understandable consequences (there is no
reasone to use the object being destroyed). But if GC performes
the destroying of the objects, a lot of errors appear at the
accessing to the members which are references, because some of
them have already been destroyed (access to the members is
realized in dtors). Such situations can be avoided, by using
«@nogc» keyword. Howewer «@nogc» keyword doesn't protect us
from using the references in dtors: we can assign some values
to the refernces, we can have access to some members by the
references and assign them some values.That is not correct in
itself.
If GC starts destroying some group of the objects, it could be
more correct, if the calls of dtros are occured of all objects
in a group before phisical memory releasing. Or GC must call
dtors of the objetcts only, which noone refers to.
The finalization order issue is one that is actually rather
difficult, if not impossible, to solve without a precise GC. It
gets even more complicated when you have to deal with cyclic
references in finalizable allocations.
