Greetings

I have a question on class destructor method. D documentation for destructors says:

"The garbage col­lec­tor is not guar­an­teed to run the de­struc­tor for all un­ref­er­enced ob­jects. Fur­ther­more, the order in which the garbage col­lec­tor calls de­struc­tors for un­ref­er­ence ob­jects is not spec­i­fied. This means that when the garbage col­lec­tor calls a de­struc­tor for an ob­ject of a class that has mem­bers that are ref­er­ences to garbage col­lected ob­jects, those ref­er­ences may no longer be valid. This means that de­struc­tors can­not ref­er­ence sub ob­jects."


Now I have a class A and it refers to subobject B. But B may or may not have other objects referring to it. As a result, an object of A is GCed, but subobject B may or may not be getting garbage collected.

In this scenario, am I allowed to make a reference to subobject B from the destructor of A? Is there a way to find out if B is garbage collected or not?

Regards
- Puneet

On 08/29/2013 06:58 AM, d coder wrote:> Greetings
>
> I have a question on class destructor method. D documentation for
> destructors says:
>
> "The garbage col­lec­tor is not guar­an­teed to run the de­struc­tor for
> all un­ref­er­enced ob­jects. Fur­ther­more, the order in which the garbage
> col­lec­tor calls de­struc­tors for un­ref­er­ence ob­jects is not
> spec­i­fied. This means that when the garbage col­lec­tor calls a
> de­struc­tor for an ob­ject of a class that has mem­bers that are
> ref­er­ences to garbage col­lected ob­jects, those ref­er­ences may no
> longer be valid. This means that de­struc­tors can­not ref­er­ence sub
> ob­jects."
>
>
> Now I have a class A and it refers to subobject B. But B may or may not
> have other objects referring to it. As a result, an object of A is GCed,
> but subobject B may or may not be getting garbage collected.
>
> In this scenario, am I allowed to make a reference to subobject B from the
> destructor of A?

The way I read it, it is exactly what the documentation warns against. No, A's destructor cannot reference B member.

> Is there a way to find out if B is garbage collected or
> not?

Not on B member itself because it is no more. :) It is conceivable to maintain a bitmap to determine whether an object is still alive. The object's destructor can flip its bit to 0.

>
> Regards
> - Puneet
>

Ali