bug#65700: time when gcs-done is updated needs to be clarified

[Shynur Xie <one.last.kiss@outlook.com>]

> Eli:
>
> > I'm not a native English speaker.  Does the POST in `post-gc-hook'
> > mean the functions will run when GC is DONE?
>
> Its being "done" doesn't necessarily have to include updating the
> count of GCs.  The main job of GC is already done by the time the
> hook is called.

Thanks for explaining.  Yes, "Its being 'done' doesn't necessarily
have to include updating the count of GCs."

My point is, IF "the functions will run when GC is DONE" THEN when
these functions are being executed, the `gcs-DONE' should have been
updated.

> Eli:
>
> > > Is this an intended behavior?  If so, I think the docstring of
> > > these variables (such as `gcs-done', `gc-elapsed', ...) need to
> > > clarify when the variable is updated.
> 
> > And `garbage-collection-messages'.
>
> What about it?

Mentioning it here is just for reference.  Maybe you want clarify when
the variable/message is updated/generated in the docstring.


> Stefan:
> Hmm... that doesn't really explain in which way this affects your
> code.

It does.

> `gcs-done` will be always smaller by 1

That's it.