Re: Weak references for GObject

[Dan Bornstein <danfuzz milk com>]

Owen Taylor <otaylor redhat com> writes:
>If resurrection for cache purposes is considered necessary (I don't
>consider it so), then I'd like to separate it out into a clearly
>defined separate facility - something like:
>
> g_object_add_last_ref_notifier();
>
>That can be emblazoned with all the appropriate warnings.

Why not just do Java-style soft references? In keeping with the other
part of your proposal, the calls would be:

 void g_object_soft_ref   (GObject     *object,
		           GWeakNotify  notify,
			   gpointer	data);
 void g_object_soft_unref (GObject     *object,
	 		   GWeakNotify  notify,
			   gpointer	data);

where the ref call simply indicates that the system shouldn't necessarily
destroy an object when the last normal reference goes away (until the unref
call is made).

You can think of it as if these functions manipulate the refcount just like
normal ref/unref, except there's a side table mapping softly-referenced
objects to their soft refcount. When memory gets tight (however you want to
define that), you look at that side table and find objects whose only
refcounts are due to soft references, and those are the ones that are
subject to immediate destruction. When that happens, the notify functions
are called, just as with weak references.

-dan