On Mon, 9 Jan 2012, Henrik Johansen wrote:
On Jan 9, 2012, at 8:46 06PM, Levente Uzonyi wrote:
On Mon, 9 Jan 2012, Mariano Martinez Peck wrote:
So..I am puzzle again. I said "In which scenario can (self
instVarsInclude: anObject) answer true, but the loop false? "
you answered: "The scenario happens when the receiver has weak slots and
the argument is referenced from one of those weak slots, but not from the
other slots."
Imagine the receiver has a weak slot XXX that points to anObject. So (self
instVarsInclude: anObject) answers true. How can the loop answer false
without a GC?
why would XXX stop pointing to anObject if there is not GC in the middle ?
The loop doesn't iterate over the indexable slots, only named ones.
grrr you are right!
Ok, so I finally got it. So previously pointersTo: would answer true even
if the slots were weak. Now it would answer false, and that's why you have
changed the method comment.
Now I am thinking if this should be the default behavior of #pointsTo:. If
I just read the selector #pointsTo: I would guess weak references are also
taken into account. So that's why I am not completely sure. Aren't there
any other impact of the system because of this change?
what about having #stronglyPointsTo: with this new version and have another
one #pointsTo: which considers weak also?
does it make sense? or it is better to directly avoid weak by defualt in
#pointsTo?
I wasn't sure about this, that's why it's not in Squeak yet. Ignoring weak
references is okay as long as these methods are only used for pointer tracing.
Levente
Even with a good comment, the naming starts to make little sense, imho?
Since #pointsTo: doesn't use primitive 132 directly, it's only used from
the pointer tracing tools, which shouldn't really follow weak references.
Does an object having weak slots mean it no longer pointsTo: the objects in
those slots?
If you mean "points to", then no. :)
Sadly, I have no better succinct suggestions. :/
Also, what happens when an object holds its (non-compact) class in a weak slot?
In other words, is:
wa := WeakArray new: 1.
wa at: 1 put: WeakArray.
self assert: (wa pointsTo: WeakArray).
a valid test?
Yes, because its class pointer points to its class (this sounds funny :)).
Levente
Cheers,
Henry
