[sc-dev] idea of how to implement a weak array

[Julian Rohrhuber <rohrhuber@xxxxxxxxxxxxxx>]

Reading about garbage collecting, I had an idea how a weak array 
could be implemented in sc. I might be totally wrong, and this is 
speculative.

An array that has been marked weak should behave as if it could not 
contain pointers (i.e. it is not scanned any further by marking it 
black instead of grey). When the memory of an object that it points 
to is reused, the array will point to some weird unpredictable data. 
The only thing that we can be reasonably sure is that the data will 
be different from the original object.

Now the weak array could be encapsuled in an object that keeps a 
normal list of  copies of all objects in the weak array. When trying 
to access an object, it would compare the data at the two locations 
and if they are not equal, return nil and remove also the copied 
object from the second list (which is then garbage collected).

This would fail in the (improbable?) case that an equal object is 
stored at the same memory address again.

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