[Vm-dev] ImageSegment, objects header and addresses

[K. K. Subramaniam]

On Tuesday 27 Jul 2010 8:02:29 pm Mariano Martinez Peck wrote:
> Now....the line I don't understand is this:
> 
>     self longAt: oop put: newOop + HeaderTypeFree.
> 
> Because 'self longAt: oop'
> will answer the object header of oop. And there, it stores a number (the
> offset). Is this possible?
> 
> In addition, it not only stores the offset, by it plus the flag
> HeaderTypeFree.
> 
> I really don't understand how you can plus an offset and the flag. What is
> the result? how should I interpret that?
A oop is an offset. Since every oop is aligned to a 4-word boundary the least 
significant two bits are always zero. So these two bits are re-used for a 
typecode (0..3).

HTH .. Subbu