HeaderTypeGC refers to a bit in the object header, not to a bit in an
object memory pointer. The usage of this bit in the object header does
not in any way conflict with bit assignment for object memory pointers.

Dave

On Mon, Oct 18, 2010 at 05:08:56PM -0700, Andreas Raab wrote:
> Can't help but remind people of this little post I did a couple years 
> back on how to add new immediate types:
> 
> http://lists.squeakfoundation.org/pipermail/vm-dev/2006-January/000429.html
> 
> Cheers,
>   - Andreas
> 
> 
> On 10/18/2010 4:41 PM, Bert Freudenberg wrote:
> >On 18.10.2010, at 13:49, Colin Putney wrote:
> >
> >>On Mon, Oct 18, 2010 at 1:38 PM, Eliot Miranda<eliot.miranda at gmail.com>  
> >>wrote:
> >>
> >>>I think immediate characters are much more generally useful, especially
> >>>considering unicode.  The current implementation of only codes 0 to 255
> >>>being == is error-prone.
> >>
> >>I enthusiastically agree. I think string handling in Squeak is pretty
> >>weak, and having efficient Characters would provide a solid basis for
> >>improving it.
> >
> >Disagree.
> >
> >You don't want to be manipulating single characters if speed matters. Much 
> >better to add primitive support to speed up WideStrings.
> >
> >Also, adding more immediate objects will slow down the system as a whole. 
> >I remember changing the tag bit check in the early days of Squeak did have 
> >a performance impact. Whether new immediates would result in a net speed 
> >win remains to be seen.
> >
> >- Bert -
> >
> >
> >
>