Re: redoing SCM representation in 2.2

[Ken Raeburn]

On May 14, 2011, at 05:47, Andy Wingo wrote:
> However, I realized that this isn't going to work on 32-bit, and for an
> unexpected reason: GC.  The problem is that the low 32-bits can be
> interpreted as a pointer, so you need to tag those bits to make the
> payloads of immediate values like integers or characters not confusable
> with pointers, and that takes away any potential advantage (wider fixnum
> range for example).

Is that really any more of an issue this way than with the current encoding -- 
if not for SCM, then for heap data structures including both SCM objects and 
integers or characters?  I thought the GC code already had to cope with things 
looking like they could be pointers but not actually corresponding to anything 
allocated via the GC library.

Ken