Re: Keeping other stuff with addresses

On 12/3/2024 8:51 AM, Stefan Monnier wrote:

another way to steal bits is over alignment.

 Yup.  I keep lamenting that Alpha didn't go for bit-addressed memory,
which would have given us 3 extra free bits from alignment (as well as
allowing pointers to bits and bitfields).

;^)
Wrt stealing bits I always revert back to the original pointer when I use it for anything to do with the system. Now, actually using the stolen bits, well we can over align on a _large_ boundary and use them for a smallish reference count and/or version counter. We can use them for state machines in some clever lock-free algorithms. We just need to only use the stolen bits for _our_ logic. Mask them off, get back to the original pointer "value" before we use that pointer for what's its pointing too. Never deference a pointer with stolen bits!!!!!!!!!!!!!!!!!!
Fair enough?