On Tue, 10 Nov 2009 18:55:25 -0000, Steven D'Aprano
<st...@remove-this-cybersource.com.au> wrote:
On Tue, 10 Nov 2009 15:46:10 +0000, Grant Edwards wrote:
On 2009-11-10, Rhodri James <rho...@wildebst.demon.co.uk> wrote:
On Sun, 08 Nov 2009 19:45:31 -0000, Terry Reedy <tjre...@udel.edu>
wrote:
I believe the use of tagged pointers has been considered and so far
rejected by the CPython developers. And no one else that I know of has
developed a fork for that. It would seem more feasible with 64 bit
pointers where there seem to be spare bits. But CPython will have to
support 32 bit machines for several years.
I've seen that mistake made twice (IBM 370 architecture (probably 360
too, I'm too young to have used it) and ARM2/ARM3). I'd rather not see
it a third time, thank you.
MacOS applications made the same mistake on the 68K. They reserved the
high-end bits in a 32-bit pointer and used them to contain
meta-information.
Obviously that was their mistake. They should have used the low-end bits
for the metadata, instead of the more valuable high-end.
Oh, ARM used the low bits too. After all, instructions were 4-byte
aligned, so the PC had all those bits going spare...
--
Rhodri James *-* Wildebeest Herder to the Masses
--
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