🚀 go-pugleaf

msb@sq.sq.com (Mark Brader) writes:
>> Well, examine the *as if* rule.  I think a run-time system is able to
>> move data under the proviso that it is able to identify all pointers
>> and update them accordingly; even if they are stored in non-pointer type
>> variables.  (I know of one Algol 68 garbage collector that did just that,
>> but it cheated.  On a tagged architecture it would certainly be possible.)
>In theory maybe, but not in practice.   Consider that you can transform
>a pointer to a character string with "%p" in sprintf(), do arbitrarily
>complex operations on the characters which end up reproducing the same
>string, then use "%p" in sscanf() to reconstruct the pointer, and the
>result must compare equal to the original pointer.

That's a pretty strong requirement, I think, but still not quite enough to
(by itself) ensure that the contents of pointer variables may not change
during execution:

	printf("%p\n", ptr);

could yield something like "<The Object Named Fred-0007>", if the architecture
supported some other constant naming scheme for objects other than their
virtual bus addresses.