🚀 go-pugleaf

> 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.

If the "as if" rule is used to make objects movable, then I think it has
to be done by a scheme with an extra level of indirection, such as the one
I outlined in my previous posting in this subthread.  In that scheme,
the thing accessed by %p would not be the real pointer but a pointer
to it, and the real pointer would be free to change.


> The questions answered are different from the question what happens if you
> write a pointer to file and read it back in.

Since it's agreed that the writing and reading does not change the bits,
I think it is all equivalent.
-- 
Mark Brader			"People with whole brains, however, dispute
SoftQuad Inc., Toronto		 this claim, and are generally more articulate
utzoo!sq!msb, msb@sq.com	 in expressing their views."	-- Gary Larson

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