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On Fri, 19 Nov 2004, Fyodor Tkachov wrote:
> A procedure variable is just an address of the entry point
> into the procedure: there is no auxiliary information
> to help the run-time system.
Is this a statement of current implementation or a statement of necessity?
Does it have to be so?
This may be similar to safe versus unsafe arrays.
In Fortran and C, an array is just an address of the 1st element and there
is no auxillary info such as index bounds. As a consequence, arrays in
Fortran or C are unsafe and lots of fun can happen using them. IN CP
arrays have been made safe and the fun is long gone, thank goodness.
How about the procedure variables? Can they be made similarily safe?
How about differentiating between safe high-level procedure variables
and low-level [untagged] procedure variables that you would need to
interface with Windows and/or Linux? The latter would only be available
under SYSTEM, same as [untagged] records and [untagged] arrays. Similar
problem, similar solution.
Note, I am not a compiler writer, so I am only posing this is a question.
I do not know whether safe procedure variables can be implemented.
I also do not know whether or not the current BB implementation is safe.
W.
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Received on Fri Nov 19 2004 - 17:17:58 UTC