Re: Which is right here - GNAT or OA ?

[Robert Dewar <robert_dewar@my-deja.com>]

In article <928569312.951.42@news.remarQ.com>,
  "Vladimir Olensky" <vladimir_olensky@yahoo.com> wrote:
>
> Vladimir Olensky wrote in message
<928529202.956.79@news.remarQ.com>>

<<simple scheme based on address range comparisons snipped>>

Obviously you cannot require such a scheme, because of course
it is inapplicable in many environments, especially with
multi-threading.

Even in environments where it might be practical, it's more
expensive than you think, because some of these ranges are
tasks specific data.

In any case, this kind of approach is certainly completely
familiar, and it would not be invalid for a compiler to
implement it, but it seems a waste of time and space to me
to attempt to guard against this kind of logic error in a
language that does not even handle the uninitialized variable
problem completely (and that too is of course quite a
deliberate decision).

It is certainly not something we would consider adding to
GNAT in any environments.

Generally the notion of erroneous in the RM is that you should
detect it if it is free or cheap, but NOT add extra code for
this kind of detection.

Yes, it could be under some kind of debugging pragma, but if
you are going to move in that direction, you want to go much
further, and in particular handle the uninitialized variable
problem, and other, much more common, and much more worrisome
cases of erroneous access.

Deallocation of static stuff is in fact a pretty easy error
to guard against, since most typically this is done in well
controlled finalization routines in any case, and it is just
a matter of having the discipline to worry about this problem
and take proper care of it when you write the finalization
routine.

And to repeat, since you keep repeating the subject, both
GNAT and OA are right here, and do what the RM intends!


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