Re: Ada subtypes and base types

[Laurent GUERBY <laurent at guerby dot net>]

On Wed, 2006-03-15 at 23:09 -0500, Robert Dewar wrote:
> Laurent GUERBY wrote:
> > On Mon, 2006-03-13 at 15:31 -0700, Jeffrey A Law wrote:
> >> On Mon, 2006-02-27 at 20:08 +0100, Waldek Hebisch wrote:
> >>
> >>> What do you mean by "abuse"?  TYPE_MAX_VALUE means maximal value
> >>> allowed by given type.
> >> As long as you're *absolutely* clear that  a variable with a
> >> restricted range can never hold a value outside that the
> >> restricted range in a conforming program, then I'll back off
> >> the "abuse" label and merely call it pointless :-)
> > 
> > Variables in a non erroneous Ada program all have their value between
> > their type bounds from the optimizer perspective (the special 'valid
> > case put aside).
> 
> Not quite right. If you have an uninitialized variable, the value is
> invalid and may be out of bounds, but this is a bounded error situation,
> not an erroneous program. So the possible effects are definitely NOT
> unbounded, and the use of such values cannot turn a program erroneous.
> (that's an Ada 95 change, this used to be erroneous in Ada 83).

Yes, thanks for the precision. I'm not sure that such difference
can reach the back-end in the current state of affairs, do you have
a case in mind?

Laurent