Re: 83/95 issue, bad code or compiler bug

[dewarr@my-dejanews.com]

In article <36587057.292493@news.pacbell.net>,
  tmoran@bix.com (Tom Moran) wrote:
> >I think you misunderstand this. The compiler is indeed f
> >free to only access 8 bits in a case like this, and
> >indeed this
> >need not really be mentioned, it is obviously correct.

> Do you mean that you understand
>    for X use at 0 range 0 .. 15;

> to mean that the compiler may not use *more* than 16 bits
> for X, but
> is perfectly free to use *less*?  I would find that
> interpretation
> bizarrely anti-useful and am certainly glad Gnat does not
> seem to do
> things that way.


Yes, that interpretation *is* bizarrely anti-useful, and
also has nothing to do with my statement. Reread the above
quote more carefully. I said *access*!

Of course the compiler must allocate the number of bits
specified, but in the above case, since the number is known
to be in the range 0..15, it is fine for the generated code
to load only the low order byte. The only time this would
make a difference is if the value was abnormal. Note that
one exception is that a 'Valid test must load all 16-bits!

Robert Dewar

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