Re: Representation clauses and streams

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

In article <wcc3dsf9xrn.fsf@world.std.com>,
  Robert A Duff <bobduff@world.std.com> wrote:
> Robert Dewar <robert_dewar@my-deja.com> writes:
>
> > Apparently some other compilers failed to follow the RM
advice
> > in the first place, which is what is giving rise to the push
> > to revise the language here.
>
> I don't think other compilers failed to follow the RM advice.
I think
> what happened is that different compilers chose different base
ranges,
> so even if all compilers follow the Advice, they don't all get
the same
> answer.  Users griped about this, which caused the ARG to get
involved.


That's quite right, some compilers used different base ranges.
Sorry for getting this confused in my previous post.

I actually think that we are mostly OK here. I think that
GNAT basically will do the right thing according to the modified
IA with changes after all (I was confused on this point).

Here is the specific case.

If you say

   type x is range -128 .. +127;
   for x'size use 8;

then (actually with or without the size clause), both the
base type and the first subtype are 8 bits, so GNAT stream
I/O uses 8 bits as expected.

Some other compiler legitimately, but not very helpfully in
this case, chose a base of 32 bits for type x above, and as
a result used four bytes for the stream which was not what
was wanted.

So I think there is no problem with GNAT here after all, or
more properly, the adjustment to GNAT to "agree" with the
new IA will not have a major impact.


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