Re: Portability questions

[Robert A Duff <bobduff@world.std.com>]

Robert Dewar <robert_dewar@my-deja.com> writes:

> In article <wccbt2ycni0.fsf@world.std.com>,
>   Robert A Duff <bobduff@world.std.com> wrote:
> 
> > Without pragma Import, the compiler can do what it likes
> > initialize B or not.  I suspect most compilers do not.  I
> > think compilers should not.
> 
> Why do you think that? This is a case where the quality and
> efficiency of the code is greatly improved by making sure
> that there are no unused garbage bits in the value, which can
> otherwise happen with packed arrays. This is very similar to
> the trade off choice of whether to clear garbage bits in records
> to speed up record comparisons.

Yes, you're right.  If there are gap bits in between components, then it
makes perfect sense for a compiler to set the whole thing to zero.

> > With pragma Import on B, I would consider it a bug for a
> > compiler to initialize B, although I'm not sure I can prove
> > that from the RM.
> 
> Most certainly pragma Import suppresses the initialization, and
> I find Bob's "not sure" here odd.

Well, I was just too lazy to look it up.  ;-)

- Bob