Re: Use aggregates (Was: Allocation question)

[Martin <martin.dowie@btopenworld.com>]

On May 11, 1:16 pm, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
> Jacob Sparre Andersen wrote on comp.lang.ada:
>
>
>
> > Olivier Scalbert wrote:
> > > procedure Fill(Image: in out Image_T; Color: Color_T) is
> > > begin
> > >       for x in Image'range(1) loop
> > >           for y in Image'range(2) loop
> > >               Image(x,y) := Color;
> > >           end loop;
> > >       end loop;
> > > end Fill;
>
> > I would sugges that you rather wrote this:
>
> >    Image := (others => (others => Color));
>
> > It is a more precise expression of what (I guess) you want done, and
> > thus it gives the compiler more precise information to work with.
>
> This is not always a good idea. On some targets, GNAT places the
> aggregate on the stack and this can raise a Storage_Error. In avionics
> programs, I remember replacing aggregates with loops for this reason.
>
> --
> Ludovic Brenta.

And not just GNAT...in fact, I'm struggling to remember a compiler
that _doesn't_ do the "large and slow (and stupid?)" aggregate for
assignment (or initialisation).

If paying customers complained compiler vendors might do something to
generate more efficient code. Sadly, sometimes the response we got
[naming no particular company] was "It meets the RM, we're not doing
anything".

Cheers
-- Martin