Re: large arrays

["Randy Brukardt" <randy@rrsoftware.com>]

"Jeff C r e e.m" <jcreem@yahoo.com> wrote in message
news:kNckd.488755$mD.84928@attbi_s02...
> From the GNAT RM (6.2)
>
>  The largest Size value permitted in GNAT is 2**31-1. Since this is a Size
> in bits, this corresponds to an object of size 256 megabytes (minus one).
> This limitation is true on all targets. The reason for this limitation is
> that it improves the quality of the code in many cases if it is known that
a
> Size value can be accommodated in an object of type Integer.

For what it's worth (probably nothing :-), Janus/Ada doesn't limit objects
on 32-bit architectures. We manage everything in terms of bytes, and only
calculate 'Size if someone asks for it (which might raise Constraint_Error
for really large objects).

But I have to sympathize with GNAT; the allocate-in-bytes designs needs a
lot of hacks to make it work for all of the sorts of representation items,
and I certainly can see why someone wouldn't want to do that.

Someone also complained that this limitation exists on all targets; I'm sure
that's because the compiler front-end uses 32-bit values for 'Size on all
targets. Otherwise, you'd have to have a 64-bit compiler before you could
compile the 64-bit compiler (we faced this same issue on the 36-bit Unisys
system).

                     Randy.