Re: setting 'Size and unchecked conversion safe here?

[Marius Amado Alves <amado.alves@netcabo.pt>]

On 11 Feb 2005, at 23:49, tmoran@acm.org wrote:

>> What I'm not sure about is whether the unused 32
>> bits are harmless or not (by definition). Thanks.
>   An Unchecked_Conversion of dissimilar sizes is clearly unsafe, simply
> because it's implementation defined how, or if, it works.

Strictly they have the same size, because I said so with Size clauses.

>   But your problem appears to be the warning on
>     for My_Access_To_Subprogram_Type'Size use 64;
> ARM 13.3(42-43) recommends that a compiler should support this.
> Presumably you don't care how the compiler places the 32 useful bits in
> the 64 bit slot, so long as you get out what you put in.

Actually I'd be happier if the unused bits could be forced to have a 
specified value, say all zeros, or all ones. To ensure a one-to-one 
mapping between the original access values and their representation 
with the extra bits. Would pragma Normalize_Scalars do the trick? I'd 
rather avoid it, because it has partition-wide effect, which is 
overkill for the case at hand, and so might even interfere with other 
parts of the program.

>   So another
> compiler might do it differently, but your program would still work
> correctly.

Excelent. That was my expectation. Thanks a lot.