Re: Legit Warnings or not

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

"Adam Beneschan" <adam@irvine.com> wrote in message 
news:b760b2c4-b774-43b6-b29e-4882470be1f4@a2g2000prf.googlegroups.com...
>On Jul 21, 8:41 am, Robert A Duff <bobd...@shell01.TheWorld.com>
>wrote:
>> Adam Beneschan <a...@irvine.com> writes:
>> > You don't have to allocate a whole new Warned_Person, just a new Name.
>>
>> Right. If you allocate a whole new Warned_Person, you can get
>> dangling pointers and dangling renamings. If I remember correctly,
>> the rules prevent renaming or 'Access of parts of Name (assuming
>> it has aliased parts).
>
>3.10.2(26), 8.5.1(5).  However, I think the language now says that
>'Access and rename of a component are OK if the discriminated object
>is known to be constrained; that means that the implementation has to
>be smart enough to know that it can't allocate a new Name in that case
>(when the entire record is assigned) but keep the same pointer and
>just copy over the data that it points to.

That's a good idea anyway, just because allocating and deallocating memory 
is expensive. We do that any time the component does not change size - which 
has the side-effect of working in any case that would be allowed by the 
mentioned rules.

                          Randy.


                                 -- Adam