Re: put of access type

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

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccmy5semnv.fsf@shell01.TheWorld.com...
> "Randy Brukardt" <randy@rrsoftware.com> writes:
>
>> "Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message
>> news:wccr5v5xlza.fsf@shell01.TheWorld.com...
>> ...
>>> I think that still works fine in Ada 95/2005 for pool-specific access
>>> types (which is the only kind that existed in Ada 83).  The only
>>> relevant language change is that you can convert from pool-specific to
>>> general.  So you have to be able to take your offset, and produce a
>>> "full" address, or whatever a general access type is represented as.  As
>>> far as I can see, the addition of user-defined storage pools to the
>>> language is irrelevant here.
>>
>> I don't see how this could work. There is no call-back to the storage 
>> pool
>> when converting from pool-specific to general access, so how could the 
>> pool
>> make the conversion?
>
> I'm lost.  You said Ada 83 compilers can represent access types as
> offsets from some known place.  I agree.  And I claim Ada 95/2005
> compilers can do the same.  Nothing to do with storage pools, which did 
> not
> exist in Ada 83.

An Ada 83 compiler can represent *all* access types as offsets from some 
known place. That's how our old CP/M compilers worked. But since Ada 95 
access types can be converted to general access types (without any sort of 
conversion function in the case of access types with a storage pool), it 
isn't possible to retain such an implementation in general. I suppose you 
could use such an implementation for a specific access type with the use of 
a special implementation-defined pragma (and then you would have to disallow 
conversions to any other access type, which is not Ada 95), but that is 
*not* the sort of implementation model that I was thinking of.

                                                 Randy.