Re: Unchecked_Deallocation vs. delete

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 11 May 2007 01:15:15 -0700, Maciej Sobczak wrote:

> On 11 Maj, 09:35, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
> 
>>> I'm not asking about the spelling (which is ugly for purpose), but
>>> about category.
>>
>> Well, as for categories, what is the benefit of having pointers? If I
>> designed Ada I would make referential derived types (of the target type)
>> instead.
> 
> That would be mess. Referential derived types (of the target type)
> when the target type is actually a base for some other type?

These are siblings.

> You mean
> - pointer as a type derived from Vehicle that can refer to Cars,
> Planes and Boats?

No. To have this it should be a pointer type to / derived from
Vehicle'Class.

(When you derive from Vehicle you obtain a member of Vehicle'Class, not the
class itself. So, no derived type knows anything about its siblings)

>>> Then put a run-time check in this Very_Hard_..._Operator.
>>
>> That might mean overhead on some architectures.
> 
> Then don't put the test and enjoy undefined behavior, just like with
> U_D.

This is what "Unchecked" stands for in Unchecked_Deallocation. Undefined
operators is in the realm of C++ (:-)).

>>>> Further even if a pointer is constructed with new, it
>>>> can be subject of GC.
>>
>>> So? GC does not prevent me from calling U_D or Very_..._Operator.
>>
>> My comment was about symmetry between new and free.
> 
> OK. But even then, GC is not a package that can be just with'ed. It is
> something that has some magic connections with the rest of the runtime
> and as such is part of the language implementation.

I think GC could be made a well-isolated package, because pointers are
typed in Ada. I don't refer to anonymous access types which are agreed
being a C-ish mess. But normal access types are named, so you can set GC at
an access type and only at it.

> The same about U_D
> - I still don't see why it is a library procedure. It plays an
> important role in the language implementation and if its allocating
> counterpart is a built-in operation, then U_D should be built-in as
> well.

If you are asking about "would be nice," then I would make both primitive
operations of the access type interface. And I certainly don't want any
more reserved dictionary words. It became a plague in Ada.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de