Unchecked_Deallocation of class-wide objects

[Maciej Sobczak <see.my.homepage@gmail.com>]

Is it legal and safe to deallocate class-wide objects?

The problem is that such an object is allocated with its concrete
type, whereas deallocation is defined for its class-wide type.
Consider:

type Shape is tagged private;
type Shape_Access is access Shape'Class;

procedure Free_Shape is new Ada.Unchecked_Deallocation
   (Object => Shape'Class, Name => Shape_Access);
-- ...

type Circle is new Shape with ...
-- ...
C : Shape_Access := new Circle;
-- ...
Free_Shape (C);

Is the Circle object allocated on the Shape-wide storage pool? From
what I understand, this is the condition for the above to work
properly.
What if Circle is allocated for some Circle_Access type which is then
converted to Shape_Access? Can it be safely deallocated?

I believe that the above is a pretty standard use-case, but I would
like to confirm that. Unfortunately, AARM is not very explicit about
this subject.

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com

Database Access Library for Ada: www.inspirel.com/soci-ada