Free'ing extended types

[Jonas Nygren <ehsjony@ehs.ericsson.se>]

I read the following in the RM on unchecked_deallocation:

13.11.2(16)
     .... The execution of a call to an instance of 
     Unchecked_Deallocation is erroneous if the object 
     was created other than by an allocator for an 
     access type whose pool is Name'Storage_Pool. 

I don't quite understand what is written but have a
vague feeling that the code example below could be
labeled 'erroneous execution' by the above paragraph.

Perhaps somebody can answer - is the following code legal:

type a is tagged with .........;
type ap is access all a'class;

procedure free is new unchecked_deallocation(a, ap);

tybe b is new a with .........; -- a is extended

p : ap := new b;

free(p);

Are 'a' and 'b' belonging to the same Name'Storage_Pool?

/jonas