How to return an empty aggregate

In my previous post I had the following:

      type Concrete is new Middle with null record;

      function Make_Concrete return Concrete is
         C : Concrete;
      begin
         return C;
      end Make_Concrete;

I would like to return the empty(?) aggregate instead of the dummy
local variable.
Is there a way to do this?

The following:

        return Concrete' (others => <>);

results in segmentation fault on my system (compiler version as
before).

Extended return with null statement works fine, but I would like to
understand the language corners involved with the aggregate.

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