Generics and parameter modes

[Martin Dowie <martin@dowie-cs.demon.co.uk>]

i have an instance of a package similar to the generic listed below.
when calling the 'size' routine the actual parameter is passed by copy
and not by reference as i had expected. this is really annoying as the
data object is a few hundred kbytes in size! is there anything in Ada95
that allows/requires this?

generic
    type an_item is private;
    maximum_number_of_items : positive;
package generic_list is
    subtype a_number_of_items is natural range 0 ..
maximum_number_of_items;
    subtype an_item_index is natural range 1 .. maximum_number_of_items;

    type a_list is private;
    -- Lots of other stuff...
    function size (list : in a_list) return a_number_of_items;
private
    type an_array_of_items is array (an_item_index) of an_item;
    type a_list is record
        current_size, current_item : a_number_of_items;
        items : an_array_of_items;
    end record;
end generic_list;

the type used in the declaration is a variant record which it self
contains variant fields within a number of the variant branches (approx.
300 bytes storage required).

i'm using Rational Apex v3 and have tried a mini version at home (using
the above) and ObjectAda seems to pass it by reference (not 100% on this
as my Intel assembler knowledge is zilch!).