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Newsgroups: comp.lang.ada
Date: Sat, 19 Oct 2013 23:29:05 -0700 (PDT)
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Subject: Re: Possible GNAT problem with aliased parameters.
From: Shark8 <onewingedshark@gmail.com>
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Xref: number.nntp.dca.giganews.com comp.lang.ada:183676
Date: 2013-10-19T23:29:05-07:00
List-Id: <comp.lang.ada>

On Saturday, October 19, 2013 3:17:17 PM UTC-6, Shark8 wrote:
>=20
>=20

My solution was to use renames on the parameters and then allocate new memo=
ry for the copies. It's not great, but there's no accessibility errors... I=
'm not sure if I ought to use Unchecked_Deallocate and/or Finalize here tho=
ugh. (Also, pools might be nice to ensure that things really do get cleaned=
 up upon scope-exit.)

-- In the Spec:
------------------------------------
    Function Create (
		    Location_Name : String; -- Unique ID-string
		    North, South, East, West,
		    Up, Down : Story_Location'Class:=3D Nowhere
		    ) return Story_Location;

-- In the Body:
------------------------------------
    Function Create (
		    Location_Name : String;
		    North, South, East, West,
		    Up, Down : Maze'Class:=3D None
		    ) return Maze is
=09
	N : Maze renames Maze(North);
	S : Maze renames Maze(South);
	E : Maze renames Maze(East);
	W : Maze renames Maze(West);
	U : Maze renames Maze(Up);
	D : Maze renames Maze(Down);
=09
	Subtype Node is Maze( Length_N =3D> Location_Name'Length );
    begin
	    Return Result : Node do
	    Result.Name :=3D Location_Name;
	    Result.Exits:=3D
		(
		   Maze.North =3D>
		     (if N =3D Nowhere then null else New Maze'( N )),
		   Maze.South =3D>
		     (if S =3D Nowhere then null else New Maze'( S )),
		   Maze.East =3D>
		     (if E =3D Nowhere then null else New Maze'( E )),
		   Maze.West =3D>
		     (if W =3D Nowhere then null else New Maze'( W )),
		   Maze.Up =3D>=20
		     (if U =3D Nowhere then null else New Maze'( U )),
		   Maze.Down =3D>
		     (if D =3D Nowhere then null else New Maze'( D )),
		   others =3D> null
		);
	End return;
    end;