I have a Shape class containing potentially many vertices, and I was contemplating making copy-constructor/copy-assignment private to prevent accidental needless copying of my heavyweight class (for example, passing by value instead of by reference).

To make a copy of Shape, one would have to deliberately call a "clone" or "duplicate" method.

Is this good practice? I wonder why STL containers don't use this approach, as I rarely want to pass them by value.