Joe Thornber 1481ed0f8a [ref_counter] Make ref_counter an abstract base class.
Forces people to override correctly.

Also make no_op_ref_counter final.
2020-04-08 12:22:28 +01:00
..
2020-04-08 12:12:59 +01:00
2020-04-08 12:12:59 +01:00
2019-03-29 12:56:31 +00:00