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
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2020-04-08 12:12:59 +01:00
2017-10-05 13:47:10 +01:00
2013-08-15 16:26:17 +01:00