https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407
--- Comment #21 from Jonathan Wakely <redi at gcc dot gnu.org> --- P.S. it's arguable whether abstract base classes should be copyable in the first place: https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rc-copy-virtual https://github.com/isocpp/CppCoreGuidelines/issues/1151
