C++11 interface pure virtual destructor

Question

UPD. There is a mark that it is a duplicate of this question. But in that question OP asks HOW to use default to define pure virtual destructor. Th

Answer 1

All I could find was:

§12.4 (5.9)

A destructor can be declared virtual (10.3) or pure virtual (10.4); if any objects of that class or any derived class are created in the program, the destructor shall be defined. If a class has a base class with a virtual destructor, its destructor (whether user- or implicitly-declared) is virtual.

leading to:

§10.4 (the class is now abstract)

10.4 (2) says:

A pure virtual function need be defined only if called with, or as if with (12.4), the qualified-id syntax (5.1).

But the narrative on destructors in §12.4 talks about destructors always being called as if by their fully qualified name (in order to prevent ambiguity).

Which means that:

• the destructor must be defined, even if pure virtual, and

• the class is now abstract.