Annex F (informative) Core undefined behavior [ub]

F.2 [basic]: Basics [ub.basic]

F.2.10[ub:lifetime.outside.glvalue.virtual]
Specified in: [basic.life]

Behavior is undefined if a glvalue referring to an object outside of its lifetime is bound to a reference to a virtual base class.
[Example 1: struct B {}; struct D : virtual B { }; void f() { D d; d.~D(); B& b = d; // undefined behavior } — end example]