Special member functions (destructor) - C++11, 19 of n

destructor

1. A destructor is used to destroy objects of its class type. The address of a destructor shall not be taken. A destructor can be invoked for a const, volatile or const volatile object.const and volatile semantics are not applied on an object under destruction. They stop being in effect when the destructor for the most derived object  starts.
   
2. A defaulted destructor for a class X is defined as deleted if:
   
   • X is a union-like class that has a variant member with a non-trivial destructor
     
   • any of the non-static data members has class type M (or array thereof) and M has a deleted destructor or a destructor that is inaccessible from the defaulted destructor
     
   • any direct or virtual base class has a deleted destructor or a destructor that is inaccessible from the defaulted destructor
     
   • or, for a virtual destructor, lookup of the non-array deallocation function results in an ambiguity or in a function that is deleted or inaccessible from the defaulted destructor.
     
3. A destructor is trivial if it is not user-provided and if:
   
   • the destructor is not virtual,
     
   • all of the direct base classes of its class have trivial destructors, and
     
   • for all of the non-static data members of its class that are of class type (or array thereof), each such class has a trivial destructor.
     
4. If a class has a base class with a virtual destructor, its destructor (whether user- or implicitly-declared) is virtual.
   
5. destructor is implicitly invoked for constructed objects with thread storage duration at thread exit
   
6. Note:
   • During object construction (constructor), be very careful the objects referenced have been fully initialized.
   • In constructor/destructor, pay close attention to calling "virtual function, dynamic_cast, typeid". They usually will NOT work as expected. So don't call these functions or operators in constructor/destructor.