std::shared_ptr<T>::~shared_ptr (3) - Linux Manuals
If *this owns an object and it is the last shared_ptr owning it, the object is destroyed through the owned deleter.
After the destruction, the smart pointers that shared ownership with *this, if any, will report a use_count() that is one less than its previous value.
Unlike std::unique_ptr, the deleter of std::shared_ptr is invoked even if the managed pointer is null.
This section is incomplete
Reason: no example
destructor (public member function of std::weak_ptr<T>)