...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Destructs the owned object if no more handler_ptr
link to it.
~handler_ptr();
If *this
owns an object and it is the last handler_ptr
owning it, the object
is destroyed and the memory deallocated using the associated deallocator.