T& operator*() const noexcept;
T* operator->() const noexcept;
Dereferences the stored pointer. The behavior is undefined if the stored pointer is null.
 Return value
T is a (possibly cv-qualified)
void, it is unspecified whether function (1) is declared.
If either function is declared despite being unspecified, it is unspecified what its return type is, except that the declaration (although not necessarily the definition) of the function is guaranteed to be legal. This makes it possible to instantiate std::shared_ptr<void>.
a = 10 a = 10
 See also
| returns the stored pointer |
(public member function)