std::future::share
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | std::shared_future<T> share(); | ||
Transfers the shared state of *this, if any, to a std::shared_future object. Multiple std::shared_future objects may reference the same shared state, which is not possible with std::future.
After calling share on a std::future, valid() == false.
| Contents | 
[edit] Parameters
(none)
[edit] Return value
A std::shared_future object containing the shared state previously held by *this, if any, constructed as if by std::shared_future<T>(std:move(*this)).
[edit] Exceptions
noexcept specification:  
noexcept
  [edit] Example
| This section is incomplete Reason: no example | 
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior | 
|---|---|---|---|
| LWG 2556 | C++11 | share()requiresvalid()to betrue | requirement removed and made noexcept | 
[edit] See also
| (C++11) | waits for a value (possibly referenced by other futures) that is set asynchronously (class template) | 


