std::promise<R>::promise (3) - Linux Manuals
promise(); (1) (since C++11)
template< class Alloc > (2) (since C++11)
promise( std::allocator_arg_t, const Alloc& alloc );
promise( promise&& other ) noexcept; (3) (since C++11)
promise( const promise& other ) = delete; (4) (since C++11)
Constructs a promise object.
1) Default constructor. Constructs the promise with an empty shared state.
2) Constructs the promise with an empty shared state. The shared state is allocated using alloc. Alloc must meet the requirements of Allocator.
3) Move constructor. Constructs the promise with the shared state of other using move semantics. After construction, other has no shared state.
4) promise is not copyable.
alloc - allocator to use to allocate the shared state
other - another promise to acquire the state from