cpp/thread/promise/set value

@1-3@ Atomically stores the into the shared state and makes the state ready. @4@ Makes the state ready

The operation behaves as though, set_exception, set_value_at_thread_exit, and set_exception_at_thread_exit acquire a single mutex associated with the promise object while updating the promise object.

An exception is thrown if there is no shared state or the shared state already stores a value or exception.

Calls to this function do not introduce data races with calls to get_future (therefore they need not synchronize with each other).

Return value
(none)

Exceptions
std on the following conditions:


 * has no shared state. The error code is set to.


 * The shared state already stores a value or exception. The error code is set to.

Additionally:

@1@ Any exception thrown by the copy constructor of @2@ Any exception thrown by the move constructor of