Cancel all operations associated with the signal set.
void cancel( asio::error_code & ec);
This function forces the completion of any pending asynchronous wait
operations against the signal set. The handler for each cancelled operation
will be invoked with the asio::error::operation_aborted
error code.
Cancellation does not alter the set of registered signals.
Set to indicate what error occurred, if any.
If a registered signal occurred before cancel()
is called, then the handlers for asynchronous
wait operations will:
These handlers can no longer be cancelled, and therefore are passed an error code that indicates the successful completion of the wait operation.