Gettable serial port option requirements

In the table below, X denotes a serial port option class, a denotes a value of X, ec denotes a value of type error_code, and s denotes a value of implementation-defined type storage (where storage is the type DCB on Windows and termios on POSIX platforms), and u denotes an identifier.

Table 19. GettableSerialPortOption requirements

expression	type	assertion/note pre/post-conditions
`const` `storage``& u = s;` `a.load(u, ec);`	`error_code`	Retrieves the value of the serial port option from the storage. If successful, sets `ec` such that `!ec` is true. If an error occurred, sets `ec` such that `!!ec` is true. Returns `ec`.