Macro declare_get_sys_info_function 

macro_rules! declare_get_sys_info_function {
    ($(#[$meta:meta])* $function_name:ident, $ok_ret_type:ty, $flag:expr) => { ... };
}

Generates a function with the following signature:

pub fn $function_name() -> Result<Option<$ok_ret_type>, BootRomApiErrorCode>

Which safely calls get_sys_info using the flag provided via the flag argument. flag is an expression that must resolve to a const variant of GetSysInfoFlag