the compiler knows the failure modes. if the file doesn't exist, the printf isn't reachable. if the file isn't at least X bytes long, the printf isnt' reachable if bytes 10-20 can't be parsed as a number the printf isn't reachable.

it's just showing if you get through these 50 checks, by the time you get to printf the bytes will have been converted to what you need, or the program will have already errored out.