Comment by orthoxerox
2 hours ago
I wasn't in this class myself, but one prof at my alma mater started his "Programming 201" class with the simplest assignment: write a C program that accepts two integers from the user and prints their sum. It actually was the only assignment for the rest of the semester, since he has a test suite that would humiliate the students gently at first, but would ultimately pipe a billion nines into stdin as the first argument.
It's a little awkward, because you'd need to parse the strings in reverse, but if all you need to do is sum, you can do it one digit at a time, while at any given moment only handling only one character from each input string, a carry byte, and one output character.
Would be fun to write a program that arranges to send the input into dc(1) and just outsource the whole problem to Ken or Rob or whoever wrote it. :)
Perfect is the enemy of good.
Once a program is available over the internet, hackers are the enemy of merely good programs that don't perfectly validate their input.
"You have to get lucky every time. We only have to get lucky once".
Sure
But in this case, C is not "good". It is more like "abysmal". "Good" is just producing a correct result or error, with no ambiguity which case applied and no UB. "Perfect" is arguing over the most usable and elegant API for it.
Could you humor a coding noob--how do you deal with utterly insane inputs like that?
Arbitrary precision arithmetic (GMP, BigInteger, etc). Numbers can take arbitrary amounts of memory, instead of just a single machine word.
Crash and report an error.
You report an error and exit cleanly with a proper operating system error code. Crashing is a quick hack, acceptable for throwaway projects but not in software used long-term.
You first ask if you really need to.
Unless you're exposing it to the internet, ever, in the entire future history of the program. Then you kind of have to, in one form or another.