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Comment by prerok | Hacker News Reader

Out of bounds exception is ok to crash the program. User input error is not ok to crash the program.

I could go into many more examples but I hope I am understood. I think these hard-coded definition of ranges at compile time are causes of far more issues than they solve.

Let's take a completely different example: size of a field in a database for a surname. How much is enough? Turns out 128 varchars is not enough, so now they've set it to 2048 (not a project I work(ed) on, but am familiar with). Guess what? Not in our data set, but theoretically, even that is not enough.

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> Out of bounds exception is ok to crash the program. User input error is not ok to crash the program.

So you validate user input, we've known how to do that for decades. This is a non-issue. You won't crash the program if you require temperatures to be between 0 and 1000 K and a user puts in 1001, you'll reject the user input.

If that user input crashes your program, you're not a very good programmer, or it's a very early prototype.

I think, if I am following things correctly, you will find that there's a limit to the "validate user input" argument - especially when you think of scenarios where multiple pieces of user input are gathered together and then have mathematical operations applied to them.

eg. If the constraint is 0..200, and the user inputs one value that is being multiplied by our constant, it's trivial to ensure the user input is less than the range maximum divided by our constant.

However, if we are having to multiply by a second, third... and so on.. piece of user input, we get to the position where we have to divide our currently held value by a piece of user input, check that the next piece of user input isn't higher, and then work from there (this assumes that the division hasn't caused an exception, which we will need to ensure doesn't happen.. eg if we have a divide by zero going on)

I mean, yeah. If you do bad math you'll get bad results and potentially crashes. I was responding to someone who was nonsensically ignoring that we validate user input rather than blindly putting it into a variable. Your comment seems like a non sequitur in this discussion. It's not like the risk you describe is unique to range constrained integer types, which is what was being discussed. It can happen with i32 and i64, too, if you write bad code.

Hmm, I was really pointing at the fact that once you get past a couple of pieces of user input, all the validation in the world isn't going to save you from the range constraints.

Assuming you want a good faith conversation, then the idea that there's bad math involved seems a bit ludicrous

I believe that the solution here is to make crashes "safe" eg with a supervisor process that should either never crash or be resumed quickly and child processes that handle operations like user inputs.

This together with the fact that the main benefit of range types is on the consumption side (ie knowing that a PositiveInt is not 0) and it is doable to use try-catch or an equivalent operation at creation time

For some reason your reply (which I think is quite good) makes me think of the adage "Be liberal in what you accept, and conservative in what you send" (Postels law).

Speaking as someone that's drunk the Go kool aid - the (general) advice is not to panic when it's a user input problem, only when it's a programmers problem (which I think is a restatement of your post)

Happens with DB constraints all the time, user gets an error and at least his session, if not whole process, crashes. And yes that too is considered bad code that needs fixing.

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