For actual correctness verification in the strong sense, you'd need to start from a specification written in a formal language so that it's machine checkable, which if I had to guess not even win.rar GmbH has.
From a philosophical perspective, there's no way to know that any piece of software is truly correct without formal verification.
But in the present, non-philosophical context, it's obvious that what we mean is, colloquially, "how well-tested is this against a variety of edge-case files which the official winrar handles correctly? Is there a test suite, and how robust is it? Plenty of software that claims to be compatible with the rar format, doesn't actually successfully read all rar files."
It's also equally obvious, in the present context, that we would prefer these steps to have been taken by the author of the software before we install it and run it on our own computers and data. The parent commenter wasn't just asking about the software's correctness for the sake of academic curiosity.
I don't know how all these test cases were generated, but at least some of them seem to have been copied (with attribution) from the test suites of earlier FOSS RAR implementations.
The ideal would be to test it against a representative corpus of real-world legacy RAR files, but I'm not sure where you'd find one.
Added, later: hey you changed your comment, added a whole paragraph.
I was immediately proven right once I pressed "update". That said, I have now deleted my snarky response that followed. Not in the game of capitalizing off of the human equivalent of a race condition.
I should make a browser addon to delay posting, this is the 2nd time this happens in the past few days.
Edit:
Nevermind, it's already a feature built into the site. Turned it on. I wonder if it applies to edits also...
Nope, doesn't seem to. Oh well, should still help.
use std::fs::File;
use std::io::prelude::*;
fn main() -> std::io::Result<()> {
let mut file = File::create("content.txt")?;
file.write_all(b"3!")?;
Ok(())
}No, it doesn't even need to compile. The mere fact that it's in Rust means it's correct.