On Tue Dec 2, 2025 at 8:25 AM JST, Timur Tabi wrote: > On Wed, 2025-11-19 at 12:36 +0900, Alexandre Courbot wrote: >> You can use the `Alignment` type here, as the rest of the code does: >> >> let size = num::usize_as_u64(obj.size()) >> .align_up(Alignment::new::<GSP_PAGE_SIZE>())?; >> >> Now `align_up` returns an error in case of overflow, that we will need >> to pass down to the caller by changing the return type of `new`. It is a >> bit annoying, but better than the behavior of `next_mutiple_of` in such >> a case, which is to panic. :) > > I see your point, but these are u64s that we're talking about. The only way > next_mutiple_of() can > panic is if obj.size() is greater than 0xFFFFFFFFFFFFF000, which is not > possible. > > I would say in this case, a panic is preferable to a convoluted error return > that will never be > exercised, because failure here indicates a coding error, not an input error.
The input data is a usize, so technically we could get an input that triggers that error. I know it's a very edge case, and clearly indicates a bug, but the general rule is: don't panic the kernel. And in Rust, if possible, don't even let me compiler insert panic-handling code. If you don't want to change the return type of the method, then maybe use `unwrap_or` and `inspect_err` to print an error before returning e.g. `0`. But others have already thought "naah, that's never gonna happen" and got burnt very publicly [1], so let's learn from that. :P [1] https://blog.cloudflare.com/18-november-2025-outage/
