Re: [PATCH v2 2/3] rust: alloc: add Vec::resize method

[Tamir Duberstein]

On Tue, Mar 18, 2025 at 8:50 PM Benno Lossin <benno.lossin@xxxxxxxxx> wrote:
>
> On Tue Mar 18, 2025 at 9:12 PM CET, Tamir Duberstein wrote:
> > On Sun, Mar 16, 2025 at 7:17 AM Andrew Ballance
> > <andrewjballance@xxxxxxxxx> wrote:
> >> +    pub fn resize(&mut self, new_len: usize, value: T, flags: Flags) -> Result<(), AllocError> {
> >> +        if new_len > self.len() {
> >> +            self.extend_with(new_len - self.len(), value, flags)
> >> +        } else {
> >> +            self.truncate(new_len);
> >> +            Ok(())
> >> +        }
> >> +    }
> >
> > You can avoid underflow checking in debug builds by using `checked_sub`:
>
> `checked_sub` doesn't only avoid underflow in debug builds, but rather
> in all builds. But the code below is a good suggestion.

Yes, I know :)

I included that language because the underflow check is likely
optimized away in release builds.

Tamir