Re: [PATCH] uaccess: rust: add strncpy_from_user

[Alice Ryhl <aliceryhl@google.com>]

On Thu, Apr 24, 2025 at 06:38:52PM +0200, Miguel Ojeda wrote:
> On Thu, Apr 24, 2025 at 5:18 PM Alice Ryhl <aliceryhl@google.com> wrote:
> >
> > +    if res < 0 {
> > +        Err(Error::from_errno(res as i32))
> > +    } else {
> > +        #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)]
> > +        assert!(res <= len);
> > +        Ok(res as usize)
> > +    }
> 
> What about:
> 
>     if res < 0 {
>         return Err(...);
>     }
> 
>     overflow_assert!(res <= len);
>     Ok(res as usize)
> 
> That follows a bit better what is usually done on the C side, in using
> early returns (especially for error paths) and in avoiding local
> `#ifdef`s.

Sure, that looks good to me.

> Of course, we can leave this `overflow_assert!` to a different patch
> later on with this code as an example use case, or a good first issue
> etc. It also allows to document it etc. Happy to send it or create the
> issue.
> 
> (I wrote that instead of `assert_overflow!` because it follows the
> `{static,debug}_assert!` patterns, i.e. it changes more the "kind" of
> assert rather than asserting a particular thing, like `_eq!` or
> `_same_type!`).

Sounds like a good good-first-issue.

Alice