Re: [PATCH v2 1/5] rust: add warn_on_err macro

["Gary Guo" <gary@garyguo.net>]

On Tue Apr 21, 2026 at 7:16 AM BST, Alexandre Courbot wrote:
> While we already have the `warn_on` macro, a common usage pattern in
> Rust is to check whether a `Result` is an error. Add a helper macro that
> allows this.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  rust/kernel/bug.rs | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
> index ed943960f851..2fefc0aeef81 100644
> --- a/rust/kernel/bug.rs
> +++ b/rust/kernel/bug.rs
> @@ -130,3 +130,13 @@ macro_rules! warn_on {
>          cond
>      }};
>  }
> +
> +/// Report a warning if `res` is an error and return it unmodified.
> +#[macro_export]
> +macro_rules! warn_on_err {
> +    ($res:expr) => {{
> +        let res = $res;
> +        let _ = $crate::warn_on!(res.is_err());
> +        res
> +    }};
> +}


I think `warn_on_err` could just be expressed as

    res.inspect_err(|_| warn_on!(true))

Best,
Gary