[PATCH v10 2/5] rust: support formatting of foreign types

[Alice Ryhl]

On Tue, May 27, 2025 at 12:18 AM Tamir Duberstein <tamird at gmail.com> wrote:
> > > +}
> > > +
> > > +fn make_ident<'a, T: IntoIterator<Item = &'a str>>(
> > > +    span: Span,
> > > +    names: T,
> > > +) -> impl Iterator<Item = TokenTree> + use<'a, T> {
> > > +    names.into_iter().flat_map(move |name| {
> > > +        [
> > > +            TokenTree::Punct(Punct::new(':', Spacing::Joint)),
> > > +            TokenTree::Punct(Punct::new(':', Spacing::Alone)),
> > > +            TokenTree::Ident(Ident::new(name, span)),
> > > +        ]
> > > +    })
> > > +}
> > > diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> > > index d31e50c446b0..fa956eaa3ba7 100644
> > > --- a/rust/macros/lib.rs
> > > +++ b/rust/macros/lib.rs
> > > @@ -10,6 +10,7 @@
> > >  mod quote;
> > >  mod concat_idents;
> > >  mod export;
> > > +mod fmt;
> > >  mod helpers;
> > >  mod kunit;
> > >  mod module;
> > > @@ -196,6 +197,24 @@ pub fn export(attr: TokenStream, ts: TokenStream) -> TokenStream {
> > >      export::export(attr, ts)
> > >  }
> > >
> > > +/// Like [`core::format_args!`], but automatically wraps arguments in [`kernel::fmt::Adapter`].
> > > +///
> > > +/// This macro allows generating `core::fmt::Arguments` while ensuring that each argument is wrapped
> > > +/// with `::kernel::fmt::Adapter`, which customizes formatting behavior for kernel logging.
> > > +///
> > > +/// Named arguments used in the format string (e.g. `{foo}`) are detected and resolved from local
> > > +/// bindings. All positional and named arguments are automatically wrapped.
> > > +///
> > > +/// This macro is an implementation detail of other kernel logging macros like [`pr_info!`] and
> > > +/// should not typically be used directly.
> > > +///
> > > +/// [`kernel::fmt::Adapter`]: ../kernel/fmt/struct.Adapter.html
> > > +/// [`pr_info!`]: ../kernel/macro.pr_info.html
> > > +#[proc_macro]
> > > +pub fn fmt(input: TokenStream) -> TokenStream {
> >
> > I'm wondering if we should name this `format_args` instead in order to
> > better communicate that it's a replacement for `core::format_args!`.
>
> Unfortunately that introduces ambiguity in cases where
> kernel::prelude::* is imported because core::format_args is in core's
> prelude.

I'm pretty sure that glob imports are higher priority than the core
prelude? Or is this because there are macros that now incorrectly use
kernel::prelude::format_args when they should use the one from core?

Alice