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macro to use syn Date: Fri, 4 Sep 2026 16:32:28 +0100 Message-ID: <20260904153226.40210-3-jackwh.whitehorn@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Rewrites the fmt! macro to use `syn` for parsing, also adds support for trailing commas in fmt! and related macros. I've checked that a range of rust modules (android binder, nova core, samples) still compile and tested the behaviour is still correct using a modified rust_print module. Signed-off-by: Jack Whitehorn Suggested-by: Alice Ryhl Suggested-by: Miguel Ojeda Link: https://github.com/Rust-for-Linux/linux/issues/1227 Link: https://github.com/Rust-for-Linux/linux/issues/1172 --- rust/macros/fmt.rs | 161 ++++++++++++++++++++++++--------------------- rust/macros/lib.rs | 4 +- 2 files changed, 90 insertions(+), 75 deletions(-) diff --git a/rust/macros/fmt.rs b/rust/macros/fmt.rs index ce6c7249305a..994a2924e6fb 100644 --- a/rust/macros/fmt.rs +++ b/rust/macros/fmt.rs @@ -1,96 +1,109 @@ // SPDX-License-Identifier: GPL-2.0 -use std::collections::BTreeSet; +use std::collections::HashMap; -use proc_macro2::{Ident, TokenStream, TokenTree}; +use proc_macro2::{Ident, TokenStream}; use quote::quote_spanned; +use syn::{ + ext::IdentExt, + parse::{Parse, ParseStream}, + parse_quote, Expr, LitStr, Result, Token, +}; -/// Please see [`crate::fmt`] for documentation. -pub(crate) fn fmt(input: TokenStream) -> TokenStream { - let mut input = input.into_iter(); - - let first_opt = input.next(); - let first_owned_str; - let mut names = BTreeSet::new(); - let first_span = { - let Some((mut first_str, first_span)) = (match first_opt.as_ref() { - Some(TokenTree::Literal(first_lit)) => { - first_owned_str = first_lit.to_string(); - Some(first_owned_str.as_str()).and_then(|first| { - let first = first.strip_prefix('"')?; - let first = first.strip_suffix('"')?; - Some((first, first_lit.span())) - }) - } - _ => None, - }) else { - return first_opt.into_iter().chain(input).collect(); +pub(crate) struct FormatArgs { + format_string: LitStr, + positional_args: Vec, + named_args: HashMap, +} + +impl Parse for FormatArgs { + fn parse(input: ParseStream<'_>) -> Result { + let format_string: LitStr = input.parse()?; + + let mut args = FormatArgs { + format_string, + positional_args: Vec::new(), + named_args: HashMap::new(), }; - // Parse `identifier`s from the format string. - // - // See https://doc.rust-lang.org/std/fmt/index.html#syntax. - while let Some((_, rest)) = first_str.split_once('{') { - first_str = rest; - if let Some(rest) = first_str.strip_prefix('{') { - first_str = rest; - continue; + if input.is_empty() { + return Ok(args); + } + input.parse::()?; + + while !input.is_empty() && !input.peek2(Token![=]) { + args.positional_args.push(input.parse()?); + if input.is_empty() { + return Ok(args); } - if let Some((name, rest)) = first_str.split_once('}') { - first_str = rest; - let name = name.split_once(':').map_or(name, |(name, _)| name); - if !name.is_empty() && !name.chars().all(|c| c.is_ascii_digit()) { - names.insert(name); - } + input.parse::()?; + } + + while !input.is_empty() { + let name: Ident = input.call(Ident::parse_any)?; + input.parse::()?; + let value: Expr = input.parse()?; + args.named_args.insert(name, value); + + if input.is_empty() { + return Ok(args); } + input.parse::()?; } - first_span - }; - let adapter = quote_spanned!(first_span => ::kernel::fmt::Adapter); + return Ok(args); + } +} - let mut args = TokenStream::from_iter(first_opt); +/// Please see [`crate::fmt`] for documentation. +pub(crate) fn fmt(args: FormatArgs) -> Result { + let FormatArgs { + format_string, + positional_args, + mut named_args, + } = args; + + let span = format_string.span(); + + // Add inline parameters as named arguments, so they are adapted appropriately + // Input: fmt!("{name}") + // Output: fmt!("{name}", name = ::kernel::fmt::Adapter(&(name))) { - let mut flush = |args: &mut TokenStream, current: &mut TokenStream| { - let current = std::mem::take(current); - if !current.is_empty() { - let (lhs, rhs) = (|| { - let mut current = current.into_iter(); - let mut acc = TokenStream::new(); - while let Some(tt) = current.next() { - // Split on `=` only once to handle cases like `a = b = c`. - if matches!(&tt, TokenTree::Punct(p) if p.as_char() == '=') { - names.remove(acc.to_string().as_str()); - // Include the `=` itself to keep the handling below uniform. - acc.extend([tt]); - return (Some(acc), current.collect::()); - } - acc.extend([tt]); - } - (None, acc) - })(); - args.extend(quote_spanned!(first_span => #lhs #adapter(&(#rhs)))); + let format_string = format_string.value(); + let mut format_string = format_string.as_str(); + while let Some((_, rest)) = format_string.split_once('{') { + format_string = rest; + + if let Some(rest) = format_string.strip_prefix('{') { + format_string = rest; + continue; } - }; - let mut current = TokenStream::new(); - for tt in input { - match &tt { - TokenTree::Punct(p) if p.as_char() == ',' => { - flush(&mut args, &mut current); - &mut args + if let Some((name, rest)) = format_string.split_once('}') { + format_string = rest; + let name = name.split_once(':').map_or(name, |(name, _)| name); + if !name.is_empty() && !name.chars().all(|c| c.is_ascii_digit()) { + let ident = Ident::new(name, span); + let expr = parse_quote!(#ident); + named_args.entry(ident).or_insert(expr); } - _ => &mut current, } - .extend([tt]); } - flush(&mut args, &mut current); } - for name in names { - let name = Ident::new(name, first_span); - args.extend(quote_spanned!(first_span => , #name = #adapter(&#name))); - } + // Wrap positional and named arguments with `kernel::fmt::Adapter` + let adapter = quote_spanned!(span => ::kernel::fmt::Adapter); + let positional_args = positional_args + .into_iter() + .map(|value| quote_spanned!(span => #adapter(&(#value)))); + let named_args = named_args + .into_iter() + .map(|(name, value)| quote_spanned!(span => #name = #adapter(&(#value)))); + + let args = [quote_spanned!(span => #format_string)] + .into_iter() + .chain(positional_args) + .chain(named_args); - quote_spanned!(first_span => ::core::format_args!(#args)) + Ok(quote_spanned!(span => ::core::format_args!(#(#args),*))) } diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index 24f96feaeb34..730607775a70 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -277,7 +277,9 @@ pub fn export(attr: TokenStream, input: TokenStream) -> TokenStream { /// [`pr_info!`]: ../kernel/macro.pr_info.html #[proc_macro] pub fn fmt(input: TokenStream) -> TokenStream { - fmt::fmt(input.into()).into() + fmt::fmt(parse_macro_input!(input)) + .unwrap_or_else(|e| e.into_compile_error()) + .into() } /// Concatenate two identifiers. -- 2.55.0