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Date: Mon, 24 Apr 2023 08:11:43 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...ts.linux.dev, Benno Lossin <benno.lossin@...ton.me>,
Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH 3/4] rust: macros: replace Self with the concrete type in #[pin_data]
When using `#[pin_data]` on a struct that used `Self` in the field
types, a type error would be emitted when trying to use `pin_init!`.
Since an internal type would be referenced by `Self` instead of the
defined struct.
This patch fixes this issue by replacing all occurrences of `Self` in
the `#[pin_data]` macro with the concrete type circumventing the issue.
Since rust allows type definitions inside of blocks, which are
expressions, the macro also checks for these and emits a compile error
when it finds `trait`, `enum`, `union`, `struct` or `impl`. These
keywords allow creating new `Self` contexts, which conflicts with the
current implementation of replacing every `Self` ident. If these were
allowed, some `Self` idents would be replaced incorrectly.
Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
Reported-by: Alice Ryhl <aliceryhl@...gle.com>
---
rust/macros/pin_data.rs | 108 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 104 insertions(+), 4 deletions(-)
diff --git a/rust/macros/pin_data.rs b/rust/macros/pin_data.rs
index c593b05d9e8c..6d58cfda9872 100644
--- a/rust/macros/pin_data.rs
+++ b/rust/macros/pin_data.rs
@@ -1,7 +1,7 @@
// SPDX-License-Identifier: Apache-2.0 OR MIT
use crate::helpers::{parse_generics, Generics};
-use proc_macro::TokenStream;
+use proc_macro::{Group, Punct, Spacing, TokenStream, TokenTree};
pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
// This proc-macro only does some pre-parsing and then delegates the actual parsing to
@@ -12,16 +12,116 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
impl_generics,
ty_generics,
},
- mut rest,
+ rest,
) = parse_generics(input);
+ // The struct definition might contain the `Self` type. Since `__pin_data!` will define a new
+ // type with the same generics and bounds, this poses a problem, since `Self` will refer to the
+ // new type as opposed to this struct definition. Therefore we have to replace `Self` with the
+ // concrete name.
+
+ // Errors that occur when replacing `Self` with `struct_name`.
+ let mut errs = TokenStream::new();
+ // The name of the struct with ty_generics.
+ let struct_name = rest
+ .iter()
+ .skip_while(|tt| !matches!(tt, TokenTree::Ident(i) if i.to_string() == "struct"))
+ .nth(1)
+ .and_then(|tt| match tt {
+ TokenTree::Ident(_) => {
+ let tt = tt.clone();
+ let mut res = vec![tt];
+ if !ty_generics.is_empty() {
+ // We add this, so it is maximally compatible with e.g. `Self::CONST` which
+ // will be replaced by `StructName::<$generics>::CONST`.
+ res.push(TokenTree::Punct(Punct::new(':', Spacing::Joint)));
+ res.push(TokenTree::Punct(Punct::new(':', Spacing::Alone)));
+ res.push(TokenTree::Punct(Punct::new('<', Spacing::Alone)));
+ res.extend(ty_generics.iter().cloned());
+ res.push(TokenTree::Punct(Punct::new('>', Spacing::Alone)));
+ }
+ Some(res)
+ }
+ _ => None,
+ })
+ .unwrap_or_else(|| {
+ // If we did not find the name of the struct then we will use `Self` as the replacement
+ // and add a compile error to ensure it does not compile.
+ errs.extend(
+ "::core::compile_error!(\"Could not locate type name.\");"
+ .parse::<TokenStream>()
+ .unwrap(),
+ );
+ "Self".parse::<TokenStream>().unwrap().into_iter().collect()
+ });
+ let impl_generics = impl_generics
+ .into_iter()
+ .flat_map(|tt| replace_self_and_deny_type_defs(&struct_name, tt, &mut errs))
+ .collect::<Vec<_>>();
+ let mut rest = rest
+ .into_iter()
+ .flat_map(|tt| {
+ // We ignore top level `struct` tokens, since they would emit a compile error.
+ if matches!(&tt, TokenTree::Ident(i) if i.to_string() == "struct") {
+ vec![tt]
+ } else {
+ replace_self_and_deny_type_defs(&struct_name, tt, &mut errs)
+ }
+ })
+ .collect::<Vec<_>>();
// This should be the body of the struct `{...}`.
let last = rest.pop();
- quote!(::kernel::__pin_data! {
+ let mut quoted = quote!(::kernel::__pin_data! {
parse_input:
@args(#args),
@sig(#(#rest)*),
@impl_generics(#(#impl_generics)*),
@ty_generics(#(#ty_generics)*),
@body(#last),
- })
+ });
+ quoted.extend(errs);
+ quoted
+}
+
+/// Replaces `Self` with `struct_name` and errors on `enum`, `trait`, `struct` `union` and `impl`
+/// keywords.
+///
+/// The error is appended to `errs` to allow normal parsing to continue.
+fn replace_self_and_deny_type_defs(
+ struct_name: &Vec<TokenTree>,
+ tt: TokenTree,
+ errs: &mut TokenStream,
+) -> Vec<TokenTree> {
+ match tt {
+ TokenTree::Ident(ref i)
+ if i.to_string() == "enum"
+ || i.to_string() == "trait"
+ || i.to_string() == "struct"
+ || i.to_string() == "union"
+ || i.to_string() == "impl" =>
+ {
+ errs.extend(
+ format!(
+ "::core::compile_error!(\"Cannot use `{i}` inside of struct definition with \
+ `#[pin_data]`.\");"
+ )
+ .parse::<TokenStream>()
+ .unwrap()
+ .into_iter()
+ .map(|mut tok| {
+ tok.set_span(tt.span());
+ tok
+ }),
+ );
+ vec![tt]
+ }
+ TokenTree::Ident(i) if i.to_string() == "Self" => struct_name.clone(),
+ TokenTree::Literal(_) | TokenTree::Punct(_) | TokenTree::Ident(_) => vec![tt],
+ TokenTree::Group(g) => vec![TokenTree::Group(Group::new(
+ g.delimiter(),
+ g.stream()
+ .into_iter()
+ .flat_map(|tt| replace_self_and_deny_type_defs(struct_name, tt, errs))
+ .collect(),
+ ))],
+ }
}
--
2.40.0
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