From 50426bde1577d17e61362bd199d487dbeb159110 Mon Sep 17 00:00:00 2001 From: Benno Lossin Date: Fri, 16 Jan 2026 11:54:20 +0100 Subject: [PATCH] rust: pin-init: rewrite `derive(Zeroable)` and `derive(MaybeZeroable)` using `syn` Rewrite the two derive macros for `Zeroable` using `syn`. One positive side effect of this change is that tuple structs are now supported by them. Additionally, syntax errors and the error emitted when trying to use one of the derive macros on an `enum` are improved. Otherwise no functional changes intended. For example: #[derive(Zeroable)] enum Num { A(u32), B(i32), } Produced this error before this commit: error: no rules expected keyword `enum` --> tests/ui/compile-fail/zeroable/enum.rs:5:1 | 5 | enum Num { | ^^^^ no rules expected this token in macro call | note: while trying to match keyword `struct` --> src/macros.rs | | $vis:vis struct $name:ident | ^^^^^^ Now the error is: error: cannot derive `Zeroable` for an enum --> tests/ui/compile-fail/zeroable/enum.rs:5:1 | 5 | enum Num { | ^^^^ error: cannot derive `Zeroable` for an enum Tested-by: Andreas Hindborg Reviewed-by: Gary Guo Signed-off-by: Benno Lossin --- rust/pin-init/internal/src/diagnostics.rs | 2 - rust/pin-init/internal/src/lib.rs | 9 +- rust/pin-init/internal/src/zeroable.rs | 155 ++++++++++------------ rust/pin-init/src/macros.rs | 124 ----------------- 4 files changed, 74 insertions(+), 216 deletions(-) diff --git a/rust/pin-init/internal/src/diagnostics.rs b/rust/pin-init/internal/src/diagnostics.rs index 555876c01babe..3bdb477c2f2b8 100644 --- a/rust/pin-init/internal/src/diagnostics.rs +++ b/rust/pin-init/internal/src/diagnostics.rs @@ -9,14 +9,12 @@ pub(crate) struct DiagCtxt(TokenStream); pub(crate) struct ErrorGuaranteed(()); impl DiagCtxt { - #[expect(dead_code)] pub(crate) fn error(&mut self, span: impl Spanned, msg: impl Display) -> ErrorGuaranteed { let error = Error::new(span.span(), msg); self.0.extend(error.into_compile_error()); ErrorGuaranteed(()) } - #[expect(dead_code)] pub(crate) fn with( fun: impl FnOnce(&mut DiagCtxt) -> Result, ) -> TokenStream { diff --git a/rust/pin-init/internal/src/lib.rs b/rust/pin-init/internal/src/lib.rs index 0e1a4724549df..4cc9b7b0cda14 100644 --- a/rust/pin-init/internal/src/lib.rs +++ b/rust/pin-init/internal/src/lib.rs @@ -11,6 +11,9 @@ #![allow(missing_docs)] use proc_macro::TokenStream; +use syn::parse_macro_input; + +use crate::diagnostics::DiagCtxt; mod diagnostics; mod helpers; @@ -30,10 +33,12 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream { #[proc_macro_derive(Zeroable)] pub fn derive_zeroable(input: TokenStream) -> TokenStream { - zeroable::derive(input.into()).into() + let input = parse_macro_input!(input); + DiagCtxt::with(|dcx| zeroable::derive(input, dcx)).into() } #[proc_macro_derive(MaybeZeroable)] pub fn maybe_derive_zeroable(input: TokenStream) -> TokenStream { - zeroable::maybe_derive(input.into()).into() + let input = parse_macro_input!(input); + DiagCtxt::with(|dcx| zeroable::maybe_derive(input, dcx)).into() } diff --git a/rust/pin-init/internal/src/zeroable.rs b/rust/pin-init/internal/src/zeroable.rs index d8a5ef3883f4b..05683319b0f7b 100644 --- a/rust/pin-init/internal/src/zeroable.rs +++ b/rust/pin-init/internal/src/zeroable.rs @@ -1,99 +1,78 @@ // SPDX-License-Identifier: GPL-2.0 -use crate::helpers::{parse_generics, Generics}; -use proc_macro2::{TokenStream, TokenTree}; +use proc_macro2::TokenStream; use quote::quote; +use syn::{parse_quote, Data, DeriveInput, Field, Fields}; -pub(crate) fn parse_zeroable_derive_input( - input: TokenStream, -) -> ( - Vec, - Vec, - Vec, - Option, -) { - let ( - Generics { - impl_generics, - decl_generics: _, - ty_generics, - }, - mut rest, - ) = parse_generics(input); - // This should be the body of the struct `{...}`. - let last = rest.pop(); - // Now we insert `Zeroable` as a bound for every generic parameter in `impl_generics`. - let mut new_impl_generics = Vec::with_capacity(impl_generics.len()); - // Are we inside of a generic where we want to add `Zeroable`? - let mut in_generic = !impl_generics.is_empty(); - // Have we already inserted `Zeroable`? - let mut inserted = false; - // Level of `<>` nestings. - let mut nested = 0; - for tt in impl_generics { - match &tt { - // If we find a `,`, then we have finished a generic/constant/lifetime parameter. - TokenTree::Punct(p) if nested == 0 && p.as_char() == ',' => { - if in_generic && !inserted { - new_impl_generics.extend(quote! { : ::pin_init::Zeroable }); - } - in_generic = true; - inserted = false; - new_impl_generics.push(tt); - } - // If we find `'`, then we are entering a lifetime. - TokenTree::Punct(p) if nested == 0 && p.as_char() == '\'' => { - in_generic = false; - new_impl_generics.push(tt); - } - TokenTree::Punct(p) if nested == 0 && p.as_char() == ':' => { - new_impl_generics.push(tt); - if in_generic { - new_impl_generics.extend(quote! { ::pin_init::Zeroable + }); - inserted = true; - } - } - TokenTree::Punct(p) if p.as_char() == '<' => { - nested += 1; - new_impl_generics.push(tt); - } - TokenTree::Punct(p) if p.as_char() == '>' => { - assert!(nested > 0); - nested -= 1; - new_impl_generics.push(tt); - } - _ => new_impl_generics.push(tt), +use crate::{diagnostics::ErrorGuaranteed, DiagCtxt}; + +pub(crate) fn derive( + input: DeriveInput, + dcx: &mut DiagCtxt, +) -> Result { + let fields = match input.data { + Data::Struct(data_struct) => data_struct.fields, + Data::Union(data_union) => Fields::Named(data_union.fields), + Data::Enum(data_enum) => { + return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum")); } + }; + let name = input.ident; + let mut generics = input.generics; + for param in generics.type_params_mut() { + param.bounds.insert(0, parse_quote!(::pin_init::Zeroable)); } - assert_eq!(nested, 0); - if in_generic && !inserted { - new_impl_generics.extend(quote! { : ::pin_init::Zeroable }); - } - (rest, new_impl_generics, ty_generics, last) + let (impl_gen, ty_gen, whr) = generics.split_for_impl(); + let field_type = fields.iter().map(|field| &field.ty); + Ok(quote! { + // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. + #[automatically_derived] + unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen + #whr + {} + const _: () = { + fn assert_zeroable() {} + fn ensure_zeroable #impl_gen () + #whr + { + #( + assert_zeroable::<#field_type>(); + )* + } + }; + }) } -pub(crate) fn derive(input: TokenStream) -> TokenStream { - let (rest, new_impl_generics, ty_generics, last) = parse_zeroable_derive_input(input); - quote! { - ::pin_init::__derive_zeroable!( - parse_input: - @sig(#(#rest)*), - @impl_generics(#(#new_impl_generics)*), - @ty_generics(#(#ty_generics)*), - @body(#last), - ); +pub(crate) fn maybe_derive( + input: DeriveInput, + dcx: &mut DiagCtxt, +) -> Result { + let fields = match input.data { + Data::Struct(data_struct) => data_struct.fields, + Data::Union(data_union) => Fields::Named(data_union.fields), + Data::Enum(data_enum) => { + return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum")); + } + }; + let name = input.ident; + let mut generics = input.generics; + for param in generics.type_params_mut() { + param.bounds.insert(0, parse_quote!(::pin_init::Zeroable)); } -} - -pub(crate) fn maybe_derive(input: TokenStream) -> TokenStream { - let (rest, new_impl_generics, ty_generics, last) = parse_zeroable_derive_input(input); - quote! { - ::pin_init::__maybe_derive_zeroable!( - parse_input: - @sig(#(#rest)*), - @impl_generics(#(#new_impl_generics)*), - @ty_generics(#(#ty_generics)*), - @body(#last), - ); + for Field { ty, .. } in fields { + generics + .make_where_clause() + .predicates + // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds` + // feature . + .push(parse_quote!(#ty: for<'__dummy> ::pin_init::Zeroable)); } + let (impl_gen, ty_gen, whr) = generics.split_for_impl(); + Ok(quote! { + // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. + #[automatically_derived] + unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen + #whr + {} + }) } diff --git a/rust/pin-init/src/macros.rs b/rust/pin-init/src/macros.rs index 682c61a587a0c..53ed5ce860fc9 100644 --- a/rust/pin-init/src/macros.rs +++ b/rust/pin-init/src/macros.rs @@ -1551,127 +1551,3 @@ macro_rules! __init_internal { ); }; } - -#[doc(hidden)] -#[macro_export] -macro_rules! __derive_zeroable { - (parse_input: - @sig( - $(#[$($struct_attr:tt)*])* - $vis:vis struct $name:ident - $(where $($whr:tt)*)? - ), - @impl_generics($($impl_generics:tt)*), - @ty_generics($($ty_generics:tt)*), - @body({ - $( - $(#[$($field_attr:tt)*])* - $field_vis:vis $field:ident : $field_ty:ty - ),* $(,)? - }), - ) => { - // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. - #[automatically_derived] - unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> - where - $($($whr)*)? - {} - const _: () = { - fn assert_zeroable() {} - fn ensure_zeroable<$($impl_generics)*>() - where $($($whr)*)? - { - $(assert_zeroable::<$field_ty>();)* - } - }; - }; - (parse_input: - @sig( - $(#[$($struct_attr:tt)*])* - $vis:vis union $name:ident - $(where $($whr:tt)*)? - ), - @impl_generics($($impl_generics:tt)*), - @ty_generics($($ty_generics:tt)*), - @body({ - $( - $(#[$($field_attr:tt)*])* - $field_vis:vis $field:ident : $field_ty:ty - ),* $(,)? - }), - ) => { - // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. - #[automatically_derived] - unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> - where - $($($whr)*)? - {} - const _: () = { - fn assert_zeroable() {} - fn ensure_zeroable<$($impl_generics)*>() - where $($($whr)*)? - { - $(assert_zeroable::<$field_ty>();)* - } - }; - }; -} - -#[doc(hidden)] -#[macro_export] -macro_rules! __maybe_derive_zeroable { - (parse_input: - @sig( - $(#[$($struct_attr:tt)*])* - $vis:vis struct $name:ident - $(where $($whr:tt)*)? - ), - @impl_generics($($impl_generics:tt)*), - @ty_generics($($ty_generics:tt)*), - @body({ - $( - $(#[$($field_attr:tt)*])* - $field_vis:vis $field:ident : $field_ty:ty - ),* $(,)? - }), - ) => { - // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. - #[automatically_derived] - unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> - where - $( - // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds` - // feature . - $field_ty: for<'__dummy> $crate::Zeroable, - )* - $($($whr)*)? - {} - }; - (parse_input: - @sig( - $(#[$($struct_attr:tt)*])* - $vis:vis union $name:ident - $(where $($whr:tt)*)? - ), - @impl_generics($($impl_generics:tt)*), - @ty_generics($($ty_generics:tt)*), - @body({ - $( - $(#[$($field_attr:tt)*])* - $field_vis:vis $field:ident : $field_ty:ty - ),* $(,)? - }), - ) => { - // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero. - #[automatically_derived] - unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*> - where - $( - // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds` - // feature . - $field_ty: for<'__dummy> $crate::Zeroable, - )* - $($($whr)*)? - {} - }; -} -- 2.47.3