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071cedc84e
Add a derive proc-macro for the `Zeroable` trait. The macro supports structs where every field implements the `Zeroable` trait. This way `unsafe` implementations can be avoided. The macro is split into two parts: - a proc-macro to parse generics into impl and ty generics, - a declarative macro that expands to the impl block. Suggested-by: Asahi Lina <lina@asahilina.net> Signed-off-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Gary Guo <gary@garyguo.net> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Link: https://lore.kernel.org/r/20230814084602.25699-4-benno.lossin@proton.me [ Added `ignore` to the `lib.rs` example and cleaned trivial nit. ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
73 lines
2.6 KiB
Rust
73 lines
2.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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use crate::helpers::{parse_generics, Generics};
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use proc_macro::{TokenStream, TokenTree};
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pub(crate) fn derive(input: TokenStream) -> TokenStream {
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let (
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Generics {
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impl_generics,
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ty_generics,
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},
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mut rest,
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) = parse_generics(input);
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// This should be the body of the struct `{...}`.
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let last = rest.pop();
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// Now we insert `Zeroable` as a bound for every generic parameter in `impl_generics`.
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let mut new_impl_generics = Vec::with_capacity(impl_generics.len());
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// Are we inside of a generic where we want to add `Zeroable`?
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let mut in_generic = !impl_generics.is_empty();
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// Have we already inserted `Zeroable`?
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let mut inserted = false;
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// Level of `<>` nestings.
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let mut nested = 0;
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for tt in impl_generics {
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match &tt {
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// If we find a `,`, then we have finished a generic/constant/lifetime parameter.
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TokenTree::Punct(p) if nested == 0 && p.as_char() == ',' => {
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if in_generic && !inserted {
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new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
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}
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in_generic = true;
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inserted = false;
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new_impl_generics.push(tt);
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}
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// If we find `'`, then we are entering a lifetime.
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TokenTree::Punct(p) if nested == 0 && p.as_char() == '\'' => {
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in_generic = false;
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new_impl_generics.push(tt);
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}
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TokenTree::Punct(p) if nested == 0 && p.as_char() == ':' => {
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new_impl_generics.push(tt);
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if in_generic {
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new_impl_generics.extend(quote! { ::kernel::init::Zeroable + });
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inserted = true;
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}
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}
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TokenTree::Punct(p) if p.as_char() == '<' => {
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nested += 1;
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new_impl_generics.push(tt);
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}
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TokenTree::Punct(p) if p.as_char() == '>' => {
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assert!(nested > 0);
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nested -= 1;
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new_impl_generics.push(tt);
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}
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_ => new_impl_generics.push(tt),
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}
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}
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assert_eq!(nested, 0);
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if in_generic && !inserted {
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new_impl_generics.extend(quote! { : ::kernel::init::Zeroable });
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}
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quote! {
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::kernel::__derive_zeroable!(
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parse_input:
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@sig(#(#rest)*),
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@impl_generics(#(#new_impl_generics)*),
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@ty_generics(#(#ty_generics)*),
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@body(#last),
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);
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}
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}
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