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rust: macros: allow generic parameter default values in #[pin_data]
Add support for generic parameters defaults in `#[pin_data]` by using the newly introduced `decl_generics` instead of the `impl_generics`. Before this would not compile: #[pin_data] struct Foo<const N: usize = 0> { // ... } because it would be expanded to this: struct Foo<const N: usize = 0> { // ... } const _: () = { struct __ThePinData<const N: usize = 0> { __phantom: ::core::marker::PhantomData<fn(Foo<N>) -> Foo<N>>, } impl<const N: usize = 0> ::core::clone::Clone for __ThePinData<N> { fn clone(&self) -> Self { *self } } // [...] rest of expansion omitted }; The problem is with the `impl<const N: usize = 0>`, since that is invalid Rust syntax. It should not mention the default value at all, since default values only make sense on type definitions. The new `impl_generics` do not contain the default values, thus generating correct Rust code. This is used by the next commit that puts `#[pin_data]` on `kernel::workqueue::Work`. Signed-off-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Reviewed-by: Gary Guo <gary@garyguo.net> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Tested-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240309155243.482334-2-benno.lossin@proton.me
1 parent 46a8106 commit 7e49a09

3 files changed

Lines changed: 20 additions & 3 deletions

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‎rust/kernel/init/macros.rs‎

Lines changed: 18 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -538,6 +538,7 @@ macro_rules! __pin_data {
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),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@body({ $($fields:tt)* }),
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) => {
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// We now use token munching to iterate through all of the fields. While doing this we
@@ -560,6 +561,9 @@ macro_rules! __pin_data {
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@impl_generics($($impl_generics)*),
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// The 'ty generics', the generics that will need to be specified on the impl blocks.
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@ty_generics($($ty_generics)*),
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// The 'decl generics', the generics that need to be specified on the struct
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// definition.
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@decl_generics($($decl_generics)*),
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// The where clause of any impl block and the declaration.
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@where($($($whr)*)?),
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// The remaining fields tokens that need to be processed.
@@ -585,6 +589,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We found a PhantomPinned field, this should generally be pinned!
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@fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*),
@@ -607,6 +612,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($($rest)*),
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@pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,),
@@ -623,6 +629,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We reached the field declaration.
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@fields_munch($field:ident : $type:ty, $($rest:tt)*),
@@ -640,6 +647,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($($rest)*),
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@pinned($($pinned)* $($accum)* $field: $type,),
@@ -656,6 +664,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We reached the field declaration.
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@fields_munch($field:ident : $type:ty, $($rest:tt)*),
@@ -673,6 +682,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($($rest)*),
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@pinned($($pinned)*),
@@ -689,6 +699,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We found the `#[pin]` attr.
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@fields_munch(#[pin] $($rest:tt)*),
@@ -705,6 +716,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($($rest)*),
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// We do not include `#[pin]` in the list of attributes, since it is not actually an
@@ -724,6 +736,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We reached the field declaration with visibility, for simplicity we only munch the
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// visibility and put it into `$accum`.
@@ -741,6 +754,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($field $($rest)*),
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@pinned($($pinned)*),
@@ -757,6 +771,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// Some other attribute, just put it into `$accum`.
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@fields_munch(#[$($attr:tt)*] $($rest:tt)*),
@@ -773,6 +788,7 @@ macro_rules! __pin_data {
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@name($name),
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@impl_generics($($impl_generics)*),
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@ty_generics($($ty_generics)*),
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@decl_generics($($decl_generics)*),
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@where($($whr)*),
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@fields_munch($($rest)*),
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@pinned($($pinned)*),
@@ -789,6 +805,7 @@ macro_rules! __pin_data {
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@name($name:ident),
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@impl_generics($($impl_generics:tt)*),
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@ty_generics($($ty_generics:tt)*),
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@decl_generics($($decl_generics:tt)*),
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@where($($whr:tt)*),
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// We reached the end of the fields, plus an optional additional comma, since we added one
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// before and the user is also allowed to put a trailing comma.
@@ -802,7 +819,7 @@ macro_rules! __pin_data {
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) => {
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// Declare the struct with all fields in the correct order.
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$($struct_attrs)*
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$vis struct $name <$($impl_generics)*>
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$vis struct $name <$($decl_generics)*>
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where $($whr)*
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{
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$($fields)*

‎rust/macros/helpers.rs‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -95,7 +95,6 @@ pub(crate) struct Generics {
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/// The generics with bounds and default values (e.g. `T: Clone, const N: usize = 0`).
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///
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/// Use this on type definitions e.g. `struct Foo<$decl_generics> ...` (or `union`/`enum`).
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#[allow(dead_code)]
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pub(crate) decl_generics: Vec<TokenTree>,
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/// The generics with bounds (e.g. `T: Clone, const N: usize`).
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///

‎rust/macros/pin_data.rs‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
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let (
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Generics {
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impl_generics,
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decl_generics: _,
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decl_generics,
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ty_generics,
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},
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rest,
@@ -77,6 +77,7 @@ pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
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@sig(#(#rest)*),
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@impl_generics(#(#impl_generics)*),
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@ty_generics(#(#ty_generics)*),
80+
@decl_generics(#(#decl_generics)*),
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@body(#last),
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});
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quoted.extend(errs);

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