Re: [PATCH 7/7] rust: init: add support for arbitrary paths in init macros

From: Gary Guo
Date: Sun Jun 25 2023 - 17:01:31 EST

On Sat, 24 Jun 2023 09:25:39 +0000
Benno Lossin <benno.lossin@xxxxxxxxx> wrote:

> Previously only `ident` and generic types were supported in the
> `{try_}{pin_}init!` macros. This patch allows arbitrary path fragments,
> so for example `Foo::Bar` but also very complex paths such as
> `<Foo as Baz>::Bar::<0, i32>`.
>
> Internally this is accomplished by using `path` fragments. Due to some
> peculiar declarative macro limitations, we have to "forget" certain
> additional parsing information in the token trees. This is achieved by
> the new `retokenize` proc macro. It does not modify the input, but just
> strips this information. For example, if a declarative macro takes
> `$t:path` as its input, it cannot sensibly propagate this to a macro that
> takes `$($p:tt)*` as its input, since the `$t` token will only be
> considered one `tt` token for the second macro. If we first pipe the
> tokens through `retokenize`, then it parses as expected.

I think this "retokenize" macro could also be functionally replaced by
`paste`. Would you mind to apply my paste patch (referenced in a
previous email) and see if it works?

Best,
Gary

>
> Suggested-by: Asahi Lina <lina@xxxxxxxxxxxxx>
> Signed-off-by: Benno Lossin <benno.lossin@xxxxxxxxx>
> ---
> rust/kernel/init/__internal.rs | 2 ++
> rust/kernel/init/macros.rs | 42 +++++++++++++++++++---------------
> rust/macros/lib.rs | 17 +++++++++++++-
> 3 files changed, 41 insertions(+), 20 deletions(-)
>
> diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs
> index 7abd1fb65e41..e36a706a4a1b 100644
> --- a/rust/kernel/init/__internal.rs
> +++ b/rust/kernel/init/__internal.rs
> @@ -9,6 +9,8 @@
>
> use super::*;
>
> +pub use ::macros::retokenize;
> +
> /// See the [nomicon] for what subtyping is. See also [this table].
> ///
> /// [nomicon]: https://doc.rust-lang.org/nomicon/subtyping.html
> diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs
> index 5dcb2e513f26..6a82be675808 100644
> --- a/rust/kernel/init/macros.rs
> +++ b/rust/kernel/init/macros.rs
> @@ -998,7 +998,7 @@ impl<$($impl_generics)*> $pin_data<$($ty_generics)*>
> macro_rules! __init_internal {
> (
> @this($($this:ident)?),
> - @typ($t:ident $(::<$($generics:ty),*>)?),
> + @typ($t:path),
> @fields($($fields:tt)*),
> @error($err:ty),
> // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
> @@ -1012,7 +1012,7 @@ macro_rules! __init_internal {
> ) => {
> $crate::__init_internal!(with_update_parsed:
> @this($($this)?),
> - @typ($t $(::<$($generics),*>)? ),
> + @typ($t),
> @fields($($fields)*),
> @error($err),
> @data($data, $($use_data)?),
> @@ -1023,7 +1023,7 @@ macro_rules! __init_internal {
> };
> (
> @this($($this:ident)?),
> - @typ($t:ident $(::<$($generics:ty),*>)?),
> + @typ($t:path),
> @fields($($fields:tt)*),
> @error($err:ty),
> // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
> @@ -1037,7 +1037,7 @@ macro_rules! __init_internal {
> ) => {
> $crate::__init_internal!(with_update_parsed:
> @this($($this)?),
> - @typ($t $(::<$($generics),*>)? ),
> + @typ($t),
> @fields($($fields)*),
> @error($err),
> @data($data, $($use_data)?),
> @@ -1048,7 +1048,7 @@ macro_rules! __init_internal {
> };
> (
> @this($($this:ident)?),
> - @typ($t:ident $(::<$($generics:ty),*>)?),
> + @typ($t:path),
> @fields($($fields:tt)*),
> @error($err:ty),
> // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
> @@ -1062,7 +1062,7 @@ macro_rules! __init_internal {
> ) => {
> $crate::__init_internal!(
> @this($($this)?),
> - @typ($t $(::<$($generics),*>)? ),
> + @typ($t),
> @fields($($fields)*),
> @error($err),
> @data($data, $($use_data)?),
> @@ -1073,7 +1073,7 @@ macro_rules! __init_internal {
> };
> (with_update_parsed:
> @this($($this:ident)?),
> - @typ($t:ident $(::<$($generics:ty),*>)?),
> + @typ($t:path),
> @fields($($fields:tt)*),
> @error($err:ty),
> // Either `PinData` or `InitData`, `$use_data` should only be present in the `PinData`
> @@ -1092,7 +1092,7 @@ macro_rules! __init_internal {
> // Get the data about fields from the supplied type.
> let data = unsafe {
> use $crate::init::__internal::$has_data;
> - $t$(::<$($generics),*>)?::$get_data()
> + $crate::init::__internal::retokenize!($t::$get_data())
> };
> // Ensure that `data` really is of type `$data` and help with type inference:
> let init = $crate::init::__internal::$data::make_closure::<_, __InitOk, $err>(
> @@ -1247,7 +1247,7 @@ fn is_zeroable<T: Zeroable>(ptr: *mut T) {}
> };
> (make_initializer:
> @slot($slot:ident),
> - @type_name($t:ident),
> + @type_name($t:path),
> @munch_fields(..Zeroable::zeroed() $(,)?),
> @acc($($acc:tt)*),
> ) => {
> @@ -1263,15 +1263,17 @@ fn is_zeroable<T: Zeroable>(ptr: *mut T) {}
> // not get executed, so it has no effect.
> ::core::ptr::write($slot, zeroed);
> zeroed = ::core::mem::zeroed();
> - ::core::ptr::write($slot, $t {
> - $($acc)*
> - ..zeroed
> - });
> + $crate::init::__internal::retokenize!(
> + ::core::ptr::write($slot, $t {
> + $($acc)*
> + ..zeroed
> + });
> + );
> }
> };
> (make_initializer:
> @slot($slot:ident),
> - @type_name($t:ident),
> + @type_name($t:path),
> @munch_fields($(,)?),
> @acc($($acc:tt)*),
> ) => {
> @@ -1279,14 +1281,16 @@ fn is_zeroable<T: Zeroable>(ptr: *mut T) {}
> // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to
> // get the correct type inference here:
> unsafe {
> - ::core::ptr::write($slot, $t {
> - $($acc)*
> - });
> + $crate::init::__internal::retokenize!(
> + ::core::ptr::write($slot, $t {
> + $($acc)*
> + });
> + );
> }
> };
> (make_initializer:
> @slot($slot:ident),
> - @type_name($t:ident),
> + @type_name($t:path),
> @munch_fields($field:ident <- $val:expr, $($rest:tt)*),
> @acc($($acc:tt)*),
> ) => {
> @@ -1299,7 +1303,7 @@ fn is_zeroable<T: Zeroable>(ptr: *mut T) {}
> };
> (make_initializer:
> @slot($slot:ident),
> - @type_name($t:ident),
> + @type_name($t:path),
> @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),
> @acc($($acc:tt)*),
> ) => {
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 9f056a5c780a..d329ab622fd4 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -12,7 +12,7 @@
> mod vtable;
> mod zeroable;
>
> -use proc_macro::TokenStream;
> +use proc_macro::{Group, TokenStream, TokenTree};
>
> /// Declares a kernel module.
> ///
> @@ -266,3 +266,18 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
> pub fn derive_zeroable(input: TokenStream) -> TokenStream {
> zeroable::derive(input)
> }
> +
> +/// Does not modify the given TokenStream, but removes any declarative macro information.
> +#[proc_macro]
> +pub fn retokenize(input: TokenStream) -> TokenStream {
> + fn id(tt: TokenTree) -> TokenTree {
> + match tt {
> + TokenTree::Group(g) => TokenTree::Group(Group::new(
> + g.delimiter(),
> + g.stream().into_iter().map(id).collect(),
> + )),
> + x => x,
> + }
> + }
> + input.into_iter().map(id).collect()
> +}
> --
> 2.41.0
>
>