linux/rust/macros/vtable.rs
Qingsong Chen 3fa7187ece rust: macros: vtable: fix HAS_* redefinition (gen_const_name)
If we define the same function name twice in a trait (using `#[cfg]`),
the `vtable` macro will redefine its `gen_const_name`, e.g. this will
define `HAS_BAR` twice:

    #[vtable]
    pub trait Foo {
        #[cfg(CONFIG_X)]
        fn bar();

        #[cfg(not(CONFIG_X))]
        fn bar(x: usize);
    }

Fixes: b44becc5ee ("rust: macros: add `#[vtable]` proc macro")
Signed-off-by: Qingsong Chen <changxian.cqs@antgroup.com>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Sergio González Collado <sergio.collado@gmail.com>
Link: https://lore.kernel.org/r/20230808025404.2053471-1-changxian.cqs@antgroup.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-08-09 21:15:07 +02:00

97 lines
3.5 KiB
Rust

// SPDX-License-Identifier: GPL-2.0
use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
use std::collections::HashSet;
use std::fmt::Write;
pub(crate) fn vtable(_attr: TokenStream, ts: TokenStream) -> TokenStream {
let mut tokens: Vec<_> = ts.into_iter().collect();
// Scan for the `trait` or `impl` keyword.
let is_trait = tokens
.iter()
.find_map(|token| match token {
TokenTree::Ident(ident) => match ident.to_string().as_str() {
"trait" => Some(true),
"impl" => Some(false),
_ => None,
},
_ => None,
})
.expect("#[vtable] attribute should only be applied to trait or impl block");
// Retrieve the main body. The main body should be the last token tree.
let body = match tokens.pop() {
Some(TokenTree::Group(group)) if group.delimiter() == Delimiter::Brace => group,
_ => panic!("cannot locate main body of trait or impl block"),
};
let mut body_it = body.stream().into_iter();
let mut functions = Vec::new();
let mut consts = HashSet::new();
while let Some(token) = body_it.next() {
match token {
TokenTree::Ident(ident) if ident.to_string() == "fn" => {
let fn_name = match body_it.next() {
Some(TokenTree::Ident(ident)) => ident.to_string(),
// Possibly we've encountered a fn pointer type instead.
_ => continue,
};
functions.push(fn_name);
}
TokenTree::Ident(ident) if ident.to_string() == "const" => {
let const_name = match body_it.next() {
Some(TokenTree::Ident(ident)) => ident.to_string(),
// Possibly we've encountered an inline const block instead.
_ => continue,
};
consts.insert(const_name);
}
_ => (),
}
}
let mut const_items;
if is_trait {
const_items = "
/// A marker to prevent implementors from forgetting to use [`#[vtable]`](vtable)
/// attribute when implementing this trait.
const USE_VTABLE_ATTR: ();
"
.to_owned();
for f in functions {
let gen_const_name = format!("HAS_{}", f.to_uppercase());
// Skip if it's declared already -- this allows user override.
if consts.contains(&gen_const_name) {
continue;
}
// We don't know on the implementation-site whether a method is required or provided
// so we have to generate a const for all methods.
write!(
const_items,
"/// Indicates if the `{f}` method is overridden by the implementor.
const {gen_const_name}: bool = false;",
)
.unwrap();
consts.insert(gen_const_name);
}
} else {
const_items = "const USE_VTABLE_ATTR: () = ();".to_owned();
for f in functions {
let gen_const_name = format!("HAS_{}", f.to_uppercase());
if consts.contains(&gen_const_name) {
continue;
}
write!(const_items, "const {gen_const_name}: bool = true;").unwrap();
}
}
let new_body = vec![const_items.parse().unwrap(), body.stream()]
.into_iter()
.collect();
tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, new_body)));
tokens.into_iter().collect()
}