zerocopy_derive/
lib.rs

1// SPDX-License-Identifier: BSD-2-Clause OR Apache-2.0 OR MIT
2//
3// Copyright 2019 The Fuchsia Authors
4//
5// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
6// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
7// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
8// This file may not be copied, modified, or distributed except according to
9// those terms.
10
11//! Derive macros for [zerocopy]'s traits.
12//!
13//! [zerocopy]: https://docs.rs/zerocopy
14
15// Sometimes we want to use lints which were added after our MSRV.
16// `unknown_lints` is `warn` by default and we deny warnings in CI, so without
17// this attribute, any unknown lint would cause a CI failure when testing with
18// our MSRV.
19#![allow(unknown_lints)]
20#![deny(renamed_and_removed_lints)]
21#![deny(
22    clippy::all,
23    clippy::missing_safety_doc,
24    clippy::multiple_unsafe_ops_per_block,
25    clippy::undocumented_unsafe_blocks
26)]
27// We defer to own discretion on type complexity.
28#![allow(clippy::type_complexity)]
29// Inlining format args isn't supported on our MSRV.
30#![allow(clippy::uninlined_format_args)]
31// `cargo-zerocopy` supplies this cfg for pinned-nightly tests. During UI tests,
32// `testutil::UiTestRunner` explicitly supplies it to the host-built proc macro;
33// ordinary `RUSTFLAGS` are not sufficient when Cargo receives `--target`.
34#![cfg_attr(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS, feature(proc_macro_def_site))]
35#![deny(
36    rustdoc::bare_urls,
37    rustdoc::broken_intra_doc_links,
38    rustdoc::invalid_codeblock_attributes,
39    rustdoc::invalid_html_tags,
40    rustdoc::invalid_rust_codeblocks,
41    rustdoc::missing_crate_level_docs,
42    rustdoc::private_intra_doc_links
43)]
44#![recursion_limit = "128"]
45
46macro_rules! ident {
47    (($fmt:literal $(, $arg:expr)*), $span:expr) => {
48        syn::Ident::new(&format!($fmt $(, crate::util::to_ident_str($arg))*), $span)
49    };
50}
51
52mod derive;
53#[cfg(test)]
54mod output_tests;
55mod repr;
56mod util;
57
58use syn::{DeriveInput, Error};
59
60use crate::util::*;
61
62// FIXME(https://github.com/rust-lang/rust/issues/54140): Some errors could be
63// made better if we could add multiple lines of error output like this:
64//
65// error: unsupported representation
66//   --> enum.rs:28:8
67//    |
68// 28 | #[repr(transparent)]
69//    |
70// help: required by the derive of FromBytes
71//
72// Instead, we have more verbose error messages like "unsupported representation
73// for deriving FromZeros, FromBytes, IntoBytes, or Unaligned on an enum"
74//
75// This will probably require Span::error
76// (https://doc.rust-lang.org/nightly/proc_macro/struct.Span.html#method.error),
77// which is currently unstable. Revisit this once it's stable.
78
79/// Defines a derive function named `$outer` which parses its input
80/// `TokenStream` as a `DeriveInput` and then invokes the `$inner` function.
81///
82/// Note that the separate `$outer` parameter is required - proc macro functions
83/// are currently required to live at the crate root, and so the caller must
84/// specify the name in order to avoid name collisions.
85macro_rules! derive {
86    ($trait:ident => $outer:ident => $inner:path) => {
87        #[proc_macro_derive($trait, attributes(zerocopy))]
88        pub fn $outer(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
89            let ast = syn::parse_macro_input!(ts as DeriveInput);
90            let ctx = match Ctx::try_from_derive_input(ast) {
91                Ok(ctx) => ctx,
92                Err(e) => return e.into_compile_error().into(),
93            };
94            let ts = $inner(&ctx, Trait::$trait).into_ts();
95            // We wrap in `const_block` as a backstop in case any derive fails
96            // to wrap its output in `const_block` (and thus fails to annotate)
97            // with the full set of `#[allow(...)]` attributes).
98            let ts = const_block([Some(ts)]);
99            #[cfg(test)]
100            crate::util::testutil::check_hygiene(ts.clone());
101            ts.into()
102        }
103    };
104}
105
106trait IntoTokenStream {
107    fn into_ts(self) -> proc_macro2::TokenStream;
108}
109
110impl IntoTokenStream for proc_macro2::TokenStream {
111    fn into_ts(self) -> proc_macro2::TokenStream {
112        self
113    }
114}
115
116impl IntoTokenStream for Result<proc_macro2::TokenStream, Error> {
117    fn into_ts(self) -> proc_macro2::TokenStream {
118        match self {
119            Ok(ts) => ts,
120            Err(err) => err.to_compile_error(),
121        }
122    }
123}
124
125derive!(KnownLayout => derive_known_layout => crate::derive::known_layout::derive);
126derive!(Immutable => derive_immutable => crate::derive::derive_immutable);
127derive!(TryFromBytes => derive_try_from_bytes => crate::derive::try_from_bytes::derive_try_from_bytes);
128derive!(FromZeros => derive_from_zeros => crate::derive::from_bytes::derive_from_zeros);
129derive!(FromBytes => derive_from_bytes => crate::derive::from_bytes::derive_from_bytes);
130derive!(IntoBytes => derive_into_bytes => crate::derive::into_bytes::derive_into_bytes);
131derive!(Unaligned => derive_unaligned => crate::derive::unaligned::derive_unaligned);
132derive!(ByteHash => derive_hash => crate::derive::derive_hash);
133derive!(ByteEq => derive_eq => crate::derive::derive_eq);
134derive!(SplitAt => derive_split_at => crate::derive::derive_split_at);
135
136/// Generates a struct whose two identically-printed field types resolve to
137/// different types. This is used to test that derives preserve type identity
138/// across macro hygiene contexts.
139#[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]
140#[doc(hidden)]
141#[proc_macro]
142pub fn __test_hygienically_mixed_into_bytes(
143    _input: proc_macro::TokenStream,
144) -> proc_macro::TokenStream {
145    use proc_macro::{Group, Ident, Span, TokenStream, TokenTree};
146
147    fn rewrite(input: TokenStream) -> TokenStream {
148        input
149            .into_iter()
150            .map(|token| match token {
151                TokenTree::Ident(ident) if ident.to_string() == "CallT" => {
152                    TokenTree::Ident(Ident::new("T", Span::call_site()))
153                }
154                TokenTree::Ident(ident) if ident.to_string() == "DefT" => {
155                    TokenTree::Ident(Ident::new("T", Span::def_site()))
156                }
157                TokenTree::Group(group) => {
158                    let mut rewritten = Group::new(group.delimiter(), rewrite(group.stream()));
159                    rewritten.set_span(group.span());
160                    TokenTree::Group(rewritten)
161                }
162                token => token,
163            })
164            .collect()
165    }
166
167    rewrite(
168        "#[derive(zerocopy_renamed::IntoBytes)] \
169         #[zerocopy(crate = \"zerocopy_renamed\")] \
170         #[repr(C)] \
171         struct IntoBytes15<DefT>(CallT, DefT);"
172            .parse()
173            .expect("test input must parse"),
174    )
175}
176
177#[cfg_attr(not(zerocopy_unstable_linux), doc(hidden))]
178#[proc_macro_derive(most_traits, attributes(zerocopy))]
179pub fn most_traits(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
180    let ast = syn::parse_macro_input!(ts as DeriveInput);
181    let ctx = match Ctx::try_from_derive_input(ast) {
182        Ok(ctx) => ctx,
183        Err(e) => return e.into_compile_error().into(),
184    }
185    .skip_on_error();
186
187    // top-level traits for which to attempt a derive
188    let derives: [(fn(&Ctx, Trait) -> _, _); 6] = [
189        (crate::derive::known_layout::derive, Trait::KnownLayout),
190        (crate::derive::derive_immutable, Trait::Immutable),
191        (crate::derive::from_bytes::derive_from_bytes, Trait::FromBytes),
192        (crate::derive::into_bytes::derive_into_bytes, Trait::IntoBytes),
193        (crate::derive::derive_split_at, Trait::SplitAt),
194        (crate::derive::unaligned::derive_unaligned, Trait::Unaligned),
195    ];
196
197    let mut tokens = proc_macro2::TokenStream::new();
198    for (derive, t) in derives {
199        tokens.extend(derive(&ctx, t))
200    }
201
202    // We wrap in `const_block` as a backstop in case any derive fails
203    // to wrap its output in `const_block` (and thus fails to annotate)
204    // with the full set of `#[allow(...)]` attributes).
205    let ts = const_block([Some(tokens)]);
206    #[cfg(test)]
207    crate::util::testutil::check_hygiene(ts.clone());
208    ts.into()
209}
210
211/// Deprecated: prefer [`FromZeros`] instead.
212#[deprecated(since = "0.8.0", note = "`FromZeroes` was renamed to `FromZeros`")]
213#[doc(hidden)]
214#[proc_macro_derive(FromZeroes)]
215pub fn derive_from_zeroes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
216    derive_from_zeros(ts)
217}
218
219/// Deprecated: prefer [`IntoBytes`] instead.
220#[deprecated(since = "0.8.0", note = "`AsBytes` was renamed to `IntoBytes`")]
221#[doc(hidden)]
222#[proc_macro_derive(AsBytes)]
223pub fn derive_as_bytes(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
224    derive_into_bytes(ts)
225}
zerocopy_derive/lib.rs

zerocopy_derive/
lib.rs
