autocxx_macro/
lib.rs

1// Copyright 2020 Google LLC
2//
3// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6// option. This file may not be copied, modified, or distributed
7// except according to those terms.
8
9#![forbid(unsafe_code)]
10
11use autocxx_parser::{IncludeCpp, SubclassAttrs};
12use proc_macro::TokenStream;
13use proc_macro2::{Ident, Span};
14use proc_macro_error::{abort, proc_macro_error};
15use quote::quote;
16use syn::parse::Parser;
17use syn::{parse_macro_input, parse_quote, Fields, Item, ItemStruct, Visibility};
18
19/// Implementation of the `include_cpp` macro. See documentation for `autocxx` crate.
20#[proc_macro_error]
21#[proc_macro]
22pub fn include_cpp_impl(input: TokenStream) -> TokenStream {
23    let include_cpp = parse_macro_input!(input as IncludeCpp);
24    TokenStream::from(include_cpp.generate_rs())
25}
26
27/// Attribute to state that a Rust `struct` is a C++ subclass.
28/// This adds an additional field to the struct which autocxx uses to
29/// track a C++ instantiation of this Rust subclass.
30#[proc_macro_error]
31#[proc_macro_attribute]
32pub fn subclass(attr: TokenStream, item: TokenStream) -> TokenStream {
33    let mut s: ItemStruct =
34        syn::parse(item).unwrap_or_else(|_| abort!(Span::call_site(), "Expected a struct"));
35    if !matches!(s.vis, Visibility::Public(..)) {
36        use syn::spanned::Spanned;
37        abort!(s.vis.span(), "Rust subclasses of C++ types must by public");
38    }
39    let id = &s.ident;
40    let cpp_ident = Ident::new(&format!("{id}Cpp"), Span::call_site());
41    let input = quote! {
42        cpp_peer: autocxx::subclass::CppSubclassCppPeerHolder<ffi:: #cpp_ident>
43    };
44    let parser = syn::Field::parse_named;
45    let new_field = parser.parse2(input).unwrap();
46    s.fields = match &mut s.fields {
47        Fields::Named(fields) => {
48            fields.named.push(new_field);
49            s.fields
50        },
51        Fields::Unit => Fields::Named(parse_quote! {
52            {
53                #new_field
54            }
55        }),
56        _ => abort!(Span::call_site(), "Expect a struct with named fields - use struct A{} or struct A; as opposed to struct A()"),
57    };
58    let subclass_attrs: SubclassAttrs = syn::parse(attr)
59        .unwrap_or_else(|_| abort!(Span::call_site(), "Unable to parse attributes"));
60    let self_owned_bit = if subclass_attrs.self_owned {
61        Some(quote! {
62            impl autocxx::subclass::CppSubclassSelfOwned<ffi::#cpp_ident> for #id {}
63        })
64    } else {
65        None
66    };
67    let toks = quote! {
68        #s
69
70        impl autocxx::subclass::CppSubclass<ffi::#cpp_ident> for #id {
71            fn peer_holder_mut(&mut self) -> &mut autocxx::subclass::CppSubclassCppPeerHolder<ffi::#cpp_ident> {
72                &mut self.cpp_peer
73            }
74            fn peer_holder(&self) -> &autocxx::subclass::CppSubclassCppPeerHolder<ffi::#cpp_ident> {
75                &self.cpp_peer
76            }
77        }
78
79        #self_owned_bit
80    };
81    toks.into()
82}
83
84/// Attribute to state that a Rust type is to be exported to C++
85/// in the `extern "Rust"` section of the generated `cxx` bindings.
86#[proc_macro_error]
87#[proc_macro_attribute]
88pub fn extern_rust_type(attr: TokenStream, input: TokenStream) -> TokenStream {
89    if !attr.is_empty() {
90        abort!(Span::call_site(), "Expected no attributes");
91    }
92    let i: Item =
93        syn::parse(input.clone()).unwrap_or_else(|_| abort!(Span::call_site(), "Expected an item"));
94    match i {
95        Item::Struct(..) | Item::Enum(..) | Item::Fn(..) => {}
96        _ => abort!(Span::call_site(), "Expected a struct or enum"),
97    }
98    input
99}
100
101/// Attribute to state that a Rust function is to be exported to C++
102/// in the `extern "Rust"` section of the generated `cxx` bindings.
103#[proc_macro_error]
104#[proc_macro_attribute]
105pub fn extern_rust_function(attr: TokenStream, input: TokenStream) -> TokenStream {
106    if !attr.is_empty() {
107        abort!(Span::call_site(), "Expected no attributes");
108    }
109    let i: Item =
110        syn::parse(input.clone()).unwrap_or_else(|_| abort!(Span::call_site(), "Expected an item"));
111    match i {
112        Item::Fn(..) => {}
113        _ => abort!(Span::call_site(), "Expected a function"),
114    }
115    input
116}
117
118/// Attribute which should never be encountered in real life.
119/// This is something which features in the Rust source code generated
120/// by autocxx-bindgen and passed to autocxx-engine, which should never
121/// normally be compiled by rustc before it undergoes further processing.
122#[proc_macro_error]
123#[proc_macro_attribute]
124pub fn cpp_semantics(_attr: TokenStream, _input: TokenStream) -> TokenStream {
125    abort!(
126        Span::call_site(),
127        "Please do not attempt to compile this code. \n\
128        This code is the output from the autocxx-specific version of bindgen, \n\
129        and should be interpreted by autocxx-engine before further usage."
130    );
131}
autocxx_macro/lib.rs

autocxx_macro/
lib.rs
