ffi_export_proc_macro/
lib.rs

1extern crate proc_macro; use ::proc_macro::TokenStream;
2use ::syn::{self,
3    ItemFn,
4    NestedMeta,
5    parse_macro_input,
6    parse_quote,
7    spanned::Spanned,
8};
9use ::quote::{
10    quote_spanned,
11};
12
13const IDENT_SUFFIX: &'static str = "__hack__";
14
15#[proc_macro_attribute] pub
16fn ffi_export (args: TokenStream, input: TokenStream) -> TokenStream
17{
18    let mut item_fn = parse_macro_input!(input as ItemFn);
19    item_fn.attrs.push(parse_quote!( #[no_mangle] ));
20    item_fn.vis = parse_quote!( pub );
21    item_fn.unsafety = parse_quote!( unsafe );
22    item_fn.abi = Some(syn::Abi {
23        extern_token: Default::default(),
24        name: match syn::parse(args) { // #[ffi_export(X?)]
25            // X = "abi" => extern "abi"
26            | Ok(NestedMeta::Literal(syn::Lit::Str(abi))) => Some(abi),
27            // else =>      extern
28            | Err(_) => None,
29            // err
30            | Ok(otherwise) => return TokenStream::from(::quote::quote_spanned! {
31                otherwise.span() => compile_error!(
32                    r#"Bad argument, expected #[ffi_export("...")] for an extern "..." declaration"#
33                );
34            }),
35        },
36    });
37    let ident = syn::Ident::new(
38        &format!("{}{}", item_fn.ident, IDENT_SUFFIX),
39        item_fn.ident.span(),
40    );
41    let block = *item_fn.block;
42    *item_fn.block = parse_quote! {
43        {
44            #[allow(dead_code)]
45            #[allow(non_camel_case_types)]
46            #[derive(ffi_export::named_hack)]
47            enum #ident {}
48
49            let guard = ffi_export::AbortOnDrop;
50            let ret = (move || #block)();
51            ::core::mem::forget(guard);
52            ret
53        }
54    };
55    TokenStream::from(quote_spanned! { item_fn.span() =>
56        #item_fn
57    })
58}
59
60#[doc(hidden)]
61#[proc_macro_derive(named_hack)] pub
62fn hack (input: TokenStream) -> TokenStream
63{
64    let input: syn::DeriveInput = parse_macro_input!(input);
65    let ident = input.ident.to_string();
66    let ident = &ident[.. ident.len() - IDENT_SUFFIX.len()];
67    let fname = syn::LitStr::new(ident, input.ident.span());
68    TokenStream::from(quote_spanned! { input.span() =>
69        macro_rules! function_name {() => (
70            #fname
71        )}
72    })
73}
ffi_export_proc_macro/lib.rs

ffi_export_proc_macro/
lib.rs
