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Correctly unpack &mut [T] into *mut T and usize

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This commit is contained in:
Jakub Konka
2019-05-14 16:52:01 +02:00
committed by Dan Gohman
parent 006198eb92
commit 52eda1498a
7 changed files with 52 additions and 11 deletions
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32
wasi-common-cbindgen/src/lib.rs
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@@ -2,7 +2,7 @@ extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn::{ArgCaptured, FnArg, Pat, PatIdent, Type, TypeReference};
use syn::{ArgCaptured, FnArg, Pat, PatIdent, Type, TypeReference, TypeSlice};
#[proc_macro_attribute]
pub fn wasi_common_cbindgen(attr: TokenStream, function: TokenStream) -> TokenStream {
@@ -36,11 +36,31 @@ pub fn wasi_common_cbindgen(attr: TokenStream, function: TokenStream) -> TokenSt
if let Type::Reference(ty @ TypeReference { .. }) = &ty {
// if we're here, then we found a &-ref
// so substitute it for *mut since we're exporting to C
let elem = &ty.elem;
arg_type.push(quote!(*mut #elem));
// we need to properly dereference the substituted raw
// pointer if we are to properly call the hostcall fn
call_arg_ident.push(quote!(&mut *#ident));
let elem = &*ty.elem;
if let Type::Slice(elem @ TypeSlice { .. }) = &elem {
// slice: &[type] or &mut [type]
// in C it requires a signature *mut type
let elem = &elem.elem;
arg_type.push(quote!(*mut #elem));
// since it's a slice, we'll need to do more work here
// simple dereferencing is not enough
// firstly, we need to add a len arg to C fn
// secondly, we need to invoke std::slice::from_raw_parts_mut(..)
let concatenated = format!("{}_len", ident);
let len_ident = syn::Ident::new(&concatenated, ident.span());
call_arg_ident.push(quote! {
std::slice::from_raw_parts_mut(#ident, #len_ident)
});
arg_ident.push(quote!(#len_ident));
arg_type.push(quote!(usize));
} else {
// & or &mut type
// so simply substitute with *mut type
arg_type.push(quote!(*mut #elem));
// we need to properly dereference the substituted raw
// pointer if we are to properly call the hostcall fn
call_arg_ident.push(quote!(&mut *#ident));
}
} else {
arg_type.push(quote!(#ty));
// non-&-ref type, so preserve whatever the arg was