Add placeholder for cbindgen proc_macro_attribute

Cargo.toml

@@ -10,6 +10,7 @@ edition = "2018"
 license = "Apache-2.0 WITH LLVM-exception"
 
 [dependencies]
+wasi-common-cbindgen = { path = "wasi-common-cbindgen" }
 cast = "0.2"
 failure = "0.1"
 libc = "0.2"
@@ -19,3 +20,5 @@ rand = "0.6"
 [lib]
 name = "wasi_common"
 crate-type = ["rlib", "staticlib", "cdylib"]
+
+[workspace]

src/hostcalls.rs

@@ -24,13 +24,16 @@ use std::ffi::{OsStr, OsString};
 use std::os::unix::prelude::{FromRawFd, OsStrExt, OsStringExt, RawFd};
 use std::time::SystemTime;
 use std::{cmp, slice};
+use wasi_common_cbindgen::wasi_common_cbindgen;
 
+#[wasi_common_cbindgen]
 pub fn proc_exit(rval: wasm32::__wasi_exitcode_t) -> () {
     // TODO: Rather than call std::process::exit here, we should trigger a
     // stack unwind similar to a trap.
     std::process::exit(dec_exitcode(rval) as i32);
 }
 
+#[wasi_common_cbindgen]
 pub fn args_get(
     wasi_ctx: &WasiCtx,
     memory: &mut [u8],

wasi-common-cbindgen/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "wasi-common-cbindgen"
+version = "0.1.0"
+authors = ["Jakub Konka <kubkon@jakubkonka.com>"]
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "0.15.34", features = ["full"] }
+quote = "0.6.12"
+proc-macro2 = "0.4.30"

wasi-common-cbindgen/src/lib.rs

@@ -0,0 +1,18 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{FnArg, ArgCaptured, Pat, PatIdent};
+use std::collections::HashMap;
+
+#[proc_macro_attribute]
+pub fn wasi_common_cbindgen(attr: TokenStream, function: TokenStream) -> TokenStream {
+    assert!(attr.is_empty());
+
+    let function = syn::parse_macro_input!(function as syn::ItemFn);
+    let result = quote! {
+        #function
+    };
+
+    result.into()
+}