chore(arbitrator): generate forward_stub at compile time

Dockerfile

@@ -155,6 +155,7 @@ COPY arbitrator/bench/Cargo.toml arbitrator/bench/
 COPY arbitrator/jit/Cargo.toml arbitrator/jit/
 COPY arbitrator/stylus/Cargo.toml arbitrator/stylus/
 COPY arbitrator/tools/wasmer arbitrator/tools/wasmer
+COPY arbitrator/wasm-libraries/forward arbitrator/wasm-libraries/forward
 COPY arbitrator/wasm-libraries/user-host-trait/Cargo.toml arbitrator/wasm-libraries/user-host-trait/Cargo.toml
 RUN bash -c 'mkdir arbitrator/{prover,jit,stylus}/src arbitrator/wasm-libraries/user-host-trait/src'
 RUN echo "fn test() {}" > arbitrator/jit/src/lib.rs && \

arbitrator/prover/.gitignore

@@ -0,0 +1 @@
+src/forward_stub.wat

arbitrator/prover/Cargo.toml

@@ -43,6 +43,9 @@ lru = "0.12.3"
 once_cell = "1.19.0"
 enum-iterator = "2.0.1"
 
+[build-dependencies]
+forward = { path = "../wasm-libraries/forward" }
+
 [dev-dependencies]
 criterion = { version = "0.5.0", features = ["html_reports"] }
 rand = "0.8.4"

arbitrator/prover/build.rs

@@ -0,0 +1,10 @@
+use std::fs::File;
+use std::io::Write;
+
+fn main() {
+    println!("cargo:rerun-if-changed=../wasm-libraries/forward");
+    let mut out = Vec::new();
+    forward::forward_stub(&mut out).expect("Failed to write stub");
+    let mut file = File::create("src/forward_stub.wat").unwrap();
+    file.write_all(&out).unwrap();
+}

arbitrator/prover/src/machine.rs

@@ -334,8 +334,10 @@ lazy_static! {
     static ref USER_IMPORTS: HashMap<String, AvailableImport> = {
         let mut imports = HashMap::default();
 
-        let forward = include_bytes!("../../../target/machines/latest/forward_stub.wasm");
-        let forward = binary::parse(forward, Path::new("forward")).unwrap();
+        let forward = include_bytes!("forward_stub.wat");
+        let forward = wat::parse_bytes(forward).expect("failed to parse forward_stub.wat");
+        let forward = binary::parse(&forward, Path::new("forward"))
+            .expect("failed to parse forward_stub.wasm");
 
         for (name, &(export, kind)) in &forward.exports {
             if kind == ExportKind::Func {

arbitrator/prover/src/test.rs

@@ -55,7 +55,7 @@ pub fn reject_ambiguous_imports() {
 
 #[test]
 pub fn test_compress() -> Result<()> {
-    let data = include_bytes!("../../../target/machines/latest/forward_stub.wasm");
+    let data = include_bytes!("forward_stub.wat");
     let mut last = vec![];
 
     for dict in [Dictionary::Empty, Dictionary::StylusProgram] {

arbitrator/wasm-libraries/forward/src/bin/mod.rs

@@ -0,0 +1,30 @@
+// Copyright 2022-2024, Offchain Labs, Inc.
+// For license information, see https://github.com/OffchainLabs/nitro/blob/master/LICENSE.md
+
+use eyre::Result;
+use forward::{forward, forward_stub};
+use std::{fs::File, path::PathBuf};
+use structopt::StructOpt;
+
+#[derive(StructOpt)]
+#[structopt(name = "arbitrator-prover")]
+struct Opts {
+    #[structopt(long)]
+    path: PathBuf,
+    #[structopt(long)]
+    stub: bool,
+}
+
+fn main() -> Result<()> {
+    let opts = Opts::from_args();
+    let file = &mut File::options()
+        .create(true)
+        .write(true)
+        .truncate(true)
+        .open(opts.path)?;
+
+    match opts.stub {
+        true => forward_stub(file),
+        false => forward(file),
+    }
+}

arbitrator/wasm-libraries/forward/src/main.rs → arbitrator/wasm-libraries/forward/src/lib.rs

@@ -1,9 +1,9 @@
 // Copyright 2022-2024, Offchain Labs, Inc.
 // For license information, see https://github.com/OffchainLabs/nitro/blob/master/LICENSE.md
 
+use std::io::Write;
+
 use eyre::Result;
-use std::{fs::File, io::Write, path::PathBuf};
-use structopt::StructOpt;
 
 /// order matters!
 const HOSTIOS: [[&str; 3]; 42] = [
@@ -51,30 +51,7 @@ const HOSTIOS: [[&str; 3]; 42] = [
     ["pay_for_memory_grow", "i32", ""],
 ];
 
-#[derive(StructOpt)]
-#[structopt(name = "arbitrator-prover")]
-struct Opts {
-    #[structopt(long)]
-    path: PathBuf,
-    #[structopt(long)]
-    stub: bool,
-}
-
-fn main() -> Result<()> {
-    let opts = Opts::from_args();
-    let file = &mut File::options()
-        .create(true)
-        .write(true)
-        .truncate(true)
-        .open(opts.path)?;
-
-    match opts.stub {
-        true => forward_stub(file),
-        false => forward(file),
-    }
-}
-
-fn forward(file: &mut File) -> Result<()> {
+pub fn forward<W: Write>(file: &mut W) -> Result<()> {
     macro_rules! wln {
         ($($text:tt)*) => {
             writeln!(file, $($text)*)?;
@@ -149,7 +126,7 @@ fn forward(file: &mut File) -> Result<()> {
     Ok(())
 }
 
-fn forward_stub(file: &mut File) -> Result<()> {
+pub fn forward_stub<W: Write>(file: &mut W) -> Result<()> {
     macro_rules! wln {
         ($($text:tt)*) => {
             writeln!(file, $($text)*)?;