Remove substrate-wasm-builder

By defining our own build script, we gain complete clarity and control over how the WASM is built. This also removes the need to patch the upstream due to it allowing pollution of the environment variables from the host. Notable appreciation is given to https://github.com/rust-lang/rust/issues/145491 for identifying an issue encountered here, with the associated PR clarifying the necessary flags for the linker to fix this.
2025-12-08 12:19:24 +00:00 · 2025-12-04 20:07:52 -05:00
parent 36ac9c56a4
commit b791256648
7 changed files with 104 additions and 90 deletions
--- a/substrate/runtime/build.rs
+++ b/substrate/runtime/build.rs
@@ -1,4 +1,90 @@
 fn main() {
-  #[cfg(not(target_family = "wasm"))]
-  substrate_wasm_builder::WasmBuilder::build_using_defaults();
+  use std::{path::PathBuf, fs, env, process::Command};
+
+  // Prevent recursing infinitely
+  if env::var("TARGET").unwrap() == "wasm32v1-none" {
+    return;
+  }
+
+  // https://github.com/rust-lang/rust/issues/145491
+  const ONE_45491: &str = "-C link-arg=--mllvm=-mcpu=mvp,--mllvm=-mattr=+mutable-globals";
+  const WASM: &str = "-C link-arg=--export-table";
+  const REQUIRED_BY_SUBSTRATE: &str = "--cfg substrate_runtime -C link-arg=--import-memory";
+  const SAFETY: &str = "-C overflow-checks=true -C panic=abort";
+  const COMPILATION: &str =
+    "-C symbol-mangling-version=v0 -C embed-bitcode=false -C linker-plugin-lto=true";
+
+  let profile = env::var("PROFILE").unwrap();
+  let release = profile == "release";
+  let rustflags = format!("{ONE_45491} {WASM} {REQUIRED_BY_SUBSTRATE} {SAFETY} {COMPILATION}");
+  let rustflags = if release {
+    format!("{rustflags} -C codegen-units=1 -C strip=symbols -C debug-assertions=false")
+  } else {
+    rustflags
+  };
+
+  let target_dir = PathBuf::from(env::var("OUT_DIR").unwrap()).join("target");
+
+  let cargo_command = || {
+    let cargo = env::var("CARGO").unwrap();
+    let mut command = Command::new(&cargo);
+    command
+      .current_dir(env::var("CARGO_MANIFEST_DIR").unwrap())
+      .env_clear()
+      .env("PATH", env::var("PATH").unwrap())
+      .env("CARGO", cargo)
+      .env("RUSTC", env::var("RUSTC").unwrap())
+      .env("RUSTFLAGS", &rustflags)
+      .env("CARGO_TARGET_DIR", &target_dir);
+    command
+  };
+
+  let workspace = {
+    let workspace = cargo_command()
+      .arg("locate-project")
+      .arg("--workspace")
+      .arg("--message-format")
+      .arg("plain")
+      .output()
+      .unwrap();
+    assert!(workspace.status.success());
+    let mut workspace = PathBuf::from(String::from_utf8(workspace.stdout).unwrap().trim());
+    assert_eq!(workspace.file_name().unwrap(), "Cargo.toml");
+    assert!(workspace.pop());
+    workspace
+  };
+
+  // Re-run anytime the workspace changes
+  // TODO: Re-run anytime `Cargo.lock` or specifically the `src` folders change
+  println!("cargo::rerun-if-changed={}", workspace.display());
+
+  let mut command = cargo_command();
+  command
+    .arg("rustc")
+    .arg("--package")
+    .arg(env::var("CARGO_PKG_NAME").unwrap())
+    .arg("--target")
+    .arg("wasm32v1-none")
+    .arg("--crate-type")
+    .arg("cdylib")
+    .arg("--no-default-features");
+  if release {
+    command.arg("--release");
+  }
+  assert!(command.status().unwrap().success());
+
+  // Place the resulting WASM blob into the parent `target` directory
+  {
+    let wasm_file = env::var("CARGO_PKG_NAME").unwrap().replace('-', "_") + ".wasm";
+    let src_file = target_dir.join("wasm32v1-none").join(&profile).join(&wasm_file);
+    let dst_file = {
+      let mut dst_dir = workspace.clone();
+      // e.g. workspace/target/debug
+      dst_dir.extend(["target", &profile]);
+      let _ = fs::create_dir_all(&dst_dir);
+      // e.g. workspace/target/debug/serai_runtime.wasm
+      dst_dir.join(&wasm_file)
+    };
+    fs::copy(&src_file, &dst_file).unwrap();
+  }
 }