musl libc builds (musl-cross-make)

.github/workflows/ci.yml

@@ -43,6 +43,10 @@ jobs:
             target: x86_64-unknown-linux-gnu
             variant: release
 
+          - os: ${{ github.repository == 'denoland/rusty_v8' && 'ubuntu-22.04-xl' || 'ubuntu-22.04' }}
+            target: x86_64-unknown-linux-musl
+            variant: release
+
           - os: ${{ github.repository == 'denoland/rusty_v8' && 'windows-2019-xxl' || 'windows-2019' }}
             target: x86_64-pc-windows-msvc
             variant: release # Note: we do not support windows debug builds.
@@ -84,6 +88,10 @@ jobs:
           python-version: 3.11.x
           architecture: x64
 
+      - name: Install cross compilation toolchain (musl)
+        if: endsWith(matrix.config.target, '-musl')
+        run: rustup target add ${{ matrix.config.target }}
+
       - name: Install cross compilation toolchain
         if: matrix.config.target == 'aarch64-unknown-linux-gnu'
         run: |

.gitmodules

@@ -28,3 +28,6 @@
 [submodule "third_party/abseil-cpp"]
 	path = third_party/abseil-cpp
 	url = https://chromium.googlesource.com/chromium/src/third_party/abseil-cpp.git
+[submodule "musl-cross-make"]
+	path = musl-cross-make
+	url = https://github.com/richfelker/musl-cross-make.git

build.rs

@@ -150,6 +150,42 @@ fn build_v8() {
     }
   }
 
+  if std::env::var("CARGO_CFG_TARGET_ENV").map_or(false, |e| e == "musl") {
+    let toolchain = build_musl_cross_make();
+
+    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+    let manifest_dir = Path::new(&manifest_dir).join("toolchain");
+    let arch = std::env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+
+    gn_args.push("use_custom_libcxx=false".to_string());
+    gn_args.push("is_clang=false".to_string());
+    gn_args.push("treat_warnings_as_errors=false".to_string());
+    gn_args.push("line_tables_only=false".to_string());
+    gn_args.push("use_gold=false".to_string());
+    gn_args.push("use_sysroot=false".to_string());
+    gn_args.push("use_lld=false".to_string());
+    gn_args.push("v8_static_library=true".to_string());
+    gn_args.push("clang_use_chrome_plugins=false".to_string());
+    // execinfo. is not available in musl
+    gn_args.push("is_debug=false".to_string());
+    gn_args.push(format!(
+      "custom_toolchain=\"{}:{}\"",
+      manifest_dir.display(),
+      arch
+    ));
+
+    let target = std::env::var("TARGET").unwrap();
+    env::set_var("TOOLCHAIN", toolchain.join("bin").display().to_string());
+    env::set_var(
+      format!("CC_{}", target.replace('-', "_")),
+      format!(
+        "{}/bin/{}-cc",
+        toolchain.display(),
+        target.replace("-unknown-", "-")
+      ),
+    );
+  }
+
   if let Some(p) = env::var_os("SCCACHE") {
     cc_wrapper(&mut gn_args, Path::new(&p));
   } else if let Ok(p) = which("sccache") {
@@ -310,6 +346,33 @@ fn download_ninja_gn_binaries() {
   env::set_var("NINJA", ninja);
 }
 
+fn build_musl_cross_make() -> PathBuf {
+  let toolchain_dir = build_dir().join("musl-cross-make");
+  if toolchain_dir.exists() {
+    println!("musl-cross-make toolchain already exists, skipping build");
+    return toolchain_dir;
+  }
+
+  std::fs::copy("config.mak", "musl-cross-make/config.mak").unwrap();
+  Command::new("make")
+    .arg("-C")
+    .arg("musl-cross-make")
+    .arg("TARGET=x86_64-linux-musl")
+    .status()
+    .unwrap();
+
+  Command::new("make")
+    .arg("-C")
+    .arg("musl-cross-make")
+    .arg("TARGET=x86_64-linux-musl")
+    .arg("install")
+    .arg(format!("OUTPUT={}", toolchain_dir.display()))
+    .status()
+    .unwrap();
+
+  toolchain_dir
+}
+
 fn static_lib_url() -> String {
   if let Ok(custom_archive) = env::var("RUSTY_V8_ARCHIVE") {
     return custom_archive;

config.mak

@@ -0,0 +1,7 @@
+MUSL_VER = 1.2.4
+GCC_VER  = 11.2.0
+
+GCC_CONFIG += --enable-default-pie
+
+DL_CMD   = curl -C - -L -s -o
+SHA1_CMD = shasum -a 1 -c

toolchain/BUILD.gn

@@ -0,0 +1,54 @@
+import("//build/config/sysroot.gni")
+import("//build/toolchain/gcc_toolchain.gni")
+
+template("cross_toolchain") {
+  gcc_toolchain(target_name) {
+    assert(defined(invoker.toolprefix), "missing toolprefix")
+
+    toolchain  = getenv("TOOLCHAIN")
+    toolprefix = "${toolchain}/${invoker.toolprefix}"
+
+    cc      = "${toolprefix}-gcc"
+    cxx     = "${toolprefix}-g++"
+    ld      = cxx
+
+    ar      = "${toolprefix}-ar"
+    readelf = "${toolprefix}-readelf"
+    nm      = "${toolprefix}-nm"
+
+    extra_ldflags = "-static"
+
+    toolchain_args = {
+      forward_variables_from(invoker.toolchain_args, "*")
+      use_remoteexec = false
+      is_clang       = false
+    }
+  }
+}
+
+cross_toolchain("aarch64") {
+  toolprefix = "aarch64-linux-musl"
+
+  toolchain_args = {
+    current_cpu = "arm64"
+    current_os  = "linux"
+  }
+}
+
+cross_toolchain("armv7") {
+  toolprefix = "armv7-linux-musleabihf"
+
+  toolchain_args = {
+    current_cpu = "arm"
+    current_os  = "linux"
+  }
+}
+
+cross_toolchain("x86_64") {
+  toolprefix = "x86_64-linux-musl"
+
+  toolchain_args = {
+    current_cpu = "x64"
+    current_os  = "linux"
+  }
+}