Use $WASI_SDK_PATH on WASI targets by default (#1562)

Author: alexcrichton

.github/workflows/main.yml

@@ -152,6 +152,8 @@ jobs:
             CXX: clang-cl
     steps:
       - uses: actions/checkout@v5
+      - run: curl -vv https://static.rust-lang.org/dist/channel-rust-1.87.0.toml.sha256
+        shell: bash
       - name: Install Rust (rustup)
         run: |
           set -euxo pipefail
@@ -277,11 +279,17 @@ jobs:
       - name: check clean Git workting tree
         uses: ./.github/actions/check-clean-git-working-tree
 
-  test-wasm32-wasip1-thread:
-    name: Test wasm32-wasip1-thread
+  test-wasi:
+    name: Test wasm32-wasi* targets
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+        - wasm32-wasip1
+        - wasm32-wasip2
+        - wasm32-wasip1-threads
     env:
-      TARGET: wasm32-wasip1-threads
+      TARGET: ${{ matrix.target }}
     steps:
       - uses: actions/checkout@v5
       - name: Install Rust (rustup)
@@ -308,9 +316,7 @@ jobs:
           wget "https://github.com/$REPO/releases/download/${VERSION}/${FILE}"
           sudo dpkg -i "${FILE}"
           WASI_SDK_PATH="/opt/wasi-sdk"
-          CC="${WASI_SDK_PATH}/bin/clang"
           echo "WASI_SDK_PATH=$WASI_SDK_PATH" >> "$GITHUB_ENV"
-          echo "CC=$CC" >> "$GITHUB_ENV"
 
       - run: cargo update
       - uses: Swatinem/rust-cache@v2
@@ -319,7 +325,7 @@ jobs:
           cache-all-crates: "true"
 
       - name: Run tests
-        run: cargo +nightly build -p $TARGET-test --target $TARGET
+        run: cargo +nightly build -p wasi-test --target $TARGET
 
       # check that there are no uncommitted changes to prevent bugs like https://github.com/rust-lang/cc-rs/issues/1411
       - name: check clean Git workting tree
@@ -417,7 +423,7 @@ jobs:
       - test
       - check-build-std
       - check-wasm
-      - test-wasm32-wasip1-thread
+      - test-wasi
       - cuda
       - msrv
       - clippy

Cargo.toml

@@ -44,7 +44,7 @@ members = [
     "dev-tools/cc-test",
     "dev-tools/gen-target-info",
     "dev-tools/gen-windows-sys-binding",
-    "dev-tools/wasm32-wasip1-threads-test",
+    "dev-tools/wasi-test",
 ]
 
 [patch.crates-io]

dev-tools/wasm32-wasip1-threads-test/Cargo.toml renamed to dev-tools/wasi-test/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "wasm32-wasip1-threads-test"
+name = "wasi-test"
 version = "0.1.0"
 edition = "2021"
 publish = false

dev-tools/wasm32-wasip1-threads-test/src/main.rs renamed to dev-tools/wasi-test/src/main.rs

@@ -2921,6 +2921,8 @@ impl Build {
                         "{}-{}-{}-{}",
                         target.full_arch, target.vendor, target.os, traditional
                     )
+                } else if target.os == "wasi" {
+                    self.autodetect_wasi_compiler(&raw_target, clang)
                 } else if target.arch == "wasm32" || target.arch == "wasm64" {
                     // Compiling WASM is not currently supported by GCC, so
                     // let's default to Clang.
@@ -4166,6 +4168,30 @@ impl Build {
         ::find_msvc_tools::find_tool_with_env(target.full_arch, tool, &BuildEnvGetter(self))
             .map(Tool::from_find_msvc_tools)
     }
+
+    /// Compiling for WASI targets typically uses the [wasi-sdk] project and
+    /// installations of wasi-sdk are typically indicated with the
+    /// `WASI_SDK_PATH` environment variable. Check to see if that environment
+    /// variable exists, and check to see if an appropriate compiler is located
+    /// there. If that all passes then use that compiler by default, but
+    /// otherwise fall back to whatever the clang default is since gcc doesn't
+    /// have support for compiling to wasm.
+    ///
+    /// [wasi-sdk]: https://github.com/WebAssembly/wasi-sdk
+    fn autodetect_wasi_compiler(&self, raw_target: &str, clang: &str) -> String {
+        if let Some(path) = self.getenv("WASI_SDK_PATH") {
+            let target_clang = Path::new(&path)
+                .join("bin")
+                .join(format!("{raw_target}-clang"));
+            if let Some(path) = self.which(&target_clang, None) {
+                if let Some(s) = path.to_str() {
+                    return s.to_string();
+                }
+            }
+        }
+
+        clang.to_string()
+    }
 }
 
 impl Default for Build {