cpubits: test detection results in CI

Adds tests for the detection results that confirm the result matches
`target_pointer_width` on every platform except `wasm`.

Updates the CI config to test on
- 32-bit Linux
- 64-bit Linux
- 64-bit Windows
- 64-bit macOS
- `wasm32-wasip1` target on `wasmtime`

Author: tarcieri

.github/workflows/cpubits.yml

@@ -17,17 +17,57 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-  build:
+  test:
     strategy:
       matrix:
-        rust:
-          - 1.85 # MSRV
-          - stable
-    runs-on: ubuntu-latest
+        include:
+          # 32-bit Linux
+          - target: i686-unknown-linux-gnu
+            platform: ubuntu-latest
+            rust: 1.85.0 # MSRV
+            deps: sudo apt update && sudo apt install gcc-multilib
+
+          # 64-bit Linux
+          - target: x86_64-unknown-linux-gnu
+            platform: ubuntu-latest
+            rust: 1.85.0 # MSRV
+
+          # 64-bit Windows
+          - target: x86_64-pc-windows-msvc
+            platform: windows-latest
+            rust: 1.85.0 # MSRV
+
+          # 64-bit macOS
+          - target: x86_64-apple-darwin
+            platform: macos-latest
+            rust: 1.85.0 # MSRV
+    runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v6
       - uses: RustCrypto/actions/cargo-cache@master
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
+          targets: ${{ matrix.target }}
+      - run: ${{ matrix.deps }}
+      - run: cargo test --target ${{ matrix.target }}
+
+  # Test WASM using `wasm32-wasip1` target on `wasmtime`
+  test-wasm:
+    test:
+      strategy:
+        matrix:
+          rust:
+            - 1.85 # MSRV
+            - stable
+    runs-on: ubuntu-latest
+    env:
+      CARGO_TARGET_WASM32_WASIP1_RUNNER: "wasmtime"
+    steps:
+      - uses: actions/checkout@v6
+      - uses: bytecodealliance/actions/wasmtime/setup@v1
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          targets: wasm32-wasip1
       - run: cargo test

cpubits/src/lib.rs

@@ -175,7 +175,7 @@ macro_rules! cpubits {
         $crate::cpubits! {
             #[cfg(enable_64bit(
                 // `cfg` selector for 64-bit targets (implicitly `any`)
-                target_family = "wasm",
+                    target_family = "wasm",
             ))]
             16 => { $( $tokens32 )* }
             32 => { $( $tokens32 )* }
@@ -268,6 +268,51 @@ macro_rules! cfg_if {
 
 #[cfg(test)]
 mod tests {
+    /// Return an integer that maps to the number of bits `cpubits` detected.
+    fn detect_bits() -> u32 {
+        cpubits! {
+            16 => { let bits = 16; }
+            32 => { let bits = 32; }
+            64 => { let bits = 64; }
+        }
+
+        bits
+    }
+
+    /// Return an integer that maps to `target_pointer_width`.
+    #[allow(dead_code)]
+    fn detect_pointer_width() -> u32 {
+        #[cfg(target_pointer_width = "16")]
+        {
+            16
+        }
+        #[cfg(target_pointer_width = "32")]
+        {
+            32
+        }
+        #[cfg(target_pointer_width = "64")]
+        {
+            64
+        }
+    }
+
+    /// Tests for `cpubits` on platforms where we expect 64-bit overrides.
+    /// The cfg gating here should match the macro
+    #[cfg(target_family = "wasm")]
+    #[test]
+    fn cpubits_with_64bit_override() {
+        // TODO(tarcieri): deliberately wrong to see if CI catches it
+        assert_eq!(42, detect_bits());
+    }
+
+    /// Tests for `cpubits` on platforms where the result matches `target_pointer_width`.
+    /// The cfg gating here should match the macro, but inverted.
+    #[cfg(not(target_family = "wasm"))]
+    #[test]
+    fn cpubits_without_override() {
+        assert_eq!(detect_pointer_width(), detect_bits());
+    }
+
     mod two_arms {
         cpubits! {
             16 | 32 => {