fix: separate MSRV per platform in CI and README

Author: roderickvd

.github/workflows/platforms.yml

@@ -24,9 +24,11 @@ on:
 
 env:
   # MSRV varies by backend due to platform-specific dependencies
-  MSRV_DEFAULT: "1.70" # Linux (ALSA), macOS (CoreAudio), Android (AAudio), iOS, JACK
-  MSRV_WINDOWS: "1.82" # Windows (WASAPI/ASIO) - due to windows crate
-  MSRV_WASIP1: "1.78" # wasm32-wasip1 target stabilized in 1.78
+  MSRV_DEFAULT: "1.70"
+  MSRV_ALSA: "1.77"
+  MSRV_WINDOWS: "1.82"
+  MSRV_WASIP1: "1.78"
+  MSRV_WASM: "1.71"
 
 jobs:
   # Linux x86_64
@@ -40,10 +42,10 @@ jobs:
         with:
           packages: libasound2-dev libjack-jackd2-dev libjack-jackd2-0 libdbus-1-dev
 
-      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+      - name: Install Rust MSRV (${{ env.MSRV_ALSA }})
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ env.MSRV_DEFAULT }}
+          toolchain: ${{ env.MSRV_ALSA }}
 
       - name: Rust Cache
         uses: Swatinem/rust-cache@v2
@@ -65,10 +67,10 @@ jobs:
         with:
           packages: libasound2-dev libjack-jackd2-dev libjack-jackd2-0 libdbus-1-dev
 
-      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+      - name: Install Rust MSRV (${{ env.MSRV_ALSA }})
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ env.MSRV_DEFAULT }}
+          toolchain: ${{ env.MSRV_ALSA }}
 
       - name: Rust Cache
         uses: Swatinem/rust-cache@v2
@@ -85,10 +87,10 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+      - name: Install Rust MSRV (${{ env.MSRV_ALSA }})
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ env.MSRV_DEFAULT }}
+          toolchain: ${{ env.MSRV_ALSA }}
           targets: armv7-unknown-linux-gnueabihf
 
       - name: Rust Cache
@@ -213,9 +215,10 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Install Rust toolchain (Android targets)
-        uses: dtolnay/rust-toolchain@stable
+      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+        uses: dtolnay/rust-toolchain@master
         with:
+          toolchain: ${{ env.MSRV_DEFAULT }}
           targets: armv7-linux-androideabi,aarch64-linux-android,i686-linux-android,x86_64-linux-android
 
       - name: Rust Cache
@@ -253,9 +256,10 @@ jobs:
       - name: Install dependencies
         run: brew install llvm
 
-      - name: Install Rust toolchain (iOS targets)
-        uses: dtolnay/rust-toolchain@stable
+      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+        uses: dtolnay/rust-toolchain@master
         with:
+          toolchain: ${{ env.MSRV_DEFAULT }}
           targets: aarch64-apple-ios,x86_64-apple-ios
 
       - name: Rust Cache
@@ -299,11 +303,11 @@ jobs:
         if: matrix.setup-emscripten
         uses: mymindstorm/setup-emsdk@v14
 
-      - name: Install Rust MSRV (${{ env.MSRV_DEFAULT }})
+      - name: Install Rust MSRV (${{ env.MSRV_WASM }})
         if: ${{ !matrix.build-worklet-beep }}
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ env.MSRV_DEFAULT }}
+          toolchain: ${{ env.MSRV_WASM }}
           targets: ${{ matrix.target }}
 
       - name: Install Rust toolchain (nightly for build-std)

README.md

@@ -9,13 +9,13 @@ Low-level library for audio input and output in pure Rust.
 
 **cpal** maintains a conservative MSRV policy for maximum backwards compatibility. However, the actual minimum Rust version required depends on which audio backend and features you're using, as each platform has different dependencies:
 
-- **Core library + ALSA, CoreAudio, AAudio (Android), JACK, Emscripten:** Rust **1.70**
+- **Core library + CoreAudio, AAudio (Android), JACK:** Rust **1.70**
+- **ALSA** (Linux/BSD):** Rust **1.77** (due to `alsa-sys` crate requirements)
 - **WASAPI/ASIO (Windows):** Rust **1.82** (due to `windows` crate requirements)
+- **WASM (`wasm-unknown`):** Rust **1.71** (due to `wasm-bindgen` crate requirements)
 - **WASM (`wasm32-wasip1`):** Rust **1.78** (target stabilized in 1.78)
 - **WASM (`audioworklet`):** Rust **nightly** (requires `-Zbuild-std` for atomics support)
 
-If you're only using `cpal` on Linux, macOS, Emscripten, or mobile platforms, Rust 1.70 is sufficient. Windows and other WASM users will need the higher versions listed above.
-
 ## Supported Platforms
 
 This library currently supports the following: