Add WASIp3 support

Author: newpavlov

.github/workflows/tests.yml

@@ -336,23 +336,58 @@ jobs:
         # Firefox doesn't support module service workers and therefor can't import scripts
         run: wasm-pack test --headless --chrome -- ${{ matrix.rust.args }}
 
-  wasi:
-    name: WASI
+  wasi_p1:
+    name: WASIp1
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: 1.85
-          targets: wasm32-wasip1,wasm32-wasip2
+          targets: wasm32-wasip1
       - name: Install Wasmtime
         run: |
-          VERSION=v24.0.0
+          VERSION=v40.0.0
           URL=https://github.com/bytecodealliance/wasmtime/releases/download/${VERSION}/wasmtime-${VERSION}-x86_64-linux.tar.xz
           wget -O - $URL | tar -xJ --strip-components=1 -C ~/.cargo/bin
           wasmtime --version
       - uses: Swatinem/rust-cache@v2
-      - name: WASI 0.1 Test
-        run: cargo test --target wasm32-wasip1
-      - name: WASI 0.2 Test
-        run: cargo test --target wasm32-wasip2
+      - run: cargo test --target wasm32-wasip1
+
+  wasi_p2:
+    name: WASIp2
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: 1.85
+          targets: wasm32-wasip2
+      - name: Install Wasmtime
+        run: |
+          VERSION=v40.0.0
+          URL=https://github.com/bytecodealliance/wasmtime/releases/download/${VERSION}/wasmtime-${VERSION}-x86_64-linux.tar.xz
+          wget -O - $URL | tar -xJ --strip-components=1 -C ~/.cargo/bin
+          wasmtime --version
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo test --target wasm32-wasip2
+
+  wasi_p3:
+    name: WASIp3
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          # TODO: switch to stable after pre-built
+          # `std` is published for wasm32-wasip3
+          toolchain: nightly-2026-01-07
+          components: rust-src
+      - name: Install Wasmtime
+        run: |
+          VERSION=v40.0.0
+          URL=https://github.com/bytecodealliance/wasmtime/releases/download/${VERSION}/wasmtime-${VERSION}-x86_64-linux.tar.xz
+          wget -O - $URL | tar -xJ --strip-components=1 -C ~/.cargo/bin
+          wasmtime --version
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo test -Zbuild-std --target wasm32-wasip3

CHANGELOG.md

@@ -9,13 +9,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - `RawOsError` type alias [#739]
 - `SysRng` behind new feature `sys_rng` [#751]
+- WASIp3 support [#779]
 
 ### Changed
 - Use Edition 2024 and MSRV 1.85 [#749]
 
 [#739]: https://github.com/rust-random/getrandom/pull/739
 [#749]: https://github.com/rust-random/getrandom/pull/749
 [#751]: https://github.com/rust-random/getrandom/pull/751
+[#779]: https://github.com/rust-random/getrandom/pull/779
 
 ## [0.3.4] - 2025-10-14
 

src/backends.rs

@@ -151,14 +151,9 @@ cfg_if! {
             if #[cfg(target_env = "p1")] {
                 mod wasi_p1;
                 pub use wasi_p1::*;
-            } else if #[cfg(any(target_env = "p2", target_env = "p3"))] {
+            } else {
                 mod wasi_p2_3;
                 pub use wasi_p2_3::*;
-            } else {
-                compile_error!(
-                    "Unknown version of WASI (only previews 1 and 2 are supported) \
-                    or Rust version older than 1.80 was used"
-                );
             }
         }
     } else if #[cfg(target_os = "hermit")] {

src/backends/wasi_p2_3.rs

@@ -1,10 +1,21 @@
-//! Implementation for WASI Preview 2.
+//! Implementation for WASIp2 and WASIp3.
 use crate::Error;
 use core::{mem::MaybeUninit, ptr::copy_nonoverlapping};
+
 #[cfg(target_env = "p2")]
-use wasip2::random::random::get_random_u64;
+use wasip2 as wasi;
+
+// Workaround to silence `unexpected_cfgs` warning
+// on Rust version between 1.85 and 1.91
+#[cfg(not(target_env = "p2"))]
 #[cfg(target_env = "p3")]
-use wasip3::random::random::get_random_u64;
+use wasip3 as wasi;
+
+#[cfg(not(target_env = "p2"))]
+#[cfg(not(target_env = "p3"))]
+compile_error!("Unknown version of WASI (only previews 1, 2 and 3 are supported)");
+
+use wasi::random::random::get_random_u64;
 
 #[inline]
 pub fn inner_u32() -> Result<u32, Error> {