WASM support

.github/workflows/rust.yml

@@ -11,7 +11,7 @@ env:
 
 jobs:
   build-std:
-    name: Build and test (std)
+    name: Build and test
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -28,7 +28,7 @@ jobs:
       - name: Run dylib-tests
         run: cargo test -p dylib-tests --features debug-assertions
   build-miri:
-    name: Build and test (Miri)
+    name: Miri
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -37,6 +37,21 @@ jobs:
           components: miri
       - name: Build
         run: cargo +nightly miri test --features debug-assertions
+  wasm:
+    name: WASM
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install wasm-pack
+        run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+      - name: Test stringleton-registry (Chrome)
+        run: cd stringleton-registry && wasm-pack test --headless --chrome --features debug-assertions && cd ..
+      - name: Test stringleton (Chrome)
+        run: cd stringleton && wasm-pack test --headless --chrome --features debug-assertions && cd ..
+      - name: Test stringleton-registry (Firefox)
+        run: cd stringleton-registry && wasm-pack test --headless --firefox --features debug-assertions && cd ..
+      - name: Test stringleton (Firefox)
+        run: cd stringleton && wasm-pack test --headless --firefox --features debug-assertions && cd ..
   lint:
     name: Lint
     runs-on: ubuntu-latest

README.md

@@ -181,6 +181,20 @@ The latter can be supported by the `spin` and `critical-section` features:
 
 Do not use these features unless you are familiar with the tradeoffs.
 
+## WASM caveats
+
+`stringleton` works in WASM binaries, but since the `wasm32-unknown-unknown`
+does not support static constructors, the `sym!(..)` macro will fall back to a
+slightly slower implementation that uses atomics and a single branch. (Note that
+WASM is normally single-threaded, so atomic operations have no overhead.)
+
+Please note that it is *not* possible to pass a `Symbol` across a WASM boundary,
+because the host and the guest have different views of memory, and use separate
+registries. However, it is possible to pass an opaque `u64` representing the
+symbol across such a boundary using `Symbol::to_ffi()` and
+`Symbol::try_from_ffi()`. Getting the string representation of the symbol is
+only possible on the side that owns the symbol.
+
 ## Name
 
 The name is a portmanteau of "string" and "singleton".

stringleton-registry/Cargo.toml

@@ -25,6 +25,9 @@ spin = { version = "0.9.8", optional = true, default-features = false, features
     "rwlock",
 ] }
 
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+wasm-bindgen-test = "0.3"
+
 [features]
 default = ["std"]
 std = ["alloc"]