Skip to content

docs: Add instructions for Wasm stdlib building and testing #85844

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
MaxDesiatov wants to merge 2 commits into
base: main
Choose a base branch
from
+15 −1
Open

docs: Add instructions for Wasm stdlib building and testing #85844

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
b182f23
Recommend `--sccache` for Wasm Swift SDK builds
MaxDesiatov Dec 4, 2025
6c389fe
Add instructions for stdlib builds
MaxDesiatov Dec 4, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
16 changes: 15 additions & 1 deletion docs/WebAssembly.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -16,13 +16,27 @@ available yet, specifically:
* Binary size is a high priority requirement. Since WebAssembly payloads are usually served in browsers,
one wouldn't want end users to download multi-megabyte binaries.

## Running Wasm stdlib tests

If you're a compiler/stdlib engineer, this invocation builds LLVM, Swift, installs those together with necessary
tools, and also builds WasmKit to execute stdlib tests:

```
./utils/build-script --build-wasm-stdlib --wasmkit --build-embedded-stdlib --build-embedded-stdlib-cross-compiling \
--install-swift --install-llvm \
'--llvm-install-components=llvm-ar;llvm-nm;llvm-ranlib;llvm-cov;llvm-profdata;llvm-objdump;llvm-objcopy;llvm-symbolizer;IndexStore;clang;clang-resource-headers;builtins;runtimes;clangd;libclang;dsymutil;LTO;clang-features-file;lld' \
--sccache
```

On macOS it's also best to avoid cross-compiling host tools from arm64 to x86 and vice versa, add this option to avoid that: `--infer-cross-compile-hosts-on-darwin=false`.

## Building Swift SDK for WebAssembly

The [Swift SDK](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0387-cross-compilation-destinations.md)
for WebAssembly is built and tested using the following command:

```bash
./utils/build-script --build-wasm-stdlib --wasmkit --install-llvm --install-swift --swiftpm --install-swiftpm \
./utils/build-script --sccache --build-wasm-stdlib --wasmkit --install-llvm --install-swift --swiftpm --install-swiftpm \
--libcxx --install-libcxx --llbuild --install-llbuild --swift-testing --install-swift-testing \
--swift-testing-macros --install-swift-testing-macros --build-embedded-stdlib --build-embedded-stdlib-cross-compiling \
'--llvm-install-components=llvm-ar;llvm-nm;llvm-ranlib;llvm-cov;llvm-profdata;llvm-objdump;llvm-objcopy;llvm-symbolizer;IndexStore;clang;clang-resource-headers;builtins;runtimes;clangd;libclang;dsymutil;LTO;clang-features-file;lld'
Expand Down