CPython WebAssembly nightly tests & unofficial builds

Test CPython WebAssembly builds with Emscripten SDK and WASI SDK. Build artifacts are available from latest scheduled Emscripten nightly tests and WASI SDK nightly tests.

The project also provides unofficial builds of CPython for Emscripten and WASI.

See availability notes and WASM README.md for platform limitations.

Emscripten build artifacts

Emscripten nightly tests

The emsdk-tot-upstream builds are using Emscripte tip-of-tree (nightlies).

Emscripten browser target

• Python-3.11dev-wasm32-emscripten-3.1.24-browser: Python 3.11 branch, Emscripten SDK 3.1.24
• Python-3.11dev-wasm32-emscripten-3.1.24-browser-debug: Python 3.11 branch, Emscripten SDK 3.1.24, debug build with additional symbols and fewer optimizations
• Python-3.11dev-wasm32-emscripten-3.1.24-browser: Python main branch (3.12), Emscripten SDK 3.1.24

The files must be served from a web server. You can use the ./wasm_webserver.py script to run a local web server and access the browser REPL from http://localhost:8000/python.html

Emscripte NodeJS target

• Python-3.11dev-wasm32-emscripten-3.1.24-node-dl: WASM dynamic linking, Python 3.11 branch, Emscripten SDK 3.1.24
• Python-3.11dev-wasm32-emscripten-3.1.24-node-dl-debug: WASM dynamic linking, Python 3.11 branch, Emscripten SDK 3.1.24, debug build with additional debug symbols and fewer optimizations
• Python-3.12dev-wasm32-emscripten-3.1.24-node-dl: WASM dynamic linking, Python main branch (3.12), Emscripten SDK 3.1.24
• Python-3.11dev-wasm32-emscripten-3.1.24-node-pthreads: WASM pthreads emulation, Python 3.11 branch, Emscripten SDK 3.1.24
• Python-3.12dev-wasm32-emscripten-3.1.24-node-pthreads: WASM pthreads emulation, Python main branch (3.12), Emscripten SDK 3.1.24
• Python-3.12dev-wasm64-emscripten-tot-upstream-node: wasm64-emscripten (MEMORY64), Python main branch (3.12), Emscripten SDK tip-of-tree.

Run:

node python.js

You may have to specify --experimental-wasm-bigint for older Node versions and --experimental-wasm-threads --experimental-wasm-bulk-memory for pthread builds.

NOTE wasm64-emscripten is experimental and requires Node >= 16 and --wasm-experimental-memory64 options.

WASI build artifacts

WASI nightly tests

• Python-3.11dev-wasm32-wasi-16: Python 3.11 with WASI-SDK 16
• Python-3.12dev-wasm32-wasi-16: Python main branch (3.12-dev) with WASI-SDK 16

Run:

wasmtime run --dir . -- python.wasm

Needs a recent version of wasmtime.

Known issues

• Emscripten 3.1.14: no main argv with PROXY_TO_PTHREAD #17338
• Emscripten 3.1.16: 64 bit time_t broke utime(), #17393
• Emscripten 3.1.20: argv handling broken #17720