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gh-84461: Add --enable-wasm-pthreads and more file systems (GH-91820)

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Christian Heimes 2022-04-23 15:59:33 +03:00 • committed by GitHub
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Tools/wasm/README.md
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@ -121,18 +121,27 @@ functions.
- The ``select`` module is limited. ``select.select()`` crashes the runtime
due to lack of exectfd support.
## processes, threads, signals
## processes, signals
- Processes are not supported. System calls like fork, popen, and subprocess
fail with ``ENOSYS`` or ``ENOSUP``.
- Signal support is limited. ``signal.alarm``, ``itimer``, ``sigaction``
are not available or do not work correctly. ``SIGTERM`` exits the runtime.
- Keyboard interrupt (CTRL+C) handling is not implemented yet.
- Browser builds cannot start new threads. Node's web workers consume
extra file descriptors.
- Resource-related functions like ``os.nice`` and most functions of the
``resource`` module are not available.
## threading
- Threading is disabled by default. The ``configure`` option
``--enable-wasm-pthreads`` adds compiler flag ``-pthread`` and
linker flags ``-sUSE_PTHREADS -sPROXY_TO_PTHREAD``.
- pthread support requires WASM threads and SharedArrayBuffer (bulk memory).
The Node.JS runtime keeps a pool of web workers around. Each web worker
uses several file descriptors (eventfd, epoll, pipe).
- It's not advised to enable threading when building for browsers or with
dynamic linking support; there are performance and stability issues.
## file system
- Most user, group, and permission related function and modules are not
@ -173,20 +182,16 @@ functions.
distutils, multiprocessing, dbm, tests and similar modules
are not shipped. All other modules are bundled as pre-compiled
``pyc`` files.
- Threading is disabled.
- In-memory file system (MEMFS) is not persistent and limited.
- Test modules are disabled by default. Use ``--enable-test-modules`` build
test modules like ``_testcapi``.
## wasm32-emscripten in node
Node builds use ``NODERAWFS``, ``USE_PTHREADS`` and ``PROXY_TO_PTHREAD``
linker options.
Node builds use ``NODERAWFS``.
- Node RawFS allows direct access to the host file system.
- pthread support requires WASM threads and SharedArrayBuffer (bulk memory).
The runtime keeps a pool of web workers around. Each web worker uses
several file descriptors (eventfd, epoll, pipe).
- Node RawFS allows direct access to the host file system without need to
perform ``FS.mount()`` call.
# Hosting Python WASM builds