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Along the way, leave a deprecated Tools/wasm/wasi/__main__.py behind for backwards-compatibility. Co-authored-by: Zachary Ware <zachary.ware@gmail.com>
59 lines
1.4 KiB
Markdown
59 lines
1.4 KiB
Markdown
# Python WASI (wasm32-wasi) build
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**WASI support is [tier 2](https://peps.python.org/pep-0011/#tier-2).**
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This directory contains configuration and helpers to facilitate cross
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compilation of CPython to WebAssembly (WASM) using WASI. WASI builds
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use WASM runtimes such as [wasmtime](https://wasmtime.dev/).
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**NOTE**: If you are looking for general information about WebAssembly that is
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not directly related to CPython, please see https://github.com/psf/webassembly.
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## Build
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See [the devguide on how to build and run for WASI](https://devguide.python.org/getting-started/setup-building/#wasi).
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## Detecting WASI builds
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### Python code
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```python
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import os, sys
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if sys.platform == "wasi":
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# Python on WASI
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...
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if os.name == "posix":
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# WASM platforms identify as POSIX-like.
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# Windows does not provide os.uname().
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machine = os.uname().machine
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if machine.startswith("wasm"):
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# WebAssembly (wasm32, wasm64 potentially in the future)
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```
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```python
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>>> import os, sys
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>>> os.uname()
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posix.uname_result(
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sysname='wasi',
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nodename='(none)',
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release='0.0.0',
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version='0.0.0',
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machine='wasm32'
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)
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>>> os.name
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'posix'
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>>> sys.platform
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'wasi'
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```
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### C code
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WASI SDK defines several built-in macros. You can dump a full list of built-ins
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with ``/path/to/wasi-sdk/bin/clang -dM -E - < /dev/null``.
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* WebAssembly ``__wasm__`` (also ``__wasm``)
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* wasm32 ``__wasm32__`` (also ``__wasm32``)
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* wasm64 ``__wasm64__``
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* WASI ``__wasi__``
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