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Merged
merged 4 commits into from
Nov 19, 2025
+21 −17
Merged

Simplify setting CLI options for WASI builds #141769

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5f305c7
Simplify setting CLI options for WASI builds
brettcannon Nov 19, 2025
3fc4ace
Merge branch 'main' into wasmtime-config
brettcannon Nov 19, 2025
6adfa7b
Fix formatting
brettcannon Nov 19, 2025
42e184c
Merge branch 'wasmtime-config' of https://github.com/brettcannon/cpyt…
brettcannon Nov 19, 2025
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33 changes: 16 additions & 17 deletions Tools/wasm/wasi/__main__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,9 @@
import sysconfig
import tempfile

CHECKOUT = pathlib.Path(__file__).parent.parent.parent.parent
HERE = pathlib.Path(__file__).parent

CHECKOUT = HERE.parent.parent.parent
assert (CHECKOUT / "configure").is_file(), (
"Please update the location of the file"
)
Expand Down Expand Up @@ -304,9 +306,7 @@ def configure_wasi_python(context, working_dir):
"specify via $WASI_SDK_PATH or --wasi-sdk"
)

config_site = os.fsdecode(
CHECKOUT / "Tools" / "wasm" / "wasi" / "config.site-wasm32-wasi"
)
config_site = os.fsdecode(HERE / "config.site-wasm32-wasi")

wasi_build_dir = working_dir.relative_to(CHECKOUT)

Expand All @@ -324,10 +324,7 @@ def configure_wasi_python(context, working_dir):
# Use PYTHONPATH to include sysconfig data which must be anchored to the
# WASI guest's `/` directory.
args = {
"GUEST_DIR": "/",
"HOST_DIR": CHECKOUT,
"ENV_VAR_NAME": "PYTHONPATH",
"ENV_VAR_VALUE": f"/{sysconfig_data_dir}",
"PYTHONPATH": f"/{sysconfig_data_dir}",
"PYTHON_WASM": working_dir / "python.wasm",
}
# Check dynamically for wasmtime in case it was specified manually via
Expand Down Expand Up @@ -417,16 +414,18 @@ def main():
default_wasi_sdk = find_wasi_sdk()
default_host_runner = (
f"{WASMTIME_HOST_RUNNER_VAR} run "
# Make sure the stack size will work for a pydebug
# build.
# Use 32 MiB stack.
"--wasm max-wasm-stack=33554432 "
# Enable thread support; causes use of preview1.
# "--wasm threads=y --wasi threads=y "
# For setting PYTHONPATH to the sysconfig data directory.
"--env PYTHONPATH={PYTHONPATH} "
# Map the checkout to / to load the stdlib from /Lib.
"--dir {HOST_DIR}::{GUEST_DIR} "
# Set PYTHONPATH to the sysconfig data.
"--env {ENV_VAR_NAME}={ENV_VAR_VALUE}"
f"--dir {os.fsdecode(CHECKOUT)}::/ "
# Flags involving --optimize, --codegen, --debug, --wasm, and --wasi can be kept
# in a config file.
# We are using such a file to act as defaults in case a user wants to override
# only some of the settings themselves, make it easy to modify settings
# post-build so that they immediately apply to the Makefile instead of having to
# regenerate it, and allow for easy copying of the settings for anyone else who
# may want to use them.
f"--config {os.fsdecode(HERE / 'wasmtime.toml')}"
)
default_logdir = pathlib.Path(tempfile.gettempdir())

Expand Down
5 changes: 5 additions & 0 deletions Tools/wasm/wasi/wasmtime.toml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
# https://docs.wasmtime.dev/cli-options.html#cli-options-using-toml-file

[wasm]
# 32 MiB; big enough for the test suite to pass under a debug build.
max-wasm-stack = 33_554_432
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