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WHL: enable Limited API-compliant (abi3) wheels #511

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WHL: enable Limited API-compliant (abi3) wheels #511

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eefd5f3
BLD: set the stage for Limited API support
neutrinoceros Feb 1, 2026
4b061a2
BLD: add support for building against Python's Limited API
neutrinoceros Feb 1, 2026
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5 changes: 5 additions & 0 deletions bottleneck/src/bottleneck.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,11 @@
#include <numpy/arrayobject.h>
#include <bn_config.h>

#ifdef Py_LIMITED_API
#define PyTuple_GET_ITEM PyTuple_GetItem
#define PyTuple_GET_SIZE PyTuple_Size
#endif

/* THREADS=1 releases the GIL but increases function call
* overhead. THREADS=0 does not release the GIL but keeps
* function call overhead low. Curly brackets are for C89
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1 change: 1 addition & 0 deletions pyproject.toml
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Expand Up @@ -99,6 +99,7 @@ skip = [
"*_i686",
"cp310-win_arm64", # no numpy wheels for this target
]
environment = { "BN_LIMITED_API" = "1" }

[tool.ruff]
exclude = [
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19 changes: 19 additions & 0 deletions setup.py
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Expand Up @@ -3,6 +3,7 @@
import os
import shutil
import sys
import sysconfig
from distutils.command.config import config as _config

from setuptools import Command, setup
Expand All @@ -11,10 +12,22 @@

import versioneer

# restrict LIMITED_API usage:
# - require BN_LIMITED_API=1
# - LIMITED_API is not compatible with free-threading (as of CPython 3.14)
USE_PY_LIMITED_API = os.getenv(
"BN_LIMITED_API", "0"
) == "1" and not sysconfig.get_config_var("Py_GIL_DISABLED")
ABI3_TARGET_VERSION = "".join(str(_) for _ in sys.version_info[:2])

@rgommers rgommers Feb 3, 2026

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This doesn't look quite right, I think we should always target the lowest-supported Python version, rather than the version that's running the build. Or do you plan to enforce (via code comment?) to handle this in the CI workflow file?

@neutrinoceros neutrinoceros Feb 3, 2026

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The problem is that when targeting a version that's older than the running interpreter, there are no guarantees that the resulting binaries will actually be backward compatible. Luckily, because cibuildwheel already runs targets in increasing Python version order, this approach works perfectly: the first (oldest) Python builds a wheel and runs tests, then all the other skip the build step and only check for forward compat by running tests.

@neutrinoceros neutrinoceros Feb 3, 2026

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see https://docs.python.org/3/c-api/stable.html#limited-api-caveats

@neutrinoceros neutrinoceros Mar 26, 2026

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@rgommers, any follow up on this ?

ABI3_TARGET_HEX = hex(sys.hexversion & 0xFFFF00F0)


define_macros = [
# keep in sync with runtime requirements (pyproject.toml)
("NPY_NO_DEPRECATED_API", "NPY_1_21_API_VERSION"),
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]
if USE_PY_LIMITED_API:
define_macros.append(("Py_LIMITED_API", ABI3_TARGET_HEX))


class config(_config):
Expand Down Expand Up @@ -151,11 +164,17 @@ def prepare_modules():
return ext


if USE_PY_LIMITED_API:
options = {"bdist_wheel": {"py_limited_api": f"cp{ABI3_TARGET_VERSION}"}}
else:
options = {}

setup(
version=versioneer.get_version(),
package_data={
"bottleneck.tests": ["data/*/*"],
},
cmdclass=cmdclass,
ext_modules=prepare_modules(),
options=options,
)
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