scikit-build-core

WARNING: Experimental. All configuration subject to change. Only scikit_build_core.build should be used (setuptools backend is experimental and likely to move to a separate package).

The following limitations are present compared to classic scikit-build:

• The minimum supported CMake is 3.15
• The minimum supported Python is 3.7

Some of these limitations might be adjusted over time, based on user requirements & effort / maintainability.

This is very much a WIP, some missing features:

• The extensionlib integration is missing
• No hatchling plugin yet
• The docs are not written
• The logging system isn't ideal yet
• Dedicated entrypoints are planned for projects wanting to support discovery
• No support for other targets besides install
• C++17 is required for the test suite because it's more fun than C++11/14
• No support for caching between builds
• No editable mode support
• No extra wheel directories (like headers) supported yet
• Wheels are not fully reproducible yet
• Windows ARM support missing

Features over classic Scikit-build:

• Better warnings, errors, and logging
• No warning about unused variables
• Automatically adds Ninja and/or CMake only as required
• No dependency on setuptools, distutils, or wheel in build mode.
• Closer to vanilla setuptools in setuptools mode, doesn't interfere with config.
• Powerful config system, including config options support in build mode.
• Automatic inclusion of site-packages in CMAKE_PREFIX_PATH
• FindPython is backported if running on CMake < 3.24 (included via hatchling in a submodule)
• Limited API / Stable ABI and pythonless tags supported via config option
• No slow generator search, ninja/make or MSVC used by default, respects CMAKE_GENERATOR
• SDists are reproducible by default (UNIX, Python 3.9+)

Currently, the recommended interface is the PEP 517 interface. There is also a setuptools-based interface that is being developed to provide a transition path for classic scikit-build.

Example

To use scikit-build-core, add it to your build-system.requires, and specify the scikit_build_core.build builder as your build-system.build-backend. You do not need to specify cmake or ninja; scikit-build-core will require them automatically if the system versions are not sufficient.

[build-system]
requires = ["scikit-build-core"]
build-backend = "scikit_build_core.build"

[project]
name = "scikit_build_simplest"
version = "0.0.1"

You can (and should) specify the rest of the entries in project, but these are the minimum to get started.

An example CMakeLists.txt:

cmake_minimum_required(VERSION 3.15...3.24)

project(${SKBUILD_PROJECT_NAME} LANGUAGES C VERSION ${SKBUILD_PROJECT_VERSION})

find_package(Python COMPONENTS Interpreter Development.Module)

Python_add_library(_module MODULE src/module.c WITH_SOABI)
set(Python_SOABI ${SKBUILD_SOABI})  # Required for PyPy support

install(TARGETS _module DESTINATION ${SKBUILD_PROJECT_NAME})

Scikit-build-core will backport FindPython from CMake 3.24 to older versions of Python, and will handle PyPy for you if you are building from PyPy. You will need to install everything you want into the full final path inside site-modules (so you will usually prefix everything by the package name).

More examples are in the tests/packages.

Configuration

Warning: still being developed, some things may change.

All configuration options can be placed in pyproject.toml, passed via -C options in pip or build (warning: pip doesn't support list options), or set as environment variables. tool.scikit-build is used in toml, skbuild. for -C options, or SKBUILD_* for environment variables. The defaults are listed below:

[tool.scikit-build]
# The PEP 517 build hooks will add ninja and/or cmake if the versions on the
# system are not at least these versions.
cmake.minimum-version = "3.15"
ninja.minimum-version = "1.5"

# Fallback on gmake/make if available and ninja is missing (Unix)
ninja.make-fallback = true

# Display logs at or above this level.
logging.level = "WARNING"

# Setting the py_abi to "cp37-abi3" would build ABI3 wheels for Python 3.7+.
# Setting the py_abi to "py3-none" would build wheels that don't depend on
# Python (ctypes, etc).
tags.py-abi = ""

# Setting this to true will expand extra tags (universal2 will add Intel and
# Apple Silicon tags, for pip <21.0.1 compatibility).
tags.extra = false

# Include and exclude patterns, in gitignore syntax. Include overrides exclude.
# Wheels include packages included in the sdist; CMake has the final say.
sdist.include = []
sdist.exclude = []

# Make reproducible SDists (Python 3.9+ and UNIX recommended). Respects
# SOURCE_DATE_EPOCH when true (the default).
sdist.reproducible = true

# The root-level packages to include. Special default: if not given, the package
# is auto-discovered if it's name matches the main name.
wheel.packages = ["src/<package>", "<package>"]

Most CMake environment variables should be supported, and CMAKE_ARGS can be used to set extra CMake args. ARCHFLAGS is used to specify macOS universal2 or cross-compiles, just like setuptools.

Acknowledgements

Support for this work was provided by NSF cooperative agreement OAC-2209877.