Cross-compiling

macOS

Intel to AppleSilicon

On macOS, AppleClang has excellent support for making Apple Silicon and Universal2 binaries (both architectures in one binary). Scikit-build-core respects ARCHFLAGS if CMAKE_SYSTEM_PROCESSOR is not in the cmake args. These values are set by cibuildwheel when cross-compiling.

Warning

If you link to any binaries, they need to be Universal2, so that you get the Apple Silicon component. This means you cannot use homebrew binaries (which are always native, and not designed to be used for building portable binaries anyway). Header-only dependencies, including NumPy, do not need to be Universal2.

Windows

Intel to ARM

Scikit-build-core respects setuptools-style DIST_EXTRA_CONFIG. If is set to a file, then scikit-build-core reads the build_ext.library_dirs paths to find the library to link to. You will also need to set SETUPTOOLS_EXT_SUFFIX to the correct suffix. These values are set by cibuildwheel when cross-compiling.

Linux

It should be possible to cross-compile to Linux, but due to the challenges of getting the manylinux RHEL devtoolkit compilers, this is currently a TODO. See py-build-cmake <https://tttapa.github.io/py-build-cmake/Cross-compilation.html>_ for an alternative package’s usage of toolchain files.

Intel to Emscripten (Pyodide)

When using pyodide-build, Python is set up to report the cross-compiling values by setting _PYTHON_SYSCONFIGDATA_NAME. This causes values like SOABI and EXT_SUFFIX to be reported by sysconfig as the cross-compiling values.

This is unfortunately incorrectly stripped from the cmake wrapper pyodide uses, so FindPython will report the wrong values, but pyodide-build will rename the .so’s afterwards.