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Build and publish macOS wheels via cibuildwheel #294

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6fd9c41
Build and publish macOS wheels via cibuildwheel
Jul 3, 2026
9dedede
Pin MACOSX_DEPLOYMENT_TARGET to the runner's macOS version
Jul 6, 2026
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34 changes: 34 additions & 0 deletions .github/scripts/cibw_before_all_macos.sh
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#!/usr/bin/env bash
# One-time (per runner) setup for building macOS wheels with cibuildwheel.
# Installs the non-Python-specific casacore dependencies via Homebrew and
# downloads the sources that cibw_before_build_macos.sh compiles once per
# Python version, mirroring docker/py_wheel.docker in the casacore repo.
set -euxo pipefail

source "$(dirname "${BASH_SOURCE[0]}")/cibw_env.sh"

# bison: casacore needs >= 3 and macOS ships 2.3. flex ships with macOS.
# No BLAS package: casacore links the Accelerate framework instead.
brew install bison ccache cfitsio fftw gcc gsl hdf5 libdeflate wcslib
ccache -M 1G

mkdir -p "$CIBW_SRC"
cd "$CIBW_SRC"

# Boost source: Boost.Python must be compiled per Python version.
boost_underscored=${CIBW_BOOST_VERSION//./_}
curl -fsSL --retry 3 \
"https://archives.boost.io/release/${CIBW_BOOST_VERSION}/source/boost_${boost_underscored}.tar.bz2" \
-o boost.tar.bz2
tar xjf boost.tar.bz2

# casacore source: libcasa_python3 must be compiled per Python version.
curl -fsSL --retry 3 \
"https://github.com/casacore/casacore/archive/refs/tags/v${CIBW_CASACORE_VERSION}.tar.gz" \
-o casacore.tar.gz
tar xzf casacore.tar.gz

# Measures data, bundled into the wheels; see CIBW_DATA in cibw_env.sh.
mkdir -p "$CIBW_DATA"
curl -fsSL --retry 3 https://www.astron.nl/iers/WSRT_Measures.ztar -o measures.tgz
tar xzf measures.tgz -C "$CIBW_DATA"
95 changes: 95 additions & 0 deletions .github/scripts/cibw_before_build_macos.sh
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#!/usr/bin/env bash
# Per-Python-version build of Boost.Python and casacore for macOS wheels.
# cibuildwheel runs this before building each wheel, with the target Python
# first on PATH as `python`. It is the macOS analogue of docker/py_wheel.docker
# in the casacore repo: libcasa_python3 embeds the CPython ABI, so both
# libraries are rebuilt per Python version into CIBW_PREFIX, where the
# python-casacore build finds them via CMAKE_PREFIX_PATH.
#
# As in the Linux wheel images, libcasa_python3 must not link a real
# libpython, or the wheels would only work with one specific interpreter:
# Python3_LIBRARY is pointed at Boost.Python and Python symbols are left
# undefined, to be resolved from the host interpreter at import time.
set -euxo pipefail

source "$(dirname "${BASH_SOURCE[0]}")/cibw_env.sh"

BREW_PREFIX=$(brew --prefix)
export PATH="$BREW_PREFIX/opt/bison/bin:$PATH"
NCPU=$(sysctl -n hw.ncpu)

PYTHON=$(command -v python)
PY_VER=$("$PYTHON" -c 'import sys; print("%d.%d" % sys.version_info[:2])')
PY_XY=${PY_VER//./}
PY_INCLUDE=$("$PYTHON" -c 'import sysconfig; print(sysconfig.get_path("include"))')

rm -rf "$CIBW_PREFIX"

# ---- Boost.Python against the target Python ------------------------------
# numpy is installed only afterwards, so that b2 skips boost_numpy, matching
# the build order in docker/py_wheel.docker.
cd "$CIBW_SRC/boost_${CIBW_BOOST_VERSION//./_}"
b2_args=()
if command -v ccache >/dev/null; then
# Route b2 through ccache too, via the darwin toolset so Boost.Python
# keeps its macOS-specific linking (no libpython; see the header).
echo "using darwin : : ccache clang++ ;" > user-config.jam
b2_args=(--user-config=user-config.jam)
fi
./bootstrap.sh --prefix="$CIBW_PREFIX" \
--with-libraries=python \
--with-python="$PYTHON" \
--with-python-version="$PY_VER"
# b2 cannot derive the include dir from a virtualenv Python; the same
# workaround as in docker/py_wheel.docker.
./b2 -j"$NCPU" "${b2_args[@]}" cxxflags="-fPIC -I$PY_INCLUDE" install

# ---- casacore against the target Python ----------------------------------
"$PYTHON" -m pip install numpy

# Flags taken from casacore's own recipes: docker/py_wheel.docker and its
# Homebrew formulae.
casacore_args=(
-DCMAKE_BUILD_TYPE=Release
-DCMAKE_INSTALL_PREFIX="$CIBW_PREFIX"
-DBUILD_TESTING=OFF
-DBUILD_PYTHON=OFF
-DBUILD_PYTHON3=ON
-DPython3_EXECUTABLE="$PYTHON"
-DPython3_INCLUDE_DIR="$PY_INCLUDE"
# Boost.Python stands in for libpython; see the header comment.
-DPython3_LIBRARY="$CIBW_PREFIX/lib/libboost_python${PY_XY}.dylib"
-DPORTABLE=TRUE
-DUSE_PCH=FALSE
-DUSE_OPENMP=OFF
-DUSE_FFTW3=ON
-DUSE_HDF5=ON
-DDATA_DIR="$CIBW_DATA"
)

# macOS-specific additions, not present in the casacore recipes.
macos_args=(
# Find the Homebrew-installed dependencies.
-DCMAKE_PREFIX_PATH="$BREW_PREFIX"
# Find the per-Python Boost built above.
-DBoost_ROOT="$CIBW_PREFIX"
# Allow undefined symbols, so that Python symbols resolve from the host
# interpreter at import time. ELF linkers allow this by default, which is
# why the Linux recipe needs no such flag.
-DCMAKE_SHARED_LINKER_FLAGS="-Wl,-undefined,dynamic_lookup"
)

# ccache makes the repeated casacore builds cheap after the first.
CCACHE_ARGS=()
if command -v ccache >/dev/null; then
CCACHE_ARGS=(
-DCMAKE_C_COMPILER_LAUNCHER=ccache
-DCMAKE_CXX_COMPILER_LAUNCHER=ccache
)
fi

rm -rf "$CIBW_SRC/casacore-build"
cmake -S "$CIBW_SRC/casacore-$CIBW_CASACORE_VERSION" -B "$CIBW_SRC/casacore-build" \
"${casacore_args[@]}" "${macos_args[@]}" "${CCACHE_ARGS[@]}"
cmake --build "$CIBW_SRC/casacore-build" --parallel "$NCPU"
cmake --install "$CIBW_SRC/casacore-build"
20 changes: 20 additions & 0 deletions .github/scripts/cibw_env.sh
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#!/usr/bin/env bash
# Shared configuration for the macOS cibuildwheel scripts. On Linux the
# equivalent values are frozen into the per-Python wheel images built from
# docker/py_wheel.docker in the casacore repo; macOS has no such images, so
# the before-* scripts build the dependencies at CI time.

# Dependency versions.
export CIBW_BOOST_VERSION="1.91.0"
export CIBW_CASACORE_VERSION="3.8.1"

# Everything under one root, so a single CMAKE_PREFIX_PATH finds both installs.
# CIBW_PREFIX, CIBW_DATA and CCACHE_DIR are duplicated as literals in
# pyproject.toml; CCACHE_DIR also appears in build_release.yml.
export CIBW_ROOT="$HOME/cibw"
export CIBW_SRC="$CIBW_ROOT/src" # extracted boost + casacore sources
export CIBW_PREFIX="$CIBW_ROOT/local" # install prefix for boost + casacore
export CCACHE_DIR="$CIBW_ROOT/ccache" # persisted across CI runs
# The leaf directory must be named "data": python-casacore installs it into
# the wheel by basename, and casacore/__init__.py expects casacore/data.
export CIBW_DATA="$CIBW_ROOT/measures/data"
17 changes: 16 additions & 1 deletion .github/workflows/build_release.yml
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Expand Up @@ -33,14 +33,29 @@ jobs:
runs-on: ${{ matrix.os }}
strategy:
matrix:
os: [ubuntu-latest] #, macos-latest]
os: [ubuntu-latest, macos-15] # macos-15 is Sequoia, arm64

steps:
- uses: actions/checkout@v7
with:
# Needed for `setuptools-scm`
fetch-depth: 0

- name: Cache compiler output from the casacore builds
if: runner.os == 'macOS'
uses: actions/cache@v6
with:
# CCACHE_DIR in .github/scripts/cibw_env.sh
path: ~/cibw/ccache
key: ccache-${{ matrix.os }}-${{ hashFiles('.github/scripts/cibw_env.sh') }}
restore-keys: ccache-${{ matrix.os }}-

# We're using Homebrew for deps, so we can only build
# wheels targeting the runner's macOS version
- name: Match wheel deployment target to the runner
if: runner.os == 'macOS'
run: echo "MACOSX_DEPLOYMENT_TARGET=$(sw_vers -productVersion | cut -d. -f1).0" >> "$GITHUB_ENV"

- name: Build wheels
uses: pypa/cibuildwheel@v4.1

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30 changes: 24 additions & 6 deletions pyproject.toml
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Expand Up @@ -51,23 +51,41 @@ Homepage = "https://github.com/casacore/python-casacore"
#########################

[tool.cibuildwheel]
build = "cp3{10,11,12,13,14}-*_x86_64"
# Each runner builds only its native architecture: x86_64 on Linux,
# arm64 on the macOS runner.
build = "cp3{10,11,12,13,14}-*"
build-verbosity = 1
environment = """ \
CXXFLAGS="-I/usr/include/cfitsio" \
LD_LIBRARY_PATH=/opt/boost/lib \
"""
test-command = "cd {package}/tests && pytest"
test-requires = "pytest"

[tool.cibuildwheel.macos]
# before-build compiles Boost.Python and casacore against each Python version,
# the macOS analogue of the per-Python Linux images below; see the script for
# details.
before-all = "bash {project}/.github/scripts/cibw_before_all_macos.sh"
before-build = "bash {project}/.github/scripts/cibw_before_build_macos.sh"
# cibuildwheel cannot source cibw_env.sh, so these are literals. Keep the
# paths in sync with CIBW_PREFIX, CIBW_DATA and CCACHE_DIR there. CMAKE_ARGS
# routes the extension build through the same ccache as the dependencies.
Comment on lines +67 to +69

@gmloose gmloose Jul 14, 2026 •
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As an alternative, you could consider to define the environment variables in pyproject.toml (in the section cibuildwheel, using the environment key/value pair) and export them in the GitHub workflow, instead of sourcing cibw_env.sh. I wrote the following job for a different project that does just that:

    - name: Get environment variables from pyproject.toml
      shell: python
      run: |
        import os, re, tomllib

        with open("pyproject.toml", "rb") as f:
            toml = tomllib.load(f)

        # Extract key-value pairs from the environment used by cibuildwheel
        matches = re.findall(
            r'(\w+)=(".*?"|\S+)',
            toml["tool"]["cibuildwheel"]["environment"]
        )

        # Add every key-value pair to the environment, so that if a value contains an
        # environment variable, it can be expanded before it is added to GITHUB_ENV.
        # This is needed, because variables in GITHUB_ENV will not be expanded.
        with open(os.environ["GITHUB_ENV"], "a") as f:
          for key, value in matches:
            value = os.path.expandvars(value.strip('"'))
            os.environ[key] = value
            f.write(f"{key}={value}\n")

The down-side to this solution is that it is harder to run cibuildwheel outside of the GitHub workflow, because there's no longer a cibw_env.sh file that you can source.

environment = """ \
CMAKE_PREFIX_PATH=$HOME/cibw/local \
CASACORE_DATA=$HOME/cibw/measures/data \
CCACHE_DIR=$HOME/cibw/ccache \
CMAKE_ARGS="-DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache" \
"""
repair-wheel-command = """\
DYLD_LIBRARY_PATH=${BOOST_INSTALL_DIR}/lib delocate-wheel \
source {project}/.github/scripts/cibw_env.sh && \
DYLD_LIBRARY_PATH=$CIBW_PREFIX/lib delocate-wheel \
--require-archs {delocate_archs} -w {dest_dir} -v {wheel}\
"""

[tool.cibuildwheel.linux]
skip = ["*-musllinux_*"]
# These paths exist inside the prebuilt wheel images selected below.
environment = """ \
CXXFLAGS="-I/usr/include/cfitsio" \
LD_LIBRARY_PATH=/opt/boost/lib \
"""

[[tool.cibuildwheel.overrides]]
select="cp310-*"
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