Troubleshooting¶
If your wheel didn't compile, check the list below for some debugging tips.
-
A mistake in your config. To quickly test your config without doing a git push and waiting for your code to build on CI, you can test the Linux build in a Docker container. On Mac or Linux, with Docker running, try
cibuildwheel --platform linux
. You'll have to bring your config into the current environment first. -
Missing dependency. You might need to install something on the build machine. You can do this in
.travis.yml
,appveyor.yml
, or.circleci/config.yml
, with apt-get, brew or choco. Given how the Linux build works, you'll need to use theCIBW_BEFORE_BUILD
option. -
Windows: missing C feature. The Windows C compiler doesn't support C language features invented after 1990, so you'll have to backport your C code to C90. For me, this mostly involved putting my variable declarations at the top of the function like an animal.
-
MacOS: calling cibuildwheel from a python3 script and getting a
ModuleNotFoundError
? Due to a (fixed) bug in CPython, you'll need to unset the__PYVENV_LAUNCHER__
variable before activating a venv.
Linux builds on Docker¶
Linux wheels are built in the manylinux
docker images to provide binary compatible wheels on Linux, according to PEP 571. Because of this, when building with cibuildwheel
on Linux, a few things should be taken into account:
-
Programs and libraries are not installed on the Travis CI Ubuntu host, but rather should be installed inside of the Docker image (using
yum
formanylinux2010
ormanylinux2014
, andapt-get
formanylinux_2_24
) or manually. The same goes for environment variables that are potentially needed to customize the wheel building.cibuildwheel
supports this by providing theCIBW_ENVIRONMENT
andCIBW_BEFORE_BUILD
options to setup the build environment inside the running Docker image. See the options docs for details on these options. -
The project directory is mounted in the running Docker instance as
/project
, the output directory for the wheels as/output
. In general, this is handled transparently bycibuildwheel
. For a more finegrained level of control however, the root of the host file system is mounted as/host
, allowing for example to access shared files, caches, etc. on the host file system. Note that this is not available on CircleCI due to their Docker policies. -
Alternative dockers images can be specified with the
CIBW_MANYLINUX_X86_64_IMAGE
,CIBW_MANYLINUX_I686_IMAGE
, andCIBW_MANYLINUX_PYPY_X86_64_IMAGE
options to allow for a custom, preconfigured build environment for the Linux builds. See options for more details.
Building macOS wheels for Apple Silicon¶
cibuildwheel
supports cross-compiling universal2
and arm64
wheels on x86_64
runners. With the introduction of Apple Silicon, you now have several choices for wheels for Python 3.9+:
x86_64
¶
The traditional wheel for Apple, loads on Intel machines, and on Apple Silicon when running Python under Rosetta 2 emulation.
Due to a change in naming, Pip 20.3+ (or an installer using packaging 20.5+) is required to install a binary wheel on macOS Big Sur.
arm64
¶
The native wheel for macOS on Apple Silicon.
Requires Pip 20.3+ (or packaging 20.5+) to install.
universal2
¶
This wheel contains both architectures, causing it to be up to twice the size (data files do not get doubled, only compiled code). It requires Pip 20.3 (Packaging 20.6+) to load on Intel, and Pip 21.0.1 (Packaging 20.9+) to load on Apple Silicon.
Note
The dual-architecture universal2
has a few benefits, but a key benefit
to a universal wheel is that a user can bundle these wheels into an
application and ship a single binary.
However, if you have a large library, then you might prefer to ship
the two single-arch wheels instead - x86_64
and arm64
. In rare cases,
you might want to build all three, but in that case, pip will not download
the universal wheels, because it prefers the most specific wheel
available.
Generally speaking, because Pip 20.3 is required for the universal2
wheel,
most packages should provide both x86_64
and universal2
wheels for now.
Once Pip 20.3+ is common on macOS, then it should be possible to ship only the
universal2
wheel.
Apple Silicon wheels are not built by default, but can be enabled by adding extra archs to the CIBW_ARCHS_MACOS
option - e.g. x86_64 arm64 universal2
. Cross-compilation is provided by the Xcode toolchain.
Important
When cross-compiling on Intel, it is not possible to test arm64
and the arm64
part of a universal2
wheel.
cibuildwheel
will raise a warning to notify you of this - these warnings be be silenced by skipping testing on these platforms: CIBW_TEST_SKIP: *_arm64 *_universal2:arm64
.
Hopefully, cross-compilation is a temporary situation. Once we have widely
available Apple Silicon CI runners, we can build and test arm64
and
universal2
wheels natively. That's why universal2
wheels are not yet built
by default, and require opt-in by setting CIBW_ARCHS_MACOS
.
Note
Your runner needs Xcode Command Line Tools 12.2 or later to build universal2
or arm64
.
So far, only CPython 3.9 supports universal2
and arm64
wheels.
Here's an example GitHub Actions workflow with a job that builds for Apple Silicon:
.github/workflows/build_macos.yml
name: Build on: [push, pull_request] jobs: build_wheels_macos: name: Build wheels on macos-10.15 runs-on: macos-10.15 steps: - uses: actions/checkout@v2 - name: Build wheels uses: pypa/cibuildwheel@v1.12.0 env: CIBW_ARCHS_MACOS: x86_64 universal2 - uses: actions/upload-artifact@v2 with: path: ./wheelhouse/*.whl
Building non-native architectures using emulation¶
cibuildwheel supports building non-native architectures on Linux, via emulation through the binfmt_misc kernel feature. The easiest way to use this is via the docker/setup-qemu-action on GitHub Actions or tonistiigi/binfmt.
Check out the following config for an example of how to set it up on GitHub
Actions. Once QEMU is set up and registered, you just need to set the
CIBW_ARCHS_LINUX
environment variable (or use the --archs
option on
Linux), and the other architectures are emulated automatically.
.github/workflows/build.yml
name: Build
on: [push, pull_request]
jobs:
build_wheels:
name: Build wheels on ${{ matrix.os }}
runs-on: ${{ matrix.os }}
strategy:
matrix:
os: [ubuntu-20.04, windows-2019, macos-10.15]
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
name: Install Python
with:
python-version: '3.7'
- name: Set up QEMU
if: runner.os == 'Linux'
uses: docker/setup-qemu-action@v1
with:
platforms: all
- name: Build wheels
uses: pypa/cibuildwheel@v1.12.0
env:
# configure cibuildwheel to build native archs ('auto'), and some
# emulated ones
CIBW_ARCHS_LINUX: auto aarch64 ppc64le s390x
- uses: actions/upload-artifact@v2
with:
path: ./wheelhouse/*.whl
Building Apple Silicon wheels on Intel¶
cibuildwheel
supports cross-compiling universal2
and arm64
wheels on x86_64
runners.
These wheels are not built by default, but can be enabled by setting the CIBW_ARCHS_MACOS
option to x86_64 arm64 universal2
. Cross-compilation is provided by the Xcode toolchain.
Important
When cross-compiling on Intel, it is not possible to test arm64
and the arm64
part of a universal2
wheel.
cibuildwheel
will raise a warning to notify you of this - these warnings be be silenced by skipping testing on these platforms: CIBW_TEST_SKIP: *_arm64 *_universal2:arm64
.
Hopefully, this is a temporary situation. Once we have widely available Apple Silicon CI runners, we can build and test arm64
and universal2
wheels more natively. That's why universal2
wheels are not yet built by default, and require opt-in by setting CIBW_ARCHS_MACOS
.
Note
Your runner image needs Xcode Command Line Tools 12.2 or later to build universal2
and arm64
.
So far, only CPython 3.9 supports universal2
and arm64
wheels.
Here's an example GitHub Actions workflow with a job that builds for Apple Silicon:
.github/workflows/build_macos.yml
name: Build
on: [push, pull_request]
jobs:
build_wheels_macos:
name: Build wheels on macos-10.15
runs-on: macos-10.15
steps:
- uses: actions/checkout@v2
- name: Build wheels
uses: pypa/cibuildwheel@v1.12.0
env:
CIBW_ARCHS_MACOS: x86_64 universal2
- uses: actions/upload-artifact@v2
with:
path: ./wheelhouse/*.whl
Windows and Python 2.7¶
Building 2.7 extensions on Windows is difficult, because the VS 2008 compiler that was used for the original Python compilation was discontinued in 2018, and has since been removed from Microsoft's downloads. Most people choose to not build Windows 2.7 wheels, or to override the compiler to something more modern.
To override, you need to have a modern compiler toolchain activated, and set DISTUTILS_USE_SDK=1
and MSSdk=1
. For example, on GitHub Actions, you would add these steps:
- name: Prepare compiler environment for Windows
if: runner.os == 'Windows'
uses: ilammy/msvc-dev-cmd@v1
with:
arch: x64
- name: Set Windows environment variables
if: runner.os == 'Windows'
shell: bash
run: |
echo "DISTUTILS_USE_SDK=1" >> $GITHUB_ENV
echo "MSSdk=1" >> $GITHUB_ENV
# invoke cibuildwheel...
cibuildwheel will not try to build 2.7 on Windows unless it detects that the above two variables are set. Note that changing to a more modern compiler will mean your wheel picks up a runtime dependency to a different Visual C++ Redistributable. You also need to be a bit careful in designing your extension; some major binding tools like pybind11 do this for you.
More on setting a custom Windows toolchain in our docs on modern C++ standards here.
Building packages with optional C extensions¶
cibuildwheel
defines the environment variable CIBUILDWHEEL
to the value 1
allowing projects for which the C extension is optional to make it mandatory when building wheels.
An easy way to do it in Python 3 is through the optional
named argument of Extension
constructor in your setup.py
:
myextension = Extension(
"myextension",
["myextension.c"],
optional=os.environ.get('CIBUILDWHEEL', '0') != '1',
)
'No module named XYZ' errors after running cibuildwheel on macOS¶
cibuildwheel
on Mac installs the distributions from Python.org system-wide during its operation. This is necessary, but it can cause some confusing errors after cibuildwheel has finished.
Consider the build script:
python3 -m pip install twine cibuildwheel
python3 -m cibuildwheel --output-dir wheelhouse
python3 -m twine upload wheelhouse/*.whl
# error: no module named 'twine'
This doesn't work because while cibuildwheel
was running, it installed a few new versions of 'python3', so the python3
run on line 3 isn't the same as the python3
that ran on line 1.
Solutions to this vary, but the simplest is to install tools immediately before they're used:
python3 -m pip install cibuildwheel
python3 -m cibuildwheel --output-dir wheelhouse
python3 -m pip install twine
python3 -m twine upload wheelhouse/*.whl
'ImportError: DLL load failed: The specific module could not be found' error on Windows¶
Visual Studio and MSVC link the compiled binary wheels to the Microsoft Visual C++ Runtime. Normally, these are included with Python, but when compiling with a newer version of Visual Studio, it is possible users will run into problems on systems that do not have these runtime libraries installed. The solution is to ask users to download the corresponding Visual C++ Redistributable from the Microsoft website and install it. Since a Python installation normally includes these VC++ Redistributable files for the version of the MSVC compiler used to compile Python, this is typically only a problem when compiling a Python 2.7 C extension with a newer compiler, e.g. to support a modern C++ standard (see the section on modern C++ standards for Python 2.7 for more details).
Additionally, Visual Studio 2019 started linking to an even newer DLL, VCRUNTIME140_1.dll
, besides the VCRUNTIME140.dll
that is included with recent Python versions (starting from Python 3.5; see here for more details on the corresponding Visual Studio & MSVC versions used to compile the different Python versions). To avoid this extra dependency on VCRUNTIME140_1.dll
, the /d2FH4-
flag can be added to the MSVC invocations (check out this issue for details and references).
To add the /d2FH4-
flag to a standard setup.py
using setuptools
, the extra_compile_args
option can be used:
ext_modules=[
Extension(
'c_module',
sources=['extension.c'],
extra_compile_args=['/d2FH4-'] if sys.platform == 'win32' else []
)
],
To investigate the dependencies of a C extension (i.e., the .pyd
file, a DLL in disguise) on Windows, Dependency Walker is a great tool.
Automatic updates¶
Selecting a moving target (like the latest release) is generally a bad idea in CI. If something breaks, you can't tell whether it was your code or an upstream update that caused the breakage, and in a worse-case scenario, it could occur during a release. There are two suggested methods for keeping cibuildwheel up to date that instead involve scheduled pull requests using GitHub's dependabot.
Option 1: GitHub Action¶
If you use GitHub Actions for builds, you can use cibuildwheel as an action:
uses: pypa/cibuildwheel@v1.12.0
This is a composite step that just runs cibuildwheel using pipx. You can set command-line options as with:
parameters, and use env:
as normal.
Then, your dependabot.yml
file could look like this:
version: 2
updates:
- package-ecosystem: "github-actions"
directory: "/"
schedule:
interval: "weekly"
ignore:
# Optional: Official actions have moving tags like v1;
# if you use those, you don't need updates.
- dependency-name: "actions/*"
Option 2: Requirement files¶
The second option, and the only one that supports other CI systems, is using a requirements-*.txt
file. The file should have a distinct name and have only one entry:
# requirements-cibw.txt
cibuildwheel==1.12.0
Then your install step would have python -m pip install -r requirements-cibw.txt
in it. Your dependabot.yml
file could look like this:
version: 2
updates:
- package-ecosystem: "pip"
directory: "/"
schedule:
interval: "daily"
This will also try to update other pins in all requirement files, so be sure you want to do that. The only control you have over the files used is via the directory option.