# Build process notes

This section contains notes on complexities in the GitHub Actions build-deploy workflow.

## macOS crypto provider

Users reported trouble with open legacy encrypted files on macOS specifically, e.g. https://github.com/pikepdf/pikepdf/issues/520

It appears this is because we were using Homebrew’s qpdf which is currently linked against Homebrew’s openssl. The error came from qpdf specifically not finding openssl’s legacy crypto provider. How exactly that comes about is unclear - it may be that delocate-wheel is inconsistent, it may be Homebrew has disabled the legacy provider, etc. Since we use gnutls for crypto and build libqpdf on the fly for Linux wheels, might as well do the same for macOS to address this.

So now we build and link against our own libqpdf, which in turn is linked against gnutls, which does not seem to have the same issues. All of our Linux and macOS builds are doing the same thing now, rather than being split on crypto provider.

## macOS generally

Here are the current constraints for building on macOS:

- General rule for macOS: build on the oldest available macOS runner.

- QPDF needs at least MACOSX_DEPLOYMENT_TARGET=”11.0” since it uses C++17.

- Homebrew requires macOS 13+, so we can’t support older versions.

- Homebrew creates binaries with MACOSX_DEPLOYMENT_TARGET=”macos-x”. Therefore, we should build on the minimum runner. For x86_64 that is macos-13.

- Setting SYSTEM_VERSION_COMPAT=0 is necessary for pip to understand MACOSX_DEPLOYMENT_TARGET=”13.0” rather than macOS X 10.x syntax.

- GitHub’s macos-14 runner is the first to be Apple Silicon. Since we use Homebrew, it can only build macos-14. We only support macos-14 for arm64. Cirrus CI did support earlier macos. We no longer use Cirrus for Apple Silicon, just for Linux ARM64.

- Environment differences between GitHub runners and Cirrus CI runners mean we need to use sudo for Cirrus CI, hence maybe_sudo.

Taking a quick peek at numpy, it may be easier to build universal2 wheels and use QEMU or Cirrus CI to confirm that they work. That would be another big build overhaul.

Users who build from source have more options and can likely get functional builds on anything newer than macOS 14.