[R-SIG-Mac] Announcement: R-devel "sonoma-arm64" Mac builds

[Simon Urbanek]

This email is mostly of interest to those that build Mac binaries or want to maintain binary compatibility with CRAN. Also if you are on an Apple Silicon Mac (M1,M2,…) and your macOS is *older* than macOS 14, please read the last paragraph at the bottom.

Our current Mac R release and package builds are targeting macOS 11 (Big Sur) for both Intel and arm64 to offer as wide coverage of users as possible. Unfortunately, Apple has removed hardware support for most Intel Macs from recent macOS versions which means that majority of Intel Mac users cannot upgrade their OS - which is reflected in our estimated macOS version user share and therefore we cannot change the target for x86_64 binaries without abandoning a large fraction of our users.

However, all arm64 (Apple Silicon) Mac hardware is supported by latest macOS versions so there is no practical obstacle for Apple Silicon users to upgrade their macOS. Therefore we are considering moving the minimum target for CRAN R binaries and packages to macOS 14 (Sonoma), because it allows us and packages to leverage several new technologies and tools. To that effect R-devel arm64 builds have been switched to a "sonoma-arm64" build target, with the corresponding repository URL of /bin/macosx/sonoma-arm64/contrib/4.6 (output of contrib.url("", type="binary") in those builds). The binaries will be built with the following setup/settings:

Host OS: macOS 15.7.1 (Sequoia)
Toolchain: Xcode/CLT 26.0, GNU Fortran 14.2 (from CRAN)
SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX14.4.sdk
MACOSX_DEPLOYMENT_TARGET=14.0

Accordingly, the recipes binaries are built using the same settings and are available in following repository:

https://mac.r-project.org/bin/darwin23/arm64/

Corresponding nightly R binaries are available as usual at

https://mac.r-project.org/sonoma/last-success/

The goal is to remove the existing big-sur-arm64 R-devel binaries in favor of the sonoma-arm64 R-devel build. Since we are still far away from the R-devel release, all this is considered experimental and may change in the future (possibly Fortran upgrade is in the cards), but given that this is not a minor change, I want to give others the opportunity to test the new setup and comment as appropriate. I would also like to hear from any Apple Silicon users that are unable to upgrade to macOS 14 or higher for whatever reason (corporate system management etc.).

Thanks,
Simon