ROOT Version: 6.30 and earlier
Platform: macOS Tahoe
Compiler: Apple Clang 17.0.0
CMake Version: 4.2.1
As reported in GitHub issue #18312, ROOT versions prior to 6.32.16 do not build successfully with CMake 4.0.0 or later. I have been trying to migrate my ROOT environment from my old MacOS 10.15.7 (Catalina) machine to a new macOS Tahoe 26.2, which has CMake 4.2.1 installed by Homebrew. None of the old builds (I’ve tried everything from 6.12 through 6.30) will build successfully.
Even if I specify -DCMAKE_POLICY_VERSION_MINIMUM=3.5 on the command line, that setting is not propagated into the various “builtin_XYZ” subpackages, which are build using their own separate CMake invocations (rather than treated as subdirectories of a single build).
Is there any hope at all of getting the required CMake modifications ported back to any of the versions prior to 6.32? Failing that, would it be possible for the ROOT developers to provide a patching recipe that end-users could apply to their own downloaded source?