Pin CMake Python lookup to PYTHON_PREFIX on macOS#6456
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find_package(Python) ignores the legacy PYTHON_* hint variables, so with
CMake's framework-first search an x86_64 Python.framework linked into
/usr/local/Frameworks (Rosetta Homebrew, set up for cross-platform x64
builds) shadows the arm64 brew python: ld discards the wrong-arch
libpython and MRTest then aborts at launch with
"symbol not found in flat namespace '_PyExc_RuntimeError'".
Pass Python_ROOT_DIR and Python_FIND_FRAMEWORK=LAST so the interpreter
selected by python${PYTHON_VERSION}-config always wins.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Grantim
approved these changes
Jul 20, 2026
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Since 2026-07-18 every
macos-build-test (arm64, Debug)job on the MACBOOK-PRO-16-2021-TBI-2 runner fails: MRTest aborts at launch with(e.g. the nightly run 29713915367 and several Dependabot PRs, while identical jobs pass on the other mac runner).
Root cause: an x86_64 (Rosetta) Homebrew was set up on that machine for producing cross-platform x64 builds, which linked an Intel
Python.frameworkinto/usr/local/Frameworks.build_source.shonly passes the legacyPYTHON_LIBRARY/PYTHON_INCLUDE_DIR/PYTHON_EXECUTABLEhints, which modernfind_package(Python)ignores, and CMake's framework-first search order prefers/usr/local/Frameworksover the arm64 brew:MRPython is then linked with unresolved flat-namespace Python symbols and dyld aborts as soon as MRTest starts.
This PR pins the lookup: pass
Python_ROOT_DIR(derived frompython${PYTHON_VERSION}-config --prefix, i.e. the interpreter already selected by PATH) andPython_FIND_FRAMEWORK=LAST, so a foreign-arch framework in/usr/local/Frameworkscan never shadow the intended Python — on CI runners or on developer macs that have both brews installed.The Intel pythons still need to be unlinked on TBI-2 itself (
arch -x86_64 /usr/local/bin/brew unlink python@3.10 python@3.14), but with this change the build no longer depends on that machine state.🤖 Generated with Claude Code