build(deps): keep Homebrew out of local dependency child builds - #5361
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build(deps): keep Homebrew out of local dependency child builds#5361zachlewis wants to merge 1 commit into
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IGNORE_HOMEBREWED_DEPS pruned prefix paths and set CMAKE_IGNORE_PATH, but CMAKE_IGNORE_PATH does not stop config-package searches, and local dependency child builds could still quietly resolve Homebrew packages we are ignoring. Concretely: with a Homebrew Imath 3.2 installed, the local OpenEXR build resolved Imath_DIR=/opt/homebrew/lib/cmake/Imath while OpenImageIO itself used the locally built Imath 3.1.10, and libOpenImageIO then failed to link with Imath_3_2 vs Imath_3_1 namespace-mangled symbol mismatches. Set CMAKE_IGNORE_PREFIX_PATH for the Homebrew prefixes (honored by config searches) and forward it to dependency child builds alongside CMAKE_IGNORE_PATH. Verified: the OpenEXR child build resolves the local deps Imath and libOpenImageIO links clean. Assisted-by: Claude Code (Fable 5) Signed-off-by: Zach Lewis <zachcanbereached@gmail.com>
This was referenced Aug 3, 2026
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Motivation
IGNORE_HOMEBREWED_DEPS=ONprunes the Homebrew prefixes from the search paths and setsCMAKE_IGNORE_PATH, butCMAKE_IGNORE_PATHis not honored by config-package searches — and the local dependency child builds launched bybuild_dependency_with_cmakecan therefore quietly resolve Homebrew packages that the parent build is deliberately ignoring.Concrete failure: with Homebrew Imath 3.2 installed, a local OpenEXR dependency build resolved
Imath_DIR=/opt/homebrew/lib/cmake/Imathwhile OpenImageIO itself compiled against the locally built Imath 3.1.10. Imath's versioned namespace is baked into every mangled symbol, so the mismatch (Imath_3_2vsImath_3_1) surfaced as unresolved symbols when linking libOpenImageIO. (This is an instance of the auto-build "sharp edges" discussed on #5313.)What this does
IGNORE_HOMEBREWED_DEPSblock, also append the Homebrew prefixes toCMAKE_IGNORE_PREFIX_PATH(CMake ≥ 3.23), which config-package searches do honor.CMAKE_IGNORE_PREFIX_PATHto dependency child builds alongside the existingCMAKE_IGNORE_PATHforwarding.What it deliberately does not do
No behavior change when
IGNORE_HOMEBREWED_DEPSis off andCMAKE_IGNORE_PREFIX_PATHis unset — both hunks are conditional on the variable being non-empty.Testing
On macOS (arm64, Homebrew Imath 3.2.2 present),
IGNORE_HOMEBREWED_DEPS=ON+OpenImageIO_BUILD_MISSING_DEPS=all:Imath_DIR=/opt/homebrew/lib/cmake/Imath; libOpenImageIO failed to link withImath_3_2/Imath_3_1symbol mismatches;Assisted-by: Claude Code (Fable 5)