build: pin explicit per-variant macOS deployment targets - #203
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The MLX build and NIF link set no deployment target, so MLX's objects inherited the build host's OS (CMake "build for host") while the NIF linked at the SDK-major .0 — producing `ld` version-mismatch warnings and a shipped floor that drifts with the runner OS. An aot build done on a macOS-26 host silently linked the macOS-26 libSystem `_Float16` helpers (`__fmaxf16`/`__fminf16`) as hard imports, so it would fail to dyld-load on the older macOS the aot variant is meant to support. Pin an explicit per-variant floor (aot 14.0; jit 26.2, since its NAX kernels and JACCL are gated on macOS SDK >= 26.2) and thread it through both the MLX CMake build (CMAKE_OSX_DEPLOYMENT_TARGET) and the NIF compile/link (MACOSX_DEPLOYMENT_TARGET) from one source of truth in mix.exs. The floor is folded into the MLX cache dir name so a change can't reuse a stale build. scripts/verify-nif-floor.sh asserts the built NIF's LC_BUILD_VERSION and that a sub-26 floor imports no macOS-26 symbols; CI and the release workflow run it per variant. Closes #202.
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Closes #202.
Problem
Neither the MLX build (
scripts/build-mlx.sh) nor the NIF link (mix.exs) sets a macOS deployment target, so:CMAKE_OSX_DEPLOYMENT_TARGETis unset), while the NIF links at the SDK-major.0→ theld: … built for newer 'macOS' version (26.4) than being linked (26.0)warnings._Float16helpers__fmaxf16/__fminf16as hard (non-weak) imports — it would fail todyld-load on the older macOS the aot variant is supposed to support. The aot artifact is portable today only because it happens to build onmacos-14.Change
Pin an explicit, per-variant floor and thread it through both halves of the build from one source of truth (
macos_deployment_target/0inmix.exs):-DCMAKE_OSX_DEPLOYMENT_TARGET(build-mlx.sh, new 5th arg).MACOSX_DEPLOYMENT_TARGET(make_env/0; clang honours it for both).Floors: aot = 14.0 (the older-macOS path; MLX's own floor), jit = 26.2 (its NAX kernels + JACCL are gated on macOS SDK ≥ 26.2). The floor is folded into the MLX cache-dir name so changing it can't reuse a stale build.
scripts/verify-nif-floor.shasserts the built NIF'sLC_BUILD_VERSIONmatches the pinned floor and that a sub-26 floor imports no macOS-26_Float16symbols. Wired intoci.yml(per variant) andrelease-nif.yml(guards the shipped artifact before packaging).Verification (on a macOS 26.5 host)
Before → after for the aot build, same host:
__fmaxf16/__fminf16LC_BUILD_VERSIONldmismatch warningsscripts/verify-nif-floor.sh … 14.0passes; correctly rejects a wrong floor (26.2).mix precommitgreen — 737 tests / 40 doctests / 79 properties, 0 failures.mix test --only conformancegreen — 52 tests, 0 failures.Notes
ci.yml/release-nif.yml(NAX includesMetalPerformancePrimitives.h, first shipped in the 26.2 SDK).macos-14/macos-26) and assert each floor — the definitive runtime check the codebase already had, now with a declared, verified minimum.