fix(lance-linalg): check fp16kernels feature before arch-specific code #5747
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The build script was checking target architecture BEFORE verifying if the fp16kernels feature was enabled. This caused builds to fail on platforms like iOS/Android when falling through to the error branch, even when the feature was disabled. The fix adds an early exit using CARGO_FEATURE_FP16KERNELS env var check (not cfg!() which checks build script features, not library features). Fixes: lance-format#5746
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Address review feedback: instead of early exit which skips build_dist_table_with_flags on x86_64, only error in the else branch when fp16kernels is explicitly requested on unsupported platforms. This preserves dist_table kernel builds on supported platforms while still allowing iOS/Android builds when fp16kernels is disabled.
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@wjones127, thanks for the speedy review, this should do it |
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This looks good. Thanks!
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lance-format#5747) ## Summary The build script was checking target architecture BEFORE verifying if the `fp16kernels` feature was enabled. This caused builds to fail on platforms like iOS/Android when falling through to the error branch, even when the feature was disabled. ## The Problem On line 78-79 of `rust/lance-linalg/build.rs`: ```rust } else { return Err("Unable to build f16 kernels on given target_arch. Please use x86_64 or aarch64 or remove the fp16kernels feature".to_string()); } ``` This error is returned for any target_arch not in the supported list (x86_64, aarch64 macos/linux, loongarch64), **before** the feature check in `build_f16_with_flags()` is ever called. Additionally, `cfg!(not(feature = "fp16kernels"))` inside `build_f16_with_flags()` checks the **build script's** features, not the library's features (build scripts are compiled for the host, not the target). ## The Fix Add an early exit using `CARGO_FEATURE_FP16KERNELS` env var check (which correctly reflects the library's features, not the build script's) **before** the target_arch branching logic. ## Testing Verified fix enables successful iOS builds with: - lancedb v0.23.1 - Tauri 2.x iOS target - `fp16kernels` feature disabled (default) Fixes: lance-format#5746
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Summary
The build script was checking target architecture BEFORE verifying if the
fp16kernelsfeature was enabled. This caused builds to fail on platforms like iOS/Android when falling through to the error branch, even when the feature was disabled.The Problem
On line 78-79 of
rust/lance-linalg/build.rs:This error is returned for any target_arch not in the supported list (x86_64, aarch64 macos/linux, loongarch64), before the feature check in
build_f16_with_flags()is ever called.Additionally,
cfg!(not(feature = "fp16kernels"))insidebuild_f16_with_flags()checks the build script's features, not the library's features (build scripts are compiled for the host, not the target).The Fix
Add an early exit using
CARGO_FEATURE_FP16KERNELSenv var check (which correctly reflects the library's features, not the build script's) before the target_arch branching logic.Testing
Verified fix enables successful iOS builds with:
fp16kernelsfeature disabled (default)Fixes: #5746