fix: dispatch hashtree at runtime on every x86_64 target - #13
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Select hashtree on x86_64 by target OS instead of compile-time CPU features, since `hashtree_hash` already picks its backend at runtime. - `isSupported()` returns true on x86_64 except macOS and Windows MSVC, the targets where `build.zig` does not assemble the x86 backends - baseline builds (for example published packages built with only `-Dtarget`) now use SHA-NI, AVX-512, AVX2, AVX or SSE instead of std SHA-256 - macOS keeps the std fallback whatever `-Dcpu` is, which fixes the undefined `_hashtree_sha256_*` link errors with `-Dcpu=haswell`
spiral-ladder
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Oct 1, 2026
**Motivation** The current hashtree-z pin sends baseline x86_64 builds through Zig's SHA-256 fallback even though hashtree selects its backend at runtime. [ChainSafe/hashtree-z#13](ChainSafe/hashtree-z#13) enables that dispatch on supported targets and fixes x86_64 macOS linking with explicit CPU features. **Description** Update `hashtree` in `build.zig.zon` from `f5c1b81` to `9b0fdad`, including the package hash generated by `zig fetch`. **AI Assistance Disclosure** Implementation was primarily AI-authored with Codex.
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Motivation
On x86_64,
isSupported()only callshashtree_hashwhen the compile-time CPU has avx512f+avx512vl, avx2+bmi2 or sha+avx. Baseline builds, including the published lodestar-z packages (built with only-Dtarget), therefore never link hashtree and hash every pair with std SHA-256, even thoughhashtree_hashselects its backend at runtime. Measured with lodestar-z on a Threadripper 1950X (SHA-NI), ReleaseSafe:Separately,
x86_64-macoswith-Dcpu=haswellfails to link today (undefined symbol: _hashtree_sha256_avx2_x8, ...) because the x86.Sfiles are not assembled for Mach-O.Description
Select hashtree on x86_64 by target OS instead of compile-time CPU features.
isSupported()returns true on x86_64 except macOS and Windows MSVC, matching the targets wherebuild.zigassembles the x86 backends-Dcpu, which also fixes the macOS link failureTested:
zig build testnatively, with-Dcpu=baseline(Debug and ReleaseSafe), the baseline test binary under qemu-x86_64qemu64,Nehalem-v2andEPYC-v1, andaarch64-linux-muslvia qemu;x86_64-macos(with and without-Dcpu=haswell),x86_64-windows-gnuandx86_64-linux-muslbuild.x86_64-windows-msvcfails the same way on main (no MSVC headers here).AI Assistance Disclosure
Primarily AI-authored with Claude Code, including the measurements.