doc: add test commands to readme#106
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…debug-build segfault (#23847) ## Problem The nightly barretenberg **debug** build has been failing (aztec-claude run [26935061960](https://github.com/AztecProtocol/aztec-claude/actions/runs/26935061960); same failure in aztec-packages runs #105/#106). The build dies with `exit status 139` (SIGSEGV) on: ``` FAILED ... ecc_tests PippengerConstantine.SimdX4MatchesScalarPathLanewise (code: 139) [ RUN ] PippengerConstantine.SimdX4MatchesScalarPathLanewise timeout: the monitored command dumped core ``` ## Root cause In `barretenberg/cpp/src/barretenberg/ecc/scalar_multiplication/pippenger_constantine.hpp`, `simd_u32x4_store` writes the result vector with: ```cpp *reinterpret_cast<SimdU32x4*>(dst) = v; ``` `SimdU32x4` is `uint32_t __attribute__((vector_size(16)))`, which carries **16-byte alignment**, so this is an *aligned* 128-bit store. But `dst` is an arbitrary `uint32_t*` — the test and fuzzer pass a stack `std::array<uint32_t, 4>` (4-byte aligned). At `-O0` (debug) the store lowers to an alignment-requiring `movaps`/`movdqa` and faults whenever `dst` is not 16-byte aligned. This only surfaces in the **debug** nightly: the helper is `[[gnu::always_inline]]`, so at `-O2` SROA promotes the local `out` array into registers and the memory store is elided — which is why the full (release) CI is green while the debug build segfaults. The SIMD x4 helpers are currently consumed only by the unit test and fuzzer (not yet wired into the MSM hot loop), so the blast radius is the test/fuzzer. ## Fix Store via `__builtin_memcpy`, which has no alignment precondition and lowers to the intended unaligned `movdqu` / NEON `st1` (the WASM `wasm_v128_store` path is unchanged). This matches the helper's documented intent. ## Verification (red/green, debug preset) Built `ecc_tests` with the `debug` CMake preset (`build-debug`, `-O0 -D_GLIBCXX_DEBUG`), matching the nightly: - **Without the fix:** `PippengerConstantine.SimdX4MatchesScalarPathLanewise` → exit **139** (SIGSEGV), reproducing the nightly. - **With the fix:** all 6 `PippengerConstantine.*` tests pass. A standalone repro confirmed the mechanism independently: the aligned store to a 4-byte-aligned destination segfaults at `-O0`; the `memcpy` form stores correctly. --- *Created by [claudebox](https://claudebox.work/v2/sessions/cadf49316638602b) · group: `slackbot`* --------- Co-authored-by: iakovenkos <sergey.s.yakovenko@gmail.com>
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Description
README update
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