fix(par2): fall back to article-size block when SliceSize exceeds file size#223
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…e size When the configured SliceSize is larger than the file being processed, the previous code clamped it to (file.Size/128)*128, which produces a block size ≈ file.Size. This creates only 1-2 input slices with a nearly-zero last slice — a pathological configuration that triggers undefined behavior in the ParPar C SIMD backend (AVX-512) on Linux x86_64, causing a segfault in CI. Instead, fall back to calculateParBlockSize() which yields a sensible number of equal slices (same as par2go's own test suite uses), and is known-safe on all platforms.
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Summary
internal/par2on Linux CI (run #25039127340)SliceSize > file.Size, the previous code clamped to(file.Size/128)*128 ≈ file.Size, creating only 1–2 input slices with a near-zero last slice — a pathological configuration that triggers undefined behavior in the ParPar C SIMD backend (AVX-512) on Linux x86_64SliceSizewhen it exceeds the file and fall back tocalculateParBlockSize(), which produces a sensible number of equal slices (same as par2go's own tests use)Test plan
./internal/par2/...unit tests pass locally (okin 0.6s)TestIntegration_NativeExecutor_RegeneratesWhenNoPar2FilesExist(the previously crashing test) should now pass on Linux CISliceSize <= file.Size