fix(t27b): reference cache writes whole rows, keys on t27c content - #6333
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Each --reference-cache row is formatted into one buffer and written with a single write_all under one lock shared by all workers, so rows cannot interleave. The t27c part of the key is an FNV-1a hash of the binary's bytes, read once per run, instead of its size and mtime, so a byte-identical copy of t27c hits. Old caches are still read; their rows just miss. Tests in cli/t27b/tests/refcache.rs. Closes #6332 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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This was referenced Oct 5, 2026
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Closes #6332. Refs #6063.
What changed (cli/t27b/src/blockers.rs only; lower.rs untouched)
cache_rowformats a row (key, path, verdict) into one buffer, newline included, with tabs/newlines in the path and newlines in the reason turned into spaces.CacheWriteropens the cache once in append mode and writes each row with a singlewrite_allunder a mutex shared by every worker. Before,writeln!on a per-row handle could split a row into several writes.binary_stamp= FNV-1a over the t27c binary's bytes, computed once inRefRunner::new, replacing size+mtime. A byte-identical copy hits; a rebuilt binary misses. Old caches are still read byread_cache; their rows just never match.read_cachealso now requires a 16-hex-digit key.Tests (cli/t27b/tests/refcache.rs)
writeln!append back makes the concurrency test fail.cargo test -p t27b: all suites pass (refcache 4/4, blockers 6, differential 14, encoder 5, macho 1, memory 8, source 24, vacuous 3).🤖 Generated with Claude Code