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…o a line-shifting edit is no longer served the old object The key hashed `-E -P` / `/EP` output, which drops line markers and collapses blank and comment lines. So inserting a comment above a function left the hashed text byte-identical while std::source_location, __builtin_LINE and every -g line table moved: one key, two different objects, and the edited file was served the object built before the edit. Reproduced end to end with the launcher: after adding three comment lines the compile was a HIT whose function reported line 2, where a real compile reports 5. The probe now keeps its markers (`-E`, `/E`), and KeyedPreprocessedText reduces each marker -- GNU's `# N "path" flags` and MSVC's `#line N "path"` -- to its line number and flags before hashing. Dropping the path keeps the key portable, which is all the suppression was for: __FILE__ is already expanded in the text, and a name recorded after preprocessing is root binding's and the prefix maps' to answer. Catch2 across two folders still shares 107 of 107. objkey-v9 / manifest-v10. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CnCkwgtUsaSM5HcgB3APNU
…g only inside @file stop sharing one object A driver expands `@file` itself, so the arguments inside it reached neither the object key nor the direct-mode manifest key -- both hashed the NAME. Reproduced with the launcher: compiling with `-O0` in the file, then changing it to `-O2`, was answered with the `-O0` object (a direct-mode HIT; `mov $0x2` where -O2 gives `mov $0x1`). ResponseFileKeyItems keys each response file's BYTES, with the source root, build tree and dependency cache replaced by their tokens so checkouts still share; no tokenizer of the launcher's can disagree with the driver's about bytes. A file that cannot be read, that names another response file, or that carries an output or dependency-file flag the launcher must read off the command line keeps the compile uncached, with the reason in the verbose trace. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CnCkwgtUsaSM5HcgB3APNU
This was referenced Oct 17, 2026
fastcache-cc: -march=native is keyed as literal text, so one CPU's object is served to another
#1688
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Two ways the compile cache served an object built from something other than what was asked, both reproduced end to end with the launcher. Builds on #1686.
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-E -P//EPoutput, which drops line markers and collapses blank and comment lines. Inserting a comment above a function therefore left the key unchanged, whilestd::source_location,__builtin_LINEand every-gline table moved.-E,/E).KeyedPreprocessedTextreduces each marker (GNU# N "path" flags, MSVC#line N "path") to its line number and flags, so the key stays portable: Catch2 across two folders still shares 107 of 107.@fileitself, so both the object key and the direct-mode manifest key hashed only its name.-O0to-O2inside the file was answered with the-O0object.ResponseFileKeyItemskeys each file's bytes, with the source root, build tree and dependency cache tokenized.objkey-v9/manifest-v10.compile-cache.md,AGENT.mdtripwire) anddocs/tools/fastcache-cc.mdare updated.Both came out of an audit of the cache for wrong-object paths; the remaining findings are being filed as separate issues.
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