137f3115a1
* fix(#4492): index the suffix window instead of pattern-matching it `MSG_SUFFIX="${CMD#*"$MSG_MATCH"}"` is quadratic in the -m message. bash tries every prefix length and compares the whole matched literal at each, and MSG_MATCH is BASH_REMATCH[0] — the entire `-m "..."` — so the cost grows with the thing being scanned. Measured on the real hook: 10.0s at 64KB, 22.0s at 96KB, 30.2s at 112KB, 40.1s at 128KB. `bash -x` with an EPOCHREALTIME PS4 attributes 10.116s of a 10.2s run to that one expansion, which computes an empty string. Conforming and non-conforming cost the same, so this is the path every commit takes, and Claude Code blocks on PreToolUse hooks. MSG_PREFIX on the line above has already located the match, so the suffix is arithmetic rather than a search. Same first-occurrence assumption both expansions always made — MSG_MATCH is a literal substring of CMD by construction. Equivalence checked across 480 comparisons on bash 3.2.57 and 5.3.15 under C, UTF-8 and SJIS locales, including multibyte text, repeated matches, metacharacters and invalid bytes. Three regression rows, all deliberately on the RESOLVE=1 path so they pin the suffix scan alone and do not depend on the separate #4429 SIGPIPE fix: non-conforming and conforming 112KB heredocs, plus a suffix-window row whose padding sits before the heredoc opener's newline so the COMMAND is large while the message stays small. Red against the true base — all three killed at the 10s bound with the head -1 sites still present — and green with only this change. Fixture sizes stay under Linux MAX_ARG_STRLEN (131072 on a 4KB-page kernel). Above it execve fails, the classifier cannot launch and the hook fails open, so a larger fixture measures the argument limit rather than the suffix scan; an earlier 131225-byte draft passed on base AND head for exactly that reason. Every row asserts empty stderr, which is what separates "validated" from "failed open". The bound is enforced by killing the process GROUP, not the direct child: the hook spawns a node classifier that inherits stdout, so killing only bash can leave the pipe open and `close` never arrives. `local/no-elapsed-assertion` forbids asserting on elapsed time, and `{ timeout }` is inert on a synchronous body, so the rows are async and the kill is the signal. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UZw5UhR474YLyE4knjHrte * chore(#4492): add changeset Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UZw5UhR474YLyE4knjHrte --------- Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Co-authored-by: Tom Boucher <trekkie@nomorestars.com>
6 lines
634 B
Markdown
6 lines
634 B
Markdown
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type: Fixed
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pr: 4539
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**`git commit` with a large `-m` message is no longer slow** — the commit-message validator hook computed the text after the message with a pattern match that is quadratic in the message length, on the path every commit takes and before the pass/fail branch, so conforming and non-conforming messages cost the same: 10.0s at a 64KB message, 30.2s at 112KB. Claude Code blocks on PreToolUse hooks, so that was dead time in front of the user. The suffix is now derived by arithmetic from the match already located on the preceding line — byte-identical output, flat 0.2s at every size measured. (#4492)
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