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The header separator pattern repeated a column group greedily
("(?:COL\|)+COL"). java.util.regex matches a greedy group repetition
recursively, so the stack depth grew with the number of columns and a
separator line with several hundred columns threw StackOverflowError.
Repeat the column group possessively so it is matched in a loop, and
order the column alternatives longest first so that alignment markers
are still recognised without backtracking.
Co-Authored-By: Claude Fable 5.2 <[email protected]>
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🟢 Approval recommended
No active review issues are recorded for the table-separator parsing change.
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What changed in this PR
This PR prevents stack overflows when the tables extension parses header separator lines with many columns.
Changes:
- Replaces recursive regex repetition with possessive repetition to avoid stack growth per column.
- Reorders column alternatives to preserve alignment recognition.
- Adds small-stack regression tests for 5,000-column tables and a separate mixed-alignment case.
| File | Description |
|---|---|
flexmark-ext-tables/src/test/java/com/vladsch/flexmark/ext/tables/TableSeparatorStackOverflowTest.java |
Tests wide-table parsing and rendering, plus alignment preservation. |
flexmark-ext-tables/src/main/java/com/vladsch/flexmark/ext/tables/internal/TableParagraphPreProcessor.java |
Updates the separator regex to avoid recursive column matching and documents the approach. |
Review effort: Balanced
raydive
approved these changes
Nov 13, 2026
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課題
https://nulab.backlog.jp/view/CASHEW_NUTS-1163
Why
テーブルのヘッダー区切り行（
|:-|:-|...）を判定する正規表現が、列数の多い行で StackOverflowError を起こす。列の繰り返しが(?:COL\|)+COLという形で、java.util.regex は貪欲なグループの繰り返しを 1 回ごとに再帰して照合するため、列数に比例してスタックを消費する。1 MB のスタックでは、区切りが:-の行は 500 列で落ちる。2026-11-12 に backlog-web の本番 Pod がこの形のスタックトレース（
java.util.regex.Pattern$...の 13 フレーム周期）を残して終了した。What
TableParagraphPreProcessor.getTableHeaderSeparatorの正規表現を、再帰しない形に書き換えた。(?:COL\|)+COL→COL(?:\|COL)++。独占的な繰り返しは再帰せずループで照合される:-:→:-→-:→-）に並べ替えた。独占的にするとバックトラックしなくなるので、並べ替えないと右寄せ・中央寄せを判定できなくなる確認したこと
TableSeparatorStackOverflowTest（512 KB のスタックで 5000 列のテーブルを parse して render、寄せ指定 4 種と混在）は、修正前に 5 件中 4 件が StackOverflowError で失敗し、修正後はすべて通るflexmark-ext-tablesのテスト 1130 件がすべて通る（mvn -pl flexmark-ext-tables -am test -Dtest='com.vladsch.flexmark.ext.tables.**'）|-:空白aからなる長さ 10 までの全文字列（約 1,220 万通り）で、修正前後の正規表現のmatches()の結果が一致する（minColumnDashes1〜4、IntelliJ ダミー識別子なし）リポジトリ全体の
mvn testはローカルでは流していない。🤖 Generated with Claude Code