automata: fix search_slots panic with zero-repetition capture #1329
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BurntSushi
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Jan 30, 2026
…ots are given The API specifically documents that the caller may provide *any* number of slots. But the onepass implementation was panicking when too many were provided. (I had only considered the case when too few were provided when I wrote one-pass implementation I think.) This already works for the PikeVM and the bounded backtracker. This commit adds tests covering those as well. Note that the bug report specifically cites a zero-repetition capture group as the instigator here. While that may have provided the circumstances for the bug to appear, the actual bug is more general than that. You don't need any capture groups at all to provoke it. You just need to provide more slots than there are in the compiled regex. Fixes #1327, Closes #1329
BurntSushi
pushed a commit
that referenced
this pull request
Jan 30, 2026
…ots are given The API specifically documents that the caller may provide *any* number of slots. But the onepass implementation was panicking when too many were provided. (I had only considered the case when too few were provided when I wrote one-pass implementation I think.) This already works for the PikeVM and the bounded backtracker. This commit adds tests covering those as well. Note that the bug report specifically cites a zero-repetition capture group as the instigator here. While that may have provided the circumstances for the bug to appear, the actual bug is more general than that. You don't need any capture groups at all to provoke it. You just need to provide more slots than there are in the compiled regex. Fixes #1327, Closes #1329
Member
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Thanks! I'm not sure why, but I can't push to this PR. So I opened #1330 which is based on this one. I tweaked the fix, added more general regression tests and massaged the wording here to not be so coupled to a zero-repetition capture group. |
Author
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Nice, thank you. I think the reason why you can't push to this PR's branch is because I forked this repo to an organization - I like to keep my forks separate from my own projects. And organization owned repositories don't allow pushes from other users, there is no option to "allow maintainers to push to this branch" unfortunately. It kinda makes sense but is a little annoying... |
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Fixes #1327
update the onepass DFA to only copy slots that exist in the cache, which may contain fewer slots than what the caller provided