Go: Regex Engine's Stale Flag Bug
A single fix targets the regular expression package's NFA engine, correcting a boundary-context bug introduced by a performance optimization that fast-forwards the search position.
Duration: PT1M55S
Episode overview
This episode is a short developer briefing from Go.
It explains recent repository work in plain language.
- Show: Go
- Published: 2026-07-06T13:04:42Z
- Audio duration: PT1M55S
Transcript excerpt
This excerpt keeps the crawler page concise. Listen to the episode or use the RSS feed for the full update.
Good day, and welcome to Go for July 6th, 2026.
Today's activity is narrow but worth understanding, because it touches how Go's regular expression engine decides what counts as a word boundary or a line start.
The one item on the board is PR 80266, filed by contributor le0pard. It addresses a subtle bug in the NFA execution engine's handling of prefix fast-forwarding. Here's the issue: when the engine can skip ahead in the input using a known prefix, it updates the current runes to reflect the new position. But it was not…
What makes this worth flagging is the comparison the author draws to the OnePass engine, a separate execution path in the same package. That engine already recalculates its context correctly after a fast-forward. So this wasn't an unknown problem in principle, it was an inconsistency between two engines solving the…
For anyone relying on regular expressions with boundary assertions, this is a correctness issue rather than a performance one. It could affect whether a pattern anchored to a word or line boundary matches correctly after the engine takes a fast-forward shortcut. The fix and its accompanying tests fall under the exec…
What's next: watch for this landing…
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