Fix infinite loop (DoS hang) on unterminated block comment#271
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`consumeMultiLineComment` looped on `!l.isEOF()` (which checks `l.current`) while only advancing the local index `i`, so on an unclosed comment like `/* unterminated` the lexer spun forever — a DoS hang. Loop on `l.peekOk(i)` instead so it terminates at end of input. Add TestConsumeUnterminatedComment to reproduce: it drains the lexer in a goroutine with a timeout, so a regression fails fast instead of hanging. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Lance726
approved these changes
Jun 10, 2026
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Problem
consumeMultiLineCommentloops on!l.isEOF(), which testsl.current, but only advances a local indexi. When a block comment is never closed,l.currentnever moves, soisEOF()never becomes true and the lexer spins forever — a denial-of-service hang on malformed input.Reproduction
(The exact 2-byte input
/*is safe becauseskipN(2)already leavescurrentat EOF, but any content after the opener triggers the hang.)Fix
Loop on
l.peekOk(i)instead, so the loop tracks the local index and terminates at end of input. When no closing*/is found, the remainder is consumed as comment — matchingconsumeSingleLineComment's behaviour.Test
TestConsumeUnterminatedCommentdrains the lexer in a goroutine guarded by a timeout, so a regression fails fast instead of hanging the test binary.🤖 Generated with Claude Code