[4.1][SourceKit] Add defensive guard for invalid offset #14869
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Invalid offset used to cause a inifinite loop in Lexer in some race condition. This is a quick fix until we fix underlying problem in SourceKit.
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@swift-ci Please test |
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Cherry-pick of #14803 for swift-4.1-branch
Explanation: In some race conditions, SourceKit could receives invalid (too high) offset value in requests. This used cause undefined behavior in
Lexersuch as infinite loop in the worst case. This quick change adds a guard to prevent to propagate invalid offset values to the Lexer.Scope: CursorInfo and RangeInfo requests for SourceKit.
Issue: rdar://problem/30346106
Risk: Very low. By this change, SourceKit guarantees to emit empty response (as expected) for cursor/range-info requests with invalid offset.
Testing: Added a regression test.
Reviewer: @akyrtzi