[6.0] Turn mishandled reinitialize-in-defer-after-consume cases into errors.
#74170
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…rors. The handling of multi-basic-block control flow in `defer` blocks looks like it was left incomplete and completely untested; I fixed a few obvious problems but it still completely lacks any analysis of conditional reinitializations. For now, change it to treat attempted reinitializations as uses-after-consumes so we raise reliable errors now instead of emitting code that causes memory corruption at runtime. Fixes rdar://129303198.
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@swift-ci Please test |
nate-chandler
approved these changes
Jun 6, 2024
tbkka
approved these changes
Jun 6, 2024
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Explanation: If an
inoutparameter's value is consumed with theconsumeoperator and reinitialized in adeferblock that also contains control flow such asif,while,switch, etc., then the compiler would miscompile the code leading to runtime memory corruption. This patch turns these mishandled cases into errors.Scope: Prevents a miscompile by adding a diagnostic.
Issue: rdar://129303198.
Original PR: #74154
Risk: Low. Turns code that would lead to corrupt code generation into hard errors.
Testing: Swift CI, test case from bug report
Reviewer: @nate-chandler