llvm-project

673750fe - [LifetimeSafety] Implement a basic use-after-free diagnostic (#149731)

[LifetimeSafety] Implement a basic use-after-free diagnostic (#149731) Implement use-after-free detection in the lifetime safety analysis with two warning levels. - Added a `LifetimeSafetyReporter` interface for reporting lifetime safety issues - Created two warning levels: - Definite errors (reported with `-Wexperimental-lifetime-safety-permissive`) - Potential errors (reported with `-Wexperimental-lifetime-safety-strict`) - Implemented a `LifetimeChecker` class that analyzes loan propagation and expired loans to detect use-after-free issues. - Added tracking of use sites through a new `UseFact` class. - Enhanced the `ExpireFact` to track the expressions where objects are destroyed. - Added test cases for both definite and potential use-after-free scenarios. The implementation now tracks pointer uses and can determine when a pointer is dereferenced after its loan has been expired, with appropriate diagnostics. The two warning levels provide flexibility - definite errors for high-confidence issues and potential errors for cases that depend on control flow.