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[LifetimeSafety] Introduce a liveness-based lifetime policy #159991

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Oct 7, 2025
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[LifetimeSafety] Introduce a liveness-based lifetime policy #159991

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24 changes: 20 additions & 4 deletions clang/include/clang/Analysis/Analyses/LifetimeSafety.h
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Original file line number Diff line number Diff line change
Expand Up @@ -29,12 +29,18 @@
namespace clang::lifetimes {

/// Enum to track the confidence level of a potential error.
enum class Confidence {
enum class Confidence : uint8_t {
None,
Maybe, // Reported as a potential error (-Wlifetime-safety-strict)
Definite // Reported as a definite error (-Wlifetime-safety-permissive)
};

enum class LivenessKind : uint8_t {
Dead, // Not alive
Maybe, // Live on some path but not all paths (may-be-live)
Must // Live on all paths (must-be-live)
};

class LifetimeSafetyReporter {
public:
LifetimeSafetyReporter() = default;
Expand All @@ -55,6 +61,7 @@ class Fact;
class FactManager;
class LoanPropagationAnalysis;
class ExpiredLoansAnalysis;
class LiveOriginAnalysis;
struct LifetimeFactory;

/// A generic, type-safe wrapper for an ID, distinguished by its `Tag` type.
Expand Down Expand Up @@ -89,6 +96,7 @@ inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, OriginID ID) {
// TODO(opt): Consider using a bitset to represent the set of loans.
using LoanSet = llvm::ImmutableSet<LoanID>;
using OriginSet = llvm::ImmutableSet<OriginID>;
using OriginLoanMap = llvm::ImmutableMap<OriginID, LoanSet>;

/// A `ProgramPoint` identifies a location in the CFG by pointing to a specific
/// `Fact`. identified by a lifetime-related event (`Fact`).
Expand All @@ -110,8 +118,16 @@ class LifetimeSafetyAnalysis {
/// Returns the set of loans an origin holds at a specific program point.
LoanSet getLoansAtPoint(OriginID OID, ProgramPoint PP) const;

/// Returns the set of loans that have expired at a specific program point.
std::vector<LoanID> getExpiredLoansAtPoint(ProgramPoint PP) const;
/// Returns the set of origins that are live at a specific program point,
/// along with the confidence level of their liveness.
///
/// An origin is considered live if there are potential future uses of that
/// origin after the given program point. The confidence level indicates
/// whether the origin is definitely live (Definite) due to being domintated
/// by a set of uses or only possibly live (Maybe) only on some but not all
/// control flow paths.
std::vector<std::pair<OriginID, LivenessKind>>
getLiveOriginsAtPoint(ProgramPoint PP) const;

/// Finds the OriginID for a given declaration.
/// Returns a null optional if not found.
Expand All @@ -138,7 +154,7 @@ class LifetimeSafetyAnalysis {
std::unique_ptr<LifetimeFactory> Factory;
std::unique_ptr<FactManager> FactMgr;
std::unique_ptr<LoanPropagationAnalysis> LoanPropagation;
std::unique_ptr<ExpiredLoansAnalysis> ExpiredLoans;
std::unique_ptr<LiveOriginAnalysis> LiveOrigins;
};
} // namespace internal
} // namespace clang::lifetimes
Expand Down
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