[clang] [LifetimeSafety] Add support for derived-to-base conversions (PR #175631)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-analysis

@llvm/pr-subscribers-clang

Author: Utkarsh Saxena (usx95)

<details>
<summary>Changes</summary>

Add support for derived-to-base conversions in lifetime analysis.

Added handling for `CK_UncheckedDerivedToBase` and `CK_DerivedToBase` cast kinds in the `FactsGenerator::VisitImplicitCastExpr` method. These cast kinds are now treated similarly to other conversions by flowing origins from source to destination.

Added a unit test `DerivedToBaseThisArg` that verifies lifetime information is correctly propagated through derived-to-base conversions when using member functions inherited from a base class.

---
Full diff: https://github.com/llvm/llvm-project/pull/175631.diff


2 Files Affected:

- (modified) clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp (+2) 
- (modified) clang/unittests/Analysis/LifetimeSafetyTest.cpp (+23) 


``````````diff
diff --git a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
index f3993b7e7e261..60b0bf7e1bdac 100644
--- a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
@@ -219,6 +219,8 @@ void FactsGenerator::VisitImplicitCastExpr(const ImplicitCastExpr *ICE) {
   case CK_NoOp:
   case CK_ConstructorConversion:
   case CK_UserDefinedConversion:
+  case CK_UncheckedDerivedToBase:
+  case CK_DerivedToBase:
     flow(Dest, SrcList, /*Kill=*/true);
     return;
   case CK_FunctionToPointerDecay:
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index b1f74a7a2c850..5c892b656d5c8 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -1778,5 +1778,28 @@ TEST_F(LifetimeAnalysisTest, TrackFirstArgument_StdAnyCast) {
   EXPECT_THAT(Origin("r"), HasLoansTo({"a"}, "p1"));
 }
 
+TEST_F(LifetimeAnalysisTest, DerivedToBaseThisArg) {
+  SetupTest(R"(
+    template <typename T>
+    struct OperatorBase {
+      const T& value() const& [[clang::lifetimebound]];
+      const T&& value() const&& [[clang::lifetimebound]];
+    };
+
+    template <typename T>
+    class StatusOr : private OperatorBase<T> {
+      public:
+        using StatusOr::OperatorBase::value;
+    };
+
+    void target() {
+      View view;
+      StatusOr<MyObj> my_obj_or;
+      view = my_obj_or.value();
+      POINT(p1);
+    }
+  )");
+  EXPECT_THAT(Origin("view"), HasLoansTo({"my_obj_or"}, "p1"));
+}
 } // anonymous namespace
 } // namespace clang::lifetimes::internal

``````````

</details>


https://github.com/llvm/llvm-project/pull/175631