[clang] [LifetimeSafety] Propagate loans through pointer arithmetic (PR #189546)

[via cfe-commits]

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@@ -378,11 +371,22 @@ void FactsGenerator::handleAssignment(const Expr *LHSExpr,
   flow(LHSList->peelOuterOrigin(), RHSList, /*Kill=*/true);
 }
 
+void FactsGenerator::handlePointerArithmetic(const BinaryOperator *BO) {
+  if (Expr *RHS = BO->getRHS(); RHS->getType()->isPointerType()) {
+    flowOrigin(*BO, *RHS);
+    return;
+  }
+  Expr *LHS = BO->getLHS();
+  assert(LHS->getType()->isPointerType() &&
+         "Pointer arithmetic must have a pointer operand");
+  flowOrigin(*BO, *LHS);
+}
+
 void FactsGenerator::VisitBinaryOperator(const BinaryOperator *BO) {
-  // TODO: Handle pointer arithmetic (e.g., `p + 1` or `1 + p`) where the
-  // result should have the same loans as the pointer operand.
   if (BO->isCompoundAssignmentOp())
     return;
+  if (BO->getType()->isPointerType() && BO->isAdditiveOp())
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NeKon69 wrote:

yes, `isAdditiveOp` checks for addition and subtraction

https://github.com/llvm/llvm-project/pull/189546