[clang] [LifetimeSafety] Model pointer-to-data-member access in the fact generator (PR #204612)

[Utkarsh Saxena via cfe-commits]

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@@ -497,6 +497,27 @@ void FactsGenerator::handlePointerArithmetic(const BinaryOperator *BO) {
 }
 
 void FactsGenerator::VisitBinaryOperator(const BinaryOperator *BO) {
+  if (BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI) {
+    // `obj.*pm` / `objptr->*pm` names a member of the object, so a borrow of it
+    // borrows the object; flow the object's origin into the result. For `.*`
+    // the object is the LHS; for `->*` it is the LHS pointer's pointee.
+    //
+    // Only the result's outer (storage) origin relates to the object: borrowing
+    // the member borrows the object's storage. Deeper levels of the result (a
+    // pointer/view member's own pointee) are the member's value, with no
+    // counterpart in the object's origin -- so the lists may differ in length
+    // and we flow just the top level, leaving the member's value untouched.
+    OriginList *Dst = getOriginsList(*BO);
+    OriginList *ObjSrc =
+        BO->getOpcode() == BO_PtrMemD
+            ? getOriginsList(*BO->getLHS())
+            : getRValueOrigins(BO->getLHS(), getOriginsList(*BO->getLHS()));
+    if (Dst && ObjSrc)
+      CurrentBlockFacts.push_back(FactMgr.createFact<OriginFlowFact>(
+          Dst->getOuterOriginID(), ObjSrc->getOuterOriginID(), /*Kill=*/true));
+    handleUse(BO->getLHS());
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usx95 wrote:

Why do we need the `use` here ?
Is it something that can be fixed by https://github.com/llvm/llvm-project/pull/205323

https://github.com/llvm/llvm-project/pull/204612