[llvm-branch-commits] [clang] [LifetimeSafety] Mark all DeclRefExpr as usages of the corresp. origin (PR #154316)

[Yitzhak Mandelbaum via llvm-branch-commits]

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@@ -559,9 +553,49 @@ class FactGeneratorVisitor : public ConstStmtVisitor<FactGeneratorVisitor> {
     return false;
   }
 
+  void handleAssignment(const Expr *LHSExpr, const Expr *RHSExpr) {
+    // Find the underlying variable declaration for the left-hand side.
+    if (const auto *DRE_LHS =
+            dyn_cast<DeclRefExpr>(LHSExpr->IgnoreParenImpCasts())) {
+      markUseAsWrite(DRE_LHS);
+      if (const auto *VD_LHS = dyn_cast<ValueDecl>(DRE_LHS->getDecl()))
+        if (hasOrigin(VD_LHS->getType()))
+          // We are interested in assignments like `ptr1 = ptr2` or `ptr = &var`
+          // LHS must be a pointer/reference type that can be an origin.
+          // RHS must also represent an origin (either another pointer/ref or an
+          // address-of).
+          addAssignOriginFact(*VD_LHS, *RHSExpr);
+    }
+  }
+
+  // A DeclRefExpr is a use of the referenced decl. It is checked for
+  // use-after-free unless it is being written to (e.g. on the left-hand side
+  // of an assignment).
+  void handleUse(const DeclRefExpr *DRE) {
+    const auto *VD = dyn_cast<ValueDecl>(DRE->getDecl());
+    if (VD && hasOrigin(VD->getType())) {
+      OriginID OID = FactMgr.getOriginMgr().get(*VD);
+      UseFact *UF = FactMgr.createFact<UseFact>(OID, DRE);
+      CurrentBlockFacts.push_back(UF);
+      assert(!UseFacts.contains(DRE));
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ymand wrote:

Why are we assuming that DRE has not already been seen? I would expect this to potentially be called for multiple DREs in a block and there's no logic inside the function that checks for uniqueness, so I gather its a precondition?

https://github.com/llvm/llvm-project/pull/154316