[llvm-branch-commits] [clang] std_move false positive (PR #170007)

[Utkarsh Saxena via llvm-branch-commits]

https://github.com/usx95 created https://github.com/llvm/llvm-project/pull/170007

None

>From a1b450994cbbac0a95ba2f06bf8172822dcb075b Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Sat, 29 Nov 2025 16:43:06 +0000
Subject: [PATCH] std_move false positive

---
 .../Analyses/LifetimeSafety/FactsGenerator.h       |  2 ++
 .../lib/Analysis/LifetimeSafety/FactsGenerator.cpp | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
index 939f421505463..eb251fa1400b6 100644
--- a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
+++ b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
@@ -101,6 +101,8 @@ class FactsGenerator : public ConstStmtVisitor<FactsGenerator> {
   // corresponding to the left-hand side is updated to be a "write", thereby
   // exempting it from the check.
   llvm::DenseMap<const DeclRefExpr *, UseFact *> UseFacts;
+
+  llvm::DenseSet<const ValueDecl* > MovedDecls;
 };
 
 } // namespace clang::lifetimes::internal
diff --git a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
index c098069720c79..41a7d69edbdd8 100644
--- a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
@@ -168,9 +168,21 @@ void FactsGenerator::VisitCXXMemberCallExpr(const CXXMemberCallExpr *MCE) {
   }
 }
 
+static bool isStdMove(const FunctionDecl *FD) {
+  return FD && FD->isInStdNamespace() && FD->getIdentifier() &&
+         FD->getName() == "move";
+}
+
 void FactsGenerator::VisitCallExpr(const CallExpr *CE) {
   handleFunctionCall(CE, CE->getDirectCallee(),
                      {CE->getArgs(), CE->getNumArgs()});
+  // Remember accessPath which moved using std::move.
+  // TODO: If there is need, this could flow-sensitive
+  if (isStdMove(CE->getDirectCallee()))
+    if (CE->getNumArgs() == 1)
+      if (auto *DRE =
+              dyn_cast<DeclRefExpr>(CE->getArg(0)->IgnoreParenImpCasts()))
+        MovedDecls.insert(DRE->getDecl());
 }
 
 void FactsGenerator::VisitCXXNullPtrLiteralExpr(
@@ -349,6 +361,8 @@ void FactsGenerator::handleLifetimeEnds(const CFGLifetimeEnds &LifetimeEnds) {
   // Iterate through all loans to see if any expire.
   for (const auto &Loan : FactMgr.getLoanMgr().getLoans()) {
     const AccessPath &LoanPath = Loan.Path;
+    if (MovedDecls.contains(LoanPath.D))
+      continue;
     // Check if the loan is for a stack variable and if that variable
     // is the one being destructed.
     if (LoanPath.D == LifetimeEndsVD)