[llvm-branch-commits] [clang] [LifetimeSafety] Handle temporaries of non-trivial view types (PR #177878)

[Utkarsh Saxena via llvm-branch-commits]

https://github.com/usx95 updated https://github.com/llvm/llvm-project/pull/177878

>From caa67f558025ef41b97eb65738c8794d4505f174 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Sat, 24 Jan 2026 20:02:17 +0000
Subject: [PATCH] Handle non-trivial view types of temporaries

---
 .../Analyses/LifetimeSafety/FactsGenerator.h  |  1 +
 .../LifetimeSafety/FactsGenerator.cpp         | 17 ++--
 clang/test/Sema/warn-lifetime-safety.cpp      | 97 +++++--------------
 3 files changed, 33 insertions(+), 82 deletions(-)

diff --git a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
index e4487b0d1dbc7..8b45337bee218 100644
--- a/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
+++ b/clang/include/clang/Analysis/Analyses/LifetimeSafety/FactsGenerator.h
@@ -48,6 +48,7 @@ class FactsGenerator : public ConstStmtVisitor<FactsGenerator> {
   void VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *OCE);
   void VisitCXXFunctionalCastExpr(const CXXFunctionalCastExpr *FCE);
   void VisitInitListExpr(const InitListExpr *ILE);
+  void VisitCXXBindTemporaryExpr(const CXXBindTemporaryExpr *BTE);
   void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *MTE);
 
 private:
diff --git a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
index 98fadaa11137f..dea868fd22ddd 100644
--- a/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/FactsGenerator.cpp
@@ -418,12 +418,14 @@ void FactsGenerator::VisitInitListExpr(const InitListExpr *ILE) {
     killAndFlowOrigin(*ILE, *ILE->getInit(0));
 }
 
+void FactsGenerator::VisitCXXBindTemporaryExpr(
+    const CXXBindTemporaryExpr *BTE) {
+  killAndFlowOrigin(*BTE, *BTE->getSubExpr());
+}
+
 void FactsGenerator::VisitMaterializeTemporaryExpr(
     const MaterializeTemporaryExpr *MTE) {
   assert(MTE->isGLValue());
-  // We defer from handling lifetime extended materializations.
-  if (MTE->getStorageDuration() != SD_FullExpression)
-    return;
   OriginList *MTEList = getOriginsList(*MTE);
   if (!MTEList)
     return;
@@ -431,15 +433,16 @@ void FactsGenerator::VisitMaterializeTemporaryExpr(
   assert((!SubExprList ||
           MTEList->getLength() == (SubExprList->getLength() + 1)) &&
          "MTE top level origin should contain a loan to the MTE itself");
-  MTEList = getRValueOrigins(MTE, MTEList);
+
+  OriginList *RValMTEList = getRValueOrigins(MTE, MTEList);
+  flow(RValMTEList, SubExprList, /*Kill=*/true);
+  OriginID OuterMTEID = MTEList->getOuterOriginID();
   if (getChildBinding(MTE)) {
     // Issue a loan to MTE for the storage location represented by MTE.
     const Loan *L = createLoan(FactMgr, MTE);
-    OriginList *List = getOriginsList(*MTE);
     CurrentBlockFacts.push_back(
-        FactMgr.createFact<IssueFact>(L->getID(), List->getOuterOriginID()));
+        FactMgr.createFact<IssueFact>(L->getID(), OuterMTEID));
   }
-  flow(MTEList, SubExprList, /*Kill=*/true);
 }
 
 void FactsGenerator::handleLifetimeEnds(const CFGLifetimeEnds &LifetimeEnds) {
diff --git a/clang/test/Sema/warn-lifetime-safety.cpp b/clang/test/Sema/warn-lifetime-safety.cpp
index c80556715fedf..ca3f239af540c 100644
--- a/clang/test/Sema/warn-lifetime-safety.cpp
+++ b/clang/test/Sema/warn-lifetime-safety.cpp
@@ -14,7 +14,6 @@ struct [[gsl::Owner]] MyObj {
   MyObj operator+(MyObj);
   
   View getView() const [[clang::lifetimebound]];
-  const int* getData() const [[clang::lifetimebound]];
 };
 
 struct [[gsl::Owner]] MyTrivialObj {
@@ -26,10 +25,6 @@ struct [[gsl::Pointer()]] View {
   View(const MyTrivialObj &); // Borrows from MyTrivialObj
   View();
   void use() const;
-
-  const MyObj* data() const;
-  const MyObj& operator*() const;
-  const MyObj* operator->() const;
 };
 
 class TriviallyDestructedClass {
@@ -1460,76 +1455,6 @@ void bar() {
 }
 }
 
-namespace DereferenceViews {
-const MyObj& testDeref(MyObj obj) {
-  View v = obj; // expected-warning {{address of stack memory is returned later}}
-  return *v;    // expected-note {{returned here}}
-}
-const MyObj* testDerefAddr(MyObj obj) {
-  View v = obj; // expected-warning {{address of stack memory is returned later}}
-  return &*v;   // expected-note {{returned here}}
-}
-const MyObj* testData(MyObj obj) {
-  View v = obj;     // expected-warning {{address of stack memory is returned later}}
-  return v.data();  // expected-note {{returned here}}
-}
-const int* testLifetimeboundAccessorOfMyObj(MyObj obj) {
-  View v = obj;           // expected-warning {{address of stack memory is returned later}}
-  const MyObj* ptr = v.data();
-  return ptr->getData();  // expected-note {{returned here}}
-}
-const int* testLifetimeboundAccessorOfMyObjThroughDeref(MyObj obj) {
-  View v = obj;         // expected-warning {{address of stack memory is returned later}}
-  return v->getData();  // expected-note {{returned here}}
-}
-} // namespace DereferenceViews
-
-namespace ViewsBeginEndIterators {
-template <typename T>
-struct [[gsl::Pointer]] Iterator {
-  Iterator operator++();
-  T& operator*() const;
-  T* operator->() const;
-  bool operator!=(const Iterator& other) const;
-};
-
-template <typename T>
-struct [[gsl::Owner]] Container {
-using It = Iterator<T>;
-It begin() const [[clang::lifetimebound]];
-It end() const [[clang::lifetimebound]];
-};
-
-MyObj Global;
-
-const MyObj& ContainerMyObjReturnRef(Container<MyObj> c) {
-  for (const MyObj& x : c) {  // expected-warning {{address of stack memory is returned later}}
-    return x;                 // expected-note {{returned here}}
-  }
-  return Global;
-}
-
-View ContainerMyObjReturnView(Container<MyObj> c) {
-  for (const MyObj& x : c) {  // expected-warning {{address of stack memory is returned later}}
-    return x;                 // expected-note {{returned here}}
-  }
-  for (View x : c) {  // expected-warning {{address of stack memory is returned later}}
-    return x;         // expected-note {{returned here}}
-  }
-  return Global;
-}
-
-View ContainerViewsOk(Container<View> c) {
-  for (View x : c) {
-    return x;
-  }
-  for (const View& x : c) {
-    return x;
-  }
-  return Global;
-}
-} // namespace ViewsBeginEndIterators
-
 namespace reference_type_decl_ref_expr {
 struct S {
   S();
@@ -1691,3 +1616,25 @@ void test() {
 }
 
 } // namespace attr_on_template_params
+
+namespace non_trivial_views {
+struct [[gsl::Pointer]] View {
+    View(const std::string&);
+    ~View(); // Forces a CXXBindTemporaryExpr.
+};
+
+View test1(std::string a) {
+  // Make sure we handle CXXBindTemporaryExpr of view types.
+  return View(a); // expected-warning {{address of stack memory is returned later}} expected-note {{returned here}}
+}
+
+View test2(std::string a) {
+  View b = View(a); // expected-warning {{address of stack memory is returned later}}
+  return b;         // expected-note {{returned here}}
+}
+
+View test3(std::string a) {
+  const View& b = View(a);  // expected-warning {{address of stack memory is returned later}}
+  return b;                 // expected-note {{returned here}}
+}
+} // namespace non_trivial_views