[clang] [clang] Merge lifetimebound and GSL code paths for lifetime analysis (PR #104906)

Haojian Wu via cfe-commits cfe-commits at lists.llvm.org
Tue Aug 20 13:42:20 PDT 2024


https://github.com/hokein updated https://github.com/llvm/llvm-project/pull/104906

>From 773a03b25a94d991206f4b517eefdf3693e6a287 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Tue, 20 Aug 2024 10:22:44 +0200
Subject: [PATCH 1/2] [clang] Merge the lifetimebound and GSL code paths for
 lifetime analysis.

---
 clang/docs/ReleaseNotes.rst                   |   2 +
 clang/lib/Sema/CheckExprLifetime.cpp          | 129 ++++++++----------
 .../Sema/warn-lifetime-analysis-nocfg.cpp     |  13 ++
 3 files changed, 72 insertions(+), 72 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 249249971dec7c..924968452819d1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -225,6 +225,8 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses when the result of a [[nodiscard]] function is discarded after being cast in C. Fixes #GH104391.
 
+- Don't emit duplicated dangling diagnostics. (#GH93386).
+
 Improvements to Clang's time-trace
 ----------------------------------
 
diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 7389046eaddde1..06eb909659d05d 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -326,66 +326,6 @@ static bool shouldTrackFirstArgument(const FunctionDecl *FD) {
   return false;
 }
 
-static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
-                                    LocalVisitor Visit) {
-  auto VisitPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
-    // We are not interested in the temporary base objects of gsl Pointers:
-    //   Temp().ptr; // Here ptr might not dangle.
-    if (isa<MemberExpr>(Arg->IgnoreImpCasts()))
-      return;
-    // Once we initialized a value with a reference, it can no longer dangle.
-    if (!Value) {
-      for (const IndirectLocalPathEntry &PE : llvm::reverse(Path)) {
-        if (PE.Kind == IndirectLocalPathEntry::GslReferenceInit)
-          continue;
-        if (PE.Kind == IndirectLocalPathEntry::GslPointerInit ||
-            PE.Kind == IndirectLocalPathEntry::GslPointerAssignment)
-          return;
-        break;
-      }
-    }
-    Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit
-                          : IndirectLocalPathEntry::GslReferenceInit,
-                    Arg, D});
-    if (Arg->isGLValue())
-      visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
-                                            Visit,
-                                            /*EnableLifetimeWarnings=*/true);
-    else
-      visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
-                                       /*EnableLifetimeWarnings=*/true);
-    Path.pop_back();
-  };
-
-  if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
-    const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());
-    if (MD && shouldTrackImplicitObjectArg(MD))
-      VisitPointerArg(MD, MCE->getImplicitObjectArgument(),
-                      !MD->getReturnType()->isReferenceType());
-    return;
-  } else if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(Call)) {
-    FunctionDecl *Callee = OCE->getDirectCallee();
-    if (Callee && Callee->isCXXInstanceMember() &&
-        shouldTrackImplicitObjectArg(cast<CXXMethodDecl>(Callee)))
-      VisitPointerArg(Callee, OCE->getArg(0),
-                      !Callee->getReturnType()->isReferenceType());
-    return;
-  } else if (auto *CE = dyn_cast<CallExpr>(Call)) {
-    FunctionDecl *Callee = CE->getDirectCallee();
-    if (Callee && shouldTrackFirstArgument(Callee))
-      VisitPointerArg(Callee, CE->getArg(0),
-                      !Callee->getReturnType()->isReferenceType());
-    return;
-  }
-
-  if (auto *CCE = dyn_cast<CXXConstructExpr>(Call)) {
-    const auto *Ctor = CCE->getConstructor();
-    const CXXRecordDecl *RD = Ctor->getParent();
-    if (CCE->getNumArgs() > 0 && RD->hasAttr<PointerAttr>())
-      VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0], true);
-  }
-}
-
 static bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
   const TypeSourceInfo *TSI = FD->getTypeSourceInfo();
   if (!TSI)
@@ -423,8 +363,10 @@ static bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
   return false;
 }
 
-static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
-                                        LocalVisitor Visit) {
+// Visit lifetimebound or gsl-pointer arguments.
+static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
+                                       LocalVisitor Visit,
+                                       bool EnableLifetimeWarnings) {
   const FunctionDecl *Callee;
   ArrayRef<Expr *> Args;
 
@@ -458,6 +400,35 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
                                        /*EnableLifetimeWarnings=*/false);
     Path.pop_back();
   };
+  auto VisitGSLPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
+    // We are not interested in the temporary base objects of gsl Pointers:
+    //   Temp().ptr; // Here ptr might not dangle.
+    if (isa<MemberExpr>(Arg->IgnoreImpCasts()))
+      return;
+    // Once we initialized a value with a reference, it can no longer dangle.
+    if (!Value) {
+      for (const IndirectLocalPathEntry &PE : llvm::reverse(Path)) {
+        if (PE.Kind == IndirectLocalPathEntry::GslReferenceInit)
+          continue;
+        if (PE.Kind == IndirectLocalPathEntry::GslPointerInit ||
+            PE.Kind == IndirectLocalPathEntry::GslPointerAssignment)
+          return;
+        break;
+      }
+    }
+    Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit
+                          : IndirectLocalPathEntry::GslReferenceInit,
+                    Arg, D});
+    if (Arg->isGLValue())
+      visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
+                                            Visit,
+                                            /*EnableLifetimeWarnings=*/true);
+    else
+      visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
+                                       /*EnableLifetimeWarnings=*/true);
+    Path.pop_back();
+  };
+
 
   bool CheckCoroCall = false;
   if (const auto *RD = Callee->getReturnType()->getAsRecordDecl()) {
@@ -478,6 +449,12 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
       CheckCoroObjArg = false;
     if (implicitObjectParamIsLifetimeBound(Callee) || CheckCoroObjArg)
       VisitLifetimeBoundArg(Callee, ObjectArg);
+    else if (EnableLifetimeWarnings) {
+      if (auto *CME = dyn_cast<CXXMethodDecl>(Callee);
+          CME && shouldTrackImplicitObjectArg(CME))
+        VisitGSLPointerArg(Callee, ObjectArg,
+                        !Callee->getReturnType()->isReferenceType());
+    }
   }
 
   for (unsigned I = 0,
@@ -485,6 +462,19 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
        I != N; ++I) {
     if (CheckCoroCall || Callee->getParamDecl(I)->hasAttr<LifetimeBoundAttr>())
       VisitLifetimeBoundArg(Callee->getParamDecl(I), Args[I]);
+    else if (EnableLifetimeWarnings) {
+      if (I == 0) {
+        if (shouldTrackFirstArgument(Callee)) { // gsl
+          VisitGSLPointerArg(Callee, Args[0],
+                          !Callee->getReturnType()->isReferenceType());
+        } else {
+          if (auto *CCE = dyn_cast<CXXConstructExpr>(Call);
+              CCE && CCE->getConstructor()->getParent()->hasAttr<PointerAttr>())
+            VisitGSLPointerArg(CCE->getConstructor()->getParamDecl(0), Args[0],
+                            true);
+        }
+      }
+    }
   }
 }
 
@@ -557,11 +547,9 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
                                        EnableLifetimeWarnings);
   }
 
-  if (isa<CallExpr>(Init)) {
-    if (EnableLifetimeWarnings)
-      handleGslAnnotatedTypes(Path, Init, Visit);
-    return visitLifetimeBoundArguments(Path, Init, Visit);
-  }
+  if (isa<CallExpr>(Init))
+    return visitFunctionCallArguments(Path, Init, Visit,
+                                      EnableLifetimeWarnings);
 
   switch (Init->getStmtClass()) {
   case Stmt::DeclRefExprClass: {
@@ -835,11 +823,8 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
     }
   }
 
-  if (isa<CallExpr>(Init) || isa<CXXConstructExpr>(Init)) {
-    if (EnableLifetimeWarnings)
-      handleGslAnnotatedTypes(Path, Init, Visit);
-    return visitLifetimeBoundArguments(Path, Init, Visit);
-  }
+  if (isa<CallExpr>(Init) || isa<CXXConstructExpr>(Init))
+    return visitFunctionCallArguments(Path, Init, Visit, EnableLifetimeWarnings);
 
   switch (Init->getStmtClass()) {
   case Stmt::UnaryOperatorClass: {
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index 09dfb2b5d96a89..86ee90ed6df8dd 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -479,3 +479,16 @@ void testForBug49342()
 {
   auto it = std::iter<char>{} - 2; // Used to be false positive.
 }
+
+namespace GH93386 {
+// verify no duplicated diagnostics are emitted.
+struct [[gsl::Pointer]] S {
+  S(const std::vector<int>& abc [[clang::lifetimebound]]);
+};
+
+S test(std::vector<int> a) {
+  return S(a);  // expected-warning {{address of stack memory associated with}}
+}
+
+auto s = S(std::vector<int>()); // expected-warning {{temporary whose address is used as value of local variable}}
+}

>From 047dc9644549e2ada45166c7bc4a94db1a4f4b51 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu at gmail.com>
Date: Tue, 20 Aug 2024 22:36:38 +0200
Subject: [PATCH 2/2] Remove the EnableLifetimeWarnings flag.

---
 clang/lib/Sema/CheckExprLifetime.cpp | 162 +++++++++++----------------
 1 file changed, 63 insertions(+), 99 deletions(-)

diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 06eb909659d05d..6612897c100c98 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -237,13 +237,11 @@ static bool pathContainsInit(IndirectLocalPath &Path) {
 
 static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
                                              Expr *Init, LocalVisitor Visit,
-                                             bool RevisitSubinits,
-                                             bool EnableLifetimeWarnings);
+                                             bool RevisitSubinits);
 
 static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
                                                   Expr *Init, ReferenceKind RK,
-                                                  LocalVisitor Visit,
-                                                  bool EnableLifetimeWarnings);
+                                                  LocalVisitor Visit);
 
 template <typename T> static bool isRecordWithAttr(QualType Type) {
   if (auto *RD = Type->getAsCXXRecordDecl())
@@ -365,8 +363,7 @@ static bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
 
 // Visit lifetimebound or gsl-pointer arguments.
 static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
-                                       LocalVisitor Visit,
-                                       bool EnableLifetimeWarnings) {
+                                       LocalVisitor Visit) {
   const FunctionDecl *Callee;
   ArrayRef<Expr *> Args;
 
@@ -381,6 +378,8 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
   if (!Callee)
     return;
 
+  bool EnableGSLAnalysis = !Callee->getASTContext().getDiagnostics().isIgnored(
+      diag::warn_dangling_lifetime_pointer, SourceLocation());
   Expr *ObjectArg = nullptr;
   if (isa<CXXOperatorCallExpr>(Call) && Callee->isCXXInstanceMember()) {
     ObjectArg = Args[0];
@@ -393,11 +392,9 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
     Path.push_back({IndirectLocalPathEntry::LifetimeBoundCall, Arg, D});
     if (Arg->isGLValue())
       visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
-                                            Visit,
-                                            /*EnableLifetimeWarnings=*/false);
+                                            Visit);
     else
-      visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
-                                       /*EnableLifetimeWarnings=*/false);
+      visitLocalsRetainedByInitializer(Path, Arg, Visit, true);
     Path.pop_back();
   };
   auto VisitGSLPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
@@ -421,11 +418,9 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
                     Arg, D});
     if (Arg->isGLValue())
       visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
-                                            Visit,
-                                            /*EnableLifetimeWarnings=*/true);
+                                            Visit);
     else
-      visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
-                                       /*EnableLifetimeWarnings=*/true);
+      visitLocalsRetainedByInitializer(Path, Arg, Visit, true);
     Path.pop_back();
   };
 
@@ -449,11 +444,11 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
       CheckCoroObjArg = false;
     if (implicitObjectParamIsLifetimeBound(Callee) || CheckCoroObjArg)
       VisitLifetimeBoundArg(Callee, ObjectArg);
-    else if (EnableLifetimeWarnings) {
+    else if (EnableGSLAnalysis) {
       if (auto *CME = dyn_cast<CXXMethodDecl>(Callee);
           CME && shouldTrackImplicitObjectArg(CME))
         VisitGSLPointerArg(Callee, ObjectArg,
-                        !Callee->getReturnType()->isReferenceType());
+                           !Callee->getReturnType()->isReferenceType());
     }
   }
 
@@ -462,17 +457,15 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
        I != N; ++I) {
     if (CheckCoroCall || Callee->getParamDecl(I)->hasAttr<LifetimeBoundAttr>())
       VisitLifetimeBoundArg(Callee->getParamDecl(I), Args[I]);
-    else if (EnableLifetimeWarnings) {
-      if (I == 0) {
-        if (shouldTrackFirstArgument(Callee)) { // gsl
-          VisitGSLPointerArg(Callee, Args[0],
-                          !Callee->getReturnType()->isReferenceType());
-        } else {
-          if (auto *CCE = dyn_cast<CXXConstructExpr>(Call);
-              CCE && CCE->getConstructor()->getParent()->hasAttr<PointerAttr>())
-            VisitGSLPointerArg(CCE->getConstructor()->getParamDecl(0), Args[0],
-                            true);
-        }
+    else if (EnableGSLAnalysis && I == 0) {
+      if (shouldTrackFirstArgument(Callee)) { // gsl
+        VisitGSLPointerArg(Callee, Args[0],
+                           !Callee->getReturnType()->isReferenceType());
+      } else {
+        if (auto *CCE = dyn_cast<CXXConstructExpr>(Call);
+            CCE && CCE->getConstructor()->getParent()->hasAttr<PointerAttr>())
+          VisitGSLPointerArg(CCE->getConstructor()->getParamDecl(0), Args[0],
+                             true);
       }
     }
   }
@@ -482,8 +475,7 @@ static void visitFunctionCallArguments(IndirectLocalPath &Path, Expr *Call,
 /// glvalue expression \c Init.
 static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
                                                   Expr *Init, ReferenceKind RK,
-                                                  LocalVisitor Visit,
-                                                  bool EnableLifetimeWarnings) {
+                                                  LocalVisitor Visit) {
   RevertToOldSizeRAII RAII(Path);
 
   // Walk past any constructs which we can lifetime-extend across.
@@ -520,8 +512,7 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
       else
         // We can't lifetime extend through this but we might still find some
         // retained temporaries.
-        return visitLocalsRetainedByInitializer(Path, Init, Visit, true,
-                                                EnableLifetimeWarnings);
+        return visitLocalsRetainedByInitializer(Path, Init, Visit, true);
     }
 
     // Step into CXXDefaultInitExprs so we can diagnose cases where a
@@ -535,21 +526,18 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
 
   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init)) {
     if (Visit(Path, Local(MTE), RK))
-      visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit, true);
   }
 
   if (auto *M = dyn_cast<MemberExpr>(Init)) {
     // Lifetime of a non-reference type field is same as base object.
     if (auto *F = dyn_cast<FieldDecl>(M->getMemberDecl());
         F && !F->getType()->isReferenceType())
-      visitLocalsRetainedByInitializer(Path, M->getBase(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, M->getBase(), Visit, true);
   }
 
   if (isa<CallExpr>(Init))
-    return visitFunctionCallArguments(Path, Init, Visit,
-                                      EnableLifetimeWarnings);
+    return visitFunctionCallArguments(Path, Init, Visit);
 
   switch (Init->getStmtClass()) {
   case Stmt::DeclRefExprClass: {
@@ -568,8 +556,7 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
       } else if (VD->getInit() && !isVarOnPath(Path, VD)) {
         Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
         visitLocalsRetainedByReferenceBinding(Path, VD->getInit(),
-                                              RK_ReferenceBinding, Visit,
-                                              EnableLifetimeWarnings);
+                                              RK_ReferenceBinding, Visit);
       }
     }
     break;
@@ -581,15 +568,13 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
     // handling all sorts of rvalues passed to a unary operator.
     const UnaryOperator *U = cast<UnaryOperator>(Init);
     if (U->getOpcode() == UO_Deref)
-      visitLocalsRetainedByInitializer(Path, U->getSubExpr(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, U->getSubExpr(), Visit, true);
     break;
   }
 
   case Stmt::ArraySectionExprClass: {
-    visitLocalsRetainedByInitializer(Path,
-                                     cast<ArraySectionExpr>(Init)->getBase(),
-                                     Visit, true, EnableLifetimeWarnings);
+    visitLocalsRetainedByInitializer(
+        Path, cast<ArraySectionExpr>(Init)->getBase(), Visit, true);
     break;
   }
 
@@ -597,11 +582,9 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
   case Stmt::BinaryConditionalOperatorClass: {
     auto *C = cast<AbstractConditionalOperator>(Init);
     if (!C->getTrueExpr()->getType()->isVoidType())
-      visitLocalsRetainedByReferenceBinding(Path, C->getTrueExpr(), RK, Visit,
-                                            EnableLifetimeWarnings);
+      visitLocalsRetainedByReferenceBinding(Path, C->getTrueExpr(), RK, Visit);
     if (!C->getFalseExpr()->getType()->isVoidType())
-      visitLocalsRetainedByReferenceBinding(Path, C->getFalseExpr(), RK, Visit,
-                                            EnableLifetimeWarnings);
+      visitLocalsRetainedByReferenceBinding(Path, C->getFalseExpr(), RK, Visit);
     break;
   }
 
@@ -624,8 +607,7 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
 /// the prvalue expression \c Init.
 static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
                                              Expr *Init, LocalVisitor Visit,
-                                             bool RevisitSubinits,
-                                             bool EnableLifetimeWarnings) {
+                                             bool RevisitSubinits) {
   RevertToOldSizeRAII RAII(Path);
 
   Expr *Old;
@@ -666,18 +648,16 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
                 if (VD && VD->getType().isConstQualified() && VD->getInit() &&
                     !isVarOnPath(Path, VD)) {
                   Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
-                  visitLocalsRetainedByInitializer(
-                      Path, VD->getInit(), Visit, true, EnableLifetimeWarnings);
+                  visitLocalsRetainedByInitializer(Path, VD->getInit(), Visit,
+                                                   true);
                 }
               } else if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L)) {
                 if (MTE->getType().isConstQualified())
                   visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(),
-                                                   Visit, true,
-                                                   EnableLifetimeWarnings);
+                                                   Visit, true);
               }
               return false;
-            },
-            EnableLifetimeWarnings);
+            });
 
         // We assume that objects can be retained by pointers cast to integers,
         // but not if the integer is cast to floating-point type or to _Complex.
@@ -706,9 +686,8 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
         // Model array-to-pointer decay as taking the address of the array
         // lvalue.
         Path.push_back({IndirectLocalPathEntry::AddressOf, CE});
-        return visitLocalsRetainedByReferenceBinding(Path, CE->getSubExpr(),
-                                                     RK_ReferenceBinding, Visit,
-                                                     EnableLifetimeWarnings);
+        return visitLocalsRetainedByReferenceBinding(
+            Path, CE->getSubExpr(), RK_ReferenceBinding, Visit);
 
       default:
         return;
@@ -723,8 +702,7 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
   //   lifetime of the array exactly like binding a reference to a temporary.
   if (auto *ILE = dyn_cast<CXXStdInitializerListExpr>(Init))
     return visitLocalsRetainedByReferenceBinding(Path, ILE->getSubExpr(),
-                                                 RK_StdInitializerList, Visit,
-                                                 EnableLifetimeWarnings);
+                                                 RK_StdInitializerList, Visit);
 
   if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
     // We already visited the elements of this initializer list while
@@ -735,14 +713,12 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
 
     if (ILE->isTransparent())
       return visitLocalsRetainedByInitializer(Path, ILE->getInit(0), Visit,
-                                              RevisitSubinits,
-                                              EnableLifetimeWarnings);
+                                              RevisitSubinits);
 
     if (ILE->getType()->isArrayType()) {
       for (unsigned I = 0, N = ILE->getNumInits(); I != N; ++I)
         visitLocalsRetainedByInitializer(Path, ILE->getInit(I), Visit,
-                                         RevisitSubinits,
-                                         EnableLifetimeWarnings);
+                                         RevisitSubinits);
       return;
     }
 
@@ -755,14 +731,12 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
       if (RD->isUnion() && ILE->getInitializedFieldInUnion() &&
           ILE->getInitializedFieldInUnion()->getType()->isReferenceType())
         visitLocalsRetainedByReferenceBinding(Path, ILE->getInit(0),
-                                              RK_ReferenceBinding, Visit,
-                                              EnableLifetimeWarnings);
+                                              RK_ReferenceBinding, Visit);
       else {
         unsigned Index = 0;
         for (; Index < RD->getNumBases() && Index < ILE->getNumInits(); ++Index)
           visitLocalsRetainedByInitializer(Path, ILE->getInit(Index), Visit,
-                                           RevisitSubinits,
-                                           EnableLifetimeWarnings);
+                                           RevisitSubinits);
         for (const auto *I : RD->fields()) {
           if (Index >= ILE->getNumInits())
             break;
@@ -771,14 +745,13 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
           Expr *SubInit = ILE->getInit(Index);
           if (I->getType()->isReferenceType())
             visitLocalsRetainedByReferenceBinding(Path, SubInit,
-                                                  RK_ReferenceBinding, Visit,
-                                                  EnableLifetimeWarnings);
+                                                  RK_ReferenceBinding, Visit);
           else
             // This might be either aggregate-initialization of a member or
             // initialization of a std::initializer_list object. Regardless,
             // we should recursively lifetime-extend that initializer.
-            visitLocalsRetainedByInitializer(
-                Path, SubInit, Visit, RevisitSubinits, EnableLifetimeWarnings);
+            visitLocalsRetainedByInitializer(Path, SubInit, Visit,
+                                             RevisitSubinits);
           ++Index;
         }
       }
@@ -799,10 +772,9 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
         Path.push_back({IndirectLocalPathEntry::LambdaCaptureInit, E, &Cap});
       if (E->isGLValue())
         visitLocalsRetainedByReferenceBinding(Path, E, RK_ReferenceBinding,
-                                              Visit, EnableLifetimeWarnings);
+                                              Visit);
       else
-        visitLocalsRetainedByInitializer(Path, E, Visit, true,
-                                         EnableLifetimeWarnings);
+        visitLocalsRetainedByInitializer(Path, E, Visit, true);
       if (Cap.capturesVariable())
         Path.pop_back();
     }
@@ -816,15 +788,14 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
         Expr *Arg = MTE->getSubExpr();
         Path.push_back({IndirectLocalPathEntry::TemporaryCopy, Arg,
                         CCE->getConstructor()});
-        visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
-                                         /*EnableLifetimeWarnings*/ false);
+        visitLocalsRetainedByInitializer(Path, Arg, Visit, true);
         Path.pop_back();
       }
     }
   }
 
   if (isa<CallExpr>(Init) || isa<CXXConstructExpr>(Init))
-    return visitFunctionCallArguments(Path, Init, Visit, EnableLifetimeWarnings);
+    return visitFunctionCallArguments(Path, Init, Visit);
 
   switch (Init->getStmtClass()) {
   case Stmt::UnaryOperatorClass: {
@@ -840,8 +811,7 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
 
       Path.push_back({IndirectLocalPathEntry::AddressOf, UO});
       visitLocalsRetainedByReferenceBinding(Path, UO->getSubExpr(),
-                                            RK_ReferenceBinding, Visit,
-                                            EnableLifetimeWarnings);
+                                            RK_ReferenceBinding, Visit);
     }
     break;
   }
@@ -854,11 +824,9 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
       break;
 
     if (BO->getLHS()->getType()->isPointerType())
-      visitLocalsRetainedByInitializer(Path, BO->getLHS(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, BO->getLHS(), Visit, true);
     else if (BO->getRHS()->getType()->isPointerType())
-      visitLocalsRetainedByInitializer(Path, BO->getRHS(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, BO->getRHS(), Visit, true);
     break;
   }
 
@@ -868,11 +836,9 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
     // In C++, we can have a throw-expression operand, which has 'void' type
     // and isn't interesting from a lifetime perspective.
     if (!C->getTrueExpr()->getType()->isVoidType())
-      visitLocalsRetainedByInitializer(Path, C->getTrueExpr(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, C->getTrueExpr(), Visit, true);
     if (!C->getFalseExpr()->getType()->isVoidType())
-      visitLocalsRetainedByInitializer(Path, C->getFalseExpr(), Visit, true,
-                                       EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, C->getFalseExpr(), Visit, true);
     break;
   }
 
@@ -974,8 +940,7 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
                                   const InitializedEntity *InitEntity,
                                   const InitializedEntity *ExtendingEntity,
                                   LifetimeKind LK,
-                                  const AssignedEntity *AEntity, Expr *Init,
-                                  bool EnableLifetimeWarnings) {
+                                  const AssignedEntity *AEntity, Expr *Init) {
   assert((AEntity && LK == LK_Assignment) ||
          (InitEntity && LK != LK_Assignment));
   // If this entity doesn't have an interesting lifetime, don't bother looking
@@ -1269,19 +1234,20 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
   };
 
   llvm::SmallVector<IndirectLocalPathEntry, 8> Path;
-  if (EnableLifetimeWarnings && LK == LK_Assignment &&
+  if (!SemaRef.getDiagnostics().isIgnored(diag::warn_dangling_lifetime_pointer,
+                                          SourceLocation()) &&
+      LK == LK_Assignment &&
       isRecordWithAttr<PointerAttr>(AEntity->LHS->getType()))
     Path.push_back({IndirectLocalPathEntry::GslPointerAssignment, Init});
 
   if (Init->isGLValue())
     visitLocalsRetainedByReferenceBinding(Path, Init, RK_ReferenceBinding,
-                                          TemporaryVisitor,
-                                          EnableLifetimeWarnings);
+                                          TemporaryVisitor);
   else
     visitLocalsRetainedByInitializer(
         Path, Init, TemporaryVisitor,
         // Don't revisit the sub inits for the intialization case.
-        /*RevisitSubinits=*/!InitEntity, EnableLifetimeWarnings);
+        /*RevisitSubinits=*/!InitEntity);
 }
 
 void checkExprLifetime(Sema &SemaRef, const InitializedEntity &Entity,
@@ -1289,10 +1255,8 @@ void checkExprLifetime(Sema &SemaRef, const InitializedEntity &Entity,
   auto LTResult = getEntityLifetime(&Entity);
   LifetimeKind LK = LTResult.getInt();
   const InitializedEntity *ExtendingEntity = LTResult.getPointer();
-  bool EnableLifetimeWarnings = !SemaRef.getDiagnostics().isIgnored(
-      diag::warn_dangling_lifetime_pointer, SourceLocation());
   checkExprLifetimeImpl(SemaRef, &Entity, ExtendingEntity, LK,
-                        /*AEntity*/ nullptr, Init, EnableLifetimeWarnings);
+                        /*AEntity*/ nullptr, Init);
 }
 
 void checkExprLifetime(Sema &SemaRef, const AssignedEntity &Entity,
@@ -1308,7 +1272,7 @@ void checkExprLifetime(Sema &SemaRef, const AssignedEntity &Entity,
 
   checkExprLifetimeImpl(SemaRef, /*InitEntity=*/nullptr,
                         /*ExtendingEntity=*/nullptr, LK_Assignment, &Entity,
-                        Init, EnableLifetimeWarnings);
+                        Init);
 }
 
 } // namespace clang::sema



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