4 files changed, 34 insertions, 2 deletions

diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index c98fbca849fa..e9e39c11ffba 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -34,6 +34,10 @@ enum LifetimeKind {
   LK_Return,
 
   /// The lifetime of a temporary bound to this entity ends too soon, because
+  /// the entity passed to a musttail function call.
+  LK_MustTail,
+
+  /// The lifetime of a temporary bound to this entity ends too soon, because
   /// the entity is the result of a statement expression.
   LK_StmtExprResult,
 
@@ -1150,6 +1154,7 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
       break;
 
     case LK_Return:
+    case LK_MustTail:
     case LK_StmtExprResult:
       if (auto *DRE = dyn_cast<DeclRefExpr>(L)) {
         // We can't determine if the local variable outlives the statement
@@ -1158,7 +1163,8 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
           return false;
         SemaRef.Diag(DiagLoc, diag::warn_ret_stack_addr_ref)
             << InitEntity->getType()->isReferenceType() << DRE->getDecl()
-            << isa<ParmVarDecl>(DRE->getDecl()) << DiagRange;
+            << isa<ParmVarDecl>(DRE->getDecl()) << (LK == LK_MustTail)
+            << DiagRange;
       } else if (isa<BlockExpr>(L)) {
         SemaRef.Diag(DiagLoc, diag::err_ret_local_block) << DiagRange;
       } else if (isa<AddrLabelExpr>(L)) {
@@ -1170,7 +1176,7 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
       } else if (auto *CLE = dyn_cast<CompoundLiteralExpr>(L)) {
         SemaRef.Diag(DiagLoc, diag::warn_ret_stack_addr_ref)
             << InitEntity->getType()->isReferenceType() << CLE->getInitializer()
-            << 2 << DiagRange;
+            << 2 << (LK == LK_MustTail) << DiagRange;
       } else {
         // P2748R5: Disallow Binding a Returned Glvalue to a Temporary.
         // [stmt.return]/p6: In a function whose return type is a reference,
@@ -1181,6 +1187,9 @@ static void checkExprLifetimeImpl(Sema &SemaRef,
             InitEntity->getType()->isReferenceType())
           SemaRef.Diag(DiagLoc, diag::err_ret_local_temp_ref)
               << InitEntity->getType()->isReferenceType() << DiagRange;
+        else if (LK == LK_MustTail)
+          SemaRef.Diag(DiagLoc, diag::warn_musttail_local_temp_addr_ref)
+              << InitEntity->getType()->isReferenceType() << DiagRange;
         else
           SemaRef.Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref)
               << InitEntity->getType()->isReferenceType() << DiagRange;
@@ -1265,6 +1274,12 @@ void checkExprLifetime(Sema &SemaRef, const InitializedEntity &Entity,
                         /*AEntity*/ nullptr, Init);
 }
 
+void checkExprLifetimeMustTailArg(Sema &SemaRef,
+                                  const InitializedEntity &Entity, Expr *Init) {
+  checkExprLifetimeImpl(SemaRef, &Entity, nullptr, LK_MustTail,
+                        /*AEntity*/ nullptr, Init);
+}
+
 void checkExprLifetime(Sema &SemaRef, const AssignedEntity &Entity,
                        Expr *Init) {
   bool EnableDanglingPointerAssignment = !SemaRef.getDiagnostics().isIgnored(
diff --git a/clang/lib/Sema/CheckExprLifetime.h b/clang/lib/Sema/CheckExprLifetime.h
index 8c8d0806dee0..903f312f3533 100644
--- a/clang/lib/Sema/CheckExprLifetime.h
+++ b/clang/lib/Sema/CheckExprLifetime.h
@@ -35,6 +35,12 @@ void checkExprLifetime(Sema &SemaRef, const InitializedEntity &Entity,
 /// sufficient for assigning to the entity.
 void checkExprLifetime(Sema &SemaRef, const AssignedEntity &Entity, Expr *Init);
 
+/// Check that the lifetime of the given expr (and its subobjects) is
+/// sufficient, assuming that it is passed as an argument to a musttail
+/// function.
+void checkExprLifetimeMustTailArg(Sema &SemaRef,
+                                  const InitializedEntity &Entity, Expr *Init);
+
 } // namespace clang::sema
 
 #endif // LLVM_CLANG_SEMA_CHECK_EXPR_LIFETIME_H
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 9664287b9a3f..9e235a46707c 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "CheckExprLifetime.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ASTLambda.h"
@@ -889,6 +890,15 @@ bool Sema::checkMustTailAttr(const Stmt *St, const Attr &MTA) {
     return false;
   }
 
+  // The lifetimes of locals and incoming function parameters must end before
+  // the call, because we can't have a stack frame to store them, so diagnose
+  // any pointers or references to them passed into the musttail call.
+  for (auto ArgExpr : CE->arguments()) {
+    InitializedEntity Entity = InitializedEntity::InitializeParameter(
+        Context, ArgExpr->getType(), false);
+    checkExprLifetimeMustTailArg(*this, Entity, const_cast<Expr *>(ArgExpr));
+  }
+
   return true;
 }
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 92274cda15e0..99423b01114c 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -8631,6 +8631,7 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
     return SkipBody->Previous;
 
   Specialization->setInvalidDecl(Invalid);
+  inferGslOwnerPointerAttribute(Specialization);
   return Specialization;
 }