[MS][clang] Error about ambiguous operator delete[] only when required (#135041)

And issue was reported in

#133950 (comment)
. Since we don't always emit vector deleting dtors, only error out about
ambiguous operator delete[] when it will be required for vector deleting
dtor emission.

Author: Fznamznon

clang/lib/Sema/SemaDeclCXX.cpp

@@ -11045,15 +11045,23 @@ bool Sema::CheckDestructor(CXXDestructorDecl *Destructor) {
       DiagnoseUseOfDecl(OperatorDelete, Loc);
       MarkFunctionReferenced(Loc, OperatorDelete);
       Destructor->setOperatorDelete(OperatorDelete, ThisArg);
-      // Lookup delete[] too in case we have to emit a vector deleting dtor;
-      DeclarationName VDeleteName =
-          Context.DeclarationNames.getCXXOperatorName(OO_Array_Delete);
-      FunctionDecl *ArrOperatorDelete = FindDeallocationFunctionForDestructor(
-          Loc, RD, VDeleteName, /*Diagnose=*/false);
-      // delete[] in the TU will make sure the operator is referenced and its
-      // uses diagnosed, otherwise vector deleting dtor won't be called anyway,
-      // so just record it in the destructor.
-      Destructor->setOperatorArrayDelete(ArrOperatorDelete);
+      if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+        // Lookup delete[] too in case we have to emit a vector deleting dtor;
+        DeclarationName VDeleteName =
+            Context.DeclarationNames.getCXXOperatorName(OO_Array_Delete);
+        // Diagnose if there is no available operator delete[] found and the
+        // destructor is exported. Vector deleting dtor body emission requires
+        // operator delete[] to be present. Whenever the destructor is exported,
+        // we just always emit vector deleting dtor body, because we don't know
+        // if new[] will be used with the type outside of the library. Otherwise
+        // when the dtor is not exported then new[]/delete[] in the TU will make
+        // sure the operator is referenced and its uses diagnosed.
+        bool Diagnose =
+            Destructor->hasAttr<DLLExportAttr>() && Destructor->isDefined();
+        FunctionDecl *ArrOperatorDelete = FindDeallocationFunctionForDestructor(
+            Loc, RD, VDeleteName, Diagnose);
+        Destructor->setOperatorArrayDelete(ArrOperatorDelete);
+      }
     }
   }
 

clang/lib/Sema/SemaExprCXX.cpp

@@ -2789,8 +2789,19 @@ bool Sema::FindAllocationFunctions(SourceLocation StartLoc, SourceRange Range,
       return true;
   }
 
+  // new[] will force emission of vector deleting dtor which needs delete[].
+  bool MaybeVectorDeletingDtor = false;
+  if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+    if (AllocElemType->isRecordType() && IsArray) {
+      auto *RD =
+          cast<CXXRecordDecl>(AllocElemType->castAs<RecordType>()->getDecl());
+      CXXDestructorDecl *DD = RD->getDestructor();
+      MaybeVectorDeletingDtor = DD && DD->isVirtual() && !DD->isDeleted();
+    }
+  }
+
   // We don't need an operator delete if we're running under -fno-exceptions.
-  if (!getLangOpts().Exceptions) {
+  if (!getLangOpts().Exceptions && !MaybeVectorDeletingDtor) {
     OperatorDelete = nullptr;
     return false;
   }
@@ -3290,8 +3301,11 @@ bool Sema::FindDeallocationFunction(SourceLocation StartLoc, CXXRecordDecl *RD,
   // Try to find operator delete/operator delete[] in class scope.
   LookupQualifiedName(Found, RD);
 
-  if (Found.isAmbiguous())
+  if (Found.isAmbiguous()) {
+    if (!Diagnose)
+      Found.suppressDiagnostics();
     return true;
+  }
 
   Found.suppressDiagnostics();
 

clang/test/SemaCXX/gh134265.cpp

@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 %s -verify -fsyntax-only
+// RUN: %clang_cc1 %s -verify=expected -fsyntax-only -triple=x86_64-unknown-linux-gnu
+// RUN: %clang_cc1 %s -verify=expected -fsyntax-only -triple=x86_64-unknown-linux-gnu -std=c++20
+// RUN: %clang_cc1 %s -verify=expected,ms -fms-extensions -fms-compatibility -triple=x86_64-pc-windows-msvc -DMS
 
 struct Foo {
   virtual ~Foo() {} // expected-error {{attempt to use a deleted function}}
@@ -13,10 +15,46 @@ struct Bar {
 
 struct Baz {
   virtual ~Baz() {}
-  static void operator delete[](void* ptr) = delete; // expected-note {{explicitly marked deleted here}}
+  static void operator delete[](void* ptr) = delete; // expected-note {{explicitly marked deleted here}}\
+                                                        ms-note{{explicitly marked deleted here}}}
+};
+
+struct BarBaz {
+  ~BarBaz() {}
+  static void operator delete[](void* ptr) = delete;
 };
 
 void foobar() {
-  Baz *B = new Baz[10]();
+  Baz *B = new Baz[10](); // ms-error {{attempt to use a deleted function}}
   delete [] B; // expected-error {{attempt to use a deleted function}}
+  BarBaz *BB = new BarBaz[10]();
+}
+
+struct BaseDelete1 {
+  void operator delete[](void *); //ms-note 3{{member found by ambiguous name lookup}}
+};
+struct BaseDelete2 {
+  void operator delete[](void *); //ms-note 3{{member found by ambiguous name lookup}}
+};
+struct BaseDestructor {
+  BaseDestructor() {}
+  virtual ~BaseDestructor() = default;
+};
+struct Final : BaseDelete1, BaseDelete2, BaseDestructor {
+  Final() {}
+};
+struct FinalExplicit : BaseDelete1, BaseDelete2, BaseDestructor {
+  FinalExplicit() {}
+  inline ~FinalExplicit() {}
+};
+
+#ifdef MS
+struct Final1 : BaseDelete1, BaseDelete2, BaseDestructor {
+  __declspec(dllexport) ~Final1() {} // ms-error {{member 'operator delete[]' found in multiple base classes of different types}}
+};
+#endif // MS
+
+void foo() {
+    Final* a = new Final[10](); // ms-error {{member 'operator delete[]' found in multiple base classes of different types}}
+    FinalExplicit* b = new FinalExplicit[10](); // ms-error {{member 'operator delete[]' found in multiple base classes of different types}}
 }