6 files changed, 44 insertions, 6 deletions

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index dd3c22bf384..7a813b08a8b 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -147,6 +147,8 @@ def CXX98CompatPedantic : DiagGroup<"c++98-compat-pedantic",
 
 def CXX11Narrowing : DiagGroup<"c++11-narrowing">;
 
+def CXX11WarnOverrideMethod : DiagGroup<"inconsistent-missing-override">;
+
 // Original name of this warning in Clang
 def : DiagGroup<"c++0x-narrowing", [CXX11Narrowing]>;
 
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index bf9148e7d26..fe878725a81 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1691,6 +1691,9 @@ def override_keyword_hides_virtual_member_function : Error<
   "%select{function|functions}1">;
 def err_function_marked_override_not_overriding : Error<
   "%0 marked 'override' but does not override any member functions">;
+def warn_function_marked_not_override_overriding : Warning <
+  "%0 overrides a member function but is not marked 'override'">,
+  InGroup<CXX11WarnOverrideMethod>;
 def err_class_marked_final_used_as_base : Error<
   "base %0 is marked '%select{final|sealed}1'">;
 def warn_abstract_final_class : Warning<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index ebcc4808b7c..811dab4345a 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -5138,6 +5138,10 @@ public:
 
   /// CheckOverrideControl - Check C++11 override control semantics.
   void CheckOverrideControl(NamedDecl *D);
+    
+  /// DiagnoseAbsenceOfOverrideControl - Diagnose if 'override' keyword was
+  /// not used in the declaration of an overriding method.
+  void DiagnoseAbsenceOfOverrideControl(NamedDecl *D);
 
   /// CheckForFunctionMarkedFinal - Checks whether a virtual member function
   /// overrides a virtual member function marked 'final', according to
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 9adba66c41f..47a84927268 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1897,6 +1897,22 @@ void Sema::CheckOverrideControl(NamedDecl *D) {
       << MD->getDeclName();
 }
 
+void Sema::DiagnoseAbsenceOfOverrideControl(NamedDecl *D) {
+  if (D->isInvalidDecl() || D->hasAttr<OverrideAttr>())
+    return;
+  CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D);
+  if (!MD || MD->isImplicit() || MD->hasAttr<FinalAttr>() ||
+      isa<CXXDestructorDecl>(MD))
+    return;
+
+  if (MD->size_overridden_methods() > 0) {
+    Diag(MD->getLocation(), diag::warn_function_marked_not_override_overriding)
+      << MD->getDeclName();
+    const CXXMethodDecl *OMD = *MD->begin_overridden_methods();
+    Diag(OMD->getLocation(), diag::note_overridden_virtual_function);
+  }
+}
+
 /// CheckIfOverriddenFunctionIsMarkedFinal - Checks whether a virtual member
 /// function overrides a virtual member function marked 'final', according to
 /// C++11 [class.virtual]p4.
@@ -4763,13 +4779,18 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
     }
   }
 
+  bool HasMethodWithOverrideControl = false,
+       HasOverridingMethodWithoutOverrideControl = false;
   if (!Record->isDependentType()) {
     for (auto *M : Record->methods()) {
       // See if a method overloads virtual methods in a base
       // class without overriding any.
       if (!M->isStatic())
         DiagnoseHiddenVirtualMethods(M);
-
+      if (M->hasAttr<OverrideAttr>())
+        HasMethodWithOverrideControl = true;
+      else if (M->size_overridden_methods() > 0)
+        HasOverridingMethodWithoutOverrideControl = true;
       // Check whether the explicitly-defaulted special members are valid.
       if (!M->isInvalidDecl() && M->isExplicitlyDefaulted())
         CheckExplicitlyDefaultedSpecialMember(M);
@@ -4788,6 +4809,13 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
     }
   }
 
+  if (HasMethodWithOverrideControl &&
+      HasOverridingMethodWithoutOverrideControl) {
+    // At least one method has the 'override' control declared.
+    // Diagnose all other overridden methods which do not have 'override' specified on them.
+    for (auto *M : Record->methods())
+      DiagnoseAbsenceOfOverrideControl(M);
+  }
   // C++11 [dcl.constexpr]p8: A constexpr specifier for a non-static member
   // function that is not a constructor declares that member function to be
   // const. [...] The class of which that function is a member shall be
diff --git a/clang/test/Parser/MicrosoftExtensions.cpp b/clang/test/Parser/MicrosoftExtensions.cpp
index ee530b8669f..85ccdc5490c 100644
--- a/clang/test/Parser/MicrosoftExtensions.cpp
+++ b/clang/test/Parser/MicrosoftExtensions.cpp
@@ -208,12 +208,12 @@ extern TypenameWrongPlace<AAAA> PR16925;
 
 __interface MicrosoftInterface;
 __interface MicrosoftInterface {
-   void foo1() = 0;
+   void foo1() = 0; // expected-note {{overridden virtual function is here}}
    virtual void foo2() = 0;
 };
 
 __interface MicrosoftDerivedInterface : public MicrosoftInterface {
-  void foo1();
+  void foo1(); // expected-warning {{'foo1' overrides a member function but is not marked 'override'}}
   void foo2() override;
   void foo3();
 };
diff --git a/clang/test/SemaCXX/MicrosoftExtensions.cpp b/clang/test/SemaCXX/MicrosoftExtensions.cpp
index 6d221a409e7..ec3dfce52c1 100644
--- a/clang/test/SemaCXX/MicrosoftExtensions.cpp
+++ b/clang/test/SemaCXX/MicrosoftExtensions.cpp
@@ -372,14 +372,15 @@ struct SomeBase {
 
   // expected-note@+2 {{overridden virtual function is here}}
   // expected-warning@+1 {{'sealed' keyword is a Microsoft extension}}
-  virtual void SealedFunction() sealed;
+  virtual void SealedFunction() sealed; // expected-note {{overridden virtual function is here}}
 };
 
 // expected-note@+2 {{'SealedType' declared here}}
 // expected-warning@+1 {{'sealed' keyword is a Microsoft extension}}
 struct SealedType sealed : SomeBase {
-  // expected-error@+1 {{declaration of 'SealedFunction' overrides a 'sealed' function}}
-  virtual void SealedFunction();
+  // expected-error@+2 {{declaration of 'SealedFunction' overrides a 'sealed' function}}
+  // FIXME. warning can be suppressed if we're also issuing error for overriding a 'final' function.
+  virtual void SealedFunction(); // expected-warning {{'SealedFunction' overrides a member function but is not marked 'override'}}
 
   // expected-warning@+1 {{'override' keyword is a C++11 extension}}
   virtual void OverrideMe() override;