From a6c1e3a56afb76876cd06e3646fd7ca57a38d4bb Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 13 Oct 2010 22:55:32 +0000
Subject: [PATCH] Diagnose when a 'static' member function overrides a virtual
 function in a base class. Fixes PR8168.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116448 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td |  2 ++
 include/clang/Sema/Sema.h                  |  2 +-
 lib/Sema/SemaDecl.cpp                      | 30 +++++++++++++++++-----
 test/SemaCXX/virtual-override.cpp          | 12 +++++++++
 4 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index bff8c054f1..ef6d05b505 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -608,6 +608,8 @@ def err_virtual_non_function : Error<
   "'virtual' can only appear on non-static member functions">;
 def err_virtual_out_of_class : Error<
   "'virtual' can only be specified inside the class definition">;
+def err_static_overrides_virtual : Error<
+  "'static' member function %0 overrides a virtual function in a base class">;
 def err_explicit_non_function : Error<
   "'explicit' can only appear on non-static member functions">;
 def err_explicit_out_of_class : Error<
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index d9057a1e0d..b1cd5628a7 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -712,7 +712,7 @@ public:
                                      MultiTemplateParamsArg TemplateParamLists,
                                      bool IsFunctionDefinition,
                                      bool &Redeclaration);
-  void AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
+  bool AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
   void CheckFunctionDeclaration(Scope *S,
                                 FunctionDecl *NewFD, LookupResult &Previous,
                                 bool IsExplicitSpecialization,
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 10785270e5..6f0a7da450 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -3153,23 +3153,28 @@ static bool FindOverriddenMethod(const CXXBaseSpecifier *Specifier,
 
 /// AddOverriddenMethods - See if a method overrides any in the base classes,
 /// and if so, check that it's a valid override and remember it.
-void Sema::AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD) {
+bool Sema::AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD) {
   // Look for virtual methods in base classes that this method might override.
   CXXBasePaths Paths;
   FindOverriddenMethodData Data;
   Data.Method = MD;
   Data.S = this;
+  bool AddedAny = false;
   if (DC->lookupInBases(&FindOverriddenMethod, &Data, Paths)) {
     for (CXXBasePaths::decl_iterator I = Paths.found_decls_begin(),
          E = Paths.found_decls_end(); I != E; ++I) {
       if (CXXMethodDecl *OldMD = dyn_cast<CXXMethodDecl>(*I)) {
         if (!CheckOverridingFunctionReturnType(MD, OldMD) &&
             !CheckOverridingFunctionExceptionSpec(MD, OldMD) &&
-            !CheckOverridingFunctionAttributes(MD, OldMD))
+            !CheckOverridingFunctionAttributes(MD, OldMD)) {
           MD->addOverriddenMethod(OldMD->getCanonicalDecl());
+          AddedAny = true;
+        }
       }
     }
   }
+  
+  return AddedAny;
 }
 
 static void DiagnoseInvalidRedeclaration(Sema &S, FunctionDecl *NewFD) {
@@ -3964,8 +3969,6 @@ void Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
         DeclarationName Name
           = Context.DeclarationNames.getCXXDestructorName(
                                         Context.getCanonicalType(ClassType));
-//         NewFD->getDeclName().dump();
-//         Name.dump();
         if (NewFD->getDeclName() != Name) {
           Diag(NewFD->getLocation(), diag::err_destructor_name);
           return NewFD->setInvalidDecl();
@@ -3979,8 +3982,23 @@ void Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
     // Find any virtual functions that this function overrides.
     if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(NewFD)) {
       if (!Method->isFunctionTemplateSpecialization() && 
-          !Method->getDescribedFunctionTemplate())
-        AddOverriddenMethods(Method->getParent(), Method);
+          !Method->getDescribedFunctionTemplate()) {
+        if (AddOverriddenMethods(Method->getParent(), Method)) {
+          // If the function was marked as "static", we have a problem.
+          if (NewFD->getStorageClass() == SC_Static) {
+            Diag(NewFD->getLocation(), diag::err_static_overrides_virtual)
+              << NewFD->getDeclName();
+            for (CXXMethodDecl::method_iterator 
+                      Overridden = Method->begin_overridden_methods(),
+                   OverriddenEnd = Method->end_overridden_methods();
+                 Overridden != OverriddenEnd;
+                 ++Overridden) {
+              Diag((*Overridden)->getLocation(), 
+                   diag::note_overridden_virtual_function);
+            }
+          }
+        }        
+      }
     }
 
     // Extra checking for C++ overloaded operators (C++ [over.oper]).
diff --git a/test/SemaCXX/virtual-override.cpp b/test/SemaCXX/virtual-override.cpp
index b1d2a3a05c..ba2b80dacd 100644
--- a/test/SemaCXX/virtual-override.cpp
+++ b/test/SemaCXX/virtual-override.cpp
@@ -276,3 +276,15 @@ namespace T12 {
     virtual B& f(); // expected-error {{virtual function 'f' has a different return type ('T12::B &') than the function it overrides (which has return type 'T12::A &&')}}
   };
 };
+
+namespace PR8168 {
+  class A {
+  public:
+    virtual void foo() {} // expected-note{{overridden virtual function is here}}
+  };
+
+  class B : public A {
+  public:
+    static void foo() {} // expected-error{{'static' member function 'foo' overrides a virtual function}}
+  };
+}
-- 
2.40.0