3 files changed, 46 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index be300539ebd..aa0b41bc7a6 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -4846,6 +4846,7 @@ bool Sema::AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD) {
       if (CXXMethodDecl *OldMD = dyn_cast<CXXMethodDecl>(*I)) {
         MD->addOverriddenMethod(OldMD->getCanonicalDecl());
         if (!CheckOverridingFunctionReturnType(MD, OldMD) &&
+            !CheckOverridingFunctionAttributes(MD, OldMD) &&
             !CheckOverridingFunctionExceptionSpec(MD, OldMD) &&
             !CheckIfOverriddenFunctionIsMarkedFinal(MD, OldMD)) {
           hasDeletedOverridenMethods |= OldMD->isDeleted();
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index e36ba2a4578..502b358315a 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -3557,10 +3557,11 @@ static void handleGNUInlineAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 static void handleCallConvAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   if (hasDeclarator(D)) return;
 
+  const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
   // Diagnostic is emitted elsewhere: here we store the (valid) Attr
   // in the Decl node for syntactic reasoning, e.g., pretty-printing.
   CallingConv CC;
-  if (S.CheckCallingConvAttr(Attr, CC))
+  if (S.CheckCallingConvAttr(Attr, CC, FD))
     return;
 
   if (!isa<ObjCMethodDecl>(D)) {
@@ -3615,7 +3616,8 @@ static void handleOpenCLKernelAttr(Sema &S, Decl *D, const AttributeList &Attr){
   D->addAttr(::new (S.Context) OpenCLKernelAttr(Attr.getRange(), S.Context));
 }
 
-bool Sema::CheckCallingConvAttr(const AttributeList &attr, CallingConv &CC) {
+bool Sema::CheckCallingConvAttr(const AttributeList &attr, CallingConv &CC, 
+                                const FunctionDecl *FD) {
   if (attr.isInvalid())
     return true;
 
@@ -3665,7 +3667,12 @@ bool Sema::CheckCallingConvAttr(const AttributeList &attr, CallingConv &CC) {
   TargetInfo::CallingConvCheckResult A = TI.checkCallingConvention(CC);
   if (A == TargetInfo::CCCR_Warning) {
     Diag(attr.getLoc(), diag::warn_cconv_ignored) << attr.getName();
-    CC = TI.getDefaultCallingConv();
+
+    TargetInfo::CallingConvMethodType MT = TargetInfo::CCMT_Unknown;
+    if (FD)
+      MT = FD->isCXXInstanceMember() ? TargetInfo::CCMT_Member : 
+                                    TargetInfo::CCMT_NonMember;
+    CC = TI.getDefaultCallingConv(MT);
   }
 
   return false;
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 6f1b489a2d2..2fae8c9f91b 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -26,6 +26,7 @@
 #include "clang/AST/TypeLoc.h"
 #include "clang/AST/TypeOrdering.h"
 #include "clang/Basic/PartialDiagnostic.h"
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/CXXFieldCollector.h"
 #include "clang/Sema/DeclSpec.h"
@@ -10950,6 +10951,40 @@ void Sema::DiagnoseReturnInConstructorExceptionHandler(CXXTryStmt *TryBlock) {
   }
 }
 
+bool Sema::CheckOverridingFunctionAttributes(const CXXMethodDecl *New,

+                                             const CXXMethodDecl *Old) {
+  const FunctionType *NewFT = New->getType()->getAs<FunctionType>();
+  const FunctionType *OldFT = Old->getType()->getAs<FunctionType>();
+
+  CallingConv NewCC = NewFT->getCallConv(), OldCC = OldFT->getCallConv();
+
+  // If the calling conventions match, everything is fine
+  if (NewCC == OldCC)
+    return false;
+
+  // If either of the calling conventions are set to "default", we need to pick
+  // something more sensible based on the target. This supports code where the
+  // one method explicitly sets thiscall, and another has no explicit calling
+  // convention.
+  CallingConv Default = 
+    Context.getTargetInfo().getDefaultCallingConv(TargetInfo::CCMT_Member);
+  if (NewCC == CC_Default)
+    NewCC = Default;
+  if (OldCC == CC_Default)
+    OldCC = Default;
+
+  // If the calling conventions still don't match, then report the error
+  if (NewCC != OldCC) {
+    Diag(New->getLocation(),

+         diag::err_conflicting_overriding_cc_attributes)

+      << New->getDeclName() << New->getType() << Old->getType();

+    Diag(Old->getLocation(), diag::note_overridden_virtual_function);

+    return true;

+  }
+
+  return false;
+}
+
 bool Sema::CheckOverridingFunctionReturnType(const CXXMethodDecl *New,
                                              const CXXMethodDecl *Old) {
   QualType NewTy = New->getType()->getAs<FunctionType>()->getResultType();