3 files changed, 44 insertions, 2 deletions
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 13a7ead76bd..1522d6399a2 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -5889,7 +5889,7 @@ static bool needsVtable(CXXMethodDecl *MD, ASTContext &Context) {
     break;
 
   case TSK_ExplicitInstantiationDeclaration:
-    return true; //FIXME: This looks wrong.
+    return false;
 
   case TSK_ExplicitInstantiationDefinition:
     // This is method of a explicit instantiation; mark all of the virtual
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 434d5563e1b..abe9363352e 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4388,8 +4388,17 @@ Sema::ActOnExplicitInstantiation(Scope *S,
   // Instantiate the members of this class template specialization.
   Def = cast_or_null<ClassTemplateSpecializationDecl>(
                                        Specialization->getDefinition());
-  if (Def)
+  if (Def) {
+    TemplateSpecializationKind Old_TSK = Def->getTemplateSpecializationKind();
+
+    // Fix a TSK_ExplicitInstantiationDeclaration followed by a
+    // TSK_ExplicitInstantiationDefinition
+    if (Old_TSK == TSK_ExplicitInstantiationDeclaration &&
+        TSK == TSK_ExplicitInstantiationDefinition)
+      Def->setTemplateSpecializationKind(TSK);
+
     InstantiateClassTemplateSpecializationMembers(TemplateNameLoc, Def, TSK);
+  }
 
   return DeclPtrTy::make(Specialization);
 }
diff --git a/clang/test/CodeGenCXX/PR6677.cpp b/clang/test/CodeGenCXX/PR6677.cpp
new file mode 100644
index 00000000000..8d168f11060
--- /dev/null
+++ b/clang/test/CodeGenCXX/PR6677.cpp
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
+
+// CHECK-NOT: @_ZTVN5test118stdio_sync_filebufIwEE = constant
+// CHECK: @_ZTVN5test018stdio_sync_filebufIwEE = constant
+
+namespace test0 {
+  struct  basic_streambuf   {
+    virtual       ~basic_streambuf();
+  };
+  template<typename _CharT >
+  struct stdio_sync_filebuf : public basic_streambuf {
+    virtual void      xsgetn();
+  };
+
+  // This specialization should cause the vtable to be emitted, even with
+  // the following extern template declaration.
+  template<> void stdio_sync_filebuf<wchar_t>::xsgetn()  {
+  }
+  extern template class stdio_sync_filebuf<wchar_t>;
+}
+
+namespace test1 {
+  struct  basic_streambuf   {
+    virtual       ~basic_streambuf();
+  };
+  template<typename _CharT >
+  struct stdio_sync_filebuf : public basic_streambuf {
+    virtual void      xsgetn();
+  };
+
+  // Just a declaration should not force the vtable to be emitted.
+  template<> void stdio_sync_filebuf<wchar_t>::xsgetn();
+}