Index: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3814,8 +3814,8 @@
   "declared %select{in global scope|with C language linkage}0 here">;
 def warn_weak_import : Warning <
   "an already-declared variable is made a weak_import declaration %0">;
-def warn_static_non_static : ExtWarn<
-  "static declaration of %0 follows non-static declaration">;
+def ext_static_non_static : Extension<
+  "redeclaring non-static %0 as static is a Microsoft extension">, InGroup<Microsoft>;
 def err_non_static_static : Error<
   "non-static declaration of %0 follows static declaration">;
 def err_extern_non_extern : Error<
Index: cfe/trunk/lib/Sema/SemaDecl.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp
+++ cfe/trunk/lib/Sema/SemaDecl.cpp
@@ -2253,6 +2253,24 @@
   return Sema::CXXInvalid;
 }
 
+// Determine whether the previous declaration was a definition, implicit
+// declaration, or a declaration.
+template <typename T>
+static std::pair<diag::kind, SourceLocation>
+getNoteDiagForInvalidRedeclaration(const T *Old, const T *New) {
+  diag::kind PrevDiag;
+  SourceLocation OldLocation = Old->getLocation();
+  if (Old->isThisDeclarationADefinition())
+    PrevDiag = diag::note_previous_definition;
+  else if (Old->isImplicit()) {
+    PrevDiag = diag::note_previous_implicit_declaration;
+    if (OldLocation.isInvalid())
+      OldLocation = New->getLocation();
+  } else
+    PrevDiag = diag::note_previous_declaration;
+  return std::make_pair(PrevDiag, OldLocation);
+}
+
 /// canRedefineFunction - checks if a function can be redefined. Currently,
 /// only extern inline functions can be redefined, and even then only in
 /// GNU89 mode.
@@ -2345,18 +2363,10 @@
   if (Old->isInvalidDecl())
     return true;
 
-  // Determine whether the previous declaration was a definition,
-  // implicit declaration, or a declaration.
   diag::kind PrevDiag;
-  SourceLocation OldLocation = Old->getLocation();
-  if (Old->isThisDeclarationADefinition())
-    PrevDiag = diag::note_previous_definition;
-  else if (Old->isImplicit()) {
-    PrevDiag = diag::note_previous_implicit_declaration;
-    if (OldLocation.isInvalid())
-      OldLocation = New->getLocation();
-  } else
-    PrevDiag = diag::note_previous_declaration;
+  SourceLocation OldLocation;
+  std::tie(PrevDiag, OldLocation) =
+      getNoteDiagForInvalidRedeclaration(Old, New);
 
   // Don't complain about this if we're in GNU89 mode and the old function
   // is an extern inline function.
@@ -2368,7 +2378,7 @@
       !New->getTemplateSpecializationInfo() &&
       !canRedefineFunction(Old, getLangOpts())) {
     if (getLangOpts().MicrosoftExt) {
-      Diag(New->getLocation(), diag::warn_static_non_static) << New;
+      Diag(New->getLocation(), diag::ext_static_non_static) << New;
       Diag(OldLocation, PrevDiag);
     } else {
       Diag(New->getLocation(), diag::err_static_non_static) << New;
@@ -3069,13 +3079,25 @@
   if (New->isInvalidDecl())
     return;
 
+  diag::kind PrevDiag;
+  SourceLocation OldLocation;
+  std::tie(PrevDiag, OldLocation) =
+      getNoteDiagForInvalidRedeclaration(Old, New);
+
   // [dcl.stc]p8: Check if we have a non-static decl followed by a static.
   if (New->getStorageClass() == SC_Static &&
       !New->isStaticDataMember() &&
       Old->hasExternalFormalLinkage()) {
-    Diag(New->getLocation(), diag::err_static_non_static) << New->getDeclName();
-    Diag(Old->getLocation(), diag::note_previous_definition);
-    return New->setInvalidDecl();
+    if (getLangOpts().MicrosoftExt) {
+      Diag(New->getLocation(), diag::ext_static_non_static)
+          << New->getDeclName();
+      Diag(OldLocation, PrevDiag);
+    } else {
+      Diag(New->getLocation(), diag::err_static_non_static)
+          << New->getDeclName();
+      Diag(OldLocation, PrevDiag);
+      return New->setInvalidDecl();
+    }
   }
   // C99 6.2.2p4:
   //   For an identifier declared with the storage-class specifier
@@ -3092,7 +3114,7 @@
            !New->isStaticDataMember() &&
            Old->getCanonicalDecl()->getStorageClass() == SC_Static) {
     Diag(New->getLocation(), diag::err_non_static_static) << New->getDeclName();
-    Diag(Old->getLocation(), diag::note_previous_definition);
+    Diag(OldLocation, PrevDiag);
     return New->setInvalidDecl();
   }
 
@@ -3100,13 +3122,13 @@
   if (New->hasExternalStorage() &&
       !Old->hasLinkage() && Old->isLocalVarDecl()) {
     Diag(New->getLocation(), diag::err_extern_non_extern) << New->getDeclName();
-    Diag(Old->getLocation(), diag::note_previous_definition);
+    Diag(OldLocation, PrevDiag);
     return New->setInvalidDecl();
   }
   if (Old->hasLinkage() && New->isLocalVarDecl() &&
       !New->hasExternalStorage()) {
     Diag(New->getLocation(), diag::err_non_extern_extern) << New->getDeclName();
-    Diag(Old->getLocation(), diag::note_previous_definition);
+    Diag(OldLocation, PrevDiag);
     return New->setInvalidDecl();
   }
 
@@ -3119,17 +3141,17 @@
       !(Old->getLexicalDeclContext()->isRecord() &&
         !New->getLexicalDeclContext()->isRecord())) {
     Diag(New->getLocation(), diag::err_redefinition) << New->getDeclName();
-    Diag(Old->getLocation(), diag::note_previous_definition);
+    Diag(OldLocation, PrevDiag);
     return New->setInvalidDecl();
   }
 
   if (New->getTLSKind() != Old->getTLSKind()) {
     if (!Old->getTLSKind()) {
       Diag(New->getLocation(), diag::err_thread_non_thread) << New->getDeclName();
-      Diag(Old->getLocation(), diag::note_previous_declaration);
+      Diag(OldLocation, PrevDiag);
     } else if (!New->getTLSKind()) {
       Diag(New->getLocation(), diag::err_non_thread_thread) << New->getDeclName();
-      Diag(Old->getLocation(), diag::note_previous_declaration);
+      Diag(OldLocation, PrevDiag);
     } else {
       // Do not allow redeclaration to change the variable between requiring
       // static and dynamic initialization.
@@ -3137,7 +3159,7 @@
       // declaration to determine the kind. Do we need to be compatible here?
       Diag(New->getLocation(), diag::err_thread_thread_different_kind)
         << New->getDeclName() << (New->getTLSKind() == VarDecl::TLS_Dynamic);
-      Diag(Old->getLocation(), diag::note_previous_declaration);
+      Diag(OldLocation, PrevDiag);
     }
   }
 
@@ -3154,7 +3176,7 @@
 
   if (haveIncompatibleLanguageLinkages(Old, New)) {
     Diag(New->getLocation(), diag::err_different_language_linkage) << New;
-    Diag(Old->getLocation(), diag::note_previous_definition);
+    Diag(OldLocation, PrevDiag);
     New->setInvalidDecl();
     return;
   }
Index: cfe/trunk/test/Misc/warning-flags.c
===================================================================
--- cfe/trunk/test/Misc/warning-flags.c
+++ cfe/trunk/test/Misc/warning-flags.c
@@ -18,7 +18,7 @@
 
 The list of warnings below should NEVER grow.  It should gradually shrink to 0.
 
-CHECK: Warnings without flags (106):
+CHECK: Warnings without flags (105):
 CHECK-NEXT:   ext_delete_void_ptr_operand
 CHECK-NEXT:   ext_expected_semi_decl_list
 CHECK-NEXT:   ext_explicit_specialization_storage_class
@@ -114,7 +114,6 @@
 CHECK-NEXT:   warn_register_objc_catch_parm
 CHECK-NEXT:   warn_related_result_type_compatibility_class
 CHECK-NEXT:   warn_related_result_type_compatibility_protocol
-CHECK-NEXT:   warn_static_non_static
 CHECK-NEXT:   warn_template_export_unsupported
 CHECK-NEXT:   warn_template_spec_extra_headers
 CHECK-NEXT:   warn_tentative_incomplete_array
Index: cfe/trunk/test/Sema/private-extern.c
===================================================================
--- cfe/trunk/test/Sema/private-extern.c
+++ cfe/trunk/test/Sema/private-extern.c
@@ -13,10 +13,10 @@
 int g3; // expected-note{{previous definition}}
 static int g3; // expected-error{{static declaration of 'g3' follows non-static declaration}}
 
-extern int g4; // expected-note{{previous definition}}
+extern int g4; // expected-note{{previous declaration}}
 static int g4; // expected-error{{static declaration of 'g4' follows non-static declaration}}
 
-__private_extern__ int g5; // expected-note{{previous definition}}
+__private_extern__ int g5; // expected-note{{previous declaration}}
 static int g5; // expected-error{{static declaration of 'g5' follows non-static declaration}}
 
 void f0() {
@@ -30,12 +30,12 @@
 }
 
 void f2() {
-  extern int g8; // expected-note{{previous definition}}
+  extern int g8; // expected-note{{previous declaration}}
   int g8; // expected-error {{non-extern declaration of 'g8' follows extern declaration}}
 }
 
 void f3() {
-  __private_extern__ int g9; // expected-note{{previous definition}}
+  __private_extern__ int g9; // expected-note{{previous declaration}}
   int g9; // expected-error {{non-extern declaration of 'g9' follows extern declaration}}
 }
 
Index: cfe/trunk/test/Sema/tentative-decls.c
===================================================================
--- cfe/trunk/test/Sema/tentative-decls.c
+++ cfe/trunk/test/Sema/tentative-decls.c
@@ -23,7 +23,7 @@
 int i1 = 2; // expected-error {{redefinition of 'i1'}}
 int i1;
 int i1;
-extern int i5; // expected-note {{previous definition is here}}
+extern int i5; // expected-note {{previous declaration is here}}
 static int i5; // expected-error{{static declaration of 'i5' follows non-static declaration}}
 
 static int i2 = 5; // expected-note 1 {{previous definition is here}}
@@ -49,7 +49,7 @@
 int redef[11]; // expected-error{{redefinition of 'redef'}}
 
 void func() {
-  extern int i6; // expected-note {{previous definition is here}}
+  extern int i6; // expected-note {{previous declaration is here}}
   static int i6; // expected-error{{static declaration of 'i6' follows non-static declaration}}
 }
 
Index: cfe/trunk/test/Sema/thread-specifier.c
===================================================================
--- cfe/trunk/test/Sema/thread-specifier.c
+++ cfe/trunk/test/Sema/thread-specifier.c
@@ -58,7 +58,7 @@
 }
 
 __thread typedef int t14; // expected-error-re {{cannot combine with previous '{{__thread|_Thread_local|thread_local}}' declaration specifier}}
-__thread int t15; // expected-note {{previous declaration is here}}
+__thread int t15; // expected-note {{previous definition is here}}
 extern int t15; // expected-error {{non-thread-local declaration of 't15' follows thread-local declaration}}
 extern int t16; // expected-note {{previous declaration is here}}
 __thread int t16; // expected-error {{thread-local declaration of 't16' follows non-thread-local declaration}}
Index: cfe/trunk/test/Sema/var-redecl.c
===================================================================
--- cfe/trunk/test/Sema/var-redecl.c
+++ cfe/trunk/test/Sema/var-redecl.c
@@ -58,5 +58,5 @@
 
 // PR3645
 static int a;
-extern int a; // expected-note {{previous definition is here}}
+extern int a; // expected-note {{previous declaration is here}}
 int a;	// expected-error {{non-static declaration of 'a' follows static declaration}}
Index: cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp
===================================================================
--- cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp
+++ cfe/trunk/test/SemaCXX/MicrosoftExtensions.cpp
@@ -144,11 +144,14 @@
 void static_func(); // expected-note {{previous declaration is here}}
 
 
-static void static_func() // expected-warning {{static declaration of 'static_func' follows non-static declaration}}
+static void static_func() // expected-warning {{redeclaring non-static 'static_func' as static is a Microsoft extension}}
 {
 
 }
 
+extern const int static_var; // expected-note {{previous declaration is here}}
+static const int static_var = 3; // expected-warning {{redeclaring non-static 'static_var' as static is a Microsoft extension}}
+
 long function_prototype(int a);
 long (*function_ptr)(int a);