Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td	(revision 113738)
+++ include/clang/Basic/DiagnosticSemaKinds.td	(working copy)
@@ -1965,6 +1965,13 @@
   "%0 may not be used as an array element due to flexible array member">;
 def err_flexible_array_init_nonempty : Error<
   "non-empty initialization of flexible array member inside subobject">;
+def ext_flexible_array_empty_aggregate : Extension<
+  "flexible array %0 in otherwise empty %select{struct|class}1 "
+  "is a Microsoft extension">, InGroup<Microsoft>;
+def ext_flexible_array_union : Extension<
+  "flexible array member %0 in a union is a Microsoft extension">,
+  InGroup<Microsoft>;
+
 def err_flexible_array_init_needs_braces : Error<
   "flexible array requires brace-enclosed initializer">;
 def err_illegal_decl_array_of_functions : Error<
@@ -2867,8 +2874,8 @@
 def err_anonymous_record_with_type : Error<
   "types cannot be declared in an anonymous %select{struct|union}0">;
 def ext_anonymous_record_with_type : Extension<
-  "types declared in an anonymous %select{struct|union}0 are a Microsoft extension">,
-  InGroup<Microsoft>;
+  "types declared in an anonymous %select{struct|union}0 are a Microsoft "
+  "extension">, InGroup<Microsoft>;
 def err_anonymous_record_with_function : Error<
   "functions cannot be declared in an anonymous %select{struct|union}0">;
 def err_anonymous_record_with_static : Error<
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp	(revision 113738)
+++ lib/Sema/SemaDecl.cpp	(working copy)
@@ -6619,10 +6619,22 @@
       FD->setInvalidDecl();
       EnclosingDecl->setInvalidDecl();
       continue;
-    } else if (FDTy->isIncompleteArrayType() && i == NumFields - 1 &&
-               Record && !Record->isUnion()) {
+    } else if (FDTy->isIncompleteArrayType() && Record && 
+               ((i == NumFields - 1 && !Record->isUnion()) ||
+                (getLangOptions().Microsoft &&
+                 (i == NumFields - 1 || Record->isUnion())))) {
       // Flexible array member.
-      if (NumNamedMembers < 1) {
+      // Microsoft is more permissive regarding flexible array.
+      // It will accept flexible array in union and also
+	    // as the sole element of a struct/class.
+      if (getLangOptions().Microsoft) {
+        if (Record->isUnion()) 
+          Diag(FD->getLocation(), diag::ext_flexible_array_union)
+            << FD->getDeclName();
+        else if (NumFields == 1) 
+          Diag(FD->getLocation(), diag::ext_flexible_array_empty_aggregate)
+            << FD->getDeclName() << Record->getTagKind();
+      } else  if (NumNamedMembers < 1) {
         Diag(FD->getLocation(), diag::err_flexible_array_empty_struct)
           << FD->getDeclName();
         FD->setInvalidDecl();
@@ -6637,7 +6649,6 @@
         EnclosingDecl->setInvalidDecl();
         continue;
       }
-      
       // Okay, we have a legal flexible array member at the end of the struct.
       if (Record)
         Record->setHasFlexibleArrayMember(true);