Index: sem_ch3.adb
===================================================================
--- sem_ch3.adb	(revision 247163)
+++ sem_ch3.adb	(working copy)
@@ -4897,6 +4897,12 @@
          end if;
       end if;
 
+      --  Remember that its parent type has a private extension. Used to warn
+      --  on public primitives of the parent type defined after its private
+      --  extensions (see Check_Dispatching_Operation).
+
+      Set_Has_Private_Extension (Parent_Type);
+
    <<Leave>>
       if Has_Aspects (N) then
          Analyze_Aspect_Specifications (N, T);
Index: usage.adb
===================================================================
--- usage.adb	(revision 247135)
+++ usage.adb	(working copy)
@@ -507,6 +507,10 @@
                                                   "(annex J) feature");
    Write_Line ("        J*   turn off warnings for obsolescent " &
                                                   "(annex J) feature");
+   Write_Line ("        .j+  turn on warnings for late dispatching " &
+                                                  "primitives");
+   Write_Line ("        .J*  turn off warnings for late dispatching " &
+                                                  "primitives");
    Write_Line ("        k+   turn on warnings on constant variable");
    Write_Line ("        K*   turn off warnings on constant variable");
    Write_Line ("        .k   turn on warnings for standard redefinition");
Index: einfo.adb
===================================================================
--- einfo.adb	(revision 247170)
+++ einfo.adb	(working copy)
@@ -619,7 +619,7 @@
    --    Is_Underlying_Full_View         Flag298
    --    Body_Needed_For_Inlining        Flag299
 
-   --    (unused)                        Flag300
+   --    Has_Private_Extension           Flag300
    --    (unused)                        Flag301
    --    (unused)                        Flag302
    --    (unused)                        Flag303
@@ -1818,6 +1818,12 @@
       return Flag155 (Id);
    end Has_Private_Declaration;
 
+   function Has_Private_Extension (Id : E) return B is
+   begin
+      pragma Assert (Is_Tagged_Type (Id));
+      return Flag300 (Id);
+   end Has_Private_Extension;
+
    function Has_Protected (Id : E) return B is
    begin
       return Flag271 (Base_Type (Id));
@@ -4891,6 +4897,12 @@
       Set_Flag155 (Id, V);
    end Set_Has_Private_Declaration;
 
+   procedure Set_Has_Private_Extension (Id : E; V : B := True) is
+   begin
+      pragma Assert (Is_Tagged_Type (Id));
+      Set_Flag300 (Id, V);
+   end Set_Has_Private_Extension;
+
    procedure Set_Has_Protected (Id : E; V : B := True) is
    begin
       Set_Flag271 (Id, V);
@@ -9363,6 +9375,7 @@
       W ("Has_Primitive_Operations",        Flag120 (Id));
       W ("Has_Private_Ancestor",            Flag151 (Id));
       W ("Has_Private_Declaration",         Flag155 (Id));
+      W ("Has_Private_Extension",           Flag300 (Id));
       W ("Has_Protected",                   Flag271 (Id));
       W ("Has_Qualified_Name",              Flag161 (Id));
       W ("Has_RACW",                        Flag214 (Id));
Index: einfo.ads
===================================================================
--- einfo.ads	(revision 247170)
+++ einfo.ads	(working copy)
@@ -1972,6 +1972,11 @@
 --       indicate if a full type declaration is a completion. Used for semantic
 --       checks in E.4(18) and elsewhere.
 
+--    Has_Private_Extension (Flag300)
+--       Defined in tagged types. Set to indicate that the tagged type has some
+--       private extension. Used to report a warning on public primitives added
+--       after defining its private extensions.
+
 --    Has_Protected (Flag271) [base type only]
 --       Defined in all type entities. Set on protected types themselves, and
 --       also (recursively) on any composite type which has a component for
@@ -6455,6 +6460,7 @@
    --    Has_Dispatch_Table                  (Flag220)  (base tagged type only)
    --    Has_Pragma_Pack                     (Flag121)  (impl base type only)
    --    Has_Private_Ancestor                (Flag151)
+   --    Has_Private_Extension               (Flag300)
    --    Has_Record_Rep_Clause               (Flag65)   (base type only)
    --    Has_Static_Discriminants            (Flag211)  (subtype only)
    --    Is_Class_Wide_Equivalent_Type       (Flag35)
@@ -6485,6 +6491,7 @@
    --    Interfaces                          (Elist25)
    --    Has_Completion                      (Flag26)
    --    Has_Private_Ancestor                (Flag151)
+   --    Has_Private_Extension               (Flag300)
    --    Has_Record_Rep_Clause               (Flag65)   (base type only)
    --    Is_Concurrent_Record_Type           (Flag20)
    --    Is_Constrained                      (Flag12)
@@ -7067,6 +7074,7 @@
    function Has_Primitive_Operations            (Id : E) return B;
    function Has_Private_Ancestor                (Id : E) return B;
    function Has_Private_Declaration             (Id : E) return B;
+   function Has_Private_Extension               (Id : E) return B;
    function Has_Protected                       (Id : E) return B;
    function Has_Qualified_Name                  (Id : E) return B;
    function Has_RACW                            (Id : E) return B;
@@ -7751,6 +7759,7 @@
    procedure Set_Has_Primitive_Operations        (Id : E; V : B := True);
    procedure Set_Has_Private_Ancestor            (Id : E; V : B := True);
    procedure Set_Has_Private_Declaration         (Id : E; V : B := True);
+   procedure Set_Has_Private_Extension           (Id : E; V : B := True);
    procedure Set_Has_Protected                   (Id : E; V : B := True);
    procedure Set_Has_Qualified_Name              (Id : E; V : B := True);
    procedure Set_Has_RACW                        (Id : E; V : B := True);
@@ -8549,6 +8558,7 @@
    pragma Inline (Has_Primitive_Operations);
    pragma Inline (Has_Private_Ancestor);
    pragma Inline (Has_Private_Declaration);
+   pragma Inline (Has_Private_Extension);
    pragma Inline (Has_Protected);
    pragma Inline (Has_Qualified_Name);
    pragma Inline (Has_RACW);
@@ -9070,6 +9080,7 @@
    pragma Inline (Set_Has_Primitive_Operations);
    pragma Inline (Set_Has_Private_Ancestor);
    pragma Inline (Set_Has_Private_Declaration);
+   pragma Inline (Set_Has_Private_Extension);
    pragma Inline (Set_Has_Protected);
    pragma Inline (Set_Has_Qualified_Name);
    pragma Inline (Set_Has_RACW);
Index: warnsw.adb
===================================================================
--- warnsw.adb	(revision 247135)
+++ warnsw.adb	(working copy)
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---          Copyright (C) 1999-2014, Free Software Foundation, Inc.         --
+--          Copyright (C) 1999-2016, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -66,6 +66,7 @@
       Warn_On_Dereference                 := Setting;
       Warn_On_Export_Import               := Setting;
       Warn_On_Hiding                      := Setting;
+      Warn_On_Late_Primitives             := Setting;
       Warn_On_Modified_Unread             := Setting;
       Warn_On_No_Value_Assigned           := Setting;
       Warn_On_Non_Local_Exception         := Setting;
@@ -147,6 +148,8 @@
         W.Warn_On_Export_Import;
       Warn_On_Hiding                      :=
         W.Warn_On_Hiding;
+      Warn_On_Late_Primitives             :=
+        W.Warn_On_Late_Primitives;
       Warn_On_Modified_Unread             :=
         W.Warn_On_Modified_Unread;
       Warn_On_No_Value_Assigned           :=
@@ -249,6 +252,8 @@
         Warn_On_Export_Import;
       W.Warn_On_Hiding                      :=
         Warn_On_Hiding;
+      W.Warn_On_Late_Primitives             :=
+        Warn_On_Late_Primitives;
       W.Warn_On_Modified_Unread             :=
         Warn_On_Modified_Unread;
       W.Warn_On_No_Value_Assigned           :=
@@ -347,6 +352,12 @@
          when 'I' =>
             Warn_On_Overlap                     := False;
 
+         when 'j' =>
+            Warn_On_Late_Primitives             := True;
+
+         when 'J' =>
+            Warn_On_Late_Primitives             := False;
+
          when 'k' =>
             Warn_On_Standard_Redefinition       := True;
 
@@ -667,6 +678,7 @@
       Warn_On_Biased_Representation       := True; -- -gnatw.b
       Warn_On_Constant                    := True; -- -gnatwk
       Warn_On_Export_Import               := True; -- -gnatwx
+      Warn_On_Late_Primitives             := True; -- -gnatw.j
       Warn_On_Modified_Unread             := True; -- -gnatwm
       Warn_On_No_Value_Assigned           := True; -- -gnatwv
       Warn_On_Non_Local_Exception         := True; -- -gnatw.x
Index: warnsw.ads
===================================================================
--- warnsw.ads	(revision 247135)
+++ warnsw.ads	(working copy)
@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 S p e c                                  --
 --                                                                          --
---          Copyright (C) 1999-2014, Free Software Foundation, Inc.         --
+--          Copyright (C) 1999-2016, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -38,6 +38,10 @@
    --  here as time goes by. And in fact a really nice idea would be to put
    --  them all in a Warn_Record so that they would be easy to save/restore.
 
+   Warn_On_Late_Primitives : Boolean := False;
+   --  Warn when tagged type public primitives are defined after its private
+   --  extensions.
+
    Warn_On_Record_Holes : Boolean := False;
    --  Warn when explicit record component clauses leave uncovered holes (gaps)
    --  in a record layout. Off by default, set by -gnatw.h (but not -gnatwa).
@@ -91,6 +95,7 @@
       Warn_On_Dereference                 : Boolean;
       Warn_On_Export_Import               : Boolean;
       Warn_On_Hiding                      : Boolean;
+      Warn_On_Late_Primitives             : Boolean;
       Warn_On_Modified_Unread             : Boolean;
       Warn_On_No_Value_Assigned           : Boolean;
       Warn_On_Non_Local_Exception         : Boolean;
Index: sem_disp.adb
===================================================================
--- sem_disp.adb	(revision 247140)
+++ sem_disp.adb	(working copy)
@@ -52,6 +52,7 @@
 with Sinfo;    use Sinfo;
 with Tbuild;   use Tbuild;
 with Uintp;    use Uintp;
+with Warnsw;   use Warnsw;
 
 package body Sem_Disp is
 
@@ -932,6 +933,57 @@
    ---------------------------------
 
    procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id) is
+      procedure Warn_On_Late_Primitive_After_Private_Extension
+        (Typ  : Entity_Id;
+         Prim : Entity_Id);
+      --  Prim is a dispatching primitive of the tagged type Typ. Warn on Prim
+      --  if it is a public primitive defined after some private extension of
+      --  the tagged type.
+
+      ----------------------------------------------------
+      -- Warn_On_Late_Primitive_After_Private_Extension --
+      ----------------------------------------------------
+
+      procedure Warn_On_Late_Primitive_After_Private_Extension
+        (Typ  : Entity_Id;
+         Prim : Entity_Id)
+      is
+         E : Entity_Id;
+
+      begin
+         if Warn_On_Late_Primitives
+           and then Comes_From_Source (Prim)
+           and then Has_Private_Extension (Typ)
+           and then Is_Package_Or_Generic_Package (Current_Scope)
+           and then not In_Private_Part (Current_Scope)
+         then
+            E := Next_Entity (Typ);
+
+            while E /= Prim loop
+               if Ekind (E) = E_Record_Type_With_Private
+                 and then Etype (E) = Typ
+               then
+                  Error_Msg_Name_1 := Chars (Typ);
+                  Error_Msg_Name_2 := Chars (E);
+                  Error_Msg_Sloc := Sloc (E);
+                  Error_Msg_N
+                    ("?j?primitive of type % defined after private " &
+                     "extension % #?", Prim);
+                  Error_Msg_Name_1 := Chars (Prim);
+                  Error_Msg_Name_2 := Chars (E);
+                  Error_Msg_N
+                    ("\spec of % should appear before declaration of type %!",
+                     Prim);
+                  exit;
+               end if;
+
+               Next_Entity (E);
+            end loop;
+         end if;
+      end Warn_On_Late_Primitive_After_Private_Extension;
+
+      --  Local variables
+
       Body_Is_Last_Primitive : Boolean   := False;
       Has_Dispatching_Parent : Boolean   := False;
       Ovr_Subp               : Entity_Id := Empty;
@@ -1591,6 +1643,13 @@
             end if;
          end;
       end if;
+
+      --  For similarity with record extensions, in Ada 9X the language should
+      --  have disallowed adding visible operations to a tagged type after
+      --  deriving a private extension from it. Report a warning if this
+      --  primitive is defined after a private extension of Tagged_Type.
+
+      Warn_On_Late_Primitive_After_Private_Extension (Tagged_Type, Subp);
    end Check_Dispatching_Operation;
 
    ------------------------------------------
