--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/ada/bindo-validators.ads	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,115 @@
+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT COMPILER COMPONENTS                         --
+--                                                                          --
+--                      B I N D O . V A L I D A T O R S                     --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--             Copyright (C) 2019, 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- --
+-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
+-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
+-- for  more details.  You should have  received  a copy of the GNU General --
+-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
+-- http://www.gnu.org/licenses for a complete copy of the license.          --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc.      --
+--                                                                          --
+------------------------------------------------------------------------------
+
+--  For full architecture, see unit Bindo.
+
+--  The following unit contains facilities to verify the validity of the
+--  various graphs used in determining the elaboration order of units.
+
+with Bindo.Graphs;
+use  Bindo.Graphs;
+use  Bindo.Graphs.Invocation_Graphs;
+use  Bindo.Graphs.Library_Graphs;
+
+package Bindo.Validators is
+
+   ----------------------
+   -- Cycle_Validators --
+   ----------------------
+
+   package Cycle_Validators is
+      Invalid_Cycle : exception;
+      --  Exception raised when the library graph contains an invalid cycle
+
+      procedure Validate_Cycles (G : Library_Graph);
+      --  Ensure that all cycles of library graph G meet the following
+      --  requirements:
+      --
+      --    * Are of proper kind
+      --    * Have enough edges to form a circuit
+      --    * No edge is repeated
+      --
+      --  Diagnose issues and raise Invalid_Cycle if this is not the case.
+
+   end Cycle_Validators;
+
+   ----------------------------------
+   -- Elaboration_Order_Validators --
+   ----------------------------------
+
+   package Elaboration_Order_Validators is
+      Invalid_Elaboration_Order : exception;
+      --  Exception raised when the elaboration order contains invalid data
+
+      procedure Validate_Elaboration_Order (Order : Unit_Id_Table);
+      --  Ensure that elaboration order Order meets the following requirements:
+      --
+      --    * All units that must be elaborated appear in the order
+      --    * No other units appear in the order
+      --
+      --  Diagnose issues and raise Invalid_Elaboration_Order if this is not
+      --  the case.
+
+   end Elaboration_Order_Validators;
+
+   ---------------------------------
+   -- Invocation_Graph_Validators --
+   ---------------------------------
+
+   package Invocation_Graph_Validators is
+      Invalid_Invocation_Graph : exception;
+      --  Exception raised when the invocation graph contains invalid data
+
+      procedure Validate_Invocation_Graph (G : Invocation_Graph);
+      --  Ensure that invocation graph G meets the following requirements:
+      --
+      --    * All attributes of edges are properly set
+      --    * All attributes of vertices are properly set
+      --
+      --  Diagnose issues and raise Invalid_Invocation_Graph if this is not the
+      --  case.
+
+   end Invocation_Graph_Validators;
+
+   ------------------------------
+   -- Library_Graph_Validators --
+   ------------------------------
+
+   package Library_Graph_Validators is
+      Invalid_Library_Graph : exception;
+      --  Exception raised when the library graph contains invalid data
+
+      procedure Validate_Library_Graph (G : Library_Graph);
+      --  Ensure that library graph G meets the following requirements:
+      --
+      --    * All attributes edges are properly set
+      --    * All attributes of vertices are properly set
+      --
+      --  Diagnose issues and raise Invalid_Library_Graph if this is not the
+      --  case.
+
+   end Library_Graph_Validators;
+
+end Bindo.Validators;