--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/ada/libgnat/s-commun.ads	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,50 @@
+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT COMPILER COMPONENTS                         --
+--                                                                          --
+--                 S Y S T E M . C O M M U N I C A T I O N                  --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--                     Copyright (C) 2001-2017, AdaCore                     --
+--                                                                          --
+-- 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.                                     --
+--                                                                          --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception,   --
+-- version 3.1, as published by the Free Software Foundation.               --
+--                                                                          --
+-- You should have received a copy of the GNU General Public License and    --
+-- a copy of the GCC Runtime Library Exception along with this program;     --
+-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
+-- <http://www.gnu.org/licenses/>.                                          --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc.      --
+--                                                                          --
+------------------------------------------------------------------------------
+
+--  Common support unit for GNAT.Sockets and GNAT.Serial_Communication
+
+with Ada.Streams;
+with System.CRTL;
+
+package System.Communication is
+   pragma Preelaborate;
+
+   function Last_Index
+     (First : Ada.Streams.Stream_Element_Offset;
+      Count : CRTL.size_t) return Ada.Streams.Stream_Element_Offset;
+   --  Compute the Last OUT parameter for the various Read / Receive
+   --  subprograms: returns First + Count - 1.
+   --
+   --  When First = Stream_Element_Offset'First and Res = 0, Constraint_Error
+   --  is raised. This is consistent with the semantics of stream operations
+   --  as clarified in AI95-227.
+
+end System.Communication;