Index: s-crtl.ads
===================================================================
--- s-crtl.ads	(revision 160834)
+++ s-crtl.ads	(working copy)
@@ -59,6 +59,9 @@ package System.CRTL is
 
    type size_t is mod 2 ** Standard'Address_Size;
 
+   type ssize_t is range -(2 ** (Standard'Address_Size - 1))
+                      .. +(2 ** (Standard'Address_Size - 1)) - 1;
+
    type Filename_Encoding is (UTF8, ASCII_8bits, Unspecified);
    for Filename_Encoding use (UTF8 => 0, ASCII_8bits => 1, Unspecified => 2);
    pragma Convention (C, Filename_Encoding);
@@ -187,10 +190,10 @@ package System.CRTL is
    function close (fd : int) return int;
    pragma Import (C, close, "close");
 
-   function read (fd : int; buffer : chars; nbytes : int) return int;
+   function read (fd : int; buffer : chars; count : size_t) return ssize_t;
    pragma Import (C, read, "read");
 
-   function write (fd : int; buffer : chars; nbytes : int) return int;
+   function write (fd : int; buffer : chars; count : size_t) return ssize_t;
    pragma Import (C, write, "write");
 
 end System.CRTL;
Index: g-sercom-linux.adb
===================================================================
--- g-sercom-linux.adb	(revision 160834)
+++ g-sercom-linux.adb	(working copy)
@@ -158,8 +158,8 @@ package body GNAT.Serial_Communications 
       Buffer : out Stream_Element_Array;
       Last   : out Stream_Element_Offset)
    is
-      Len : constant int := Buffer'Length;
-      Res : int;
+      Len : constant size_t := Buffer'Length;
+      Res : ssize_t;
 
    begin
       if Port.H = null then
@@ -264,8 +264,8 @@ package body GNAT.Serial_Communications 
      (Port   : in out Serial_Port;
       Buffer : Stream_Element_Array)
    is
-      Len : constant int := Buffer'Length;
-      Res : int;
+      Len : constant size_t := Buffer'Length;
+      Res : ssize_t;
 
    begin
       if Port.H = null then
@@ -273,11 +273,12 @@ package body GNAT.Serial_Communications 
       end if;
 
       Res := write (int (Port.H.all), Buffer'Address, Len);
-      pragma Assert (Res = Len);
 
       if Res = -1 then
          Raise_Error ("write failed");
       end if;
+
+      pragma Assert (size_t (Res) = Len);
    end Write;
 
    -----------
Index: g-socthi-vms.adb
===================================================================
--- g-socthi-vms.adb	(revision 160834)
+++ g-socthi-vms.adb	(working copy)
@@ -292,7 +292,7 @@ package body GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res : C.int;
 
@@ -314,7 +314,7 @@ package body GNAT.Sockets.Thin is
 
       GNAT_Msg := Msghdr (VMS_Msg);
 
-      return ssize_t (Res);
+      return System.CRTL.ssize_t (Res);
    end C_Recvmsg;
 
    ---------------
@@ -324,7 +324,7 @@ package body GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res : C.int;
 
@@ -346,7 +346,7 @@ package body GNAT.Sockets.Thin is
 
       GNAT_Msg := Msghdr (VMS_Msg);
 
-      return ssize_t (Res);
+      return System.CRTL.ssize_t (Res);
    end C_Sendmsg;
 
    --------------
Index: g-socthi-vms.ads
===================================================================
--- g-socthi-vms.ads	(revision 160834)
+++ g-socthi-vms.ads	(working copy)
@@ -43,6 +43,7 @@ with GNAT.OS_Lib;
 with GNAT.Sockets.Thin_Common;
 
 with System;
+with System.CRTL;
 
 package GNAT.Sockets.Thin is
 
@@ -52,10 +53,7 @@ package GNAT.Sockets.Thin is
 
    package C renames Interfaces.C;
 
-   use type C.size_t;
-   type ssize_t is range -(2 ** (C.size_t'Size - 1))
-     .. +(2 ** (C.size_t'Size - 1) - 1);
-   --  Signed type of the same size as size_t
+   use type System.CRTL.ssize_t;
 
    function Socket_Errno return Integer renames GNAT.OS_Lib.Errno;
    --  Returns last socket error number
@@ -149,7 +147,7 @@ package GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Select
      (Nfds      : C.int;
@@ -161,7 +159,7 @@ package GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Sendto
      (S     : C.int;
Index: g-socthi-vxworks.adb
===================================================================
--- g-socthi-vxworks.adb	(revision 160834)
+++ g-socthi-vxworks.adb	(working copy)
@@ -309,7 +309,7 @@ package body GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res : C.int;
 
@@ -323,7 +323,7 @@ package body GNAT.Sockets.Thin is
          delay Quantum;
       end loop;
 
-      return ssize_t (Res);
+      return System.CRTL.ssize_t (Res);
    end C_Recvmsg;
 
    ---------------
@@ -333,7 +333,7 @@ package body GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res : C.int;
 
@@ -347,7 +347,7 @@ package body GNAT.Sockets.Thin is
          delay Quantum;
       end loop;
 
-      return ssize_t (Res);
+      return System.CRTL.ssize_t (Res);
    end C_Sendmsg;
 
    --------------
Index: g-socthi-vxworks.ads
===================================================================
--- g-socthi-vxworks.ads	(revision 160834)
+++ g-socthi-vxworks.ads	(working copy)
@@ -43,6 +43,7 @@ with GNAT.OS_Lib;
 with GNAT.Sockets.Thin_Common;
 
 with System;
+with System.CRTL;
 
 package GNAT.Sockets.Thin is
 
@@ -50,10 +51,7 @@ package GNAT.Sockets.Thin is
 
    package C renames Interfaces.C;
 
-   use type C.size_t;
-   type ssize_t is range -(2 ** (C.size_t'Size - 1))
-     .. +(2 ** (C.size_t'Size - 1) - 1);
-   --  Signed type of the same size as size_t
+   use type System.CRTL.ssize_t;
 
    function Socket_Errno return Integer renames GNAT.OS_Lib.Errno;
    --  Returns last socket error number
@@ -147,7 +145,7 @@ package GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Select
      (Nfds      : C.int;
@@ -159,7 +157,7 @@ package GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Sendto
      (S     : C.int;
Index: g-socthi-mingw.adb
===================================================================
--- g-socthi-mingw.adb	(revision 160834)
+++ g-socthi-mingw.adb	(working copy)
@@ -269,7 +269,7 @@ package body GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res   : C.int;
       Count : C.int := 0;
@@ -287,19 +287,20 @@ package body GNAT.Sockets.Thin is
       --  not available in all versions of Windows. So, we use C_Recv instead.
 
       for J in Iovec'Range loop
-         Res := C_Recv
-           (S,
-            Iovec (J).Base.all'Address,
-            C.int (Iovec (J).Length),
-            Flags);
+         Res :=
+           C_Recv
+            (S,
+             Iovec (J).Base.all'Address,
+             C.int (Iovec (J).Length),
+             Flags);
 
          if Res < 0 then
-            return ssize_t (Res);
+            return System.CRTL.ssize_t (Res);
          else
             Count := Count + Res;
          end if;
       end loop;
-      return ssize_t (Count);
+      return System.CRTL.ssize_t (Count);
    end C_Recvmsg;
 
    --------------
@@ -369,10 +370,11 @@ package body GNAT.Sockets.Thin is
 
                --  Check out-of-band data
 
-               Length := C_Recvfrom
-                 (S, Buffer'Address, 1, Flag,
-                  From    => System.Null_Address,
-                  Fromlen => Fromlen'Unchecked_Access);
+               Length :=
+                 C_Recvfrom
+                  (S, Buffer'Address, 1, Flag,
+                   From    => System.Null_Address,
+                   Fromlen => Fromlen'Unchecked_Access);
                --  Is Fromlen necessary if From is Null_Address???
 
                --  If the signal is not an out-of-band data, then it
@@ -404,7 +406,7 @@ package body GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
       Res   : C.int;
       Count : C.int := 0;
@@ -423,21 +425,23 @@ package body GNAT.Sockets.Thin is
       --  instead.
 
       for J in Iovec'Range loop
-         Res := C_Sendto
-           (S,
-            Iovec (J).Base.all'Address,
-            C.int (Iovec (J).Length),
-            Flags => Flags,
-            To    => MH.Msg_Name,
-            Tolen => C.int (MH.Msg_Namelen));
+         Res :=
+           C_Sendto
+            (S,
+             Iovec (J).Base.all'Address,
+             C.int (Iovec (J).Length),
+             Flags => Flags,
+             To    => MH.Msg_Name,
+             Tolen => C.int (MH.Msg_Namelen));
 
          if Res < 0 then
-            return ssize_t (Res);
+            return System.CRTL.ssize_t (Res);
          else
             Count := Count + Res;
          end if;
       end loop;
-      return ssize_t (Count);
+
+      return System.CRTL.ssize_t (Count);
    end C_Sendmsg;
 
    --------------
Index: g-socthi-mingw.ads
===================================================================
--- g-socthi-mingw.ads	(revision 160834)
+++ g-socthi-mingw.ads	(working copy)
@@ -42,6 +42,7 @@ with Interfaces.C.Strings;
 with GNAT.Sockets.Thin_Common;
 
 with System;
+with System.CRTL;
 
 package GNAT.Sockets.Thin is
 
@@ -49,10 +50,7 @@ package GNAT.Sockets.Thin is
 
    package C renames Interfaces.C;
 
-   use type C.size_t;
-   type ssize_t is range -(2 ** (C.size_t'Size - 1))
-     .. +(2 ** (C.size_t'Size - 1) - 1);
-   --  Signed type of the same size as size_t
+   use type System.CRTL.ssize_t;
 
    function Socket_Errno return Integer;
    --  Returns last socket error number
@@ -146,7 +144,7 @@ package GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Select
      (Nfds      : C.int;
@@ -158,7 +156,7 @@ package GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Sendto
      (S     : C.int;
Index: g-socthi.adb
===================================================================
--- g-socthi.adb	(revision 160834)
+++ g-socthi.adb	(working copy)
@@ -95,13 +95,13 @@ package body GNAT.Sockets.Thin is
    function Syscall_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
    pragma Import (C, Syscall_Recvmsg, "recvmsg");
 
    function Syscall_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
    pragma Import (C, Syscall_Sendmsg, "sendmsg");
 
    function Syscall_Sendto
@@ -307,15 +307,15 @@ package body GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
-      Res : ssize_t;
+      Res : System.CRTL.ssize_t;
 
    begin
       loop
          Res := Syscall_Recvmsg (S, Msg, Flags);
          exit when SOSC.Thread_Blocking_IO
-           or else Res /= ssize_t (Failure)
+           or else Res /= System.CRTL.ssize_t (Failure)
            or else Non_Blocking_Socket (S)
            or else Errno /= SOSC.EWOULDBLOCK;
          delay Quantum;
@@ -331,15 +331,15 @@ package body GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t
+      Flags : C.int) return System.CRTL.ssize_t
    is
-      Res : ssize_t;
+      Res : System.CRTL.ssize_t;
 
    begin
       loop
          Res := Syscall_Sendmsg (S, Msg, Flags);
          exit when SOSC.Thread_Blocking_IO
-           or else Res /= ssize_t (Failure)
+           or else Res /= System.CRTL.ssize_t (Failure)
            or else Non_Blocking_Socket (S)
            or else Errno /= SOSC.EWOULDBLOCK;
          delay Quantum;
Index: g-socthi.ads
===================================================================
--- g-socthi.ads	(revision 160834)
+++ g-socthi.ads	(working copy)
@@ -43,6 +43,7 @@ with GNAT.OS_Lib;
 with GNAT.Sockets.Thin_Common;
 
 with System;
+with System.CRTL;
 
 package GNAT.Sockets.Thin is
 
@@ -54,10 +55,7 @@ package GNAT.Sockets.Thin is
 
    package C renames Interfaces.C;
 
-   use type C.size_t;
-   type ssize_t is range -(2 ** (C.size_t'Size - 1))
-     .. +(2 ** (C.size_t'Size - 1) - 1);
-   --  Signed type of the same size as size_t
+   use type System.CRTL.ssize_t;
 
    function Socket_Errno return Integer renames GNAT.OS_Lib.Errno;
    --  Returns last socket error number
@@ -148,7 +146,7 @@ package GNAT.Sockets.Thin is
    function C_Recvmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Select
      (Nfds      : C.int;
@@ -160,7 +158,7 @@ package GNAT.Sockets.Thin is
    function C_Sendmsg
      (S     : C.int;
       Msg   : System.Address;
-      Flags : C.int) return ssize_t;
+      Flags : C.int) return System.CRTL.ssize_t;
 
    function C_Sendto
      (S     : C.int;
Index: s-tasdeb.adb
===================================================================
--- s-tasdeb.adb	(revision 160834)
+++ s-tasdeb.adb	(working copy)
@@ -362,10 +362,11 @@ package body System.Tasking.Debug is
    -----------
 
    procedure Write (Fd : Integer; S : String; Count : Integer) is
-      Discard : Integer;
+      Discard : System.CRTL.ssize_t;
       pragma Unreferenced (Discard);
    begin
-      Discard := System.CRTL.write (Fd, S (S'First)'Address, Count);
+      Discard := System.CRTL.write (Fd, S (S'First)'Address,
+                                    System.CRTL.size_t (Count));
       --  Is it really right to ignore write errors here ???
    end Write;
 
Index: s-os_lib.adb
===================================================================
--- s-os_lib.adb	(revision 160834)
+++ s-os_lib.adb	(working copy)
@@ -2309,8 +2309,11 @@ package body System.OS_Lib is
       N  : Integer) return Integer
    is
    begin
-      return Integer (System.CRTL.read
-        (System.CRTL.int (FD), System.CRTL.chars (A), System.CRTL.int (N)));
+      return
+        Integer (System.CRTL.read
+                   (System.CRTL.int (FD),
+                    System.CRTL.chars (A),
+                    System.CRTL.size_t (N)));
    end Read;
 
    -----------------
@@ -2718,8 +2721,11 @@ package body System.OS_Lib is
       N  : Integer) return Integer
    is
    begin
-      return Integer (System.CRTL.write
-        (System.CRTL.int (FD), System.CRTL.chars (A), System.CRTL.int (N)));
+      return
+        Integer (System.CRTL.write
+                   (System.CRTL.int (FD),
+                    System.CRTL.chars (A),
+                    System.CRTL.size_t (N)));
    end Write;
 
 end System.OS_Lib;
