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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: GNAT Ada.Direct_IO bug
Date: Sun, 7 Sep 2014 14:58:54 +0200
Organization: cbb software GmbH
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Date: 2014-09-07T14:58:54+02:00
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I have verified this under Windows 7 64-bit (NTFS) and 32-bit Linux and
Fedora. It seems that the implementation of GNAT Ada.Direct_IO is limited
to 2Gb file sizes regardless that the underlying OS has no such constraint.
Here is the test program:
------------------------------------------------------------
with Ada.Direct_IO;
with Ada.Text_IO;  use Ada.Text_IO;

procedure Test_DIO is
   type Block is array (1..1024) of Character;
   for Block'Size use 1024*8;
   package DIO is new Ada.Direct_IO (Block);
   File : DIO.File_Type;
   Data : Block := (others => ' ');
begin
   DIO.Create (File);
   for Giga in 1..2 loop
      for Mega in 1..1024 loop
         for Kilo in 1..1024 loop
	        DIO.Write (File, Data);
         end loop;
      end loop;
      Put_Line ("File size" & DIO.Count'Image (DIO.Size (File)) & "
Kbytes");
   end loop;
end Test_DIO;
------------------------------------------------------------- 
Under Windows [GNAT GPL gpl-2014 (20140405)] it silently wraps the file to
zero size. So the output looks like:

>test_dio.exe
File size 1048576 Kbytes
File size 0 Kbytes

32-bit Debian [4.9.1 (Debian 4.9.1-4)] exposes the same behavior as
Windows.

[64-bit Fedora and Debian work as expected]

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de