Re: Files and controlled types

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 9 Mar, 04:12, "Jeffrey R. Carter" <spam.jrcarter....@spam.acm.org>
wrote:

> > File types are not Controlled.
> > What is the rationale for this?
>
> What makes you think they're not controlled.

a) AARM
b) trivial test

> The ARM only gives the public view,
> which is limited private; there's nothing to prevent the full view from being
> controlled.

There is nothing that mandates it and therefore I have to assume it is
not done. This is actually what I see in tests.

> In addition, the descriptions of Ada.Sequential_IO, Ada.Direct_IO,
> and Ada.Text_IO all include the language "The type File_Type needs finalization
> (see 7.6)".

This is very good - I haven't notice it.
It is very good, because then instead of broken library definition we
can talk about implementation bugs - these are easier to fix.

My little test follows:

with Ada.Text_IO;
procedure A is

   procedure New_File (I : in Integer) is
      Name : String := "temp/" & Integer'Image (I) & ".txt";
      F : Ada.Text_IO.File_Type;
   begin
      Ada.Text_IO.Put_Line ("Opening " & Name);
      Ada.Text_IO.Create (F, Ada.Text_IO.Out_File, Name);
--      Ada.Text_IO.Close (F);
   end New_File;

begin
   for I in -1000 .. -1 loop
      New_File (I);
   end loop;
end;

This program creates 1000 files with names "temp/-1000.txt",
"temp/-999.txt", etc. (I use negative counters because I don't want to
waste my time with that useless space in front of the image of
positive integer value).
If the File_Type has finalization, then this program is expected to
finish correctly without the Close call (uncommented above).
On my computer it fails with USE_ERROR after creating 253 files. If we
add the three standard I/O streams, we get a reasonable assumption
that the program has hit an implementation limit (256?) of open file
descriptors.
If I uncomment the Close call, the program properly creates full 1000
set of files.
I expect Close to be called automatically as part of finalization.

So - is it the implementation (GNAT) bug?

Or maybe the finalization is concerned with memory management only
(buffers, etc.) and not with external resources? In that case I
consider it a bug in AARM.

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com