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From: Preben Randhol <randhol+abuse@pvv.org>
Newsgroups: comp.lang.ada
Subject: Re: I/O - exception handling
Date: Mon, 26 May 2003 16:57:14 +0000 (UTC)
Organization: Norwegian university of science and technology
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Sergey Koshcheyev wrote:
> 
> OK, I'll try to explain my problem on your example. You report the error.
> Then, where do you close the file you're reading from?
>  - If you close it inside the exception block, you leak the file, since it
> will not be closed on errors.
>  - If you close it outside the exception block, then the problem is that
> Close can raise an exception too, and the code gets uglier.
>  - If you close it while handling exceptions, the exception you're handling
> might have occured while opening the file, and closing a non-open file will
> cause another exception.
> 
> So, are there any other possibilites, or which of these three is generally
> considered the best?

OK understand. *I* would then do:

   procedure Safe_Close (File : File_Type) 
   is
   begin
      if Is_Open (File) then
         begin
            Close (File);
         exception
            --  Close can raise exceptions too!
            when others => null;
         end;
      end if;
   end Safe_Close;


   procedure One_Of_Your_Procedures_That_Open_Files 
   is
   begin
      Open (File, Name => "test.txt", Mode => In_File);
      Get_Line (File, S1);
      Get_Line (File, S2);

      Safe_Close (File);
   exception
      when others =>
         Safe_Close (File);
   end Read_Something;

Now you can use the Safe_Close in any function you like.

-- 
Preben Randhol                    http://www.pvv.org/~randhol/