Re: Ada.Text_IO.Get_Line issue in windows

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 06/02/2015 10:54 PM, tornenvi wrote:
> 
> I believe I have found the problem in that file (a-tigeli.adb)
> 
> I believe line 193 which is
> 
>    elsif ch /= LM then
> 
> should read
> 
>    elsif ch /= LM and ch /=EOF then

In context, this is

         ch := Getc (File);

         --  If we get EOF after already reading data, this is an incomplete
         --  last line, in which case no End_Error should be raised.

         if ch = EOF and then Last < Item'First then
            raise End_Error;

         elsif ch /= LM then

            --  Buffer really is full without having seen LM, update col

            Last := Last + 1;
            Item (Last) := Character'Val (ch);
            File.Col := File.Col + Count (Last - Item'First + 1);
            return;
         end if;

We can see that if EOF is encountered after reading characters into Item then
the EOF is incorrectly stored in Item, so you have found an error in Get_Line.

While your change will work, it might be better to rewrite the "if" as

if ch = EOF then
   if Last < Item'First then
      raise End_Error;
   end if;
elsif ch = LM then
   null;
else -- ch /= EOF and ch /= LM
   ...
end if;

to divide the code into the 3 cases of interest: EOF, in which case we either
raise End_Error or do nothing, depending on Last; LM, do nothing; and anything
else, store the character in Item.

It's disturbing that EOF can be converted into a valid Character.

-- 
Jeff Carter
"Frankie Wolf, wanted by Federal authorities for
dancing with a mailman."
Take the Money and Run
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