Ada.Text_IO.Get_Line issue in windows

Ada.Text_IO.Get_Line issue in windows

[tornenvi]

Hello,

   I have found some unexpected behavior for calls to Ada.Text_IO.Get_Line
   on windows when reading from a text that has only one line in it.

   The program below simply reads the first line of a text file into a 6
   character buffer, and outputs the length of the line read, the line and
   the line again as hex.

   I use windows notepad to create the test file Test.txt.

   When using Test.txt with the one line of text
    ABCD
   with no blank line at the end of the file I get output 1 below

-- Output 1 ------------------------------------------------------
Length=  4
Line=[ABCDXX]
Line as hex=[414243445858]
------------------------------------------------------------------

   as expected. However if Test.txt is the one line of text
    ABCDE
   with no blank line at the end of the file then I get output 2 below

-- Output 2 -----------------------------------------------------
Length=  6
Line=[ABCDE ]
Line as hex=[4142434445ff]
-----------------------------------------------------------------

   I receive an unexpected length of 6, expected 5. The fact that the last two
   characters are not 'XX' is acceptable since ARM A.10.7 19 says
   "The values of characters not assigned are not specified."

   I get the same output 2 if I compile the program with
   GNAT GPL 2014, 2013,2012 or 2011 or with mingw FSF GNAT 4.7.0-1 or 4.8.1-4.

   However if I compile with mingw FSF GNAT 4.5.2-1 , 4.5.0-1, 4.4.0 or
   3.4.5 then I get the expected output 3 below

-- Output 3 -----------------------------------------------------
Length=  5
Line=[ABCDEX]
Line as hex=[414243444558]
-----------------------------------------------------------------

   Under windows the one line text file does not have an end of line
   character (usually CRLF) which means it is not a canonical text file
   as described here

   http://docs.adacore.com/gnat_rm-docs/html/gnat_rm/gnat_rm/the_implementation_of_standard_i_o.html#text-io

   however that section also states that text_io can be use to read non canonical text files
   and the very last line of that section says
   "Every LF character is considered to end a line, and there is an
     implied LF character at the end of the file."

   this indicates to me that there should be an implied LF at the end of the
   file and I should be getting the expected output 3 result for
   all the compilers.

   Is this a bug in the windows builds of GNAT?





---- Program -----------------------------------------------------
with Ada.Text_IO;

procedure FileRead is


   TestFileName : constant string := "Test.txt";
   TestFile : Ada.Text_IO.File_Type;

   Line   : string(1..6) := "XXXXXX";
   Length : natural;

   function ToHex(Msg : string) return string is
     Hex   : constant array (0..15) of character := "0123456789abcdef";
     Str   : String(1..Msg'length*2) := (others => ' '); -- 2 hex digits per byte
     Index : Integer :=1;
     ByteValue : Integer;
   begin
     for i in Msg'Range loop
       ByteValue := character'Pos(Msg(i));
       Str(Index) := Hex(ByteValue / 16);
       Index := Index + 1;
       Str(Index) := Hex(ByteValue mod 16);
       Index := Index + 1;
     end loop;
     return Str;
   end;

begin

   Ada.Text_IO.Open( TestFile, Ada.Text_IO.IN_FILE, TestFileName );
   if not Ada.Text_IO.End_Of_File(TestFile) then
     Ada.Text_IO.Get_Line( TestFile, Line, Length );
     Ada.Text_IO.Put_Line("Length= " & integer'image(Length));
     Ada.Text_IO.Put_Line("Line=[" & Line & "]");
     Ada.Text_IO.Put_Line("Line as hex=[" & ToHex(Line) & "]");
   end if;

exception

   when E: others =>
     Ada.Text_IO.Put_Line("Exception");

end;
-------------------------------------------------------------

Re: Ada.Text_IO.Get_Line issue in windows

[AdaMagica]

As you say, it's a nonregular file. Are you sure the documentation you cite is up to date with your GNAT implementation? Obviously it isn't.

Re: Ada.Text_IO.Get_Line issue in windows

[tornenvi]

On 6/2/2015 12:14 PM, AdaMagica wrote:
> As you say, it's a nonregular file. Are you sure the documentation you cite is up to date with your GNAT implementation? Obviously it isn't.
>

I know by the definition it is a nonregular file however it is a "standard" windows text file.
Earlier versions of the compiler did handle it correctly.

I just checked the gnat reference manual for gcc 5.1 direct from gnu.org and the documentation is still the same.

I also found in a-textio.ads ...

   -----------------------------------
    -- Handling of Format Characters --
    -----------------------------------

    --  Line marks are represented by the single character ASCII.LF (16#0A#).
    --  In DOS and similar systems, underlying file translation takes care
    --  of translating this to and from the standard CR/LF sequences used in
    --  these operating systems to mark the end of a line. On output there is
    --  always a line mark at the end of the last line, but on input, this
    --  line mark can be omitted, and is implied by the end of file.

So I believe the intent of the compiler code is as described in the documentation.

I did some more digging and it seems that the Get_line function was modified and separated out into its
own package (a-tigeli.adb) and the code in this file is different from what it used to be.

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


There is even a comment already there saying

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

it just looks like the EOF was not checked for before
adding the last character.


I will post a bug report to gcc.gnu.org/bugzilla for the FSF compiler.

I could not find any way to report a bug to Adacores libre site,
is there some where I should report it to?

Is there any point? I assume Adacore will be the ones processing the FSF gcc ada
bugs anyway.

Re: Ada.Text_IO.Get_Line issue in windows

[Jeffrey R. Carter]

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
143

Re: Ada.Text_IO.Get_Line issue in windows

[tornenvi]

On 6/3/2015 4:02 PM, Jeffrey R. Carter wrote:
> 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.
>

I have already reported the bug on bugzilla, the link to it is below.

   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66390

You can add your suggested change to the bug report, or I can update it if you like.
However I'm not set up to report patch files (tested) so I am only
adding the changes as comments to the bug report.

Also note that line 84 of \gcc\ada\a-tigeli.adb reads

   memset (S, 10, size_t (N));

I believe the hardcoded '10' here should be 'LM'.

I have added it as a comment to the bug report.

Re: Ada.Text_IO.Get_Line issue in windows

[Simon Wright]

tornenvi <tornenvi@gmail.com> writes:

>   Is this a bug in the windows builds of GNAT?

It took me some time to realise that Emacs was automatically adding a
linefeed to the end of the example file. Now I see that the behaviour
you report is present in all the Mac OS X compilers I have from GNAT GPL
2011 to 2014 and GCC 4.6 to 5.1.

For reference,
  $ echo -n "abcde" >Test.txt
does the trick.

Re: Ada.Text_IO.Get_Line issue in windows

[Simon Clubley]

On 2015-06-03, Simon Wright <simon@pushface.org> wrote:
> tornenvi <tornenvi@gmail.com> writes:
>
>>   Is this a bug in the windows builds of GNAT?
>
> It took me some time to realise that Emacs was automatically adding a
> linefeed to the end of the example file.

That behaviour is adjustable in Emacs and the default with early versions
of Emacs was _not_ to add the line terminator to the final record in the
file.

I have had the following line in my .emacs since the 1990s:

	(setq require-final-newline t)

However, your comment above implies that the default has changed so I
don't know if that's now obsolete in the very latest Emacs versions.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world

Re: Ada.Text_IO.Get_Line issue in windows

[Simon Wright]

Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> writes:

> On 2015-06-03, Simon Wright <simon@pushface.org> wrote:

>> It took me some time to realise that Emacs was automatically adding a
>> linefeed to the end of the example file.
>
> That behaviour is adjustable in Emacs and the default with early
> versions of Emacs was _not_ to add the line terminator to the final
> record in the file.
>
> I have had the following line in my .emacs since the 1990s:
>
> 	(setq require-final-newline t)
>
> However, your comment above implies that the default has changed so I
> don't know if that's now obsolete in the very latest Emacs versions.

Looks as though text-mode (& message-mode?) set it to t (my global
default is nil).

C-h v:

require-final-newline is a variable defined in `files.el'.
Its value is t
Original value was nil
Local in buffer *unsent followup to Simon Clubley on comp.lang.ada*; global value is nil

  This variable is safe as a file local variable if its value
  satisfies the predicate `symbolp'.

Documentation:
Whether to add a newline automatically at the end of the file.

A value of t means do this only when the file is about to be saved.
A value of `visit' means do this right after the file is visited.
A value of `visit-save' means do it at both of those times.
Any other non-nil value means ask user whether to add a newline, when saving.
A value of nil means don't add newlines.

Certain major modes set this locally to the value obtained
from `mode-require-final-newline'.

You can customize this variable.

Re: Ada.Text_IO.Get_Line issue in windows

[wowwomenonwheels205]

Postal Lottery: Turn $6 into $60,000 in 90 days, GUARANTEED

I found this in a news group and decided to try it. A little while
back, I was browsing through newsgroups, just like you are now and
came across a message just like this that said you could make
thousands of dollars within weeks with only an initial investment of
$6.00!!!

So I thought yeah right, this must be a scam!!! But like most of us, I
was curious, so I kept reading. Anyway, it said that you send $1.00 to
each of the 6 names and addresses stated in the message. You then
place your own name and address at the bottom of the list at #6 and
post the message in at least 200 news groups. (There are thousands to
choose from). No catch, that was it.

So after thinking it over, and talking to a few people first. I
thought about trying it. I figured, what have I got to lose except 6
stamps and $6.00, right? So I invested the measly $6.00!!! Guess what?
Within 7 days I started getting money in the mail!!! I was shocked!!!
I figured it would end soon, but the money just kept coming in!!! In
my first week, I had made about $25.00. By the end of the second week,
I had made a total of over $1,000.00!!! In the third week, I had over
$10,000.00 and it is still growing!!! This is now my fourth week and I
have made a total of just over $42,000.00 and it is still coming in
rapidly!!! It's certainly worth $6.00 and 6 stamps!!! I have spent
more than that on the lottery!!!

Let me tell you how this works and most importantly, why it works!!!

Also, make sure you print a copy of this message now. So you can get
the information off of it as you need it. I promise you that if you
follow the directions exactly, that you will start making more money
than you thought possible by doing something so easy!!!

Suggestion: Read this entire message carefully!!! (Print it out or
download it.) Follow the simple directions and watch the money come
in!!! It's easy!!! It's legal!!! Your investment is only $6.00 (plus
postage).

IMPORTANT: This is not a rip-off!!! It is not illegal!!! ? It is
almost entirely risk free and it really works!!! If all of the
following instructions are adhered to, you will receive extraordinary
dividends!!!

Please note: Follow these directions EXACTLY, and $60,000.00 or more
can be yours in 20 to 90 days!!! This program remains successful
because of the honesty and the integrity of the participants!!! Please
continue its success by carefully adhering to the instructions.

You will now become part of the mail order business. In this business
your product is not solid or tangible, it is a service. You are in the
business of developing mailing lists. Many large corporations are
happy to pay big bucks for quality lists. However, the money made from
a mailing list is secondary to the income which is made from people
like you and me asking to be included on your mailing list!!!

Here are the 4 easy steps to success:-

Step 1:- Get 6 separate pieces of paper and write the following on
each piece of paper.

PLEASE PUT ME ON YOUR MAILING LIST

Now get 6 U.S. dollar bills and place ONE inside each of the 6 pieces
of paper so the bills will not be seen through the envelopes (to
prevent mail theft). Next, place one paper in each of the 6 envelopes
and seal them, you should now have 6 sealed envelopes. Each with a
piece of paper stating the above phrase, your name and address, and a
$1.00 bill.

THIS IS ABSOLUTELY LEGAL!!! YOU ARE REQUESTING A LEGITIMATE SERVICE
AND YOU ARE PAYING FOR IT!!!

Like most of us, I was a little skeptical and a little worried about
the legal aspect of it all. So I checked it out with the U.S. Postal
Service and they confirmed that it is indeed legal!!!

Mail the 6 envelopes to the following addresses:-
D. Kumar
Room 2.36 Burkhardt House
Oxford Place, Victoria Park
M14 5RR Manchester
ENGLAND

T. Perce
11505 Headley Avenue
Cleveland, Oh 44111

T. Beckers
Rijksweg 46
6267AH Cadier en Keer
The Netherlands

J. Eddolls
144 Pursey Drive
Bradley Stoke
Bristol
BS32 8DP
United Kingdom

Louis Joseph
1933 Highway 35, #104
Wall, NJ 07719

Jesse Quiroz
2845 Franklin #1001 
Mesquite, Texas 75150

Step 2:- Now take the #1 name off the list that you see above, move
the other names up (6 becomes 5, 5 becomes 4, etc.) and add your name
as number 6 on the list.

Step 3:- Change anything you need to, but try to keep this message as
close to what you see as possible. Now, post your amended message to
at least 200 news groups. I think there are close to 24,000 groups!!!
All you need is 200, but remember, the more you post, the more money
you make!!! This is perfectly legal!! If you have any doubts, refer to
Title18 Sec. 1302 & 1341 of the postal lottery laws. Keep a copy of
these steps for yourself and whenever you need money, you can use it
again.

Please remember that this program remains successful because of the
honesty and the integrity of the participants and by their carefully
adhering to the directions!!!

Look at it this way. If you are of integrity, the program will
continue and the money that so many others have received will come
your way!!!

Note: - You may want to retain every name and address sent to you,
either on your computer or hard copy and keep the notes people send
you. This verifies that you are truly providing a service. Also, it
might be a good Idea to wrap the $1 bills in dark paper to reduce the
risk of mail theft.

So, as each post is downloaded and the directions carefully followed,
six members will be reimbursed for their participation as a list
developer with one dollar each. Your name will move up the list
geometrically so that when your name reaches the #1 position, you will
be receiving thousands of dollars in cash!!! What an opportunity for
only $6.00!!! ($1.00 for each of the first six people listed above).

Send it now, add your own name to the list and your in business!!!


DIRECTIONS FOR HOW TO POST TO A NEWS GROUP!!!

Step 1:- You do not need to re-type this entire message to do your own
posting. Simply put your cursor at the beginning of this message and
drag your cursor to the bottom of this message and select copy from
the edit menu. This will copy the entire message into the computer
memory.

Step 2:- Open a blank note pad file and place your cursor at the top
of the blank page. From the edit menu select paste. This will paste a
copy of the message into notepad so that you can add your name to the
list.

Step 3:- Save your new notepad file as a txt file. If you want to do
your posting in a different setting, you'll always have this file to
go back to.

Step 4:- Use Netscape or Internet Explorer and try searching for
various news groups (on-line forums, message boards, chat sites,
discussions, etc.)

Step 5:- Visit these message boards and post this message as a new
message by highlighting the text of this message from your notepad and
selecting paste from the edit menu. Fill in the subject, this will be
the header that everybody sees as they scroll through the list of
postings in a particular group. Click the post message button. You've
done your first one! Congratulations!!! All you have to do is jump to
different news groups and post away, after you get the hang of it, it
will take about 30 seconds for each news group!

REMEMBER, THE MORE NEWS GROUPS YOU POST IN, THE MORE MONEY YOU WILL
MAKE!!! (But you have to post a minimum of 200).

That's it!!! You will begin receiving money from around the world
within days!!! You may eventually want to rent a P.O. Box due to the
large amount of mail you will receive. If you wish to stay anonymous,
you can invent a name to use, as long as the postman will deliver it.

JUST MAKE SURE ALL THE ADDRESSES ARE CORRECT!!!

Now the why part. Out of 200 postings, say you receive only 5 replies
(a very low example). So then you made $5.00 with your name at #6 on
the letter. Now, each of the 5 persons who sent you $1.00 make the
minimum 200 postings, each with your name at #5 and only 5 persons
respond to each of the original 5, that is another $25.00 for you. Now
those 25 each make 200 MINIMUM posts with your name at #4 and only 5
replies each, you will bring in an additional $125.00!!! Now, those
125 persons turn around and post the minimum 200 with your name at #3
and only receive 5 replies each, you will make an additional
$625.00!!! OK, now here is the fun part, each of those 625 persons
post a minimum 200 messages with your name at #2 and they each only
receive 5 replies, that
just made you $3,125.00!!! Those 3,125 persons will all deliver this
message to 200 news groups. If just 5 more reply you will receive
$15,625.00!!! All with an original investment of only $6.00!!! Amazing
isn't it!!!! When your name is no longer on the list, you just take
the latest posting in the news groups and send out another $6.00 to
the names on the list, putting your name at number 6 again.

You must realize that thousands of people all over the world are
joining the internet and reading these messages every day!!! Just like
you are now!!! So, can you afford $6.00 and see if it really works?
I'm glad I did!!! People have said, "what if the plan is played out
and no one sends you the money?" So what!!! What are the chances of
that happening, when there are tons of new honest users and new honest
people who are joining the internet and news groups everyday and are
willing to give it a try? Estimates are at 20,000 to 50,000 new users,
every day!!!

REMEMBER PLAY HONESTLY AND FAIRLY AND THIS WILL REALLY WORK!!!

-- Comments/Feedback (please post your feedback/experiences here) --

Not bad for 1 hr's work....made me around $5320 in roughly 35 days
Anthony M - TX

Hello, I rcvd 269 bucks in the post in 2 weeks.
Dan Miami - FL

I had to wait around 10 days before I had any results - $13,450 as of
3rd Jan 2003 to date (14th Feb 2003).Am gonna re-post it again for
more money!!
Del from Alberta - Canada

Only received around  588 in the post the last 2 months since I
started the program but I'd posted to approx. 100 newsgroups.
James P - Manchester, UK

Cool....didn't expect much out of this "scam" initially but I have pay
my credit card bill
Mustafa - Jordan

For $6,I made $246 in 2 weeks
ROMEO2326 - Little Rock, AR -US of A

Hey, just droppin a line to say that after posting to well over 820
newsgroups on google and my ISP newsgroup server over a period of 4
1/2 months ,Ive raked in $54280 . Mucho dinero baby!!!! Peace 
Drew Dallas - TX