GNU logs - #29311, boring messages

Message sent to bug-diffutils@HIDDEN:

Subject: bug#29311: Byte comparison from cmp diffutils
Resent-From: "s3gmentationfault@HIDDEN" <s3gmentationfault@HIDDEN>
Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org>
Resent-CC: bug-diffutils@HIDDEN
Resent-Date: Wed, 15 Nov 2017 23:07:01 +0000
Resent-Message-ID: <handler.29311.B.151078720024709 <at> debbugs.gnu.org>
Resent-Sender: help-debbugs@HIDDEN
To: 29311 <at> debbugs.gnu.org
From: "s3gmentationfault@HIDDEN" <s3gmentationfault@HIDDEN>
Message-ID: <dea15b8c-ab12-becd-88b5-3c8d20d1d36b@HIDDEN>
Date: Wed, 15 Nov 2017 23:44:29 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: list
Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org
Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org>

Hi, i write this message because cmp command from diffutils give an 
unexpected result if is used on binary files:
if we try to compare two different files (not symlink, not hardlink 
etc..), cmp say that the differ from 42 byte.

~ > LC_ALL=C cmp /usr/bin/g++ /usr/bin/gcc
/usr/bin/g++ /usr/bin/gcc differ: char 42, line 1

During a discussion another member convinced me to try hexdump for do 
that� comparison than i have see that those file differ for many bytes 
then 42, so i have try to write a program for do that, just for sure 
(the program is silly i have also forget to return EXIT_SUCCESS, and as 
default if it find a different byte the consider all other byte 
different but is only for this demonstration)
src: https://arin.ga/swsNn1

~ > CFLAGS=-O3 make diffbyte_gcc && ./diffbyte_gcc
they diff by: 766087 byte

so something absolutely does not work:
some clarifications: I have see just now that using C as language it say 
char, but in my language it say "byte" ("/bin/g++ /bin/gcc differenza: 
byte 42, riga 1").
However that is indifferent since in manpage it use only "byte" term, so 
i expect that it compare bytes, not only ascii text; The manpages at 
description say:� "Compare two files byte by byte".

For do other example, the wc command with -c option really counts the bytes:

~ > printf "\u2592"|wc -c
3

~ > printf "ciao\0x8" | wc -c
7

and (except for the sparse files) also du and wc report the same result 
with binary files:

~ > du -b /bin/gcc
993584� /bin/gcc

~ > wc -c /bin/gcc
993584 /bin/gcc

 From info i read:
The 'cmp' command compares two files, and if they differ, tells the 
first byte and line number where they differ or reports that one file is 
a prefix of the other.
Bytes and lines are numbered starting with 1. The arguments of 'cmp' are 
as follows:

I do not know if it is meant that the comparison stops at the first line 
or rather when one of the two buffers differs from the other but 
manpages and program options say that it compare byte
so it should do

Message sent:

Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-Mailer: MIME-tools 5.505 (Entity 5.505)
Content-Type: text/plain; charset=utf-8
X-Loop: help-debbugs@HIDDEN
From: help-debbugs@HIDDEN (GNU bug Tracking System)
To: "s3gmentationfault@HIDDEN" <s3gmentationfault@HIDDEN>
Subject: bug#29311: Acknowledgement (Byte comparison from cmp diffutils)
Message-ID: <handler.29311.B.151078720024709.ack <at> debbugs.gnu.org>
References: <dea15b8c-ab12-becd-88b5-3c8d20d1d36b@HIDDEN>
X-Gnu-PR-Message: ack 29311
X-Gnu-PR-Package: diffutils
Reply-To: 29311 <at> debbugs.gnu.org
Date: Wed, 15 Nov 2017 23:07:02 +0000

Thank you for filing a new bug report with debbugs.gnu.org.

This is an automatically generated reply to let you know your message
has been received.

Your message is being forwarded to the package maintainers and other
interested parties for their attention; they will reply in due course.

Your message has been sent to the package maintainer(s):
 bug-diffutils@HIDDEN

If you wish to submit further information on this problem, please
send it to 29311 <at> debbugs.gnu.org.

Please do not send mail to help-debbugs@HIDDEN unless you wish
to report a problem with the Bug-tracking system.

--=20
29311: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=3D29311
GNU Bug Tracking System
Contact help-debbugs@HIDDEN with problems

Message sent to bug-diffutils@HIDDEN:

Subject: bug#29311: Byte comparison from cmp diffutils
References: <dea15b8c-ab12-becd-88b5-3c8d20d1d36b@HIDDEN>
In-Reply-To: <dea15b8c-ab12-becd-88b5-3c8d20d1d36b@HIDDEN>
Resent-From: "s3gmentationfault@HIDDEN" <s3gmentationfault@HIDDEN>
Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org>
Resent-CC: bug-diffutils@HIDDEN
Resent-Date: Thu, 16 Nov 2017 00:15:02 +0000
Resent-Message-ID: <handler.29311.B29311.15107912545653 <at> debbugs.gnu.org>
Resent-Sender: help-debbugs@HIDDEN
To: 29311 <at> debbugs.gnu.org
From: "s3gmentationfault@HIDDEN" <s3gmentationfault@HIDDEN>
Message-ID: <ab0d7896-b73c-e2d9-9675-2b38794e5615@HIDDEN>
Date: Thu, 16 Nov 2017 00:24:57 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: list
Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org
Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org>

Hi, i write this message regarding to my previous bug report, i have see 
just now that posix section of manpages say:
"The cmp utility shall write no output files are the same. Under default 
options, if they differ, it� shall write tostandard� output the byte and 
line number at which the first difference occurred. Bytes and lines 
shall be numbered beginning with 1."

so now it's all clare.

Last modified: Mon, 25 Nov 2019 12:00:02 UTC

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997 nCipher Corporation Ltd, 1994-97 Ian Jackson.