GNU bug report logs - #24154
bug in 'diff -B'

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 24154 in the body.
You can then email your comments to 24154 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "Zieg, Mark (KSC-ESC-624)[VENCORE-ESC]" <mark.zieg <at> nasa.gov>
To: "bug-diffutils <at> gnu.org" <bug-diffutils <at> gnu.org>
Subject: bug in 'diff -B'
Date: Thu, 4 Aug 2016 21:43:45 +0000

Hello,

When diffing an empty file against a one-byte file using -B (--ignore-blank-lines), diff incorrectly reports that the files are identical, even though they aren't even the same size.  The problem does not occur with files of 2 bytes or longer.  I tested this with diffutils 2.8, 3.2 and 3.3.

How to reproduce:

# create a one-byte file "foo"
deedwl262 [~/work/test] mzieg 09:17 PM $ echo -n x > foo

# create a zero-byte file "bar"
deedwl262 [~/work/test] mzieg 09:17 PM $ echo -n > bar

# confirm file sizes
deedwl262 [~/work/test] mzieg 09:18 PM $ ls -la
-rw-rw-r-- 1 mzieg unixusers 0 Aug  4 21:18 bar
-rw-rw-r-- 1 mzieg unixusers 1 Aug  4 21:17 foo

# verify "diff" works as expected
deedwl262 [~/work/test] mzieg 09:18 PM $ diff foo bar
1d0
< x
\ No newline at end of file

# verify "diff -w" works as expected
deedwl262 [~/work/test] mzieg 09:18 PM $ diff -w foo bar
1d0
< x
\ No newline at end of file

# verify "diff -b" works as expected
deedwl262 [~/work/test] mzieg 09:18 PM $ diff -b foo bar
1d0
< x
\ No newline at end of file

# HERE IS THE PROBLEM: diff -B does NOT work as expected
deedwl262 [~/work/test] mzieg 09:18 PM $ diff -B foo bar 

# change "foo" to a 2-byte file
deedwl262 [~/work/test] mzieg 09:18 PM $ echo  -n xy > foo

# now "diff -B" works as expected
deedwl262 [~/work/test] mzieg 09:19 PM $ diff -B foo bar 
1d0
< xy
\ No newline at end of file

Regards,

Mark Zieg
mark <at> zieg.com

Message #10 received at 24154-done <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: "Zieg, Mark (KSC-ESC-624)[VENCORE-ESC]" <mark.zieg <at> nasa.gov>
Cc: 24154-done <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#24154: bug in 'diff -B'
Date: Thu, 4 Aug 2016 16:30:43 -0700

On Thu, Aug 4, 2016 at 2:43 PM, Zieg, Mark (KSC-ESC-624)[VENCORE-ESC]
<mark.zieg <at> nasa.gov> wrote:
> When diffing an empty file against a one-byte file using -B (--ignore-blank-lines), diff incorrectly reports that the files are identical, even though they aren't even the same size.  The problem does not occur with files of 2 bytes or longer.  I tested this with diffutils 2.8, 3.2 and 3.3.
...
> # HERE IS THE PROBLEM: diff -B does NOT work as expected
> deedwl262 [~/work/test] mzieg 09:18 PM $ diff -B foo bar

Thank you for the report. I confirm it was a problem with diffutils-3.3:

$ /usr/bin/diff --version|head -1
diff (GNU diffutils) 3.3
$ printf 1 > 1; : > 0; /usr/bin/diff -B 0 1
$ printf 1 > 1; : > 0; /usr/bin/diff -B 1 0
$

It was fixed with this commit, which will be part of the imminent
diffutils-3.4 release:

commit d2fd9d4683ef60c259a3b426f71cef1b89ff383d
Author: Paul Eggert <eggert <at> cs.ucla.edu>
Date:   Wed Sep 3 15:58:03 2014 -0700

    diff: fix bug with diff -B and incomplete lines

    Reported by Navin Kabra via Eric Blake in:
    http://bugs.gnu.org/18402
    * src/util.c (analyze_hunk): Don't mishandle incomplete
    lines at end of file.
    * tests/no-newline-at-eof: Test for the bug.

So I've marked this auto-created "issue" as resolved.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.