GNU bug report logs - #28796
diff 3.6 still reports a diff on identical lines

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

From: Vincent Lefevre <vincent <at> vinc17.net>
To: bug-diffutils <at> gnu.org
Subject: diff 3.6 still reports a diff on identical lines
Date: Thu, 12 Oct 2017 14:51:53 +0200

[Message part 1 (text/plain, inline)]

On some pair of files, "diff" reports a diff on identical lines.

I reported

  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=16848

against diff 3.3 a few years ago, but diff 3.6 (under Debian/unstable,
x86_64) has a similar problem. See the attached archive.

"out.diff", generated with "diff -u out1 out2", has at line 12622:

@@ -241913,9 +241895,9 @@
 3
 4
 5
-L: 409
-L: 409
-2
+L: 361
+L: 361
+2
 1
 2
 4

And if I run "diff -u -I L out1 out2", I also get the above chunk,
while it shouldn't appear.

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

[bug.tar.xz (application/octet-stream, attachment)]

Message #8 received at 28796 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Vincent Lefevre <vincent <at> vinc17.net>, 28796 <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#28796: diff 3.6 still reports a diff on
 identical lines
Date: Mon, 16 Oct 2017 01:32:46 -0700

Vincent Lefevre wrote:
> On some pair of files, "diff" reports a diff on identical lines.

Yes, that's a problem, though strictly speaking not a bug. You can use the 
--minimal option to avoid this problem. No doubt there's an efficient way to 
change "diff" to avoid this particular problem even when --minimal is not used, 
although that will take a bit of thinking.

Message #11 received at 28796 <at> debbugs.gnu.org (full text, mbox):

From: Vincent Lefevre <vincent <at> vinc17.net>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 28796 <at> debbugs.gnu.org
Subject: Re: [bug-diffutils] bug#28796: diff 3.6 still reports a diff on
 identical lines
Date: Mon, 23 Oct 2017 13:54:36 +0200

On 2017-10-16 01:32:46 -0700, Paul Eggert wrote:
> Vincent Lefevre wrote:
> > On some pair of files, "diff" reports a diff on identical lines.
> 
> Yes, that's a problem, though strictly speaking not a bug. You can use the
> --minimal option to avoid this problem. No doubt there's an efficient way to
> change "diff" to avoid this particular problem even when --minimal is not
> used, although that will take a bit of thinking.

OK. This would be useful, as --minimal is overkill on my original
files (15.87s with --minimal, 2.73s without it), even though I can
afford to waste a bit of time in the rare cases I need to do such
a diff on huge files.

-- 
Vincent Lefèvre <vincent <at> vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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