GNU bug report logs - #76452
3.11 critical bug: diff -Naur a b does not show a unified diff when one of the file is empty

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#76452: closed (3.11 critical bug: diff -Naur a b does not
 show a unified diff when one of the file is empty)
Date: Sat, 22 Feb 2025 06:12:03 +0000

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Your message dated Fri, 21 Feb 2025 23:11:22 -0700
with message-id <27b53198-137f-4e37-8f99-b539e365d4ff <at> cs.ucla.edu>
and subject line Re: [bug-diffutils] bug#76452: 3.11 critical bug: diff -Naur a b does not show a unified diff when one of the file is empty
has caused the debbugs.gnu.org bug report #76452,
regarding 3.11 critical bug: diff -Naur a b does not show a unified diff when one of the file is empty
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
76452: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76452
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Kate Deplaix <kit-ty-kate <at> outlook.com>
To: "bug-diffutils <at> gnu.org" <bug-diffutils <at> gnu.org>
Subject: 3.11 critical bug: diff -Naur a b does not show a unified diff when
 one of the file is empty
Date: Thu, 20 Feb 2025 15:25:05 +0000

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Hi,

While using diffutils 3.11 instead of 3.10, i've noticed a critical bug in diff reproducible with the following setup:

$ cd /tmp
$ mkdir a b
$ touch a/test
$ echo content > b/test

With diffutils 3.10, "diff -Naur a b" returns:

diff -Naur a/test b/test
--- a/test   2025-02-20 14:50:07.870258052 +0000
+++ b/test   2025-02-20 14:50:18.957287641 +0000
@@ -0,0 +1 @@
+content

but with diffutils 3.11, the same command returns:

File a/test is a regular empty file while file b/test is a regular file

Given no mention of this change appear in the changelog, i'm guessing this is an unintended change. In my opinion this bug is critical and the 3.11 release should be marked as broken to avoid more distributions using it.

Warm regards,
Kate Deplaix

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Collin Funk <collin.funk1 <at> gmail.com>
Cc: 76452-done <at> debbugs.gnu.org, Kate Deplaix <kit-ty-kate <at> outlook.com>
Subject: Re: [bug-diffutils] bug#76452: 3.11 critical bug: diff -Naur a b does
 not show a unified diff when one of the file is empty
Date: Fri, 21 Feb 2025 23:11:22 -0700

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Thanks for the diagnosis and the patch. I installed the attached 
instead, so as to decouple this part of the code from the part that 
turns file types into strings.

[0001-diff-don-t-treat-empty-files-as-a-different-file-typ.patch (text/x-patch, attachment)]

[0001-maint-mention-bug-76452-in-NEWS.patch (text/x-patch, attachment)]

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