GNU bug report logs - #64485
"diff -y" broken since yesterday

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

From: Bruno Haible <bruno <at> clisp.org>
To: bug-diffutils <at> gnu.org
Subject: "diff -y" broken since yesterday
Date: Wed, 05 Jul 2023 19:30:31 +0200

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

Hi Paul,

I'm trying to understand the meaning of 'in_position' and 'out_position' in
function 'print_half_line'. While doing this, I spotted a bug:

$ cat foo1.txt
a
ab
abc
$ cat foo2.txt
ab
abcd
$ src/diff -t -y foo1.txt foo2.txt
a                                                                <
ab                                                                   ab
abc                                                                |  abcd

This is obviously not how it's intended to be. The attached patch fixes it.
The cause is that in the case of a character of width 1, the assignment

  out_position = in_position;

was lost in commit 05cdf3102ef3fb261db311a3e5d090fb63dbc792 (yesterday).
With this patch, the result is again as it should be:

$ src/diff -t -y foo1.txt foo2.txt
a                                                               <
ab                                                                 ab
abc                                                             |  abcd

The patch also improves comments in this function. So that next time,
I (or anyone else) don't spent 30 minutes to understand the difference
between 'in_position' and 'out_position'.

Bruno

[0001-diff-Fix-diff-y-output.patch (text/x-patch, attachment)]

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