Subject: Re: bug#49624: compilation message end-column function off-by-one bug

From: Eli Zaretskii <[email-masked]>
Date: Sun, 18 Jul 2021 22:10:05 +0300

> From: Mattias Engdegård <[email-masked]>
> Date: Sun, 18 Jul 2021 21:00:41 +0200
> Cc: Stefan Monnier <[email-masked]>, Juri Linkov <[email-masked]>
> 
> Compilation message patterns (in compilation-regexp-alist and -alist) can indicate starting and ending line and column numbers, either by supplying regexp match numbers or functions that return the respective line/column numbers when called. In other words, the integer N can be understood as a shorthand for the function
> 
> (lambda () (and (match-beginning N) (string-to-number (match-string N))))
> 
> except that isn't true for the ending column where there is a difference of 1; an END-COL function returning 13 means that the error's last column is 12.

Isn't that because END-COL is the first column _beyond_ the last
column?