GNU bug report logs - #49624
compilation message end-column function off-by-one bug

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From: Mattias Engdegård <mattiase <at> acm.org>
To: 49624 <at> debbugs.gnu.org
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>, Juri Linkov <juri <at> linkov.net>
Subject: bug#49624: compilation message end-column function off-by-one bug
Date: Sun, 18 Jul 2021 21:00:41 +0200

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

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.

There does not seem to be a good justification for this nor is it documented so it's probably just a bug; proposed patch attached below. Does it warrant a mention in etc/NEWS?

[0001-Fix-off-by-one-error-in-compilation-rule-end-column-.patch (application/octet-stream, attachment)]

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