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From: Philipp Stephani <p.stephani2@gmail.com>
To: Rajeev Narang <rajeev.jnk@sivalik.com>
Cc: 47391@debbugs.gnu.org, Emacs developers <emacs-devel@gnu.org>
Subject: Re: bug#47391: 27.2; static list return from function and nconc
Date: Thu, 25 Mar 2021 16:28:26 +0100	[thread overview]
Message-ID: <CAArVCkRmjEXQdhCod0mhOa0MRqM=quqcbESOCJHpbz2jnoyoLg@mail.gmail.com> (raw)
In-Reply-To: <87r1k32sir.fsf@hm.sivalik.com>

Am Do., 25. März 2021 um 16:23 Uhr schrieb Rajeev Narang via Bug
reports for GNU Emacs, the Swiss army knife of text editors
<bug-gnu-emacs@gnu.org>:
>
> (defun fn () '(1 2))
>
> (nconc (fn) '(3))
> -> (1 2 3)

This is undefined behavior/unsupported. The value that (fn) evaluates
to is immutable, but nconc mutates it.

>
> (nconc (fn) '(3))
> -> (1 2 3 3) ? should be (1 2 3)
>
> If this is not a bug, then hfy-invisible, hfy-face-to-style-i may need to be fixed.

If they use this pattern, then they should indeed be fixed.



  reply	other threads:[~2021-03-25 15:28 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-25 14:54 bug#47391: 27.2; static list return from function and nconc Rajeev Narang via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-03-25 15:28 ` Philipp Stephani [this message]
2021-03-25 15:43   ` Stefan Monnier
2021-03-25 15:55 ` Gregory Heytings
2021-03-25 15:58   ` Stefan Monnier
2021-03-25 16:03     ` Gregory Heytings

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