From: Alan Mackenzie <acm@muc.de>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: Paul Eggert <eggert@cs.ucla.edu>,
Emacs Development <emacs-devel@gnu.org>
Subject: Re: Should undefined behavior be encouraged in Emacs?
Date: Mon, 3 Oct 2011 09:20:46 +0000 [thread overview]
Message-ID: <20111003092046.GA3248@acm.acm> (raw)
In-Reply-To: <jwvipo6zsfg.fsf-monnier+emacs@gnu.org>
Hi, Stefan.
On Sun, Oct 02, 2011 at 11:11:58PM -0400, Stefan Monnier wrote:
> > The argument given for undefined behavior is that it simplifies
> > maintenance of Emacs internals.
> I like to keep some corner of the behavior undefined, when I think
> that user code that depends on such details is undesirable (e.g. return
> values of primitives which are only called for side-effects).
There are few functions called solely for side effects. For example,
`goto-char' is frequently found thusly:
(and
...
...
(goto-char anchor-point)
...
...)
. Strictly speaking this behaviour is undefined because the return
value (which everybody knows to be anchor-point) is undefined. Strictly
speaking, one has to write it like this:
(and
...
...
(progn (goto-char anchor-point) t)
...
...)
, which is a pain in the alist. Surely the return value of things like
`goto-char' should be defined?
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2011-10-03 9:20 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-03 1:39 Should undefined behavior be encouraged in Emacs? Paul Eggert
2011-10-03 3:11 ` Stefan Monnier
2011-10-03 6:39 ` Andreas Röhler
2011-10-03 7:29 ` Stephen J. Turnbull
2011-10-03 8:58 ` Andreas Röhler
2011-10-06 2:17 ` Stephen J. Turnbull
2011-10-06 17:30 ` Richard Stallman
2011-10-06 19:49 ` Stephen J. Turnbull
2011-10-06 20:08 ` Andreas Röhler
2011-10-06 20:12 ` Lars Magne Ingebrigtsen
2011-10-06 20:46 ` Eli Zaretskii
2011-10-07 5:23 ` Andreas Röhler
2011-10-07 7:44 ` Stephen J. Turnbull
2011-10-07 7:52 ` John Wiegley
2011-10-07 17:27 ` Stephen J. Turnbull
2011-10-07 8:38 ` Alan Mackenzie
2011-10-07 15:26 ` Barry Warsaw
2011-10-07 18:06 ` ken manheimer
2011-10-07 18:21 ` Barry Warsaw
2011-10-07 18:46 ` Óscar Fuentes
2011-10-07 19:59 ` ken manheimer
2011-10-07 18:41 ` Drew Adams
2011-10-08 13:49 ` Miles Bader
2011-10-08 14:34 ` Drew Adams
2011-10-03 13:16 ` Stefan Monnier
2011-10-03 9:20 ` Alan Mackenzie [this message]
2011-10-03 9:52 ` Eli Zaretskii
2011-10-03 8:29 ` Andreas Schwab
2011-10-03 9:53 ` Eli Zaretskii
2011-10-03 13:13 ` Richard Stallman
2011-10-03 15:15 ` Dave Abrahams
2011-10-04 1:55 ` Richard Stallman
2011-10-04 2:18 ` Dave Abrahams
2011-10-03 16:14 ` Eli Zaretskii
2011-10-03 16:27 ` Andreas Schwab
2011-10-03 16:41 ` Eli Zaretskii
2011-10-04 1:55 ` Richard Stallman
2011-10-03 20:53 ` Paul Eggert
2011-10-03 14:49 ` Dave Abrahams
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