GNU bug report logs - #25166
It shouldn't be possible to set the function cell of t

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

From: Philipp <p.stephani2 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Sun, 11 Dec 2016 10:41:13 +0100

You can set the function cell of nil and t using `fset' and friends.
But you can't call the `nil' function using (nil) (it does work with
(t)).  I think that attempting to set the function cell of nil and t is
almost always a bug -- probably the programmer wanted to set a real
symbol, but some of the constants got passed.  I propose to signal an
error (e.g. `setting-constant') whenever the function cell of nil and t
is modified; maybe the same should happen for keywords.


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Message #8 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Philipp <p.stephani2 <at> gmail.com>
Cc: 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Sun, 11 Dec 2016 13:38:57 -0500

Philipp wrote:

> You can set the function cell of nil and t using `fset' and friends.
> But you can't call the `nil' function using (nil) (it does work with
> (t)).  I think that attempting to set the function cell of nil and t is
> almost always a bug -- probably the programmer wanted to set a real
> symbol, but some of the constants got passed.  I propose to signal an
> error (e.g. `setting-constant') whenever the function cell of nil and t
> is modified; maybe the same should happen for keywords.

I just did this yesterday...
See https://debbugs.gnu.org/25110, ba8e883, and 3fd4433.

Message #15 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Philipp <p.stephani2 <at> gmail.com>
Cc: 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Mon, 12 Dec 2016 15:25:44 -0500

Glenn Morris wrote:

> Philipp wrote:
>
>> You can set the function cell of nil and t using `fset' and friends.
>> But you can't call the `nil' function using (nil) (it does work with
>> (t)).  I think that attempting to set the function cell of nil and t is
>> almost always a bug -- probably the programmer wanted to set a real
>> symbol, but some of the constants got passed.  I propose to signal an
>> error (e.g. `setting-constant') whenever the function cell of nil and t
>> is modified; maybe the same should happen for keywords.
>
> I just did this yesterday...
> See https://debbugs.gnu.org/25110, ba8e883, and 3fd4433.

And now see also ffb1302. :)
Anyway, I only did "nil", since as you say "t" can actually be called as
a function. But you are right that it's probably unintended.

Message #18 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50; It shouldn't be possible to set the function
 cell of nil and t
Date: Mon, 26 Dec 2016 19:29:17 +0000

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

Glenn Morris <rgm <at> gnu.org> schrieb am Mo., 12. Dez. 2016 um 21:25 Uhr:

> Glenn Morris wrote:
>
> > Philipp wrote:
> >
> >> You can set the function cell of nil and t using `fset' and friends.
> >> But you can't call the `nil' function using (nil) (it does work with
> >> (t)).  I think that attempting to set the function cell of nil and t is
> >> almost always a bug -- probably the programmer wanted to set a real
> >> symbol, but some of the constants got passed.  I propose to signal an
> >> error (e.g. `setting-constant') whenever the function cell of nil and t
> >> is modified; maybe the same should happen for keywords.
> >
> > I just did this yesterday...
> > See https://debbugs.gnu.org/25110, ba8e883, and 3fd4433.
>
> And now see also ffb1302. :)
> Anyway, I only did "nil", since as you say "t" can actually be called as
> a function. But you are right that it's probably unintended.
>
>
Thanks! Interestingly the behavior was already added in 1994 (commit
c15c5d408d696928862ca2848a359231e373556c), but apparently reverted later.
I'd suggest to simply reinstate that commit.

[Message part 2 (text/html, inline)]

Message #21 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50; It shouldn't be possible to set the function
 cell of nil and t
Date: Mon, 26 Dec 2016 19:41:00 +0000

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

Philipp Stephani <p.stephani2 <at> gmail.com> schrieb am Mo., 26. Dez. 2016 um
20:29 Uhr:

> Glenn Morris <rgm <at> gnu.org> schrieb am Mo., 12. Dez. 2016 um 21:25 Uhr:
>
> Glenn Morris wrote:
>
> > Philipp wrote:
> >
> >> You can set the function cell of nil and t using `fset' and friends.
> >> But you can't call the `nil' function using (nil) (it does work with
> >> (t)).  I think that attempting to set the function cell of nil and t is
> >> almost always a bug -- probably the programmer wanted to set a real
> >> symbol, but some of the constants got passed.  I propose to signal an
> >> error (e.g. `setting-constant') whenever the function cell of nil and t
> >> is modified; maybe the same should happen for keywords.
> >
> > I just did this yesterday...
> > See https://debbugs.gnu.org/25110, ba8e883, and 3fd4433.
>
> And now see also ffb1302. :)
> Anyway, I only did "nil", since as you say "t" can actually be called as
> a function. But you are right that it's probably unintended.
>
>
> Thanks! Interestingly the behavior was already added in 1994 (commit
> c15c5d408d696928862ca2848a359231e373556c), but apparently reverted later.
> I'd suggest to simply reinstate that commit.
>

Here's a patch.

[Message part 2 (text/html, inline)]

[0001-Prevent-setting-the-function-cell-of-t-Bug-25166.txt (text/plain, attachment)]

Message #24 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Philipp Stephani <p.stephani2 <at> gmail.com>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: rgm <at> gnu.org, 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Mon, 26 Dec 2016 21:47:21 +0200

> From: Philipp Stephani <p.stephani2 <at> gmail.com>
> Date: Mon, 26 Dec 2016 19:29:17 +0000
> Cc: 25166 <at> debbugs.gnu.org
> 
>  And now see also ffb1302. :)
>  Anyway, I only did "nil", since as you say "t" can actually be called as
>  a function. But you are right that it's probably unintended.
> 
> Thanks! Interestingly the behavior was already added in 1994 (commit
> c15c5d408d696928862ca2848a359231e373556c), but apparently reverted later. I'd suggest to simply
> reinstate that commit. 

It was reverted in 32e5c58ca969ec30d31520da52c9866cafa62927.  Perhaps
Stefan could tell why he did that (the log message doesn't say).

Message #27 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: rgm <at> gnu.org, Philipp Stephani <p.stephani2 <at> gmail.com>,
 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Tue, 27 Dec 2016 10:15:29 -0500

> It was reverted in 32e5c58ca969ec30d31520da52c9866cafa62927.  Perhaps
> Stefan could tell why he did that (the log message doesn't say).

Because there doesn't seem to be any good reason to single out nil and
t in this respect and because those things aren't terribly dangerous.


        Stefan

Message #30 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Cc: rgm <at> gnu.org, p.stephani2 <at> gmail.com, 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Wed, 28 Dec 2016 00:49:04 +0200

> From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
> Cc: Philipp Stephani <p.stephani2 <at> gmail.com>, rgm <at> gnu.org,
>         25166 <at> debbugs.gnu.org
> Date: Tue, 27 Dec 2016 10:15:29 -0500
> 
> > It was reverted in 32e5c58ca969ec30d31520da52c9866cafa62927.  Perhaps
> > Stefan could tell why he did that (the log message doesn't say).
> 
> Because there doesn't seem to be any good reason to single out nil and
> t in this respect and because those things aren't terribly dangerous.

So therefore we shouldn't reinstate that now.

Message #33 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: rgm <at> gnu.org, p.stephani2 <at> gmail.com, 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Tue, 27 Dec 2016 18:11:25 -0500

>> Because there doesn't seem to be any good reason to single out nil and
>> t in this respect and because those things aren't terribly dangerous.
> So therefore we shouldn't reinstate that now.

Yes, that's my opinion.


        Stefan

Message #36 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>, Eli Zaretskii <eliz <at> gnu.org>
Cc: rgm <at> gnu.org, 25166 <at> debbugs.gnu.org
Subject: Re: bug#25166: 26.0.50; It shouldn't be possible to set the function
 cell of nil and t
Date: Mon, 01 May 2017 14:44:44 +0000

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

Stefan Monnier <monnier <at> iro.umontreal.ca> schrieb am Mi., 28. Dez. 2016 um
00:11 Uhr:

> >> Because there doesn't seem to be any good reason to single out nil and
> >> t in this respect and because those things aren't terribly dangerous.
> > So therefore we shouldn't reinstate that now.
>
> Yes, that's my opinion.
>
>
>
Well, my opinion is obviously different, so the maintainer should decide.

[Message part 2 (text/html, inline)]

Message #39 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Philipp Stephani <p.stephani2 <at> gmail.com>
Cc: rgm <at> gnu.org, 25166 <at> debbugs.gnu.org, monnier <at> iro.umontreal.ca
Subject: Re: bug#25166: 26.0.50; It shouldn't be possible to set the function
 cell of nil and t
Date: Mon, 01 May 2017 18:12:33 +0300

> From: Philipp Stephani <p.stephani2 <at> gmail.com>
> Date: Mon, 01 May 2017 14:44:44 +0000
> Cc: rgm <at> gnu.org, 25166 <at> debbugs.gnu.org
> 
> Stefan Monnier <monnier <at> iro.umontreal.ca> schrieb am Mi., 28. Dez. 2016 um 00:11 Uhr:
> 
>  >> Because there doesn't seem to be any good reason to single out nil and
>  >> t in this respect and because those things aren't terribly dangerous.
>  > So therefore we shouldn't reinstate that now.
> 
>  Yes, that's my opinion.
> 
> Well, my opinion is obviously different, so the maintainer should decide. 

One maintainer has already decided, see above.

Message #42 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> users.sourceforge.net>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Philipp Stephani <p.stephani2 <at> gmail.com>, 25166 <at> debbugs.gnu.org,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#25166: 26.0.50; It shouldn't be possible to set the function
 cell of nil and t
Date: Fri, 27 Oct 2017 13:59:25 -0400

# fset of nil is already covered in Bug#25110
retitle 25166 It shouldn't be possible to set the function cell of t
tags 25166 wontfix
close 25166
quit

On Mon, May 1, 2017 at 11:12 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
>> From: Philipp Stephani <p.stephani2 <at> gmail.com>
>> Date: Mon, 01 May 2017 14:44:44 +0000
>> Cc: rgm <at> gnu.org, 25166 <at> debbugs.gnu.org
>>
>> Stefan Monnier <monnier <at> iro.umontreal.ca> schrieb am Mi., 28. Dez. 2016 um 00:11 Uhr:
>>
>>  >> Because there doesn't seem to be any good reason to single out nil and
>>  >> t in this respect and because those things aren't terribly dangerous.
>>  > So therefore we shouldn't reinstate that now.
>>
>>  Yes, that's my opinion.
>>
>> Well, my opinion is obviously different, so the maintainer should decide.
>
> One maintainer has already decided, see above.

Seems final enough, closing as wontfix.

PS for an example of why singling out nil makes sense (but this
doesn't apply to t) see [1].
Summary: (autoload #'nil "something" nil t) silently succeeds but
makes forward-word, backward-word, etc, (fail to) funcall nil.

[1]: https://github.com/jwiegley/use-package/issues/512

Message #51 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Noam Postavsky <npostavs <at> users.sourceforge.net>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 25166 <at> debbugs.gnu.org,
 Philipp Stephani <p.stephani2 <at> gmail.com>
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Sat, 28 Oct 2017 12:16:28 -0400

> PS for an example of why singling out nil makes sense (but this
> doesn't apply to t) see [1].
> Summary: (autoload #'nil "something" nil t) silently succeeds but
> makes forward-word, backward-word, etc, (fail to) funcall nil.

Why would someone do (autoload #'nil "something" nil t) ?


        Stefan

Message #54 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> users.sourceforge.net>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 25166 <at> debbugs.gnu.org,
 Philipp Stephani <p.stephani2 <at> gmail.com>
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Sat, 28 Oct 2017 12:45:57 -0400

Stefan Monnier <monnier <at> iro.umontreal.ca> writes:

>> PS for an example of why singling out nil makes sense (but this
>> doesn't apply to t) see [1].
>> Summary: (autoload #'nil "something" nil t) silently succeeds but
>> makes forward-word, backward-word, etc, (fail to) funcall nil.
>
> Why would someone do (autoload #'nil "something" nil t) ?

By accident.  It's a bug in use-package.

    (use-package foo-pkg :commands <commands-to-autoload>)

Creates autoloads for all the commands in <commands-to-autoload>, which
can be a symbol, or a list of symbols.  But nil is also a symbol, so
passing an empty list makes an autoload for nil (because use-package
checks for symbolp before listp), rather than making autoloads for 0
commands.

Message #57 received at 25166 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Noam Postavsky <npostavs <at> users.sourceforge.net>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 25166 <at> debbugs.gnu.org,
 Philipp Stephani <p.stephani2 <at> gmail.com>
Subject: Re: bug#25166: 26.0.50;
 It shouldn't be possible to set the function cell of nil and t
Date: Sun, 29 Oct 2017 14:10:39 -0400

> By accident.  It's a bug in use-package.

That's a rare accident, which I assume has been fixed already (if not,
it's another argument in favor of saying that it's not important).
Nothing that warrants adding special error detection.


        Stefan

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