GNU bug report logs - #70568
30.0.50; build warnings on 'x86_64-pc-linux-gnu'

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

From: David Ponce <da_vid <at> orange.fr>
To: bug-gnu-emacs <at> gnu.org
Subject: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Thu, 25 Apr 2024 17:11:54 +0200

Hello,

When I build Emacs configured for 'x86_64-pc-linux-gnu' on Fedora 39 with gcc 13.2.1
the below warnings are reported:


1) ./configure --with-x-toolkit=lucid --with-native-compilation=no

..
  CC       xterm.o
xterm.c: In function ‘x_alloc_nearest_color_1’:
xterm.c:9374:27: warning: potential null pointer dereference [-Wnull-dereference]
 9374 |   if (dpyinfo->visual_info.class == DirectColor)
      |       ~~~~~~~~~~~~~~~~~~~~^~~~~~
xterm.c:9374:27: warning: potential null pointer dereference [-Wnull-dereference]
...
  CC       eval.o
In file included from eval.c:25:
lisp.h: In function ‘internal_lisp_condition_case’:
lisp.h:1129:15: warning: variable ‘sym’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
 1129 |   Lisp_Object sym = XSYMBOL_WITH_POS (a)->sym;
      |               ^~~
eval.c:1413:43: warning: argument ‘var’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
 1413 | internal_lisp_condition_case (Lisp_Object var, Lisp_Object bodyform,
      |                               ~~~~~~~~~~~~^~~
...

2) ./configure --with-x-toolkit=gtk3 --with-cairo-xcb --with-native-compilation=no

...
  CC       eval.o
In file included from eval.c:25:
lisp.h: In function ‘internal_lisp_condition_case’:
lisp.h:1129:15: warning: variable ‘sym’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
 1129 |   Lisp_Object sym = XSYMBOL_WITH_POS (a)->sym;
      |               ^~~
eval.c:1413:43: warning: argument ‘var’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
 1413 | internal_lisp_condition_case (Lisp_Object var, Lisp_Object bodyform,
      |                               ~~~~~~~~~~~~^~~
...


In both cases (Lucid, gtk3) the reported warnings don't seem to affect run.
Thanks

Message #8 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: David Ponce <da_vid <at> orange.fr>, Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Sat, 27 Apr 2024 12:37:45 +0300

> Date: Thu, 25 Apr 2024 17:11:54 +0200
> From:  David Ponce via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> Hello,
> 
> When I build Emacs configured for 'x86_64-pc-linux-gnu' on Fedora 39 with gcc 13.2.1
> the below warnings are reported:
> 
> 
> 1) ./configure --with-x-toolkit=lucid --with-native-compilation=no
> 
> ..
>    CC       xterm.o
> xterm.c: In function ‘x_alloc_nearest_color_1’:
> xterm.c:9374:27: warning: potential null pointer dereference [-Wnull-dereference]
>   9374 |   if (dpyinfo->visual_info.class == DirectColor)
>        |       ~~~~~~~~~~~~~~~~~~~~^~~~~~
> xterm.c:9374:27: warning: potential null pointer dereference [-Wnull-dereference]
> ...
>    CC       eval.o
> In file included from eval.c:25:
> lisp.h: In function ‘internal_lisp_condition_case’:
> lisp.h:1129:15: warning: variable ‘sym’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
>   1129 |   Lisp_Object sym = XSYMBOL_WITH_POS (a)->sym;
>        |               ^~~
> eval.c:1413:43: warning: argument ‘var’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
>   1413 | internal_lisp_condition_case (Lisp_Object var, Lisp_Object bodyform,
>        |                               ~~~~~~~~~~~~^~~
> ...
> 
> 2) ./configure --with-x-toolkit=gtk3 --with-cairo-xcb --with-native-compilation=no
> 
> ...
>    CC       eval.o
> In file included from eval.c:25:
> lisp.h: In function ‘internal_lisp_condition_case’:
> lisp.h:1129:15: warning: variable ‘sym’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
>   1129 |   Lisp_Object sym = XSYMBOL_WITH_POS (a)->sym;
>        |               ^~~
> eval.c:1413:43: warning: argument ‘var’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
>   1413 | internal_lisp_condition_case (Lisp_Object var, Lisp_Object bodyform,
>        |                               ~~~~~~~~~~~~^~~
> ...
> 
> 
> In both cases (Lucid, gtk3) the reported warnings don't seem to affect run.
> Thanks

Paul, are those real warnings, or just false alarms?

Message #11 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Eli Zaretskii <eliz <at> gnu.org>, David Ponce <da_vid <at> orange.fr>
Cc: 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Sat, 27 Apr 2024 15:20:36 -0700

On 2024-04-27 02:37, Eli Zaretskii wrote:
> Paul, are those real warnings, or just false alarms?
Hard to say; someone who understands that part of the code would have to 
look at it in more detail.

I typically don't worry about these warnings unless they're generated by 
a default build (no 'configure' options except perhaps 
--enable-gcc-warnings) with the most recent GCC. This is because these 
warnings are usually false alarms these days, except perhaps for 
recently-added code.

On my list of things to do is to get Emacs to build with 
--enable-gcc-warnings and GCC 14, which is sort of out now (it's part of 
Fedora 40).

Message #14 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>, Po Lu <luangruo <at> yahoo.com>
Cc: da_vid <at> orange.fr, 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Sun, 28 Apr 2024 08:04:10 +0300

Message #17 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>, Po Lu <luangruo <at> yahoo.com>
Cc: da_vid <at> orange.fr, 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Sun, 28 Apr 2024 08:05:04 +0300

> Date: Sat, 27 Apr 2024 15:20:36 -0700
> Cc: 70568 <at> debbugs.gnu.org
> From: Paul Eggert <eggert <at> cs.ucla.edu>
> 
> On 2024-04-27 02:37, Eli Zaretskii wrote:
> > Paul, are those real warnings, or just false alarms?
> Hard to say; someone who understands that part of the code would have to 
> look at it in more detail.

Thanks.  Perhaps Po Lu (CC'ed) can?

Message #20 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: Po Lu <luangruo <at> yahoo.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: da_vid <at> orange.fr, Paul Eggert <eggert <at> cs.ucla.edu>, 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Sun, 28 Apr 2024 13:31:47 +0800

Eli Zaretskii <eliz <at> gnu.org> writes:

>> Date: Sat, 27 Apr 2024 15:20:36 -0700
>> Cc: 70568 <at> debbugs.gnu.org
>> From: Paul Eggert <eggert <at> cs.ucla.edu>
>> 
>> On 2024-04-27 02:37, Eli Zaretskii wrote:
>> > Paul, are those real warnings, or just false alarms?
>> Hard to say; someone who understands that part of the code would have to 
>> look at it in more detail.
>
> Thanks.  Perhaps Po Lu (CC'ed) can?

Definitely a false alarm, if the eassume above wasn't explicit enough.
It's impossible for a display connection not managed by Emacs to enter
functions that call x_display_info_for_display.

Message #23 received at 70568 <at> debbugs.gnu.org (full text, mbox):

From: David Ponce <da_vid <at> orange.fr>
To: Paul Eggert <eggert <at> cs.ucla.edu>, Eli Zaretskii <eliz <at> gnu.org>
Cc: 70568 <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Wed, 1 May 2024 09:18:27 +0200

On 28/04/2024 00:20, Paul Eggert wrote:
> On 2024-04-27 02:37, Eli Zaretskii wrote:
>> Paul, are those real warnings, or just false alarms?
> Hard to say; someone who understands that part of the code would have to look at it in more detail.
> 
> I typically don't worry about these warnings unless they're generated by a default build (no 'configure' options except perhaps --enable-gcc-warnings) with the most recent GCC. This is because these warnings are usually false alarms these days, except perhaps for recently-added code.
> 
> On my list of things to do is to get Emacs to build with --enable-gcc-warnings and GCC 14, which is sort of out now (it's part of Fedora 40).

Since Paul committed changes to pacify GCC 14 warnings, Emacs builds cleanly.
For me this bug can be closed.

Thanks!

Message #28 received at 70568-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: David Ponce <da_vid <at> orange.fr>, Eli Zaretskii <eliz <at> gnu.org>
Cc: 70568-done <at> debbugs.gnu.org
Subject: Re: bug#70568: 30.0.50; build warnings on 'x86_64-pc-linux-gnu'
Date: Wed, 1 May 2024 00:26:05 -0700

On 5/1/24 00:18, David Ponce wrote:
> Since Paul committed changes to pacify GCC 14 warnings, Emacs builds 
> cleanly.
> For me this bug can be closed.

Thanks for checking; closing the bug report.

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