GNU bug report logs - #39948
28.0.50; crash in fchmodat

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

From: Stephen Berman <stephen.berman <at> gmx.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 15:16:43 +0100

I updated from master today and now Emacs is crashing when I use Gnus.
The first time it happened I been reading news groups for a while, then
email arrived and when I pulled it into Gnus, Emacs crashed.  Then I
restarted Emacs under GDB and now get the crash already on starting Gnus
(with my initializations; it doesn't happen when I start an unconfigured
Gnus in Emacs -Q).  I tried to get a full backtrace, but the output of
`bt full' seemed to be in an endless loop; here's the start of the
backtrace:

Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
0x000000000060c9b2 in fchmodat (dir=dir <at> entry=-100,
    file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov",
    mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
65      {
(gdb) bt full
#0  0x000000000060c9b2 in fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
#1  0x000000000060cae4 in orig_fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
#2  0x000000000060c9e0 in fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
#3  0x000000000060cae4 in orig_fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
#4  0x000000000060c9e0 in fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
#5  0x000000000060cae4 in orig_fchmodat
    (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
   ter/lib/fchmodat.c:33

This pattern repeated for tens of thousands of frames, then I
interrupted it and typed `c':

(gdb) c
Continuing.

Thread 1 "emacs" hit Breakpoint 1, terminate_due_to_signal (sig=sig <at> entry=11,
    backtrace_limit=backtrace_limit <at> entry=40)
    at /home/steve/src/emacs/emacs-master/src/emacs.c:370
370     {
(gdb)
Continuing.
Fatal error 11: Segmentation fault
Backtrace:
/home/steve/build/emacs-master/src/emacs[0x524450]
/home/steve/build/emacs-master/src/emacs[0x5068e0]
/home/steve/build/emacs-master/src/emacs[0x522745]
/home/steve/build/emacs-master/src/emacs[0x522772]
/home/steve/build/emacs-master/src/emacs[0x5227cf]
/home/steve/build/emacs-master/src/emacs[0x522895]
/lib/libpthread.so.0(+0x12680)[0x7ffff61a5680]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x2f)[0x60c9db]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
/home/steve/build/emacs-master/src/emacs(fchmodat+0x34)[0x60c9e0]
/home/steve/build/emacs-master/src/emacs[0x60cae4]
...

Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
raise (sig=sig <at> entry=11) at ../sysdeps/unix/sysv/linux/raise.c:50
50      ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.



In GNU Emacs 28.0.50 (build 5, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, cairo version 1.16.0)
 of 2020-03-06 built on strobe-lfs84
Repository revision: c996fe1ec69de0082043397d4965d08cb94892fb
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: Linux From Scratch

Recent messages:
Loading /home/steve/.emacs.d/srb/srb-mail.el (source)...done
Loading /home/steve/.emacs.d/srb/srb-elisp.el (source)...done
Loading todo-mode...done
Loading /home/steve/.emacs.d/srb/srb-cal+diary+appt.el (source)...done
Loading /home/steve/.emacs.d/srb/srb-global-key-bindings.el (source)...done
Preparing diary...
No diary entries for Friday, March 6, 2020
Preparing diary...done
Appointment reminders enabled
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure 'CFLAGS=-Og -g3' PKG_CONFIG_PATH=/opt/qt5/lib/pkgconfig'

Configured features:
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INOTIFY ACL GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF ZLIB
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Major mode: Lisp Interaction

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Load-path shadows:
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backquote threads dbusbind inotify lcms2 dynamic-setting
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Memory information:
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 (symbols 48 24562 4)
 (strings 32 152593 3058)
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Message #8 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: 39948 <at> debbugs.gnu.org
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 16:31:50 +0100

>>>>> On Fri, 06 Mar 2020 15:16:43 +0100, Stephen Berman <stephen.berman <at> gmx.net> said:

    Stephen> I updated from master today and now Emacs is crashing when I use Gnus.
    Stephen> The first time it happened I been reading news groups for a while, then
    Stephen> email arrived and when I pulled it into Gnus, Emacs crashed.  Then I
    Stephen> restarted Emacs under GDB and now get the crash already on starting Gnus
    Stephen> (with my initializations; it doesn't happen when I start an unconfigured
    Stephen> Gnus in Emacs -Q).  I tried to get a full backtrace, but the output of
    Stephen> `bt full' seemed to be in an endless loop; here's the start of the
    Stephen> backtrace:

Wild Guess: does reverting 07da629926daf849aab248175c88cf53a5e21558
help? Or maybe 9d626dffc6ba62c0d7a1a5c712f576ed8684fd66 ?

Robert

Message #11 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: 39948 <at> debbugs.gnu.org
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 17:45:13 +0200

> From: Stephen Berman <stephen.berman <at> gmx.net>
> Date: Fri, 06 Mar 2020 15:16:43 +0100
> 
> I updated from master today and now Emacs is crashing when I use Gnus.
> The first time it happened I been reading news groups for a while, then
> email arrived and when I pulled it into Gnus, Emacs crashed.  Then I
> restarted Emacs under GDB and now get the crash already on starting Gnus
> (with my initializations; it doesn't happen when I start an unconfigured
> Gnus in Emacs -Q).  I tried to get a full backtrace, but the output of
> `bt full' seemed to be in an endless loop; here's the start of the
> backtrace:
> 
> Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
> 0x000000000060c9b2 in fchmodat (dir=dir <at> entry=-100,
>     file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov",
>     mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
> 65      {
> (gdb) bt full
> #0  0x000000000060c9b2 in fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
> #1  0x000000000060cae4 in orig_fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
> #2  0x000000000060c9e0 in fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
> #3  0x000000000060cae4 in orig_fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
> #4  0x000000000060c9e0 in fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>     at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
> #5  0x000000000060cae4 in orig_fchmodat
>     (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
>    ter/lib/fchmodat.c:33
> 
> This pattern repeated for tens of thousands of frames, then I
> interrupted it and typed `c':

Sounds like infinite recursion, which causes stack overflow.

Message #14 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Robert Pluim <rpluim <at> gmail.com>
Cc: 39948 <at> debbugs.gnu.org
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 17:26:54 +0100

On Fri, 06 Mar 2020 16:31:50 +0100 Robert Pluim <rpluim <at> gmail.com> wrote:

>>>>>> On Fri, 06 Mar 2020 15:16:43 +0100, Stephen Berman
> <stephen.berman <at> gmx.net> said:
>
>     Stephen> I updated from master today and now Emacs is crashing
>     Stephen> when I use Gnus.  The first time it happened I been
>     Stephen> reading news groups for a while, then email arrived and
>     Stephen> when I pulled it into Gnus, Emacs crashed.  Then I
>     Stephen> restarted Emacs under GDB and now get the crash already
>     Stephen> on starting Gnus (with my initializations; it doesn't
>     Stephen> happen when I start an unconfigured Gnus in Emacs -Q).  I
>     Stephen> tried to get a full backtrace, but the output of `bt
>     Stephen> full' seemed to be in an endless loop; here's the start
>     Stephen> of the backtrace:
>
> Wild Guess: does reverting 07da629926daf849aab248175c88cf53a5e21558
> help? Or maybe 9d626dffc6ba62c0d7a1a5c712f576ed8684fd66 ?

Reverting 07da629 does appear to prevent the crash.  Specifically, as a
sanity check, before reverting, I ran my build from master under GDB
again, started Gnus, but now Emacs didn't crash; however, then I
composed a mail to myself in Gnus and upon sending it, Emacs did crash
exactly as before in fchmodat.  This I did `git revert -n
07da629926daf849aab248175c88cf53a5e21558', rebuilt, started Emacs again,
started Gnus, there was no crash, sent a mail to myself, again with no
crash, and pulled the mail into Gnus also without the crash.  So it
appears that that commit is indeed the cause of the crash.  Thanks for
pinpointing it.

Steve Berman

Message #17 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 39948 <at> debbugs.gnu.org, Stephen Berman <stephen.berman <at> gmx.net>,
 Paul Eggert <eggert <at> cs.ucla.edu>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 17:45:49 +0100

>>>>> On Fri, 06 Mar 2020 17:45:13 +0200, Eli Zaretskii <eliz <at> gnu.org> said:

    >> From: Stephen Berman <stephen.berman <at> gmx.net>
    >> Date: Fri, 06 Mar 2020 15:16:43 +0100
    >> 
    >> I updated from master today and now Emacs is crashing when I use Gnus.
    >> The first time it happened I been reading news groups for a while, then
    >> email arrived and when I pulled it into Gnus, Emacs crashed.  Then I
    >> restarted Emacs under GDB and now get the crash already on starting Gnus
    >> (with my initializations; it doesn't happen when I start an unconfigured
    >> Gnus in Emacs -Q).  I tried to get a full backtrace, but the output of
    >> `bt full' seemed to be in an endless loop; here's the start of the
    >> backtrace:
    >> 
    >> Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
    >> 0x000000000060c9b2 in fchmodat (dir=dir <at> entry=-100,
    >> file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov",
    >> mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
    >> 65      {
    >> (gdb) bt full
    >> #0  0x000000000060c9b2 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:65
    >> #1  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
    >> #2  0x000000000060c9e0 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
    >> #3  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:33
    >> #4  0x000000000060c9e0 in fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> at /home/steve/src/emacs/emacs-master/lib/fchmodat.c:134
    >> #5  0x000000000060cae4 in orig_fchmodat
    >> (dir=dir <at> entry=-100, file=file <at> entry=0x4be6b40 "/home/steve/Mail/unsorted.nov", mode=mode <at> entry=384, flags=flags <at> entry=0)
    >> ter/lib/fchmodat.c:33
    >> 
    >> This pattern repeated for tens of thousands of frames, then I
    >> interrupted it and typed `c':

    Eli> Sounds like infinite recursion, which causes stack overflow.

lib/fchmodat.c:fchmodat can call lib/fchmodat.c:orig_fchmodat, which
can call fchmodat. Presumably that last one is meant to be the system
fchmodat, but itʼs calling the fchmodat.c:fchmodat one instead. CC'ing
Paul.

Robert

Message #20 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Robert Pluim <rpluim <at> gmail.com>
Cc: 39948 <at> debbugs.gnu.org
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 06 Mar 2020 22:17:51 +0100

On Fri, 06 Mar 2020 17:26:54 +0100 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> On Fri, 06 Mar 2020 16:31:50 +0100 Robert Pluim <rpluim <at> gmail.com> wrote:
>
>>>>>>> On Fri, 06 Mar 2020 15:16:43 +0100, Stephen Berman
>> <stephen.berman <at> gmx.net> said:
>>
>>     Stephen> I updated from master today and now Emacs is crashing
>>     Stephen> when I use Gnus.  The first time it happened I been
>>     Stephen> reading news groups for a while, then email arrived and
>>     Stephen> when I pulled it into Gnus, Emacs crashed.  Then I
>>     Stephen> restarted Emacs under GDB and now get the crash already
>>     Stephen> on starting Gnus (with my initializations; it doesn't
>>     Stephen> happen when I start an unconfigured Gnus in Emacs -Q).  I
>>     Stephen> tried to get a full backtrace, but the output of `bt
>>     Stephen> full' seemed to be in an endless loop; here's the start
>>     Stephen> of the backtrace:
>>
>> Wild Guess: does reverting 07da629926daf849aab248175c88cf53a5e21558
>> help? Or maybe 9d626dffc6ba62c0d7a1a5c712f576ed8684fd66 ?
>
> Reverting 07da629 does appear to prevent the crash.  Specifically, as a
> sanity check, before reverting, I ran my build from master under GDB
> again, started Gnus, but now Emacs didn't crash; however, then I
> composed a mail to myself in Gnus and upon sending it, Emacs did crash
> exactly as before in fchmodat.  This I did `git revert -n
> 07da629926daf849aab248175c88cf53a5e21558', rebuilt, started Emacs again,
> started Gnus, there was no crash, sent a mail to myself, again with no
> crash, and pulled the mail into Gnus also without the crash.  So it
> appears that that commit is indeed the cause of the crash.  Thanks for
> pinpointing it.

I also got the crash using Tramp, so I guess 9d626dff also needs to be
fixed (or reverted).

Steve Berman

Message #23 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: 39948 <at> debbugs.gnu.org, Robert Pluim <rpluim <at> gmail.com>,
 Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Fri, 6 Mar 2020 15:54:07 -0800

On 3/6/20 8:45 AM, Robert Pluim wrote:

> lib/fchmodat.c:fchmodat can call lib/fchmodat.c:orig_fchmodat, which
> can call fchmodat. Presumably that last one is meant to be the system
> fchmodat, but itʼs calling the fchmodat.c:fchmodat one instead.

Yes, orig_fchmodat is supposed to call the system fchmodat.

Do you get the same problem with 'make bootstrap'? If not, we're done.

Otherwise, to help debug this please send the preprocessor output when 
compiling lib/fchmodat.c. Something like this:

rm lib/fchmodat.o
make V=1
Now, repeat the GCC command that compiles lib/fchmod.c, except use 'gcc 
-E' instead of 'gcc -c'.

Also, what are the values of HAVE_FCHMODAT (see src/config.h), and of 
GNULIB_FCHMODAT and REPLACE_FCHMODAT (look at the output of the command 
'diff -u lib/sys_stat.in.h lib/sys/stat.h')? Also, please double-check 
lib/gnulib.mk for those three values.

From your symptoms I would guess for you HAVE_FCHMODAT and 
GNULIB_FCHMODAT are 1 but REPLACE_FCHMODAT is 0. But if that's the case, 
your build shouldn't be compiling lib/fchmodat.c at all, because 
'configure' says this:

  if test $HAVE_FCHMODAT = 0 || test $REPLACE_FCHMODAT = 1; then
    gl_LIBOBJS="$gl_LIBOBJS fchmodat.$ac_objext"
  fi

and so we need to investigate why this 'if' is being triggered,

Message #26 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 39948 <at> debbugs.gnu.org, Robert Pluim <rpluim <at> gmail.com>,
 Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Sat, 07 Mar 2020 01:30:58 +0100

On Fri, 6 Mar 2020 15:54:07 -0800 Paul Eggert <eggert <at> cs.ucla.edu> wrote:

> On 3/6/20 8:45 AM, Robert Pluim wrote:
>
>> lib/fchmodat.c:fchmodat can call lib/fchmodat.c:orig_fchmodat, which
>> can call fchmodat. Presumably that last one is meant to be the system
>> fchmodat, but itʼs calling the fchmodat.c:fchmodat one instead.
>
> Yes, orig_fchmodat is supposed to call the system fchmodat.
>
> Do you get the same problem with 'make bootstrap'? If not, we're done.

I was just about to shut down for the night when your mail arrived, so I
did `make bootstrap' but got the same crash both when sending a mail
with Gnus and when transfering a file with Tramp.  I'll follow up on
your other suggestions on Saturday and report back.

Steve Berman

Message #29 received at 39948 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 39948 <at> debbugs.gnu.org, Robert Pluim <rpluim <at> gmail.com>,
 Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Sat, 07 Mar 2020 14:43:29 +0100

On Sat, 07 Mar 2020 01:30:58 +0100 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> On Fri, 6 Mar 2020 15:54:07 -0800 Paul Eggert <eggert <at> cs.ucla.edu> wrote:
>
>> On 3/6/20 8:45 AM, Robert Pluim wrote:
>>
>>> lib/fchmodat.c:fchmodat can call lib/fchmodat.c:orig_fchmodat, which
>>> can call fchmodat. Presumably that last one is meant to be the system
>>> fchmodat, but itʼs calling the fchmodat.c:fchmodat one instead.
>>
>> Yes, orig_fchmodat is supposed to call the system fchmodat.
>>
>> Do you get the same problem with 'make bootstrap'? If not, we're done.
>
> I was just about to shut down for the night when your mail arrived, so I
> did `make bootstrap' but got the same crash both when sending a mail
> with Gnus and when transfering a file with Tramp.  I'll follow up on
> your other suggestions on Saturday and report back.

>> Otherwise, to help debug this please send the preprocessor output when
>> compiling lib/fchmodat.c. Something like this:
>>
>> rm lib/fchmodat.o
>> make V=1
>> Now, repeat the GCC command that compiles lib/fchmod.c, except use 'gcc -E'
>> instead of 'gcc -c'.
>>
>> Also, what are the values of HAVE_FCHMODAT (see src/config.h), and of
>> GNULIB_FCHMODAT and REPLACE_FCHMODAT (look at the output of the command 
>> 'diff -u lib/sys_stat.in.h lib/sys/stat.h')? Also, please double-check
>> lib/gnulib.mk for those three values.
>>
>> From your symptoms I would guess for you HAVE_FCHMODAT and GNULIB_FCHMODAT are
>> 1 but REPLACE_FCHMODAT is 0. But if that's the case, your build shouldn't be
>> compiling lib/fchmodat.c at all, because 'configure' says this:
>>
>>   if test $HAVE_FCHMODAT = 0 || test $REPLACE_FCHMODAT = 1; then
>>     gl_LIBOBJS="$gl_LIBOBJS fchmodat.$ac_objext"
>>   fi
>>
>> and so we need to investigate why this 'if' is being triggered,

It appears that my OP was a false alarm.  I build emacs out-of-tree but
several months ago I ran `make TAGS' in the source directory and that
seems to have also compiled the files in the source lib/, since it
contained object files dated from that time.  Is it possible that these
were used when building in the build directory?  Anyway, I ran `make
distclean' in the Emacs source directory and also in the lib/ build
directory, then reconfigured and rebuilt Emacs, and now I no longer get
the crash.

Unfortunately, I rashly did this before trying out your other
suggestions, so I no longer have the previous state to check.  But I can
at least confirm that HAVE_FCHMODAT, GNULIB_FCHMODAT and
REPLACE_FCHMODAT are (now) all set to 1.

I'll keep running with this build and if the crash does not happen
anymore, I'll close the bug later today or tomorrow, unless someone
wants further testing or clarification.

Thanks for the helpful feedback.

Steve Berman

Message #34 received at 39948-done <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Robert Pluim <rpluim <at> gmail.com>, 39948-done <at> debbugs.gnu.org,
 Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#39948: 28.0.50; crash in fchmodat
Date: Sun, 08 Mar 2020 21:28:10 +0100

On Sat, 07 Mar 2020 14:43:29 +0100 Stephen Berman <stephen.berman <at> gmx.net> wrote:

> I'll keep running with this build and if the crash does not happen
> anymore, I'll close the bug later today or tomorrow, unless someone
> wants further testing or clarification.

Closed.

Steve Berman

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