Re: [XForms] Problem with fdesign (fdesigns menu bar) (fwd)

[Michal Szymanski]

I have built the current git version
(https://git.savannah.gnu.org/git/xforms.git) on Ubuntu 20.04 and
Rocky Linux 8.5 and got the same problem: fdesign segfaults when
'File' is clicked on. 

Following Clive's hint I have found just 4 places XStoreName is used:

lib/canvas.c:            XStoreName( flx->display, sp->window, ob->label );
lib/canvas.c:            XStoreName( flx->display, sp->window, name );
lib/popup.c:        XStoreName( flx->display, popup->win, popup->title );
lib/xpopup.c:        XStoreName( flx->display, m->win, m->title );

but I do not have any idea how to fix the problem. I have even
localized the segfault to be originating in 'xpopup.c', with m->title
being 0x0, so I made it point to an empty static string (""). The
program did not segfault on "File" but aborted on "SaveAs" from File
popup, saying 
munmap_chunk(): invalid pointer
Abort (core dumped)

so I surrendered.

Any more hints? Without working fdesign the whole library is pretty unusable :(

regards, Michal

On Wed, Jun 30, 2021 at 02:27:35AM +0100, Clive Stubbings wrote:
> 
> Hi,
> 
> There has been a regression in the xorg libX11
> 
> It is likely this is your issue - it was spotted in one of my xforms programs 
> a few weeks ago by one of my users.
> 
> XStoreName used to tolerate a NULL pointer (it checked before using it). New 
> code has been added ahead of that check.
> 
> If your system has recently updated its libraries, thats likely the cause.
> 
> I believe it has now been fixed upstream thanks to the person who spotted the 
> problem feeding the cause back to the developers and a new version should 
> come through in due course.
> 
> If you need a quicker fix, hack the library to make sure it doesn't pass a 
> NULL pointer to XStoreName.
> 
> Cheers
> Clive
> 
> 
> 
> On Sun, 27 Jun 2021, ternaryd wrote:
> 
> >On Sat, 26 Jun 2021 15:47:12 -0700
> >Coby Hochstein <cjh39@cox.net> wrote:
> >
> >>Hello,
> >>
> >>when I load fdesign and click on the "File"
> >>menu bar fdesign segmentation faults.
> >>I'm running xforms-1.2.4
> >>
> >>(gdb) run
> >>Starting program: /usr/local/bin/fdesign
> >>[Thread debugging using libthread_db enabled]
> >>Using host libthread_db library
> >>"/lib/arm-linux-gnueabihf/libthread_db.so.1".
> >>
> >>Program received signal SIGSEGV, Segmentation
> >>fault.
> >>strlen () at ../sysdeps/arm/armv6/strlen.S:26
> >>26 ../sysdeps/arm/armv6/strlen.S: No such
> >>file or directory.
> >>(gdb)
> >
> >
> >>Any idea ?
> >
> >fdesign is calculating the string length of a
> >string pointing to NULL.
> >
> >Use a version of fdesign compiled with debugging
> >enabled, run it again until crash, and check the
> >coredump in gdb. Use the "up" command until you
> >reach a stack level belonging to fdesign (or
> >xforms). You should see which pointer is NULL.
> >Then you can try to figure out, why it is NULL
> >and how to fix it.
> >
> >   $ ulimit -c unlimited
> >   $ ./fdesign ...
> >   $ gdb ./fdesign coredump
> >   (gdb> up
> >   ...
> >
> >you can query the value of any variable at the
> >time of the crash with
> >
> >   (gdb) p varname
> >
> >HTH
> >
> >-- 
> >Cris
> >

-- 
  Michal Szymanski (msz at astrouw dot edu dot pl)
  Warsaw University Observatory, Warszawa, POLAND