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

From: Clive Stubbings
Subject: Re: [XForms] Problem with fdesign (fdesigns menu bar) (fwd)
Date: Thu, 12 May 2022 16:01:48 +0100 (BST)


-       XStoreName(flx->display, m->win, m->title);
+       XStoreName(flx->display, m->win, m->title ? m->title : "");


On Thu, 12 May 2022, Michal Szymanski wrote:

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:


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.


On Sun, 27 Jun 2021, ternaryd wrote:

On Sat, 26 Jun 2021 15:47:12 -0700
Coby Hochstein <cjh39@cox.net> wrote:


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

Program received signal SIGSEGV, Segmentation
strlen () at ../sysdeps/arm/armv6/strlen.S:26
26 ../sysdeps/arm/armv6/strlen.S: No such
file or directory.

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



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

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