[SOLVED] Segfault in libQt5XcbQpa.so.5.10.0

Altoid · 12-15-2017, 04:36 AM

Hello:

For some unknown reason, my Master PDF Editor will not start.

My setup:

Code:

[groucho@groucho ~]$ uname -a
Linux groucho 4.12.10-pclos1 #1 SMP Wed Aug 30 08:17:56 CDT 2017 x86_64 x86_64 x86_64 GNU/Linux
[groucho@groucho ~]$

Master PDF Editor is v.4.3.61-1pclos2017.

It worked perfectly well up until a couple of days ago.

A terminal with dmesg shows this:

Code:

[groucho@groucho ~]$ dmesg | grep pdfeditor
[  547.073778] masterpdfeditor[4950]: segfault at 8 ip 00007f03d34496fc sp 00007ffd6343ce10 error 4 in libQt5XcbQpa.so.5.10.0[7f03d3408000+154000]
[groucho@groucho ~]$

Looking in a bit further I see that kwallet is also affected:

Code:

[groucho@groucho ~]$ dmesg | grep segfault
[   87.452780] kwalletd5[3200]: segfault at 8 ip 00007fb04f1846fc sp 00007ffd9185d590 error 4 in libQt5XcbQpa.so.5.10.0[7fb04f143000+154000]
[  547.073778] masterpdfeditor[4950]: segfault at 8 ip 00007f03d34496fc sp 00007ffd6343ce10 error 4 in libQt5XcbQpa.so.5.10.0[7f03d3408000+154000]
[groucho@groucho ~]$

I have not found a command line argument to fetch the Qt5 version installed so I searched through the installed files in SPM.

SPM lists 34 files with the qt5 string in their name installed on my system. Most of them (25) are version 5.10.0-1pclos2017.

SPM lists no broken packages or missing dependencies.

Any ideas on how to troubleshoot this further?

Thanks in advance.

A.

pan64 · 12-15-2017, 05:27 AM

so what's happened a couple of days ago? It is usually an incompatibility among libraries used by the app.

Altoid · 12-15-2017, 05:35 AM

Hello:

Quote:

Originally Posted by pan64

so what's happened a couple of days ago? It is usually an incompatibility among libraries used by the app.

PCLinuxOS is a rolling release.
There have been a number of updates in the past fortnight but I cannot say which or when as I do not use Master PDF EDitor or look at dmesg everyday.

Beyond what dmesg shows, how can I trace the problem?

I have not found a way to troubleshoot Qt5.

Thanks in advance,

A.

pan64 · 12-15-2017, 05:50 AM

this is not obviously Qt5, probably something else... You may check the stack trace, if there was a coredump to find out which other libraries may be involved.
And if there was no other idea you need to get back the old libs to run it.

Altoid · 12-15-2017, 12:47 PM

Hello:

Quote:

Originally Posted by pan64

this is not obviously Qt5, probably something else...

OK

Quote:

Originally Posted by pan64

You may check the stack trace, if there was a coredump to find out which other libraries may be involved.

No idea how to...
Would you explain to me how to do that?
ie: stack trace

Quote:

Originally Posted by pan64

And if there was no other idea you need to get back the old libs to run it.

I have no idea as to what libs may have been replaced. =-/

Thanks in advance.

A.

pan64 · 12-15-2017, 01:56 PM

you can use ldd to check what libs were used.

Altoid · 12-15-2017, 04:03 PM

Hello:

Quote:

Originally Posted by pan64

you can use ldd to check what libs were used.

While trying to find the executable to both kwallet and Master PDF Editor to use ldd, I came across some data that may hold a clue as to what is going on.

Code:

[groucho@groucho ~]$ kwalletd5
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-groucho'
Segmentation fault
[groucho@groucho ~]$

I get the very same output with Master PDF Editor:

Code:

[groucho@groucho ~]$ /opt/master-pdf-editor-4/masterpdfeditor4 %f
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-groucho'
Segmentation fault

It seems that XDG_RUNTIME_DIR is not set properly.

I have read some web pages that (?) relate this problem to user privileges, so thinking it could be some permission problem (you never know) and as PCLinuxOS does not have sudo) I tried the same as root:

Code:

[root@groucho groucho]# kwalletd5
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Segmentation fault
[root@groucho groucho]# /opt/master-pdf-editor-4/masterpdfeditor4 %f
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Segmentation fault

So ...
Back to the drawing board.

Any ideas?

Thanks in advance,

A.

pan64 · 12-16-2017, 05:17 AM

https://specifications.freedesktop.o...ec-latest.html
see specification of XDG_RUNTIME_DIR
https://unix.stackexchange.com/quest...time-root-when

Altoid · 12-16-2017, 05:54 AM

Hello:

Quote:

Originally Posted by pan64

[url]
https://unix.stackexchange.com/quest...time-root-when

Yes, I have seen this.

Quote:

Originally Posted by link

Basically, that's a per-user temporary file directory, to use by the XDG (Freedesktop.Org) compatible apps.
In Debian, this variable is normally set by the pam_systemd PAM module, on an interactive login.

PCLinuxOS is a rolling release and does not use systemd so maybe pam_systemd is not involved.
Maybe some PAM module was updated lately?

I cannot make much out of the other link, rather above my head.
Much less seeing about fixing this.

Thanks in advance.

A.

Altoid · 12-18-2017, 07:13 PM

Quote:

Originally Posted by Altoid

Hello:

For some unknown reason, my Master PDF Editor will not start.
My setup:

Code:

[groucho@groucho ~]$ uname -a
Linux groucho 4.12.10-pclos1 #1 SMP Wed Aug 30 08:17:56 CDT 2017 x86_64 x86_64 x86_64 GNU/Linux
[groucho@groucho ~]$

Master PDF Editor is v.4.3.61-1pclos2017.

It worked perfectly well up until a couple of days ago.

A terminal with dmesg shows this:

Code:

[groucho@groucho ~]$ dmesg | grep pdfeditor
[  547.073778] masterpdfeditor[4950]: segfault at 8 ip 00007f03d34496fc sp 00007ffd6343ce10 error 4 in libQt5XcbQpa.so.5.10.0[7f03d3408000+154000]
[groucho@groucho ~]$

Looking in a bit further I see that kwallet is also affected:

Code:

[groucho@groucho ~]$ dmesg | grep segfault
[   87.452780] kwalletd5[3200]: segfault at 8 ip 00007fb04f1846fc sp 00007ffd9185d590 error 4 in libQt5XcbQpa.so.5.10.0[7fb04f143000+154000]
[  547.073778] masterpdfeditor[4950]: segfault at 8 ip 00007f03d34496fc sp 00007ffd6343ce10 error 4 in libQt5XcbQpa.so.5.10.0[7f03d3408000+154000]
[groucho@groucho ~]$

I think I may have found the problem and if so, it is Qt related.

I did a search for just error 4 in libQt5XcbQpa.so.5.10.0 and have come across some recent information on the web which would indicate that my issue may be related to both Qt5.10.0 and the fact that I use the XDM Display Manager instead of Gnome.

It is a Qt bug report from early this month:
https://bugreports.qt.io/browse/QTBUG-65235

The issue would seem (at least to me) to be the same:

Quote:

Originally Posted by OP

I can't run multiple software...
tested with:
qv4l2
gqrx
octave
All the same error:

Dez 15 18:01:12 fwalder-pc kernel: qv4l2[3545]: segfault at 8 ip 00007fe4fd9cc40f sp 00007ffc6d6d36a0 error 4 in libQt5XcbQpa.so.5.10.0[7fe4fd990000+15c000]

Apparently there are two solutions to this: a workaround and a fix.

Quote:

Originally Posted by OP

Gatis Paeglis added a comment - 3 days ago
Fixed by https://codereview.qt-project.org/#/c/213803/

The only workaround for this is to enable RANDR extension on your X server. You can see which extensions currently are loaded in the output of xdpyinfo command line tool.

Just for completion's sake:

Code:

[groucho@groucho ~]$ xdpyinfo | grep RandR
[groucho@groucho ~]$

I knew RandR was not being loaded and that the workaround was not a feasible option for me:

Code:

[groucho@groucho ~]$ cat /var/log/Xorg.0.log | grep WW
	(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[    59.758] (WW) xf86OpenConsole: setpgid failed: Operation not permitted
[    59.758] (WW) xf86OpenConsole: setsid failed: Operation not permitted
[    59.790] (WW) Falling back to old probe method for v4l
[    59.809] (WW) Unresolved symbol: fbGetGCPrivateKey
[    59.831] (WW) NVIDIA: The Composite and Xinerama extensions are both enabled, which
[    59.831] (WW) NVIDIA:     is an unsupported configuration.  The driver will continue
[    59.831] (WW) NVIDIA:     to load, but may behave strangely.
[    59.831] (WW) NVIDIA: Xinerama is enabled, so RandR has likely been disabled by the
[    59.831] (WW) NVIDIA:     X server.
[    62.227] (WW) NVIDIA(0): Not registering RandR
[    62.297] (WW) NVIDIA(1): Not registering RandR
[    62.425] (WW) NVIDIA(2): Not registering RandR

So it would seem that leaves the fix as the only option:
https://codereview.qt-project.org/#/c/213803/

Quote:

Originally Posted by Commit message

Commit Message
xcb: verify if xrandr present before using xcb_randr* APIs

Not doing so might break the connection. We have had similar
issues before, e.g. QTBUG-45312.

Change-Id: I95f15d24773fc92b052578bd72d1ba264d0a5f63
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Uli Schlachter <psychon@znc.in>

My problem now is that I don't have the slightest clue as to what to do with this info. =-'

Any ideas as to how, short of waiting for an update to the Qt files, to proceed?

Thanks in advance,

G.

pan64 · 12-19-2017, 03:28 AM

you have the possibility to download the sources and rebuild Qt. or wait until it is released.

_roman_ · 12-19-2017, 08:09 AM

or try to revert your box

did you file a bug for your distro?

Altoid · 12-19-2017, 10:07 AM

Hello:

Quote:

Originally Posted by pan64

you have the possibility to download the sources and rebuild Qt. ...

I'm afraid that is way over my head.

Thanks anyhow.

A.

Altoid · 12-19-2017, 10:10 AM

Hello:

Quote:

Originally Posted by _roman_

... did you file a bug for your distro?

Yes.
The distro's maintainers (PCLinuxOS) are aware of the problem with Qt5.
Have to wait for Qt5's next version with the fixed library.

Thanks for your input.

A.

Altoid · 12-24-2017, 06:30 AM

Hello:

Quote:

Originally Posted by Altoid

The distro's maintainers (PCLinuxOS) are aware of the problem with Qt5.
Have to wait for Qt5's next version with the fixed library.

I've found that there a a few other applications besides kwallet and Mastrr PDF Editor that will not start until this gets fixed, which has become rather annoying.

Not having a timeline for the release of Qt5's next version with the fixed library, I was wondering how to go about rolling back to the previous version, the one that did not unhinge up my setup ie: Qt wise.

Is that possible to do with apt-get?

Thanks in advance.

A.