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Bug 623922

Summary: dev-qt/qtgui Segfault in X11 forwarding over ssh since upgrading to 5.7
Product: Gentoo Linux Reporter: David Flogeras <dflogeras2>
Component: Current packagesAssignee: Qt Bug Alias <qt>
Status: RESOLVED FIXED    
Severity: normal CC: tsmksubc
Priority: Normal    
Version: unspecified   
Hardware: All   
OS: Linux   
Whiteboard:
Package list:
Runtime testing required: ---

Description David Flogeras 2017-07-05 19:23:12 UTC
Since upgrading to qt-5.7, there is now a segfault when starting a remote application over SSH.

#0  0x00007ffff56e00e8 in raise () from /lib64/libc.so.6
#1  0x00007ffff56e153a in abort () from /lib64/libc.so.6
#2  0x00007ffff65ea969 in QMessageLogger::fatal(char const*, ...) const ()
   from /usr/lib64/libQt5Core.so.5
#3  0x00007fffef60da96 in QXcbConnection::QXcbConnection(QXcbNativeInterface*, bool, unsigned int, char const*) () from /usr/lib64/libQt5XcbQpa.so.5
#4  0x00007fffef612fb5 in QXcbIntegration::QXcbIntegration(QStringList const&, int&, char**) () from /usr/lib64/libQt5XcbQpa.so.5
#5  0x00007ffff7ff447d in ?? ()
   from /usr/lib64/qt5/plugins/platforms/libqxcb.so
#6  0x00007ffff6ab04fb in QPlatformIntegrationFactory::create(QString const&, QStringList const&, int&, char**, QString const&) ()
   from /usr/lib64/libQt5Gui.so.5
#7  0x00007ffff6abddaa in QGuiApplicationPrivate::createPlatformIntegration()
    () from /usr/lib64/libQt5Gui.so.5
#8  0x00007ffff6abeb6d in QGuiApplicationPrivate::createEventDispatcher() ()
   from /usr/lib64/libQt5Gui.so.5
#9  0x00007ffff679caec in QCoreApplicationPrivate::init() ()
   from /usr/lib64/libQt5Core.so.5
#10 0x00007ffff6abfe0f in QGuiApplicationPrivate::init() ()
   from /usr/lib64/libQt5Gui.so.5
#11 0x00007ffff78d9d79 in QApplicationPrivate::init() ()
   from /usr/lib64/libQt5Widgets.so.5

Strikingly similar to

https://github.com/qbittorrent/qBittorrent/issues/6515



Reproducible: Always
Comment 1 Michael Palimaka (kensington) gentoo-dev 2017-07-06 14:37:59 UTC
I *think* I heard reports of something similar and it was fixed in 5.9. If we can track down the fix, we could try to backport it.
Comment 2 Davide Pesavento (RETIRED) gentoo-dev 2017-12-02 05:38:15 UTC
@David, can you try 5.9.3 please?
Comment 3 David Flogeras 2017-12-02 06:16:30 UTC
Absolutely, although it might be a couple days before I can get to it.

To be clear, should I upgrade both the local and remote systems?  Just remote/just local?  I'm not sure which end of things this bug lies.

Also, I forget if downgrading Qt again is supported or blocked (like glibc is).  If this is a one-way thing it will determine which machine(s) I use to test with.
Comment 4 Davide Pesavento (RETIRED) gentoo-dev 2017-12-02 06:26:24 UTC
(In reply to David Flogeras from comment #3)
> Absolutely, although it might be a couple days before I can get to it.
Thanks.

> To be clear, should I upgrade both the local and remote systems?  Just
> remote/just local?  I'm not sure which end of things this bug lies.
Just the remote one (where the app is running). On the local system you don't have to have the qt libraries installed at all.

> Also, I forget if downgrading Qt again is supported or blocked (like glibc
> is).  If this is a one-way thing it will determine which machine(s) I use to
> test with.
I can't say it's supported, but it's not explicitly blocked either. In the worst case, you can always emerge -C qt-5.9 && emerge qt-5.7
Comment 5 David Flogeras 2017-12-04 19:35:10 UTC
@Davide

Seems to work for me.  After upgrading a machine, I tried remotely logging in with "ssh [host] -YC" then I ran both a raw Qt application of my own, as well as okular/gwenview from plasma5.  They all came through the tunnel as expected.

Thanks for the ping.
Comment 6 Davide Pesavento (RETIRED) gentoo-dev 2017-12-05 02:03:38 UTC
Closing then. Thanks for testing.