Bug in libX11 or something near ?

Philippe philippe.raven@gmail.com
Sun Jun 23 18:41:00 GMT 2019

Hi Jon,
glad to view an answer !
Just for your information, since I posted, I did some others tests, and I
can reproduce it with k3b (which use qt4) but NOT with kcalc (which use
Then I tried some little python tests from Envisage for qt5 and wasn't able
to reproduce this crash.

So I guess there's something wrong with qt4.

Tomorrow I'll try your snapshot to confirm or not your fix !

Thanks for your time.

On Sun, Jun 23, 2019 at 7:57 PM Jon Turney <jon.turney@dronecode.org.uk>

> On 18/06/2019 17:07, Philippe wrote:
> > I'm using Cygwin/X and identified a critical bug using some piece of
> > software.
> > I don't really know where to begin, but I'm able to crash some
> applications
> > via the application's menu, only with Cygwin/X (no crash with Xming, and
> no
> > crash under any Linux distributions).
> >
> > For information, It goes through VirtualGL. I'll give the example on how
> to
> > reproduce it with a free software : Paraview (under linux).
> >
> > So you open Paraview, then clic on "View" > show the "Toolbars" submenu,
> > then you move your mouse directly on the "Sources" or "Edit" menu, then
> it
> > crashes immediately. The only error message in the linux shell (from
> where
> > it was launched) is "paraview: Fatal IO error: client killed".
> >
> > I got those lines in the XWin.0.log file :
> > SetupSysMenu: GetSystemMenu() failed for HWND 0x130746
> > winTopLevelWindowProc - WM_DESTROY - WM_WM_KILL
> Thanks for reporting this problem, and the clear reproduction steps.
> This is an interesting bug in the Cygwin X server's multiwindow mode. It
> seems that under some circumstances, when removing a WM_TRANSIENT_FOR
> window which in turn had a child WM_TRANSIENT_FOR window (e.g. a menu
> which has a sub-menu), the X server's integrated WM would get confused
> and think that the main window had been closed (so terminating the
> application).
> I've has a go at fixing this and uploaded a snapshot at [1].  Perhaps
> you could try that and see if it improves things for you?
> (I guessed you are using 64-bit Cygwin. If you need a 32-bit build
> instead, please let me know and I'll generate one)
> [1]
> ftp://cygwin.com/pub/cygwinx/x86_64/XWin.20190623-git-210c90b328cf8f18.exe.bz2
> --
> Jon Turney
> Volunteer Cygwin/X X Server maintainer

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