Forwarding this bug from a Ubuntu reporter:
https://bugs.edge.launchpad.net/ubuntu/+source/xorg-server/+bug/281077

[Problem]
Xdmx crashed with SIGSEGV in dmxCreateGC() when running an Xdmx server under Xephyr, while running xdmx version 1.5.1-1ubuntu2


[Original Report]
Xdmx crashed with SIGSEGV in dmxCreateGC()
running version 1.5.1-1ubuntu2

How to reproduce:
* start an Xephyr server
* start an Xdmx server. which connects to the Xephyr server

What happend: Xdmx throws a segfault
What I expected: Xdmx should not throw a segfault

There is already a patch in the master branch of xorg-xserver:
http://cgit.freedesktop.org/xorg/xserver/commit/?id=6f1d5147cb394b7c83c4c1447c78890fa2b40a45

But with this one I get an strange behavior when I just want to move the mouse in Xephyr:
...
[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.
...

If I connect an xterm to the Xdmx server I get a segfault in miPaintWindow.

ProblemType: Crash
Architecture: amd64
CrashCounter: 1
DistroRelease: Ubuntu 8.10
ExecutablePath: /usr/bin/Xdmx
Package: xdmx 2:1.5.1-1ubuntu2
ProcAttrCurrent: unconfined
ProcCmdline: Xdmx :3 -auth xdmx-xauth-3 -display :1
ProcEnviron:
 SHELL=/bin/bash
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=de_DE.UTF-8
Signal: 11
SourcePackage: xorg-server
Stacktrace:
 #0 0x000000000043e51a in dmxCreateGC ()
 #1 0x0000000000516fdd in CreateScratchGC ()
 #2 0x000000000051713e in CreateGCperDepth ()
 #3 0x000000000051c245 in main ()
StacktraceTop:
 dmxCreateGC ()
 CreateScratchGC ()
 CreateGCperDepth ()
 main ()
Title: Xdmx crashed with SIGSEGV in dmxCreateGC()
Uname: Linux 2.6.27-6-generic x86_64
UserGroups: adm admin audio cdrom dialout dip floppy fuse lpadmin plugdev pulse pulse-access pulse-rt sambashare video

[Script to reproduce issue]
mcookie > xephyr-cookie
export COOKIE=`cat xephyr-cookie`
rm -f xephyr-xauth-1; echo "add :1 . $COOKIE" | xauth -f xephyr-xauth-1
echo "add :1 . " $COOKIE | xauth
Xephyr :1 -auth xephyr-xauth-1 -reset 2> /dev/null &

sleep 1

# mcookie > xephyr-cookie
# export COOKIE=`cat xephyr-cookie`
# rm -f xephyr-xauth-2; echo "add :2 . $COOKIE" | xauth -f xephyr-xauth-2
# echo "add :2 . " $COOKIE | xauth
# Xephyr :2 -auth xephyr-xauth-2 -reset &

mcookie > xdmx-cookie
export COOKIE=`cat xdmx-cookie`
rm -f xdmx-xauth-3; echo "add :3 . $COOKIE" | xauth -f xdmx-xauth-3
echo "add :3 . " $COOKIE | xauth
# gdb --args ./Project/X/xorg-server-1.5.1/obj-x86_64-linux-gnu/hw/dmx/Xdmx  :3 -auth xdmx-xauth-3 -display :1
Xdmx  :3 -auth xdmx-xauth-3 -display :1 &

sleep 2

DISPLAY=:3 xterm