Created attachment 141090 [details]
xinitrc script to run the session

Here is the xinitrc script that I am using to run the session in which to run the trigger program. So basically I run

startx $PWD/xinitrc

which starts Xorg, the dbus bus, the at-spi2 daemons, and runs xterm, and in the xterm, I run the generate_keyboard_event.py script.

Interestingly, in my original .xinitrc, I had a setxkbmap call early in the script, to work around https://bugs.freedesktop.org/show_bug.cgi?id=26402 . It happens that this makes the crash not to happen. So possibly this bug is related to 26402.

Created attachment 141091 [details]
Xorg log

And here is the Xorg log, and here are the actual lines:

0x1b38dd is in xorg_backtrace (../../../../os/backtrace.c:127).
127	    for (i = 0; i < size; i++) {
0x1b7599 is in OsSigHandler (../../../../os/osinit.c:138).
135	    xorg_backtrace();
138	    if (sip->si_code == SI_USER) {
0x153ddd is in _XkbSetMapChecks (../../../../xkb/xkb.c:2387).
2387	    xkb = xkbi->desc;
0x15b37f is in ProcXkbSetMap (../../../../xkb/xkb.c:2656).
2655	            rc = _XkbSetMapChecks(client, other, stuff, tmp);
2656	            if (rc != Success)
0x5b008 is in Dispatch (../../../../dix/dispatch.c:478).
476	                    result = XaceHookDispatch(client, client->majorOp);
477	                    if (result == Success)

so it seems like an issue within xkb.

And to explain what at-spi's registryd is doing, it is basically changing one keycode of the keymap temporarily to be able to simulate through XTest any keysym, even if not currently available in the current keyboard map. One can read that in 

https://gitlab.gnome.org/GNOME/at-spi2-core/blob/master/registryd
/deviceeventcontroller-x11.c#L693

which looks for a keycode which will not pose problem

https://gitlab.gnome.org/GNOME/at-spi2-core/blob/master/registryd/deviceeventcontroller-x11.c#L211

which checks whether the keysym is available somewhere in the keyboard map.

https://gitlab.gnome.org/GNOME/at-spi2-core/blob/master/registryd/deviceeventcontroller-x11.c#L164

which does the actual temporary change.

Created attachment 141093 [details]
simpler reproducer

Here is a simpler reproducer, just copy/pasted from at-spi's registryd. Now I can just run

startx /usr/bin/xterm

and run ./remap in the xterm, and get the same crash.

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