ctwm craches in NetBSD 9.1 if move cursor from up to down to apps pictogram on intel driver

[Dmitrii Postolov <dpostolov%yandex.ru@localhost>]

Hi! Sorry for my bad English...

I probably found a strange bug in ctwm and NetBSD 9.1.

Hardware: Intel NUC5PPYH SoC Intel N3700 Braswell, 4GB RAM (ex-Atom).

I am using the following settings for xorg.conf:
Option "Accel" "false"
Option "AccelMethod" "uxa"
...
Driver "intel"

If not use Option "Accel" "false" then X don't start, but if use "Accel" "false" and not use "AccelMethod" "uxa" then artifacts on screen (parts of horizontal lines).

In NetBSD 9.1 and ctwm: if move mouse cursor to Applications and move it from left to right to pictogram then all OK, but if move cursor from up to down to Applications pictogram, then ctwm craches. 

Video of ctwm crash: https://yadi.sk/i/JV5F6jab_DdICA

This problem is observed only with "intel" video driver. If use "wsfb" video driver then all OK.

---

Part of NetBSD 9.1 boot log:

kern info: [drm] Memory usable by graphics device = 2048M
kern info: [drm] Supports vblank timestamp caching Rev 2 (21.10.2013)
kern info: [drm] Driver supports precise vblank timestamp query
kern info: [drm] failed to find VBIOS tables
i915drmkms0: interrupting at ioapic0 pin 16 (i915drmkms0)
intelfb0 at i915drmkms0
intelfb0: framebuffer at 0xffffd5806315d000, size 1920x1080, depth 32, stride 7680
wsdisplay0 at intelfb0 kbmux 1: console (default, vt100 emulation), using wskbd0

Errors on screen if ctwm craches:

(EE)
(EE) Backtrace:
(EE) 0: /usr/X11R7/bin/X (xorg_backtrace+0x3f) [0x5bb4953]
(EE) 1: /usr/X11R7/bin/X (os_move_fd+0x72) [0x5bb0b59]
(EE) 2: /usr/lib/libc.so.12 (_sigtramp_siginfo_2+0x0) [0x7c947ea1d50]
(EE)
(EE) Segmentation fault at adress 0x374120
(EE)
Fatal server error:
(EE) Caught signal 11 (Segmentation fault)
Server aborting
(EE)
(EE)
X connection to :0 broken (explicit kill or server shutdown)
xinit: connection to X server lost

--- 

best regards,
Dmitrii Postolov
dpostolov%yandex.ru@localhost