This is SBCL 0.9.16, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
Caught 'memory fault' at the top level. Please report this.
0: (SB-DEBUG:BACKTRACE 100 #<SB-IMPL::STRING-OUTPUT-STREAM {10040C8641}>)
1: (STUMPWM::BACKTRACE-STRING)
2: ((LAMBDA (STUMPWM::C)) #<SB-KERNEL::MEMORY-FAULT-ERROR {10040C7E81}>)
3: (SIGNAL #<SB-KERNEL::MEMORY-FAULT-ERROR {10040C7E81}>)
4: (ERROR SB-KERNEL::MEMORY-FAULT-ERROR)
5: (SB-KERNEL::MEMORY-FAULT-ERROR)
6: ("foreign function: call_into_lisp")
7: ("foreign function: post_signal_tramp")
8: (XLIB:GET-WM-CLASS #<XLIB:WINDOW :0 E00282>)
9: (STUMPWM::XWIN-CLASS #<XLIB:WINDOW :0 E00282>)
10: (STUMPWM::XWIN-TO-WINDOW #<XLIB:WINDOW :0 E00282>)
11: (STUMPWM::PLACE-WINDOW
     #S<screen #<XLIB:SCREEN :0.0 1024x1280x24 TRUE-COLOR>>
     #<XLIB:WINDOW :0 E00282>)
12: (STUMPWM::ADD-WINDOW
     #S<screen #<XLIB:SCREEN :0.0 1024x1280x24 TRUE-COLOR>>
     #<XLIB:WINDOW :0 E00282>)
13: (STUMPWM::PROCESS-MAPPED-WINDOW
     #S<screen #<XLIB:SCREEN :0.0 1024x1280x24 TRUE-COLOR>>
     #<XLIB:WINDOW :0 E00282>)
14: ((LABELS #:G159)
     :PARENT
     #<XLIB:WINDOW :0 135>
     :SEND-EVENT-P
     NIL
     :WINDOW
     #<XLIB:WINDOW :0 E00282>)
15: (STUMPWM::HANDLE-EVENT
     :DISPLAY
     #<XLIB:DISPLAY :0 (The X.Org Foundation R70101000)>
     :EVENT-KEY
     :MAP-REQUEST
     :EVENT-CODE
     20
     :SEND-EVENT-P
     NIL
     :SEQUENCE
     977
     :PARENT
     #<XLIB:WINDOW :0 135>
     :EVENT-WINDOW
     #<XLIB:WINDOW :0 135>
     :WINDOW
     #<XLIB:WINDOW :0 E00282>)
16: (XLIB:PROCESS-EVENT
     #<XLIB:DISPLAY :0 (The X.Org Foundation R70101000)>
     :HANDLER
     #<FUNCTION STUMPWM::HANDLE-EVENT>
     :TIMEOUT
     NIL
     :PEEK-P
     NIL
     :DISCARD-P
     NIL
     :FORCE-OUTPUT-P
     T)
17: (STUMPWM::STUMPWM-INTERNAL-LOOP)
18: (STUMPWM::STUMPWM-INTERNAL-LOOP)
19: (STUMPWM::STUMPWM-INTERNAL ":0")
20: (STUMPWM ":0")
21: ((LAMBDA ()))
22: ((LABELS SB-IMPL::RESTART-LISP))