The XEmacs session for a colleague at work crashed a few minutes ago.  He
invoked it as

    xemacs -u skipm fname &

When it crashed XEmacs reported this:

    Fatal error (11).

    Your files have been auto-saved.
    Use `M-x recover-session' to recover them.

    Your version of XEmacs was distributed with a PROBLEMS file that may describe
    your crash, and with luck a workaround.  Please check it first, but do report
    the crash anyway.

    Please report this bug by invoking M-x report-emacs-bug, or by selecting
    `Send Bug Report' from the Help menu.  If that won't work, send ordinary
    email to `xemacs-beta at xemacs.org'.  *MAKE SURE* to include this entire
    output from this crash, especially including the Lisp backtrace, as well as
    the XEmacs configuration from M-x describe-installation (or equivalently,
    the file `Installation' in the top of the build tree).

    *Please* try *hard* to obtain a C stack backtrace; without it, we are unlikely
    to be able to analyze the problem.  Locate the core file produced as a result
    of this crash (often called `core' or `core.<process-id>', and located in
    the directory in which you started XEmacs or your home directory), and type

     gdb /opt/app/bin/xemacs core

    then type `where' at the debugger prompt.  No GDB on your system?  You may
    have DBX, or XDB, or SDB.  (Ask your system administrator if you need help.)
    If no core file was produced, enable them (often with `ulimit -c unlimited')
    in case of future recurrance of the crash.

    Lisp backtrace follows:

     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # bind (inhibit-quit)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # (unwind-protect ...)
     # bind (inhibit-quit)
     # (condition-case ... . error)
     # (catch top-level ...)

I pulled this backtrace from the core file:

    #0  0xd0900a95 in kill () from /lib/libc.so.1
    #1  0x080c14a4 in fatal_error_signal (sig=11) at emacs.c:3800
    #2  0xd08ffdcf in __sighndlr () from /lib/libc.so.1
    #3  0xd08f6375 in call_user_handler () from /lib/libc.so.1
    #4  <signal handler called>
    #5  byte_scan_buffer (buf=0xe29ae00, target=10, st=15961, en=0, count=-27, shortage=0x0, allow_quit=0) at search.c:744
    #6  0x08189737 in find_next_newline_no_quit (buf=0xd0723f68, from=15962, count=-27) at search.c:783
    #7  0x08171d2a in point_in_line_start_cache (w=0x8ce2400, point=1, min_past=0) at redisplay.c:7803
    #8  0x081721f5 in start_with_line_at_pixpos (w=0x8ce2400, point=1, pixpos=160) at redisplay.c:8154
    #9  0x08172c63 in redisplay_window (window=147727360, skip_selected=589) at redisplay.c:6132
    #10 0x081723f9 in redisplay_window (window=147314688, skip_selected=1) at redisplay.c:6597
    #11 0x08173990 in redisplay_frame (f=0x8f7ac00, preemption_check=1) at redisplay.c:6597
    #12 0x08173ce8 in redisplay_device (d=0x86ee500, automatic=-797833240) at redisplay.c:7028
    #13 0x081740af in redisplay_without_hooks () at redisplay.c:7103
    #14 0x080de011 in Fnext_event (event=137251748, prompt=136849412) at event-stream.c:2288
    #15 0x080a4e2d in Fcommand_loop_1 () at cmdloop.c:599
    #16 0x080a4ef1 in command_loop_1 (unused_dummy=136849412) at cmdloop.c:505
    #17 0x080ca3fe in condition_case_1 (handlers=136849508, bfun=0x80a4ed8 <command_loop_1>, barg=136849412, hfun=0x80a495c <cmd_error>, harg=136849412) at eval.c:1946
    #18 0x080a4b18 in command_loop_2 (unused_dummy=136849412) at cmdloop.c:262
    #19 0x080c4ca9 in internal_catch (tag=-797819032, func=0x80a4ae4 <command_loop_2>, arg=136849412, threw=0x0, thrown_tag=0x0, backtrace_before_throw=0x0) at eval.c:1552
    #20 0x080a4bf6 in initial_command_loop (load_me=-797819032) at cmdloop.c:313
    #21 0x080c2f29 in xemacs_21_5_b28_i386_pc_solaris2_10 (argc=4, argv=0x8046cc8, unused_envp=0x0, restart=0) at emacs.c:2667
    #22 0x080c3915 in main (argc=-797819032, argv=0xd0723f68, unused_envp=0x8046cdc) at emacs.c:3172

I have no further details than that though the core file remains.  If you
think there is more I can dig out of the core dump I'd be happy to poke
around.  Just let me know.