[danny@vmware143 ~]$ /usr/src/redhat/BUILD/xemacs-21.4.15/src/xemacs Fatal error: assertion failed, file bytecode.c, line 1479, abort()

Fatal error (6).

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 necessary, send
ordinary email to `crashes@xemacs.org'.  *MAKE SURE* to include 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 /usr/src/redhat/BUILD/xemacs-21.4.15/src/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:

  viper-mode()
  toggle-viper-mode()
  (progn (toggle-viper-mode) (customize-set-variable (quote viper-mode) viper-mode))
  eval((progn (toggle-viper-mode) (customize-set-variable (quote viper-mode) viper-mode)))
  # (condition-case ... . error)
  # (catch top-level ...)
Aborted (core dumped)
[danny@vmware143 ~]$

[danny@vmware143 ~]$ gdb /usr/src/redhat/BUILD/xemacs-21.4.15/src/xemacs core.5590

#0  0x005287a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
(gdb) up
#1  0x00569cc6 in kill () from /lib/tls/libc.so.6
(gdb) up
#2  0x080acfd5 in fatal_error_signal (sig=6) at emacs.c:642
642       kill (getpid (), sig);
(gdb) up
#3  <signal handler called>
(gdb) up
#4  0x005287a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
(gdb) up
#5  0x00569825 in raise () from /lib/tls/libc.so.6
(gdb) up
#6  0x0056b289 in abort () from /lib/tls/libc.so.6
(gdb) up
#7  0x080ad504 in assert_failed (file=0x81c2358 "bytecode.c", line=1479,
    expr=0x81c0a36 "abort()") at emacs.c:3429
3429      abort ();
(gdb) up
#8  0x0808f714 in execute_rare_opcode (stack_ptr=0xbff921e4,
    program_ptr=0xa93d6b5 "", opcode=0) at bytecode.c:1479
1479          abort();
(gdb) print opcode
$1 = 0
(gdb) up
#9  0x0808fcc2 in execute_optimized_program (program=Variable "program" is not available.
) at bytecode.c:658
658                 stack_ptr = execute_rare_opcode (stack_ptr, program_ptr, opcode);
(gdb) print opcode
$2 = 5590
(gdb) list
653
654             default:
655               if (opcode >= Bconstant)
656                 PUSH (constants_data[opcode - Bconstant]);
657               else
658                 stack_ptr = execute_rare_opcode (stack_ptr, program_ptr, opcode);
659               break;
660
661             case Bvarref:
662             case Bvarref+1:
(gdb)