KKCC backtrace overflow, adjust KKCC_BT_STACK_SIZE.
Maybe it is a loop?

Fatal error: assertion failed, file c:\Hacking\cvs.xemacs.org\XEmacs\xemacs-21.5-clean\src\alloc.c, line 3382, ABORT()

Fatal error.

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 `crashes@xemacs.org'.  *MAKE SURE* to include this entire output
from this crash, especially including the Lisp backtrace, as well as the
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file `Installation' in the top of the build tree).

If you are fortunate enough to have some sort of debugging aid installed
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*please* include it, as it will make our life far easier.


Lisp backtrace follows:

  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  ("(in garbage collection)" "[internal]")
  # bind (enter-time exit-time result func info args interactive-p funsym)
  elp-wrapper(bench-mark-large-list nil nil)
  # bind (args)
  bench-mark-large-list()
  # bind (tmp-foo times)
  bench-handler-large-list(1)
  # bind (test-name benches arg)
  bench(1)
  # bind (command-debug-status)
  call-interactively(bench)
  command-execute(bench t)
  # bind (_execute_command_keys_ _execute_command_name_ prefix-arg)
  execute-extended-command(nil)
  # bind (command-debug-status)
  call-interactively(execute-extended-command)
  (dispatch-event "[internal]")
  # (condition-case ... . error)
  # (catch top-level ...)