Seg fault and 100% CPU when using \override Staff.StaffSymbol #'ledger-positions

[Peekay Ex]

hello,

I've been trying to work out what the values in the brackets actually
do in relation to each other and the ledger lines to be able to
clearly document them for the average user to understand.

I still don't really understand them, but while experimenting with
values if I use this example with the command lilypond-book --pdf

@lilypond[verbatim,quote,relative=2]
\override Staff.StaffSymbol #'ledger-positions = #'(1)
f'4 a, a,, f
@end lilypond

or any *single* value in the brackets, I get a seg fault.

If I use this value for example

@lilypond[verbatim,quote,relative=2]
\override Staff.StaffSymbol #'ledger-positions = #'(1 1 1)
f'4 a, a,, f
@end lilypond

LilyPond just sits at 'Drawing systems....' during compilation and
while I don't see memory creep up (at least after 2 minutes), I have
one of my multiple CPUs at constant 100%.

If I ctrl-c out (after any duration) I get

--snip--
^CTraceback (most recent call last):
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line
742, in <module>
    main ()
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line 725, in main
    chunks = do_file (files[0])
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line
608, in do_file
    do_process_cmd (chunks, input_fullname, global_options)
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line
476, in do_process_cmd
    options.formatter, options.lily_output_dir)
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line
429, in process_snippets
    logfile)
  File "/home/jlowe/lilypond-git/build/out/bin/lilypond-book", line
406, in system_in_directory
    progress_p=1)
  File 
"/home/jlowe/lilypond-git/build/out/lib/lilypond/current/python/lilylib.py",
line 217, in subprocess_system
    retval = proc.wait()
  File "/usr/lib/python2.6/subprocess.py", line 1170, in wait
    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
  File "/usr/lib/python2.6/subprocess.py", line 465, in _eintr_retry_call
    return func(*args)
KeyboardInterrupt
--snip--

I just wondered if this indicated other potential issues bearing in
mind that I am probably putting in an illegal syntax.

However,

@lilypond[verbatim,quote,relative=2]
\override Staff.StaffSymbol #'ledger-positions = #'(1 2 1)
f'4 a, a,, f
@end lilypond

works (or at least it doesn't hang or seg fault).

I still don't really understand what the values do at this point :)

-- 
--
James