Re: [Lilypond-auto] Issue 2990 in lilypond: \RemoveEmptyStaves in StaffGroup context crashes

[lilypond]

Comment #15 on issue 2990 by address@hidden: \RemoveEmptyStaves in  
StaffGroup context crashes
http://code.google.com/p/lilypond/issues/detail?id=2990

You're right that this check is intended to weed out this problem.
There is nothing, however, preventing a custom engraver or callback from  
creating cyclical element trees in some other way.

I would recommend going with this patch and deleting the check in  
process_acknowledged in favor of the more general one I've written in  
pointer-group-interface.  It seems that it is better to devise a general  
solution to a problem (cyclical element lists) rather than creating  
instance-specific solutions along the way.

You are right that the check in the axis-group-engraver is more efficient  
than my solution.  However, I'm still interested in seeing benchmarks.  It  
is a tradeoff between efficiency and completeness, and if efficiency  
doesn't take a big hit, I think it's important to be complete.