unbalenced \override and \revert

[Laurent Martelli]

Hi, 

I know that the manual says :

       If you revert a setting which was not set in the first place,
    then it has no effect. However, if the setting was set as a system
    default, it may remove the default value, and this may give
    surprising results, including crashes.  In other words,
    `\override' and `\revert', must be carefully balanced.

However, I wish that crashes when reverting a not previously overriden
property should be avoided. Undefined behavior is acceptable, but as a
programmer, a segfault is not :-)

This sample crashes lily version 1.4.12 :

\score { \notes \relative c' {
  \property Staff.instrument = #(make-instr-name 5)  
  \time 4/4
 
%  \property Voice.Slur \override #'attachment = #'(head . stem)
  des16( c b bes a aes g fis f e ees d )des8 des'-. |
  \property Voice.Slur \revert #'attachment
  c16( b bes a gis g fis f e dis d cis )c4 |
}
\paper {}
\midi {}
}


Regards,
Laurent

-- 
Laurent Martelli
address@hidden              http://www.bearteam.org/~laurent/