Re: Crash with simultaneous-duplicating music function and \once\offset

[Aaron Hill]

On 2018-07-15 18:21, Simon Albrecht wrote:
> Hello everybody,
>
> this combination of a custom music function that combines the music
> simultaneously with itself and a \once\offset command causes LilyPond
> to crash (exit with return code 11):
>
> %%%%%%%%%%%%
> \version "2.19.82"
> test =
> #(define-music-function (parser location mus) (ly:music?)
>   #{ << $mus $mus >> #})
>
> \test { \once\offset length 1 Stem 4 }
> %%%%%%%%%%%%

Seems the custom music function is not needed to reproduce a crash.

%%%%
  \version "2.19.82"
  music = { \once \offset length 5 Stem 4 4 }
  << \music \music >>
%%%%

This also results in:

> GNU LilyPond 2.19.82
> Processing `crash.ly'
> Parsing...
> Interpreting music...
> Preprocessing graphical objects...
> fish: “lilypond crash.ly” terminated by signal SIGSEGV (Address 
> boundary error)

Omitting the \once lets the example compile.  And use of \undo works in 
lieu of \once:

%%%%
  \version "2.19.82"
  longStem = \offset length 5 Stem
  music = { \longStem 4 \undo \longStem 4 }
  << \music \music >>
%%%%

However, attempting to test the "tweak" variant of \offset...

%%%%
  \version "2.19.82"
  music = { \offset Stem.length 5 4 4 }
  << \music \music >>
%%%%

...produced a different error:

> GNU LilyPond 2.19.82
> Processing `crash.ly'
> Parsing...
> Interpreting music...lilypond: 
> /home/gub/NewGub/gub/target/linux-64/src/lilypond-git.sv.gnu.org--lilypond.git-stable-2.20/lily/context-def.cc:232: 
> std::vector<Context_def*> 
> Context_def::internal_path_to_acceptable_context(SCM, Output_def*, SCM, 
> std::set<const Context_def*>*) const: Assertion `(!(6 & ((scm_t_bits) 
> (0? (*(SCM*)0=(type_sym)): type_sym))) && ((0x7f & ((((scm_t_bits) (0? 
> (*(SCM*)0=((((SCM *)((scm_t_cell *) (((scm_t_bits) (0? 
> (*(SCM*)0=((((type_sym))))): (((type_sym)))))))) [((0))]))): (((SCM 
> *)((scm_t_cell *) (((scm_t_bits) (0? (*(SCM*)0=((((type_sym))))): 
> (((type_sym)))))))) [((0))])))))) == 5))' failed.
> fish: “lilypond crash.ly” terminated by signal SIGABRT (Abort)

Figuring that perhaps the parser is confused by the naked duration, I 
tried this:

%%%%
  \version "2.19.82"
  music = { \offset Stem.length 5 c'4 4 }
  << \music \music >>
%%%%

It compiles, but produces two staves as output rather than combining the 
notes on one staff.  I am almost certainly overlooking an important 
detail in parsing which would explain this difference, but it is still 
confusing to say the least.

-- Aaron Hill