Re: Segfault with voice and empty music

[David Kastrup]

Roman Stawski <address@hidden> writes:

> Hi folks
>
> I've noticed the following problem in 2.19.16 after updating from 2.19.11.
>
> When the code below compiles I get the error
>     "warning: cannot find Voice `refrain"
> and then the  compilation segfaults.

Which is not something we want to see.

> It seems that the empty music and the voices don't play well
> together inside the inner double brackets. Any ideas, anyone?

This is very likely the fix to issues 2010, 1551, 702
<URL:https://code.google.com/p/lilypond/issues/detail?id=2010>. After
this fix, putting synchronized music and independent non-synchronized
music of different length at the same level will likely cause trouble.

A segfault, however, is more trouble than permissible.

> (Duh: The reason that I'm generating empty music is that I'm
>  conditionally inserting other lyrics in the real piece.)

Possibly making this a skip may help?  Not really sure.

> Roman
>
> ---- Problem code follows
>
> \version "2.19.16"
>
> <<
>   \new Staff {
>     \new Voice = "couplet" \relative c' { \voiceOne c2 }
>     \new Voice = "refrain" \relative c' { \voiceOne c2 }
>   }
>
>   #(make-music 'Music)  %% OK
>   \tag #'optional <<
>     #(make-music 'Music) %% NOT OK
>     \new Lyrics \lyricsto "couplet" { Foo }
>     \new Lyrics \lyricsto "refrain" { Bar }
>   >>
>   #(make-music 'Music)  %% OK
>>>

Backtrace is

#0  is_alias (sym=0xb67b20d0, this=0x0) at context.cc:514
#1  find_context_below (where=0x0, type=0xb67b20d0, id="refrain")
    at context.cc:594
#2  0x080f66ce in Lyric_combine_music_iterator::find_voice (this=0x87816d0)
    at lyric-combine-music-iterator.cc:275
#3  0x080f6d1e in check_new_context (this=0x87816d0)
    at lyric-combine-music-iterator.cc:239
#4  Lyric_combine_music_iterator::check_new_context_callback (self=0x87816d0, 
    ev=0xb7289f90) at lyric-combine-music-iterator.cc:230
#5  0x0810757f in dispatch (sev=0xb7289f90, this=<optimized out>)
    at dispatcher.cc:147
#6  Dispatcher::dispatch_callback (self=0x8749240, ev=0xb7289f90)
    at dispatcher.cc:75
#7  0x0810757f in dispatch (sev=0xb7289f90, this=<optimized out>)
    at dispatcher.cc:147
#8  Dispatcher::dispatch_callback (self=0x8631050, ev=0xb7289f90)
    at dispatcher.cc:75
#9  0x0810757f in dispatch (sev=0xb7289f90, this=<optimized out>)
    at dispatcher.cc:147
#10 Dispatcher::dispatch_callback (self=0x8776cd8, ev=0xb7289f90)
    at dispatcher.cc:75
#11 0x08107b3f in dispatch (sev=<optimized out>, this=0x8776398)
    at dispatcher.cc:147
#12 Dispatcher::broadcast (this=0x8776398, ev=0x8786f98) at dispatcher.cc:203
#13 0x081036e5 in Context::internal_send_stream_event (this=0x8776508, 
    type=0xb6813670, origin=0x0, props=0xbfffc700) at context.cc:505
#14 0x081039a2 in Context::create_context (this=0x8776508, cdef=0x87281c8, 
    id="refrain", ops=0x404) at context.cc:370
#15 0x081045e3 in Context::create_unique_context (this=0x8776508, 
    name=0xb67b20d0, id="refrain", operations=0x404) at context.cc:128
#16 0x081047ee in Context::create_unique_context (this=0x8777e88, 
    name=0xb67b20d0, id="refrain", operations=0x404) at context.cc:140
#17 0x0828565b in Context_specced_music_iterator::construct_children (
    this=0x8786e08) at context-specced-music-iterator.cc:45
#18 0x08100869 in Music_iterator::get_iterator (this=0x8777838, m=0x87460c0)
    at music-iterator.cc:153
#19 0x08072d14 in Sequential_iterator::next_element (this=0x8777838)
    at sequential-iterator.cc:198
#20 0x080729ab in Sequential_iterator::process (this=0x8777838, until=...)
    at sequential-iterator.cc:234
#21 0x0819e756 in Music_wrapper_iterator::process (this=0x86302a0, m=...)
    at music-wrapper-iterator.cc:70
#22 0x0833bd64 in Simultaneous_music_iterator::process (this=0x8749360, 
    until=...) at simultaneous-music-iterator.cc:98
#23 0x08130c0a in Global_context::run_iterator_on_me (this=0x8748d78, 
    iter=0x8749360) at global-context.cc:170
#24 0x082c205a in ly_interpret_music_expression (mus=0xb719b2e8, 
    ctx=0xb7228598) at global-context-scheme.cc:118
#25 0x082c24ab in ly_run_translator (mus=0xb719b2e8, output_def=0xb7204dd8)
    at global-context-scheme.cc:145
#26 0x0821b055 in Score::book_rendering (this=0x8747e48, layoutbook=0x8748018, 
    default_def=0x8734cc0) at score.cc:141

and the rest is not really interesting.

-- 
David Kastrup