Re: Beaming and slurs across staves

[David Kastrup]

Andrew Bernard <address@hidden> writes:

> I keep finding situations using beamed groups across staves where
> adding a slur or a phrasing slur causes lilypond to fail with the
> following error:
>
>
> Processing `/home/andro/work/lilypond/fp/exp-slur-crash.ly'
> Parsing...
> Interpreting music...
> Preprocessing graphical objects...
> Finding the ideal number of pages...
> Fitting music on 1 page...
> Drawing systems...
> /home/andro/work/lilypond/fp/exp-slur-crash.ly:15:6: warning: no
> viable initial configuration found: may not find good beam slope
> c32
> [\( c
> lilypond:
> /home/gub/NewGub/gub/target/linux-64/src/lilypond-git.sv.gnu.org--lilypond.git-release-unstable/flower/include/interval.hh:227:
> T Interval_t::center() const [with T = double]: Assertion `!is_empty
> ()' failed.
>
> Refer to the MWE here for an example. This occurs in 2.19.41 at least.
> I have not tried previous versions.
>
> In other scenarios in my score even when the warning about not finding
> a good beam slope is not emitted I still get the crash reliably in
> this type of situation.
>
> Is this a bug?

Likely a faulty assertion.  Versions of LilyPond previous to something
around 2.19.20 were compiled/distributed with assertions turned off.  A
failed assertion usually indicates a condition that the program cannot
sensibly deal with and that should never occur.  Well, here it occurs
and likely the program had some way of meddling on.  Which likely
warrants more of a (non-fatal) programming_error until the malcondition
has been diagnosed and fixed.

-- 
David Kastrup