error while using graphviz

[Thomas Morley]

This came up in the german LilyPond-Forum.
http://www.lilypondforum.de/index.php?topic=2179.0

Following
http://www.lilypond.org/doc/v2.19/Documentation/contributor/tracing-object-relationships
to use graphviz on the content of the file input/regression/graphviz.ly, i.e.

\version "2.16.0" %% ofcourse compiled with 2.19.37
\include "graphviz-init.ly"

#(whitelist-grob 'NoteHead)
#(whitelist-grob 'Stem)
#(whitelist-grob 'Flag)

#(for-each whitelist-symbol '(stencil style duration-log
                  stem-attachment end-position staff-position
                  glyph-name
                  direction))


\book { \score {
  c'4
} }



#(ly:progress (call-with-output-string
  (lambda (port) (graph-write graph port))))
#(ly:set-grob-modification-callback #f)
#(ly:set-property-cache-callback #f)




returns an error while calling the pdf with
dot -Tpdf graphviz.log > graphviz.pdf


Error: graphviz.log: syntax error in line 38 near '-20'

The line in question:
15 [label="NoteHead\n/home/harm/lilypond-git/lily/font-interface.cc:37\nfont
<- #<Font_metric ("emmentaler-20" . 0.569055118110236"]

Escaping the "-signs, i.e. using \" instead cures it.

Not sure whether it's a lilypond- or graphviz-problem

Cheers,
  Harm

P.S.
graphviz-init.ly contains a definition for `grob-name', could be
deleted and it's usage replaced by `grob::name'