Re: invalid read in Context::properties_dict()

[Dan Eble]

When the segfault occurs, multiple contexts in the call stack have already had 
their mark_smob() method called.  I guess that means they're all invalid, and 
their memory might have been reallocated.  Is that correct?

For a while, I have been using the following scheme code to define instrument 
names for voices together with the notes for the voice, e.g.

    aNotes = \relative g {
      #(set-voice-name "T1")
      c4 d e f . . .
    }

Did something change in 2.16 that would make this start to segfault, or was it 
always invalid and just now started failing by chance?  Thanks.

#(define-markup-command (on-the-fly-context layout props procedure context arg) 
(symbol? markup?)
  "Apply the @var{procedure} markup command to
@var{arg}. @var{procedure} should take a single argument."
  (let* ((anonymous-with-signature (lambda (layout props context arg) 
(procedure layout props context arg))))
    (set-object-property! anonymous-with-signature
                          'markup-signature
                          (list ly:context? markup?))
    (interpret-markup layout props (list anonymous-with-signature context 
arg))))

#(define (set-voice-name newName)
   (let ((m (make-music 'ApplyContext)))

     (define (do-it context)
       (let* ((voiceNames (ly:context-property context 'voiceNames)))

         (if (list? voiceNames)
             (set! voiceNames (append voiceNames (list newName)))
             (set! voiceNames (list newName)))

         (ly:context-set-property! context 'voiceNames voiceNames)))

     (set! (ly:music-property m 'procedure) do-it)

     (context-spec-music m 'Staff)))

#(define-public (print-voice-names-or-default layout props context default)
   (let ((voiceNames (ly:context-property context 'voiceNames)) % segfault 
occurs in ly:context-property
         (props (cons (list '(baseline-skip . 2.4)) props)))
     (if (null? voiceNames)
         (interpret-markup layout props (make-column-markup default))
         (interpret-markup layout props (make-column-markup voiceNames)))))

#(define-public (set-auto-instrument-name defaultNames)
   (let ((m (make-music 'ApplyContext)))

     (define (do-it context)
         (ly:context-set-property!
          context 'instrumentName
          (cons on-the-fly-context-markup
                (list print-voice-names-or-default context defaultNames))))

     (set! (ly:music-property m 'procedure) do-it)
     (context-spec-music m 'Staff)))

-- 
Dan