Re: [Denemo-devel] midi input weirdness

[Richard Shann]

I have fixed this bug. I think it would only have affected 64 bit
machines - there was no prototype for a function returning a pointer,
instead the return value was cast to a pointer, so when the pointer was
too large it crashed...
Richard

On Sun, 2014-03-23 at 17:31 +0000, Richard Shann wrote:
> Ha!
> I was just entering a sonata by Cannabich and it got to an A# which it
> sounded on the organ, and found that indeed it had entered B-flat.
> So then I remembered that I had just been writing of the dangers of
> using the Modulation Wheel to change the set of sharps and flats (the
> "enharmonic set").
> So I saved the score and upped the modulation wheel and bingo! it
> segfaulted
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000004cac8b in scheme_output_midi_bytes (input=0x44af220)
>     at ../../denemo/src/scheme-callbacks.c:4316
> 4316    for (i = 0, next = bytes; *next; next++)
> (gdb) call gtk_main()
> 
> the call to gtk_main() brought the program back to life.
> 
> So, it seems this may be a fairly reliable way of triggering the bug.
> Not one that could be automated however.
> For now, stick to the buttons in the MIDI-in control panel or the
> Input->MIDI menu for changing the enharmonic set.
> 
> Any threading experts who can give advice on how to debug this - please
> do!
> 
> Richard
> 
> On Sun, 2014-03-23 at 15:11 +0000, Richard Shann wrote:
> > On Sun, 2014-03-23 at 09:41 -0500, Jeremiah Benham wrote:
> > > I may be a bit confused. I thought this was all dependant upon how the
> > > modwheel is set on the midi controller.
> > 
> > Well, it doesn't matter how you last left the mod wheel - only changes
> > to the mod wheel that you make after starting Denemo are registered.
> > 
> > >  When I do midi input I put the modwheel half way if I was in the key
> > > of c and then move it up if I start to see flats when sharps are
> > > expected and visa versa. I was not sure if that is how it is supposed
> > > to work but I think I remember Richard talking about this once so I
> > > tried it and it worked.
> > 
> > yes, the default callback for the mod wheel does exactly that. I didn't
> > mention it because there is a threading bug with audio output which
> > makes it crash on occasions. (It makes notes of different pitches to let
> > you know which range of sharps/flats you have set, higher ones for
> > sharper ranges).
> > 
> >  In fact I recently had this threading bug bite me while entering
> > figured bass by MIDI filter, which also uses a timer to turn off a midi
> > note. I discovered something remarkable: as I was running under gdb the
> > segfault from the threading bug left me at the gdb prompt. I executed
> > the following:
> > 
> > call gtk_main()
> > 
> > this also returned me to the prompt (the note was still playing) but
> > after a couple more invocations the program was running again and I
> > could save my work. I didn't write to the list about this yet, as I
> > don't want to give the impression that this is something a typical user
> > is likely to encounter, but it is a serious worry. I have been over the
> > threading code, as best I can and did not see where the trouble lay.
> > The crash occurs in the function
> > 
> > scheme_output_midi_bytes()
> > 
> > where the data are nonsensical - it is in a timer callback to turn of a
> > note that has been started earlier.
> > 
> > If anyone can review the code to see where the threading bug arises I
> > would sleep easier at night.
> > 
> > Richard
> > 
> > 
> > 
> > 
> > 
> > _______________________________________________
> > Denemo-devel mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/denemo-devel
> 
> 
> 
> _______________________________________________
> Denemo-devel mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/denemo-devel