[chuck-users] segmentation fault / OSC

[Stephen Sinclair]

2009/3/30 Bozelos Dimitris <dbozelos at yahoo.gr>:
> Hi Kassen,
>
> thanks a lot and sorry for the late reply I had trouble last days with the
> latest fedora updates and wouldn't ChucK that much!
>
> FROM: Kassen
>
> Hey, Dimitris!
>
>>  For some reason I constantly get a "segmentation fault" fatal error
>> sometimes just after some seconds I run my shreds. What does this mean?
>
> Typically it means you tried to address something that doesn't exist/ isn't
> instantiated. It can also mean there is some bug in ChucK that affects you.
>
> Well, I found out that an accumulator that I had was causing the trouble. I
> was receiving a variable through osc and doing (inside an infinite
> time-loop) something like
>
> while( event.nextMsg() )
> {
>     event.getFloat() +=> a;
> }
>
> I don't really know why it was crushing, it shouldn't. when I removed this
> part everything was ok.
>
>> Once or twice I had an "OSC packet ...: buffer (or stack) overflow" error.
>> Is there a buffer or a limit on the messages you send / receive?
>
> I don't know :¬)
> I'm certain there must be some limit somewhere but I'm not sure what or
> where it is.
>
> What probably happened here is that I was being sent the messages faster
> than receiving them, so if I had an osc message coming every 100 ms and I
> had
>
> while( true )
> {
>     while( event.nextMsg() ) { ... }
>     1000::ms => now;
> }
>
> the messages might have been accumulating so there was the buffer overflow.
> Although it shouldn't be, I think.
>
> But I actually have a question here about the OSC events: is there any smart
> way to have some code executed on an event independently of the time of the
> infinite time-loop? To be more clear, let's say I have an BiQuad filter and
> I want to control its frequency over the network through OSC. So,
>
> while( true )
> {
>     while( event.nextMsg() )
>     {
>         event.getFloat() => f.pfreq;
>     }
>
>     // do other stuff
>
>     1::second => now;
> }
>
> This have the consequence, if I'm not mistaken, that every 1 second chuck
> will check for new messages and if messages are sent every 300 ms and for
> some reason we need the loop to run every one second the frequency is
> actually updated once a second with the last of the 3 received values
> instead of 3 times a second.
>
> The only way around I can think now is to declare the filter in a public
> class as a static object and have a separate shred that runs with a faster
> time-loop and update the filter this way. But this might lead to
> unreasonable many shreds like one for gain, one for frequency etc. Moreover
> this will mean that I will be able to have only one BiQuad filter working
> this way. So I see this solution highly problematic. Any ideas?

Yo,

You can wait on the event itself, so that your loop will wake up every
time a message comes in.

while( true )
{
    while( event.nextMsg() )
    {
        event.getFloat() => f.pfreq;
    }
    1::second => now;
}

If you need to "do other stuff", I suggest doing this event loop in a
shred by sporking it.


Steve