[PD-dev] How to pass indeterminate args to a thread
B. Bogart
ben at ekran.org
Fri Feb 27 19:46:02 CET 2009
I figured that doing this with a PD type was unlikely, so I started
messing with creating a structure for my args and passing a pointer to
that.
So I have defined my structure for a single float arg:
struct floatArgStruct {
gphoto2_struct *gphoto2;
t_symbol *s;
};
just under the typedef for the external structure. (Is the external
struct a better place for its def?)
Then the function that is executed from the PD selector:
static void wrapGetConfig(gphoto2_struct *gphoto2, t_symbol *s) {
int ret;
pthread_t thread1;
// instance of structure
struct floatArgStruct threadArgs;
// packaging arguments into structure
threadArgs.gphoto2 = gphoto2;
threadArgs.s = s;
post("I'm about to start the thread.");
// Create thread
ret = pthread_create( &thread1, NULL, mythread, (void *)threadArgs);
}
which populates the structure, and starts the thread. The struct stuff
appears to work here)
Above this is the def of the function that is to execute in the thread:
void *mythread(struct floatArgStruct *threadArgs) {
int i;
post("thread start.");
post("My symbol: %s", threadArgs.s->s_name); // line 92
outlet_float(threadArgs.gphoto2->x_obj.ob_outlet, 0.00001);
post("thread end.");
}
The errors I'm confused about are:
gphoto2.c:92: error: request for member 's' in something not a structure
or union
gphoto2.c:93: error: request for member 'gphoto2' in something not a
structure or union
Which means that the structure is not being passed to the thread code
correctly, as its not recognized as a structure.
Next gcc complains about the way I'm initiating the thread:
gphoto2.c:112: error: cannot convert to a pointer type
gphoto2.c:112: warning: passing argument 3 of 'pthread_create' from
incompatible pointer type
In the tutorial the function args were cast as (void *) which does not
seem to be working in this case.
Does anyone have any code that does this kind of job I could look at?
Or is it obvious I'm doing something really wrong?
This is my first exploration into threads and custom structs (not
counting the external struct) so I may have it totally wrong.
Thanks,
B.
B. Bogart wrote:
> Hey all,
>
> I've got some simple threading code working, and it looks like that will
> fix my HUP issues with PD and my gphoto external.
>
> Problem I'm having is that I need to pass thread arguments as a pointer
> to a structure.
>
> Are there some PD types I can use to make this work? (A_GIMME?)
>
> Or do I need to make struct that holds the *argv argc stuff, pass that
> structure to the thread, and have it unpack the content?
>
> Also my code function that executes the thread does not wait for the
> threads to complete.
>
> What is the best way to make my object output a bang when the thread is
> complete?
>
> Any advice appreciated.
>
> Thanks,
> B.
>
>
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