[PD-dev] trying to understand class_new

[Christof Ressi]

> and then in function class_new vp is empty so while (*vp) doesn’t go through it
What do you mean by "empty", when exactly is "vp" empty and how did you 
test?

"vp" is initially set to "type1", which in the case of pdint_setup() is 
"A_DEFFLOAT". So it would be very strange if "vp" was initially empty in 
the case pdint_setup(). The while loop sets "vp" to the next vararg and 
increments the pointer until it encounters "A_NULL" (= 0). So finally, 
"*vp" will always be 0, if that is what you mean by empty.

Or did you mean "vp" itself is NULL? This would be even stranger, 
because it points to the stack.

Do your run the code in a debugger? If yes, post the stack trace. If 
not, well, use a debugger :-)

BTW, which device are you using?

Christof

On 22.03.2020 09:13, Boštjan Jerko wrote:
> Hi Christof,
>
> the problem is that I don’t really know what happens but it goes something like that:
>
> calling pd_init -> pd_init_systems -> conf_init -> x_connective_setup -> pdint_setup
>
> and then in function class_new vp is empty so while (*vp) doesn’t go through it and after exiting class_new the microcontroller stops with a hard error.
> So maybe the question is really - should the vp be empty and if not - why is that happening?
>
> B.
>
>> On 21 Mar 2020, at 13:58, Christof Ressi <info at christofressi.com> wrote:
>>
>> Hi,
>>
>>> The code compiles but I get the error when running in the pdint_setup where pdint_new in class_new breaks with an error.
>>> My idea is to first try to understand the code hence my question:
>> I think first you should post the error you get ;-) Maybe the problem is trivially solved without having to look at  code for class_new() at all.
>>> What does class_new do?
>> It creates a new Pd class (t_pd). The class contains all the methods and some metadata. It also registers a creator function in pd_objectmaker, which is the factory object for all classes.
>>
>> When you type "[foo 0]" you really send a message "obj <x> <y> foo 0" to the canvas, which in turn sends a message "foo 0" to pd_objectmaker, which finally returns a newly created instance (given that it can find a creator method for "foo").
>>
>> But again, I think the problem is likely trivial and those implementation details shouldn't concern you, unless you want to learn about Pd internals, of course :-)
>>
>> Christof
>>
>> On 21.03.2020 13:20, Boštjan Jerko wrote:
>>> Hi,
>>>
>>> I’m trying to port libpd to stm32. I don’t need gui so working only on connecting pd script to the output (which is DAC from stm32 in my case).
>>> The code compiles but I get the error when running in the pdint_setup where pdint_new in class_new breaks with an error.
>>> My idea is to first try to understand the code hence my question:
>>> What does class_new do?
>>>
>>> My guess is connecting puredata command with a function in C. Am I correct or completely missing the point?
>>>
>>> Thanks.
>>>
>>> B.
>>>
>>>
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>>
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