[PD] arguments not passed to an external

Alexandros Drymonitis via Pd-list pd-list at lists.iem.at
Tue May 27 21:41:49 CEST 2014

On Tue, May 27, 2014 at 6:19 PM, Martin Peach <martin.peach at sympatico.ca>wrote:

> On 2014-05-27 04:00, Alexandros Drymonitis wrote:
>>     The parameters are passed on the stack, so if it's a little-endian
>>     machine the first two bytes will be the same for a short as for an
>> int.
>>     (Big-endians would think argc was zero). The problem arises when the
>>     called routine looks for the first argv which it expects to find
>>     right after the short argc on the stack. The caller put a four-byte
>>     int there so the next two bytes will be zero and all the pointers to
>>     the argvs will be wrong.
>> Since my laptop's processor is an Intel Core 2, it's a little edian one,
>> right? How can I make my code versatile so that it can compile on either
>> little or big endian machines? I'm reading Pd's source code ([phasor~]'s
>> code, for example) but it's beyond my understanding. I kind of
>> understand the beginning of d_osc.c where the code will try to determine
>> the endianess of the machine, but when it comes to sorting arguments out
>> depending on the endianess, I'm at loss.
> You don't need to know the endianness of the machine. The compiler and
> linker take care of that. (You could use the htons() function on a test
> short like 1234 to see if the result is the same as the input. If they are
> the same then you have a big-endian machine.)
> As long as you declare your 'new' routine with argc as an int it will just
> work.
>  Another important question I still have is, how do I determine whether
>> there is a signal coming in the object's inlets, so I know whether to
>> use the values passed via arguments, or the vectors passed from the dsp
>> method. I'm asking the same thing over and over again...I'll stop for now.
> I think if you get all zeros on the vector for the inlet you can assume
> it's not connected. So use the argument values until you get non-zero on
> the inlet vectors.
I thought about that, but I do need to send zeros to the vectors some times
(for example, raising a signal to a power, raising to the zeroth power will
yield a DC of 1, which might be useful sometimes). Of course I can send
signals with offsets and subtract the offset in the code, but I don't think
this is good design. I'd rather not be able to use arguments.

> Martin
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