[PD-dev] how to dinamically allocate t_atom & t_float size?

[Alexandre Torres Porres]

well, as for the atom size in the GUI objects I'm using getbytes/freebytes
and I guess that's the way to go.

as for the other issue, it's for a median~ external that takes medians and
we're now using malloc/realloc for a temp t_float variable that gets the
block size value inside the "dsp" function. see =>
https://github.com/porres/pd-else/blob/master/Classes/Source/median~.c#L78

I use this to get the median of bits of a signal block from FFT amplitudes,
so, yeah, block sizes can be big but not too big.

anyway, seems to be working fine but if you have suggestions I'm all ears.

thanks a lot

Em sex., 4 de dez. de 2020 às 11:43, Christof Ressi <info at christofressi.com>
escreveu:

> alloca() "allocates" memory on the stack. This is done by simply
> incrementing the stack pointer. So it's extremely fast and - more
> importantly - equally fast for all sizes.
>
> malloc(), on the other hand, actually uses the system memory allocator
> which can take arbitrarily long and might even block!
>
> Generally, you should avoid using any malloc() in real-time code paths.
> Instead, pre-allocate temporary buffers (e.g. in the "dsp" method) or
> allocate on the stack (but note the caveats mentioned in the other mails).
>
> Christof
> On 04.12.2020 03:28, Alexandre Torres Porres wrote:
>
> I'm using getbytes and freebytes for now, any disadvantages over alloca?
>
> thanks!
>
> Em qui., 3 de dez. de 2020 às 20:59, David Rush <kumoyuki at gmail.com>
> escreveu:
>
>> On Thu, 3 Dec 2020 at 23:15, Alexandre Torres Porres <porres at gmail.com>
>> wrote:
>>
>>> Hi, when compiling ELSE for camomille in windows, me and Esteban are
>>> getting some errors. Offending pieces of code are when trying to do things
>>> like
>>>
>>> t_atom at[ac];
>>>
>>
>> If you want to maintain straight C compiler compatibility
>>
>>         t_atom* at = (t_atom*)malloc(ac * sizeof(t_atom));
>>
>> but you have to remember to free(at), &cet. You can avoid the free() if
>> you HAVE_ALLOCA with
>>
>>         t_atom* at = (t_atom*)alloca(ac * sizeof(t_atom));
>>
>> if you want to do it the C++ way without a std::vector<t_atom>
>>
>>         t_atom* at = new t_atom[ac];
>>
>> but again you will have to
>>
>>         delete at;
>>
>> For my own externals, I write them all in C++ and use STL. Making the
>> change from the C-world allocation of PD to the C++ world is not so hard,
>> but it does involve a tiny bit of trickery which I only justify through
>> expediency.
>>
>> - d
>>
>
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