S-Function vector output without dimension defined

Hi all.

My question is:

Is it possible somehow define an output interface to generate a "C" S-Function with an output as vector with the dimension not defined?

For ex. if i defined

def.OutputFcnSpec=['void fc_MyFunc (int16 u1, uint8 u2[], y1[])'];

is not possible for y1 not indicate the dimension for my knowledge, it must define y1[dimension-vector] and not as possible for input u2[]

When i launch the

legacy_code('sfcn_cmex_generate', def);

an error is reported.

I found a very cumbersome way to do it manually, but I wanted to understand if there is a way to do it automatically through some particular semantics or command that I do not know.

My ultimate goal is to have a mex file to use as a Simulink block for the library usage of my SW component.

Thank you in advance,

LuLa

Answer 1

[Anushka]

Hi @Luca,

It is not possible to define an output (‘y1[]’) with undefined or variable dimension in the ‘OutputFcnSpec’ when using ‘legacy_code’ with 'sfcn_cmex_generate'. Unlike inputs, output dimensions must be explicitly defined in the function signature (e.g., ‘y1[10]’), because Simulink requires fixed output dimensions for S-Functions at compile time.

You can try the following workarounds:

1. You can use manual modification after code generation (as you mentioned).

2. You can use “mdlInitializeSizes” in a hand-written wrapper ‘S-Function’ to set output dimensions dynamically but this is not automated via ‘legacy_code’.

You can refer to the following documentation of “mdInitializeSizes” for a better understanding: https://in.mathworks.com/help/simulink/sfg/mdlinitializesizes.html

Hope this helps!

[Luca]

Thank you so much, have a nice day.

Kind regards