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Calling anexternal C function that returns a pointer to a struct

Calling anexternal C function that returns a pointer to a struct

Hello,

I'm trying to call an external C function that returns a pointer to a struct.

Here is the program I use (in OpenModelica :

record rec
  Integer a;
  Integer b;
end rec;

function Chirp
  input Real id;
  input Real id2;
  output rec u;

  external u = Chirp(id, id2) annotation(Library = "Chirp");
end Chirp;

model ChirpSignal
  rec u;
  parameter Real id = 1;
  parameter Real id1 = 2;
equation
  u = Chirp(id, id1);
end ChirpSignal;


the programm in C is :

typedef struct {
int id1;
int id2;
}mystruct;


mystruct* Chirp(double a,double b)
{
mystruct* test;
test = malloc(sizeof(mystruct));
test->id1 = 2;
test->id2  =3;

return test;
}


The problem is that I don't have the right to change the C-program, I have to keep it like it is.
Can anybody please tell me if there is something to change in the OpenModelica programm so as to make it work.
Thank you.



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Re: Calling anexternal C function that returns a pointer to a struct

help please !!!!

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Re: Calling anexternal C function that returns a pointer to a struct

What is the error message?

Adeel.

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Re: Calling anexternal C function that returns a pointer to a struct

Hi Adeel,

this is the error message I get :

"assert | debug | <p>ERROR: Too many event iterations. System is inconsistent. Simulation terminate.</p>"

I have to say that when I try to return a struct instead of a pointer to a struct, it works just fine. for exemple the following exemple works fine :

typedef struct {
int id1;
int id2;
}mystruct;

mystruct Chirp(double a,double b)
{
mystruct test;
//test = malloc(sizeof(mystruct));
test.id1 = 1;
test.id2 = 2;
return test;
}

do you have any idea or solution for my problem?
Thank you.

olaama

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Re: Calling anexternal C function that returns a pointer to a struct

Hi adeel it's me again,

In the definition of "record rec" I changer the Integers by Real, and I don't have the error anymore, but the values I get for a and b are totally absurd. (Instead of having a=2 and b=3, I get a = 4.31109e-308, b=2.78583e+165.
Any Idea ?

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Re: Calling anexternal C function that returns a pointer to a struct

Note that Modelica spec says structs are passed by reference. This means you cannot return them from a function, but need to pass the output as an argument to the function.

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