Custom C Code question: How do set extern variables from simulink model

I have a simple C code file that has four extern variables (three inputs, one output)

main.c:

#include <math.h>
#include "main.h"

extern float A1;
extern float A2;
extern float A3;

extern float OUTPUT;

void do_something(void) {
	OUTPUT = cos(A1) * sin(A2) * cos(A3);
}

main.h:

void do_something(void);

I wish to add this C code to my stateflow model and output the variable OUTPUT

This is how I currently have my custom c code setting

The 'include directories' sections only has a '.' so that every file in included (currently only main.h). And the 'source file' section is empty

My models are setup like this

I can the following error:

[Alexander Dingwall]

I can upload the model if that makes it easier

[James Tursa]

I am not familiar with Stateflow, but as far as the C code is concerned, where are the variables A1, A2, A3, and OUTPUT defined? Are you sure you are including/linking the file(s) where they are actually defined?

[Alexander Dingwall]

This is the problem. I don't want to define these variables using another .c file. I want to set them using stateflow. I can't find a way to tell the C compiler this, so it thinks these variables are not defined, when I actually want them defined using the A1, A2 and A3 stateflow inputs.

[James Tursa]

"I don't want to define these variables using another .c file"

But that is specifically what the extern keyword does ... it instructs the compiler that these variables are defined in another file. All variables in your code have to be defined somewhere. You might have Stateflow specific code for setting these variables to values, but the variables still must be defined somewhere.

[Alexander Dingwall]

Okay, thank you. I suppose I will have to find a work around.