How do I write the following callback function?

[coffeenet]

Hi,
I am very green in Linux. That is why I posted here.
The title was too short.
I need to write a callback function from a shared library that will call to a function that is inside the executable.
I am too green to linux, that I am not even share if Linux uses *.exe files ><
Any, I will try to explain what I am trying to do here:

//Executable

void functionA()
{
//code that calls to functions inside EXE
}
 
void functionB()
{
//code that calls to functions inside EXE
}
 
void functionC()
{
//code that calls to functions inside the Executable
}
 
//Shared Library
void functionSL()
{
// I need to call functionA(), functionB() & functionC()
}

So, instead of writing three callback functions.
I did the following:

//Executable
void functionABC()
{
functionA();
functionB();
functionC();
}
 
//Shared library
//Must call functionABC()

Therefore, unfortunately, even if I would create a shared library, and place functionA(), functionB() functionC() inside it, I will still have create Callback functions for the functions that are called from within functionA/B/C() ><

Furthermore, this is not my code. I am trying to add some simple functionality there. I did it on windows, and now I need to test it on Linux. But, I can't seem to get the right syntax for callback functions there.

Any ideas on "Callback functions to a function that is inside an executable?"
Thanx!

[Rubberman]

One method would be to have a global variable that is a function pointer which is either initialized to null, or a stub function. The executable would set the pointer to a valid function of its own, then the shared library can call the function that the executable has "registered" with the global variable. This is not an uncommon technique, and one I have used in the past.