registers as function arguments in C

[hg_fs2002]

I would like to know how is it possible to pass registers as function arguments in C. Let's say I have something like this:

int main() {
    register a,b;
    a = b;
    register c = a;
    return 0;
}

I want to extract a = b as a new function. Considering what we do for variables, if I return register "a" as function return I will get this error: "function definition declared 'register'".
Another option is passing arguments as function variables But obviously it is not possible to pass a register az a pointer because they are not memory location to assign them an address. So, I am wondering what would be the correct way to extract "a = b" as a new function?

[Unimportant]

int add( int * a, int * b )
{
  return *a + *b;
}
register int * a( & var1 ), * b( & var 2);
int c( add( a, b ) );

Considering you didn't define a type, I suggest you avoid using registers for the time being.

[hg_fs2002]

Thanks! Actually this is a type of code I need to extract, that's not my own code. I did not understand what you exactly did! Is there any simpler way to do that?

[Unimportant]

I created a regular function called add, which receives two pointers to integer as arguments, and returns an integer.

I declared two pointers to integer as registers, and instantiated them with the address of two arbitrary integers.

Finally, I instantiated an integer with the return value of the first function, accepting the two register variables as arguments.

[Unimportant]

For the purpose of understanding someone else's code, you can essentially ignore the register keyword altogether. The compiler itself probably does it better anyway.