Changing function declaration and definition syntax

[Phrunsys Emmason via Gcc-help <gcc-help@xxxxxxxxxxx>]

Hello Im new to gcc I would love to try out by changing the function
declaration and syntax for C. Initially the syntax is:

Declaration:
int foo (int a, int b);

Definition:
int foo (int a, int b) {
    return a + b;
}

I want it to be:

foo (int a, int b) int;

foo (int a, int b) int {
     return a + b;
}

What files do I have to modify and their respective functions? I am using
gcc 13.0.0