defarg.c

//This source code is for C99
//Pseudo default-argument feature for C99
#include <stdio.h>

#define func(...) func_impl(__VA_ARGS__, -1)

void func_impl(int arg1, int arg2, int arg3, ...);
int main(int argc, char *argv[]);

void func_impl(int arg1, int arg2, int arg3, ...)
{
    printf("func() called with argument %d, %d ,%d\n", arg1, arg2, arg3);
}

int main(int argc, char *argv[])
{
    //func(1); //error
    func(1,2);
    func(1,2,3);
    func(500, 400);
    func(700, 200, 400, 700); //can't be error
    return 0;
}