C Macro Hackery

/**
 * A nonexhaustive list of macro hackerys
 */

/* -- default parameters from dev.to/rdentato (annotated) -- */
/* vrg.h - reuseable for multiple programs */
/* count how many args are passed to a variadic macro */
#define vrg_cnt(vrg1, vrg2, vrg3, vrgN, ...) vrgN
#define vrg_argn(...) vrg_cnt(__VA_ARGS__, 3, 2, 1, 0)
/* concatenate name with number of args: "_MyFunc" + "1" -> "_MyFunc1" */
#define vrg_cat0(x, y) x ## y
#define vrg_cat(x, y) vrg_cat0(x, y)
/* main macro used in definition */
#define vrg(vrg_f, ...) vrg_cat(vrg_f, vrg_argn(__VA_ARGS__))(__VA_ARGS__)

/* example.c */
#include "vrg.h"
#include <stdio.h>

/* using the number of arguments to decide which function to call */
#define MyFunc(...) vrg(_MyFunc, __VA_ARGS__)
/* prepare a macro for every possible number of arguments */
#define _MyFunc1(element) _MyFunc(element, -1, NULL)
#define _MyFunc2(element, id) _MyFunc(element, id, NULL)
#define _MyFunc3(element, id, pInput) _MyFunc(element, id, pInput)
void *_MyFunc(void *element, int id, const void *pInput) {
    printf("Calling MyFunc() with args %p, %d, %p\n", element, id, pInput);
}