Loop on generic type len array

test.c

#include <stdio.h>

#define LOOP_ON_GENERIC(T, A, AL, I) \
  T* I = NULL;                       \
  T** I##_p = NULL;                  \
  if (A)                             \
    for(I##_p = A, I = *I##_p;       \
        I##_p < A + AL;              \
        I##_p++, I = (I##_p < A + AL ? *I##_p:NULL))

struct t {
  int xx;
  char yy;
};

void main() {
  /* Lets do easy with some chars */
  char a = 'a';
  char b = 'b';
  char c = 'c';

  char* x[] = {&a, &b, &c};
  size_t x_len = 3;

  LOOP_ON_GENERIC(char, x, x_len, e) {
    printf("now at item %c\n", *e);
  }


  /* What if empty? */
  char** y = NULL;
  size_t y_len = 0;

  LOOP_ON_GENERIC(char, y, y_len, f) {
    printf("now at item %c\n", *e);
  }


  /* Why not something more complex */
  struct t ta = {.xx=10, .yy='A'};
  struct t tb = {.xx=12, .yy='A'+2};
  struct t tc = {.xx=14, .yy='A'+4};
  struct t td = {.xx=16, .yy='A'+6};

  struct t* tx[] = {&ta, &tb, &tc, &td};
  size_t tx_len = sizeof(tx)/sizeof(struct t*);
  

  LOOP_ON_GENERIC(struct t, tx, tx_len, q) {
    printf("now at item %d %c\n", q->xx, q->yy);
  }
}