#include <stdio.h>
#include <stdlib.h>

#define KIND int kind;
#define example_kind 1

typedef struct {
  KIND
} value_t;

typedef struct {
  KIND
  int foo;
} example_t;

int main() {
  value_t *value = (value_t *)malloc(sizeof(example_t));
  ((example_t *)value)->kind = example_kind;
  ((example_t *)value)->foo = 42;

  switch (value->kind) {
  case example_kind:
    printf("example_t with foo=%d\n",
           ((example_t *)value)->foo);
    break;
  default:
    printf("unknown value kind\n");
  }

  return 0;
}