my_sizeof.c

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

#define my_sizeof(type)                                                        \
  ({                                                                           \
    __typeof__(type) _a[2];                                                    \
    (size_t) & _a[1] - (size_t)&_a[0];                                         \
  })

/* The lost art of structure packing:
 * http://www.catb.org/esr/structure-packing/
 *
 * So how did the declairation order decided in those huge structs in Linux kernel?
 */
struct st {
  int a;
  int b;
  char ss;
  int *kk;
};

int main() {
  int c[7];
  struct st ttt;
  printf("my_sizeof: %lu\n", my_sizeof(ttt));
  printf("sizeof: %lu\n", sizeof(ttt));

  return 0;
}