memory alignment

memali.c

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

//memory alignment
//alloc a variable at least 4 bytes memory in struct, struct t and struct st have same size, struct ft has 16 bytes
struct t {
  int i;
  char a;
  char *b;
  double d;
};

struct st {
  int i;
  char a;
  char a1;
  char a2;
  char a3;
  char *b;
  double d;
};

struct ft {
  char a;
  short b;
  char c;
  int d;
  char e[2];
};

int main()
{
  printf("sizeof(struct t) == sizeof(struct st) == %d, %d\n", sizeof(struct t), sizeof(struct st));
  printf("sizeof(struct ft): %d\n", sizeof(struct ft));
  printf("i:%d, a:%d, b:%d, c:%d\n", offsetof(struct f, i), offsetof(struct f, a), offsetof(struct f, b), offsetof(struct f, c));
  return 0;
}