#include <stdio.h>

static int diff_ptr (const void *p1, const void *p2)
{
  const char *c1 = (const char *) p1;
  const char *c2 = (const char *) p2;
  return (int) (c2 - c1);
}

static int check_ptr (const void *base, const void *off, int expect)
{
  int v = diff_ptr (base, off);
  if (v == expect)
    return 1;
  printf (" expect %d, but we got %d", expect, v);
  return 0;
}

/* First packing */
#pragma pack(1)
struct sP1_1 {
  char a;
  char b;
  short c;
};

struct sP1_2 {
  char a;
  unsigned char b;
  short c;
};

struct sP1_3 {
  char a : 1;
  unsigned char b : 1;
  short c;
};

struct sP1_4 {
  char a : 1;
  char b : 1;
  short c;
};

#pragma pack(2)
struct sP2_1 {
  char a;
  char b;
  short c;
};
struct sP2_2 {
  char a;
  unsigned char b;
  short c;
};
struct sP2_4 {
  char a : 1;
  char b : 1;
  short c;
};

#pragma pack(4)
struct sP4_1 {
  char a;
  char b;
  short c;
};
struct sP4_2 {
  char a;
  unsigned char b;
  short c;
};
struct sP4_4 {
  char a : 1;
  char b : 1;
  short c;
};

#pragma pack(8)
struct sP8_1 {
  char a;
  char b;
  short c;
};
struct sP8_2 {
  char a;
  unsigned char b;
  short c;
};
struct sP8_4 {
  char a : 1;
  char b : 1;
  short c;
};

#define chk(STR, FIELD, EXPECT) \
  { struct STR a##STR; \
    if (!check_ptr (&a##STR, &a##STR.FIELD, EXPECT)) \
      printf (" %s (%s - .) == %d: failed\n", "a" #STR, #FIELD, EXPECT); \
  }

#define siz(STR, SZ) \
  if (sizeof (struct STR) != SZ) \
    printf ("sizeof(%s): is %d and not equal to expected %d\n", #STR, (int) sizeof (struct STR), SZ); \

int main()
{
  chk(sP1_1, b, 1);
  chk(sP1_1, c, 2);
  siz(sP1_1, 4);
  chk(sP1_2, b, 1);
  chk(sP1_2, c, 2);
  siz(sP1_2, 4);
  chk(sP1_3, c, 1);
  siz(sP1_3, 3);

  chk(sP2_1, b, 1);
  chk(sP2_1, c, 2);
  siz(sP2_1, 4);
  chk(sP2_2, b, 1);
  chk(sP2_2, c, 2);
  siz(sP2_2, 4);

  chk(sP4_1, b, 1);
  chk(sP4_1, c, 2);
  siz(sP4_1, 4);
  chk(sP4_2, b, 1);
  chk(sP4_2, c, 2);
  siz(sP4_2, 4);

  chk(sP8_1, b, 1);
  chk(sP8_1, c, 2);
  siz(sP8_1, 4);
  chk(sP8_2, b, 1);
  chk(sP8_2, c, 2);
  siz(sP8_2, 4);

  chk(sP1_4, c, 1);
  siz(sP1_4, 3);
  chk(sP2_4, c, 2);
  siz(sP2_4, 4);
  chk(sP4_4, c, 2);
  siz(sP4_4, 4);
  chk(sP8_4, c, 2);
  siz(sP8_4, 4);
  return 0;
}