#include <stdio.h>

typedef union 
{
  unsigned short M;
  struct
  {
    unsigned short :15;
    unsigned short c1:1;
  }S;
}k_o;

typedef union __attribute__((packed, scalar_storage_order("big-endian")))
{
  unsigned short M;
  struct __attribute__((packed, scalar_storage_order("big-endian")))
  {
    unsigned short :15;

    unsigned short c1:1;
  }S;
}k_o_gcc;

int main()
{
  k_o ko = { .M=0 };
  ko.S.c1 = 1;
  printf("old struct = %d\n", ko.M);
  k_o_gcc kogcc = { .M=0 };
  kogcc.S.c1 = 1;
  printf("new struct = %d\n", kogcc.M);
  return 0;
}