printf("sizeof mybf %d\n", sizeof mybf);
printf("offset a = %d\n", offsetof(struct bf, a));
printf("offset c = %d\n", offsetof(struct bf, c));
printf("sizeof mybf %d\n", sizeof mybf);
printf("offset a = %d\n", offsetof(struct bf, a));
printf("offset c = %d\n", offsetof(struct bf, c));