#define BITS_TO_BYTES(bits) ((bits)/8 + !!((bits)%8))

C에서 비트필드배열 만들 때 쓸만할 것 같음.

#define BITS_A 5
#define BITS_B 3
#define BITS_C 2
char bitfield[BITS_TO_BYTES(BITS_A + BITS_B + BITS_C)];