预处理

#if 0
#define FIVE 5
#define SIX  6
#define TEEE
#if defined TEEE
#   if FIVE > SIX
#       define INIT_CACHE(cache) {.flag = 2}
#   elif FIVE < SIX 
#       define INIT_CACHE(cache) {.flag = 1}
#   else
#       error "compare wrong"
#   endif
#else
#error "NOT define"
#endif
#endif