宏的实参列表中出现预处理指令
C++-Undefined-Behavior-72
示例：
#define PRINT(s) printf(#s)
PRINT(
#ifdef MAC // Undefined behavior
rabbit
#else
hamster
#endif
);依据
ISO/IEC 14882:2003 16.3(10)-undefined
ISO/IEC 14882:2011 16.3(11)-undefined
示例：
#define PRINT(s) printf(#s)
PRINT(
#ifdef MAC // Undefined behavior
rabbit
#else
hamster
#endif
);