#if 0
#warning good
#endif

#if 1
#warning good
#else

#define GOOD 1
#if GOOD
#warning good
#else
#undef GOOD

#define GOOD 0
#if !GOOD
#warning good
#else
#undef GOOD

#define GOOD 1
#if 0
#warning good
#endif
#undef GOOD

#define GOOD 0
#if 0
#warning good
#endif
#undef GOOD