#define a   z   \
            x

#define a(b)    z   \
                x

#define ab(b)   z   \
                x

#define abc(b)  z   \
                x

#define abcd(b) z   \
                x


#if FOO
#   define D(a, ...) B(FOO(a, __LINE__, __VA_ARGS__))
#   define C(msg)           \
        PP_WRAP_CODE(       \
            if (!msg)       \
            {               \
                BAR();      \
                BARBAR();   \
                BARBARBAR();\
            })
#else
#   define C(msg, ...)      EMPTY
#endif
