ref: 75f5c7d3948bc647b21272c2e0bcbf841fb4d9f7
dir: /cmd/cpp/cat.test/
#define NOP(x) x #define CAT(a, b) a ## b #define EOF (-1) x NOP(CAT(foo, EOF)) y x NOP(CAT(EOF, foo)) y x CAT(, EOF) y y CAT(foo,) x x CAT(,foo) y X NOP(CAT(,)) y #define BAR 3 #define FOO CAT(BAR, 3) FOO