一个是两个单词,一个是三个单词
别笑,这在预处理阶段的确是一个区别
#define PROCESS(a) t##a )
#define PROCESS_2(a) t2##a )
#define PROCESS_3(a) t3##a
#define tlong "hel" PROCESS_2(
#define t2long "lo" PROCESS_3(
#define t3 "!"
#define t3int " world!"printf("%s",PROCESS(long long)); // 输出 hello!
printf("%s",PROCESS(long long int)); // 输出 hello world!